JP2001081678A - Method for producing leather-like substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply produce a sheet having natural leather-like touch feeling and excellent in flexibility, sense of fullness and surface smoothness. SOLUTION: This method for producing a leather-like substance comprises a fiber-based substrate comprising ultrafine fiber, a polyurethane-based elastomer impregnated and coagulated into the interior of the fiber substrate and a resin for applying the surface of the elastomer. The method for producing the leather- like substance comprises (1) a step using a polyurethane-based emulsion having heat-sensitive gelling property as the polyurethane-based elastomer for impregnation and impregnating the emulsion into the interior of the fiber substrate and coagulating the emulsion, (2) a step using a resin emulsion as a resin solution for applying to the surface of the fiber substrate and applying the resin emulsion to the surface of the fiber substrate and coagulating the emulsion, and (3) a step using a sea-island cross section fiber or a readily spittable fiber as the fiber and removing sea component in the fiber by an organic solvent or an alkaline aqueous solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a leather-like sheet substrate. More specifically, the present invention relates to a method for producing a leather-like sheet substrate in which an emulsion resin is provided inside and on a surface of a fibrous base material made of ultrafine fibers.

[0002]

2. Description of the Related Art Sheets using a resin component such as polyurethane as a binder for a fibrous base material have been conventionally produced as a substitute for natural leather. Among such sheets,
When the fibrous base material is made of ultrafine fibers, it gives a feeling very similar to natural leather, and is therefore used as so-called high-grade suede artificial leather. As a typical production method, after applying a resin such as polyurethane to a nonwoven fabric made of sea-island composite spun fiber or mixed spun fiber,
A method for dissolving or decomposing and removing sea components in fibers with an organic solvent or an aqueous alkali solution to obtain ultrafine fibers, and dissolving the sea components of sea-island composite spun fibers or mixed spun fibers with an organic solvent or an aqueous alkali solution Alternatively, there is a method in which a resin such as polyurethane is applied after a fibrous base material composed of ultrafine fibers is produced by decomposing and removing. In the above production method, conventionally, as a method for applying a resin such as polyurethane, a solution of a resin represented by polyurethane, such as dimethylformamide (DMF), is impregnated into a fibrous base material and then coagulated in a non-solvent such as water. A so-called wet coagulation method is employed. This wet coagulation method can produce a sheet having a texture close to that of natural leather, but on the other hand, compared to a dry coagulation method in which an aqueous emulsion of a resin such as polyurethane is impregnated into a fibrous base material and then dried. There are drawbacks in that the productivity is inferior and the use of harmful organic solvents such as DMF is indispensable.

[0003]

For the above reasons, attempts have been made to replace the wet coagulation method with the dry coagulation method. However, a texture comparable to a leather-like sheet obtained by the wet coagulation method has been obtained. Not yet expressed. One of the reasons is that the sheet obtained by the dry coagulation method has a hard texture due to the structure in which the resin clings to the fibers in the drying process and is constrained, and the gap where there is no resin is larger than the resin application by the wet coagulation method. Because it can be done, the sense of fulfillment is inferior. However, in the dry coagulation method, it is possible to obtain a sheet without using an organic solvent by using an aqueous emulsion,
Since it is extremely important from the viewpoint of environmental compatibility and extremely effective in simplifying the process, it is expected to become one of the more important methods for producing leather-like sheets in the future.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the problems when the above-mentioned emulsion is used, and as a result, the texture has been improved as compared with the conventional emulsion-based resin application. The present inventors have found a method for producing a leather-like sheet substrate using a fibrous substrate composed of ultrafine fibers, and have completed the present invention based on these findings.

That is, the present invention relates to a method for producing a leather-like sheet substrate comprising a fibrous base material composed of ultrafine fibers, a polyurethane-based elastic body impregnated and solidified inside, and a resin coating the surface, the following (1): Steps (1) to (1) a step of using a thermosetting gelling polyurethane-based emulsion as a polyurethane-based elastic body to be impregnated, impregnating it with a fibrous base material and coagulating it, and (2) a resin to be coated on the surface. A step of using a resin emulsion as a liquid, applying it to the surface, and coagulating it. (3) Using a sea-island cross-section fiber or easily splittable fiber as a fiber, and removing sea components in the fiber with an organic solvent or an alkaline aqueous solution to obtain a fiber. A process for producing a leather-like sheet substrate, comprising the steps of: .

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The fibrous base material used in the present invention is not particularly limited as long as it is an ultrafine fiber having an appropriate thickness and a sense of fulfillment and a soft texture. A fibrous base material made of various kinds of ultrafine fibers used in the production can be used. The term “fibrous base material composed of ultrafine fibers” as used herein refers to a polymer which is a sea component of a composite spun fiber or a mixed spun fiber having an islands-in-sea cross section composed of two or more types of polymer materials having no compatibility. The substance is different from other polymer substances in solubility in organic solvents or decomposability in alkaline aqueous solution. When extracted or decomposed and removed, non-woven fabrics or knitted fabrics made of ultrafine fibers become substantially only island components. The fibrous base material, or two or more types of high-molecular substances having no compatibility are continuously present in a state of being bonded in the fiber axis direction, and by performing a chemical treatment or a physical treatment. It is a fibrous base material such as a nonwoven fabric or a knitted fabric which is made of a fiber which easily peels off at the interface of the polymer substance and becomes extremely fine.

