JP2005213411A - Porous structural body, its manufacturing method and leather-like structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method whereby a porous structural body can be manufactured, wherein the porous structural body has a good texture such as flexibility, elasticity and resilience and has a porous structure having dense and uniform open cells excellent in stability (heat resistance and wet heat resistance) formed on a polyurethane layer formed near or on the surface of a fibrous substrate, despite the use of an aqueous polyurethane resin. <P>SOLUTION: In the manufacturing method of the porous structure, a mixture containing (A) the aqueous polyurethane resin, (B) polyvinyl alcohol, (C) an aqueous polyisocyanate crosslinking agent and (D) an associative thickener is applied to the fibrous substrate to obtain a precursor, and the precursor is subsequently wet-heated and dried by dry-heat to obtain the porous structure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a porous structure, a porous structure and a leather-like structure, and more particularly, a method for producing a porous structure in which an aqueous polyurethane resin is applied to a fiber substrate and dried, and the method And a leather-like structure in which a skin layer is provided on the porous structure.

  Conventionally, as a substitute for natural leather, various leather preparations such as artificial leather treated with a polyurethane resin using a non-woven fabric as a base material and synthetic leather treated with a polyurethane resin using a woven fabric or a knitted fabric as a base material have been manufactured. As such a leather preparation, a product (porous structure) in which a porous structure is formed in a polyurethane resin layer inside a base material is generally used in order to make the texture, breathability, etc. close to those of natural leather. .

  As a method for forming a porous structure in the polyurethane resin layer as described above, conventionally, after applying an organic solvent solution of a polyurethane resin to a fiber base material, the polyurethane resin is a poor solvent for the polyurethane resin and is compatible with the organic solvent. There has been known a method called a wet coagulation method in which a coagulation liquid (usually water) is allowed to coagulate and then washed and dried. However, the wet coagulation method using an organic solvent such as dimethylformamide has problems in terms of fire risk, deterioration of working environment, environmental pollution such as air and water quality, and the like. Therefore, conventionally, a process for recovering the organic solvent has been added in order to solve these problems, but the problem remains in that a large amount of recovery and disposal costs and labor are required.

  Therefore, in order to solve such a problem, studies have been conventionally made to shift the polyurethane resin applied to the fiber base material from an organic solvent type to an aqueous system. That is, if a porous structure can be obtained with a water-based polyurethane resin, the organic solvent is not used, so that the recovery cost and labor can be reduced, and further, there is a risk of fire, deterioration of the working environment, and environmental pollution. It has been expected that this problem will be solved at the same time.

  However, in the case of a production method in which a porous structure is formed in a polyurethane resin layer using an aqueous polyurethane resin, generally, a nonporous film is easily formed without forming pores in the resin layer. Even if the porous structure is formed, the particles are fused in the subsequent drying step to form a nonporous film, and the resulting porous structure is poor in flexibility, elasticity and rebound, and has a poor texture. There was a new problem of becoming something. For this reason, the following proposals have conventionally been made to prevent the resin layer from becoming non-porous with respect to a method for producing a porous structure using such an aqueous polyurethane resin, but a sufficient method has not yet been found. There wasn't.

  That is, Japanese Patent Application Laid-Open No. 52-28904 (Patent Document 1) proposes a method of coagulating in a hot water a synthetic resin emulsion imparted with a heat-sensitive coagulability by adding a heat-sensitive gelling agent. However, in this method, although a porous structure is temporarily formed in the polyurethane resin layer inside the fiber base material by hot water coagulation, its heat resistance is low, so that in the subsequent drying step, pore shrinkage or non-porosity As a result, a porous structure having a good texture could not be obtained. In addition, a part of the impregnating liquid flows out during the hot water coagulation and coagulates in the bath, and the coagulated gel is reattached to the surface of the work piece, so that the texture is further deteriorated.

  Japanese Patent Application Laid-Open No. 2000-290879 (Patent Document 2) discloses a method of thermally coagulating an aqueous resin composition comprising an aqueous urethane resin having a thermal coagulation temperature of 40 to 90 ° C. and an associative thickener with steam. Has been proposed. However, even in this method, although a porous structure is temporarily formed in the polyurethane resin layer inside the fiber base material, the heat resistance is low, so that the pores shrink or become nonporous in the subsequent drying step. As a result, a porous structure having a good texture could not be obtained.

  Japanese Patent Laid-Open No. 2001-172882 (Patent Document 3) adds a water-soluble highly crystalline natural product to a water-based urethane resin emulsion, and further renders the water-soluble highly crystalline natural product water-insoluble in a heat-heat coagulation process. A method of forming a porous structure in a polyurethane resin layer by using a crosslinking agent and an additive together has been proposed. However, in this method, cohesiveness is increased due to metal crosslinking with a divalent metal salt or silicate added as a crosslinking agent, and the resulting porous structure becomes hard and brittle, and also has a good texture. A porous structure could not be obtained.

  Further, JP-A-1-104634 (Patent Document 4) describes a heat-sensitive coagulable and heat-expandable polyurethane emulsion composition comprising a heat-sensitive coagulable polyurethane emulsion and a heat-expandable plastic microballoon as essential components. A method of treatment in water or steam at 180 ° C. has been proposed. In the publication, a cross-linking agent such as methylol melamine type, aziridine type, epoxy type or block isocyanate type, colorant such as water dispersible pigment, calcium carbonate In addition, it is described that a filler such as aluminum hydroxide, a thickener such as polyvinyl alcohol, an antioxidant, and an ultraviolet absorber may be added as desired. However, even if a thickening agent such as a blocked isocyanate-based crosslinking agent or polyvinyl alcohol is added to the heat-sensitive coagulating polyurethane emulsion described in the publication, it is difficult to form a porous structure in the polyurethane resin layer. Even if a porous structure is formed, its heat resistance is low, so that pores shrink or become non-porous in the subsequent drying step, and a porous structure having a good texture cannot be obtained. In fact, in the method described in the publication, it is necessary to add a heat-expandable plastic microballoon in order to form a porous structure. Therefore, coloring due to heat burn caused by the microballoon is generated and further formed. Since the pores are independent and have a large pore size, it was impossible to obtain a porous structure having a good texture.

As described above, none of the conventional methods for producing a porous structure using a water-based polyurethane resin has yet yielded a good porous structure such as a texture, and a porous structure obtained using an organic solvent-based polyurethane resin. The porous structure (leather preparation) that has the same uniformity and stability of the porous structure as the porous structure and has good texture and breathability has not been obtained using water-based polyurethane resin. Met.
Japanese Patent Laid-Open No. 52-28904 JP 2000-290879 A JP 2001-172882 A JP-A-1-104634

  The present invention has been made in view of the above-described problems of the prior art, and a polyurethane resin layer is formed in the vicinity of and on the surface of a fiber base material in spite of using an aqueous polyurethane resin. A porous structure having open cells that are dense, uniform and excellent in stability (heat resistance and moist heat resistance) is formed in the layer, and has a good texture such as flexibility, elasticity, and resilience. It is an object of the present invention to provide a method capable of producing In addition, the present invention provides a porous structure having a texture comparable to that of a porous structure obtained using an organic solvent-based polyurethane resin, despite being obtained by such a method using an aqueous polyurethane resin. It is an object of the present invention to provide an adhesive structure and a leather-like structure in which a skin layer is provided on the porous structure.

  As a result of intensive studies to achieve the above object, the present inventors applied a mixed liquid containing a water-based polyurethane resin, polyvinyl alcohol, an aqueous polyisocyanate-based crosslinking agent and an associative thickener to a fiber base material. A polyurethane resin layer is formed in the vicinity of and on the surface of the fiber substrate by wet heat heating and dry heat drying after obtaining the precursor, and the polyurethane resin layer is dense, uniform and excellent in stability. The present inventors have found that a porous structure having a good texture can be obtained, and the present invention has been completed.

  That is, the method for producing a porous structure of the present invention comprises (A) an aqueous polyurethane resin, (B) polyvinyl alcohol, (C) an aqueous polyisocyanate-based crosslinking agent, and (D) an associative thickener. Is applied to a fiber base material to obtain a precursor, and then the precursor is subjected to wet heat drying and dry heat drying.

  In the mixed solution used in the method for producing a porous structure of the present invention, the blending ratio of (A) water-based polyurethane resin and (B) polyvinyl alcohol is (A) :( B ) = 100: 1 to 100: 40, and the blending ratio of (B) polyvinyl alcohol and (C) aqueous polyisocyanate crosslinking agent is (B) :( C) = 100: 10 in terms of solid content. It is preferable that it is -100: 100.

  The (A) aqueous polyurethane resin used in the method for producing a porous structure of the present invention comprises (a) an isocyanate group-terminated prepolymer obtained by reacting a polyol and (b) a polyisocyanate, and (c) an HLB. An aqueous system obtained by dispersing in water using a nonionic surfactant having a value of 7 to 16 and then chain-extending with (d) a polyamine compound having two or more amino groups and / or imino groups A polyurethane resin is preferred.

