Blocked polyisocyanate composition, paint composition, curing agent for water-based paint, water-based paint composition and coating film

Abstract

To provide a block polyisocyanate composition, a paint composition, and an aqueous paint composition having excellent low-temperature curing properties and storage stability, as well as a coating film formed from the block polyisocyanate composition. [Solution] A blocked polyisocyanate composition comprising a blocked polyisocyanate (a), a blocking agent dissociation catalyst (b), and a nonionic emulsifier (c) having an HLB value of 12 to 19, wherein the blocked polyisocyanate (a) contains a hydrophilic group (a1), and the blocking agent dissociation catalyst (b) contains a quaternary ammonium salt.

Description

[Technical Field]

[0001] This disclosure relates to a block polyisocyanate composition, a paint composition, a curing agent for aqueous paints, an aqueous paint composition, and a coating film. [Background technology]

[0002] A method is known in which polyisocyanates are inactivated by reacting them with a compound containing active hydrogen groups called a blocking agent. The blocked polyisocyanate obtained by this method does not react with the main component (polyol, etc.) at room temperature, but when heated, the blocking agent dissociates, regenerating the isocyanate groups, which then react with the main component to form crosslinks. Therefore, with this method, the pot life is not significantly limited, and it is possible to pre-mix the main component and curing agent to form a paint. Furthermore, blocked polyisocyanates can also be applied to water-based paints.

[0003] On the other hand, in recent years, there has been a demand for block polyisocyanates that can cure at lower temperatures than conventional materials, with the aim of reducing costs and carbon dioxide emissions during baking, and also to enable coating of plastic components. For this purpose, for example, Patent Document 1 discloses a resin composition for polyurethane coatings comprising a blocked polyisocyanate compound (A), a compound (B) having two or more active hydrogens in its molecule, and a catalyst (C) consisting of a quaternary ammonium organic acid salt of a specific structure. Patent Document 1 states that this resin composition for polyurethane coatings can be cured at low temperatures, has excellent coating film properties, is excellent in terms of resistance to yellowing of the cured resin and storage stability of the coating, and is highly safe with no concern about environmental pollution such as water pollution. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 08-170048 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, even with the polyurethane coating resin composition using the blocking agent dissociation catalyst described in Patent Document 1, the low-temperature curing properties and storage stability are not fully satisfied in the case of an aqueous coating composition. Therefore, one aspect of this disclosure aims to provide a block polyisocyanate composition, a paint composition, a curing agent for aqueous paints, and an aqueous paint composition having excellent low-temperature curing properties and storage stability. Another aspect of this disclosure aims to provide a coating film obtained from the aqueous paint composition. [Means for solving the problem]

[0006] Each aspect of this disclosure provides at least the following [1] to

[11] .

[0007] [1] It contains a blocked polyisocyanate (a), a blocking agent dissociation catalyst (b), and a nonionic emulsifier (c) with an HLB value of 12-19. The aforementioned block polyisocyanate (a) contains a hydrophilic group (a1), The blocking agent dissociation catalyst (b) contains a quaternary ammonium salt, A blocked polyisocyanate composition in which the content of the blocking agent dissociation catalyst (b) is 0.0001 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the blocked polyisocyanate (a).

[0008] [2] [1] The blocked polyisocyanate composition according to claim 1, wherein the blocked polyisocyanate (a) is blocked with one or more blocking agents selected from the group consisting of oxime compounds and active methylene compounds.

[0009] [3] The blocked polyisocyanate composition according to [1] or [2], wherein the blocked polyisocyanate (a) contains a structure derived from an aliphatic polyisocyanate having 4 to 6 carbon atoms or a derivative thereof.

[0010] [4] The blocked polyisocyanate composition according to any one of [1] to [3], wherein the hydrophilic group (a1) is a group derived from a nonionic hydrophilic compound having a number average molecular weight of 600 to 2000.

[0011] [5] The blocked polyisocyanate composition according to any one of [1] to [4], wherein the content of the hydrophilic group (a1) is 5 to 30 parts by mass with respect to 100 parts by mass of the blocked polyisocyanate (a).

[0012] [6] The blocked polyisocyanate composition according to any one of [1] to [5], wherein the quaternary ammonium salt contains a cationic group represented by the following formula (1).

[0013] [Chemical formula]

[0014] [In formula (1), R 1 represents an alkyl group having 1 to 16 carbon atoms which may have a hydroxy group, an amino group or an alkoxy group as a substituent, or an aryl group having 6 to 16 carbon atoms, and R 2 to R 4 each independently represent an alkyl group having 1 to 8 carbon atoms.

[0015] [7] A blocked polyisocyanate composition containing a blocked polyisocyanate (a), a blocking agent dissociation catalyst (b), and a nonionic emulsifier (c) having an HLB value of 12 to 19, wherein the blocked polyisocyanate (a) contains a hydrophilic group (a1), and the blocking agent dissociation catalyst (b) contains a quaternary ammonium salt.

[0016] [8] A paint composition comprising a main component and a curing agent, comprising the block polyisocyanate composition described in any one of [1] to [7].

[0017] [9] A curing agent for aqueous paints comprising a block polyisocyanate composition as described in any one of items [1] to [7].

[0018]

[10] It contains a blocked polyisocyanate (a), a blocking agent dissociation catalyst (b), a nonionic emulsifier (c) with an HLB value of 12-19, and water. The aforementioned block polyisocyanate (a) contains a hydrophilic group (a1), The blocking agent dissociation catalyst (b) contains a quaternary ammonium salt, An aqueous paint composition in which the content of the blocking agent dissociation catalyst (b) is 0.0001 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the blocked polyisocyanate (a).

[0019]

[11] A coating film formed from the aqueous coating composition described in

[10] . [Effects of the Invention]

[0020] According to one aspect of this disclosure, a block polyisocyanate composition, a paint composition, a curing agent for aqueous paints, and an aqueous paint composition having excellent low-temperature curing properties and storage stability can be provided. Furthermore, according to another aspect of this disclosure, a coating film obtained from the aqueous paint composition can be provided. [Modes for carrying out the invention]

[0021] The following describes exemplary embodiments of each aspect of this disclosure. However, the embodiments of this disclosure are not limited in any way to the embodiments described below. In this specification, numerical ranges indicated using "~" indicate a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. Also, unless otherwise explicitly stated, the units of the numbers before and after "~" are the same. Furthermore, the upper and lower limits described individually can be combined in any way.

