Polyisocyanate composition, polyaspartic acid coating composition, and coating film

Abstract

Provided are: a polyisocyanate composition which contains a polyisocyanate that is derived from a diisocyanate and a polyol, the diisocyanate being at least one type selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, and the polyol being at least one type selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates; the polyol is at least one type selected from the group consisting of a polyester polyol and a polyoxyalkylene polyol, the number average molecular weight of the polyol is 200-2000 and the average number of hydroxyl groups is 2 or 3, and the polyisocyanate contains a urethane group and an allophanate group in one molecule. The molar ratio of allophanate groups to urethane groups in the polyisocyanate composition is 2 / 98 or more and 30 / 70 or less.

Description

Technical Field

[0001] The present invention relates to a polyisocyanate composition, a polyaspartic acid coating composition and a coating film. Background Art

[0002] Aliphatic polyaspartic acid coating compositions within polyurea coating compositions are composed of an amino-containing aspartic acid ester compound and an isocyanate-containing aliphatic and / or alicyclic polyisocyanate composition. Aromatic polyurea coating compositions significantly reduce yellowing of the coating film due to UV exposure, a drawback of aromatic polyurea coating compositions, and have been used in a wide range of applications, including various coatings, flooring materials, and waterproofing materials.

[0003] Aspartic acid ester compounds have lower viscosities than the main polyols used in polyurethane coating compositions, significantly reducing the amount of diluent solvent in polyaspartic acid coating compositions. This allows for high-solids and solvent-free formulations. Furthermore, due to the rapid reactivity of the amino groups in aspartic acid ester compounds with the isocyanate groups of aliphatic and / or alicyclic polyisocyanates, polyaspartic acid coating compositions offer advantages over polyurethane coating compositions, such as faster curing speeds even at room temperature and superior mechanical strength.

[0004] For example, Patent Document 1 discloses a polyaspartic acid coating composition comprising a polyisocyanate compound having a specific relationship among the contents (mol %) of isocyanurate groups, iminooxadiazinedione groups, uretdione groups, allophanate groups, and biuret groups. This polyaspartic acid coating composition has the following advantages: the polyisocyanate composition has a low viscosity suitable for high-solids formulations and solvent-free formulations, while maintaining curability and drying properties. Furthermore, a coating film obtained using this polyaspartic acid coating composition also exhibits excellent chemical resistance, hardness, and weather resistance.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2018 / 163953 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] However, although the polyaspartic acid coating composition proposed in Patent Document 1 achieves high solid fractionation, it does not mention the suppression of crystallization of the polyisocyanate composition used as a curing agent component, nor the elongation of a coating film obtained using the polyaspartic acid coating composition at low temperatures of around -20°C.

[0010] The present invention has been made in view of the above circumstances and provides a polyisocyanate composition having good viscosity, capable of suppressing crystallization, and having good appearance, weather resistance, and elongation at -20°C when formed into a coating film, as well as a polyaspartic acid coating composition and coating film using the polyisocyanate composition.

[0011] Solutions for solving problems

[0012] That is, the present invention includes the following aspect 1.

[0013] (1) A polyisocyanate composition comprising a polyisocyanate derived from a diisocyanate and a polyol,

[0014] The diisocyanate is at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates,

[0015] The polyol is at least one selected from the group consisting of polyester polyol and polyoxyalkylene polyol,

[0016] The polyol has a number average molecular weight of 200 or more and 2000 or less and an average number of hydroxyl groups of 2 or 3,

[0017] The polyisocyanate contains a carbamate group and an allophanate group in one molecule.

[0018] The polyisocyanate composition has a molar ratio of allophanate groups to urethane groups of 2 / 98 or more and 30 / 70 or less.

[0019] (2) The polyisocyanate composition according to (1), wherein the ratio of the molar amount of the uretdione group to the total molar amount of the isocyanurate group, the uretdione group, the allophanate group, and the urethane group is 0.3 mol% or more and 20 mol% or less.

[0020] (3) The polyisocyanate composition according to (1) or (2), wherein the ratio of the molar amount of the isocyanurate group to the total molar amount of the isocyanurate group, the uretdione group, the allophanate group, and the urethane group is 0.01 mol% or more and 20.00 mol% or less.

[0021] (4) The polyisocyanate composition according to any one of (1) to (3), wherein the polyol includes two types of the polyester polyols having structures different from each other, or includes the polyester polyol and the polyoxyalkylene polyol.

[0022] (5) The polyisocyanate composition according to any one of (1) to (4), wherein the content of the polyoxyalkylene polyol is 30% by mass or less relative to the total mass of the polyol.

[0023] (6) The polyisocyanate composition according to any one of (1) to (5), wherein the content of the polyol having an average hydroxyl number of 3 is 30% by mass or less based on the total mass of the polyol.

[0024] (7) The polyisocyanate composition according to any one of (1) to (6), which is a curing agent for polyaspartic acid coatings.

[0025] (8) A polyaspartic acid coating composition comprising the polyisocyanate composition according to any one of (1) to (7) and an aspartic acid ester compound.

[0026] (9) A coating film formed by curing the polyaspartic acid coating composition described in (8).

[0027] The present invention includes the following aspect 2.

[0028] (1) A polyisocyanate composition comprising a polyisocyanate derived from a diisocyanate, a first polyol, and a second polyol,

[0029] The diisocyanate is at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates,

[0030] The first polyol has a number average molecular weight of 200 or more and 2000 or less, an average number of hydroxyl groups of 2 or 3, and is at least one selected from the group consisting of polyester polyols and polyoxyalkylene polyols.

[0031] The second polyol is a branched monool, diol or triol having 2 to 20 carbon atoms.

[0032] The molar ratio of the allophanate group to the urethane group in the polyisocyanate composition is 0 / 100 or more and 30 / 70 or less.

[0033] (2) The polyisocyanate composition according to (1), wherein the content of the second polyol is 1% by mass or more and 30% by mass or less relative to the total mass of the first polyol and the second polyol.

[0034] (3) The polyisocyanate composition according to (1) or (2), wherein the second polyol is a branched diol having 3 to 20 carbon atoms.

[0035] (4) The polyisocyanate composition according to any one of (1) to (3), wherein the molar ratio of the allophanate group to the urethane group is 2 / 98 or more and 30 / 70 or less.

[0036] (5) The polyisocyanate composition according to any one of (1) to (4), wherein the ratio of the molar amount of the uretdione group to the total molar amount of the isocyanurate group, the uretdione group, the allophanate group, and the urethane group is 0.3 mol% or more and 20 mol% or less.

[0037] (6) The polyisocyanate composition according to any one of (1) to (5), wherein the ratio of the molar amount of the isocyanurate group to the total molar amount of the isocyanurate group, the uretdione group, the allophanate group, and the urethane group is 0.01 mol% or more and 20.00 mol% or less.

[0038] (7) The polyisocyanate composition according to any one of (1) to (6), wherein the first polyol comprises two types of the polyester polyols having structures different from each other, or comprises the polyester polyol and the polyoxyalkylene polyol.

[0039] (8) The polyisocyanate composition according to any one of (1) to (7), wherein the content of the polyoxyalkylene polyol is 30% by mass or less relative to the total mass of the first polyol and the second polyol.

[0040] (9) The polyisocyanate composition according to (1), wherein the content of the polyol having an average number of hydroxyl groups of 3 is 30% by mass or less relative to the total mass of the first polyol and the second polyol.

[0041] (10) The polyisocyanate composition according to any one of (1) to (9), which is a curing agent for polyaspartic acid coatings.

[0042] (11) A polyaspartic acid coating composition comprising the polyisocyanate composition according to any one of (1) to (10) and an aspartic acid ester compound.

[0043] (12) A coating film formed by curing the polyaspartic acid coating composition described in (11).

[0044] Effects of the Invention

[0045] The polyisocyanate composition according to the above embodiment can provide a polyisocyanate composition having good viscosity, inhibited crystallization, and excellent appearance, weather resistance, and elongation at -20°C when formed into a coating film. The polyaspartic acid coating composition according to the above embodiment comprises the polyisocyanate composition and, when formed into a coating film, has excellent appearance, weather resistance, and elongation at -20°C. The coating film according to the above embodiment is formed by curing the polyaspartic acid coating composition and has excellent appearance, weather resistance, and elongation at -20°C. DETAILED DESCRIPTION

[0046] Hereinafter, a mode for implementing the present invention (hereinafter referred to as "this embodiment") will be described in detail. The present invention is not limited to the following embodiment. The present invention can be implemented by appropriately modifying the present invention within the scope of its gist.

[0047] In addition, in this specification, "polyol" refers to a compound having two or more hydroxyl groups (-OH).

[0048] In this specification, "polyisocyanate" refers to a reaction product in which a plurality of monomeric compounds (monomers) having one or more isocyanate groups (-NCO) are bonded together.

[0049] Polyisocyanate composition of embodiment 1

[0050] The polyisocyanate composition of this embodiment includes a polyisocyanate derived from a diisocyanate, wherein the diisocyanate is at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, and the polyol is at least one selected from the group consisting of polyester polyols and polyoxyalkylene polyols.

[0051] The polyol has a number average molecular weight of 200 or more and 2000 or less, and an average number of hydroxyl groups of 2 or 3.

[0052] The polyisocyanate contains a urethane group and an allophanate group in one molecule.

[0053] In the polyisocyanate composition of the present embodiment, the molar ratio of the allophanate group relative to the carbamate group (the molar ratio of the allophanate group / carbamate group) is 2 / 98 or more and 30 / 70 or less, preferably 3 / 97 or more and 30 / 70 or less, more preferably 5 / 95 or more and 20 / 80 or less. By having the molar ratio of the allophanate group / carbamate group be above the above lower limit, crystallization can be suppressed, and the polyisocyanate composition of the present embodiment can be mixed as a uniform curing agent in a coating composition, particularly a polyaspartic acid coating composition. Thus, a coating film having excellent curability, surface appearance, and elongation at low temperatures of about -20°C can be obtained. On the other hand, by having the molar ratio of the allophanate group / carbamate group be below the above upper limit, a coating film having excellent weather resistance can be obtained.

[0054] The molar ratio of allophanate groups to carbamate groups can be determined, for example, by 13 Specifically, it can be calculated by the method described in the Examples below.

[0055] The polyisocyanate composition of the present embodiment has the above-mentioned configuration, and can provide a coating film having good viscosity, suppressed crystallization, and good appearance, weather resistance, and elongation at -20°C.

[0056] The polyisocyanate composition of the present embodiment can be suitably used as a curing agent for a polyaspartic acid coating composition containing an aspartic acid ester compound as a main component, that is, a curing agent for a polyaspartic acid coating.

[0057] Next, each component contained in the polyisocyanate composition of this embodiment will be described in detail below.

[0058] [Polyisocyanate]

[0059] The polyisocyanate contained in the polyisocyanate composition of this embodiment is derived from a diisocyanate and a polyol. The diisocyanate is at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, and the polyol is at least one selected from the group consisting of polyester polyols and polyoxyalkylene polyols. In other words, the polyisocyanate is a reaction product of the diisocyanate and the polyol.

[0060] In addition, polyisocyanates contain carbamate groups and allophanate groups in one molecule. Carbamate groups are formed by the reaction of the isocyanate groups of diisocyanates and the hydroxyl groups of polyols. In addition, allophanate groups are formed by the reaction of the isocyanate groups of carbamate groups and diisocyanates, or the reaction of the isocyanate groups of two diisocyanates and the hydroxyl groups of one polyol.

[0061] The polyisocyanate may have other functional groups such as an isocyanurate group and a uretdione group in addition to the urethane group and the allophanate group.

[0062] Alternatively, the polyisocyanate composition of the present embodiment may further include, in addition to the polyisocyanate having a carbamate group and an allophanate group in the molecule, a polyisocyanate having any one of the functional groups of a carbamate group and an allophanate group, or a polyisocyanate having other functional groups such as an isocyanurate group and a uretdione group alone or in combination of two or more thereof.

[0063] In the polyisocyanate composition of the present embodiment, the ratio of the molar weight of uretdione group relative to the total molar weight of isocyanurate group, uretdione group, allophanate group and carbamate group is preferably more than 0.3 mol % and below 20 mol %, more preferably more than 1 mol % and below 10 mol %, further preferably more than 2 mol % and below 10 mol %.The ratio by the molar weight of uretdione group is more than the above-mentioned lower limit, and the viscosity of polyisocyanate composition becomes lower, can make high solids coating.On the other hand, the ratio by the molar weight of uretdione group is below the above-mentioned upper limit, can make the low temperature elongation when making film better.

[0064] In the polyisocyanate composition of the present embodiment, the ratio of the molar amount of isocyanurate group relative to the total molar amount of isocyanurate group, uretdione group, allophanate group and carbamate group is preferably 0.01 mol % or more and 20.00 mol % or less, more preferably 0.01 mol % or more and 10.00 mol % or less, further preferably 0.01 mol % or more and 5.00 mol % or less, particularly preferably 0.01 mol % or more and 3.00 mol % or less. By making the ratio of the molar amount of isocyanurate group be below the above-mentioned upper limit value, the low-temperature elongation when filming can be made is better. On the other hand, the low-temperature elongation when filming can be made is better the less the molar amount of isocyanurate group is.

[0065] The molar amount of each functional group in the polyisocyanate composition can be determined, for example, by 13 The molar ratio of the specific functional groups can be determined by C-NMR spectroscopy, and can be calculated using the calculated molar ratio of each functional group. Specifically, the ratio can be calculated using the method described in the Examples below.

[0066] [Diisocyanate]

[0067] The diisocyanate is at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates.

[0068] Examples of the aliphatic diisocyanate include, but are not limited to, 1,4-diisocyanatobutane, 1,5-diisocyanatopentane (hereinafter sometimes referred to as "PDI"), ethyl (2,6-diisocyanato)hexanoate, 1,6-diisocyanatohexane (hereinafter sometimes referred to as "HDI"), 1,9-diisocyanatononane, 1,12-isocyanatododecane, 2,2,4-trimethyl-1,6-diisocyanatohexane, and 2,4,4-trimethyl-1,6-isocyanatohexane. These aliphatic diisocyanates may be used alone or in combination of two or more.

[0069] Examples of the alicyclic diisocyanate include, but are not limited to, 1,3-bis(isocyanatomethyl)cyclohexane and 1,4-bis(isocyanatomethyl)cyclohexane (hereinafter sometimes referred to as "hydrogenated XDI"), 1,3-diisocyanatocyclohexane and 1,4-diisocyanatocyclohexane, 3,5,5-trimethyl-1-isocyanato-3-(isocyanatomethyl)cyclohexane (hereinafter sometimes referred to as "IPDI"), 4,4'-diisocyanato-dicyclohexylmethane (hereinafter sometimes referred to as "hydrogenated MDI"), 2,5-diisocyanatomethylnorbornane and 2,6-isocyanatomethylnorbornane. These alicyclic diisocyanates may be used alone or in combination of two or more.

[0070] These aliphatic diisocyanates and alicyclic diisocyanates may be used alone or in combination of two or more.

[0071] Among these, as the diisocyanate, PDI, HDI, IPDI, hydrogenated XDI or hydrogenated MDI is preferred, PDI, HDI or IPDI is more preferred, and HDI is further preferred.

[0072] In the production of polyisocyanate, in addition to the above-mentioned diisocyanate, the following isocyanate monomers may be further used.

[0073] (1) Aromatic diisocyanates such as diphenylmethane-4,4'-diisocyanate (MDI), 1,5-naphthalene diisocyanate, toluene diisocyanate (TDI), xylylene diisocyanate (XDI), and m-tetramethylxylylene diisocyanate (TMXDI).

[0074] (2) Triisocyanates such as 4-isocyanatemethyl-1,8-octamethylene diisocyanate (hereinafter sometimes referred to as “NTI”), 1,3,6-hexamethylene triisocyanate (hereinafter sometimes referred to as “HTI”), bis(2-isocyanatoethyl) 2-isocyanatoglutarate (hereinafter sometimes referred to as “GTI”), and lysine triisocyanate (hereinafter sometimes referred to as “LTI”).

