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Nepheline syenite powder with controlled particle size and novel method of making same

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Nepheline syenite powder with controlled particle size and novel method of making same


An ultra-fine inorganic powder for use as a filler and formed from a hard, naturally occurring mined material, in particular nepheline syenite, where the powder has a targeted controlled maximum particle size of less than 5 microns and a generally uncontrolled minimum particle size.

Browse recent Unimin Corporation patents - New Canaan, CT, US
Inventors: Scott Van Remortel, Robert Ratcliff, Ibezim Anazia, Louis M. Schlesinger
USPTO Applicaton #: #20120263954 - Class: 428402 (USPTO) - 10/18/12 - Class 428 
Stock Material Or Miscellaneous Articles > Coated Or Structually Defined Flake, Particle, Cell, Strand, Strand Portion, Rod, Filament, Macroscopic Fiber Or Mass Thereof >Particulate Matter (e.g., Sphere, Flake, Etc.)



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The Patent Description & Claims data below is from USPTO Patent Application 20120263954, Nepheline syenite powder with controlled particle size and novel method of making same.

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US 20120263954 A1 20121018 US 13456307 20120426 13 20060101 A
C
08 K 3 34 F I 20121018 US B H
20060101 A
B
32 B 5 16 L I 20121018 US B H
US 428402 106467 NEPHELINE SYENITE POWDER WITH CONTROLLED PARTICLE SIZE AND NOVEL METHOD OF MAKING SAME US 12215643 20080627 PENDING US 13456307 US 60958757 20070709 Van Remortel Scott
Bakersville NC US
omitted US
Ratcliff Robert
Bakersville NC US
omitted US
Anazia Ibezim
Burnsville NC US
omitted US
Schlesinger Louis M.
Spruce Pine NC US
omitted US
UNIMIN CORPORATION 02
New Canaan CT US

An ultra-fine inorganic powder for use as a filler and formed from a hard, naturally occurring mined material, in particular nepheline syenite, where the powder has a targeted controlled maximum particle size of less than 5 microns and a generally uncontrolled minimum particle size.

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CROSS REFERENCES TO RELATED APPLICATIONS

This application is a divisional application that claims priority on U.S. application Ser. No. 12/215,643 filed Jun. 27, 2008 (UMEE 2 00090 (I); UNM-19913) and Provisional Application upon which it claims priority, i.e. Ser. No. 60/958,757 filed Jul. 9, 2007 (UMEE 2 00090 P). These two applications and Publication No. 2009-0013905 (UMEE 2 00090 (I); UNM-19913) published on Jan. 15, 2009 are hereby incorporated by reference herein.

Since this application merely claims a second inventive concept disclosed in prior copending application Ser. No. 12/215,643, it is a divisional application based upon said prior application. Information expressing the statement of invention and objects of the new claimed invention has replaced the statement of invention and objects of the prior claimed invention. Furthermore some unnecessary and irrelevant passages have been removed. This application does not include any new matter.

THE NEPHELINE SYENITE INDUSTRY

The present invention relates to the art of fine grain nepheline syenite powder as a category in the nepheline syenite industry and more particularly to a novel “ultra-fine” nepheline syenite powder having controlled particle size and the method of making this novel ultra-fine nepheline syenite powder. Coatings and films using the novel ultra-fine nepheline syenite powder constitute a further aspect of this invention.

Unimin Corporation of New Canaan, Conn. is a leading source of mined raw nepheline syenite, which is a natural occurring rock formed from several minerals and is found in deposits in only limited areas of the world. Nepheline syenite is an rock having feldspar as its major mineral and substantially no free silica. More particularly, Nepheline syenite is naturally occurring rock constituting a mixture of Na feldspar, K feldspar and nepheline. (NaAISiO4). It has a low level of free silicon dioxide. This material can be described as either syenitic and/or syenitic feldspar. Nepheline syenite can have about 99% feldspar and can be formed by more than one feldspar. The nepheline syenite industry has developed technology that is used for grinding and crushing raw nepheline syenite rock and then converting the particulated nepheline syenite into usable fine grain powder. Thus, the field to which the present invention is directed is the industry of nepheline syenite and the technology of converting nepheline syenite as mined into usable form that is a commercial powder. In about 2001, Unimin Corporation, after substantial research and development, invented an ultra-fine nepheline syenite powder, which powder was believed to be the smallest commercially available and economically producible nepheline syenite powder. This was the first ultra-fine nepheline syenite powder and was sold under the trademark Minex 10. This powder had a maximum particle or grain size D99 substantially above 15 microns. However, it was classified as “ultra-fine” nepheline syenite powder because it had a maximum particle size of less than about 20 microns. However, in some instances maximum particle size is referred to as the D95 value. Minex 10 was the smallest nepheline syenite powder available to the market for many years. Such “ultra-fine” nepheline syenite powder had the smallest commercially available grain size. After years of research and development Unimin Corporation, again using its expertise and know-how acquired at extremely high cost over many years of work by its employees invented a novel version of ultra-fine nepheline syenite powder. This new ultra-fine nepheline syenite powder had a maximum grain size D99 of less than 10 microns, which was the size believed at that time to be unobtainable for commercial production. Such smaller grain size ultra-fine nepheline syenite powder was found to create drastically different physical characteristics and properties in certain commercial products, such as coatings and films. Consequently, the recently invented nepheline syenite powder that imparted improved, albeit different physical characteristics and properties to many end products was believed to be the ultimate in nepheline syenite powder, especially for coatings and films. This powder created a new art for using naturally occurring materials and is the art to which the present invention is directed. This newly developed ultra-fine nepheline syenite powder has now been introduced into the market under the trademark Minex 12. Prior to Minex 12 the only other commercially available ultra-fine nepheline syenite powder was sold as Minex 7 or Minex 10. Minex 7 having a maximum grain size D99 of about 20 microns and was “ultra-fine” as this term is used herein and used in the art of the present invention. Minex 7, Minex 10 and Minex 12 are classified as ultra-fine nepheline syenite powders and are the commercially available nepheline syenite powders to which the present invention is an improvement.

A larger nepheline syenite powder, which is greater than “ultra-fine” grade, is Minex 4 having a maximum grain size D99 of about 40 microns and a D99.9 grain size of about 60 microns. All these commercially available nepheline syenite powders define prior art to the invention and form the background to which the present invention is directed. The art is nepheline syenite powder as an area in the nepheline syenite industry. After Minex 12, with a maximum grain size D99 of less than 10 microns was introduced as the commercial nepheline syenite powder, it was determined that this extremely small ultra-fine nepheline syenite powder imparted substantial advantages to a large variety of commercial products including coatings, films, and inks, to name a few. These same properties are also realized by use of the present invention. To complete the background of the nepheline syenite powder art, prior U.S. patent application Ser. No. 11/803,093, filed on May 11, 2007 (UMEE 2 00075) is incorporated herein as background information for the various uses of “ultra-fine” nepheline syenite powder, which is the classification of the powder to which the present invention is directed. The present invention is an improvement and substantial advance in the art of nepheline syenite powder and in the sub-art of “ultra-fine” nepheline syenite powder which is a powder having a maximum grain size D99 of generally less than about 20 microns. In view of this background, this application relates to the specific processes used to produce a novel ultra-fine nepheline syenite powder, which novel powder is used in several applications found to be uniquely enhanced by ultra-fine nepheline syenite powder, such applications as coatings of the clear, ultra violet cured, hard, semi-transparent, and powdered types. This application discloses a novel “ultra-fine” nepheline syenite powder, the novel method of producing this novel ultra-fine nepheline syenite powder and the coatings and films using such novel ultra-fine nepheline syenite powder.

Nepheline Syenite Background Information

The present invention relates to the nepheline syenite powder art; however, before describing the advance constituting the invention of the present application, a general understanding of the nepheline syenite industry itself as evidenced by the patented technology will illustrate the difference between the general nepheline syenite industry and the specific art of the present invention, which art is commercial grade nepheline syenite powder and particularly ultra-fine nepheline syenite powder.

Standard ground nepheline syenite in particulate form has been a commercial product for many years. Indeed, nepheline syenite powder in particulated form has been used extensively to make industrial compounds and to instill enhanced properties in liquid coatings, ceramics, glass, etc. For illustrations of representative products or compounds employing standard processed particulate nepheline syenite, the following U.S. patents are incorporated by reference. Consequently, the general properties and procedures for using existing nepheline syenite particles need not be repeated.

Koenig 2,261,884 use as flux in ceramic Lyle 2,262,951 color ingredient in glass Thiess 2,478,645 porcelain glaze Hummel 2,871,132 glazing compound Huffcut 3,389,002 heat and corrosion resistant coating Weyand 3,486,706 binder for grinding agent Waters 3,917,489 ceramic flux Harris 3,998,624 source of metal aluminum silicate Brown 4,028,289 inorganic filler Chastant 4,130,423 natural silicate for slag formation Funk 4,183,760 alumina ceramic Aishima 4,242,251 alumina silicate filler Seeney 4,396,431 inorganic binder Drolet 4,468,473 SiO2 source Shoemaker 4,639,576 electrode coating Goguen 4,640,797 polymer filler Vajs 4,743,625 vitrifying material Holcombe 5,066,330 refractory filler Kohut 5,153,155 non-plastic filler Slagter 6,569,923 polymer cement White 6,790,904 liquid coating

Other uses of standard, ground nepheline syenite have been recently suggested. Representative examples of such newer applications of ground nepheline syenite are disclosed in the following United States patent publications:

Schneider 2002/0137872 scratch resistant coating Zarnoch 2002/0173597 filler in resin powder Fenske 2003/0056696 filler for polymer cement Burnell 2003/0085383 suspending filler Burnell 2003/0085384 heat curable resin White 2003/0224174 filler in liquid coating Schneider 2003/0229157 scratch resistant powder coating Giles 2004/0068048 filler for rubber Finch 2005/0059765 filler for plastic coating Adamo 2005/0214534 extender for curable composition Duenckel 2006/0081371 sintering aid Schneider 2006/0160930 corrosion resistant coating Dorgan 2006/0235113 filler for polymer

Ground nepheline syenite and larger grain nepheline syenite powder are used as a filler or extender in paints, coatings, plastics and paper. It is a desirable material because it contains virtually no free silica and still functions as effectively as a free silica based filler or extender. Nepheline syenite is an inorganic material that is a naturally occurring mined substance having substantially no free silica and which is hard since it has a Mohs number of 6. The material is an inorganic oxide having mechanical characteristics similar to the free silica materials for which it is used as a substitute in various industries. These mechanical properties of ground nepheline syenite are realized by the use of a fine grain particulate form of nepheline syenite, which is sometimes a powder that has a grain size greater than about 15-60 microns. These known ground and powdered nepheline syenite products are quite abrasive for manufacturing equipment. Consequently, the granular nepheline syenite has a high tendency to abrade and erode quite rapidly equipment used in processing the various compounds, even compounds incorporating the fine grain powder of the prior art. It has been determined that by reducing the fine grain size of any inorganic oxide material, such as nepheline syenite, the abrasive properties of the material are reduced. It is common to provide ground nepheline syenite with a relatively small grain size for the purpose of allowing effective dispersion of the product aided by the use of nepheline syenite powder. The advantage of dispersing fine grain nepheline syenite in the carrier product is discussed in several patents, such as Gundlach U.S. Pat. Nos. 5,380,356; Humphrey 5,530,057; Hermele 5,686,507; Broome 6,074,474; and, McCrary Publication No. US 2005/0019574. These representative patent publications show fine grain nepheline syenite and are incorporated by reference herein as background information regarding the present invention. These disclosures illustrate the advantages of providing this inorganic oxide in a very fine grain size for a variety of applications. In US Publication 2005/00019574 there is a discussion that microcrystalline silica is a preferred filler in plastic. Ground nepheline syenite from Unimin Corporation, New Canaan, Conn., is thus provided as a fine grain silica deficient silicate in the form of a sodium potassium alumino silicate. The particles of this nepheline syenite are finely divided and have a grain size in the range of about 2 to about 60 microns. This widely used commercial product having this grain size and wide particle size distributions has been sold as an additive that provides the nepheline syenite properties.