[0022] <Blocked polyisocyanate composition> The blocked polyisocyanate composition of this embodiment contains a blocked polyisocyanate (a), a blocking agent dissociation catalyst (b), and a nonionic emulsifier (c) having an HLB value of 12 to 19. The aforementioned block polyisocyanate (a) contains a hydrophilic group (a1), The blocking agent dissociation catalyst (b) contains a quaternary ammonium salt.

[0023] Blocked polyisocyanate (a) is hydrophilic because it contains a hydrophilic group (a1). Therefore, blocked polyisocyanate (a) can also be called an aqueous blocked polyisocyanate.

[0024] The HLB value used here is an abbreviation for Hydrophobic Lipophile Balance, and it is a numerical value that represents the balance between the hydrophobic and hydrophilic properties of an emulsifier. HLB value of nonionic emulsifier (N HLB This can be calculated, for example, from the following formula (I) proposed by Griffin. In formula (I), E and P are the mass percentages of the polyoxyalkylene portion and the polyhydric alcohol portion in the emulsifier molecule, respectively.

[0025]

number

[0026] The HLB values ​​of the nonionic emulsifier (c) used in the examples described later were taken from the manufacturer's catalog values.

[0027] The blocked polyisocyanate composition can impart low-temperature curability to the blocked polyisocyanate composition, the paint curing agent, and the paint composition and aqueous paint composition containing the blocked polyisocyanate composition. Furthermore, when the blocked polyisocyanate composition is incorporated into an aqueous paint composition, it exhibits excellent storage stability over time. Therefore, according to one embodiment of the present disclosure, a blocked polyisocyanate composition that is excellent in both low-temperature curability and storage stability can be provided. Here, "excellent low-temperature curing properties" means that even when cured at low temperatures (for example, below 100°C), it is possible to form a coating film that is difficult to dissolve with solvents (for example, methyl ethyl ketone) and has high hardness. The reason for obtaining such effects is not clear, but the inventors speculate as follows. By including a nonionic emulsifier with an HLB value of 12-19 as an emulsifier, the above effects are obtained by (1) allowing the blocked polyisocyanate (a) and the blocking agent dissociation catalyst (b) to be mixed in a well dispersed state, making it easier for the blocking agent dissociation effect to occur, and (2) suppressing coalescence with the main component (polyol, etc.), thereby improving paint stability.

[0028] <Blocked polyisocyanate (a)> Blocked polyisocyanate (a) is a compound that can be derived from a polyisocyanate that does not have isocyanate groups blocked by a blocking agent (hereinafter also simply referred to as "polyisocyanate"). Blocked polyisocyanate is, for example, a reaction product of a polyisocyanate, a hydrophilic compound containing a hydrophilic group (a1), and a blocking agent. That is, in blocked polyisocyanate (a), the hydrophilic group (a1) is bonded to the polyisocyanate via a urethane group, and at least some of the isocyanate groups in the polyisocyanate are blocked by the blocking agent.

[0029] (Polyisocyanate) Polyisocyanates are compounds having multiple isocyanate groups (free isocyanate groups). Examples of polyisocyanates include aromatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates, and their polyisocyanate derivatives. Examples of polyisocyanate derivatives include isocyanurates, allophanates, and biuretes.

[0030] From the viewpoint of improving the yellowing resistance of the cured coating film, it is preferable that the polyisocyanate does not have an aromatic ring. That is, it is preferable that the polyisocyanate is a non-aromatic polyisocyanate. Examples of non-aromatic polyisocyanates include aliphatic polyisocyanates such as hexamethylene diisocyanate, tetramethylene diisocyanate, 2-methyl-pentane-1,5-diisocyanate, 3-methyl-pentane-1,5-diisocyanate, lysine triisocyanate, and trioxyethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate, cyclohexyl diisocyanate, hydrogenated diphenylmethane diisocyanate, norbornane diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, and hydrogenated tetramethylxylene diisocyanate, and derivatives thereof.

[0031] From the viewpoint of further improving curability, the polyisocyanate preferably contains an aliphatic polyisocyanate having 4 to 6 carbon atoms or a derivative thereof, and more preferably contains a hexamethylene diisocyanate or a derivative thereof. In other words, the blocked polyisocyanate (a) preferably contains a blocked polyisocyanate having a structure derived from an aliphatic polyisocyanate having 4 to 6 carbon atoms or a derivative thereof, and more preferably contains a blocked polyisocyanate having a structure derived from a hexamethylene diisocyanate or a derivative thereof. As a derivative of hexamethylene diisocyanate, at least one selected from the group consisting of isocyanurate, allophanate, and biuret is preferably used.

[0032] When using polyisocyanates containing isocyanurate compounds, from the viewpoint of further improving low-temperature curability, the isocyanurate trimer content (isocyanurate trimer content) based on the total mass of the polyisocyanate may be 50% by mass or more, and the isocyanurate group content (isocyanurate group content) relative to the total (100 mol%) of isocyanurate groups and allophanate groups in the polyisocyanate may be greater than 80 mol%. The upper limit of the isocyanurate trimer content may be 80% by mass, and the upper limit of the isocyanurate group content may be 99 mol%.

[0033] (Blocking agent) Blocked polyisocyanate (a) contains a structure derived from the blocking agent. Examples of blocking agents include alcohol-based blocking agents such as methanol, ethanol, n-butanol, isobutanol, 2-ethylhexanol, butyl cellosolve, propylene glycol monomethyl ether, ethylene glycol, and benzyl alcohol; phenol-based blocking agents such as phenol, cresol, ethylphenol, butylphenol, and 2-hydroxypyridine; lactam-based blocking agents such as ε-caprolactam, δ-valerolactam, and γ-butyrolactam; formaldehyde oxime, acetaldehyde oxime, acetone oxime, and methyl ether. Oxime-based blocking agents such as tylketoxime, methylisobutylketoxime, and cyclohexanone oxime; imidazole, 2-methylimidazole, 4-methylimidazole, 2,4-dimethylimidazole, 2-ethylimidazole, 2-propylimidazole, 2-isopropylimidazole, 4-methyl-2-propylimidazole, 2-phenylimidazole, 4-phenylimidazole, 5-phenylimidazole, 2-methyl-4-phenylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-Heptol Imidazole-based blocking agents such as tadecylimidazole, amine-based blocking agents such as diphenylamine, diisopropylamine, isopropylethylamine, meldrumic acid, dimethyl malonate, diethyl malonate, di-n-butyl malonate, di-t-butyl malonate, di-2-ethylhexyl malonate, methyl n-butyl malonate, ethyl n-butyl malonate, methyl s-butyl malonate, ethyl s-butyl malonate, methyl t-butyl malonate, ethyl t-butyl malonate, diethyl methylmalonate, dibenzyl malonate, diphenyl malonate, benzyl malonate Active methylene-based blocking agents such as dimethyl, ethylphenyl malonate, t-butylphenyl malonate, isopropyl malonate, methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, n-butyl acetoacetate, t-butyl acetoacetate, and other alkyl acetoacetates, benzyl acetoacetate, phenyl acetoacetate, 2-acetoacetoxyethyl methacrylate, acetylacetone, ethyl cyanoacetate, pyrazole, 3,5-dimethylpyrazole, 3,5-diisopropylpyrazole, 3,5-diphenylpyrazole, 3,Examples of pyrazole-based blocking agents include 5-di-t-butylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 3-methyl-5-phenylpyrazole. These blocking agents may be used individually or in combination of two or more. Among these, from the viewpoint of storage stability, one or more selected from the group consisting of oxime compounds and active methylene compounds are preferred, oxime compounds are more preferred, and methyl ethyl ketoxime is even more preferred.

