JPH06184207A - Production of fluorine-containing polymer - Google Patents

Abstract

PURPOSE:To efficiently produce a polymer good in heat resistance, solvent resistance and chemical resistance in a polymerization medium little in environment by polymerizing monomers consisting mainly of a fluoroolefin in a perfluoroalkylether as a polymerization medium. CONSTITUTION:A perfluoroalkylether (e.g. diperfluoropropylether) as a polymerization medium, 1,1-dichloro-2,2,3,3,3-pentafluoropropane as a chain transfer agent, tetrafluoroethylene, (perfluorobutyl)ethylene and ethylene as monomers, and di(perfluorobutyryl)peroxide as a polymerization initiator, etc., are charged to a deaerated stainless steel reaction vessel, and subsequently reacted at 50 deg.C for 3hr, while charging the mixture of tetrafluoroethylene with ethylene in the reaction system, thus efficiently producing the objective fluorine-containing polymer good in heat resistance, solvent resistance, chemical resistance, etc., in the polymerization medium reduced in environmental disruption such as ozone stratosphere disruption.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing a fluorine-containing polymer, and more specifically, it uses a polymerization medium that causes less environmental damage and has good heat resistance, solvent resistance, chemical resistance and the like. The present invention relates to a method for efficiently producing a fluorine-containing polymer.

[0002]

Fluorine-containing polymers are polymeric materials having excellent heat resistance, solvent resistance, chemical resistance, etc., and are utilized in various applications by taking advantage of their characteristics.

Solution polymerization methods, suspension polymerization methods, and emulsion polymerization methods are known as methods for producing a fluorine-containing polymer. As a polymerization medium for the solution polymerization method or the suspension polymerization method, chlorofluorocarbon or the like is not used. An active solvent is usually used from the viewpoint of giving a high molecular weight copolymer and the rate of polymerization.
Specific examples of the chlorofluorocarbon include trichlorofluoromethane, dichlorodifluoromethane, trichlorotrifluoroethane, dichlorotetrafluoroethane and the like, but trichlorotrifluoroethane is mainly used from the viewpoint of handling.

By the way, in recent years, ozone layer depletion has been taken up internationally as a global environmental destruction problem, and chlorofluorocarbon has been pointed out as a causative substance thereof, and it is heading for global abolition. For this reason, it has become necessary to stop the use of chlorofluorocarbons used in producing the fluorine-containing polymer.

As an alternative to this chlorofluorocarbon, hydrofluorocarbons containing hydrogen atoms have been proposed because they have a low ozone depletion potential. However, conventionally, a substance having a C—H bond has been known to exhibit chain transfer property to a fluoroolefin, and hydrochlorofluorocarbon containing a hydrogen atom is used for producing a high molecular weight fluoroolefin polymer. It was thought to be difficult to use as a polymerization medium.
Although t-butanol (Japanese Patent Publication No. 52-24073) is known as a substitute for other polymerization media, it is necessary to polymerize at a high pressure in order to obtain a sufficiently high molecular weight.

[0006]

Under the circumstances described above, the present invention is a chlorofluorocarbon which has a high polymerization rate, can sufficiently increase the molecular weight of the fluorine-containing polymer, and has a large ozone depletion coefficient. The present invention has been made for the purpose of providing a method for efficiently producing a fluorine-containing polymer having excellent heat resistance, solvent resistance and chemical resistance without using.

[0007]

The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, perfluoroalkyl ether has a low chain transfer property. It was found that the purpose could be achieved.

That is, the present invention is characterized in that a perfluoroalkyl ether is used as the polymerization medium in producing a fluorine-containing polymer containing a fluoroolefin unit as a main constituent unit by polymerization in a polymerization medium. Provided is a method for producing a fluorine-containing polymer.

The fluoropolymer containing a fluoroolefin unit as a main constituent unit in the present invention is obtained by polymerizing a fluoroolefin monomer alone in a perfluoroalkyl ether or by copolymerizing with a fluoroolefin monomer. It is produced by copolymerizing a monomer other than the fluoroolefin monomer.

The fluoroolefin monomer used in the present invention is an olefin having at least one fluorine atom in the molecule, and from the viewpoint of polymerizability and properties of the resulting polymer, it is preferably fluorocarbon having 2 or 3 carbon atoms. It is an olefin monomer.

Specific examples of such a fluoroolefin monomer include CF ₂ ═CF ₂ , CF ₂ ═CFCl, C
F ₂ = fluoro ethylene type such as CH ₂ , CF ₂ = CF
A fluoropropylene-based material such as CF ₃ or CF ₂ ═CHCF ₃ . These fluoroolefin monomers may be used alone or in combination of two or more.