SUMMARY OF BACKGROUND

The present invention relates to the unique technique of producing ultra-fine powder from nepheline syenite a naturally occurring igneous rock containing substantially no free silica and which is hard since it has a Mohs number of 6. This technology advance has resulted from a desire to produce ultra-fine nepheline syenite powder having a very small maximum particle size. Nepheline syenite powder is relatively inexpensive, hard and free of silica composite rock; consequently, it presents tremendous benefits for fillers in coatings and films. Such products utilize the nepheline syenite powder as an extender or filler to impart unique physical characteristics to coatings, films or other thin substrates. Over many years substantial research and development by Unimin Corporation, assignee of this application, the leader in the nepheline syenite industry was able to produce only a commercially viable nepheline syenite powder having a maximum particle size, usually referred to as the D99 particle size, of over about 15 microns. This powder was believed by the industry to be the finest commercial version of nepheline syenite powder. Such small ultra-fine powder was sold under the trademark Minex 10 and gained substantially commercial acceptance because of the unique properties of the material and its small size. It was “ultra-fine” which is defined as having a maximum particle size D99 of less than 20 microns.

STATEMENT OF INVENTION

After tremendous commercial success of the Minex 10 nepheline syenite powder, Unimin Corporation invested substantial expense and research and development time directed toward inventing a commercially viable nepheline syenite powder which would have a controlled maximum particle size of less than 15 microns, but could still be manufactured and sold at a competitive price to the ultimate users. In this way, the hard nepheline syenite powder would be ultra-fine and would have a maximum particle size at a level that drastically reduced the wear of equipment employed in producing the coating or film. With this objective of producing an improved commercial nepheline syenite powder in the ultra-fine nepheline syenite industry, Unimin developed a new nepheline syenite powder as disclosed in U.S. application Ser. No. 11/703,384 filed Feb. 7, 2007 with an application No. 2 008-0015104 published on Jan. 17, 2008.

The present invention is the result of a further research and development by Unimin Corporation wherein the maximum particle size D99 of the ultra-fine nepheline syenite powder has been reduced to a D99 value of less than 5 microns. This new product, which is the subject in this application, has tremendous improvement over all prior ultra-fine nepheline syenite powders. Consequently, nepheline syenite powder with all of its commercial advantages can be used as a substitute for nano fillers heretofore produced chemically and at great expense. The present invention is directed toward a naturally occurring mined powder that contains a feldspar and, preferably, to a nepheline syenite powder having the smallest maximum particle size D99 now obtainable in the industry.

Parent application Ser. No. 12/215,643 filed Jun. 27, 2008 discloses the result of the aforementioned research and development program conducted by Unimin Corporation, which program resulted in various inventions in the nepheline syenite powder technology. In the parent application the particular invention claimed was the primary aspect of the research and development project. This primary aspect was a unique ultra-fine nepheline syenite powder having a top cut of less than 20 microns and a bottom cut in the general range of 2-7 microns. The various newly discovered nepheline syenite powders of this project had unique physical properties and presented substantial and distinct advantages. The present application is a divisional of the parent application and relates to another or second invention made during the research and development project disclosed in the parent application. This alternative invention relates to an ultra-fine nepheline syenite powder having a targeted maximum particle size that is controlled to a targeted value of less than 5 microns. This alternative or second invention is defined in the claims of this divisional application and presents a second commercially viable and producible ultra-fine nepheline syenite powder invented at Unimin Corporation. Indeed, this second novel powder had nano size particles since the maximum particle size is less than 5 microns. Examples of this second novel powder have a targeted maximum particle size of 2 microns and 4 microns. The advantages of this second invention described in the parent application are documented herein.

In accordance with the present invention, there is provided an ultra-fine nepheline syenite powder. This powder has a targeted controlled maximum particle size of less than 5 microns (for instance 4 microns and 2 microns) and a generally uncontrolled minimum particle size, thus, creating a targeted minimum particle size of 0 microns. This powder is described herein as the “−5” nepheline syenite powders developed by assignee in its disclosed research and development program. Embodiments of this invention are powders having a targeted maximum particle size of 2 microns or a targeted maximum size of 4 microns. In each case, the targeted maximum size is less than 5 microns. The maximum particle size is generally defined as a D99 particle size or more practical, the D95 particle size.

In accordance with the present invention, there is provided an ultra-fine inorganic powder formed from a hard, naturally occurring mined material having substantially no free silica, the powder having a targeted controlled maximum particle size of less than 5 microns and a generally uncontrolled minimum particle size creating a targeted minimum particle size of zero microns.

In accordance with other aspects of the present invention, there is provided an ultra-fine nepheline syenite powder having a maximum particle size D99 of less than 5 microns and preferably in the range of 2-4 microns. Such particles have not heretofore been known in the nepheline syenite field of technology.

In accordance with another aspect of the present invention, the novel very small ultra-fine nepheline syenite powder is produced by using a wet mode of operation for producing the grinding of the particles in a vertical stirred mill.

In accordance with another aspect of the present invention, the novel very small ultra-fine nepheline syenite powder of the present invention is produced by a pre-processed nepheline syenite powder with a maximum particle size D99 in the range of 20-100 microns. Furthermore, the feedstock has a moisture content of less than 0.8% by weight. Consequently, the new nepheline syenite powder defined in the claims of this application is produced from a pre-processed nepheline syenite powder which in many instances is a commercial Minex powder produced and sold by Unimin Corporation.

In accordance with another aspect of the present invention, the novel powder defined above has a particle size distribution with a narrow particle size spread between the D99 particle size and the D1 particle size. This narrow particle size spread is in the general range of 2-4 microns.

In accordance with still another aspect of the present invention, there is provided a method for making an ultra-fine nepheline syenite powder comprising providing a feedstock of pre-processed nepheline syenite powder, milling the feedstock into an intermediate powder, and air classifying the intermediate powder to a targeted particle size D99 of less than 5 microns. This method is preferably milled in a wet mode in a vertical stirred mill; however, it is also milled in a jet mill where the jet mill is preferably a fluid bed opposed flow jet mill.

In accordance with another aspect of the present invention, the nepheline syenite powder has a controlled maximum particle size of less than 5 microns and preferably a D99 particle size in the range of about 2-4 microns to impart a specific, very distinct characteristic to the coating or film using the novel powder of the present invention.

The primary aspect of the present invention is provision of an ultra-fine nepheline syenite powder having a substantially controlled, or targeted, very small maximum particle size of less than 5 microns. By controlling the maximum particle size of the nepheline syenite powder, the range of distribution of particle size is made quite narrow to impart distinct and repeatable physical characteristics to the coatings and/or films utilized in the present invention.

In accordance with another aspect of the present invention, the ultra-fine nepheline syenite powder of the present invention has a controlled maximum particle size of less than 5 microns, and is produced by utilizing a pre-processed nepheline syenite feedstock that is preferably a commercial pre-processed nepheline syenite powder, such as Minex 7 and Minex 10. The novel ultra-fine nepheline syenite powder of the present invention has a moisture content less than 0.8% by weight and a narrow particle size range between the D1 particle size and the D99 particle size. Consequently, the distribution of particles is a very narrow range to give consistent and well defined physical characteristics to coatings and films or any other product using this new ultra-fine nepheline syenite powder.

In accordance with the invention, the new ultra-fine nepheline syenite powder has a controlled “targeted” maximum particle size, which is usually defined as a D99 particle size. The term “target value” or “targeted” is a value imparted to the maximum grain size in accordance with the practical applications of the present invention. As known in the relevant technologies, the exact maximum particle size may vary unintentionally from the targeted value that is used to define the metes and bounds of the present invention.

In yet a further aspect of the present invention, the nepheline syenite feedstock is processed by an air classifier. Indeed, the novel ultra-fine nepheline syenite powder is formed by various processes, one involving air classification. The other involving a series of air classifiers and the other a mill and air classifier in series constituting a continuous process. In accordance with an aspect of the present invention, the mill used in one method for producing the ultra-fine nepheline syenite powder of the present invention is an air jet mill. Furthermore, the smaller embodiment of the present invention, such as the 0×2 powder, is produced by a vertical stirred mill with or without grinding aids. Furthermore, in making this embodiment of the invention, the vertical stirred mill is operated in a wet mode; however, it can be operated in a dry mode as can the opposed jet mill, especially for larger maximum particle sizes, such as the 0×4 powder example.

Nepheline syenite is a naturally occurring rock constituting a mixture of sodium feldspar, potassium feldspar and nepheline (Na Al SiO4). This material is substantially free of silica dioxide. Furthermore, this material can be described as either syenite or syenite feldspar. Consequently, the present invention is applicable to nepheline syenite and also other syenite materials having drastically low free silicon dioxide. The general description of nepheline syenite is applicable to an understanding of the present invention and is used to define the nepheline syenite rock formation constituting the material used in practicing the invention.

The invention comprises a unique “ultra-fine” nepheline syenite powder, new and novel methods of making such powders, use of the powder as a filter for coatings and films and the coatings or films using the novel nepheline syenite powder.

The present invention relates to controlling particle size distribution and particle size upper limits in systems of nepheline syenite particles. Although efforts have been undertaken in the prior art to produce nepheline syenite powder with a generally reduced particle size, artisans in the related field have not recognized the many benefits the physical properties that can be realized from a very low controlled maximum particle size for the nepheline syenite powder, i.e. a D99 particle size of less than 5 microns and generally in the range of 2-4 microns.

The present invention provides a nepheline syenite particle system exhibiting a very low abrasiveness. Indeed, the Einlehner value of the present invention is a number substantially less than 50. The present invention provides a nepheline syenite particle system exhibiting a very low gloss and extremely beneficial optical characteristics.

The present invention also relates to numerous products and applications made possible by the use of the nepheline syenite particle system constituting this aspect of the present invention. The use and incorporation of the various particle systems described herein provide new strategies and applications for nepheline syenite powder.

An object of the present invention is the provision of a filler for coatings and films, which filler is an ultra-fine nepheline syenite powder produced from pre-processed nepheline syenite powder. In this new powder the maximum particle size is controlled to a given value thereby reducing abrasive properties of the filler. The new ultra-fine nepheline syenite powder shows low gloss and less abrasion to processing or application equipment. These properties of the novel filler, produced in accordance with this object of the present invention improves the coating hardness and abrasive resistance of the coating and produces distinct properties in the coating or film because of the very low controlled maximum particle size of the nepheline syenite powder.

Another object of the present invention is the provision of an ultra-fine nepheline syenite powder, which powder has a controlled maximum particle size not heretofore obtainable in the nepheline syenite powder industry. This controlled maximum particle size is less than 5 microns and preferably in the general range of 2-4 microns.

Another object of the present invention is the provision of a unique novel method of producing the novel ultra-fine nepheline syenite powder having a controlled maximum particle size with values less than 5 microns.

Still a further object of the present invention is the provision of a filler utilizing the novel nepheline syenite powder, as defined above, which filler is employed in coatings and/or films to produce a novel coating or film with distinct physical characteristics.

Yet another object of the present invention is the provision of a novel ultra-fine nepheline syenite powder having a controlled particle size distribution defined by a very low maximum particle size. By having a novel particle size distribution in the range of 0 microns to less than 5 microns (such as 4 microns), the powder has a very low abrasive characteristic for manufacturing equipment and a drastically improved repeatability of properties imparted by the filler in the product using the inventive nepheline syenite powder.