[0034] Blocked polyisocyanate (a) may have free isocyanate groups, but from the viewpoint of storage stability, it is preferable that it does not have free isocyanate groups. For example, all of the active isocyanate groups in blocked polyisocyanate (a) may be blocked isocyanate groups. Here, active isocyanate groups mean both free isocyanate groups and blocked isocyanate groups.

[0035] <Hydrophilic compounds having a hydrophilic group (a1)> Blocked polyisocyanate (a) contains a hydrophilic group (a1). In other words, blocked polyisocyanate (a) contains a structure derived from a hydrophilic compound that contains a hydrophilic group (a1). Examples of hydrophilic compounds include nonionic hydrophilic compounds, anionic hydrophilic compounds, and cationic hydrophilic compounds. These hydrophilic compounds may be used individually or in combination of two or more. Among these, nonionic hydrophilic compounds or anionic hydrophilic compounds are preferred due to their ease of manufacture, and nonionic hydrophilic compounds are more preferred.

[0036] (Nonionic hydrophilic compound) Examples of nonionic hydrophilic compounds include poly(oxyalkylene) glycols and poly(oxyalkylene) monoalkyl ethers. Among these, poly(oxyalkylene) monoalkyl ethers are preferred as nonionic hydrophilic compounds from the viewpoint of lowering the viscosity of the blocked polyisocyanate composition.

[0037] The lower limit of the number average molecular weight of the nonionic hydrophilic compound is preferably 200, more preferably 400, and even more preferably 600. When the number average molecular weight is above the above lower limit, the water dispersibility of the block polyisocyanate composition tends to be better. The upper limit of the number average molecular weight of the nonionic hydrophilic compound is preferably 4000, more preferably 3000, and even more preferably 2000. When the number average molecular weight is below the above upper limit, the hardness of the aqueous coating composition containing the block polyisocyanate composition tends to be better. In other words, the number average molecular weight of the nonionic hydrophilic compound, particularly poly(oxyalkylene) monoalkyl ether, is preferably 200 to 4000, more preferably 400 to 3000, and even more preferably 600 to 2000.

[0038] (Anionic hydrophilic compounds) Examples of anionic hydrophilic compounds include carboxyl group-containing compounds and sulfonic acid group-containing compounds. Among these, carboxyl group-containing compounds are preferred as anionic hydrophilic compounds due to their ease of manufacture and compatibility with aqueous paint compositions. Examples of carboxyl group-containing compounds include monohydroxycarboxylic acids, dihydroxycarboxylic acids, and their derivatives. Among these, monohydroxycarboxylic acids or dihydroxycarboxylic acids are preferred as carboxyl group-containing compounds, with monohydroxycarboxylic acids being more preferred. When using a carboxyl group-containing compound or a sulfonic acid group-containing compound as the anionic hydrophilic compound, it is preferable to neutralize the block polyisocyanate composition with a neutralizing agent after its manufacture. Examples of neutralizing agents include alkali metals, alkaline earth metals, ammonia, trimethylamine, triethylamine, dimethylethanolamine, and other tertiary amines.

[0039] (Cationic hydrophilic compounds) Examples of cationic hydrophilic compounds include hydroxyl group-containing amino compounds. When using hydroxyl group-containing amino compounds, it is preferable to neutralize the block polyisocyanate composition with a neutralizing agent after its preparation. Examples of neutralizing agents include organic acids such as acetic acid, propionic acid, butanoic acid, and 2-ethylhexanoic acid.

[0040] From the viewpoint of obtaining an aqueous coating composition with superior low-temperature curing properties, the content of hydrophilic group (a1) is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, based on the total amount of isocyanate compounds in the isocyanate composition obtained by dissociating the blocking agent from the blocked polyisocyanate (a). From the viewpoint of obtaining an aqueous coating composition with superior storage stability, the content of hydrophilic group (a1) is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, based on the total amount of isocyanate compounds in the isocyanate composition obtained by dissociating the blocking agent from the blocked polyisocyanate (a). From these viewpoints, the content of hydrophilic group (a1) is preferably 1 to 50% by mass, more preferably 3 to 40% by mass, and even more preferably 5 to 30% by mass, based on the total amount of isocyanate compounds in the isocyanate composition obtained by dissociating the blocking agent from the blocked polyisocyanate (a). In this specification, "isocyanate compound" means a compound having an isocyanate group.

[0041] From the viewpoint of obtaining an aqueous coating composition with superior low-temperature curing properties, the content of hydrophilic group (a1) is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of block polyisocyanate (a). From the viewpoint of obtaining an aqueous coating composition with superior storage stability, the content of hydrophilic group (a1) is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, per 100 parts by mass of block polyisocyanate (a). From these viewpoints, the content of hydrophilic group (a1) is preferably 1 to 30 parts by mass, more preferably 3 to 20 parts by mass, and even more preferably 5 to 15 parts by mass, per 100 parts by mass of block polyisocyanate (a).

[0042] Blocked polyisocyanate (a) can be obtained, for example, by reacting a polyisocyanate with a hydrophilic compound having a hydrophilic group (a1) and a blocking agent. That is, blocked polyisocyanate (a) can be a reaction product of a polyisocyanate, a hydrophilic compound having a hydrophilic group (a1), and a blocking agent. The polyisocyanate, the hydrophilic compound having a hydrophilic group (a1), and the blocking agent may each be used individually or in combination of two or more. If an aromatic polyisocyanate is not used as the polyisocyanate, the yellowing resistance of the cured coating film can be improved.