[0075] [Polyol]

[0076] The number average molecular weight of the polyol is 200 to 2000, preferably 300 to 1500, more preferably 350 to 1200, and even more preferably 400 to 1000. By setting the number average molecular weight of the polyol to be above the lower limit, the elongation at low temperatures of approximately -20°C when the coating film is formed is significantly improved. On the other hand, by setting the number average molecular weight of the polyol to be below the upper limit, the viscosity of the polyisocyanate composition can be kept low, enabling the formation of a high-solids coating.

[0077] The number average molecular weight Mn of the polyol is, for example, a polystyrene-standard number average molecular weight measured by GPC. In addition, when two or more polyols are mixed and used, the number average molecular weight of the mixture is calculated.

[0078] The viscosity of the polyol at 25°C is preferably 90 mPa·s to 3000 mPa·s, more preferably 100 mPa·s to 2500 mPa·s, and even more preferably 100 mPa·s to 2000 mPa·s. By setting the viscosity of the polyol to be above the lower limit, the elongation at low temperatures of approximately -20°C when the coating film is formed is significantly improved. On the other hand, by setting the viscosity of the polyol to be below the upper limit, the viscosity of the polyisocyanate composition can be maintained at a lower level, enabling the formation of a high-solids coating.

[0079] The viscosity of the polyol at 25° C. can be measured by the method described in the Examples below.

[0080] The average number of hydroxyl groups in the polyol is 2 or 3.

[0081] By using a polyol with an average hydroxyl number of 2, the viscosity of the polyisocyanate composition is lowered, enabling the production of high-solids coatings. Furthermore, since the polyisocyanate has fewer side chains, the resulting coating exhibits greater elongation at low temperatures of around -20°C.

[0082] Furthermore, by using a polyol having an average hydroxyl number of 3, crystallization can be further suppressed, and the polyisocyanate composition of this embodiment can be incorporated into a coating composition, particularly a polyaspartic acid coating composition, as a uniform curing agent. This can result in a coating film with even better curability and surface appearance.

[0083] The polyol is at least one selected from the group consisting of polyester polyols and polyoxyalkylene polyols.

[0084] (Polyester polyol)

[0085] The number average molecular weight of the polyester polyol is 200 or more and 2000 or less, preferably 300 or more and 1500 or less, more preferably 350 or more and 1200 or less, and further preferably 400 or more and 1000 or less.

[0086] Examples of the polyester polyol include any of the following (1) and (2).

[0087] (1) Polyester polyols obtained by condensation reaction of a single dibasic acid or a mixture of two or more dibasic acids with a single divalent or higher alcohol or a mixture of two or more divalent or higher alcohols.

[0088] (2) Polycaprolactone polyols obtained by ring-opening polymerization of ε-caprolactone using a divalent or higher alcohol.

[0089] Examples of the dibasic acid include succinic acid, adipic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, succinic anhydride, maleic acid, phthalic acid, glutaric acid, suberic acid, azelaic acid, sebacic acid, decanedioic acid, itaconic acid, itaconic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, tetrahydrophthalic acid, and carboxylic acids such as tetrahydrophthalic acid.

[0090] Examples of the divalent or higher polyol include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, cyclohexanediol, 2-ethyl-1,3-hexanediol, trimethylolpropane, glycerol, pentaerythritol, 2-hydroxymethylpropanediol, ethoxylated trimethylolpropane, 1,3-propanediol, pentane-1,5-diol, heptane-1,7-diol, octane-1,8-diol, nonane-1,9-diol, decane-1,10-diol, and dodecane-1, 1,2-diol, cyclohexane-1,4-dimethanol, 4,4'-(1-methylethylene)bicyclohexanol, 1,1,1-trihydroxymethylethane, hexane-1,2,6-triol, dipropylene glycol, propane-1,2-diol, butane-1,3-diol, hexane-1,2-diol, 2-methylpentane-2,4-diol, 3-methyl-1,5-pentanediol, octane-1,2-diol, 2-butyl-2-ethylpropane-1,3-diol, decane-1,2-diol, 2-methyl-1,3-propanediol, etc.

[0091] Among them, as the polyester polyol, bifunctional or trifunctional polycaprolactone polyol is preferred.

[0092] Examples of commercially available bifunctional polycaprolactone polyols include "PLACCEL 205H" (number average molecular weight 530), "PLACCEL 210" (number average molecular weight 1000), "PLACCEL 210CP" (number average molecular weight 1000), "PLACCEL 212" (number average molecular weight 1250), "PLACCEL 212CP" (number average molecular weight 1250), "PLACCEL 220" (number average molecular weight 2000), and "PLACCEL 220CPB" (number average molecular weight 2000). "Capa2043" (number average molecular weight 400, viscosity at 25°C 246 mPa·s), "Capa2054" (number average molecular weight 550, viscosity at 25°C 360 mPa·s), "Capa2085" (number average molecular weight 830, viscosity at 25°C 627 mPa·s), "Capa2067A" (number average molecular weight 650, viscosity at 25°C 493 mPa·s), etc., manufactured by Ingevity.

[0093] In addition, commercially available bifunctional polyester polyols include, for example, "Kuraray polyol P-510" manufactured by Kuraray Corporation (number average molecular weight 500, viscosity at 25°C 540 mPa·s); "ODX2406" manufactured by DIC Corporation (number average molecular weight 440, viscosity at 25°C 460 mPa·s); and the like.

[0094] Examples of commercially available trifunctional polycaprolactone polyols include "PLACCEL 305" (number average molecular weight 550), "PLACCEL 308" (number average molecular weight 850), "PLACCEL 309" (number average molecular weight 900), "PLACCEL 312" (number average molecular weight 1250), and "PLACCEL 320" (number average molecular weight 2000) manufactured by Daicel; "ODX 2542C" (number average molecular weight 850) manufactured by DIC Corporation; and "Capa 3050" (number average molecular weight 540, viscosity at 60° C. 160 mPa·s) and "Capa 23091" (number average molecular weight 900, viscosity at 60° C. 165 mPa·s) manufactured by Ingevity Corporation.

[0095] (Polyoxyalkylene polyol)

[0096] Polyoxyalkylene polyols are polyols containing -O(CH2) nThe divalent to tetravalent polyol having a repeating unit represented by - can be derived from a divalent to tetravalent alcohol and ethylene oxide, propylene oxide, tetrahydrofuran, or the like. Furthermore, there are no particular limitations, and for example, it can be obtained by cationic polymerization of ethylene oxide, propylene oxide, tetrahydrofuran, or the like using a divalent to tetravalent alcohol as an initiator in the presence of a catalyst.

[0097] The number average molecular weight of the polyoxyalkylene polyol is preferably 200 or more and 2000 or less, more preferably 200 or more and 1500 or less, and further preferably 200 or more and 1000 or less.

[0098] As initiators, diols were used: ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, 1,3-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, cyclohexanediol, pentaerythritol, 2-hydroxymethylpropanediol, 2-ethyl-1,3-hexanediol, 1,3-propanediol, pentane-1,5-diol, heptane-1,7-diol, octane-1,8-diol, nonane-1,9-diol, decane-1,10-diol, dodecane-1,12-diol, cyclohexane-1,4-dimethanol, 4,4'-diol. Examples include (1-methylethylene)bicyclohexanol, 1,1,1-trimethylolethane, hexane-1,2,6-triol, dipropylene glycol, propane-1,2-diol, butane-1,3-diol, hexane-1,2-diol, 2-methylpentane-2,4-diol, 3-methyl-1,5-pentanediol, octane-1,2-diol, 2-butyl-2-ethylpropane-1,3-diol, decane-1,2-diol, and 2-methyl-1,3-propanediol; triols include glycerol and trimethylolpropane; and tetraols include pentaerythritol. From the perspective of obtaining a low-viscosity polyisocyanate component, branched polyols are preferred.

[0099] As the catalyst, a strong basic catalyst such as a hydroxide of lithium, sodium, potassium, or the like, an alkoxide, or an alkylamine can be used.

[0100] Cationic polymerization of ethylene oxide, propylene oxide, tetrahydrofuran, etc. is preferably carried out under a nitrogen atmosphere, wherein ethylene oxide, propylene oxide, tetrahydrofuran, etc. and the above-mentioned initiator are charged in a molar ratio set to a ratio to achieve a predetermined molecular weight, and a catalyst is further added in an amount of 0.1 ppm to 100 ppm relative to the ethylene oxide, propylene oxide, tetrahydrofuran, etc., and the reaction is carried out at a temperature of 150° C. to 200° C. for 4 hours to 10 hours.

[0101] Examples of commercially available bifunctional polyoxyalkylene polyols include "ECOTRION H1000" (number average molecular weight 1000, viscosity at 25°C 489 mPa·s) and "ECOTRION H2000" (number average molecular weight 2000, viscosity at 25°C 1701 mPa·s) manufactured by SK Chemicals; "Velvet H250" (number average molecular weight 227, viscosity at 25°C 107 mPa·s) manufactured by Allessa; and "BioPTMG650" (number average molecular weight 655, viscosity at 25°C 351 mPa·s) manufactured by Mitsubishi Chemical Corporation.

[0102] The polyol preferably contains two types of polyester polyols having different structures or contains a polyester polyol and a polyoxyalkylene polyol. When the polyol contains the above combination of two types of polyols, crystallization can be further suppressed.

[0103] When two polyester polyols having different structures are used in combination, or when a polyester polyol and a polyoxyalkylene polyol are used, the mixing ratio may be appropriately adjusted so that the number average molecular weight falls within the above range. For example, these polyester polyols may be mixed in a mass ratio of 3:1 to 1:3, 2:1 to 1:2, or 1.5:1 to 1:1.5.

[0104] The content of the polyoxyalkylene polyol is preferably 30% by mass or less relative to the total mass of the polyol, more preferably 28% by mass or less, further preferably 15% by mass or less, and particularly preferably 10% by mass or less. By making the content of the polyoxyalkylene polyol below the above upper limit, the weather resistance when the coating film is prepared can be made better. The lower limit of the polyoxyalkylene polyol is not particularly limited, and for example, can be 0% by mass, 1% by mass, 2% by mass, 3% by mass, etc.

[0105] When a polyol having an average hydroxyl number of 2 and a polyol having an average hydroxyl number of 3 are used in combination, it is preferred to contain more polyol having an average hydroxyl number of 2 than polyol having an average hydroxyl number of 3. Specifically, the content of the polyol having an average hydroxyl number of 3 is preferably 30% by mass or less, more preferably 28% by mass or less, further preferably 15% by mass or less, and particularly preferably 10% by mass or less, relative to the total mass of the polyol. By setting the content of the polyol having an average hydroxyl number of 3 below the above upper limit, the elongation at low temperatures of around -20°C when the coating film is formed can be improved. The lower limit of the content of the polyol having an average hydroxyl number of 3 is not particularly limited, and for example, it may be 0%, 1%, 2%, 3%, or the like.

[0106] <Other ingredients>

[0107] The polyisocyanate composition of the present embodiment preferably contains one or more selected from the group consisting of ultraviolet absorbers and light stabilizers. By containing ultraviolet absorbers and light stabilizers, a coating film with better weather resistance can be obtained.

[0108] The ultraviolet absorber is not particularly limited, and examples thereof include benzotriazole-based compounds, triazine-based compounds, benzophenone-based compounds, and cyanoacrylate-based compounds.

[0109] The benzotriazole-based compound is not particularly limited, and examples thereof include Tinuvin P·PS·99-2·213·234·326·329·360·384-2·571·900·928·970·1130 manufactured by BASF Japan Co., Ltd.; Adekastab LA-24·29·31RG·31G·32·36·36RG·F70 manufactured by ADEKA Co., Ltd.; and EVERSORB 70·71·72·73·74·75·76·77·78·79·80·81·82·88·89·109·234 manufactured by Taiwan Everlight Chemical Industry Co., Ltd.

[0110] The triazine compound is not particularly limited, and examples thereof include Tinuvin 400, 400-DW, 405, 460, 477, 479, 479-DW, 1577ED, and 1600, manufactured by BASF Japan Co., Ltd., and EVERSORB 40, 41FD, and 45, manufactured by Taiwan Everlight Chemical Co., Ltd.

[0111] The benzophenone compound is not particularly limited, and examples thereof include Chimassorb 81·81FL and Uvinul 3049·3050 manufactured by BASF Japan Co., Ltd.; Adekastab 1413 manufactured by ADEKA Corporation; and EVERSORB 10·11·12·51·52 manufactured by Taiwan Everlight Chemical Co., Ltd.

[0112] The cyanoacrylate compound is not particularly limited, and examples thereof include Uvinul 3030FF, 3035, and 3039 (trade names) manufactured by BASF Japan Co., Ltd.

[0113] From the viewpoint of maintaining the weather resistance of the coating film for a long period of time, benzotriazole-based compounds, triazine-based compounds, or benzophenone-based compounds are preferred, and benzotriazole-based compounds or triazine-based compounds are more preferred.

[0114] The light stabilizer is not particularly limited, and specific examples thereof include hindered amine compounds.

[0115] The hindered amine compound is not particularly limited, and examples thereof include Tinuvin 111FDL·123·123-DW·PA144·152·249·292·783FDL·765 manufactured by BASF Japan Co., Ltd.; Adekastab LA-52·57·63P·68·72·77Y·77G·81·402AF manufactured by ADEKA Co., Ltd.; and EVERSORB 60·61·90·91FD·93·94FD·95·765·S02 manufactured by Taiwan Everlight Chemical Industry Co., Ltd.

[0116] The ultraviolet absorber and the light stabilizer can be used alone or in combination of two or more.

[0117] The total amount of the ultraviolet absorber and the light stabilizer added is preferably 10 ppm by mass or more and 15,000 ppm by mass or less relative to the total mass of the polyisocyanate composition.

[0118] The polyisocyanate composition of this embodiment may further contain an antioxidant.

[0119] Examples of the antioxidant include hindered phenol-based antioxidants.

[0120] The hindered phenol-based antioxidant is not particularly limited, and examples thereof include butylated hydroxytoluene (hereinafter sometimes referred to as "BHT"); trade names "Irganox 1010", "Irganox 1135", "Irganox 1330", "Irganox 3114", "Irganox 565", and "Irganox 1520L" manufactured by BASF; and trade names "Adekastab AO-20", "Adekastab AO-30", "Adekastab AO-50", "Adekastab AO-60", and "Adekastab AO-80" manufactured by ADEKA Corporation.

[0121] <Method for producing polyisocyanate composition>

[0122] The polyisocyanate composition of the present embodiment can be obtained by simultaneously carrying out a urethanization reaction to form a carbamate group and an allophanation reaction to form an allophanate group in the presence of an excess of diisocyanate, and removing unreacted diisocyanate monomers after completion of the reactions.

[0123] The urethanization reaction can be carried out by mixing an excess amount of diisocyanate and polyol and, if necessary, adding a urethanization reaction catalyst.

[0124] The urethanization reaction catalyst is not particularly limited, and examples thereof include tin-based compounds, zinc-based compounds, and amine-based compounds.

[0125] The urethanization reaction temperature is preferably 50°C or higher and 160°C or lower, and more preferably 60°C or higher and 120°C or lower.

[0126] When the urethanization reaction temperature is equal to or lower than the above upper limit, coloration of the polyisocyanate tends to be more effectively suppressed.

[0127] The urethanization reaction time is preferably 30 minutes to 4 hours, more preferably 1 hour to 3 hours, and even more preferably 1 hour to 2 hours.

[0128] The ratio of the molar amount of the isocyanate group of isocyanate monomers to the molar amount of the hydroxyl group of alcohol (mol ratio of isocyanate group / hydroxyl group) is preferably more than 2 / 1 and less than 50 / 1. By making this mol ratio be more than the above-mentioned lower limit, polyisocyanate viscosity can be made lower. By making this mol ratio be below the above-mentioned upper limit, the yield of the polyisocyanate containing carbamate group can be further improved.

[0129] The allophanation reaction can be carried out after the above-mentioned urethanation reaction, and can be carried out by reacting an isocyanate group with a formed urethanate group, or by reacting two isocyanate groups with one hydroxyl group. The allophanation reaction can be carried out using an allophanation reaction catalyst.

