Aqueous polyurethane resin dispersion, coating composition, laminate, and polyurethane resin film

Abstract

The present invention pertains to an aqueous polyurethane resin dispersion in which particles of a polyurethane resin (A) are dispersed in an aqueous medium (B), The polyurethane resin (A) has a structure derived from an acidic group-free polyol (a), a structure derived from a polyisocyanate (b), and a structure derived from an acidic group-containing polyol (c); the average particle diameter of the particles of the polyurethane resin (A) is 30-80 nm, the average particle diameter being obtained by dynamic light scattering; the acidic group-free polyol (a) contains a polycarbonate polyol; and a film having a thickness of 40 μm obtained by heating the aqueous polyurethane resin dispersion for 2 hours at 60°C and then heating at 120°C for 2 hours has an elastic modulus of 400-900 MPa. The aqueous polyurethane resin dispersion can contribute to the achievement of Goal 7 of Sustainable Development Goals (SDGs), for example.

Description

Aqueous polyurethane resin dispersion, coating composition, laminate, and polyurethane resin film

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

[0002] Aqueous polyurethane resin dispersions can produce coating layers that have adhesive properties, abrasion resistance, and rubber-like properties, and are environmentally friendly materials that can reduce volatile organic compounds compared to conventional solvent-based polyurethanes, so they are increasingly being used to replace solvent-based polyurethanes.

[0003] Polycarbonate polyols are useful compounds used as raw materials for polyurethane resins, and by reacting them with isocyanate compounds, durable polyurethane resins can be produced that are used in rigid foams, flexible foams, paints, adhesives, synthetic leather, ink binders, etc. Polyurethane resins using polycarbonate polyols are characterized by the high cohesive strength of the carbonate groups, and are said to have excellent hydrolysis resistance, heat resistance, oil resistance, elastic recovery, abrasion resistance, and weather resistance compared to those using polyether polyols or polyester polyols (see Non-Patent Document 1). Patent Documents 1 and 2 also disclose water-dispersible polycarbonate-based polyurethane resin compositions and coating layers obtained from the resin compositions.

[0004] WO2012 / 165569WO2024 / 018708

[0005] "Latest Polyurethane Materials and Application Technology" CMC Publishing, Chapter 2, Page 43

[0006] The inventors have found that there is room for improvement in terms of achieving both film-forming ability and solvent resistance in the dispersibility of aqueous polyurethane resin dispersions as described in Patent Documents 1 and 2. That is, there has been a need to further improve the film-forming ability of aqueous polyurethane resin dispersions and the solvent resistance of urethane resin films obtained from aqueous polyurethane resin dispersions while maintaining the dispersibility of the aqueous polyurethane resin dispersions.

[0007] An object of the present invention is to provide an aqueous polyurethane resin dispersion having excellent film-forming properties and solvent resistance.

[0008] The present invention has the following features. [1] An aqueous polyurethane resin dispersion comprising particles of a polyurethane resin (A) dispersed in an aqueous medium (B), wherein the polyurethane resin (A) has a structure derived from an acidic group-free polyol (a), a structure derived from a polyisocyanate (b), and a structure derived from an acidic group-containing polyol (c), the particles of the polyurethane resin (A) have an average particle size of 30 to 80 nm, the average particle size being a value determined by dynamic light scattering, the acidic group-free polyol (a) comprises a polycarbonate polyol, and the aqueous polyurethane resin dispersion is heated at 60°C for 2 hours and then at 120°C for 2 hours, and the modulus of elasticity of a 40 μm-thick film obtained is from 400 MPa to 900 MPa. [2] The aqueous polyurethane resin dispersion according to [1], wherein the polyisocyanate (b) is an alicyclic polyisocyanate. [3] The aqueous polyurethane resin dispersion according to [1] or [2], wherein the total content of urethane bonds and urea bonds in the polyurethane resin (A) is 13.0 to 25.0 mass% based on the solids content of the polyurethane resin (A). [4] The aqueous polyurethane resin dispersion according to any one of [1] to [3], wherein the content of structures derived from polycarbonate polyols relative to the structures derived from all polyols contained in the polyurethane resin (A) is 60.0 to 95.0 mass%. [5] The aqueous polyurethane resin dispersion according to any one of [1] to [4], wherein the acidic group-free polyol (a) further contains, as an optional component, only a polyester polyol and / or a polyether polyol, and the polyurethane resin (A) further has a structure derived from a compound (d) having a total of two or more groups selected from the group consisting of hydroxyl groups and amino groups (provided that the compound is not a polycarbonate polyol, a polyester polyol, a polyether polyol, or an acidic group-containing polyol (c)). [6] The aqueous polyurethane resin dispersion according to [5], wherein the compound (d) contains a polyamine compound having two primary amino groups and one or more secondary amino groups in one molecule and having no hydroxyl group.[7] The aqueous polyurethane resin dispersion according to any one of [1] to [6], wherein the molar ratio of the isocyanate groups of the polyisocyanate (b) to the total hydroxyl groups of the acidic group-free polyol (a) and the acidic group-containing polyol (c) (isocyanate groups / hydroxyl groups) is 0.5 to 3.0. [8] A coating composition comprising the aqueous polyurethane resin dispersion according to any one of [1] to [7]. [9] The coating composition according to [8], further comprising a water-insoluble organic solvent.

[10] The coating composition according to [8] or [9], for coating a metal substrate.

[11] A laminate having a metal substrate and a coating layer thereon, obtained by drying the coating composition according to any one of [8] to

[10] .

[12] A polyurethane resin film obtained by drying a composition comprising the aqueous polyurethane resin dispersion according to any one of [1] to [7].

[0009] The present invention provides an aqueous polyurethane resin dispersion having excellent film-forming properties and solvent resistance.

[0010] [Explanation of Terms] In this specification, the term "acidic group" refers to a carboxy group, a sulfonic acid group, a phosphoric acid group, or a phenolic hydroxyl group, and does not include hydroxyl groups other than phenolic hydroxyl groups.

[0011] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. Furthermore, when a composition contains multiple substances corresponding to each component, the amount of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified.

[0012] In this specification, the term "process" does not only include independent processes, but also includes processes that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0013] [Aqueous Polyurethane Resin Dispersion] The aqueous polyurethane resin dispersion contains particles of polyurethane resin (A) dispersed in an aqueous medium. In the aqueous polyurethane resin dispersion, the polyurethane resin (A) has a structure derived from an acidic group-free polyol (a), a structure derived from a polyisocyanate (b), and a structure derived from an acidic group-containing polyol (c). In the aqueous polyurethane resin dispersion, the particles of the polyurethane resin (A) have an average particle size of 30 to 80 nm, where the average particle size is a value determined by dynamic light scattering. In the aqueous polyurethane resin dispersion, the acidic group-free polyol (a) contains a polycarbonate polyol. The aqueous polyurethane resin dispersion is heated at 60°C for 2 hours and then at 120°C for 2 hours to obtain a 40 μm-thick film, which has an elastic modulus of 400 MPa or more and 900 MPa or less.

[0014] The use of an aqueous polyurethane resin dispersion can reduce the amount of solvent used, which can contribute to the achievement of, for example, Goal 7 of the SDGs (Sustainable Development Goals). Furthermore, the aqueous polyurethane resin dispersion preferably has excellent solvent resistance and excellent resistance to hydrocarbon solvents. Furthermore, the aqueous polyurethane resin dispersion may have excellent dispersibility in addition to film-forming properties and solvent resistance.

[0015] <Polyurethane Resin (A)> The polyurethane resin (A) has a structure derived from the acidic group-free polyol (a), a structure derived from the polyisocyanate (b), and a structure derived from the acidic group-containing polyol (c). The polyurethane resin (A) may also contain an additional structure in addition to the structures derived from (a) to (c). Examples of such additional structures include a structure derived from a compound (d) having a total of two or more groups selected from the group consisting of hydroxyl groups and amino groups (but is not the acidic group-free polyol (a) or the acidic group-containing polyol (c)), a structure derived from a neutralizing agent (e), and a structure derived from another compound (f).

[0016] (Acidic Group-Free Polyol (a)) As the acidic group-free polyol (a), known polyols can be used. For example, polymer polyols such as polycarbonate polyols, polyester polyols, polyether polyols, polyester polyether polyols, polyurethane polyols, polyesteramide polyols, and acrylic polyols (all of which have terminal hydroxyl groups), and low molecular weight polyols such as ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, trimethylolpropane, and glycerin can be used. Among these, from the viewpoint of improving solvent resistance, at least one selected from the group consisting of polycarbonate polyols, polyester polyols, and polyether polyols is preferred, and polycarbonate polyols are more preferred.

[0017] Polycarbonate polyols can be obtained by reacting one or more polyol components with a carbonate ester or phosgene. From the viewpoints of safety and handling of reagents, etc., polycarbonate polyols obtained by reacting one or more polyol monomers with a carbonate ester are preferred because they are easy to produce and do not produce terminal chlorinated products as by-products.

[0018] Known polyol monomers can be used as polyol monomers constituting the polycarbonate polyol. For example, aliphatic polyols such as linear aliphatic diols such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, and 1,9-nonanediol, and branched aliphatic diols such as 2-methyl-1,3-propanediol, 1,5-hexanediol, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, and neopentyl glycol; trifunctional or higher polyhydric alcohols such as trimethylolpropane and pentaerythritol; 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanediol, 1,3-cyclopentanediol, 1,4-cycloheptanediol, and 2,5-bis(hydroxymethyl)methyl Examples of suitable polyols include alicyclic polyols such as diols having an alicyclic structure in the main chain, such as (ethyl)-1,4-dioxane, 2,7-norbornanediol, tetrahydrofuran dimethanol, and 1,4-bis(hydroxyethoxy)cyclohexane; aromatic diols such as 1,4-benzenedimethanol, 1,3-benzenedimethanol, 1,2-benzenedimethanol, 4,4'-naphthalenedimethanol, and 3,4'-naphthalenedimethanol; polyester polyols of hydroxycarboxylic acids and diols, such as polyester polyols of 6-hydroxycaproic acid and hexanediol; polyester polyols of dicarboxylic acids and diols, such as polyester polyols of adipic acid and hexanediol; and polyether polyols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Among these, alicyclic polyols and / or aliphatic polyols are preferred from the viewpoint of solvent resistance. As the alicyclic polyol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanediol are more preferred. As the aliphatic polyol, a linear aliphatic diol or a branched aliphatic diol is more preferred, and a linear aliphatic diol is even more preferred.As the linear aliphatic diol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol are more preferred, and as the branched aliphatic diol, 2-methyl-1,3-propanediol and 3-methyl-1,5-pentanediol are more preferred.

