Elastic bicomponent and biconstituent fibers, and methods of making cellulosic structures from the same

Abstract

The elasticity of elastic, absorbent structures, e.g., diapers, is improved without a significant compromise of the absorbency of the structure by the use of bicomponent and / or biconstituent elastic fibers. The absorbent structures typically comprise a staple fiber, e.g., cellulose fibers, and a bicomponent and / or a biconstituent elastic. The bicomponent fiber typically has a core / sheath construction. The core comprises an elastic thermoplastic elastomer, preferably a TPU, and the sheath comprises a homogeneously branched polyolefin, preferably a homogeneously branched substantially linear ethylene polymer. In various embodiments of the invention, the elasticity is improved by preparation techniques that enhance the ratio of elastic fiber: cellulose fiber bonding versus cellulose fiber:cellulose fiber bonding. These techniques include wet and dry high intensity agitation of the elastic fibers prior to mixing with the cellulose fibers, deactivation of the hydrogen bonding between cellulose fibers, and grafting the elastic fiber with a polar group containing compound, e.g. maleic anhydride.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a division of U.S. Ser. No. 10 / 799,168, filed Mar. 12, 2004, which is a division of U.S. Ser. No. 10 / 195,279, filed Jul. 15, 2002, which claims the benefit of U.S. Provisional Application No. 60 / 306,003, filed Jul. 17, 2001.FIELD OF THE INVENTION [0002] This invention relates to elastic fibers. In one aspect, the invention relates to bicomponent elastic fibers while in another aspect, the invention relates to biconstituent elastic fibers. In another aspect, the invention relates to bicomponent and biconstituent elastic fibers having a core / sheath construction. In yet another aspect, the invention relates to such fibers in which the polymer that forms the sheath has a lower melting point than the polymer that forms the core. In still another embodiment, the invention relates to methods of forming elastic cellulosic structures from a combination of cellulosic fibers and elastic bicomponent and / or biconstituent fibers ha...

AI Technical Summary

Benefits of technology

[0013] In another embodiment of the invention, for those nonelastic staple fibers that bind to one another due to hydrogen bonding, e.g., cellulose fibers, the ratio of nonelastic staple fibers bonded to elastic fibers versus nonelastic staple fibers bonded to other nonelastic staple fibers is increased by treating the nonelastic staple fibers, prior to or simultaneously with blending these fibers with the elastic fibers, with a debonding agent, e.g., a quaternary ammonium compound containing one or more acid groups. The debonding agent deactivates at least a part of the hydrogen bonding between the nonelastic staple fibers.

[0014] In another embodiment of the invention, blending of nonelastic staple fibers with elastic fibers is enhanced by blending the fibers in an aqueous media, preferably in the presence of a surfactant and with intense agitation. This procedure enhances the separation of the elastic fibers from one another, and thus makes each fiber more accessible for bonding with a nonelastic staple fiber. This method can be used alone or in combination with one or more other fiber separation embodiments of this invention.

[0015] In another embodiment of the invention, high intensity air mixing is used to separate elastic fibers from one another prior to blending with staple fibers. This technique also promotes separation of the elastic fibers from one another, and this, in turn, improves their accessibility for bonding with the staple fibers. This embodiment of the invention can also be used alone or in combination with one or more other embodiments of the invention.

Problems solved by technology

Unfortunately, many of these structures require some degree of elasticity for reasons of comfort and use, e.g., a diaper conforming to the contours of the human body or a wipe having the touch and drape of cloth, and if the structure is not sufficiently elastic, gaps will form within it.

However, the mere blending of staple fibers with elastic fibers often is not enough to obtain the full benefit of the elastic fiber without compromising the absorbency of the staple fiber.

As a result, unless a highly uniform mixture of the two fibers is formed during the construction of the absorbent structure, the two types of fibers tend to segregate and the benefit of the elastomeric fibers is reduced or lost.