Blocked isocyanates and coating agents

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]

[0001] 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. [Background technology]

[0002] Blocked isocyanates are isocyanates that dissociate the blocking agent when heated, regenerating the isocyanate group. Blocked isocyanates have excellent chemical resistance and processability. For this reason, blocked isocyanates are widely used as curing agents for two-component curing polyurethane resins.

[0003] For example, the following blocked isocyanates are known. In these blocked isocyanates, the isocyanate groups of a xylylene diisocyanate derivative are blocked with a blocking agent. The xylylene diisocyanate derivative contains an isocyanurate derivative of xylylene diisocyanate. In addition, in a chromatogram obtained by measuring the xylylene diisocyanate derivative by gel permeation chromatography, the area of ​​a peak having a peak top between a polystyrene-equivalent molecular weight of 500 or more and less than 600 accounts for 20% or more and 40% or less of the area of ​​all peaks. In addition, the blocking agent contains at least one selected from the group consisting of a pyrazole-based blocking agent, an imidazole-based blocking agent, and an oxime-based blocking agent (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-85009 Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, blocked isocyanates are required to have excellent chemical resistance depending on the application. For example, a coating film using blocked isocyanates may be formed on the surface of a resin film. In such cases, chemicals contained in the resin film (such as residual monomers) may seep into the coating film. Therefore, cured films using blocked isocyanates require chemical resistance.

[0006] However, the above-mentioned blocked isocyanates may not have sufficient chemical resistance.

[0007] The present invention relates to a blocked isocyanate having excellent chemical resistance, and a coating agent containing the blocked isocyanate. [Means for solving the problem]

[0008] The present invention [1] relates to a blocked isocyanate in which the isocyanate group of a tolylene diisocyanate derivative is blocked with a blocking agent, the tolylene diisocyanate derivative containing an isocyanurate derivative of tolylene diisocyanate, the isocyanurate derivative of tolylene diisocyanate containing a tri- or higher nucleus isocyanurate of tolylene diisocyanate, the tri- or higher nucleus isocyanurate of tolylene diisocyanate containing three or more isocyanurate groups, and is a derivative compound containing seven or more molecules of tolylene diisocyanate, the tolylene diisocyanate derivative being a blocked isocyanate in which, in a chromatogram obtained by measuring the tolylene diisocyanate derivative by gel permeation chromatography, the area ratio of the peak area corresponding to the tri- or higher nucleus isocyanurate of tolylene diisocyanate to the area of ​​all peaks is 40% or more, and the blocking agent contains a pyrazole-based blocking agent.

[0009] The present invention [2] includes the blocked isocyanate according to the above [1], in which, in a chromatogram obtained by measuring the tolylene diisocyanate derivative by gel permeation chromatography, the area of ​​the peak corresponding to the isocyanurate tri- or higher nucleus compound of the tolylene diisocyanate accounts for 70% or more of the area of ​​all peaks.

[0010] The present invention [3] relates to the blocked isocyanate according to [1] or [2] above, wherein the isocyanurate derivative of tolylene diisocyanate comprises a mono-nuclear isocyanurate of tolylene diisocyanate, which contains one isocyanurate group and is a derivative compound containing three molecules of tolylene diisocyanate, and wherein, in a chromatogram obtained by measuring the tolylene diisocyanate derivative by gel permeation chromatography, the ratio (area ratio of tri- or more nuclear isomers / area ratio of mono-nuclear isomers) of the area of ​​the peak corresponding to the mono-nuclear isocyanurate of tolylene diisocyanate to the area of ​​all peaks is 1.0 or more and 18.0 or less.

[0011] The present invention [4] includes a coating agent containing a curing agent containing the blocked isocyanate described in any one of the above [1] to [3] and a base agent containing a polyol component. [Effects of the Invention]

[0012] In the blocked isocyanate of the present invention, the isocyanate group of the tolylene diisocyanate derivative is blocked with a blocking agent. The tolylene diisocyanate derivative also contains an isocyanurate derivative of tolylene diisocyanate. The isocyanurate derivative of tolylene diisocyanate contains a predetermined proportion of isocyanurate trinuclear or higher nuclei of tolylene diisocyanate. Furthermore, the blocking agent contains a pyrazole-based blocking agent. Therefore, the blocked isocyanate of the present invention can provide a cured film with excellent chemical resistance. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a gel permeation chromatogram of the tolylene diisocyanate derivative in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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 a reaction product of the tolylene diisocyanate derivative and the blocking agent.

[0015] The tolylene diisocyanate derivative (TDI derivative) is a polyisocyanate composition containing an isocyanate group. The tolylene diisocyanate derivative (TDI derivative) contains an isocyanurate derivative of tolylene diisocyanate (TDI isocyanurate) as a main component. The content of the main component is 90 mass% or more of the total amount of the tolylene diisocyanate derivative.

[0016] An isocyanurate derivative of tolylene diisocyanate contains one or more isocyanurate groups (isocyanurate rings) in the molecule. Furthermore, an isocyanurate derivative of tolylene diisocyanate (TDI isocyanurate) is a multimer of tolylene diisocyanate. Examples of the multimer include an isocyanurate mononuclear (trimeric), an isocyanurate dinuclear (pentameric), an isocyanurate trinuclear (septameric), and an isocyanurate tetranuclear (nonameric).

[0017] The term "n-molecular isocyanurate (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).

[0018] The isocyanurate derivative of tolylene diisocyanate can be obtained, for example, by the following method: tolylene diisocyanate is subjected to an isocyanuration reaction in the presence of a known isocyanuration catalyst.

[0019] Examples of tolylene diisocyanates include 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 in combination.

[0020] When 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate are used in combination, their proportions are appropriately set depending on the purpose and application. For example, based on the total moles of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, the proportion of 2,4-tolylene diisocyanate is, for example, 50 mol% or more, preferably 60 mol% or more, and more preferably 70 mol% or more. Based on the total moles of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, the proportion of 2,4-tolylene diisocyanate is, for example, 99 mol% or less, preferably 95 mol% or less, and more preferably 90 mol% or less. Based on the total moles of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, the proportion of 2,6-tolylene diisocyanate is, for example, 1 mol% or more, preferably 5 mol% or more, and more preferably 10 mol% or more. Furthermore, the amount of 2,6-tolylene diisocyanate relative to the total amount of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate is, for example, 50 mol % or less, preferably 40 mol % or less, and more preferably 30 mol % or less.

