JP2007169819A - Method for producing solvent-free synthetic leather - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a post-embossable synthetic leather adapted to regulation such as environmental problems, sick house syndrome, etc., usable for vehicles, furniture, etc., and having high durability by using a composition obtained in the absence of a solvent without using an organic solvent or water as a diluent at normal temperature. <P>SOLUTION: The post-embossable synthetic leather having the high durability is obtained as follows. A mixture (A) composed of a polycarbonate diol which is a liquid at normal temperature and a single-chain alkylene glycol that is a liquid at normal temperature, an MDI compound (B) which is a liquid at normal temperature and an amine catalyst (C) are used and the mixing ratio of the mixture (A) to the MDI compound (B) is regulated to 0.8-1.2 mol of isocyanate groups in the MDI compound (B) to 1 mol of hydroxy groups in the mixture (A). Uniform mixing is carried out at normal temperature with an instantaneous mixer and the resultant mixture is then cast onto mold release paper, heated and then laminated onto a base fabric. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  This invention is capable of post-embossing by casting a composition obtained without solvent at room temperature without using an organic solvent or water as a diluent and casting it on a release paper and then bonding the base fabric. The present invention relates to a method for producing a highly durable synthetic leather.

Synthetic leather is obtained by laminating polyurethane resin on a base fabric made of woven fabric or knitted fabric on a release paper. As a general manufacturing method,
(1) An organic solvent solution of a polyurethane resin is cast on a release paper as a releasable base material, and is heated and dried to evaporate the organic solvent contained therein. A dry laminating method obtained by bonding together.
(2) A direct coating method obtained by directly coating a base fabric with an organic solvent solution of a polyurethane resin and drying by heating.
(3) A polyurethane resin solution dissolved in dimethylformamide is directly coated or impregnated on a base fabric, and then immersed in a coagulation bath containing water as a main component to coagulate the polyurethane resin, resulting in a wet coagulation obtained as a porous layer Law.
Etc.

  However, as a result of recent environmental problems, regulations due to sick house syndrome, etc., the use of organic solvents has been socially restricted, and even in the production of synthetic leather, those containing no organic solvent are desired.

  As countermeasures, water-based and solvent-free are polarized. Water-based types lack coating uniformity on release paper, and require a large amount of heat during drying compared to organic solvent-based types. In terms of physical properties, water resistance, hydrolysis resistance and the like are insufficient.

  As for solvent-free, simply removing the polyurethane resin solution consisting of organic solvent that has been used in the past makes the viscosity high due to its very high degree of polymerization, and uniform coating on release paper is possible. There was a problem that it became impossible. Further, when the degree of polymerization is reduced to a level at which coating is possible, there is a problem that the strength and durability of the obtained film are insufficient.

  About solvent-free, in order to solve the above-mentioned problems, (A) component in which a semi-solid or solid isocyanate group-containing urethane prepolymer at room temperature is dissolved by heating at 60 to 250 ° C. can react with these ( A polyol component exhibiting crystallinity is added to a method of producing a polyurethane porous body by mixing the component (B) (Patent Documents 1 and 2) or a composition comprising the polyol component (A) and the polyisocyanate component (B). A solventless adhesive composition (Patent Document 3) that improves the adhesive strength by containing a certain amount has been proposed.

  In addition, a composition comprising a block urethane prepolymer obtained by reacting an isocyanate group of a terminal isocyanate group-containing prepolymer comprising a polyol and a polyfunctional isocyanate with a blocking agent and a compound having two or more active hydrogens is applied on a substrate. A method for producing a leather-like product (Patent Document 4) has also been proposed, which comprises heating in the range of 100 to 250 ° C. to dissociate the blocking agent and then reacting.

However, the methods described in Patent Documents 1 to 3 above and the composition to be obtained both require that the compounded liquid and the coating head of the coating machine be heated to a certain temperature, and mass production of stable quality is achieved. Have a problem. In addition, the production method described in Patent Document 4 requires a high temperature and time for dissociation of the blocking agent, and has a problem with odor due to the dissociated blocking agent.
JP 2002-249534 A JP 2004-216880 A JP 2002-249745 A JP 2003-73984 A

  The present invention pays attention to the problems of the above-mentioned conventional methods for producing solvent-free synthetic leather, solves these problems, has high durability that can be used for applications such as vehicles, furniture, etc., and rear embossing. The object is to provide synthetic leather that can be processed by different materials and means.

