Butane diisocyanate composition, polyisocyanate composition, polyurethane-resin-forming composition, coating composition, and coating film

Abstract

Provided is a butane diisocyanate composition which includes an allophanate of butane diisocyanate that has a structure derived from one or more C1-C10 monohydric alcohols and a structure derived from butane diisocyanate and which has a molar allophanate group proportion (RE), shown by equation (E), of 75-100 mol%. Equation (E): RE=E / (A+B+C+D+E+F+G)×100 [In equation (E), A, B, C, D, E, F, and G respectively indicate the total numbers of moles of isocyanurate groups derived from a butane diisocyanate derivative, uretdione groups, iminooxadiadione groups, urethane groups, allophanate groups, urea groups, and biuret groups contained in the butane diisocyanate composition.]

Description

Butane diisocyanate composition, polyisocyanate composition, polyurethane resin-forming composition, coating composition and coating film

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

[0002] Polyurethane coatings using general-purpose aliphatic polyisocyanates such as hexamethylene diisocyanate and pentamethylene diisocyanate as curing agents have the advantages of lower baking temperatures and high weather resistance, and as demand for them increases, the required performance is also becoming higher.

[0003] Patent Document 1 discloses a polyisocyanate composition containing an allophanate derivative of xylylene diisocyanate and an isocyanurate derivative of xylylene diisocyanate, in which the content of the allophanate dimolecules of xylylene diisocyanate is 25% by mass or more but less than 50% by mass and the content of the isocyanurate trimolecules of xylylene diisocyanate is 5% by mass or more but less than 35% by mass, relative to the total amount of the polyisocyanate composition. According to Patent Document 1, this polyisocyanate composition has a relatively low viscosity, excellent coatability, excellent pot life and quick drying, and contributes to the provision of a polyurethane resin that is excellent in mechanical strength and chemical resistance.

[0004] Furthermore, Patent Document 2 discloses a polyisocyanate composition containing at least one isocyanate compound selected from aliphatic diisocyanates, alicyclic diisocyanates, and isocyanate prepolymers obtained therefrom, a branched diol having 9 to 60 carbon atoms, and a monoalcohol having 2 to 50 carbon atoms, the polyisocyanate composition having an allophanate group / isocyanurate group molar ratio of 100 / 0 to 75 / 25, a uretdione content of 15 mass% or less, and two specific polyisocyanates. According to Patent Document 2, this polyisocyanate composition is a low-viscosity or high-functionality polyisocyanate composition with excellent solubility in low-polarity organic solvents, and contributes to the provision of high-solids coating compositions using low-polarity organic solvents or coating compositions with excellent curability.

[0005] JP 2021-38303 A JP 2005-48179 A

[0006] However, in recent years in particular, the market has become increasingly demanding in terms of the performance required of polyurethane coating films, and there is a strong demand for the development of polyisocyanate compositions that have low viscosity, excellent workability, and are useful for producing coating films with high hardness.

[0007] Therefore, one aspect of the present disclosure is directed to providing a polyisocyanate composition that has low viscosity, excellent workability, and contributes to the production of a coating film with high hardness. Other aspects of the present disclosure are directed to providing a butane diisocyanate composition that contributes to the production 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.

[0008] In some aspects, the present disclosure provides the following [1] to [9].

[0009] [1] An allophanate of butane diisocyanate having a structure derived from one or more monoalcohols having 1 to 10 carbon atoms and a structure derived from butane diisocyanate, wherein the molar ratio of allophanate groups represented by the following formula (E) (R Ｅ) is 75 to 100 mol %. Ｅ = E / (A + B + C + D + E + F + G) × 100 ... formula (E) [In formula (E), A, B, C, D, E, F, and G represent the total number of moles of isocyanurate groups in the isocyanurate form of butane diisocyanate, uretdione groups in the uretdione form of butane diisocyanate, iminooxadiazinedione groups in the iminooxadiazinedione form of butane diisocyanate, urethane groups in the urethane form of butane diisocyanate, allophanate groups in the allophanate form of butane diisocyanate, urea groups in the urea form of butane diisocyanate, and biuret groups in the biuret form of butane diisocyanate, which are contained in the butane diisocyanate composition.] [2] The butane diisocyanate composition according to [1], wherein the monoalcohol has 1 to 7 carbon atoms. [3] The butane diisocyanate composition according to [1], wherein the monoalcohol has 1 to 5 carbon atoms. [4] The molar ratio (R Ｅ The butane diisocyanate composition according to any one of [1] to [3], wherein the proportion of methyl group in the butane diisocyanate composition is 90 to 100 mol %. [5] A polyisocyanate composition comprising the butane diisocyanate composition according to any one of [1] to [4]. [6] The polyisocyanate composition according to [5], wherein the viscosity at 25°C is 1000 mPa·s or less. [7] A polyurethane resin-forming composition comprising the polyisocyanate composition according to [5] or [6] and a polyol. [8] A coating composition comprising the polyisocyanate composition according to [5] or [6] and a compound having two or more isocyanate-reactive groups. [9] A coating film comprising a cured product of the coating composition according to [8].

[0010] According to one aspect of the present disclosure, it is possible to provide a polyisocyanate composition that has low viscosity, excellent workability, and contributes to the production of a coating film with high hardness. According to other aspects of the present disclosure, it is possible to provide a butane diisocyanate composition that contributes to the production 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.

[0011] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. Furthermore, unless specifically stated otherwise, the units of the numerical values ​​before and after "to" are the same. In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range may be replaced with the upper or lower limit of a numerical range of another stage. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. Furthermore, the upper and lower limits individually described can be arbitrarily combined. Furthermore, unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more types. When multiple substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified.

[0012] In this specification, "(meth)acrylic" means at least one of acrylic and its corresponding methacrylic. The same applies to other similar expressions such as "(meth)acrylate." Furthermore, a "butane diisocyanate composition" means a composition containing butane diisocyanate and / or a derivative thereof. Furthermore, a composition containing "a group" means that the composition contains a compound having a group. Furthermore, in this specification, butane diisocyanate may be abbreviated as "BDI," and an isocyanate group may be abbreviated as "NCO group."

[0013] Preferred embodiments of each aspect of the present disclosure will be described below, although the aspects of the present disclosure are not limited to the following embodiments.

