Blocked polyisocyanate composition, coating composition, and cationic electrodeposition coating composition

Abstract

Provided are a blocked polyisocyanate composition, a coating composition, and a cationic electrodeposition coating composition that have storage stability and excellent low-temperature curing properties. [Solution] A blocked polyisocyanate composition containing a blocked polyisocyanate obtained from a polyisocyanate and a blocking agent, wherein the blocking agent contains one or more compounds represented by the following formula (1): TIFF0007815507000008.tif6181

Description

[Technical Field]

[0001] The present invention relates to a blocked polyisocyanate composition, a coating composition and a cationic electrodeposition coating composition which are excellent in low-temperature curing properties. [Background technology]

[0002] Cationic electrodeposition paints have been widely used for automobile parts, electrical equipment parts, other industrial equipment, etc., which require excellent coating workability and good corrosion resistance of the coating films they form.

[0003] Generally, cationic electrodeposition coating compositions are provided in the form of a mixture of two components: a resin emulsion component in which a resin component consisting of a cationic resin (e.g., an amino group-containing epoxy resin) and a curing agent (also called a crosslinking agent, e.g., a blocked polyisocyanate compound) is mixed and dispersed in an aqueous medium, and a pigment dispersion paste component containing a pigment dispersed with a pigment dispersion resin. This coating composition is used in a coating bath, and an electric current is passed through the substrate as the cathode and the counter electrode as the anode to form a deposited coating film on the substrate. The deposited coating film is then heated to form a crosslinked and cured coating film.

[0004] The heating temperature during the above coating film formation is usually higher than 160°C, but to reduce energy costs, there is a growing demand for lower temperatures (80 to 160°C, preferably 80 to 140°C). This is called low-temperature baking.

[0005] In order to perform the low-temperature baking, a low-temperature curing blocked polyisocyanate compound is generally used as a curing agent. For example, Patent Document 1 discloses a method for producing a cationic electrodeposition coating composition in which three components, a low-temperature curing blocked polyisocyanate compound, an amino group-containing epoxy resin, and a pigment dispersion paste, are separately dispersed in water and mixed. However, although the storage stability is good, further improvement in low-temperature curing properties may be required. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2017 / 138445 Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved by the present invention is to provide a blocked polyisocyanate composition, a coating composition and a cationic electrodeposition coating composition which have storage stability and excellent low-temperature curing properties. [Means for solving the problem]

[0008] As a result of extensive investigations aimed at solving the above-mentioned problems, the inventors have found that the above-mentioned problems can be solved by a blocked polyisocyanate composition obtained from a blocking agent having a specific chemical structure and a polyisocyanate, and have thus completed the present invention. That is, the present invention provides the following blocked polyisocyanate composition, coating composition, and cationic electrodeposition coating composition. [1] A blocked polyisocyanate composition containing a blocked polyisocyanate obtained from a polyisocyanate and a blocking agent, The blocking agent is represented by the formula (1): TIFF0007815507000001.tif6181

[0009] (In formula (1), A 1 is a carbon atom or a nitrogen atom, A 2 is a carbon atom or a nitrogen atom, A 3 is a carbon atom or a nitrogen atom, A 4 is a carbon atom or a nitrogen atom, A 5 is a carbon atom or a nitrogen atom, R1 is A 1 is a carbon atom, it is a hydrogen atom or a monovalent organic group, and A 1 is absent when it is a nitrogen atom, R 2 is A 2 is a carbon atom, it is a hydrogen atom or a monovalent organic group, and A 2 is absent when it is a nitrogen atom, R 3 is A 3 is a carbon atom, it is a hydrogen atom or a monovalent organic group, and A 3 is absent when it is a nitrogen atom, R 4 is A 4 is a carbon atom, it is a hydrogen atom or a monovalent organic group, and A 4 is absent when it is a nitrogen atom, R 5 is A 5 is a carbon atom, it is a hydrogen atom or a monovalent organic group, and A 5 is absent when it is a nitrogen atom, R 6 is a hydrogen atom or a monovalent organic group, X is a nitrogen atom or a sulfur atom, Z is a hydrogen atom or is absent; R 1 ~R 6 two or more of may be linked to form a cyclic structure, When X is a nitrogen atom, R 6 is a hydrogen atom or a monovalent organic group, When X is a nitrogen atom and Z is not present, X and the ring form a double bond and R 6 is R 1 ~R 5 It forms a ring with one or more of the following: When X is a sulfur atom, Z is absent. It has one or more NH or SH groups in the molecule. A blocked polyisocyanate composition comprising one or more compounds represented by the formula: [2] The blocking agent is represented by the formulas (1-1) to (1-19): TIFF0007815507000002.tif189150

[0010] (In formulas (1-1) to (1-19), R 10 ~R 30 is a monovalent organic group, n11, n12, n15, n16, n17, n27, n28, n29, and n30 are integers from 0 to 5, n13 and n14 are integers from 0 to 6, n18 and n25 are integers from 0 to 10, n20 is an integer from 0 to 4, n21 is an integer of 0 to 3, n22, n23, n24, and n26 are integers from 0 to 8, R 11 ~R 18 , R 20 ~R 30 When there are two or more, they may be the same or different, R 10 and R 11 Two or more of the above, and R 19 and R 20 two or more of these may be linked to form a cyclic structure, R 12 ~R 18 , R 21 ~R 30 When there are two or more, two or more may be linked to form a cyclic structure.) The blocked polyisocyanate composition according to [1], which contains one or more compounds represented by the following formula: [3] The blocked polyisocyanate composition according to [1] or [2], wherein the polyisocyanate is an aromatic polyisocyanate. [4] A coating composition comprising the blocked polyisocyanate composition according to any one of [1] to [3] and an active hydrogen group-containing resin. [5] A cationic electrodeposition coating composition comprising the blocked polyisocyanate composition according to any one of [1] to [3] and an amino group-containing epoxy resin. [Effects of the Invention]

[0011] When used as a coating curing agent, the blocked polyisocyanate composition of the present invention can impart excellent low-temperature curing properties to a coating composition while maintaining good storage stability. Furthermore, the blocked polyisocyanate composition of the present invention can provide a coating composition and a cationic electrodeposition coating composition that have good finish and excellent corrosion resistance. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Blocked Polyisocyanate Composition> The present invention relates to a blocked polyisocyanate composition (A) containing a blocked polyisocyanate (a) obtained from a polyisocyanate and a blocking agent.

