CA1189828A - Laminated polymer membrane with intervening reinforcement thereof - Google Patents
Laminated polymer membrane with intervening reinforcement thereofInfo
- Publication number
- CA1189828A CA1189828A CA000394201A CA394201A CA1189828A CA 1189828 A CA1189828 A CA 1189828A CA 000394201 A CA000394201 A CA 000394201A CA 394201 A CA394201 A CA 394201A CA 1189828 A CA1189828 A CA 1189828A
- Authority
- CA
- Canada
- Prior art keywords
- film
- fluorine
- polymer
- membrane
- cation exchange
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/12—Layered products comprising a layer of synthetic resin next to a fibrous or filamentary layer
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/10—Supported membranes; Membrane supports
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/10—Supported membranes; Membrane supports
- B01D69/107—Organic support material
- B01D69/1071—Woven, non-woven or net mesh
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/10—Supported membranes; Membrane supports
- B01D69/108—Inorganic support material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
- B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
- B32B5/024—Woven fabric
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- 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
-
- 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
- C08J5/2237—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds containing fluorine
-
- 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
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B13/00—Diaphragms; Spacing elements
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2305/00—Condition, form or state of the layers or laminate
- B32B2305/08—Reinforcements
-
- 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 two-step lamination process is disclosed for the manufacture of a cation permeable membrane having areas of thin wall construction, the membrane having a cation exchange polymer matrix with a reinforcement fabric embedded therein. The process comprises laminating at 150-350°C a first film and a reinforcement fabric, the latter contacting a porous support material, using a vacuum that draws the first film onto the reinforcement fabric and partially into contact with the porous surface, separating the reinforcement fabric and first film from the porous support material whereby a laminate is obtained with holes in at least 5% of the surface area of the film, and then laminating the resulting structure to a second film. The films are of a fluorine-containing polymer with pendant side chains having sulfonyl or carboxyl groups. The membrane obtained is substantially free of holes, and has utility in membrane ion exchange, reverse osmosis devices or in electrolytic cells such as chloralkali cells.
A two-step lamination process is disclosed for the manufacture of a cation permeable membrane having areas of thin wall construction, the membrane having a cation exchange polymer matrix with a reinforcement fabric embedded therein. The process comprises laminating at 150-350°C a first film and a reinforcement fabric, the latter contacting a porous support material, using a vacuum that draws the first film onto the reinforcement fabric and partially into contact with the porous surface, separating the reinforcement fabric and first film from the porous support material whereby a laminate is obtained with holes in at least 5% of the surface area of the film, and then laminating the resulting structure to a second film. The films are of a fluorine-containing polymer with pendant side chains having sulfonyl or carboxyl groups. The membrane obtained is substantially free of holes, and has utility in membrane ion exchange, reverse osmosis devices or in electrolytic cells such as chloralkali cells.
Description
8~
TITLE
LAMINATED POLYMER ME~BRANE
WITH INTERVENING REINFORCEMENT
BACKGROUND OF T~IE INVENTION
_ The present invention relates to a reinfor-ced cation permeable polymexic membrane, whlch for support and strength contains a reinforcement fabric embedded therein, and to a process of formation.
Polymeric cation permeable films, also called membranes, are known and have utility in membrane ion exchanger, reverse osmosis devices and electrolytic cells such as chlor-alkali cells for the manufacture of chlorine, caustic soda and hydrogen.
For commercial use, these films are generally rein-forced with a fabric to impart strength.
U.S. Patents 3,770,567; 3,849,243; 3,902,947 and 3,925,135`are directed to reinforced cation perme-able membranes and methods of manufacture in which a support material is embedded in the membrane.
In these patents various embodiments initially employing a film containing a first polymer layer with sulfonyl groups present as cation exchange groups and a second polymer layer with sulfonyl groups present as -SO2M wherein M represents a halogen atom are disclosed. These latter sulfonyl groups do not function for ion exchange. Thereafter a support material, e.g., a reinforcement fahric, is laminated under vacuum conditions to the polymer layer contain-ing sulfonyl groups present as -SO2~ whereby the support material is embedded in this polymer layer.
After embedment of the support material, cation permeability is introduced across the thickness of the film by conversion of`sulfonyl groups pres~n-t as -SO2M into cation exchange groups. Examples of cation exchange groups include -(SO2NH2)mQ or -(SO3)nMe wherein Q is H, cation of an alkali metal or cation oE an alkaline earth metal and m is the valence of Q and Me is a metallic cation and n is the valence of Me.
In U.S. Patents 3,770,567; 3,849,243;
3,902,947 and 3,925,135, the thickness o-f reinforce-ment fabric controls the minimum thickness of the membrane since the fabric is laminated to and embed-ded in a layer of polymer. Some fibers of the reinforcement fabric are near to the surface of the membrane.
Summary of the Invention The present invention is directed to a pro-cess of formation of a reinforced membrane, suitable for conversion to a cation exchange membrane, in which the following steps are employed;
(a) laminating at a temperature from 150C to about 350C first surfaces of both a first film and a reinforcement fabric, whereby said reinforcement Eabric contacts a support material and during laminating a portion of the first surface of the first film contacts said support material, said film comprising a fluorine containing polymer with pendant side chains comprising sulfonyl groups present as -SO2F or -SO2Cl, or car-boxyl groups present as -COOR where R is lower alkyl, each of said sulfonyl or car-boxyl groups being attached to a carbon atom which has at least one fluorine atom connected thereto;
(b) separating said first film from said support material whereby a laminate is ob-tained with holes in an area at least 5 percent of an overall surface area of said first film;
(c) laminating at a temperature from about 150C to about 350C a second film to both (i) the first surface of the first film and (ii) a second surface of said reinforcing fabric, causing embedment of said fabric and causing formation of a membrane sub-stantially free of holes, said second film comprising a fluorine-containing polymer with pendant side chains comprising sul-fonyl groups present as -SO2F or -SO2C1, or carboxyl groups present as -COOR where R is lower alkyl, each of said sulfonyl or carboxyl groups being attached to a carbon atom which has at least one fluorine atom connected thereto.
The present invention also relates to a reinforced cation permeable membrane substan-tially free of holes with areas of thin wall construc-tion, said membrane comprising a matrix of at least one fluorine-containing polymer having pendant side chains comprising sulfonyl groups or carboxyl groups preser~t as ion exchange groups, with a rein-forcement fabric embedded in the matrix, each of said sulfonyl groups or carboxyl groups being attached to a carbon atom having at least one fluorine atom connected thereto. A preferred membrane has a greater thickness of polymer in portions of the membrane where individual reinforcement fiber is present`in comparison to areas where no reinforcement fiber exists.
~:~8~2~
A5 emplo~ed herein, the term "embedded" is used to mean that the reinforcement ~abric is sub-stantially covered by the matrix of fluorine-contain-ing polymer, except that the abric ma~ not be so co~ered at ~ome of the crossover points of the fibers in the fabric, ~here the fa~ric has a greater thick-ness.
Detailed Des~cription of the Invention The present invention relates to a cation permeable membrane containing a reinforcement fabric.
The membrane has thin wall portions where no reinfor-cement fibers are present and thicker wall portions where reinforcement fiber adds bulk to the membrane.
The process ~f making the membrane with a reinforcement material embedded therein uses a two-step lamination procedure. In a first step an intermediate polymer and a reinforcement ~abric are laminated with partial embedment of the fabric. Prior to a second lamination step, holes are fonmed in the polymer film which partially encapsulates the fabric.
In the second lamination step, a second polymer film serves both to complete embedment of the reinforce-ment fabric and to cover substantially all of the holes in the first film.
One polymer suitable for use in the membrane initially comprises an intenmediate fluorine-contain-ing polymer with pendant side chains comprising sulfonyl groups present as -SO2~ or -SO2Cl, preferably -SO2F, wherein each of said sulonyl groups is attached to a carbon atom which has at least one fluorine atom connected thereto. This type o~ poly-mer is thermoplastic, i.e., it softens at ele~ated temperatures and allows a reinforcement material to be laminated and embedded within this pol~mer.
Suitable intermediat~ pol~ers include those made fxom at least two classes of monomers~ A fixst class includes vinyl fluoride, hexaEluoropropylene, vinylidene fluoride, tri~luoroethylene, chlorotri-5 fluoroethylene, perfluorotalkyl vinyl ether~, tetra-fluoroethylene and mixtures thereof. For a preferred mode a vinyl monomer will not contain hydrogen since the presence of hydrogen results in decreased chemical stability of the pol~mer. A second class of monomers for preparation of the copolymer contains the precur-sor -SO2F or -SO2Cl, preferably -SO2F. Examples of such monomers include CF2=CFR~SO2F, wherein R~ is a bifunctional per~luorinated radical (which can contain ether linkages) comprising 2 to 8 carbon atoms. Generally, the sulfonyl group in the polymer chain will be attached to a carbon atom which has at least one fluorine atom at~ached thereto. If the sulfonyl group is attached directly to the poly-mer chain, the carbon in the chain to which it is attached will have a fluorine atom attached thereto.
A preferred intermediate polymer is per~luorinated;
an example of such polymer is formed from tetra~luoro-ethylene and perfluoro(3,6-dioxa 4-methyl 7-octene ~ulfonyl fluoride). Generally, this pre~erred polymer comprises 10 to 60 percent by weight of the perfluoro-(3,6-dioxa-4-methyl-7~octene sulfonyl fluoride), and more preferably, 25 to 50 percent by weight~
Another pol~mer suitable for use in the membrane comprises an intermediate fluorine-contain-ing pol~mer having a ~luorinated hydrocarbon backbonechain to which are attached penda~t side chains which caxxy carboxyl functional groups. The pendant side chains can contain, for example, f CF~ W groups wherein ~ is F ~r CF3, n is 1 to 12 ! and W i~ -COOR or ~CN, where R is lo~er ~lkyl. Ordinarily, the func-tisnal group in the side chains of the polymer will be present in terminal o f CF ~ W groups. Such polymers ~ V J n can be prepared from ~onomers which are fluorinated or fluorine substituted vinyl compounds. The polymers are usually made from at least two monomers. At least one monomer is a fluorinated vinyl compound from the first group described hereinabove in reference to polymers containing sulfonyl groups. Additionally, at least one monomer is a fluorinated monomer which contains a group which can be hydrolyzed to a carbox-ylic acid group, e.g., a carboalkoxy or nitrile group, in a side chain as set forth above.
