JP2000248473A - Leather-like sheet and method for producing the same - Google Patents

Abstract

(57) [Summary] [Problem] Leather that maintains an enamel feeling even after a lapse of time, has excellent color tone, texture and surface abrasion resistance, and suppresses color tone change on the surface of a grain surface layer even in products other than enamel tone. Provide the like sheet. A method for producing a leather-like sheet in which a base material layer is made of a nonwoven fabric and a porous polyurethane and has a grain surface layer on at least one surface, wherein the base material layer has a part of a main chain or a side chain made of polyurethane. A sheet obtained by impregnating a nonwoven fabric with a solution of the polyurethane containing the obtained silicone polymer and then wet-solidifying the solution is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leather-like sheet having a grained surface which has an enameled surface and has little change in glossiness of the surface, which is used for shoes and bags.

[0002]

2. Description of the Related Art Hitherto, glossy leather-like sheets with a glossy surface have been used for shoes and bags because of their high-class appearance. As a method for producing this leather-like sheet with a grain surface, a method of applying a skin layer to a substrate surface by a method generally called a dry method is used because the texture of the leather-like sheet is flexible and the process is simple. Have been. Among leather-like sheets, the one that gives the skin layer a smooth and transparent feeling to express a sense of quality and has a high gloss and gloss on the surface is called enamel, and is evaluated as having high added value I have. As a method for producing a base material layer constituting such a leather-like sheet with a silver surface, conventionally, a cloth such as a nonwoven fabric or a woven or knitted fabric is impregnated with a polyurethane solution and wet-solidified to form a polyurethane into a porous sponge state. The method is commonly used. In this method, the porous polyurethane needs to adjust the physical strength, the speed at the time of wet coagulation for adjusting the texture, and the pore size of the sponge to be formed. Is generally used because it is effective in a small amount.

[0003] However, when a base layer is prepared using a silicone-based coagulation control agent, and a silver surface layer is applied to the surface of the base layer and then the enamel-like finish is applied, the polyurethane layer constituting the base layer is gradually removed from the polyurethane layer. Polyurethane oligomers appear on the surface of the silver layer due to migration, causing fogging, impairing transparency, and further losing the depth of color to lose luxury. In addition, even in the case of a normal leather-like sheet having a glossy surface without a glossy surface, migration causes clouding, causing a problem that the color tone changes to whitish and the surface appearance changes.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, that is, the obtained enamel-like raw material maintains an enamel feeling even after a lapse of time, and is excellent in color tone, texture and surface wear resistance. Another object of the present invention is to provide a leather-like sheet that suppresses a change in color tone on the surface of a grain surface layer even in cases other than an enamel-like leather-like sheet.

[0005]

Means and Method for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, have reached the present invention.
That is, the present invention provides a leather-like sheet in which the base material layer is composed of a nonwoven fabric and a porous polyurethane, and has a silver surface layer on at least one side, and the porous polyurethane is composed of a polyurethane in which a urethane-modified silicone polymer is mixed. A leather-like sheet characterized by the fact that, in the present invention, the base material layer is made of a nonwoven fabric and a porous polyurethane,
In a method for producing a leather-like sheet having a silver layer on at least one side, a nonwoven fabric is impregnated with a polyurethane solution containing a silicone polymer in which a part of a main chain or a side chain is polyurethane, and the solution is wet-coagulated. A method for producing a leather-like sheet, characterized in that:

Hereinafter, embodiments of the present invention will be described in detail. The nonwoven fabric used in the present invention is not particularly limited as long as it has a resilience, strength, and thickness to express a leather-like texture, but is preferably a nonwoven fabric obtained by entanglement of fibers three-dimensionally. . As the polymer constituting the fiber used for the nonwoven fabric, 6-nylon,
At least one selected from melt-spinnable polyamides such as 6,6-nylon, polyethylene terephthalate, polybutylene terephthalate, cation-dyeable modified polyethylene terephthalate and other melt-spinnable polyesters, and polyolefins. Types of polymers. Also, the fiber cross section obtained by combining a plurality of polymers is in a sea-island state,
So-called sea-island fibers or splittable composite fibers may be used. Further, the nonwoven fabric may be composed of a plurality of types of fibers. From the viewpoint of texture, the use of the above-mentioned sea-island type fibers is preferable, but when emphasis is placed on tensile strength, moldability after the application of a silver-coated layer and cost, use fibers made of a single polymer such as polyester or nylon. You may. The fiber nonwoven fabric is preferably a nonwoven fabric composed of a bundle of ultrafine fibers from the viewpoint of obtaining a leather-like texture. The ultrafine fiber bundle is obtained by dissolving or decomposing the sea component polymer from the sea-island type fiber.