  The invention according to claim 1 comprises a mixture (A) comprising a polycarbonate diol that is liquid at normal temperature and a single-chain alkylene glycol, an MDI compound (B) that is liquid at normal temperature, and an amine catalyst (C). The mixing ratio of the mixture (A) and the liquid MDI compound (B) at normal temperature is 0.8 to 0.8 mol of the isocyanate group in the MDI compound (B) with respect to 1 mol of hydroxyl group in the mixture (A). After 1.2 mol of the mixture (A) and the MDI compound (B) are uniformly mixed at room temperature with an instantaneous mixer, the mixture is cast on a release paper, and the base fabric is heated. It is a method for producing a solventless, highly durable synthetic leather capable of post-embossing.

  The invention according to claim 2 is the invention according to claim 1, wherein the polycarbonate diol which is liquid at room temperature reacts with a liquid polycarbonate diol having a weight average molecular weight of 400 to 4000 and a diisocyanate to form hydroxyl groups at both ends. It consists of a polycarbonate diol containing a urethane bond having a weight average molecular weight of 800 to 7000.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the mixture ratio of polycarbonate diol and alkylene glycol in the mixture (A) consisting of polycarbonate diol and single-chain alkylene glycol which is liquid at normal temperature is These are characterized in that the respective molar fractions are 20:80 to 100: 0.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the MDI compound (B) which is liquid at room temperature is crude MDI, carbodiimidized modified MDI alone or a mixture thereof. It is characterized by that.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the amine catalyst (C) is 1,8-diaza-bicyclo (5,4,0) undecene-7. And a salt of an acid selected from octylic acid, phenol, formic acid, and p-toluenesulfonic acid, and these or a mixture of the mixture (A) and the MDI compound (B) that is liquid at room temperature. It is characterized by containing 20 to 100 ppm with respect to the total weight.

  According to the present invention described in the above claims, a mixture (A) composed of polycarbonate diol and a single-chain alkylene glycol which are liquid at normal temperature, an MDI compound (B) which is liquid at normal temperature, and an amine catalyst (C) are used. Therefore, it is possible to uniformly stir at room temperature without solvent without using an organic solvent or water as a diluent, and the organic solvent currently used for the synthetic leather is also commonly used. Cast the compound obtained from the above (A), (B), (C) onto the release paper, and apply the base fabric after heating. Thus, it is possible to obtain a highly durable synthetic leather that can be embossed and is suitable for applications such as furniture and vehicles.

  Hereinafter, the present invention will be described in detail. First, in order to satisfy the handling property at room temperature and the durability of the obtained synthetic leather in the present invention with a solvent-free urethane resin compound, polycarbonate diol used as a main material and a single chain alkylene are used. All of the glycol and the MDI compound must be liquid at room temperature.

  Moreover, generally the temperature in synthetic leather manufacture at the time of using the urethane resin solution which consists of organic solvents is 80-130 degreeC, and heating time is the range for 0.5 to 3 minutes.

  Under such temperature conditions, the mixture (A) of a polycarbonate diol and a single-chain alkylene glycol which are liquid at normal temperature reacts with the MDI compound (B) which is liquid at normal temperature, so that the base fabric can be laminated. In order to increase the molecular weight, an amine-based catalyst (C) is required for promoting the reaction. As this catalyst (C), 1,8-diaza-bicyclo (5,4,0) undecene-7 (hereinafter referred to as “the catalyst”) is used. , Which is abbreviated as DBU) and a salt of various organic acids, the mixture (A) of the polycarbonate diol and the single-chain alkylene glycol which are liquid at normal temperature and the MDI compound (B) which is liquid at normal temperature It is necessary to contain 20 to 100 ppm with respect to the total weight.

  As such a polycarbonate diol which is liquid at room temperature, those having a weight average molecular weight of 400 to 4000 can be used, and the composition is hexylene glycol and butylene glycol, hexylene glycol and 3-methyl-1,5-pentanediol. Polycarbonate diol which is made amorphous by using two or more kinds of glycols as typified by the above can be used.

