JP7435117B2 - Modified polyisocyanate composition - Google Patents

Description

The present invention relates to modified polyisocyanate compositions.

Conventionally, non-yellowing polyisocyanates derived from aliphatic isocyanates such as 1,6-hexamethylene diisocyanate (hereinafter referred to as HDI) and alicyclic isocyanates such as isophorone diisocyanate (hereinafter referred to as IPDI) have poor weather resistance. Due to its excellent properties, it is used as a hardening agent for paints and adhesives. Among them, 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 purpose.

On the other hand, when used in paints and the like, polyisocyanurate derived from IPDI has been particularly used because the strength of the resulting coating film is also required (for example, Patent Document 1).

However, as the strength of the coating film increases, its conformability to the substrate, which is a property contradictory to high strength, tends to be impaired, and there is also a need for improvement in the resistance of the coating film to scratches.

Japanese Patent Application Publication No. 2002-293873

The present invention has been made in view of the above-mentioned background art, and provides a polyisocyanate composition that can obtain a cured coating film that not only has excellent substrate followability and adhesion, but also has excellent scratch resistance. The object of the present invention is to provide a coating composition using this as a curing agent.

As a result of repeated studies, the present inventors found that the present invention includes HDI nurate-type polyisocyanates and adducts of HDI derivatives containing HDI monomers and diols having a molecular weight of 300 or less having a cyclic group, and has a specific average functional group number. The inventors have discovered that the above problems can be solved by using a polyisocyanate composition within the range specified above, and have arrived at the present invention.

That is, the present invention includes the following embodiments.

[1] A polyisocyanate composition comprising an HDI nurate type polyisocyanate (A) and an adduct (B) of an HDI derivative containing an HDI monomer and a diol having a molecular weight of 300 or less having a cyclic group, the polyisocyanate composition comprising: The molar ratio of isocyanurate groups and urethane groups in the polyisocyanate composition is isocyanurate group/urethane group = 50/50 to 95/5, and the total ratio of isocyanurate groups and urethane groups in the polyisocyanate composition is , 75 to 100 mol% of the total functional groups in isocyanate group residues in the polyisocyanate composition, and the average number of functional groups in the polyisocyanate composition is 3.4 to 4.4. A polyisocyanate composition.

[2] The polyisocyanate composition as described in [1] above, wherein the diol having a cyclic group and having a molecular weight of 300 or less is hydrogenated bisphenol A.

[3] The polyisocyanate composition as described in [1] or [2] above, wherein the polyisocyanate composition contains 25 mol% or less of a polyisocyanate having an allophanate group derived from a monol.

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

[5] A coating composition comprising the polyurethane resin composition according to [4] above.

[6] A coating film formed from the coating composition according to [5] above.

[7] A multilayer coating film comprising at least one coating film according to [6] above.

The polyisocyanate composition of the present invention can provide a polyisocyanate composition that has excellent coating film performance such as hardness of a cured coating film, followability to a substrate, and scratch resistance, and a coating composition using the polyisocyanate composition as a curing agent. can.

The polyisocyanate composition of the present invention contains an HDI nurate polyisocyanate (A) and an adduct (B) of an HDI derivative containing an HDI monomer and a diol having a cyclic group and a molecular weight of 300 or less.

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 include, in addition to HDI, tetramethylene diisocyanate, pentamethylene diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate, lysine diisocyanate, trioxyethylene diisocyanate, etc. be able to. HDI may be used alone or in combination with other aliphatic diisocyanates, or may be used in combination with alicyclic diisocyanates such as isophorone diisocyanate and norbornene diisocyanate.

The HDI nurate type polyisocyanate (A) (hereinafter also referred to as component (A) or (A)) in the present invention is a product obtained by cyclization polymerization of three HDI monomer molecules. Note that this nurate type polyisocyanate may become a polyisocyanate having pentamerized or multimerized isocyanurate groups.

Next, an HDI derivative (B1) containing an HDI monomer in the present invention (hereinafter also referred to as component (B1)) and a diol (B2) having a molecular weight of 300 or less having a cyclic group (hereinafter also simply referred to as component (B2)) ) (hereinafter also simply referred to as (B) component or (B)) will be explained.

The component (B1) contains an HDI monomer and an HDI derivative such as an HDI nurate and an HDI allophanate.

Component (B2) is a diol having a cyclic group such as an aromatic ring, an alicyclic ring, or a heterocyclic ring in the molecule.

