JPH021165B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing copolymers. More specifically, the present invention relates to a method for producing a copolymer of perfluoroacrylic acid or a derivative thereof and another fluorine-containing polymerizable monomer by emulsion polymerization.

The production of copolymers by copolymerizing perfluoroacrylic acid or its derivatives with other fluorine-containing polymerizable monomers is described in Japanese Patent Publication No. 55-23567. This copolymer has better heat resistance, chemical resistance, electrical properties, etc. than homopolymers of fluorine-containing polymerizable monomers or mutual copolymers thereof. It has the advantage of having better crosslinking moldability and crosslinked product properties without sacrificing desirable properties. A copolymer exhibiting such favorable properties is produced by a copolymerization reaction of perfluoroacrylic acid or a derivative thereof and another fluorine-containing polymerizable monomer,
Although the above-mentioned patent publication states that the copolymerization reaction may be carried out by any polymerization method such as emulsion polymerization, suspension polymerization, or bulk polymerization, only the bulk polymerization method is shown as an example. In the emulsion polymerization method, the polymerization reaction does not proceed as shown in the comparative example below.

When this copolymerization reaction is carried out by emulsion polymerization method,
The present inventors have conducted various studies regarding the reasons why the polymerization reaction does not substantially proceed. Perfluoroacrylic acid or its derivatives do not undergo normal radical polymerization reactions when used alone, and even when copolymerized, the rate of radical polymerization is slow. Since it is more hydrophilic than polymerizable monomers, it was thought that the formation of micelles, which is thought to be an important factor for the initiation reaction of emulsion polymerization, was hindered. Based on this idea, in order to form stable micelles in the initial stage of polymerization and to effectively copolymerize perfluoroacrylic acid or its derivatives, a polymerization method similar to the seed polymerization method was developed. It was discovered here that adopting this method is extremely effective, and the present invention has been completed.

Therefore, the present invention relates to a method for producing a copolymer using an emulsion polymerization method, and the production of this copolymer involves the following steps: This is accomplished by homopolymerizing other fluorine-containing polymerizable monomers and subsequently carrying out a copolymerization reaction between the comonomers.

Perfluoroacrylic acid or its derivatives include perfluoroacrylic acid, perfluoromethacrylic acid or their esters, metal salts, amides, nitriles, etc., especially alkyl esters such as methyl, ethyl, propyl, allyl esters, benzyl esters, etc. Ester, toluyl ester, etc. are preferred.

Other fluorine-containing polymerizable monomers copolymerized with these include, for example, tetrafluoroethylene, trifluoroethylene, trifluorochloroethylene, 1,1-difluoro-2,2-dichloroethylene, 1,1 -difluoro-2-chloroethylene, hexafluoropropylene, pentafluoropropylene, vinylidene fluoride, vinyl fluoride,
1 such as hexafluoroisobutylene, octafluoroisobutylene, perfluorobutadiene, perfluorovinylcyclohexane, trifluoronitrosomethane, trifluoronitrosoethane, etc.
A species or two or more species may be used.

Emulsion polymerization in which the polymerization reaction is carried out is carried out using common fluorocarbon emulsifiers, such as sodium salts of perfluorooctanoic acid, p-perfluorohexenoxybenzenesulfonic acid, p-fluorohexenoxybenzoic acid, perfluoroether carboxylic acid, etc. It is carried out in the presence of an emulsifier consisting of potassium salts, ammonium salts, etc.

A radical polymerization initiator and, if necessary, a degree of polymerization regulator such as chloroform, carbon tetrachloride, and acetone are added to the polymerization system. In a polymerization reaction conducted in an inert atmosphere such as nitrogen gas, other fluorine-containing polymerizable monomers are first homopolymerized, and the initiation and constant continuation of this polymerization reaction is caused by a decrease in the pressure inside the reaction vessel. Once confirmed, perfluoroacrylic acid or a derivative thereof is charged alone or together with a fluorine-containing polymerizable monomer and copolymerized again at a predetermined temperature, generally about 30 to 120°C. Then, when the reaction pressure has decreased, a fluorine-containing polymerizable monomer is further charged to continue the copolymerization reaction, and a predetermined amount of fluorine-containing polymerizable monomer is charged, and the pressure is approximately 10 kg/cm. The reaction is terminated when the temperature drops to ² . By continuing the polymerization reaction in this way for about 1 to 10 hours, a copolymer is obtained as a white and stable latex, and if necessary, by salting out, a white powdery copolymer can be obtained. Can be done.

This copolymer, as also shown in the following table,
It has particularly good solubility in various solvents and can therefore be used as an oil-based paint.

