Aqueous urethane resin dispersion and coating material composition, and the coating film thereof.

Abstract

To provide an aqueous urethane resin dispersion which is used for a composition forming a coating film having sufficient hardness, in low temperature drying at 20-100°C.SOLUTION: An aqueous polyurethane resin dispersion contains a polyurethane resin and an aqueous medium, wherein the polyurethane resin has a structural unit derived from polyester polyol (A) obtained by reacting polyol (Aa) with a dicarboxylic acid (Ab), and a structural unit derived from polyisocyanate (B), 80 mass% or more of polyol (Aa1) having a branched chain is contained in the total amount of the polyol (Aa), 80 mass% or more of an aromatic dicarboxylic acid (Ab1) is contained in the total amount of the dicarboxylic acid (Ab), and the aqueous polyurethane resin dispersion can contribute to SDGs (Sustainable Development Goals).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an aqueous urethane resin dispersion.

Background Art

[0002] Aqueous polyurethane resin dispersions can obtain a coating film having adhesiveness, abrasion resistance, and rubbery properties, and can reduce volatile organic compounds compared to conventional solvent-based polyurethanes. Therefore, they are materials that are increasingly replacing solvent-based polyurethanes as environmentally friendly materials. Aqueous polyurethane resin dispersions are used, for example, as materials with fracture resistance properties used for intermediate coats in automotive exterior finishes. When used as a film, paint or coating material, or a material with fracture resistance properties, an aqueous polyurethane resin dispersion is applied to a substrate or the like using a coating device such as a bar coater, a roll coater, or an air spray. A coating film is formed on the substrate by heating and drying the applied aqueous polyurethane resin dispersion.

[0003] It is known that a coating film obtained by applying an aqueous urethane resin dispersion made from polycarbonate polyol is excellent in light resistance, heat resistance, hydrolysis resistance, and oil resistance (see Patent Document 1).

[0004] On the other hand, a coating film obtained from an aqueous urethane resin dispersion using polyester polyol is known to be excellent in adhesion to various substrates (Patent Documents 2 to 4). Patent Document 2 describes that a polyurethane resin aqueous dispersion obtained by crosslinking a urethane prepolymer having an isocyanate group at the terminal, which is composed of a polyester glycol composed of an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, and a branched glycol, a polyol having three or more hydroxyl groups, an organic diisocyanate, and a chain extender having a free carboxyl group with water, is excellent in adhesion to a wide variety of resins and can obtain a coating film with high transparency and uniformity.

[0005] Patent Document 3 describes an aqueous polyurethane resin dispersion composed of a polyester polyol having aromatic dicarboxylic acid, aliphatic dicarboxylic acid, and branched glycol as constituent components, and a polyol having three or more hydroxyl groups, which has high adhesion to a wide range of plastic substrates and excellent water resistance and blocking resistance. Patent Document 4 describes how a polyurethane resin composition with excellent solvent resistance, adhesion, and flexibility to polar solvents can be obtained by a special emulsification method. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-120757 [Patent Document 2] Japanese Patent Publication No. 2016-084415 [Patent Document 3] Japanese Patent Publication No. 2002-234931 [Patent Document 4] Japanese Patent Publication No. 2013-155335 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Although the polyurethane resin compositions using polyester polyols described in Patent Documents 2 to 4 have been shown to have high adhesion to various resins, they did not provide sufficient adhesion or hardness in the coating film when dried at a low temperature (e.g., 80°C) for a short time (e.g., 10 minutes). Furthermore, in applications requiring fracture-resistant materials, conventional aqueous polyurethane resin dispersions require a drying process at 140°C or higher because they contain melamine crosslinking agents.

[0008] From the perspective of reducing greenhouse gas emissions, lowering the drying temperature from the conventional 140°C or higher to 20-100°C when creating coatings is expected to reduce energy costs and environmental impact. Furthermore, for applications requiring fracture resistance, the resulting coating needs to have sufficient hardness.

[0009] Therefore, the object of the present invention is to provide an aqueous urethane resin dispersion that can be used in a composition that forms a coating film having sufficient hardness when dried at low temperatures of 20 to 100°C. [Means for solving the problem]

[0010] The inventors have discovered that by using a special polyester polyol, an aqueous urethane resin dispersion can be obtained that provides a highly hard coating film through low-temperature, short-time drying. In a preferred embodiment, they have also found that an aqueous urethane resin dispersion can be provided that provides a coating film with high elastic modulus, excellent adhesion to the substrate, and high fracture energy through low-temperature, short-time drying. By enabling low-temperature, short-time processing, it is possible to contribute to the achievement of SDGs (Sustainable Development Goals) Goal 7, etc.

[0011] The present invention is specifically as follows: [1] An aqueous polyurethane resin dispersion comprising a polyurethane resin and an aqueous medium, The polyurethane resin has constituent units derived from a polyester polyol (A) composed of a polyol (Aa) and a dicarboxylic acid (Ab), and constituent units derived from a polyisocyanate (B). The total amount of the polyol (Aa) contains 80% by mass or more of a branched polyol (Aa1), An aqueous polyurethane resin dispersion containing 80% by mass or more of aromatic dicarboxylic acid (Ab1) in the total amount of the dicarboxylic acid (Ab). [2] An aqueous polyurethane resin dispersion of [1], wherein the polyurethane resin further comprises a constituent unit derived from an acidic group-containing polyol (C) and a constituent unit derived from a chain extender (E). [3] An aqueous polyurethane resin dispersion of [1], wherein the two carboxyl groups in the aromatic dicarboxylic acid (Ab) are in a para position on the benzene ring. [4] An aqueous polyurethane resin dispersion of [1], wherein the branched polyol (Aa1) is a diol having a quaternary carbon atom. [5] An aqueous polyurethane resin dispersion of [2], wherein the chain extender (E) is a polyamine. [6] The aqueous polyurethane resin dispersion of [1], wherein the polyurethane resin has constituent units derived from polyester polyol (A) and polyol (F) other than acid group-containing polyol. [7] The aqueous polyurethane resin dispersion of [6], wherein the polyol (F) is a polyether polyol and / or a polycarbonate polyol. [8] An aqueous polyurethane resin dispersion of [6] wherein the polyol (F) has 2 hydroxyl groups. [9] An aqueous polyurethane resin dispersion of [6], wherein the mass ratio of the polyester polyol (A) to the polyol (F) is 50:50 to 90:10.

[10] An aqueous polyurethane resin dispersion of [1], comprising 50 to 100% by mass of an alicyclic polyisocyanate in the total amount of the polyisocyanate (B).

[11] The aqueous polyurethane resin dispersion of [1], wherein the weight-average molecular weight of the polyurethane resin is 100,000 or more.

[12] An aqueous polyurethane resin dispersion of [1], wherein the hydroxyl value of the polyester polyol (A) is 55 to 140 mg KOH / g. A coating material composition comprising an aqueous polyurethane resin dispersion of

[13] [1]. A coating film obtained by applying and drying the coating material composition of

[14]

[13] .

[15] The coating film of

[14] obtained by drying the coating material composition at 80°C for 10 minutes, wherein the coating film is 13-15 μm thick and has a König hardness of more than 120. A method for manufacturing a coating film, comprising the step of drying the coating material composition of

[16]

[13] at 20°C to 100°C.

