JP6433423B2 - Synthetic leather - Google Patents

Description

  The present invention relates to synthetic leather.

  Conventionally, highly durable synthetic leather has been used as a vehicle seat or furniture seat. For high durability synthetic leather, a polyurethane resin material containing polyol, isocyanate, chain extender and solvent is coated on a releasable carrier such as release paper, and then heated as necessary to evaporate the solvent in the resin material. In addition, a cross-linking reaction of the resin is caused to form a skin layer, and if necessary, an intermediate layer of polyurethane resin is formed. Further, an adhesive layer and a raw cloth are sequentially laminated, and then the adhesive is cured by heating. It is generally manufactured by a dry method in which a raw cloth and a polyurethane resin layer such as a skin layer or an intermediate layer are integrated (Patent Document 1).

JP2011-236284-A

The skin layer and the intermediate layer of the highly durable synthetic leather are composed of a one-pack type or two-pack type polyurethane resin. When high durability is particularly required, a polycarbonate urethane resin is used for the skin layer. On the other hand, in order to obtain the appearance, texture (texture), abrasion resistance, and peel strength required for vehicle seats and furniture seats, the conventional fabric weight is 200 g / m ² or more as a raw fabric of high durability synthetic leather. Knitted fabric, woven fabric, non-woven fabric, etc. are used.

In recent years, for the purpose of improving the fuel efficiency of a vehicle, weight reduction of each part has been studied in gram units, and the weight reduction of vehicle interior materials such as high durability synthetic leather is being demanded. In conventional high-durability synthetic leather, raw fabric occupies 60 to 80% of the weight of synthetic leather. Therefore, the use of raw fabric with a basis weight of less than 200 g / m ² can easily achieve the purpose of weight reduction. At the same time, the cost can be reduced. However, synthetic leather manufactured by a dry method using a lighter weight fabric than the conventional one having a basis weight of less than 200 g / m ² has a problem that it is difficult to obtain a texture due to thinness and wear resistance is also reduced. there were. Further, if it is attempted to compensate for the deterioration of the texture by increasing the thickness of the polyurethane resin layer, there is a problem that the texture of the synthetic leather becomes hard and the purpose of reducing the weight cannot be achieved. Furthermore, in the conventional synthetic leather, the adhesive layer is formed by a two-component urethane adhesive containing polyol and isocyanate. In order to cure after applying the urethane adhesive and pasting it together with the raw cloth In addition, since curing at 50 ° C. for about 48 hours is required, the production efficiency of synthetic leather is low and the production cost is high.

As a result of earnest research to solve the above problems, the present inventors have used a specific urethane-based adhesive, and even if a lightweight raw cloth with a basis weight of less than 200 g / m ² is used, it is equivalent to the conventional one. To find out that it has appearance, texture (texture), abrasion resistance, peel strength, and requires only a very short time for bonding to a green fabric, which can greatly improve the production efficiency of synthetic leather. It came.

That is, the present invention
(1) Synthetic leather formed by laminating a polyurethane resin layer on a raw cloth through an adhesive layer, and the raw cloth has a basis weight of less than 200 g / m ² , and the adhesive layer has a terminal isocyanate group blocking agent. A urethane adhesive containing a blocked urethane prepolymer, an amine-based cross-linking agent, and heat-expandable fine particles is heated to foam the heat-expandable fine particles, and the urethane prepolymer and the amine-based cross-linking agent are subjected to a cross-linking reaction. Synthetic leather comprising a formed polyurethane resin containing foamed thermally expandable fine particles,
(2) The synthetic leather according to (1), wherein the urethane prepolymer that undergoes a crosslinking reaction with the amine-based crosslinking agent is a urethane prepolymer that has been deblocked by the heating .
(3) The synthetic leather according to (1), wherein the content of thermally expandable fine particles in the urethane-based adhesive (ratio in the adhesive component excluding the solvent) is 1.5 to 5% by weight,
(4) The synthetic leather according to (1), wherein the amine-based crosslinking agent is an aliphatic diamine, an aliphatic triamine, or a mixture of an aliphatic diamine and an aliphatic triamine,
Is a summary.

