JPS62285907A - Production of tetrafluoroethylene/fluorovinyl ether copolymer - Google Patents

Abstract

PURPOSE:To obtain the title copolymer at a low cost in good efficiency of production, by copolymerizing tetrafluoroethylene with a fluorovinyl ether in an aqueous medium containing a specified amount of a fluorine-containing surfactant and free of any buffer. CONSTITUTION:Tetrafluoroethylene and a fluorovinyl ether (e.g., perfluoropropyl vinyl ether) and added to an aqueous medium containing 30-300ppm of a fluorine-containing surfactant (e.g., ammonium perfluorooctanoate) and free of any buffer. A polymerization initiator (e.g., diperoxy succinic acid) is further added thereto, and the mixture is copolymerized to obtain the title copolymer. In this way, the polymerization can be performed even at a high polymer concentration, so that the efficiency of production can be increased. In addition use of an expensive solvent is not necessary, and a copolymer of excellent heat stability can be produced.

Description

Detailed Description of the Invention; 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing a tetrafluoroethylene-fluorovinyl ether copolymer.

[Prior Art] Conventionally, a solution polymerization method or an emulsion polymerization method has been proposed as a method for producing a tetrafluoroethylene-fluorovinyl ether copolymer. For example, Japanese Patent Publication No. 48-2223 discloses a solution polymerization method using CCl2FCClF2 as a solvent, and Japanese Patent Publication No. 48-41942 discloses a solution polymerization method using a perfluorinated solvent or a chlorofluoroalkane as a medium in the presence of a hydrogen-containing chain transfer agent. is listed. However, in the case of such solution polymerization methods, the solution viscosity increases as the polymerization progresses, making it difficult to stir the polymerization system, resulting in poor dispersion of the resulting copolymer, and making it difficult to control the polymerization heat. . Therefore, in the solution polymerization method, it is necessary to keep the polymer concentration low, resulting in poor production efficiency, and it is also economically disadvantageous because a large amount of expensive solvent is used.

On the other hand, the application of the so-called emulsion polymerization method, in which copolymerization is carried out in an aqueous medium containing a dispersant, a buffering agent, etc.
No. 20788) has also been proposed. This emulsion polymerization method requires a large amount of expensive fluorosurfactant that can be used as a dispersant, which is not only economically disadvantageous, but also has disadvantages such as complicating cleaning of the produced polymer and processing of waste liquid. be. In addition, in such emulsion polymerization methods, the resulting polymer tends to decompose and become colored under high temperatures due to the influence of residual dispersants and buffering agents, resulting in poor electrical properties, or due to leaching of ionic impurities. However, some disadvantages are recognized, such as disadvantages in chemical applications.

[Problems to be Solved by the Invention] The purpose of the present invention is to solve the problems in the prior art as described above, and to provide a tetrafluoroethylene-fluorovinyl ether copolymer that can be used in a wide range of applications. It is an object of the present invention to provide a manufacturing method that is efficient and advantageous for industrial implementation.

[Means for Solving the Problems] The present invention was made to solve the above-mentioned problems, and consists of tetrafluoroethylene and fluorovinyl ether containing 30 to 300 ppm of a fluorine-based surfactant and substantially The present invention provides a novel method for producing a tetrafluoroethylene-fluorovinyl ether copolymer, which is characterized by copolymerizing the copolymer in an aqueous medium containing no buffering agent.

In the present invention, the fluoroalkyl vinyl ether has the general formula CF2-aCF(OCF2CF)x-0-(CF2)y
cF2X In the formula, X is CF3 hydrogen or fluorine, x = 0 to 4, Te = 0 to 7, Oh
Examples include those represented by CF3 (Z-〇~3), among which CF2 = CF for the reason of maintaining high temperature strength.
OC3F7, CF? It is preferable to use =gCFOCF2CF-CF3.

In the present invention, the amount of fluorovinyl ether used is such that the content of fluorovinyl ether in the copolymer is 0.1
It is preferable to set the content to 1 to 5 mol %, preferably 1 to 3 mol %, for the reason that a copolymer with high high temperature strength can be industrially produced smoothly and advantageously.

In the present invention, the copolymerization reaction is carried out at 30 to 300 ppm,
It is important that the reaction be carried out in an aqueous medium containing preferably 50 to 200 ppm of a fluorosurfactant and substantially free of buffering agents. If the amount of surfactant used is too small than the above range, the polymerization rate will be extremely low, while if it is too large, the thermal stability of the resulting copolymer will decrease, both of which are not preferred. In addition, the use of buffering agents and non-fluorinated surfactants are disadvantageous because they result in a decrease in the thermal stability and electrical properties of the resulting copolymer, and furthermore, they lead to leaching of ionic impurities from the molded product. .

The fluorine-based surfactant is preferably an anionic one, and among these, ammonium salts of long-chain perfluorocarboxylic acids such as ammonium perfluorooctanoate or ammonium perfluorononanoate are preferably employed.

In the present invention, as the polymerization initiator, one that is soluble in an aqueous medium is used, and one that exhibits a radical generating ability at a temperature of 50 to 100°C is particularly suitable. Such initiators include inorganic initiators such as redox initiators made of persulfates such as ammonium persulfate, hydrogen peroxide, or their combinations with reducing agents such as sodium bisulfite and sodium pyrosulfite, and furthermore, disuccinic acid. Examples include dibasic acid peroxides such as peroxide, diglutaric acid peroxide, and monosuccinic acid peroxide, and organic initiators such as azobisisobutyramidine dihydrochloride.

