Blocked isocyanate composition, coating material composition, and coating film

Abstract

This blocked isocyanate composition comprises a blocked isocyanate derived from a polyisocyanate compound and a blocking agent, wherein the polyisocyanate compound includes a polyisocyanate compound represented by general formula (III).

Description

Blocked isocyanate composition, coating composition and coating film

[0001] The present invention relates to a blocked isocyanate composition, a coating composition, and a coating film. This application claims priority to Japanese Patent Application No. 2023-126444, filed on August 2, 2023, the contents of which are incorporated herein by reference.

[0002] In recent years, users in the paint and coatings industry have become increasingly aware of environmental issues. Against this backdrop, the importance of environmentally conscious coating technology is growing, and there is a shift from solvent-based paints to high-solid, water-based, and powder paints. Powder paints do not use any organic solvents, so there are no concerns about fire or poisoning. Furthermore, because paint can be recovered and reused, there is less environmental pollution, and there is a growing demand for powdered polyurethane paints.

[0003] Current mainstream polyurethane powder coatings are produced by melt-mixing a polyester polyol as a base agent and a blocked polyisocyanate as a curing agent in an extruder at a temperature at which the blocking agent does not dissociate, and then pulverizing the mixture to produce a coating. For example, Patent Document 1 discloses a blocked polyisocyanate in which the isocyanate groups of a polyisocyanate derived from isophorone diisocyanate (hereinafter sometimes referred to as "IPDI") are blocked with a blocking agent such as ε-caprolactam.

[0004] Furthermore, for example, Patent Documents 2 and 3 disclose polyurethanedione curing agents that use polyisocyanates derived from IPDI and do not use blocking agents.

[0005] Furthermore, Patent Document 4 discloses a polyurethanedione curing agent that uses a polyisocyanate derived from tolylene diisocyanate or hexamethylene diisocyanate (hereinafter sometimes referred to as "HDI") and does not use a blocking agent.

[0006] These polyurethane diurethion curing agents can be used as curing agents for powder coatings because the urethionine group formed by two moles of isocyanate groups dissociates into two moles of isocyanate groups again during coating baking and can react with polyols.

[0007] JP 61-31744, JP 64-5627, JP 2-16332, JP 57-46447

[0008] In recent years, there has been a demand for polyurethane powder curing agents that combine blocking resistance with good coating film appearance. However, the powder coating curing agents described in Patent Documents 1 to 4 have excellent blocking resistance, but have problems with the coating film appearance, such as the gloss and smoothness (image clarity) of the cured coating film.

[0009] The present invention has been made in view of the above circumstances and provides a blocked isocyanate composition that, when formed into a coating film, exhibits excellent gloss and smoothness while maintaining good blocking resistance. It also provides a coating composition and a coating film using the blocked isocyanate composition.

[0010] [1] A blocked isocyanate composition containing a blocked isocyanate derived from a polyisocyanate compound and a blocking agent, wherein the polyisocyanate compound contains a polyisocyanate compound represented by the following general formula (III): (In general formula (III), R ０１ are organic groups, and may be the same or different. ０１ At least one of R is a group represented by the following general formula (II)-1: ０２ is an organic group and a side chain derived from a blocking agent. ０２ may contain a ring structure instead of (In general formula (II)-1, plural Y １１ are each independently a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms which may contain an ester structure and / or an ether structure. １１ may be the same or different. １１is a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms. The wavy line represents a bond. [2] In the general formula (III), R ０１ are both groups represented by general formula (II)-1. [3] The blocked isocyanate composition according to [1] or [2], which has a glass transition temperature of 50°C or higher and 120°C or lower. [4] The blocked isocyanate composition according to any one of [1] to [3], wherein the polyisocyanate compound further contains a triisocyanate represented by the following general formula (IV): (In general formula (IV), a plurality of Y １０ are each independently a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms which may contain an ester structure and / or an ether structure. １０ may be the same or different. １０is a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms.) [5] The blocked isocyanate composition according to [4], wherein the proportion of the triisocyanate represented by general formula (IV) contained in the polyisocyanate compound is 20% by mass or more and 70% by mass or less. [6] The blocked isocyanate composition according to any one of [1] to [5], wherein the blocking agent comprises a blocking agent having a dissociation temperature of 120°C or more and 150°C or less. [7] The blocked isocyanate composition according to any one of [1] to [6], wherein the blocking agent comprises an amine-based thermally dissociable blocking agent (b1) having a cycloalkane structure and a thermally dissociable blocking agent (b2) different from the amine-based thermally dissociable blocking agent (b1). [8] The blocked isocyanate composition according to [7], wherein the proportion of the amine-based thermally dissociable blocking agent (b1) relative to the total molar amount of the blocking agents is 20 mol% or more and 95 mol% or less. [9] The blocked isocyanate composition according to [7], wherein the proportion of the amine-based thermally dissociable blocking agent (b1) relative to the total molar amount of the blocking agents is 40 mol% or more and 80 mol% or less.

[10] The blocked isocyanate composition according to [7], wherein the thermally dissociable blocking agent (b2) is at least one selected from the group consisting of pyrazole-based compounds, oxime-based compounds, lactam-based compounds, alcohol-based compounds, and triazole-based compounds.

[11] The blocked isocyanate composition according to [7], wherein the thermally dissociable blocking agent (b2) is a pyrazole-based compound or a triazole-based compound.

[12] The blocked isocyanate composition according to [7], wherein the proportion of the thermally dissociable blocking agent (b2) relative to the total molar amount of the blocking agents is 20 mol% or more and 60 mol% or less.

[13] The blocked isocyanate composition according to any one of [1] to

[12] , which is in a powder form at 23°C.

[14] The blocked isocyanate composition according to any one of [1] to

[13] , which contains an amorphous portion.

[15] A coating composition comprising the blocked isocyanate composition according to any one of [1] to

[14] and an active hydrogen compound.

[16] A coating film obtained by curing the coating composition according to

[15] .

[17] A coating composition comprising the blocked isocyanate composition according to any one of [1] to

[16] and a polyol having a Tg of 60°C or less.

[18] The coating composition according to

[17] , wherein the polyol is a fluorine polyol.

[19] A coating film obtained by curing the coating composition according to

[17] .

[20] A method for producing a blocked isocyanate composition, comprising a first step of reacting an aliphatic triisocyanate with a blocking agent having an active hydrogen on the N atom to obtain a prepolymer which is an aliphatic triisocyanate polymer and has a biuret structure, and a second step of further reacting the obtained prepolymer with the blocking agent.

[21] The method for producing a blocked isocyanate composition according to

[20] , wherein the blocking agent having an active hydrogen on the N atom used in the first step is an amine-based thermally dissociable blocking agent (b1) having a cycloalkane structure, and the blocking agent used in the second step comprises the amine-based thermally dissociable blocking agent (b1) having a cycloalkane structure and a thermally dissociable blocking agent (b2) different from the amine-based thermally dissociable blocking agent (b1).

[0011] The blocked isocyanate composition of the above embodiment can provide a blocked isocyanate composition that maintains good blocking resistance while providing a coating film that exhibits excellent gloss and smoothness (image clarity). The coating composition of the above embodiment contains the blocked isocyanate composition and provides a coating film that exhibits excellent gloss and smoothness. The coating film of the above embodiment is obtained by curing the coating composition and exhibits excellent gloss and smoothness.

[0012] Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. The following present 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] <Blocked Isocyanate Composition> The blocked isocyanate composition of this embodiment contains a blocked isocyanate derived from a polyisocyanate compound and a blocking agent. The blocked isocyanate is a reaction product of a polyisocyanate compound and a blocking agent. In other words, at least a portion of the isocyanate groups in the polyisocyanate compound are blocked with a blocking agent.

[0014] <Polyisocyanate Compound> The polyisocyanate compound includes a polyisocyanate compound represented by the following general formula (III): In the present invention, "polyisocyanate" is a general term for compounds having two or more isocyanate groups.

