JP2009067966A - Coating agent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating agent capable of forming a coating having excellent rust-preventing properties with a level permitting various base material surfaces not to rust, and which does not cause discoloration (yellowing). <P>SOLUTION: This coating agent comprises a urethane resin (D), dispersed in an aqueous medium, that is produced by reacting a polyol (A) containing at least one selected from the group consisting of an alicyclic structure-containing polyol (a1), a hydrophilic group-containing polyol (a2), a polyester polyol (a3) and a polycarbonate polyol (a4) with an aliphatic polyisocyanate (B) and a chain extender (C). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an aqueous coating agent capable of forming a coating film for the purpose of protecting the surface of various substrates and imparting design properties.

  The coating agent has the role of protecting the surface of the substrate from external factors in addition to the role of imparting design properties to the surface of various substrates. In recent years, there has been a demand for high durability of the coating film to be formed. It is growing. As a coating agent capable of forming a highly durable coating film, for example, a prepolymer obtained by reacting diisocyanate, 1,4-cyclohexanedimethanol, glycol polyether and carboxyl group-containing diol or triol is used. A water-based polyurethane resin for rust prevention obtained by emulsifying with a chain extender is known (for example, see Patent Document 1).

  Here, the rust prevention property is a property that prevents corrosion of the base material caused when the base material containing metal mainly comes into contact with moisture, water, salt water, etc. in the atmosphere, and has been particularly demanded in recent years. One of the physical properties.

  Although the water-based polyurethane resin for rust prevention can form a coating film having excellent rust prevention properties, it has a very high level of rust prevention property in order to further ensure the protection of the substrate. Among the above-mentioned polyurethane resins, the required performance has not been reached one step further, while a coating agent capable of forming a coating film having anticorrosion properties such as the above has been demanded.

  Moreover, the above-mentioned humidity, water, etc. may cause not only corrosion of the base material but also discoloration of the coating film. Since the coating film formed by the coating agent also has the role of imparting design properties to the substrate as described above, it is also desirable that the coating agent can form a coating film that does not cause discoloration as much as possible. ing.

  However, in reality, a coating agent that has excellent anticorrosive properties and can form a coating film that hardly causes discoloration (yellowing) has not yet been found.

JP 2004-256790 A

  The problem to be solved by the present invention is to provide a coating agent that has an excellent anticorrosive property that can prevent the occurrence of rust on the surface of various base materials and that can form a coating film that does not cause discoloration (yellowing). Is to provide.

  As a result of diligent studies to solve the above-mentioned problems, the present inventors have found that a polyurethane resin-containing coating agent in which an aliphatic cyclic structure and a structure derived from a polyester polyol or a polycarbonate polyol coexist can be used for moisture or salt water. The present inventors have found that it is possible to form a coating film that has a very excellent anticorrosion property and can hardly be discolored, which can prevent the corrosion of the base material from the influence of the above.

  That is, the present invention includes an aliphatic cyclic structure-containing polyol (a1), a hydrophilic group-containing polyol (a2), and one or more selected from the group consisting of a polyester polyol (a3) and a polycarbonate polyol (a4). A coating agent comprising a urethane resin (D) obtained by reacting a polyol (A), an aliphatic polyisocyanate (B), and a chain extender (C) in an aqueous medium. It is.

  The coating agent of the present invention is excellent in anticorrosion properties, can form a coating film that hardly causes discoloration, and also has excellent adhesion to a metal substrate or the like.

The best mode for carrying out the invention will be described below.
The coating agent of the present invention comprises at least one selected from the group consisting of an aliphatic cyclic structure-containing polyol (a1), a hydrophilic group-containing polyol (a2), a polyester polyol (a3) and a polycarbonate polyol (a4). The urethane resin (D) obtained by reacting the polyol (A) containing other polyols, if necessary, the aliphatic polyisocyanate (B), and the chain extender (C) is dispersed in an aqueous medium. It is a thing. The coating agent of this invention may contain other components other than the said polyurethane resin as needed.

  First, the urethane resin (D) used in the present invention will be described.

