JP2973517B2 - Fluorine-based electrodeposition coating composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an anion-type electrodeposition coating composition having excellent weather resistance, and more specifically, to an anion-type electrodeposition coating composition by performing electrodeposition coating on a conductive material such as a metal. The present invention relates to an anionic electrodeposition coating composition capable of imparting excellent weather resistance.

(Conventional technology) Conventionally, acrylic-melamine-based, polyester-melamine-based, acryl-urethane-based, and the like are known as electrodeposition coatings having good weather resistance, and are widely used for painting electric equipment products and building materials. I have.

Recently, a fluororesin-based electrodeposition paint has begun to be introduced.

However, the fluorinated polymer used for electrodeposition coating, which is currently being introduced, does not itself electrophoretically precipitate on the object to be coated to form a coating film. The resin was made to coexist with a hydrophilic resin or the surface of a fluoropolymer particle was coated with an electrophoretic resin.
Therefore, a uniform electrodeposition film of a fluoropolymer cannot be formed, the excellent properties of the fluoropolymer are not sufficiently exhibited, and the adhesion to the object to be coated is poor. Was.

Attempts have also been made to incorporate carboxyl groups into some fluoropolymers, but due to the unique properties of fluoropolymers that do not become aqueous unless extremely high acid values are used, a durable coating film has been obtained. Not in.

(Problems to be Solved by the Invention) An object of the present invention is to provide an electrodeposition method in which a fluorine-containing polymer capable of easily dissolving or dispersing in water even with a bottom acid value and capable of electrophoresis is used as a film-forming main component. It is to provide a coating composition.

(Means for Solving the Problems) The present inventors have conducted intensive studies to obtain an electrodeposition paint having excellent weather resistance, and as a result, have reacted a hydroxyl group-containing fluororesin with a vinyl group-containing acid anhydride. An aqueous dispersion (C) of a carboxyl group-containing modified polymer, which is a copolymerization product of a vinyl group-containing reaction product (A) obtained by the reaction and a polymerizable vinyl monomer (B) containing a carboxyl group-containing vinyl monomer, It has been found that the above problem can be solved by localizing a carboxyl group effective for aqueous conversion to a polymer side chain by using the same, and completed the present invention.

That is, the present invention relates to a reaction between a vinyl group-containing reaction product (A) obtained by reacting a hydroxyl group-containing fluororesin with a vinyl group-containing acid anhydride and a polymerizable vinyl monomer (B) containing a carboxyl group-containing vinyl monomer. Carboxyl group-containing modified polymer obtained by copolymerization, preferably having an acid value of 5 to 5
A fluorine-containing electrodeposition coating composition comprising an aqueous dispersion (C) of a carboxyl group-containing modified polymer in the range of 40 and a water-soluble or water-dispersible amino resin (D).

As the hydroxyl group-containing fluororesin used in the present invention, any conventionally known ones can be used.For example, a fluoroolefin and a hydroxyl group-containing monomer or a monomer having a group convertible to a hydroxyl group by hydrolysis or the like is an essential component. And those obtained by further copolymerizing other vinyl monomers are used.

As the fluoroolefin, vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, bromotrifluoroethylene, pentafluoropropylene, hexafluoropropylene, or trifluoromethyl-trifluorovinyl ether, pentafluoroethyl -Trifluorovinyl ether or heptafluoropropyl-
Typical examples include perfluoroalkyl-perfluorovinyl ethers such as trifluorovinyl ether, and the use of tetrafluoroethylene, vinylidene fluoride, chlorotrifluoroethylene, or hexafluoropropylene is particularly preferred. These fluoroolefin monomers may be used alone or in combination of two or more.

As the hydroxyl group-containing monomer, 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 3-hydroxybutyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 5-hydroxypentyl vinyl ether Vinyl ethers containing a hydroxyl group, such as, and 6-hydroxyhexyl vinyl ether, are preferably used.