Examples of diols having such a cyclic group include bis(β-hydroxyethyl)benzene, naphthalenedimethanol, cyclohexanediol, hydrogenated bisphenol A, cyclohexanedimethanol, isosorbide, 2,4-dihydroxypyridine, 2,5- Examples include dihydroxy-1,4-dithiane. Among these, alicyclics are preferred from the viewpoint of weather resistance, and hydrogenated bisphenol A is particularly preferred.

Component (B1) and component (B2) as described above react to form a urethane bond, resulting in component (B).

The molar ratio of isocyanurate groups to urethane groups in the polyisocyanate composition of the present invention is isocyanate groups/urethane groups = 50/50 to 95/5, preferably 58/42 to 92/8. The total proportion of isocyanurate groups and urethane groups in the polyisocyanate composition is 75 to 100 mol%, preferably 75 to 99 mol%, of the total functional groups in the isocyanate group residues in the polyisocyanate composition. . Further, the average number of functional groups of the polyisocyanate composition containing component (A) and component (B) is 3.4 to 4.4, preferably 3.5 to 4.2. If it is less than the lower limit, there is a risk of a decrease in scratch resistance, and if it exceeds the upper limit, there is a risk of deterioration in workability.

The molar ratio of isocyanurate groups to urethane groups in the polyisocyanate composition, the total ratio of isocyanurate groups to urethane groups in the polyisocyanate composition, and the average number of functional groups in the polyisocyanate composition are as described above. By doing so, a coating film having high strength, high substrate followability, and high scratch resistance can be obtained.

Moreover, the polyisocyanate composition in the present invention may contain a polyisocyanate having an allophanate group derived from a monool. The polyisocyanate having allophanate groups preferably contains 25 mol% or less of allophanate groups based on the functional groups in the isocyanate group residues of the polyisocyanate composition. Moreover, it is also suitable to contain 1 mol% or more. By including the polyisocyanate, the viscosity of the polyisocyanate composition can be lowered, and workability during coating is further improved. However, if it exceeds 25 mol%, the hardness of the coating film may be insufficient.

In obtaining the polyisocyanate having an allophanate group, examples of monools that can be used include methanol, ethanol, propanol, n-butanol, isobutanol, n-pentanol, 2-pentanol, n-hexanol, and 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, cyclohexane methanol, and other monoalcohols. Among these, 2-ethylhexanol, methanol, and cyclohexanemethanol are preferred.

Next, a specific method for producing the polyisocyanate composition of the present invention will be explained.

In the first step, HDI and monoalcohol are charged in an amount such that isocyanate groups are in excess of hydroxyl groups, and a urethane reaction is performed at 20 to 120°C in the presence or absence of an organic solvent to form isocyanate groups. Terminal prepolymer I is produced. Here, as a guideline for the urethanization reaction, the presence or absence of completion is determined based on the isocyanate group content and refractive index increase value determined by neutralization titration.

In the second step, a catalyst is introduced into the isocyanate group-terminated prepolymer I, and the isocyanurate is produced at 50 to 150°C in the presence or absence of an organic solvent until the desired isocyanate group content and molecular weight are achieved. Allophanatization is performed to produce isocyanate group-terminated prepolymer II.

In the third step, the reaction is stopped by adding a reaction terminator to the isocyanate group-terminated prepolymer II.

In the fourth step, a hydroxyl group-containing compound is charged into the isocyanate group-terminated prepolymer II in an amount such that the isocyanate groups are in excess of the hydroxyl groups, and a urethane reaction is performed at 20 to 150°C to produce an isocyanate group-terminated prepolymer III. do. Here, as a guideline for the urethanization reaction, whether or not it is completed is determined based on the isocyanate group content and refractive index increase value determined by neutralization titration. Furthermore, a mixture of a commercially available nurate type polyisocyanate (for example, Coronate HXLV (trade name), manufactured by Tosoh Corporation) with HDI can also be used as the isocyanate group-terminated prepolymer II. In that case, the addition of the reaction terminator shown in the second step is not necessary.

In these first to fourth steps, the reaction proceeds under a stream of nitrogen gas or dry air.

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

Here, as the catalyst in the second step, a quaternary ammonium salt, a carboxylic acid metal salt, or the like can be used.

