Blocked polyisocyanate composition, one-component coating composition, coating film and coated article

Abstract

Provided are a blocked polyisocyanate composition that exhibits good low-temperature curing properties when formed into a coating film, a one-component coating composition using the same, and a coating film and a coated article using the one-component coating composition. [Solution] A blocked polyisocyanate composition that exhibits good low-temperature curing properties when formed into a coating film comprises a blocked polyisocyanate derived from a polyisocyanate and a blocking agent, one or more organic acids and / or inorganic acids (A), and one or more trivalent metals (X), wherein the mass ratio of X to A, X / A, is 0.01 to 5.0, the content of X is 0.001% by mass or more and 20% by mass or less, based on the total mass of the blocked polyisocyanate composition, and the blocking agent comprises a compound having a heterocycle containing three or more nitrogen atoms.

Description

[Technical Field]

[0001] The present invention relates to a blocked polyisocyanate composition, a one-component coating composition, a coating film, and a coated article. This application claims priority based on Japanese Patent Application No. 2019-142538, filed on August 1, 2019, the contents of which are incorporated herein by reference. [Background technology]

[0002] Conventionally, polyurethane resin paints have excellent abrasion resistance, chemical resistance, and stain resistance. In particular, polyurethane resin paints using polyisocyanates obtained from aliphatic diisocyanates or alicyclic diisocyanates have even better weather resistance, and demand for such paints is on the rise.

[0003] However, polyurethane resin paints are generally two-component, which makes their use extremely inconvenient. That is, ordinary polyurethane resin paints consist of two components, a polyol and a polyisocyanate, and the polyol and polyisocyanate must be stored separately and mixed before application. Furthermore, once the two components are mixed, the paint gels within a short time, making it unusable. These problems with polyurethane resin paints make their use in automated painting extremely difficult in fields where line painting is performed, such as automotive painting or low-voltage painting.

[0004] In addition, because isocyanates readily react with water, they cannot be used in water-based paints such as electrodeposition paints. Furthermore, when using paints containing isocyanates, the sprayer and coating tank must be thoroughly cleaned after use, significantly reducing work efficiency. To address the above-mentioned issues, the use of blocked polyisocyanates, in which all active isocyanate groups are blocked with a blocking agent, has been proposed. These blocked polyisocyanates do not react with polyols at room temperature. However, heating dissociates the blocking agent, regenerating the active isocyanate groups, which then react with polyols to initiate a crosslinking reaction, thereby addressing the above-mentioned issues. Therefore, numerous blocking agents have been investigated, with representative examples including phenol and methyl ethyl ketoxime.

[0005] However, when using blocked polyisocyanates using these blocking agents, a high baking temperature of 140° C. or higher is generally required. The need for baking at a high temperature is not only disadvantageous in terms of energy, but also requires the substrate to be heat-resistant, which is a factor limiting its applications.

[0006] On the other hand, examples of blocked polyisocyanate compositions that can form crosslinked coating films at baking temperatures of 140°C or less include blocked polyisocyanate compositions that use a pyrazole-based compound as a blocking agent (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] European Patent No. 0159117 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in recent years, from the viewpoint of global environmental protection and in view of the strong demand for application to plastics with low heat resistance, there has been a strong demand for blocked polyisocyanate compositions that cure at temperatures below 100°C.

[0009] The present invention has been made in view of the above circumstances, and provides a blocked polyisocyanate composition and a one-component coating composition that have good low-temperature curing properties when formed into a coating film, a one-component coating composition using the blocked polyisocyanate composition, and a coating film and a coated article using the one-component coating composition. [Means for solving the problem]

[0010] That is, the present invention includes the following aspects. (1) A blocked polyisocyanate composition comprising a blocked polyisocyanate derived from a polyisocyanate and a blocking agent, one or more organic acids and / or inorganic acids (A), and one or more metal and / or quaternary ammonium cations (X), the mass ratio X / A of X to A is 0.01 to 5.0; The content of X is 0.001% by mass or more and 20% by mass or less relative to the total mass of the blocked polyisocyanate composition, and A blocked polyisocyanate composition, wherein the blocking agent comprises a compound having a heterocycle containing one or more nitrogen atoms. (2) A blocked polyisocyanate derived from a polyisocyanate and a blocking agent, and a compound represented by the following general formula (I): (A)nX (I) In the formula (I), A represents a group in which one hydrogen atom has been removed from an organic acid or an inorganic acid, X represents a metal or a quaternary ammonium cation, and n represents the valence of X and is an integer of 1 or more. and one or more organic acid salts and / or inorganic acid salts represented by the following formula: the mass ratio X / nA of X to A is 0.01 to 5.0; The content of X is 0.001% by mass or more and 20% by mass or less relative to the total mass of the blocked polyisocyanate composition, and A blocked polyisocyanate composition, wherein the blocking agent comprises a compound having a heterocycle containing one or more nitrogen atoms. (3) The blocked polyisocyanate composition according to (1) or (2), wherein X is a metal. (4) The blocked polyisocyanate composition according to (3), wherein X is a monovalent or trivalent metal. (5) The blocked polyisocyanate composition according to (4), wherein X is a monovalent metal. (6) The blocked polyisocyanate composition according to (4), wherein X is a trivalent metal. (7) The blocked polyisocyanate composition according to (6) above, wherein the blocking agent is a compound having a heterocycle containing three or more nitrogen atoms. (8) A blocked polyisocyanate composition comprising a blocked polyisocyanate derived from a polyisocyanate and a blocking agent, and one or more organic acid salts, wherein the blocking agent comprises a compound having a heterocycle containing one or more nitrogen atoms. (9) The blocked polyisocyanate composition according to (8), wherein the blocking agent is a compound having a heterocycle containing two or more nitrogen atoms. (10) The blocked polyisocyanate composition according to (9) above, wherein the blocking agent is a compound having a heterocycle containing three or more nitrogen atoms. (11) The blocked polyisocyanate composition according to any one of (8) to (10) above, wherein the organic acid salt is a carboxylate. (12) The blocked polyisocyanate composition according to (11) above, wherein the content of the counter cation of the carboxylate is 0.1% by mass or more and 20% by mass or less, based on the total mass of the blocked polyisocyanate. (13) The blocked polyisocyanate composition according to (11) or (12) above, wherein the carboxylate is a metal carboxylate or a carboxylate of a quaternary ammonium cation. (14) The blocked polyisocyanate composition according to (13) above, wherein the carboxylate is a metal carboxylate. (15) The blocked polyisocyanate composition according to (14) above, wherein the metal species of the carboxylic acid metal salt is a monovalent or trivalent metal. (16) The blocked polyisocyanate composition according to (15) above, wherein the metal species of the carboxylic acid metal salt is a monovalent metal. (17) The blocked polyisocyanate composition according to (15) above, wherein the metal species of the carboxylic acid metal salt is a trivalent metal. (18) A blocked polyisocyanate derived from a polyisocyanate, a hydrophilic compound, and a blocking agent; one or more carboxylates; A blocked polyisocyanate composition comprising: A blocked polyisocyanate composition, wherein the blocking agent is a compound having a heterocycle containing one or more nitrogen atoms. (19) The blocked polyisocyanate composition according to (18) above, wherein the blocking agent is a compound having a heterocycle containing two or more nitrogen atoms. (20) The blocked polyisocyanate composition according to (19) above, wherein the blocking agent is a compound having a heterocycle containing three or more nitrogen atoms. (21) The blocked polyisocyanate composition according to any one of (18) to (20) above, wherein the hydrophilic compound is a nonionic hydrophilic compound. (22) The blocked polyisocyanate composition according to (21) above, wherein the nonionic hydrophilic compound is a polyalkylene glycol monoalkyl ether. (23) The blocked polyisocyanate composition according to any one of (18) to (22), wherein the content of the counter cation of the carboxylate is 0.1% by mass or more and 20% by mass or less, based on the total mass of the blocked polyisocyanate. (24) The blocked polyisocyanate composition according to any one of (18) to (23) above, wherein the carboxylate is a metal carboxylate or a carboxylate of a quaternary ammonium cation. (25) The blocked polyisocyanate composition according to (24), wherein the carboxylate is a metal carboxylate. (26) The blocked polyisocyanate composition according to (25) above, wherein the metal species of the carboxylic acid metal salt is a monovalent or trivalent metal. (27) The blocked polyisocyanate composition according to (26) above, wherein the metal species of the carboxylic acid metal salt is a monovalent metal. (28) The blocked polyisocyanate composition according to (26) above, wherein the metal species of the carboxylic acid metal salt is a trivalent metal. (29) The blocked polyisocyanate composition according to any one of (1) to (28) above, further comprising one or more surfactants. (30) A one-component coating composition comprising the blocked polyisocyanate composition according to any one of (1) to (29) above and a polyvalent active hydrogen compound. (31) A one-component coating composition comprising a blocked polyisocyanate, a carboxylate, and a polyvalent active hydrogen compound, the blocked polyisocyanate is derived from a polyisocyanate and a blocking agent, A one-component coating composition, wherein the blocking agent comprises a compound having a heterocycle containing one or more nitrogen atoms. (32) A one-component coating composition comprising a blocked polyisocyanate, a carboxylate, and a polyvalent active hydrogen compound, the blocked polyisocyanate is derived from a polyisocyanate, a hydrophilic compound, and a blocking agent; A one-component coating composition, wherein the blocking agent is a compound having a heterocycle containing one or more nitrogen atoms. (33) The one-component coating composition according to (31) or (32) above, wherein the blocking agent is a compound having a heterocycle containing two or more nitrogen atoms. (34) The one-component coating composition according to (33) above, wherein the blocking agent is a compound having a heterocycle containing three or more nitrogen atoms. (35) The one-component coating composition according to any one of (30) to (34) above, further comprising a urethanization catalyst. (36) A coating film obtained by curing the one-component coating composition according to any one of (30) to (35) above. (37) A coated article having the coating film according to (36). [Effects of the Invention]

[0011] The blocked polyisocyanate composition and one-component coating composition of the above-mentioned aspects can provide a blocked polyisocyanate composition and one-component coating composition that exhibit good low-temperature curing properties when formed into a coating film. The coating film of the above-mentioned aspect is obtained by curing the one-component coating composition and exhibits good low-temperature curing properties. The coated article of the above aspect includes the coating film exhibiting good low-temperature curing properties. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "embodiment") will be described in detail. The following embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out by appropriately modifying it within the scope of its gist.

[0013] In this specification, the term "polyol" refers to a compound having two or more hydroxy groups (-OH). In this specification, the term "polyisocyanate" refers to a reaction product in which a plurality of monomer compounds having one or more isocyanate groups (-NCO) (hereinafter abbreviated as "isocyanate monomers") are bonded together.

[0014] <Blocked polyisocyanate composition> A blocked polyisocyanate composition according to a first embodiment of the present invention comprises a blocked polyisocyanate derived from a polyisocyanate and a blocking agent, one or more organic acids and / or inorganic acids (A), and one or more metal and / or quaternary ammonium cations (X), wherein the mass ratio of X to A, X / A, is 0.01 to 5.0, the content of X is 0.001% by mass or more and 20% by mass or less, relative to the total mass of the blocked polyisocyanate composition, and the blocking agent comprises a compound having a heterocycle containing one or more nitrogen atoms.

[0015] A blocked polyisocyanate composition according to a second embodiment of the present invention comprises a blocked polyisocyanate derived from a polyisocyanate and a blocking agent, and one or more organic acid salts and / or inorganic acid salts represented by the following general formula (I), wherein the mass ratio of X to A, X / nA, is 0.01 to 5.0, the content of X is 0.001 mass% or more and 20 mass% or less, relative to the total mass of the blocked polyisocyanate composition, and the blocking agent comprises a compound having a heterocycle containing one or more nitrogen atoms. (A)nX (I) In the formula (I), A represents a group in which one hydrogen atom has been removed from an organic acid or inorganic acid, X represents a metal or quaternary ammonium cation, and n represents the valence of X and is an integer of 1 or more.

[0016] A blocked polyisocyanate composition according to a third embodiment of the present invention comprises a blocked polyisocyanate derived from a polyisocyanate and a blocking agent, and one or more organic acid salts, wherein the blocking agent comprises a compound having a heterocycle containing one or more nitrogen atoms.

[0017] A blocked polyisocyanate composition according to a fourth embodiment of the present invention comprises a blocked polyisocyanate derived from a polyisocyanate, a hydrophilic compound, and a blocking agent, and one or more carboxylates, wherein the blocking agent comprises a compound having a heterocycle containing one or more nitrogen atoms.

[0018] A blocked polyisocyanate derived from a polyisocyanate and a blocking agent is a reaction product of a polyisocyanate and a blocking agent, in which at least a portion (preferably all) of the isocyanate groups of the polyisocyanate are blocked with the blocking agent.

[0019] A blocked polyisocyanate derived from a polyisocyanate, a hydrophilic compound, and a blocking agent is a reaction product of the polyisocyanate, the hydrophilic compound, and the blocking agent. Some of the isocyanate groups of the polyisocyanate are blocked with the blocking agent, and some of the isocyanate groups of the polyisocyanate form bonds with functional groups of the hydrophilic compound, thereby introducing hydrophilic groups.

[0020] The blocking agent includes a compound having a heterocycle containing one or more nitrogen atoms, preferably a compound having a heterocycle containing two or more nitrogen atoms, and more preferably a compound having a heterocycle containing three or more nitrogen atoms.

[0021] The blocked polyisocyanate composition of the embodiment has the above-described configuration, and thus exhibits good low-temperature curability when formed into a coating film. The components of the blocked polyisocyanate composition of the embodiment will be described in detail below.

[0022] <Blocked polyisocyanate> The blocked polyisocyanate is a blocked polyisocyanate derived from a polyisocyanate and a blocking agent, or a blocked polyisocyanate derived from a polyisocyanate, a hydrophilic compound, and a blocking agent.

[0023] [Polyisocyanate] Polyisocyanate is a reaction product obtained by reacting a plurality of monomer compounds having two or more isocyanate groups (-NCO) (hereinafter, sometimes referred to as "isocyanate monomers").

[0024] The isocyanate monomer preferably has a carbon number of 4 to 30. Specific examples of the isocyanate monomer include the following: These isocyanate monomers may be used alone or in combination of two or more. (1) Aromatic diisocyanates such as diphenylmethane-4,4'-diisocyanate (MDI), 1,5-naphthalene diisocyanate, tolylene diisocyanate (TDI), xylylene diisocyanate, and m-tetramethylxylylene diisocyanate (TMXDI); (2) Aliphatic diisocyanates such as 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate (hereinafter sometimes referred to as "HDI"), 2,2,4-trimethyl-1,6-diisocyanatohexane, 2,4,4-trimethyl-1,6-hexamethylene diisocyanate, 2-methylpentane-1,5-diisocyanate (MPDI), and lysine diisocyanate (hereinafter sometimes referred to as "LDI"); (3) Alicyclic diisocyanates such as isophorone diisocyanate (hereinafter sometimes referred to as "IPDI"), 1,3-bis(diisocyanatemethyl)cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, diisocyanate norbornane, and di(isocyanatemethyl)norbornane: (4) Triisocyanates such as 4-isocyanatomethyl-1,8-octamethylene diisocyanate (hereinafter sometimes referred to as "NTI"), 1,3,6-hexamethylene triisocyanate (hereinafter sometimes referred to as "HTI"), bis(2-isocyanatoethyl) 2-isocyanatoglutarate (hereinafter sometimes referred to as "GTI"), and lysine triisocyanate (hereinafter sometimes referred to as "LTI").

[0025] Among these, the isocyanate monomer is preferably one or more diisocyanates selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, as this will result in better weather resistance of the resulting coating film.Furthermore, the isocyanate monomer is more preferably HDI or IPDI, as it is easily available industrially.

[0026] As the isocyanate monomer, either an aliphatic diisocyanate or an alicyclic diisocyanate may be used alone or in combination, but it is preferable to use an aliphatic diisocyanate alone or a combination of an aliphatic diisocyanate and an alicyclic diisocyanate, and it is particularly preferable to use HDI alone or HDI and IPDI. By using an aliphatic diisocyanate and an alicyclic diisocyanate in combination, the toughness and elasticity of the resulting coating film can be further improved.

