Modified polyisocyanate composition and paint composition using the same

Abstract

To provide: a polyisocyanate composition with which there can be obtained a cured coating film having not only excellent substrate followability and adhesion but also excellent scratch resistance; and a coating composition using the same as a curing agent.SOLUTION: A polyisocyanate composition comprises: a nurate-type polyisocyanate (A) of HDI; and a polyallophanate derived from HDI and a diol having a cyclic group, where a molar ratio of (A) and (B) in the polyisocyanate composition, (A) / (B), is 90 / 10-0 / 100.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a modified polyisocyanate composition. [Background technology]

[0002] Traditionally, non-yellowing polyisocyanates derived from aliphatic isocyanates such as hexamethylene diisoanate (hereinafter also called HDI) and alicyclic isocyanates such as isophorone diisocyanate (hereinafter also called IPDI) have been used as curing agents for paints and adhesives due to their excellent weather resistance. Among these, polyisocyanate types containing isocyanurate bonds have high chemical and thermal stability, and are particularly excellent in weather resistance, heat resistance, and durability, and are therefore widely used depending on the application.

[0003] On the other hand, when used in paints and the like, the strength of the resulting coating film is also required, so polyisocyanurates derived from IPDI have been particularly used (for example, Patent Document 1).

[0004] However, as coatings become stronger, their ability to conform to the substrate, a property that is inversely related to high strength, tends to be compromised, and there is also a need to improve the coating's resistance to scratches. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2002-293873 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The present invention has been made in view of the above-described background art, and aims to provide a polyisocyanate composition that can produce a cured coating film that is excellent not only in substrate conformability and adhesion but also in scratch resistance, and a paint composition using the same as a curing agent. [Means for solving the problem]

[0007] As a result of extensive research, the inventors of the present invention have found that the above problems can be solved by using a polyisocyanate composition containing a nurate-type polyisocyanate of HDI and an allophanate-type polyisocyanate of HDI and a diol having a cyclic group in specific component ratios, and in which the average number of functional groups is within a specific numerical range, and have arrived at the present invention.

[0008] In other words, the present invention includes the following embodiments.

[0009] [1] A polyisocyanate composition comprising a nurate-type polyisocyanate of HDI (A) and a polyallophanate (B) which is a reaction product of HDI and a diol having a cyclic group, characterized in that the molar ratio of (A) to (B) in the polyisocyanate composition is (A) / (B) = 90 / 10 to 0 / 100.

[0010] [2] The polyisocyanate composition according to [1] above, characterized in that the diol having a cyclic group has one or more cyclic structures, the cyclic structures are alicyclic or heterocyclic, and the hydroxyl group is a primary hydroxyl group or a secondary hydroxyl group.

[0011] [3] The polyisocyanate composition according to [1] or [2] above, characterized in that the diol having a cyclic group has one or more cyclic structures, and the cyclic structures are five-membered rings or six-membered rings.

[0012] [4] A polyurethane resin composition comprising the polyisocyanate composition described in any of [1] to [3] above and a polyol.

[0013] [5] A paint composition comprising the polyurethane resin composition described in [4] above.

[0014] [6] A coating film formed from the coating composition described in [5] above. [Effects of the Invention]

[0015] The present invention provides a polyisocyanate composition that exhibits excellent coating film performance, such as hardness of the cured coating film, substrate conformability, and scratch resistance, as well as a paint composition using this as a curing agent. [Modes for carrying out the invention]

[0016] The polyisocyanate composition of the present invention comprises a nurate-type polyisocyanate of HDI (A) and a polyallophanate (B) which is a reaction product of HDI and a diol having a cyclic group.

[0017] The HDI used in the polyisocyanate composition of the present invention is a type of aliphatic diisocyanate monomer (hereinafter also simply referred to as aliphatic diisocyanate), and is a diisocyanate compound that does not contain a benzene ring in its structure. Examples of aliphatic diisocyanates other than HDI include tetramethylene diisocyanate, pentamethylene diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate, lysine diisocyanate, trioxyethylene diisocyanate, etc. HDI may be used alone or in combination with other aliphatic diisocyanates, or in combination with alicyclic diisocyanates such as isophorone diisocyanate and norbornene diisocyanate.

[0018] In the present invention, the nurate-type polyisocyanate (A) of HDI (hereinafter also referred to as component (A) or (A)) is obtained by cyclopolymerization of three HDI monomer molecules. This nurate-type polyisocyanate may also be a polyisocyanate having pentamerized or macromerized isocyanurate groups.