The urethane resin (D) used in the present invention comprises an aliphatic cyclic structure derived from an aliphatic cyclic structure-containing polyol (a1) described later and a polyester polyol (a3) from the viewpoint of forming a coating film excellent in corrosion resistance. And a structure derived from at least one polyol selected from the group consisting of polycarbonate polyol (a4).
The urethane resin (D) has a hydrophilic group for stable dispersion in an aqueous medium, and specifically, a hydrophilic group derived from a hydrophilic group-containing polyol (a2) described later. Have

  Examples of the hydrophilic group contained in the urethane resin (D) include an anionic group, a cationic group, and a nonionic group, and among them, a carboxyl group, a carboxylate group, a sulfonic acid group, a sulfonate group, and the like. It is more preferable to use an anionic group. Moreover, when the said hydrophilic group is an anionic group or a cationic group, it is preferable to exist in the range of 50-1000 mmol / kg with respect to the whole urethane resin (D). Moreover, when a hydrophilic group is a nonionic group, it is preferable to exist in the range of 1-10 mass% with respect to the said polyurethane resin (D).

  As said urethane resin (D), after reacting a polyol (A) and aliphatic polyisocyanate (B) and manufacturing a urethane prepolymer, what made it high molecular weight using the chain extender (C) is used. It is preferable to use it. Specifically, it is preferable to use one having a weight average molecular weight in the range of 5,000 to 200,000 in order to form a coating film having excellent durability such as corrosion resistance.

  The urethane resin (D) includes, for example, an aliphatic cyclic structure-containing polyol (a1) having a molecular weight in the range of 50 to 500, a hydrophilic group-containing polyol (a2), in the absence of a solvent or in the presence of an organic solvent. A polyol (A) containing at least one selected from the group consisting of polyester polyol (a3) and polycarbonate polyol (a4), and other polyols as necessary, and an aliphatic polyisocyanate (B). Then, a urethane prepolymer is produced, and then the hydrophilic group in the urethane prepolymer is neutralized as necessary, and mixed with an aqueous medium to make it aqueous and mixed with a chain extender (C). And can be produced by reacting them.

  Here, as the aliphatic cyclic structure-containing polyol (a1) contained in the polyol (A), for example, 1,4-cyclohexanedimethanol, bis (hydroxymethyl) cyclohexane and the like can be used. It is preferable to use a relatively low molecular weight polyol having a molecular weight of 50 to 500, and using 1,4-cyclohexanedimethanol provides a coating agent capable of forming a coating film with excellent anticorrosion properties. More preferable.

  The aliphatic cyclic structure-containing polyol (a1) is more preferably used in an amount of 5 to 50% by mass based on the whole polyol (A) in order to obtain a coating agent capable of forming a coating film having excellent anticorrosion properties.

  Moreover, as hydrophilic group containing polyol (a2) contained in the said polyol (A), an anionic group containing polyol, a cationic group containing polyol, and a nonionic group containing polyol can be used, for example, It is preferable to use an anionic group-containing polyol.

  As the anionic group-containing polyol, for example, a carboxyl group-containing polyol or a sulfonic acid group-containing polyol can be used.

  Examples of the carboxyl group-containing polyol include 2,2′-dimethylolpropionic acid, 2,2′-dimethylolbutanoic acid, 2,2′-dimethylolbutyric acid, 2,2′-dimethylolvaleric acid, and the like. Among them, it is preferable to use 2,2′-dimethylolpropionic acid. Moreover, the carboxyl group-containing polyester polyol obtained by making the said carboxyl group-containing polyol and various polycarboxylic acids react can also be used.

  Examples of the sulfonic acid group-containing polyol include dicarboxylic acids such as 5-sulfoisophthalic acid, sulfoterephthalic acid, 4-sulfophthalic acid, and 5 [4-sulfophenoxy] isophthalic acid, and salts thereof, and the low molecular weight polyol. Polyester polyol obtained by reacting can be used.

  The anionic groups are preferably partially or wholly neutralized with a basic compound or the like in order to exhibit good water dispersibility.

  Examples of basic compounds that can be used for neutralizing the anionic group include organic amines such as ammonia, triethylamine, and morpholine, alkanolamines such as monoethanolamine and diethylethanolamine, Na, K, Li, and the like. Metals containing can be used. The basic compound is preferably used in the range of basic compound / anionic group = 0.5 to 3.0 (molar ratio) from the viewpoint of improving the water dispersion stability of the resulting coating agent. It is more preferable to use in the range which becomes 0.9-2.0 (molar ratio).

