Polyurethane water-based dispersion and water-based paint

Abstract

Improves the adhesion and UV resistance of the coating film to resin. [Solution] The polyurethane aqueous dispersion according to the embodiment comprises a polyurethane resin (A) containing a polyester polyol as a constituent dispersed in an aqueous dispersion medium, a carbodiimide group-containing compound (B), and a compound (C) having two groups represented by the following general formula (1) per molecule. The polyurethane resin (A) has a carboxy group. In formula (1), R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms, and R 2 represents a hydrocarbon group having 1 to 3 carbon atoms, and * represents a bond. [Formula 1] JPEG0007723852000015.jpg23135

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a polyurethane aqueous dispersion and a water-based paint containing the same. [Background technology]

[0002] Aqueous polyurethane dispersions obtained by dispersing a polyurethane resin in an aqueous dispersion medium are widely used in paints, inks, adhesives, etc. For example, Patent Documents 1 and 2 disclose blending a crosslinking agent having a functional group reactive with an acidic group and / or a hydroxyl group into an aqueous ink containing an aqueous polyester-based urethane resin, and list as the crosslinking agent hydrazide compounds, carbodiimide compounds, oxazoline compounds, epoxy compounds, isocyanate compounds, and aziridine compounds. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-146694 [Patent Document 2] Japanese Patent Publication No. 2021-147428 Summary of the Invention [Problem to be solved by the invention]

[0004] When a polyurethane aqueous dispersion is used as a coating material to be applied to the surface of a resin such as a polyester resin, the coating film is required to have good adhesion (adhesion) to the resin to be coated. Furthermore, when used as a primer, the coating film is required to have good adhesion to the resin substrate as well as good adhesion to the topcoat layer applied via the primer. Thus, polyurethane aqueous dispersions require good adhesion to the resin.

[0005] The inventors have found that the adhesion of a coating film to a resin can be improved by incorporating a carbodiimide group-containing compound. However, when the coating film is used as a primer, for example, and is then irradiated with ultraviolet (UV) rays and then coated with a topcoat layer to form a three-layer structure, the coating film exhibits poor adhesion, i.e., poor UV-resistant adhesion.

[0006] In the above Patent Documents 1 and 2, specifically, a carbodiimide compound or a hydrazide compound is blended with a polyurethane resin, and adipic acid dihydrazide is used as the hydrazide compound. However, Patent Documents 1 and 2 do not disclose the use of a specific hydrazide group-containing compound in combination with a carbodiimide compound, or the improvement in UV adhesion resistance thereby.

[0007] An object of an embodiment of the present invention is to provide a polyurethane aqueous dispersion that can improve the adhesion and UV resistance of a coating film to a resin, and a water-based paint using the same. [Means for solving the problem]

[0008] The present invention includes the embodiments shown below. [1] A polyurethane aqueous dispersion in which a polyurethane resin (A) containing a polyester polyol as a constituent component is dispersed in an aqueous dispersion medium, The polyurethane resin (A) has a carboxy group, The polyurethane aqueous dispersion contains a carbodiimide group-containing compound (B) and a compound (C) having two groups represented by the following general formula (1) in one molecule: [ka] In general formula (1), R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms, and R 2 represents a hydrocarbon group having 1 to 3 carbon atoms, and * represents a bond. Polyurethane water-based dispersion.

[0009] [2] The compound (C) includes a compound represented by the following general formula (3): [ka] In general formula (3), R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms, and R 2 represents a hydrocarbon group having 1 to 3 carbon atoms, and m represents an integer of 1 to 12. The polyurethane aqueous dispersion according to [1]. [3] The polyurethane aqueous dispersion according to [1] or [2], wherein the polyester polyol contains an aromatic polyester polyol. [4] The aqueous polyurethane dispersion according to any one of [1] to [3], wherein the carbodiimide group-containing compound (B) contains 100 to 350 moles of carbodiimide groups per 100 moles of carboxy groups in the polyurethane resin (A). [5] The polyurethane aqueous dispersion according to any one of [1] to [4], wherein the content of the compound (C) is 0.1 to 20 parts by mass per 100 parts by mass of the polyurethane resin (A). [6] An aqueous paint comprising the polyurethane aqueous dispersion according to any one of [1] to [5]. [7] The water-based paint according to [6], which is used as a primer. [Effects of the Invention]

[0010] According to an embodiment of the present invention, the adhesion and UV resistance of the coating film to the resin can be improved. DETAILED DESCRIPTION OF THE INVENTION

[0011] The polyurethane aqueous dispersion according to this embodiment (hereinafter sometimes simply referred to as aqueous dispersion) contains a polyurethane resin (A), a carbodiimide group-containing compound (B), a compound (C) having two groups represented by general formula (1) in one molecule, and an aqueous dispersion medium (D).

[0012] [Polyurethane resin (A)] The polyurethane resin (A) is obtained by reacting a polyol with a polyisocyanate, and is a polymer having a urethane bond in the molecule. In this embodiment, the polyurethane resin (A) contains a polyester polyol as a constituent component. This improves adhesion to polyester resin substrates. In this specification, "containing a polyester polyol as a constituent component" means that the polyester polyol is used as a raw material (monomer) for synthesizing the polyurethane resin (A), and the polyurethane resin (A) has a structure derived from the polyester polyol.

[0013] The polyester polyol is a polyol having a plurality of ester bonds (-COO-) in the molecule, and is preferably one obtained by a condensation reaction between a polycarboxylic acid and a compound containing a polyhydroxy group.

[0014] The polycarboxylic acid is preferably a dicarboxylic acid, and examples thereof include aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid, succinic acid, sebacic acid, azelaic acid, maleic acid, and fumaric acid. Any of these may be used alone or in combination of two or more.

[0015] The polyvalent hydroxy group-containing compound is preferably a diol, and examples thereof include aliphatic diols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol, and aromatic diols such as bisphenols such as bisphenol A and bisphenol F, and alkylene oxide adducts thereof. Any of these may be used alone or in combination of two or more.

