JPH0749480B2 - Method for producing fluorine-containing copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a coating material applied to the surface of various plastic materials to impart various physical properties, for example, a plastic core material such as polymethylmethacrylate as an optical fiber. The present invention relates to a method for producing a fluoropolymer having excellent properties as a sheath material and the like, and more particularly to a method for producing a copolymer composed of vinylidene fluoride, hexafluoroacetone and other fluoroolefins.

[Prior Art] Conventionally, in the production of this main copolymer, it is general to use a radical copolymerization method as a polymerization reaction, and usually, an oil-soluble radical initiator is used in an organic solvent,
The reaction is carried out at a temperature in the range of 0 to 130 ° C. Examples of the organic solvent include saturated hydrocarbons such as n-hexane and n-heptane, fluorine-based solvents such as dichlorotetrafluoroethane and trichlorotrifluoroethane, and ester-based and ketone-based solvents. In particular, trichlorotrifluoroethane is most advantageous in terms of its solubility, flammability, etc. In practice, trichlorotrifluoroethane is used for the polymerization.

Due to its stability, the use of trichlorotrifluoroethane has been restricted in recent years because it causes destruction of the ozone layer.

Therefore, using various solvents using this trichlorotrifluoroethane, the use of a solvent replacing trichlorotrifluoroethane is being investigated, and even in this type of polymerization reaction, a non-polluting solvent instead of trichlorotrifluoroethane is being investigated. A polymerization method using is desired, but it is not sufficient in terms of solubility and the like, and there is no satisfactory reaction yield.

[Specific Means for Solving Problems] The inventors of the present invention have arrived at the present invention as a result of earnest studies in view of such problems. That is, the present invention is a method for producing a fluorine-containing copolymer, characterized in that a perfluoroether compound is used as a solvent in a polymerization reaction of a copolymer of vinylidene fluoride, hexafluoroacetone and other fluoroolefins.

In the present invention, trifluoroethylene or tetrafluoroethylene can be used as the other fluoroolefin, and it is of course possible to use both of them to form a quaternary copolymer.

In the present invention, the component ratio of vinylidene fluoride, hexafluoroacetone and other fluoroolefins is not particularly limited, and copolymers of various compositions can be produced, but it is obtained when the content of each component increases. The copolymer generally exhibits the following physical properties.

As the content of hexafluoroacetone increases, it becomes too soft and the hardness decreases. Further, when the content of tetrafluoroethylene increases, the melt moldability deteriorates. In addition, the transparency decreases as the content of trifluoroethylene increases. The transparency decreases as the content of vinylidene fluoride increases.

Therefore, the composition may be determined according to the desired physical properties in consideration of these characteristics.

For example, considering transparency, heat resistance, etc., in general,
Vinylidene fluoride 30-85 mol%, hexafluoroacetone 1-35 mol%, other fluoroolefins 5-50
A range of mol% is preferred.

In the present invention, a perfluoroether compound is used as a polymerization solvent, but perfluoroether is one in which all hydrogen atoms in the molecule are replaced by fluorine, and 3M's trade name Fluorinert is generally commercially available. ing.

The best polymerization solvent is (In the formula, n is 3 or 4, and any F may be substituted with a perfluoroalkyl group.) In the perfluoro cyclic ether represented by the formula, n is 3 and the side chain is -C. ₂
Fluorinert FC-72 mainly composed of F ₅ and Fluorinert FC-75 mainly composed of n = 3 and a side chain of -C ₄ F ₉ .

Although a polymerization reaction is carried out using such a solvent,
The reaction mode is not particularly limited, but a general polymerization method will be described below.

While charging the polymerization solvent into the autoclave and stirring, degassing after substituting with an inert gas such as nitrogen, charging a predetermined amount of the raw material monomer, as a polymerization initiator, heptafluorobutyric peroxide, di-normal propyl peroxycarbonate, etc. Is pressed into the solution as a solution in a polymerization solvent.
These polymerization initiators may be appropriately selected and used depending on the reaction conditions, particularly the reaction temperature, and the amount used is preferably in the range of 0.5 to 2% by weight with respect to the raw material monomer. If it is less than this range, the polymerization reaction does not proceed sufficiently, and if it exceeds this range, there is no particular effect commensurate with the amount added, so that it is not economical.

