JP6840939B2 - Polyisocyanate composition and coating composition using it - Google Patents

Description

The present invention relates to a low-viscosity polyisocyanate composition useful as a curing agent for obtaining a polyurethane resin and the like, and a coating composition using the same as a curing agent.

Conventionally, in the fields of paints / coatings and adhesives, non-yellowing polyisocyanates derived from aliphatic isocyanates such as 1,6-hexamethylene diisocyanate (hereinafter referred to as HDI) have excellent weather resistance. Among them, the polyisocyanate type containing an isocyanurate bond has high chemical and thermal stability, and is particularly excellent in weather resistance, heat resistance, and durability, so that it is widely used according to its application, and further applications. Expected to develop.

When this type having an isocyanurate bond is used as a curing agent, it is difficult to handle due to its high viscosity, and it must be diluted with an organic solvent or the like before use. Recently, awareness of reducing the environmental load has increased, and in order to reduce the amount of organic solvent used, it has been proposed to reduce the viscosity of polyisocyanate used as a curing agent. By lowering the viscosity of the polyisocyanate, the handleability at the time of coating is improved, and the amount of the organic solvent used in the coating composition can be reduced.

Currently, as a technique for reducing the viscosity of polyisocyanate, polyisocyanate having a uretdione bond can be mentioned. A polyisocyanate having a uretdione bond can achieve a low viscosity, but has a problem of poor thermal stability and weather resistance. (Patent Documents 1 and 2)

Further, as one of the techniques for reducing the viscosity, a polyisocyanate having an allophanate bond obtained by reacting HDI with an aliphatic monoalcohol can be mentioned (Patent Document 3). The allophanate group is superior in thermal stability and weather resistance to the uretdione group. However, polyisocyanates containing an allophanate bond also have problems of poor chemical and thermal stability and poor weather resistance as compared with the above-mentioned isocyanurate bond.

A polyisocyanate containing an allophanate bond and an isocyanurate bond obtained by reacting HDI with a monool having 11 to 20 carbon atoms is disclosed (Patent Document 4). However, there is a problem that the amount of isocyanate groups contained in one molecule (hereinafter, isocyanate content) is low.

In a coating composition composed of a combination with a polyol, the higher the isocyanate content, the higher the concentration of urethane bonds obtained by reacting with the hydroxyl groups in the polyol of the entire coating composition, and the mechanical properties of the urethane coating film are improved. Therefore, polyisocyanate having a high isocyanate content is eagerly desired.

Japanese Unexamined Patent Publication No. 5-32759 Japanese Unexamined Patent Publication No. 2013-224350 Japanese Unexamined Patent Publication No. 2003-137966 Japanese Unexamined Patent Publication No. 2012-255101

The present invention has been made in view of the above-mentioned background techniques, and is excellent in mechanical properties, adhesion, and weather resistance by ensuring a high isocyanate content while maintaining chemical and thermal stability while maintaining low viscosity. It is an object of the present invention to provide a polyisocyanate composition and a coating composition using the same as a curing agent.

As a result of repeated studies, the present inventors have found that the above-mentioned problem can be solved by an aliphatic polyisocyanate obtained by reacting a specific monoalcohol with HDI in the presence of a specific allophanate isocyanurate catalyst. The present invention has been reached.

That is, the present invention includes the following embodiments.

[1] A polyisocyanate obtained by reacting hexamethylene diisocyanate with a monoalcohol having 1 to 3 carbon atoms in the presence of a quaternary ammonium salt as an allophanate-isocyanurate conversion catalyst.

[2] A polyisocyanate having a molar ratio of an allophanate group / isocyanurate group in the polyisocyanate according to the above [1] of 50/50 to 20/80.

[3] When the amount of uretdione in the polyisocyanate according to the above [1] or [2] is 5% or less as a peak area in gel permeation chromatography measurement and the viscosity at 25 ° C. is 500 mPa · s or less. A polyisocyanate.

[4] A method for producing a polyisocyanate, which comprises reacting hexamethylene diisocyanate with a monoalcohol having 1 to 3 carbon atoms in the presence of a quaternary ammonium salt as an allophanate-isocyanurate conversion catalyst.

[5] A two-component automobile paint composition containing the polyisocyanate and the polyol according to any one of the above [1] to [3].

The polyisocyanate defined in [1] above can be obtained by reacting HDI with a monoalcohol having 1 to 3 carbon atoms in the presence of a quaternary ammonium salt as an allophanate-isocyanurate conversion catalyst. This polyisocyanate is produced through a complicated allophanate-isocyanurate conversion reaction, and some polymer compounds may be produced, and those having a bonding group other than an allophanate group and an isocyanurate group, such as a uretdione group, may be produced. .. Since such reactions occur in a complex manner, it is possible to show the structure of each individual binding group, but the structure of the entire obtained polymerization product is very complicated, so it is not possible to express them by a structural formula. The current situation is that it cannot be done at all. That is, the polyisocyanate specified in the above [1] cannot be directly specified by its structure, but can be specified only by the process for obtaining the polyisocyanate.

