JP2811350B2 - Cationic electrodeposition coating composition for casting products - Google Patents

Description

The present invention relates to a cationic electrodeposition coating composition for casting products.

[Conventional technology]

Cast products generally have large heat capacities and have fine and sharp irregularities on the surface derived from their manufacturing method.

Normally, baking-hardening paint is applied for the purpose of imparting excellent rust-preventive performance to cast products.However, due to the characteristics of the casting, the atmosphere temperature in the baking furnace must be adjusted to give the required baking energy to cure the coated paint. Extremely high temperature (40 to 80 than normal curing temperature)
℃ high temperature), and the temperature of the object to be coated (casting) does not reach the temperature required for curing unless baking is performed for a long time. Therefore, the coated paint will be kept at a temperature lower than its curing temperature for a long time, so that the hot melt flow of the paint will occur, and it will be possible to form a uniform coating conforming to sharp irregularities on the surface of the object to be coated. However, when the thickness of the projections is extremely thin, or in extreme cases, the base of the object to be coated may be exposed, and sufficient rust prevention performance cannot be obtained.

[Problems to be solved by the invention]

In order to solve such a problem and give sufficient rust preventive performance to the cast product, means such as performing thick film coating or adjusting the fluidity of the paint have been conventionally proposed, but the surface of the cast product has been proposed. In order to cover the irregularities sufficiently, a film thickness of 50 μm or more is usually required, and it is difficult to obtain such a thick coating by electrodeposition coating with a cationic electrodeposition coating material having originally excellent rust-preventive power.

Also JP-A-63-62897, JP-A-63-39972, JP-A-63-62897
The method of controlling the fluidity during the curing process shown in -63761 and the like, although the coating of the projections is considerably improved, it is necessary to raise the atmosphere temperature in the baking furnace. A certain amount of flow could not be prevented, which was insufficient for recent demands for high rust prevention performance. Further, in these cases, when the fluidity is extremely suppressed, there is a problem that minute holes are generated in the thin film and rust is generated therefrom.

Accordingly, an object of the present invention is to provide a coating composition which is suitable for coating cast products and has excellent rust prevention performance.

[Means for solving the problem]

The present inventors have conducted intensive studies and found that, when a casting product is coated with a cationic electrodeposition coating composition that can be cured at a temperature of 60 to 130 ° C., the irregularities on the surface of the workpiece are sufficiently uniformly coated. The present invention was found to be able to impart extremely excellent rust prevention performance, and completed the present invention.

The present invention relates to the following components: (1) a resin containing a cationic group and active hydrogen (component 1); and (2) a polyisocyanate having an isocyanurate, allohanate or biuret structure, oxime, acetylacetone, malonic diester and Reaction product with a blocking agent selected from acetoacetate (component 2-
a); or a reaction product of a polyol having a triazine ring or a derivative thereof, a polyisocyanate, and a blocking agent selected from oxylene, acetylacetone, malonic diester and acetoacetic ester (component 2-
b); and (3) 1 to 20% by weight of a polymerizable monomer containing two or more vinyl groups in one molecule, 5 to 25% by weight of a polymerizable basic monomer, and the remaining other polymerizable monomers. It is a cationic electrodeposition coating composition for a casting product containing an emulsion (component 3) copolymerized in water.

Component 1 used in the present invention may be, for example, a resin obtained by reacting an epoxy group-containing resin with a cationizing agent, or a cationic group-containing α, β-unsaturated ethylene compound and an active hydrogen-containing α, β-unsaturated ethylene compound. Further, there may be mentioned a copolymer obtained by adding another polymer ethylene compound thereto. This may be mixed and used.

Examples of the epoxy group-containing resin for preparing Component 1 include a polyepoxy resin synthesized from a polyphenol compound and epichlorohydrin, a resin obtained by epoxidizing a polyalkylene oxide terminal, and oxidizing an unsaturated ethylene group in a metal catalyst. Epoxidized polybutadiene resin, epoxidized polybutadiene resin, or a copolymer of glycidyl (meth) acrylate and another polymerizable ethylene compound.
Mixtures of more than one type are included. The polyphenols that can be used herein include, for example, 2,2-bis (4'-hydroxyphenyl) -propane, 1,1'-bis (4'-hydroxyphenyl) -ethane, bis (4-hydroxy Phenyl) -methane, 4,4'-dihydroxybenzophenone, 2,2-bis (4'-hydroxy-tert-butyl-phenyl) -propane, 1,1,2,2-tetra (44-hydroxyphenyl) Enyl) -ethane, 4,4'-dihydroxydiphenyl ether, phenol novolak, cresol novolak and the like.