[17] A coating material composition according to

[13] for a primer or base coat for metal exterior.

[18] A coating material composition according to

[13] for a material with fracture resistance characteristics.

[19] A coating material composition according to

[13] for a floor coat, a plastic or rubber coat.

[20] A steel plate treatment agent containing the coating material composition according to

[13] .

Advantages of the Invention

[0012] The composition containing the aqueous polyurethane resin dispersion of the present invention forms a coating film having sufficient hardness in low-temperature drying at 20 to 100°C.

Modes for Carrying Out the Invention

[0013] The present invention is an aqueous polyurethane resin dispersion containing a polyurethane resin and an aqueous medium, where the polyurethane resin has a structural unit derived from a polyester polyol (A) composed of a polyol (Aa) and a dicarboxylic acid (Ab), and a structural unit derived from a polyisocyanate (B), where the total amount of the polyol (Aa) contains 80% by mass or more of a polyol (Aa1) having a branched chain, and the total amount of the dicarboxylic acid (Ab) contains 80% by mass or more of an aromatic dicarboxylic acid, and is an aqueous polyurethane resin dispersion.

[0014] It is preferable that the polyurethane resin further has a structural unit derived from an acidic group-containing polyol (C), a structural unit derived from a chain extender (E), and a structural unit derived from a polyol (F) other than the components (A) and (C). Also, it is preferable that the aqueous polyurethane resin dispersion is neutralized by a neutralizing agent (D) for the above polyurethane resin.

[0015] In other words, in polyurethane resins, the polyol (X) that reacts with polyisocyanate (B) to constitute the polyurethane resin includes polyester polyol (A), optionally acidic group-containing polyol (C), and optionally polyol (F). On the other hand, the polyol (Aa) that reacts with dicarboxylic acid (Ab) to constitute polyester polyol (A) includes branched polyol (Aa1) and optionally linear polyol (Aa2). Furthermore, the dicarboxylic acid (Ab) includes aromatic dicarboxylic acid (Ab1) and optionally aliphatic dicarboxylic acid (Ab2).

[0016] In this specification, "substantially 100% by mass" means that it does not contain other components to such an extent that they alter the properties of the aqueous polyurethane resin dispersion or the function and properties of the coating film obtained from the aqueous polyurethane resin dispersion, but it does not exclude the inclusion of other components to an extent that does not impair the function or properties.

[0017] <Polyester polyol (A)> Polyester polyol (A) is a polyol composed of polyol (Aa) and dicarboxylic acid (Ab). Polyester polyol (A) can be obtained by a method similar to that of known polyester production methods, which involve dehydrating and condensing polyol (Aa) and dicarboxylic acid (Ab).

[0018] From the viewpoint of obtaining a coating film with high hardness through low-temperature, short-time drying, the polyester polyol (A) is preferably present in an amount of 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and particularly preferably 80% by mass or more, of the total polyol (X) constituting the polyurethane resin. Within this range, a coating film with high elastic modulus can also be obtained through low-temperature, short-time drying. Furthermore, from the viewpoint of obtaining a coating film with high adhesion through low-temperature, short-time drying, the polyester polyol (A) is preferably present in an amount of 100% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less, of the total polyol (X) constituting the polyurethane resin.

[0019] The polyester polyol (A) preferably has two hydroxyl groups. In other words, it is preferably a polyester diol. This is because the aqueous polyurethane resin dispersion can form a coating film with excellent hardness and adhesion without crosslinking, so crosslinking is not necessarily required.

[0020] The acid value of polyester polyol (A) is preferably 0.01 to 5.0 mgKOH / g. Within this range, a polyurethane resin with particularly good physical properties can be obtained using it as a raw material. The acid value is more preferably 0.01 to 1.0 mgKOH / g, and even more preferably 0.01 to 0.5 mgKOH / g. By setting it within this range, the hardness of the coating film obtained by drying the aqueous urethane resin dispersion and the adhesion to the electrodeposited surface can be improved. In this specification, the acid value shall be the value measured in accordance with the indicator titration method of JIS K 1557.

[0021] The hydroxyl value of polyester polyol (A) is preferably 22.5 to 280 mg KOH / g, more preferably 35 to 225 mg KOH / g, even more preferably 55 to 140 mg KOH / g, and particularly preferably 55 to 125 mg KOH / g. Within this range, the hardness of the coating film obtained by drying the aqueous urethane resin dispersion and its adhesion to the electrodeposited surface can be improved. In this specification, the hydroxyl value shall be the value measured in accordance with Method B of JIS K 1557.

[0022] The number-average molecular weight Mn of polyester polyol (A) is preferably 400 to 5000. Within this range, fluidity (e.g., viscosity of 500 to 10000 cP) can be easily obtained under heating (e.g., 75°C), and it is easy to handle. The number-average molecular weight Mn is more preferably 500 to 3000, even more preferably 800 to 2000, and particularly preferably 900 to 2000. In this specification, the number-average molecular weight Mn is the number-average molecular weight calculated based on the hydroxyl value measured in accordance with JIS K 1577. Specifically, the hydroxyl value is measured and calculated using the terminal group determination method, with the formula being (56.1 × 1000 × valency) / hydroxyl value (in this formula, the unit of hydroxyl value is [mgKOH / g]). In the above formula, the valency is the number of hydroxyl groups in one molecule.

[0023] <Polyol (Aa)> The polyol (Aa) used in this invention reacts with the dicarboxylic acid (Ab), described later, to form a polyester polyol (A).

[0024] The polyol (Aa) contains a branched-chain polyol (Aa1), the amount of which is 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass, and even more preferably substantially 100% by mass, based on the total amount of polyol (Aa).

[0025] The branched polyol (Aa1) refers to a polyol having a tertiary or quaternary carbon atom in one molecule. Examples include 1,2-propylene glycol, 1-methyl-1,3-butylene glycol, 2-methyl-1,3-butylene glycol, neopentyl glycol, 1-methyl-1,4-pentanediol, 2-methyl-1,4-pentanediol, 3-methyl-1,4-pentanediol, 1-methyl-1,5-pentanediol, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,2-dimethylbutylene glycol, 1,3-dimethylbutylene glycol, 2,3-dimethylbutylene glycol, and 1,4-dimethylbutylene glycol. However, from the viewpoint of improving the hardness and adhesion of the resulting coating film, among these, a diol having a quaternary carbon atom is preferred, and neopentyl glycol is more preferred. Furthermore, the branched polyol preferably has 4 to 8 carbon atoms, and the branched chain represents a hydrocarbon group, preferably an alkyl group having 1 to 4 carbon atoms, and more preferably an alkyl group having 1 to 2 carbon atoms. These branched polyols (Aa1) can be used alone or in combination of two or more types.

[0026] Polyol (Aa) may include not only branched polyols (Aa1) but also straight-chain polyols (Aa2). As the linear polyol (Aa2), short-chain aliphatic diols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol can be used, with 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol being preferred. The content of the linear polyol (Aa2) is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably substantially 0% by mass, based on the total amount of polyol (Aa). These linear polyols (Aa2) can be used individually or in combination of two or more.