[0014] <BDI Composition> One aspect of the present disclosure is a BDI composition containing an allophanate of BDI (hereinafter also referred to as "allophanate (A)") having a structure derived from one or more monoalcohols having 1 to 10 carbon atoms and a structure derived from BDI (butane diisocyanate), and having a molar ratio (R Ｅ ) is 75 to 100 mol %. Ｅ = E / (A + B + C + D + E + F + G) × 100 ... formula (E) [In formula (E), A, B, C, D, E, F, and G represent the total number of moles of isocyanurate groups in the isocyanurate form of BDI, uretdione groups in the uretdione form of BDI, iminooxadiazinedione groups in the iminooxadiazinedione form of BDI, urethane groups in the urethane form of BDI, allophanate groups in the allophanate form of BDI, urea groups in the urea form of BDI, and biuret groups in the biuret form of BDI, which are contained in the BDI composition.]

[0015] The BDI composition can be used to prepare a polyisocyanate composition that has low viscosity, excellent workability, and contributes to the production of a coating film with high hardness. The low viscosity of the polyisocyanate composition can be confirmed, for example, by the viscosity at 25°C measured with a rheometer. The high hardness of the coating film obtained using the polyisocyanate composition can be confirmed, for example, by the Martens hardness of the coating film at 23°C.

[0016] The BDI composition may be a composition composed of a BDI derivative. That is, the BDI composition contains an allophanate (A) and has a molar ratio (R Ｅ The BDI composition may be a BDI derivative in which the amount of BDI is 75 to 100 mol %. The BDI composition may contain compounds other than the BDI derivative.

[0017] BDI derivatives consist of compounds derived from BDI. BDI derivatives may also be mixtures of multiple compounds derived from BDI. Examples of compounds derived from BDI include compounds having a structure derived from BDI (e.g., a reaction residue of BDI remaining after the reaction of BDI with a compound having an isocyanate-reactive group). In this specification, BDI, which is the raw material for BDI derivatives, may be referred to as a "BDI monomer."

[0018] Examples of compounds derived from BDI include allophanate forms of BDI, isocyanurate forms of BDI, uretdione forms of BDI, iminooxadiazinedione forms of BDI, urethane forms of BDI, urea forms of BDI, and biuret forms of BDI. The allophanate forms of BDI are compounds derived from BDI monomers that have an allophanate group (a group formed by the reaction of two BDI monomer molecules with one hydroxyl group-containing compound) and have a group represented by formula (1). The isocyanurate forms of BDI are compounds derived from BDI monomers that have an isocyanurate group (a group formed by cyclopolymerization of three BDI monomer molecules) and have a group represented by formula (2). The uretdione forms of BDI are compounds derived from BDI monomers that have a uretdione group and have a group represented by formula (3). The iminooxadiazinedione derivative 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 derivative of BDI is a compound derived from a BDI monomer that has a urethane group and has a group represented by formula (5). The urea derivative of BDI is a compound derived from a BDI monomer that has a urea group and has a group represented by formula (6). The biuret derivative of BDI is a compound derived from a BDI monomer that has a biuret group and has a group represented by formula (7).

[0019]

[0020] The BDI composition may contain, as a BDI derivative, the above-mentioned compound other than the allophanate form of BDI (for example, at least one selected from the group consisting of an isocyanurate form of BDI, a uretdione form of BDI, an iminooxadiazinedione form of BDI, a urethane form of BDI, a urea form of BDI, and a biuret form of BDI).

[0021] The BDI composition may contain, as a BDI derivative, an allophanate of BDI having at least one group selected from the group consisting of an isocyanurate group, a uretdione group, an iminooxadiadione group, a urethane group, a urea group, and a biuret group. That is, the allophanate of BDI contained in the BDI composition may be at least one selected from the group consisting of an isocyanurate of BDI, a uretdione of BDI, an iminooxadiadione of BDI, a urethane of BDI, a urea of ​​BDI, and a biuret of BDI. Thus, the BDI derivative may include a compound having two or more functional groups selected from the group consisting of an isocyanurate group, a uretdione group, an iminooxadiadione group, a urethane group, an allophanate group, a urea group, and a biuret group in one molecule. A compound having both an allophanate group and an isocyanurate group (a compound that is both an allophanate and an isocyanurate) corresponds to both an allophanate of BDI and an isocyanurate of BDI. The same applies to other combinations of groups.

[0022] Examples of BDI monomers that are raw materials for BDI derivatives include 1,2-butane diisocyanate, 1,3-butane diisocyanate, 1,4-butane diisocyanate, 2,3-butane diisocyanate, and mixtures thereof. The BDI monomer may contain 1,4-butane diisocyanate due to the high reactivity of the isocyanate group bonded to the primary carbon. From the same viewpoint as above, the proportion of 1,4-butane diisocyanate in the BDI monomer may be 90% by mass or more, 95% by mass or more, or 100% by mass. In particular, from the viewpoint of enhancing the effect of the reactivity of the isocyanate group, the raw material for the allophanate form of BDI may contain 1,4-butane diisocyanate, and the proportion of 1,4-butane diisocyanate in the raw material for the allophanate form 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 will be described as an example, but unless otherwise specified, the present invention is not limited to this.

[0023] In one embodiment, the BDI composition may be an isocyanate composition. That is, the BDI composition may contain an isocyanate compound (a compound having an isocyanate group). For example, a BDI derivative (e.g., an allophanate of BDI) contained in the BDI composition may contain an isocyanate compound, or the allophanate (A) may contain an isocyanate compound.

[0024] The NCO group (isocyanate group) of the isocyanate compound may be blocked with a known blocking agent for the purpose of extending the pot life and achieving a one-component coating composition. For example, some or all of the NCO groups of a BDI derivative (such as an allophanate of BDI) may be blocked with a blocking agent. Blocked polyisocyanates are inactive at room temperature, but upon heating, the blocking agent dissociates, reactivating the NCO group and causing it to react 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 methylenes, mercaptans, acid amides, acid imides, imidazoles, ureas, oximes, amines, imides, and pyrazoles can be used. Note that when the BDI composition contains a blocked isocyanate compound, the NCO group content and viscosity described below are measured after the blocking agent dissociates.

[0025] The NCO group content of the BDI composition may be 5% by mass or more, 10% by mass or more, or 15% by mass or more, based on the total mass of the solids in the BDI composition, from the viewpoint of increasing the amount of NCO groups used for crosslinking of the polyurethane resin. The NCO group content of the BDI composition may be 30% by mass or less, 28% by mass or less, or 25% by mass or less, based on the total mass of the solids in the BDI composition, from the viewpoint of reducing the content of low-molecular-weight components such as BDI monomers and suppressing odor. From these viewpoints, the NCO group content of the BDI composition may be, for example, 5 to 30% by mass, 10 to 28% by mass, or 15 to 25% by mass, based on the total mass of the solids in the BDI composition. The solids in the BDI composition refer to components other than the solvent contained in the BDI composition.

