JP2023120565A - blocked isocyanate and coating agent - Google Patents

Abstract

To provide a blocked isocyanate that has excellent chemical resistance, and to provide a coating agent that contains the blocked isocyanate.SOLUTION: The blocked isocyanate is a blocked isocyanate in which the isocyanate group of a TDI derivative is blocked with a blocking agent. The TDI derivative contains TDI isocyanurate derivative. The TDI isocyanurate derivative includes TDI isocyanurate 3 or more core body. The TDI isocyanurate 3 or more core body contains isocyanurate group by 3 or more, and is a derivative compound including 7 or more molecule TDI. In a chromatogram obtained by measuring a tolylene diisocyanate derivative by gel permeation chromatography, the area ratio of the area of a peak corresponding to TDI isocyanurate 3 or more core body to the area of all peaks is 40% or more. The blocking agent contains a pyrazole-based blocking agent.SELECTED DRAWING: None

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 an isocyanate that dissociates a blocking agent by heating to regenerate an isocyanate group. Blocked isocyanates have excellent chemical resistance and processability. Therefore, blocked isocyanate is widely used as a curing agent for two-component curing type polyurethane resins.

For example, the following blocked isocyanates are known. In this blocked isocyanate, the isocyanate group of the xylylene diisocyanate derivative is blocked with a blocking agent. Xylylene diisocyanate derivatives include isocyanurate derivatives of xylylene diisocyanate. In addition, in the chromatogram when the xylylene diisocyanate derivative is measured by gel permeation chromatography, the area ratio of the area of the peak with the peak top between 500 and less than 600 in terms of polystyrene molecular weight to the area of all peaks is 20%. 40% or less. Also, 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 (see, for example, Patent Document 1).

Japanese Unexamined Patent Application Publication No. 2021-85009

On the other hand, blocked isocyanates are required to have excellent chemical resistance depending on their uses. For example, a coating film using blocked isocyanate may be formed on the surface of a resin film. In such a case, chemicals (residual monomers, etc.) contained in the resin film may exude to the coating film. Therefore, a cured film using blocked isocyanate is required to have chemical resistance.

However, the above blocked isocyanates may not have sufficient chemical resistance.

The present invention is a blocked isocyanate having excellent chemical resistance and a coating agent containing the blocked isocyanate.

The present invention [1] is a blocked isocyanate in which the isocyanate group of a tolylene diisocyanate derivative is blocked with a blocking agent, wherein the tolylene diisocyanate derivative contains an isocyanurate derivative of tolylene diisocyanate, The isocyanurate derivative includes an isocyanurate with three or more nuclei of tolylene diisocyanate, and the isocyanurate with three or more nuclei of tolylene diisocyanate contains three or more isocyanurate groups and seven or more molecules of tolylene diisocyanate. It is a derivative compound, and in the chromatogram when the tolylene diisocyanate derivative is measured by gel permeation chromatography, the area ratio of the area of the peak corresponding to the trinuclear isocyanurate of the tolylene diisocyanate to the area of all peaks is 40% or more, and the blocking agent contains a blocked isocyanate containing a pyrazole-based blocking agent.

The present invention [2] is a chromatogram obtained by measuring the tolylene diisocyanate derivative by gel permeation chromatography. It contains the blocked isocyanate described in [1] above, which has an area ratio of 70% or more.

In the present invention [3], the isocyanurate derivative of tolylene diisocyanate contains a mononuclear isocyanurate of tolylene diisocyanate, and the mononuclear isocyanurate of tolylene diisocyanate contains one isocyanurate group, It is a derivative compound containing three molecules of tolylene diisocyanate, and in the chromatogram when the tolylene diisocyanate derivative is measured by gel permeation chromatography, the area of the peak corresponding to the mononuclear isocyanurate of the tolylene diisocyanate, The area ratio of the peak area corresponding to the isocyanurate trinuclear or higher isocyanurate of the tolylene diisocyanate to the total peak area (area ratio of trinuclear or higher isocyanurate) relative to the area ratio of the total peak area (area ratio of trinuclear or higher isocyanurate). (area ratio of 3 or more nuclei/area ratio of 1 nucleus) is 1.0 or more and 18.0 or less, the blocked isocyanate according to the above [1] or [2].

The present invention [4] includes a coating agent containing a curing agent containing the blocked isocyanate according to any one of [1] to [3] above and a main agent containing a polyol component.

In the blocked isocyanate of the present invention, the isocyanate group of the tolylene diisocyanate derivative is blocked with a blocking agent. Tolylene diisocyanate derivatives also include isocyanurate derivatives of tolylene diisocyanate. The isocyanurate derivative of tolylene diisocyanate contains a trinuclear or higher isocyanurate derivative of tolylene diisocyanate in a predetermined ratio. Furthermore, the blocking agent contains a pyrazole-based blocking agent. Therefore, according to the blocked isocyanate of the present invention, a cured film having excellent chemical resistance can be obtained.

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

In the blocked isocyanate of the present invention, the isocyanate group of the tolylene diisocyanate derivative is blocked with a blocking agent. In other words, the blocked isocyanate is the reaction product of a tolylene diisocyanate derivative and a blocking agent.

Tolylene diisocyanate derivatives (TDI derivatives) are polyisocyanate compositions containing isocyanate groups. A tolylene diisocyanate derivative (TDI derivative) contains an isocyanurate derivative of tolylene diisocyanate (TDI isocyanurate) as a main component. In addition, the content ratio of the main component is 90% by mass or more with respect to the total amount of the tolylene diisocyanate derivative.

Isocyanurate derivatives of tolylene diisocyanate contain one or more isocyanurate groups (isocyanurate rings) in the molecule. An isocyanurate derivative of tolylene diisocyanate (TDI isocyanurate) is a polymer of tolylene diisocyanate. Multimers include, for example, isocyanurate mononuclear (trinuclear), isocyanurate dinuclear (pentamolecular), isocyanurate trinuclear (heptamolecular), and isocyanurate tetranuclear (9 molecules body).

The isocyanurate n-molecular body (n: natural number) refers to a derivative in which n molecules (n: natural number) of tolylene diisocyanate are bonded via an isocyanurate group (isocyanurate ring).

An isocyanurate derivative of tolylene diisocyanate can be obtained, for example, by the following method. That is, tolylene diisocyanate is subjected to an isocyanurate reaction in the presence of a known isocyanurate catalyst.

Tolylene diisocyanates include, for example, 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate. These can be used alone or in combination of two or more. Preferably, 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate are used together.