  Moreover, it is preferable that the thermal coagulation temperature of (A) water-based polyurethane resin used in the manufacturing method of the porous structure of this invention is 40 to 90 degreeC.

  Furthermore, (B) polyvinyl alcohol used in the method for producing a porous structure of the present invention has a saponification degree of 70 mol% or more, and a 4 mass% aqueous solution having a viscosity at 20 ° C of 10.0 to 75. It is preferably 0 mPa · s.

  The (D) associative thickener used in the method for producing a porous structure of the present invention is preferably an associative thickener having a polyethylene chain and a urethane bond in the molecule.

  The porous structure of the present invention is a porous structure obtained by the production method of the present invention.

  Furthermore, the leather-like structure of the present invention is a leather-like structure characterized in that a skin layer is provided on at least one surface of the porous structure obtained by the production method of the present invention.

  In addition, in the porous structure of the present invention obtained by the production method of the present invention, dense, uniform, and highly stable open cells are formed in the polyurethane resin layer formed near and on the surface of the fiber substrate. A porous structure is formed. Although the specific reason why such a porous structure is obtained by the present invention is not clear, the present inventors infer as follows. That is, in the method for producing a porous structure of the present invention, a mixture containing (A) an aqueous polyurethane resin and (B) polyvinyl alcohol, (C) an aqueous polyisocyanate crosslinking agent and (D) an associative thickener. Since the liquid is applied to the fiber base material, during the subsequent wet heat heating, (A) the heat-sensitive coagulation property of the water-based polyurethane resin and (D) the action of particle aggregation by the associative thickener, A porous structure having dense and uniform open cells is formed in the polyurethane resin layer formed on the surface, and a porous structure is formed by (B) polyvinyl alcohol and (C) an aqueous polyisocyanate-based crosslinking agent. The present inventors speculate that the stability is remarkably improved by reinforcing the strength of the polyurethane particles that are being treated.

  According to the production method of the present invention, it is possible to form a porous structure in the polyurethane resin layer formed near and on the surface of the fiber base material even though the water-based polyurethane resin is used. Furthermore, according to the production method of the present invention, the polyurethane resin layer is formed with a porous structure having open cells that are dense, uniform, and excellent in stability (heat resistance and heat and humidity resistance), and are flexible and elastic. In addition, it is possible to manufacture a porous structure having a good texture such as rebound.

  Since the water-based polyurethane resin is used in the production method of the present invention as described above, it becomes possible to reduce the recovery cost and labor of the organic solvent generated when the organic solvent-based polyurethane resin is used, and further to fire. It is possible to simultaneously solve the problems of danger, deterioration of working environment, and environmental pollution.

  Therefore, according to the present invention, a porous structure having a texture comparable to that of a porous structure obtained using an organic solvent-based polyurethane resin despite being obtained by a method using an aqueous polyurethane resin. It is possible to provide a structure and a leather-like structure in which a skin layer is provided on the porous structure.

  Hereinafter, the manufacturing method of the porous structure of the present invention, the porous structure, and the leather-like structure will be described in detail according to preferred embodiments. In the method for producing a porous structure of the present invention, a mixed liquid containing (A) an aqueous polyurethane resin, (B) polyvinyl alcohol, (C) an aqueous polyisocyanate crosslinking agent and (D) an associative thickener is used as a fiber. After the precursor is obtained by applying to a substrate, the precursor is heated with wet heat and dried with dry heat to obtain a porous structure.

[(A) Water-based polyurethane resin]
As the (A) water-based polyurethane resin according to the present invention, (i) hydrophilic functional groups such as a carboxyl group, a sulfone group, and a quaternary ammonium group are introduced into the polyurethane resin skeleton and can be made aqueous without using an emulsifier. Self-emulsifying water-based polyurethane resins and (ii) forced emulsification-type water-based polyurethane resins obtained by phase inversion emulsification of a polyurethane resin having no hydrophilic functional group with an emulsifier can be used. From the viewpoint that the pores of the porous structure obtained in the inside tend to be denser, it is preferable to use (ii) a forced emulsification type aqueous polyurethane resin.

  As such a forced emulsification type water-based polyurethane resin, the particle diameter of the water-based polyurethane resin is fine, the dispersibility in water is good and the dispersion state is stable, and the resulting resin film is flexible and tough, After (a) an isocyanate group-terminated prepolymer obtained by reacting a polyol and (b) a polyisocyanate is dispersed in water using (c) a nonionic surfactant having an HLB value of 7 to 16. (D) Those obtained by chain extension reaction with a polyamine compound having two or more amino groups and / or imino groups are preferred. In the present invention, the HLB value is a value calculated by the Griffin equation.

  The polyol (a) suitably used in the present invention is not particularly limited as long as it has two or more hydroxyl groups, and examples thereof include polyester polyol, polycarbonate polyol, polyether polyol and the like.

  Examples of such polyester polyols 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, copolycondensate of 1,6-hexanediol, adipic acid and dimer acid, nonane Examples thereof include polycondensates of diol and dimer acid, and copolycondensates of ethylene glycol, adipic acid and dimer acid.

  Examples of the polycarbonate polyol include polytetramethylene carbonate diol, polyhexamethylene carbonate diol, poly-1,4-cyclohexanedimethylene carbonate diol, and the like.

  Further, as the polyether polyol, for example, polyethylene glycol, polypropylene glycol, polytetramethylene glycol homopolymer, block copolymer, random copolymer, ethylene oxide and propylene oxide, ethylene oxide and butylene oxide random copolymer, A block copolymer etc. can be mentioned. Furthermore, polyether ester polyols having an ether bond and an ester bond can also be used.

  These (a) polyols can be used individually by 1 type, or can also be used in combination of 2 or more type. In addition, it is preferable that the average molecular weight of these polyols is 500-5,000.

  (B) The polyisocyanate preferably used in the present invention is not particularly limited, and aromatic polyisocyanate, aliphatic polyisocyanate and alicyclic polyisocyanate having two or more isocyanate groups can be used. is there. Specifically, aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate; isophorone Examples thereof include alicyclic polyisocyanates such as diisocyanate, hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate, norbornane diisocyanate, and 1,3-bis (isocyanatomethyl) cyclohexane.

  Such (b) polyisocyanate can be used individually by 1 type, or can also be used in combination of 2 or more type. Among these polyisocyanates (b), the aliphatic polyisocyanate and the alicyclic polyisocyanate compound are preferable from the viewpoint that a non-yellowing polyurethane resin can be obtained, and hexamethylene diisocyanate and isophorone diisocyanate. More preferably, dicyclohexylmethane diisocyanate, norbornane diisocyanate and 1,3-bis (isocyanatomethyl) cyclohexane are used.

  When the above-mentioned (a) polyol and (b) polyisocyanate are reacted to produce an isocyanate group-terminated prepolymer, a low molecular weight chain extender can be used as necessary.

  Examples of such a low molecular weight chain extender include compounds having two or more hydrogen atoms capable of reacting with an isocyanate group, and the molecular weight is preferably 300 or less. Examples of the low molecular weight chain extender include low molecular weight polyvalents such as ethylene glycol, propylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol and sorbitol. Alcohols: Low molecular weight polyamines such as ethylenediamine, propylenediamine, hexamethylenediamine, diaminocyclohexylmethane, piperazine, 2-methylpiperazine, isophoronediamine, diethylenetriamine, and triethylenetetramine. These low molecular weight chain extenders can be used individually by 1 type, or can also be used in combination of 2 or more type.

  In the present invention, the specific method for producing the isocyanate group-terminated prepolymer is not particularly limited. For example, a conventionally known one-stage so-called one-shot method, a multi-stage isocyanate polyaddition reaction method, or the like may be employed. Is possible. The reaction temperature at this time is preferably 40 to 150 ° C. At this time, a reaction catalyst such as dibutyltin dilaurate, stannous octoate, dibutyltin-2-ethylhexanoate, triethylamine, triethylenediamine, or N-methylmorpholine can be added as necessary. It is also possible to add an organic solvent that does not react with the isocyanate group during or after the reaction. Examples of such an organic solvent include acetone, methyl ethyl ketone, toluene, tetrahydrofuran, dioxane, dimethylformamide, N-methylpyrrolidone, and the like.

  Next, after the obtained isocyanate group-terminated prepolymer was dispersed in water using (c) a nonionic surfactant having an HLB value of 7 to 16, (d) an amino group and / or an imino group By carrying out a chain elongation reaction with a polyamine compound having 2 or more, a forced emulsification type aqueous polyurethane resin can be obtained.