[0013] This will be explained in detail below.

[0014] Blocked polyisocyanate (a) The blocked polyisocyanate (a) is a product of an addition reaction between a polyisocyanate and an isocyanate blocking agent in approximately stoichiometric amounts. The polyisocyanate used in the blocked polyisocyanate (a) may be a known polyisocyanate, such as tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, diphenylmethane-2,2'-diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, crude MDI (polymethylene polyphenylisocyanate), bis(isocyanatomethyl)cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, or isophorone diisocyanate; a cyclized polymer or biuret of these polyisocyanate compounds; or a combination thereof.

[0015] In particular, aromatic polyisocyanates such as tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, crude MDI, etc. (preferably crude MDI, etc.) are more preferred for their corrosion resistance. In the present invention, the term "aromatic polyisocyanate" refers to a polyisocyanate having an aromatic group.

[0016] The blocking agent used in the blocked polyisocyanate (a) of the present invention is a compound represented by the following formula (1). TIFF0007815507000003.tif6181

[0017] In formula (1), A 1 is a carbon atom or a nitrogen atom, A 2 is a carbon atom or a nitrogen atom, A 3 is a carbon atom or a nitrogen atom, A 4 is a carbon atom or a nitrogen atom, A 5 is a carbon atom or a nitrogen atom, R 1 is A 1 is a carbon atom, it is a hydrogen atom or a monovalent organic group, and A 1 is absent when it is a nitrogen atom, R 2 is A 2 is a carbon atom, it is a hydrogen atom or a monovalent organic group, and A 2 is absent when it is a nitrogen atom, R 3 is A 3 is a carbon atom, it is a hydrogen atom or a monovalent organic group, and A 3 is absent when it is a nitrogen atom, R 4 is A 4 is a carbon atom, it is a hydrogen atom or a monovalent organic group, and A 4 is absent when it is a nitrogen atom, R5 is A 5 is a carbon atom, it is a hydrogen atom or a monovalent organic group, and A 5 is absent when it is a nitrogen atom, R 6 is a hydrogen atom or a monovalent organic group, X is a nitrogen atom or a sulfur atom, Z is a hydrogen atom or is absent; R 1 ~R 6 Two or more of A may be linked to form a cyclic structure, 1 ~A 5 When one or more of the groups are nitrogen atoms, X and Z are absent and R 6 may be directly bonded to the ring, When X is a nitrogen atom, R 6 is a hydrogen atom or a monovalent organic group, When X is a nitrogen atom and Z is not present, X and the ring form a double bond and R 6 is R 1 ~R 5 It forms a ring with one or more of the following: When X is a sulfur atom, Z is absent. It has one or more NH or SH groups in the molecule.

[0018] R in formula (1) 1 ~R 6 When is an organic group, examples of the organic group include one or more of an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, a heterocyclic group, a halogen group, a cyano group, a hydroxyl group, an amino group, and an alkoxy group. Of these, the organic group is preferably one or more of an alkyl group, a halogen group, a cyano group, a hydroxyl group, and an amino group. Furthermore, two or more of these groups may be linked to each other to form a ring.

[0019] In the description of groups (atomic groups) in this specification, when a notation does not specify whether they are substituted or unsubstituted, it encompasses both groups (atomic groups) that have no substituents and groups (atomic groups) that have substituents. For example, the term "alkyl group" encompasses not only alkyl groups that have no substituents (unsubstituted alkyl groups) but also alkyl groups that have substituents (substituted alkyl groups).

[0020] The blocking agent used in the blocked polyisocyanate (a) of the present invention is preferably a compound in which Z in formula (1) is a hydrogen atom, and 1 ~A 5 are preferably all carbon atoms. From the viewpoint of low-temperature curing properties and storage stability, the compounds are preferably those represented by the following formulas (1-1) to (1-19). TIFF0007815507000004.tif189150

[0021] In formulas (1-1) to (1-19), R 10 ~R 30 is a monovalent organic group, n11, n12, n15, n16, n17, n27, n28, n29, and n30 are integers from 0 to 5, n13 and n14 are integers from 0 to 6, n18 and n25 are integers from 0 to 10, n20 is an integer from 0 to 4, n21 is an integer of 0 to 3, n22, n23, n24, and n26 are integers from 0 to 8, R 11 ~R 18 , R 20 ~R 30 When there are two or more, they may be the same or different, R 10 and R 11 Two or more of the above, and R 19 and R 20 two or more of these may be linked to form a cyclic structure, R 12 ~R 18 , R21 ~R 30 When there are two or more, two or more may be linked to form a cyclic structure. Among these, one or more of the compounds represented by formulae (1-1), (1-3), (1-4) and (1-8) are preferred, and one or more of the compounds represented by formulae (1-1) and (1-8) are particularly preferred.

[0022] In formulas (1-1) to (1-19), R 10 ~R 30 The monovalent organic group is represented by R 1 ~R 6 The organic group may be the same as the organic group described above.

[0023] Examples of the organic group include monovalent organic groups such as alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, aryl groups, and heterocyclic groups, among which alkyl groups and alkenyl groups are particularly preferred. The monovalent organic group may contain at least one selected from the group consisting of oxygen atoms, nitrogen atoms, sulfur atoms, and halogen atoms, and may be bonded to other substituents in formula (1) to form a cyclic structure.

