JP2014172941A - Block isocyanate and coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a block isocyanate haing relatively long pot life, excellent in low temperature curing property, and further little in residual amount of a block agent after curing, and to provide a coating composition obtained by using the block isocyanate.SOLUTION: A polyisocyanate compound and a block agent represented by the general formula (1) are reacted to obtain a block isocyanate. (1), where R1 to R5 are same or different and represent a linear or cyclic alkyl group or a phenyl group, two or more of R1 to R3 may form one or more cyclic alkyl group, and R4 and R5 may form one or more cyclic alkyl group.

Description

  The present invention relates to a blocked isocyanate and a coating composition, and particularly relates to a blocked isocyanate used as a curing agent and a coating composition containing the blocked isocyanate.

  Block isocyanate is isocyanate that dissociates upon heating and the isocyanate group is regenerated, and has a long pot life and excellent processability. Therefore, polyol components (main agent) and isocyanate components (curing agents) such as paints and adhesives are used. As a curing agent for polyurethane resins obtained by curing and.

  As such a blocked isocyanate, for example, a blocked isocyanate obtained by reacting a polyol-modified polyisocyanate with a blocking agent composed of a secondary amine has been proposed. More specifically, for example, a blocked isocyanate obtained by reacting a blocking agent such as 2,6-dimethylpiperidine and diisopropylamine with a prepolymer obtained by the reaction of a polycarbonate diol and diphenylmethane diisocyanate has been proposed ( For example, see Patent Document 1 (Examples 1 and 2).)

  In addition to the above, as a blocked isocyanate, for example, a blocked isocyanate obtained by reacting polyisocyanate with a blocking agent composed of a secondary amine and a hydrophilizing agent has also been proposed. In addition, as such a blocking agent, more specifically, for example, a blocking agent represented by the following formula (2) obtained by adding tert-butylamine to crotonic acid methyl ester and reacting it has been proposed. (For example, see Patent Document 2 (Example 6).)

JP 2003-48950 A Special table 2007-519964 gazette

  On the other hand, when a blocked isocyanate is used as a curing agent, it is usually necessary to dissociate (deprotect) the blocking agent by heating and cure it. In recent years, from the viewpoint of reducing energy and cost, It is required to dissociate the blocking agent at a low temperature, that is, low temperature curability.

  However, the blocked isocyanate obtained using the above blocking agent needs to be heated to a relatively high temperature (for example, 100 ° C. or higher) at the time of curing, and the low-temperature curability is not sufficient. In the case of curing at a low temperature, the blocking agent tends to remain without volatilizing, and the physical properties after curing may be poor.

  In addition, when such a blocked isocyanate is used as a curing agent for curing a polyol component or the like (main agent), a long pot life is required from the viewpoint of workability during use.

  An object of the present invention is to provide a blocked isocyanate having a relatively long pot life and excellent in low-temperature curability and having a small residual amount of the blocked agent after curing, and a coating composition obtained using the blocked isocyanate To provide things.

  In order to achieve the above object, the blocked isocyanate of the present invention is obtained by reacting a polyisocyanate compound and a blocking agent represented by the following general formula (1).

(Wherein R1 to R5 are the same or different from each other, and represent a chain or cyclic alkyl group or a phenyl group. Also, two or more of R1 to R3 form one or more cyclic alkyl groups. R4 to R5 may form one or more cyclic alkyl groups.
In the blocked isocyanate of the present invention, it is preferable that the polyisocyanate compound contains an aliphatic polyisocyanate and an alicyclic polyisocyanate.

  In the blocked isocyanate of the present invention, in the general formula (1), the total number of carbon atoms of R1 to R5 is preferably 12 or less.

  In the blocked isocyanate of the present invention, in the general formula (1), it is preferable that R1 to R3 are all methyl groups.

  In the blocked isocyanate of the present invention, it is preferable that R4 and R5 in the general formula (1) form a cyclic alkyl group.

  Moreover, the coating composition of this invention is characterized by containing said blocked isocyanate and a polyol compound.

  The blocked isocyanate of the present invention has a relatively long pot life, is excellent in low-temperature curability, and has a small amount of remaining blocking agent after curing. Therefore, the coating composition of the present invention is excellent in workability at the time of use, can be reduced in energy and cost, and is excellent in physical properties after curing.

  The blocked isocyanate of the present invention can be obtained by reacting a polyisocyanate compound and a blocking agent (described later).

  Examples of the polyisocyanate compound include polyisocyanate monomers and polyisocyanate derivatives.

  Examples of the polyisocyanate monomer include polyisocyanates such as aromatic polyisocyanates, araliphatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates.