[0015]

[0016] (In general formula (III), R ０１ are organic groups, and may be the same or different. ０１ At least one of R is a group represented by the following general formula (II)-1: ０２ is an organic group and a side chain derived from a blocking agent. ０２ may contain a ring structure instead of

[0017]

[0018] (In general formula (II)-1, multiple Y11s each independently represent a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms which may contain an ester structure and / or an ether structure. Multiple Y11s may be the same or different. R11 represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms. A wavy line represents a bond.)

[0019] <General Formula (III)> The polyisocyanate compound represented by general formula (III) has a biuret structure. The biuret structure is a polyisocyanate consisting of one molecule of a blocking agent having an active hydrogen on the N atom and two molecules of an isocyanate monomer, and is represented by general formula (III). In this case, the blocking agent having an active hydrogen on the N atom functions as a biuretizing agent, which will be described later.

[0020] <R ０１ In general formula (III), R ０１ is an organic group. ０１ At least one of the R is a group represented by general formula (II)-1. ０１ may be the same or different. In this embodiment, two R ０１At least one of the R ０１ are preferably groups represented by general formula (II)-1.

[0021] R ０１ Among these, examples of groups other than the group represented by general formula (II)-1 include tetramethylene diisocyanate (TMDI), pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexane-1,6-diisocyanate, 2-methylpentane-1,5-diisocyanate (MPDI), 1,3-bis(isocyanatomethyl)-cyclohexane (1,3-H6-XDI), 3( 4)-isocyanatomethyl-1-methyl-cyclohexyl isocyanate (IMCI); residues obtained by removing the isocyanate group from isophorone diisocyanate (IPDI), bis(isocyanatomethyl)-norbornane (NBDI), 1,3-bis(isocyanatomethyl)-benzene, 1,3-bis(2-isocyanatopropyl-2)benzene, and 4,4'-dicyclohexylmethane diisocyanate (H12MDI). ０１ When is a monovalent organic group, it may be a residue obtained by removing one isocyanate group from an isocyanate monomer such as a diisocyanate. The group represented by general formula (II)-1 may be a residue obtained by removing one isocyanate group from a triisocyanate.

[0022] In this embodiment, the molecular weight of the triisocyanate that is the source of the group represented by general formula (II)-1 is preferably from 200 to 350, more preferably from 200 to 300, and particularly preferably from 220 to 270. When the molecular weight of the aliphatic triisocyanate is equal to or greater than the above lower limit, blocking resistance tends to be more excellent, while when the molecular weight is equal to or less than the above upper limit, compatibility with the base resin can be improved.

[0023] <R ０２ In general formula (III), R ０２ is an organic group, which is a residue obtained by removing an active hydrogen group from a blocking agent having an active hydrogen on the N atom. ０２ -NH-R０２ represents a blocking agent having an active hydrogen atom on the N atom, ０２ Two R ０２ may each be a monovalent organic group, and two R ０２ may be bonded to form a divalent organic group. ０２ may be the same or different. ０２ Alternatively, the compound may contain a ring structure instead of the above. Examples of blocking agents having an active hydrogen on the N atom include acid amide-based, imidazole-based, urea-based, amine-based, pyrazole-based, and triazole-based compounds. More specific examples of blocking agents are shown below. (1) Acid amides: acetanilide, acetic acid amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam, etc. (2) Imidazoles: imidazole, 2-methylimidazole, etc. (3) Ureas: urea, thiourea, ethyleneurea, etc. (4) Amines: diphenylamine, aniline, carbazole, di-n-propylamine, diisopropylamine, isopropylethylamine, dicyclopentylamine, dicyclohexylamine, isopropylcyclohexylamine, etc. (5) Pyrazoles: pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole, etc. (6) Triazoles: 1,2,4-triazole, 1,2,3-triazole, etc. Note that R ０２ The blocking agent from which the formula (I) is derived functions as a biuretizing agent that reacts with an isocyanate monomer to form a biuret structure and also functions to block an isocyanate group, but may be different from the blocking agents used in the reaction with the polyisocyanate composition, such as blocking agents (b1) and (b2) described below.

[0024] <Y １１ In the general formula (II-1), a plurality of Y １１ are each independently a single bond or a divalent aliphatic hydrocarbon group having 1 to 20 carbon atoms which may contain at least one structure selected from the group consisting of an ester structure and an ether structure. １１ may be the same or different.

[0025] The aliphatic hydrocarbon group may be linear, branched, or cyclic. Examples of the linear or branched aliphatic hydrocarbon group include an alkanediyl group (alkylene group), an alkylidene group, etc. Examples of the cyclic aliphatic hydrocarbon group include a cycloalkylene group, etc. Among these, Y １１ The aliphatic hydrocarbon group is preferably an alkylene group having 1 to 6 carbon atoms.

[0026] Also, Y １１ In the above formula, examples of the divalent aliphatic hydrocarbon group having 1 to 20 carbon atoms and containing at least one selected from the group consisting of an ester structure and an ether structure include groups represented by the following general formula (V): ２ ) ｎ１ -X-(CH ２ ) ｎ２ -*2 (V)

[0027] In the general formula (V), *1 represents a bond to C in the general formula (II)-1, and *2 represents a bond to NCO in the general formula (II). Furthermore, n1 and n2 are each independently an integer of 0 to 20 that satisfies 1≦n1+n2≦20, but it is preferred that both n1 and n2 are not 0, and that n2, which is bonded to NCO, is 1 or greater.

[0028] Among these, n1 and n2 are more preferably each independently an integer of 0 to 4, and even more preferably an integer of 0 to 2. Preferred combinations of n1 and n2 include, for example, n1=0 and n2=2, and n1=2 and n2=2.

[0029] In the general formula (V), X is an ester group or an ether group. Among these, X is preferably an ester group because the reaction rate increases.

[0030] Also, there are multiple Y １１ When at least one of the above is an aliphatic hydrocarbon group, the weather resistance of the coating film obtained by using the blocked isocyanate composition of this embodiment as a curing agent for a coating composition can be improved.

[0031] Also, there are multiple Y １１ When at least one of the above has an ester structure, the heat resistance of the blocked isocyanate composition of the present embodiment can be further improved, and the reactivity of the isocyanate group can be further increased when the blocked isocyanate composition is used as a curing agent for a coating composition.

[0032] Preferably, there are multiple Y １１ When at least one of the Y １１ When all of the above are composed of only aliphatic hydrocarbon groups, the hydrolysis resistance of the blocked isocyanate composition of the present embodiment can be further improved.

[0033] (R １１ ) In general formula (II)-1, R １１ is a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 12 carbon atoms. １ The aliphatic hydrocarbon group in R is not particularly limited, and examples thereof include alkyl groups, alkenyl groups, and alkynyl groups. １１ is preferably a hydrogen atom.

[0034] In this embodiment, a plurality of Y １１ In the case where at least one of the above has an aliphatic hydrocarbon group, preferred triisocyanates that are the source of the group represented by the general formula (II)-1 include, for example, 4-isocyanatomethyl-1,8-octamethylene diisocyanate (hereinafter referred to as "NTI", molecular weight 251) disclosed in JP-B-63-15264 (Patent Document 3), and 1,8-octamethylene diisocyanate (hereinafter referred to as "NTI", molecular weight 251) disclosed in JP-A-57-198760 (Reference Document 1). ,3,6-hexamethylene triisocyanate (hereinafter referred to as "HTI", molecular weight 209), bis(2-isocyanatoethyl) 2-isocyanatoglutarate (hereinafter referred to as "GTI", molecular weight 311) disclosed in JP-B-4-1033 (Reference 2), and lysine triisocyanate (hereinafter referred to as "LTI", molecular weight 267) disclosed in JP-A-53-135931 (Reference 3).

[0035] Among these, NTI, GTI or LTI is preferred, and NTI or LTI is more preferred, from the viewpoint of further improving the reactivity of the isocyanate group.