  (C) There is no restriction | limiting in particular in the structure of the nonionic surfactant used as a component, For example, polyoxyethylene distyryl phenyl ether type nonionic surfactant, polyoxyethylene propylene distyryl phenyl ether type nonionic Surfactants, polyoxyethylene tristyryl phenyl ether type nonionic surfactants, polyoxyethylene propylene tristyryl phenyl ether type nonionic surfactants, pluronic type nonionic surfactants, HLB value is 7 It is possible to select and use those having ˜16 (more preferably 9 to 15). Here, when the HLB value of the component (c) is less than 7, it is difficult to disperse the isocyanate group-terminated prepolymer, or the stability tends to be inferior even if it can be dispersed. On the other hand, when the HLB value exceeds 16, it becomes difficult to emulsify and disperse the prepolymer, or water resistance tends to be inferior even if it is dispersible.

  These nonionic surfactants can be used individually by 1 type, or can also be used in combination of 2 or more type. In addition, although the usage-amount of a nonionic surfactant can be suitably selected by the hydrophilic property of the isocyanate group terminal prepolymer which is a substance emulsified, Usually, with respect to 100 weight part of isocyanate group terminal prepolymers, The amount is preferably 0.5 to 10 parts by weight, and more preferably 1 to 6 parts by weight. When the amount of the nonionic surfactant used is less than 0.5 parts by weight based on 100 parts by weight of the isocyanate group-terminated prepolymer, it tends to be difficult to obtain a stable emulsified dispersion state. Moreover, when the usage-amount of a nonionic surfactant exceeds 10 weight part with respect to 100 weight part of isocyanate group terminal prepolymers, it exists in the tendency for the water resistance of the polyurethane resin obtained to fall.

  When the isocyanate group-terminated prepolymer is emulsified and dispersed in water, it is preferable to use mechanical shearing force because phase inversion emulsification occurs. There is no restriction | limiting in particular in the emulsification apparatus which gives a mechanical shearing force, For example, a homomixer, a homogenizer, etc. can be mentioned. It is preferable that the isocyanate group-terminated prepolymer is emulsified and dispersed in water in a temperature range of room temperature to 40 ° C. to suppress the reaction between the isocyanate group and water or the nonionic surfactant as much as possible. Furthermore, reaction inhibitors such as phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, p-toluenesulfonic acid, adipic acid, benzoyl chloride can be added as necessary.

  (D) Examples of the polyamine compound having two or more amino groups and / or imino groups include ethylenediamine, propylenediamine, tetramethylenediamine, hexamethylenediamine, diaminocyclohexylmethane, piperazine, hydrazine, 2-methylpiperazine, and isophoronediamine. Diamine such as norbornanediamine, diaminodiphenylmethane, tolylenediamine, xylylenediamine; polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, iminobispropylamine, tris (2-aminoethyl) amine; diprimary Amidoamines derived from amines and monocarboxylic acids; water-soluble amine derivatives such as di-primary amine monoketimines; oxalic acid dihydrazide, malonic acid dihydrazide, co Succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide, 1,1'-ethylenehydrazine, 1,1'-trimethylenehydrazine, 1,1'- Examples thereof include hydrazine derivatives such as (1,4-butylene) dihydrazine. These (d) components can be used individually by 1 type, or can also be used in combination of 2 or more type.

  The chain extension reaction of the isocyanate group-terminated prepolymer can be carried out by adding the component (d) to the emulsion dispersion of the isocyanate group-terminated prepolymer described above, or the isocyanate group-terminated prepolymer in the component (d). It is also possible to carry out by adding the emulsified dispersion. The chain extension reaction is preferably performed at a reaction temperature of 20 to 40 ° C., and is usually completed in 30 to 120 minutes. When an organic solvent is used in producing the isocyanate group-terminated prepolymer, for example, it is preferable to remove the organic solvent by distillation under reduced pressure or the like after the chain extension reaction is completed.

  The heat-sensitive coagulation temperature of the water-based polyurethane resin used in the present invention is preferably 40 to 90 ° C, more preferably 40 to 80 ° C, and particularly preferably 45 to 60 ° C. Here, the thermal coagulation temperature means that 50 g of an aqueous dispersion of an aqueous polyurethane resin is placed in a glass beaker equipped with a thermometer, and the beaker is gradually heated with hot water at 95 ° C. while stirring the contents. Refers to the temperature at which it loses fluidity and solidifies. When the heat-sensitive coagulation temperature is less than 40 ° C., a porous structure is formed inside the fiber base material, but the storage stability of the water-based polyurethane resin itself is poor, and it tends to solidify during storage at high temperatures such as in summer. It is in. On the other hand, if the thermal coagulation temperature exceeds 90 ° C., the thermal coagulation property is not sharp, so that the fineness of the pores of the porous structure formed inside the fiber base material is poor and the texture tends to be hard.

[(B) polyvinyl alcohol]
The polyvinyl alcohol (B) according to the present invention is not particularly limited, but from the viewpoint that the formation of the porous structure inside the fiber base material is more reliably prevented from being inhibited, the saponification degree may be 70 mol% or more. Preferably, it is more preferably 85 mol% or more. Here, the saponification degree is a percentage value of the number of hydroxyl groups with respect to the total number of carboxyl groups and hydroxyl groups in polyvinyl alcohol. When the saponification degree of the polyvinyl alcohol used is less than 70 mol%, the strength retention of the porous structure formed is weak, and the pores tend to shrink or become non-porous during drying. On the other hand, if the degree of saponification of polyvinyl alcohol is 85 mol% or more, the strength retention of the porous structure formed tends to be higher.

  The degree of polymerization of (B) polyvinyl alcohol according to the present invention is not particularly limited, but from the viewpoint that the formation of a porous structure is more reliably inhibited, the (B) 4% by mass aqueous solution of polyvinyl alcohol at 20 ° C. It is preferable to use one having a viscosity of 10.0 to 65.0 mPa · s, and more preferably 20.0 to 50.0 mPa · s. Here, the viscosity of a 4% by mass aqueous solution of polyvinyl alcohol is a value calculated according to the method described in JIS K 6726, and the higher the viscosity, the higher the degree of polymerization of polyvinyl alcohol. When the viscosity of the 4% by mass aqueous solution is less than 10.0 mPa · s, the strength retention of the porous structure obtained inside the fiber base material is weak, and the pores tend to shrink or become nonporous during drying. On the other hand, when the viscosity of the 4 mass% aqueous solution exceeds 65.0 mPa · s, a porous structure is formed inside the fiber base material, but the viscosity of the mixed solution tends to be difficult to perform stably. It is in. In addition, when the viscosity of the 4% by mass aqueous solution is 20.0 to 50.0 mPa · s, the strength holding power tends to be higher and more stable processing tends to be possible.

  (B) Polyvinyl alcohol can be obtained from a conventionally known production method. For example, polyvinyl acetate obtained by synthesizing vinyl acetate from acetic acid, oxygen, and ethylene and polymerizing vinyl acetate is used as an alkali. Can be produced by saponification. Further, as (B) polyvinyl alcohol, commercially available products such as Gohsenol NH-26, NH-20, AH-22, AH-17, GH-23, GM-14, and KH manufactured by Nippon Synthetic Chemical Industry Co., Ltd. -20, Goosefimmer K-210, Z-320, Z-410, Kuraray Kuraray PVA-HC, PVA-124, PVA-110, PVA-617, PVA-627, and the like. These can be used singly or in combination of two or more.

[(C) Aqueous polyisocyanate crosslinking agent]
The (C) aqueous polyisocyanate-based crosslinking agent according to the present invention refers to a compound imparted with a self-emulsifying property by introducing a hydrophilic chain into a hydrophobic polyisocyanate as a raw material. In addition to the hydrophilic chain, the aqueous polyisocyanate crosslinking agent may further introduce a lipophilic chain as necessary. Such an aqueous polyisocyanate-based crosslinking agent has high compatibility and dispersibility in (A) water-based polyurethane resin and (B) polyvinyl alcohol, good self-emulsification dispersibility in water, and a long pot life. And by using such (C) aqueous polyisocyanate crosslinking agent in combination with the above-mentioned (A) aqueous polyurethane resin and (B) polyvinyl alcohol, the polyurethane resin layer is uniformly dispersed inside the fiber substrate, In addition, a dense, uniform and excellent porous structure is formed in the polyurethane resin layer.

  Examples of the polyisocyanate used as a raw material for such an aqueous polyisocyanate-based crosslinking agent include aromatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates, and isocyanate-modified products obtained from the reaction of these polyisocyanates. Can be mentioned.