Yet another object of the present invention is the provision of a method of forming the ultra-fine nepheline syenite powder described above, which powder are characterized by having a relatively small particle size diameter D99 and a relatively narrow particle size distribution between the D99 particle size and the D1 particle size.

Still a further object of the present invention is the provision of an ultra-fine nepheline syenite powder with a controlled grain size distribution that is a highly bright material usable for filler applications and in clear coatings. The unique novel nepheline syenite powder of the present invention can be formed into a concentrate and then dispersed into a coating or other matrix material and has a drastically decreased settling tendency.

Still another object of the present invention is the provision of an ultra-fine nepheline syenite powder with a controlled particle size distribution, which powder, when used for ultra-violet, clear or semi-transparent coatings, results in a superior clarity compared to competitive filters, can be used with up to 20-25% loading, is UV transparent, is easily dispersed into low viscosity systems and increases film hardness and scratch resistance. By the control of the particle size distribution to a low level, these properties in the coating are unique and can be duplicated by subsequent use of the novel and defined particle size controlled ultra-fine nepheline syenite powder of the invention.

Yet a further object of the present invention is a novel ultra-fine nepheline syenite powder, as defined, which powder, when used in a coating, retains weathering durability increases hardness and block resistance for kitchen and appliances applications and offers higher gloss than large grain size nepheline syenite powder.

The novel nepheline syenite powder has a controlled maximum particle size to minimize abrasion and equipment wear and has superior cost/performance balance versus expensive “nano” fillers. The present nepheline syenite powder is a direct competitor to such nano fillers and imparts the advantages of nepheline syenite powder to a filler used as a substitute for the expensive, chemically produced nano fillers.

Yet another object of the present invention is the provision of a coating containing the novel ultra-fine nepheline syenite powder, which coating is clear, hard and resistant to scratches. This novel filler is relatively inexpensive as compared to other nano fillers. Coatings using the new ultra-fine nepheline syenite powder as a filler is curable by exposure to ultra-violet radiation (i.e. is UV curable). Consequently, the coating using the novel ultra-fine nepheline syenite powder is reliably curable and curable in a repeatable fashion due to the control particle size distribution of the present invention.

All of these objects and advantages and the statements of the present invention have been determined experimentally and tested to allow description of the physical characteristics imparted by the novel ultra-fine nepheline syenite powder to products, such as coatings and films. These advantageous properties are repeatable because of the nano particle size distribution of the novel ultra-fine nepheline syenite powder. The coatings or films are inexpensive due to the fact that this very small, novel nepheline syenite powder can be easily dispersed at high loadings in coatings and films. Furthermore this new nepheline syenite powder has substantially no free silica, which characteristic of nepheline syenite is another advantage of the novel “ultra-fine” nepheline syenite powder. This is especially important for an ultra-fine powder that can become air borne during subsequent handling and processing.

Still a further object of the present invention is the provision of an ultra-fine powder used as a filler, which filler has a novel controlled maximum particle size and is derived from naturally occurring block formations.

These and other objects and advantages are part of the disclosure and will become more apparent in the following description taken together with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow chart schematically illustrating a method for producing the novel ultra-fine nepheline syenite powders;

FIG. 2 is a block diagram of a method of producing the claimed nepheline syenite powder of the parent application from either Minex 4 or Minex 7;

FIG. 3 is a block diagram of the method of producing one version of the ultra-fine nepheline syenite powder claimed in the parent application where the feedstock has the desired controlled maximum particle size;

FIG. 4 is a block diagram schematically illustrating a method of producing a version of the ultra-fine nepheline syenite powder claimed in this divisional application;

FIG. 5 is a schematic and flow chart of the method produced by the equipment schematically illustrated in FIG. 1;

FIG. 6 is a table of the target particle sizes of several samples of ultra-fine nepheline syenite powder, including nepheline syenite powder in accordance with the present invention and setting forth the particle size distribution between D1 and D99.9 where the target values are D5 and D99 of the samples;

FIG. 7 is a graph illustrating nominal sizes of samples described in the table of FIG. 6 and illustrating the targeted grain sizes of the ultra-fine nepheline syenite powder samples, including novel powders of the present invention;

FIG. 8 is a graph of various particle size distributions of nepheline syenite particles having no controlled minimum particle size as in samples defined in the graph of FIG. 7 and the table of FIG. 6;

FIG. 9 is a graph of particle size distribution for samples having nominal 2 micron minimum particle size;

FIG. 10 is a graph similar to FIG. 9 illustrating an ultra-fine nepheline syenite powder with a controlled minimum grain size of 4-6 microns;

FIG. 11 is a graph of the average contrast ratio of black and white test panels having coatings with various known and preferred embodiments of the present invention;

FIG. 12 is a graph of 20° gloss of powder coatings with various known and preferred embodiments of the present invention;

FIG. 13 is a block diagram of a second preferred embodiment of an inventive method for producing ultra-fine nepheline syenite powder having the characteristics of a novel powder;

FIG. 13A is a schematic diagram of an opposed air jet mill of the type used in practicing the method described in FIG. 13;

FIG. 14 is a block diagram like the diagram of FIG. 13 showing the second preferred method for producing ultra-fine nepheline syenite powder of the parent application showing use of a generic dry mill and an additional process to make a small particle size powder with only a controlled maximum particle size as on this divisional application;

FIG. 15 is a block diagram schematically illustrating another method of producing nepheline syenite powder with a targeted grain size of 5×15 and alternatively 6×15;

FIG. 16 is a block diagram similar to the block diagram of FIG. 14 illustrating a method for producing ultra-fine nepheline syenite powder, wherein the target grain size is 5×15 and where the powder is produced by removing only the lower particle sizes from the feedstock having a desired controlled maximum grain size;

FIG. 17 is a graph representing ultra-fine nepheline syenite powders produced by the method disclosed in FIG. 16;

FIG. 18 is a graph similar to FIG. 17 describing ultra-fine nepheline syenite powders produced by using the method schematically illustrated in FIG. 15; and,

FIG. 19 is a chart showing particle size distribution curves for samples (9)-(11).

Having thus defined the drawings, further features of the invention will be hereinafter described.

The advantages of the present invention, i.e. the novel “ultra-fine” nepheline powder having certain particle size distributions, are, in addition to and sometimes duplicative of, the advantages discussed in the introductory portion of the present disclosure. The disclosures establish the merit of various aspects of the present invention. Indeed, there are distinct advantages of using the nepheline syenite powder and systems described herein in certain coatings and other products. Nepheline syenite powder having a grain size of less than about 15 microns is known, but controlling the particle size distribution as described herein is not known. There was little known about the tremendous combinations of properties and characteristics to be imparted to products by the novel grain size distributions and control of particle sizes of the present invention. The concept of controlling the grain size of nepheline syenite powder, again this invention, was not pursued and the advantages were not realized until the present inventive act.

Preferred Particle Systems

It is instructive to explain certain designations and nomenclature described herein. Particle sizes, unless indicated otherwise, are given in microns, 10−6 meters. As will be appreciated by those skilled in the art, particle sizes are expressed in diameters. Although diameters imply a spherical or round shape, the term diameter as used herein also refers to the span or maximum width of a particle that is not spherical. Typically, ranges of particle sizes or size distributions are noted. For example, for a range of 2 to 10 microns, a designation of “2×10” is typically used. Also, if no lower size limit is designated for the range at issue, the collection of particles is referred to as “minus” and then the upper size limit is noted. Thus, for example, for a collection of particles having no lower size limit and an upper size limit of less than 5 microns, the designation “minus 5” or “−5” is used. Another designation used herein is “Dn” where n is some numerical value between 0 and 100. This value refers to a proportion or percentile of particles having a certain maximum diameter. For example, in a particle population having a target size of 0 to 18 microns, for instance, the median maximum diameter (D50) may be 2.5 microns, the largest diameter in the 99th percentile of the population (D99) may be 16 microns, and the largest diameter in the 1st percentile of the population (D1) may be 0.1 microns. These values, particularly when taken collectively, provide an indication as to the “spread” or distribution of particle sizes in the particular system. The spread is preferably between D95 and D5, but it can be between D5 and D99 or D1 and D99.

Certain nepheline syenite particle systems with particular size distributions and characteristics have been discovered. The preferred embodiments nepheline syenite particle systems of the invention claimed in the parent application are a 2×10 system, a 4×15 system, a 5×15 system, and 6×15 system. These systems exhibit surprisingly and unexpected beneficial physical properties including, but not limited to reduced abrasiveness, reduced gloss, and increased hardness and reduce friction, lower oil absorption for higher loading and better rheology. Tables 1-4 set forth below, present typical, preferred, and most preferred values for the D1, D50, and D99 size characteristics of various preferred embodiment nepheline syenite particle systems in accordance with the invention claimed in the parent application. All particle sizes noted are in microns.

TABLE 1 2 × 10 Preferred Embodiment Particle System D1 D50 D99 Typical 0.2-2.6 2.9-4.7 8.1-10.9 Preferred 0.3-2.3 3.3-4.3 8.5-10.5 Most Preferred 0.8-1.8 3.8 9.0-10.0

TABLE 2 4 × 15 Preferred Embodiment Particle System D1 D50 D99 Typical 0.9-3.7 7.9-9.7 14.3-17.1 Preferred 1.3-3.3 8.3-9.3 14.7-16.7 Most Preferred 1.8-2.8 8.8 15.2-16.2

TABLE 3 5 × 15 Preferred Embodiment Particle System D1 D50 D99 Typical 3.3-6.1 8.4-10.4 14.6-17.5 Preferred 3.7-5.7 8.9-9.9  15.1-17.1 Most Preferred 4.2-5.2 9.4 15.6-16.6

TABLE 4 6 × 15 Preferred Embodiment Particle System D1 D50 D99 Typical 3.1-5.9 9.1-11.1 16.5-19.4 Preferred 3.5-5.5 9.6-10.6 16.9-18.9 Most Preferred 4.0-5.0 10.1 17.4-18.4

Significantly reduced abrasiveness of nepheline syenite particle systems can be obtained by using particle systems having a relatively small particle size for the upper size limit, and a relatively “tight” particle size distribution. For example, in one embodiment, the system has a median or D50 size of 8-11 microns, a lower or D1 size limit of 2-5 microns, and an upper or D99 size limit of 15-19 microns. This embodiment particle system exhibits an Einlehner value of 180-200. In another embodiment particle system, the system has a D50 size of 3-4 microns, a D1 size limit of 1-2 microns, and a D99 size limit of 9-10 microns. This system exhibits an Einlehner value of 70-90.

Significantly reduced gloss and frequently while maintaining clarity can be achieved by use of certain embodiment particle systems described herein. An embodiment particle system having a D50 size of 8-11 microns, a D1 size of 2-5 microns, and a D99 size of 15-18 microns, exhibits a 20 degree gloss of less than 50, and preferably 40-50, and a 60 degree gloss of less than 95 and preferably 80-95.

Equipment Used to Produce Powder

A method for forming the various particle systems described herein is by use of a vertical stirred ball mill, also sometimes referred to as an attrition mill in the industry. Such a mill is commercially available from Union Process Attritor Co. in Akron, Ohio and is illustrated in U.S. patents, such as U.S. Pat. Nos. 4,850,541 and 4,979,686, which are both incorporated by reference herein.

Generally, three types of Attritors are available—a batch Attritor, a continuous Attritor, and a circulation grinding Attritor.

The batch Attritor consists of a jacketed vessel filled with grinding media. Either hot or cold water or low pressure steam is run through the specially designed jacket for temperature control.

Production size Attritors are equipped with a built-in pumping system which maintains circulation during grinding for accelerated attrition and uniformity. The pump can also be used for discharging.

In the batch Attritor, the material is fed into the jacketed tank and is ground until the dispersion and desired particle size are achieved. No premix is necessary as it is accomplished in the grinding chamber. Ingredients can be added at any time. Inspection and formula corrections can be made during the grinding process without stopping the machine.

