JP7260965B2 - blocked isocyanate and coating agent - Google Patents

Description

TECHNICAL FIELD The present invention relates to a blocked isocyanate and a coating agent, and more particularly to a blocked isocyanate and a coating agent containing the blocked isocyanate.

A blocked isocyanate is generally an isocyanate in which the blocking agent is dissociated by heating and the isocyanate group is regenerated. It is used as a curing agent for compounding two-component curing type polyurethane resins. A blocked isocyanate is obtained by reacting a polyisocyanate compound with a blocking agent.

It is known that xylylene diisocyanate and its isocyanurate derivative can be used as such a polyisocyanate compound (see, for example, Patent Document 1).

JP 2017-082208 A

However, when a blocked isocyanate is obtained by using an isocyanurate derivative obtained by simply converting xylylene diisocyanate into an isocyanurate, there is a problem that weather resistance and compatibility cannot be sufficiently improved.

An object of the present invention is to provide a blocked isocyanate having excellent weather resistance and compatibility, and a coating agent containing the blocked isocyanate.

The present invention [1] is a blocked isocyanate in which the isocyanate group of an isocyanate compound is blocked with a blocking agent, wherein the isocyanate compound contains an isocyanurate of xylylene diisocyanate, and the isocyanurate of xylylene diisocyanate is an alcohol It is a blocked isocyanate that has been modified with a class.

The present invention [2] contains the blocked isocyanate according to [1] above, wherein the alcohol is a dihydric alcohol.

In the present invention [3], the amount of modification of the alcohol with respect to 100 parts by mass of the xylylene diisocyanate exceeds 4 parts by mass and is 10 parts by mass or less, and the isocyanurate conversion rate of the isocyanate group of xylylene diisocyanate is , 15% by mass or more and less than 25% by mass of the blocked isocyanate described in [1] or [2] above.

The present invention [4] includes a coating agent containing a curing agent containing the blocked isocyanate described in the above [1] to [3] and a main agent containing a macropolyol.

In the blocked isocyanate of the present invention, the isocyanate group of the isocyanate compound is blocked with a blocking agent. Therefore, a coating agent having excellent storage stability can be obtained.

The isocyanate compound contains an isocyanurate of xylylene diisocyanate, and the isocyanurate of xylylene diisocyanate is modified with an alcohol. Therefore, a coating agent having excellent weather resistance and compatibility can be obtained.

Since the coating agent of the present invention contains the blocked isocyanate of the present invention, a cured film having excellent weather resistance and compatibility can be obtained.

In the blocked isocyanate of the present invention, the isocyanate group of the isocyanate compound is blocked with a blocking agent.

Specifically, a blocked isocyanate is a reaction product of an isocyanate compound and a blocking agent.

The isocyanate compound contains the isocyanurate of xylylene diisocyanate.

The isocyanurate of xylylene diisocyanate is a trimer of xylylene diisocyanate.

Examples of xylylene diisocyanate include 1,2-xylylene diisocyanate, 1,3-xylylene diisocyanate and 1,4-xylylene diisocyanate.

These xylylene diisocyanates can be used alone or in combination of two or more.

Xylylene diisocyanate preferably includes 1,4-xylylene diisocyanate, 1,3-xylylene diisocyanate, and more preferably 1,3-xylylene diisocyanate.

Moreover, such an isocyanurate of xylylene diisocyanate is modified with an alcohol by a method described later.

Specifically, such an isocyanurate of xylylene diisocyanate is obtained by subjecting xylylene diisocyanate and an alcohol to a urethanization reaction, then adding an isocyanurate catalyst to the urethane reaction liquid to obtain the urethane reaction liquid ( Specifically, xylylene diisocyanate and reaction products of xylylene diisocyanate and alcohols, hereinafter the same) are subjected to an isocyanurate reaction, and if necessary, unreacted xylylene diisocyanate is removed. can get.

More specifically, first, xylylene diisocyanate and alcohol are mixed and urethanized.

From the viewpoint of storage stability and reactivity, xylylene diisocyanate may contain an acid component.

The acid component is not particularly limited, and examples thereof include inorganic acids such as hydrogen chloride (hydrochloric acid), sulfuric acid, nitric acid and phosphoric acid, and organic acids such as sulfonic acid and acetic acid.

The acid component can be used singly or in combination of two or more.

The acid component preferably includes an inorganic acid, and more preferably includes hydrogen chloride.

The content of the acid component is not particularly limited. , 30 ppm or more, more preferably 40 ppm or more, for example, 100 ppm or less, preferably 80 ppm or less, more preferably 75 ppm or less, further preferably 70 ppm or less.

The acid component content is measured as a hydrogen chloride equivalent (ie acidity) in accordance with JIS K-1603-2:2007 (the same shall apply hereinafter).

The xylylene diisocyanate purity (that is, the content of xylylene diisocyanate in the xylylene diisocyanate composition) is, for example, 98.0% by mass or more, preferably 98.5% by mass or more, more preferably 99.0% by mass. % or more, and usually less than 100% by mass.

Examples of alcohols include monohydric alcohols and polyhydric alcohols.

Monohydric alcohols are organic compounds having one hydroxyl group in one molecule, and include methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n -nonanol, n-decanol, n-undecanol, n-dodecanol (lauryl alcohol), n-tridecanol, n-tetradecanol, n-pentadecanol, n-hexadecanol, n-heptadecanol, n-octa Linear monohydric alcohols such as decanol (stearyl alcohol), n-nonadecanol, eicosanol, isopropanol, isobutanol, sec-butanol, tert-butanol, isopentanol, isohexanol, isoheptanol, isooctanol, 2 -ethylhexan-1-ol, isononanol, isodecanol, 5-ethyl-2-nonanol, trimethylnonyl alcohol, 2-hexyldecanol, 3,9-diethyl-6-tridecanol, 2-isoheptylisoundecanol, 2- Examples include branched monohydric alcohols such as octyldodecanol and other branched alkanols (having 5 to 20 carbon atoms), preferably branched monohydric alcohols, and more preferably isobutanol.

