Surface smoothing agent for polyurethane coating film, composition, curing agent, polyurethane resin forming composition, paint composition and coating film

Abstract

A composition comprising a polyisocyanate, the polyisocyanate comprising a derivative derived from an aliphatic diisocyanate, and a content of a cyclic compound represented by the following formula (1) being 0.1 to 15 mass % relative to the total amount of the composition: [Formula 1] JPEG0007613642000015.jpg32149 [In formula (1), n ​​is an integer from 1 to 6, and R 1 and R 2 are each independently a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms.]

Description

[Technical field]

[0001] The present disclosure relates to a surface-smoothing agent for polyurethane coatings, a composition, a curing agent, a polyurethane resin-forming composition, a paint composition, and a coating. [Background technology]

[0002] Known curing agents for forming urethane coating films include those containing derivatives derived from general-purpose aliphatic isocyanates such as hexamethylene diisocyanate, pentamethylene diisocyanate, etc. Polyurethane coating films formed using such curing agents have advantages such as reduced baking temperature and high weather resistance, and as demand increases, the required performance is also becoming higher.

[0003] Here, Patent Document 1 discloses a polyisocyanate composition containing a derivative modified with 1.0 to 5.0 parts by mass of isobutyl alcohol relative to 100 parts by mass of pentamethylene diisocyanate and a uretdione derivative consisting of two isocyanate molecules of pentamethylene diisocyanate in a predetermined ratio. According to Patent Document 1, a coating material containing a polyurethane resin obtained from this polyisocyanate composition can improve its hardness, chemical resistance, and surface smoothness in a well-balanced manner. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6482657 [Non-patent literature]

[0005] [Non-Patent Document 1] Journal of Organic Chemistry 1978,43,1544-1546 [Non-Patent Document 2] Zhurnal Vsesoyuznogo Khimicheskogo Obshchestva im. DI Mendeleeva 1979,24,310-311 Summary of the Invention [Problem to be solved by the invention]

[0006] However, particularly in recent years, the market has been demanding increasingly higher performance for polyurethane coating films, and there is a strong demand for the development of new surface smoothing agents for polyurethane coating films that can impart coating film smoothness.

[0007] In view of the above, some aspects of the present disclosure are directed to providing a surface smoothing agent for polyurethane coating films, a composition, a curing agent, a polyurethane resin-forming composition, and a coating composition, which contribute to the production of coating films having excellent surface smoothness. Another aspect of the present disclosure is directed to providing a coating film having excellent surface smoothness. [Means for solving the problem]

[0008] In some aspects, the present disclosure provides the following [1] to

[10] .

[0009] [1] A composition comprising a polyisocyanate, The polyisocyanate includes a derivative derived from an aliphatic diisocyanate, A composition, wherein the content of a cyclic compound represented by the following formula (1) is 0.1 to 15 mass % based on the total amount of the composition: [ka] [In formula (1), n ​​is an integer of 1 to 6, and R 1 and R 2 are each independently a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms.]

[0010] [2] The composition according to [1], wherein the derivative comprises an isocyanurate derived from an aliphatic diisocyanate.

[0011] [3] The composition according to [1] or [2], wherein the aliphatic diisocyanate comprises butane diisocyanate.

[0012] [4] R 1 and the above R 2 each independently represents a hydrogen atom, an aliphatic group having 1 to 20 carbon atoms, an alicyclic group having 3 to 20 carbon atoms, or an aromatic group having 6 to 20 carbon atoms, The composition according to any one of [1] to [3], wherein the aliphatic group, the alicyclic group, and the aromatic group may be substituted with a substituent, and may contain one or more atoms selected from the group consisting of an oxygen atom, a nitrogen atom, and a sulfur atom.

[0013] [5] R 1 and the above R 2 one of which is a hydrogen atom and the other is a monovalent organic group having 1 to 20 carbon atoms.

[0014] [6] A curing agent for forming a polyurethane resin, comprising the composition according to any one of [1] to [5].

[0015] [7] A polyurethane resin-forming composition comprising the composition according to any one of [1] to [5] and a polyol.

[0016] [8] A coating composition comprising the polyurethane resin-forming composition according to [7].

[0017] [9] A coating film comprising a cured product of the coating composition according to [8].

[0018]

[10] A surface smoothing agent for polyurethane coatings, comprising a cyclic compound represented by the following formula (1):

[0019] [ka] [In formula (1), n ​​is an integer of 1 to 6, and R 1 and R 2 are each independently a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms.] Effect of the Invention

[0020] According to some aspects of the present disclosure, it is possible to provide a surface smoothing agent for polyurethane coating films, a composition, a curing agent, a polyurethane resin-forming composition, and a paint composition, which contribute to the production of coating films having excellent surface smoothness. According to another aspect of the present disclosure, it is possible to provide a coating film having excellent surface smoothness. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] In the present specification, the numerical range indicated by "~" indicates a range including the numerical values ​​described before and after "~" as the minimum and maximum values, respectively. In addition, unless specifically stated otherwise, the units of the numerical values ​​described before and after "~" are the same. In the numerical ranges described in stages in this specification, the upper limit or lower limit of a certain stage of the numerical range may be replaced with the upper limit or lower limit of the numerical range of another stage. In addition, in the numerical ranges described in this specification, the upper limit or lower limit of the numerical range may be replaced with a value shown in the examples. In addition, the upper limit and lower limit values ​​described individually can be arbitrarily combined. In addition, in this specification, "(meth)acrylic" means at least one of acrylic and the corresponding acrylic.

[0022] Preferred embodiments of each aspect of the present disclosure will be described below. However, each aspect of the present disclosure is not limited to the following embodiments.

[0023] <Surface smoothing agent for polyurethane coating> A surface leveling agent for polyurethane coatings according to one embodiment of the present disclosure contains a cyclic compound represented by formula (1) (hereinafter referred to as "cyclic compound A").

[0024] [ka]

[0025] In formula (1), n ​​is an integer of 1 to 6. Therefore, the cyclic compound A can be said to be a compound having a cyclic urea group having a 5- to 10-membered ring in the molecule. 1 and R 2 are each independently a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms.