[0021] Examples of isocyanuration catalysts include tetraalkylammonium hydroxides, trialkylhydroxyalkylammonium hydroxides, weak organic acid salts thereof, metal salts of alkylcarboxylic acids, metal chelate compounds of β-diketones, Friedel-Crafts catalysts, organometallic compounds, and aminosilyl group-containing compounds. Metal salts of alkylcarboxylic acids are preferred. Examples of alkylcarboxylic acids include acetic acid, caproic acid, octylic acid, myristic acid, and naphthenic acid. Examples of metal salts include sodium salts, potassium salts, calcium salts, magnesium salts, tin salts, zinc salts, and lead salts. These can be used alone or in combination. The isocyanuration catalyst can also be used as a solution and / or dispersion.

[0022] The addition ratio of the isocyanurate catalyst (solid content equivalent) relative to 100 parts by mass of tolylene diisocyanate is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more, and the addition ratio of the isocyanurate catalyst (solid content equivalent) relative to 100 parts by mass of tolylene diisocyanate is, for example, 3.0 parts by mass or less, preferably 1.0 part by mass or less.

[0023] The form of the isocyanuration catalyst used is not particularly limited. For example, a known solid isocyanuration catalyst can be used. Alternatively, a known solution of the isocyanuration catalyst can be used. Preferably, a solution of the isocyanuration catalyst is used.

[0024] The solution of the isocyanurate catalyst can contain the above-mentioned isocyanurate catalyst and a known organic solvent. Examples of organic solvents include alkyl esters, alcohols, ethers, ketones, and nitriles. These can be used alone or in combination of two or more. The solids concentration of the solution (the content of the isocyanurate catalyst) is appropriately set depending on the purpose and application.

[0025] When the solution of the isocyanuration catalyst contains an alcohol, the alcohol serves as a solvent for the catalyst. The alcohol as a solvent is distinguished from the alcohol as a modifying agent described below. More specifically, the amount of the alcohol as a solvent is small compared to the amount of the alcohol as a modifying agent. More specifically, the amount of the 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.

[0026] Tolylene diisocyanate and an isocyanuration catalyst undergo an isocyanuration reaction under an inert gas atmosphere and normal pressure (atmospheric pressure).

[0027] The tolylene diisocyanate and the isocyanuration catalyst preferably undergo an isocyanuration reaction in the presence of an organic solvent. Examples of the organic solvent include the organic solvents described above. Preferred examples of the organic solvent include alkyl esters.

[0028] The reaction conditions for the isocyanurate-forming reaction are appropriately set from the viewpoint of adjusting the ratio of the isocyanurate trinuclear or higher nucleus compound described below within the range described below.

[0029] For example, when tolylene diisocyanate and an isocyanuration catalyst undergo an isocyanuration reaction in the presence of an organic solvent, the reaction temperature of the isocyanuration reaction is, for example, room temperature (e.g., 25°C) or higher, preferably 40°C or higher, and more preferably 50°C or higher. The reaction temperature of the isocyanuration reaction is, for example, 100°C or lower, preferably 90°C or lower. The reaction time of the isocyanuration reaction is, for example, 30 minutes or longer, preferably 1 hour or longer, and more preferably 2 hours or longer. The reaction time of the isocyanuration reaction is, for example, 12 hours or shorter, preferably 10 hours or shorter, and more preferably 8 hours or shorter.

[0030] The conversion rate of isocyanate groups to isocyanurate is appropriately set from the viewpoint of adjusting the ratio of the isocyanurate trinuclear or higher nucleus compound described below within the range described below.

[0031] The isocyanate conversion rate of the isocyanate group is, for example, 30% by mass or more, preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and particularly preferably 65% ​​by mass or more. The isocyanate conversion rate of the isocyanate group 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.

[0032] In the isocyanuration reaction, for example, after the isocyanurate conversion rate reaches a desired value, a catalyst deactivator is added. This stops the isocyanuration reaction. Examples of catalyst deactivators include phosphoric acid compounds, sulfonic acid compounds, and sulfonamide compounds. These can be used alone or in combination of two or more. The amount of catalyst deactivator added is appropriately determined depending on the purpose and application.

[0033] This makes it possible to obtain an isocyanurate derivative of tolylene diisocyanate.

[0034] The isocyanurate derivative of tolylene diisocyanate may be modified with known alcohols as a modifying agent, if necessary.

[0035] The isocyanurate derivative modified with alcohols can be obtained, for example, by the following method. First, some of the isocyanate groups of tolylene diisocyanate are subjected to a urethane reaction with alcohols to obtain tolylene diisocyanate modified with alcohols. Next, the tolylene diisocyanate modified with alcohols is subjected to an isocyanuration reaction in the presence of an isocyanuration catalyst.

[0036] Alternatively, an isocyanurate derivative modified with an alcohol can be obtained, for example, by the following method. First, tolylene diisocyanate is subjected to an isocyanuration reaction in the presence of an isocyanuration catalyst to obtain an isocyanurate derivative of tolylene diisocyanate. Next, some of the isocyanate groups of the isocyanurate derivative of tolylene diisocyanate are subjected to a urethane reaction with an alcohol.

[0037] By these methods, isocyanurate derivatives of tolylene diisocyanate modified with alcohols can be obtained.

[0038] The isocyanurate derivative of tolylene diisocyanate is contained in the reaction product liquid in the above reaction. In other words, the reaction product liquid is a tolylene diisocyanate derivative.

[0039] That is, the reaction product liquid can be used as it is as a tolylene diisocyanate derivative. Alternatively, unreacted tolylene diisocyanate (and / or its alcohol-modified product) can be separated from the reaction product liquid and used as a tolylene diisocyanate derivative.

[0040] Methods for separating unreacted tolylene diisocyanate (and / or its alcohol-modified product) include, for example, distillation and extraction, preferably distillation. Examples of distillation methods include thin-film distillation. The distillation conditions are appropriately set depending on the purpose and application.

[0041] 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 separated from the reaction product liquid.

[0042] Preferably, the unreacted tolylene diisocyanate (and / or its alcohol-modified product) is not separated from the reaction product liquid, but the reaction conditions for the isocyanuration reaction are adjusted to reduce the amount of unreacted tolylene diisocyanate (and / or its alcohol-modified product).

[0043] More specifically, the reaction conditions for the isocyanurate reaction are preferably adjusted so that the ratio of the tri- or higher isocyanurate nucleus compound described below falls within the range described below. This allows tolylene diisocyanate to be reacted. In other words, the amount of unreacted tolylene diisocyanate is reduced.

