JPH0625567A - Cationic electrodeposition coating composition - Google Patents

Abstract

PURPOSE:To obtain a cationic electrodeposition coating composition improved both in covering properties at cut ends of metal-coated material and smoothness of electrodeposition coating film. CONSTITUTION:This coating composition consists essentially of (A) 1-20 pts.wt. acrylic resin fine particles having an internal crosslinking structure and 5-500nm particle diameter, (B) 5-30 pts.wt. thermoplastic resin, (C) 40-70 pts.wt. amino group-containing epoxy resin and (D) 10-35 pts.wt. block isocyanate curing agent resin.

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 which improves both the coating property of the cut end of a metal coated object and the smoothness of the electrodeposition coating film.

[0002]

2. Description of the Related Art A conventional cationic electrodeposition coating composition is designed so that an uncured coating film is melted by heat during baking of the coating film in order to have high rust preventive power and high smoothness of the coating surface. There is. Therefore, the cut end portion of the metal-coated object does not have a coating film remaining due to the fluidity of the coating film, and corrosion progresses from the cut end portion. Therefore, as disclosed in JP-A-63-39972, by using various rheology control agents for controlling the viscosity of the electrodeposition paint, the coating film remains at the cut end of the steel sheet. It was

[0003]

However, in such a conventional cationic electrodeposition coating composition, the coating film remains at the cut end of the metal object to be coated, but the rust preventive power is exerted. In the general part of the article to be coated, there is a problem that the fluidity of the coating film is poor and the smoothness of the coating film is impaired, which adversely affects the appearance of the coating film after intermediate coating and top coating.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found the problem by adding a thermoplastic resin to a cationic electrodeposition coating composition containing a rheology control agent. The present invention has been accomplished and the present invention has been achieved.

The cationic electrodeposition coating composition of the present invention has an internal crosslinked structure and contains 1 to 20 parts by weight of acrylic resin fine particles having a particle diameter of 5 to 500 nm, 5 to 30 parts by weight of a thermoplastic resin, and an amino group. It is characterized by comprising 40 to 70 parts by weight of an epoxy resin and 10 to 35 parts by weight of a blocked isocyanate curing agent resin as main components. Components that can be used in the present invention
Acrylic resin fine particles with a particle size of 5 to 500 nm with an internal cross-linking structure of (A) are prepared by adding a polyfunctional polymerizable unsaturated compound (a) and another polymerizable monomer (b) in the presence of an emulsifier and an initiator. Further monomers (a) and monomers obtainable by emulsion polymerization
It can be obtained by bulk polymerization of (b), mechanical pulverization and sieving. Polyfunctional polymerizable unsaturated compound (a) is 1
It is not particularly limited as long as it is an unsaturated compound having two or more polymerizable unsaturated groups in the molecule, but ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate,
Trimethylolpropane trimethacrylate, trimethylolpropane dimethacrylate, diallyl phthalate, allyl methacrylate, divinylbenzene and the like can be used. On the other hand, the polymerizable monomer (b) is an α, β ethylenically unsaturated monomer such as acrylic acid, methacrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate,
Butyl (meth) acrylate, (meth) acrylic acid, 2-ethylhexyl and other (meth) acrylic acid and their alkyl esters, (meth) acrylic acid, 2-hydroxyethyl, methacrylic acid, 4-hydroxybutyl, and other (meth) acrylic acid
Hydroxyalkyl esters of acrylic acid and monomers such as styrene and vinyl acetate can be used. The proportion of the polyfunctional polymerizable unsaturated compound (a) in the composition of the fine particles is
0.5 to 10 parts by weight, preferably 1 to 5 parts by weight are used. As the emulsifier used when obtaining the particles by emulsion polymerization, the emulsifier used in ordinary emulsion polymerization can be used, but since it is used in cationic electrodeposition coating, a cationic or nonionic emulsifier and a combination thereof can be used. As the initiator, a usual radical polymerization initiator can be used. The particle size of the fine particles must be in the range of 5 to 500 nm.
If it is less than 500 nm, the ability to control the rheology cannot be fully exerted, and if it is more than 500 nm, the stability of the coating becomes extremely poor. If the content of component (A) is more than 20 parts by weight, the smoothness of the coated surface will be significantly deteriorated and it will not be practically applicable, and if it is less than 1 part by weight, the rust preventive power of the cut end of the metal coated object will be obtained. Absent.