When 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate are used together, the proportions thereof are appropriately set according to the purpose and application. For example, 2,4-tolylene diisocyanate is, for example, 50 mol % or more, preferably 60 mol % or more, more preferably 2,4-tolylene diisocyanate with respect to the total moles of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate. is 70 mol % or more. Further, 2,4-tolylene diisocyanate is, for example, 99 mol% or less, preferably 95 mol% or less, more preferably 95 mol% or less, based on the total moles of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate. is 90 mol % or less. Further, 2,6-tolylene diisocyanate is, for example, 1 mol % or more, preferably 5 mol % or more, more preferably 5 mol % or more, based on the total moles of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate. is 10 mol % or more. 2,6-tolylene diisocyanate is, for example, 50 mol% or less, preferably 40 mol% or less, more preferably , 30 mol % or less.

Isocyanurate catalysts include, for example, tetraalkylammonium hydroxides, trialkylhydroxyalkylammonium hydroxides, organic weak acid salts thereof, metal salts of alkylcarboxylic acids, metal chelate compounds of β-diketones, and Friedel-Crafts. Catalysts, organometallic compounds, and aminosilyl group-containing compounds are included. Metal salts of alkylcarboxylic acids are preferred. Alkyl carboxylic acids include, for example, acetic acid, caproic acid, octylic acid, myristic acid and naphthenic acid. Metal salts include, for example, sodium, potassium, calcium, magnesium, tin, zinc and lead salts. These can be used alone or in combination of two or more. It should be noted that the isocyanurating catalyst can also be used as a solution and/or dispersion.

The addition ratio of the isocyanurate-forming catalyst (in terms of solid content) is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more with respect to 100 parts by mass of tolylene diisocyanate. The addition ratio of the isocyanurate-forming catalyst (in terms of solid content) is, for example, 3.0 parts by mass or less, preferably 1.0 parts by mass or less with respect to 100 parts by mass of tolylene diisocyanate.

Moreover, the mode of use of the isocyanurate-forming catalyst is not particularly limited. For example, known solid isocyanuration catalysts can be used. Also, solutions of known isocyanurating catalysts can be used. Preferably a solution of the isocyanurating catalyst is used.

The isocyanurating catalyst solution can contain the above isocyanurating catalyst and a known organic solvent. Organic solvents include, for example, alkyl esters, alcohols, ethers, ketones and nitriles. These can be used alone or in combination of two or more. The solid concentration of the solution (the content of the isocyanurate-forming catalyst) is appropriately set according to the purpose and application.

When the isocyanurate-forming catalyst solution contains an alcohol, the alcohol is a solvent for the catalyst. Alcohols as solvents are distinguished from alcohols as denaturants, which will be described later. More specifically, the amount of alcohol as solvent is small compared to the amount of alcohol as modifier. More specifically, the amount of alcohol as a solvent is, for example, 1 part by mass or less, preferably 0.5 parts by mass or less, per 100 parts by mass of tolylene diisocyanate.

Tolylene diisocyanate and an isocyanurate-forming catalyst undergo an isocyanurate-forming reaction under an inert gas atmosphere and normal pressure (atmospheric pressure).

Also, the tolylene diisocyanate and the isocyanurate-forming catalyst preferably undergo the isocyanurate-forming reaction in the presence of an organic solvent. Examples of the organic solvent include the above-described organic solvents. Alkyl esters are preferably used as the organic solvent.

The reaction conditions for the isocyanurate-forming reaction are appropriately set from the viewpoint of adjusting the ratio of the isocyanurate with three or more nuclei to the range described below.

For example, when tolylene diisocyanate and an isocyanurate-forming catalyst undergo an isocyanurate-forming reaction in the presence of an organic solvent, the reaction temperature for the isocyanurate-forming reaction is, for example, room temperature (e.g., 25°C) or higher, preferably 40°C. above, and more preferably above 50°C. Moreover, the reaction temperature of the isocyanurate-forming reaction is, for example, 100° C. or lower, preferably 90° C. or lower. In addition, the reaction time of the isocyanurate-forming reaction is, for example, 30 minutes or longer, preferably 1 hour or longer, and more preferably 2 hours or longer. In addition, the reaction time of the isocyanurate-forming reaction is, for example, 12 hours or less, preferably 10 hours or less, and more preferably 8 hours or less.

The isocyanurate conversion rate of the isocyanate group is appropriately set from the viewpoint of adjusting the ratio of the isocyanurate with three or more nuclei to the range described below.

The isocyanurate conversion rate of isocyanate groups is, for example, 30% by mass or more, preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, and particularly preferably 65% by mass or more. is. In addition, the isocyanurate conversion rate of isocyanate groups is, for example, 90% by mass or less, preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less.

In an isocyanuration reaction, for example, a catalyst deactivator is added after the isocyanurate conversion reaches a desired value. This terminates the isocyanuration reaction. Catalyst deactivators include, for example, phosphoric acid compounds, sulfonic acid compounds and sulfonamide compounds. These can be used alone or in combination of two or more. The amount of the catalyst deactivator to be added is appropriately set according to the purpose and application.

Thereby, an isocyanurate derivative of tolylene diisocyanate can be obtained.

If necessary, the isocyanurate derivative of tolylene diisocyanate may be modified with known alcohols as modifiers.

Isocyanurate derivatives modified with alcohols can be obtained, for example, by the following method. That is, first, a part of the isocyanate groups of tolylene diisocyanate and an alcohol are subjected to a urethanization reaction to obtain alcohol-modified tolylene diisocyanate. Next, the alcohol-modified tolylene diisocyanate is isocyanurated in the presence of an isocyanurate catalyst.

In addition, alcohol-modified isocyanurate derivatives can also be obtained, for example, by the following method. That is, first, tolylene diisocyanate is subjected to an isocyanurate reaction in the presence of an isocyanurate catalyst to obtain an isocyanurate derivative of tolylene diisocyanate. Next, a part of the isocyanate groups of the isocyanurate derivative of tolylene diisocyanate and an alcohol are subjected to a urethanization reaction.

These methods yield isocyanurate derivatives of alcohol-modified tolylene diisocyanate.

The isocyanurate derivative of tolylene diisocyanate is included in the reaction product liquid in the above reaction. In other words, the reaction product liquid is a tolylene diisocyanate derivative.

That is, the reaction product liquid can be used as it is as a tolylene diisocyanate derivative. Also, unreacted tolylene diisocyanate (and/or its alcohol-modified form) can be separated from the reaction product liquid and used as a tolylene diisocyanate derivative.

