JP7343371B2 - Blocked isocyanate and coating agent - Google Patents

Description

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.

Blocked isocyanate is generally an isocyanate whose blocking agent dissociates and the isocyanate group is regenerated by heating.Because it has excellent storage stability and processability, it is used when using the main agent and curing agent in paints, adhesives, etc. It is used as a curing agent for two-component curing polyurethane resins. Moreover, a blocked isocyanate is obtained by reacting a polyisocyanate compound and a blocking agent.

It is known to use xylylene diisocyanate derivatives as polyisocyanate compounds in such block isocyanates. More specifically, for example, a blocked isocyanate obtained by reacting a trimethylolpropane adduct of xylylene diisocyanate with 1,1,3,3-tetramethylguanidine and 3,5-dimethylpyrazole as blocking agents. is known (for example, see Patent Document 1).

JP 2019-143004 Publication

On the other hand, block isocyanates are required to have excellent storage stability depending on the intended use. However, the above-mentioned blocked isocyanates may not have sufficient storage stability.

An object of the present invention is to provide a blocked isocyanate with excellent storage stability and a coating agent containing the blocked isocyanate.

The present invention [1] is a blocked isocyanate in which an isocyanate group of a xylylene diisocyanate derivative is blocked with a blocking agent, wherein the xylylene diisocyanate derivative contains an isocyanurate derivative of xylylene diisocyanate, and the xylylene diisocyanate derivative contains an isocyanurate derivative of xylylene diisocyanate. In the chromatogram obtained by measuring gel permeation chromatography, the area ratio of the area of the peak having a polystyrene equivalent molecular weight of 500 or more and less than 600 to the area of all peaks is 20% or more and 40% or less. , the blocking agent contains a blocked isocyanate containing at least one selected from the group consisting of a pyrazole blocking agent, an imidazole blocking agent, and an oxime blocking agent.

The present invention [2] provides that, in a chromatogram obtained by gel permeation chromatography measurement of the xylylene diisocyanate derivative, the area of a peak having a peak top with a molecular weight of 500 or more and less than 600 in terms of polystyrene is based on the area of all peaks. The blocked isocyanate described in [1] above has an area ratio of 30% or more, and the blocking agent contains a pyrazole-based blocking agent and/or an imidazole-based blocking agent.

The present invention [3] includes a coating agent characterized by containing a curing agent containing the blocked isocyanate described in [1] or [2] above, and a main ingredient containing a macropolyol.

In the blocked isocyanate of the present invention, the xylylene diisocyanate derivative contains an isocyanurate derivative of xylylene diisocyanate, and the isocyanate group of the xylylene diisocyanate derivative is blocked with a specific blocking agent. Furthermore, in a chromatogram obtained by gel permeation chromatography measurement of a xylylene diisocyanate derivative, the area ratio of the area of a peak having a peak top with a polystyrene equivalent molecular weight of 500 or more and less than 600 to the area of all peaks falls within a specific range. It is.

Therefore, the blocked isocyanate of the present invention has excellent storage stability.

Since the coating agent of the present invention contains the blocked isocyanate of the present invention, it has excellent storage stability.

FIG. 1 is a gel permeation chromatogram of the xylylene diisocyanate derivative in Example 1.

In the blocked isocyanate of the present invention, isocyanate groups of a xylylene diisocyanate derivative are blocked with a blocking agent.

In other words, a blocked isocyanate is a reaction product of a xylylene diisocyanate derivative and a blocking agent.

A xylylene diisocyanate derivative is a polyisocyanate composition containing isocyanate groups, and contains an isocyanurate derivative of xylylene diisocyanate as a main component (in a proportion of 90% by mass or more based on the total amount of xylylene diisocyanate derivatives). .

Isocyanurate derivatives of xylylene diisocyanate are multimers of xylylene diisocyanate containing one or more isocyanurate groups (isocyanurate rings) in the molecule. Examples of the multimer include isocyanurate trimolecular bodies, isocyanurate pentamolecular bodies, isocyanurate heptadole bodies, and the like.

Note that the isocyanurate n molecule body (n: natural number) refers to a derivative in which n molecules (n: natural number) of xylylene diisocyanate are bonded via an isocyanurate group (isocyanurate ring).

The isocyanurate derivative of xylylene diisocyanate can be obtained by subjecting xylylene diisocyanate to an isocyanurate reaction in the presence of an isocyanurate catalyst (described later).

Further, the isocyanurate derivative of xylylene diisocyanate is preferably modified with an alcohol.

That is, the isocyanurate derivative of xylylene diisocyanate is preferably prepared by first subjecting xylylene diisocyanate and alcohol to a urethane reaction, and then adding an isocyanurate catalyst to the urethane reaction solution. It is obtained by subjecting xylylene diisocyanate and a reaction product of xylylene diisocyanate and alcohol (the same applies hereinafter) to an isocyanurate reaction, and then, if necessary, removing unreacted xylylene diisocyanate.