[0027] In the polyisocyanate of the present embodiment, when an aliphatic diisocyanate and an alicyclic diisocyanate are used in combination, the mass ratio of the structural units derived from the aliphatic diisocyanate to the structural units derived from the alicyclic diisocyanate is preferably 50 / 50 or more and 95 / 5 or less, more preferably 60 / 40 or more and 90 / 10 or less, and even more preferably 70 / 30 or more and 80 / 20 or less. When the mass ratio of the structural units derived from the aliphatic diisocyanate to the structural units derived from the alicyclic diisocyanate is equal to or greater than the above lower limit, a decrease in flexibility of the resulting coating film can be more effectively prevented, whereas when the mass ratio is equal to or less than the above upper limit, the hardness of the resulting coating film can be further improved.

[0028] The mass ratio of the structural units derived from aliphatic diisocyanates to the structural units derived from alicyclic diisocyanates can be calculated using the following method. First, the masses of the unreacted aliphatic diisocyanates and the unreacted alicyclic diisocyanates are calculated from the mass of the unreacted diisocyanates after the reaction and the aliphatic diisocyanate concentrations and alicyclic diisocyanate concentrations in the unreacted diisocyanates obtained by gas chromatographic measurement. Next, the calculated masses of the unreacted aliphatic diisocyanates and the unreacted alicyclic diisocyanates are subtracted from the masses of the charged aliphatic diisocyanates and alicyclic diisocyanates, respectively, and the resulting differences are taken as the masses of the structural units derived from aliphatic diisocyanates and the structural units derived from alicyclic diisocyanates, respectively. Next, the mass of the structural units derived from the aliphatic diisocyanate is divided by the mass of the structural units derived from the alicyclic diisocyanate to obtain the mass ratio of the structural units derived from the aliphatic diisocyanate to the structural units derived from the alicyclic diisocyanate.

[0029] Specific examples of polyisocyanates derived from the above isocyanate monomers include, but are not limited to, the following (1) to (8). (1) A polyisocyanate compound having a uretdione structure obtained by cyclodimerization of two isocyanate groups. (2) A polyisocyanate compound having an isocyanurate structure and an iminooxadiazinedione structure obtained by cyclotrimerizing three isocyanate groups. (3) A polyisocyanate compound having a biuret structure obtained by reacting three isocyanate groups with one water molecule. (4) A polyisocyanate compound having an oxadiazinetrione structure obtained by reacting two isocyanate groups with one molecule of carbon dioxide. (5) A polyisocyanate compound having a plurality of urethane groups obtained by reacting one isocyanate group with one hydroxyl group. (6) A polyisocyanate compound having an allophanate structure obtained by reacting two isocyanate groups with one hydroxyl group. (7) A polyisocyanate compound having an acylurea group obtained by reacting one isocyanate group with one carboxy group. (8) A polyisocyanate compound having a urea structure obtained by reacting one isocyanate group with one primary or secondary amine.

[0030] That is, the polyisocyanate includes not only polyisocyanates derived from the above-mentioned isocyanate monomers, but also polyisocyanates that are reaction products obtained by reacting multiple isocyanate monomers (including the above-mentioned diisocyanates) with compounds other than the above-mentioned isocyanate monomers (for example, alcohols, water, and amines).

[0031] In the polyisocyanate of this embodiment, the molar ratio of urethane groups to allophanate groups (urethane groups / allophanate groups) is preferably from 0 / 10 to 2 / 8, and more preferably from 0 / 10 to 1 / 9. When the urethane group / allophanate group ratio is within the above range, the low-temperature curing properties of the resulting coating film can be further improved.

[0032] The urethane group / allophanate group ratio can be calculated, for example, using the following method. 13C-NMR is measured using Biospin Avance600 (trade name) manufactured by Bruker under the following conditions.

[0033] (Measurement conditions) 13C-NMR device: AVANCE600 (manufactured by Bruker) Cryoprobe (Bruker) CryoProbe CPDUL 600S3-C / HD-05Z Resonance frequency: 150MHz Concentration: 60wt / vol% Shift standard: CDCl3 (77 ppm) Accumulation count: 10,000 times Pulse program: zgpg30 (proton fully decoupled, waiting time 2 seconds)

[0034] Next, from the measurement results obtained, the integral value of the following signals is divided by the number of carbon atoms being measured, and the molar amount of each functional group is calculated from the value obtained. The molar amount of urethane groups thus obtained is then divided by the molar amount of allophanate groups, thereby calculating the urethane group / allophanate group ratio.

[0035] Allophanate group: integral value around 154 ppm ÷ 1 (number of carbon atoms) Urethane group: integral value around 156.5 ppm ÷ 1 (number of carbon atoms) - integral value of allophanate group

[0036] The polyisocyanate may be a polyisocyanate having an isocyanurate group, which is composed of three diisocyanate molecules (hereinafter, this may be referred to as an "isocyanurate trimer"). The content of the isocyanurate trimer is preferably 8% by mass or more, more preferably 10% by mass or more, and even more preferably 12% by mass or more, based on the total mass of the polyisocyanate.

[0037] The content of the isocyanurate trimer can be calculated, for example, by the following method. The polyisocyanate used in the production of the blocked polyisocyanate composition is measured by gel permeation chromatography (GPC). Next, from the measurement results obtained, the ratio of the area of ​​the isocyanurate trimer to the area of ​​the entire component is calculated, and this ratio can be used as the content of the isocyanurate trimer in the component.

[0038] The polyisocyanate is preferably a polyisocyanate derived from the above-mentioned isocyanate monomer and a polymerizable alcohol having a number average molecular weight of 400 to 5,000 and an average number of hydroxyl groups of 3 to 8. The term "polymerizable alcohol" used herein refers to an alcohol obtained by polymerizing a monomer having a polymerizable group and a hydroxyl group. On the other hand, the term "non-polymerizable alcohol" refers to an alcohol having no polymerizable group.

[0039] Furthermore, it is preferable that the polyisocyanate derived from the above-mentioned isocyanate monomer and polymerizable alcohol satisfies the following conditions (1) to (3). (1) The content of the structural unit derived from the polymerizable alcohol is 22% by mass or more and 80% by mass or less based on the total mass of the polyisocyanate. (2) The average number of isocyanate functional groups is 3.0 or more and 20 or less. (3) The weight average molecular weight (Mw) / number average molecular weight (Mn) is 3.5 or more and 15 or less.

[0040] Regarding condition (1), the content of structural units derived from polymerizable alcohols (hereinafter sometimes abbreviated as "PO content") is preferably 22% by mass or more and 80% by mass or less, more preferably 22% by mass or more and 75% by mass or less, even more preferably 30% by mass or more and 75% by mass or less, and particularly preferably 35% by mass or more and 75% by mass or less, relative to the total mass of the polyisocyanate. By ensuring that the PO content is within the above range, it is possible to further improve the adhesion to the substrate and the low-temperature curing properties of the coating film formed therefrom. The PO content can be calculated using the following formula.

[0041] PO content (mass%) = Mass of PO charged / mass of polyisocyanate obtained × 100

[0042] Regarding condition (2), the average number of isocyanate functional groups is preferably 3.5 to 20, more preferably 4.0 to 15, even more preferably 4.5 to 10, and particularly preferably 5.0 to 9.0. When the average number of isocyanate functional groups is within the above range, the reactivity with the hydroxyl groups of the base resin can be made better. The average number of isocyanate functional groups can be calculated using the method described in the Examples below.

[0043] Regarding the condition (3), Mw / Mn is preferably 3.0 or more and 15 or less, more preferably 3.5 or more and 12 or less, even more preferably 3.5 or more and 11 or less, and particularly preferably 4.0 or more and 11 or less. By ensuring that the Mw / Mn is within the above range, the adhesion to the substrate and the low-temperature curing properties of the coating film formed can be further improved. The Mw / Mn of the polyisocyanate can be calculated using the Mw and Mn measured by GPC, specifically, the method described in the examples below.

[0044] The polyisocyanate derived from the above-mentioned isocyanate monomer and polymerizable alcohol, by satisfying the above-mentioned conditions (1) to (3), has a highly flexible structure and is more likely to form a crosslinked structure when mixed with the base resin, resulting in excellent low-temperature curing properties when formed into a coating film.

[0045] The above-mentioned various polyisocyanates may be used alone or in combination of two or more kinds.

[0046] (Polymerizable alcohol) The polymerizable alcohol is preferably a polyol having a number average molecular weight of 400 or more and 5000 or less and an average number of hydroxyl groups of 3 or more and 8 or less.

[0047] The number average molecular weight of the polymerizable alcohol is preferably 400 or more and 5,000 or less, more preferably more than 500 and 5,000 or less, even more preferably 550 or more and 4,500 or less, and particularly preferably 850 or more and 4,000 or less. When the number average molecular weight of the polymerizable alcohol is within the above range, the polyisocyanate derived from the isocyanate monomer and the polymerizable alcohol has a highly flexible structure, and is more likely to form a crosslinked structure when mixed with the main agent, resulting in excellent low-temperature curing properties when formed into a coating film.

[0048] The average number of hydroxyl groups in the polymerizable alcohol is preferably 3 or more and 8 or less, more preferably 3 or more and 6 or less, even more preferably 3 or more and 5 or less, and particularly preferably 3 or 4. Specific examples of the polymerizable alcohol include polyester polyol, polyether polyol, acrylic polyols, polyolefin polyols, and the like.

[0049] The polyester polyol can be obtained, for example, by subjecting a dibasic acid, either alone or in a mixture of two or more kinds, to a condensation reaction with a polyhydric alcohol, either alone or in a mixture of two or more kinds. Examples of the dibasic acid include succinic acid, adipic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, and other carboxylic acids. Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, cyclohexanediol, trimethylolpropane, glycerin, pentaerythritol, 2-methylolpropanediol, and ethoxylated trimethylolpropane. As a specific method for producing the polyester polyol, for example, the above components can be mixed and heated to about 160° C. or more and 220° C. or less to carry out a condensation reaction. Alternatively, for example, polycaprolactones obtained by ring-opening polymerization of lactones such as ε-caprolactone with polyhydric alcohols can also be used as the polyester polyol. From the viewpoint of the weather resistance and yellowing resistance of the resulting coating film, the polyester polyol obtained by the above-mentioned production method is preferably modified using an aliphatic diisocyanate, an alicyclic diisocyanate, or a compound obtained from these.

[0050] The polyether polyol can be obtained, for example, by using any one of the following methods (1) to (3). (1) A method of obtaining polyether polyols by random or block addition of an alkylene oxide or a mixture thereof to a polyhydroxy compound or a mixture thereof using a catalyst. Examples of the catalyst include hydroxides of lithium, sodium, potassium, etc., strong basic catalysts, composite metal cyanide complexes, etc. Examples of the strong basic catalysts include alcoholates and alkylamines, and examples of the composite metal cyanide complexes include metalloporphyrins and zinc hexacyanocobaltate complexes. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, and styrene oxide. (2) A method of obtaining polyether polyols by reacting a polyamine compound with an alkylene oxide. Examples of the polyamine compound include ethylenediamines. Examples of the alkylene oxide include the same as those exemplified in (1). (3) A method in which acrylamide or the like is polymerized using the polyether polyols obtained by (1) or (2) as a medium to obtain so-called polymer polyols. Examples of the polyvalent hydroxy compound include the following compounds (i) to (vi). (i) diglycerin, ditrimethylolpropane, pentaerythritol, dipentaerythritol, etc.; (ii) sugar alcohol compounds such as erythritol, D-threitol, L-arabinitol, ribitol, xylitol, sorbitol, mannitol, galactitol, and rhamnitol; (iii) monosaccharides such as arabinose, ribose, xylose, glucose, mannose, galactose, fructose, sorbose, rhamnose, fucose, and ribonucleotides; (iv) disaccharides such as trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, and melibiose; (v) trisaccharides such as raffinose, gentianose, and melezitose; (vi) Tetrasaccharides such as stachyose.

[0051] The acrylic polyols are not particularly limited, but examples thereof include copolymers of a single or a mixture of an ethylenically unsaturated bond-containing monomer having a hydroxyl group and a single or a mixture of other ethylenically unsaturated bond-containing monomers copolymerizable therewith. The ethylenically unsaturated bond-containing monomer having a hydroxyl group is not particularly limited, but examples thereof include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate. The other ethylenically unsaturated bond-containing monomer copolymerizable with the ethylenically unsaturated bond-containing monomer having a hydroxyl group is not particularly limited, and examples thereof include acrylic acid esters, methacrylic acid esters, unsaturated carboxylic acids, unsaturated amides, vinyl-based monomers, and vinyl-based monomers having a hydrolyzable silyl group. Examples of acrylic acid esters include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, benzyl acrylate, and phenyl acrylate. Examples of methacrylic acid esters include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, benzyl methacrylate, and phenyl methacrylate. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, and itaconic acid. Examples of unsaturated amides include acrylamide, methacrylamide, N,N-methylenebisacrylamide, diacetone acrylamide, diacetone methacrylamide, maleic acid amide, and maleimide. Examples of vinyl monomers include glycidyl methacrylate, styrene, vinyltoluene, vinyl acetate, acrylonitrile, and dibutyl fumarate. Examples of vinyl monomers having a hydrolyzable silyl group include vinyltrimethoxysilane, vinylmethyldimethoxysilane, and γ-(meth)acryloxypropyltrimethoxysilane.

[0052] Examples of polyolefin polyols include hydroxyl-terminated polybutadiene and hydrogenated products thereof.

[0053] Among these, polyester polyols are preferred as the polymerizable alcohol, and polycaprolactone polyols obtained by ring-opening polymerization of ε-caprolactone with a low-molecular-weight polyol are more preferred.

[0054] (Production method of polyisocyanate) The method for producing polyisocyanate will be described in detail below. Polyisocyanates can be obtained, for example, by simultaneously carrying out an allophanate reaction to form allophanate groups, a uretdione reaction to form uretdione groups, an iminooxadiazinedione reaction to form iminooxadiazinedione groups, an isocyanurate reaction to form isocyanurate groups, a urethanization reaction to form urethane groups, and a biuret reaction to form biuret groups in the presence of an excess of isocyanate monomer, and then removing the unreacted isocyanate monomer after the completion of the reactions. That is, the polyisocyanate obtained by the above reaction is a reaction product in which a plurality of the above-mentioned isocyanate monomers are bonded together and has one or more groups selected from the group consisting of allophanate groups, uretdione groups, iminooxadiazinedione groups, isocyanurate groups, urethane groups, and biuret groups. Alternatively, the above reactions may be carried out separately and the resulting polyisocyanates may be mixed in a specific ratio. From the viewpoint of ease of production, it is preferable to carry out the above reaction at one time to obtain the polyisocyanate, but from the viewpoint of freely adjusting the molar ratio of each functional group, it is preferable to produce them separately and then mix them.

[0055] (1) Method for producing allophanate group-containing polyisocyanate The allophanate group-containing polyisocyanate can be obtained by adding an alcohol to an isocyanate monomer and using an allophanate reaction catalyst.

[0056] The alcohol used to form the allophanate group is preferably an alcohol formed only from carbon, hydrogen and oxygen. Specific examples of the alcohol include, but are not limited to, monoalcohols, dialcohols, etc. These alcohols may be used alone or in combination of two or more. Examples of monoalcohols include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, and nonanol. Examples of the dialcohol include ethylene glycol, 1,3-butanediol, neopentyl glycol, and 2-ethylhexanediol. Among these, the alcohol is preferably a monoalcohol, and more preferably a monoalcohol having a molecular weight of 200 or less.

