Modified epoxy resin composition and aqueous coating agent

Abstract

To provide a modified epoxy resin composition that exhibits superior solvent resistance and ensures high water-whitening resistance in a coating film formed by drying under comparatively mild conditions.SOLUTION: The present invention relates to a modified epoxy resin composition comprising a polymer composed of a reaction product (A) formed from an epoxy resin (a1) containing a bisphenol-type epoxy resin (a1-1), an amine (a2) containing an alkanolamine (a2-1), and an ethylenically unsaturated monomer (a3) having a glycidyl group, and a monomer component (B) containing an ethylenically unsaturated monomer (b1) having a carboxyl group, wherein the amount of the component (a1-1) used is 85 wt.% or more relative to 100 wt.% of the component (a1), and a primary hydroxyl value represented by a specific formula is more than 60 mgKOH / g and 120 mgKOH / g or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a modified epoxy resin composition and an aqueous coating agent. [Background technology]

[0002] The coating films obtained using water-based coating agents have inferior rust prevention properties compared to solvent-based coating agents. As the range of applications expands, there is a demand for improved levels of water whitening resistance and initial hardness in addition to rust prevention properties.

[0003] As resin compositions for forming such coating films, the present applicant has disclosed, for example, a vinyl-modified epoxy resin aqueous solution that uses a combination of an aromatic epoxy resin and an aliphatic epoxy resin (Patent Document 1), and a modified epoxy resin composition that contains a specific dialkanolamine and a chain aliphatic amine and has a primary hydroxyl value of 10 to 60 mgKOH / g (Patent Document 2).However, with these modified epoxy resin compositions, the coating films dried under milder conditions exhibited poor water-whitening resistance and also had insufficient solvent resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-120340 [Patent Document 2] Patent No. 7188634 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a modified epoxy resin composition which exhibits excellent solvent resistance and has high water whitening resistance even when the coating film obtained is dried under relatively mild conditions. [Means for solving the problem]

[0006] The present inventors have conducted extensive research and have found a solution to the above problems, thereby completing the present invention. That is, the present invention relates to the following modified epoxy resin composition and aqueous coating agent.

[0007] 1. A polymer comprising, as constituent components, a reaction product (A) consisting of an epoxy resin (a1) containing a bisphenol-type epoxy resin (a1-1), an amine (a2) containing an alkanolamine (a2-1), and an ethylenically unsaturated monomer (a3) ​​having a glycidyl group, and a monomer component (B) containing an ethylenically unsaturated monomer (b1) having a carboxyl group, The amount of component (a1-1) used is 85% by weight or more relative to 100% by weight of component (a1), A modified epoxy resin composition having a primary hydroxyl value represented by the following formula (1) of more than 60 mgKOH / g and not more than 120 mgKOH / g. (Equation 1) (Primary hydroxyl value of modified epoxy resin composition) = (Number of hydroxyl groups of alkanolamine) × (Molecular weight of potassium hydroxide) / (Weight of nonvolatile content of all constituent components)

[0008] 2. The modified epoxy resin composition according to item 1 above, wherein the component (a2-1) contains a monoalkanolamine and a dialkanolamine.

[0009] 3. The modified epoxy resin composition according to item 1 or 2 above, wherein the component (B) further contains a styrene (b2) and / or a (meth)acrylic acid ester (b3).

[0010] 4. The modified epoxy resin composition according to item 1 or 2 above, wherein the ratio of component (A) to component (B) [(A) / (B)] is 60 / 40 to 99 / 1 by weight of nonvolatile matter.

[0011] 5. An aqueous coating agent comprising the modified epoxy resin composition according to item 1 or 2 above. [Effects of the Invention]

[0012] The modified epoxy resin composition of the present invention exhibits excellent solvent resistance, and even a coating film obtained by drying under relatively mild conditions has high resistance to water whitening. DETAILED DESCRIPTION OF THE INVENTION

[0013] The modified epoxy resin composition of the present invention contains a polymer composed of a specific reaction product (A) (hereinafter referred to as component (A)) and a monomer component (B) (hereinafter referred to as component (B)) containing an ethylenically unsaturated monomer (b1) having a carboxyl group (hereinafter referred to as component (b1)). Each component will be described in detail below.

[0014] [About component (A)] Component (A) is a reaction product of an epoxy resin (a1) (hereinafter referred to as component (a1)), an amine (a2) (hereinafter referred to as component (a2)), and an ethylenically unsaturated monomer (a3) ​​(hereinafter referred to as component (a3)) having a glycidyl group. Here, the ethylenically unsaturated monomer refers to a monomer having either a carbon-carbon double bond, a carbon-carbon triple bond, or both in the molecule (the same applies hereinafter).

[0015] [(a1) Component] Component (a1) contains a bisphenol-type epoxy resin (a1-1) (hereinafter referred to as component (a1-1)). By using component (a1-1), the aqueous coating agent has high adhesion to the substrate, and the coating film tends to exhibit excellent rust prevention properties.

[0016] Examples of the component (a1-1) include reaction products of bisphenols and haloepoxides such as epichlorohydrin or 2-methylepichlorohydrin.