Polyhydric alcohols are organic compounds having two or more hydroxyl groups in one molecule, and examples thereof include ethylene glycol, propylene glycol (1,2- or 1,3-propanediol or mixtures thereof), butylene glycol (1, 2- or 1,3- or 1,4-butylene glycol or mixtures thereof), 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2, alkane diols such as 2,2-trimethylpentanediol and 3,3-dimethylolheptane; dihydric alcohols such as ether diols such as diethylene glycol, triethylene glycol and dipropylene glycol; trihydric alcohols such as isopropanolamine; tetramethylolmethane (pentaerythritol); tetrahydric alcohols such as diglycerin; pentahydric alcohols such as xylitol; Examples include hexahydric alcohols such as inositol and dipentaerythritol, heptahydric alcohols such as perseitol, and aliphatic polyhydric alcohols such as octahydric alcohols such as sucrose.

Alcohols include preferably polyhydric alcohols, more preferably aliphatic polyhydric alcohols, still more preferably dihydric alcohols, particularly preferably butylene glycol, and most preferably 1,3-butylene glycol.

If the alcohol is a dihydric alcohol, a coating agent (described later) with excellent weather resistance and compatibility can be obtained.

The blending ratio of alcohols (the amount of alcohol modified with respect to 100 parts by mass of xylylene diisocyanate) is, for example, 2 parts by mass or more, preferably more than 4 parts by mass, more preferably more than 100 parts by mass of xylylene diisocyanate. is 5 parts by mass or more, for example, 15 parts by mass or less, preferably 10 parts by mass or less, and more preferably 8 parts by mass or less.

The amount of modification is synonymous with the amount of modification of alcohol with respect to isocyanurate of isocyanurate of xylylene diisocyanate modified with alcohol.

If the amount of modification is at least the lower limit, a coating agent (described later) with excellent weather resistance and compatibility can be obtained.

Moreover, if the amount of modification is equal to or less than the upper limit, a coating agent (described later) having excellent weather resistance can be obtained.

The equivalent ratio (NCO/OH) of the isocyanate group of xylylene diisocyanate to the hydroxyl group of the alcohol is, for example, 5 or more, preferably 10 or more, more preferably 20 or more, and usually 1000 or less.

Such mixing of xylylene diisocyanate and alcohols is carried out, for example, in an atmosphere of an inert gas such as nitrogen gas under normal pressure (atmospheric pressure). As the mixing conditions, the mixing temperature is, for example, room temperature (e.g., 25° C.) or higher, preferably 40° C. or higher, for example, 100° C. or lower, preferably 90° C. or lower, and the mixing time is, for example, 3 minutes or longer. , preferably 12 minutes or more, for example, 10 hours or less, preferably 6 hours or less.

In the above urethanization reaction, the urethane conversion rate of xylylene diisocyanate is, for example, 3% by mass or more, preferably 5% by mass or more, and is, for example, 25% by mass or less.

The urethane conversion rate can be obtained by calculating the rate of decrease in the concentration of isocyanate groups in the urethane reaction liquid with respect to the concentration of isocyanate groups in xylylene diisocyanate.

Next, an isocyanurate-forming catalyst is added to the obtained urethane reaction liquid, and the urethane reaction liquid is subjected to an isocyanurate-forming reaction.

The isocyanurate-forming catalyst is not particularly limited as long as it is an effective catalyst for isocyanurate-forming. Weak acid salts such as trialkylhydroxyalkylammonium hydroxides such as trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, triethylhydroxypropylammonium and triethylhydroxyethylammonium, and organic weak acid salts thereof such as acetic acid, caproic acid, octylic acid, Alkali metal salts of alkylcarboxylic acids such as myristic acid, metal salts of the above alkylcarboxylic acids such as tin, zinc and lead, metal chelate compounds of β-diketones such as aluminum acetylacetone and lithium acetylacetone, such as aluminum chloride , Friedel-Crafts catalysts such as boron trifluoride, various organometallic compounds such as titanium tetrabutylate and tributylantimony oxide, and aminosilyl group-containing compounds such as hexamethylsilazane.

Specific examples include Zwitter ion type hydroxyalkyl quaternary ammonium compounds, and more specific examples include N-(2-hydroxypropyl)-N,N,N-trimethylammonium-2 -ethylhexanoate, N,N-dimethyl-N-hydroxyethyl-N-2-hydroxypropylammonium hexanoate, triethyl-N-2-hydroxypropylammonium hexadecanoate, trimethyl-N-2-hydroxypropyl ammonium phenyl carbonate, trimethyl-N-2-hydroxypropylammonium formate, and the like.

These isocyanurate-forming catalysts can be used alone or in combination of two or more.

The isocyanuration catalyst preferably includes tetraalkylammonium hydroxide, more preferably tetrabutylammonium hydroxide.

The mode of use of the isocyanurate catalyst is not particularly limited, and the solid content of the isocyanurate catalyst may be used directly, or a catalyst solution obtained by dissolving the isocyanurate catalyst in an organic solvent may be used. .

Preferably, the isocyanuration catalyst is used as catalyst solution.

Examples of organic solvents in the catalyst solution include alcohols (e.g., methanol, ethanol, propanol, butanol, etc.), ketones (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), nitriles (e.g., acetonitrile, etc.). ), alkyl esters (e.g., methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, etc.), glycol ether esters (e.g., methyl cellosolve acetate, ethyl cellosolve acetate, methyl carbitol acetate, ethyl carbitol acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, 3-methyl-3-methoxybutyl acetate, ethyl-3-ethoxypropionate, etc.), ethers (e.g., diethyl ether, tetrahydrofuran, dioxane, etc.), polar aprotons (e.g., , N-methylpyrrolidone, dimethylformamide, N,N'-dimethylacetamide, dimethylsulfoxide, hexamethylphosphonylamide, etc.). The organic solvents can be used singly or in combination of two or more.

Among the organic solvents, preferred are glycol ether esters, and more preferred is propylene glycol methyl ether acetate.

The solid content concentration (the content of the isocyanurate-forming catalyst) of the catalyst solution is, for example, 60.0% by mass or less, preferably 50.0% by mass or less, and more preferably 10.0% by mass or less.

The addition ratio of the isocyanurate catalyst (in terms of solid content) is, for example, 0.001 parts by mass or more, preferably 0.005 parts by mass or more, for example 0.1 parts by mass, per 100 parts by mass of the urethane reaction liquid. Below, it is preferably 0.05 parts by mass or less.

If the addition ratio of the isocyanurate-forming catalyst is at least the above lower limit, the urethane reaction liquid can be reliably subjected to the isocyanurate-forming reaction. If the addition ratio of the isocyanurate-forming catalyst is equal to or less than the above upper limit, gel generation can be stably suppressed when the isocyanurate-forming catalyst is added to the urethane reaction liquid.

