Butane diisocyanate derivative, polyisocyanate composition, polyurethane resin formative composition, coating composition and coating film

Abstract

To provide a butane diisocyanate derivative which is excellent in quick dryness and can lower a baking temperature of a coating film.SOLUTION: A butane diisocyanate derivative has at least one functional group selected from an isocyanurate group, an urethodione group, an iminooxadione group, an urethane group, an allophanate group, an urea group, and a biuret group, wherein a molar ratio (RG) of the biuret group in the butane diisocyanate derivative, which is represented by expression (G): G / (A+B+C+D+E+F+G)×100, where A, B, C, D, E, F and G each represent the isocyanurate group, the urethodione group, the iminooxadione group, the urethane group, the allophanate group, the urea group, and the biuret group, is 20 to 100 mol%.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a butane diisocyanate derivative, a polyisocyanate composition, a polyurethane resin-forming composition, a coating composition, and a coating film. [Background technology]

[0002] From the viewpoint of reducing the environmental impact, there has been active development of polyisocyanate compositions that pursue drying and low-temperature curing properties. When polyisocyanate compositions have excellent drying properties, the thermal energy required for the curing reaction can be reduced.

[0003] Here, Patent Document 1 discloses a polyisocyanate composition obtained from at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, and containing a polyisocyanate compound consisting of an allophanate group and an isocyanurate group at a predetermined content or more. According to Patent Document 1, by using a coating composition containing this polyisocyanate composition, a coating film excellent in curability and coating film appearance can be provided.

[0004] Also, Patent Document 2 discloses a polyisocyanate having a predetermined viscosity, which contains a predetermined amount of aliphatic diisocyanate monomer units, a predetermined amount of polyol units, and a predetermined amount of monoalcohol units relative to the total amount of the polyisocyanate, and which contains a predetermined amount of diisocyanate monomer. According to Patent Document 2, this polyisocyanate has excellent curing properties due to reaction with an active hydrogen compound. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-024930 A [Patent Document 2] JP 2015-203104 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, particularly in recent years, the market has come to require increasingly higher performance from polyurethane coating films, and there has been a strong demand for the development of polyisocyanate compositions that are quick-drying and capable of being cured at low temperatures.

[0007] Therefore, one aspect of the present disclosure is directed to providing a polyisocyanate composition that is excellent in quick drying and can reduce the baking temperature of a coating film. Another aspect of the present disclosure is directed to providing a butane diisocyanate derivative that contributes to the preparation of the polyisocyanate composition. Still other aspects of the present disclosure are directed to providing a polyurethane resin-forming composition, a coating composition, and a coating film using the polyisocyanate composition. [Means for solving the problem]

[0008] In some aspects, the present disclosure provides the following [1] to [7].

[0009] [1] A butane diisocyanate derivative having at least one functional group selected from an isocyanurate group, a uretdione group, an iminooxadiadione group, a urethane group, an allophanate group, a urea group, and a biuret group, Formula (G): G / (A+B+C+D+E+F+G)×100...Formula (G) [In the formula, A, B, C, D, E, F, and G represent the molar ratios of the isocyanurate group, the uretdione group, the iminooxadiadione group, the urethane group, the allophanate group, the urea group, and the biuret group, respectively.] The molar ratio of the biuret group in the butane diisocyanate derivative (R G ) is 20 to 100 mol %. [2] The molar ratio of the biuret group (RG ) is 20 to 90 mol %, Formula (B): B / (A+B+C+D+E+F+G)×100...Formula (B) [In the formula, A, B, C, D, E, F, and G represent the molar ratios of the isocyanurate group, the uretdione group, the iminooxadiadione group, the urethane group, the allophanate group, the urea group, and the biuret group, respectively.] The molar ratio of the uretdione group in the butane diisocyanate derivative (R B ) is 10 to 70 mol %. [3] The molar ratio of the uretdione groups (R B ) is 10 to 60 mol %. [4] A polyisocyanate composition comprising the butane diisocyanate derivative according to any one of [1] to [3]. [5] A polyurethane resin-forming composition comprising the polyisocyanate composition according to [4] and a polyol. [6] A coating composition comprising the polyisocyanate composition according to [4] and a compound having two or more isocyanate-reactive groups. [7] A coating film comprising a cured product of the coating composition according to [6]. Effect of the Invention

[0010] According to one aspect of the present disclosure, it is possible to provide a polyisocyanate composition that is excellent in quick-drying property and can reduce the baking temperature of a coating film. According to another aspect of the present disclosure, it is possible to provide a butane diisocyanate derivative that contributes to the preparation of the polyisocyanate composition. According to still other aspects of the present disclosure, it is possible to provide a polyurethane resin-forming composition, a coating composition, and a coating film using the polyisocyanate composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In this specification, a numerical range indicated using "~" indicates a range including the numerical values ​​described before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this specification, the upper limit or lower limit of a numerical range in a certain stage may be replaced with the upper limit or lower limit of a numerical range in 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. Furthermore, the upper limit and lower limit values ​​described individually can be combined in any combination.

[0012] 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.

[0013] <Butane diisocyanate derivative and polyisocyanate composition> The butane diisocyanate derivative according to one embodiment of the present disclosure has at least one functional group selected from an isocyanurate group, a uretdione group, an iminooxadiadione group, a urethane group, an allophanate group, a urea group, and a biuret group, Formula (G): G / (A+B+C+D+E+F+G)×100...Formula (G) [In the formula, A, B, C, D, E, F, and G represent the molar ratios of the isocyanurate group, the uretdione group, the iminooxadiadione group, the urethane group, the allophanate group, the urea group, and the biuret group, respectively.] The molar ratio of the biuret group in the butane diisocyanate derivative (R G ) is 20 to 100 mol %. In the following description, butane diisocyanate may be abbreviated as "BDI."

