JPH06104704B2 - Method for producing fluorine-containing copolymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a fluorine-containing copolymer used in a room temperature curable fluororesin coating material.

[Conventional technology]

In recent years, fluorine-containing copolymers that can be cured at room temperature have begun to be used as fluororesin paints. Fluorine-containing copolymers that are actually often used in room-temperature-curable fluororesin coatings are alternating copolymers of fluoroolefin and various vinyl ether compounds (JP-A-49-13229, JP-A-57-3
4107 and JP-A-59-189108), it is produced by solution polymerization in an organic medium.

When the aliphatic carboxylic acid vinyl ester, which is cheaper than vinyl ether, is replaced with some vinyl ether and copolymerized with fluoroolefin, the polymerizability of fluoroolefin is not good, so the amount of fluoroolefin contained in the copolymer is vinyl ether only. Less than when copolymerized.
The low amount of fluoroolefin contained in the fluorocopolymer means that the loss of fluoroolefin is large, and when the fluoroolefin content of the copolymer is low, this copolymer is the main component. The hardness and weather resistance of the coating film are not good.

[Object of the Invention]

The inventors of the present invention have made extensive studies on a method for producing a fluoroolefin / aliphatic carboxylic acid vinyl ester / vinyl ether copolymer, and found that fluoroolefin, an aliphatic carboxylic acid vinyl ester, vinyl ether, etc., present in the polymerization system. The present invention has been achieved by the new finding that the amount of fluoroolefin contained in the copolymer changes depending on the total concentration of the monomer.

An object of the present invention is to provide a method for obtaining a fluorocopolymer having a high fluoroolefin content.

[Structure of Invention]

The gist of the present invention is to use 45 mol or more of the above monomer and 100 mol of the organic medium in total when copolymerizing fluoroolefin, aliphatic carboxylic acid vinyl ester and hydroxyalkyl vinyl ether in the organic medium. The present invention resides in a method for producing a characteristic fluorine-containing copolymer.

The amount of fluoroolefin, aliphatic carboxylic acid vinyl ester and hydroxyalkyl vinyl ether used is
When the amount of fluoroolefin, aliphatic carboxylic acid vinyl ester, hydroxyalkyl vinyl ether and the total amount of organic medium is less than 45 mol, the molar ratio of fluoroolefin, aliphatic carboxylic acid vinyl ester and hydroxyalkyl vinyl ether is 45 mol or more. Even in the same case, the amount of fluoroolefin contained in the produced copolymer is smaller than that in the case of 45 mol or more. When the amount of fluoroolefin contained in the copolymer is small, it is impossible to obtain sufficient physical and chemical properties as a paint. The preferred amount of fluoroolefin contained in the copolymer is 50 to 80 mol%.

As the fluoroolefin, known fluorine-containing monomers such as chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropene, fluoroalkyl vinyl ether, vinyl fluoride, vinylidene fluoride and trifluoroethylene can be used. The amount of fluoroolefin used is usually 20 to 50 mol per 100 mol of all monomers,
It is preferably 25 to 40 mol.

The aliphatic carboxylic acid vinyl ester usually has 6 carbon atoms.
To 18 such as vinyl versatate, vinyl laurate, vinyl stearate and the like. The amount of the aliphatic carboxylic acid vinyl ester used is usually 1 to 20 mol, preferably 3 to 18 mol, based on 100 mol of all the monomers.

The hydroxyalkyl group of the hydroxyalkyl vinyl ether usually has 2 to 6 carbon atoms. The hydroxyl group is usually attached at the ω position, but it may be at another position. The amount of hydroxyalkyl vinyl ether used is usually 1 to 20 mol, preferably 3 to 18 mol, per 100 mol of all the monomers.

The hydroxyalkyl group of the hydroxyalkyl vinyl ether usually has 2 to 6 carbon atoms. The hydroxyl group is usually attached at the ω position, but it may be at another position. The amount of hydroxyalkyl vinyl ether used is usually 1 to 20 mol, preferably 3 to 18 mol, per 100 mol of all the monomers.

As the organic medium, those generally used when preparing a fluoropolymer can be used. Examples of the organic medium include esters, aromatics, ketones, glymes, alcohols, amides, sulfoxides and the like. The organic medium may be a mixture.