Examples of quaternary ammonium salts include 2-hydroxypropyltrimethylammonium octylate (DABCO TMR, manufactured by Sankyo Air Products), tetramethylammonium acetate, tetrabutylthylammonium acetate, tetramethylammonium carbonate, and methyltriethyl. Ammonium carbonate, ethyltrimethylammonium carbonate, propyltrimethylammonium carbonate, butyltrimethylammonium carbonate, pentyltrimethylammonium carbonate, hexyltrimethylammonium carbonate, heptyltrimethylammonium carbonate, octyltrimethylammonium carbonate, nonyltrimethylammonium carbonate salt, decyltrimethylammonium carbonate, decyltrimethylammonium carbonate, undecyltrimethylammonium carbonate, dodecyltrimethylammonium carbonate, tridecyltrimethylammonium carbonate, tetradecyltrimethylammonium carbonate, heptadecyltrimethylammonium carbonate, hexadecyl Examples include trimethylammonium carbonate, octadecyltrimethylammonium carbonate, (2-hydroxypropyl)trimethylammonium carbonate, hydroxyethyltrimethylammonium carbonate, 1-methyl 1-azania-4-methylpiperidinium carbonate, and the like. 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, octylic acid, and myristylic acid. can be used alone or in combination of two or more.

The reaction terminator in the third step is one that has the effect of deactivating the catalyst, and specifically includes inorganic acids such as phosphoric acid and hydrochloric acid, organic acids having sulfonic acid groups, sulfamic acid groups, etc. Known compounds such as esters and acyl halides are used. These reaction terminators can be used alone or in combination of two or more. As for the timing of addition, it is preferable to add immediately after the completion of the reaction.

Further, the amount of the reaction terminator added varies depending on the reaction terminator and the type of catalyst used, but is preferably 0.5 to 10 equivalents of the catalyst, particularly preferably 0.8 to 5.0 equivalents. If the amount of the reaction terminator is less than the lower limit, the storage stability of the resulting polyisocyanate composition tends to decrease, and if it exceeds the upper limit, the polyisocyanate composition may be colored.

The "excessive amount of isocyanate groups" in the first and fourth steps means that the molar ratio of isocyanate groups of organic diisocyanate to hydroxyl groups of diol is 3 to 100 (R=isocyanate group/hydroxyl group) when charging raw materials. It is preferable to prepare so that R=5 to 100, and more preferably to prepare so that R=5 to 100. When it is less than the lower limit, the molecular weight of the reaction product becomes high, and there is a possibility that high viscosity and gelation may occur. If the upper limit is exceeded, there is a risk that the product yield will decrease, leading to a decrease in productivity, and that sufficient coating film strength may not be obtained.

Further, the reaction temperature of the urethanization reaction is preferably 20 to 150°C, more preferably 60 to 130°C. In addition, a known urethanization catalyst can be used during the urethanization reaction.

The reaction time for the urethanization reaction varies depending on the presence or absence of a catalyst, its type, and temperature, but generally 10 hours or less, preferably 1 to 5 hours is sufficient.

In the first to fourth steps, a method in which the reaction is carried out without using an organic solvent or the like or a method in which the reaction is carried out in the presence of an organic solvent is appropriately selected.

When the reaction is carried out in the presence of an organic solvent, it is preferable to use an organic solvent that does not affect the reaction. 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, and ethylene glycol. Glycol ether esters such as ethyl ether acetate, propylene glycol monomethyl ether acetate, 3-methyl-3-methoxybutyl acetate, ethyl-3-ethoxypropionate, ethers such as dioxane, halogens such as methylene iodide, monochlorobenzene, etc. Examples include polar aprotic solvents such as hydrogenated hydrocarbons, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, and hexamethylphosphonylamide. These solvents can be used alone or in combination of two or more.

The organic solvent used in the reaction is removed at the same time as free HDI is removed in the fifth step.

The fifth step is a purification step. For example, free unreacted substances present in the reaction mixture are removed by thin film distillation or extraction using an organic solvent at 120 to 150°C under a high vacuum of 10 to 100 Pa. The residual content of HDI is 1% by mass or less. It should be noted that if the residual content of HDI exceeds the upper limit, there is a risk of generating odor and decreasing storage stability.

The polyisocyanate composition obtained by purification can be made into a blocked isocyanate using a known blocking agent for the purpose of extending the pot life or making the coating composition one-component. As a result, the blocked polyisocyanate is inactive at room temperature, but when heated, the blocking agent dissociates and the isocyanate group becomes activated again, giving it the potential to react with active hydrogen groups. can be added.