[0014] According to the above BDI derivative, it is possible to prepare a polyisocyanate composition that has excellent quick-drying properties and can reduce the baking temperature of the coating film.The fact that the polyisocyanate composition has excellent quick-drying properties can be confirmed, for example, by determining the rate constant of coating film curing from a rigid pendulum test.In addition, the fact that the coating film obtained using the polyisocyanate composition can be baked at a low temperature can be confirmed, for example, by the curing start temperature of the coating film made of the coating composition prepared using the polyisocyanate composition.

[0015] A polyisocyanate composition according to another embodiment of the present disclosure includes a BDI derivative, The BDI derivative has at least one functional group selected from an isocyanurate group, a uretdione group, an iminooxadiadione group, a urethane group, an allophanate group, a urea group, and a biuret group; Formula (G): G / (A+B+C+D+E+F+G)×100...Formula (G) [In the formula, A, B, C, D, E, F, and G represent the molar ratios of the isocyanurate group, the uretdione group, the iminooxadiadione group, the urethane group, the allophanate group, the urea group, and the biuret group, respectively.] The molar ratio of the biuret group in the butane diisocyanate derivative (R G ) is 20 to 100 mol %. That is, the BDI derivative is preferably the above-mentioned BDI derivative.

[0016] The polyisocyanate composition tends to be excellent in quick drying property. Furthermore, the polyisocyanate composition makes it easy to lower the baking temperature of the coating film.

[0017] The BDI derivative is a mixture of a plurality of compounds derived from a BDI monomer. The BDI derivative includes, for example, one or more compounds selected from the group consisting of an isocyanurate of BDI, a uretdione of BDI, an iminooxadiazinedione of BDI, a urethane of BDI, an allophanate of BDI, a urea of ​​BDI, and a biuret of BDI. Preferably, the BDI derivative includes a biuret of BDI. The BDI biuret is a compound having a biuret group among the compounds derived from a BDI monomer, and has a group represented by formula (1).

[0018] [ka]

[0019] Examples of BDI monomers that are raw materials for the biuret of BDI include 1,2-butane diisocyanate, 1,3-butane diisocyanate, 1,4-butane diisocyanate, 2,3-butane diisocyanate, and mixtures thereof. The raw material for the biuret of BDI preferably contains 1,4-butane diisocyanate because the isocyanate group bonded to the primary carbon has high reactivity. The ratio of 1,4-butane diisocyanate in the raw material for the biuret of BDI may be 90% by mass or more, 95% by mass or more, or 100% by mass. In the following, an embodiment in which 1,4-butane diisocyanate is used as the BDI monomer may be described as an example, but unless otherwise specified, the present invention is not limited thereto.

[0020] The molar ratio of biuret groups (R G ) is 20 to 100 mol %, and may be 30 mol % or more, 40 mol % or more, or 50 mol % or more, and may be 90 mol % or less, 85 mol % or less, or 75 mol % or less. When the molar ratio of biuret groups is 50 mol % or more, the quick-drying property tends to be further improved, and when the molar ratio of biuret groups is 75 mol % or less, the viscosity tends to be further reduced. The molar ratio of biuret groups can be determined, for example, by using a nuclear magnetic resonance (NMR) device. 13It can be measured by C-NMR method. More specifically, it can be measured in accordance with the examples described later.

[0021] The BDI derivative preferably contains a uretdione form in addition to a biuret form. The uretdione form of BDI is a compound derived from a BDI monomer and has a uretdione group, and has a group represented by formula (2).

[0022] [ka]

[0023] In the BDI derivatives, Formula (B): B / (A+B+C+D+E+F+G)×100...Formula (B) [In the formula, A, B, C, D, E, F, and G represent the molar ratios of the isocyanurate group, the uretdione group, the iminooxadiadione group, the urethane group, the allophanate group, the urea group, and the biuret group, respectively.] The molar ratio of the uretdione group in the butane diisocyanate derivative (R B ) is preferably 10 to 70 mol %, and may be 15 mol % or more, 20 mol % or more, or 30 mol % or more, and may be 65 mol % or less, 60 mol % or less, or 50 mol % or less. When the molar ratio of uretdione groups is 30 mol % or more, there is a tendency that the viscosity can be further reduced, and when the molar ratio of uretdione groups is 50 mol % or less, there is a tendency that a coating film with higher hardness can be obtained. The molar ratio of uretdione groups can be determined, for example, by using a nuclear magnetic resonance (NMR) device. 13 It can be measured by C-NMR method. More specifically, it can be measured in accordance with the examples described later.

[0024] In addition to the biuret and uretdione derivatives, the BDI derivative may contain one or more compounds selected from the group consisting of isocyanurate, iminooxadiazinedione, urethane, allophanate, and urea. The isocyanurate of BDI is a compound derived from a BDI monomer that has an isocyanurate group and has a group represented by formula (3). The iminooxadiazinedione of BDI is a compound derived from a BDI monomer that has an iminooxadiazinedione group and has a group represented by formula (4). The urethane of BDI is a compound derived from a BDI monomer that has a urethane group and has a group represented by formula (5). The allophanate of BDI is a compound derived from a BDI monomer that has an allophanate group and has a group represented by formula (6). The urea of ​​BDI is a compound derived from a BDI monomer that has a urea group and has a group represented by formula (7).