[0057] The allophanatization reaction catalyst includes, but is not limited to, alkyl carboxylates of tin, lead, zinc, bismuth, zirconium, zirconyl, and the like. Examples of tin alkylcarboxylates (organotin compounds) include tin 2-ethylhexanoate and dibutyltin dilaurate. Examples of lead alkylcarboxylates (organic lead compounds) include lead 2-ethylhexanoate. Examples of zinc alkylcarboxylates (organic zinc compounds) include zinc 2-ethylhexanoate. Examples of bismuth alkylcarboxylates include bismuth 2-ethylhexanoate. Examples of zirconium alkylcarboxylates include zirconium 2-ethylhexanoate. Examples of zirconyl alkylcarboxylates include zirconyl 2-ethylhexanoate. These catalysts can be used alone or in combination of two or more.

[0058] Furthermore, the isocyanurate-forming reaction catalyst described below can also serve as the allophanate-forming reaction catalyst. When the allophanate-forming reaction is carried out using the isocyanurate-forming reaction catalyst described below, an isocyanurate-type polyisocyanate is naturally also produced. Among these, it is preferable from the viewpoint of economical production to carry out the allophanate formation reaction and the isocyanurate formation reaction using an isocyanurate formation catalyst described below as the allophanate formation reaction catalyst.

[0059] The lower limit of the amount of the allophanate reaction catalyst used is preferably 10 ppm by mass, more preferably 20 ppm by mass, even more preferably 40 ppm by mass, and particularly preferably 80 ppm by mass, relative to the mass of the charged isocyanate monomer. The upper limit of the amount of the allophanate reaction catalyst used is preferably 1000 ppm by mass, more preferably 800 ppm by mass, even more preferably 600 ppm by mass, and particularly preferably 500 ppm by mass, relative to the mass of the charged isocyanate monomer. That is, the amount of the allophanate reaction catalyst used is preferably 10 ppm by mass or more and 1000 ppm by mass or less, more preferably 20 ppm by mass or more and 800 ppm by mass or less, even more preferably 40 ppm by mass or more and 600 ppm by mass or less, and particularly preferably 80 ppm by mass or more and 500 ppm by mass or less, relative to the mass of the charged isocyanate monomer.

[0060] The lower limit of the allophanatization reaction temperature is preferably 40°C, more preferably 60°C, further preferably 80°C, and particularly preferably 100°C. The upper limit of the allophanate reaction temperature is preferably 180°C, more preferably 160°C, and even more preferably 140°C. That is, the allophanate reaction temperature is preferably 40°C or higher and 180°C or lower, more preferably 60°C or higher and 160°C or lower, even more preferably 80°C or higher and 140°C or lower, and particularly preferably 100°C or higher and 140°C or lower. By setting the allophanate reaction temperature to the above lower limit or higher, the reaction rate can be further improved. By setting the allophanate reaction temperature to the above upper limit or lower, coloration of the polyisocyanate tends to be more effectively suppressed.

[0061] (2) Method for producing uretdione group-containing polyisocyanate When a polyisocyanate-containing polyisocyanate having uretdione groups is derived from an isocyanate monomer, it can be produced, for example, by polymerizing the isocyanate monomer using a uretdione reaction catalyst or by heat. The uretdione-forming reaction catalyst is not particularly limited, but examples thereof include tertiary phosphines such as trialkylphosphine, tris(dialkylamino)phosphine and cycloalkylphosphine, Lewis acids, and the like. Examples of trialkylphosphines include tri-n-butylphosphine and tri-n-octylphosphine. Examples of tris(dialkylamino)phosphines include tris-(dimethylamino)phosphine. Examples of cycloalkylphosphines include cyclohexyl-di-n-hexylphosphine. Examples of Lewis acids include boron trifluoride and zinc oxychloride.

[0062] Many of the catalysts for the uretdione formation reaction can also promote the isocyanurate formation reaction at the same time. When a uretdione-forming reaction catalyst is used, it is preferable to add a deactivator for the uretdione-forming reaction catalyst such as phosphoric acid or methyl paratoluenesulfonate to terminate the uretdione-forming reaction when the desired yield is achieved.

[0063] When one or more diisocyanates selected from the group consisting of the aliphatic diisocyanates and the alicyclic diisocyanates are heated without using a uretdione reaction catalyst to obtain a polyisocyanate having uretdione groups, the heating temperature is preferably 120° C. or higher, more preferably 150° C. or higher and 170° C. or lower, and the heating time is preferably 1 hour or longer and 4 hours or shorter.

[0064] (3) Method for producing iminooxadiazinedione group-containing polyisocyanate When an iminooxadiazinedione group-containing polyisocyanate is derived from an isocyanate monomer, an iminooxadiazinedione-forming reaction catalyst is usually used.

[0065] Examples of the iminooxadiazinedione catalyst include those shown in 1) or 2) below. 1) (Poly)hydrogen fluoride represented by the general formula M[Fn] or the general formula M[Fn(HF)m]. (wherein m and n are integers satisfying the relationship m / n>0. M is an n-charged cation (mixture) or one or more radicals with a total valence of n.) 2) General formula R 1 -CR'2-C(O)O-, or general formula R 2 A compound comprising a compound represented by =CR'-C(O)O- and a quaternary ammonium cation or a quaternary phosphonium cation. (In the formula, R 1 and R 2 are each independently a linear, branched, or cyclic, saturated or unsaturated perfluoroalkyl group having from 1 to 30 carbon atoms. A plurality of R's are each independently selected from the group consisting of a hydrogen atom, and an alkyl group and an aryl group having from 1 to 20 carbon atoms, which may contain a heteroatom.

[0066] Specific examples of the compound 1) ((poly)hydrogen fluoride) include tetramethylammonium fluoride hydrate, tetraethylammonium fluoride, and the like. Specific examples of the compound 2) include 3,3,3-trifluorocarboxylic acid, 4,4,4,3,3-pentafluorobutanoic acid, 5,5,5,4,4,3,3-heptafluoropentanoic acid, and 3,3-difluoroprop-2-enoic acid.

[0067] Among them, as the iminooxadiazinedione-forming reaction catalyst, 1) is preferred from the viewpoint of availability, and 2) is preferred from the viewpoint of safety.

[0068] The lower limit of the amount of the iminooxadiazinedione catalyst used is not particularly limited, but from the viewpoint of reactivity, it is preferably 5 ppm, more preferably 10 ppm, and even more preferably 20 ppm in mass ratio relative to the mass of the charged isocyanate monomer. The upper limit of the amount of the iminooxadiazinedione catalyst used is preferably 5000 ppm, more preferably 2000 ppm, and even more preferably 500 ppm by mass relative to the mass of the charged isocyanate monomer, from the viewpoints of suppressing coloration and discoloration of the product and controlling the reaction. That is, the amount of the iminooxadiazinedione catalyst used is preferably 5 ppm or more and 5000 ppm or less, more preferably 10 ppm or more and 2000 ppm or less, and even more preferably 20 ppm or more and 500 ppm or less, by mass ratio relative to the mass of the charged isocyanate monomer.

[0069] The lower limit of the reaction temperature for the iminooxadiazinedione formation is not particularly limited, but from the viewpoint of the reaction rate, it is preferably 40°C, more preferably 50°C, and even more preferably 60°C. The upper limit of the reaction temperature for the iminooxadiazinedione formation is preferably 150°C, more preferably 120°C, and even more preferably 110°C, from the viewpoint of suppressing coloration and discoloration of the product. That is, the reaction temperature for the iminooxadiazinedione formation is preferably 40°C or higher and 150°C or lower, more preferably 50°C or higher and 120°C or lower, and even more preferably 60°C or higher and 110°C or lower.

[0070] The iminooxadiazinedione formation reaction can be terminated when the desired iminooxadiazinedione group content is reached. The iminooxadiazinedione formation reaction can be terminated, for example, by adding an acidic compound to the reaction solution. Examples of acidic compounds include phosphoric acid, acidic phosphate esters, sulfuric acid, hydrochloric acid, and sulfonic acid compounds. This neutralizes the iminooxadiazinedione formation reaction catalyst or inactivates it by thermal decomposition or chemical decomposition. After the reaction is terminated, filtration is performed, if necessary.

[0071] (4) Method for producing isocyanurate group-containing polyisocyanate Examples of catalysts for deriving polyisocyanates containing isocyanurate groups from isocyanate monomers include commonly used isocyanuration reaction catalysts. The isocyanurate reaction catalyst is not particularly limited, but is preferably a basic catalyst in general. Specific examples of the isocyanurate reaction catalyst include the following: (1) Hydroxides of tetraalkylammonium such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium, and organic weak acid salts of the above tetraalkylammonium such as acetate, propionate, octylate, caprate, myristate, and benzoate. (2) Hydroxides of aryltrialkylammonium such as benzyltrimethylammonium and trimethylphenylammonium, and organic weak acid salts of the above aryltrialkylammonium such as acetate, propionate, octylate, caprate, myristate, and benzoate. (3) Hydroxyalkylammonium hydroxides such as trimethylhydroxyethylammonium, trimethylhydroxypropylammonium, triethylhydroxyethylammonium, and triethylhydroxypropylammonium, and organic weak acid salts such as acetates, propionates, octylates, caprates, myristates, and benzoates of the above hydroxyalkylammoniums. (4) Metal salts of tin, zinc, lead, etc. of alkylcarboxylic acids such as acetic acid, propionic acid, caproic acid, octylic acid, capric acid, and myristic acid. (5) Metal alcoholates such as sodium and potassium. (6) Aminosilyl group-containing compounds such as hexamethylenedisilazane. (7) Mannich bases. (8) A mixture of a tertiary amine and an epoxy compound. (9) Phosphorus compounds such as tributylphosphine.

[0072] Among these, from the viewpoint of preventing the generation of unnecessary by-products, the isocyanuration reaction catalyst is preferably a quaternary ammonium hydroxide or a weak organic acid salt, and more preferably a tetraalkylammonium hydroxide, a weak organic acid salt of a tetraalkylammonium, an aryltrialkylammonium hydroxide, or a weak organic acid salt of an aryltrialkylammonium.

[0073] The upper limit of the amount of the isocyanurate reaction catalyst used is preferably 1000 ppm by mass, more preferably 500 ppm by mass, and even more preferably 100 ppm by mass, relative to the mass of the charged isocyanate monomer. On the other hand, the lower limit of the amount of the isocyanurate reaction catalyst used is not particularly limited, but may be, for example, 10 ppm by mass.

[0074] The isocyanurate reaction temperature is preferably 50° C. or higher and 120° C. or lower, and more preferably 60° C. or higher and 90° C. or lower. When the isocyanurate reaction temperature is equal to or lower than the upper limit, coloration of the polyisocyanate tends to be more effectively suppressed.

[0075] When a desired conversion rate (the ratio by mass of polyisocyanate produced in the isocyanuration reaction to the mass of the charged isocyanate monomer) is reached, the isocyanuration reaction is stopped by adding an acidic compound (e.g., phosphoric acid, acidic phosphate ester, etc.). In order to obtain polyisocyanate, it is necessary to stop the reaction in an early stage. However, since the reaction rate of the isocyanuration reaction is very fast in the early stage, it is difficult to stop the reaction in an early stage, and therefore the reaction conditions, particularly the amount and method of adding the catalyst, must be carefully selected. For example, a method of adding the catalyst in portions at regular intervals is recommended as a suitable method.

[0076] Therefore, the conversion rate of the isocyanurate reaction to obtain polyisocyanate is preferably 10% by mass or more and 60% by mass or less, more preferably 15% by mass or more and 55% by mass or less, and even more preferably 20% by mass or more and 50% by mass or less. When the conversion rate of the isocyanurate reaction is equal to or less than the upper limit, the viscosity of the blocked polyisocyanate composition containing the polyisocyanate can be made lower. When the conversion rate of the isocyanurate reaction is equal to or greater than the lower limit, the reaction termination operation can be more easily carried out.

[0077] When deriving a polyisocyanate containing an isocyanurate group, a monohydric to hexahydric alcohol can be used in addition to the above isocyanate monomer. Examples of the usable monohydric to hexahydric alcohol include non-polymerizable alcohols and polymerizable alcohols.

[0078] Examples of non-polymerizable alcohols include polyhydric alcohols such as monoalcohols, diols, triols, and tetraols. Examples of monoalcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, n-pentanol, n-hexanol, n-octanol, n-nonanol, 2-ethylbutanol, 2,2-dimethylhexanol, 2-ethylhexanol, cyclohexanol, methylcyclohexanol, and ethylcyclohexanol. Examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,2-propanediol, 1,5-pentanediol, and 2-methyl-2,3-butanediol. Examples of the hexanediol include hexanediol, 1,6-hexanediol, 1,2-hexanediol, 2,5-hexanediol, 2-methyl-2,4-pentanediol, 2,3-dimethyl-2,3-butanediol, 2-ethyl-hexanediol, 1,2-octanediol, 1,2-decanediol, 2,2,4-trimethylpentanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2,2-diethyl-1,3-propanediol. Examples of triols include glycerin and trimethylolpropane. An example of the tetraols is pentaerythritol. The polymerizable alcohol is not particularly limited, but examples thereof include the polymerizable alcohols described above.

[0079] (5) Method for producing urethane group-containing polyisocyanate When a polyisocyanate containing a urethane group is derived from an isocyanate monomer, it can be produced, for example, by mixing an excess of the isocyanate monomer with an alcohol, and adding a urethanization reaction catalyst as necessary.

[0080] Examples of the alcohol include the same alcohols as those exemplified in the above "Method for producing isocyanurate group-containing polyisocyanate."

[0081] The urethanization reaction catalyst is not particularly limited, but examples thereof include tin-based compounds, zinc-based compounds, and amine-based compounds.

[0082] The urethane reaction temperature is preferably 50°C or higher and 160°C or lower, and more preferably 60°C or higher and 120°C or lower. When the urethanization reaction temperature is equal to or lower than the upper limit, coloration of the polyisocyanate tends to be more effectively suppressed.

[0083] The urethane reaction time is preferably 30 minutes to 4 hours, more preferably 1 hour to 3 hours, and even more preferably 1 hour to 2 hours.

[0084] The molar ratio of the isocyanate groups of the isocyanate monomer to the molar amount of the hydroxyl groups of the alcohol is preferably 2 / 1 or more and 50 / 1 or less. When this molar ratio is equal to or more than the lower limit, the viscosity of the polyisocyanate can be made lower. When this molar ratio is equal to or less than the upper limit, the yield of the urethane group-containing polyisocyanate can be increased.

[0085] (6) Method for producing biuret group-containing polyisocyanate The biuretizing agent for deriving a polyisocyanate containing a biuret group from an isocyanate monomer is not particularly limited, but examples thereof include water, monohydric tertiary alcohols, formic acid, organic primary monoamines, and organic primary diamines.

[0086] The amount of isocyanate groups per mole of biuretizing agent is preferably 6 moles or more, more preferably 10 moles or more, and even more preferably 10 moles or more but 80 moles or less. If the molar amount of isocyanate groups per mole of biuretizing agent is equal to or greater than the above-mentioned lower limit, the viscosity of the polyisocyanate will be sufficiently low, and if it is equal to or less than the above-mentioned upper limit, the curability of the coating composition will be further improved.

[0087] A solvent may be used in the biuretization reaction, as long as it dissolves the isocyanate monomer and the biuretization agent such as water and forms a homogeneous phase under the reaction conditions.

[0088] Specific examples of the solvent include ethylene glycol-based solvents and phosphoric acid-based solvents.

[0089] Examples of ethylene glycol solvents include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol mono-n-propyl ether acetate, ethylene glycol monoisopropyl ether acetate, ethylene glycol mono-n-butyl ether acetate, ethylene glycol diacetate, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol di-n-propyl ether, ethylene glycol diisopropyl ether, ethylene glycol di-n-butyl ether, ethylene glycol methyl ethyl ether, ethylene glycol methyl isopropyl ether, ethylene glycol methyl-n-butyl ether, ethylene glycol ethyl-n-propyl ether, ethylene glycol ethyl isopropyl ether, ethylene glycol ethyl-n-butyl ether, ethylene glycol-n-propyl-n-butyl ether, ethylene glycol isopropyl-n-butyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol mono-n-propyl ether acetate, diethylene glycol monoisopropyl ether acetate, diethylene glycol mono-n-butyl ether acetate, diethylene glycol diacetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol di-n-propyl ether, diethylene glycol diisopropyl ether, diethylene glycol di-n-butyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl isopropyl ether, diethylene glycol methyl-n-propyl ether, diethylene glycol methyl-n-butyl ether, diethylene glycol ethyl isopropyl ether, diethylene glycol ethyl-n-propyl ether, diethylene glycol ethyl-n-butyl ether, diethylene glycol-n-propyl-n-butyl ether, and diethylene glycol isopropyl-n-butyl ether.

