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  Efficient necked bonded laminates and methods of making sameUSPTO Application #: 20060003656Title: Efficient necked bonded laminates and methods of making same Abstract: The present invention provides an elastic necked-bonded laminate material or elastic neck stretched bonded laminate material including at least one necked material joined to at least one elastic sheet that has been stretched in the cross-machine direction and allowed to relax prior to joining with the necked material. The elastic sheet can be stretched prior to being joined with the necked material or following the joining to the necked material. Also disclosed is a method of producing a elastic necked-bonded laminate material including the step of stretching the elastic sheet in a macroscopic stretching apparatus, such as between the nip of a series of spaced apart discs on two axles. (end of abstract) Agent: Kimberly-clark Worldwide, Inc. - Neenah, WI, US Inventor: Michael T. Morman USPTO Applicaton #: 20060003656 - Class: 442327000 (USPTO) Related Patent Categories: Fabric (woven, Knitted, Or Nonwoven Textile Or Cloth, Etc.), Nonwoven Fabric (i.e., Nonwoven Strand Or Fiber Material) The Patent Description & Claims data below is from USPTO Patent Application 20060003656. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF INVENTION [0001] The present invention relates to methods of making elastic clothlike laminates, including laminates made from necked materials and elastic layers. In particular, the present invention relates to methods of making necked bonded laminates which can then be used at least as personal care product construction materials, such as bodyside facing liner material (or topsheets), outercovers, waist elastic materials, side panel materials and ear materials. The present invention also relates to apparatus that can be used in such methods, as well as other methods of manufacture. BACKGROUND OF THE INVENTION [0002] Polymeric films and nonwoven webs may be manufactured into personal care products and components of products so inexpensively that the products could be viewed as disposable after only one or a few uses. Such nonwoven webs may include bonded carded webs and webs formed by nonwoven extrusion processes such as meltblowing processes and spunbonding processes. Representatives of such products include articles such as diapers, adult incontinence devices, swimwear, feminine care products, and training pants. Other such personal care disposable products include tissues, wipes, mattress pads, veterinary products, mortuary products, article covers and medical related protective products such as garments worn in a medical setting, face masks, sterilization wraps and hospital packaging materials. [0003] Some of the challenges associated with products in these groupings include the provision of an elastic material which is resilient and flexible while still having a pleasing feel. One specific problem is the provision of an elastic material which does not feel plastic or rubbery, a characteristic common to most elastic polymer materials. [0004] It is generally known that the tactile properties of the elastic materials can be improved by forming a laminate of the elastic material with one or more nonelastic materials on the outer surface(s) of the elastic material. For instance, in one such laminate material, a nonelastic material is joined to an elastic material while the elastic material is in a stretched condition so that when the elastic material is relaxed, the nonelastic material gathers between the locations where it is bonded to the elastic material. The resulting elastic laminate material is stretchable to the extent that the nonelastic material gathered between the bond locations allows the elastic material to elongate. In the stretch bonded laminate process, a just -formed (or pre-formed) elastic material is stretched and then attached to the gatherable material. The elastic is then allowed to retract gathering the gatherable material and forming the stretch bonded laminate. Elastic materials just formed from the melt inherently have elastic performance on a "first time stretch" that is not as good (having higher immediate set) as opposed to subsequent stretches. The "first time stretch" is accomplished while forming the stretch bonded laminate material so the elastic performance of the finished stretch bonded laminate is high. For the purposes of this application, the term "first time stretch" refers to the first stretch of an elastic layer following formation. It could occur either during a manufacturing process, or alternatively by a consumer in using a product. For example, in the case of personal care products, a "first time stretch" may occur when a consumer opens a personal care garment to insert a user's legs or waist (such as in a diaper) and/or stretches a garment to secure it about their person. An example of this type of stretch bonded laminate material is disclosed, for example, by U.S. Pat. No. 4,720,415 to Vander Wielen et al., and U.S. Pat. No. 5,385,775 to Wright and Publication No. WO 01/88245, each of which are hereby incorporated by reference in its entirety. While stretch bonded laminate materials are effective in providing high levels of stretch and recovery, it is often not necessary to utilize such high performance elastic materials throughout an entire personal care product. It has been found that stretch bonded laminate materials tend to be fairly costly to manufacture and their inclusion in a product necessarily increases the cost of the end product to the consumer. It would therefore be desirable to provide efficient elastic materials, at a