Monomers having a group that can be converted to a hydroxyl group by hydrolysis or the like include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinylmethyldiethoxysilane, vinyltris (β-methoxyethoxy) silane, and allyltrimethoxysilane , Trimethoxysilylethyl vinyl ether, methyldimethoxysilylethylvinylether, trimethoxysilylpropylvinylether, triethoxysilylpropylvinylether, methyldimethoxysilylpropylvinylether, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxy Monomers containing a hydrolyzable silyl group such as propyltriethoxysilane and γ- (meth) acryloyloxypropylmethyldimethoxysilane It can be mentioned over.

Other monomers include alkyl vinyl ethers or substituted alkyl vinyl ethers, cycloalkyl vinyl ethers, carboxylic acid vinyl esters,
Representative examples include α-olefins, various halogenated olefins other than fluoroolefins, aromatic vinyl compounds, methacrylates, acrylates, and the like.

Further, as a preferable example of the hydroxyl group-containing fluororesin, "Fluonate K-700" manufactured by Dainippon Ink and Chemicals, Inc. and the like can be mentioned. The hydroxyl value of this hydroxyl group-containing fluororesin is preferably in the range of 30 to 150, and particularly preferably in the range of 40 to 130. When the hydroxyl value is less than 30, the dispersion stability of the carboxyl group-containing modified polymer in an aqueous medium tends to be poor, which is not preferable. If the hydroxyl value exceeds 150, the water resistance of the resulting coating film tends to decrease due to excessive hydroxyl groups, which is not preferable.

Any acid anhydride having a vinyl group can be used as the acid anhydride containing a vinyl group, but it is particularly preferable to use acrylic acid anhydride and / or methacrylic anhydride.

In the present invention, the ratio of the used amount of the hydroxyl group-containing fluororesin and the vinyl group-containing acid anhydride is determined by the hydroxyl group-containing fluororesin.
Acid anhydrides containing vinyl groups with respect to 90 to 99.5% by weight.
It is in the range of 2 to 10% by weight, preferably 0.5 to 8% by weight.
If the amount of the acid anhydride containing a vinyl group is less than 0.2% by weight, the dispersion stability of the carboxyl group-containing modified polymer in an aqueous medium tends to be poor, which is not preferable. On the other hand, when the amount of the acid anhydride containing a vinyl group is more than 10% by weight, the carboxyl group-containing modified polymer tends to have a high molecular weight in an aqueous medium during polymerization and tends to gel, which is not preferable. When reacted with an acid anhydride containing this vinyl group, for example, methacrylic anhydride, A reactant containing a vinyl group represented by the formula is obtained.

The polymerizable vinyl monomer (B) used for the copolymerization reaction with the vinyl group-containing reactant is a polymerizable vinyl monomer containing a carboxyl group-containing vinyl monomer. The content ratio of the carboxyl group-containing vinyl monomer in the polymerizable vinyl monomer is not particularly limited, but is at least 5% by weight.
It is preferable to contain a certain amount. If the content ratio of the carboxyl group-containing vinyl monomer in the polymerizable vinyl monomer is too small, the dispersion stability and electrodeposition properties of the resin in the aqueous medium, the adhesion to the metal of the coated film and the solvent resistance are all poor. It is not good because it tends to be worse.

Examples of the carboxyl group-containing vinyl monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid,
Maleic acid, fumaric acid and the like can be mentioned. Other polymerizable vinyl monomers usable as a mixture with the carboxyl group-containing vinyl monomer include, for example, styrene-based monomers such as styrene, vinyltoluene, 2-methylstyrene, t-butylstyrene, and chlorostyrene: methyl acrylate, acrylic Ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-acrylate
Acrylates such as octyl, decyl acrylate, dodecyl acrylate, etc .: methyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, n-methacrylic acid Methacrylates such as octyl, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate: monomers containing hydroxyl groups such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate: N -Methylol (meth) acrylamide, N-butoxymethyl (meth)
N-substituted (meth) acrylic monomers such as acrylamide: N, N-dimethylaminoethyl (meth) acrylate,
N, N-diethylaminoethyl (meth) acrylate, N, N
-Tertiary amino group-containing monomers represented by dimethylaminopropyl (meth) acrylate: vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, etc. Carboxylic acid vinyl ester: or methyl, ethyl, n-propyl, isopropyl, n-
Examples thereof include a vinyl ether having an alkyl group such as butyl, isobutyl, t-butyl, isoamyl, n-hexyl, n-octyl, and 2-ethylhexyl, or a substituent-containing alkyl group such as hydroxyethyl and hydroxybutyl.

