JPH11293178A - Fluororesin-containing aqueous dispersion for coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fluororesin-containing aqueous dispersion for coating material, excellent in weatherability, water resistance and pollution resistance, and capable of providing a coating film having high gloss. SOLUTION: This aqueous dispersion is obtained by carrying out emulsion polymerization of a monomer mixture consisting essentially of (a) 5-70 mol.% fluoroolefin, (b) 20-80 mol.% acrylic acid cyclohexyl ester which may have a substituent group at cyclohexyl group and (c) 0.1-10 mol.% ethylenic unsaturated monomer having hydrophilic function groups excluding hydroxyl group and dispersing the resultant fluorine-containing copolymer into an aqueous medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous dispersion of a fluorine-containing resin, and more particularly to an aqueous dispersion of a fluorine-containing resin for coatings which is excellent in weather resistance, water resistance and stain resistance and which can provide a high gloss coating film. It relates to a dispersion.

[0003]

2. Description of the Related Art In the field of paints, volatilization of organic solvents contained in paints has become a problem from the viewpoint of harm to the human body and protection of the global environment. From this viewpoint, the development of water-based paints has been vigorous. Aqueous resin dispersions obtained by emulsion polymerization are generally used. Among them, aqueous coatings of fluorine-containing resins, which are excellent in weather resistance and chemical resistance, have attracted attention, for example, aqueous dispersion of a copolymer containing fluoroolefin, polyoxyethylene group-containing macromonomer and hydroxyl group-containing monomer as essential components. Resin (JP-A-2-225550) and an aqueous resin dispersion obtained by emulsion-polymerizing a fluoroolefin, an olefin, a vinyl carboxylate, a monoethylenically unsaturated dicarboxylic acid, an internal crosslinking agent and a reactive emulsifier (JP-A-Heisei 2-225550). 3-33148) and the like have been proposed. However, the former is poor in water resistance due to the strong hydrophilicity of the copolymer, and is inferior in stain resistance because the coated film using the copolymer cannot remove adhered dirt because the coating film is soft. In the latter, since the resin particles of the aqueous resin dispersion are crosslinked, there is a problem that the film formability of the paint is inferior, the gloss of the coating film is low, and the weather resistance is insufficient.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an aqueous dispersion of a fluorine-containing resin having excellent film-forming properties, stain resistance, high gloss and weather resistance.

[0005]

Means for Solving the Problems As a result of diligent studies, the present inventors have found that an aqueous dispersion of a fluorine-containing copolymer having a specific composition containing a cyclohexyl acrylate which may have a substituent on the cyclohexyl group. However, they have found that the above-mentioned problems can be solved, and have completed the present invention. That is, in the present invention, the ratio of the essential constituent monomers based on the total amount of all the monomers is (a) a fluoroolefin: 5 to 70 mol%,
(B) cyclohexyl acrylate which may have a substituent in the cyclohexyl group: 20 to 80 mol%,
(C) An ethylenically unsaturated monomer having a hydrophilic functional group other than a hydroxyl group: 0.1 to 10 mol%, a fluorinated copolymer obtained by emulsion polymerization of a monomer mixture in an aqueous medium. This is an aqueous dispersion of a fluorine-containing resin for coatings, which is dispersed in water.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. Examples of the (a) fluoroolefin in the present invention include chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, vinylidene fluoride, and vinyl fluoride. Among these, chlorotrifluoroethylene and tetrafluoroethylene are preferable from the viewpoint of easy handling.

The (b) cyclohexyl acrylate which may have a substituent in the cyclohexyl group in the present invention includes cyclohexyl acrylate, te
rt-butylcyclohexyl, hydroxymethylcyclohexyl acrylate, cyclohexylmethyl acrylate,
Examples include isobornyl acrylate, adamantyl acrylate, and tricyclodecynyl acrylate.
Among these, cyclohexyl acrylate is preferred from the viewpoint of copolymerizability.