This isocyanurate-forming reaction is carried out, for example, in an inert gas atmosphere such as nitrogen gas under normal pressure (atmospheric pressure). As reaction conditions for the isocyanurate reaction, the reaction temperature is, for example, room temperature (e.g., 25°C) or higher, preferably 40°C or higher, more preferably 60°C or higher, for example, 100°C or lower, preferably 90°C. and the reaction time is, for example, 30 minutes or longer, preferably 1 hour or longer, more preferably 2 hours or longer, for example 12 hours or shorter, preferably 10 hours or shorter, more preferably 8 hours or shorter. be.

In the above isocyanurate-forming reaction, the conversion rate of isocyanurate of xylylene diisocyanate is, for example, 10% by mass or more, preferably 15% by mass or more, more preferably 18% by mass or more, and, for example, 30% by mass. % or less, preferably 25 mass % or less, more preferably 23 mass % or less.

If the isocyanurate conversion rate is at least the above lower limit, a coating agent (described later) with excellent weather resistance can be obtained.

Moreover, if the isocyanurate conversion rate is equal to or less than the above upper limit, a coating agent (described later) having excellent compatibility can be obtained.

The above isocyanurate conversion rate can be obtained by calculating the reduction rate of the isocyanate group concentration of the isocyanurate reaction liquid after the isocyanurate reaction with respect to the isocyanate group concentration of the urethane reaction liquid.

In coating agents (described later), weather resistance and compatibility depend on the above alcohol modification amount and isocyanurate conversion.

That is, when the coating agent (described later) contains a polyol component (main agent) and an isocyanate (curing agent) having a free isocyanate group, the main agent and curing agent are reacted with each other just before use. From the viewpoint of improving weather resistance, there is a tendency to increase the conversion rate of isocyanurate by increasing the amount of alcohol modification.

On the other hand, when the coating agent (described later) contains a polyol component (main agent) and blocked isocyanate (curing agent) blocked by a blocking agent, the main agent and curing agent are blended in advance, and the blocking agent is added at the time of use. It is dissociated and reacted, and it is required to ensure weather resistance and to improve the compatibility of the curing agent with the main agent.

Therefore, in the blocked isocyanate of the present invention, while increasing the amount of alcohol modification, if the isocyanurate conversion rate is decreased, specifically, the above-mentioned modification amount of alcohol is reduced to 100 parts by mass of xylylene diisocyanate. , more than 4 parts by mass, preferably 5 parts by mass or more, and 10 parts by mass or less, preferably 8 parts by mass or less, and the above isocyanurate conversion rate is 15% by mass or more, preferably 18 parts by mass. If it is at least 25% by mass and preferably at most 23% by mass, it is possible to obtain a coating agent (described later) which has excellent weather resistance and excellent compatibility with the main agent of the curing agent.

In the above isocyanurate-forming reaction, known additives such as antioxidants and co-catalysts (eg, organic phosphites) can be added as necessary.

The additive preferably includes an antioxidant.

Antioxidants include, for example, phenolic antioxidants and hindered phenolic antioxidants. From the viewpoint of hygiene, hindered phenolic antioxidants are preferred. Specific examples of hindered phenol-based antioxidants include, for example, 2,6-di(tert-butyl)-4-methylphenol (also known as dibutylhydroxytoluene, hereinafter sometimes abbreviated as BHT), [3-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoyloxy]-2,2-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl ) propanoyloxymethyl]propyl]3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate (Irganox 1010, manufactured by Ciba Japan, trade name), octadecyl 3-(3,5-di -tert-butyl-4-hydroxyphenyl) propionate (Irganox 1076, manufactured by Ciba Japan, trade name), 3-(4-hydroxy-3,5-diisopropylphenyl) propionic acid octyl ester (Irganox 1135, Ciba Japan Co., Ltd., trade name), bis[3-(3-methyl-4-hydroxy-5-tert-butylphenyl)propionic acid] ethylene bisoxybisethylene (Irganox 245, Ciba Japan Co., trade name) ) and the like.

These antioxidants can be used alone or in combination of two or more.

From the viewpoint of hygiene, the antioxidant preferably includes hindered phenol antioxidants other than BHT, more preferably octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl ) propionate (Irganox 1076, manufactured by Ciba Japan Co., Ltd., trade name).

The timing of adding the additive is not particularly limited, and it may be added to the xylylene diisocyanate or urethane reaction solution before the isocyanurate-forming reaction, or added to the isocyanurate reaction solution during the isocyanurate-forming reaction. Further, it may be added to the isocyanurate reaction solution after the isocyanurate-forming reaction. Preferably, it is added to xylylene diisocyanate.

The addition ratio of the additive is appropriately set according to the purpose and application.

In the above reaction, the isocyanurate-forming reaction is terminated by adding a catalyst deactivator after the isocyanurate conversion reaches the above range.

Examples of catalyst deactivators include phosphoric acid compounds, sulfonic acid compounds, and sulfonamide compounds.

Examples of phosphoric acid compounds include phosphoric acid and phosphoric acid esters. Phosphate esters include, for example, methyl phosphate, ethyl phosphate, propyl phosphate, butyl phosphate, dipropyl phosphate, butoxyethyl phosphate, 2-ethylhexyl phosphate, bis(2-ethylhexyl) phosphate, phosphoric acid (C12-18) alkyl, isotridecyl phosphate, oleyl phosphate, tetracosyl phosphate, ethylene glycol phosphate, 2-hydroxyethyl methacrylate phosphate, dibutyl phosphate and the like.

Examples of sulfonic acid compounds include sulfonic acid and sulfonic acid esters. Sulfonic acids include, for example, dodecylbenzenesulfonic acid and p-toluenesulfonic acid. Sulfonic acid esters include, for example, dodecylbenzenesulfonic acid alkyl esters such as methyl dodecylbenzenesulfonate, ethyl dodecylbenzenesulfonate, propyl dodecylbenzenesulfonate, and butyl dodecylbenzenesulfonate; p-toluenesulfonic acid alkyl esters such as ethyl sulfonate, propyl p-toluenesulfonate, and butyl p-toluenesulfonate;

Examples of sulfonamide compounds include aromatic sulfonamides (e.g., benzenesulfonamide, dimethylbenzenesulfonamide, sulfanilamide, o- and p-toluenesulfonamide, hydroxynaphthalenesulfonamide, naphthalene-1-sulfonamide, naphthalene -2-sulfonamide, m-nitrobenzenesulfonamide, p-chlorobenzenesulfonamide, etc.), aliphatic sulfonamides (e.g., methanesulfonamide, N,N-dimethylmethanesulfonamide, N,N-dimethylethanesulfonamide, N,N-diethylmethanesulfonamide, N-methoxymethanesulfonamide, N-dodecylmethanesulfonamide, N-cyclohexyl-1-butanesulfonamide, 2-aminoethanesulfonamide, etc.).