  Further, as the cationic group-containing polyol, for example, a tertiary amino group-containing polyol can be used. Specifically, N-methyl-diethanolamine, a compound having two epoxies in one molecule, and a secondary amine. A polyol obtained by reacting with can be used.

  It is preferable that a part or all of the cationic group is neutralized with an acidic compound such as formic acid, acetic acid, propionic acid, succinic acid, glutaric acid, tartaric acid and adipic acid.

  Further, the tertiary amino group as the cationic group is preferably partly or entirely quaternized. As the quaternizing agent, for example, dimethyl sulfate, diethyl sulfate, methyl chloride, ethyl chloride and the like can be used, and dimethyl sulfate is preferably used.

  Further, as the nonionic group-containing polyol, polyalkylene glycol having a structural unit derived from ethylene oxide can be used.

  The amount of the hydrophilic group-containing polyol (a2) used needs to be determined in consideration of the amount of the hydrophilic group to be imparted in the resulting urethane resin (D), but is generally 0.1 to 10% by mass. It is preferable that

  As the polyol (A), it is important to use at least one selected from the group consisting of polyester polyol (a3) and polycarbonate polyol (a4). In particular, when it is desired to improve the substrate adhesion of the coating film formed using the coating agent of the present invention, it is preferable to use the polyester polyol (a3). When it is desired to improve the durability, the polycarbonate is used. It is preferable to use a polyol (a4).

  The structure derived from the polyester polyol (a3) or the polycarbonate polyol (a4) coexists in the aliphatic cyclic structure derived from the polyol (a1) in the urethane resin (D), so that the coating having excellent anticorrosion properties is obtained. A coating agent capable of forming a film can be obtained.

  The polyester polyol (a3) can be produced by, for example, a method of reacting a low molecular weight polyol and a polycarboxylic acid, a method of ring-opening polymerization reaction of a cyclic ester compound such as ε-caprolactone, or the like.

  Examples of the low molecular weight polyol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and neo. Pentyl glycol, 1,8-octanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (molecular weight 300-6000), dipropylene glycol, tripropylene glycol Bishydroxyethoxybenzene, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, bisphenol A, hydrogenated bisphenol A, hydroquinone and their alkylene oxide adducts. be able to.

  Examples of the polycarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid. Acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, 1,2-bis (phenoxy) ethane-p , P′-dicarboxylic acid, and anhydrides or ester-forming derivatives thereof can be used.

  Moreover, as said polycarbonate polyol (a4), what is obtained by esterifying carbonic acid and an aliphatic polyol etc. can be used, for example. Specifically, diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol or polytetramethylene glycol (PTMG), and dimethyl carbonate And reaction products with diphenyl carbonate, phosgene and the like.

  The polyester polyol (a3) or polycarbonate polyol (a4) is preferably used in an amount of 50 to 95% by mass with respect to the entire polyol (A).

  Moreover, as said polyol (A), you may use other polyols together in addition to said (a1)-(a4).

  As said other polyol, the polyol etc. which do not have an aliphatic cyclic structure, a hydrophilic group, etc. can be used, for example. In addition, although polyether polyol can also be used as said other polyol, since there exists a tendency for durability and base-material adhesiveness to fall, it is preferable not to use as much as possible.

  As the aliphatic polyisocyanate (B) that reacts with the polyol (A), a chain polyisocyanate or a polyisocyanate having an aliphatic cyclic structure can be used. Specifically, diisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, hydrogenated diphenylmethane diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate are used alone or in combination of two or more. Can be used in combination.

  As the aliphatic polyisocyanate (B), it is preferable to use the aliphatic cyclic structure-containing polyisocyanate, which can further improve the corrosion resistance of the coating film formed by the coating agent of the present invention. And discoloration of a coating film can be prevented.

The aliphatic polyisocyanate (B) may be used in combination with an aromatic polyisocyanate as long as the effects of the present invention are not impaired.
Examples of the polyisocyanate include aromatic diisocyanates such as phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate.