[0007] Among them, a leather-like sheet from which sea-island type fibers are obtained is preferable because it has a texture and a feeling very similar to natural leather. The sea-island type sea component and the island component are referred to as an island component in the portion where the component A completely surrounds the component A in a certain cross section of the fiber, and B is referred to as a sea component. However, even when the component A is not completely surrounded by the component B and partially exposed outside the fiber, the component A is included in the island component. Component A may be composed of two or more polymer substances. Examples of such a polymer substance include polyamides such as 6-nylon, 6,12-nylon, 6,6-nylon, modified nylon, polyesters such as polyethylene terephthalate and modified polyesters, polyethylene, polystyrene, polypropylene and the like. Among polyolefins, polyvinylidene chloride, polyvinyl acetate, polymethacrylate, polyvinyl alcohol, polyurethane elastomers, etc., two or more kinds having different solubility in organic solvents such as toluene and perchrene or decomposability in alkaline aqueous solution. The substance can be selected and used. The weight ratio between the sea component and the island component in the conjugate spun fiber or the mixed spun fiber can be appropriately selected depending on the use of the obtained leather-like sheet. Generally, the island component / sea component = 15
/ 85-85 / 15, preferably 25 / 75-75 / 2
The ratio is 5.

[0008] Further, fibers which generate such ultrafine fibers are used in combination with ordinary synthetic fibers, shrinkable fibers, latent spontaneously extensible shrinkable fibers, special porous fibers, semi-synthetic fibers, natural fibers and the like. There is no problem in using a fibrous base material such as an entangled nonwoven fabric formed as long as the leather-like texture characteristic of ultrafine fibers is not impaired. Examples of such fibers include polyester-based fibers, nylon-based fibers, and acrylic-based fibers.

The thickness of the fibrous base material can be arbitrarily selected depending on the intended use of the obtained sheet and is not particularly limited, but is preferably 0.3 to 3.0 mm, more preferably 0.6 to 3.0 mm.
2.5 mm is more preferred. The apparent density of the fibrous base material is preferably from 0.1 to 0.5 g / cm ³ after obtaining an extremely fine sheet to obtain a sheet having a soft texture.
5 g / cm ³ is more preferred. 0.5g / apparent density
When the size is larger than cm ³ , the obtained sheet tends to have no stiffness or have a rubber-like texture. On the other hand, when the apparent density is less than 0.1 g / cm ³ , the resilience and the feeling of waist are inferior, and the texture like natural leather tends to be impaired. In addition, these fibers and fibrous base materials made of these fibers may be treated with a known dye, pigment, water repellent, softener, light stabilizer, penetrant, or the like in advance.

[0010] Among them, a non-woven fabric made of mixed spun fiber in which the sea component is polyethylene or polystyrene and the island component is 6-nylon, or a non-woven fabric made of a composite spun fiber in which the sea component is polyethylene or polystyrene and the island component is polyethylene terephthalate After impregnating and solidifying a polyurethane-based emulsion as described below, a resin emulsion is applied to the surface, and then a leather-like sheet substrate obtained by dissolving and removing polyethylene or polystyrene with toluene has a texture very similar to natural leather. Since it becomes a material for artificial leather having, it can be suitably used.

The polyurethane-based elastic material used in the present invention is a polyurethane-based emulsion having a thermosensitive gelling property. The elasticity at 90 ° C. of a 100 μm-thick film obtained by drying the polyurethane emulsion at 50 ° C. is 1.0 × 10 ^{7 to} 5.0 × 10 ⁸ (dyn /
cm ² ). Such a polyurethane resin has an elastic modulus of 1.0 × 10 at 90 ° C., which is often used in conventional nonwoven fabric binders and the like.
Compared to a polyurethane resin of less than ⁷ (dyn / cm ² ), the fibers do not cling to the polyurethane resin and are not restricted, so that a leather-like sheet excellent in a sense of fulfillment can be obtained, and the elastic modulus at 90 ° C. is 5.0. × 10 ⁸ (dyn / c
m ² ) than when a larger urethane resin is used,
A soft texture is obtained. Further, when ultra-fine fibers impregnated with a polyurethane-based elastic material are heated with an organic solvent such as hot toluene, the temperature of the polyurethane elastic material used is reduced to 160 ° C.
Is preferably not less than 1.0 × 10 ⁷ (dyn / cm ² ) because the resulting leather-like sheet has a small thickness and exhibits an excellent texture.

Such an emulsion may be either a W / O type or an O / W type, and may contain an organic solvent or may be a complete aqueous system containing no organic solvent. It is preferable to use an aqueous emulsion containing no organic solvent from the viewpoint of productivity in the process. Further, the polyurethane-based emulsion includes a composite-type polyurethane-based emulsion obtained by emulsion polymerization of an ethylenically unsaturated monomer such as methyl methacrylate or butyl acrylate in the presence of the polyurethane emulsion. Further, even if another resin is used in combination with the polyurethane resin constituting the emulsion, there is no problem as long as the texture of the obtained leather-like sheet is not impaired.

Resins which can be used in combination with such polyurethane resins include natural rubber and acrylonitrile-butadiene copolymer, polychloroprene, styrene-butadiene copolymer, polybutadiene, polyisoprene, ethylene-propylene copolymer, polyacrylate. And synthetic elastic polymers such as acrylate-type copolymers, silicone, polyvinyl acetate, polyvinyl chloride, polyester-polyether block copolymers, and ethylene-vinyl acetate copolymers.

As the polyurethane constituting the polyurethane emulsion of the present invention, a raw material polyurethane can be obtained by appropriately combining the following components such as a polymer polyol component, an isocyanate component and a chain extender.

The high molecular polyol constituting the polyurethane emulsion used in the present invention includes, for example,
Examples thereof include polyester polyol, polyether polyol, polycarbonate polyol, and polyester polycarbonate polyol. Polyester polyols of these high molecular polyols are subjected to direct esterification or transesterification of dicarboxylic acid or an ester-forming derivative such as an ester or anhydride thereof with a polyol, or a lactone is opened according to a conventional method. It can be produced by ring polymerization.

