JPS6211115B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a soft leather-like sheet with excellent deterioration resistance, particularly hydrolysis resistance. More specifically, the present invention relates to a method for producing a leather-like sheet with high commercial value by a wet coagulation method from a solution of a specific polyurethane elastomer prepared using a specific coagulation regulator and a fibrous material. Leather-like sheets made of polyurethane elastomer and fibrous materials are called artificial leather or synthetic leather, and are widely used as a substitute for natural leather in shoes, bags, cases, balls, belts, clothing, etc. There are wet coagulation methods, dry coagulation methods, and semi-dry coagulation methods for producing the leather-like sheets, and among these methods, the wet coagulation method using polyurethane elastomer is currently the most widely adopted method for producing high-grade leather-like sheets. ing. When obtaining a leather-like sheet by the wet coagulation method, it is important that the wet coagulation property is good, that is, that the desired uniform sponge structure is formed within the polyurethane elastomer layer, and that the surface is flat. Must be in good condition. If the wet coagulation property is poor, the quality of the product, particularly the flatness of the surface, wrinkles in the texture, moisture permeability, etc., will be poor, and the commercial value will be significantly reduced. Wet coagulability varies greatly depending on the type of polyurethane elastomer. Polyurethane elastomers with soft segments made of polyalkylene ester glycol obtained by the condensation reaction of glycol with a small number of carbon atoms and dicarboxylic acid are hydrophilic with a cloudiness value of 13 or more. It has good wet coagulation properties. For this reason, this type of polyurethane elastomer is widely used in leather-like sheets currently produced. However, during use, the polyurethane elastomer is hydrolyzed and degraded by water or bacteria such as mold, which not only greatly impairs its appearance but also causes its functionality to deteriorate. It often happens that you can't even do it. Therefore, many attempts have been made to improve the coagulation properties of hydrophobic polyurethane elastomers with excellent deterioration resistance and cloudiness of 13 or less and use them in leather-like sheets. Higher alcohol in solution,
Polyurethane elastomer liquid can be prepared by adding carboxylic acid, ester, ether, ketone, polyalkylene ether glycol, etc. to the extent that the transparency of the solution is not lost, by adding a large amount of water-soluble substances, or by using a non-solvent for polyurethane elastomer. Methods such as making a colloid or adding salt to a coagulation bath have no effect on these hydrophobic polyurethane elastomers, or even if they have some effect, it is extremely difficult to prepare a polyurethane elastomer solution. However, it has not been successful due to drawbacks such as poor stability of the polyurethane elastomer solution. The present inventors used a hydrophobic polyurethane elastomer with a cloudiness value of 13 or less to obtain a leather-like sheet with good deterioration resistance and excellent appearance, texture, creases, moisture permeability, etc. As a result of extensive consideration of coagulation conditions, etc.,
A polyurethane elastomer solution composition obtained by dissolving a specified amount of a specific salt in water and adding it to a polyurethane elastomer solvent to precipitate the salt as fine particles is added to a polyurethane elastomer solution. By using the appearance,
It has been found that a leather-like sheet with very good quality can be obtained. In other words, the present invention provides a method for producing a soft leather-like sheet with excellent deterioration resistance from a solution of a fibrous material and a specific polyurethane elastomer by a wet coagulation method. Leather-like sheets with high commercial value can now be easily obtained operationally. First, the leather-like sheet of the present invention is made of a fibrous material and a polyurethane elastomer, and in addition to the leather-like sheet in which the fibrous material is filled with a porous polyurethane elastomer, the fibrous material or these sheets are provided with a polymer as a binder. It is a leather-like sheet consisting of a fibrous base and a polyurethane elastomer covering layer. The fibrous material can be made from ordinary fibers such as cotton, linen, wool, rayon, acetate, nylon, polyester, polyacrylonitrile, vinylon, polyolefin, etc., single spun fibers, mixed spun fibers thereof, composite spun fibers, etc. Non-woven, woven or knitted fabrics can be used. Next, a polyurethane elastomer solution, which is a feature of the present invention, is impregnated into the above-mentioned fibrous material in the case of a leather-like sheet without a covering layer, and impregnated with the above-mentioned fibrous material in the case of a leather-like sheet with a covering layer. The polyurethane elastomer solution is used to impregnate and/or coat the material, then wet coagulation is carried out, unnecessary substances including the solvent are extracted and removed with the solvent or it and water, and then drying is carried out. . In the polyurethane elastomer solution composition of the present invention, a hydrophobic polyurethane elastomer solution having a cloudiness value of 13 or less necessarily contains fine particles of a salt insoluble in the polyurethane elastomer solvent and water.
