JP2013083031A - Method for producing porous structure - Google Patents

Abstract

Provided is a method for producing a porous structure in which a large number of micropores are uniformly mixed without being crushed, and have both a soft texture and a sense of fulfillment.
A method for producing a porous structure including the following steps.
Step (1): (A) a hydrophilic functional group-containing resin, (B) an ammonium salt, and (C) a nonionic thickener, and the blending amount of component (B) is the solid content of component (A) 0 to 100 parts by mass
. A step of preparing an aqueous dispersion having a viscosity of 25 to 10 parts by mass and having a viscosity of 10 to 100 Pa · s.
Step (2): A step of applying or impregnating the aqueous dispersion onto the fibrous base material.
Step (3): A step of forming a porous body by subjecting the aqueous dispersion to heat-sensitive gelation.
Step (4): A step of drying and solidifying the porous body.
[Selection figure] None

Description

The present invention relates to a method for producing a porous structure. That is, a leather-like sheet structure such as artificial leather or synthetic leather, or a porous structure such as a fiber product impregnated with a porous resin coating or impregnated, more specifically, a porous layer having continuous porosity is formed inside or above the substrate. The present invention relates to a method for producing a porous structure having a structure closer to natural leather.

Conventionally, natural leather is strong and has excellent air permeability, and thus has been used for various items such as clothing and shoes taking advantage of this characteristic. However, natural leather is expensive. For various reasons such as animal welfare, artificial leather-like materials closer to natural leather are required as substitutes for natural leather, and various production methods have been proposed. Most of them are structures similar to natural leather, that is, a method for obtaining a porous structure, and porous structures such as a porous sheet and a porous fabric obtained are artificial leather,
Often used in clothing and shoes as artificial leather like synthetic leather.

Conventionally, as a method for manufacturing such a porous structure, a base material is impregnated or coated with a polymer such as polyurethane as a solution of an organic solvent, and the solvent is not dissolved and the solvent is miscible with the solvent. The polymer is coagulated by processing, and then wet-coagulation method or dry-coagulation method, which is dried after removing the solvent. The synthetic resin melt is extruded into a film using an extruder on the synthetic resin layer formed on the substrate. An integrated melt film forming method, a method of forming a porous film from a W / O emulsion, and the like have been proposed.

However, in the wet coagulation method, since many of the water-soluble organic solvents used are highly flammable and highly toxic, in order to prevent fire hazard, work environment deterioration, natural environment deterioration due to drainage, etc., There is a problem that the cost of equipment and recovery becomes high. In addition, the melt film-forming method requires a temperature of 150 to 200 ° C. to produce a synthetic resin melt, and requires heating and pressurization to extrude, resulting in a work risk. . Furthermore, in the method of forming a porous film from the W / O type emulsion, the shrinkage during solvent evaporation and drying is large, and once the porous film is crushed, there are many restrictions on environmental conditions in controlling the porosity, In addition, as with the wet coagulation method, there is a problem that many water-soluble organic solvents used have strong flammability and toxicity.

Therefore, formation of a porous structure using an aqueous emulsion resin that does not use an organic solvent has been studied.
For example, Patent Document 1 discloses a method for producing a leather base material, in which a fiber base material is impregnated with a mixture of an aqueous emulsion made of a carboxyl group-containing polyurethane resin and an ammonium salt of a carboxylic acid, and then heat-gelled and dried. Is disclosed.
Patent Document 2 discloses a porous sheet formed of an aqueous dispersion containing a polymer elastic body, water-repellent particles, and a cross-linking agent and not causing precipitation or gelation. The porous sheet has a thickness of 10 to 500 μm, and 500 to 500 micropores having an average pore diameter of 1 to 20 μm inside.
15,000 pieces / mm ² exist, the breaking strength is 1 to 15 N / mm ² , and the breaking elongation is 100 to 50
0%.
Patent Document 3 discloses a mixture in which an aqueous thermoplastic binder solution is combined with at least one selected from the group consisting of inorganic compounds, water-soluble organic polymers, poorly water-soluble organic polymers, and high cloud point surfactants. A method of forming a porous body by impregnating, coating or spraying a substrate and heating with wet heat is disclosed.

JP 2006-036960 A Japanese Patent No. 3796573 Japanese Patent No. 3981242

However, in the production method of Patent Document 1, since self-emulsification type water-based emulsion resin is used for heat-sensitive gelation, the gelling strength is strong and the urethane resin is uniformly applied to the nonwoven fabric while preventing migration. However, if the water-based emulsion is simply converted into a heat-sensitive gel, the urethane resin does not exhibit a foamed structure and is in a film state, so there is a limit to softening the texture.
Since the aqueous dispersion used in the porous sheet of Patent Document 2 does not gel, if the temperature is rapidly increased to increase the drying efficiency, the porous material cannot be stably obtained. In order to obtain a porous material stably, it is necessary to raise the temperature stepwise in several steps, which is problematic in productivity.
Since the aqueous dispersion used in the porous sheet of Patent Document 3 uses a forced emulsification type emulsion, the film strength at the time of thermal gelation is weak, and the water dispersion is caused by the sheet conveyance during the drying process and the influence of migration. When the liquid flows, there is a problem that a stable foam structure cannot be obtained.
Furthermore, the foam and the porous sheet disclosed in Patent Documents 2 to 3 are water-soluble polymers among non-woven fabrics composed of sea-island fiber composite fibers having a water-soluble polymer component as one component, particularly in the production of artificial leather. When the hot water treatment for the purpose of ultrafinening is performed by removing the components, the porous structure absorbs the hot water and is damaged or crushed.
As described above, a technique capable of stably producing a porous structure is not disclosed.
The present invention has been made in view of the above-described problem, and by forming a porous layer having continuous porosity inside or on the base material, a porous structure closer to the texture and mechanical properties of natural leather is produced. It is an object to provide a method.

