JPH06184205A - 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 perfluorobenzene as polymerization medium. CONSTITUTION:A perfluorobenzene as a polymerization medium, tetrafluoroethylene, (perfluorobutyl)ethylene and ethylene as monomers, and the 1wt.% perfluorobenzene solution of di(perfluorobutyryl)peroxide, as a polymerization initiator are charged to a deaerated stainles 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 tetafluoroethylene 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]

DISCLOSURE OF THE INVENTION As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that perfluorobenzene has a low chain transfer property, and by using this as a polymerization medium, its purpose is improved. It has been found that

That is, the present invention is characterized by using perfluorobenzene 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 constitutional unit in the present invention is a fluoropolymer in which a fluoroolefin monomer is polymerized alone in perfluorobenzene or is copolymerized with the fluoroolefin monomer. It is produced by copolymerizing a monomer other than the olefin monomer.

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

In the present invention, perfluorobenzene is used as the polymerization medium, but it is also possible to use perfluorobenzene 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 of 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 perfluorobenzene. However, a compound having a large chain transfer constant may be dissolved in perfluorobenzene 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 perfluorobenzene and 0.2 of hexane.
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% perfluorobenzene 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, 60 g of a white copolymer was obtained as a slurry. The copolymer has a melting point of 273 ° C., a thermal decomposition starting point of 355 ° C., and a temperature of 300 ° C.
Good compression moldings were obtained at molding temperatures of. The tensile strength of the molded product is 455 kg / cm ² , and the tensile elongation is 370.
%Met.

Example 2 A stainless steel reaction vessel having an internal volume of 1.2 liter was degassed, and 1410 g of perfluorobenzene 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% perfluorobenzene 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 2.7 hours, 64 g of a white copolymer was obtained as a slurry. The copolymer had a melting point of 306 ° C. and a thermal decomposition starting point of 467 ° C., and gave a good compression molded product at a molding temperature of 340 ° C. Tensile strength of molded product is 348kg
/ Cm ² , and the tensile elongation was 3750%.

Example 3 400 g of hexafluoropropylene was charged in place of 32 g of perfluoro (propyl vinyl ether), and the amount of perfluorobenzene charged was 1 in place of 1410 g.
Polymerization was carried out in the same manner as in Example 2 except that the amount was 000 g, and after 3.5 hours, 76 g of a white copolymer was obtained as a slurry. The copolymer had a melting point of 282 ° 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 328
The kg / cm ² and tensile elongation were 348%.

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 perfluorobenzene, and 1,1-dichloro-2,2,3,3 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. it can.

Claims (2)

[Claims] 1. A process for producing a fluoropolymer containing a fluoroolefin unit as a main constituent unit by polymerization in a polymerization medium, wherein perfluorobenzene is used as the polymerization medium. Law. 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. .