Stock material or miscellaneous articles – Pile or nap type surface or component – Nap type surface
Reexamination Certificate
2001-11-26
2004-05-11
Juska, Cheryl A. (Department: 1771)
Stock material or miscellaneous articles
Pile or nap type surface or component
Nap type surface
C428S904000, C442S071000, C442S072000, C442S074000, C442S102000, C427S389900, C427S412000
Reexamination Certificate
active
06733859
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a napped leather-like sheet material with a nap having a good feel and touch and to a method of producing the same. More particularly, the invention relates to a leather-like, i.e., artificial leather, sheet material having a natural leather suede-like or nubuck-like velvety, smooth surface touch, an appropriate extent of flexibility with reduced firmness and a good feel or touch and giving a sensation of being of high quality, and to a method of producing the same.
2. Description of the Prior Art
With leather-like sheet materials having a napped surface (napped leather-like sheet materials), the feel and touch thereof largely depends on the sensation felt upon touching the surface. A number of proposals have so far been made for improving the surface touch of napped leather-like sheet materials. As typical of such prior art technology, there may be mentioned, among others, (1) the method of adding a wet touch to napped leather-like sheet materials which comprises providing the same with a softening agent and (2) the method of adding a dry touch to napped leather-like sheet materials which comprises providing the same with a silicone resin. These methods (1) and (2) have been widely employed in the industry as methods of improving the surface touch of napped leather-like sheet materials.
The above prior art methods (1) and (2) can indeed improve the surface touch to a certain extent but not yet to a fully satisfactory extent. Thus, no napped leather-like sheet materials having a natural leather suede-like or nubuck-like velvety, smooth surface touch, excellent in flexibility with reduced firmness, and having a feel or touch suggestive of being of high quality have been obtained as yet.
In a field other than that of leather-like sheet materials, a proposal has been made to produce cloths having a silk-like dry touch by providing the cloths with a natural silk protein or the like (e.g. Japanese Unexamined Patent Applications laid open under Nos. Kokai H05-78979 and Kokai H06-316871).
Accordingly, the present inventors made experiments to apply this method to napped leather-like sheet materials. Although an increased coating weight of a silk protein provided a silk-like touch to napped leather-like sheet materials, any napped leather-like sheet materials having a natural leather suede-like or nubuck-like velvety touch, excellent in flexibility with reduced firmness, and having a surface touch giving a sensation of being of high quality could not be obtained.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a napped leather-like sheet material having a natural leather suede-like or nubuck-like feel or touch, namely a velvety, smooth surface touch, as well as flexibility with reduced firmness and excellent in feel and touch and giving a quality sensation, without impairing the mechanical characteristics, such as tensile tenacity, which are intrinsic in napped leather-like sheet materials, and a method of producing the same. Thus, the invention is a napped leather-like sheet material provided with (1) at least one silk protein substance selected from among silk proteins and partial hydrolyzates of silk proteins, and (2) a softening agent, on the napped surface on one or both sides.
The invention is also a method of producing napped leather-like sheet materials which comprises applying a solution containing at least one silk protein substance selected from among silk proteins and partial hydrolyzates of silk proteins and a softening agent, or applying a solution containing such silk protein substance and a solution containing a softening agent simultaneously or one by one, i.e., separately, to the napped surface of a napped leather-like sheet material composed of an entangled nonwoven fabric made of ultrafine filaments or fibers and an elastomeric polymer, or elastomer, contained in the nonwoven fabric, and having a nap made of ultrafine fibers raised on one or both sides.
DETAILED DESCRIPTION OF THE INVENTION
The napped leather-like sheet material according to the invention is based on a napped leather-like sheet material composed of an entangled nonwoven fabric made of ultrafine fibers and an elastomer contained therein and having a nap made of ultrafine fibers raised on one or both sides.
Referring to the napped leather-like sheet material, the fineness of the ultrafine fibers constituting the napped leather-like sheet material is not particularly restricted but, generally, it is preferred that both the ground structure (entangled nonwoven fabric portion) and the nap be formed of ultrafine fibers with a fineness of 0.0001 to 0.5 decitex, preferably 0.0001 to 0.1 decitex. When the fineness of the ultrafine fibers, in particular the fineness of the ultrafine fibers forming the nap, is in excess of 0.5 decitex, the surface touch can hardly be rendered natural leather suede-like or nubuck-like. On the other hand, if the fineness of the ultrafine fibers is less than 0.0001 decitex, the dyeability will be lower and the color tone tends to become poor.
The ultrafine fibers may be made of any of fiber-forming polymers, for example aromatic ring-containing polyesters such as polyethylene terephthalate, polypropylene terephthalate and polybutylene terephthalate; polyamides such as nylon-6, nylon-66, nylon-12, nylon-610, and copolymers thereof; and polyolefins such as polyethylene and polypropylene. Among them, ultrafine fibers formed of a polyester and/or a polyamide, in particular a polyamide, are preferred from the viewpoint of strength, of feel and touch and/or of dyeability, for instance.
In the napped leather-like sheet material, the ultrafine fibers mentioned above are in an entangled state to form an entangled nonwoven fabric, and an elastomer is contained in the interfibrous spaces in the entangled nonwoven fabric.
The elastomer to be contained in the entangled nonwoven fabric may be any of those known high-molecular elastomers. Thus, mention may be made of natural rubbers, SBR, NBR, polychloroprene, polyisoprene, chlorosulfonylated polyethylene, polyisobutylene, isobutylene-isoprene rubbers, acrylic rubbers, polyurethane elastomers, polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polystyrene-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, polydiene-based thermoplastic elastomers, chlorinated thermoplastic elastomers and the like, and these can be used either singly or in combination of two or more.
Among them, polyurethane elastomers (elastic polyurethane resins) are preferably used from the viewpoint of the feel and touch, dyeability, wear resistance, tensile strength and other mechanical characteristics of napped leather-like sheet materials, for instance.
Those polyurethane resins which have elasticity can all be used as the polyurethane elastomers. Particularly preferred, however, are segmented polyurethanes producible by using a polymer diol having a number average molecular weight of 500 to 5,000 as a soft segment component and an organic diisocyanate as a hard segment component and reacting these components with each other together with a low-molecular weight chain extender.
The above polymer diol to be used in the production of segmented polyurethanes includes, among others, polyester diols obtainable by reacting a dicarboxylic acid component with a diol component, polylactone diols, polycarbonate diols, polyester polycarbonate diols and polyether diols. One or two or more of these polymer diols can be used. When a polymer diol having a number average molecular weight of less than 500 is used in producing segmented polyurethanes, the soft segment becomes too short and the resulting polyurethanes will lack flexibility; hence it may become difficult to obtain natural leather-like napped sheet materials. If, conversely, the number average molecular weight of the polymer diol exceeds 5,000, the proportion of urethane bonds in the polyurethane relatively decreases, resulting in decreases in durability, heat resistanc
Makiyama Norio
Nobuto Yoshiki
Yoneda Hisao
Juska Cheryl A.
Kuraray Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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