  Alternatively, these polycarbonate diols which are liquid at room temperature are reacted with diisocyanates typified by hexamethylene diisocyanate and tolylene diisocyanate in a molar ratio of 2: 1 or 3: 2 so that a urethane bond is contained in the molecule, And the polycarbonate diol made into the reaction thing of the weight average molecular weight which has a hydroxyl group in both ends is 800-7000, Preferably 1000-5000 can also be used.

  As described above, a polycarbonate diol which is liquid at room temperature and contains hydroxyl groups at both ends by reacting with urethane bonds in the molecule is compared with a polycarbonate diol which is liquid at room temperature synthesized only with carbonate bonds. Therefore, it tends to be excellent in chemical resistance, solvent resistance, and rebound resilience of the film, and is particularly useful for synthetic leather in vehicles and furniture. Further, when the weight average molecular weight is less than 800, the polycarbonate diol containing a urethane bond in the molecule by reacting is insufficient in chemical resistance, solvent resistance, and the impact resilience of the film. When it is larger than 7000, the liquid state of the obtained polycarbonate diol at normal temperature is not stable, which causes trouble.

  As the single-chain alkylene glycol that is liquid at room temperature, ethylene glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, diethylene glycol, and the like can be used.

  The ratio of the polycarbonate diol that is liquid at normal temperature and the single-chain alkylene glycol is 20:80 to 100: 0, preferably 30:70 to 100: 0, in each molar fraction. This is because when the polycarbonate diol that is liquid at room temperature is 20% or less, the texture of the resultant synthetic leather becomes hard and a problem arises in flexibility.

  Next, as the MDI compound which is liquid at room temperature, a glue MDI, a carbodiimidized modified MDI alone or a mixture thereof can be used. The above-mentioned glue MDI is an isocyanate compound having a functional group number of about 2.8, which is made amorphous by including isomers such as 2,4'-diphenylmethane diisocyanate and dimers in 4,4'-diphenylmethane diisocyanate. It is. Crude refers to a mixture of at least two materials, as described above, rather than crude, ie, a single product.

  The carbodiimidized modified MDI is an isocyanate compound having a functional group number of about 2.0, which is decrystallized by decarboxylating two molecules of 4,4'-diphenylmethane diisocyanate and containing a dimer bonded via a carbodiimide bond. It is.

  These normal liquid MDI compounds (B) are low in vapor pressure, safe to handle, and are almost bifunctional isocyanate compounds. Therefore, the urethane resins obtained are mainly linear polymers, and are suitable for post-embossing. Is also good.

  These MDI compounds (B) which are liquid at normal temperature have a ratio of isocyanate groups of (B) to 1 mol of hydroxyl groups contained in a mixture (A) of polycarbonate diol and single-chain alkylene glycol which are liquid at normal temperature. It is necessary to mix | blend so that it may become 0.8-1.2 mol, desirably 0.9-1.1 mol. When the proportion of the isocyanate group in (B) is lower than 0.8 mol, the polymerization degree of the polyurethane resin obtained by the reaction of (A) and (B) is lowered, and the film strength of the obtained synthetic leather is also Lower. As a result, the durability is inferior. In addition, when the ratio of the isocyanate group in (B) is higher than 1.2 mol, the excess isocyanate group reacts with moisture in the air or moisture contained in the base fabric over time, but the bond formed here Is a urea bond, an allophanate bond or a burette bond, which has a weaker binding force than a urethane bond, and is undesirable in the durability of the resulting synthetic leather. Further, the allophanate bond and burette bond generated at the same time are not desirable because the polyurethane resin is made three-dimensional and the post-embossing suitability is lowered.

  As the amine catalyst (C), a salt composed of DBU and a selected organic acid can be used. These catalysts are used for accelerating the reaction between the mixture (A) of polycarbonate diol and single-chain alkylene glycol which are liquid at normal temperature and the MDI compound (B) which is liquid at normal temperature. The usage-amount is 20-100 ppm (preferably 30-50 ppm) with respect to the total weight of said (A) and (B). This is because when the amount of the catalyst is less than 20 ppm, the reaction promoting effect is insufficient and the reaction cannot be sufficiently performed under the temperature conditions described above, and when more than 100 ppm is used, the above (A), (B), (C) Viscosity after blending rapidly increases and uniform coatability cannot be expected, or after finishing as a synthetic leather product, the remaining amine compound increases, which impedes durability properties such as hydrolysis resistance. Depending on what happens.