Next, the thermoplastic resin as the component (B) that can be used in the present invention means a baking temperature of a general electrodeposition coating (about 100 ° C.).
Up to 200 ° C.) A synthetic resin having fluidity at a temperature of 200 ° C. or less, having a chemical structure composed of a linear or branched polymer, and having an hydroxyl group having an OH value of 0.2 mmol / g or less. The wet film deposited on the coated object by applying current from the electrodeposition paint containing this thermoplastic resin is partially fused by the Joule heat generated at the same time to promote defoaming of the electrolytic gas and densify the wet film. In addition to having the effect of reducing the fluidity of the coating film due to acrylic fine particles during baking of the coating film (improving the coating property of the cut edge of the metal object and simultaneously decreasing the coating surface smoothness) By the effect, it is possible to improve the coverage of the cut end portion and the smoothness of the coated surface. Examples of such thermoplastic resin include polyethylene resin, polystyrene resin, xylene resin,
Examples thereof include ketone resins, vinyl acetate resins, phenoxy resins, butadiene resins, vinyl chloride resins, vinylidene chloride resins, and linear unsaturated polyester resins. Further, the softening point of these thermoplastic resins is preferably about 100 ° C. or lower for the above reason (densification of the wet film). If the content of the component (B) is more than 30 parts by weight, the rust preventive power on the general surface is reduced, and if it is less than 5 parts by weight, the effect of improving the smoothness of the coated surface is not exhibited.

Examples of the component (C) used in the present invention include those obtained by reacting an epoxy group-containing resin with a cationizing agent. Examples of the epoxy group-containing resin for producing the component (C) include a polyepoxy resin synthesized from a polyphenol compound and epichlorohydrin, a resin obtained by epoxidizing a polyalkylene oxide terminal, and an unsaturated ethylene group oxidized in a metal catalyst. Examples of the epoxidized polybutadiene resin, a copolymer of glycidyl (meth) acrylate and another polymerizable ethylene compound, or a mixture of two or more of them. Examples of polyphenols that can be used here include 2,2-bis (4'-hydroxyphenyl) -ethane, bis (4-hydroxyphenyl) -methane, 4,4'-dihydroxybenzophenone and 2,2'-bis. (4'-hydroxy-
tert-butyl-phenyl) -propane, 1,1,2,2
-Tetra (4-hydroxyphenyl) -ethane, 4,
4'-dihydroxydiphenyl ether, phenol novolac, cresol novolac and the like can be mentioned. The epoxy group-containing resin may be chain-extended with a polycarboxylic acid, a polyamine, a polyester polyol, a polyisocyanate or the like, if necessary. Examples of the cationizing agent to be reacted with the epoxy group-containing resin include alkyl group, aryl group and / or alkanol group-containing primary or secondary amine, tertiary amine salt and the like. Examples of these include methylamine, ethylamine, propylamine, benzylamine,
Primary amines such as monoethanolamine and propanolamine, secondary amines such as diethylamine, dipropylamine, N-methylbenzylamine, N-methylethanolamine and diethanolamine, ethylenediamine,
Polyethylene such as diethylenetriamine, dimethylaminopropylamine, diethylaminopropylamine, hydroxyethylaminoethylamine, a reaction product of hexamethylenediamine and Cardura E-10 (manufactured by Shell Chemical Co., Ltd.), a reaction product of tetraethylenetriamine and butylglycidyl ether, and the like. Examples thereof include ketimines and the like obtained by the reaction of primary amines and ketones, which are reacted with the epoxy group-containing resin by a known method and then converted into an acid, particularly preferably an organic carboxylic acid such as formic acid, acetic acid or lactic acid. Is neutralized and becomes a cationic group. Furthermore, triethylamine, triethanolamine, N, N-dimethylethanolamine, N-methyldiethanolamine, etc. are added to boric acid, carbonic acid,
Examples of inorganic acids such as hydrochloric acid include tertiary amines neutralized with organic acids such as formic acid, acetic acid, lactic acid, and propionic acid. The reaction of the epoxy group-containing resin with the cationizing agent can be carried out by a known method to obtain the resin of the component of the present invention. When the content of the component (C) is more than 70 parts by weight, the smoothness of the coated surface is not good, and when it is less than 40 parts by weight, the stability as an electrodeposition coating composition is significantly impaired.

