JP4582944B2 - Synthetic leather and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a synthetic leather that is used for clothing, shoes, bags, furniture, and the like and that does not impair the texture of a fibrous base material, and a method for producing the same.
[0002]
[Prior art]
Conventionally, a urethane-based thermoplastic resin solution is applied onto release paper that has been laminated with polypropylene or coated with a silicone resin, and dried by heating to form a film, which is used as a skin layer, and is adhered onto this skin layer. A synthetic leather manufacturing method for obtaining a synthetic leather by applying a two-component urethane resin solution as a layer and bonding a fibrous base material such as a nonwoven fabric, a woven fabric, or a knitted fabric before or immediately after drying is widely known. ing. What is bonded before drying is called wet laminating, and what is bonded immediately after drying is called dry laminating.
[0003]
And as an adhesive used in this case, for example, a resin component comprising a polyurethane resin having a hydroxyl group at the terminal and an isocyanate compound such as trifunctional isocyanate obtained by adding tolylene diisocyanate or hexamethylene diisocyanate to trimethylolpropane, A two-component adhesive dissolved in an organic solvent such as toluene or methyl ethyl ketone is widely known.
[0004]
In this case, as a method of applying the adhesive, there is a dot-like application such as a whole surface application by knife coating or a gravure coating.
In the case of the wet laminating method using a solvent-type two-component adhesive, it is difficult to soften the texture of the synthetic leather obtained by adjusting the coating amount and applying the entire surface or scattered coating.
In the case of the dry laminating method using a solvent type two-component adhesive, the texture and the adhesive strength between the skin layer and the fibrous base material tend to vary depending on the dry state of the adhesive, that is, the adhesive is excessively dried. Then, the texture can be made soft, but the adhesive strength cannot be obtained, and if the adhesive is insufficiently dried, a problem similar to the wet laminating method occurs. Therefore, as long as a solvent-type two-component adhesive is used, it has been difficult to obtain a synthetic leather having a soft texture and desired adhesive strength.
For these reasons, there has been a demand for the development of a synthetic leather having a new structure that does not impair the soft texture, more precisely, the texture of the fibrous base material, and a method for producing the same.
[0005]
[Problems to be solved by the invention]
The present invention has been made in order to solve the above-mentioned problems in the case of using an organic solvent-type adhesive, and has a good appearance, the texture of the fibrous base material as it is, and a good fibrous base material. The synthetic leather which has the adhesive strength of a skin layer and a skin layer, and its manufacturing method are provided.
[0006]
[Means for Solving the Problems]
In the synthetic leather of the present invention, a skin layer made of a urethane-based thermoplastic resin is bonded to a fiber base material with a reactive hot-melt adhesive having a melting temperature of 60 to 130 ° C. made of a thermoplastic resin. In the synthetic leather, the mode in which the adhesive intervenes is characterized in that the porosity is 50 to 95% and the average intervening amount is 5 to 50 g / m ² . In addition, the porosity here is a ratio of the area in which the adhesive is not interposed. Specifically, the porosity = ((the area of the synthetic leather) − (the portion in which the adhesive is interposed). Area)) × 100 / (area of synthetic leather). However, the area here means that synthetic leather is seen in a plan view.
[0007]
In the synthetic leather manufacturing method of the present invention, a urethane thermoplastic resin solution or an aqueous dispersion is coated on a releasable sheet to form a film that becomes a skin layer, and the film is made of a thermoplastic resin. A reactive hot melt adhesive having a melting temperature of 60 to 130 ° C. is melted by heating and applied discontinuously, and when the adhesive is in a molten state, that is, immediately after coating or immediately after reheating, a fibrous base material It is by sticking together.
[0008]
The releasable sheet used in the present invention may be any film, paper, woven fabric, etc., and one side of the sheet is in a state of poor adhesion after the urethane-based thermoplastic resin solution or dispersion used in the present invention is dried and solidified. And a Teflon film, a polyethylene terephthalate film, a nylon taffeta coated with a silicon resin, a release paper laminated with a polyolefin film on paper, or a release paper coated with a silicon resin.
