JPH06157612A - Production of fluoropolymer - Google Patents

Abstract

PURPOSE:To produce a fluoropolymer excellent in resistances to heat, solvents, and chemicals while using a polymn. medium hardly polluting the environment. CONSTITUTION:A compd. of the formula: CF2ClCF2CHClF is used as the polymn. medium in the process for producing a fluoropolymer having fluoroolefin units as the main structural units.

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-based polymer, and more specifically, it uses a polymerization medium that causes less environmental damage and has excellent heat resistance, solvent resistance, chemical resistance and the like. The present invention relates to a method for efficiently producing a fluoropolymer.

[0002]

2. Description of the Related Art In recent years, since fluorine-based polymers are polymeric materials having excellent heat resistance, solvent resistance and chemical resistance,
Utilizing its characteristics, it is used for various purposes.

Solution polymerization method, suspension polymerization method and emulsion polymerization method are known as a method for producing a fluorine-based polymer, and a solvent such as chlorofluorocarbon is not used as a polymerization medium in the solution polymerization method or suspension polymerization method. 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 the production of fluoropolymers.

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 a fluoropolymer, and has a large ozone depletion coefficient. It was made for the purpose of providing a method for efficiently producing a fluorine-based polymer having excellent heat resistance, solvent resistance and chemical resistance without using

[0007]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, CF ₂ ClC has been obtained.
It has been found that F ₂ CHClF has a low chain transfer property, and the purpose thereof can be achieved by using it as a polymerization medium.

That is, the present invention is characterized in that CF ₂ ClCF ₂ CHClF is used as the polymerization medium when producing a fluoropolymer containing a fluoroolefin unit as a main constituent unit by polymerization in a polymerization medium. Is a method for producing a fluorine-based polymer.

The fluorine-containing polymer containing a fluoroolefin unit as a main constituent unit in the present invention is CF ₂ Cl.
It is produced by polymerizing a fluoroolefin monomer alone in CF ₂ CHClF or by copolymerizing the following monomers other than the fluoroolefin monomer that is copolymerized with the fluoroolefin 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 ) 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, CF ₂ is used as the polymerization medium.
It is also possible to use ClCF ₂ CHClF 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 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 is appropriately selected from those conventionally used according to the polymerization method. be able to. For example,
Di- (chlorofluoroacyl) -peroxide, di-
(Perfluoroacyl) -peroxide, di- (ω-
Hydroperfluoroacyl) -peroxide, t-
Examples thereof include organic peroxides such as butyl peroxyisobutyrate and diisopropyl peroxydicarbonate, and azo compounds such as azobisisobutyronitrile. The amount of the polymerization initiator used depends on the type, the polymerization reaction conditions, etc.
Although it can be appropriately changed, it is usually 0.005 to 5% by weight, particularly 0.05 to 5% by weight based on the whole monomers to be polymerized.
About 0.5% by weight is adopted.

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. This compound is CF ₂ ClCF ₂ C.
Must be soluble in HClF. However, a compound having a large chain transfer constant may be dissolved in CF ₂ ClCF ₂ CHClF even in consideration of the ease of controlling the molecular weight. It is also desirable to have a low ozone depletion potential. Examples of compounds that meet these requirements include hydrocarbons such as hexane, hydrofluorocarbons such as CF ₂ H ₂ , ketones such as acetone, alcohols such as methanol and ethanol, and mercaptans such as methyl mercaptan. is there. 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 1 A stainless steel reaction vessel having an internal volume of 1.2 liter was degassed, and 1410 g of CF ₂ ClCF ₂ CHClF, 1.8.
g (perfluorobutyl) ethylene, 85 g tetrafluoroethylene, and 5.9 g ethylene were charged. While maintaining the temperature at 50 ° C., a 1 wt% perfluorohexane solution of di (perfluorobutyryl) -peroxide as a polymerization initiator was charged 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 into the system,
The reaction pressure was maintained at 8.1 kg / cm ² . The polymerization initiator was charged intermittently so that the polymerization rate was almost constant, and a total of 24 cc was charged. After 3 hours, 68 g of a white copolymer was obtained as a slurry. The copolymer has a melting point of 2
The temperature was 74 ° C and the starting point of thermal decomposition was 352 ° C, and a good compression molded product was obtained at a molding temperature of 300 ° C. The tensile strength of the molded product was 465 kg / cm ² , and the tensile elongation was 440%.

Example 2 A stainless steel reaction vessel having an internal volume of 1.2 liter was degassed, and 1420 g of CF ₂ ClCF ₂ CHClF, 32 g
Of perfluoropropyl vinyl ether and 80 g of tetrafluoroethylene were charged. While maintaining the temperature at 50 ° C., a 1 wt% perfluorohexane solution of di (perfluorobutyryl) -peroxide as a polymerization initiator was charged to start the reaction. During the reaction, tetrafluoroethylene was introduced into the system to keep the reaction pressure at 5.0 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 3.2 hours, 62 g of a white copolymer was obtained as a slurry. The copolymer has a melting point of 307 ° C. and a thermal decomposition starting point of 480 ° C.
And a good compression molded product was obtained at a molding temperature of 340 ° C. The tensile strength of the molded product is 392 kg / cm ² ,
The tensile elongation was 367%.

Example 3 400 g of hexafluoropropylene was charged in place of 32 g of perfluoropropyl vinyl ether, and CF ₂ C was added.
Polymerization was carried out in the same manner as in Example 2 except that the charged amount of 1CF ₂ CHClF was changed to 1000 g instead of 1420 g. After 3.5 hours, 67 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 445 ° C., and gave a good compression molded product at a molding temperature of 340 ° C. The tensile strength of the molded product is 34
The tensile elongation was 4 kg / cm ² and 340%.

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

Reference Example 1 Example 1 was repeated except that 1255 g of 1,1,2-trichlorotrifluoroethane was charged instead of CF ₂ ClCF ₂ CHClF, and 1.5 g of hexane was charged as a chain transfer agent.
Polymerization was carried out in the same manner as in, 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. The tensile strength of the molded product is 431 kg / cm ² , and the tensile elongation is 450%.
Met.

[0022]

According to the method of the present invention, the ozone depletion effect is much lower, and the desired fluorine-containing polymer can be produced with an efficiency comparable to that in the case of using a conventional trichlorotrifluoroethane solvent.

Claims (2)

[Claims] 1. When producing a fluorine-containing polymer containing a fluoroolefin unit as a main constituent unit by polymerization in a polymerization medium, CF ₂ Cl is used as the polymerization medium.
A method for producing a fluorine-based polymer, which comprises using CF ₂ CHClF. 2. The method according to claim 1, wherein the fluorine-based polymer is a tetrafluoroethylene / ethylene copolymer, a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene / hexafluoropropylene copolymer. .