[0017] Examples of bisphenols include reaction products of phenol or 2,6-dihalophenol (hereinafter referred to as phenols) and aldehydes (e.g., formaldehyde, acetaldehyde, etc.); reaction products of phenols and ketones (e.g., acetone, acetophenone, cyclohexanone, benzophenone, etc.); oxidation reaction products of dihydroxyphenyl sulfide with peracid; and etherification reaction products of hydroquinone. More specifically, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) and bis(4-hydroxyphenyl)methane (bisphenol F) are examples. These may be used alone or in combination of two or more. Among these, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) is preferred because it provides excellent coating film hardness and rust resistance.

[0018] Commercially available products of the component (a1) include, for example, “Epotohto YD-011,” “Epotohto YD-014,” “Epotohto YD-017,” “Epotohto YD-019,” and “Epotohto YD-128” (all manufactured by Nippon Steel Chemical & Material Co., Ltd.).

[0019] The amount of component (a1-1) used is 85% by weight or more, based on 100% by weight of component (a1), in terms of nonvolatile weight. When the amount of component (a1) used is 85% by weight or more, the coating film exhibits excellent solvent resistance. Furthermore, the coating film obtained by drying under relatively mild conditions also exhibits high resistance to water whitening. From the same viewpoint, the amount of component (a1-1) used is preferably 90% by weight or more, more preferably 95% by weight or more, and even more preferably 100% by weight.

[0020] The component (a1) may be used in combination with an epoxy resin (a1-2) other than a bisphenol-type epoxy resin (hereinafter also referred to as component (a1-2)). Examples of the component (a1-2) include aliphatic epoxy resins, aromatic epoxy resins, etc. These may be used alone or in combination of two or more.

[0021] Examples of aliphatic epoxy resins include resins containing glycidyl esters of aliphatic dibasic acids, glycidyl ethers of aliphatic polyols, and glycidyl ethers of polyether polyols.

[0022] Examples of aliphatic dibasic acids include sebacic acid, azelaic acid, dodecanoic acid, malonic acid, succinic acid, glutaric acid, adipic acid, 8,11-dimethyl-7,11-octadecadiene-1,18-dicarboxylic acid, 7-ethyloctadecanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid.

[0023] Examples of the aliphatic polyol include 1,4-butanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol.

[0024] Examples of polyether polyols include diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, heptaethylene glycol, octaethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, pentapropylene glycol, hexapropylene glycol, polyethylene glycol, polypropylene glycol, polyoxyethylene polyoxypropylene glycol, polybutylene glycol, etc. Commercially available products include, for example, "Denacol EX-832," "Denacol EX-841," and "Denacol EX-931" (all manufactured by Nagase ChemteX Corporation).

[0025] Examples of aromatic epoxy resins include cresol novolac type epoxy resins, phenol novolac type epoxy resins, triphenolmethane type epoxy resins, triphenolethane type epoxy resins, trisphenol type epoxy resins, diphenyl ether type epoxy resins, and biphenyl type epoxy resins.

[0026] The amount of component (a1-2) used is usually 15% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less, and even more preferably 0% by weight, in terms of non-volatile weight, because this tends to give a coating film with excellent solvent resistance and also tends to give a coating film obtained by drying under relatively mild conditions with high water-whitening resistance.

[0027] The physical properties of the component (a1) include, for example, an epoxy group concentration of 0.4×10 -3 ~5.5×10 -3 eq / g is preferable, and 0.5×10 -3 ~3.5×10 -3 The epoxy group concentration of component (a1) is more preferably about eq / g. The method for calculating the epoxy group concentration of component (a1) is as described in JP 2019-137862 A.

[0028] Component (a2) contains alkanolamine (a2-1) (hereinafter referred to as component (a2-1)). Use of component (a2-1) tends to provide a coating film with excellent solvent resistance, and also tends to provide a coating film obtained by drying under relatively mild conditions with high water-whitening resistance.

[0029] The amount of component (a2-1) used is preferably 60% by weight or more, more preferably 75% by weight or more, even more preferably 85% by weight or more, even more preferably 90% by weight or more, and particularly preferably 100% by weight, of 100% by weight of component (a2), in terms of non-volatile weight, so that the coating film tends to have excellent solvent resistance and the coating film obtained by drying under relatively mild conditions tends to exhibit high resistance to water whitening.

[0030] As the component (a2-1), monoalkanolamines and dialkanolamines are preferred.

[0031] The monoalkanolamine is an amine having one alkanol group, and from the viewpoint of reactivity with component (a1), a monoalkanolamine having one NH bond (secondary monoalkanolamine) or a monoalkanolamine having two NH bonds (primary monoalkanolamine) is preferred.

[0032] Examples of monoalkanolamines having one N-H bond (secondary monoalkanolamines) include N-methylethanolamine, N-ethylethanolamine, Nn-propylethanolamine, N-isopropylethanolamine, Nn-butylethanolamine, N-isobutylethanolamine, Ns-butylethanolamine, Nt-butylethanolamine, N-phenylethanolamine, N-benzylethanolamine, N-methylbutanolamine, N-ethylbutanolamine, Nn-propylbutanolamine, N-isopropylbutanolamine, N-butylbutanolamine, N-isobutylbutanolamine, etc. These may be used alone or in combination of two or more.

