CA1171385A - Cation exchange membrane of flurorinated polymer for an electrolysis - Google Patents
Cation exchange membrane of flurorinated polymer for an electrolysisInfo
- Publication number
- CA1171385A CA1171385A CA000358104A CA358104A CA1171385A CA 1171385 A CA1171385 A CA 1171385A CA 000358104 A CA000358104 A CA 000358104A CA 358104 A CA358104 A CA 358104A CA 1171385 A CA1171385 A CA 1171385A
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- Prior art keywords
- membrane
- groups
- cation exchange
- surface layer
- membrane according
- Prior art date
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Classifications
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
- C25B1/46—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in diaphragm cells
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/20—Manufacture of shaped structures of ion-exchange resins
- C08J5/22—Films, membranes or diaphragms
- C08J5/2206—Films, membranes or diaphragms based on organic and/or inorganic macromolecular compounds
- C08J5/2218—Synthetic macromolecular compounds
- C08J5/2231—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds
- C08J5/2243—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds obtained by introduction of active groups capable of ion-exchange into compounds of the type C08J5/2231
- C08J5/225—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds obtained by introduction of active groups capable of ion-exchange into compounds of the type C08J5/2231 containing fluorine
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2327/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
- C08J2327/02—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment
- C08J2327/12—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
Abstract
ABSTRACT OF THE DISCLOSURE
A cation exchange membrane of a fluorinated polymer for use in electrolysis comprises a copolymer of a fluorinated olefin and a fluorovinyl compound having the formula wherein X represents -F or -CF3; Y and Y' respectively represents -F or a C1 - C10 perfluoroalkyl group; l is 0 to 3; m is 0 or 1;
n is 0 to 12 and M represents hydrogen atom or an alkali metal atom; and a modified surface layer of said cation exchange membrane on the anode side which has -SO3M groups formed by converting -COOM groups
A cation exchange membrane of a fluorinated polymer for use in electrolysis comprises a copolymer of a fluorinated olefin and a fluorovinyl compound having the formula wherein X represents -F or -CF3; Y and Y' respectively represents -F or a C1 - C10 perfluoroalkyl group; l is 0 to 3; m is 0 or 1;
n is 0 to 12 and M represents hydrogen atom or an alkali metal atom; and a modified surface layer of said cation exchange membrane on the anode side which has -SO3M groups formed by converting -COOM groups
Description
1~713~35 The present invention relates to a cation exchange membrane made of a fluorinated polymer for use in electrolysis.
More particularly, the present invention relates to a cation exchange membrane made of a fluorinated polymer which provides a high current efficiency and a low e-~e~t-r-Lc resistance in the electrolysis of an aqueous solution of an alkali metal chloride.
It has been proposed to use the cation exchange membrane made of a fluorina-ted copolymer proudced by copolymerizing a fluorinated olefin, such as CF2=CF2, and a fluorovinyl ether having sulfonic acid group or a functional group convertible to sulfonic group such as CF2=CFOCF2CF(CF3)OCF2CF2SO2F, and hydrolyzing the fluorinated copolymer to convert -SO2F groups into -SO3H groups, as a membrane for the electrolysis of an alkali metal chloride (see U.S. Patent No. 4,025,405). When the cation exchange membrane made of the fluorinated copolymer is used as a membrane for the electrolysis of an alkali metal chloride, excellent acid resistance, chlorine resistance and alkali resistance are found. However, it is difficult to maintain a high current efficiency with increasing concentration of the alkali metal hydroxide productO
It has been proposed, in order to overcome such disadvantage, to improve the characteristics of the cation exchange membrane by converting the sulfonic acid groups as the ï,on exchange gxoups of the fluorinated polymer into carboxylic acid groups by treating with a reducing agent or an oxidizing agent. (See U.S. Patent No. 4,151,053 and U.S. Patent No.
4,200,711). The resulting modified cation exchange membrane has an ion exchange capacity of only up to about 0.9 meq./g.
polymer because of the high polarity of the sulfonic acid group.
It is difficult to obtain a cation exchange membrane having greater ion exchange capacity.
When sulfonic acid groups which provide small ion ~L7~385 exchange capacity are converted into carboxylic acid groups, the ,3/ec~ric~/
-e~e~t-~e resistance is higher. Therefore, only a thin surface layer in the cathode side should be converted into carboxylic acid groups. When carboxylic acid groups are in contact with an aqueous solution of an alkali me-tal hydroxide of high concentration at a high temperature for a long time, the carboxylic acid groups are gradually decomposed. When the mod-ified cation exchange membrane is continuously used, the desired characteristics deteriorate. It is necessary to treat the membrane once more so as to convert the sulfonic acid groups 1nto carboxylic acid groups. In order to convert sulfonic acid groups into carboxylic acid groups in the thin layer of the e/e~C7~
nembrane so as to prevent the increase of clcctri-e resistance, it is necessary to operate carefully and it is not easy to control the operations on an industrial scale.
It has also been proposed to use a cation exchange membrane made of a fluorinated copolymer of a fluorinated olefin, such as CF2=CF2, and a fluorovinyl ether having carboxylic acid group or a funetional group eonvertible to carboxylic acid group, such as CF2=CFO(CF2) COOM, wherein n is l to 12 and M
represents hydrogen atom or an alkali metal atom, as a membrane for the electrolysis of an alkali metal chloride (see U.S. Patent No. 4,065,366 and U.S. Patent No. 4,202,743). When such cation exc'nange membrane is used, the degree of dissociation of carboxylic acid groups is lowered causing a rise in cell voltage when operating at low pH with the addition of an acid, such as hydrochloric acid, so as to control the concentration of oxygen in the chlorine gas formed in an anode compartment.
The present invention provides a cation exchange membrane made of a fluorinated polymer for use in the electrolysis which is different from the conventional cation exchange membrane made of fluorinated polymers imparting a high current efficiency 1~1385 and a low electric resistance in the electrolysis and eliminating retreatment of the membrane for its recovery from deterioration of its characteristics.
The present invention also provides a cation exchange membrane which is easily produced and can be used at low pH in an anode compartment.
According to the present invention there is provided a cation exchange membrane made of a fluorinated polymer for use in the electrolysis which comprises a copolymer of a fluorinated olefin and a fluorovinyl compound having the formula:
CF2=CX- (OCF2CFY~O~CFY'~COOM
wherein X represents -F or -CF3; Y and Y' respectively represents -F or a Cl - C10 perfluoroalkyl group; Q is 0 to 3; m is 0 or 1;
n is 0 to 12 and M represents hydrogen atom or an alkali metal atom; said cation exchange membrane having a modified surface layer on an anode side which layer has -SO3M groups formed by converting -COOM groups.
