JPWO2018186141A1 - Method for producing porous body - Google Patents

Abstract

  The present invention provides a method for easily obtaining a porous material by coagulating an aqueous urethane resin composition using a specific coagulant. Specifically, the present invention provides a method for producing a porous body characterized in that an aqueous urethane resin composition is applied to a substrate and immersed in an aqueous metal salt solution heated to 40 ° C. or higher. The metal salt used for the coagulant is preferably sodium chloride. Moreover, it is preferable that the said water-based urethane resin composition contains the water-based urethane resin (A) which has an aromatic ring. The content of the aromatic ring in the aqueous urethane resin (A) is preferably in the range of 0.8 to 8 mol / kg. The aqueous urethane resin (A) is preferably made from aromatic polyisocyanate, especially diphenylmethane diisocyanate. According to the production method of the present invention, a porous body excellent in texture can be easily obtained without using an organic solvent.

Description

  The present invention relates to a method for producing a porous body that can be used for producing, for example, synthetic leather.

  A water-based urethane resin composition in which a urethane resin is dispersed in an aqueous medium can reduce the environmental burden compared to conventional organic solvent-based urethane resin compositions, so that materials for producing synthetic leather, coating agents, adhesives, etc. In recent years, it has been used favorably.

  The leather-like sheet is generally composed of a fiber base material such as a non-woven fabric, an intermediate layer composed of a porous layer or the like as needed, and a skin layer. The fiber base material is a leather-like sheet. For the purpose of improving the bending resistance and texture, a fiber base material such as nonwoven fabric impregnated with an aqueous urethane resin composition and heat-coagulated (impregnated layer) is used.

  Examples of the aqueous urethane resin composition for impregnation of the fiber base material include an aqueous urethane resin composition containing a polyurethane resin having a carboxyl group and / or a sulfonic acid group, a thermal coagulant, and an aqueous medium. (For example, refer to Patent Document 1).

  However, in the coagulation of the aqueous urethane resin composition by heat-sensitive coagulation, the viscosity of the urethane resin compound is once lowered by heating, the intermediate layer coating solution is absorbed by the fiber base material, and further the resin is applied to the fiber intersection by capillary action. It has been pointed out that the film obtained is inferior in flexibility and flexibility and easily damaged because the resin tends to adhere and the resin restrains the fibers.

Japanese Patent Laying-Open No. 2015-7172

  The problem to be solved by the present invention is to provide a production method in which an organic solvent is not used and a porous body having excellent texture can be obtained.

  This invention provides the manufacturing method of the porous body characterized by apply | coating an aqueous | water-based urethane resin composition to a base material, and making it immersed in the metal salt aqueous solution heated at 40 degreeC or more.

  According to the production method of the present invention, a porous body having excellent texture can be obtained. Therefore, the said porous body can be used conveniently for manufacture of synthetic leather.

  The manufacturing method of the porous body of this invention makes it an essential requirement to apply | coat an aqueous | water-based urethane resin composition to a base material, and to make it immersed in the metal salt aqueous solution heated at 40 degreeC or more.

  In the present invention, it is essential to use an aqueous metal coagulant solution as the coagulant. By using the coagulant, the uniformity of the resin adhesion state is improved and porous, so that a porous body having an excellent texture can be obtained. Moreover, since a coagulation | solidification speed | rate improves by heating a coagulant to 40 degreeC or more, the water-based urethane resin can be coagulated and the coagulation | solidification which has the further outstanding texture is obtained. If the temperature of the coagulant is less than 40 ° C., the aqueous urethane resin cannot be coagulated. The heating temperature of the coagulant is preferably in the range of 40 to 100 ° C, more preferably 40 to 80 ° C. In the present invention, “porous body” refers to a material having a large number of pores.

  As the metal salt, for example, calcium nitrate, calcium chloride, zinc nitrate, zinc chloride, magnesium acetate, aluminum sulfate, sodium chloride and the like can be used. These metal salts may be used alone or in combination of two or more. Among these, the thickening and coagulation speed of the aqueous urethane resin composition is fast, and the fiber adhesion and restraint of the resin due to the capillary phenomenon can be suppressed, so that sodium chloride is used from the point that an even better texture is obtained. preferable.