In addition to the above, examples of the catalyst deactivator include monochloroacetic acid and benzoyl chloride.

These catalyst deactivators can be used alone or in combination of two or more.

The catalyst deactivator also acts as a storage stabilizer for the isocyanurate reaction solution.

Catalyst deactivators preferably include phosphoric acid compounds and/or sulfonic acid compounds. In other words, the catalyst deactivator preferably includes phosphoric acid and/or sulfonic acid, or esters thereof.

From this point of view, the catalyst deactivator is more preferably sulfonic acid, and particularly preferably dodecylbenzenesulfonic acid.

The mode of use of the catalyst deactivator is not particularly limited, and the active ingredient of the catalyst deactivator may be used directly, or a catalyst deactivator solution in which the catalyst deactivator is dissolved in the above organic solvent may be used. Preferably, a catalyst deactivator solution is used.

When the catalyst deactivator is used as the catalyst deactivator solution, the organic solvent preferably includes glycol ether esters, more preferably propylene glycol methyl ether acetate.

In addition, the active ingredient concentration of the catalyst deactivator (the content ratio of the catalyst deactivator) is, for example, 10% by mass or more, preferably 20% by mass or more, for example, 70% by mass or less, preferably 60% by mass or less. is.

Further, the addition ratio of the catalyst deactivator (in terms of active ingredients) is, for example, 300 ppm or more, preferably 400 ppm or more, for example, 3000 ppm or less, preferably 1000 ppm or less, relative to the total amount of the isocyanurate reaction solution. More preferably, it is 800 ppm or less.

As a result, an isocyanurate reaction solution containing the isocyanurate of xylylene diisocyanate and unreacted xylylene diisocyanate can be obtained.

Further, to the obtained isocyanurate reaction solution, if necessary, by adding a known acid such as hydrogen chloride or a xylylene diisocyanate having a high acidity (for example, a xylylene diisocyanate composition having an acidity of 2000 ppm or more). , the acidity can also be adjusted.

In this method, after the isocyanurate-forming reaction is completed, a separated liquid containing isocyanurate of xylylene diisocyanate and a recovered liquid containing unreacted xylylene diisocyanate are separated from the isocyanurate reaction liquid. .

Although the method for separating these is not particularly limited, for example, a thin film distillation apparatus is used.

Distillation conditions for thin film distillation include a distillation temperature of, for example, 120° C. or higher, preferably 150° C. or higher, and for example, 250° C. or lower, preferably 200° C. or lower. Also, the distillation pressure (absolute pressure) is, for example, 1 PaA or higher and, for example, 60 PaA or lower.

Also, the feed amount of the isocyanurate reaction solution is, for example, 1 g/hour or more, preferably 5 g/hour or more, and is, for example, 1000 g/hour or less, preferably 500 g/hour or less.

Thereby, the separated liquid containing the isocyanurate of xylylene diisocyanate is separated as a high boiling point component.

If necessary, the above organic solvent can be added in an appropriate proportion to the separated liquid containing the isocyanurate of xylylene diisocyanate to adjust the solid content concentration.

In such a case, the solid content concentration is, for example, 10% by mass or more, preferably 20% by mass or more, and for example, 100% by mass or less, preferably 90% by mass or less.

In such a case, the isocyanurate of xylylene diisocyanate can be reacted with a blocking agent to be described later in the reaction liquid containing the organic solvent.

If necessary, the above-mentioned catalyst deactivator (storage stabilizer) can be further added to the separated liquid containing the isocyanurate of xylylene diisocyanate to adjust the content ratio within the above range.

In addition, the separated liquid containing isocyanurate of xylylene diisocyanate may optionally contain known additives such as plasticizers, antiblocking agents, heat stabilizers (such as the above sulfonamide compounds), light resistance Stabilizers, antioxidants, release agents, pigments, dyes, lubricants, fillers, anti-hydrolysis agents and the like can be added.

This gives an alcohol-modified isocyanurate of xylylene diisocyanate.

In addition, since the isocyanurate of xylylene diisocyanate is modified with an alcohol, a coating agent (described later) having excellent weather resistance and compatibility can be obtained.

The blocked isocyanate is obtained by reacting the above isocyanate compound with a blocking agent.

The blocking agent is not particularly limited, and known blocking agents are employed. Examples include imidazole compounds, imidazoline compounds, pyrimidine compounds, guanidine compounds , phenol compounds, active methylene compounds, amine compounds, imines, -based compounds, oxime-based compounds, carbamic acid-based compounds, urea-based compounds, acid amide-based (lactam-based) compounds, acid imide-based compounds, triazole-based compounds, pyrazole-based compounds, mercaptan-based compounds, bisulfites, and the like.

Examples of imidazole compounds include imidazole (dissociation temperature 100° C.), benzimidazole (dissociation temperature 120° C.), 2-methylimidazole (dissociation temperature 70° C.), 4-methylimidazole (dissociation temperature 100° C.), 2-ethyl imidazole (dissociation temperature 70° C.), 2-isopropylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole and the like.

Examples of imidazoline compounds include 2-methylimidazoline (dissociation temperature: 110° C.) and 2-phenylimidazoline.

Examples of pyrimidine compounds include 2-methyl-1,4,5,6-tetrahydropyrimidine.

Examples of guanidine-based compounds include 3,3-dialkylguanidines such as 3,3-dimethylguanidine; 3-tetraalkylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene and the like.