The epoxy group-containing resin may be chain-extended with a polycarboxylic acid, a polyamine, a polyester polyol, a polyether polyol, a polyisocyanate, or the like, if necessary.

Examples of the cationizing agent to be reacted with the epoxy group-containing resin include an alkyl group, an aryl group and / or an alkanol group-containing primary or secondary amine, a tertiary amine salt, a secondary sulfide salt, Tertiary phosphine salts and the like. Examples of these include primary amines such as methylamine, ethylamine, propylamine, benzylamine, monoethanolamine, propanolamine, diethylamine, dipropylamine, N-
Methylbenzylamine, N-methylethanolamine,
Secondary amines such as diethanolamine, ethylenediamine, diethylenetriamine, dimethylaminopropylamine, diethylaminopropylamine, hydroxyethylaminoethylamine, a reaction product of hexamethylenediamine and Cardilla E-10 (manufactured by Ciel Chemical Co., Ltd.), tetraethylenetriamine and butylglycidyl Examples thereof include polyamines such as a reaction product with an ether, ketimines obtained by reacting a primary amine with a ketone, and the like. These are reacted with the epoxy group-containing resin by a known method, and are preferably acid, particularly preferably formic acid. Is neutralized with an organic carboxylic acid such as acetic acid or lactic acid to form a cationic group. Further, triethylamine, triethanolamine, N-N-dimethylethanolamine, N-methyldiethanolamine, N, N-diethylethanolamine, etc., and inorganic acids such as boric acid, carbonic acid, hydrochloric acid or formic acid, acetic acid, lactic acid, propionic acid, etc. Tertiary amine salts, such as tertiary amine salts, diethyl sulfide, diphenyl sulfide, thiodiethanol, etc., neutralized with an organic acid as described above, tertiary sulfonium salts, triethyl phosphine, phenyl dimethyl phosphine And quaternary phosphonium salts obtained by neutralizing in, diphenylmethylphosphine, triphenylphosphine and the like with the above-mentioned acids.

The reaction between the epoxy group-containing resin and the cationizing agent can be carried out by a known method to obtain the resin of the present invention component 1.

The above-mentioned cationic group-containing α, β-
Examples of the unsaturated ethylene compound include dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminopropyl methacrylamide, dimethylaminostyrene, vinylpyridine, allylamine,
Examples thereof include those obtained by reacting a diisocyanate half-blocked with an alkanolamine to a hydroxyl group-containing acrylic monomer.

Examples of the active hydrogen-containing α, β-unsaturated ethylene compound to be copolymerized with the cation group-containing α, β-unsaturated ethylene compound include carboxyl group-containing vinyl monomers such as acrylic acid and methacrylic acid, allyl alcohol,
-Hydroxyl ethyl acrylate, 2-hydroxyethyl methacrylate, a hydroxyl group-containing vinyl monomer such as 3-hydroxypropyl methacrylate, further, such a hydroxyl group-containing vinyl monomer, ethyl acetoacetate, dimethyl malonate and the like, a compound,
Compounds obtained by subjecting .epsilon.-caprolactone to redox polymerization are exemplified.

The other polymerizable ethylene compounds that can be further added as desired include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate.
(Meth) acrylates such as acrylate and stearyl (meth) acrylate; vinyl compounds such as styrene vinyl toluene, vinyl acetate, vinyl chloride and vinyl fluoride; vinylidene compounds such as vinylidene fluoride and vinylidene chloride; butadiene, pentadiene and cumarone And indene. In preparing a copolymer of these compounds, a conventional radical polymerization reaction is carried out at room temperature to 200 ° C. using a radical polymerization initiator such as azobisisobutyronitrile, dikimyl peroxide, t-butyl peroxide, and the like. By doing so, a resin of the present invention component 1 is obtained.

In the above reaction, if necessary, a solvent such as toluene, xylene, ethyl cellosolve, butyl cellosolve, or methyl isobutyl ketone, or a chain transfer agent such as normal dodecyl mercaptan or mercaptopropionic acid may be used.