The fluorinated copolymer of the ~luorinated olefin and the fluorovinyl compound having carboxylic acid groups may be a polymer having a large ion exchange capacity such as up to 2.0 meq./g. dry polymer though it is difficult in the sulfonic acid type fluorinated copolymer. A cation exchange membrane made of the fluarinated copolymer having such large ion exchange capacity has a low electrical resistance. When a part of carboxylic acid groups on the anode side, are converted into sulfonic acid groups, the electrical' resistance can be further lowered. Since the electrical, resistance is lowered by the conversion, it is un-necessary to precisel~ control the ratio of the conversion into sulfonic acid groups in the surface layer. The control for the conversion is easy and xetreatment is not needed. Moreover, the surface layer of the membrane on the anode side is converted into ~ ' - `
-1~71~
- sulfonic acid groups, whereby the electrical resistance of the membrane does not increase and the cell voltage does not increase even though an acid is added to the anode compartment for a low pH.
The cation exchange membrane of the present invention has a~structure of the copolymer of the fluorinated olefin and the fluorovinyl compound having carboxylic acid groups. ~ny copolymer can be used so long as it has such structure in the electrolysis of an aqueous solution of an alkali meta] chloride.
It is preferably a copolymer of the fluorinated olefin and a fluorovinyl compound having a carboxylic acid or a functional group convertible into a carboxylic acid group.
The fluorovinyl compounds having a carboxylic acid group or the functional group convertible into the carboxylic acid group have the formula:
CF2=CX-(OCF2CFY)Q-~O ~ CFY~tn----A
wherein X, Y, Y', Q, m and n are defined above and A represents -COOM or a functional group which is convertible to -COOM by hydrolysis or neutralization, such as -CN, -COF, -COORl, -COOM
or -COONR2R3; Rl represents a Cl 10 alkyl group; R2 and R3 respectively represent~-H or Rl; Ml represents a quaternary ammonium group.
From the viewpo''nts of its properties and availability, it i5 preferable to use the fluorovinyl compound having the above~mentioned formula wherein X is -F; Y lS ~F or -CF3; Y' is -F; Q is 0 to 1; m is 0 to 1; n is 0 to 8; A is -COF or -COORl.
It is preferable to use a fluorovinyl compound having the follow-ing ~ormula: CF2=CF-(OCF2CF ~ O-(CF ~ COOM
wherein p is 0 or 1; q is 1 to 5 and M is defined above.
Typical fluorovinyl compounds include CF2 CF~CF2)1_8CCH3~
` 1~71385 CF2 = CF(CF2)1 8Cc2H5r - COF d CF2 - CF(CF2)1-8 , an CF2 = CFOCF2CF(CF3)OCF2CF2CF2COOCH3 The fluorinated olefins are preferably compounds having the formula:
CF2 = CZZ' wherein Z and Z' respectively represent -F, -CQ, -H or -CF3.
It is preferable to use a tetrafluoroethylene, trifluorochloro-ethylene, hexafluoropropylene, trifluoroethylene, vinylidene fluoride and vinyl fluoride. It is optimum to use a perfluoro-ethylene such as tetrafluoroethylene.
In the process of the invention is is possible to use two or more types of the functional fluorovinyl monomers and the fluorinated olefins, respectively.
~ O~n c~S
It is also possible to add one or more other ~s~r, such as a fluorovinyl ether having the formula:
CF2 = CFO~f wherein ~ represents a Cl 10 perfluoroalkyl group; and a divinyl monomer e.g. CF2=CF-CF=CF2 and CF2=CFO(CF2)1 4OCF=CF2.
The content of the specific fluorovinyl component is important since it closely relates to the characteristics of the cation exchange membrane and it is selected so as to give an ion exchange capacity of preferably 0.9 to 4.0 meq./g. dry polymer, especially 1.1 to 2.0 meq./g. dry polymer. When it is too small, the ion exchange function is too low and the clcc~ic resistance is too high. When it is too high, the mechanical strength of the cation exchange membrane is not high enough and the water content is too large so as to have inferior electric characteristics such as current efficiency.
The copolymerization of the fluorinated olefin and the specific fluorovinyl compound can be carried out with or without an inert organic solven-t or aqueous medium in the presence ~7~385 of a polymerization initiator such as a peroxy compound, an azo compound or irradiation of ultraviolet rays or ionized radio-active rays by the conventional processes such as the processes disclosed in U.S. Pa-tent No. 4,116,888 and U.S. Patent No. 4,138,373.
The polymerization may be bulk polymerization, solution polymerization, suspension polymerization or emulsion polymerization.
In the production of the fluorinated copolymer of the present invention, one or more of the fluorovinyl compounds and one or more of the fluorinated olefin is desired, one or more of the other comonomers can be copolymerizedO
The fluorinated copolymer used for the present invention preferably has a TQ (a temperature for a melt volumetric flow rate of 100 mm3/second) of 130 to 350C especially 160 to 300C
(which relates to the molecular weight).
The fluorinated copolymer can be fabricated to obtain a cation exchange membrane by conventional processes, such as the press-molding process; the roll-molding process; the extrusion-molding process; the solution-spreading process; the dispersion-molding process or the powder-molding process.
The membrane should be non-porous and dense so as to provide high ion selectivity in the cation exchange membrane. The waterpermeabilityof the membrane is preferably less than 100 ml./
hr./m2, especially less than 10 ml./hr./m2 under a pressure of 1 mH2O (60C; pH=l.00; 4N-NacQ~. The thickness of the membrane is preferably in a range of 10 to 500~, especially 50 to 300~.
When the fluorinated copolymer does not have carboxylic acid groups but has functional groups convertible into carboxylic acid groups, the copolymer is before or preferably after the fabrication treated such that the functional groups are converted into carboxylic acid groups. For example, when the functional groups are acid ester groups, acid amide groups, or ~uaternary ammonium salt groups, the copolymer is hydrolyzed or neutralized 38~
in an alcoholic solution of an acid or a base to convert the functional groups into carboxylic acid groups.
When the copolymer is fabricated into the cation exchange membrane, it is possible to blend an olefin polymer, such as polyethylene and polypropylene or a fluorinated polymer, such as polytetrafluoroethylene and the copolymer of ethylene and tetrafluoroethylene. It is also possible to support the fluorinated polymer on supports such as woven fabrics>nets, nonwoven fabrics and porous films made of such olefin polymer or fluorinated polymer.
The process for converting carboxylic acid groups in the surface layer of the carboxylic acid type cation exchange membrane on the anode side into sulfonic acid ~4~ is not critical and can be selected from various processes. For example,-the following reaction can be carried out for the cation exchange membrane made of a copolymer having -(CF2)2COOM' (M' represents a lower alkyl group) as branched chains.
The ester groups of copolymer are hydrolyzed in an aqueous solution of a base to form the branched chains having the formula -(CF2)2COOM" (M" represents an alkali metal atom) and then, further converted into -CF=CF2 groups by a decarbonation reaction and then further converted into sulfonic acid groups by reacting with sulfuryl fluoride and hydrolyzing.