As the polyol constituting the polyester polyol, those generally used in the production of polyester can be used. Examples thereof include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol and 1,3-propanediol. , 2-methyl-1,3-propanediol, 2,
2-diethyl-1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butylene glycol, 1,4-butanediol, 2-methyl-1,4-
Hexamethylene glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 2,7-dimethyl-1,8-octane Diol 1,
2 carbon atoms such as 9-nonanediol, 2,8-dimethyl-1,9-nonanediol and 1,10-decanediol
Alicyclic diols such as 1,4-cyclohexanediol, cyclohexanedimethanol and dimethylcyclooctanedimethanol; aromatic dihydric alcohols such as 1,4-bis (β-hydroxyethoxy) benzene Can be mentioned. These diols may be used alone or in combination of two or more. Further, a compound having a trifunctional or higher hydroxyl group may be used together with the above diol, for example, glycerin, trimethylolethane, trimethylolpropane,
Trimethylolbutane, butanetriol, hexanetriol, pentaerythritol and the like can be mentioned. These polyols may be used alone,
Two or more kinds may be used in combination.

As the dicarboxylic acid constituting the polyester polyol, those generally used in the production of polyester can be used. For example, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid , Sebacic acid, dodecanedioic acid, methyl succinic acid, 2-methylglutaric acid, 3,8-dimethyl,
3-methylglutaric acid, trimethyladipic acid, 2-methyloctanedioic acid, 3,8-dimethyldecanedioic acid, 3,
An aliphatic dicarboxylic acid having 4 to 12 carbon atoms such as 7-dimethyldecane diacid; an alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid; an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, orthophthalic acid, and naphthalenedicarboxylic acid; Ester-forming derivatives and the like can be mentioned. These dicarboxylic acids may be used alone or in combination of two or more.

Examples of the lactone include ε-caprolactam and β-methyl-δ-valerolactone.

Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly (methyltetramethylene glycol) and the like. These polyether polyols may be used alone or in combination of two or more.

As the polycarbonate polyol, for example, those obtained by reacting a polyol with a carbonate compound such as dialkyl carbonate, alkylene carbonate, diaryl carbonate and the like can be used. As the polyol constituting the polycarbonate diol, the polyols exemplified above as the constituent components of the polyester polyol can be used. Examples of the dialkyl carbonate include dimethyl carbonate, diethyl carbonate, and the like. Further, the alkylene carbonate diol includes ethylene carbonate, and the diaryl carbonate includes diphenyl carbonate.

As the polyester polycarbonate polyol, for example, those obtained by simultaneously reacting a polyol, a dicarboxylic acid and a carbonate compound can be used. Alternatively, a polyester polyol and a polycarbonate polyol which are synthesized in advance by the above-described method and then reacted with a carbonate compound or reacted with a polyol and a dicarboxylic acid can be used.

The number average molecular weight of the high molecular polyol is 500
5,000 is preferable, and 600-3000 is more preferable. In addition, the number average molecular weight of the polymer polyol referred to in the present invention is a number average molecular weight calculated on the basis of a hydroxyl value measured according to JIS K1577.

The polymer polyol is a polymer polyol 1
Even if the number of hydroxyl groups per molecule is more than 2, there is no problem in use as long as it does not hinder the emulsion synthesis. As a means for obtaining a polymer polyol having more than two hydroxyl groups, the number of hydroxyl groups in one molecule is three so that the number of hydroxyl groups per molecule of an arbitrary polymer polyol when producing the polymer polyol is three. The method of using a low molecular polyol as described above, by mixing a high molecular diol and a high molecular polyol having 3 or more hydroxyl groups in one molecule during polyurethane polymerization, the number of hydroxyl groups per one molecule can be increased. Examples of the method include numbers. That is, as a method for producing a polymer polyol having more than two hydroxyl groups, for example, when producing the above-mentioned polyester polyol, it can be produced by using a compound having three or more functional hydroxyl groups in combination. Of course, other methods such as a method using tricarboxylic acid may be used.

The isocyanate compound used in the present invention is not particularly limited, and is a known aliphatic, alicyclic or aromatic compound containing an isocyanate group in a molecule conventionally used in the production of ordinary emulsion polyurethane. May be used, for example, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, isophorone diisocyanate,
P-phenylene diisocyanate, 1,5-naphthalene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 3,3'-dichloro-
4,4'-diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, and the like. Among these organic isocyanate compounds, it is preferable to use an aromatic isocyanate compound such as tolylene diisocyanate or 4,4'-diphenylmethane diisocyanate because the obtained polyurethane resin has excellent solvent resistance. Alternatively, it is particularly effective when applying a resin by emulsion prior to dissolving and removing the sea component of the mixed spun fiber. These organic isocyanates may be used alone or in combination of two or more.

There is no particular limitation on the chain extender, and any chain extender conventionally used in the production of ordinary emulsion polyurethanes may be used, and a hydrogen atom capable of reacting with an isocyanate group is added in the molecule. It is preferable to use a low molecular compound having a molecular weight of 400 or less, which contains two or more compounds. For example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanediol, bis (β-hydroxyethyl) terephthalate, 3-methyl-1,5-
Diols such as pentanediol, cyclohexanediol, xylylene glycol, 1,4-bis (β-hydroxyethoxy) benzene, neopentyl glycol, hydrazine, ethylenediamine, propylenediamine, xylylenediamine, isophoronediamine, piperazine and its derivatives, phenylene Diamine, tolylenediamine, xylenediamine, adipic dihydrazide, isophthalic dihydrazide, hexamethylenediamine, diamines such as 4,4'-diaminophenylmethane, 4,4'-dicyclohexylmethanediamine, triamines such as diethylenetriamine, and aminoethyl alcohol And amino alcohols such as aminopropyl alcohol. These low molecular weight compounds may be used alone or in combination of two or more.