The carboxyl group-containing modified polymer used in the present invention is produced by solution-polymerizing the vinyl group-containing reaction product (A) and the polymerizable vinyl monomer (B).

The carboxyl group-containing modified polymer thus produced has a low acid value of 5 to 40, but a carboxyl group useful for water dispersion is localized in the side chain of the polymer. It has the feature that it can be made aqueous without greatly reducing its properties. In the present invention, the ratio of the vinyl group-containing reaction product (A) to the polymerizable vinyl monomer containing a carboxyl group-containing vinyl monomer (B) is 40 to 95% by weight in terms of the weight ratio. Parts and a polymerizable vinyl monomer (B) containing a carboxyl group-containing vinyl monomer in the range of 5 to 60 parts.

Further, a vinyl group-containing reaction product (A) and a polymerizable vinyl monomer (B) containing a carboxyl group-containing vinyl monomer
Examples of the polymerization initiator used for the copolymerization reaction with the above include ordinary radical polymerization initiators such as azobisisobutyronitrile and benzoyl peroxide.

Examples of the organic solvent used for the copolymerization reaction include alcohols such as methanol, ethanol, propanol and butanol; ether alcohols such as methyl cellosolve and ethyl cellosolve; ether esters such as methyl cellosolve acetate and ethyl cellosolve acetate; hexane and toluene. And halogenated hydrocarbons such as trichloroethane; and ethyl ether, acetone, methyl ethyl ketone, diisobutyl ketone, and ethyl acetate.

The acid value of the resin content of the modified carboxyl group-containing polymer which is a copolymer of the vinyl group-containing reaction product (A) and the polymerizable vinyl monomer (B) is in the range of 5 to 40, preferably 8 to
35, more preferably from 10 to 30. When the acid value of the resin solid content is 5 or less, the solubility in water is deteriorated, and the electrodeposition coatability is undesirably reduced. On the other hand, if the acid value of the resin solids exceeds 40, the water resistance of the coating film tends to decrease, which is not preferable.

The aqueous dispersion (C) of the carboxyl group-containing modified polymer used in the present invention is obtained by adding a basic compound in an amount such that the pH of the dispersion becomes 6.5 or more to the carboxyl group-containing modified polymer obtained by the above polymerization reaction. And by dispersing the modified polymer in an aqueous medium. The basic compound used here is preferably ammonia or a volatile amine. Inorganic bases are not preferable because they tend to remain in the film and deteriorate water resistance. Examples of the amine include alkylamines such as trimethylamine, triethylamine and butylamine; alcoholamines such as dimethylaminoethanol, diethanolamine and aminomethylpropanol; and morpholine.

In the present invention, the aqueous medium means water alone having at least 10% by weight of water or a mixture with a hydrophilic organic solvent.

Examples of the hydrophilic organic solvent include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, etc., methyl cellosolve, ethyl cellosolve, and the like. Cellosolves such as isopropyl cellosolve, butyl cellosolve, and secondary butyl cellosolve, glycol ethers such as ethyl carbitol, dioxane, dimethylformamide, diacetone alcohol, and tetrahydrofuran can be used. If it is necessary to reduce the amount of organic solvent contained, use a solvent with a low boiling point, such as acetone or methyl ethyl ketone, or a solvent azeotropic with water, such as butanol or butyl cellosolve, as a reaction solvent or dissolution aid, and dissolve in an aqueous medium. By subsequently distilling at normal pressure or reduced pressure, an aqueous dispersion of a carboxyl group-containing modified polymer containing a low organic solvent can be obtained stably and easily.

The water-soluble or water-dispersible amino resin (D) suitable in the present invention may be any one in which at least a part of the methylol group is alkoxylated with a lower alcohol with an alkoxylated methylol melamine. As a lower alcohol,
One or more of methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like can be used.

