JP2000336287A - Low gloss lead-free cationic electrodeposition coating composition, coating film forming method and coated material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide lead-free cationic electrodeposition coating compositions cable of obtaining low gloss coating films easy to find low temperature curability and the strain and deformation of substrates without using lead based compounds and tin based catalysts, a method for forming coating films and coated materials. SOLUTION: Low gloss lead-free cationic electrodeposition coating compositions comprise a cationic group-containing base resin, a blocked isocyanate based curing agent, and a zinc compound with a content of the zinc compound of 0.2-1 pt.wt. in terms of zinc ion based on 100 pts.wt. of the coating solids content and do not contain a tin based catalyst. Preferably, the compositions further comprise crosslinked resin fine particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cationic electrodeposition coating composition, and more particularly to a low gloss lead-free cationic electrodeposition coating composition.

[0002]

2. Description of the Related Art Cationic electrodeposition coating compositions are used for undercoating of automobile bodies and parts, and coating films having high corrosion resistance are required. In order to realize this high corrosion resistance, a general cationic electrodeposition coating composition contains a basic lead pigment as a rust preventive pigment. However, use of lead-based pigments is being avoided from the viewpoint of preventing environmental pollution. Therefore, there is a need for a cationic electrodeposition coating composition that can achieve the same corrosion resistance as when a lead-based compound is used without using a lead-based compound.

[0003] Cationic electrodeposition coating compositions are required to have not only high corrosion resistance but also low-temperature curability. this is,
By setting the baking temperature at the time of electrodeposition coating low, it is intended to reduce the energy cost required at the time of electrodeposition coating. Conventional cationic electrodeposition coating compositions include:
Usually, a tin-based catalyst is used. However, similarly to the lead-based compound, the use of the tin-based catalyst is being avoided from the viewpoint of preventing environmental pollution. Furthermore, since the basic lead pigment is known to also act as a curing catalyst, a cationic electrodeposition coating composition having low-temperature curability even without containing these compounds is required.

[0004] Such a problem is described in, for example, Japanese Patent Application Laid-Open No. 7-2
This problem has been solved by the cationic electrodeposition coating compositions disclosed in JP-A-58586, JP-A-5-320544 and JP-A-6-33001.

[0005]

However, when the above various cationic electrodeposition coating compositions are used as an undercoating film, the surface of the resulting electrodeposition coating film is too glossy, and the base material is distorted or bent. It is difficult to find such a coating, which impairs the practicality of the coating line.

Therefore, the problem to be solved by the present invention is as follows:
An object of the present invention is to provide a cationic electrodeposition coating composition having high corrosion resistance and low-temperature curability without using a lead-based rust-preventive pigment and a tin-based catalyst and capable of obtaining a low-gloss coating film.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above-mentioned problems, and as a result, have reached the present invention. The means for solving the problem are as follows.

[0008] 1. Containing a cationic group-containing base resin, a blocked isocyanate-based curing agent, and a zinc compound,
A low-gloss lead-free cationic electrodeposition paint, characterized in that the content of the zinc compound is 0.2 to 1 part by weight based on 100 parts by weight of the solid content of the paint as zinc ions and does not contain a tin-based catalyst. 1. a composition; 2. The above low gloss lead-free cationic electrodeposition coating composition further containing the above crosslinked resin fine particles; 3. The above low gloss lead-free cationic electrodeposition coating composition, wherein the crosslinked resin fine particles are 1 to 15 parts by weight based on 100 parts by weight of the resin solid content. The zinc compound / crosslinkable resin fine particle weight ratio is 1
4. The above low gloss lead-free cationic electrodeposition coating composition, wherein the composition is / 60 to 1/1. 5. The above low gloss lead-free cationic electrodeposition coating composition, wherein the cationic group-containing base resin is obtained by cationizing an amino group-containing polymer with a water-soluble organic acid or inorganic acid. 6. The above low gloss lead-free cationic electrodeposition coating composition, wherein the cationic group-containing base resin is an oxazolidone ring-containing epoxy resin; The blocking agent of the blocked isocyanate curing agent is
At least one of phenols, lactams and oximes
A low gloss lead-free cationic electrodeposition coating composition as described above;

[0008] 8. Using the above low gloss lead-free cationic electrodeposition coating composition as a base material, dry the undercoating film to a dry film thickness of 5 to 4
8. a coating film forming method for forming a film having a thickness of 0 μm and further forming a top coat film; A coated article on which a coating film is formed by the above coating film forming method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The present invention provides a base resin containing a cationic group,
It contains a blocked isocyanate-based curing agent and a zinc compound, and the content of the zinc compound is 0.2 to 1 part by weight based on 100 parts by weight of the solid content of the paint as zinc ions, and includes a tin-based catalyst. The present invention is a low gloss lead-free cationic electrodeposition coating composition characterized in that it does not have any. The low gloss of the present invention refers to 80 or less, preferably 70 or less in a 60-degree gloss measurement.