As a method for producing the polyurethane emulsion used in the present invention, a production method generally used for producing an emulsion of polyurethane can be used. For example, forcible water is used under high mechanical shearing force in the presence of an emulsifier. Mention may be made of emulsified nonionic emulsions. In addition, a self-emulsifying emulsion obtained from a hydrophilic resin can be used. Examples of the forced emulsification method include a phase inversion emulsification method in which a liquid polyurethane polymer after completion of the reaction is emulsified with the emulsifier, and a chain extension reaction with a chain extender such as an amine at the same time as emulsifying and dispersing the terminal isocyanate prepolymer. And a prepolymer method obtained by increasing the molecular weight. A prepolymer method is particularly preferable to obtain a particularly good abrasion sheet.

Further, in order to improve the emulsifying dispersibility,
In order to introduce a nonionic hydrophilic group such as a polymer adduct such as ethylene oxide into the side chain of the polymer molecular skeleton of the polyurethane, or to improve solvent resistance, heat resistance and hot water resistance, trimethylolpropane or the like is used. Modification means by modifying the polyurethane itself, such as forming a crosslinked structure by reacting the above trifunctional glycol, trifunctional amine, etc., can also be suitably used in the present invention.

The polyurethane emulsion used in the present invention may further contain, if necessary, known additives such as, for example,
Surfactants such as light stabilizers, antioxidants, ultraviolet absorbers, penetrants, thickeners, fungicides, polyvinyl alcohol,
Water-soluble polymer compounds such as carboxymethyl cellulose, dyes, pigments, fillers, coagulation regulators and the like can be blended.

In the present invention, it is important that these emulsions have a thermosensitive gelling property. When an emulsion having no heat-sensitive gelling property is used, if dried by hot air after impregnation, the emulsion particles cannot be uniformly applied due to generation of migration, and physical properties such as strength and elongation and flexibility of the obtained sheet, texture, etc. When coagulating in warm water, the emulsion flows out into the coagulating hot water bath. In order to make the emulsion particles thermally gelled without causing migration substantially and to provide the emulsion particles uniformly, a substance called a so-called migration inhibitor is added to the emulsion, or the resin itself has a thermosensitive gelling property.

In the former case, examples of the heat-sensitive gelling agent to be used include inorganic salts, polyethylene glycol type nonionic surfactant, polyvinyl methyl ether, polypropylene glycol, silicone polyether copolymer, polysiloxane and the like. And one or more of these can be used. Among them, a combination of an inorganic salt and a polyethylene glycol-type nonionic surfactant is preferable because it gives a suitable result. Such polyethylene glycol type nonionic surfactants include, for example, ethylene oxide adducts of higher alcohols, ethylene oxide adducts of alkylphenols, ethylene oxide adducts of fatty acids, ethylene oxide adducts of fatty acid esters of polyhydric alcohols, Examples thereof include an ethylene oxide adduct of a higher alkylamine and an ethylene oxide adduct of polypropylene glycol. As the inorganic salts, monovalent or divalent metal salts which lower the cloud point of the nonionic surfactant are more preferable. Examples thereof include sodium carbonate, sodium sulfate, calcium chloride, calcium sulfate, zinc oxide, zinc chloride, magnesium chloride, potassium chloride, potassium carbonate, sodium nitrate, and lead nitrate. The compounding amount of the heat-sensitive coagulant is 100
0.2 to 20 parts by weight based on parts by weight is preferred.

The above-prepared emulsion is impregnated into the above-mentioned fibrous base material such as a nonwoven fabric and squeezed with a press roll or the like to obtain an appropriate amount of impregnation with a doctor knife or the like. It can be coagulated in a bath, coagulated in a steam atmosphere and then dried in a drier, or coagulated during drying directly in a drier at 50-150 ° C. Particularly, among these, solidification in warm water or solidification using steam is preferable because heat-sensitive coagulation proceeds promptly and gives a softer texture. During the impregnation of the emulsion, an aqueous solution or an aqueous emulsion of a surfactant having wet permeability can be applied to the fibrous base material prior to the impregnation of the emulsion in order to perform the impregnation uniformly and promptly.

The amount of the resin applied to the sheet by impregnating and drying the polyurethane-based emulsion is preferably 5 to 150% by weight, more preferably 10 to 100% by weight, based on the weight of the fiber component after the fineness. More preferably, the content is 20 to 80% by weight. If the resin adhesion amount is less than 5% by weight, the resulting sheet lacks a sense of fulfillment and the leather-like texture tends to be poor. On the other hand, if it exceeds 150% by weight, the resulting sheet tends to be hard and the leather-like texture tends to be poor.

In the present invention, it is important to coat a resin emulsion on the surface after the above-mentioned fibrous base material is impregnated with the polyurethane-based elastic material. Thereby, the surface of the fibrous base material is smoothed, and the fibers can be fixed. By performing this treatment, if a brushing treatment is performed to obtain a suede-like leather-like sheet by buffing,
The fluff can give a uniform and smooth surface touch, and when a surface layer is applied to obtain a so-called silvery leather-like sheet, it gives smooth and fine wrinkles, making it extremely natural leather. A close texture can be given.

The resin emulsion used for the above-mentioned surface coating is not particularly limited, but preferred examples thereof include polyurethane emulsion, acrylic emulsion, polyurethane-acryl composite emulsion, and styrene-based emulsion. Acrylic composite emulsions can be used more favorably because they impart excellent smoothness to the surface of the leather-like sheet.