The -(CF2)2COO~" groups are converted into -CF2CF2H
groups by treating the copolymer in a conc. alkali metal hydroxide solution at high temperature and then further converted into sulfonic acid groups by reacting with chlorosulfonic acid as well as the complex of sulfur trioxide with pyridine or dioxane.
The --(CF2)2COOI~" groups of the copolymer are converted into -(CF2)2COOH groups and then converted into -(CF2)2I groups by reacting with iodine in the presence of a peroxide and then - converted into -(CF2)2MgBr or -(CF2)2Li groups by reacting with 1~7~385 a Grignard reagent or alkyl lithium, repsectively and then con~erted into -(CF2)2S02C~ by reacting with sulfonyl chloride.
-(CF2)2I groups can be also converted directly into -(CF2)2S02CQ
by sulfur trioxide and chlorine in the presence of zinc.
-(CF2)2S02CQ groups are further converted into sulfonic acid groups by hydrolyzing them.
The surface layer of the membrane on the anode side in which the -COOM groups are converted into -S03M groups may be a thin layer having a depth of preferably at least 1.0 ~, especially in a range of 5.0 to 100~ and up to about 1/3 o the thickness of the membrane in view of improved electro-chemical properties.
The process for treating only one surface, includes various techniques, for example, the other surface is protected by a desired film before the treatment or two sheets of the membranes are overlapped and sealed a~ the peripheral part before the treatment.
The resulting cation exchange membrane made of a fluorinated polymer of the present invention can be used for the electrolysis of an aqueous solution of an alkali metal chloriae to produce an alkali metal hydroxide and chlorine. It is also possible t~ use it in the electrolysis of alkali metal carbonate, alkali metal sulfate or water. The apparatus for ~the electrolysis can be any electrolytlc system including (Solid Polymer Electrolyte) SPE in which the membrane is brought into contact with the electrodes.
The present invention will be further illustrated by way of the following Examples.
EXAMPLE 1:
A copolymer having an ion exchange capacity of 1.47 meq./g. polymer and TQ of 235C was produced by copolymerizing CF~=CF2 and CF2=CFO(CF2)3COOCH3 in a bul~ polymerization at 65C
~7~385 with azobisisobutyronitrile as the initiator. The copolymer was fabricated to form a film having a thickness of 300~ by press-moulding, at 235C. Two sheets of the film were overlapped and peripheral parts were sealed with a packing made of polytetrafluoroethylene and the films were dipped into a 25 wt.%
aqueous solution of sodium hydroxide at 90C for 1 hr. The films were washed with water and heat-treated in an electric oven at fh~r~
~3;~ 250C. The films wereJdipped into a tetra~lyme solution of cesium fluoride at 70C for 5 hr. to form sulfuryl fluoride.
The films were taken up and the sealed part was opened to separate them into two sheets of the membrane. Each membrane was dipped into a 25 wt.% aqueous solution of sodium hydroxide at 90C for 16 hrs. Both surfaces of the membrane weîe observed by surface infrared spectrography. On the treated surface, the absorption of -SO3Na group at 1060 cm 1 was found and on thè
non-treated surface, the absorption of -COONa group at 1680 cm 1 was found. According to a measurement of XMA for sulfur in the sectional direction of the membrane, it was confirmed that the surface layer of SO3Na groups reached to a depth of 10~ from the surface. A two compartment cell was assembled with the cation exchange membrane having the surface layer of -SO3Na groups in an anode side to use it for the electrolysis.
A ruthenium oxide coated titanium electrode was used as an anode and a stainless steel electrode was used as the 7~ .
cathode and the distance between the electrodes was set ~ 2.2 cm and the effective area of the membrane was 25 cm2. The electrolysis of an aqueous solution of sodium chloride was carried out under the following conditions.
A 4N NaCQ aqueous solu-tion was charged into the anode compartment and an 8N-NaOH aqueous solution was charged into the cathode compartment. The electrolysis was carried out by feeding a 4N-NaCQ aqueous solution into the anode compartment at a rate ~L71385 of 150 cc/hr. and feeding a O.lN-NaOH aqueous,solution into the cathode compartment at a rate of 2.7 cc/hr., and a current density of 20 A/dm , at 92C whilst maintaining the pH of the anolyte at 1.2 by adding hydrochloric acid into the anode compartment so as to decrease the concentration of the oxygen in chlorine yas to less than 1.5%.
The aqueous solution of sodium chloride which over-flowed from the anode compartment and the aqueous solution of sodium hydroxide which overflowed from the cathode compartment wëre collected. The current efficiency was measured by the amount of the resulting sodium hydroxide.
As a result of the electrolysis, 40 wt.% of sodium hydroxide was obtained at a current efficiency of 94% and a cell voltage of 3.5 V. The membrane maintained stable characteristics over a long time.
However, the same electrolysis was carried out with the addition of hydrochloric acid into the anode compartment using the non-treated membrane in which the conversion of the surface layer into -S03Na groups in the anode side was not carried'out.
The cell voltage increased to 4.3 V.
EX~MPLE 2:
A film having a thickness of 300~ was prepared by press-moulding the fluorinated copolymer by the process of Example 1. Two sheets of the film were overlapped and the per-ipheral parts were seâled and dipped into a SO w~/% aqueous solution of sodium hydroxide at 120C for 40 hr. The films were washed with water and treatedwithchlorosulfonic acid. The two sheets of the treated film were separated into two membranes.
Each membrane was treated with a 25 wt.% aqueous solution of sodium hydroxide at 90C for 16 hrs.
, According to surface infrared spectrography, it was found that one surface layer of the membrane had -S03Na groups 1~713~3~
and the other surface layer had -COONa groups. According to the observation of XMA for sulfur, the depth of the surface layer having -SO3Na groups was 25~.
In accordance with the process of Example 1 except using the resulting membrane, the electrolysis was carried out by adding hydrochloric acid into the anode compartment so as to maintain the concentration of oxygen to less than 1.5~. The pH
in the anode compartment was 1Ø
As a result of the electrolysis, a 40 wt.% aqueous solution of sodium hydroxide was produced at a cell voltage of 3.5 V under stable conditions. When a non-treated cation exchange membrane, in which the conversion to -SO3Na groups had not been made, was used in the same-electrolysis, the cell voltage was 4.6 V.
The same reaction procedure as described above was used for a film prepared by pressmoulding the fluorinated copolymer of CF2=CF2 and CF2=CFOCF2COOC~3 which was polymerized in bulk at 45C using diisopropyl peroxydicarbonate as the initiator and had an ion exchange capacity of 1.45 meq./g. and TQ of 230C. From the surface infrared and XMA measurements, it was confirmed that one surface of the membrane had -SO3Na groups and their depth was 20~.