[0027] <Dicarboxylic acid (Ab)> The polyol (Aa) used in this invention reacts with a dicarboxylic acid (Ab) to form a polyester polyol (A).

[0028] The dicarboxylic acid (Ab) contains aromatic dicarboxylic acid (Ab1), and its content is 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass, and even more preferably substantially 100% by mass, based on the total amount of dicarboxylic acid (Ab).

[0029] Examples of aromatic dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, tetrahydrophthalic acid, etc., or reactive derivatives such as acid anhydrides, alkyl esters, and acid halides thereof. Phthalic acid, isophthalic acid, and terephthalic acid are preferred, and these aromatic dicarboxylic acids may have a C1-C4 alkyl group and / or a C1-C4 alkoxy group on their aromatic ring. These aromatic dicarboxylic acids can be used alone or in combination of two or more. Among these, from the viewpoint of increasing the hardness of the resulting coating film, it is preferable that the two carboxyl groups in the aromatic dicarboxylic acid are in a para position on the benzene ring, and terephthalic acid is more preferred.

[0030] The dicarboxylic acid (Ab) may include an aliphatic dicarboxylic acid (Ab2) in addition to the aromatic dicarboxylic acid (Ab1). The aliphatic dicarboxylic acid is not particularly limited, but examples include malonic acid, succinic acid, tartaric acid, oxalic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, alkylsuccinic acid, linolenic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, etc., or reactive derivatives such as acid anhydrides, alkyl esters, and acid halides thereof. These aliphatic dicarboxylic acids can be used alone or in combination of two or more. The content of the aliphatic dicarboxylic acid is 20% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably substantially 0% by mass, based on the total amount of dicarboxylic acid (Ab).

[0031] <(A) and (C) other polyols (F)> Polyurethane resin may contain polyol (F) in addition to polyester polyol (A) and acidic group-containing polyol (C) described later, as a component that can be reacted with polyisocyanate (B) described later to form a polyurethane resin. Such polyols (F) are preferably present in amounts of less than 70% by mass, more preferably less than 60% by mass, even more preferably 10 to 50% by mass, and particularly preferably 10 to 40% by mass, of the total polyols (X) constituting the polyurethane resin. The type and amount of polyols (F) can be appropriately adjusted by those skilled in the art, as long as the effects of the present invention are not impaired. Other polyols (F) may not be present in the polyols.

[0032] As the polyol (F), any known polyol can be used. Examples include high molecular weight polyols such as polycarbonate polyols; polyethylene glycol, polypropylene glycol, polytetramethylene glycol, random copolymers and block copolymers of ethylene oxide and propylene oxide, ethylene oxide and butylene oxide, and polyether polyols such as polytetramethylene ether glycol; short-chain aliphatic diols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 3-methyl-1,5-pentanediol, and 2-butyl-2-ethyl-1,3-propanediol; alicyclic diols such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and hydrogenated bisphenol A; and diols such as bisphenol A, hydroquinone, bishydroxyethoxybenzene, and their alkylene oxide adducts. Polyol (F) can be used alone or in combination of two or more types. Among these, high molecular weight polyols are preferred from the viewpoint of substrate adhesion and fracture energy, and polyether polyols and / or polycarbonate polyols are more preferred. The polyol (F) described above may be a commercially available product or one that has been prepared individually.

[0033] The polyol (F) preferably has two hydroxyl groups; in other words, it is preferably a diol. This is because the aqueous polyurethane resin dispersion can form a coating film with excellent hardness and adhesion without crosslinking, so crosslinking is not necessarily required. From the viewpoint of adhesion, it is preferable not to have crosslinking.

[0034] The number-average molecular weight of the high molecular weight polyol is preferably 500 to 10000, more preferably 650 to 5000, and even more preferably 900 to 3000.

[0035] The hydroxyl value of the high molecular weight polyol is preferably 10 to 225, more preferably 22 to 175, and even more preferably 37 to 125.

[0036] Polycarbonate polyols used as polyol (F) are obtained by reacting one or more polyol components with a carbonate ester or phosgene. From the standpoint of safety and ease of handling of reagents, and because there is no by-production of terminal chlorinated products, polycarbonate polyols obtained by reacting one or more polyol monomers with a carbonate ester are preferred.

[0037] Known polyol components can be used for polycarbonate polyols. Examples include aliphatic polyols such as linear aliphatic diols like 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol, and branched aliphatic diols like 2-methyl-1,3-propanediol and 2-methyl-1,5-pentanediol; diols having an alicyclic structure in the main chain, such as 1,4-cyclohexanedimethanol; and polyester polyols and polyether polyols. The polyol component of polycarbonate polyols may be used alone or in combination of multiple types.

[0038] Polycarbonate polyols may contain fewer ether or ester bonds in their molecules than the average number of carbonate bonds in one molecule, provided that the properties of the polycarbonate polyol are not impaired.

[0039] The mass ratio of polyester polyol (A) to polyol (F) is preferably 50:50 to 90:10, more preferably 55:45 to 80:20, and even more preferably 60:40 to 70:30. The above mass ratio is preferable because it allows for high adhesion to the electrodeposited surface and increased fracture energy while maintaining high König hardness with low-temperature, short-time drying at 80°C for 10 minutes.

[0040] <Polyisocyanate (B)> Known polyisocyanates (B) can be used. For example, 1,3-phenylenediisocyanate, 1,4-phenylenediisocyanate, 2,4-tolylenediisocyanate (TDI), 2,6-tolylenediisocyanate, 4,4'-diphenylmethanediisocyanate (MDI), 2,4-diphenylmethanediisocyanate, 4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanate Aromatic polyisocyanates such as anatodiphenylmethane, 1,5-naphthylene diisocyanate, 4,4',4''-triphenylmethane triisocyanate, m-isocyanatophenylsulfonyl isocyanate, and p-isocyanatophenylsulfonyl isocyanate; ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate (PDI), and hexamethylene diisocyanate (HDI). Aliphatic polyisocyanates such as dodecamethylene diisocyanate, 1,6,11-undecane triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethyl caproate, bis(2-isocyanatoethyl) fumarate, bis(2-isocyanatoethyl) carbonate, and 2-isocyanatoethyl-2,6-diisocyanatohexanoate; isophorone Examples include alicyclic polyisocyanates such as diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate (hydrogenated TDI), bis(2-isocyanatoethyl)-4-diclohexene-1,2-dicarboxylate, 2,5-norbornane diisocyanate, and 2,6-norbornane diisocyanate. Polyisocyanate (B) may have part or all of its structure derivatized by isocyanuration, carbodiimide, or biuretization. Polyisocyanate (B) may be used alone or in combination of multiple types.

[0041] Among the polyisocyanates (B) described above, alicyclic polyisocyanates are preferred from the viewpoint of substrate adhesion, and 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI) is more preferred from the viewpoint of hardness and fracture energy. In polyisocyanate (B), the amount of alicyclic polyisocyanate is preferably 50 to 100% by mass, more preferably 70 to 100%, and even more preferably 90 to 100%.

[0042] Polyisocyanate (B) may be used alone or in combination of multiple types. It is preferable that polyisocyanate (B) does not contain blocked isocyanates. This is because, when aqueous polyurethane resin dispersions are used as coating films, they cure at low temperatures, and blocked isocyanates, which require high temperatures to release the block and activate the isocyanate, are unsuitable.

