JPS6318633B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a cathode-deposited electrodeposition paint that contains a lead-based rust-preventive pigment and that prevents anode contamination and has good bath stability. In recent years, cathodic deposition type electrodeposition paints have begun to be used in large numbers as paints for automobile bodies, automobile parts, building materials, etc. because they have superior corrosion resistance compared to the conventionally used anodic deposition type electrodeposition paints. Cathode deposition type electrodeposition coating compositions have excellent corrosion resistance such as epoxy resin, acrylic resin, urethane resin, or polyamine having a main skeleton of polybutadiene resin as the vehicle component (resin component), and are usually neutralized with an organic acid and dissolved in water. It is used after being dissolved or dispersed in water. Cathode deposition type electrodeposition paint compositions have fairly good corrosion resistance of the resin itself, but in recent years, the required performance for corrosion resistance has become even higher. It has become common practice for rust pigments to be added. Lead-based rust-preventing pigments are mainly composed of lead oxide and lead silicate, but they also contain some water-soluble compounds, which are converted into lead-based rust-preventing pigments through an electrolytic reaction when DC voltage is applied. It is often found that certain compounds associated with this problem are deposited on the anode, contaminating the anode or impairing the stability of the bath. When such a phenomenon occurs, the electrical resistance of the anode increases, which not only causes disadvantages such as a higher voltage required for painting and an increased amount of electricity required for painting, but also makes it difficult to improve corrosion resistance. However, there are disadvantages such as reducing the amount of active ingredients in the lead-based pigment required for the process and further deteriorating the stability of the electrodeposition solution. As a result of various studies to solve the above problems, the inventors found that the general formula

By adding 0.01 to 5 parts by weight of a compound represented by the formula (where R represents a hydrogen atom, a hydroxyl group, or an organic residue having 1 to 10 carbon atoms) to 100 parts by weight of the resin component, other The inventors have discovered that the above drawbacks can be greatly improved without deteriorating performance, and have arrived at the present invention. That is, the present invention comprises (A) 100 parts by weight of a resin component neutralized with an acid to make it water-soluble or water-dispersible, (B) 1 to 100 parts by weight of a rust-preventing pigment containing lead, and (C) represented by the following formula. 0.01 to 5 parts by weight of compound

The present invention relates to a cathodically deposited electrodeposition coating composition containing as an essential component the formula: (wherein R represents a hydrogen atom, a hydroxyl group, or an organic residue having 1 to 10 carbon atoms) The resin component of the cathodically deposited electrodeposition coating composition in the present invention is usually a basic resin neutralized with an organic or inorganic acid, such as an epoxy resin, an acrylic resin, or a urethane resin into which an amine group has been introduced. , polybutadiene resin, etc. These resin components generally have 1 in the organic main chain.
or more amine groups, and has the following formula: (Here, R ₁ and R ₂ are hydrogen or usually have 1 to 1 carbon atoms.
20 organic residues, P indicates the main chain portion, and n is a natural number. ) are typical, and these are neutralized with organic or inorganic acids and are generally expressed by the following formula: (Here, R ₃ represents hydrogen or an organic residue usually having 1 to 20 carbon atoms.) It produces an ion represented by the following formula and is water-soluble or water-dispersible. In this case, in the epoxy resin, etc.,
It is also possible to simultaneously introduce an amine group and neutralize with an acid, thereby producing a quaternary ammonium ion represented by the above formula and making it water-soluble or water-dispersible. When this is used as an electrodeposition paint, ions of the resin component mainly migrate electrophoretically and deposit on the cathode. The acids used include organic acids such as acetic acid, hydroxyl acetic acid, propionic acid, butyric acid, and lactic acid, and inorganic acids such as phosphoric acid and hydrochloric acid. As the halogenated hydrocarbon, methyl chloride, ethyl chloride, etc. are used. This water solubilization or water dispersion usually produces an aqueous solution or dispersion containing 5 to 20 wt% of the resin component. Many of these resin components themselves are already known; for example, one in which the main chain portion is composed of a butadiene-based polymer has already been disclosed by the applicant (Japanese Patent Laid-Open No. 119727/1983).
JP-A-52-147638, JP-A-53-16048, JP-A-53-117030, JP-A-53-132510, JP-A-53
-No. 133772, Patent Application No. 1983-69931, Patent Application No. 1972-
No. 117857). In addition, it has already been revealed that the main chain portion is epoxy resin (Special Publication No. 49-
No. 23807, JP-A-46-41592, JP-A-48-51924
No., JP-A-49-53630, JP-A-51-103135). It has also been clarified that the main chain portion is acrylic resin or urethane resin (Special Publication No. 12395-1970, Publication No. 12396-1973, Publication No. 12396-1973, Special Publication No.
