Textile structures are produced from a variety of materials both natural and manmade. Numerous processes are used in the production of these structures, for example, spinning, weaving, knitting, tufting, carding, and needlepunching. The structures thus produced can be dimensionally unstable. Several techniques are used to stabilize these structures, for example, latex treatment or lamination. Some of these treatments require solvents or chemicals with an undesirable environmental impact. Another technique is the blending of nonadhesive fibers with potentially adhesive binder fibers to form a yarn or other textile structure, then activating the potentially adhesive fibers to bond them to the other fibers. The use of binder fibers in stabilizing nonwoven materials is described in U.S. Pat. Nos. 2,277,049 and 2,464,301. Twisted yarns made with binder fibers having a melting point of 110.degree.-170.degree. C. are described in European Patent No. 324,773. Wrap staple yarns containing low melting binder wrap strands based on copolyamides and copolyesters with melting points less than 149.degree. C. are described in U.S. Pat. No. 4,668,552. Binder fibers made from a blend of branched low density polyethylene having a melting point of about 107.degree. C. and crystalline polypropylene are disclosed in U.S. Pat. No. 4,634,739. The use of polyethylene fibers with melting points higher than 110.degree. C., and polypropylene fibers in needled, nonwoven webs is described in U.S. Pat. Nos. 5,077,874 and 5,199,141. Because of the small differential in the melting points of the two fibers, this combination of fibers in the nonwoven structure requires precise control of the heat treatment temperatures to prevent any adverse effect on the primary fibers of the structure, i.e., polypropylene fibers.
It would therefore be desirable to provide a significant differential between the melting point of the primary fibers of a textile structure and the binder fibers, providing a more forgiving process for thermal treatment in the production of dimensionally stable textile structures. This differential can be achieved by providing binder fibers with a sufficiently low melting temperature. However, prior to the instant invention, no one has been able to produce binder fibers comprising linear low density polyethylene fibers having a melting point less than 109.degree. C.
USPTO Backgrounds
USPTO Backgrounds