  Reaction of the said polyol (A) and aliphatic polyisocyanate (B) should just be a well-known and usual method, for example, the isocyanate which the said aliphatic polyisocyanate (B) with respect to the hydroxyl group which the said polyol (A) has is The group equivalent ratio is preferably 1.05 to 3, more preferably 1.1 to 2.

  Examples of the organic solvent that can be used in producing the urethane resin (D) include ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran and dioxane; acetate esters such as ethyl acetate and butyl acetate; Nitriles: Amides such as dimethylformamide and N-methylpyrrolidone can be used alone or in combination of two or more. In particular, it is preferable to use methyl ethyl ketone or N-methylpyrrolidone because the urethane resin (D) is easily dissolved.

  As the chain extender used when producing the urethane resin (D), polyamine, other active hydrogen atom-containing compounds, and the like can be used.

  Examples of the polyamine include ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4′-dicyclohexylmethanediamine, and 3,3′-. Diamines such as dimethyl-4,4′-dicyclohexylmethanediamine, 1,4-cyclohexanediamine; N-hydroxymethylaminoethylamine, N-hydroxyethylaminoethylamine, N-hydroxypropylaminopropylamine, N-ethylaminoethylamine, Diamines containing one primary amino group and one secondary amino group such as N-methylaminopropylamine; polyamines such as diethylenetriamine, dipropylenetriamine and triethylenetetramine; hydrazine, N Hydrazines such as N′-dimethylhydrazine and 1,6-hexamethylenebishydrazine; dihydrazides such as succinic acid dihydrazide, adipic acid dihydrazide, glutaric acid dihydrazide, sebacic acid dihydrazide, and isophthalic acid dihydrazide; β-semicarbazide propionic acid hydrazide; Semicarbazides such as 3-semicarbazide-propyl-carbazic acid ester and semicarbazide-3-semicarbazide methyl-3,5,5-trimethylcyclohexane can be used.

  Examples of the other active hydrogen-containing compound include ethylene glycol, diethylene recall, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexamethylene glycol, and sucrose. Glycols such as methylene glycol, glycerin and sorbitol; phenols such as bisphenol A, 4,4′-dihydroxydiphenyl, 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenyl sulfone, hydrogenated bisphenol A, hydroquinone , And water can be used alone or in combination of two or more thereof within a range in which the storage stability of the coating agent of the present invention is not lowered.

  The chain extender (C) is preferably used in such a range that the equivalent ratio of the amino group of the polyamine to the excess isocyanate group is 1.9 or less (equivalent ratio). It is more preferable to use in the range of (equivalent ratio). By using the chain extender (C) in the above-described range, it is possible to improve the durability and corrosion resistance of the coating film formed by the resulting coating agent.

  In addition, the urethane resin (D) used in the production of the coating agent of the present invention can be made aqueous, for example, by the following method.

  [Method 1] After neutralizing or quaternizing some or all of the hydrophilic groups of the urethane prepolymer (D ') obtained by reacting the polyol (A) and the aliphatic polyisocyanate (B), water In which the urethane resin (D) is dissolved or dispersed in water by dissolving in water or dispersing in water and then chain extending using the same chain extender as described above.

  [Method 2] Urethane prepolymer (D ′) and a chain extender similar to those described above are charged in a reaction vessel in a batch or divided, and a urethane resin (D) is produced by chain extension reaction, and then obtained. A method of neutralizing or quaternizing some or all of the hydrophilic groups in the obtained polyurethane resin and then adding water to disperse in water.

  In [Method 1] to [Method 2], an emulsifier may be used as necessary. In addition, when water is dissolved or dispersed, a machine such as a homogenizer may be used as necessary.

  Examples of the emulsifier include nonionic emulsifiers such as polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styryl phenyl ether, polyoxyethylene sorbitol tetraoleate, and polyoxyethylene / polyoxypropylene copolymer. Fatty acid salts such as sodium oleate, alkyl sulfate esters, alkyl benzene sulfonates, alkyl sulfosuccinates, naphthalene sulfonates, polyoxyethylene alkyl sulfates, alkane sulfonate sodium salts, sodium alkyl diphenyl ether sulfonates, etc. Anionic emulsifiers; Cationic emulsifiers such as alkylamine salts, alkyltrimethylammonium salts, and alkyldimethylbenzylammonium salts. It is. Among these, from the viewpoint of maintaining the excellent storage stability of the coating agent of the present invention, it is basically preferable to use an anionic or nonionic emulsifier. Moreover, as long as the mixing stability of the coating agent of the present invention can be maintained, for example, a cationic emulsifier and an amphoteric emulsifier may be used in combination.