  Examples of water used for the coagulant include ion exchange water, distilled water, and tap water. These waters may be used alone or in combination of two or more.

  As content of the said metal salt, it is preferable that it is the range of 1-50 mass% in the said metal salt aqueous solution, and it is more preferable that it is the range of 2-20 mass%.

  Examples of the base material include a base fabric; polyester such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyolefin, polyacrylate, polyvinyl chloride, polyethylene, polypropylene ethylene vinyl alcohol, polyurethane, polyamide, polyimide, and the like. The obtained sheet or film can be used. Among these, when the porous body obtained by the present invention is used as a synthetic leather, it is preferable to use a base fabric because an excellent texture can be obtained.

  As said base fabric, a nonwoven fabric, a woven fabric, a knitted fabric etc. can be used, for example. For example, polyester fiber, nylon fiber, acrylic fiber, polyurethane fiber, acetate fiber, rayon fiber, polylactic acid fiber, cotton, hemp, silk, wool, and blended fibers thereof are used as the fiber substrate. can do.

  The porous body is formed by applying an aqueous urethane resin composition to a substrate and immersing it in the aqueous metal salt solution heated to 40 ° C. or higher.

  Examples of the method for applying the aqueous urethane resin composition to a substrate include a method using a roll coater, knife coater, spray coater, gravure coater, comma coater, T-die coater, applicator and the like. .

  Next, the coated product is further immersed in a coagulation bath containing the metal salt aqueous solution heated to 40 ° C. or more, whereby the urethane resin in the aqueous urethane resin composition is solidified to obtain a porous body. The immersion / solidification time at this time is, for example, in the range of 1 to 30 minutes.

  After obtaining the porous body, if necessary, it can be immersed in running water for 10 minutes to 2 hours after solidification to wash away unnecessary coagulants.

  As an aqueous | water-based urethane resin composition which can be used in this invention, the thing containing an aqueous | water-based urethane resin (A) and an aqueous medium (B) can be used, for example.

  The aqueous urethane resin (A) can be dispersed in an aqueous medium (B) described later. For example, the aqueous urethane resin having a hydrophilic group such as an anionic group, a cationic group, or a nonionic group; An aqueous urethane resin or the like that is forcibly dispersed in the aqueous medium (B) with an emulsifier can be used. These aqueous urethane resins (A) may be used alone or in combination of two or more. Among these, from the viewpoint of production stability, it is preferable to use an aqueous urethane resin having a hydrophilic group, the solidification property to the coagulant is further improved by the electric double layer compression effect, and the texture is further improved. In view of the above, it is more preferable to use an aqueous urethane resin having an anionic group.

  Examples of the method for obtaining the aqueous urethane resin having an anionic group include a method using as a raw material one or more compounds selected from the group consisting of a compound having a carboxyl group and a compound having a sulfonyl group.

  Examples of the compound having a carboxyl group include 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolpropionic acid, and the like. . These compounds may be used alone or in combination of two or more.

  Examples of the compound having a sulfonyl group include 3,4-diaminobutanesulfonic acid, 3,6-diamino-2-toluenesulfonic acid, 2,6-diaminobenzenesulfonic acid, N- (2-aminoethyl)- 2-aminoethylsulfonic acid or the like can be used. These compounds may be used alone or in combination of two or more.

  The carboxyl group and sulfonyl group may be partially or completely neutralized with a basic compound in the aqueous urethane resin composition. Examples of the basic compound include organic amines such as ammonia, triethylamine, pyridine, and morpholine; alkanolamines such as monoethanolamine and dimethylethanolamine; metal base compounds including sodium, potassium, lithium, calcium, and the like. Can do.

  Examples of the method for obtaining the aqueous urethane resin having a cationic group include a method using one or more of compounds having an amino group as a raw material.

  Examples of the compound having an amino group include compounds having primary and secondary amino groups such as triethylenetetramine and diethylenetriamine; N-alkyl dialkanolamines such as N-methyldiethanolamine and N-ethyldiethanolamine, and N-methyl. A compound having a tertiary amino group such as N-alkyldiaminoalkylamine such as diaminoethylamine and N-ethyldiaminoethylamine can be used. These compounds may be used alone or in combination of two or more.