[0043] The amount of polyisocyanate (B) used is preferably such that the ratio of isocyanate groups of polyisocyanate (Ab) to hydroxyl groups of the total polyol (the sum of polyester polyol (A), polyol (F), and acidic group-containing polyol (C)) (isocyanate groups / hydroxyl groups (molar ratio)) is 1.6 to 2.3, and particularly preferably 1.65 to 2.05.

[0044] <Acidic group-containing polyol (C)> An acidic group-containing polyol (C) is one that contains two or more hydroxyl groups and one or more acidic groups in a single molecule. An acidic group-containing polyol (C) may be used alone or in combination of multiple types.

[0045] As the acidic group-containing polyol (C), known polyols can be used. For example, dimethylolalkanoates 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 are examples. Among these, dimethylolalkanoates with 4 to 12 carbon atoms containing two methylol groups are preferred from the viewpoint of ease of availability, and among dimethylolalkanoates, 2,2-dimethylolpropionic acid is more preferred.

[0046] From the viewpoint of resin dispersibility, the acidic group-containing polyol (C) is preferably present in an amount of 4 to 20% by mass, more preferably in an amount of 8 to 18% by mass, even more preferably in an amount of 10 to 16% by mass, and particularly preferably in an amount of 12 to 15% by mass, of the total polyol (X) constituting the polyurethane resin.

[0047] In an aqueous polyurethane resin dispersion, the total hydroxyl group equivalent number of the polyester polyol (A), acidic group-containing polyol (C), and polyol (F) is preferably 50 to 4000. If the hydroxyl group equivalent number is within this range, the aqueous polyurethane resin dispersion containing the obtained polyurethane resin is easily manufactured. From the viewpoint of the rupture energy of the coating film obtained from the aqueous polyurethane resin dispersion, the hydroxyl group equivalent number is preferably 100 to 2500, more preferably 120 to 1500, and particularly preferably 150 to 1000.

[0048] The hydroxyl group equivalents can be calculated using the following formulas (1) and (2). Number of hydroxyl groups equivalent to each polyol component = Molecular weight of each polyol component / Number of hydroxyl groups in each polyol component ... (1) Total hydroxyl group equivalents of polyol components = M / Total number of moles of polyol components ... (2) In equation (2), M represents [[Number of hydroxyl group equivalents of polyester polyol (A) × Number of moles of polyester polyol (A)] + [Number of hydroxyl group equivalents of acidic group-containing polyol (C) × Number of moles of acidic group-containing polyol (C)] + [Number of hydroxyl group equivalents of polyol (F) × Number of moles of polyol (F)].

[0049] <Neutralizing agent (D)> The neutralizing agent (D) may be used alone or in combination of multiple types.

[0050] As the neutralizing agent (D), known substances can be used. For example, non-volatile bases such as sodium hydroxide and potassium hydroxide; tertiary amines such as trimethylamine, triethylamine, dimethylethanolamine, methyldiethanolamine, and triethanolamine; secondary amines such as dimethylamine, diethylamine, and dibutylamine; primary amines such as ethylenediamine, methylamine, ethylamine, and butylamine; and ammonia can be used.

[0051] The neutralizing agent (D) described above preferably has a boiling point of 200°C or lower, and more preferably in the range of -50 to 180°C, since it volatilizes at the temperature during drying of the aqueous medium in the coating material composition (usually 50 to 180°C) and disappears from the polyurethane film, thereby obtaining even higher hardness. When obtaining a dried coating film in a short time of a few seconds to 1 hour at a low temperature of 100°C or lower, its boiling point preferably has a boiling point of 130°C or lower, and more preferably has a boiling point of 110°C or lower.

[0052] When using the neutralizing agent (D) described above, the amount used is preferably in the range of 0.8 to 1.2 times the number of moles of acidic groups in the acidic group-containing polyol (C) contained in the aqueous polyurethane resin dispersion. If the amount of the neutralizing agent (D) used is 0.8 times or more the number of moles of acidic groups contained in the aqueous polyurethane resin dispersion, the stability of the resulting dispersion is high, and if it is 1.2 times or less, a coating film with high hardness, substrate adhesion, and fracture energy can be obtained in a short time of a few seconds to 10 minutes under low-temperature drying conditions of 100°C or below.

[0053] <Chain extender (E)> The chain extender (E) is a compound that reacts with the isocyanate group of the polyurethane prepolymer. The chain extender (E) may be used alone or in combination of multiple types. In this specification, polyols that also function as chain extenders are not included in chain extender (E) but are included in polyol (X).

[0054] Known substances can be used as the chain extender (E). Examples include amines such as ethylenediamine, 1,4-tetramethylenediamine, 2-methyl-1,5-pentanediamine, 1,4-butanediamine, 1,6-hexamethylenediamine, 1,4-hexamethylenediamine, 3-aminomethyl-3,5,5-trimethylcyclohexylamine, 1,3-bis(aminomethyl)cyclohexane, xylylenediamine, piperazine, 2,5-dimethylpiperazine, and aminoethylethanolamine; and water, with amines being preferred.

[0055] Among the above chain extenders (E), diamines with a number-average molecular weight (Mn) of 300 or less are preferred. Having a Mn of 300 or less is necessary to increase the cohesive strength of the polyurethane resin, and the use of diamines is preferable not only for increasing the Mn of the polyurethane resin and improving its durability, but also from the viewpoint of rupture energy.

[0056] The amount of the chain extender (E) added is preferably less than or equal to the equivalent amount of isocyanate groups that serve as chain extension starting points in the resulting urethane polymer. If the amount of chain extender (E) added exceeds the equivalent amount of isocyanate groups, the molecular weight of the chain-extended urethane polymer may decrease, reducing its cohesive force and potentially lowering its breaking energy.

[0057] In addition to the examples above, the chain extender (E) may also be a compound having three or more functional groups that are reactive with isocyanate groups. By using such a compound, it becomes easier to control the content of N(C=O)NH groups. As a result, it becomes easier to control the drying rate when forming a coating film. Examples of such compounds include polyamines having a total of three or more amino groups and / or imino groups in one molecule, and compounds such as diethylenetriamine can be used.

[0058] <Polyurethane resin> The polyurethane resin in the aqueous polyurethane resin dispersion of the present invention preferably has the following characteristics.

[0059] The number-average molecular weight (Mn) of the polyurethane resin is preferably 50,000 or more, and more preferably 100,000 or more, from the viewpoint of the rupture energy of the low-temperature dried coating film. By setting the number-average molecular weight to 50,000 or more, the coating film obtained by drying the composition at a temperature of 100°C or below exhibits a superior rupture energy. There is no particular upper limit as long as it can be synthesized and has a viscosity that allows it to be handled as an aqueous dispersion. The upper limit of the number-average molecular weight is usually 2,000,000 or less, and preferably 1,000,000 or less.

[0060] The weight-average molecular weight (Mw) of the polyurethane resin is preferably 100,000 or more, and more preferably 400,000 or more. A weight-average molecular weight within the above range is preferable from the viewpoint of the rupture energy of the coating film.