  Moreover, when manufacturing the coating agent of this invention, you may use a hydrophilic group containing compound as an adjuvant which assists the water dispersibility of a urethane resin (D).

  As such a hydrophilic group-containing compound, an anionic group-containing compound, a cationic group-containing compound, an amphoteric group-containing compound, or a nonionic group-containing compound can be used, but the excellent storage stability of the coating agent of the present invention can be used. From the viewpoint of maintaining, it is preferable to use a nonionic group-containing compound.

  The nonionic group-containing compound includes a group having at least one active hydrogen atom in the molecule and consisting of a repeating unit of ethylene oxide, and a group consisting of a repeating unit of ethylene oxide and another repeating unit of alkylene oxide. A compound having at least one functional group selected from the group can be used.

  For example, polyoxyethylene glycol or polyoxyethylene-polyoxypropylene having a number average molecular weight of 300 to 20,000 containing at least 30% by mass of repeating units of ethylene oxide and containing at least one active hydrogen atom in the polymer Nonionic group-containing compounds such as copolymer glycols, polyoxyethylene-polyoxybutylene copolymer glycols, polyoxyethylene-polyoxyalkylene copolymer glycols or monoalkyl ethers thereof, or polyester polys obtained by copolymerizing these It is possible to use compounds such as ether polyols.

  Moreover, the coating agent of this invention can use various additives together according to a use etc. Examples of such additives include boric acid, phosphoric acid, silane coupling agents, zirconium compounds, oxazoline compounds and various crosslinking agents, filler dispersants, colloidal silica, colloidal alumina, inorganic pigments, anti-blocking agents such as resin beads, Antistatic agents, antifoaming agents, viscosity modifiers, and various leveling agents can be used as long as they do not impair the stability of the paint. Among them, stabilizers having a semicarbazide group, oxidations having a structure derived from phenol It is more preferable to use a combination of an inhibitor and a stabilizer having a structure derived from a hindered amine from the viewpoint of improving weather resistance stability.

  Examples of the stabilizer having a semicarbazide group include burette-tri (hexamethylene-N, N-dimethylsemicarbazide), 1,6-hexamethylenebis (N, N-dimethylsemicarbazide), 1,1,1,1- Tetramethyl-4,4 (methylene-di-P-phenylene) semicarbazide can be used alone or in combination of two or more.

  The stabilizer having a semicarbazide group is preferably used in a range of 0.1 to 5 parts by mass, and used in a range of 0.5 to 2 parts by mass with respect to 100 parts by mass of the urethane resin (D). More preferably. By using a stabilizer having a semicarbazide group in the above-described range, the durability and light resistance of the coating film formed by the coating agent of the present invention can be improved.

  Examples of the antioxidant having a phenol-derived structure include 2,6-di-tert-butyl-4-methylphenol, 2,2′-methylenebis (6-tert-butyl-4-methylphenol), 4 , 4′-butylidenebis (6-t-butyl-3-methylphenol), 4,4′-thiobis (6-t-butyl-3-methylphenol), 3,9-bis [2- [3- (3 -T-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], thiodiethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propyl Lopionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N, N′-hexane-1,6-diylbis [3- (3,5-di-tert-butyl) -4-hydroxyphenyl) propionamide], benzenepropanoic acid, 3,5-bis (1,1-dimethylethyl) -4-hydroxy, C7-C9 side chain alkyl ester, 2,4-dimethyl-6- (1- Methylpentanedecyl) phenol, diethyl [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] phosphonate, 3,3 ′, 3 ″, 5,5 ′, 5 ″- Hexa-tert-butyl-a, a ′, a ″-(methylene-2,4,6-triyl) tri-p-cresol, calcium diethylbis [[[[3,5-biyl (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] phosphonate, 4,6-bis (octylthiomethyl) -O-cresol, ethylenebis (oxyethylene) bis [3- (5-tert-butyl) -4-hydroxy-m-tolyl) opionate], hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) opionate], 1,3,5-tris (3,5-di-) -Tert-Butyl-4-hydroxybenzyl) -1,3-5-triazine-2,4,6 (1H, 3H, 5H) -trione, reaction of triphenylbenzeneamine with 2,4,4-trimethylpentene Product, 2,6-di-tert-butyl-4- (4,6-bis (octylthio) -1,3,5-triazin-2-ylamino) phenol The may be used alone or in combination of two or more.

