JPS5842308B2 - Artificial leather manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing artificial leather that has excellent moisture permeability, excellent flexibility, and good durability.

It is known to deposit porous coating layers onto a substrate for use as a leather replacement.

When such a porous material has so-called coarse pores with a large pore diameter, the tensile strength, scratch strength, tear strength, and other strengths of the artificial leather are poor. Attempts have been made to reduce the porosity and increase the strength.

However, this method has a serious drawback in that the bending ridge quality of the artificial leather deteriorates.

Therefore, this method cannot be applied to fields where durability is required, such as shoe applications.

The inventors of the present invention have conducted studies aimed at completing a coating layer that does not reduce its flexibility even when the coating layer containing coarse pores is reduced in thickness and made into fine pores, and as a result, they have arrived at the following invention. .

That is, an object of the present invention is to provide an artificial leather having excellent flexibility, durability, and moisture permeability.

The object of the present invention is to produce artificial leather by reducing the thickness of the coating layer to 70% or less of the original thickness by heat pressing from a leather-like sheet having a porous coating layer in which coarse pores are present. In the method, as the leather-like sheet,
A sulfosuccinic acid ester compound having a structure represented by the following structural formula (1) is added and mixed to a hygroscopic solvent solution of a polyurethane elastomer in an amount of 10 parts or more per 100 parts of the polyurethane elastomer and within a range where the composition does not lose fluidity. This is achieved by using a sheet material having a porous coating layer containing coarse pores formed on a fibrous sheet by wet coagulating a polyurethane composition.

(In the formula, R1 and R2 are alkyl groups having 1 to 18 carbon atoms, and R1 and R2 may be the same or different, and M is hydrogen or a monovalent alkali metal.

) A polyurethane emulsion is known in which a sulfosuccinate type surfactant is combined with a polymeric sulfone group-containing compound and a hydrazide-elongated polyurethane containing a polyethylene glycol chain.

However, this method uses a sulfosuccinic acid ester type surfactant as a surfactant that is naturally required in the production of an aqueous polyurethane emulsion, and therefore, the amount of the sulfosuccinate type surfactant added is substantially 2 to 100 parts per 100 parts of polyurethane.
A small amount of 3% is used.

There is also known a method in which an elastomer solution containing an anionic surfactant such as a sulfosuccinate as a bubble regulator is applied onto a fabric and wet-coagulated (Japanese Patent Publication No. 46-2597).

However, in this method, a sulfosuccinic acid ester, etc. is added for the purpose of arbitrarily adjusting the shape and size of the bubbles in the porous film, and the amount of addition is also based on 100 parts of elastomer, referring to the examples. , a small amount of about 3-5% is used.

Surprisingly, in the process of the present invention, adding a sulfosuccinate compound to a solution of polyurethane in a hygroscopic solvent in a much higher amount than required in the preparation of the emulsion or cell control elastomer solution results in the formation of such a composition. The coating layer is wet-coagulated to form a porous structure with coarse pores, and by heat pressing, the thickness of the coating layer is reduced and even when the pores are made fine, there is no decrease in flexibility and an extremely durable artificial leather can be obtained. It turned out that this had the unexpected effect of increasing

Particularly in the case of shoe applications, it is necessary to have good durability in both weather resistance and flexibility, and the present invention provides excellent effects in terms of these properties.

The porous coating layer of the leather-like sheet used in the present invention is
Particularly effective are those in which 50% or more of the total porosity consists of coarse pores with a maximum diameter of 50 microns or more.

The maximum diameter here refers to the longest distance of the hole measured from a cross-sectional photograph of the coating layer.

Such effects cannot be achieved unless the amount of the sulfosuccinate compound added is 10 parts or more per 100 parts of the polyurethane elastomer.

Preferably, an amount of 20 parts or more is required.

If the amount added is too large, the composition will lose its fluidity, so the upper limit of the amount added is just before the composition loses its fluidity.

The sulfosuccinate compound used in the present invention has a structure represented by formula 1, and monoesters and diesters are used.

For example, dibutyl ester, diisobutyl ester, cyamyl ester, dioctyl ester, dioctyl ester, di-2-ethylhexyl ester and the like are particularly preferred.

Sodium is usually used as M and can be added to the polyurethane solution as a sodium salt.

Polyurethane elastomers that can be used in the present invention include:
A prepolymer obtained by reacting a polymeric diol having hydroxyl groups at both ends of polyether, polyester, or polyether ester with an excess of organic diisocyanate is chain-extended using a polyfunctional chain extender such as diamine or glycol. used.

Among such polyurethane elastomers, those that are particularly effective in combination with sulfosuccinic acid have a gel point value defined below in the range of 1.0 to 10.0, more preferably in the range of 2.0 to 7.0. It is something that goes into.

The gel point mentioned here is 1 of the polyurethane elastomer.
Pure water is added dropwise to a 100CA% dimethylformamide solution at 25° C. under stirring, and it is defined as the amount of water (CC,) required to be added until the entire solution becomes cloudy.