[0016] The polyester polyol is preferably an aromatic polyester polyol. That is, in a preferred embodiment, the polyester polyol includes an aromatic polyester polyol. The use of an aromatic polyester polyol can improve the water-resistant adhesion of a coating film to a resin. The aromatic polyester polyol is a polyester polyol having an aromatic ring in the molecule, and it is sufficient that at least one of the polycarboxylic acid and the polyvalent hydroxy group-containing compound contains an aromatic ring. The amount of aromatic polyester polyol relative to 100% by mass of polyester polyol is preferably 50% by mass or more, more preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass.

[0017] The molecular weight of the polyester polyol is not particularly limited, and the number average molecular weight (Mn) may be 500 to 5,000, 800 to 4,000, or 1,000 to 3,000, for example.

[0018] In this specification, the number average molecular weight (Mn) is a value measured by GPC (gel permeation chromatography) and calculated using a calibration curve of standard polystyrene. Specifically, the GPC conditions are as follows: columns: "TSKgel G4000HXL + TSKgel G3000HXL + TSKgel G2000HXL + TSKgel G1000HXL + TSKgel G1000HXL" manufactured by Tosoh Corporation, mobile phase: THF (tetrahydrofuran), mobile phase flow rate: 1.0 mL / min, column temperature: 40°C, sample injection volume: 50 μL, and sample concentration: 0.2% by mass.

[0019] The amount of polyester polyol in the polyol constituting the polyurethane resin (A) is not particularly limited, but is, for example, preferably 60 to 99 mass % relative to 100 mass % of the polyol, more preferably 70 to 97 mass %, more preferably 75 to 95 mass %, and even more preferably 80 to 90 mass %.

[0020] In this specification, when the amount of each component constituting the polyol is based on 100% by mass of the polyol, if the polyol contains a carboxyl group-containing polyol described below, the carboxyl group is calculated as being in the acid form. Similarly, the amount of the carboxyl group-containing polyol is calculated as being in the acid form.

[0021] In this embodiment, the polyurethane resin (A) has a carboxy group, which can react with the carbodiimide group-containing compound (B) to form a crosslinked structure during heat drying of the aqueous dispersion. In this specification, unless otherwise specified, the carboxy group is a concept that includes not only the acid type (-COOH) but also the salt type, i.e., the carboxyl group (-COOX, where X is a cation that forms a salt with a carboxylic acid), and the acid type and the salt type may be mixed.

[0022] Examples of salts of carboxylic acid bases include alkali metal salts such as sodium salts and potassium salts, alkaline earth metal salts such as magnesium salts and calcium salts, ammonium salts, amine salts (primary amine salts, secondary amine salts, tertiary amine salts), and quaternary ammonium salts. Among these, salts of volatile bases such as ammonium salts and amine salts are preferred. When the base is a volatile base, the carboxyl group is easily converted to an acid form by evaporation during heating and drying of the aqueous dispersion, which improves reactivity with the carbodiimide group-containing compound (B) and can enhance the effect of improving the adhesion of the coating film to the resin.

[0023] In this embodiment, the acid value of the polyurethane resin (A) is not particularly limited and may be, for example, 5 to 45 mgKOH / g, 5 to 25 mgKOH / g, 7 to 20 mgKOH / g, or 10 to 15 mgKOH / g. An acid value of 5 mgKOH / g or more facilitates emulsification of the polyurethane resin (A) in an aqueous dispersion medium. An acid value of 45 mgKOH / g or less can enhance the effect of improving the adhesion of a coating film to the resin.

[0024] In this specification, the acid value can be determined in accordance with JIS K0070-1992 from the amount (mg) of KOH required to neutralize the carboxyl groups contained in 1 g of polyurethane resin (A). When polyurethane resin (A) is a salt of a volatile base, the volatile base evaporates when the mass of polyurethane resin (A) is measured, so the acid value is a value calculated based on the mass of the acid-form polyurethane resin, which is the nonvolatile content. Thus, the mass of polyurethane resin (A) in this specification refers to the mass of the nonvolatile content.

[0025] In order to introduce a carboxy group into the polyurethane resin (A), it is preferable to use a carboxy group-containing polyol together with a polyester polyol as the polyol used to synthesize the polyurethane resin (A). That is, it is preferable that the polyurethane resin (A) contains a carboxy group-containing polyol as a constituent component.

[0026] Examples of carboxyl group-containing polyols include carboxylic acid-containing compounds such as dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, dihydroxymaleic acid, 2,6-dihydroxybenzoic acid, and tartaric acid, as well as derivatives and salts thereof. Any of these may be used alone or in combination of two or more.

[0027] The amount of the carboxyl group-containing polyol in the polyol is not particularly limited, and may be, for example, 0.5 to 15% by mass, 1 to 10% by mass, 2 to 8% by mass, or 3 to 6% by mass relative to 100% by mass of the polyol.

[0028] The polyol used to synthesize the polyurethane resin (A) may further include a polyalkylene glycol. That is, the polyurethane resin (A) preferably further includes a polyalkylene glycol as a constituent. By including a polyalkylene glycol, for example, when the polyurethane aqueous dispersion is used as a primer and the resin constituting the topcoat layer includes a polyalkylene glycol as a constituent, adhesion to the topcoat layer can be improved.

[0029] Examples of polyalkylene glycols include polyethylene glycol, polytrimethylene glycol, polypropylene glycol, polytetramethylene glycol, polybutylene glycol, and copolymers using two or more of these constituent monomers. The molecular weight of the polyalkylene glycol is not particularly limited, and the number average molecular weight (Mn) may be, for example, 500 to 5,000, 800 to 4,000, or 1,000 to 3,000.

[0030] The amount of polyalkylene glycol in the polyurethane resin (A) (i.e., the amount of structures derived from polyalkylene glycol) is preferably 5 to 15 parts by mass, more preferably 7 to 13 parts by mass, and even more preferably 8 to 10 parts by mass, relative to 100 parts by mass of the polyurethane resin (A). The amount of polyalkylene glycol in the polyol is not particularly limited, and may be, for example, 3 to 25% by mass, 5 to 20% by mass, or 10 to 15% by mass relative to 100% by mass of the polyol.

