Stain-resistant synthetic leather

Abstract

To provide an artificial leather that exerts anti-staining performance and is less prone to make water stain remain thereon.SOLUTION: An artificial leather is formed by stacking at least a fiber fabric substrate, a resin layer, and a surface treatment layer in this order. The surface treatment layer is formed of at least aqueous polyurethane resin, a cross-linking agent, and a composition containing hydrophilic compound. The hydrophilic compound is a mixture of polymethacrylic acid alkyl, polymethacrylic acid, and polymethacrylic acid ethylene oxide. Content of the mixture of polymethacrylic acid alkyl, polymethacrylic acid, and polymethacrylic acid ethylene oxide is preferably 50 to 100 pts. mass with respect to aqueous polyurethane resin 100 pts.mass.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to synthetic leather, and more particularly to synthetic leather that exhibits stain-resistant properties.

[0002] Synthetic leather, which has a fiber fabric substrate and a layer of synthetic resin, is similar to natural leather. Because synthetic leather is lighter and easier to handle than natural leather, it is used in a wide range of applications, including vehicle interiors, furniture such as sofas and chair seats, and clothing such as jackets and coats.

[0003] However, once dirt adheres to the surface of synthetic leather, it is difficult to wipe it off completely, and as a result, stains tend to be more noticeable on synthetic leather in light colors such as white or beige.

[0004] Countermeasures include coating the surface of synthetic leather with a water-repellent paint or coating the surface of synthetic leather with a hydrophilic paint. The former makes it difficult for dirt to adhere to synthetic leather, but since water-repellent paints are mostly solvent-based, this is not desirable from the perspective of health and environmental hazards. The latter is intended to make it possible to easily wipe off dirt even if it adheres to synthetic leather (Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-191820 Summary of the Invention [Problem to be solved by the invention]

[0006] However, because hydrophilic paint has a high affinity with water, if water is left on synthetic leather coated with hydrophilic paint, water marks are likely to remain after drying. Once water marks appear, they are difficult to completely remove, and the appearance is poor. Therefore, an object of the present invention is to solve the above problems and to provide synthetic leather that exhibits stain-resistant properties, and in particular, that is less likely to leave water marks. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems and have invented synthetic leather that exhibits stain-resistant properties, particularly synthetic leather that is less likely to leave water marks.

[0008] The present invention provides the following. (1) Synthetic leather having stain-resistant properties, which is composed of at least a fiber fabric substrate, a resin layer, and a surface treatment layer laminated in this order, wherein the surface treatment layer is formed from a composition containing at least an aqueous polyurethane resin, a crosslinking agent, and a hydrophilic compound, and the hydrophilic compound is a mixture of polyalkyl methacrylate, polymethacrylic acid, and poly(ethylene oxide methacrylate). (2) Synthetic leather with stain-resistant properties according to (1), characterized in that it contains 50 to 100 parts by mass of a mixture of alkyl polymethacrylate, polymethacrylic acid, and poly(ethylene oxide methacrylate) per 100 parts by mass of aqueous polyurethane resin. (3) Synthetic leather having stain-resistant properties according to (1) or (2), characterized in that it further contains an ethylene-acrylic acid copolymer as a hydrophilic compound. (4) Synthetic leather having antifouling properties according to any one of (1) to (3), characterized in that it further contains, as a hydrophilic compound, a water-soluble polymer obtained by graft-polymerizing polyvinyl alcohol with polyvinylpyrrolidone. [Effects of the Invention]

[0009] The present invention can be used for a variety of purposes, such as interior materials for vehicles, furniture such as sofas and chair seats, and clothing, because even if dirt adheres to the surface, it can be easily wiped off and water marks are unlikely to remain. DETAILED DESCRIPTION OF THE INVENTION

[0010] The synthetic leather of the present invention comprises at least a fiber fabric substrate, a resin layer, and a surface treatment layer laminated in this order, and the surface treatment layer is formed from a composition containing at least a water-based polyurethane resin, a crosslinking agent, and a hydrophilic compound. In this specification, the mass ratios of the crosslinking agent and the hydrophilic compound to the aqueous polyurethane resin are all solid content ratios.