Methods for separating unreacted tolylene diisocyanate (and/or its alcohol-modified form) include, for example, distillation and extraction, preferably distillation. Distillation methods include, for example, thin film distillation. Incidentally, the distillation conditions are appropriately set according to the purpose and application.

Preferably, when the isocyanurate conversion rate is relatively low (for example, 65% by mass or less, preferably 30% by mass or less), unreacted tolylene diisocyanate (and/or its alcohol modified product) is reacted Separated from the product liquid.

Preferably, without separating unreacted tolylene diisocyanate (and/or its alcohol modified form) from the reaction product liquid, the reaction conditions for the above isocyanurate-forming reaction are adjusted to remove unreacted tolylene diisocyanate ( and/or alcohol denatures thereof).

More specifically, preferably, the reaction conditions in the above isocyanurate-forming reaction are adjusted, and the ratio of trinuclear isocyanurate to be described later is adjusted to the range described later. Thereby, tolylene diisocyanate is subjected to the reaction. That is, the amount of unreacted tolylene diisocyanate is reduced.

In such cases, an operation for separating unreacted tolylene diisocyanate is unnecessary. That is, preferably, unreacted tolylene diisocyanate (and/or alcohol-modified form thereof) is not separated from the reaction product liquid.

In other words, preferably, the reaction product liquid is used as it is as the tolylene diisocyanate derivative.

The reaction product liquid can contain the above organic solvent. In such cases, solutions and/or dispersions of tolylene diisocyanate derivatives are obtained. Moreover, the reaction product liquid does not need to contain the above organic solvent. In such cases, solid tolylene diisocyanate derivatives are obtained. That is, the tolylene diisocyanate derivative may be solid or in solution and/or dispersion.

When the tolylene diisocyanate derivative is a solution and/or dispersion liquid, the solid content concentration is, for example, 10% by mass or more, preferably 20% by mass or more. Also, the solid content concentration is, for example, 99% by mass or less, preferably 90% by mass or less.

The above organic solvent can be added to the solution and/or dispersion of the tolylene diisocyanate derivative to adjust the solid content concentration within the above range. Further, the above organic solvent can be distilled off from the solution and/or dispersion of the tolylene diisocyanate derivative to adjust the solid content concentration within the above range.

The tolylene diisocyanate derivative can contain additives. Additives include, for example, antioxidants, cocatalysts, heat stabilizers, light stabilizers, release agents, plasticizers, antiblocking agents, pigments, dyes, lubricants, fillers, and hydrolysis inhibitors. These can be used alone or in combination of two or more. The addition ratio and addition timing of the additive are appropriately set according to the purpose and application.

In the tolylene diisocyanate derivative, the isocyanurate derivative of tolylene diisocyanate is, as an essential component, an isocyanurate trinuclear or higher isocyanurate (7 or more molecules) consisting of 7 or more molecules of tolylene diisocyanate (and optionally blended alcohols). contains.

In addition, the isocyanurate derivative of tolylene diisocyanate can contain, as an optional component, an isocyanurate mononuclear body (trimolecular body) composed of, for example, three molecules of tolylene diisocyanate (and alcohols blended if necessary). . Furthermore, the isocyanurate derivative of tolylene diisocyanate can contain, as an optional component, an isocyanurate binuclear compound composed of 5 molecules of tolylene diisocyanate (and optionally blended alcohols).

The mononuclear (trimolecular) isocyanurate of tolylene diisocyanate is a derivative compound containing one isocyanurate group and three molecules of tolylene diisocyanate.

In the tolylene diisocyanate derivative, the mass ratio of the mononuclear isocyanurate of tolylene diisocyanate can be obtained as an area ratio (GPC area ratio) in a gel permeation chromatogram. The GPC area ratio of the mononuclear isocyanurate indicates the ratio of the area of the peak corresponding to the mononuclear isocyanurate of tolylene diisocyanate to the total peak area in the gel permeation chromatogram.

More specifically, the GPC area ratio of mononuclear isocyanurate is calculated by the following method. That is, the tolylene diisocyanate derivative is measured with a gel permeation chromatograph equipped with a differential refractometer to obtain a chromatogram. Then, the ratio (area ratio) of the area of peaks having peak tops in the range of 400 or more and less than 550 in terms of polystyrene equivalent molecular weight (number average molecular weight) to the area of all peaks in the chromatogram is calculated. This area ratio is the GPC area ratio of the mononuclear isocyanurate. The GPC area ratio of mononuclear isocyanurate indicates the mass ratio of mononuclear isocyanurate in the tolylene diisocyanate derivative. In the following, the GPC area ratio of mononuclear isocyanurate may be referred to as Mn400-550 area ratio or mononuclear body area ratio.

From the viewpoint of chemical resistance, the Mn400-550 area ratio (mononuclear body area ratio) of the tolylene diisocyanate derivative is, for example, 3% or more, preferably 5% or more, more preferably 8% or more, and still more preferably , 10% or more. Further, from the viewpoint of chemical resistance, the Mn400-550 area ratio (mononuclear body area ratio) of the tolylene diisocyanate derivative is, for example, 50% or less, preferably 40% or less, more preferably 30% or less, and further Preferably, it is 20% or less, particularly preferably 15% or less.

The isocyanurate dinuclear (pentamolecular) of tolylene diisocyanate is a derivative compound containing two isocyanurate groups and five molecules of tolylene diisocyanate.

In the tolylene diisocyanate derivative, the mass ratio of the isocyanurate binuclear compound of tolylene diisocyanate can be obtained as an area ratio (GPC area ratio) in a gel permeation chromatogram. The GPC area ratio of the isocyanurate binuclear compound indicates the ratio of the area of the peak corresponding to the isocyanurate binuclear compound of tolylene diisocyanate to the total peak area in the gel permeation chromatogram.

More specifically, the GPC area ratio of the isocyanurate binuclear compound is calculated by the following method. That is, the tolylene diisocyanate derivative is measured with a gel permeation chromatograph equipped with a differential refractometer to obtain a chromatogram. Then, the ratio (area ratio) of the area of peaks having peak tops in the range of 750 or more and less than 900 in terms of polystyrene equivalent molecular weight (number average molecular weight) to the area of all peaks in the chromatogram is calculated. This area ratio is the GPC area ratio of the isocyanurate binuclear compound. The GPC area ratio of the isocyanurate binuclear compound indicates the mass ratio of the isocyanurate binuclear compound in the tolylene diisocyanate derivative. In the following, the GPC area ratio of the isocyanurate binuclear compound may be referred to as the Mn750-900 area ratio or the binuclear compound area ratio.