[0024] Examples of the compound represented by formula (1-1) include N-methylaniline, N-ethylaniline, N-propylaniline, N-butylaniline, N-isopropylaniline, N-tert-butylaniline, N-methyl-o-toluidine, N-methyl-m-toluidine, N-methyl-p-toluidine, 2-fluoro-N-methylaniline, 3-fluoro-N-methylaniline, and 4-fluoro-N-methylaniline.

[0025] Examples of the compound represented by formula (1-2) include benzenethiol, o-toluenethiol, m-toluenethiol, p-toluenethiol, 2-aminobenzenethiol, 3-aminobenzenethiol, 4-aminobenzenethiol, 2-fluorobenzenethiol, 3-fluorobenzenethiol, and 4-fluorobenzenethiol.

[0026] Examples of the compound represented by formula (1-3) include indoline, 2-methylindoline, 3-methylindoline, 4-methylindoline, 5-methylindoline, 6-methylindoline, and 7-methylindoline.

[0027] Examples of the compound represented by formula (1-4) include indole, 2-methylindole, 3-methylindole, 4-methylindole, 5-methylindole, 6-methylindole, 7-methylindole, 2-hydroxyindole, 3-hydroxyindole, 4-hydroxyindole, 5-hydroxyindole, 6-hydroxyindole, 7-hydroxyindole, 2-aminoindole, 3-aminoindole, 4-aminoindole, 5-aminoindole, 6-aminoindole, 7-aminoindole, 2-cyanoindole, 3-cyanoindole, 4-cyanoindole, 5-cyanoindole, 6-cyanoindole, and 7-cyanoindole.

[0028] An example of the compound represented by formula (1-5) is indole-2-thiol.

[0029] Examples of the compound represented by formula (1-6) include indazole, 5-methylindazole, 5-hydroxyindazole, 5-aminoindazole, 5-cyanoindazole, and 5-fluoroindazole.

[0030] Examples of the compound represented by formula (1-7) include indazole, 5-methylindazole, 5-hydroxyindazole, 5-aminoindazole, 5-cyanoindazole, and 5-fluoroindazole.

[0031] Examples of the compound represented by formula (1-8) include 1,2,3,4-tetrahydroquinoline, 2-methyl-1,2,3,4-tetrahydroquinoline, 3-methyl-1,2,3,4-tetrahydroquinoline, 4-methyl-1,2,3,4-tetrahydroquinoline, 5-methyl-1,2,3,4-tetrahydroquinoline, 6-methyl-1,2,3,4-tetrahydroquinoline, 7-methyl-1,2,3,4-tetrahydroquinoline, and 8-methyl-1,2,3,4-tetrahydroquinoline.

[0032] Examples of the compound represented by formula (1-9) include 4-(methylamino)pyridine.

[0033] Examples of the compound represented by formula (1-10) include adenine.

[0034] Examples of the compound represented by formula (1-11) include 5,10-dihydrophenazine.

[0035] Examples of the compound represented by formula (1-12) include phenoxazine.

[0036] Examples of the compound represented by formula (1-13) include phenothiazine.

[0037] Examples of the compound represented by formula (1-14) include 9,10-dihydroacridine.

[0038] Examples of the compound represented by formula (1-15) include 1,2,3,4-tetrahydroquinoxaline.

[0039] Examples of the compound represented by formula (1-16) include 6-azaindole.

[0040] Examples of the compound represented by formula (1-17) include 5-azaindole.

[0041] Examples of the compound represented by formula (1-18) include 7-azaindole.

[0042] Examples of the compound represented by formula (1-19) include 4-azaindole.

[0043] <Paint composition> The coating composition according to the second aspect of the present invention contains the above-mentioned blocked polyisocyanate composition (A) and an active hydrogen group-containing resin (B).

[0044] Active hydrogen group-containing resin (B) The active hydrogen group-containing resin (B) that can be used in the coating composition of the present invention can be any known resin without particular limitation, as long as it has a reactive functional group that can crosslink with the blocked polyisocyanate composition and can crosslink with the blocked polyisocyanate composition (A).

[0045] Examples of reactive functional groups that can crosslink with the blocked polyisocyanate composition include reactive functional groups having active hydrogen such as hydroxyl groups, amino groups, carboxyl groups, and active methylene groups, as well as epoxy groups and carboxylic anhydride groups.

[0046] Examples of the active hydrogen group-containing resin (B) include acrylic resins, polyester resins, epoxy resins, alkyd resins, polyether resins, polyurethane resins, and polyamide resins, which can be used alone or in combination of two or more. Among these, at least one resin selected from acrylic resins (B1), polyester resins (B2), and epoxy resins (B3) is preferred.

[0047] The active hydrogen group-containing resin (B) may be in a dissolved state in the coating composition, or may be in a dispersed state (for example, in an emulsion state in an aqueous solvent). When in a dispersed state, it may be in the form of crosslinked resin particles.

[0048] The acrylic resin (B1) that can be used in the coating composition of the present invention can be produced by radical copolymerization of acrylic monomers.

[0049] Examples of the acrylic monomer include hydroxyl group-containing acrylic monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and addition products of 2-hydroxyethyl (meth)acrylate and caprolactone (for example, trade names of Placcel FA-2 and FM-3 manufactured by Daicel Corporation); aromatic vinyl monomers such as styrene, vinyl toluene, and α-methylstyrene; methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n- Examples thereof include butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, polyalkylene glycol (meth)acrylate, isobornyl (meth)acrylate, (meth)acrylic acid, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-di-t-butylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylamide. These may be used alone or in combination of two or more.

[0050] In this specification, (meth)acrylic means acrylic or methacrylic, and (meth)acrylate means acrylate or methacrylate, respectively. The acrylic resin (B1) can be obtained by subjecting the above-mentioned monomers to a radical copolymerization reaction by a known method.

[0051] The hydroxyl value of the acrylic resin (B1) is usually within a range of 0.1 to 300 mgKOH / g, preferably within a range of 10 to 200 mgKOH / g, and the weight average molecular weight is usually within a range of 1,000 to 100,000, preferably within a range of 2,000 to 30,000.

