JPH11106687A - Cationic electrocoating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition capable of providing a electrocoating having excellent corrosion resistance and finishing properties without using a rust preventative pigment such as a lead compound, etc., having a problem in antipollution measure and useful for coating, etc., for a car body of an automobile by including an aqueous solution of specific bismuth salts of organic acids. SOLUTION: This cationic electrocoating composition contains an aqueous solution of bismuth salts of two or more kinds of organic acids including one or more kinds of aliphatic alkoxycarboxylic acids preferably regulated so that the content of the bismuth based on 100 pts.wt. solid component of the resin in the electrocoating material may be 0.01-10 pts.wt. The aliphatic alkoxycarboxylic acid is the one having <<=16 number of carbons and exemplified by methoxyacetic acid. The using amount of the aliphatic alkoxycarboxylic acid based on the total of the organic acids is preferably 50-99 mol.%. The organic acid without the aliphatic alkoxycarboxylic acid is preferably an aliphatic carboxylic acid having <=6 number of carbons, such as acetic acid.

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 lead free paint capable of forming an electrodeposition coating film having excellent anticorrosion properties and finish even without a lead compound.
And a cationic electrodeposition coating composition.

[0002]

2. Description of the Related Art Electrodeposition paints are required to have high performance, since they can form a coating film having excellent throwing power and excellent performance such as durability and corrosion resistance. It is widely used in application fields, for example, painting of automobile bodies, painting of electric appliances, and the like.

[0003] In order to further improve the corrosion resistance of the electrodeposition paint, a rust inhibitor such as a lead compound or a chromium compound has been blended, but these are very harmful, and their use is considered as a measure against pollution. Had a problem. Therefore, various studies have been made on non-toxic or low-toxic rust preventive agents that can replace these lead compounds and chromium compounds, and bismuth, zinc, and the like are known as metal species that exhibit rust preventive ability.

Accordingly, the present applicant has proposed a cationic electrodeposition coating material containing a bismuth compound (for example, see Japanese Patent Application Laid-Open No. HEI 5-
No. 65439). According to the electrodeposition paint, a coating film excellent in anticorrosion property and low-temperature curability can be formed, but there is a problem that the bismuth compound is not sufficiently uniformly dispersed due to insolubility in water, so that a sediment easily occurs in the paint. Was.

[0005] On the other hand, as a method using bismuth, Japanese Patent Application Laid-Open Nos. 7-506870, 9-505837, 9-502225 and 9-60046 disclose aliphatic hydroxycarboxylic acid. An electrodeposition coating material containing a bismuth salt is disclosed. In these methods, unless an aliphatic hydroxycarboxylic acid such as lactic acid is used as a neutralizing agent for the electrodeposition paint, the stability of the coating solution is poor and a sediment is generated. Also, when a large amount of the lactic acid is used, the curability of the electrodeposited coating film is lowered due to its strong acidity at the time of electrodeposition coating, and the corrosion resistance of the coating film is adversely affected.

[0006]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, by adding an aqueous solution of a specific organic acid bismuth salt to an electrodeposition paint, a uniform solution was formed in the electrodeposition bath. The present inventors have found that an electrodeposition coating film having excellent finishability and corrosion resistance can be obtained without using a lead compound or the like, and the present invention has been achieved.

That is, the present invention is an aqueous solution of a bismuth salt comprising two or more organic acids, wherein at least one of the organic acids is an aqueous solution of an organic acid bismuth salt which is an aliphatic alkoxycarboxylic acid. To provide a cationic electrodeposition coating composition.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, an aqueous solution of an organic acid bismuth salt is produced by reacting two or more organic acids with a bismuth compound in the presence of water, and at least one of the organic acids is aliphatic. It uses an alkoxycarboxylic acid.

The aliphatic alkoxycarboxylic acid used for producing the organic acid bismuth salt aqueous solution is, for example, one having a total carbon number of 16 or less, preferably 8 or less, and particularly an aliphatic hydrocarbon group (divalent). Is preferably a compound having 6 or less carbon atoms and having a methoxy group or an ethoxy group as an alkoxy group, and specific examples include methoxyacetic acid, ethoxyacetic acid, and 3-methoxypropionic acid. Of these, methoxyacetic acid is particularly preferred. These may be used alone or in combination of two or more. The proportion of the aliphatic alkoxycarboxylic acid used in the organic acid component is 50 to 99 mol% of 100 mol% of the whole acid,
Preferably 66 to 98 mol%, more preferably 70 to 98 mol%.
Preferably it is in the range of 97 mol%. If the use ratio is less than 50 mol%, it becomes difficult to synthesize a water-soluble bismuth salt, which is not desirable.