  The antioxidant having a structure derived from phenol is preferably used in a range of 0.1 to 5 parts by mass with respect to 100 parts by mass of the urethane resin (D). It is more preferable to use within a range. By using the antioxidant (D) having a phenol-derived structure in the above-described range, the durability and light resistance of the coating film formed by the coating agent of the present invention can be improved.

  Examples of the stabilizer having a hindered amine-derived structure include N, N ′, N ″, N ′ ″-tetrakis- (4,6-bis- (butyl- (N-methyl-2,2,6, 6-tetramethylpiperidin-4-yl) amino) -triazin-2-yl) -4,7-diazadecane-1,10-diamine, dibutylamine, 1,3,5-triazine, N, N′-bis ( 2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine · N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine polycondensate, poly [{ 6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} Hexamethylene {(2,2,6,6-teto Lamethyl-4-piperidyl) imino}], dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, bis (2,2,6,6-decanedioic acid) Reaction product of tetramethyl-1 (octyloxy) -4-piperidyl) ester, 1,1-dimethylethyl hydroperoxide and octane, bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[ 3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] butyl malonate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl 1,2, 2,6,6-pentamethyl-4-piperidyl sebacate (mixture), bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, etc. alone or in combination Can be used in combination.

  The stabilizer having a structure derived from the hindered amine is preferably used in a range of 0.1 to 5 parts by mass with respect to 100 parts by mass of the urethane resin (D), and a range of 0.5 to 2 parts by mass. It is more preferable to use in. By using the stabilizer having a hindered amine-derived structure in the above-described range, the durability and light resistance of the coating film formed by the coating agent of the present invention can be improved.

  The aforementioned additives can be appropriately mixed, for example, during the production of the urethane resin (D). Among these, before dissolving or dispersing the urethane resin (D) in water, mixing the organic solvent solution of the urethane resin (D) and the stabilizer additive can produce a coating agent having excellent dispersion stability. It is preferable in manufacturing.

  The coating agent of the present invention can form a coating film having very excellent anticorrosive properties on the surface of various substrates.

  Examples of the base material include galvanized steel sheets used for applications such as automobiles, home appliances, and building material products, plated steel sheets such as aluminum-zinc alloy plated steel sheets, stainless steel sheets, aluminum sheets, copper sheets, aluminum alloy sheets, and electromagnetic steel sheets. A metal substrate such as a plastic substrate, a substrate made of an inorganic material such as concrete, or the like can be used.

  Moreover, it is preferable to use the coating agent of this invention as what is called a coating agent for metal surface treatment used when providing weather resistance etc. to the surface of a metal base material especially among various base materials mentioned above.

  The coating agent of the present invention can be applied to the surface of the base material by a method such as a roll coater method, a spray method, a dipping method, or a brush coating method. After coating, it is possible to form a desired coating film on the surface of the substrate by heating and drying, for example, in the range of 60 to 200 ° C. for several seconds to 10 minutes.

  Although the film thickness of the said coating film can be suitably adjusted according to the use etc. with which a metal is used, it is preferable that it is normally about 0.5 micrometer-20 micrometers.

  Hereinafter, the present invention will be described more specifically with reference to examples.

[Example 1]
100 parts by mass of polyester polyol obtained by reacting neopentyl glycol, 1,6-hexanediol and adipic acid in a nitrogen-substituted container equipped with a thermometer, a nitrogen gas introduction tube and a stirrer, In a mixed solvent of 59 parts by weight of methyl ethyl ketone and 119 parts by weight of methyl pyrrolidone, 13 parts by weight of 2-dimethylolpropionic acid, 21 parts by weight of 1,4-cyclohexanedimethanol, 43 parts by weight of dicyclohexylmethane diisocyanate, and 36 parts by weight of isophorone diisocyanate To obtain an organic solvent solution of a urethane prepolymer having an isocyanate group at the molecular end.