[0052] In this specification, the number-average molecular weight and weight-average molecular weight are values ​​obtained by converting the retention time (retention volume) measured using a gel permeation chromatograph (GPC) into the molecular weight of polystyrene using the retention time (retention volume) of a standard polystyrene of known molecular weight measured under the same conditions. Specifically, the gel permeation chromatograph used was "HLC8120GPC" (trade name, manufactured by Tosoh Corporation) and four columns, "TSKgel G-4000HXL," "TSKgel G-3000HXL," "TSKgel G-2500HXL," and "TSKgel G-2000HXL" (trade names, all manufactured by Tosoh Corporation), under the conditions of tetrahydrofuran as the mobile phase, a measurement temperature of 40°C, a flow rate of 1 mL / min, and an RI detector. The measurement of the amino group-containing epoxy resin (b3) described below used "tetrahydrofuran (containing 1 wt.% triethanolamine)" as the mobile phase.

[0053] The polyester resin (B2) that can be used in the coating composition of the present invention can be produced by an esterification reaction and / or transesterification reaction between an acid component and an alcohol component.

[0054] The acid component may be any compound that is commonly used as an acid component in the production of polyester resins, without any particular limitation. Examples of the acid component that can be used include alicyclic polybasic acids, aliphatic polybasic acids, aromatic polybasic acids, aromatic monocarboxylic acids, aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, and lower alkyl esters of these acids.

[0055] Alicyclic polybasic acids are generally compounds having one or more alicyclic structures (mainly 4- to 6-membered rings) and two or more carboxyl groups in one molecule, acid anhydrides of such compounds, and esters of such compounds.

[0056] Aliphatic polybasic acids are generally aliphatic compounds having two or more carboxyl groups in one molecule, acid anhydrides of such compounds, and esterified products of such compounds.

[0057] Aromatic polybasic acids are generally aromatic compounds having two or more carboxyl groups in one molecule, acid anhydrides of such aromatic compounds, and esters of such aromatic compounds. If necessary, aromatic monocarboxylic acids, aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, etc. can also be used.

[0058] As the alcohol component, compounds that are commonly used as alcohol components in the production of polyester resins can be used without particular limitation, but those containing dihydric alcohols such as alicyclic diols, aliphatic diols, and aromatic diols, and trihydric or higher polyhydric alcohols are preferred.

[0059] The polyester resin (B2) can be produced by reacting the acid component and alcohol component by a known method. The polyester resin (B2) can also be modified with fatty acids, fats and oils, polyisocyanate compounds, epoxy compounds, etc. during the preparation of the resin or after the esterification reaction and / or transesterification reaction.

[0060] From the viewpoint of finished quality, the number average molecular weight of the polyester resin (B2) is generally within a range of 1,000 to 20,000, preferably 1,050 to 10,000, and more preferably 1,100 to 5,000.

[0061] The hydroxyl value of the polyester resin (B2) is generally 20 to 300 mgKOH / g, preferably 30 to 250 mgKOH / g, and more preferably 40 to 180 mgKOH / g, from the viewpoint of the curability of the resulting coating film.

[0062] The epoxy resin (B3) that can be used in the coating composition of the present invention can be obtained by reacting an epoxy resin (B3-1) with a modifier (B3-2).

[0063] The epoxy resin (B3-1) that can be used as a raw material for the epoxy resin (B3) is a compound having at least one, preferably two or more, epoxy groups per molecule, with a number average molecular weight of at least 300, preferably 400 to 4,000, and more preferably 800 to 2,500, and an epoxy equivalent of at least 160, preferably 180 to 2,500, and more preferably 400 to 1,500. The epoxy resin (B3-1) may be, for example, a compound obtained by reacting a polyphenol compound with an epihalohydrin (e.g., epichlorohydrin).

[0064] Examples of polyphenol compounds used to form the epoxy resin (B3-1) include bis(4-hydroxyphenyl)-2,2-propane [bisphenol A], bis(4-hydroxyphenyl)methane [bisphenol F], bis(4-hydroxycyclohexyl)methane [hydrogenated bisphenol F], 2,2-bis(4-hydroxycyclohexyl)propane [hydrogenated bisphenol A], 4,4'-dihydroxybenzophenone, bis(4-hydroxyphenyl)-1,1-ethane, bis(4-hydroxyphenyl)-1,1-isobutane, bis(4-hydroxy-3-tert-butyl-phenyl)-2,2-propane, bis(2-hydroxynaphthyl)methane, tetra(4-hydroxyphenyl)-1,1,2,2-ethane, 4,4'-dihydroxydiphenyl sulfone, phenol novolac, and cresol novolac.

[0065] Furthermore, as the epoxy resin (B3-1) obtained by the reaction of a polyphenol compound with an epihalohydrin, a resin derived from bisphenol A and represented by the following formula is particularly suitable.

[0066] [ka]

[0067] Here, n=0 to 8 is preferred.

[0068] Commercially available products of such epoxy resins (B3-1) include those sold by Mitsubishi Chemical Corporation under the trade names jER828EL, jER1002, jER1004, and jER1007.

[0069] Examples of the modifier (B3-2) that can be used as a raw material for the epoxy resin (B3) include polyhydric alcohols, monohydric alcohols, acidic compounds, phenols, amine compounds, lactones, isocyanate compounds, and xylene formaldehyde compounds.

[0070] Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-methylpentane-2,4-diol, 2,2,4-trimethyl-1,3-pentanediol, triethylene glycol, and 2-butyl-2-ethyl-1,3-propanediol. Examples of suitable dihydric alcohols include tricyclodecane dimethanol, triethylene glycol, neopentyl glycol, 1,4-cyclohexanediol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, bisphenol A, bisphenol F, hydrogenated bisphenol A, and hydrogenated bisphenol F; polyether diols such as polyethylene glycol, polypropylene glycol, and polybutylene glycol; trihydric alcohols such as glycerin, trimethylolpropane, and tris(2-hydroxyethyl)isocyanurate; tetrahydric alcohols such as pentaerythritol; polyester polyols, and acrylic polyols.