  Examples of the aromatic polyisocyanate include tolylene diisocyanate (2,4- or 2,6-tolylene diisocyanate or a mixture thereof) (TDI), phenylene diisocyanate (m-, p-phenylene diisocyanate or a mixture thereof), 4, 4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate (NDI), diphenylmethane diisocyanate (4,4'-, 2,4'- or 2,2'-diphenylmethane diisocyanate or mixtures thereof) (MDI), Examples include aromatic diisocyanates such as 4,4′-toluidine diisocyanate (TODI) and 4,4′-diphenyl ether diisocyanate.

  Examples of the araliphatic polyisocyanate include xylylene diisocyanate (1,3- or 1,4-xylylene diisocyanate or a mixture thereof) (XDI), tetramethylxylylene diisocyanate (1,3- or 1,4-tetra). Methyl xylylene diisocyanate or a mixture thereof (TMXDI), aromatic aliphatic diisocyanates such as ω, ω′-diisocyanate-1,4-diethylbenzene, and the like.

  Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate (tetramethylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate), 1 , 5-pentamethylene diisocyanate (PDI), 1,6-hexamethylene diisocyanate (HDI), 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanate methyl capate Group diisocyanate and the like.

Examples of the alicyclic polyisocyanate include 1,3-cyclopentane diisocyanate, 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate), and 3-isocyanatomethyl-3. , 5,5-trimethylcyclohexylisocyanate (isophorodiisocyanate) (IPDI), methylenebis (cyclohexylisocyanate) (4,4'-, 2,4'- or 2,2'-methylenebis (cyclohexylisocyanate, these Trans, Trans - body, Trans, Cis body, Cis, Cis body, or mixtures _thereof)) (H 12 _MDI), methylcyclohexane diisocyanate (methyl-2,4-cyclohexane Isocyanate, methyl-2,6-cyclohexane diisocyanate), norbornane diisocyanate (various isomers or mixtures thereof) (NBDI), bis (isocyanatomethyl) cyclohexane (1,3- or 1,4-bis (isocyanatomethyl) cyclohexane Or a mixture thereof) (H ₆ XDI) and the like.

  These polyisocyanate monomers can be used alone or in combination of two or more.

  Examples of the polyisocyanate derivative include a multimer (for example, dimer, trimer (for example, isocyanurate-modified product, iminooxadiazinedione-modified product), pentamer, 7) of the polyisocyanate monomer described above. ), Allophanate-modified products (for example, allophanate-modified products produced from the reaction of the above-described polyisocyanate monomer and a low molecular weight polyol described below), polyol-modified products (for example, polyisocyanate monomer and below-mentioned). Polyol modified products (alcohol adducts, etc.) produced by reaction with low molecular weight polyols, biuret modified products (for example, biuret modified products produced by reaction of the above polyisocyanate monomer with water or amines, etc.) ), Modified urea (for example, the above-mentioned polyisocyanate monomer and diamine) Urea-modified products produced by the reaction), oxadiazine trione-modified products (for example, oxadiazine trione produced by the reaction of the above-mentioned polyisocyanate monomer and carbon dioxide gas), carbodiimide-modified products (the above-mentioned polyisocyanate). Carbodiimide modified products produced by decarboxylation condensation reaction of monomers), uretdione modified products, uretonimine modified products, and the like.

  Furthermore, examples of the polyisocyanate derivative include polymethylene polyphenyl polyisocyanate (crude MDI, polymeric MDI).

  These polyisocyanate derivatives can be used alone or in combination of two or more.

  These polyisocyanate compounds can be used alone or in combination of two or more.

  When two or more types of polyisocyanate compounds are used in combination, for example, at the time of production of blocked isocyanate, two or more types of polyisocyanate compounds may be reacted simultaneously, and each polyisocyanate compound is used individually. The obtained blocked isocyanate may be mixed.

  Preferred examples of the polyisocyanate compound include aliphatic polyisocyanates and derivatives thereof, and alicyclic polyisocyanates and derivatives thereof. More preferably, a combination thereof (that is, the polyisocyanate compound is aliphatic polyisocyanate and alicyclic). And polyisocyanate).

  If the above polyisocyanate compound is used, a blocked isocyanate having a relatively long pot life and excellent in low-temperature curability can be obtained.

  In the present invention, the blocking agent is represented by the following general formula (1).

(Wherein R1 to R5 are the same or different from each other, and represent a chain or cyclic alkyl group or a phenyl group. Also, two or more of R1 to R3 form one or more cyclic alkyl groups. R4 to R5 may form one or more cyclic alkyl groups.
In the general formula (1), R1 to R5 are the same as or different from each other, and represent a chain or cyclic alkyl group or a phenyl group.

  Examples of the chain alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, tert-pentyl, hexyl, heptyl, octyl, nonyl, isononyl, decyl, dodecyl. And straight chain or branched alkyl groups having 1 to 12 carbon atoms.

  Examples of the cyclic alkyl group include cycloalkyl groups having 3 to 12 carbon atoms such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, and cyclododecyl.