  Examples of such aromatic isocyanates include phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, naphthylene diisocyanate, diphenylmethane diisocyanate, and the isomers thereof. Examples of the aliphatic polyisocyanate include 1,6-hexamethylene diisocyanate and 1,12-dodecane diisocyanate. Furthermore, examples of the alicyclic polyisocyanate include cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and norbornane diisocyanate. In addition, as the isocyanate-modified product, an isocyanate-terminated compound obtained by a reaction between the diisocyanate or the like and a compound having active hydrogen, or a reaction of the polyisocyanate described above, for example, a uretdioneization reaction, an isocyanuration reaction, a carbodiimidization reaction And an isocyanate-modified product obtained by uretiminization reaction and the like. These isocyanate-modified products use a known uretdione-forming catalyst, isocyanurate-forming catalyst, etc., usually at a reaction temperature of 0 to 90 ° C., in the absence of a solvent, or in the presence of an inert solvent commonly used in the urethane industry. It can be produced from a raw material polyisocyanate. Examples of the uretdione conversion catalyst and the isocyanurate conversion catalyst include tertiary amines, alkyl-substituted ethyleneimines, tertiary alkyl phosphines, acetylacetone metal salts, metal salts of various organic acids, and the like. These catalysts can be used individually by 1 type, or can also be used in combination of 2 or more type. Examples of the inert solvent include toluene, methyl ethyl ketone, and ethyl acetate.

  And among the above polyisocyanates, from the viewpoint that water dispersibility, stability of isocyanate groups after water dispersion, non-yellowing and the like tend to be good, from the reaction of aliphatic polyisocyanate and alicyclic polyisocyanate The resulting isocyanate-modified product is preferred, and a polyisocyanate having an isocyanurate ring having an average number of functional groups of 2 or more is more preferred.

  In order to introduce a hydrophilic chain into these raw material polyisocyanates, the following nonionic (nonionic) compounds or ionic compounds may be used.

  Examples of the nonionic compound include an alkylene oxide adduct of alcohol or fatty acid. As the alcohol, any of linear, branched, and cyclic alcohols can be used, and alcohols having 1 to 4 carbon atoms (for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, etc.) can be used. preferable. From the viewpoint of fatty acid, for example, acetic acid, propionic acid, butanoic acid and the like can be mentioned. The addition form of alkylene oxide may be one single addition, or may be random or block addition of two or more alkylene oxides. The number of added moles of alkylene oxide is preferably 3 to 90, and more preferably 5 to 50. Moreover, it is preferable that it is 70% or more of ethylene oxide in all the alkylene oxide units.

  From the viewpoint of ionic compounds, anionic compounds such as fatty acid salts, sulfonates, phosphate esters, sulfate esters, primary amine salts, secondary amine salts, tertiary amine salts, quaternary ammonium salts And cationic compounds such as pyridinium salts and amphoteric compounds such as sulfobetaine.

  In the production of the aqueous polyisocyanate compound, examples of the compound that introduces a lipophilic chain into the raw material polyisocyanate include octyl alcohol, nonyl alcohol, decyl alcohol, undecyl alcohol, lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol. And higher alcohols having 8 or more carbon atoms such as cetyl alcohol and cinnamyl alcohol. Moreover, the fatty acid ester whose sum of the carbon number of the fatty acid and alcohol used as a raw material is 8 or more can be used. In this case, examples of the fatty acid used as a raw material include α-oxypropionic acid, oxysuccinic acid, dioxysuccinic acid, ε-oxypropane-1,2,3-tricarboxylic acid, α-hydroxybutyric acid, β-hydroxybutyric acid, hydroxystearic acid. Examples include acids, ricinoleic acid, ricinoelaidic acid, ricinostearolic acid, salicylic acid, mandelic acid, and the like, for example, methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, dodecyl alcohol. And lauryl alcohol. When such an oleophilic chain is present in the vicinity of the isocyanate group, when the aqueous polyisocyanate compound is dispersed in water, it is possible to three-dimensionally protect the isocyanate group from water and prolong the pot life. It is.

  The production of the aqueous polyisocyanate compound can generally be carried out at 50 to 130 ° C., and an inert solvent, a catalyst or the like can be used as necessary.

  In the aqueous polyisocyanate compound, the equivalent ratio of active hydrogen of the compound that adds a hydrophilic chain to 1 equivalent of the isocyanate group of the raw material polyisocyanate is preferably 1 to 30%, and preferably 8 to 20%. More preferred. If the content of the hydrophilic chain is too small, the self-emulsification dispersibility tends to be poor. On the other hand, if the content of the hydrophilic chain is too large, the affinity between the water-based polyisocyanate compound and water increases, There is a tendency that the stability of the aqueous polyisocyanate compound in water decreases. Moreover, it is preferable that the equivalent ratio of the active hydrogen of the compound which adds a lipophilic chain | strand is 0.1-25% with respect to 1 equivalent of isocyanate groups of raw material polyisocyanate, and it is more preferable that it is 2-15%. . If the content of the lipophilic chain is too small, the surface chemical protection of the isocyanate group cannot be sufficiently performed, and the pot life tends to be shortened when dispersed in water. When there is too much content of, there exists a tendency for water dispersion stability to fall.

  The aqueous polyisocyanate crosslinking agent according to the present invention is preferably a hydrophilic chain-containing isocyanurate-modified product because it has a long pot life and the heat resistance of the resulting porous structure is more excellent. An aqueous polyisocyanate compound in which a hydrophilic chain is introduced into methylene diisocyanate is particularly preferred. Commercially available aqueous polyisocyanate compounds can be used, for example, Bihijoule 3100 manufactured by Sumitomo Bayer Urethane Co., Ltd., Aquanate 100, 200 manufactured by Nippon Polyurethane Chemical Co., Ltd., Asahi Kasei Co., Ltd. Examples include Duranate WB40-80D, WE50-100, and the like.

[(D) Associative thickener]
Generally speaking, polymer thickeners include water-soluble polymer thickeners in addition to (D) associative thickeners. Here, (D) the associative thickener means that the hydrophobic group of the component to be thickened interacts with the hydrophobic group of the associative thickener to physically connect the particles to each other. Is used in the production method of the present invention from the viewpoint that the effect of thickening is high and the pores of the porous structure become dense. Further, in the present invention, since (D) an associative thickener is contained in the mixed solution together with (B) polyvinyl alcohol and the like, excellent suitability for coating on the surface of the fiber substrate is imparted. . Furthermore, since (D) the associative thickener reinforces the strength of the polyurethane resins by physical crosslinking between the particles, the stability of the porous structure also tends to be improved. On the other hand, although the water-soluble polymer thickener has a high thickening effect, it inhibits the formation of pores having a porous structure and becomes a nonporous film, and thus is not suitable for the production method of the present invention.

  Here, the (D) associative thickener according to the present invention is not particularly limited as long as it does not inhibit the formation of a porous structure. 54-80349, JP 58-213074, JP 60-49022, JP 52-25840, JP 9-67563, JP 9-71766, JP 2000-290879), associative thickeners obtained by copolymerizing nonionic urethane monomers as other associative monomers with other acrylic monomers (for example, JP-A-62-292979 and JP-A-10). And an associative thickener having an aminoplast skeleton (for example, described in WO9664015). Among such (D) associative thickeners, from the viewpoint of the fineness of pores of the porous structure and strength retention, an associative thickener having a polyethylene glycol chain and a urethane bond in the molecular chain is used. An associative thickener in which both ends of a urethane prepolymer obtained by reacting polyethylene glycol and diisocyanate are blocked with hydrophobic groups is more preferable.

  Moreover, what is marketed can be used for (D) associative type thickener, For example, Rohm and Haas company primal QR-708, RM-825, RM-870, RM-8W; Asahi Denka Co., Ltd. Adecanol UH-420, UH-550, UH-750; San Nopco SN thickener 603, 612, A-803, A-812, A-814; Sanyo Chemical Co., Ltd. bis riser AP-2, etc. be able to. These can be used individually by 1 type, or can also be used in combination of 2 or more type.

[Method for producing porous structure]
In the method for producing a porous structure of the present invention, first, the (A) aqueous polyurethane resin, (B) polyvinyl alcohol, (C) aqueous polyisocyanate crosslinking agent and (D) associative thickener are contained. The mixed liquid to be applied is applied to the fiber substrate to obtain a precursor.

  In the mixed solution, the blending ratio of (A) water-based polyurethane resin and (B) polyvinyl alcohol is preferably (A) :( B) = 100: 1 to 100: 40 in terms of solid mass, It is more preferable that A) :( B) = 100: 5 to 100: 30. If the blending ratio of (B) polyvinyl alcohol is smaller than the above range, the diameter of the pores to be formed is increased and the strength retention (heat resistance, moist heat resistance, etc.) of the porous structure is weakened. It tends to shrink or become nonporous. On the other hand, when the blending ratio of (B) polyvinyl alcohol is larger than the above range, the strength retention of the porous structure becomes weak, and the pores tend to shrink or become nonporous during drying.