[0036] In this embodiment, a plurality of Y １１ When at least one of the above has an ester structure, preferred examples of the triisocyanate that is the source of the group represented by general formula (II)-1 include GTI (molecular weight 311) disclosed in JP-B-4-1033 (Reference 2) and LTI (molecular weight 267) disclosed in JP-A-53-135931 (Reference 3).

[0037] In this embodiment, a plurality of Y １１ When at least one of the above groups consists solely of an aliphatic hydrocarbon group, preferred examples of the triisocyanate that is the source of the group represented by general formula (II)-1 include NTI (molecular weight 251) disclosed in JP-B-63-15264 (Patent Document 3) and HTI (molecular weight 209) disclosed in JP-A-57-198760 (Reference Document 1).

[0038] The triisocyanate compound that is the source of the group represented by general formula (II)-1 in this embodiment can be obtained by isocyanating an amine such as an amino acid derivative, an ether amine, or an alkyl triamine.

[0039] Examples of the amino acid derivatives include 2,5-diaminovaleric acid, 2,6-diaminohexanoic acid, aspartic acid, and glutamic acid. Because these amino acid derivatives are diamine monocarboxylic acids or monoamine dicarboxylic acids, triamines having ester groups can be obtained by esterifying the carboxyl groups with alkanolamines such as ethanolamine. The resulting triamines having ester groups can be converted into triisocyanates containing an ester structure by, for example, phosgenating the amine.

[0040] Examples of the etheramine include polyoxyalkylene triamines such as "D403" (trade name) manufactured by Mitsui Fine Chemicals, Inc. These etheramines are triamines, and can be converted into triisocyanate compounds containing an ether structure by phosgenation of the amines, for example.

[0041] Examples of the alkyltriamine include triisocyanatononane (4-aminomethyl-1,8-octanediamine), etc. These alkyltriamines are triamines, and can be converted into triisocyanate compounds containing only hydrocarbons by amine phosgenation or the like.

[0042] A method for forming a biuret structure includes a method using a biuretizing agent. The biuretizing agent is preferably a blocking agent having an active hydrogen atom on the N atom, as described above, and examples thereof include organic secondary monoamines, organic secondary diamines, pyrazole compounds, and triazole compounds. A solvent can be used during the biuretization reaction. The solvent can dissolve the triisocyanate monomer or diisocyanate monomer and the biuretizing agent, such as water, to form a homogeneous phase under reaction conditions.

[0043] Specific examples of the solvent include ethylene glycol-based solvents such as 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, Examples of the ethylene glycol ether acetate include 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.

[0044] Preferred ethylene glycol solvents include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol diacetate, and diethylene glycol dimethyl ether. Phosphate-based solvents include trimethyl phosphate, triethyl phosphate, tripropyl phosphate, and tributyl phosphate, with trimethyl phosphate and triethyl phosphate being preferred. These solvents can be used alone or in combination.

[0045] 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 and the like tend to be effectively prevented, which is preferable.

[0046] The polyisocyanate compound of the present embodiment may further contain a triisocyanate represented by the general formula (IV).

[0047]

[0048] (In general formula (IV), a plurality of Y １０ are each independently a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms which may contain an ester structure and / or an ether structure. １０ may be the same or different. １０ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms.

[0049] Y in general formula (IV) １０ , R １０ The explanation regarding Y in the general formula (II) １ , R １ This is similar to the explanation for

[0050] The proportion of the triisocyanate represented by general formula (IV) relative to the total mass of the polyisocyanate compound is preferably 20% by mass or more and 70% by mass or less, and more preferably 40% by mass or more and 60% by mass or less. When the proportion is equal to or more than the lower limit, the image clarity of the coating film tends to be better, while when the proportion is equal to or less than the upper limit, the blocking resistance can be improved.

[0051] The ratio of the triisocyanate represented by general formula (IV) to the total mass of the polyisocyanate compound can be determined, for example, from the blending amounts (molar amounts) of the raw materials used in the production and the peak area ratio obtained by GPC measurement of the blocked isocyanate composition. As the detector for GPC, for example, an RI (refractive index) detector can be used.

[0052] Furthermore, the polyisocyanate compound of the present embodiment may include, in addition to the polyisocyanate compound represented by general formula (I), a compound having a uretdione structure, a compound having an allophanate structure, a compound having an iminodioxadiazinedione structure, a compound having a urethane structure, and a compound having an isocyanurate structure.

[0053] In the blocked isocyanate composition of this embodiment, the dissociation temperature of the blocking agent is preferably 120°C or higher and 150°C or lower. The dissociation temperature of the blocking agent in this specification is an index possessed by the blocked isocyanate composition and can be measured by the method described in the Examples. When the dissociation temperature of the blocking agent is 120°C or higher and 150°C or lower, the composition exhibits excellent low-temperature curing properties. The dissociation temperature of the blocking agent is more preferably 120°C or higher and 140°C or lower, and even more preferably 125°C or higher and 135°C or lower.

[0054] Furthermore, the form of the blocked isocyanate composition of this embodiment is not particularly limited, but is preferably in powder form. That is, when the blocked isocyanate composition of this embodiment is in powder form, it can also be referred to as a powder curing agent composition for a coating material. More specifically, the blocked isocyanate composition of this embodiment is preferably in powder form at 23°C. The term "powder form" refers to, for example, an aggregate of particles having a particle diameter of 300 μm or less, more preferably 150 μm or less. The content of particles having a particle diameter of 300 μm or less, more preferably 150 μm or less, is preferably 95% by volume or more relative to the total volume of the blocked isocyanate composition.

[0055] The blocked isocyanate composition of the present embodiment preferably contains an amorphous portion.

[0056] <Blocking Agent> Examples of blocking agents used in the blocked isocyanate composition of the present embodiment include alcohol-based, alkylphenol-based, phenol-based, active methylene, mercaptan-based, acid amide-based, acid imide-based, imidazole-based, urea-based, oxime-based, amine-based, imide-based, and pyrazole-based compounds. More specific examples of blocking agents are shown below. (1) Alcohols: alcohols such as methanol, ethanol, 2-propanol, n-butanol, sec-butanol, 2-ethyl-1-hexanol, 2-methoxyethanol, 2-ethoxyethanol, and 2-butoxyethanol; (2) Alkylphenols: mono- and di-alkylphenols having an alkyl group having 4 or more carbon atoms as a substituent, such as mono-alkylphenols such as n-propylphenol, iso-propylphenol, n-butylphenol, sec-butylphenol, t-butylphenol, n-hexylphenol, 2-ethylhexylphenol, n-octylphenol, and n-nonylphenol; di-n-propylphenol, diisopropylphenol, isopropyl cresol, di-n-butylphenol, di-t-butylphenol, di-sec-butylphenol, di-n-octylphenol, di-2-ethylhexylphenol, and di-n-nonylphenol; (3) Phenol-based: phenol, cresol, ethylphenol, styrenated phenol, hydroxybenzoic acid ester, etc.; (4) Active methylene-based: dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone, etc.; (5) Mercaptan-based: butyl mercaptan, dodecyl mercaptan, etc.; (6) Acid amide-based: acetanilide, acetic acid amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam, etc.; (7) Acid imide-based: succinimide, maleic acid imide, etc.; (8) Imidazole-based: imidazole, 2-methylimidazole, etc.; (9) Urea-based: urea, thiourea, ethylene urea, etc.; (10) Oxime-based: formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, cyclohexanone oxime, etc.; (11) Amine-based:Diphenylamine, aniline, carbazole, di-n-propylamine, diisopropylamine, isopropylethylamine, dicyclopentylamine, dicyclohexylamine, isopropylcyclohexylamine, etc., (12) Imine-based compounds: ethyleneimine, polyethyleneimine, etc., (13) Bisulfites: sodium bisulfite, etc., (14) Pyrazole-based compounds: pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole, etc., (15) Triazole-based compounds: 3,5-dimethyl-1,2,4-triazole, etc.;

[0057] The blocking agent used in the blocked isocyanate composition of this embodiment preferably contains an amine-based thermally dissociable blocking agent (b1) containing a cycloalkane structure and a thermally dissociable blocking agent (b2) different from the amine-based thermally dissociable blocking agent (b1). Hereinafter, the "amine-based thermally dissociable blocking agent (b1) containing a cycloalkane structure" may be referred to as the "blocking agent (b1)," and the "thermally dissociable blocking agent (b2) different from the amine-based thermally dissociable blocking agent (b1)" may be referred to as the "blocking agent (b2)."

