JPH06248014A - Production of fluorinated polymer - Google Patents

Abstract

PURPOSE:To efficiently produce a polymer containing fluoroolefin units as main constituting units, little in the disruption of environments and excellent in heat resistance, etc., by using a specific perfluoroalkene-hydrogen fluoride adduct as a polymerization medium. CONSTITUTION:A fluoroalkane (perfluoroalkene-hydrogen fluoride adduct) obtained by adding hydrogen fluoride to the double bond of a perfluoroalkene produced by the anionic oligomerization of tetrafluoroethylene or hexafluoropropylene is used as a polymerization medium. In the medium a fluoroolefin monomer alone or the monomer and a copolymerizable monomer excluding the fluoroolefin monomer are polymerized to provide the objective polymer. The polymerization medium is preferably used in an amount of 5-50 times the whole weight of the monomers.

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-containing polymer, and more specifically, it uses a polymerization medium which causes little environmental damage and has excellent heat resistance, solvent resistance and chemical resistance. The present invention relates to a method for efficiently producing a polymer.

[0002]

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

Solution polymerization methods, suspension polymerization methods, and emulsion polymerization methods are known as methods for producing fluoropolymers. As a polymerization medium for the solution polymerization method or 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. 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 the fluoropolymer, and has a large ozone depletion coefficient. The present invention has been made for the purpose of providing a method for efficiently producing a fluoropolymer excellent in heat resistance, solvent resistance and chemical resistance without using.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a double bond of perfluoroalkene obtained by anionic oligomerization of tetrafluoroethylene (TFE) or hexafluoropropylene (HFP). Fluoroalkane obtained by adding hydrogen fluoride to (hereinafter, simply referred to as "hydrogen fluoride adduct of perfluoroalkene") has a low chain transfer property, and by using this as a polymerization medium, the above object can be achieved. I found that.

That is, the present invention uses a hydrogen fluoride adduct of perfluoroalkene as the polymerization medium when producing a fluoropolymer containing a fluoroolefin unit as a main constituent unit by polymerization in a polymerization medium. A method for producing a fluoropolymer characterized by the above.

The fluoropolymer containing a fluoroolefin unit as a main constituent unit in the present invention is obtained by polymerizing a fluoroolefin monomer alone in a hydrogen fluoride adduct of perfluoroalkene, or a fluoroolefin monomer. It is produced by copolymerizing the following monomers other than the fluoroolefin monomer that is copolymerized with the body.

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 less carbon atoms in view of polymerizability and properties of the resulting polymer. 3 is a fluoroolefin monomer.

Specific examples of such a fluoroolefin monomer include TFE, CF ₂ ═CFCl, and CF ₂ ═C.
Fluoroethylene series such as H ₂ , HFP, CF ₂ = CH
It is a fluoropropylene type such as CF 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 ) _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) and the like. System, CH ₃ OC (= O) CF ₂ C
F ₂ CF ₂ OCF = CF ₂ or FSO ₂ CF ₂ CF ₂ OC
It can also be used in combination with vinyl ether having a group such as F (CF ₃ ) CF ₂ OCF = CF ₂ which can be easily converted into a carboxylic acid group or a sulfonic acid group. Also,
You may combine with olefin type monomers, such as ethylene, propylene, and isobutylene.

The hydrogen fluoride adduct of perfluoroalkene in the present invention includes TFE trimer, tetramer, pentamer, or HFP dimer, trimer double bond with hydrogen fluoride. The compound obtained by addition of is suitable, and a mixture of hydrogen fluoride adducts of these perfluoroalkenes may be used.

In the present invention, a hydrogen fluoride adduct of perfluoroalkene 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 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.
The polymerization initiator to be used can be appropriately selected from those conventionally used according to the type of polymerization. For example, organic peroxides such as di (chlorofluoroacyl) peroxide, di (perfluoroacyl) peroxide, di (ω-hydroperfluoroacyl) peroxide, t-butylperoxyisobutyrate and diisopropylperoxydicarbonate, Examples thereof include azo compounds such as azobisisobutyronitrile. The amount of the polymerization initiator used can be appropriately changed depending on the type, the polymerization reaction conditions, etc., but usually it is 0.0
05 to 5% by weight, particularly about 0.05 to 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, as the polymerization reaction temperature, an optimum value can be selected depending on the type of the polymerization initiation source, etc.
Approximately 90 ° C can be adopted. The reaction pressure can be appropriately selected, but is usually ^{2 to} 100 kg / cm ² , and especially 5 to
It is desirable to adopt about 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 the hydrogen fluoride adduct of perfluoroalkene. . However, a compound having a large chain transfer constant may be dissolved in a hydrogen fluoride adduct of perfluoroalkene 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, CF
Hydrofluorocarbons such as ₂ H ₂ , CF ₃ CF
Hydchlorofluorocarbons such as ₂ CHCl ₂ ,
Examples include 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.