The polyisocyanate composition of the present invention is a polyisocyanate composition having a low viscosity, maintaining chemical and thermal stability, ensuring a high isocyanate content, and having excellent mechanical properties, substrate adhesion, and weather resistance. A coating composition using this as a curing agent can be provided.

In addition, due to its low viscosity, it imparts permeability to the underlayer coating film such as the intermediate coating film and the base film, and can be expected to improve the physical properties of the multi-layer coating film.

The present invention will be described in detail below.

The polyisocyanate of the present invention contains HDI and a monoalcohol having 1 to 3 carbon atoms in the presence of a quaternary ammonium salt as a catalyst for promoting allophanate formation and isocyanurate formation (hereinafter referred to as an allophanate isocyanurate conversion catalyst). It is obtained by reacting.

The aliphatic diisocyanate monomer (hereinafter, also simply referred to as aliphatic diisocyanate) that can be used in the polyisocyanate composition of the present invention is a diisocyanate compound that does not contain a benzene ring in its structure. Examples of the aliphatic diisocyanate include HDI, tetramethylene diisocyanate, 2-methyl-pentane-1,5-diisocyanate, 3-methyl-pentane-1,5-diisocyanate, lysine diisocyanate, and trioxyethylene diisocyanate. Of these, HDI is preferable because of its weather resistance and easy industrial availability. The aliphatic diisocyanate may be used alone or in combination, or may be used in combination with an alicyclic diisocyanate typified by isophorone diisocyanate or norbornene diisocyanate.

Examples of the alcohol that can be used in the polyisocyanate composition of the present invention include methanol, ethanol, 1-propanol, and 2-propanol, which are monoalcohols having 1 to 3 carbon atoms. The above alcohols may be used alone or in combination. Among these, methanol and ethanol are more preferable in order to increase the isocyanate content. Monoalcohols having 4 or more carbon atoms include 1-butanol, 2-butanol, isobutanol, 1-pentanol, 2-pentanol, isoamyl alcohol, 1-hexanol, 2-hexanol, 1-heptanol, 1-octanol, 2 -Ethyl-1-hexanol, 3,3,5-trimethyl-1-hexanol, 1-tridecanol, 2-tridecanol, 2-octyldodecanol, pentadecanol, palmityl alcohol, stearyl alcohol, cyclopentanol, cyclohexanol , Methylcyclohexanol, trimethylcyclohexanol, etc., but when these are used as modifiers, the isocyanate content becomes low, and the amount of urethane bonds in the urethane coating film using polyisocyanate as a curing agent. Is reduced, and there is concern that the mechanical properties will deteriorate.

The isocyanurate group, which is one of the constituents of the polyisocyanate composition of the present invention, is a cyclization polymerization of diisocyanate monomers and is represented by the following formula. This is a polyisocyanate having a tri-quantified, pent-quantified, or a large amount of isocyanurate groups.

[R in the formula represents a hexamethylene group].

Further, the allophanate group, which is another constituent component of the polyisocyanate composition of the present invention, is further added to the urethane group after the hydroxyl group of the monoalcohol reacts with the isocyanate group of the aliphatic diisocyanate to form a urethane bond. It is obtained by reacting another isocyanate group and is represented by the following formula.

[R in the formula represents a hexamethylene group. R'represents an alkyl group having 1-3 carbon atoms].

Further, the molar ratio of the isocyanurate group to the allophanate group contained in the polyisocyanate composition of the present invention can be in the range of 50/50 to 80/20 for the isocyanurate group / allophanate group. If the molar ratio of isocyanurate groups is less than the lower limit, the physical characteristics and weather resistance of the coating film may deteriorate. If it exceeds the upper limit, the viscosity of the polyisocyanate may increase.

The uretdione group described in the polyisocyanate composition of the present invention is a linearly polymerized isocyanate group and is represented by the following formula. The uretdione compound of the present invention refers to a diisocyanate dimer having a uretdione group composed of two diisocyanate monomer molecules.

[R in the formula represents a hexamethylene group].

The polyisocyanate composition of the present invention can be obtained in an amount of 5% or less of the uretdione compound contained in the total composition of the polyisocyanate. If it is 5% or less, the thermal stability and weather resistance of the coating film can be ensured, and if the amount of uretdione exceeds 5%, the thermal stability and weather resistance of the coating film may deteriorate. is there.

The viscosity of the polyisocyanate composition of the present invention at 25 ° C. is preferably 500 mPa · s or less, more preferably 450 mPa · s. If it exceeds 500 mPa · s, the viscosity of the used paint may increase and handling may deteriorate.

Next, a specific method for producing the polyisocyanate composition will be described.

In the first step, organic diisocyanate and monoalcohol are charged with an excess amount of isocyanate groups with respect to the hydroxyl group, and are subjected to a urethanization reaction at 20 to 60 ° C. in the presence or absence of an organic solvent to terminate the isocyanate groups. 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 the refractive index increase value by the neutralization titration method.

In the second step, an allophanate / isocyanurate-forming catalyst is charged into the isocyanate group-terminated prepolymer I, and isocyanurate-ization / allophanate is performed at 50 to 150 ° C. until the desired isocyanate group content and molecular weight are reached. The isocyanate group-terminated prepolymer II is produced.

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

In these first to third steps, the reaction is allowed to proceed under nitrogen gas or a dry air stream.

