JP3244818B2 - Method for producing fluoropolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel process for producing a fluorine-containing polymer, and more particularly, to a method for producing a polymer having low heat resistance, solvent resistance and chemical resistance by using a polymerization medium which does not cause environmental destruction. The present invention relates to a method for efficiently producing a fluoropolymer.

[0002]

2. Description of the Related Art In recent years, fluoropolymers are polymer materials having excellent heat resistance, solvent resistance, chemical resistance and the like.
Utilizing its features, it is used for various purposes.

[0003] As a method for producing a fluoropolymer, a solution polymerization method , a suspension polymerization method, and an emulsion polymerization method are known. As a polymerization medium for the solution polymerization method and the suspension polymerization method, chlorofluorocarbon or the like is used. An active solvent is generally used from the viewpoint of providing a high molecular weight copolymer and the polymerization rate. Specific examples of the chlorofluorocarbon include trichlorofluoromethane, dichlorodifluoromethane, trichlorotrifluoroethane, dichlorotetrafluoroethane, and the like. Trichlorotrifluoroethane is mainly used from the viewpoint of handling.

In recent years, the ozone layer depletion has been taken up internationally as a problem of environmental destruction on a global scale, and chlorofluorocarbon has been pointed out as a causative substance thereof. For this reason, it has become necessary to stop using the chlorofluorocarbon used in producing the fluoropolymer.

As a substitute for the chlorofluorocarbon, a hydrofluorocarbon containing a hydrogen atom has been proposed because of its small ozone depletion potential. However, conventionally, a substance having a C—H bond is known to exhibit a chain transfer property to a fluoroolefin, and a hydrochlorofluorocarbon containing a hydrogen atom is converted to a high-molecular-weight fluoroolefin-based polymer. It was considered difficult to use it as a polymerization medium in such a case.
As a substitute for other polymerization media, t- tert -butanol (Japanese Patent Publication No. 52-24073) is known, but in order to obtain a sufficiently high molecular weight,
It is necessary to polymerize at high pressure.

[0006]

Under such circumstances, the present invention provides a chlorofluorocarbon having a high polymerization rate, a sufficiently high molecular weight of a fluoropolymer, and a large ozone destruction coefficient. An object of the present invention is to provide a method for efficiently producing a fluoropolymer having excellent heat resistance, solvent resistance, and chemical resistance without using a polymer.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, (perhaloalkyl) ethane has a small chain transfer property, and by using this as a polymerization medium, It has been found that the purpose can be achieved.

That is, the present invention is characterized in that (perhaloalkyl) ethane is used as the polymerization medium in producing a fluoropolymer containing a fluoroolefin unit as a main constituent unit by polymerization in a polymerization medium. To provide a method for producing a fluoropolymer.

In the present invention, the fluoropolymer containing a fluoroolefin unit as a main constituent unit may be obtained by polymerizing a fluoroolefin monomer alone in (perhaloalkyl) ethane or copolymerizing with a fluoroolefin monomer. It is produced by copolymerizing the following monomers other than the above-mentioned fluoroolefin monomer.

[0010] The present invention fluoroolefin monomer used in is an olefin having at least one fluorine atom in the molecule, preferably, from the viewpoint of the nature of the polymerizable and the resulting polymer, 2 or 3 carbon atoms Is a fluoroolefin monomer.

Specific examples of such fluoroolefin monomers include CF ₂ ＝ CF ₂ , CF ₂ ＣＦCFCl, and CF ₂ ＝
Fluoroethylene such as CH ₂ , CF ₂ ＣＦCFCF
₃ , CF ₂ ＣＨCHCF ₃ and other fluoropropylene-based compounds. These fluoroolefin monomers may be used alone or in combination of two or more.