From the viewpoint of chemical resistance, the Mn750-900 area ratio (binuclear body area ratio) of the tolylene diisocyanate derivative is, for example, 3% or more, preferably 5% or more, more preferably 8% or more, and still more preferably , 10% or more. Further, from the viewpoint of chemical resistance, the Mn750-900 area ratio (binuclear body area ratio) of the tolylene diisocyanate derivative is, for example, 40% or less, preferably 30% or less, more preferably 20% or less. .

A tolylene diisocyanate isocyanurate with 3 or more nuclei (7 or more molecules) is a derivative compound containing 3 or more isocyanurate groups and 7 or more molecules of tolylene diisocyanate.

In the tolylene diisocyanate derivative, the mass ratio of the isocyanurate trinuclear or higher form of tolylene diisocyanate can be determined as the area ratio (GPC area ratio) in a gel permeation chromatogram. The GPC area ratio of the trinuclear isocyanurate represents the ratio of the area of the peak corresponding to the trinuclear isocyanurate of tolylene diisocyanate to the total peak area in the gel permeation chromatogram.

More specifically, the GPC area ratio of trinuclear isocyanurate is calculated by the following method. That is, the tolylene diisocyanate derivative is measured with a gel permeation chromatograph equipped with a differential refractometer to obtain a chromatogram. Then, the ratio (area ratio) of the area of peaks having peak tops in the range of 1000 or more and less than 10000 in terms of polystyrene equivalent molecular weight (number average molecular weight) to the area of all peaks in the chromatogram is calculated. This area ratio is the GPC area ratio of trinuclear isocyanurate. The GPC area ratio of tri- or more nucleus isocyanurate indicates the mass ratio of tri- or more nucleus isocyanurate in the tolylene diisocyanate derivative. In the following description, the GPC area ratio of trinuclear isocyanurate may be referred to as Mn1000-10000 area ratio or trinuclear isocyanurate area ratio.

From the viewpoint of chemical resistance, the Mn1000-10000 area ratio (three-nucleus or more body area ratio) of the tolylene diisocyanate derivative is 40% or more, preferably 50% or more, more preferably 60% or more, further preferably 70% or more, particularly preferably 75% or more. Further, from the viewpoint of chemical resistance, the Mn1000-10000 area ratio (3-nucleus or more body area ratio) of the tolylene diisocyanate derivative is, for example, 97% or less, preferably 95% or less, more preferably 90% or less, More preferably 85% or less, particularly preferably 80% or less.

Also, from the viewpoint of chemical resistance, the ratio of the Mn1000-10000 area ratio (three or more nucleus unit area ratio) of the tolylene diisocyanate derivative to the Mn400-550 area ratio (one nucleus unit area ratio) of the tolylene diisocyanate derivative (3-nucleus or more body area ratio/1-nucleus body area ratio) is, for example, 0.5 or more, preferably 1.0 or more, more preferably 3.0 or more, further preferably 5.0 or more, especially Preferably, it is 7.0 or more. Also, from the viewpoint of chemical resistance, the ratio of the Mn1000-10000 area ratio (three or more nucleus unit area ratio) of the tolylene diisocyanate derivative to the Mn400-550 area ratio (one nucleus unit area ratio) of the tolylene diisocyanate derivative (3-nucleus or more body area ratio/1-nucleus body area ratio) is, for example, 20.0 or less, preferably 18.0 or less, more preferably 15.0 or less, further preferably 10.0 or less, especially Preferably, it is 8.0 or less.

Tolylene diisocyanate derivatives can contain derivatives other than isocyanurate derivatives (other derivatives) as unavoidable impurities. More specifically, in the synthesis of isocyanurate derivatives of tolylene diisocyanate, derivatives other than isocyanurate derivatives may be by-produced. Therefore, the tolylene diisocyanate derivative may inevitably contain derivatives other than the isocyanurate derivative of tolylene diisocyanate.

Examples of derivatives other than isocyanurate derivatives include allophanate derivatives of tolylene diisocyanate, biuret derivatives of tolylene diisocyanate, and uretdione derivatives of tolylene diisocyanate. These content ratios are appropriately set within a range that does not impair the excellent effects of the present invention. For example, the content of the derivative other than the isocyanurate derivative is, for example, 10% by mass or less, preferably 5% by mass or less, relative to the total amount of the tolylene diisocyanate derivative.

A blocked isocyanate is obtained by reacting the above tolylene diisocyanate derivative with a blocking agent.

The blocking agent contains a pyrazole-based blocking agent as an essential component. 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, and 3-methyl-5-phenylpyrazole mentioned. These can be used alone or in combination of two or more. 3,5-dimethylpyrazole (DMP) is preferred.

If the blocking agent contains a pyrazole-based blocking agent, a cured film (described later) with excellent chemical resistance can be obtained. Moreover, if the blocking agent contains a pyrazole-based blocking agent, turbidity of the blocked isocyanate can be suppressed, and excellent handleability can be obtained.

Moreover, the blocking agent can contain, as an optional component, a blocking agent other than the pyrazole-based blocking agent (another blocking agent). Examples of blocking agents other than pyrazole blocking agents include imidazole blocking agents, oxime blocking agents, phenol blocking agents, alcohol blocking agents, imine blocking agents, amine blocking agents, carbamic acid blocking agents, and urea. system blocking agents, imide blocking agents, mercaptan blocking agents, active methylene blocking agents, and acid amide blocking agents (lactam blocking agents). These can be used alone or in combination of two or more.

The ratio of the blocking agent other than the pyrazole-based blocking agent (other blocking agent) is appropriately set within a range that does not impair the excellent effects of the present invention. For example, the mass ratio of the blocking agent other than the pyrazole-based blocking agent is, for example, 10% by mass or less, preferably 5% by mass or less, more preferably 0% by mass, relative to the total amount of the blocking agents. Moreover, the mass ratio of the pyrazole-based blocking agent is, for example, 90% by mass or more, preferably 95% by mass or more, and more preferably 100% by mass with respect to the total amount of the blocking agents. In other words, the blocking agent more preferably consists of a pyrazole-based blocking agent.

A method for reacting the tolylene diisocyanate derivative and the blocking agent is not particularly limited, and a known method is employed. For example, the tolylene diisocyanate derivative and the blocking agent are reacted under an inert gas atmosphere and normal pressure (atmospheric pressure).