In the fourth step, the isocyanate group-terminated prepolymer II is removed by thin film distillation or solvent extraction until the content of free organic diisocyanate is less than 1% by mass.

Here, the "amount of excess isocyanate group" in the first step means that the molar ratio of the isocyanate group of the organic diisocyanate to the hydroxyl group of monool is 20 to 75 when R = isocyanate group / hydroxyl group when the raw material is charged. It is preferable to prepare so as to be, and it is more preferable to prepare so that R = 15 to 50. If it is less than the lower limit, the amount of the polyisocyanate composition having a higher molecular weight than the target product is increased, which may lead to an increase in viscosity. If it exceeds the upper limit, the amount of allophanate in the polyisocyanate composition may decrease, resulting in an increase in viscosity and a decrease in product yield, which may lead to a decrease in productivity.

The reaction temperature of the urethanization reaction of the present invention is preferably 20 to 70 ° C, more preferably 30 to 60 ° C. A known urethanization catalyst can be used in the urethanization reaction. Specifically, an organometallic compound such as dibutyltin diacetate, dibutyltin dilaurate, or dioctyltin dilaurate, an organic amine such as triethylenediamine or triethylamine, or a salt thereof is selected and used. These catalysts can be used alone or in combination of two or more.

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

Examples of the allophanate-isocyanurate-forming catalyst in the second step include the allophanate-isocyanurate-forming catalyst shown below.

The allophanate isocyanurate-forming catalyst is generally preferably one having basicity, and for example, carboxylic acids such as acetic acid of alkylammonium such as tetramethylammonium, tetraethylammonium, octyltrimethylammonium, dodecyltrimethylammonium and trioctylmethylammonium, and capric acid. Examples thereof include organic weak acid salts such as acids and alkyl carbonates, and metal salts of alkylcarboxylic acids such as acetic acid, caproic acid, octyl acid and myristic acid such as tin, zinc, lead and bismuth.

Among these, an organic weak acid salt of alkylammonium is preferable from the viewpoint of solubility in HDI, allophanate, and isocyanurate reaction activity.

The amount of the allophanate / isocyanurate-forming catalyst used is preferably 0.001 to 1.0% by mass, more preferably 0.005 to 0.1% by mass, based on the total mass of the organic diisocyanate and the monoalcohol.

If it is less than the lower limit, the allophanation reaction and the isocyanurate-forming reaction do not proceed sufficiently, the amount of urethane group-containing polyisocyanate that is a precursor of the polyisocyanate composition increases, and the average number of functional groups decreases. There is a risk of lowering the physical characteristics of the coating film and lowering the productivity and yield. On the other hand, if it exceeds the upper limit, the amount of the polyisocyanate composition having a higher molecular weight than the target product is increased, which may lead to an increase in viscosity and a decrease in reactivity control.

The reaction temperature of the allophanate reaction and the isocyanurate-forming reaction is preferably 50 to 150 ° C, more preferably 60 to 100 ° C.

Further, the molar ratio of the allophanate group to the isocyanurate group contained in the obtained polyisocyanate composition is set in the range of 50/50 to 80/20 of the isocyanurate group / allophanate group by appropriately adjusting the reaction time. It is possible. If the molar ratio of isocyanurate groups is less than the lower limit, mechanical properties and weather resistance may deteriorate. If it exceeds the upper limit, the viscosity of the polyisocyanate may increase.

Further, in the production of the polyisocyanate composition, a method of carrying out the reaction without containing an organic solvent or the like or a method of carrying out the reaction in the presence of an organic solvent is appropriately selected.

When the reaction is carried out in the presence of an organic solvent, an organic solvent that does not affect the reaction can be used. Specific examples of the organic solvent include aliphatic hydrocarbons such as octane, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, ketones such as methylisobutylketone and cyclohexanone, and 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, ethyl-3-ethoxypropionate, ethers such as dioxane, methylene iodide, monochlorobenzene, etc. Examples thereof include halogenated hydrocarbons of the above, polar aproton solvents such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, hexamethylphosphonylamide and the like. 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 the removal of the free organic diisocyanate in the fourth step.

The reaction terminator in the third step has an action of inactivating the activity of the catalyst, and specifically, an organic acid having an inorganic acid such as phosphoric acid or hydrochloric acid, a sulfonic acid group, a sulfamic acid group, or the like. Known compounds such as acids, esters thereof and acyl halides are used. These reaction terminators can be used alone or in combination of two or more. It is preferable that the addition time is prompt after the reaction is completed.

The amount of the reaction terminator added varies depending on the type of the reaction terminator and the catalyst used, but is preferably 0.5 to 10 equivalents of the catalyst, and 0.8 to 5.0 equivalents is particularly preferable. If the amount of the reaction terminator is small, the storage stability of the obtained polyisocyanate composition tends to decrease, and if it is too large, the polyisocyanate composition may be colored.

In the purification step of the fourth step, the free unreacted organic diisocyanate present in the reaction mixture is removed by a thin film distillation method or extraction with an organic solvent at 120 to 150 ° C. under a high vacuum of, for example, 10 to 100 Pa. By the method, the residual unreacted organic diisocyanate content is reduced to 1.0% by mass or less. If the residual content of the organic diisocyanate exceeds the upper limit, odor may be generated and the storage stability may be lowered.