[0019] Next, the polyaliphatic acid ester (B) which is the reaction product of HDI and a diol having a cyclic group in the present invention (hereinafter also referred to as component (B) or (B)) is a polyaliphatic acid ester in which an HDI monomer has been further added to a urethane compound obtained by reacting an HDI monomer and a diol having a cyclic group.

[0020] (B) The diol having a cyclic group is preferably a diol having a cyclic group such as an aromatic ring, an alicyclic ring, or a heterocyclic ring in the molecule. Examples of such diols having a cyclic group include bis(β-hydroxyethyl)benzene, naphthalenedimethanol, cyclohexanediol, hydrogenated bisphenol A, cyclohexanedimethanol, isosorbide, 2,4-dihydroxypyridine, 2,5-dihydroxy-1,4-dithiane, and the like. Among them, alicyclic groups are preferred from the viewpoint of weather resistance, and hydrogenated bisphenol A, cyclohexanedimethanol, isosorbide, and spiroglycol are particularly preferred, and hydrogenated bisphenol A is particularly preferred.

[0021] The molar ratio of component (A) and component (B) in the polyisocyanate composition in the present invention is (A) / (B)=90 / 10 to 0 / 100, preferably 85 / 15 to 30 / 70, and more preferably 80 / 20 to 50 / 50. When the amount of component (B) is less than the lower limit, the scratch resistance may decrease. The polyisocyanate composition containing component (A) and component (B) can be obtained by a production method in which component (A) and component (B) are generated simultaneously, or a production method in which component (A) and component (B) are each produced and then mixed so as to have a predetermined molar ratio.

[0022] By setting the molar ratio of component (A) and component (B) in the polyisocyanate composition as described above, a coating film having high strength, high substrate followability, and high scratch resistance can be obtained.

[0023] Furthermore, the polyisocyanate composition in the present invention may contain a polyisocyanate having an allophanate group derived from HDI and monool in an amount of 25 mol% or less. Including the aforementioned polyisocyanate can lower the viscosity of the polyisocyanate composition, improving workability during coating. However, if the content exceeds 25 mol% of the polyisocyanate composition, the hardness of the coating film may be insufficient.

[0024] Examples of monoalloyls that can be used to obtain the polyisocyanate include methanol, ethanol, propanol, n-butanol, isobutanol, n-pentanol, 2-pentanol, n-hexanol, 2-hexanol, n-heptanol, n-octanol, 2-ethylhexanol, 3,3,5-trimethyl-1-hexanol, n-tridecanol, 2-tridecanol, 2-octyldodecanol, pentadecanol, palmityl alcohol, stearyl alcohol, cyclopentanol, cyclohexanol, methylcyclohexanol, trimethylcyclohexanol, and cyclohexanemethanol. Among these, 2-ethylhexanol, methanol, and cyclohexanemethanol are preferred.

[0025] Next, a specific method for producing the polyisocyanate composition of the present invention will be described.

[0026] In the first step, HDI and a diol are charged in an amount that results in an excess of isocyanate groups relative to hydroxyl groups, and an isocyanate-terminated prepolymer I is produced by urethane reaction at 20-120°C, either in the presence or absence of an organic solvent. Here, the completion of the urethane reaction is determined by the isocyanate group content and the rise in refractive index, which are measured by neutralization titration.

[0027] In the second step, an isocyanurate and allophanate catalyst is charged into isocyanate-terminated prepolymer I, and isocyanurate and allophanate are carried out at 50-150°C, either in the presence or absence of an organic solvent, until the desired isocyanate group content and molecular weight are achieved, thereby producing isocyanate-terminated prepolymer II.

[0028] In the third step, the reaction is stopped by adding a reaction termination agent to isocyanate-terminated prepolymer II to obtain isocyanate-terminated prepolymer III.

[0029] These first to third steps are carried out under the conditions of nitrogen gas or a stream of dry air.

[0030] In the fourth step, isocyanate-terminated prepolymer III is removed by thin-film distillation or solvent extraction until the free HDI content is less than 1% by mass.

[0031] In the second step, the isocyanurate-allophanate catalyst can be a quaternary ammonium salt or a metal carboxylate salt. In this invention, the isocyanurate-allophanate catalyst is a catalyst that has both isocyanurate and allophanate functions.