In the polyurethane constituting the polyurethane emulsion or the polyurethane-acryl composite emulsion, the polymer polyol may be a polyether such as polytetramethylene glycol or polypropylene glycol, a polyester such as polyethylene adipate or polycaprolactone, or a polyhexamethylene carbonate. And isocyanate compounds used in non-yellowing polyurethanes, such as aliphatic or alicyclic isocyanates such as isophorone diisocyanate and aromatics such as tolylene diisocyanate and 4,4'-diphenylmethane diisocyanate. Although there is an isocyanate, it may be appropriately adopted according to the required performance of the leather-like sheet and the required performance in each step. For example, in the case of removing the alkali-soluble polyester which is a sea component of the microfiber-generating fiber with an aqueous alkaline solution after coating and drying the emulsion, a polyether-based polymer having excellent alkali resistance and hydrolysis resistance as a high molecular weight polyol, When using a high molecular weight polycarbonate-based polyol, or removing polyethylene or polystyrene, which is the sea component of microfiber-generating fibers, with hot toluene or the like, polyurethane using an aromatic isocyanate with excellent solvent resistance of the resin In order to obtain a leather-like sheet having excellent light fastness, use of an aliphatic isocyanate-based polyurethane may be mentioned. These emulsions may be used alone or in combination of two or more. Such emulsions include an O / W type and a W / O type, either of which may be used or used in combination. In the present invention, from the viewpoint of environmental safety, such a coating emulsion preferably contains a small amount of an organic solvent even if it contains an organic solvent, and more preferably contains no organic solvent.

The viscosity of the emulsion used for the surface coating is not particularly limited as long as it does not hinder the production process. However, when the viscosity is low, most of the emulsion penetrates into the interior of the fibrous base material, In some cases, the amount of resin contributing to smoothing is significantly reduced. Therefore, the viscosity of the emulsion is 5 cps
The above, especially those with 20 cps or more are preferably used.
Further, a viscosity modifier such as a commercially available thickener may be used to adjust the viscosity. The concentration of the emulsion can be changed according to the viscosity required for the coating treatment, the target application amount, and the target adhesion state. From the viewpoint of handling, the solid content is preferably 10% by weight to 70% by weight. More preferably, it is in the range of 20% by weight to 60% by weight. The amount of the resin applied by the emulsion coating is the sum of the weight of the fiber component after the formation of the ultrafine fibers and the weight of the polyurethane elastic body that has been dried to be a resin after the impregnation, which is 1%.
As 00 parts by weight, the adhesion amount in a state where the emulsion is dried to become a resin after coating is 0.2 to 25 parts by weight, preferably 0.5 to 15 parts by weight, more preferably 1.0 to 1.0 parts by weight.
The amount is in the range of 10 parts by weight. When the applied amount exceeds 25 parts by weight, the flexibility of the obtained leather-like sheet tends to be impaired, and when it is less than 0.2 parts by weight, the emulsion surface coat is insufficient and the leather-like sheet is insufficient. Therefore, it is difficult to improve surface smoothness.

Typical examples of the method of applying the emulsion used for the above surface coating include a method of coating an appropriate amount using a gravure roll, a doctor knife, or the like. Particularly, when a gravure roll is used, an excellent smooth surface is obtained. Are preferably used because they can form The treatment of the emulsion for surface coating may be performed at any time after the heat-sensitive gelling polyurethane emulsion is impregnated into the fibrous base material.・ Drying may be performed at the same time as drying, or coagulation of heat-sensitive gelling polyurethane emulsion.
After drying, it may be coated and dried.

Accordingly, the leather-like sheet of the present invention can be obtained, for example, by sequentially performing the following steps (1) to (6). (1) A step of impregnating a fibrous base material with a thermosetting gelling polyurethane-based emulsion and coagulating it (2) A step of drying (3) A step of applying the emulsion to the surface and drying (4) An organic solvent or an aqueous alkali solution Removing the sea component of the fibrous base material to ultrafine fibers, or exfoliating easily splittable fibers at the interface to ultrafine fibers (5) Dyeing process (6) Buffing and suede-like leather Or a process of providing a surface layer to give a leather-like sheet with a tone of silver. The order of each step can be changed or omitted as necessary. For example, the step (4) is performed first, the step (2) is not carried out as described above, and the step (3) is simultaneously performed. The step (5) or the step (5) is performed depending on the intended use of the leather-like sheet. (6) may be omitted.

In the present invention, the average thickness of the ultrafine fibers is preferably 0.5 denier or less, and if it exceeds 0.5 denier, a soft natural leather-like texture cannot be obtained. More preferably, it is 0.3 denier or less on average, and particularly preferably 0.1 denier or less and 0.0001 denier or more on average. The average thickness of the ultrafine fibers referred to in the present invention is obtained by calculating the number of ultrafine fibers from a micrograph of a cross section of the ultrafine fiber bundle, and dividing the total denier of the ultrafine fiber bundle by the number.

The sheet obtained by the present invention is a sheet having a moderate flexibility and a sense of fulfillment, and includes mattresses, bag lining materials, clothing interlining, shoe cores, cushioning materials, automobile interior materials, wall materials, carpets. It can be suitably used for example. Further, by buffing, a suede-like leather-like sheet is obtained, which can be suitably used for clothing, furniture, such as chairs and sofas, car seat, and wall materials. Further, by applying polyurethane or the like to one surface by a known method, it can be suitably used as artificial leather with silver tone used for sports shoes, men's shoes, bags and the like.