[0044] In such a case, there is no need to separate the unreacted tolylene diisocyanate, that is, preferably, the unreacted tolylene diisocyanate (and / or its alcohol-modified product) is not separated from the reaction product liquid.

[0045] In other words, the reaction product liquid is preferably used as it is as the tolylene diisocyanate derivative.

[0046] The reaction product liquid may contain the organic solvent. In such a case, a solution and / or dispersion of the tolylene diisocyanate derivative is obtained. Alternatively, the reaction product liquid may not contain the organic solvent. In such a case, a solid tolylene diisocyanate derivative is obtained. That is, the tolylene diisocyanate derivative may be a solid, or may be a solution and / or dispersion.

[0047] When the tolylene diisocyanate derivative is in the form of a solution and / or dispersion, the solid content concentration is, for example, 10% by mass or more, preferably 20% by mass or more, and for example, 99% by mass or less, preferably 90% by mass or less.

[0048] The solid content concentration can be adjusted to the above range by adding the above organic solvent to the solution and / or dispersion of the tolylene diisocyanate derivative. Alternatively, the solid content concentration can be adjusted to the above range by distilling off the above organic solvent from the solution and / or dispersion of the tolylene diisocyanate derivative.

[0049] The tolylene diisocyanate derivative may contain additives. Examples of additives include antioxidants, cocatalysts, heat stabilizers, light stabilizers, release agents, plasticizers, antiblocking agents, pigments, dyes, lubricants, fillers, and hydrolysis inhibitors. These may be used alone or in combination of two or more. The proportions and timing of addition of the additives are appropriately determined depending on the purpose and application.

[0050] Among the tolylene diisocyanate derivatives, the isocyanurate derivative of tolylene diisocyanate contains, as an essential component, an isocyanurate trinuclear or higher compound (seven or more molecules) consisting of seven or more molecules of tolylene diisocyanate (and alcohols blended as necessary).

[0051] The isocyanurate derivative of tolylene diisocyanate may contain, as an optional component, for example, an isocyanurate mononuclear compound (trimer) consisting of three molecules of tolylene diisocyanate (and alcohols blended as necessary). Furthermore, the isocyanurate derivative of tolylene diisocyanate may contain, as an optional component, an isocyanurate dinuclear compound consisting of five molecules of tolylene diisocyanate (and alcohols blended as necessary).

[0052] The monoisocyanurate (trimolecular) of tolylene diisocyanate is a derivative compound that contains one isocyanurate group and three molecules of tolylene diisocyanate.

[0053] In the tolylene diisocyanate derivative, the mass proportion of the monoisocyanurate nucleus of tolylene diisocyanate can be determined as the area fraction in a gel permeation chromatogram (GPC area fraction). The GPC area fraction of the monoisocyanurate nucleus indicates the proportion of the area of ​​the peak corresponding to the monoisocyanurate nucleus of tolylene diisocyanate to the area of ​​all peaks in the gel permeation chromatogram.

[0054] More specifically, the GPC area ratio of the isocyanurate mononuclear compound is calculated by the following method. That is, a tolylene diisocyanate derivative is measured using a gel permeation chromatograph equipped with a differential refractometer to obtain a chromatogram. Then, the ratio (area ratio) of the area of ​​the peak having a peak top in the polystyrene-equivalent molecular weight (number average molecular weight) range of 400 or more and less than 550 to the area of ​​all peaks in the chromatogram is calculated. This area ratio is the GPC area ratio of the isocyanurate mononuclear compound. The GPC area ratio of the isocyanurate mononuclear compound indicates the mass proportion of the isocyanurate mononuclear compound in the tolylene diisocyanate derivative. Hereinafter, the GPC area ratio of the isocyanurate mononuclear compound may be referred to as the Mn400-550 area ratio or the mononuclear compound area ratio.

[0055] From the viewpoint of chemical resistance, the Mn400-550 area ratio (mononuclear area ratio) of the tolylene diisocyanate derivative is, for example, 3% or more, preferably 5% or more, more preferably 8% or more, and even more preferably 10% or more. Also, from the viewpoint of chemical resistance, the Mn400-550 area ratio (mononuclear area ratio) of the tolylene diisocyanate derivative is, for example, 50% or less, preferably 40% or less, more preferably 30% or less, even more preferably 20% or less, and particularly preferably 15% or less.

[0056] The diisocyanurate (pentamer) of tolylene diisocyanate is a derivative compound containing two isocyanurate groups and five molecules of tolylene diisocyanate.

[0057] In the tolylene diisocyanate derivative, the mass proportion of the isocyanurate dinuclear compound of tolylene diisocyanate can be determined as the area ratio in a gel permeation chromatogram (GPC area ratio). The GPC area ratio of the isocyanurate dinuclear compound indicates the ratio of the area of ​​the peak corresponding to the isocyanurate dinuclear compound of tolylene diisocyanate to the area of ​​all peaks in the gel permeation chromatogram.

[0058] More specifically, the GPC area ratio of the isocyanurate dinuclear compound is calculated by the following method. That is, a tolylene diisocyanate derivative is measured using a gel permeation chromatograph equipped with a differential refractometer to obtain a chromatogram. Then, the ratio (area ratio) of the area of ​​the peak having a peak top in the range of polystyrene-equivalent molecular weight (number average molecular weight) of 750 or more and less than 900 to the area of ​​all peaks in the chromatogram is calculated. This area ratio is the GPC area ratio of the isocyanurate dinuclear compound. The GPC area ratio of the isocyanurate dinuclear compound indicates the mass ratio of the isocyanurate dinuclear compound in the tolylene diisocyanate derivative. Hereinafter, the GPC area ratio of the isocyanurate dinuclear compound may be referred to as the Mn750-900 area ratio or the dinuclear compound area ratio.

[0059] From the viewpoint of chemical resistance, the Mn750-900 area ratio (dinuclear area ratio) of the tolylene diisocyanate derivative is, for example, 3% or more, preferably 5% or more, more preferably 8% or more, and even more preferably 10% or more. Also, from the viewpoint of chemical resistance, the Mn750-900 area ratio (dinuclear area ratio) of the tolylene diisocyanate derivative is, for example, 40% or less, preferably 30% or less, and more preferably 20% or less.

[0060] A tri- or higher isocyanurate (seven or more molecules) of tolylene diisocyanate is a derivative compound that contains three or more isocyanurate groups and seven or more molecules of tolylene diisocyanate.