  In the mixed solution, the blending ratio of (B) polyvinyl alcohol and (C) aqueous polyisocyanate crosslinking agent is (B) :( C) = 100: 10 to 100: 100 in terms of solid mass. Is preferable, and (B) :( C) = 100: 15 to 100: 80 is more preferable. When the blending ratio of the (C) aqueous polyisocyanate crosslinking agent is smaller than the above range, the strength retention of the porous structure is weakened, and the pores tend to shrink or become nonporous during drying. On the other hand, when the blending ratio of the (C) aqueous polyisocyanate-based crosslinking agent exceeds the above range, the resulting porous structure tends to lack elasticity and become brittle, and as a result, a satisfactory flexible texture can be obtained. It tends to be difficult.

  Moreover, in this invention, the compounding ratio of (A) water-based polyurethane resin and (D) associative type thickener in a liquid mixture is (A) :( D) = 100: 0.1 in conversion of solid content. 100: 20 is preferable, and (A) :( D) = 100: 1 to 100: 10 is more preferable. When the blending ratio of the (D) associative thickener is smaller than the above range, the mixed solution tends to penetrate into the inside of the fiber base material and a stable porous structure cannot be formed on the surface of the fiber base material. On the other hand, when the blending ratio of the (D) associative thickener exceeds the above range, the strength retention of the resulting porous structure is weakened, so that the pores tend to shrink and become nonporous during drying.

  In addition to (A) water-based polyurethane resin, (B) polyvinyl alcohol, (C) aqueous polyisocyanate-based crosslinking agent and (D) associative thickener, the mixed solution does not impair the effects of the present invention. Other water dispersions, for example, vinyl acetate-based, ethylene vinyl acetate-based, acrylic, acrylic styrene-based emulsions; styrene-butadiene-based, acrylonitrile-butadiene-based, acrylic-butadiene-based latex; polyethylene-based Polyolefin-based ionomers; polyurethanes, polyesters, polyamides, epoxy-based resins, and the like can be used in combination.

  Further, in the mixed solution, a moisture absorbing agent for efficiently taking in steam at the time of subsequent wet heat heating within the range not impairing the effect of the present invention, and (A) a heat sensitive coagulant for lowering the heat sensitive coagulation temperature of the water-based polyurethane resin. An additive for imparting processability may be added. Examples of the hygroscopic agent include urea, protein, glycerin, polyoxyethylene nonionic surfactant and the like. Examples of the heat-sensitive coagulant include sodium silicofluoride, potassium silicofluoride; hydrochloric acid, nitric acid, sulfuric acid, ammonium phosphate, sodium, potassium, calcium, magnesium, zinc, barium, nickel, tin, lead, iron, and the like. Polyvalent metal salts such as aluminum; polyether thioether glycols, polyether-modified polydimethylsiloxane compounds; alkylene oxide adducts of alkylphenol-formalin condensates and the like. Additives for imparting processability include, for example, alcohol-based nonionic surfactants, acetylene glycol-based special surfactants, silicone-based surfactants, fluorine-based surfactant leveling agents; oxidation Stabilizers such as inhibitors, light-resistant stabilizers, UV inhibitors, etc .; antifoaming agents such as mineral oils and silicones; urethanization catalysts, colorants such as plasticizers and pigments, pot life extenders, etc. It is done.

  In the production method of the present invention, the mixture is applied to at least one surface of the fiber base material to obtain a precursor, and then the precursor is dried by wet heat heating with steam and dry heat drying to obtain polyurethane. The resin layer can be formed near and on the surface of the fiber substrate, and further, a porous structure having open cells that are uniform, dense and excellent in stability can be formed in the obtained polyurethane resin layer. .

  The fiber base material used in the present invention is not particularly limited as long as the mixed liquid can be applied and, after drying, a porous structure can be formed near and on the surface of the fiber base material. It is preferable to use a woven fabric, a knitted fabric or a non-woven fabric. From the viewpoint of the material of the fiber substrate, natural fibers such as wool, silk, and cotton, and synthetic fibers such as polyamide fibers, polyester fibers, and acrylic fibers can be mentioned. Among them, fibers using polyamide fibers and polyester fibers are used. The substrate is particularly preferable because it tends to obtain a texture and quality close to those of natural leather. In order to prevent the mixed solution from penetrating into the fiber substrate, these fiber base materials are coated with a polymer aqueous solution such as polyvinyl alcohol or carboxymethyl cellulose, a silicone water repellent before applying the mixed solution. It is also possible to pre-treat with a fluorine-based water repellent or the like.

There is no restriction | limiting in particular in the method of apply | coating a liquid mixture to a fiber base material, For example, the conventionally well-known method of directly coating on the fiber base material surface using a gravure coater, a knife coater, a comma coater, an air knife coater etc. is applicable. Moreover, although the density | concentration and process conditions of a liquid mixture can be suitably selected according to the thickness and raw material of a fiber raw material, the quantity of the liquid mixture to apply | coat is an quantity used as 15-350 g / m < ² > after drying. Is preferable, and the amount of 35 to 250 g / m ² is more preferable. Moreover, it is preferable that the viscosity of a liquid mixture is 2000-18000 mPa * s, and it is more preferable that it is 3000-10000 mPa * s. When the above upper limit is exceeded, cracks are formed in the porous structure obtained on the surface of the fiber substrate, and the quality tends to be lowered. On the other hand, when it becomes smaller than the above lower limit, the mixed solution penetrates into the fiber base, and there is a tendency that a stable porous structure is not formed on the surface from the vicinity of the fiber base. In addition, the said viscosity is a value at the time of rotating at 30-60 rpm according to a conventional method using a No. 4 rotor in BM viscometer.

  Moreover, there is no restriction | limiting in particular as a method of moist heat heating, For example, a high-temperture steamer (HTS) and a high pressure steamer (HPS) can be used, and it is continuous processing. From the viewpoint of properties, it is preferable to use a high tenpulcher steamer (HTSS). Further, in order to shorten the processing time or to form a denser porous structure, a high temperature steamer (HTSS) or a high pressure steamer (HPSS) is used as necessary. .) Etc. can be applied together with microwave irradiation drying. The treatment time for wet heat heating is preferably from 3 minutes to 20 minutes, more preferably from 5 to 10 minutes. The steam flow rate is preferably 30 L / min to 300 L / min, and more preferably 100 L / min to 200 L / min. There is no restriction | limiting in particular also about the method of dry heat drying, For example, the dry heat drying by a pin tenter, hot air drying, far-infrared heating, etc. are mentioned. In addition, after wet heat heating or heat sensitive drying, it can wash | clean with cold water or warm water, and can remove the nonionic surfactant and (D) associative type | mold thickener contained in (A) water-based polyurethane resin.

[Porous structure]
The porous structure of the present invention is obtained by the production method of the present invention, and a polyurethane resin layer is formed in the vicinity of and on the surface of the fiber substrate, and the polyurethane resin layer is uniform, dense and stable. The porous structure which has the open cell excellent also in the property is formed.

  It is also possible to produce a porous structure using a nonwoven fabric having a fiber layer having a three-dimensional structure similar to the collagen fiber structure of natural leather as a fiber base material, and to use this as artificial leather. Furthermore, it is also possible to produce a porous structure using a knitted fabric or a woven fabric as a fiber base material, and to make it a synthetic leather.

[Leather-like structure]
The leather-like structure of the present invention is obtained by providing a skin layer on at least one surface of the porous structure obtained by the production method of the present invention. As described above, the method for forming the skin layer may be any conventionally known method. (I) An adhesive is applied on the skin layer formed on the release paper, and is bonded to the porous structure of the present invention. Moisture evaporation or pasting after moisture evaporation, then release paper transfer method to release the release paper from the skin layer; (ii) The skin layer formed on the release paper was pasted to the porous structure by heat And (iii) a spray method in which the composition for forming the skin layer is directly sprayed on the porous structure of the present invention; (iv) a gravure coater for forming the skin layer; A direct coating method in which coating is performed on the porous structure of the present invention with a knife coater, a comma coater, an air knife coater, or the like can be mentioned. From the viewpoint of physical properties of the skin layer, a release paper transfer method is most preferable. The skin layer and the adhesive used in the release paper transfer method may be any as long as they can be bonded to the porous structure of the present invention, but from the viewpoint of the texture and physical properties, polyurethane resin From the viewpoint of VOC and environmental load, it is desirable to be aqueous or solvent-free.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

  In Examples and Comparative Examples, the porous structures were evaluated by the following methods.

(1) Cross-sectional observation of porous structure Using a scanning electron microscope [Hitachi, Ltd., S-2400], observe the cross-section of the porous structure and adhere to the vicinity and on the surface of the fiber substrate. The state of the porous structure formed in the polyurethane resin layer was evaluated according to the following criteria.
4: A porous structure having dense and uniform open cells was confirmed throughout the polyurethane resin layer.
3: A porous structure having dense open cells in most of the polyurethane resin layer was confirmed.
2: A porous structure was confirmed in a part of the polyurethane resin layer.
1: Formation of a porous structure was not confirmed in the polyurethane resin layer (non-porous state).