The present inventors have intensively studied to develop a method for producing an excellent porous structure free from the problems of the prior art, and a polymer elastic body comprising a hydrophilic functional group-containing resin on a fibrous base material. A porous structure having a continuous pore formed by a method for producing a porous structure comprising the following steps (1) to (4): The present invention was completed by finding that a porous structure (including a porous sheet and a fabric) close to the texture and mechanical properties of natural leather can be obtained by forming a layer inside the substrate.
Step (1): (A) a hydrophilic functional group-containing resin, (B) an ammonium salt, and (C) a nonionic thickener, and the blending amount of component (B) is the solid content of component (A) 0 to 100 parts by mass
. A step of preparing an aqueous dispersion having a viscosity of 25 to 10 parts by mass and having a viscosity of 10 to 100 Pa · s.
Step (2): A step of applying or impregnating the aqueous dispersion onto the fibrous base material.
Step (3): A step of forming a porous body by subjecting the aqueous dispersion to heat-sensitive gelation.
Step (4): A step of drying and solidifying the porous body.
That is, the method for producing a porous structure according to the present invention is characterized in that a mixture comprising specific components is applied to or impregnated on a fibrous base material, a porous body is formed by heating, and dried. is there.

The porous structure of the present invention has a porous layer having continuous porosity inside and / or above the base material, and a large number of micropores are uniformly mixed without being crushed. Have both.
The porous structure can be used for high-quality suede-like or silver-added artificial leather by raising the surface or applying a coating, while maintaining excellent productivity and the porosity of the present invention. The structure can be formed stably.

2 is an electron micrograph of a cross section in the thickness direction of the porous structure obtained in Example 1. FIG. 4 is an electron micrograph of a cross section in the thickness direction of a porous structure obtained in Comparative Example 2. FIG.

The present invention is a method for producing a porous structure in which a polymeric elastic body comprising a hydrophilic functional group-containing resin is applied to or impregnated on a fibrous base material, comprising the following steps (1) to (4): Including.
Step (1): (A) a hydrophilic functional group-containing resin, (B) an ammonium salt, and (C) a nonionic thickener, and the blending amount of component (B) is the solid content of component (A) 0 to 100 parts by mass
. A step of preparing an aqueous dispersion having a viscosity of 25 to 10 parts by mass and having a viscosity of 10 to 100 Pa · s.
Step (2): A step of applying or impregnating the aqueous dispersion onto the fibrous base material.
Step (3): A step of forming a porous body by subjecting the aqueous dispersion to heat-sensitive gelation.
Step (4): A step of drying and solidifying the porous body.
Hereinafter, these steps (1) to (4) and the porous structure obtained by the method for producing a porous structure of the present invention will be described in detail.

[Step (1): Preparation of aqueous dispersion]
The aqueous dispersion prepared in this step contains (A) a hydrophilic functional group-containing resin, (B) an ammonium salt, and (C) a nonionic thickener. Moreover, it is preferable that other additives, such as (D) crosslinking agent and a foaming agent (E), are included as needed.
In addition, the viscosity of the aqueous dispersion prepared in this step is maintained at the viscosity immediately after the preparation or rises until the thermal gelation treatment in step (3) described later is completed. That is, the viscosity of the aqueous dispersion during the temperature increase in the step (3) is maintained at the same level as that immediately after the preparation, and the aqueous dispersion reaches the heat-sensitive coagulation temperature. To increase the viscosity. Therefore, regardless of the substrate used, a porous structure can be obtained without changing the state of adhesion to the impregnated fibrous substrate during the thermal gelation treatment.
The viscosity of the aqueous dispersion until the heat-sensitive gelation treatment is completed is preferably 10 to 100 Pa · s, more preferably 20 to 20 when measured at 6 revolutions / minute using a single cylindrical rotational viscometer. 80 Pa · s, more preferably 30 to 75 Pa · s. The viscosity is 10 Pa
-If it is more than s, even if it heats up by a heat-sensitive gelling process, the adhesion state to a base material can be maintained and a porous structure can be obtained irrespective of the kind of fibrous base material. Moreover, if it is 100 Pa.s or less, it is optimal for handling.
Hereinafter, the components contained in the aqueous dispersion of the present invention will be described.

<(A) Hydrophilic functional group-containing resin>
The (A) hydrophilic functional group-containing resin (hereinafter also referred to as the component (A)) used in the present invention has a hydrophilic functional group and can be emulsified without using an anionic or nonionic surfactant. It is an emulsification type aqueous emulsion resin.
In a forced emulsification type aqueous emulsion resin that requires the addition of a surfactant, gelation in the thermal gelation treatment is insensitive and film formation after gelation tends to be insufficient. When the forced emulsification type water-based emulsion resin is used, it is necessary to perform the thermal gelation treatment and the drying and solidification at a low temperature for a long time, and the production efficiency is extremely poor. In addition, the use of a surfactant has inferior physical properties such as peel strength of the resulting film with respect to the substrate, and the surfactant bleeds on the surface of the film over time, which impairs the appearance of the film surface. .
On the other hand, the self-emulsifying type water-based emulsion resin does not have the above-mentioned problems, and the heat-sensitive gelation treatment and the drying and solidification can be performed at a high temperature and in a short time, so that the production efficiency is remarkably improved. Moreover, since the film | membrane which consists of a self-emulsification type water-based emulsion resin has a low swelling rate with respect to hot water and has the outstanding hot water resistance, it can suppress the damage | damage of the film | membrane by a hot water process.

(A) As a hydrophilic functional group of a component, a carboxyl group, a sulfonyl group, a quaternary ammonium group etc. are mentioned. These hydrophilic functional groups may be contained alone or in combination of two or more.
Examples of the resin constituting the component (A) include hydrophilic functional group-containing aqueous emulsion polyurethane resins, polyacrylic resins, and mixtures of polyurethane resins and polyacrylic resins.
Among these, from the viewpoint of flexibility, an aqueous emulsion polyurethane resin containing a hydrophilic functional group is preferable.

Examples of the synthesis method of component (A) include (a) organic diisocyanate, (b) polyol, (c) hydrophilic function obtained by reacting a compound having a hydrophilic functional group and two or more active hydrogens. After neutralizing the group-containing isocyanate group-terminated prepolymer and self-emulsifying in water,
(D) It can be obtained by chain extension reaction using a chain extender.

