JPH06157611A - 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: A(CH2)nOH (wherein A is perhaloalkyl; and (n) is 1 or 2) 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 which 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. As a polymerization medium of the solution polymerization method or 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 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 As a result of intensive studies for achieving the above-mentioned object, the inventors of the present invention have shown that the compound shown in Chemical formula 2 (wherein A is a perhaloalkyl group, n is 1 or 2). It has been found that (1) has a low chain transfer property, and that its purpose can be achieved by using this as a polymerization medium.

[0008]

Embedded image A (CH ₂ ) _n OH

That is, according to the present invention, when a fluorine-based polymer containing a fluoroolefin unit as a main constituent unit is produced by polymerization in a polymerization medium, the compound represented by Chemical Formula 2 (where A is And a perhaloalkyl group, n being 1 or 2.).

The fluorine-containing polymer containing a fluoroolefin unit as a main constituent unit in the present invention is a fluoroolefin monomer in a compound represented by Chemical formula 2 (where A is a perhaloalkyl group and n is 1 or 2). It is produced by polymerizing the body alone or by copolymerizing the following monomers other than the fluoroolefin monomer which 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, it is necessary to use the compound represented by Chemical formula 2 (where A is a perhaloalkyl group and n is 1 or 2) as a polymerization medium. The perhaloalkyl group A is linear or branched, preferably linear, and has 1 to 8 carbon atoms, preferably 1 to 6 carbon atoms, and more preferably 1 to 4 carbon atoms. As the halogen of the perhaloalkyl group A, it is preferable to contain only fluorine or fluorine and chlorine at the same time in order to obtain a polymer having a high molecular weight. A particularly preferred perhaloalkyl group A is a perfluoroalkyl group.

In the present invention, the compound represented by Chemical formula 2 (wherein A is a perhaloalkyl group and n is 1 or 2) may be used as a polymerization medium in the presence of an inert solvent such as water. The amount of the polymerization medium used may vary depending on the kind 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.
It is double.

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 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. This compound is a compound represented by the formula (2) (where A is a perhaloalkyl group and n is 1 or 2.)
Must be soluble in. However, a compound having a large chain transfer constant may be dissolved in a compound represented by Chemical formula 2 (wherein A is a perhaloalkyl group and n is 1 or 2) 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 ,
Hydchlorofluorocarbons such as CF ₃ 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.

[0019]

【Example】

Example 1 A stainless steel reaction vessel having an internal volume of 1.2 liter was degassed, and 2,2,2-trifluoroethanol [CF ₃ CH 2 was used.
₂ OH] 1300 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% 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 = 5
3/47) was introduced and the reaction pressure was maintained at 9.5 kg / cm ² . The polymerization initiator was intermittently charged so that the polymerization rate was almost constant, and a total of 17 cc was charged. After 3 hours, 70 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 340 ° C.
And a good compression molded product was obtained at a molding temperature of 300 ° C. The tensile strength of the molded product is 422 kg / cm ² ,
The tensile elongation was 450%.

Example 2 A stainless steel reaction vessel having an internal volume of 1.2 liters was degassed, and 1,2,2,2-trifluoroethanol (1400 g),
32 g of perfluoropropyl vinyl ether and 80 g of tetrafluoroethylene were charged. Maintaining the temperature at 50 ° C., di (perfluorobutyryl) -as a polymerization initiator
A 1 wt% perfluorohexane solution of peroxide was charged to start the reaction. During the reaction, tetrafluoroethylene was introduced into the system, and the reaction pressure was 6.2 kg / cm ²
Held in. The polymerization initiator was charged intermittently so that the polymerization rate was almost constant, and 8 cc in total was charged. After 3.5 hours, 75 g of a white copolymer was obtained as a slurry. The copolymer has a melting point of 310 ° C. and a thermal decomposition starting point of 485.
C. and a molding temperature of 340.degree. C. gave good compression molded articles. Tensile strength of the molded product is 422 kg / cm
² , the tensile elongation was 380%.

Example 3 400 g of hexafluoropropylene was charged in place of 32 g of perfluoropropyl vinyl ether, and 2,2,2
Polymerization was performed in the same manner as in Example 2 except that the amount of 2-trifluoroethanol charged was 1,000 g instead of 1,400 g, and after 3.5 hours, 65 g of a white copolymer was obtained as a slurry. The copolymer has a melting point of 285.
C., the starting point of thermal decomposition was 435.degree. C., and a good compression molded product was obtained at a molding temperature of 340.degree. The tensile strength of the molded product was 342 kg / cm ² , and the tensile elongation was 350%.

Example 4 Instead of 2,2,2-trifluoroethanol, 2,
2,3,3,3-Pentafluoropropanol [CF ₃
CF ₂ CH ₂ OH] was charged, and polymerization was carried out in the same manner as in Example 1 to obtain 74 g of a white copolymer in a slurry state after 3.2 hours. The copolymer has a melting point of 27.
The temperature was 5 ° C., the starting point of thermal decomposition was 380 ° C., and a good compression molded product was obtained at a molding temperature of 300 ° C. The tensile strength of the molded product was 475 kg / cm ² , and the tensile elongation was 450%.

Comparative Example 1 In a stainless steel reactor having an internal volume of 1.2 liters, 500 g of deoxygenated 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 1,2,2,2-trifluoroethanol instead of 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 1.5 g of hexane was charged as a chain transfer agent.
g of 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.,
A molding temperature of 300 ° C. gave good compression moldings. The tensile strength of the molded product was 431 kg / cm ² , and the tensile elongation was 450%.

[0025]

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 (3)

[Claims] 1. When producing a fluorine-containing polymer containing a fluoroolefin unit as a main constituent unit by polymerization in a polymerization medium, the compound represented by Chemical formula 1 as the polymerization medium (wherein A is a perhaloalkyl group, n is 1) or 2) is used. Embedded image A (CH ₂ ) _n OH 2. The method according to claim 1, wherein A is a linear perhaloalkyl group having 1 to 8 carbon atoms. 3. 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. .