Examples of phenolic compounds include phenol, cresol, ethylphenol, n-propylphenol, isopropylphenol, n-butylphenol, s-butylphenol, t-butylphenol, n-hexylphenol, 2-ethylhexylphenol, n-octylphenol, n -nonylphenol, di-n-propylphenol, diisopropylphenol, isopropylcresol, di-n-butylphenol, di-s-butylphenol, di-t-butylphenol, di-n-octylphenol, di-2-ethylhexylphenol, di-n -nonylphenol, nitrophenol, bromophenol, chlorophenol, fluorophenol, dimethylphenol, styrenated phenol, methyl salicylate, methyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, 2-ethylhexyl hydroxybenzoate, 4- [(dimethylamino)methyl]phenol, 4-[(dimethylamino)methyl]nonylphenol, bis(4-hydroxyphenyl)acetic acid, 2-hydroxypyridine (dissociation temperature 80° C.), 2- or 8-hydroxyquinoline, 2- Chloro-3-pyridinol, pyridine-2-thiol (dissociation temperature 70° C.) and the like.

Active methylene compounds include, for example, Meldrum's acid, dialkyl malonate (e.g., dimethyl malonate, diethyl malonate, di-n-butyl malonate, di-t-butyl malonate, di-2-ethylhexyl malonate, malonic acid Methyl n-butyl, ethyl n-butyl malonate, methyl s-butyl malonate, ethyl s-butyl malonate, methyl t-butyl malonate, ethyl t-butyl malonate, diethyl methylmalonate, dibenzyl malonate, malonate diphenyl acid, benzylmethyl malonate, ethylphenyl malonate, t-butylphenyl malonate, isopropylidene malonate, etc.), alkyl acetoacetates (e.g. methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate) , n-butyl acetoacetate, t-butyl acetoacetate, benzyl acetoacetate, phenyl acetoacetate, etc.), 2-acetoacetoxyethyl methacrylate, acetylacetone, ethyl cyanoacetate and the like.

Examples of amine compounds include dibutylamine, diphenylamine, aniline, N-methylaniline, carbazole, bis(2,2,6,6-tetramethylpiperidinyl)amine, di-n-propylamine, diisopropylamine ( dissociation temperature 130° C.), isopropylethylamine, 2,2,4- or 2,2,5-trimethylhexamethyleneamine, N-isopropylcyclohexylamine (dissociation temperature 140° C.), dicyclohexylamine (dissociation temperature 130° C.), Bis(3,5,5-trimethylcyclohexyl)amine, piperidine, 2,6-dimethylpiperidine (dissociation temperature 130°C), t-butylmethylamine, t-butylethylamine (dissociation temperature 120°C), t-butylpropylamine , t-butylbutylamine, t-butylbenzylamine (dissociation temperature 120°C), t-butylphenylamine, 2,2,6-trimethylpiperidine, 2,2,6,6-tetramethylpiperidine (dissociation temperature 80°C) , (dimethylamino)-2,2,6,6-tetramethylpiperidine, 2,2,6,6-tetramethyl-4-piperidine, 6-methyl-2-piperidine, 6-aminocaproic acid and the like.

Examples of imine compounds include ethyleneimine, polyethyleneimine, 1,4,5,6-tetrahydropyrimidine and guanidine.

Examples of oxime compounds include formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketone oxime (dissociation temperature 130° C.), cyclohexanone oxime, diacetylmonoxime, benzophenoxime, 2,2,6,6-tetramethyl Cyclohexanone oxime, diisopropyl ketone oxime, methyl t-butyl ketone oxime, diisobutyl ketone oxime, methyl isobutyl ketone oxime, methyl isopropyl ketone oxime, methyl 2,4-dimethylpentyl ketone oxime, methyl 3-ethylheptyl ketone oxime, methyl isoamyl ketone oxime, n-amyl ketone oxime, 2,2,4,4-tetramethyl-1,3-cyclobutanedione monoxime, 4,4'-dimethoxybenzophenone oxime, 2-heptanone oxime and the like.

Carbamic acid compounds include, for example, phenyl N-phenylcarbamate.

Urea-based compounds include, for example, urea, thiourea, and ethyleneurea.

Acid amide (lactam) compounds include, for example, acetanilide, N-methylacetamide, acetic amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam, pyrrolidone, 2,5-piperazinedione, laurolactam, and the like. be done.

Examples of acid imide compounds include succinimide, maleic acid imide, and phthalimide.

Examples of triazole compounds include 1,2,4-triazole and benzotriazole.

Examples of pyrazole compounds include pyrazole, 3,5-dimethylpyrazole (dissociation temperature 120° C.), 3,5-diisopropylpyrazole, 3,5-diphenylpyrazole, 3,5-di-t-butylpyrazole, 3- methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, 3-methyl-5-phenylpyrazole and the like.

Mercaptan compounds include, for example, butyl mercaptan, dodecyl mercaptan, hexyl mercaptan and the like.

Bisulfites include, for example, sodium bisulfite.

Blocking agents can be used alone or in combination of two or more.

Blocking agents are preferably phenol compounds , active methylene compounds, oxime compounds and pyrazole compounds, more preferably oxime compounds and pyrazole compounds, still more preferably methyl ethyl ketone oxime and 3,5-dimethylpyrazole. , 3,5-dimethylpyrazole is particularly preferred from the viewpoint of weather resistance and compatibility.

In order to react the isocyanate compound and the blocking agent, the isocyanate compound and the blocking agent are mixed.

As for the mixing ratio of the isocyanate compound and the blocking agent, the equivalent ratio (active group/isocyanate group) of the active group that reacts with the isocyanate group in the blocking agent (that is, the blocking group) to the isocyanate group of the isocyanate compound is, for example, It is 0.8 or more, preferably 1.0 or more, and is, for example, 1.5 or less, preferably 1.2 or less, more preferably 1.1 or less.

Moreover, the above reaction is carried out, for example, under atmospheric pressure in an atmosphere of an inert gas (eg, nitrogen gas, argon gas, etc.).

As the reaction conditions, the reaction temperature is, for example, 20° C. or higher, preferably 30° C. or higher, and, for example, 80° C. or lower, preferably 70° C. or lower, and the reaction time is 0.5 hours. Above, it is preferably 1 hour or more, and is, for example, 6 hours or less, preferably 3 hours or less.

The completion of the reaction can be determined, for example, by using infrared spectroscopy and measurement of amine equivalent to confirm disappearance or reduction of isocyanate groups.

Moreover, the above reaction may be carried out in the absence of a solvent or, for example, in the presence of a solvent.

Examples of the solvent include the above organic solvents.

Moreover, in the above reaction, if necessary, a blocking catalyst can be added.

