JPH1180622A - Cationic electrocoating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cationic electrocoating compsn. which can improve the anticorrosive and finishing properties without use of any anticorrosive pigment, such as a lead compd. by adding an aq. soln. of a bismuth salt of an org. acid contg. an aliph. hydroxycarboxylic acid to a cationic electrocoating. SOLUTION: An org. acid comprising 20 to 99 mol.%, pref. 30 to 95 mol.%, still pref. 40 to 90 mol.%, 10C or higher aliph. hydroxycarboxylic acid and a 6C or lower, pref. 5C or lower, aliph. carboxylic acid is reacted in an amt. of 3 to 8 mol, pref. 3.4 to 7 mol, with 1 mol bismuth oxide in the presence of water to obtain an aq. soln. of a bismuth salt of two or more org. acids. To 100 pts.wt. on a resin solid content basis of a cationic electrocoating are added the aq. soln. of a bismuth salt of an org. acid and optionally acetic acid and/or formic acid as a neutralizing agent and 0 to 8 pts.wt., pref. 0.05 to 5 pts.wt., arom. carboxylate of a dialkyltin so that the bismuth content of the compsn. is 0.01 to 10 pts.wt., pref. 0.05 to 5 pts.wt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrodeposition coating composition, and more particularly, to a lead-free electrodeposition coating composition capable of forming an electrodeposition coating film having excellent anticorrosion properties and finish even without a lead compound. About things.

[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, it is possible to form a coating film having excellent anticorrosion properties and low-temperature curability, but there is a problem that the bismuth compound is insoluble in water and is not sufficiently uniformly dispersed, so that sediment is easily generated in the paint. there were.

[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 with 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 hydroxycarboxylic acid. An electrodeposition coating composition is provided.

[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, and at least one of the organic acids is prepared by using an aliphatic hydroxycarboxylic acid. Become.

Examples of the aliphatic hydroxycarboxylic acid used for producing the organic acid bismuth salt aqueous solution include glycolic acid, glyceric acid, lactic acid, dimethylolpropionic acid, dimethylolbutyric acid, dimethylolvaleric acid, and the like. Tartaric acid, malic acid, hydroxymalonic acid, dihydroxysuccinic acid, trihydroxysuccinic acid, hydroxymethylmalonic acid and the like, among which monocarboxylic acids are useful, among which lactic acid, dimethylolpropionic acid, dimethylo- Rubutyric acid is preferred, and lactic acid is particularly preferred. These may be used alone or in combination of two or more. Those having a chain length of 10 or more carbon atoms are not desirable because they may hinder the water solubility of the bismuth salt.

The proportion of the aliphatic hydroxycarboxylic acid used in the organic acid component is based on 100 mol% of the total acid.
It is preferably in the range of 20 to 99 mol%, preferably 30 to 95 mol%, more preferably 40 to 90 mol%. If the use ratio is less than 20 mol%, it becomes difficult to synthesize a water-soluble bismuth salt, and if it exceeds 99 mol%, the finish of the resulting electrodeposition coating film may be undesirably reduced.

The organic acid other than the above aliphatic hydroxycarboxylic acid can be used without any particular limitation as long as it does not prevent the bismuth salt from being solubilized in water. 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 organic acid bismuth salt aqueous solution include bismuth oxide and bismuth hydroxide, 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. The organic acid is 3
If the amount is less than 8 moles, it is difficult to make the bismuth salt water-soluble, and if the amount exceeds 8 moles, an excessive amount of acid enters the electrodeposition bath, and the electrodeposition coatability is undesirably reduced. Similarly, when bismuth hydroxide is used, 1.5 to 4 organic acids are added to 1 mole of the same.
Mol, preferably 1.7 to 3.5 mol.

The above-mentioned aqueous solution of the organic acid bismuth salt may be added to the electrodeposition coating composition before the electrodeposition coating composition is dispersed in water, or may be added after the electrodeposition coating composition is dispersed in water. You may. 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 defined, 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 primary and secondary mixed 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 above 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 resin. ) 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 with 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. Examples of the blocking agent satisfying such requirements include 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 can 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 have excellent 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 may 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 modifier.

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 content concentration is about 5 to 40% by weight, and the pH is further increased to 5.5 to 5.5% 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 the electrodeposition coating film which 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.

[0028]

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 Cation Electrodeposition Clear Emulsion
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 at 130 to 150.degree. 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 epoxy resin-amine adduct, heated to 100 ° C., kept for 1 hour, cooled to room temperature, and varnished with an epoxy resin-amino-polyamide addition resin having a solid content of 68% and an amine value of 65 was obtained. Obtained.

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

In the cationic emulsion for a cationic electrodeposition a, an emulsion a was used except that 11.5 parts of 10% formic acid and 22.5 parts of 10% lactic acid were used as a neutralizing agent instead of 15 parts of 10% acetic acid. By the same operations, a clear emulsion b for cationic electrodeposition having a solid content of 34.0% and a clear emulsion c for cationic electrodeposition having a solid content of 31.3% were obtained.

(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 with an epoxy equivalent of about 950 Production Example 1 200 g of 90% lactic acid (lactic acid) 2 mol), 60 g (1 mol) of acetic acid, and 623 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 reaction solution was cleared of yellow solids and became transparent, deionized water 33 was added.
47 g were added to obtain an aqueous solution of lactic acid / bismuth acetate having a solid content of 10%.