More specifically, in this method, first, xylylene diisocyanate and alcohol are mixed and subjected to a urethane reaction.

As xylylene diisocyanate, 1,2-xylylene diisocyanate (o-xylylene diisocyanate (o-XDI)), 1,3-xylylene diisocyanate (m-xylylene diisocyanate (m-XDI)), 1,4- Xylylene diisocyanate (p-xylylene diisocyanate (p-XDI)) is mentioned as a structural isomer.

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

Preferred xylylene diisocyanates include 1,3-xylylene diisocyanate and 1,4-xylylene diisocyanate, more preferably 1,3-xylylene diisocyanate.

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, such as ethylene glycol, propylene glycol (1,2- or 1,3-propanediol or a mixture 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, Alkanediols such as 2,2-trimethylpentanediol, 3,3-dimethylolheptane; dihydric alcohols such as ether diols such as diethylene glycol, triethylene glycol, dipropylene glycol; trihydric alcohols such as isopropanolamine, e.g. tetramethylolmethane (pentaerythritol), tetrahydric alcohols such as diglycerin, pentahydric alcohols such as xylitol, e.g. sorbitol, mannitol, allitol, iditol, dulcitol, altritol, Examples include aliphatic polyhydric alcohols such as hexahydric alcohols such as inositol and dipentaerythritol, heptahydric alcohols such as perseitol, and octahydric alcohols such as sucrose.

From the viewpoint of storage stability, the alcohols are preferably polyhydric alcohols, more preferably aliphatic polyhydric alcohols, even more preferably dihydric alcohols, particularly preferably butylene glycol, and most preferably 1,3 -Butylene glycol.

The blending ratio of alcohols (the amount of modification of alcohol to 100 parts by mass of xylylene diisocyanate) is, for example, 0.5 parts by mass or more, preferably 0.5 parts by mass or more, based on 100 parts by mass of xylylene diisocyanate, from the viewpoint of storage stability. , more than 1 part by weight, more preferably 2 parts by weight or more, for example 15 parts by weight or less, preferably 10 parts by weight or less, and even more preferably 5 parts by weight or less.

In addition, the blending ratio (modification amount) of the alcohol is the same as the modification amount of the alcohol relative to the isocyanurate derivative in the isocyanurate derivative of xylylene diisocyanate that has been modified with the alcohol.

Further, the equivalent ratio (NCO/OH) of the isocyanate group of the xylylene diisocyanate to the hydroxy 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 alcohol is carried out, for example, in an inert gas atmosphere such as nitrogen gas and under normal pressure (atmospheric pressure). As for 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 higher. , 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, for example, 25% by mass or less.

The above urethane conversion rate can be determined by calculating the rate of decrease in the isocyanate group concentration of the urethane reaction solution with respect to the isocyanate group concentration of xylylene diisocyanate.

Next, in this method, 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 hydroxides of trialkylhydroxyalkylammonium such as trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, triethylhydroxypropylammonium, triethylhydroxyethylammonium, and their organic weak acid salts, such as acetic acid, caproic acid, octylic acid, Alkali metal salts of alkyl carboxylic acids such as myristic acid, e.g. metal salts such as tin, zinc, lead, etc. of the alkyl carboxylic acids mentioned above; e.g. metal chelate compounds of β-diketones such as aluminum acetylacetone, lithium acetylacetone, e.g. aluminum chloride , Friedel-Crafts catalysts such as boron trifluoride, various organometallic compounds such as titanium tetrabutyrate and tributylantimony oxide, and aminosilyl group-containing compounds such as hexamethylsilazane.

Specifically, examples include Zwitter ion type hydroxyalkyl quaternary ammonium compounds, and more specifically, 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 Examples include ammonium phenyl carbonate and trimethyl-N-2-hydroxypropylammonium formate.

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

Preferably, the isocyanurating catalyst includes tetraalkylammonium hydroxide, and more preferably tetrabutylammonium hydroxide.

The form 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 in which the isocyanurate catalyst is dissolved in an organic solvent may be used. .

Preferably, the isocyanuration catalyst is used as a catalyst solution.

In the catalyst solution, examples of organic solvents 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 alone 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 isocyanurating 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 isocyanurating catalyst (in terms of solid content) is, for example, 0.001 part by mass or more, preferably 0.005 part by mass or more, for example, 0.1 part by mass, per 100 parts by mass of the urethane reaction liquid. The amount is preferably 0.05 parts by mass or less.