[0019] The carbonate ester is not particularly limited, and examples thereof include aliphatic carbonate esters such as dimethyl carbonate and diethyl carbonate; aromatic carbonate esters such as diphenyl carbonate; and cyclic carbonate esters such as ethylene carbonate. In addition, phosgene or the like capable of producing polycarbonate polyol can also be used. Among these, aliphatic carbonate esters are preferred, and dimethyl carbonate is more preferred, in view of the ease of producing polycarbonate polyol.

[0020] Known polyester polyols can be used. Examples include polyester polyols obtained by esterifying a polyol (e.g., a polyol having a molecular weight of 50 to 500) with a polycarboxylic acid; polyester polyols obtained by ring-opening polymerization of a cyclic ester compound such as ε-caprolactone; and copolymer polyester polyols thereof. Specific examples of polyester polyols include polyethylene adipate diol, polybutylene adipate diol, polyethylene butylene adipate diol, poly(neopentyl glycol terephthalate) diol, polyhexamethylene isophthalate adipate diol, polyethylene succinate diol, polybutylene succinate diol, polyethylene sebacate diol, polybutylene sebacate diol, poly-ε-caprolactone diol, poly(3-methyl-1,5-pentylene adipate) diol, and polyester diols such as polycondensates of 1,6-hexanediol and dimer acid.

[0021] As the polyol, for example, the above-mentioned polyol monomers can be used, etc. Furthermore, polyether polyols described below may also be used as the polyol.

[0022] Examples of polycarboxylic acids include aliphatic polycarboxylic acids such as succinic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid; aromatic polycarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid; and anhydrides of the aliphatic polycarboxylic acids and aromatic polycarboxylic acids.

[0023] Known polyether polyols can be used. Examples include polyethylene glycol, poly(1,2-propylene glycol), poly(1,3-propylene glycol), poly(1,3-tetramethylene glycol), poly(1,4-tetramethylene glycol), poly(1,6-hexamethylene glycol), polyoxyethylene triol, polyoxypropylene triol, polyoxyethylene polyoxypropylene triol, random copolymers or block copolymers of ethylene oxide and propylene oxide, random copolymers or block copolymers of ethylene oxide and butylene oxide, and random copolymers or block copolymers of propylene oxide and butylene oxide. In terms of solvent resistance, poly(1,4-tetramethylene glycol) is preferred.

[0024] The polyester polyether polyol can be obtained by reacting the polyester polyol with the polyether polyol.

[0025] The number average molecular weight (Mn) of the acidic group-free polyol (a) is preferably 800 to 5,000. If Mn is 800 or more, the tensile breaking energy of the resulting coating film may increase. If Mn is 5,000 or less, the reactivity of the acidic group-free polyol (a) with the polyisocyanate (b) is not reduced, and problems such as the urethane prepolymer production process taking a long time, the reaction not proceeding sufficiently, or the viscosity of the polycarbonate polyol increasing, making it difficult to handle, do not occur. In this specification, Mn is defined as the hydroxyl value and １ The value is calculated by H-NMR or calculated from the quantitative value of the polyol by gas chromatography after alkaline hydrolysis.

[0026] The hydroxyl value of the acidic group-free polyol (a) is preferably 20 to 1,200 mgKOH / g, more preferably 30 to 1,000 mgKOH / g. A hydroxyl value within the above range is preferred in terms of improved film-forming properties. In this specification, the hydroxyl value refers to the number of milligrams (mg) of potassium hydroxide equivalent to the hydroxyl groups in 1 g of sample, and can be measured by Method A of JIS K 1557. The acidic group-free polyol (a) may be used alone or in combination of two or more types.

[0027] (Polyisocyanate (b)) As the polyisocyanate (b), known compounds can be used. For example, aromatic polyisocyanate compounds such as 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate (TDI), 2,6-tolylene diisocyanate, and 4,4'-diphenylmethane diisocyanate (MDI); and aliphatic polyisocyanate compounds such as ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate (PDI), and hexamethylene diisocyanate (HDI). and alicyclic polyisocyanate compounds such as isophorone diisocyanate (IPDI), dicyclohexylmethane 4,4'-diisocyanate (H12MDI, hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate (hydrogenated TDI), bis(2-isocyanatoethyl)-4-dicyclohexene-1,2-dicarboxylate, 2,5-norbornane diisocyanate, and 2,6-norbornane diisocyanate. The structure of the polyisocyanate (b) may be partially or entirely derivatized by isocyanuration, carbodiimidization, biuretization, or the like.

[0028] Among the polyisocyanates (b), from the viewpoint of controlling reactivity, etc., an aliphatic polyisocyanate compound and / or an alicyclic polyisocyanate compound is preferred, and from the viewpoint of improving film-forming properties and solvent resistance, an alicyclic polyisocyanate compound is more preferred, and at least one selected from the group consisting of isophorone diisocyanate (IPDI), 4,4'-diphenylmethane diisocyanate (MDI), and dicyclohexylmethane 4,4'-diisocyanate (H12MDI) is particularly preferred. The polyisocyanates (b) may be used alone or in combination of two or more types.

[0029] (Acidic Group-Containing Polyol (c)) The acidic group-containing polyol (c) contains two or more hydroxyl groups and one or more acidic groups in one molecule.

[0030] Known acidic group-containing polyols can be used as the acidic group-containing polyol (c). Examples include dimethylolalkanoic acids such as 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid; N,N-bishydroxyethylglycine, N,N-bishydroxyethylalanine, 3,4-dihydroxybutanesulfonic acid, and 3,6-dihydroxy-2-toluenesulfonic acid. Among these, from the viewpoint of ease of availability, dimethylolalkanoic acids having 4 to 12 carbon atoms and containing two methylol groups are preferred, and among dimethylolalkanoic acids, 2,2-dimethylolpropionic acid is more preferred. The acidic group-containing polyol (c) may be used alone or in combination of two or more types.

[0031] (Compound (d) Having a Total of Two or More Groups Selected from the Group Consisting of Hydroxyl Groups and Amino Groups (However, This Is Not the Case of the Non-Acidic Group-Containing Polyol (a) and the Acidic Group-Containing Polyol (c))) Compound (d) Having a Total of Two or More Groups Selected from the Group Consisting of Hydroxyl Groups and Amino Groups (However, This Is Not the Case of the Non-Acidic Group-Containing Polyol (a) and the Acidic Group-Containing Polyol (c)) (hereinafter also referred to as "Compound (d)")) is a component that increases the molecular weight of polyurethane resin (A). Compound (d) is a compound that is reactive with the isocyanato group of polyurethane prepolymer, which is a synthetic intermediate in the production of polyurethane resin (A). Compounds that are reactive with the isocyanato group of polyurethane prepolymer, which is a synthetic intermediate of polyurethane resin (A), are called chain extenders, and compound (d) is a type of chain extender. Note that examples of chain extenders other than compound (d) include water. Here, the "amino group" in compound (d) refers to a primary amino group or a secondary amino group.

[0032] The compound (d) may vary depending on the range of the acidic group-free polyol (a). For example, when the acidic group-free polyol (a) further contains only polyester polyol and / or polyether polyol as an optional component, the compound (d) is not a polycarbonate polyol, a polyester polyol, a polyether polyol, or an acidic group-containing polyol (c). That is, in the above case, polyols other than polycarbonate polyol, polyester polyol, polyether polyol, and acidic group-containing polyol (c) are considered to be the compound (d).

[0033] Examples of the compound (d) include polyamine compounds (i.e., compounds having two or more amino groups in one molecule and no hydroxyl groups), amino alcohol compounds (i.e., compounds having one or more hydroxyl groups in one molecule and one or more amino groups in one molecule), and the like.

[0034] Examples of polyamine compounds include diamine compounds having only primary amino groups, diamine compounds having only secondary amino groups, polyamine compounds having a total of three or more primary amino groups and / or secondary amino groups in one molecule, and other polyamine compounds.

[0035] Examples of diamine compounds having only primary amino groups include hydrazine, ethylenediamine, 1,4-tetramethylenediamine, 2-methyl-1,5-pentanediamine, 1,4-butanediamine, 1,6-hexamethylenediamine, adipodihydrazide, 1,4-hexamethylenediamine, 3-aminomethyl-3,5,5-trimethylcyclohexylamine, 1,3-bis(aminomethyl)cyclohexane, xylylenediamine, and polyetheramines.

[0036] Examples of diamine compounds having only secondary amino groups include piperazine and 2,5-dimethylpiperazine.

[0037] Polyamines having a total of three or more primary amino groups and / or secondary amino groups per molecule include polyamines having a total of three or more primary amino groups per molecule, polyamines having a total of three or more secondary amino groups per molecule, polyamines having two or more primary amino groups and one or more secondary amino groups per molecule, and polyamines having one or more primary amino groups and two or more secondary amino groups per molecule.The polyamines having a total of three or more primary amino groups and / or secondary amino groups per molecule are preferably polyamines having two primary amino groups and one or more secondary amino groups per molecule.

[0038] Examples of polyamines having a total of three or more primary amino groups and / or secondary amino groups per molecule include triamine compounds such as diethylenetriamine, bis(2-aminopropyl)amine, and bis(3-aminopropyl)amine; tetramine compounds such as tripropylenetetramine, N-(benzyl)triethylenetetramine, N,N'''-(dibenzyl)triethylenetetramine, and N-(benzyl)-N'''-(2-ethylhexyl)triethylenetetramine; pentamine compounds such as tetraethylenepentamine and tetrapropylenepentamine; hexamine compounds such as pentaethylenehexamine and pentapropylenehexamine; and polyalkyleneimine compounds such as polyethyleneimine and polypropyleneimine.