The polyisocyanate composition obtained by purification can be made into a blocked isocyanate by using a known blocking agent for the purpose of extending the pot life and liquefying the coating composition. As a result, the blocked polyisocyanate is inactive at room temperature, but the blocking agent is dissociated by heating, and the isocyanate group is activated again, which has a potential function of reacting with the active hydrogen group. Can be added.

The blocking agent that can be used in the present invention is a compound having one active hydrogen in the molecule, for example, alcohol-based, alkylphenol-based, phenol-based, active methylene, mercaptan-based, acid amide-based, acid imide-based, and the like. There are imidazole-based, urea-based, oxime-based, amine-based, imide-based, pyrazole-based compounds and the like.

The polyisocyanate composition thus obtained has an average number of functional groups of 2.0 to 5.0 obtained from the number average molecular weight obtained by gel permeation chromatography measurement (hereinafter referred to as GPC measurement or simply GPC). The range. If it is less than the lower limit, the crosslink density may decrease and the solvent resistance and the physical properties of the coating film may decrease. Further, if it exceeds the upper limit value, the viscosity of the polyisocyanate may increase.

The number average molecular weight of the polyisocyanate composition is preferably 500 to 3000, more preferably 500 to 2500, and most preferably 500 to 2000. If it is less than the lower limit, the adhesion may be lowered, and if it exceeds the upper limit, the viscosity of the polyisocyanate may be increased.

Further, the polyisocyanate composition obtained by a series of reactions can be obtained with the coating composition of the present invention by blending a polyol.

Here, the polyol used in the coating composition of the present invention is not particularly limited, but is a compound containing an active hydrogen group as a reactive group with an isocyanate group, and is a polyester polyol, a polyether polyol, or the like. Polycarbonate polyols, polyolefin polyols, acrylic polyols, silicone polyols, castor oil-based polyols, fluorine-based polyols, ester exchanges of two or more types of polyols, hydroxyl group-terminated prepolymers that have undergone urethanization reaction with polyisocyanates, and the like are preferably used. These can also be used as one kind or a mixture of two or more kinds.

<Polyester polyol>
Specific examples of polyester polyols include phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, succinic acid, tartaric acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimeric acid, suberic acid, glutaconic acid, and 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 and other dicarboxylic acids One or more of acids or anhydrides thereof, 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-dimethylolheptan, diethylene glycol, Dipropylene glycol, neopentyl glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, diol dimerate, ethylene oxide or propylene oxide adduct of bisphenol A, bis (β-hydroxyethyl) benzene, xylyl Examples thereof include those obtained by a condensation polymerization reaction with one or more kinds of low molecular weight polyols having a molecular weight of 500 or less, such as lenglycol, glycerin, trimethylolpropane, and pentaerythritol. In addition, lactone-based polyester polyols obtained from ring-open polymerization of cyclic ester (so-called lactone) monomers such as ε-caprolactone, alkyl-substituted ε-caprolactone, δ-valerolactone, and alkyl-substituted δ-valerolactone can be mentioned. Further, a polyester-amide polyol obtained by substituting a small molecule polyamine such as hexamethylenediamine, isophorone diamine, or monoethanolamine or a low molecular weight amino alcohol as a part of the low molecular weight polyol can also be used.

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

<Polycarbonate polyol>
Specific examples of the polycarbonate polyol 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-dimethylolheptan, diethylene glycol, dipropylene glycol , Neopentyl glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, dimer acid diol, ethylene oxide or propylene oxide adduct of bisphenol A, bis (β-hydroxyethyl) benzene, xylylene glycol, One or more low-molecular-weight polyols such as glycerin, trimethylolpropane, and pentaerythritol, dialkyl carbonates such as dimethyl carbonate and diethyl carbonate, alkylene carbonates such as ethylene carbonate and propylene carbonate, diphenyl carbonate, dinaphthyl carbonate, and dianthryl. Examples thereof include those obtained from a dealcoholization reaction or a dephenolization reaction with diaryl carbonates such as carbonate, diphenanthryl carbonate, diindanyl carbonate, and tetrahydronaphthyl carbonate.

Further, a polyol obtained by transesterification reaction of a polycarbonate polyol, a polyester polyol and a low molecular weight polyol can also be preferably used.

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

<Acrylic polyol>
Examples of the acrylic polyol include an acrylic acid ester and / or a methacrylic acid ester [hereinafter referred to as (meth) acrylic acid ester], an acrylic acid hydroxy compound having at least one hydroxyl group in the molecule which can be a reaction point, and / or a methacrylic acid. Examples thereof include a hydroxy compound [hereinafter referred to as (meth) acrylic acid hydroxy compound] and a polymerization initiator obtained by copolymerizing an acrylic monomer using heat energy, light energy such as ultraviolet rays or electron beams.