[0031] The polyol used to synthesize the polyurethane resin (A) may further include a polyol having three or more functional groups. Preferred examples of polyols having three or more functional groups include low-molecular-weight polyhydric alcohols (preferably trihydric alcohols) such as trimethylolpropane, glycerin, and pentaerythritol. The amount of such tri- or higher functional polyols is not particularly limited, and may be, for example, 0.1 to 5% by mass, 0.2 to 3% by mass, or 0.3 to 1% by mass relative to 100% by mass of the polyol.

[0032] The polyol used to synthesize the polyurethane resin (A) may contain polyols other than those mentioned above. Examples of such other polyols include polymer polyols such as polycarbonate polyols, polyether polyols other than polyalkylene glycols, and polybutadiene polyols. Examples of other polyols that may be used include low-molecular-weight diols such as ethylene glycol, propylene glycol, propanediol, butanediol, pentanediol, 3-methyl-1,5-pentanediol, hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, bisphenol A, bisphenol F, bisphenol S, and hydrogenated bisphenol A. These other polyols may be used alone or in combination.

[0033] The amount of polyol constituting the polyurethane resin (A) (i.e., the amount of polyol-derived structure) is not particularly limited, and may be, for example, 70 to 90 parts by mass or 75 to 85 parts by mass per 100 parts by mass of the polyurethane resin (A).

[0034] Examples of polyisocyanates used to synthesize the polyurethane resin (A) include aromatic polyisocyanates, araliphatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates.

[0035] Examples of aromatic polyisocyanates include diphenylmethane diisocyanate (MDI), polymeric MDI, tolylene diisocyanate (TDI), naphthalene diisocyanate, and modified products thereof such as isocyanurates, adducts, biurets, allophenates, and carbodiimides.

[0036] Examples of aromatic aliphatic polyisocyanates include xylylene diisocyanate (XDI), ω,ω'-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene, and modified products thereof such as isocyanurates, adducts, biurets, allophenates, and carbodiimides.

[0037] Examples of aliphatic polyisocyanates include tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, and modified versions thereof such as isocyanurates, adducts, biurets, allophenates, and carbodiimides.

[0038] Examples of alicyclic polyisocyanates include isophorone diisocyanate (IPDI), dicyclohexylmethane 4,4'-diisocyanate (hydrogenated MDI), hydrogenated xylylene diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, and modified products thereof such as isocyanurates, adducts, biurets, allophenates, and carbodiimides.

[0039] These polyisocyanates may be used alone or in combination of two or more.

[0040] Among the above polyisocyanates, it is preferable to use aromatic ring-containing polyisocyanates such as aromatic polyisocyanates and aromatic aliphatic polyisocyanates, and it is more preferable to use aromatic aliphatic polyisocyanates. The amount of aromatic ring-containing polyisocyanate relative to 100% by mass of polyisocyanate is not particularly limited, and may be, for example, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass.

[0041] The amount of polyisocyanate constituting the polyurethane resin (A) (i.e., the amount of polyisocyanate-derived structure) is not particularly limited, and may be, for example, 10 to 30 parts by mass or 15 to 25 parts by mass per 100 parts by mass of the polyurethane resin (A).

[0042] In one embodiment, examples of the polyurethane resin (A) include the following (A1) and (A2). (A1) An anionic polyurethane resin obtained by reacting a polyol containing a polyester polyol and a carboxyl group-containing polyol with a polyisocyanate to synthesize an isocyanate group-containing urethane prepolymer, and then extending the chain of the urethane prepolymer with a chain extender. (A2) A hydroxyl group-containing anionic polyurethane resin obtained by reacting a polyol including a polyester polyol and a carboxyl group-containing polyol with a polyisocyanate.

[0043] [Carbodiimide group-containing compound (B)] The carbodiimide group-containing compound (B) is a compound that contains a carbodiimide group (-N=C=N-) in the molecule, and reacts with the carboxy group of the polyurethane resin (A).

[0044] The carbodiimide group-containing compound (B) may be a carbodiimide group-containing compound used as an aqueous crosslinking agent. It is preferably a polycarbodiimide, which is a polymer having a carbodiimide group in the molecule, and more preferably an aqueous polycarbodiimide in which a hydrophilic segment has been introduced into a polycarbodiimide having multiple carbodiimide groups in the molecule. Examples of such aqueous polycarbodiimides include water-soluble types such as "Carbodilite V-02," "Carbodilite V-02-L2," "Carbodilite SV-02," "Carbodilite V-04," and "Carbodilite V-10," and emulsion / dispersion types such as "Carbodilite E-02" and "Carbodilite E-05" (all manufactured by Nisshinbo Chemical Inc.).

[0045] The NCN equivalent of the carbodiimide group-containing compound is not particularly limited, and may be, for example, 300 to 600, or 350 to 500. Here, the NCN equivalent represents the chemical formula weight per mole of carbodiimide group.

[0046] [Compound (C)] Compound (C) is a compound having two groups (hereinafter referred to as hydrazide groups) represented by the following general formula (1) in the molecule, and is hereinafter referred to as hydrazide group-containing compound (C). Here, the hydrazide group also encompasses within its concept the atomic group constituting the semicarbazide group formed by bonding -NH- to the bond in formula (1). [ka]

[0047] In formula (1), R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms, and R 2 represents a hydrocarbon group having 1 to 3 carbon atoms, and * represents a bond. R 1 is preferably a hydrocarbon group having 1 to 3 carbon atoms. 1 may be the same or different, and two R 2 may be the same or different.

[0048] The hydrocarbon group having 1 to 3 carbon atoms is a monovalent hydrocarbon group that may be saturated or unsaturated and may be linear or branched, and is preferably an alkyl group, i.e., a methyl group, an ethyl group, or a propyl group, and more preferably a methyl group.