From the viewpoint of thermal stability of the resulting copolymer, dibasic acid peroxides can be preferably employed.

In the present invention, the copolymerization reaction is preferably carried out at a temperature range of 50 to 100°C. When the temperature is lower than 50°C, the polymerization rate decreases, and when it exceeds 100°C, it tends to become difficult to control the polymerization rate and molecular weight.

In the present invention, the reaction pressure is not particularly limited, but from the viewpoint of the copolymerization reaction rate, it is preferable to carry out the reaction in a pressurized system, and usually about 10 to 30 kg/cm2 is employed.

The use of chain transfer agents can also be employed in the present invention to control the melting properties of the resulting copolymer. Suitable chain transfer agents include liquid solvents such as methanol, ethanol, cyclohexane, methyl ether, or hydrogen,
methane.

Gaseous chain transfer agents such as ethane are exemplified, and methanol can be preferably employed from the viewpoint of high temperature strength and thermal stability of the resulting copolymer. In this case, the amount of methanol used is 0.03 to 0.25% by weight in the aqueous medium.
It is preferable to set it as approximately.

[Example] Next, the present invention will be explained in more detail with reference to Examples.

In the following Examples and Comparative Examples, the volumetric flow rate, copolymer composition, and thermal stability of the produced copolymers were measured and evaluated by the following methods.

Copolymer composition: A method for measuring the content of PPVE in a copolymer of tetrafluoroethylene (TFE) and perfluoropropyl vinyl ether (PPVE) is known in Japanese Patent Publication No. 48-2223, and based on the results of IR analysis, the following Calculate using the formula.

This method was also applied in this specification.

Volumetric flow rate: In this specification, the volumetric flow rate is a value that serves as a guideline for the molecular weight of a copolymer, and is defined as follows.

Using a Koka type flow tester manufactured by Shimadzu Corporation, the copolymer was placed in a cylinder with an inner diameter of 9.5 mm.
After maintaining the temperature at 380° C. for 5 minutes, it was extruded through an orifice with an inner diameter of 2.1 mm and a length of 8 cm under a piston load of 7 kg, and the extrusion speed (mm 3 /sec) at this time was determined.

Thermal stability: Take 5g of the produced copolymer in a chalet, After heating at 380 °C for 2 hours in an electric furnace.

The white sample was placed on paper and the difference in color tone from the copolymer before heating was observed. The evaluation was rated as Δ when there was no coloration that could be seen with the naked eye, Δ when there was some coloring, and × when there was significant coloration.

Metal elution property: After immersing 10 g of the produced copolymer in 100 mQ of 65% nitric acid at room temperature for 6 days, metal ions in the nitric acid solution were measured by emission spectrometry.

Electricity is also k1ga+ ~ Ri se＞+y+? lJ-bloodΔ
Ammonium perfluorononanoate (A
FN: fluorine-based surfactant) was dissolved and charged into a degassed stainless steel autoclave with an internal capacity of 1 t2. Then, 0.5 g of methanol and 30.7 g of dopa-fluoropropyl vinyl ether (PPVE) are introduced, heated to 70°0 with stirring, and kept at a constant temperature.

Tetrafluoroethylene (TFE) t-pressure is 15 kg
/cm2, then 30 d of a 2.8 wt $ aqueous solution of disuccinic acid peroxide (D S A P) was injected under pressure to start the reaction. When the pressure starts to drop, add more tetrafluoroethylene to increase the pressure to 15'kg/c.
Keep it at m2. After 2.5 hours had passed from the start of the reaction, the autoclave was cooled, unreacted gas was purged to complete the reaction, and the copolymer was recovered.

The recovered copolymer was washed repeatedly with water and then heated at 150°C for 1
It was oven dried for 2 hours.

The yield, PPVE, flow rate, and thermal stability of each of the obtained copolymers are summarized in Table 1.

Table 1 Comparative Example 5 Polymerization was carried out in the same manner as in Example 2, except that 7 g of disodium hydrogen phosphate was added as a buffer, and 58 g of copolymer was obtained.
I got it.

The results of the thermal stability and metal elution tests of this copolymer are shown in Table 2 in comparison with those of Example 2.

Table 2 Example 4 Polymerization was carried out in the same manner as in Example 2 except that 38.5 g of perfluoroisobutyl vinyl ether (PI BVE) was used as perfluorovinyl ether, and copolymer 71
I got 8.

The thermal stability of this copolymer was good.

[Effects of the Invention] According to the production method of the present invention, compared to known solution polymerization methods,
Since polymerization can be carried out even at high polymer concentrations, production efficiency is greatly improved and the use of expensive solvents can be avoided. On the other hand, the thermal stability of the produced copolymer resin is superior to that of known emulsion polymerization methods. Thus, the present invention provides a method for efficiently and inexpensively producing a copolymer with excellent thermal stability and electrical properties that can be applied to a wide range of applications such as electrical equipment parts, electric wires, and chemical industry parts. It is something.

Continuing amendment March 1986/ρ day

Claims (1)

[Scope of Claims] 1. A tetrafluoroethylene characterized by copolymerizing tetrafluoroethylene and fluorovinyl ether in an aqueous medium containing 30 to 300 ppm of a fluorosurfactant and substantially free of a buffer. A method for producing an ethylene-fluorovinyl ether copolymer. 2. The content of fluorovinyl ether in the copolymer is 1
The manufacturing method according to claim 1, wherein the content is 3 mol %. 3. The manufacturing method according to claim 1, wherein the aqueous medium contains 0.03 to 0.25% by weight of methanol.