Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Nonwoven fabric – Including strand or fiber material which is a monofilament...
Reexamination Certificate
2000-07-03
2004-07-27
Cole, Elizabeth M. (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Nonwoven fabric
Including strand or fiber material which is a monofilament...
C428S364000, C428S365000, C428S373000, C428S904000, C442S363000, C442S364000, C057S225000, C057S226000
Reexamination Certificate
active
06767853
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fibrous substrate for artificial leather that has less rubbery feeling and repellence feeling than conventional artificial leather, is excellent in denseness feeling and has texture like soft natural leather.
2. Description of the Prior Art
At present, artificial leather is generally produced by a method which comprises impregnating a nonwoven fabric comprising fibers (referred to as microfine fiber-forming fibers) which are composed of a non-elastic polymer such as nylon or polyester and come to generate microfine fibers with a solution of an elastic polymer, mainly polyurethane, in an amount of 15-60% by weight of the nonwoven fabric, solidifying the elastic polymer by a wet process or a dry process, and then generating bundles of microfine fibers from the microfine fiber-forming fibers, or the like method. According to this method, the elastic polymer with which the fabric is impregnated is solidified into a sponge or block form to make a structure wherein the solidified elastic polymer covers and encircles the microfine fiber bundles. Therefore, the resultant artificial leather has strong rubbery feeling and repellence feeling that are peculiar to the elastic polymer, and is inferior to natural leather in feeling performances such as texture, drapeability, and denseness feeling and surface feeling of the surface. Since the elastic polymer is used in a solvent system, production steps such as solvent-recovery are complicated so that productivity is bad. In many cases, the solvent is harmful for human bodies. Thus, the above-mentioned method is involved in environmental problems upon the production.
Incidentally, natural leather is composed only of fibers and has a structure wherein several hundreds of very fine microfibrils of collagen are bundled into a fiber (about 0.05-1.0 denier); from several fibers to several tens of the fibers are made up to a fiber bundle (1-10 deniers); and microfibrils, fibers or fiber bundles are three-dimensionally and densely entangled with each other. For artificial leather, there are also suggested many trials for obtaining texture, denseness feeling and appearance that are very similar to those peculiar to natural leather, using a fibrous substrate composed only of fibers wherein a fibrous elastic polymer is used as a binder.
For example, Japanese Patent Application Laid-Open (JP-A) Nos. 59-211664, 59-211666, 60-45656, 60-139879, 63-12744, 64-52872, 2-14056 etc. disclose methods for producing a leather-like sheet by blending sea-island type microfine fiber-forming fibers whose island component is an elastic polymer with non-elastic fibers to prepare a nonwoven fabric, and then removing the sea component of the sea-island type microfine fiber-forming fibers to generate elastic microfine fibers. In these methods, pieces of the elastic polymer, which is the island component, agglutinate to each other to be bundled/integrated by treatment with the solvent upon extraction and removal of the sea component, even if the microfibers comprising the elasticpolymer are made sufficiently fine at the stage of the microfine fiber-forming fibers. Finally, a single thick fiber is produced. For this reason, the fineness of the elastic polymer that can be industrially produced exceeds 2 deniers. The elastic polymer and the non-elastic polymer are separately made into fiber bundles, so that only a part of the microfine fibers comprising the non-elastic polymer is bound with the elastic polymer. Thus, large parts of fibers comprising the non-elastic polymer are in a loose state. As a result, many of the microfine fibers are not bound and easily fall out from the leather-like sheet.
As examples of the fiber form in which an elastic polymer and a non-elastic polymer coexist in a single fiber bundle, JP-A Nos. 61-194247, 10-37057 etc. disclose methods using core-sheath type composite fibers wherein its core component is an elastic polymer and its sheath component is a blend polymer in which a non-elastic polymer is dispersed in an island form in a sea component comprising a soluble polymer. JP-A-Nos. 5-339863, 5-339864 etc. disclose methods using composite fibers wherein a soluble polymer in which an elastic polymer is dispersed in an island form and a soluble polymer in which a non-elastic polymer is dispersed in an island form are put on each other side-by-side. According to the former methods, the non-elastic polymer can be made into microfibers. However, the number of strands of the fiber comprising the elastic polymer is only one; therefore, the fineness of the elastic polymer that can be industrially produced is a large value over 1 denier. According to the latter methods, upon dissolution/removal of the soluble component, the elastic polymer agglutinates into thick fibers so that the fibers have strong repellence feeling and rubbery feeling. Thus, no artificial leather like natural leather can be obtained.
As described above, in all of the above-mentioned methods, the fineness of fibers comprising elastic polymer exceeds 1 denier and is too large as compared with natural leather. Therefore, no texture like natural leather can be obtained, and the denseness and smoothness of their surface are poor.
Examples using composite fibers wherein an elastic polymer and a non-elastic polymer are divided are disclosed in JP-A-Nos. 62-41375, 62-78246, 2-160964, 6-173173, etc. According to these methods, the industrial limits of both the fineness of fibers comprising the non-elastic polymer and that of fibers comprising the elastic polymer are about 0.5 denier. The fineness of both the obtained non-elastic fibers and elastic fibers is larger than that of natural leather. Texture like natural leather cannot be expected.
According to all of the methods, which have been disclosed up to the present, using an elastic polymer in a fiber form, the fineness of the elastic polymer is far larger than that of natural leather. As a result, texture and appearance are far and away from those of natural leather.
SUMMARY OF THE INVENTION
As described above, any elastic polymer cannot be made into microfibers according to the prior art, so that texture and appearance like natural leather cannot be gained. An object of the present invention is to attain conversion of an elastic polymer into microfibers and provide a fibrous substrate for artificial leather which has less rubbery feeling and repellence feeling than artificial leather in the prior art, has denseness feeling, and has texture and appearance like soft natural leather.
In order to obtain artificial leather having texture and appearance like natural leather, the inventors eagerly made investigations on methods by which an elastic polymer as an island component is made into microfine fibers without agglutination/integration of pieces of the polymer even if a sea component is extracted and removed with a solvent or the like. If microfine fibers (A) comprising an elastic polymer are adjacent to each other, they agglutinate to each other and are integrated into bundles upon the extraction and removal. Upon the extraction and removal, however, microfine fibers (B) comprising a non-elastic polymer do not agglutinate to each other. A hint was obtained from this fact. Thus, the inventors tried a method wherein the microfine fibers (B) comprising the non-elastic polymer encircle the microfine fibers (A) comprising the elastic polymer for preventing the phenomenon that pieces of the elastic polymer are integrated into bundles. From microfine fiber-forming fibers wherein many microfine fibers (B) comprising the non-elastic polymer are substantially homogeneously dispersed in a sea component polymer containing many of the dispersed microfine fibers (A) comprising the elastic polymer, the sea component polymer is extracted and removed by a solvent. As a result, the elastic polymer is separated into microfibers, so as to form microfine fiber bundles wherein the micro fine fibers (A) comprising the elastic polymer and the microfine fibers (B) comprising th
Nakayama Kimio
Tamba Yoshihiro
Yamasaki Tsuyoshi
Cole Elizabeth M.
Kuraray Co. Ltd.
Pierce Jeremy R.
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