Catalyst composition, blocked polyisocyanate composition, coating material composition, coating film, and method for forming coating film

Abstract

A catalyst composition used for dissociating a blocking agent from a blocked polyisocyanate, said catalyst composition comprising: a quaternary ammonium salt including a quaternary ammonium cation represented by formula (1) and an organic acid anion; and an alcohol compound having a molecular weight of 350 or less, wherein the ratio of the alcohol compound content to the quaternary ammonium salt content is 4-99 by mass ratio. (In formula (1), R1 to R4 each independently represents a C1-4 alkyl group.)

Description

Catalyst composition, blocked polyisocyanate composition, coating composition, coating film, and method for forming coating film

[0001] The present disclosure relates to a catalyst composition, a blocked polyisocyanate composition, a coating composition, a coating film, and a method for forming a coating film.

[0002] Polyisocyanates have been known as curing agents used in paints, etc. For example, polyurethane resin paints, which are a combination of polyol and polyisocyanate, are known to have excellent abrasion resistance, chemical resistance, and stain resistance.

[0003] Paints using polyisocyanate as a curing agent are generally two-component compositions, in which the base component (e.g., polyol) and polyisocyanate are stored separately and mixed before use. However, once mixed, the paint cures in a short time, resulting in a short usable time and a problem with workability during application. Furthermore, because polyisocyanate reacts easily with water, it was impossible to use the above-mentioned paints in water-based paints such as electrodeposition paints.

[0004] One known method for addressing these issues is to inactivate polyisocyanate by reacting it with a blocking agent. The blocked polyisocyanate obtained by this method does not react with the base resin (such as a polyol) at room temperature, but when heated, the blocking agent dissociates, regenerating the isocyanate group, which then reacts with the base resin to form crosslinks. Therefore, this method does not limit the usable time, and it is possible to mix the base resin and curing agent in advance to form a paint, making it possible to apply polyisocyanate to water-based paints.

[0005] As a catalyst for dissociating a blocking agent from a blocked polyisocyanate (hereinafter also referred to as a "blocking agent dissociation catalyst"), for example, a quaternary ammonium salt is known (see Patent Document 1).

[0006] Japanese Patent Application Publication No. 08-170048

[0007] While the above-mentioned quaternary ammonium salts are useful as blocking agent dissociation catalysts, they can cause discoloration of the coating film during coating film formation. Although Patent Document 1 describes that cured resins using specific quaternary ammonium salts have superior yellowing resistance compared to cured resins using organometallic catalysts, the effect is still insufficient.

[0008] Therefore, one aspect of the present disclosure aims to provide a catalyst composition that can impart curability to a coating composition containing a blocked polyisocyanate and can also suppress discoloration during coating film formation.

[0009] The present disclosure provides at least the following [1] to

[10] .

[0010] [1] A catalyst composition used to dissociate a blocking agent from a blocked polyisocyanate, the catalyst composition comprising: a quaternary ammonium salt containing a quaternary ammonium cation represented by the following formula (1) and an organic acid anion; and an alcohol compound having a molecular weight of 350 or less, wherein the ratio of the content of the alcohol compound to the content of the quaternary ammonium salt is 4 to 99 by mass: [In formula (1), R １ ~R ４ each independently represents an alkyl group having 1 to 4 carbon atoms.

[0011] [2] The catalyst composition according to [1], wherein the quaternary ammonium salt comprises an acetate salt.

[0012] [3] The catalyst composition according to [1] or [2], wherein the alcohol compound comprises an aliphatic alcohol.

[0013] [4] A blocked polyisocyanate composition comprising a blocked polyisocyanate and the catalyst composition according to any one of [1] to [3].

[0014] [5] The blocked polyisocyanate composition according to [4], wherein the content of the quaternary ammonium salt is 0.0001 to 40 parts by mass per 100 parts by mass of the blocked polyisocyanate.

[0015] [6] The blocked polyisocyanate composition according to [4] or [5], wherein the blocked polyisocyanate contains a structure derived from an aliphatic polyisocyanate or an alicyclic polyisocyanate, or a derivative thereof.

[0016] [7] The blocked polyisocyanate composition according to any one of [4] to [6], wherein the blocked polyisocyanate has at least one group selected from the group consisting of an isocyanate group blocked with an oxime-based blocking agent and an isocyanate group blocked with a pyrazole-based blocking agent.

[0017] [8] A coating composition comprising a base agent and a curing agent, wherein the curing agent comprises a blocked polyisocyanate, and the base agent or the curing agent comprises the catalyst composition described in any one of [1] to [3], or the curing agent comprises the blocked polyisocyanate composition described in any one of [4] to [7].

[0018] [9] A coating film formed from the coating composition according to [8].

[0019]

[10] A method for forming a coating film, comprising the steps of applying the coating composition according to [8] to a substrate and heating at 60 to 120°C to cure a coating film made of the coating composition.

[0020] According to one aspect of the present disclosure, it is possible to provide a catalyst composition that can impart curability to a coating composition containing a blocked polyisocyanate and can also suppress discoloration during coating film formation.

[0021] Illustrative embodiments of the present disclosure will be described below. However, the present disclosure is not limited to the following embodiments. In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​written before and after "to" as the minimum and maximum values, respectively. Furthermore, unless specifically stated otherwise, the numerical values ​​written before and after "to" have the same units. Furthermore, individually stated upper and lower limit values ​​can be combined in any combination.

[0022] <Catalyst Composition> One embodiment of the present disclosure is a catalyst composition used to dissociate a blocking agent from a blocked polyisocyanate, the catalyst composition containing a quaternary ammonium salt (hereinafter also referred to as "quaternary ammonium salt (1)") containing a quaternary ammonium cation represented by the following formula (1) (hereinafter also referred to as "quaternary ammonium cation (1)") and an organic acid anion, and an alcohol compound (hereinafter also referred to as "low-molecular-weight alcohol") having a molecular weight of 350 or less, wherein the ratio of the content of the low-molecular-weight alcohol to the content of the quaternary ammonium salt (1) is 4 to 99 by mass. [In formula (1), R １ ~R ４ each independently represents an alkyl group having 1 to 4 carbon atoms.

