JPH08333423A - Production of perfluorocarbon copolymer - Google Patents

Abstract

PURPOSE: To produce a perfluorocarbon copolymer containing a large proportion of a perfluorocarbon monomer having a functional group of sulfonic acid type easily in high yields by using a medium less depletive to the ozonosphere. CONSTITUTION: A perfluorocarbon monomer having a functional group of sulfonic acid type and a perfluoroolefin are subjected to solution polymerization by using a medium being a fluoroalkane prepared by hydrogenating the double bond of a perfluoroalkene obtained by oligomerizing tetrafluoroethylene or hexafluoropropylerne.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a perfluorocarbon copolymer having a sulfonic acid type functional group.

[0002]

_2. Description of the Related Art CF ₂ = CFOCF ₂ CF (CF ₃ ) O
Copolymerization of a perfluorocarbon monomer having a sulfonic acid type functional group such as CF ₂ CF ₂ SO ₂ F and a fluoroolefin such as C ₂ F ₄ has various uses such as an ion exchange material and a separation membrane material. As a method for producing such a perfluorocarbon polymer having a sulfonic acid type functional group, solution polymerization using a fluorine-based solvent such as trichlorotrifluoroethane as a medium in terms of giving a high molecular weight polymer and the polymerization rate. Has been adopted.

However, the use of certain fluorine-containing solvents such as trichlorotrifluoroethane, which has been adopted in conventional solution polymerization, is restricted because of the fear of destroying ozone in the atmosphere. The development of alternative solvents is required.

As an alternative to trichlorotrifluoroethane, hydrofluorocarbons containing hydrogen atoms are
It is proposed because it has a small ozone depletion potential. However, conventionally, it has been known that a substance having a C—H bond exhibits chain transfer property to a fluoroolefin,
It is considered difficult to use a hydrochlorofluorocarbon containing a hydrogen atom as a polymerization medium in the production of a high molecular weight fluoroolefin polymer. 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.

[0005]

DISCLOSURE OF THE INVENTION The present invention has a high polymerization rate even when a polymer having a high ion exchange capacity is produced without using the above-mentioned solvent which has a high risk of depleting ozone in the atmosphere. Provided is a method by which a perfluorocarbon copolymer having a sulfonic acid type functional group capable of sufficiently increasing the molecular weight of a polymer can be easily produced in a high yield.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and comprises a sulfonic acid type functional group-containing perfluorocarbon monomer and a perfluoroolefin, and tetrafluoroethylene or hexafluoropropylene. Provided is a method for producing a perfluorocarbon copolymer having a sulfonic acid type functional group, which comprises solution-polymerizing a fluoroalkane hydrogenated to a double bond of a perfluoroalkene obtained by oligomerization as a medium. .

The present invention will be described in detail below. As the sulfonic acid type functional group-containing perfluorocarbon monomer used in the present invention, a wide range can be used. As a preferable example, a fluorovinyl compound represented by Chemical formula 1 is exemplified. In still of 1, p is 0 to 3, m is 0 to 3, n is 0 to 12, q is 0 or 1, X is -F or CF _3, Z is F or -CF ₃ , A is a sulfonic acid type functional group, which is a functional group that is converted into SO ₃ H by hydrolysis.

[0008]

[Chemical 1] CF ₂ = CF- (OCF ₂ CFX) _p- (O) _q- (CF ₂ ) _n- (CF ₂ CFZ) _m -A

Usually, from the viewpoint of easy availability, X and Z
-SO is -CF _3, p 0 or 1, m is 0, n is 0 to 8, q is 0 or 1, and A is the like copolymerization reactivity
₂ F is preferred.

As a preferable representative example of the above fluorovinyl compound, the compound of Chemical formula 2 and the like can be mentioned.