[0061] In the tolylene diisocyanate derivative, the mass proportion of tri- or higher isocyanurate nuclei of tolylene diisocyanate can be determined as the area ratio in a gel permeation chromatogram (GPC area ratio). The GPC area ratio of tri- or higher isocyanurate nuclei indicates the ratio of the area of ​​the peak corresponding to the tri- or higher isocyanurate nuclei of tolylene diisocyanate to the area of ​​all peaks in the gel permeation chromatogram.

[0062] More specifically, the GPC area ratio of a tri- or higher isocyanurate nucleus compound is calculated by the following method. That is, a tolylene diisocyanate derivative is measured using a gel permeation chromatograph equipped with a differential refractometer to obtain a chromatogram. Then, the ratio (area ratio) of the area of ​​a peak having a peak top in the range of a polystyrene-equivalent molecular weight (number average molecular weight) of 1,000 or more to less than 10,000 relative to the area of ​​all peaks in the chromatogram is calculated. This area ratio is the GPC area ratio of a tri- or higher isocyanurate nucleus compound. The GPC area ratio of a tri- or higher isocyanurate nucleus compound indicates the mass proportion of the tri- or higher isocyanurate nucleus compound in the tolylene diisocyanate derivative. Hereinafter, the GPC area ratio of a tri- or higher isocyanurate nucleus compound may be referred to as the Mn1,000-10,000 area ratio or the tri- or higher isocyanurate area ratio.

[0063] From the viewpoint of chemical resistance, the Mn1000-10000 area ratio (area ratio of trinuclear or higher units) of the tolylene diisocyanate derivative is 40% or more, preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, and particularly preferably 75% or more. Also, from the viewpoint of chemical resistance, the Mn1000-10000 area ratio (area ratio of trinuclear or higher units) of the tolylene diisocyanate derivative is, for example, 97% or less, preferably 95% or less, more preferably 90% or less, even more preferably 85% or less, and particularly preferably 80% or less.

[0064] Furthermore, from the viewpoint of chemical resistance, the ratio of the Mn1000-10000 area ratio (area ratio of tri- or more nuclei) of the tolylene diisocyanate derivative to the Mn400-550 area ratio (area ratio of mononuclei) of the tolylene diisocyanate derivative (area ratio of tri- or more nuclei / area ratio of mononuclei) is, for example, 0.5 or more, preferably 1.0 or more, more preferably 3.0 or more, even more preferably 5.0 or more, and particularly preferably 7.0 or more. Furthermore, from the viewpoint of chemical resistance, the ratio of the Mn1000-10000 area fraction (area fraction of trinuclear or more nuclei) of the tolylene diisocyanate derivative to the Mn400-550 area fraction (area fraction of mononuclear bodies) of the tolylene diisocyanate derivative (area fraction of trinuclear or more nuclei / area fraction of mononuclear bodies) is, for example, 20.0 or less, preferably 18.0 or less, more preferably 15.0 or less, even more preferably 10.0 or less, and particularly preferably 8.0 or less.

[0065] The tolylene diisocyanate derivative may contain derivatives other than the isocyanurate derivative (other derivatives) as inevitable impurities. More specifically, in the synthesis of an isocyanurate derivative of tolylene diisocyanate, derivatives other than the isocyanurate derivative may be by-produced. Therefore, the tolylene diisocyanate derivative may inevitably contain derivatives other than the isocyanurate derivative of tolylene diisocyanate.

[0066] Examples of derivatives other than isocyanurate derivatives include allophanate derivatives of tolylene diisocyanate, biuret derivatives of tolylene diisocyanate, and uretdione derivatives of tolylene diisocyanate. The content ratio of these is appropriately set within a range that does not impair the excellent effects of the present invention. For example, the content ratio of derivatives other than isocyanurate derivatives is, for example, 10% by mass or less, preferably 5% by mass or less, based on the total amount of tolylene diisocyanate derivatives.

[0067] The blocked isocyanate can be obtained by reacting the above tolylene diisocyanate derivative with a blocking agent.

[0068] The blocking agent contains a pyrazole-based blocking agent as an essential component. Examples of pyrazole-based 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. These can be used alone or in combination of two or more. Preferably, 3,5-dimethylpyrazole (DMP) is used.

[0069] When the blocking agent contains a pyrazole-based blocking agent, a cured film (described later) with excellent chemical resistance can be obtained. Furthermore, when the blocking agent contains a pyrazole-based blocking agent, cloudiness of the blocked isocyanate can be suppressed, and excellent handleability can be obtained.

[0070] The blocking agent may also contain, as an optional component, a blocking agent other than a pyrazole-based blocking agent (other blocking agent). Examples of blocking agents other than pyrazole-based blocking agents include imidazole-based blocking agents, oxime-based blocking agents, phenol-based blocking agents, alcohol-based blocking agents, imine-based blocking agents, amine-based blocking agents, carbamic acid-based blocking agents, urea-based blocking agents, imide-based blocking agents, mercaptan-based blocking agents, active methylene-based blocking agents, and acid amide-based blocking agents (lactam-based blocking agents). These may be used alone or in combination of two or more types.

[0071] The proportion of blocking agents other than pyrazole-based blocking agents (other blocking agents) is appropriately set within a range that does not impair the excellent effects of the present invention. For example, the mass proportion of blocking agents other than pyrazole-based blocking agents relative to the total amount of blocking agents is, for example, 10% by mass or less, preferably 5% by mass or less, and more preferably 0% by mass. Furthermore, the mass proportion of pyrazole-based blocking agents relative to the total amount of blocking agents is, for example, 90% by mass or more, preferably 95% by mass or more, and more preferably 100% by mass. In other words, the blocking agent preferably consists of a pyrazole-based blocking agent.

[0072] The method for reacting the tolylene diisocyanate derivative with the blocking agent is not particularly limited, and a known method can be used. For example, the tolylene diisocyanate derivative is reacted with the blocking agent in an inert gas atmosphere under normal pressure (atmospheric pressure).

[0073] The mixing ratio of the tolylene diisocyanate derivative and the blocking agent is adjusted according to the ratio of the isocyanate groups of the tolylene diisocyanate derivative to the active groups (blocking groups that block the isocyanate groups) of the blocking agent.

[0074] More specifically, the ratio of the active groups of the blocking agent (blocking groups that block isocyanate groups) to the isocyanate groups of the tolylene diisocyanate derivative (blocking groups / isocyanate groups) is, for example, 0.8 or more, preferably 1.0 or more. Also, the ratio of the active groups of the blocking agent (blocking groups that block isocyanate groups) to the isocyanate groups of the tolylene diisocyanate derivative (blocking groups / isocyanate groups) is, for example, 1.5 or less, preferably 1.2 or less, more preferably 1.1 or less.