Here, the cloudiness value means that 50g of a polyurethane elastomer solution (solvent dimethylformamide) with a concentration of 5% by weight is kept at 50°C, and while stirring with a magnetic stirrer, dimethylformamide/
A 1/1 mixed solution of dimethylformamide/water is dropped little by little using a biuret, and this is the amount (in cc) of a 1/1 mixed solution of dimethylformamide/water added when the polyurethane elastomer solution becomes cloudy. Polyurethane elastomers with a cloudiness value of 13 or less include polyhexamethylene adipate glycol,
There are polyurethane elastomers such as polycaprolactone glycol, polyalkylene ester glycol, polypropylene glycol, and polyalkylene ether glycol as soft segments such as polytetramethylene glycol, and diols having 2 to 4 carbon atoms are used as chain extenders. Also, as the diisocyanate, diphenylmethane-4,4'-diisocyanate is preferably used. In particular, the present invention greatly improves wet coagulation properties, improves deterioration resistance, appearance,
A polyurethane elastomer containing polytetramethylene glycol as a soft segment, which has good quality such as texture, texture, moisture permeability, and flexibility, is most suitable. The composition of the polyurethane elastomer, that is, the ratio of hard segments to soft segments, influences wet coagulation properties and product quality, and the N content based on diisocyanate is usually desirably 3 to 6% by weight. Also, the concentration of polyurethane elastomer is 5
It can be used in a range of 35% by weight, but from the viewpoint of operability and product quality, 10 to 30% by weight is preferable. The salt used together with the polyurethane elastomer must not only have the properties described above, but must also exist as stable fine particles in the polyurethane elastomer solution. Such salts include sodium chloride, potassium chloride, sodium bromide, potassium bromide, magnesium sulfate, sodium sulfate, sodium carbonate, ammonia sulfate, and sodium hydrogen carbonate, among which sodium chloride, potassium chloride, and magnesium sulfate are particularly has a large effect. The amount of these salts used is preferably in the range of 0.01 to 10% by weight, particularly 0.1 to 5% by weight in the solution. usage amount
If it is less than 0.01% by weight, there is no effect, and if it exceeds 10% by weight, the stability of the salt in the solution may deteriorate and precipitation may occur, and the quality of the product may deteriorate. There is also a method of mechanically pulverizing the salt in a dry state, but in the present invention, an aqueous solution of a predetermined salt concentration is prepared in advance, and this aqueous salt solution is stirred in a polyurethane elastomer solvent. The method of using a composition liquid obtained by precipitating the salt as fine particles by dropping the salt into a liquid causes uniform coagulation in wet coagulation, resulting in a product of good quality. Further, even if the salt is used alone, it is not useful for improving wet coagulation properties, and an aqueous solution of the salt must be precipitated in a polyurethane elastomer solvent. The amount of water used should be kept within a range that does not impair the transparency of the polyurethane elastomer solution, and is usually about 0.1 to 8% by weight, most preferably 1 to 6% by weight. Water consumption is 0.1
If the amount is less than 8% by weight, there is no effect, and if the amount is more than 8% by weight, the solution becomes cloudy or gelatinous, resulting in poor stability. The polyurethane elastomer solution may contain stabilizers, fillers, pigments, dyes, etc., as well as polymers with good compatibility in the solution state, such as polyvinyl chloride, polyvinyl acetate, polyvinyl formal, methacrylic acid resin, etc., as necessary. Vinylidene chloride-acrylonitrile copolymer and vinyl chloride-vinyl acetate copolymer can be mixed. Although the polyurethane elastomer solution can be used in any of the binder coating layers of the fibrous material as described above, it