Hereinafter, the present invention will be described specifically with reference to Examples and the like, but the present invention is not limited to these Examples. In the following Examples and Comparative Examples, the elastic modulus at 90 ° C. of the film obtained by drying the polyurethane emulsion, the thermal gelation temperature,
The texture and surface smoothness of the sheet were evaluated by the following methods.

[Elastic modulus at 90 ° C.] A polyurethane emulsion having a thickness of 100 μm obtained by drying at 50 ° C.
m, using a viscoelasticity analyzer FT Rheospectral DVE-V4 manufactured by Rheology Co., Ltd.
The measurement was performed at 1 Hz, and the elastic modulus at 90 ° C. was obtained.

[Thermal Gelation Temperature] 10 g of the emulsion was weighed into a test tube, and the temperature was raised while stirring in a constant temperature hot water bath at 90 ° C. to obtain a gel when the fluid lost its fluidity and became a gel. The temperature was defined as the thermal gelation temperature.

[Hand] When the sheet has a natural leather-like hand, it is judged as "O" and the sheet lacks flexibility.
Or, the case where the sheet did not exhibit a natural leather-like texture due to lack of fulfillment was judged as "x".

[Surface Smoothness] The surface of the actually obtained sheet was traced by hand, and those having extremely smooth surface touch were classified as class 5, and those having strong roughness were rated as class 1, and evaluated according to the following criteria. 5th grade: extremely smooth 4th grade: excellent smoothness 3rd grade: smooth 2nd grade: slightly rough 1st grade: strong roughness

Table 1 shows the abbreviations of the compounds used in the text.

[Table 1]

<Manufacture of fibrous base material> [Reference Example 1] A multicomponent fiber (6 denier, 4 denier, 51 mm) obtained by mixing and spinning 40 parts of highly fluid polyethylene and 60 parts of 6-nylon was drawn. Nylon is an ultrafine fiber component: the number of islands in the fiber cross section is about 600), and a fiber entangled nonwoven fabric having an apparent density of 0.160 g / cm ³ was produced through each process of card, cross wrapper, and needle punch. . The nonwoven fabric was heated and the sea component polyethylene was melted and heat-fixed to obtain a fiber-entangled nonwoven fabric having an apparent density of 0.285 g / cm ³ , which had been smoothed on both sides. Hereinafter, this nonwoven fabric is abbreviated as nonwoven fabric.

REFERENCE EXAMPLE 2 A three-dimensional entangled nonwoven fabric comprising 70 parts of polyethylene terephthalate and 30 parts of low-density polyethylene, having 15 islands (polyethylene terephthalate is an island component) and a fineness of 4 denier sea-island fibers was prepared.
Shrink in warm water so as to have an area shrinkage of 30%, and fix the sea component polyethylene by melting and heat to obtain an apparent density of 0.35.
g / cm ³ of a nonwoven fabric as a fiber entangled nonwoven fabric which had been smoothed on both sides was obtained. Hereinafter, this nonwoven fabric is abbreviated as nonwoven fabric.

Reference Example 3 Copolymerized polyester obtained by reacting ethylene glycol with 5-sodium sulfoisophthalic acid and terephthalic acid as sea components (content of 5-sodium sulfoisophthalic acid component) 5.0 mol%) using nylon-6 as an island component,
A composite spun fiber having an island / sea component ratio of 65/35 and 16 islands was spun, stretched three times, mechanically crimped, and dried.
The staple was cut to a length of 3 mm to a thickness of 3 denier. Next, this staple is weighted by the cross wrap method 3
A web of 80 g / m ² was formed, and then needle punching was performed from both sides. It was further shrunk in hot air and pressed with a calender roll to produce an entangled nonwoven fabric with a smooth surface. The basis weight of this nonwoven fabric was 400 g / m ² , and the apparent specific gravity was 0.32. Hereinafter, this nonwoven fabric is abbreviated as nonwoven fabric.

Example 1 <Production of Thermosensitive Gelated Polyurethane Emulsion> In a three-necked flask, 600.0 g of PMSA1850, TDI
And weighed 114.8 g of DMPA and 7.95 g of DMPA, and stirred at 90 ° C. for 2 hours in a dry nitrogen atmosphere to quantitatively react hydroxyl groups in the system to obtain an isocyanate-terminated prepolymer. After 228.3 g of MEK was added thereto and uniformly stirred, the temperature in the flask was lowered to 40 ° C., and TEA was added to 6.
After adding 00 g, the mixture was stirred for 10 minutes. Next, as an emulsifier, an aqueous solution in which 53.3 g of Emulgen 930 (manufactured by Kao Corporation, nonionic surfactant) was dissolved in 478.5 g of distilled water was added to the prepolymer, and the mixture was stirred for 1 minute with a homomixer to emulsify. 13.2 g, IPDA
Was dissolved in 230.3 g of distilled water, and the mixture was stirred for 1 minute with a homomixer to carry out a chain extension reaction. Thereafter, MEK was removed by a rotary evaporator, and distilled water was added to obtain a polyurethane emulsion having a solid content of 40% by weight. 20 parts by weight of distilled water and 4 parts by weight of a heat-sensitive coagulant (water: a mixture of Kao, nonionic surfactant emulgen 910: calcium chloride in a weight ratio of 5: 4: 1) based on 80 parts by weight of the polyurethane emulsion And a polyurethane emulsion having heat-sensitive gelling properties (hereinafter referred to as PU emulsion). Thermal emulsion gelation temperature of PU emulsion is 5
2 ° C. The elastic modulus at 90 ° C. of the film obtained by drying this emulsion is 5.0 × 10 ⁷ (dy).
n / cm ² ).