[0012] Cationic group-containing base resin Specific examples of the cationic group-containing base resin include amino group-containing polymers such as formic acid, acetic acid, propionic acid, lactic acid, citric acid, malic acid, tartaric acid, and acrylic acid. Cationized by an acid or an inorganic acid such as hydrochloric acid or phosphoric acid; tertiary amino group-containing polymer quaternized; and epoxy group-containing polymer containing a sulfide compound or a phosphine compound in the presence of the above water-soluble organic acid. The cationized amino group-containing polymer is preferable.

Examples of the amino group-containing polymer include those having an epoxy resin, an acrylic resin, a polyether resin, a polyurethane resin, or a polyamide resin as a skeleton. The introduction of an amino group into each resin can be carried out by a method well known to those skilled in the art. For example, in the case of an epoxy resin, it can be carried out by adding an amine compound to the epoxy group. is there. Among them, preferred are epoxy resin, acrylic resin and polyurethane resin from the viewpoint of high corrosion resistance.

The cationizable functional group-containing base resin contains a primary and / or secondary hydroxyl group and a tertiary amino group, and has an amino value of 30 to 150, more preferably
45 to 120 and an average molecular weight of 200 to 20,000
It is preferred that When the amino value is less than 30, it is difficult to obtain a stable emulsion, and when it exceeds 150, there is a possibility that problems may occur in the electrodeposition coating workability such as coulomb efficiency and resolubility.

More preferred as the cationizable functional group-containing base resin is a modified epoxy resin containing an oxazolidone ring in the molecule. It is particularly preferred that this has the above-mentioned special value. This modified epoxy resin can be obtained by subjecting a bis-urethane compound reacted with a diisocyanate compound or a hetero-urethane compound reacted with another active hydrogen compound to a dealcoholization reaction with an epoxy resin. By using a modified epoxy resin containing an oxazolidone ring as the base resin, the thinning of the electrodeposition coating film due to loss on heating hardly occurs.

Blocked Isocyanate-Based Curing Agent The blocked isocyanate-based curing agent contained in the low gloss lead-free cationic electrodeposition coating composition of the present invention is obtained by adding a blocking agent to an isocyanate group contained in a polyisocyanate compound. The number of blocked isocyanate groups contained in one molecule of the blocked isocyanate-based curing agent used in the present invention is preferably three or more.

The polyisocyanate compound includes:
Alkylene diisocyanates such as trimethylene diisocyanate, trimethylhexamethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, cycloalkylene diisocyanates such as bis (isocyanatomethyl) cyclohexane, cyclopentane diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, tolylene diisocyanate, phenylene diisocyanate Aromatic diisocyanates such as diphenylmethane diisocyanate, diphenyl ether diisocyanate, araliphatic diisocyanates such as xylylene diisocyanate and diisocyanate diethylbenzene, triphenylmethane triisocyanate, triisocyanate benzene, triisocyanate Triisocyanates such as ruene, tetraisocyanates such as diphenyldimethylmethanetetraisocyanate, polymerized polyisocyanates such as dimers or trimers of tolylene diisocyanate, and ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane And a terminal isocyanate-containing compound obtained by reacting a low-molecular-weight active hydrogen-containing organic compound such as hydrogenated bisphenol A, hexanetriol, glycerin, pentaerythritol, castor oil, and triethanolamine.

Examples of the blocking agent include phenols, lactams, oximes, alcohols, amino alcohols, amines or imides, compounds containing active methylene, or mercaptans, acid amides, imidazoles, ureas, carbamines. Acid salts, sulfites and the like.

As the blocking agent used in the present invention, it is preferable to use at least one blocking agent selected from phenols, lactams, and oximes from the viewpoint of low-temperature curability. Is also good.

Examples of the phenols include phenol, cresol, xylenol, t-butylphenol, p-nonylphenol, p-tert-octylphenol, and hydroxybenzoic acid.

As lactams, ε-caprolactam,
γ-butyrolactam, δ-valerolactam, β-propiolactam and the like.

As the oximes, formamidoxime,
Acetoxime, acetoaldoxime, cyclohexane oxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime and the like can be mentioned.