EXAMPLE 3:
A copolymer having an ion exchange capacity of 1.37 meq./g. polymer and TQ of 210C was produced by copolymerizing CF2=CF2 and CF2=cFo(cF2)3coocH3 and CF2=CFCF2fF(CF2)3CCH3 (ratio of 80 : 20) in bulk polymerization at 65C with azobis-isobutyronitrile as the initiator. The copolymer was fabricated 3a to form a film having a thickness of 300~ by press-moulding at 210C. Two sheets of the film were overlapped and peripheral parts were sealed with a packing made of polytetrafluoroethylene and the films were dipped into a 25 wt.% aqueous solution of sodium hydroxide at 90C for 1 hr. and then dipped into conc.
HC~ at 90C for 1 hr. The films were washed with water and dried and dipped into 1,2-difluoro-1,1,2,2-tetrachloroethane at 90C for 1 hr. to greatly swell the surface. After cooling iodine and benzoylperoxide were added and the reaction system was kept at 90C for 5 hrs. The films were washed with methanol and dried.
According to the surface infrared spectrography, it was confirmed that carboxylic acid groups were converted into CF2I groups by the absorption at 760 cm 1.
The films were dipped into a tetrahydrofuran solution of C6H5MgBr at -70C for 5 hr. and then at -40C for 2 hrs.
The solution was further cooled at -70C and admixed with excess of SO2C~2 and was heated from -70C to the ambient temperature during 24 hours. The films were taken up and washed with dilute hydrochloric acid and with water and were separated into two membranes. Each membrane was dipped into 25 wt.% aqueous solution of sodiumhydroxide at 90C for 16 hr. Ac~cording to the surface infrared spectrography of the membrane, it was confirmed that the treated surface layer had -SO3Na groups and the other surface layer had -COONa groups.
More particularly, the present invention relates to a cation exchange membrane made of a fluorinated polymer which provides a high current efficiency and a low e-~e~t-r-Lc resistance in the electrolysis of an aqueous solution of an alkali metal chloride.
It has been proposed to use the cation exchange membrane made of a fluorina-ted copolymer proudced by copolymerizing a fluorinated olefin, such as CF2=CF2, and a fluorovinyl ether having sulfonic acid group or a functional group convertible to sulfonic group such as CF2=CFOCF2CF(CF3)OCF2CF2SO2F, and hydrolyzing the fluorinated copolymer to convert -SO2F groups into -SO3H groups, as a membrane for the electrolysis of an alkali metal chloride (see U.S. Patent No. 4,025,405). When the cation exchange membrane made of the fluorinated copolymer is used as a membrane for the electrolysis of an alkali metal chloride, excellent acid resistance, chlorine resistance and alkali resistance are found. However, it is difficult to maintain a high current efficiency with increasing concentration of the alkali metal hydroxide productO
It has been proposed, in order to overcome such disadvantage, to improve the characteristics of the cation exchange membrane by converting the sulfonic acid groups as the ï,on exchange gxoups of the fluorinated polymer into carboxylic acid groups by treating with a reducing agent or an oxidizing agent. (See U.S. Patent No. 4,151,053 and U.S. Patent No.
4,200,711). The resulting modified cation exchange membrane has an ion exchange capacity of only up to about 0.9 meq./g.
polymer because of the high polarity of the sulfonic acid group.
It is difficult to obtain a cation exchange membrane having greater ion exchange capacity.
When sulfonic acid groups which provide small ion ~L7~385 exchange capacity are converted into carboxylic acid groups, the ,3/ec~ric~/
-e~e~t-~e resistance is higher. Therefore, only a thin surface layer in the cathode side should be converted into carboxylic acid groups. When carboxylic acid groups are in contact with an aqueous solution of an alkali me-tal hydroxide of high concentration at a high temperature for a long time, the carboxylic acid groups are gradually decomposed. When the mod-ified cation exchange membrane is continuously used, the desired characteristics deteriorate. It is necessary to treat the membrane once more so as to convert the sulfonic acid groups 1nto carboxylic acid groups. In order to convert sulfonic acid groups into carboxylic acid groups in the thin layer of the e/e~C7~
nembrane so as to prevent the increase of clcctri-e resistance, it is necessary to operate carefully and it is not easy to control the operations on an industrial scale.
It has also been proposed to use a cation exchange membrane made of a fluorinated copolymer of a fluorinated olefin, such as CF2=CF2, and a fluorovinyl ether having carboxylic acid group or a funetional group eonvertible to carboxylic acid group, such as CF2=CFO(CF2) COOM, wherein n is l to 12 and M
represents hydrogen atom or an alkali metal atom, as a membrane for the electrolysis of an alkali metal chloride (see U.S. Patent No. 4,065,366 and U.S. Patent No. 4,202,743). When such cation exc'nange membrane is used, the degree of dissociation of carboxylic acid groups is lowered causing a rise in cell voltage when operating at low pH with the addition of an acid, such as hydrochloric acid, so as to control the concentration of oxygen in the chlorine gas formed in an anode compartment.
The present invention provides a cation exchange membrane made of a fluorinated polymer for use in the electrolysis which is different from the conventional cation exchange membrane made of fluorinated polymers imparting a high current efficiency 1~1385 and a low electric resistance in the electrolysis and eliminating retreatment of the membrane for its recovery from deterioration of its characteristics.
The present invention also provides a cation exchange membrane which is easily produced and can be used at low pH in an anode compartment.
According to the present invention there is provided a cation exchange membrane made of a fluorinated polymer for use in the electrolysis which comprises a copolymer of a fluorinated olefin and a fluorovinyl compound having the formula:
CF2=CX- (OCF2CFY~O~CFY'~COOM
wherein X represents -F or -CF3; Y and Y' respectively represents -F or a Cl - C10 perfluoroalkyl group; Q is 0 to 3; m is 0 or 1;
n is 0 to 12 and M represents hydrogen atom or an alkali metal atom; said cation exchange membrane having a modified surface layer on an anode side which layer has -SO3M groups formed by converting -COOM groups.
The fluorinated copolymer of the ~luorinated olefin and the fluorovinyl compound having carboxylic acid groups may be a polymer having a large ion exchange capacity such as up to 2.0 meq./g. dry polymer though it is difficult in the sulfonic acid type fluorinated copolymer. A cation exchange membrane made of the fluarinated copolymer having such large ion exchange capacity has a low electrical resistance. When a part of carboxylic acid groups on the anode side, are converted into sulfonic acid groups, the electrical' resistance can be further lowered. Since the electrical, resistance is lowered by the conversion, it is un-necessary to precisel~ control the ratio of the conversion into sulfonic acid groups in the surface layer. The control for the conversion is easy and xetreatment is not needed. Moreover, the surface layer of the membrane on the anode side is converted into ~ ' - `
-1~71~
- sulfonic acid groups, whereby the electrical resistance of the membrane does not increase and the cell voltage does not increase even though an acid is added to the anode compartment for a low pH.
The cation exchange membrane of the present invention has a~structure of the copolymer of the fluorinated olefin and the fluorovinyl compound having carboxylic acid groups. ~ny copolymer can be used so long as it has such structure in the electrolysis of an aqueous solution of an alkali meta] chloride.