<(Meta) acrylic acid ester>
Specific examples of the (meth) acrylic acid ester include alkyl esters having 1 to 20 carbon atoms. Specific examples of such (meth) acrylic acid ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and pentyl (meth) acrylate. (Meta) such as (meth) hexyl acrylate, -2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate. Acrylic acid alkyl ester; ester of (meth) acrylic acid with alicyclic alcohol such as cyclohexyl (meth) acrylate; (meth) acrylic acid aryl ester such as (meth) phenyl acrylate, benzyl (meth) acrylate. Can be mentioned. Such (meth) acrylic acid esters may be used alone or in combination of two or more.

<(Meta) hydroxy acrylate compound>
Specific examples of the (meth) hydroxy acrylate compound include at least one hydroxyl group in the molecule that can serve as a reaction point with polyisocyanate, and specifically, 2-hydroxyethyl acrylate and 2-hydroxy. Examples thereof include hydroxyacrylate compounds such as propyl acrylate, 4-hydroxybutyl acrylate, 3-hydroxy-2,2-dimethylpropyl acrylate and pentaerythritol triacrylate. Examples thereof include hydroxymethacrylic acid compounds such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 3-hydroxy-2,2-dimethylpropyl methacrylate and pentaerythritol trimethacrylate. These (meth) hydroxy acrylate compounds may be used alone or in combination of two or more.

<Silicone polyol>
Specific examples of the silicone polyol include a vinyl group-containing silicone compound obtained by polymerizing γ-methacryloxypropyltrimethoxysilane and the like, and α, ω-dihydroxypolydimethylsiloxane, α, which has at least one terminal hydroxyl group in the molecule. Examples thereof include polysiloxanes such as ω-dihydroxypolydiphenylsiloxane.

<Castor oil-based polyol>
Specific examples of castor oil-based polyols include linear or branched polyester polyols obtained by reacting castor oil fatty acids with polyols. Further, dehydrated castor oil, partially dehydrated partially dehydrated castor oil, and hydrogenated castor oil can also be used.

<Fluorine-based polyol>
Specific examples of the fluorine-based polyol are linear or branched polyols obtained by a copolymerization reaction containing a fluorine-containing monomer and a monomer having a hydroxy group as essential components. Here, the fluorine-containing monomer is preferably a fluoroolefin, for example, tetrafluoroethylene, chlorotrifluoroethylene, trichlorofluoroethylene, hexafluoropropylene, vinylidene fluoride, vinyl fluoride, trifluoromethyltrifluoroethylene. Can be mentioned. Examples of the monomer having a hydroxyl group include hydroxyalkyl vinyl ether such as hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether and cyclohexanediol monovinyl ether, hydroxyalkyl allyl ether such as 2-hydroxyethyl allyl ether, and vinyl hydroxyalkyl crotonate. Hydroxy group-containing carboxylic acid vinyl such as, or a monomer having a hydroxyl group such as an allyl ester can be mentioned.

Further, the polyol preferably has an active hydrogen group number (average number of functional groups) of 1.9 to 6.0 in one molecule. If the number of active hydrogen groups is less than the lower limit, the physical properties of the coating film may deteriorate. Further, if it exceeds the upper limit value, the adhesion may be lowered.

The number average molecular weight of the polyol is preferably in the range of 750 to 50,000. If it is less than the lower limit value, the adhesion may be lowered, and if it exceeds the upper limit value, the solubility in a low-polarity organic solvent may be lowered or the adhesion may be lowered.

The proportion of the polyisocyanate composition of the two-component coating composition and the polyol 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 =. It is preferable to mix so that the isocyanate group / hydroxyl group is 0.5 to 2.5. If it is less than the lower limit, the number of hydroxyl groups becomes excessive, which may lead to a decrease in adhesion. In addition, the crosslink density may decrease, the durability may decrease, and the mechanical strength of the coating film may decrease. If it exceeds the upper limit, the isocyanate group becomes excessive and reacts with the moisture in the air, which may cause swelling of the coating film and a decrease in adhesion due to the swelling.

Examples of the organic solvent used as the diluting solvent include ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate, acetic acid-n-butyl and cellosolve acetate, alcohols such as butanol and isopropyl alcohol, and toluene. , Xylene, cyclohexane, mineral spirit, hydrocarbons such as naphtha, etc., can be appropriately selected and used according to the purpose and application. These solvents may be used alone or in combination of two or more.

Further, as the two-component coating composition, a known urethanization catalyst can be appropriately used in consideration of pot life, curing conditions, working conditions and the like. Specifically, an organometallic compound such as dibutyltin diacetate, dibutyltin dilaurate, or dioctyltin dilaurate, an organic amine such as triethylenediamine or triethylamine, or a salt thereof is selected and used. These catalysts can be used alone or in combination of two or more.

The curing conditions of the two-component 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. It is preferable to have.

The two-component coating composition obtained by the present invention may contain, if necessary, an antioxidant such as 2,6-di-tert-butyl-4-methylphenol, an ultraviolet absorber, a pigment, a dye, and the like. Additives such as solvents, flame retardants, hydrolysis inhibitors, lubricants, plasticizers, fillers, antistatic agents, dispersants, catalysts, storage stabilizers, surfactants, leveling agents and the like can be appropriately added.