  In the general formula (1), two or more of R1 to R3 may form one or more cyclic alkyl groups.

  Examples of the cyclic alkyl group formed by R1 to R3 include the above cycloalkyl groups having 3 to 12 carbon atoms. The cyclic alkyl group may be formed by, for example, R1 and R2, may be formed by R2 and R3, may be formed by R1 and R3, and is formed by all of R1 to R3. It may be.

  In the general formula (1), R4 to R5 may form one or more cyclic alkyl groups.

  Examples of the cyclic alkyl group formed by R4 to R5 include the aforementioned cycloalkyl group having 3 to 12 carbon atoms.

  The total number of carbon atoms of R1 to R5 in the general formula (1) is usually 5 or more, for example, 15 or less, preferably 12 or less, and more preferably 9 or less.

  When the total number of carbon atoms of R1 to R5 exceeds the above upper limit, the blocking agent may easily remain after curing.

  On the other hand, if the total number of carbon atoms of R1 to R5 is within the above range, the blocking agent can be prevented from remaining after curing, and further has a relatively long pot life and excellent low-temperature curability. Blocked isocyanate can be obtained.

  More specifically, as such a blocking agent, for example, tert-butyl-isopropylamine (total carbon number of R1 to R5 is 5), tert-butyl-sec-butylamine (total carbon number of R1 to R5 is 6), All of R1 to R5 such as 1,1-dimethylpropyl-isopropylamine (total carbon number of R1 to R5 of 6) and 1,1-dimethylpropyl-sec-butylamine (total carbon number of R1 to R5 of 7) are alkyl groups. A blocking agent having 5 to 15 carbon atoms in total of R1 to R5, such as tert-butyl-cyclohexylamine (8 carbon atoms in total from R1 to R5), tert-butyl-cyclooctylamine (total carbon number in R1 to R5) 10), 1,1-dimethylpropyl-cyclohexylamine (total number of carbon atoms of R1 to R5 is 9), 1,1-dimethylpropyl- R1-R3 such as crooctylamine (R1-R5 total carbon number 11) is an alkyl group, and R4-R5 forms a cyclic alkyl group. It is done.

The blocking agent is preferably a blocking agent in which R1 to R3 are all methyl groups in the general formula (1), that is, a blocking agent in which a tert-butyl group is bonded to a nitrogen atom. More specific examples of such blocking agents include tert-butyl-isopropylamine, tert-butyl-sec-butylamine, tert-butyl-cyclohexylamine, and tert-butyl-cyclooctylamine. If R3 is all methyl groups, a blocked isocyanate having excellent low-temperature curability can be obtained.

  The blocking agent is preferably a blocking agent in which R4 and R5 form a cyclic alkyl group in the general formula (1), that is, a blocking agent in which a cyclic alkyl group is bonded to a nitrogen atom. More specifically, examples of such blocking agents include tert-butyl-cyclohexylamine, tert-butyl-cyclooctylamine, 1,1-dimethylpropyl-cyclohexylamine, 1,1-dimethylpropyl-cyclooctylamine. Etc.

  If R4 and R5 form a cyclic alkyl group, a blocked isocyanate having a particularly long pot life can be obtained.

  As the blocking agent, more preferably, in the general formula (1), R1 to R3 are all alkyl groups, particularly preferably methyl groups, and R4 and R5 are cyclic alkyl groups having 3 to 12 carbon atoms. Particularly preferred is a blocking agent forming a cyclohexyl group, and more specifically, tert-butyl-cyclohexylamine.

  When such a blocking agent is used, a blocked isocyanate having a relatively long pot life and excellent in low-temperature curability (for example, less than 100 ° C.) can be obtained.

  These blocking agents can be used alone or in combination of two or more.

  The blocked isocyanate can be obtained, for example, by reacting a polyisocyanate compound with a blocking agent.

  More specifically, for example, the equivalent ratio of the active group that reacts with the isocyanate group in the blocking agent to the isocyanate group of the polyisocyanate compound and the blocking agent (active group / isocyanate group) is, for example, The reaction is carried out at a blending ratio of 0.5 or more, preferably 0.8 or more, for example, 2.0 or less, preferably 1.5 or less, more preferably 1.25 or less.

  More specifically, the blending ratio of such a polyisocyanate compound and a blocking agent is, for example, 5 parts by mass or more, preferably 10 parts by mass or more with respect to 100 parts by mass of the polyisocyanate compound. Yes, for example, 100 parts by mass or less, preferably 90 parts by mass or less.

  As reaction conditions, for example, the reaction temperature is, for example, 0 ° C. or more, preferably 20 ° C. or more under an atmosphere of an inert gas (eg, nitrogen gas, argon gas, etc.) under atmospheric pressure, 80 ° C. or lower, preferably 60 ° C. or lower. The reaction time is, for example, 0.5 hours or more, preferably 1.0 hours or more, for example, 24 hours or less, preferably 12 hours or less.