<Preparation of Leather-Like Sheet> The PU emulsion was immersed in a nonwoven fabric and squeezed with a press roll.
The sheet was solidified in a hot water bath at 0 ° C. for 1 minute, and further dried in a hot air dryer at 130 ° C. for 30 minutes to obtain a sheet.
Further, a 20% solids aqueous solution of Bon Coat 1510NS (polyurethane emulsion manufactured by Dainippon Ink and Chemicals, Inc.) was applied thereon using a 150 mesh gravure roll, and
It was dried in a hot air dryer at 0 ° C. for 10 minutes. The amount of adhesion of the surface-coated polyurethane resin to the leather-like sheet is 2
% By weight. Treating this sheet in hot toluene,
The sheet was squeezed 5 times with a press roll of ² kg / cm ² to remove polyethylene as a sea component, thereby obtaining a sheet containing 6-nylon ultrafine fiber bundle entangled nonwoven fabric containing polyurethane. The total weight of the resin impregnated and coated was 60% by weight based on the weight of the nonwoven fiber. When this sheet was buffed with emery paper, a natural leather-like sheet having excellent surface smoothness, flexibility and fulfillment was obtained. Table 2 shows the results of the evaluation of the texture and the surface smoothness by the above method.

Comparative Example 1 An emulsion was prepared in the same manner as in Example 1 except that no heat-sensitive gelling agent was added to the emulsion. Hereinafter, it is called a PU emulsion. This P
The thermosensitive gelation temperature of the U emulsion was measured by the test method described above, but no gelling behavior was observed even at 90 ° C.
90 ° C. of the film obtained by drying this emulsion
Was 5.0 × 10 ⁷ (dyn / cm ² ). Example 1 except that this PU emulsion was used.
A sheet was produced in the same manner as described above. When the non-woven fabric impregnated with the emulsion was immersed in a warm water bath, a cloudy liquid of the emulsion flowed into the bath tub and contaminated the bath tub. The following procedure of coating the surface with a polyurethane resin and extracting toluene was performed in the same procedure to obtain a sheet. The attached weight of the resin was 40% by weight based on the weight of the nonwoven fabric. This sheet was not entirely paper-like without sagging. Table 2 shows the results of the evaluation of the texture and the surface smoothness by the above method.

Comparative Example 2 A leather-like sheet was produced in the same synthetic procedure as in Example 1 except that the surface coating treatment of the polyurethane emulsion with a gravure roll was not performed. The resin adhesion weight was 55% by weight based on the weight of the nonwoven fabric. When this sheet was buffed with emery paper, it had flexibility and a sense of fulfillment, but was inferior to the sheet obtained in Example 1 in terms of surface smoothness. Table 2 shows the results of the evaluation of the texture and the surface smoothness by the above method.
Shown in

Example 2 <Production of Polyurethane Emulsion> In a three-necked flask, 238.5 g of PHC2000 and PMSA1850 were added.
238.5 g of MDI, 200.0 g of MDI, and 8.05 g of DMPA were weighed, and dried at 70 ° C. for 2 hours under a dry nitrogen atmosphere.
With stirring, the hydroxyl groups in the system were quantitatively reacted to obtain an isocyanate-terminated prepolymer. Toluene 22
After adding 4.1 g and uniformly stirring, the temperature in the flask was lowered to 40 ° C., 6.07 g of TEA was added, and the mixture was stirred for 10 minutes. Next, Emulgen 930 as an emulsifier
An aqueous solution of 37.50 g of nonionic surfactant (manufactured by Kao) in 675 g of distilled water was added to the prepolymer, and the mixture was emulsified by stirring with a homomixer for 1 minute.
An aqueous solution obtained by dissolving 14.41 g of TA and 43.60 g of IPDA in 221.4 g of distilled water was added, and the mixture was stirred with a homomixer for 1 minute to perform a chain extension reaction. Then, after removing toluene and water by a rotary evaporator, distilled water was added to obtain a polyurethane emulsion having a solid content of 40 wt%. To 80 parts by weight of this polyurethane emulsion, 20 parts by weight of distilled water and 1.5 parts by weight of calcium chloride as a heat-sensitive gelling agent were blended to obtain a polyurethane emulsion having a heat-sensitive gelling property (hereinafter referred to as PU emulsion). Was. The thermal gelation temperature of the PU emulsion was 45 ° C. The elastic modulus at 90 ° C. of the film obtained by drying this emulsion was 3.0 × 1.
0 ⁸ (dyn / cm ² ).

<Preparation of Leather-Like Sheet> The PU emulsion was immersed in a non-woven fabric, squeezed by a press roll, solidified in a steam atmosphere at a gauge pressure of 0.3 kg / cm ² for 1 minute, and further heated at 130 ° C. with hot air. The sheet was obtained by drying in a dryer for 20 minutes. 150 on this
A 40% solids aqueous solution of Boncoat 1510NS (Polyurethane emulsion manufactured by Dainippon Ink and Chemicals, Inc.) was applied using a mesh gravure roll, and dried in a hot-air dryer at 130 ° C. for 10 minutes. The adhesion amount of the surface-coated polyurethane resin to the leather-like sheet was 7% by weight. The surface of this sheet coated with a polyurethane resin is treated in hot toluene, and squeezed five times with a 2 kg / cm ² press roll to remove polyethylene as a sea component, thereby forming a polyethylene terephthalate ultrafine fiber bundle fiber entangled nonwoven fabric. A sheet containing polyurethane was obtained. The attached weight of the resin was 62% by weight based on the weight of the nonwoven fabric fiber. When this sheet was buffed with emery paper, a natural leather-like sheet having excellent surface smoothness, flexibility and fulfillment was obtained. Table 2 shows the results of the evaluation of the texture and the surface smoothness by the above method.