[0026] The cyclic compound A can improve the surface smoothness of the polyurethane coating film.

[0027] From the viewpoints of feasibility on an industrial scale and improving compatibility with polyisocyanate, n in formula (1) may be an integer of 1 to 4. That is, the cyclic compound A may be a compound having a cyclic urea group having a 5- to 8-membered ring.

[0028] R in formula (1) 1 and R 2 From the viewpoint of improving the mechanical properties of the coating film, one of the groups may be a hydrogen atom and the other may be a monovalent organic group having 1 to 20 carbon atoms.

[0029] The monovalent organic group may have 3-18 carbon atoms, or may have 6-17 carbon atoms.

[0030] From the viewpoint of improving compatibility with polyisocyanate and suppressing deterioration of coating film properties, the monovalent organic group may be an aliphatic group having 1 to 20 carbon atoms, an alicyclic group having 3 to 20 carbon atoms, or an aromatic group having 6 to 20 carbon atoms. These groups may be substituted with a substituent and may contain one or more atoms selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms. In other words, the aliphatic group, alicyclic group, and aromatic group in this specification include groups consisting of only carbon atoms and hydrogen atoms, as well as groups in which a part of the group is substituted with a substituent and / or one or more atoms selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms.

[0031] The number of the substituents may be, for example, 1 to 5. Examples of the substituents include a hydroxyl group, an alkoxy group, an amino group, an amide group, a carboxyl group, a carbonyl group, an ester group, an ether group, a thiol group, a thioether group, a vinyl group, an aryl group, an isocyanate group, and a halogeno group. In particular, when a monovalent organic group is substituted with an isocyanate group, that is, when the cyclic compound A is an isocyanate compound, the cyclic compound A is chemically bonded in the polyurethane coating film, so that the cyclic compound A can be prevented from being liberated. The number of isocyanate groups possessed by the cyclic compound may be 2 or more, but is 1 from the viewpoint of improving the smoothness of the coating film.

[0032] The aliphatic group having 1 to 20 carbon atoms may be linear or branched. Examples of the aliphatic group having 1 to 20 carbon atoms include an alkyl group, an alkoxy group, an alkenyl group, a hydroxyalkyl group, a hydroxyalkoxy group, an alkyl group substituted with an alkoxy group, a haloalkyl group, a dihaloalkyl group, a trihaloalkyl group, an alkylamino group, an aminoalkyl group, an alkoxycarbonyl group, an alkylcarbonyl group, a monoalkylamide group which may be substituted with an isocyanate group, and an alkylamide group. The carbon chain of these groups may be linear or branched.

[0033] Examples of the alicyclic group having 3 to 20 carbon atoms include a cycloalkyl group and a bicycloalkyl group.

[0034] Examples of the aromatic group having 6 to 20 carbon atoms include a phenyl group, an alkoxyphenyl group, an arylamino group, a diarylamino group, an arylalkylamino group, a cyclic amino group, an arylcarbonyl group, and an aroyl group.

[0035] From the viewpoint of improving the mechanical properties of the coating film, the monovalent organic group may be a group represented by the following formula (i). [ka]

[0036] In formula (i), X is CH or N, and R 3 and R 4 are each independently a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, and * is a bond bonded to N in formula (1). From the viewpoint of further improving the mechanical properties of the coating film, X may be N. Examples of the monovalent organic group are the same as the examples of the monovalent organic group described above, except for the number of carbon atoms. For example, R 3 and R 4 From the viewpoint of compatibility with polyisocyanate, R may be an aliphatic group having 1 to 18 carbon atoms, an alicyclic group having 3 to 18 carbon atoms, or an aromatic group having 6 to 18 carbon atoms. 3 and R 4 R may be a monovalent organic group substituted with an isocyanate group from the viewpoint of preventing the release of the cyclic compound from the coating film. 3 and R 4 From the viewpoint of further improving the mechanical properties of the coating film while maintaining good compatibility with the polyisocyanate, one of the groups may be a hydrogen atom and the other may be a monovalent organic group having 1 to 18 carbon atoms.

[0037] From the viewpoint of improving compatibility with polyisocyanate and preventing separation from the coating film, the cyclic compound A may be a compound represented by the following formula (1A). [ka]

[0038] In formula (1A), m may be an integer of 1-4.

[0039] Specific examples of the cyclic compound A include compounds represented by the following formulas (2) to (4). [ka]

[0040] The cyclic compound A can be synthesized, for example, according to the synthesis methods described in Non-Patent Documents 1-2 and the like, or the synthesis methods described in the Examples described later. In addition, the cyclic compound A can be obtained by carrying out an isocyanuration reaction of an aliphatic diisocyanate in a diluted state with an organic solvent to proceed with the reaction to generate the cyclic compound A. Hereinafter, the reaction to generate the cyclic compound A is called a cyclization reaction. Details of the isocyanuration will be described later.

[0041] The cyclic compound A may be the main component of the surface smoothing agent for polyurethane coating films. The surface smoothing agent for polyurethane coating films may consist of only the cyclic compound A, or may contain components other than the cyclic compound A (such as components mixed in during the production of the cyclic compound A). The content of the cyclic compound A may be, for example, 60% by mass or more, 80% by mass or more, or 90% by mass or more based on the total mass of the surface smoothing agent for polyurethane coating films.

[0042] <Composition> A composition according to one embodiment of the present disclosure is a composition containing a polyisocyanate (hereinafter also referred to as a "polyisocyanate composition"), in which the polyisocyanate contains a derivative (hereinafter also referred to as a "derivative A") derived from an aliphatic diisocyanate, and the content of the above-mentioned cyclic compound A is 0.1 to 15 mass % with respect to the total amount of the composition (polyisocyanate composition).

[0043] The composition can be used as a curing agent for forming a polyurethane resin. The composition can provide a curing agent that contributes to the formation of a polyurethane coating film having excellent surface smoothness.

[0044] The aliphatic diisocyanate may be, for example, a diisocyanate represented by OCN-R-NCO (R is an alkylene group having 2 to 30 carbon atoms which may be substituted with a substituent). The alkylene group may have 2 to 4 carbon atoms. Examples of the substituent include an alkyl group, a carbonyl group, an ester group, a vinyl group, an aryl group, an ether group, a thioether group, and a halogeno group.

