JPH06184206A - 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 the disruption of the ozone stratosphere by polymerizing monomers consisting mainly of a fluoroolefin in a perfluorooxane as a polymerization medium. CONSTITUTION:A perfluorooxane as a polymerization medium, tetrafluoroethylene, (perfluorobutyl)ethylene and ethylene as monomers, and the 1wt.% perfluorooxane solution of di(perfluorobutyryl)peroxyde as a polymerization initiator are charged to a dearated stainless steel reaction vessel, started in their polymerization at 50 deg.C, and subsequently polymerized under a reaction pressure of 8.7kg/cm<2> 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., and having a high mol.wt. in the polymerization medium reduced in environmental disruption such as ozone stratosphere destruction.

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 which 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 fluoropolymer.

[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 fluoropolymers. As a polymerization medium for the solution polymerization methods or suspension polymerization methods, chlorofluorocarbons and the like are 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 fluoropolymer.

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 fluoropolymer, and has a large ozone depletion coefficient. The present invention has been made for the purpose of providing a method for efficiently producing a fluoropolymer excellent in heat resistance, solvent resistance and chemical resistance without using

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that perfluorooxane has a low chain transfer property, and by using it as a polymerization medium, It was found that the purpose could be achieved.

That is, the present invention is characterized by using perfluorooxane as the polymerization medium in producing a fluoropolymer containing a fluoroolefin unit as a main constituent unit by polymerization in a polymerization medium. A method for producing a fluoropolymer is provided.

The fluoropolymer containing a fluoroolefin unit as a main constituent unit in the present invention is obtained by polymerizing the fluoroolefin monomer alone in perfluorooxane or by copolymerizing with the 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 is preferably fluorocarbon having 2 or 3 carbon atoms in view of polymerizability and properties of the resulting polymer. 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 ) _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) and the like. 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.

Although perfluorooxane is used as the polymerization medium in the present invention, it is also possible to use perfluorooxane containing an inert solvent such as water. The amount of the polymerization medium used may vary depending on the type of the monomer to be polymerized, but is 3 to 10 relative to the weight of the total amount of the monomers.
The amount is 0 times, preferably 5 to 50 times.

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 perfluorooxane. However, a compound having a large chain transfer constant may be dissolved in perfluorooxane 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 include hydrocarbons such as hexane,
Hydrofluorocarbons such as CF ₂ H ₂ , CF ₃
Hydrochlorofluorocarbons such as CF ₂ CHCl ₂ , ketones such as acetone, alcohols such as methanol and ethanol, and mercaptans such as methyl mercaptan. The addition amount may vary depending on the magnitude of the chain transfer constant of the compound used, but may be about 0.01 to 50% by weight with respect to the polymerization medium.

[0017]

【Example】

Example 1 A stainless steel reaction vessel having an internal volume of 1.2 liter was degassed, and 1352 g of perfluorooxane and 0.2 of hexane were used.
g, (perfluorobutyl) ethylene 1.8 g, tetrafluoroethylene 85 g, and ethylene 5.9 g were charged. While maintaining the temperature at 50 ° C., a 1 wt% perfluorooxane solution of di (perfluorobutyryl) peroxide was charged as a polymerization initiator to start the reaction. During the reaction, a mixed gas of tetrafluoroethylene and ethylene (molar ratio C ₂ F ₄ / C ₂ H ₄ = 53/47) was introduced to maintain the reaction pressure at 8.7 kg / cm ² . The polymerization initiator was charged intermittently so that the polymerization rate was almost constant, and 12 cc in total was charged. After 3 hours, 65 g of a white copolymer was obtained as a slurry. The copolymer has a melting point of 272 ° C., a thermal decomposition starting point of 365 ° C., and a temperature of 300 ° C.
Good compression moldings were obtained at molding temperatures of. The tensile strength of the molded product is 475 kg / cm ² , and the tensile elongation is 380.
%Met.

Example 2 A stainless steel reactor having an internal volume of 1.2 liter was degassed, and 1410 g of perfluorooxane and 0.2 of hexane were used.
g, perfluoro (propyl vinyl ether) 32 g,
80 g of tetrafluoroethylene was charged. Temperature 50
The temperature was maintained at 0 ° C., and a 1 wt% perfluorooxane solution of di (perfluorobutyryl) peroxide was charged as a polymerization initiator to start the reaction. During the reaction, tetrafluoroethylene was introduced into the system and the reaction pressure was 5.0 kg /
It was held at 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, 76 g of a white copolymer was obtained as a slurry. The copolymer had a melting point of 308 ° C. and a thermal decomposition starting point of 455 ° C., and gave a good compression molded product at a molding temperature of 340 ° C. Tensile strength of the molded product is 375kg
/ Cm ² , and the tensile elongation was 380%.

Example 3 400 g of hexafluoropropylene was charged in place of 32 g of perfluoro (propyl vinyl ether), and the amount of perfluorooxane charged was 1 in place of 1410 g.
Polymerization was performed in the same manner as in Example 2 except that the amount was 000 g, and after 3.5 hours, 67 g of a white copolymer was obtained as a slurry. The copolymer had a melting point of 285 ° C. and a thermal decomposition starting point of 440 ° C., and gave a good compression molded product at a molding temperature of 340 ° C. Tensile strength of molded product is 354
The kg / cm ² and the tensile elongation were 320%.

Comparative Example 1 A stainless steel reaction vessel 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. for 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 1,255 g of 1,1,2-trichlorotrifluoroethane was charged instead of charging perfluorooxane, and 1,1-dichloro-2,2,3 was used instead of 0.2 g of hexane as a chain transfer agent. , 3,3-Pentafluoropropane 1
Polymerization was carried out in the same manner as in Example 1 except that 3.5 g was charged, and after 2 and a half hours, 48 g of a white copolymer was obtained as a slurry. The copolymer had a melting point of 274 ° C. and a thermal decomposition starting point of 352 ° C., and gave a good compression molded product at a molding temperature of 300 ° C. Tensile strength of molded product is 431k
The g / cm ² and tensile elongation were 450%.

[0022]

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

Claims (2)

[Claims] 1. When producing a fluoropolymer containing a fluoroolefin unit as a main constituent unit by polymerization in a polymerization medium, perfluorooxane is used as the polymerization medium. Production method. 2. The method according to claim 1, wherein the fluoropolymer is a tetrafluoroethylene / ethylene copolymer, a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene / hexafluoropropylene copolymer. .