[0071] Examples of the monohydric alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, pentanol, hexanol, n-octanol, 2-ethylhexanol, dodecyl alcohol, stearyl alcohol, and benzyl alcohol.

[0072] Examples of the acidic compound include acetic acid, propionic acid, butyric acid, valeric acid, acrylic acid, oleic acid, glycolic acid, lactic acid, benzoic acid, gallic acid, fatty acids, and dibasic acids.

[0073] Examples of the phenols include phenol, cresol, ethylphenol, para-tert-butylphenol, nonylphenol, catechol, resorcinol, and 4-tert-butylcatechol.

[0074] The amine compound may be any amine compound containing at least one active hydrogen atom reactive with an epoxy group, and may be used without particular limitation. Examples include mono- or di-alkylamines such as monomethylamine, dimethylamine, monoethylamine, diethylamine, monoisopropylamine, diisopropylamine, monobutylamine, and dibutylamine; alkanolamines such as monoethanolamine, diethanolamine, mono(2-hydroxypropyl)amine, di(2-hydroxypropyl)amine, monomethylaminoethanol, and monoethylaminoethanol; alkylene polyamines such as ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, tetraethylenepentamine, pentaethylenehexamine, diethylaminopropylamine, diethylenetriamine, and triethylenetetramine; alkylene imines such as ethyleneimine and propyleneimine; and cyclic amines such as piperazine, morpholine, and pyrazine. These amines may also be used in combination with amines obtained by ketiminizing primary amines. These may be used alone or in combination of two or more.

[0075] The epoxy resin (B3) can be produced by reacting the epoxy resin (B3-1) and the modifier (B3-2) by a known method.

[0076] The number average molecular weight of the epoxy resin (B3) is generally within the range of 1,000 to 50,000, preferably 1,300 to 20,000, and more preferably 1,600 to 10,000, from the viewpoints of paint stability, finish, corrosion resistance, etc. The hydroxyl value of the epoxy resin (B3) is generally within the range of 10 to 300 mgKOH / g, preferably 20 to 250 mgKOH / g, and even more preferably 30 to 200 mgKOH / g, from the viewpoint of the curability of the resulting coating film.

[0077] The proportions of the blocked polyisocyanate composition (A) and the active hydrogen group-containing resin (B) in the coating composition of the present invention, based on the total mass of the resin solids in the coating composition, are preferably within the ranges of usually 10 to 60 mass%, preferably 15 to 55 mass%, for component (A) and usually 10 to 90 mass%, preferably 20 to 80 mass%, for component (B), in order to obtain coated articles with excellent finish and curing properties. A ratio outside these ranges may undesirably impair either the coating properties or the coating film performance.

[0078] The coating composition of the present invention is not particularly limited, but may contain, in addition to components (A) and (B), as necessary, a pigment dispersion paste, a solvent such as water or an organic solvent, a neutralizing agent, a surfactant, a surface conditioner, a thickener, an anti-settling agent, an ultraviolet absorber, a light stabilizer, an anti-foaming agent, a dissociation catalyst, a plasticizer, and the like.

[0079] The pigment dispersion paste is a pigment such as a color pigment, an anti-rust pigment, or an extender pigment that has been dispersed into fine particles in advance. For example, the pigment dispersion paste can be prepared by blending a pigment dispersion resin, a neutralizing agent, a solvent, and a pigment, and dispersing the mixture in a dispersion mixer such as a ball mill, a sand mill, or a pebble mill.

[0080] As the pigment, any known pigment can be used without any particular limitation, and examples thereof include titanium dioxide, zinc oxide, zinc phosphate, aluminum phosphate, zinc molybdate, calcium molybdate, iron blue, ultramarine, cobalt blue, copper phthalocyanine blue, indanthrone blue, synthetic yellow iron oxide, transparent red iron oxide (yellow), bismuth vanadate, titanium yellow, zinc yellow, monoazo yellow, isoindolinone yellow, metal complex azo yellow, quinophthalone yellow, benzimidazolone yellow, red iron oxide, monoazo red, quinacridone red, azo lake (Mn salt), quinacridone magenta, anthanthrone orange, and dianthraquinone. Coloring pigments such as nonyl red, perylene maroon, quinacridone magenta, perylene red, diketopyrrolopyrrole chrome vermilion, chlorinated phthalocyanine green, brominated phthalocyanine green, pyrazolone orange, benzimidazolone orange, dioxazine violet, and perylene violet; extender pigments such as baryta powder, barium sulfate, barium carbonate, calcium carbonate, gypsum, clay, white carbon, diatomaceous earth, talc, magnesium carbonate, alumina white, gloss white, and mica powder; and rust-preventive pigments such as aluminum phosphomolybdate, aluminum tripolyphosphate, and zinc oxide (zinc white) can be added.

[0081] As the solvent, known solvents such as water and organic solvents can be used without limitation, but it is preferable that the solvent contains water. Examples of the organic solvent include hydrocarbons such as toluene, xylene, cyclohexane, and n-hexane; esters such as methyl acetate, ethyl acetate, and butyl acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, and isobutyl methyl ketone; amides such as dimethylformamide and dimethylacetamide; alcohols such as methanol, ethanol, n-propanol, and isopropanol; ether alcohol compounds such as ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, and propylene glycol monomethyl ether; and mixtures thereof.

[0082] In addition, as the dissociation catalyst for the isocyanate blocking agent, bismuth-based compounds, zinc-based compounds, titanium-based compounds, amidine-based compounds, phosphazene-based compounds, quaternary salt-based compounds, proazaphosphatrane-based compounds, etc. can be suitably used.

[0083] When applying paint using the paint composition of the present invention, known coating methods such as brush coating, roller coating, dipping coating, bar coder coating, applicator coating, curtain coating, spray coating, rotary atomization coating, and electrodeposition coating can be used without particular limitation.

[0084] The thickness of the coating film is not particularly limited, but can generally be within the range of 5 to 60 μm, preferably 10 to 40 μm, based on the dry coating film.