[0025] [ka]

[0026] The BDI derivative is a compound derived from a BDI monomer, which has one functional group selected from an isocyanurate group, a uretdione group, an iminooxadiadione group, a urethane group, an allophanate group, a urea group, and a biuret group, and may also include a compound having two or more different groups among these in one molecule. For example, the BDI derivative may include a compound having a biuret group and a uretdione group (a compound that is both a biuret and a uretdione). Such a compound corresponds to both a biuret of BDI and a uretdione of BDI.

[0027] The NCO content of the BDI derivative may be 10% by mass or more, 20% by mass or more, or 25% by mass or more based on the total mass of the solid content in the polyisocyanate composition, from the viewpoint of increasing the number of NCO groups used for crosslinking of the polyurethane resin. The NCO content of the BDI derivative may be 35% by mass or less, 32% by mass or less, or 30% by mass or less based on the total mass of the solid content in the polyisocyanate composition, from the viewpoint of reducing the content of low molecular weight components such as BDI monomers to suppress odor. From these viewpoints, the NCO content of the BDI derivative may be, for example, 10 to 35% by mass based on the total mass of the solid content in the polyisocyanate composition.

[0028] The BDI derivative may be blocked with a known blocking agent for the purpose of extending the pot life and forming a one-component coating composition. That is, a part or all of the NCO groups of the compound derived from the BDI monomer may be blocked with a blocking agent. The blocked polyisocyanate is inactive at room temperature, but when heated, the blocking agent dissociates and the isocyanate group is activated again, so that it reacts with the active hydrogen group. The blocking agent is a compound having one active hydrogen in the molecule, and known blocking agents such as alcohols, alkylphenols, phenols, active methylene, mercaptans, acid amides, acid imides, imidazoles, ureas, oximes, amines, imides, and pyrazoles can be used.

[0029] The polyisocyanate composition may contain components other than the BDI derivative, or may consist only of the BDI derivative. Examples of the other components include 1,6-hexane diisocyanate (hereinafter sometimes abbreviated as "HDI") and its derivatives.

[0030] The polyisocyanate composition may contain isocyanate compounds other than BDI derivatives (e.g. polyisocyanates such as BDI monomer, HDI monomer, and HDI derivatives) as other components, but the content of BDI monomer in the polyisocyanate composition is preferably 5% by mass or less, more preferably 1% by mass or less (substantially does not contain BDI monomer). The content of isocyanate compounds other than BDI derivatives in the polyisocyanate composition is preferably 50% by mass or less, more preferably 1% by mass or less (substantially does not contain isocyanate compounds other than BDI derivatives). The above content is based on the total mass of solids in the polyisocyanate composition.

[0031] The polyisocyanate composition may contain an organic solvent as another component, which will be described later, but the content of the organic solvent in the polyisocyanate composition is preferably 50% by mass or less, and more preferably 20% by mass or less (substantially no organic solvent is contained). The above content is based on the total mass of the solid content in the polyisocyanate composition.

[0032] The viscosity of the polyisocyanate composition at 25°C is preferably 8000mPa·s or less, more preferably 5000mPa·s or less, even more preferably 4000mPa·s or less, even more preferably 1000mPa·s or less, and particularly preferably 500mPa·s or less. When the viscosity is 5000mPa·s or less, the polyisocyanate composition has good workability without being diluted with a large amount of solvent, and the solid content concentration of the coating composition can be further increased. The viscosity of the polyisocyanate composition at 25°C may be, for example, 100mPa·s or more, 200mPa·s or more, or 300mPa·s or more. When the viscosity is 100mPa·s or more, the obtained coating film tends to have a higher hardness. The preferred range of the viscosity of the BDI derivative at 25°C is the same as the above range, in that a polyisocyanate composition having the above viscosity is easily obtained.

[0033] The BDI derivatives and polyisocyanate compositions described above are suitably used as a curing agent component of a coating composition. That is, another embodiment of the present disclosure is a curing agent for a coating containing the above BDI derivative, and still another embodiment of the present disclosure is a curing agent for a coating comprising the above polyisocyanate composition. As the main agent for these curing agents for coatings, an isocyanate-reactive compound (such as a polyol) described later can be used.

[0034] <Method for producing BDI derivative> The method for producing the BDI derivative of the present embodiment includes a multimerization step of obtaining a biuret body of BDI and a uretdione body of BDI by performing a biuretization reaction for forming a biuret group and a uretdionization reaction for forming a uretdione group.

[0035] The biuretization reaction is carried out by reacting a reactant (for example, a BDI monomer) with a biuretizing agent. Examples of the biuretizing agent include water, a monohydric tertiary alcohol, formic acid, hydrogen sulfide, a primary amine compound, and the like. The biuretizing agent can be used alone or in combination of two or more. From the viewpoint of reactivity, it is preferable to use water.

[0036] The amount of the biuretizing agent used is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 4 parts by mass, based on 100 parts by mass of the charged amount of BDI.

[0037] The reaction temperature of the biuretization reaction is preferably 80 to 200°C, more preferably 100 to 180°C. When the reaction temperature of the biuretization reaction using a biuretization catalyst is 80°C or higher, the reaction time can be shortened, so that the coloring of the polyisocyanate composition can be further suppressed. Further, when the reaction temperature of the biuretization reaction is 80 to 200°C, it is easy to adjust the molar ratio of the biuret group to the uretdione group to 10 to 70 mol%.