[0023] The catalyst composition imparts curability to a coating composition containing a blocked polyisocyanate and can suppress discoloration during coating film formation (before and after curing of the coating film). Furthermore, since the catalyst composition is less likely to undergo color change (e.g., yellowing) over time, the catalyst composition is also expected to have the effect of suppressing coating film discoloration due to catalyst color change. Furthermore, by using a linear aliphatic monoalcohol having 1 to 4 carbon atoms in the catalyst composition, low-temperature curing properties can be imparted to a coating composition containing a blocked polyisocyanate, and a coating film with good hardness can be formed even when curing is performed at a low temperature, for example, around 80°C.

[0024] (Quaternary Ammonium Salt) The quaternary ammonium salt (1) contains one or more quaternary ammonium cations (1) and one or more organic acid anions. Here, "the quaternary ammonium salt (1) contains multiple quaternary ammonium cations (1)" is synonymous with "the catalyst composition contains multiple quaternary ammonium salts (1) with different quaternary ammonium cations (1)," and "the quaternary ammonium salt (1) contains multiple organic acid anions" is synonymous with "the catalyst composition contains multiple quaternary ammonium salts (1) with different organic acid anions." The organic acid anions in the multiple quaternary ammonium salts (1) with different quaternary ammonium cations (1) may be the same or different, and the organic acid anions in the multiple quaternary ammonium salts (1) with different organic acid anions may be the same or different.

[0025] The quaternary ammonium cation is represented by the above formula (1). １ ~R ４ Examples of the alkyl group (an alkyl group having 1 to 4 carbon atoms) represented by the formula (I) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a t-butyl group. The alkyl group may be a linear alkyl group (a methyl group, an ethyl group, an n-propyl group, an n-butyl group) from the viewpoint of easily obtaining a coating composition having excellent curability and from the viewpoint of further suppressing coloration during coating film formation (before and after curing of the coating film). The linear alkyl group may be a methyl group or an ethyl group from the viewpoint of enhancing the above-mentioned effect, and may be a methyl group from the viewpoint of further enhancing the above-mentioned effect.

[0026] Specific examples of the quaternary ammonium cation (1) include tetramethylammonium cation, tetraethylammonium cation, tetra-n-propylammonium cation, tetra-n-butylammonium cation, trimethylmono-n-butylammonium cation, triethylmonomethylammonium cation, tri-n-propylmonomethylammonium cation, tri-n-butylmonomethylammonium cation, tri-n-butylmonoethylammonium cation, and trimethylmonoethylammonium cation. The quaternary ammonium cation (1) may contain a tetramethylammonium cation from the viewpoint of easily obtaining a coating composition with excellent curability and from the viewpoint of being able to further suppress coloration during coating film formation (before and after curing of the coating film).

[0027] The organic acid anion is an anion derived from an organic acid. The organic acid anion may be an aliphatic monocarboxylate ion. Here, the aliphatic monocarboxylate ion in this specification is an anion represented by the formula (2): R ５ -COO － (In formula (2), R ５ represents a hydrogen atom or an aliphatic hydrocarbon group. The organic acid anion may have, for example, 1 to 12 carbon atoms, 1 to 7 carbon atoms, or 1 to 3 carbon atoms. Specific examples of organic acid anions include a formate ion, an acetate ion, a 2-ethylhexanoate ion (an octylate ion), a laurate ion, a cyclohexanecarboxylate ion, and a pivalate ion.

[0028] The organic acid anion may contain an aliphatic monocarboxylate ion having 1 to 12 carbon atoms, from the viewpoint of making it easier to obtain a coating composition with superior curability and from the viewpoint of further suppressing discoloration during coating film formation (before and after curing of the coating film). The aliphatic monocarboxylate ion having 1 to 12 carbon atoms may be an ion of a fatty acid having 1 to 7 carbon atoms, from the viewpoint of enhancing the above-mentioned effect; may be an ion of a fatty acid having 1 to 3 carbon atoms, from the viewpoint of further enhancing the above-mentioned effect; or may be an acetate ion, from the viewpoint of further enhancing the above-mentioned effect. In this specification, a quaternary ammonium salt containing an acetate ion may be referred to as an acetate salt.

[0029] The quaternary ammonium cation (1) and the organic acid anion can be combined in any desired manner. Specific examples of the quaternary ammonium salt (1) include trimethylmono-n-butylammonium acetate and tetramethylammonium acetate. These may be used alone or in combination of two or more. In particular, when tetramethylammonium acetate is used, a coating composition having even more excellent curability is more likely to be obtained, and coloration during coating film formation (before and after curing of the coating film) tends to be further suppressed.

[0030] The content of the quaternary ammonium salt (1) may be 1% by mass or more, or may be 2% by mass or more, based on the total mass of the catalyst composition, from the viewpoint of making it easier to obtain a coating composition with superior curability. The content of the quaternary ammonium salt (1) may be 15% by mass or less, 10% by mass or less, or 5% by mass or less, based on the total mass of the catalyst composition, from the viewpoint of making it easier to obtain a coating composition with superior curability and from the viewpoint of further reducing color change over time and coloration of the coating film. From these viewpoints, the content of the quaternary ammonium salt (1) may be, for example, 1 to 15% by mass, 1 to 10% by mass, or 2 to 5% by mass, based on the total mass of the catalyst composition.

[0031] (Low Molecular Weight Alcohol) The low molecular weight alcohol is an alcohol compound having a molecular weight of 350 or less. The molecular weight of the low molecular weight alcohol may be 18 or more, 30 or more, 60 or more, or 100 or more, and may be 300 or less, 150 or less, 100 or less, or 80 or less, or may be 18 to 350, 30 to 350, 60 to 350, 100 to 350, 18 to 300, 18 to 150, 18 to 100, or 18 to 80. The lower the molecular weight of the low molecular weight alcohol, the greater the effect of improving curability and the effect of reducing coloration of the coating film. The unit of molecular weight is g / mol.

[0032] The low molecular weight alcohol may be an aliphatic alcohol or an aromatic alcohol. Either one or both of these may be used, but when an aliphatic alcohol is used, coloration of the catalyst composition and the coating film can be further reduced. The aliphatic alcohol may be linear or branched, and may have a ring structure. The carbon number of the low molecular weight alcohol may be 1 to 30, 1 to 8, or 1 to 4.