[0075] The reaction temperature between the tolylene diisocyanate derivative and the blocking agent is, for example, 20° C. or higher, or preferably 30° C. or higher. The reaction temperature between the tolylene diisocyanate derivative and the blocking agent is, for example, 80° C. or lower, or preferably 70° C. or lower.

[0076] The reaction time between the tolylene diisocyanate derivative and the blocking agent is, for example, 0.5 hours or more, preferably 1 hour or more, and the reaction time between the tolylene diisocyanate derivative and the blocking agent is, for example, 6 hours or less, preferably 3 hours or less.

[0077] The completion of the reaction is determined by confirming the disappearance or reduction of the isocyanate groups by a known method.

[0078] In the above reaction, a known organic solvent may be added as needed, and the amount of the organic solvent added may be appropriately determined depending on the purpose and application.

[0079] In the above reaction, a known blocking catalyst may be added as needed, and the amount of the blocking catalyst added may be appropriately determined depending on the purpose and application.

[0080] Then, by reacting the tolylene diisocyanate derivative with the blocking agent as described above, the isocyanate group of the tolylene diisocyanate derivative (specifically, the isocyanurate derivative of tolylene diisocyanate) is blocked by the blocking agent, resulting in a blocked isocyanate.

[0081] The tolylene diisocyanate derivative and the blocking agent preferably react in the presence of an organic solvent. More specifically, the tolylene diisocyanate derivative is preferably in the form of a solution and / or dispersion. The tolylene diisocyanate derivative and the blocking agent react in the presence of the organic solvent contained in the solution and / or dispersion.

[0082] In such a case, a solution and / or dispersion of the blocked isocyanate is obtained. Alternatively, the tolylene diisocyanate derivative and the blocking agent may be reacted in the absence of a solvent. In such a case, a solid blocked isocyanate is obtained. That is, the blocked isocyanate may be a solid, or may be a solution and / or dispersion.

[0083] When the blocked isocyanate is in the form of a solution and / or dispersion, the solid content concentration is, for example, 10% by mass or more, preferably 20% by mass or more, and for example, 99% by mass or less, preferably 90% by mass or less.

[0084] The solids concentration can be adjusted to the above range by adding an organic solvent to the blocked isocyanate solution and / or dispersion, or by distilling off the organic solvent from the blocked isocyanate solution and / or dispersion.

[0085] In such blocked isocyanates, the isocyanate groups of the tolylene diisocyanate derivative are blocked with a blocking agent. The tolylene diisocyanate derivative also contains an isocyanurate derivative of tolylene diisocyanate. The isocyanurate derivative of tolylene diisocyanate contains a predetermined proportion of isocyanurate trinuclear or higher nuclei of tolylene diisocyanate. Furthermore, the blocking agent contains a pyrazole-based blocking agent. Therefore, the above-mentioned blocked isocyanate can provide a cured film with excellent chemical resistance.

[0086] 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, polyurethane resins obtained using an isocyanurate derivative of xylylene diisocyanate (XDI) have relatively flexible molecular skeletons and crystalline structures. As a result, the chemical resistance of polyurethane resins obtained using an isocyanurate derivative of xylylene diisocyanate (XDI) may be relatively low.

[0087] On the other hand, in isocyanurate derivatives of tolylene diisocyanate (TDI), the isocyanate group is directly bonded to the aromatic ring. Therefore, polyurethane resins obtained using isocyanurate derivatives of tolylene diisocyanate (TDI) have a relatively rigid molecular skeleton and crystalline structure. As a result, the chemical resistance of polyurethane resins obtained using isocyanurate derivatives of tolylene diisocyanate (TDI) is relatively high.

[0088] In particular, among the above-mentioned blocked isocyanates, the isocyanurate derivative of tolylene diisocyanate (TDI) contains a specific proportion of tri- or higher isocyanurate units of tolylene diisocyanate (TDI). The tri- or higher isocyanurate units of tolylene diisocyanate (TDI) can make the molecular skeleton and crystalline structure of the polyurethane resin more rigid. Therefore, the tri- or higher isocyanurate units can produce polyurethane resins with particularly excellent chemical resistance.

[0089] Furthermore, in the above-mentioned blocked isocyanate, since the blocking agent contains a pyrazole-based blocking agent, a polyurethane resin having particularly excellent chemical resistance can be obtained.

[0090] That is, the above-mentioned blocked isocyanate can provide a cured film with excellent chemical resistance.

[0091] Furthermore, even if the isocyanurate derivative of tolylene diisocyanate (TDI) contains a tri- or higher nucleus isocyanurate of tolylene diisocyanate (TDI), cloudiness of the blocked isocyanate is suppressed if the blocking agent contains a pyrazole-based blocking agent.

[0092] As a result, the blocked isocyanates are suitable for use as curing agents (crosslinking agents) for resins in various industrial fields, such as coatings, paints, inks, and adhesives. Examples of resins include polyurethane resins, polyolefin resins, polyacrylic resins, and polyester resins.

[0093] The blocked isocyanate is particularly preferably used as a curing agent for polyurethane resins in the field of coating agents.

[0094] The coating agent contains a curing agent containing the above-mentioned blocked isocyanate and a base 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. The two-component curing coating agent is a two-component kit that includes an individually prepared curing agent and a base agent. The one-component curing coating agent is a mixed composition that includes a curing agent and a base agent. The above-mentioned curing agent contains a blocked isocyanate. Therefore, the coating agent is preferably a one-component curing coating agent.

[0095] The curing agent may contain other blocked isocyanates in addition to the above-mentioned blocked isocyanates. The content ratio of the other blocked isocyanates in the curing agent is appropriately set depending on the purpose and application. Preferably, the curing agent does not contain other blocked isocyanates. In other words, the curing agent is composed of the above-mentioned blocked isocyanates (blocked isocyanates in which the isocyanate group of a tolylene diisocyanate derivative is blocked with a blocking agent).

[0096] In the base material, the polyol component preferably contains a macropolyol, that is, the base material preferably contains a macropolyol.

[0097] The macropolyol is a relatively high molecular weight organic compound having two or more hydroxyl groups in the molecule, and the number average molecular weight of the macropolyol is, for example, more than 400 and, for example, 20,000 or less.

[0098] The number average molecular weight can be calculated from the hydroxyl equivalent weight and the average number of hydroxyl groups by a known method. The number average molecular weight can also be measured as a polystyrene-equivalent molecular weight by gel permeation chromatography (the same applies hereinafter).

[0099] Examples of macropolyols include 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.