  The synthetic leather of the present invention is lightweight but excellent in appearance, texture (texture), abrasion resistance, and peel strength, and has high durability that can be used as a vehicle seat, a furniture seat, and the like. In addition, the synthetic leather of the present invention can be produced in an extremely short time as compared with conventional synthetic leather, and has high production efficiency, so that the production cost can be reduced.

It is a longitudinal cross-sectional view which shows one embodiment of the synthetic leather of this invention. It is a longitudinal cross-sectional view which shows the different embodiment of the synthetic leather of this invention. It is a longitudinal cross-sectional view which shows an example of the method of manufacturing the synthetic leather of this invention. 2 is an electron micrograph of a cross section of the synthetic leather of Example 2. FIG. 4 is an electron micrograph of a cross section of a synthetic leather of Comparative Example 2. 4 is an electron micrograph of a cross section of a synthetic leather of Comparative Example 3. 6 is an electron micrograph of a cross section of a synthetic leather of Comparative Example 4.

  In the synthetic leather 1 of the present invention shown in FIG. 1, a raw cloth 2 and a skin layer 3 which is a polyurethane resin layer are laminated and integrated through an adhesive layer 4, and a surface treatment layer 5 is provided on the surface of the skin layer 3. It is provided and configured. The adhesive layer 4 contains foamed thermally expandable fine particles 7.

The raw fabric 2 includes synthetic fibers such as polyester, polyamide and polyacrylonitrile, natural fibers such as cotton and hemp, knitted fabrics, woven fabrics and non-woven fabrics made of recycled fibers such as rayon, suf and acetate alone or a mixed fiber thereof. Any of those conventionally used as a raw fabric for synthetic leather can be used. Among these, those having a basis weight of less than 200 g / m ² are used. The raw cloth 2 may be raised or may not be raised. The raw fabric 2, but preferably has a basis weight of 190 g / ^{m 2} or less, particularly the basis weight is preferably from 100~180g / ^{m 2.} Further, those having a tensile strength of 200 N / 3 cm or more (JIS K6772) and a tear strength of 20 N or more (JIS K6772) are preferable.

  Any polyurethane resin can be used as the polyurethane resin constituting the skin layer 3 as long as it is conventionally used for the skin layer of synthetic leather. Specifically, polyester polyurethane resin, polyether polyurethane resin, polycaprolactone polyurethane resin, polyester / polyether copolymer polyurethane resin, polyamino acid / polyurethane copolymer resin, polycarbonate diol component and non-yellowing diisocyanate component, and Examples thereof include non-yellowing polycarbonate polyurethane resins obtained by reacting low molecular chain extenders and the like. In addition, polyvinyl chloride resin or synthetic rubber may be mixed with the above polyurethane resin as long as various physical properties as synthetic leather are not impaired. The polyurethane resin forming the skin layer is prepared by dissolving a polyol, polyisocyanate, and a crosslinking agent in an organic solvent such as methyl ethyl ketone, toluene, dimethylformamide, or a solvent such as water, and if necessary, a colorant, a filler, It is formed by applying, drying, and crosslinking a polyurethane resin solution to which various additives such as a light stabilizer, an ultraviolet absorber, an antioxidant, a flame retardant, and a crosslinking agent are added. The polyurethane resin solution can be either a one-component type or a two-component type. The skin layer 3 is preferably formed to a thickness of 10 to 60 μm, more preferably 20 to 50 μm. A drawing pattern or the like may be provided on the surface of the skin layer 3.

  The synthetic leather 1 of the present invention is provided with an intermediate layer 6 between the skin layer 3 and the adhesive layer 4 as shown in FIG. The layer 3 and the intermediate layer 6 may be used. As the polyurethane resin constituting the intermediate layer 6, the same polyurethane resin as that constituting the skin layer 3 can be used. The intermediate layer 6 may have a foam structure. The thickness of the intermediate layer 6 is preferably 10 to 100 μm for the non-foamed structure and 50 to 1000 μm for the foamed structure. The intermediate layer 6 is not limited to one layer, and two or more layers can be provided.

