Aqueous polyurethane resin composition and polyurethane film

Abstract

This aqueous polyurethane resin composition comprises an aqueous polyurethane resin obtained by extending, with (D) a polyamine having two or more amino groups and / or imino groups in one molecule, a chain of a neutralized product of an isocyanate group-terminated prepolymer that is a reaction product of (A) a polyisocyanate, (B) a polyol, and (C) a diol having a carboxy group and / or a carboxylate group, wherein the polyisocyanate (A) includes (a-1) isophorone diisocyanate and (a-2) hexamethylene diisocyanate; and the polyamine (D) includes at least one selected from the group consisting of (d-1) piperazine and (d-2) dibasic acid dihydrazides.

Description

Aqueous polyurethane resin composition and polyurethane film

[0001] The present invention relates to an aqueous polyurethane resin composition and a polyurethane film.

[0002] Generally, natural rubber and synthetic rubber, which are used as elastic materials, contain allergens and may cause allergic reactions in some users upon contact. Therefore, alternative materials are required for applications that involve contact with the skin (e.g., glove applications), and polyurethane, which has rubber elasticity, has attracted attention as such a material.

[0003] Aqueous polyurethane resins are used in a variety of applications, such as paints, adhesives, synthetic leather, artificial leather, and film molded articles. Among these, film molded articles include, for example, gloves, finger cots, and condoms, which are usually produced by the salt coagulation method.

[0004] For example, WO 2013 / 176257 (Patent Document 1) describes an aqueous polyurethane dispersion for use in film moldings, which is obtained by neutralizing an isocyanate-terminated prepolymer obtained by reacting a polyisocyanate (A) composed of diphenylmethane diisocyanate (a1) and an alicyclic diisocyanate (a2), a random copolymer of ethylene oxide and tetrahydrofuran (B), a polyol (C) having a number-average molecular weight of 1,000 to 5,000, a polyhydric alcohol-based chain extender (D) having a number-average molecular weight of 400 or less, and a diol compound (E) having a carboxyl group, dispersing the resulting neutralized product in water, and then subjecting the resulting product to a chain extension reaction using an amine-based chain extender (F). Examples of alicyclic diisocyanates include isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexylene diisocyanate, bis(2-isocyanatoethyl)-4-cyclohexene-1,2-dicarboxylate, 2,5- or 2,6-norbornane diisocyanate, etc. However, the film molded article obtained by the method described in this document has the problem of being poor in flexibility and elongation at break.

[0005] Furthermore, Japanese Patent Laid-Open Publication No. 2010-189556 (Patent Document 2) describes an aqueous polyurethane resin composition containing an aqueous polyurethane resin produced from a polyisocyanate and a polyhydroxy compound, and a nonionic surfactant, and having a resin solids concentration of 50% by weight or more, wherein the aqueous polyurethane resin satisfies the following conditions: (1) 50% by weight or more of the polyisocyanate is diphenylmethane diisocyanate, and (2) the amount of hydrophilic groups contained in the aqueous polyurethane resin is 0.03 to 0.30 mmol per 1 g of resin solids. Examples of polyisocyanates other than diphenylmethane diisocyanate include aliphatic polyisocyanates such as 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, and dimer acid diisocyanate, and alicyclic polyisocyanates such as 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, 3-isocyanatomethyl-3,3,5-trimethylcyclohexane (isophorone diisocyanate), bis-(4-isocyanatocyclohexyl)methane (hydrogenated MDI), and norbornane diisocyanate. However, the film molded article obtained by the method described in this document also has problems such as poor flexibility and elongation at break.

[0006] International Publication No. 2013 / 176257 Japanese Patent Application Laid-Open No. 2010-189556

[0007] The present invention has been made in view of the problems associated with the prior art, and an object of the present invention is to provide an aqueous polyurethane resin composition that has good film-forming properties in a salt coagulation method and that can be used to obtain a polyurethane film that has good flexibility, tensile strength at break, and elongation at break.

[0008]

[0006] As a result of intensive research to achieve the above object, the present inventors have found that by using a combination of isophorone diisocyanate (IPDI), which when used alone produces a polyurethane film with poor tensile strength, and hexamethylene diisocyanate (HDI), which when used alone produces an aqueous polyurethane resin composition with poor film-formability, as a polyisocyanate, and by using at least one selected from the group consisting of piperazine (PIP) and dibasic acid dihydrazide (ADH) as a chain extender, an aqueous polyurethane resin composition with good film-formability can be obtained in a salt coagulation method, and further that by using such an aqueous polyurethane resin composition, a polyurethane film with good flexibility, tensile strength at break, and elongation at break can be obtained, thereby completing the present invention.

[0009] The present invention provides the following aspects.

[0010] [1] An aqueous polyurethane resin composition comprising an aqueous polyurethane resin that is a chain-extended product of a neutralized product of an isocyanate-terminated prepolymer, which is a reaction product of (A) a polyisocyanate, (B) a polyol, and (C) a diol having a carboxy group and / or a carboxylate group, with (D) a polyamine having two or more amino groups and / or imino groups per molecule, wherein the (A) polyisocyanate comprises (a-1) isophorone diisocyanate and (a-2) hexamethylene diisocyanate, and the (D) polyamine comprises at least one member selected from the group consisting of (d-1) piperazine and (d-2) dibasic acid dihydrazide.

[0011] [2] The aqueous polyurethane resin composition according to [1], wherein the (B) polyol contains (b-1) polytetramethylene glycol.

[0012] [3] The aqueous polyurethane resin composition according to [1] or [2], further comprising a carbodiimide-based crosslinking agent.

[0013] [4] The aqueous polyurethane resin composition according to any one of [1] to [3], wherein the molar ratio ((a-1):(a-2)) of the (a-1) isophorone diisocyanate to the (a-2) hexamethylene diisocyanate is 10:90 to 90:10.

[0014] [5] The aqueous polyurethane resin composition according to any one of [1] to [4], wherein the total amount of the (a-1) isophorone diisocyanate and the (a-2) hexamethylene diisocyanate is 60 mol% or more based on the total amount of the (A) polyisocyanate.

[0015] [6] The hydrazide group (—NHNH) in the polyamine (D) ２ ), the ratio of the total number of hydrazide groups and imino groups in the (d-1) piperazine and the (d-2) dibasic acid dihydrazide to the total number of amino groups and imino groups is 50 mol % or more.

[0016] [7] The aqueous polyurethane resin composition according to any one of [1] to [6], wherein the total content of carboxy groups and carboxylate groups in the aqueous polyurethane resin is 0.5 to 2.0 mass%.

[0017] [8] The aqueous polyurethane resin composition according to [2], wherein the number average molecular weight of the polytetramethylene glycol (b-1) is 1,000 to 4,000, and the content of the polytetramethylene glycol (b-1) is 70 to 98 mass% based on the total amount of the polyol (B) and the diol (C).

[0018] [9] The aqueous polyurethane resin composition according to [3], wherein the content of the reactive group (—N═C═N—) contained in the carbodiimide crosslinking agent is 2.5 to 100 mol per 100 mol of the total amount of carboxy groups and carboxylate groups in the aqueous polyurethane resin.

[0019]

[10] A polyurethane film formed from the aqueous polyurethane resin composition according to any one of [1] to [9].