It is preferably a copolymer of the fluorinated olefin and a fluorovinyl compound having a carboxylic acid or a functional group convertible into a carboxylic acid group.
The fluorovinyl compounds having a carboxylic acid group or the functional group convertible into the carboxylic acid group have the formula:
CF2=CX-(OCF2CFY)Q-~O ~ CFY~tn----A
wherein X, Y, Y', Q, m and n are defined above and A represents -COOM or a functional group which is convertible to -COOM by hydrolysis or neutralization, such as -CN, -COF, -COORl, -COOM
or -COONR2R3; Rl represents a Cl 10 alkyl group; R2 and R3 respectively represent~-H or Rl; Ml represents a quaternary ammonium group.
From the viewpo''nts of its properties and availability, it i5 preferable to use the fluorovinyl compound having the above~mentioned formula wherein X is -F; Y lS ~F or -CF3; Y' is -F; Q is 0 to 1; m is 0 to 1; n is 0 to 8; A is -COF or -COORl.
It is preferable to use a fluorovinyl compound having the follow-ing ~ormula: CF2=CF-(OCF2CF ~ O-(CF ~ COOM
wherein p is 0 or 1; q is 1 to 5 and M is defined above.
Typical fluorovinyl compounds include CF2 CF~CF2)1_8CCH3~
` 1~71385 CF2 = CF(CF2)1 8Cc2H5r - COF d CF2 - CF(CF2)1-8 , an CF2 = CFOCF2CF(CF3)OCF2CF2CF2COOCH3 The fluorinated olefins are preferably compounds having the formula:
CF2 = CZZ' wherein Z and Z' respectively represent -F, -CQ, -H or -CF3.
It is preferable to use a tetrafluoroethylene, trifluorochloro-ethylene, hexafluoropropylene, trifluoroethylene, vinylidene fluoride and vinyl fluoride. It is optimum to use a perfluoro-ethylene such as tetrafluoroethylene.
In the process of the invention is is possible to use two or more types of the functional fluorovinyl monomers and the fluorinated olefins, respectively.
~ O~n c~S
It is also possible to add one or more other ~s~r, such as a fluorovinyl ether having the formula:
CF2 = CFO~f wherein ~ represents a Cl 10 perfluoroalkyl group; and a divinyl monomer e.g. CF2=CF-CF=CF2 and CF2=CFO(CF2)1 4OCF=CF2.
The content of the specific fluorovinyl component is important since it closely relates to the characteristics of the cation exchange membrane and it is selected so as to give an ion exchange capacity of preferably 0.9 to 4.0 meq./g. dry polymer, especially 1.1 to 2.0 meq./g. dry polymer. When it is too small, the ion exchange function is too low and the clcc~ic resistance is too high. When it is too high, the mechanical strength of the cation exchange membrane is not high enough and the water content is too large so as to have inferior electric characteristics such as current efficiency.
The copolymerization of the fluorinated olefin and the specific fluorovinyl compound can be carried out with or without an inert organic solven-t or aqueous medium in the presence ~7~385 of a polymerization initiator such as a peroxy compound, an azo compound or irradiation of ultraviolet rays or ionized radio-active rays by the conventional processes such as the processes disclosed in U.S. Pa-tent No. 4,116,888 and U.S. Patent No. 4,138,373.
The polymerization may be bulk polymerization, solution polymerization, suspension polymerization or emulsion polymerization.
In the production of the fluorinated copolymer of the present invention, one or more of the fluorovinyl compounds and one or more of the fluorinated olefin is desired, one or more of the other comonomers can be copolymerizedO
The fluorinated copolymer used for the present invention preferably has a TQ (a temperature for a melt volumetric flow rate of 100 mm3/second) of 130 to 350C especially 160 to 300C
(which relates to the molecular weight).
The fluorinated copolymer can be fabricated to obtain a cation exchange membrane by conventional processes, such as the press-molding process; the roll-molding process; the extrusion-molding process; the solution-spreading process; the dispersion-molding process or the powder-molding process.
The membrane should be non-porous and dense so as to provide high ion selectivity in the cation exchange membrane. The waterpermeabilityof the membrane is preferably less than 100 ml./
hr./m2, especially less than 10 ml./hr./m2 under a pressure of 1 mH2O (60C; pH=l.00; 4N-NacQ~. The thickness of the membrane is preferably in a range of 10 to 500~, especially 50 to 300~.
When the fluorinated copolymer does not have carboxylic acid groups but has functional groups convertible into carboxylic acid groups, the copolymer is before or preferably after the fabrication treated such that the functional groups are converted into carboxylic acid groups. For example, when the functional groups are acid ester groups, acid amide groups, or ~uaternary ammonium salt groups, the copolymer is hydrolyzed or neutralized 38~
in an alcoholic solution of an acid or a base to convert the functional groups into carboxylic acid groups.
When the copolymer is fabricated into the cation exchange membrane, it is possible to blend an olefin polymer, such as polyethylene and polypropylene or a fluorinated polymer, such as polytetrafluoroethylene and the copolymer of ethylene and tetrafluoroethylene. It is also possible to support the fluorinated polymer on supports such as woven fabrics>nets, nonwoven fabrics and porous films made of such olefin polymer or fluorinated polymer.
The process for converting carboxylic acid groups in the surface layer of the carboxylic acid type cation exchange membrane on the anode side into sulfonic acid ~4~ is not critical and can be selected from various processes. For example,-the following reaction can be carried out for the cation exchange membrane made of a copolymer having -(CF2)2COOM' (M' represents a lower alkyl group) as branched chains.
The ester groups of copolymer are hydrolyzed in an aqueous solution of a base to form the branched chains having the formula -(CF2)2COOM" (M" represents an alkali metal atom) and then, further converted into -CF=CF2 groups by a decarbonation reaction and then further converted into sulfonic acid groups by reacting with sulfuryl fluoride and hydrolyzing.
The -(CF2)2COO~" groups are converted into -CF2CF2H
groups by treating the copolymer in a conc. alkali metal hydroxide solution at high temperature and then further converted into sulfonic acid groups by reacting with chlorosulfonic acid as well as the complex of sulfur trioxide with pyridine or dioxane.
The --(CF2)2COOI~" groups of the copolymer are converted into -(CF2)2COOH groups and then converted into -(CF2)2I groups by reacting with iodine in the presence of a peroxide and then - converted into -(CF2)2MgBr or -(CF2)2Li groups by reacting with 1~7~385 a Grignard reagent or alkyl lithium, repsectively and then con~erted into -(CF2)2S02C~ by reacting with sulfonyl chloride.
-(CF2)2I groups can be also converted directly into -(CF2)2S02CQ
by sulfur trioxide and chlorine in the presence of zinc.
-(CF2)2S02CQ groups are further converted into sulfonic acid groups by hydrolyzing them.