[0011]

Embedded image CF ₂ ═CFO (CF ₂ ) _1-8 SO ₂ F CF ₂ ═CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) _{1-8
SO 2 F CF 2 = CF (} CF 2) 0-8 SO 2 F CF 2 = CF (OCF 2 CF (CF 3)) 1-5 SO 2 F

In the present invention, the perfluoroolefin copolymerized with the perfluorocarbon monomer having a sulfonic acid type functional group as described above is preferably exemplified by tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene and the like. It In the present invention, the above-mentioned perfluoroolefin and perfluorocarbon monomer having a sulfonic acid type functional group may not only be used in combination of two or more, but in addition to these monomers, other components such as carboxylic acid type functional group may be used. With perfluorocarbon monomer, CF ₂ = CF
OR _f (R _f represents a perfluoroalkyl group having 1 to 10 carbon atoms) or CF ₂ ═CF—CF═CF ₂ , CF
₂ = CFO (CF ₂ ) _1-4 OCF = CF ₂ It is also possible to use one kind or two or more kinds of divinyl monomers.

In the present invention, it is necessary to use a fluoroalkane in which hydrogen has been added to the double bond of perfluoroalkene obtained by preferably anionic oligomerization of tetrafluoroethylene or hexafluoropropylene as a polymerization medium as described above. Is. In the above-mentioned oligomerization, when the degree of polymerization is too high, the boiling point of the solvent becomes high and it becomes difficult to separate it from the produced polymer. Therefore, the obtained perfluoroalkene is preferably a 2-10-mer, more preferably a 2-mer.
It is preferable to be a pentamer. Often used in a mixture of dimers to tetramers. Further, it is preferable that the hydrogen addition to the perfluoroalkene be almost completely carried out with respect to the double bond. In the presence of a perfluoroalkene having a non-hydrogenated double bond,
The polymerization rate decreases and the progress of polymerization is hindered. Therefore, the perfluoroalkene having a non-hydrogenated double bond is preferably 10 ppm or less, more preferably 5 ppm or less.

In the present invention, a perfluorocarbon polymer having a high proportion of a perfluorocarbon monomer having a sulfonic acid type functional group can be produced by copolymerization in the above-mentioned fluoroalkane solvent. The copolymerization ratio of the perfluorocarbon monomer having a functional group is 20% by weight or more, and particularly 25-60.
Weight percent of perfluorocarbon polymer can be produced.

When the perfluorocarbon polymer having a sulfonic acid type functional group obtained by the present invention is used as an ion exchange membrane, the copolymerization ratio of the perfluorocarbon monomer having a sulfonic acid type functional group is large as described above. Therefore, the ion exchange capacity is 0.5 to 2.
It has a wide range of 0 meq / g dry resin.
In the present invention, even if such an ion exchange capacity is increased, the molecular weight of the produced polymer can be increased, and therefore, the ion exchange membrane can have excellent mechanical properties and electrochemical properties.

The molecular weight of the perfluorocarbon polymer having a sulfonic acid type functional group obtained in the present invention is important because it is related to the mechanical properties and film-forming property of the copolymer, but it is expressed by the value of TQ. 150 ° C. or higher, preferably 170 to 340 ° C., particularly 180 to 280 ° C.

In the present invention, the term "TQ" is defined as follows. That is, the temperature at which the volumetric flow rate related to the molecular weight of the copolymer is 100 mm ³ / sec is TQ.
Is defined as Here, the volume flow rate is 3
0 kg / cm ² under pressure, diameter 1 mm at constant temperature, length 2 m
The amount of the copolymer melted and flowed out from the orifice of m is shown in the unit of mm ³ / sec.

The "ion exchange capacity" was determined as follows. That is, the SO ₃ H type copolymer film was left in 1N HCl at 60 ° C. for 5 hours to be completely converted to H type, and washed sufficiently with water so that HCl did not remain. After that, 0.5 g of this H-type film was added with 2N of 0.1N NaOH.
The mixture was allowed to stand at room temperature for 2 days in an aqueous solution containing 5 ml.
The membrane is then removed and the amount of NaOH in the solution is adjusted to 0.1
It is obtained by back titration with N HCl.

In the present invention, in the copolymerization reaction of a fluorocarbon monomer having a sulfonic acid type functional group with a perfluoroolefin, the amount of the fluoroalkane used as a polymerization solvent is changed to a fluoroalkane / a fluorocarbon monomer having a sulfonic acid type functional group. 20/1 by weight ratio
If the amount of fluoroalkane used is too large, which is preferably controlled to 10/1 or less, the size of the reactor becomes large, or the operation and operation surface such as separation and recovery of the copolymer is performed. Is disadvantageous.