Blocking agents that can be used in the present invention include compounds having one active hydrogen in the molecule, such as alcohol-based, alkylphenol-based, phenol-based, active methylene-based, mercaptan-based, acid amide-based, acid imide-based, Examples include imidazole-based, urea-based, oxime-based, amine-based, imide-based, and pyrazole-based compounds.

The polyisocyanate composition obtained through a series of reactions can be blended with a polyol to obtain the polyurethane resin composition of the present invention.

Here, 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 reactive group with an isocyanate group, such as polyester polyol, polyether polyol, Polycarbonate polyols, polyolefin polyols, acrylic polyols, silicone polyols, castor oil polyols, fluorine polyols, transesterified products of two or more types of polyols, and hydroxyl-terminated prepolymers reacted with polyisocyanates to form urethanes are preferably used, These can also be used singly or as a mixture of two or more.

<Polyester polyol>
Examples of polyester polyols include phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, succinic acid, tartaric acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, glutaconic acid, azelaic acid, and 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, etc., or dicarboxylic acids such as these. and one or more types of anhydrides of 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, ethylene oxide and propylene oxide adducts of bisphenol A, bis(β-hydroxyethyl)benzene, xylylene glycol, Examples include those obtained from a polycondensation reaction with one or more types of low-molecular polyols having a molecular weight of 500 or less, such as glycerin, trimethylolpropane, and pentaerythritol. Also included are lactone-based polyester polyols obtained from 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, a polyester-amide polyol obtained by replacing a part of the low-molecular polyol with a low-molecular polyamine such as hexamethylene diamine, isophorone diamine, or monoethanolamine or a low-molecular amino alcohol can also be used.

<Polyether polyol>
Examples of polyether polyols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol. Diol, 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, pentaerythritol, etc. A compound having two or more active hydrogen groups, preferably two to three, such as molecular polyols or low molecular polyamines such as ethylenediamine, propylene diamine, toluenediamine, metaphenylene diamine, diphenylmethane diamine, and xylylene diamine. As an initiator, polyether polyols obtained by addition polymerization of alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, etc., or alkyl glycidyl ethers such as methyl glycidyl ether, and aryl glycidyl ethers such as phenyl glycidyl ether. and polyether polyols obtained by ring-opening polymerization of cyclic ether monomers such as tetrahydrofuran and the like.

<Polycarbonate polyol>
Examples of polycarbonate polyols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 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, ethylene oxide and propylene oxide adducts of bisphenol A, bis(β-hydroxyethyl)benzene, xylylene glycol, glycerin, trimethylol One or more types of low-molecular polyols such as propane and pentaerythritol, dialkyl carbonates such as dimethyl carbonate and diethyl carbonate, alkylene carbonates such as ethylene carbonate and propylene carbonate, diphenyl carbonate, dinaphthyl carbonate, dianthryl carbonate, and diphenylene carbonate. Examples include those obtained from a dealcoholization reaction or dealcoholization reaction with diaryl carbonates such as nanthryl carbonate, diindanyl carbonate, and tetrahydronaphthyl carbonate.

Furthermore, polyols obtained by transesterification of polycarbonate polyols, polyester polyols, and low-molecular-weight polyols can also be suitably used.

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

<Acrylic polyol>
Acrylic polyols include acrylic esters and/or methacrylic esters [hereinafter referred to as (meth)acrylic esters], and acrylic acid hydroxy compounds and/or methacrylic acid having at least one or more hydroxyl groups in the molecule that can serve as reaction sites. Examples include those obtained by copolymerizing a hydroxy compound [hereinafter referred to as a (meth)acrylic acid hydroxy compound] and a polymerization initiator with an acrylic monomer using thermal energy or light energy such as ultraviolet rays or electron beams.

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

<(meth)acrylic acid hydroxy compound>
(Meth)acrylic acid hydroxy compounds have at least one hydroxyl group in the molecule that can serve as a reaction site with polyisocyanate, and specifically, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, etc. , 4-hydroxybutyl acrylate, 3-hydroxy-2,2-dimethylpropyl acrylate, pentaerythritol triacrylate, and other hydroxy acrylic compounds. Also included are methacrylic acid hydroxy compounds such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 3-hydroxy-2,2-dimethylpropyl methacrylate, and pentaerythritol trimethacrylate. These (meth)acrylic acid hydroxy compounds may be used alone or in combination of two or more.