As alcohols, methanol, ethanol, propanol, isopropanol, butanol,
Amyl alcohol, hexyl alcohol, 2-ethylhexanol, heptyl alcohol, octyl alcohol, cyclohexanol, benzyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2 -Ethylhexyl ether,
Examples include diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, diethylene glycol mono-2-ethylhexyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monohexyl ether, and propylene glycol mono-2-ethylhexyl ether. be able to.

Examples of amino alcohols include dimethylethanolamine, dimethylpropanolamine, dimethylisopropanolamine, dimethylbutanolamine, diethylethanolamine, 2- [2- (dimethylamino) ethoxy] ethanol, and 2- (2- [2- (dimethyl Amino) ethoxy] ethoxy) ethanol, 1- [2
-(Dimethylamino) ethoxy] -2-propanol,
Examples thereof include 1- (1- [1- (dimethylamino) -2-propoxy] -2-propoxy) -2-propanol.

Examples of the amines or imides include diphenylamine, xylidine, carbazole, dibutylamine, succinimide, and phthalimide.

Examples of the active methylene-containing compound include diethyl malonate, methyl acetoacetate, ethyl acetoacetate and the like.

In the low gloss lead-free cationic electrodeposition coating composition of the present invention, the base resin / hardener solids ratio is preferably 50/50 to 90/10, and more preferably 60/40 to 80/20. It is. If the ratio is out of the above range, a problem may occur in the curability.

Zinc Compound The zinc compound used in the low-gloss, lead-free cationic electrodeposition coating composition of the present invention is considered to function as a curing aid to reduce gloss.
As the zinc compound contained in the low-gloss lead-free cationic electrodeposition coating composition of the present invention, any zinc ion that can be ionized as zinc ions in the electrodeposition coating can be used.
Specifically, an inorganic zinc compound such as ZnO, Zn (OH) ₂ , ZnAl ₂ O ₄ , or a metal salt of the following organic acid zinc can be used. The zinc compound may be contained in two or more kinds.

As the organic zinc compound, formic acid, acetic acid, butyric acid, caproic acid, octylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, neodecanoic acid, acrylic acid, crotonic acid, isocrotonic acid, undecylenic acid , Oleic acid, erucic acid, sorbic acid, linoleic acid, linolenic acid, bisphenylacetic acid, bisphenylbutyric acid, bisphenylpropionic acid, biscyclopentanecarboxylic acid, bisacetoacetic acid, benzoic acid, methylbenzoic acid, bismethoxybenzoic acid, Vistastar Zinc metal salts with mono- or di-organic acids such as butylbenzoic acid, bishydroxybenzoic acid, phthalic anhydride, terephthalic acid, succinic acid, maleic acid, maleic anhydride, fumaric acid and the like.

Further, the above-mentioned zinc compound includes various pigments described below,
In particular, it can be contained as a pigment treating agent used for suppressing the water-soluble component of the rust preventive pigment. In this case, preferred are zinc diacetate, zinc dioctylate, zinc dilaurate, and zinc dibenzoate.

The content of the zinc compound is from 0.2 to 1 part by weight, preferably from 0.5 to 1 part by weight, based on 100 parts by weight of the solid content of the paint as zinc ions. If the amount is less than 0.2 part by weight, a low gloss coating film is not formed, and even if the amount exceeds 1 part by weight, an effect equivalent to the addition cannot be obtained.

Crosslinked Resin Particles The low gloss lead-free cationic electrodeposition coating composition of the present invention comprises:
In order to further reduce gloss, crosslinked resin particles can be included. The crosslinked resin particles may be any resin such as an acrylic resin, an epoxy resin, a phenol resin, and a melamine resin, but are preferably acrylic resin particles from the viewpoint of ease of production. The average particle size is preferably from 0.02 to 30 μm. When the average particle size is less than 0.02 μm, the decrease in gloss hardening is small,
If it exceeds 30 μm, the coating film becomes rough and dirty.
More preferably, it is 0.1 to 5 μm.

When the crosslinked resin particles are acrylic resin,
The crosslinked acrylic resin fine particles comprise (a) a monomer having two or more radically polymerizable ethylenically unsaturated groups in the molecule (monomer for crosslinking reaction) and (b) a polymerizable group in the molecule. One monofunctional monomer is copolymerized in an aqueous medium or a non-aqueous organic medium by emulsion polymerization, soap-free emulsion polymerization, suspension polymerization, NAD polymerization, precipitation polymerization, solution polymerization, or the like. It is obtained by separating, crushing and cleaving. When obtaining particles of 0.02 to 0.6 μm, emulsion polymerization, soap-free emulsion polymerization and NAD polymerization,
In order to obtain particles of 0.2 to 30 μm, precipitation polymerization is suitable. Considering that fine particles having a predetermined particle size can be obtained, it is preferable to use emulsion polymerization or soap-free emulsion polymerization.