[0049] The hydrazide group-containing compound (C) includes compounds represented by the following general formula (2). [ka]

[0050] In formula (2), R 1 and R 2 are R in formula (1), respectively.1 and R 2 Similar to R 3 represents a divalent organic group having 1 to 12 carbon atoms, preferably 2 to 10 carbon atoms, and more preferably 3 to 8 carbon atoms.

[0051] In one embodiment, the hydrazide group-containing compound (C) preferably includes a compound having two semicarbazide groups per molecule, specifically a disemicarbazide compound (C1) represented by the following general formula (3): In this case, the amount of the disemicarbazide compound (C1) in 100% by mass of the hydrazide group-containing compound (C) is not particularly limited, but is preferably 50% by mass or more, more preferably 70% by mass or more, and may be 100% by mass. [ka]

[0052] In formula (3), R 1 and R 2 are R in formula (1), respectively. 1 and R 2 m represents an integer of 1 to 12, preferably an integer of 2 to 10, and more preferably an integer of 3 to 8.

[0053] A specific preferred example of the hydrazide group-containing compound (C) is 1,6-hexamethylenebis(N,N-dimethylsemicarbazide).

[0054] [Aqueous dispersion medium (D)] The aqueous dispersion medium (D) is a dispersion medium containing water, and may be water or a mixed medium of water and a hydrophilic organic solvent. From the viewpoint of dispersion stability of the aqueous dispersion, the aqueous dispersion medium (D) is preferably water, and may contain an organic solvent, but preferably in a small amount. In one embodiment, the aqueous dispersion medium (D) preferably contains 70 mass % or more of water, more preferably 80 mass % or more of water, more preferably 90 mass % or more of water, and may be 100 mass % of water. That is, in the aqueous dispersion medium (D), the mass ratio of water / hydrophilic organic solvent is preferably 70 / 30 to 100 / 0, more preferably 80 / 20 to 100 / 0, and even more preferably 90 / 10 to 100 / 0.

[0055] As the hydrophilic organic solvent, various organic solvents that are soluble in water can be used, and examples thereof include lower monohydric alcohols such as methanol, ethanol, and propanol; polyhydric alcohols such as ethylene glycol and glycerin; and aprotic polar solvents such as N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide, and acetonitrile.

[0056] [Polyurethane water-based dispersion] The polyurethane aqueous dispersion is an aqueous dispersion in which a polyurethane resin (A) is dispersed in an aqueous dispersion medium (D), and contains a carbodiimide group-containing compound (B) and a hydrazide group-containing compound (C). By blending the carbodiimide group-containing compound (B) into the aqueous dispersion of the polyurethane resin (A), the adhesion of the coating film to the resin can be improved. Furthermore, by blending the hydrazide group-containing compound (C), UV adhesion resistance can be improved.

[0057] The content of the carbodiimide group-containing compound (B) in the polyurethane aqueous dispersion is preferably set as follows: The aqueous dispersion preferably contains 100 to 350 moles of carbodiimide groups in the carbodiimide group-containing compound (B) per 100 moles of carboxy groups in the polyurethane resin (A).

[0058] By setting the number of moles of carbodiimide groups to an amount equal to or greater than the number of moles of carboxy groups, carbodiimide groups are more likely to remain in the cured coating film. These remaining carbodiimide groups can enhance the effect of improving the adhesion of the coating film to resins, particularly to the topcoat layer. It is believed that the remaining carbodiimide groups contribute to adhesion to the acrylate resin contained in the topcoat layer, but this is not limited to this. Furthermore, by setting the number of carbodiimide groups to 350 moles or less, the effect of improving the adhesion of the coating film to resin substrates, particularly UV-resistant adhesion, can be enhanced. The amount of carbodiimide groups per 100 moles of carboxy groups is more preferably 120 to 320 moles, more preferably 180 to 300 moles, and even more preferably 220 to 280 moles.

[0059] To enhance the effect, the content of the hydrazide group-containing compound (C) in the polyurethane aqueous dispersion is preferably 0.1 to 20 parts by mass relative to 100 parts by mass of the polyurethane resin (A), more preferably 0.3 to 18 parts by mass, more preferably 1 to 15 parts by mass, and even more preferably 2 to 10 parts by mass.

[0060] The content of polyurethane resin (A) in the polyurethane aqueous dispersion is not particularly limited, and may be, for example, 5 to 50 mass %, 7 to 40 mass %, 10 to 30 mass %, or 15 to 25 mass % relative to the total mass of the aqueous dispersion.

[0061] The particle size of the polyurethane resin (A) in the polyurethane aqueous dispersion is not particularly limited, and may be, for example, an average particle size of 0.001 to 0.5 μm. Here, the average particle size is the 50% cumulative particle size (d50) measured using a "Microtrac UPA-UZ152" manufactured by Nikkiso Co., Ltd.

[0062] The polyurethane aqueous dispersion may contain other components as long as the effects of the polyurethane aqueous dispersion are not impaired. The other components may be contained in the resin particles as a dispersoid, or may be contained separately dispersed or dissolved in the aqueous dispersion medium (D). For example, in the polyurethane aqueous dispersion, the resin particles as a dispersoid may be composed solely of the polyurethane resin (A), or may contain other components in addition to the polyurethane resin (A). The polyurethane aqueous dispersion may also contain a surfactant for dispersing the polyurethane resin (A) in the aqueous dispersion medium (D). The carbodiimide group-containing compound (B) and the hydrazide group-containing compound (C) may be contained in the resin particles, but if they are hydrophilic or water-soluble, they may be contained separately dispersed or dissolved in the aqueous dispersion medium (D).