In addition, as a method for applying the urethane-based thermoplastic resin solution or the aqueous dispersion to the release sheet, a normal coating method such as a knife coater, a comma coater, a reverse coater, or the like can be used.
[0009]
The urethane-based thermoplastic resin solution is, for example, a conventionally known urethane-based thermoplastic resin obtained by reacting an organic polyisocyanate, a high-molecular-weight polyol, and a chain extender with a prepolymer method or a one-shot method, dimethylformamide, It is obtained by dissolving in an organic solvent inert to isocyanate such as methyl ethyl ketone.
The urethane-based thermoplastic resin dispersion is obtained by reacting a conventionally known organic polyisocyanate, a high molecular weight polyol and a chain extender. For example, a high molecular polyol and an organic diisocyanate in an organic solvent. Is prepared by adding a chain extender to increase the molecular weight and removing the organic solvent by reducing the pressure. It is done.
[0010]
Examples of organic polyisocyanates include aromatic isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, polymethylene polyphenyl diisocyanate, aromatic aliphatic diisocyanates such as xylylene diisocyanate, phenylene diisocyanate, methylenebiscyclohexyl diisocyanate, hexamethylene diisocyanate, Examples thereof include organic diisocyanates such as aliphatic diisocyanates such as forone diisocyanate and cyclohexane diisocyanate.
[0011]
High molecular weight polyols include polyester, polyether, polylactone, and polycarbonate polyols.
Polyester polyols include polyhydric alcohols such as ethylene glycol, propylene glycol, 1,4-butanediol and neopentyl glycol, and fatty acids or carboxylic acids such as adipic acid, sebacic acid, azelaic acid, terephthalic acid and maleic acid. And polyester diol obtained by a condensation reaction.
[0012]
Examples of the polyether polyol include polyalkylene ether diols such as polyethylene glycol, polypropylene ether glycol, polytetramethylene glycol, and polyhexamethylene glycol.
[0013]
Examples of the polylactone diol include polycaprolactone glycol, polypropiolactone glycol, and polyvalerolactone glycol.
[0014]
Examples of the polycarbonate polyol include a polycarbonate diol obtained by a dealcoholization reaction between a polyhydric alcohol such as ethylene glycol, propylene glycol, 1,4-butanediol and the like, diethyl carbonate, diphenyl carbonate and the like, and a dephenol reaction. Can be mentioned.
[0015]
As chain extenders, short-chain diols such as ethylene glycol and 1,4-butanediol, various diamines such as ethylenediamine, propylenediamine, hexamethylenediamine, tolylenediamine, xylylenediamine, diphenyldiamine, diaminodiphenylmethane, and the like Water etc. are mentioned.
[0016]
As the hot melt adhesive made of a thermoplastic resin, a polyamide system, a polyester system, an ethylene-vinyl acetate copolymer system, a polyurethane system, or the like having a melting temperature of 50 to 230 ° C. can be used.
[0017]
Of these, polyamide-based and polyester-based adhesives generally have a high melting temperature of 200 to 250 ° C. and sufficient heat resistance, but the problem is that they cannot be used for skin layers and fibrous base materials that are weak against heat. In addition, since ethylene-vinyl acetate copolymer adhesives are generally low at 50 to 80 ° C., there is a problem of heat resistance. Therefore, it is preferable to use a reactive hot melt adhesive. The reactive hot melt adhesive can be heated and melted at a relatively low temperature, and after adhering it to an adherend, a crosslinking reaction is caused by an appropriate method to improve the heat resistance after adhesion.
In the present invention, it is preferable to use a reactive hot-melt adhesive having a melting temperature of 60 to 130 ° C. If the temperature is lower than 60 ° C, the initial adhesive strength may not be exhibited in summer, and initial peeling may occur. When a material exceeding 130 ° C is used, depending on the material of the skin layer or the fibrous base material, the skin layer or the fibrous base material There is a possibility that the material softens and causes an appearance failure.