The organic acid other than the above-mentioned aliphatic alkoxycarboxylic acid can be used without particular limitation as long as it does not prevent the bismuth salt from being water-soluble, and aliphatic carboxylic acids having 6 or less, preferably 5 or less carbon atoms are suitable. Can be used for Examples of the aliphatic carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, succinic acid, adipic acid, and glutaric acid, and formic acid, acetic acid, and propionic acid are particularly preferable.
These may be used alone or in combination of two or more.

Examples of the bismuth compound used for producing the above-mentioned organic acid bismuth salt aqueous solution include bismuth oxide, bismuth hydroxide, and basic bismuth carbonate, with bismuth oxide being particularly preferred. The aqueous solution of bismuth organic acid salt is obtained, for example, by reacting 1 to 8 mol of bismuth oxide with 3 to 8 mol, preferably 3.4 to 7 mol of organic acid in the presence of water. When the amount of the organic acid is less than 3 moles, it is difficult to make the bismuth salt water-soluble, and when the amount exceeds 8 moles, an excessive amount of acid enters the electrodeposition bath and electrodeposition coating property is undesirably reduced. Similarly, when bismuth hydroxide is used, 1.5 to 4 moles, preferably 1.7 to 4 moles of an organic acid is added to 1 mole of the same.
It can be obtained by reacting 3.5 mol. When the organic acid bismuth salt aqueous solution is added to the electrodeposition coating composition,
It may be added before the aqueous dispersion of the electrodeposition coating composition or after the aqueous dispersion of the electrodeposition coating composition. The solid concentration of the organic acid bismuth salt aqueous solution is not particularly limited when it is added before the aqueous dispersion of the electrodeposition coating composition, but when it is added after the aqueous dispersion of the electrodeposition coating composition, the organic acid bismuth salt aqueous solution is added. Is desirably 60% by weight or less. Such an operation is necessary for uniformly dispersing the aqueous solution of the organic acid bismuth salt in the electrodeposition coating composition. In addition, from the viewpoint of easiness of formulation of the paint and storage stability, it is preferable to add an aqueous solution of an organic acid bismuth salt after dispersing the electrodeposition paint composition in water.

The amount of the organic acid bismuth salt aqueous solution to be added is not strictly specified, and can be varied over a wide range according to the performance required for the electrodeposition paint. It is suitable that the bismuth content is from 0.01 to 10 parts by weight, preferably from 0.05 to 5 parts by weight, based on 100 parts by weight of the resin solids.
When the bismuth content is less than 0.01 parts by weight, the rust-preventive property of the formed coating film is not sufficient, and when it exceeds 10 parts by weight,
The stability of the electrodeposition paint tends to decrease. The electrodeposition coating composition to which the organic acid bismuth salt aqueous solution is added is a cationic type, and as the base resin, any resin such as an epoxy-based, acrylic-based, polybutadiene-based, alkyd-based, or polyester-based resin may be used. Among them, a polyamine resin represented by, for example, an amine-added epoxy resin is preferable.

Examples of the amine-added epoxy resin include (i) adducts of polyepoxy compounds with primary mono- and polyamines, secondary mono- and polyamines, or mixed primary and secondary polyamines (for example, US Pat. 3,984
(Ii) an adduct of a polyepoxide compound with a secondary mono- and polyamine having a ketiminated primary amino group (see, for example, US Pat. No. 4,011).
(Iii) a reaction product obtained by etherification of a polyepoxide compound with a ketiminated hydroxy compound having a primary amino group (see, for example, JP-A-59-43013). ) And the like.

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 epoxy groups.
0, preferably 400-4000, more preferably 80
Those having a number average molecular weight in the range of 0 to 2,000 are suitable, and those obtained by the reaction of a polyphenol compound with epichlorohydrin are particularly preferable. Polypheno which can be used for forming the polyepoxide compound
For example, bis (4-hydroxyphenyl) -2,2-propane, 4,4-dihydroxybenzophenone, 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, tetra (4-hydroxyphenyl)-
Examples thereof include 1,1,2,2-ethane, 4,4-dihydroxydiphenyl sulfone, phenol novolak, and cresol novolak.

The polyepoxide compound is a polyol,
It may be partially reacted with polyether polyol, polyester polyol, polyamidoamine, polycarboxylic acid, polyisocyanate compound, or the like, and further, graft polymerization of ε-caprolactone, acrylic monomer, or the like. It may be made to be.