Examples of the monomer (a) having two or more radically polymerizable ethylenically unsaturated groups in the molecule (monomer for crosslinking reaction) include, for example, ethylene glycol diacrylate, ethylene glycol dimethacrylate, and triglyceride. Ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylpropane trimethacrylate,
1,4-butanediol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, penta Erythritol tetramethacrylate, glycerol dimethacrylate, glycerol diacrylate, glycerol ataloxydimethacrylate, 1,1,1-trishydroxymethylethanediacrylate, 1,1,1-trishydroxymethylethanetriacrylate, 1,1,1- Trishydroxymethylethane dimethacrylate, 1,1,1-trishydroxymethylethane trime Acrylate, 1,1,1-trihydroxy methyl propane diacrylate, 1,1,
1-trihydroxymethylpropane triacrylate,
1,1,1-trihydroxymethylpropane dimethacrylate, 1,1,1-trihydroxymethylpropane trimethacrylate, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, diallyl terephthalate, diallyl phthalate and divinylbenzene And the like.

On the other hand, (b) monofunctional monomers having one polymerizable group in the molecule include, for example, carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid and maleic acid. Acids, fumaric acid and the like; hydroxyl group-containing monomers such as 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, allyl alcohol, methallyl alcohol; Nitrogen-containing alkyl acrylates or methacrylates such as dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate. Polymerizable amides such as acrylamide, methacrylamide, etc .; polymerizable nitriles such as acrylonitrile, methacrylonitrile, etc .; alkyl acrylates or methacrylates such as methyl acrylate, methyl methacrylate, ethyl acrylate, n-
Butyl acrylate, n-butyl methacrylate, 2-
Ethylhexyl acrylate and the like; polymerizable aromatic compounds such as styrene, α-methylstyrene, vinyltoluene, t-butylstyrene and the like; α-olefins such as ethylene and propylene; vinyl compounds such as vinyl acetate and vinyl propionate; Compounds such as butadiene and isoprene; silicon-containing alkyl acrylate, methacrylate or silicon-containing vinyl compounds such as γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane and vinyltriethoxysilane; and fluorine-containing compounds. it can.

The crosslinked resin fine particles preferably have a cationic group such as a cationized amino group with a carboxylic acid or a quaternary ammonium group in order to maintain a stable dispersion state in a paint and an electrodeposition bath. It becomes suitable. In order to introduce a cationic group into the above-mentioned crosslinked resin fine particles, a monomer having an ethylenically unsaturated bond and a basic group, for example, dimethylaminoethyl (meth) acrylate, vinylpyridines, or the like is used to synthesize the crosslinked resin fine particles. There is a method in which the above-mentioned monomer is used as one component of the above-mentioned monofunctional monomer (b), or polymerization is carried out using an initiator which gives a cationic terminal.

The crosslinked resin fine particles thus produced can be isolated by a method such as filtration, spray drying, freeze drying or the like, and used as such or after being pulverized to an appropriate particle size using a mill or the like. Further, the synthesized dispersion can be used as it is or after replacing the solvent.

When the low gloss lead-free cationic electrodeposition coating composition of the present invention contains crosslinked resin fine particles, the content thereof is set so as to obtain a desired glossiness. The amount is 1 to 15 parts by weight, preferably 2 to 10 parts by weight, based on 100 parts by weight of the resin solid content which is the sum of the solid content of the blocked isocyanate-based curing agent. When the amount of the crosslinked resin fine particles is less than 1 part by weight, color unevenness tends to occur, and when the amount exceeds 15 parts by weight, coating workability is reduced.

When crosslinked resin fine particles are contained, the weight ratio of the zinc compound to the crosslinked resin fine particles is more preferably 1/60 to 1/1. If the weight ratio is less than 1/60, the low-temperature curability may be insufficient, and if it exceeds 1/1, the smoothness of the coating film may be impaired.

Other Components and Production Method The low gloss lead-free cationic electrodeposition coating composition of the present invention can use metal ions other than zinc ions in addition to the above components. Examples of such a combined metal ion include cerium, bismuth, copper, iron, cobalt, nickel, molybdenum, and the like.
Alternatively, they can be used by adding them to paints as organic acid metal salts of these metals.