Further, CF ₃ CF ₂ CF ₂ CF ₂ CH is used as a monomer copolymerized with these fluoroolefin monomers.
= CH ₂ and CF ₃ CF ₂ CF ₂ CF ₂ CF = CH ₂ and other perfluoroalkyl groups having 4 to 12 carbon atoms (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
It can be used in combination with a vinyl ether having a group which can be easily converted to a carboxylic acid group or a sulfonic acid group, such as (CF ₃ ) CF ₂ OCF ＝ CF ₂ . Moreover, you may combine with olefin-type monomers, such as ethylene, propylene, and isobutylene. In the present invention,
The copolymer is tetrafluoroethylene / ethylene copolymer
Body, tetrafluoroethylene / perfluoro (alkyl
Vinyl ether) copolymer or tetrafluoroethylene
/ Hexafluoropropylene copolymer is preferred
New

In the present invention, it is necessary to use (perhaloalkyl) ethane as a polymerization medium. In the present invention and (perhaloalkyl) ethane refers ethane to have a perhaloalkyl group. If the chain length of the perhaloalkyl group is too short, the boiling point is too low and a gas is formed at room temperature, which is inconvenient to handle. The perhaloalkyl group is linear or branched and has 2 to 12 carbon atoms.
It is preferably 2 to 10, more preferably 3 to 6. Pa
-Haloalkyl group having 2 to 8 carbon atoms, linear perhaloal
It is also preferable that it is a kill group. The halogen of the perhaloalkyl group, it is preferable to obtain a polymer of high molecular weight fluorine alone or fluorine with chlorine is contained in together. Particularly preferred as perhaloalkyl groups are perfluoroalkyl groups.

In the present invention, (perhaloalkyl) ethane may be used as a polymerization medium by adding an inert solvent such as water. The amount of the polymerization medium is that obtained by changing the kind of monomer to be polymerized, based on the weight of the monomer based on the total amount of 3 to 100 times, preferably 5 to 50 times.

In the present invention, the polymerization method is a solution weight.
Either a legal method or a suspension polymerization method can be used.
The polymerization initiator used is conventionally used depending on the type of polymerization.
Select from theChoiceit can. For example,Screw
(Chlorofluoroacyl)-OkiShiDoScrew(Perf
Luoroacyl)-OkiShiDoScrew(Ω-Hydropar
Fluoroacyl)-OkiShiDo, tert-Butyl par
Oxyisobutyrate, diisopropyl peroxydica
Organic peroxides such as carbonates, azobisisobutyroni
Azo compounds such as tolyl are exemplified. Use of polymerization initiator
Dosage may be changed appropriately depending on the type, polymerization reaction conditions, etc.so
ComeHowever, usually, with respect to the entire monomer to be polymerized,
0.005 to 5% by weight, especially about 0.05 to 0.5% by weight
Degree is adopted.

In the polymerization reaction of the present invention, a wide range of reaction conditions can be employed without any particular limitation. For example, the optimum value of the polymerization reaction temperature can be selected depending on the type of the polymerization initiation source and the like, but usually about 0 ° C to 100 ° C, particularly about 30 ° C to 90 ° C can be adopted. Although the reaction pressure is also Ru can be selected as appropriate, usually 2~100kg / cm ^2, in particular it is desirable to employ a 5 to 20 kg / cm ² degree.
In the present invention, Ru obtained advantageously operating polymerization without requiring reaction pressure excessive, higher pressures can be employed, it is possible under a reduced pressure. Further, the present invention can be carried out by a suitable 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, and this compound needs to be soluble in (perhaloalkyl) ethane. However, a compound having a large chain transfer constant may be slightly dissolved in (perhaloalkyl) ethane in consideration of the ease of controlling the molecular weight. It is also desirable to have a small ozone depletion potential. Compounds that meet these requirements are, for example, hydrocarbon such as hexane, hydrofluorocarbons such as CF ₂ H _2, high <br/> mud chlorofluorocarbons such as CF ₃ CF ₂ CHCl _2, ketones such as acetone s, alcohols such as methanol, ethanol, or the like mercaptans such as methyl mercaptan.
The amount of addition may vary depending on the magnitude of the chain transfer constant of the compound to be used, but may be employed from about 0.01% by weight to about 50% by weight based on the polymerization medium.

[0018]

Example 1 A stainless steel reaction vessel having an internal volume of 1.2 liters was degassed, and 1312 g of (perfluorooctyl) ethane, 1.8 g of (perfluorobutyl) ethylene, 85 g of tetrafluoroethylene, and 5. 9 g were charged. And maintaining the temperature at 50 ° C., charged with 1 wt% of perfluorohexane solution of bis (perfluoro-butyryl) Pas Oki Passes as a polymerization initiator, to initiate 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, and the reaction pressure was maintained at 8.9 kg / cm ² . The polymerization initiator was charged intermittently so that the polymerization rate was almost constant, and a total of 12
cc was charged. After 3 hours, 65 g of a white copolymer was obtained as a slurry. The copolymer has a melting point of 275 ° C.
The starting point of thermal decomposition was 355 ° C., and a good compression molded product was obtained at a molding temperature of 300 ° C. The molded article had a tensile strength of 445 kg / cm ² and a tensile elongation of 420%.