A preferred class of polymers has khe repeating unit~
CF - CF2 ~ C~2 - CX2 ~ CF - CF2 CF2 q CFz ~ m O
~t~ ~
C~ - R3 CF ~ R3 ~Rl t _ p SO2R2 r 0 wherein m is 0, 1 or 2, p is 0 ~o 10, q is 3 to 15, r is 0 to 10, s is O, 1, 2 or 3 t is 1, 2 or 3 u is 1 or 2 the X's taken together are four fluorines or three fluorines and one chlorine, Y is F or CF3, Z is F or CF3, Rl is lower alkyl, R is F or Cl and R is F, Cl or a Cl to C10 perfluoroalkyl radical, with the proviso that at least one of p and r is at least 1.
Polymers containing carboxyl functional groups, or both carboxyl and sulfonyl functional groups, and their preparation, are described for example in British Patent 1,145,445, U.S.P. 3,506,635, U.S.P. 3,852,326, South African Patents 78/2221 (Du Pont, published 1979 May 30) and 78/2223 (Du Pont, granted 1979 September 5) and Japanese Patent Publications 38486/77 (Asahi Glass, 20 published 1978 November 29) and 28586/77 (Asahi Glass, published 1978 February 14).
Preferred intermediate carboxyl-containing polymers include copolymers of tetrafluoroethylene and Cf2=cF-o-cF2-cF-o-cF2-coocH3 CF2=CF-O-CF2-CF-O-CF2-CF2-COOCH3, CF
CF2=CF-O-(CF2)3COOCH3 or CF =CF-O-CF CF-O-(CF2)3COOCH3-Generally, such copolymers will contain 10 to 65% by weight, preferably 25 to 50% by weight, of the carboxyl-containing monomer.
It is also possible to use a blend of two or more polymers, such as a blend of a polymer having ~8~ 8 suifo~yl ~unctionality ~ith a pol~er having carboxyl functionality. The blends may also optionally include an inert polymer such as a copolymer of tetra~luoro-ethylene and per~luoroprop~lene, sometimes termed ~luoroethylenepropylene polymers and well known in the art.
The reinforcement fabric for embedment in the membrane can be either woven or u~woYen, although ~ wo~en abric is preferred. The individual fibers of the ~abric should be able to withstand a tempera-ture from about 150C to about 350C, since these temperatures are employed in the laminating steps.
With this pro~iso, the individual reinforcing fibers can be made from conventional materials, since their main purpose is to strengthen the membrane. Due to chemical inertness, reinforcement materials made from perfluorinated polymers have been found to be pre~
ferred. The polymers include those made from tetrafluoroethylene and copolymers of tetrafluoro-ethylene with hexafluoropropylene and perfluoro(alkylvinyl ethers) with alkyl heing l to 10 carbon atoms such as perfluoro~propyl vinyl ether). An example of a most pre~erred reinforcement material is polytetrafluoroethylene. Supporting fihers made from chlorotrifluoroethylene polymers are also use-ful. Other suitable reinorcing materlals include quartz and glass. Such reinforcement ~ibers and their use to strengthen polymers in a mem~rane are well known in the prior art.
In the pxocadure of embedding ~he reinforce-ment abric within the membrane, a first or initial lamination step is employed. First sur~acas of ~oth an intermediate pol~mer film and a reinfoxce-ment fabric are laminated to one another at an elevated temperature of from about 240C to about ~8~Zi~
320~C, preferably about 260C to 290C~ At such temperature the intermediate polymer film functions to parti~lly embed the reinforcement fabric. A
second and opposite surface portion of the fabric surface does not contact the intermediate polymex film and is not embedded therein. During such lamination, a support material ser~es to support the reinforcement fabric which in turn supports the intermediate polymer film. ~t elevated temperature, a first surface of the film is laminated to a first surface of the fabric~ In the lamination both first surfaces are forced together so that a portion of the first surface of the film also contacts the support material. The film follows surface contours of the fa~ric and contacts the support material between fiber interstices.
It is a requirement in the present process that prior to a second laminating step, holes, i.e., perforations, are formed in the first film of intermedia~.e polymer which partially embeds the reinforcement fabric. A portion of these holes can be introduced during the first lamination. Prefer-ably these holes are formed subsequent to this step by separation of the reinforcement fabric from the support ~aterial. A portion of the fir5~ 9UrfaCe of intermediate polymer film colltacts and adheres to this support surface. Separa~ion of the reinforce-ment fabric from the support material causes hole formation. The greater the contact and adh~rence of the ~irst fiLm to the support surface, ~he greater the tendency for holes to form in the flrst film.
Another m~ox consideratian for dete~minin~ the area in ~hich hole formation takes place is the thic~ness of the first inte~mediate pol~mer ~il~. This polymer 3~
~L~L8~ 8 film generall~ has a thickness from 0.5 to 5 mil~ and pre~erably fxom l to 3 mils. Other considerations determining the total area of holes in the ~ilm in which no polymer i5 present include the size, number a~d spacing o~ the reinforcing fibers. Generally, the film after lamination will contain holes in which no polymer is present in an area at least 5 percent of the overall surface area o~ the film (i.e., on a basis of both the polymer area and hole are~), preferably at least 10 percent, and more preferably a~ least 20 percent.
After the initial step of lamination of a first film of intermediate polymer to a reinforcement fabric, a second lamination is necessary. At an elevated temperature of from about 150C to about 350C, preferably about 180C to 290C, a second intermediate polymer film is laminated to a second (i.e., upper) surface of the reinforcement fabric and the first intermediate polymer ~ilm (to its first surface). The reinforcement fabric becomes sandwiched between the first and second intermediate films and is embedded in these films. The second intexmediate polymer film covers the first film in areas which have become perforated to form a membxane substantially free of holes. It is understood that "substantially free o~ holes" also includes "free of hole~" since a mem~ra~e without holes is preferred.
The second film o~ intermediate polymer generally is present in a thickness from 0.5 to 10 mils, and preferably from l to 5 mils. A thicker film can be employed but ~auses fonmation of a membrane with an increased thickness.
The rein~orcement fabric contacts the ~irs-t and second films in sepaxate laminatin~ steps ~ith these matarial~ forced together, e.g., by use of ~39~
J.~
pressure rolls~ It is a re~uirement in the present invention tha~ ~he ~irst and second films axe contacted with the reinforcement fabric in two separate steps rather than simultaneously. Embedment of the reinforcing fabric in one lamination step is avoided in the practice of the present invention.
In a preferred mode of lamination, the reinforcement fa~ric is supported on a porous support material (e.g., porous support paper described in U.S.P. 3,770,567) between a vacuum source and a first intermediate pol~mer film. At elevated temperature an applied vacuum (causing a pressure ~ifferential of at least 5 mm mercury) pulls the first film down onto ~he reinforcement fabric and pulls a portion of the first film into contact with the porous support material.
After this laminating step in which the reinfoxcement fabric is partially embedded, both the reinforcement fabric and film are separated from the support paper. This separation causes holes to form in the polymer film.
In a second lamination step, a vacuum source is also empLoyedO In relationship to this source, the ~irst film and partially embedded rein~orcement fabriG
are reversed ~rom the first lamination step. The first film is supported and contacts porous support paperO A second intermediate polymer film ls contac~
ted with the partially embedded reinforcing fabric and the fir~t polymer film. Applied vacuum (causing a pre~sure differential of at least 5 mm mercury) pulls the second ~il~ onto the reinforcement fab~ic and onto the first fil~ ~o cause embedment o~ the reinforcement fabric. The holes in the first film allow the ~acuum to pull the second film against the reinforcement fabric and the first film. The second film covers the perforations of the first film and allows formation of a membrane substantially free of holes.
The laminate, i.e., membrane, from the first and second lamination steps has reinforcement fabric embedded in a matrix of polymer. Generally films not less than 0.5 mil are employed in the first and second lamination steps.
The laminate, i.e., membrane from a first and second lam;natlon steps, has thin wall portions, which meansthat the overall thickness of the membrane will vary in its different sections. This difference is due, at least in part, to the reinforcement fabric adding bulk to the membrane.
Also, due to the lamination procedur~, holes are formed in a first polymer film prior to a second lamination step~ This technique allows a matrix of polymer in which the reinforcement fabric is embedded to have different thicknesses. Solely on basis of thickness of polymer, the membrane, in a preferred mode, has portions of greater thichaess where rein-forcement fabric is present in comparison to porkions where no reinforcement fiber is present.
After formation of the membrane, the inter-mediate polymer of the membrane is chemically con-verted to a cation exchange polymer. The con-figuration of the resulting cation permeable membrane remains the same as the membrane con taining intermediate polymer. Therefore, the preceding remarks (directed to the membrane containing intermediate polymer) remain in relationship to the cation permeable membrane. The chemical conversion is by reacting sulfonyl groups in the polymer which are present as -SO2F or -SO2Cl, preferably -SO2F, to cation exchange groups. Examples of cation exchange groups include -(SO2NH2)mQ where Q is H and cation of an alkali or an alkaline earth metal and m is the valence of Q, and -(SO3)nMe wherein Me is a cation and n is the valence of Me. Another type of ion exchange group can be formed by reaction of the sulfonyl groups in the intermediate polymer with a primary amine to form N-monosubstituted sulfonamide groups. The same or different layers of the membrane can have different cation exchange groups. Conversion of sulfonyl groups to ion exchange groups or sites is disclosed in U.S.P.
3,282,875; 3,718,627; 3,773,634; 3,909,378; German OS 2,437,395 (Du Pont, published 1975 April 17) and OS 2,447,540 (Du Pont, published 1975 June 19).