The Model 01 Attritor available from Union Process Attritor Co. is a very useful research tool for testing various formulations and grinding conditions. The lab model 1-S can be used for an accurate scale-up test machine. The most important factor is to keep the peripheral tip speed constant and the media to slurry ratio about the same. Generally in the 1-S, the media/slurry ratio is 1:3/4, but in the production unit it is 1:1, therefore grinding times are somewhat longer in the larger machines, such as the 200-S and 400-S.

Another system is the continuous Attritor (C or H machine) which is best-suited for continuous, large production quantities. The continuous Attritor has a tall, narrow, jacketed tank into which a well premixed slurry is pumped in through the bottom and discharged at the top. Grids located at both the bottom and top of the machine retain the media.

The fineness of the processed material depends on the residence or “dwell time,” which is defined as the length of time the material to be processed stays in the grinding chamber.

The dwell time is controlled by the pumping rate. The slower the pumping rate, the longer the dwell time, and hence the finer the grind.

The dwell time is calculated by dividing the void volume by the pumping rate. Void volume is the entire volume of the tank minus the media and the agitator shaft and arms. Therefore, scale-up for a “C” machine is determined by calculating the dwell time of a particular product and dividing this into the void volume of the larger unit. This is assuming the same tip speeds for both units. For quick scale-up, one can ratio the gross tank capacities.

One prerequisite of the continuous Attritor is that it needs a well mixed, uniform, homogeneous feed. Also a good metering pump is required, such as a gear or moyno pump.

The continuous Attritor can be set up in series. By using larger media in the first unit, which is equipped with grids having larger openings, the system can accept a coarser feed size. The subsequent units can have smaller media, resulting in a finer grind.

Another system to produce novel powder uses a device called the circulation grinding Attritor (Q machine) and has been developed in the last few years. This system is a combination of an Attritor and a large holding tank which is generally 10 times the size of the attritor. The Attritor is filled with media and contains grids which, as in the continuous Attritor system, restrain the media while the slurry is allowed to pass through.

One of the essential requirements of the Q Attritor is the high circulating (pumping) rate. The entire contents of the holding tank are passed through the Attritor at least once every 7½ minutes, or about 8 times per hour.

This high pumping rate results in a faster grind and a narrower particle size distribution. This phenomenon is explained by the principle of preferential grinding. The fast pumping stream through the agitated media bed makes the Q-machine grinding chamber act as a dynamic sieve or filter, allowing the fines to pass and move quickly through, while the coarser particles follow a more tortuous path through the media bed.

With the circulation process, unlike the continuous attritor with the slurry making a single pass, the material makes many passes through the grinding chamber until the desired particle size is obtained.

Generally a gear pump is used which is a good metering pump. However, for abrasive and high viscosity slurries, a diaphragm or moyno pump is used.

It may also be preferred, in certain applications to use one or more grinding aids when forming the preferred embodiment particle systems described herein. Representative examples of such particle systems include, but are not limited to tri-ethanolamine, ethyl alcohol, acetic acid, silicone glycol surfactants, and combinations thereof. Of these, tri-ethanolamine is preferred.

Using an attrition mill produces a powder that can be used to practice the invention. The output powder is processed into a system of nepheline syenite particles having a relatively small size and a relatively narrow particle size distribution can be produced.

Advantages in Products and Applications

It has been found that the nepheline syenite powder systems described herein dramatically reduce wear on mechanical equipment. Thus, in one aspect, the present invention provides a nepheline syenite powder with a novel particle or grain size distribution whereby it greatly reduces wear.

Nepheline syenite powder of the present invention drastically reduces wear on equipment processing the product using the novel inorganic powder. By providing a grain size distribution not heretofore available for nepheline syenite powder the Einlehner Abrasive Value (EAV) is substantially less than 200 and about 100 or less. Certain powder systems described herein exhibit Einlehner Abrasive Values of 180-200; 70-90; and 15-20.

Another novel aspect of the present invention is its use to obtain properties attributed only to the novel nepheline syenite powder in various applications. The new powder has a considerably less abrasive effect on equipment than commercially available ultra fine nepheline syenite powder.

It has also been discovered that the nepheline syenite powder systems described herein are easily dispersed in resin systems, drastically reduce settling, and exhibit a high brightness. By using the powder with a particle or grain size distribution forming an aspect of the present invention, coatings can be created by controlled, specific loading of the nepheline syenite particle systems to increase clarity, increase the effect on gloss, and stability of the coating. Consequently, nepheline syenite powder with a novel particle size distribution has been found to enhance characteristics of the coatings in a manner not obtainable by larger grain nepheline syenite powder now available.

Nepheline syenite powder having larger particle or grain size has been used as a filler and/or extender in paint, coatings, plastics, rubber and other materials. The nepheline syenite powder imparts a variety of physical properties and technical enhancements to these systems, such as improved scrub and abrasion resistance in coatings. It has been discovered that the novel nepheline syenite powder having controlled particle size distribution developed as one aspect of the present invention offers surprisingly improved levels of optical performance while maintaining other critical performance properties of coating. Thus, the novel nepheline syenite powder is particularly beneficial for clear coatings and films.

The particle size material having a particle or grain size distribution as described herein has been proven successful in a coating with the powder used as a filler or extender, a clear coating, a cured coating, a wood coating, a powdered coating including clear coating, automotive clear coating, coil coating, sealants, paper laminates for pictures and other structures and inks. All of these products have enhanced physical characteristics based upon the use of the nepheline syenite powder with the novel particle size distribution.

The present invention has resulted in another group of new products that are enhanced by using nepheline syenite powder with specific size distribution with a loading of 10-25% or higher by weight. These products have used nepheline syenite of a substantially greater grain size, such as ground nepheline syenite. They have enhanced characteristics because they have a high loading of nepheline syenite powder with controlled size distributions. This class includes ultraviolet cured coating, nitrocellulose lacquer, acrylic lacquer, solvent based cured varnish, aqueous coatings such as lacquer, acrylic urethane and other urethane coatings, and 100% solids coatings. These coatings are enhanced by using the nepheline syenite powder described herein. Additional products in this class of goods improved by using the nepheline syenite powder, other than coatings, are adhesives, sealants, inks and paper laminates for simulated wood of furniture, films, coatings and other structures. They are new and novel because they use the nepheline syenite powder having a controlled particle size distribution.

In accordance with yet another aspect of the present invention, the novel nepheline syenite powder is used to provide a product from the class consisting of clear coatings, sealants, paper laminates, aqueous coatings, solvent based coatings, UV cured coatings, water based coatings with resin free pigment paste, nitrocellulose clear lacquer, acrylic lacquer, clear solvent based acid cured varnish, aqueous lacquer, acrylic urethane coating, aqueous clear PUD urethane coatings, 100% solids clear UV coatings and powder coatings. Also, the novel nepheline syenite powder is used in a “concentrate”, such as a paste or predispersant that is incorporated into polymer systems used as coatings, plastics or rubber articles. The loading or percent of powder added to the final product is carried by the concentrate into such product.

It has been discovered that the nepheline syenite particle systems described herein when incorporated into coatings or other formulations, can significantly increase the hardness and resistance of the coating. By using the powder with a particular size distribution forming another aspect of the invention, coatings can be created with controlled particle size distribution to increase block and abrasion resistance, and increase hardness, along with other characteristics.

The present invention also provides substantial physical benefits in clear coatings, powdered coatings, ultraviolet cured coatings and other applications which benefits have been realized when compared to various products using commercially available nepheline syenite powder and other commercial fillers. One of the applications that has been found to benefit substantially by the use of the novel nepheline syenite powder of the invention is powder coatings, which may be clear or colored.

In accordance with another aspect of the present invention there is provided another group of commercial or final products including the nepheline syenite powder with a controlled particle size distribution. This group consists of clear liquid wood coating, clear liquid coating for flexible substrates, clear liquid coating for rigid substrates, nail polish, glass, metallurgical slag, refractory fillers, and pigment paste to make coatings.

A further aspect of the invention is a new product that now includes a specific nepheline syenite powder with a certain size distribution. The product is selected from the class consisting of opaque liquid coatings, coatings of less than 10 microns in thickness, inks, powder coatings, ceramic bodies, glazes, plastic fillers, rubber fillers, color concentrates or pastes and sealants. These products use the nepheline syenite powder to produce enhanced physical characteristics and properties as explained herein.

Optical Properties Analysis

Existing and new particle size distributions were formulated in a standard clear acrylic powder coating at Reichhold Chemicals in Durham, N.C. Minex 10 and 12 were used along with new particle size ranges. The new particle size ranges tested were 0×2, 0×4, 2×10, 2×6, 4×15, and 6×15 microns. This was done to determine the effect of particle size on clarity and gloss. As described below, in terms of gloss reduction and clarity, the midsize ranges 4×15 and 6×15 microns performed the best and their use represent a new and novel strategy to reduce the gloss of a clear acrylic powder coating while maintaining good clarity. Previously, powder formulators had to use materials such as waxes to reduce gloss at the expense of performance. The finer sizes showed the best gloss as expected, but also had increased yellowness, which was unacceptable. The ability to lower gloss by as much as 50% while maintaining clarity with controlled particle size distributions has the potential to open new areas of application for nepheline syenite.

The fillers were compared on an equal weight basis. The formulations were premixed at 2000 rpm in a Hentchell FM-10 mill for two minutes. This is an initial grinding and mixing stage for powder coatings. This mixture was then further mixed and melted in a W&P ZSK 30 mm twin screw extruder with zone #1 at 110° C. and zone #2 at 80° C. The material exits the extruder onto chilled rollers and resembles a ribbon. This material was then ground in a Retsch Brinkman mill and sieved at −170 mesh. The 170 material was then used as the paint material. The coatings were sprayed onto cold rolled steel and steel penopac panels with a target final thickness of 1.5 to 2.0 mils (0.0015-0.0020 inches). The panels were then baked at 204° C. peak metal temperature for 10 minutes.

Contrast ratio was determined by using black and white penopac panels that were coated and measured using a Macbeth Coloreye 3000. The contrast ratio is the indication of the difference in the reflectance measured over black and white. This measurement was used as an indicator of haze in a clear coating. New and novel sized nepheline syenite products were tested in a clear powder coating formulation. Measured contrast ratios for the tested samples are provided in FIG. 11. Generally, the various new systems exhibited comparable or superior contrast ratios as systems of Minex 10 and 12. The effects of particle size on clarity and gloss were studied and can be found in FIG. 12.

Referring to FIG. 12, the gloss followed generally accepted trends that the finer sizes (0×2 and 0×4 microns) will produce a higher gloss, but did show a bit of yellowing as evidenced in higher b* values from TAPPI brightness measurements. TAPPI brightness is frequently used as a measure of the reflectance of papers. The spectral and geometric conditions for TAPPI brightness are specified in TAPPI Method of Test T452, “Brightness of pulp, paper, and paperboard (directional reflectance at 457 nm),” herein incorporated by reference. The mid-range grades 4×15 and 6×15 microns gave excellent results for both clarity and gloss. In this case, a lower gloss is of benefit, as clear coatings usually have to use additives, such as waxes, to decrease the gloss. This is an important development because maintaining clarity while lowering gloss is a significant step forward for clear powder coatings. It also appears from the data with the 2×10 and 2×6 microns products that the best product for this would be a product in the 4×15 to 6×15 microns range.

All the coatings showed similar depth of image results with only slight differences. As expected also, the unfilled system had the highest depth of image (DOI) reading.

In powder coatings formulations, it is usually difficult to reduce gloss and maintain clarity at the same time. However, with the 4×15 and 6×15 microns powders, it was possible to maintain excellent clarity while gloss was reduced by as much as 50% from the unfilled system.