[0026] The BDI composition is described in more detail below.

[0027] (Allophanate (A)) The allophanate (A) is a compound having a structure derived from one or more monoalcohols having 1 to 10 carbon atoms and a structure derived from BDI, and has an allophanate reaction structure containing these structures. Here, the monoalcohol-derived structure may be rephrased as a reaction residue of the monoalcohol remaining after the reaction of the monoalcohol with BDI. Furthermore, the BDI-derived structure may be rephrased as a reaction residue of BDI remaining after the reaction of the monoalcohol with BDI.

[0028] A monoalcohol having 1 to 10 carbon atoms is, for example, an allophanate modifier. The monoalcohol is represented by R—OH (R represents an organic group), and in a monoalcohol having 1 to 10 carbon atoms, R has 1 to 10 carbon atoms. The number of carbon atoms in R may be 1 to 8, 1 to 7, 1 to 6, 1 to 5, 1 to 4, 1 to 3, or 1 to 2. When R has 1 to 7 carbon atoms, the balance between viscosity and coating hardness tends to be good; when R has 1 to 5 carbon atoms, a coating film with higher hardness tends to be obtained; and when R has 1 to 4 carbon atoms, a coating film with even higher hardness tends to be obtained. R is, for example, a saturated or unsaturated hydrocarbon group. The hydrocarbon group may be linear or branched and may have a cyclic structure. The cyclic structure may be an alicyclic or aromatic ring. The hydrocarbon group may have a substituent. That is, at least a portion of the hydrogen atoms of the hydrocarbon group may be substituted with a substituent. Examples of the substituent include a halogeno group (a chloro group, a fluoro group), a nitro group, and a vinyl group.

[0029] Specific examples of monoalcohols having 1 to 10 carbon atoms include methanol, ethanol, vinyl alcohol, 1-propanol, 2-propanol (isopropanol), 3-chloro-1-propanol, 2,3-dichloro-1-propanol, 2-methyl-2-nitro-1-propanol, 1-butanol, 2-butanol, 3-methyl-1-butanol, 1-pentanol, cyclopentanol, 1-hexanol, cyclohexanol, methylcyclohexanol, 1-heptanol, 1-octanol, 2-ethyl-1-hexanol, 1-nonanol, etc. Among these, saturated aliphatic alcohols not having a functional group, such as methanol and 2-propanol (isopropanol), can increase the NCO group content.

[0030] The allophanate (A) may have a structure derived from two or more monoalcohols having 1 to 10 carbon atoms. The allophanate (A) having a structure derived from two or more monoalcohols having 1 to 10 carbon atoms may consist of one compound, or two or more compounds. For example, the allophanate (A) may contain one compound obtained by reacting two or more monoalcohols having 1 to 10 carbon atoms with BDI, or may contain a mixture of two or more compounds obtained by reacting two or more monoalcohols having 1 to 10 carbon atoms with BDI.

[0031] The allophanate (A) may have a structure derived from a monoalcohol having 11 or more carbon atoms. However, when the monoalcohol-derived structures of the allophanate (A) have an average of 1 to 10 carbon atoms, a coating film with higher hardness tends to be obtained. From the viewpoint of making it easier to obtain a coating film with a higher hardness, the average number of carbon atoms of the monoalcohol-derived structures of the allophanate (A) may be 1 to 8, 1 to 7, 1 to 6, 1 to 5, or 1 to 4. Here, the average number of carbon atoms is calculated based on the following calculation formula. [Calculation formula for average number of carbon atoms] Average number of carbon atoms (number) of n types of monoalcohol-derived structures = (a １ ×b １ +a ２ ×b ２ +a ３ ×b ３ +...+aｎ ×b ｎ ) / (b １ +b ２ +b ３ +...+b ｎ ) [wherein, a １ ~a ｎ represents the number of carbon atoms in the 1st to nth monoalcohol-derived structures, and b １ ~b ｎ represent the molar ratios of the structures derived from the 1st to nth monoalcohols, respectively.]

[0032] The number of carbon atoms in the monoalcohol-derived structure can be calculated by identifying the monoalcohol-derived structure (chemical structure) contained in the BDI composition and then determining the molar ratio of each structure. Specifically, the monoalcohol-derived structure (chemical structure) is first identified by analyzing the MS spectrum pattern of the decomposition product obtained by pyrolysis GC-MS measurement of the BDI composition. １ By measuring H-NMR, it is possible to calculate the molar ratio of structures derived from various monoalcohols. If all of the monoalcohols used have reacted, or can be considered to have reacted, it is possible to calculate the molar ratio by pyrolysis GC-MS measurement, if the type and amount of the monoalcohol used are known. １ The molar ratios of structures derived from various monoalcohols can be calculated without using H-NMR measurement.

[0033] The allophanate (A) can be obtained, for example, by reacting one or more monoalcohols having 1 to 10 carbon atoms with BDI (allophanation reaction). That is, the allophanate (A) may be an allophanation reaction product of one or more monoalcohols having 1 to 10 carbon atoms with BDI. The reaction product may contain compounds other than the allophanate (A). Details of the allophanation reaction will be described later.

[0034] (molar ratio of allophanate groups (R Ｅ )) The molar ratio of allophanate groups in the BDI composition (R Ｅ) is 75 to 100 mol %, and may be 80 mol % or more, 85 mol % or more, 90 mol % or more, or 95 mol % or more, or 99 mol % or less, 98 mol % or less, or 97 mol % or less, or may be 80 to 99 mol %, 85 to 98 mol %, 90 to 97 mol %, 90 to 100 mol %, or 95 to 100 mol %. When the molar ratio of allophanate groups is 90 mol % or more, the viscosity tends to be further reduced. The molar ratio (R Ｅ In calculating the total number of moles of each functional group, it is not necessary to specify the total number of moles of each functional group. For example, １３ The molar ratio (R Ｅ More specifically, it can be measured in accordance with the examples described below.

[0035] (Viscosity) The viscosity of the BDI composition at 25°C may be 1500 mPa·s or less, or may be 1000 mPa·s or less, 500 mPa·s or less, 250 mPa·s or less, or 200 mPa·s or less. When the viscosity is 1000 mPa·s or less, a polyisocyanate composition having good workability can be obtained without diluting it with a large amount of solvent, and the solids concentration of the coating composition can be further increased. The viscosity of the BDI composition at 25°C may be, for example, 10 mPa·s or more, 30 mPa·s or more, or 60 mPa·s or more. When the viscosity is 10 mPa·s or more, the resulting coating film tends to have higher hardness. From these perspectives, the viscosity of the BDI composition at 25°C may be 10 to 1500 mPa·s, 30 to 1000 mPa·s, 60 to 500 mPa·s, 10 to 250 mPa·s, or 10 to 200 mPa·s.

