JPH07118598A - Water-base coating composition - Google Patents

Abstract

PURPOSE:To obtain the title composition which gives a film excellent in weatherability and corrosion resistance and is useful for cationic electrodeposition coating by using a specified fluoro-copolymer, a specified fluorine-free resin, and a curing agent as the essential constituents. CONSTITUTION:The composition contains as the essential constituents a hydroxylated fluoro-copolymer (e.g. a copolymer obtained by reacting chlorotrifluoroethylene, cyclohexyl vinyl ether, ethyl vinyl ether and omega- hydroxybutyl vinyl ether) preferably having a hydroxyl value of 10-230mgKOH/g polymer, a fluorine-free resin containing cationic groups, preferably comprising an amine-modified epoxy, acrylic or polybutadiene resin, and a curing agent (e.g. blocked isocyanate).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous coating composition which forms a coating film having excellent weather resistance and corrosion resistance.

[0002]

2. Description of the Related Art Conventionally, cationic electrodeposition paints have been used for coating metal parts such as automobile undercoats, automobile parts, and parts for low-power applications.

[0003]

These coatings are carried out for the purpose of improving the corrosion resistance, but the weather resistance is not always good, and a coating having both corrosion resistance and weather resistance has not been obtained. Therefore, it has been desired to develop a water-based paint that satisfies both weather resistance and corrosion resistance.

[0004]

A fluorine-containing copolymer having a hydroxyl group is disclosed in JP-B-55-44083 or JP-B-60-21686, and it is possible to provide a coating material having extremely excellent weather resistance. Are known. The present inventors have studied the development of a water-based coating that achieves both corrosion resistance and weather resistance, and found that the above object can be achieved by using a hydroxyl group-containing fluorocopolymer and a cationic group-containing non-fluorine-based resin in combination. It was That is, the present invention is a composition for an aqueous coating composition, which contains a fluorine-containing copolymer having a hydroxyl group, a non-fluorine-containing resin having a cationic group and a curing agent as essential components.

The fluorine-containing copolymer containing hydroxyl groups used in the present invention contains 20 to 80 mol% of polymerized units based on fluoroolefin and 20 to 80 mol% of polymerized units based on monomer containing hydroxyl group. Is preferably adopted. When the amount of the polymerized units based on fluoroolefin is less than the above proportion, the weather resistance of the weather resistant coating is not sufficiently exhibited, which is not preferable. On the other hand, if the ratio is higher than the above range, it becomes difficult to make the compound water-soluble or water-dispersible, which may make it unsuitable for water-based paints, which is not preferable. In particular, those containing 30 to 70 mol% of polymerized units based on a fluoroolefin and 30 to 70 mol% of polymerized units based on a hydroxyl group-containing monomer are preferably used.

The fluoroolefin used here is CClF.
= CF ₂ , CHCl = CF ₂ , CCl ₂ = CF ₂ , CClF = CClF, CHF = CCl ₂ , CH ₂ =
Fluoroethylenes such as CClF, CCl ₂ = CClF, CF ₂ ClCF = CF
₂ , CF ₃ CCl = CF ₂ , CF ₃ CF = CFCl, CF ₂ ClCCl = CF ₂ , CF ₂ ClCF = CF
Cl, CFCl ₂ CF = CF ₂ , CF ₃ CCl = CClF, CF ₃ CCl = CCl ₂ , CClF ₂ CF = C
Cl ₂ , CCl3 CF = CF ₂ , CF ₂ ClCCl = CCl ₂ , CFCl ₂ CCl = CCl ₂ , CF ₃
CF = CHCl, CClF ₂ CF = CHCl, CH ₃ CCl = CHCl, CHF ₂ CCl = CCl ₂ ,
CF ₂ ClCH = CCl ₂ , CF2ClCCl = CHCl, CCl ₃ CF = CHCl, CCl ₃ CF = C
Fluoroprohens such as HCl, CHBrCF = CCl ₂ , CF ₃ CCl = CFC
Fluoroolefins having 4 or more carbon atoms such as F ₃ , CF ₂ = CFCF ₂ CClF ₂ , CF ₃ CF ₂ CF = CCl ₂ can be mentioned.