[0058] The blocking agent (b1) is an amine-based thermally dissociable blocking agent containing a cycloalkane structure. "Thermal dissociability" refers to the property that the blocking agent bonded to the isocyanate group dissociates upon heating, regenerating the isocyanate group. The temperature required for dissociation varies depending on the structure of the blocking agent, but is, for example, 40°C or higher and 300°C or lower.

[0059] The glass transition temperature of the blocked isocyanate composition tends to be higher with the addition of blocking agent (b1) and lower with the addition of blocking agent (b2). Therefore, by adjusting the contents of blocking agents (b1) and (b2), the glass transition temperature of the blocked isocyanate composition can be adjusted to a specific range. Furthermore, depending on the type of blocking agent (b2), it is possible not only to adjust the glass transition temperature but also to improve the coating film appearance and low-temperature curing properties. The glass transition temperature is preferably 50°C or higher and 120°C or lower.

[0060] (Blocking Agent (b1)) The blocking agent (b1) is not particularly limited, but from the viewpoint of reactivity, a secondary amine compound is preferable. Examples of the blocking agent (b1) include dicyclohexylamine, dicyclopentylamine, isopropylcyclohexylamine, isobutylcyclohexylamine, methylcyclohexylamine, ethylcyclohexylamine, etc. These compounds may be used alone or in combination of two or more.

[0061] (Blocking Agent (b2)) In this embodiment, in addition to the blocking agent (b1), it is preferable to contain a thermally dissociable blocking agent (b2) different from the blocking agent (b1). From the viewpoints of the effect of reducing the glass transition temperature of the blocked isocyanate composition and improving the appearance of the coating film, the blocking agent (b2) is preferably (1) a pyrazole-based compound, (2) an oxime-based compound, (3) a lactam-based compound, (4) an alcohol-based compound, or (5) a triazole-based compound.

[0062] More specific examples of the blocking agent (b2) include the following: (1) Pyrazole compounds: pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole, etc. (2) Oxime compounds: formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, cyclohexanone oxime, acetophenone oxime, etc. (3) Lactam compounds: ε-caprolactam, etc. (4) Alcohol compounds: methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, sec-butanol, 2-ethyl-1-hexanol, cyclohexanol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, benzyl alcohol, trifluoroethanol, hexafluoro-2-propanol, 2-methyl-1-propanol, 1-dodecanol, 1-octadecanol, phenol, tert-butanol, etc. (5) Triazole compounds: 1,2,4-triazole, 1,2,3-triazole, etc.

[0063] Among these, as the blocking agent (b2), pyrazole-based compounds or triazole-based compounds are preferred because of their excellent low-temperature curing properties, and pyrazole-based compounds are more preferred because of their excellent blocking resistance.

[0064] In the blocked isocyanate composition of this embodiment, the proportion of the blocking agent (b1) relative to the total molar amount of the blocking agents is preferably 20 mol% or more and 95 mol% or less, and more preferably 40 mol% or more and 80 mol% or less, although not particularly limited thereto. When the proportion of the blocking agent (b1) is equal to or greater than the above-mentioned lower limit, the blocked isocyanate composition can have excellent blocking resistance. When the proportion of the blocking agent (b1) is equal to or less than the above-mentioned upper limit, the blocked isocyanate composition can have excellent low-temperature curability and excellent gloss and smoothness when formed into a coating film.

[0065] The ratio of the blocking agent (b1) to the total molar amount of the blocking agents can be calculated, for example, by dividing the amount (molar amount) of the amine compound used during production by the total amount (molar amount) of the blocking agents, and multiplying the result by 100 (calculation method 1). １ H-NMR and １３ It can be calculated from the area value of the peak derived from each blocking agent by C-NMR (Calculation Method 2).

[0066] In the production stage of the blocked isocyanate composition, the proportion of the blocking agent (b1) may be adjusted by the above-mentioned calculation method 1. When calculating the proportion of the blocking agent (b1) in an already produced blocked isocyanate composition, the calculation may be performed by the above-mentioned calculation method 2.

[0067] The blocked isocyanate composition of the present embodiment has the above-described configuration, and therefore can provide a coating film that exhibits excellent low-temperature curing properties while maintaining good blocking resistance, and that also exhibits excellent gloss and smoothness (image clarity).

[0068] In the blocked isocyanate composition of this embodiment, the proportion of the blocking agent (b2) relative to the total molar amount of the blocking agents is preferably 20 mol % or more and 60 mol % or less, although not particularly limited thereto. When the proportion of the blocking agent (b2) is equal to or greater than the above-mentioned lower limit, the blocked isocyanate composition can have excellent low-temperature curability or excellent gloss and smoothness. When the proportion of the blocking agent (b2) is equal to or less than the above-mentioned upper limit, the blocked isocyanate composition can have excellent blocking resistance.

[0069] The ratio of the blocking agent (b2) to the total molar amount of the blocking agents can be calculated, for example, by dividing the amount (molar amount) of the amine compound used during production by the total amount (molar amount) of the blocking agents, and multiplying the result by 100 (calculation method 1). １ H-NMR and １３ It can be calculated from the area value of the peak derived from each blocking agent by C-NMR (Calculation Method 2).

[0070] In the production stage of the blocked isocyanate composition, the proportion of the blocking agent (b2) may be adjusted by the above-mentioned calculation method 1. When calculating the proportion of the blocking agent (b2) in an already produced blocked isocyanate composition, the calculation may be performed by the above-mentioned calculation method 2.

[0071] <Method for Producing Blocked Isocyanate Composition> The method for producing a blocked isocyanate composition of the present embodiment includes, for example, a first step of reacting an aliphatic triisocyanate with a blocking agent having an active hydrogen on an N atom to obtain a prepolymer which is an aliphatic triisocyanate polymer and has a biuret structure, and a second step of blocking the isocyanate groups of the obtained prepolymer with the blocking agent (hereinafter, this may be referred to as a "blocking reaction").

[0072] In the first step, an NH group derived from an isocyanate group formed by the reaction of a blocking agent having an active hydrogen atom with an isocyanate group reacts with another isocyanate group to form a biuret group. The content of the biuret group-containing polymer in the blocked isocyanate composition is preferably 30 wt % to 80 wt %.

[0073] The amine compound used in the first step (polymerization) preferably contains an amine-based thermally dissociable blocking agent (b1) containing a cycloalkane structure, more preferably an amine-based thermally dissociable blocking agent (b1) containing a cycloalkane structure. The blocking agent used in the second step (blocking reaction) preferably contains an amine-based thermally dissociable blocking agent (b1) containing a cycloalkane structure and a thermally dissociable blocking agent (b2) different from the amine-based thermally dissociable blocking agent (b1).

[0074] In the blocking reaction, all or part of the isocyanate groups of the prepolymer can be blocked. When all of the isocyanate groups of the prepolymer are blocked, the ratio of the total number of moles of the blocking agent to the number of moles of the isocyanate groups of the aliphatic triisocyanate (total number of moles of blocking agent / number of moles of isocyanate groups) is preferably 0.8 or more and 1.3 or less. When the blocking agent is blended in a proportion that satisfies the above ratio, excess or unreacted blocking agent remains.