No. 37147, Special Publication No. 50-24982, Special Publication No. 51-2491
No., Japanese Patent Publication No. 48-101431). In these resin components, it has been revealed that isocyanate-based compounds are introduced or added to the skeleton resin for the purpose of curing the coating film or increasing the crosslinking density (Japanese Patent Laid-Open No. 51924-1989). , JP-A-53-2578, JP-A-54-28338, JP-A-54-
No. 144434), resin components using these so-called block isocyanates can also be used in the present invention. The lead-containing rust preventive pigment used in the present invention includes lead oxides or lead salts of metal oxino acids such as silicon, chromium, and molybdenum, which are commonly used as rust preventive pigments in paints, such as PbO,
These include lead silicate, basic lead silicochromate, basic lead chromate, lead silicomolybdate, etc. whose main ingredients are PbSiO ₂ etc. These amounts range from 1 to 100 parts by weight of the resin component.
100 parts by weight, preferably 2 to 20 parts by weight. As mentioned above, the coating composition itself which essentially contains two components, the resin component and the lead-containing anticorrosion pigment, is known. The present invention further provides a general formula for 100 parts by weight of the resin component.

A major feature is that it contains 0.01 to 5 parts by weight, preferably 0.1 to 1.0 parts by weight, of a compound represented by the formula (R is the same as above). If the amount is less than 0.01 part by weight, no effect can be expected, whereas if it is more than 5 parts by weight, there will be disadvantages such as impairing the smoothness of the coated surface and reducing curability. Representative examples of these compounds referred to in the present invention include hydroquinone, catechol, resorcinol, methylhydroquinone, and tert-butylcatechol. These compounds can be added at any stage before or after the water solubilization or water dispersion of the resin. 0.01 to 5 per 100g of resin component in the electrodeposition bath
If it is present in an amount of 0.1 to 1.0 parts by weight, it will exhibit effects such as preventing anodic precipitation of metal compounds and improving bath stability. In addition to the above-mentioned three necessary components, the electrodeposition coating composition of the present invention may contain a hydrophilic solvent, a surfactant, a curing agent, a colored pigment, and the like. Hydrophilic solvents include ethanol, n-propanol, isopropanol, n-butanol,
Alcohol solvents such as sec-butanol, tert-bratanol, isobutanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether Glycol ether solvents such as methyl acetate, ethyl acetate, isopropyl acetate, methyl acetoacetate, ethyl acetoacetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl acetate , ester solvents such as acetic acid diethylene glycol monobutyl ether are used. These amounts are usually resin components
It can be contained in an amount of 5 to 50 parts by weight per 100 parts by weight. Note that it is advantageous to use this hydrophilic activator when making the above-described resin water-soluble by dissolving the resin in advance in this solvent and then making it water-soluble. In addition, as the surfactant, nonionic and/or cationic surfactants are preferred, and nonionic surfactants include polyethylene glycol alkyl ester, polyethylene glycol alkyl ether, polyethylene glycol alkyl phenyl ether, and polyethylene glycol alkyl amide. Polyethylene glycol compounds such as sorbitan aliphatic ester, polyhydric alcohol partial ester compounds such as sorbitan aliphatic ester, etc. are used.
As the cationic surfactant, long-chain aliphatic amine salts and quaternary ammonium salts are used. As described above, conventionally known cathodically deposited electrodeposition coating compositions can be used for the present invention. The amount used is usually 0.01 to 5 parts by weight per 100 parts by weight of resin component. In addition, blocked isocyanate is often included in cathodically deposited electrodeposited paint compositions as a curing agent for cathodically deposited electrodeposited paints, but metal compounds such as tin are sometimes added as decomposers for the blocked isocyanate to promote low-temperature curing. is commonly done. Furthermore, metal compounds such as cobalt salts and manganese salts are often added to oxidative polymerization-curing cathodic deposition type electrodeposition paints such as those based on polybutadiene to promote curing. In the present invention, such a curing agent can be contained generally in an amount of 0.01 to 5 parts by weight per 100 parts of the resin component. Examples of pigments include coloring pigments such as carbon black, titanium white, red iron oxide, and other extender pigments. For example, cathodically deposited electrodeposition paints are used as an undercoat, so they are available in black, gray, or brown colors. In the case of black, 1 to 5 parts by weight of carbon black is added to 100 parts by weight of resin, and an extender pigment is added. 3 to 10 parts by weight can be added. In the case of gray color, titanium white is added to black. The present invention will be further explained below with reference to Examples and Comparative Examples. Example 1 Bisphenol A with an epoxy equivalent weight of about 500
500 parts of type epoxy resin (trade name: Epicote 1001, a product of Ciel Chemical Co., Ltd.) was heated and dissolved in 200 parts of ethyl cellosolve acetate, and 105 parts of diethanolamine was added at 80°C and reacted at 100°C for 2 hours to obtain an amine value of 90. An amine-added epoxy resin is obtained. Next, tolylene diisocyanate (2,4-
90 parts of ethyl cellosolve was added dropwise to 174 parts (TDI = 80%, 2.6-TDI = 20%) at 60°C over 2 hours, and 264 parts of the obtained blocked isocyanate compound was added to the above amine by reacting for another 2 hours. Add to epoxy resin and react at 80℃ for 15 hours to obtain amine value.