[0032] Examples of quaternary ammonium salts include 2-hydroxypropyltrimethylammonium octylate (DABCO TMR, manufactured by Sankyo Air Products Co., Ltd.), tetramethylammonium acetate, tetrabutyltylammonium acetate, tetramethylammonium carbonate, methyltriethylammonium carbonate, ethyltrimethylammonium carbonate, propyltrimethylammonium carbonate, butyltrimethylammonium carbonate, pentyltrimethylammonium carbonate, hexyltrimethylammonium carbonate, heptyltrimethylammonium carbonate, octyltrimethylammonium carbonate, nonyltrimethylammonium carbonate, decyltrimethylammonium carbonate, decyltrimethylammonium carbonate, undecyltrimethylammonium carbonate, dodecyltrimethylammonium carbonate, and tridecyltrimethylammonium carbonate. Examples include salts, tetradecyltrimethylammonium carbonate, heptadecyltrimethylammonium carbonate, hexadecyltrimethylammonium carbonate, octadecyltrimethylammonium carbonate, (2-hydroxypropyl)trimethylammonium carbonate, hydroxyethyltrimethylammonium carbonate, 1-methyl-1-azania-4-methylpiperidinium carbonate, trimethyloctylammonium acetate, trimethyldodecylammonium acetate, trimethyloctylammonium formate, trimethyldodecylammonium formate, N-(2-hydroxypropyl)-N,N,N-trimethylammonium octanoate, and N-(2-hydroxypropyl)-N,N,N-trimethylammonium formate. Examples of carboxylic acid metal salts include zinc salts, tin salts, and zirconium salts of carboxylic acids such as acetic acid, propionic acid, valeric acid, butyric acid, undecylic acid, capric acid, octic acid, and myristyl acid, which can be used alone or in combination of two or more.

[0033] The reaction stopper in the third step is an agent that deactivates the catalyst. Specifically, known compounds such as inorganic acids like phosphoric acid and hydrochloric acid, organic acids having sulfonic acid groups, sulfamic acid groups, etc., and their esters and acyl halides can be used. These reaction stoppers can be used alone or in combination of two or more. It is preferable to add them as soon as possible after the reaction is complete.

[0034] Furthermore, the amount of reaction stopper added varies depending on the type of reaction stopper and catalyst used, but it is preferably 0.5 to 10 equivalents of the catalyst, and more preferably 0.8 to 5.0 equivalents. If the amount of reaction stopper is too small, the storage stability of the resulting polyisocyanate composition is likely to decrease, and if it is too large, the polyisocyanate composition may become discolored.

[0035] In the first step, the "amount of excess isocyanate groups" refers to the amount of isocyanate groups in the organic diisocyanate and hydroxyl groups in the diol that is preferably charged so that the molar ratio R = isocyanate groups / hydroxyl groups is 3 to 200, and more preferably so that R = 5 to 100. If it is below the lower limit, the molecular weight of the reaction product will be high, which may lead to high viscosity and gelation. If it exceeds the upper limit, the product yield will decrease, which may lead to a decrease in productivity and may result in insufficient coating strength.

[0036] Furthermore, the reaction temperature for the urethane formation reaction of the present invention is preferably 20 to 150°C, and more preferably 60 to 130°C. In addition, known urethane formation catalysts can be used during the urethane formation reaction.

[0037] The reaction time for the urethane formation reaction varies depending on the presence and type of catalyst and the temperature, but generally, 10 hours or less, preferably 1 to 5 hours, is sufficient.

[0038] In steps 1 to 3, methods for carrying out the reaction without organic solvents or in the presence of organic solvents are appropriately selected.

[0039] When carrying out a reaction in the presence of an organic solvent, it is preferable to use an organic solvent that does not affect the reaction. Examples of organic solvents include aliphatic hydrocarbons such as octane, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, ketones such as methyl isobutyl ketone and cyclohexanone, esters such as butyl acetate and isobutyl acetate, glycol ether esters such as ethylene glycol ethyl ether acetate, propylene glycol monomethyl ether acetate, 3-methyl-3-methoxybutyl acetate and ethyl-3-ethoxypropionate, ethers such as dioxane, halogenated hydrocarbons such as methylene iodide and monochlorobenzene, and polar aproton solvents such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide and hexamethylphosphonylamide. These solvents can be used alone or in combination of two or more.

[0040] The organic solvent used in the reaction is removed simultaneously during the removal of free HDI in the fourth step.

[0041] The fourth step is a purification step, and it is preferable to reduce the residual content of free, unreacted HDI present in the reaction mixture to 1% by mass or less by methods such as thin-film distillation or extraction with an organic solvent under a high vacuum of 10-100 Pa at 120-150°C. If the residual content of HDI exceeds the upper limit, it may lead to the generation of odor and a decrease in storage stability.