Examples of blocked catalysts include basic compounds, and specific examples include alkali metal alcoholates such as sodium methylate, sodium ethylate, sodium phenolate, potassium methylate, tetramethylammonium, Hydroxides of tetraalkylammonium such as tetraethylammonium, tetrabutylammonium, acetates such as tetraalkylammonium, weak organic acid salts such as octylate, myristate, benzoate such as acetic acid, caproic acid, octyl Acids, alkali metal salts of alkylcarboxylic acids such as myristic acid, metal salts of the above alkylcarboxylic acids such as tin, zinc, and lead, aminosilyl group-containing compounds such as hexamethylenedisilazane, such as lithium and sodium , hydroxides of alkali metals such as potassium. These blocked catalysts can also be used as a solution dissolved in the above solvents or alcohols such as water, methanol, ethanol and propyl alcohol, if necessary.

These blocked catalysts can be used alone or in combination of two or more.

The blending ratio of the blocking catalyst is not particularly limited, but for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass with respect to 100 parts by mass of the isocyanate compound. It is at least 3 parts by mass, preferably 2 parts by mass or less, more preferably 0.3 parts by mass or less, still more preferably 0.2 parts by mass or less.

Then, by reacting the isocyanate compound with the blocking agent as described above, the isocyanate group of the isocyanate compound (specifically, the isocyanurate of xylylene diisocyanate) is blocked by the blocking agent to obtain a blocked isocyanate.

Moreover, such blocked isocyanate can also be used, for example, as a solution dissolved in the above solvent.

When the blocked isocyanate is dissolved in a solvent, the solid content concentration is, for example, 1% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, and for example, 95% by mass or less, preferably is 90% by mass or less.

In such blocked isocyanate, the isocyanate group of the isocyanate compound is blocked with a blocking agent. Therefore, a coating agent (described later) having excellent storage stability can be obtained.

Further, the isocyanate compound contains an isocyanurate of xylylene diisocyanate, and the isocyanurate of xylylene diisocyanate is modified with an alcohol. Therefore, a coating agent (described later) having excellent weather resistance and compatibility can be obtained.

The coating agent of the present invention contains a curing agent containing the above-described blocked isocyanate and a main agent containing a polyol component. This coating agent is obtained, for example, by separately preparing a curing agent comprising the above-described blocked isocyanate and a main agent comprising a polyol component, and blending them.

Curing agents can also contain other blocked isocyanates in addition to the blocked isocyanates described above.

Other blocked isocyanates include aliphatic diisocyanates such as 1,5-pentamethylene diisocyanate (PDI) and 1,6-hexamethylene diisocyanate (HDI) and blocked isocyanates of derivatives thereof such as bis(isocyanatomethyl). Alicyclic diisocyanates such as cyclohexane (H ₆ XDI), methylenebis(cyclohexyl isocyanate) (H ₁₂ MDI), norbornane diisocyanate (NBDI), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI) or their Derivative blocked isocyanates, for example, aromatic diisocyanates such as diphenylmethane diisocyanate (MDI) and tolylene diisocyanate (TDI), and blocked isocyanates of derivatives thereof.

Derivatives include, for example, isocyanurate derivatives, allophanate derivatives, biuret derivatives, uretdione derivatives, and alcohol-denatured products (adducts) with trihydric or higher alcohols.

The blending ratio of other blocked isocyanates is appropriately set according to the purpose and application.

The polyol component contains macropolyols. That is, the main agent contains macropolyol.

The macropolyol is a compound having two or more hydroxyl groups and having a number average molecular weight of 300 or more, preferably 400 or more, more preferably 500 or more, usually 20000 or less, preferably 10000 or less. Polyether polyols (e.g., polyoxyalkylene (carbon number (C) 2-3) polyols, polytetramethylene ether polyols, etc.), polyester polyols (e.g., adipic acid-based polyester polyols, phthalic acid-based polyester polyols, lactone-based polyester polyols etc.), polycarbonate polyols, polyurethane polyols (for example, polyether polyols, polyester polyols, polyols obtained by modifying polycarbonate polyols with polyisocyanate to urethane-modified), epoxy polyols, vegetable oil polyols, polyolefin polyols, acrylic polyols, vinyl monomer-modified polyols, etc. be done.

The hydroxyl value of the macropolyol is, for example, 50 mgKOH/g or more, and is, for example, 500 mgKOH/g or less, preferably 300 mgKOH/g or less, more preferably 180 mgKOH/g or less, still more preferably 150 mgKOH/g or less. , Especially preferably, it is 100 mgKOH/g or less.

Macropolyols can be used alone or in combination of two or more.

Preferred macropolyols include acrylic polyols and polyester polyols.

The polyol component can also include low molecular weight polyols.

Low-molecular-weight polyols include the alcohols described above, preferably polyhydric alcohols, more preferably dihydric to octahydric alcohols, still more preferably dihydric alcohols, trihydric alcohols, particularly preferably dihydric alcohols is mentioned.

Low-molecular-weight polyols can be used alone or in combination of two or more.

The blending ratio of the low-molecular-weight polyol is appropriately set according to the purpose and application.

The polyol component preferably consists of macropolyols.

The form of use of the polyol component is not particularly limited, and the polyol component may be used as it is, or a polyol component solution obtained by dissolving the polyol component in the above organic solvent may be used.

When the polyol component is used as the polyol component solution, preferred organic solvents include butyl acetate and cyclohexane.

The active ingredient concentration of the polyol component (polyol component content) is, for example, 10% by mass or more, preferably 20% by mass or more, for example, 80% by mass or less, preferably 70% by mass or less.

The blending ratio of the curing agent containing the blocked isocyanate and the main agent containing the macropolyol is, for example, the equivalent ratio of the isocyanate group of the blocked isocyanate (isocyanate group blocked by the blocking agent) to the hydroxyl group of the macropolyol (isocyanate group/activity hydrogen group) is, for example, 0.1 or more, preferably 0.2 or more, more preferably 0.3 or more, particularly preferably 0.9 or more, for example, 5 or less, preferably 3 or less, or more Preferably, the ratio is 1.1 or less.

When such a coating agent is used, the blocking agent is dissociated from the blocked isocyanate by, for example, heating.

The dissociation conditions are not particularly limited as long as the blocking agent in the blocked isocyanate dissociates. Specifically, the dissociation temperature is, for example, 40°C or higher, preferably 50°C or higher, such as 160°C. It is below.

The reaction time of the regenerated isocyanate group of the blocked isocyanate and the hydroxyl group of the polyol compound under heating conditions is, for example, 10 minutes or more, preferably 20 minutes or more, and for example, 60 minutes or less, preferably 30 minutes or less. is.