When the present invention is carried out, the fluoride anion is desorbed from the produced copolymer, and this may serve as a catalyst to cyclize the hydroxyalkyl vinyl ether. An organic or inorganic weakly basic substance such as a tertiary amine or carbonate is added to the above. The amount of the weakly basic substance used is usually 0.01 to 5 parts by weight, preferably 0.1 to 1 part by weight, based on 100 parts by weight of the organic medium.

The polymerization of the present invention is carried out using a radical initiator. Examples of radical initiators include azobisisobutyronitrile, azo compounds such as azobisvaleronitrile, isobutyryl peroxide, octanoyl peroxide,
Examples thereof include peroxides such as di-isopropyl peroxide. The radical initiator is usually 0.1 to
3 parts by weight are used.

The polymerization temperature of the polymerization of the present invention is 0 to 150 ° C., preferably 5
To 95 ° C, the polymerization pressure is 0 to 50 kg / cm ² G, preferably 0 to
It is 15 kg / cm ² G.

The fluorine-containing copolymer obtained by the production method of the present invention can be used as it is as a lacquer type coating, but it is used by adding a curing agent having two or more groups capable of reacting with the hydroxyl group contained in the copolymer. can do. Examples of the curing agent include hexamethylene-di-isocyanate trimer, tolylene-di-isocyanate, isophorone-
Isocyanates such as di-isocyanate and block type isocyanate, melamines such as methylol melamine and butyrol melamine, urea resins, hexamethylene-di-
There are acid halides such as carbonyl chloride. The curing agent is usually used in an amount of 0.5 to 2 equivalents based on 1 equivalent of hydroxyl groups.

When the fluorine-containing copolymer obtained by the production method of the present invention is used as a coating material, in addition to the above curing agent, a curing accelerator, a pigment, a viscosity modifier, a leveling agent, an anti-gelling agent, an anti-skinning agent, and an ultraviolet ray. Absorbents, solvents, etc. can be added.

〔Example〕

Example 1 Butyl acetate 19 in a 1000 ml autoclave equipped with a stirrer
7.2g (1.698mol), ethyl acetate 84.5g (0.959mol), toluene 28.1g (0.305mol), dimethylbenzylamine 0.5
ml (0.003mol), Versatile vinylate (Shell Petrochemical Veovar 10, hereinafter referred to as VA) 174.2g (0.880mo)
l) and hydroxybutyl vinyl ether (hereinafter HBV
Called E. ) 43.6 g (0.376 mol) was charged, and after sealing, purging with nitrogen gas, chlorotrifluoroethylene (hereinafter CT
It is called FE. ) 220 g (1.897 mol) was charged. in this case,
The number of moles of monomers of VA, HBVE and CTFE is 51.6 moles based on 100 moles of these monomers and the organic medium in total.

After heating the autoclave to 65 ° C., 2.5 g of azobisisobutyronitrile was added to initiate polymerization. The temperature was maintained for 18 hours with stirring. Autoclave pressure initially 5.9k
It was g / cm ² G, but gradually decreased, and finally 4.3 kg / cm ² G
Met.

After cooling, residual monomer was released. Solids concentration 52.7
650 g of a fluorine-containing copolymer solution having a weight% was obtained.

A part of the obtained solution was poured into isopropanol to solidify the fluorocopolymer. Then, washed with isopropanol, dried, and then subjected to elemental analysis and ¹ H-NM
R analysis was performed. As a result, the fluorine-containing copolymer was
It was found to consist of E52.8 mol%, VA32.2 mol% and HBVE14.9 mol%, and CTFE was contained at 67.2% of the charged amount.

Elemental analysis: carbon 48.9%, chlorine 13.2% and fluorine 20.9% ¹ H-NMR analysis: δ (ppm); 0.7 to 2.0 (side chain methyl group and methine group), 3.4 to 4.1 (side chain methylene group).

Example 2 The amount of CTFE in Example 1 was changed to 146.8 g (1.266 mol), and VA, HB
A fluorine-containing copolymer solution was prepared in the same manner as in Example 1, except that the number of moles of VE and CTFE monomers was 46.0% with respect to 100 moles of the total of these monomers and the organic medium. 615 g of a fluorine-containing copolymer solution having a solid content concentration of 50.3% by weight was obtained.

A part of the obtained solution was taken to obtain a fluorinated copolymer in the same manner as in Example 1. Elemental analysis and ¹
1 H-NMR analysis was performed. As a result, it was found that the fluorine-containing copolymer was composed of 45.4 mol% of CTFE, 41.1 mol% of VA and 13.5 mol% of HBVE, and CTFE was contained in 74.3% of the charged amount.