[0063] [Method for producing aqueous dispersion] The method for producing the polyurethane aqueous dispersion according to this embodiment is not particularly limited. In one embodiment, the aqueous dispersion containing the anionic polyurethane resin (A1) may be produced by the following steps (a1) to (a5). Step (a1): A step of reacting a polyol containing a polyester polyol and a carboxyl group-containing polyol with a polyisocyanate to synthesize an isocyanate group-containing urethane prepolymer. Step (a2): A step of neutralizing the carboxyl groups of the isocyanate group-containing urethane prepolymer. Step (a3): A step of dispersing the isocyanate group-containing urethane prepolymer in an aqueous dispersion medium (D). Step (a4): A step of extending the chain of the isocyanate group-containing urethane prepolymer with a chain extender. Step (a5): A step of mixing a carbodiimide group-containing compound (B) and a hydrazide group-containing compound (C) with an aqueous dispersion containing the chain-extended anionic polyurethane resin.

[0064] In the above step (a1), the polyisocyanate may be used so that the amount of isocyanate groups is stoichiometrically in excess of the amount of hydroxy groups contained in the polyol, for example, so that the equivalent ratio of hydroxy groups to isocyanate groups (NCO / OH) is 1.05 to 1.70 (more preferably 1.10 to 1.60).

[0065] In step (a1), the reaction between the polyol and the polyisocyanate may be carried out without an organic solvent, or may be carried out in an organic solvent having no active hydrogen group, such as methyl ethyl ketone or acetone.

[0066] In the above step (a2), examples of the base used to neutralize the carboxy group include non-volatile bases such as sodium hydroxide and potassium hydroxide, tertiary amines such as trimethylamine, triethylamine, dimethylethanolamine, methyldiethanolamine and triethanolamine, and volatile bases such as ammonia.

[0067] In the above step (a3), the method for dispersing the urethane prepolymer in the aqueous dispersion medium is not particularly limited, and examples include (i) a method in which the urethane prepolymer or a solution thereof is added to the aqueous dispersion medium while stirring it with a homogenizer, a homomixer, or the like, and (ii) a method in which the aqueous dispersion medium is added to the urethane prepolymer or a solution thereof while stirring it with a homogenizer, a homomixer, or the like.

[0068] In the above step (a4), the chain extender is not particularly limited, and examples thereof include water and polyvalent amine compounds such as aliphatic polyamine compounds (e.g., ethylenediamine, trimethylenediamine, propylenediamine, diethylenetriamine, triethylenetetramine), aromatic polyamine compounds (e.g., metaxylenediamine, tolylenediamine, diaminodiphenylmethane), and alicyclic polyamine compounds (e.g., piperazine, isophoronediamine).

[0069] The neutralization in step (a2), the dispersion in step (a3), and the chain elongation in step (a4) may be performed in this order, or two or more steps may be performed simultaneously. For example, when ammonia water is used to neutralize the carboxyl group, dispersion in an aqueous dispersion medium may be performed simultaneously with the neutralization, and chain elongation may be further performed with water. When the reaction between the polyol and the polyisocyanate in step (a1) is performed in an organic solvent, the organic solvent may be removed after dispersion in an aqueous dispersion medium in step (a3). When a compound that does not react with an isocyanate group is used as the hydrazide group-containing compound (C), the compound may be added at any stage of steps (a1) to (a4).

[0070] In one embodiment, the aqueous dispersion containing the anionic polyurethane resin (A2) may be produced by the following steps (b1) to (b4). Step (b1): A step of synthesizing a hydroxy group-containing polyurethane resin by reacting a polyol containing a polyester polyol and a carboxy group-containing polyol with a polyisocyanate. Step (b2): A step of neutralizing the anionic groups of the hydroxy group-containing polyurethane resin. Step (b3): A step of dispersing the hydroxy group-containing polyurethane resin in an aqueous dispersion medium (D). Step (b4): A step of mixing a carbodiimide group-containing compound (B) and a hydrazide group-containing compound (C) with an aqueous dispersion containing a hydroxy group-containing polyurethane resin.

[0071] In the above step (b1), the polyol is used so that the amount of hydroxy groups is stoichiometrically in excess of the amount of isocyanate groups contained in the polyisocyanate, for example, so that the equivalent ratio of hydroxy groups to isocyanate groups (NCO / OH) is 0.70 to 0.95 (more preferably 0.75 to 0.90).

[0072] The neutralization in step (b2) and the dispersion in step (b3) may be performed in this order, or may be performed simultaneously. For example, when ammonia water is used to neutralize the carboxyl group, dispersion in an aqueous dispersion medium may be performed simultaneously with neutralization. Note that when the reaction between the polyol and the polyisocyanate in step (b1) is performed in an organic solvent, the organic solvent may be removed after dispersion in an aqueous dispersion medium in step (b3).

[0073] [Water-based paint] The aqueous coating material according to this embodiment contains the polyurethane aqueous dispersion described above, and therefore contains an aqueous dispersion medium (D), a polyurethane resin (A) dispersed in the aqueous dispersion medium, a carbodiimide group-containing compound (B), and a hydrazide group-containing compound (C). This aqueous coating material can be applied to various substrates, such as resin substrates and metal substrates. However, because the aqueous dispersion exhibits excellent adhesion to resins, it is suitable for use as an aqueous coating material for application to substrates with resin surfaces. More preferably, this aqueous coating material is for application to polyester resin substrates, such as PET (polyethylene terephthalate) film, PBT (polybutylene terephthalate) film, and PEN (polyethylene naphthalate) film. The substrate may be a film or a plate-like substrate, and the shape, such as thickness, is not particularly limited.

[0074] In one embodiment, the aqueous coating material may be a primer coating material used as a primer. For example, the aqueous coating material according to this embodiment may be applied to a resin substrate such as a polyester resin substrate to form a coating film, and then an ultraviolet-curable resin (UV-curable resin) is applied as a topcoat layer on the coating film to form a UV-curable resin layer. One example of the use of such a laminate is an optical film. The coating material made of the aqueous coating material according to this embodiment has excellent adhesion to resin substrates such as polyester resins, and also has excellent adhesion to UV-curable resins. Therefore, it is suitable for use as such a primer.