Further, in the polymerization of the present invention, the reaction pressure is preferably controlled to 1 kg / cm ² or more. If the reaction pressure is too low, it is difficult to maintain the polymerization reaction rate at a level that is practically satisfactory, and it is difficult to form a high molecular weight copolymer. Further, if the reaction pressure is too low, the content ratio of the fluorocarbon monomer having a sulfonic acid type functional group in the produced copolymer becomes high, and as a result, the mechanical strength and the ion exchange due to the increased water content of the produced copolymer are increased. Performance will be reduced.

Further, the reaction pressure is 50 kg / in terms of the reaction apparatus or the work operation in industrial practice.
It is desirable to control to below cm ² . It is possible to employ a reaction pressure higher than this range, but the difficulty becomes greater. Thus, in the present invention, the reaction pressure is preferably ^{2 to} 50 kg / cm ² , particularly ^{2 to} 30 kg / cm ² .
^It is best to select from the range of ² .

In the copolymerization reaction of the present invention, conditions and operations other than the above reaction conditions are not particularly limited and can be adopted over a wide range. For example, as the reaction temperature, an optimum value may be selected depending on the kind of the weight initiation source, the reaction molar ratio, etc. However, usually, too high temperature or too low temperature is disadvantageous to industrial practice, and therefore 20 to 90 ° C. Preferably 30
Approximately 80 ° C is selected.

In the present invention, it is desirable to select, as the polymerization initiation source, one which exhibits high activity at the above-mentioned suitable reaction temperature. For example, ionizing radiation that is highly active even at room temperature or lower can be adopted, but it is usually more advantageous in industrial practice to use an azo compound or a peroxin compound.

The polymerization initiation source preferably adopted in the present invention is
Diacyl peroxides such as disuccinic acid peroxide, benzoyl peroxide, lauroyl peroxide and dipentafluoropropionyl peroxide, which show high activity under the copolymerization reaction conditions, 2,2′-azobis (2-amidinopropane) hydrochloric acid Salts, azo compounds such as 4,4′-azobis (4-cyanovaleric acid) and azobisisobutynitrile, peroxyesters such as t-butylperoxyisobutyrate and t-butylperoxypivalate, Peroxydicarbonates such as diisopropyl peroxydicarbonate and di-2-ethylhexyl peroxydicarbonate, and hydroperoxides such as diisopropylbenzene hydroperoxide.

In the present invention, the concentration of the polymerization initiation source is preferably 0.0001 to 3% by weight, and more preferably 0.0001 to 2.0% by weight, based on all the monomers. By decreasing the concentration of the starting source, it is possible to increase the molecular weight of the produced copolymer, and it is possible to produce a produced copolymer having a high ion exchange capacity. If the starting source concentration is too high, the tendency of decreasing the molecular weight increases, which is disadvantageous. In addition, a molecular weight modifier or the like used in ordinary solution polymerization may be added. Further, an inert organic solvent can be used in combination as long as it does not inhibit the copolymerization reaction in the present invention and has little chain transfer.

Therefore, in the present invention, it is preferable to control the concentration of the produced copolymer to 40% by weight or less, preferably 30% by weight or less. If the concentration is too high, there are problems such as an increase in the nonuniformity of the copolymer composition and an increase in the polymerization torque, which causes the suspension of stirring.

In the present invention, at the end of the polymerization, hydrochlorofluorocarbons such as CCl ₂ FCH ₃ (AK-141b), hydrocarbons such as methanol and hexane, and chlorohydrocarbons such as methylene chloride and chloroform are preferably used. The resulting copolymer is added and coagulated and separated.

The perfluorocarbon copolymer having a sulfonic acid type functional group produced by the present invention is used in various fields, and is preferably used as, for example, an ion exchange membrane. When used for an ion exchange membrane, the sulfonic acid type perfluorocarbon copolymer can be formed into a membrane by an appropriate means. For example, if necessary, the functional group is hydrolyzed to be converted into a sulfonic acid group, and such a hydrolysis treatment can be performed before or after film formation. Usually, it is preferable to carry out hydrolysis treatment after film formation. Various kinds of film forming means can be adopted, and for example, known or well-known methods such as hot melt molding, latex molding, and cast molding by dissolving in a suitable solution can be appropriately adopted. Furthermore, a membrane having a different ion exchange capacity or a membrane having a different functional group such as a carboxylic acid group is used.
It is also possible to stack more layers. Further, reinforcement with cloth, fibers, non-woven fabric or the like can be added.