The reaction temperature is usually selected from the range of 10 to 100 ° C. If the temperature is too low, the reaction rate will be too slow to be efficient, and if it is too high, it will be dangerous because the pressure will be high depending on the composition of the raw material. It may be determined in consideration of these. About 30 hours is usually sufficient for the reaction, and after the reaction is completed, it is preferable to purge the residual gas and then stabilize the remaining hexafluoroacetone as hemiacetal with methanol or the like. After that, the polymerization product is obtained by a commonly used means.

In the polymerization reaction of the present invention, the solubility of the polymerization product in the perfluoroether, which is the polymerization solvent, is appropriate, so that the reaction yield and the stability of the polymerization product are excellent. Moreover, since the boiling point of the polymerization solvent is relatively high, the selection range of the reaction temperature condition and the selection range of the polymerization initiator are widened, and the recovery of the solvent after the reaction and the escape of the solvent in the reaction system can be prevented.

Hereinafter, the present invention will be described in detail with reference to examples.

Example 1 An autoclave having an internal volume of 1 was charged with 530 Perfluoro cyclic ether-Fluorinate FC-72 manufactured by 3M, and the inside of the autoclave was replaced with nitrogen while stirring, and then deaerated. After repeating this operation 3 times, 27.0 g of hexafluoroacetone, 8.8 g of trifluoroethylene and 52.1 g of vinylidene fluoride were charged, and the internal temperature in the autoclave was adjusted to 2
The temperature was adjusted to 6 ° C. Next, heptafluorobutyric peroxide (HFBP) was added as a polymerization initiator
The reaction temperature was adjusted to 3 by charging 15 g of a 5% by weight solution of FC-72.
The temperature was maintained at 0 ± 1 ° C, and stirring was continued for 18 hours. After completion of the reaction, the residual gas was purged and the residual hexafluoroacetone was stabilized as hemiacetal with methanol to stabilize it.

The polymer slurry was extracted from the autoclave and solid-liquid separated to obtain the polymer as a cake.

The cake was washed with methanol, separated and dried to obtain a copolymer (56.0 g). The yield was 63.7%.

Melt index (MI), thermal decomposition temperature (T
m), crystallization temperature (Cp), and molecular weight were measured, and the results are shown in Table 1.

In addition, each physical property evaluation was performed as follows.

MI: The dried resin is measured with an MI meter (TAKARA L203-6531).

Tm, Cp: The strand obtained by the MI meter was used for DSC
Measured with DSC CN8085E1).

Molecular weight: Measured by gel permeation chromatography (CP8000, manufactured by Tosoh Corporation). Number average molecular weight (converted to polystyrene) Examples 2 to 4, Comparative Examples 1 to 3, and Reference Example In the same manner as in Example 1, the composition of the raw material monomers and the polymerization solvent were set as shown in Table 1 to carry out the polymerization reaction. The physical properties were measured. The results are shown in Table 1.

As is clear from this table, in the case where the perfluoro cyclic ether which is the polymerization solvent of the present invention was used, the yield was higher than that in the case where the polymerization reaction was performed using trichlorotrifluoroethane (reference example). Are almost the same, and the reaction hardly progresses with other solvents, or the yield thereof is extremely low, which is clearly different from the polymerization result of the present invention.

[Effects of the Invention] According to the method of the present invention, it is possible to efficiently produce a fluorinated copolymer excellent in various physical properties without using trichlorotrifluoroethane whose use is restricted due to ozone destruction and the like. In addition, since the reaction conditions, in particular, the reaction temperature can be selected in a wide range, the reaction can be easily performed by appropriately changing the reaction conditions depending on the desired physical properties.

Claims (1)

[Claims] 1. A copolymer of vinylidene fluoride, hexafluoroacetone and other fluoroolefins, wherein the other fluoroolefin is one or more fluoroolefins selected from the group consisting of trifluoroethylene and tetrafluoroethylene. The method for producing a fluorine-containing copolymer is characterized in that the polymerization reaction of the fluorine-containing copolymer is carried out using a perfluoro cyclic ether as a solvent.