[0090] Examples of the phosphoric acid solvent include trimethyl phosphate, triethyl phosphate, tripropyl phosphate, and tributyl phosphate.

[0091] These solvents may be used alone or in combination of two or more.

[0092] Among these, the ethylene glycol solvent is preferably ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol diacetate, or diethylene glycol dimethyl ether. As the phosphoric acid-based solvent, trimethyl phosphate or triethyl phosphate is preferred.

[0093] The biuretization reaction temperature is preferably 70° C. or higher and 200° C. or lower, and more preferably 90° C. or higher and 180° C. or lower. By keeping the temperature at or below the upper limit, coloration of the polyisocyanate tends to be more effectively prevented.

[0094] The above-mentioned allophanate formation reaction, uretdione formation reaction, iminooxadiazinedione formation reaction, isocyanurate formation reaction, urethanization reaction, and biuret formation reaction may be carried out sequentially, or some of them may be carried out in parallel.

[0095] Furthermore, when producing a polyisocyanate derived from an isocyanate monomer and a polymerizable alcohol, the polyisocyanate can be obtained, for example, by reacting an isocyanate group of the isocyanate monomer with a hydroxyl group of a polyol.

[0096] The molar ratio (NCO / OH) of the isocyanate groups of the diisocyanate to the hydroxyl groups of the polyol is preferably 3 / 1 or more and 30 / 1 or less, more preferably 10 / 1 or more and 20 / 1 or less. When the NCO / OH is equal to or more than the above lower limit, it is possible to effectively prevent the viscosity of the resulting polyisocyanate composition from increasing too much. On the other hand, when the NCO / OH is equal to or less than the above upper limit, it is possible to effectively prevent the productivity of the resulting polyisocyanate composition from decreasing.

[0097] The reaction temperature is preferably 50°C or higher and 200°C or lower, and more preferably 50°C or higher and 150°C or lower. When the reaction temperature is equal to or higher than the lower limit, the reaction proceeds more efficiently, while when the reaction temperature is equal to or lower than the upper limit, undesirable side reactions such as discoloration of the resulting polyisocyanate composition can be more effectively suppressed. The reaction time is preferably in the range of 0.5 hours to 5 hours.

[0098] After or simultaneously with the reaction between the isocyanate group of the diisocyanate and the hydroxyl group of the polyol, at least one reaction selected from the group consisting of the allophanate formation reaction, uretdione formation reaction, iminooxadiazinedione formation reaction, isocyanurate formation reaction, urethanization reaction, and biuret formation reaction can be carried out, and among these, the isocyanurate formation reaction is preferred. By carrying out the isocyanurate formation reaction, the hardness of the resulting coating film can be further improved.

[0099] After the completion of the various reactions, the unreacted isocyanate monomer can be removed from the reaction solution by thin film distillation, extraction, or the like to obtain a polyisocyanate.

[0100] Furthermore, an antioxidant or an ultraviolet absorber may be added to the obtained polyisocyanate, for example, for the purpose of suppressing coloration during storage. Examples of antioxidants include hindered phenols such as 2,6-di-tert-butyl-p-cresol. Examples of ultraviolet absorbers include benzotriazole and benzophenone. These antioxidants and ultraviolet absorbers may be used alone or in combination of two or more. The amount of these added is preferably 10 ppm by mass or more and 500 ppm by mass or less relative to the mass of the polyisocyanate.

[0101] (Physical properties of polyisocyanate) The isocyanate group content of the polyisocyanate is more preferably 5% by mass or more and 25% by mass or less, more preferably 5% by mass or more and 23% by mass or less, even more preferably 6% by mass or more and 20% by mass or less, and most preferably 8% by mass or more and 17% by mass or less. The isocyanate group content can be measured by the method described in the examples below.

[0102] The number average molecular weight of the polyisocyanate is preferably from 500 to 10,000, more preferably from 1,000 to 5,000, even more preferably from 1,200 to 4,800, and most preferably from 1,500 to 4,600. When the number average molecular weight is at least the above lower limit, a decrease in the flexibility of the coating film can be more effectively prevented, while when the number average molecular weight is at most the above upper limit, a decrease in the smoothness of the coating film can be more effectively prevented. The number average molecular weight of the polyisocyanate can be measured by the method described in the examples below.

[0103] The weight average molecular weight of the polyisocyanate is preferably 500 or more and 100,000 or less, more preferably 4,000 or more and 50,000 or less, even more preferably 4,500 or more and 49,000 or less, and most preferably 5,000 or more and 48,500 or less. The weight average molecular weight of the polyisocyanate can be measured by the method described in the examples below.

[0104] [Blocking agent] When the blocked polyisocyanate is a blocked polyisocyanate derived from a polyisocyanate and a blocking agent, the blocking agent includes a compound having a heterocycle containing one or more nitrogen atoms, preferably a compound having a heterocycle containing two or more nitrogen atoms, and more preferably a compound having a heterocycle containing three or more nitrogen atoms.

[0105] When the blocked polyisocyanate is derived from a polyisocyanate, a hydrophilic compound, and a blocking agent, the blocking agent is a compound having a heterocycle containing one or more nitrogen atoms. Among them, from the viewpoint of low-temperature curing properties, the blocking agent is preferably a compound having a heterocycle containing two or more nitrogen atoms, and more preferably a compound having a heterocycle containing three or more nitrogen atoms.

[0106] In any of the above blocked polyisocyanates, the content of the compound having a heterocycle containing three or more nitrogen atoms relative to the total mass of the blocking agent is preferably 50 mass% or more, more preferably 60 mass% or more, even more preferably 70 mass% or more, particularly preferably 90 mass% or more, and most preferably 100 mass%, i.e., it is most preferable that the blocking agent consists solely of the compound having a heterocycle containing three or more nitrogen atoms.

[0107] Examples of compounds having a heterocycle containing one or more nitrogen atoms include those shown below. 1) Aziridine-based blocking agents such as ethyleneimine; 2) Azetidine-based blocking agents such as azecyclobutane; 3) Azolidine-based blocking agents such as pyrrolidine; 4) Azole blocking agents such as pyrrole and 2H-pyrrole; 5) Imidazoline-based blocking agents such as 2-methylimidazoline and 2-phenylimidazoline; 6) Pyrimidine-based blocking agents such as 2-methyl-1,4,5,6-tetrahydropyrimidine; 7) Diazole-based blocking agents such as pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole, imidazole, 2-methylimidazole, 4-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-methyl-2-phenylimidazole, benzimidazole, and 2-methylbenzimidazole; 8) Triazole-based blocking agents such as 1,2,4-triazole, 1,2,3-triazole, and 3,5-dimethyl-1,2,4-triazole 9) tetrazole-based blocking agents such as 1H-1,2,3,4-tetrazole; 10) Pyridine-based blocking agents such as 2-(methylamino)pyridine, 4-hydroxypyridine, and 2-hydroxypyridine. Among these, diazole-based blocking agents such as pyrazole-based blocking agents or triazole-based blocking agents are preferred, and triazole-based blocking agents are more preferred.

[0108] [Hydrophilic compound] The hydrophilic compound is a compound having a hydrophilic group, and preferably has one or more active hydrogen groups per molecule of the hydrophilic compound to react with one isocyanate group of the polyisocyanate. Specific examples of the active hydrogen groups include hydroxyl groups, mercapto groups, carboxylic acid groups, amino groups, and thiol groups.

[0109] Examples of the hydrophilic group include a nonionic hydrophilic group, a cationic hydrophilic group, and an anionic hydrophilic group. These hydrophilic groups may be used alone or in combination of two or more. Among them, a nonionic hydrophilic group is preferred as the hydrophilic group from the viewpoints of availability and being less susceptible to electrical interaction with the compound.

[0110] (Hydrophilic compound having a nonionic hydrophilic group) Specific examples of hydrophilic compounds having a nonionic hydrophilic group (hereinafter sometimes referred to as "nonionic hydrophilic compounds") include monoalcohols and compounds in which ethylene oxide is added to the hydroxyl group of an alcohol. Examples of monoalcohols include methanol, ethanol, and butanol. Examples of compounds in which ethylene oxide is added to the hydroxyl group of an alcohol include ethylene glycol, diethylene glycol, and polyethylene glycol. These nonionic hydrophilic compounds also have an active hydrogen group that reacts with an isocyanate group. Among these, as the nonionic hydrophilic compound, polyalkylene glycol monoalkyl ethers in which alkylene oxide is added to the hydroxyl group of a monoalcohol are preferred, and polyethylene glycol monoalkyl ethers are more preferred, because they can improve the water dispersibility of the blocked polyisocyanate composition with a small amount used.

[0111] The number of ethylene oxide addition units in the ethylene oxide-added compound is preferably 4 or more and 30 or less, and more preferably 4 or more and 20 or less. When the number of ethylene oxide addition units is equal to or more than the above-mentioned lower limit, water dispersibility tends to be more effectively imparted to the blocked polyisocyanate composition, and when the number of ethylene oxide addition units is equal to or less than the above-mentioned upper limit, the blocked polyisocyanate composition tends to be less likely to precipitate during low-temperature storage.

[0112] From the viewpoint of the aqueous dispersion stability of the blocked polyisocyanate composition, the lower limit of the amount of nonionic hydrophilic groups added to the polyisocyanate (hereinafter, may be referred to as the "nonionic hydrophilic group content") is preferably 1 mass %, more preferably 3 mass %, even more preferably 4 mass %, and particularly preferably 4.5 mass %, relative to the mass of the solid content of the blocked polyisocyanate composition. Furthermore, from the viewpoint of the water resistance of the resulting coating film, the upper limit of the content of the nonionic hydrophilic group is preferably 30 mass%, more preferably 20 mass%, even more preferably 10 mass%, and particularly preferably 8 mass%, relative to the mass of the solid content of the blocked polyisocyanate composition. That is, the upper limit of the content of the nonionic hydrophilic group is preferably from 1% by mass to 30% by mass, more preferably from 3% by mass to 20% by mass, even more preferably from 4% by mass to 10% by mass, and particularly preferably from 4.5% by mass to 8% by mass, relative to the mass of the solid content of the blocked polyisocyanate composition. When the content of the nonionic hydrophilic group is within the above range, the blocked polyisocyanate composition disperses better in water, and the water resistance of the resulting coating film tends to be improved.

[0113] (Hydrophilic compound having a cationic hydrophilic group) Specific examples of hydrophilic compounds having a cationic hydrophilic group (hereinafter sometimes referred to as "cationic hydrophilic compounds") include compounds having both a cationic hydrophilic group and an active hydrogen group. A compound having an active hydrogen group such as a glycidyl group may also be used as a hydrophilic compound. In this case, a compound having an isocyanate group and a compound having an active hydrogen group are reacted in advance to add a functional group such as a glycidyl group, and then a compound such as a sulfide or a phosphine is reacted. From the viewpoint of ease of production, a compound having both a cationic hydrophilic group and an active hydrogen group is preferred.

[0114] Specific examples of compounds having both a cationic hydrophilic group and an active hydrogen group include dimethylethanolamine, diethylethanolamine, diethanolamine, methyldiethanolamine, etc. Tertiary amino groups added using these compounds can also be quaternized with, for example, dimethyl sulfate or diethyl sulfate.

[0115] The reaction between the cationic hydrophilic compound and the polyisocyanate can be carried out in the presence of a solvent. In this case, the solvent is preferably one that does not contain an active hydrogen group, and specific examples thereof include ethyl acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol dimethyl ether.

[0116] The cationic hydrophilic groups added to the polyisocyanate are preferably neutralized with a compound having an anionic group, such as a carboxy group, a sulfonic acid group, a phosphate group, a halogen group, or a sulfate group. Specific examples of compounds having a carboxy group include formic acid, acetic acid, propionic acid, butyric acid, and lactic acid. Specific examples of compounds having a sulfonic acid group include ethanesulfonic acid. Specific examples of compounds having a phosphate group include phosphoric acid and acidic phosphate esters. Specific examples of compounds having a halogen group include hydrochloric acid. Specific examples of compounds having a sulfate group include sulfuric acid. Among these, compounds having an anionic group are preferably compounds having a carboxy group, and more preferably acetic acid, propionic acid or butyric acid.

[0117] (hydrophilic compound having an anionic hydrophilic group) Specific examples of the anionic hydrophilic group include a carboxy group, a sulfonic acid group, a phosphate group, a halogen group, and a sulfate group.

[0118] Specific examples of hydrophilic compounds having an anionic hydrophilic group (hereinafter, sometimes referred to as "anionic hydrophilic compounds") include compounds having both an anionic group and an active hydrogen group, and more specific examples include compounds having a carboxy group of a monohydroxycarboxylic acid or polyhydroxycarboxylic acid as the anionic group.

[0119] Examples of monohydroxycarboxylic acids include 1-hydroxyacetic acid, 3-hydroxypropanoic acid, 12-hydroxy-9-octadecanoic acid, hydroxypivalic acid, and lactic acid.

[0120] Examples of compounds having a carboxy group of a polyhydroxycarboxylic acid as an anionic group include dimethylolacetic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolpentanoic acid, dihydroxysuccinic acid, and dimethylolpropionic acid.

[0121] Further, compounds having both a sulfonic acid group and an active hydrogen group are also included, and more specifically, for example, isethionic acid is included.

[0122] Among these, hydroxypivalic acid or dimethylolpropionic acid is preferred as a compound having both an anionic group and an active hydrogen group.

[0123] The anionic hydrophilic group added to the polyisocyanate is preferably neutralized with an amine compound, which is a basic substance. Specific examples of the amine compound include ammonia and water-soluble amino compounds. Specific examples of water-soluble amino compounds include monoethanolamine, ethylamine, dimethylamine, diethylamine, triethylamine, propylamine, dipropylamine, isopropylamine, diisopropylamine, triethanolamine, butylamine, dibutylamine, 2-ethylhexylamine, ethylenediamine, propylenediamine, methylethanolamine, dimethylethanolamine, diethylethanolamine, and morpholine. Tertiary amines such as triethylamine and dimethylethanolamine can also be used. These amine compounds can be used alone or in combination.

[0124] <Organic acids, inorganic acids, metals, quaternary ammonium cations> The blocked polyisocyanate composition of the first embodiment contains one or more organic acids and / or inorganic acids (A) and one or more metal and / or quaternary ammonium cations (A).

[0125] The blocked polyisocyanate composition of the second embodiment contains an organic acid salt and / or an inorganic acid salt represented by the following general formula (I). (A)nX (I) In the formula (I), A represents a group in which one hydrogen atom has been removed from an organic acid or inorganic acid, X represents a metal or quaternary ammonium cation, and n represents the valence of X and is an integer of 1 or more.

[0126] Examples of organic acids include aliphatic monocarboxylic acids (such as formic acid, acetic acid, propionic acid, octylic acid, 2-ethylhexanoic acid, and capric acid), aliphatic polycarboxylic acids (such as oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid), aromatic monocarboxylic acids (such as benzoic acid, toluic acid, and ethylbenzoic acid), aromatic polycarboxylic acids (such as phthalic acid, isophthalic acid, terephthalic acid, nitrophthalic acid, and trimellitic acid), phenolic compounds (such as phenol and resorcinol), sulfonic acid compounds (such as alkylbenzenesulfonic acid, toluenesulfonic acid, and benzenesulfonic acid), and phosphoric acid compounds. Examples of inorganic acids include halogen acids (hydrochloric acid, bromic acid, etc.), nitric acid, sulfuric acid, phosphinic acid, and phosphonic acid. From the viewpoint of low-temperature curing properties, A is preferably a group in which one hydrogen atom has been removed from an organic acid, more preferably a carboxylic acid, and even more preferably an aliphatic monocarboxylic acid (preferably having 1 to 12 carbon atoms).