[0038] The biuretization reaction may be stopped when the target isocyanate group content and biuret group content are reached. When the reaction temperature of the biuretization reaction is 80 to 200° C., the reaction time of the biuretization reaction is, for example, 0.5 to 6 hours.

[0039] The biuretization reaction may be carried out in the presence of a generally known biuretization catalyst. Examples of the biuretization catalyst include polysubstituted carboxylic acids or their anhydrides, acidic phosphate ester compounds, etc. The biuretization catalyst may be used alone or in combination of two or more.

[0040] From the viewpoints of preventing coloration and storage stability, it is preferable to use an acidic phosphate ester compound such as dibutyl phosphate, diethyl phosphate, etc., as the biuretization catalyst. The acidic phosphate ester compound can also be generated in the reaction system by hydrolysis of a phosphate ester compound such as triethyl phosphate, tributyl phosphate, etc.

[0041] The amount of the biuretization catalyst used is preferably 0.01 to 10 parts by mass, and more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the charged amount of BDI.

[0042] The reaction temperature of the biuretization reaction when a biuretization catalyst is used is preferably 60 to 200° C., more preferably 80 to 180° C. When the reaction temperature of the biuretization reaction when a biuretization catalyst is used is 60° C. or higher, the reaction time can be shortened, and coloration of the polyisocyanate composition can be further suppressed. In addition, when the reaction temperature of the biuretization reaction when a biuretization catalyst is used is 60 to 200° C., it is easy to adjust the molar ratio of biuret groups to uretdione groups to 10 to 70 mol%.

[0043] The biuretization reaction using the biuretization catalyst may be stopped when the target isocyanate group content and biuret group content are reached. When the reaction temperature of the biuretization reaction using the biuretization catalyst is 60 to 200° C., the reaction time of the biuretization reaction using the biuretization catalyst is, for example, 0.5 to 5 hours.

[0044] The uretdione reaction may be carried out in the presence of a generally known uretdione catalyst, for example, a tertiary phosphine such as trialkylphosphine or tribenzylphosphine, or a Lewis acid such as boron trifluoride or zinc trichloride.

[0045] When a uretdione-forming catalyst is used, the uretdione-forming reaction may be terminated by adding phosphoric acid, methyl paratoluenesulfonate, or the like, when the molar ratio of biuret groups to uretdione groups reaches a desired value.

[0046] The uretdione reaction can also be carried out by heating the reactants (e.g., BDI monomer) without using a uretdione catalyst as described above. From the viewpoint of suppressing the production of by-products, it is preferable to carry out the uretdione reaction only by heating without using a uretdione reaction catalyst. The heating temperature is preferably 80°C or higher, more preferably 100 to 170°C, and even more preferably 110 to 160°C. When the heating temperature is 80 to 170°C, it is easy to adjust the molar ratio of biuret groups and uretdione groups to 10 to 70 mol% while suppressing the production of by-products.

[0047] The biuretization reaction and the uretdione reaction may be carried out under an inert gas atmosphere such as nitrogen, argon, etc. Specifically, BDI may be introduced into a reaction vessel, and an inert gas such as nitrogen, argon, etc. may be introduced into the vessel to make the reaction atmosphere an inert gas atmosphere, and then the biuretization reaction and the uretdione reaction may be carried out by the above-mentioned method.

[0048] The biuretization reaction and the uretdione reaction may be carried out in the absence of an organic solvent or in the presence of an organic solvent. When the reaction is carried out in the presence of an organic solvent, it is preferable to use an organic solvent that does not affect the reaction and has a boiling point equal to or higher than the reaction temperature. 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, polar aprotic solvents such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, and hexamethylphosphonylamide. From the viewpoint of suppressing the generation of high molecular weight substances, it is particularly preferable to use a polar solvent that has a high affinity with the biuretization agent. The organic solvent may be used alone or in combination of two or more kinds.

[0049] The biuretization reaction and the uretdione reaction can be carried out sequentially or in parallel. When the biuretization reaction and the uretdione reaction are carried out in parallel, the timing of starting and stopping the reaction may be simultaneous or different. For example, the uretdione reaction of BDI may be started to advance the uretdione formation of BDI, and then the uretdione formation and the biuretization reaction may be carried out on a reactant containing a uretdione body of BDI. In the polymerization step, the biuretization reaction and the uretdione formation are preferably carried out simultaneously. In the polymerization step, the biuretization reaction is more preferably carried out after the uretdione formation reaction by heat (after the start of the reaction). If the uretdione formation reaction by heat is carried out after the biuretization reaction, the polymerization of the biuret body may be promoted, and viscosity may increase, the isocyanate group content may decrease, and the like may occur, so it is preferable not to carry out the uretdione formation reaction after the biuretization reaction.

[0050] More specifically, the polymerization step is preferably a step including a first heating step in which a reaction product containing BDI (BDI monomer) is heated to 80° C. or higher, and a second heating step in which the reaction product after the first heating step is heated at 80 to 200° C. in the presence of the biuretization reaction agent. In this method, at least the first heating step is a uretdione reaction of BDI, and the second heating step is a biuret reaction of a reaction product containing a uretdione form of BDI (for example, a mixture of unreacted BDI monomer and a uretdione form of BDI). The heating conditions of the first heating step are the same as the preferred range of the heating temperature of the uretdione reaction described above, and the heating conditions of the second heating step are the same as the preferred range of the reaction temperature of the biuret reaction described above. In the second heating step, the uretdione reaction may be allowed to proceed simultaneously with the biuret reaction.