In the present invention, (c) the ethylenically unsaturated monomer having a hydrophilic functional group other than a hydroxyl group includes an ethylene group having a hydrophilic functional group such as a carboxyl group or a salt thereof, a sulfone group or a salt thereof, and an amino group. It is an unsaturated monomer. Here, an ethylenically unsaturated monomer having a hydroxyl group is not preferred because of its poor stability in emulsion polymerization or in an aqueous dispersion. As the ethylenically unsaturated monomer having a carboxyl group, acrylic acid, methacrylic acid,
Crotonic acid, itaconic acid, maleic acid, fumaric acid, vinyl acetic acid, and the like.Examples of the monomer having a sulfone group include vinyl sulfonic acid, styrene sulfonic acid,
Allylsulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid and the like can be mentioned. As the salt of the monomer, a salt of ammonia, an amine or an alkali metal is preferable.

Examples of the monomer having an amino group include methacrylamide, acrylamide, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate and aminopropyl vinyl ether.
Among these, a monomer having a carboxyl group or a salt thereof and a monomer having a sulfone group or a salt thereof are preferable because of excellent stability during production and storage of the dispersion.

The proportion of the above essential constituent monomers in the fluorine-containing copolymer in the present invention is (a): 5 to 70 mol%, and (b): 20 to 80, based on the total amount of all the monomers.
Mol% and (c): 0.1 to 10 mol%, preferably (a): 20 to 50 mol%, (b): 40 to 70 mol%.
Mol% and (c): 1 to 8 mol%. (A) is 6
If it exceeds 0 mol%, the stability of the dispersion of the fluorocopolymer decreases, and if it is less than 5 mol%, the weather resistance of the fluorocopolymer decreases. If (b) exceeds 80 mol%, the weather resistance decreases, and if it is less than 10 mol%, the gloss and water resistance of the obtained coating film decrease. When (c) exceeds 10 mol%, the water resistance of the coating film decreases, and when it is less than 0.1 mol%, the stability of the dispersion of the fluorocopolymer decreases.

The fluorine-containing copolymer of the present invention may be copolymerized with other monomers as long as the physical properties are not impaired. Examples of such comonomers include α- such as ethylene, propylene and isobutylene. Olefins, chloroethylenes such as vinyl chloride and vinylidene chloride, alkyl vinyl ethers such as ethyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether and cyclohexyl vinyl ether, vinyl propionate, vinyl caproate, vinyl pivalate, Veova-9 (trade name, manufactured by Shell Chemical Co., Ltd.), vinyl carboxylate such as vinyl cyclohexanecarboxylate and vinyl benzoate, methyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate, etc. Methacrylates of methyl acrylate, ethyl acrylate, Purobiru acrylate, isopropyl acrylate, n- butyl acrylate, isobutyl acrylate, s- butyl acrylate, t-
Butyl, neopentyl acrylate, ethylhexyl acrylate, isodecyl acrylate, lauryl acrylate,
Tridecyl acrylate, stearyl acrylate, benzyl acrylate, tetrahydrofurfuryl acrylate, methoxyethyl acrylate, dimethylaminoethyl acrylate, chloroethyl acrylate, trifluoroethyl acrylate and heptadecafluorooctylethyl acrylate .

The glass transition temperature (hereinafter referred to as Tg) of the fluorinated copolymer in the present invention is preferably in the range of 10 to 60 ° C. If the temperature is higher than 60 ° C., cracks easily occur in the coating film, and if the temperature is lower than 10 ° C., the coating film is softened and contaminants easily adhere. The molecular weight of the fluorinated copolymer is 500 as a number average molecular weight (in terms of polystyrene) by gel permeation chromatography (hereinafter referred to as GPC).
0 to 1,000,000 is preferable, and 10,000 to 500,000 is more preferable. When the molecular weight exceeds 1,000,000, the film-forming property is reduced, and 50
If it is less than 00, the strength of the coating film decreases.

The fluorinated copolymer of the present invention is produced by emulsion polymerization of the above-mentioned components (a) to (c) in the presence of a radical-generating polymerization initiator. The emulsifier to be used is preferably an anionic / nonionic combination. Examples of the anionic emulsifier include perfluorooctanoic acid sodium salt, potassium salt or ammonium salt, perfluorooctanesulfonic acid sodium salt and ammonium salt and the like. Examples include fluorine-based anionic emulsifiers, and hydrocarbon-based anionic emulsifiers such as ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate, sodium polyoxyethylene alkyl ether sulfate and sodium alkanesulfonate. Of these, hydrocarbon-based emulsifiers are preferred for the stability of the aqueous dispersion and the prevention of cissing of the coating film. Examples of nonionic emulsifiers include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester, and polyoxyethylene fatty acid ester. Fluorinated nonionic emulsifiers such as hydrocarbon nonionic emulsifiers, perfluoroalkylethylene oxide adducts and monohydropolyfluoroalkylethylene oxide adducts, and reactive emulsifiers such as the Aqualon RN series (Daiichi Kogyo Seiyaku Co., Ltd.) Can be used.
Among these, hydrocarbon nonionic emulsifiers are preferred from the viewpoint of the fineness of the particle size of the obtained copolymer and cost, and polyoxyethylene alkyl ether and polyoxyethylene alkyl phenyl ether are particularly preferred.