The component used as the component 2-a of the present invention is obtained by dimerizing or trimerizing two or more molecules of diisocyanate, and having a biuret bond, an allohanate bond and an isocyanurate bond in the molecule, and having two or more active groups. Polyurethane or polyol having an isocyanurate bond and having two or more active isocyanate groups and a diisocyanate as described above and having a urethane bond in the molecule and having two or more active isocyanate groups. It is obtained by reacting one or a mixture of two or more isocyanate compounds with oxime, acetylacetone, malonic diester and / or acetoacetate as a blocking agent.

Examples of the diisocyanate include hexamethylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, xylene diisocyanate, and isophorone diisocyanate. Examples of the oxime include methyl ethyl ketoxime, methyl isobutyl ketoxime, acetoxime, 2-butanone oxime, and propanol oxime. Examples of the malonic acid diester include malonic acid methyl ethyl ester, dimethyl malonate, and dibutyl malonate. Examples of the acetoacetate include methyl acetoacetate, ethyl acetoacetate, and butyl acetoacetate.

The component used as the component 2-b of the present invention is a reaction obtained by reacting a polyol containing a triazine ring or a derivative thereof, such as cyanuric acid, isocyanuric acid, and melamine, with a polyisocyanate and a blocking agent as described above. Product. Examples of the polyol compound containing such a triazine ring and its derivative include tris-2-hydroxyethyl isocyanurate and a reaction product of tris glycidyl ethyl isocyanurate and acrylic acid.

Such an isocyanate and a substance capable of reacting with the isocyanate are reacted at room temperature to 200 ° C. in the presence of an inert organic solvent such as toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, isophorone, and dioxane to react with the components 2-a and 2-a of the present invention. 2-b is obtained. The reaction may use a catalyst such as an organic tin compound tertiary amine, if necessary.

The amount of the component 2-a or 2-b used in the present invention may be an amount sufficient to remove the block when the electrodeposition coating film is baked and react and harden with a hydroxyl group, an amino group, etc. in the resin. 1
Is preferably 0.1 to 2.0 parts by weight based on 1 part by weight of the solid content.

Examples of the polymerizable monomer having two or more vinyl groups in one molecule used for producing Component 3 of the present invention include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and propylene glycol di (meth) acrylate. , Dipropylene glycol di (meth) acrylate, 1,3-butylene di (meth) acrylate, 1,4-pentanedi (meth) acrylate, 1,6
-Hexane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, glycerin tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, allyl (meth) acrylate, triallyl isocyanurate, divinylbenzene, and the like.

The polymerizable basic monomers used for preparing the component 3 include dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) acrylate, monomethylaminoethyl (meth) acrylate, and dimethylaminopropyl. (Meth) acrylamide, diethylaminoethyl (meth) acrylamide, 4-vinylpyridine, 2-
Examples thereof include a reaction compound of ethyl-5-vinylpyridine and glycidyl (meth) acrylate with a secondary amine such as diethylamine, dibutylamine, diethanolamine, and the like.

Other polymerizable monomers copolymerized with the above monomers include ethylene, propylene, butadiene, vinyl chloride, vinyl acetate, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate,
Examples thereof include (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and glycidyl (meth) acrylate, styrene, acrylonitrile, and the like.

The emulsion of Component 3 used in the present invention contains 2 per molecule.
1-20% by weight of polymerizable monomer having at least two vinyl groups
Preferably 3 to 15% by weight and 5 to 5 polymerizable basic monomers.
A mixture containing 25% by weight and the rest of other polymerizable monomers is prepared, and a nonionic surfactant (eg, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester) used for ordinary aqueous emulsion polymerization is prepared. And the like, and a reaction initiator (for example, ammonium persulfate, potassium persulfate, etc.) used in ordinary aqueous emulsion polymerization, and emulsion polymerization is performed in water by a known method.

When the amount of the polymerizable monomer having two or more vinyl groups in one molecule is less than 1% by weight in the mixture of the above-mentioned polymerizable monomers, the particle size of the particles in the emulsion becomes large and the stability of the coating becomes poor. If it exceeds 20% by weight, gelation occurs during the emulsion polymerization, which is not preferable.

When the amount of the polymerizable basic monomer is less than 5% by weight, the eutectoid to the electrodeposition coating film is poor (the content of the emulsion in the electrodeposition coating is significantly smaller than the content of the emulsion in the electrodeposition coating). Does not exhibit rust prevention performance.

On the other hand, if it exceeds 25% by weight, there is a problem that unevenness in the thickness of the coating film occurs, which is not preferable.