Table: Solvents that can form a 10% polymer solution at room temperature (1) Vinylidene fluoride homopolymer: dimethylformamide, dimethylacetamide (2) Vinylidene fluoride-hexafluoropropylene (copolymerization weight ratio 10:3) copolymer : Dimethylformamide, dimethylatomamide, dimethyl sulfoxide [hot: acetone, ethyl acetate, N-methylpyrrolidone, diacetone alcohol, dioxane, tetrahydrofuran, methyl ethyl ketone] (3) Methyl trifluoroacrylate-vinylidene fluoride (copolymerization) Weight ratio 10:1) Copolymer: dimethylformamide, dimethylacetamide,
Dimethyl sulfoxide [hot: acetone/dimethylformamide (5/5), nitropropane/dimethylformamide (5/5)] (4) Methyl trifluoroacrylate-vinylidene fluoride-hexafluoropropylene (copolymerization weight ratio 10) :2:1) Ternary copolymer: dimethylformamide, dimethylacetamide, dimethyl sulfoxide, ethyl acetate, acetone, ethyl malonate, diacetone alcohol, dioxane, methyl ethyl ketone, tetrahydrofuran, and perfluoroacrylic acid or its derivatives. Since the copolymer latex can be easily thickened with alkali such as ammonia, it can also be used as a water-based fluororesin paint.

As described above, the method according to the present invention enables copolymerization of perfluoroacrylic acid or its derivatives with other fluorine-containing polymerizable monomers by emulsion polymerization, which is superior to bulk polymerization. disadvantages,
In other words, it effectively eliminates the following disadvantages: difficulty in removing reaction heat, post-processing steps such as reprecipitation, drying, and pulverization required to obtain the resulting copolymer, and low polymerization rate. The present invention has the effect that a latex, which has an effective use in itself, can be obtained at a polymerization rate of almost quantitative or close to that.

Next, the present invention will be explained with reference to examples.

Example 1 A 500 ml autoclave was charged with 200 ml of water, 0.2 g of sodium perfluorohexenoxybenzenesulfonate, and 3 ml of chloroform, and the autoclave was thoroughly purged with nitrogen. Then, vinylidene fluoride 15
g, 0.4 g of ammonium persulfate and 10 ml of water, and the internal temperature was raised to 80°C. When the polymerization reaction has started and the pressure inside the autoclave has decreased from about 40 kg/cm ² to about 5 kg/cm ² , 7 g of methyl trifluoromethacryl and 19 g of vinylidene fluoride are charged. Continuing the polymerization reaction at 80℃, the pressure increases again to about 40℃.
When the weight drops from Kg/cm ² to about 5 Kg/cm ² , repeat the operation of adding vinylidene fluoride. In the end, 61
g of vinylidene fluoride was charged, and the polymerization reaction was terminated about 3 hours after the start of the reaction.

A white and stable latex with a solid content of 23.9%.
324g was obtained, resulting in a polymerization rate of 94.6%.
The methyl trifluoroacrylate-vinylidene fluoride copolymer obtained by salting out this latex was [η]=0.42 (30
℃), its infrared absorption spectrum shows a slightly broad absorption of carboxyl groups around 1750 cm ^-1 , and it is soluble in solvents such as acetone and ethyl acetate at room temperature.

Comparative Example A 500 ml autoclave was charged with 200 ml of water, 0.2 g of sodium perfluorohexenoxybenzenesulfonate, and 3 ml of chloroform, and thoroughly purged with nitrogen. Then ammonium persulfate
0.4 g, 10 ml of water, 5 g of methyl trifluoroacrylate, and 47 g of vinylidene fluoride. 80
℃ to carry out a polymerization reaction, but almost no decrease in pressure was observed, and even after about 3 hours, no latex was formed and only a dark green aqueous solution was present.

Example 2 530 ml of water, 5.3 g of perfluoroether carboxylic acid, and 0.5 g of sodium carbonate are charged into an autoclave having a capacity of 1, and the autoclave is thoroughly purged with nitrogen.
Then 58 g of hexafluoropropylene, 80 g of vinylidene fluoride and 2.6 g of ammonium persulfate.
and raise the internal temperature to 70℃. When the polymerization reaction starts and the pressure inside the autoclave drops from about 40 kg/cm ² to about 5 kg/cm ² , 26 g of methyl trifluoroacrylate and 30 g of vinylidene fluoride are added.
g was injected under pressure, and the polymerization reaction was continued at 80°C. When the pressure dropped again from about 40Kg/ ^cm2 to about 5Kg/ ^cm2 , the operation of adding vinylidene fluoride was repeated, and finally
247g of vinylidene fluoride was charged. The polymerization reaction is terminated approximately 5.5 hours after the start of the reaction.

A white and stable latex with a solid content concentration of 34.9%.
783g was obtained, resulting in a polymerization rate of 83.6%.
The methyl trifluoroacrylate-vinylidene fluoride-hexafluoropropylene terpolymer obtained by salting out this latex has a slightly broad absorption of carboxyl groups near 1750 cm ^-1 in the infrared absorption spectrum. When concentrated ammonia water is added to this latex, it instantly turns brown, thickens, and becomes creamy. This also supports the existence of carboxyl groups in the copolymer.

Claims (1)

[Claims] 1. When copolymerizing perfluoroacrylic acid or a derivative thereof with another fluorine-containing polymerizable monomer, after homopolymerizing the other fluorine-containing polymerizable monomer, the above-mentioned comonomer is A method for producing a copolymer by an emulsion polymerization method, which is characterized by carrying out a copolymerization reaction between molecules.