Comparative Example 3 A leather-like sheet was produced in the same synthetic procedure as in Example 2, except that the surface coating treatment of the polyurethane emulsion with a gravure roll was not performed. The resin adhesion weight was 50% by weight based on the weight of the nonwoven fabric. When this sheet was buffed with emery paper, it had flexibility and a sense of fulfillment, but was inferior to the sheet obtained in Example 1 in surface smoothness. Table 2 shows the results of the evaluation of the texture and the surface smoothness by the above method.

Example 3 <Production of polyurethane emulsion> In a three-necked flask, 100.0 g of PMSA1850, PTG1000
200 g, PHC2000 200.0 g, TDI 104.6 g, DMPA 6.52 g were weighed, and stirred at 90 ° C. for 2 hours under a dry nitrogen atmosphere to quantitatively react hydroxyl groups in the system, Was obtained. After adding 191.8 g of toluene thereto and stirring the mixture uniformly, the temperature in the flask was lowered to 40 ° C.
92 g was added and the mixture was stirred for 10 minutes. Next, an aqueous solution obtained by dissolving 44.8 g of Emulgen 147 (manufactured by Kao, nonionic surfactant) as an emulsifier in 404 g of distilled water was added to the prepolymer, and the mixture was stirred for 1 minute with a homomixer to emulsify. An aqueous solution in which 04 g and 8.29 g of IPDA were dissolved in 240 g of distilled water was added, and the mixture was stirred for 1 minute with a homomixer to perform a chain extension reaction. Thereafter, toluene was removed by a rotary evaporator, and distilled water was added to obtain a polyurethane emulsion having a solid content of 40% by weight. 20 parts by weight of distilled water and a heat-sensitive coagulant (water: Kao, nonionic surfactant Emulgen 9) were added to 80 parts by weight of this polyurethane emulsion.
4 parts by weight of a 10: calcium chloride mixed solution at a weight ratio of 5: 4: 1) were blended to obtain a polyurethane emulsion having heat-sensitive gelling property (hereinafter, referred to as PU emulsion). The thermal gelation temperature of the PU emulsion is 52
° C. The film obtained by drying this emulsion has an elastic modulus at 90 ° C. of 5.0 × 10 ⁷ (dyn).
/ Cm ² ).

<Preparation of Leather-Like Sheet> PU emulsion was immersed in a non-woven fabric and squeezed with a press roll.
The sheet was solidified in a hot water bath at 0 ° C. for 1 minute, and further dried in a hot air dryer at 130 ° C. for 30 minutes to obtain a sheet.
The sea component was extracted from this sheet in a 40 g / l aqueous solution of sodium hydroxide at 90 ° C. (bath ratio 50: 1). During the treatment for one hour, the sheet was squeezed five times with a press roll of ² kg / cm ² to obtain a sheet containing 6-nylon ultrafine fiber non-woven fabric containing polyurethane. The attached weight of the resin was 55% by weight based on the weight of the nonwoven fabric fiber after removing the sea component. Further, a 25% solid content aqueous solution of Superflex E-4500 (a polyurethane emulsion manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was applied thereon with a 150 mesh gravure roll, and the solution was heated to 130 ° C.
For 10 minutes in a hot air dryer. The adhesion amount of the surface-coated polyurethane resin to the leather-like sheet was 1% by weight. By bonding a polyurethane film on release paper to the sheet with an adhesive, a leather-like sheet having a texture close to that of natural leather with silver was obtained. Table 2 shows the results of the evaluation of the texture and the surface smoothness by the above method.

Comparative Example 4 A leather-like sheet was produced in the same procedure as in Example 3, except that the surface coating treatment of the polyurethane emulsion with a gravure roll was not performed.
By bonding a polyurethane film on release paper to the sheet with an adhesive, a leather-like sheet with a silver tone was obtained.
The obtained sheet had large wrinkles and surface smoothness of Example 3.
It was inferior to the sheet obtained in the above. Table 2 shows the results of the evaluation of the texture and the surface smoothness by the above method.

[0060]

[Table 2]

[0061]

According to the production method of the present invention, use of a fibrous base material composed of ultrafine fibers, impregnation and coagulation inside the fibrous base material, application of a resin by a polyurethane emulsion, and resin by a surface coat of the resin emulsion By giving, a leather-like sheet having a natural leather-like texture excellent in flexibility, fullness, surface smoothness and the like can be produced.

Claims (3)

[Claims] 1. A method for producing a leather-like sheet substrate comprising a fibrous base material composed of ultrafine fibers, a polyurethane-based elastic body impregnated and solidified inside, and a resin coating the surface, the following (1) to (3): Step (1) A step of using a polyurethane-based emulsion having heat-sensitive gelling properties as a polyurethane-based elastic body to be impregnated, and impregnating it with a fibrous base material and coagulating it (2) A resin as a resin liquid to be coated on the surface Step of using an emulsion and applying it to the surface and coagulating it (3) Using sea-island cross section fiber or easily splittable fiber as the fiber, and removing the sea component in the fiber with an organic solvent or an alkaline aqueous solution, or removing the fiber A method for producing a leather-like sheet base, comprising a step of dividing the fibers into ultrafine fibers. 2. A polyurethane emulsion to be impregnated in step (1) is dried at 50.degree. C. to obtain a 100 .mu.m thick film having an elastic modulus at 90.degree.
^{2. The} method according to claim 1, wherein the value is in the range of 0 × 10 ^{7 to} 5.0 × 10 ⁸ (dyn / cm ² ). 3. The method according to claim 1, wherein steps (1), (2) and (3) are sequentially performed.