[0020] According to the present invention, it is possible to obtain an aqueous polyurethane resin composition that has good film-forming properties in a salt coagulation method and that can be used to obtain a polyurethane film that has good flexibility, tensile strength at break, and elongation at break.

[0021] The present invention will be described in detail below based on preferred embodiments thereof.

[0022] <Aqueous polyurethane resin composition> First, the aqueous polyurethane resin composition of the present invention will be described. The aqueous polyurethane resin composition of the present invention contains an aqueous polyurethane resin that is a chain-extended product of a neutralized product of an isocyanate-terminated prepolymer, which is a reaction product of (A) a polyisocyanate, (B) a polyol, and (C) a diol having a carboxy group and / or a carboxylate group, with (D) a polyamine having two or more amino groups and / or imino groups per molecule.

[0023] (A) Polyisocyanate The (A) polyisocyanate used in the present invention contains (a-1) isophorone diisocyanate (IPDI) and (a-2) hexamethylene diisocyanate (HDI). In the present invention, by using IPDI and HDI in combination, an aqueous polyurethane resin composition having good film-forming properties and a polyurethane film having good flexibility, tensile strength, and elongation at break can be obtained.

[0024] In the aqueous polyurethane resin composition of the present invention, the molar ratio ((a-1):(a-2)) of (a-1) IPDI to (a-2) HDI is preferably 10:90 to 90:10. By incorporating (a-1) IPDI and (a-2) HDI at such a molar ratio, an aqueous polyurethane resin composition having good film-forming properties and a polyurethane film having good flexibility, tensile strength, and elongation at break tend to be obtained. On the other hand, if the molar ratio of (a-1) IPDI exceeds the upper limit, the elongation at break of the resulting polyurethane film tends to decrease. On the other hand, if the molar ratio of (a-2) HDI exceeds the upper limit, the film-forming properties of the aqueous polyurethane resin composition tend to decrease. On the other hand, if the molar ratio of (a-2) HDI exceeds the upper limit, the film-forming properties of the aqueous polyurethane resin composition tend to decrease. On the other hand, if the molar ratio of (a-2) HDI exceeds the lower limit, the film-forming properties of the resulting polyurethane film tend to decrease. Furthermore, from the viewpoint of further suppressing a decrease in the film-forming properties of the aqueous polyurethane resin composition and a decrease in the breaking elongation of the resulting polyurethane film, it is more preferable that the molar ratio of (a-1) IPDI to (a-2) HDI ((a-1):(a-2)) is 30:70 to 70:30.

[0025] Furthermore, in the aqueous polyurethane resin composition of the present invention, the total amount of (a-1) IPDI and (a-2) HDI is preferably 60 mol % or more, based on the total amount of (A) polyisocyanate. By including (a-1) IPDI and (a-2) HDI in such a total amount, an aqueous polyurethane resin composition having good film-forming properties and a polyurethane film having good flexibility, tensile strength, and elongation at break tend to be obtained. On the other hand, if the total amount is less than the lower limit, the film-forming properties of the aqueous polyurethane resin composition tend to be reduced, and the elongation at break and tensile strength of the resulting polyurethane film tend to be reduced. Furthermore, from the viewpoint of further suppressing the deterioration of the film-forming properties of the aqueous polyurethane resin composition and the deterioration of the elongation at break and tensile strength of the resulting polyurethane film, the total amount is more preferably 70 mol % or more, and 100 mol %, i.e., a composition consisting solely of (a-1) IPDI and (a-2) HDI, is particularly preferred.

[0026] In the aqueous polyurethane resin composition of the present invention, when the total amount of (a-1) IPDI and (a-2) HDI is less than 100% by mass based on the total amount of (A) polyisocyanate, examples of polyisocyanates other than IPDI and HDI (hereinafter referred to as "other polyisocyanates") that are used in combination include aromatic polyisocyanates, aliphatic polyisocyanates (excluding HDI), and alicyclic polyisocyanates (excluding IPDI). Examples of aromatic polyisocyanates include toluene diisocyanate (TDI), xylylene diisocyanate (XDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate (NDI), and tetramethylxylylene diisocyanate. Examples of aliphatic polyisocyanates (excluding HDI) include trimethylhexamethylene diisocyanate. Examples of alicyclic polyisocyanates (excluding IPDI) include 1,3-bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane diisocyanate (hydrogenated MDI, H12MDI), norbornane diisocyanate, etc. These other polyisocyanates may be used alone or in combination of two or more.

[0027] (B) Polyols Examples of the (B) polyols used in the present invention include polyether polyols, polycarbonate polyols, polyester polyols, and low-molecular-weight polyols, and are distinguished from the (C) diols having a carboxy group and / or a carboxylate group, which will be described later.

[0028] In the present invention, it is preferable that at least a part of the (B) polyol contains a polyether polyol, and it is particularly preferable that (b-1) polytetramethylene glycol (PTMG) is contained. In the present invention, the use of (b-1) PTMG tends to provide an aqueous polyurethane resin composition with better film-forming properties and a polyurethane film with better flexibility, tensile strength, and elongation at break.

[0029] The number average molecular weight of (b-1) PTMG is preferably 1,000 to 4,000. Use of (b-1) PTMG with such a number average molecular weight tends to result in an aqueous polyurethane resin composition with better film-forming properties and a polyurethane film with better flexibility, tensile strength, and elongation at break. On the other hand, if the number average molecular weight of (b-1) PTMG is less than the lower limit, the film-forming properties of the aqueous polyurethane resin composition and the flexibility and elongation at break of the resulting polyurethane film tend to decrease. On the other hand, if the number average molecular weight exceeds the upper limit, the tensile strength of the resulting polyurethane film tends to decrease. Furthermore, from the viewpoint of further improving the flexibility and elongation at break of the polyurethane film, the lower limit of the number average molecular weight of (b-1) PTMG is more preferably 1,500 or more, and particularly preferably 2,000 or more. Furthermore, from the viewpoint of further improving the tensile strength of the polyurethane film, the upper limit of the number average molecular weight of (b-1) PTMG is more preferably 3,500 or less.

[0030] In the aqueous polyurethane resin composition of the present invention, the content of (b-1) PTMG is preferably 70 to 98% by mass relative to the total amount of (B) polyol and (C) diol described below. By including (b-1) PTMG in such an amount, an aqueous polyurethane resin composition having better film-forming properties and a polyurethane film having better flexibility, tensile strength, and elongation at break tend to be obtained. On the other hand, if the content of (b-1) PTMG is less than the lower limit, the flexibility and tensile strength of the resulting polyurethane film tend to decrease. On the other hand, if the content of (b-1) PTMG exceeds the upper limit, the content of (C) diol becomes insufficient, making it difficult to emulsify the aqueous polyurethane resin, and the film-forming properties of the aqueous polyurethane resin composition and the tensile strength of the resulting polyurethane film tend to decrease. Furthermore, from the viewpoint of further suppressing the decrease in flexibility and tensile strength of the resulting polyurethane film, the lower limit of the content of (b-1) PTMG is more preferably 90% by mass or more. Furthermore, from the viewpoint of further suppressing the decrease in the film-forming properties of the aqueous polyurethane resin composition and the tensile strength of the resulting polyurethane film, the upper limit of the content of (b-1) PTMG is more preferably 96 mass % or less.