[0045] Specific examples of the aliphatic diisocyanate include ethane diisocyanate, propane diisocyanate, butane diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, etc. Among these, when butane diisocyanate is used (i.e., when the polyisocyanate composition contains a derivative derived from an aliphatic diisocyanate including butane diisocyanate), compatibility with the cyclic compound A is good, and the coating film tends to have a higher hardness.

[0046] The aliphatic diisocyanate may be used alone or in combination of two or more kinds. In other words, the derivative A may be rephrased as a derivative derived from at least one aliphatic diisocyanate.

[0047] The derivative A may be an isocyanurate, an iminooxadiazinedione, an oxadiazinetrione, a uretdione, an allophanate, a biuret, an adduct with a compound having a hydroxyl group, or the like. In particular, when an isocyanurate is used as the derivative A (i.e., when the polyisocyanate composition contains an isocyanurate derived from an aliphatic diisocyanate), the weather resistance and hardness of the resulting coating film tend to be improved. The isocyanurate may be a mononuclear isocyanurate (an aliphatic diisocyanate trimer having one isocyanurate group) or a polynuclear isocyanurate, or a mixture thereof.

[0048] The content of the isocyanurate mononuclear may be 40% by mass or more, 50% by mass or more, or 60% by mass or more, based on the total amount of the polyisocyanate composition, from the viewpoint of improving the weather resistance and hardness of the resulting coating film. The content of the isocyanurate mononuclear may be 85% by mass or less, 75% by mass or less, or 65% by mass or less, based on the total amount of the polyisocyanate composition, from the viewpoint of improving the workability of the resulting coating material. From the above viewpoint, the content of the isocyanurate mononuclear may be 40 to 85% by mass, based on the total amount of the polyisocyanate composition.

[0049] The content of the isocyanurate mononuclear compound can be measured, for example, by gel permeation chromatography (GPC). More specifically, it can be measured in accordance with the examples described later.

[0050] The content of derivative A may be 80 to 99.9% by mass relative to the total amount of the polyisocyanate composition, from the viewpoint of easily obtaining a cured film having better surface smoothness. From the same viewpoint, the content of derivative A may be 85% by mass or more, 90% by mass or more, 92% by mass or more, or 95% by mass or more, and 99% by mass or less, or 98% by mass or less, relative to the total amount of the polyisocyanate composition. In addition, when the cyclic compound A is a derivative derived from an aliphatic diisocyanate, the above "content of derivative A" does not include the content of the cyclic compound A. The same applies to the content of derivative A in the "total amount of the content of derivative A and the content of cyclic compound A" described later.

[0051] The cyclic compound A is a compound represented by the above formula (1). Details of the cyclic compound A are omitted because they are the same as those of the cyclic compound A contained in the above surface smoothing agent for polyurethane coating films.

[0052] From the viewpoint of making it easier to obtain a cured film having superior surface smoothness, the content of the cyclic compound A may be 1 mass % or more or 2 mass % or more, and may be 10 mass % or less, 8 mass % or less, or 5 mass % or less, relative to the total amount of the polyisocyanate composition.

[0053] In this embodiment, the content of cyclic compound A relative to the total content of derivative A and cyclic compound A may be 0.1 to 15 mass %. The content may be 1 mass % or more, or 2 mass % or more, and may be 10 mass % or less, 8 mass % or less, or 5 mass % or less.

[0054] The content of the cyclic compound A can be measured, for example, by gel permeation chromatography (GPC). More specifically, it can be measured in accordance with the examples described later.

[0055] The polyisocyanate composition may contain components other than the above-mentioned compounds (components mixed in during the production of derivative A, components mixed in during the production of cyclic compound A, etc.) to the extent that the effects of the present disclosure are not impaired.

[0056] The polyisocyanate composition may be obtained by mixing a derivative A synthesized in advance with a cyclic compound A. For example, the polyisocyanate composition can be prepared by adding a cyclic compound A to a composition containing a polyisocyanate obtained by isocyanurating an aliphatic diisocyanate. As described above, the polyisocyanate composition can also be obtained by carrying out an isocyanuration reaction of an aliphatic diisocyanate in a diluted state with an organic solvent.

[0057] A commonly known isocyanuration catalyst can be used for the isocyanuration to form an isocyanurate group. Examples of the isocyanuration catalyst for aliphatic diisocyanates include quaternary onium salts, carboxylate metal salts, and aminosilyl group-containing compounds. These isocyanuration catalysts can be used alone or in combination of two or more.

[0058] The isocyanurate catalyst may be an aminosilyl group-containing compound such as aminosilane or silyl urea from the viewpoint of suppressing the formation of high molecular weight substances. In particular, when a disilazane such as hexamethyldisilazane or heptamethyldisilazane is used, the formation of high molecular weight substances can be further suppressed.

[0059] The amount of these catalysts used varies depending on the type of catalyst used, but may be 0.01 to 10% by mass, or may be 0.1 to 3% by mass, based on the amount of the charged isocyanate compound.

[0060] The reaction temperature for isocyanuration may be 60 to 180° C., or may be 100 to 160° C. When the reaction temperature for isocyanuration is 60° C. or higher, the reaction time can be shortened, and coloration of the polyisocyanate composition can be further suppressed.

[0061] In the isocyanuration, a reaction terminator may be added to stop the reaction when the target isocyanate group content and molecular weight are reached. The reaction terminator has the effect of deactivating the catalyst, and specific examples thereof include water and compounds having a hydroxyl group. Alcohols may be used as the reaction terminator. These terminators may be used alone or in combination of two or more. It is preferable to add the reaction terminator promptly after the target isocyanate group content and molecular weight are reached.

[0062] The amount of the reaction terminator to be added varies depending on the type of reaction terminator and the type of catalyst used, but may be 0.1 to 3.5 equivalents of the catalyst, or may be 0.8 to 2.5 equivalents. When the reaction terminator is 0.1 equivalent or more, the storage stability of the resulting polyisocyanate composition is further improved. When the reaction terminator is 3.5 equivalents or less, the generation of the reaction product of the reaction terminator and the aliphatic diisocyanate can be further suppressed, so that the decrease in the isocyanate group content can be more highly suppressed.