[0018]

【Example】

[Synthesis Example 1] A mixture of HFP dimers was placed in an Inconel reactor having an inner diameter of 1 inch filled with a chromium-aluminum composite oxide catalyst at 230 ° C., and the contact time was 30 seconds together with 2.5 mole times of hydrogen fluoride. And the product was recovered. HFP dimer mixture of hydrogen fluoride adduct of a boiling point of 63 to 67 ° C. by distillation [CF ₃ CF (CF
₃ ) CFHCF ₂ CF ₃ , CF ₃ CF (CF ₃ ) CF ₂
CFHCF ₃ , CF ₃ CH (CF ₃ ) CF ₂ CF ₂ CF
₃ ] was obtained.

[Example 1] A stainless steel reaction vessel having an internal volume of 1.2 liter was degassed, and 1300 g of a mixture of perfluoroalkene with hydrogen fluoride adduct obtained in Synthesis Example 1, (perfluorobutyl) ethylene 1. 8g, TFE85g,
5.9 g of ethylene was charged. While maintaining the temperature at 50 ° C., a 1% by weight perfluorohexane solution of di (perfluorobutyryl) peroxide was charged as a polymerization initiator to start the reaction. During the reaction, a mixed gas of TFE and ethylene in the system (molar ratio TFE / ethylene = 53/47)
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 14 cc was charged. After 3 hours, 85 g of a white copolymer was obtained as a slurry. The copolymer has a melting point of 272 ° C. and a thermal decomposition starting point of 345 ° C.
A molding temperature of 0 ° C. gave good compression moldings. The tensile strength of the molded product is 455 kg / cm ² , and the tensile elongation is 4.
It was 70%.

[Example 2] A stainless steel reaction vessel having an internal volume of 1.2 liters was degassed, and 1400 g of the hydrogen fluoride adduct mixture of perfluoroalkene obtained in Synthesis Example 1, 32 g of perfluoropropyl vinyl ether, and 80 g of TFE.
Was charged. Keeping the temperature at 50 ° C., 1% by weight of di (perfluorobutyryl) peroxide as a polymerization initiator
A perfluorohexane solution was charged to start the reaction. During the reaction, TFE was introduced into the system to adjust the reaction pressure to 5.1.
It was maintained at 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 3.5 hours, 85 g of a white copolymer was obtained as a slurry. The copolymer had a melting point of 305 ° C. and a thermal decomposition starting point of 435 ° C., and gave a good compression molded product at a molding temperature of 340 ° C. Tensile strength of the molded product is 475
The kg / cm ² and tensile elongation were 350%.

Example 3 400 g of HFP was charged instead of 32 g of perfluoropropyl vinyl ether, and the amount of the hydrogen fluoride adduct mixture of perfluoroalkene obtained in Synthesis Example 1 was changed to 1000 g instead of 1400 g. Polymerization was carried out in the same manner as in Example 2, and after 2.5 hours, 32 g of a white copolymer was obtained as a slurry. The copolymer has a melting point of 295 ° C. and a thermal decomposition starting point of 432.
C. and a molding temperature of 340.degree. C. gave good compression molded articles. Tensile strength of the molded product is 350kg / cm
² , the tensile elongation was 320%.

Comparative Example 1 A stainless steel reactor having an internal volume of 1.2 liters was charged with deoxidized water 500 g, t-butanol 200 g, and disuccinic acid peroxide 0.65 g.
The reaction was carried out while maintaining the temperature at 65 ° C. During the reaction, a mixed gas of TFE and ethylene (molar ratio TFE / ethylene = 53/47) is introduced into the system to maintain the reaction pressure 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 initiation temperature of 3
It was 61 ° C. The molded product compression-molded at 300 ° C. had a low molecular weight and was brittle.

Reference Example 1 Instead of charging the hydrogen fluoride adduct mixture of perfluoroalkene obtained in Synthesis Example 1, 1,
1,255 g of 1,2-trichlorotrifluoroethane was charged, and 1,1-dichloro-2,2,2 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 3,3,3-pentafluoropropane was charged, and after 2 and a half hours, 35 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 350 ° C.
And a good compression molded product was obtained at a molding temperature of 300 ° C. The tensile strength of the molded product is 430 kg / cm ² ,
The tensile elongation was 470%.

[0024]

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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuya Oharu 1150 Hazawa-machi, Kanagawa-ku, Yokohama, Kanagawa Prefecture Asahi Glass Co., Ltd. Central Research Laboratory

Claims (2)

[Claims] 1. When producing a fluoropolymer containing a fluoroolefin unit as a main constituent unit by polymerization in a polymerization medium, it is obtained by anionic oligomerization of tetrafluoroethylene or hexafluoropropylene as the polymerization medium. A process for producing a fluoropolymer, which comprises using a fluoroalkane obtained by adding hydrogen fluoride to a double bond of a perfluoroalkene. 2. The method according to claim 1, wherein the fluoropolymer is a tetrafluoroethylene / ethylene copolymer, a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene / hexafluoropropylene copolymer.