[0031] In the aqueous polyurethane resin composition of the present invention, (b-1) a polyol other than PTMG (hereinafter referred to as "other polyol") may be used in combination. Examples of other polyols include polyether polyols (excluding PTMG), polycarbonate polyols, polyester polyols, and low-molecular-weight polyols. Such other polyols may be used alone or in combination of two or more.

[0032] Examples of polyether polyols (excluding PTMG) include polyols formed by block or random copolymerization of two or more species selected from ethylene oxide, propylene oxide, and tetrahydrofuran, polypropylene glycol, polyethylene glycol, etc. The number average molecular weight of such polyether polyols (excluding PTMG) is not particularly limited, but is preferably 500 to 5,000.

[0033] Examples of polycarbonate polyols include those obtained by dealcoholization reaction, dephenolation reaction, etc. of polyols (e.g., ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanedimethanol, or ethylene oxide or propylene oxide adducts of bisphenol A, trimethylolpropane, glycerin, pentaerythritol, etc.) with carbonates (e.g., diethylene carbonate, dimethyl carbonate, diethyl carbonate, diphenyl carbonate, etc.). The number average molecular weight of such polycarbonate polyol is not particularly limited, but is preferably 500 to 5,000.

[0034] Examples of polyester polyols include those obtained by polycondensation reaction of dibasic acids (e.g., phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, succinic acid, malonic acid, adipic acid, sebacic acid, 1,4-cyclohexyldicarboxylic acid, maleic acid, fumaric acid, etc.) with the polyols exemplified as raw materials for the polycarbonate polyol. The number average molecular weight of such polyester polyols is not particularly limited, but is preferably 500 to 5,000.

[0035] Examples of low-molecular-weight polyols include ethylene glycol, 1,4-butanediol, hexamethylene glycol, trimethylolpropane, pentaerythritol, sorbitol, etc. The number-average molecular weight of such low-molecular-weight polyols is not particularly limited, but is preferably 400 or less.

[0036] (C) Diol (C) used in the present invention is a carboxy group (—COOH) and / or a carboxylate group (—COO －Examples of diols having a carboxy group or the like (hereinafter collectively referred to as "carboxy group or the like") include 2,2-dimethylolpropionic acid (dimethylolpropanoic acid, DMPA), 2,2-dimethylolbutanoic acid (DMBA), and salts thereof. Examples of the salts include ammonium salts, mono-, di-, or tri-alkyl (preferably, C1-C4 alkyl) amine salts, mono-, di-, or trialkanol (preferably, C1-C4 alkanol) salts, and alkali metal salts (preferably, sodium salts, potassium salts).

[0037] In the aqueous polyurethane resin composition of the present invention, the diol (C) may be a polyester diol having a pendant carboxy group or the like obtained by reacting the diol having a carboxy group or the like with a dicarboxylic acid (e.g., an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, etc.). Furthermore, a polyester diol obtained by reacting the diol having a carboxy group or the like with the diol not having a carboxy group or the like can also be used as the diol (C).

[0038] In the aqueous polyurethane resin composition of the present invention, such diols (C) may be used alone or in combination of two or more.

[0039] In the aqueous polyurethane resin composition of the present invention, the total content of carboxy groups and carboxylate groups (carboxy groups, etc.) in the aqueous polyurethane resin is preferably 0.5 to 2.0% by mass. By including carboxy groups, etc. in such a total amount, an aqueous polyurethane resin composition with better film-forming properties and a polyurethane film with better flexibility, tensile strength, and elongation at break tend to be obtained. On the other hand, if the total amount of carboxy groups, etc. is less than the lower limit, coagulation by salt in the salt coagulation method tends to be weaker, and the tensile strength and elongation at break of the resulting polyurethane film tend to be lower. Furthermore, the aqueous polyurethane resin tends to be less emulsifiable, making stable film formation difficult. On the other hand, if the total amount of carboxy groups, etc. exceeds the upper limit, salt coagulation in the salt coagulation method tends to be stronger, making the resulting polyurethane film more susceptible to cracking and reducing the film-forming properties of the aqueous polyurethane resin composition. Furthermore, from the viewpoint of further suppressing decreases in the tensile strength and elongation at break of the resulting polyurethane film, the lower limit of the total amount of carboxy groups, etc. is more preferably 0.8% by mass or more. Furthermore, from the viewpoint of further suppressing the deterioration of the film-forming properties of the aqueous polyurethane resin composition, the upper limit of the total amount of carboxy groups and the like is more preferably 1.5 mass % or less.

[0040] [Isocyanate Group-Terminated Prepolymer] The isocyanate group-terminated prepolymer used in the present invention is a reaction product of the (A) polyisocyanate, the (B) polyol, and the (C) diol having a carboxy group or the like.

[0041] The method for producing such an isocyanate-terminated prepolymer is not particularly limited, and examples include the conventionally known single-stage so-called one-shot method and the multi-stage isocyanate polyaddition reaction method. The reaction temperature is preferably 40 to 150°C. In this case, if necessary, a reaction catalyst such as dibutyltin dilaurate, stannous octoate, dibutyltin di-2-ethylhexoate, triethylamine, triethylenediamine, N-methylmorpholine, or bismuth tris(2-ethylhexanoate), or a reaction inhibitor such as phosphoric acid, sodium hydrogen phosphate, paratoluenesulfonic acid, adipic acid, or benzoyl chloride may be added.

[0042] Furthermore, an organic solvent that does not react with isocyanate groups may be added during or after the reaction. Examples of such organic solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dioxane, dimethylformamide, dimethyl sulfoxide, toluene, xylene, ethyl acetate, butyl acetate, and methylene chloride. These organic solvents can be removed by heating under reduced pressure after the prepolymer is emulsified and dispersed and chain-extended.

[0043] When producing an isocyanate-terminated prepolymer, the molar ratio of isocyanate groups to hydroxyl groups (NCO / OH) in the raw material is preferably 100 / 95 to 100 / 65, more preferably 100 / 90 to 100 / 70, and particularly preferably 100 / 85 to 100 / 75. By adjusting the molar ratio of isocyanate groups to hydroxyl groups in the raw material within this range, the resulting isocyanate-terminated prepolymer is easily emulsified and dispersed, and an aqueous polyurethane resin composition with good film-forming properties and a polyurethane film with good flexibility, tensile strength, and elongation at break are obtained. On the other hand, if the NCO / OH ratio is below the lower limit, the resulting isocyanate-terminated prepolymer tends to have a high viscosity and is difficult to emulsify and disperse, and the resulting polyurethane film tends to have a low tensile strength. On the other hand, if the NCO / OH ratio exceeds the upper limit, the film-forming properties of the resulting aqueous polyurethane resin composition and the flexibility and elongation at break of the resulting polyurethane film tend to be low.

[0044] The free isocyanate group content in the isocyanate group-terminated prepolymer obtained in this manner is preferably 0.2 to 3.5% by mass, more preferably 0.3 to 3.4% by mass, even more preferably 0.5 to 2.5% by mass, and particularly preferably 0.87 to 1.10% by mass. By using an isocyanate group-terminated prepolymer having such a free isocyanate group content, an aqueous polyurethane resin composition having good film-forming properties and a polyurethane film having good flexibility, tensile strength, and elongation at break can be obtained. On the other hand, if the free isocyanate group content is below the lower limit, the tensile strength of the resulting polyurethane film tends to decrease. On the other hand, if the free isocyanate group content exceeds the upper limit, the film-forming properties of the resulting aqueous polyurethane resin composition and the flexibility and elongation at break of the resulting polyurethane film tend to decrease.