[0018]
Examples of the reactive hot-melt adhesive include urethane-based moisture-curable hot-melt adhesives and UV-curable hot-melt adhesives containing a hydroxyl group-containing polyester resin, an epoxy compound, and a photopolymerization initiator. Among these, a urethane-based moisture-curable hot melt adhesive having a low melt viscosity is preferable.
[0019]
The urethane-based moisture-curable hot melt adhesive is an adhesive mainly composed of a prepolymer having a terminal isocyanate group by reaction of at least one or more high molecular weight polyols and at least one or more organic polyisocyanates. If necessary, a tackifier, a wax, a plasticizer, a catalyst, a stabilizer, a filler, a thermoplastic resin, a pigment, and the like may be added to the adhesive.
[0020]
As the high molecular weight polyol, the aforementioned polyester polyol, the aforementioned polyether polyol, the aforementioned polycarbonate polyol, acrylic polyol, polyolefin polyol, castor oil polyol, and the like can be used.
As the acrylic polyol, a polymerizable monomer having a hydroxyl group such as hydroxylethyl acrylate, hydroxylbutyl acrylate, trimethylolpropane acrylic acid monoester, or acrylic acid, methacrylic acid, styrene, acrylonitrile, α-methylstyrene Etc. are obtained by copolymerization.
As the polyolefin polyol, a hydroxyl group-containing polybutadiene, a hydrogenated hydroxyl group-containing polybutadiene, or the like can be used.
[0021]
As the organic polyisocyanate, the same organic diisocyanate as described above can be used.
The tackifier is added for the purpose of improving the wettability with respect to the skin layer or the fibrous base material or imparting a tack at the time of application. For example, rosin and its derivatives, terpene resins, petroleum resins and the like are known adhesives. An imparting agent can be used.
The wax is added for the purpose of adjusting the melt viscosity of the hot melt adhesive or adjusting the curing time. For example, paraffin wax, microcrystalline wax, polyethylene wax, and the like can be used.
[0022]
Examples of the fibrous base material include polyamide fibers such as nylon 6 and nylon 66, polyester fibers, polyacrylonitrile fibers, polyvinyl alcohol fibers, semi-synthetic fibers such as triacetate, and fabrics made of mixed fibers such as synthetic fibers and cotton. Knitted fabrics, non-woven fabrics and the like. In particular, for a synthetic leather having a soft texture, a knitted fabric is preferable because of high drape.
Further, a urethane-based thermoplastic resin solution or aqueous dispersion is applied to or impregnated into a woven fabric, knitted fabric, nonwoven fabric or the like made of the fibrous base material, and is obtained by dry solidification or wet solidification, such as a wet microporous layer. A fibrous base material having a high polymer attached thereto can be used.
[0023]
Dissolving hot melt adhesive by heating and applying discontinuously means that it is not a continuous film as in the case of full-surface application. Although it is preferable, it may be patterned or linear as long as desired adhesive strength and texture can be maintained. As a coating method, a commercially available hot melt applicator can be used.
There are two types of hot melt applicators: a spray gun system with a heating mechanism around the nozzle, a gravure roll system with a heating mechanism inside the roll, and a rotary screen system that allows the screen to be heated. In order to maintain the adhesive strength, a gravure roll method and a rotary screen method are preferable.
[0024]
The amount of application in the form of lines and dots may be set as appropriate depending on the fibrous base material used, but the amount of inclusion when synthetic leather is used, and the average amount of inclusion is preferably 5 to 50 g / m ^2. . Moreover, the synthetic leather which made use of the texture of a fibrous base material can be obtained by the porosity of 50-95% under said average amount of inclusion.