[0063] When carrying out a cyclization reaction (i.e., when carrying out an isocyanuration reaction of an aliphatic diisocyanate in a state diluted with an organic solvent to produce a cyclic compound A), the cyclization reaction is facilitated by using an aliphatic diisocyanate having 4 or less carbon atoms. Among these, the use of butane diisocyanate provides a good balance between the reaction rates of the cyclization reaction and the isocyanuration reaction.

[0064] When carrying out a cyclization reaction, an organic solvent having a boiling point equal to or higher than the reaction temperature may be used, which does not affect the reaction. Examples of the organic solvent include aliphatic hydrocarbons such as octane, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, ketones such as methyl isobutyl ketone and cyclohexanone, esters such as butyl acetate and isobutyl acetate, glycol ether esters such as ethylene glycol ethyl ether acetate, propylene glycol monomethyl ether acetate, 3-methyl-3-methoxybutyl acetate, and ethyl-3-ethoxypropionate, ethers such as dioxane, halogenated hydrocarbons such as methylene iodide and monochlorobenzene, and polar aprotic solvents such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, and hexamethylphosphonylamide. These solvents may be used alone or in combination of two or more.

[0065] The substrate concentration may be 20 to 80% by mass, 30 to 70% by mass, or 40 to 60% by mass. If the substrate concentration is within the above range, the cyclization reaction time can be shortened, and thus coloring and thickening of the product can be further suppressed.

[0066] The cyclization reaction time varies depending on the type of catalyst used, the amount of catalyst added, the substrate concentration, the reaction temperature, etc., but may be 150 minutes or less, 140 minutes or less, or 120 minutes or less. By setting the cyclization reaction time to 150 minutes or less, the production amount of cyclic compound A can be easily controlled to 15 mass% or less.

[0067] The above-mentioned isocyanuration reaction and cyclization reaction can be carried out sequentially or in parallel. During or after the isocyanuration reaction, the reaction system is diluted with an organic solvent and then the cyclization reaction is carried out, thereby preventing coloration of the reaction solution and thickening of the product.

[0068] The organic solvent used in the reaction may be removed at the same time as the free aliphatic diisocyanate is removed. In order to remove the free aliphatic diisocyanate, for example, a removal method by thin film distillation at 90 to 140°C under a high vacuum of 10 to 300 Pa or an extraction method using an organic solvent may be applied. The residual content of the free aliphatic diisocyanate present in the reaction solution may be 5% by mass or less. When the residual content of the aliphatic diisocyanate is 5% by mass or less, the generation of odor can be further suppressed and the decrease in storage stability can be suppressed.

[0069] For the purpose of extending the pot life, making the coating composition one-component, etc., the polyisocyanate in the polyisocyanate composition may be made into a blocked isocyanate by using a known blocking agent. That is, the polyisocyanate in the polyisocyanate composition may be a blocked isocyanate. Blocked isocyanates are inactive at room temperature, but when heated, the blocking agent dissociates and the isocyanate group is activated again, so that a latent function of reacting with an active hydrogen group can be added.

[0070] The blocking agent is a compound having one active hydrogen in the molecule, and examples thereof include alcohol-based, alkylphenol-based, phenol-based, active methylene, mercaptan-based, acid amide-based, acid imide-based, imidazole-based, urea-based, oxime-based, amine-based, imide-based, and pyrazole-based compounds.

[0071] The polyisocyanate composition described above may be used as a curing agent alone or in combination with other components.

[0072] <Hardening agent> A curing agent according to one embodiment of the present disclosure is a curing agent for forming a polyurethane resin, which contains the composition (polyisocyanate composition) according to the above embodiment.

[0073] The above curing agent makes it possible to form a polyurethane coating film having excellent surface smoothness.

[0074] The curing agent may consist of only the polyisocyanate composition, or may contain components other than the polyisocyanate composition. Examples of the components other than the polyisocyanate composition include additives that can be contained in the coating composition described below.

[0075] The content of cyclic compound A in the curing agent may be 0.1 to 15 mass% relative to the total content of derivative A and cyclic compound A, or may be 1 mass% or more, or 2 mass% or more, or may be 10 mass% or less, 8 mass% or less, or 5 mass% or less.

[0076] <Polyurethane resin-forming composition> A polyurethane resin-forming composition according to one embodiment of the present disclosure includes the polyisocyanate composition of the above embodiment and a polyol. The polyurethane resin-forming composition may be a composition including the curing agent of the above embodiment and a polyol.

[0077] The polyurethane resin-forming composition can be used in a coating material for forming a coating film. The polyurethane resin-forming composition can provide a coating material composition capable of forming a polyurethane coating film having excellent surface smoothness.

[0078] The polyurethane resin-forming composition may be a one-liquid type composition in which all of the components are contained in one liquid, or may be a multi-liquid type composition in which the components are separated and present in a plurality of liquids. For example, the polyurethane resin-forming composition may contain a first liquid (main agent) containing a polyol and a second liquid (curing agent) containing a polyisocyanate composition. The polyurethane resin-forming composition may contain the first liquid, the second liquid, and a third liquid other than these. When the polyurethane resin-forming composition is a multi-liquid type composition, the other components (catalyst, etc.) may be contained in the first liquid, the second liquid, or the third liquid.

[0079] The polyol is a compound containing an active hydrogen group as a reactive group with an isocyanate group. The polyol is not particularly limited, and polyester polyol, polyether polyol, polycarbonate polyol, polyolefin polyol, acrylic polyol, silicone polyol, castor oil polyol, fluorine polyol, ester exchange product of two or more kinds of polyol, and hydroxyl group-terminated prepolymers that have undergone urethane reaction with polyisocyanate can be used. These may be used alone or in combination of two or more kinds.