[0051] From the viewpoint of increasing the amount of uretdione, the first heating step may be a step of heating the reaction mixture to 80° C. or higher and then holding the reaction mixture at a temperature of 80° C. or higher. The holding temperature is the same as the preferred range of the heating temperature for the uretdione formation reaction. The holding time is preferably 1 to 6 hours, more preferably 2 to 5 hours.

[0052] After the reaction is completed, unreacted BDI monomer (free BDI) may be removed from the reaction solution containing the reaction product. That is, the method for producing a BDI derivative may further include a BDI removal step of removing free BDI after the polymerization step. In order to remove free BDI, for example, a removal method by thin film distillation at 90 to 130°C under a high vacuum of 10 to 100 Pa, an extraction method using an organic solvent, etc. are used. The above removal is preferably performed so that the residual content of free BDI present in the reaction solution is 5% by mass or less. If the residual content of free BDI is 5% by mass or less, the generation of odor can be further suppressed and the decrease in storage stability can be further suppressed. When an organic solvent is used in the above reaction, the organic solvent can be removed simultaneously with the removal of the free BDI.

[0053] The method for producing a BDI derivative may further include a step of blocking the BDI derivative with the above-mentioned blocking agent after the multimerization step or the BDI removal step.

[0054] The BDI derivative (or the reaction solution containing the BDI derivative) obtained by the above method can be used as a polyisocyanate composition as it is or after mixing with the other components described above. The polyurethane resin-forming composition according to one embodiment of the present disclosure can be obtained by blending the polyisocyanate composition obtained in this manner with a polyol.

[0055] <Polyurethane resin-forming composition> A polyurethane resin-forming composition according to one aspect of the present disclosure includes the polyisocyanate composition of the above embodiment and a polyol. The composition has a polyurethane resin-forming property, and the polyurethane resin is formed as a reaction product of the polyisocyanate and the polyol by reacting the polyisocyanate (e.g., a BDI derivative) and the polyol in the composition.

[0056] The polyol is a compound having two or more hydroxyl groups, which are active hydrogen groups, as reactive groups with isocyanate groups. The polyol is not particularly limited, but polyester polyol, polyether polyol, polycarbonate polyol, polyolefin polyol, acrylic polyol, silicone polyol, castor oil polyol, fluorine polyol, ester exchange product of two or more polyols, hydroxyl group-terminated prepolymers that have been subjected to urethane reaction with polyisocyanate, etc. can be suitably used. The polyol can be used alone or in combination of two or more.

[0057] (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.

[0058] (Polyether polyol) Examples of polyether polyols include polyether polyols obtained by addition polymerization of alkylene oxides using compounds having two or more, preferably two to three, 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.

[0059] (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.

[0060] (Polyolefin polyol) Examples of polyolefin polyols include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, and hydrogenated polyisoprene.

[0061] (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.

[0062] [(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.

[0063] [(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.

[0064] (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.

[0065] (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.

[0066] (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 is preferably 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.

[0067] The number of active hydrogen groups (average number of functional groups) in one molecule of the polyol is preferably 1.9 to 6.0. If the number of active hydrogen groups is within the above range, the resulting coating film tends to exhibit superior hardness.

[0068] The number average molecular weight of the polyol is preferably in the range of 750 to 50,000. When the number average molecular weight of the polyol is equal to or more than the lower limit, the adhesion tends to be further improved. When the number average molecular weight of the polyol is equal to or less than the upper limit, the solubility in low polarity organic solvents tends to be further improved, and the adhesion tends to be further improved.

[0069] In the polyurethane resin forming composition, the content ratio of the polyisocyanate composition and the polyol is not particularly limited, but the molar ratio R (isocyanate group / hydroxyl group) of the isocyanate group in the polyisocyanate composition and the hydroxyl group in the polyol is preferably 0.5 to 2.5. When the molar ratio R is equal to or greater than the lower limit, the hydroxyl group does not become too excessive, so that the adhesion tends to be further improved, and the decrease in crosslink density is suppressed, so that the durability and mechanical strength of the coating film tend to be further improved. When the molar ratio R is equal to or less than the upper limit, the isocyanate group does not become too excessive, so that the reaction with moisture in the air is suppressed, so that the swelling of the coating film is further reduced, and the associated decrease in adhesion tends to be further suppressed.

[0070] The polyurethane resin-forming composition may be a one-liquid type composition in which all of the constituent components are contained in one liquid, or a multi-liquid type composition in which the constituent components are present separately in multiple liquids. The multi-liquid type composition may, for example, comprise a first liquid (base agent) containing a polyol and a second liquid (curing agent) consisting of a polyisocyanate composition.

[0071] The polyurethane resin forming composition may contain a dilution solvent. When the polyurethane resin forming composition is a multi-liquid type, the dilution solvent may be contained in either the first liquid or the second liquid, or may be contained in both. The dilution solvent is, for example, an organic solvent. Examples of the dilution solvent include ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, esters such as ethyl acetate, butyl acetate, and cellosolve acetate, alcohols such as butanol and isopropyl alcohol, and hydrocarbons such as toluene, xylene, cyclohexane, mineral spirits, and naphtha. The dilution solvent can be appropriately selected and used depending on the purpose and application. The dilution solvent can be used alone or in combination of two or more.

[0072] The polyurethane resin forming composition may contain a urethanization catalyst. As the urethanization catalyst, a known urethanization catalyst can be used appropriately in consideration of pot life, curing conditions, working conditions, etc. Specific 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 or salts thereof. The urethanization catalyst can be used alone or in combination of two or more.