[0011] [Fiber fabric substrate] The fiber fabric substrate may be any fabric material using fibers, such as knitted fabric, woven fabric, or nonwoven fabric. The fibers forming the fiber fabric substrate are not particularly limited, and examples thereof include synthetic fibers and natural fibers. Examples of synthetic fiber materials include, but are not limited to, polyester, polyamide, acrylic, and nylon. Examples of natural fiber materials include cotton, linen, and rayon. The thickness of the fiber fabric substrate is not particularly limited, but considering the mechanical strength and texture of the synthetic leather, the thickness is preferably 100 μm or more and 2000 μm or less, and more preferably 300 μm or more and 1000 μm or less. The basis weight of the fiber substrate is also not particularly limited, but similarly to the thickness, considering the mechanical strength and texture of the synthetic leather, the basis weight is preferably 10 g / m or more. 2 More than 500g / m 2 Preferably, it is 20 g / m or less. 2 More than 300g / m 2 More preferably, it is:

[0012] [Resin layer] The resin layer is a layer having at least a surface layer. The resin layer may be formed by laminating a surface layer and an adhesive layer in this order from the surface side, or an intermediate layer may be interposed between the surface layer and the adhesive layer. The intermediate layer may be a single layer or a multi-layer structure of two or more layers.

[0013] The resin constituting the surface layer may be any resin that can be used in the resin layer of synthetic leather, but polyurethane resin or vinyl chloride resin is preferred.

[0014] Any polyurethane resin that can be used for the surface layer of synthetic leather can be used, and specific examples include polyester polyurethane resins, polyether polyurethane resins, polycaprolactone polyurethane resins, polyester / polyether copolymer polyurethane resins, polyamino acid / polyurethane copolymer resins, non-yellowing polycarbonate polyurethane resins obtained by reacting a polycarbonate diol component with a non-yellowing diisocyanate component and a low-molecular-weight chain extender, etc. Furthermore, polyvinyl chloride resins, synthetic rubbers, etc. may be mixed with the above polyurethane resins as long as the physical properties of synthetic leather are not impaired.

[0015] Any vinyl chloride resin that can be used for the skin layer of synthetic leather can be used as the vinyl chloride resin. Specifically, polyvinyl chloride, copolymers of vinyl chloride monomers with other monomers copolymerizable therewith, or blends of these resins can be used. Examples of other monomers copolymerizable with the vinyl chloride monomer include ethylene, propylene, vinyl acetate, vinylidene chloride, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, maleic acid, and acrylonitrile fumarate.

[0016] When the surface layer is made of vinyl chloride resin, a plasticizer is blended in addition to the vinyl chloride resin in order to more effectively exhibit flexibility similar to that of natural leather. Examples of the plasticizer include common phthalate ester plasticizers such as dioctyl phthalate (DOP), diisononyl phthalate (DINP), butyl benzyl phthalate (BBP), diisodecyl phthalate (DIDP), and diundecyl phthalate (DUP); common fatty acid ester plasticizers such as dioctyl adipate (DOA), dioctyl sebacate (DOS), and dioctyl azelaate (DOZ); polymeric plasticizers such as trioctyl trimellitate plasticizers and polyester adipic acid plasticizers such as polypropylene adipate; sebacic acid plasticizers; and phosphate ester plasticizers such as tricresyl phosphate (TCP), trixylenyl phosphate (TXP), tris(isopropylphenyl)phosphate, tributyl phosphate, triethyl phosphate, triphenyl phosphate, and triethylphenyl phosphate.

[0017] The thickness of the skin layer is not particularly limited, but is preferably formed to a thickness of 10 μm or more and 500 μm or less, and more preferably formed to a thickness of 10 μm or more and 400 μm or less.

[0018] The intermediate layer may be made of any resin that can be used for synthetic leather resin layers, as in the case of the surface layer, but polyurethane resins or vinyl chloride resins are preferred. Specific examples of polyurethane resins and polyvinyl chloride resins are the same as those for the surface layer. The intermediate layer may be a foamed layer or a non-foamed layer. The means for foaming the intermediate layer include physical foaming by mechanical stirring, chemical foaming by adding a foaming agent, and pseudo foaming by adding hollow fine particles.

[0019] The adhesive layer is provided to improve adhesion between a synthetic resin layer such as a surface layer and a fiber fabric substrate. As with the surface layer and intermediate layer, any resin that can be used in a resin layer of synthetic leather can be used as the resin constituting the adhesive layer, but polyurethane resin or vinyl chloride resin is preferred. The adhesive layer may be a foamed layer or a non-foamed layer. The means for forming the adhesive layer into a foamed layer is the same as the means for forming the intermediate layer into a foamed layer.

[0020] The resin compositions constituting the surface layer, intermediate layer, and adhesive layer may contain various additives such as pigments, fillers, dispersants, antifoaming agents, matting agents, and lubricants, to the extent that the physical properties of each layer are not impaired.