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

Here, the adherend is not particularly limited, and stainless steel, phosphoric acid-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, phenol resin , Melamine resin, polyacetal resin, chlorinated polyolefin resin, polyolefin resin, polyamide resin, polyether ether ketone resin, polyphenylene sulfide resin, NBR resin, chloroprene resin, SBR resin, 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 having a coating layer that can be intermediately formed on the surface of the adherend can be used.

Since the film thickness of the coating film formed on the surface layer of the adherend is excellent in recoatability and durability, a film thickness of at least 10 μm may be formed on the adherend. If the film thickness is less than 10 μm, the durability is lowered, and the coating film may be torn due to impact.

Since the polyisocyanate composition of the present invention has a very low viscosity, high solid differentiation is possible and the amount of organic solvent can be reduced when it is used as a two-component coating composition.

As described above, the polyisocyanate composition of the present invention and the two-component coating composition are suitably used for automobile coating applications.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to the following Examples.

<Synthesis of polyisocyanate composition>
<Example 1>
990 g of hexamethylene diisocyanate (manufactured by Tosoh Corporation, NCO content: 49.9% by mass, hereinafter referred to as HDI) and 990 g of hexamethylene diisocyanate (manufactured by Tosoh Corporation, hereinafter referred to as HDI) in a 1-liter capacity four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube 10 g of methanol was charged, and the mixture was heated to 40 ° C. with stirring to carry out a urethanization reaction for 1 hour. After that, the temperature was raised to 60 ° C., 0.85 g of dodecyltrimethylammonium methyl carbonate (diluted with 10% 2-ethylhexanol), which is an isocyanurate-forming catalyst, was added to the reaction solution, and a predetermined reaction conversion rate was obtained at 70 ° C. After the reaction was carried out until the above temperature was reached, 0.11 g of an acidic phosphoric acid ester (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) as a reaction terminator was added, and the terminator reaction was carried out at 50 ° C. for 1 hour. Here, excess HDI was removed from the reaction product by thin film distillation (conditions: 140 ° C., 0.04 kPa), and the NCO content was 21.9% by mass, the viscosity (25 ° C.) was 415 mPa · s, and the free HDI content was 0. 250 g of 2 mass% modified polyisocyanate P-1 was obtained. When the modified polyisocyanate P-1 was measured by NMR, the molar ratio of the isocyanurate group to the allophanate group was 59/41. Moreover, when GPC measurement was performed, the uretdione form in all the components was 1.8%.

<NMR: Measurement of allophanate group / isocyanurate group / urethane group content>
(1) Measuring device: ECX400M (manufactured by JEOL Ltd., 1H-NMR)
(2) Measurement temperature: 23 ° C
(3) Sample concentration: 0.1 g / 1 ml
(4) Number of integrations: 16
(5) Relaxation time: 5 seconds (6) Solvent: Deuterium dimethyl sulfoxide (7) Chemical shift criterion: Hydrogen atom signal of methyl group in deuterium dimethyl sulfoxide (2.5 ppm)
(8) Evaluation method: Bonding from the area ratio of the signal of the hydrogen atom bonded to the nitrogen atom of the allophanate group near 8.5 ppm and the signal of the hydrogen atom of the methylene group adjacent to the nitrogen atom of the nurate group near 3.7 ppm. Measure the content of groups

<Measurement of uretdione concentration>
GPC measurement similar to the number average molecular weight measurement was performed, and the peak area% corresponding to twice the molecular weight of diisocyanate was defined as the uretdione body weight.

<GPC: Measurement of molecular weight>
(1) Measuring instrument: HLC-8220 (manufactured by Tosoh Corporation)
(2) Column: TSKgel (manufactured by Tosoh)
・ G3000H-XL
・ G2500H-XL
-G2000H-XL, G1000H-XL
(3) Carrier: THF (tetrahydrofuran)
(4) Detector: RI (refractive index) detector (5) Temperature: 40 ° C
(6) Flow velocity: 1.000 ml / min
(7) Calibration curve: Standard polystyrene (manufactured by Tosoh Corporation)
F-80 (Molecular weight: 7.06 × 105, Molecular weight distribution: 1.05)
F-20 (molecular weight: 1.90 x 105, molecular weight distribution: 1.05)
F-10 (Molecular weight: 9.64 × 104, Molecular weight distribution: 1.01)
F-2 (Molecular weight: 1.81 × 104, Molecular weight distribution: 1.01)
F-1 (Molecular weight: 1.02 × 104, Molecular weight distribution: 1.02)
-A-5000 (Molecular weight: 5.97 × 103, Molecular weight distribution: 1.02)
-A-2500 (Molecular weight: 2.63 × 103, Molecular weight distribution: 1.05)
A-500 (Molecular weight: 5.0 × 102, Molecular weight distribution: 1.14)
(8) Sample solution concentration: 0.5% THF solution

<Examples 2 to 6, reference example >
Synthesis was carried out under the conditions shown in Table 1, and each modified polyisocyanate was obtained in the same procedure as in Example 1.