<Silicone polyol>
Examples of silicone polyols include vinyl group-containing silicone compounds obtained by polymerizing γ-methacryloxypropyltrimethoxysilane, α,ω-dihydroxypolydimethylsiloxane, α,ω- Mention may be made of polysiloxanes such as dihydroxypolydiphenylsiloxane.

<Castor oil-based polyol>
Examples of castor oil-based polyols include linear or branched polyester polyols obtained by reacting castor oil fatty acids with polyols. Furthermore, dehydrated castor oil, partially dehydrated castor oil that is partially dehydrated, and hydrogenated castor oil that has hydrogen added thereto can also be used.

<Fluorine polyol>
Examples of the fluorine-based polyol include linear or branched polyols obtained by a copolymerization reaction of a fluorine-containing monomer and a monomer having a hydroxyl group as an essential component. Here, the fluorine-containing monomer is preferably a fluoroolefin, such as tetrafluoroethylene, chlorotrifluoroethylene, trichlorofluoroethylene, hexafluoropropylene, vinylidene fluoride, vinyl fluoride, trifluoromethyltrifluoroethylene. can be mentioned. 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 hydroxyalkyl vinyl crotonate. Monomers having hydroxyl groups such as hydroxyl group-containing vinyl carboxylates or allyl esters may be mentioned.

Further, the polyol preferably has a number of active hydrogen groups (average number of functional groups) in one molecule of 1.9 to 6.0. If the number of active hydrogen groups is less than the lower limit, the physical properties of the coating film may deteriorate. Moreover, when the upper limit is exceeded, there is a possibility that the adhesion may be reduced.

Further, the number average molecular weight of the polyol is preferably in the range of 250 to 50,000. If it is less than the lower limit, there is a risk of a decrease in adhesion, and if it exceeds the upper limit, there is a risk of a decrease in solubility in low polar organic solvents and a decrease in adhesiveness.

Moreover, the polyurethane resin composition of the present invention can be suitably used as a coating composition. The ratio of the polyisocyanate composition and the polyol in the coating composition is not particularly limited, but the molar ratio of the isocyanate group in the isocyanate composition to the hydroxyl group in the polyol is R = isocyanate group/hydroxyl group. It is preferable to mix so that the ratio is 0.5 to 2.5. If it is less than the lower limit, there will be an excess of hydroxyl groups, which may lead to a decrease in adhesion. Furthermore, the crosslinking density may decrease, leading to a decrease in durability and mechanical strength of the coating film. When the upper limit is exceeded, the isocyanate group becomes excessive and reacts with moisture in the air, which may cause blistering of the coating film and a concomitant decrease in adhesion.

Examples of organic solvents used as diluting solvents include ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, esters such as ethyl acetate, butyl acetate, and cellosolve acetate, alcohols such as butanol and isopropyl alcohol, toluene, and xylene. , cyclohexane, mineral spirits, naphtha, and other hydrocarbons, depending on the purpose and use. These solvents may be used alone or in combination of two or more.

Further, the coating composition may appropriately use a known urethanization catalyst in consideration of pot life, curing conditions, working conditions, and the like. Specifically, organic metal compounds such as dibutyltin diacetate, dibutyltin dilaurate, and dioctyltin dilaurate, organic amines such as triethylenediamine and triethylamine, and salts thereof are selected and used. These catalysts can be used alone or in combination of two or more.

Further, the curing conditions for the coating composition are not particularly limited, but 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. preferable.

The coating composition obtained by the present invention may contain, for example, antioxidants such as 2,6-di-tert-butyl-4-methylphenol, ultraviolet absorbers, pigments, dyes, solvents, Additives such as a refractor, a hydrolysis inhibitor, a lubricant, a plasticizer, a filler, an antistatic agent, a dispersant, a catalyst, a storage stabilizer, a surfactant, a leveling agent, etc. can be blended as appropriate.

Further, the coating composition obtained according to the present invention is applied onto the surface of an adherend by a known method such as spraying, brushing, dipping, or using a coater to form a coating film.

The adherends here are not particularly limited, and include stainless steel, phosphate-treated steel, zinc steel, iron, copper, aluminum, brass, glass, slate, acrylic resin, polycarbonate resin, polyethylene terephthalate resin, and 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 , adherends molded from materials such as melamine resin, polyacetal resin, chlorinated polyolefin resin, polyolefin resin, polyamide resin, polyether ether ketone resin, polyphenylene sulfide resin, NBR resin, chloroprene resin, SBR resin, SEBS resin, etc. An olefin resin such as polyethylene or polypropylene that has been subjected to corona discharge treatment or other surface treatment, or an adherend on which a coating layer that can be formed as an intermediate layer is formed on the surface of the adherend can be used.