[0045] It should be noted that the (A) polyisocyanate, the (B) polyol, and the (C) diol all have a plurality of reaction sites, and the isocyanate-terminated prepolymer obtained by reacting such (A) polyisocyanate, the (B) polyol, and the (C) diol has a complex structure and cannot be directly represented by a general formula (structural formula).

[0046] [Neutralized Product of Isocyanate-Terminated Prepolymer] The neutralized product of the isocyanate-terminated prepolymer used in the present invention is a product in which the carboxy groups in the isocyanate-terminated prepolymer have been neutralized. Such a neutralized product of the isocyanate-terminated prepolymer may be produced by (i) neutralizing the carboxy groups in the isocyanate-terminated prepolymer obtained by reacting the (A) polyisocyanate, the (B) polyol, and the (C) diol using a known method, or by (ii) mixing the (A) polyisocyanate, the (B) polyol, and the (C) diol, neutralizing the carboxy groups in the (C) diol using a known method, and then reacting the neutralized (C) diol with the (A) polyisocyanate and the (B) polyol. The neutralized product of the isocyanate-terminated prepolymer can also be produced by (iii) reacting the (A) polyisocyanate, the (B) polyol, and the (C) diol in which the carboxyl group or the like is a salt of a carboxyl group.

[0047] In the production methods (i) and (ii) above, the basic compound used to neutralize the carboxyl group and the like is not particularly limited, and examples thereof include amines such as trimethylamine, triethylamine, tri-n-propylamine, tributylamine, N-methyl-diethanolamine, N,N-dimethylmonoethanolamine, N,N-diethylmonoethanolamine, triethanolamine, etc.; alkali metal hydroxides such as potassium hydroxide, sodium hydroxide, etc.; ammonia, etc. Among these, tertiary amines such as trimethylamine, triethylamine, tri-n-propylamine, tributylamine, etc. are particularly preferred.

[0048] In the production methods (i) and (ii) described above, when neutralizing the carboxyl groups and the like, the amount of the neutralizing basic compound used is preferably 0.5 to 1.5 equivalents, more preferably 0.6 to 1.4 equivalents, and particularly preferably 0.7 to 1.3 equivalents, relative to the carboxyl groups and the like. By adjusting the amount of the neutralizing basic compound used within the above range, the resulting isocyanate-terminated prepolymer is easily emulsified and dispersed, and an aqueous urethane resin composition with good storage stability is obtained. On the other hand, if the amount of the neutralizing basic compound used is less than the above lower limit, emulsification properties and storage stability tend to deteriorate. On the other hand, adding the neutralizing basic compound in an amount exceeding the above upper limit does not further improve emulsification properties and storage stability, and is therefore economically undesirable.

[0049] In the neutralized product of the isocyanate group-terminated prepolymer, the carboxy group (—COOH) and the carboxylate group (—COO) derived from the diol (C) － ) and 50% or more of the total number of moles of carboxylate groups (—COO － ), and 60% or more of the groups are carboxylate groups (—COO － ), and more preferably 70% or more of the alkyl groups are carboxylate groups (—COO － It is more preferable that the carboxylate group (-COO － By neutralizing the isocyanate group-terminated prepolymer so that the ratio of the carboxylate group (-COO) falls within the above range, the resulting isocyanate group-terminated prepolymer can be easily emulsified and dispersed, and an aqueous urethane resin composition with good storage stability can be obtained. － If the proportion of ) is less than the lower limit, emulsifiability and storage stability tend to deteriorate.

[0050] (D) Polyamine The (D) polyamine (chain extender) having two or more amino groups and / or imino groups (hereinafter collectively referred to as "amino groups, etc.") per molecule used in the present invention includes at least one selected from the group consisting of (d-1) piperazine (PIP) and (d-2) dibasic acid dihydrazide (ADH). In the present invention, by using (d-1) PIP and / or (d-2) ADH as the chain extender, an aqueous polyurethane resin composition having good film-forming properties and a polyurethane film having good flexibility, tensile strength, and elongation at break can be obtained.

[0051] Examples of (d-2) dibasic acid dihydrazides (ADHs) include dihydrazides of saturated aliphatic dicarboxylic acids having a total of 2 to 12 carbon atoms (including the carbon atoms of the COOH groups), such as oxalic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, and dodecanoic acid dihydrazide. Of these, adipic acid dihydrazide is preferred. Using a dihydrazide of a saturated aliphatic carboxylic acid having a total of more than 12 carbon atoms tends to reduce the crosslink density and decrease the breaking strength of the resulting polyurethane film.

[0052] In the aqueous polyurethane resin composition of the present invention, the hydrazide group (—NHNH) in (d-1) PIP and (d-2) ADH is ２It is preferable that the ratio of the total number of hydrazide groups, amino groups, and imino groups in the (D) polyamine is 50 mol % or more relative to the total number of hydrazide groups, amino groups, and imino groups in the (D) polyamine. By incorporating at least one selected from the group consisting of (d-1) PIP and (d-2) ADH in the above-mentioned ratio, an aqueous polyurethane resin composition having good film-forming properties and a polyurethane film having good flexibility, tensile strength, and elongation at break tend to be obtained. On the other hand, if the ratio is below the above-mentioned lower limit, the elongation at break and tensile strength of the resulting polyurethane film tend to decrease. Furthermore, from the viewpoint of further suppressing the decrease in the elongation at break and tensile strength of the resulting polyurethane film, the ratio is more preferably 70 mol % or more, and particularly preferably 100 mol %, i.e., a case where the composition is composed of only at least one selected from the group consisting of (d-1) PIP and (d-2) ADH.

[0053] In the aqueous polyurethane resin composition of the present invention, it is preferable to use only at least one selected from the group consisting of (d-1) PIP and (d-2) ADH as the (D) polyamine. However, polyamines other than PIP and ADH (hereinafter referred to as "other polyamines") may be used in combination as long as the effects of the present invention are not impaired. Examples of other polyamines include polyamines having two amino groups or the like per molecule, such as ethylenediamine, tetramethylenediamine, hexamethylenediamine, hydrazine, isophoronediamine, norboranediamine, diaminodiphenylmethane, tolylenediamine, and xylylenediamine; and polyamines having three or more amino groups or the like per molecule, such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and iminobispropylamine. Such other polyamines may be used in combination either individually or in combination.

[0054] [Aqueous Polyurethane Resin] The aqueous polyurethane resin contained in the aqueous polyurethane resin composition of the present invention is a chain-extended product obtained by chain-extending a neutralized product of the isocyanate-terminated prepolymer using the (D) polyamine.

[0055] (Emulsification and Dispersion) During chain elongation of the neutralized isocyanate-terminated prepolymer, the neutralized isocyanate-terminated prepolymer is first emulsified and dispersed in water. The emulsification and dispersion method is not particularly limited, and examples thereof include conventionally known methods using a homomixer, homogenizer, disper, or the like. The neutralized isocyanate-terminated prepolymer can be emulsified and dispersed in water at a temperature within a range of 0 to 40°C without the addition of an emulsifier. This can suppress the reaction between the isocyanate group and water. Furthermore, when emulsifying and dispersing the neutralized isocyanate-terminated prepolymer, a reaction inhibitor such as phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, paratoluenesulfonic acid, adipic acid, or benzoyl chloride may be added as necessary.