[0075] In one embodiment, the coating composition may be used as a primer in the following applications: A primer is applied to both sides (side A and side B) of a resin substrate such as a PET film, and dried to form a primer layer. Next, a UV-curable resin is applied to side A and irradiated with UV light to form a UV-curable resin layer. After that, a UV-curable resin is applied to side B and irradiated with UV light to form a UV-curable resin layer. In such applications, if UV irradiation on side A causes deterioration of the primer in the primer layer on side B, even if a UV-curable resin is subsequently applied to side B and cured, the adhesion of the UV-curable resin layer to the primer layer may be poor. The water-based coating composition according to this embodiment is less susceptible to deterioration due to UV irradiation and has excellent UV-resistant adhesion, so even in such applications, the adhesion of the coating film can be improved on both sides A and B.

[0076] The ultraviolet curable resin constituting the topcoat layer is not particularly limited, and examples thereof include acrylate resins such as epoxy acrylate, urethane acrylate, polyester acrylate, etc. In one embodiment, an ultraviolet curable resin containing polyalkylene glycol as a constituent may be used.

[0077] The aqueous coating material may or may not contain other aqueous resins generally used as film-forming components in aqueous coating materials in combination with the polyurethane resin (A). Examples of other aqueous resins include water-soluble or water-dispersible acrylic resins, water-soluble or water-dispersible polyester resins, water-soluble or water-dispersible alkyd resins, and water-soluble or water-dispersible cellulose resins.

[0078] The contents of the polyurethane resin (A), carbodiimide group-containing compound (B), and hydrazide group-containing compound (C) in the aqueous paint are not particularly limited, and for example, the total of these three components may be 20 to 100 mass%, 50 to 100 mass%, or 70 to 100 mass%, relative to 100 mass% of the total resin solids content in the aqueous paint. The solids concentration of the aqueous paint is also not particularly limited, and may be, for example, 5 to 50 mass%, or 6 to 30 mass%.

[0079] The water-based paint may also contain various additives generally used in water-based paints, provided that the effects of the water-based paint are not impaired. Examples of such additives include wetting agents, pigments, ultraviolet absorbers, light stabilizers, surface conditioners, inorganic fillers, organic fillers, dispersing aids, preservatives, rust inhibitors, antioxidants, silane coupling agents, antifoaming agents, viscosity modifiers, antistatic agents, crosslinking agents, and organic solvents. [Example]

[0080] The present invention will be explained in more detail below based on examples and comparative examples, but the present invention is not limited thereto.

[0081] Details of each component used in the examples are as follows:

[0082] [Polyol] Aromatic polyester polyol 1: Functional group number 2, number average molecular weight 1000, solid content 70% by mass, dilution solvent MEK. The synthesis method is as follows: A reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping tank, and nitrogen gas inlet tube was charged with 16.2 parts by mass of succinic anhydride and 83.8 parts by mass of bisphenol A ethylene oxide adduct ("Newpol BPE-20NK" manufactured by Sanyo Chemical Industries, Ltd.), and the temperature was raised to 250°C with stirring under a nitrogen stream. The reaction was continued until the acid value reached 5 mgKOH / g or less (2.92 parts by mass of distilled water), and the mixture was cooled to 70°C. 41.61 parts by mass of methyl ethyl ketone was added to obtain aromatic polyester polyol 1.

[0083] Aromatic polyester polyol 2: Functional group number 2, number average molecular weight 2000, solid content 70% by mass, dilution solvent MEK. The synthesis method is as follows: A reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping tank, and nitrogen gas inlet tube was charged with 19.9 parts by mass of succinic anhydride and 80.1 parts by mass of bisphenol A ethylene oxide adduct ("Newpol BPE-20NK" manufactured by Sanyo Chemical Industries, Ltd.), and the temperature was raised to 250°C with stirring under a nitrogen stream. The reaction was continued until the acid value reached 5 mgKOH / g or less (3.58 parts by mass of distilled water), and the mixture was cooled to 70°C. 41.32 parts by mass of methyl ethyl ketone was added to obtain aromatic polyester polyol 2.

[0084] Aromatic polyester polyol 3: Functional group number 2, number average molecular weight 1000, solid content 70% by mass, dilution solvent MEK. The synthesis method is as follows. A reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping tank, and nitrogen gas inlet tube was charged with 40.9 parts by mass of isophthalic acid, 19.89 parts by mass of adipic acid, 25.14 parts by mass of neopentyl glycol, and 14.07 parts by mass of ethylene glycol, and the mixture was heated to 250° C. with stirring under a nitrogen stream. The reaction was continued until the acid value reached 5 mgKOH / g or less (13.76 parts by mass of distilled water), and the mixture was cooled to 70° C. After that, 36.96 parts by mass of methyl ethyl ketone was added to obtain aromatic polyester polyol 3.

[0085] Aliphatic polyester polyol: Functional group number 2, number average molecular weight 1000, solid content 70% by mass, dilution solvent MEK. The synthesis method is as follows: A reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping tank, and nitrogen gas inlet tube was charged with 53.1 parts by mass of adipic acid and 46.9 parts by mass of neopentyl glycol, and the mixture was heated to 250° C. with stirring under a nitrogen stream. The reaction was continued until the acid value reached 5 mgKOH / g or less (13.08 parts by mass of distilled water), and the mixture was cooled to 70° C., followed by the addition of 37.25 parts by mass of methyl ethyl ketone to obtain an aliphatic polyester polyol.