CF ₃ CF ₂ CF ₂ CF ₂ CH is used as a monomer which is copolymerized with these fluoroolefin monomers.
= CH ₂ or _{CF 3 CF 2 CF 2 CF 2} CF = CH , such ₂ carbon atoms of the perfluoroalkyl group having 4 to 12 (perfluoroalkyl) ethylene, R _f (OCFXCF
₂ ) Perfluorovinyl ether such as _m OCF = CF ₂ (wherein R _f is a perfluoroalkyl group having 1 to 6 carbon atoms, X is a fluorine atom or a trifluoromethyl group, and m is an integer of 1 to 6). System, CH ₃ OC (= O) CF ₂ CF ₂
CF ₂ OCF = CF ₂ or FSO ₂ CF ₂ CF ₂ OCF
(CF ₃₎ CF may be used in combination with vinyl ether having ₂ OCF = CF ₂ easily carboxylic acid group or a sulfonic acid group can be converted into a group such as. Further, it may be combined with an olefin-based monomer such as ethylene, propylene or isobutylene.

In the present invention, it is necessary to use perfluoroalkyl ether as a polymerization medium. If the boiling point of perfluoroalkyl ether is too low, it becomes a gas at room temperature and it is inconvenient to handle, and if the boiling point is too high, it takes time and effort to separate the polymer and the solvent. The most preferred compound is diperfluoropropyl ether or perfluoro (butyl methyl ether).

In the present invention, a perfluoroalkyl ether may be used as a polymerization medium containing an inert solvent such as water. The amount of the polymerization medium used can vary depending on the type of monomer to be polymerized,
The amount is 3 to 100 times, preferably 5 to 50 times the weight of the total amount of the monomers.

In the present invention, either a solution polymerization method or a suspension polymerization method can be adopted as the polymerization method, and the polymerization initiator to be used can be appropriately selected from those conventionally used according to the polymerization method. it can. For example, organic peroxides such as di (chlorofluoroacyl) peroxide, di (perfluoroacyl) peroxide, di (ω-hydroperfluoroacyl) peroxide, t-butylperoxyisobutyrate and diisopropylperoxydicarbonate. Examples thereof include oxides and azo compounds such as azobisisobutyronitrile. The amount of the polymerization initiator used can be appropriately changed depending on the type, the polymerization reaction conditions, etc.
Normally 0.005 per total monomer to be polymerized
˜5 wt%, especially 0.05 to 0.5 wt%.

In the polymerization reaction of the present invention, a wide range of reaction conditions can be adopted without particular limitation. For example, the polymerization reaction temperature can be selected as an optimum value depending on the type of the polymerization initiation source and the like, but is usually about 0 to 100 ° C., and particularly 3
A temperature of about 0 to 90 ° C can be adopted. Further, the reaction pressure can be appropriately selected, but it is usually preferable to adopt ² to 100 kg / cm ² , particularly 5 to 20 kg / cm ² .
In the present invention, the polymerization can be advantageously carried out without requiring an excessive reaction pressure, but a higher pressure can be adopted and a reduced pressure condition is also possible. Further, the present invention can be carried out by an appropriate operation such as a batch system or a continuous system.

In the polymerization in the present invention, a compound having a chain transfer property is usually added for the purpose of controlling the molecular weight of the polymer, but this compound needs to be soluble in perfluoroalkyl ether. However, a compound having a large chain transfer constant may be dissolved in a perfluoroalkyl ether even in consideration of the ease of controlling the molecular weight. It is also desirable to have a low ozone depletion potential. Compounds that meet these requirements are, for example, hydrocarbons such as hexane, hydrofluorocarbons such as CF ₂ H ₂ , hydrochlorofluorocarbons such as CF ₃ CF ₂ CHCl ₂ , ketones such as acetone, methanol, ethanol, etc. Alcohols or mercaptans such as methyl mercaptan. The addition amount may vary depending on the magnitude of the chain transfer constant of the compound used, but is about 0.01 to 50% by weight with respect to the polymerization medium.
Weight percentages may be employed.