[0036] The BDI composition described above is used, for example, as a curing agent component of a coating composition. That is, another aspect of the present disclosure is a coating curing agent containing the BDI composition. Note that an isocyanate-reactive compound (such as a polyol) described below can be used as the base component of the coating curing agent.

[0037] <Polyisocyanate composition> A polyisocyanate composition according to another embodiment of the present disclosure contains the allophanate compound (A). Details of the allophanate compound (A) are the same as those described above.

[0038] In one embodiment, the polyisocyanate composition may include the BDI composition according to one aspect of the present disclosure. In another embodiment, the polyisocyanate composition may include a BDI composition according to one aspect of the present disclosure, and the molar ratio (R Ｅ R′) may be 75 to 100 mol %. Ｅ '=E' / (A'+B'+C'+D'+E'+F'+G')×100 ...Formula (E') [In formula (E'), R Ｅ A′ represents the molar ratio of allophanate groups, and A′, B′, C′, D′, E′, F′, and G represent the total number of moles of isocyanurate groups, uretdione groups, iminooxadiadione groups, urethane groups, allophanate groups, urea groups, and biuret groups, respectively, contained in the polyisocyanate composition.]

[0039] The polyisocyanate composition tends to have low viscosity and excellent workability. Furthermore, the polyisocyanate composition is likely to produce a coating film with high hardness.

[0040] Molar ratio (R Ｅ ') may be 80 mol% or more, 85 mol% or more, 90 mol% or more, or 95 mol% or more, or may be 99 mol% or less, 98 mol% or less, or 97 mol% or less, or may be 80 to 99 mol%, 85 to 98 mol%, 90 to 97 mol%, 90 to 100 mol%, or 95 to 100 mol%.

[0041] The polyisocyanate composition may consist solely of BDI and a BDI derivative, or may consist solely of a BDI derivative. The content of BDI in the polyisocyanate composition may be 5% by mass or less, 1% by mass or less, or 0% by mass, based on the total mass of the solids in the polyisocyanate composition.

[0042] The polyisocyanate composition may contain components other than BDI and BDI derivatives. The other components may be isocyanate compounds. Examples of such isocyanate compounds include 1,6-hexane diisocyanate (hexamethylene diisocyanate, hereinafter sometimes abbreviated as "HDI") and 1,5-pentane diisocyanate (pentamethylene diisocyanate), as well as derivatives thereof. From the viewpoint of easily obtaining a coating film with high hardness, the content of isocyanate compounds other than BDI derivatives in the polyisocyanate composition may be 50% by mass or less, 1% by mass or less, or even 0% by mass, based on the total mass of solids in the polyisocyanate composition. From the same viewpoint, the content of HDI and its derivatives in the polyisocyanate composition may be within the above-mentioned range.

[0043] The polyisocyanate composition may contain an organic solvent (for example, an organic solvent used in the production of the BDI composition described later, a dilution solvent described later, etc.) as another component, but the content of the organic solvent in the polyisocyanate composition may be 50 mass % or less, 20 mass % or less, 1 mass % or less, or 0 mass % or less, based on the total mass of the polyisocyanate composition.

[0044] The NCO group content of the polyisocyanate composition may be 5% by mass or more, 10% by mass or more, or 15% by mass or more, and may be 30% by mass or less, 28% by mass or less, or 25% by mass or less, or may be 5 to 30% by mass, 10 to 28% by mass, or 15 to 25% by mass, based on the total mass of the solid content in the polyisocyanate composition. Note that the solid content in the polyisocyanate composition means components other than the solvent contained in the polyisocyanate composition.

[0045] The viscosity of the polyisocyanate composition at 25°C may be 1500 mPa·s or less, or may be 1000 mPa·s or less, 500 mPa·s or less, 250 mPa·s or less, or 200 mPa·s or less. When the viscosity is 1000 mPa·s or less, good workability is achieved without the need for dilution with a large amount of solvent, allowing the solids concentration of the coating composition to be further increased. The viscosity of the polyisocyanate composition at 25°C may be, for example, 10 mPa·s or more, 30 mPa·s or more, or 60 mPa·s or more. When the viscosity is 10 mPa·s or more, the resulting coating film tends to have higher hardness. From these viewpoints, the viscosity of the polyisocyanate composition at 25°C may be 10 to 1500 mPa·s, 30 to 1000 mPa·s, 60 to 500 mPa·s, 10 to 250 mPa·s, or 10 to 200 mPa·s.

[0046] The polyisocyanate composition described above is used, for example, as a curing agent component of a coating composition. That is, another aspect of the present disclosure is a coating curing agent comprising the polyisocyanate composition. Note that an isocyanate-reactive compound (such as a polyol) described below can be used as the base component of the coating curing agent.

[0047] <Method for Producing BDI Composition> A method for producing a BDI composition according to another embodiment of the present disclosure includes a step of obtaining a composition containing an allophanate of BDI by performing an allophanation reaction to form allophanate groups (allophanation step). This production method may be the method for producing the BDI composition according to the above embodiment.

[0048] The allophanation step may be a step of obtaining a composition containing an allophanate form of BDI by an allophanation reaction between a reactant containing a BDI monomer and an allophanation modifier containing a monoalcohol having 1 to 10 carbon atoms. The allophanation reaction is carried out by reacting the reactant with the allophanation modifier.

[0049] As the monoalcohol having 1 to 10 carbon atoms, the above-mentioned monoalcohols having 1 to 10 carbon atoms can be used. The allophanate modifier may contain a monoalcohol having 11 or more carbon atoms. The allophanate modifiers can be used alone or in combination of two or more.

[0050] The amount of allophanate modifier used (for example, the amount of monoalcohol used) varies depending on the molecular weight of the allophanate modifier used, but may be 0.5 to 40 parts by mass, or may be 1 to 30 parts by mass, per 100 parts by mass of the charged amount of BDI.

[0051] The reaction temperature of the allophanate formation reaction may be 80 to 180° C., or may be 100 to 150° C. When the reaction temperature of the allophanate formation reaction is 80° C. or higher, the reaction time can be shortened, and therefore, coloration of the BDI composition can be further suppressed.

[0052] The allophanate formation reaction may be terminated when the target NCO group content and allophanate group content are reached. When the reaction temperature of the allophanate formation reaction is 80 to 180°C, the reaction time of the allophanate formation reaction is, for example, 0.5 to 6 hours.