The above-mentioned base resin may be any of an external cross-linking type and an internal (or self) cross-linking type. ) Can be a conventionally known crosslinking agent such as a polyisocyanate compound or an amino resin,
Particularly, a block polyisocyanate compound is preferable. In addition, as the internally crosslinked type resin, a resin into which a block polyisocyanate type is introduced is preferable.

The block polyisocyanate compound which can be used in the above externally crosslinked type can be an addition reaction product of a stoichiometric amount of a polyisocyanate compound and an isocyanate blocking agent. Examples of the polyisocyanate compound include tolylene diisocyanate, xylylene diisocyanate, and phenylenedi isocyanate.
Aromatic, alicyclic or aliphatic such as bis (isocyanatemethyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, isophorone diisocyanate Polyisocyanate compounds and ethylene glycol, propylene glycol, trimethylolpropane, hexanetriol, in excess of these isocyanate compounds.
Examples thereof include a terminal isocyanate-containing compound obtained by reacting a low-molecular-weight active hydrogen-containing compound such as castor oil.

On the other hand, the isocyanate blocking agent is one which blocks by adding to the isocyanate group of the polyisocyanate compound, and the block polyisocyanate compound formed by the addition is stable at room temperature and about 100%. When heated to 200 ° C., it is desirable that the blocking agent be dissociated to regenerate a free isocyanate group. Blocking agents satisfying such requirements include, for example, lactam compounds such as ε-caprolactam and γ-butyrolactam; oxime compounds such as methylethylketoxime and cyclohexanone oxime; phenol, para-t-butylphenol, and cresol. Phenolic compounds such as n-butanol;
Aliphatic alcohols such as ethylhexanol; aromatic alkyl alcohols such as phenylcarbinol and methylphenylcarbonol; ether alcohol compounds such as ethylene glycol monobutyl ether; Can be mentioned. Of these, oxime-based and lactam-based blocking agents are dissociable at relatively low temperatures, and are particularly suitable from the viewpoint of curability of the electrodeposition coating composition.

The method for introducing a block isocyanate group into the base resin in the self-crosslinking type having a block isocyanate group in the base resin molecule may be a conventionally known method. It can be introduced by reacting a free isocyanate group in the partially blocked polyisocyanate compound with an active hydrogen-containing portion in the base resin.

In the case of a cationic resin, the resin is usually neutralized and made water-soluble by neutralizing the resin with an aliphatic carboxylic acid, particularly a water-soluble organic acid such as acetic acid and / or formic acid. This is performed by dispersing in water. At that time, part or all of the organic acid bismuth salt aqueous solution can be used for neutralization. It is preferable to use acetic acid and / or formic acid as the neutralizing agent because they are excellent in finishing properties, throwing power, and low-temperature curability.

The electrodeposition coating composition of the present invention may further contain a tin compound. Examples of the tin compound include organic tin oxides such as dibutyltin oxide and dioctyltin oxide; dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dioctyltin benzoateoxy, and dibutyltin benzoate. Tooxy, dioctyltin dibenzoate, aliphatic or aromatic carboxylate salts of dialkyltin such as dibutyltin dibenzoate, etc. It is suitable. The content of the tin compound in the electrodeposition coating composition is not strictly defined, and can be varied over a wide range according to the performance required for the electrodeposition coating. It is preferable that the tin content per 100 parts by weight of the resin solid content is in the range of 0 to 8 parts by weight, preferably 0.05 to 5 parts by weight.

The electrodeposition coating composition of the present invention can further contain a zinc compound. As the zinc compound,
Examples include zinc phosphate, zinc formate, zinc acetate, zinc molybdate, zinc oxide, zinc phosphomolybdate, and the like. The content of the zinc compound in the electrodeposition coating composition is not strictly defined, and can be varied over a wide range according to the performance and the like required for the electrodeposition coating composition. The zinc content per 100 parts by weight of the resin solid content is 0 to 8 parts by weight, preferably 0.05 to
It is preferred that the amount be within the range of 5 parts by weight.

The electrodeposition coating composition of the present invention may further contain, if necessary, coating additives such as a coloring pigment, an extender pigment, an organic solvent, a pigment dispersant, and a coating surface adjusting agent.

The electrodeposition coating composition of the present invention can be applied to a desired substrate surface by electrodeposition coating. In general, the electrodeposition coating is diluted with deionized water or the like so that the solid concentration becomes about 5 to 40% by weight, and the pH is further adjusted to 5.0 to 5.0% by weight.
The electrodeposition bath comprising the electrodeposition coating composition of the present invention adjusted to a range of 9.0 can be usually adjusted to a bath temperature of 15 to 35 ° C. and a load voltage of 100 to 400 V.