[0007] As a method for producing the nonwoven fabric, a known method is used. Preferably, a method of obtaining a web by carding, laminating the web and entangled by a needle punching method to obtain a nonwoven fabric is preferred. As a method for laminating the nonwoven fabric, a cross wrap method in which the nonwoven fabric is folded in an oblique direction is preferable in view of the balance between the strength and the elongation of the nonwoven fabric. As the entanglement method, a known method such as entanglement with a water flow or an air flow may be used, but a method in which the fibers are entangled with a barb of a needle to advance the entanglement is preferable. The nonwoven fabric obtained for improving the smoothness of the surface of the base material layer sheet may be subjected to surface treatment. Examples of the surface treatment include a method of pressing with a calender roll of high heat, a method of pressing a non-woven fabric with a mirror roll that has been cooled after heating, and preferably heating the non-woven fabric in a state where the non-woven fabric is gripped so that the area does not change due to heat. Then, a method of adjusting the thickness to a predetermined value by pressing is preferable from the viewpoint of the surface feeling of the polyurethane layer, the surface feeling of the fibrous nonwoven fabric, and the feeling. In particular, when the nonwoven fabric is composed of sea-island type fibers, the surface component treatment partially melts the sea component polymer to fix the form of the nonwoven fabric, thereby improving the smoothness of the surface and the further enamel feeling. It is preferable to achieve.

A nonwoven fabric obtained by the above treatment is impregnated with a polyurethane solution, and the polyurethane is solidified in a porous state to obtain a base material layer. The impregnation method includes a method of applying a solution containing a polymer elastic body and allowing the solution to penetrate into the inside, or a method of directly impregnating the nonwoven fabric with the polymer elastic body solution.However, polyurethane exists in the space constituted by the nonwoven fabric. The method is not particularly limited as long as the method is performed. The polyurethane to be impregnated is not particularly limited as long as it is a polyurethane having alkali resistance, hydrolysis resistance, hot water resistance and forming a porous layer at the time of coagulation in a poor solvent, but has a soft segment of 6 to 10 carbon atoms. Selected from the group consisting of polyester diols, polylactone diols, polycarbonate diols, polyether diols, and the like, obtained by reacting an alkane diol with a dicarboxylic acid or an ester-forming derivative thereof;
Having a number of primary hydroxyl groups, the number average molecular weight is 500 to
5,000 at least one high molecular weight polyol, diisocyanate and, if necessary, a molecular weight of 5
It is obtained by reacting less than 00 chain extenders. In particular, polyester diols obtained by reacting an alkanediol having 6 to 10 carbon atoms with a dicarboxylic acid or an ester-forming derivative thereof are preferable in that the effects of the present invention can be highly achieved.

As the alkanediol having 6 to 10 carbon atoms, 3-methyl-1,5-pentanediol, 1,1
Examples thereof include 6-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol. If the alkanediol has less than 6 carbon atoms, the effect of the present invention is slightly reduced when polyurethane is used, and the durability, particularly the hydrolysis resistance, may be deteriorated. On the other hand, if the number of carbon atoms is larger than 10, the polyurethane becomes hard when formed into a polyurethane, the texture of the obtained sheet may be deteriorated, or a desired porous structure may not be obtained. Representative examples of dicarboxylic acids include aliphatic dicarboxylic acids such as succinic acid, phthalic acid, glutaric acid, adipic acid, azelaic acid and sebacic acid, and aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid. The number average molecular weight of the polymer diol is preferably in the range of 500 to 5000.