[0033] Examples of monoalkanolamines having two NH bonds (primary monoalkanolamines) include monomethanolamine, monoethanolamine, monopropanolamine, 1-amino-2-propanol, 2-amino-1-propanol, 2-amino-2-methyl-1-propanol, 4-amino-1-butanol, 5-amino-1-pentanol, 6-amino-1-hexanol, etc. These may be used alone or in combination of two or more.

[0034] Of these, monoalkanolamines having two NH bonds (primary monoalkanolamines) are preferred, with monomethanolamine, monoethanolamine, and monopropanolamine being more preferred, in view of making it easier to adjust the molecular weight of the component (A).

[0035] The amount of monoalkanolamine used is preferably 20 to 80% by weight, more preferably 25 to 70% by weight, and even more preferably 35 to 65% by weight, based on 100% by weight of component (a2-1), in terms of non-volatile weight, as this tends to give a coating film with excellent solvent resistance and also tends to give a coating film obtained by drying under relatively mild conditions with high water-whitening resistance.

[0036] The dialkanolamine is an amine having two alkanol groups, and from the viewpoint of reactivity with the component (a1), a dialkanolamine having an NH bond (secondary dialkanolamine) is preferred. Examples of dialkanolamines having an NH bond (secondary dialkanolamine) include diethanolamine, di-n-propanolamine, diisopropanolamine, bis(2-hydroxybutyl)amine, bis(2-hydroxypentyl)amine, and bis(2-hydroxyhexyl)amine. These may be used alone or in combination of two or more.

[0037] Among these, diethanolamine, di-n-propanolamine, and diisopropanolamine are more preferred because the coating film tends to have excellent solvent resistance and the coating film obtained by drying under relatively mild conditions tends to exhibit high water whitening resistance.

[0038] The amount of dialkanolamine used is preferably 10 to 75% by weight, more preferably 20 to 65% by weight, and even more preferably 30 to 60% by weight, based on 100% by weight of component (a2-1), in terms of the non-volatile weight, since this tends to give the coating film excellent solvent resistance and also tends to give the coating film obtained by drying under relatively mild conditions excellent water-whitening resistance.

[0039] The component (a2) may further contain an amine (a2-2) other than the component (a2-1) (hereinafter referred to as the component (a2-2)).

[0040] Examples of the component (a2-2) include aliphatic amines, alicyclic amines, and aromatic amines.

[0041] Examples of the aliphatic amine include monoalkyl monoamines, monoalkenyl amines, dialkyl monoamines, dialkenyl monoamines, and alkane diamines.

[0042] Examples of monoalkyl monoamines include methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, s-butylamine, t-butylamine, n-pentylamine, isopentylamine, n-hexylamine, n-heptylamine, n-octylamine, isooctylamine, 2-ethylhexylamine, n-nonylamine, n-decylamine, isodecylamine, n-undecylamine, n-dodecylamine (n-laurylamine), n-tridecylamine, n-tetradecylamine (n-myristylamine), n-pentadecylamine, n-hexadecylamine (n-palmitylamine), n-heptadecylamine, n-octadecylamine (n-stearylamine), isooctadecylamine (isostearylamine), etc. These may be used alone or in combination of two or more.

[0043] Examples of monoalkenyl monoamines include vinylamine, allylamine, butenylamine, pentenylamine, hexenylamine, heptenylamine, octenylamine, nonenylamine, decenylamine, undecenylamine, dodecenylamine, tridecenylamine, tetradecenylamine, pentadecenylamine, hexadecenylamine, heptadecenylamine, octadecenylamine (oleylamine, etc.), nonadecenylamine, icosenylamine, and dodecenylamine. These may be used alone or in combination of two or more. Furthermore, the position of the carbon-carbon double bond in these monoalkenylamines is not particularly limited, and their structural isomers may also be used freely.

[0044] Examples of dialkyl monoamines include dimethylamine, N-ethylmethylamine, diethylamine, N-ethyl-N-(n-propyl)amine, di-n-propylamine, n-propylisopropylamine, diisopropylamine, di-n-butylamine, diisobutylamine, di-s-butylamine, di-t-butylamine, Nn-butylethylamine, Ns-butylethylamine, Nt-butylethylamine, Nn-butylpropylamine, Ns-butylpropylamine, Nt-butylpropylamine, and Nt-butylisopropylamine. Examples of suitable amines include dipentylamine (diamylamine), diisopentylamine (diisoamylamine), dihexylamine, diheptylamine, dioctylamine, bis(2-ethylhexyl)amine, dinonylamine, didecylamine, diundecylamine, didodecylamine (dilaurylamine), ditridecylamine, ditetradecylamine (dimyristylamine), dipentadecylamine, dihexadecylamine (dipalmitylamine), diheptadecylamine, and dioctadecylamine (distearylamine). These may be used alone or in combination of two or more.

[0045] Examples of dialkenyl monoamines include divinylamine, diallylamine, dibutenylamine, dipentenylamine, dihexenylamine, diheptenylamine, dioctenylamine, dinonenylamine, didecenylamine, diundecenylamine, didodecenylamine, ditridecenylamine, ditetradecenylamine, dipentadecenylamine, dihexadecenylamine, diheptadecenylamine, dioctadecenylamine, dinonadecenylamine, diicosenylamine, didodecenylamine, etc. Furthermore, the position of the carbon-carbon double bond in these dialkenylamines is not particularly limited, and structural isomers thereof can also be freely used.