[0127] X in the above general formula (I) represents a metal or a quaternary ammonium cation.

[0128] Examples of metals include sodium, potassium, lithium, cesium, nickel, cobalt, cadmium, barium, calcium, zinc, manganese, copper, cerium, zirconium, iron, lead, germanium, antimony, aluminum, titanium, and bismuth. Among these, monovalent metals are preferred as metal species from the viewpoint of storage stability of the one-component coating composition, and Group 1 elements such as sodium, potassium, lithium, and cesium are more preferred from the viewpoint of low-temperature curing properties. Furthermore, from the viewpoint of coating film performance, trivalent metals such as bismuth and iron are preferred.

[0129] Examples of the quaternary ammonium cation include the following: (1) Tetraalkylammonium such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium. (2) Aryltrialkylammoniums such as benzyltrimethylammonium and trimethylphenylammonium. (3) Trimethylhydroxyethylammonium, trimethylhydroxypropylammonium, triethylhydroxyethylammonium, triethylhydroxypropylammonium. Among these, tetraalkylammonium and aryltrialkylammonium are preferred.

[0130] The mass ratio X / A of X to A is 0.01 to 5.0, preferably 0.03 to 3.0, more preferably 0.05 to 2.0, even more preferably 0.08 to 1.5, and particularly preferably 0.1 to 1.0, from the viewpoint of low-temperature curing properties and coating film performance.

[0131] The organic acid and / or inorganic acid (A) and the metal and / or quaternary ammonium cation (X) preferably exist in the form of a salt represented by the following general formula (I). (A)nX (I) In the formula (I), A represents a group in which one hydrogen atom has been removed from an organic acid or inorganic acid, X represents a metal or quaternary ammonium cation, and n represents the valence of X and is an integer of 1 or more.

[0132] The molar ratio X / nA of X to A in the organic acid salt and / or inorganic acid salt is 0.01 to 5.0, preferably 0.03 to 3.0, more preferably 0.05 to 2.0, even more preferably 0.08 to 1.5, and particularly preferably 0.1 to 1.0, from the viewpoints of low-temperature curing properties and coating film performance.

[0133] The content of X is from 0.001% by mass to 20% by mass, preferably from 0.1% by mass to 10% by mass, more preferably from 0.5% by mass to 10% by mass, and most preferably from 1.6% by mass to 10% by mass, relative to the total mass of the blocked polyisocyanate composition. When the content is equal to or less than the upper limit, the storage stability and solvent resistance of the one-component coating composition become better, and when the content is equal to or more than the lower limit, the low-temperature curing property becomes better.

[0134] The blocked polyisocyanate composition of the third embodiment contains one or more organic acid salts. The organic acid salt is preferably a salt represented by the general formula (I) mentioned in the first and second embodiments, and is preferably a carboxylate. The blocked polyisocyanate composition of the fourth embodiment includes one or more carboxylate salts.

[0135] <Carboxylate> Examples of carboxylates include quaternary ammonium salts of carboxylic acids whose counter cation is a quaternary ammonium ion, and metal carboxylates, with metal carboxylates being preferred from the standpoint of low-temperature curing properties.

[0136] Examples of quaternary ammonium salts of carboxylic acids (carboxylates of quaternary ammonium cations) include those shown below. (1) Organic weak acid salts such as acetates, propionates, octylates, caprates, myristates, and benzoates of tetraalkylammonium such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium. (2) Organic weak acid salts such as acetates, propionates, octylates, caprates, myristates, and benzoates of aryltrialkylammonium salts such as benzyltrimethylammonium and trimethylphenylammonium. (3) Organic weak acid salts such as acetates, propionates, octylates, caprates, myristates, and benzoates of trimethylhydroxyethylammonium, trimethylhydroxypropylammonium, triethylhydroxyethylammonium, and triethylhydroxypropylammonium. Among these, propionates and caprates of tetraalkylammonium such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium, and propionates and caprates of aryltrialkylammonium such as benzyltrimethylammonium and trimethylphenylammonium are preferred.

[0137] Examples of metal species of the metal carboxylate include sodium, potassium, lithium, cesium, nickel, cobalt, cadmium, barium, calcium, zinc, manganese, copper, cerium, zirconium, iron, lead, germanium, antimony, aluminum, titanium, and bismuth. Among these, monovalent metals are preferred as the metal species from the viewpoint of storage stability of the one-component coating composition. Furthermore, from the viewpoint of low-temperature curing, Group 1 elements such as sodium, potassium, lithium, and cesium are more preferred. Furthermore, from the viewpoint of coating film performance, trivalent metals such as bismuth and iron are preferred.

[0138] The carboxylic acid of the carboxylate metal salt includes both monocarboxylic acids and dicarboxylic acids, and examples thereof include saturated aliphatic acids, unsaturated acids, and aromatic acids such as formic acid, acetic acid, acrylic acid, methacrylic acid, propionic acid, butyric acid, hexanoic acid, octylic acid, octanoic acid, capric acid, stearic acid, oleic acid, eicosanoic acid, myristic acid, benzoic acid, etc. Of these, the carboxylic acid of the carboxylate metal salt is preferably one having 1 to 12 carbon atoms from the viewpoint of compatibility, and more preferably an aliphatic acid having 1 to 12 carbon atoms from the viewpoint of coating film yellowing.

[0139] Specific examples of preferred metal carboxylates include sodium propionate, potassium acetate, potassium propionate, potassium 2-ethylhexanoate, cesium acetate, lithium acetate, and bismuth 2-ethylhexanoate.

[0140] The content of the counter cation of the carboxylate is preferably from 0.001% by mass to 20% by mass, more preferably from 0.1% by mass to 20% by mass, more preferably from 0.3% by mass to 15% by mass, even more preferably from 0.5% by mass to 10% by mass, and even more preferably from 0.5% by mass to 6% by mass, relative to the total mass of the blocked polyisocyanate. When the content is equal to or less than the upper limit, the storage stability and solvent resistance of the one-component coating composition become better, and when the content is equal to or more than the lower limit, the low-temperature curing property becomes better.

[0141] <Method for producing blocked polyisocyanate composition> When the blocked polyisocyanate composition is a blocked polyisocyanate derived from a polyisocyanate and a blocking agent, it can be obtained, for example, by reacting a polyisocyanate with the blocking agent. The blocking reaction between the polyisocyanate and the blocking agent can be carried out regardless of the presence or absence of a solvent, and a blocked polyisocyanate is obtained.

[0142] From the viewpoint of storage stability of the one-component coating composition, the mixing ratio of the polyisocyanate and the blocking agent is preferably such that the molar ratio of the active hydrogen groups contained in the blocking agent relative to the isocyanate groups contained in the polyisocyanate is 1, is 0.5 or more and 3.0 or less, more preferably 0.8 or more and 2.0 or less, and even more preferably 1 or more and 1.5 or less.

[0143] In the reaction step, the reaction temperature and reaction time are appropriately determined depending on the progress of the reaction. The reaction temperature is preferably 0° C. or higher and 150° C. or lower, and the reaction time is preferably 0.5 hours or higher and 24 hours or lower. When the blocking reaction is carried out using two or more blocking agents, they may be carried out simultaneously, or one blocking agent may be used first and the remaining free isocyanate groups may then be blocked with the other blocking agent.

[0144] In addition, in the reaction, a known ordinary catalyst may be used as necessary. The catalyst is not particularly limited, but examples thereof include the following catalysts (1) to (6). The catalysts shown below may be used alone or in combination. (1) Organotin compounds such as tin octanoate, tin 2-ethyl-1-hexanoate, tin ethylcaproate, tin laurate, tin palmitate, dibutyltin oxide, dibutyltin dichloride, dibutyltin diacetate, dibutyltin dimaleate, dibutyltin dilaurate, dioctyltin diacetate, and dioctyltin dilaurate; (2) Organic zinc compounds such as zinc chloride, zinc octanoate, zinc 2-ethyl-1-hexanoate, zinc 2-ethylcaproate, zinc stearate, zinc naphthenate, and zinc acetylacetonate; (3) organic titanium compounds; (4) organic zirconium compounds; (5) Tertiary amines such as triethylamine, tributylamine, N,N-diisopropylethylamine, and N,N-dimethylethanolamine; (6) Diamines such as triethylenediamine, tetramethylethylenediamine, and 1,4-diazabicyclo[2.2.2]octane.

[0145] The completion of the reaction can be determined by, for example, confirming the disappearance or reduction of isocyanate groups using infrared spectroscopy or the like.

[0146] When a solvent is used, it is preferable to use a solvent that is inactive to isocyanate groups. When a solvent is used, the content of solids derived from the polyisocyanate and the blocking agent relative to 100 parts by mass of the blocked polyisocyanate composition may usually be from 10 parts by mass to 95 parts by mass, preferably from 20 parts by mass to 80 parts by mass, and more preferably from 30 parts by mass to 70 parts by mass.

[0147] Alternatively, when the blocked polyisocyanate contained in the blocked polyisocyanate composition is a blocked polyisocyanate derived from a polyisocyanate, a hydrophilic compound, and a blocking agent, it can be obtained, for example, by reacting a polyisocyanate, a hydrophilic compound, and a blocking agent.

[0148] The reaction of the isocyanate group of the polyisocyanate with the hydrophilic compound and the reaction of the polyisocyanate with the blocking agent can be carried out simultaneously, or one of the reactions can be carried out first and then the second reaction can be carried out. Among these, it is preferred to carry out the reaction of the isocyanate group with the hydrophilic compound first to obtain a polyisocyanate modified with the hydrophilic compound (hereinafter sometimes referred to as a "modified polyisocyanate"), and then to react the obtained modified polyisocyanate with the blocking agent.

[0149] The reaction between polyisocyanate and hydrophilic compound may be carried out using an organic metal salt, a tertiary amine compound, or an alcoholate of an alkali metal as a catalyst. Examples of metals constituting the organic metal salt include tin, zinc, and lead. Examples of the alkali metal include sodium.

[0150] The reaction temperature between the polyisocyanate and the hydrophilic compound is preferably −20° C. or higher and 150° C. or lower, and more preferably 30° C. or higher and 100° C. or lower. When the reaction temperature is equal to or higher than the lower limit, reactivity tends to be increased. Furthermore, when the reaction temperature is equal to or lower than the upper limit, side reactions tend to be more effectively suppressed.

[0151] It is preferable to completely react the hydrophilic compound with the polyisocyanate so that no unreacted hydrophilic compound remains. This tends to more effectively prevent a decrease in the aqueous dispersion stability of the blocked isocyanate composition of the present embodiment and in the curability when the blocked isocyanate composition is prepared as an aqueous coating composition.

[0152] The blocking reaction between the polyisocyanate or modified polyisocyanate and the blocking agent can be carried out regardless of the presence or absence of a solvent, to obtain a blocked polyisocyanate.

[0153] The blocking reaction can be carried out by the reaction exemplified in the production method in which the above-mentioned blocked polyisocyanate is a blocked polyisocyanate derived from a polyisocyanate and a blocking agent.

[0154] When water or a solvent is used, it is sufficient to use a solvent that is inactive to an isocyanate group.

[0155] When a solvent is used, the content of solids derived from the polyisocyanate and the blocking agent relative to 100 parts by mass of the blocked polyisocyanate composition may usually be from 10 parts by mass to 95 parts by mass, preferably from 20 parts by mass to 80 parts by mass, and more preferably from 30 parts by mass to 70 parts by mass.

[0156] When water is used, it is preferable to add a predetermined amount in portions or dropwise. When water is added in portions, it is preferable to add the predetermined amount in 4 to 8 portions. Furthermore, it is preferable to maintain the liquid temperature at 50°C or higher when the concentration of blocked polyisocyanate relative to water is 55% by mass or higher, 45°C or higher but lower than 50°C when the concentration is 45% by mass or higher but lower than 55% by mass, and lower than 50°C when the concentration is lower than 45% by mass.

[0157] When water is added all at once or when the liquid temperature is 80° C. or higher but lower than 20° C., the average particle size (average dispersed particle size) of the water dispersion of the blocked polyisocyanate increases, which may result in reduced stability of the water dispersion, such as the occurrence of precipitation or separation. The concentration of the blocked polyisocyanate in the water dispersion composition obtained in this manner is preferably 10% by mass or higher and 40% by mass or lower.

[0158] In any of the above-mentioned methods for producing a blocked polyisocyanate composition, the carboxylate may be added either before or after the blocking reaction, but in order to prevent deterioration of the carboxylate, it is preferable to add the carboxylate after the blocking reaction and then lower the temperature to 100°C or less. The amount of carboxylate added is preferably such that the content of the counter cation of the carboxylate falls within the above-mentioned range.

[0159] The blocked polyisocyanate composition of the above embodiment may further contain one or more selected from the group consisting of an antioxidant, a light stabilizer, a polymerization inhibitor, and a surfactant, and preferably contains a surfactant.

[0160] Examples of antioxidants and light stabilizers include aliphatic, aromatic, or alkyl group-substituted aromatic esters of phosphoric acid or phosphorous acid, hypophosphorous acid derivatives; phosphorus compounds such as phenylphosphonic acid, phenylphosphinic acid, diphenylphosphonic acid, polyphosphonates, dialkylpentaerythritol diphosphites, and dialkylbisphenol A diphosphites; phenol derivatives (particularly hindered phenol compounds); sulfur-containing compounds such as thioether compounds, dithioacid salt compounds, mercaptobenzimidazole compounds, thiocarbanilide compounds, and thiodipropionic acid esters; and tin compounds such as tin maleates and dibutyltin monoxide. These may be contained alone or in combination of two or more.

[0161] Examples of polymerization inhibitors include hydroquinones, phenols, cresols, catechols, benzoquinones, etc. Specific examples of polymerization inhibitors include benzoquinone, p-benzoquinone, p-toluquinone, p-xyloquinone, naphthoquinone, 2,6-dichloroquinone, hydroquinone, trimethylhydroquinone, catechol, pt-butylcatechol, 2,5-di-t-butylhydroquinone, monomethylhydroquinone, p-methoxyphenol, 2,6-di-t-butyl-p-cresol, hydroquinone monomethyl ether, etc. These may be contained alone or in combination of two or more.

[0162] Examples of surfactants include known anionic surfactants, cationic surfactants, and amphoteric surfactants.

[0163] <One-component coating composition> A one-component coating composition according to a fifth embodiment of the present invention comprises the blocked polyisocyanate composition according to any of the first to fourth embodiments and a polyvalent active hydrogen compound. A one-component coating composition according to a sixth embodiment of the present invention comprises a blocked polyisocyanate, a carboxylate, and a polyvalent active hydrogen compound, wherein the blocked polyisocyanate is derived from a polyisocyanate and a blocking agent, and the blocking agent comprises a compound having a heterocycle containing one or more nitrogen atoms (preferably two or more, more preferably three or more). A one-component coating composition according to a seventh embodiment of the present invention comprises a blocked polyisocyanate, a carboxylate, and a polyvalent active hydrogen compound, wherein the blocked polyisocyanate is derived from a polyisocyanate, a hydrophilic compound, and a blocking agent, and the blocking agent comprises a compound having a heterocycle containing one or more nitrogen atoms (preferably two or more, more preferably three or more).

[0164] In the one-component coating compositions of the sixth and seventh embodiments, when the curing agent component containing the blocked polyisocyanate does not contain a carboxylate, the carboxylate may be added to the main component containing the polyvalent active hydrogen compound, or the carboxylate may be mixed with the blocked polyisocyanate and the polyvalent active hydrogen compound during production of the one-component coating composition.

[0165] The one-component coating composition of the above embodiment has the above-mentioned constitution, and thereby a coating film with good low-temperature curing properties can be obtained. Furthermore, the one-component coating composition of the seventh embodiment, which contains a hydrophilic blocked polyisocyanate, can obtain a coating film with excellent appearance. Each of the components contained in the one-component coating compositions of the fifth to seventh embodiments will be described in detail below. The blocked polyisocyanate composition, blocked polyisocyanate, and carboxylate contained in the one-component coating compositions of these embodiments may be the same as those described in the "blocked polyisocyanate composition" of the first to fourth embodiments.