[0039] Other polyamines include diamine compounds having one primary amino group and one secondary amino group in one molecule.

[0040] The polyol compound is as described above in connection with the acidic group-free polyol (a), and the compounds exemplified as low-molecular-weight polyols are preferred.

[0041] Examples of the amino alcohol compounds include ethanolamine, butanolamine, hexanolamine, N-(aminoethyl)ethanolamine, 3,5-diaminobenzyl alcohol, 1,3-diamino-2-propanol, 2,2'-(ethylenebisimino)bisethanol, N-(2-hydroxyethyl)-N'-(2-aminoethyl)ethylenediamine, N-(3-hydroxypropyl)ethylenediamine, 2-[bis(2-aminoethyl)amino]ethanol, 1-[2-[(2-aminoethyl)amino]ethyl]amino-2-propanol, N,N-bis(hydroxyethyl)diethylenetriamine, N １ , N ４ -bis(hydroxyethyl)diethylenetriamine, N １ -(2-hydroxypropyl)triethylenetetraamine, N ４ 2-(2-hydroxypropyl)triethylenetetraamine, 2-(2-aminoethylamino)ethanol, and the like.

[0042] Compound (d) is preferably at least one selected from the group consisting of polyamine compounds and aminoalcohol compounds, and is particularly preferably a polyamine compound. The proportion of polyamine compounds having two primary amino groups and one or more secondary amino groups per molecule in compound (d) is preferably 10 to 100 mol %, and particularly preferably 50 to 100 mol %.

[0043] The number average molecular weight (Mn) of the compound (d) is preferably 300 or less. When the Mn of the compound (d) is 300 or less, the cohesive strength of the polyurethane resin (A) can be increased. The compound (d) may be used alone or in combination of two or more types.

[0044] (Neutralizing Agent (e)) When the polyurethane resin (A) has a structure derived from the acidic group-containing polyol (c), the polyurethane resin (A) has an acidic group. In this case, the polyurethane resin (A) may have a structure derived from a neutralizing agent (e) to neutralize the acidic group.

[0045] Known neutralizing agents can be used as the neutralizing agent (e). Examples of the neutralizing agent (e) include organic amines, inorganic alkali salts, and ammonia. Examples of organic amines include trimethylamine, triethylamine, tri-n-propylamine, triisopropylamine, tributylamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N-phenyldiethanolamine, 2-dimethylaminoethanol, 2-(dimethylamino)-2-methyl-1-propanol, diethylethanolamine, N-methylmorpholine, and pyridine. Examples of inorganic alkali salts include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. From the viewpoint of workability, organic amines are preferred, and triethylamine is more preferred.

[0046] The boiling point of the neutralizing agent (e) is preferably 200°C or lower, and particularly preferably in the range of -50 to 180°C. When the boiling point of the neutralizing agent (e) is within the above range, when forming a coating layer of the aqueous polyurethane resin dispersion, the neutralizing agent (e) volatilizes at the temperature (usually 40 to 200°C) used when drying the aqueous medium (B) and disappears from the polyurethane resin coating layer, which tends to result in even better film-forming properties. When forming a polyurethane resin coating layer at a drying temperature of 100°C or lower in a short time of several seconds to 1 hour, the boiling point of the neutralizing agent (e) is preferably 130°C or lower, and particularly preferably 110°C or lower. The neutralizing agent (e) may be used alone or in combination of two or more types.

[0047] (Other Compounds (f)) Examples of the other compounds (f) include monoalcohols and monoamines. When the other compounds (f) are monoalcohols or monoamines, a polyurethane resin (A) having non-reactive molecular terminals is obtained. Examples of monoalcohols include ethanol, n-propanol, isopropanol, n-butanol, hexanol, and octanol. Examples of monoamines include ethylamine, n-propylamine, isopropylamine, n-butylamine, and n-hexylamine. The other compounds (f) may be used alone or in combination.

[0048] (Hydroxyl equivalents of the acidic group-free polyol (a), the acidic group-containing polyol (c), and the other compounds (f)) In the polyurethane resin (A), the total hydroxyl equivalents of the acidic group-free polyol (a), the acidic group-containing polyol (c), and the polyols contained in the other compounds (f) is preferably 50 to 4,000. If the hydroxyl equivalents are within this range, the production of the aqueous polyurethane resin dispersion is easy. From the viewpoint of the storage stability of the aqueous polyurethane resin dispersion, the hydroxyl equivalents is preferably 100 to 3,500, more preferably 120 to 3,000, and particularly preferably 130 to 2,500.

[0049] The number of hydroxyl equivalents can be calculated by the following formulas (1) and (2): Number of hydroxyl equivalents of each polyol component = molecular weight of each polyol component / number of hydroxyl groups in each polyol component (1) Number of total hydroxyl equivalents of polyol components = M / total number of moles of polyol components (2) In formula (2), M represents [[number of hydroxyl equivalents of acidic group-free polyol (a) × number of moles of acidic group-free polyol (a)] + [number of hydroxyl equivalents of acidic group-containing polyol (c) × number of moles of acidic group-containing polyol (c)] + [number of hydroxyl equivalents of polyol contained in other compound (f) × number of moles of that polyol]].

[0050] (Preferred Structure of Polyurethane Resin (A)) In the polyurethane resin (A), it is preferable that the acidic group-free polyol (a) further contains only polyester polyol and / or polyether polyol as an optional component. In this case, it is more preferable that the polyurethane resin (A) further has a structure derived from a compound (d) having a total of two or more groups selected from the group consisting of hydroxyl groups and amino groups (however, this is not a polycarbonate polyol, polyester polyol, polyether polyol, or acidic group-containing polyol (c)). In the polyurethane resin (A), it is preferable that the polyisocyanate (b) is an alicyclic polyisocyanate. In the polyurethane resin (A), it is preferable that the compound (d) contains a polyamine compound having two primary amino groups and one or more secondary amino groups in one molecule and having no hydroxyl groups. In addition, in the polyurethane resin (A), it is particularly preferable that the compound (d) is a combination of a polyamine compound having two primary amino groups and one or more secondary amino groups in one molecule and a diamine compound having only primary amino groups.

[0051] (Characteristics of Polyurethane Resin (A)) <Urethane Bond and Urea Bond> In the polyurethane resin (A), the total content of urethane bonds and urea bonds is preferably 13.0 to 25.0 mass%, more preferably 13.5 to 20.0 mass%, and particularly preferably 14.0 to 20.0 mass%, based on the solid content of the polyurethane resin (A).

[0052] By setting the total content of the urethane bond and the urea bond to 13.0% by mass or more, the film-forming ability of the aqueous polyurethane resin dispersion may be improved, and by setting the total content of the urethane bond and the urea bond to 25.0% by mass or less, the solvent resistance may be improved and the adhesion to the substrate may be improved.

[0053] From the viewpoint of solvent resistance, the content of urethane bonds in the polyurethane resin (A) is preferably 5.0 to 22.0 mass %, particularly preferably 8.0 to 22.0 mass %, based on the solid content.

[0054] From the viewpoint of solvent resistance, the content of urea bonds in the polyurethane resin (A) is preferably 2.0 to 22.0 mass %, particularly preferably 4.0 to 16.0 mass %, based on the solid content.

[0055] The content ratio of urethane bonds and the content ratio of urea bonds in the polyurethane resin (A) can be controlled by the molecular weight of each of the acidic group-free polyol (a), the polyisocyanate (b), the acidic group-containing polyol (c), and the compound (d), the number of hydroxyl groups, isocyanato groups, and amino groups in one molecule, and the usage ratio of each raw material on a solids basis in the aqueous polyurethane resin dispersion.

[0056] The content of carbonate bonds in polyurethane resin (A) is preferably 15 to 40% by mass, more preferably 18 to 35% by mass, and particularly preferably 18 to 30% by mass, based on the solid content. When the content of carbonate bonds is 15% by mass or more, film-forming ability and solvent resistance tend to be improved. Furthermore, when the content of carbonate bonds is 40% by mass or less, the elastic modulus tends to be higher.

[0057] The content of urethane bonds, urea bonds, carbonate bonds, etc. in the polyurethane resin (A) can be calculated from the charged amounts, molecular weights of each raw material, and molecular weights or mole numbers of portions corresponding to each structure.

[0058] <<Alicyclic Structure Content>> The content of the alicyclic structure in the polyurethane resin (A) is preferably 10 to 50 mass%, particularly preferably 10 to 35 mass%. In this specification, the content of the alicyclic structure in the polyurethane resin (A) can be measured by 1H-NMR.

[0059] <Weight-Average Molecular Weight> The weight-average molecular weight (Mw) of the polyurethane resin (A) is preferably 100,000 to 10,000,000, more preferably 200,000 to 5,000,000, and particularly preferably 300,000 to 2,000,000. The weight-average molecular weight is measured by gel permeation chromatography (GPC), and a converted value obtained from a previously prepared calibration curve of standard polystyrene can be used. When the weight-average molecular weight of the polyurethane resin (A) is 100,000 to 10,000,000, film-forming properties tend to be better.

[0060] <Acid Value> The acid value of the polyurethane resin (A) is preferably 5 to 40 mgKOH / g, more preferably 8 to 35 mgKOH / g, and particularly preferably 10 to 30 mgKOH / g. Setting the acid value of the polyurethane resin (A) in the range of 5 to 40 mgKOH / g tends to improve storage stability. The acid value can be measured in accordance with the indicator titration method of JIS K 1557. When the polyurethane resin (A) contains a structure derived from a neutralizer (e), the measurement is performed after removing the neutralizer (e) used to neutralize the acidic groups. For example, when an organic amine is used as the neutralizer (e), the aqueous polyurethane resin dispersion can be applied to a glass plate and dried at a temperature of 60°C and a reduced pressure of 20 mmHg for 24 hours to obtain a coating layer. The resulting coating layer can then be dissolved in N-methylpyrrolidone (NMP), and the acid value can be measured in accordance with the indicator titration method of JIS K 1557. The acid value of the polyurethane resin (A) can be controlled by the content of the acidic group-containing polyol (c).