[0053] The allophanation reaction may be carried out in the presence of, for example, a commonly known allophanation catalyst. Examples of the allophanation catalyst that can be used include metal salts of carboxylic acids (metal salts of alkali metals such as lithium, sodium, and potassium; metal salts of alkaline earth metals such as magnesium, calcium, and barium; metal salts of other typical metals such as tin and lead; and metal salts of transition metals such as manganese, iron, cobalt, nickel, copper, zinc, and zirconium). Examples of the carboxylic acid include monocarboxylic acids and polycarboxylic acids.

[0054] As the allophanate catalyst, from the viewpoint of suppressing the production of polymers and side reactions other than allophanation, at least one selected from the group consisting of zirconium 2-ethylhexanoate, tin 2-ethylhexanoate, zinc 2-ethylhexanoate, iron 2-ethylhexanoate, and titanium tetrakis(2-ethylhexanoate) may be used. In particular, when at least one selected from the group consisting of zirconium 2-ethylhexanoate and tin 2-ethylhexanoate is used, the production of polymers and side reactions other than allophanation can be further suppressed. The allophanate catalysts can be used alone or in combination of two or more.

[0055] The amount of the allophanate catalyst used may be 0.001 to 10 parts by mass, or may be 0.01 to 3 parts by mass, per 100 parts by mass of the charged amount of BDI.

[0056] The reaction temperature of the allophanation reaction when an allophanation catalyst is used may be 80 to 160°C, or may be 100 to 140°C. When the reaction temperature of the allophanation reaction when an allophanation catalyst is used is 80°C or higher, the reaction time can be shortened, thereby further suppressing discoloration of the BDI composition. Furthermore, when the reaction temperature of the allophanation reaction when an allophanation catalyst is used is 160°C or lower, side reactions such as isocyanuration can be further suppressed, and the viscosity can be further reduced.

[0057] The allophanation reaction using an allophanation catalyst may be terminated by adding a reaction terminator when the target NCO group content and allophanate group content are reached. When the reaction temperature of the allophanation reaction using an allophanation catalyst is 80 to 160°C, the reaction time of the allophanation reaction using an allophanation catalyst is, for example, 0.1 to 3 hours.

[0058] The reaction terminator is a compound that has the effect of deactivating the catalyst. As the reaction terminator, for example, inorganic acids such as phosphoric acid and hydrochloric acid, organic acids having a sulfonic acid group, a sulfamic acid group, etc., esters thereof, and known compounds such as acyl halides can be used. The reaction terminator can be used alone or in combination of two or more. The reaction terminator may be added promptly after the target NCO group content is reached.

[0059] The amount of reaction terminator added varies depending on the type of reaction terminator, the type of allophanation catalyst used, etc., but may be 0.1 to 3.5 equivalents, or 0.8 to 2.5 equivalents, relative to 1 equivalent of the allophanation catalyst. When the amount of reaction terminator used is 0.1 equivalent or more relative to 1 equivalent of the allophanation catalyst, the storage stability of the resulting polyisocyanate composition is further improved. When the amount of reaction terminator used is 3.5 equivalents or less relative to 1 equivalent of the allophanation catalyst, coloration of the resulting BDI composition can be further suppressed.

[0060] The allophanation reaction may be carried out under an inert gas atmosphere such as nitrogen, argon, etc. Specifically, a reactant containing 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 allophanation reaction may be carried out by the method described above.

[0061] The allophanatization reaction may be carried out in the absence or presence of an organic solvent. When the reaction is carried out in the presence of an organic solvent, an organic solvent having a boiling point equal to or higher than the reaction temperature may be used, as long as it does not affect the reaction. Examples of organic solvents 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, dimethyl sulfoxide, and hexamethylphosphonylamide. From the viewpoint of suppressing the formation of high-molecular-weight compounds, a polar solvent having a high affinity for monoalcohols may be used. The organic solvents may be used alone or in combination of two or more.

[0062] After the reaction is complete, unreacted BDI monomer (free BDI) may be removed from the reaction solution containing the reaction product. That is, the method for producing a BDI composition may further include a BDI removal step for removing free BDI after the allophanation step. To remove free BDI, for example, a removal method using thin-film distillation at 90 to 130°C under a high vacuum of 10 to 100 Pa, or an extraction method using an organic solvent, may be used. The removal may be carried out so that the residual content of free BDI in the reaction solution is 5% by mass or less. A residual content of free BDI of 5% by mass or less can further suppress odor generation and a decrease in storage stability. When an organic solvent is used in the reaction, the organic solvent can be removed simultaneously with the removal of free BDI.

[0063] The method for producing a BDI composition may further include a step of blocking the isocyanate groups in the BDI composition with the above-mentioned blocking agent after the allophanation step or the BDI removal step.

[0064] The BDI composition (or a reaction solution containing the BDI composition) obtained by the above method can be used as a polyisocyanate composition either directly or after being mixed 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.

[0065] According to the above method, by using at least one member selected from the group consisting of zirconium oxide 2-ethylhexanoate, tin 2-ethylhexanoate, zinc 2-ethylhexanoate, iron 2-ethylhexanoate, and titanium tetrakis(2-ethylhexanoate), as the allophanate catalyst, the molar ratio of allophanate groups can be increased, and the molar ratio of allophanate groups (R Ｅ A BDI composition in which the mol % of bis(2-methyl-2-methyl-1,2-diol) is 75 to 100 mol % can be prepared.

[0066] 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 polyurethane resin-forming properties, and a polyurethane resin is formed as a reaction product of the polyisocyanate and the polyol by reaction of the polyisocyanate (e.g., a BDI derivative) and the polyol in the composition.

[0067] 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 for example, polyester polyol, polyether polyol, polycarbonate polyol, polyolefin polyol, acrylic polyol, silicone polyol, castor oil polyol, fluorine-based polyol, transesterification product of two or more polyols, hydroxyl group-terminated prepolymers obtained by urethane reaction with polyisocyanate, etc. can be used. The polyol can be used alone or in combination of two or more.

[0068] (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 portion of the low-molecular-weight polyol with a low-molecular-weight polyamine or low-molecular-weight amino alcohol such as hexamethylenediamine, isophoronediamine, or monoethanolamine.

[0069] (Polyether Polyol) Examples of polyether polyols include polyether polyols obtained by addition polymerization of alkylene oxides using a compound having two or more, preferably two to three, active hydrogen groups as an initiator, such as low molecular weight polyols or low molecular weight polyamines. 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.

[0070] (Polycarbonate polyol) Examples of polycarbonate polyols include those obtained by the dealcoholization or dephenolation reaction of one or more low molecular weight polyols with 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 transesterification of polycarbonate polyol, polyester polyol, and low molecular weight polyol.