[0166] <Polyvalent active hydrogen compounds> The polyvalent active hydrogen compound is not particularly limited, but examples thereof include polyols, polyamines, alkanolamines, etc. These polyvalent active hydrogen compounds may be contained alone or in combination of two or more. Among them, polyols are preferred as the polyvalent active hydrogen compound.

[0167] [Polyol] Examples of polyols include polyester polyols, polyether polyols, acrylic polyols, polyolefin polyols, fluorine polyols, polycarbonate polyols, polyurethane polyols, etc. These polyols may be contained alone or in combination of two or more. Among these, polyester polyols and acrylic polyols are preferred as polyols.

[0168] (polyester polyol) The polyester polyol can be obtained, for example, by subjecting a dibasic acid, either alone or in a mixture of two or more kinds, to a condensation reaction with a polyhydric alcohol, either alone or in a mixture of two or more kinds.

[0169] Examples of the dibasic acid include succinic acid, adipic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, and other carboxylic acids.

[0170] Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, cyclohexanediol, trimethylolpropane, glycerin, pentaerythritol, 2-methylolpropanediol, and ethoxylated trimethylolpropane.

[0171] Alternatively, for example, polycaprolactones obtained by ring-opening polymerization of lactones such as ε-caprolactone with polyhydric alcohols can also be used as polyester polyols.

[0172] (Polyether polyol) The polyether polyols are not particularly limited, but examples thereof include the following (1) to (3).

[0173] (1) Polyether polyols obtained by random or block addition of a single or mixture of alkylene oxides to a single or mixture of polyhydric hydroxy compounds using a catalyst. Examples of the catalyst include hydroxides (lithium, sodium, potassium, etc.), strongly basic catalysts (alcoholates, alkylamines, etc.), and composite metal cyanide complexes (metalloporphyrins, zinc hexacyanocobaltate complexes, etc.). Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, and styrene oxide. (2) Polyether polyols obtained by reacting a polyamine compound with an alkylene oxide. Examples of the polyamine compound include ethylenediamines. Examples of the alkylene oxide include the same as those exemplified in (1). (3) Polymer polyols obtained by polymerizing acrylamide or the like using the polyether polyols obtained in (1) or (2) as a medium.

[0174] Examples of the polyvalent hydroxy compound include the following compounds (i) to (vi). (i) Diglycerin, ditrimethylolpropane, pentaerythritol, dipentaerythritol, etc. (ii) Sugar alcohol compounds such as erythritol, D-threitol, L-arabinitol, ribitol, xylitol, sorbitol, mannitol, galactitol, and rhamnitol. (iii) Monosaccharides such as arabinose, ribose, xylose, glucose, mannose, galactose, fructose, sorbose, rhamnose, fucose, and ribonucleotides. (iv) Disaccharides such as trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, and melibiose. (v) Trisaccharides such as raffinose, gentianose, and melezitose. (vi) Tetrasaccharides such as stachyose.

[0175] (acrylic polyol) The acrylic polyol is not particularly limited, but examples thereof include those obtained by copolymerizing a single or a mixture of an ethylenically unsaturated bond-containing monomer having a hydroxy group with a single or a mixture of other ethylenically unsaturated bond-containing monomers copolymerizable therewith.

[0176] The ethylenically unsaturated bond-containing monomer having a hydroxy group is not particularly limited, but examples thereof include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate. These may be used alone or in combination of two or more. Among these, hydroxyethyl acrylate or hydroxyethyl methacrylate is preferred.

[0177] Other ethylenically unsaturated bond-containing monomers copolymerizable with the above-mentioned monomers include, for example, the following (1) to (6), which may be used alone or in combination of two or more.

[0178] (1) Acrylic acid esters such as methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, benzyl acrylate, and phenyl acrylate. (2) Methacrylate esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, benzyl methacrylate, and phenyl methacrylate. (3) Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid. (4) Unsaturated amides such as acrylamide, methacrylamide, N,N-methylenebisacrylamide, diacetone acrylamide, diacetone methacrylamide, maleic acid amide, and maleimide. (5) Vinyl monomers such as glycidyl methacrylate, styrene, vinyl toluene, vinyl acetate, acrylonitrile, and dibutyl fumarate. (6) Vinyl monomers having a hydrolyzable silyl group, such as vinyltrimethoxysilane, vinylmethyldimethoxysilane, and γ-(meth)acryloxypropyltrimethoxysilane.

[0179] (Polyolefin polyol) The polyolefin polyol is not particularly limited, but examples thereof include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, and hydrogenated polyisoprene.

[0180] The number of hydroxyl groups statistically possessed by one molecule of the polyol (hereinafter, sometimes referred to as the "average number of hydroxyl groups") is preferably at least 2. When the average number of hydroxyl groups of the polyol is at least 2, it tends to be possible to further suppress a decrease in the crosslink density of the coating film obtained by curing the one-component coating composition of the present embodiment.

[0181] (Fluoropolyol) In this specification, the term "fluorine polyol" refers to a polyol containing fluorine in the molecule. Specific examples of the fluorine polyol include copolymers of fluoroolefins, cyclovinyl ethers, hydroxyalkyl vinyl ethers, and monocarboxylic acid vinyl esters, as disclosed in JP-A-57-34107 (Reference 1) and JP-A-61-275311 (Reference 2).

[0182] (Polycarbonate polyol) The polycarbonate polyols are not particularly limited, but examples thereof include the following (1) to (4). (1) Dialkyl carbonates such as dimethyl carbonate; (2) alkylene carbonates such as ethylene carbonate; (3) diaryl carbonates such as diphenyl carbonate; (4) A compound obtained by polycondensation of low molecular weight carbonate compounds such as those described in (1) to (3) above.

[0183] (Polyurethane polyol) The polyurethane polyol is not particularly limited, but can be obtained, for example, by reacting a polyol not containing a carboxy group with an isocyanate component in a conventional manner. Examples of the polyol not containing a carboxy group include low molecular weight ones such as ethylene glycol and propylene glycol, and high molecular weight ones such as acrylic polyol, polyester polyol and polyether polyol.

[0184] [Hydroxyl value of polyol] The hydroxyl value of the polyol per resin is not particularly limited, but is preferably 10 mg KOH / g resin or more and 300 mg KOH / g resin or less. When the hydroxyl value per resin is equal to or greater than the lower limit, a decrease in crosslink density is suppressed, and the desired physical properties tend to be more fully achieved. When the hydroxyl value per resin is equal to or less than the upper limit, an excessive increase in crosslink density is suppressed, and the mechanical properties of the coating film obtained by curing the one-component coating composition of this embodiment tend to be further improved. The hydroxyl value of the polyol can be measured in accordance with JIS K1557.

[0185] [Polyamine] The polyamine is not particularly limited, but is preferably one having two or more primary amine groups or secondary amine groups in one molecule, and more preferably one having three or more primary amine groups or secondary amine groups in one molecule. Specific examples of polyamines include the following (1) to (3). (1) Diamines such as ethylenediamine, propylenediamine, butylenediamine, triethylenediamine, hexamethylenediamine, 4,4'-diaminodicyclohexylmethane, piperazine, 2-methylpiperazine, and isophoronediamine; (2) Chain polyamines having three or more amino groups, such as bishexamethylenetriamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentamethylenehexamine, and tetrapropylenepentamine; (3) Cyclic polyamines such as 1,4,7,10,13,16-hexaazacyclooctadecane, 1,4,7,10-tetraazacyclodecane, 1,4,8,12-tetraazacyclopentadecane, and 1,4,8,11-tetraazacyclotetradecane.

[0186] [Alkanolamines] As used herein, the term "alkanolamine" refers to a compound having an amino group and a hydroxyl group in one molecule. Specific examples of alkanolamines include monoethanolamine, diethanolamine, aminoethylethanolamine, N-(2-hydroxypropyl)ethylenediamine, mono-, di-(n- or iso-)propanolamine, ethylene glycol-bis-propylamine, neopentanolamine, and methylethanolamine.

[0187] <Urethanization catalyst> The one-component coating composition of the above embodiment preferably further contains a urethanization catalyst.

[0188] The urethanization catalyst may be any compound different from the above-mentioned carboxylates, and may be a basic compound or a Lewis acid compound.

[0189] Examples of basic compounds include metal hydroxides, metal alkoxides, metal acetylacetinates, hydroxides of onium salts, halides of onium salts, metal salts of active methylene compounds, onium salts of active methylene compounds, aminosilanes, amines, phosphines, etc. Suitable onium salts are ammonium salts, phosphonium salts, and sulfonium salts.

[0190] Examples of the Lewis acid compound include organotin compounds, organozinc compounds, organotitanium compounds, and organozirconium compounds.

[0191] Among these, from the viewpoint of low-temperature curing properties, the urethanization catalyst is preferably an organotin compound, and more preferably dioctyltin (DOT) or dibutyltin dilaurate (DBTDL).

[0192] When the urethanization catalyst is an organotin compound, the content of the urethanization catalyst is not particularly limited, but for example, the content of tin (Sn) in the organotin compound can be 0.01 parts by mass or more and 0.5 parts by mass or less, 0.03 parts by mass or more and 0.45 parts by mass or less, or 0.05 parts by mass or more and 0.40 parts by mass or less, relative to 100 parts by mass of the polyvalent active hydrogen compound.

[0193] In the one-component coating composition, when a blocked polyisocyanate derived from a polyisocyanate and a triazole-based blocking agent, a carboxylic acid metal salt in which the metal species is a trivalent metal, and a urethane catalyst are present, the blocked isocyanate dissociates at low temperatures to firmly form urethane crosslinks, which makes it possible to achieve both high coating film hardness and high solvent resistance while curing at low temperatures, which is preferable.

[0194] <Other resin components> The one-component coating composition of the above embodiment may further contain other resin components such as existing melamine resins, epoxy resins, polyurethane resins, etc., as needed.

[0195] <Other additives> When the one-component coating composition of the above embodiment contains a polyol having a carboxy group, it may further contain other curing agents as a curing agent component, such as an oxazoline group-containing compound, a carbodiimide group-containing compound, etc. These compounds may be contained alone or in combination of two or more.

[0196] When the one-component coating composition of the above embodiment contains a polyol having a carbonyl group, it may further contain other curing agents as the upper curing agent component, such as a hydrazide group-containing compound, a semicarbazide group-containing compound, etc. These compounds may be contained alone or in combination of two or more.

[0197] The one-component coating composition of the above embodiment may further contain other additives, such as a curing agent, an antioxidant, an ultraviolet absorber (light stabilizer), a pigment, a metal powder pigment, a rheology control agent, or a curing accelerator, as necessary. Other curing agents include, for example, melamine resins, urea resins, epoxy group-containing compounds or resins, carboxy group-containing compounds or resins, acid anhydrides, alkoxysilane group-containing compounds or resins, and hydrazide compounds. Examples of the antioxidant and ultraviolet absorber include those exemplified in the above "blocked polyisocyanate composition." Examples of pigments include titanium oxide, carbon black, indigo, quinacridone, and pearl mica. Examples of metal powder pigments include aluminum. Examples of the rheology control agent include hydroxyethyl cellulose, urea compounds, and microgels. Examples of the curing accelerator include organometallic compounds other than the above-mentioned urethane catalysts. Examples of metals include tin, zinc, and lead.

[0198] <Method of manufacturing one-component coating composition> The one-component coating composition of the above embodiment can be obtained by mixing the above-mentioned blocked polyisocyanate composition, or the above-mentioned blocked polyisocyanate, carboxylate salt, and polyvalent active hydrogen compound, and, if necessary, a urethanization catalyst, other resin components, other additives, and the like, using a known method.

[0199] For example, in the case of an aqueous-based one-component coating composition, a polyvalent active hydrogen compound or its aqueous dispersion or solution is added with a carboxylate salt if the blocked polyisocyanate composition does not contain a carboxylate salt, and optionally, additives such as a urethane catalyst, a curing agent capable of reacting with the crosslinkable functional group in the polyvalent active hydrogen compound, a carboxylate salt, a curing catalyst, a solvent, pigments (extender pigments, colored pigments, metallic pigments, etc.), an ultraviolet absorber, a light stabilizer, a radical stabilizer, an anti-yellowing agent to suppress discoloration during the baking process, a coating surface conditioner, a flow adjuster, a pigment dispersant, an antifoaming agent, a thickener, and a film-forming aid. Next, the above-mentioned blocked polyisocyanate composition or the above-mentioned blocked polyisocyanate or its aqueous dispersion is added as a curing agent, and if necessary, water or a solvent is further added to adjust the viscosity. Then, the mixture is forcibly stirred with a stirring device to obtain an aqueous one-component coating composition.

[0200] To produce a solvent-based one-component coating composition, first, a polyhydric active hydrogen compound or its solvent dilution is mixed with a carboxylate salt if the blocked polyisocyanate composition does not contain one, and optionally with a urethane catalyst, a curing agent capable of reacting with the crosslinkable functional group in the polyhydric hydroxy compound, a carboxylate salt, a curing catalyst, a solvent, pigments (extender pigments, colored pigments, metallic pigments, etc.), UV absorbers, light stabilizers, radical stabilizers, anti-yellowing agents to suppress discoloration during the baking process, coating surface conditioners, flow control agents, pigment dispersants, defoamers, thickeners, and film-forming aids. The blocked polyisocyanate composition or the polyisocyanate is then added as a curing agent, and, if necessary, a solvent is further added to adjust the viscosity. The mixture is then stirred by hand or using a stirring device such as a mixer to obtain a solvent-based coating composition.

[0201] <Application> The one-component coating composition of this embodiment is suitably used as a primer, intermediate coat, or top coat on metals such as steel plates and surface-treated steel plates, plastics, inorganic materials such as ceramics, glass, and concrete by roll coating, curtain flow coating, spray coating, electrostatic coating, bell coating, immersion, roller coating, brush coating, or the like. The one-component coating composition of the present embodiment is suitably used for imparting cosmetic properties, weather resistance, acid resistance, rust prevention, chipping resistance, adhesion, etc. to pre-coated metals including rust-proof steel plates, painted parts of automobiles, painted parts of plastics, etc. The one-component coating composition of this embodiment is also useful as an adhesive, a pressure-sensitive adhesive, an elastomer, a foam, a surface treatment agent, and the like.

[0202] <Coating film> The coating film of this embodiment is obtained by curing the one-component coating composition of the above embodiment. The coating film of this embodiment has excellent low-temperature curing properties. Furthermore, when the one-component coating composition of the above embodiment is a hydrophilic blocked polyisocyanate, the coating film has excellent appearance. The coating film of the present embodiment can be obtained by applying the one-component coating composition of the above embodiment using a known method such as roll coating, curtain flow coating, spray coating, bell coating, or electrostatic coating, and then drying or baking at room temperature to harden the composition. The coating film obtained by curing the one-component coating composition has urethane bonds formed from the isocyanate groups derived from the polyisocyanate before the blocking reaction and the hydroxyl groups derived from the polyol. Therefore, the coating film of this embodiment formed from the one-component coating composition tends to have excellent chemical resistance, heat resistance, water resistance, etc., which are characteristics of general urethane crosslinked coating films.

[0203] <Painted items> The coated article of this embodiment includes the coating film of the above embodiment. By including the coating film of the above embodiment, the coated article of this embodiment has excellent low-temperature curing properties. Furthermore, when a hydrophilic blocked polyisocyanate is used as a curing agent component, the coating film has excellent appearance.

[0204] The coated article of this embodiment has the above-mentioned coating film that is excellent in chemical resistance, heat resistance, water resistance, etc., and is further endowed with cosmetic properties, acid resistance, rust prevention, chipping resistance, adhesion, etc. [Example]

[0205] The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to these examples. However, Examples 1 to 22, 24 to 30, 34, 37, 38, 40 to 67, and 69 to 74 are reference examples. In addition, in Examples 23, 31 to 33, 35, 36, 39, 68, and 75 to 80, the "content of X; mass %" in each table is mass % relative to the total mass of the blocked polyisocyanate. The methods for measuring various physical properties and evaluating various properties are explained below. Unless otherwise specified, "parts" and "%" mean "parts by mass" and "% by mass", respectively.