[0021] [Surface treatment layer] The surface treatment layer of the synthetic leather of the present invention is formed from a composition consisting of at least an aqueous polyurethane resin, a crosslinking agent, and a hydrophilic compound, and the hydrophilic compound is a mixture of poly(alkyl methacrylate), poly(methacrylic acid), and poly(ethylene oxide methacrylate).

[0022] Examples of aqueous polyurethane resins include polycarbonate-based polyurethanes, polyether-based polyurethanes, polyester-based polyurethanes, and modified products thereof, with polycarbonate-based polyurethanes being preferred due to their excellent durability. The above water-based polyurethane resins may be used alone or in combination of two or more.

[0023] The crosslinking agent is preferably a carbodiimide compound and / or an oxazoline compound. Carbodiimide compounds and oxazoline compounds react with carboxyl groups, and therefore react with the aqueous polyurethane resin and the hydrophilic compound mixture of poly(alkyl methacrylate), poly(methacrylic acid), and poly(ethylene oxide methacrylate) when forming the surface treatment layer. Therefore, the hydrophilic compound is incorporated into the resin skeleton of the surface treatment layer, making it less likely to fall off or denature, and providing long-term antifouling properties. An isocyanate compound may be used in combination as a crosslinking agent. Examples of the isocyanate compound include water-dispersible polyfunctional aromatic isocyanates, water-dispersible polyfunctional aliphatic isocyanates, water-dispersible fatty acid-modified polyfunctional aliphatic isocyanates, water-dispersible blocked polyfunctional aliphatic isocyanates, and other blocked polyisocyanates; and water-dispersible polyisocyanate prepolymers. The amount of the crosslinking agent added is preferably in the range of 5 to 80 parts by mass per 100 parts by mass of the aqueous polyurethane resin.

[0024] In the present invention, in addition to the above crosslinking agent, an epoxy compound, an aziridine compound, etc. may be used in combination as needed.

[0025] The surface treatment layer contains a mixture of alkyl polymethacrylate, polymethacrylic acid, and poly(ethylene oxide methacrylate) as a hydrophilic compound. The mixture of alkyl polymethacrylate, polymethacrylic acid and poly(ethylene oxide methacrylate) is highly hydrophilic, so even if dirt adheres to the surface, it can be easily removed by wiping with water. When a surface treatment layer containing a hydrophilic compound is in contact with water for a long time, water marks tend to remain after the water has dried. However, a mixture of poly(alkyl methacrylate), poly(methacrylic acid), and poly(ethylene oxide methacrylate) is hydrophilic, but water marks are less likely to remain. This is presumably because the side chains are long and less likely to bleed.

[0026] The mixture of polyalkyl methacrylate, polymethacrylic acid, and poly(ethylene oxide methacrylate) is preferably added in a ratio of 50 to 100 parts by mass per 100 parts by mass of the aqueous polyurethane resin. If the amount is less than 50 parts by mass, the hydrophilicity becomes insufficient and the desired antifouling performance tends to be insufficient. On the other hand, if the amount exceeds 100 parts by mass, water marks tend to appear, heat resistance tends to deteriorate, and discoloration tends to occur when used at high temperatures.

[0027] As the hydrophilic compound, in addition to the mixture of the above-mentioned polyalkyl methacrylate, polymethacrylic acid and poly(ethylene oxide methacrylate), an ethylene-acrylic acid copolymer may also be used. As the ethylene-acrylic acid copolymer, it is preferable that the proportion of ethylene used is 70 to 95 mass % and the proportion of acrylic acid used is 5 to 30 mass %. The ethylene-acrylic acid copolymer is neutralized and used as an aqueous dispersion. Examples of neutralizing agents include sodium hydroxide, ammonia, alkylamines, and alkanolamines, and sodium salts neutralized with sodium hydroxide are preferred. The addition of ethylene-acrylic acid copolymer improves the light resistance of the surface treatment layer, making it possible to provide synthetic leather with excellent stain resistance over a long period of time. The reason for this improvement in light resistance is unclear, but it is thought to be because, being an olefin-based resin, the resin itself has high light stability and is reactive with the carbodiimide-based and oxazoline-based crosslinking agents. The amount of ethylene-acrylic acid copolymer added is preferably 20 to 50 parts by mass per 100 parts by mass of the aqueous polyurethane resin. If the amount is less than 20 parts by mass, the light resistance tends to be insufficient, and if the amount is more than 50 parts by mass, water marks tend to remain.