The mixing ratio of the tolylene diisocyanate derivative and the blocking agent is adjusted according to the ratio between the isocyanate group of the tolylene diisocyanate derivative and the active group of the blocking agent (blocking group that blocks the isocyanate group).

More specifically, the ratio of the active group (blocking group that blocks the isocyanate group) of the blocking agent to the isocyanate group of the tolylene diisocyanate derivative (blocking group/isocyanate group) is, for example, 0.8 or more, preferably 1.0 or more. Further, the ratio of the active group (blocking group that blocks the isocyanate group) of the blocking agent to the isocyanate group of the tolylene diisocyanate derivative (blocking group/isocyanate group) is, for example, 1.5 or less, preferably 1.2 or less. , more preferably 1.1 or less.

The reaction temperature between the tolylene diisocyanate derivative and the blocking agent is, for example, 20° C. or higher, preferably 30° C. or higher. Also, the reaction temperature between the tolylene diisocyanate derivative and the blocking agent is, for example, 80° C. or lower, preferably 70° C. or lower.

The reaction time between the tolylene diisocyanate derivative and the blocking agent is, for example, 0.5 hours or longer, preferably 1 hour or longer. Also, the tolylene diisocyanate derivative and the blocking agent are allowed to react for, for example, 6 hours or less, preferably 3 hours or less.

The completion of the reaction is determined by confirming disappearance or reduction of isocyanate groups by a known method.

Moreover, in the above reaction, a known organic solvent may be blended, if necessary. The mixing ratio of the organic solvent is appropriately set according to the purpose and application.

Moreover, in the above reaction, a known blocking catalyst may be blended, if necessary. The blending ratio of the blocked catalyst is appropriately set according to the purpose and application.

By reacting the tolylene diisocyanate derivative and the blocking agent as described above, the isocyanate groups of the tolylene diisocyanate derivative (specifically, the isocyanurate derivative of tolylene diisocyanate) are blocked by the blocking agent. The result is a blocked isocyanate.

Moreover, the tolylene diisocyanate derivative and the blocking agent are preferably reacted in the presence of an organic solvent. More specifically, preferably the tolylene diisocyanate derivative is in solution and/or dispersion. Then, the tolylene diisocyanate derivative and the blocking agent react in the presence of the organic solvent contained in the solution and/or dispersion.

In such cases, solutions and/or dispersions of blocked isocyanates are obtained. Moreover, the tolylene diisocyanate derivative and the blocking agent may be reacted in the absence of a solvent. In such cases, solid blocked isocyanates are obtained. That is, the blocked isocyanate may be solid or in solution and/or dispersion.

When the blocked isocyanate is a solution and/or dispersion, the solid content concentration is, for example, 10% by mass or more, preferably 20% by mass or more. Also, the solid content concentration is, for example, 99% by mass or less, preferably 90% by mass or less.

An organic solvent can be added to the blocked isocyanate solution and/or dispersion to adjust the solid concentration within the above range. In addition, the solid content concentration can be adjusted to the above range by distilling off the organic solvent from the blocked isocyanate solution and/or dispersion.

In such blocked isocyanates, the isocyanate groups of the tolylene diisocyanate derivative are blocked with a blocking agent. Tolylene diisocyanate derivatives also include isocyanurate derivatives of tolylene diisocyanate. The isocyanurate derivative of tolylene diisocyanate contains a trinuclear or higher isocyanurate derivative of tolylene diisocyanate in a predetermined ratio. Furthermore, the blocking agent contains a pyrazole-based blocking agent. Therefore, according to the blocked isocyanate, a cured film having excellent chemical resistance can be obtained.

More specifically, for example, in an isocyanurate derivative of xylylene diisocyanate (XDI), the isocyanate group is not directly bonded to the aromatic ring but is bonded via a methylene group. Therefore, a polyurethane resin obtained using an isocyanurate derivative of xylylene diisocyanate (XDI) has a relatively flexible molecular skeleton and crystal structure. As a result, the chemical resistance of polyurethane resins obtained using isocyanurate derivatives of xylylene diisocyanate (XDI) can be relatively poor.

On the other hand, in the isocyanurate derivative of tolylene diisocyanate (TDI), the isocyanate group is directly bonded to the aromatic ring. Therefore, a polyurethane resin obtained using an isocyanurate derivative of tolylene diisocyanate (TDI) has a relatively rigid molecular skeleton and crystal structure. As a result, the chemical resistance of the polyurethane resin obtained using the isocyanurate derivative of tolylene diisocyanate (TDI) is relatively high.

In particular, in the above blocked isocyanate, the isocyanurate derivative of tolylene diisocyanate (TDI) contains three or more nuclei of tolylene diisocyanate (TDI) isocyanurate in a predetermined ratio. Trinuclear or more isocyanurate of tolylene diisocyanate (TDI) can make the molecular skeleton and crystal structure of the polyurethane resin more rigid. Therefore, an isocyanurate with three or more nuclei can provide a polyurethane resin having particularly excellent chemical resistance.

Furthermore, in the blocked isocyanate described above, the blocking agent contains a pyrazole-based blocking agent, so that a polyurethane resin having particularly excellent chemical resistance can be obtained.

That is, according to the blocked isocyanate, a cured film having excellent chemical resistance can be obtained.

Furthermore, even if the isocyanurate derivative of tolylene diisocyanate (TDI) contains a trinuclear isocyanurate of tolylene diisocyanate (TDI), if the blocking agent contains a pyrazole-based blocking agent, the blocked isocyanate turbidity is suppressed.

As a result, the above-mentioned blocked isocyanate is suitably used as a curing agent (crosslinking agent) for resins in various industrial fields. Industrial fields include, for example, the coating field, the paint field, the ink field and the adhesive field. Examples of resins include polyurethane resins, polyolefin resins, polyacrylic resins and polyester resins.

Particularly preferably, the above-mentioned blocked isocyanate is suitably used as a curing agent for polyurethane resins in the field of coating agents.

The coating agent contains a curing agent containing the above-described blocked isocyanate and a main agent containing a polyol component. The coating agent may be, for example, a two-component curing coating agent or a one-component curing coating agent. A two-component curable coating agent is a two-component kit that separately includes a curing agent and a main agent that are individually adjusted. A one-component curable coating agent is a mixed composition containing a curing agent and a main agent. The above curing agents include blocked isocyanates. Therefore, the coating agent is preferably a one-component curable coating agent.

Curing agents can also contain other blocked isocyanates in addition to the blocked isocyanates described above. The content of the other blocked isocyanate in the curing agent is appropriately set according to the purpose and application. Preferably, the curing agent does not contain other blocked isocyanates. That is, the curing agent is composed of the above-mentioned blocked isocyanate (blocked isocyanate in which the isocyanate group of the tolylene diisocyanate derivative is blocked with a blocking agent).

