JPH07268281A - Fluorine-based aqueous coating composition - Google Patents

Abstract

(57) [Summary] [Structure] A fluoropolymer obtained by neutralizing at least a part of the carboxyl groups of a fluoropolymer having a carboxyl group with a basic compound, and an isocyanate curing agent dispersed in water. Fluorine-based aqueous coating composition. [Effect] When used as an electrodeposition paint, the coating film performance, especially the corrosion resistance, can be greatly improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorine-based aqueous coating composition, particularly a fluorine-based electrodeposition coating composition.

[0002]

2. Description of the Related Art Recently, as an electrodeposition coating composition having excellent weather resistance, those obtained by dispersing or dissolving a fluoropolymer in an aqueous medium are disclosed in JP-A-62-59676 and JP-A-62-127362.
It is proposed in the Gazette and the like.

In these fluorine-based anion electrodeposition coating compositions, aminoplast such as melamine resin is used as a curing agent. Fluorine-based anionic electrodeposition paint can greatly improve the durability of the coating film as compared with acrylic-based electrodeposition paint.

[0004]

However, there is a problem that the improvement in corrosion resistance is small when cured with aminoplast.

[0005]

The present invention has been made to solve the above-mentioned problems, in which at least a part of the carboxyl groups of the fluoropolymer having a carboxyl group is neutralized with a basic compound. The water-based coating composition is characterized by containing the following fluoropolymer and an isocyanate curing agent as essential components and dispersing these in water.

The fluorinated polymer having a carboxyl group in the present invention can be obtained by the method described in JP-A-58-136605, that is, the fluorinated polymer having a hydroxyl group is treated with a dibasic acid anhydride. , A method of introducing a carboxyl group, a method of polymerizing a fluoroolefin, an ethylenically unsaturated compound and an unsaturated carboxylic acid, a copolymer of a vinyl ester compound, an allyl ester compound and the like to produce a carboxyl group by hydrolysis. The fluorinated polymer thus obtained can be produced by a method such as hydrolysis.

Examples of the fluorine-containing polymer having a hydroxyl group include copolymers containing a polymerized unit based on a hydroxyl group-containing monomer such as hydroxyalkyl vinyl ether, hydroxyalkyl acrylate, hydroxyalkyl methacrylate, allyl alcohol and methallyl alcohol. To be

Further, the above-mentioned groups of a copolymer containing a polymerized unit based on a monomer having a group capable of being converted into a hydroxyl group by hydrolysis such as vinyl carboxylate or allyl carboxylate or alcoholysis are converted into hydroxyl groups. There are things.

Another method for producing a fluorinated polymer having a carboxyl group is a fluorinated polymer having a hydroxyl group such as a condensed polymer type obtained by a reaction of fluorinated polyols with epichlorohydrin, and the like. Various compounds represented by the following chemical formula 1, specifically, succinic anhydride, glutaric anhydride, itaconic anhydride, adipic anhydride,
Dibasic such as 1,2-cyclohexanedicarboxylic acid anhydride, cis-4-cyclohexene acid anhydride, 1,2-dicarboxylic acid anhydride, phthalic anhydride, 1,8-naphthalic anhydride, maleic anhydride An example of the method is a method of reacting an acid anhydride to convert at least a part of hydroxyl groups into an ester group represented by the general formula —OC (═O) —RCOOH.

[0010]

[Chemical 1] However, R in Chemical formula 1 represents a divalent organic group.

Specific examples of the unsaturated carboxylic acid to be copolymerized include acrylic acid, methacrylic acid, crotonic acid, 3-butenoic acid, 4-pentenoic acid, 2-hexenoic acid, 3-hexenoic acid, 5-hexenoic acid, 2 -Heptenoic acid, 3-heptenoic acid, 3-octenoic acid, 2-nonenoic acid, 3-nonenoic acid, 9
-Decenoic acid, 10-undecenoic acid, 2-tridecenoic acid.

Further, a fluoropolymer obtained by copolymerizing a monomer such as a vinyl ester compound or an allyl ester compound, which produces a carboxyl group by hydrolysis, is converted into a fluoropolymer having a carboxyl group by hydrolysis. Obtainable.

The fluorine-containing polymer having a carboxyl group has 20 units of polymerized units based on fluoroolefin.
Those containing ˜80 mol% are preferably adopted. A fluoroalkyl ester copolymer of acrylic acid or methacrylic acid produces excellent effects such as oil repellency,
In terms of weather resistance, it is slightly worse than the fluoropolymer copolymerized with a fluoroolefin, which is not preferable.