[0100] As the macropolyol, preferably, an acrylic polyol and a polyester polyol are used, and more preferably, a polyester polyol is used.

[0101] The number average molecular weight of the macropolyol is, for example, more than 400, preferably 500 or more, more preferably 1000 or more, and even more preferably 1500 or more. The number average molecular weight of the macropolyol is, for example, 20000 or less, preferably 15000 or less, more preferably 10000 or less, and even more preferably 5000 or less.

[0102] 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. The average number of hydroxyl groups in the macropolyol is, for example, 4 or less, preferably 3 or less, more preferably less than 3, and even more preferably 2.8 or less.

[0103] The hydroxyl value of the macropolyol is, for example, 50 mgKOH / g or more. 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, and even more preferably 150 mgKOH / g or less.

[0104] The macropolyols can be used alone or in combination of two or more kinds.

[0105] The polyol component may also contain a low-molecular-weight polyol. The polyol component preferably does not contain a low-molecular-weight polyol. That is, the polyol component preferably consists of a macropolyol. That is, the base material preferably consists of a macropolyol.

[0106] The blending ratio of the curing agent containing the blocked isocyanate to the base agent containing the polyol component is adjusted according to the equivalent ratio of the isocyanate groups of the blocked isocyanate (isocyanate groups blocked with a blocking agent) to the hydroxyl groups of the polyol component.

[0107] More specifically, the equivalent ratio (isocyanate group / active hydrogen group) of the isocyanate group of the blocked isocyanate (isocyanate group blocked with a blocking agent) to the hydroxyl groups of the polyol component is, for example, 0.1 or more, preferably 0.5 or more, and more preferably 0.9 or more. Also, the equivalent ratio (isocyanate group / active hydrogen group) of the isocyanate group of the blocked isocyanate (isocyanate group blocked with a blocking agent) to the hydroxyl groups of the polyol component is, for example, 5 or less, preferably 3 or less, and more preferably 1.1 or less.

[0108] The coating agent may also contain, for example, a solvent. The solvent is mixed with the curing agent and / or the base agent at any ratio. The solids concentration of the curing agent and the base agent are appropriately set depending on the purpose and application.

[0109] The coating agent may further contain additives as needed. Examples of additives include curing accelerators, UV absorbers, light stabilizers, fillers, silane coupling agents, epoxy resins, catalysts, coatability improvers, leveling agents, nucleating agents, lubricants, release agents, antifoaming agents, 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 additives are not particularly limited and may be appropriately determined depending on the purpose and application.

[0110] Furthermore, since such a coating agent contains the blocked isocyanate of the present invention, a cured film (described below) with excellent chemical resistance can be obtained.

[0111] A cured film can be obtained from the coating agent, for example, by applying the coating agent to a substrate.

[0112] The substrate is not particularly limited, and may be a known resin film. Examples of the resin include (meth)acrylic resin, polyester resin, and polycarbonate resin. Preferably, (meth)acrylic resin is used.

[0113] The method for applying the coating agent to the substrate is not particularly limited, and any known application method can be used, such as dip coating, spray coating, roll coating, doctor blade coating, screen printing, bar coating, and applicator application.

[0114] The amount of coating agent to be applied is determined appropriately depending on the purpose and application.

[0115] Next, in this method, the coating agent applied to the substrate is heated to dissociate the blocking agent of the blocked isocyanate. The dissociation conditions are those 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. The dissociation temperature is, for example, 200°C or lower, preferably 180°C or lower.

[0116] In this method, the isocyanate groups regenerated by dissociation of the blocking agent (the isocyanate groups of the curing agent) are reacted with the hydroxyl groups of the polyol component in the base resin to form a urethane at the dissociation temperature. The reaction time is, for example, 10 minutes or more, preferably 20 minutes or more. The reaction time is, for example, 60 minutes or less, preferably 30 minutes or less.

[0117] This dissociates the blocking agent in the blocked isocyanate, and the regenerated isocyanate group of the blocked isocyanate reacts with the hydroxyl group of the polyol component, thereby curing the coating agent. As a result, a cured film of the coating agent is obtained. Furthermore, aging can be performed under appropriate conditions, if necessary.

[0118] Such a cured film has excellent chemical resistance because it is obtained using the above-mentioned coating agent. [Example]

[0119] Specific numerical values ​​of blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be replaced with the corresponding upper limit values ​​(numeric values ​​defined as "not more than" or "less than") or lower limit values ​​(numeric values ​​defined as "not less than" or "exceeding") of blending ratios (content ratios), physical property values, parameters, etc. described in the above "Description of the Invention." Furthermore, unless otherwise specified in the following description, "parts" and "%" are based on mass.

[0120] 1.GPC measurement method The sample was subjected to gel permeation chromatography (GPC) measurement, and the area ratio of each peak area to the total peak area in the resulting chromatogram (chart) was calculated.

[0121] 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 content of isocyanurate mononuclear bodies (trimeric bodies).

[0122] The area ratio of the peak having a peak top in the range of polystyrene-equivalent molecular weight of 1000 or more and less than 10000 (Mn1000-10000 area ratio) was defined as the content of isocyanurate trinuclear or higher compounds (seven or more molecules).

[0123] For the GPC measurement, approximately 0.03 g of the sample was collected, methyl urethane-treated with methanol, excess methanol was removed, and 10 mL of tetrahydrofuran was added to dissolve the sample. The resulting solution was then subjected to GPC measurement under the following conditions.

[0124] Analytical equipment: High-speed GPC equipment HLC-8320 (manufactured by Tosoh) Detector: Differential refractive index detector Eluent: tetrahydrofuran Separation column: The following (1) to (4) are connected in series (1) TSKgel guardcolum HXL-L 6.0 x 40 (Tosoh Corporation) (2) TSKgel G1000HXL 7.8 x 300 (Tosoh Corporation) (3) TSKgel G2000HXL 7.8 x 300 (Tosoh Corporation) (4) TSKgel G3000HXL 7.8 x 300 (Tosoh Corporation) Measurement temperature: 40℃ Flow rate: 1mL / min Sample injection volume: 100μL Analysis device: Eco SEC (manufactured by Tosoh Corporation) System correction Standard material name: Polystyrene Calibration curve creation method: A graph of retention time and molecular weight was created using TOSOH TSKstandard Polystyrene with different molecular weights. Injection volume, injection concentration: 100μL, 1mg / mL

[0125] The gel permeation chromatogram of the polyisocyanate composition of Example 1 is shown in FIG.