As the (a) organic diisocyanate (hereinafter also referred to as the component (a)), an aliphatic diisocyanate, an alicyclic diisocyanate and an aromatic diisocyanate having two isocyanate groups can be used.
Examples of such component (a) include aliphatic diisocyanate compounds such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate, norbornane diisocyanate, 1,3-bis (isocyanate). And cycloaliphatic diisocyanate compounds such as natomethyl) cyclohexane, aromatic diisocyanate compounds such as tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate.
Also, these alkyl-substituted products, alkoxy-substituted products, nitro-substituted products, prepolymer modified products with polyhydric alcohols, carbodiimide modified products, urea modified products, burette modified products,
Dimerization or trimerization reaction products can also be used, and organic diisocyanates other than the above compounds can also be used. These components (a) can be used alone or in combination of two or more.
Among these, aliphatic diisocyanate compounds and alicyclic diisocyanate compounds are preferable from the viewpoint of yellowing resistance, thermal stability, and light stability of the component (A) to be obtained and the formed film, and hexamethylene diisocyanate and isophorone diisocyanate. More preferred are dicyclohexylmethane diisocyanate, norbornane diisocyanate and 1,3-bis (isocyanatomethyl) cyclohexane.

(B) The polyol (hereinafter also referred to as the component (b)) is not particularly limited as long as it has two or more hydroxyl groups, and other than polyester polyol, polycarbonate polyol, polyether polyol, etc. Examples thereof include polyether ester polyols having an ester bond.
Examples of the polyester polyol include polyethylene adipate, polybutylene adipate, polyethylene butylene adipate, polyhexamethylene isophthalate adipate, polyethylene succinate, polybutylene succinate, polyethylene sebacate, polybutylene sebacate, poly-ε-caprolactone diol, Poly (3-methyl-1
, 5-pentylene) adipate, polycondensate of 1,6-hexanediol and dimer acid, 1
, 6-hexanediol, adipic acid and dimer acid, polycondensate of nonanediol and dimer acid, ethylene glycol, adipic acid and dimer acid, and the like.

Examples of the polycarbonate polyol include polytetramethylene carbonate diol, polyhexamethylene carbonate diol, poly-1,4-cyclohexanedimethylene carbonate diol, and 1,6-hexanediol polycarbonate polyol.
Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol homopolymer, block copolymer, random copolymer, ethylene oxide and propylene oxide, ethylene oxide and butylene oxide random copolymer, and block copolymer. A polymer etc. are mentioned.

These components (b) can be used alone or in combination of two or more.
Among these, polycarbonate polyol or polyether polyol is preferred from the viewpoint that sufficient durability can be imparted to the substrate.
(B) As an average molecular weight of a component, Preferably it is 500-5000, More preferably, it is 10
It is 00-3000.

Examples of the compound (c) having a hydrophilic functional group and two or more active hydrogens (hereinafter also referred to as the component (c)) include 2,2-dimethylol lactic acid, 2,2-dimethylol propionic acid, 2 2,2-dimethylolbutanoic acid, 2,2-dimethylolvaleric acid, 3,4-diaminobutanesulfonic acid, 3,6-diamino-2-toluenesulfonic acid, and the like.

In addition, as component (c), a pendant type hydrophilic functional group obtained by reacting a diol having a hydrophilic functional group with an aromatic dicarboxylic acid or aromatic disulfonic acid, aliphatic dicarboxylic acid or aliphatic disulfonic acid, or the like. Examples thereof include polyester polyol having a group. Instead of the diol having the hydrophilic functional group, a diol having no hydrophilic functional group may be mixed and reacted as a diol component.
In addition, these (c) components can also be used individually or in combination of 2 or more types.

The acid value of (A) component is adjusted with the compounding quantity of (c) component. It is preferable to blend the component (c) so that the acid value of the component (A) is preferably 5 to 50 KOH mg / g, more preferably 10 to 40 KOH mg / g. If the acid value of the component (A) is 5 KOHmg / g or more, the resin has excellent mechanical stability and mixing stability with other components, and the acid value of the component (A) is 50K.
If it is OHmg / g or less, an aqueous dispersion having an appropriate viscosity can be prepared, and the water resistance of the resulting film is also preferred. Here, the acid value is measured by a method disclosed in, for example, Japanese Industrial Standard JIS K5400.

When synthesizing the isocyanate group-terminated prepolymer by reacting the components (a) to (c), a low molecular weight chain extender having two or more active hydrogen atoms can be used as necessary.
The molecular weight of the low molecular weight chain extender is preferably 400 or less, more preferably 300 or less.
Specific examples of the low molecular weight chain extender include ethylene glycol, propylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol,
Low molecular weight polyalcohols such as trimethylolpropane, pentaerythritol, sorbitol; low molecular weight polyamines such as ethylenediamine, propylenediamine, hexamethylenediamine, diaminocyclohexylmethane, piperazine, 2-methylpiperazine, isophoronediamine, diethylenetriamine, triethylenetetramine, etc. Can be mentioned.
These low molecular weight chain extenders can be used alone or in combination of two or more.

The synthesis method for obtaining the hydrophilic functional group-containing isocyanate group-terminated prepolymer is not particularly limited, and can be obtained, for example, by a conventionally known one-stage so-called one-shot method or multi-stage isocyanate polyaddition reaction method. The reaction temperature at this time is preferably 40 to 150 ° C.
In the reaction, if necessary, dibutyltin dilaurate, stannous octoate, dibutyltin-2-ethylhexanoate, triethylamine, triethylenediamine,
A reaction catalyst such as N-methylmorpholine may be added.

Moreover, as a neutralization method of a hydrophilic functional group containing isocyanate group terminal prepolymer, a well-known method can be used suitably before preparation or after preparation. In this case, the neutralizing agent to be used is not particularly limited. For example, trimethylamine, triethylamine, tri-n-propylamine, tributylamine, N-methyl-diethanolamine, N, N-dimethylmonoethanolamine, N, N- Examples thereof include amines such as diethyl monoethanolamine and triethanolamine, potassium hydroxide, sodium hydroxide, ammonia and the like. Among these, tertiary amines having no hydroxyl group such as trimethylamine, triethylamine, tri-n-propylamine, and tributylamine are preferable.

Next, as an emulsifying device used for self-emulsification in water after neutralization, there is no particular limitation,
Examples thereof include a homomixer, a homogenizer, and a disper. In addition, the self-emulsification is preferably performed by self-emulsification in water in the temperature range of room temperature to 40 ° C. without using an emulsifier to suppress the reaction between the isocyanate group and water as much as possible. Furthermore, when self-emulsifying in this way, reaction inhibitors such as phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, paratoluenesulfonic acid, adipic acid, benzoyl chloride are added as necessary. May be.