[0130] Examples of the allophanation reaction catalyst include, but are not limited to, alkyl carboxylates of tin, lead, zinc, bismuth, zirconium, zirconyl, and the like.

[0131] Examples of tin alkyl carboxylates (organotin compounds) include tin 2-ethylhexanoate and dibutyltin dilaurate.

[0132] Examples of the lead alkyl carboxylate (organolead compound) include lead 2-ethylhexanoate.

[0133] Examples of zinc alkyl carboxylates (organozinc compounds) include zinc 2-ethylhexanoate.

[0134] Examples of bismuth alkyl carboxylates include bismuth 2-ethylhexanoate.

[0135] Examples of zirconium alkyl carboxylates include zirconium 2-ethylhexanoate.

[0136] Examples of the alkyl carboxylate of zirconyl include zirconyl 2-ethylhexanoate.

[0137] These catalysts can be used alone or in combination of two or more.

[0138] The lower limit of the amount of the allophanation reaction catalyst used is preferably 10 mass ppm, more preferably 15 mass ppm, further preferably 18 mass ppm, and particularly preferably 20 mass ppm, relative to the mass of the charged isocyanate monomer.

[0139] The upper limit of the amount of the allophanation reaction catalyst used is preferably 1000 mass ppm, more preferably 800 mass ppm, further preferably 500 mass ppm, and particularly preferably 300 mass ppm, relative to the mass of the charged isocyanate monomer.

[0140] That is, the usage amount of the above-mentioned allophanation reaction catalyst is preferably 10 mass ppm or more and 1000 mass ppm or less relative to the mass of the isocyanate monomer input, more preferably 15 mass ppm or more and 800 mass ppm or less, further preferably 18 mass ppm or more and 500 mass ppm or less, and particularly preferably 20 mass ppm or more and 300 mass ppm or less.

[0141] Moreover, as a lower limit of the allophanation reaction temperature, 80 degreeC is preferable, and 100 degreeC is more preferable.

[0142] Moreover, as an upper limit of the allophanation reaction temperature, 200 degreeC is preferable, and 180 degreeC is more preferable.

[0143] That is, the allophanation reaction temperature is preferably 80°C or higher and 200°C or lower, and more preferably 100°C or higher and 180°C or lower.

[0144] When the allophanation reaction temperature is equal to or higher than the above lower limit, the reaction rate can be further increased. When the allophanation reaction temperature is equal to or lower than the above upper limit, coloration of the polyisocyanate tends to be more effectively suppressed.

[0145] In the allophanation reaction, the molar ratio of allophanate groups to carbamate groups (molar ratio of allophanate groups / carbamate groups) can be adjusted to the above range by confirming the increase in the refractive index of the reaction solution. The reaction is stopped when the refractive index of the reaction solution reaches the desired value.

[0146] <Characteristics of Polyisocyanate Composition>

[0147] The isocyanate group content of the polyisocyanate composition of the present embodiment is preferably 5.0% by mass or more and 20.0% by mass or less, more preferably 6.0% by mass or more and 18.0% by mass or less, further preferably 7.0% by mass or more and 15.0% by mass or less, particularly preferably 7.5% by mass or more and 13.0% by mass or less, and most preferably 8.5% by mass or more and 12.5% by mass or less. By setting the isocyanate group content to be above the above lower limit, the concentration of urea bonds that serve as bonding points in the coating film can be further increased, and the weather resistance of the resulting coating film can be improved. On the other hand, by setting the isocyanate group content to be below the above upper limit, the concentration of urea bonds that serve as bonding points in the coating film can be suppressed from increasing excessively, and the elongation at low temperatures of around -20°C when the resulting coating film is improved.

[0148] The isocyanate group content can be measured by the method described in Examples below.

[0149] The lower limit of the viscosity of the polyisocyanate composition of this embodiment at 25°C is preferably 100 mPa·s, more preferably 500 mPa·s, even more preferably 700 mPa·s, and particularly preferably 800 mPa·s. On the other hand, the upper limit of the viscosity is preferably 3000 mPa·s, more preferably 2500 mPa·s, even more preferably 2000 mPa·s, and particularly preferably 1700 mPa·s.

[0150] That is, the viscosity of the polyisocyanate composition of the present embodiment at 25°C is preferably 100 mPa·s or more and 3000 mPa·s or less, more preferably 500 mPa·s or more and 2500 mPa·s or less, further preferably 700 mPa·s or more and 2000 mPa·s or less, and particularly preferably 800 mPa·s or more and 1700 mPa·s or less.

[0151] By setting the viscosity to be above the lower limit, workability during coating preparation tends to be further maintained. On the other hand, by setting the viscosity to be below the upper limit, the amount of solvent used in preparing the polyaspartic acid coating composition can be further reduced.

[0152] The viscosity can be measured by the method described in the examples below.

[0153] <<Polyisocyanate composition of embodiment 2>>

[0154] The polyisocyanate composition of the present embodiment contains a polyisocyanate derived from a diisocyanate, a first polyol, and a second polyol.

[0155] The diisocyanate is at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates.

[0156] The first polyol has a number average molecular weight of 200 to 2000, an average number of hydroxyl groups of 2 or 3, and is at least one selected from the group consisting of polyester polyols and polyoxyalkylene polyols.

[0157] The second polyol is a branched monool, diol, or triol having 2 to 20 carbon atoms.

[0158] Allophanate group is relative to the mol ratio (mol ratio of allophanate group / carbamate group) of carbamate group for more than 0 / 100 and below 30 / 70, is preferably more than 2 / 98 and below 30 / 70, is preferably more than 3 / 97 and below 30 / 70, more preferably more than 5 / 95 and below 20 / 80.Be more than the above-mentioned lower limit by the mol ratio of allophanate group / carbamate group, can further suppress crystallization, can be compounded in coating composition, particularly polyaspartic acid coating composition by the polyisocyanate composition of present embodiment as uniform curing agent.Thus, can obtain the film of curability and surface appearance excellence.On the other hand, be below the above-mentioned upper limit by the mol ratio of allophanate group / carbamate group, can obtain the film of weather resistance excellence.

[0159] The molar ratio of allophanate groups to carbamate groups can be determined, for example, by 13 Specifically, it can be calculated using the method described in the Examples below.

[0160] The polyisocyanate composition of the present embodiment has the above-mentioned configuration, and can provide a coating film having good viscosity, suppressed crystallization, and good appearance, weather resistance, and elongation at -20°C.

[0161] The polyisocyanate composition of the present embodiment can be suitably used as a curing agent for a polyaspartic acid coating composition containing an aspartic acid ester compound as a main component, that is, a curing agent for a polyaspartic acid coating.

[0162] Next, each component contained in the polyisocyanate composition of this embodiment will be described in detail below.

[0163] <Polyisocyanate>

[0164] The polyisocyanate contained in the polyisocyanate composition of the present embodiment is derived from a diisocyanate, a first polyol, and a second polyol. That is, the polyisocyanate is a reaction product of a diisocyanate, a first polyol, and a second polyol.

[0165] The polyisocyanate composition of the present embodiment may be a mixture of a diisocyanate, a polyisocyanate which is a reaction product of a first polyol and a second polyol, and a polyisocyanate which is a reaction product of a diisocyanate and a first polyol or a polyisocyanate which is a reaction product of a diisocyanate and a second polyol.

[0166] Furthermore, the polyisocyanate contains a urethane group, which is formed by the reaction of the isocyanate group of the diisocyanate with the hydroxyl group of the first polyol or the second polyol.

[0167] Furthermore, the polyisocyanate may contain a carbamate group and an allophanate group in one molecule. The allophanate group is formed by the reaction of a carbamate group with an isocyanate group of a diisocyanate, or by the reaction of two isocyanate groups of a diisocyanate with one hydroxyl group of the first polyol or the second polyol.

[0168] Furthermore, the polyisocyanate may have other functional groups such as an isocyanurate group and a uretdione group in addition to the carbamate group in one molecule.

[0169] Alternatively, the polyisocyanate composition of this embodiment may further include, in addition to the polyisocyanate having a carbamate group, a polyisocyanate having a carbamate group and an allophanate group in the molecule; a polyisocyanate having other functional groups such as an allophanate group, an isocyanurate group, a uretdione group, etc., alone or in combination of two or more thereof.

[0170] In the polyisocyanate composition of the present embodiment, the molar amount of uretdione group is preferably more than 0 mol % and less than 20 mol % relative to the ratio of the total molar amount of isocyanurate group, uretdione group, allophanate group and carbamate group, more preferably more than 0.3 mol % and less than 20 mol %, further preferably more than 1 mol % and less than 10 mol %, particularly preferably more than 2 mol % and less than 10 mol %. The ratio by the molar amount of uretdione group is more than the above-mentioned lower limit, can further suppress the crystallization of polyisocyanate composition, can the polyisocyanate composition of the present embodiment be coordinated in coating composition, particularly polyaspartic acid coating composition as uniform curing agent. Thus, can obtain the coating film of excellent curability and surface appearance. In addition, the viscosity of polyisocyanate composition becomes lower, can make high solids coating. On the other hand, the ratio by the molar amount of uretdione group is below the above-mentioned upper limit, can make the low-temperature elongation when making coating film better.

[0171] In the polyisocyanate composition of the present embodiment, the ratio of the molar amount of isocyanurate group relative to the total molar amount of isocyanurate group, uretdione group, allophanate group and carbamate group is preferably 0.01 mol % or more and 20.00 mol % or less, more preferably 0.01 mol % or more and 10.00 mol % or less, further preferably 0.01 mol % or more and 5.00 mol % or less, particularly preferably 0.01 mol % or more and 3.00 mol % or less. By making the ratio of the molar amount of isocyanurate group be below the above-mentioned upper limit value, the low-temperature elongation when filming can be made is better. On the other hand, the low-temperature elongation when filming can be made is better the less the molar amount of isocyanurate group is.

[0172] The molar amount of each functional group in the polyisocyanate composition can be determined, for example, by 13 The molar ratio of the specific functional groups can be determined by C-NMR spectroscopy, and can be calculated using the calculated molar ratio of each functional group. Specifically, the ratio can be calculated using the method described in the Examples below.

[0173] [Diisocyanate]

[0174] The diisocyanate is at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates.

[0175] Examples of the aliphatic diisocyanate include, but are not limited to, 1,4-diisocyanatobutane, 1,5-diisocyanatopentane (hereinafter sometimes referred to as "PDI"), ethyl (2,6-diisocyanato)hexanoate, 1,6-diisocyanatohexane (hereinafter sometimes referred to as "HDI"), 1,9-diisocyanatononane, 1,12-isocyanatododecane, 2,2,4-trimethyl-1,6-diisocyanatohexane, and 2,4,4-trimethyl-1,6-isocyanatohexane. These aliphatic diisocyanates may be used alone or in combination of two or more.

[0176] Examples of the alicyclic diisocyanate include, but are not limited to, 1,3-bis(isocyanatomethyl)cyclohexane and 1,4-bis(isocyanatomethyl)cyclohexane (hereinafter sometimes referred to as "hydrogenated XDI"), 1,3-diisocyanatocyclohexane and 1,4-diisocyanatocyclohexane, 3,5,5-trimethyl-1-isocyanato-3-(isocyanatomethyl)cyclohexane (hereinafter sometimes referred to as "IPDI"), 4-4'-diisocyanato-dicyclohexylmethane (hereinafter sometimes referred to as "hydrogenated MDI"), 2,5-diisocyanatomethylnorbornane and 2,6-isocyanatomethylnorbornane. These alicyclic diisocyanates may be used alone or in combination of two or more.

[0177] These aliphatic diisocyanates and alicyclic diisocyanates may be used alone or in combination of two or more.

[0178] Among these, as the diisocyanate, PDI, HDI, IPDI, hydrogenated XDI or hydrogenated MDI is preferred, PDI, HDI or IPDI is more preferred, and HDI is further preferred.

[0179] In the production of polyisocyanate, in addition to the above-mentioned diisocyanate, the following isocyanate monomers may be further used.

[0180] (1) Aromatic diisocyanates such as diphenylmethane-4,4'-diisocyanate (MDI), 1,5-naphthalene diisocyanate, toluene diisocyanate (TDI), xylylene diisocyanate (XDI), and m-tetramethylxylylene diisocyanate (TMXDI).

[0181] (2) Triisocyanates such as 4-isocyanatemethyl-1,8-octamethylene diisocyanate (hereinafter sometimes referred to as “NTI”), 1,3,6-hexamethylene triisocyanate (hereinafter sometimes referred to as “HTI”), bis(2-isocyanatoethyl) 2-isocyanatoglutarate (hereinafter sometimes referred to as “GTI”), and lysine triisocyanate (hereinafter sometimes referred to as “LTI”).

[0182] [First polyol]

[0183] The number average molecular weight of the polyol is 200 to 2000, preferably 300 to 1500, more preferably 350 to 1200, and even more preferably 400 to 1000. By setting the number average molecular weight of the polyol to be above the lower limit, the elongation at low temperatures of approximately -20°C when the coating film is formed is significantly improved. On the other hand, by setting the number average molecular weight of the polyol to be below the upper limit, the viscosity of the polyisocyanate composition can be kept low, enabling the formation of a high-solids coating.

[0184] The number average molecular weight Mn of the polyol is, for example, a polystyrene-standard number average molecular weight measured by GPC. In addition, when two or more polyols are mixed and used, the number average molecular weight of the mixture is calculated.

[0185] The viscosity of the polyol at 25°C is preferably 90 mPa·s to 3000 mPa·s, more preferably 100 mPa·s to 2500 mPa·s, and even more preferably 100 mPa·s to 2000 mPa·s. By setting the viscosity of the polyol to be above this lower limit, the elongation at low temperatures of around -20°C when formed into a coating film is significantly improved. On the other hand, by setting the viscosity of the polyol to be below this upper limit, the viscosity of the polyisocyanate composition can be kept lower, enabling the formation of a high-solids coating.

[0186] The viscosity of the polyol at 25° C. can be measured by the method described in the Examples below.

[0187] The average number of hydroxyl groups in the polyol is 2 or 3.

[0188] By using a polyol with an average hydroxyl number of 2, the viscosity of the polyisocyanate composition is lowered, enabling the production of high-solids coatings. Furthermore, since the polyisocyanate has fewer side chains, the resulting coating exhibits greater elongation at low temperatures of around -20°C.

[0189] Furthermore, by using a polyol having an average hydroxyl number of 3, crystallization can be further suppressed, and the polyisocyanate composition of this embodiment can be incorporated into a coating composition, particularly a polyaspartic acid coating composition, as a uniform curing agent. This can result in a coating film with even better curability and surface appearance.

[0190] The polyol is at least one selected from the group consisting of polyester polyols and polyoxyalkylene polyols.

[0191] (Polyester polyol)

[0192] The number average molecular weight of the polyester alcohol is 200 or more and 2000 or less, preferably 300 or more and 1500 or less, more preferably 350 or more and 1200 or less, and further preferably 400 or more and 1000 or less.

[0193] Examples of the polyester polyol include any of the following (1) and (2).

[0194] (1) Polyester polyols obtained by condensation reaction of a single dibasic acid or a mixture of two or more dibasic acids with a single divalent or higher alcohol or a mixture of two or more divalent or higher alcohols.

[0195] (2) Polycaprolactone polyols obtained by ring-opening polymerization of ε-caprolactone using a divalent or higher alcohol.

[0196] Examples of the dibasic acid include succinic acid, adipic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, succinic anhydride, maleic acid, phthalic acid, glutaric acid, suberic acid, azelaic acid, sebacic acid, decanedioic acid, itaconic acid, itaconic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, tetrahydrophthalic acid, and carboxylic acids such as tetrahydrophthalic acid.

