JP2512610B2 - Method for producing fluorine-containing copolymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a fluorinated copolymer.

(Prior Art and Problems to be Solved by the Invention) Conventionally, fluorine-containing resins have excellent chemical resistance, heat resistance, and electrical characteristics and have been used in a wide range of industrial fields. Further, recently, various functionalities such as piezoelectricity, gas selective permeability, and transparency have been imparted to these fluorine-containing resins to apply them to special applications, which have been actively performed recently.

As a result of repeated research aimed at producing a fluorine-containing copolymer excellent in chemical resistance, mechanical strength, heat resistance, etc., the present inventors have found that tetrafluoroethylene and CF ₂ = CFOCH ₂ (C
F ₂ ) _n X (where X is a hydrogen atom or a halogen atom,
n is an integer of 1 or more. ), A copolymer with a fluorine-containing vinyl ether, wherein the proportion of the monomer unit based on the above-mentioned fluorine-containing vinyl ether is 0.5 to 40 mol%, was successfully produced, and has already been proposed. Wish 1-
No. 264046).

The above copolymer has excellent chemical resistance, mechanical strength, and heat resistance, even though it contains hydrogen atoms derived from fluorine-containing vinyl ether in the molecule, and is also excellent in melt moldability. .

However, this copolymer has a large change in the melt viscosity due to a change in the molding temperature, that is, the temperature dependence of the melt viscosity is large, and has some problems in improving the dimensional accuracy of the molded product during molding. Was there.

Therefore, an object of the present invention is to provide a fluorocopolymer having a small temperature dependence of melt viscosity.

(Means for Solving the Problems) In view of the above-mentioned problems, the present inventors have added various fluorovinyl ethers as a third monomer at the time of copolymerization of tetrafluoroethylene and fluorine-containing vinyl ether, and copolymerization As a result of repeating the experiment, it was found that when the copolymer was copolymerized by adding fluorodivinyl ether having a specific structure, the obtained copolymer had a small temperature dependence of melt viscosity. Further, it was found that the obtained copolymer was excellent not only in chemical resistance but also in mechanical strength, and completed the present invention.

That is, the present invention provides (a) tetrafluoroethylene 40 to 98 mol% (b) the following formula [I] CF ₂ = CFOCH ₂ R _f [I] (wherein Rf is a perfluoroalkyl group having 1 to 8 carbon atoms). 1 to 40 mol% of the fluoromonovinyl ether represented by the formula (1) and (c) 1 to 20 mol% of the fluorodivinyl ether represented by the following formula [II] CF ₂ = CF0CF ₂ CF ₂ OCF = CF ₂ [II] A method for producing a fluorine-containing copolymer, which comprises copolymerizing.

The fluoromonovinyl ether represented by the above general formula [I] used in the present invention has a perfluoroalkyl group bonded to an oxygen atom, and the fluoroalkyl group is
It is a group represented by CH2.Rf (where Rf is a perfluoroalkyl group having 1 to 8 carbon atoms), and specific examples are as follows.

CF ₂ = CFOCH ₂ CF ₃ , CF ₂ = CFOCH ₂ CF ₂ CF ₃ , CF ₂ = CFOCH ₂ (CF ₂ ) ₂ CF ₃ , CF ₂ = CFOCH ₂ (CF ₂ ) ₃ CF ₃ , CF ₂ = CFOCH ₂ ( CF ₂ ) ₄ CF ₃ , CF ₂ = CFOCH ₂ (CF ₂ ) ₅ CF ₃ , CF ₂ = CFOCH ₂ (CF ₂ ) ₆ CF ₃ , CF ₂ = CFOCH ₂ (CF ₂ ) ₇ CF ₃ , the fluoro of the present invention The divinyl ether cannot achieve the object of the present invention unless it has the structure represented by the general formula [II]. That is, an alkylene group sandwiched between two vinyloxy groups must have 2 carbon atoms. When the number of carbon atoms is 3 or more, the copolymer is copolymerized with tetrafluoroethylene and the fluoromonovinyl ether represented by the above general formula [I], but the obtained copolymer is not preferable because the melt molding becomes difficult. Also, carbon number is 1
In the case of, it is not preferable because it is difficult to synthesize the monomer itself.