In the main agent, the polyol component preferably contains a macropolyol. That is, the main agent preferably contains a macropolyol.

A macropolyol is an organic compound having two or more hydroxyl groups in its molecule and having a relatively high molecular weight. The number average molecular weight of the macropolyol is, for example, greater than 400 and, for example, 20,000 or less.

The number average molecular weight can be calculated by a known method from the hydroxyl equivalent and the average number of hydroxyl groups. Also, the number average molecular weight can be measured as a polystyrene-equivalent molecular weight by gel permeation chromatography (the same applies hereinafter).

Macropolyols include, for example, polyether polyols, polyester polyols, polycarbonate polyols, polyurethane polyols, epoxy polyols, vegetable oil polyols, polyolefin polyols, acrylic polyols and vinyl monomer-modified polyols. These macropolyols can be used alone or in combination of two or more.

Macropolyols preferably include acrylic polyols and polyester polyols, and more preferably polyester polyols.

The number average molecular weight of the macropolyol is, for example, over 400, preferably 500 or more, more preferably 1000 or more, even more preferably 1500 or more. Also, the number average molecular weight of the macropolyol is, for example, 20,000 or less, preferably 15,000 or less, more preferably 10,000 or less, and even more preferably 5,000 or less.

The average number of hydroxyl groups in the macropolyol is, for example, 2 or more, preferably more than 2, and more preferably 2.1 or more. In addition, the average number of hydroxyl groups of the macropolyol is, for example, 4 or less, preferably 3 or less, more preferably less than 3, and still more preferably 2.8 or less.

The hydroxyl value of the macropolyol is, for example, 50 mgKOH/g or more. Also, the hydroxyl value of the macropolyol 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.

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

The polyol component can also include low molecular weight polyols. The polyol component preferably does not contain low molecular weight polyols. That is, the polyol component preferably consists of macropolyols. That is, the main agent preferably consists of a macropolyol.

The blending ratio of the curing agent containing the blocked isocyanate and the main component containing the polyol component is adjusted according to the equivalent ratio of the isocyanate group of the blocked isocyanate (the isocyanate group blocked by the blocking agent) to the hydroxyl group of the polyol component. be.

More specifically, the equivalent ratio (isocyanate group/active hydrogen group) of the isocyanate group of the blocked isocyanate (the isocyanate group blocked by the blocking agent) to the hydroxyl group of the polyol component is, for example, 0.1 or more, preferably , 0.5 or more, more preferably 0.9 or more. In addition, the equivalent ratio (isocyanate group/active hydrogen group) of the isocyanate group of the blocked isocyanate (the isocyanate group blocked by the blocking agent) to the hydroxyl group of the polyol component is, for example, 5 or less, preferably 3 or less, more preferably. is less than or equal to 1.1.

The coating agent can also contain solvents, for example. The solvent is blended with the curing agent and/or the main agent in any proportion. The solid content concentration of the curing agent and the solid content concentration of the main agent are appropriately set according to the purpose and application.

Moreover, the coating agent can further contain an additive as needed. Examples of additives include curing accelerators, ultraviolet absorbers, light stabilizers, fillers, silane coupling agents, epoxy resins, catalysts, coatability improvers, leveling agents, nucleating agents, lubricants, release agents, Defoamers, thickeners, plasticizers, surfactants, pigments, pigment dispersants, dyes, organic particles, inorganic particles, antifungal agents, flame retardants, adhesion improvers, and matting agents. The amount and timing of addition of the additive are not particularly limited, and are appropriately set according to the purpose and application.

And since such a coating agent contains the blocked isocyanate of the present invention, a cured film (described later) having excellent chemical resistance can be obtained.

As a method of obtaining a cured film from a coating agent, for example, the coating agent is applied to a substrate.

The substrate is not particularly limited and includes known resin films. Examples of resins include (meth)acrylic resins, polyester resins and polycarbonate resins. (Meth)acrylic resins are preferred.

The method of applying the coating agent to the substrate is not particularly limited, and a known application method is employed. Examples of coating methods include dip coating, spray coating, roll coating, doctor blade, screen printing, bar coating, and applicator coating.

The coating amount of the coating agent is appropriately set according to the purpose and application.

The method then heats the coating applied to the substrate to dissociate the blocked isocyanate blocking agent. Dissociation conditions are conditions under which the blocking agent in the blocked isocyanate dissociates. For example, the dissociation temperature is, for example, 100° C. or higher, preferably 120° C. or higher. Also, the dissociation temperature is, for example, 200° C. or lower, preferably 180° C. or lower.

In this method, the isocyanate groups (isocyanate groups of the curing agent) regenerated by the dissociation of the blocking agent and the hydroxyl groups of the polyol component in the main agent are subjected to a urethanization reaction at the dissociation temperature. The reaction time is, for example, 10 minutes or longer, preferably 20 minutes or longer. Also, the reaction time is, for example, 60 minutes or less, preferably 30 minutes or less.

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 polyol component to cure the coating agent. As a result, a cured film of the coating agent is obtained. Also, if necessary, aging can be performed under appropriate conditions.

Since such a cured film is obtained using the above coating agent, it has excellent chemical resistance.

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. GPC Measurement Method The sample was subjected to gel permeation chromatography (GPC) measurement, and the area ratio of the area of each peak to the area of all peaks in the obtained chromatogram (chart) was determined.

Then, the area ratio of the peak having a peak top in the range of polystyrene equivalent molecular weight of 400 or more and less than 550 (Mn400-550 area ratio) was defined as the isocyanurate mononuclear (trimolecular) content.

In addition, the area ratio of peaks having peak tops in the range of polystyrene equivalent molecular weight of 1000 or more and less than 10000 (Mn 1000-10000 area ratio) was defined as the content of isocyanurate with 3 or more nuclei (7 or more molecules).

In the GPC measurement, about 0.03 g of a sample was taken, methylurethane was added with methanol, excess methanol was removed, and 10 mL of tetrahydrofuran was added to dissolve the sample. Then, the obtained solution was subjected to GPC measurement under the following conditions.