[0197] Examples of the divalent or higher polyol include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, cyclohexanediol, 2-ethyl-1,3-hexanediol, trimethylolpropane, glycerol, pentaerythritol, 2-hydroxymethylpropanediol, ethoxylated trimethylolpropane, 1,3-propanediol, pentane-1,5-diol, heptane-1,7-diol, octane-1,8-diol, nonane-1,9-diol, decane-1,10-diol, and dodecane-1, 1,2-diol, cyclohexane-1,4-dimethanol, 4,4'-(1-methylethylene)bicyclohexanol, 1,1,1-trimethylolethane, hexane-1,2,6-triol, dipropylene glycol, propane-1,2-diol, butane-1,3-diol, hexane-1,2-diol, 2-methylpentane-2,4-diol, 3-methylpentane-1,5-diol, octane-1,2-diol, 2-butyl-2-ethylpropane-1,3-diol, decane-1,2-diol, 2-methyl-1,3-propanediol, etc.

[0198] Among them, as the polyester polyol, bifunctional or trifunctional polycaprolactone polyol is preferred.

[0199] Examples of commercially available bifunctional polycaprolactone polyols include "PLACCEL 210" (number average molecular weight 1000), "PLACCEL 210CP" (number average molecular weight 1000), "PLACCEL 212" (number average molecular weight 1250), "PLACCEL 212CP" (number average molecular weight 1250), "PLACCEL 220" (number average molecular weight 2000), "PLACCEL 220CPB" (number average molecular weight 2000), and "PLACCEL 220" (number average molecular weight 2000). CPT" (number average molecular weight 2000); trade names "Capa2043" (number average molecular weight 400, viscosity at 25°C 246mPa·s), "Capa2054" (number average molecular weight 550, viscosity at 25°C 360mPa·s), "Capa2085" (number average molecular weight 830, viscosity at 25°C 627mPa·s), "Capa2067A" (number average molecular weight 650, viscosity at 25°C 493mPa·s), etc. manufactured by Ingevity.

[0200] In addition, commercially available bifunctional polyester polyols include, for example, "Kuraray polyol P-510" manufactured by Kuraray Corporation (number average molecular weight 500, viscosity at 25°C 540 mPa·s); "ODX2406" manufactured by DIC Corporation (number average molecular weight 440, viscosity at 25°C 460 mPa·s); and the like.

[0201] Examples of commercially available trifunctional polycaprolactone polyols include "PLACCEL 305" (number average molecular weight 550), "PLACCEL 308" (number average molecular weight 850), "PLACCEL 309" (number average molecular weight 900), "PLACCEL 312" (number average molecular weight 1250), and "PLACCEL 320" (number average molecular weight 2000) manufactured by Daicel; "ODX 2542C" (number average molecular weight 850) manufactured by DIC Corporation; and "Capa 3050" (number average molecular weight 540, viscosity at 60° C. 160 mPa·s) and "Capa 23091" (number average molecular weight 900, viscosity at 60° C. 165 mPa·s) manufactured by Ingevity Corporation.

[0202] (Polyoxyalkylene polyol)

[0203] Polyoxyalkylene polyols are polyols containing -O(CH2) n The divalent to tetravalent polyol having a repeating unit represented by - can be derived from a divalent to tetravalent alcohol and ethylene oxide, propylene oxide, tetrahydrofuran, or the like. Furthermore, there are no particular limitations, and for example, it can be obtained by cationic polymerization of ethylene oxide, propylene oxide, tetrahydrofuran, or the like using a divalent to tetravalent alcohol as an initiator in the presence of a catalyst.

[0204] The number average molecular weight of the polyoxyalkylene polyol is preferably 200 or more and 2000 or less, more preferably 200 or more and 1500 or less, and further preferably 200 or more and 1000 or less.

[0205] As initiators, diols were used: ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, 1,3-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, cyclohexanediol, pentaerythritol, 2-hydroxymethylpropanediol, 2-ethyl-1,3-hexanediol, 1,3-propanediol, pentane-1,5-diol, heptane-1,7-diol, octane-1,8-diol, nonane-1,9-diol, decane-1,10-diol, dodecane-1,12-diol, cyclohexane-1,4-dimethanol, 4,4'-diol. Examples include (1-methylethylene)bicyclohexanol, 1,1,1-trimethylolethane, hexane-1,2,6-triol, dipropylene glycol, propane-1,2-diol, butane-1,3-diol, hexane-1,2-diol, 2-methylpentane-2,4-diol, 3-methylpentane-1,5-diol, octane-1,2-diol, 2-butyl-2-ethylpropane-1,3-diol, decane-1,2-diol, and 2-methyl-1,3-propanediol; triols include glycerol and trimethylolpropane; and tetraols include pentaerythritol. From the perspective of obtaining a low-viscosity polyisocyanate component, branched polyols are preferred.

[0206] As the catalyst, a strong basic catalyst such as a hydroxide of lithium, sodium, potassium, or the like, an alkoxide, or an alkylamine can be used.

[0207] Cationic polymerization of ethylene oxide, propylene oxide, tetrahydrofuran, etc. is preferably carried out under a nitrogen atmosphere, wherein ethylene oxide, propylene oxide, tetrahydrofuran, etc. and the above-mentioned initiator are charged in a molar ratio set to a ratio to achieve a predetermined molecular weight, and a catalyst is further added in an amount of 0.1 ppm to 100 ppm relative to the ethylene oxide, propylene oxide, tetrahydrofuran, etc., and the reaction is carried out at a temperature of 150° C. to 200° C. for 4 hours to 10 hours.

[0208] Examples of commercially available bifunctional polyoxyalkylene polyols include "ECOTRION H1000" (number average molecular weight 1000, viscosity at 25°C 489 mPa·s) and "ECOTRION H2000" (number average molecular weight 2000, viscosity at 25°C 1701 mPa·s) manufactured by SK Chemicals; "Velvet H250" (number average molecular weight 227, viscosity at 25°C 107 mPa·s) manufactured by Allessa; and "BioPTMG650" (number average molecular weight 655, viscosity at 25°C 351 mPa·s) manufactured by Mitsubishi Chemical Corporation.

[0209] The polyol preferably contains two types of polyester polyols having different structures or contains a polyester polyol and a polyoxyalkylene polyol. When the polyol contains the above combination of two types of polyols, crystallization can be further suppressed.

[0210] When two polyester polyols having different structures are used in combination, or when a polyester polyol and a polyoxyalkylene polyol are used, the mixing ratio may be appropriately adjusted so that the number average molecular weight falls within the above range. For example, these polyester polyols may be mixed in a mass ratio of 3:1 to 1:3, 2:1 to 1:2, or 1.5:1 to 1:1.5.

[0211] The content of the polyoxyalkylene polyol is preferably 30% by mass or less relative to the total mass of the first polyol and the second polyol, more preferably 28% by mass or less, further preferably 15% by mass or less, and particularly preferably 10% by mass or less. By making the content of the polyoxyalkylene polyol below the above upper limit, the weather resistance when the coating film is prepared can be made better. The lower limit of the polyoxyalkylene polyol is not particularly limited, and for example, can be 0% by mass, 1% by mass, 2% by mass, 3% by mass, etc.

[0212] When a polyol having an average hydroxyl number of 2 and a polyol having an average hydroxyl number of 3 are used in combination, it is preferred to contain more polyol having an average hydroxyl number of 2 than polyol having an average hydroxyl number of 3. Specifically, the content of the polyol having an average hydroxyl number of 3 is preferably 30% by mass or less, more preferably 28% by mass or less, further preferably 15% by mass or less, and particularly preferably 10% by mass or less, relative to the total mass of the first polyol and the second polyol. By setting the content of the polyol having an average hydroxyl number of 3 below the upper limit, the elongation at low temperatures of around -20°C when the coating is formed can be improved. The lower limit of the content of the polyol having an average hydroxyl number of 3 is not particularly limited and may be, for example, 0%, 1%, 2%, 3%, or the like.

[0213] [Second polyol]

[0214] In the polyisocyanate composition of this embodiment, by using a second polyol in addition to the first polyol, crystallization can be suppressed with little turbidity, and the polyisocyanate composition of this embodiment can be incorporated into a coating composition, particularly a polyaspartic acid coating composition, as a uniform curing agent. This allows for the production of a coating film with excellent curability and surface appearance.

[0215] The second polyol is a monool, diol, or triol having a branched chain and having 2 to 20 carbon atoms.

[0216] The monohydric alcohol may contain one or more selected from the group consisting of an ether group, an ester group, a carbonyl group, and a phenyl group in the molecule. For example, it may be benzyl alcohol. Preferably, it is a monohydric alcohol composed solely of saturated hydrocarbon groups. More preferably, it is a branched monohydric alcohol. Examples of such monohydric alcohols include 1-hexanol, 2-hexanol, 1-heptanol, 1-octanol, 2-ethyl-1-hexanol, 3,3,5-trimethyl-1-hexanol, tridecanol, pentadecanol, palmityl alcohol, stearyl alcohol, cyclopentanol, cyclohexanol, methylcyclohexanol, and trimethylcyclohexanol.

[0217] Examples of the diol include linear aliphatic diols such as ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; and branched aliphatic diols such as 2-ethyl-1,3-hexanediol, 2,4-diethyl-1,5-pentanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-pentanediol, and 2,2-diethyl-1,3-propanediol. These may be used alone or in combination of two or more. Among these, branched aliphatic diols are preferably used because they can further suppress crystallization.

[0218] Examples of the triol include glycerin and trimethylolpropane.

[0219] Among them, the second polyol is preferably a diol having a branched chain and having a carbon number of 3 to 20. By using a diol having a branched chain and having a carbon number of 3 to 20, crystallization can be further suppressed.

[0220] The content of the second polyol can be set to 35% by mass or less relative to the total mass of the first polyol and the second polyol, preferably 1% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 20% by mass or less, further preferably 5% by mass or more and 15% by mass or less, and particularly preferably 8% by mass or more and 12% by mass or less. By setting the content of the second polyol to above the above lower limit, crystallinity can be better maintained with almost no turbidity, and the polyisocyanate composition of this embodiment can be incorporated into a coating composition, particularly a polyaspartic acid coating composition, as a more uniform curing agent. Thus, a coating film with better curability and surface appearance can be obtained. On the other hand, by setting the content of the second polyol to below the above upper limit, the viscosity can be lowered and improved. In addition, the elongation at a low temperature of about -20°C when the coating film is formed can be improved.

[0221] <Other ingredients>

[0222] The polyisocyanate composition of the present embodiment preferably contains one or more selected from the group consisting of ultraviolet absorbers and light stabilizers. By containing ultraviolet absorbers and light stabilizers, a coating film with better weather resistance can be obtained.

[0223] The ultraviolet absorber is not particularly limited, and examples thereof include benzotriazole-based compounds, triazine-based compounds, benzophenone-based compounds, and cyanoacrylate-based compounds.

[0224] The benzotriazole-based compound is not particularly limited, and examples thereof include Tinuvin P·PS·99-2·213·234·326·329·360·384-2·571·900·928·970·1130 manufactured by BASF Japan Co., Ltd.; Adekastab LA-24·29·31RG·31G·32·36·36RG·F70 manufactured by ADEKA Co., Ltd.; and EVERSORB 70·71·72·73·74·75·76·77·78·79·80·81·82·88·89·109·234 manufactured by Taiwan Everlight Chemical Industry Co., Ltd.

[0225] The triazine compound is not particularly limited, and examples thereof include Tinuvin 400, 400-DW, 405, 460, 477, 479, 479-DW, 1577ED, and 1600, manufactured by BASF Japan Co., Ltd., and EVERSORB 40, 41FD, and 45, manufactured by Taiwan Everlight Chemical Co., Ltd.

[0226] The benzophenone compound is not particularly limited, and examples thereof include Chimassorb 81·81FL and Uvinul 3049·3050 manufactured by BASF Japan Co., Ltd.; Adekastab 1413 manufactured by ADEKA Corporation; and EVERSORB 10·11·12·51·52 manufactured by Taiwan Everlight Chemical Co., Ltd.

[0227] The cyanoacrylate compound is not particularly limited, and examples thereof include Uvinul 3030FF, 3035, and 3039 (trade names) manufactured by BASF Japan Co., Ltd.

[0228] From the viewpoint of maintaining the weather resistance of the coating film for a long period of time, a benzotriazole-based compound, a triazine-based compound, or a benzophenone-based compound is preferred, and a benzotriazole-based compound or a triazine-based compound is more preferred.

[0229] The light stabilizer is not particularly limited, and specific examples thereof include hindered amine compounds.

[0230] The hindered amine compound is not particularly limited, and examples thereof include Tinuvin 111FDL·123·123-DW·PA144·152·249·292·783FDL·765 manufactured by BASF Japan Co., Ltd.; Adekastab LA-52·57·63P·68·72·77Y·77G·81·402AF manufactured by ADEKA Co., Ltd.; and EVERSORB 60·61·90·91FD·93·94FD·95·765·S02 manufactured by Taiwan Everlight Chemical Industry Co., Ltd.

[0231] The ultraviolet absorber and the light stabilizer can be used alone or in combination of two or more.

[0232] The total amount of the ultraviolet absorber and the light stabilizer added is preferably 10 ppm by mass or more and 15,000 ppm by mass or less relative to the total mass of the polyisocyanate composition.

[0233] The polyisocyanate composition of this embodiment may further contain an antioxidant.

[0234] Examples of the antioxidant include hindered phenol-based antioxidants.

[0235] The hindered phenol-based antioxidant is not particularly limited, and examples thereof include butylated hydroxytoluene (hereinafter sometimes referred to as "BHT"); trade names "Irganox 1010", "Irganox 1135", "Irganox 1330", "Irganox 3114", "Irganox 565", and "Irganox 1520L" manufactured by BASF; and trade names "Adekastab AO-20", "Adekastab AO-30", "Adekastab AO-50", "Adekastab AO-60", and "Adekastab AO-80" manufactured by ADEKA Corporation.

[0236] <Method for producing polyisocyanate composition>

[0237] The polyisocyanate composition of this embodiment can be obtained by reacting an excess of diisocyanate, a first polyol, and a second polyol simultaneously, or by reacting an excess of diisocyanate with a first polyol and then with a second polyol, or by reacting an excess of diisocyanate with a second polyol and then with the first polyol, or by mixing a polyisocyanate obtained by reacting an excess of diisocyanate with a first polyol and a polyisocyanate obtained by reacting an excess of diisocyanate with a second polyol. Furthermore, unreacted diisocyanate monomers may be removed after completion of each reaction.

[0238] The reaction of an excess of diisocyanate with the first polyol or the second polyol is a well-known urethanization reaction.

[0239] The urethanization reaction can be carried out by mixing an excess amount of diisocyanate and polyol and, if necessary, adding a urethanization reaction catalyst.

[0240] The urethanization reaction catalyst is not particularly limited, and examples thereof include tin-based compounds, zinc-based compounds, and amine-based compounds.

[0241] The urethanization reaction temperature is preferably 50°C or higher and 160°C or lower, and more preferably 60°C or higher and 120°C or lower.

[0242] When the urethanization reaction temperature is below the above upper limit, coloration of the polyisocyanate tends to be more effectively suppressed.

[0243] The urethanization reaction time is preferably 30 minutes to 4 hours, more preferably 1 hour to 3 hours, and even more preferably 1 hour to 2 hours.

[0244] The ratio of the molar amount of the isocyanate group of isocyanate monomers to the molar amount of the hydroxyl group of alcohol (mol ratio of isocyanate group / hydroxyl group) is preferably more than 2 / 1 and less than 50 / 1. By making this mol ratio be more than the above-mentioned lower limit, polyisocyanate viscosity can be made lower. By making this mol ratio be below the above-mentioned upper limit, the yield of the polyisocyanate containing carbamate group can be further improved.

[0245] After the above-mentioned urethanization reaction, an allophanation reaction can be implemented. The allophanation reaction can be carried out by reacting an isocyanate group with a formed urethanation group or by reacting two isocyanate groups with a hydroxyl group. That is, the allophanation reaction can be carried out after the above-mentioned urethanization reaction, or the polyisocyanate obtained by performing the above-mentioned urethanization reaction can be mixed with the polyisocyanate obtained by performing the allophanation reaction. The allophanation reaction can be carried out using an allophanation reaction catalyst.