  Next, in the present invention, for the purpose of improving the post-embossing suitability, a foam regulating silicone for incorporating foam generated during stirring into the synthetic leather as a foamed cell, and a nonporous synthetic leather skin resin layer are formed. A silicone additive such as defoaming silicone that removes foam generated during stirring for the purpose of mixing with a mixture (A) of a polycarbonate diol that is liquid at normal temperature and a single-chain alkylene glycol, and an MDI compound (B that is liquid at normal temperature) ) To 1000 to 10000 ppm (preferably 3000 to 7000 ppm). This is because when the amount of silicone is less than 1000 ppm, the foam regulating or defoaming effect is not sufficient, and when it is used more than 10,000 ppm, the silicone additive bleeds on the surface of the obtained synthetic leather, which hinders the synthetic leather. Is caused by

  Furthermore, inorganic fillers such as silica, calcium carbonate and talc are used to improve film strength, and oxybisbenzenesulfonyl hydrazide, azodicarbonamide and urea compounds are used to actively produce foamed cells. And pyrolytic organic foaming agents typified by a mixture thereof, microbeads filled with an inert gas, or microballoons that are beaded by heating them.

  Furthermore, in the case where the synthetic leather is obtained by laminating urethane resin twice or three times or more in this invention, the portion that becomes the first skin layer resin and the second interlayer resin is post-embossed. Although it is unsuitable for maintaining suitability, only the adhesive layer resin used for bonding to the base fabric is a liquid trimeric polyisocyanate that is liquid at room temperature for the purpose of improving the adhesion to the base fabric. The MDI compound (B) can also be used in combination.

  In the present invention, as means for uniformly mixing using an instantaneous mixer at room temperature, for example, a two-component automatic metering and mixing device such as Twinflow VR50 / 100 manufactured by Tomita Engineering may be used. Is a mixture of a polycarbonate diol and a single-chain alkylene glycol (A) that is liquid at room temperature, an MDI compound (B) that is liquid at room temperature, and an amine catalyst (C) separately in a coating part having an instantaneous mixing mixer. Each is supplied from a filled tank and can be coated on release paper immediately after uniform mixing. The amine catalyst (C) is previously mixed with (A) or (B), and the mixture of (A) and (C) and (B) or (B) and (C) It is also possible to coat the mixture and (A) on the release paper immediately after mixing them uniformly using an instantaneous mixing mixer comprising two tanks.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by these Examples. All the parts are parts by weight.

  1000 parts of polycarbonate diol which is liquid at room temperature, consisting of hexylene glycol having a weight average molecular weight of 2000 having hydroxyl groups at both ends and 3-methyl-1,5-pentanediol, carbodiimidized modified MDI (manufactured by Nippon Polyurethane Industry Co., Ltd., Millionate MTL , NCO content: 29.0%) 120.2 parts, DBU / phenol salt 0.0336 parts in a room set at 25 ° C., uniformly mixed using an instantaneous mixing mixer, and about 100 μm thick on the release paper It was coated as a skin and adhesive layer resin. Next, after heating at 120 ° C. for 5 minutes, the warp yarn is made of polyester and the weft yarn is made of rayon and bonded using a press roll heated to 120 ° C. and aged at 80 ° C. for 48 hours. Peeling gave a synthetic leather.

  First, 92.7 parts of tolylene diisocyanate are reacted with 950 parts of polycarbonate diol which is liquid at normal temperature and consists of hexylene glycol having a weight average molecular weight of 1000 and butylene glycol having hydroxyl groups at both ends and having hydroxyl groups at both ends. Polycarbonate diol 1032.7 parts at room temperature containing urethane bonds having a weight average molecular weight of 2174 in the molecule, 2.25 parts of 2-methyl-1,3-propanediol, Crude MDI (manufactured by Nippon Polyurethane Industry Co., Ltd., Millionate MR -100, NCO content: 31.25%) 141.1 parts, DBU / octylate 0.0328 parts, antifoam silicone (manufactured by Shin-Etsu Chemical Co., Ltd., KF-96) 5 parts as in Example 1. After mixing with the above method and coating the release paper to a thickness of about 20 μm, Heating to obtain a skin resin layer.