The surface layer of the membrane on the anode side in which the -COOM groups are converted into -S03M groups may be a thin layer having a depth of preferably at least 1.0 ~, especially in a range of 5.0 to 100~ and up to about 1/3 o the thickness of the membrane in view of improved electro-chemical properties.
The process for treating only one surface, includes various techniques, for example, the other surface is protected by a desired film before the treatment or two sheets of the membranes are overlapped and sealed a~ the peripheral part before the treatment.
The resulting cation exchange membrane made of a fluorinated polymer of the present invention can be used for the electrolysis of an aqueous solution of an alkali metal chloriae to produce an alkali metal hydroxide and chlorine. It is also possible t~ use it in the electrolysis of alkali metal carbonate, alkali metal sulfate or water. The apparatus for ~the electrolysis can be any electrolytlc system including (Solid Polymer Electrolyte) SPE in which the membrane is brought into contact with the electrodes.
The present invention will be further illustrated by way of the following Examples.
EXAMPLE 1:
A copolymer having an ion exchange capacity of 1.47 meq./g. polymer and TQ of 235C was produced by copolymerizing CF~=CF2 and CF2=CFO(CF2)3COOCH3 in a bul~ polymerization at 65C
~7~385 with azobisisobutyronitrile as the initiator. The copolymer was fabricated to form a film having a thickness of 300~ by press-moulding, at 235C. Two sheets of the film were overlapped and peripheral parts were sealed with a packing made of polytetrafluoroethylene and the films were dipped into a 25 wt.%
aqueous solution of sodium hydroxide at 90C for 1 hr. The films were washed with water and heat-treated in an electric oven at fh~r~
~3;~ 250C. The films wereJdipped into a tetra~lyme solution of cesium fluoride at 70C for 5 hr. to form sulfuryl fluoride.
The films were taken up and the sealed part was opened to separate them into two sheets of the membrane. Each membrane was dipped into a 25 wt.% aqueous solution of sodium hydroxide at 90C for 16 hrs. Both surfaces of the membrane weîe observed by surface infrared spectrography. On the treated surface, the absorption of -SO3Na group at 1060 cm 1 was found and on thè
non-treated surface, the absorption of -COONa group at 1680 cm 1 was found. According to a measurement of XMA for sulfur in the sectional direction of the membrane, it was confirmed that the surface layer of SO3Na groups reached to a depth of 10~ from the surface. A two compartment cell was assembled with the cation exchange membrane having the surface layer of -SO3Na groups in an anode side to use it for the electrolysis.
A ruthenium oxide coated titanium electrode was used as an anode and a stainless steel electrode was used as the 7~ .
cathode and the distance between the electrodes was set ~ 2.2 cm and the effective area of the membrane was 25 cm2. The electrolysis of an aqueous solution of sodium chloride was carried out under the following conditions.
A 4N NaCQ aqueous solu-tion was charged into the anode compartment and an 8N-NaOH aqueous solution was charged into the cathode compartment. The electrolysis was carried out by feeding a 4N-NaCQ aqueous solution into the anode compartment at a rate ~L71385 of 150 cc/hr. and feeding a O.lN-NaOH aqueous,solution into the cathode compartment at a rate of 2.7 cc/hr., and a current density of 20 A/dm , at 92C whilst maintaining the pH of the anolyte at 1.2 by adding hydrochloric acid into the anode compartment so as to decrease the concentration of the oxygen in chlorine yas to less than 1.5%.
The aqueous solution of sodium chloride which over-flowed from the anode compartment and the aqueous solution of sodium hydroxide which overflowed from the cathode compartment wëre collected. The current efficiency was measured by the amount of the resulting sodium hydroxide.
As a result of the electrolysis, 40 wt.% of sodium hydroxide was obtained at a current efficiency of 94% and a cell voltage of 3.5 V. The membrane maintained stable characteristics over a long time.
However, the same electrolysis was carried out with the addition of hydrochloric acid into the anode compartment using the non-treated membrane in which the conversion of the surface layer into -S03Na groups in the anode side was not carried'out.
The cell voltage increased to 4.3 V.
EX~MPLE 2:
A film having a thickness of 300~ was prepared by press-moulding the fluorinated copolymer by the process of Example 1. Two sheets of the film were overlapped and the per-ipheral parts were seâled and dipped into a SO w~/% aqueous solution of sodium hydroxide at 120C for 40 hr. The films were washed with water and treatedwithchlorosulfonic acid. The two sheets of the treated film were separated into two membranes.
Each membrane was treated with a 25 wt.% aqueous solution of sodium hydroxide at 90C for 16 hrs.
, According to surface infrared spectrography, it was found that one surface layer of the membrane had -S03Na groups 1~713~3~
and the other surface layer had -COONa groups. According to the observation of XMA for sulfur, the depth of the surface layer having -SO3Na groups was 25~.
In accordance with the process of Example 1 except using the resulting membrane, the electrolysis was carried out by adding hydrochloric acid into the anode compartment so as to maintain the concentration of oxygen to less than 1.5~. The pH
in the anode compartment was 1Ø
As a result of the electrolysis, a 40 wt.% aqueous solution of sodium hydroxide was produced at a cell voltage of 3.5 V under stable conditions. When a non-treated cation exchange membrane, in which the conversion to -SO3Na groups had not been made, was used in the same-electrolysis, the cell voltage was 4.6 V.
The same reaction procedure as described above was used for a film prepared by pressmoulding the fluorinated copolymer of CF2=CF2 and CF2=CFOCF2COOC~3 which was polymerized in bulk at 45C using diisopropyl peroxydicarbonate as the initiator and had an ion exchange capacity of 1.45 meq./g. and TQ of 230C. From the surface infrared and XMA measurements, it was confirmed that one surface of the membrane had -SO3Na groups and their depth was 20~.
EXAMPLE 3:
A copolymer having an ion exchange capacity of 1.37 meq./g. polymer and TQ of 210C was produced by copolymerizing CF2=CF2 and CF2=cFo(cF2)3coocH3 and CF2=CFCF2fF(CF2)3CCH3 (ratio of 80 : 20) in bulk polymerization at 65C with azobis-isobutyronitrile as the initiator. The copolymer was fabricated 3a to form a film having a thickness of 300~ by press-moulding at 210C. Two sheets of the film were overlapped and peripheral parts were sealed with a packing made of polytetrafluoroethylene and the films were dipped into a 25 wt.% aqueous solution of sodium hydroxide at 90C for 1 hr. and then dipped into conc.
HC~ at 90C for 1 hr. The films were washed with water and dried and dipped into 1,2-difluoro-1,1,2,2-tetrachloroethane at 90C for 1 hr. to greatly swell the surface. After cooling iodine and benzoylperoxide were added and the reaction system was kept at 90C for 5 hrs. The films were washed with methanol and dried.