[0246] Examples of the allophanation reaction catalyst include, but are not limited to, alkyl carboxylates of tin, lead, zinc, bismuth, zirconium, zirconyl, and the like.

[0247] Examples of tin alkyl carboxylates (organotin compounds) include tin 2-ethylhexanoate and dibutyltin dilaurate.

[0248] Examples of the lead alkyl carboxylate (organolead compound) include lead 2-ethylhexanoate.

[0249] Examples of zinc alkyl carboxylates (organozinc compounds) include zinc 2-ethylhexanoate.

[0250] Examples of bismuth alkyl carboxylates include bismuth 2-ethylhexanoate.

[0251] Examples of zirconium alkyl carboxylates include zirconium 2-ethylhexanoate.

[0252] Examples of the alkyl carboxylate of zirconyl include zirconyl 2-ethylhexanoate.

[0253] These catalysts can be used alone or in combination of two or more.

[0254] The lower limit of the amount of the allophanation reaction catalyst used is preferably 10 mass ppm, more preferably 15 mass ppm, further preferably 18 mass ppm, and particularly preferably 20 mass ppm, relative to the mass of the charged isocyanate monomer.

[0255] The upper limit of the amount of the allophanation reaction catalyst used is preferably 1000 mass ppm, more preferably 800 mass ppm, further preferably 500 mass ppm, and particularly preferably 300 mass ppm, relative to the mass of the charged isocyanate monomer.

[0256] That is, the usage amount of the above-mentioned allophanation reaction catalyst is preferably 10 mass ppm or more and 1000 mass ppm or less relative to the mass of the isocyanate monomer input, more preferably 15 mass ppm or more and 800 mass ppm or less, further preferably 18 mass ppm or more and 500 mass ppm or less, and particularly preferably 20 mass ppm or more and 300 mass ppm or less.

[0257] Moreover, as a lower limit of the allophanation reaction temperature, 80 degreeC is preferable, and 100 degreeC is more preferable.

[0258] Moreover, as an upper limit of the allophanation reaction temperature, 200 degreeC is preferable, and 180 degreeC is more preferable.

[0259] That is, the allophanation reaction temperature is preferably 80°C or higher and 200°C or lower, and more preferably 100°C or higher and 180°C or lower.

[0260] When the allophanation reaction temperature is equal to or higher than the above lower limit, the reaction rate can be further increased. When the allophanation reaction temperature is equal to or lower than the above upper limit, coloration of the polyisocyanate tends to be more effectively suppressed.

[0261] In the allophanation reaction, the molar ratio of allophanate groups to carbamate groups (molar ratio of allophanate groups / carbamate groups) can be adjusted to the above range by confirming the increase in the refractive index of the reaction solution. The reaction is stopped when the refractive index of the reaction solution reaches the desired value.

[0262] <Characteristics of Polyisocyanate Composition>

[0263] The isocyanate group content of the polyisocyanate composition of the present embodiment is preferably 5.0% by mass or more and 20.0% by mass or less, more preferably 7.0% by mass or more and 18.0% by mass or less, further preferably 7.5% by mass or more and 15.0% by mass or less, particularly preferably 8.5% by mass or more and 15.0% by mass or less, and most preferably 10.0% by mass or more and 13.5% by mass or less. By setting the isocyanate group content to be above the above lower limit, the concentration of urea bonds that serve as bonding points in the coating film can be further increased, and the weather resistance of the resulting coating film can be improved. On the other hand, by setting the isocyanate group content to be below the above upper limit, the concentration of urea bonds that serve as bonding points in the coating film can be suppressed from increasing excessively, and the elongation at low temperatures of around -20°C when the resulting coating film is improved.

[0264] The isocyanate group content can be measured by the method described in Examples below.

[0265] The lower limit of the viscosity of the polyisocyanate composition of this embodiment at 25°C is preferably 100 mPa·s, more preferably 500 mPa·s, even more preferably 700 mPa·s, and particularly preferably 800 mPa·s. On the other hand, the upper limit of the viscosity is preferably 3000 mPa·s, more preferably 2500 mPa·s, even more preferably 2000 mPa·s, and particularly preferably 1750 mPa·s.

[0266] That is, the viscosity of the polyisocyanate composition of the present embodiment at 25°C is preferably 100 mPa·s or more and 3000 mPa·s or less, more preferably 500 mPa·s or more and 2500 mPa·s or less, further preferably 700 mPa·s or more and 2000 mPa·s or less, and particularly preferably 800 mPa·s or more and 1750 mPa·s or less.

[0267] By setting the viscosity to be above the lower limit, workability during coating preparation tends to be further maintained. On the other hand, by setting the viscosity to be below the upper limit, the amount of solvent used in preparing the polyaspartic acid coating composition can be further reduced.

[0268] The viscosity can be measured by the method described in the examples below.

[0269] Polyaspartic acid coating composition

[0270] The polyaspartic acid coating composition of the present embodiment comprises the polyisocyanate composition of the above-mentioned embodiment 1 or 2 and an aspartic acid ester compound.

[0271] The aspartic acid ester compound is a compound represented by the following general formula (I).

[0272]

[0273] In the general formula (I), X 11 It is an n-valent organic group obtained by removing the primary amino group of an n11-valent polyamine. 11 and R 12 are the same or different organic groups that are inactive with respect to isocyanate groups under the reaction conditions. n11 is an integer greater than or equal to 2.

[0274] X in formula (I) 11There are no particular restrictions, but from the viewpoint of yellowing resistance, an organic group based on an aliphatic and / or alicyclic polyamine having no aromatic group is preferred, for example, an organic group based on an n11-valent polyamine selected from the group consisting of ethylenediamine, 1,2-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 2,5-diamino-2,5-dimethylhexane, 2,2,4-trimethyl-1,6-diaminohexane and / or 2,4,4-trimethyl-1,6-diaminohexane, 1,11-diamino Undecane, 1,12-diaminododecane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane, 2,4-hexahydrotoluenediamine and / or 2,6-hexahydrotoluenediamine, 2,4'-diaminodicyclohexylmethane and / or 4,4'-diaminodicyclohexylmethane, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, 2,4,4'-triamino-5-methyldicyclohexylmethane, and polyether polyamines having a number average molecular weight of 148 to 6000 in which a primary amino group is bonded to an aliphatic group.

[0275] Among them, as X 11 , preferably an organic group based on 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 2,2,4-trimethyl-1,6-diaminohexane and / or 2,4,4-trimethyl-1,6-diaminohexane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane, 4,4'-diaminodicyclohexylmethane or 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane. In addition, an organic group based on 4,4'-diaminodicyclohexylmethane or 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane is more preferred.

[0276] R in formula (I) 11 and R 12 The term "inactive with respect to isocyanate groups under the reaction conditions" means that these groups do not have a Zerewitinoff-active hydrogen-containing group such as a hydroxyl group, an amino group, or a thiol group (a C—H acidic compound).

[0277] R 11 and R 12 Each of them is independently preferably an alkyl group having 1 to 10 carbon atoms, and more preferably a methyl group, an ethyl group or a butyl group.

[0278] Among them, n11 in formula (I) is preferably an integer of 2 or more and 6 or less, more preferably an integer of 2 or more and 4 or less, and even more preferably 2.

[0279] Preferred examples of the aspartic acid ester compound include an aspartic acid ester compound derived from two molecules of aspartic acid having a secondary amino group and one molecule of 4,4'-diaminodicyclohexylmethane.

[0280] Commercially available aspartic acid ester compounds can be used. Examples of commercially available aspartic acid ester compounds include "Amicure IC-221" (amine value 188 mgKOH / resin g, viscosity 450 mPa·s (representative value measured at 25°C)), "Amicure IC-321" (amine value 190 mgKOH / resin g, viscosity 450 mPa·s (representative value measured at 25°C)), and "Amicure IC-322" (amine value 189 mgKOH / resin g, viscosity 150 mPa·s (representative value measured at 25°C)) manufactured by Evonik; and "Feispartic F420" (amine value 201 mgKOH / resin g, viscosity 1450 mPa·s (representative value measured at 25°C)), and "Feispartic F520" (amine value 189 mgKOH / resin g, viscosity 1400 mPa·s (representative value measured at 25°C)) manufactured by Feiyang.

[0281] The above-mentioned aspartic acid ester compounds may be used alone or in combination of two or more.

[0282] The method for producing the aspartic acid ester compound is not particularly limited, and the aspartic acid ester compound can be produced, for example, by reacting a primary polyamine represented by the following formula (II) with a maleate or fumarate represented by the following formula (III).

[0283] X 11 -[NH2] n11 (II)

[0284] R 11 OOC-CH=CH-COOR 12 (III)

[0285] (In the above formula, X 11 、R 11 、R 12 、n11 have the same meaning as those in formula (I).

[0286] Suitable polyamines are not particularly limited, and for example, 11 The base of the above-mentioned diamine.

[0287] In addition, suitable maleate or fumarate is not particularly limited, and for example, R in formula (I) 11 and R 12 The group specified in R 11 and R 12Of these, preferably R 11 and R 12 The maleate or fumarate is an alkyl group having 1 to 10 carbon atoms, and more preferably dimethyl maleate, diethyl maleate, dibutyl maleate, dimethyl fumarate, diethyl fumarate, or dibutyl fumarate.

[0288] The preparation of aspartic acid ester compounds from the described starting materials is preferably carried out at a temperature range of 0°C to 100°C. The starting materials are used in a ratio such that at least one olefinic double bond, preferably only one olefinic double bond, is present per primary amino group. Excess starting materials can be removed by distillation after the reaction, if necessary. The reaction can be carried out neat or in the presence of a suitable solvent (not particularly limited, for example, methanol, ethanol, propanol, dioxane, or a mixture of such solvents).

[0289] <Isocyanate / Amino Group>

[0290] The molar ratio of isocyanate groups in the polyisocyanate composition to amino groups in the aspartic acid ester compound (isocyanate groups / amino groups) is preferably 1 / 10 to 10 / 1, more preferably 1 / 5 to 5 / 1, and even more preferably 1 / 2 to 2 / 1.

[0291] By setting the isocyanate group / amino group ratio above the above lower limit, the base agent does not become excessive, and the elongation at low temperatures of around -20°C when the coating film is formed can be improved. Furthermore, by setting the isocyanate group / amino group ratio within the above numerical range, a good balance between isocyanate groups and amino groups can be maintained, further increasing the concentration of urea bonds serving as bonding points in the coating film, and improving the weather resistance of the resulting coating film.

[0292] <Other ingredients>

[0293] The polyaspartic acid coating composition of the present embodiment may further contain other main components such as a polyvalent active hydrogen compound containing a polyol, a melamine resin, an epoxy resin, and a polyurethane resin, as needed.

[0294] In addition, when the above-mentioned polyol has a carboxyl group, an oxazoline group-containing compound and a carbodiimide group-containing compound may be mixed. In addition, when the above-mentioned polyol has a carbonyl group, a hydrazide group-containing compound and a semicarbazide group-containing compound may be mixed. These compounds may be mixed alone or in combination of two or more.

[0295] The polyaspartic acid coating composition of this embodiment preferably further comprises a surface conditioner as an additive in order to achieve a better appearance when formed into a coating film. The type of surface conditioner is not particularly limited, and examples thereof include silicone-based and acrylic-based agents.

[0296] The content of the surface conditioner is preferably 0.05% to 5% by mass relative to the resin component of the polyaspartic acid coating composition. By setting the surface conditioner content above the lower limit, the appearance of the resulting coating film can be further improved. On the other hand, by setting the surface conditioner content below the upper limit, the resulting coating film exhibits improved crater resistance, recoatability, and stain resistance.

[0297] As the silicone surface conditioner, commercially available products can be used, for example, BYK-300, BYK-302, BYK-306, BYK-307, BYK-310, BYK-313, BYK-315N, BYK-320, BYK-322, BYK-323, BYK-325, BYK-326, BYK-330, BYK-331, BYK-333, BYK-342, BYK-370, BYK-375, BYK-377, BYK-378, BYK-3760 (manufactured by BYK); DISPARLON 1711EF, DISPARLON 1761, DISPARLON LS-001, DISPARLON LS-050, DISPARLON LS-280, DISPARLON LS-460, DISPARLON LS-480 (manufactured by Kusumoto Chemical Co., Ltd.); Tego Flow425, Tego Glide 100, Tego Glide 110, Tego Glide130, Tego Glide 406, Tego Glide420, Tego Glide 432, Tego Glide 435, Tego Glide 440, Tego Glide 450, Tego Glide482, Tego Glide 485, Tego Glide ZG400, Tego wet KL245, Tego wet 250, Tego wet 260, Tego wet 265, Tego wet 270, Tego wet 280 (manufactured by Evonik Tego Chemie Co., Ltd.), etc. They can be used individually or in combination of 2 or more types.

[0298] As acrylic surface conditioners, commercially available products can be used, for example, BYK-350, BYK-354, BYK-355, BYK-356, BYK-358N, BYK-361N, BYK-392, BYK-394, BYK-3441 (manufactured by BYK Corporation); DISPARLON LF-1983, DISPARLON LF-1984, LF-1985, DISPARLON UVX-35, DISPARLON UVX-36 (manufactured by Kusumoto Chemical Co., Ltd.); Tego Flow 300, Tego Flow 370, Tego Flow ATF2, Tego Flow ZFS460 (manufactured by Evonik Tego Chemie Co., Ltd.), etc. These may be used alone or in combination of two or more.

[0299] As other types of surface conditioners other than those mentioned above, commercially available products can be used, for example, BYK-399, BYK-3440, BYK-3550, BYK-3560, BYK-3565, BYK-SILCLEAN 3700, BYK-SILCLEAN 3701, BYKETOL-OK (manufactured by BYK); DISPARLON UVX-272, DISPARLON UVX-2285, DISPARLON LHP-810, DISPARLON NSH-8430HF, DISPARLON LHP-90, DISPARLON LHP-91, DISPARLON LHP-95, DISPARLON LHP-96 (manufactured by Kusumoto Chemicals Co., Ltd.), etc. These may be used alone or in combination of two or more.

[0300] The polyaspartic acid coating composition of this embodiment preferably further contains a defoaming / foam suppressing / degassing agent as an additive in order to achieve a better appearance when formed into a coating film. The type of the defoaming / foam suppressing / degassing agent is not particularly limited, and examples thereof include silicone-based and polymer-based agents.

[0301] The content of the defoaming / foam suppressing / degassing agent is preferably 0.05% to 5% by mass relative to the resin component of the polyaspartic acid coating composition. By setting the content of the defoaming / foam suppressing / degassing agent to above the lower limit, workability during mixing and stirring can be improved, and the appearance of the resulting coating film can be enhanced. On the other hand, by setting the content of the defoaming / foam suppressing / degassing agent to below the upper limit, the resulting coating film exhibits improved crater resistance, recoatability, and stain resistance.

[0302] As the silicone defoaming / foam suppressing / degassing agent, commercially available products can be used, for example, BYK-063, BYK-065, BYK-066N, BYK-067A, BYK-077, BYK-081, BYK-1799 (manufactured by BYK); DISPARLON 1930N, DISPARLON 1934, DISPARLON SPX-44 (manufactured by Kusumoto Chemicals Co., Ltd.); Tego Airex 900, Tego Airex 916, Tego Airex 931, Tego Airex 935, Tego Airex 962, Tego Airex 980, Tego Foamex N (manufactured by Evonik Tego Chemie), etc. These may be used alone or in combination of two or more.

[0303] As the polymer-based defoaming, antifoaming, and deaerating agent, commercially available products can be used, for example, BYK-051N, BYK-052N, BYK-054, BYK-055, BYK-057, BYK-354, BYK-392, BYK-1752, BYK-1788, BYK-1790, BYK-1791, BYK-1794 (manufactured by BYK); DISPARLON OX-60, DISPARLON OX-6140, DISPARLON OX-70, DISPARLON OX-710, DISPARLON OX-750HF, DISPARLON OX-77EF, DISPARLON OX-880EF, DISPARLON OX-881, DISPARLON OX-883HF, DISPARLON LAP-10, DISPARLON LAP-20, DISPARLON LAP-30, DISPARLON 1952, DISPARLON 1958, DISPARLON 1960, DISPARLON P-410EF, DISPARLON PD-7, DISPARLON P-420, DISPARLON P-450, DISPARLON OX-881, DISPARLON OX-883HF, DISPARLON LAP-10, DISPARLON P-425, DISPARLON UVX-188, DISPARLON UVX-189, DISPARLON UVX-190 (manufactured by Kusumoto Chemicals Co., Ltd.); Tego Airex 910, Tego Airex920, Tego Airex 936, Tego Airex 944, Tego Airex 955 (manufactured by Evonik Tego Chemie Co., Ltd.), etc. These may be used alone or in combination of two or more.