As a result, the blocking agent in the blocked isocyanate can be dissociated, and the regenerated isocyanate groups of the blocked isocyanate can react with the hydroxyl groups of the macropolyol to cure the coating agent.

The curing reaction can also proceed by aging at room temperature (20-30° C.).

In the above explanation, when the coating agent was used, the blocking agent was dissociated from the blocked isocyanate and the coating agent was cured. The agent can also be cured.

Also, such a coating agent can be used by dissolving it in a solvent, for example.

Examples of the solvent include the above organic solvents, preferably ethyl acetate. These can be used alone or in combination of two or more.

When the coating agent (main agent and curing agent) is dissolved in a solvent, the solid content concentration is, for example, 1% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more. 95% by mass or less, preferably 90% by mass or less.

In addition, if necessary, the coating agent further includes the above acidic compound, curing accelerator, ultraviolet absorber, light stabilizer, filler, silane coupling agent, epoxy resin, catalyst, coatability improver, leveling agents, nucleating agents, lubricants, release agents, antifoaming agents, thickeners, plasticizers, surfactants, pigments, pigment dispersants, dyes, organic or inorganic fine particles, antifungal agents, flame retardants, adhesion improvers, Additives such as matting agents can be included.

The timing of addition of these additives is not particularly limited, and may be added in advance to each component (blocked isocyanate, macropolyol, etc.), or may be added simultaneously when mixing each component. Alternatively, it may be added separately after mixing the above components.

Since such a coating agent contains the blocked isocyanate, it is possible to obtain a cured film (described later) that is excellent in weather resistance and compatibility.

Then, as a method of obtaining a cured film from a coating agent, for example, the coating agent is applied to a base material and cured under the above conditions.

The base material is not particularly limited, and examples thereof include (meth)acrylic resins such as polymethyl methacrylate resins, polycarbonate resins, and the like.

The method of applying the coating agent to the substrate is not particularly limited, and for example, coating by dip coating, spray coating, roll coating, doctor blade method, screen printing, etc., for example, bar coater, applicator, etc. The casting etc. which were used are mentioned.

Thereby, a cured film is obtained.

Moreover, if necessary, the cured film can be cured at 20° C. or higher and 300° C. or lower for 1 minute or longer and 30 days or shorter.

The resulting cured film contains the blocked isocyanate, and therefore has excellent weather resistance and compatibility.

Thus, the above blocked isocyanate is suitable for use as a coating agent.

Specific numerical values such as the mixing ratio (content ratio), physical property values, and parameters used in the following description are described in the above "Mode for Carrying Out the Invention", the corresponding mixing ratio (content ratio ), physical properties, parameters, etc. can. In the description below, "parts" and "%" are based on mass unless otherwise specified.

1. Details of Components Components used in Examples, Comparative Examples and Reference Examples are described below.
Takenate D-110N: trimethylolpropane modified xylylene diisocyanate, manufactured by Mitsui Chemicals, Inc., solid content concentration 75%, solvent (ethyl acetate)
1,3-BG: 1,3-butylene glycol IBA: isobutanol TMP: trimethylolpropane DMP: 3,5-dimethylpyrazole MEKO: methyl ethyl ketone oxime Q-166: acrylic polyol, Orester Q-166 (trade name, Mitsui chemical company), solvent (butyl acetate, cyclohexane), hydroxyl value (solid content) 60 mgKOH/g, hydroxyl value (in solvent) 29 mgKOH/g, solid content concentration 40%
Q-750: acrylic polyol, Orester Q-750 (trade name), manufactured by Mitsui Chemicals, solvent (butyl acetate, cyclohexane), hydroxyl value (solid content) 200 mgKOH/g, hydroxyl value (in solvent) 80 mgKOH/g, Solid content concentration 40%
LNB-800: polyester polyol, Takelac LNB-800 (trade name), hydroxyl value (solid content) 138 mgKOH/g, manufactured by Mitsui Chemicals, solid content concentration 100%
U-26: Polyester polyol, Takelac U-26 (trade name, manufactured by Mitsui Chemicals, Inc.) solvent replacement product, solvent (butyl acetate, cyclohexane), hydroxyl value (solid content) 162 mg KOH / g, hydroxyl value (in solvent) 114 mg KOH / g, solid content concentration 70%
2. Production of blocked isocyanate Example 1
Hydrogen chloride was added to 1,3-xylylene diisocyanate (m-XDI, manufactured by Mitsui Chemicals, Inc.) to adjust the acidity (according to JIS K-1603-2:2007) to 50 ppm.

In a reactor equipped with a thermometer, a stirrer, a condenser, and a nitrogen inlet tube, 100 parts by mass of the above 1,3-xylylenediisocyanate and octadecyl 3-(3,5-di-tert- 0.021 parts by mass (0.02 phr) of butyl-4-hydroxyphenyl)propionate (hindered phenol-based antioxidant, trade name: Irganox 1076, manufactured by Ciba Japan Co., Ltd.) was charged, and at 60 to 65 ° C. Mixed.

Then, 7 parts by mass of 1,3-butylene glycol was added to the mixture at 70° C. to 75° C. and mixed to carry out a urethanization reaction.

Next, a propylene glycol methyl ether acetate solution of tetrabutylammonium hydroxide (isocyanurate catalyst, TBAOH (37% methanol solution)) (solid concentration: 3.7% by mass) was added to the resulting urethane reaction solution. . The amount added was adjusted so that TBAOH (37% methanol solution) was 0.11 parts by mass (0.04 parts by mass as an active ingredient) with respect to the urethane reaction solution.

Next, while mixing the urethane reaction solution, 1,3-xylylene diisocyanate was subjected to an isocyanurate conversion reaction at 70° C. to 75° C. until the isocyanurate conversion of xylylene diisocyanate reached 20%.

Next, a propylene glycol methyl ether acetate solution (active ingredient concentration: 50% by mass) of dodecylbenzenesulfonic acid (DDBSA, catalyst deactivator) was added to the resulting isocyanurate reaction solution to terminate the isocyanurate reaction. . The amount added was adjusted so that DDBSA was 0.054 parts by mass (the ratio of DDBSA added was 500 ppm with respect to the isocyanurate reaction solution).

Then, the resulting isocyanurate reaction solution was further stirred at 70-75°C for 30 minutes. Next, in order to adjust the acidity, 2.66 parts by mass of a previously prepared xylylene diisocyanate composition having a high acidity (acidity of 2400 ppm) was added to the isocyanurate reaction solution, stirred for 30 minutes, and then cooled to 50°C or less. .