Since the coating film formed on the surface layer of the adherend has excellent recoatability and durability, it is sufficient to form the coating film on the adherend to a thickness of at least 10 μm. If the film thickness is less than 10 μm, the durability will decrease and there is a risk that the coating film will break due to impact.

Furthermore, when creating a multilayer coating film, the resin used for the lower layer may be, for example, epoxy, alkyd, melamine, acrylic, urethane, or the like, and preferably is a water-based resin. Although the thickness of the multilayer coating film is not particularly limited, it is preferable to form a film thickness of at least 10 μm as a dry coating film. The multi-layer coating here refers to the resin used for the lower layer being applied to the surface of the adherend by a known method such as spraying, dipping, or coater to form at least one coating layer, and then the present invention A coating film having two or more coating layers formed by applying a coating composition containing a polyisocyanate composition according to a known method such as spraying, dipping, or using a coater.

Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to these Examples. Note that percentages in the examples are based on mass unless otherwise specified.

<Synthesis of polyisocyanate composition>
<Example 1>
In a 1-liter four-necked flask equipped with a stirrer, thermometer, cooling tube, and nitrogen gas introduction tube, 976.5 g of HDI (manufactured by Tosoh Corporation, NCO content: 49.9% by mass) and 2-ethylhexanol were added. (Octanol (trade name), manufactured by KH Neochem Co., Ltd., hereinafter referred to as 2-EHOH) was charged at 1.0 g, and heated to 60°C. - Ethylhexanol 10% dilution) was added, and the reaction was carried out at 60°C until the predetermined reaction conversion rate shown in Table 1 was reached. , manufactured by Johoku Kagaku Kogyo Co., Ltd. (hereinafter referred to as JP-508)) was added thereto, and the reaction was stopped at 60° C. for 1 hour to obtain reaction product C-1. Subsequently, 21.5 g of hydrogenated bisphenol A (trade name, manufactured by Maruzen Petrochemical Co., Ltd., hereinafter referred to as HBPA) was added to the obtained C-1, and the mixture was heated to 120°C with stirring to give a predetermined amount of The urethanization reaction was carried out until the reaction conversion rate was reached to obtain a reaction product D-1. Excess HDI was removed from D-1 by thin film distillation (conditions: 140° C., 0.04 kPa) to obtain 450 g of polyisocyanate composition P-1 having a calculated functional group number of 3.7.

The NCO content of P-1 was 20.3%, and the viscosity at 25° C. was about 6,500 mPa·s. When P-1 was measured by ¹ H-NMR, the molar ratio of isocyanurate groups, urethane groups, and allophanate groups was 90/9/1.

<NMR: Measurement of isocyanurate group, urethane group, allophanate group content>
(1) Measuring device: ECX400M (manufactured by JEOL Ltd., ^1H -NMR)
(2) Measurement temperature: 23℃
(3) Sample concentration: 0.1g/1ml
(4) Number of accumulations: 16
(5) Relaxation time: 5 seconds (6) Solvent: Deuterium dimethyl sulfoxide (7) Chemical shift standard: Hydrogen atom signal of methyl group in deuterium dimethyl sulfoxide (2.5 ppm)
(8) Evaluation method: Signal of the hydrogen atom of the methylene group adjacent to the nitrogen atom of the isocyanurate group around 3.7 ppm, signal of the hydrogen atom bonded to the nitrogen atom of the urethane group around 7.0 ppm, 8. The content of the bonding group was measured from the area ratio of the signal of the hydrogen atom bonded to the nitrogen atom of the allophanate group at around 5 ppm.

<Examples 2 to 4>
Polyisocyanate compositions P-2 to P-4 were obtained in the same manner as in Example 1 using the charging ratios shown in Table 1.

<Example 5>
934.8 g of HDI and 3.3 g of methanol (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) were placed in a 1-liter four-necked flask equipped with a stirrer, thermometer, cooling tube, and nitrogen gas introduction tube, and the mixture was heated at 60°C. 1 g of trimethyloctylammonium methyl carbonate (diluted with 2-ethylhexanol 10%), which is an isocyanurate and allophanate catalyst, was added, and the reaction was continued at 60°C until the predetermined reaction conversion rate shown in Table 1 was reached. After this, 0.2 g of JP-508 was added and the reaction was terminated at 60° C. for 1 hour to obtain reaction product C-5. Subsequently, 61.9 g of HBPA was charged into the obtained C-5, and the mixture was heated to 120° C. with stirring to undergo a urethane reaction until a predetermined reaction conversion rate was reached to obtain a reaction product D-5. . Excess HDI was removed from D-5 by thin film distillation (conditions: 140° C., 0.04 kPa) to obtain 475 g of polyisocyanate composition P-5 having a calculated functional group number of 3.6.