If the proportion of 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 it is more than the above-mentioned ratio, it becomes difficult to make it water-soluble or water-dispersible, and it may not be suitable for electrodeposition coating, which is not preferable. Particularly, a fluoropolymer having a polymerized unit based on a fluoroolefin of 30 to 70 mol% is preferable.

Here, the fluoroolefin is CClF.
= CF ₂ , CHCl = CF ₂ , CCl ₂ = CF ₂ , CClF = CClF, CHF = CCl ₂ , CH _{2
= CClF, CCl 2 = CClF,} CF 2 = CF 2, CF 2 = CH 2 or the like of _{tetrafluoroethylene, CF 2 ClCF = CF 2,} CF 3 CCl = CF 2, CF 3 CF = CFCl, CF 2 ClCCl
= CF ₂ , CF ₂ Cl CF = CFCl, CFCl ₂ CF = CF ₂ , CF ₃ CCl = CClF, CF ₃ CC
l = CCl ₂ , CClF ₂ CF = CCl ₂ , CCl ₃ CF = CF ₂ , CF ₂ ClCCl = CCl ₂ , CFC
l 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 , CF ₂ ClCCl = CHCl, CCl ₃ CF =
_{CHCl, CCl 3 CF = CHCl,} CHBrCF = CCl 2 CF 2 = CFOCF 3, CF 2 = CFOC
Fluoropropenes such as ₃ F ₇ , CF ₃ CCl = CFCF ₃ , CF ₂ = CFCF ₂ C
Fluoroolefins having 4 or more carbon atoms such as ClF ₂ , CF ₃ CF ₂ CF = CCl ₂ can be mentioned. These fluoroolefins may be used alone or in combination of two or more.

Further, another copolymerizable monomer may be added to the above copolymer within a range not losing its characteristics.
The following monomers can be exemplified. Olefins such as ethylene, propylene and isobutylene, haloolefins such as vinyl chloride and vinylidene chloride, vinyl carboxylates such as vinyl acetate, vinyl butyrate, vinyl pivalate, vinyl benzoate and vinyl versatate, ethyl vinyl ether, n -Alkyl vinyl ethers such as butyl vinyl ether, octyl vinyl ether, neopentyl vinyl ether and cyclohexyl vinyl ether, aromatic vinyl ethers such as phenyl vinyl ether, benzyl vinyl ether and naphthyl vinyl ether, isopropenyl ethers such as methyl isopropenyl ether and propyl isopropenyl ether, formic acid Allyl, allyl butyrate, allyl benzoate, allyl carboxylates such as allyl cyclohexanecarboxylate, allyl ethyl ether, Allyl ethers such as Le allyl phenyl ether, ethyl acrylate, acrylic acid-methacrylic acid esters of methyl methacrylate, and the like.

The fluorine-containing copolymer of the present invention has a number average molecular weight of 2,000 to 100,000, preferably 6,000 to 6,000.
A polymer having a molecular weight distribution of 30,000 and a molecular weight distribution of 4.0 or less, preferably 3.0 or less is suitable. If the molecular weight is less than 2,000, the weather resistance and chemical resistance are poor, and if it exceeds 100,000, the viscosity of the coating is high, and there is a problem in workability.

The copolymer of the present invention is a copolymerization reaction in which a polymerization initiator such as a polymerization initiator or ionizing radiation is allowed to act in the presence or absence of a polymerization catalyst in a monomer mixture in a predetermined ratio. It can be manufactured by carrying out. Here, as the polymerization initiator, a water-soluble one or an oil-soluble one can be appropriately used depending on the polymerization type or the polymerization medium.

Specifically, as the water-soluble initiator, a persulfate such as potassium persulfate, hydrogen peroxide or a redox initiator composed of these and a reducing agent such as sodium bisulfite and sodium thiosulfate, and further these Inorganic initiators such as those in which a small amount of iron, ferrous salt, silver nitrate, etc. coexist, or dibasic acid oxides such as disuccinic acid peroxide, diglutaric acid peroxide, and monosuccinic acid peroxide, azobisisobutylamidine dibasic Examples include organic initiators such as acid salts.

Further, as the oil-soluble initiator, a peroxyester type peroxide such as t-butylperoxyacetate, a dialkylperoxydicarbonate such as diisopropylperoxydicarbonate, benzoyl peroxide, azobisisobutyro Examples include nitrile and the like.

The amount of the polymerization initiator used can be appropriately changed depending on the kind and the conditions of the copolymerization reaction, but usually about 0.05 to 0.5% by weight is adopted with respect to the total amount of the monomers to be copolymerized. To be done.