[0061] The acid value of polyurethane resin is not particularly limited, but is preferably 18-40 mgKOH / g on a solid content basis, and more preferably 20-35 mgKOH / g. When the acid value of polyurethane resin is greater than 40 mgKOH / g on a solid content basis, the dispersibility in aqueous media tends to deteriorate. When the acid value is less than 18 mgKOH / g on a solid content basis, the adhesion to the substrate tends to decrease. The acid value can be measured in accordance with the indicator titration method of JIS K 1557. In the measurement, the neutralizing agent used to neutralize the acidic group should be removed before measurement. For example, when organic amines are used as neutralizing agents, the aqueous polyurethane resin dispersion can be applied to a glass plate, dried at 60°C under reduced pressure of 20 mmHg for 24 hours, and the resulting coating film can be dissolved in N-methylpyrrolidone (NMP) and the acid value can be measured in accordance with the indicator titration method of JIS K 1557.

[0062] <Water-based polyurethane resin dispersion> The aqueous polyurethane resin dispersion comprises the polyurethane resin and an aqueous medium, wherein the polyurethane resin is dispersed in the aqueous medium. Examples of aqueous media include tap water, deionized water, distilled water, ultrapure water, and mixed media of water and hydrophilic organic solvents. 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, and diethylene glycol; amides such as β-alkoxypropionamide, typified by KJ Chemical's "KJCMPA(R)-100"; and hydroxyl-containing tertiary amines such as 2-(dimethylamino)-2-methyl-1-propanol (DMAP).

[0063] The amount of hydrophilic organic solvent in the aqueous medium is preferably 0 to 20% by mass, more preferably 0 to 15% by mass, and even more preferably 0 to 10% by mass.

[0064] The pH of the aqueous polyurethane resin dispersion is preferably 5.0 to 10.0, more preferably 6.0 to 9.5, and even more preferably 6.5 to 9.0.

[0065] The proportion of polyurethane resin in the aqueous dispersion is preferably 5 to 60% by mass, more preferably 20 to 50% by mass.

[0066] <Method for producing aqueous polyurethane resin dispersion> Aqueous polyurethane resin dispersions can be produced by known methods described in International Publication No. 2016 / 039396, etc. For example, the following production methods can be cited. The first manufacturing method involves mixing all the raw materials, reacting them, and dispersing them in an aqueous medium to obtain an aqueous polyurethane resin dispersion. The second manufacturing method involves reacting the entire polyol component with a polyisocyanate to produce a prepolymer, neutralizing the acidic groups of the prepolymer, dispersing it in an aqueous medium, and reacting it with a chain extender to obtain an aqueous polyurethane resin dispersion. As a method for producing an aqueous polyurethane resin dispersion, the second method described above is preferred because it allows for easy control of the molecular weight.

[0067] In particular, in the present invention, an aqueous polyurethane resin dispersion can be produced by a method comprising the following (I) to (IV) and optionally (V). (I) A step of reacting a polyester polyol (A), a polyisocyanate (B), an arbitrary acidic group-containing polyol (C), and an arbitrary polyol (F) in the presence or absence of an organic solvent to obtain a polyurethane prepolymer. (II) A step of neutralizing the acidic groups of the polyurethane prepolymer with a neutralizing agent (D), (III) A step of dispersing the polyurethane prepolymer in an aqueous medium, (IV) A step of increasing the molecular weight of the polyurethane prepolymer with a chain extender (E), and optionally, (V) Step to remove organic solvents.

[0068] <Coating material composition> The aqueous polyurethane resin dispersion is used in a coating material composition. In this specification, a coating material composition refers to a material that forms a coating film when applied to an electrodeposited surface, steel plate, wood, or plastic substrate using a spray, brush, applicator, bar coater, or the like.

[0069] The coating material composition contains the aqueous polyurethane resin dispersion as an essential component, but may also contain other resins and / or other additives as needed. Hereinafter, when the term "coating material composition" is used in this specification, it includes not only compositions containing other resins, additives, etc., but also compositions consisting solely of the aqueous polyurethane resin dispersion.

[0070] Examples of the aforementioned other resins include acrylic resins, olefin resins, polyester resins, vinyl chloride resins, and nylon resins in emulsion form. Among these, acrylic emulsions, polyolefin emulsions, and polyester emulsions are preferred, and a coating material composition obtained by mixing at least one of these as an optional component is preferred.

[0071] Other additives that can be used include, for example, film-forming aids, curing agents, crosslinking agents, surface modifiers, emulsifiers, thickeners, urethane catalysts, fillers, foaming agents, pigments, dyes, oil repellents, hollow foams, flame retardants, defoamers, leveling agents, and anti-blocking agents. These additives may be used individually or in combination of two or more.

[0072] As a surface modifier, any substance that can eliminate defects in the coating film caused by changes in viscosity, surface tension, and foam formation associated with high molecular weight can be used without particular limitations. Examples include various surface modifiers, leveling agents, wetting agents, and defoaming agents such as acrylic, vinyl, silicone, fluorine, cellulose, natural wax, and water-soluble organic solvents, as well as surfactants, with wetting agents being particularly preferred.

[0073] Glycol ethers are an example of film-forming aids.

[0074] The method for producing the coating material composition is not particularly limited, but known production methods can be used. For example, it can be produced by stirring and mixing the aqueous polyurethane resin dispersion, and as optional components, the other resins and various additives mentioned above.

[0075] In the coating material composition, the mixing ratio of the aqueous polyurethane resin dispersion to the other resin is preferably 100 / 0 to 10 / 90 (solids mass ratio), more preferably 100 / 0 to 15 / 85, even more preferably 90 / 10 to 20 / 80, and particularly preferably 80 / 20 to 30 / 70, from the viewpoint of substrate adhesion and fracture energy.

[0076] <Curing method> The coating material composition can be cured and a coating film obtained by heating it to a temperature of 20°C or higher, preferably 100°C or lower, and more preferably 80°C or lower. Specifically, the coating material composition can be applied to various plastic substrates such as electrodeposited surfaces, steel plates, wood, polycarbonate resin, acrylic resin, polyethylene terephthalate (PET) resin, and acrylonitrile butadiene styrene (ABS) resin using a spray, brush, applicator, bar coater, etc., and cured by holding it in an oven or heating bath at 100°C or lower, preferably 80°C, for 1 to 120 minutes, preferably 1 to 60 minutes, more preferably 1 to 45 minutes, and even more preferably 1 to 20 minutes. The dry film thickness of the coating film is preferably adjusted to 0.5 to 200 μm, more preferably 1 to 100 μm, even more preferably 5 to 50 μm, and particularly preferably 10 to 40 μm. When used as a primer, base coat, etc. in a multi-layer coating, after applying it to the various substrates mentioned above, for example, it can be held at room temperature to 80°C for 1 to 30 minutes, preferably 1 to 10 minutes, more preferably 2 to 6 minutes, and then another base coat can be applied as an optional component. After drying at the same drying temperature and time, a top coat (referred to as a clear coat depending on the application) can be applied and then heat-cured at 100°C or below, preferably 80°C or below, for 10 to 120 minutes, preferably 20 to 90 minutes, more preferably 30 to 60 minutes. A coating film is obtained by drying the coating material composition at 20°C to 100°C.