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

This isocyanurate reaction is carried out, for example, in an inert gas atmosphere such as nitrogen gas and 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 more, preferably 1 hour or more, more preferably 2 hours or more, for example 12 hours or less, preferably 10 hours or less, and even more preferably 8 hours or less. be.

In the above isocyanurate reaction, the isocyanurate conversion rate of xylylene diisocyanate is, for example, 10% by mass or more, preferably 20% by mass, from the viewpoint of adjusting the Mn500-600 area ratio (triple body area ratio) described later. % or more, more preferably 25% by mass or more, and for example, 50% by mass or less, preferably 45% by mass or less, and more preferably 35% by mass or less.

Through such an isocyanurate reaction, an isocyanurate derivative of xylylene diisocyanate is obtained.

In addition, in the above-mentioned isocyanurate reaction, known additives such as an antioxidant and a co-catalyst (eg, organic phosphite) can be added as necessary.

Preferably, the additive includes an antioxidant.

Examples of the antioxidant include phenolic antioxidants and hindered phenolic antioxidants, and from the viewpoint of hygiene, hindered phenolic antioxidants are preferred. Specifically, the hindered phenolic 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, Ciba Japan Co., Ltd., trade name), 3-(4-hydroxy-3,5-diisopropylphenyl) propionic acid octyl ester (Irganox 1135, Ciba Japan Co., Ltd.)・Bis[3-(3-methyl-4-hydroxy-5-tert-butylphenyl)propionic acid]ethylenebisoxybisethylene (Irganox 245, manufactured by Ciba Japan Co., Ltd., trade name) ), etc.

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

From the viewpoint of hygiene, the antioxidant is preferably a hindered phenolic antioxidant other than BHT, and more preferably octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl). ) propionate (Irganox 1076, manufactured by Ciba Japan, 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 reaction, or it may be added to the isocyanurate reaction solution during the isocyanurate reaction. Furthermore, it may be added to the isocyanurate reaction solution after the isocyanurate reaction. Preferably, it is added to xylylene diisocyanate.

The addition ratio of additives is appropriately set depending on the purpose and use.

Further, in the above reaction, the isocyanurate conversion reaction is stopped by adding a catalyst deactivator after the isocyanurate conversion rate reaches the above range.

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

Examples of the phosphoric acid compound include phosphoric acid and phosphoric ester. Examples of phosphoric acid esters include methyl phosphate, ethyl phosphate, propyl phosphate, butyl phosphate, dipropyl phosphate, butoxyethyl phosphate, 2-ethylhexyl phosphate, bis(2-ethylhexyl) phosphate, and 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 the sulfonic acid compound include sulfonic acid and sulfonic acid ester. Examples of the sulfonic acid include dodecylbenzenesulfonic acid and paratoluenesulfonic acid. Examples of sulfonic acid esters include alkyl dodecylbenzenesulfonates such as methyl dodecylbenzenesulfonate, ethyl dodecylbenzenesulfonate, propyl dodecylbenzenesulfonate, butyl dodecylbenzenesulfonate, and methyl paratoluenesulfonate, paratoluene, etc. Examples include para-toluenesulfonic acid alkyl esters such as ethyl sulfonate, propyl para-toluenesulfonate, and butyl para-toluenesulfonate.

Sulfonamide compounds include, for example, 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 (for example, 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.

Note that the catalyst deactivator also acts as a storage stabilizer for the above-mentioned isocyanurate reaction solution.

Preferable examples of the catalyst deactivator include phosphoric acid compounds and/or sulfonic acid compounds. In other words, the catalyst deactivator preferably includes phosphoric acid and/or sulfonic acid, or an ester thereof.

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

The usage form 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 prepared by dissolving the catalyst deactivator in the above organic solvent may be used. May be used. Preferably, a catalyst deactivator solution is used.

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

In addition, the active ingredient concentration of the catalyst deactivator (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. It 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, and, for example, 3000 ppm or less, preferably 1000 ppm or less, based on the total amount of the isocyanurate reaction liquid. More preferably, it is 800 ppm or less.

Thereby, an isocyanurate reaction solution containing the isocyanurate derivative of xylylene diisocyanate and unreacted xylylene diisocyanate can be obtained.

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

The method for separating these is not particularly limited, but for example, a thin film distillation apparatus may be used.

Regarding the distillation conditions in thin film distillation, the distillation temperature is, for example, 120°C or higher, preferably 150°C or higher, and, for example, 250°C or lower, preferably 200°C or lower. Further, the distillation pressure (absolute pressure) is, for example, 1 PaA or more and, for example, 60 PaA or less.

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

As a result, a separated liquid containing the isocyanurate derivative of xylylene diisocyanate is separated as a high-boiling component.

The obtained separated liquid can be made into a xylylene diisocyanate derivative (polyisocyanate composition) containing an isocyanurate derivative of xylylene diisocyanate.