[0033] The low-molecular-weight alcohol may be a monoalcohol having one hydroxyl group (-OH group) in the molecule, or a polyol having two or more hydroxyl groups (-OH groups) in the molecule. Either one or both of these may be used, but when a monoalcohol is used, coloration of the coating film can be further reduced.

[0034] Specific examples of low molecular weight alcohols include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, 2-ethylhexanol, 3,3,5-trimethyl-1-hexanol, n-tridecanol, 2-tridecanol, 2-octyldodecanol, pentadecanol, palmityl alcohol, stearyl alcohol, cyclopentanol, cyclohexanol, methylcyclohexanol, trimethylcyclohexanol, cyclohexanemethanol, heneicosanol, ceryl alcohol, ethylene glycol, 1,2-propanediol, 1,3-butanediol, and 1,4-butanediol. Examples of such diols include diol, 1,5-propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, 2,2-diethyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-n-hexadecane-1,2-ethylene glycol, 2-n-eicosane-1,2-ethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, and pentaerythritol. These may be used alone or in combination of two or more. Among these, from the viewpoint of further reducing the coloration of the catalyst composition and the coating film, straight-chain aliphatic monoalcohols having 1 to 8 carbon atoms (methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, and n-octanol) may be used, and from the viewpoint of imparting low-temperature curing properties to the coating composition, straight-chain aliphatic monoalcohols having 1 to 4 carbon atoms may be used.

[0035] The ratio of the content of the low-molecular-weight alcohol to the content of the quaternary ammonium salt (1) (content of low-molecular-weight alcohol / content of quaternary ammonium salt (1)) is 4 to 99 by mass, and from the viewpoint of further reducing color change over time and coloration of the coating film, may be 5 or more, 8 or more, 15 or more, 30 or more, or 40 or more, and may be 80 or less, 60 or less, 55 or less, or 50 or less, or may be 5 to 80, 5 to 60, 5 to 55, 5 to 50, 8 to 50, 15 to 50, 30 to 50, or 40 to 50.

[0036] (Other Components) The catalyst composition may further contain components other than the quaternary ammonium salt (1) and the low-molecular-weight alcohol. For example, the catalyst composition may contain a blocking agent dissociation catalyst other than the quaternary ammonium salt (1). The content of the blocking agent dissociation catalyst other than the quaternary ammonium salt (1) in the catalyst composition may be 0 to 0.5% by mass, or may be 0.2% by mass or less, or 0.1% by mass or less, based on the total mass of the blocking agent dissociation catalyst.

[0037] The catalyst composition can be prepared by mixing the quaternary ammonium salt (1), the low molecular weight alcohol, and any other optional components.

[0038] <Blocked Polyisocyanate Composition> One embodiment of the present disclosure is a blocked polyisocyanate composition comprising a blocked polyisocyanate, the quaternary ammonium salt (1), and a low-molecular-weight alcohol. The blocked polyisocyanate composition may also comprise the catalyst composition of the above embodiment. That is, the blocked polyisocyanate composition may be a composition comprising a blocked polyisocyanate and the catalyst composition of the above embodiment.

[0039] The blocked polyisocyanate composition can impart curability to the coating composition and can also suppress coloration during coating film formation.

[0040] (Blocked Polyisocyanate) A blocked polyisocyanate is a compound having an isocyanate group blocked with a blocking agent (hereinafter also referred to as a "blocked isocyanate group"). A blocked polyisocyanate is derived, for example, from a polyisocyanate that does not have an isocyanate group blocked with a blocking agent (hereinafter also referred to as an "unblocked polyisocyanate"). That is, a blocked polyisocyanate has, for example, a structure derived from an unblocked polyisocyanate (for example, a structure remaining after removing an isocyanate group from an unblocked polyisocyanate) and an isocyanate group blocked with a blocking agent.

[0041] [Unblocked Polyisocyanate] The unblocked polyisocyanate is a compound having a plurality of isocyanate groups (free isocyanate groups). Examples of the unblocked polyisocyanate include aromatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates, and polyisocyanate derivatives thereof. Examples of the derivatives include isocyanurates, allophanates, and biurets.

[0042] The unblocked polyisocyanate does not need to have an aromatic ring, from the viewpoint of improving the yellowing resistance of the cured coating film. That is, the unblocked polyisocyanate may be an aliphatic polyisocyanate, an alicyclic polyisocyanate, or a derivative thereof (hereinafter referred to as a "non-aromatic polyisocyanate"). In other words, the blocked polyisocyanate may have a structure derived from an aliphatic polyisocyanate, an alicyclic polyisocyanate, or a derivative thereof (for example, a structure remaining after removing an isocyanate group from an aliphatic polyisocyanate, an alicyclic polyisocyanate, or a derivative thereof). 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. Examples of derivatives include isocyanurates, allophanates, and biurets. The derivative may be an isocyanate group-containing prepolymer obtained by reacting the above-mentioned polyisocyanate with a polyol, or a derivative of the prepolymer (for example, an isocyanurate, an allophanate, a biuret, etc.). As the polyol, for example, a diol having 2 to 9 carbon atoms is used. Examples of such diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol.

[0043] The unblocked polyisocyanate may contain an aliphatic polyisocyanate having an aliphatic hydrocarbon group having 4 to 6 carbon atoms or a derivative thereof from the viewpoint of further improving curability, and may contain hexamethylene diisocyanate or a derivative thereof from the viewpoint of further improving curability. In other words, the blocked polyisocyanate may have a structure derived from an aliphatic polyisocyanate having an aliphatic hydrocarbon group having 4 to 6 carbon atoms or a derivative thereof, or may have a structure derived from hexamethylene diisocyanate or a derivative thereof. The derivative of an aliphatic polyisocyanate having an aliphatic hydrocarbon group having 4 to 6 carbon atoms (e.g., hexamethylene diisocyanate) may be at least one selected from the group consisting of an isocyanurate, an allophanate, and a biuret. These derivatives may also be derivatives of the isocyanate group-containing prepolymer described above. Among these, when the derivative of an aliphatic polyisocyanate having an aliphatic hydrocarbon group having 4 to 6 carbon atoms (e.g., hexamethylene diisocyanate) is an isocyanurate, that is, when the blocked polyisocyanate has a structure derived from an isocyanurate of an aliphatic polyisocyanate having an aliphatic hydrocarbon group having 4 to 6 carbon atoms (e.g., a trivalent group remaining after removing three isocyanate groups from the isocyanurate), higher coating hardness tends to be obtained. When the unblocked polyisocyanate contains an isocyanurate, from the viewpoint of further improving coating hardness, the content of isocyanurate trimer (isocyanurate trimer content) based on the total mass of the unblocked polyisocyanate may be 50 mass% or more, and the content of isocyanurate groups (isocyanurate group content) relative to the total (100 mol%) of isocyanurate groups and allophanate groups in the unblocked polyisocyanate may be more 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% by mole.