Analysis device: High-speed GPC device HLC-8320 (manufactured by Tosoh)
Detector: Differential refractometer Eluent: Tetrahydrofuran Separation column: The following (1) to (4) are connected in series (1) TSKgel guardcolumn HXL-L 6.0 × 40 (manufactured by Tosoh Corporation)
(2) TSKgel G1000HXL 7.8×300 (manufactured by Tosoh Corporation)
(3) TSKgel G2000HXL 7.8×300 (manufactured by Tosoh Corporation)
(4) TSKgel G3000HXL 7.8×300 (manufactured by Tosoh Corporation)
Measurement temperature: 40°C
Flow rate: 1mL/min
Sample injection volume: 100 μL
Analysis device: Eco SEC (manufactured by Tosoh Corporation)
・System correction Standard substance name: Polystyrene
Calibration curve creation method: A graph of retention time and molecular weight was created using TOSOH TSK standard Polystyrene with different molecular weights.
Injection volume, injection concentration: 100 μL, 1 mg/mL

A gel permeation chromatogram of the polyisocyanate composition of Example 1 is shown in FIG.

In FIG. 1, peak No. 5 indicates an isocyanurate mononuclear body. That is, the peak No. with respect to the total peak area. The area ratio of 5 is the GPC area ratio of the mononuclear isocyanurate.

Moreover, in FIG. 4 indicates an isocyanurate dinuclear compound. That is, the peak No. with respect to the total peak area. The area ratio of 4 is the GPC area ratio of the isocyanurate dinuclear compound.

Moreover, in FIG. 1 to No. 3 indicates an isocyanurate trinuclear or higher isomer. That is, the peak No. with respect to the total peak area. 1 to No. The area ratio (total) of 3 is the GPC area ratio of trinuclear isocyanurate.

2. Production of blocked isocyanates

(1) Synthesis of polyisocyanate Synthesis Example 1
In a four-necked flask equipped with a stirrer, a thermometer, a condenser and a nitrogen gas introduction tube, 100 parts by mass of tolylene diisocyanate (Cosmonate T-80 manufactured by Mitsui Chemicals SKC Polyurethane Co., Ltd.) and butyl acetate are added under a nitrogen atmosphere. 60 parts by mass, 0.2 parts by mass of 2,6-di-tert-butyl-p-cresol (antioxidant), and 0.05 parts by mass of tetraphenyldipropylene glycol diphosphite (antioxidant) After charging, the inside of the flask was heated to 60°C.

Then, 0.1 part by mass of m-cresol (promoter) was added to the flask. Also, a solution of the isocyanurate catalyst was added dropwise to the flask over 30 minutes.

The solution of the isocyanurate catalyst includes 0.4 parts by mass of mineral spirit solution of calcium naphthenate (solid content concentration of 47 mass%, catalyst solid content of 0.19 mass parts), 40 parts by mass of butyl acetate, n- It was a mixture with 0.1 part by mass of butanol.

The temperature in the flask was then adjusted to 60°C ± 3°C. Then, the above mixture was allowed to react until the isocyanurate conversion rate of isocyanate groups reached 70% by mass.

After that, 0.5 parts by mass of o-toluenesulfonic acid amide (reaction terminator) was added to the flask to stop the reaction. As a result, a tolylene diisocyanate derivative containing an isocyanurate derivative of tolylene diisocyanate was obtained. Also, the tolylene diisocyanate derivative was diluted with butyl acetate to obtain a polyisocyanate solution with a solid concentration of 50%.

Synthesis example 2
In a four-necked flask equipped with a stirrer, thermometer, condenser and nitrogen gas inlet tube, under a nitrogen atmosphere, tolylene diisocyanate (Mitsui Chemicals SKC Polyurethane Co., Ltd. Cosmonate T-80, 2,4-tolylene diisocyanate / 2,6-tolylene diisocyanate = 80 mol/20 mol) 100 parts by mass, 60 parts by mass of butyl acetate, and 0.2 parts by mass of 2,6-di-tert-butyl-p-cresol (antioxidant) , and 0.05 parts by mass of tetraphenyldipropylene glycol diphosphite (antioxidant) were charged, and the inside of the flask was heated to 60°C.

Then, 0.1 part by mass of m-cresol (promoter) was added to the flask. Also, a solution of the isocyanurate catalyst was added dropwise to the flask over 30 minutes. The isocyanurate catalyst solution was a mixture of 0.4 parts by weight of calcium naphthenate/mineral spirit solution (isocyanurate catalyst), 40 parts by weight of butyl acetate and 0.1 parts by weight of n-butanol.

The temperature in the flask was then adjusted to 60°C ± 3°C. Then, the above mixture was allowed to react until the isocyanurate conversion rate of the isocyanate groups reached 30% by mass.

Then, 0.5 parts by mass of o-toluenesulfonic acid amide (reaction terminator) was added to the flask to stop the reaction. Thus, a reaction product liquid was obtained.

Then, the reaction product liquid was subjected to thin film distillation (pressure: 200 PaA, temperature: 100°C, feed amount: 10 g/hour). The butyl acetate was thereby distilled off.

Then, the high boiling point liquid obtained by the above thin film distillation was further subjected to thin film distillation (pressure: 50 PaA, temperature: 160°C, feed amount: 5 g/hour). This distilled off unreacted tolylene diisocyanate.

As described above, a tolylene diisocyanate derivative was obtained. The tolylene diisocyanate derivative was diluted with butyl acetate to obtain a polyisocyanate solution with a solid concentration of 50%.

Synthesis example 3
The above mixture was reacted until the isocyanurate conversion of the isocyanate groups was 62%. A polyisocyanate solution with a solid concentration of 50% was obtained in the same manner as in Synthesis Example 2 except for this.

Synthesis example 4
The above mixture was reacted until the isocyanurate conversion of the isocyanate groups was 75%. A polyisocyanate solution with a solid concentration of 50% was obtained in the same manner as in Synthesis Example 1 except for this.

Synthesis example 5
The above mixture was reacted until the isocyanurate conversion of the isocyanate groups was 24%. A polyisocyanate solution with a solid concentration of 50% was obtained in the same manner as in Synthesis Example 2 except for this.

Synthesis example 6
The above mixture was reacted until the isocyanurate conversion of the isocyanate groups was 20%. A polyisocyanate solution with a solid concentration of 50% was obtained in the same manner as in Synthesis Example 2 except for this.

Synthesis example 7
The above mixture was reacted until the isocyanurate conversion of the isocyanate groups was 78%. A polyisocyanate solution with a solid concentration of 50% was obtained in the same manner as in Synthesis Example 1 except for this.

Synthesis example 8
A xylylene diisocyanate derivative was obtained by the method described in Example 1 of JP-A-2021-85009.