Next, the resulting isocyanurate reaction solution is subjected to thin film distillation (pressure: 60 PaA or less, temperature: 160° C., feed amount: 5 g/hour) to obtain a separated liquid containing the isocyanurate of xylylene diisocyanate and unreacted xylylene. The collected liquid containing diisocyanate was separated.

Ethyl acetate was added to the obtained separated liquid to adjust the solid content concentration to 75% by mass, and 0.04 parts by mass of p-toluenesulfonamide was added as a heat stabilizer.

As a result, an isocyanurate of 1,3-xylylene diisocyanate modified with 1,3-butylene glycol (7 parts by mass of alcohol modification, isocyanurate conversion of xylylene diisocyanate of 20%) was obtained.

The isocyanurate conversion rate was calculated by the following method.

Specifically, the isocyanate group concentrations of the urethane reaction solution and the isocyanurate reaction solution were measured according to the n-dibutylamine method of JIS K-1556 (2006).

Next, the isocyanurate conversion rate was obtained by calculating the rate of decrease in the isocyanate group concentration of the isocyanurate reaction liquid with respect to the isocyanate group concentration of the urethane reaction liquid.

Next, 44.4 parts by mass of DMP (blocking agent/isocyanate group = 1.02 (mol/mol)) was added as a blocking agent to 100 parts by mass of the isocyanurate of 1,3-xylylene diisocyanate, and the mixture was heated to 40 to 60°C. The reaction was allowed to proceed for 1 to 2 hours, and when the amine equivalent reached 20,000 or more, the reaction was stopped, and then ethyl acetate was added so that the solid content concentration was 70%.

Example 2, Example 5, Example 6, Example 8, Example 11 to Example 13, Example 16, Example 17, Example 19, Example 22 to Example 24, Example 27, Example 28, Example 30, Example 33 to Example 35, Example 38, Example 39, Example 41, Example 44 , Comparative Example 1 to Comparative Example 2 4, Reference Example 1 to Reference Example 8
A blocked isocyanate was obtained in the same manner as in Example 1, except that the formulation was changed according to the descriptions in Tables 1 to 4.
3. Production of cured film The blocked isocyanate of Example 1 and Q-166 were mixed at an equivalent ratio of 1.0 (NCO/OH = 1.0), and isopropyl alcohol was added so that the solid content concentration was 50%. Mixing at 23° C. for 5 minutes and then deaeration by sonication for 10 minutes gave a coating agent.

The resulting coating agent was applied to PMMA (polymethyl methacrylate) and a steel plate (SPCC steel plate, PBN-144 treated product) using a 4-mil applicator and heated in an oven at 150°C for 30 minutes to obtain a cured film. rice field.

Example 2, Example 5, Example 6, Example 8, Example 11 to Example 13, Example 16, Example 17, Example 19, Example 22 to Example 24, Example 27, Example 28, Example 30, Example 33 to Example 35, Example 38, Example 39, Example 41, Example 44, Comparative Example 1 to Comparative Example 4, Reference Example 1 to Reference Example 8
A cured film was obtained in the same manner as in Example 1, except that the formulation was changed according to the descriptions in Tables 1 to 4.
4. Evaluation (compatibility)
The haze of the cured film applied to PMMA of each example, each comparative example and each reference example was measured using a haze meter (NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd.).

Compatibility was evaluated according to the following criteria. The results are shown in Tables 1-4.
Evaluation criteria:
A: Less than 0.5 A: 0.5 or more and less than 1.
△: 1 or more and less than 20 ×: 20 or more (weather resistance)
Using an accelerated weather resistance tester (ultraviolet fluorescent light weather meter FUV, manufactured by Suga Test Instruments Co., Ltd.), the cured film applied to PMMA of each example, each comparative example and each reference example was tested in the daytime (60 ° C. × relative humidity 10 % x 4 hours x light irradiation) and nighttime (50°C x 95% relative humidity x 4 hours x no light irradiation) for 125 cycles. The cured film before and after the treatment was evaluated with a color difference meter (SE2000, manufactured by Nippon Denshoku Industries Co., Ltd.) to calculate the color difference (ΔE) before and after the treatment. Further, the glossiness was evaluated with a glossmeter (Nippon Denshoku Industries Co., Ltd., VG2000), and the gloss retention rate (after 1000 hours) was calculated when the initial glossiness was 100.

The color difference was evaluated according to the following criteria. The results are shown in Tables 1-4.
Evaluation criteria:
A: Less than 5 A: 5 or more and less than 10.
Δ: 10 or more and less than 15 ×: 15 or more or whitening In addition, the glossiness was evaluated according to the following criteria. The results are shown in Tables 1-4.
Evaluation criteria:
A: 95% or more B: 90% or more and less than 95%.
△: 50% or more and less than 90% ×: less than 50% or whitening (pencil hardness)
For the cured films applied to the steel sheets of each example, each comparative example and each reference example, the hardness at which the cured film does not break was evaluated according to JIS K 5600-5-4 (load: 1000 g). The results are shown in Tables 1-4.

Claims (4)

A blocked isocyanate in which the isocyanate group of the isocyanate compound is blocked with a blocking agent,
The isocyanate compound contains an isocyanurate of xylylene diisocyanate,
The isocyanurate of xylylene diisocyanate is an alcohol-modified isocyanurate of xylylene diisocyanate,
The amount of modification of the alcohol with respect to 100 parts by mass of the xylylene diisocyanate is 7 parts by mass or more and 15 parts by mass or less,
The isocyanurate conversion rate of the isocyanate group of the xylylene diisocyanate is 15% by mass or more and 20% by mass or less,
The alcohols are linear alkanemonools having 1 to 20 carbon atoms, branched alkanemonools having 3 to 20 carbon atoms, and/or alkanediols having 2 to 9 carbon atoms. A blocked isocyanate characterized by: 2. The blocked isocyanate according to claim 1, wherein the alcohol is an alkanediol having 2 to 9 carbon atoms . 3. The blocked isocyanate according to claim 1, wherein the modified amount of said alcohol with respect to 100 parts by mass of said xylylene diisocyanate is 10 parts by mass or less. A coating agent comprising a curing agent containing the blocked isocyanate according to any one of claims 1 to 3 and a main agent containing a macropolyol.