<Comparative example 1>
HDI996g and 4g of methanol were placed in a 1-liter four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube, and these were heated to 50 ° C. with stirring to form isocyanurate and uretdione. When 1.4 g of trioctylphosphine as a catalyst was added and the reaction was carried out at 50 ° C. until a predetermined reaction conversion rate was reached, 2.0 g of p-menthane hydroperoxide as a reaction terminator was added and 50. A stop reaction was carried out at ° C. for 2 hours. Excess HDI was removed from this reaction product by thin film distillation (conditions: 125 ° C., 0.04 kPa), NCO content 22.0% by mass, viscosity (25 ° C.) 100 mPa · s, free HDI content 0.3. 250 g of modified polyisocyanate H-1 by mass% was obtained. When the modified polyisocyanate H-1 was measured by NMR, the molar ratio of the isocyanurate group to the allophanate group was 95/5. Moreover, when GPC measurement was performed, the uretdione form in all the components was 40%.

<Comparative example 2>
970 g of HDI and 30 g of methanol were placed in a 1-liter four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube, and these were heated to 85 ° C. while stirring for a 3-hour urethanization reaction. Was done. Then, 0.1 g of zirconium octylate, which is an allophanation catalyst, is added to this reaction solution, and the reaction is carried out at 110 ° C. until a predetermined reaction conversion rate is reached, and then an acidic phosphate ester (JP), which is a reaction terminator. -508, manufactured by Johoku Chemical Industry Co., Ltd.) 0.1 g was added, and a stop reaction was carried out at 50 ° C. for 1 hour. Excess HDI was removed from this reaction product by thin film distillation (conditions: 140 ° C., 0.04 kPa), NCO content was 20.1% by mass, viscosity (25 ° C.) was 100 mPa · s, and free HDI content was 0.1. 300 g of modified polyisocyanate H-2 by mass was obtained. When the modified polyisocyanate H-2 was measured by NMR, the molar ratio of the isocyanurate group to the allophanate group was 2/98. Moreover, when GPC measurement was performed, the uretdione form in all the components was 1.0%.

<Comparative example 3>
A 1-liter-capacity four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube is charged with 997 g of HDI, 2 g of 1,3-butanediol, and 1 g of phenol, and is an isocyanurate-forming catalyst. 0.85 g of dodecyltrimethylammonium methyl carbonate (diluted by 10% 2-ethylhexanol) was charged and reacted at 50 ° C. for 1.5 hours. Immediately after that, the temperature was raised to 65 ° C. and the reaction was carried out for 1 hour. 11 g was added and a stop reaction was carried out for 1 hour. Excess HDI was removed from this reaction product by thin film distillation (conditions: 130 ° C., 0.04 kPa), NCO content was 23.2% by mass, viscosity (25 ° C.) was 1,180 mPa · s, and free HDI content was 0. .. Obtained 130 g of modified polyisocyanate H-3 in an amount of 2% by mass. Infrared absorption analysis (IR) of the modified polyisocyanate H-3 confirmed that the isocyanurate group was strongly absorbed and that the allophanate group was weakly absorbed. When the modified polyisocyanate H-3 was measured by NMR, the molar ratio of the isocyanurate group to the allophanate group was 90/10. Moreover, when GPC measurement was performed, the uretdione form in all the components was 1.5%.

<Comparative example 4>
HDI 995 g and 1,3-butanediol 5 g were placed in a 1-liter capacity four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube, and these were heated to 60 ° C. while stirring. The urethanization reaction was carried out for 1 hour. To this reaction solution, 0.85 g of dodecyltrimethylammonium methyl carbonate (diluted with 10% 2-ethylhexanol), which is an isocyanurate-forming catalyst, was added, and the reaction was carried out at 70 ° C. to a predetermined reaction conversion rate, and then the reaction was stopped. 0.11 g of an acidic phosphate ester (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) as an agent was added, and a termination reaction was carried out at 50 ° C. for 1 hour. Excess HDI was removed from this reaction product by thin film distillation (conditions: 140 ° C., 0.04 kPa), NCO content was 22.3% by mass, viscosity (25 ° C.) was 1500 mPa · s, and free HDI content was 0.2. 250 g of modified polyisocyanate H-4 by mass was obtained. When the modified polyisocyanate H-4 was measured by NMR, the molar ratio of the isocyanurate group to the allophanate group was 60/40. Moreover, when GPC measurement was performed, the uretdione form in all the components was 1.1%.

<Comparative example 5>
990 g of HDI and 10 g of butanol were placed in a 1-liter-capacity four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube, and these were heated to 40 ° C. while stirring for 1 hour. Was done. After that, the temperature was raised to 60 ° C., 0.85 g of dodecyltrimethylammonium methyl carbonate (diluted with 10% 2-ethylhexanol), which is an isocyanurate-forming catalyst, was added to the reaction solution, and a predetermined reaction conversion rate was obtained at 70 ° C. After the reaction was carried out up to, 0.11 g of an acidic phosphoric acid ester (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) as a reaction terminator was added, and the terminator reaction was carried out at 50 ° C. for 1 hour. Excess HDI was removed from this reaction product by thin film distillation (conditions: 140 ° C., 0.04 kPa), NCO content was 22.1% by mass, viscosity (25 ° C.) was 350 mPa · s, and free HDI content was 0.2. 170 g of modified polyisocyanate H-5 by mass% was obtained. When the modified polyisocyanate H-5 was measured by NMR, the molar ratio of the isocyanurate group to the allophanate group was 37/63. Moreover, when GPC measurement was performed, the uretdione form in all the components was 1.6%.