As the polymer diol, polyester, polylactone, polycarbonate and polyether can be used alone or in a mixture at an arbitrary ratio. When the number average molecular weight of the polymer polyol is less than 500, when a polyurethane sheet is impregnated to obtain a fibrous sheet having a porous layer on the surface, the base layer is hard and lacks a balance of feeling, which is not preferable. When a polyurethane solution having a number average molecular weight of more than 5000 is impregnated with a polyurethane solution and a leather-like sheet having a porous layer on the surface is further obtained, the urethane group concentration is reduced, so that the abrasion resistance is reduced and the durability is reduced. Inferiority and hydrolysis resistance, it is difficult to obtain a balanced leather-like sheet. The polyurethane may be polymerized with a chain extender, and examples of the low molecular chain extender include ethylene glycol, propylene glycol, butanediol, and hexanediol.

Aromatic diisocyanates,
Aliphatic compounds are preferred, but aromatic compounds are preferred from the viewpoint of texture and durability. As aromatic isocyanates,
For example, 4,4'-diphenylmethane isocyanate,
Examples include tolylene diisocyanate, phenylene diisocyanate, xylylene diisocyanate, and the like.

Suitable polyurethanes include, as polyols, one selected from polyester diols such as polycaprolactam diol, polymethylpentane adipate diol and polybutylene adipate diol, and other polymer diols such as polyethylene glycol. It is preferable to use in combination with an ether-based diol in terms of texture, sponge-forming properties, and tensile strength and tear strength of a fibrous sheet impregnated with polyurethane of a fiber nonwoven fabric. In the present invention, a polyurethane solution obtained by dissolving or dispersing polyurethane in a solvent or dispersant is mixed with a polyurethane-modified silicone polymer, and the mixed solution is impregnated into a nonwoven fabric and then coagulated to obtain a base material layer. Additives such as a colorant, a light stabilizer and a dispersant are added to the polyurethane solution to be impregnated according to the purpose.

In the present invention, as described above, a coagulation regulator is added for controlling the pore diameter of the porous body after coagulation. As the coagulation regulator used in the present invention, a coagulation regulator in which a part of a silicone main chain or a side chain is converted to polyurethane is added. Further, it may be added as a mixture with another coagulation regulator, but when the coagulation regulator is a compound that migrates to the surface of the leather surface of the leather-like sheet over time, the present invention The effect decreases. Conventionally used silicone-based coagulation regulators exist in the porous polyurethane layer, and even when the porous polyurethane layer is completely solidified, the silicone-based coagulation regulator is gradually removed from the porous polyurethane layer over time. Bleed on the surface. At the same time, the silicone-based coagulation regulator causes the oligomer of the polyurethane to bleed on the surface, and the polyurethane oligomer becomes fine crystals and the color tone becomes whitish. The present inventors substitute a silicone-based coagulation regulator with a compound in which a part of a silicone main chain or a side chain is polyurethane, thereby having a coagulation control ability and controlling coagulation in a porous polyurethane layer. The agent was stopped, and it was further found that the polyurethane oligomer hardly bleeds on the porous surface. As a result, it was found that a leather-like sheet with little color change was obtained.

In order to make a part of the silicone main chain or side chain into a polyurethane, a silicone compound having a reactive organic functional group is reacted with an organic polyisocyanate under conditions in which one or more isocyanate groups are excessive, and the remaining isocyanate is reacted. A method in which a polyol having at least one active hydrogen group is reacted with the group in an organic solvent is preferable. In addition, the isocyanate groups in the coagulation regulator reacted with the polyol in order to react the remaining isocyanate groups in the coagulation regulator with the isocyanate groups in the polyurethane solution applied to the surface and fix the coagulation regulator in the polyurethane layer. It is preferable that they remain afterwards. A silicone-based coagulation regulator in which a part of the silicone main chain or side chain is made into a polyurethane is a silicone compound having a reactive organic functional group and an organic polyisocyanate. Can be easily obtained by reacting at a functional group ratio in which at least one is excessive.