(2) Texture of the porous structure The texture (flexibility) of the porous structure was evaluated according to the following five criteria (first grade [crude] to fifth grade [flexible]).
5: Texture that is soft and extremely rich in rebound resilience 4: Texture that is soft and rich in rebound resilience 3: Texture that is soft but slightly lacks resilience 2: Slightly rough and paper-like (paper-like) texture 1: Rough and paper-like (paper-like) texture.

(3) Heat resistance of porous structure After allowing the porous structure to stand in a hot air dryer (TABAI SAFETYOVEN SPH-200) at 120 ° C for 200 hours, the cross section was scanned with a scanning electron microscope [Hitachi, Ltd., S- 2400], the state of the porous structure formed in the polyurethane resin layer adhering to and near the surface of the fiber substrate was evaluated according to the following criteria.
4: A porous structure having dense and uniform open cells was confirmed throughout the polyurethane resin layer.
3: A porous structure having dense open cells in most of the polyurethane resin layer was confirmed.
2: A porous structure was confirmed in a part of the polyurethane resin layer.
1: Formation of a porous structure was not confirmed in the polyurethane resin layer (non-porous state).

(4) Moisture and heat resistance of porous structure The porous structure was placed in a thermo-hygrostat (TABAI EY-101) at 70 ° C and 95% RH. After being allowed to stand for 2 weeks under the above conditions, the cross section was observed using a scanning electron microscope [Hitachi, Ltd., S-2400], and in the polyurethane resin layer adhering to and near the surface of the fiber substrate. The state of the formed porous structure was evaluated according to the following criteria.
4: A porous structure having dense and uniform open cells was confirmed throughout the polyurethane resin layer.
3: A porous structure having dense open cells in most of the polyurethane resin layer was confirmed.
2: A porous structure was confirmed in a part of the polyurethane resin layer.
1: Formation of a porous structure was not confirmed in the polyurethane resin layer (non-porous state).

  Below, although the synthesis | combining method (Synthesis Examples 1-2) of a water-based polyurethane resin and the manufacturing method (Examples 1-12 and Comparative Examples 1-5) of a porous structure are shown, the amount of solid content in it Indicates the percentage of residual mass after each sample was dried at 105 ° C. for 3 hours.

Synthesis Example 1 (Aqueous dispersion of aqueous polyurethane resin)
In a four-necked flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube, 76.1 g of 1,6-hexanediol polycarbonate polyol (average molecular weight 1000), polyoxyethylene polypropylene random copolymer glycol (average molecular weight) 1000, oxyethylene group content 70%) 16.9 g, 1,4-butanediol 1.5 g, trimethylolpropane 1.9 g, dibutyltin dilaurate 0.001 g and methyl ethyl ketone 60 g were mixed and mixed uniformly, and then dicyclohexyl 40.4 g of methane diisocyanate was added and reacted at 75 ° C. for 300 minutes to obtain a methyl ethyl ketone solution of an isocyanate group-terminated prepolymer (content of free isocyanate group relative to the solid content was 2.1% by mass).

  After cooling this solution to 30 ° C. or less, 0.1 g of decyl phosphate ester and 6.0 g of polyoxyethylene tristyryl phenyl ether (HLB value = 15) were added and mixed uniformly, and then using a disper blade, Further, 254 g of water was gradually added to carry out phase inversion emulsification and dispersion. To this, 2.0 g of piperazine and a polyamine aqueous solution in which 0.8 g of diethylenetriamine was dissolved in 11.3 g of water were added and stirred for 90 minutes to obtain a polyurethane dispersion.

  Further, the solvent was removed at 35 ° C. under reduced pressure, and a stable aqueous system having a solid content of 35.0% by mass, a viscosity of 50.0 mPa · s (BM viscometer, No. 1 rotor, 60 rpm), and an average particle size of 0.52 μm. An aqueous dispersion of polyurethane resin was obtained. The heat-sensitive coagulation temperature of this water-based polyurethane resin was 45 ° C.

Synthesis Example 2 (Aqueous polyurethane resin aqueous dispersion)
In a four-necked flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube, 76.1 g of 1,6-hexanediol polycarbonate polyol (average molecular weight 1000), polyoxyethylene polypropylene random copolymer glycol (average molecular weight) 1000, oxyethylene group content 70%) 16.9 g, 1,4-butanediol 1.5 g, trimethylolpropane 1.9 g, dibutyltin dilaurate 0.001 g and methyl ethyl ketone 60 g were mixed and mixed uniformly, and then dicyclohexyl 40.4 g of methane diisocyanate was added and reacted at 75 ° C. for 300 minutes to obtain a methyl ethyl ketone solution of an isocyanate group-terminated prepolymer (content of free isocyanate group based on solid content was 2.1% by mass).

  After cooling this solution to 30 ° C. or less, 0.1 g of decyl phosphate and 6.0 g of polyoxyethylene tristyryl phenyl ether (HLB = 15) were added and mixed uniformly, and then water was added using a disper blade. 254 g was gradually added and phase-inverted emulsified and dispersed. To this, 2.0 g of piperazine and a polyamine aqueous solution in which 0.8 g of diethylenetriamine was dissolved in 11.3 g of water were added and stirred for 90 minutes to obtain an aqueous polyurethane dispersion.

  Further, after removing the solvent at 35 ° C. under reduced pressure, 1% by mass of Vixen AG-25 (Nikka Chemical Co., Ltd., anionic surfactant) was added, the solid content was 35.0%, and the viscosity was 50.0 mPa · s. (BM viscometer, No. 1 rotor, 60 rpm) An aqueous dispersion of a stable aqueous polyurethane resin having an average particle size of 0.52 μm was obtained. The heat-sensitive coagulation temperature of this water-based polyurethane resin was 80 ° C.

Example 1
(Pretreatment of fiber substrate)
A polyester (100%) woven fabric was impregnated with NK GUARD NDN-7E [manufactured by Nikka Chemical Co., Ltd., fluorine-based water repellent], and then dried with hot air at 100 ° C. for 1 minute for water repellent pretreatment. .

(Manufacture of porous structure)
100 g of aqueous dispersion of aqueous polyurethane resin obtained in Synthesis Example 1, Gohsenol NH-26 [manufactured by Nippon Synthetic Chemical Industry Co., Ltd., polyvinyl alcohol, saponification degree 99 mol%, viscosity at 20 ° C. of 4 mass% aqueous solution 67 mPa · s , 100% by weight of solid content] 70 g of 10% by weight aqueous solution, Bihijoule 3100 [manufactured by Sumitomo Bayer Urethane Co., Ltd., an aqueous polyisocyanate-based cross-linking agent in which a hydrophilic chain is introduced into isocyanurate-modified hexamethylene diisocyanate, solid content of 100% by weight ] 3 g, Vis riser AP-2 [manufactured by Sanyo Kasei Kogyo Co., Ltd., associative thickener, solid content 30 mass%] 10 g are mixed, and the viscosity is 4000 mPa · s (BM viscometer, No. 4 rotor, 60 rpm). The mixed solution was adjusted.

  The blending ratio of each component in the liquid mixture in terms of mass is as follows: aqueous polyurethane resin: polyvinyl alcohol = 100: 20, polyvinyl alcohol: crosslinking agent = 100: 43, aqueous polyurethane resin: thickening agent = 100: 8. 6.

After applying this mixed solution on the fiber substrate pretreated as described above using a knife coater so that the coating thickness is 300 μm (the coating weight after drying is 250 g / m ² ), the vapor pressure is 39 kPa. H. adjusted to a steam flow rate of 200 L / min. T.A. Wet and heat for 5 minutes in S (Sakurai dyeing industry, Type: HT-3-550), then wash in hot water bath at 70 ° C. for 10 minutes and squeeze excess water with mangle, It was left to dry at 100 ° C. for 10 minutes with a hot air dryer (TABAI SAFETYOVEN SPH-200) to obtain a porous structure. The obtained porous structure was evaluated as described above, and the results are shown in Table 1.

Example 2
In Example 1, in place of the 10% by mass aqueous solution of gohsenol NH-26, goosenol NH-20 [manufactured by Nippon Synthetic Chemical Industry Co., Ltd., polyvinyl alcohol, saponification degree 99 mol%, viscosity at 20 ° C. of 4% by mass aqueous solution A porous structure was obtained in the same manner as in Example 1 except that a 10% by mass aqueous solution of 40 mPa · s, solid content 100% by mass] was used. The obtained porous structure was evaluated as described above, and the results are shown in Table 1. Moreover, the scanning electron micrograph of the cross section of the porous structure obtained in Example 2 is shown in FIG.

Example 3
In Example 1, instead of a 10% by mass aqueous solution of GOHSENOL NH-26, GOHSENOL NL-05 [manufactured by Nippon Synthetic Chemical Industry Co., Ltd., polyvinyl alcohol, saponification degree 99 mol%, viscosity at 20 ° C. of 4% by mass aqueous solution A porous structure was obtained in the same manner as in Example 1 except that a 10% by mass aqueous solution having a solid content of 5 mPa · s and a solid content of 100% by mass was used. The obtained porous structure was evaluated as described above, and the results are shown in Table 1.