[0042] The purified polyisocyanate composition can also be blocked using a known blocking agent for the purpose of extending pot life and creating a one-liquefaction paint composition. This allows the blocked polyisocyanate, which is inert at room temperature, to be reactivated by heating, causing the blocking agent to dissociate and the isocyanate groups to reactivate, thereby adding potential functionality that allows it to react with active hydrogen groups.

[0043] Blocking agents that can be used in the present invention are compounds having one active hydrogen atom in their molecule, and examples include alcohol-based, alkylphenol-based, phenol-based, active methylene, mercaptan-based, acid amide-based, acid imide-based, imidazole-based, urea-based, oxime-based, amine-based, imide-based, and pyrazole-based compounds.

[0044] The polyisocyanate composition obtained from a series of reactions can be combined with a polyol to obtain the polyurethane resin composition of the present invention.

[0045] Herein, the polyol used in the polyurethane resin composition of the present invention is not particularly limited, and is a compound containing an active hydrogen group as a reactant with an isocyanate group. Polyester polyols, polyether polyols, polycarbonate polyols, polyolefin polyols, acrylic polyols, silicone polyols, castor oil-based polyols, fluorine-based polyols, transesterified products of two or more polyols, and hydroxyl-terminated prepolymers obtained by urethane reaction with polyisocyanate are preferably used, and these can be used individually or as a mixture of two or more.

[0046] <Polyester Polyol> Examples of polyester polyols include one or more dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, succinic acid, tartaric acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, glutaconic acid, azelaic acid, sebacic acid, 1,4-cyclohexyldicarboxylic acid, α-hydromuconic acid, β-hydromuconic acid, α-butyl-α-ethylglutaric acid, α,β-diethylsuccinic acid, maleic acid, fumaric acid, or their anhydrides, and ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentane. Examples include those obtained by condensation polymerization reactions with one or more low molecular weight polyols with a molecular weight of 500 or less, such as diols, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, dimer acid diols, ethylene oxide or propylene oxide adducts of bisphenol A, bis(β-hydroxyethyl)benzene, xylylene glycol, glycerin, trimethylolpropane, and pentaerythritol. Also, examples include lactone-based polyester polyols obtained by ring-opening polymerization of cyclic ester (so-called lactone) monomers such as ε-caprolactone, alkyl-substituted ε-caprolactone, δ-valerolactone, and alkyl-substituted δ-valerolactone. Furthermore, polyester-amide polyols obtained by replacing some of the low molecular weight polyols with low molecular weight polyamines or low molecular weight amino alcohols such as hexamethylenediamine, isophoronediamine, and monoethanolamine can also be used.

[0047] <Polyether polyol> Examples of polyether polyols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, dimer acid diol, bisphenol A, bis(β-hydroxyethyl)benzene, xylylene glycol, glycerin, trimethylolpropane, and pentaerythritol. Examples of polyether polyols include those obtained by addition polymerization of alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide, using a compound having two or more, preferably two to three, active hydrogen groups, such as low molecular weight polyols like 1400, or low molecular weight polyamines such as ethylenediamine, propylenediamine, toluenediamine, metaphenylenediamine, diphenylmethanediamine, and xylylenediamine, as an initiator, or polyether polyols obtained by ring-opening polymerization of alkyl glycidyl ethers such as methyl glycidyl ether, aryl glycidyl ethers such as phenyl glycidyl ether, and cyclic ether monomers such as tetrahydrofuran.

[0048] <Polycarbonate polyol> Examples of polycarbonate polyols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, dimer acid diols, and ethylene oxide and propylene oxide of bisphenol A. Examples include those obtained from de-alcoholization or de-phenolization reactions of one or more low-molecular-weight polyols such as adducts, bis(β-hydroxyethyl)benzene, xylylene glycol, glycerin, trimethylolpropane, and pentaerythritol with dialkyl carbonates such as dimethyl carbonate and diethyl carbonate, alkylene carbonates such as ethylene carbonate and propylene carbonate, and diaryl carbonates such as diphenyl carbonate, dinaphthyl carbonate, diantryl carbonate, diphenanthryl carbonate, diindanyl carbonate, and tetrahydronaphthyl carbonate.

[0049] Furthermore, polyols obtained by transesterification reactions of polycarbonate polyols, polyester polyols, and low molecular weight polyols can also be suitably used.