And after making it self-emulsify in water, it is made to carry out chain extension reaction using (d) chain extension agent, and the aqueous dispersion of (A) hydrophilic functional group containing resin can be obtained.
(D) The chain extender is preferably a polyamine compound having two or more amino groups and / or imino groups, such as ethylenediamine, propylenediamine, tetramethylenediamine, hexamethylenediamine, diaminocyclohexylmethane, piperazine, hydrazine, 2 -Diamines such as methylpiperazine, isophoronediamine, norbornanediamine, diaminodiphenylmethane, tolylenediamine, xylylenediamine; diethylenetriamine, triethylenetetramine, tetraethylenepentamine, iminobispropylamine, tris (2-aminoethyl) amine, etc. Polyamines; amidoamines derived from diprimary amines and monocarboxylic acids; water-soluble amine derivatives of diprimary amines such as monoketimines; oxalic acid dihydrazide, malonic acid Hydrazides, dihydrazide succinate, dihydrazide glutarate, adipic acid, sebacic acid dihydrazide, maleic acid dihydrazide fumaric acid, itaconic acid dihydrazide, 1,1'-ethylene hydrazine, 1,1
And hydrazine derivatives such as '-trimethylene hydrazine and 1,1'-(1,4-butylene) dihydrazine. These polyamine compounds can be used alone or in combination of two or more.
The chain extension reaction is preferably performed at a reaction temperature of 20 to 40 ° C., and the reaction is performed in 30 to 120 minutes.

The value of 100% modulus of the component (A) is preferably 1 to 12 MPa, more preferably 2 to 9 MPa. If the value of 100% modulus is 1 MPa or more, heat resistance,
A porous structure having excellent hot water resistance and little change in the foam structure in the drying step and the hot water extraction step can be formed. When the pressure is 12 MPa or less, a flexible texture porous structure can be obtained. In addition, the value of 100% modulus means using a dumbbell-shaped No. 3 test piece,
Predetermined tensile stress (MP when the distance between the marked lines is 100% extended (doubled)
It is the value of a) and is measured according to JIS K 6251 (1993).

The hydrophilic functional group content of the component (A) is preferably 0.5 to 4.0% by mass, more preferably 1.0 to 2.0% by mass. If the hydrophilic functional group content is 0.5% by mass or more, the storage stability of the component (A) is good, and if it is 4.0% by mass or less, the thermal gelation temperature is in an appropriate temperature range. The effect of preventing migration can be obtained.

Furthermore, it is preferable to hold | maintain (A) component in the self-emulsified state, Preferably the pH value of the state is 7.0-9.0, More preferably, it is 7.5-8.5. pH value is 7.0
If it is above, the storage stability of (A) component is good, and if pH is 9.0 or less, the effect of sufficient migration prevention will be acquired.

<(B) Ammonium salt>
The aqueous dispersion of the present invention contains (B) an ammonium salt (hereinafter also referred to as component (B)).
The component (A) is a self-emulsifying type water-based emulsion resin, and by itself, it does not gel unless it is at a relatively high temperature (about 90 ° C.), but by adding the component (B), the temperature is about 60 ° C. The component (A) can be gelled.
In the aqueous dispersion of the present invention, the blending amount of the component (B) is 0.25 to 10 parts by mass, preferably 0.5 to 9 parts by mass with respect to 100 parts by mass of the solid content of the component (A). More preferably, it is 1-7 mass parts. When the blending amount of component (B) is less than 0.25 parts by mass, gelation by heat-sensitive gelation treatment is not sufficiently performed, and a porous structure cannot be obtained stably. Moreover, when the compounding quantity of (B) component exceeds 10 mass parts, the thermal gelation temperature will be 40 degrees C or less, and the storage stability of an aqueous dispersion liquid falls remarkably, such as a viscosity raise and a gelled material generate | occur | producing.

(B) As an ammonium salt (hereinafter also referred to as (B) component), hydrochloric acid, nitric acid, phosphoric acid,
Examples thereof include ammonium salts such as sulfuric acid and carboxylic acid. Carboxylic acids include formic acid, acetic acid,
Saturated fatty acids such as propionic acid, butyric acid, valeric acid, caproic acid, capric acid, stearic acid;
Unsaturated fatty acids such as oleic acid and linoleic acid; aromatic carboxylic acids such as benzoic acid, phthalic acid, isophthalic acid and terephthalic acid; saturated dicarboxylic acids such as malic acid, citric acid, succinic acid, malonic acid, succinic acid and adipic acid Unsaturated carboxylic acids such as fumaric acid and maleic acid; lactic acid, acrylic acid, polyacrylic acid, polymaleic acid and the like.
Among these, from the viewpoint of impregnation of the mixed liquid, migration prevention of the component (A) during the drying process, and removal easily by volatilization during drying or washing with water after drying, and less remaining in the film. , An ammonium sulfate salt, or an ammonium salt of a carboxylic acid having 1 to 10 carbon atoms is preferred, and an ammonium sulfate salt or an ammonium salt of a carboxylic acid having 1 to 4 carbon atoms is more preferred. These (B) components may use what is marketed.

In the film forming method of the present invention, when the component (B) is mixed with the component (A), the component (B) can be mixed in a solid (powder) state. From the viewpoint of maintaining the stability of the liquid, it is more preferable to dissolve the component (B) in water and mix it with the component (A) in the form of an aqueous solution. The pH value of the aqueous solution containing the component (B) at this time is preferably 7.0 to 9.0, more preferably 7.5 to 8.5. When the pH value is 7.0 or more, generation of precipitates can be suppressed when mixing with the component (A), and when the pH value is 9.0 or less, sufficient migration of the component (A) is achieved. The effect of prevention is acquired.

<(C) Nonionic thickener>
The aqueous dispersion of the present invention contains (C) a nonionic thickener (hereinafter also referred to as (C) component).
By using a nonionic thickener, the viscosity of the aqueous dispersion impregnated in the fibrous base material is maintained at the viscosity immediately after impregnation or increases even when the temperature is increased by the thermal gelation treatment. ,
By including a thickener, the viscosity of the aqueous dispersion increases, and a porous structure can be obtained stably.
In general, the viscosity of an aqueous dispersion used for impregnation of a fibrous base material is less than 1 Pa · s, and an aqueous dispersion having a viscosity of 10 to 100 Pa · s, which is a preferred viscosity range of the present invention, is used. When using, as a method of impregnating the fibrous base material, in addition to the method of immersing the fibrous base material in the aqueous dispersion, the aqueous dispersion is forcibly rubbed into the fibrous base using a driving roll. The method is preferably used.
As the nonionic thickener of component (C), by addition of component (B) or heat-sensitive gelation treatment,
Those with little change in the thickening effect due to changes in temperature and pH of the aqueous dispersion that occur in the process until the gelation of the film is completed are preferably used. Among the associative thickeners and water-soluble polymer thickeners You can choose from.