Examples of the hydroxyl group-containing monomer include hydroxylalkyl vinyl ether, hydroxylalkyl allyl ether, hydroxylalkyl vinyl ester, vinyl alcohol, allyl alcohol, methallyl alcohol, hydroxyalkyl acrylate and hydroxyalkyl methacrylate.

A method in which a vinyl ester of a carboxylic acid is copolymerized with a fluoroolefin and then hydrolyzed to form a hydroxyl group of a fluorine-containing copolymer having a hydroxyl group can be adopted. The hydroxyl value of the fluorine-containing copolymer containing hydroxyl groups is 1
0-230 KOH / g polymer, preferably 30-18
It is 0 KOH / g polymer, and when it is less than 10 mg KOH / g polymer, the stability of the coating is poor and a precipitate is formed when it is made into an aqueous coating, and when it exceeds 230 KOH / g polymer, the water resistance of the coating film is deteriorated, which is not preferable.

According to desired physical properties of the coating film (hardness, gloss, dispersibility of pigment, etc.), alkyl vinyl ether, alkyl allyl ether, alkyl vinyl ester, alkyl allyl ester, cycloalkyl vinyl ether, fluoroalkyl vinyl ether, etc. are appropriately copolymerized. You can also

Examples of the non-fluorine-based resin containing a cationic group include epoxy resin-based, acrylic resin-based, polybutadiene resin-based or polyurethane resin-based resins, and particularly amine-modified epoxy resin, amine-modified acrylic resin or amine-modified polybutadiene resin. preferable. These resins can be used alone or in combination of two or more.

The mixing ratio of the hydroxyl group-containing fluorine-containing copolymer and the cationic group-containing non-fluorine-based resin is 0.01 to 100 parts by weight with respect to 1 part by weight of the former, preferably 1 part by weight of the former. The latter is 0.05 to 20 parts by weight.

As the curing agent, a blocked isocyanate compound, aminoplast or the like can be used. As the aminoplast, melamine resin, guanamine resin, urea resin and the like can be used, but in the present invention, among melamine resins in particular, at least a part of one or more lower alcohols such as methanol, ethanol, propanol and butanol is used. The use of chemically etherified methylolmelamine resins is preferred. The curing agent is preferably used in a proportion of about 5 to 100 parts by weight per 100 parts by weight of the hydroxyl group-containing fluorocopolymer.

In the aqueous coating composition of the present invention, the hydroxyl group-containing fluorocopolymer, the cationic group-containing non-fluorine-based resin, the curing agent and the ultraviolet absorber are dissolved or dispersed in an aqueous medium. Here, as the aqueous medium, water may be used alone, but preferably contains an organic solvent in order to enhance the stability of the composition.

The organic solvent is water-soluble and has an affinity for the resin in order to stabilize the coating composition, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, secondary butanol. , Alcohols such as tertiary butanol, pentanol, etc., methyl cellosolve, ethyl cellosolve,
It is preferable to use cellosolves such as isopropyl cellosolve, butyl cellosolve, and secondary butyl cellosolve.

The amount of the organic solvent is usually relative to the resin solid content.
It is used in the range of 2.5 to 150% by weight. The coating composition of the present invention is usually prepared by using the resin solid content concentration in the range of about 3 to 50% by weight, and can be used by mixing with a commonly used colorant, coating additive and the like. The coating composition of the present invention is particularly useful as a cationic electrodeposition coating composition.

In the coating composition thus prepared, the metal article is used as a cathode, and a direct current voltage is applied between the counter electrode and the metal article. A fluorine-containing copolymer electrodeposition coating film having a uniform and excellent gloss is formed on the surface of an article. The composition of the present invention has a baking temperature of 130 to 250 ° C., preferably 1
It has the advantage that it is achieved at 40-230 ° C. for 15-60 minutes. When it is necessary to adjust the gloss of the electrodeposition coating film, a conventional inorganic or organic matting agent may be added.

[0017]

EXAMPLES Examples will be shown below to more specifically describe the present invention. In addition, the number of parts in the examples indicates parts by weight unless otherwise specified.