  The adhesive layer 4 for bonding the polyurethane resin layer such as the skin layer 3 and the intermediate layer 6 and the raw cloth 2 is composed of a urethane prepolymer in which a terminal isocyanate group is blocked with a blocking agent, an amine-based crosslinking agent, and a thermal expansion property. The urethane adhesive containing fine particles is heated to foam the thermally expandable fine particles, and is formed by a polyurethane resin containing foamed thermally expandable fine particles, which is obtained by crosslinking the urethane prepolymer and the amine crosslinking agent. Yes. Examples of the urethane prepolymer in which the terminal isocyanate group used in the urethane adhesive is blocked with a blocking agent include aliphatic diol and phosgene, diallyl carbonate, or the like, as described in JP-A-2006-70059. What blocked the terminal isocyanate group of the urethane prepolymer obtained from the polycarbonate diol liquid at 25 degreeC which is a reaction material with a cyclic carbonate, and organic diisocyanate with the blocking agent is mentioned. As the aliphatic diol, those conventionally used as polyurethane raw materials can be used, for example, polyols such as ethylene glycol, propylene glycol, butylene glycol, and dicarboxylic acids such as succinic acid, maleic acid, and adipic acid. Polyester diol which is a dehydration condensate of the above; polyether diol which is ethylene oxide, propylene oxide, butylene oxide alone or two or more kinds of ring-opening polymers.

  As the organic diisocyanate, conventionally known polyurethane raw materials can be used, and are not particularly limited. For example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate. 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 3,3′-dimethyl-4,4′-biphenylene diisocyanate, 3,3′-dimethoxy-4,4′-biphenylene diisocyanate, 3,3 '-Dichloro-4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate Tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, 1,3-bis (isocyanatomethyl) -cyclohexane 1,4-bis (isocyanatomethyl) -cyclohexane, hydrogenated xylylene diisocyanate, isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, 2-isocyanatocyclohexyl-2′-isocyanatocyclohexylmethane, 4-isocyanato Cyclohexyl-2′-isocyanatocyclohexylmethane, 3,3′-dimethyl-4,4′-dicyclohexylmethane diisocyanate, , 5-bicyclo [2,2,1] heptanebis (isocyanatomethyl), 2,6-bicyclo [2,2,1] heptanebis (isocyanatomethyl), etc., and these may be used alone or in combination of two or more. can do.

  Examples of the blocking agent for blocking the terminal isocyanate group of the urethane prepolymer obtained by reacting polycarbonate diol and organic diisocyanate so that the terminal is an isocyanate group include ketoximes, lactams, phenols, pyrazoles, and active methylene compounds. Examples thereof include ketoximes and lactams that can easily block isocyanate groups and can be deblocked at 120 to 180 ° C. The ketoximes include methyl ethyl ketoxime, cyclohexanone oxime, acetone oxime, 3-methyl-2-butanone oxime, 2-pentanone oxime, 3-pentanone oxime, 4-methyl-2-pentanone oxime, 2-heptanone oxime, 3 -Heptanone oxime and acetophenone oxime are preferable, and as a lactam, (epsilon) -caprolactam is preferable.

  The urethane-based adhesive for constituting the adhesive layer 4 contains an amine-based crosslinking agent and thermally expandable fine particles together with the urethane prepolymer whose terminal isocyanate group is blocked with the blocking agent. Aliphatic polyamines are used as amine-based crosslinking agents, such as ethylenediamine, 1,2-propanediamine, 1,3-propylenediamine, 1,6-hexamethylenediamine, piperazine, 2-methylpiperazine, 2,5-dimethyl. Piperazine, N, N′-diaminopiperazine, isophoronediamine, 4,4′-diaminocyclohexylmethane, 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane, 1,2-cyclohexanediamine, 1,4- Cyclohexanediamine, aminoethylethanolamine, aminopropylethanolamine, aminohexylethanolamine, aminoethylpropanolamine, aminopropylpropanolamine, aminohexylpropanolamine, 2,5-bis (aminomethyl) bis (B) Aliphatic diamines such as [2,2,1] heptane and 2,6-bis (aminomethyl) bicyclo [2,2,1] heptane; Aliphatic triamines such as diethylenetriamine and dipropylenetriamine; Triethylenetetramine and hydrazine And acid hydrazides. Among these, 4,4′-diaminocyclohexylmethane, 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane, isophoronediamine, 2,5-bis (aminomethyl) bicyclo [2,2,1] Preferred are aliphatic diamines such as heptane and 2,6-bis (aminomethyl) bicyclo [2,2,1] heptane, aliphatic triamines such as diethylenetriamine and dipropylenetriamine, and triethylenetetramine. Group triamines and mixtures thereof are preferred. The ratio between the blocked isocyanate group of the urethane prepolymer blocked with the isocyanate group and the amine crosslinking agent is a molar ratio, blocked isocyanate group: amine crosslinking agent = 1.35: 1.00 to 0.00. 95: 1.00 is preferable, and 1.25: 1.00 to 1.00: 1.00 is particularly preferable.