[0086] Dimethylolpropionic acid: 2,2-bis(hydroxymethyl)propionic acid, 2 functional groups 2,2-Dimethylolbutyric acid: 2,2-bis(hydroxymethyl)butyric acid, functional group 2 Trimethylolpropane: Functional group number 3 PEG1000: Polyethylene glycol, functional group number 2, number average molecular weight 1000, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. "PEG 1000"

[0087] [Polyisocyanate] XDI: Xylylene diisocyanate (functional group number 2) TDI: Tolylene diisocyanate (functional groups: 2) HDI: Hexamethylene diisocyanate (functional group 2)

[0088] [Neutralizer] Ammonia water: 25% by weight aqueous solution Triethylamine

[0089] [Crosslinking agent] (Carbodiimide group-containing compound) Water-soluble polycarbodiimide 1: "Carbodilite SV-02" manufactured by Nisshinbo Chemical Co., Ltd., solid content 40% by mass (solvent: water), NCN equivalent 430 Water-soluble polycarbodiimide 2: "Carbodilite V-02-L2" manufactured by Nisshinbo Chemical Inc., solid content 40% by mass (solvent: water), NCN equivalent 385 (Epoxy group-containing compound) Epoxy compound 1: "Denacol EX-614B" manufactured by Nagase ChemteX Corporation, solid content 100% by mass, epoxy equivalent weight 173

[0090] [Additives] (hydrazide group-containing compound) HN-130: 1,6-hexamethylenebis(N,N-dimethylsemicarbazide), "HN-130" manufactured by Mitsubishi Gas Chemical Company, Ltd. (Other additives) Sodium sulfite

[0091] The polyurethane aqueous dispersions were evaluated as follows.

[0092] [Initial adhesion] The polyurethane aqueous dispersion was used as a primer coating, and the adhesion of the coating film to resin (particularly the adhesion between the primer layer and the UV-cured resin layer) was evaluated using the following method in a triple-layered configuration of PET film / primer layer / UV-cured resin layer.

[0093] A polyethylene terephthalate (PET) film ("Lumirror T-60" manufactured by Toray Industries, Inc.) was used as the substrate, and the substrate surface was degreased with isopropyl alcohol. Next, the following polyurethane aqueous dispersion formulation was applied to the substrate with a bar coater to a dry film thickness of 1 μm, and the coating was dried at 180°C for 1 minute to obtain a test piece X on which a polyurethane resin coating film was formed.

[0094] Polyurethane water-based dispersion formulation: A formulation was prepared by adding water to the polyurethane aqueous dispersion of each Example or Comparative Example so that the solid content was 10% by mass, and then adding 0.2% by mass of a wetting agent ("Neocol SW-C" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) relative to 100% by mass of the aqueous dispersion.

[0095] The following UV-curable resin formulation was applied to the coating film of test piece X using a bar coater to a film thickness of 12 μm. Then, a high-pressure mercury lamp was used to irradiate the surface coated with the UV-curable resin formulation with 600 mJ / cm . 2 The specimen Y was irradiated with ultraviolet light of 1000 kJ / s to obtain a specimen Y. A 1 mm cross-cut adhesion test was carried out in accordance with JIS K5400-8.5:1990 using the specimen Y as a sample, and the initial adhesion between the PET film, the primer layer, and the UV-cured resin layer was calculated using the following formula. The test was carried out twice (n=1 and n=2), and the average value was calculated. Initial adhesion (%) = 100 - (number of peeled squares)

[0096] UV-curable resin formulation: New Frontier BPE-4 (Dai-ichi Kogyo Seiyaku Co., Ltd.) / New Frontier PHE (Dai-ichi Kogyo Seiyaku Co., Ltd.) / Omnirad 184 (IGM Resins BV) = 32.7 / 64.3 / 3 (mass ratio)

[0097] [UV resistance and adhesion] The surface of the coating film of the above test piece X was exposed to 600 mJ / cm using a high-pressure mercury lamp. 2 After irradiating the coating with ultraviolet light of 600 mJ / cm, the above UV-curable resin formulation was applied to the coating film with a bar coater to a film thickness of 12 μm. Next, a high-pressure mercury lamp was used to irradiate the surface coated with the UV-curable resin formulation with 600 mJ / cm. 2 The specimen was irradiated with ultraviolet light of 1000 kJ / s to obtain test piece Z. Using test piece Z as a sample, a 1 mm cross-cut adhesion test was carried out in accordance with JIS K5400-8.5:1990, and the UV resistance of the PET film, primer layer, and UV-cured resin layer was calculated using the following formula. The test was carried out twice (n=1 and n=2), and the average value was calculated. UV resistance adhesion (%) = 100 - (number of peeled squares)

[0098] [Water-resistant adhesion] The test piece X was immersed in hot water at 100° C. for 48 hours. After that, it was cooled to room temperature, and the test piece X was taken out. The surface was rubbed with a finger while wet to check the condition, and the result was evaluated according to the following criteria. A: No peeling (good water-resistant adhesion) B: Peeling occurred (poor water-resistant adhesion)

[0099] [Example 1] A four-neck flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen gas inlet tube was charged with 92.5 parts by weight (64.8 parts by weight as solids) of aromatic polyester polyol 1, 3.0 parts by weight of dimethylolpropionic acid, 0.5 parts by weight of trimethylolpropane, 9.8 parts by weight of PEG 1000, and 100 parts by weight of methyl ethyl ketone, and thoroughly mixed and dissolved. Next, 21.9 parts by weight of XDI was added as polyisocyanate, and the mixture was allowed to react at 70-75°C for 300 minutes to obtain a methyl ethyl ketone solution of an isocyanate group-containing urethane prepolymer. The resulting urethane prepolymer solution had a free isocyanate group content of 1.2% by weight relative to the solids. The resulting urethane prepolymer solution was cooled to 60°C, and while stirring with a homogenizer, a solution of 3.5 parts by weight of 25% ammonia water and 350 parts by weight of water was gradually added to emulsify and disperse the mixture. The emulsion was then stirred at 40°C for 1 hour to complete the chain extension reaction with water. Methyl ethyl ketone was distilled off under heating and reduced pressure, and water was added to adjust the solids content, yielding an aqueous dispersion with a solids content of 25% by mass. 62.5 parts by mass (25.0 parts by mass as solids) of water-soluble polycarbodiimide 1 and 5 parts by mass of HN-130 were added to the resulting aqueous dispersion and stirred to obtain the polyurethane aqueous dispersion of Example 1. In the resulting polyurethane aqueous dispersion, the acid value of the polyurethane resin was 12.5 mgKOH / g. Furthermore, the amount of carbodiimide groups per 100 moles of carboxy groups in the polyurethane resin was 260 moles.