The radical-generating polymerization initiator includes:
Oil-soluble organic peroxides such as diisopropylperoxydicarbonate, tertiary butyl peroxypivalate, benzoyl peroxide, lauroyl peroxide, and water-soluble organic peroxides such as succinic acid peroxide and tertiary butyl hydroperoxide Oil-soluble azo compounds such as azobisisobutyronitrile and azobisisovaleronitrile, azobis (imidazolin-2-yl) propane hydrochloride, azobis (methylimidazolin-2-yl) propane hydrochloride,
Water-soluble azo compounds such as azobisamidinopropane hydrochloride and azobiscyanovaleric acid, and water-soluble inorganic peroxides such as ammonium persulfate and potassium persulfate can be used. Among these, a water-soluble polymerization initiator is preferable. In the case of redox polymerization, it is preferable to use sodium hydrogen sulfite, sodium sulfite, Rongalit, ascorbic acid, etc. in combination as a reducing agent.

The polymerization conditions are not particularly limited.
The preferred polymerization temperature in the preferred reaction is 20-100 ° C
The preferred pressure is 1 to 200 kg / cm ² and the preferred polymerization time is 3 to 40 hours. The monomers used for the polymerization may be initially charged in batches at an early stage, or a pre-emulsion of a part of the monomers or a monomer and an emulsifier may be sequentially added as the polymerization proceeds. Also, after adding a fluorine-containing copolymer component having a high Tg and performing the first-stage polymerization,
A fluorine-containing copolymer component having a low Tg may be added and the second-stage polymerization may be performed to obtain a fluorine-containing copolymer having a core / shell structure. It is preferable to add potassium carbonate, sodium hydrogen carbonate, disodium phosphate, and the like as a pH adjuster.

When the aqueous fluororesin dispersion of the present invention is used as a paint, if necessary, titanium oxide,
Iron oxide, phthalocyanine blue, benzidine yellow,
Pigments such as quinacridone red and carbon black,
Additives such as metal powders such as stainless steel powder, aluminum powder and bronze powder, pigment dispersants, UV absorbers, surface conditioners, thickeners, fungicides, rust inhibitors, film forming aids, and curing accelerators. Can be added. The coating composition obtained from the fluororesin aqueous dispersion is usually used in the coating field.
It can be used in a conventional method, and for example, it can be applied to a coating substrate such as a steel plate, stainless steel, aluminum, concrete, mortar, plastic and wood by spraying, brushing and rolling. Hereinafter, specific examples will be described.

[0017]

EXAMPLE 1 In a 2 liter autoclave equipped with a stirrer, 230 g of ion-exchanged water, 3.2 g of ammonium perfluorooctanoate as an anionic emulsifier, and polyoxyethylene nonylphenyl ether as a nonionic emulsifier, Kao Corporation ), 7.7 g of Emulgen 906 and 7.7 g of Emulgen 930, 16.7 g of cyclohexyl acrylate (hereinafter referred to as CHA) as a monomer, pH
2.7 g of ammonium bicarbonate as an adjusting agent and 0.7 g of ammonium hydrogen sulfite as a reducing agent are added, and degassing and nitrogen replacement are repeated three times, followed by degassing, and 510 g of chlorotrifluoroethylene (hereinafter referred to as CTFE). It is. After the temperature was raised to 40 ° C., an aqueous solution in which 10.3 g of ammonium persulfate was dissolved in 65 g of pure water was added as a polymerization initiator at a constant rate over 1 to 5 hours. Further, 3.8 g of ammonium perfluorooctanoate, 9.3 g of Emulgen 906 and 9.3 g of Emulgen 930 were added to 120 g of pure water, and CHA was added thereto.
150.2 g and acrylic acid (hereinafter referred to as AA)
The dispersion having 5.6 g dispersed therein was used as an additional monomer to raise the temperature 1
After a lapse of time, the mixture was added at a constant rate for 5 hours, and polymerization was performed for a total of 10 hours. Thereafter, the mixture is cooled to room temperature and unreacted CTF
E, purge the autoclave and allow
8% by weight of a fluororesin aqueous dispersion (E1) was obtained. At this time, no aggregate of the aqueous fluororesin dispersion was observed. As a result of measuring the particle size of the dispersion, the particle size distribution was monodisperse, and the average particle size was 0.09 μm. A part of the obtained dispersion was put into methanol, washed and dried, and used for various analyses. The number average molecular weight in terms of polystyrene measured by GPC was 150,000, and Tg was 38 ° C. 13.5 wt% was subjected to fluorine analysis of the copolymer, ¹ H-NMR and ¹³ C-
According to NMR, the composition of the copolymer was CTFE / CHA / A
It was confirmed that A = 36/61/3 (mol%).
Based on the E1 obtained above, coating compositions were prepared at the compounding ratios shown in the following test examples, and each evaluation test was carried out.