  Examples of the heat-expandable fine particles contained in the urethane-based adhesive include microcapsules in which liquid low-boiling hydrocarbons that are vaporized by heating are wrapped with a thermoplastic resin film such as acrylonitrile-based resin. The amount of thermally expandable fine particles added to the urethane-based adhesive (ratio in the adhesive component excluding the solvent) is usually 0.5 to 10% by weight, more preferably 1.5 to 5% by weight. The particle size of the microcapsules and the difference in the thermal expansion coefficient of the thermally expandable fine particles are adjusted. For example, when the particle size is about 30 μm and the coefficient of thermal expansion is about 7 times, 0.8 to 7% by weight is preferable, but if it is less than 1.5% by weight, it is difficult to obtain a sufficient product thickness and exceeds 5% by weight. Therefore, it is difficult to obtain sufficient peel strength, so the addition amount is more preferably 1.5 to 5% by weight. The thermally expandable fine particles preferably have a maximum expansion temperature of 120 to 180 ° C. If the maximum expansion temperature is less than 120 ° C, foaming may occur due to heat during preliminary drying when applying and drying the urethane-based adhesive, and if it exceeds 180 ° C, There is a possibility that damage such as shrinkage may be caused to the urethane resin or raw cloth by heat. As the thermally expandable fine particles, for example, Matsumoto Microsphere (trade name) manufactured by Matsumoto Yushi Seiyaku Co., Ltd. can be used. As the thermally expandable fine particles having a maximum expansion temperature of 120 to 180 ° C., F-30, F36LV, F-36, F-48, F-50, F78K, F-79, F-80S, F-82, F-100, F-102, F-105, F-170, FN-100MD (all Matsumoto Microsphere product number).

  The surface treatment layer 5 is provided on the surface of the skin layer 3 as necessary for the purpose of polishing the surface of the skin layer 3 or the like. The surface treatment layer can be provided, for example, by coating the surface of the skin layer 3 with a coating liquid in which polyurethane resin, silicon, organic filler, or the like is dispersed in an organic solvent or water.

  Next, the method for producing the synthetic leather of the present invention shown in FIG. 1 will be described with reference to FIG. As shown in FIG. 3 (a), first, a polyurethane resin solution for constituting the skin layer is applied on the releasable carrier 8 such as a release paper, and the solvent in the applied polyurethane resin solution is evaporated and dried. The skin layer 3 is formed by causing a crosslinking reaction of the resin. For the application of the polyurethane resin solution, a knife coater, a comma doctor, a roll coater, a reverse roll coater, a rotary screen coater, a gravure coater, and other appropriate means are employed. The releasable carrier 8 such as release paper may have a smooth surface on the side on which the polyurethane resin solution is applied, or may have a drawn pattern or the like. When the releasable carrier 8 with a drawn pattern or the like is used, the pattern of the releasable carrier 8 is transferred to the surface of the outer skin layer 3 of the synthetic leather 1 to obtain a synthetic leather in which a design by the drawn pattern or the like appears. Can do.

  Next, as shown in FIG. 3B, an adhesive for forming an adhesive layer is applied on the skin layer 3. For the application of the adhesive, a method similar to the application of the polyurethane resin solution for forming the skin layer can be employed. The application amount of the adhesive varies depending on the texture of the target synthetic leather, but it is preferable to apply the adhesive so that the thickness at the time of application (wet time) is 100 to 300 μm. The applied adhesive is dried at a temperature at which the blocking agent in the urethane prepolymer in which the terminal isocyanate group is blocked with the blocking agent is not dissociated, and is preferably dried at 120 ° C. or less to form the adhesive layer 4a.

