JPH0774317B2 - Resin composition for electrodeposition paint - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for electrodeposition coating which is capable of forming a coating film which is excellent in rust prevention and curability at low temperature.

[0002]

2. Description of the Related Art Electrodeposition paints are excellent in throwing power and can form a coating film having excellent performance such as durability and corrosion resistance. For example, it is widely used for painting automobile bodies, painting electric appliances, and the like.

In order to further improve the anticorrosion property of the electrodeposition paint, a rust preventive pigment, for example, a lead compound such as lead chromate, basic lead silicate, strontium chromate or a chromium compound is often blended. However, the compound is a very harmful substance, and its use is problematic in terms of pollution control.
Therefore, as non-toxic or low-toxic rust preventive pigments replacing the lead compounds and the like, conventionally, zinc phosphate, iron phosphate, aluminum phosphate, calcium phosphate, zinc molybdate, calcium molybdate, zinc oxide, iron oxide, molybdenum phosphonate are used. The use of aluminum oxide, zinc phosphomolybdate, etc. has been studied, but these compounds do not have the rust preventive ability of the above-mentioned lead compounds and chromium compounds and are not practically satisfactory.

[0004]

The main object of the present invention is to form a coating film having an excellent anticorrosive property equivalent to or better than the above-mentioned rust-preventive pigment, which is problematic in terms of pollution control, without using it. It is to provide a resin composition for an electrodeposition coating composition.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies on metal species that exhibit excellent rust-preventing ability equivalent to or higher than that of lead compounds and chromium compounds in electrodeposition paints. Bismuth is effective, and by blending a pigment coated with a bismuth compound, not only a resin composition for electrodeposition coating which gives a coating film having very excellent anticorrosion properties can be obtained, but also the bake curing temperature of the coating film. Therefore, the present invention has been completed, and the present invention has been completed.

[0006] That is, the present invention provides a resin composition for electrodeposition coating, which comprises at least one pigment coated with a bismuth compound.

Examples of the bismuth compound with which the pigment is coated in the present invention include bismuth hydroxide, bismuth oxide, bismuth nitrate, bismuth benzoate, bismuth citrate, and bismuth oxycarbonate. It is possible to use a combination of two or more species.

On the other hand, as the pigment (base pigment) coated with the bismuth compound, any pigment can be used without particular limitation as long as it is a pigment usually used in electrodeposition paints. For example, titanium oxide, carbon black, Coloring pigments such as red iron oxide; extender pigments such as clay, mica, barita, talc, calcium carbonate and silica; rust preventive pigments such as zinc phosphate and iron phosphate. Among them, titanium oxide and clay (aluminum Silicate) is preferred.

The coating amount of the bismuth compound on the pigment is not strictly limited and can be varied over a wide range depending on the kind of the pigment used, the type of the bismuth compound, etc. 0.1 to 5 as bismuth (based on metal) based on the weight of pigment
A range of 0% by weight, particularly 5 to 40% by weight is preferable.

The method of forming the bismuth compound coating on the base pigment can be carried out by mixing the base pigment and the bismuth compound according to a conventional wet or dry method. Particularly preferred is a method in which a base pigment and a bismuth compound are sufficiently mixed in a water-dispersed slurry state by a wet method, followed by drying and pulverizing. More specifically, for example, the base pigment is dispersed in an aqueous medium to form a slurry, and a solution in which a bismuth compound is dissolved in an aqueous medium (for example, an acid aqueous solution, an aqueous alcohol solution, etc.) is added to the slurry and mixed sufficiently. , Heat treatment and / or if necessary
Alternatively, after the neutralization treatment, the coated pigment is separated, washed, dried, and optionally pulverized to obtain a pigment coated with a bismuth compound (hereinafter,
"Bismuth coating pigment") can be obtained.

The bismuth coating pigment obtained as described above can be introduced into the resin composition for electrodeposition coating composition in the same manner as the compounding of the pigment into the ordinary resin composition for electrodeposition coating composition. After the pigment paste is prepared by treating it with a suitable dispersing resin component in a dispersion mixer such as a ball mill, it can be blended with a binder (vehicle) resin component for paint.

The content of the above-mentioned bismuth coating pigment in the resin composition for electrodeposition coating is not strictly defined and can be varied over a wide range depending on the performance required for the electrodeposition coating, 0.1 to 5 per 100 parts by weight of the resin solid content of the resin composition for electrodeposition paint
It is suitable that the amount is 0 parts by weight, preferably 1 to 30 parts by weight. If the content is less than 0.1 part by weight, the rust-preventive property of the coating film formed is not sufficient, while if it exceeds 50 parts by weight, the stability of the coating resin composition tends to decrease.