is more effective when used in the latter. Therefore, in the case of leather-like sheets with a porous covering layer, the covering layer should necessarily be prepared from the polyurethane elastomer solution. In the present invention, uniform giant pores are created in the polyurethane elastomer layer, and wet coagulation is preferably carried out in a coagulation bath with a relatively high non-solvent concentration and low temperature. The leather-like sheet obtained as described above is finally subjected to finishing treatments such as softening agent treatment, buffing, coloring, embossing or fir processing. The present invention will be specifically described below with reference to Examples. All percentages in this example are by weight. Example 1 First, 34 parts of an aqueous sodium chloride solution having a concentration of 14% was added dropwise little by little to 360 parts of dimethylformamide with stirring to prepare a fine particle dispersion of sodium chloride. Next, 394 parts of this dispersion and 6 parts of carbon black were mixed with polytetramethylene glycol, ethylene glycol, and diphenylmethane-4.
Polyurethane elastomer synthesized from 4'-diisocyanate (N content 5.0%, cloudiness value 4) 25%
The solution was added to 600 parts of a dimethylformamide solution, stirred and mixed well, and the defoamed solution was impregnated into a nonwoven fabric of nylon fibers to give a solid content of 100 g/m ^{2 .}
A leather-like sheet [A] was produced by coating the sheet so that the sheet was coated, coagulating it in an aqueous solution containing 40% dimethylformamide at 40°C for 30 minutes, removing the solvent with warm water at 60-70°C for 2 hours, and drying. . In this product, many uniform giant pores were observed in both the fibrous base and the coating layer, and the surface flatness was also very good. On the other hand, three types of polyurethane elastomer solutions were prepared by removing only sodium chloride, water, or both sodium chloride and water from the polyurethane elastomer solution, and leather was prepared from these solutions and a nonwoven fabric of nylon fibers in the same manner as above. Similar sheets [B], [C] and [D] were manufactured. However, mechanically ground (using a mortar) sodium chloride was used to prepare the polyurethane elastomer solution used for producing the leather-like sheet [C]. Compared to the leather-like sheet [A], both the fibrous base and the coating layer had fewer large pores, were non-uniform, and had poor surface flatness. The above leather-like sheets [A], [B], [C] and [D] are made of the same polyurethane elastomer 6 as above.
%, carbon black 3%, dimethylformamide 21%, acetone 35% and cyclohexanone 35%
A solution consisting of 7% of the same polyurethane elastomer as above, 23% of dimethylformamide, and acetone.
A solution consisting of 35% and 35% cyclohexanone was applied sequentially using the gravure method at a solid content of 3g/m ² and 1.5g/m ² , respectively, and after drying, a rough fabric pattern was embossed, and then fir processing was performed. I went. As shown in Table 1, these evaluation results show that the leather-like sheet [A] has not only flatness, but also wrinkles and wrinkles.
The texture, moisture permeability, etc. were extremely good. Furthermore, when men's shoes were made using this and worn, no abnormalities such as cracking were observed even after one year had passed, and the product value was high.
On the other hand, leather-like sheets [B], [C], and [D] were all very inferior in appearance and quality to leather-like sheet [A], and had low commercial value.

[Table] Example 2 Polyester polyurethane elastomer with N content of 4.0% synthesized from polyethylene propylene adipate glycol 1,4-butane glycol and diphenylmethane-4,4'-diisocyanate (cloudiness value 18) 15%, carbon black 0.5%
A nonwoven fabric of mixed spun fibers of nylon and polystyrene (mixing ratio 1:1) was impregnated with a solution consisting of 1.2% stearyl alcohol and 83.3% dimethylformamide, and the mixture was heated at 40°C containing 50% dimethylformamide.