[0077] <Physical properties of the coating film> The coating material composition can be dried after application to obtain a coating film. The breaking energy of the coating film obtained from the coating material composition, as measured by the method described in the examples, is preferably 100 MPa or higher, more preferably 110 MPa or higher, and even more preferably 120 MPa or higher. The above values ​​can be achieved, for example, in an embodiment in which polyol (F) is used and polyester polyol (A) and polyol (F) are within a specific range.

[0078] The adhesion of the coating film obtained from the coating material composition to the electrodeposited surface, as measured by the method described in the Examples, is preferably 80 / 100 or higher, and more preferably 100 / 100. Here, in the present invention, the evaluation of the adhesion of the coating film is expressed as "n / 100". n means the number of squares remaining when at least one square peeled off under the test conditions described below. The conditions for the adhesion test are described in detail in the Examples section. The above values ​​can be achieved, for example, in an embodiment in which polyol (F) is used and polyester polyol (A) and polyol (F) are within a specific range.

[0079] The measured König hardness of a 13-15 μm coating film obtained by drying a coating film from the coating material composition at 80°C for 10 minutes using the method described in the examples is preferably greater than 120, and more preferably 123 or higher.

[0080] The elastic modulus of the coating film obtained from the coating material composition of the present invention, as measured by the method described in the examples, is preferably 1400 MPa or higher, more preferably 1500 MPa or higher, and even more preferably 2000 MPa or higher.

[0081] <Application> The coating material composition can be suitably used as a primer material, a base coat material, and a fracture-resistant material. In this specification, a fracture-resistant material refers to a material used as a protective agent for a substrate and which itself has properties that make it difficult to break against physical impacts such as collisions, flying stones, and drops. The coating material composition containing the aqueous polyurethane resin dispersion of the present invention can be suitably used as a fracture-resistant material.

[0082] The primer materials, base coat materials, and fracture-resistant materials are useful for a wide range of applications, including floor coatings, coatings for various plastic substrates such as polycarbonate resin, acrylic resin, polyethylene terephthalate (PET) resin, and acrylonitrile butadiene styrene (ABS) resin, as well as coatings for rubber, steel plate treatment agents, and primers or base coats for metal exteriors such as automobiles, trucks, and trains. They are particularly useful for use as primers or base coats for metal exteriors. [Examples]

[0083] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto. The following physical property measurements were performed.

[0084] (1) The weight-average molecular weight of the polyurethane resin in the aqueous polyurethane resin dispersion was measured by gel permeation chromatography (GPC), and the converted value obtained from a pre-prepared calibration curve of standard polystyrene is indicated. (2) The acid value was measured in accordance with the indicator titration method of JIS K 1557.

[0085] (3) Dispersibility was confirmed by the absence of particles larger than 1 μm in the particle size distribution. The particle size distribution was measured using a HORIBA LA-960V2 laser diffraction / scattering particle size distribution analyzer.

[0086] (4) The König hardness of the coating film was evaluated as follows: Dipropylene glycol n-butyl ether (Dawanol® DPnB, manufactured by Ando Parachemy) was added as a film-forming aid at a concentration of 2% by mass to each aqueous polyurethane resin dispersion, and a silicone-based surfactant (BYK-345, manufactured by Bic Chemie) was added at a concentration of 0.5% by mass to each aqueous polyurethane resin dispersion. The resulting coating material composition was uniformly applied to an automotive cationic electrodeposition coating board manufactured by Nippon Test Panel using a bar coater #20. The board was then dried at 80°C for 10 minutes. The thickness of the resulting coating film was 13-15 μm. In the laminate of the electrodeposition coating board and the polyurethane resin coating film obtained above, the König hardness of the polyurethane resin coating film was measured in accordance with ISO 1522.

[0087] (5) The adhesion of the coating film to the electrodeposited layer surface was evaluated as follows: A coating material composition was prepared by adding 2% by mass of Dawanol® DPnB as a film-forming aid and 0.5% by mass of a silicone-based surfactant (BYK-345, manufactured by BYChemie Inc.) to an aqueous polyurethane resin dispersion and mixing the mixture. This composition was applied to an automotive steel sheet cation electrodeposited plate (manufactured by Nippon Test Panel Co., Ltd.) using a bar coater #20, heated and dried at 80°C for 10 minutes, and a grid peel test was performed using the obtained coating film. Cuts were made in the coating film at 1 mm intervals vertically and horizontally over an area of ​​10 mm x 10 mm, and after applying adhesive tape and peeling it off, the number of squares remaining on the electrodeposited layer surface was visually counted and evaluated. For example, if 15 out of 100 squares remained in the peel test, it was recorded as 15 / 100.

[0088] (6) The tensile properties of the coating film were evaluated as follows. A coating material composition was prepared by adding 4.7% by mass of Dawanol® DPnB as a film-forming aid and 0.5% by mass of a silicone-based surfactant (BYK-345, manufactured by BYK Chemie) to an aqueous polyurethane resin dispersion and mixing the mixture. This composition was then applied to a PET film to a dry film thickness of 70 μm. The film was then left at room temperature for 15 hours, dried at 60°C for 2 hours, and then at 120°C for another 2 hours to create the coating film. The elastic modulus of the polyurethane resin film was measured according to the method in accordance with JIS K 7311. The rupture energy of the coating film was determined by integrating the stress from zero elongation to the rupture point elongation on the elongation-stress curve. The measurement conditions were a measurement temperature of 23°C, humidity of 50%, and a tensile speed of 100 mm / min. (7) The number-average molecular weight and hydroxyl value of the raw materials are catalog values.

[0089] [Example 1] <Manufacturing of aqueous polyurethane resin dispersion (1)> Polyester polyol HS(registered trademark) 2F-136P (manufactured by Toyokuni Oil Co., Ltd.; LOT. GL7832; number average molecular weight 1079; hydroxyl value 104.0 mg KOH / g; polyester polyol obtained by dehydration condensation of neopentyl glycol (hereinafter also referred to as "NPG") and terephthalic acid (hereinafter also referred to as "TPA"), 152 g) and polytetramethylene ether glycol (PTMG2000, manufactured by Mitsubishi Chemical Corporation; number average molecular weight 1955; hydroxyl value 57.4 mg KOH / g) 38.0g of (hereinafter also referred to as "PTMG2000"), 2,2-dimethylolpropionic acid (28.0g), and 4,4'-dicyclohexylmethane diisocyanate (hereinafter also referred to as "H12MDI") (181.6g) were heated in dipropylene glycol dimethyl ether (hereinafter also referred to as "DMM") (102.2g) in the presence of dibutyltin dilaurine (0.0606g) under a nitrogen atmosphere at 80-85°C for 4 hours. The reaction mixture was cooled to 80°C, and triethylamine (21.1g) was added and mixed. 362.7g of this mixture was then added to water (569.6g) under vigorous stirring. Next, 60.6 g of a 35% by mass aqueous solution of 2-methyl-1,5-pentanediamine (hereinafter also referred to as "MPMD") and 8.0 g of 8.0 g of 35% by mass 2-(2-aminoethylamino)ethanol (hereinafter also referred to as "AEEA") were added to obtain aqueous polyurethane resin dispersion (1) (weight-average molecular weight of polyurethane resin: 460,000, acid value: 27.0).