  Next, as shown in FIG. 3 (c), after the green cloth 2 is laminated on the adhesive layer 4a, the heat-expandable fine particles in the adhesive layer 4a are foamed by heating and the isocyanate group is blocked. The prepolymer is deblocked to crosslink the urethane prepolymer and the amine-based crosslinking agent, thereby forming the adhesive layer 4 including the foamed thermally expandable fine particles 7 as shown in FIG. The heating temperature after laminating the raw cloth 2 varies depending on the type of blocking agent that blocks the terminal isocyanate group of the urethane prepolymer, the type of thermally expandable fine particles, etc., but the maximum expansion temperature is 120 to 180 ° C. Select expandable fine particles and select a urethane prepolymer that is blocked so that the deblocking of the urethane prepolymer occurs at 120 to 180 ° C. and the reaction between the urethane prepolymer and the amine-based crosslinking agent occurs. Heating at ~ 180 ° C is preferred. The heating time is preferably 1 to 5 minutes.

  Thereafter, the releasable carrier 8 is peeled off, and the surface treatment layer 5 is provided on the surface of the skin layer 3 as necessary, whereby the synthetic leather 1 shown in FIG. 1 can be obtained. The surface treatment layer 5 can be formed by a method such as a gravure coater, a reverse roll coater, or a spray coater. In the case of the synthetic leather 1 shown in FIG. 2 having the intermediate layer 6, the intermediate layer 6 is formed by the same method as that for the skin layer 3 after forming the skin layer 3 and before forming the adhesive layer 4 a. It can be manufactured in the same manner as the method shown in FIG.

  Hereinafter, the present invention will be described in more detail with reference to specific examples.

Example 1
(Skin layer)
20 parts by weight each of dimethylformamide and methyl ethyl ketone as a solvent with respect to 100 parts by weight of one-component non-yellowing polycarbonate polyurethane resin (manufactured by DIC Corporation: trade name “Crisbon NY328FTR”, solid content 20% by weight), black pigment (Dic Co., Ltd .: trade name “Dilack L-1770”) After adding 20 parts by weight, the mixture is stirred and mixed on the uneven surface of the release paper (Dai Nippon Printing Co., Ltd .: trade name “DE-73”). Then, it was applied so that the thickness after drying was 25 ± 5 μm, and dried in an oven at 100 ° C. for 3 minutes to form a skin layer having a thickness of 30 μm.

(Adhesive layer)
Aliphatic diamine (manufactured by BASF: trade name “Lalomin C260”) as a crosslinking agent with respect to 100 parts by weight of urethane prepolymer whose terminal isocyanate group is blocked with ketoxime (manufactured by DIC Corporation: trade name “Urehyper SU-009”). ”) 5 parts by weight, thermal expansion microcapsules having a maximum expansion temperature of 160 to 180 ° C., an average particle size of 30 μm, and an expansion coefficient of about 7 times (manufactured by Matsumoto Yushi Seiyaku Co., Ltd .: trade name“ Matsumoto Microsphere ”) FN-100MD ") 1 part by weight, an adhesive containing 15 parts by weight of dimethylformamide as a solvent was applied onto the skin layer so as to have a thickness of 170 µm (when wet), and dried in an oven at 120 ° C for 2 minutes. A thermally expandable microcapsule formed an unfoamed adhesive layer.

(Lamination with raw cloth)
On the adhesive layer, a single-sided knitted fabric with a thickness of 550 μm and a basis weight of 120 g / m ² is laminated and bonded as a raw fabric, and then heated in an oven at 180 ° C. for 2 minutes to foam the thermally expandable microcapsules. The skin layer and the knitted fabric were joined and integrated through an adhesive layer in which the urethane prepolymer and the crosslinking agent were reaction-cured. Thereafter, the release paper was peeled off to obtain a synthetic leather. Table 1 shows the physical properties of the obtained synthetic leather. The thickness of the adhesive layer made of a polyurethane resin containing the foamed thermally expandable microcapsules was 170 μm.