[0075] The blocking reaction may be carried out in the absence of a solvent, or, if necessary, may be carried out using an organic solvent that is not reactive with an isocyanate group. The organic solvent is not particularly limited, but specific examples thereof include the following:

[0076] (i) Aliphatic hydrocarbon solvents such as hexane, heptane, and octane. (ii) Alicyclic hydrocarbon solvents such as cyclohexane and methylcyclohexane. (iii) Ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. (iv) Ester solvents such as methyl acetate, ethyl acetate, butyl acetate, and isobutyl acetate. (v) Aromatic solvents such as toluene, xylene, diethylbenzene, mesitylene, anisole, and chlorobenzene. (vi) Glycol solvents such as ethylene glycol monoethyl ether acetate, 3-methyl-3-methoxybutyl acetate, and propylene glycol monomethyl ether acetate. (vii) Ether solvents such as diethyl ether, tetrahydrofuran, and dioxane. (viii) Halogenated hydrocarbon solvents such as dichloromethane, 1,2-dichloroethane, and chloroform. (ix) Pyrrolidone solvents such as N-methyl-2-pyrrolidone. (x) Amide-based solvents such as N,N-dimethylacetamide and N,N-dimethylformamide, (xi) Sulfoxide-based solvents such as dimethyl sulfoxide, (xii) Lactone-based solvents such as γ-butyrolactone, (xiii) Amine-based solvents such as morpholine.

[0077] These organic solvents may be used alone or in combination of two or more kinds, and can be removed after the reaction.

[0078] In addition, a catalyst may be used in the blocking reaction. Examples of the catalyst include, but are not limited to, organic metal salts of tin, zinc, lead, etc.; tertiary amine compounds; and alcoholates of alkali metals such as sodium.

[0079] The blocking reaction can generally be carried out at a temperature of −20° C. or higher and 150° C. or lower, preferably 0° C. or higher and 120° C. or lower, and more preferably 10° C. or higher and 100° C. or lower. When the temperature of the blocking reaction is equal to or higher than the above lower limit, the reaction rate can be further increased, and when the temperature is equal to or lower than the above upper limit, side reactions can be further suppressed.

[0080] After the blocking reaction, a neutralization treatment may be performed by adding an acidic compound or the like. As the acidic compound, an inorganic acid or an organic acid may be used. Examples of inorganic acids include hydrochloric acid, phosphorous acid, and phosphoric acid. Examples of organic acids include methanesulfonic acid, p-toluenesulfonic acid, dioctyl phthalate, and dibutyl phthalate.

[0081] <Physical Properties of Blocked Isocyanate Composition> The blocked isocyanate composition of the present embodiment preferably has an effective isocyanate group (NCO) content of 10% by mass or more and 30% by mass or less, and more preferably 12% by mass or more and 25% by mass or less.

[0082] The "effective isocyanate group (NCO) content" referred to here is a quantification of the amount of blocked isocyanate groups present in the blocked isocyanate composition after the blocking reaction and capable of participating in a crosslinking reaction, and is expressed as the mass % of isocyanate groups relative to the total mass of the blocked isocyanate composition after the blocking reaction. The effective NCO content can be calculated, for example, by the following formula. In the following formula, "NCO %" refers to the isocyanate group content of the triisocyanate compound (I).

[0083] (Effective NCO content (mass%)) = [(content of solids in blocked isocyanate composition (mass%)) × {(mass of triisocyanate compound (I) used in blocking reaction) × NCO%}] / (mass of blocked isocyanate composition after blocking reaction)

[0084] <Coating composition> The coating composition of this embodiment contains the blocked isocyanate composition and an active hydrogen compound described above. The coating composition of this embodiment is preferably in a powder form at 23°C. In addition, it preferably contains an amorphous portion.

[0085] The coating composition of this embodiment contains the above-described blocked isocyanate composition as a curing agent component, thereby providing a coating film with excellent gloss and smoothness.

[0086] <<Active hydrogen compound>> The active hydrogen compound is not particularly limited, but specifically, it is a compound having two or more active hydrogens bonded in the molecule, for example, a polyol compound, a polyamine compound, a polythiol compound, etc. Among them, from the viewpoint of toughness, a polyol compound is preferred as the active hydrogen compound. In particular, when a polyol compound is used as the active hydrogen compound, the coating composition is also called a polyurethane coating composition.

[0087] [Polyol Compound] The polyol compound is not particularly limited, but specific examples include polyester polyol, acrylic polyol, polyether polyol, polyolefin polyol, fluorine polyol, polycarbonate polyol, epoxy resin, urethane polyol, etc. Among them, one or more polyols selected from the group consisting of polyester polyols, acrylic polyols, and fluorine polyols that are liquid or solid at room temperature (a temperature of about 20° C. or higher and 30° C. or lower) are preferred.

[0088] When a polyol with a low Tg is used, the blocking property of the coating composition tends to decrease. The blocked polyisocyanate composition of this embodiment can maintain blocking property even when a polyol with a low Tg is used. Therefore, the blocked polyisocyanate composition of this embodiment is suitable for combination with a polyol with a Tg of 60°C or less or a fluorine polyol that generally has a low Tg.

[0089] The fluorine polyol is a polyol containing fluorine in the molecule, and examples thereof include copolymers of fluoroolefins, cyclovinyl ethers, hydroxyalkyl vinyl ethers, and monocarboxylic acid vinyl esters, as disclosed in JP-A-57-34107 (Reference 3) and JP-A-61-275311 (Reference 4).

[0090] Examples of polyester polyols include, but are not limited to, products obtained by condensation reaction of a dibasic acid or a mixture thereof with a polyhydric alcohol or a mixture thereof. Examples of dibasic acids include, but are not limited to, at least one dibasic acid selected from the group consisting of carboxylic acids such as succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, and terephthalic acid.

[0091] In the coating composition of this embodiment, the molar equivalent ratio of the available isocyanate groups of the blocked isocyanate composition to the hydroxyl groups of the polyol compound ([available isocyanate groups] / [hydroxyl groups]) can usually be set to 1 / 10 or more and 10 / 1 or less. Note that the term "available isocyanate groups (available NCO)" used here refers to isocyanate groups present in the blocked isocyanate composition that can participate in a crosslinking reaction.

[0092] The hydroxyl value of the polyol compound is preferably 20 mgKOH / g or more and 200 mgKOH / g or less, more preferably 30 mgKOH / g or more and 200 mgKOH / g or less, and even more preferably 40 mgKOH / g or more and 180 mgKOH / g or less. When the hydroxyl value of the polyol compound is equal to or more than the lower limit, a decrease in crosslink density can be prevented, and the desired physical properties can be more fully achieved. On the other hand, when the hydroxyl value of the polyol compound is equal to or less than the upper limit, an excessive increase in crosslink density can be suppressed, and the mechanical properties of the coating film can be maintained at a higher level.

[0093] The acid value of the polyol compound is preferably 1 mgKOH / g or more and 60 mgKOH / g or less, more preferably 2 mgKOH / g or more and 50 mgKOH / g or less, even more preferably 4 mgKOH / g or more and 40 mgKOH / g or less, and particularly preferably 6 mgKOH / g or more and 30 mgKOH / g or less.

[0094] When the acid value of the polyol compound is equal to or greater than the above lower limit, the storage stability can be further improved, whereas when the acid value is equal to or less than the above upper limit, the water resistance of the resulting coating film can be further improved.

[0095] When the polyol compound is a fluoropolyol, the acid value of the fluoropolyol is preferably 10 mgKOH / g or less.

[0096] <<Other Additives>> In addition to the blocked isocyanate composition and the active hydrogen compound, the coating composition of the present embodiment may further contain various additives depending on the purpose and application, such as a curing-accelerating catalyst, an antioxidant, an ultraviolet absorber, a light stabilizer, a pigment, a leveling agent, a plasticizer, a rheology control agent, a surfactant, etc.