The blocked isocyanate curing agent resin of component (D) that can be used in the present invention is stable at room temperature when the reaction product of the isocyanate group with a certain compound is active hydrogen such as hydroxyl group or amino group. However, at a high temperature (usually 80 to 250 ° C.), any polyisocyanate species which is reactive with the active hydrogen by regenerating the isocyanate group by thermal decomposition may be used. Any suitable organic polyisocyanate may be used to prepare the blocked isocyanate curing agent resin. For example, aliphatic isocyanates such as trimethylene-, tetramethylene-, hexamethylene-diisocyanate, cycloalkylene isocyanates such as 1,4-cyclohexane-, 1,2-cyclohexane-, isophorone-diisocyanate, m-phenylene-1,4- Aromatic isocyanates such as naphthalene-diisocyanate, 4,4-
Aromatic-aliphatic isocyanates such as diphenylmethane-, 2,4- or 2,6-tolylene 4,4'-toluidine-, 1,4-xylylene-diisocyanate, dianisidine diisocyanate, 4,4-diphenyl ether diisocyanate and chloro- Unsubstituted aromatic isocyanates such as diphenylene diisocyanate, triphenylmethane-4,4 ', 4 "-triisocyanate, 1,3,5-triisocyanate benzene, 2,
4,6-triisocyanate Triisocyanate such as toluene, 4,4'-diphenyl-dimethylmethane-
Examples thereof include tetraisocyanates such as 2,2 ′, 5,5′-tetraisocyanate, and polymerized polyisocyanates such as dimers and trimers of the above diisocyanates. Additionally, the organic polyisocyanate may be a prepolymer derived from the following polyols, which react with excess polyisocyanate to give a prepolymer having isocyanate end groups, the polyol being a polyether. A simple polyol as described below may be used, including a polyester polyol containing a polyol or a polyether. Those simple polyols include glycols such as ethylene glycol and propylene glycol and glycerin, trimethylolpropane, hesantriol, pentaerythritol and the like, and monoethers and polyethers such as diethyl glycol, tripropylene glycol and the like, i.e. Other polyols such as alkylene oxide condensates of Alkylene oxides that condense with these polyols to form polyethers include ethylene oxide, propylene oxide, butylene oxide, styrene oxide and the like.
These are generally hydroxy-terminat
ed) It is called a polyether and may be linear or branched. Examples of polyethers are polyoxyethylene glycol having a molecular weight of 1540, polyoxypropylene glycol having a molecular weight of 1025, polyoxytetramethylene glycol, polyoxyhexamethylene glycol, polyoxynanomethylene glycol, polyoxydecamethylene glycol and those. And the like. Other types of polyoxyalkylene glycol ethers can also be used. Particularly useful polyether polyols are ethylene glycol, diethylene glycol,
Triethylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,6-hexanediol and mixtures thereof, glycerin trimethylolethane, trimethylolpropane, 1,2,6-hexanetriol, pentaerythritol, It is made by reacting a polyol such as dipentaerythritol, tripentaerythritol, polypentaerythritol, sorbitol, methyl glycosides, sucrose and the like with an alkylene oxide such as ethylene oxide, propylene oxide, a mixture thereof and the like. Examples of the blocking agent for the above isocyanate include methyl, ethyl, chloroethyl, propyl, butyl, amyl, hexyl, heptyl, octyl, nonyl, 3,3,3.
Aliphatic alcohols such as 5-trimethylhexanol, decyl and lauryl alcohol and the like, alicyclic alcohols such as cyclopentanol, cyclohexanol and the like, aromatic-alkyl alcohols such as phenylcarbinol, methylphenylcarbinol and the like. , Mono-alcohols such as hydroxy group-containing vinyl compounds such as 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate, hydroxylamines such as N, N-dimethylethanolamine and N, N-diethylethanolamine, methyl ethyl ketone oxime, acetone Examples thereof include oximes such as oximes and cyclohexanone oximes, and lactams such as ε-caprolactam.
The blocked isocyanate curing agent resin of component (D) that can be used in the present invention is prepared by reacting the organic isocyanate with an amount of the blocking agent sufficient to completely react the free isocyanate groups. If the content of the component (D) is less than 10 parts by weight, the degree of cross-linking of the coating film is reduced, so that the rust preventive power cannot be obtained, and if it is more than 35 parts by weight, physical properties of the coating film are deteriorated.