  Examples of a method for obtaining the aqueous urethane resin having a nonionic group include a method using one or more compounds having an oxyethylene structure as a raw material.

  Examples of the compound having an oxyethylene structure include polyether polyols having an oxyethylene structure such as polyoxyethylene glycol, polyoxyethylene polyoxypropylene glycol, and polyoxyethylene polyoxytetramethylene glycol. These compounds may be used alone or in combination of two or more.

  Examples of the emulsifier that can be used in obtaining the aqueous urethane resin that is forcibly dispersed in the aqueous medium (B) include polyoxyethylene nonyl phenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styryl phenyl ether, Nonionic emulsifiers such as polyoxyethylene sorbitol tetraoleate and polyoxyethylene / polyoxypropylene copolymers; fatty acid salts such as sodium oleate, alkyl sulfate esters, alkylbenzene sulfonates, alkyl sulfosuccinates, naphthalene sulfonates Anionic emulsifiers such as salts, polyoxyethylene alkyl sulfates, alkane sulfonate sodium salts, sodium alkyl diphenyl ether sulfonates; alkyl amine salts, alkyl trimethyl Ammonium salts, such as cationic emulsifiers such as alkyl dimethyl benzyl ammonium salts can be used. These emulsifiers may be used alone or in combination of two or more.

  Specifically as said water-based urethane resin (A), the polyisocyanate (a1), polyol (a2), the raw material used in order to manufacture the water-based urethane resin which has an above described hydrophilic group, and a chain | strand as needed What can be obtained by using an extending | stretching agent (a3) as a raw material can be used. These reactions can use known urethanization reactions.

  As the water-based urethane resin (A), an aromatic ring is used because of its low solubility in the coagulant used in the present invention, easy maintenance of a good solidified state and easy porosity, and a further improved texture. It is preferable to use an aqueous urethane resin.

  As content of the aromatic ring of the said water-based urethane resin (A), it is preferable that it is the range of 0.8-8 mol / kg, and it is more preferable that it is the range of 1-6 mol / kg.

  The aromatic ring is supplied from either the polyisocyanate (a1) or the polyol (a2) as a raw material, but is supplied from the polyisocyanate (a1) from the viewpoint of easy availability of the raw material and production stability. That is, it is preferable to use an aromatic polyisocyanate.

  Examples of the aromatic polyisocyanate include phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, polymethylene polyphenyl polyisocyanate, carbodiimidized diphenylmethane polyisocyanate, and the like. These polyisocyanates may be used alone or in combination of two or more. Among these, it is preferable to use diphenylmethane diisocyanate from the viewpoint of easy availability of raw materials and texture.

  Examples of other polyisocyanates that can be used for the polyisocyanate (a1) include hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, and dimer acid diisocyanate. An aliphatic or alicyclic polyisocyanate such as norbornene diisocyanate can be used. These polyisocyanates may be used alone or in combination of two or more.

  As said polyol (a2), polyether polyol, polyester polyol, polyacryl polyol, polycarbonate polyol, polybutadiene polyol, etc. can be used, for example. These polyols may be used alone or in combination of two or more.

  The number average molecular weight of the polyol (a2) is preferably in the range of 500 to 8,000, and more preferably in the range of 800 to 4,000, from the viewpoint of the mechanical strength of the resulting film. In addition, the number average molecular weight of the said polyol (a2) shows the value measured by the gel permeation column chromatography (GPC) method.

  Examples of the chain extender (a3) include ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 1,2-cyclohexanediamine, 1, Amino groups such as 3-cyclohexanediamine, 1,4-cyclohexanediamine, 4,4′-dicyclohexylmethanediamine, 3,3′-dimethyl-4,4′-dicyclohexylmethanediamine, 1,4-cyclohexanediamine, and hydrazine; Chain extender having: ethylene glycol, diethylene recall, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexamethylene glycol, saccharo , Glycol, glycerine, sorbitol, bisphenol A, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, and the like can be used a chain extender having a hydroxyl group such as trimethylol propane. These chain extenders may be used alone or in combination of two or more. Among these, it is preferable to use a chain extender having a hydroxyl group from the viewpoint that oil grip properties and chemical resistance can be further improved.