[0056] (Chain Extension) Next, the neutralized isocyanate-terminated prepolymer thus emulsified and dispersed in water is chain-extended using the (D) polyamine to form an aqueous polyurethane resin, thereby obtaining the aqueous polyurethane resin composition of the present invention.

[0057] During chain elongation of the neutralized isocyanate-terminated prepolymer, the amount of the polyamine (D) used is preferably an amount containing 0.5 to 2.5 equivalents of amino groups relative to the free isocyanate groups of the neutralized isocyanate-terminated prepolymer, more preferably an amount containing 0.6 to 1.4 equivalents of amino groups, and particularly preferably an amount containing 0.7 to 1.3 equivalents of amino groups. By adjusting the amount of the polyamine (D) used within the above range, an aqueous polyurethane resin having an appropriate crosslink density is formed, and an aqueous polyurethane resin composition having good film-forming properties and a polyurethane film having good flexibility, tensile strength, and elongation at break are obtained. On the other hand, if the amount of the polyamine (D) used is less than the lower limit, molecular weight elongation tends to be insufficient, and the tensile strength of the resulting polyurethane film tends to be reduced. On the other hand, if the amount of the polyamine (D) used is greater than the upper limit, molecular weight elongation tends to be insufficient, and the tensile strength of the resulting polyurethane film tends to be reduced, or the resulting polyurethane film tends to be yellowed due to residual amino groups at the terminals.

[0058] The chain extension method is not particularly limited, and for example, a method of adding the (D) polyamine to an emulsion dispersion of the neutralized isocyanate-terminated prepolymer to extend the chain, or a method of adding the emulsion dispersion of the neutralized isocyanate-terminated prepolymer to the (D) polyamine to extend the chain is preferred. The reaction between the neutralized isocyanate-terminated prepolymer and the amine is completed at a reaction temperature of 20 to 50°C, usually within 30 to 120 minutes after mixing the neutralized isocyanate-terminated prepolymer and the polyamine (D).

[0059] Like the (A) polyisocyanate, the (B) polyol, and the (C) diol, the (D) polyamine also has a plurality of reaction sites, and the chain-extended product of the neutralized product of the isocyanate-terminated prepolymer (aqueous polyurethane resin) obtained by chain-extending the neutralized product of the isocyanate-terminated prepolymer using such a (D) polyamine also has a complex structure, similar to the isocyanate-terminated prepolymer, and cannot be directly represented by a general formula (structural formula).

[0060] [Aqueous Polyurethane Resin Composition] The aqueous polyurethane resin composition of the present invention contains the aqueous polyurethane resin, i.e., the chain-extended product of the neutralized product of the isocyanate-terminated prepolymer with the polyamine (D). In the aqueous polyurethane resin composition of the present invention, the polyurethane nonvolatile content (resin solids concentration) is preferably 20 to 60 mass%, more preferably 30 to 50 mass%. Aqueous polyurethane resin compositions having such a polyurethane nonvolatile content exhibit good film-forming properties. The polyurethane nonvolatile content can be adjusted by adding or removing water from the aqueous polyurethane resin composition. Furthermore, when the aqueous polyurethane resin composition contains an organic solvent, the organic solvent is preferably removed by distillation, for example, under reduced pressure at a temperature of 30 to 80°C.

[0061] (Crosslinking Agent) The aqueous polyurethane resin composition of the present invention preferably further contains a crosslinking agent capable of reacting with carboxy groups in the aqueous polyurethane resin during film formation. By further incorporating a crosslinking agent capable of reacting with carboxy groups in the aqueous polyurethane resin during film formation, a polyurethane film with excellent solvent resistance tends to be obtained. Examples of such crosslinking agents include polyepoxy-based crosslinking agents, water-dispersible carbodiimide-based crosslinking agents, water-soluble oxazoline-based crosslinking agents, and water-dispersible polyisocyanate-based crosslinking agents. Among these crosslinking agents, water-dispersible carbodiimide-based crosslinking agents are preferred from the viewpoint of achieving compatibility between the flexibility, tensile strength, and breaking elongation of the resulting polyurethane film.

[0062] The water-dispersible carbodiimide crosslinking agent is not particularly limited, and examples thereof include an emulsion dispersion of a carbodiimide compound obtained by reacting a polyisocyanate having two or more isocyanate groups in one molecule with a sulfonic acid group-containing compound or a nonionic hydrophilic group compound in the presence of a carbodiimidization catalyst to remove carbon dioxide. Examples of the polyisocyanate include 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate, 2,4,6-triisopropylphenyl diisocyanate, 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, and hydrogenated tolylene diisocyanate.

[0063] The content of the crosslinking agent is preferably an amount such that the content of reactive groups (-N=C=N-) contained in the carbodiimide crosslinking agent is 2.5 to 100 mol per 100 mol of the total amount of carboxy groups and carboxylate groups (e.g., carboxy groups) in the aqueous polyurethane resin. By adjusting the content of the crosslinking agent within this range, the aqueous polyurethane resin can be crosslinked at an appropriate crosslink density, tending to produce a polyurethane film with better flexibility, tensile strength, and breaking elongation. On the other hand, if the content of the crosslinking agent is below the lower limit, the crosslink density of the aqueous polyurethane resin decreases, and the tensile strength of the resulting polyurethane film tends to decrease. On the other hand, if the content of the crosslinking agent is above the upper limit, the crosslink density of the aqueous polyurethane resin becomes too high, tending to produce a polyurethane film with reduced flexibility and breaking elongation.

[0064] (Surfactant) The aqueous polyurethane resin composition of the present invention preferably further contains at least one surfactant selected from the group consisting of anionic surfactants and nonionic surfactants. The aqueous polyurethane resin composition of the present invention containing the surfactant has improved storage stability and film-forming properties, and the resulting polyurethane film has improved flexibility, tensile strength, and elongation at break.

[0065] Examples of the anionic surfactant include aliphatic carboxylates (having 8 to 22 carbon atoms), alkyl sulfates (having 8 to 22 carbon atoms), alkyl sulfonates (having 8 to 22 carbon atoms), polyoxyalkylene alkyl ether sulfates (having an alkyl group having 8 to 22 carbon atoms, oxyalkylene groups such as oxyethylene groups and oxypropylene groups, which may be added alone or in combination of two or more, and the number of moles added is 1 to 20), polyoxyalkylene phenyl ether sulfates (having an oxyalkylene group such as oxyethylene groups and oxypropylene groups, which may be added alone or in combination of two or more, and the number of moles added is 1 to 20), and polyoxyalkylene phenyl ether sulfates (having an oxyalkylene group such as oxyethylene groups and oxypropylene groups, which may be added alone or in combination of two or more, and the number of moles added is 1 to 20). , two or more of which may be added, the number of moles being 1 to 20), polyoxyalkylene styryl phenyl ether sulfate salts (number of styryl groups: 1 to 3, oxyalkylene groups include oxyethylene groups, oxypropylene groups, etc., and only one of these may be added, or two or more of which may be added, the number of moles being 1 to 20), sulfated oils, sulfated fatty acid esters, and alkyl phosphate mono- or diester salts (having 3 to 22 carbon atoms). Among these, alkyl sulfate salts, polyoxyalkylene alkyl ether sulfate salts, and polyoxyalkylene styryl phenyl ether sulfate salts are preferred. Examples of the salts include salts of alkali metals such as sodium and potassium, ammonium salts, and mono-, di-, or trialkanolamine salts (having 1 to 4 carbon atoms in the alkanol portion). These anionic surfactants may be used alone or in combination of two or more.