[0073] The polyurethane resin-forming composition may contain, as 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, leveling agents, etc. When the polyurethane resin-forming composition is a multi-liquid type, these additives may be contained in either the first liquid or the second liquid, or in both.

[0074] The polyurethane resin-forming composition can be suitably used as a coating composition.

[0075] <Paint composition and coating> A coating composition according to one aspect of the present disclosure includes the polyisocyanate composition of the above embodiment and a compound having two or more isocyanate-reactive groups (hereinafter, referred to as an isocyanate-reactive compound). A coating film according to one aspect of the present disclosure includes a cured product of the coating composition described above.

[0076] The isocyanate-reactive compound may be a polyol. That is, the coating composition may contain the polyurethane resin-forming composition of the above embodiment. The isocyanate-reactive compound may be a polyamine, an amino alcohol, or the like, as long as it has two or more isocyanate-reactive groups (e.g., active hydrogen groups).

[0077] The coating film has high hardness because the coating composition contains the polyisocyanate composition of the above embodiment. The Martens hardness of the coating film at 23° C. is preferably 100 N / mm 2 More preferably, 104N / mm 2 More preferably, 110N / mm 2 The Martens hardness can be measured in accordance with JIS Z2255.

[0078] 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.

[0079] 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, phenol 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 made of such materials, polyethylene and polypropylene that have been subjected to corona discharge treatment or other surface treatment, and adherends having a coating layer formed on the surface of the adherend that can be an intermediate layer, can be used.

[0080] The curing conditions for the coating composition are not particularly limited, but preferably the curing temperature is −5 to 150° C., the humidity is 10 to 95% RH, and the curing time is 0.5 to 336 hours.

[0081] The coating film formed on the surface layer of the adherend has excellent recoatability and durability, so it is sufficient to form a coating film of at least 10 micrometers on the adherend. If the coating film is 10 micrometers or more, durability is improved and the occurrence of breakage of the coating film due to impact can be further suppressed. EXAMPLES

[0082] 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.

[0083] <Example 1> (Preparation of Polyisocyanate Composition) A 1-liter four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube was charged with 800 g of BDI (1,4-butane diisocyanate, NCO content: 60.0 mass%), which was heated to 80°C, and 11.2 g of water as a biuret reaction agent, 90 g of tetrahydrofuran as a solvent, and 4.8 g of dibutyl phosphate as a biuret catalyst were added and stirred for 4 hours. After cooling the reaction solution, excess BDI and the solvent were removed by thin-film distillation (conditions: 110°C, 0.04 kPa) to obtain 152 g of polyisocyanate composition P-1. The properties of the obtained polyisocyanate composition P-1 are shown in Table 1. In this example, the properties of the polyisocyanate composition were measured by the following method.

[0084] (Measurement of the molar ratio of each functional group) The molar ratios of the isocyanurate group, uretdione group, iminooxadiadione group, urethane group, allophanate group, urea group, and biuret group contained in the polyisocyanate composition were determined by ECX400M (trade name) manufactured by JEOL Ltd. 13 The carbon-carbon NMR spectroscopy was used to determine the carbon-carbon NMR spectroscopy results.

[0085] Specifically, the polyisocyanate composition was first dissolved in deuterated chloroform containing 0.2 mass% of tetramethylsilane to prepare a measurement sample. The sample concentration was 0.2 g / 1 mL mass%. The chemical shift reference was the carbon signal of chloroform at 77.16 ppm. 13 The signal areas of the carbon atoms corresponding to the isocyanurate group, the uretdione group, the iminooxadiadione group, the urethane group, the allophanate group, the urea group, and the biuret group were measured by C-NMR, and the molar ratio of each functional group was calculated by the following formula. The resonance frequency was 125 MHz, and the number of integrations was 2048. Next, the molar ratio of the biuret group in the butane diisocyanate derivative represented by formula (G) (R G ), the molar ratio of the uretdione group in the butanediisocyanate derivative of formula (B) (R B ) was calculated. G / (A+B+C+D+E+F+G)×100...Formula (G) [In the formula, A, B, C, D, E, F, and G represent the molar ratios of the isocyanurate group, the uretdione group, the iminooxadiadione group, the urethane group, the allophanate group, the urea group, and the biuret group, respectively.] B / (A+B+C+D+E+F+G)×100...Formula (B) [In the formula, A, B, C, D, E, F, and G represent the molar ratios of the isocyanurate group, the uretdione group, the iminooxadiadione group, the urethane group, the allophanate group, the urea group, and the biuret group, respectively.]

[0086] Molar ratio of isocyanurate group: A = signal area around 148.7 ppm / 3 Molar ratio of uretdione groups: B = signal area around 157.4 ppm / 2 Molar ratio of iminooxadiazinedione group: Signal area around C = 139.3 ppm / 1 Molar ratio of urethane group: D = signal area around 156.6 ppm / 1 Molar ratio of allophanate group: E = signal area around 153.5 ppm / 1 Molar ratio of urea group: F = signal area around 157.5 ppm / 1 Molar ratio of biuret groups: G = signal area around 156.1 ppm / 2

[0087] (Viscosity measurement) The viscosity of the obtained polyisocyanate composition (BDI derivative) was measured in a 25° C. environment using a rheometer (HAAKE MARS60, manufactured by Thermo Fisher Scientific).

[0088] (Measurement of NCO content) The NCO content of the resulting polyisocyanate composition (BDI derivative) was determined by reacting the composition with a secondary amine and then back titrating the unreacted secondary amine with hydrochloric acid.