[0071] (Polyolefin Polyol) Examples of polyolefin polyols include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, and hydrogenated polyisoprene.

[0072] (Acrylic Polyol) Examples of acrylic polyols include those obtained by polymerizing or copolymerizing an acrylic acid ester and / or a methacrylic acid ester (hereinafter referred to as a (meth)acrylic acid 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.

[0073] [(Meth)acrylic acid esters] 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.

[0074] [(Meth)acrylic Acid Hydroxy Compound] The (meth)acrylic acid hydroxy compound has at least one hydroxyl group in the molecule that can serve as 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. 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 compounds can be used alone or in combination of two or more.

[0075] (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.

[0076] (Castor oil-based polyol) Examples of the castor oil-based polyol 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.

[0077] (Fluorine-Based Polyol) Examples of fluorine-based polyols include linear or branched polyols obtained by copolymerization of a fluorine-containing monomer and a monomer having a hydroxy group as an essential component. Here, the fluorine-containing monomer is preferably a fluoroolefin. Examples of fluorine-containing monomers include tetrafluoroethylene, chlorotrifluoroethylene, trichlorofluoroethylene, hexafluoropropylene, vinylidene fluoride, vinyl fluoride, and trifluoromethyltrifluoroethylene. Furthermore, examples of monomers 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 crotonate; and hydroxy group-containing allyl esters.

[0078] 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 tends to exhibit superior hardness.

[0079] The number average molecular weight of the polyol may be 750 to 50,000. When the number average molecular weight of the polyol is equal to or greater than the lower limit, adhesion tends to be further improved. When the number average molecular weight of the polyol is equal to or less than the upper limit, solubility in low-polarity organic solvents tends to be further improved, and adhesion tends to be further improved.

[0080] The content ratio of the polyisocyanate composition to the polyol in the polyurethane resin-forming composition is not particularly limited, but the molar ratio R of the isocyanate groups in the polyisocyanate composition to the hydroxyl groups in the polyol (isocyanate groups / hydroxyl groups) may be 0.5 to 2.5. When the molar ratio R is equal to or greater than the above-mentioned lower limit, the hydroxyl groups do not become too excessive, which tends to further improve adhesion, and also suppresses a decrease in crosslink density, making it easier to improve durability and the mechanical strength of the coating film. When the molar ratio R is equal to or less than the above-mentioned upper limit, the isocyanate groups do not become too excessive, which suppresses reaction with moisture in the air, which tends to further reduce swelling of the coating film and further suppress the associated decrease in adhesion.

[0081] The polyurethane resin-forming composition may be a one-component composition in which all of the constituent components are contained in one component, or a multi-component composition in which the constituent components are present in multiple components. The multi-component composition may, for example, comprise a first component (base) containing a polyol and a second component (curing agent) consisting of a polyisocyanate composition.

[0082] The polyurethane resin-forming composition may contain a dilution solvent. When the polyurethane resin-forming composition is a multi-component type, the dilution solvent may be contained in either the first or second component, or 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.

[0083] The polyurethane resin-forming composition may contain a urethanization catalyst. As the urethanization catalyst, a known urethanization catalyst can be used as appropriate, taking into consideration pot life, curing conditions, working conditions, and the like. 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.

[0084] The polyurethane resin-forming composition may contain, as needed, 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-component type, these additives may be contained in either the first or second component, or in both components.

[0085] The polyurethane resin-forming composition can be used, for example, as a coating composition.

[0086] <Coating composition and coating film> A coating composition according to one aspect of the present disclosure comprises 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). Furthermore, a coating film according to one aspect of the present disclosure comprises a cured product of the coating composition.

[0087] 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).

[0088] 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 25 N / mm ２Above, 40N / mm ２ Above, 50N / mm ２ Above, 60N / mm ２ or more than 95N / mm ２ The Martens hardness can be measured in accordance with JIS Z2255.

[0089] The coating film can be formed by applying the coating composition onto the surface of the substrate by a known method such as spraying, brushing, dipping, or using a coater, and then curing the composition.

[0090] The adherend is not particularly limited, and examples thereof include stainless steel, phosphate-treated steel, zinc 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 treatment, or those having an intermediate layer formed on the surface of these, can be used.

[0091] The curing conditions for the coating composition are not particularly limited, but may be a curing temperature of -5 to 150°C, a humidity of 10 to 95% RH, and a curing time of 0.5 to 336 hours.

[0092] The thickness of the coating film formed on the surface of the adherend may be 10 μm or more from the viewpoint of excellent recoatability and durability. A coating film of 10 μm or more improves durability and further prevents the coating film from breaking due to impact.

[0093] 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.

[0094] Example 1 Preparation of Polyisocyanate Composition (BDI Composition) 971 g of 1,4-BDI (1,4-butane diisocyanate, NCO group content: 60.0% by mass) was charged into a 1-liter four-neck flask equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet tube. The flask was heated to 55°C, and 29 g of methanol (manufactured by Wako Pure Chemical Industries, Ltd.), an allophanate modifier (monoalcohol), and 120 mg of Nikka Octix Zirconium (2-ethylhexanoic acid zirconium oxide, product name: Nippon Chemical Industry Co., Ltd.), an allophanate catalyst, were added. After the temperature rise in the reaction solution due to the heat generated by urethanization had ceased, the temperature was raised to 110°C and the mixture was stirred for 40 minutes. Thereafter, 109 mg of JP-508 (2-ethylhexyl acid phosphate, product name: Johoku Chemical Industry Co., Ltd.), a reaction terminator, was added, and the reaction solution was cooled. Excess 1,4-BDI was removed by thin-film distillation (conditions: 110°C, 0.04 kPa) to obtain 313 g of polyisocyanate composition P-1, which is a BDI composition. The properties of the obtained polyisocyanate composition P-1 are shown in Table 1. In this example, the properties of the polyisocyanate composition (BDI composition) were measured by the following methods.

[0095] (Measurement of Molar Ratio of Each Functional Group) The molar ratio of allophanate groups contained in the polyisocyanate composition (BDI composition) was measured using ECX400M (trade name) manufactured by JEOL Ltd. １３ It was determined by C-NMR.

[0096] Specifically, a measurement sample was prepared by dissolving the polyisocyanate composition in deuterated chloroform containing 0.2% by mass of tetramethylsilane. The sample concentration was 0.2 g / 1 mL by mass. The chemical shift reference was the carbon signal of chloroform at 77.16 ppm. １３The signal areas of carbon atoms corresponding to isocyanurate groups, uretdione groups, iminooxadiadione groups, urethane groups, allophanate groups, urea groups, and biuret groups were determined by C-NMR measurement at a resonance frequency of 125 MHz and an accumulation count of 1024.