At the same time, the carboxyl functional groups in -COOR form where R is lower alkyl, generally Cl to C5 alkyl, or in -CN form, are hydrolyzed to -COOH groups. Such conversion is ordinarily and conveniently accomplished by hydrolysis with acid or base, such that. the various functional groups described above in relation to the intermediate polymers are converted respectviely to the free acids or the alkali metal salts thereof. Such hydrolysis can be carried out with an aqueous solution of a mineral acid or an alkali me-tal hydroxide. Base hydrolysis is preferred as it is ~aster and more complete. Use of hot solutions, such as near the boiling point of the solution, is preferred for rapid hydrolysis. The time required for hydrolysis increases with the thick-ness of the structure. It is also of advantage toinclude a water-miscible organic compound such as dimethylsulfoxide in the hydrolysis bath.
The cation exchange membrane so made has reinforcement fabric embedded therein. The membrane 5 will have thin wall construction, meaning the membrane will have different thickness, particularly less overall thickness where no reinforcement fibers are present.
Although the reinforcement -fabric is embedded in a matrix of ion exchange polymer, it is understood that the composition of the matrix does not have to be uniform. Preferably the polymer differs on opposite surface portions of the reinforcement fabric.
In the Eirst laminate procedure, an intermediate polymer is employed whlch can differ from the intermediate polymer of the second lamination step. This difference in the polymer matrix remains after conversion of sulfonyl and carboxyl groups in the intermediate polymers into ion exchange groups. To describe this difference in polymer matrix in the cation exchange membrane, the term "base polymer" is employed and means the polymer without reference to any cation exchange groups thereon.
For purposes of illustration two polymers derived Lrom the same comonomers but with different equivalent weights (containing either the same or different cation exchange groups) are different base polymers~ two polymers which differ only in the type of cation exchange groups are the same base polymer. In a preferred cation exchange membrane, different base polymers contact opposite sides of the reinforcement fabric.
In accordance to the preceding definition of base polymer, the cation exchange membranes dis-closed in U.S. Patents 3,770,567; 3,849,243; 3,902,947 and 3,925,135 do not disclose different base polymers on opposite sides of the reinforcement fabric.
The membranes formed by the present ~ 3L8~
in~ention when present ~s a cation permeable membrane ha~e utility in membrane ion exchange devices, reverse osmosis devices or in electrolytic cells such as chlor-alkali cells. These membranes have S the advantage that the reinforcement fabric is embedded in the membrane while at the same time the thickness of the membrane will be a different and thinner construction in some of the portions of the membrane where no reinforcing fabric i5 present. The presence of areas of thinner wall construction means less polymer need be present in the membrane in comparison with other types of cation permeable membranes containing reinfoxcement fibers embedded therein. Also in some uses of the cation permeable membrane, e.g~, as a separator in a chlor-alkali cell, it is preferred to employ thin membranes since the electrical resistance can increase as the thickness o the membrane increases. The presence of thin wall areas in a reinforced membrane can translate into reduced power consumption in operation o~ an elec-trolytic cell. It is understood that a oation exchange membxane for this type of use is preferably perfluorinated.
Although the present process has been described in laminating two films to a reinforcement fabric, it i5 understood that various alternate embodLments are intended to be Pncompassed by this invention. For example~ in the second l~minatins step, several ilms can be simultaneously laminated to the product from the first lamination. Al~o cation exchange groups can be present in a layer o~ polymer film undergoing lamination provided sul~onyl groups present a~ S02F or ~50~Cl or carboxyl groups presen~
as ~COOR or -CN groups are on the surface of the ~ ~ ~ 9 pol~mer fil~s under~oing lamination.
In reg~rd to the ~luorinated carboxylate esters referred to herein, the term "perfluorinated"
xefers to the carboxylic acid poxtion of the ester, and not to the R group derived from a hydrocarbon alcohol. Such esters are referred to herein as perfluorinated, inasmuch as the R group i3 lost during hydrolysis when the ester groups are ~ydrolyzed to carboxylic acid groups.
The following examples are pro~ided to illustrate the invention. In these examples equivalent weight (E~) of an intermediate polymer is given and is weight of a polymer in grams of one equi~alent of potential ion exchange capacity. All percentages are by weight unless otherwise indicated.
The laminating equipment employed comprised a hollow roll with an internal heater and an internal vac~um source. The hollow roll contained a series of circumferential glot5 on its surface which allowed the internal vacuum source to draw web or sheet feed materials in the direction o~ the hollow xoll.
cuxved stationary plate with a radiant heater faced the top surface of the hollow roll with a spacing of about 1/4 inch between their two surfaces.
As a por~ion of the laminating equipmen~, porous support paper was used in contacting the hollow roll as a support material to preven~ adherence of polymer film to ~he roll surfac~ and to allow vacuum to pull material being laminated in the direc tion of the hollow roll. Also, the support paper allowed openings to be fonmed in a pol~mer ~ilm in a fi~st lamination step. Feed and takeoff means were p~o~ided for the materials bein~ lami~ated. In the ~eed means one idlPr ~oll o~ smaller di~meter than the hollo~ roll was pro~ided ~or support pap~r and materials undergoing lamination~ The feed and takeoff means were positioned to allow feed material to pass around the hollow roll over a distance of about 5/6 of its circumference. ~ further idler roll was pro-vided for the support paper allowins its separation from the other materials undergoing lamination.
Takeoff means were provided for the support paper and a laminate.
In formation of a laminate, a support paper of 90-pound weight basis manufactured by Water Vliet Company, designated Hi-Sette Enamel*, black printed on one side with I~mont Flexolume Black No. 61-R-5589 was employed. This support paper had a minimum porosity speci~ication of 0.006 S.C.F.M. per square inch under ~n air pressure differential of 40 cm of mercury. Also employed was a reinorc~ment fabric of T 900 G Teflon~ polytetrafluoroethylene/rayon fabric having 14 polytetrafluoroethylene txeads/inch (200 denier each) and 56 rayon threads/inch (S0 denier each) woven i~ a plain weave and a 2-mil film o a polymer of tetrafluoroethylene and perfluoro(3,6-dioxa-4-methyl-7-octene-sulfonyl fluoride). This ~S polymer had an equivalent weight of 1100.
In the lamination step the feed materials were ~ed to the hollow roll with the support paper contacting the hollow roll on its unprlnted side, contacting the support paper was the reinforcement fabric and contacting this fabric was the 2-mil polymer film. Lamination speed of the feed materials was 24 inches per minute with the roll temperature controlled at 237C and the plate temperature controlled at 300C.
A vacuum of 24.8 inches of mercury was appliedO
*denotes trade mark This lamination step caused the pol~er film to contact the support paper in areas wherein no reinforcement fabric ~as present~ In the first lamination step, separation of the suppoxt paper from the laminate o~ the reinforcement fabric and copolymer film caused holes to form in the polymer film in an area gxeater than 5 percent of the surface area of the film (on basis of fîlm and hole areas).
For a second lamination step, support paper of the same kind was used, except the paper was sprayed with silicone oil to prevent sticking. On the silicone treated side of the suppor~ paper was contacted the laminate from the first lamination with the reinfoxcement fabric facing away from the support paFer. On the reinforcement fabric portion of the laminate was contacted an 0.5 mil polymer film of tetrafluoroeth~lene and per1uoro(3,6-dioxa-4---methyl 7-octenesul~onyl fluoride) with an equivalent weight of 1600. With the support paper contacting the hollow roll, a second lamination step was per-~ormed. Lamination speed was 24 inches per minute;
roll temperature was 232C; plate temperature was 296C; vacuum applied was 15 inches of mercury.
Af~er this second lamination step and separation o~ the support paper, visual examination showed the laminate to ~e completel~ free of any holes.
A reinforced membrane was made employing the apparatus and a similar procedure described in Example 1. The procedure o~ this Example employed in a first lamination ste~ a 2 mil 1100 EW (i.e~, equivalent weight~ film o~ a polym~r of tetra-fluoroethylene and perfluoro(3,6-dioxa-4-methyl-7~
octenesulfonyl ~luoride) and a reinforcement fabric of T 900 G Teflon~ polytetrafluoroet~lene/rayon fabric ~9~
(described in Example 1).
For the second lamination step a 5 mil 1200 EW film of a polymer of tetr~fluoroethylene and perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) was employed with one side having been contacted and reacted to a depth of 1.3 mils with n~butylamine. The unreacted side of the 5-mil film (which cont~s unreacted pendant -S02F groups) was laminated in a similar pro-cedure as the second lamination disclosed in Example 1~
The resulting laminate had virtually ~o lea~s as determined by a ~acuum operated leak detector apparatus.
Although the membrane was not converted to a cation exchange membrane, it could have ~een easily undertaken by reaction of the -SO2F groups; e.g., by immersion of the laminate in potassium hydroxide.
Exam~es 3 and 4 ~ . = ~ . =
Employing a similar procedure as in Example 1, a 2-mil ilm of 1100 EW polymer of tetrafluoroethylene and perfluoro(3,6~dioxa-4-methyl-7-octenesulfonyl fluoride) and a reinforcement fabric of T 900 G Teflon~ polytetra-fluorcethylene/rayon fabric were continually laminat~d; there-after a l-mil film of 1500 EW polymer of tetrafluoroethyle~e and perfluoro(3,6-dioxa-4-methyl-7~x~esulfonyl fluoride) was employed m a seco~d lammation~
The resulting l~late was uniform, leak free and the reinforcement fahric was well ~ded therein.
Fbr Exa~ple 4, a simllar procedure as in Example 3 was employel excspt m the second lamination a 1.5~mdl 1500 EW
polymer fi ~ was ussd (in place of the 1 mil 1500 EW polymer fil~).
m e ~w~ Laminates of EXamples 3 a~ 4 were to~ally hydrolyz~d by ~nnersion in 11% solution of potassium hydroxide in 30% aque~us dime~hyl sulfoxide a~
90C for a~2u~ one hour, followed by boil m g in distilled water ~r thirt~ minutes, The two membranes ~ere leak ~ree.
The cation exchange membranes of Examples 3 and 4 were mounced in 3-inch diameter laboratory chlor-alkali cells with the higher equivalent weight portion of the membrane facing the cathode compartment.