[0089] <Example 2> In a 1-liter four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube, 800 g of BDI, 90 g of 1,4-dioxane as a solvent, and 11.2 g of water as a biuretization reactant were charged, and the mixture was heated to 140° C. and stirred for 3 hours. After cooling the reaction solution, excess BDI and the solvent were removed by thin-film distillation (conditions: 110° C., 0.04 kPa) to obtain 208 g of polyisocyanate composition P-2. The properties of the obtained polyisocyanate composition P-2 are shown in Table 1.

[0090] <Example 3> 800g of BDI was charged into a 1-liter four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube, and the mixture was heated to 140°C and stirred for 3 hours. 5.6g of water as a biuret reaction agent and 90g of 1,4-dioxane as a solvent were added and stirred for 3 hours. After cooling the reaction solution, excess BDI and the solvent were removed by thin-film distillation (conditions: 110°C, 0.04kPa) to obtain 176g of polyisocyanate composition P-3. The properties of the obtained polyisocyanate composition P-3 are shown in Table 1.

[0091] <Example 4> 800 g of BDI was charged into a 1-liter four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube, and the mixture was heated to 140° C. and stirred for 4 hours. 4.0 g of water as a biuret reaction agent and 89 g of 1,4-dioxane as a solvent were added and stirred for 3 hours. After cooling the reaction solution, excess BDI and the solvent were removed by thin-film distillation (conditions: 110° C., 0.04 kPa) to obtain 163 g of polyisocyanate composition P-4. The properties of the obtained polyisocyanate composition P-4 are shown in Table 1.

[0092] <Example 5> 800 g of BDI was charged into a 1-liter four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube, and the mixture was heated to 140° C. and stirred for 5 hours. 2.4 g of water as a biuret reaction agent and 89 g of 1,4-dioxane as a solvent were added and stirred for 3 hours. After cooling the reaction solution, excess BDI and the solvent were removed by thin-film distillation (conditions: 110° C., 0.04 kPa) to obtain 136 g of polyisocyanate composition P-5. The properties of the obtained polyisocyanate composition P-5 are shown in Table 1.

[0093] <Comparative Example 1> 800 g of BDI was charged into a 1-liter four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube, and the mixture was heated to 140° C. and stirred for 5 hours. 0.8 g of water as a biuret reaction agent and 89 g of 1,4-dioxane as a solvent were added and stirred for 3 hours. After cooling the reaction solution, excess BDI and the solvent were removed by thin-film distillation (conditions: 110° C., 0.04 kPa) to obtain 112 g of polyisocyanate composition P-6. The properties of the obtained polyisocyanate composition P-6 are shown in Table 1.

[0094] <Comparative Example 2> In Comparative Example 2, Desmodur N 100 (manufactured by Covestro) produced from HDI (1,6-hexane diisocyanate) was used as is as isocyanate composition P-7. The properties of each are shown in Table 1.

[0095] <Synthesis Example 1> (Preparation of acrylic polyol for coating film evaluation) A 300-milliliter four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a dropping funnel was charged with 70 g of butyl acetate and heated to 120°C. 60 g of methyl methacrylate (manufactured by Mitsubishi Gas Chemical Co., Ltd.), 14 g of butyl acrylate (manufactured by Nippon Shokubai Co., Ltd.), 21 g of 2-hydroxyethyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.), 5 g of isobornyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd.), and 2 g of Perbutyl O (manufactured by NOF Corp., 2-ethylperoxyhexane-tert-butyl) were added to the dropping funnel, and this mixture was dropped into the reaction solution over 4 hours. The reaction solution was then held at 120°C for 1 hour, and 30 g of butyl acetate and 1 g of Perbutyl O were added to the dropping funnel, and this mixture was dropped into the reaction solution over 1 hour. After that, the mixture was held at 120°C for 3 hours and cooled to room temperature, and acrylic polyol A-1 was obtained. A-1 had a hydroxyl value of 101 mgKOH / g per resin solid content as measured by a method conforming to JIS K1557. In addition, the appearance was a transparent liquid, the solid content was 50% by mass, and the glass transition temperature was 52°C.

[0096] <Synthesis Example 2> 70g of butyl acetate was charged into a 300ml four-neck flask equipped with a stirrer, a thermometer, a cooling tube, and a dropping funnel, and the temperature was raised to 120°C. 40g of methyl methacrylate, 30g of butyl acrylate, 25g of 2-hydroxyethyl acrylate, 5g of isobornyl acrylate, and 2g of perbutyl O were added to the dropping funnel, and this mixture was dropped into the reaction solution over 4 hours. The reaction solution was then kept at 120°C for 1 hour, 30g of butyl acetate and 1g of perbutyl O were added to the dropping funnel, and this mixture was dropped into the reaction solution over 1 hour. After that, the mixture was kept at 120°C for 3 hours and cooled to room temperature, and acrylic polyol A-2 was obtained. A-2 had a hydroxyl value of 121 mgKOH / g per resin solid content as measured by a method conforming to JIS K1557. In addition, the appearance was a transparent liquid, the solid content was 50% by mass, and the glass transition temperature was 15°C.