  In addition, completion | finish of reaction can be judged by employ | adopting infrared spectroscopy etc. and confirming the loss | disappearance or reduction | decrease of an isocyanate group, for example.

  Further, the polyisocyanate compound and the blocking agent can be reacted in the absence of a solvent, but for example, they can be reacted in the presence of a solvent.

  Examples of the solvent include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, nitriles such as acetonitrile, alkyl esters such as methyl acetate, ethyl acetate, butyl acetate, and isobutyl acetate, such as n-hexane. Aliphatic hydrocarbons such as n-heptane and octane, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, aromatic hydrocarbons such as toluene, xylene and ethylbenzene, such as methyl cellosolve acetate, Ethyl cellosolve acetate, methyl carbitol acetate, ethyl carbitol acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, 3-methyl-3-methoxybut Glycol ether esters such as diacetate and ethyl-3-ethoxypropionate, such as diethyl ether, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl Ethers such as ethers, for example, halogenated aliphatic hydrocarbons such as methyl chloride, methylene chloride, chloroform, carbon tetrachloride, methyl bromide, methylene iodide, dichloroethane, such as N-methylpyrrolidone, dimethylformamide, N , N′-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphonylamide and other polar aprotic compounds, and further propylene glycol - like monomethyl ether 2-acetate. These solvents can be used alone or in combination of two or more.

  Thereby, the block polyisocyanate in which the isocyanate group of the polyisocyanate compound was blocked by the blocking agent can be obtained.

  Such a block polyisocyanate has a relatively long pot life and is excellent in low-temperature curability.

  Moreover, such a block polyisocyanate can be used, for example, dissolved in the above-mentioned solvent.

  In the case of dissolving the block polyisocyanate in a solvent, the solid content concentration thereof is, for example, 1% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, for example, 95% by mass or less, Preferably, it is 90 mass% or less.

  And the above-mentioned block isocyanate is used suitably as a hardening | curing agent of the coating composition prepared as a two-component curable polyurethane resin, for example.

  The coating composition of the present invention contains the above-described blocked isocyanate and a polyol compound. In such a coating composition, for example, the curing agent made of the above-mentioned blocked isocyanate and the main agent made of a polyol compound are individually prepared and blended at the time of use.

  Examples of the polyol compound include a low molecular weight polyol and a high molecular weight polyol.

  The low molecular weight polyol is a compound having two or more hydroxyl groups and a number average molecular weight of less than 300, preferably less than 400, such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2,2,2-trimethyl Pentanediol, 3,3-dimethylolheptane, alkane (C7-20) diol, 1,3- or 1,4-cyclohexanedimethanol and mixtures thereof, 1,3- or 1,4-cyclohexanediol and their Mixture, hydrogenated bisphenol A, 1,4-dihydroxy- -Dihydric alcohols such as butene, 2,6-dimethyl-1-octene-3,8-diol, bisphenol A, diethylene glycol, triethylene glycol, dipropylene glycol, such as glycerin, trimethylolpropane, triisopropanolamine Trihydric alcohols such as tetramethylolmethane (pentaerythritol), dihydric alcohols and the like, pentavalent alcohols such as xylitol, such as sorbitol, mannitol, allitol, iditol, dulcitol, altritol, inositol, dipentol Examples include hexavalent alcohols such as erythritol, for example, 7-valent alcohols such as perseitol, and 8-valent alcohols such as sucrose.

  These low molecular weight polyols can be used alone or in combination of two or more.

  The high molecular weight polyol is a compound having two or more hydroxyl groups and a number average molecular weight of 300 or more, preferably 400 or more, and more preferably 500 or more. For example, polyether polyol, polyester polyol, polycarbonate polyol, polyurethane polyol, Examples include epoxy polyols, vegetable oil polyols, polyolefin polyols, acrylic polyols, and vinyl monomer-modified polyols.

  Examples of the polyether polyol include polyoxyalkylene polyol and polytetramethylene ether polyol.

  The polyoxyalkylene polyol is, for example, an addition polymer of alkylene oxide starting from the above-described low molecular weight polyol, aromatic polyamine, aliphatic polyamine or the like.

  Examples of the alkylene oxide include propylene oxide, ethylene oxide, butylene oxide, styrene oxide, and the like. These alkylene oxides can be used alone or in combination of two or more. Of these, propylene oxide and ethylene oxide are preferable. The polyoxyalkylene polyol includes, for example, a random and / or block copolymer of propylene oxide and alkylene oxide such as ethylene oxide.

  Examples of the polytetramethylene ether polyol include a ring-opening polymer obtained by cationic polymerization of tetrahydrofuran, and an amorphous (non-crystalline) obtained by copolymerizing an alkyl-substituted tetrahydrofuran or the above-described dihydric alcohol with a polymerization unit such as tetrahydrofuran. Property) polytetramethylene ether glycol and the like.