[0061] <<Effective Acid Value>> The effective acid value of the aqueous polyurethane resin dispersion is determined by the product of the degree of neutralization and the acid value. The degree of neutralization is determined by the equivalent ratio of the amino group derived from the neutralizing agent (e) to the acid group derived from the acid group-containing polyol (c). The degree of neutralization can be determined by quantifying the salt derived from the neutralizing agent (e) in the aqueous polyurethane resin dispersion by gas chromatography. For example, when triethylamine is used as the neutralizing agent (e) and 2,2-dimethylolpropionic acid is used as the acid group-containing polyol (c), the ammonium salt (COO － N (C ２ H ５ ) ３ H ＋ ) is quantified. The acid value can be determined by the method described above when the polyurethane resin (A) contains a structure derived from the neutralizing agent (e). The degree of neutralization is the ratio of the amino groups derived from the neutralizing agent (e) to the acidic groups derived from the acidic group-containing polyol (c), expressed in mole percent. For example, if the amount of neutralizing agent (e) used is 1.1 equivalents per equivalent of the acidic groups in the polyurethane prepolymer, the degree of neutralization is 110%. When the degree of neutralization exceeds 100%, the acid value and the effective acid value are the same.

[0062] The effective acid value of the aqueous polyurethane resin dispersion is preferably 12 to 20 mgKOH / g, particularly preferably 14 to 19 mgKOH / g. When the effective acid value of the polyurethane resin (A) is 14 to 19 mgKOH / g, the film-forming ability and solvent resistance tend to be better.

[0063] By reducing the degree of neutralization, particles of a polyurethane resin (A) with a high acid value can achieve the same effect as particles of a polyurethane resin (A) with a low acid value. Typically, the polyurethane resin (A) is present in the aqueous polyurethane resin dispersion in a fully neutralized state, so the effective acid value of the polyurethane resin (A) in the aqueous polyurethane resin dispersion is equal to the acid value of the polyurethane resin (A). For example, when a solution is prepared by adding an amount of base sufficient to neutralize 70% of the acid groups present in a water-soluble polymer with an acid value of 20 KOH mg / g, the effective acid value becomes 14 KOH mg / g, and the same effect as an aqueous polyurethane resin dispersion containing a polyurethane resin (A) with an acid value of 14 KOH mg / g can be obtained. Therefore, by partially neutralizing particles of a polyurethane resin (A) with a high acid value, the effective acid value can be lowered and the dispersibility can be adjusted to a more desirable state.

[0064] <Crosslinking point density> The crosslinking point density of the polyurethane resin (A) is 1.0 × 10 －４ ~1.0 x 10 －３ It is preferable that the crosslinking point density is in the range of 1.0×10 －４ When the crosslinking point density is 1.0×10 mol / g or more, an increase in viscosity tends to be suppressed even when a non-water-soluble organic solvent described later is added, and storage stability is sufficient. －３ When the content is less than 1 / mol / g, the tensile elongation at break increases, and a coating layer having excellent impact resistance tends to be obtained.

[0065] (Composition of polyurethane resin (A)) The content ratio of each structure in the polyurethane resin (A) is preferably as follows. In this specification, the content ratio of each component in the polyurethane resin (A) is a value calculated from the charged amount. The charged amount indicates the amount of each component used when producing the polyurethane resin (A). In the production of the polyurethane resin (A), each component is almost completely reacted, so the charged amount is taken as the content ratio in the polyurethane resin (A).

[0066] The content of the structure derived from the acidic group-free polyol (a) in the polyurethane resin (A) is preferably from 35 to 85% by mass, particularly preferably from 40 to 80% by mass.

[0067] The content of the structure derived from polyisocyanate (b) in the polyurethane resin (A) is preferably from 10 to 60 mass %, particularly preferably from 20 to 50 mass %.

[0068] The content of the structure derived from the acidic group-containing polyol (c) in the polyurethane resin (A) is preferably from 0.5 to 20% by mass, and particularly preferably from 1.0 to 10% by mass.

[0069] The content of the structure derived from polyisocyanate (b) is preferably such that the molar ratio of isocyanate groups in polyisocyanate (b) to hydroxyl groups in the acidic group-free polyol (a) and the acidic group-containing polyol (c) (isocyanate groups / hydroxyl groups) is 0.5 to 3.0, particularly preferably 1.2 to 2.0.

[0070] When the polyurethane resin (A) has a structure derived from the compound (d), the content of the structure derived from the compound (d) in the polyurethane resin (A) is preferably 0 to 15.5 mass%, and particularly preferably 1.0 to 8.0 mass%.

[0071] The content of the structure derived from compound (d) is preferably an amount equal to or less than the equivalent of the isocyanato group that serves as the chain extension initiation point in the polyurethane prepolymer, which is a synthetic intermediate for polyurethane resin (A), and particularly preferably an amount equal to 0.70 to 0.99 equivalents of the isocyanato group in the polyurethane prepolymer. Adding compound (d) in an amount equal to or less than the equivalent of the isocyanato group in the polyurethane prepolymer tends to improve solvent resistance without reducing the molecular weight of the chain-extended polyurethane resin (A).

[0072] Furthermore, the content ratio of the polycarbonate polyol-derived structure relative to the total polyol-derived structures contained in the polyurethane resin (A) is preferably 60.0 to 95.0 mass%, particularly preferably 80.0 to 95.0 mass%. Here, "all polyols contained in the polyurethane resin (A)" refers to the acidic group-free polyol (a), the acidic group-containing polyol (c), and other compounds (f) that are polyol compounds. Here, when the acidic group-free polyol (a) further contains only polyester polyol and / or polyether polyol as an optional component, the "all polyols" includes "polyol compound (d)." Furthermore, "polyol compound (d)" is a compound having two or more hydroxyl groups and zero or one or more amino groups.

[0073] When the aqueous polyurethane resin dispersion has a structure derived from the neutralizer (e), the content ratio of the structure derived from the neutralizer (e) is preferably in the range of 0.6 to 1.2 times the number of moles of acidic groups contained in the polyurethane resin (A). When the content ratio of the structure derived from the neutralizer (e) is 0.6 times or more the number of moles of acidic groups, the dispersibility of the polyurethane resin (A) in the aqueous polyurethane resin dispersion is high, and when it is 1.2 times or less, a coating film with high substrate adhesion can be obtained in a short time of several minutes to 1 hour under low-temperature drying at 100°C or less. Note that when a coating layer (also referred to as a coating film, cured layer, cured film, or dried film) of the aqueous polyurethane resin dispersion is obtained by applying the aqueous polyurethane resin dispersion to a substrate and then drying and curing the aqueous polyurethane resin dispersion, the neutralizer (e) may volatilize during drying, and the polyurethane resin (A) in the coating layer may not contain a structure derived from the neutralizer (e).

[0074] The neutralizer (e) is preferably used in an amount such that the pH of the aqueous polyurethane resin dispersion is about 6.0 to 9.0. When the neutralizer is added to the urethane resin (A), the amount of the neutralizer added is preferably 0.1 to 1.5 equivalents, more preferably 0.6 to 1.2 equivalents, relative to the acidic groups derived from the acidic group-containing polyol (c). From the viewpoint of improving solvent resistance, the amount of the neutralizer added is more preferably less than 1.0 equivalent.

[0075] When the polyurethane resin (A) has a structure derived from the other compound (f), the content of the structure derived from the other compound (f) in the polyurethane resin (A) is preferably less than 2 mass%, and particularly preferably less than 1 mass%.

[0076] <Particles of polyurethane resin (A)> The average particle size of the polyurethane resin (A) particles is 30 to 80 nm. If the average particle size of the polyurethane resin (A) particles is less than 30 nm, film-forming properties are poor. If the average particle size of the polyurethane resin (A) particles is more than 80 nm, filterability may be poor. The average particle size of the polyurethane resin (A) particles is preferably 40 to 75 nm, and particularly preferably 50 to 70 nm. The average particle size of the polyurethane resin (A) particles is a value determined by dynamic light scattering (DLS). The average particle size of the polyurethane resin (A) particles can be controlled by setting the effective acid value within the aforementioned range.

[0077] <Method for producing polyurethane resin (A)> The polyurethane resin (A) can be obtained by any method as long as the desired polyurethane resin (A) is obtained. For example, the polyurethane resin (A) can be obtained by a production method including a step of reacting an acidic group-free polyol (a), a polyisocyanate (b), and an acidic group-containing polyol (c). In addition, the polyurethane resin (A) is preferably a polyurethane resin (A) obtained by the method for producing an aqueous polyurethane resin dispersion described below.

[0078] <Aqueous Medium (B)> The aqueous medium (B) is water or a mixed medium of water and a hydrophilic organic solvent. Examples of water include tap water, ion-exchanged water, distilled water, and ultrapure water. Examples of hydrophilic organic solvents include ketones such as acetone and ethyl methyl ketone; pyrrolidones such as N-methylpyrrolidone and N-ethylpyrrolidone; ethers such as diethyl ether and dipropylene glycol dimethyl ether; alcohols such as methanol, ethanol, n-propanol, isopropanol, ethylene glycol, diethylene glycol, and glycerin; polyhydric alcohol alkyl ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether; amides such as β-alkoxypropionamide, typified by "KJCMPA(R)-100" manufactured by KJ Chemical Co.; and hydroxyl group-containing tertiary amines such as 2-(dimethylamino)-2-methyl-1-propanol (DMAP). The aqueous medium (B) may be used alone or in combination of two or more types.

[0079] <Additional Component (C)> The aqueous polyurethane resin dispersion may contain an additional component (C) as needed. The aqueous polyurethane resin dispersion may not contain the additional component (C). Examples of the additional component (C) include other resins and / or other additives. The additional component (C) can be appropriately selected depending on the application of the aqueous polyurethane resin dispersion.

[0080] Examples of other resins include polyester resins, acrylic resins, polyether resins, polycarbonate resins, polyurethane resins other than the polyurethane resin (A), epoxy resins, alkyd resins, polyolefin resins, and vinyl chloride resins.