[0080] (Polyester polyol) Examples of polyester polyols include those obtained by a condensation polymerization reaction between one or more dicarboxylic acids or anhydrides thereof and one or more low molecular weight polyols having a molecular weight of not more than 500. Examples of dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, succinic acid, tartaric acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, glutaconic acid, azelaic acid, sebacic acid, 1,4-cyclohexyldicarboxylic acid, α-hydromuconic acid, β-hydromuconic acid, α-butyl-α-ethylglutaric acid, α,β-diethylsuccinic acid, maleic acid, and fumaric acid. Examples of low molecular weight polyols having a molecular weight of 500 or less include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, dimer diol, bisphenol A, ethylene oxide or propylene oxide adducts of bisphenol A, bis(β-hydroxyethyl)benzene, xylylene glycol, glycerin, trimethylolpropane, and pentaerythritol. Also usable are lactone-based polyester polyols obtained by ring-opening polymerization of cyclic ester (so-called lactone) monomers such as ε-caprolactone, alkyl-substituted ε-caprolactone, δ-valerolactone, alkyl-substituted δ-valerolactone, etc. Furthermore, it is also possible to use polyester-amide polyols obtained by replacing a part of the low molecular weight polyol with a low molecular weight polyamine or low molecular weight amino alcohol such as hexamethylenediamine, isophoronediamine, monoethanolamine, etc.

[0081] (Polyether polyol) Examples of polyether polyols include polyether polyols obtained by addition polymerization of alkylene oxides using compounds having two or more (e.g., 2 to 3) active hydrogen groups, such as low molecular weight polyols and low molecular weight polyamines, as initiators. Examples of low molecular weight polyols include the same compounds exemplified as the low molecular weight polyols having a molecular weight of 500 or less. Examples of low molecular weight polyamines include ethylene diamine, propylene diamine, toluene diamine, metaphenylene diamine, diphenylmethane diamine, xylylene diamine, etc. Examples of alkylene oxides include ethylene oxide, propylene oxide, butylene oxide, etc. In addition, polyether polyols obtained by ring-opening polymerization of alkyl glycidyl ethers such as methyl glycidyl ether, aryl glycidyl ethers such as phenyl glycidyl ether, and cyclic ether monomers such as tetrahydrofuran can also be used.

[0082] (Polycarbonate polyol) Examples of polycarbonate polyols include those obtained by a dealcoholization reaction or a dephenolation reaction between one or more low molecular weight polyols and diaryl carbonates. Examples of low molecular weight polyols include the same compounds as those exemplified as low molecular weight polyols having a molecular weight of 500 or less. Examples of diaryl carbonates include dialkyl carbonates such as dimethyl carbonate and diethyl carbonate, alkylene carbonates such as ethylene carbonate and propylene carbonate, diphenyl carbonate, dinaphthyl carbonate, dianthryl carbonate, diphenanthryl carbonate, diindanyl carbonate, and tetrahydronaphthyl carbonate. In addition, examples of polycarbonate polyols include polyols obtained by ester exchange reaction between polycarbonate polyol, polyester polyol, and low molecular weight polyol.

[0083] (Polyolefin polyol) Examples of polyolefin polyols include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, and hydrogenated polyisoprene.

[0084] (Acrylic polyol) Examples of acrylic polyols include those obtained by polymerizing or copolymerizing an acrylic ester and / or a methacrylic ester (hereinafter referred to as a (meth)acrylic ester), an acrylic acid hydroxy compound and / or a methacrylic acid hydroxy compound (hereinafter referred to as a (meth)acrylic acid hydroxy compound), and a polymerization initiator using light energy such as ultraviolet light or an electron beam, or heat energy.

[0085] ((Meth)acrylic acid ester) Examples of (meth)acrylic acid esters include alkyl esters having 1 to 20 carbon atoms. Examples of such (meth)acrylic acid esters include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, and dodecyl (meth)acrylate; esters of (meth)acrylic acid with alicyclic alcohols such as cyclohexyl (meth)acrylate; and (meth)acrylic acid aryl esters such as phenyl (meth)acrylate and benzyl (meth)acrylate. The (meth)acrylic acid esters can be used alone or in combination of two or more.

[0086] ((Meth)acrylic acid hydroxy compound) The (meth)acrylic acid hydroxy compound has at least one hydroxyl group in the molecule that can be a reaction site with polyisocyanate. Examples of the (meth)acrylic acid hydroxy compound include acrylic acid hydroxy compounds such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 3-hydroxy-2,2-dimethylpropyl acrylate, and pentaerythritol triacrylate. In addition, methacrylic acid hydroxy compounds such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 3-hydroxy-2,2-dimethylpropyl methacrylate, and pentaerythritol trimethacrylate can also be used. The (meth)acrylic acid hydroxy compound can be used alone or in combination of two or more.

[0087] (Silicone polyol) Examples of silicone polyols include vinyl group-containing silicone compounds obtained by polymerizing γ-methacryloxypropyltrimethoxysilane, and polysiloxanes having at least one terminal hydroxyl group in the molecule, such as α,ω-dihydroxypolydimethylsiloxane and α,ω-dihydroxypolydiphenylsiloxane.

[0088] (Castor oil-based polyol) Examples of castor oil-based polyols include linear or branched polyester polyols obtained by reacting castor oil fatty acids with polyols. In addition, dehydrated castor oil, partially dehydrated castor oil, and hydrogenated castor oil can also be used.

[0089] (Fluorine-based polyol) The fluorine-based polyol may be, for example, a linear or branched polyol obtained by copolymerization of a fluorine-containing monomer and a monomer having a hydroxyl group as essential components. Here, the fluorine-containing monomer may be a fluoroolefin. Examples of the fluorine-containing monomer include tetrafluoroethylene, chlorotrifluoroethylene, trichlorofluoroethylene, hexafluoropropylene, vinylidene fluoride, vinyl fluoride, trifluoromethyltrifluoroethylene, etc. In addition, examples of the monomer having a hydroxyl group include hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and cyclohexanediol monovinyl ether, hydroxyalkyl allyl ethers such as 2-hydroxyethyl allyl ether, hydroxyl group-containing vinyl carboxylates such as hydroxyalkyl vinyl crotonates, and hydroxyl group-containing allyl esters.

[0090] The number of active hydrogen groups (average number of functional groups) in one molecule of the polyol may be 1.9 to 6.0. If the number of active hydrogen groups is within the above range, the resulting coating film exhibits excellent hardness.

