JPH07145207A - Method of coagulation separation - Google Patents

Abstract

(57) [Summary] [Structure] From a solution of a sulfonic acid type functional group-containing perfluorocarbon polymer using a fluorine-based solvent having a low ozone depletion coefficient, a solvent for aggregating hydrochlorofluorocarbon having a low ozone depletion coefficient is used A method of aggregating and separating the coalescence. [Effect] A sulfonic acid type functional group-containing polymer having a molecular weight and an ion exchange capacity within target ranges is produced, and the polymer can be efficiently aggregated and separated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coagulation separation in which a copolymer of perfluorocarbon having a sulfonic acid type functional group is precipitated from the copolymer.

[0002]

2. Description of the Related Art Perfluorocarbon polymers having a sulfonic acid type functional group are used in a wide range of applications including ion exchange membranes because they have various excellent properties. For example, in membranes for alkaline electrolysis, electrodialysis, various organic electrosynthesis, solid electrolytes for fuel cells, ozone generation electrolysis, water electrolysis, polymer catalysts for organic synthesis and polymerization, membrane materials for dehumidifying and humidifying devices, etc. used.

Conventionally, the polymer was produced by a solution polymerization method in chlorofluorocarbon such as trichlorotrifluoroethane. Also, when coating the polymer on various substrates, a solvent such as trichlorotrifluoroethane has been used. However, it is said that certain fluorine-based solvents such as trichlorotrifluoroethane, which are easily available and inexpensive, may destroy the ozone layer in the atmosphere, and their use is limited, so hydrochlorofluorocarbons and hydro-carbons are used as alternative solvents. Fluorocarbon,
Fluorocarbons are being applied. Further, when the polymer is coagulated and separated from a trichlorotrifluoroethane solution of the polymer, a chlorofluorocarbon such as trichlorofluoromethane was used as a coagulation solvent, but the solvent at the time of polymerization of the polymer was changed. Therefore, the aggregating solvent used has also been required to be changed.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to solve the above problems. That is, the object of the present invention is to use a fluorine-based solvent that does not damage the ozone layer as a copolymerization reaction solvent of a vinyl monomer having a sulfonic acid type functional group, and to control the molecular weight and the ion exchange capacity characteristics of the copolymer. It is an object of the present invention to provide a method for obtaining a combined solution and coagulating and separating the copolymer from the solution using a coagulating solvent that does not damage the ozone layer.

[0005]

The present invention provides a method for aggregating and separating a perfluorocarbon polymer from a fluorine-based solvent solution of a perfluorocarbon polymer having a sulfonic acid type functional group by using an aggregating solvent. The system solvent is at least one type of fluorine solvent having a boiling point of 10 to 250 ° C. selected from the group consisting of hydrochlorofluorocarbon, hydrofluorocarbon, and fluorocarbon, and the aggregating solvent does not dissolve the perfluorocarbon polymer. And a method for aggregating and separating a perfluorocarbon polymer having a sulfonic acid type functional group.

The fluorine-based solvent in the solution of the perfluorocarbon polymer having a sulfonic acid type functional group of the present invention has a boiling point of 10 ° C. to 250 ° C., and hydrochlorofluorocarbon (HCFC), hydrofluorocarbon (HFC), and At least one fluorine-based solvent selected from the group consisting of fluorocarbons (FC) is used. In particular, those having a boiling point of 20 ° C. to 200 ° C. are preferable from the viewpoints of solvent recyclability, easy drying of the polymer after aggregation and separation, easy handling at room temperature, and the like.

The structure of HCFC, HFC, and FC may be linear, branched, or cyclic, but the number of carbon atoms in HCFC is 2 to 4, and that in HFC and FC is 4-1.
Two ranges are preferred. Specifically, as HCFC, C
HCl ₂ CF ₂ CF ₃ or CFHClCF ₂ CF ₂ C
1 is particularly preferable because it is inexpensive in terms of performance and industrially available. As HFC, C ₄ F ₉ C ₂ H ₅ ,
(CF ₃ ) ₂ CFCFHCFHCF ₃ , C ₆ F ₁₃ H, C
Etc. _{6 F 13 C 2 H 5,} C 8 F 17 C 2 H 5 are preferred. F
As C, C ₆ F ₁₄ , C ₈ F ₁₈ , (C ₄ F ₉ ) ₃ N,
The compound of formula 1, the compound of formula 2, the compound of formula 3 and the like are preferable, and those containing a hetero atom as exemplified are also preferably used.

[0008]

[Chemical 2]

On the other hand, the hydrochlorofluorocarbon (HCFC) used for aggregating and separating the perfluorocarbon polymer solution from the polymer is as follows:
As long as it does not dissolve the polymer, the one having a boiling point of 20 ° C. to 200 ° C. and the one having 2 to 4 carbon atoms can be exemplified over a wide range like the above-mentioned fluorine-based solvent. Specifically, CCl ₂ FCH ₃ is particularly preferable because of its characteristics, industrial availability, and low cost.