That is, in a reactor equipped with a thermometer, a stirrer, a cooling pipe, and a nitrogen inlet pipe, 100 parts by mass of 1,3-xylylene diisocyanate (m-XDI, manufactured by Mitsui Chemicals, Inc.) and 3 octadecyl -(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (hindered phenolic antioxidant, trade name: Irganox 1076, manufactured by Ciba Japan) 0.021 parts by mass (0.02 phr) and mixed at 60°C to 65°C.

Then, 2 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 (solid concentration: 3.7% by mass) of tetrabutylammonium hydroxide (isocyanurate catalyst, TBAOH (37% methanol solution)) 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 reaction at 70° C. to 75° C. until the conversion rate of the isocyanurate derivative of xylylene diisocyanate reached 31%. .

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

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

In addition, the xylylene diisocyanate derivative was measured by gel permeation chromatography (GPC) in the same manner as described above, and the area ratio of the area of each peak to the area of all peaks in the resulting chromatogram (chart) was determined.

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

In addition, in the xylylene diisocyanate derivative, the area ratio of the peak having a peak top in the range of polystyrene equivalent molecular weight 1000 or more and less than 10000 (Mn1000-10000 area ratio) and

Synthesis example 9
The above mixture was reacted until the isocyanurate conversion of the isocyanate groups was 35%. A polyisocyanate solution with a solid concentration of 50% was obtained in the same manner as in Synthesis Example 2 except for this.

Examples 1-6 and Comparative Examples 1-4
A polyisocyanate solution and a blocking agent were blended in the combinations shown in Table 1. The ratio (blocking group/isocyanate group) of the active group (blocking group that blocks the isocyanate group) of the blocking agent to the isocyanate group of the polyisocyanate solution was adjusted to 1.02.

Then, the polyisocyanate solution and the blocking agent were reacted at 40 to 60° C. for 1 to 2 hours, and the reaction was stopped when the amine equivalent became 20,000 or more. After that, butyl acetate was added to the reaction mixture to adjust the solid content concentration to 60% by mass. This gave a solution of blocked isocyanate.

3. Evaluation (1) Chemical resistance Polyester polyol (Takelac U-25 (trade name) manufactured by Mitsui Chemicals, Inc., hydroxyl value: 135 mgKOH/g, solid content concentration: 75%) was prepared as a main agent. Also, as a curing agent, a solution of blocked isocyanate shown in Table 1 was prepared.

A polyester polyol and a solution of blocked isocyanate were mixed. The equivalent ratio of the isocyanate groups of the blocked isocyanate to the hydroxyl groups of the polyester polyol was set to 1.0. Then, thinner (ethyl acetate: butyl acetate: propylene glycol monomethyl ether acetate = 1:1:1 mixture) was added to these mixtures and mixed at 23°C for 5 minutes. Thereby, the solid content concentration of the mixture was adjusted to 50% by mass.

The mixture was then sonicated for 10 minutes to degas. A coating liquid was thus obtained.

The coating liquid was applied to a glass plate (JIS, R, 3202, thickness 2 mm) using a 4 mil applicator. The coating was then heated in an oven at 150°C for 30 minutes. After that, the coating film was aged for 3 days in a constant temperature room at 23° C. and 55% humidity. Thus, a cured film was obtained.

The paper cloth was cut into 1 cm squares. A paper waste was impregnated with 4-hydroxybutyl acrylate (trade name of 4HBA manufactured by Mitsubishi Chemical Corporation). Then, the paper waste was attached to the cured film of the coating liquid. The paper waste and cured film were then heated in an oven at 80° C. for 30 minutes. After that, the paper waste was removed from the cured film. In addition, the surface of the cured film was wiped off, and the state of the surface was visually observed. Evaluation criteria are described below.

A: No change was observed on the surface of the cured film.
O: A thin mark was confirmed on the surface of the cured film. However, clouding of the cured film was not confirmed.
Δ: No fogging of the cured film was observed.
x: Swelling, shrinking and/or peeling of the cured film was confirmed.

(2) Turbidity Immediately after the blocked isocyanate solution was prepared, the blocked isocyanate solution was placed in a 100 mL glass bottle. The presence or absence of turbidity was visually confirmed while illuminating the blocked isocyanate solution with a light. Evaluation criteria are described below.

O: Turbidity was not confirmed.
Δ: Slight turbidity was confirmed.
x: Turbidity was clearly confirmed.

The details of the abbreviations in the table are described below.
DMP: 3,5-dimethylpyrazole MEKO: methyl ethyl ketone oxime

Claims (4)

A blocked isocyanate in which the isocyanate group of a tolylene diisocyanate derivative is blocked with a blocking agent,
The tolylene diisocyanate derivative contains an isocyanurate derivative of tolylene diisocyanate,
The isocyanurate derivative of tolylene diisocyanate includes an isocyanurate trinuclear or higher form of tolylene diisocyanate,
The trinuclear isocyanurate form of tolylene diisocyanate is a derivative compound containing 3 or more isocyanurate groups and 7 or more molecules of tolylene diisocyanate,
In the chromatogram when measuring the tolylene diisocyanate derivative by gel permeation chromatography,
The area ratio of the peak area corresponding to the isocyanurate trinuclear or higher form of tolylene diisocyanate to the total peak area is 40% or more,
A blocked isocyanate in which the blocking agent contains a pyrazole-based blocking agent. In the chromatogram when measuring the tolylene diisocyanate derivative by gel permeation chromatography,
2. The blocked isocyanate according to claim 1, wherein the area ratio of the peak area corresponding to the trinuclear isocyanurate form of tolylene diisocyanate to the total peak area is 70% or more. The isocyanurate derivative of tolylene diisocyanate includes a mononuclear isocyanurate of tolylene diisocyanate,
The mononuclear isocyanurate of tolylene diisocyanate is a derivative compound containing one isocyanurate group and containing three molecules of tolylene diisocyanate,
In the chromatogram when measuring the tolylene diisocyanate derivative by gel permeation chromatography,
With respect to the area ratio of the peak area corresponding to the mononuclear isocyanurate of the tolylene diisocyanate to the area of all peaks (mononuclear body area ratio),
The ratio of the area ratio of the peak area corresponding to the three or more nuclei isocyanurate isocyanurate of the tolylene diisocyanate to the area of all peaks (area ratio of three or more nuclei) (area ratio of three or more nuclei/one nucleus) is from 1.0 to 18.0, the blocked isocyanate according to claim 1 or 2. a curing agent comprising the blocked isocyanate according to any one of claims 1 to 3;
A coating agent containing a main agent containing a polyol component.