The composition ratio of the carboxyl group-containing modified polymer and the water-soluble or water-dispersible amino resin (D) in the fluorine-containing electrodeposition coating composition of the present invention is 10 to 90 parts by weight of the carboxyl group-containing modified polymer, Or water-dispersible amino resin (D)
It can be used in the range of 90 to 10 parts by weight.

The fluorine-based electrodeposition coating composition of the present invention can be produced, for example, by the following method.

That is, an aqueous dispersion (C) of the carboxyl group-containing modified polymer and a water-soluble or water-dispersible amino resin (D) are added to a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser in the presence of an organic solvent. Mix under or in the absence. Emulsification is performed by adding water during or after the mixing. In the fluorine-based electrodeposition coating composition of the present invention, the reaction time and baking time can be reduced by adding an acid. Examples of the acid that can be added in the present invention include organic acids such as formic acid, acetic acid, oxalic acid, and sulfonic acid compounds, and examples of the inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid. In the present invention, use of a sulfonic acid compound is particularly preferred. Examples of the sulfonic acid compound include methanesulfonic acid, ethanesulfonic acid, n-nonylbenzenesulfonic acid, and p-toluenesulfonic acid. The acid is used in an amount of 10% by weight or less, preferably 5% by weight or less, based on the film-forming component of the coating composition.

The fluorinated electrodeposition coating composition of the present invention may be applied by the same method as it is on a conventional electrodeposition coating line, and the resulting coating film has excellent adhesion to an object to be coated and extremely excellent weather resistance. A film can be obtained.

(Examples) Examples will be shown below for describing the present invention in more detail, but the present invention is not limited to these examples. Parts and% in Examples are parts by weight and% by weight, respectively, unless otherwise specified.

Example 1 [Production of reaction product (A) having vinyl group] Fluonate K-700 200 parts Methacrylic anhydride 4 parts Phthalic anhydride 1 part Triethylamine 0.5 parts (In the above composition, Fluonate K-700 is Dainippon Ink Chemicals A hydroxyl group-containing fluororesin manufactured by Kogyo Co., Ltd., which has a nonvolatile content of 50% and a solid content of hydroxyl group of 48.)
Was heated to 80 ° C. while stirring the contents, followed by stirring at the same temperature for 2 hours to obtain a vinyl group-containing reaction product.

[Preparation of aqueous dispersion (C) of carboxyl group-containing modified polymer] Vinyl group-containing reaction product obtained above 205.5 parts Isopropanol 103 parts Methacrylic acid 4.0 parts N-butyl methacrylate 40 parts Perbutyl-O 2 parts ( In the above composition, perbutyl-O is t-butylperoxy-2-ethylhexanoate (radical polymerization initiator) manufactured by NOF Corporation. The mixture was heated to 80 ° C, the remaining mixture was gradually added dropwise over 4 hours while maintaining the temperature, and the mixture was stirred at the same temperature for 4 hours to obtain carboxyl. A group-containing modified polymer was obtained.

To the reaction solution containing the modified polymer obtained above was added 7 parts of triethylamine, and after uniform mixing, deionized water was added dropwise over 30 minutes to give an aqueous dispersion having a solid content of 30.3%, pH 8.8, and a solid acid value of 18. A liquid was obtained. The obtained aqueous dispersion was further concentrated under reduced pressure to obtain an aqueous dispersion of a carboxyl group-containing modified polymer having a solid content of 45.2%.

Aqueous dispersion of the resulting carboxyl group-containing modified polymer
To 120 parts, 30 parts of methoxybutoxy-mixed methylolmelamine was charged and stirred, and 100 parts of deionized water was further added to prepare a fluorine-based electrodeposition coating composition. An aluminum plate was connected to the anode and a stainless steel plate was connected to the cathode, and a voltage of 200 V was applied to the fluorine-based electrodeposition coating composition to conduct electricity. After washing with water,
Hot air drying was performed at 150 ° C. for 20 minutes. The coating film formed on the aluminum plate was excellent in alkali resistance and acid resistance, and had excellent gloss even after irradiation for 1000 hours with a sunshine weatherometer.