The concentration of the polymer solution is usually 0.01 to 30.
%, More preferably 0.1 to 20% by weight is used. When coagulating, the weight ratio of the polymer solution / HCFC for coagulation is usually about 5/95 to 70/30. If the proportion of the polymer solution is too small, the volumetric efficiency of the tank used for aggregation is lowered, and if it is too large, the aggregation state of the polymer becomes insufficient. More preferably from 10/90
It is 60/40.

Mixing of the polymer solution with HCFC for coagulation
Usually, the HCFC for aggregation is added to the solution while stirring, but the solution may be added to the HCFC while stirring. With the addition, the polymer becomes particles and aggregates / precipitates. Aggregated particles are separated by filtration or the like and dried to recover the copolymer.

As the perfluorocarbon polymer having a sulfonic acid type functional group which is aggregated and separated by the method of the present invention, those known or well known can be exemplified in a wide range. Suitable examples include a copolymer of tetrafluoroethylene and a perfluorocarbon monomer having a sulfonic acid type functional group. The perfluorocarbon monomer has a general formula of CF ₂ ═CF—
_{(OCF 2 CFX) p - (} O) q - (CF 2) a - (C
During F ₂ CFZ) _b -Y (wherein, p is 0 to 3, q is 0 or 1, a is 0 to 12, b is 0 to 3, X is -F or -CF _3, Z is is -F or -CF _3, Y is fluoro vinyl compound is exemplified represented by a is) sulfonic acid functional groups. Usually, from the viewpoint of easy availability, X and Z are —CF ₃ , p is 0 or 1, b is 0,
a is 0 to 8, q is 0 or 1, and Y is preferably —SO ₂ F in view of copolymerization reactivity.

A preferred representative example of the above fluorovinyl compound is CF ₂ ═CFO (CF ₂ ) _s SO ₂ F (s
Is _{1~8), CF 2 = CFOCF 2} CF (CF 3) O
(CF ₂ ) _s SO ₂ F (s is 1 to 8), CF ₂ = CF
(CF ₂ ) _t SO ₂ F (t is 0 to 8), CF ₂ = CF
(OCF ₂ CF (CF ₃ )) _m OCF ₂ CF ₂ SO ₂ F
(M is 1 to 5) and the like. In particular, the general formula CF _{2
= CF (OCF 2 CF (CF} 3)) n OCF 2 CF 2 S
A fluorovinyl compound of O ₂ F (n is 0 to 2) is preferable.

In the present invention, not only can tetrafluoroethylene and the above-mentioned sulfonic acid type functional group-containing perfluorovinyl monomer be used in combination of two or more, but also other components such as carboxylic acid can be used in addition to these monomers. Type functional group-containing perfluorocarbon monomer, CF ₂ =
CFORf (Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms) or CF ₂ = CF-CF = CF
One divinyl monomers such as _2, or two or more can be used together.

When the sulfonic acid type functional group-containing perfluorocarbon polymer obtained by the present invention is used as an ion exchange membrane, the ion exchange capacity is 0.5 to
It is selected from a wide range of 2.0 meq / g dry resin, but by adopting the conditions described below, the molecular weight of the produced copolymer can be increased even if the ion exchange capacity is increased, and The mechanical properties and durability of the copolymer do not deteriorate. Although the ion exchange capacity varies depending on the type of the copolymer even in the above range, it is preferably 0.6 mm equivalent / g dry resin or more, particularly 0.7 mm equivalent / g dry resin or more, It is preferable in terms of mechanical properties and electrochemical performance as an ion exchange membrane.

The molecular weight of the sulfonic acid type functional group-containing perfluorocarbon polymer obtained in the present invention is important because it is related to the mechanical performance and film-forming property as an ion exchange membrane, and is expressed by the value of T _Q. Then, the temperature is 150 ° C. or higher, preferably 170 to 340 ° C., and particularly preferably 180 to 280 ° C. The term “T _Q ” is defined as follows: T _Q is defined as the temperature at which a volumetric flow rate of 100 mm ³ / sec is related to the molecular weight of the copolymer. The volume flow rate of the copolymer was 30 kg / cm ² under pressure, the diameter was 1 mm and the length was 2 at a constant temperature.
The amount of the copolymer melted and flowed out from the orifice of mm is shown in the unit of mm ³ / sec.

The "ion exchange capacity" is obtained as follows. That is, the H-type cation exchange resin membrane 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. Then, 0.5 g of this H-type film was added to 0.1 N Na
And allowed to stand 2 days at room temperature in a solution in 25 cm ³ of OH formed by adding water 25 cm ^3. Then, the film is taken out and the amount of NaOH in the solution is determined by back titration with 0.1N HCl.

The sulfonic acid type functional group-containing perfluorocarbon polymer produced in 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 functional group-containing perfluorocarbon polymer can be formed into a membrane by an appropriate means. For example, if necessary, a sulfonic acid type functional group is converted into a sulfonic acid group by hydrolysis, and such hydrolysis treatment can be performed before or after film formation. Usually, after film formation, it is preferable. Various types of film forming means can be adopted,
For example, known or well-known methods such as heat-melt molding, latex molding, and injection molding by dissolving in a suitable solution can be appropriately adopted. Furthermore, it is also possible to laminate two or more layers with a film having a different ion exchange capacity or a film having a different functional group such as a carboxylic acid group. Further, reinforcement with cloth, fibers, non-woven fabric or the like can be added.