A research and development program was conducted by Unimin Corporation, the leading manufacturer of nepheline syenite powder. This research and development program resulted in various novel nepheline syenite powders as so far described in this application. One embodiment of the development work related to a nepheline syenite powder having a controlled maximum particle size and a controlled minimum particle size. In the preferred embodiment of this invention, the maximum particle size D99 was about 15 microns and the targeted minimum particle size D5 was about 5 microns. This is the 5×15 powder described in this application and constitutes the preferred embodiment of the invention defined in the claims of the parent application. In this same research and development program, specific work was conducted toward a second inventive concept and defined in this application wherein the maximum particle size is controlled to an extremely low level of less than 5 microns. The two targeted embodiments of this inventive concept disclosed in the application involves a powder with a controlled maximum particle size targeted at 4 microns and a controlled maximum particle size targeted at 2 microns. This second inventive concept is defined in the claims of this divisional application and includes the novel nepheline syenite powders described as examples 3 and 4 in FIGS. 6 and 7 and shown as graphs in the chart of FIG. 8. The advantages of these two embodiments of the second inventive concept in the research and development program are set forth in the explanatory and comparative graphs of FIG. 11 and FIG. 12. The extreme advantage of the second embodiment of the research and development program is disclosed best in FIG. 12 as having a gloss characteristic substantially better than other disclosed nepheline syenite powders. Indeed, it approaches the characteristics of a “blank” sample. The first novel powder of the research and development program is, thus, defined in the claims of the parent application and the alternative or second novel ultra-fine nepheline syenite powder invented during the research and development program is claimed in this divisional application.

In the initial development project, bulk samples of preprocessed nepheline syenite industrial grade #75 were subjected to three different types of commercial ultra-fine grinding mills. These mills and vendors are listed below.

    • 1. VibroKinetic Ball Mill (MicroGrinding Systems, Inc., Little Rock, Ark.)
    • 2. Fluid Bed Opposed Flow Jet Mill (Hosokawa-Alpine Micron Powder Systems, Summit, N.J.). See Konetzka U.S. Pat. No. 6,543,710 which is incorporated by reference herein.
    • 3. Vertical Stirred Ball Mill (VSB-M) a.k.a. Attrition Mill (Union Process Attritor Co., Akron, Ohio). See Szeavari U.S. Pat. No. 4,979,686 which is incorporated by reference herein.

Each mill was used to produce two products 1) 5×15 microns with a mean particle size of 7.5 microns and 2) minus 5 microns with a mean particle size of about 1.2 microns. Distinctions in the test procedures and unique obstacles encountered are discussed below.

Test products were subjected to laser diffraction size analysis with a Beckman Coulter LS 13 320 Particle Size Analyzer. A “Nepheline Syenite” optical model was used instead of a “Fraunhofer” optical model. In addition, BET surfaces area measurements and Tappi brightness measurements of each product were made. Scanning electron micrographs, SEM, of select products were also taken.

Vibro-Kinetic Ball Mill—The VibroKinetic Ball mill was operated in closed circuit with an air classifier.

Fluid Bed Opposed Flow Jet Mill—Hosokawa-Alpine produced the −5 and 2×15 micron products by grinding to <15 microns in the Jet Mill and air classifying this product to remove the minus 5 micron material.

VSB-Mill (a.k.a. Attrition Mill)—Attrition milling can be done either wet or dry. This work was done wet, and tests were performed with two different types of attrition mills: 1) a Model 1-S Mill and 2) a Q-2 Mill. The 1-S Mill operates in a batch mode and was used to produce the finer (−5 micron) product. The Q-2 Mill operates in a circulatory mode. This means that the mill product is re-circulated from the bottom of the mill to the top. Since finer particles follow a less torturous path descending through the media, the coarser particles stay in the mill longer and are preferentially ground. A narrower particle size distribution generally results. This mill was used to produce the −15 micron product. The Union Process Attritor Co. had no means to classify −5 micron material from the −15 micron product to make a 5×15 micron product so a classifier was used.

Size distributions of the products obtained are shown in Table 5. Samples 5 and 6 exhibited a significantly “tighter” or narrower distribution than the other samples. Tappi brightness, L*, a*, b* color values, and BET surface area values are shown in Table 6.

TABLE 5 Particle Size Analyses of Processed Nepheline Syenite Sample Grind D99,99 D97 D95 D90 D75 D50 D25 D1 Mean 1 Vibro (−5 μm) 26.29 16.48 14.30 10.29 4.90 2.32 1.05 0.42 3.93 2 Vibro (−15 μm) 61.63 22.72 18.36 13.22 6.04 2.34 0.87 0.37 5.14 3 Jet (−5 μm) 5.53 4.06 3.83 3.49 2.92 2.29 1.71 1.10 2.27 4 Jet (−15 μm) 11.60 8.30 7.82 7.00 5.55 4.09 2.98 2.31 4.40 5 VSB-M (−5 μm) 2.64 1.81 1.66 1.43 0.93 0.52 0.34 0.26 0.69 6 VSB-M (−15 μm) 11.49 6.43 5.09 3.40 1.99 1.13 0.53 0.32 1.60

TABLE 6 Color and Surface Area Analyses of Ultra-Fine Products Tappi BET Bright- Surface Sample Grind ness L* A* b* Area 1 Vibro (−5μ) 81.50 92.240 −0.182 3.874 NA 2 Vibro (−15μ) 78.20 91.324 0.067 4.580 NA 3 Jet (−5μ) 87.80 94.312 −0.066 0.452 3.5 4 Jet (−15μ) 87.85 94.075 −0.088 0.511 2.3 5 VSB-M (−5μ) 92.44 96.625 −0.125 0.743 17.1 6 VSB-M (−15μ) 88.41 94.660 −0.195 0.996 19.0

Vibro-Kinetic Ball Mill—Neither of the products from this mill had suitable size distribution (Table 5). The top sizes were too coarse, while the overall distributions were too wide. The brightness results (Table 6) show that the material was discolored, despite the fact that several mill and cyclone liner changes were made to prevent this.

Fluid Bed Opposed Flow Jet Mill—The −5 micron product (Sample 3 in Table 5) had an appropriate top size but a greater mean particle size (2.3 microns) than the 1.2 micron value that was originally targeted. The brightness of this product was nearly 88%. The −15 micron product (Sample 4 in Table 5) had an appropriate top size but a lesser mean particle size (4.4 microns) than the 7.5 micron value that was originally targeted. The brightness of this product was also 88%.

VSB-Mill (a.k.a Attrition Mill)—Both the nominal −5 and −15 micron products (Samples 5 and 6 in Table 5) turned out to be far finer than targeted. Increased confidence in the new dispersion method, as well as the BET surface area measurements (Table 6), verified the unexpected fineness of both products. The brightness values obtained (Table 6) were greater than those obtained with the jet milled products.

The research and development project as described above resulted in a new level of know-how establishing that the novel nepheline syenite powder is obtainable by proper selection of manufacturing techniques. The reported initial research and development project resulted in a discovery of the unique process disclosed generally in FIGS. 1 and 5. Selection of preferred methods was a major development in the nepheline syenite art and resulted finally in the ability to produce economically a first novel nepheline syenite powder having a controlled maximum grain size and a controlled minimum grain size with a very narrow particle size distribution, and a second novel nepheline syenite powder with a nano-size controlled, targeted maximum particle size. Consequently, it was ultimately learned that the 5×15 powder, the preferred embodiment of the first novel powder, could indeed be produced and more importantly produced in a manner to become a commercial ultra-fine nepheline syenite powder. The research and development program as discussed above which developed the know-how to produce the novel ultra-fine nepheline syenite powders involved discovery of the criteria that the minimum grain size of the novel powder ultimately would involve controlling the final air classifier stage to operate at a slower feed rate. Furthermore, there were other process modifications necessary for converting the selected and invented method of producing the desired nepheline syenite powder. Producing a −5 micron product involved some changes to the air classifier. It is also contemplated that a Ball Mill could readily produce both −5 products, the 0×2 and 0×4 powders. Smaller media would probably be needed. The mill has several systemic features that make it superior to earlier generation tumbling mills: 1) its control system, in which load cells constantly measure the media charge and load and 2) its open circuit air system, which while more expensive, increases classifier efficiency by keeping the air temperature at a lower level as well as at a higher moisture level.

Seven (7) potential grinding aids were considered. The additives were compared with the results obtained with a control sample, in which the grinding rate was measured and the times in which a coating of particles was observed to form on the mill liner (1.5 hours) and mill media (2.0 hours) were observed. The time for particle agglomeration to occur (3.0 hours) was also noted. The findings were as follows:

Tri-ethanolamine was the best additive. It provided a far faster grinding rate than the control and no coating was observed on either the mill liner or media until after 2.5 hours of grinding. It is also the least costly additive considered and would be useful for grinding all particle size ranges. Improved air classifier efficiency is likely using this additive.

Other additives that showed promise were a mixture of ethyl alcohol and acetic acid and silicone glycol surfactant.

One additive, ethylene glycol, actually had a negative effect on grinding.

In this research and development program, the objective was to produce coating filler samples of specific, narrow particle size ranges to enable research to study the effects of particle size on gloss, flatting, and abrasion resistance, particularly in powder coatings.

Powder coatings filler samples were produced using the method of FIGS. 1 and 5. A Nissin Engineering, Inc. Model TC-15-NS Turbo Classifier, equipped with a fine rotor for classification in the very fine to ultra-fine size range of 0.5-20 microns was used. As is shown in FIG. 1, the classifier also has a microprocessor that provides automatic calculations of operating conditions. The operator enters the desired cut size (in microns) and the density (g/cm3) of the mineral being classified via a touch screen panel. Then, the microprocessor calculates the classifier rotor speed (rpm) and classifier air required (in m3/min). As an example, a 5 microns cut with 2.7-g/cm3 nepheline syenite requires a rotor speed of 8,479 rpm and an airflow rate of 1.2 m3/min). A schematic of the classification process is shown in FIGS. 1 and 5.

Eleven nominally sized distributions were produced as shown in FIG. 7.

Particle size distribution (PSD) results of the products made with the TC-15-NS Classifier are summarized in Table 7, and grouped as follows: a) PSDs with no minimum bottom size as claimed in this divisional application, b) PSDs with nominal 2 microns bottom size which may be claimed later, and c) PSDs with nominal bottom sizes of 4 microns to 6 microns claimed in the parent application. Complete PSDs of these groups are plotted in FIGS. 8-10, respectively, with corresponding Sample ID's shown.

TABLE 7 Actual Size Distributions of Targeted Products Group of Target Actual Size Filler Size D99.9 D99 D95 D90 D75 D50 D25 D10 D5 D1 No minimum 0 × 10 10.5 8.93 7.44 6.51 4.79 3.10 1.90 0.73 0.25 0.11 Bottom Size 0 × 6 5.83 5.40 4.86 4.48 3.50 2.15 0.64 0.39 0.33 0.26 0 × 4 5.07 4.63 4.15 2.41 1.78 0.58 0.40 0.32 0.29 0.25 0 × 2 2.74 2.38 1.99 1.74 1.19 0.70 0.43 0.33 0.29 0.25 Nominal 2-μm 2 × 15 11.7 10.6 9.37 8.54 6.86 4.67 3.10 2.41 2.16 1.87 Bottom Size 2 × 10 10.7 9.46 7.95 7.05 5.42 3.79 2.61 1.93 1.65 1.29 2 × 6 6.54 5.70 4.92 4.44 3.60 2.77 2.11 1.67 1.47 1.21 2 × 4 6.25 5.50 4.63 4.13 3.24 2.36 1.65 1.11 0.31 0.11 4-μm to 6-μm 4 × 15 17.1 15.7 14.2 13.2 11.2 8.82 6.99 5.78 5.16 2.33 Bottom Size 5 × 15 17.1 16.1 14.6 13.7 11.7 9.41 7.46 6.20 5.57 4.68 6 × 15 18.6 17.9 16.1 14.8 12.4 10.1 8.02 6.46 5.72 4.47

The air classifier did a reasonably good job at making the target cuts. Eleven distinct samples were produced for the powder coatings studies.