"Production Example of Hydroxyl Group-Containing Fluorine-Containing Copolymer"
35 parts of chlorotrifluoroethylene, 11 parts of cyclohexyl vinyl ether, 4.3 parts of ethyl vinyl ether, 15 parts of ω-hydroxybutyl vinyl ether, 98 parts of xylene, ethanol in an autoclave (withstand pressure of 50 kg / cm ² ) made of stainless steel with an internal volume of 200 cc. 28
Parts, 0.5 parts of azobisisobutyronitrile, and 1.5 parts of anhydrous potassium carbonate were charged, and after cooling with liquid nitrogen to remove dissolved air by solidification degassing, a reaction was carried out at 65 ° C. for 16 hours, A hydroxyl group-containing fluoropolymer was obtained. The obtained polymer had an intrinsic viscosity of 0.11 dl / g measured at 30 ° C. in tetrahydrofuran.

About 60% by weight of xylene solution of the obtained fluorine-containing copolymer having hydroxyl group (having a hydroxyl value of about 120 mgKOH / g polymer) was evaporated to remove the solid content of the copolymer, and butyl cellosolve was newly added. Dissolves in about 70
It was a solution of wt% butyl cellosolve.

Example 1 Epicoat 828EL (epoxy resin manufactured by Yuka Shell Co., Ltd.)
72 parts of butyl cellosolve was added to 105 parts, and the mixture was stirred at 100 ° C. for 30 minutes. Next, 9.2 parts of NN'-dimethylaminoethanol, 9.4 parts of lactic acid and 9.4 parts of water were added, and the temperature was 90 ° C.
The reaction was carried out for 2 hours to obtain an amine-modified epoxy resin. Next, 37 parts of a butyl cellosolve solution of the hydroxyl group-containing fluorine-containing copolymer produced in the above Production Example, 55 g of LS-2800 (block isocyanate produced by Sumitomo Bayer Urethane Co., Ltd.),
Dilaurate (0.003 parts) was added and mixed well with a disper. Then, water was gradually added to obtain an aqueous dispersion having a solid content of 10% by weight. Using this coating composition, a zinc phosphate-treated iron plate was electrodeposited and the performance of the resulting coating film was measured. The measurement results are shown in Table 1.

Example 2 Butyl cellosolve solution 3 of a fluorine-containing copolymer having a hydroxyl group
The performance of the coating film obtained in the same manner as in Example 1 was measured except that 7 parts contained 4.49 parts of TINUVIN1130 (UV absorber manufactured by Ciba-Geigy) and 1.5 parts of TINUVIN123 (radical scavenger manufactured by Ciba-Geigy). did. The measurement results are shown in Table 1.

Example 3 Anodizing treatment (alumite film thickness 10
The same procedure as in Example 1 was carried out except that an aluminum plate subjected to (μ) was used. Table 1 shows the measurement results of coating film performance.

Example 4 Instead of the iron plate, anodizing treatment (alumite film thickness 10
The same procedure as in Example 2 was performed except that an aluminum plate subjected to (μ) was used. Table 1 shows the measurement results of coating film performance.

Comparative Example 1 Example 1 except that the fluorine-containing copolymer containing a hydroxyl group was not used.
The performance of the coating film obtained in the same manner as above was measured. The results are shown in Table 1.

Comparative Example 2 Anodizing treatment (alumite film thickness 10
The same procedure as in Comparative Example 1 was carried out except that an aluminum plate subjected to (μ) was used. Table 1 shows the measurement results of coating film performance.

[0026]

[Table 1]

[0027]

EFFECT OF THE INVENTION The aqueous coating composition of the present invention forms a coating film having excellent weather resistance and corrosion resistance, and is suitable for applications such as cationic electrodeposition coating.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C09D 163/00 PKD

Claims (3)

[Claims] 1. A composition for an aqueous coating material, which comprises a fluorine-containing copolymer having a hydroxyl group, a non-fluorine-containing resin having a cationic group and a curing agent as essential components. 2. The aqueous coating composition according to claim 1, wherein the hydroxyl group-containing fluorocopolymer has a hydroxyl value of 10 to 230 mg KOH / g polymer. 3. The aqueous coating composition according to claim 1, wherein the non-fluorine-containing resin having a cationic group is an amine-modified epoxy resin, an amine-modified acrylic resin or an amine-modified polybutadiene resin.