[0050] <Polyolefin polyol> Examples of polyolefin polyols include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, and hydrogenated polyisoprene.

[0051] <Acrylic polyol> Examples of acrylic polyols include those obtained by copolymerizing acrylic monomers with an acrylic acid ester and / or methacrylic acid ester (hereinafter referred to as (meth)acrylic acid ester), a hydroxy acrylate compound and / or hydroxy methacrylic acid compound (hereinafter referred to as (meth)acrylic acid hydroxy compound) having at least one hydroxyl group in the molecule that can act as a reaction site, and a polymerization initiator, using thermal energy, ultraviolet light, electron beams, or other light energy.

[0052] <(meth)acrylic acid ester> Examples of (meth)acrylic acid esters include alkyl esters having 1 to 20 carbon atoms. Examples of such (meth)acrylic acid esters include alkyl (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, and dodecyl (meth)acrylate; esters of (meth)acrylic acid with alicyclic alcohols such as cyclohexyl (meth)acrylate; and aryl (meth)acrylic acid esters such as phenyl (meth)acrylate and benzyl (meth)acrylate. Such (meth)acrylic acid esters may be used alone or in combination of two or more types.

[0053] <(meth)acrylate hydroxy compound> Examples of (meth)acrylate hydroxy compounds include those having at least one hydroxyl group in the molecule that can act as a reaction site with polyisocyanate, specifically hydroxy acrylate compounds such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 3-hydroxy-2,2-dimethylpropyl acrylate, and pentaerythritol triacrylate. Other examples include methacrylate hydroxy compounds such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 3-hydroxy-2,2-dimethylpropyl methacrylate, and pentaerythritol trimethacrylate. These (meth)acrylate hydroxy compounds may be used individually or in combination of two or more.

[0054] <Silicone polyol> Examples of silicone polyols include vinyl group-containing silicone compounds obtained by polymerizing γ-methacryloxypropyltrimethoxysilane, and polysiloxanes such as α,ω-dihydroxypolydimethylsiloxane and α,ω-dihydroxypolydiphenylsiloxane, which have at least one terminal hydroxyl group in their molecules.

[0055] <Castor oil-based polyols> Examples of castor oil-based polyols include linear or branched polyester polyols obtained by the reaction of castor oil fatty acids with polyols. Dehydrated castor oil, partially dehydrated castor oil, and hydrogenated castor oil can also be used.

[0056] <Fluorine-based polyols> Examples of fluorinated polyols include linear or branched polyols obtained by copolymerization of a fluorine-containing monomer and a monomer having a hydroxyl group as essential components. Here, the fluorine-containing monomer is preferably a fluoroolefin, such as tetrafluoroethylene, chlorotrifluoroethylene, trichlorofluoroethylene, hexafluoropropylene, vinylidene fluoride, vinyl fluoride, and trifluoromethyltrifluoroethylene. Examples of monomers having a hydroxyl group include hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and cyclohexanediol monovinyl ether, hydroxyalkyl allyl ethers such as 2-hydroxyethyl allyl ether, and hydroxyl group-containing vinyl carboxylates or allyl esters.

[0057] Furthermore, the polyol preferably has an active hydrogen group count (average number of functional groups) of 1.9 to 6.0 per molecule. If the number of active hydrogen groups is below the lower limit, the properties of the coating film may deteriorate. If it exceeds the upper limit, the adhesion of the coating film may deteriorate.

[0058] Furthermore, the number-average molecular weight of the polyol is preferably in the range of 250 to 50,000. If it is below the lower limit, there is a risk of reduced adhesion, and if it exceeds the upper limit, there is a risk of reduced solubility in low-polarity organic solvents and reduced adhesion.

[0059] Furthermore, the polyurethane resin composition of the present invention can be suitably used as a paint composition. The ratio of the polyisocyanate composition to the polyol in the paint composition is not particularly limited, but it is preferable to blend them so that the molar ratio of isocyanate groups in the isocyanate composition to hydroxyl groups in the polyol is 0.5 to 2.5, where R = isocyanate groups / hydroxyl groups. If the ratio is below the lower limit, there will be an excess of hydroxyl groups, which may lead to a decrease in adhesion. In addition, the crosslinking density may decrease, which may lead to a decrease in durability and a decrease in the mechanical strength of the coating film. If the ratio is above the upper limit, there will be an excess of isocyanate groups, which may react with moisture in the air, potentially causing blistering of the coating film and a resulting decrease in adhesion.