[0304] As other types of defoaming, antifoaming, and degassing agents other than those mentioned above, commercially available products can be used, for example, BYK-088, BYK-141 (manufactured by BYK Corporation); DISPARLON OX-66EF, DISPARLON OX-715 (manufactured by Kusumoto Chemicals Co., Ltd.); Tego Airex 940, Tego Airex 945, Tego Airex 950, Tego Airex 986 (manufactured by Evonik TegoChemie Co., Ltd.), etc. These may be used alone or in combination of two or more.

[0305] The polyaspartic acid coating composition of the present embodiment may further contain one or more selected from the group consisting of the above-mentioned ultraviolet absorbers and light stabilizers.

[0306] The polyaspartic acid coating composition of this embodiment may also contain molecular sieves. Molecular sieves are the name for natural or synthetic zeolites with a high internal surface area and uniform pore size. Molecular sieves have high adsorption capacity. Therefore, molecular sieves are particularly useful as adsorbents, such as water absorbents.

[0307] Preferred molecular sieves have a pore size of 2.0 angstroms or more and 10 angstroms or less, preferably 2.5 angstroms or more and 4.0 angstroms or less, and more preferably about 3.0 angstroms.

[0308] The polyaspartic acid coating composition of the present embodiment generally contains 0.1% by mass to 15% by mass, preferably 0.5% by mass to 8% by mass, of molecular sieves based on the total mass.

[0309] The polyaspartic acid coating composition of the present embodiment may further contain a matting agent. The matting agent is not particularly limited, and examples thereof include dry silica and precipitated silica.

[0310] The dry silica is not particularly limited, and examples thereof include "ACEMATT 3400," "ACEMATT 3300," and "ACEMATT TS100," manufactured by Evonik Japan Co., Ltd.

[0311] The precipitated silica is not particularly limited, and examples thereof include trade names "ACEMAT 3600", "ACEMAT OK607 (LC)", "ACEMAT OK390", "ACEMAT OK900", "ACEMAT OK520", "ACEMAT OK500", "ACEMAT OK412", "ACEMAT HK390", "ACEMAT 790", "ACEMAT 82", "ACEMAT HK520", "ACEMAT HK400", "ACEMAT 810", "ACEMAT HK125", and "ACEMAT HK440" manufactured by Evonik Japan Co., Ltd.

[0312] The matting agent may be surface-treated or untreated. Among them, dry silica is particularly preferably used.

[0313] The polyaspartic acid coating composition of the present embodiment is usually blended with a matting agent in an amount of 3% by mass or more and 20% by mass or less based on the total mass of the polyaspartic acid coating composition.

[0314] The polyaspartic acid coating composition of the present embodiment may further contain a dispersant. Commercially available dispersants may be used, for example, the BYK company's trade names "DESPERBYK-103," "DESPERBYK-145," "DESPERBYK-2155," and "DESPERBYK-2159." These may be used alone or in combination of two or more.

[0315] The polyaspartic acid coating composition of the present embodiment generally contains 0.1% by mass or more and 15% by mass or less, and preferably 0.3% by mass or more and 8% by mass or less, of a dispersant based on the total mass of the polyaspartic acid coating composition.

[0316] The polyaspartic acid coating composition of this embodiment may further contain, as other ingredients, pigments such as titanium oxide, carbon black, indigo, quinacridone, and pearlescent mica; metal powder pigments such as aluminum; rheology control agents such as hydroxyethyl cellulose, urea compounds, and microgels; surface conditioners; curing accelerators such as tin compounds, zinc compounds, and amine compounds, etc.

[0317] <Method for producing polyaspartic acid coating composition>

[0318] The polyaspartic acid coating composition of this embodiment is obtained by mixing the above-mentioned aspartic acid ester compound with other components as needed to obtain a mixture, then adding the above-mentioned polyisocyanate composition as a curing agent to this mixture, and mixing them using a known method. A solvent may or may not be used. Since the viscosity of the polyaspartic acid coating composition of this embodiment is lower than that of conventional polyaspartic acid coating compositions, it can be manufactured while maintaining workability even in a high-solids formulation.

[0319] <Purpose>

[0320] The polyaspartic acid coating composition of this embodiment is suitable for use as a primer, mid-coat or topcoat on metals such as steel plates and surface-treated steel plates, plastics, inorganic materials such as ceramics, glass, and concrete by roller coating, curtain coating, spray coating, electrostatic coating, bell coating, dipping, roller coating, brush coating, etc.

[0321] The polyaspartic acid coating composition of this embodiment is suitable for imparting aesthetic properties, weather resistance, acid resistance, rust resistance, chipping resistance, and adhesion to pre-coated metals including rust-proof steel sheets, automotive painted parts, and plastic painted parts.

[0322] Furthermore, the polyaspartic acid coating composition of the present embodiment is also useful as an adhesive, a pressure-sensitive adhesive, an elastomer, a foam, a surface treatment agent, and the like.

[0323] Furthermore, the polyaspartic acid coating composition of this embodiment softens the coating film, increases the crosslinking density of the coating film, and exhibits particularly excellent weather resistance. Therefore, the polyaspartic acid coating composition of this embodiment is suitable for heavy-duty corrosion protection coatings on structures exposed to harsh environments such as wind, rain, snow, and temperature fluctuations, such as bridges, highways, transmission towers, and wind turbine generator systems (towers, blades, etc.), which require long-term weather resistance.

[0324] Coating

[0325] The coating film of this embodiment is formed by curing the above-mentioned polyaspartic acid coating composition.

[0326] The coating film of this embodiment is excellent in weather resistance and elongation at low temperatures of approximately -20°C.

[0327] The coating film of this embodiment is obtained by applying the polyaspartic acid coating composition using a known method such as roller coating, curtain coating, spray coating, bell coating, or electrostatic coating, and curing it through a room temperature drying or baking step.

[0328] Example

[0329] Hereinafter, the present embodiment will be described in more detail with reference to Examples, but the present embodiment is not limited to these Examples.

[0330] The following describes various methods for measuring properties and various evaluation methods. It should be noted that, unless otherwise specified, "parts" and "%" refer to "parts by mass" and "mass %."

[0331] <Measurement Methods of Physical Properties>

[0332] [Physical properties 1]

[0333] (NCO content (mass %))

[0334] The NCO content (isocyanate content, mass %) of the polyisocyanate composition is measured as follows. After accurately weighing (Wg) the polyisocyanate composition manufactured in the manufacturing example 1g or more and 3g or less in a conical flask, 20mL of toluene is added to completely dissolve the polyisocyanate composition. Then, 10mL of a toluene solution of 2 equivalents of di-n-butylamine is added, and after complete mixing, it is left at room temperature for 15 minutes. Furthermore, 70mL of isopropyl alcohol is added to the solution and completely mixed. The solution is titrated using an indicator with 1 equivalent hydrochloric acid solution (factor F) to obtain a titration value V2mL. For the same titration operation, the titration value V1mL is obtained without using polyisocyanates. According to the titration value V2mL and titration value V1mL obtained, the NCO content (mass %) of the polyisocyanate is calculated based on the following formula.

[0335] (NCO content (mass %)) = (V1-V2) × F × 42 / (W × 1000) × 100

[0336] [Physical Properties 2]

[0337] (Molar ratio of each functional group)

[0338] The obtained polyisocyanate composition was subjected to a filtration reaction using Biosspin Avance 600 (trade name) manufactured by Bruker Corporation. 13 C-NMR measurement: Specific measurement conditions are as follows.

[0339] (Measurement conditions).

[0340] 13 C-NMR apparatus: AVANCE 600 (manufactured by Bruker).

[0341] Cryogenic probe (manufactured by Bruker).

[0342] CryoProbe (registered trademark).

[0343] CPDUL.

[0344] 600S3-C / HD-05Z.

[0345] Resonant frequency: 150MHz.

[0346] Concentration: 60wt / vol%.

[0347] Shift standard: CDCl3 (77 ppm).

[0348] Cumulative number of times: 10,000 times.

[0349] Pulse program: zgpg30 (proton complete decoupling method, waiting time 2 seconds)

[0350] The molar ratios of isocyanurate groups, uretdione groups, allophanate groups, and carbamate groups were determined by dividing the integral value of the following signal by the number of carbon atoms measured. Next, B / A (molar ratio), C×100 / (A+B+C+D) (molar %), and D×100 / (A+B+C+D) (molar %) were calculated, assuming the number of moles of carbamate groups is A, the number of moles of allophanate groups is B, the number of moles of isocyanurate groups is C, and the number of moles of uretdione groups is D.

[0351] Isocyanurate group: (integrated value around 148.6 ppm) ÷ 3

[0352] Ureatdione group: (integrated value around 157.8 ppm) ÷ 2

[0353] Carbamate group: (integrated value around 156.5 ppm) ÷ 1

[0354] Allophanate group: (integrated value around 154 ppm) ÷ 1

[0355] <Evaluation Method>

[0356] [Evaluation 1]

[0357] (Viscosity of polyisocyanate composition (mPa·s))

[0358] The viscosity of the polyisocyanate composition was measured at 25° C. using an E-type viscometer (trade name: RE-85R, manufactured by Toki Sangyo Co., Ltd.) A standard rotor (1°34′×R24) was used for the measurement. The rotation speed was set as follows.

[0359] (Speed)

[0360] 100 rpm (less than 128 mPa·s)

[0361] 50 rpm (128 mPa·s or higher and less than 256 mPa·s)

[0362] 20 rpm (256 mPa·s or higher and less than 640 mPa·s)

[0363] 10 rpm (640 mPa·s or higher and less than 1280 mPa·s)

[0364] 5r.pm (1280mPa.s or more and less than 2560mPa.s)

[0365] 2.5 rpm (2560 mPa·s or more and less than 5120 mPa·s)

[0366] (Evaluation Criteria)

[0367] A: 1500mPa·s or less

[0368] B: More than 1500mPa·s and less than 2000mPa·s

[0369] C: More than 2000mPa·s and less than 3000mPa·s

[0370] D: more than 3000mPa·s

[0371] [Evaluation 2]

[0372] (Crystallinity of Polyisocyanate Composition)

[0373] The turbidity of the polyisocyanate composition at room temperature (23° C.) was measured as transmittance (%) at 550 nm in UV measurement using JASCO V-650. The measured transmittance was evaluated according to the following criteria.

[0374] (Evaluation Criteria)

[0375] A: Transmittance at 550nm is over 90%

[0376] B: Transmittance at 550nm is 80% or more and less than 90%

[0377] C: Transmittance at 550nm is 70% or more and less than 80%

[0378] D: Transmittance at 550nm is less than 70%

[0379] [Production of polyaspartic acid coating composition]

[0380] The aspartic acid ester compound "Feispartic F420" (manufactured by Feiyang Co., Ltd., amine value 201 mgKOH / g resin) and each polyisocyanate composition were blended to achieve an NCO / NH ratio of 1.1 (molar ratio). The coating solids content was adjusted to 80% by mass with n-butyl acetate to obtain a polyaspartic acid coating composition. For Examples 1-17, the polyaspartic acid coating compositions were prepared by the method described below.

[0381] [Evaluation 3]

[0382] (Appearance of coating film)

[0383] The polyaspartic acid coating composition obtained by the above method was applied to a glass plate using an applicator to a dry film thickness of 40 μm to 60 μm. After application, the composition was cured for 7 days at 23°C and 50% humidity to produce a coating film. The appearance of each coating film was evaluated according to the following criteria.

[0384] (Evaluation Criteria)

[0385] A: The surface is very smooth, with no visible bumps.

[0386] B: The surface is smooth, but small irregularities are slightly observed.

[0387] C: The surface is very uneven and has many wrinkles.

[0388] [Evaluation 4]

[0389] (Weather resistance of coating film)

[0390] The polyaspartic acid coating composition obtained by the above method was applied to a whiteboard using an applicator to a dry film thickness of 40 μm to 60 μm. After application, the coating was cured for 7 days at 23°C and 50% humidity to produce a coating film. The coating film was then evaluated using a dew panel light control weather meter (FDP) manufactured by Suga Test Instruments Co., Ltd. under the conditions of JIS K5600-7-8. The weather resistance of each coating film was evaluated according to the following evaluation criteria.

[0391] (Evaluation Criteria)

[0392] A: After 2500 hours of exposure, the 60-degree gloss retention rate is more than 90%

[0393] B: After 2000 hours of exposure, the 60-degree gloss retention rate is more than 90%

[0394] C: 60-degree gloss retention after 1500 hours of exposure is 80% or more and less than 90%

[0395] D: 60-degree gloss retention after 1500 hours of exposure is less than 80%

[0396] [Rating 5]

[0397] (Low-temperature elongation of coating film)

[0398] The polyaspartic acid coating composition obtained by the above method was applied to a polypropylene (PP) plate using an applicator to a dry film thickness of 40 μm to 60 μm. After application, the coating was cured for 7 days at 23°C and 50% humidity to obtain each coating film. The elongation of the coating film was measured at a temperature of -20°C using a tensile testing machine (ORIENTEC, RTE-1210) and a thermostatic bath (ORIENTEC, TLA-R3T-FW) at a tensile speed of 20 mm / min and a clamping distance of 20 mm. The low-temperature elongation of each coating film was evaluated according to the evaluation criteria shown below.

[0399] (Evaluation Criteria)

[0400] A: Coating elongation is more than 300%

[0401] B: The elongation of the coating film is 200% or more and less than 300%

[0402] C: Coating elongation is 150% or more and less than 200%

[0403] D: Coating elongation is 0% or more and less than 150%

[0404] <Production of Polyisocyanate Composition>

[0405] [Example 1-1]

[0406] (Production of Polyisocyanate Composition PA1-a1)

[0407] The atmosphere in a four-necked flask equipped with a stirrer, thermometer, and condenser was purged with nitrogen. 450 g of HDI, 74 g of Capa 2043 (manufactured by Ingevity; hereinafter sometimes referred to as "PCL1"), and 74 g of Capa 2085 (manufactured by Ingevity; hereinafter sometimes referred to as "PCL2"), a polycaprolactone polyol, were added and a urethanization reaction was carried out at 100°C for 2 hours with stirring. After the temperature was raised to 130°C, 0.11 g of a 2-ethyl-1-hexanol solution containing 20% by mass of zirconyl 2-ethylhexanoate as an allophanation catalyst was added. When the refractive index of the reaction solution rose to 0.00094, 1.0 g of a 2-ethyl-1-hexanol solution containing 10% by mass of pyrophosphoric acid (a solution prepared by diluting "Phosphoric Acid (105%)" manufactured by Taihei Chemical Industry with 2-ethyl-1-hexanol) was added to stop the reaction. After filtering the reaction solution, unreacted HDI was removed using a down-flow thin film distillation apparatus at 150°C (0.2 Torr) for the first time, 150°C (0.2 Torr) for the second time, and 160°C (0.2 Torr) for the third time. The obtained polyisocyanate composition was a liquid with a viscosity of 1,630 mPa·s and an NCO content of 9.4% by mass. The molar ratio of allophanate group / urethane group was 10 / 90. The obtained polyisocyanate composition was designated as PA1-a1.