52, a basic resin composition (A) having a solid content of 81% was obtained. 5 parts of dibutyltin dilaurylate was added to this mixture to form a homogeneous solution. Next, 30 parts of polyethylene glycol having a number average molecular weight of 1000 and 100 parts of acetic acid were added to 372 parts of this solution for neutralization, and then 691 parts of deionized water was added to obtain a composition (A') having a solid content of 30%. Per 100 parts by weight of the solid content of this composition (A'), 10 parts by weight of lead silicomolybdate (PbO・SiO ₂・MoO ₃ ) and 2 parts by weight of carbon black were blended, and then 0.2 parts of hydroquinone and deionized water were added. was added to prepare an electrodeposition paint liquid (A'') with a solid content of 15%. This electrodeposition paint liquid (A'') was placed in two stainless steel beakers, and the stainless steel beaker was used as an anode. A DC voltage of 150 V was applied for 3 minutes at 30° C. using Bonderite #3114 treated plate, a product of the company, as a cathode. After removing the painted board from the electrodepositing solution and washing it with water,
When baked at ℃ for 30 minutes, a smooth coating surface was obtained, and this product had excellent corrosion resistance. When the inner surface of the stainless steel beaker 2 used as the anode was examined, no deposits were found at all. Comparative Example 1 An electrodeposition paint was prepared in exactly the same manner as in Example 1, except that hydroquinone was not added, and electrodeposition coating was performed in the same manner. When the inner surface of the stainless steel beaker 2 used as the anode was examined, reddish-brown deposits were found on the entire surface where the electrodeposition solution was applied. As is clear from the comparison between Example 1 and Comparative Example 1, it is clear that the anode is significantly contaminated when hydroquinone is not added. Example 2 Polybutadiene with a number average molecular weight of 2000 (Nippon Petrochemical Co., Ltd., Nisseki Polybutadiene B-2000)
was maleated to create maleated polybutadiene with an acid value of 80. 1000 parts by weight of this maleated polybutadiene and 200 g of ethyl cellosolve were charged into a 3-separable flask equipped with a dropping funnel and a distillation device and heated to 150°C.
N,N-dimethylaminopropylamine by heating to
Add 95.4 parts by weight from the dropping funnel over 15 minutes while distilling off the produced water, then add monoethanolamine.
Add 28.5 parts by weight from the dropping funnel over 15 minutes, then distill off the produced water and ethyl cellosolve.
The reaction was continued at 150° C. for 5 hours to obtain a resin solution (B) with a solid content concentration of 87%, an acid value of 0.4, and an amine value of 43. Next, 100 g of bisphenol type epoxy resin (Epicoat #1001, manufactured by Ciel Chemical Co., Ltd.) and acrylic acid.
15g, N,N-dimethylethanolamine 0.5g,
23 g of ethyl cellosolve was placed in a 200 ml separable flask and reacted at 100° C. for 5 hours with vigorous stirring to synthesize a solution (C) of acrylic acid-modified epoxy resin. The acid value of this product was 0.8. After thoroughly mixing 460 g of resin solution (B), 90 g of acrylic acid-modified epoxy resin solution (C), and 26 g of ethyl cellosolve, 10.6 g of acetic acid was added for neutralization, and deionized water was added little by little until the solid content was 25%. Aqueous dispersion (B′)
I got it. After blending 5 g of lead silicate (PbO/nPbSiO ₂ ) and 1 g of carbon black per 100 g of solid content in the aqueous dispersion (B'), 1 g of manganese acetate, 1.0 g of ter-butylcatechol, and deionized water were added to form a solid. A 20% electrodeposition paint solution (B'') was prepared.The electrodeposition paint solution (B') was put into two stainless steel beakers, and the stainless steel beaker was used as an anode. 3114 treated plate) as a cathode,
A DC voltage of 180 V was applied for 3 minutes at 30°C. Remove the painted plate from the electrodepositing solution, wash it with water, and then heat it at 180℃ for 30 minutes.