[0085] The baking drying of the coating film is carried out by heating the coating film using drying equipment such as an electric hot air dryer or a gas hot air dryer to a surface temperature of 80 to 160°C, preferably 80 to 140°C, for 3 to 180 minutes, preferably 10 to 50 minutes. A cured coating film can be obtained by the baking drying.

[0086] Examples of substrates that can be coated in the present invention include automobile bodies, automobile parts, motorcycle parts, household appliances, other appliances, etc., and the materials used are not particularly limited and may include metals, plastics, inorganic materials, wood, fiber materials, etc. In the case of metal substrates, for example, the surface may be cleaned as needed by alkaline degreasing or the like, and then further subjected to a surface treatment as needed by phosphate conversion treatment, chromate treatment, etc., and the substrate may also be coated with a primer paint or the like. A coated article can be obtained by coating the coating composition of the present invention on the above-mentioned substrate.

[0087] <Cationic electrodeposition coating composition> The cationic electrodeposition coating composition according to the third embodiment of the present invention contains the above-mentioned blocked polyisocyanate composition (A) and an amino group-containing epoxy resin (b3).

[0088] Amino group-containing epoxy resin (b3) As the amino group-containing epoxy resin (b3) that can be used in the cationic electrodeposition coating composition of the present invention, an epoxy resin that uses an amine compound as the modifier (B3-2) for the above epoxy resin (B3) can be used.

[0089] The amine compound may be any amine compound containing at least one active hydrogen atom reactive with an epoxy group, and may be used without particular limitation. Examples include mono- or di-alkylamines such as monomethylamine, dimethylamine, monoethylamine, diethylamine, monoisopropylamine, diisopropylamine, monobutylamine, and dibutylamine; alkanolamines such as monoethanolamine, diethanolamine, mono(2-hydroxypropyl)amine, di(2-hydroxypropyl)amine, monomethylaminoethanol, and monoethylaminoethanol; alkylene polyamines such as ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, tetraethylenepentamine, pentaethylenehexamine, diethylaminopropylamine, diethylenetriamine, and triethylenetetramine; alkylene imines such as ethyleneimine and propyleneimine; and cyclic amines such as piperazine, morpholine, and pyrazine. These amines may also be used in combination with amines obtained by ketiminizing primary amines. These may be used alone or in combination of two or more.

[0090] The amine value of the amino group-containing epoxy resin (b3) is preferably in the range of 30 to 80 mg KOH / g resin solid content, more preferably 40 to 70 mg KOH / g resin solid content, from the viewpoint of improving water dispersibility and anticorrosion properties.

[0091] Furthermore, the amino group-containing epoxy resin (b3) can be modified with a modifier, if necessary. Such modifiers are not particularly limited as long as they are resins or compounds reactive with epoxy resins. Examples of modifiers that can be used include polyols, polyether polyols, polyester polyols, polyamidoamines, polycarboxylic acids, fatty acids, polyisocyanate compounds, compounds obtained by reacting polyisocyanate compounds, lactone compounds such as ε-caprolactone, acrylic monomers, compounds obtained by polymerizing acrylic monomers, xylene formaldehyde compounds, and epoxy compounds. These modifiers can be used alone or in combination of two or more.

[0092] The addition reaction of the above amine compound and modifier to the epoxy resin (B3) can usually be carried out in an appropriate solvent at a temperature of about 50 to about 170°C, preferably about 60 to about 150°C, for about 1 to 6 hours, preferably about 1 to 5 hours.

[0093] Cationic electrodeposition coating composition The proportions of the blocked polyisocyanate composition (A) and the amino group-containing epoxy resin (b3) in the cationic electrodeposition coating composition of the present invention are preferably within the ranges of 5 to 95 mass %, preferably 20 to 50 mass %, of component (A) and 5 to 95 mass %, preferably 50 to 80 mass %, of component (b3), based on the total mass of the solid contents of the above components (A) and (b3), in order to obtain coated articles with good paint stability, excellent finish, and corrosion resistance. A ratio outside these ranges is not preferred, as it may impair either the above-mentioned paint properties or the coating film performance.

[0094] The method for producing the cationic electrodeposition coating composition of the present invention is not particularly limited, but for example, the composition can be obtained by thoroughly mixing the blocked polyisocyanate composition (A) and the amino group-containing epoxy resin (b3) with various additives such as surfactants and surface conditioners, as necessary, to prepare a compounded resin, dispersing it in water, and thoroughly mixing this with epoxy resin crosslinked particles, a pigment dispersion paste, water, an organic solvent, a neutralizing agent, etc. Any known organic acid can be used as the neutralizing agent without any particular limitation, and among these, formic acid, lactic acid, or a mixture thereof is preferred.

[0095] The pigment dispersion paste is a pigment such as a color pigment, an anti-rust pigment, or an extender pigment that has been dispersed into fine particles in advance. For example, the pigment dispersion paste can be prepared by blending a pigment dispersing resin, a neutralizing agent, and a pigment, and dispersing the mixture in a dispersing mixer such as a ball mill, a sand mill, or a pebble mill.

[0096] As the pigment dispersing resin, any known resin can be used without any particular limitation, and examples thereof include epoxy resins or acrylic resins having a hydroxyl group and a cationic group, surfactants, tertiary amine-type epoxy resins, quaternary ammonium salt-type epoxy resins, tertiary sulfonium salt-type epoxy resins, tertiary amine-type acrylic resins, quaternary ammonium salt-type acrylic resins, and tertiary sulfonium salt-type acrylic resins.

[0097] As the pigment, any known pigment can be used without any particular limitation, and examples of pigments that can be added include coloring pigments such as titanium oxide, carbon black, and red iron oxide; extender pigments such as clay, mica, baryta, calcium carbonate, and silica; and rust-preventive pigments such as aluminum phosphomolybdate, aluminum tripolyphosphate, and zinc oxide (zinc white).