[0043] The order in which the polyisocyanate, hydrophilic compound, and blocking agent are reacted is not particularly limited, but it is preferable to react the polyisocyanate and hydrophilic compound to obtain an isocyanate group-terminated precursor, and then react the obtained isocyanate group-terminated precursor with the blocking agent.

[0044] The reaction between polyisocyanate and hydrophilic compound may be carried out, for example, in the presence of a solvent. Suitable solvents include aromatic solvents such as toluene and xylene, ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as ethyl acetate and butyl acetate, and glycol ether solvents such as ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate and diethylene glycol diethyl ether. The reaction temperature may be 20 to 200°C. The reaction time may be, for example, 1 to 10 hours. The amounts of polyisocyanate and hydrophilic compound used may be adjusted so that the content of the hydrophilic group (a1) falls within the above range. The reaction proceeds even without a catalyst, but the reaction can also be accelerated by using a known urethane reaction catalyst.

[0045] The reaction between the isocyanate group-terminated precursor and the blocking agent can be carried out according to the reaction conditions of a normal blocking reaction. The reaction between the isocyanate group-terminated precursor and the blocking agent may be carried out at room temperature or with heating. Regardless of whether heating is used, the temperature of the reaction solution may be, for example, 20 to 200°C.

[0046] The method for producing blocked polyisocyanate (a) is not limited to the above. For example, if the reaction product obtained after reacting a polyisocyanate with a hydrophilic compound and a blocking agent has free isocyanate groups, blocked polyisocyanate (a) can also be obtained by reacting the free isocyanate groups of the reaction product with a modifying agent such as an active hydrogen group-containing compound.

[0047] Furthermore, as the polyisocyanate (polyisocyanate without isocyanate groups blocked by the blocking agent), a polyisocyanate having hydrophilic groups (e.g., alkoxy polyethylene oxide groups) may be used instead of a polyisocyanate without hydrophilic groups. In this case, blocked polyisocyanate (a) can also be obtained by reacting the hydrophilic polyisocyanate with the blocking agent.

[0048] Furthermore, instead of the above-mentioned polyisocyanate (polyisocyanate without isocyanate groups blocked by a blocking agent), blocked polyisocyanate (a) can also be obtained by using blocked polyisocyanate. For example, blocked polyisocyanate (a) can also be obtained by reacting a blocked polyisocyanate without hydrophilic groups (alkoxy polyethylene oxide groups) with the above-mentioned hydrophilic compound.

[0049] Blocked polyisocyanates may be used individually or in combination of two or more types. For example, two or more blocked polyisocyanates derived from different types of polyisocyanates may be used in combination.

[0050] From the viewpoint of obtaining an aqueous coating composition with superior low-temperature curing properties, the content of blocked polyisocyanate (a) may be 40% by mass or more, based on the total solid content of the blocked polyisocyanate composition, and may also be 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, or 80% by mass or more. From the viewpoint of improving the storage stability of the aqueous coating composition, the content of blocked polyisocyanate (a) may be 100% by mass or less, based on the total solid content of the blocked polyisocyanate composition, and may also be 95% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less. From these viewpoints, the content of blocked polyisocyanate (a) may be, for example, 40 to 100% by mass, based on the total solid content of the blocked polyisocyanate composition. Furthermore, the total solid content of a blocked polyisocyanate composition means the total amount of the blocked polyisocyanate composition minus the amount of the solvent if the blocked polyisocyanate composition contains a solvent, and the total amount of the blocked polyisocyanate composition if the blocked polyisocyanate composition does not contain a solvent.

[0051] <Blocking agent dissociation catalyst (b)> The blocking agent dissociation catalyst (b) contains a quaternary ammonium salt. As the quaternary ammonium salt, any quaternary ammonium salt known as a blocking agent dissociation catalyst can be used without particular limitation. However, from the viewpoint of easily obtaining an aqueous coating composition excellent in low-temperature curability, it is preferable to use a quaternary ammonium salt containing a cationic group represented by the following formula (1).

[0052]

Chemical formula

[0053] In formula (1), R 1 represents an alkyl group having 1 to 16 carbon atoms which may have a hydroxy group, an amino group or an alkoxy group as a substituent, or an aryl group having 6 to 16 carbon atoms, and R 2 ~R 4 each independently represents an alkyl group having 1 to 8 carbon atoms.

[0054] The alkyl group represented by R 1 may have 1 to 10 carbon atoms or 6 to 8 carbon atoms. Specific examples of the alkyl group represented by R 1 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, a 2-ethylhexyl group, a 2-propylheptyl group, a nonyl group, a decyl group, an isodecyl group, a dodecyl group, a hexadecyl group, etc. These groups may be substituted with one or more hydroxy groups, one or more amino groups, or one or more alkoxy groups. The carbon number of the alkoxy group may be, for example, 1 to 8, 1 to 6, 1 to 4 or 1 to 2. Examples of the alkoxy group include a methoxy group, an ethoxy group, a butoxy group, a propyloxy group, a pentyloxy group, a hexyloxy group, etc.

[0055] Examples of aryl groups having 6 to 16 carbon atoms include phenyl, naphthyl, anthryl, tolyl, xylyl, cumenyl, vinylphenyl, biphenylyl, and phenanthryl groups.

[0056] R 1 From the viewpoint of obtaining an aqueous coating composition with superior low-temperature curing properties, the alkyl group is preferably an unsubstituted alkyl group or a hydroxyalkyl group, and more preferably an unsubstituted alkyl group. Among unsubstituted alkyl groups, alkyl groups having 1 to 10 carbon atoms are preferred, alkyl groups having 6 to 8 carbon atoms are more preferred, alkyl groups having 8 carbon atoms are even more preferred, and an n-octyl group is particularly preferred.

[0057] R 2 ~R 4 The number of carbon atoms in the alkyl group represented by R may be 1 to 4 or 1 to 2. 2 ~R 4 Specific examples of alkyl groups represented by include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group, etc. From the viewpoint of easily obtaining an aqueous coating composition with superior low-temperature curing properties, R 2 ~R 4 It is preferable that all of them are methyl groups.

[0058] From the viewpoint of obtaining an aqueous coating composition with even better low-temperature curing properties, the quaternary ammonium salt is preferably having a structure represented by the following formula (2) or (3), and more preferably having a structure represented by the following formula (2).