  The amount used in the case of using the chain extender (a3) is the sum of the polyisocyanate (a1), the polyol (a2) and the chain extender (a3) from the point that the durability of the film can be further improved. The mass is preferably in the range of 0.5 to 20 mass%, more preferably in the range of 1 to 10 mass%.

  The aqueous urethane resin (A) preferably has a urea bond content of 1.2 mol / kg or less from the viewpoint that the discoloration over time can be controlled without impairing the texture.

  Since the urea bond is formed when the polyisocyanate reacts with a chain extender having an amino group or an amine formed by reacting isocyanate with water, the amount of the chain extender having an amino group used is reduced. The urea bond content of the aqueous urethane resin (A) can be adjusted by adjusting and further urethanizing the isocyanate before emulsification. The urea bond content indicates a value calculated by the following general formula (1).

  As a manufacturing method of the said water-based urethane resin (A), the urethane prepolymer which has an isocyanate group is manufactured by making the said polyisocyanate (a1) and the said polyol (a2) react, for example, Then, as needed The urethane prepolymer and the chain extender (a3) are reacted with each other; the polyisocyanate (a1), the polyol (a2) and, if necessary, the chain extender (a3) in a lump. And the like. These reactions may be performed at 50 to 100 ° C. for 3 to 10 hours, for example.

  The molar ratio of the total hydroxyl group and amino group of the polyol (a2) and the chain extender (a3) to the isocyanate group of the aromatic polyisocyanate (a1) [(isocyanate group) / (hydroxyl group). And amino group)] is preferably in the range of 0.8 to 1.2, and more preferably in the range of 0.9 to 1.1.

  When manufacturing the said water-based urethane resin (A), it is preferable to deactivate the isocyanate group which remains in the said water-based urethane resin (A). When the isocyanate group is deactivated, it is preferable to use an alcohol having one hydroxyl group such as methanol. As the usage-amount of the said alcohol, it is preferable that it is the range of 0.001-10 mass parts with respect to 100 mass parts of water-based urethane resin (A).

  Moreover, when manufacturing the said urethane resin (A), you may use an organic solvent. Examples of the organic solvent include ketone compounds such as acetone and methyl ethyl ketone; ether compounds such as tetrahydrofuran and dioxane; acetic ester compounds such as ethyl acetate and butyl acetate; nitrile compounds such as acetonitrile; dimethylformamide and N-methylpyrrolidone. Amide compounds and the like can be used. These organic solvents may be used alone or in combination of two or more. The organic solvent is preferably removed by a distillation method or the like when obtaining an aqueous urethane resin composition.

  As the aqueous medium (B), for example, water, an organic solvent miscible with water, a mixture thereof, or the like can be used. Examples of the organic solvent miscible with water include alcohol solvents such as methanol, ethanol, n- and isopropanol; ketone solvents such as acetone and methyl ethyl ketone; polyalkylene glycol solvents such as ethylene glycol, diethylene glycol and propylene glycol; Alkyl lactate solvents such as N-methyl-2-pyrrolidone and the like can be used. These aqueous media may be used alone or in combination of two or more. Among these, it is preferable to use only water or a mixture of water and an organic solvent miscible with water, and more preferable to use only water from the viewpoint of safety and reduction of environmental load.

  The mass ratio [(A) / (B)] of the aqueous urethane resin (A) and the aqueous medium (B) is preferably in the range of 10/80 to 70/30 from the viewpoint of workability. The range of 20/80 to 60/40 is more preferable.

  The aqueous urethane resin composition used in the present invention may contain other additives as required in addition to the urethane resin (A) and the aqueous medium (B).