The ion-exchange membrane produced from the perfluorocarbon copolymer having a sulfonic acid type functional group, which is produced by the present invention, has various excellent performances and is therefore widely used in various fields, purposes and applications. obtain. For example, it is preferably used as a diffusion dialysis, an ozone generating electrolysis, an electrolytic reduction, a diaphragm of a fuel cell, and the like, particularly in a field requiring touch resistance. In particular, when it is used as a cation exchange membrane for alkaline electrolysis, it can exhibit high performance especially in a laminated membrane with a carboxylic acid type membrane.

[0030]

EXAMPLES Next, examples of the present invention will be described in more detail, but it goes without saying that the present invention is not limited to these examples.

[Example 1] Hexafluoropropylene gas was blown into a potassium fluoride-dimethylformamide medium at room temperature under normal pressure to obtain a mixture of a dimer and a trimer. Raney nickel was added to this mixture in a catalytic amount and hydrogen was blown into the mixture at room temperature to obtain a hydrogen adduct. This hydrogenated product is (CF ₃ ) ₂ CFCFHCFHCF ₃ :
_{CF 3 CFHCH (CF (CF 3} ) 2) 2: (CF 3)
₂ CHCH (CF ₂ CF ₃ ) CF (CF ₃ ) ₂ ≈2:
It was a 1: 1 mixture. 68.5 g of a solvent consisting of a mixture of the above hydrogen adducts, asobisisobutyronitrile 0.
08g and _{CF 2 = CFOCF 2 CF (CF} 3) OCF
92.0 g of ₂ CF ₂ SO ₂ F was charged into a stainless steel autoclave having an internal volume of 0.2 liter, sufficiently degassed with liquid nitrogen, and then heated to 70 ° C.
The charge polymerization was started up to 0.6 kg / cm ² . During the reaction, tetrafluoroethylene was introduced from outside the system to keep the pressure constant. After 6 hours, unreacted tetrafluoroethylene was purged to terminate the polymerization, and the obtained polymer solution was mixed with 1,1-dichloro-1-fluoroethane (AK
-141b), agglomerated, washed and dried to obtain 18.0 g of a copolymer.

The ion exchange capacity of the copolymer was 1.01 meq / g dry resin and TQ was 236 ° C. A tough film was obtained by press-forming the copolymer at 250 ° C., and a sulfonic acid type ion exchange membrane was obtained by hydrolysis with a 25% NaOH aqueous solution.

Example 2 Tetrafluoroethylene was added to 1
Polymerization and post-treatment were carried out in the same manner as in Example 1 except that charging polymerization was started up to 1.6 kg / cm ^2, tetrafluoroethylene was introduced from outside the system during the reaction, and the pressure was kept constant, The ion-exchange capacity of the obtained copolymer was 0.96 meq / g dry resin and TQ was 258 ° C.

[Example 3] Polymerization and post-treatment were carried out in the same manner as in Example 2 except that the polymer solution obtained at the end of the polymerization was coagulated with methanol. The ion exchange capacity of the obtained copolymer was found to be 0.96 meq / g dry resin,
TQ was 258 ° C.

[0035]

EFFECT OF THE INVENTION A copolymer containing a large amount of a perfluorocarbon monomer having a sulfonic acid type functional group can be easily obtained in a high yield, and since no specific CFC is used, the production is less likely to cause ozone destruction. Law is provided.

Claims (2)

[Claims] 1. A medium is a fluoroalkane obtained by hydrogenating a perfluorocarbon monomer having a sulfonic acid type functional group and a perfluoroolefin to a double bond of a perfluoroalkene obtained by oligomerizing tetrafluoroethylene or hexafluoropropylene. A method for producing a perfluorocarbon copolymer having a sulfonic acid type functional group, which is characterized by performing solution polymerization as the above. 2. A perfluorocarbon monomer having a sulfonic acid type functional group is CF ₂ ═CFOCF ₂ CF (CF
₃ ) OCF ₂ CF ₂ SO ₂ F and the perfluoroolefin is tetrafluoroethylene.