The low gloss lead-free cationic electrodeposition coating composition of the present invention may further contain a pigment, various additives and a solvent other than water as other components, if necessary.
Pigments such as titanium oxide; red iron oxide; coloring pigments such as carbon black; aluminum silicate; extender pigments such as precipitated barium sulfate; and, for example, phosphomolybdic acid and aluminum, ferric iron, titanium, zirconium, manganese, cobalt, nickel and copper. Aluminum phosphomolybdate, zinc phosphomolybdate which is a salt with a divalent or trivalent metal salt such as zinc, silicon and the like; for example, tripolyphosphoric acid, metaphosphoric acid, pyrophosphoric acid and the like; Condensed phosphate which is a salt of, specifically, aluminum dihydrogen tripolyphosphate, aluminum metaphosphate,
A rust preventive pigment such as ferric pyrophosphate can also be added. When the composition contains a pigment, the composition may further contain a pigment dispersing resin.

As the solvent, in addition to water, ethyl cellosolve, propyl cellosolve, butyl cellosolve, methanol, ethanol, isopropyl alcohol, n-butanol, isobutanol, ethylene glycol dimethyl ether, diacetone alcohol, 4-methoxy-4-methylpentanone -2, acetone, methyl ethyl ketone,
Water-miscible organic solvents such as methoxybutanol, dioxane, ethylene glycol monoethyl ether acetate and water-immiscible solvents such as xylene, toluene, methyl isobutyl ketone, hexane, carbon tetrachloride, 2-ethylhexanol, isophorone, cyclohexane, benzene, etc. Organic solvent.

The low gloss lead-free cationic electrodeposition coating composition of the present invention can be obtained by dispersing the above components and other components in water by a method known to those skilled in the art.

The film forming method of a coating film forming method of the present invention, with respect to the substrate, using the above low gloss lead-free cationic electrodeposition coating composition, to form an undercoat coating film with a dry thickness of 5 to 40 m, Further, a top coat is formed. An electrodepositable material can be used as the base material. The formation of the undercoat film is based on cationic electrodeposition, but the cationic electrodeposition follows a method known per se, and generally, the solid content concentration is reduced by diluting with deionized water. 5 to 40% by weight, preferably 15 to 25% by weight, and further from the above low gloss lead-free cationic electrodeposition coating composition whose pH has been adjusted within the range of 5.5 to 8.5. The electrodeposition bath is usually adjusted to a bath temperature of 20 ° C. to 35 ° C. and a load voltage of 1
It can be performed under the condition of 00 to 450V.

The thickness of the electrodeposition coating is a dry film thickness of 5 to 40.
μm, preferably in the range of 10 to 30 μm, and it is preferable to set the above-mentioned electrodeposition coating conditions so as to obtain this film thickness. In addition, baking of the coating film is generally 10
0 to 200 ° C, preferably 10 to 140 ° C to 160 ° C.
Suitably, this is done for a time period of 30 minutes.

On the undercoat film thus formed, an intermediate coat film is formed if necessary, and then a topcoat film is formed. The intermediate coating film and the top coating film can be formed by applying a coating material and coating conditions used for coating an outer plate of an automobile or the like.

[0047]

Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

Production Example 1 Blocked isocyanate curing
Preparation of Agent A In a five-necked flask equipped with a reflux condenser, a stirrer, a dropping funnel and a nitrogen inlet tube, 168 parts by weight of hexamethylene diisocyanate and 73.2 parts by weight of methyl isobutyl ketone (hereinafter abbreviated as "MIBK"). 50
C., and 34.6 parts by weight of trimethylolpropane was gradually added dropwise while maintaining the internal temperature not to exceed 60.degree. Then, 106.7 parts by weight of methyl ethyl ketoxime was added dropwise while keeping the internal temperature not exceeding 70 ° C.
After completion of the dropwise addition, the mixture was kept at 70 ° C. for 1 hour until the peak of the isocyanate group disappeared from the IR spectrum, 3.9 parts by weight of butanol was added, and the mixture was cooled to prepare a blocked isocyanate curing agent A. The solids content was 80%.

Preparation Example 2 Preparation of Amino Group-Containing Polymer In a reaction vessel prepared separately from Preparation Example 1, 681 parts by weight of a liquid epoxy resin having an epoxy equivalent of 188 (trade name “DER-331J” manufactured by Dow Chemical Company), bisphenol A269 parts by weight, 88 parts by weight of nonylphenol and M
115 parts by weight of IBK were charged and heated to 140 ° C. to completely dissolve. After adding 5 parts by weight of a 2% solution of 2-ethyl-4-methylimidazole (98% of xylene) as a reaction catalyst, the mixture was reacted at 140 to 150 ° C., and an epoxy equivalent of 1 was added.
After adding 146 parts by weight of MIBK with 210 as the end point,
Cooled to 105 ° C. Subsequently, 47 parts by weight of n-methylethanolamine and 54 parts by weight of 73% of diethylenetriamine methylisobutyleneketimine (MIBK solution) were added, and the mixture was kept at 120 ° C. for 1 hour to obtain an amino group-containing polymer.

