Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
2000-10-25
2002-11-12
Seidleck, James J. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C428S424800, C428S474400, C428S516000, C428S520000
Reexamination Certificate
active
06479154
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to coextruded elastomeric breathable films for use in conformable garments and personal care products. More particularly, the present invention relates to multilayered films and film laminates for use with fabrics in disposable garments and personal care products.
BACKGROUND OF THE INVENTION
The present invention is directed to thin multilayer films and their use in laminates and articles made therefrom. Film laminates have become an important article of commerce, finding a wide variety of applications, including use within various articles; for example, as outer covers for personal care products such as diapers, training pants, incontinence garments, feminine hygiene products and the like. In addition, film laminates have found use in various other bodily articles such as garments, surgical gowns, protective workwear, wound dressings, bandages and the like. The film can provide the desired barrier properties to the article while other materials laminated thereto can provide additional desired characteristics, such as abrasion resistance and/or good hand. In addition, in order to increase the comfort of the wearer, film laminates have been desirably “breathable”, in the sense that the laminates act as a barrier to liquids, but allow water vapor and air to pass therethrough. By achieving and maintaining high breathability, it is possible to provide an article that is more comfortable to wear since the migration of water vapor through the fabric helps reduce and/or limit discomfort from excess moisture trapped against the skin. Thus, such an article can potentially contribute to an overall improved skin wellness. Therefore, it is often desirable to use a film to achieve desired comfort levels in an article. To this end, films have been engineered to achieve specific desired objectives.
For instance, while a variety of film laminates are known in the art, one particularly useful laminate uses a breathable barrier comprising a stretched filled multilayered (as opposed to a monolayer) microporous film. Such films are typically comprised of a relatively thick and often more expensive core layer, encompassing the majority of the film material, and relatively thinner outer skin layers. The core layer is often filled with particles or other matter and then crushed or stretched to form a fine pore network throughout the layer. The pores result from the separation of the polymer from the filler particles. The film-pore network allows relatively high levels of gas and water vapor to pass through the film while acting as a barrier to liquids and particulate matter. The amount of filler within the film and the degree of stretching is controlled so as to create a network of micropores of a size and/or frequency to impart the desired level of breathability to the fabric.
An exemplary stretched filled-film is described in commonly assigned WO Patent Application 96/19346 to McCormack which discloses a multilayered filled-film comprising a breathable microporous core layer made from an extrudable thermoplastic polymer such as a polyolefin, including copolymers and/or blends thereof. One or more breathable microporous skin layers are attached to the core layer. McCormack emphasizes use of a generic type core layer and specifically designed skin layers. The described skin layers include extrudable thermoplastic polymers and/or additives designed to impart specialized properties to the overall film. The selection of skin layer polymers in the McCormack reference depends on the overall film attributes desired. Possible skin layer polymers are described, including homopolymers, copolymers and blends of polyolefins as well as ethylene vinyl acetate (EVA), ethylene ethyl acrylate (EEA), ethylene acrylic acid (EAA), ethylene methyl acrylate (EMA), ethylene butyl acrylate (EBA), polyester (PET), nylon, ethylene vinyl alcohol (EVOH), polystyrene, polyurethane and olefinic thermoplastic elastomers. Additionally, McCormack describes the use of anti-block material to improve processing and/or to prevent unwanted adhesion of layers. The particulate filled-film of McCormack can be stretched to impart breathability. The stretched film may then be laminated to a nonwoven web to create a laminate that takes advantage of the strength and integrity of the nonwoven web and the barrier properties of the stretched film. The McCormack reference does not provide for the use of higher performance elastomers, while still providing a relatively high level of breathability at low cost.
Films have also been designed with skin layers that specifically help to reduce the occurrence of die lip buildup, that is the residual buildup of filler particles which tend to accumulate on an extruder die as the filled polymer is extruded during the film manufacturing process. This buildup of material on the die lip slows the manufacturing process since it requires the process to be stopped in order for the die lip to be scraped clean of the excess material. Such skin layers including EVA, are often used in order to reduce this accumulation of the filler particles.
Commonly assigned WO Patent Application 99/14262 to Shawver et al. describes a breathable microporous film comprised of a thermoplastic polymer blend of a first polyethylene polymer having a density below 0.89 g/cm
3
, a second polyethylene polymer having a density above about 0.90 g/cm
3
, and a filler. In particular, the reference describes the use of a single site/metallocene catalyzed polyethylene as a film component. While the attributes of this film are described as providing good breathability and body conformance, as well as not suffering from shrinkage when exposed to heat, the Shawver reference does not describe strategically placed higher cost elastomeric materials to help buttress the elastomeric properties of lower cost elastomers in a film, nor the use of higher performance elastomers while still achieving relatively high levels of breathability. Although such films demonstrate elastic properties, a film having better elastic properties than that of metallocene catalyzed polyethylene elastomers is desirable.
In addition to breathability of the multilayered film laminate, the ability of the laminate to exhibit higher performance elastic properties allows a garment made therefrom to provide better body conformance. However, providing a low cost multilayered laminate that achieves the desired conformance and breathability is problematic, particularly with stretched filled-films. In order to achieve good body conformance, the polymer composition of the film layers desirably should have good stretch and recovery properties and yet must also be capable of allowing formation and retention of pores upon processing. These two objectives are often at odds with each other.
For instance, U.S. Pat. No. 5,691,034 to Krueger et al. describes a multilayered elastomeric laminate with microtextured skin layers. The multilayered laminate is comprised of at least one elastomeric layer and at least one thin skin layer prepared by coextrusion. The laminate is illustrated in the patent as having three layers. Following coextrusion, the laminate is stretched past the elastic limit of the skin layers and allowed to recover. While the Krueger reference provides for the use of costly high performance elastomeric materials, it does not provide for breathability in the described laminate. This is particularly difficult to achieve using higher performance elastomers since these elastomers also lead to pore closure following stretching. Essentially, because of the retraction properties of the elastomer materials, the micropores necessary to make the film breathable do not always remain open after the stretching process.
One solution to this problem has been to add additional filler to reduce the tendency for the material to retract, thus allowing more micropores to remain open, thereby producing a breathable product. However, this decrease in the retraction attribute produces a higher percent set in the final product, that is generally a perc
Fitts, Jr. James Russell
Reavis Jennifer Rebecca
Shane Richard Macferran
Shawver Susan Elaine
Uitenbroek Duane Girard
Bissett Melanie
Flack Steven D.
Kimberly--Clark Worldwide, Inc.
Seidleck James J.
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