The resin composition for electrodeposition coating composition of the present invention may be either anionic type or cationic type, but in general, cationic type is preferable from the viewpoint of corrosion resistance, and the base resin is epoxy type or acrylic type. Although any of a resin of a system, a polybutadiene system, an alkyd system, or a polyester system can be used, a polyamine resin represented by, for example, an amine-added epoxy resin is preferable.

As the amine-added epoxy resin, for example, an adduct of (i) a polyepoxide compound and a primary mono- and polyamine, a secondary mono- and polyamine or a primary and secondary mixed polyamine (for example, US Pat. 984
299); (ii) Adducts of polyepoxide compounds with secondary mono- and polyamines having ketiminated primary amino groups (e.g. U.S. Pat. No. 4,012).
No. 7,438); (iii) a reaction product obtained by etherification of a polyepoxide compound and a ketiminized hydroxy compound having a primary amino group (see, for example, JP-A-59-43013). Can be mentioned.

The polyepoxide compound used for producing the amine-added epoxy resin is a compound having two or more epoxy groups in one molecule, and generally has at least 20.
0, preferably 400 to 4000, more preferably 80
Those having a number average molecular weight in the range of 0 to 2000 are suitable, and those obtained by reacting a polyphenol compound with epichlorohydrin are particularly preferable. Examples of the polyphenol compound that can be used for forming the polyepoxide compound include bis (4-hydroxyphenyl) -2,2-propane, 4,4-dihydroxybenzophenone and bis (4-hydroxyphenyl) -1,1-.
Ethane, bis- (4-hydroxyphenyl) -1,1-
Isobutane, bis (4-hydroxy-tert-butyl-phenyl) -2,2-propane, bis (2-hydroxynaphthyl) methane, 1,5-dihydroxynaphthalene, bis (2,4-dihydroxyphenyl) methane, tetra ( 4-hydroxyphenyl) -1,1,2,2-ethane, 4,4-dihydroxydiphenyl sulfone, phenol novolac, cresol novolac and the like can be mentioned.

The polyepoxide compound may be partially reacted with a polyol, a polyether polyol, a polyester polyol, a polyamidoamine, a polycarboxylic acid, a polyisocyanate compound or the like, and further, ε-caprolactone, an acrylic monomer or the like. May be graft-polymerized.

The above-mentioned base resin may be of either an external cross-linking type or an internal (or self) cross-linking type, and examples of the curing agent used in the case of the external cross-linking type resin include (block ) It can be a conventionally known crosslinking agent such as a polyisocyanate compound or an amino resin,
Blocked polyisocyanate compounds are sometimes preferred. Further, as the internal cross-linking type resin, one introduced with a block polyisocyanate type is suitable.

The blocked isocyanate compound that can be used in the external crosslinking type can be an addition reaction product of a theoretical amount of a polyisocyanate compound and an isocyanate blocking agent. Examples of the polyisocyanate compound include aromatic compounds such as tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, bis (isocyanatomethyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, and isophorone diisocyanate, alicyclic compounds or aliphatic compounds. Group isocyanate-containing compounds obtained by reacting low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, trimethylolpropane, hexanetriol, and castor oil with an excess amount of polyisocyanate compounds of the group and these isocyanate compounds. .

On the other hand, the above-mentioned isocyanate blocking agent is one which blocks by adding to the isocyanate group of the polyisocyanate compound, and the blocked isocyanate compound produced by the addition is stable at room temperature and when heated to about 100 to 200 ° C. It is desirable that the blocking agent can be dissociated to regenerate a free isocyanate group. Examples of the blocking agent satisfying such requirements are lactam compounds such as ε-caprolactam and γ-butyrolactam; methylethylketoxime,
Oxime-based compounds such as cyclohexanone oxime; phenol-based compounds such as phenol, para-t-butylphenol and cresol; aliphatic alcohols such as n-butanol and 2-ethylhexanol; aromatics such as phenylcarbinol and methylphenylcarbinol Alkyl alcohols; ether alcohol compounds such as ethylene glycol monobutyl ether and the like can be mentioned.

Of these, the oxime-based and lactam-based blocking agents are blocking agents that dissociate at a relatively low temperature, and thus are particularly preferable from the viewpoint of curability of the resin composition for electrodeposition coating.

As a method of introducing a blocked isocyanate group into a base resin in a type having a blocked isocyanate group in a base resin molecule and self-crosslinking, a conventionally known method can be used, for example, a partially blocked polyisocyanate compound. It can be introduced by reacting the free isocyanate group therein with the active hydrogen-containing portion in the base resin.