In addition to these components, if necessary, additives commonly used in emulsion polymerization such as an antifoaming agent and a pH adjuster may be contained.

The amount of the above-mentioned emulsion to be used is 1 to 30% by weight, preferably 5 to 15% by weight in terms of solid content in the composition of the present invention. 30
When used in an amount of more than 1% by weight, unevenness in film thickness occurs.

To prepare the cationic electrodeposition coating composition of the present invention,
Mixing component 1 and component 2-a or 2-b and component 3,
This is neutralized with an appropriate acid, for example, an inorganic acid such as boric acid, phosphoric acid, sulfuric acid, or hydrochloric acid, or an organic acid such as formic acid, acetic acid, or lactic acid, preferably alone or in combination, and then dissolved or dispersed in water.

Component 1, Component 2-a or Component 2- according to the present invention.
In addition to the above components, conventional additives such as pigments, solvents, and surfactants may be appropriately added to the cationic electrodeposition coating composition comprising b and component 3.

Any conventional pigments may be used, for example, inorganic pigments such as iron oxide, carbon black, titanium dioxide, clay, talc, barium sulfate, cadmium yellow, cadmium red, lead chromate, and strontium chromate, and phthalocyanine blue. And organic pigments such as phthalocyanine green.

In the electrodeposition method using the composition of the present invention, a conductive anode and a conductive cathode (a cast product having a surface to be coated) are inserted into the composition of the present invention, and usually 10 to
A voltage of 500 V is applied to deposit a coating film on the cathode surface. Electrodeposition conditions may vary widely, but are generally known in the art. After electrodeposition coating using the coating composition of the present invention, for example, 130 ° C. or less, preferably 60
It can be cured by heating at ~ 120 ° C.

〔Example〕

Hereinafter, the present invention will be described with reference to Production Examples and Examples,
Parts and percentages are by weight.

Production Example 1 (Component 1) Propylene glycol methyl ether 950 in a reaction vessel
Parts and 1900 parts of a bisphenol A type epoxy resin having an epoxy equivalent of 475, and heated and dissolved. Then, at 80 ° C., 200 parts of diethanolamine and 120 parts of diethylaminopropylamine are added, and the mixture is reacted for 3 hours to give a resin composition having a solid content of 70%. A was obtained.

Production Example 2 (Component 1) In a 34-neck flask, 626 parts of propylene glycol methyl ether and 1,300 parts of EPU-3 (Asahi Denka Co., Ltd., urethane-modified epoxy resin) were charged and dissolved by heating. 60 parts of diethylaminopropylamine was added and reacted at 120 ° C. for 3 hours. After cooling to room temperature, the resin was taken out to obtain a resin composition B having a solid content of 70%.

Production Example 3 (Component 1) In a reaction vessel, 448 parts of butyl cellosolve, and an epoxy equivalent of 940
Was added and heated to dissolve. Next, the mixture was cooled to 80 ° C., charged with 105 parts of diethanolamine, and reacted for 2 hours to obtain a resin composition C having a solid content of 70%.
I got

Production Example 4 (Component 2-a) In a 24-neck flask, 410 parts of xylene and 504 parts of a biuret-type trimer of hexamethylene diisocyanate were charged, and with stirring, 480 parts of diethyl malonate and 20 parts of dibutyltin dilaurate were added. After 6 hours of reaction at 100 ° C., 100 parts of butyl cellosolve was added, and the mixture was further reacted at 120 ° C. for 1 hour to obtain a curing agent D having a solid content of 65%. The unreacted isocyanate group content was 0%.

Production Example 5 (Component 2-a) 206 parts of xylene and 206 of dioxane were placed in a 24-neck flask.
Part, isocyanurate type 3 of tolylene diisocyanate
522 parts of methylmer ketoxime 2 at 20 ° C.
61 parts are dripped over 1 hour. Thereafter, the reaction was carried out at 60 ° C. for 3 hours, 10 parts of butyl cellosolve was added, and the reaction was carried out at 60 ° C. for 1 hour to obtain a curing agent E having a solid content of 65%. The unreacted isocyanate group content was 0%.

Production Example 6 (Component 2-b) A 24-neck flask was charged with 568 parts of xylene, 504 parts of hexamethylene diisocyanate, 213 parts of trishydroxyethyl isocyanurate, and 7 parts of dibutyltin dilaurate, and reacted at 90 ° C. for 4 hours. Thereafter, 350 parts of acetylacetone was added and reacted at 120 ° C. for 4 hours to obtain a curing agent F having a solid content of 65%. When the unreacted isocyanate group content of this product was measured, it was 0%.