Example 2
A synthetic leather was obtained in the same manner as in Example 1 except that the thermally expandable microcapsule in the adhesive was 3 parts by weight, and the adhesive was applied on the skin layer so as to be 170 μm (wet). Table 1 shows the physical properties of the obtained synthetic leather. Moreover, the electron micrograph (JEOL Co., Ltd. scanning electron microscope: JSM6700F, magnification 30 times) of this synthetic leather cross section is shown in FIG. The thickness of the adhesive layer made of a polyurethane resin containing the foamed thermally expandable microcapsules was 320 μm.

Example 3
A synthetic leather was obtained in the same manner as in Example 1 except that the thermally expandable microcapsule in the adhesive was 5 parts by weight, and the adhesive was applied onto the skin layer so as to be 170 μm (when wet). Table 1 shows the physical properties of the obtained synthetic leather. The thickness of the adhesive layer made of a polyurethane resin containing the foamed thermally expandable microcapsules was 470 μm.

Example 4
A synthetic leather was obtained in the same manner as in Example 1 except that the heat-expandable microcapsule in the adhesive was 7 parts by weight and the adhesive was applied on the skin layer so that the thickness was 170 μm (wet). Table 1 shows the physical properties of the obtained synthetic leather. The thickness of the adhesive layer made of a polyurethane resin containing the foamed thermally expandable microcapsules was 720 μm.

Example 5
170 μm (wet) on the skin layer using an adhesive with 3 parts by weight of thermally expandable microcapsules and 5.54 parts by weight of aliphatic triamine (manufactured by BASF: trade name “Baxodur EC310”) as a crosslinking agent Synthetic leather was obtained in the same manner as in Example 1 except that the coating was applied in the same manner as in Example 1. Table 1 shows the physical properties of the obtained synthetic leather. The thickness of the adhesive layer made of a polyurethane resin containing the foamed thermally expandable microcapsules was 320 μm.

Example 6
3 parts by weight of thermally expandable microcapsules, and 2.25 parts by weight of aliphatic diamine (manufactured by BASF: trade name “Laromin C260”) and aliphatic triamine (manufactured by BASF: trade name “Baxodur EC310” as a crosslinking agent) ) Synthetic leather was obtained in the same manner as in Example 1 except that 2.77 parts by weight of the adhesive was applied onto the skin layer so as to be 170 μm (when wet). Table 1 shows the physical properties of the obtained synthetic leather. The thickness of the adhesive layer made of a polyurethane resin containing the foamed thermally expandable microcapsules was 320 μm.

Comparative Example 1
A synthetic leather was obtained in the same manner as in Example 1 except that an adhesive not containing heat-expandable microcapsules was used and the adhesive was applied on the skin layer so as to have a thickness of 170 μm (when wet). Table 1 shows the physical properties of the obtained synthetic leather. The thickness of the adhesive layer was 90 μm.

Comparative Example 2
Instead of 1 part by weight of thermally expandable microcapsules, 4 parts by weight of azodicarbonamide powder (manufactured by Eiwa Kasei Co., Ltd .: trade name “Vinole DW # 6”) as a foaming agent and urea powder (Yewa Kasei Co., Ltd.) as a foaming aid Company: Trade name “Cell Paste 101”) 4 parts by weight of adhesive was used, and the adhesive was applied onto the skin layer to a thickness of 170 μm (when wet) in the same manner as in Example 1. Synthetic leather was obtained. Table 1 shows the physical properties of the obtained synthetic leather. Moreover, the electron micrograph (30 times) of this synthetic leather is shown in FIG. The thickness of the adhesive layer was 160 μm.

Comparative Example 3
Instead of 1 part by weight of thermally expandable microcapsules, an adhesive containing 5 parts by weight of 4,4-oxybis (benzenesulfonylhydrazide) powder (manufactured by Eiwa Chemical Co., Ltd .: trade name “Neoselbon N # 5000”) as a foaming agent is used. A synthetic leather was obtained in the same manner as in Example 1 except that it was applied to the outer skin layer so as to have a thickness of 170 μm (when wet). Table 1 shows the physical properties of the obtained synthetic leather. Moreover, the electron micrograph (30 times) of this synthetic leather is shown in FIG. The thickness of the adhesive layer was 270 μm.