[0081] Examples of other additives that can be used include water-insoluble organic solvents, curing agents, wetting agents, surface conditioners, surfactants, emulsifiers, thickeners, urethanization catalysts, fillers, foaming agents, oil repellents, pigments, dyes, film-forming aids, hollow foams, flame retardants, antifoaming agents, leveling agents, antiblocking agents, ultraviolet absorbers, light stabilizers, plasticizers, antisettling agents, polymerization initiators, polymerization inhibitors, dispersants, penetration promoters, moisturizing agents, fixing agents, preservatives, antioxidants, antifungal agents, chelating agents, sensitizers, and pH adjusters.

[0082] Examples of the water-insoluble organic solvent include alkyl esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, n-propyl acetate, isopropyl acetate, n-hexyl acetate, benzyl acetate, ethyl propionate, n-propyl propionate, isopropyl propionate, n-butyl propionate, isobutyl propionate, and sec-butyl propionate; ketones such as methyl n-butyl ketone, methyl isobutyl ketone, 2-heptanone, diethyl ketone, di-n-propyl ketone, and di-n-butyl ketone; ethers such as di-n-propyl ether, diisopropyl ether, di-n-butyl ether, and anisole; aromatics such as toluene, xylene, and chlorobenzene; alcohols such as 1-hexanol, 1-heptanol, and 2-ethylhexanol; and aliphatics such as n-butyl chloride, chloroform, hexane, and octane.

[0083] Known curing agents can be used, such as polyisocyanate compounds, polycarbodiimide compounds, amino resins, epoxy group-containing compounds, and aziridine compounds.

[0084] Known wetting agents can be used, including, for example, anionic surfactants such as sulfates of higher alcohols, salts of sulfates of higher alcohols, alkylbenzenesulfonates, and polyoxyethylene alkylphenylsulfonates; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and oxyethylene-oxypropylene block polymers; and silicone surfactants.

[0085] The coalescing agent is generally a hydrophilic compound that promotes film formation. Examples of the coalescing agent include pyrrolidone compounds such as N-methylpyrrolidone, N-ethylpyrrolidone, N-propylpyrrolidone, N-isopropylpyrrolidone, N-butylpyrrolidone, N-cyclohexylpyrrolidone, N-octylpyrrolidone, N-phenylpyrrolidone, and vinylpyrrolidone; alcohol compounds such as methanol, ethanol, isopropanol, n-butanol, and n-hexanol; and glycol compounds such as propylene glycol, diethylene glycol, propylene glycol, triethylene glycol, and polyethylene glycol, with pyrrolidone compounds being preferred. The coalescing agent can also serve as the aqueous medium (B) in which the polyurethane resin is dispersed.

[0086] As the polymerization initiator, known initiators can be used, for example, persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate, azo compounds such as 2,2'-azobisisobutyronitrile and 2,2'-azobis(2,4-dimethylvaleronitrile), and peroxides such as hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, and lauroyl peroxide.

[0087] As the pigment, inorganic pigments or organic pigments can be used. These can be used alone or in combination of two or more kinds. Mixed crystals can also be used. The further component (C) can be used alone or in combination of two or more kinds.

[0088] (Composition of aqueous polyurethane resin dispersion) The content (solids content) of polyurethane resin (A) in the aqueous polyurethane resin dispersion is preferably 10 to 90% by mass, more preferably 15 to 60% by mass, and particularly preferably 20 to 50% by mass. The content (solids content) of aqueous medium (B) in the aqueous polyurethane resin dispersion is preferably 10 to 90% by mass, preferably 40 to 85% by mass, and particularly preferably 50 to 80% by mass. In the aqueous polyurethane resin dispersion, the amount of hydrophilic organic solvent in the aqueous medium (B) is preferably 0 to 20% by mass. The content (solids content) of further component (C) in the aqueous polyurethane resin dispersion is preferably 50% by mass or less, more preferably 0.0001 to 35% by mass, and particularly preferably 0.001 to 20% by mass. The pH of the aqueous polyurethane resin dispersion is preferably 5.0 to 9.0.

[0089] <40 μm Film of Aqueous Polyurethane Resin Dispersion> A 40 μm film of an aqueous polyurethane resin dispersion (hereinafter also referred to as "aqueous polyurethane resin dispersion film") is a 40 μm film obtained by heating the aqueous polyurethane resin dispersion at 60° C. for 2 hours and then at 120° C. for 2 hours. The elastic modulus of the aqueous polyurethane resin dispersion film is 400 MPa or more and 900 MPa or less. From the viewpoint of solvent resistance, the elastic modulus of the aqueous polyurethane resin dispersion is preferably 450 MPa or more and 800 MPa or less, and particularly preferably 500 MPa or more and 800 MPa or less. In this specification, the elastic modulus of the aqueous polyurethane resin dispersion is measured by the tensile test specified in JIS K7311. The elastic modulus of the aqueous polyurethane resin dispersion can be adjusted by adjusting the content ratio of the alicyclic structure in the polyurethane resin (A) to the above-mentioned range, adjusting the total content ratio of the urethane bond and the urea bond to the above-mentioned range, or the like. Specifically, the elastic modulus of the aqueous polyurethane resin dispersion can be adjusted by adjusting the total content of urethane bonds and urea bonds to a range of 13.0 to 25.0 mass% based on the solid content of the polyurethane resin (A) and adjusting the content of the alicyclic structure in the polyurethane resin (A) to a range of 10 to 50 mass%.

[0090] The "film of aqueous polyurethane resin dispersion" for measuring the elastic modulus is a film consisting of only polyurethane resin (A), or a film containing only polyurethane resin (A) and, as optional components, one or more components selected from the group consisting of a film-forming aid and a hydrophilic organic solvent.

[0091] The method for producing a film of the aqueous polyurethane resin dispersion includes a step of applying the aqueous polyurethane resin dispersion to a substrate to obtain a substrate coated with the aqueous polyurethane resin dispersion, a step of drying the substrate coated with the aqueous polyurethane resin dispersion to obtain a coating layer of the aqueous polyurethane resin dispersion, and a step of separating the coating layer of the aqueous polyurethane resin dispersion from the substrate to obtain a film of the aqueous polyurethane resin dispersion. Here, the aqueous polyurethane resin dispersion used in the method for producing a film of the aqueous polyurethane resin dispersion is an aqueous polyurethane resin dispersion consisting of only a polyurethane resin (A) and an aqueous medium (B), or an aqueous polyurethane resin dispersion containing only a polyurethane resin (A), an aqueous medium (B), and, as an optional component, one or more components selected from the group consisting of a coalescing agent and a hydrophilic organic solvent.

[0092] The drying conditions for producing a film of the aqueous polyurethane resin dispersion are such that the aqueous polyurethane resin dispersion is heated at 60° C. for 2 hours and then at 120° C. for 2 hours. For example, a method can be used in which a substrate coated with the aqueous polyurethane resin dispersion is heated at 60° C. for 2 hours and then at 120° C. for 2 hours. In this case, the temperature can be raised from room temperature (25° C.) to 60° C. over 20 minutes, maintained at 60° C. for 2 hours, raised from 60° C. to 120° C. over 20 minutes, maintained at 120° C. for 2 hours, and then lowered from 120° C. to room temperature over 40 minutes.

[0093] Examples of methods for applying the aqueous polyurethane resin dispersion include dipping, roll coating, reverse roll coating, gravure roll coating, screen coating, spray coating, airless spray coating, knife coating, air knife coating, bar coating, spin coating, and curtain coating.

[0094] In the method for producing a film of the aqueous polyurethane resin dispersion, the substrate is not particularly limited. Examples of the substrate include those to which the coating composition is applied, which will be described later, and may be inorganic substrates such as glass and metal, or elastomer substrates.

[0095] (Method for Producing Aqueous Polyurethane Resin Dispersion) The method for producing the aqueous polyurethane resin dispersion is not particularly limited as long as it is a method that can disperse particles of the polyurethane resin (A) in the aqueous medium (B). The method for producing the aqueous polyurethane resin dispersion preferably includes the following steps: (I) a step of reacting the acidic group-free polyol (a), the polyisocyanate (b), the acidic group-containing polyol (c), and optionally other compounds (f) in the presence of an organic solvent to obtain a polyurethane prepolymer, (II) a step of mixing the polyurethane prepolymer with water, and (III) a step of reacting the polyurethane prepolymer with a compound (d).

[0096] Furthermore, when a neutralizing agent (e) is used, a step of neutralizing the acidic groups of the polyurethane prepolymer with the neutralizing agent (e) may be included after step (I). In addition, a step of removing the organic solvent may be included as step (IV). Here, the amount of the neutralizing agent (e) used is preferably 0.6 to 1.2 equivalents, more preferably 0.6 to 1.0 equivalents, and particularly preferably 0.65 to 0.95 equivalents per equivalent of the acidic groups of the polyurethane prepolymer.

[0097] In addition, when the polyurethane resin (A) does not contain a structure derived from the compound (d), the polyurethane prepolymer obtained in step (I) or step (II) can be used as the polyurethane resin (A). In addition, in the method for producing the aqueous polyurethane resin dispersion, the further component (C) can be added in any step.

[0098] In addition to the above, the aqueous polyurethane resin dispersion can be produced by a known method described in known literature (for example, WO2016 / 039396, WO2016 / 163394, etc.).

[0099] In the step (I), the polyurethane prepolymer is obtained by reacting an acidic group-free polyol (a), a polyisocyanate (b), an acidic group-containing polyol (c), and optionally other compounds (f). Thus, the polyurethane prepolymer has a structure derived from the acidic group-free polyol (a), a structure derived from the polyisocyanate (b), a structure derived from the acidic group-containing polyol (c), and optionally a structure derived from other compounds (f).

[0100] The polyurethane prepolymer is preferably selected so that the content of free isocyanato groups is in the range of 0.5 to 5.0 mass % based on the solid content of the polyurethane prepolymer, in terms of improving dispersibility in water.

[0101] The acid value (AV) of the polyurethane prepolymer is preferably 4 to 40 mgKOH / g, more preferably 6 to 38 mgKOH / g, and particularly preferably 8 to 35 mgKOH / g. By making the acid value of the polyurethane prepolymer 4 mgKOH / g or more, dispersibility in aqueous media and storage stability tend to be improved. Furthermore, by making the acid value of the polyurethane prepolymer 40 mgKOH / g or less, the flexibility of printed matter tends to be increased. Furthermore, the drying properties of the ink when it is dried tend to be improved.