Production Example 7 (Conventional curing agent) A 24-neck flask was charged with 486 parts of toluene, 522 parts of tolylene diisocyanate, 339 parts of ε-caprolactam, and 134 parts of trimethylolpropane, and reacted at 60 ° C for 6 hours, and then reacted with butyl cellosolve 50. Then, the mixture was reacted at 90 ° C. for 1 hour to obtain a curing agent G having a solid content of 65%.

Production Example 8 (aqueous emulsion solution) (component 3) In a clean 34-necked flask equipped with a thermometer, a reflux condenser, and a stirrer, 82 parts of deionized water and HLB 12.8 polyoxyethylene alkyl ether (Sanyo Chemical ( 0.3 parts of Nonipol Soft SS-70) and polyoxyethylene nonylphenol ether of HLB 16.0 (Nonipol 20 manufactured by Sanyo Chemical Co., Ltd.)
0) 0.4 part was charged and heated under stirring and kept at 80 ° C.

Meanwhile, in a separate container, methyl methacrylate 22 parts, n-butyl acrylate 50 parts, 2-hydroxyethyl methacrylate 10 parts, dimethylaminoethyl methacrylate 10 parts,
8 parts of dipropylene glycol dimethacrylate, 149.2 parts of deionized water, and 0.8 part of Nonipol Soft SS-70 described above were charged and sufficiently mixed and emulsified with a homomixer.

After 12.5 parts of this monomer mixture was put into the above aqueous solution of the emulsifier kept at 80 ° C., 2.0 parts of a 15% aqueous solution of ammonium persulfate was added, and the remaining monomer mixture was dropped at a constant speed over 1.0 hour.

Then, while maintaining the temperature at 80 ° C, the ammonium persulfate
1.0 part of a 15% aqueous solution was added dropwise over 20 minutes. Further, after keeping at 80 ° C. for 2 hours, the mixture was cooled to room temperature and removed after a long time. Thus, an aqueous emulsion solution H having a solid content of 30% was obtained.

Production Example 9 A pigment dispersion having a solid content of 50% was obtained with the following composition.

Resin composition C 1430 parts Acetic acid 60 Deionized water 2990 Carbon black 250 Kaolin 1900 Dibutyltin dilaurate 100 Basic lead silicate 300 Diacetone alcohol 70 Total 7100 These mixtures are sandmilled to a particle size of 5μ or less (measured with a gauge). ).

Examples 1 to 5, Comparative Examples 1 to 4 Compositions A to H of Production Examples 1 to 8 and the pigment dispersion of Production Example 9 were blended as shown in Table 1 below, and deionized water was added to a solid content of 20%. The obtained cationic electrodeposition paint was electrodeposited on a casting plate (width 70 mm, length 150 mm, surface roughness Rmax about 100 μ, manufactured by Japan Test Panel Co., Ltd.) under electrodeposition conditions of 200 V for 3 minutes. The printing was performed under the following printing conditions. Thereafter, a salt spray test, a solvent resistance and a film thickness of the projections of the obtained coated plate were examined. Table 1 shows the results. Each component in the table is based on weight.

[Effects of the Invention] Using the coating composition of the present invention, a cast product which is baked at a relatively low temperature and has an excellent rust-preventive effect can be obtained.

Continuation of the front page (72) Inventor Masaaki Nakashio 9-4 Showa 9-4, Chiryu-shi, Aichi 13-502 (58) Field surveyed (Int.Cl. ⁶ , DB name) C09D 5 / 44,175 / 04-175 / 16

Claims (1)

(57) [Claims] (1) a resin containing a cationic group and active hydrogen (component 1); and (2) a polyisocyanate having an isocyanurate, allohanate or biuret structure, oxime, acetylacetone, malonic diester and acetoacetate. Reaction product with a blocking agent selected from
a) a reaction product of a polyol having a triazine ring or a derivative thereof, a polyisocyanate, and a blocking agent selected from oximes, acetylacetones, malonic diesters, and astacetic esters (component 2-b);
And (3) 1 to 20% by weight of a polymerizable monomer having two or more vinyl groups in one molecule, 5 to 25% by weight of a polymerizable basic monomer and the rest of other polymerizable monomers are copolymerized in water. A cationic electrodeposition coating composition for a casting product, comprising: a cured emulsion (component 3).