[0066] Examples of the nonionic surfactant include alkylene oxide adducts of ethylenediamine (examples of alkylene oxides include ethylene oxide, propylene oxide, etc., and these may be added alone or in combination of two or more, and the number of moles added is 3 to 500), polyoxyethylene-polyoxypropylene copolymers (the total number of moles added of oxyethylene groups and oxypropylene groups is 3 to 500), alkylene oxide adducts of aliphatic alcohols (having 8 to 22 carbon atoms) (examples of alkylene oxides include ethylene oxide, propylene oxide, etc., and these may be added alone or in combination of two or more, and the number of moles added is 3 to 100), and alkylene oxide adducts of mono-, di-, or tristyrenated phenols (examples of alkylene oxides include ethylene oxide, propylene oxide, etc., and these may be added alone or in combination of two or more, and the number of moles added is 3 to 100). Among these, alkylene oxide adducts of mono-, di-, or tristyrenated phenols are preferred. These nonionic surfactants may be used alone or in combination of two or more.

[0067] The method for blending the surfactant in the aqueous polyurethane resin composition of the present invention is not particularly limited, and for example, the surfactant may be added during the preparation of the aqueous polyurethane resin composition, for example, when the isocyanate group-terminated prepolymer neutralized product is emulsified and dispersed in water. Alternatively, the surfactant may be added after the preparation of the aqueous polyurethane resin composition, for example, when the polyurethane non-volatile content (resin solid content concentration) is prepared or when a crosslinking agent is blended into the aqueous polyurethane resin composition.

[0068] The content of the surfactant is not particularly limited, but from the viewpoint of obtaining an aqueous polyurethane resin composition excellent in storage stability and film-forming ability, and also obtaining a polyurethane film excellent in flexibility, tensile strength, and elongation at break, the content is preferably 0.5 to 10 parts by mass, and more preferably 1 to 7 parts by mass, per 100 parts by mass of the polyurethane resin (resin solid content) in the aqueous polyurethane resin composition.

[0069] <Polyurethane Film> Next, the polyurethane film of the present invention will be described. The polyurethane film of the present invention is formed from the aqueous polyurethane resin composition of the present invention. Such a polyurethane film can be produced, for example, by a method using the aqueous polyurethane resin composition and a coagulation liquid in combination, i.e., a salt coagulation method. Specifically, examples include a method in which a mold is immersed in a coagulation liquid to form a coagulated layer on the mold, which is then immersed in the aqueous polyurethane resin composition to form a film, and then dried; or a method in which the aqueous polyurethane resin composition is applied to a mold to form an aqueous polyurethane resin composition layer on the mold, which is then applied with a coagulation liquid to form a film, and then dried.

[0070] The coagulation liquid is a solution of a coagulant in water or alcohol as a solvent. Examples of coagulants used in the present invention include inorganic salts such as metal halides (e.g., sodium chloride, calcium chloride, magnesium chloride, zinc chloride, aluminum chloride, etc.), nitrates (e.g., sodium nitrate, calcium nitrate, zinc nitrate, etc.), acetates (e.g., sodium acetate, calcium acetate, zinc acetate, etc.), and sulfates (e.g., calcium sulfate, magnesium sulfate, aluminum sulfate, etc.); and acids such as formic acid, acetic acid, citric acid, and boric acid. These coagulants may be used alone or in combination. Among these coagulants, calcium nitrate is particularly preferred because it has excellent coagulation properties and can achieve a coagulation effect in a short period of time. Furthermore, the coagulation liquid may contain a small amount of surfactant to ensure uniform adhesion of the coagulant to the mold, or calcium carbonate or calcium stearate to prevent film adhesion, as needed.

[0071] The mold used in producing the polyurethane film is not particularly limited, and various conventional molds such as those made of porcelain, glass, or metal can be used. The mold preheating temperature and immersion time can be appropriately set depending on the composition of the aqueous polyurethane resin composition and the thickness of the polyurethane film. The molding temperature is also not particularly limited, but is preferably 100 to 200°C, more preferably 110 to 200°C, in order to shorten the molding time.

[0072] The thickness of the polyurethane film of the present invention thus obtained is not particularly limited, as it differs depending on the application, but is preferably 0.01 to 1 mm, more preferably 0.02 to 0.5 mm.

[0073] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples. The (A) polyisocyanate, (B) polyol, (C) carboxyl group-containing diol, neutralizing amine, and (D) polyamine used in the examples and comparative examples are shown in Table 1.

[0074]

[0075] The nonvolatile polyurethane content in the aqueous polyurethane resin composition was measured by the following method.

[0076] <Polyurethane Non-volatile Content> 5 g of the aqueous polyurethane resin composition was weighed out and placed on an aluminum foil dish and dried in an oven at 105°C for 30 minutes. The polyurethane non-volatile content (mass%) was calculated using the following formula: Polyurethane non-volatile content = (mass of polyurethane resin after drying / mass of aqueous polyurethane resin composition before drying) × 100.

[0077] Example 1 PTMG2000 (222.55 g, 111.3 mmol), 1,4-BD (1.59 g, 17.7 mmol), DMPA (8.65 g, 64.6 mmol), and 185.25 g of methyl ethyl ketone as a solvent were weighed into a four-neck flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, and after uniformly mixing, IPDI (26.89 g, 121.0 mmol) and HDI (20.32 g, 121.0 mmol) as polyisocyanates were added, and the mixture was allowed to react at 80±5° C. for 90 minutes to obtain a methyl ethyl ketone solution of an isocyanate group-terminated urethane prepolymer having a free isocyanate group content of 0.95% by mass. To this solution, TEA (5.22 g, 51.7 mmol) was added and neutralized at 50°C to obtain a methyl ethyl ketone solution containing the neutralized isocyanate-terminated urethane prepolymer. 657 g of water was gradually added to this solution and stirred to emulsify and disperse the isocyanate-terminated urethane prepolymer. PIP (4.17 g, 48.4 mmol) was added as a chain extender to this emulsion dispersion, and the mixture was stirred at 40±5°C for 90 minutes. After that, the solvent was removed (methyl ethyl ketone was removed) at 40°C under reduced pressure. Water was then added appropriately to obtain an aqueous polyurethane resin composition (yield: 947 g) with a polyurethane nonvolatile content of 30.0% by mass.