[0126] In Fig. 1, Peak No. 5 represents an isocyanurate mononuclear product. In other words, the area ratio of Peak No. 5 to the total peak area is the GPC area ratio of the isocyanurate mononuclear product.

[0127] 1, Peak No. 4 represents an isocyanurate dimer. That is, the area ratio of Peak No. 4 to the total peak area is the GPC area ratio of the isocyanurate dimer.

[0128] 1, peaks No. 1 to No. 3 represent isocyanurate tri- or higher nucleus compounds. That is, the area ratio (total) of peaks No. 1 to No. 3 to the total peak area is the GPC area ratio of isocyanurate tri- or higher nucleus compounds.

[0129] 2. Production of blocked isocyanates

[0130] (1) Synthesis of polyisocyanate Synthesis Example 1 A four-neck flask equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet tube was charged with 100 parts by mass of tolylene diisocyanate (Cosmonate T-80, manufactured by Mitsui Chemicals SKC Polyurethanes Inc.), 60 parts by mass of butyl acetate, 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) under a nitrogen atmosphere, and the inside of the flask was heated to 60°C.

[0131] Next, 0.1 parts by mass of m-cresol (co-catalyst) was added to the flask, and the solution of the isocyanurate catalyst was added dropwise to the flask over 30 minutes.

[0132] The isocyanurate catalyst solution was a mixture of 0.4 parts by mass of a mineral spirit solution of calcium naphthenate (solid content concentration 47% by mass, catalyst solid content 0.19 parts by mass), 40 parts by mass of butyl acetate, and 0.1 parts by mass of n-butanol.

[0133] Next, the temperature inside the flask was adjusted to 60° C.±3° C. Then, the mixture was reacted until the conversion rate of isocyanate groups to isocyanurate reached 70% by mass.

[0134] Then, 0.5 parts by mass of o-toluenesulfonic acid amide (reaction terminator) was added to the flask to terminate the reaction. This resulted in a tolylene diisocyanate derivative containing an isocyanurate derivative of tolylene diisocyanate. The tolylene diisocyanate derivative was then diluted with butyl acetate to obtain a polyisocyanate solution with a solids concentration of 50%.

[0135] Synthesis Example 2 A four-neck flask equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet tube was charged under a nitrogen atmosphere with 100 parts by mass of tolylene diisocyanate (Cosmonate T-80 manufactured by Mitsui Chemicals SKC Polyurethanes Inc., 2,4-tolylene diisocyanate / 2,6-tolylene diisocyanate = 80 mol / 20 mol), 60 parts by mass of butyl acetate, 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), and the inside of the flask was heated to 60°C.

[0136] Next, 0.1 parts by mass of m-cresol (cocatalyst) was added to the flask. An isocyanuration catalyst solution was also added dropwise to the flask over 30 minutes. The isocyanuration catalyst solution was a mixture of 0.4 parts by mass of calcium naphthenate-mineral spirit solution (isocyanuration catalyst), 40 parts by mass of butyl acetate, and 0.1 parts by mass of n-butanol.

[0137] Next, the temperature inside the flask was adjusted to 60° C.±3° C. Then, the above mixture was reacted until the conversion rate of isocyanate groups to isocyanurate reached 30% by mass.

[0138] Next, 0.5 parts by mass of o-toluenesulfonic acid amide (reaction terminator) was added to the flask to terminate the reaction, thereby obtaining a reaction product liquid.

[0139] Next, the reaction product liquid was subjected to thin-film distillation (pressure: 200 PaA, temperature: 100°C, feed rate: 10 g / hour), thereby distilling off butyl acetate.

[0140] Next, 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 rate: 5 g / hour), thereby distilling off unreacted tolylene diisocyanate.

[0141] As a result of the above, a tolylene diisocyanate derivative was obtained, which was then diluted with butyl acetate to obtain a polyisocyanate solution with a solid content of 50%.

[0142] Synthesis Example 3 The mixture was reacted until the conversion rate of isocyanate groups to isocyanurate reached 62%. Except for this, a polyisocyanate solution with a solids concentration of 50% was obtained in the same manner as in Synthesis Example 2.

[0143] Synthesis Example 4 The mixture was reacted until the conversion rate of isocyanate groups to isocyanurate reached 75%. Except for this, a polyisocyanate solution with a solids concentration of 50% was obtained in the same manner as in Synthesis Example 1.

[0144] Synthesis Example 5 The mixture was reacted until the conversion rate of isocyanate groups to isocyanurate reached 24%. A polyisocyanate solution with a solids concentration of 50% was obtained in the same manner as in Synthesis Example 2, except for this.

[0145] Synthesis Example 6 The mixture was reacted until the conversion rate of isocyanate groups to isocyanurate reached 20%. Except for this, a polyisocyanate solution with a solids concentration of 50% was obtained in the same manner as in Synthesis Example 2.

[0146] Synthesis Example 7 The mixture was reacted until the conversion rate of isocyanate groups to isocyanurate reached 78%. Except for this, a polyisocyanate solution with a solids concentration of 50% was obtained in the same manner as in Synthesis Example 1.

[0147] Synthesis Example 8 A xylylene diisocyanate derivative was obtained by the method described in Example 1 of JP 2021-85009 A.

[0148] That is, 100 parts by mass of 1,3-xylylene diisocyanate (m-XDI, manufactured by Mitsui Chemicals, Inc.) and 0.021 parts by mass (0.02 phr) of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (hindered phenol-based antioxidant, trade name: Irganox 1076, manufactured by Ciba Japan) were charged into a reactor equipped with a thermometer, a stirrer, a cooling tube, and a nitrogen inlet tube under a nitrogen atmosphere, and mixed at 60°C to 65°C.

[0149] Next, 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 urethane reaction.

[0150] 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 resulting urethane reaction liquid. The amount of TBAOH (37% methanol solution) added was adjusted to 0.11 parts by mass (0.04 parts by mass as active ingredient) relative to the urethane reaction liquid. Next, while mixing the urethane reaction liquid, 1,3-xylylene diisocyanate was subjected to an isocyanurate-forming reaction at 70°C to 75°C until the conversion rate of the xylylene diisocyanate to the isocyanurate derivative reached 31%.

[0151] Next, a propylene glycol methyl ether acetate solution (active ingredient concentration 50% by mass) of dodecylbenzenesulfonic acid (DDBSA, catalyst deactivator) was added to the resulting reaction product solution to terminate the isocyanurate reaction. The amount of DDBSA added was adjusted to 0.054 parts by mass (the proportion of DDBSA added was 500 ppm relative to the reaction product solution).