Production Example 3 Production of Emulsion A The blocked isocyanate-based curing agent A obtained in Production Example 1 was added to 1405 parts by weight of the amino group-containing polymer obtained in Production Example 2.
692 parts by weight and n-hexyl cellosolve 59 parts by weight were mixed at 90 ° C. for 30 minutes, neutralized with 88% formic acid 14.6 parts by weight, and then a plasticizer (trade name “Newpol YG-1”, manufactured by Sanyo Chemical Co., Ltd.) ") 18 parts by weight and deionized water 3113
A part by weight was added, the mixture was slowly diluted, and the organic solvent was removed under reduced pressure to obtain an emulsion A having a solid content of 36.0%.

Production Example 4 Production of Pigment Dispersion Paste Bisphenol type epoxy resin having an epoxy equivalent of 450 was reacted with 2-ethylhexanol half-blocked isophorone diisocyanate to give 1- (2-hydroxyethylthio) -2-propanol and dimethylolpropion. 135.3 parts by weight of a resin varnish for pigment dispersion which has been tertiary sulfonium-modified with an acid (tertiary sulfonation ratio: 70.6%
Resin solid content 60%), 435.0 parts by weight of ion-exchanged water,
8.5 parts by weight of carbon black, 72.0 parts by weight of kaolin, 345.0 parts by weight of titanium dioxide and 75.0 parts by weight of aluminum phosphomolybdate are dispersed by a sand grind mill, and further dispersed until the particle size becomes 10 μm or less. It was pulverized to obtain a pigment dispersion paste.

Production Example 5 Oxazolidone ring-containing polymer
Of a reflux condenser, a thermometer, was prepared three-necked flask fitted with a stirrer and a dropping funnel. In this flask,
Mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate in a ratio of 8: 2 54
Parts by weight and 136 parts by weight of methyl isobutyl ketone were added and stirred, and 11 parts by weight of methanol was further added dropwise from a dropping funnel over 30 minutes. The temperature in the flask was maintained at 60 ° C., and the reaction was carried out for 30 minutes. Thereafter, 54 parts by weight of ethylene glycol mono-2-ethylhexyl ether was added dropwise from the dropping funnel over 1 hour. The reaction was continued while maintaining the temperature at 60 to 65 ° C., and the reaction was terminated when the absorption spectrum of the isocyanate group disappeared in the infrared absorption spectrum. Next, 285 parts by weight of an epoxy resin having an epoxy equivalent of 475 and 380 parts by weight of an epoxy resin having an epoxy equivalent of 950, each of which was synthesized from bisphenol A and epichlorohydrin, were added to the flask and mixed uniformly. Then, the flask was heated to 120 ° C., 0.62 parts by weight of benzyldimethylamine was added, and the reaction was carried out while distilling off by-produced methanol using a decanter. Thereby, the epoxy equivalent is 1120
Was obtained. Next, the flask was cooled, and 29 parts by weight of diethanolamine, 22 parts by weight of N-methylethanolamine, and a ketimine compound of aminoethanolamine (79% methyl isobutyl ketone solution) 3
3 parts by weight were added and reacted at 110 ° C. for 2 hours. After the reaction, the mixture was diluted with methyl isobutyl ketone until the nonvolatile content became 80% to obtain an oxazolidone ring-containing polymer.

Production Example 6 Blocked isocyanate curing
Preparation of Agent B A three-necked flask equipped with a reflux condenser, a thermometer and a stirrer was prepared. Trimeric hexamethylene diisocyanate and methyl ethyl ketoxime were added to the flask, and the trimer hexamethylene diisocyanate was blocked with methyl ethyl ketoxime. The obtained blocked isocyanate is treated with a mixed solvent containing methyl isobutyl ketone and butanol at a ratio of 95: 5,
A blocked isocyanate-based curing agent B having a solid content of 95% was obtained.

Production Example 7 Production of Emulsion B 140 parts by weight of the polymer B obtained in Production Example 5 (in terms of solids), 60 parts by weight of the blocked isocyanate curing agent B obtained in Production Example 6 (in terms of solids), and acetic acid 3.15
The parts by weight were mixed to obtain a paint dispersion. After adding deionized water with stirring, the organic solvent was removed under reduced pressure to obtain an emulsion B having a solid content of 36%.