[0044] [Blocked Isocyanate Group] A blocked isocyanate group is an isocyanate group blocked with a blocking agent, and has a structure derived from the blocking agent (for example, a structure remaining after removing an isocyanate-reactive group such as a hydroxyl group from the blocking agent).

[0045] Examples of the blocking agent 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; oxime-based blocking agents such as formaldoxime, acetaldoxime, acetoneoxime, methyl ethyl ketoxime, methyl isobutyl ketoxime, and cyclohexanone oxime; imidazole, 2-methylimidazole, 4-methyl imidazole-based blocking agents such as imidazole, 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, and 2-heptadecylimidazole; pyrazole-based blocking agents such as 3,5-dimethylpyrazole, 3-methylpyrazole, and pyrazole; amine-based blocking agents such as diphenylamine, diisopropylamine, and isopropylethylamine; triazole, 1,2,4-triazole, 3,5-dimethyl-1,2,Examples of the blocking agent include triazole-based blocking agents such as 4-triazole, malonic acid esters (dimethyl malonate, diethyl malonate, diisopropyl 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, dibenzyl malonate, diphenyl malonate, benzyl methyl malonate, ethyl phenyl malonate, t-butylphenyl malonate, isopropylidene malonate, etc.), acetoacetate esters (methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, n-butyl acetoacetate, t-butyl acetoacetate, benzyl acetoacetate, phenyl acetoacetate, etc.), and active methylene-based blocking agents such as 2-acetoacetoxyethyl methacrylate, acetylacetone, and ethyl cyanoacetate. These blocking agents may be used alone or in combination of two or more. Among these, storage stability is likely to be improved when an oxime-based blocking agent (particularly methyl ethyl ketoxime) is used, and curability is likely to be improved when a pyrazole-based blocking agent (particularly 3,5-dimethylpyrazole) is used.

[0046] In view of the above, in one embodiment, the blocked polyisocyanate may have at least one group selected from the group consisting of an isocyanate group blocked with an oxime-based blocking agent and an isocyanate group blocked with a pyrazole-based blocking agent.

[0047] The blocked polyisocyanate may have a free isocyanate group, but if the blocked polyisocyanate does not have a free isocyanate group, storage stability can be further improved. From the viewpoint of further improving storage stability, all of the available isocyanate groups in the blocked polyisocyanate may be blocked isocyanate groups. Here, the available isocyanate groups refer to both free isocyanate groups and blocked isocyanate groups.

[0048] The blocked polyisocyanate can be obtained, for example, by reacting a polyisocyanate having free isocyanate groups, such as the unblocked polyisocyanate, with the blocking agent. That is, the blocked polyisocyanate can be a reaction product of a polyisocyanate having free isocyanate groups and the blocking agent. The polyisocyanate having free isocyanate groups and the blocking agent may each be used alone or in combination of two or more. When an aromatic polyisocyanate is not used as the polyisocyanate having free isocyanate groups, the yellowing resistance of the cured coating film can be further improved.

[0049] The blocked polyisocyanate may be a compound derived from a reaction product of a polyisocyanate having a free isocyanate group and a blocking agent, or may be a compound obtained by reacting the reaction product of a polyisocyanate having a free isocyanate group and a blocking agent with a compound capable of reacting with the free isocyanate group in the reaction product (e.g., an active hydrogen group-containing compound, etc.).

[0050] The reaction between the polyisocyanate having free isocyanate groups and the blocking agent can be carried out according to the reaction conditions for a typical blocking reaction. The reaction can be carried out at room temperature or with heating. Regardless of whether heating is performed or not, the temperature of the reaction solution can be, for example, 20 to 200°C.

[0051] The blocked polyisocyanates may be used singly or in combination of two or more. For example, two or more blocked polyisocyanates derived from different types of unblocked polyisocyanates may be used in combination.

[0052] The content of the block polyisocyanate may be 40% by mass or more, 60% by mass or more, or 80% by mass or more, based on the total solids content of the block polyisocyanate composition, from the viewpoint of easily obtaining a coating composition with excellent curability. The content of the block polyisocyanate may be less than 100% by mass, or 95% by mass or less, or 90% by mass or less, based on the total solids content of the block polyisocyanate composition, from the viewpoint of improving the storage stability of the coating. From these viewpoints, the content of the block polyisocyanate may be, for example, 40% by mass or more but less than 100% by mass, or 60 to 95% by mass, or 80 to 90% by mass, based on the total solids content of the block polyisocyanate composition. Note that, when the block polyisocyanate composition contains a solvent, the total solids content of the block polyisocyanate composition refers to the amount obtained by excluding the amount of the solvent from the total amount of the block polyisocyanate composition. When the block polyisocyanate composition does not contain a solvent, the total solids content of the block polyisocyanate composition refers to the amount obtained by excluding the amount of the solvent from the total amount of the block polyisocyanate composition.

[0053] (Quaternary ammonium salt and low molecular weight alcohol) The details of the quaternary ammonium salt (1) and the low molecular weight alcohol are the same as those of the quaternary ammonium salt (1) and the low molecular weight alcohol contained in the catalyst composition. In addition, the ratio of the content of the low molecular weight alcohol to the content of the quaternary ammonium salt (1) can be the same range as the range exemplified as the ratio of the content of the low molecular weight alcohol to the content of the quaternary ammonium salt (1) in the catalyst composition.