[0206] <Measurement and evaluation methods> [Physical Properties 1] (Isocyanate group (NCO) content of polyisocyanate) Approximately 1 g to 3 g of polyisocyanate was weighed out (W g) into an Erlenmeyer flask. 20 mL of toluene was then added to dissolve the polyisocyanate. 10 mL of a 2 N toluene solution of di-n-butylamine was then added, mixed, and left at room temperature for 15 minutes. 70 mL of isopropyl alcohol was then added and mixed. This solution was then titrated with a 1 N hydrochloric acid solution (Factor F) as an indicator. The titration value obtained was designated V2 mL. The same procedure was then performed without the polyisocyanate, and the titration value obtained was designated V1 mL. The isocyanate group (NCO) content of the polyisocyanate was then calculated using the following formula: NCO content (mass%) = (V1-V2)×F×42 / (W×1000)×100

[0207] [Physical Properties 2] (Number-average molecular weight, weight-average molecular weight and molecular weight distribution of polyisocyanate) Using polyisocyanate as a sample, the number-average molecular weight Mn and weight-average molecular weight Mw of the polyisocyanate were determined as number-average molecular weight and weight-average molecular weight relative to polystyrene by gel permeation chromatography (GPC) using the following equipment and conditions. The molecular weight distribution Mw / Mn was determined by dividing the weight-average molecular weight by the number-average molecular weight.

[0208] (Measurement conditions) Device: HLC-802A (Tosoh Corporation) Column: G1000HXL x 1 (Tosoh Corporation) G2000HXL x 1 (Tosoh Corporation) G3000HXL x 1 (Tosoh Corporation) Carrier: Tetrahydrofuran Flow rate: 0.6mL / min Sample concentration: 1.0% by mass Injection volume: 20μL Temperature: 40℃ Detection method: differential refractometer

[0209] [Physical Properties 3] (Average number of isocyanate functional groups in polyisocyanate) Using polyisocyanate as a sample, the average number of isocyanate functional groups was calculated according to the following formula: In the formula, Mn is the number average molecular weight of the polyisocyanate, and NCO% is the isocyanate group (NCO) content. Average isocyanate number = Mn×NCO%×0.01 / 42

[0210] [Physical Properties 4] (HDI / IPDI) The mass ratio of structural units derived from HDI to structural units derived from IPDI in the polyisocyanate composition (HDI / IPDI) was calculated using the following method. First, the mass of unreacted HDI and the mass of unreacted IPDI were calculated from the mass of unreacted diisocyanate after the reaction and the HDI and IPDI concentrations in this unreacted diisocyanate obtained by gas chromatographic measurement. The calculated mass of unreacted HDI and the mass of unreacted IPDI were subtracted from the charged mass of HDI and the mass of IPDI, respectively, and the resulting differences were used as the mass of structural units derived from HDI and the mass of structural units derived from IPDI, respectively. Next, the mass of structural units derived from HDI was divided by the mass of structural units derived from IPDI to obtain HDI / IPDI.

[0211] [Physical Properties 5] (Solid content of blocked polyisocyanate composition) The solid content of the blocked polyisocyanate composition was determined as follows. First, an aluminum dish with a bottom diameter of 38 mm was precisely weighed. Then, approximately 1 g of the blocked polyisocyanate composition produced in the Examples and Comparative Examples was precisely weighed (W1) on the aluminum dish. The blocked polyisocyanate composition was then adjusted to a uniform thickness. The blocked polyisocyanate composition on the aluminum dish was then kept in an oven at 105°C for 1 hour. After the aluminum dish returned to room temperature, the blocked polyisocyanate composition remaining on the aluminum dish was precisely weighed (W2). The solids content of the blocked polyisocyanate composition was then calculated using the following formula: Solid content of blocked polyisocyanate composition [mass%] = W2 / W1 × 100

[0212] [Physical Properties 6] (Available Isocyanate Group (NCO) Content of Blocked Polyisocyanate Composition) The content of available isocyanate groups (NCO) in the blocked polyisocyanate composition was determined as follows. The "effective isocyanate group (NCO) content" referred to here is a quantification of the amount of blocked isocyanate groups present in the blocked polyisocyanate composition after the blocking reaction and capable of participating in a crosslinking reaction, and is expressed as % by mass of the isocyanate groups. The effective NCO content was calculated by the following formula: In the formula, the "NCO %" and "solid content of blocked polyisocyanate composition" used the values ​​calculated in the above Physical Property 1 and Physical Property 2, respectively. When the sample was diluted with a solvent or the like, the value in the diluted state was calculated.

[0213] Effective NCO content [mass%] = [(solid content [mass%] of blocked polyisocyanate composition) × {(mass of polyisocyanate used in blocking reaction) × NCO%}] / (mass of blocked polyisocyanate composition after blocking reaction)

[0214] [Physical Properties 7] (A and X Contents in Blocked Polyisocyanate Composition) The contents of the organic acid, inorganic acid (A), metal, and quaternary ammonium cation (X) contained in the blocked polyisocyanate composition were measured by the following method 1 or 2. For example, Method 1 is used when analyzing organic acids and inorganic acids that are easily ionized metal salts such as quaternary ammonium cations and potassium acetate, while Method 2 is used when analyzing organic acids with a large carbon number, such as bismuth 2-ethylhexanoate.

[0215] (Method 1) Ultrapure water was added to the sample, mixed, and left to stand for several hours. The aqueous layer was then filtered and measured by ion chromatography to obtain the anion and cation contents of the organic acid salts and inorganic acid salts. The measurement conditions are as follows: (Measurement conditions) Equipment: Shimadzu ion chromatograph Column: Shim-pack-IC-C4 4.6mm ID x 150mmL, 7μm (Shimadzu) Mobile phase: A) 3.5mmol / L Oxalic Acid B) 1mmol / L 18-crown-6 Flow rate: 1.0mL / min Sample concentration: 1.0% by mass Injection volume: 50μL Temperature: 45℃ Detection: CDD

[0216] (Method 2) The sample was diluted with ethyl acetate and measured by gas chromatography mass spectrometry to obtain the content of organic acids. The measurement conditions are as follows: (Measurement conditions) Device: Thermoelectron Voyager Column: DB-5 0.25mm I.D x 30m Film thickness: 1.0μm Temperature: Column: 100℃ - 5℃ / min → 250℃ - 20℃ / min → 320℃ (10min) Inlet: 320℃ Injection volume: 0.1μL Split ratio: 1 / 15 Detection: GC / MS: EI method (electron impact ionization method)

[0217] When X was a heavy metal, the content was calculated by ICP emission spectroscopy. First, approximately 0.2 g of sample was placed in a quartz insert container, 6 ml of 68% nitric acid was added, and the sample was placed in a Teflon (registered trademark) decomposition container containing a temperature-adjusting solvent. The sample was then decomposed by microwave heating at 210°C for 45 minutes (hold: 15 minutes), and then diluted with ultrapure water to a total volume of approximately 100 g. The metal content of this test solution was measured.

[0218] (Mass ratio of X to A (X / (n)A) The mass ratio of X to A (X / (n)A) was calculated from the contents obtained by the above measurement method.

[0219] [Evaluation 1] Low temperature curing Each one-component coating composition prepared in the Examples and Comparative Examples was applied to a polypropylene (PP) plate using an air spray gun to a dry film thickness of 30 μm. The coating was then dried at 23°C for 15 minutes. It was then baked at a predetermined temperature for 30 minutes to obtain a cured coating film. The resulting cured coating film was left at 23°C for 1 hour and peeled off from the PP plate. The mass (hereinafter referred to as the "mass before immersion") was then precisely weighed, and the sample was immersed in acetone at 20°C for 24 hours. The mass after immersion (hereinafter referred to as the "mass of undissolved portion") was then precisely weighed. The ratio of the mass of undissolved portion to the mass before immersion (gel fraction) was then calculated. The calculated gel fraction was then evaluated for low-temperature curability based on the following evaluation criteria.

[0220] (Evaluation criteria) ◎: Gel fraction 80% or more by mass at 80°C 〇: Gel fraction 80% or more by mass at 90℃ △: Gel fraction 80% or more by mass at 100°C △×: Gel fraction at 100°C is 70% by mass or more and less than 80% by mass ×: Gel fraction less than 70% by mass at 110°C

[0221] [Evaluation 2] Solvent resistance Each one-component coating composition prepared in the Examples and Comparative Examples was applied to a glass plate using an air spray gun to a dry film thickness of 30 μm. The coating was then dried at 23°C for 15 minutes. It was then baked at a predetermined temperature for 30 minutes to obtain a cured coating film. The resulting cured coating film was left at 23°C for 1 hour, and then cotton pads soaked in xylene and ethanol were placed on the cured coating film. The coating film was then left at a predetermined temperature (80°C or 100°C) for 5 minutes, after which the appearance of the coating film was observed.

[0222] (Evaluation criteria) ◎: No change ○: No whitening or swelling △: Swelling ×:Dissolution

[0223] [Evaluation 3] Coating appearance Each one-component coating composition was applied to a glass plate with an applicator to a dry film thickness of 30 μm. The plate was then baked at 80°C for 30 minutes to obtain a cured coating. The cured coating was visually inspected for foreign matter, and the appearance of the coating was evaluated based on the following criteria.

[0224] (Evaluation criteria) ◎: No foreign matter ○: 1 to 5 foreign objects △: 6 to 10 foreign objects ×: 11 or more foreign objects

[0225] [Evaluation 4] Storage stability of one-component coating composition Each one-component coating composition was stored at 40°C for 10 days, and then its appearance was evaluated for storage stability based on the following evaluation criteria.

[0226] (Evaluation criteria) ○: Liquid (still paintable after 10 days storage at 40°C) △: Partial subsidence ×: gelation

[0227] <Synthesis of Polyisocyanate> [Synthesis Example 1] (Synthesis of Polyisocyanate P-1) A four-neck flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet, and dropping funnel was conditioned with a nitrogen atmosphere and charged with 600 parts by mass of HDI and half of 60 parts by mass of polycaprolactone triol (manufactured by Daicel Corporation, "PLACCEL303" (trade name), average number of hydroxyl groups: 3, number-average molecular weight: 310) (hereinafter sometimes referred to as "PLC303"). The mixture was then reacted at a reactor temperature of 80°C for 30 minutes with stirring, after which the remaining half of the PLC303 was added and the urethane reaction was carried out for an additional hour. The reactor temperature was then raised to 70°C, and tetramethylammonium hydroxide was added. When the yield reached 47% by mass, phosphoric acid was added to terminate the reaction. The reaction solution was filtered, and unreacted HDI was removed using a thin-film distillation apparatus to obtain polyisocyanate P-1.

[0228] [Synthesis Examples 2 to 4] (Synthesis of Polyisocyanates P-2 to P-4) Each polyisocyanate was synthesized in the same manner as in Synthesis Example 1, except that the compositions and blending amounts shown in Table 1 were used.

[0229] [Synthesis Example 5] (Synthesis of Polyisocyanate P-5) A four-neck flask equipped with a thermometer, stirring blade, and reflux condenser was charged with 1,000 parts by mass of HDI and 2 parts by mass of 2-ethylhexane-1,3-diol under a nitrogen stream, and the temperature inside the reactor was maintained at 70°C while stirring. Tetramethylammonium hydroxide was added, and when the yield reached 40% by mass, phosphoric acid was added to stop the reaction. The reaction solution was filtered, and unreacted HDI was removed using a thin-film distillation apparatus to obtain polyisocyanate P-5.

[0230] The composition, amount added and physical properties of each polyisocyanate are shown in Table 1 below. In Table 1, the abbreviations for polyols indicate the following types.

[0231] (Polyol) PLC303: "PLACCEL303" (trade name), manufactured by Daicel Corporation, average number of hydroxyl groups: 3, number average molecular weight: 310 PLC308: "PLACCEL308" (trade name), manufactured by Daicel Corporation, average number of hydroxyl groups: 3, number average molecular weight: 850 PLC312: "PLACCEL312" (trade name), manufactured by Daicel Corporation, average number of hydroxyl groups: 3, number average molecular weight: 1250

[0232] [Table 1]

[0233] <Production of Blocked Polyisocyanate Composition> [Example 1] (Production of Blocked Polyisocyanate Composition BL-a1) A four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube was conditioned with a nitrogen atmosphere, and 30.4 parts by mass of 1,2,3-triazole was gradually added to 100 parts by mass of polyisocyanate P-1 obtained in Synthesis Example 1. The mixture was stirred for 1 to 4 hours at a temperature of 80°C or higher but lower than 120°C. FT-IR spectroscopy was then performed to confirm that the isocyanate groups had been blocked. 84.5 parts by mass of N,N-dimethylformamide was then added to the reaction mixture, and the mixture was stirred at 60°C until homogenous, yielding blocked polyisocyanate composition BL-a1.

[0234] [Examples 2 to 4, 7 to 10 and Comparative Example 1] (Production of Blocked Polyisocyanate Compositions BL-a2 to BL-a4, BL-a7 to BL-a9, BL-b1, and BL-b2) Each blocked polyisocyanate composition was produced in the same manner as in Example 1, except that the compositions and blending amounts shown in Tables 2 and 3 were used.

[0235] [Example 5] (Production of Blocked Polyisocyanate Composition BL-a5) A four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube was conditioned with a nitrogen atmosphere, and 23.1 parts by mass of 1,2,3-triazole was gradually added to 100 parts by mass of the polyisocyanate P-3 obtained in Synthesis Example 3. The mixture was stirred for 1 to 4 hours at a temperature of 80°C or higher but lower than 120°C. The reaction mixture was then subjected to FT-IR spectroscopy to confirm that the isocyanate groups had been blocked. 75.6 parts by mass of N,N-dimethylformamide was then added to the reaction mixture, and the mixture was stirred at 60°C until homogenous. 4.7 parts by mass of a 56% by mass solution of benzyltrimethylammonium caprate in methanol was then added to the reaction mixture to obtain blocked polyisocyanate composition BL-a5.

[0236] [Example 6] (Production of Blocked Polyisocyanate Composition BL-a6) A blocked polyisocyanate composition BL-a6 was produced in the same manner as in Example 5, except that the composition and blending amounts shown in Table 3 were used.

[0237] The composition, blending amount and physical properties of each blocked polyisocyanate composition are shown in Tables 2 and 3 below. In Tables 2 and 3, the types of blocking agents, carboxylic acid salts, and solvents are as follows: The same will be shown in the subsequent tables.

[0238] (blocking agent) B-1: 3,5-dimethylpyrazole B-2: 1,2,3-triazole B-3: 1,2,4-triazole B-4: Methyl ethyl ketoxime

[0239] (Carboxylate) C-1: Benzyltrimethylammonium caprate (methanol solution containing 56% by mass of benzyltrimethylammonium caprate relative to the total mass of the solution) C-4-1: Sodium propionate (methanol solution containing 10% by mass of sodium propionate relative to the total mass of the solution)

[0240] (solvent) DMF: N,N-dimethylformamide DPM: Dipropylene glycol monomethyl ether

[0241] [Table 2]

[0242] [Table 3]

[0243] <Production of one-component coating composition> [Example 11] (Production of one-component coating composition D-a1) 10.0 parts by mass of an acrylic polyol (Allnex Corporation, "Setalux 1767" (trade name), hydroxyl value 150 mg KOH / g resin, solids concentration 65% by mass), 8.9 parts by mass of the blocked polyisocyanate composition BL-a1 obtained in Example 1, and 10.3 parts by mass of DMF were blended. Next, 0.4 parts by mass of tetramethylammonium propionate (a methanol solution containing 47% by mass of tetramethylammonium propionate relative to the total mass of the solution) and 0.0267 parts by mass of urethanization catalyst U-810 (Nitto Kasei, dioctyl tin) were added and mixed until uniform, yielding one-component coating composition D-a1.

[0244] [Examples 12 to 39 and Comparative Examples 2 to 6] (Production of one-component coating compositions D-a2 to D-a29 and D-b1 to D-b5) Each one-component coating composition was produced in the same manner as in Example 11, except that the compositions and blending amounts shown in Tables 4 to 10 were used.