[0090] [Example 2] <Manufacturing of aqueous polyurethane resin dispersion (2)> Polyester polyol HS(registered trademark) 2F-136P (manufactured by Toyokuni Oil Co., Ltd.; LOT. GL7832; number average molecular weight 1079; hydroxyl value 104.0 mg KOH / g; polyester polyol obtained by dehydration condensation of neopentyl glycol and terephthalic acid, 117.0 g), polytetramethylene ether glycol (PTMG2000, manufactured by Mitsubishi Chemical Corporation; number average molecular weight 1955; hydroxyl value 57.4 mg KOH / g, 78.2 g), 2,2-dimethylolpropionic acid (27.8 g), and 4,4'-dicyclohexylmethane diisocyanate (175.3 g) were heated in dipropylene glycol dimethyl ether (101.1 g) in the presence of dibutyltin dilaurate (0.0817 g) under a nitrogen atmosphere at 80-85°C for 5 hours. The reaction mixture was cooled to 80°C, and 364.5g of the mixture, to which triethylamine (20.6g) was added and mixed, was added to water (572.5g) under vigorous stirring. Then, 35% by mass of 2-methyl-1,5-pentanediamine aqueous solution (56.0g) and 35% by mass of 2-(2-aminoethylamino)ethanol (8.0g) were added to obtain aqueous polyurethane resin dispersion (2) (weight-average molecular weight of polyurethane resin 790,000, acid value 27.0).

[0091] [Example 3] <Manufacturing of aqueous polyurethane resin dispersion (3)> Polyester polyol HS(registered trademark) 2F-136P (manufactured by Toyokuni Oil Co., Ltd.; LOT. GL7832; number average molecular weight 1079; hydroxyl value 104.0 mg KOH / g; polyester polyol obtained by dehydration condensation of neopentyl glycol and terephthalic acid, 180.2 g), 2,2-dimethylolpropionic acid (27.5 g), and 4,4'-dicyclohexylmethane diisocyanate (184.7 g) were heated in dipropylene glycol dimethyl ether (142.3 g) in the presence of dibutyltin dilaurate (0.1512 g) under a nitrogen atmosphere at 80-85°C for 4.5 hours. The reaction mixture was cooled to 80°C, and triethylamine (20.4 g) was added and mixed. Of this mixture, 392.4 g was added to water (541.5 g) under strong stirring. Next, a 35% by mass aqueous solution of 2-methyl-1,5-pentanediamine (59.7 g) and a 35% by mass 2-(2-aminoethylamino)ethanol (8.0 g) were added to obtain an aqueous polyurethane resin dispersion (3) (weight-average molecular weight of polyurethane resin: 690,000, acid value: 27.2).

[0092] [Example 4] <Manufacturing of aqueous polyurethane resin dispersion (4)> Polyester polyol HS(registered trademark) 2F-136P (manufactured by Toyokuni Oil Co., Ltd.; LOT. GL7832; number average molecular weight 959; hydroxyl value 117.0 mg KOH / g; polyester polyol obtained by dehydration condensation of neopentyl glycol and terephthalic acid, 102.5 g), polytetramethylene ether glycol (PTMG650, manufactured by Mitsubishi Chemical Corporation; number average molecular weight 650; hydroxyl value 172.7 mg KOH / g, 68.0 g) (hereinafter also referred to as "PTMG650"), 2,2-dimethylolpropionic acid (28.9 g), and 4,4'-dicyclohexylmethane diisocyanate (210.3 g) were heated in dipropylene glycol dimethyl ether (105.0 g) in the presence of dibutyltin dilaurate (0.1373 g) under a nitrogen atmosphere at 80-85°C for 5.5 hours. The reaction mixture was cooled to 80°C, and 361.6g of the mixture, to which triethylamine (21.6g) was added and mixed, was added to water (567.3g) under vigorous stirring. Then, 35% by mass of 2-methyl-1,5-pentanediamine aqueous solution (58.2g) and 35% by mass of 2-(2-aminoethylamino)ethanol (15.9g) were added to obtain aqueous polyurethane resin dispersion (4) (weight-average molecular weight of polyurethane resin 750,000, acid value 27.2).

[0093] [Example 5] <Manufacturing of aqueous polyurethane resin dispersion (5)> Polyester polyol HS (registered trademark) 2F-136P (manufactured by Toyokuni Oil Co., Ltd.; LOT. GL7832; number average molecular weight 959; hydroxyl value 117.0 mg KOH / g; polyester polyol obtained by dehydration condensation of neopentyl glycol and terephthalic acid, 114.4 g) and polycarbonate polyol ETERNACOLL (registered trademark) UH200 (hereinafter also referred to as "UH200") (manufactured by Ube Industries, Ltd.; number average molecular weight 1952; hydroxyl value 57.5 mg KOH / g; 76.0 g of polycarbonate polyol obtained by reacting 1,6-hexanediol with dimethyl carbonate), 2,2-dimethylolpropionic acid (28.2 g), and 4,4'-dicyclohexylmethane diisocyanate (181.9 g) were heated in dipropylene glycol dimethyl ether (101.0 g) in the presence of dibutyltin dilaurate (0.1821 g) under a nitrogen atmosphere at 80-85°C for 5.0 hours. The reaction mixture was cooled to 80°C, and triethylamine (21.1 g) was added and mixed. Of this mixture, 370.2 g was added to water (572.9 g) under vigorous stirring. Next, a 35% by mass aqueous solution of 2-methyl-1,5-pentanediamine (51.4 g) and a 35% by mass 2-(2-aminoethylamino)ethanol (15.9 g) were added to obtain an aqueous polyurethane resin dispersion (5) (weight-average molecular weight of polyurethane resin: 670,000, acid value: 27.0).

[0094] [Comparative Example 1] <Manufacturing of aqueous polyurethane resin dispersion (6)> Polyester polyol (number average molecular weight 10¹³; hydroxyl value 110.8 mg KOH / g, 180.2 g) obtained by dehydration condensation of hexanediol (hereinafter also referred to as "HD") and terephthalic acid (hereinafter also referred to as "TPA") was heated with 4,4'-dicyclohexylmethane diisocyanate (192.7 g) in dipropylene glycol dimethyl ether (145.1 g) in the presence of dibutyltin dilaurine (0.1174 g) under a nitrogen atmosphere at 80-90°C for 8.0 hours, but no urethane reaction proceeded.

[0095] [Comparative Example 2] <Manufacturing of aqueous polyurethane resin dispersion (7)> A polyester polyol (number average molecular weight 1000; hydroxyl value 112.2 mg KOH / g, 180.1 g) obtained by dehydration condensation of hexanediol and isophthalic acid (hereinafter also referred to as "IPA"), 2,2-dimethylolpropionic acid (28.7 g), and 4,4'-dicyclohexylmethane diisocyanate (192.4 g) were heated in dipropylene glycol dimethyl ether (145.0 g) in the presence of dibutyltin dilaurate (0.1348 g) under a nitrogen atmosphere at 80-85°C for 4.5 hours. The reaction mixture was cooled to 80°C, and triethylamine (21.4 g) was added and mixed. Of this mixture, 392.5 g was added to water (539.9 g) under vigorous stirring. Next, a 35% by mass aqueous solution of 2-methyl-1,5-pentanediamine (62.7 g) and a 35% by mass 2-(2-aminoethylamino)ethanol (8.0 g) were added to obtain an aqueous polyurethane resin dispersion (7) (weight-average molecular weight of polyurethane resin: 660,000, acid value: 27.5).