Example 2 The initially charged monomer was CTFE / CHA / ethyl acrylate (hereinafter referred to as EA) = 510 g / 10.0 g / 4.
3 g, and the additional monomer was CHA / EA / AA = 90.0
Polymerization was carried out in the same manner as in Example 1 except that the amount was changed to g / 39.0 g / 5.6 g, to obtain a fluorine-containing resin aqueous dispersion (E2) having a solid content of 35% by weight. At this time, no aggregate of the aqueous fluororesin dispersion was observed. As a result of measuring the particle size of the dispersion, the particle size distribution was monodisperse, and the average particle size was 0.09 μm. The number average molecular weight of the obtained copolymer was 180,000 and Tg was 34 ° C. The fluorine analysis value of this copolymer was 14.3% by weight. As a result of analysis in the same manner as in Example 1, CTFE / CHA
/ EA / AA = 35/37/25/3 (mol%). Based on the E2 obtained above, coating compositions were prepared at the compounding ratios shown in the following test examples, and each evaluation test was carried out.

Example 3 The initially charged monomer was CTFE / CHA / tertiary butyl acrylate (hereinafter referred to as tBA) = 400 g / 1.
0.0 g / 5.5 g, and CHA / tBA
Polymerization was carried out in the same manner as in Example 1 except that /AA=90.0 g / 50.0 g / 5.6 g, and the solid content was 3
5% by weight of a fluororesin aqueous dispersion (E3) was obtained. At this time, no aggregate of the aqueous fluororesin dispersion was observed. As a result of measuring the particle size of the dispersion, the particle size distribution was monodisperse, and the average particle size was 0.10 μm. The number average molecular weight of the obtained copolymer is 190,000,
Tg was 40 ° C. The fluorine analysis value of this copolymer was 11.5% by weight, and the same analysis as in Example 1 revealed that CTFE / CHA / tBA / AA = 31/40/27.
/ 2 (mol%). Based on the E3 obtained above, coating compositions were prepared at the compounding ratios shown in the following test examples, and each evaluation test was carried out.

Comparative Example 1 In the same autoclave as in Example 1, ion-exchanged water 49 was added.
5 g, 3.6 g of perfluorooctanoic acid ammonium salt, 110 g of ethyl vinyl ether (hereinafter, referred to as EVE), 7.5 g of hydroxybutyl vinyl ether (hereinafter, referred to as HBVE), and a number average molecular weight of 700
Polyoxyethylene vinyl ether (hereinafter referred to as EO)
VE) (22.5 g) and potassium carbonate (5 g).
After degassing and nitrogen replacement were repeated three times, degassing was performed, and CTFE1
90 g was charged. After the temperature was raised to 30 ° C., 0.8 g of ammonium persulfate and 0.1% of sodium hydrogen sulfite as a reducing agent.
23 g was injected to initiate polymerization. Thereafter, polymerization was carried out for 12 hours, unreacted CTFE was purged, and the autoclave was opened to open a fluorine-containing aqueous dispersion (E) having a solid content of 39%.
4) was obtained. At this time, no aggregate of the aqueous fluororesin dispersion was observed. As a result of measuring the particle size of the dispersion, the particle size distribution was monodisperse, and the average particle size was 0.15 μm. A part of the obtained dispersion was put into methanol, washed and dried to obtain a copolymer for analysis. The obtained copolymer had a number average molecular weight in terms of polystyrene measured by GPC of 58,000 and a Tg of 12 ° C. Fluorine analysis of the copolymer revealed that it was 28.0% by weight. From ¹ H-NMR and ¹³ C-NMR, the copolymer composition was CTFE / EVE / HBVE / EOVE = 5.
0/47/2/1 (mol%). Based on the E4 obtained above, coating compositions were prepared at the compounding ratios shown in the following Test Examples, and each evaluation test was carried out.