lower cost. [0005] It is also known to laminate (or bond) a necked (neckable) material to an elastic sheet to produce a neck bonded laminate. This process involves an elastic member being bonded to a non-elastic member while only the non-elastic member is extended in one direction (usually the MD) and necked in the transverse direction so as to reduce its dimension in the direction orthogonal to the extension. Such is described in detail in U.S. Pat. Nos. 4,965,122, 4,981,747, 5,226,992, and 5,336,545 to Morman, each of which is incorporated by reference herein in its entirety. While such neck bonded laminates may be less costly to produce than stretch bonded laminates, the production of such laminates is often not efficient. In particular, it has been found that the use of the non-elastic nonwoven materials on such elastic sheets drags on the elastic sheets. Further, the bonding of the non-elastic members (sheet(s)) to the elastic member (sheet(s)) is accomplished using a process which does not take total advantage of the elastic sheet properties. In forming a necked bonded laminate, the "first time stretch" of the elastomeric layer doesn't occur, so essentially the "first time stretch", which is done by the consumer, may not have the desired elastic properties unless very expensive elastomers are used. [0006] It would be desirable to utilize a less costly material such as a necked and bonded laminate that took greater advantage of the elastic sheet material properties in the laminate. It would therefore also be desirable to alter the neck bonded laminate manufacturing process in order to more efficiently produce a higher performance neck bonded laminate when used in an end product. The term higher performance necked bonded laminate shall mean a performance of the neck bonded laminate in a product that offers lower permanent set upon stretching and lower force to extend upon usage of a product by a consumer, as compared to current similarly formulated neck bonded laminate materials in personal care products. [0007] It is also known to utilize intermeshing grooved rolls or discs on axle apparatus for stretching nonwoven webs. For instance, it is known to use grooved rolls generally to stretch a formed elastic and non-elastic neck bonded laminate. See for example U.S. Publication 20040121687. However, such grooved roll stretching apparatus have posed problems from a manufacturing perspective, as they often lead to equipment failure if the rolls are not properly aligned, or alternatively to material failure if the roll speed and alignment are not controlled. Such grooved rolls, if not properly aligned (groove/peak and speed alignment) can be unduly harsh on nonwoven materials. Also, to date, such apparatus have not been used to benefit the elastic performance of elastic sheets themselves, (making only such elastic sheets more efficient without impacting the nonelastic sheet material) early in a manufacturing processes. There is therefore a need for more efficient elastic low cost laminates for use in personal care products and methods for making such laminates. It is to such needs that the current invention is directed. Definitions [0008] The term "elastic" is used herein to mean any material which, upon application of a biasing force, is stretchable, that is, elongatable, to a stretched, biased length which is at least about 150 percent of its relaxed unbiased length, and which will recover at least 50 percent of its elongation upon release of the stretching, elongating force. A hypothetical example would be a one (1) inch sample of a material which is elongatable to at least 1.50 inches and which, upon being elongated to 1.50 inches and released, will recover to a length of not more than 1.25 inches. Many elastic materials may be stretched by much more than 50 percent of their relaxed length, for example, 80 percent or more, and many of these will recover to substantially their original relaxed length, for example, to within 105 percent of their original relaxed length, upon release of the stretching force. [0009] As used herein, the term "nonelastic" refers to any material which does not fall within the definition of "elastic," above. [0010] As used herein, the term "recover" refers to a contraction (or retraction) of a stretched material upon termination of a biasing force following stretching of the material by application of the biasing force. For example, if a material having a relaxed, unbiased length of one (1) inch is elongated 50 percent by stretching to a length of one and one half (1.5) inches the material would be elongated 50 percent (0.5 inch) and would have a stretched length that is 150 percent of its relaxed length. If this exemplary stretched material contracted, that is recovered to a length of one and one tenth (1.1) inches after release of the biasing and stretching force, the material would have recovered 80 percent (0.4 inch) of its one-half (0.5) inch elongation. Recovery may be expressed as [(maximum stretch length-final sample length)/(maximum stretch length-initial sample length)] times 100. [0011] As used herein, the term "nonwoven web" means a web that has a structure of individual fibers or threads which are interlaid, but not in an identifiable, repeating manner. Nonwoven webs have been, in the past, formed by a variety of processes such as, for example, meltblowing processes, spunbonding processes and bonded carded web processes. Laminates containing such web materials may be formed and are considered a nonwoven material laminate. [0012] As used herein, the term "microfibers" means small diameter fibers having an average diameter not greater than about 100 microns, for example, having a diameter