[0059] [ka]

[0060] [ka]

[0061] The anionic group of the quaternary ammonium salt may be, for example, an organic acid group or an inorganic acid group. Examples of organic acid groups include fatty acid groups and monoalkyl carbonate groups. Examples of inorganic acid groups include halogen groups (e.g., fluoro groups, chloro groups, bromo groups, etc.), hydroxyl groups, bicarbonate groups, and carbonate groups.

[0062] The number of carbon atoms in a fatty acid group (aliphatic monocarboxylic acid group) may be, for example, 1 to 12, 1 to 7, or 1 to 3. Specific examples of fatty acid groups include formic acid, acetate, octic acid, lauric acid, cyclohexanecarboxylic acid, and pivalic acid.

[0063] The number of carbon atoms in a monoalkyl carbonate group may be, for example, 1 to 8, or 1 to 4 or 1 to 2. Specific examples of monoalkyl carbonate groups include methyl carbonate, ethyl carbonate, propyl carbonate, and butyl carbonate.

[0064] From the viewpoint of obtaining aqueous coating compositions with superior low-temperature curing properties, the anionic group of the quaternary ammonium salt is preferably a fatty acid group having 1 to 12 carbon atoms, a monoalkyl carbonate group having 1 to 8 carbon atoms, or a hydroxyl group; more preferably a fatty acid group having 1 to 7 carbon atoms or a monoalkyl carbonate group having 1 to 4 carbon atoms; and even more preferably a monoalkyl carbonate group having 1 to 2 carbon atoms.

[0065] From the above viewpoint, it is preferable that the quaternary ammonium salt is composed of a combination of a cationic group represented by any of the above formulas (1) to (3) and a fatty acid group having 1 to 12 carbon atoms, a monoalkyl carbonate group having 1 to 8 carbon atoms, or a hydroxyl group.

[0066] Suitable examples of quaternary ammonium salts include trimethyl n-octylammonium bicarbonate, trimethyl n-octylammonium monomethyl carbonate, trimethyl n-octylammonium carbonate, tetramethylammonium acetate, hexadecyltrimethylammonium hydroxide, trimethyl(2-hydroxypropyl)ammonium 2-ethylhexanoic acid, tetramethylammonium bicarbonate, tetraethylammonium bicarbonate, tetran-propylammonium bicarbonate, tetran-butylammonium bicarbonate, triethylmonomethylammonium bicarbonate, trin-propylmonomethylammonium bicarbonate, trin-butylmonomethylammonium bicarbonate, trin-butylmonoethylammonium bicarbonate, tetramethylammonium monomethyl carbonate, tetraethylammonium monoethyl carbonate, tetran-butylammonium monobutyl carbonate, triethylmonomethylammonium monomethyl carbonate, trin-propylmonomethylammonium monomethyl carbonate, trin-butylmonomethylammonium monomethyl carbonate, trin-butylmonoethylammonium monoethyl carbonate, tetramethylammonium carbonate, and tetran-butylammonium carbonate. Among these, paint compositions exhibiting particularly excellent low-temperature curing properties are easily obtained when trimethyl n-octylammonium monomethyl carbonate is used. Quaternary ammonium salts may be used individually or in combination of two or more.

[0067] The blocked polyisocyanate composition may contain a blocking agent dissociation catalyst (b) other than a quaternary ammonium salt, but the proportion of the quaternary ammonium salt in the total blocking agent dissociation catalyst may be 0.0001 to 100% by mass, 0.001 to 100% by mass, or 0.01 to 100% by mass.

[0068] From the viewpoint of improving low-temperature curability, the content of the blocking agent dissociation catalyst (b) may be 0.0001 parts by mass or more per 100 parts by mass of blocked polyisocyanate (a), and may be 0.001 parts by mass or more, 0.01 parts by mass or more, 1 part by mass or more, 5 parts by mass or more, 10 parts by mass or more, 15 parts by mass or more, 20 parts by mass or more, or 25 parts by mass or more. From the viewpoint of improving the storage stability of the paint, the content of the blocking agent dissociation catalyst (b) may be 40 parts by mass or less per 100 parts by mass of blocked polyisocyanate (a), and may be 35 parts by mass or less, 30 parts by mass or less, 25 parts by mass or less, or 20 parts by mass or less. From these viewpoints, the content of the blocking agent dissociation catalyst (b) may be, for example, 0.0001 to 40 parts by mass per 100 parts by mass of blocked polyisocyanate (a).

[0069] <Emulsifier> The blocked polyisocyanate composition contains a nonionic emulsifier (c) with an HLB value of 12 to 19. The lower limit of the HLB value may be 13 or higher, and may be 14 or higher, 15 or higher, 16 or higher, 17 or higher, or 18 or higher. The upper limit of the HLB value may be 19 or lower, and may be 18 or lower, 17 or lower, 16 or lower, 15 or lower, 14 or lower, or 13 or lower. The nonionic emulsifier (c) is not particularly limited, but examples include the compound represented by the following formula (4) (hereinafter also referred to as "compound (4)").

[0070] [ka]

[0071] (In formula (4), R 11 R is an alkylene group having 2 to 10 carbon atoms. 12 (This is an alkyl group having 1 to 22 carbon atoms or an aryl group having 6 to 32 carbon atoms. n11 is a number between 1.0 and 100.)

[0072] (R 11 ) R 11From the viewpoint of imparting hydrophilicity, it is an alkylene group having 2 to 10 carbon atoms. 11 Examples of alkylene groups with 2 to 10 carbon atoms in R include ethylene, n-propylene, n-butylene, n-pentyl, n-hexyl, n-butyl, n-octyl, n-nonyl, and n-decyl groups. From the viewpoint of imparting greater hydrophilicity, R 11 As such, an ethylene group or a propylene group is preferred.

[0073] (R 12 ) R 12 R is an alkyl group having 1 to 22 carbon atoms or an aryl group having 6 to 32 carbon atoms. 12 Examples of alkyl groups having 1 to 22 carbon atoms in R include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group, n-nonyl group, n-decyl group, etc. 12 Examples of aryl groups having 6 to 32 carbon atoms include phenyl groups and naphthyl groups.