[0018]

【Example】

 Example 1 A stainless steel reaction vessel having an internal volume of 1.2 liters was degassed.
1352 g of diperfluoropropyl ether, chain
1,1-dichloro-2,2,3,3,3-as a transfer agent
13.5 g of pentafluoropropane, (perfluorobutene
Chill) ethylene 1.8 g, tetrafluoroethylene 85
g and 5.9 g of ethylene were charged. Keep temperature at 50 ℃
As a polymerization initiator, di (perfluorobutyryl) para
-Oxide 1 wt% diperfluoropropyl ether
Solution was charged to start the reaction. During the reaction,
Mixed gas of trafluoroethylene and ethylene (molar ratio C
₂ F_Four / C₂ H_Four = 53/47) and the reaction pressure
8.9 kg / cm² Held in. Polymerization initiator is the polymerization rate
Is intermittently charged so that
c prepared. After 3 hours, 63 g of white copolymer was slurried.
-It was obtained as a condition. The copolymer has a melting point of 276 ° C., a heat
Decomposition start point is 335 ° C, good at molding temperature of 300 ° C
A compression molded product was obtained. Tensile strength of molded product is 4
52 kg / cm ² The tensile elongation was 475%.

Example 2 A stainless steel reaction vessel having an internal volume of 1.2 liter was degassed, and 1410 g of diperfluoropropyl ether, 32 g of perfluoropropyl vinyl ether, 1,1-dichloro-2,2,3,3,3. -Pentafluoropropane 1
3.5 g and tetrafluoroethylene 80 g were charged.
While maintaining the temperature at 50 ° C., a 1 wt% diperfluoropropyl ether solution of di (perfluorobutyryl) peroxide was charged as a polymerization initiator to start the reaction. During the reaction, tetrafluoroethylene was introduced into the system,
The reaction pressure was kept at 5.2 kg / cm ² . The polymerization initiator was intermittently charged so that the polymerization rate became almost constant, and a total of 7 cc was charged. After 2.2 hours, 73 g of a white copolymer was obtained as a slurry. The copolymer had a melting point of 307 ° C. and a thermal decomposition starting point of 460 ° C., and gave a good compression molded product at a molding temperature of 340 ° C. The tensile strength of the molded product was 405 kg / cm ² , and the tensile elongation was 350%.

Example 3 Polymerization was carried out in the same manner as in Example 2 except that 400 g of hexafluoropropylene was charged instead of 32 g of perfluoropropyl vinyl ether, and 1000 g was added instead of 1410 g of diperfluoropropyl ether. After 3.5 hours, 48 g of a white copolymer was obtained as a slurry. The copolymer has a melting point of 285 ° C.,
The thermal decomposition starting point was 450 ° C, and a good compression molded product was obtained at a molding temperature of 340 ° C. The tensile strength of the molded product was 332 kg / cm ² , and the tensile elongation was 340%.

Comparative Example 1 A reaction vessel made of stainless steel having an internal volume of 1.2 liters was charged with 500 g of deoxygenated water, 200 g of t-butanol and 0.65 g of disuccinic acid peroxide, and the temperature was kept at 65 ° C. to carry out the reaction. went. During the reaction, a mixed gas of tetrafluoroethylene and ethylene (molar ratio C ₂ F ₄ / C ₂ H ₄ = 53
/ 47) was introduced and the reaction pressure was maintained at 9 kg / cm ² . After 4 hours, 24.6 g of a white copolymer was obtained.
The copolymer had a melting point of 269 ° C. and a thermal decomposition starting temperature of 361 ° C. The molded product compression-molded at 300 ° C. had a low molecular weight and was brittle.

Reference Example 1 Instead of charging diperfluoropropyl ether 1,
Polymerization was carried out in the same manner as in Example 1 except that 1,255 g of 1,2-trichlorotrifluoroethane was charged, and after 2 and a half hours, 48 g of a white copolymer was obtained as a slurry. The copolymer has a melting point of 274 ° C and a thermal decomposition starting point of 352 ° C.
And a good compression molded product was obtained at a molding temperature of 300 ° C. The tensile strength of the molded product is 431 kg / cm ² ,
The tensile elongation was 450%.

[0023]

According to the method of the present invention, a desired fluorine-containing polymer can be produced by using a polymerization medium having a much lower ozone depletion effect with an efficiency comparable to that obtained by using a conventional trichlorotrifluoroethane solvent. can do.

Claims (3)

[Claims] 1. When producing a fluorine-containing polymer containing a fluoroolefin unit as a main constitutional unit by polymerization in a polymerization medium, a perfluoroalkyl ether is used as the polymerization medium. Production method. 2. The method according to claim 1, wherein the perfluoroalkyl ether is diperfluoropropyl ether or perfluoro (butyl methyl ether). 3. The method according to claim 1, wherein the fluorine-containing polymer is a tetrafluoroethylene / ethylene copolymer, a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene / hexafluoropropylene copolymer. .