In the xylylene diisocyanate derivative (polyisocyanate composition), the isocyanurate derivative of xylylene diisocyanate contains an isocyanurate trimolecular body of xylylene diisocyanate as an essential component, and as an optional component, an isocyanurate derivative of xylylene diisocyanate. It can contain isocyanurate pentamolecular bodies, isocyanurate heptamolecular bodies of xylylene diisocyanate, and the like.

In the xylylene diisocyanate derivative (polyisocyanate composition), the mass ratio of the isocyanurate trimolecular body of xylylene diisocyanate is determined by measuring the xylylene diisocyanate derivative (polyisocyanate composition) using a gel permeation chromatograph equipped with a differential refractometer. In a chromatogram measured using a polystyrene equivalent molecular weight (number average molecular weight), the area ratio of the area of a peak having a peak top in the range of 500 to 600 to the area of all peaks (hereinafter referred to as Mn500-600 area ratio, or , is sometimes referred to as the trimolecular body area ratio).

The Mn500-600 area ratio (trimolecule area ratio) of the xylylene diisocyanate derivative is 20% or more, preferably 25% or more, from the viewpoint of suppressing high viscosity and improving the ease of manufacturing blocked isocyanate. From the viewpoint of storage stability of the blocked isocyanate, it is 40% or less, preferably 38% or less.

In particular, when the blocking agent described below contains a pyrazole-based blocking agent and/or an imidazole-based blocking agent, from the viewpoint of storage stability of the blocked isocyanate, it is more preferably 30% or more, and even more preferably 32% or more. Yes, and preferably 36% or less.

Note that the Mn500-600 area ratio (trimole area ratio) indicates the content ratio (mass ratio) of isocyanurate trimoles of xylylene diisocyanate to the total amount of the xylylene diisocyanate derivative (polyisocyanate composition).

In addition, in the xylylene diisocyanate derivative (polyisocyanate composition), the content ratio of isocyanurate polymers (pentamolecular, heptadone, etc.) of xylylene diisocyanate other than the isocyanurate trimolecular is not particularly limited, and is and is set as appropriate depending on the purpose.

Moreover, the xylylene diisocyanate derivative (polyisocyanate composition) can further contain derivatives other than the isocyanurate derivative as unavoidable impurities.

That is, in the above urethanization reaction and isocyanuration reaction, depending on the reaction conditions, in addition to the isocyanurate derivative of xylylene diisocyanate, for example, an allophanate derivative of xylylene diisocyanate, a biuret derivative of xylylene diisocyanate, a uretdione of xylylene diisocyanate, etc. Derivatives and the like may be obtained as by-products.

In such a case, the mass proportion of derivatives other than the isocyanurate derivative in the xylylene diisocyanate derivative (polyisocyanate composition) is appropriately set within a range that does not impair the excellent effects of the present invention. For example, the mass ratio of derivatives other than isocyanurate derivatives to the total amount of xylylene diisocyanate derivatives (polyisocyanate composition) is, for example, 10% by mass or less, preferably 5% by mass or less.

Moreover, in this method, the solid content concentration can be adjusted by adding the above-mentioned organic solvent in an appropriate ratio to the xylylene diisocyanate derivative (the above-mentioned separated liquid), if necessary.

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.

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

In addition, the separated liquid containing the isocyanurate derivative of xylylene diisocyanate may contain known additives, such as plasticizers, antiblocking agents, heat stabilizers (such as the above-mentioned sulfonamide compounds), as necessary. Light stabilizers, antioxidants, mold release agents, pigments, dyes, lubricants, fillers, hydrolysis inhibitors, and the like can be added.

Note that, for example, without separating as described above, the isocyanurate reaction solution containing an organic solvent can be reacted with the blocking agent described below as a xylylene diisocyanate derivative (polyisocyanate composition).

The blocked isocyanate is obtained by reacting the above xylylene diisocyanate derivative (polyisocyanate composition) with a blocking agent.

In the present invention, the blocking agent contains at least one selected from the group consisting of pyrazole blocking agents, imidazole blocking agents, and oxime blocking agents.

Examples of pyrazole blocking agents include pyrazole, 3,5-dimethylpyrazole (DMP, 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, etc. It will be done. These can be used alone or in combination of two or more. Preferably, 3,5-dimethylpyrazole (DMP) is used.

Examples of imidazole blocking agents include imidazole (IMZ, dissociation temperature 100°C), benzimidazole (dissociation temperature 120°C), 2-methylimidazole (dissociation temperature 70°C), 4-methylimidazole (dissociation temperature 100°C), Examples include 2-ethylimidazole (dissociation temperature 70°C), 2-isopropylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole. These can be used alone or in combination of two or more. Preferred is imidazole (IMZ).