In the above-mentioned copolymerization reaction, the reaction mode is not particularly limited, and bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization and the like can be adopted, but the stability of the polymerization operation, the produced copolymer From the standpoint of ease of separation, etc., emulsion polymerization in an aqueous medium or alcohols such as t-butanol,
Solution polymerization using an ester, a saturated halogenated hydrocarbon containing one or more fluorine atoms, an aromatic hydrocarbon such as xylene, etc. as a solvent is preferable.

The reaction temperature can be appropriately selected, but usually about 10 ° C to 100 ° C can be adopted. The reaction pressure can be appropriately selected, but is usually 1 to 100 kg / cm ^2.
It is desirable to adopt g, especially about 2 to 50 kg / cm ² · g. The intrinsic viscosity of the produced copolymer is preferably 0.05 to 2.0 dl / g.

In order to control the intrinsic viscosity of the produced copolymer within the above range, a reaction medium having a relatively large chain transfer constant may be used, or the copolymerization reaction may be appropriately carried out in the presence of a chain transfer agent. preferable.

The reaction for converting the hydroxyl groups of the fluoropolymer into the carboxyl groups may be carried out either partially or entirely. However, the acid value of the fluoropolymer having a carboxyl group is at least 10 mg KO
It is preferably H / g.

If the amount of the carboxyl group is too small, that is, if the acid value is less than 10 mgKOH / g, it is difficult to make the aqueous solution, and if the acid value is too large, the alkali resistance and boiling water resistance of the coating film are poor. It may decrease, which is not preferable. The acid value is preferably 10 to 150 mgKOH /
Fluorine-containing polymers having about g, especially about 10 to 100 mgKOH / g are preferably used.

Further, it is preferable that at least a part of the above-mentioned hydroxyl group remains because it can react with the curing agent to obtain a coating film excellent in solvent resistance and the like. Particularly, those containing a hydroxyl group at a ratio of about 10 to 150 mgKOH / g are preferably used.

The isocyanate-based curing agent is a compound having two or more isocyanate groups in the molecule which reacts with the hydroxyl group of the fluoropolymer to form a urethane bond, and the isocyanate group is blocked with a blocking agent. Is preferably used.

The compound having two or more isocyanate groups in the molecule may be either aliphatic or aromatic, such as m-phenylene diisocyanate and p-.
Phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 2,4-tolylene diisocyanate,
2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,4-xylylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 1,3-cyclopentane diisocyanate,
Examples of diisocyanates include 1,4-cyclohexane diisocyanate and isophorone diisocyanate.

Further, triphenylmethane-4,4 ',
Triisocyanates such as 4 ″ -triisocyanate, 1,3,5-triisocyanate benzene, 2,4,6-triisocyanate toluene, 4,4′-diphenyldimethylmethane-2,2 ′, 5,5 ′ Examples thereof include tetraisocyanates such as tetraisocyanate, but dimers and trimers of tolylene diisocyanate, isophorone diisocyanate and the like can also be used.

Further, it may be a prepolymer derived from a polyol, a polyether or a polyester, and examples of the polyol in this case include ethylene glycol, propylene glycol, 1,6-hexanediol, glycerin, trimethylolpropane, pentaerythritol and diethylene glycol. , Tripropylene glycol and the like.

Examples of the polyether include polyoxyethylene glycol and polyoxypropylene glycol, and examples of the polyester include a reaction product of a dihydric alcohol and a dibasic acid.

Examples of the blocking agent include methyl alcohol, ethyl alcohol, propyl alcohol,
Aliphatic, alicyclic or aromatic monoalcohols such as butyl alcohol, cyclopentyl alcohol, cyclohexyl alcohol, benzyl alcohol, hydroxyl ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, dimethyl ethanol amine, diethyl ethanol amine, etc. And hydroxylamines, oximes such as acetone oxime, methyl ethyl ketone oxime, and cyclopentanone oxime, and lactams such as ε-caprolactam and δ-valerolactam.

The curing agent is preferably used in a proportion of about 5 to 100 parts by weight per 100 parts by weight of the fluoropolymer.

The composition for electrodeposition coating composition obtained according to the present invention contains a urethane catalyst such as dibutyltin dilaurate in an amount of 0.
It can be cured more quickly by adding 5 to 5.0% by weight. It is also possible to add a pigment, and if necessary, a wetting agent, a surfactant, an aggregating solvent and the like are added, and the mixture is dispersed and mixed by a usual paint disperser to obtain an electrodeposition paint.