According to the surface infrared spectrography, it was confirmed that carboxylic acid groups were converted into CF2I groups by the absorption at 760 cm 1.
The films were dipped into a tetrahydrofuran solution of C6H5MgBr at -70C for 5 hr. and then at -40C for 2 hrs.
The solution was further cooled at -70C and admixed with excess of SO2C~2 and was heated from -70C to the ambient temperature during 24 hours. The films were taken up and washed with dilute hydrochloric acid and with water and were separated into two membranes. Each membrane was dipped into 25 wt.% aqueous solution of sodiumhydroxide at 90C for 16 hr. Ac~cording to the surface infrared spectrography of the membrane, it was confirmed that the treated surface layer had -SO3Na groups and the other surface layer had -COONa groups.
Claims (20)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A non-porous dense cation exchange membrane made of a fluorinated polymer for use in electrolysis which comprises a copolymer of a fluorinated olefin and a fluorovinyl compound having the formula, wherein X represents -F or -CF3; Y and Y' respectively represents -F or a C1-C10 perfluoroalkyl group; l is 0 to 3; m is 0 or 1, n is 0 to 12 and M represents a hydrogen atom or an alkali metal atom;
with a modified surface layer of said cation exchange membrane on the anode side which has -SO3M groups formed therein by con-verting -COOM groups, the content of the fluorovinyl compound being such as to give an ion exchange capacity of 0.9 to 4.0 meq./g. dry polymer.
with a modified surface layer of said cation exchange membrane on the anode side which has -SO3M groups formed therein by con-verting -COOM groups, the content of the fluorovinyl compound being such as to give an ion exchange capacity of 0.9 to 4.0 meq./g. dry polymer.
2. The cation exchange membrane according to claim 1, wherein said fluorovinyl compound is a compound having the formula, wherein p is 0 or 1;
g is 1 to 5 and M represents a hydrogen atom or an alkali metal atom.
g is 1 to 5 and M represents a hydrogen atom or an alkali metal atom.
3. The cation exchange membrane according to claim 1, wherein said cation exchange membrane has a modified surface layer having -OCF2SO3M groups on the anode side and a surface layer having -OCF2COOM groups on the cathode side.
4. The cation exchange membrane according to claim 1, 2 or 3, wherein said surface layer of said cation exchange membrane on the anode side has -SO3M groups as ion-exchange groups to a depth of at least 1.0 µ.
5. The cation exchange membrane according to claim 1, 2 or 3, wherein an ion exchange capacity of -SO3M groups in said modi-fied surface layer is in a range of 1.0 to 4.0 meq./g. dry polymer.
6. The cation excahnge membrane according to claim 1, 2 or 3, wherein the -S03M groups are those formed by converting M groups via intermediate groups of -CF=CF2, -CF2H or -CF2I.
7. A membrane according to claim 1, 2 or 3, in which the fluorovinyl compound is selected from CH2 CFO (CF2) 1-8 COOCH3' CH2 CFO (CF2) 1-8 COOC2H5' CF2 = CF (CF2)1-8 COF, and CF2 = CFOCF2CF (CF3) OCF2CF2CF2COOCH3.
B. A membrane according to claim 1, 2 or 3, in which the fluorinated olefin has the formula CF2 = CZZ ' wherein Z and Z' respectively represent -F, -Cl, -H or -CF3.
9. A membrane according to claim l, 2 or 3, in which the fluorinated olefin is selected from a tetrafluoroethylene, trifluorochloroethylene, hexafluoropropylene, trifluoroethylene, vinylidene fluoride and vinyl fluoride.
10. A membrane according to claim l, 2 or 3, in which the fluorinated olefin is a perfluoroethylene.
11. A membrane according to claim 1, 2 or 3, in which the copolymer includes another fluorovinyl ether having the formula CF2 = CFORf, wherein Rf represents a C1-10 perfluoro-alkyl group.
12. A membrane according to claim 1, 2 or 3, which has an ion exchange capacity of 0.9 to 4.0 meq./g. dry polymer.
13. A membrane according to claim 1, 2 or 3, which has an ion exchange capacity of 1.1 to 2.0 meq./g. dry polymer.
14. A membrane as claimed in claim 1, 2 or 3 which has a water permeability of less than 100 ml/hr/m2.
15. A membrane as claimed in claim 1, 2 or 3, which has a water permeability of less than 10 ml/hr/m .
16. A membrane as claimed in claim 1, 2 or 3, having a thickness of 10 to 500µ.
17. A membrane as claimed in claim 1, 2 or 3, having a thickness of 50 to 500 µ.
18. A membrane as claimed in claim 1, 2 or 3, in which the thickness of the surface layer is 5.0 to 100 µ.
19. A membrane as claimed in claim 1, 2 or 3, in which the modified surface layer does not extend to more than 1/2 the thickness of said membrane.
20. A membrane as claimed in claim 1, 2 or 3, in which the modified surface layer does not extend to more than 1/2 the thickness of said membrane, which has an ion exchange capacity of 1.1 to 2.0 meq./g. dry polymer, which has a water permeability of less than 100 ml/hr/m2 and which has a low electrical resistance.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP102750/1979 | 1979-08-14 | ||
| JP10275079A JPS5629685A (en) | 1979-08-14 | 1979-08-14 | Fluorine containing cation exchange membrane for electrolysis |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1171385A true CA1171385A (en) | 1984-07-24 |
Family
ID=14335888
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000358104A Expired CA1171385A (en) | 1979-08-14 | 1980-08-12 | Cation exchange membrane of flurorinated polymer for an electrolysis |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4340680A (en) |
| EP (1) | EP0025644B1 (en) |
| JP (1) | JPS5629685A (en) |
| CA (1) | CA1171385A (en) |
| DE (1) | DE3066002D1 (en) |
Families Citing this family (37)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS55160028A (en) * | 1979-05-31 | 1980-12-12 | Asahi Chem Ind Co Ltd | Improved fluorinated cation exchange membrane and production thereof |
| JPS5665988A (en) * | 1979-10-31 | 1981-06-04 | Toyo Soda Mfg Co Ltd | Electrolysis method of alkali chloride |
| US4433082A (en) * | 1981-05-01 | 1984-02-21 | E. I. Du Pont De Nemours And Company | Process for making liquid composition of perfluorinated ion exchange polymer, and product thereof |
| US4454247A (en) * | 1981-12-14 | 1984-06-12 | E. I. Du Pont De Nemours & Company | Ion exchange membranes |