Example 2 The same fluororesin as Fluoronate K-700 was used instead of Fluoronate K-700 except that it had a hydroxyl value of 102,
Except that 2 parts of methacrylic anhydride and 4 parts of acrylic acid except phthalic anhydride were used, and 15 parts of methyl methacrylate and 10 parts of butyl acrylate were newly added instead of n-butyl methacrylate. An aqueous dispersion having a solid content of 32.5%, a pH of 8.2 and an acid value of 28 was obtained in the same manner as in Example 1.
An aqueous dispersion of a carboxyl group-containing modified polymer was obtained from this aqueous dispersion in the same manner as in Example 1. 20 parts of methoxymethylated melamine was added to 120 parts of the obtained aqueous dispersion of the carboxyl group-containing modified polymer, and 100 parts of deionized water was further added to prepare a fluorine-based electrodeposition coating composition. Electrodeposition coating was performed. The coating film formed on the aluminum plate was excellent in alkali resistance and acid resistance, and had excellent gloss even after irradiation for 1000 hours with a sunshine weatherometer.

Comparative Example 1 Fluonate K-700 was placed in the same reaction vessel as in Example 1.
Was added to 5 parts of trimellitic anhydride, and the mixture was kept at 80 ° C. for 5 hours to obtain a composition having an acid value of 28 to which trimellitic anhydride was added. Then an aqueous solution containing 5 parts of triethylamine 15
The mixture was neutralized, and then deionized water was added dropwise, but could not be dispersed in water.

Comparative Example 2 Fluonate K-700 was placed in the same reaction vessel as in Example 1.
Was added to 25 parts of trimellitic anhydride, and the mixture was kept at 80 ° C. for 5 hours to add trimellitic anhydride to obtain a composition.
Thereafter, 15 parts of an aqueous solution containing 25 parts of triethylamine was added for neutralization. Then, when deionized water was added dropwise, solids 23.5
%, PH 8.6, and an aqueous dispersion having an acid value of 114. The obtained aqueous dispersion was further concentrated under reduced pressure to obtain an aqueous dispersion of a carboxyl group-containing modified copolymer for comparison, which had a solid content of 43.4% and in which carboxyl groups were not localized. To 120 parts of the obtained aqueous dispersion, 30 parts of methylol melamine mixed with methoxybutoxy was charged and stirred, and 100 parts of deionized water was further added to prepare a fluorine-based electrodeposition coating composition. The present fluorine-based electrodeposition coating composition was subjected to electrodeposition coating in the same manner as in Example 1. The coating film formed on the aluminum plate had poor alkali resistance, and the coated plate after irradiation for 400 hours with a sunshine weatherometer had countless small cracks.

(Effect of the Invention) Since the fluorine-based electrodeposition coating composition of the present invention can be easily dissolved or dispersed in water and electrophoresed even at a low acid value, a coating film having extremely excellent weather resistance can be obtained. Obtainable.

Claims (5)

(57) [Claims] 1. A vinyl-containing reaction product (A) obtained by reacting a hydroxyl-containing fluororesin with a vinyl-containing acid anhydride and a polymerizable vinyl monomer (B) containing a carboxyl-containing vinyl monomer. A fluorine-containing electrodeposition coating composition comprising an aqueous dispersion (C) of a carboxyl group-containing modified polymer obtained by copolymerizing the above and a water-soluble or water-dispersible amino resin (D). 2. A fluorine-containing electrodeposition coating composition according to claim 1, wherein acrylic acid and / or methacrylic anhydride are used as the acid anhydride containing a vinyl group. 3. The hydroxyl group-containing fluororesin has a hydroxyl value of 30 to 15.
3. The fluorine-based electrodeposition coating composition according to claim 1, wherein the value is 0. 4. The modified carboxyl group-containing polymer having an acid value of 5
4. The method according to claim 1, wherein the number is from 40 to 40.
Item 8. The fluorine-based electrodeposition coating composition according to Item. 5. The use amount of the hydroxyl group-containing fluororesin and the vinyl group-containing acid anhydride is from 90 to 99.5% by weight of the hydroxyl group-containing fluororesin to 0.2 to 10% by weight of the vinyl group-containing acid anhydride. The fluorine-based electrodeposition coating composition according to any one of claims 1 to 4, wherein