Examples of associative thickeners include, for example, JP-A-54-80349 and JP-A-58-213.
No. 074, JP-A-60-49022, JP-B-52-25840, JP-A-9-67563, JP-A-9-71766, etc .; Associative thickeners obtained by copolymerizing nonionic urethane monomers described in JP-A-62-2292879 and JP-A-10-1210230 with other acrylic monomers as associative monomers; Examples include associative thickeners having the aminoplast skeleton described above, and those having strong nonionic properties are selected.
Among these, an associative thickener having a polyethylene glycol chain and a urethane bond in the molecular chain is preferable from the viewpoint of the fineness of pores of the porous structure and strength retention. As a commercial item, Neo sticker S (made by Nikka Chemical Co., Ltd.) etc. are mentioned.

Examples of the water-soluble polymer thickener include cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl hydroxypropyl cellulose, carboxymethyl cellulose; starches such as soluble starch, carboxymethyl starch, and methyl starch. Derivatives: Alginic acid type such as sodium alginate, propylene glycol ester alginate; guar gum, carrageenan, galactan, gum arabic, locust bin gum, quince seed, tragacanth gum, pectin, mannan, starch, xanthan gum, dextran, succinoglucan, curdlan, hyaluronic acid And natural polysaccharides such as salts thereof; natural proteins such as casein, gelatin, collagen, albumin; polyalkylene Coal, polyoxyethylene glycol distearate, myristoyl polyoxyethylene stearyl ether, polyoxyethylene sorbitan triisostearate, polyoxyethylene methyl glucose (mono, di or tri) laurate, polyoxyethylene methyl glucose (mono, di or Tri) myristate, polyoxyethylene methyl glucose (mono, di or tri) palmitate, polyoxyethylene methyl glucose (mono, di or tri) stearate, polyoxyethylene methyl glucose (mono, di or tri) isostearate, Polyoxyalkylene nonionic polymers such as polyoxyethylene methyl glucose (mono, di or tri) oleate;
Examples include polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl methyl ether, carboxyvinyl polymer, vinyl polymers such as sodium polyacrylate, and mixtures thereof. Among these, those having strong nonionic properties are selected. As a commercial item, HE
C AX-15 (Sumitomo Seika Chemicals Co., Ltd., hydroxyethyl cellulose), Aron A-50
P (manufactured by Toagosei Co., Ltd., sulfonic acid monomer copolymer acrylic thickener), Kelzan (
Sanki Co., Ltd., high molecular polysaccharide (xanthan gum)) and the like.
In particular, as a nonionic thickening agent, a high molecular polysaccharide is preferable because it can easily have a porous structure, and particularly xanthan gums can easily form a porous structure very stably during thermal gelation.
In addition, when a film is formed using a water-soluble polymer thickener, a cleaning process is performed after the film is formed in order to suppress the bleed of the thickener in the film over time and the occurrence of stickiness due to moisture absorption. It is preferable to go through.
These nonionic thickeners can be used alone or in combination of two or more,
In order to stably obtain a porous structure, a high molecular polysaccharide is preferably used, and among these, xanthan gum is more preferable.
Xanthan gum is a kind of high molecular polysaccharide, and its molecular weight is generally about 2 million to 5000.
Ten thousand. Xanthan gum is composed of 2 glucose molecules, 2 mannose molecules, and glucuronic acid repeating units. The main chain of xanthan gum is the same as that of cellulose with β-1,4 bonds of D-glucose, and two mannoses in the side chain. It has a special structure in which one glucuronic acid is contained in between. Xanthan gum also includes potassium, sodium and calcium salts. And when mixed with water, it becomes viscous. A porous structure that influences the aggregation state of polymer elastic particles when gelling a polymer elastic material comprising a hydrophilic functional group-containing resin due to the special structure of xanthan gum having a high molecular weight and the above long side chain. Is estimated to be obtained.

The blending amount of component (C) is preferably 0.5 with respect to 100 parts by mass of the solid content of component (A).
-20 mass parts, More preferably, it is 1-15 mass parts, More preferably, it is 1.5-10 mass parts. If it is 0.5 parts by mass or more, the viscosity of the aqueous dispersion can be maintained in a sufficiently high state until the heat-sensitive gelation treatment in step (3) is completed, so that a porous structure is stably formed. can do. On the other hand, if it is 20 parts by mass or less, an aqueous dispersion having a viscosity in an optimum range for handling can be obtained.

The viscosity of the aqueous dispersion of the present invention immediately after preparation is preferably 10 to 100 Pa · s, more preferably 20 to 80 Pa · s, when measured at 6 revolutions / minute using a single cylindrical rotational viscometer.
More preferably, it is 30-75 Pa.s. When the viscosity is 10 Pa · s or more, bubbles are not easily collapsed when forming the porous structure, and when the viscosity is 100 Pa · s or less, the fibrous base material can be impregnated. Note that, as described above, the viscosity of the aqueous dispersion is maintained or increased at the viscosity immediately after the preparation until the thermal gelation treatment in the step (3) is completed. The porous structure can be obtained while maintaining the adhesion state of the aqueous dispersion to the fibrous base material.