[0097] The curing accelerator catalyst is not particularly limited, but specific examples include tin compounds, zinc compounds, titanium compounds, cobalt compounds, bismuth compounds, zirconium compounds, and amine compounds. Examples of tin compounds include dibutyltin dilaurate, dibutyltin diacetate, dioctyltin dilaurate, dimethyltin dineodecanoate, and tin bis(2-ethylhexanoate). Examples of zinc compounds include zinc 2-ethylhexanoate and zinc naphthenate. Examples of titanium compounds include titanium 2-ethylhexanoate and titanium diisopropoxybis(ethylacetonate). Examples of cobalt compounds include cobalt 2-ethylhexanoate and cobalt naphthenate. Examples of bismuth compounds include bismuth 2-ethylhexanoate and bismuth naphthenate. Examples of zirconium compounds include zirconium tetraacetylacetonate, zirconyl 2-ethylhexanoate, and zirconyl naphthenate.

[0098] <Method for Producing Coating Composition> When the coating composition of this embodiment is a powder coating composition, it can be produced, for example, by the method shown below. First, an active hydrogen compound (preferably a polyol compound) and the above-mentioned blocked isocyanate composition are kneaded together with the various additives as needed using an extruder or the like at a temperature range of 80°C to 140°C. The kneaded mixture is pulverized using a pulverizer, and the resulting pulverized product can be used as a powder coating composition. The average particle size of the resulting powder coating composition can be adjusted to, for example, 10 μm to 200 μm.

[0099] Alternatively, when producing a solvent-based coating composition, first, the various additives described above are added to the active hydrogen compound or its solvent dilution as needed. Next, the blocked isocyanate composition described above is added as a curing agent, and if needed, a solvent is further added to adjust the viscosity. Next, the mixture is stirred by hand or with a stirring device such as a mixer to obtain a solvent-based coating composition.

[0100] <Coating Film> The coating film of this embodiment is obtained by curing the coating composition described above. The coating film of this embodiment has excellent appearance such as gloss and image clarity.

[0101] The coating film of this embodiment can be produced, for example, by the following method: A coating composition (preferably a powder coating composition) is applied to the surface of a substrate by a commonly used method such as spray coating, roll coating, curtain flow coating, electrostatic coating, etc. Then, a uniform coating film is formed on the substrate by heating and baking at a temperature of 150°C or higher.

[0102] The coated body is primarily a metal plate, such as a stainless steel plate, an aluminum plate, a titanium plate, a cold-rolled steel plate, a zinc-plated steel plate, a chromium-plated steel plate, an aluminum-plated steel plate, or a nickel-plated steel plate. If necessary, the surface of the metal plate may be cleaned by alkaline degreasing or the like, or the metal surface may be chemically treated to improve adhesion to the coating film.

[0103] The metal plate may be a metal molded product that has been previously formed into a predetermined shape. Alternatively, if necessary, a primer layer may be previously formed on the metal surface. The coating thickness of the primer layer is preferably 100 μm or less.

[0104] The blocking agent released from the coating composition described above during baking onto the metal sheet is highly volatile, and little of it remains in the furnace. Furthermore, the resulting coating film has excellent weather resistance, impact resistance, surface gloss, and other properties. Therefore, precoated metal sheets provided with coating films obtained by curing the coating composition described above are suitable for use in, for example, household electrical appliances such as outer cases, doors, and other parts of refrigerators, washing machines, air conditioners, microwave ovens, and the like; building materials such as net fences and pipe fences, and road materials such as guardrails; automobile parts and automobile bodies such as wipers, coil springs, and bumpers; parts and bodies of specialized equipment such as civil engineering equipment and cultivators; office furniture such as steel furniture and steel shelves; and electrical equipment parts such as distribution boards, switchboards, radiators, and transformers. Because of their wide range of applications, the scope of application is not limited to those listed above.

[0105] Furthermore, examples of coated objects other than metal plates include concrete products, wood products, and plastic products.

[0106] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples in any way.

[0107] <Evaluation Items> According to the methods described below, the blocked isocyanate compositions produced in the Examples and Comparative Examples, the coating compositions containing the blocked isocyanate compositions, and the coating films obtained by curing the coating compositions were measured for various physical properties and evaluated.

[0108] <<Methods for Measuring Physical Properties>> [Physical Property 1] (Isocyanate Group (NCO) Content) The NCO content (mass%) of a triisocyanate compound and a polyisocyanate compound was determined by neutralizing the isocyanate groups in a measurement sample with an excess of 2N amine and then performing back titration with 1N hydrochloric acid.

[0109] [Physical Property 2] (Latent Isocyanate Group (NCO) Content) When a blocking agent having an active hydrogen on an N atom was reacted as a biuretizing agent, the latent NCO content (mass%) of the polyisocyanate compound was calculated using the following formula.

[0110] (Latent NCO content) = (NCO content of polyisocyanate compound) + [(content of raw isocyanate compound) x (NCO content of raw isocyanate compound) x {2 x (molar modification rate of biuretizing agent relative to raw isocyanate groups) - 1} + (total mass of polyisocyanate compounds) x (NCO content of polyisocyanate compound)] / (total mass of polyisocyanate compounds)

[0111] [Physical Property 3] (Available Isocyanate Group (NCO) Content) The available NCO content (mass%) of the blocked isocyanate composition was calculated using the following formula.

[0112] (Effective NCO content) = {(Content of raw isocyanate compound) × (NCO content or latent NCO content of raw isocyanate compound)} / (Total mass of blocked isocyanate composition)

[0113] [Property 4] (Proportion of triisocyanate represented by general formula (IV)) The proportion of triisocyanate represented by general formula (IV) was calculated from the peak area ratio in GPC measurement using the following apparatus: Apparatus: "HLC-8120GPC" (trade name) manufactured by Tosoh Corporation Column: "TSKgel Super H1000" (trade name) x 1, "TSKgel Super H2000" (trade name) x 1, "TSKgel Super H3000" (trade name) x 1, manufactured by Tosoh Corporation Carrier: tetrahydrofuran Detection method: differential refractometer Sample concentration: 0.5 wt / vol%, Flow rate: 0.6 mL / min, Column temperature: 40°C.

[0114] Evaluation Method

[0115] [Evaluation 1] (Blocking Resistance) A solid blocked isocyanate composition was crushed into a uniform powder, placed in a glass bottle, and left to stand in an oven at 45°C for 10 days. The bottle was then removed from the oven and the condition was visually inspected. The evaluation criteria were as follows: (Blocking Resistance Evaluation Criteria) A: No change B: Slight blocking C: Almost complete blocking D: Complete blocking

[0116] [Evaluation 1] (Paint blocking resistance) Polyester polyol (trade name "UPIKACOAT GV-150" manufactured by Japan U-PICA Corporation, Tg = 59°C) and each blocked isocyanate composition were blended in a ratio such that the molar equivalent ratio of available isocyanate groups to hydroxyl groups was 1.0, pulverized into a uniform powder, stirred, placed in a glass bottle, and left to stand in an oven at 45°C for 10 days. Thereafter, the bottle was removed from the oven, and the condition was visually confirmed. The evaluation criteria were as follows. (Evaluation criteria for blocking resistance) A: No change B: Slight blocking C: Almost complete blocking D: Complete blocking

[0117] [Production of Coating Composition C-1] A polyester polyol (trade name "UPICACOAT GV-150" manufactured by Japan U-PICA Corporation, Tg = 59°C) and each blocked isocyanate composition were blended in a ratio such that the molar equivalent ratio of available isocyanate groups to hydroxyl groups was 1.0. Next, 0.4 parts by mass of dibutyltin dilaurate, calculated as the mass of tin based on the mass of the coating solids, was added, and then chloroform was added to give a coating solids content of 30% by mass, thereby obtaining each coating composition C-1.