The NCO content of P-5 was 18.5%, and the viscosity at 25° C. was about 14,000 mPa·s. When P-5 was measured by ¹ H-NMR, the molar ratio of isocyanurate groups, urethane groups, and allophanate groups was 65/25/10.

<Examples 6-7, 17>
Polyisocyanate compositions P-6 to P-7 and P-14 were obtained in the same manner as in Example 5 using the charging ratios shown in Tables 1 and 5.

<Example 8>
965.5 g of HDI and 11.9 g of cyclohexane methanol (manufactured by Kanto Kagaku Co., Ltd.) were placed in a 1-liter four-necked flask equipped with a stirrer, thermometer, cooling tube, and nitrogen gas introduction tube, and the mixture was heated at 60°C. 1 g of trimethyloctylammonium methyl carbonate (diluted with 2-ethylhexanol 10%), which is an isocyanurate and allophanate catalyst, was added, and the reaction was continued at 60°C until the predetermined reaction conversion rate shown in Table 1 was reached. After this, 0.2 g of JP-508 was added and the reaction was stopped at 60° C. for 1 hour to obtain reaction product C-8. Subsequently, 21.5 g of HBPA was charged into the obtained C-8, and the mixture was heated to 120° C. while stirring, and the urethane reaction was carried out until a predetermined reaction conversion rate was reached to obtain a reaction product D-8. . Excess HDI was removed from D-8 by thin film distillation (conditions: 140° C., 0.04 kPa) to obtain 484 g of polyisocyanate composition P-8 having a calculated functional group number of 3.6.

The NCO content of P-8 was 19.6%, and the viscosity at 25°C was about 6,300 mPa·s. When P-8 was measured by ¹ H-NMR, the molar ratio of isocyanurate groups, urethane groups, and allophanate groups was 82/8/10.

<Example 18>
Polyisocyanate composition P-15 was obtained in the same manner as in Example 8 using the charging ratio shown in Table 1.

<Comparative Examples 1-2>
Polyisocyanate compositions P-9 to 10 were obtained in the same manner as in Example 1 using the charging ratios shown in Table 1.

<Comparative example 3>
Polyisocyanate composition P-11 was obtained in the same manner as in Example 5 using the charging ratio shown in Table 1.

<Comparative example 4>
Coronate HK: HDI polyisocyanurate (trade name: Coronate HK, manufactured by Tosoh Corporation) was used.

<Comparative example 5>
T1890: IPDI polyisocyanurate (trade name: VESTANAT T1890/100, manufactured by EVONIK) was used.

<Comparative example 11>
Coronate HXLV: HDI polyisocyanurate (trade name: Coronate HXLV, manufactured by Tosoh Corporation) was used.

<Preparation of two-component coating composition (1)>
As shown in Tables 3 and 4, the coating composition for evaluation was prepared by blending a polyol and a polyisocyanate composition so that R (molar ratio of isocyanate groups/hydroxyl groups) = 1.0, and further reducing the solid content with an organic solvent. Coating compositions (S-1 to S-13) were prepared so that the amount was 50% (the unit of blending amount is g). Acrylic polyol (trade name: Acridic 49-394-IM, hydroxyl value: 25 mgKOH/g, solid content: 50%, manufactured by DIC) was used as the polyol, and butyl acetate was used as the organic solvent.

<Preparation of two-component coating composition (2)>
As shown in Table 6, the coating composition for evaluation was prepared by blending a polyol and a polyisocyanate composition so that R (molar ratio of isocyanate groups/hydroxyl groups) = 1.2, and further adding an organic solvent to reduce the solid content to 25%. Coating compositions (S-14 to S-20) were prepared in such a manner that the amount was in g. Acrylic polyol (trade name: Acridic 49-394-IM, hydroxyl value: 25 mgKOH/g, solid content: 50%, manufactured by DIC) was used as the polyol, and butyl acetate was used as the organic solvent.