[0046] Examples of alkanediamines include ethylenediamine, 1,3-propanediamine, propane-1,2-diamine, 1,2-butanediamine, 1,3-butanediamine, 1,4-butanediamine, 1,2-pentanediamine, 1,3-pentanediamine, 1,4-pentanediamine, 1,5-pentanediamine, 1,2-hexanediamine, 1,3-hexanediamine, 1,4-hexanediamine, 1,5-hexanediamine, 1,6-hexanediamine, trimethylhexanediamine, etc. These may be used alone or in combination of two or more.

[0047] Examples of alicyclic amines include cycloalkyl monoamines such as cyclopentylamine, cyclohexylamine, 2-methylcyclohexylamine, 3-methylcyclohexylamine, 4-methylcyclohexylamine, cycloheptylamine, and cyclooctylamine; N-alkyl cycloalkyl monoamines such as N-methylcyclopentylamine, N-ethylcyclopentylamine, N-methylcyclohexylamine, and N-ethylcyclohexylamine; and cycloalkane diamines such as 1,2-cyclopentanediamine, 1,3-cyclopentanediamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, and isophoronediamine. These may be used alone or in combination of two or more.

[0048] Examples of aromatic amines include aniline, methylaniline, dimethylaniline, ethylaniline, n-propylaniline, isopropylaniline, n-butylaniline, isobutylaniline, n-pentylaniline, n-hexylaniline, nonylaniline, dodecylaniline, benzylamine, phenethylamine, etc. These may be used alone or in combination of two or more.

[0049] When the amount of the (a2) component is taken as 100% by weight, the amount of the (a2-2) component used is preferably 40% by weight or less, more preferably 25% by weight or less, even more preferably 15% by weight or less, even more preferably 10% by weight or less, and particularly preferably 0% by weight.

[0050] The component (a3) ​​is an ethylenically unsaturated monomer having a glycidyl group, and its structure is introduced into the component (A) to facilitate the addition of the component (B).

[0051] Examples of component (a3) ​​include glycidyl (meth)acrylate, 2-methylglycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 1,2-epoxy-4-vinylcyclohexane, which may be used alone or in combination of two or more. Among these, glycidyl acrylate and glycidyl methacrylate are preferred.

[0052] The ratio of the use of components (a1), (a2), and (a3) ​​is {(number of epoxy groups in component (a1)) + (number of epoxy groups in component (a3))} / (number of active hydrogen atoms in amino groups in component (a2)) is about 100 / 120 to 100 / 80, preferably about 100 / 110 to 100 / 90, and more preferably about 100 / 105 to 100 / 95. By setting the ratio within this range, component (A) is more likely to exhibit excellent coating film performance. The method for calculating the number of epoxy groups and the number of active hydrogen atoms in amino groups is as described in JP 2019-137862 A.

[0053] Furthermore, polyisocyanate may be used as a constituent of component (A) if necessary.

[0054] Examples of polyisocyanates include aromatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates, etc. These may be used alone or in combination of two or more.

[0055] Examples of aromatic polyisocyanates include xylylene diisocyanate, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, orthotoluidine diisocyanate, polyphenyl polyisocyanate, etc. These may be used alone or in combination of two or more.

[0056] Examples of aliphatic polyisocyanates include butane-1,4-diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, etc. These may be used alone or in combination of two or more.

[0057] Examples of alicyclic polyisocyanates include cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, isophorone diisocyanate, etc. These may be used alone or in combination of two or more.

[0058] The amount of polyisocyanate used is preferably about 0.005 to 2, more preferably about 0.05 to 0.5, in terms of the ratio of {number of isocyanate groups in polyisocyanate} / {number of hydroxyl groups in components (a1) to (a3)}. The method for calculating the number of isocyanate groups and the number of hydroxyl groups is as described in JP 2019-137862 A.

[0059] The component (A) can be obtained by reacting the components (a1), (a2), and (a3), and optionally a polyisocyanate. The production conditions include a reaction temperature of typically 50 to 250° C., and preferably 80 to 150° C. The reaction time is typically 3 to 12 hours, and preferably 3 to 8 hours.

[0060] In the production method, a hydrophilic organic solvent may be used. Examples of hydrophilic organic solvents include alkylene glycol monoethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-butyl ether, and propylene glycol mono-t-butyl ether; dialkylene glycol monoethers such as diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, and dipropylene glycol methyl ether; alkoxy alcohols such as 3-methoxybutanol and 3-methoxy-3-methylbutanol; cellosolves such as methyl cellosolve, ethyl cellosolve, n-butyl cellosolve, and t-butyl cellosolve; cellosolve acetates such as methyl cellosolve acetate and ethyl cellosolve acetate; and aliphatic monoalcohols such as isopropyl alcohol and n-butyl alcohol. These may be used alone or in combination. Furthermore, the hydrophilic solvent may be further added after the production of component (A). The amount of the hydrophilic organic solvent used is preferably adjusted so that the reaction concentration is about 30 to 80% by weight.

[0061] [About component (B)] The component (B) is a monomer component containing an ethylenically unsaturated monomer (b1) having a carboxyl group (hereinafter referred to as component (b1)), and makes the modified epoxy resin composition more easily dispersible in water.