[0097] The total number of moles of each functional group is expressed by the following formulas (a), (b), (c), (d), (e), (f), and (g) using the signal area of ​​the carbon atom corresponding to each functional group and the proportionality constant "α." By substituting these formulas into formula (E), the molar ratio of allophanate groups was calculated when the sum of the total number of moles of each functional group contained in the polyisocyanate composition was taken as 100 mol %. Total number of moles of isocyanurate groups: A = signal area near 148.7 ppm / 3 × α (formula (a)) Total number of moles of uretdione groups: B = signal area near 157.4 ppm / 2 × α (formula (b)) Total number of moles of iminooxadiazinedione groups: C = signal area near 139.3 ppm / 1 × α (formula (c)) Total number of moles of urethane groups: D = signal area near 156.6 ppm / 1 × α (formula (d)) Total number of moles of allophanate groups: E = signal area near 153.5 ppm / 1 × α (formula (e)) Total number of moles of urea groups: F = signal area near 157.5 ppm / 1 × α (formula (f)) Total number of moles of biuret groups: G = signal area near 156.1 ppm / 2 × α (formula (g)

[0098] (Measurement of Viscosity) The viscosity of the obtained polyisocyanate composition (BDI composition) was measured in an environment of 25°C using a rheometer (trade name: HAAKE MARS60, manufactured by Thermo Fisher Scientific).

[0099] (Measurement of NCO Group Content) The NCO group content of the obtained polyisocyanate composition (BDI composition) was determined by reacting the composition with a secondary amine and then back-titrating the unreacted secondary amine with hydrochloric acid.

[0100] Example 2 947 g of 1,4-BDI was charged into a 1-liter four-neck flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube. The flask was heated to 55°C, and 53 g of isopropanol (manufactured by Wako Pure Chemical Industries, Ltd.), an allophanation modifier, and 230 mg of nicka octyl zirconium, an allophanation catalyst, were added. After the temperature rise in the reaction solution due to the heat generated by urethanization had ceased, the temperature was raised to 110°C and the mixture was stirred for 4 hours. 210 mg of JP-508, a reaction terminator, was then added, and the reaction solution was cooled. Excess 1,4-BDI was removed by thin-film distillation (conditions: 110°C, 0.04 kPa), yielding 331 g of polyisocyanate composition P-2, a BDI composition. The properties of the resulting polyisocyanate composition P-2 are shown in Table 1.

[0101] Example 3 947 g of 1,4-BDI was charged into a 1-liter four-neck flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube. The flask was heated to 55°C, and 53 g of isopropanol, an allophanation modifier, and 200 mg of Nikka Octix tin (2-ethylhexanoate tin, product name, manufactured by Nippon Chemical Industry Co., Ltd.), an allophanation catalyst, were added. After the temperature rise in the reaction solution due to the heat generated by urethanization had ceased, the temperature was raised to 110°C and the mixture was stirred for 3 hours. 182 mg of JP-508, a reaction terminator, was then added, and the reaction solution was cooled. Excess 1,4-BDI was removed by thin-film distillation (conditions: 110°C, 0.04 kPa), yielding 340 g of polyisocyanate composition P-3, a BDI composition. The properties of the resulting polyisocyanate composition P-3 are shown in Table 1.

[0102] Example 4 947 g of 1,4-BDI was charged into a 1-liter four-neck flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube. The flask was heated to 55°C, and 53 g of isopropanol, an allophanation modifier, and 200 mg of Nikka Octix tin, an allophanation catalyst, were added. After the temperature rise in the reaction solution due to the heat generated by urethanization had ceased, the temperature was raised to 110°C and the mixture was stirred for 4 hours. Subsequently, 182 mg of JP-508, a reaction terminator, was added, and the reaction solution was cooled. Excess 1,4-BDI was removed by thin-film distillation (conditions: 110°C, 0.04 kPa), yielding 348 g of polyisocyanate composition P-4, a BDI composition. The properties of the resulting polyisocyanate composition P-4 are shown in Table 1.

[0103] Example 5: 924 g of 1,4-BDI was charged into a 1-liter four-neck flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube. The flask was heated to 55°C, and 76 g of 3-methyl-1-butanol (Tokyo Chemical Industry Co., Ltd.), an allophanation modifier, and 140 mg of nicka octyl zirconium, an allophanation catalyst, were added. After the temperature rise in the reaction solution due to the heat generated by urethanization had ceased, the temperature was raised to 110°C and the mixture was stirred for 40 minutes. Subsequently, 128 mg of JP-508, a reaction terminator, was added, and the reaction solution was cooled. Excess 1,4-BDI was removed by thin-film distillation (conditions: 110°C, 0.04 kPa), yielding 353 g of polyisocyanate composition P-5, a BDI composition. The properties of the resulting polyisocyanate composition P-5 are shown in Table 1.

[0104] Example 6 913 g of 1,4-BDI was charged into a 1-liter four-neck flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube. The flask was heated to 55°C, and 87 g of 1-hexanol (manufactured by Wako Pure Chemical Industries, Ltd.), an allophanation modifier, and 160 mg of nicka octyl zirconium, an allophanation catalyst, were added. After the temperature rise in the reaction solution due to the heat generated by urethanization had ceased, the temperature was raised to 110°C and the mixture was stirred for 1.4 hours. 146 mg of JP-508, a reaction terminator, was then added, and the reaction solution was cooled. Excess 1,4-BDI was removed by thin-film distillation (conditions: 110°C, 0.04 kPa), yielding 364 g of polyisocyanate composition P-6, a BDI composition. The properties of the resulting polyisocyanate composition P-6 are shown in Table 1.

[0105] Example 7: 892 g of 1,4-BDI was charged into a 1-liter four-neck flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube. The flask was heated to 55°C, and 108 g of 2-ethyl-1-hexanol (Wako Pure Chemical Industries, Ltd.), an allophanation modifier, and 200 mg of nicka octyl zirconium, an allophanation catalyst, were added. After the temperature rise in the reaction solution due to the heat generated by urethanization had ceased, the temperature was raised to 110°C and the mixture was stirred for 1.4 hours. Subsequently, 182 mg of JP-508, a reaction terminator, was added, and the reaction solution was cooled. Excess 1,4-BDI was removed by thin-film distillation (conditions: 110°C, 0.04 kPa), yielding 384 g of polyisocyanate composition P-7, a BDI composition. The properties of the resulting polyisocyanate composition P-7 are shown in Table 1.

