JPH06298809A - Production of ethylene-tetrafluoroethylene copolymer - Google Patents

Abstract

PURPOSE:To produce at a low cost an ethylene-tetrafluoroethylene copolymer which has no chorine atom bonded to the polymer chain terminal and is excellent in resistances to heat, solvents, and chemicals. CONSTITUTION:The copolymer is produced by using, as the polymn. medium, a 3-10C hydrofluorocarbon having at least one fluorine atom and at least one hydrogen atom provided that the number of hydrogen atoms is not more than that of fluorine atoms and by using, as the chain transfer agent, an alcohol such as methanol.

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 an ethylene-tetrafluoroethylene copolymer (hereinafter abbreviated as ETFE), specifically by using a specific polymerization medium, a polymerization initiator and a chain transfer agent. , A method for efficiently producing ETFE having good heat resistance, solvent resistance, chemical resistance and the like.

[0002]

2. Description of the Related Art Since ETFE is a polymer material having excellent heat resistance, solvent resistance, chemical resistance, etc., ETFE is utilized in various applications by taking advantage of its characteristics.

As a method for producing ETFE, a solution polymerization method, a suspension polymerization method and an emulsion polymerization method are known, and an inert solvent such as chlorofluorocarbon is used as a polymerization medium in the solution polymerization method or the suspension polymerization method. In view of giving a high molecular weight copolymer and the rate of polymerization, it is usually used. Specific examples of the chlorofluorocarbon include trichlorofluoromethane, dichlorodifluoromethane, trichlorotrifluoroethane, dichlorotetrafluoroethane and the like, but trichlorotrifluoroethane is mainly used from the viewpoint of handling.

However, when a chlorofluorocarbon typified by the above-mentioned trichlorotrifluoroethane is used as a polymerization medium for ETFE, a small amount of chlorofluorocarbon reacts with the polymer-growth end radicals of the copolymer to cause a polymer molecular chain. Some have chlorine bound to the end of. The carbon at the end of the polymer chain
The chlorine bond has poor thermal stability, and if the copolymer is left at high temperature for a long time, it may cause coloration of the copolymer, and if the copolymer is used as a wire coating material, the polymer terminal of chlorine decomposes during coating molding. This will cause corrosion of the core wire.

Further, as a polymerization solvent for the fluoropolymer,
Perfluorocarbons such as perfluorohexane are known. However, methanol, which is often used as a chain transfer agent for producing a fluoropolymer having excellent thermal stability and moldability, and the compatibility with perfluorocarbon are poor, and perfluorocarbon is used as a polymerization solvent and methanol for chain transfer. When polymerization is performed as an agent, it is very difficult to obtain a polymer having a desired molecular weight.

When perfluorocarbon is used as a polymerization solvent, a fluorine-containing organic peroxide is usually used as a polymerization initiator. When ETFE is polymerized, a perfluorocopolymer such as tetrafluoroethylene-peroxide is used. Compared to the case of polymerizing a fluoro (propyl vinyl ether) copolymer, the efficiency of the polymerization is inferior, the amount of the polymerization initiator used becomes considerably large, and it is necessary to use a large amount of expensive fluorine-containing organic peroxide. And is economically disadvantageous.

[0007]

Under the above circumstances, the present invention has no polymer in which chlorine is bonded to the end of the polymer molecular chain of ETFE, and has no heat resistance, solvent resistance, or resistance. It is an object of the present invention to provide a method for economically and efficiently producing ETFE having excellent chemical properties.

[0008]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that a specific hydrofluorocarbon is used and an alcohol such as methanol is used as a chain transfer agent. We have found that we can achieve that purpose.

That is, according to the present invention, when ETFE is produced by polymerization in a polymerization medium, a hydrofluorocarbon having 3 to 10 carbon atoms containing a fluorine atom and at least one hydrogen atom and at most the same number as the fluorine atom is used as the polymerization medium. A method for producing ETFE, which is characterized in that an alcohol is used as a chain transfer agent.