<(D) Crosslinking agent>
In the aqueous dispersion of the present invention, from the viewpoint of forming a crosslinked structure and improving the durability of the porous structure, and from the viewpoint of promoting curing and improving production efficiency, it reacts with the hydrophilic functional group of the component (A). Do (
D) It is preferable to use a crosslinking agent (hereinafter also referred to as component (D)) in combination.
From the above viewpoint, the content of the component (D) is based on 100 parts by mass of the solid content of the component (A).
Preferably it is 1.0-5.0 mass parts, More preferably, it is 1.2-4.5 mass parts, More preferably, it is 1.5-4.0 mass parts.
Although there is no restriction | limiting in particular as (D) component, An oxazoline type crosslinking agent, an epoxy-type crosslinking agent, an isocyanate type crosslinking agent, a carbodiimide type crosslinking agent, etc. are preferable.
As the oxazoline-based crosslinking agent, a compound having two or more oxazolinyl groups can be used. For example, a copolymer of 2-isopropenyl-2-oxazoline, butyl acrylate, and methyl methacrylate, 2-isopropenyl- Copolymer of 2-oxazoline, ethyl acrylate and methyl methacrylate, copolymer of 2-isopropenyl-2-oxazoline and styrene, copolymer of 2-isopropenyl-2-oxazoline, styrene and acrylonitrile , A copolymer of 2-isopropenyl-2-oxazoline, styrene, butyl acrylate, and divinylbenzene.

Examples of the epoxy-based crosslinking agent include sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanurate, glycerol Polyglycidyl ether, trimethylolpropane polyglycidyl ether, resorcin diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, Propylene glycol diglycidyl ether, dipro Glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol glycidyl ether,
Examples thereof include adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, hydroquinone diglycidyl ether, bisphenol S diglycidyl ether, terephthalic acid diglycidyl ester, dibromoneopentyl glycol diglycidyl ether, and the like.

Examples of isocyanate crosslinking agents include liquid MDI such as tolylene diisocyanate, diphenylmethane diisocyanate (MDI), polyphenylpolymethyl polyisocyanate, crude MDI, hexamethylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, hydrogenated diphenylmethane. Diisocyanate,
Examples include compounds in which isocyanate groups are protected with isophorone diisocyanate, trimers that are isocyanurate rings, trimethylolpropane adducts, and the like with a blocking agent.

Examples of the carbodiimide-based crosslinking agent include polyisocyanate compounds obtained by reacting a compound having one functional group capable of reacting with an isocyanate group such as a hydroxyl group or an amino group in the presence of a carbodiimidization catalyst. A carbodiimide resin or the like can be used. Examples of the polyisocyanate compound include hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, xylylene diisocyanate, norbornane diisocyanate, and isophorone diisocyanate. Examples of the compound having one functional group capable of reacting with an isocyanate group include monoalkyl ether of polyethylene glycol, monoalkyl ether of random or block copolymer of polyethylene glycol-polypropylene glycol, and the like.
These crosslinking agents may be used alone or in combination of two or more.

<(E) Other additives>
In the aqueous dispersion of the present invention, various additives can be used in combination as long as the object of the present invention is not impaired. Examples of additives include pigments, dyes, auxiliary binders, leveling agents, thixotropic agents, antifoaming agents, fillers, foaming agents, antisettling agents, ultraviolet absorbers, antioxidants, thinning agents, wetting agents, Examples thereof include coloring inhibitors. Such additives may be used alone or in combination of two or more. In addition, as above-mentioned, it is preferable that the aqueous dispersion liquid of this invention does not contain surfactant.
Among the above additives, it is particularly preferable to add a foaming agent. By adding a foaming agent, the foaming ratio (the volume after foaming with respect to the volume of the dispersion) can be easily prepared. As such a foaming agent, a commonly used one can be used.

The amount of water added in the aqueous dispersion of the present invention is appropriately adjusted so that the dispersion has a desired viscosity in order to adjust the solid content and the viscosity. Specifically, it is preferably 20 to 250 parts by mass, and more preferably 30 to 200 parts by mass with respect to 100 parts by mass of the solid content of the aqueous dispersion.

[Step (2): Application or impregnation to fibrous base material]
The method for applying or impregnating the aqueous dispersion of the present invention to the fibrous base material is not particularly limited. For example, in the case of impregnation, a known impregnation method can be adopted, and the fibrous base material is incorporated into the aqueous dispersion. A method of immersing the material and a method of forcibly rubbing the aqueous dispersion into the fibrous base material using a driving roll are preferably used. For the purpose of adjusting the amount of aqueous dispersion impregnated into the fibrous base material,
It is also possible to add a treatment for pressing the fibrous base material impregnated with the aqueous dispersion and scraping off the aqueous dispersion adhering to the surface. Also, a known method can be adopted for application to the fiber substrate,
It is also a preferred form that both the coating layer and the impregnation are performed simultaneously with a coating machine represented by a comma coater or knife coater.

The fibrous base material to be impregnated is appropriately selected for the purpose and application, and natural fibers such as cotton and hemp, P
Nonwoven fabrics made of synthetic fibers such as ET, nylon, polyethylene, polypropylene, etc. are mentioned. Among them, nonwoven fabrics that can be applied to artificial leather substrates are preferred, and the fibrous base material is made of hot water extraction type sea-island fibers. Nonwoven fabric is preferred. The hot-water extraction type sea-island fiber nonwoven fabric can extract the water-soluble polymer component constituting the sea-island fiber by hot-water extraction, and at the same time, can wash the nonionic thickener used in the aqueous dispersion. The porous structure of the present invention is
(A) Since it consists of hydrophilic functional group containing resin, the swelling rate by a hot water process is low, it is excellent in hot water resistance, and it can suppress the foaming damage by hot water.

Such a sea-island fiber may be of a type in which either the sea component or the island component is extracted and removed, but the polymer (island component) constituting the ultrafine fiber when the sea component is extracted and removed (extreme fiber generation type fiber) For example, melt-spinnable polyamides such as 6-nylon and 66-nylon, polyethylene terephthalate, polybutylene phthalate, isophthalic acid-modified polyester, and cationic dyeable modified polyethylene terephthalate are possible. And at least one polymer selected from polyesters such as polypropylene and polyolefins typified by polypropylene.
In addition, it is important that the component to be extracted and removed (sea component) is a component composed of a water-soluble polymer component and spinnable. For example, as the water-soluble polymer component, a known polymer can be used as long as it is a polymer that can be extracted with water or an aqueous solvent, but it is preferable to use polyvinyl alcohol copolymers that are soluble in an aqueous solvent. . The volume ratio between the sea component and the island component of this ultrafine fiber generating fiber is 1: 2 to 2: 1, and the fineness of the ultrafine fiber after extracting the sea component is 0. 0 in terms of texture and fulfillment. A range of 01 to 0.0001 dtex is preferable.