of from about 0.5 microns to about 50 microns, more particularly, microfibers may have an average diameter of from about 4 microns to about 40 microns. [0013] As used herein, the term "meltblown fibers" means fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into a high velocity gas (e.g. air) stream which attenuates the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin, the disclosure of which is hereby incorporated by reference. [0014] As used herein, the terms "spunbonded fibers" and "spunbond fibers" shall be used interchangeably and shall refer to small diameter fibers which are formed by extruding a molten thermoplastic material as filaments from a plurality of fine, usually circular, capillaries of a spinnerette with the diameter of the extruded filaments then being rapidly reduced as by, for example, eductive drawing or other well-known spunbonding mechanisms. The production of spunbonded nonwoven webs is illustrated in patents such as, for example, in U.S. Pat. No. 4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 to Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S. Pat. Nos. 3,338,992 and 3,341,394 to Kinney, U.S. Pat. No. 3,542,615 to Dobo et al. The disclosures of these patents are hereby incorporated by reference. [0015] As used herein, the term "bonded carded webs" refers to webs that are made from staple fibers which are usually purchased in bales. The bales are placed in a fiberizing unit/picker which separates the fibers. Next, the fibers are sent through a combining or carding unit which further breaks apart and aligns the staple fibers in the machine direction so as to form a machine direction-oriented fibrous nonwoven web. Once the web has been formed, it is then bonded by one or more of several bonding methods. One bonding method is powder bonding wherein a powdered adhesive is distributed throughout the web and then activated, usually by heating the web and adhesive with hot air. Another bonding method is pattern bonding wherein heated calender rolls or ultrasonic bonding equipment is used to bond the fibers together, usually in a localized bond pattern through the web and/or alternatively the web may be bonded across its entire surface if so desired. When using bicomponent staple fibers, through-air bonding equipment is, for many applications, especially advantageous. [0016] As used herein, the term "conjugate fibers" refers to fibers which have been formed from at least two polymers extruded from separate extruders but spun together to form one fiber. Conjugate fibers are also sometimes referred to as multicomponent or bicomponent fibers. The polymers are usually different from each other though conjugate fibers may be monocomponent fibers. The polymers are arranged in substantially constantly positioned distinct zones across the cross-section of the conjugate fibers and extend continuously along the length of the conjugate fibers. The configuration of such conjugate fiber may be, for example, a sheath/core arrangement wherein one polymer is surrounded by another or may be a side by side arrangement, a pie arrangement or an "islands-in-the-sea" arrangement. Conjugate fibers are taught in U.S. Pat. No. 5,108,820 to Kaneko et al., U.S. Pat. No. 4,795,668 to Krueger et al., and U.S. Pat. No. 5,336,552 to Strack et al. Conjugate fibers are also taught in U.S. Pat. No. 5,382,400 to Pike et al., and may be used to produce crimp in the fibers by using the differential rates of expansion and contraction of the two or more polymers. For two component fibers, the polymers may be present in varying desired ratios. The fibers may also have shapes such as those described in U.S. Pat. No. 5,277,976 to Hogle et al., U.S. Pat. No. 5,466,410 to Hills and U.S. Pat. Nos. 5,069,970 and 5,057,368 to Largman et al., which describe fibers with unconventional shapes. [0017] As used herein, the term "sheet" means a layer which may either be a film or a nonwoven web. [0018] As used herein, the term "necked material" refers to any material which has been narrowed in at least one dimension by application of a tensioning force in another direction (dimension). [0019] As used herein, the term "neckable material" means any material which can be necked. [0020] As used herein, the term "percent neckdown" refers to the ratio determined by measuring the difference between the un-necked dimension and the necked dimension of the neckable material and then dividing that difference by the un-necked dimension of the neckable material multiplied by a 100. [0021] As used herein, the terms "elastic necked-bonded material" or "neck-bonded laminate" shall be used interchangeably and refer to a material having an elastic sheet joined to a necked material at least at two places. The elastic sheet may be joined to the necked material at intermittent points or may be completely bonded thereto. The joining is accomplished while the elastic sheet and the necked material are in juxtaposed configuration. The elastic necked-bonded material is elastic in a direction generally parallel to the direction of neckdown of the necked material and may be stretched in that direction to the breaking point of the necked material. An elastic necked-bonded material may include more than two layers. For example, the elastic sheet may have necked material joined to both of its sides so that a three-layer composite or laminate elastic necked-bonded material is formed having a structure of necked material/elastic sheet/necked material. Additional elastic sheets and/or necked material layers may be added. Yet other combinations of elastic sheets and necked materials may be used. Continue reading... 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