[0102] The "acid value of the polyurethane prepolymer" refers to the acid value of the so-called solid content, excluding the solvent used in producing the polyurethane prepolymer and the neutralizing agent used to disperse the polyurethane prepolymer in an aqueous medium.

[0103] Specifically, the acid value of the polyurethane prepolymer can be calculated by the following formula (3).

[0104] [Acid value of polyurethane prepolymer]=[(number of millimoles of acidic group-containing polyol)×(number of acidic groups in one molecule of acidic group-containing polyol)]×56.1 / [total mass of polyisocyanate, acidic group-containing polyol, and acidic group-free polyol] (3)

[0105] In this way, the acid value of the polyurethane prepolymer is adjusted by the content ratio of the acidic group-containing polyol (c) in all polyols that form the polyurethane prepolymer.

[0106] The step (III) of reacting the polyurethane prepolymer with the compound (d) is a step of bonding the polyurethane prepolymers together and adjusting the molecular weight of the polyurethane resin to a target range. In the step (I), when the acidic group-free polyol (a) contains only a polyester polyol and / or a polyether polyol as an optional component, the compound (d) used in the step (III) is not a polycarbonate polyol, a polyester polyol, a polyether polyol, or an acidic group-containing polyol (c).

[0107] The step (III) may be carried out slowly under cooling, or in some cases, the reaction may be accelerated under heating conditions of 90° C. or less. The reaction time under cooling may be, for example, 0.5 to 24 hours, and the reaction time under heating conditions of 90° C. or less may be, for example, 0.1 to 6 hours.

[0108] <Uses of aqueous polyurethane resin dispersion> The aqueous polyurethane resin dispersion can be used as a raw material for adhesives, coating agents, and films. The aqueous polyurethane resin dispersion can also be used to form a coating layer (a dried film of the aqueous polyurethane resin dispersion) using the aqueous polyurethane resin dispersion on various substrates. Here, the aqueous polyurethane resin dispersion may be an aqueous polyurethane resin dispersion consisting only of polyurethane resin (A) particles and an aqueous medium (B), or may be an aqueous polyurethane resin dispersion containing an additional component (C).

[0109] [Coating Composition] The coating composition contains the aqueous polyurethane resin dispersion. The coating composition may contain an additional component (C). That is, the coating composition may be an aqueous polyurethane resin dispersion consisting only of particles of polyurethane resin (A) and an aqueous medium (B), or an aqueous polyurethane resin dispersion consisting only of particles of polyurethane resin (A), an aqueous medium (B), and an additional component (C). The additional component (C) may be contained in the aqueous polyurethane resin dispersion, or may be mixed with the aqueous polyurethane resin dispersion when producing the coating composition.

[0110] Examples of additional components (C) that may be included in the coating composition include water-insoluble organic solvents, plasticizers, antifoaming agents, leveling agents, mildew inhibitors, rust inhibitors, matting agents, flame retardants, tackifiers, thixotropic agents, lubricants, antistatic agents, viscosity reducers, thickeners, diluents, pigments, dyes, UV absorbers, light stabilizers, antioxidants, and fillers. Examples of coating agents include paints, inks (e.g., water-soluble inks), and surface treatment agents for various substrates. For example, when the coating composition is used as an aqueous ink, the coating composition may contain a pigment as additional component (C). It is preferable that the coating composition contains a water-insoluble organic solvent. Even when the coating composition contains a water-insoluble organic solvent, the increase in viscosity tends to be suppressed, and storage stability is sufficient.

[0111] <Substrate> Substrates to which the coating composition can be applied include metals, plastics, inorganic materials, fiber materials, and other substrates.

[0112] Examples of metals include iron, aluminum, brass, copper, tinplate, stainless steel, zinc-plated steel, and zinc alloy (Zn—Al, Zn—Ni, Zn—Fe, etc.)-plated steel. When the substrate is a metal, it may be subjected to a surface treatment such as phosphate treatment, chromate treatment, or composite oxide treatment. Furthermore, the substrate may be subjected to a primer coat and / or intermediate coat for the purpose of protecting the substrate. In this case, the coating composition can be used as a top coat.

[0113] Examples of plastics include resins such as polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, and epoxy resin, as well as plastic materials such as various FRPs. Examples of inorganic materials include glass, cement, and concrete. Examples of fibrous materials include wood, paper, and cloth. Other substrates include building materials such as wallpaper, flooring, and tiles, as well as leather.

[0114] The substrate is preferably a metal, and therefore the coating composition is preferably a coating composition for coating a metal substrate.

[0115] <Coating Layer> The coating layer is obtained by drying the coating composition. The thickness of the coating layer can be appropriately selected depending on the application. The thickness of the coating layer is preferably 0.1 to 100 μm, more preferably 1 to 90 μm, and even more preferably 5 to 60 μm.

[0116] <Method for Producing Coating Layer> The method for producing the coating layer is not particularly limited. The coating layer is preferably obtained by the method for producing a laminate described below.

[0117] <Laminate> When the aqueous polyurethane resin dispersion is used to form a coating layer of the aqueous polyurethane resin dispersion on various substrates, a laminate is obtained. The laminate comprises the coating layer of the aqueous polyurethane resin dispersion described above and a substrate. The coating layer of the aqueous polyurethane resin dispersion is a resin film adhered to the substrate, and may also be called a dried film of the aqueous polyurethane resin dispersion, a coated film of the aqueous polyurethane resin dispersion, a cured film of the aqueous polyurethane resin dispersion, or the like.

[0118] An additional coating film may be formed between the substrate and the coating layer of the aqueous polyurethane resin dispersion. For example, the substrate may be subjected to a surface treatment or provided with an undercoat film as necessary, and then a coating layer of the aqueous polyurethane resin dispersion may be formed thereon. Furthermore, an additional coating film may be formed on the coating layer of the aqueous polyurethane resin dispersion. The method for forming the additional coating film in the laminate is not particularly limited, and methods known to those skilled in the art may be used.

[0119] The method for producing the laminate is not particularly limited, and examples thereof include the following methods: Step 1: applying a coating composition onto a substrate, and Step 2: drying the coating composition to form a coating layer of the aqueous polyurethane resin dispersion.

[0120] The method for applying the coating composition to the substrate is not particularly limited, and includes the methods described above as the method for applying the aqueous polyurethane resin dispersion.

[0121] The thickness of the coating composition is not particularly limited, but it is preferably a thickness that will result in the thickness of the coating layer of the aqueous polyurethane resin dispersion.

[0122] A coating layer of an aqueous polyurethane resin dispersion can be obtained by applying a coating composition to a substrate, drying the composition, and curing the composition. To improve adhesion to the substrate, the coating composition may be applied to the substrate and then dried by heating or other means to cure the coating composition. Examples of the heating method include a heating method using the heat of reaction itself and a heating method that combines the heat of reaction with active heating of the mold. Examples of active heating of the mold include a method in which the mold is placed in a hot air oven, electric furnace, or infrared induction heating furnace for heating.

[0123] The heating temperature is preferably 10 to 200° C., and more preferably 60 to 160° C. By heating at such a temperature, drying can be carried out more efficiently.

[0124] The heating time is preferably 0.0001 to 20 hours, more preferably 1 to 10 hours. By using such a heating time, a laminate having a coating layer with higher hardness can be obtained.

[0125] The method for producing the laminate may further include a step of performing a surface treatment on the substrate, a step of providing a primer film on the substrate, and a step of providing a primer film and an intermediate coat film on the substrate, depending on the type of substrate on which the coating layer is provided.

[0126] <Polyurethane Resin Film> A polyurethane resin film can be obtained by drying a composition containing an aqueous polyurethane resin dispersion. That is, a coating layer of the aqueous polyurethane resin dispersion can be used as an independent film. The composition containing the aqueous polyurethane resin dispersion used to obtain the polyurethane resin film may contain an additional component (C). That is, the composition containing the aqueous polyurethane resin dispersion may be an aqueous polyurethane resin dispersion consisting only of polyurethane resin (A) particles and an aqueous medium (B), or an aqueous polyurethane resin dispersion consisting only of polyurethane resin (A) particles, an aqueous medium (B), and an additional component (C). Applications of the film include release films; packaging for food, textiles, miscellaneous goods, etc.; and surface decoration, protection, and advertising of substrates. The composition containing the aqueous polyurethane resin dispersion used to obtain the polyurethane resin film preferably contains one or more components selected from the group consisting of a wetting agent, a film-forming aid, and a polymerization initiator. The polyurethane resin film can be produced by a method including a laminate production method. For example, in the laminate production method, a releasable substrate can be used as the substrate to peel the coating layer of the aqueous polyurethane resin dispersion from the laminate. The coating layer of the aqueous polyurethane resin dispersion can then be used as an independent film.

[0127] Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to the Examples and Comparative Examples. Physical properties were measured as follows. (1) Hydroxyl value: Measured in accordance with Method B of JIS K 1557. (2) Number average molecular weight (Mn) and hydroxyl value: The number average molecular weight and hydroxyl value of polycarbonate polyol and polyester polyol are catalog values.

[0128] (3) Solvent resistance: As a solvent, SOLVESSO ＴＭ 100 (manufactured by Ando Parachemie Co., Ltd.; solvent naphtha (petroleum-based) light aroma) was used. 10.0 g of the aqueous polyurethane resin dispersion was applied to a glass plate to a thickness of 100 to 130 μm, and heated at 80°C for 15 minutes to obtain a polyurethane resin film with a thickness of 40 μm. Here, when the solid content of the aqueous polyurethane resin dispersion was 38% by mass, the applied thickness was 100 μm. Furthermore, when the solid content of the aqueous polyurethane resin dispersion was 30% by mass, the applied thickness was 130 μm. The obtained polyurethane resin film was peeled from the glass plate and punched out with a cutter to prepare a test specimen. The obtained test specimen was immersed in a solvent at 27°C for 16 hours, and the film weight before and after immersion was measured. The swelling ratio of the film in the solvent was calculated using the following formula. (Swelling ratio (%)) = [(film weight after solvent immersion) - (film weight before solvent immersion)] / (film weight before solvent immersion) x 100 Based on the swelling ratio, the solvent resistance of the film was evaluated according to the following criteria: ⊚: Swelling ratio is less than 60%. ◯: Swelling ratio is 60% or more and 90% or less. ×: Swelling ratio is more than 90%.