[0062] Examples of component (b1) include α,β-unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; α,β-unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, muconic acid and citraconic acid; anhydrides of the above carboxylic acids; and alkali metal salts of the above carboxylic acids such as sodium salts and potassium salts. These may be used alone or in combination of two or more. Among these, (meth)acrylic acid, maleic acid, fumaric acid and itaconic acid are preferred, and methacrylic acid and acrylic acid are more preferred, in terms of good dispersibility of the modified epoxy resin composition in water.

[0063] The amount of component (b1) used is preferably about 0.1 to 20 parts by weight, more preferably about 1 to 10 parts by weight, per 100 parts by weight of component (A), in order to ensure good dispersion of the modified epoxy resin composition in water.

[0064] When the component (b1) is used, a carbodiimide may be used as needed.

[0065] Examples of carbodiimides include poly(4,4'-diphenylmethanecarbodiimide), poly(tolylcarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(3,3'-dimethyl-4,4'-diphenylmethanecarbodiimide), poly(naphthylenecarbodiimide), poly(1,6-hexamethylenecarbodiimide), poly(1,4-tetramethylenecarbodiimide), poly(1,3-cyclohexylenecarbodiimide), poly(1,4-cyclohexylenecarbodiimide), poly(1,3 Examples of suitable carbodiimides include N,N'-triethylphenylenecarbodiimide), poly(4,4'-methylenebiscyclohexylcarbodiimide), poly(1,3-diisopropylphenylenecarbodiimide), poly(1-methyl-3,5-diisopropylphenylenecarbodiimide), poly(isopropylphenylenecarbodiimide), N,N'-dicyclohexylcarbodiimide, N,N'-diisopropylcarbodiimide, N,N'-diisopropylphenylcarbodiimide, and N-ethyl-N'-(3-dimethylaminopropyl)-carbodiimide hydrochloride. Commercially available carbodiimides include "Carbodilite E-02," "Carbodilite V-02," and "Carbodilite V-04" (all manufactured by Nisshinbo Chemical Inc.). These may be used alone or in combination of two or more.

[0066] The amount of carbodiimide used is preferably about 0.005 to 2, more preferably about 0.05 to 0.5, in terms of the ratio of {number of imide groups in carbodiimide} / {number of carboxyl groups in component (b1)}.

[0067] The number of imide groups in a carbodiimide is the molar amount of the carbodiimide charged multiplied by the number of imide groups per molecule of carbodiimide. When multiple carbodiimides are used, the number of imide groups is the sum of the numbers of imide groups in each component.

[0068] The number of carboxyl groups in component (b1) is the molar amount of component (b1) multiplied by the number of carboxyl groups per molecule of component (b1). When multiple components (b1) are used, the number of carboxyl groups is the sum of the numbers of carboxyl groups in each component.

[0069] The component (B) may further contain a styrene (b2) (hereinafter referred to as the component (b2)) and / or a (meth)acrylic acid ester (b3) (hereinafter referred to as the component (b3)).

[0070] Examples of the component (b2) include styrene, α-methylstyrene, t-butylstyrene, dimethylstyrene, acetoxystyrene, hydroxystyrene, vinyltoluene, chlorovinyltoluene, etc. These may be used alone or in combination of two or more.

[0071] The amount of component (b2) used is preferably about 0.1 to 40 parts by weight, and more preferably about 1 to 20 parts by weight, per 100 parts by weight of component (A).

[0072] Examples of component (b3) include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, etc. These may be used alone or in combination of two or more. Of these, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate are preferred because they tend to provide excellent water-resistant adhesion to the coating film.

[0073] The amount of component (b3) used is preferably about 0.1 to 40 parts by weight, and more preferably about 1 to 20 parts by weight, per 100 parts by weight of component (A). degree is more preferable.

[0074] Furthermore, component (B) may contain, if necessary, a monomer component (b4) (hereinafter referred to as component (b4)) other than components (b1) to (b3). Examples of component (b4) include ethylenically unsaturated monomers having a sulfonic acid group, such as styrenesulfonic acid, methallyl sulfonic acid, methallyloxybenzenesulfonic acid, allyloxybenzenesulfonic acid, acrylamido-2-methylpropanesulfonic acid, and acrylamido-t-butylsulfonic acid; vinyl carboxylates, such as vinyl acetate and vinyl propionate; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate; Examples include (meth)acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 7-hydroxyheptyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; (meth)acrylamides such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, and N-ethyl-N-methyl(meth)acrylamide; and (meth)acrylonitrile. These may be used alone or in combination of two or more.

[0075] The amount of component (b4) used is preferably about 0.1 to 40 parts by weight per 100 parts by weight of component (A).

[0076] The polymerization method for components (A) and (B) is preferably a solution polymerization method. The conditions are, for example, in the presence of a polymerization initiator, a temperature of about 60 to 150°C, preferably about 70 to 140°C, and a time of about 1 to 8 hours, preferably about 2 to 6 hours. The aforementioned organic solvent may also be used in the system.

[0077] The ratio of the (A) component to the (B) component used is preferably (A) / (B)=60 / 40 to 99 / 1, more preferably 70 / 30 to 97 / 3, and even more preferably 80 / 20 to 95 / 5 by weight of nonvolatile matter, in order to ensure good dispersion of the modified epoxy resin composition in water and excellent rust prevention of the coating film.