If necessary, the electrodeposition coating composition of the present invention contains additives such as pigments, neutralizing agents, pigment dispersants, and curing catalysts.
Deionized water or the like is added. When cationic electrodeposition coating is carried out using the electrodeposition coating composition of the present invention, solids in the aqueous liquid are 5 to 30%, and the liquid temperature is 20 to 35 ° C. Apply a coating voltage of 50-400V between 1 and 5 minutes. After washing the coated object with water, in a baking oven
It can be baked at 100 to 200 ° C. for 10 to 30 minutes to form a dry coating film having good edge coverage and smooth coating surface.

[0010]

EXAMPLES The present invention will be described below with reference to production examples, examples, comparative examples and test examples of acrylic resin fine particles, amino group-containing epoxy resin, blocked isocyanate curing agent and pigment dispersant.

Production Example 1 Using the compounding ingredients shown in Table 1, acrylic resin fine particles were produced by the following method.

[0012]

[Table 1]

The ingredients (1), (2) and (3) were placed in a 1 liter 4-necked flask equipped with a stirrer, a thermometer and a condenser, and the mixture was stirred and heated to 60 ° C. Ingredients (8),
A 10% solution of VA-061 prepared by mixing (9) and (10) was added and held for 10 minutes, and then the mixture of compounding ingredients (4), (5), (6) and (7) was added in 2 hours. It was dropped at a constant speed. After the dropping is completed, 2 more at 60 ℃
After holding for a time, it was cooled to room temperature and taken out. The resulting emulsion A-1 has a solid content of 20% and an average particle size of 115n.
m (measured by LPA-3000 manufactured by Otsuka Electronics Co., Ltd.).

Production Example 2 Using the compounding ingredients shown in Table 2, an amino group-containing epoxy resin was produced by the following method.

[0015]

[Table 2]

A 6 liter 4-necked flask equipped with a cooling tube, a thermometer and a stirrer was charged with the above-mentioned components (1), (2) and (5), dissolved at 100 ° C and then cooled to 60 ° C. , Ingredients
The mixture of (3) and (4) was added. 80 ° C while paying attention to heat generation
The mixture was kept for 2 hours to obtain an amino-modified epoxy resin solution C-1 containing a tertiary amino group of 2.5 mmol / g solid content.
The solid content of this product was 70%.

Production Example 3 Using the compounding ingredients shown in Table 3, a blocked isocyanate type curing agent was produced by the following method.

[0018]

[Table 3]

In the same manner as in Production Example 1, the ingredients (1) and (2) were placed in a 2-liter 4-necked flask equipped with a stirrer, a thermometer, and a cooling tube.
Was added and the compounding component (3) was added dropwise over 1 hour while maintaining the temperature at 40 ° C under stirring. After completion of dropping, hold at 40 ° C for 1 hour, then add compounding component (4) and heat up to 60 ° C and react at 60 ° C until the residual isocyanate group ratio becomes 0, and the solid content is 70%. A blocked isocyanate curing agent solution D-1 was obtained.

Production Example 4 A pigment dispersion liquid was produced by the following method using the ingredients shown in Table 4.

[0021]

[Table 4]

The above-mentioned components (1), (2) and (3) were charged into a clean 10 liter cylindrical stainless steel container and stirred with a dissolver to dissolve them. Further compounding ingredients (4), (5), (6), (7),
Add (8) and (9) to this, mix thoroughly, and then disperse with a 1.5 liter motor mill (bead type disperser manufactured by Eiger Co., Ltd.) until the gub gauge particle size becomes 5 μm or less, and stabilize at a solid content of 50%. An excellent pigment dispersion was obtained.