In the present invention, the molar ratio of tetrafluoroethylene / ethylene is usually 30/70 to 95 /.
ETFE can be produced by copolymerizing tetrafluoroethylene and ethylene in the hydrofluorocarbon at 5, especially 40/60 to 90/10.

In addition to tetrafluoroethylene and ethylene, a small amount of comonomer may be further copolymerized. These comonomers CF ₂ = CFCl, fluoro ethylenes such as _{CF 2 = CH 2, CF 2} = CFCF 3, CF 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 = CH ₂ or other perfluoroalkyl group having 4 to 12 carbon atoms, R _f
(OCFXCF ₂ ) _m OCF = CF ₂ (wherein R _f represents a perfluoroalkyl group having 1 to 6 carbon atoms, X represents a fluorine atom or a trifluoromethyl group, and m represents an integer of 1 to 5.)
Perfluorovinyl ethers such as CH ₃ OC (=
O) CF ₂ CF ₂ CF ₂ OCF = CF ₂ or FSO ₂ CF
Vinyl ethers having a group that can be easily converted into a carboxylic acid group or a sulfonic acid group such as ₂ CF ₂ OCF (CF ₃ ) CF ₂ OCF = CF ₂ can be used alone or in combination of two or more kinds. Further, it may be combined with an olefin-based monomer such as propylene or isobutylene.

The copolymerization ratio of these comonomers is usually E
It is preferably used in an amount of 30 mol% or less, particularly 0.1 to 15 mol%, based on TFE.

The polymerization medium used in the present invention must be a saturated organic compound composed of 3 to 10 carbons, fluorine, and 1 or more and the same number or less of hydrogen as the number of fluorines. . If the number of carbon atoms is 2 or less, the boiling point will be too low and the polymerization pressure will rise, and if it is 11 or more, the boiling point will be too high and it will be difficult to separate the polymer and the polymerization medium after polymerization, which is disadvantageous in production. If no hydrogen is present, methanol cannot be used as a chain transfer agent as described above. Further, if hydrogen is present in excess of the number of fluorine, the hydrogen will undergo chain transfer, which is not desirable.

A particularly preferred polymerization medium is C ₄ F ₄ H ₄ , C
₄ F ₈ H ₂ , C ₅ F ₁₁ H, C ₅ F ₁₀ H ₂ , C ₆ F ₁₃ H,
C ₆ F ₁₂ H ₂ or C ₆ F ₉ H ₅ , specifically 1,
1,2,2-tetrafluorocyclobutane, CF ₂ HC
F ₂ CF ₂ CF ₂ H, CF ₃ CFHCF ₂ CF ₂ CF
₃ , CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ H, CF ₃ CF ₂
CFHCF ₂ CF ₃ , CF ₃ CFHCFHCF ₂ CF
₃ , CF ₂ HCF ₂ CF ₂ CF ₂ CF ₂ H, CF ₂ HC
FHCF ₂ CF ₂ CF ₃ , CF ₃ CF ₂ CF ₂ CF ₂ C
F ₂ CF ₂ H, CF ₃ CH (CF ₃ ) CF ₂ CF ₂ CF
₃ , CF ₃ CF (CF ₃ ) CFHCF ₂ CF ₃ , CF ₃
CF (CF ₃ ) CFHCFHCF ₃ , CF ₃ CH (CF ₃
) CFHCF ₂ CF ₃ , CF ₂ HCF ₂ CF ₂ CF ₂
CF ₂ CF ₂ H, CF ₃ CF ₂ CF ₂ CF ₂ CH ₂ CH ₃
And so on.

In the present invention, the hydrofluorocarbon may be used as a polymerization medium containing an inert solvent such as water. The amount of the polymerization medium used can vary depending on the type of monomer to be polymerized,
The amount is 3 to 100 times, preferably 5 to 50 times the weight of the whole monomer.

In the present invention, either a solution polymerization method or a suspension polymerization method can be adopted as the polymerization method. The polymerization initiator used may be a fluorine-based or hydrocarbon-based organic peroxide or an azo compound,
Hydrocarbon-based organic peroxides are preferable in terms of thermal stability and economy of the copolymer.

