JPH0586134A - Production of fluorocopolymer - Google Patents

Abstract

PURPOSE:To obtain effectively a carboxyl-terminated copolymer excellent in adhesion to substrate and dispersion of pigment by copolymerizing a fluoroolefin with a specified unsaturated monomer and an unsaturated monomer containing a functional group in a specified ratio in the presence of a radical polymerization initiator containing a carboxylic acid unit. CONSTITUTION:30-70mol% fluoroolefin (e.g. chlorotrifluoroethylene) is copolymerized with 30-70mol% unsaturated monomer of the formula: CH2=CH<1> O(C=O)kR<2> [wherein R<1> is H or CH3; R<2> is (cyclo)alkyl; and k is 0 or 1] and 0.5-10mol% unsaturated monomer having a functional group (e.g. hydroxybutyl vinyl ether) in the presence of a radical polymerization initiator containing a carboxylic acid unit (e.g. 4,4'-azobis-4-cyanovaleric acid).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a fluorine-containing copolymer.

[0002]

2. Description of the Related Art Conventionally, attempts have been made to introduce a carboxyl group into a polymer substance to impart hydrophilicity, improve adhesion, dyeability, dispersibility, etc., and introduce a crosslinking site / ion exchange group. In many cases, general polymer substances are industrially used.

On the other hand, as a method for producing a carboxyl group-containing fluoropolymer, a dibasic acid anhydride is allowed to act on a hydroxyl group-containing fluoropolymer in an organic solvent so that at least a part of the hydroxyl groups becomes a carboxyl group-containing ester group. A conversion method has been proposed (Japanese Patent Laid-Open No. 58-136605).
issue).

[0004]

This method is a so-called polymer reaction, and if the manufacturing process is somewhat complicated, there is a problem in that the number of processes is increased, which is a disadvantage in terms of production.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. (A) Fluorine-containing olefin 30 to 70 mol%, (b) Unsaturation represented by the general formula A 30 to 70 mol% of a monomer and 0.5 to 10 mol% of a functional group-containing unsaturated monomer (c) are copolymerized in the presence of a radical polymerization initiator having a carboxylic acid unit. A method for producing a carboxylic acid group-containing fluorocopolymer. A: CH ₂ = CR ¹ O (C = 0) _k R ² (However, R ¹ is H or CH ₃ , R ²
Is an alkyl group or a cycloalkyl group, k is 0 or 1
Is)

In the present invention, tetrafluoroethylene and chlorotrifluoroethylene are preferably used as the fluorinated olefin as the component (a), but hexafluoropropylene and perfluoroalkyl vinyl ether can also be used.

As the unsaturated monomer represented by the general formula A as the component (b), ethyl vinyl ether, n-butyl vinyl ether, cyclohexyl vinyl ether, ethyl isopropenyl ether, n-butyl isopropenyl ether, 2, 2, 3 , 3 Tetrafluoropropyl vinyl ether and other vinyl ethers, vinyl acetate, vinyl acetate such as isopropenyl acetate, n-vinyl butyrate, isopropenyl n-butyrate, vinyl valerate, vinyl isovalerate, vinyl pivalate and vinyl laurate. Is exemplified.

The functional group-containing monomer of component (c) generally has 3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 6-hydroxyhexyl vinyl ether having a hydroxyl group, an epoxy group or a trialkoxysilyl group as a functional group, Cyclohexanedimethanol monovinyl ether, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, glycidyl vinyl ether, glycidyl methacrylate, trimethoxyvinylsilane and the like are used.

Each of the above components is not limited to a single component, and it is possible to use a mixture of two or more components.

When the component (a) is used in a ratio below the range, not only is it unfavorable in terms of weather resistance and chemical resistance,
Inconvenience occurs in manufacturing. On the other hand, if it is used in a proportion higher than this, not only inconveniences in terms of production but also in the solvent solubility of the obtained copolymer is lowered, which is not preferable.