[0091] The number average molecular weight of the polyol may be in the range of 750 to 50000. When the number average molecular weight of the polyol is 750 or more, the adhesion is further improved, and when it is 50000 or less, the solubility in low-polarity organic solvents is further improved, and the adhesion is further improved.

[0092] In the polyurethane resin forming composition, the content ratio of the polyisocyanate composition and the polyol is not particularly limited, but the molar ratio of the isocyanate group in the polyisocyanate composition to the hydroxyl group in the polyol (R = isocyanate group / hydroxyl group) may be 0.5 to 2.5. When the molar ratio is 0.5 or more, the hydroxyl group does not become too excessive, and the adhesion is further improved. In addition, the decrease in crosslink density is suppressed, and the durability and mechanical strength of the coating film become further improved. When the molar ratio is 2.5 or less, the isocyanate group does not become too excessive, and the reaction with moisture in the air is suppressed, so the swelling of the coating film is further reduced, and the associated decrease in adhesion is further suppressed. From the same viewpoint as above, the ratio of the total number of moles of isocyanate groups contained in the isocyanate group-containing compound contained in the polyurethane resin-forming composition to the total number of moles of hydroxyl groups contained in the hydroxyl group-containing compound contained in the polyurethane resin-forming composition (R'=isocyanate groups / hydroxyl groups) may be 0.5 to 2.5.

[0093] The organic solvent used as the dilution solvent can be appropriately selected from the group consisting of ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, etc., esters such as ethyl acetate, butyl acetate, cellosolve acetate, etc., alcohols such as butanol, isopropyl alcohol, etc., hydrocarbons such as toluene, xylene, cyclohexane, mineral spirits, naphtha, etc., depending on the purpose and application. These solvents may be used alone or in combination of two or more.

[0094] <Paint composition> A coating composition according to one embodiment of the present disclosure includes the polyurethane resin-forming composition of the above embodiment.

[0095] The coating composition may contain a known urethanization catalyst as appropriate, taking into consideration pot life, curing conditions, working conditions, etc. Examples of the urethanization catalyst include organometallic compounds such as dibutyltin diacetate, dibutyltin dilaurate, and dioctyltin dilaurate, and organic amines such as triethylenediamine and triethylamine, and salts thereof. These catalysts may be used alone or in combination of two or more.

[0096] The curing conditions for the coating composition are not particularly limited, but the curing temperature may be from -5 to 150°C, the humidity may be from 10 to 95% RH, and the curing time may be from 0.5 to 336 hours.

[0097] If necessary, additives such as antioxidants such as 2,6-di-tert-butyl-4-methylphenol, ultraviolet absorbers, pigments, dyes, solvents, flame retardants, hydrolysis inhibitors, lubricants, plasticizers, fillers, antistatic agents, dispersants, catalysts, storage stabilizers, surfactants, and leveling agents can be appropriately blended into the coating composition.

[0098] <Coating film (cured film)> A coating film according to one embodiment of the present disclosure includes a cured product of the coating composition according to the above embodiment.

[0099] The coating film is formed using the coating composition of the above embodiment. Therefore, the coating film has excellent surface smoothness. The excellent surface smoothness of the coating film can be confirmed, for example, by the arithmetic mean roughness of the coating film at 23°C. The arithmetic mean roughness of the coating film can be measured in accordance with JIS B0601. The arithmetic mean roughness of the coating film at 23°C can be, for example, 150 nm or less, 125 nm or less, or 100 nm or less.

[0100] The coating film can be formed by applying the coating composition onto the surface of the adherend by a known method such as spraying, brushing, dipping, or using a coater, and then curing the composition.

[0101] The adherend is not particularly limited, and examples thereof include stainless steel, phosphate-treated steel, galvanized steel, iron, copper, aluminum, brass, glass, slate, acrylic resin, polycarbonate resin, polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene phthalate resin, polystyrene resin, AS resin, ABS resin, polycarbonate-ABS resin, 6-nylon resin, 6,6-nylon resin, MXD6 nylon resin, polyvinyl chloride resin, polyvinyl alcohol resin, polyurethane resin, phenolic resin, melamine resin, polyacetal resin, chlorinated polyolefin resin, polyolefin resin, polyamide resin, polyether ether ketone resin, polyphenylene sulfide resin, NBR resin, chloroprene resin, SBR resin, and SEBS resin. Adherends molded from materials such as polyethylene and polypropylene that have been subjected to corona discharge treatment or other surface treatments, and adherends on which a coating layer that can be an intermediate is formed on the surface of the adherend can be used.

[0102] The thickness of the coating film formed on the surface layer of the adherend may be 10 μm or more from the viewpoint of obtaining a coating film excellent in recoatability, durability, etc. When the thickness is 10 μm or more, durability is improved and the occurrence of breakage of the coating film due to impact can be further suppressed. EXAMPLES

[0103] The contents of the present disclosure will be described in more detail below using examples and comparative examples, but the present disclosure is not limited to the following examples.

[0104] First, synthesis examples for producing a compound having a cyclic urea group (cyclic compound A) contained in the polyisocyanate composition of the present embodiment will be specifically described, but the cyclic compound contained in the polyisocyanate composition according to one aspect of the present disclosure is not limited to these.

[0105] <Synthesis Example 1> In a 100mL four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube, 1.0g of 1,3-Diazocan-2-one and 1.2g of triethylamine were charged and dissolved in 41g of methylene chloride. This was heated to 80°C, and 1.3g of 2-ethylhexanoyl chloride was slowly dropped over 20 minutes and stirred for 60 minutes. The reaction solution was then cooled to room temperature, and the precipitated hydrochloride was removed by filtration. The methylene chloride in the filtrate was distilled off under reduced pressure using an evaporator. 20g of water was added to the concentrate and stirred vigorously. The precipitate was then collected by filtration and washed with 5.0g of water to obtain 1.5g of a cyclic compound Cy-1. Cy-1 is represented by the following formula (2).