[0118] [Production of Coating Composition C-2] Polyester polyol (trade name "UPICACOAT GV-570" available from Japan U-PICA Corporation, Tg = 60°C) and each blocked isocyanate composition were blended in a ratio such that the molar equivalent ratio of available isocyanate groups to hydroxyl groups was 1.0. Next, 1.0 part by mass of benzoin relative to the mass of the coating solids and 40 parts by mass of titanium oxide relative to the mass of the coating solids were added, and then the coating was adjusted with chloroform to a ratio such that the coating solids content was 37% by mass, thereby obtaining each coating composition C-2.

[0119] [Evaluation 2] (Unbinding temperature (impact resistance test)) Each of the prepared coating compositions C-1 was applied to an alodine-treated aluminum plate in a dry film thickness of 40 μm and baked at 120 to 180°C for 30 minutes to obtain a coating film. The curability of the obtained coating film was measured using a DuPont impact resistance tester. The plate on which the coating film had been formed was placed on a support stand, an impact point (Φ1 / 2) was installed, and a 500 g load was dropped from a height of 30 cm, and the state of the coating film was observed. The lowest baking temperature at which no cracks or splits were observed in the coating film was taken as the unbinding temperature.

[0120] [Evaluation 3] (Gloss of coating film) The prepared coating composition C-2 was applied to an electrodeposited plate in a dry film thickness of 40 μm and baked at 150°C for 30 minutes to obtain a coating film. The 20° gloss of the prepared coating film was measured using a gloss meter UGV-6P (manufactured by Suga Test Instruments Co., Ltd.). The evaluation criteria are as follows. (Gloss evaluation criteria) A: Gloss of 80% or more B: Gloss of 75% or more but less than 80% C: Gloss of 70% or more but less than 75% D: Gloss less than 70%

[0121] [Evaluation 4] (Image clarity (DOI) of coating film) The prepared coating composition C-2 was applied to an electrodeposited plate in a dry film thickness of 40 μm and baked at 150° C. for 30 minutes to obtain a coating film. The prepared coating film was measured using a Wave-Scan Dual (manufactured by BYK) to obtain a DOI value. The evaluation criteria are as follows. (Evaluation criteria for DOI) A: Image clarity value of 80% or more B: Image clarity value of 75% or more but less than 80% C: Image clarity value of 70% or more but less than 75% D: Image clarity value of less than 70%

[0122] <Synthesis of Triisocyanate Compound> [Synthesis Example 1] (Synthesis of NTI) In a four-neck flask equipped with a stirrer, thermometer, and gas inlet tube, 1,060 g of 4-aminomethyl-1,8-octamethylenediamine (hereinafter sometimes referred to as "triamine") was dissolved in 1,500 g of methanol, and 1,800 mL of 35% by mass concentrated hydrochloric acid was slowly added dropwise to the solution while cooling. The solution was then concentrated by removing methanol and water under reduced pressure, and dried at 60°C / 5 mmHg for 24 hours to obtain triamine hydrochloride as a white solid. 650 g of the resulting triamine hydrochloride was suspended as a fine powder in 5,000 g of o-dichlorobenzene, and the reaction solution was heated with stirring. Next, when the reaction solution reached 100°C, phosgene was started to be blown in at a rate of 200 g / hour, and the temperature was continued to be raised. Next, when the reaction solution reached 180°C, the temperature was maintained, and phosgene was continued to be blown in for 12 hours. Subsequently, the dissolved phosgene and the solvent were distilled off under reduced pressure, and the residue was then vacuum distilled to obtain 420 g of colorless, transparent NTI having a boiling point of 161° C. to 163° C. / 1.2 mmHg. The NCO content of NTI was 50.0% by mass.

[0123] Synthesis Example 2 (Synthesis of HTI) 602 g of triethyl 1,3,6-hexamethylenetricarboxylate was reacted with hydrazine hydrate in a conventional manner to obtain 445 g of 1,3,6-hexamethylenetricarboxylic acid trihydrazide. This was then reacted with sodium nitrite in an aqueous solution in the presence of hydrochloric acid to form the corresponding triazide, which was then extracted with benzene and the extract was dried. The benzene solution thus obtained was added dropwise to refluxing benzene for thermal decomposition. The triisocyanate obtained by distilling off the benzene was rectified under vacuum to obtain 246 g of colorless, transparent HTI having a boiling point of 152°C to 154°C / 1.3 mmHg. The NCO content of HTI was 60.1% by mass.

[0124] Synthesis Example 3 (Synthesis of LTI) 122.2 g of ethanolamine, 100 ml of o-dichlorobenzene, and 420 ml of toluene were placed in a four-neck flask equipped with a stirrer, thermometer, and gas inlet tube, and ice-cooled hydrogen chloride gas was introduced to convert the ethanolamine to hydrochloride. Next, 182.5 g of lysine hydrochloride was added, and the reaction solution was heated to 80°C to dissolve the ethanolamine hydrochloride. Hydrogen chloride gas was then introduced to convert it to lysine dihydrochloride. Hydrogen chloride gas was then passed through at a rate of 20 to 30 ml / min, and the reaction solution was heated to 116°C and maintained at this temperature until water no longer distilled off. The resulting reaction mixture was recrystallized in a mixture of methanol and ethanol to obtain 165 g of lysine β-aminoethyl ester trihydrochloride. 100 g of this lysine β-aminoethyl ester trihydrochloride was suspended as a fine powder in 1200 ml of o-dichlorobenzene, and the reaction solution was heated with stirring. When the temperature reached 120°C, phosgene was started to be blown in at a rate of 0.4 mol / hour. The mixture was maintained for 10 hours, and then the temperature was raised to 150°C. Most of the suspension dissolved. After cooling, the mixture was filtered, and the dissolved phosgene and solvent were distilled off under reduced pressure. After vacuum distillation, 80.4 g of colorless, transparent LTI having a boiling point of 155°C to 157°C / 0.022 mmHg was obtained. The NCO content of the LTI was 47.1% by weight.

[0125] <Synthesis of Polyisocyanate (Prepolymer)> [Synthesis Example 4] (Synthesis of PI-1) A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube was conditioned with a nitrogen atmosphere, and 100 g of NTI, 20 g of trimethyl phosphate, 20 g of methyl cellosolve acetate, and 3.2 g of water were charged, and the temperature was maintained at 90°C for 1 hour. Thereafter, the temperature was increased to 160°C and maintained for 2 hours. The reaction liquid was filtered, and the solvent was removed using a falling thin-film distillation apparatus, yielding polyisocyanate compound PI-1. The NCO content of the resulting polyisocyanate compound PI-1 was 28.9% by mass.

[0126] Synthesis Example 5 Synthesis of PI-2' A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube was conditioned with a nitrogen atmosphere, and 100 g of NTI, 20 g of trimethyl phosphate, 20 g of methyl cellosolve acetate, and 2.1 g of water were charged, and the temperature was maintained at 90°C for 1 hour. Thereafter, the temperature was increased to 160°C and maintained for 2 hours. The reaction solution was filtered, and the solvent was removed using a falling thin-film distillation apparatus to obtain polyisocyanate compound PI-1'. The NCO content of the obtained polyisocyanate compound PI-2' was 36.2% by mass.

[0127] Synthesis Example 6 Synthesis of PI-3 A four-neck flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube was purged with nitrogen and charged with 100 g of LTI, 20 g of trimethyl phosphate, 20 g of methyl cellosolve acetate, and 2.5 g of water, and the temperature was maintained at 90°C for 1 hour. Thereafter, the temperature was increased to 160°C and maintained for 2 hours. The reaction solution was filtered, and the solvent was removed using a falling thin-film distillation apparatus to obtain polyisocyanate compound PI-3. The NCO content of the obtained polyisocyanate compound PI-3 was 30.6% by mass.

[0128] Synthesis Example 7 Synthesis of PI-3 A four-neck flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube was conditioned with a nitrogen atmosphere, and 100 g of HDI, 20 g of trimethyl phosphate, 20 g of methyl cellosolve acetate, and 1.3 g of water were charged, and the temperature was maintained at 90°C for 1 hour. Thereafter, the temperature was increased to 160°C and maintained for 2 hours. The reaction solution was filtered, and then unreacted monomers and the solvent were removed using a falling thin-film distillation apparatus, yielding polyisocyanate compound PI-4. The NCO content of the resulting polyisocyanate compound PI-4 was 21.2% by mass.