With respect to the component (b), if it is used in a ratio higher than this, the weather resistance and chemical resistance are lowered, and if it is used in a ratio lower than this, the solubility in a solvent is lowered, and it is used for coating applications. Is not suitable.

This ratio of the component (c) is used to introduce a curing site necessary for forming a cured coating film of the copolymer.

Further, units based on other monomers may be contained within the range not impairing the properties of the copolymer. Examples of such a monomer include olefins such as ethylene, propylene and isobutylene, haloolefins such as vinyl chloride and vinylidene chloride, unsaturated carboxylic acid esters such as methyl methacrylate, vinyl carboxylates such as vinyl acetate. It is possible.

In the present invention, it is important to use a radical polymerization initiator having a carboxylic acid unit as the polymerization initiator. Examples of such a polymerization initiator include 4,4′-azobis-4-cyanovaleric acid and 3,3′-azobis-3-
Examples thereof include azo compounds containing a carboxylic acid unit such as cyanobutanoic acid, and dibasic acid peroxides such as disuccinic acid peroxide and diglutaric acid peroxide. A compound represented by Chemical formula 1 (n is an integer of 1 to 3) is particularly preferable.

[0015]

[Chemical 1]

The amount of the polymerization initiator to be used can be changed depending on the kind, the conditions of the copolymerization reaction and the like, but usually about 0.1 to 5% by weight is used with respect to the monomer.

The reaction system in the copolymerization reaction is not particularly limited, and in the presence of a commonly used radical polymerization initiator, bulk polymerization, pendulum polymerization, vaporization polymerization, solution polymerization and the like can be adopted. Emulsion polymerization in an aqueous medium, alcohols such as t-butanol, etc. from the viewpoint of stability of reaction operation, easiness of separation of produced copolymer, etc.
Solution polymerization using an ester, a saturated halogenated hydrocarbon containing one or more fluorine atoms, an aromatic hydrocarbon such as xylene, toluene and the like as a solvent is preferably adopted.

As the reaction operation, an ordinary method such as a batch system, a semi-continuous system or a continuous system is adopted. Further, in order to control the molecular weight of the produced copolymer, it is also possible to appropriately carry out the copolymerization reaction in the presence of a chain transfer agent.

The obtained copolymer utilizes a functional group such as a hydroxyl group, an epoxy group or a trialkoxysilyl group introduced as a curing site in the copolymer, and a curing agent is used from room temperature to about 200 ° C. The coating film having a crosslinked structure can be formed by curing at the temperature of.

As the curing agent, when the functional group is a hydroxyl group, butylated or methylated melamine resin, butylated or methylated urea resin, hexamethylene diisocyanate, isophorone diisocyanate and other isocyanates and adducts thereof are used. When the functional group is an epoxy group, various amines are used.

Various solutions can be used to prepare the solution-type coating composition of the present copolymer. Aromatic hydrocarbons such as xylene and toluene, alcohols such as n-butanol, esters such as butyl acetate, etc. In addition to ketones such as methyl isobutyl ketone and glycol ethers such as ethyl cellosolve, various commercially available thinners can be adopted.

Mixing of the copolymer and the solvent is carried out by a ball mill, a paint shaker, a sand mill, a jet mill,
It can be carried out by using various equipment such as a triple roll, a kneader and the like which are usually used for coating. At this time, the pigment,
A dispersion stabilizer, a viscosity modifier, a leveling agent, an anti-gelling agent, an ultraviolet absorber, etc. can also be added.

