JPH06157675A - Production of tetrafluoroethylene copolymer - Google Patents

Abstract

PURPOSE:To obtain the subject copolymer good in heat, solvent and chemical resistances, etc., by using a polymerization medium reduced in environmental disruption. CONSTITUTION:A process for producing a copolymer of tetrafluoroethylene with hexafluoropropylene or a copolymer of tetrafluoroethylene with perfluoroalkyl vinyl ether by using perfluorohexane as a polymerization medium is provided.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a copolymer of tetrafluoroethylene and hexafluoropropylene (hereinafter referred to as FEP
, Or a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (hereinafter abbreviated as PFA), and more specifically, a heat resistance and solvent resistance using a polymerization medium that causes less environmental damage. The present invention relates to a method for efficiently producing FEP or PFA having good properties and chemical resistance.

[0002]

2. Description of the Related Art In recent years, since FEP or PFA is a polymer material having excellent heat resistance, solvent resistance, chemical resistance, etc., it has been utilized for various purposes by making full use of its characteristics.

As a method for producing FEP or PFA, a solution polymerization method, a suspension polymerization method and an emulsion polymerization method are known. As a polymerization medium for the solution polymerization method or the suspension polymerization method, an inert gas such as chlorofluorocarbon is used. A solvent is usually used from the viewpoint of giving a high molecular weight copolymer and the polymerization rate. 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. Therefore, FEP or PF
It has become necessary to stop the use of chlorofluorocarbons used in the production of A.

As an alternative to this chlorofluorocarbon, hydrofluorocarbons containing hydrogen atoms have been proposed because they have a low ozone depletion potential. However, conventionally, it has been known that a substance having a C—H bond exhibits a chain transfer property with respect to a fluoroolefin such as tetrafluoroethylene, and a hydrochlorofluorocarbon containing a hydrogen atom is treated with a high molecular weight FEP or PFA.
It was thought to be difficult to use as a polymerization medium in the manufacture of. Although t-butanol (Japanese Patent Publication No. 52-24073) and the like are known as alternatives as other polymerization media, it is necessary to polymerize at high pressure in order to obtain a sufficiently high molecular weight.

[0006]

Under the circumstances described above, the present invention provides a chlorofluorocarbon which has a high polymerization rate, can sufficiently increase the molecular weight of FEP or PFA, and has a large ozone depletion coefficient. The purpose of the present invention is to provide a method for efficiently producing FEP or PFA having excellent heat resistance, solvent resistance, and chemical resistance without using it.

[0007]

DISCLOSURE OF THE INVENTION As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that perfluorohexane 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 provides a method for producing a tetrafluoroethylene-based copolymer characterized by using perfluorohexane as the polymerization medium in producing FEP or PFA by polymerization in a polymerization medium. To do.

The FEP in the present invention is preferably a copolymer obtained by polymerizing tetrafluoroethylene and hexafluoropropylene in the presence of a polymerization initiator and having a hexafluoropropylene content of 8 to 20% by weight. A copolymer obtained by similarly polymerizing tetrafluoroethylene and perfluoroalkyl vinyl ether and having a perfluoroalkyl vinyl ether content of 2 to 10% by weight is preferable.

As the perfluoroalkyl vinyl ether, R _f (OCFXCF ₂ ) _m OCF = CF ₂
(In the formula, R _f is a perfluoroalkyl group having 1 to 6 carbon atoms,
X is a fluorine atom or a trifluoromethyl group, m is 1 to 6
Represents the integer. ) Is preferable.

The FEP or PFA may be further copolymerized with the following comonomer. For example, CF ₂ = C
FCl, fluoroethylene such as CF ₂ = CH _2, C
F ₂ = fluoropropylenes such as CHCF ₃ , CF ₃
CF ₂ CF ₂ CF ₂ CH = CH ₂ or CF ₃ CF ₂ CF ₂
CF ₂ CF = carbon number of the perfluoroalkyl group such as CH ₂ is 4 to 12 (perfluoroalkyl) _{ethylenes, CH 3 OC (= O)} CF 2 CF 2 CF 2 OCF = C
F ₂ and FSO ₂ CF ₂ CF ₂ OCF (CF ₃ ) CF ₂ O
Vinyl ethers having a group that can be easily converted into a carboxylic acid group or a sulfonic acid group such as CF = CF ₂ , ethylene,
It is an olefin such as propylene or isobutylene.

These comonomers may be used alone or in combination of two or more.

The copolymerization ratio of these comonomers is usually
30 mol% or less relative to FEP or PFA, especially 0.1
-15 mol% is preferably adopted.

In the present invention, perfluorohexane may be used as a polymerization medium containing 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 5 times the weight of the total amount of the monomers.
It is 0 times the amount.

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, but this compound needs to be soluble in perfluorohexane. However, a compound having a large chain transfer constant may be dissolved in perfluorohexane 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 are, for example, hydrocarbons such as hexane, hydrofluorocarbons such as CF ₂ H ₂ , hydechlorofluorocarbons such as CF ₃ CF ₂ CHCl ₂ , ketones such as acetone, methanol,
Examples include alcohols such as ethanol and mercaptans such as methyl mercaptan. The addition amount may vary depending on the size of the chain transfer constant of the compound used,
About 0.01% to about 50% by weight can be used with respect to the polymerization medium.

[0018]

【Example】

Example 1 A stainless steel reaction vessel having an internal volume of 1.2 liters was degassed, and 1410 g of perfluorohexane, 32 g of perfluoropropyl vinyl ether, 80 g of tetrafluoroethylene, and 1.5 g of hexane as a chain transfer agent were charged. The temperature was kept at 50 ° C., and a 1 wt% perfluorohexane 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 kept at 5.1 kg / cm ² . The polymerization initiator was intermittently charged so that the polymerization rate became almost constant, and the total amount was 8
cc prepared. After 2.1 hours, 75 g of a white copolymer was obtained as a slurry. The copolymer has a melting point of 307.
C., the starting point of thermal decomposition was 450.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 412 kg / cm ² , and the tensile elongation was 360%.

Example 2 400 g of hexafluoropropylene was charged in place of 32 g of perfluoropropyl vinyl ether, and 100 g of perfluorohexane was charged in place of 1410 g.
Polymerization was carried out in the same manner as in Example 1 except that the amount was 0 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. Tensile strength of molded product is 372kg
/ Cm ² , and the tensile elongation was 320%.

Reference Example 1 Polymerization was carried out in the same manner as in Example 1 except that 1410 g of 1,1,2-trichlorotrifluoroethane was charged instead of perfluorohexane, and after 2 and a half hours, 70 g of a white copolymer was slurried. It was obtained as a state. The copolymer has a melting point of 308 ° C., a thermal decomposition starting point of 430 ° C., and a melting point of 340 ° C.
Good compression moldings were obtained at molding temperatures of. The tensile strength of the molded product is 420 kg / cm ² , and the tensile elongation is 370.
%Met.

[0021]

EFFECT OF THE INVENTION According to the method of the present invention, the ozone depletion effect is much lower, and the desired FEP or P is obtained with an efficiency comparable to that obtained by using the conventional trichlorotrifluoroethane solvent.
FA can be produced.

Claims (1)

[Claims] 1. When producing a copolymer of tetrafluoroethylene and hexafluoropropylene or a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether by polymerization in a polymerization medium, perfluorohexane is used as the polymerization medium. A method for producing a tetrafluoroethylene-based copolymer, which is used.