[0078] Examples of the polymerization initiator include azo compounds such as 2,2'-azobisisobutyronitrile and 2,2'-azobis-2,4-dimethylvaleronitrile, and organic peroxides such as benzoyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, t-butylperoxy-2-ethylhexanoate, dicumyl peroxide, and lauroyl peroxide. These may be used alone or in combination of two or more.

[0079] The amount of the polymerization initiator used is preferably 0.5 to 10 parts by weight, and more preferably 1 to 5 parts by weight, per 100 parts by weight of the total of the components (A) and (B).

[0080] Examples of organic solvents include those listed in the section on the production method for component (A). The amount of organic solvent used may be adjusted so that the reaction concentration is about 30 to 90% by weight. The polymer obtained by the production method may contain a solvent, but it is preferable to remove it by distillation under reduced pressure or the like, so that the content is less than 20% by weight.

[0081] When the polymer obtained by the above-mentioned production method is used in an aqueous coating agent, it is dissolved or dispersed by adding water. To facilitate dissolution or dispersion in water, the polymer is preferably neutralized with a base (i.e., to form a base-neutralized modified epoxy resin composition). The pH after neutralization is preferably 7 to 10. Examples of bases used as neutralizing agents include amines such as ammonia, triethylamine, and N,N-dimethylethanolamine, and alkali metal hydroxides such as potassium hydroxide and sodium hydroxide. These may be used alone or in combination of two or more. Among these, ammonia and amines are preferred because they are easily volatilized during drying.

[0082] The modified epoxy resin composition of the present invention may contain additives such as surface conditioners, surfactants, ultraviolet absorbers, antioxidants, antifoaming agents, wetting agents, and rust inhibitors, as needed, which may be used alone or in combination of two or more.

[0083] The primary hydroxyl value (unit: mgKOH / g) is an important physical property of the modified epoxy resin composition of the present invention, because the coating film tends to have excellent solvent resistance and the coating film obtained by drying under relatively mild conditions tends to exhibit high water-whitening resistance. This value can be calculated using the number of hydroxyl groups in the alkanolamine, the molecular weight of potassium hydroxide (Mw 56.11), and the weight of the nonvolatile content of all constituent components according to Equation 1. (Formula 1) (Primary hydroxyl value of modified epoxy resin composition) = (number of hydroxyl groups of alkanolamine) × (molecular weight of potassium hydroxide) / (weight of nonvolatile content of all components)

[0084] The number of hydroxyl groups in an alkanolamine is expressed as the product of the number of moles of the alkanolamine and the number of hydroxyl groups. For example, the number of hydroxyl groups in 0.8 moles of diethanolamine is 0.8 x 2 = 1.6, since the number of hydroxyl groups in diethanolamine is 2. Similarly, the number of hydroxyl groups in 0.5 moles of monoethanolamine is 0.5 x 1 = 0.5, since the number of hydroxyl groups in monoethanolamine is 1. When multiple alkanolamines are used, the number of hydroxyl groups in each is calculated and added together to determine the number of hydroxyl groups in the alkanolamine.

[0085] When a polyisocyanate is used, it can react with the hydroxyl groups of the alkanolamine, so the net number of hydroxyl groups of the alkanolamine is calculated by subtracting the number of isocyanate groups of the polyisocyanate calculated by the above-mentioned method from the number of hydroxyl groups of the alkanolamine.

[0086] The nonvolatile weight of all constituent components is the sum of the charged weights of the nonvolatile contents of each constituent component of component (A) and each monomer component belonging to component (B) (the same applies hereinafter).

[0087] The primary hydroxyl value is more than 60 mgKOH / g and not more than 120 mgKOH / g. When the primary hydroxyl value is within this range, the coating film tends to have excellent solvent resistance, and the coating film obtained by drying under relatively mild conditions tends to exhibit high water whitening resistance. From the same viewpoint, the primary hydroxyl value is preferably 65 to 110 mgKOH / g, more preferably 65 to 100 mgKOH / g, and even more preferably 65 to 90 mgKOH / g.

[0088] As for other physical properties of the modified epoxy resin composition, the total hydroxyl value is preferably 240 to 350 mgKOH / g, more preferably 250 to 320 mgKOH / g, and even more preferably 255 to 300 mgKOH / g, from the viewpoints that the coating film tends to have excellent solvent resistance and that the coating film obtained by drying under relatively mild conditions tends to exhibit high water-whitening resistance. The total hydroxyl value (unit: mhKOH / g) can be calculated using (Equation 2) using the number of hydroxyl groups in the modified epoxy resin composition, the molecular weight of potassium hydroxide (Mw 56.11), and the weight of the nonvolatile content of all constituent components of the modified epoxy resin composition. (Equation 2) (Total hydroxyl value of modified epoxy resin composition) = (number of hydroxyl groups in modified epoxy resin composition) × (molecular weight of potassium hydroxide) / (weight of nonvolatile content of all constituent components)

[0089] The number of hydroxyl groups in the modified epoxy resin composition is determined as the sum of the numbers of hydroxyl groups in components (a1) to (a3). The number of hydroxyl groups in component (a1) can be calculated by multiplying the molar amount of component (a1) charged by the number of hydroxyl groups per molecule, including the hydroxyl groups generated upon ring-opening of the epoxy groups in component (a1). When component (a1) contains multiple components, the number of hydroxyl groups in component (a1) is the sum of the numbers of hydroxyl groups in each component. The same applies to the number of hydroxyl groups in component (a3). The number of hydroxyl groups in component (a2) is as described above.