The ratio of the fluoromonovinyl ether represented by the above general formula [I] must be in the range of 1 to 40 mol%,
It is preferably in the range of ˜30 mol%. When the proportion of the fluoromonovinyl ether represented by the above general formula [I] is less than 1 mol%, the resulting fluorocopolymer has poor melt moldability, and when it exceeds 40 mol%, the fluorocopolymer is obtained. However, it is not solid but becomes oily, so its use is limited. The proportion of the fluorodivinyl ether represented by the above general formula [II] must be in the range of 1 to 20 mol%, preferably 2 to 10 mol%. When the ratio of the fluorodivinyl ether represented by the general formula [II] is less than 1 mol%, the temperature dependence of the melt viscosity of the obtained fluorocopolymer cannot be improved,
When it exceeds 20 mol%, the crosslink density becomes too high and the melt moldability deteriorates, which is not preferable. Furthermore, since the increase / decrease in the proportion of tetrafluoroethylene is the relative increase / decrease in the compounds represented by the general formulas [I] and [II], the compounds represented by the general formulas [I] and [II] will be described. For this reason, tetrafluoroethylene must be 40 to 98 mol%, preferably 60 to 88 mol%.

As the above-mentioned copolymerization method of each monomer, known polymerization methods such as solution polymerization, emulsion polymerization, suspension polymerization and the like are adopted without any limitation. It is particularly preferably adopted because the mechanical strength is improved. That is, it is a solution polymerization method in which each of the above-mentioned monomers is dissolved in an organic solvent and copolymerized in the presence of a radical polymerization initiator.

 The above solution polymerization method will be described in detail below.

The organic solvent used in the solution polymerization is not particularly limited, but generally, chlorofluorocarbon and perfluoro compound are preferably used. For example, trichlorotrifluoroethane, dichlorotetrafluoroethane, trichlorofluoromethane, dichlorodifluoromethane,
Fluorine-based solvents such as perfluorocyclohexane, perfluorocyclobutane, perfluorotributylamine, perfluorotriamylamine and perfluoropolyethers are preferable. As a specific example of the polymerization method, a deoxygenated organic solvent, fluoromonovinyl ether and fluorodivinyl ether are added to a pressure vessel equipped with a stirrer and a thermometer. The ratio of addition to these organic solvents is such that the viscosity increases as the polymerization proceeds and stirring becomes difficult, and the heat of polymerization cannot be removed due to insufficient stirring and it is not difficult to maintain the polymerization. Selected by range. Usually, fluoromonovinyl ether and fluorodivinyl ether are added to 100 parts by weight of organic solvent in total.
It is preferable to select from the range of 0.1 to 30 parts by weight, preferably 1 to 10 parts by weight. Further, in order to facilitate removal of the heat of polymerization and stirring, water in an amount of 0.3 to 10 times the weight of the organic solvent can coexist.

Next, in order to deoxidize the inside of the reaction container, for example, the operation of degassing after cooling and solidifying the contents of the reaction container is repeated. Then, tetrafluoroethylene (hereinafter abbreviated as TFE) is added to the gas phase portion of the reaction vessel. After increasing the pressure of TFE to a predetermined pressure, a radical generator as a polymerization initiator is dissolved in an organic solvent and added, and polymerization is carried out while maintaining the temperature at the polymerization temperature.

The polymerization time varies depending on the pressure of TFE, the amount of the radical generator added, and the like, but a copolymer is sufficiently formed if it is several hours to several tens hours.

Examples of the polymerization initiator used in this method include dialkyl peroxides, diacyl peroxides, peroxydicarbonates, and azo compounds. Considering the heat resistance of the copolymer generally obtained, a fluorine-containing, preferably perfluoro, radical generator is used.
For example, a fluorine-containing diacyl peroxide represented by the following formula is preferably used.

Examples of the radical generator that can be preferably used in the present invention are as follows.

The amount of the above radical generator used cannot be unconditionally determined depending on the solvent used, the polymerization conditions, especially the polymerization temperature,
0.5 against the fluorine-containing vinyl ether normally used for polymerization
The radical generator corresponding to ˜20 mol%, preferably 1 to 10 mol% may be added at the time of charging. Further, depending on the conditions and composition, it may be difficult for the polymerization to proceed. In such a case, it is an effective means to add a radical generator again during the polymerization.