| US4871703A (en) * | 1983-05-31 | 1989-10-03 | The Dow Chemical Company | Process for preparation of an electrocatalyst |
| JPS60251290A (en) * | 1984-05-29 | 1985-12-11 | Asahi Glass Co Ltd | Manufacture of potassium hydroxide |
| DE3429182A1 (en) * | 1984-08-08 | 1986-02-20 | Hoechst Ag, 6230 Frankfurt | METHOD FOR THE ELECTROLYSIS OF SODIUM CHLORIDE |
| EP0192143B1 (en) * | 1985-02-09 | 1996-01-10 | Asahi Kasei Kogyo Kabushiki Kaisha | Permeable polymer membrane for desiccation of gas |
| US5110385A (en) * | 1985-05-31 | 1992-05-05 | The Dow Chemical Company | Method for forming polymer composite films using a removable substrate |
| US4650551A (en) * | 1985-05-31 | 1987-03-17 | The Dow Chemical Company | Supported ion exchange membrane films |
| US4784882A (en) * | 1985-05-31 | 1988-11-15 | The Dow Chemical Company | Method for forming composite polymer films |
| US4650711A (en) * | 1985-05-31 | 1987-03-17 | The Dow Chemical Company | Method for sizing polytetrafluoroethylene fabrics |
| US4784900A (en) * | 1985-05-31 | 1988-11-15 | University Of Bath | Method for sizing polytretrafluoroethylene fabrics |
| US5114515A (en) * | 1985-05-31 | 1992-05-19 | The Dow Chemical Company | Method for forming polymer composite films using removable substrates |
| US4610762A (en) * | 1985-05-31 | 1986-09-09 | The Dow Chemical Company | Method for forming polymer films having bubble release surfaces |
| US4668372A (en) * | 1985-12-16 | 1987-05-26 | The Dow Chemical Company | Method for making an electrolytic unit from a plastic material |
| US4668371A (en) * | 1985-12-16 | 1987-05-26 | The Dow Chemical Company | Structural frame for an electrochemical cell |
| US4670123A (en) * | 1985-12-16 | 1987-06-02 | The Dow Chemical Company | Structural frame for an electrochemical cell |
| US4666580A (en) * | 1985-12-16 | 1987-05-19 | The Dow Chemical Company | Structural frame for an electrochemical cell |
| US4666579A (en) * | 1985-12-16 | 1987-05-19 | The Dow Chemical Company | Structural frame for a solid polymer electrolyte electrochemical cell |
| US4778723A (en) * | 1986-06-20 | 1988-10-18 | The Dow Chemical Company | Method for sizing polytetrafluoroethylene fibers, yarn, or threads |
| US4698243A (en) * | 1986-06-20 | 1987-10-06 | The Dow Chemical Company | Method for sizing and hydrolyzing polytetrafluoroethylene fabrics, fibers, yarns, or threads |
| US4731263A (en) * | 1986-09-26 | 1988-03-15 | The Dow Chemical Company | Method for the preparation of ionomer films |
| US4752370A (en) * | 1986-12-19 | 1988-06-21 | The Dow Chemical Company | Supported membrane/electrode structure combination wherein catalytically active particles are coated onto the membrane |
| US4889577A (en) * | 1986-12-19 | 1989-12-26 | The Dow Chemical Company | Method for making an improved supported membrane/electrode structure combination wherein catalytically active particles are coated onto the membrane |
| US5039389A (en) * | 1986-12-19 | 1991-08-13 | The Dow Chemical Company | Membrane/electrode combination having interconnected roadways of catalytically active particles |
| US4738741A (en) * | 1986-12-19 | 1988-04-19 | The Dow Chemical Company | Method for forming an improved membrane/electrode combination having interconnected roadways of catalytically active particles |
| US4940525A (en) * | 1987-05-08 | 1990-07-10 | The Dow Chemical Company | Low equivalent weight sulfonic fluoropolymers |
| US5013414A (en) * | 1989-04-19 | 1991-05-07 | The Dow Chemical Company | Electrode structure for an electrolytic cell and electrolytic process used therein |
| US5595676A (en) * | 1992-07-30 | 1997-01-21 | Imperial Chemical Industries Plc | Fluorinated polymers |
| US5654109A (en) * | 1995-06-30 | 1997-08-05 | The Dow Chemical Company | Composite fuel cell membranes |
| ES2154231B1 (en) * | 1999-07-22 | 2001-12-01 | David Systems Technology Sl | SUITABLE FLUID COMPOSITION FOR THE PRODUCTION AND REPAIR OF ION EXCHANGE MEMBRANES. |
| WO2005049661A1 (en) | 2003-11-20 | 2005-06-02 | Daikin Industries, Ltd. | Process for production of fluorine-containing polymers and fluorine-containing polymers |
| JP5494644B2 (en) * | 2009-02-23 | 2014-05-21 | 旭硝子株式会社 | Cation exchange membrane, method for producing the same, and electrolytic cell using the same |
| WO2012157714A1 (en) * | 2011-05-18 | 2012-11-22 | 旭硝子株式会社 | Fluorine-containing copolymer and ion exchange membrane |
| EP3012352B1 (en) * | 2013-06-19 | 2017-07-12 | Asahi Kasei Kabushiki Kaisha | Fluorine-containing polymer, cation exchange membrane, and electrolysis vessel |
| KR101655363B1 (en) | 2013-11-21 | 2016-09-07 | 주식회사 아모그린텍 | Deionization Equipment |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4151053A (en) * | 1975-07-09 | 1979-04-24 | Asahi Kasei Kogyo Kabushiki Kaisha | Cation exchange membrane preparation and use thereof |
| JPS5224177A (en) * | 1975-07-09 | 1977-02-23 | Asahi Chem Ind Co Ltd | Manufacturing method of fluorocarbon cathion exchange membrane |
| GB1518387A (en) * | 1975-08-29 | 1978-07-19 | Asahi Glass Co Ltd | Fluorinated cation exchange membrane and use thereof in electrolysis of an alkali metal halide |
| GB1501819A (en) * | 1976-05-03 | 1978-02-22 | Asahi Glass Co Ltd | Electrodialysis for aqueous solution of base |
| SE7712836L (en) * | 1976-12-02 | 1978-06-03 | Du Pont | POLYFLUOROALLYLOXY COMPOUNDS |
| GB2014590B (en) * | 1978-02-08 | 1982-06-16 | Toyo Soda Mfg Co Ltd | Process for producing cation exchange membrane |
| JPS6023776B2 (en) * | 1979-01-24 | 1985-06-10 | 東ソー株式会社 | Manufacturing method of cation exchange membrane |
-
1979
- 1979-08-14 JP JP10275079A patent/JPS5629685A/en active Pending
-
1980
- 1980-07-23 US US06/171,286 patent/US4340680A/en not_active Expired - Lifetime
- 1980-08-12 CA CA000358104A patent/CA1171385A/en not_active Expired
- 1980-08-14 EP EP80302811A patent/EP0025644B1/en not_active Expired
- 1980-08-14 DE DE8080302811T patent/DE3066002D1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5629685A (en) | 1981-03-25 |
| EP0025644B1 (en) | 1983-12-28 |
| US4340680A (en) | 1982-07-20 |
| EP0025644A1 (en) | 1981-03-25 |
| DE3066002D1 (en) | 1984-02-02 |
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