Production Example 2 In a flask, 300 g of 90% lactic acid (3 mol as lactic acid), 60 g (1 mol) of acetic acid, and 541 g of deionized water were placed.
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 reaction solution was cleared of yellow solids and became transparent, deionized water 34
To the solution, 04 g of a lactic acid / bismuth acetate aqueous solution having a solid content of 10% was obtained.

Production Example 3 200 g of 90% lactic acid (2 mol as lactic acid), 60 g (1 mol) of acetic acid, and 595 g of deionized water were placed in a flask.
And heated to 70 ° C. Then, 260 g (1.0 mol) of bismuth hydroxide was slowly added thereto,
And reacted for 7 hours. After confirming that the reaction solution was free of white solids and became transparent, deionized water 3
404 g was added to obtain a lactic acid / bismuth acetate aqueous solution having a solid content of 10%.

Production Example 4 In a flask, 268 g (2 mol) of dimethylolpropionic acid, 60 g (1 mol) of acetic acid, and 1219 of deionized water were added.
g and heated to 70 ° C. Then, 233 g (0.5 mol) of bismuth oxide was slowly added thereto,
And reacted for 4 hours. After confirming that the reaction solution was free of yellow solids and became transparent, deionized water 3
560 g was added to obtain an aqueous solution of dimethylolpropionic acid / bismuth acetate having a solid content of 10%.

Production Example 5 A flask was charged with 200 g of 90% lactic acid (2 mol as lactic acid), 74 g (1 mol) of propionic acid, and 643 g of deionized water, and heated to 60 ° C. Next, 233 g (0.5 mol) of bismuth oxide was slowly added thereto,
The mixture was stirred and reacted at 60 ° C. for 5 hours. After confirming that the reaction solution had no yellow solid and became transparent, 3450 g of deionized water was added to obtain an aqueous solution of bismuth lactic acid / propionate having a solid content of 10%.

Examples and Comparative Examples An aqueous solution of an organic acid bismuth salt having the composition shown in Table 1 was added to the above-mentioned cationic electrodeposition clear emulsion, followed by stirring to obtain each cationic electrodeposition paint.

(Note 2) Bismuth lactate: A commercially available reagent containing 2 mol of lactic acid per 1 mol of bismuth, powder (Note 3) Bismuth acetate: 3 mol of acetic acid per 1 mol of bismuth
4 moles of commercial reagents, powder (Note 4) 40% LSN105: trade name, manufactured by Sankyoki Gosei Co., Ltd., 40% solution of dibutyltin dibenzoate in butyl cellosolve / methyl isobutyl ketone

[0040]

[Table 1]

Coating test In each of the cationic electrodeposition coatings obtained in the above Examples and Comparative Examples,
0.8 × 150 × 70 chemically treated with Palbond # 3030 (manufactured by Nippon Parkerizing Co., Ltd., zinc phosphate treating agent)
mm cold-rolled dull steel plate was immersed and used as a cathode for electrodeposition coating. Electrodeposition conditions were as follows: a voltage of 300 V, an electrodeposition coating film having a thickness of about 20 μm (based on a dry film thickness) was formed, washed with water, and baked. 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 electrodeposited plate obtained at a baking temperature of 150 ° C. was coated with methyl isobutyl ketone by four layers of gauze at a pressure of about 4 kg / cm ² for about 3 times. The appearance of the coated surface when rubbing the length of 4 cm for 20 reciprocations was visually evaluated according to 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. A cross-cut wound was made on the electrodeposited coating plate with a knife so as to reach the substrate, and this was cut into 8 pieces according to JIS Z-2371.
Perform a salt water spray test for 40 hours,
The blister width was 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 quite conspicuous on the flat part. ×: The maximum width of rust and blisters is 3 mm or more from the cut part, and blisters are generated on the entire coated surface. (* 3) Paint stability: Each paint was stirred for 48 hours, and the presence or absence of sediment after standing was observed.

：: no sedimentation △: slight sedimentation ×: remarkable sedimentation

[0046]

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.

[0047]

[Table 2]

Continuation of 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-Yawata, Hiratsuka-shi, Kanagawa Kansai Paint stock In company

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 hydroxycarboxylic acid. Coating composition. 2. The use ratio of the aliphatic hydroxycarboxylic acid in the organic acid component is 20 to 99 mol%.
The cationic electrodeposition coating composition according to the above. 3. The cationic electrodeposition coating composition according to claim 1, wherein an aliphatic hydroxycarboxylic acid and an aliphatic carboxylic acid having 6 or less carbon atoms are used as the organic acid component. 4. The cationic electrodeposition coating composition according to claim 1, wherein the aliphatic hydroxycarboxylic acid is lactic acid. 5. The cationic electrodeposition coating composition according to claim 3, wherein the aliphatic carboxylic acid having 6 or less carbon atoms is acetic acid. 6. The cationic electrodeposition coating composition according to claim 1, wherein the organic acid bismuth salt is obtained by reacting 1 to 8 mol of bismuth oxide with 3 to 8 mol of an organic acid. 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 dialkyltin aromatic carboxylate.