[0054] The content of the quaternary ammonium salt (1) may be 0.0001 parts by mass or more, 0.001 parts by mass or more, 0.01 parts by mass or more, 0.1 parts by mass or more, or 1 part by mass or more, relative to 100 parts by mass of the blocked polyisocyanate, from the viewpoint of easily obtaining a coating composition with excellent curability. The content of the quaternary ammonium salt (1) may be 40 parts by mass or less, 30 parts by mass or less, 20 parts by mass or less, 10 parts by mass or less, or 5 parts by mass or less, relative to 100 parts by mass of the blocked polyisocyanate, from the viewpoint of improving the storage stability of the coating. From these viewpoints, the content of the quaternary ammonium salt (1) may be, for example, 0.0001 to 40 parts by mass, 0.001 to 30 parts by mass, 0.01 to 20 parts by mass, 0.1 to 10 parts by mass, or 1 to 5 parts by mass, relative to 100 parts by mass of the blocked polyisocyanate. When the blocked polyisocyanate composition contains a catalyst composition, the content of the catalyst composition may be adjusted so that the content of the quaternary ammonium salt (1) falls within the above range.

[0055] (Other Components) The blocked polyisocyanate composition may further contain other components in addition to the blocked polyisocyanate, the quaternary ammonium salt (1), and the low-molecular-weight alcohol. Examples of the other components include additives such as pigments, dispersion stabilizers, viscosity modifiers, leveling agents, antigelling agents, light stabilizers, antioxidants, UV absorbers, heat resistance improvers, inorganic and organic fillers, plasticizers, lubricants, antistatic agents, reinforcing materials, and catalysts.

[0056] The blocked polyisocyanate composition may contain a solvent as another component. Examples of the solvent include benzene, toluene, xylene, cyclohexane, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, n-butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate, diethylene glycol dimethyl ether, and 1,4-dioxane. These solvents may be used alone or in combination of two or more. The content of the solvent may be 0 to 95% by mass, 5 to 90% by mass, or 10 to 80% by mass, based on the total mass of the blocked polyisocyanate composition.

[0057] The blocked polyisocyanate composition may contain unblocked polyisocyanate (e.g., polyisocyanate remaining as an unreacted product) and may contain unreacted blocking agent. The content of unblocked polyisocyanate contained in the blocked polyisocyanate composition may be 5% by mass or less, or even 0% by mass, based on the total solid content of the blocked polyisocyanate composition. The content of unreacted blocking agent contained in the blocked polyisocyanate composition may be 5% by mass or less, or even 0% by mass, based on the total solid content of the blocked polyisocyanate composition.

[0058] The effective isocyanate group content (hereinafter referred to as "effective NCO content") of the blocked polyisocyanate composition may be 4 to 28% by mass, 5 to 22% by mass, or 6 to 16% by mass, from the viewpoint of further enhancing the curability of the coating material. Here, the effective NCO content refers to the isocyanate groups present in the blocked polyisocyanate composition that can participate in a crosslinking reaction, expressed in mass %, and can be rephrased as the content of free isocyanate groups in the polyisocyanate composition obtained by dissociating the blocking agent from the blocked polyisocyanate 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 a measurement sample (the polyisocyanate composition obtained by dissociating the blocking agent from the blocked polyisocyanate) with an excess of secondary amine, followed by back titration of the unreacted secondary amine with hydrochloric acid.

[0059] The above-described blocked polyisocyanate composition can be prepared by mixing the blocked polyisocyanate, the previously prepared catalyst composition, and other optional components. The blocked polyisocyanate composition can also be prepared by mixing the blocked polyisocyanate, the quaternary ammonium salt (1), a low-molecular-weight alcohol, and other optional components. The blocked polyisocyanate composition is used, for example, as a curing agent for a paint composition (e.g., a low-temperature curing paint composition). That is, another embodiment of the present disclosure is a curing agent for a paint (e.g., a low-temperature curing paint) comprising the blocked polyisocyanate composition.

[0060] <Paint Composition> Another embodiment of the present disclosure is a paint composition containing a base agent and a curing agent, the paint composition containing a blocked polyisocyanate and the catalyst composition of the above embodiment. The paint composition may contain the above-mentioned blocked polyisocyanate composition. Details of the blocked polyisocyanate contained in the paint composition are the same as those of the blocked polyisocyanate contained in the above-mentioned blocked polyisocyanate composition.

[0061] The coating composition may be a one-component composition in which all of the constituent components are contained in one component, or a multi-component composition in which the constituent components are present in multiple components. A multi-component coating composition may comprise a first component containing a base agent and a second component containing a curing agent. The blocked polyisocyanate is contained in the second component as a curing agent, but the catalyst composition may be contained in either the first or second component. Similarly, when the coating composition contains other components that can be contained in the blocked polyisocyanate composition, these components may be contained in either the first or second component. When the catalyst composition is contained in the second component, the blocked polyisocyanate composition of the above embodiment may be used as the second component.

[0062] The coating composition contains a blocked polyisocyanate and the catalyst composition of the embodiment, and therefore, the coating composition can suppress coloration during the production of the coating film (before and after curing of the coating film).

[0063] The base agent contains, for example, an active hydrogen group-containing compound. Examples of active hydrogen groups include hydroxyl groups and amino groups. The average number of functional groups (average number of active hydrogen groups) of the active hydrogen group-containing compound is 2 or more, for example, 2 to 50. Examples of active hydrogen-containing compounds having such an average number of functional groups include polyols, polyamines, and amino alcohols. In particular, when the base agent contains a polyol as the active hydrogen group-containing compound, better curability is likely to be obtained, and a coating film with less coloration is likely to be obtained.

[0064] The number average molecular weight of the active hydrogen group-containing compound is, for example, 500 to 20,000, and may be 500 to 10,000. Examples of active hydrogen group-containing compounds having such a number average molecular weight include polyurethane resins, polyamide resins, saturated or unsaturated polyester resins, alkyd resins modified with saturated or unsaturated fatty acids, acrylic resins, fluororesins, epoxy resins, and cellulose resins (all of which are resins containing active hydrogen groups). From the viewpoints of film performance such as gloss, thickness, hardness, durability, flexibility, and drying speed, as well as cost, at least one compound selected from the group consisting of saturated or unsaturated polyester resins, alkyd resins modified with saturated or unsaturated fatty acids, and acrylic resins may be used.