[0245] The composition, blending amount, physical properties and evaluation of each one-component coating composition are shown in Tables 4 to 17 below. In Tables 4 to 10, the types of carboxylates and urethanization catalysts are as follows: The same will be shown in the subsequent tables.

[0246] (Carboxylate of quaternary ammonium cation) C-1: Benzyltrimethylammonium caprate (methanol solution containing 56% by mass of benzyltrimethylammonium caprate relative to the total mass of the solution) C-2: Tetramethylammonium caprate (methanol solution containing 47% by mass of tetramethylammonium caprate relative to the total mass of the solution) C-3: Tetramethylammonium propionate (methanol solution containing 47% by mass of tetramethylammonium propionate relative to the total mass of the solution)

[0247] (metal carboxylates) C-4-1: Sodium propionate (methanol solution containing 10% by mass of sodium propionate relative to the total mass of the solution: monovalent metal salt) C-5-1: Potassium acetate (methanol solution containing 10% by mass of potassium acetate relative to the total mass of the solution: monovalent metal salt) C-6-1: Potassium propionate (methanol solution containing 10% by mass of potassium propionate relative to the total mass of the solution: monovalent metal salt) C-7-1: Potassium 2-ethylhexanoate (2-ethylhexanoic acid solution containing 15% by mass of potassium 2-ethylhexanoate relative to the total mass of the solution: monovalent metal salt) C-8-1: Cesium acetate (methanol solution containing 10% by mass of cesium acetate relative to the total mass of the solution: monovalent metal salt) C-9-1: Lithium acetate (methanol solution containing 10% by mass of cesium acetate relative to the total mass of the solution: monovalent metal salt) C-10: Bismuth 2-ethylhexanoate (2-ethylhexanoic acid solution containing 25% by mass of bismuth 2-ethylhexanoate relative to the total mass of the solution: trivalent metal salt) C-11: 2-ethylhexanoic acid tin (divalent metal salt) C-12: Iron 2-ethylhexanoate (a mineral spirit solution containing 6% by weight of iron based on the total weight of the solution: a trivalent metal salt)

[0248] (Urethanization catalyst) U-810: Dioctyltin (manufactured by Nitto Kasei)

[0249] [Table 4]

[0250] [Table 5]

[0251] [Table 6]

[0252]

Table 7

[0253]

Table 8

[0254]

Table 9

[0255]

Table 10

[0256]

Table 11

[0257]

Table 12

[0258]

Table 13

[0259]

Table 14

[0260]

Table 15

[0261] Table 16

[0262] [Table 17]

[0263] As can be seen from the above table, the one-component coating composition containing a blocked polyisocyanate using a triazole-based blocking agent and a carboxylate salt had good low-temperature curability and solvent resistance when formed into a coating film. Furthermore, among the one-component coating compositions D-a27, D-a29, and D-b5 (Examples 37, 39, and Comparative Example 6) that used bismuth 2-ethylhexanoate as the carboxylate, one-component coating composition D-a29, which used a blocked polyisocyanate with 1,2,3-triazole as the blocking agent, had good low-temperature curing properties and solvent resistance when formed into a coating film, whereas one-component coating composition D-b5, which used a blocked polyisocyanate with methyl ethyl ketoxime as the blocking agent, had poor low-temperature curing properties and solvent resistance when formed into a coating film. Furthermore, among the one-component coating compositions D-a10 to D-a13 (Examples 20 to 23) which differ in the type and amount of carboxylate, the one-component coating composition D-a11 (Example 21), which used cesium acetate as the carboxylate, showed particularly good low-temperature curing properties when formed into a coating film. Furthermore, among the one-component coating compositions D-a12 to D-a13 (Examples 22 to 23) containing different types of carboxylate, the one-component coating composition D-a13, which used a trivalent carboxylate (bismuth 2-ethylhexanoate) as the carboxylate, had better solvent resistance than the one-component coating composition D-a12, which used a monovalent carboxylate (lithium acetate). Similarly, among the one-component coating compositions D-a15 and D-a25 (Examples 25 and 35) which contain different types of carboxylate, the one-component coating composition D-a25, which uses a trivalent carboxylate (iron 2-ethylhexanoate) as the carboxylate, has better solvent resistance than the one-component coating composition D-a15, which uses a monovalent carboxylate (potassium acetate). Furthermore, among the one-component coating compositions D-a22 and D-a24 (Examples 32 and 34) which differ in the type of carboxylate, the one-component coating composition D-a22, which used a trivalent carboxylate (bismuth 2-ethylhexanoate) as the carboxylate, had better low-temperature curing properties and solvent resistance than the one-component coating composition D-a24, which used a divalent carboxylate (tin 2-ethylhexanoate). Furthermore, among the one-component coating compositions D-a14 to D-a16 (Examples 24 to 26) which differ in the type and amount of carboxylate, the one-component coating compositions D-a14 and D-a16 (Examples 24 and 26) which used sodium propionate or potassium propionate as the carboxylate showed particularly good low-temperature curing properties when formed into a coating film. Furthermore, among the one-component coating compositions D-a3 and D-a17 (Examples 13 and 27) which differ in whether or not they contain a urethane catalyst, the one-component coating composition D-a3 (Example 13) which contained a urethane catalyst showed better low-temperature curing properties when formed into a coating film.

[0264] On the other hand, a one-component coating composition containing a blocked polyisocyanate using a blocking agent other than an azole-based blocking agent and a carboxylate, or a one-component coating composition containing a blocked polyisocyanate using a triazole-based blocking agent but not a carboxylate, showed poor low-temperature curing properties when formed into a coating film.

[0265] Blocked polyisocyanates using pyrazole-based blocking agents have been confirmed to have improved solvent resistance at 100°C when combined with carboxylates.

[0266] <Production of Blocked Polyisocyanate Composition 2> [Example 40] (Production of Blocked Polyisocyanate Composition BL-a10) A four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser was charged with 100 parts by mass of the polyisocyanate P-1 obtained in Synthesis Example 1 and 28.9 parts by mass of methoxypolyethylene glycol (MPG-081, 15 ethylene oxide repeating units, manufactured by Nippon Nyukazai Co., Ltd.) under a nitrogen stream. The mixture was heated to 120°C and stirred for 2 hours. The reaction mixture was then cooled to approximately 80°C to 110°C, and 38.0 parts by mass of 3,5-dimethylpyrazole was added. A blocking reaction was carried out at approximately 80°C to 120°C for 4 hours. FT-IR spectroscopy was then performed to confirm that the isocyanate groups had been blocked. 383.5 parts by mass of water was then added. The mixture was stirred at 50°C until homogeneous, yielding blocked polyisocyanate composition BL-a10.

[0267] [Examples 41 to 46 and 50 to 52] (Production of Blocked Polyisocyanate Compositions BL-a11 to BL-a16 and BL-a20 to BL-a22) Each blocked polyisocyanate composition was produced in the same manner as in Example 39, except that the compositions and blending amounts shown in Tables 18 to 20 were used.

[0268] [Example 47] (Blocked polyisocyanate composition BL-a17) A four-neck flask equipped with a thermometer, stirring blade, and reflux condenser was charged with 100 parts by weight of P-3 obtained in Synthesis Example 3 and 22.0 parts by weight of MPG-081 under a nitrogen stream. The mixture was heated to 120°C and stirred for 2 hours. The reaction mixture was then cooled to approximately 80°C to 110°C, and 20.8 parts by weight of 1,2,3-triazole was added. A blocking reaction was carried out at approximately 80°C to 120°C for 4 hours. FT-IR spectroscopy was then performed to confirm that the isocyanate groups had been blocked. 302.5 parts by weight of water was then added, and the mixture was stirred at 50°C until homogenous. 27.4 parts by weight of a 56% by weight methanol solution of benzyltrimethylammonium caprate was then added to the reaction mixture to obtain blocked polyisocyanate composition BL-a17.

[0269] [Examples 48 to 49] (Blocked polyisocyanate compositions BL-a18 to BL-a19) Each blocked polyisocyanate composition was produced in the same manner as in Example 47, except that the compositions and blending amounts shown in Table 19 were used.

[0270] The composition, blending amount and physical properties of each blocked polyisocyanate composition are shown in Tables 18 to 20 below. In Tables 18 to 20, the types of hydrophilic compounds and carboxylates are as follows: The same will be shown in the subsequent tables.

[0271] (hydrophilic compound) A-1: Methoxypolyethylene glycol (manufactured by Nippon Nyukazai Co., Ltd., product name "MPG-081", ethylene oxide repeating units: 15) A-2: Polyethylene glycol monomethyl ether (manufactured by Nippon Nyukazai Co., Ltd., trade name "MPG-130", ethylene oxide repeating units: 9.4) A-3: Hydroxypivalic acid

[0272] (Carboxylate) C-1: Benzyltrimethylammonium caprate (methanol solution containing 56% by mass of benzyltrimethylammonium caprate relative to the total mass of the solution) C-4-2: Sodium propionate C-5-2: Potassium acetate

[0273] [Table 18]

[0274] [Table 19]

[0275] [Table 20]

[0276] <Production of one-component coating composition 2> [Example 53] (Production of one-component coating composition D-a30) 10.0 parts by mass of an acrylic dispersion (Allnex Corporation, "SETAQUA6510" (trade name), hydroxyl group concentration 4.2% (based on resin), solid content concentration 42% by mass) and 15.1 parts by mass of the blocked polyisocyanate BL-a10 produced in Example 40 were blended. Next, 0.3 parts by mass of sodium propionate and 0.2262 parts by mass of an aqueous emulsion (Borchers, "LH-10" (trade name)) containing 10% by mass of dibutyltin dilaurate (DBTDL) relative to the total mass of the emulsion were added to obtain one-component coating composition D-a30.

[0277] [Examples 54 to 80 and Comparative Examples 7 to 10] (Production of one-component coating compositions D-a31 to D-a57, D-b6 to D-b8, and D-b10) Each one-component coating composition was produced in the same manner as in Example 53, except that the compositions and blending amounts shown in Tables 21 to 27 were used.

[0278] The composition, blending amount, physical properties and evaluation of each one-component coating composition are shown in Tables 21 to 33 below. In Tables 21 to 27, the types of carboxylates and urethanization catalysts are as follows:

[0279] (Carboxylate) C-1: Benzyltrimethylammonium caprate (methanol solution containing 56% by mass of benzyltrimethylammonium caprate relative to the total mass of the solution) C-2: Tetramethylammonium caprate (methanol solution containing 47% by mass of tetramethylammonium caprate relative to the total mass of the solution) C-3: Tetramethylammonium propionate (methanol solution containing 47% by mass of tetramethylammonium propionate relative to the total mass of the solution) C-4-2: Sodium propionate C-5-2: Potassium acetate C-6-2: Potassium propionate C-7-2: Potassium 2-ethylhexanoate C-8-2: Cesium acetate C-9-2: Lithium acetate C-10: Bismuth 2-ethylhexanoate (2-ethylhexanoic acid solution containing 25% by mass of bismuth 2-ethylhexanoate based on the total mass of the solution)

[0280] (Urethanization catalyst) LH-10: an aqueous emulsion containing 10% by mass of dibutyltin dilaurate (DBTDL) based on the total mass of the emulsion (manufactured by Borchers, "LH-10" (trade name))

[0281] (external emulsifier) N707-SF: Polyoxyethylene polycyclic phenyl ether sulfate (manufactured by Nippon Nyukazai Co., Ltd., "Newcol 707-SF" (trade name))

[0282] [Table 21]

[0283] [Table 22]

[0284] [Table 23]

[0285] [Table 24]

[0286] Table 25

[0287] Table 26

[0288] Table 27

[0289] Table 28

[0290] Table 29

[0291]

Table 30

[0292] Table 31

[0293] Table 32

[0294]

Table 33

[0295] As can be seen from Tables 21 to 33, the one-component coating compositions D-a30 to D-a57, which comprised a polyisocyanate, a hydrophilic compound, a blocked polyisocyanate derived from a pyrazole-based or triazole-based blocking agent, and a carboxylate, exhibited good low-temperature curability when formed into coating films, and also exhibited excellent coating film appearance. Furthermore, among the one-component coating compositions D-a42 to D-a48 (Examples 65 to 71) which differ in the type and amount of carboxylate, the one-component coating compositions D-a43 and D-a46 to D-a48 (Examples 66 and 69 to 71) which used cesium acetate, sodium propionate, potassium acetate, or potassium propionate as the carboxylate showed particularly good low-temperature curing properties when formed into a coating film, and the one-component coating compositions D-a43 to D-a45 and D-a47 to D-a48 (Examples 66 to 68 and 70 to 71) which had a counter cation (X) content of less than 2.0 showed better storage stability. Furthermore, among the one-component coating compositions D-a42 to D-a45 (Examples 65 to 68) which differ in the type and amount of carboxylate, the one-component coating composition D-a45 (Example 68), which used a trivalent metal salt as the carboxylate, had better solvent resistance. Furthermore, among the one-component coating compositions D-a46 to D-a47 and D-a49 to D-a50 (Examples 69 to 70 and 72 to 73) which differ in the presence or absence of a urethane catalyst, the one-component coating compositions D-a46 to D-a47 (Examples 69 to 70) which contained a urethane catalyst showed particularly good low-temperature curing properties when formed into a coating film.

[0296] On the other hand, the one-component coating compositions D-b6 to D-b8 (Comparative Examples 7 to 9), which contained a blocked polyisocyanate derived from a polyisocyanate, a hydrophilic compound, and a pyrazole-based blocking agent or a triazole-based blocking agent, but did not contain a carboxylate, had good storage stability and good appearance when formed into a coating film, but poor low-temperature curing properties and solvent resistance when formed into a coating film. [Industrial Applicability]

[0297] The blocked polyisocyanate composition and one-component coating composition of the present embodiment can provide a blocked polyisocyanate composition and one-component coating composition that exhibit good low-temperature curing properties when formed into a coating film. The one-component coating composition of the present embodiment is suitable for use as a primer, intermediate coat, or top coat on materials such as metals, plastics, and inorganic materials. The one-component coating composition of the present embodiment is suitable for imparting cosmetic properties, weather resistance, acid resistance, rust prevention, chipping resistance, adhesion, and the like to pre-coated metals including rust-resistant steel plates, painted parts of automobiles, painted parts of plastics, and the like. The one-component coating composition of the present embodiment is also useful as a urethane raw material for adhesives, pressure-sensitive adhesives, elastomers, foams, surface treatment agents, and the like.

Claims

1. The composition comprises a blocked polyisocyanate derived from a polyisocyanate and a blocking agent, one or more organic acids and / or inorganic acids (A), one or more metals (X), and a polyvalent active hydrogen compound, X is a trivalent metal, the mass ratio X / A of X to A is 0.01 to 5.0; The content of X is 0.001% by mass or more and 20% by mass or less relative to the total mass of the blocked polyisocyanate, and the blocking agent comprises a compound having a heterocycle, the heterocycle containing three or more nitrogen atoms; The organic acid and / or inorganic acid (A) and the metal (X) are represented by the following general formula (I): (A)n-X (I) In the formula (I), A represents a group in which one hydrogen atom has been removed from an organic acid or an inorganic acid, X represents a metal, n represents the valence of X, and n=3. A one-component coating composition derived from a salt represented by In the one-component coating composition, A is a carboxylic acid.

2. The one-component coating composition according to claim 1 , wherein a hydrophilic group is introduced into the blocked polyisocyanate.

3. 3. The one-component coating composition according to claim 2, wherein the hydrophilic group is a nonionic hydrophilic group.

4. The one-component coating composition according to claim 3 , wherein the nonionic hydrophilic group is derived from a polyalkylene glycol monoalkyl ether.

5. The one-component coating composition according to any one of claims 1 to 4, further comprising one or more surfactants.

6. The one-component coating composition according to any one of claims 1 to 5, further comprising a urethanization catalyst.

7. A coating film obtained by curing the one-component coating composition according to any one of claims 1 to 6.

8. A coated article comprising the coating film of claim 7.

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