In the present invention, at least a part of the carboxyl groups of the fluoropolymer having a carboxyl group is neutralized with a basic compound. The neutralization ratio is 50 to 10 in order to improve the water dispersibility of the fluoropolymer.
0% is preferable.

Examples of such a basic compound include monomethylamine, dimethylamine, trimethylamine, diisopropylamine, triisopropylamine,
Primary or tertiary alkylamines such as monobutylamine, dibutylamine, tributylamine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, dimethylaminoethanol, diethylaminoethanol, etc. Alkanolamines, ethylenediamine, propylenediamine,
Examples thereof include alkylenepolyamines such as diethylenetriamine and triethylenetetramine, alkyleneimines such as ethyleneimine and propyleneimine, ammonia, piperazine, morpholine, pyrazine and pyridine.

The particle size of the water-based paint of the present invention is 30 nm.
It is preferably about 300 nm. If it is less than 30 nm, the coating material becomes water-soluble, which is not preferable. Also, 300
If it exceeds nm, sedimentation occurs due to the adhesion of particles, which is not preferable.

In the present invention, it is possible to add an ultraviolet absorber. In that case, stable weather resistance can be achieved. Examples of the ultraviolet absorber used include methyl salicylate, phenyl salicylate, cresyl salicylate,
Salicylic acid esters such as benzyl salicylate; 2-hydroxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-5-chlorobenzophenone, 2-aminobenzophenone, and ADEKA -Examples include benzophenones such as high molecular weight modified products such as T-57 sold by Argus.

Further, 2- (2'-hydroxy-5'-t
-Butylphenyl) benzotriazole, 2- (2'-
Hydroxy-5'-t-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-5'-
Methoxyphenyl) benzotriazole, 2- (2'-
Hydroxyl-3 ', 5'-di-neobentylphenyl) benzotriazole, as well as Tinuvin 90 from Ciba-Geigy
Benzotriazoles such as high molecular weight modified products sold as 0, 1130, ethyl 2-cyano-3,3-diphenylacrylate, 2-ethylhexyl 2-cyano-3,3-diphenylacrylate, α-cyano -Β-methyl-
Substituted acrylonitriles such as methyl 4-methoxycinnamate may be mentioned.

Further, 2,2'-thiobis (4-octylphenolate) nickel complex salt, {2,2'-thiobis (4-t
-Octylphenolate)}-n-butylamine / nickel complex salts such as nickel complex salts; dimethyl p-methoxybenzylidene malonate, resorcinol monobenzoate, hexamethylphosphoric triamide, ultraviolet rays such as 2,5-diphenyl-p-benzoquinone Absorbent, bis (2,2,6,6
-Tetramethyl-4-piperidine) sebacate, dimethyl-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, succinate,
2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl) as well as ADEKA ARGUS Examples include hindered amine light stabilizers such as high molecular weight modified products such as those sold as MARK LA57.62.63.67.68. These are preferably used alone or as a mixture of two or more.

The ultraviolet absorber is preferably used in the range of about 0.1 to 15 parts by weight per 100 parts by weight of the fluoropolymer. When the amount of the ultraviolet absorber is too small, the effect of improving light resistance cannot be sufficiently obtained, and
If the amount is too large, the effect will be saturated, which is not appropriate.

In the electrodeposition coating composition of the present invention, the above-mentioned fluoropolymer, curing agent, ultraviolet absorber and the like are 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. Examples of such an organic solvent are water-soluble and have an affinity with the resin for stabilizing the electrodeposition coating composition, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, secondary butanol, Alcohols such as tertiary butanol, pentanol and the like, cellosolves such as methyl cellosolve, ethyl cellosolve, isopropyl cellosolve, butyl cellosolve and secondary butyl cellosolve are used.

The amount of the organic solvent in the electrodeposition coating composition is in the range of 2.5 to 150% by weight based on the coating film forming component.
The electrodeposition coating composition of the present invention usually has a resin solid content concentration of 3 to
It is prepared and used in the range of about 50% by weight. At this time, a commonly used colorant, paint additive and the like can be mixed and used. In the electrodeposition coating composition thus prepared, the metal article is used as an anode, a direct current voltage is applied between the counter electrode and the metal article, and the metal article is pulled up and heated or baked without or after washing. A fluoropolymer electrodeposition coating film having a uniform and excellent gloss is formed on the surface of the article. The electrodeposition coating composition of the present invention has a coating film heated and baked at 130 to 250 ° C, preferably 140 ° C.
It has the advantage that it is achieved under conditions of ~ 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.