The cells were operated at 2 amperes/inch2, 80C and a 22-23% NaCl anolyte and after two days the following results were obtained~
ProductCell CausticVolta~eEfficiency ~ ~ .
Example 3 3.25 N 3.6 86%
Example 4 3.25 N 3.8 88%
Exam~le 5 A reinforced membrane was made employins the apparatus and a similar procedure described in Example 1. The procedure of this example employed in the first laminatio~ step a 2-mil film of a copolymer of 40.5% by wt. tetrafluoroethylene and 59.5% by wt.
perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) having an equivalent weight of 1100, and a calendered leno weave fabric having 200-denier polytetrafluoro-ethylene yarn in the warp and 400-denier polytetra~
fluoroethyl-ene yarn in the fill (fabric designation T-24C), For th~ second lamination step a 5~mil film of a copolymer of 37~ by wt. of tetrafluoroethylene and 63 wt. of CF~=CF-O-CF2 CF-O-CF2 CF~-COOC~3 ha~ing an equivalent weight of 1149 was employedO In this step a speed of ~4 mches/min was used with the vacuum roll at 220C and the c ~ed plate at 278C, a~d the support papex was à porous siliconercoated paper (Par'cwick ~3300*manufactured by the Paper Corporation of U~ited States). The resulting *denotes trade mark , . . .. . .. .
3S3~
laminate was uni~orm and leaX~ree. The fabric was ~ell embedded therein~
The laminate ~as converted t-o ~n ion ex-change membrane having -S03H groups in one layer and -COOH groups in the other layer by immersion in a hydrolysis bath of 13~ potassium hydroY~ide in 30%
aqueous dimethyl sulfoxide at 90C for 1 hour, followed by boiling in distilled water for 30 mi~utes.
The membrane was free of leaks.
The membrane was mounted in a chloralkali cell with the carboxyl side of the membrane facing the cathode compartment, and was tested under conditions specified in Examples 3 and 4. Representa-tive test data are as follows:
NaOH Current ~ Voltage ~ Efficienc~
.__ 1 4.55 3~.20 90.7 9 4.22 29.37 94.6 36 4.48 35.27 8901 57 4.20 35.98 87.7 76 4.87 35.90 83.6 10~ 4.73 30.73 85.2 125 4.43 32.80 84.9 Exam~le 6 A reinforced membrane was made employlng the apparatus and a similar procedure described in Example 1. The procedure of this example employed in the first lamination step a 2~mil film of a copolymer of 40% by wt. o~ tetrarluoroethylene and 60% by wto of C~2=CF-O~CF2 CF-O-CF2 CF~-COOCH3 having a~ equivalent weight of 1052 and T-24C fabric (described in Example 5). In this step the lamination was at a speed of 12 inches/min, with the ~acuum roll at 200C and the curved platP at 225C, and the support paper Partwick ~3300.
, ~or the second lamination step a 5-mil film of the same 1052-e~uivalent weight carboxyl poIymer described in the first paragraph of this example was employed~ The laminatlon was carried out as in the first step of this example except at a speed of 24 inches/min. The resulting laminate was free of leaks and the fabric was well embedded therein.
The laminate was converted to an ion exchange membrane having carboxylic acid groups in both layers by hydrolysis and washing as described in Example 5.
The membrane was tested in a chloralkali cell under conditions specified in Examples 3 and 4.
Representative test data are as follows.
NaOH Cu.rrent Days Voltase ~ Efficiency 1 4.50 27069 88.8 6 4.59 29.41 91.1 4.62 30.23 ~9.4 38 4.69 29.02 91.3 56 4.70 30.91 89.5 69 4.75 30.77 94.1 99 5.15 37.8~ 8~.6 122 5.10 35.50 86.7 2S 139 5.06 36.31 84.1 148 4.9~ 31.92 89.5 171 4.83 26.64 a9.2 ~'5~
The process of the invention provides a membrane which, after conversion to ion exchange form, is useful for various ion exchange purposes, such as packing for ion exchange devices, reverse osomosis, and as membrane for separating the compartments of various electrochemical cells which comprise in general an anode, a cathode, an anode compartment
TITLE
LAMINATED POLYMER ME~BRANE
WITH INTERVENING REINFORCEMENT
BACKGROUND OF T~IE INVENTION
_ The present invention relates to a reinfor-ced cation permeable polymexic membrane, whlch for support and strength contains a reinforcement fabric embedded therein, and to a process of formation.
Polymeric cation permeable films, also called membranes, are known and have utility in membrane ion exchanger, reverse osmosis devices and electrolytic cells such as chlor-alkali cells for the manufacture of chlorine, caustic soda and hydrogen.
For commercial use, these films are generally rein-forced with a fabric to impart strength.
U.S. Patents 3,770,567; 3,849,243; 3,902,947 and 3,925,135`are directed to reinforced cation perme-able membranes and methods of manufacture in which a support material is embedded in the membrane.
In these patents various embodiments initially employing a film containing a first polymer layer with sulfonyl groups present as cation exchange groups and a second polymer layer with sulfonyl groups present as -SO2M wherein M represents a halogen atom are disclosed. These latter sulfonyl groups do not function for ion exchange. Thereafter a support material, e.g., a reinforcement fahric, is laminated under vacuum conditions to the polymer layer contain-ing sulfonyl groups present as -SO2~ whereby the support material is embedded in this polymer layer.
After embedment of the support material, cation permeability is introduced across the thickness of the film by conversion of`sulfonyl groups pres~n-t as -SO2M into cation exchange groups. Examples of cation exchange groups include -(SO2NH2)mQ or -(SO3)nMe wherein Q is H, cation of an alkali metal or cation oE an alkaline earth metal and m is the valence of Q and Me is a metallic cation and n is the valence of Me.
In U.S. Patents 3,770,567; 3,849,243;
3,902,947 and 3,925,135, the thickness o-f reinforce-ment fabric controls the minimum thickness of the membrane since the fabric is laminated to and embed-ded in a layer of polymer. Some fibers of the reinforcement fabric are near to the surface of the membrane.
Summary of the Invention The present invention is directed to a pro-cess of formation of a reinforced membrane, suitable for conversion to a cation exchange membrane, in which the following steps are employed;
(a) laminating at a temperature from 150C to about 350C first surfaces of both a first film and a reinforcement fabric, whereby said reinforcement Eabric contacts a support material and during laminating a portion of the first surface of the first film contacts said support material, said film comprising a fluorine containing polymer with pendant side chains comprising sulfonyl groups present as -SO2F or -SO2Cl, or car-boxyl groups present as -COOR where R is lower alkyl, each of said sulfonyl or car-boxyl groups being attached to a carbon atom which has at least one fluorine atom connected thereto;
(b) separating said first film from said support material whereby a laminate is ob-tained with holes in an area at least 5 percent of an overall surface area of said first film;
(c) laminating at a temperature from about 150C to about 350C a second film to both (i) the first surface of the first film and (ii) a second surface of said reinforcing fabric, causing embedment of said fabric and causing formation of a membrane sub-stantially free of holes, said second film comprising a fluorine-containing polymer with pendant side chains comprising sul-fonyl groups present as -SO2F or -SO2C1, or carboxyl groups present as -COOR where R is lower alkyl, each of said sulfonyl or carboxyl groups being attached to a carbon atom which has at least one fluorine atom connected thereto.
The present invention also relates to a reinforced cation permeable membrane substan-tially free of holes with areas of thin wall construc-tion, said membrane comprising a matrix of at least one fluorine-containing polymer having pendant side chains comprising sulfonyl groups or carboxyl groups preser~t as ion exchange groups, with a rein-forcement fabric embedded in the matrix, each of said sulfonyl groups or carboxyl groups being attached to a carbon atom having at least one fluorine atom connected thereto. A preferred membrane has a greater thickness of polymer in portions of the membrane where individual reinforcement fiber is present`in comparison to areas where no reinforcement fiber exists.
~:~8~2~
A5 emplo~ed herein, the term "embedded" is used to mean that the reinforcement ~abric is sub-stantially covered by the matrix of fluorine-contain-ing polymer, except that the abric ma~ not be so co~ered at ~ome of the crossover points of the fibers in the fabric, ~here the fa~ric has a greater thick-ness.
Detailed Des~cription of the Invention The present invention relates to a cation permeable membrane containing a reinforcement fabric.
The membrane has thin wall portions where no reinfor-cement fibers are present and thicker wall portions where reinforcement fiber adds bulk to the membrane.
The process ~f making the membrane with a reinforcement material embedded therein uses a two-step lamination procedure. In a first step an intermediate polymer and a reinforcement ~abric are laminated with partial embedment of the fabric. Prior to a second lamination step, holes are fonmed in the polymer film which partially encapsulates the fabric.
In the second lamination step, a second polymer film serves both to complete embedment of the reinforce-ment fabric and to cover substantially all of the holes in the first film.
One polymer suitable for use in the membrane initially comprises an intenmediate fluorine-contain-ing polymer with pendant side chains comprising sulfonyl groups present as -SO2~ or -SO2Cl, preferably -SO2F, wherein each of said sulonyl groups is attached to a carbon atom which has at least one fluorine atom connected thereto. This type o~ poly-mer is thermoplastic, i.e., it softens at ele~ated temperatures and allows a reinforcement material to be laminated and embedded within this pol~mer.
Suitable intermediat~ pol~ers include those made fxom at least two classes of monomers~ A fixst class includes vinyl fluoride, hexaEluoropropylene, vinylidene fluoride, tri~luoroethylene, chlorotri-5 fluoroethylene, perfluorotalkyl vinyl ether~, tetra-fluoroethylene and mixtures thereof. For a preferred mode a vinyl monomer will not contain hydrogen since the presence of hydrogen results in decreased chemical stability of the pol~mer. A second class of monomers for preparation of the copolymer contains the precur-sor -SO2F or -SO2Cl, preferably -SO2F. Examples of such monomers include CF2=CFR~SO2F, wherein R~ is a bifunctional per~luorinated radical (which can contain ether linkages) comprising 2 to 8 carbon atoms. Generally, the sulfonyl group in the polymer chain will be attached to a carbon atom which has at least one fluorine atom at~ached thereto. If the sulfonyl group is attached directly to the poly-mer chain, the carbon in the chain to which it is attached will have a fluorine atom attached thereto.