When the average amount of inclusion is small, the adhesive strength is insufficient, and when it is large, the presence of the adhesive itself is felt. Further, when the porosity is small, the texture becomes stiff, and when the porosity is large, it is difficult to maintain the adhesive strength.
In synthetic leather, the adhesive strength between the skin layer and the fibrous base material is somewhat different depending on the application, but it is preferable that the synthetic leather has an adhesive strength of 10 N / 3 cm or more according to the measurement method described below.
[0025]
【Example】
Hereinafter, the present invention will be described with reference to examples.
The adhesive strengths described in the examples and comparative examples are as follows: test pieces of 10 cm in the vertical direction and 3 cm in the horizontal direction are cut out, the skin layer and the fibrous base material are peeled off slightly, and the respective ends are measured with a Tensilon tensile tester It was expressed by tensile and measured peel strength.
[0026]
Example 1
A urethane-based thermoplastic resin solution having a 100% modulus of 7.0 MPa is applied to the release paper with drawing by a knife coater so as to have a dry thickness of 20 μm, followed by hot-air drying at 100 ° C. for 2 minutes, and a polyurethane skin layer It was. Next, a urethane-based moisture-curing hot melt adhesive (Dainippon Ink & Chemicals, Tyhose NH-300) having a 100% modulus of 3.5 MPa as an adhesive is melted at a melting temperature of 120 ° C. on the skin layer. Apply a screen with an average adhesion amount of 20 g / m ² in the form of dots (spots) with a rate of 70%. Immediately after that, a nylon tricot is pasted together with a nip roll heated to 60 ° C. After the reaction of the adhesive is completed, the release paper is removed. It peeled.
The obtained synthetic leather was very soft and draped so that the texture of the fiber base material was hardly impaired. Further, the adhesive strength between the fiber base material and the skin layer was 19.6 N / 3 cm, which was favorable for clothing.
[0027]
(Comparative Example 1)
In the adhesion between the polyurethane skin layer and the fiber base material of Example 1, a knife coater at 20 g (solid content) / m ² using a urethane two-component adhesive having a solid content of 30% by weight with a 100% modulus of 2.0 MPa. The same as Example 1 except that the entire surface was applied and wet-laminated.
The obtained synthetic leather was hard because the texture of the fiber base material was damaged, and had almost no drape. Further, the adhesive strength between the fiber base material and the skin layer was as weak as 5.0 N / 3 cm and could not be used as a synthetic leather.
[0028]
(Comparative Example 2)
Comparative Example 1 except that a 100% modulus was 2.0 MPa and a urethane two-component adhesive with a solid content of 30% by weight was applied to the entire surface with a knife coater at 40 g (solid content) / m ² and wet laminated. Same as
Although the adhesive strength between the fiber base material and the skin layer of the obtained synthetic leather was 15.6 N / 3 cm, the texture of the fiber base material was impaired and it was hard.
[0029]
(Comparative Example 3)
In the adhesion between the polyurethane skin layer and the fiber base material of Example 1, a 70% porosity dot-like (spot-like shape) using a urethane two-component adhesive having a solid content of 30% by weight with a 100% modulus of 2.0 MPa. ) And 40 g / cm ² at 30 g (solid content) / m ² by a gravure coater, and the same as Example 1 except that it was dry laminated.
The obtained synthetic leather is very soft so that the texture of the fiber base material is hardly impaired, has a drape property, and hardly feels a foreign matter, but the adhesive strength between the fiber base material and the skin layer is 0.4 N. / 3 cm, and it was unbearable for use as clothing.
[0030]
(Example 2)
Implemented except that 100% modulus 5MPa moisture permeable urethane resin (Dainippon Ink Chemical Co., Ltd., Crisbon S-525) was applied on the release paper with drawing with a knife coater to a dry thickness of 10μm. Synthetic leather was obtained in the same manner as in Example 1.
The resulting synthetic leather is very has drape soft texture, and had a superior moisture permeable waterproof (moisture permeability 5000g / m ² / 24h, water pressure resistance 6000mmH ₂ O). The adhesive strength was 19.6 N / 3 cm.