After coagulating with an aqueous solution of for 30 minutes, the polystyrene was extracted and removed with hot toluene, dehydrated with hot water, and dried to produce a fibrous substrate made of porous fibers. On the other hand, the same polyurethane elastomer solution used in Example 1 and the same polyester-based polyurethane elastomer solution as above were separately coated onto a polyethylene sheet at a solid content of 80 g/m ² , and a 30°C aqueous solution containing 40% dimethylformamide was applied. After coagulating for 30 minutes, it was peeled off from the support, stearyl alcohol was extracted and removed with methanol, and then dried to produce porous films [E] and [F], respectively. All of these had many uniform giant pores and had good surface flatness. Leather-like sheets [E] and [F] were obtained by bonding these porous sheets to the above-mentioned fibrous substrate whose surface had been smoothed by buffing. Finally, to these, 5% polyurethane elastomer synthesized from polyethylene glycol, ethanolamine and diphenylmethane-4,4'-diisocyanate, 2% methacrylic acid resin, Irgaran
A solution consisting of 2% BrackGBL (manufactured by CiBa Geigy), 21% dimethylformamide, 36% acetone, and 34% cyclohexanone was applied at a solid content of 3.5 g/ ^m2 , and after drying, a hair pattern was embossed. Ivy.
All of these items have flatness, texture, creases,
It had good moisture permeability. When men's shoes were made and worn using these, no abnormality was observed in the shoes using the leather-like sheet [E] even after one year, but when using the leather-like sheet [F]
Shoes using this product began to crack severely after just two weeks. Example 3 Polyurethane elastomer with N content of 4.3% synthesized from polycaprolactone glycol, ethylene glycol and diphenylmethane-4,4'-diisocyanate (white turbidity value 9) 11%, polyvinyl chloride 2%, finely ground magnesium sulfate 1% A mixed spun fiber of polyethylene and nylon (mixing ratio 1:1) was impregnated with a solution consisting of 2% water and 84% dimethylacetamide, coagulated in an aqueous solution containing 20% dimethylacetamide at 35°C for 30 minutes, and then heated. Polyethylene was extracted and removed with toluene, solvent removed with hot water, and then dried to obtain a fibrous base consisting of fine fiber bundles. Furthermore, this was treated with an aqueous dispersion containing 2% polyamide-type weak cation activator, dried, and then the surface was uniformly buffed.
LanyiBrown3R (manufactured by Sumitomo Chemical KK) 2% owf.
After dyeing at a bath ratio of 1:50 and a bath temperature of 60°C, soaping, drying and fir processing were performed. This thing has many uniform huge holes inside.
The texture, appearance, etc. were good.

Claims (1)

[Scope of Claims] 1. When producing a leather-like sheet by a wet coagulation method from a hydrophobic polyurethane elastomer with a cloudiness value of 13 or less and a fibrous material, the material is water-soluble but insoluble in the solvent of the polyurethane elastomer. A salt and water that can be dispersed as fine particles in a polyurethane elastomer solution are added to the polyurethane elastomer solvent by dissolving 0.01 to 5% by weight of the salt in 0.1 to 8% by weight of water based on the polyurethane solution. 1. A method for producing a soft leather-like sheet, characterized by using a polyurethane elastomer solution composition obtained by adding a composition solution in which the polyurethane elastomer is precipitated as fine particles to a polyurethane elastomer solution. 2. The method for producing a leather-like sheet according to claim 1, wherein the polyurethane elastomer is synthesized from polytetramethylene glycol, diphenylmethane-4,4'-diisocyanate, and _C2 to _C4 glycol. 3 Claim 1 in which coagulation is performed by wet coagulation method
A method for producing a leather-like sheet according to item 1 or 2.