Examples of oxime-based blocking agents include formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketone oxime (MEKO, dissociation temperature 130°C), cyclohexanone oxime, diacetylmonoxime, penzophenoxime, 2,2,6,6 -tetramethylcyclohexanone 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-ethyl heptyl ketone oxime, Examples include methylisoamylketone oxime, n-amylketone oxime, 2,2,4,4-tetramethyl-1,3-cyclobutanedione monooxime, 4,4'-dimethoxybenzophenone oxime, and 2-heptanone oxime. These can be used alone or in combination of two or more. Preferably, methyl ethyl ketone oxime (MEKO) is used.

When the blocking agent contains at least one selected from the group consisting of pyrazole-based blocking agents, imidazole-based blocking agents, and oxime-based blocking agents, excellent storage stability can be obtained.

From the viewpoint of improving storage stability, the blocking agent is preferably selected depending on the Mn500-600 area ratio (trimolecular body area ratio) of the xylylene diisocyanate derivative.

That is, when the Mn500-600 area ratio (tri-molecule area ratio) of the xylylene diisocyanate derivative is 30% or more (preferably 35% or more), from the viewpoint of storage stability, the blocking agent is preferably contains a pyrazole-based blocking agent and/or an imidazole-based blocking agent, more preferably one of a pyrazole-based blocking agent or an imidazole-based blocking agent, and even more preferably 3,5-dimethylpyrazole (DMP) or It contains imidazole (IMZ), and particularly preferably consists of 3,5-dimethylpyrazole (DMP) or imidazole (IMZ).

In addition, when the Mn500-600 area ratio (trimolecular area ratio) of the xylylene diisocyanate derivative is less than 30% (preferably 25% or less), from the viewpoint of storage stability, the blocking agent is preferably contains an oxime-based blocking agent, more preferably methyl ethyl ketone oxime (MEKO), particularly preferably methyl ethyl ketone oxime (MEKO).

In addition, the blocking agent may include other blocking agents (for example, imidazoline blocking agent, pyrimidine blocking agent, guanidine blocking agent, alcohol blocking agent, phenol blocking agent, Active methylene blocking agent, amine blocking agent, imine blocking agent, carbamate blocking agent, urea blocking agent, acid amide (lactam) compound, acid imide blocking agent, triazole blocking agent, mercaptan blocking agent agents, bisulfites, etc.). Preferably, the blocking agent does not contain any other blocking agent and is made of at least one selected from the group consisting of pyrazole-based blocking agents, imidazole-based blocking agents, and oxime-based blocking agents, and more preferably pyrazole-based blocking agents. and/or an imidazole-based blocking agent, more preferably a pyrazole-based blocking agent or an imidazole-based blocking agent.

In order to react the xylylene diisocyanate derivative and the blocking agent, for example, the xylylene diisocyanate derivative and the blocking agent are mixed.

The mixing ratio of the xylylene diisocyanate derivative and the blocking agent is determined by the equivalent ratio of the active group (i.e., blocking group) that reacts with the isocyanate group in the blocking agent to the isocyanate group of the xylylene diisocyanate derivative (active group/isocyanate group). is, for example, 0.8 or more, preferably 1.0 or more, and, for example, 1.5 or less, preferably 1.2 or less, more preferably 1.1 or less.

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

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

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

Furthermore, the above reaction may be carried out without a solvent or, for example, in the presence of a solvent.

Examples of the solvent include the above-mentioned organic solvents.

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

Examples of the blocking catalyst include basic compounds, specifically, alkali metal alcoholates such as sodium methylate, sodium ethylate, sodium phenolate, and potassium methylate; for example, tetramethylammonium; Tetraalkylammonium hydroxides such as tetraethylammonium, tetrabutylammonium, organic weak acid salts such as acetate, octylate, myristate, benzoate of tetraalkylammonium, such as acetic acid, caproic acid, octyl acids, alkali metal salts of alkylcarboxylic acids such as myristic acid, metal salts such as tin, zinc, lead, etc. of the alkylcarboxylic acids mentioned above, compounds containing aminosilyl groups such as hexamethylenedisilazane, e.g. lithium, sodium , hydroxides of alkali metals such as potassium, and the like. Moreover, these blocked catalysts can also be used as a solution dissolved in the above-mentioned 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. For example, the amount is 3 parts by weight or less, preferably 2 parts by weight or less, more preferably 0.3 parts by weight or less, still more preferably 0.2 parts by weight or less.

By reacting the xylylene diisocyanate derivative with the blocking agent as described above, the isocyanate group of the xylylene diisocyanate derivative (specifically, the isocyanurate derivative of xylylene diisocyanate) is blocked by the blocking agent, and the blocking agent is blocked. Isocyanate is obtained.