A preferred intermediate polymer is per~luorinated;
an example of such polymer is formed from tetra~luoro-ethylene and perfluoro(3,6-dioxa 4-methyl 7-octene ~ulfonyl fluoride). Generally, this pre~erred polymer comprises 10 to 60 percent by weight of the perfluoro-(3,6-dioxa-4-methyl-7~octene sulfonyl fluoride), and more preferably, 25 to 50 percent by weight~
Another pol~mer suitable for use in the membrane comprises an intermediate fluorine-contain-ing pol~mer having a ~luorinated hydrocarbon backbonechain to which are attached penda~t side chains which caxxy carboxyl functional groups. The pendant side chains can contain, for example, f CF~ W groups wherein ~ is F ~r CF3, n is 1 to 12 ! and W i~ -COOR or ~CN, where R is lo~er ~lkyl. Ordinarily, the func-tisnal group in the side chains of the polymer will be present in terminal o f CF ~ W groups. Such polymers ~ V J n can be prepared from ~onomers which are fluorinated or fluorine substituted vinyl compounds. The polymers are usually made from at least two monomers. At least one monomer is a fluorinated vinyl compound from the first group described hereinabove in reference to polymers containing sulfonyl groups. Additionally, at least one monomer is a fluorinated monomer which contains a group which can be hydrolyzed to a carbox-ylic acid group, e.g., a carboalkoxy or nitrile group, in a side chain as set forth above.
A preferred class of polymers has khe repeating unit~
CF - CF2 ~ C~2 - CX2 ~ CF - CF2 CF2 q CFz ~ m O
~t~ ~
C~ - R3 CF ~ R3 ~Rl t _ p SO2R2 r 0 wherein m is 0, 1 or 2, p is 0 ~o 10, q is 3 to 15, r is 0 to 10, s is O, 1, 2 or 3 t is 1, 2 or 3 u is 1 or 2 the X's taken together are four fluorines or three fluorines and one chlorine, Y is F or CF3, Z is F or CF3, Rl is lower alkyl, R is F or Cl and R is F, Cl or a Cl to C10 perfluoroalkyl radical, with the proviso that at least one of p and r is at least 1.
Polymers containing carboxyl functional groups, or both carboxyl and sulfonyl functional groups, and their preparation, are described for example in British Patent 1,145,445, U.S.P. 3,506,635, U.S.P. 3,852,326, South African Patents 78/2221 (Du Pont, published 1979 May 30) and 78/2223 (Du Pont, granted 1979 September 5) and Japanese Patent Publications 38486/77 (Asahi Glass, 20 published 1978 November 29) and 28586/77 (Asahi Glass, published 1978 February 14).
Preferred intermediate carboxyl-containing polymers include copolymers of tetrafluoroethylene and Cf2=cF-o-cF2-cF-o-cF2-coocH3 CF2=CF-O-CF2-CF-O-CF2-CF2-COOCH3, CF
CF2=CF-O-(CF2)3COOCH3 or CF =CF-O-CF CF-O-(CF2)3COOCH3-Generally, such copolymers will contain 10 to 65% by weight, preferably 25 to 50% by weight, of the carboxyl-containing monomer.
It is also possible to use a blend of two or more polymers, such as a blend of a polymer having ~8~ 8 suifo~yl ~unctionality ~ith a pol~er having carboxyl functionality. The blends may also optionally include an inert polymer such as a copolymer of tetra~luoro-ethylene and per~luoroprop~lene, sometimes termed ~luoroethylenepropylene polymers and well known in the art.
The reinforcement fabric for embedment in the membrane can be either woven or u~woYen, although ~ wo~en abric is preferred. The individual fibers of the ~abric should be able to withstand a tempera-ture from about 150C to about 350C, since these temperatures are employed in the laminating steps.
With this pro~iso, the individual reinforcing fibers can be made from conventional materials, since their main purpose is to strengthen the membrane. Due to chemical inertness, reinforcement materials made from perfluorinated polymers have been found to be pre~
ferred. The polymers include those made from tetrafluoroethylene and copolymers of tetrafluoro-ethylene with hexafluoropropylene and perfluoro(alkylvinyl ethers) with alkyl heing l to 10 carbon atoms such as perfluoro~propyl vinyl ether). An example of a most pre~erred reinforcement material is polytetrafluoroethylene. Supporting fihers made from chlorotrifluoroethylene polymers are also use-ful. Other suitable reinorcing materlals include quartz and glass. Such reinforcement ~ibers and their use to strengthen polymers in a mem~rane are well known in the prior art.
In the pxocadure of embedding ~he reinforce-ment abric within the membrane, a first or initial lamination step is employed. First sur~acas of ~oth an intermediate pol~mer film and a reinfoxce-ment fabric are laminated to one another at an elevated temperature of from about 240C to about ~8~Zi~
320~C, preferably about 260C to 290C~ At such temperature the intermediate polymer film functions to parti~lly embed the reinforcement fabric. A
second and opposite surface portion of the fabric surface does not contact the intermediate polymex film and is not embedded therein. During such lamination, a support material ser~es to support the reinforcement fabric which in turn supports the intermediate polymer film. ~t elevated temperature, a first surface of the film is laminated to a first surface of the fabric~ In the lamination both first surfaces are forced together so that a portion of the first surface of the film also contacts the support material. The film follows surface contours of the fa~ric and contacts the support material between fiber interstices.
It is a requirement in the present process that prior to a second laminating step, holes, i.e., perforations, are formed in the first film of intermedia~.e polymer which partially embeds the reinforcement fabric. A portion of these holes can be introduced during the first lamination. Prefer-ably these holes are formed subsequent to this step by separation of the reinforcement fabric from the support ~aterial. A portion of the fir5~ 9UrfaCe of intermediate polymer film colltacts and adheres to this support surface. Separa~ion of the reinforce-ment fabric from the support material causes hole formation. The greater the contact and adh~rence of the ~irst fiLm to the support surface, ~he greater the tendency for holes to form in the flrst film.
Another m~ox consideratian for dete~minin~ the area in ~hich hole formation takes place is the thic~ness of the first inte~mediate pol~mer ~il~. This polymer 3~
~L~L8~ 8 film generall~ has a thickness from 0.5 to 5 mil~ and pre~erably fxom l to 3 mils. Other considerations determining the total area of holes in the ~ilm in which no polymer i5 present include the size, number a~d spacing o~ the reinforcing fibers. Generally, the film after lamination will contain holes in which no polymer is present in an area at least 5 percent of the overall surface area o~ the film (i.e., on a basis of both the polymer area and hole are~), preferably at least 10 percent, and more preferably a~ least 20 percent.
After the initial step of lamination of a first film of intermediate polymer to a reinforcement fabric, a second lamination is necessary. At an elevated temperature of from about 150C to about 350C, preferably about 180C to 290C, a second intermediate polymer film is laminated to a second (i.e., upper) surface of the reinforcement fabric and the first intermediate polymer ~ilm (to its first surface). The reinforcement fabric becomes sandwiched between the first and second intermediate films and is embedded in these films. The second intexmediate polymer film covers the first film in areas which have become perforated to form a membxane substantially free of holes. It is understood that "substantially free o~ holes" also includes "free of hole~" since a mem~ra~e without holes is preferred.
The second film o~ intermediate polymer generally is present in a thickness from 0.5 to 10 mils, and preferably from l to 5 mils. A thicker film can be employed but ~auses fonmation of a membrane with an increased thickness.
The rein~orcement fabric contacts the ~irs-t and second films in sepaxate laminatin~ steps ~ith these matarial~ forced together, e.g., by use of ~39~
J.~
pressure rolls~ It is a re~uirement in the present invention tha~ ~he ~irst and second films axe contacted with the reinforcement fabric in two separate steps rather than simultaneously. Embedment of the reinforcing fabric in one lamination step is avoided in the practice of the present invention.
In a preferred mode of lamination, the reinforcement fa~ric is supported on a porous support material (e.g., porous support paper described in U.S.P. 3,770,567) between a vacuum source and a first intermediate pol~mer film. At elevated temperature an applied vacuum (causing a pressure ~ifferential of at least 5 mm mercury) pulls the first film down onto ~he reinforcement fabric and pulls a portion of the first film into contact with the porous support material.
After this laminating step in which the reinfoxcement fabric is partially embedded, both the reinforcement fabric and film are separated from the support paper. This separation causes holes to form in the polymer film.
In a second lamination step, a vacuum source is also empLoyedO In relationship to this source, the ~irst film and partially embedded rein~orcement fabriG
are reversed ~rom the first lamination step. The first film is supported and contacts porous support paperO A second intermediate polymer film ls contac~
ted with the partially embedded reinforcing fabric and the fir~t polymer film. Applied vacuum (causing a pre~sure differential of at least 5 mm mercury) pulls the second ~il~ onto the reinforcement fab~ic and onto the first fil~ ~o cause embedment o~ the reinforcement fabric. The holes in the first film allow the ~acuum to pull the second film against the reinforcement fabric and the first film. The second film covers the perforations of the first film and allows formation of a membrane substantially free of holes.
The laminate, i.e., membrane, from the first and second lamination steps has reinforcement fabric embedded in a matrix of polymer. Generally films not less than 0.5 mil are employed in the first and second lamination steps.
The laminate, i.e., membrane from a first and second lam;natlon steps, has thin wall portions, which meansthat the overall thickness of the membrane will vary in its different sections. This difference is due, at least in part, to the reinforcement fabric adding bulk to the membrane.
Also, due to the lamination procedur~, holes are formed in a first polymer film prior to a second lamination step~ This technique allows a matrix of polymer in which the reinforcement fabric is embedded to have different thicknesses. Solely on basis of thickness of polymer, the membrane, in a preferred mode, has portions of greater thichaess where rein-forcement fabric is present in comparison to porkions where no reinforcement fiber is present.