[0078] In this aqueous polyurethane resin composition, (1) the molar ratio of isocyanate groups to hydroxyl groups (NCO / OH [molar ratio]), (2) the molar ratio of (a-1) isophorone diisocyanate to (a-2) hexamethylene diisocyanate (IPDI:HDI [molar ratio]), (3) the ratio of the total amount of (a-1) isophorone diisocyanate and (a-2) hexamethylene diisocyanate to the total amount of (A) polyisocyanate (the (IPDI + HDI) content [mol %] in the total amount of (A)), and (4) the ratio of the content of (b-1) polytetramethylene glycol to the total amount of (B) polyol and (C) diol (the PTMG content [mass %] in the total amount of (B) + (C)). (5) The ratio of the total number of hydrazide groups and imino groups in (d-1) piperazine and (d-2) dibasic acid dihydrazide to the total number of hydrazide groups, amino groups, and imino groups in (D) polyamine (the ratio [mol %] of the total number of hydrazide groups and imino groups in (PIP + ADH) to the total number of hydrazide groups, amino groups, and imino groups in (D)) (6) The ratio of the total content of carboxy groups and carboxylate groups in the aqueous polyurethane resin (the content of COOH and other groups in the polyurethane resin [mass %]) was calculated from the amounts of raw materials charged. These results are shown in Table 2.

[0079] Next, water (250 g) for dilution was added to the obtained aqueous polyurethane resin composition (500 g) and mixed to obtain an aqueous polyurethane treatment liquid having a polyurethane nonvolatile content adjusted to 20 mass %.

[0080] (Examples 2 to 28 and Comparative Examples 1 to 10) Aqueous polyurethane resin compositions and aqueous polyurethane treatment liquids were prepared in the same manner as in Example 1, except that the types and amounts of (A) polyisocyanate, (B) polyol, (C) diol having a carboxy group and / or a carboxylate group, neutralizing amine, and (D) polyamine were changed as shown in Tables 2 to 8. Furthermore, the above-mentioned (1) to (6) for the obtained aqueous polyurethane resin compositions were calculated in the same manner as in Example 1. The results are shown in Tables 2 to 8.

[0081] Examples 29-30: 13.0 g of a water-dispersible carbodiimide crosslinker (NK Assist CI-02, manufactured by Nicca Chemical Co., Ltd., nonvolatile content 40% by mass) and 250 g of water for dilution were added to and mixed with 500 g of the aqueous polyurethane resin composition obtained in Examples 1 and 2 to obtain an aqueous polyurethane treatment liquid in which the nonvolatile content of the polyurethane resin was adjusted to 20% by mass. In this treatment liquid, the content of reactive groups (—N═C═N—) contained in the crosslinker was 35 mol per 100 mol of carboxy groups in the aqueous polyurethane resin.

[0082] (Comparative Example 11) In a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet tube, PTMG2000 (222.95 g, 113.0 mmol), 1,4-BD (7.14 g, 79.3 mmol), and 185.25 g of methyl ethyl ketone as a solvent were weighed and mixed uniformly. After uniform mixing, IPDI (26.72 g, 120.4 mmol) and HDI (20.19 g, 120.2 mmol) were added as polyisocyanates, and the mixture was allowed to react at 80 ± 5 ° C. for 90 minutes to obtain a methyl ethyl ketone solution of an isocyanate-terminated urethane polymer having a free isocyanate content of 0.95% by mass. To this solution, 5 g each of a 10-mol ethylene oxide adduct, a 20-mol ethylene oxide adduct, and a 30-mol ethylene oxide adduct of tristyrenated phenol were added, and the mixture was emulsified using a disper to obtain a methyl ethyl ketone solution containing the isocyanate-group urethane prepolymer. To this solution, 648 g of water was gradually added and stirred to emulsify and disperse the isocyanate-terminated urethane prepolymer. To this emulsion dispersion, PIP (4.14 g, 48.1 mmol) was added as a chain extender and stirred at 40±5° C. for 90 minutes, followed by a solvent removal (methyl ethyl ketone removal) treatment at 40° C. under reduced pressure to obtain an aqueous polyurethane resin composition (yield: 947 g) with a polyurethane resin nonvolatile content of 30.0% by mass.

[0083] Next, water (250 g) for dilution was added to the obtained aqueous polyurethane resin composition (500 g) and mixed to obtain an aqueous polyurethane treatment liquid with a polyurethane nonvolatile content adjusted to 20 mass %. Furthermore, the above-mentioned (1) to (6) for the obtained aqueous polyurethane resin composition were calculated in the same manner as in Example 1. The results are shown in Table 8.

[0084] The aqueous polyurethane treatment solutions obtained in the Examples and Comparative Examples were measured for film-forming ability, flexibility, tensile strength, elongation at break, and film thickness by the following methods. The results are shown in Tables 2 to 9. Note that the flexibility, tensile strength, and elongation at break were not evaluated for polyurethane films with poor film-forming ability (D).

[0085] The solvent resistance of the polyurethane films formed from the aqueous polyurethane treatment solutions obtained in Examples 1, 2, 29, and 30 was measured by the following method. The results are shown in Table 9.

[0086] <Film Formability> A ceramic plate (200 mm long x 75 mm wide) was immersed in a 10% calcium nitrate aqueous solution for 10 seconds, extending 180 mm in the vertical direction. The plate was then removed and dried in an oven at 100°C for 3 minutes to form a calcium nitrate film on the ceramic plate. Next, the ceramic plate with the calcium nitrate film formed on its surface was immersed in an aqueous polyurethane treatment solution diluted to a polyurethane nonvolatile content of 20% by mass for 10 seconds, extending 150 mm in the vertical direction. The ceramic plate was then removed. This resulted in the formation of a gel film of aqueous polyurethane resin gelled by salt coagulation on the surface of the ceramic plate. This gel film was then dried and aged in an oven at 120°C for 20 minutes, and the film was peeled off from the ceramic plate to obtain a polyurethane film with a thickness of 0.06 mm. The polyurethane film was visually observed and evaluated for film formability according to the following criteria.

[0087] The length of the formed polyurethane film was also measured, and the ratio of the reduced length to the length (150 mm) of the ceramic plate immersed in the aqueous polyurethane treatment solution (shrinkage rate) was calculated using the following formula: Shrinkage rate = {(length immersed in aqueous polyurethane treatment solution - length of formed polyurethane film) / length immersed in aqueous polyurethane treatment solution} x 100, and was used as one of the criteria for film formability. A: The film had neither cracks nor pinholes, and the shrinkage rate was less than 3% (excellent). B: The film had neither cracks nor pinholes, and the shrinkage rate was 3% or more but less than 5% (good). C: The film had neither cracks nor pinholes, but the shrinkage rate was 5% or more (slightly poor). D: The film had cracks and / or pinholes (poor).

[0088] <Film Thickness Measurement> The film thickness of the polyurethane film was measured using a film thickness measuring device "DIAL THICKNESS GAUGE H-MT (0.01-10 mm)" manufactured by PEACOCK.

[0089] <Tensile test> A dumbbell-shaped No. 3 test piece defined in JIS K6251 (2023) was prepared from the polyurethane film (film thickness: 0.06 mm) prepared for the evaluation of film-forming properties described above. Using this test piece, a tensile test was carried out at a pulling rate of 500 mm / min using a tensile tester ("Autograph AGS-X" manufactured by Shimadzu Corporation) in accordance with JIS K6251 (2023).

[0090] <Flexibility> In the above tensile test, the tensile stress (tensile load) was measured when the test piece was elongated by 100% (when it was elongated to twice the original length), and calculated using the following formula: 100% modulus (MPa) = tensile load (N) at 100% elongation / cross-sectional area of ​​test piece (mm ２) and evaluated the flexibility according to the following criteria. A: 100% modulus is 1.0 MPa or more and less than 2.0 MPa (excellent). B: 100% modulus is 2.0 MPa or more and less than 3.0 MPa (good). C: 100% modulus is 3.0 MPa or more and less than 4.0 MPa (slightly poor). D: 100% modulus is less than 1.0 MPa or 4.0 MPa or more (poor). Note that the smaller the 100% modulus value, the more flexible the film is; however, when the 100% modulus is less than 1.0 MPa, the film is too soft and is therefore judged to be poor as a film molding.