[0106] Comparative Example 1 A 1-liter four-neck flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube was charged with 908 g of HDI (1,6-hexane diisocyanate, NCO group content: 50% by mass), heated to 55°C, and then 92 g of 2-ethyl-1-hexanol, an allophanation modifier, and 150 mg of nicka octyl zirconium, an allophanation catalyst, were added. After the temperature rise in the reaction solution due to the heat generated by urethanization had ceased, the temperature was raised to 110°C and the mixture was stirred for 1.5 hours. Thereafter, 137 mg of JP-508, a reaction terminator, was added, and the reaction solution was cooled. Excess HDI was removed by thin-film distillation (conditions: 140°C, 0.04 kPa), yielding 370 g of polyisocyanate composition P-8, an HDI composition. The properties of the resulting polyisocyanate composition P-8 are shown in Table 1.

[0107] Comparative Example 2: 947 g of 1,4-BDI was charged into a 1-liter four-neck flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube. This was heated to 55°C, and 53 g of isopropanol, an allophanation modifier, and 200 mg of zinc bis(2-ethylhexanoate) (manufactured by Wako Pure Chemical Industries, Ltd.), an allophanation catalyst, were added. After the temperature rise in the reaction solution due to the heat generated by urethanization had ceased, the temperature was raised to 110°C and the mixture was stirred for 1.2 hours. Subsequently, 182 mg of JP-508, a reaction terminator, was added, and the reaction solution was cooled. Excess 1,4-BDI was removed by thin-film distillation (conditions: 110°C, 0.04 kPa), yielding 396 g of polyisocyanate composition P-9, a BDI composition. The properties of the resulting polyisocyanate composition P-9 are shown in Table 1.

[0108] Comparative Example 3: 843 g of 1,4-BDI was charged into a 1-liter four-neck flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube. The flask was heated to 55°C, and 157 g of isotridecanol (manufactured by KH Neochem Co., Ltd.), an allophanation modifier, and 140 mg of nicka octyl zirconium, an allophanation catalyst, were added. After the temperature rise in the reaction solution due to the heat generated by urethanization had ceased, the temperature was raised to 110°C and the mixture was stirred for 1.2 hours. Subsequently, 128 mg of JP-508, a reaction terminator, was added, and the reaction solution was cooled. Excess 1,4-BDI was removed by thin-film distillation (conditions: 110°C, 0.04 kPa), yielding 410 g of polyisocyanate composition P-10, a BDI composition. The properties of the resulting polyisocyanate composition P-10 are shown in Table 1.

[0109] Synthesis Example 1 Preparation of Acrylic Polyol for Coating Evaluation Into a 300 ml four-neck flask equipped with a stirrer, a thermometer, a condenser, and a dropping funnel, 70 g of butyl acetate (manufactured by Wako Pure Chemical Industries, Ltd.) was charged and heated to 120°C. To the dropping funnel were added 40 g of methyl methacrylate (manufactured by Mitsubishi Gas Chemical Company, Inc.), 30 g of butyl acrylate (manufactured by Nippon Shokubai Co., Ltd.), 25 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 Corporation, 2-ethylperoxyhexane-tert-butyl), and this mixture was added dropwise to the reaction solution over 4 hours. Thereafter, the reaction solution was maintained at 120°C for 1 hour, and then 30 g of butyl acetate and 1 g of Perbutyl O were added to the dropping funnel, and this mixture was added dropwise to the reaction solution over 1 hour. Thereafter, the mixture was maintained at 120°C for 3 hours and cooled to room temperature, yielding acrylic polyol A-1. A-1 was prepared according to JIS K 1557, the hydroxyl value per resin solid content was 121 mgKOH / g. The appearance was a transparent liquid, the solid content was 50 mass %, and the glass transition temperature was 15°C.

[0110] <Evaluation> (Coating Hardness Evaluation) Coating compositions (two-component coating compositions) comprising the obtained polyisocyanate compositions P-1 to P-10 and an acrylic polyol were prepared, and coating films (cured films) were formed using the obtained coating compositions. The Martens hardness of the formed cured films was measured. Specifically, first, acrylic polyol A-1 and polyisocyanate compositions P-1 to P-10 were blended so that the equivalent ratio of hydroxyl groups to isocyanate groups was 1:1, and then butyl acetate was used to adjust the coating solids content to 40% by mass to obtain a coating composition. Next, the obtained coating composition was applied to a steel plate (JIS G 3141, product name: SPCC-SB, processing method: PF-1077, manufactured by Paltec Co., Ltd.) so that the coating film (uncured film) had a thickness of 20 μm. Thereafter, the coating film was dried for 1 hour in an environment of a temperature of 23 ° C. and a relative humidity of 50%, and then the dried coating film was heat-treated in an 80 ° C. dryer for 24 hours. Subsequently, the heat-treated coating film was aged for 7 days or more in an environment at a temperature of 23°C and a relative humidity of 50%, 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 in accordance with JIS Z 2255 using HM2000 (trade name, manufactured by Fisher Instruments).

[0111]

Claims

1. A butane diisocyanate allophanate having a structure derived from one or more monoalcohols having 1 to 10 carbon atoms and a structure derived from butane diisocyanate, wherein the molar ratio of allophanate groups represented by the following formula (E) (R Ｅ ) is 75 to 100 mol %. Ｅ = E / (A + B + C + D + E + F + G) × 100 ... formula (E) [In formula (E), A, B, C, D, E, F, and G represent the total number of moles of isocyanurate groups in the isocyanurate form of butane diisocyanate, uretdione groups in the uretdione form of butane diisocyanate, iminooxadiazinedione groups in the iminooxadiazinedione form of butane diisocyanate, urethane groups in the urethane form of butane diisocyanate, allophanate groups in the allophanate form of butane diisocyanate, urea groups in the urea form of butane diisocyanate, and biuret groups in the biuret form of butane diisocyanate, which are contained in the butane diisocyanate composition, respectively.] 2. The butane diisocyanate composition according to claim 1, wherein the monoalcohol has 1 to 7 carbon atoms.

3. The butane diisocyanate composition according to claim 1, wherein the monoalcohol has 1 to 5 carbon atoms.

4. The molar ratio of the allophanate groups (R Ｅ 2. The butane diisocyanate composition according to claim 1, wherein the isocyanate content is 90 to 100 mol %.

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

6. The polyisocyanate composition according to claim 5, having a viscosity at 25°C of 1000 mPa·s or less.

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

8. A coating composition comprising the polyisocyanate composition according to claim 5 and a compound having two or more isocyanate-reactive groups.

9. A coating film comprising a cured product of the coating composition according to claim 8.

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