Examples of hydrocarbon-based organic peroxides include diacyl peroxides such as acetyl peroxide and isobutyryl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate and di-n-propyl peroxydicarbonate. , T-butylperoxyisobutyrate, t-butylperoxypivalate, t-butylperoxy-3,
Examples include peroxyesters such as 5,5-trimethylhexanoate.

The amount of the polymerization initiator used can be appropriately changed depending on the type, the copolymerization reaction conditions and the like, but usually 0.005 to 5% by weight based on the whole monomers to be polymerized, In particular, about 0.05 to 0.5% by weight is adopted.

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 copolymer.
It is preferable to use alcohols such as ethanol, n-propanol and i-propanol, especially methanol having a small molecular weight and high thermal stability. By using alcohols as a chain transfer agent, it is possible to obtain ETFE having excellent heat resistance and moldability, that is, the copolymer is not colored and die swell is small during melt molding of the copolymer.
The addition amount of alcohols varies depending on the polymerization mode and the polymerization reaction conditions, but may be about 0.01 to 50% by weight with respect to the polymerization medium.

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 it is also possible to employ a higher pressure, and it is possible to carry out even under reduced pressure conditions. Also,
The present invention can be carried out by an appropriate operation such as a batch system or a continuous system.

[0021]

EXAMPLES In the examples, the volumetric flow rate was measured by a high-lower flow tester at a temperature of 300 ° C., a load of 30 kg, and an inner diameter of 1
This is a measurement of the capacity (mm ³ ) per unit time (second) of the polymer flowing out from the nozzle having a length of 2 mm and a land length of 2 mm.

Example 1 A stainless steel reaction vessel having an internal volume of 1.2 liter was degassed, and CF ₃ CF ₂ CF ₂ CF ₂ CH ₂ C was used as a polymerization medium.
1350 g of H ₃ and 1. 1 of methanol as a chain transfer agent.
8 g was charged, and tetrafluoroethylene 85 g and ethylene 5.9 g were charged. Maintaining the temperature at 65 ° C., a 10 wt% 1,3-dichloro-1,2,2,3,3-pentafluoropropane (R-225cb) solution of t-butylperoxyisobutyrate as a polymerization initiator. The reaction was started by charging 3 ml. 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 13.5 g.
/ Cm ² was maintained.

After 3 hours, 85 g of a white copolymer was obtained as a slurry. The copolymer had a melting point of 278 ° C., a thermal decomposition starting point of 360 ° C. and a volume flow rate of 53, and at a molding temperature of 300 ° C., a good compression molded product without coloring was obtained. The tensile strength of the molded product was 428 kg / cm ² , and the tensile elongation was 440%. Even if the obtained molded product was kept at 250 ° C. for 3 days, almost no coloring was observed. 300 ° C
The die swell when extruded at a extrusion rate of 360 mm / min using a die having an inner diameter of 1.0 mm and a length of 10.0 mm was 1.15.

Example 2 A stainless steel reaction vessel having an internal volume of 1.2 liter was degassed, and CF ₃ CF (CF ₃ ) CFHCFH was used as a polymerization medium.
550 g of CF ₃ , 700 g of demineralized water and 75 g of methanol as a chain transfer agent were charged, and 45 g of tetrafluoroethylene, 3.7 g of ethylene, (perfluorobutyl)
0.8 g of ethylene was charged. While maintaining the temperature at 50 ° C., 3 ml of a 10 wt% R-225cb solution of diisopropyl peroxydicarbonate 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 and the reaction pressure was maintained at 17.5 g / cm ² . After 6 hours, 55 g of a white copolymer was obtained as a slurry. The copolymer had a melting point of 269 ° C., a thermal decomposition starting point of 345 ° C., a volume flow rate of 62, and gave a good compression molded product with no coloration at a molding temperature of 300 ° C. The tensile strength of the molded product is 400 kg / cm ² , and the tensile elongation is 4.
It was 90%. Even if the obtained molded product was kept at 250 ° C. for 3 days, almost no coloring was observed. The die swell when extruded in the same manner as in Example 1 was 1.20.