After formation of the membrane, the inter-mediate polymer of the membrane is chemically con-verted to a cation exchange polymer. The con-figuration of the resulting cation permeable membrane remains the same as the membrane con taining intermediate polymer. Therefore, the preceding remarks (directed to the membrane containing intermediate polymer) remain in relationship to the cation permeable membrane. The chemical conversion is by reacting sulfonyl groups in the polymer which are present as -SO2F or -SO2Cl, preferably -SO2F, to cation exchange groups. Examples of cation exchange groups include -(SO2NH2)mQ where Q is H and cation of an alkali or an alkaline earth metal and m is the valence of Q, and -(SO3)nMe wherein Me is a cation and n is the valence of Me. Another type of ion exchange group can be formed by reaction of the sulfonyl groups in the intermediate polymer with a primary amine to form N-monosubstituted sulfonamide groups. The same or different layers of the membrane can have different cation exchange groups. Conversion of sulfonyl groups to ion exchange groups or sites is disclosed in U.S.P.
3,282,875; 3,718,627; 3,773,634; 3,909,378; German OS 2,437,395 (Du Pont, published 1975 April 17) and OS 2,447,540 (Du Pont, published 1975 June 19).
At the same time, the carboxyl functional groups in -COOR form where R is lower alkyl, generally Cl to C5 alkyl, or in -CN form, are hydrolyzed to -COOH groups. Such conversion is ordinarily and conveniently accomplished by hydrolysis with acid or base, such that. the various functional groups described above in relation to the intermediate polymers are converted respectviely to the free acids or the alkali metal salts thereof. Such hydrolysis can be carried out with an aqueous solution of a mineral acid or an alkali me-tal hydroxide. Base hydrolysis is preferred as it is ~aster and more complete. Use of hot solutions, such as near the boiling point of the solution, is preferred for rapid hydrolysis. The time required for hydrolysis increases with the thick-ness of the structure. It is also of advantage toinclude a water-miscible organic compound such as dimethylsulfoxide in the hydrolysis bath.
The cation exchange membrane so made has reinforcement fabric embedded therein. The membrane 5 will have thin wall construction, meaning the membrane will have different thickness, particularly less overall thickness where no reinforcement fibers are present.
Although the reinforcement -fabric is embedded in a matrix of ion exchange polymer, it is understood that the composition of the matrix does not have to be uniform. Preferably the polymer differs on opposite surface portions of the reinforcement fabric.
In the Eirst laminate procedure, an intermediate polymer is employed whlch can differ from the intermediate polymer of the second lamination step. This difference in the polymer matrix remains after conversion of sulfonyl and carboxyl groups in the intermediate polymers into ion exchange groups. To describe this difference in polymer matrix in the cation exchange membrane, the term "base polymer" is employed and means the polymer without reference to any cation exchange groups thereon.
For purposes of illustration two polymers derived Lrom the same comonomers but with different equivalent weights (containing either the same or different cation exchange groups) are different base polymers~ two polymers which differ only in the type of cation exchange groups are the same base polymer. In a preferred cation exchange membrane, different base polymers contact opposite sides of the reinforcement fabric.
In accordance to the preceding definition of base polymer, the cation exchange membranes dis-closed in U.S. Patents 3,770,567; 3,849,243; 3,902,947 and 3,925,135 do not disclose different base polymers on opposite sides of the reinforcement fabric.
The membranes formed by the present ~ 3L8~
in~ention when present ~s a cation permeable membrane ha~e utility in membrane ion exchange devices, reverse osmosis devices or in electrolytic cells such as chlor-alkali cells. These membranes have S the advantage that the reinforcement fabric is embedded in the membrane while at the same time the thickness of the membrane will be a different and thinner construction in some of the portions of the membrane where no reinforcing fabric i5 present. The presence of areas of thinner wall construction means less polymer need be present in the membrane in comparison with other types of cation permeable membranes containing reinfoxcement fibers embedded therein. Also in some uses of the cation permeable membrane, e.g~, as a separator in a chlor-alkali cell, it is preferred to employ thin membranes since the electrical resistance can increase as the thickness o the membrane increases. The presence of thin wall areas in a reinforced membrane can translate into reduced power consumption in operation o~ an elec-trolytic cell. It is understood that a oation exchange membxane for this type of use is preferably perfluorinated.
Although the present process has been described in laminating two films to a reinforcement fabric, it i5 understood that various alternate embodLments are intended to be Pncompassed by this invention. For example~ in the second l~minatins step, several ilms can be simultaneously laminated to the product from the first lamination. Al~o cation exchange groups can be present in a layer o~ polymer film undergoing lamination provided sul~onyl groups present a~ S02F or ~50~Cl or carboxyl groups presen~
as ~COOR or -CN groups are on the surface of the ~ ~ ~ 9 pol~mer fil~s under~oing lamination.
In reg~rd to the ~luorinated carboxylate esters referred to herein, the term "perfluorinated"
xefers to the carboxylic acid poxtion of the ester, and not to the R group derived from a hydrocarbon alcohol. Such esters are referred to herein as perfluorinated, inasmuch as the R group i3 lost during hydrolysis when the ester groups are ~ydrolyzed to carboxylic acid groups.
The following examples are pro~ided to illustrate the invention. In these examples equivalent weight (E~) of an intermediate polymer is given and is weight of a polymer in grams of one equi~alent of potential ion exchange capacity. All percentages are by weight unless otherwise indicated.
The laminating equipment employed comprised a hollow roll with an internal heater and an internal vac~um source. The hollow roll contained a series of circumferential glot5 on its surface which allowed the internal vacuum source to draw web or sheet feed materials in the direction o~ the hollow xoll.
cuxved stationary plate with a radiant heater faced the top surface of the hollow roll with a spacing of about 1/4 inch between their two surfaces.
As a por~ion of the laminating equipmen~, porous support paper was used in contacting the hollow roll as a support material to preven~ adherence of polymer film to ~he roll surfac~ and to allow vacuum to pull material being laminated in the direc tion of the hollow roll. Also, the support paper allowed openings to be fonmed in a pol~mer ~ilm in a fi~st lamination step. Feed and takeoff means were p~o~ided for the materials bein~ lami~ated. In the ~eed means one idlPr ~oll o~ smaller di~meter than the hollo~ roll was pro~ided ~or support pap~r and materials undergoing lamination~ The feed and takeoff means were positioned to allow feed material to pass around the hollow roll over a distance of about 5/6 of its circumference. ~ further idler roll was pro-vided for the support paper allowins its separation from the other materials undergoing lamination.
Takeoff means were provided for the support paper and a laminate.
In formation of a laminate, a support paper of 90-pound weight basis manufactured by Water Vliet Company, designated Hi-Sette Enamel*, black printed on one side with I~mont Flexolume Black No. 61-R-5589 was employed. This support paper had a minimum porosity speci~ication of 0.006 S.C.F.M. per square inch under ~n air pressure differential of 40 cm of mercury. Also employed was a reinorc~ment fabric of T 900 G Teflon~ polytetrafluoroethylene/rayon fabric having 14 polytetrafluoroethylene txeads/inch (200 denier each) and 56 rayon threads/inch (S0 denier each) woven i~ a plain weave and a 2-mil film o a polymer of tetrafluoroethylene and perfluoro(3,6-dioxa-4-methyl-7-octene-sulfonyl fluoride). This ~S polymer had an equivalent weight of 1100.
In the lamination step the feed materials were ~ed to the hollow roll with the support paper contacting the hollow roll on its unprlnted side, contacting the support paper was the reinforcement fabric and contacting this fabric was the 2-mil polymer film. Lamination speed of the feed materials was 24 inches per minute with the roll temperature controlled at 237C and the plate temperature controlled at 300C.
A vacuum of 24.8 inches of mercury was appliedO
*denotes trade mark This lamination step caused the pol~er film to contact the support paper in areas wherein no reinforcement fabric ~as present~ In the first lamination step, separation of the suppoxt paper from the laminate o~ the reinforcement fabric and copolymer film caused holes to form in the polymer film in an area gxeater than 5 percent of the surface area of the film (on basis of fîlm and hole areas).
For a second lamination step, support paper of the same kind was used, except the paper was sprayed with silicone oil to prevent sticking. On the silicone treated side of the suppor~ paper was contacted the laminate from the first lamination with the reinfoxcement fabric facing away from the support paFer. On the reinforcement fabric portion of the laminate was contacted an 0.5 mil polymer film of tetrafluoroeth~lene and per1uoro(3,6-dioxa-4---methyl 7-octenesul~onyl fluoride) with an equivalent weight of 1600. With the support paper contacting the hollow roll, a second lamination step was per-~ormed. Lamination speed was 24 inches per minute;
roll temperature was 232C; plate temperature was 296C; vacuum applied was 15 inches of mercury.
Af~er this second lamination step and separation o~ the support paper, visual examination showed the laminate to ~e completel~ free of any holes.
A reinforced membrane was made employing the apparatus and a similar procedure described in Example 1. The procedure o~ this Example employed in a first lamination ste~ a 2 mil 1100 EW (i.e~, equivalent weight~ film o~ a polym~r of tetra-fluoroethylene and perfluoro(3,6-dioxa-4-methyl-7~
octenesulfonyl ~luoride) and a reinforcement fabric of T 900 G Teflon~ polytetrafluoroet~lene/rayon fabric ~9~
(described in Example 1).
For the second lamination step a 5 mil 1200 EW film of a polymer of tetr~fluoroethylene and perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) was employed with one side having been contacted and reacted to a depth of 1.3 mils with n~butylamine. The unreacted side of the 5-mil film (which cont~s unreacted pendant -S02F groups) was laminated in a similar pro-cedure as the second lamination disclosed in Example 1~
The resulting laminate had virtually ~o lea~s as determined by a ~acuum operated leak detector apparatus.
Although the membrane was not converted to a cation exchange membrane, it could have ~een easily undertaken by reaction of the -SO2F groups; e.g., by immersion of the laminate in potassium hydroxide.