  Next, 87 parts of tolylene diisocyanate are reacted with 1000 parts of polycarbonate diol which is liquid at room temperature and consists of hexylene glycol having a weight average molecular weight of 1000 and butylene glycol having hydroxyl groups at both ends, and a weight having hydroxyl groups at both ends. Polycarbonate diol 1084 parts at room temperature containing urethane bonds with an average molecular weight of 2174 in the molecule, 166.6 parts of Millionate MTL, 0.0933 parts of DBU / phenol salt, foam-stabilized silicone (manufactured by Toray Dow Corning, SH- 194) 5 parts were mixed in the same manner as in Example 1, and laminated as a foamed adhesive layer resin to a thickness of about 150 μm on the previously obtained skin resin layer. After heating at 120 ° C. for 5 minutes, Example In the same manner as in No. 1, it was bonded to a raised cloth to obtain a synthetic leather.

  450 parts of a polycarbonate diol which is liquid at room temperature consisting of hexylene glycol having a hydroxyl group at both ends and a weight-average molecular weight of 3000 and 3-methyl-1,5-pentanediol, 41.3-methyl-1,5-pentanediol Part, 152.1 parts of Millionate MTL and 3 parts of foam regulating silicone (SH-194) were mixed in the same manner as in Example 1, and coated on a release paper to a thickness of about 100 μm, and then at 120 ° C. for 5 minutes. By heating, an outer skin / foaming intermediate resin layer was obtained.

Next, 950 parts of polycarbonate diol composed of hexylene glycol having a weight average molecular weight of 2000 having hydroxyl groups at both ends and butylene glycol at room temperature, 2.25 parts of 2-methyl-1,3-propanediol, crude MDI ( Millionate MR-100) 141.1 parts, DBU / octylate 0.0328 parts, antifoam silicone (KF-96) 5 parts, trimeric polyisocyanate that is liquid at room temperature (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate HX, 50 parts of HDI-based isocyanurate, NCO content: 21.3%) was laminated as an adhesive layer resin to a thickness of about 50 μm on the skin-and-foamed intermediate resin layer obtained in the same manner as in Example 1. A synthetic leather was obtained by laminating with a raised cloth.
(Comparative Example 1)

1000 parts of polycarbonate diol that is liquid at room temperature, consisting of hexylene glycol having a hydroxyl group at both ends and having a weight average molecular weight of 2000 and 3-methyl-1,5-pentanediol, 86.9 parts of Millionate MTL, DBU / phenol salt 0 .0326 parts were mixed in the same manner as in Example 1, coated on release paper to a thickness of about 100 μm as a skin and adhesive layer resin, and then bonded to a raised cloth in the same manner as in Example 1 to produce synthetic leather Got.
(Comparative Example 2)

100 parts of a polycarbonate diol which is composed of hexylene glycol and butylene glycol having a hydroxyl group at both ends and having a weight average molecular weight of 2,000 at room temperature, 40.5 parts of 2-methyl-1,3-propanediol, Millionate MR-100 147. 8 parts and 0.0058 parts of DBU / octylate were mixed in the same manner as in Example 1 and coated on the release paper to a thickness of about 100 μm as a skin and adhesive layer resin. A synthetic leather was obtained by laminating with a blanket.
(Comparative Example 3)

  Example 1 1000 parts of polycarbonate diol, 141.1 parts of Millionate MR-100, and 0.137 parts of DBU / phenol salt, which are composed of hexylene glycol having a weight average molecular weight of 2000 having hydroxyl groups at both ends and butylene glycol at room temperature and liquid at room temperature. 1 and mixed onto the release paper to a thickness of about 100 μm as a skin and adhesive layer resin, and then bonded to a raised cloth in the same manner as in Example 1 to obtain a synthetic leather.

  The synthetic leathers obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to performance tests such as uniform coatability, post-embossing suitability, synthetic leather texture, and hydrolysis resistance. The results are shown in Table 1. The evaluation methods and evaluation criteria for these tests are as follows.