The sea-island fiber non-woven fabric may be produced by tangling a short fiber having a length of 20 to 75 mm into a short fiber web by a card method and then using a needle punch or a high-speed fluid. A long fiber web may be formed simultaneously with spinning by the method, and then entangled with a needle punch or a high-speed fluid.

[Step (3): Gelation of aqueous dispersion]
The aqueous dispersion impregnated into the fibrous base material in the previous step is heat-sensitive gelled and solidified into a gel. By performing heat-sensitive gelation and making it into a gel, compared to the case where moisture is evaporated by drying without gelation, migration of the aqueous dispersion is suppressed and a uniform coating state or impregnation state in the thickness direction is achieved. Can be obtained. The thermal coagulation temperature at which the aqueous dispersion gels is preferably 30.
It is -80 degreeC, More preferably, it is 40-70 degreeC. Here, the heat-sensitive coagulation temperature is a temperature at which the aqueous dispersion is gelled, and 50 g of the aqueous dispersion is taken in a 100 mL glass beaker and the beaker is heated to 95 ° C. while stirring the contents. This is the temperature at which the contents gradually lose their fluidity and solidify when heated gradually in a bath. If the heat-sensitive coagulation temperature is 30 ° C. or higher, it is possible to prevent the dispersion from gelling in the summer atmosphere, and if it is 80 ° C. or lower, the heat-sensitive gelation is sharply expressed. Therefore, the migration prevention property can be sufficiently exhibited in the next drying step.

Examples of the heat-sensitive gelling treatment include a wet heat treatment and a heat treatment using infrared rays. In particular, wet heat treatment with steam is preferable from the viewpoint of obtaining a good gelled state. Wet heat treatment with steam can be processed if the steam temperature is equal to or higher than the thermal coagulation temperature of the aqueous dispersion. However, in order to perform more stable production, the steam temperature is set to "thermal coagulation temperature + 10 ° C" or higher. It is preferable to set the temperature. The specific steam temperature is preferably 40 to 140.
° C, more preferably 60 to 120 ° C.
Moreover, the humidity at the time of performing the wet heat treatment with steam is preferable because drying from the surface is suppressed as it approaches 100%. The steam treatment time is preferably 5 seconds to 30 minutes, more preferably 10 seconds to 20 minutes, from the viewpoint of sufficiently forming a gelled film.
In addition, the wet heat treatment with steam and other methods can be used in combination. Other methods include
For example, solidification methods such as infrared rays, electromagnetic waves, and high frequencies can be mentioned.

[Step (4): Formation of porous structure]
The gel-like aqueous dispersion obtained by the heat-sensitive gelation treatment in the previous step is dried and solidified to form a porous structure. Examples of the drying and solidification method include drying methods such as hot air heating, infrared heating, electromagnetic wave heating, high-frequency heating, and cylinder heating. Among these methods, hot air drying is preferable from the viewpoint of running cost and continuous productivity. In addition, these drying methods can also be used individually or in combination of 2 or more types.
The drying temperature is preferably 60 to 190 ° C., more preferably 80 to 150 ° C., from the viewpoint that the formed porous structure is not deteriorated and deteriorated by heat and can be sufficiently dried, and the drying efficiency is improved. It is. The treatment time is preferably 1 to 20 minutes, more preferably 2 to 5 minutes, from the viewpoint of sufficient drying and productivity.

(Hot water extraction process)
When the hot water extraction type sea-island fiber nonwoven fabric is used as the base material, the nonwoven fabric that has been subjected to the hot water extraction treatment may be impregnated with the aqueous dispersion of the present invention. After impregnating the dispersion, it can be hydrothermally treated to form an ultrafine nonwoven fabric.
As a specific hot water extraction treatment method, the sea component in the nonwoven fabric is dissolved and removed with hot water to leave the island component in the form of ultrafine fibers. The removal of the sea component with hot water can be performed according to known methods and conditions conventionally employed in the production of artificial leather and the like.

[Porous structure]
The porous structure of the present invention has a porous layer having porosity inside, and a large number of micropores are uniformly mixed without being crushed, and has both a soft texture and a sense of fulfillment. The porous structure can be used for a high-quality suede-like or silver-colored sheet by raising the surface or applying a coating, while maintaining excellent productivity, and the porous structure of the present invention. The body can be formed stably.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by this Example.

[Example 1]
Nylon 6 (1015BK manufactured by Ube Industries) is used as a sea component, and water-soluble thermoplastic PVA (Exeval CP-4104MI manufactured by Kuraray Co., Ltd., melting point 209 ° C., MFR measured by M method of JIS K7210: 80 g / min, viscosity average polymerization degree 330, with a saponification degree of 98.4 mol%) as an island component, and using a fusion compound spinning die having 12 islands (islands) per sea-island type multicomponent fiber, sea components / islands It discharged from the nozzle | cap | die at 255 degreeC so that it might become mass ratio 50/50 of a component. Discharge from the base by adjusting the air in the air jet suction device installed directly below the base so that the spinning speed obtained indirectly from the ratio of the discharge amount per unit time and the fineness of the obtained long fibers is 2500 m / min. Average fineness of 2 by cooling while making the polymer polymer indexed
. A 53 decitex nylon porous hollow fiber generating composite fiber was spun. The composite fiber was continuously collected on a mobile net installed directly under the suction device, and then pressed using a metal roll having a surface temperature of room temperature to obtain a composite fiber web having a basis weight of 45 g / m ² .

The resulting composite fiber web was uniformly applied to the web surface using a spray while overlapping the resulting composite fiber web so as to have a basis weight equivalent to 8 webs using a cross wrapper. Next, using a 1-barb felt needle with a distance of 5 mm from the needle tip to the barb, needle punching is alternately performed on both sides of the web with the setting so that the tip of the needle stabbed into the composite fiber web protrudes up to 8 mm from the opposite side. Went. The total number of pierced needles is 1450
A nonwoven fabric with a basis weight of 344 g / m ² was obtained by performing a needle punching process so as to be in line / cm ² to entangle the composite fibers.