The amount of the coagulation regulator to be added is preferably in the range of 0.1 to 30 parts by weight based on 100 parts by weight of the solid content of polyurethane. If the amount is less than 0.1 part by weight, the amount of addition is small, and the control of the pore size of the polyurethane wet sponge is insufficient, so that a leather-like sheet having a good texture cannot be obtained. When added in an amount exceeding 30 parts by weight,
Since a large amount of the silicone compound is present in the wet sponge, the surface touch becomes silicone rubber-like, which is not preferable. More preferably, it is in the range of 0.2 to 5 parts by weight.

Known silicone oils can be used as the silicone compound having a reactive organic functional group. Specific examples include silicone oils represented by the following chemical formula, but are not limited to the following formulas as long as desired effects can be obtained.

Amino-modified silicone oil

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Epoxy-modified silicone oil

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Alcohol-modified silicone oil

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[0020] Mercapto-modified silicone oil

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Carboxyl-modified silicone oil

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Specific examples of the organic polyisocyanate to be reacted with these silicone compounds include aromatic, aliphatic, and alicyclic compounds such as 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, phenylene diisocyanate, and xylylene diisocyanate. One. After reacting the silicone compound with the organic polyisocyanate, it is preferable to react the resulting isocyanate group-containing compound with a polyol having one or more active hydrogen groups. Specific examples include, for example, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,8-octanediol, 1,9
-Nonanediol, 1,10-decanediol and the like. This reaction is preferably carried out in an organic solvent for reasons such as the reactivity of the organic polyisocyanate group.Preferred organic solvents used for this include dimethylformamide, but other known organic solvents may be used. Good.

The thus obtained urethane-modified silicone polymer is mixed with a polyurethane solution impregnated in a nonwoven fabric. As described above, the amount to be mixed is in the range of 0.1 to 30 parts by weight based on 100 parts by weight of the solid content of the polyurethane to be impregnated. If the amount is less than 0.1 part by weight, the silicone content is low, the coagulation controllability is low, and the coagulation rate of polyurethane cannot be controlled. Therefore, it is difficult to obtain a suitable porous polyurethane sponge, and the resulting leather-like sheet has a hard feel, which is not preferable as a leather-like sheet. When the amount exceeds 30 parts by weight, the amount of the silicone-containing group increases, and the surface of the base layer has a large amount of the silicone group. Is undesirably reduced. More preferably 0.2 to 5
It is within the range of parts by weight.

The organic solvent used as a solvent for the polyurethane in the present invention is not particularly limited as long as it is an inert organic solvent for each reaction raw material. Examples of the solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, and the like.
Examples thereof include tetrahydrofuran, dimethylformamide, cyclohexane, ethyl acetate, butyl acetate, methanol, ethanol, isopropyl alcohol, ethyl cellosolve, hexane, toluene, and xylene.

The proportion of polyurethane in the base material layer is 10% or more by weight, preferably 30 to 70% by weight, as a solid content in order to give the base material layer a soft feel and elastic recovery.
% Range. If the proportion of the polyurethane is less than 10%, a smooth surface cannot be obtained, and pores of the dense polyurethane porous layer are not formed and the feeling becomes hard, which is not preferable. On the other hand, when the polyurethane ratio exceeds 70%, the desired leather-like texture is not obtained due to the resilience of the polyurethane, which is not preferable.

The sheet in which the non-woven fabric is impregnated with the polyurethane solution is coagulated and solidified in a non-solvent solution of polyurethane to obtain a fibrous substrate filled with porous polyurethane. Water is used as the non-solvent. To reduce the pore size of the porous polyurethane layer, a water-based polyurethane solvent is used in an amount of 3 to 50.
Solidification and solidification may be performed in a solution mixed in the range of weight%. A more preferable condition is a case where 5 to 20% of a solvent, particularly dimethylformamide (abbreviated as DMF) is mixed with water from the viewpoint of concentration control and coagulation rate.