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

When the blocked isocyanate is dissolved in a solvent, the solid content concentration thereof 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 a blocked isocyanate, the xylylene diisocyanate derivative contains an isocyanurate derivative of xylylene diisocyanate, and the isocyanate group of the xylylene diisocyanate derivative is blocked with a specific blocking agent. Furthermore, in a chromatogram obtained by gel permeation chromatography measurement of a xylylene diisocyanate derivative, the area ratio of the area of a peak having a peak top with a polystyrene equivalent molecular weight of 500 or more and less than 600 to the area of all peaks falls within a specific range. It is.

Therefore, the above-mentioned blocked isocyanate has excellent storage stability.

As a result, the above-mentioned blocked isocyanate is used as a curing agent (crosslinking agent) for known resins such as polyurethane resins, polyolefin resins, polyacrylic resins, and polyester resins, for example, in the fields of coating agents, paints, inks, adhesives, etc. ) is suitably used.

In particular, the above-mentioned blocked isocyanate is suitably used as a curing agent for polyurethane resin in the field of coating agents.

The coating agent of the present invention contains a curing agent containing the above-mentioned blocked isocyanate and a main ingredient containing a polyol component. This coating agent can be obtained, for example, by separately preparing a curing agent made of the above-mentioned blocked isocyanate and a main ingredient made of a polyol component, and then blending them.

The curing agent can also contain other blocked isocyanates in addition to the above-mentioned blocked isocyanates.

Other blocked isocyanates include blocked isocyanates of aliphatic diisocyanates such as 1,5-pentamethylene diisocyanate (PDI) and 1,6-hexamethylene diisocyanate (HDI), or derivatives thereof, such as bis(isocyanatomethyl). Alicyclic diisocyanates such as _cyclohexane (H ₆ Blocked isocyanates of derivatives, such as aromatic diisocyanates such as diphenylmethane diisocyanate (MDI) and tolylene diisocyanate (TDI), and blocked isocyanates of derivatives thereof.

Examples of the derivative include isocyanurate derivatives, allophanate derivatives, biuret derivatives, uretdione derivatives, and trihydric alcohol adducts.

The blending ratio of other blocked isocyanates is appropriately set depending on the purpose and use.

The polyol component contains a macropolyol. That is, the main ingredient contains a macropolyol.

A macropolyol is a compound having two or more hydroxyl groups and a number average molecular weight of 300 or more, preferably 400 or more, more preferably 500 or more, but usually 20,000 or less, preferably 10,000 or less, for example, Polyether polyols (e.g. polyoxyalkylene (carbon number (C) 2-3) polyols, polytetramethylene ether polyols, etc.), polyester polyols (e.g. adipic acid polyester polyols, phthalic acid polyester polyols, lactone polyester polyols) ), polycarbonate polyols, polyurethane polyols (e.g. polyols obtained by urethane-modifying polyether polyols, polyester polyols, polycarbonate polyols, etc. with polyisocyanates), epoxy polyols, vegetable oil polyols, polyolefin polyols, acrylic polyols, vinyl monomer-modified polyols, etc. It will be done.

The hydroxyl value of the macropolyol is, for example, 50 mgKOH/g or more, and, 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. , particularly preferably 100 mgKOH/g or less.

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

Preferable macropolyols include acrylic polyols and polyester polyols.

The polyol component can also include low molecular weight polyols.

The low molecular weight polyol is an organic compound having two or more hydroxyl groups in one molecule and having a molecular weight of 40 or more and less than 400, preferably less than 300. Examples of the low molecular weight polyol include the above-mentioned alcohols, preferably polyhydric alcohols, more preferably dihydric to octahydric alcohols, still more preferably dihydric alcohols, trihydric alcohols, and particularly preferably dihydric alcohols. Examples include alcohols.

The low molecular weight polyols can be used alone or in combination of two or more types.

The blending ratio of the low molecular weight polyol is appropriately set depending on the purpose and use.

The polyol component preferably consists of a macropolyol.

Note that the usage form 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-mentioned organic solvent may be used.

When the polyol component is used as a polyol component solution, the organic solvent preferably includes butyl acetate and cyclohexane.

Further, the active ingredient concentration of the polyol component (the content ratio of the polyol component) is, for example, 10% by mass or more, preferably 20% by mass or more, and, 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 ingredient containing the polyol component is, for example, the equivalent ratio of the isocyanate group (isocyanate group blocked by the blocking agent) of the blocked isocyanate to the hydroxyl group of the polyol component (isocyanate group/active 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, 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, but specifically, the dissociation temperature is, for example, 40°C or higher, preferably 50°C or higher, such as 160°C. It is as follows.

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

Thereby, the blocking agent in the blocked isocyanate is dissociated, and the regenerated isocyanate group of the blocked isocyanate is reacted with the hydroxyl group of the polyol component, thereby making it possible to cure the coating agent.