The pressure of TFE sufficiently polymerization reaction be in the range of ^{1Kg / cm 2 G~30Kg / cm 2} G proceeds, but the preferred pressure 1Kg / cm ² G~10
It is Kg / cm ² G. TFE is generally used when the TFE pressure is low.
A copolymer with a low content of
The content of TFE becomes high and the production rate of the copolymer becomes high. Of course, the polymerization will proceed even if the lower and upper limits of the pressure are exceeded, but if the pressure is too high, the disadvantage will be that the apparatus will be considerably expensive. The temperature at the time of polymerization is determined by using the decomposition rate of the radical generator used as one guide, but it is usually 0.
C. to 100.degree. C., preferably about 5.degree. C. to 80.degree. 5 ° C for fluorine-containing or perfluoro-diacyl peroxide, which has a large decomposition rate even at low temperatures.
It is preferably about -60 ° C.

The produced copolymer is recovered by separating the organic solvent (and water) from the polymerization mixture. In this case, water can be easily separated from the copolymer by filtration, but the organic solvent may not be recovered by filtration because the copolymer is dispersed in a high concentration. In such a case, the copolymer can be recovered by using a centrifugal separator or by separating the copolymer from the solvent under reduced pressure.

(Effect) The fluorine-containing copolymer obtained by the method of the present invention is 1
-40 mol% of the fluoromonovinyl ether-based monomer unit represented by the general formula [I] and 1-20 mol% of the fluorodivinyl ether-based monomer unit represented by the general formula [II]. Despite the fact that the copolymer contains hydrogen atoms in the molecule, it has good chemical resistance and is comparable to that of commercially available perfluoro resins.

This copolymer has little temperature dependence of melt viscosity, and the melt viscosity at each temperature is significantly increased by increasing the amount of the monomer unit represented by the general formula [II]. Furthermore, this copolymer has also been improved in mechanical strength, and has a tensile strength about 50 to 90 kg / cm ² which is larger than that of the copolymer not using the fluorodivinyl ether represented by the general formula [II] for the polymerization. Show.

Therefore, the fluorine-containing copolymer obtained in the present invention can be used as a film, a tube, a packing material, a lining material, and other molded articles in the industrial field requiring chemical resistance. In addition, it has excellent electrical characteristics and can be used for connectors, substrate materials, insulating materials and the like in the fields of electricity and electronics. In particular, the monomer unit based on the fluoromonovinyl ether represented by the general formula [I] is
Since the fluorine-containing copolymer of more than 10 and up to 40 mol% is soft at room temperature and has excellent transparency, it can be used as a surface coating material.

(Examples) Hereinafter, the present invention will be specifically described with reference to Examples. The measured value was determined as follows.

1. Mechanical properties (1) Tensile strength measurement Compliant with JIS K7113 (2) Preparation of test piece Fluorine-containing copolymer powder was pressed at a temperature of 280 ° C. for 1
A sheet having a thickness of ~ 2 mm was prepared, and test pieces necessary for the above test method were prepared.

2. Thermal properties (1) Thermal decomposition temperature Thermoflex (R-TG-DTA: manufactured by Rigaku Denki Co., Ltd.)
Was used and the temperature rising rate was set to 10 ° C./min, and measurement was performed in air.

(2) Measurement of softening point It was measured using HDT & VSPTTESTER (manufactured by Toyo SEIKI Co., Ltd.).

3. Measurement of melt viscosity A high-performance melt viscosity measuring device was used.

A die having a diameter of 0.5 mm and a length of 5 mm was used, and a load of 50 kg / cm ² was applied for measurement.

4. Optical Properties A film having a thickness of 100 μm was prepared from the fluorocopolymer powder by the same method as described in 1- (2) Preparation of test piece, and the absorbance of this film with respect to light of 250 nm was measured. It was measured.

Example 1 1,3,2-trichloro-1,2,2 purified in advance by distillation in a stainless steel autoclave No. 3 equipped with a stirrer
-Trifluoroethane 1, CF ₂ = CFOCH ₂ CF ₂ CF ₃ 88g, CF
₂ = CFOCF ₂ CF ₂ OCF = CF ₂ 15 g was added. The autoclave was cooled with liquid oxygen to solidify the contents and then deaerated with a vacuum pump. Further, nitrogen was introduced up to a pressure of 3 Kg / cm ^{2, and} the temperature was raised (about -5 ° C) while maintaining the pressure until the contents were dissolved. This operation was repeated 3 times to remove oxygen in the autoclave. Once again, it was cooled and solidified with liquid oxygen and degassed with a vacuum pump, then the temperature was raised, and when the temperature reached about 18 ° C, TFE was increased to 3.7%.
After introducing at a pressure of Kg / cm ² to saturate and dissolve TFE, the introduction valve of TFE was closed. Then, as a polymerization initiator (CF ₃ C
3.5 cc of 1,1,2-trichloro-1,2,2-trifluoroethane containing 0.5 g of F ₂ CF ₂ CO _{2 2} was injected.