[0100] [Examples 2 to 17 and Comparative Examples 1 to 3] The types and amounts (parts by mass) of polyol, polyisocyanate, neutralizing agent, crosslinking agent, and additives were changed as shown in Tables 1 to 4 below, and otherwise the same procedures as in Example 1 were carried out to obtain aqueous polyurethane dispersions of Examples 2 to 17 and Comparative Examples 1 to 3.

[0101] The initial adhesion, UV-resistant adhesion, and water-resistant adhesion were evaluated for the polyurethane aqueous dispersions of Examples 1 to 17 and Comparative Examples 1 to 3. The results are shown in Tables 1 to 4.

[0102] In Tables 1 to 4, the amount of polyester polyol is the amount of solids, which is the active ingredient, and the value in parentheses is the amount including the solvent. In Tables 1 to 4, the amount of carbodiimide group-containing compound is the amount of each component including the solvent, and the value in parentheses is the amount of solids, which is the active ingredient. "Solids content of polyurethane resin" is the solids concentration (mass%) of the polyurethane resin in the aqueous dispersion before the addition of the crosslinking agent and additives. "(Carbodiimide groups * 100) / carboxy groups [mol]" is the amount (mol) of carbodiimide groups in the carbodiimide group-containing compound per 100 moles of carboxy groups in the polyurethane resin.

[0103] [Table 1]

[0104] [Table 2]

[0105] [Table 3]

[0106] [Table 4]

[0107] The results are shown in Tables 1 to 4. In Comparative Example 1, the incorporation of the carbodiimide group-containing compound (B) resulted in excellent initial adhesion, but the absence of the hydrazide group-containing compound (C) resulted in poor UV-resistant adhesion. In Comparative Example 2, sodium sulfite was incorporated as an additive, and initial adhesion was poor despite the incorporation of the carbodiimide group-containing compound (B). In Comparative Example 3, epoxy compound 1 was incorporated as a crosslinking agent instead of the carbodiimide group-containing compound (B), resulting in poor initial adhesion.

[0108] In contrast, Examples 1 to 17 exhibited excellent initial adhesion and UV adhesion resistance. Comparing Example 1, Example 11, and Example 12, it was found that, as a polyisocyanate, an aromatic ring-containing polyisocyanate was superior to an aliphatic polyisocyanate in initial adhesion and UV adhesion resistance. Comparing Example 1 and Example 14, it was found that, as a neutralizing agent, ammonia tended to provide better initial adhesion than a tertiary amine (triethylamine). Comparing Example 1, Example 7, Example 8, and Example 17, it was found that an aromatic polyester polyol was superior to an aliphatic polyester polyol in water-resistant adhesion.

[0109] The various numerical ranges described in this specification can be arbitrarily combined with their upper and lower limits, and all such combinations are considered to be preferred numerical ranges described in this specification. Furthermore, a numerical range described as "X to Y" means from X to Y.

[0110] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their omissions, substitutions, modifications, etc. are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents.

Claims

1. A polyurethane aqueous dispersion obtained by dispersing a polyurethane resin (A) containing a polyester polyol as a constituent component in an aqueous dispersion medium, The polyurethane resin (A) has a carboxy group, The polyurethane aqueous dispersion contains a carbodiimide group-containing compound (B) and a compound (C) represented by the following general formula (2): 【Chemical 1】 In general formula (2), R １ represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms, R ２ represents a hydrocarbon group having 1 to 3 carbon atoms, and R 3 represents a divalent organic group having 1 to 12 carbon atoms; Polyurethane water-based dispersion.

2. A polyurethane aqueous dispersion obtained by dispersing a polyurethane resin (A) containing a polyester polyol as a constituent component in an aqueous dispersion medium, The polyurethane resin (A) has a carboxy group, The polyurethane aqueous dispersion contains a carbodiimide group-containing compound (B) and a compound (C) having two groups represented by the following general formula (1) in one molecule: 【Chemistry 2】 In general formula (1), R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms, R 2 represents a hydrocarbon group having 1 to 3 carbon atoms, * represents a bond, The compound (C) includes a compound represented by the following general formula (3): 【Chemistry 3】 In general formula (3), R １ represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms, R ２ represents a hydrocarbon group having 1 to 3 carbon atoms, and m represents an integer of 1 to 12. Polyurethane water-based dispersion.

3. The aqueous polyurethane dispersion according to claim 1 , wherein the polyester polyol comprises an aromatic polyester polyol.

4. A polyurethane aqueous dispersion obtained by dispersing a polyurethane resin (A) containing a polyester polyol as a constituent component in an aqueous dispersion medium, The polyurethane resin (A) has a carboxy group, The polyurethane aqueous dispersion contains a carbodiimide group-containing compound (B) and a compound (C) having two groups represented by the following general formula (1) in one molecule: 【Chemistry 4】 In general formula (1), R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms, R 2 represents a hydrocarbon group having 1 to 3 carbon atoms, * represents a bond, The polyurethane aqueous dispersion contains 100 to 350 moles of carbodiimide groups in the carbodiimide group-containing compound (B) relative to 100 moles of carboxy groups in the polyurethane resin (A).

5. A polyurethane aqueous dispersion obtained by dispersing a polyurethane resin (A) containing a polyester polyol as a constituent component in an aqueous dispersion medium, The polyurethane resin (A) has a carboxy group, The polyurethane aqueous dispersion contains a carbodiimide group-containing compound (B) and a compound (C) having two groups represented by the following general formula (1) in one molecule: 【Chemistry 5】 In general formula (1), R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms, R 2 represents a hydrocarbon group having 1 to 3 carbon atoms, * represents a bond, The polyurethane aqueous dispersion contains the compound (C) in an amount of 0.1 to 20 parts by mass per 100 parts by mass of the polyurethane resin (A).

6. An aqueous paint comprising the polyurethane aqueous dispersion according to any one of claims 1 to 5.

7. The water-based paint according to claim 6, which is used as a primer.

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