Example 4
In Example 1, instead of a 10% by mass aqueous solution of GOHSENOL NH-26, GOHSENOL GH-17 [manufactured by Nippon Synthetic Chemical Industry Co., Ltd., polyvinyl alcohol, saponification degree 88 mol%, viscosity at 20 ° C. of 4% by mass aqueous solution A porous structure was obtained in the same manner as in Example 1 except that a 10% by mass aqueous solution of 30 mPa · s and a solid content of 100% by mass was used. The obtained porous structure was evaluated as described above, and the results are shown in Table 1.

Example 5
In Example 1, instead of 10 mass% aqueous solution of gohsenol NH-26, gohsenol KH-20 [manufactured by Nippon Synthetic Chemical Industry Co., Ltd., polyvinyl alcohol, saponification degree 79 mol%, 4 mass% aqueous solution at 20 ° C A porous structure was obtained in the same manner as in Example 1 except that a 10% by mass aqueous solution having a viscosity of 45 mPa · s and a solid content of 100% by mass was used. The obtained porous structure was evaluated as described above, and the results are shown in Table 1.

Example 6
In Example 1, instead of a 10% by mass aqueous solution of gohsenol NH-26, GOHSENOL KP-08 [manufactured by Nippon Synthetic Chemical Industry Co., Ltd., polyvinyl alcohol, saponification degree 72 mol%, 4% by weight aqueous solution at 20 ° C. A porous structure was obtained in the same manner as in Example 1 except that a 10% by mass aqueous solution having a viscosity of 7 mPa · s and a solid content of 100% by mass was used. The obtained porous structure was evaluated as described above, and the results are shown in Table 1.

Example 7
In Example 1, instead of 10% by mass aqueous solution of GOHSENOL NH-26, GOCELAN L-032 [manufactured by Nippon Synthetic Chemical Industry Co., Ltd., polyvinyl alcohol, saponification degree 99 mol%, viscosity at 20 ° C. of 4% by mass aqueous solution A porous structure was obtained in the same manner as in Example 1 except that a 10% by mass aqueous solution having a solid content of 5 mPa · s and a solid content of 100% by mass was used. The obtained porous structure was evaluated as described above, and the results are shown in Table 1.

Example 8
100 g of an aqueous dispersion of the aqueous polyurethane resin obtained in Synthesis Example 1, Gohsenol NH-20 [manufactured by Nippon Synthetic Chemical Industry Co., Ltd., polyvinyl alcohol, saponification degree 99 mol%, 4 mass% viscosity at 20 ° C. of 40 mPa · s, 100% by mass of solid content] 150 g of 10% by weight aqueous solution, Bihijoule 3100 [manufactured by Sumitomo Bayer Urethane Co., Ltd., aqueous polyisocyanate-based cross-linking agent in which a hydrophilic chain is introduced into isocyanurate-modified hexamethylene diisocyanate, solid content of 100% %] 6.5 g, Viscolizer AP-2 [manufactured by Sanyo Kasei Kogyo Co., Ltd., associative thickener, solid content 30% by mass] 10 g, and a viscosity of 4000 mPa · s (BM viscometer, A porous structure was obtained in the same manner as in Example 2 except that the mixture of No. 4 rotor and 60 rpm was used.
The obtained porous structure was evaluated as described above, and the results are shown in Table 1.

  In addition, the compounding ratio by the mass conversion of each component in a liquid mixture is aqueous polyurethane resin: polyvinyl alcohol = 100: 43, polyvinyl alcohol: crosslinking agent = 100: 43, aqueous polyurethane resin: thickening agent = 100: 8.6.

Example 9
100 g of an aqueous dispersion of the aqueous polyurethane resin obtained in Synthesis Example 1, Gohsenol NH-20 [manufactured by Nippon Synthetic Chemical Industry Co., Ltd., polyvinyl alcohol, saponification degree 99 mol%, 4 mass% viscosity at 20 ° C. of 40 mPa · s, 10% by weight aqueous solution with a solid content of 100% by weight, Bihijoule 3100 [manufactured by Sumitomo Bayer Urethane Co., Ltd., an aqueous polyisocyanate-based cross-linking agent in which a hydrophilic chain is introduced into isocyanurate-modified hexamethylene diisocyanate, solid content of 100% by weight %] 0.13 g, Viscolizer AP-2 [manufactured by Sanyo Kasei Kogyo Co., Ltd., associative thickener, solid content 30% by mass] 10 g, and a viscosity of 4000 mPa · s (BM viscometer, A porous structure was obtained in the same manner as in Example 2 except that the mixture of No. 4 rotor and 60 rpm was used. The obtained porous structure was evaluated as described above, and the results are shown in Table 1.

  In addition, the compounding ratio by conversion of the solid content of each component in the liquid mixture is water-based polyurethane resin: polyvinyl alcohol = 100: 0.9, polyvinyl alcohol: crosslinking agent = 100: 43, water-based polyurethane resin: thickening agent = 100: 8.6.

Example 10
100 g of an aqueous dispersion of the aqueous polyurethane resin obtained in Synthesis Example 1, Gohsenol NH-20 [manufactured by Nippon Synthetic Chemical Industry Co., Ltd., polyvinyl alcohol, saponification degree 99 mol%, 4 mass% viscosity at 20 ° C. of 40 mPa · s, 10% by weight aqueous solution with a solid content of 100% by weight, Bihijoule 3100 (manufactured by Sumitomo Bayer Urethane Co., Ltd.), an aqueous polyisocyanate-based crosslinking agent in which a hydrophilic chain is introduced into isocyanurate-modified hexamethylene diisocyanate, solid content of 100% %] 7.4 g, Viscolizer AP-2 [manufactured by Sanyo Kasei Kogyo Co., Ltd., associative thickener, solid content 30% by mass] 10 g mixed, viscosity 4000 mPa · s (BM viscometer, A porous structure was obtained in the same manner as in Example 1 except that a mixture of No. 4 rotor and 60 rpm was used. . The obtained porous structure was evaluated as described above, and the results are shown in Table 1.

  In addition, the compounding ratio by mass conversion of the solid content of each component in the mixed solution is water-based polyurethane resin: polyvinyl alcohol = 100: 20, polyvinyl alcohol: crosslinking agent = 100: 105, water-based polyurethane resin: thickening agent = 100: 8.6.

Example 11
100 g of an aqueous dispersion of an aqueous polyurethane resin obtained from Synthesis Example 1, Gohsenol NH-20 [manufactured by Nippon Synthetic Chemical Industry Co., Ltd., polyvinyl alcohol, saponification degree 99 mol%, 4 mass% viscosity at 20 ° C. of 40 mPa · s, 100% by weight of solid content] 70 g of 10% by weight aqueous solution, Bihijoule 3100 [Sumitomo Bayer Urethane, isocyanurate-modified hexamethylene diisocyanate aqueous polyisocyanate-based crosslinking agent, solid content of 100% by weight] Viscosity 4000 mPa · s (BM viscometer, No. 4 rotor) obtained by mixing 10 g of 5 g, Viserizer AP-2 [manufactured by Sanyo Chemical Industries, Ltd., associative thickener, solid content 30% by mass] A porous structure was obtained in the same manner as in Example 1 except that the mixed solution at 60 rpm was used. The obtained porous structure was evaluated as described above, and the results are shown in Table 1.

  In addition, the compounding ratio by conversion of the solid content of each component in the mixed solution is water-based polyurethane resin: polyvinyl alcohol = 100: 20, polyvinyl alcohol: crosslinking agent = 100: 7, water-based polyurethane resin: thickening agent = 100: 8.6.

Example 12
A porous structure was obtained in the same manner as in Example 2, except that the aqueous dispersion of the aqueous polyurethane resin obtained in Synthesis Example 2 was used instead of the aqueous dispersion of the aqueous polyurethane resin obtained in Synthesis Example 1. Obtained. The obtained porous structure was evaluated as described above, and the results are shown in Table 1.

Comparative Example 1
100 g of an aqueous dispersion of the aqueous polyurethane resin obtained in Synthesis Example 1 and 10 g of Bisriser AP-2 [manufactured by Sanyo Chemical Industries, Ltd., associative thickener, solid content 30% by mass] are mixed, and the viscosity is 2800 mPa -A mixed solution of s (BM viscometer, No. 4 rotor, 60 rpm) was obtained. A porous structure was obtained in the same manner as in Example 1 except that this mixed solution was used. The obtained porous structure was evaluated as described above, and the results are shown in Table 1.

  In addition, the compounding ratio by mass conversion of the solid content of each component in the mixed solution is water-based polyurethane resin: polyvinyl alcohol = 100: 0, polyvinyl alcohol: cross-linking agent = 0: 0, water-based polyurethane resin: thickener = 100: 8.6. Moreover, the scanning electron micrograph of the cross section of the porous structure obtained in the comparative example 1 is shown in FIG. .