<Comparative Examples 6 and 7> were synthesized under the conditions shown in Table 1 to obtain each modified polyisocyanate by the same procedure as in Comparative Example 5.

<Preparation of two-component paint composition>
As shown in Table 2, the amount of the polyol and the obtained polyisocyanate composition were blended so that R (molar ratio of isocyanate group / hydroxyl group) = 1, and titanium oxide (trade name: trade name:) was further blended as a pigment. A two-component coating composition (S-1 to S-14) was prepared by blending CR-90, crystal structure: rutile type, manufactured by Ishihara Sangyo Co., Ltd., and an organic solvent so that the solid content was 50% (S-1 to S-14). The unit of compounding amount is g). Here, an acrylic polyol (trade name: Acrydic A-801, hydroxyl value: 50 mgKOH / g, solid content: 50%, manufactured by DIC Corporation) is used as the polyol, and butyl acetate is used as the organic solvent. Prepared.

<Painting method and preparation of test pieces>
The prepared two-component coating composition is applied to an arbitrary film thickness using a steel plate (JIS G3141, trade name: SPCC-SB, treatment method: PF-1077, manufactured by PALTEK Corporation) degreased with methyl ethyl ketone. did. Then, it was heat-treated in a dryer at a temperature of 60 ° C. for 1 hour, and then cured in an environment of a temperature of 23 ° C. and a relative humidity of 50% for 7 days to obtain coated coating films S-1 to S-14.

<Weather resistance>
An accelerated test of weather resistance was carried out on a coating film prepared from the paints obtained by the formulations shown in Table 2 under the following conditions.
-Test equipment: QUV (manufactured by Q-LAB)
・ Lamp: EL-313
・ Illuminance: 0.59w / m2
・ Λmax: 313nm
1 cycle: 12 hours [UV irradiation: 8 hours (temperature 70 ° C), condensation: 4 hours (temperature 50 ° C)]
・ Test time: 864 hours <Evaluation criteria>
According to JIS Z8741, the glossiness at 60 ° was measured with a haze-gloss reflect meter, and the gloss retention rate was calculated. Gloss retention is calculated by the following formula: Gloss retention (%) = 100 x Gloss after weather resistance test ÷ Initial gloss (Equation)
・ 50% or more: (Evaluation: A)
・ 45% or more and less than 49%: (Evaluation: B)
・ Less than 40%: (Evaluation: C)

<Permeability evaluation>
As a primer for the base, an aqueous acrylic polyol (product name: Barnock WE-303, manufactured by DIC Corporation) is applied in the form of a PP plate using an applicator, pre-dried at room temperature for 40 minutes, and then 20 in a dryer at 60 ° C. A minute heat treatment was performed. Further, the two-component coating composition prepared in Table 2 was applied over the primer using an applicator, pre-dried at room temperature for 15 minutes, and then heat-treated in a dryer at 90 ° C. for 30 minutes. After that, the coating film was peeled off from the PP plate, and the coated surface on the primer side was measured by IR.
<Evaluation criteria>
Based on the peak absorbance of the measured IR spectrum with a wave number of 700, the absorbance of the peak with a wave number of 2270 was measured, and the absorbance ratio was calculated by the following formula.
(Absorbance of peak with wavenumber 2270 / Absorbance of peak with wavenumber 700) x 1000 (Equation)
1.0 or higher: A
Less than 1.0: B

<Adhesion evaluation>
The two-component coating composition prepared in Table 2 was applied to an acrylic plate using an applicator so as to have an arbitrary film thickness. Then, it was cured in an environment of a temperature of 23 ° C. and a relative humidity of 50% for 1 hour, and heat-treated at 80 ° C. for 10 hours to obtain a coated coating film.
<Evaluation criteria>
The obtained coating film was subjected to an adhesion test by a cross-cut method according to JIS K5600-5-6.
Classification 0 to 1: A
Classification 2-5: B

Claims (5)

Hexamethylene diisocyanate and 1 or 2 carbon atoms in the presence of a quaternary ammonium salt having a cation structure of octyltrimethylammonium or dodecyltrimethylammonium and an anion structure of methyl carbonate as an allophanate isocyanurate-forming catalyst. Polyisocyanate obtained by reacting with monoalcohol. The polyisocyanate according to claim 1, wherein the molar ratio of the allophanate group / isocyanurate group in the polyisocyanate is 50/50 to 20/80. The polyisocyanate according to claim 1 or 2, wherein the amount of uretdione in the polyisocyanate is 5% or less as a peak area in gel permeation chromatography measurement, and the viscosity at 25 ° C. is 500 mPa · s or less. Hexamethylene diisocyanate and hexamethylene diisocyanate with one or two carbon atoms as an allophanate isocyanurate-forming catalyst in the presence of a quaternary ammonium salt having a cation structure of octyltrimethylammonium or dodecyltrimethylammonium and an anion structure of methyl carbonate . A method for producing a polyisocyanate, which comprises reacting with a monoalcohol. A two-component automobile paint composition containing the polyisocyanate and the polyol according to any one of claims 1 to 3.