[0065] The blending ratio of the base agent and curing agent in the coating composition may be adjusted based on the ratio of the total amount of available isocyanate groups in the curing agent to the total amount of active hydrogen groups in the base agent. The ratio of the total amount of available isocyanate groups in the curing agent to the total amount of active hydrogen groups in the base agent may be 1 / 9 to 9 / 1, or 2 / 8 to 8 / 2, in molar ratio. When the molar ratio is within the above range, better curability can be obtained.

[0066] The content of the catalyst composition in the coating composition may be adjusted so that the content of the quaternary ammonium salt (1) per 100 parts by mass of the blocked polyisocyanate falls within the above-mentioned range (e.g., 0.0001 to 40 parts by mass), similar to the content of the catalyst composition in the blocked polyisocyanate composition.

[0067] The coating composition can be used as an automotive topcoat paint, a chipping-resistant paint, an electrodeposition paint, a paint for automotive parts, a paint for automotive repair, pre-coated metals and rust-proof steel sheets for metal products such as home appliances and office equipment, a paint for building materials, a paint for plastics, an adhesive, an adhesion promoter, a sealant, etc.

[0068] <Coating Film and Method for Forming Coating Film> Another embodiment of the present disclosure is a coating film formed from the coating composition of the above embodiment.

[0069] The coating film may be an uncured coating film consisting of a mixture of the base agent and curing agent in the coating composition of the above embodiment, or may be a coating film (cured coating film) formed by curing the uncured coating film. The cured coating film contains, for example, a reaction product of the base agent and curing agent. When the base agent contains a polyol as an active hydrogen group-containing compound, the cured coating film may contain a polyurethane resin that is a reaction product of the polyol and a polyisocyanate derived from a blocked polyisocyanate. The coating film thickness is, for example, 5 to 40 μm. The coating film may be a thin film with a thickness of less than 20 μm.

[0070] Another embodiment of the present disclosure is a method for forming a coating film, comprising the steps of applying the coating composition of the above embodiment to a substrate and curing the coating film (uncured coating film) made of the coating composition.

[0071] The coating composition may be applied by known techniques such as roll coating, curtain flow coating, spray coating, electrostatic coating, bell coating, electrodeposition coating, etc. The amount of coating composition to be applied, the thickness of the coating film, etc. may be appropriately determined depending on the material of the surface to be coated, etc.

[0072] Curing of a coating film (uncured coating film) made from a coating composition may be carried out by heating the coating film. The heating temperature (baking temperature) may be, for example, 200°C or lower, and the heating time (baking time) may be, for example, 10 to 180 minutes. Furthermore, when a linear aliphatic monoalcohol having 1 to 4 carbon atoms is used as the low-molecular-weight alcohol, a cured coating film with good hardness can be formed even when baking is carried out at a low temperature of 120°C or lower (e.g., 60 to 120°C).

[0073] Examples of substrates include molded articles made of materials such as stainless steel, phosphate-treated steel, zinc-coated steel, iron, copper, aluminum, brass, glass, acrylic polyol, polycarbonate resin, polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene phthalate resin, polystyrene resin, AS resin, ABS resin, polycarbonate-ABS resin, 6-nylon resin, 6,6-nylon resin, MXD6 nylon resin, polyvinyl chloride resin, polyvinyl alcohol resin, polyurethane resin, phenolic resin, melamine resin, polyacetal resin, chlorinated polyolefin resin, polyolefin resin, polyamide resin, polyether ether ketone resin, polyphenylene sulfide resin, NBR resin, chloroprene resin, SBR resin, and SEBS resin, as well as surface-treated molded articles. The surface-treated article may also be a molded article (surface-treated molded article) made of an olefin resin such as polyethylene or polypropylene that has been subjected to a surface treatment such as corona discharge treatment.

[0074] 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.

[0075] Synthesis Example 1 (Synthesis of Polyisocyanate) 995 g of hexamethylene diisocyanate (hereinafter referred to as HDI), 5.0 g of 1,3-butanediol (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.3 g of phenol (manufactured by Tokyo Chemical Industry Co., Ltd.) were charged into a four-neck flask equipped with a stirrer, thermometer, heating device, nitrogen seal tube, and condenser, and a urethane-forming reaction was carried out at 80°C for 2 hours under a nitrogen stream. Thereafter, 0.04 g of potassium 2-ethylhexanoate (manufactured by Tokyo Chemical Industry Co., Ltd.), an isocyanuration catalyst, was added, and an isocyanuration reaction was carried out at 70°C for 2 hours. After the NCO content reached 40.0% by mass, 0.15 g of JP-508 (manufactured by Johoku Chemical Industry Co., Ltd.) was added to carry out a termination reaction, and the reaction solution was cooled to room temperature. This reaction solution was subjected to thin-film distillation at a temperature of 130°C and a pressure of 0.04 kPa to remove unreacted HDI, thereby obtaining a purified polyisocyanate (hereinafter referred to as "Polyisocyanate A-1"). Polyisocyanate A-1 had an NCO content of 21.8% by mass and a viscosity at 25°C of approximately 2,500 mPa s.