[0098] As the solvent, known solvents such as water and organic solvents can be used without limitation, but it is preferable that the solvent contains water. Examples of the organic solvent include hydrocarbons such as toluene, xylene, cyclohexane, and n-hexane; esters such as methyl acetate, ethyl acetate, and butyl acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, and isobutyl methyl ketone; amides such as dimethylformamide and dimethylacetamide; alcohols such as methanol, ethanol, n-propanol, and isopropanol; ether alcohol compounds such as ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, and propylene glycol monomethyl ether; and mixtures thereof.

[0099] In addition, as the dissociation catalyst for the isocyanate blocking agent, bismuth-based compounds, zinc-based compounds, titanium-based compounds, amidine-based compounds, phosphazene-based compounds, quaternary salt-based compounds, proazaphosphatrane-based compounds, and the like can be suitably used, and from the standpoints of environment and safety, it is preferable to use bismuth-based compounds.

[0100] Paint film formation method The substrates to be coated with the cationic electrodeposition coating composition of the present invention include automobile bodies, motorcycle parts, household appliances, other appliances, etc., and are not particularly limited as long as they are made of metal.

[0101] Examples of metal steel sheets to be coated include cold-rolled steel sheets, galvannealed steel sheets, electrogalvanized steel sheets, electrolytic zinc-iron double-layer plated steel sheets, organic composite plated steel sheets, Al materials, Mg materials, and the like, as well as these metal sheets whose surfaces have been cleaned by alkaline degreasing or the like, as necessary, and then subjected to surface treatments such as phosphate conversion treatment and chromate treatment.

[0102] The cationic electrodeposition coating composition can be applied to the surface of the desired substrate by cationic electrodeposition coating. The cationic electrodeposition method generally involves preparing a bath containing the cationic electrodeposition coating composition, which has been diluted with deionized water or the like to a solids concentration of approximately 5 to 40% by mass, preferably 10 to 25% by mass, and further adjusted to a pH of 4.0 to 9.0, preferably 5.5 to 7.0. The bath temperature is typically adjusted to 15 to 35°C, and a voltage of 100 to 400 V, preferably 150 to 350 V, is applied to the substrate as the cathode. After electrodeposition coating, excess cationic electrodeposition coating is typically removed by thorough rinsing with ultrafiltrate (UF filtrate), reverse osmosis water (RO water), industrial water, pure water, or the like.

[0103] The thickness of the electrodeposition coating is not particularly limited, but can generally be within the range of 5 to 40 μm, preferably 10 to 30 μm, based on the dried coating. The bake drying of the coating is carried out by heating the electrodeposition coating using drying equipment such as an electric hot air dryer or a gas hot air dryer at a temperature of 80 to 160°C, preferably 80 to 140°C, at the surface temperature of the coated object, for 10 to 180 minutes, preferably 20 to 50 minutes. A cured coating can be obtained by the bake drying. [Example]

[0104] The present invention will be described in more detail below with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited thereto. In each example, "parts" means parts by mass, and "%" means % by mass.

[0105] Preparation of blocked polyisocyanate compositions Example A1 Into a reaction vessel, 267 parts of Cosmonate M-200 (trade name, manufactured by Mitsui Chemicals, Inc., crude MDI, NCO group content 31.3%) and 120 parts of methyl isobutyl ketone were added and heated to 60° C. 214 parts of N-methylaniline were added dropwise over 2 hours, and the temperature was then raised to 65° C. Sampling was performed over time while maintaining this temperature, and infrared absorption spectroscopy confirmed that the absorption of unreacted isocyanate groups had disappeared, yielding a blocked polyisocyanate composition A-1 with a resin solids content of 80%.

[0106] Example A2 Into a reaction vessel, 267 parts of Cosmonate M-200 (trade name, manufactured by Mitsui Chemicals, Inc., crude MDI, NCO group content 31.3%) and 131 parts of methyl isobutyl ketone were added and heated to 60° C. To this, 269 parts of tetrahydroquinoline were added dropwise over 2 hours, and then the temperature was raised to 65° C. Sampling was performed over time while maintaining this temperature, and infrared absorption spectroscopy confirmed that the absorption of unreacted isocyanate groups had disappeared, yielding a blocked polyisocyanate composition A-2 with a resin solids content of 80%.

[0107] Comparative example A3 Into a reaction vessel, 267 parts of Cosmonate M-200 (trade name, manufactured by Mitsui Chemicals, Inc., crude MDI, NCO group content 31.3%) and 117 parts of methyl isobutyl ketone were added and heated to 60° C. To this, 50 parts of propylene glycol and 150 parts of diethylene glycol monobutyl ether were added dropwise over 2 hours, and then the temperature was raised to 100° C. Sampling was performed over time while maintaining this temperature, and infrared absorption spectroscopy confirmed that the absorption of unreacted isocyanate groups had disappeared, yielding a blocked polyisocyanate composition A-3 with a resin solids content of 80%.

[0108] Comparative example A4 Into a reaction vessel, 267 parts of Cosmonate M-200 (trade name, manufactured by Mitsui Chemicals, Inc., crude MDI, NCO group content 31.3%) and 110 parts of methyl isobutyl ketone were added and heated to 60° C. 174 parts of methyl ethyl ketoxime was added dropwise over 1 hour, and then the temperature was raised to 80° C. Sampling was performed over time while maintaining this temperature, and infrared absorption spectroscopy confirmed that the absorption of unreacted isocyanate groups had disappeared, yielding a blocked polyisocyanate composition A-4 with a resin solids content of 80%.

[0109] Preparation of amino group-containing epoxy resin (b3) Manufacturing Example 1 Into a flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a reflux condenser, 1,200 parts of jER828EL (trade name, epoxy resin manufactured by Mitsubishi Chemical Corporation, epoxy equivalent 190, number average molecular weight 350), 500 parts of bisphenol A, and 0.2 parts of dimethylbenzylamine were added, and the mixture was allowed to react at 130°C until the epoxy equivalent reached 850.