[0045]

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.

[Synthesis of Raw Material Fluoropolymer] Internal Volume 200
cc stainless steel autoclave with stirrer (pressure resistance 50 kg
/ cm ² ) 35 parts of chlorotrifluoroethylene, 11 parts of cyclohexyl vinyl ether, 4.3 parts of ethyl vinyl ether
Parts, ω-hydroxybutyl vinyl ether 15 parts, xylene 98 parts, ethanol 28 parts, azobisisobutyronitrile
Charge 0.5 parts and 1.5 parts of anhydrous potassium carbonate, cool with liquid nitrogen and remove dissolved air by solidification degassing.
The reaction was carried out at ℃ for 16 hours to obtain a hydroxyl group-containing fluoropolymer.

The polymer obtained is in tetrahydrofuran.
The intrinsic viscosity measured at 30 ° C. was 0.11 dl / g. The resulting fluorine-containing polymer containing hydroxyl groups (with a hydroxyl value of approximately 120 mgKOH
/ g-resin) in a 60% by weight xylene solution was heated to 90 ° C., 3.6 parts of succinic anhydride was added to 100 parts of the polymer, and 0.2 parts of triethylamine was further added and reacted for 2 hours.

When the infrared spectrum of the reaction solution was measured, the characteristic absorption of anhydrous acid (1850 cm ⁻¹ , 1780 c
m ⁻¹ ) has disappeared after the reaction and the carboxylic acid (1710 cm
^-1 ) and ester (1735 cm ^-1 ) absorptions were observed. Thus, the acid value of the fluoropolymer having a carboxyl group introduced was 20 mgKOH / g-resin, and the hydroxyl value was 100 mgKOH / g-resin. The obtained fluoropolymer was prepared by evaporating the solvent once and isolating the polymer solids, and then dissolving the polymer in isopropyl alcohol to prepare a 60 wt% isopropyl alcohol solution. Next, 5.18 parts of TINUVIN 1130 (manufactured by Ciba Geigy) was dissolved in this isopropyl alcohol solution.

[Preparation of electrodeposition liquid] In a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser, 135 parts of the fluoropolymer solution prepared in Synthesis Example and isophorone diisocyanate fully blocked with ε-caprolactam were added. Charge 36 parts of 80 wt% methyl ethyl ketone solution, add 4 parts of triethanolamine while continuing stirring, and then add butyl cellosolve.
26 parts was added, and 150 parts of deionized water was further added to prepare an electrodeposition coating solution. Deionized water was further added to this stock solution for electrodeposition paint to prepare a resin solids concentration of 10% by weight to obtain an electrodeposition paint.

[Electrodeposition] A 10 μm-thick anodized aluminum plate was used as the anode, and a stainless plate was provided as the counter electrode. The distance between the electrodes was 15 cm, the pole ratio was + / − = 2/1, and the liquid temperature was 20 ° C. ,
After applying DC current for 3 minutes at a voltage of 160 V, take out the aluminum plate and wash it thoroughly with water, and then at 180 ° C for 30 minutes.
After baking for minutes, the electrodeposition coating was completed.

[Coating film performance] The coated plate was subjected to a weather resistance test and a corrosion resistance test. The results are shown in Table 1.

COMPARATIVE EXAMPLE Instead of using a 80% by weight solution of isophorone diisocyanate wholly blocked with ε-caprolactam in methyl ethyl ketone, a methyl ethyl mixed etherified methylol melamine (trade name, Cymel 1116, manufactured by Mitsui Toatsu Co., Ltd.) was used. The same procedure as in Example was carried out except that 20 parts were used.

[0053]

[Table 1]

[0054]

As is apparent from the above description, the aqueous coating composition of the present invention forms a coating film having excellent liquid stability, high weather resistance and high corrosion resistance.

Claims (4)

[Claims] 1. A fluorine-based water-based coating composition comprising a fluorine-containing polymer obtained by neutralizing at least a part of the carboxyl groups of a fluorine-containing polymer having a carboxyl group with a basic compound and an isocyanate curing agent in water. Composition. 2. The composition according to claim 1, wherein the fluoropolymer is a fluoroolefin-based copolymer containing 20 to 80 mol% of polymerized units based on fluoroolefin. 3. The composition according to claim 1, wherein the fluorine-containing polymer has an acid value of 10 to 150 mg KOH / g. 4. The composition according to claim 1, wherein the water-based paint is an electrodeposition paint.