[0060] Furthermore, the organic solvent used as a diluent can be appropriately selected and used according to the purpose and application from the group consisting of, for example, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; esters such as ethyl acetate, butyl acetate, and cellosolve acetate; alcohols such as butanol and isopropyl alcohol; and hydrocarbons such as toluene, xylene, cyclohexane, mineral spirits, and naphtha. These solvents may be used alone or in combination of two or more.

[0061] Furthermore, the paint composition may utilize any known urethane catalyst, taking into consideration pot life, curing conditions, and working conditions. Specifically, organometallic compounds such as dibutyltin diacetate, dibutyltin dilaurate, and dioctyltin dilaurate, or organic amines such as triethylenediamine and triethylamine, or their salts may be selected and used. These catalysts can be used individually or in combination of two or more.

[0062] Furthermore, while there are no particular limitations on the curing conditions for the paint composition, it is preferable that the curing temperature is -5 to 120°C, the humidity is 10 to 95% RH, and the curing time is 0.5 to 168 hours.

[0063] The coating composition obtained according to the present invention may optionally contain additives such as antioxidants (e.g., 2,6-di-tert-butyl-4-methylphenol), ultraviolet absorbers, pigments, dyes, solvents, flame retardants, hydrolysis inhibitors, lubricants, plasticizers, fillers, antistatic agents, dispersants, catalysts, storage stabilizers, surfactants, and leveling agents.

[0064] Furthermore, the paint composition obtained by the present invention is applied to the surface of an object by known methods such as spraying, brushing, dipping, or coating to form a paint film.

[0065] The adherend is not particularly limited, and adherends can be molded from materials such as stainless steel, phosphated steel, zinc-plated steel, iron, copper, aluminum, brass, glass, slate, acrylic resin, polycarbonate resin, polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene phthalate resin, polystyrene resin, AS resin, ABS resin, polycarbonate-ABS resin, 6-nylon resin, 6,6-nylon resin, MXD6 nylon resin, polyvinyl chloride resin, polyvinyl alcohol resin, polyurethane resin, phenolic resin, melamine resin, polyacetal resin, chlorinated polyolefin resin, polyolefin resin, polyamide resin, polyetheretherketone resin, polyphenylene sulfide resin, NBR resin, chloroprene resin, SBR resin, SEBS resin, etc., olefin resins such as polyethylene and polypropylene that have undergone corona discharge treatment or other surface treatments, or adherends on which a coating layer that can serve as an intermediate layer has been formed on the surface of the adherend.

[0066] The thickness of the coating film formed on the surface of the substrate should be at least 10 μm, as this provides excellent recoating properties and durability. If the film thickness is less than 10 μm, durability will decrease, and the coating may tear due to impact. [Examples]

[0067] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In the examples, the % notation is based on mass unless otherwise specified.

[0068] <Synthesis of Polyisocyanate Composition> <Example 1> Into a 1-liter four-necked flask equipped with a stirrer, thermometer, cooling tube, and nitrogen gas inlet tube, 960 g of HDI and 40 g of hydrogenated bisphenol A (hereinafter referred to as HBPA) were charged, and this was heated to 60°C. After HBPA was dissolved, 0.2 g of octyltrimethylammonium methyl carbonate (10% diluted with 2-ethylhexanol), which is an isocyanuration-allophanatization catalyst, was added, and the reaction was carried out at 60°C until a predetermined reaction conversion rate was reached. Then, 0.2 g of JP-508, which is a reaction terminator, was added, and a termination reaction was carried out at 60°C for 1 hour. Excess HDI was removed by thin-film distillation (conditions: 140°C, 0.04 kPa), and 300 g of polyisocyanate composition P-1 was obtained.

[0069] The NCO content of P-1 was 20.0%, and the viscosity at 25°C was about 7,600 mPa·s. P-1 was 1 Measured by 1H-NMR, the molar ratio of isocyanurate groups to allophanate groups was 50 / 50.

[0070] <NMR: Measurement of Isocyanurate Group, Urethane Group, and Allophanate Group Contents> (1) Measuring device: ECX400M (manufactured by JEOL Ltd., 1 1H-NMR) (2) Measuring temperature: 23°C (3) Sample concentration: 0.1 g / 1 ml (4) Number of integrations: 16 (5) Relaxation time: 5 seconds (6) Solvent: Deuterated dimethyl sulfoxide (7) Chemical shift standard: Hydrogen atom signal of methyl group in deuterated dimethyl sulfoxide (2.5 ppm) (8) Evaluation method: The content of bonding groups was measured from the integral values ​​of the signals of the hydrogen atom of the methylene group adjacent to the nitrogen atom of the nurate group at around 3.7 ppm, the hydrogen atom bonded to the nitrogen atom of the urethane group at around 7.0 ppm, and the hydrogen atom bonded to the nitrogen atom of the allophanate group at around 8.5 ppm.