Polyurethanes having such a gel point include polyurethanes made from a mixed diol of polytetramethylene ether glycol and polyester diol, and blocks containing structural units in the main chain in which a polytetramethylene glycol chain and a dicarboxylic acid residue are adjacent. Particular preference is given to polyurethanes from copolymeradiols.

In the present invention, polyurethane is used as a solution in a hygroscopic solvent, and preferred hygroscopic solvents include dimethylformamide, diethylformamide, dimethylacetamide, dimethylsulfoxide, hexamethylphosphoramide, and the like.

The sulfosuccinate compound can be added to the polyurethane solution as it is or dissolved in a solvent to form a composition.

In addition, colorants, weathering agents, coagulation regulators, other surfactants, resins, and the like may be appropriately added to the composition.

When a polymer having a softening point lower than that of a polyurethane polymer, such as polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, or acrylic polymer, is mixed into the polyurethane composition of the present invention. is preferable because the coating layer can be easily smoothed.

Such a composition exhibits excellent properties for use in artificial leather and is therefore suitable for coating fibrous sheets. In particular, the coating layer containing coarse pores with a maximum diameter of 50 microns or more is reduced in thickness to reduce the size of the coarse pores. It has very excellent properties as a coating layer constituent when micropores are formed, and it has a particularly remarkable effect on bending properties where weather resistance is required.

A leather-like sheet having a coating layer containing coarse pores is obtained by applying such a composition to a fibrous sheet and wet-coagulating it with a liquid that is non-solvent for polyurethane and miscible for polyurethane solvent. .

Methods such as wet transfer and bonding can also be used.

As the fibrous sheet, it is preferable to use a sheet obtained by impregnating a nonwoven fabric, woven fabric, knitted fabric, or a combination thereof with a polymer solution or emulsion and wet coagulating or dry coagulating, and in particular, a nonwoven fabric is used as the main material. A fibrous sheet is impregnated with a resin solution or emulsion, or after impregnation, the resin solution or emulsion is applied one or more times to the side to be coated with the polyurethane composition while it is still wet. Most suitable for the present invention is one obtained by substantially penetrating the inside of the nonwoven fabric sheet and forming a density gradient due to the resin inside the nonwoven fabric sheet.

In the present invention, the leather-like sheet having the porous coating layer thus obtained is heat-pressed to reduce the thickness of the coating layer to 70% or less of the original thickness to make it microporous, thereby maintaining tensile strength while maintaining flexibility. , improve various strengths such as scratch strength and tear strength.

If the coating thickness is reduced by 70% or more of the original thickness, these strengths will not be sufficiently improved, which is not preferable.

When heat pressing is performed, a smooth product cannot be obtained simply by passing the material through heated rolls.

A preferred method is to pass between a pair of rolls where at least the contacting side of the covering layer is heated, and then the covering layer is applied to the leather-like sheet at least 115 mm around the circumference of the heated rolls with an adhesive strength greater than that which does not fall off due to mutual overlap. This is a method in which the film is passed under conditions such that it self-adheres, and then it is peeled off from the hot roll.

In such a method, a heating temperature of 120 to 250°C is used, and a heating temperature of 170 to 220°C is particularly preferred.

Known top coating and other finishing treatments can be applied to the artificial leather obtained according to the present invention, and furthermore, kneading treatment and dyeing treatment can also be added.

The present invention will be explained in detail below using Examples.

All parts used in the following examples are by weight.

Example l A) Production of polyurethane composition To 400 parts of a 25% dimethylformamide solution of polyurethane (polytetramethylene ether glycol-diphenylmethane-4,4-diisocyanate-ethylenediamine type, gel point 1.80) was added vinyl chloride and vinyl acetate. 40 parts of a 25% polymer solution in dimethylformamide, 28 parts of sodium dioctyl sulfosuccinate, 3% carbon black to polyurethane, and 2 parts of dimethylformamide.
00 parts were added and mixed to obtain a polyurethane composition.

This polyurethane composition had a viscosity of about 150 poise and had good fluidity.

For comparison, a comparative polyurethane composition was obtained in exactly the same manner except that sodium dioctyl sulfosuccinate was not added.

B) Manufacture of artificial leather A needle-punched nonwoven fabric made of polyester staples with a fineness of 0.8 denier and a length of 511L and 11L is impregnated with a 15% dimethylformamide solution of polyester urethane, wet coagulated with water, washed with hot water, and dried to increase the thickness. 1.41t
A fibrous sheet of No. 1 was obtained.

The amount of polyurethane applied in the sheet is 60 parts per 100 parts of fiber.
It was a department.

The polyurethane composition obtained above was applied onto the fibrous sheet using a coating blade with a thickness of 1.5 mm, wet-coagulated with water, washed with hot water, and dried to form a leather-like sheet with a coating layer of 480 microns thick. I got it.

The coating layer of the leather-like sheet has a maximum diameter of 150 mm in the layer.
It had a porous structure with coarse pores on the order of microns.