Further, when the polyurethane solution is impregnated, a polyurethane solution layer is applied on the surface of the polyurethane solution to be present, and the impregnated polyurethane solution and the applied polyurethane solution are simultaneously wet-solidified to form a polyurethane porous coating layer. A method using a base material may be used. Further, a method may be used in which after impregnated polyurethane is wet-coagulated, a solution of polyurethane is applied to the surface and wet-coagulated to obtain a substrate having a polyurethane porous coating layer. Further, a method in which a polyurethane porous coating layer is separately formed and bonded to the surface of the base material may be used. It is preferable to add a urethane-modified silicone polymer to the polyurethane constituting the polyurethane porous coating layer, similarly to the polyurethane used for the base layer, in order to prevent clouding of the surface of the silver surface layer. In this case, suitable compounds and the amount of the urethane-modified silicone polymer are the same as those described above. Of course, the porous coating layer may not be formed on the substrate surface.

The surface of the obtained fibrous sheet is subjected to treatments such as coloring, gloss adjustment, and shaping to obtain a leather-like sheet. As the coloring agent, gloss adjusting agent, etc., known ones can be used.However, since the substrate surface is preferably a porous polyurethane, in terms of adhesion, the coloring agent, gloss adjusting agent, etc. are mixed with polyurethane. It is preferably used. Further, as a method of shaping the surface, a method of applying a polymer elastic solution on release paper and bonding a solidified film to the sheet is preferable from the viewpoint of cost and simplicity. A method may be used in which the surface of a leather-like sheet is pressed against a heated metal surface having a mirror surface to make the surface mirror-finished and enameled. Alternatively, a method of forming a leather-like irregular pattern on the surface by a heated embossing roll having leather-like irregularities on the surface may be used.

[0029]

The leather-like sheet obtained according to the present invention comprises:
It has features similar to natural leather in terms of texture, surface appearance, and surface properties, and has little change in surface appearance over time. The leather-like sheet of the present invention can be used as a secondary material for various accessories in addition to materials for shoes, bags, and interiors.

[0030]

EXAMPLES Next, the embodiments of the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. Parts and percentages in the examples relate to weight unless otherwise specified.

Example 1 Nylon / polyethylene was mixed with a chip at a ratio of 50/50, and the mixture was spun with an extruder to spin sea-island fibers (an island component of nylon and a sea component of polyethylene). Cut 4 denier short fibers were obtained. The fibers were carded, and a web was laminated by a cross lap method, and then entangled nonwoven fabric was obtained by needle punching. Next, the nonwoven fabric was heated while being held so as not to cause an area change due to heat, and the polyethylene component in the fiber was pressed as an adhesive to adjust the thickness to 47% before the treatment. The basis weight of the obtained nonwoven fabric was 400 g / m2. Next, a terminal aminopropylpolymethylsiloxane having an amino group as a reactive functional group was used, and tetramethylene diisocyanate was used as an organic polyisocyanate, and polypropylene glycol was used as a polyol, and the total of the amino group in the polysiloxane molecule and the hydroxyl group in the polyol molecule was used. The coagulation regulator A was obtained by reacting at a functional group ratio such that the number of groups and the number of isocyanate groups of the isocyanate component were 1: 1. The weight ratio of the polyurethane component to the polysiloxane component in the obtained coagulation control was 1: 1.

DMF of polyurethane consisting of polymethylpentane adipate and polyethylene glycol having an average molecular weight of 2,000 and having a mean molecular weight of 4,4'-diphenylmethane diisocyanate and butanediol
The solution is mixed with the coagulation regulator A and black pigment as additives at a ratio of 3 parts coagulation regulator A and 10 parts black pigment to polyurethane solids, and impregnated with the solution into the fibrous sheet. And wet coagulated with water containing 15% DMF. The obtained fibrous sheet is treated with hot toluene which does not dissolve the island component in the fiber but can dissolve the sea component, extracts and removes the polyethylene component in the fiber, and has a basis weight of 450 g / m ² and a thickness of 1. A base layer having a thickness of 3 mm and a polyurethane / fiber ratio of 55/45 was obtained. The fineness of the monofilament of the obtained ultrafine nylon fibers of the fibrous base is 0.1.
It was 06 denier and had a soft texture.
Thereafter, a 15 micron thick film of a polyester-based polyurethane was bonded to one surface of the fibrous sheet with a polyurethane-based adhesive. The leather-like sheet was measured at 90 ° C. for 10 days to promote the cloudiness, and no change in gloss was observed.