[0071] <Examples 2, 3, 5, 8, 9> Polyisocyanate compositions P-2, P-3, P-5, P-8, and P-9 were obtained using the same method as in Example 1, with the preparation ratios shown in Table 1.

[0072] <Example 4> In a 1-liter four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube, 945 g of HDI and 55 g of HBPA were charged and heated to 60°C. After the HBPA dissolved, 0.2 g of zirconium octoate, an allophanate catalyst, was added and the mixture was reacted at 60°C until the desired reaction conversion rate was reached. Then, 0.2 g of JP-508, a reaction stopper, was added and the reaction was stopped at 60°C for 1 hour. Excess HDI was removed by thin-film distillation (conditions: 140°C, 0.04 kPa) to obtain 300 g of polyisocyanate composition P-4.

[0073] The NCO content of P-4 was 17.4%, and its viscosity at 25°C was approximately 36,000 mPa·s. 1 ¹H-NMR measurements revealed that the molar ratio of isocyanurate groups to allophanate groups was 0 / 100.

[0074] <Example 6> 976 g of HDI and 24 g of HBPA were charged into a 1-liter four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube, and the mixture was heated to 60°C. After the HBPA dissolved, 0.2 g of trimethyldodecylammonium formate (10% diluted 2-ethylhexanol), an isocyanurate and allophanate catalyst, was added, and the mixture was reacted at 60°C until the desired reaction conversion rate was reached. Then, 0.2 g of JP-508, a reaction stopper, was added, and the reaction was stopped at 60°C for 1 hour. Excess HDI was removed by thin-film distillation (conditions: 140°C, 0.04 kPa) to obtain 300 g of polyisocyanate composition P-6.

[0075] The NCO content of P-6 was 21.2%, and its viscosity at 25°C was approximately 4,800 mPa·s. 1 ¹H-NMR measurements revealed that the molar ratio of isocyanurate groups to allophanate groups was 70 / 30.

[0076] <Example 7> In a 1-liter four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube, 976 g of HDI and 24 g of HBPA were charged and heated to 60°C. After the HBPA dissolved, 0.2 g of tin octylate, an isocyanurate and allophanate catalyst, was added and the reaction was carried out at 60°C until the desired reaction conversion rate was reached. Then, 0.2 g of JP-508, a reaction stopper, was added and the reaction was stopped at 60°C for 1 hour. Excess HDI was removed by thin-film distillation (conditions: 140°C, 0.04 kPa) to obtain 300 g of polyisocyanate composition P-7.

[0077] The NCO content of P-7 was 21.2%, and its viscosity at 25°C was approximately 5,100 mPa·s. 1 ¹H-NMR measurements revealed that the molar ratio of isocyanurate groups to allophanate groups was 70 / 30.

[0078] <Comparative Examples 1-3> Polyisocyanate compositions P-10 to P-12 were obtained using the same method as in Example 1, with the preparation ratios shown in Table 1.

[0079] <Comparative Examples 4-6> Polyisocyanate compositions P-13 to P-15 were obtained using the same method as in Example 6, with the preparation ratios shown in Table 1.

[0080] <Comparative Example 7> Coronate HXR was used.

[0081] <Comparative Example 8> VESTANAT T1890 / 100 was used.

[0082] [Table 1]

[0083] [Table 2]

[0084] The ingredients listed in Tables 1 and 2 are as follows: • HDI: Hexamethylene diisocyanate, manufactured by Tosoh Corporation, NCO content: 49.9% by mass • Hydrogenated bisphenol A: Manufactured by Wako Pure Chemical Industries, Ltd. Isosorbide: Manufactured by Tokyo Chemical Industry Co., Ltd. • Cyclohexanedimethanol: Manufactured by Tokyo Chemical Industry Co., Ltd. • Spiroglycol: Manufactured by Mitsubishi Gas Chemical Company • Octyltrimethylammonium methylcarbonate: Manufactured by Koei Chemical Industry Co., Ltd. • Zirconium octylate: Nikka Octix Zirconium, manufactured by Nippon Chemical Industries, Ltd., product name. • Trimethyldodecylammonium formate: Manufactured by Koei Chemical Industry Co., Ltd. • Tin octoate: Nikka Octix Tin, manufactured by Nippon Chemical Industries, Ltd., product name • JP-508: Acidic phosphate ester, manufactured by Johoku Chemical Industry Co., Ltd., product name • Coronate HXR: HDI polyisocyanurate, manufactured by Tosoh Corporation, product name • VESTANAT T1890 / 100: Polyisocyanurate of isophorone diisocyanate, manufactured by EVONIK, trade name.

