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

Abstract: 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.

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 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.

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

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