[0074] (n11) n11 represents the number of repeating oxyalkylene groups, i.e., the degree of polymerization of compound (4). Furthermore, compound (4) is not a single component, but an aggregate of substances with different n11 values. Therefore, n11 is expressed as the average value of the degree of polymerization. Moreover, from the viewpoint of water dispersibility, water dispersion stability, and coating film appearance, the lower limit of n11 is preferably 1.0, and more preferably 2.0. When n11 is above the above lower limit, water dispersibility is improved, and the composition can be dispersed more easily. Furthermore, the upper limit of n11, which is the average degree of polymerization, is preferably 100 and more preferably 50, from the viewpoint of water dispersibility and coating film hardness. When n11 is below the above upper limit, excessive viscosity increases such as gelation of the block polyisocyanate composition can be more effectively prevented, and it tends to disperse more easily in water. In other words, the average value of the degree of polymerization, n11, is preferably between 1.0 and 100, and more preferably between 2.0 and 50.

[0075] Examples of commercially available compounds (4) include "Newcol® 710-F" (HLB value 13.3), "Newcol® 714(80)" (HLB value 15.0), "Newcol® 723(60)" (HLB value 16.6), "Newcol® 1020" (HLB value 17.4), "Newcol® 740(60)" (HLB value 17.9), and "Newcol® 780(60)" (HLB value 18.9), all manufactured by Nippon Emulsifier Co., Ltd. The above nonionic emulsifiers may be used alone or in combination of two or more types.

[0076] The content of the nonionic emulsifier (c) is preferably 1 to 50 parts by mass, and more preferably 3 to 40 parts by mass, per 100 parts by mass of block polyisocyanate (a). If the content is 1 part by mass or more, the block polyisocyanate composition can be easily dispersed in water. If the content is 50 parts by mass or less, the low-temperature curability is improved. The content of the nonionic emulsifier (c) may be 5 parts by mass or more, 7 parts by mass or more, 9 parts by mass or more, 10 parts by mass or more, or 35 parts by mass or less, 30 parts by mass or less, 25 parts by mass or less, or 20 parts by mass or less.

[0077] (Other ingredients) The blocked polyisocyanate composition may contain a solvent. Hydrophilic solvents are preferably used as the solvent. Examples of solvents include water, ethylene glycol, propylene glycol, 1,4-butanediol, methyl ethyl ketone, acetone, ethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol dimethyl ether, N-methylpyrrolidone, ethylene glycol monoethyl ether acetate, and diethylene glycol diethyl ether. These solvents may be used alone or in combination of two or more.

[0078] The solvent content may be 0 to 90% by mass, 5 to 80% by mass, or 10 to 70% by mass, based on the total mass of the blocked polyisocyanate composition.

[0079] The blocked polyisocyanate composition may contain polyisocyanate (for example, polyisocyanate remaining as unreacted material) and may contain unreacted blocking agents. The polyisocyanate content in the blocked polyisocyanate composition may be 5% by mass or less, or 0% by mass, based on the total solid content of the blocked polyisocyanate composition. The unreacted blocking agent content in the blocked polyisocyanate composition may be 5% by mass or less, or 0% by mass, based on the total solid content of the blocked polyisocyanate composition.

[0080] The block polyisocyanate composition may further contain additives such as pigments, dispersion stabilizers, viscosity modifiers, leveling agents, gelation inhibitors, light stabilizers, antioxidants, ultraviolet absorbers, heat resistance improvers, inorganic and organic fillers, plasticizers, lubricants, antistatic agents, reinforcing materials, and catalysts.

[0081] The effective isocyanate group content (hereinafter referred to as "effective NCO content") of the blocked polyisocyanate composition may be 4 to 10% by mass, 3 to 20% by mass, or 3 to 28% by mass or more, from the viewpoint of further improving the curability of the paint. Here, the effective NCO content is expressed in mass percent as the isocyanate groups that can participate in the crosslinking reaction present in the blocked polyisocyanate composition, and the effective NCO content is expressed in mass percent as the isocyanate groups that can participate in the crosslinking reaction present in the blocked polyisocyanate composition, and can be rephrased as the content of free isocyanate groups in the polyisocyanate composition obtained by dissociating the blocking agent from the blocked isocyanate, relative to the total mass of the blocked polyisocyanate composition (free NCO content). The free NCO content can be determined by reacting the isocyanate groups in the sample (a polyisocyanate composition obtained by dissociating a blocking agent from a blocked isocyanate) with an excess secondary amine, and then back-titrating the unreacted secondary amine with hydrochloric acid.

[0082] The blocked polyisocyanate composition described above is obtained by mixing the blocked polyisocyanate (a), the blocking agent dissociation catalyst (b), the nonionic emulsifier (c), and any other components that may be included. The blocked polyisocyanate composition is suitably used as a curing agent component in aqueous paint compositions. That is, another embodiment of the present disclosure is a curing agent for aqueous paints comprising the blocked polyisocyanate composition described above.

[0083] (Water-based paint composition / paint composition) Another embodiment of the present disclosure is an aqueous coating composition comprising a compound having two or more isocyanate-reactive groups (hereinafter referred to as "isocyanate-reactive compound"), the blocked polyisocyanate (a), the blocking agent dissociation catalyst (b) containing the quaternary ammonium salt, the nonionic emulsifier (c), and water. Another embodiment of the present disclosure is a coating composition comprising a main component and a curing agent, comprising the above-mentioned block polyisocyanate composition. The main component is an isocyanate-reactive compound. The curing agent may be the above-mentioned block polyisocyanate composition, or may further contain other polyisocyanate components. Details of the blocked polyisocyanate (a), blocking agent dissociation catalyst (b), quaternary ammonium salt, and nonionic emulsifier (c) (including preferred embodiments) are the same as the details of the blocked polyisocyanate (a), quaternary ammonium salt, blocking agent dissociation catalyst (b), and nonionic emulsifier (c) contained in the blocked polyisocyanate composition of the above embodiment.

[0084] The water-based paint composition contains a blocked polyisocyanate (a), a quaternary ammonium salt, and a nonionic emulsifier (c), and therefore has excellent low-temperature curing properties.

[0085] Isocyanate-reactive compounds have two or more isocyanate-reactive groups (e.g., active hydrogen groups). Examples of isocyanate-reactive groups include hydroxyl groups and amino groups. Examples of isocyanate-reactive compounds include polyols, polyamines, and amino alcohols. Among these, polyols are preferably used. Examples of polyols include acrylic polyols, polyester polyols, polyether polyols, epoxy polyols, polycarbonate polyols, and polylactone polyols. The hydroxyl value of polyols may be, for example, 10 to 300 mg KOH / g per solid content.