[0028] Furthermore, a water-soluble polymer obtained by grafting polyvinyl alcohol with polyvinylpyrrolidone (hereinafter referred to as "PVA-PVP graft copolymer") may be used as the hydrophilic compound. PVA-PVP graft copolymer has excellent heat resistance and is resistant to thermal degradation. Therefore, when PVA-PVP graft copolymer is contained in the surface treatment layer, it exhibits the effect of maintaining hydrophilicity for a long period of time. In addition, because the PVA-PVP graft copolymer has a basic skeleton of polyvinyl alcohol with hydroxyl groups, it reacts with the isocyanate compound crosslinker and is incorporated into the resin skeleton that forms the surface treatment layer. By being incorporated into the resin skeleton, the PVA-PVP graft copolymer is prevented from falling off over time. In other words, by including the PVA-PVP graft copolymer in the surface treatment layer, it is possible to reliably maintain hydrophilicity over the long term. The amount of PVA-PVP graft copolymer added is preferably 5 to 30 parts by mass relative to 100 parts by mass of the aqueous polyurethane resin. If the amount is less than 5 parts by mass, heat resistance tends to be insufficient, and if the amount is more than 30 parts by mass, water marks tend to remain.

[0029] If necessary, known additives such as pigments, antioxidants, ultraviolet absorbers, catalysts, inorganic fine particles such as silica, and organic fillers may be added to the surface treatment layer.

[0030] The surface treatment layer of the synthetic leather of the present invention can be formed by preparing a coating liquid containing a composition for forming the surface treatment layer and applying the coating liquid onto the resin layer (skin layer). The method for applying this coating liquid is not particularly limited, and can be formed by known methods such as the gravure method and the reverse method. Also, a method of applying the coating onto the resin layer and then drying in a heating oven is preferred. The temperature conditions for drying are preferably 80 to 150°C, more preferably 120 to 140°C, from the viewpoint of the reactivity of the crosslinking agent.

[0031] A primer layer may be provided between the surface treatment layer and the resin layer to improve adhesion. The primer layer is a layer made of resin, and known additives such as pigments, antioxidants, ultraviolet absorbers, catalysts, inorganic fine particles such as silica, and organic fillers may be added as needed.

[0032] The synthetic leather of the present invention has been described above. The synthetic leather of the present invention can be used for various purposes, but is particularly suitable for use as interior materials for vehicles, furniture, and clothing. [Example]

[0033] The present invention will be described in detail below with reference to examples. The present invention is not limited to these examples, and various applications are possible within the scope of the technical concept of the present invention.

[0034] [Creating a synthetic leather base] The resin composition for forming the surface layer was applied onto release paper using a comma coater, and the temperature was gradually increased from 80°C to 120°C. After reaching 120°C, the coating was dried for 5 minutes to obtain a surface layer with a thickness of approximately 15 µm. Next, the adhesive layer-forming resin composition was applied onto the surface layer formed on the release paper using a comma coater and dried at 120° C. to obtain an adhesive layer with a thickness of about 30 μm. Next, at the timing when adhesiveness was developed in the adhesive layer, a woven fiber fabric substrate (a polyester fabric knitted from 150 denier polyester yarn on a circular knitting machine) was attached. Finally, the fabric was wound into a roll and aged at 50°C for 48 hours. After that, the release paper was peeled off, and a synthetic leather base was created by laminating the surface layer, adhesive layer, and fiber fabric substrate in this order from the surface side. The resin composition for forming the surface layer and the resin composition for forming the adhesive layer are as follows.

[0035] [Resin composition for forming skin layer] Main component: Polycarbonate polyurethane resin (DIC Corporation "Crisbon NY335FT") 100 parts by weight Solvent: DMF 30 parts by weight, ethyl acetate 10 parts by weight ·White pigment 10 parts by mass The viscosity was adjusted to 800 mPa·sec (measured with a Brookfield viscometer at a liquid temperature of 25°C).

[0036] [Resin composition for forming adhesive layer] Main component: Polycarbonate polyurethane resin (DIC Corporation "Crisbon TA205FT") 100 parts by weight Crosslinking agent: 12 parts by mass of an isocyanate compound (DIC Corporation's "Burnoc DN950") Solvent: DMF 30 parts by weight, MEK 30 parts by weight Catalyst: DIC Corporation's "Crisbon Accel T81-E": 1 part by weight The viscosity was adjusted to 800 mPa·sec (measured with a Brookfield viscometer at a liquid temperature of 25°C).

[0037] Examples 1 to 5, Comparative Examples 1 to 2 The composition for forming a surface treatment layer shown in Table 1 was applied to the above synthetic leather base using a gravure roll, heated in an oven at 130°C, and then aged at 50°C for 48 hours to obtain synthetic leather with a surface treatment layer having a coating thickness of approximately 2 μm.