[0076] ( １ H-NMR: Measurement of isocyanurate group content) Polyisocyanate A-1 １ H-NMR measurement was carried out to determine the isocyanurate group content (the content of isocyanurate groups relative to the total (100 mol%) of isocyanurate groups and allophanate groups). Specifically, the isocyanurate group content was calculated from the area of ​​the signal of the hydrogen atom of the methylene group adjacent to the nitrogen atom of the isocyanurate group at around 3.7 ppm and the signal of the hydrogen atom bonded to the nitrogen atom of the allophanate group at around 8.5 ppm. The isocyanurate group content was 89 mol%. １ H-NMR measurement was carried out under the following measurement conditions: [Measurement conditions] (1) Measurement equipment: ECX400M (manufactured by JEOL Ltd.) １ H-NMR) (2) Measurement temperature: 23°C (3) Sample concentration: 0.1 g / 1 ml (4) Number of accumulations: 16 (5) Relaxation time: 5 seconds (6) Solvent: deuterium dimethyl sulfoxide (7) Chemical shift reference: hydrogen atom signal of methyl group in deuterium dimethyl sulfoxide (2.5 ppm)

[0077] Examples 1 to 5 and Comparative Examples 1 to 3 (Preparation of Catalyst Compositions) In Examples 1 to 5, catalyst compositions 1 to 5 were prepared by mixing an alcohol listed in Table 1 with a 25 mass % methanol solution (manufactured by Tokyo Chemical Industry Co., Ltd.) of tetramethylammonium acetate (hereinafter referred to as "TMA-Ac"), a quaternary ammonium salt, at the mass ratio [alcohol / quaternary ammonium salt] shown in Table 1. Note that the "alcohol" in the mass ratio [alcohol / quaternary ammonium salt] refers to the total amount of the alcohol listed in Table 1 and the methanol in the methanol solution.

[0078] In Comparative Example 1, a 25 mass% methanol solution of TMA-Ac was used as catalyst composition 6, and in Comparative Example 2, a 10 mass% methanol solution of tetramethylammonium hydroxide (hereinafter referred to as "TMA-OH") (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as catalyst composition 7.

[0079] In Comparative Example 3, catalyst composition 8 was prepared by mixing an alcohol shown in Table 1 with a 10 mass % methanol solution of TMA-OH (manufactured by Tokyo Chemical Industry Co., Ltd.), which is a quaternary ammonium salt, in the mass ratio [alcohol / quaternary ammonium salt] shown in Table 1.

[0080] (Evaluation of Discoloration Resistance) Catalyst compositions 1 to 8 were stored at 80°C for 48 hours, and the b* values ​​of the catalyst compositions according to the CIE Lab standard were measured before and after storage using a spectrophotometer COH7700 manufactured by Nippon Denshoku Kogyo Co., Ltd. The "rate of change in b* value" was calculated from the b* values ​​before and after storage (initial b* value and b* value after storage) using the following formula, and the resistance of the catalyst compositions to discoloration over time (discoloration resistance) was evaluated based on this rate of change: Rate of change in b* value (unit: %) = 100 × (b* value after storage - initial b* value) / initial b* value

[0081] The evaluation criteria are shown below, and the results are shown in Table 1. If the evaluation was B, the catalyst composition was evaluated to have sufficient discoloration resistance. A: The rate of change in b* value was 0% or more and less than 30%. B: The rate of change in b* value was 30% or more and less than 60%. C: The rate of change in b* value was 60% or more.

[0082] (Preparation of Blocked Polyisocyanate Compositions) Blocked polyisocyanate compositions (blocked polyisocyanate compositions 1 to 8) of Examples 1 to 5 and Comparative Examples 1 to 3 were prepared using catalyst compositions 1 to 8, respectively, by the following method.

[0083] Into a four-neck flask equipped with a stirrer, a thermometer, a heating device, a nitrogen seal tube, and a condenser, 515 g of polyisocyanate A-1 and 250 g of butyl acetate were charged and stirred for 30 minutes, and then 234 g of methyl ethyl ketoxime (manufactured by Ube Industries, Ltd., "MEKO" in the table) (equivalent ratio relative to the amount of polyisocyanate A-1 mixed was 1.0) was charged in three divided portions so that the temperature did not exceed 80°C. Thereafter, the mixture was reacted at 70°C for 2 hours, and the infrared absorption spectrum (IR measurement) showed that the peak of the NCO group (2270 cm) －１ When the color (around 100%) disappeared, the mixture was cooled to room temperature, and catalyst compositions 1 to 8 were added so that the amount of TMA-Ac or TMA-OH added was 22.5 g, followed by stirring for 30 minutes. By the above operations, blocked polyisocyanate compositions 1 to 8 were obtained, respectively.

[0084] (Preparation of Coating Compositions) Coating compositions (Coating Compositions 1 to 8) of Examples 1 to 5 and Comparative Examples 1 to 3 were prepared using blocked polyisocyanate compositions 1 to 8, respectively. Specifically, the coating compositions were prepared by mixing Acrydic A-801 (manufactured by DIC Corporation, acrylic polyol, solids concentration 50 mass%, hydroxyl value 50 mgKOH / g, trade name, "A801" in the table) as the main agent, blocked polyisocyanate composition ("BPI" in the table) as the curing agent, and butyl acetate (manufactured by Kishida Chemical Co., Ltd., "BtAc" in the table). The blending amounts of each component were as shown in Table 1.

[0085] (Preparation of coating films and evaluation of coloration) Coating compositions 1 to 8 were applied to substrates under the following conditions and cured to obtain coating films (cured coating films) of Examples 1 to 5 and Comparative Examples 1 to 3, respectively. At this time, a BYK-GARDNER colorimeter (product name: SPECTRO2GUIDE) was used to measure the b* value of the cured coating film according to the CIE Lab standard. The results are shown in Table 1. The substrate used was a color steel plate (white) (manufactured by Yutaka Panel Service, 0.8 mm thick). [Conditions] Coating method: using an applicator Humidity conditions: 50% RH Temperature conditions: 23°C Drying (curing) conditions: forced drying at 160°C for 1 hour Film thickness: approximately 20 μm

[0086] (Curability evaluation 1: Hardness measurement of film cured at 160°C) The coating film obtained above (cured coating film) was subjected to a pendulum hardness evaluation under the following conditions in accordance with ISO 1522. A pendulum hardness of 30 or more can be said to have good hardness. The results are shown in Table 1. [Conditions] Testing equipment: BYK pendulum hardness tester byko-swing Pendulum: Konig pendulum Oscillation start angle: 6° Oscillation end angle: 3° Oscillation time: 1.4 seconds

[0087] (Curability evaluation 2: Measurement of hardness of film cured at 80°C) Coating compositions 1 to 6 were applied to substrates under the following conditions and cured to obtain coating films (cured coating films) of Examples 1 to 5 and Comparative Example 1, respectively. Color steel plate (white) (manufactured by Yutaka Panel Service Co., Ltd., 0.8 mm thick) was used as the substrate. [Conditions] - Application method: Use of applicator - Humidity conditions: 50% RH - Temperature conditions: 23°C - Drying (curing) conditions: Forced drying at 80°C for 20 minutes - Film thickness: Approximately 20 μm

[0088] The hardness of the coating film (cured coating film) obtained above was measured in the same manner as in Curability Evaluation 1. The results are shown in Table 1.