  In addition, amorphous (noncrystalline) means that it is liquid at normal temperature (25 ° C.).

  Amorphous polytetramethylene ether glycol is, for example, a copolymer of tetrahydrofuran and alkyl-substituted tetrahydrofuran (for example, 3-methyltetrahydrofuran) (tetrahydrofuran / alkyl-substituted tetrahydrofuran (molar ratio)) = 15 / 85-85 / 15, a number average molecular weight of 500 to 4000, preferably 800 to 2500), for example, a copolymer of tetrahydrofuran and a branched glycol (such as neopentyl glycol) (tetrahydrofuran / branched glycol (molar ratio)) = 15/85 to 85/15, number average molecular weight 500 to 4000, preferably 800 to 2500).

  Examples of the polyester polyol include polycondensates obtained by reacting the above-described low molecular weight polyol and polybasic acid under known conditions.

  Examples of the polybasic acid include oxalic acid, malonic acid, succinic acid, methyl succinic acid, glutaric acid, adipic acid, 1,1-dimethyl-1,3-dicarboxypropane, and 3-methyl-3-ethylglutaric acid. , Azelaic acid, sebacic acid, other saturated aliphatic dicarboxylic acids (C11-13) such as maleic acid, fumaric acid, itaconic acid, other unsaturated aliphatic dicarboxylic acids such as orthophthalic acid, isophthalic acid, terephthalic acid , Toluene dicarboxylic acid, naphthalene dicarboxylic acid, other aromatic dicarboxylic acids such as hexahydrophthalic acid, other alicyclic dicarboxylic acids such as dimer acid, hydrogenated dimer acid, het acid and other carboxylic acids, And acid anhydrides derived from these carboxylic acids, such as oxalic anhydride, succinic anhydride , Maleic anhydride, phthalic anhydride, 2-alkyl (C12-C18) succinic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, and acid halides derived from these carboxylic acids, such as oxalic acid Examples include dichloride, adipic acid dichloride, and sebacic acid dichloride.

  Further, as the polyester polyol, for example, a plant-derived polyester polyol, specifically, a hydroxyl group-containing vegetable oil fatty acid (for example, castor oil fatty acid containing ricinoleic acid, 12-hydroxystearic acid, using the above-described low molecular weight polyol as an initiator, And vegetable oil-based polyester polyols obtained by subjecting a hydroxycarboxylic acid such as hydrogenated castor oil fatty acid and the like to a condensation reaction under known conditions.

  Further, as the polyester polyol, for example, the above-described low molecular weight polyol (preferably dihydric alcohol) is used as an initiator, for example, lactones such as ε-caprolactone and γ-valerolactone, for example, L-lactide, D- Examples thereof include polycaprolactone polyol, polyvalerolactone polyol obtained by ring-opening polymerization of lactides such as lactide, and lactone polyester polyol obtained by copolymerizing the above-described dihydric alcohol.

  As the polycarbonate polyol, for example, a ring-opening polymer of ethylene carbonate using the above-described low molecular weight polyol (preferably a dihydric alcohol) as an initiator, for example, 1,4-butanediol, 1,5-pentanediol, Examples thereof include amorphous polycarbonate polyols obtained by copolymerizing a dihydric alcohol such as 3-methyl-1,5-pentanediol or 1,6-hexanediol with a ring-opening polymer.

  Further, the polyurethane polyol is a ratio in which the equivalent ratio (OH / NCO) of the hydroxyl group (OH) to the isocyanate group (NCO) of the polyester polyol, polyether polyol and / or polycarbonate polyol obtained as described above exceeds 1, By reacting with polyisocyanate, it can be obtained as polyester polyurethane polyol, polyether polyurethane polyol, polycarbonate polyurethane polyol, or polyester polyether polyurethane polyol.

  Examples of the epoxy polyol include an epoxy polyol obtained by a reaction of the above-described low molecular weight polyol with a polyfunctional halohydrin such as epichlorohydrin or β-methylepichlorohydrin.

  Examples of the vegetable oil polyol include hydroxyl group-containing vegetable oils such as castor oil and coconut oil. For example, castor oil polyol, or ester-modified castor oil polyol obtained by reaction of castor oil fatty acid and polypropylene polyol can be used.

  Examples of the polyolefin polyol include polybutadiene polyol and partially saponified ethylene-vinyl acetate copolymer.

  Examples of the acrylic polyol include a copolymer obtained by copolymerizing a hydroxyl group-containing acrylate and a copolymerizable vinyl monomer copolymerizable with the hydroxyl group-containing acrylate.

  Examples of the hydroxyl group-containing acrylate include 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, 2,2-dihydroxymethylbutyl (meth) acrylate, polyhydroxyalkyl maleate, Examples thereof include polyhydroxyalkyl fumarate. Preferably, 2-hydroxyethyl (meth) acrylate etc. are mentioned.