Comparative Example 2
100 g of an aqueous dispersion of the water-based polyurethane resin obtained in Synthesis Example 1, Bihijoule 3100 [manufactured by Sumitomo Bayer Urethane Co., Ltd., an aqueous polyisocyanate-based crosslinking agent in which a hydrophilic chain is introduced into isocyanurate-modified hexamethylene diisocyanate, solid content 100 [Mass%] 3 g and Viserizer AP-2 [manufactured by Sanyo Chemical Industries, Ltd., associative thickener, solid content 30% by mass] were mixed, and the viscosity was 3100 mPa · s (BM viscometer, No. 4, rotor, 60 rpm). ) Was obtained. A porous structure was obtained in the same manner as in Example 1 except that this mixed solution was used. The obtained porous structure was evaluated as described above, and the results are shown in Table 1.

  The solid content ratio of each component of the mixed solution in terms of mass is water-based polyurethane resin: polyvinyl alcohol = 100: 0, polyvinyl alcohol: crosslinking agent = 0: 3, water-based polyurethane resin: thickening agent = 100: 8.6.

Comparative Example 3
100 g of an aqueous dispersion of the aqueous polyurethane resin obtained in Synthesis Example 1, Gohsenol NH-20 [manufactured by Nippon Synthetic Chemical Industry Co., Ltd., polyvinyl alcohol, saponification degree 99 mol%, 4 mass% viscosity at 20 ° C. of 40 mPa · s, 100% by weight of solid content] and 70 g of 10% by weight aqueous solution and Vis riser AP-2 [manufactured by Sanyo Chemical Industries, Ltd., associative thickener, solid content of 30% by weight] are mixed, and the viscosity is 4000 mPa · s. A liquid mixture (BM viscometer, No. 4, rotor, 60 rpm) was obtained. A porous structure was obtained in the same manner as in Example 1 except that this mixed solution was used. The obtained porous structure was evaluated as described above, and the results are shown in Table 1.

  In addition, the compounding ratio by mass conversion of the solid content of each component in the mixed solution is water-based polyurethane resin: polyvinyl alcohol = 100: 20, polyvinyl alcohol: crosslinking agent = 100: 0, water-based polyurethane resin: thickening agent = 100: 8.6.

Comparative Example 4
100 g of an aqueous dispersion of the aqueous polyurethane resin obtained in Synthesis Example 1, Gohsenol NH-26 [manufactured by Nippon Synthetic Chemical Industry Co., Ltd., polyvinyl alcohol, saponification degree 99 mol%, viscosity at 20 ° C. of 4 mass% aqueous solution at 67 mPa · s, 10% by weight aqueous solution with a solid content of 100% by weight, NK assist FU [manufactured by Nikka Chemical Co., Ltd., methyl ethyl ketoxime block product of aromatic polyisocyanate, solid content of 40% by weight, NCO content after block dissociation Is mixed with 7.5 g of Viscoser AP-2 [manufactured by Sanyo Kasei Kogyo Co., Ltd., associative thickener, 30 mass% of solid content] with a viscosity of 4000 mPa · s (BM Viscometer, No. 4 rotor, 60 rpm) was obtained. A porous structure was obtained in the same manner as in Example 1 except that this mixed solution was used. The obtained porous structure was evaluated as described above, and the results are shown in Table 1.

  In addition, the compounding ratio by the mass conversion of each component in this liquid mixture is aqueous polyurethane resin: polyvinyl alcohol = 100: 20, polyvinyl alcohol: crosslinking agent = 100: 43, aqueous polyurethane resin: thickening agent = 100. : 8.6.

  In each of Examples 1 to 12, a polyurethane resin layer was formed near and on the surface of the fiber substrate, and a porous structure having open cells was formed in the resin layer.

  In Examples 1 to 7, the polyvinyl alcohol used in the mixed solution is changed, but in any case, a porous structure having dense and uniform open cells is formed in the polyurethane resin phase, and it is flexible and cushioning. A rich texture was also obtained. Among them, in Examples 1, 2, 4, and 5, a porous structure having dense and uniform open cells was maintained even after the heat resistance and heat and humidity resistance tests, and the porous structure was heat resistance and heat and humidity resistance. It was confirmed that the strength retention strength was excellent.

  In Examples 2, 8 and 9, the mixing ratio of the water-based polyurethane resin: polyvinyl alcohol in the mixed solution was changed, and a porous structure having excellent texture (flexibility) was obtained. In particular, in Example 2, it was confirmed that the porous structure was excellent in heat resistance and moist heat resistance and excellent in strength retention.

  In Examples 2, 10 and 11, the blending ratio of polyvinyl alcohol: crosslinking agent in the mixed solution was changed, but all of them formed a porous structure having dense and uniform open cells, and in particular, In Examples 2 and 10, it was confirmed that the porous structure was excellent in heat resistance and moist heat resistance and excellent in strength retention.

  In Examples 2 and 12, the heat-sensitive coagulation temperature of the water-based polyurethane resin was changed, and both had a porous structure excellent in texture (flexibility), and in Example 2, the porous structure was obtained. Was excellent in heat resistance and moist heat resistance, and was confirmed to be excellent in strength retention.

  (A), (B), (C), in Comparative Examples 1 to 4 using a mixed solution lacking any of the essential components of (D), all are polyurethane resin layers in the fiber substrate A sufficient porous structure was not formed therein, and the texture (softness) was remarkably inferior.

  As described above, according to the production method of the present invention, a polyurethane resin layer is formed in the vicinity of and on the surface of the fiber base material in spite of using the water-based polyurethane resin, and in the polyurethane resin layer. A porous structure with open cells that is dense, uniform and excellent in stability (heat resistance and moist heat resistance) is formed, producing a porous structure with good texture such as flexibility, elasticity and rebound It becomes possible to do.

  Therefore, according to the production method of the present invention, the organic solvent-based polyurethane resin can be replaced with a water-based polyurethane resin, and the recovery cost and labor of the organic solvent generated when the organic solvent-based polyurethane resin is used can be reduced. In addition, it is possible to simultaneously solve the problems of fire hazard, work environment deterioration, and environmental pollution.

  Furthermore, although the porous structure obtained by the production method of the present invention is obtained by a method using an aqueous polyurethane resin, the porous structure is obtained by using an organic solvent-based polyurethane resin. Because of its incomparable texture, the porous structure can be used as it is in industrial fields such as vehicles, furniture, clothing, shoes, bags, sundries, etc. It is also possible to provide leather preparations with excellent quality.

It is a scanning electron micrograph of the cross section of the polyurethane resin layer on the fiber substrate surface vicinity of the porous structure obtained in Example 2, and the surface. 2 is a scanning electron micrograph of a cross section of a polyurethane resin layer near and on the surface of a fiber substrate of a porous structure obtained in Comparative Example 1. FIG.

Claims (8)

  After applying a mixed liquid containing (A) an aqueous polyurethane resin, (B) polyvinyl alcohol, (C) an aqueous polyisocyanate-based crosslinking agent and (D) an associative thickener to a fiber base material to obtain a precursor A method for producing a porous structure, wherein the precursor is obtained by wet heat drying and dry heat drying to obtain a porous structure.   In the mixed solution, the blending ratio of (A) the water-based polyurethane resin and (B) polyvinyl alcohol is (A) :( B) = 100: 1 to 100: 40 in terms of solid mass, (B) The blending ratio of the polyvinyl alcohol and the (C) aqueous polyisocyanate crosslinking agent is (B) :( C) = 100: 10 to 100: 100 in terms of solid mass, 2. The manufacturing method of the porous structure of description.   (A) An aqueous polyurethane resin is an isocyanate group-terminated prepolymer obtained by reacting (a) a polyol and (b) a polyisocyanate, and (c) a nonionic surfactant having an HLB value of 7 to 16 is used. 3. A water-based polyurethane resin obtained by performing a chain extension reaction with a polyamine compound having two or more amino groups and / or imino groups after being dispersed in water. The manufacturing method of the porous structure of description.   The method for producing a porous structure according to any one of claims 1 to 3, wherein the (A) water-based polyurethane resin has a thermal coagulation temperature of 40 ° C to 90 ° C.   (B) The polyvinyl alcohol has a saponification degree of 70 mol% or more, and a 4 mass% aqueous solution having a viscosity at 20 ° C of 10.0 to 75.0 mPa · s. The manufacturing method of the porous structure as described in any one of 1-4.   (D) The associative thickener is an associative thickener having a polyethylene chain and a urethane bond in the molecule, and the porosity according to any one of claims 1 to 5 Manufacturing method of structure.   A porous structure obtained by the production method according to claim 1. The leather-like structure provided with the skin layer in the at least one surface of the porous structure obtained by the manufacturing method as described in any one of Claims 1-6.