The Nissin Engineering Model TC-15-NS of FIG. 1 is an excellent laboratory and small-scale pilot classifier. It is precise, accurate, and relatively easy to operate.

Classification Method (FIGS. 1-12)

The initial research and development project resulted in method A using a Nissin Engineering Turbo Classifier Model TC-15-N-S as shown in FIG. 1 to produce examples (1)-(11) reported in FIG. 6. It was discovered that this air classifier operated in a unique manner could produce the desired nepheline syenite powders constituting the inventive aspect of the present invention. Classifier 10 is equipped with a microprocessor that calculates operating conditions based upon the mineral's specific gravity and the cut off point “x” for producing one extreme of the desired ultra-fine nepheline syenite powder. Method A disclosed in FIG. 1 utilizes the Turbo Classifier 10 in which a feedstock comprising a pre-processed nepheline syenite powder, such as a commercial powder or a powder previously processed. Indeed, the feedstock can be a prior run of the classifier. The feedstock is introduced as indicated by feedstock supply or block 12. In the preferred embodiment, pre-processed nepheline syenite powder is introduced into classifier 10 as indicated by line 14. In one operation, the initial feedstock from supply 12 through line 14 is Minex 7 having a controlled maximum particle size or grain size greater than 20 microns, but in this instance, less than about 45 microns. This pre-processed commercial nepheline syenite powder with a controlled maximum grain size is introduced into classifier 10 for a purpose of producing various nepheline syenite powders with a first run having targeted maximum particle size (D99) distribution and then a subsequent run where “x” is the targeted minimum particle size D5. This procedure produces samples (5)-(11), as shown in the first column of FIG. 6. Each of these novel ultra-fine nepheline syenite powders have a minimum particle size (D5) controlled by classifier 10 as removed from collector 40 as well as a maximum grain size produced in a prior run and removed from collector 50. This intermediate powder produced by a first run through classifier 10 is used for the minimum size run.

Method A using classifier 10 includes a data input block 20 where an operator inserts the specific gravity of the nepheline syenite powder. The maximum size D99 for examples (5)-(11) and then the minimum size D5 for examples (5)-(11) are selectively entered as set value “x.” Data from block 20 is directed through line 22 to a microprocessor stage 30. Microprocessor stage 30 sets the classifier air flow and the rotor speed of the classifier. Selected information is provided to the classifier through line 32 to operate classifier 10 for controlling first the upper and then the lower grain size of the final powder. During the first run the cyclone section of classifier 10 separated particles greater than the desired minimum particle size value x as set by microprocessor 30. This intermediate powder is deposited into collector or block 40 through line 42. The intermediate powder with a controlled maximum particle size is removed from collector 40 and introduced into supply 12 for reprocessing by classifier 10 with set particle size “x” at the targeted minimum particle size D5 of examples (5)-(11). In this procedure the final novel ultra-fine nepheline syenite powder is deposited into collector or block 50 by line 52. This second operation may require more than a single pass through the classifier and the particle size value “x” may be progressively reduced. Small fines are discharged from classifier 10 into block 60 through line 62.

Classifier 10 employs a classifier disk in accordance with standard technology and a cyclone to process the feedstock entering the classifier through line 14. See English U.S. Pat. No. 4,885,832 for a representative description of this known technology. Microprocessor 30 controls the air for dispersion and for the classifier as indicated by block 70. Thus, when examples (5)-(11) shown in FIG. 6 are to be produced, microprocessor 30 is set for a determined particle size “x” which size is controlled by the rotating rotor disk and the cyclone of the classifier. Consequently, in practice nepheline syenite feedstock is classified by the Turbo Classifier 10 using a combination of the classifier disk and cyclone. The particle size D99 or D5 is computer controlled by adjusting the rotational speed of the disk and the air flow over the disk. When setting a specific size, D99 or D5, three factions are collected. The faction less than the set value “x” which is directed to collector or block 40. The large faction greater than the set value, is separated by the disk of the Turbo Classifier 10 and deposited “x” into collector 50. The waste faction is directed to block 60 and contains mostly very fine particles but also large particles that were not collected by the classifier disk. This waste material is discarded.

Classifier 10 is set by an operator by the data input at stage or block 20 to control the classifier disk and the cyclone air so that the set particle size “x” is separated as indicated by either block 40, 50. If the classifier is set to the desired targeted minimum particle size D5, the powder is collected at block 50. If the collected powder is to have a maximum grain size or particle size, it is either previously or subsequently passed through the classifier again and the data entered at block 20 is the maximum grain size. The powder is collected from block 40. Thus, by both a lower cut and upper cut of particle size by classifier 10, the novel ultra-fine nepheline syenite powders claimed in the parent application are produced. Method A is also disclosed in FIG. 5 wherein Minex 4 is the feedstock introduced into the feed hopper or block 12 for the first run of classifier 10A, 10B. Minex 4 has a maximum grain size controlled at about 60 microns. However, an alternate pre-processed nepheline syenite powder initial feedstock (Minex 7) with a maximum grain size of about 40 microns is also contemplated. Minex 4 and Minex 7 are not defined as “ultra-fine” nepheline syenite powder, which is a powder having a maximum grain size less than about 20 microns. The substantial advantages of “ultra-fine” nepheline syenite powder have been recently discovered and are known in the art, especially when the ultra-fine nepheline syenite powder is used as a filler in coatings or films.

Operation of method A as described in FIGS. 1 and 5 is used to produce ultra-fine nepheline syenite powder with various targeted sizes as set forth in the novel samples (5)-(11) of FIG. 6. The targeted sizes have resulted in the actual particle size distributions recorded in table of FIG. 6. Method A is the first preferred embodiment of a type of process discovered to be useful in practicing the invention claimed in the parent application, which invention relates to an ultra-fine nepheline syenite powder having a controlled minimum particle size D5 and, in the practical embodiments of the invention, having a controlled maximum particle size D99. Referring now to the actual particle size distribution for targeted samples (5)-(11) described in FIG. 6, there are eleven different powders samples identified as samples (1)-(11) and made by method A. The first four samples (1)-(4) of powders processed by method A have targeted maximum grain size D99, but have no controlled minimum grain size D5. Samples (3)-(4) is produced by the classifier used in method A and constitutes a powder within the definition of the present invention. These related samples, i.e. samples (3)-(4), have a grain size distribution recorded in FIG. 6 and shown in the curves in FIG. 8.

As indicated in this description, one broad concept of the new ultra-fine nepheline syenite powder is control of the minimum grain size to create a narrow particle size spread. The secondary aspect of this first invention claimed in the parent application is control of the maximum grain size. Samples (5)-(8) of FIG. 6 are embodiments of one novel ultra-fine nepheline syenite powder. The minimum particle size of the samples is targeted at 2 microns with the created spread of less than about 12 microns (such as example 5). However, the samples have the actual distribution shown in the curves of FIG. 9. All of these novel nepheline syenite powders have a targeted minimum particle size D5 of 2 microns. Classifier 10 accurately controls the minimum size, but is less accurate in merely letting the powder taper randomly to a zero level at D1 as in samples (3)-(4). Samples (5)-(11) have been processed by method A to have a maximum controlled grain size D95 or D99, which is the second aspect of the invention. Controlling the top and bottom particle sizes of a sample results in control of the narrow particle size distribution of the invention. Sample (5) has a targeted maximum particle size of 15 microns. The other samples (6)-(8) have controlled minimum particle size of 2 microns and a controlled maximum grain size D95 or D99 of 10, 6 and 4 microns, respectively. These samples are shown in the curves of FIG. 9. In accordance with the preferred implementation of the first invention, the minimum particle size is controlled in the general range of 4-7 microns as set forth in samples (9)-(11) of FIG. 6. However, the minimum grain size is in the range of 2-7 microns under the first invention. These preferred implementations of the present invention, samples (9)-(11) have a controlled maximum particle size of about 15 microns and have the actual grain size distribution as shown in the table of FIG. 6 and in the graph of FIG. 10. In summary, the classifier 10 can be used to control the maximum particle size of the nepheline syenite powder as in samples (3)-(4) constituting the invention claimed in this divisional application. However, in accordance with the first invention classifier 10 is used in method A to produce an ultra-fine nepheline syenite powder where the minimum particle size is controlled to give a narrow particle size distribution. This concept of controlling the lower grain size of the nepheline syenite powder is combined with controlling the maximum particle size of the nepheline syenite powder as in samples (5)-(11). These samples have the targeted particle sizes and the actual particle size distribution provided in FIG. 6 and illustrated in the particle size distribution curves of FIGS. 9 and 10.

Method A can be operated to produce the novel ultra-fine nepheline syenite powder by performing the steps set forth in FIGS. 2 and 3. Method A, as shown in FIG. 2, is used to produce samples (5)-(11) as disclosed in FIGS. 6 and 7. A commercial grade of nepheline syenite powder having a maximum particle or grain size greater than about 30 or 40 microns is introduced as the feedstock in hopper 12 as indicated by block 100. Since this material, which may be Minex 4 or Minex 7, has a relatively large controlled maximum grain size, it is first passed through classifier 10 as indicated by block 102 to control the minimum particle size. Thereafter, it is passed through classifier 10 to control the maximum grain size as indicated by block 104. This procedure makes a powder as indicated by block 110. The two classifying stages are normally reversed. If a 15 micron controlled maximum particle size is desired for the novel ultra-fine nepheline syenite powder, the commercial, pre-processed powder Minex 10 could be used as the commercial feedstock, as shown in block 112 in FIG. 3. The feedstock has the desired maximum particle size and is merely passed through the classifier set to remove the smaller particles. The minimum particle size is established, as indicated by block 114 of FIG. 3. This procedure produces samples (12)-(15), as described in connection with FIGS. 6 and 7. The maximum grain size is controlled by the inherent maximum particle size of incoming commercial feedstock, i.e. Minex 10. The feedstock itself has the desired controlled maximum particle size of about 15 microns. Turning now to the alternative method disclosed in FIG. 4, classifier 10 is used to produce an ultra-fine nepheline syenite powder by merely removing the particle sizes above a given value. Such powder does not result in creation of an ultra-fine nepheline syenite powder with a controlled minimum particle size. FIGS. 2-4 are disclosed since they represent various operations of method A to make ultra-fine nepheline syenite powders. If it is desired to remove only particle size below a minimum value, then the maximum controlled grain size is determined by the maximum particle size or grain size of the incoming commercial feedstock. Consequently, Minex 4 or Minex 7 could not be used as the commercial feedstock for such method. In this process, the commercial feedstock must have a maximum grain size sought for the final powder. This is illustrated in FIG. 3.