[0110] Next, 160 parts of diethanolamine and 65 parts of a ketimine compound of diethylenetriamine and methyl isobutyl ketone were added, and the mixture was allowed to react at 120°C for 4 hours. After that, 480 g of ethylene glycol monobutyl ether was added to obtain a solution of amino group-containing epoxy resin EPA-1 with a solid content of 80%. The amino group-containing epoxy resin EPA-1 had an amine value of 58 mgKOH / g and a number average molecular weight of 2,100.

[0111] Manufacture of pigment dispersion resins Manufacturing Example 2 In a flask equipped with a stirrer, thermometer, dropping funnel, and reflux condenser, 1010 parts of jER828EL (trade name, epoxy resin manufactured by Mitsubishi Chemical Corporation, epoxy equivalent weight 190, number average molecular weight 350), 390 parts of bisphenol A, 240 parts of PLACCEL 212 (trade name, polycaprolactone diol manufactured by Daicel Chemical Industries, Ltd., weight average molecular weight approximately 1250), and 0.2 parts of dimethylbenzylamine were added and reacted at 130°C until the epoxy equivalent reached approximately 1090. Next, 134 parts of dimethylethanolamine and 150 parts of a 90% lactic acid aqueous solution were added, and the reaction was continued at 90°C until the epoxy groups disappeared. Next, propylene glycol monomethyl ether was added to adjust the solids content, resulting in a pigment dispersion resin containing a quaternary ammonium salt group with a solids content of 60%.

[0112] Pigment dispersion paste manufacturing Manufacturing Example 3 8.3 parts (solids content 5 parts) of the pigment dispersion resin containing a quaternary ammonium base and having a solids content of 60% obtained in Production Example 2, 14.5 parts of titanium oxide, 7 parts of refined clay, 0.3 parts of carbon black, 2 parts of bismuth hydroxide, and 20.3 parts of deionized water were added and dispersed in a ball mill for 20 hours to obtain a pigment dispersion paste P-1 having a solids content of 55%.

[0113] Preparation of cationic electrodeposition coating composition Example B1 37.5 parts (solid content: 30 parts) of the blocked polyisocyanate composition A-1 obtained in Example A1 and 87.5 parts (solid content: 70 parts) of the amino group-containing epoxy resin EPA-1 solution obtained in Production Example 1 were mixed, and 13 parts of 10% acetic acid was further added and stirred uniformly. Deionized water was then added dropwise over a period of about 15 minutes with vigorous stirring to obtain an emulsion with a solid content of 34%. Next, 294 parts of the above emulsion (solid content 100 parts), 52.4 parts of the pigment dispersion paste P-1 obtained in Production Example 3, and 350 parts of deionized water were added to produce cationic electrodeposition paint X-1 with a solid content of 20%.

[0114] Examples B2 to B4, Comparative Examples B1 to B2 Cationic electrodeposition coating compositions (X-2) to (X-6) were produced in the same manner as in Example B1, except that the formulations shown in Table 1 below were used. The results of the evaluation tests (low-temperature curing property, storage stability) described below are also shown in the table.

[0115] [Table 1]

[0116] All of the blend amounts in Table 1 above are values ​​based on solid content.

[0117] Creating test panels The substrates used were cold-rolled steel sheets (150 mm (length) × 70 mm (width) × 0.8 mm (thickness)) that had been subjected to a chemical conversion treatment (product name: Palbond #3020, manufactured by Nippon Parkerizing Co., Ltd., zinc phosphate treatment agent). The substrates were electrodeposited with the cationic electrodeposition paints obtained in the Examples and Comparative Examples to a dry film thickness of 15 μm, and the coatings were baked and dried at 140°C for 20 minutes to obtain test panels.

[0118] <Low temperature curing (gel fraction)> The curability (gel fraction) at 140°C was evaluated from the obtained test plates. The grades are A and B, which are passing grades, and C, which is failing grades. A: Gel fraction is 80% or more, B: Gel fraction is 60% or more and less than 80%; C: The gel fraction is less than 60%.

[0119] <Storage stability (finish after storage)> The resulting cationic electrodeposition paint was placed in a sealed container and stored for 30 days at 40°C. Next, a cold-rolled steel plate (150 mm (length) × 70 mm (width) × 0.8 mm (thickness)) that had been subjected to a chemical conversion treatment (trade name: Palbond #3020, manufactured by Nippon Parkerizing Co., Ltd., zinc phosphate treatment agent) was used as the substrate, and the stored cationic electrodeposition paint was electrodeposited to a dry film thickness of 17 μm, and the plate was baked and dried at 150°C for 20 minutes to obtain a test plate. Furthermore, the surface roughness value (Ra) of the coated surface of the obtained test plate was measured at a cutoff of 0.8 mm using a Surftest 301 (product name, surface roughness meter, manufactured by Mitutoyo Corporation) and evaluated according to the following criteria: A to B are pass, and C is fail. A: Surface roughness value (Ra) is less than 0.25, B: Surface roughness value (Ra) is 0.25 or more and less than 0.3; C: The surface roughness value (Ra) is 0.3 or more.

Claims

1. A cationic electrodeposition coating composition comprising a blocked polyisocyanate composition containing a blocked polyisocyanate obtained from a polyisocyanate and a blocking agent, and an amino group-containing epoxy resin, The blocking agent is represented by formula (1-1) or formula (1-8): (In formulas (1-1) and (1-8), R 10 , R 11 , and R 18 each represent a monovalent organic group selected from an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, and a heterocyclic group; n11 is an integer from 0 to 5, n18 is an integer from 0 to 10, When there are two or more R 11 s and R 18 s, they may be the same or different from each other; Two or more of R 11 may be linked to form a cyclic structure; When there are two or more R 18 s, they may be linked to form a cyclic structure. A cationic electrodeposition coating composition comprising one or more compounds represented by the formula:

2. A cationic electrocoating paint composition as described in claim 1, wherein the polyisocyanate is an aromatic polyisocyanate.

Images