[0038] The details of the raw materials shown in Table 1 are as follows: Water-based polyurethane resin: Dow Chemical Company, UD4 Crosslinker 1: Isocyanate compound, manufactured by LANXESS, BI220 Crosslinking agent 2: Carbodiimide compound, manufactured by Nisshinbo Chemical Co., Ltd., Carbodilite SV02 Hydrophilic compound 1: A mixture of polybutyl methacrylate, polymethacrylic acid, and poly(ethylene oxide methacrylate), manufactured by Takamatsu Oil & Fat Co., Ltd., SWX349R Hydrophilic compound 2: Sodium salt of ethylene-acrylic acid copolymer, manufactured by Sumitomo Seika Chemicals Co., Ltd., Zaixen N Hydrophilic compound 3: Water-soluble polymer in which polyvinyl alcohol is grafted with polyvinylpyrrolidone, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Pittscol V7154 Hindered amine light stabilizer: BASF Tinuvin T765 UV absorber: BASF Tinuvin T751 Antioxidant 1: BASF Irganox 1135 Antioxidant 2: ADEKA Corporation, ADK STAB 1500 The numerical values ​​of the raw materials in Table 1 are in units of "parts by mass" and are all solid content amounts.

[0039] The resulting synthetic leather was subjected to the following water mark confirmation test and stain resistance tests 1 to 3. The results are shown in Table 1.

[0040] [Water mark confirmation test] The synthetic leather obtained was cut into a 100mm x 100mm test piece, on which 5mL of room temperature pure water was dropped and left to stand at 25°C and 30% humidity. After 24 hours, the appearance of the test piece was checked and evaluated according to the following criteria. ◎ No abnormalities in appearance 〇···Some faint water marks remain × Clear circular water marks remain

[0041] [Anti-fouling test 1] The synthetic leather obtained in each of the Examples and Comparative Examples was cut into a circular test piece having a diameter of 150 mm, and the color difference ΔE was measured before and after "rubbing." The "rubbing" here refers to first rubbing a soiled cloth (EMPA #104) against the test piece 1000 times in a flat abrasion tester at a load pressure of 2 MPa, then replacing the soiled cloth with a new one and repeating the same procedure three times for a total of 3000 times rubbing of the test piece. Next, the test piece that has been soiled with the soiled cloth is rubbed with a white cloth sufficiently moistened with distilled water 10 times in a flat abrasion tester at a load pressure of 30 kPa.

[0042] [Anti-fouling test 2] For the synthetic leathers obtained in each of the Examples and Comparative Examples, after the light resistance test, the same test as the above stain resistance test 1 was carried out, and the color difference ΔE before and after "rubbing" was measured. The conditions for the light resistance test are as follows. Light resistance test: Using a fade meter, the test piece is exposed to ultraviolet light for 400 hours at a black panel temperature of 83°C.

[0043] [Anti-fouling test 3] For the synthetic leathers obtained in each of the Examples and Comparative Examples, after the heat resistance test, the same test as the stain resistance test 1 was carried out, and the color difference ΔE before and after "rubbing" was measured. The conditions for the heat resistance test are as follows: Heat resistance test: The test piece is placed in a gear oven and left to stand at 100°C for 600 hours for heat treatment.

[0044] [Table 1]

[0045] The results of each example and comparative example show that the synthetic leathers of Examples 1 to 5 have excellent stain-resistant properties and do not leave water marks.

Claims

1. In a synthetic leather having at least a fiber fabric substrate, a resin layer, and a surface treatment layer laminated in this order, The surface treatment layer is formed from a composition containing at least a water-based polyurethane resin, a crosslinking agent, and a hydrophilic compound, and the hydrophilic compound is a mixture of polyalkyl methacrylate, polymethacrylic acid, and poly(ethylene oxide methacrylate).

2. 2. The synthetic leather having stain-resistant properties according to claim 1, characterized in that the synthetic leather contains 50 to 100 parts by mass of a mixture of alkyl polymethacrylate, polymethacrylic acid, and poly(ethylene oxide methacrylate) per 100 parts by mass of the aqueous polyurethane resin.

3. 3. The stain-resistant synthetic leather according to claim 1, further comprising an ethylene-acrylic acid copolymer as a hydrophilic compound.

4. 4. The synthetic leather having stain-resistant properties according to claim 1, further comprising, as a hydrophilic compound, a water-soluble polymer obtained by graft-polymerizing polyvinyl alcohol with polyvinylpyrrolidone.

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