[0023]

[Example 1] 11.9 g of xylene, 67.7 g of t-butanol, 55.8 g of cyclohexyl vinyl ether, 3.6 g of ethyl vinyl ether were placed in a stainless steel autoclave with a stirrer (pressure resistance 25 kg / cm ² ) having an internal volume of 260 cc. 1.2 g of hydroxybutyl vinyl ether,
1.8 g of potassium carbonate and 0.60 g (0.5% by weight) of 4,4′-azobis-4-cyanovaleric acid were charged, and dissolved oxygen was removed by solidification degassing with liquid nitrogen. Then, 58.6 g of chlorotrifluoroethylene is introduced into the autoclave, and the temperature is gradually raised. When the temperature inside the autoclave reached 65 ° C, the pressure was 5.7 kg / cm.
² is shown.

Thereafter, the reaction is continued under stirring for 10 hours, and when the pressure is reduced to 2.8 kg / cm ² , the autoclave is cooled with ice to stop the reaction. After reaching room temperature, the unreacted monomers are purged and the autoclave is opened.

The obtained polymer solution is precipitated in water, washed and dried to recover the polymer. The polymer yield was 71.5 g, and the monomer conversion rate was 60.0%.
Intrinsic viscosity of the obtained polymer (in tetrahydrofuran,
(30 ° C.) was 0.30. When the IR spectrum of the polymer was measured, absorption of a carboxyl group was recognized at 1720 cm ^-1 . When the acid value of the polymer was measured by a titration method, it was 0.7 (mgKOH / g).

Comparative Example 1 A polymer was synthesized in the same manner as in Example 1 except that the initiator was changed to AIBN. The polymer yield was 73.0 g, the monomer conversion rate was 61.0%, and the intrinsic viscosity was 0.31. The acid value was 0.

Example 2 2.0 g of the polymer synthesized in Example 1 and Comparative Example 1 were dissolved in 10 g of xylene, respectively, and 4.2 g of titanium oxide (Ishihara Sangyo CR-90) was dissolved.
In addition, they were mixed and dispersed with a paint shaker. The time until a sufficiently dispersed state (5 micron or less with a particle gauge) was measured (pigment dispersibility test). The polymer of Example 1 was about 1.5 hours, and Comparative Example 1 was about 3.5 hours. there were.

[Example 3] The polymers synthesized in Example 1 and Comparative Example 1 were melt-heated and adhered on a stainless specular plate using a heating oven to a thickness of about 20 µm at 280 ° C for 5 minutes. When a cross-cut cross-cut adhesion test (adhesion test) was performed on the obtained coating surface, the former was 100/100 and the latter was 80/100.

[Example 4-7] Polymerization reaction and pigment dispersibility / adhesion test were conducted under the same conditions as in Example 1-3.
Collectively shown in Table 1.

[0030]

[Table 1]

In Table 1, CTFE in the column of monomer is chlorotrifluoroethylene, CHVE is cyclohexyl vinyl ether, EVE is ethyl vinyl ether, HB.
VE is hydroxybutyl vinyl ether, GVE is glycidyl vinyl ether, and the numbers indicate mol%. The initiator is a compound represented by Chemical formula 2, and the numbers are% by weight with respect to the monomers.

[0032]

[Chemical 2]

[0033]

According to the method of the present invention, a carboxyl group-containing fluorocopolymer can be produced simply and effectively. Further, the copolymer has excellent effects in pigment dispersibility and substrate adhesion, and is particularly useful as a raw material resin for paints. On the other hand, by introducing a carboxyl group, an internal catalytic effect such as melamine curing and urethane curing can be exhibited.

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Claims (1)

[Claims] 1. (a) 30 to 70 mol% of a fluorinated olefin, (b) 30 to 70 mol% of an unsaturated monomer represented by the general formula A,
(C) 0.5 to 10 mol% of a functional group-containing unsaturated monomer is copolymerized in the presence of a radical polymerization initiator having a carboxylic acid unit, and a terminal carboxylic acid group-containing fluorine-containing copolymer is obtained. Manufacturing method. A: CH ₂ = CR ¹ O (C = 0) _k R ² (However, R ¹ is H or CH ₃ , R ²
Is an alkyl group or a cycloalkyl group, k is 0 or 1
Is)