  Examples of the copolymerizable vinyl monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, and s-butyl ( Alkyls such as (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, isononyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl acrylate, etc. (Meth) acrylates (1 to 12 carbon atoms), for example, aromatic vinyl such as styrene, vinyltoluene and α-methylstyrene, for example, vinyl cyanide such as (meth) acrylonitrile, ) Vinyl monomers containing carboxyl groups such as acrylic acid, fumaric acid, maleic acid, itaconic acid, or alkyl esters thereof such as ethylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, hexanediol di (meth) ) Acrylates, oligoethylene glycol di (meth) acrylates, alkane polyol poly (meth) acrylates such as trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, such as 3- (2-isocyanate-2- And vinyl monomers containing an isocyanate group such as propyl) -α-methylstyrene.

  The acrylic polyol can be obtained by copolymerizing these hydroxyl group-containing acrylate and copolymerizable vinyl monomer in the presence of a suitable solvent and polymerization initiator.

  The acrylic polyol includes, for example, silicone polyol and fluorine polyol.

  Examples of the silicone polyol include a modified polysiloxane polyol in which a hydroxyl group is introduced into a dialkylpolysiloxane, and a copolymerizable vinyl monomer in the copolymerization of the acrylic polyol described above, for example, γ-methacryloxypropyltrimethoxysilane. An acrylic polyol in which a silicone compound containing a vinyl group is added.

  As the fluorine polyol, for example, in the copolymerization of the acrylic polyol described above, as the copolymerizable vinyl monomer, for example, an acrylic polyol in which a fluorine compound containing a vinyl group such as tetrafluoroethylene or chlorotrifluoroethylene is blended may be mentioned. .

  The vinyl monomer-modified polyol can be obtained by a reaction between the above-described high molecular weight polyol and a vinyl monomer.

  These high molecular weight polyols can be used alone or in combination of two or more.

  These polyol compounds can be used alone or in combination of two or more.

  The polyol compound is preferably a high molecular weight polyol, more preferably an acrylic polyol.

  And in such a coating composition, at the time of the use, block isocyanate (curing agent) and a polyol compound (main agent) are mix | blended, and a blocking agent is dissociated from block isocyanate.

  In the blending of a blocked isocyanate (curing agent) and a polyol compound (main agent), for example, an organic solvent solution of block isocyanate in bulk (bulk, solid content concentration of 100% by mass) or blocked isocyanate having a solid content concentration of 1% by mass or more. And, for example, a bulk (bulk, solid content: 100%) polyol compound or an organic solvent solution of a polyol compound having a solid content concentration of 1% by mass or more is blended.

  The blending ratio of the blocked isocyanate (curing agent) and the polyol compound (main agent) is, for example, an equivalent ratio of the isocyanate group of the blocked isocyanate (isocyanate group blocked by the blocking agent) to the hydroxyl group of the polyol compound (isocyanate group / active hydrogen). Group) is, for example, 0.05 or more, preferably 0.1 or more, more preferably 0.2 or more, for example, 5 or less, preferably 3 or less, more preferably 2 or less. .

  The dissociation conditions are not particularly limited as long as the blocking agent in the blocked isocyanate is dissociated. Specifically, the dissociation temperature is, for example, 50 ° C. or higher, preferably 70 ° C. or higher. It is less than 120 ° C, preferably less than 100 ° C.

  And by this, while dissociating the blocking agent in blocked isocyanate, the isocyanate group which block isocyanate reproduced | regenerated, and the hydroxyl group of a polyol compound can be made to react, a coating composition can be hardened, and the coating film which consists of polyurethane resins Can be obtained.

  The reaction time under heating conditions of the isocyanate group regenerated by the blocked isocyanate and the hydroxyl group of the polyol compound is, for example, 10 minutes or more, preferably 20 minutes or more, for example, 60 minutes or less, preferably 30 minutes or less. It is. If reaction time is more than the said minimum, hardening reaction will fully advance, and if it is below the said upper limit. Process energy can be reduced.

  Moreover, hardening reaction advances also by making it age | cure | ripen at room temperature (20-30 degreeC). Therefore, when aging at room temperature after the heating process, the above dissociation conditions can be lowered, and the heating time can be further shortened. Furthermore, when there is no restriction | limiting in the time to harden | cure, it can be hardened only by making it age at room temperature (20-30 degreeC), without heating. This is presumed that the blocked agent of the blocked isocyanate of the present invention easily volatilizes even at room temperature (20-30 ° C.), so that the reaction of dissociation equilibrium proceeds to the dissociation side and is cured.