[0106] [ka]

[0107] <Synthesis Example 2> In a 50mL three-neck flask equipped with a stirrer and nitrogen gas inlet tube, 1.0g of 1,2-diisocyanatoethane and 4.0g of ethyl acetate were charged, heated to 40°C, 2.2g of dioctylamine was slowly dripped in over 10 minutes, and stirred for 30 minutes. The ethyl acetate was then distilled off under reduced pressure using an evaporator to obtain 3.2g of the cyclic compound Cy-2. Cy-2 is represented by the following formula (3).

[0108] [ka]

[0109] <Example 1> (Synthesis of polyisocyanate composition) A 1L four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube was charged with 500g of 1,4-butane diisocyanate (NCO content: 60.0% by mass, hereinafter abbreviated as BDI), which was heated to 100°C, 5.0g of hexamethyldisilazane, an isocyanurate catalyst, was added, and the mixture was heated to 120°C and stirred for 1.7 hours. Then, 500g of butyl acetate was added and stirred for 15 minutes. Then, the mixture was cooled to 50°C in a water bath, and 3.0g of ethanol, a reaction terminator, was added, and the reaction was terminated at 50°C for 30 minutes. After cooling the reaction solution, excess BDI and butyl acetate were removed by thin-film distillation (conditions: 110°C, 0.04kPa), and 62g of polyisocyanate composition P-1 was obtained. P-1 contained 1.6% by mass of a compound represented by the following formula (4) (cyclic compound Cy-3) and 59.0% by mass of an isocyanurate mononuclear product. In this example, the content of the cyclic compound and the content of the isocyanurate mononuclear product were measured by the following method.

[0110] [ka]

[0111] (Measurement of the content of cyclic compounds and mononuclear isocyanurate compounds) The content of cyclic compounds and the content of mononuclear isocyanurate compounds relative to the total amount of the polyisocyanate composition were measured by GPC using the following apparatus. Equipment: HLC-8420 (Tosoh Corporation) Column: TSKgel (Tosoh Corporation) G3000H-XL, G2000H-XL, G1000H-XL, one of each connected in series Carrier: Tetrahydrofuran Detection method: Differential refractive index detector

[0112] The differential refractive index peak of the cyclic compound differs depending on the chemical structure of the cyclic compound, but in the case of Cy-3 (compound of formula (4)), it appears at a retention time of about 25.9 minutes. The area of ​​this peak was obtained, and the content of the cyclic compound was calculated by the following formula. Content of cyclic compounds (mass%) = peak area at retention time 25.9 minutes / total area of ​​all peaks × 100 The retention times of Cy-1 and Cy-2 are approximately 25.1 and 26.4 min, respectively.

[0113] The differential refractive index peak of the isocyanurate mononuclear compound differs depending on the type of aliphatic diisocyanate used, but when 1,4-butane diisocyanate is used, it appears at a retention time of about 23.8 minutes. The area of ​​this peak was determined, and the content of the isocyanurate mononuclear compound was calculated using the following formula. Content of isocyanurate mononuclear compound (mass%) = peak area at retention time 23.8 minutes / total area of ​​all peaks × 100

[0114] <Example 2> 500g of BDI was charged into a 1L four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube, and this was heated to 100°C, 5.0g of hexamethyldisilazane, which is an isocyanurate catalyst, was added, and the temperature was raised to 120°C and stirred for 1.7 hours. Then, 500g of butyl acetate was added and stirred for 45 minutes. Then, the temperature was lowered to 50°C in a water bath, 3.0g of ethanol, which is a reaction terminator, was added, and the termination reaction was carried out at 50°C for 30 minutes. After cooling the reaction solution, excess BDI and butyl acetate were removed by thin film distillation (conditions: 110°C, 0.04kPa), and 62g of polyisocyanate composition P-2 was obtained. P-2 contained 4.2% by mass of the compound (Cy-3) represented by formula (4) and 57.2% by mass of isocyanurate mononuclear bodies.

[0115] <Example 3> 500g of BDI was charged into a 1L four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube, and this was heated to 100°C, 5.0g of hexamethyldisilazane, which is an isocyanurate catalyst, was added, and the temperature was raised to 120°C and stirred for 1.7 hours. Then, 500g of butyl acetate was added and stirred for 80 minutes. Then, the temperature was lowered to 50°C in a water bath, 3.0g of ethanol, which is a reaction terminator, was added, and the termination reaction was carried out at 50°C for 30 minutes. After cooling the reaction solution, excess BDI and butyl acetate were removed by thin film distillation (conditions: 110°C, 0.04kPa), and 62g of polyisocyanate composition P-3 was obtained. P-3 contained 8.3% by mass of the compound (Cy-3) represented by formula (4) and 54.5% by mass of isocyanurate mononuclear bodies.

[0116] <Example 4> A 300 mL three-neck flask equipped with a stirrer and a nitrogen gas inlet tube was charged with 150 g of C-HXLV (HDI-based isocyanurate composition, manufactured by Tosoh Corporation) and 0.75 g of Cy-1, and stirred for 0.5 hours to obtain polyisocyanate composition P-4. P-4 contained 4.5 mass% of the compound (Cy-1) represented by formula (2) and 63.9 mass% of a mononuclear isocyanurate.

[0117] <Example 5> 500g of BDI was charged into a 1L four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube, and this was heated to 100°C, 5.0g of hexamethyldisilazane, which is an isocyanurate catalyst, was added, and the temperature was raised to 120°C and stirred for 1.7 hours. Then, the temperature was lowered to 50°C in a water bath, 3.0g of ethanol, which is a reaction terminator, was added, and the reaction was stopped at 50°C for 30 minutes. After cooling the reaction solution, excess BDI was removed by thin-film distillation (conditions: 110°C, 0.04kPa), and 62g of a polyisocyanate composition was obtained. 150g of the obtained polyisocyanate composition and 1.5g of Cy-2 were charged into a 300mL three-neck flask equipped with a stirrer and a nitrogen gas inlet tube, and stirred for 0.5 hours to obtain P-5. P-5 contained 8.9% by mass of the compound (Cy-2) represented by formula (3) and 54.6% by mass of an isocyanurate mononuclear compound.