Example 2 A stainless steel reaction vessel having an inner volume of 1.2 liters was degassed, and 1410 g of ( perfluorooctyl) ethane, 32 g of perfluoro ( propyl vinyl ether ) and 80 g of tetrafluoroethylene were charged. The temperature was maintained at 50 ° C., and bis (perfluorobutyryl ) was used as a polymerization initiator.
They were charged 1 wt% perfluorohexane solution of Pas Oki shea de, to initiate the reaction. During the reaction, tetrafluoroethylene was introduced into the system, and the reaction pressure was maintained at 5.1 kg / cm ² . The polymerization initiator was intermittently charged so that the polymerization rate was almost constant, and a total of 7 cc was charged. After 2.2 hours, 71 g of a white copolymer was obtained in a slurry state. The copolymer has a melting point of 308 ° C. and a thermal decomposition starting point of 450 ° C.
And a good compression molded product was obtained at a molding temperature of 340 ° C. The tensile strength of the molded product is 397 kg / cm ² ,
The tensile elongation was 357%.

Example 3 The same method as in Example 2 was used except that 400 g of hexafluoropropylene was charged instead of 32 g of perfluoro ( propyl vinyl ether ) , and the charged amount of (perfluorooctyl) ethane was changed to 1000 g instead of 1410 g. The polymerization was carried out, and after 3.5 hours, 67 g of a white copolymer was obtained in a slurry state. The copolymer has a melting point of 285.
° C, the thermal decomposition starting point was 440 ° C, and a good compression-molded product was obtained at a molding temperature of 340 ° C. The molded product had a tensile strength of 354 kg / cm ² and a tensile elongation of 320%.

Example 4 Polymerization was carried out in the same manner as in Example 1 except that (perfluorobutyl) ethane was charged instead of (perfluorooctyl) ethane. After 3.1 hours, 72 g of a white copolymer was slurried. Obtained as a state. The copolymer has a melting point of 27.
The temperature was 1 ° C, the starting point of thermal decomposition was 343 ° C, and a good compression molded product was obtained at a molding temperature of 300 ° C. The molded product had a tensile strength of 456 kg / cm ² and a tensile elongation of 410%.

The stainless steel reaction vessel of Comparative Example 1 inner volume 1.2 liters, deoxygenated water 500 g, t ert - butanol 200 g, it was charged disuccinic acid peroxide 0.65 g. The reaction was performed 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), and the reaction pressure was increased to 9 kg / cm.
^It was kept at ² . After 4 hours, 24.6 g of a white copolymer was obtained. This copolymer had a melting point of 269 ° C. and a thermal decomposition onset temperature of 361 ° C. The molded product obtained by compression molding at 300 ° C. had a low molecular weight and was brittle.

Reference Example 1 Instead of charging (perfluorooctyl) ethane, 1,
1255 g of 1,2-trichlorotrifluoroethane was charged, and 3,3 -dichloro-1,1,1 was used as a chain transfer agent .
Polymerization was carried out in the same manner as in Example 1 except that 13.5 g of 1,2,2 -pentafluoropropane was charged, and after 2 and a half hours, 48 g of a white copolymer was obtained in a slurry state. 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%.

[0024]

According to the method of the present invention, ozone depletion effects much lower, cut with manufacturing the desired fluorine-containing polymer with an efficiency comparable to the case of using the conventional trichlorotrifluoroethane solvent.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08F 2/00-2/60 C08F 14 / 18,214 / 18 CA (STN)

Claims (3)

(57) [Claims] 1. A method for producing a fluoropolymer containing a fluoroolefin unit as a main constituent unit by polymerization in a polymerization medium, wherein (perhaloalkyl) ethane is used as the polymerization medium. Manufacturing method. 2. A process according to claim 1 perhaloalkyl group in (perhaloalkyl) ethane is linear perhaloalkyl group having 2 to 8 carbon atoms. 3. A fluorine-containing polymer is a tetrafluoroethylene / ethylene copolymer, tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer or a tetrafluoroethylene / hexafluoropropylene copolymer according to claim 1 or 3. The production method according to 2 .