(A) Self-emulsifying water-based emulsion of carboxyl group-containing polyurethane resin (polycarbonate-based, not thermally gelled up to 90 ° C., but gelled at 60 ° C. when ammonium sulfate is added) 250 parts by mass (of which the solid content is 100 parts by mass), (B) 3.75 parts by mass of ammonium sulfate, (C) 2.5 parts by mass of nonionic thickener (trade name: Kelzan (xanthan gum), manufactured by Sanki Co., Ltd.), (D) cross-linking agent ( An aqueous dispersion containing 3.75 parts by mass (trade name: NK Assist CI, manufactured by Nikka Chemical Co., Ltd., carbodiimide crosslinking agent) was prepared. In addition, about the prepared aqueous dispersion, the viscosity of 25 degreeC and 60 degreeC was measured with the following method.
Next, the non-woven fabric was impregnated with the prepared aqueous dispersion and then pressed with a nip roll to adjust the adhesion ratio of the aqueous dispersion to the weight of the non-woven fabric to 150%. In addition, the impregnated nonwoven fabric was subjected to a heat-sensitive gelation treatment with steam at 90 ° C. at a relative humidity of 60% for 10 minutes, and then 150 ° C.
Was dried with hot air for 10 minutes to produce a porous structure.

Then, after grinding both sides 10/100 mm using 240th paper, 95 ° C
In the hot water, the island component PVA was dissolved and removed from the conjugate fiber in the nonwoven fabric by the dip × nip method so that the hot water immersion time was 20 minutes. The extraction rate is 92.0% by mass, and the resulting product has a thickness of 1
. A porous structure made of polyurethane and a synthetic nonwoven fabric of nylon porous hollow fibers having a diameter of 16 mm and a basis weight of 274 g / m ² and having 12 hollow portions in the cross section was obtained. This porous structure was used as a base material for artificial leather. Observation of cross section of the obtained base material for artificial leather with an electron micrograph (600
As a result, the resin and fibers inside the substrate had a non-adhesive structure, the resin itself was a fine porous body, and the texture was flexible. The cross-sectional photograph of the obtained base material for artificial leather is shown in FIG.

(1) Measurement of Viscosity of Aqueous Dispersion About the prepared aqueous dispersion, a single cylindrical rotational viscometer (trade name: Bismetron VG-A)
1. Viscosity at 25 ° C. and 60 ° C. was measured at 6 revolutions / minute using Shibaura System Co., Ltd. The viscosity of the aqueous dispersion of Example 1 was 35 Pa · s at 25 ° C. and 42 Pa · s at 60 ° C., and increased when compared with the viscosity immediately after preparation when the temperature was raised to the thermal coagulation temperature.

[Comparative Examples 1 and 2]
A nonwoven fabric having a foamed film was prepared in the same process as in Example 1 except that the composition of the components (A) to (E) was changed as shown in Table 1. As a result of evaluating the obtained porous structure, it was as shown in Table 1. A cross-sectional photograph of the artificial leather substrate obtained in Comparative Example 1 is shown in FIG.

[Comparative Example 3]
A non-woven fabric having a foamed film was prepared in the same manner as in Example 1 except that the heat-sensitive gelation treatment was not performed. As a result of evaluating the obtained porous structure, it was as shown in Table 1.

[Comparative Example 4]
In the composition of the dispersion liquid of Example 1, (C) component was implemented except having changed to 5.0 parts by weight of Aron A-20P (manufactured by Toagosei Co., Ltd., acrylic thickener, anionic thickener). A nonwoven fabric having a foamed film was produced in the same process as in Example 1. As a result of evaluating the obtained porous structure, it was as shown in Table 1.

In the porous structure of Example 1, the resin was uniformly distributed, the porous structure was good, and the texture was flexible.

The porous structure of Comparative Example 1 is not sufficiently gelled due to the small amount of ammonium sulfate in the dispersion, and the resulting porous structure has a large resin migration on both sides, resulting in a porous structure. Could not be obtained.
Since the porous structure of Comparative Example 2 contained a large amount of ammonium sulfate in the dispersion, a porous structure was not obtained, and the texture was hard.
Since the porous structure of Comparative Example 3 was not subjected to heat-sensitive gelation, it was not sufficiently gelled, the resin migrated on both sides, and a porous structure could not be obtained.
Since the porous structure of Comparative Example 4 was changed to an anionic thickener, the viscosity of the aqueous dispersion decreased from the application to the completion of the thermal gelation treatment, and the migration of the resin on both sides was large, resulting in a porous structure. Could not be obtained.

The method for forming a porous structure of the present invention is useful as a method for producing a base material having a film on the surface used for production of interior materials for vehicles, furniture, clothing, shoes, bags, bags, sandals, sundries, etc. .

Claims (10)

A method for producing a porous structure comprising a fibrous base material coated or impregnated with a polymer elastic body comprising a hydrophilic functional group-containing resin, comprising the following steps (1) to (4): A method for producing a porous structure.
Step (1): (A) a hydrophilic functional group-containing resin, (B) an ammonium salt, and (C) a nonionic thickener, and the blending amount of component (B) is the solid content of component (A) 0 to 100 parts by mass
. A step of preparing an aqueous dispersion having a viscosity of 25 to 10 parts by mass and having a viscosity of 10 to 100 Pa · s.
Step (2): A step of applying or impregnating the aqueous dispersion onto the fibrous base material.
Step (3): A step of forming a porous body by subjecting the aqueous dispersion to heat-sensitive gelation.
Step (4): A step of drying and solidifying the porous body. The method for producing a porous structure according to claim 1, wherein the (C) nonionic thickener is a polymeric polysaccharide. The method for producing a porous structure according to claim 1 or 2, wherein the (C) nonionic thickener is xanthan gum. The method for producing a porous structure according to any one of claims 1 to 3, wherein the aqueous dispersion further contains (D) a crosslinking agent. The method for producing a porous structure according to any one of claims 1 to 4, wherein the fibrous base material is a nonwoven fabric. The method for producing a porous structure according to any one of claims 1 to 5, wherein the fibrous base material is a non-woven fabric made of hot water extraction type sea-island fibers. (A) The manufacturing method of the porous structure of any one of Claims 1-6 whose hydrophilic functional group containing resin is a hydrophilic functional group containing water-based emulsion polyurethane resin. The heat-sensitive gelling treatment in step (3) is performed with steam at 40 to 140 ° C.
The manufacturing method of the porous structure of any one of -7. The manufacturing method of the porous structure of any one of Claims 1-8 including the process wash | cleaned with a hot water after a process (4). The artificial leather base | substrate obtained from the manufacturing method of the porous structure of any one of Claims 1-9.

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