[0118] <Comparative Example 1> 500g of BDI was charged into a 1L four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube, and this was heated to 100°C, 5.0g of hexamethyldisilazane, which is an isocyanurate catalyst, was added, and the temperature was raised to 150°C and stirred for 1.0 hour. Then, the temperature was lowered to 50°C in a water bath, 3.0g of ethanol, which is a reaction terminator, was added, and the termination reaction was carried out at 50°C for 30 minutes. After cooling the reaction solution, excess BDI was removed by thin film distillation (conditions: 110°C, 0.04kPa), and 65g of polyisocyanate composition P-6 was obtained. P-6 contained 0.08% by mass of the compound (Cy-3) represented by formula (4) and 61.1% by mass of isocyanurate mononuclear bodies.

[0119] <Comparative Example 2> 150 g of C-HXLV and 3.0 g of Cy-1 were charged into a 300 mL three-neck flask equipped with a stirrer and a nitrogen gas inlet tube, and stirred for 0.5 hours to obtain polyisocyanate composition P-7. P-7 contained 16.5% by mass of the compound (Cy-1) represented by formula (2) and 55.9% by mass of a mononuclear isocyanurate. was included.

[0120] <Comparative Example 3> In a 1L four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube, 500g of BDI and 500g of butyl acetate were charged, and this was heated to 100°C, 7.5g of hexamethyldisilazane, which is an isocyanurate catalyst, was added, and the temperature was raised to 120°C and stirred for 2.0 hours. Thereafter, the temperature was lowered to 50°C in a water bath, 4.5g of ethanol, which is a reaction terminator, was added, and the termination reaction was carried out at 50°C for 30 minutes. After cooling the reaction solution, excess BDI and butyl acetate were removed by thin film distillation (conditions: 110°C, 0.04kPa), and 60g of polyisocyanate composition P-8 was obtained. P-8 contained 21.0% by mass of the compound (Cy-3) represented by formula (4) and 41.2% by mass of isocyanurate mononuclear bodies.

[0121] <Comparative Example 4> In a 1L four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube, 500g of 1,6-hexane diisocyanate (HDI) and 500g of butyl acetate were charged, and this was heated to 100°C, 7.5g of hexamethyldisilazane, which is an isocyanurate catalyst, was added, and the temperature was raised to 120°C and stirred for 2.0 hours. Thereafter, the temperature was lowered to 50°C in a water bath, 4.5g of ethanol, which is a reaction terminator, was added, and the termination reaction was carried out at 50°C for 30 minutes. After cooling the reaction solution, excess HDI and butyl acetate were removed by thin-film distillation (conditions: 130°C, 0.04kPa), and 61g of polyisocyanate composition P-9 was obtained. P-9 contained 65.4% by mass of isocyanurate mononuclear bodies, but did not contain cyclic compounds.

[0122] <Preparation of two-component coating composition and evaluation of surface smoothness> After preparing a coating composition consisting of the obtained polyisocyanate composition and acrylic polyol, the coating composition was used to form a coating film, and the surface smoothness of the formed coating film was evaluated. Specifically, an acrylic polyol (trade name: Acrydic A-801, hydroxyl value: 50 mg KOH / resin g, solid content: 50 mass%, manufactured by DIC Corporation) and a polyisocyanate composition were mixed so that the equivalent ratio of hydroxyl groups to isocyanate groups was 1:1, and then butyl acetate was added to prepare a coating composition with a coating solid content of 40 mass%. Next, the obtained coating composition was applied to a steel plate (JIS G3141, trade name: SPCC-SB, treatment method: PF-1077, manufactured by Paltec Co., Ltd.) so that the resin film thickness was 20 μm. After that, it was dried for 1 hour in an environment at a temperature of 23 ° C and a relative humidity of 50%, and then heat-treated for 30 minutes in a dryer at 150 ° C. Then, it was aged for 3 days or more in an environment at a temperature of 23 ° C and a relative humidity of 50%, to obtain a coating film. Next, the arithmetic mean roughness of the coating film was measured in accordance with JIS B0601 using a scanning white light interference microscope VS1530 (product name, manufactured by Hitachi High-Technologies Corporation). The surface smoothness of the coating film was evaluated based on the arithmetic mean roughness of Comparative Example 4. The results are shown in Table 1.

[0123] [Table 1]

[0124] As shown in Table 1, the coating films prepared from the polyisocyanate compositions P-1 to P-5 had good surface smoothness. From these findings, the polyisocyanate compositions of Examples 1 to 5 were polyisocyanate compositions that contributed to the preparation of coating films having excellent surface smoothness.

Claims

1. A composition comprising a polyisocyanate, The polyisocyanate includes a derivative derived from an aliphatic diisocyanate, A composition, wherein the content of a cyclic compound represented by the following formula (1) is 0.1 to 15 mass % based on the total amount of the composition: 【Chemistry 1】 [In formula (1), n ​​is an integer from 1 to 6, and R １ is a hydrogen atom, R ２ is a monovalent organic group having 1 to 20 carbon atoms and represented by the following formula (i). 【Chemistry 2】 [In formula (i), X is CH or N, R 3 and R 4 are each independently a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, and * is a bond bonded to N in formula (1)]

2. The composition of claim 1 , wherein the derivative comprises an isocyanurate derived from an aliphatic diisocyanate.

3. The composition of claim 1 or 2, wherein the aliphatic diisocyanate comprises butane diisocyanate.

4. A curing agent for forming a polyurethane resin comprising the composition of claim 1.

5. A polyurethane resin-forming composition comprising the composition according to claim 1 and a polyol.

6. A coating composition comprising the polyurethane resin-forming composition according to claim 5.

7. A coating film comprising a cured product of the coating composition according to claim 6.

8. A surface smoothing agent for polyurethane coatings, comprising a cyclic compound represented by the following formula (1): 【Chemistry 3】 [In formula (1), n ​​is an integer from 1 to 6, and R １ is a hydrogen atom, R ２ is a monovalent organic group having 1 to 20 carbon atoms and represented by the following formula (i). 【Chemistry 4】 [In formula (i), X is CH or N, R 3 and R 4 are each independently a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, and * is a bond bonded to N in formula (1)]

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