Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2000-03-16
2003-02-11
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S015000, C428S085000, C428S151000, C428S903000, C428S904000, C428S391000, C428S396000, C428S397000, C428S401000, C442S060000, C442S168000, C442S169000, C442S334000, C442S340000
Reexamination Certificate
active
06517938
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet that is used as a substrate of a suede-like or smooth-like artificial leather sheet, and a production process thereof. Specifically, the present invention relates to an artificial leather substrate that is soft and dense, and has excellent processability.
2. Description of the Background
Hitherto, a fiber-entangled nonwoven fabric that is used as an artificial leather sheet substrate is usually subjected to a shrinking treatment in order to improve softness and denseness of an artificial leather sheet. Since early times, for fiber-entangled nonwoven fabrics comprising a polyamide-based fiber, many techniques have been suggested for shrinking the fiber by treating the polyamide-based fiber in the fiber-entangled nonwoven fabric with an aqueous solution of calcium chloride, zinc chloride or lithium chloride, or an aqueous solution or a dispersion solution of phenol, benzylalcohol, benzoic acid or the like, and swelling the fiber.
Incidentally, in the case of fiber-entangled nonwoven fabrics comprising polyester fiber, there is known a technique of using the property that a low draw ratio fiber or a high-speed spun fiber of polyethylene telephthalate has thermal shrinkage to shrink and densify the fiber-entangled nonwoven fabrics. For example, Japanese Patent Publications No. 53-20561 and No. 53-20562 describe production of a suede-like artificial leather by treating a woven fabric of multi-component fiber comprising polyamide and polyester with a chemical agent such as benzyl alcohol so as to shrink and exfoliate the polyamide component.
Japanese Patent Laid-Open No. 3-90619 describes a process for producing a fabric using a polyamide/polyester-based separate-type composite fiber, which comprises treating a cylindrical or flat woven fabric comprising the copolymerized polyamide/polyester-based separate-type composite fiber with a heated alkali solution to separate the fiber constituting polymers, shrink the fiber, and consequently obtain the surface covered with only the microfine polyester fiber, and then developing the woven fabric with only a dye for the polyester fiber.
Japanese Patent No. 2786868 describes a process for producing a suede-like artificial leather sheet, which comprises the steps of treating a nonwoven fabric composed of sea-island section fiber comprising polyamide as an island component and polyethylene as a sea component with an aqueous solution of benzoic acid to shrink the polyamide.
As described above, in these methods the polyamide-based fiber is treated with an aqueous solution or a dispersion solution of an agent such as phenol, benzylalcohol or benzoic acid, to swell or shrink the fiber. According to these methods, however, a change in the concentration of the treating solution is easily caused by evaporation or sublimation. There arises a serious problem that stabilization of the shrinkage ratio is difficult by the change. Moreover, the polyamide-based fiber deteriorates easily by the swelling or shrinking treatment. There is also a problem in the technique for controlling it.
The chemical agents described above have a serious problem with respect to safety. Accordingly, satisfactory measures must be taken for a working environment or against environmental pollution, and facilities for recollecting the used chemical agents are essential. Thus, a large burden is imposed on industrial production.
Recently, the degree of the demand about the hand touch, the sense of the touch or color is increasing large year by year. For example, the number of colors is increased, and it is important that the difference in color between the external layer and the internal layer in the section of an artificial leather sheet is reduced. For example, in the case that in a post step dyeing is applied to the artificial leather sheet comprising a polyester-based fiber entangled nonwoven fabric and a polyurethane-based elastic polymer, the color fastness thereof becomes very low when the disperse dye with which the fiber is dyed sticks to the polyurethane. Therefore, the following dyeing method is used: a method of dyeing the polyester fiber with the disperse dye, removing the disperse dye stuck to the polyurethane, and re-dyeing the polyurethane with a metal complex dye. In such a method, however, the steps are complicated. There also remains such a problem that when a resin is applied to the surface to turn it into a smooth-like surface or the surface is thermally embossed to obtain grains, the disperse dye in the polyester fiber is transferred to the polyurethane so that the color fastness drops.
When an artificial leather sheet comprising a polyamide-based fiber entangled nonwoven fabric and a polyurethane-based polymer is dyed with a metal complex dye in a post dyeing step, relatively good color fastness can be expected. However, it becomes insufficient to shrink and densify the fiber entangled nonwoven fabric. Thus, it is difficult to obtain sheet having dense feeling like natural leather. This artificial leather sheet has a problem that the feeling thereof is soft but is like rubber.
The suede-like product also has a problem that if importance is attached to softness, contact points of its fiber and polyurethane polymer must be made fewer, and in this case its surface napped fiber falls out.
SUMMARY OF THE INVENTION
In the light of the problems described above, an object of the present invention is to provide an artificial leather sheet substrate that is soft and dense, and is excellent in processability and that is obtained by shrinkage-processing a nonwoven fabric which comprises a polyamide-based microfine fiber-forming fiber and which is easy in handling and results in stable shrinkage ratio; and a production process thereof.
Thus, the present invention provides an artificial leather sheet substrate, comprising:
a fiber entangled nonwoven fabric composed of bundles of a polyamide-based microfine fibers comprising a polyamide or a polyamide composition having a hot toluene swelling degree of 2 to 10%, and having a fineness of 0.1 decitex or less;
an elastic polymer and a releasing agent between the bundles; and
a releasing agent inside of the bundles.
Preferable is the above-mentioned polyamide-based fiber is a fiber comprising a polyamide or a polyamide composition comprising a nylon-6 unit and a nylon- 12 unit. Preferable is also the above-mentioned artificial leather sheet substrate, wherein the releasing agent present between the microfine fiber bundles and inside the microfine fiber bundle is a salt compound of a polyamide derivative and a silicone-based compound.
The present invention is a process for producing an artificial leather sheet substrate comprising a polyamide-based microfine fiber and an elastic polymer, comprising:
producing a fiber entangled nonwoven fabric from a polyamide microfine fiber-forming fiber,
treating the fiber entangled nonwoven fabric with hot water to shrink the fabric by 15 to 50% in area,
impregnating the shrunk fiber entangled nonwoven fabric with an elastic polymer, converting the microfine fiber-forming fiber into bundles of microfine fine fibers, adding a releasing agent to the bundles of microfine fine fibers, and drying the bundles of microfine fine fibers.
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description.
DETAILED DESCRIPTION OF THE INVENTION
The microfine fiber-forming fiber in the present invention may be a fiber having a sea-island section structure where its island component comprises a polyamide having the above-mentioned swelling degree and its sea component is preferably polyethylene, and more preferably low-density polyethylene. As the method for converting the microfine fiber-forming fiber to bundles of microfine fibers, there is generally used a method of extracting and removing polyethylene as the sea component with hot toluene at 75 to 95° C. The polyamide-based
Andoh Hidekazu
Tamba Yoshihiro
Yamasaki Tsuyoshi
Boss Wendy
Jones Deborah
Kurray Co., Ltd.
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