Examples 1 to 5 and Comparative Examples 1 to 3 Each resin and solvent having the formulations shown in Table 5 were charged in a 5 liter 4-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a decompression device. A predetermined amount of solvent was removed at -100 ° C under a pressure of 50-60 mmHg. After that, in a cylindrical stainless steel container charged with deionized water and formic acid, the desolvated resin mixture was gradually added under sufficient stirring to emulsify the solid content.
A 35% resin emulsion was obtained. Furthermore, a predetermined amount of deionized water, a pigment dispersion liquid, and a microgel emulsion were added thereto to obtain an electrodeposition coating solution.

Test Example With respect to these cationic electrodeposition coating compositions, a conductive object to be coated was immersed in an electrodeposition bath of each electrodeposition coating composition at a bath temperature of 28 ° C. according to the following coating method, and the electrode was used as a counter electrode. Between a certain anode,
Electric current was applied for 3 minutes at a voltage such that the film thickness after baking was 20 μm. The properties and performance of the obtained coating film are evaluated by the following test methods,
The results obtained are shown in Table 5.

[0025]

[Table 5]

Coating Method The cationic electrodeposition coating compositions of Examples 1 to 5 and Comparative Examples 1 to 3 were placed in a vinyl chloride container, and the coated material was used as a cathode at 28 ° C. under stirring, and the average film was baked. Cationic electrodeposition coating was performed under the electrodeposition conditions where the thickness was 20 μm.

[Table 6 coating object] SPCC plate (150 x 70 x 0.8 mm) and cutter blade (manufactured by Olfa Co., Ltd.) specified in JIS G 3141 The coating object is treated with zinc phosphate before cationic electrodeposition coating. gave. Baking conditions 175 ℃ x 20 minutes

Test method

[Table 7] Corrosion resistance test method A hot water spray test specified in JIS Z 2371 was carried out. For the SPCC plate, a cross cut reaching the substrate was put on the electrodeposition coated surface, and a salt spray test was conducted for 1000 hours to confirm the degree of rusting. The evaluation was performed as follows. ◯: Good. Δ: Slightly good. X: Inferior With the cutter blade, a salt spray test was performed for 168 hours to count the number of rusts. Smoothness of coated surface The center line average roughness (Ra) was measured and evaluated as follows. ○: Ra = 0.45 to 0.60 Δ: Ra = 0.60 to 0.75 ×: Ra = 0.75 or more

[0028]

As described above, according to the present invention, acrylic resin fine particles having a predetermined amount of the internal cross-linking structure and a particle diameter of 5 to 500 nm, a thermoplastic resin, and an amino group-containing epoxy are used. Since it is a cationic electrodeposition coating composition consisting mainly of resin and blocked isocyanate curing agent resin, it can improve both the edge rust prevention of steel sheet and the smoothness of the electrodeposition coating film. Therefore, when the intermediate coating and the top coating are applied under the same conditions, the effect of the coating clarity after the top coating being equal to or higher than that of the electrodeposition coating composition without the thermoplastic resin can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Ken Fukui, 6-1073 Minamitsukaguchi-cho, Amagasaki-shi, Hyogo Within Shinto Paint Co., Ltd. (72) Kouji Tsujimoto 6-10, Minamitsukaguchi-machi, Amagasaki-shi, Hyogo No. 73 Shinto Paint Co., Ltd. (72) Inventor Naoki Kondo 6-1073 Minamitsukaguchi-cho, Amagasaki City, Hyogo Prefecture Shinto Paint Co., Ltd.

Claims (1)

[Claims] 1. (A) It has an internal crosslinked structure and a particle size of 5 to 50.
1 to 20 parts by weight of 0 nm acrylic resin fine particles, (B) 5 to 30 parts by weight of thermoplastic resin, (C) 40 to 70 parts by weight of amino group-containing epoxy resin, and (D) blocked isocyanate curing agent resin 10 A cationic electrodeposition coating composition, characterized in that the main component is about 35 parts by weight.