[0129] A four-neck flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen-inlet tube was purged with nitrogen and charged with 100 g of NTI, 43.3 g of dicyclohexylamine as a biuretizing agent, and 34.4 g of 3,5-dimethylpyrazole, and the temperature was maintained at 140° C. for 7 hours to obtain polyisocyanate compound PI-5. The resulting polyisocyanate compound PI-5 had a latent NCO content of 23.2% by mass.

[0130] [Synthesis Examples 9 to 16] (Synthesis of PI-6 to 13) Polyisocyanate compounds were obtained in the same manner as in Synthesis Example 7, except that the types, amounts of isocyanate and biuretizing agent, reaction temperature and reaction time were as shown in Tables 1 and 2. The latent NCO contents of the obtained polyisocyanate compounds are shown in Tables 1 and 2.

[0131]

[0132]

[0133] In Tables 1 and 2, the abbreviations used for materials refer to the above-mentioned NTI, HTI, and LTI as well as the following materials: HDI: hexamethylene diisocyanate DCHA: dicyclohexylamine DCPA: dicyclopentylamine DIPA: diisopropylamine CL: ε-caprolactam Pz: 3,5-dimethylpyrazole

[0134] In Tables 1 and 2, the prepolymer structure (estimated main structure) represents the following structure.

[0135]

[0136]

[0137]

[0138]

[0139] In the prepolymer structures (estimated main structures) in Tables 1 and 2, R １ ~R ４ represents the following structure: １ ~R ３are residues obtained by removing one isocyanate group from NTI, HTI, and LTI, respectively, and may include a structure obtained by removing an isocyanate group at a position different from that of the structure below.

[0140]

[0141] Example 1 Production of Blocked Isocyanate Composition BI-1 A four-neck flask equipped with a stirrer, a thermometer, and a gas inlet tube was purged with nitrogen, and 100.0 parts by mass of PI-5, 29.6 parts by mass of dicyclopentylamine, and 8.0 parts by mass of 3,5-dimethylpyrazole were added and reacted with stirring for 2 hours at 120° C. After completion of the reaction, blocked isocyanate composition BI-1 was obtained.

[0142] [Examples 2 to 9 and Comparative Examples 1 to 5] (Production of Blocked Isocyanate Compositions BI-1 to BI-14) Each blocked isocyanate composition was obtained in the same manner as in Example 1, except that the types and amounts of isocyanate and blocking agent were as shown in Tables 3 and 4.

[0143] The effective NCO content and the proportion of the triisocyanate represented by general formula (IV) (abbreviated as "proportion of (IV)" in Tables 3 and 4) of each of the obtained blocked isocyanate compositions are shown in Tables 3 and 4 below. The evaluation results are also shown in Tables 3 and 4 below.

[0144]

[0145]

[0146] In Tables 3 and 4, the abbreviations used for materials refer to the following materials in addition to the abbreviations used in Tables 1 and 2: Trz: 1,2,4-triazole

[0147] Examples 1 to 9 maintained good blocking resistance and provided excellent gloss and smoothness (image clarity) when formed into a coating film. Comparative Examples 1 and 3 to 5 provided poor blocking resistance. Comparative Example 2 provided poor smoothness (image clarity) when formed into a coating film.

[0148] The blocked isocyanate composition of the present embodiment can provide a blocked isocyanate composition that has excellent gloss and image clarity when formed into a coating film while maintaining good blocking resistance.

Claims

1. A blocked isocyanate composition comprising a blocked isocyanate derived from a polyisocyanate compound and a blocking agent, the polyisocyanate compound comprising a polyisocyanate compound represented by the following general formula (III): (In general formula (III), R ０１ are organic groups, which may be the same or different. ０１ At least one of R is a group represented by the following general formula (II)-1. ０２ is an organic group and a side chain derived from a blocking agent. ０２ may contain a ring structure instead of (In general formula (II)-1, a plurality of Y １１ are each independently a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms which may contain an ester structure and / or an ether structure. １１ may be the same or different. １１ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms. The wavy line represents a bond.

2. In the general formula (III), R ０１ The blocked isocyanate composition according to claim 1, wherein each of the above is a group represented by general formula (II)-1.

3. The blocked isocyanate composition according to claim 1 or 2, having a glass transition temperature of 50°C or higher and 120°C or lower.

4. The blocked isocyanate composition according to claim 1 or 2, wherein the polyisocyanate compound further contains a triisocyanate represented by the following general formula (IV): (In general formula (IV), a plurality of Y １０ are each independently a single bond or a divalent hydrocarbon group having 1 to 20 carbon atoms which may contain an ester structure and / or an ether structure. １０ may be the same or different. １０ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms.

5. The blocked isocyanate composition according to claim 3, wherein the proportion of the triisocyanate represented by general formula (IV) contained in the polyisocyanate compound is 20% by mass or more and 70% by mass or less.

6. The blocked isocyanate composition according to claim 1 or 2, wherein the blocking agent includes a blocking agent having a dissociation temperature of 120°C or higher and 150°C or lower.

7. The blocked isocyanate composition according to claim 1 or 2, wherein the blocking agent comprises an amine-based thermally dissociable blocking agent (b1) having a cycloalkane structure and a thermally dissociable blocking agent (b2) different from the amine-based thermally dissociable blocking agent (b1).

8. The blocked isocyanate composition according to claim 7, wherein the ratio of the amine-based thermally dissociable blocking agent (b1) to the total molar amount of the blocking agents is 20 mol % or more and 95 mol % or less.

9. The blocked isocyanate composition according to claim 7, wherein the ratio of the amine-based thermally dissociable blocking agent (b1) to the total molar amount of the blocking agents is 40 mol % or more and 80 mol % or less.

10. The blocked isocyanate composition according to claim 7, wherein the thermally dissociable blocking agent (b2) is at least one selected from the group consisting of pyrazole compounds, oxime compounds, lactam compounds, alcohol compounds, and triazole compounds.

11. The blocked isocyanate composition according to claim 7, wherein the thermally dissociable blocking agent (b2) is a pyrazole-based compound or a triazole-based compound.

12. The blocked isocyanate composition according to claim 7, wherein the ratio of the thermally dissociable blocking agent (b2) to the total molar amount of the blocking agents is 20 mol % or more and 60 mol % or less.

13. The blocked isocyanate composition according to claim 1 or 2, which is in powder form at 23°C.

14. The blocked isocyanate composition according to claim 1 or 2, which contains an amorphous portion.

15. A coating composition comprising the blocked isocyanate composition according to claim 1 or 2 and an active hydrogen compound.

16. A coating film obtained by curing the coating composition according to claim 15.

17. A coating composition comprising the blocked isocyanate composition according to claim 1 or 2 and a polyol having a Tg of 60°C or less.

18. The coating composition according to claim 17, wherein the polyol is a fluorine polyol.

19. A coating film obtained by curing the coating composition according to claim 17.

20. A method for producing a blocked isocyanate composition, comprising: a first step of reacting an aliphatic triisocyanate with a blocking agent having an active hydrogen on the N atom to obtain a prepolymer which is an aliphatic triisocyanate polymer and has a biuret structure; and a second step of further reacting the obtained prepolymer with the blocking agent.

21. A method for producing a blocked isocyanate composition according to claim 20, wherein the blocking agent having an active hydrogen on a N atom used in the first step is an amine-based thermally dissociable blocking agent (b1) having a cycloalkane structure, and the blocking agent used in the second step comprises an amine-based thermally dissociable blocking agent (b1) having a cycloalkane structure and a thermally dissociable blocking agent (b2) different from the amine-based thermally dissociable blocking agent (b1).

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