[0408] [Examples 1-2]

[0409] (Production of Polyisocyanate Composition PA1-a2)

[0410] The interior of a four-necked flask equipped with an agitator, a thermometer, and a condenser was purged with nitrogen, and 450 g of HDI, 74 g of PCL1, and 74 g of PCL2 were added. The mixture was stirred at 100° C. for 2 hours to form a carbamate. After heating to 140° C., the allophanate reaction was carried out for 3 hours. After 3 hours, the temperature was lowered to room temperature to stop the reaction. After filtering the reaction solution, a downward thin film distillation apparatus was used to remove unreacted HDI at 150° C. (0.2 Torr) for the first time, 150° C. (0.2 Torr) for the second time, and 160° C. (0.2 Torr) for the third time. The resulting polyisocyanate composition was a liquid with a molar ratio of allophanate group / carbamate group of 10 / 90. The resulting polyisocyanate composition was referred to as PA1-a2.

[0411] [Examples 1-3]

[0412] (Manufacture of polyisocyanate composition PA1-a3)

[0413] The types and amounts of raw materials are as shown in the table below, and the reaction was stopped when the refractive index of the reaction liquid increased to 0.00032. A polyisocyanate composition PA1-a3 was produced in the same manner as in Example 1-1.

[0414] [Examples 1-4]

[0415] (Production of Polyisocyanate Composition PA1-a4)

[0416] The types and amounts of raw materials are as shown in the table below, and the reaction was stopped when the refractive index of the reaction solution increased to 0.0028. A polyisocyanate composition PA1-a4 was produced in the same manner as in Example 1-1.

[0417] [Examples 1-6 to 1-13, and Examples 1-15 and 1-18]

[0418] (Manufacture of polyisocyanate compositions PA1-a6 to PA1-a13, PA1-a15, and PA1-a17)

[0419] Each polyisocyanate composition was produced by the same method as in Example 1-1 except that the types and blending amounts of the raw materials were as described in the following table.

[0420] [Examples 1-5]

[0421] (Manufacture of polyisocyanate composition PA1-a5)

[0422] A nitrogen atmosphere was created in a four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and dropping funnel. 100 parts by mass of HDI was added, and the temperature inside the reactor was maintained at 60°C while stirring. 0.15 parts by mass of a solution of tetrabutylammonium acetate, an isocyanurate catalyst, diluted to 10% by mass with 2-ethyl-1-hexanol was added to the flask to allow the isocyanurate reaction to proceed. Phosphoric acid was added to terminate the reaction when the NCO content of the reaction solution reached 43.8% by mass. The reaction solution was then held at 90°C for 1 hour. The cooled reaction solution was filtered, and unreacted HDI was removed using a thin-film evaporator. This yielded an isocyanurate-type polyisocyanate with an NCO content of 23.1% by mass and a viscosity of 1350 mPa·s at 25°C.

[0423] The obtained isocyanurate-type polyisocyanate was mixed so that the molar amount of the isocyanurate group in the polyisocyanate composition PA1-a1 obtained in Example 1-1 relative to the total molar amount of the isocyanurate group, uretdione group, allophanate group and urethane group was 22 mol %, thereby obtaining a polyisocyanate composition PA1-a5.

[0424] [Examples 1-14]

[0425] (Manufacture of polyisocyanate composition PA1-a14)

[0426] To the polyisocyanate composition PA1-a6 obtained in Example 1-6, a light stabilizer (hindered amine compound, manufactured by BASF Japan Ltd., trade name "Tinuvin 765") was added so as to provide 1.0 mass % relative to the total mass of the polyisocyanate composition to obtain a polyisocyanate composition PA1-a14.

[0427] [Examples 1-16]

[0428] (Production of Polyisocyanate Composition PA1-a16)

[0429] The atmosphere in a four-necked flask equipped with a stirrer, thermometer, and condenser was purged with nitrogen, and 1200 g of HDI and 93 g of 2-ethyl-1-hexanol were added. A urethanization reaction was carried out at 90°C with stirring for 1 hour. After the temperature was raised to 130°C, 0.42 g of a mineral spirits solution containing 20% by mass of zirconyl 2-ethylhexanoate as an allophanation catalyst was added. After 60 minutes, when the refractive index of the reaction solution had risen to 0.0055, 3.9 g of a 2-ethyl-1-hexanol solution containing 10% by mass of pyrophosphoric acid (a solution prepared by diluting "Phosphoric Acid (105%)" manufactured by Taihei Chemical Industry Co., Ltd. with 2-ethyl-1-hexanol) was added to terminate the reaction. The reaction solution was filtered, and unreacted HDI was removed using a downflow thin-film distillation apparatus at a first pass at 150°C (0.2 Torr) and a second pass at 160°C (0.2 Torr). The obtained allophanate polyisocyanate compound was a transparent liquid with a yield of 330 g, a viscosity of 100 mPa·s, an NCO content of 17.4% by mass, and an allophanate group / isocyanurate group molar ratio of 97 / 3.

[0430] 22 parts by mass of the obtained allophanate polyisocyanate was mixed with 78 parts by mass of the polyisocyanate composition PA1-a15 obtained in Example 1-15 to obtain a polyisocyanate composition PA1-a16.

[0431] [Comparative Example 1-1]

[0432] (Production of Polyisocyanate Composition PA1-b1)

[0433] The interior of a four-necked flask equipped with a stirrer, thermometer, and condenser was purged with nitrogen, and 450 g of HDI, 74 g of PCL1, and 74 g of PCL2 were added. The urethanization reaction was carried out at 100°C for 2 hours under stirring. After filtering the reaction liquid, unreacted HDI was removed using a down-flow thin film distillation apparatus at 150°C (0.2 Torr) for the first time, 150°C (0.2 Torr) for the second time, and 160°C (0.2 Torr) for the third time. The resulting polyisocyanate composition was a liquid with a viscosity of 1,560 mPa·s and an NCO content of 9.1% by mass. The resulting polyisocyanate composition was designated PA1-b1.

[0434] [Comparative Example 1-2]

[0435] (Manufacture of polyisocyanate composition PA1-b2)

[0436] The types and amounts of raw materials are as shown in the table below, and the reaction was stopped when the refractive index of the reaction solution increased to 0.0046. A polyisocyanate composition PA1-b2 was produced in the same manner as in Example 1-1.

[0437] <Manufacturing of Coating Composition>

[0438] [Examples 1-17]

[0439] To the polyisocyanate composition PA1-a15 obtained in Example 1-15, in the above-mentioned method for producing the polyaspartic acid coating composition, molecular sieves (MS) (manufactured by Union Showa Co., Ltd., trade name "3A powder"; hereinafter sometimes referred to as "3A-MS") were added in an amount of 1.7% by mass relative to the total mass of the polyaspartic acid coating composition to obtain a coating composition.

[0440] Various physical properties and evaluation results are shown in the following tables. Note that the abbreviations in the tables refer to the following compounds.

[0441] (Polyol)

[0442] Polyester polyols

[0443] PCL1: Polycaprolactone polyol "Capa2043", manufactured by Ingevity, number average molecular weight Mn 400, average number of hydroxyl groups 2, viscosity at 25°C 246 mPa·s

[0444] PCL2: Polycaprolactone polyol "Capa2085", manufactured by Ingevity, number average molecular weight Mn 830, average number of hydroxyl groups 2, viscosity at 25°C 627 mPa·s

[0445] PCL3: Polycaprolactone polyol "ODX2542C", manufactured by DIC Corporation, number average molecular weight Mn 850, average number of hydroxyl groups 3, viscosity at 25°C 1,270 mPa·s

[0446] PCL4: Polycaprolactone polyol "Capa2054", manufactured by Ingevity, number average molecular weight Mn 550, average number of hydroxyl groups 2, viscosity at 25°C 360 mPa·s

[0447] PCL5: Polycaprolactone polyol "Capa2067A", manufactured by Ingevity, number average molecular weight Mn650, average number of hydroxyl groups 2, viscosity at 25°C 493 mPa·s

[0448] PES: Polyester polyol "Kuraray polyol P-510", manufactured by Kuraray Co., Ltd., number average molecular weight Mn 500, average number of hydroxyl groups 2, viscosity at 25°C 540 mPa·s

[0449] Polyoxyalkylene polyols

[0450] PPG1: "ECOTRION H1000", manufactured by SK chemicals, number average molecular weight Mn 1000, average number of hydroxyl groups 2, viscosity at 25°C 489 mPa·s

[0451] PPG2: "ECOTRION H2000", manufactured by SK chemicals, number average molecular weight Mn 2000, average number of hydroxyl groups 2, viscosity at 25°C 1701 mPa·s

[0452] PPG3: "Velvet H250", manufactured by Allessa, number average molecular weight Mn 227, average number of hydroxyl groups 2, viscosity at 25°C 107 mPa·s

[0453] PTMG: "BioPTMG650", manufactured by Mitsubishi Chemical Corporation, number average molecular weight Mn655, average number of hydroxyl groups 2, viscosity at 25°C 351 mPa·s

[0454] [Table 1-1]

[0455]

[0456] [Table 1-2]

[0457]

[0458] [Table 1-3]

[0459]

[0460] As shown in the table above, polyisocyanate compositions PA1-a1 to PA1-a17 (Examples 1-1 to 1-16, 1-18) meeting all of the aforementioned compositions exhibited viscosities as low as 3000 mPa·s or less, readily mixing with aspartic acid ester compounds even in high-solids formulations. Furthermore, their crystallinity exhibited little turbidity. This suggests that when these polyisocyanate compositions are used as curing agents for polyaspartic acid coating compositions, they can be uniformly mixed, resulting in excellent curability and coating film smoothness. Furthermore, coating films obtained using polyaspartic acid coating compositions incorporating these polyisocyanate compositions exhibited excellent appearance, weather resistance, and low-temperature elongation.

[0461] In addition, in a comparison of polyisocyanate compositions PA1-a1 and PA1-a2 (Examples 1-1 and 1-2), which have different molar ratios of uretdione groups, a tendency was observed that the lower the molar ratio of uretdione groups, the better the low-temperature elongation of the resulting coating film. On the other hand, a tendency was observed that the higher the molar ratio of uretdione groups, the lower the viscosity of the polyisocyanate composition, the better the viscosity.

[0462] Furthermore, in a comparison of polyisocyanate compositions PA1-a1, PA1-a3, and PA1-a4 (Examples 1-1, 1-3, and 1-4), and PA1-a14 and PA1-a16 (Examples 1-14 and 1-16), each having a different molar ratio B / A of allophanate groups to urethane groups, it was observed that the higher the molar ratio B / A, the higher the transparency of the polyisocyanate composition and the more suppressed crystallization. On the other hand, a tendency was observed to improve the weather resistance and low-temperature elongation of the resulting coating film as the molar ratio B / A decreased.

[0463] In addition, in a comparison of polyisocyanate compositions PA1-a1 and PA1-a5 (Examples 1-1 and 1-5) having different molar ratios of isocyanurate groups, a tendency was observed that the lower the molar ratio of isocyanurate groups, the better the low-temperature elongation of the resulting coating film.

[0464] Furthermore, in a comparison of the polyisocyanate compositions PA1-a1, PA1-a6, PA1-a8, PA1-a10 to PA1-a13, and PA1-a15 (Examples 1-1, 1-6, 1-8, 1-10 to 1-13, and 1-15) containing different types of polyols, a tendency was observed for the combined use of two polyester polyols to result in superior weather resistance when the resulting coating film was prepared. A tendency was observed for the combined use of two polyester polyols having an average hydroxyl number of 2 to result in lower viscosity and superior low-temperature elongation when the resulting coating film was prepared.

[0465] In comparison with the polyisocyanate composition PA1-a17 (Examples 1-18) containing only one type of polyol, a tendency was observed to further suppress crystallization by combining two types of polyester polyols.

[0466] In addition, in a comparison of polyisocyanate compositions PA1-a6 and PA1-a7 (Examples 1-6 and 1-7) having different mixing ratios of the polyester polyol and the polyoxyalkylene polyol, a tendency was observed that the weather resistance of the coating film was improved as the mixing ratio of the polyester polyol increased.

[0467] In addition, in a comparison of PA1-a8 and PA1-a9 (Examples 1-8 and 1-9), which have different mixing ratios of a polyester polyol having an average hydroxyl number of 2 and a polyester polyol having an average hydroxyl number of 3, a tendency was observed that the elongation of the coating film when formed was improved as the mixing ratio of the polyester polyol having an average hydroxyl number of 2 increased.

[0468] Furthermore, in a comparison of polyisocyanate compositions PA1-a6 and PA1-a14 (Examples 1-6 and 1-14), which differ in the presence or absence of a UV absorber when forming a polyaspartic acid coating composition, a tendency was observed to show that the addition of a UV absorber resulted in superior weather resistance in the resulting coating film.

[0469] On the other hand, the polyisocyanate composition PA1-b1 (Comparative Example 1-1) having no allophanate group was turbid and had poor crystallinity. In addition, the appearance of the coating film was also poor.

[0470] Furthermore, the polyisocyanate composition PA1-b2 (Comparative Example 1-2), in which the molar ratio of allophanate groups to carbamate groups was 50 / 50 but exceeded 30 / 70, had a high viscosity of 3100 mPa·s, making it difficult to mix with an aspartic acid ester compound to prepare a polyaspartic acid coating composition without using a solvent. Furthermore, the resulting coating film had poor appearance, weather resistance, and low-temperature elongation.

[0471] <Production of Polyisocyanate Composition>

[0472] [Example 2-1]

[0473] (Production of Polyisocyanate Composition PA2-a1)

[0474] The interior of a four-necked flask equipped with a stirrer, thermometer, and condenser was purged with nitrogen. Then, 450 g of HDI, 67 g of Capa 2043 (Ingevity Corporation, sometimes referred to as "PCL1"), a polycaprolactone polyol, 67 g of Capa 2085 (Ingevity Corporation, sometimes referred to as "PCL2"), and 14 g of 2-ethyl-1,3-hexanediol were added. A urethanization reaction was carried out at 100°C for 2 hours with stirring. After the temperature was raised to 130°C, 0.11 g of a 2-ethyl-1-hexanol solution containing 20% by mass of zirconyl 2-ethylhexanoate as an allophanation catalyst was added. When the refractive index of the reaction solution increased to 0.001, 1.0 g of a 2-ethyl-1-hexanol solution containing 10% by mass of pyrophosphoric acid (a solution prepared by diluting "Phosphoric Acid (105%)" manufactured by Taihei Chemical Industry with 2-ethyl-1-hexanol) was added to stop the reaction. After filtering the reaction solution, unreacted HDI was removed using a down-flow thin film distillation apparatus at 150°C (0.2 Torr) for the first time, 150°C (0.2 Torr) for the second time, and 160°C (0.2 Torr) for the third time. The obtained polyisocyanate composition was a liquid with a viscosity of 1,720 mPa.s and an NCO content of 10.5% by mass. The molar ratio of allophanate group / urethane group was 10 / 90. The obtained polyisocyanate composition was designated as PA2-a1.

[0475] [Example 2-2 to Example 2-3, Example 2-9 to Example 2-14 and Example 2-16]

[0476] (Manufacture of polyisocyanate compositions PA2-a2 to PA2-a3, PA2-a9 to PA2-a14, and PA2-a16)

[0477] Each polyisocyanate composition was produced by the same method as in Example 2-1 except that the types and blending amounts of the raw materials were as described in the following table.

[0478] [Examples 2-4]

[0479] (Production of Polyisocyanate Composition PA2-a4)

[0480] The interior of a four-necked flask equipped with a stirrer, thermometer, and condenser was purged with nitrogen, and 450 g of HDI, 67 g of PCL1, 67 g of PCL2, and 14 g of 2-ethyl-1,3-hexanediol were added. The urethanization reaction was carried out at 100°C for 2 hours under stirring. After filtering the reaction liquid, unreacted HDI was removed using a down-flow thin film distillation apparatus at 150°C (0.2 Torr) for the first time, 150°C (0.2 Torr) for the second time, and 160°C (0.2 Torr) for the third time. The resulting polyisocyanate composition was a liquid with a viscosity of 1,590 mPa·s and an NCO content of 10.1% by mass. The resulting polyisocyanate composition was designated PA2-a4.

[0481] [Examples 2-5]

[0482] (Production of Polyisocyanate Composition PA2-a5)

[0483] The types and amounts of raw materials are as shown in the table below, and the reaction was stopped when the refractive index of the reaction liquid increased to 0.00033. A polyisocyanate composition PA2-a5 was produced in the same manner as in Example 2-1.