Next, 10 parts by mass of triethylamine is added to the organic solvent solution of the urethane prepolymer to neutralize part or all of the carboxyl groups of the urethane prepolymer, and 331 parts by mass of water is further added and sufficiently stirred. As a result, an aqueous dispersion of urethane resin was obtained.
Next, 8 parts by mass of a 25% by mass aqueous ethylenediamine solution is added to the aqueous dispersion, and the resulting urethane resin is chain-extended by stirring, followed by aging and desolvation, so that the non-volatile content is 30% by mass. Coating agent (I) was obtained.

[Example 2]
In a nitrogen-substituted container equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, polycarbonate diol (“Nipporan 980R” manufactured by Nippon Polyurethane Industry Co., Ltd., hydroxyl group equivalent 1000 g / equivalent) 100 parts by mass, 2,2-di 13 parts by mass of methylolpropionic acid, 21 parts by mass of 1,4-cyclohexanedimethanol, 43 parts by mass of dicyclohexylmethane diisocyanate and 36 parts by mass of isophorone diisocyanate are reacted in a mixed solvent of 59 parts by mass of methyl ethyl ketone and 119 parts by mass of methylpyrrolidone. Thus, an organic solvent solution of a urethane prepolymer having an isocyanate group at the molecular end was obtained.

Next, 10 parts by mass of triethylamine is added to the organic solvent solution of the urethane prepolymer to neutralize part or all of the carboxyl groups of the urethane prepolymer, and 331 parts by mass of water is further added and sufficiently stirred. As a result, an aqueous dispersion of urethane resin was obtained.
Next, 8 parts by mass of a 25% by mass aqueous ethylenediamine solution is added to the aqueous dispersion, and the resulting urethane resin is chain-extended by stirring, followed by aging and desolvation, so that the non-volatile content is 30% by mass. A coating agent (II) was obtained.

[Comparative Example 1]
In a nitrogen-substituted container equipped with a thermometer, a nitrogen gas introduction tube, and a stirrer, 100 parts by mass of polyether polyol (“PTMG 2000”, manufactured by Mitsubishi Chemical Industries, Ltd., hydroxyl group equivalent 1000 g / equivalent), 2,2-di 13 parts by mass of methylolpropionic acid, 21 parts by mass of 1,4-cyclohexanedimethanol, 43 parts by mass of dicyclohexylmethane diisocyanate, and 36 parts by mass of isophorone diisocyanate are reacted in a mixed solvent of 59 parts by mass of methyl ethyl ketone and 119 parts by mass of methylpyrrolidone. Thus, an organic solvent solution of a urethane prepolymer having an isocyanate group at the molecular end was obtained.

Next, 10 parts by mass of triethylamine is added to the organic solvent solution of the urethane prepolymer to neutralize part or all of the carboxyl groups of the urethane prepolymer, and 331 parts by mass of water is further added and sufficiently stirred. As a result, an aqueous dispersion of urethane resin was obtained.
Next, 8 parts by mass of a 25% by mass aqueous ethylenediamine solution is added to the aqueous dispersion, and the resulting urethane resin is chain-extended by stirring, followed by aging and desolvation, so that the non-volatile content is 30% by mass. Coating agent (III) was obtained.

[Comparative Example 2]
100 parts by mass of polyester polyol obtained by reacting neopentyl glycol, 1,6-hexanediol and adipic acid in a nitrogen-substituted container equipped with a thermometer, a nitrogen gas introduction tube and a stirrer, Reaction of 13 parts by mass of 2-dimethylolpropionic acid, 21 parts by mass of 1,4-cyclohexanedimethanol and 85 parts by mass of 4,4′-diphenylmethane diisocyanate in a mixed solvent of 61 parts by mass of methyl ethyl ketone and 85 parts by mass of methylpyrrolidone By doing so, an organic solvent solution of a urethane prepolymer having an isocyanate group at the molecular end was obtained.