[0086] Isocyanate-reactive compounds may be used in an emulsified, dispersed, or dissolved state in water. In other words, an aqueous paint composition may contain an isocyanate-reactive compound-containing liquid (solution, dispersion, emulsion, or suspension) obtained by emulsifying, dispersing, or dissolving an isocyanate-reactive compound in water. The isocyanate-reactive compound-containing liquid may also contain a neutralizing agent for ammonia or water-soluble amino compounds (such as triethylamine or tertiary amines like 2-(dimethylamino)ethanol).

[0087] The equivalent ratio of isocyanate-reactive groups to active isocyanate groups ([isocyanate-reactive groups] / [active isocyanate groups]) in an aqueous paint composition is determined by the required film properties and is not particularly limited, but is usually in the range of 0.2 to 2.

[0088] The aqueous paint composition may contain other components that may be included in the above-mentioned block polyisocyanate composition.

[0089] A water-based paint composition may be a one-component composition in which all constituent components are contained in a single liquid, or it may be a multi-component composition in which the constituent components exist separately in multiple liquids. A multi-component water-based paint composition may comprise a first liquid (main component) containing an isocyanate-reactive compound, and a second liquid (curing agent) containing a blocked polyisocyanate (a). In this case, other constituent components (blocking agent dissociation catalyst and other components) may be contained in the first liquid, in the second liquid, or in liquids different from the first and second liquids.

[0090] Water-based paint compositions can be used as top and intermediate coatings for automobiles, chipping-resistant paints, electrodeposition paints, paints for automobile parts, paints for automobile repairs, pre-coated metals and rust-resistant steel sheets for metal products such as home appliances and office equipment, paints for building materials, paints for plastics, adhesives, adhesion promoters, sealants, etc.

[0091] <coating film> Another embodiment of the present disclosure is a coating film formed from the aqueous coating composition of the above embodiment.

[0092] The coating film includes a cured product of the aqueous coating composition of the above embodiment. The coating film can be formed by applying the aqueous coating composition onto a substrate using a known method and curing the coating film (uncured coating film) made of the aqueous coating composition. Examples of known methods include roll coating, curtain flow coating, spray coating, electrostatic coating, bell coating, electrodeposition coating, etc. The amount of aqueous coating composition applied, the thickness of the coating film, etc., can be appropriately determined depending on the material of the surface to be coated, etc.

[0093] The curing of a coating film made from an aqueous paint composition may be performed by heating the coating film. The heating temperature (baking temperature) may be, for example, 200°C or less, and the heating time (baking time) may be, for example, 10 to 180 minutes. According to the aqueous paint composition of this embodiment, a good cured coating film can be obtained even when baking is performed at a low temperature of 100°C or less. [Examples]

[0094] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0095] <Example 1> (Production of block polyisocyanate compositions) In a four-necked flask equipped with a stirrer, thermometer, heating device, nitrogen seal tube, and condenser, 316 g of Coronate 2793 (manufactured by Tosoh Corporation, hexamethylene diisocyanate trimer, NCO content 14.3% by mass, trade name), 35 g of MPEG-1000 (manufactured by Nippon Emulsifier Co., Ltd., polyethylene glycol monomethyl ether, number average molecular weight = 1000, trade name), and 343 g of diethyldiglycol (manufactured by Nippon Emulsifier Co., Ltd., diethylene glycol diethyl ether, trade name, "DEDG" in Table 1) were charged. The flask was then purged with nitrogen, and the mixture was heated to 80°C while stirring. The reaction was carried out at the same temperature for 4 hours to obtain an isocyanate-terminated precursor having an alkoxy polyethylene oxide group as a hydrophilic group. Next, 105g of methyl ethyl ketoxime (manufactured by Fujifilm Wako Pure Chemical Industries, "MEKO" in Table 1) was added, keeping the temperature below 80°C, and the mixture was reacted at 70°C for 2 hours. An infrared absorption spectrum (IR measurement) was then performed, revealing the peak of the NCO group (2270cm²). -1 Once the surrounding area had disappeared, the mixture was cooled to room temperature, and 125 g of trimethylmono-n-octylammonium monomethyl carbonate solution (manufactured by Tosoh Corporation, solid content concentration 55% by mass, "TMOA-MC" in Table 1) and 76 g of Newcol 710-F (manufactured by Nippon Emulsifier Co., Ltd., HLB value 13.3, "A-1" in Table 1) were added and stirred for 30 minutes to obtain a composition containing blocked polyisocyanate (blocked polyisocyanate composition (BI-1)).

[0096] <Example 2> A blocked polyisocyanate composition (BI-2) was obtained in the same manner as in Example 1, except that Newcol 714(80) (manufactured by Nippon Emulsifier Co., Ltd., HLB value 15.0, "A-2" in Table 1) was used instead of Newcol 710-F in Example 1.

[0097] <Example 3> A blocked polyisocyanate composition (BI-3) was obtained in the same manner as in Example 1, except that Newcol 723(60) (manufactured by Nippon Emulsifier Co., Ltd., HLB value 16.6, "A-3" in Table 1) was used instead of Newcol 710-F in Example 1.

[0098] <Example 4> A blocked polyisocyanate composition (BI-4) was obtained in the same manner as in Example 1, except that Newcol 1020 (manufactured by Nippon Emulsifier Co., Ltd., HLB value 17.4, "A-4" in Table 1) was used instead of Newcol 710-F in Example 1.

[0099] <Example 5> A blocked polyisocyanate composition (BI-5) was obtained in the same manner as in Example 1, except that Newcol 740(60) (manufactured by Nippon Emulsifier Co., Ltd., HLB value 17.9, "A-5" in Table 1) was used instead of Newcol 710-F in Example 1.

[0100] <Example 6> A blocked polyisocyanate composition (BI-6) was obtained in the same manner as in Example 1, except that Newcol 780(60) (manufactured by Nippon Emulsifier Co., Ltd., HLB value 18.9, "A-6" in Table 1) was used instead of Newcol 710-F.

[0101] <Comparative Example 1> A blocked polyisocyanate composition (BI-7) was obtained in the same manner as in Example 1, except that the amounts of the materials were changed to the amounts shown in Table 1.

[0102] <Comparative Example 2> A blocked polyisocyanate composition (BI-8) was obtained in the same manner as in Example 1, except that Newcol 80 (manufactured by Nippon Emulsifier Co., Ltd., HLB value 6.4, "A-7" in Table 2) was used instead of Newcol 710-F in Example 1.