Further, the curing reaction can also proceed by aging at room temperature (20 to 30°C).

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

Examples of the solvent include the above-mentioned 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 thereof is, for example, 1% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, for example, It is 95% by mass or less, preferably 90% by mass or less.

In addition, the coating agent may further contain the above acidic compounds, curing accelerators, ultraviolet absorbers, light stabilizers, fillers, silane coupling agents, epoxy resins, catalysts, coatability improvers, leveling agents, etc., as necessary. agent, nucleating agent, lubricant, mold release agent, antifoaming agent, thickener, plasticizer, surfactant, pigment, pigment dispersant, dye, organic or inorganic fine particles, antifungal agent, flame retardant, adhesion improver, It may contain additives such as matting agents.

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

Since such a coating agent contains the above-mentioned blocked isocyanate, it has excellent storage stability.

As a method for obtaining a cured film from a coating agent, for example, the coating agent is applied to a base material and subjected to a curing reaction under the above conditions.

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

The method of applying the coating agent to the base material is not particularly limited, and examples include application by dip coating, spray coating, roll coating, doctor blade method, screen printing, etc., for example, bar coater, applicator, etc. Examples include the casting used.

A cured film is thereby obtained.

Further, if necessary, the cured film can be cured at 20° C. or higher and 300° C. or lower for 1 minute or more and 30 days or less.

Thus, the above-mentioned blocked isocyanate is suitably used as a coating agent.

Specific numerical values such as blending ratios (content ratios), physical property values, parameters, etc. used in the following description are the corresponding blending ratios (content ratios) described in the above "Details of Carrying Out the Invention". ), physical property values, parameters, etc. can be replaced by the upper limit value (value defined as "less than" or "less than") or lower limit value (value defined as "more than" or "exceeding"). can. Furthermore, in the following description, unless otherwise specified, "parts" and "%" are based on mass.

1. GPC measurement method A sample was measured by gel permeation chromatography (GPC), and the area ratio of each peak area to the area of all peaks in the obtained chromatogram (chart) was determined.

Then, the area ratio of the peak having the peak top in the polystyrene equivalent molecular weight range of 500 or more and less than 600 (Mn500-600 area ratio) was defined as the content ratio of the isocyanurate trimolecular body.

In the GPC measurement, about 0.04 g of a sample was taken, and after methylurethanization with methanol, excess methanol was removed, and 10 mL of tetrahydrofuran was added to dissolve it. Then, the obtained solution was subjected to GPC measurement under the following conditions.
(1) Analyzer: Alliance (Waters)
(2) Pump: Alliance 2695 (Waters)
(3) Detector: 2414 type differential refraction detector (Waters)
(4) Eluent: Tetrahydrofuran
(5) Separation column: Plgel GUARD + Plgel 5μm Mixed-C x 3 (50 x 7.5 mm, 300 x 7.5 mm)
Manufacturer: Polymer Laboratories
Product number: PL1110-6500
(6) Measurement temperature: 40℃
(7) Flow rate: 1mL/min
(8) Sample injection volume: 100μL
(9) Analysis device: EMPOWER data processing device (Waters)
・System correction (1) Standard material name: Polystyrene
(2) Calibration curve creation method: Using TOSOH's TSK standard Polystyrene with different molecular weights, a graph of retention time and molecular weight was created.
(3) Injection volume, injection concentration: 100μL, 1mg/mL
Note that a gel permeation chromatogram of the polyisocyanate composition of Example 1 is shown in FIG.

2. Production of blocked isocyanate Examples 1 to 9, Comparative Examples 1 to 6 and Reference Examples 1 to 10
100 parts by mass of 1,3-xylylene diisocyanate (m-XDI, manufactured by Mitsui Chemicals) and octadecyl 3-( 0.021 part by mass (0.02 phr) of 3,5-di-tert-butyl-4-hydroxyphenyl) propionate (hindered phenolic antioxidant, trade name: Irganox 1076, manufactured by Ciba Japan). Charge and mix at 60°C to 65°C.

Next, 2 parts by mass of 1,3-butylene glycol were added to the mixture at 70° C. to 75° C. and mixed to cause a urethanization reaction.

Next, a propylene glycol methyl ether acetate solution (solid content concentration 3.7% by mass) of tetrabutylammonium hydroxide (isocyanurate catalyst, TBAOH (37% methanol solution)) was added to the obtained 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 added at 70°C to 75°C until the conversion rate of the isocyanurate derivative of xylylene diisocyanate reached the values listed in Tables 1 and 2. was subjected to an isocyanurate reaction.

Note that the conversion rate of the isocyanurate derivative was calculated by the following method.