[0152] The resulting reaction product liquid was then stirred at 70 to 75°C for an additional 30 minutes. The resulting reaction product liquid was then subjected to thin-film distillation (pressure: 60 PaA or less, temperature: 160°C, feed rate: 5 g / hour) to separate a separated liquid containing the xylylene diisocyanate derivative from a recovered liquid containing unreacted xylylene diisocyanate. Ethyl acetate was added to the separated liquid to adjust the solids concentration to 75% by mass, and 0.04 parts by mass of paratoluenesulfonamide was added as a heat stabilizer. This yielded a solution of the xylylene diisocyanate derivative.

[0153] Furthermore, the xylylene diisocyanate derivative was measured by gel permeation chromatography (GPC) in the same manner as above, and the area ratio of the area of ​​each peak in the obtained chromatogram (chart) to the area of ​​all peaks was determined.

[0154] In the xylylene diisocyanate derivative, the area ratio of the peak having a peak top in the range of polystyrene-equivalent molecular weight of 500 or more and less than 600 (Mn500-600 area ratio) was taken as the content of isocyanurate mononuclear bodies (trimers).

[0155] 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 of 1000 or more but less than 10000 (Mn1000-10000 area ratio) was taken as the content of isocyanurate trinuclear or higher (seven or more molecules).

[0156] Synthesis Example 9 The mixture was reacted until the conversion rate of isocyanate groups to isocyanurate reached 35%. Except for this, a polyisocyanate solution with a solids concentration of 50% was obtained in the same manner as in Synthesis Example 2.

[0157] Examples 1 to 6 and Comparative Examples 1 to 4 The polyisocyanate solution and blocking agent were blended in the combination shown in Table 1. The ratio of the active groups of the blocking agent (blocking groups that block isocyanate groups) to the isocyanate groups of the polyisocyanate solution (blocking groups / isocyanate groups) was adjusted to 1.02.

[0158] 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 reached 20,000 or more. Then, butyl acetate was added to the reaction mixture to adjust the solids concentration to 60% by mass. This produced a blocked isocyanate solution.

[0159] 3. Evaluation (1) Chemical resistance A polyester polyol (Takelac U-25 (trade name), manufactured by Mitsui Chemicals, hydroxyl value: 135 mg KOH / g, solid content: 75%) was prepared as the base resin. A solution of the blocked isocyanate listed in Table 1 was prepared as the curing agent.

[0160] A solution of polyester polyol and blocked isocyanate was mixed. The equivalent ratio of the isocyanate groups of the blocked isocyanate to the hydroxyl groups of the polyester polyol was 1.0. Then, thinner (a 1:1:1 mixture of ethyl acetate, butyl acetate, and propylene glycol monomethyl ether acetate) was added to the mixture, and the mixture was mixed at 23°C for 5 minutes. This adjusted the solids concentration of the mixture to 50% by mass.

[0161] The mixture was then ultrasonicated for 10 minutes to degas the mixture, thereby obtaining a coating liquid.

[0162] The coating solution was applied to a glass plate (JIS R 3202, thickness 2 mm) using a 4 mil applicator. The coating film was then heated in an oven at 150°C for 30 minutes. The coating film was then aged for 3 days in a thermostatic chamber at 23°C and 55% humidity. This resulted in a cured film.

[0163] A paper towel was cut into 1 cm squares. The paper towel was also impregnated with 4-hydroxybutyl acrylate (4HBA, product name, manufactured by Mitsubishi Chemical Corporation). The paper towel was then attached to the cured film of the coating liquid. The paper towel and cured film were then heated in an oven at 80°C for 30 minutes. The paper towel was then removed from the cured film. The surface of the cured film was also wiped, and the surface condition was visually observed. The evaluation criteria are as follows:

[0164] ⊚: No change was observed on the surface of the cured film. ◯: Thin marks were observed on the surface of the cured film, but no cloudiness of the cured film was observed. △: No clouding of the cured film was observed. ×: Swelling, shrinkage and / or peeling of the cured film was observed.

[0165] (2) Turbidity Immediately after preparing the blocked isocyanate solution, the blocked isocyanate solution was poured into a 100 mL glass bottle. Then, while shining a light into the blocked isocyanate solution, the presence or absence of turbidity was visually confirmed. The evaluation criteria are as follows:

[0166] ○: No turbidity was observed. △: Slight turbidity was observed. ×: Turbidity was clearly observed.

[0167] [Table 1]

[0168] Details of the abbreviations in the table are given below. DMP: 3,5-dimethylpyrazole MEKO: Methyl ethyl ketone oxime

Claims

1. 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 tolylene diisocyanate contains 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, the proportion of 2,4-tolylene diisocyanate is 50 mol % or more and 99 mol % or less based on the total moles of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, The isocyanurate derivative of tolylene diisocyanate includes a tri- or higher nucleus isocyanurate derivative of tolylene diisocyanate, The tri- or higher isocyanurate of tolylene diisocyanate is a derivative compound containing three or more isocyanurate groups and seven or more molecules of tolylene diisocyanate, In the chromatogram obtained by measuring the tolylene diisocyanate derivative by gel permeation chromatography, the area ratio of the peak area corresponding to the isocyanurate trinuclear or higher compound of the tolylene diisocyanate to the area of ​​all peaks is 40% or more and 97% or less, A blocked isocyanate, wherein the blocking agent contains a pyrazole-based blocking agent.

2. In the chromatogram obtained by 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 isocyanurate trinuclear or higher nucleus compound of the tolylene diisocyanate to the area of ​​all peaks is 70% or more.

3. The isocyanurate derivative of tolylene diisocyanate includes a mononuclear isocyanurate derivative of tolylene diisocyanate, The mono-isocyanurate of tolylene diisocyanate is a derivative compound containing one isocyanurate group and three molecules of tolylene diisocyanate, In the chromatogram obtained by measuring the tolylene diisocyanate derivative by gel permeation chromatography, The area ratio of the peak area corresponding to the isocyanurate mononuclear body of the tolylene diisocyanate to the area of ​​all peaks (mononuclear body area ratio) The area ratio of the peak area corresponding to the isocyanurate trinuclear or higher of the tolylene diisocyanate to the area of ​​all peaks (trinuclear or higher area ratio) The blocked isocyanate according to claim 1 or 2, wherein the ratio (area ratio of trinuclear or more nuclei / area ratio of mononuclear nuclei) is 1.0 or more and 18.0 or less.

4. A curing agent comprising the blocked isocyanate according to any one of claims 1 to 3; A coating agent comprising a base agent containing a polyol component.

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