To show properties of the invention, the nepheline syenite powder disclosed in FIGS. 6 and 7 was formulated in a clear acrylic powder coating. This is to determine the effect of the particle size of the inventive powder or clarity in gloss. In terms of gloss reduction and clarity the powder with a minimum particle size of 4 and a maximum particle size of 15 (4×15) or a minimum size of 6 and a maximum size of 15 (6×15) performed the best and represent a new and novel way to reduce the gloss of a clear acrylic powder coating while maintaining good clarity. Previously, powder forming a filler had to be combined with material, such as wax, to reduce gloss. This was at the expense of performance. The ability to lower gloss by as much as 50% while maintaining clarity with controlled particle distribution size, as in the present invention, has resulted in opening new areas of application for nepheline syenite powder. To counteract the effect of lowering gloss while maintaining clarity in acrylic powder coating, various powders having the novel features were compared with other fillers in acrylic powder coating. Powders of the present invention were compared to the values obtained by Minex 10 and Minex 12. Minex 10 and Minex 12 are both “ultra-fine” nepheline syenite powders, but they have no control over the minimum particle size. In the test procedure, coatings with various fillers were sprayed onto cold rolled steel. Steel panels with a coating having a target final thickness of 1.5-2.0 mils were produced. The panels with the various coatings were baked at 204° C. each for ten minutes. The contrast ratio was determined by using black and white panels that were coated and measured with a Macbth Coloreye 3000. The contrast ratio is indication of the difference in the respective measurement over black and white. This measurement was used as an indicator of the haze in a clear coating. The new and novel nepheline syenite powders were tested in a clear powder coating. The mid size powder as mentioned before gave excellent results for both clarity and gloss. As indicated, lower gloss is a benefit in clear coatings because they usually have to use additives, such as waxes to decrease the gloss. This is an important development because maintaining clarity while lowering gloss is a significant step forward for clear powder coatings. The results of these comparisons are shown in FIGS. 11 and 12 as already described. In summary, the novel nepheline syenite powders maintain excellent clarity while gloss was reduced by as much as 50% from the unfilled system.

Milling and Classifying Methods (FIGS. 13-19)

The ultra-fine nepheline syenite powder of the invention claimed in the parent application involves control of both the minimum particle size and the maximum particle size of a feedstock which has been converted from a pre-processed commercial powder. As discussed previously, a preferred method of producing such novel powder involves the use of an opposed air jet mill followed by a classifier or an attrition mill operated in a dry mode followed by an air classifier. The dry mill grinds the incoming pre-processed nepheline syenite powder feedstock into a powder having reduction in the maximum particle size. This is the normal operation of a mill; however, in accordance invention claimed in the parent application, the mill for reducing the maximum grain size is used to produce a powder where the maximum grain size is a value less than about 20 microns. Thus, the resulting dual processed nepheline syenite powder is “ultra-fine”. This subsequently milled pre-processed powder feedstock is converted into an intermediate powder with a controlled maximum particle size. Then the intermediate powder is passed through an air classifier to obtain the targeted minimum particle size so that the resulting powder is new and is an ultra-fine nepheline syenite with both a controlled maximum particle size and a controlled minimum particle size. This process produces a narrow particle size distribution. This dual process creates a powder having the advantageous improved characteristic of the new powder. Of the many technologies investigated to produce the new nepheline syenite powder, the first preferred implementation was the classifying method A disclosed in FIGS. 1 and 5. It has been found that the preferred practical embodiment of the invention involves the use of a mill to dry grind pre-processed nepheline syenite powder feedstock having a controlled grain size substantially greater than 20 microns and less than 100 microns.

This second preferred embodiment or practical implementation of the invention claimed in the parent application is method B disclosed in FIG. 13. Method B involves use of Industrial Grade 75 pre-processed nepheline syenite feedstock having a controlled maximum particle size of about 60 microns. The maximum particle size D99 of this feedstock is about 60 microns to produce the controlled particle size of the nepheline syenite powder. Industrial Grade 75 has no controlled minimum particle size, but the particle size of this feedstock merely converges toward zero at D1. Method B involves the use of an opposed air jet mill from Hosokawa Alpine and sold as AFG Model 400. This opposed air jet mill 202 is the second preferred mill used in practicing the invention of the invention claimed in the parent application and is illustrated as the mill for method B shown in FIG. 13. Such mill is schematically illustrated in Zampini U.S. Pat. No. 5,423,490 and Konetzka U.S. Pat. No. 6,543,710, which are incorporated by reference herein. This fluidized bed opposed jet mill use air jet mill for grinding the feedstock. As compressed air exits internal nozzles, it is accelerated to extremely high speeds. In expanding, the energy contained in the compressed gas is converted to kinetic energy. The velocity of the air exiting the Laval nozzle or nozzles exceeds the speed of sound. The air is the grinding gas. Gas and powder from the fluidized bed is comminuted as the result of interparticle collision of the air jets, especially in the areas where opposed jets intersect. The fluidized bed opposed jet mill has a dynamic deflector-wheel classifier so the fineness of the particles is a function of the wheel speed. See Zampini U.S. Pat. No. 5,423,490 for a jet nozzle design. The feedstock is ground by mill 202 set to the targeted maximum particle size which in the illustrated embodiment is 15 microns. This opposed jet mill is disclosed in FIG. 13A and directs ground nepheline syenite powder through line 202a to an air classifier 204, which classifier, in the preferred embodiment, is an Alpine Model 200 ATP. Feedstock enters the classifier as the classifier air flows through the rotating classifying wheel. This wheel extracts fines and conveys them by air from the classifier. The coarse material is rejected by the classifying wheel and exits the lower discharge valve for the powder that has a controlled minimum particle size. This air classifier is set to remove particles having a size less than the targeted minimum particle size. Product passing through lines 204a is collected as indicated by block or collector 210. Method B is developed primarily for producing the novel ultra-fine nepheline syenite powders identified as samples (5)-(11) illustrated in FIG. 6. In the representative use of method B illustrated in FIG. 13, 5×15 sample (10) is produced. However, method B is also applicable for the other examples mentioned and, indeed, to produce the other samples of the invention as set forth in FIGS. 6 and 7.

An opposed air jet mill performs the dry grinding function of block 202 in FIG. 13. This device is schematically illustrated as opposed air jet 220 in FIG. 13A. Mill 220 accepts pre-processed nepheline syenite feedstock from block or supply 200 and directing the feedstock into hopper 222. The feedstock has a maximum particle size previously imparted to the commercial feedstock powder. This maximum particle size is in the general range of 20-150 microns. The commercial feedstock enters mill 220 through feed hopper or funnel 222 and is then conveyed into the mill by the compressed air or gas inlet 224 from a supply of compressed air or gas 226. To grind the incoming feedstock compressed grinding air is introduced into the mill through inlet 230 connected to a compressed grinding air source 232. In accordance with this type of commercially available grinding mill, as already explained, there is a grinding chamber 240 where the feedstock is subject to high speed air jets. The chamber has a replaceable liner 242 and a grinding air manifold or recirculating air chamber 244. Ground particles having a reduced grain size from the feedstock are directed to outlet 260 surrounded by a vortex finder 262. The ground particles P are drastically reduced in size from the incoming feedstock FS. The commutation or grinding is performed by the opposed air jets in chamber 240. In one use of mill 220, the particles exiting from outlet 260 has the desired maximum particle size, i.e. the targeted D99 size. In another use of mill 220, there is a classifier set at the maximum particle size and the ground powder from outlet 260 is larger, but is subsequently classified to the desired maximum particle size. In the equipment used in method B, mill 220 has a variable speed internal classifier wheel which is adjusted to separate particle sizes less than a desired target size. The separated particles exit by gravity through line 202a into a collector 202b. Particles in line 202a shown in the illustrated embodiment of the invention have a maximum grain size of 15 microns. Particles having larger particle size, but entering into the classifier 270 from outlet 260 are directed through line 272 back into the grinding chamber with incoming feedstock FS at funnel or hopper 222. Powder from the classifier wheel enter line 202a and is deposited in collector 202b. The powder has a controlled maximum particle size. It is then bagged and introduced into air classifier 204, as indicated by dashed line 202c. The opposed air jet mill is the preferred dry mill used in practicing method B as shown in FIG. 13. However, before a disclosure of an implementation of method B shown in FIG. 13, a generic version of this method is method C illustrated in FIG. 14.

Method C uses a pre-processed commercial feedstock having a maximum controlled grain size of less than about 45 microns. This feedstock is commercially available as Minex 7 from Unimin Corporation. Feedstock from supply 300 is directed through feed line 302 into a dry mill 304. This mill can be an attrition vertical stirred dry mill in a closed circuit or, preferably, an opposed air jet mill as used in the second preferred embodiment of the invention as shown in FIG. 13. Thus, method C is a generic version and employs a dry mill 304 that produces a powder having a maximum particle size matching a selected maximum targeted particle size. This intermediate powder is transferred to line 306. The dry mill normally combined with an air classifier and having a coarse powder return indicated schematically as line 304a. As an alternative mill 304 grinds the feedstock and directs its output to an internal classifier and then to line 306. Irrespective of the dry milling step 304 of method C, the output of the dry mill and/or air classifier is the intermediate powder in line 306. This intermediate powder is directed to air classifier 308 that removes particle sizes less than the targeted minimum particle size. In the illustrated embodiment this D5 target is 5 microns. From air classifier 308, the desired ultra-fine nepheline syenite powder is directed by line 308a into a collector 310. The product is identified as a 5×15 powder having a targeted maximum particle size D99 of 15 microns and a targeted minimum particle size D5 of 5 microns. Process C is, indeed, a generic version of the preferred embodiment illustrated in FIG. 13; however, it also includes an auxiliary process operation. Minex 12 has only a maximum particle size. Fine nepheline syenite powder from air classifier 308 is directed through line 308b into an air classifier 322 set to remove particles greater than the maximum particle size. Thus, classifier 322 essentially directs the material from line 308b into collector 320 for subsequent use as Minex 12 with only a controlled maximum targeted particle size.

The first and second preferred methods developed for producing a novel ultra-fine nepheline syenite powder are the types of process used in methods A and B, the latter of which is generically disclosed as method C. For completeness, the research and development program also invented alternative methods for making the novel ultra-fine nepheline syenite powder claimed in the parent application. These alternative methods constitute further advances in the nepheline syenite powder art of the nepheline syenite industry. One alternative is disclosed in FIG. 15. Method D utilizes a pre-processed. Commercial nepheline syenite powder feedstock, such as Minex 7 having a controlled maximum particle size of about 45 microns. This commercial feedstock from supply 330 is conveyed by line 332 into a first air classifier 340 that operates in accordance with somewhat standard practice in separating from the feedstock any particle having a maximum particle size of a targeted amount, illustrated as 15 microns. This operation of an air classifier creates an intermediate powder that is conveyed through line 342 into second air classifier 350. Air classifier 350 is a second classifying stage and removes particles having a size less than the targeted minimum particle size, illustrated as 5 microns. By using the two stage air classifier concept of method D, the desired novel ultra-fine nepheline syenite powder is directed to collector 360 through line 362. By using the dual or two stage air classifier process, a desired nepheline syenite powder is produced and deposited in collector 360. In practice, the air classifiers 340, 350 are Alpine Model 200 ATP. Another appropriate classifier is shown in Saverse U.S. Pat. No. 4,551,241 and English U.S. Pat. No. 4,885,832. These patents are incorporated by reference herein. Intermediate powder from line 342 is directed into the feed inlet air flow line of second air classifier 350. Consequently, the intermediate powder from the first stage air classifier 340 moves into the second stage air classifier 350. The intermediate powder is directed into the classification chamber of classifier 350 where the lighter small particles float upward into the variable speed classifier wheel and are discarded. The coarse material falls downward into a collection drum or collector 360. Thus, the product in collector 360 is a product having both the targeted maximum particle size and the targeted minimum particle size. Other aspects of the development project resulting in the present inventions are schematically illustrated in FIG. 15. Method D is modified as indicated to perform method D′. In this modified procedure, second stage air classifier 350 is replaced by second stage air classifier 350a, which is set to a different targeted minimum particle size D5. This setting has been 4 microns and the disclosed 6 microns. Another modification of method D is illustrated as method D″. In this alternative method to make the invention claimed in the parent application two separate classifiers 370, 380 are operated in series to gradually increase the minimum particle size of the novel powder ultimately deposited in collector 360. Methods D, D′ and D″ are all multiple stage classifier methods to produce the novel nepheline syenite powder as so far described and generally set forth in FIGS. 6 and 7. Method B described in FIGS. 13 and 14 is now the preferred method used for making samples with a targeted minimum particle size and a targeted maximum grain size of the type illustrated in FIGS. 6 and 7 and also specifically illustrated as samples (20) and (21) in FIG. 18. To illustrate that the maximum particle sizes is “controlled” as in methods A, B and C, samples (20) and (21) of FIG. 18 have an upper particle size cut off to a particular maximum particle size. This control of the maximum size of samples (20)-(21) is indicated by lines 280 and 282.