Comparative Example 2 CTFE / CTFE was performed by the method described in the example of JP-A-3-33148.
Ethylene / vinyl acetate / itaconic acid / "Eleminol J
S-2 "[sodium alkyl allyl sulfosuccinate manufactured by Sanyo Chemical Industry Co., Ltd.] / 1,9-decadiene / VES
= 41/15/41/1/1 / 0.5 / 0.5 to obtain an aqueous resin dispersion (E5). The number average molecular weight of the obtained copolymer in terms of polystyrene measured by GPC was 1
50,000 and Tg was 40 ° C. The copolymer was analyzed for fluorine and found to be 22.0%. Based on the E5 obtained above, coating compositions were prepared at the compounding ratios shown in the following test examples, and each evaluation test was carried out.

Test Example Evaluation with White Paint (Preparation of White Paint) Titanium oxide [CR-C available from Ishihara Sangyo Co., Ltd.]
97], 200.0 g, pigment dispersant [SN Dispersant 5027 manufactured by San Nopco Co., Ltd.] 10.0 g, antifoaming agent [FS Antifoam 013 manufactured by Dow Corning Co., Ltd.]
B] After removing glass beads from a mill base (hereinafter referred to as a mill) obtained by mixing and dispersing 1.0 g, 98.0 g of ion-exchanged water, and 260 g of glass beads using a homodisper, an aqueous dispersion E1 was prepared. Table 1 below for E5
And the mixture was stirred at the weight ratio shown in Table 1 to prepare a white paint.

[0023]

[Table 1] CS12: Chisso Corporation 2,2,4-trimethylpentanediol-1,3-monoisobutyrate Thickener: 10% by weight aqueous solution of ADEKANOL UH420 manufactured by Asahi Denka Co., Ltd.

(Coating and Test) A 0.6 mm aluminum plate (allodined 5052P material) was coated with ureol 800, which is an acrylic urethane paint manufactured by Kawakami Paint Co., Ltd.
One day later, the white paint composition obtained above was applied using a bar coater so that the dry film thickness was 30 μm. The coated plate was dried at room temperature for one week and then subjected to the following test. Gloss value: A 60 ° gloss value was measured by the method described in JIS K5400. Water resistance: The coated plate was immersed in warm water at 40 ° C. for 3 days, the gloss value before and after the test was measured, and the retention was calculated. Stain resistance: The obtained coating film was subjected to an exposure test at an angle of 45 degrees for 6 months in an industrial zone in the southern part of Nagoya City, and the difference in lightness (ΔL value) before and after the test was calculated. -Weather resistance: One cycle consists of spraying ion-exchanged water from the backside of the coated surface for 4 hours after continuous irradiation for 4 hours using QUV (Fluorescent UV weathering tester manufactured by Q Panel Co., Ltd.).
The 60-degree gloss retention (%) after the 50 cycle test was shown. The results of the above tests are shown in Table 2 below.

[0025]

[Table 2]

[0026]

The aqueous dispersion of a fluorine-containing resin for a paint according to the present invention gives a coating film having not only weather resistance but also high gloss and stain resistance, and thus is widely used for various paint applications.

Claims (1)

[Claims] (1) The proportion of an essential constituent monomer based on the total amount of all monomers is (a) 5-70 mol% of fluoroolefin, and (b) cyclohexyl group has a substituent. Efficient cyclohexyl acrylate: 20-80 mol%, (c) ethylenically unsaturated monomer having a hydrophilic functional group other than hydroxyl group: 0.1-10 mol%, emulsion polymerization of monomer mixture An aqueous dispersion of a fluorinated resin for coatings, wherein the fluorinated copolymer obtained by the above is dispersed in an aqueous medium.