[0090] When a polyisocyanate is used, it may react with these hydroxyl groups, and therefore the net number of hydroxyl groups in the modified epoxy resin composition is determined by subtracting the number of isocyanate groups in the polyisocyanate calculated by the above-mentioned method from the number of hydroxyl groups in components (a1) to (a3).

[0091] Furthermore, the nonvolatile content of the modified epoxy resin composition is preferably 25 to 40% by weight, more preferably 30 to 40% by weight.

[0092] Furthermore, the viscosity at a nonvolatile content of 33% by weight and at a temperature of 25°C is preferably 200 to 4000 mPa·s, more preferably 400 to 3000 mPa·s, in view of ease of forming a coating using the modified epoxy resin composition.

[0093] The aqueous coating agent of the present invention contains the modified epoxy resin composition and can be used as a paint or surface treatment agent for substrates such as wood, paper, textiles, plastics, ceramics, iron, and non-ferrous metals (e.g., degreased dull steel sheets).

[0094] In preparing the aqueous coating agent of the present invention, for example, color pigments such as carbon black and titanium oxide; extender pigments such as talc, calcium carbonate, and barium sulfate; rust-preventive pigments such as aluminum phosphomolybdate, zinc phosphate, and zinc oxide; metal compounds such as cobalt compounds, nickel compounds, and zirconium compounds; silane coupling agents, colloidal silica, and the like can be appropriately blended. Furthermore, if necessary, curing agents such as melamine resins, urea resins, isocyanates, blocked isocyanates, and carbodiimides, additives such as colorants, plasticizers, dispersants, and rust inhibitors, and the aforementioned organic solvents may also be appropriately blended. The nonvolatile content of the aqueous coating agent is preferably 20 to 80% by weight, more preferably 30 to 60% by weight.

[0095] The physical properties of the aqueous coating agent of the present invention are, for example, a nonvolatile concentration of 30 to 60% by weight and a viscosity at 25°C of usually about 10 to 500 mPa·s, preferably about 50 to 300 mPa·s. [Example]

[0096] The present invention will be described in more detail below through examples and comparative examples. However, the technical scope of the present invention is not limited by these descriptions. In the examples, "parts" and "%" are by weight unless otherwise specified.

[0097] (viscosity) A solution of the modified epoxy resin composition with a nonvolatile content of 33% was left to stand in a thermostatic bath at 25°C, and then the viscosity was measured using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.).

[0098] (Total hydroxyl value and primary hydroxyl value) The total hydroxyl value of the modified epoxy resin composition was calculated from Equation 2, and the primary hydroxyl value was calculated from Equation 1. (Equation 2) (Total hydroxyl value of modified epoxy resin composition) = (number of hydroxyl groups in modified epoxy resin composition) × (molecular weight of potassium hydroxide) / (weight of nonvolatile content of all constituent components) (Formula 1) (Primary hydroxyl value of modified epoxy resin composition) = (number of hydroxyl groups of alkanolamine) × (molecular weight of potassium hydroxide) / (weight of nonvolatile content of all components)

[0099] Example 1 A reactor equipped with a stirrer, condenser, thermometer, and nitrogen gas inlet tube was charged with 200 parts of t-butyl cellosolve, 300 parts of bisphenol A epoxy resin (trade name: "Epotohto YD-011," epoxy equivalent: 475 g / eq, manufactured by Nippon Steel Chemical & Material Co., Ltd.), and 6 parts of glycidyl methacrylate. The mixture was dissolved at 120°C under a nitrogen stream. Then, 10.6 parts of diethanolamine and 17.5 parts of monoethanolamine were added and reacted for 7 hours to obtain reaction product (A-1). Next, a mixture of 15.0 parts of acrylic acid, 10.0 parts of styrene, 10.0 parts of methyl acrylate, and 4 parts of t-butylperoxy-2-ethylhexanoate was charged to the dropping funnel and added dropwise to the reaction system over 1 hour. The mixture was then kept at room temperature for 3 hours. After cooling to 80°C, 14 parts of a 28% aqueous ammonia solution and 525 parts of water were added in that order and mixed to obtain a modified epoxy resin composition with a non-volatile content of 33%. The physical properties are shown in Table 1 (the same applies hereinafter).

[0100] Examples 2 to 14, Comparative Examples 1 to 7 Modified epoxy resin compositions were obtained using the compositions shown in Table 1 in the same manner as in Example 1.

[0101] (Preparation of aqueous coating agent) Mixtures of the following compositions were mixed in a paint shaker to prepare aqueous coating agents. (composition) 200 parts of each modified epoxy resin composition Talc 38 parts Carbon black 4 parts Zinc oxide 8 parts Zinc phosphate anti-rust pigment 2.8 parts 18 parts calcium carbonate 10 parts ion-exchanged water

[0102] (Preparation of coating film (1)) The aqueous coating agent was applied to a degreased dull steel plate (SPCC-SD, 0.8 × 70 × 150 mm) (hereinafter referred to as SPCC-SD) using a bar coater so that the film thickness after drying would be 25 to 30 μm. After drying at a temperature of 80°C for 20 minutes, the coating was left to stand for 6 days in an environment of a temperature of 23°C and a humidity of 60%, thereby producing coating film (1).