[0129] (4) Elastic modulus of polyurethane resin film: An aqueous polyurethane resin dispersion was applied to a glass plate and heated at 60°C for 2 hours and then at 120°C for 2 hours to obtain a polyurethane resin film with a thickness of 40 μm. The obtained polyurethane resin film was peeled from the glass plate and punched out using a Super Dumbbell (registered trademark) cutter (SDK-300) manufactured by Dumbbell Co., Ltd. to prepare a test specimen. The obtained test specimen was subjected to a tensile test using a Tensilon universal testing machine RTG-1250 manufactured by A&D Co., Ltd. in accordance with JIS K 7311. The measurement conditions were a 23°C, 50% humidity environment, a 500 N load cell, and a tensile speed of 100 mm / min.

[0130] (5) Film-forming property: The film-forming property of the aqueous polyurethane resin dispersion was evaluated from the appearance of the film obtained in "(4) Elastic modulus of polyurethane resin film". ⊚: No cracks in the film. ◯: Partial cracks in the film. ×: Cracks in the entire film, making tensile testing impossible.

[0131] (6) Dispersibility: After carrying out step (I) in the production method for aqueous polyurethane resin dispersions (i.e., a step of reacting an acidic group-free polyol (a), a polyisocyanate (b), an acidic group-containing polyol (c), and optionally other compounds (f) in the presence of an organic solvent to obtain a polyurethane prepolymer) and then carrying out a step of neutralizing the acidic groups of the polyurethane prepolymer obtained in step (I) with a neutralizing agent (e), the polyurethane prepolymer was evaluated for its dispersibility in water based on the following criteria. For example, in Example 1, the reaction mixture was cooled to 80°C, and triethylamine (18.6 g) was added and mixed thereto. 390 g of this mixture was added to water (565 g) under vigorous stirring, and the dispersibility of the aqueous polyurethane resin dispersion was evaluated based on the following criteria. ◯: The polyurethane prepolymer was dispersible in water. ×: The polyurethane prepolymer was not dispersible in water.

[0132] (7) Average particle size: A value determined by dynamic light scattering (DLS). A sample solution was prepared by diluting the aqueous polyurethane resin dispersion 10 times with ultrapure water. The average particle size of the obtained sample solution was measured at 25°C using a particle size distribution analyzer "ELSZ-2000" (trade name, manufactured by Otsuka Electronics Co., Ltd.). The measured average particle size was taken as the average particle size of the polyurethane resin contained in the aqueous polyurethane resin dispersion.

[0133] Example 1 Aqueous Polyurethane Resin Dispersion (U1) Polycarbonate polyol (product name "ETERNACOLL (registered trademark) UH-100" manufactured by UBE Corporation; number average molecular weight 1,000; hydroxyl value 112.2 mg KOH / g; reaction product of 1,6-hexanediol and dimethyl carbonate, 300 g), 27.4 g of 2,2-dimethylolpropionic acid (DMPA), and dicyclohexylmethane 4,4'-diisocyanate (H12MDI, 218 g) were heated in ethyl methyl ketone (MEK, 113 g) in the presence of dibutyltin dilaurate (0.3 g) under a nitrogen atmosphere at 75 to 85°C for 5 hours. The reaction mixture was cooled to 80°C, and triethylamine (18.6 g) was added and mixed. 390 g of the resulting mixture was added to water (565 g) with vigorous stirring. Next, 25.3 g of a 35% by mass aqueous solution of diethylenetriamine (DETA) and 19.9 g of a 35% by mass aqueous solution of 2-methyl-1,5-pentanediamine (MPMD) were added to obtain an aqueous dispersion of a polyurethane resin. The aqueous dispersion was then distilled until the solid content reached 38% by mass, obtaining an aqueous polyurethane resin dispersion (U1).

[0134] Example 2 Aqueous Polyurethane Resin Dispersion (U2) Polycarbonate polyol (product name "ETERNACOLL (registered trademark) UH-100" manufactured by UBE Corporation; number average molecular weight 1,000; hydroxyl value 112.2 mg KOH / g; reaction product of 1,6-hexanediol and dimethyl carbonate, 300 g), 27.4 g of 2,2-dimethylolpropionic acid (DMPA), and dicyclohexylmethane 4,4'-diisocyanate (H12MDI, 218 g) were heated in ethyl methyl ketone (MEK, 113 g) in the presence of dibutyltin dilaurate (0.3 g) under a nitrogen atmosphere at 75 to 85°C for 5 hours. The reaction mixture was cooled to 80°C, and triethylamine (14.5 g) was added and mixed. 388 g of the resulting mixture was added to water (567 g) with vigorous stirring. Next, 25.3 g of a 35% by mass aqueous solution of diethylenetriamine (DETA) and 19.9 g of a 35% by mass aqueous solution of 2-methyl-1,5-pentanediamine (MPMD) were added to obtain an aqueous dispersion of a polyurethane resin. The aqueous dispersion was then distilled until the solid content reached 38% by mass, obtaining an aqueous polyurethane resin dispersion (U2).

[0135] Example 3 Aqueous Polyurethane Resin Dispersion (U3) Polycarbonate polyol (product name "ETERNACOLL (registered trademark) UH-100" manufactured by UBE Corporation; number average molecular weight 1,000; hydroxyl value 112.2 mg KOH / g; reaction product of 1,6-hexanediol and dimethyl carbonate, 300 g), 27.4 g of 2,2-dimethylolpropionic acid (DMPA), and dicyclohexylmethane 4,4'-diisocyanate (H12MDI, 218 g) were heated in ethyl methyl ketone (MEK, 112 g) in the presence of dibutyltin dilaurate (0.3 g) under a nitrogen atmosphere at 75 to 85°C for 5 hours. The reaction mixture was cooled to 80°C, and triethylamine (16.5 g) was added and mixed. 392 g of the resulting mixture was added to water (562 g) with vigorous stirring. Next, 25.3 g of a 35% by mass aqueous solution of diethylenetriamine (DETA) and 20.7 g of an 18% by mass aqueous solution of ethylenediamine (EDA) were added to obtain an aqueous dispersion of a polyurethane resin. The aqueous dispersion was then distilled until the solid content reached 38% by mass, obtaining an aqueous polyurethane resin dispersion (U3).

[0136] Example 4 Aqueous Polyurethane Resin Dispersion (U4) Polycarbonate polyol (product name "ETERNACOLL (registered trademark) UH-100" manufactured by UBE Corporation; number average molecular weight 1,000; hydroxyl value 112.2 mg KOH / g; reaction product of 1,6-hexanediol and dimethyl carbonate, 300 g), 25.4 g of 2,2-dimethylolpropionic acid (DMPA), and 180 g of isophorone diisocyanate (IPDI) were heated in 105 g of ethyl methyl ketone (MEK) in the presence of 0.3 g of dibutyltin dilaurate under a nitrogen atmosphere at 75 to 85°C for 5 hours. The reaction mixture was cooled to 80°C, and 17.3 g of triethylamine was added and mixed. 388 g of the resulting mixture was added to 564 g of water with vigorous stirring. Next, 25.3 g of a 35% by mass aqueous solution of diethylenetriamine (DETA) and 22.6 g of a 35% by mass aqueous solution of 2-methyl-1,5-pentanediamine (MPMD) were added to obtain an aqueous dispersion of a polyurethane resin. The aqueous dispersion was then distilled until the solid content reached 38% by mass, obtaining an aqueous polyurethane resin dispersion (U4).

[0137] Example 5 Aqueous Polyurethane Resin Dispersion (U5) A polycarbonate polyol (product name "ETERNACOLL (registered trademark) UP-100" manufactured by UBE Corporation; number average molecular weight 1,000; hydroxyl value 112.2 mgKOH / g; polycarbonate polyol obtained by reacting 2-methyl-1,3-propanediol with dimethyl carbonate, 300 g) and a polyether polyol (product name "PTMG2000" manufactured by Mitsubishi Chemical Corporation; number average molecular weight 2, Polytetramethylene ether glycol (33.0 g, hydroxyl value 56.1 mg KOH / g), 29.9 g of 2,2-dimethylolpropionic acid (DMPA), and dicyclohexylmethane 4,4'-diisocyanate (H12MDI, 234 g) were heated in ethyl methyl ketone (122 g) in the presence of dibutyltin dilaurate (0.3 g) under a nitrogen atmosphere at 75 to 85°C for 5 hours. The reaction mixture was cooled to 80°C, and triethylamine (18.1 g) was added and mixed. 393 g of the mixture was then added to water (562 g) with vigorous stirring. Next, a 35% by weight aqueous solution of diethylenetriamine (DETA) (25.3 g) and an 18% by weight aqueous solution of ethylenediamine (EDA) (19.6 g) were added to obtain an aqueous dispersion of polyurethane resin. Next, the aqueous dispersion was distilled until the solid content reached 38% by mass, thereby obtaining an aqueous polyurethane resin dispersion (U5).

[0138] Comparative Example 1 Aqueous Polyurethane Resin Dispersion (U6) Polycarbonate polyol (product name "ETERNACOLL (registered trademark) UH-200" manufactured by UBE Corporation; number average molecular weight 2,000; hydroxyl value 56.1 mg KOH / g; reaction product of 1,6-hexanediol and dimethyl carbonate, 300 g), 19.9 g of 2,2-dimethylolpropionic acid (DMPA), and dicyclohexylmethane 4,4'-diisocyanate (H12MDI, 129 g) were heated in N-methylpyrrolidone (NMP, 149 g) in the presence of dibutyltin dilaurate (0.3 g) under a nitrogen atmosphere at 75 to 85°C for 5 hours. The reaction mixture was cooled to 80°C, and triethylamine (15.0 g) was added and mixed. 398 g of the resulting mixture was added to water (577 g) with vigorous stirring. Next, 24.7 g of a 35% by mass aqueous solution of diethylenetriamine (DETA) was added to obtain the aqueous dispersion (U6) of polyurethane resin having a solid content of 30% by mass.