  Examples of the other additives include, for example, an emulsifier, a neutralizer, a thickener, a crosslinking agent, a urethanization catalyst, a silane coupling agent, a filler, a thixotropic agent, a tackifier, a wax, a heat stabilizer, and light resistance. Stabilizer, fluorescent brightener, foaming agent, pigment, dye, conductivity imparting agent, antistatic agent, moisture permeability improver, water repellent, oil repellent, hollow foam, flame retardant, water absorbent, moisture absorbent, extinguishing agent An odorant, a foam stabilizer, an antiblocking agent, an hydrolysis inhibitor, and the like can be used. These additives may be used alone or in combination of two or more.

  The said emulsifier can use the same thing as the emulsifier which can be used when obtaining the water-based urethane resin disperse | distributed in the said aqueous medium (B) compulsorily. These emulsifiers may be used alone or in combination of two or more. Among these, it is preferable to use a nonionic emulsifier from the point which can improve the water dispersion stability of water-based urethane resin (A), and the point which a texture improves further.

  The amount used in the case of using the emulsifier is preferably in the range of 0.1 to 30 parts by mass with respect to 100 parts by mass of the aqueous urethane resin (A) from the viewpoint of water dispersion stability and texture. A range of 1 to 10 parts by mass is more preferable.

  The neutralizing agent neutralizes the carboxyl group when an anionic aqueous urethane resin is used as the aqueous urethane resin (A). For example, the neutralizing agent is non-volatile such as sodium hydroxide or potassium hydroxide. A tertiary amine compound such as trimethylamine, triethylamine, dimethylethanolamine, methyldiethanolamine, or triethanol; These neutralizing agents may be used alone or in combination of two or more.

  The amount of the neutralizing agent used is preferably in the range of 0.8 to 1.2 times the number of moles of carboxyl groups contained in the aqueous urethane resin (A).

  As mentioned above, as the aqueous urethane resin composition used in the present invention, aromatic polyisocyanate from the point that it becomes easier to coagulate with the coagulant, the point that the texture is further improved, and the water dispersion stability is improved, It is preferable to use an aqueous urethane resin composition containing an aqueous urethane resin (A) having an anionic group obtained by reacting a polyol and a chain extender, an aqueous medium (B), and a nonionic emulsifier.

  When the porous body of the present invention is used as a synthetic leather, by using a base fabric as the base material, a synthetic leather having a base fabric and an intermediate layer of the porous body can be obtained. Moreover, you may provide a skin layer on the said intermediate | middle layer as needed. Examples of a method for producing a skin layer on the intermediate layer include, for example, a method in which a material for forming a skin layer is applied on the intermediate layer and dried; the skin layer produced on a release paper is the intermediate layer. And the like.

  As a material for forming the skin layer, for example, a known aqueous urethane resin, solvent-based urethane resin, solvent-free urethane resin, aqueous acrylic resin, silicone resin, polypropylene resin, polyester resin, or the like can be used. These resins may be used alone or in combination of two or more.

  After producing the synthetic leather, for example, it may be aged at 30 to 100 ° C. for 1 to 10 days as necessary.

  Hereinafter, the present invention will be described in more detail with reference to examples.

[Synthesis Example 1] Preparation of aqueous urethane resin composition (X-1) Polycarbonate polyol ("Nipporan 980R" manufactured by Nippon Polyurethane Co., Ltd.) in the presence of 3,281 parts by mass of methyl ethyl ketone and 0.1 part by mass of stannous octylate , Number average molecular weight; 2,000) 1,000 parts by mass, 17 parts by mass of 2,2-dimethylolpropionic acid, 47 parts by mass of ethylene glycol, and 344 parts by mass of diphenylmethane diisocyanate have a solution viscosity of 20,000 mPa · s. After making it react at 70 degreeC until it reached s, 3 mass parts of methanol was added, reaction was stopped, and the methyl ethyl ketone solution of aqueous | water-based urethane resin (A-1) was obtained. The urethane resin solution was mixed with 70 parts by mass of polyoxyethylene distyrenated phenyl ether (Hydrophile-Lipophile Balance (hereinafter abbreviated as “HLB”); 14) and 13 parts by mass of triethylamine. The emulsified liquid in which the aqueous urethane resin (A-1) was dispersed in water was obtained by adding part by mass and emulsifying by phase inversion emulsification.
Subsequently, methyl ethyl ketone was distilled off from the emulsion to obtain an aqueous urethane resin composition (X-1) having a nonvolatile content of 40% by mass.