Next, 10 parts by mass of triethylamine is added to the organic solvent solution of the urethane prepolymer to neutralize part or all of the carboxyl groups of the urethane prepolymer, and 377 parts by mass of water is further added and sufficiently stirred. As a result, an aqueous dispersion of urethane resin was obtained.
Next, 8 parts by mass of a 25% by mass aqueous ethylenediamine solution is added to the aqueous dispersion, and the resulting urethane resin is chain-extended by stirring, followed by aging and desolvation, so that the non-volatile content is 30% by mass. Coating agent (IV) was obtained.

[Evaluation method of anticorrosion]
1. Salt water resistance After the surface of a galvanized steel sheet that has not been surface-treated is degreased using isopropyl alcohol and toluene, the coating agents obtained in the examples and comparative examples are dried so that the film thickness of the dried coating film becomes 3 μm. The sample was applied using a bar coater and dried for 5 minutes using a dryer adjusted to 100 ° C.
The surface of the steel plate (test plate) obtained by the above method was scratched with a cutter knife and subjected to a salt spray test (SST; manufactured by Suga Test Instruments Co., Ltd.) for 50 hours. The extent of occurrence of white rust was evaluated by area.
If the ratio of the area where white rust occurs to the area of the coating film is approximately 75% or less, it can be said that the salt water resistance of a practically sufficient level is obtained.

2. Water resistance A coating agent obtained in Examples and Comparative Examples was applied on a base material made of polypropylene film using a bar coater so that the film thickness of the dry coating film was 150 μm, and was cast at room temperature of 23 ° C. and humidity. Dried in a 65% environment.
After drying, the coating film was heated at 108 ° C. for 2 hours, then heat treated at 140 ° C. for 5 minutes, aged at room temperature of 23 ° C. and humidity of 65% for 1 day or more, and then peeled off from the substrate. This was used as a test film.
The test film obtained by the above method was immersed in water at 40 ° C. for 24 hours, and the degree of whitening of the film after immersion was evaluated by the following index.

[Criteria]
○: Level at which whitening cannot be visually confirmed △: Level at which whitening can be slightly confirmed visually: Level at which clear whitening can be visually confirmed

3. Moisture and heat resistance:
The coating agent obtained in Examples and Comparative Examples was applied on a base material made of polypropylene film using a bar coater so that the film thickness of the dried coating film was 150 μm, and was cast at room temperature of 23 ° C. and humidity of 65%. In an environment of
After drying, the coating film was heated at 108 ° C. for 2 hours, then heat treated at 140 ° C. for 5 minutes, aged at room temperature of 23 ° C. and humidity of 65% for 1 day or more, and then peeled off from the substrate. This was used as a test film.
The test film obtained by the above-described method was subjected to a heat and humidity resistance test for 200 hours in an environment of 95% humidity at 70 ° C., and the state of the film after the test was evaluated by the following index.

[Criteria]
○: Film strength 100% M is the same level as before evaluation Δ: Film strength 100% M is maintained at a level of 51% or more before evaluation ×: Film strength 100% M is maintained at a level of 50% or less before evaluation

[Evaluation method of yellowing resistance]
The coating agent obtained in Examples and Comparative Examples was applied on a base material made of polypropylene film using a bar coater so that the film thickness of the dried coating film was 150 μm, and was cast at room temperature of 23 ° C. and humidity of 65%. In an environment of
After drying, the coating film was heated at 108 ° C. for 2 hours, then heat treated at 140 ° C. for 5 minutes, aged at room temperature of 23 ° C. and humidity of 65% for 1 day or more, and then peeled off from the substrate. This was used as a test film.
The test film obtained by the above method was subjected to a heat discoloration test in which it was left at 150 ° C. for 1 hour, and the degree of yellowing of the film after the test was evaluated by the following index.

[Criteria]
○: Level at which yellowing cannot be visually confirmed △: Level at which yellowing can be slightly confirmed visually: Level at which clear yellowing can be visually confirmed

Claims (1)

A polyol (A) comprising an aliphatic cyclic structure-containing polyol (a1), a hydrophilic group-containing polyol (a2), and one or more selected from the group consisting of a polyester polyol (a3) and a polycarbonate polyol (a4); A coating agent comprising a urethane resin (D) obtained by reacting an aliphatic polyisocyanate (B) and a chain extender (C) dispersed in an aqueous medium.