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

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

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

Next, the obtained isocyanurate reaction solution was further stirred at 70 to 75°C for 30 minutes. Next, the obtained isocyanurate reaction liquid was subjected to thin film distillation (pressure: 60 PaA or less, temperature: 160°C, feed amount: 5 g/hour) to separate the separated liquid containing the isocyanurate derivative of xylylene diisocyanate and the unreacted The recovered liquid containing xylylene diisocyanate was separated from the recovered liquid.

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 paratoluenesulfonamide was added as a heat stabilizer.

Thereby, an isocyanurate derivative of 1,3-xylylene diisocyanate modified with 1,3-butylene glycol was obtained. In addition, the area ratio of trimolecular bodies of the obtained isocyanurate derivative was measured.

Next, 1.02 mol (blocking agent/isocyanate group=1.02( mol/mol)) and reacted at 40 to 60°C for 1 to 2 hours. The reaction was stopped when the amine equivalent reached 20,000 or more. Then, ethyl acetate was added to make the solid concentration 70%. Added.

This resulted in a blocked isocyanate solution.

Thereafter, the obtained blocked isocyanate solution, Q-166 (acrylic polyol, solvent substituted product of OLESTAR Q-166 (trade name, manufactured by Mitsui Chemicals), solvent (butyl acetate, cyclohexane), hydroxyl value (solid content), ) 60mgKOH/g, hydroxyl value (in solvent) 29mgKOH/g, solid content concentration 40%) were mixed at an equivalent ratio of 1.0 (NCO/OH = 1.0) so that the solid content concentration was 50%. Isopropyl alcohol was added to the mixture, mixed at 23° C. for 5 minutes, and then subjected to ultrasonic treatment for 10 minutes to defoam to obtain a coating agent.

The obtained 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. Ta.

Comparative example 7
Takenate D-110N (trimethylolpropane modified xylylene diisocyanate, manufactured by Mitsui Chemicals, solids concentration 75%, solvent (ethyl acetate)), 1,1,3,3-tetramethylguanidine and 3,5- Dimethylpyrazole was mixed.

More specifically, 0.8 mol of 3,5-dimethylpyrazole was mixed with 1 mol of the isocyanate group of Takenate D-110N, stirred at room temperature, and then added to 1 mol of the above isocyanate group. Then 0.2 mol of 1,3,3-tetramethylguanidine was added and stirred at room temperature. Thereafter, FT-IR spectrum was measured and it was confirmed that the isocyanate groups were blocked, thereby obtaining blocked isocyanate.

Further, ethyl acetate was added to the blocked isocyanate so that the solid content concentration was 70%. This resulted in a blocked isocyanate solution.

Then, a cured film was obtained in the same manner as in Example 1.

3. Evaluation (storage stability)
The blocked isocyanate solution was placed in a 100 mL glass bottle, the bottle was purged with nitrogen, the bottle was sealed with a metal lid, and the bottle was stored in an oven at 60°C.

After 8 weeks, the hue (APHA) of the blocked isocyanate solution was visually evaluated in accordance with JIS K 0071-1 (2017).

The evaluation criteria are shown below.
◎: No change before and after storage ○: Change in hue (APHA) before and after storage less than 50 △: Change in hue (APHA) before and after storage 50 or more and less than 100 ×: Change in hue (APHA) before and after storage 50 100 or more

Details of the abbreviations in the table are given below.
DMP: 3,5-dimethylpyrazole IMZ: imidazole MEKO: methyl ethyl ketone oxime DEM: diethyl malonate TMG: 1,1,3,3-tetramethylguanidine

Claims (3)

A blocked isocyanate in which the isocyanate group of a xylylene diisocyanate derivative is blocked with a blocking agent,
The xylylene diisocyanate derivative contains an isocyanurate derivative of xylylene diisocyanate in a proportion of 90% by mass or more based on the total amount of the xylylene diisocyanate derivative ,
In the chromatogram obtained when the xylylene diisocyanate derivative is measured by gel permeation chromatography, the area ratio of the area of the peak having a peak top with a polystyrene equivalent molecular weight of 500 or more and less than 600 to the area of all peaks is 20% or more. 40% or less,
The blocking agent is 3,5-dimethylpyrazole, imidazole, or methyl ethyl ketone oxime.
Blocked isocyanate characterized by: In the chromatogram obtained when the xylylene diisocyanate derivative is measured by gel permeation chromatography, the area ratio of the area of a peak having a peak top with a polystyrene equivalent molecular weight of 500 or more and less than 600 to the area of all peaks is 30% or more. and
The blocking agent is 3,5-dimethylpyrazole or imidazole.
Blocked isocyanate according to claim 1, characterized in that: A coating agent comprising a curing agent containing the blocked isocyanate according to claim 1 or 2 and a main ingredient containing a macropolyol.

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