Synthesis Example 2 Preparation of Aqueous Urethane Resin Composition (X-2) Polyether polyol (“PTMG2000” Mitsubishi Kasei Co., Ltd.) in the presence of 3,281 parts by weight of methyl ethyl ketone and 0.1 part by weight of stannous octylate Manufactured, number average molecular weight; 2,000) 1,000 parts by mass, 17 parts by mass of 2,2-dimethylolpropionic acid, 47 parts by mass of ethylene glycol, and 344 parts by mass of diphenylmethane diisocyanate have a solution viscosity of 20,000 mPa -After making it react at 70 degreeC until it reaches s, 3 mass parts of methanol was added, reaction was stopped, and the methyl ethyl ketone solution of the water-based urethane resin (A-2) was obtained. The urethane resin solution is mixed with 70 parts by mass of polyoxyethylene distyrenated phenyl ether (HLB; 14) and 13 parts by mass of triethylamine, and then 800 parts by mass of ion-exchanged water is added to effect phase inversion emulsification. An emulsion in which the urethane resin (A-2) was dispersed in water was obtained.
Subsequently, methyl ethyl ketone was distilled off from the emulsion to obtain an aqueous urethane resin composition (X-2) having a nonvolatile content of 40% by mass.

[Synthesis Example 3] Preparation of aqueous urethane resin composition (X-3) Polyester polyol ("Placcel 220" manufactured by Daicel Corporation, in the presence of 3,281 parts by mass of methyl ethyl ketone and 0.1 part by mass of stannous octylate, Number average molecular weight: 2,000) 1,000 parts by mass, 17 parts by mass of 2,2-dimethylolpropionic acid, 47 parts by mass of ethylene glycol, and 344 parts by mass of diphenylmethane diisocyanate have a solution viscosity of 20,000 mPa · s. Then, the reaction was stopped at 70 ° C. until the temperature reached, and the reaction was stopped by adding 3 parts by mass of methanol to obtain a methyl ethyl ketone solution of the aqueous urethane resin (A-3). The urethane resin solution is mixed with 70 parts by mass of polyoxyethylene distyrenated phenyl ether (HLB; 14) and 13 parts by mass of triethylamine, and then 800 parts by mass of ion-exchanged water is added to effect phase inversion emulsification. An emulsion in which the urethane resin (A-3) was dispersed in water was obtained.
Subsequently, methyl ethyl ketone was distilled off from the emulsion to obtain an aqueous urethane resin composition (X-3) having a nonvolatile content of 40% by mass.

[Example 1]
100 parts by mass of the aqueous urethane resin composition (X-1) obtained in Synthesis Example 1, 5 parts by mass of a thickener (“Borch Gel L75N” manufactured by Borcher), a carbodiimide crosslinking agent (“Carbodilite SV manufactured by Nisshinbo Chemical Co., Ltd.) −02 ”) 4 parts by mass and 100 parts by mass of ion-exchanged water were stirred for 2 minutes at 2,000 rpm with a mechanical mixer, and then defoamed with a vacuum deaerator to prepare a blended solution.
Subsequently, the said liquid mixture was apply | coated to the nonwoven fabric base material surface by knife coating (clearance of 100 micrometers). Subsequently, the coating substrate was immersed in a 20% by mass aqueous solution of sodium chloride heated to 60 ° C. for 3 minutes to solidify the coating film. Then, it was immersed in water for 60 minutes, the excess coagulant was wash | cleaned, and the porous body was obtained by making it dry at 120 degreeC for 30 minutes.

[Examples 2-3]
A porous body was obtained in the same manner as in Example 1 except that the type of the aqueous urethane resin composition used was changed as shown in the table.