[0019]

【Example】

Example 1 64.8 of CF ₂ ClCF ₂ CFHCl
g, 0.08 g of azobisisobutyl nitrile and C
F ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO
92.2 g of ₂ F was charged into a stainless steel autoclave having a volume of 0.2 liter, fully degassed with liquid nitrogen, and then brought to 70 ° C. to obtain tetrafluoroethylene (CF ₂ = CF
₂ ) was charged to 10.6 kg / cm ² to initiate polymerization. During the reaction, CF ₂ = CF ₂ was introduced into the system to keep the pressure constant. After 10 hours, unreacted CF ₂ ═CF ₂ was purged to terminate the polymerization. CF ₂ = CF ₂ obtained
And CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂
CFCl ₂ was added to 100 g of a 17% solution of a SO ₂ F copolymer.
CH ₃ was added under stirring with 200 g. The precipitated particulate solid was filtered, washed with CFCl ₂ CH ₃ and then dried,
A white copolymer was obtained. The ion exchange capacity of the copolymer was 1.0 meq / g dry resin. Also, 25
A strong transparent film was obtained by press forming at 0 ° C.

[Example 2] Polymerization reaction solvent CF ₂ ClCF
Except that the ₂ CFHCl was changed to _{C 8 F 17 C 2 H 5} 68.0g , a similar reaction operation as in Example 1, 1 copolymer
200 g of CFCl ₂ CH ₃ was added to 100 g of the 1.5% solution with stirring. Precipitated particulate solid is filtered to remove CFCl
After washing with ₂ CH ₃ , it was dried to obtain a translucent copolymer. The ion exchange capacity of the copolymer is 1.1 meq /
g dry resin. In addition, a tough transparent film was obtained by press forming at 250 ° C.

[Example 3] Reaction solvent CF ₂ ClCF ₂ C
The procedure of Example 1 was repeated, except that FHCl was changed to 73.3 g of the compound of the formula 3, and the copolymer 10.
100 g of a 3% solution was obtained, 200 g of CFCl ₂ CH ₃ was added, and the mixture was aggregated to separate the copolymer. The ion exchange capacity of the copolymer was 1.0 meq / g dry resin.

[Comparative Example 1] 1 of the copolymer obtained in Example 1
200 g of CHCl ₂ CF ₃ was added to the 7% solution under stirring, but no copolymer was deposited.

[0023]

EFFECT OF THE INVENTION A sulfonic acid type functional group-containing polymer having a molecular weight and an ion exchange capacity within the target values is produced, and the polymer can be smoothly and advantageously aggregated and separated.

Claims (6)

[Claims] 1. A method for aggregating and separating the perfluorocarbon polymer from a solution of a perfluorocarbon polymer having a sulfonic acid type functional group in a fluorine-based solvent using an aggregating solvent, wherein the fluorine-based solvent is hydrochlorofluorocarbon or hydro Boiling point 10 to 250 ° C. selected from the group consisting of fluorocarbons and fluorocarbons
Of at least one fluorine-based solvent, wherein the aggregating solvent is a hydrochlorofluorocarbon that does not dissolve the perfluorocarbon polymer, and a method for aggregating and separating a perfluorocarbon polymer having a sulfonic acid type functional group. . 2. The hydrochlorofluorocarbon as a fluorine-based solvent is CHCl ₂ CF ₂ CF ₃ or CFHClC.
The method according to claim 1, wherein the method is F ₂ CF ₂ Cl. 3. Hydrofluorocarbon as a fluorine-based solvent is C ₄ F ₉ C ₂ H ₅ , (CF ₃ ) ₂ CFCFHCFH.
CF ₃ , C ₆ F ₁₃ H, C ₆ F ₁₃ C ₂ H ₅ , and C ₈ F
The method for coagulation separation according to claim 1, wherein the fluorine-based solvent is at least one kind selected from the group consisting of ₁₇ C ₂ H ₅ . 4. The fluorocarbon of the fluorine-based solvent is C ₆
The at least one fluorine-based solvent selected from the group consisting of F ₁₄ , C ₈ F ₁₈ , (C ₄ F ₉ ) ₃ N, the compound of formula 1, the compound of formula 2, and the compound of formula 3. Method of flocculation and separation. [Chemical 1] 5. The method for aggregation / separation according to any one of claims 1 to 4, wherein the hydrochlorofluorocarbon of the aggregation solvent is CCl ₂ FCH ₃ . 6. A perfluorocarbon polymer having a sulfonic acid type functional group is tetrafluoroethylene and a general formula C.
F ₂ = CF (OCF ₂ CF (CF ₃ )) _n OCF ₂ CF
_A copolymer of ₂ SO ₂ F (n is 0 to 2).
5. The method for aggregation and separation according to any one of 5 above.