[0103] (Evaluation of coating film) (1) Solvent resistance A cotton swab soaked in propylene glycol monomethyl ether was moved back and forth across the surface of the coating film (1), and the number of times it was moved back and forth was counted until the coating film peeled off. The higher the number of times, the better the solvent resistance. The results are shown in Table 1 (same below).

[0104] (2) Water whitening resistance According to JIS K5600-6-2, the appearance of the coating film was visually observed after immersion in warm water at 40°C for 10 days. The evaluation criteria are as follows: (Evaluation criteria) 5: No bleaching at all 4: Almost no bleaching 3: Slightly bleached 2: Almost bleached 1: Completely bleached

[0105] (5) Rust prevention The test was carried out in accordance with JIS K5600-7-9, and the results were expressed as the width (mm) of the cellophane tape peeled off after 10 and 20 days of salt spray testing.

[0106] (Preparation of coatings (2) and (3)) In the preparation of the coating film (1), the drying conditions were changed to a temperature of 60° C. for 20 minutes to prepare the coating film (2). Furthermore, in the preparation of the coating film (1), the coating film (3) was prepared by leaving the film for 6 days in an environment of a temperature of 23°C and a humidity of 60% without drying under heat. The resulting coating films (2) and (3) were evaluated for water whitening resistance in the same manner as above.

[0107] [Table 1]

[0108] [Component (A)] Component (a1) YD-011: Bisphenol A epoxy resin (product name: "Epotohto YD-011", Mw 900, epoxy equivalent: 475 g / eq, number of hydroxyl groups per molecule before ring opening: 2 (after ring opening: 4), manufactured by Nippon Steel Chemical & Material Co., Ltd.) YD-014: Bisphenol A epoxy resin (product name: "Epotohto YD-014", Mw 1400, epoxy equivalent: 950 g / eq, number of hydroxyl groups per molecule before ring opening: 3.7 (after ring opening: 5.7), manufactured by Nippon Steel Chemical & Material Co., Ltd.) YD-128: Bisphenol A epoxy resin (product name: "Epotohto YD-128", Mw 378, epoxy equivalent: 189 g / eq, number of hydroxyl groups per molecule before ring opening: 0 (after ring opening: 2), manufactured by Nippon Steel Chemical & Material Co., Ltd.) EX-841: Polyethylene glycol diglycidyl ether (trade name: "Denacol EX-841", Mw 744, epoxy equivalent: 372 g / eq, number of hydroxyl groups per molecule before ring-opening: 0 (after ring-opening: 2), manufactured by Nagase ChemteX Corporation) EX-931: Polypropylene glycol diglycidyl ether (trade name: "Denacol EX-931", Mw: 940, epoxy equivalent: 472 g / eq, number of hydroxyl groups per molecule before ring-opening: 0 (after ring-opening: 2), manufactured by Nagase ChemteX Corporation) (a2) Component DEA: Diethanolamine (molecular weight: 105.1, number of hydroxyl groups: 2) DIPA: Diisopropanolamine (molecular weight: 133.2, number of hydroxyl groups: 2) MEA: Monoethanolamine (molecular weight: 61, number of hydroxyl groups: 1) SA: Stearylamine (molecular weight: 269.6) OLA: Oleylamine (molecular weight: 267.5) DBA: Di-n-butylamine (molecular weight: 129.3) (a3) Component GMA: Glycidyl methacrylate (epoxy equivalent: 142.2 g / eq, number of hydroxyl groups per molecule before ring opening: 0 (after ring opening: 1)) [(B) Component] AA: Acrylic acid St: Styrene MA: Methyl acrylate

Claims

1. The polymer comprises, as constituent components, a reaction product (A) consisting of an epoxy resin (a1) containing a bisphenol-type epoxy resin (a1-1), an amine (a2) containing an alkanolamine (a2-1), and an ethylenically unsaturated monomer (a3) ​​having a glycidyl group, and a monomer component (B) containing an ethylenically unsaturated monomer (b1) having a carboxyl group, The amount of component (a1-1) used is 85% by weight or more relative to 100% by weight of component (a1), A modified epoxy resin composition having a primary hydroxyl value represented by the following formula (1) of more than 60 mgKOH / g and not more than 120 mgKOH / g: (Equation 1) (Primary hydroxyl value of modified epoxy resin composition) = (Number of hydroxyl groups of alkanolamine) × (Molecular weight of potassium hydroxide) / (Weight of nonvolatile content of all constituent components)

2. 2. The modified epoxy resin composition according to claim 1, wherein the component (a2-1) comprises a monoalkanolamine and a dialkanolamine.

3. 3. The modified epoxy resin composition according to claim 1, wherein the component (B) further comprises a styrene (b2) and / or a (meth)acrylic acid ester (b3).

4. 3. The modified epoxy resin composition according to claim 1, wherein the ratio of component (A) to component (B) [(A) / (B)] is 60 / 40 to 99 / 1 by weight of nonvolatile components.

5. An aqueous coating agent comprising the modified epoxy resin composition according to claim 1 or 2.

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