The thus obtained leather-like sheet of the present invention was heated to 180°C with a pair of embossing rolls engraved with pore-like grains.
Roll clearance is 0.3 times the thickness of the leather-like sheet,
Immediately after passing through the clearance part by passing the roll at a circumferential speed of 0.80 m/min, the coating layer is self-adhered to the engraving roll heated to 180 ° C., and the distance of x of the roll circumference is kept self-adhesive. When it was then peeled off, the thickness of the coating layer decreased to 270 microns (58% of the original thickness).
Moreover, the coarse pores in the coating layer were made fine, and the artificial leather of the present invention having a porous coating layer entirely composed of micropores was obtained.

On the other hand, artificial leather was produced in exactly the same manner from a comparative polyurethane composition.

The properties of both artificial leathers were as shown in Table 1.

In other words, from Table 1, the artificial leather of the present invention has good weather resistance, flexibility, and low-temperature flexibility, while the comparative example has good flexibility and flexibility.
It has poor weather resistance, especially its flexibility after weathering treatment.

It is clear that the artificial leather of the present invention exhibits a remarkable effect on the flexibility required for such weather resistance.

Example 2 A) Preparation of polyurethane composition Polytetramethylene ether glycol (MW=205
0) From a block copolymer diol obtained by condensing 1 mole of phthalic acid and 2 moles of ethylene glycol, and diphenylmethane-4,4'-diisocyanate and diphenylmethane-4,47-diamitsiphenylmethane. To 400 parts of a 25% dimethylformamide solution of a polyurethane elastomer (gelling point 3.2), 5 parts of polyvinyl butyral, 32 parts of sodium di-2-ethylhexylsulfosuccinate, 3% carbon black to the polyurethane, and dimethyl 230 parts of formamide was added and mixed to obtain a polyurethane composition.

This polyurethane composition had a viscosity of about 130 poise and had good fluidity.

For comparison, a comparative polyurethane composition was obtained in exactly the same manner except that sodium di-2-ethylhexylsulfosuccinate was not added.

B) Manufacture of artificial leather The polyurethane composition of the present invention was coated on the same fibrous sheet as in Example 1 using a reverse roll coater, wet coagulated with water, washed with hot water, and dried to form a porous sheet with a thickness of 520 microns. A leather-like sheet having a laminated coating layer was obtained.

The coating layer of the leather-like sheet has a maximum diameter of 16 mm in the layer.
It had coarse pores of about 0 micron.

The thus obtained leather-like sheet of the present invention was passed through a hot roll in the same manner as in Example 1 to obtain an artificial leather laminated with a microporous coating layer having a thickness of 250 mm (48% of the original thickness). I got it.

On the other hand, a comparative artificial leather was produced in exactly the same manner using a comparative polyurethane composition.

The properties of both artificial leathers were as shown in Table 2.

From Table 2, it is clear that the examples of the present invention, like Example 1, have excellent weather resistance and bending properties.

Moreover, the bending properties of the inventive example using polyurethane with a gel point of 3.2 were superior to the inventive example of Example 1, which used polyurethane with a gel point of 1.8.

Example 3 A) Production of polyurethane composition In the polyurethane composition of Example 2, the amount of sodium di-2-ethylhexyl sulfosuccinate was changed as shown in Table 3, and the other conditions were the same as in Example 2. A polyurethane composition was produced.

B) Manufacture of artificial leather A needle-punched nonwoven fabric is obtained from 16 polymer array fibers in which the sea component is polystyrene and the island component is polyester, and after impregnating it with a polyurethane emulsion, the sea component is extracted with percrene to create an impregnated nonwoven fabric. I got it.

Further, this impregnated nonwoven fabric is impregnated with an acrylic ester emulsion, and then, while it is still wet, the acrylic ester emulsion is coated with a gravure coater so that it substantially penetrates into the inside of the nonwoven fabric, so that the thickness with a binder density gradient is 1. A fibrous sheet of 21rL and 11L was obtained.

The above-mentioned polyurethane composition was laminated on the obtained fibrous sheet in the same manner as in Example 1, and the mixture was passed through a hot roll to produce artificial leather.

The properties of each artificial leather were as shown in Table 3. From Table 3, it is clear that the purpose of the present invention, which is to improve the bending properties that require weather resistance, cannot be achieved unless the amount of the sulfosuccinate compound added is 10 parts or more, and that 20 parts or more is particularly preferred.

Claims (1)

[Scope of Claims] 1. Artificial leather is produced by reducing the thickness of the coating layer to 70% or less of the original thickness by heat pressing from a leather-like sheet having a porous coating layer in which coarse pores are present. In the method, the leather-like sheet is prepared by adding 10 parts or more of a sulfosuccinate compound having a structure represented by the following structural formula to 100 parts of the polyurethane elastomer in a hygroscopic solvent solution of the polyurethane elastomer and causing the composition to lose fluidity. An artificial leather characterized by using a sheet-like material having on a fibrous sheet a porous coating layer containing coarse pores formed by wet-coagulating a polyurethane composition which is added and mixed within a range that does not cause the artificial leather to bend. Manufacturing method. (In the formula, R1 and R2 are alkyl groups having 1 to 18 carbon atoms, and R1 and R2 may be the same or different, and M is hydrogen or a monovalent alkali metal.)