[0091] <Tensile strength> In the above tensile test, the tensile load (N) at break of the test piece was measured, and the tensile strength was evaluated according to the following criteria. A: The tensile load at break of the film was 10.0 N or more (excellent). B: The tensile load at break of the film was 6.0 N or more and less than 10.0 N (good). C: The tensile load at break of the film was 5.0 N or more and less than 6.0 N (slightly poor). D: The tensile load at break of the film was less than 5.0 N (poor).

[0092] <Break elongation> In the above tensile test, the length of extension of the gauge length until the test piece broke was measured, and the break elongation was calculated using the following formula: Break elongation (%) = {(Gauge distance at break - Gauge distance before test) / Gauge distance before test)} x 100, and evaluated according to the following criteria. A: Break elongation of 900% or more (excellent). B: Break elongation of 600% or more and less than 900% (good). C: Break elongation of 500% or more and less than 600% (slightly poor). D: Break elongation of less than 500% (poor).

[0093] <Solvent Resistance> A test piece (5 cm x 2 cm) made from the polyurethane film (film thickness 0.06 mm) produced during the evaluation of film formability above was immersed in a 95% by mass aqueous ethanol solution at 20°C, and the state thereafter was visually observed, and the solvent resistance was evaluated according to the following criteria: A: It took 10 minutes or more after immersion for the film to break or dissolve. B: It took 5 minutes or more but less than 10 minutes after immersion for the film to break or dissolve. C: It took less than 5 minutes after immersion for the film to break or dissolve.

[0094]

[0095]

[0096]

[0097]

[0098]

[0099]

[0100]

[0101]

[0102] As shown in Tables 2 to 9, it was found that the aqueous polyurethane resin compositions of the present invention (Examples 1 to 30) containing (a-1) isophorone diisocyanate and (a-2) hexamethylene diisocyanate as the (A) polyisocyanate and containing at least one selected from the group consisting of (d-1) piperazine and (d-2) dibasic acid dihydrazide as the (D) polyamine have good film-forming properties and can give polyurethane films with good flexibility, tensile strength, and elongation at break.

[0103] Furthermore, it was found that the aqueous polyurethane resin compositions of the present invention further containing a carbodiimide-based crosslinking agent (Examples 29 and 30) had superior solvent resistance compared to the compositions not containing a carbodiimide-based crosslinking agent (Examples 1 and 2).

[0104] On the other hand, when (a-1) isophorone diisocyanate was used alone as (A) polyisocyanate (Comparative Example 1), it was found that the tensile strength of the resulting polyurethane film was deteriorated.

[0105] Furthermore, it was found that when (a-2) hexamethylene diisocyanate was used alone as (A) polyisocyanate (Comparative Example 2), film-forming properties were deteriorated.

[0106] Furthermore, when a polyisocyanate other than (a-1) isophorone diisocyanate and (a-2) hexamethylene diisocyanate was used as the (A) polyisocyanate (Comparative Examples 3, 4, and 7), the flexibility and elongation at break of the resulting polyurethane film were found to be deteriorated.

[0107] Furthermore, when (a-1) isophorone diisocyanate or (a-2) hexamethylene diisocyanate was used as the (A) polyisocyanate in combination with other polyisocyanates (Comparative Examples 5 and 6), the flexibility and elongation at break of the resulting polyurethane film were also found to be deteriorated.

[0108] Furthermore, even when (a-1) isophorone diisocyanate and (a-2) hexamethylene diisocyanate were contained as the (A) polyisocyanate, when a polyamine other than (d-1) piperazine and (d-2) dibasic acid dihydrazide was used as the (D) polyamine (Comparative Examples 8 to 10), it was found that the film-forming properties were deteriorated, and the flexibility, tensile strength, and elongation at break of the obtained polyurethane film were deteriorated.

[0109] Furthermore, it was found that when (C) diol having a carboxy group and / or a carboxylate group was not used as a raw material and the resin did not contain a carboxy group or a carboxylate group (Comparative Example 11), film-forming properties were deteriorated.

[0110] As described above, according to the present invention, it is possible to obtain an aqueous polyurethane resin composition that has good film-forming properties in a salt coagulation method and that can be used to obtain a polyurethane film that has good flexibility, tensile strength at break, and elongation at break.

[0111] Therefore, the polyurethane film of the present invention has flexibility, tensile strength at break, and elongation at break comparable to those of natural rubber and synthetic rubber, and is therefore useful as a film for use in, for example, gloves, finger cots, condoms, etc., and is particularly useful as a film for gloves.

Claims

1. An aqueous polyurethane resin composition comprising an aqueous polyurethane resin which is a chain-extended product of a neutralized isocyanate-terminated prepolymer, which is the reaction product of (A) a polyisocyanate, (B) a polyol, and (C) a diol having a carboxy group and / or a carboxylate group, with (D) a polyamine having two or more amino groups and / or imino groups per molecule, wherein the (A) polyisocyanate comprises (a-1) isophorone diisocyanate and (a-2) hexamethylene diisocyanate, and the (D) polyamine comprises at least one member selected from the group consisting of (d-1) piperazine and (d-2) dibasic acid dihydrazide.

2. The aqueous polyurethane resin composition according to claim 1, wherein the polyol (B) comprises polytetramethylene glycol (b-1).

3. The aqueous polyurethane resin composition according to claim 1, further comprising a carbodiimide crosslinking agent.

4. The aqueous polyurethane resin composition according to claim 1, wherein the molar ratio ((a-1):(a-2)) of the (a-1) isophorone diisocyanate to the (a-2) hexamethylene diisocyanate is 10:90 to 90:

10.

5. The aqueous polyurethane resin composition according to claim 1, wherein the total amount of (a-1) isophorone diisocyanate and (a-2) hexamethylene diisocyanate is 60 mol % or more based on the total amount of (A) polyisocyanate.

6. The aqueous polyurethane resin composition according to claim 1, wherein the ratio of the total number of hydrazide groups and imino groups in the (d-1) piperazine and the (d-2) dibasic acid dihydrazide to the total number of hydrazide groups, amino groups, and imino groups in the (D) polyamine is 50 mol % or more.

7. The aqueous polyurethane resin composition according to claim 1, wherein the total content of carboxy groups and carboxylate groups in the aqueous polyurethane resin is 0.5 to 2.0% by mass.

8. The aqueous polyurethane resin composition according to claim 2, wherein the number average molecular weight of the (b-1) polytetramethylene glycol is 1,000 to 4,000, and the content of the (b-1) polytetramethylene glycol is 70 to 98 mass% based on the total amount of the (B) polyol and the (C) diol.

9. The aqueous polyurethane resin composition according to claim 3, wherein the content of reactive groups (-N=C=N-) contained in the carbodiimide crosslinking agent is 2.5 to 100 mol per 100 mol of the total amount of carboxy groups and carboxylate groups in the aqueous polyurethane resin.

10. A polyurethane film formed from the aqueous polyurethane resin composition according to any one of claims 1 to 9.

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