[0085] <Preparation of two-component paint composition> As shown in Tables 3 and 4, the paint formulations for evaluation were prepared by blending a polyol and a polyisocyanate composition so that R (molar ratio of isocyanate groups / hydroxyl groups) = 1.0, and then adding an organic solvent to prepare paint compositions (S-1 to S-17) with a solid content of 50% (amounts are in grams). Acrylic polyol (trade name: Acrydic 49-394-IM, hydroxyl value: 25 mg KOH / g, solid content: 50%, manufactured by DIC Corporation) was used as the polyol, and butyl acetate was used as the organic solvent.

[0086] <Painting method and preparation of test specimens> The prepared coating compositions S-1 to S-17 were applied to steel plates (JIS G3141, product name: SPCC-SB, processing method: PF-1077, manufactured by Paltec Co., Ltd.) and ABS plates (black, manufactured by Yutaka Panel Service Co., Ltd.) using an applicator to achieve a film thickness of approximately 20 μm after drying. Subsequently, the coatings were dried for 1 hour at a temperature of 23°C and a relative humidity of 50%, then heat-treated in an 80°C dryer for 12 hours, and then cured for 1 day at a temperature of 23°C and a relative humidity of 50% to obtain a coating film.

[0087] <Coating film evaluation> The two-component paint compositions shown in Tables 3 and 4 were used to create coating films using the above painting method, and were subjected to evaluations of indentation hardness, substrate conformability, and scratch resistance.

[0088] <Indentation hardness evaluation and evaluation criteria> In accordance with ISO 14577, the indentation strength of the coating applied to the steel plate was evaluated under the following conditions. A rating of A or B indicates good performance. Test equipment: Fischerscope HM2000 (manufactured by Fischer Instruments) Indenter: Vickers diamond Test load: 5mN Test temperature: 25℃ ·80 N / mm 2 Above: (Evaluation) A ·70 N / mm 2 Above 80 N / mm 2 Less than: (Evaluation) B ·70 N / mm 2 Less than: (Evaluation) C <Substrate Followability Evaluation and Evaluation Criteria> In accordance with JIS K5600-5-3, a substrate followability test by weight drop resistance was carried out on the coating film applied to the steel sheet. The results are shown in Tables 3 and 4. It can be said that it is good for Evaluations A and B. ·100 cm: (Evaluation) A ·90 cm or more and less than 100 cm: (Evaluation) B ·Less than 90 cm: (Evaluation) C <Scratch Resistance Evaluation and Evaluation Criteria> Five pieces of gauze were stacked, and a 500 g load was applied to the coating film applied to the ABS board using a Kagaku Shinkin type wear test machine (Friction Tester II type, manufactured by Yasuda Seiki Seisakusho) for 200 reciprocating wear tests. The 20° gloss of the test surface of the coating film was measured with a micro trigloss gloss meter (manufactured by BYK), and the gloss retention rate was measured. The results are shown in Tables 3 and 4. It can be said that it is good for Evaluations A and B. ·90% or more: (Evaluation) A ·85% or more and less than 90%: (Evaluation) B ·Less than 85%: (Evaluation) C

[0089]

Table 3

[0090]

Table 4

Claims

1. A polyisocyanate composition comprising a nurate-type polyisocyanate (A) of hexamethylene diisocyanate, and a polyallophanate (B) which is a reaction product of hexamethylene diisocyanate and a diol having a cyclic group, The diols having a cyclic group are bis(β-hydroxyethyl)benzene, naphthalenedimethanol, cyclohexanediol, hydrogenated bisphenol A, cyclohexanedimethanol, isosorbide, 2,4-dihydroxypyridine, or 2,5-dihydroxy-1,4-dithiane. A polyisocyanate composition characterized in that the molar ratio of (A) to (B) in the polyisocyanate composition is (A) / (B) = 90 / 10 to 30 / 70.

2. A polyurethane resin composition comprising the polyisocyanate composition and a polyol as described in claim 1.

3. A paint composition comprising the polyurethane resin composition described in Claim 2.

4. A coating film formed from the coating composition described in Claim 3.

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