[0139] Comparative Example 2 Aqueous Polyurethane Resin Dispersion (U7) Polycarbonate polyol (product name "ETERNACOLL (registered trademark) UH-100" manufactured by UBE Corporation; number average molecular weight 1,000; hydroxyl value 112.2 mg KOH / g; reaction product of 1,6-hexanediol and dimethyl carbonate, 300 g), 27.4 g of 2,2-dimethylolpropionic acid (DMPA), and dicyclohexylmethane 4,4'-diisocyanate (H12MDI, 218 g) were heated in ethyl methyl ketone (MEK, 113 g) in the presence of dibutyltin dilaurate (0.3 g) under a nitrogen atmosphere at 75 to 85°C for 5 hours. The reaction mixture was cooled to 80°C, and triethylamine (20.7 g) was added and mixed. 391 g of the mixture was added to water (564 g) with vigorous stirring. Next, 25.3 g of a 35% by mass aqueous solution of diethylenetriamine (DETA) and 19.9 g of a 35% by mass aqueous solution of 2-methyl-1,5-pentanediamine (MPMD) were added to obtain an aqueous dispersion of polyurethane resin. The aqueous dispersion was then distilled until the solids content reached 38% by mass, obtaining aqueous polyurethane resin dispersion (U7). Due to the poor film-forming properties of aqueous polyurethane resin dispersion (U7), a film with a thickness of 40 μm could not be obtained.

[0140] Comparative Example 3 Aqueous Polyurethane Resin Dispersion (U8) Polyether polyol (product name "PTMG1000" manufactured by Mitsubishi Chemical Corporation; number average molecular weight 1,000; hydroxyl value 112.2 mg KOH / g; polytetramethylene ether glycol, 300 g), 2,2-dimethylolpropionic acid (DMPA) 27.4 g, and dicyclohexylmethane 4,4'-diisocyanate (H12MDI, 218 g) were heated in ethyl methyl ketone (MEK, 113 g) in the presence of dibutyltin dilaurate (0.3 g) under a nitrogen atmosphere at 75 to 85°C for 5 hours. The reaction mixture was cooled to 80°C, and 390 g of the mixture was added to water (565 g) with vigorous stirring. Next, 25.3 g of a 35% by mass aqueous solution of diethylenetriamine (DETA) and 19.9 g of a 35% by mass aqueous solution of 2-methyl-1,5-pentanediamine (MPMD) were added to obtain an aqueous dispersion of polyurethane resin. The aqueous dispersion was then distilled until the solid content reached 38% by mass, obtaining aqueous polyurethane resin dispersion (U8).

[0141] Comparative Example 4 Aqueous Polyurethane Resin Dispersion (U9) A polycarbonate polyol (product name "ETERNACOLL (registered trademark) UC-100" manufactured by UBE Corporation; number average molecular weight 1,000; hydroxyl value 112.2 mgKOH / g; polycarbonate diol obtained by reacting 1,4-cyclohexanedimethanol with a carbonate ester, 173 g) and a polyether polyol (product name "PTMG2000" manufactured by Mitsubishi Chemical Corporation; number average molecular weight 2.0 00; hydroxyl value 56.1 mg KOH / g; polytetramethylene ether glycol (30.0 g), 25.4 g of 2,2-dimethylolpropionic acid (DMPA), and dicyclohexylmethane 4,4'-diisocyanate (H12MDI, 183 g) were heated in N-ethylpyrrolidone (NEP, 165 g) in the presence of dibutyltin dilaurate (0.3 g) under a nitrogen atmosphere at 75 to 85°C for 5 hours. The reaction mixture was cooled to 80°C, and triethylamine (19.2 g) was added and mixed. 398 g of the resulting mixture was added to water (531 g) with vigorous stirring. Next, a 35% by weight aqueous solution of 2-methyl-1,5-pentanediamine (MPMD) (71.2 g) was added to obtain an aqueous dispersion (U9) of polyurethane resin. The solids content was 30% by weight.

[0142]

[0143] In Table 1, "PCD / all polyols" means the content ratio of structures derived from polycarbonate polyols to structures derived from all polyols contained in the polyurethane resin. "Total content of urethane bonds and urea bonds" means the total content ratio of urethane bonds and urea bonds in the polyurethane resin.

[0144] In Table 1, the abbreviations are as follows: UH-100: Product name "ETERNACOLL (registered trademark) UH-100" manufactured by UBE Corporation; number average molecular weight 1,000; hydroxyl value 112.2 mg KOH / g; polycarbonate polyol obtained by reacting 1,6-hexanediol with dimethyl carbonate. UH-200: Product name "ETERNACOLL (registered trademark) UH-200" manufactured by UBE Corporation; number average molecular weight 2,000; hydroxyl value 56.1 mg KOH / g; polycarbonate polyol obtained by reacting 1,6-hexanediol with dimethyl carbonate. UP-100: Product name "ETERNACOLL (registered trademark) UP-100" manufactured by UBE Corporation; number average molecular weight 1,000; hydroxyl value 112.2 mg KOH / g; polycarbonate polyol obtained by reacting 2-methyl-1,3-propanediol with dimethyl carbonate. UC-100: Product name "ETERNACOLL (registered trademark) UC-100" manufactured by UBE Corporation; number average molecular weight 1,000; hydroxyl value 112.2 mg KOH / g; polycarbonate diol obtained by reacting 1,4-cyclohexanedimethanol with a carbonate ester. PTMG1000: Product name "PTMG1000" manufactured by Mitsubishi Chemical Corporation; number average molecular weight 1,000; hydroxyl value 112.2 mg KOH / g; polytetramethylene ether glycol. PTMG2000: Product name "PTMG2000" manufactured by Mitsubishi Chemical Corporation; number average molecular weight 2,000; hydroxyl value 56.1 mg KOH / g; polytetramethylene ether glycol. H12MDI: Dicyclohexylmethane 4,4'-diisocyanate. IPDI: Isophorone diisocyanate. DMPA: 2,2-dimethylolpropionic acid DETA: diethylenetriamine MPMD: 2-methyl-1,5-pentamethylenediamine EDA: ethylenediamine

[0145] The results in Table 1 show that the aqueous polyurethane resin dispersions of the Examples had excellent film-forming properties and solvent resistance. Furthermore, the results in Table 1 show that the aqueous polyurethane resin dispersions of the Examples had good dispersibility. A comparison of Examples 1 to 5 with Comparative Example 1 shows that solvent resistance is improved by setting the elastic modulus to 400 MPa or higher. A comparison of Examples 1 to 5 with Comparative Example 2 shows that the larger the average particle size of the polyurethane resin, the higher the solvent resistance. A comparison of Examples 1 to 5 with Comparative Examples 3 and 4 shows that the higher the content ratio of structures derived from polycarbonate polyol relative to all polyol-derived structures contained in the polyurethane resin, the higher the solvent resistance.

[0146] On the other hand, Comparative Examples 1 and 3 show that when the modulus of elasticity of a 40 μm thick film of the polyurethane resin dispersion was less than 400 MPa, the solvent resistance was poor. Also, Comparative Example 2 shows that when the average particle size of the polyurethane resin was less than 30 nm, the film-forming ability was poor. Furthermore, Comparative Example 4 shows that when the modulus of elasticity of a 40 μm thick film of the polyurethane resin dispersion exceeded 900 MPa, the solvent resistance was poor.

Claims

1. An aqueous polyurethane resin dispersion in which particles of a polyurethane resin (A) are dispersed in an aqueous medium (B), wherein the polyurethane resin (A) has a structure derived from an acidic group-free polyol (a), a structure derived from a polyisocyanate (b), and a structure derived from an acidic group-containing polyol (c), the particles of the polyurethane resin (A) have an average particle size of 30 to 80 nm, the average particle size being a value determined by a dynamic light scattering method, the acidic group-free polyol (a) comprises a polycarbonate polyol, and the aqueous polyurethane resin dispersion is heated at 60°C for 2 hours and then at 120°C for 2 hours, resulting in a 40 μm thick film having an elastic modulus of 400 MPa or more and 900 MPa or less.

2. The aqueous polyurethane resin dispersion according to claim 1, wherein the polyisocyanate (b) is an alicyclic polyisocyanate.

3. The aqueous polyurethane resin dispersion according to claim 1, wherein the total content of urethane bonds and urea bonds in the polyurethane resin (A) is 13.0 to 25.0 mass% based on the solid content of the polyurethane resin (A).

4. The aqueous polyurethane resin dispersion according to claim 1, wherein the content of structures derived from polycarbonate polyol relative to all structures derived from polyols contained in the polyurethane resin (A) is 60.0 to 95.0 mass%.

5. The aqueous polyurethane resin dispersion according to claim 1, wherein the acidic group-free polyol (a) further contains, as an optional component, only a polyester polyol and / or a polyether polyol, and the polyurethane resin (A) further has a structure derived from a compound (d) having a total of two or more groups selected from the group consisting of hydroxyl groups and amino groups (however, this is not a polycarbonate polyol, polyester polyol, polyether polyol, or acidic group-containing polyol (c)).

6. The aqueous polyurethane resin dispersion according to claim 5, wherein compound (d) comprises a polyamine compound having two primary amino groups and one or more secondary amino groups in one molecule and no hydroxyl group.

7. The aqueous polyurethane resin dispersion according to claim 1, wherein the molar ratio of the isocyanate groups of the polyisocyanate (b) to the total hydroxyl groups of the acidic group-free polyol (a) and the acidic group-containing polyol (c) (isocyanate groups / hydroxyl groups) is 0.5 to 3.

0.

8. A coating composition comprising the aqueous polyurethane resin dispersion according to any one of claims 1 to 7.

9. The coating composition according to claim 8, further comprising a water-insoluble organic solvent.

10. The coating composition of claim 8 for coating a metal substrate.

11. A laminate comprising a metal substrate and a coating layer formed thereon by drying the coating composition according to claim 8.

12. A polyurethane resin film obtained by drying a composition containing the aqueous polyurethane resin dispersion according to any one of claims 1 to 7.

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