[0097] <Evaluation> (Curing start temperature evaluation) A coating composition (two-liquid coating composition) consisting of the obtained polyisocyanate compositions P-1 to P-7 and acrylic polyol A-1 was prepared, and the curing initiation temperature of the obtained coating composition was measured by a rigid pendulum test using RPT-3000W (trade name, manufactured by A&D Co., Ltd.) to evaluate the curability of the polyisocyanate compositions P-1 to P-7. Specifically, first, the acrylic polyol A-1 and the polyisocyanate compositions P-1 to P-7 were mixed so that the hydroxyl group and isocyanate group equivalent ratio was 1:1, and then the coating solid content was adjusted to 50 mass% with butyl acetate to obtain a coating composition. Next, the obtained coating composition was painted on a steel plate (JIS G3141, trade name: SPCC-SB, manufactured by Paltec Co., Ltd.) so that the coating thickness was 20 μm. Next, the steel plate was heated at a heating rate of 2.5°C / min, and the temperature at which the period of the pendulum (frame: FRB-300, edge: RBE-160) began to decay was determined, and this temperature was taken as the curing start temperature of the coating film.

[0098] (Curing speed evaluation) Coating compositions (two-liquid coating compositions) consisting of the obtained polyisocyanate compositions P-1 to P-7 and acrylic polyol A-1 were prepared, and the curing speed of the obtained coating compositions was measured by a rigid pendulum test using RPT-3000W (trade name, manufactured by A&D Co., Ltd.) to evaluate the curability of the polyisocyanate compositions P-1 to P-7. Specifically, first, the acrylic polyol A-1 and the polyisocyanate composition were mixed so that the hydroxyl group and isocyanate group equivalent ratio was 1:1, and then the coating solid content was adjusted to 50 mass% with butyl acetate to obtain a coating composition. Next, the obtained coating composition was painted on a steel plate (JIS G3141, trade name: SPCC-SB, manufactured by Paltec Co., Ltd.) so that the coating thickness was 20 μm. Next, the steel plate was heated at 100 ° C for 40 minutes to measure the periodic damping of the pendulum (frame: FRB-300, edge: RBE-160). The relative storage modulus E'r was calculated from formula (X), plotted against the heating time, and then fitted with formula (Y) to calculate the curing rate constant k.

[0099] Formula (X):E'r=ω2 -α 2 -ω0 2 (In the formula, ω is the damping rate of the amplitude, α is the angular velocity of the pendulum oscillation, and ω0 is the angular velocity of the pendulum oscillation when there is no sample.)

[0100] Formula (Y): E'r(t)=E'r(∞)[1-exp{-k(tt d )}] (where E'r(∞) is the asymptotic value of E'r, k is the cure rate constant, t is time, t d represents the delay time.)

[0101] (Coating hardness evaluation) A coating composition (two-liquid coating composition) consisting of the obtained polyisocyanate compositions P-1 to P-7 and the acrylic polyol A-2 was prepared, a coating film (cured film) was formed using the obtained coating composition, and the Martens hardness of the formed cured film was measured. Specifically, first, the acrylic polyol A-2 and the polyisocyanate compositions P-1 to P-7 were mixed so that the hydroxyl group and isocyanate group equivalent ratio was 1:1, and then the coating solid content was adjusted to 40 mass% with butyl acetate to obtain a coating composition. Next, the obtained coating composition was applied to a steel plate (JIS G3141, product name: SPCC-SB, processing method: PF-1077, manufactured by Paltec Co., Ltd.) so that the thickness of the coating film (uncured film) was 20 μm. Thereafter, the coating film was dried for 1 hour under an environment of a temperature of 23 ° C. and a relative humidity of 50%, and then the dried coating film was heat-treated in a dryer at 80 ° C. for 24 hours. The coating film after the heat treatment was then aged for 7 days or more under an environment of 23°C temperature and 50% relative humidity to obtain a coating film (cured film) containing a cured product of the coating composition. The Martens hardness of the obtained coating film (cured film) was measured using HM2000 (product name, manufactured by Fisher Instruments) in accordance with JIS Z2255.

[0102] [Table 1]

Claims

1. A butane diisocyanate derivative having at least one functional group selected from an isocyanurate group, a uretdione group, an iminooxadiadione group, a urethane group, an allophanate group, a urea group, and a biuret group, Formula (G): G / (A+B+C+D+E+F+G)×100...Formula (G) [In the formula, A, B, C, D, E, F, and G represent the molar ratios of the isocyanurate group, the uretdione group, the iminooxadiadione group, the urethane group, the allophanate group, the urea group, and the biuret group, respectively.] The molar ratio of the biuret group in the butane diisocyanate derivative (R Ｇ ) is 20 to 100 mol %.

2. The molar ratio of the biuret group (R Ｇ ) is 20 to 90 mol %, Formula (B): B / (A+B+C+D+E+F+G)×100...Formula (B) [In the formula, A, B, C, D, E, F, and G represent the molar ratios of the isocyanurate group, the uretdione group, the iminooxadiadione group, the urethane group, the allophanate group, the urea group, and the biuret group, respectively.] The molar ratio of the uretdione group in the butane diisocyanate derivative (R Ｂ 2. The butane diisocyanate derivative according to claim 1, wherein the content of the isocyanate in the butane diisocyanate derivative is 10 to 70 mol %.

3. The molar ratio of the uretdione group (R Ｂ 3. The butane diisocyanate derivative according to claim 2, wherein the content of the isocyanate in the butane diisocyanate derivative is 10 to 60 mol %.

4. A polyisocyanate composition comprising the butane diisocyanate derivative according to any one of claims 1 to 3.

5. A polyurethane resin-forming composition comprising the polyisocyanate composition according to claim 4 and a polyol.

6. A coating composition comprising the polyisocyanate composition according to claim 4 and a compound having two or more isocyanate-reactive groups.

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

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