In the case of a cationic resin, the base resin is usually neutralized and made water-soluble by neutralizing the resin with a water-soluble organic acid such as formic acid, acetic acid or lactic acid to make it water-soluble or water-dispersible. In the case of an anionic resin, it can be carried out by neutralizing with an alkali such as amine or alkali metal hydroxide in place of the water-soluble organic acid, and solubilizing / dispersing in water. .

In the resin composition for electrodeposition coating composition of the present invention, if necessary, a coloring pigment, an extender pigment, a rust preventive pigment, an organic solvent,
A paint additive such as a pigment dispersant or a paint surface modifier may be added.

The resin composition for electrodeposition coating composition of the present invention can be coated on a desired substrate surface by electrodeposition coating. The electrodeposition coating is generally diluted with deionized water or the like so that the solid content concentration is about 5 to 40% by weight, and the pH is adjusted to 5.5.
The temperature of the electrodeposition bath comprising the resin composition for electrodeposition coating composition of the present invention adjusted within the range of ˜9.0 is usually adjusted to a bath temperature of 15 to 35 ° C. and a load voltage of 100 to 400 V. it can.

The film thickness of the electrodeposition coating film which can be formed using the resin composition of the present invention is not particularly limited, but in general, it is preferably in the range of 10 to 40 μm based on the cured coating film. . The baking temperature of the coating film is generally 100 to
A range of 200 ° C is suitable.

[0026]

According to the present invention, a bismuth compound-coated pigment (bismuth coating pigment) is contained in a resin composition for electrodeposition coating composition, so that a rust preventive pigment such as a lead compound which is problematic in pollution control can be obtained. Without using
It is possible to provide a resin composition for electrodeposition coating which gives an electrodeposition coating film having an excellent rust preventive property which is almost equal to or higher than the case of blending the rust preventive pigment. It is not clear why the resin composition for electrodeposition coating composition of the present invention has such excellent rustproofing properties, but it is presumed that the bismuth coating pigment has some action at the interface with the article to be coated. Furthermore, when the resin composition for electrodeposition coating composition of the present invention is a blocked isocyanate curing type, since the bismuth coating pigment also acts as a catalyst for dissociating the blocked isocyanate group, it is very excellent in low temperature curability,
It is possible to form a coating film having significantly improved coating film physical properties at low temperature curing.

[0027]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. "Parts" and "%" mean "parts by weight" and "% by weight".

Production Example 1 2700 4% aqueous ammonia solution in a 5-liter 4-necked flask
180 parts of titanium oxide was uniformly dispersed in 80 parts of the solution. 1,100 solution of bismuth dissolved in dilute nitric acid
Parts were added dropwise over about 100 minutes. During this period, the titanium oxide dispersed slurry was maintained at 80 ° C ± 2 ° C. After the dropping is completed,
After aging at the same temperature for 30 minutes, suction filtration was performed to separate and remove the filtrate, and the remaining pigment cake was poured into 1,000 parts of warm water at 80 ° C ± 2 ° C. After stirring for 30 minutes, suction filtration was carried out again, and the obtained pigment cake was dried at 90 ° C. for 12 hours and then pulverized to obtain titanium oxide coated with bismuth oxide hydroxide. From the chemical analysis, the content of bismuth was 33% with respect to titanium oxide.

Production Example 2 The same operation as in Production Example 1 was carried out except that purified clay was used in place of titanium oxide in Production Example 1 to obtain a purified clay having hydrous oxide bismuth coating. The bismuth content of this pigment was 33%.

Example 1 1900 parts of Epon 1004 (* 1) was dissolved in 1012 parts of butyl cellosolve, and 124 parts of diethylamine was added to 80 to 80 parts.
After dropping at 100 ° C and holding at 120 ° C for 2 hours, an epoxy resin-amine adduct having an amine value of 47 was obtained.

Next, 1000 parts of a dimer acid type polyamide resin having an amine value of 100 [trade name "Bersamide 460", manufactured by Henkel Hakusui Co., Ltd.] was dissolved in 429 parts of methyl isobutyl ketone and heated under reflux at 130 to 150 ° C.
The produced water was distilled off to change the terminal amino group of the amide resin to ketimine. This is kept at 150 ° C. for about 3 hours and cooled to 60 ° C. after the distillation of water is stopped. Then add this to the epoxy resin-amine adduct and add 100 ° C.
After heating for 1 hour and cooling to room temperature, a varnish of epoxy resin-amino-polyamide addition resin having a solid content of 68% and an amine value of 65 was obtained.