Uniform coatability test: Uniform coatability when mixed in a room set at 25 ° C. using an instantaneous mixing mixer and coated on a release paper to a thickness of about 100 μm as a skin and adhesive layer resin. Was evaluated as follows.
○: Uniform coating has been achieved. X: Coating streaks occurred and uniform coating was not achieved.

Post-embossing suitability test: A copper embossed plate heated to 130 ° C. was pressed onto synthetic leather, cooled to room temperature, gently peeled off the embossed plate, and the embossing suitability of the surface of the synthetic leather was evaluated as follows.
A: The embossed pattern is sufficiently transferred. ○: Embossed pattern is transferred. Δ: Only a part of the embossed pattern is transferred. X: The embossed pattern is not transferred.

Synthetic leather texture evaluation test: Hardness, volume feeling and rebound resilience felt when a synthetic leather was bent were determined as follows.
A: Very good. ○: Good. Δ: Somewhat problematic. ×: Unusable.

Hydrolysis resistance test: The synthetic leather was kept at 70 ° C. under 95% RH for 10 weeks, and then the surface of the synthetic leather was scratched with nails, and the following judgment was made based on the ease of scratching.
○: Not scratched. (Triangle | delta): Although a damage | wound is attached, it does not peel from a base material. X: The coating film is partially peeled from the substrate.
It was determined.

Ethanol resistance test: Ethanol was dropped on the surface of the synthetic leather, covered with a small glass petri dish, and allowed to stand for 24 hours. Thereafter, the surface state of the synthetic leather was determined as follows.
A: No change at all. ○: A trace is left. Δ: Partial change is observed. X: The surface has changed greatly.

From Table 1 above, all the synthetic leathers obtained in this invention showed good results. On the other hand, the synthetic leather obtained in Comparative Example 1 lacked elasticity, and a so-called sag phenomenon occurred, causing problems. The synthetic leather obtained in Comparative Example 2 had a hard texture and poor post-embossing suitability. Further, the synthetic leather obtained in Comparative Example 3 was intensely heated and thickened immediately after uniform mixing, and could not be applied uniformly on the release paper.

Claims (5)

  A mixture (A) composed of a polycarbonate diol and a single-chain alkylene glycol which is liquid at normal temperature, an MDI compound (B) which is liquid at normal temperature, and an amine catalyst (C), and is liquid at the normal temperature and the mixture (A). The mixture ratio of the MDI compound (B) is 0.8 to 1.2 mol of the isocyanate group in the MDI compound (B) with respect to 1 mol of the hydroxyl group in the mixture (A). After the uniform mixing of A) and the MDI compound (B) with an instantaneous mixer at room temperature, the mixture is cast on a release paper and bonded to a base fabric after heating. A process for producing solvent-free, high-durability synthetic leather that can be embossed.   The polycarbonate diol which is liquid at normal temperature comprises a polycarbonate diol containing urethane bonds having a weight average molecular weight of 800 to 7000 having hydroxyl groups at both ends by reacting a liquid polycarbonate diol having a weight average molecular weight of 400 to 4000 and a diisocyanate. Item 2. A method for producing a solventless synthetic leather according to Item 1.   The mixture ratio of polycarbonate diol and alkylene glycol in the mixture (A) composed of polycarbonate diol and single-chain alkylene glycol which is liquid at room temperature is 20:80 to 100: 0 in terms of the respective molar fraction%. Or the manufacturing method of the solvent-free synthetic leather of 2.   The method for producing a solventless synthetic leather according to any one of claims 1 to 3, wherein the MDI compound (B) which is liquid at normal temperature is crude MDI, carbodiimidized modified MDI alone or a mixture thereof. The amine catalyst (C) is a salt of 1,8-diaza-bicyclo (5,4,0) undecene-7 and one kind of acid selected from octylic acid, phenol, formic acid and p-toluenesulfonic acid. And these single or a mixture is contained in 20-100 ppm with respect to the total weight of the said mixture (A) and the said MDI compound (B) liquid at normal temperature, The statement in any one of Claims 1-4 Method for producing solvent-free synthetic leather.