After baking for a few minutes, a glossy and smooth coating surface was obtained, and the corrosion resistance of this coating film (20 μm) was very good. When the inner surface of the stainless steel beaker 2 used as the anode was examined, no deposits were found at all. A stability test was conducted by applying electrodeposition coating 10 times under the above coating conditions on two sheets every 3 days, but no changes were observed in the film thickness or surface condition, and the storage stability was excellent. . Furthermore, no deposits were observed on the anode stainless steel beaker after 20 electrodeposition coatings. Comparative Example 2 An electrodeposition coating liquid that was exactly the same as in Example 2 was prepared except that ter-butylcatechol was not added, and
I did the same test. The smoothness of the coated surface deteriorated after the fifth coating (after 15 days), and by the tenth coat (after 30 days), only a coating film with a significantly poor coating surface was obtained. In addition, red and colored deposits were observed all over the stainless steel anode even after one coat of paint, and the number of deposits increased with each coat of paint. After the 10th painting (after 30 days), the electrodeposition paint was taken out, the stainless steel beaker was thoroughly washed with water, dried, and a fluorescent X-ray analysis of the deposits was performed, and large amounts of lead and manganese were detected. , iron, cobalt, and nickel were not detected. Example 3 Polybutadiene with a number average molecular weight of 2000 (Nippon Petrochemical Co., Ltd., Nisseki Polybutadiene B-2000)
was epoxidized using peracetic acid to synthesize epoxidized polybutadiene with an oxirane oxygen content of 6.0%. 1000 g of this epoxidized polybutadiene, 300 g of ethyl cellosolve, and 46 g of dimethylamine were charged into two autoclaves and reacted at 150° C. for 5 hours.
Next, after removing the pressure and evaporating unreacted dimethylamine, 10 g of hydroquinone and 72 g of acrylic acid were charged and reacted at 150°C for 1 hour, resulting in a solution of modified polybutadiene having amino groups and acrylic acid ester groups.
(D) was synthesized. This product had a solid content concentration of 79%, an acid value of 0.5, and an amine value of 39.5. Next, 380g of the modified polybutadiene solution (D) and the acrylic acid-modified epoxy resin solution used in Example 2.
After mixing 50 g of (C) well, add 8 g of acetic acid to neutralize it, and then add deionized water little by little to achieve a solid content concentration of 22%.
An aqueous dispersion (D') was prepared. Per 100 g of solid content in the aqueous dispersion (D'), 5 g of lead silicomolybdate (PbO・SiO ₂・MoO ₃ ) and 1 g of carbon black were added, and then 1 g of manganese acetate was added to deionized water to give a solid content of 20%. Paint liquid (D″)
was prepared. Electrodeposition paint solution (D'') was placed in two stainless steel beakers, and a DC voltage of 220V was applied for 3 minutes at 30℃ using the stainless steel beaker as an anode and an untreated steel plate (dull mild steel plate) as a cathode.The coated plate was electrodeposited. After removing from the liquid and washing with water, 170
After baking at ℃ for 30 minutes, a glossy and smooth coating surface was obtained, and this coating film (20μ) had excellent corrosion resistance. When the inner surface of the stainless steel beaker 2 used as the anode was examined, no deposits were found at all. Comparative Example 3 A test was conducted under exactly the same conditions as in Example 3, except that hydroquinone was not added during resin synthesis. When the inner surface of the stainless steel beaker used as an anode was examined, black and colored deposits were found all over the area covered with the electrodepositing solution.

Claims (1)

[Scope of Claims] 1 (A) 100 parts by weight of a resin component neutralized with acid to make it water-soluble or water-dispersible, (B) 1 to 100 parts by weight of a rust preventive pigment containing lead, and (C) the following formula A cathode-deposited type characterized by containing as an essential component 0.01 to 5 parts by weight of a compound represented by [Formula] (where R represents a hydrogen atom, a hydroxyl group, or an organic residue having 1 to 10 carbon atoms) Electrodeposition paint composition. 2. The composition according to claim 1, wherein component (C) is selected from hydroquinone, catechol, resorcinol, methylhydroquinone and tert-butylcatechol.