  In such a method, if necessary, for example, a reaction solvent, a catalyst, an epoxy resin, a coating is applied to one or both of the blocked isocyanate (curing agent) and the polyol compound (main agent). Additives such as stability improvers, leveling agents, antifoaming agents, stabilizers such as antioxidants and UV absorbers, plasticizers, surfactants, pigments, fillers, organic or inorganic fine particles, antifungal agents, etc. can do. The compounding amount of the additive is appropriately determined depending on the purpose and application.

  The coating composition has a relatively long pot life and is excellent in workability at the time of use because of the use of the blocked isocyanate having excellent low-temperature curability, and has low energy and low cost. Can be achieved.

  The blocked isocyanate of the present invention is not limited to the above-mentioned polyurethane resin, and can be used as a curing agent for various known resins such as polyolefin resin, polyacrylic resin, and polyester resin.

  Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example. “Part” and “%” are based on mass unless otherwise specified. Moreover, the numerical value of the Example shown below can be substituted for the numerical value (namely, upper limit value or lower limit value) described in embodiment.

Synthesis example 1
7.31 g of tert-butylamine was dissolved in 17.50 g of ethanol. Next, 10.01 g of crotonic acid methyl ester was added to this solution while stirring at room temperature, and the mixture was reacted at 70 ° C. for 72 hours. Thereafter, the solvent is distilled off under reduced pressure, and the precipitate is removed by filtration, so that the compound represented by the following formulas (2) and (3) is mixed at a molar ratio of 17:83 in the form of a crotonic acid alkyl ester block. An agent (hereinafter sometimes abbreviated as CAE) was obtained.

(Preparation of blocked isocyanate)
Example 1
In a 100 mL reactor equipped with a stirrer, a thermometer, a condenser and a nitrogen gas introduction tube, 170N of Takenate, 202.90 g (NCO group: 1.00 mol) at room temperature, 219.762 g of methyl isobutyl ketone (MIBK) as a solvent And mixed well. Thereafter, 126.743 g (1.10 mol) of tert-butyl-isopropylamine (hereinafter sometimes abbreviated as tBiPA) was added as a blocking agent, and the mixture was stirred at room temperature for 5 hours.

  Then, by measuring an FT-IR spectrum, it was confirmed that the isocyanate was blocked, and a blocked isocyanate having a solid content concentration of 60% by mass was obtained.

Examples 2-10, Comparative Examples 1-5
A blocked isocyanate was obtained in the same manner as in Example 1 except that the formulation shown in Table 1 was used.

  The details of the abbreviations in the table are as follows. The abbreviations are the same for the following tables.

Takenate 127N: trimer of bis (isocyanatomethyl) cyclohexane, isocyanate group content 13.5%, manufactured by Mitsui Chemicals Takenate 170N: trimer of hexamethylene diisocyanate, isocyanate group content 20.7%, manufactured by Mitsui Chemicals Takenate 110N: trimethylolpropane adduct of xylylene diisocyanate (polyol-modified product), isocyanate group content 11.5%, manufactured by Mitsui Chemicals Takenate 160N: trimethylolpropane adduct of hexamethylene diisocyanate (polyol-modified product), isocyanate group Content 12.6%, Mitsui Chemicals tBiPA: tert-butyl-isopropylamine, Aldrich tBCHA: tert-butyl-cyclohexylamine, Aldrich TMPDI: 2 2,6,6, -tetramethylpiperidine, Tokyo Chemical Industry DiPA: Diisopropylamine, Tokyo Chemical Industry DMPDI: 2,6-dimethylpiperidine, Tokyo Chemical Industry CAE: Crotonic acid alkyl ester obtained in Synthesis Example 1 Blocking agent (preparation of coating composition)
Example 11
The blocked isocyanate obtained in Example 1 was added to an acrylic polyol (Q182, manufactured by Mitsui Chemicals) solution in which the concentration was adjusted by adding MIBK as a solvent so that the final solid content concentration of the coating composition was 50% by mass. Was added so that the molar ratio of the hydroxyl group of the acrylic polyol and the latent isocyanate group of the block polyisocyanate composition was 1, and the mixture was stirred for 30 minutes to prepare a coating composition.

  Then, the curing temperature, pot life and room temperature curability of the obtained coating composition were evaluated by the following methods. The results are shown in Table 2.

Examples 12-20, Comparative Examples 6-10
A coating composition was prepared in the same manner as in Example 1 except that the formulation shown in Table 2 was used.

  Then, the curing temperature, pot life and room temperature curability of the obtained coating composition were evaluated by the following methods. The results are shown in Table 2.

Evaluation (curing temperature)
The coating composition was applied on a polypropylene (PP) plate with an applicator to a thickness of 250 μm, cured for 30 minutes at a predetermined temperature, and then aged at room temperature for 24 hours. Acetone / methanol = 1/1 (vol. / Vol) It was immersed in a mixed solvent at 23 ° C. for 24 hours.