[0103] <Comparative Example 3> A blocked polyisocyanate composition (BI-9) was obtained in the same manner as in Example 1, except that Newcol 704 (manufactured by Nippon Emulsifier Co., Ltd., HLB value 9.2, "A-8" in Table 2) was used instead of Newcol 710-F in Example 1.

[0104] <Comparative Example 4> A blocked polyisocyanate composition (BI-10) was obtained in the same manner as in Example 1, except that Newcol 85 (manufactured by Nippon Emulsifier Co., Ltd., HLB value 11.4, "A-9" in Table 2) was used instead of Newcol 710-F in Example 1.

[0105] <Comparative Examples 5-7> Block polyisocyanate compositions (BI-11 to BI-13) were obtained in the same manner as in Example 1, except that the amounts of the materials were changed to the amounts shown in Table 1.

[0106] [Table 1]

[0107] [Table 2]

[0108] The hydrophilic group introduction rates in Tables 1 and 2 represent the introduction rate of hydrophilic groups (alkoxypolyethylene oxide groups) in the isocyanate group-terminated precursors, and are equal to the alkoxypolyethylene oxide group content in the isocyanate composition obtained by dissociating the blocking agent from the blocked polyisocyanate in the blocked polyisocyanate composition, based on the total amount of isocyanate compounds.

[0109] The effective NCO content is the content of effective isocyanate groups in the blocked polyisocyanate composition. It was determined by adding an excess of secondary amine relative to the isocyanate groups to the blocked polyisocyanate composition, heating it at a temperature above the dissociation temperature of the oxime-based blocking agent (e.g., 160°C) for a sufficient time for the blocking agent to dissociate (e.g., 1 hour), reacting the free isocyanate groups with the secondary amine, and then back-titrating the unreacted secondary amine with hydrochloric acid.

[0110] <Rating> (Preparation of water-based paint composition) Aqueous paint compositions of Examples 1-6 and Comparative Examples 1-7 were prepared using the block polyisocyanate compositions of Examples 1-6 and Comparative Examples 1-7, respectively. Specifically, the aqueous paint compositions were prepared by mixing the main component, Barnock WE-301 (manufactured by DIC, acrylic emulsion, solids content 45% by mass, hydroxyl value 36 mg KOH / g, trade name), the curing agent, the block polyisocyanate composition, and water, and stirring at high speed at 2000 rpm for 2 minutes using a homomixer. The amounts (in g) used for the main component (Barnock WE-301), curing agent (block polyisocyanate composition), and water are shown in Tables 3 and 4. Note that the amounts of the main component shown in Tables 3 and 4 represent the total mass including the solvent.

[0111] (Evaluation of low-temperature curing properties) [Gel fraction measurement] The aqueous paint composition prepared above was applied to release paper to a thickness of 200 μm before drying. The resulting coating was left to stand at room temperature for 60 minutes, and then baked in a constant temperature bath at 80°C for 20 minutes. The baked coating (cured coating) was immersed in methyl ethyl ketone at room temperature for 24 hours, and the gel fraction was determined. The gel fraction was calculated using the following formula. The results are shown in Tables 3 and 4. Gel fraction (unit: mass%) = Mass of coating film after immersion (mass of undissolved portion) / Mass of coating film before immersion × 100

[0112] If the gel fraction measured above was 65% by mass or higher, it was evaluated as having excellent low-temperature curing properties.

[0113] (Storage stability assessment) Water-based paint compositions were left to stand at 40°C, and their dispersion state before and after standing was visually observed to evaluate their storage stability. The number of days during which the composition remained liquid and no precipitate formed after standing was also evaluated.

[0114] [Table 3]

[0115] [Table 4]

Claims

1. It contains a blocked polyisocyanate (a), a blocking agent dissociation catalyst (b), and a nonionic emulsifier (c) having an HLB value of 12 to 19. The aforementioned block polyisocyanate (a) contains a hydrophilic group (a1), The blocking agent dissociation catalyst (b) contains a quaternary ammonium salt, A blocked polyisocyanate composition in which the content of the blocking agent dissociation catalyst (b) is 0.0001 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the blocked polyisocyanate (a).

2. The blocked polyisocyanate composition according to claim 1, wherein the blocked polyisocyanate (a) is blocked with an oxime compound blocking agent.

3. The block polyisocyanate composition according to claim 1, wherein the block polyisocyanate (a) comprises a structure derived from an aliphatic polyisocyanate having 4 to 6 carbon atoms or a derivative thereof.

4. The blocked polyisocyanate composition according to claim 1, wherein the hydrophilic group (a1) is a group derived from a nonionic hydrophilic compound having a number average molecular weight of 600 to 2000.

5. The block polyisocyanate composition according to claim 1, wherein the content of the hydrophilic group (a1) is 5 to 15 parts by mass per 100 parts by mass of the block polyisocyanate (a).

6. The blocked polyisocyanate composition according to claim 1, wherein the quaternary ammonium salt comprises a cationic group represented by the following formula (1). 【Chemistry 1】 [In formula (1), R １ R represents an alkyl group having 1 to 16 carbon atoms, or an aryl group having 6 to 16 carbon atoms, which may have a hydroxyl group, an amino group, or an alkoxy group as a substituent. ２ ~R ４ Each of these independently represents an alkyl group having 1 to 8 carbon atoms.

7. It contains a blocked polyisocyanate (a), a blocking agent dissociation catalyst (b), and a nonionic emulsifier (c) having an HLB value of 12 to 19. The aforementioned block polyisocyanate (a) contains a hydrophilic group (a1), A blocked polyisocyanate composition wherein the blocking agent dissociation catalyst (b) contains a quaternary ammonium salt.

8. A paint composition comprising a main component and a curing agent, wherein the paint composition comprises the block polyisocyanate composition described in any one of claims 1 to 7.

9. A curing agent for aqueous paints comprising the block polyisocyanate composition according to any one of claims 1 to 7.

10. It contains a blocked polyisocyanate (a), a blocking agent dissociation catalyst (b), a nonionic emulsifier (c) with an HLB value of 12 to 19, and water. The aforementioned block polyisocyanate (a) contains a hydrophilic group (a1), The blocking agent dissociation catalyst (b) contains a quaternary ammonium salt, An aqueous paint composition in which the content of the blocking agent dissociation catalyst (b) is 0.0001 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the blocked polyisocyanate (a).

11. A coating film formed from the aqueous coating composition according to claim 10.

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