Production Example 8 Production of Crosslinkable Resin Fine Particles 100 parts by weight of ethylene glycol monomethyl ether were charged into a 2 liter kolben equipped with a stirrer, a nitrogen inlet tube, a temperature controller, a condenser, and a decanter.
The temperature was raised to and kept at 0 ° C. Two dropping funnels were prepared, and 100 parts by weight of ethylene glycol monomethyl ether was added to one of them, and N-methyl-N- (vinylbenzyl) was placed therein.
75 parts by weight of taurine was dissolved. At this time, a small amount of dimethylethanolamine was added as a solubilizer. Further, 50 parts by weight of 2-hydroxyethyl acrylate, 10 parts by weight of acrylic acid, 110 parts by weight of methyl methacrylate, 110 parts by weight of styrene, 145 parts by weight of n-butyl acrylate and 10 parts by weight of lauryl mercaptan were mixed into one dropping funnel, Bisisobutyronitotyl 10
Parts by weight were dissolved. The contents of the two dropping funnels were added dropwise over 120 minutes, and then the temperature was maintained at 100 ° C. and stirring was continued for 60 minutes. Next, the solvent of this resin solution was removed by a rotary evaporator, and an acrylic resin having a resin solid content of 96% and a number average molecular weight of 4,500 was obtained. In a 1 liter reaction vessel equipped with a stirrer, cooling pipe and temperature controller,
306 parts by weight of deionized water, 18 parts by weight of the acrylic resin obtained in the above step, and 2.6 parts by weight of dimethylethanolamine were charged and heated to 80 ° C. while stirring. After the contents are dissolved, the temperature is maintained at 80 ° C. while stirring,
An aqueous solution consisting of 4.8 parts by weight of azobiscyanovaleric acid, 4.56 parts by weight of dimethylethanolamine and 48 parts by weight of deionized water was charged thereto. Then, styrene 2
6.6 parts by weight, 79.8 parts by weight of methyl methacrylate,
A mixed liquid consisting of 53.2 parts by weight of n-butyl acrylate, 53.2 parts by weight of ethylene glycol dimethacrylate, 53.2 parts by weight of ethyl acrylate, and 16.0 parts by weight of diethylaminoethyl acrylate was dropped over 60 minutes. After the addition, a mixed aqueous solution consisting of 1.2 parts by weight of azobiscyanovaleric acid, 1.14 parts by weight of dimethylethanolamine and 12 parts by weight of deionized water was further added at the same temperature, and stirring was continued for 60 minutes to give a particle diameter of 146 nm. Cationic crosslinkable resin fine particles having a crosslink degree of 0.9532 mmol / g and a nonvolatile content of 45% were obtained.

Production Example 9 Cationic electrodeposition paint A series
Pigment dispersion paste 91 parts by weight obtained in the emulsion A 414 parts by weight Production Example 4 obtained in Production Example 3,
While stirring, 485 parts by weight of deionized water, 10 parts by weight of 2-ethylhexyl cellosolve, and zinc acetate as a zinc compound were added in the amount of zinc ion shown in Table 1, and a cationic electrode having a nonvolatile content of 20% and belonging to the present invention was added. Three types of coating materials A series and two types not belonging to the present invention were obtained.

Production Example 10 Cationic electrodeposition paint B series
Producing a pigment dispersion paste 115 amount parts obtained in Production Example 7 Emulsion B 564.3 parts by weight Production Example 7 obtained in, stirring deionized water 783 parts by weight thereto, 2-
Ethylhexyl cellosolve, 10 parts by weight, zinc acetate as a zinc compound was added at the zinc ion amount shown in Table 1, and the crosslinked resin fine particles obtained in Production Example 8 were further added at the compounding amount shown in Table 1 to reduce the nonvolatile content. Three types of 20% cationic electrodeposition paint B series were obtained.

Examples 1-6 and Comparative Examples 1-2 Cold-rolled untreated steel sheets were degreased and pretreated with a zinc phosphate chemical conversion treatment (Surfdine 5000, manufactured by Nippon Paint Co., Ltd.) to form a cathode. The cationic electrodeposition paints obtained in Production Examples 9 and 10 were electrodeposited at an applied voltage of 150 to 250 V and a bath temperature of 28 ° C. so that the dry film pressure became 20 μm. The obtained electrodeposition coating film was washed with water and baked at 150 ° C. and 160 ° C. for 20 minutes. The gloss and curability of each of the obtained coating films were examined. Table 1 shows the results
Shown in

On the electrodeposition coating film baked at 150 ° C., an intermediate coating (“Olga S-90 Sealer Gray (N
-6) ", manufactured by Nippon Paint Co., Ltd., is applied by air spraying so as to have a dry film thickness of 40 μm, and baked at 140 ° C. for 30 minutes to form an intermediate coating film. Then, a paint for an automobile body (“ Olga TO Black ”) ", Nippon Paint Co., Ltd.)
Air spray painting so as to have a dry film thickness of 30 μm,
It was baked at 140 ° C. for 30 minutes to form a top coat.
The test plate thus obtained was evaluated for sharpness.