Powder samples (12)-(15) listed in the table of FIG. 7 have been described as powders that could be made by removal of only particles below the targeted minimum particle size D5; however, in practice these powders are actually produced by the methods that control the maximum particle size also. In other words, previously described samples (12)-(15), which were identified as controlling only the minimum particle size, are preferably produced by controlling both the minimum particle size and also the maximum particle size. Samples (12)-(15) can be made by either cutting both the top and bottom particle sizes or starting with an ultra-fine commercial powder and cutting only the bottom particle size. This latter process is indicated as samples (16)-(19) in the graph of FIG. 17. In summary, it is within the broadest scope of the invention claimed in the parent application to produce the novel ultra-fine nepheline syenite powder with a controlled minimum particle size by starting with a pre-processed commercial ultra-fine nepheline syenite powder, such as Minex 10, having a controlled maximum particle size of about 15 microns. This is generally disclosed in FIG. 7 and specifically presented in FIG. 17. To complete this description, a method for practicing the present invention process by the act of controlling only the minimum particle size is disclosed as method E in FIG. 16. This further method involves using a specific commercial nepheline syenite feedstock, which is already “ultra-fine” and has a controlled maximum particle size in the range of 13-18 microns. Minex 10 with a controlled maximum particle size of 15-20 microns is directed from supply 370 through line 372 into classifier 380. Classifier 380 is set to remove smaller particle sizes so that the minimum particle size of the powder is controlled. Such powder is directed through line 382 into collector 390. Thus, in this particular alternative method, an ultra-fine nepheline syenite powder is merely processed by a classifier that removes all particles having a size less than x microns. In the sample illustrated in FIG. 17 the set size is 4, 6 or 8 microns. In the illustrated embodiment of this alternative method, the set particle size is 5 microns. These samples of the novel nepheline syenite powder are made by the method E. If the maximum particle size needs particle control, methods A-D are used for these samples. The preferred samples of this particular novel ultra-fine nepheline syenite powder (4×15, 5×15 and 6×15) is set forth in the curves of FIG. 19 and constituting samples (9)-(11) respectively of FIG. 6. In these curves, the D50 particle size is less than 10 microns. This provides low tendency to settle and high transparency.

Small Particle Size Alternative

Parent provisional application Ser. No. 60/958,757, filed Jul. 9, 2007 (UMEE 2 00090 P; UNM-19913) was incorporated by reference in co-pending application Ser. No. 12/215,643 filed Jun. 27, 2008 from which this application is a continuation. Provisional application 60/958,757 (UMEE 2 00090 P; UNM-19913) is incorporated by reference herein since it stresses an alternative to the embodiment described in FIGS. 13-19.

The broad invention relates to “controlled particle size distribution” of an inorganic powder formed from a hard, naturally occurring mined material having substantially no free silica, in particular nepheline syenite powder, used as a “hard filler.” The first embodiment is the larger 5×15 powder and the alternative is the −5 powder where the targeted maximum particle size is less than 5 microns, i.e. examples of 2 microns and 4 microns.

One type of new powder was a powder with a “zero” bottom size and controlled top size as used in the −5 powder. Two controlled top sizes were 2 microns and 4 microns in the −5 powder alternative development. Classification of powder in both embodiments defines “fines” as particles less than 0.5 microns.

In the alternative powder, described as the −5 powder, the powder has “targeted” sizes of 0×2 or 0×4. The targeted 2 microns maximum particle sizes and the targeted 4 microns maximum particle size are defined as the top cut particle sizes or the −5 powder. These powders have “No minimum bottom size.”

The actual top cut particle size of the targeted 0×2 particle size is D99.9 of 2.74 microns, D99 of 2.38 microns and D95 of 1.99 microns. The D1 particle size is 0.25, while the D5 particle size is 0.29. These “zero” targeted particle sizes merely have “fines” removed.

The actual top cut particle size of the targeted 0×4 particle size is D99.9 of 5.07 microns, D99 of 4.63 microns and D95 of 4.15 microns. The D1 particle size is 0.25 microns and the D5 particle size is 0.29 microns. These “zero” targeted particle sizes merely have “fines” removed.

Powder with no minimum bottom size is shown by the graphs 2, 3, 4 in FIG. 8 of this application. The targeted controlled particle size of 0×2 microns had the lowest tested Einlehner number of 16.9. This number is a measure of abrasive action on processing equipment and is very important when using fillers made from a hard rock, such as nepheline syenite.

In a first run of nepheline syenite powder having a “target size” of 4 microns, the D99 particle size was 4.6 microns. In a second run of nepheline syenite powder having a “target size” of 2 microns, the D99 particle size was 2.4 microns.

The 0×4 and 0×2 powders (i.e., the −5 powder alternative invention) “have better light gathering and transmittance properties.” The “0×4 size has noticeably greater light transmittance properties.” Furthermore, the −5 powder alternative invention is useful for obtaining deeper cure in UV cure coatings.” “Optical clarity was best for the 0×2 followed by 0×4 size range.” Optical clarity “improves with finer particle size.”Overall, the 0×4 and 0×2 show more performance improvements and results suggest they can even benefit UV cure or accelerate UV cure time.”

Minex 0×2 powder and Minex 0×4 powder (the −5 powder alternative invention) “result in the least scattering of light.”

The preferred method of producing the alternative −5 micron powder (0×2 and 0×4) is disclosed as using a vertical stirred ball mill (VSB) operated in a wet mode. This mill was an S-1 mill from Union Process Attritor Company of Akron, Ohio. The −5 microns powder was Sample 53-36-3 having a targeted top size of 2 microns and an actual top size D99.99 of 2.64 microns. This is the 0×2 powder version of the −5 microns powder. A fluid bed opposed flow jet mill produced Sample 53-38-1 with a targeted 4 microns top size with an actual top size D99.99 of 5.53 microns. These values are shown in Table 5. This is the 0×4 powder of the −5 powder alternative.

In summary, the provisional application discloses a preferred method of producing the alternative −5 micron powder as using vertical stirred ball mill, with or without a grinding aid, but preferably operated in a “wet mode.” The powder is preferably marketed as a “slurry”, but is also to be marketed dry if needed. As an alternative, the −5 powder is produced by a fluid bed opposed jet mill operated in a dry mode and classified by an air classifier.

Having thus described the invention, the following is claimed: 1. An ultra-fine inorganic powder for use as a filler and formed from a hard, naturally occurring mined material having substantially no free silica, said powder having a targeted controlled maximum particle size of less than 5 microns and a generally uncontrolled minimum particle size creating a targeted minimum particle size of zero microns. 2. An ultra-fine powder as defined in claim 1 wherein said powder has a Mohs number of 6. 3. An ultra-fine powder as defined in claim 1 wherein said powder contains the mineral feldspar. 4. An ultra-fine powder as defined in claim 3 wherein a majority of said powder contains at least one feldspar mineral. 5. An ultra-fine powder as defined in claim 3 wherein said powder is syenitic. 6. An ultra-fine powder as defined in claim 1 wherein said powder is syenitic. 7. An ultra-fine powder as defined in claim 3 wherein said powder is nepheline syenite. 8. The ultra-fine nepheline syenite powder defined in claim 7 wherein said powder has a D99 particle size of less than 5 microns. 9. The ultra-fine nepheline syenite powder as defined in claim 8 wherein said powder has a D99 particle size in the range of about 2 microns to about 4 microns. 10. The ultra-fine nepheline syenite powder as defined in claim 7 wherein said powder has a D99 particle size in the range of about 2 microns to about 4 microns. 11. The ultra-fine nepheline syenite powder as defined in claim 7 wherein said targeted maximum particle size is in the general range of 2-4 microns. 12. The ultra-fine nepheline syenite powder as defined in claim 8 wherein said powder is produced in vertical stirred mill. 13. The ultra-fine nepheline syenite powder as defined in claim 12 wherein said vertical stirred mill is operated in the wet mode. 14. The ultra-fine nepheline syenite powder as defined in claim 7 wherein said powder is produced in vertical stirred mill. 15. The ultra-fine nepheline syenite powder as defined in claim 14 wherein said vertical stirred mill is operated in the wet mode. 16. The ultra-fine nepheline syenite powder as defined in claim 11 wherein said powder is produced from a pre-processed nepheline syenite powder with a maximum particle size D99 in the range of 20-100 microns, and a moisture content of less than 0.8% by weight. 17. The ultra-fine nepheline syenite powder as defined in claim 8 wherein said powder is produced from a pre-processed nepheline syenite powder with a maximum particle size D99 in the range of 20-100 microns, and a moisture content of less than 0.8% by weight. 18. The ultra-fine nepheline syenite powder as defined in claim 7 wherein said powder is produced from a pre-processed nepheline syenite powder with a maximum particle size D99 in the range of 20-100 microns, and a moisture content of less than 0.8% by weight. 19. The ultra-free nepheline syenite powder as defined in claim 7 wherein said powder has a particle size distribution with a narrow particle size spread between the D99 particle size and the D1 particle size. 20. The ultra-fine nepheline syenite powder as defined in claim 19 wherein said D99 particle size is in the range of about 2-4 microns. 21. The ultra-fine nepheline syenite powder as defined in claim 9 wherein the targeted maximum particle size is a D99 particle size of about 2 microns. 22. The ultra-fine nepheline syenite powder as defined in claim 7 wherein the targeted maximum particle size is a D99 particle size of about 2 microns. 23. The ultra-fine nepheline syenite powder defined in claim 7 wherein the targeted maximum particle size is a D99 particle size of about 4 microns. 24. A filler for a coating comprising an ultra-fine nepheline syenite powder as defined in claim 9. 25. A filler for a coating comprising an ultra-fine nepheline syenite powder as defined in claim 7. 26. A coating comprising a filler as defined in claim 25. 27. A coating comprising a filler as defined in claim 24. 28. An ultra-fine nepheline syenite powder having a targeted controlled maximum particle size of less than 5 microns and a generally uncontrolled minimum particle size of zero microns, wherein the D50 particles size of said powder is less than 1 micron. 29. The ultra-fine nepheline syenite powder as defined in claim 28 wherein said maximum particle size is in the general range of about 2-4 microns. 30. The ultra-fine nepheline syenite powder as defined in claim 28 wherein said maximum particle size has a targeted particle size of about 2 microns. 31. The ultra-fine nepheline syenite powder as defined in claim 28 wherein said maximum particle size has a targeted particle size of about 4 microns. 32. An ultra-fine inorganic powder for use as a filler and formed from a hard, naturally occurring mined material having feldspar as its major mineral and having substantially no free silica, said powder having a targeted controlled maximum particle size of less than 5 microns and a generally uncontrolled minimum particle size creating a targeted minimum particle size of zero microns. 33. An ultra-fine powder as defined in claim 32 wherein said powder is syenitic. 34. An ultra-fine powder as defined in claim 33 wherein said powder is nepheline syenite. 35. The ultra-fine nepheline syenite powder defined in claim 32 wherein said powder has a D99 particle size of less than 5 microns. 36. The ultra-fine nepheline syenite powder as defined in claim 35 wherein said powder has a D99 particle size in the range of about 2 microns to about 4 microns.


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stats Patent Info
Application #
US 20120263954 A1
Publish Date
10/18/2012
Document #
13456307
File Date
04/26/2012
USPTO Class
428402
Other USPTO Classes
106467
International Class
/
Drawings
17



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