The thickness of an electrodeposition coating film that can be formed using the electrodeposition coating composition of the present invention is not particularly limited,
Generally, it is preferably in the range of 10 to 40 μm based on the cured coating film. Further, the baking and curing temperature of the coating film is generally suitable in the range of 100 to 200 ° C.

[0026]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited by this. “Parts” and “%” are “parts by weight” and “% by weight”
Is shown.

Preparation of clear emulsion for cationic electrodeposition
Formed "Epon 1004" (Note 1) 1900 parts were dissolved in 1012 parts of butyl cellosolve, diethylamine 124 parts of a 8
After dropping at 0 to 100 ° C, the mixture was kept at 120 ° C for 2 hours to obtain an epoxy resin-amine adduct having an amine value of 47.

Next, 1000 parts of a dimer acid type polyamide resin having an amine value of 100 (trade name: "Vasamide 460", a product of Henkel Hakusui Co., Ltd.) is dissolved in 429 parts of methyl isobutyl ketone, and the solution is heated to 130 to 150 ° C. The resulting water was distilled off to convert the terminal amino group of the amide resin to ketimine. This was kept at 150 ° C. for about 3 hours, and cooled to 60 ° C. after the distillation of water was stopped. Next, this was added to the above-mentioned epoxy resin-amine adduct, heated to 100 ° C., kept for 1 hour and cooled to room temperature to obtain a varnish of an epoxy resin-amino-polyamide addition resin having a solid content of 68% and an amine value of 65. Obtained.

103 parts of the varnish obtained above (70 parts in solid content of resin), 30 parts of 2-ethylhexyl alcohol blocked product of tolylene diisocyanate (solid content), 10 parts
% Acetic acid was mixed and uniformly stirred, and 150 parts of deionized water was added dropwise over about 15 minutes with vigorous stirring to obtain a cationic electrodeposition clear emulsion having a solid content of 33.6%.

(Note 1) "Epon 1004": Bisphenol A type epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd. Production of bismuth salt of organic acid bismuth salt having an epoxy equivalent of about 950 Production Example 1 180 g of methoxyacetic acid (methoxyacetic acid) was placed in a flask. 2 mol), 60 g (1 mol) of acetic acid, and 6 parts of deionized water.
42 g were charged and heated to 60 ° C. Then, 233 g (0.5 mol) of bismuth oxide was slowly added thereto, and
The mixture was stirred and reacted at 0 ° C. for 4 hours. After confirming that the reaction solution had no yellow solid and became transparent, 3345 g of deionized water was added to obtain an aqueous solution of methoxyacetic acid / bismuth acetate having a solid content of 10%.

Production Example 2 A flask was charged with 225 g of methoxyacetic acid (2.5 mol as methoxyacetic acid), 30 g (0.5 mol) of acetic acid, and 665 g of deionized water, and heated to 60 ° C. Next, 233 g (0.5 mol) of bismuth oxide was slowly added thereto, and the mixture was stirred and reacted at 60 ° C. for 4 hours. After confirming that the yellow solid matter disappeared in the reaction solution and it became transparent,
3461 g of deionized water was added to obtain an aqueous solution of methoxyacetic acid / bismuth acetate having a solid content of 10%.

Production Example 3 A flask was charged with 270 g of methoxyacetic acid (3 mol as methoxyacetic acid), 60 g (1 mol) of acetic acid, and 5 ml of deionized water.
71 g was charged and heated to 60 ° C. Then, 233 g (0.5 mol) of bismuth oxide was slowly added thereto, and
The mixture was stirred and reacted at 0 ° C. for 3 hours. After confirming that the reaction solution had no yellow solid and became transparent, 3401 g of deionized water was added to obtain an aqueous solution of methoxyacetic acid / bismuth acetate having a solid content of 10%.

Production Example 4 312 g of 3-methoxypropionic acid (3-
3 mol of methoxypropionic acid), 60 g of acetic acid (1
Mol), and 608 g of deionized water, and heated to 70 ° C. Next, 233 g of bismuth oxide (0.5 g
Mol) was added slowly, and the mixture was stirred and reacted at 70 ° C. for 4 hours. After confirming that the reaction solution had no yellow solid and became transparent, 3638 g of deionized water was added to obtain an aqueous solution of 3-methoxypropionic acid / bismuth acetate having a solid content of 10%.