Elemental analysis: carbon 53.3%, chlorine 10.8% and fluorine 17.1
%. ¹ H-NMR analysis: δ (ppm); 0.7 to 2.0 (side chain methyl group and methine group), 3.4 to 4.1 (side chain methylene group).

Comparative Example In the same autoclave as in Example 1, the same amounts of butyl acetate, ethyl acetate, toluene and dimethylbenzylamine as in Example 1 and 125 g (0.631 mol) of VA and 29.3 g of HBVE (0.23 g) were obtained.
52mol) was charged, sealed and purged with nitrogen gas, CTFE155
g (1.336 mol) was charged. In this case, VA, HBVE, CTFE
The number of moles of the monomer is the sum of these monomers and the organic medium.
It is 42.8 mol per 100 mol.

After heating the autoclave to 65 ° C., 2.5 g of azobisisobutyronitrile was added to initiate polymerization. The temperature was maintained for 18 hours with stirring.

After cooling, residual monomer was released. Solids concentration 42.9
543 g of a fluorine-containing copolymer solution with a weight% was obtained.

A part of the obtained solution was taken to obtain a fluorinated copolymer in the same manner as in Example 1. Elemental analysis and ¹
1 H-NMR analysis was performed. As a result, it was found that the fluorine-containing copolymer was composed of 45.2 mol% of CTFE, 40.3 mol% of VA and 14.5 mol% of HBVE, and 53.0% of the charged amount of CTFE was contained.

Elemental analysis: carbon 53.3%, chlorine 10.9% and fluorine 17.1
%. ¹ H-NMR analysis: δ (ppm); 0.7 to 2.0 (side chain methyl group and methine group), 3.4 to 4.1 (side chain methylene group).

Reference Example and Comparative Reference Example Butyl acetate was added to the fluorocopolymer solution prepared in Example 1 and Comparative Example, and diluted to 45% by weight. Diluted solution 10
35 g of rutile type titanium oxide and 8 g of xylene are added to 0 g,
Mix with paint shaker for 1 hour. 2 mg of dibutyltin laurate was added to each mixture, and
Hexamethylene-di-isocyanate trimer (Coronate EH manufactured by Nippon Polyurethane Co., Ltd.) in a mixture prepared from the fluorinated copolymer solution of 8.6 g, the same as the above in the mixture prepared from the fluorinated copolymer solution of Comparative Example 10.1 g of hexamethylene-di-isocyanate trimer was added. Further xylene was added to each mixture to bring the viscosity of the mixture to about 300 centipoise.

The mixture prepared above was applied to an aluminum plate (treated by BT-712 manufactured by Japan Test Panel Co., Ltd.) with a brush, and the temperature was 25 ° C.
It was left to cure for 24 hours at 80 ° C. for 8 hours. The average thickness of the coating film after curing was 30 μm. Pencil hardness test (JIS K 5400) using an aluminum plate with a coating as a sample
And a weather resistance test was conducted. As the weather resistance test, a Du Cycle tester (manufactured by Suga Test Instruments Co., Ltd., light source: sunshine carbon, panel temperature: 63 ° C, cycle: 60 minutes)
/ 60 minutes [lights on / off]), the 60 ° -60 ° specular gloss (JIS Z8741) before and after the 360-hour exposure treatment was measured, and the gloss retention rate was investigated. The results are shown in the table.

[Effects of the Invention] According to the production method of the present invention, simply fluoroolefin,
Fluorine-containing copolymer containing a large amount of fluoroolefin by using aliphatic carboxylic acid vinyl ester and hydroxyalkyl vinyl ether in a certain amount or more with respect to the total amount of fluoroolefin, aliphatic carboxylic acid vinyl ester, hydroxyalkyl vinyl ether and organic medium. With less loss of fluoroolefin.

Although the amount of fluoroolefin contained in the fluorocopolymer increases as the charging ratio of fluoroolefin increases, this method causes a large loss of fluoroolefin.

Claims (1)

[Claims] 1. When copolymerizing fluoroolefin, aliphatic carboxylic acid vinyl ester and hydroxyalkyl vinyl ether in an organic medium, the monomer is used in an amount of 45 mol or more per 100 mol of the total amount of the monomer and the organic medium. And a method for producing a fluorine-containing copolymer.