[0031]
(Comparative Example 4)
In the adhesion between the polyurethane skin layer and the fiber base material of Example 2, 40 g (solid content) / m ² using a moisture-permeable urethane two-component adhesive having a 100% modulus of 1.5 MPa and a solid content of 30 wt%. The same as Example 2 except that the entire surface was coated with a knife coater and wet-laminated.
The obtained synthetic leather was hard because the texture of the fiber base material was damaged, and had almost no drape. It was also significantly decreased when compared with Example 2 in moisture permeability 1400g / m ² / 24h. The adhesive strength between the fiber substrate and the skin layer was 22.5 N / 3 cm.
[0032]
(Example 3)
Synthetic leather as in Example 2 except that a urethane-based thermoplastic resin solution was applied to the raised surface of a raised cloth as a fiber base material and wet-solidified to form a wet microporous layer. Got.
The resulting synthetic leather, as it no soft a little different than the texture of the fiber substrate and, as it has excellent moisture-permeation and water-proof characteristics (moisture permeability 5000g / m ² / 24h, water pressure resistance 6000mmH ₂ O) there were. The adhesive strength between the fiber substrate and the skin layer was 25.0 N / 3 cm (wet microporous layer fracture).
[0033]
(Comparative Example 5)
In the adhesion between the polyurethane skin layer and the fiber substrate of Example 3, a knife coater at 20 g (solid content) / m ² using a urethane two-component adhesive having a solid content of 30% by weight with a 100% modulus of 1.5 MPa. The same as Example 3 except that the entire surface was applied and dry laminated.
Texture of the resulting artificial leather is made as rigid as compared to Example 3, the moisture permeability was also decreased to 1500g / m ² / 24h. The adhesive strength between the fiber substrate and the skin layer was 22.5 N / 3 cm.
[0034]
[Effect of the present invention]
As described above, the synthetic leather of the present invention was able to have sufficient adhesive strength between the fiber base material and the skin layer, while almost unchanged from the texture of the fiber base material, It can be suitably used in the fields of clothing, shoes, bags, furniture, especially sports clothing and nursing clothing.
Moreover, according to the method for producing synthetic leather of the present invention, in the step of bonding the fiber base material and the skin layer, the step of evaporating the solvent is not necessary, and therefore the line of this step can be shortened. In addition, the viscosity of the hot melt adhesive can be controlled by the heating temperature. As a result, the amount of adhesive adhering to the skin layer and the amount of penetration into the fiber base can be controlled easily and accurately. Even if it is made discontinuous (a dotted shape, a line shape, or a web shape by spraying), a desired adhesive strength between the fiber substrate and the skin layer can be secured.
In particular, if a reactive hot melt type adhesive is used, it can be bonded at a relatively low temperature, so that the operation of the bonding process is facilitated. Synthetic leather with good appearance can be obtained.

Claims (3)

In the synthetic leather in which the skin layer made of a urethane-based thermoplastic resin is bonded to a fiber base material with a reactive hot-melt adhesive having a melting temperature of 60 to 130 ° C. made of a thermoplastic resin, the adhesive Is a synthetic leather in which the porosity is 50 to 95% represented by the formula (1) and the average amount is 5 to 50 g / m ² .
Reactive hot-melt adhesive bonding in which a urethane-based thermoplastic resin solution or aqueous dispersion is applied onto a releasable sheet to form a skin layer, and the melting temperature of the thermoplastic resin is 60 to 130 ° C. on the skin layer A method for producing synthetic leather, in which an agent is melted by heating and applied discontinuously, and is bonded to a fibrous base material when the adhesive is in a molten state. The method for producing synthetic leather according to claim 2, wherein the reactive hot-melt adhesive having a melting temperature of 60 to 130 ° C is application by a gravure roll with a heating mechanism or application by a rotary screen with a heating mechanism.