<Coating method and preparation of single layer coating test piece>
The prepared coating compositions S-1 to S-13 were applied to a steel plate (JIS G3141, product name: SPCC-SB, treatment method: PF-1077, manufactured by Paltech) using an applicator to give a film thickness of about 20 μm after drying. I applied it to make it look like this. Thereafter, after drying for 1 hour at a temperature of 23°C and a relative humidity of 50%, heat treatment was performed for 12 hours in an 80°C dryer, and then curing for 24 hours at a temperature of 23°C and a relative humidity of 50%. A coating film was obtained.

<Coating method and preparation of multilayer coating test piece>
Aqueous acrylic emulsion (product name: Burnock WE-303, manufactured by DIC Corporation, glass transition temperature: 15°C) was applied to a steel plate (JIS G3141, product name: SPCC-SB, treatment method: PF-1077, manufactured by Pultech) to a dry film thickness. It was spray-painted so that the thickness was 20 μm. Next, heat treatment was performed in a dryer at 50° C. for 1 hour, and the evaluation coating compositions (S-14 to S-20) obtained above were spray coated to a dry film thickness of 25 μm. Thereafter, after drying for 1 hour at a temperature of 23°C and a relative humidity of 50%, heat treatment was performed for 12 hours in an 80°C dryer, and then curing for 24 hours at a temperature of 23°C and a relative humidity of 50%. A coating film was obtained.

<Coating film evaluation>
The coating film evaluation was carried out using a coating film prepared using the coating compositions shown in Tables 3, 4, and 6 by the above-mentioned coating method, and evaluated by indentation hardness evaluation, substrate followability evaluation, and scratch resistance evaluation.

<Indentation hardness evaluation and evaluation criteria>
According to ISO 14577, indentation hardness was evaluated under the following conditions. The results are shown in Tables 3, 4 and 6. A rating of A or B is considered good.
Test equipment: Fischerscope HM2000 (manufactured by Fischer Instruments)
Indenter: Vickers diamond Test load: 5mN
Test temperature: 25℃
・80N/mm ² or more: (Evaluation) A
・50N/mm ² or more - 80N/mm less than ² : (Evaluation) B
・Less than 50N/mm ² : (Evaluation) C.

<Base material followability evaluation and evaluation criteria>
In accordance with JIS K5600-5-3, a substrate followability test was conducted based on weight drop resistance. The results are shown in Tables 3 and 4. A rating of A or B is considered good.
・100cm: (Evaluation) A
・More than 90cm to less than 100cm: (Evaluation) B
・Less than 90cm: (Evaluation) C.

<Abrasion resistance evaluation and evaluation criteria>
Five layers of gauze were stacked, and a 200-reciprocal abrasion test was conducted at a load of 500 g using a Gakushin type abrasion tester (friction tester type II) (manufactured by Yasuda Seiki Seisakusho). The test surface of the coating film was observed using a scanning white interference microscope (manufactured by Hitachi High-Tech Science), and the depth of the wear scar was measured. The results are shown in Tables 3 and 4. If the rating is A, it can be said to be good.
・Less than 30 nm: (Evaluation) A
・30-50nm: (Evaluation) B
・50 nm or more: (Evaluation) C

Claims (7)

A polyisocyanate composition comprising a nurate polyisocyanate (A) of hexamethylene diisocyanate, and an adduct (B) of a hexamethylene diisocyanate derivative containing a hexamethylene diisocyanate monomer and a diol having a molecular weight of 300 or less having a cyclic group,
The molar ratio of isocyanurate groups to urethane groups in the polyisocyanate composition is isocyanurate groups/urethane groups = 50/50 to 95/5,
The total proportion of isocyanurate groups and urethane groups in the polyisocyanate composition is 75 to 100 mol% of the total of functional groups generated by reaction of isocyanate groups in the polyisocyanate composition, and
A polyisocyanate composition characterized in that the average number of isocyanate groups in the polyisocyanate composition is 3.4 to 4.4. 2. The polyisocyanate composition according to claim 1, wherein the diol having a cyclic group and having a molecular weight of 300 or less is hydrogenated bisphenol A. The polyisocyanate composition according to claim 1 or 2, characterized in that the polyisocyanate composition contains 25 mol% or less of a polyisocyanate having an allophanate group derived from a monol. A polyurethane resin composition comprising the polyisocyanate composition according to any one of claims 1 to 3 and a polyol. A coating composition comprising the polyurethane resin composition according to claim 4. A coating film formed from the coating composition according to claim 5. A multilayer coating film comprising at least one coating film according to claim 6.