Then, the mass of the part which did not melt | dissolve in a mixed solvent with respect to the mass before immersing in a mixed solvent was calculated as a gel fraction, and the temperature at which the gel fraction became 60% or more was made into hardening temperature. Those having a curing temperature of 80 ° C. or lower were rated as “◎”, those having a curing temperature of 90 ° C. were evaluated as “○”, and those having a curing temperature of 100 ° C. or higher were evaluated as “X”.
(Pot life evaluation)
After preparing the coating composition, it was stored at 23 ° C., and the number of days until fluidity disappeared when the container was tilted to 90 degrees was observed as the number of days until gelation. Evaluation was made with ◎ indicating that the number of days until gelation was 20 days or more, ◯ indicating less than 19 days and 3 days or more, and ○ indicating less than 3 days.
(Normal temperature curing)
A coating film applied on a polypropylene (PP) plate to a thickness of 250 μm with an applicator and aged for 72 hours at room temperature (23 ° C.) was mixed with acetone / methanol = 1/1 (vol / vol) mixed solvent at 23 ° C. for 24 hours. Soaked for hours.

  Thereafter, the mass of the portion not dissolved in the mixed solvent relative to the mass before dipping in the mixed solvent was calculated as a gel fraction, and ◎, 20% or more and 40% when the gel fraction was 40% or more. Less than 10% and less than 20% were evaluated as Δ, and less than 10% as x.

(Volatilization rate of blocking agent at normal temperature)
tert-Butyl-isopropylamine (tBiPA) was weighed 0.100 g in a pre-measured aluminum petri dish, allowed to stand in the atmosphere (23 ° C.) for 5 minutes, and then re-measured for the mass of volatilized tBiPA. Estimated amount. As a result, all tBiPA was volatilized after 5 minutes.

  On the other hand, when the crotonic acid alkyl ester block agent (CAE) obtained in Synthesis Example 1 was measured in the same manner, 87% by mass after 5 minutes and 38% by mass after 60 minutes remained.

Example 21
A mixed blocked isocyanate was obtained by stirring 20 parts by weight of the blocked isocyanate of Example 4 and 80 parts by weight of the blocked isocyanate of Example 1 at room temperature.

  Next, the resulting mixed blocked isocyanate was added with methyl isobutyl ketone (MIBK) as a solvent so that the solid content concentration of the final coating composition was 50% by mass, and the concentration was adjusted to an acrylic polyol (Q182, Mitsui). A coating composition was prepared by adding to the (chemical) solution such that the molar ratio of the hydroxyl group of the acrylic polyol to the latent isocyanate group of the mixed blocked isocyanate was 1, and stirring for 30 minutes.

  Then, the curing temperature, pot life, and room temperature curability of the obtained coating composition were evaluated by the above methods. The results are shown in Table 3.

Examples 22 to 27, Comparative Examples 11 to 12
A coating composition was prepared in the same manner as in Example 21 except that the formulation shown in Table 3 was used.

  Then, the curing temperature, pot life, and room temperature curability of the obtained coating composition were evaluated by the above methods. The results are shown in Table 3.

  In Table 3, it is described that block isocyanate 1 (BI1) and block isocyanate 2 (BI2) are mixed, and the blending ratio thereof is described as block isocyanate 1 (BI1) / block isocyanate 2 (BI2). .

(Remaining amount of blocking agent after heating)
1.5 g of the blocked isocyanate of Example 1 was weighed in an aluminum petri dish whose mass was measured in advance, heat-treated in an oven at 110 ° C. for 30 minutes, and then the mass was measured again. When the amount of the blocking agent remaining was calculated from the mass change, 32% by mass of the blocking agent remained. The remaining amount was calculated on the assumption that all the solvent was volatilized.

  Moreover, when it measured similarly about the blocked isocyanate of the comparative example 4, the residual amount of the blocking agent was 91 mass%.

Claims (6)

A polyisocyanate compound, and
A blocked isocyanate obtained by reacting a blocking agent represented by the following general formula (1).

(Wherein R1 to R5 are the same or different from each other, and represent a chain or cyclic alkyl group or a phenyl group. Also, two or more of R1 to R3 form one or more cyclic alkyl groups. R4 to R5 may form one or more cyclic alkyl groups. The polyisocyanate compound is
The blocked isocyanate according to claim 1, comprising an aliphatic polyisocyanate and an alicyclic polyisocyanate. In the general formula (1),
The blocked isocyanate according to claim 1 or 2, wherein the total number of carbon atoms of R1 to R5 is 12 or less. In the general formula (1),
The blocked isocyanate according to any one of claims 1 to 3, wherein R1 to R3 are all methyl groups. In the general formula (1),
The blocked isocyanate according to any one of claims 1 to 4, wherein R4 and R5 form a cyclic alkyl group.   A coating composition comprising the blocked isocyanate according to any one of claims 1 to 5 and a polyol compound.