Evaluation method and evaluation criteria Gloss: The coating film obtained by baking at 150 ° C. was measured with a gloss meter (B
The gloss was measured at 60 degrees using YK-Gardner GmbH. Curability: The coating film was rubbed 50 times with gauze dipped in methyl isobutyl ketone, and the curability was determined based on the surface condition of the coating film. The evaluation criteria are as follows. …: No change in coating film. Δ: There are coating streaks. ×: The gauze is colored. Sharpness: The sharpness of the test plate formed up to the top coat was measured by a sharpness measuring device (PGD meter manufactured by Tokyo Koden Co., Ltd.).
(The higher the measured value, the better the sharpness.)

[0061]

[Table 1]

[0062]

The low gloss lead-free cationic electrodeposition coating composition of the present invention contains a specific amount of a zinc compound.
It has high corrosion resistance and low-temperature curability, and can provide a low gloss coating film. This is because the zinc compound contained in the low gloss lead-free cationic electrodeposition coating composition of the present invention becomes a zinc ion and functions as a curing aid, thereby accelerating the reaction and obtaining high corrosion resistance and low-temperature curability. In particular, it is considered that by selectively promoting the reaction between the base resin and the curing agent on the coating film surface, macroscopic irregularities are formed on the coating film surface, and a coating film with low gloss can be obtained. Therefore, the low-gloss lead-free cationic electrodeposition coating composition of the present invention can easily find distortion and bending of a substrate in a coating line, and can improve practicality.

The low gloss lead-free cationic electrodeposition coating composition of the present invention does not contain a lead compound and a tin catalyst which cause environmental pollution, and can be used as an environmentally friendly water-based paint. .

Further, when a top coat is applied on a coating film obtained from the low gloss lead-free cationic electrodeposition coating composition of the present invention, a coating film having good image clarity can be obtained, so that a high appearance of an automobile or the like can be obtained. Can be used to form a multi-layer coating film.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 163/00 C09D 163/00 175/04 175/04 // C08G 18/58 C08G 18/58 18/80 18/80 F term (reference) 4D075 CA33 CB02 DB02 DC12 EB32 EB38 EB56 EC10 4J034 BA03 DK00 DK03 HA01 HA07 HA08 HC03 HC12 HC17 HC22 HC61 HC64 HC65 HC67 HC71 HC73 HD02 HD03 HD04 HD05 HD07 HD15 MA01 RA07 4J038 DB01 DG302

Claims (9)

[Claims] 1. A coating composition comprising a cationic group-containing base resin, a blocked isocyanate-based curing agent, and a zinc compound, wherein the content of the zinc compound is 1% of the paint solid content as zinc ions.
A low-gloss, lead-free cationic electrodeposition coating composition which is 0.2 to 1 part by weight based on 00 parts by weight and does not contain a tin-based catalyst. 2. The low gloss lead-free cationic electrodeposition coating composition according to claim 1, further comprising fine particles of a crosslinked resin. 3. The low gloss lead-free cationic electrodeposition coating composition according to claim 1, wherein the content of the crosslinked resin fine particles is 1 to 15 parts by weight based on 100 parts by weight of the resin solid content. 4. The low gloss lead-free cationic electrodeposition coating composition according to claim 2, wherein the weight ratio of the zinc ion to the crosslinked resin fine particles is 1/60 to 1/1. 5. The low-gloss, lead-free resin according to claim 1, wherein the cationic group-containing base resin is obtained by cationizing an amino group-containing polymer with a water-soluble organic acid or inorganic acid. Cationic electrodeposition coating composition. 6. The low gloss lead-free cationic electrodeposition coating composition according to claim 1, wherein the cationic group-containing base resin is an oxazolidone ring-containing epoxy resin. 7. The low-gloss lead-free cationic electrodeposition according to claim 1, wherein the blocking agent of the blocked isocyanate-based curing agent is at least one of phenols, lactams, and oximes. Paint composition. 8. An undercoat film having a dry film thickness of 5 to 40 μm is formed on a substrate by using the low gloss lead-free cationic electrodeposition coating composition according to any one of claims 1 to 7; A coating film forming method for forming a coating film. 9. A coated article on which a coating film is formed by the coating film forming method according to claim 8.