Examples and Comparative Examples To the above cationic electrodeposition clear emulsion, an aqueous solution of an organic acid bismuth salt or the like having the composition shown in Table 1 was added and stirred to obtain each cationic electrodeposition paint.

(Note 2) 40% LSN 105: trade name, manufactured by Sankyoki Gosei Co., Ltd., 40% solution of dibutyltin dibenzoate in butyl cellosolve / methyl isobutyl ketone

[0036]

[Table 1]

Coating test In each of the cationic electrodeposition coatings obtained in the above Examples and Comparative Examples,
0.8x150x70mm cold rolled dull steel sheet (untreated sheet) without chemical conversion treatment and Palbond # 3080 (Nippon Part
Cold-rolled dull steel plates (chemical conversion plates) of the same size that had been chemically treated with
This was used as a cathode for electrodeposition coating. The electrodeposition conditions were a voltage of 300 V, a film thickness (based on a dry film thickness) of about 20 μm.
After forming an electrodeposited coating film having a thickness of m and washing with water, baking was performed. The baking was performed using an electric hot air drier with an atmosphere temperature of two stages and a baking time of 20 minutes. Table 2 shows the performance test results of the obtained coated plates.

The performance test was performed according to the following method.

(* 1) Curability: The coated surface of each electrodeposition coated plate obtained at a baking temperature of 150 ° C. was applied with four layers of gauze impregnated with methyl isobutyl ketone at a pressure of about 4 kg / cm ² . The coating surface appearance was visually evaluated when the length of about 3 to 4 cm was rubbed 20 reciprocations by the following criteria. ：: No scratches are found on the painted surface. 傷: Scratches are found on the coated surface, but the substrate is not visible. X: The coating film is dissolved and the substrate is visible. (* 2) Corrosion resistance: each obtained at a baking temperature of 170 ° C. A cross-cut wound was made on the electrodeposition coated plate with a knife so as to reach the substrate, and this was cut for 480 hours using an untreated plate and 840 hours using a chemical conversion plate according to JIS Z-2371.
A time salt spray test was performed, and rust from knife scratches and blister width were evaluated according to the following criteria.

○: The maximum width of rust and blisters is less than 2 mm from the cut part (one side) △: The maximum width of rust and blisters is 2 mm or more from the cut part 3
mm (one side) and blisters are significantly conspicuous on the flat part. ×: The maximum width of rust and blisters is 3 mm or more from the cut part, and blisters are observed on the entire coated surface.

[0041]

According to the present invention, a specific organic acid bismuth salt aqueous solution is contained in an electrodeposition coating composition, so that a rust preventive pigment such as a lead compound which is problematic in pollution control can be used. An electrodeposition coating film having excellent or superior anticorrosion properties and finish properties equal to or higher than the case where this is blended is obtained.

[0042]

[Table 2]

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tadayoshi Hiraki 4-171-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Prefecture Inside Kansai Paint Co., Ltd. (72) Akira Tominaga 4-171-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Seki Nishi Paint Co., Ltd.

Claims (9)

[Claims] 1. An aqueous solution of a bismuth salt comprising two or more organic acids, wherein at least one of the organic acids is an aqueous solution of an organic acid bismuth salt which is an aliphatic alkoxycarboxylic acid. Coating composition. 2. The use ratio of the aliphatic alkoxycarboxylic acid in the organic acid component is 50 to 99 mol%.
The cationic electrodeposition coating composition according to the above. 3. The cationic electrodeposition coating composition according to claim 1, wherein the aliphatic alkoxycarboxylic acid has a total carbon number of 16 or less. 4. The cationic electrodeposition coating composition according to claim 1, wherein the alkoxy group of the aliphatic alkoxycarboxylic acid is a methoxy group or an ethoxy group. 5. The cationic electrodeposition coating composition according to claim 1, wherein the aliphatic alkoxycarboxylic acid is methoxyacetic acid. 6. The cationic electrodeposition coating composition according to claim 1, wherein an aliphatic alkoxycarboxylic acid and an aliphatic carboxylic acid having 6 or less carbon atoms are used as the organic acid component. 7. The method according to claim 1, wherein the aqueous solution of the organic acid bismuth salt is blended so that the bismuth content is 0.01 to 10 parts by weight based on 100 parts by weight of the resin solids in the electrodeposition paint. Item 8. The cationic electrodeposition coating composition according to item 1. 8. The cationic electrodeposition coating composition according to claim 1, wherein acetic acid and / or formic acid is used as a neutralizing agent in the cationic electrodeposition coating composition. 9. The cationic electrodeposition coating composition according to claim 1, further comprising a tin compound.