[0096] [Comparative Example 3] <Manufacturing of aqueous polyurethane resin dispersion (8)> Polycarbonate diol ETERNACOLL® UM90(1 / 3) (manufactured by Ube Industries; number average molecular weight 873; hydroxyl value 128.5 mg KOH / g; 179.9 g of polycarbonate diol obtained by reacting 1,4-cyclohexanedimethanol, 1,6-hexanediol (molar ratio 1:3) with a carbonate ester) (hereinafter also referred to as "UM90(1 / 3)"), 2,2-dimethylolpropionic acid (29.5 g), and 4,4'-dicyclohexylmethane diisocyanate (208.5 g) were heated in dipropylene glycol dimethyl ether (76.0 g) in the presence of dibutyltin dilaurate (0.2930 g) under a nitrogen atmosphere at 80-85°C for 5 hours. The reaction mixture was cooled to 80°C, and 340.7g of the mixture, to which triethylamine (21.9g) was added and mixed, was added to water (587.9g) under vigorous stirring. Then, 35% by mass of 2-methyl-1,5-pentanediamine aqueous solution (65.5g) and 35% by mass of 2-(2-aminoethylamino)ethanol (8.0g) were added to obtain aqueous polyurethane resin dispersion (8) (weight-average molecular weight of polyurethane resin 660,000, acid value 27.5).

[0097] [Comparative Example 4] <Manufacturing of aqueous polyurethane resin dispersion (9)> Polycarbonate diol ETERNACOLL® UM90(3 / 1) (manufactured by Ube Industries; number average molecular weight 903; hydroxyl value 124.3 mg KOH / g; 170.0 g of polycarbonate diol obtained by reacting 1,4-cyclohexanedimethanol and 1,6-hexanediol (molar ratio 3:1) with a carbonate ester) (hereinafter also referred to as "UM90(3 / 1)"), 2,2-dimethylolpropionic acid (27.5 g), and 4,4'-dicyclohexylmethane diisocyanate (194.6 g) were heated in dipropylene glycol dimethyl ether (143.0 g) in the presence of dibutyltin dilaurate (0.1950 g) under a nitrogen atmosphere at 80-85°C for 5 hours. The reaction mixture was cooled to 80°C, and 390.0g of the mixture, to which triethylamine (20.5g) was added and mixed, was added to water (539.0g) under vigorous stirring. Then, 35% by mass of 2-methyl-1,5-pentanediamine aqueous solution (63.6g) and 35% by mass of 2-(2-aminoethylamino)ethanol (8.0g) were added to obtain an aqueous polyurethane resin dispersion (9) (weight-average molecular weight of polyurethane resin: 690,000, acid value: 27.0).

[0098] [Table 1]

[0099] [Table 2]

[0100] [Table 3]

[0101] As shown in Examples 1-5 of Table 2, the coating obtained by applying and heat-treating the aqueous urethane resin dispersion of the present invention exhibits high König hardness with low-temperature, short-time drying at 80°C for 10 minutes. In addition to polyester polyol (A), using polyether polyol or polycarbonate polyol as other polyol (F) can improve adhesion to the electrodeposited surface and fracture energy while maintaining high König hardness with low-temperature, short-time drying at 80°C for 10 minutes (see Examples 2, 4, and 5). If a branched-chain polyol is not included as a component of polyester polyol (A), and a non-branched-chain polyol is used as a component of polyester polyol (A), the König hardness of the coating film after drying at 80°C for 10 minutes is low (see Comparative Example 2). When polyester polyol (A) is replaced with polycarbonate polyol, the König hardness of the coating film dried at 80°C for 10 minutes is lower (see Comparative Examples 3 and 4). [Industrial applicability]

[0102] The composition containing the aqueous urethane resin dispersion of the present invention exhibits high hardness when the coating film is dried at low temperatures of 100°C or below and in a short time. Therefore, it is expected to contribute to reducing greenhouse gas emissions by enabling low-temperature drying in applications such as floor coatings, coatings for plastic substrates or rubber, steel plate treatment agents, and vehicle primer layers.

Claims

1. An aqueous polyurethane resin dispersion comprising a polyurethane resin and an aqueous medium, The polyurethane resin has constituent units derived from a polyester polyol (A) composed of a polyol (Aa) and a dicarboxylic acid (Ab), and constituent units derived from a polyisocyanate (B). The total amount of the polyol (Aa) contains 80% by mass or more of a branched polyol (Aa1), An aqueous polyurethane resin dispersion comprising 80% by mass or more of aromatic dicarboxylic acid (Ab1) in the total amount of the dicarboxylic acid (Ab), An aqueous polyurethane resin dispersion wherein the polyurethane resin has constituent units derived from the polyester polyol (A) and a polyol (F) other than the acidic group-containing polyol, and the polyol (F) is a polyether polyol and / or a polycarbonate polyol.

2. The aqueous polyurethane resin dispersion according to claim 1, wherein the polyurethane resin further comprises a constituent unit derived from an acidic group-containing polyol (C) and a constituent unit derived from a chain extender (E).

3. The aqueous polyurethane resin dispersion according to claim 1, wherein the two carboxyl groups in the aromatic dicarboxylic acid in the dicarboxylic acid (Ab) are in a para position on the benzene ring.

4. The aqueous polyurethane resin dispersion according to claim 1, wherein the branched polyol (Aa1) is a diol having quaternary carbon atoms.

5. The aqueous polyurethane resin dispersion according to claim 2, wherein the chain extender (E) is a polyamine.

6. The aqueous polyurethane resin dispersion according to claim 1, wherein the polyol (F) has 2 hydroxyl groups.

7. The aqueous polyurethane resin dispersion according to claim 1, wherein the mass ratio of the polyester polyol (A) to the polyol (F) is 50:50 to 90:

10.

8. The aqueous polyurethane resin dispersion according to claim 1, wherein the total amount of the polyisocyanate (B) contains 50 to 100% by mass of an alicyclic polyisocyanate.

9. The aqueous polyurethane resin dispersion according to claim 1, wherein the weight-average molecular weight of the polyurethane resin is 100,000 or more.

10. The aqueous polyurethane resin dispersion according to claim 1, wherein the hydroxyl value of the polyester polyol (A) is 55 to 140 mg KOH / g.

11. A coating material composition comprising the aqueous polyurethane resin dispersion described in claim 1.

12. A coating film obtained by applying and drying the coating material composition according to claim 11.

13. The coating film according to claim 12, wherein the coating material composition is dried at 80°C for 10 minutes, and the resulting coating film is 13 to 15 μm thick, and the König hardness of the coating film is greater than 120.

14. A method for producing a coating film, comprising the step of drying the coating material composition according to claim 11 at 20°C to 100°C.

15. A coating material composition according to claim 11, for use as a primer or base coat for metal exteriors.

16. A coating material composition according to claim 11 for use with fracture-resistant materials.

17. The coating material composition according to claim 11 for use as a floor coat, plastic or rubber coating.

18. A steel plate treatment agent containing the coating material composition described in claim 11.

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