[Comparative Example 1]
100 parts by mass of the aqueous urethane resin composition (X-1) obtained in Synthesis Example 1, 5 parts by mass of a thickener (“Borch Gel L75N” manufactured by Borcher), a carbodiimide crosslinking agent (“Carbodilite SV manufactured by Nisshinbo Chemical Co., Ltd.) −02 ”) 4 parts by mass and 100 parts by mass of ion-exchanged water were stirred for 2 minutes at 2,000 rpm with a mechanical mixer, and then defoamed with a vacuum deaerator to prepare a blended solution.
Subsequently, the said liquid mixture was apply | coated to the nonwoven fabric base material surface by knife coating (clearance of 100 micrometers). Subsequently, it was dried at 100 ° C. for 10 minutes by the gear type hot air dryer, thereby obtaining an article by thermal coagulation.

[Comparative Example 2]
In Example 1, it carried out like Example 1 except having used the coagulation bath of 20 mass% sodium chloride aqueous solution of 10 degreeC instead of the coagulation bath of 20 mass% sodium chloride heated at 60 degreeC. The aqueous urethane resin composition (X-1) did not solidify.

[Measurement method of number average molecular weight]
The number average molecular weight of the polyol or the like used in the synthesis examples shows a value measured under the following conditions by gel permeation column chromatography (GPC) method.

Measuring device: High-speed GPC device (“HLC-8220GPC” manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were connected in series.
"TSKgel G5000" (7.8 mm ID x 30 cm) x 1 "TSKgel G4000" (7.8 mm ID x 30 cm) x 1 "TSKgel G3000" (7.8 mm ID x 30 cm) x 1 “TSKgel G2000” (7.8 mm ID × 30 cm) × 1 detector: RI (differential refractometer)
Column temperature: 40 ° C
Eluent: Tetrahydrofuran (THF)
Flow rate: 1.0 mL / min Injection amount: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4 mass%)
Standard sample: A calibration curve was prepared using the following standard polystyrene.

(Standard polystyrene)
"TSKgel standard polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-550" manufactured by Tosoh Corporation

[Evaluation method of odor during processing]
The smell was sniffed 1 m above the coagulation bath layer being processed and evaluated as follows.
“T”; feels odor.
“F”; no odor is felt.

[Evaluation Method for Adhesion State of Aqueous Urethane Resin to Fiber Substrate]
Articles obtained in Examples and Comparative Examples were observed using a scanning electron microscope “SU3500” (200 times magnification) manufactured by Hitachi High-Technologies Corporation, and evaluated as follows.
“T”; a porous structure is confirmed in the aqueous urethane resin layer formed on the surface of the base fabric.
“F”: No porous structure is confirmed in the aqueous urethane resin layer formed on the surface of the base fabric.

[Texture evaluation method]
The articles obtained in Examples and Comparative Examples were evaluated as follows according to the touch feeling when touched by hand.
“A”: Both the tension and the sense of fulfillment are excellent.
“B”: Feeling tight and full.
“C”; feeling of tightness and fullness are slightly inferior.
“D”; no tightness or fullness is felt.

Abbreviations in Table 1 will be described.
"MDI"; diphenylmethane diisocyanate

  It turned out that the intermediate | middle layer for synthetic leather obtained in Examples 1-3 which is this invention is excellent in a texture. Moreover, since no organic solvent was used, the problem of odor did not occur.

  On the other hand, Comparative Example 1 is an embodiment in which solidification by thermal coagulation was performed, but the texture was poor.

  In Comparative Example 2, the coagulation bath was not heated and was used at 10 ° C., but it did not coagulate.

Claims (6)

A method for producing a porous body, comprising applying a water-based urethane resin composition to a substrate and immersing the substrate in an aqueous metal salt solution heated to 40 ° C or higher. The method for producing a porous body according to claim 1, wherein the metal salt is sodium chloride. The method for producing a porous body according to claim 1 or 2, wherein the aqueous urethane resin composition contains an aqueous urethane resin (A) having an aromatic ring. The method for producing a porous body according to claim 3, wherein the content of the aromatic ring of the aqueous urethane resin (A) is in the range of 0.8 to 8 mol / kg. The method for producing a porous body according to claim 3 or 4, wherein the aqueous urethane resin (A) is made from aromatic polyisocyanate. The method for producing a porous body according to claim 5, wherein the aromatic polyisocyanate is diphenylmethane diisocyanate.