Exam~es 3 and 4 ~ . = ~ . =
Employing a similar procedure as in Example 1, a 2-mil ilm of 1100 EW polymer of tetrafluoroethylene and perfluoro(3,6~dioxa-4-methyl-7-octenesulfonyl fluoride) and a reinforcement fabric of T 900 G Teflon~ polytetra-fluorcethylene/rayon fabric were continually laminat~d; there-after a l-mil film of 1500 EW polymer of tetrafluoroethyle~e and perfluoro(3,6-dioxa-4-methyl-7~x~esulfonyl fluoride) was employed m a seco~d lammation~
The resulting l~late was uniform, leak free and the reinforcement fahric was well ~ded therein.
Fbr Exa~ple 4, a simllar procedure as in Example 3 was employel excspt m the second lamination a 1.5~mdl 1500 EW
polymer fi ~ was ussd (in place of the 1 mil 1500 EW polymer fil~).
m e ~w~ Laminates of EXamples 3 a~ 4 were to~ally hydrolyz~d by ~nnersion in 11% solution of potassium hydroxide in 30% aque~us dime~hyl sulfoxide a~
90C for a~2u~ one hour, followed by boil m g in distilled water ~r thirt~ minutes, The two membranes ~ere leak ~ree.
The cation exchange membranes of Examples 3 and 4 were mounced in 3-inch diameter laboratory chlor-alkali cells with the higher equivalent weight portion of the membrane facing the cathode compartment.
The cells were operated at 2 amperes/inch2, 80C and a 22-23% NaCl anolyte and after two days the following results were obtained~
ProductCell CausticVolta~eEfficiency ~ ~ .
Example 3 3.25 N 3.6 86%
Example 4 3.25 N 3.8 88%
Exam~le 5 A reinforced membrane was made employins the apparatus and a similar procedure described in Example 1. The procedure of this example employed in the first laminatio~ step a 2-mil film of a copolymer of 40.5% by wt. tetrafluoroethylene and 59.5% by wt.
perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) having an equivalent weight of 1100, and a calendered leno weave fabric having 200-denier polytetrafluoro-ethylene yarn in the warp and 400-denier polytetra~
fluoroethyl-ene yarn in the fill (fabric designation T-24C), For th~ second lamination step a 5~mil film of a copolymer of 37~ by wt. of tetrafluoroethylene and 63 wt. of CF~=CF-O-CF2 CF-O-CF2 CF~-COOC~3 ha~ing an equivalent weight of 1149 was employedO In this step a speed of ~4 mches/min was used with the vacuum roll at 220C and the c ~ed plate at 278C, a~d the support papex was à porous siliconercoated paper (Par'cwick ~3300*manufactured by the Paper Corporation of U~ited States). The resulting *denotes trade mark , . . .. . .. .
3S3~
laminate was uni~orm and leaX~ree. The fabric was ~ell embedded therein~
The laminate ~as converted t-o ~n ion ex-change membrane having -S03H groups in one layer and -COOH groups in the other layer by immersion in a hydrolysis bath of 13~ potassium hydroY~ide in 30%
aqueous dimethyl sulfoxide at 90C for 1 hour, followed by boiling in distilled water for 30 mi~utes.
The membrane was free of leaks.
The membrane was mounted in a chloralkali cell with the carboxyl side of the membrane facing the cathode compartment, and was tested under conditions specified in Examples 3 and 4. Representa-tive test data are as follows:
NaOH Current ~ Voltage ~ Efficienc~
.__ 1 4.55 3~.20 90.7 9 4.22 29.37 94.6 36 4.48 35.27 8901 57 4.20 35.98 87.7 76 4.87 35.90 83.6 10~ 4.73 30.73 85.2 125 4.43 32.80 84.9 Exam~le 6 A reinforced membrane was made employlng the apparatus and a similar procedure described in Example 1. The procedure of this example employed in the first lamination step a 2~mil film of a copolymer of 40% by wt. o~ tetrarluoroethylene and 60% by wto of C~2=CF-O~CF2 CF-O-CF2 CF~-COOCH3 having a~ equivalent weight of 1052 and T-24C fabric (described in Example 5). In this step the lamination was at a speed of 12 inches/min, with the ~acuum roll at 200C and the curved platP at 225C, and the support paper Partwick ~3300.
, ~or the second lamination step a 5-mil film of the same 1052-e~uivalent weight carboxyl poIymer described in the first paragraph of this example was employed~ The laminatlon was carried out as in the first step of this example except at a speed of 24 inches/min. The resulting laminate was free of leaks and the fabric was well embedded therein.
The laminate was converted to an ion exchange membrane having carboxylic acid groups in both layers by hydrolysis and washing as described in Example 5.
The membrane was tested in a chloralkali cell under conditions specified in Examples 3 and 4.
Representative test data are as follows.
NaOH Cu.rrent Days Voltase ~ Efficiency 1 4.50 27069 88.8 6 4.59 29.41 91.1 4.62 30.23 ~9.4 38 4.69 29.02 91.3 56 4.70 30.91 89.5 69 4.75 30.77 94.1 99 5.15 37.8~ 8~.6 122 5.10 35.50 86.7 2S 139 5.06 36.31 84.1 148 4.9~ 31.92 89.5 171 4.83 26.64 a9.2 ~'5~
The process of the invention provides a membrane which, after conversion to ion exchange form, is useful for various ion exchange purposes, such as packing for ion exchange devices, reverse osomosis, and as membrane for separating the compartments of various electrochemical cells which comprise in general an anode, a cathode, an anode compartment
2~
a~d a cathode compa~tment. The ion exchange membrane is particularl~ useful ~or the membxane of a chloralk~li cell.
a~d a cathode compa~tment. The ion exchange membrane is particularl~ useful ~or the membxane of a chloralk~li cell.
Claims (29)
1. A process for making a reinforced membrane comprising the steps of:
(a) laminating at a temperature from about 150°C to about 350°C first surfaces of both a first film and a reinforcement fabric, wherein said reinforcement fabric contacts a porous support material and laminating by means of a vacuum causing a pressure differential of at least 5 mm Hg, which draws the first surface of the first film onto the reinforcement fabric and forces a portion of the first surface of the first film into contact with said porous support material;
said film comprising a fluorine-containing polymer with pendant side chains comprising sulfonyl groups present as -SO2F or -SO2Cl, or carboxyl groups present as -COOR where R
is lower alkyl, or -CN groups, each of said sulfonyl or carboxyl groups being attached to a carbon atom which has at least one fluorine atom connected thereto;
(b) separating said reinforcement fabric and said first film from said porous support material whereby a laminate is obtained with holes in an area at least 5% of an overall surface area of said film;
(c) laminating at a temperature from about 150°C to 350°C a second film with (i) portions of the first surface of said first film, and (ii) a second surface of said reinforce-ment fabric, and laminating by means of a vacuum causing a pressure differential of at least 5 mm Hg which draws the second film onto (i) and (ii), said second film comprising a fluorine-containing polymer with pendant side chains comprising sulfonyl groups present as -SO2F or -SO2Cl, or carboxyl groups present as -COOR where R is lower alkyl, or -CN groups, each of said sulfonyl or carboxyl groups being attached to a carbon atom which has at least one fluorine atom connected thereto, causing embedment of said fabric in a matrix of at least one said fluorine-containing polymer and causing formation of a membrane substan-tially free of holes.
(a) laminating at a temperature from about 150°C to about 350°C first surfaces of both a first film and a reinforcement fabric, wherein said reinforcement fabric contacts a porous support material and laminating by means of a vacuum causing a pressure differential of at least 5 mm Hg, which draws the first surface of the first film onto the reinforcement fabric and forces a portion of the first surface of the first film into contact with said porous support material;
said film comprising a fluorine-containing polymer with pendant side chains comprising sulfonyl groups present as -SO2F or -SO2Cl, or carboxyl groups present as -COOR where R
is lower alkyl, or -CN groups, each of said sulfonyl or carboxyl groups being attached to a carbon atom which has at least one fluorine atom connected thereto;
(b) separating said reinforcement fabric and said first film from said porous support material whereby a laminate is obtained with holes in an area at least 5% of an overall surface area of said film;
(c) laminating at a temperature from about 150°C to 350°C a second film with (i) portions of the first surface of said first film, and (ii) a second surface of said reinforce-ment fabric, and laminating by means of a vacuum causing a pressure differential of at least 5 mm Hg which draws the second film onto (i) and (ii), said second film comprising a fluorine-containing polymer with pendant side chains comprising sulfonyl groups present as -SO2F or -SO2Cl, or carboxyl groups present as -COOR where R is lower alkyl, or -CN groups, each of said sulfonyl or carboxyl groups being attached to a carbon atom which has at least one fluorine atom connected thereto, causing embedment of said fabric in a matrix of at least one said fluorine-containing polymer and causing formation of a membrane substan-tially free of holes.
2. The process of Claim 1 wherein in (a) and (c) said temperature is from about 180°C to 290°C.
3. The process of Claim 1 wherein in (a) and (b) said holes are formed in an area of at least 10%
of the overall surface area of the first film.
of the overall surface area of the first film.
4. The process of Claim 3 wherein in (a) and (b) said holes are formed in an area of at least 20% of the overall surface area of the first film.
5. The process of Claim 1 wherein said first film has a thickness from 0.5 to 5 mils.
6. The process of Claim 5 wherein said first film has a thickness from 1 to 3 mils.
7. The process of Claim 5 wherein said second film has a thickness from 0.5 to 10 mils.
8. The process of Claim 7 wherein said second film has a thickness from 1 to 5 mils.
9. The process of Claim 1 wherein said reinforcement fabric is woven.
10. The process of Claim 1 wherein in (a) and (c) any said sulfonyl groups are present as -SO2F, and any said carboxyl groups are present as -COOR.
11. The process of Claim 1 wherein in (a) and (c), said polymer is perfluorinated.
12. The process of Claim 11 wherein in (a) and (c), said polymer is a copolymer of tetrafluoro-ethylene and perfluoro (3,6-dioxa-4-methyl-7-octene-sulfonyl fluoride).
13. The process of Claim 11 wherein in at least one of steps (a) and (c), said polymer is a copolymer of tetrafluoroethylene and ;
CF2=CF-O-(CF2)3COOCH3 or .