Example 2 Using the fibrous nonwoven fabric used in Example 1, terminal alcohol propyl polymethylsiloxane having an alcohol group as a reactive organic functional group of the polysiloxane main chain, tetramethylene diisocyanate as an organic polyisocyanate, Using a polypropylene glycol as the polyol, the coagulation regulator B is reacted by reacting the total number of amino groups in the polysiloxane molecule and the hydroxyl group in the polyol with the isocyanate group of the isocyanate component at a functional group ratio of 1: 1. Obtained. To the nonwoven fabric, a DMF solution of polyurethane (polyurethane composed of polymethylpentane adipate and polyethylene glycol having an average molecular weight of 2000 and composed of 4,4'-diphenylmethane diisocyanate and butanediol) was added with a coagulation regulator B at a solid content of 100 parts of polyurethane. On the other hand, a solution was prepared by adding 3 parts of the black pigment and 10 parts of the black pigment to 100 parts of the polyurethane solid content. The obtained polyurethane solution was impregnated into a fiber nonwoven fabric, coagulated in the same coagulation bath as in Example 1, and the polyethylene constituting the fiber was removed with hot toluene. A polyurethane is applied to the surface of the fibrous base material by a gravure method, and 180
The surface was heat-treated at ℃ to obtain a leather-like sheet having a silver surface layer on the surface. This leather-like sheet is 90
The change with time of the surface was measured at a temperature of 10 ° C. for 10 days, but no change in gloss was observed.

Comparative Example 1 Polyurethane (a polymer diol having an average molecular weight of 2,000 and consisting of polymethylpentane adipate and polyethylene glycol having a molecular weight of 2,000, 4, 4 ') was added to the nonwoven fabric obtained in Example 1.
A polyurethane-based DMF solution consisting of diphenylmethane diisocyanate and butanediol is mixed with a silicone-based coagulation regulator containing a polysiloxane component and a black pigment, and the mixture is charged into a mixed solution of DMF / water = 15/85 at 35 ° C. to obtain a polyurethane. Was coagulated. Example 1 with surface
A polyurethane film was adhered to the surface in the same manner as described above, and gravure and calendering were performed for polishing, and the surface condition was observed at 90 ° C. for occurrence of cloudiness. Result 3
After a day, the surface became whitish, and when the surface was wiped with a cloth and confirmed, a difference in glossiness was clearly observed between the wiped portion and the unwiped portion, and clouding due to migration was confirmed.

Comparative Example 2 Polyurethane (a polymer diol having an average molecular weight of 2,000 consisting of polymethylpentane adipate and polyethylene glycol, 4, 4 ′) was added to the nonwoven fabric obtained in Example 1.
-Dimethylformamide of polyurethane comprising diphenylmethane diisocyanate and butanediol)
(Hereinafter referred to as DMF) solution, and only a black pigment was mixed.
The mixture was poured into a mixed solution of MF / water = 15/85 to coagulate the polyurethane. The texture of the obtained sheet is harder than that of the natural leather and the sheet obtained in Example 1, and the surface has dents of about 1 mm in diameter in some places, resulting in poor surface appearance and poor evaluation as a leather-like sheet. became.

Claims (2)

[Claims] 1. A leather-like sheet having a substrate layer composed of a nonwoven fabric and a porous polyurethane, and having a silver surface layer on at least one surface, wherein the porous polyurethane is mixed with a urethane-modified silicone polymer. A leather-like sheet made of polyurethane. 2. A method for producing a leather-like sheet in which a base material layer is composed of a nonwoven fabric and a porous polyurethane and has a silver surface layer on at least one side, wherein a silicon polymer in which a part of a main chain or a side chain is polyurethaneized. A method for producing a leather-like sheet, comprising impregnating a nonwoven fabric with a solution of a polyurethane containing, and then wet-solidifying the solution.