Example 3 As a polymerization initiator, 5 of perfluorobutyryl peroxide was used.
Polymerization was carried out in the same manner as in Example 1 except that 3 ml of a wt% R-225cb solution was charged and the reaction was started. Since the progress of polymerization slowed during the reaction, 1 ml of a 5 wt% R-225cb solution of perfluorobutyryl peroxide was charged each time to accelerate the polymerization reaction rate. A total of 10 ml of a polymerization initiator was charged, and after 3 hours, 80 g of a copolymer was obtained as a slurry.

The copolymer had a melting point of 275 ° C., a thermal decomposition starting point of 365 ° C. and a volume flow rate of 32, and at a molding temperature of 300 ° C., a good compression-molded product with no coloration was obtained. The tensile strength of the molded product is 460 kg / cm ² , and the tensile elongation is 480%.
Met. Even if the obtained molded product was kept at 250 ° C. for 3 days, almost no coloring was observed. The die swell when extruded in the same manner as in Example 1 was 1.15.

Example 4 A compound obtained by adding tetrafluoroethylene and hexafluoropropylene using AlCl ₃ / CFCl ₃ as a catalyst and hydrogenating the resulting adduct using a Pd / C catalyst. CF ₃ CF ₂ CFHCFHCF ₃ 130
Polymerization was performed in the same manner as in Example 1 except that 0 g was charged. After 2.5 hours, 90 g of a white copolymer was obtained as a slurry.

The copolymer had a melting point of 276 ° C., a thermal decomposition starting point of 365 ° C., and a volume flow rate of 41, and gave a good compression molded product with no coloration at a molding temperature of 300 ° C. The tensile strength of the molded product is 465 kg / cm ² , and the tensile elongation is 480%.
Met. Even if the obtained molded product was kept at 250 ° C. for 3 days, almost no coloring was observed. The die swell when extruded as in Example 1 was 1.14.

Comparative Example 1 90 g in the same manner as in Example 1 except that the polymerization medium was 1,1,2-trichlorotrifluoroethane (1200 g).
A copolymer of The copolymer had a melting point of 276 ° C., a thermal decomposition starting point of 357 ° C., a volume flow rate of 58, and gave a good compression molded product with no coloration at a molding temperature of 300 ° C. The tensile strength of the molded product is 445 kg / cm ² , and the tensile elongation is 4.
It was 20%. When the obtained molded product was kept at 250 ° C. for 3 days, it was colored brown. The die swell when extruded in the same manner as in Example 1 was 1.17.

Comparative Example 2 Polymerization was carried out in the same manner as in Example 1 except that the polymerization medium was 700 g of hexane, but the polymerization hardly proceeded.

[0032]

EFFECTS OF THE INVENTION According to the present invention, ETFE having no chlorine bonded to the end of the polymer molecular chain thereof and having excellent heat resistance, solvent resistance, and chemical resistance can be produced economically and efficiently. It can be manufactured.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Kato 1150, Hazawa-machi, Kanagawa-ku, Kanagawa Prefecture Asahi Glass Co., Ltd. Central Research Laboratory (72) Inventor Haruhisa Miyake 1150, Hazawa-machi, Kanagawa-ku, Yokohama Kanagawa Prefecture Asahi Glass Co., Ltd. Central Research Center

Claims (3)

[Claims] 1. A method for producing an ethylene-tetrafluoroethylene copolymer by polymerization in a polymerization medium, wherein the polymerization medium has 3 to 10 carbon atoms containing a fluorine atom and at least one hydrogen atom and at most hydrogen atoms. A method for producing an ethylene-tetrafluoroethylene copolymer, which comprises using hydrofluorocarbon and alcohols as a chain transfer agent. 2. The alcohol is methanol.
Manufacturing method. 3. The method according to claim 1, wherein a hydrocarbon-based organic peroxide is used as the polymerization initiator.