[0089] Example 6 A four-necked flask equipped with a stirrer, a thermometer, a heating device, a nitrogen seal tube, and a condenser was charged with 450.6 g of Desmodur W (a hydrogenated product of diphenylmethane diisocyanate, manufactured by Sumika Covestro Urethane Co., Ltd., NCO content = 32.0 mass%) as polyisocyanate A-2 and 250 g of butyl acetate, and the mixture was stirred for 30 minutes. Then, 299.3 g of MEKO (equivalent ratio relative to the amount of Desmodur W mixed was 1.0) was charged in three portions so that the temperature did not exceed 80°C. Thereafter, the mixture was reacted at 70°C for 2 hours, and the peak of the NCO group (2270 cm) was observed in the infrared absorption spectrum (IR measurement). －１ When the color (around 100%) disappeared, the mixture was cooled to room temperature, and catalyst composition 1 was added so that the amount of TMA-Ac added was 22.5 g, followed by stirring for 30 minutes. By the above operations, blocked polyisocyanate composition 9 was obtained.

[0090] A coating composition and a coating film were prepared in the same manner as in Example 1, except that blocked polyisocyanate composition 9 was used instead of blocked polyisocyanate composition 1, and evaluation of coloration and curability was carried out. The results are shown in Table 2.

[0091] Example 7 A four-neck flask equipped with a stirrer, a thermometer, a heating device, a nitrogen seal tube, and a condenser was charged with 551.8 g of VESTANAT T1890 / 100 (an isocyanurate of isophorone diisocyanate, manufactured by Evonik, NCO content = 17.3 mass%) as polyisocyanate A-3 and 250 g of butyl acetate, and the mixture was stirred for 30 minutes. Then, 198.1 g of MEKO (equivalent ratio relative to the amount of VESTANAT T1890 / 100 mixed: 1.0) was charged in three portions so that the temperature did not exceed 80°C. Thereafter, the mixture was reacted at 70°C for 2 hours, and the infrared absorption spectrum (IR measurement) showed a peak of the NCO group (2270 cm －１ When the color (around 100%) disappeared, the mixture was cooled to room temperature, and catalyst composition 1 was added so that the amount of TMA-Ac added was 22.5 g, followed by stirring for 30 minutes. By the above operations, blocked polyisocyanate composition 10 was obtained.

[0092] A coating composition and a coating film were prepared in the same manner as in Example 1, except that blocked polyisocyanate composition 10 was used instead of blocked polyisocyanate composition 1, and evaluation of coloration and curability was carried out. The results are shown in Table 2.

[0093] Example 8 A four-necked flask equipped with a stirrer, a thermometer, a heating device, a nitrogen seal tube, and a condenser was charged with 500.4 g of Polyisocyanate A-1 and 250.0 g of butyl acetate and stirred for 30 minutes, after which 249.6 g of 3,5-dimethylpyrazole (manufactured by Tokyo Chemical Industry Co., Ltd., "DMP" in the table) (equivalent ratio relative to the amount of Polyisocyanate A-1 mixed was 1.0) was charged in three divided portions so that the temperature did not exceed 80°C. Thereafter, the mixture was reacted at 70°C for 2 hours, and the infrared absorption spectrum (IR measurement) showed a peak corresponding to an NCO group (at 2270 cm －１ When the color (around 100%) disappeared, the mixture was cooled to room temperature, and catalyst composition 1 was added so that the amount of TMA-Ac added was 22.5 g, followed by stirring for 30 minutes. By the above operations, blocked polyisocyanate composition 11 was obtained.

[0094] A coating composition and a coating film were prepared in the same manner as in Example 1, except that blocked polyisocyanate composition 11 was used instead of blocked polyisocyanate composition 1, and evaluation of coloration and curability was carried out. The results are shown in Table 2.

[0095]

[0096]

[0097] Details of the alcohols in the table are as follows: Methanol (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 32) n-Butanol (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 74) n-Octanol (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 130) Ethylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 62)

Claims

1. A catalyst composition used to dissociate a blocking agent from a blocked polyisocyanate, comprising: a quaternary ammonium salt containing a quaternary ammonium cation represented by the following formula (1) and an organic acid anion; and an alcohol compound having a molecular weight of 350 or less, wherein the ratio of the content of the alcohol compound to the content of the quaternary ammonium salt is 4 to 99 by mass. [In formula (1), R １ ~R ４ each independently represents an alkyl group having 1 to 4 carbon atoms.

2. The catalyst composition of claim 1, wherein said quaternary ammonium salt comprises an acetate salt.

3. The catalyst composition of claim 1, wherein the alcohol compound comprises an aliphatic alcohol.

4. A blocked polyisocyanate composition comprising a blocked polyisocyanate and the catalyst composition according to any one of claims 1 to 3.

5. The blocked polyisocyanate composition according to claim 4, wherein the content of the quaternary ammonium salt is 0.0001 to 40 parts by mass per 100 parts by mass of the blocked polyisocyanate.

6. The blocked polyisocyanate composition according to claim 4, wherein the blocked polyisocyanate contains a structure derived from an aliphatic polyisocyanate or an alicyclic polyisocyanate or a derivative thereof.

7. The blocked polyisocyanate composition according to claim 4, wherein the blocked polyisocyanate has at least one group selected from the group consisting of an isocyanate group blocked with an oxime-based blocking agent and an isocyanate group blocked with a pyrazole-based blocking agent.

8. A coating composition comprising a base agent and a curing agent, wherein the curing agent comprises a blocked polyisocyanate, and the base agent or the curing agent comprises the catalyst composition according to any one of claims 1 to 3.

9. A coating film formed from the coating composition according to claim 8.

10. A method for forming a coating film, comprising the steps of applying the coating composition according to claim 8 to an object to be coated and heating the applied coating at 60 to 120°C to cure the coating film made of said coating composition.

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