Comparative Example 4
In place of the adhesive of Example 1, 100 parts by weight of a non-yellowing polyurethane resin (manufactured by DIC Corporation: trade name “Chrisbon TA205FT”), a trimethylolpropane addition product of tolylene diisocyanate as a crosslinking agent (Nippon Polyurethane) Kogyo Co., Ltd .: trade name “Coronate L”) 15 parts by weight, 3 parts by weight of thermally expandable microcapsules (Matsumoto Microsphere FN-100MD) as in Example 1, 20 parts each of dimethylformamide and methyl ethyl ketone as solvents. Except that it was applied to the outer skin layer to a thickness of 170 μm (wet) using an adhesive mixed with 5 parts by weight of an amine catalyst (manufactured by DIC Corporation: trade name “Accel HM”). A synthetic leather was produced in the same manner as in Example 1. However, after applying the raw cloth to the adhesive layer, it was necessary to cure at 50 ° C. for 48 hours until the raw cloth and the skin layer were reliably integrated. Table 1 shows the physical properties of the obtained synthetic leather. Moreover, the electron micrograph (30 times) of this synthetic leather is shown in FIG. The thickness of the adhesive layer made of a polyurethane resin containing the foamed thermally expandable microcapsules was 320 μm.

* 1
The adhesive layer foamed state was taken with a scanning electron microscope (manufactured by JEOL Ltd .: JSM6700F, magnification 150 times, width 800 μm × length 600 μm) with a cross section of the obtained synthetic leather (5 points selected arbitrarily). The cell size (longest side) of each heat-expanded microcapsule in the adhesive layer was measured, and the average cell size was calculated. And it evaluated on the following references | standards from the average of cell size and the state of a cell bubble.
(Circle): The average of cell size is 70-150 micrometers, and the state of a cell bubble is a closed cell.
X: The average cell size is out of the range of 70 to 150 μm, or the cell bubble state is not a closed cell.

* 2
The appearance of the synthetic leather was evaluated based on the following criteria by visually observing the state of wrinkles generated when the surface of the synthetic leather was picked with a finger.
○: Wrinkles close to real leather.
X: It has wrinkles (floating wrinkles) different from the main skin.

* 3
The texture of the synthetic leather was evaluated according to the following criteria from the softness and volume when touching the surface of the synthetic leather.
○: Soft and voluminous.
Δ: Slightly hard or slightly inferior in volume.
X: Hard or inferior in volume.

* 4
The abrasion resistance was evaluated according to the following criteria by performing a taper abrasion test in accordance with JIS K6902 and measuring the number of rotations of the worn wheel until the skin layer of the synthetic leather was worn and the lower layer was exposed.
A: The number of rotations of the wear wheel until the lower layer is exposed is 5000 times or more.
(Triangle | delta): The rotation speed of the wear ring until a lower layer is exposed is 2000 times or more and less than 5000 times.
X: The number of rotations of the wear wheel until the lower layer is exposed is less than 2000 times.

* 5
The peel strength was evaluated based on the following criteria by measuring the peel strength based on the method of JIS K6772 peel test.
○: 30 N / 3 cm or more.
Δ: 20 N / 3 cm or more and less than 30 N / 3 cm.
X: Less than 20 N / 3 cm.

Claims (4)

A synthetic leather formed by laminating a polyurethane resin layer with an adhesive layer on a raw cloth, and the raw cloth has a basis weight of less than 200 g / m ² , and the adhesive layer has a terminal isocyanate group blocked with a blocking agent. A urethane adhesive containing a urethane prepolymer, an amine-based crosslinking agent, and thermally expandable fine particles is heated to foam the thermally expandable fine particles, and the urethane prepolymer and the amine-based crosslinking agent are subjected to a crosslinking reaction. A synthetic leather comprising a polyurethane resin containing foamed thermally expandable fine particles. The synthetic leather according to claim 1, wherein the urethane prepolymer that undergoes a crosslinking reaction with the amine-based crosslinking agent is a urethane prepolymer that is deblocked by the heating .   The synthetic leather according to claim 1, wherein the content of the heat-expandable fine particles in the urethane-based adhesive (ratio in the adhesive component excluding the solvent) is 1.5 to 5% by weight.   The synthetic leather according to claim 1, wherein the amine-based crosslinking agent is an aliphatic diamine, an aliphatic triamine, or a mixture of an aliphatic diamine and an aliphatic triamine.