When the polymerization was continued for 50 hours, the pressure in the autoclave dropped to about the vapor pressure of 1,1,2-trichloro-1,2,2-trifluoroethane, so the polymerization was stopped. afterwards,
Solvent and unpolymerized CF ₂ = CFOCH ₂ CF ₂ CF _{3 in the} autoclave
And CF ₂ = CFOCF ₂ CF ₂ OCF = CF ₂ are connected to a vacuum pump via a trap that collects by cooling, and the pressure in the autoclave is reduced while stirring, and the solvent used and unpolymerized fluoromonovinyl ether and fluorodivinyl ether are removed. Collected in trap. After completely removing the solvent, the autoclave was opened and a white powdery copolymer was formed. When the obtained copolymer was dried under reduced pressure at 150 ° C. for 10 hours, about 310 g of the copolymer was obtained.

Moreover, when the collected solvent was analyzed by gas chromatography, unpolymerized CF ₂ = CFOCH ₂ CF ₂ CF ₃ and CF ₂ = CFOCF ₂ CF ₂ O
Almost no CF = CF ₂ was detected, indicating that the charged fluorovinyl ether was polymerized at a conversion rate of almost 100%.

Without the use of Comparative Example 1 Fluoro divinyl ether _{CF 2 = CFOCF 2 CF 2 OCF} = CF 2, prepared in TFE and _{CF 2 = CFOCH 2 CF 2 CF} 3 only the copolymer in a similar manner as in Example 1.

CF ₂ = CFOCH ₂ CF ₂ CF ₃ is 88.0 g (preparation composition 15.0 mol%)
used. When the polymerization was carried out for 50 hours, the polymerization was almost completed. As in Example 1, CF ₂ = CFOCH ₂ CF ₂ CF ₃ and T
When the conversion rate of FE was calculated, it was almost 99% in each case. When the obtained copolymer was dried under reduced pressure, it was about 250 g.

Examples 2 to 6 Using the polymerization apparatus and method of Example 1, fluorine-containing copolymers having different compositions were synthesized. Table 1 shows the conditions changed from Example 1 and the monomer conversion rate.

Example 7 CF ₂ = CFOCH ₂ CF ₃ was used as fluoromonovinyl ether.
Polymerization was carried out in the same manner as in Example 1 except that 43.2 g (preparation composition: 10 mol%) was used. When the polymerization was carried out for 45 hours, the polymerization was almost completed. When the conversion rates of fluoromonovinyl ether, fluorodivinyl ether and TFE were determined in the same manner as in Example 1, they were all about 99%. When the obtained copolymer was dried under reduced pressure, it was about 250 g.

Example 8 CF ₂ = CFOCH ₂ C ₂ F ₅ as fluoromonovinyl ether
Polymerization was carried out in the same manner as in Example 1 except that 31.7 g (preparation composition: 6 mol%) was used. When the polymerization was carried out for 20 hours, the polymerization was almost completed. As in Example 1, fluoromonovinyl ether, fluorodivinyl ether and
When the conversion rate of TFE was calculated, it was almost 100% in all cases. When the obtained copolymer was dried under reduced pressure, it was about 245 g.

Example 9 The thermal decomposition temperature, melt viscosity, tensile strength, softening point and absorbance of the fluorocopolymers obtained in Examples 1 to 8 and Comparative Example 1 were measured, and the results are shown in Table 2. Further, the data of melt viscosity in Table 2 is shown in the graph of FIG. Further, as a result of immersing in concentrated H ₂ SO ₄ and 50% NaOH aqueous solution at 100 ° C. for 7 days, no weight change was observed in any of the copolymers. The copolymers Nos. 1 to 7 were flexible and soft copolymers.

[Brief description of drawings]

FIG. 1 is a graph showing the temperature dependence of the melt viscosity of the fluorocopolymer obtained by the method of the present invention.

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Claims (1)

(57) [Claims] 1. A (a) tetrafluoroethylene 40 to 98 mol% (b) the following formula CF2 = CFOCH ₂ Rf (although, Rf is a a perfluoroalkyl group having 1 to 8 carbon atoms) fluoro monovinyl ether represented by 1 to 40 mol% and (c) 1 to 20 mol% of fluorodivinyl ether represented by the following formula CF ₂ = CF0CF ₂ CF ₂ OCF = CF ₂ are copolymerized, and a method for producing a fluorine-containing copolymer. .