103 parts of the varnish obtained above (70 parts by resin solid content), 30 parts of 2-ethylhexyl alcohol blocked product of xylylene diisocyanate (by solid content), 1
After 15 parts of 0% acetic acid was mixed and uniformly stirred, 150 parts of deionized water was added dropwise over about 15 minutes with strong stirring to obtain a cationic emulsion for cationic electrodeposition having a solid content of 33.6%. To 298 parts of this clear emulsion was added 69.7 parts of a pigment paste having the formulation shown in Formula 1 in Table 1 below with stirring, and the mixture was diluted with 271.3 parts of deionized water to obtain a cationic electrodeposition coating composition.

(* 1) Epon 1004: Bisphenol A type epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd. and having an epoxy equivalent of about 950.

Example 2 and Comparative Examples 1 to 3 The same as Example 1 except that instead of the pigment paste of Formulation 1 in Example 1, pigment pastes of the formulations shown in Formulations 2 to 5 of Table 1 below were used. The operation was performed to obtain the cationic electrodeposition coating composition shown in Table 1.

Coating test In the electrodeposition paints obtained in Examples 1 and 2 and Comparative Examples 1 to 3,
0.8 × 150 × 70 chemical treated with Palbond # 3030 (Zinc phosphate treatment agent manufactured by Nippon Parkerizing Co., Ltd.)
mm cold rolled dull steel plate was dipped, and electrodeposition coating was performed using it as a cathode. The electrodeposition condition is a voltage of 300 V, and an electrodeposition coating film having a film thickness (based on the dry film thickness) of about 20 μ is formed.
After washing with water, baking was performed. The baking was carried out using an electric hot air dryer with the atmospheric temperature set to 6 stages and the baking time set to 20 minutes. The performance test results of the obtained coated plate are shown in Table 2 below.

[0036]

[Table 1]

[0037]

[Table 2]

The performance test was carried out according to the following method.

(* 2) Anticorrosion: A cross-cut scratch was made with a knife on the electrodeposition coating film so as to reach the base, and this was JIS
A salt spray test was performed for 840 hours according to Z2371, and evaluated by rust from knife scratches and blistering width.

⊚: The maximum width of rust or blisters is less than 1 mm from the cut portion (one side).

◯: The maximum width of rust or blisters is 1 mm or more and less than 2 mm (one side) from the cut portion.

Δ: The maximum width of rust or blisters is 2 mm or more and less than 3 mm (one side) from the cut portion, and blisters are considerably conspicuous on the flat surface portion.

X: The maximum width of rust or blisters is 3 mm or more from the cut portion, and blister is observed on the entire coated surface.

(* 3) Curability: The coated surface of each of the obtained electrodeposition coated plates was covered with four layers of gauze impregnated with methyl isobutyl ketone to give a length of about 3-4 cm at a pressure of about 4 kg / cm ^2. The appearance of the coated surface after rubbing 20 times was visually evaluated.

◯: No scratch is observed on the coated surface.

Δ: Scratches are recognized on the coated surface, but the base material is not visible.

X: The coating film is dissolved and the substrate is visible.

(* 4) Impact resistance: Using a DuPont type impact tester, the impact diameter is 1/2 inch and the falling weight height is 50c.
The test was conducted under the conditions of m and a measurement atmosphere of 20 ° C., and the impacted concave portions were visually evaluated.

◯: No abnormality Δ: Some small cracks are seen ×: Large cracks are seen (* 5) 3 coat image clarity: Amino alkyd intermediate coating paint manufactured by Kansai Paint Co., Ltd. on the electrodeposition coated surface Amylak TP-37
"Gray" is applied by spray coating to a dry film thickness of about 35 microns, and baked at 140 ° C for 20 minutes.
Furthermore, Kansai Paint Co., Ltd. amino alkyd top coating "Amilak TM13 White" was applied by spray coating to a dry film thickness of about 35 microns, and the temperature was 140 ° C.
The image clarity of the coated plate baked for 20 minutes was evaluated using an image clarity measuring device [manufactured by Suga Test Instruments Co., Ltd.].

◎: Measured value is 80 or more ○: 〃 75 or more and less than 80 △: 〃 70 or more and less than 75 ×: 〃 less than 70

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C09D 5/08 PQE 7/12 PSJ

Claims (4)

[Claims] 1. A resin composition for electrodeposition coating composition, which comprises at least one pigment coated with a bismuth compound. 2. A pigment coated with a bismuth compound is added in an amount of 0.1 to 5 per 100 parts by weight of the resin solid content of the composition.
The composition according to claim 1, which contains 0 part by weight. 3. The composition according to claim 1, wherein the pigment is titanium oxide. 4. The composition according to claim 1, wherein the pigment is clay (aluminum silicate).