[0484] [Examples 2-6]

[0485] (Production of Polyisocyanate Composition PA2-a6)

[0486] The types and amounts of raw materials are as shown in the table below, and the reaction was stopped when the refractive index of the reaction solution increased to 0.003. A polyisocyanate composition PA2-a6 was produced in the same manner as in Example 2-1.

[0487] [Example 2-7]

[0488] (Production of Polyisocyanate Composition PA2-a7)

[0489] The interior of a four-necked flask equipped with a stirrer, thermometer, and condenser was purged with nitrogen. 450 g of HDI, 67 g of PCL1, 67 g of PCL2, and 14 g of 2-ethyl-1,3-hexanediol were added and stirred at 100°C for 2 hours to form a urethanate. The temperature was raised to 140°C, and the allophanate reaction was continued for 3 hours. After 3 hours, the temperature was lowered to room temperature to terminate the reaction. The reaction liquid was filtered, and unreacted HDI was removed using a downflow thin-film distillation apparatus at 150°C (0.2 Torr) for the first time, 150°C (0.2 Torr) for the second time, and 160°C (0.2 Torr) for the third time. The resulting polyisocyanate composition was a liquid with a molar ratio of allophanate groups to urethanate groups of 10 / 90. The resulting polyisocyanate composition was designated PA2-a7.

[0490] [Example 2-8]

[0491] (Production of Polyisocyanate Composition PA2-a8)

[0492] A nitrogen atmosphere was created in a four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and dropping funnel. 100 parts by mass of HDI was added, and the temperature inside the reactor was maintained at 60°C while stirring. 0.15 parts by mass of a solution of tetrabutylammonium acetate, an isocyanurate catalyst, diluted to 10% by mass with 2-ethyl-1-hexanol was added to the flask to allow the isocyanurate reaction to proceed. Phosphoric acid was added to terminate the reaction when the NCO content of the reaction solution reached 43.8% by mass. The reaction solution was then held at 90°C for 1 hour. The cooled reaction solution was filtered, and unreacted HDI was removed using a thin-film evaporator. This yielded an isocyanurate-type polyisocyanate with an NCO content of 23.1% by mass and a viscosity of 1350 mPa·s at 25°C.

[0493] The obtained isocyanurate-type polyisocyanate was mixed with the polyisocyanate composition PA2-a1 obtained in Example 2-1 so that the molar amount of the isocyanurate group relative to the total molar amount of the isocyanurate group, uretdione group, allophanate group and urethane group was 22 mol%, thereby obtaining a polyisocyanate composition PA2-a8.

[0494] [Example 2-15]

[0495] (Production of Polyisocyanate Composition PA2-a15)

[0496] To the polyisocyanate composition PA2-a9 obtained in Example 2-9, a light stabilizer (hindered amine compound, manufactured by BASF Japan Ltd., trade name "Tinuvin 765") was added so as to provide 1.0 mass % relative to the total mass of the polyisocyanate composition to obtain a polyisocyanate composition PA2-a15.

[0497] [Example 2-17]

[0498] (Production of Polyisocyanate Composition PA2-a17)

[0499] The atmosphere in a four-necked flask equipped with a stirrer, thermometer, and condenser was purged with nitrogen, and 1200 g of HDI and 93 g of 2-ethyl-1-hexanol were added. A urethanization reaction was carried out at 90°C with stirring for 1 hour. After the temperature was raised to 130°C, 0.42 g of a mineral spirits solution containing 20% by mass of zirconyl 2-ethylhexanoate as an allophanation catalyst was added. After 60 minutes, when the refractive index of the reaction solution had risen to 0.0055, 3.9 g of a 2-ethyl-1-hexanol solution containing 10% by mass of pyrophosphoric acid (a solution prepared by diluting "Phosphoric Acid (105%)" manufactured by Taihei Chemical Industry Co., Ltd. with 2-ethyl-1-hexanol) was added to terminate the reaction. The reaction solution was filtered, and unreacted HDI was removed using a downflow thin-film distillation apparatus at a first temperature of 150°C (0.2 Torr) and a second temperature of 160°C (0.2 Torr). The obtained allophanate polyisocyanate compound was a transparent liquid with a yield of 330 g, a viscosity of 100 mPa·s, an NCO content of 17.4%, and an allophanate group / isocyanurate group molar ratio of 97 / 3.

[0500] 21 parts by mass of the obtained allophanate polyisocyanate was mixed with 79 parts by mass of the polyisocyanate composition PA2-a16 obtained in Example 2-16 to obtain a polyisocyanate composition PA2-a17.

[0501] [Comparative Example 2-1]

[0502] (Production of Polyisocyanate Composition PA2-b1)

[0503] The interior of a four-necked flask equipped with a stirrer, thermometer, and condenser was purged with nitrogen, and 450 g of HDI, 74 g of PCL1, and 74 g of PCL2 were added. The urethanization reaction was carried out at 100°C for 2 hours while stirring. After filtering the reaction liquid, unreacted HDI was removed using a down-flow thin film distillation apparatus at 150°C (0.2 Torr) for the first time, 150°C (0.2 Torr) for the second time, and 160°C (0.2 Torr) for the third time. The resulting polyisocyanate composition was a liquid with a viscosity of 1,560 mPa·s and an NCO content of 9.1% by mass. The resulting polyisocyanate composition was designated PA2-b1.

[0504] <Manufacturing of Coating Composition>

[0505] [Example 2-18]

[0506] To the polyisocyanate composition PA2-a16 obtained in Example 2-16, in the above-mentioned method for producing the polyaspartic acid coating composition, molecular sieves (MS) (manufactured by Union Showa Co., Ltd., trade name "3A powder"; hereinafter sometimes referred to as "3A-MS") were added in an amount of 1.7% by mass relative to the total mass of the polyaspartic acid coating composition to obtain a coating composition.

[0507] Various physical properties and evaluation results are shown in the following tables. Note that the abbreviations in the tables refer to the following compounds.

[0508] (First polyol)

[0509] Polyester polyols

[0510] PCL1: Polycaprolactone polyol "Capa2043", manufactured by Ingevity, number average molecular weight Mn 400, average number of hydroxyl groups 2, viscosity at 25°C 246 mPa·s

[0511] PCL2: Polycaprolactone polyol "Capa2085", manufactured by Ingevity, number average molecular weight Mn 830, average number of hydroxyl groups 2, viscosity at 25°C 627 mPa·s

[0512] PCL3: Polycaprolactone polyol "ODX2542C", manufactured by DIC Corporation, number average molecular weight Mn 850, average number of hydroxyl groups 3, viscosity at 25°C 1,270 mPa·s

[0513] PCL4: Polycaprolactone polyol "Capa2054", manufactured by Ingevity, number average molecular weight Mn 550, average number of hydroxyl groups 2, viscosity at 25°C 360 mPa·s

[0514] PES: Polyester polyol "Kuraray polyol P-510", manufactured by Kuraray Co., Ltd., number average molecular weight Mn 500, average number of hydroxyl groups 2, viscosity at 25°C 540 mPa·s

[0515] Polyoxyalkylene polyols

[0516] PPG1: "ECOTRION H1000", manufactured by SK chemicals, number average molecular weight Mn 1000, average number of hydroxyl groups 2, viscosity at 25°C 489 mPa·s

[0517] PTMG: "BioPTMG650", manufactured by Mitsubishi Chemical Corporation, number average molecular weight Mn655, average number of hydroxyl groups 2, viscosity at 25°C 351 mPa·s

[0518] (Second polyol)

[0519] Diol1: 2-ethyl-1,3-hexanediol

[0520] Diol2: 2,4-diethyl-1,5-pentanediol

[0521] [Table 2-1]

[0522]

[0523] [Table 2-2]

[0524]

[0525] [Table 2-3]

[0526]

[0527] As shown in the table above, polyisocyanate compositions PA2-a1 to PA2-a17 (Examples 2-1 to 2-17) meeting all of the aforementioned compositions exhibited viscosities as low as 3000 mPa·s or less, readily mixing with aspartic acid ester compounds even in high-solids formulations. Furthermore, their crystallinity exhibited little turbidity. This suggests that when these polyisocyanate compositions are used as curing agents for polyaspartic acid coating compositions, they can be uniformly mixed, resulting in excellent curability and coating film smoothness. Furthermore, coating films obtained using polyaspartic acid coating compositions incorporating these polyisocyanate compositions exhibited excellent appearance, weather resistance, and low-temperature elongation.

[0528] In addition, in a comparison of polyisocyanate compositions PA2-a1 and PA2-a3 (Examples 2-1 and 2-3) having different amounts of the second polyol, a tendency was observed that the viscosity became lower and better as the amount of the second polyol was reduced, and the low-temperature elongation when formed into a coating film became more excellent.

[0529] In addition, in a comparison of polyisocyanate compositions PA2-a1 and PA2-a4 to PA2-a6 (Examples 2-1 and 2-4 to 2-6) having different molar ratios B / A of allophanate groups to urethane groups, it was observed that the higher the molar ratio B / A, the higher the transparency of the polyisocyanate composition, and the more suppressed the tendency for crystallization. On the other hand, it was observed that the lower the molar ratio B / A, the better the weather resistance and low-temperature elongation of the resulting coating film.

[0530] In addition, in a comparison of polyisocyanate compositions PA2-a1 and PA2-a7 (Examples 2-1 and 2-7) having different molar ratios of uretdione groups, a tendency was observed that the lower the molar ratio of uretdione groups, the better the low-temperature elongation of the coating film.

[0531] In addition, in a comparison of polyisocyanate compositions PA2-a1 and PA2-a8 (Examples 2-1 and 2-8) having different molar ratios of isocyanurate groups, a tendency was observed that the lower the molar ratio of isocyanurate groups, the better the low-temperature elongation of the resulting coating film.

[0532] Furthermore, in a comparison of the polyisocyanate compositions PA2-a1, PA2-a9, PA2-a11, PA2-a13 to PA2-a14, and PA2-a16 (Examples 2-1, 2-9, 2-11, 2-13 to 2-14, and 2-16), which differ in the types of polyols used in the composition, it was observed that the combination of two polyester polyols tended to result in superior weather resistance when the resulting coating film was prepared. The combination of two polyester polyols having an average hydroxyl number of 2 also tended to result in lower viscosity and superior low-temperature elongation when the resulting coating film was prepared.

[0533] In addition, a comparison of polyisocyanate compositions PA2-a9 and PA2-a10 (Examples 2-9 and 2-10), which have different mixing ratios of polyester polyol and polyoxyalkylene polyol, shows that increasing the mixing ratio of polyester polyol leads to better weather resistance of the resulting coating film. On the other hand, increasing the mixing ratio of polyoxyalkylene polyol tends to further suppress crystallization.

[0534] In addition, when the polyaspartic acid coating composition was prepared, a comparison was made between the polyisocyanate compositions PA2-a9 and PA2-a15 (Examples 2-9 and 2-15) that differed in the presence or absence of a UV absorber. It was observed that the addition of the UV absorber resulted in a tendency for the coated film to have better weather resistance.

[0535] On the other hand, the polyisocyanate composition PA2-b1 (Comparative Example 2-1) not containing the second polyol was turbid and had poor crystallinity. In addition, the appearance of the coating film was also poor.

[0536] Industrial Application Possibilities

[0537] The polyisocyanate composition of this embodiment provides a polyisocyanate composition having good viscosity, inhibited crystallization, and excellent appearance, weather resistance, and elongation at -20°C when formed into a coating film. The polyaspartic acid coating composition of this embodiment comprises the polyisocyanate composition and, when formed into a coating film, has excellent appearance, weather resistance, and elongation at -20°C. The coating film of this embodiment is formed by curing the polyaspartic acid coating composition and has excellent appearance, weather resistance, and elongation at -20°C.

Claims

1. A polyisocyanate composition comprising a polyisocyanate derived from a diisocyanate and a polyol, The diisocyanate is at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, The polyol is at least one selected from the group consisting of polyester polyol and polyoxyalkylene polyol, The polyol has a number average molecular weight of 200 or more and 2000 or less and an average number of hydroxyl groups of 2 or 3, The polyisocyanate contains a carbamate group and an allophanate group in one molecule. The polyisocyanate composition has a molar ratio of allophanate groups to urethane groups of 2 / 98 or more and 30 / 70 or less.

2. The polyisocyanate composition according to claim 1, wherein The ratio of the molar amount of the uretdione group to the total molar amount of the isocyanurate group, the uretdione group, the allophanate group, and the urethane group is 0.3 mol% or more and 20 mol% or less.

3. The polyisocyanate composition according to claim 1, wherein The ratio of the molar amount of the isocyanurate group to the total molar amount of the isocyanurate group, the uretdione group, the allophanate group, and the urethane group is 0.01 mol% or more and 20.00 mol% or less.

4. The polyisocyanate composition according to claim 1, wherein The polyol includes two types of the polyester polyols having structures different from each other, or includes the polyester polyol and the polyoxyalkylene polyol.

5. The polyisocyanate composition according to claim 1, wherein The content of the polyoxyalkylene polyol is 30% by mass or less relative to the total mass of the polyol.

6. The polyisocyanate composition according to claim 1, wherein The content of the polyol having an average number of hydroxyl groups of 3 is 30% by mass or less based on the total mass of the polyol. The polyisocyanate composition according to claim 1 , which is a curing agent for polyaspartic acid coatings. 8 . A polyaspartic acid coating composition comprising the polyisocyanate composition according to claim 1 and an aspartic acid ester compound.

9. A coating film formed by curing the polyaspartic acid coating composition according to claim 8.

10. A polyisocyanate composition comprising a polyisocyanate derived from a diisocyanate, a first polyol and a second polyol, The diisocyanate is at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, The first polyol has a number average molecular weight of 200 or more and 2000 or less, an average number of hydroxyl groups of 2 or 3, and is at least one selected from the group consisting of polyester polyols and polyoxyalkylene polyols. The second polyol is a branched monohydric alcohol having 2 to 20 carbon atoms, a branched dihydric alcohol having 2 to 20 carbon atoms, or a branched trihydric alcohol having 2 to 20 carbon atoms. The molar ratio of the allophanate group to the urethane group in the polyisocyanate composition is 0 / 100 or more and 30 / 70 or less.

11. The polyisocyanate composition according to claim 10, wherein The content of the second polyol is 1% by mass or more and 30% by mass or less relative to the total mass of the first polyol and the second polyol.

12. The polyisocyanate composition according to claim 10, wherein The second polyol is a branched diol having 3 to 20 carbon atoms.

13. The polyisocyanate composition according to claim 10, wherein The molar ratio of the allophanate group to the urethane group is 2 / 98 or more and 30 / 70 or less.

14. The polyisocyanate composition according to claim 10, wherein The ratio of the molar amount of the uretdione group to the total molar amount of the isocyanurate group, the uretdione group, the allophanate group, and the urethane group is 0.3 mol% or more and 20 mol% or less.

15. The polyisocyanate composition according to claim 10, wherein The ratio of the molar amount of the isocyanurate group to the total molar amount of the isocyanurate group, the uretdione group, the allophanate group, and the urethane group is 0.01 mol% or more and 20.00 mol% or less.

16. The polyisocyanate composition according to claim 10, wherein The first polyol includes two types of the polyester polyols having structures different from each other, or includes the polyester polyol and the polyoxyalkylene polyol.

17. The polyisocyanate composition according to claim 10, wherein The content of the polyoxyalkylene polyol is 30% by mass or less relative to the total mass of the first polyol and the second polyol.

18. The polyisocyanate composition according to claim 10, wherein The content of the polyol having an average number of hydroxyl groups of 3 is 30% by mass or less relative to the total mass of the first polyol and the second polyol. The polyisocyanate composition according to claim 10 , which is a curing agent for polyaspartic acid coatings.

20. A polyaspartic acid coating composition comprising the polyisocyanate composition according to any one of claims 10 to 19 and an aspartic acid ester compound.

21. A coating film formed by curing the polyaspartic acid coating composition according to claim 20.

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