CF2=CF-O-(CF2)3COOCH3 or .
14. The process of Claim 11 wherein in at least one of steps (a) and (c), said polymer is a copolymer of tetrafluoroethylene and
15. The process of Claim 1 wherein in step (c) said second film is a combination of a first layer of fluorine-containing polymer with pendant side chains comprising sulfonyl groups present as -SO2F or -SO2Cl in non-adherent contact with a second layer of fluorine-containing polymer with pendant side chains comprising carboxyl groups present as -COOR where R is lower alkyl, said second film disposed so that said first layer contacts said reinforcing fabric and said first film.
16. The process of Claim 1 wherein said membrane of (c) is converted into a cation exchange membrane by conversion of said sulfonyl groups present as -SO2F or -SO2Cl to form cation exchange groups, and of said carboxyl groups present as -COOR or -CN
into -COOCH groups or Na or K salt thereof.
into -COOCH groups or Na or K salt thereof.
17. The cation exchange membrane made by the process of Claim 16.
18. The cation exchange membrane of Claim 17 wherein opposite surfaces of the reinforcement fabric contact different base polymers.
19. The cation exchange membrane of Claim 18 wherein said base polymers have different equivalent weights.
20. The cation exchange membrane of Claim 18 wherein said base polymers contain different cation exchange groups.
21. The cation exchange membrane of Claim 17 wherein said matrix of at least one fluorine-containing polymer is perfluorinated.
22. The cation exchange membrane of Claim 21 wherein at least one layer of said matrix of at least one fluorine-containing polymer is formed from a polymer of tetrafluoroethylene and perfluoro (3,-6-dioxa-4-methyl-7-octenesulfonyl fluoride).
23. The cation exchange membrane of Claim 21 wherein at least one layer of said matrix of at least one fluorine-containing polymer is formed from a copolymer of tetrafluoroethylene and .
24. The cation exchange membrane of Claim 21 wherein at least one layer of said matrix of at least one fluorine-containing polymer is formed from a polymer of tetrafluoroethylene and .
25. The cation exchange membrane of Claim 21 wherein at least one layer of said matrix of at least one fluorine-containing polymer is formed from a copolymer of tetrafluoroethylene and CF2=CF-O-(CF2)3COOCH3.
26. The cation exchange membrane of Claim 21 wherein at least one layer of said matrix of at least one fluorine-containing polymer is formed from a polymer of tetrafluoroethylene and .
27. The cation exchange membrane of Claim 17 wherein said matrix consists of first, second and third layers, said second layer being between and in adherent contact with said first and third layers, said first layer being formed from a said fluorine-containing polymer with pendant side chains comprising carboxyl groups present as -COOR, said second layer being formed from a said fluorine-containing polymer with pendant side chains comprising sulfonyl groups present as -SO2F, said third layer being formed from a said fluorine-containing polymer with pendant side chains comprising sulfonyl groups present as -SO2F, and reinforcement fabric embedded at least predominantly in said second and third layers.
28. The cation exchange membrane of Claim 17 where said reinforcement fabric is woven.
29. An electrochemical cell which comprises an anode compartment, an anode situated within said anode compartment, a cathode compartment, a cathode situated within said cathode compartment, and, between said compartments, said membrane of Claim 17.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US225,640 | 1981-01-16 | ||
| US06/225,640 US4341605A (en) | 1981-01-16 | 1981-01-16 | Process for cation permeable membrane with reinforcement fabric embedded therein and product thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1189828A true CA1189828A (en) | 1985-07-02 |
Family
ID=22845642
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000394201A Expired CA1189828A (en) | 1981-01-16 | 1982-01-14 | Laminated polymer membrane with intervening reinforcement thereof |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4341605A (en) |
| JP (1) | JPS57139127A (en) |
| BE (1) | BE891795A (en) |
| CA (1) | CA1189828A (en) |
| DE (1) | DE3201119A1 (en) |
| FR (1) | FR2498116B1 (en) |
| GB (1) | GB2091167B (en) |
Families Citing this family (28)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4877499A (en) * | 1984-11-05 | 1989-10-31 | The Dow Chemical Company | Membrane unit for electrolytic cell |
| US4894128A (en) * | 1986-05-05 | 1990-01-16 | The Dow Chemical Company | Membrane unit for electrolytic cell |
| US4735193A (en) * | 1985-02-08 | 1988-04-05 | Uop Inc. | Separation of a monosaccharide with mixed matrix membranes |
| US4606740A (en) * | 1985-04-15 | 1986-08-19 | Uop Inc. | Separation of polar gases from nonpolar gases |
| US4608060A (en) * | 1985-04-15 | 1986-08-26 | Uop Inc. | Separation of polar gases from nonpolar gases |
| WO1986007075A1 (en) * | 1985-05-31 | 1986-12-04 | The Dow Chemical Company | Novel fluoropolymer solutions |
| US5114515A (en) * | 1985-05-31 | 1992-05-19 | The Dow Chemical Company | Method for forming polymer composite films using removable substrates |
| US5110385A (en) * | 1985-05-31 | 1992-05-05 | The Dow Chemical Company | Method for forming polymer composite films using a removable substrate |
| US4784882A (en) * | 1985-05-31 | 1988-11-15 | The Dow Chemical Company | Method for forming composite polymer films |
| US4650551A (en) * | 1985-05-31 | 1987-03-17 | The Dow Chemical Company | Supported ion exchange membrane films |
| US4784900A (en) * | 1985-05-31 | 1988-11-15 | University Of Bath | Method for sizing polytretrafluoroethylene fabrics |
| US4650711A (en) * | 1985-05-31 | 1987-03-17 | The Dow Chemical Company | Method for sizing polytetrafluoroethylene fabrics |
| US4824508A (en) * | 1985-12-09 | 1989-04-25 | The Dow Chemical Company | Method for making an improved solid polymer electrolyte electrode using a liquid or solvent |
| US4654104A (en) * | 1985-12-09 | 1987-03-31 | The Dow Chemical Company | Method for making an improved solid polymer electrolyte electrode using a fluorocarbon membrane in a thermoplastic state |
| US4826554A (en) * | 1985-12-09 | 1989-05-02 | The Dow Chemical Company | Method for making an improved solid polymer electrolyte electrode using a binder |
| 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 |
| JP2753731B2 (en) * | 1989-06-05 | 1998-05-20 | 旭化成工業株式会社 | Preparation method of fluorine ion exchange membrane |
| DE3928934C2 (en) * | 1989-08-31 | 1999-04-29 | Sartorius Gmbh | Textile reinforced microporous membrane filter, process for its preparation and its use |
| JP3075580B2 (en) * | 1991-04-05 | 2000-08-14 | 旭硝子株式会社 | Fluorine-containing cation exchange membrane for electrolysis |
| US5384019A (en) * | 1993-10-29 | 1995-01-24 | E. I. Du Pont De Nemours And Company | Membrane reinforced with modified leno weave fabric |
| US5567626A (en) * | 1995-04-11 | 1996-10-22 | Pall Corporation | Method of detecting biological materials using a polyvinyllidene fluoride membrane |
| US6503295B1 (en) * | 2000-09-20 | 2003-01-07 | Chevron U.S.A. Inc. | Gas separations using mixed matrix membranes |
| US7037949B2 (en) | 2001-02-07 | 2006-05-02 | Asahi Kasei Chemicals Corporation | Ion-exchange resin membrane and method for producing the same |
| US6726744B2 (en) | 2001-11-05 | 2004-04-27 | Uop Llc | Mixed matrix membrane for separation of gases |
| US7306647B2 (en) * | 2004-11-19 | 2007-12-11 | Chevron U.S.A. Inc. | Mixed matrix membrane with mesoporous particles and methods for making and using the same |
| US7344585B1 (en) | 2005-08-31 | 2008-03-18 | Uop Llc | Mixed matrix membrane for gas separation |
| JP5483887B2 (en) * | 2006-03-08 | 2014-05-07 | クナノ アーベー | Method for synthesis of epitaxial semiconductor nanowires on Si without metal |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3004904A (en) * | 1955-05-25 | 1961-10-17 | Nalco Chemical Co | Electronegative selective permeable membrane and method of production |
| US3371785A (en) * | 1965-06-19 | 1968-03-05 | Kurita Industrial Co Ltd | Method of dehydrating sludge |
| US3494468A (en) * | 1968-01-02 | 1970-02-10 | North American Rockwell | Reverse osmosis system |
| US3616121A (en) * | 1969-07-23 | 1971-10-26 | Addressograph Multigraph | Composite identification card |
| US3925135A (en) * | 1971-11-08 | 1975-12-09 | Du Pont | Method of making laminates of support material and fluorinated polymer containing pendant side chains containing sulfonyl groups |
| US3849243A (en) * | 1971-11-08 | 1974-11-19 | Du Pont | Laminates of support material and fluorinated polymer containing pendant side chains containing sulfonyl groups |
| US3770567A (en) * | 1971-11-08 | 1973-11-06 | Du Pont | Laminates of support material and fluorinated polymer containing pendant side chains containing sulfonyl groups |
| US3902947A (en) * | 1973-08-01 | 1975-09-02 | Du Pont | Process for preparing laminates of support material and fluorinated polymer containing pendant side chains containing sulfonyl groups |
| US3985501A (en) * | 1974-01-04 | 1976-10-12 | E. I. Du Pont De Nemours And Company | Ion-exchange fabric of fluorinated polymer containing pendant side chains with sulfonyl groups |
| GB2031438B (en) * | 1978-09-27 | 1983-01-12 | Diamond Shamrock Corp | Fabric-reinforced ion exchange membranes |
| US4324606A (en) * | 1979-12-27 | 1982-04-13 | E. I. Du Pont De Nemours And Company | Process for forming a reinforced membrane |
-
1981
- 1981-01-16 US US06/225,640 patent/US4341605A/en not_active Expired - Lifetime
-
1982
- 1982-01-13 JP JP57002899A patent/JPS57139127A/en active Pending
- 1982-01-13 FR FR8200410A patent/FR2498116B1/en not_active Expired
- 1982-01-14 GB GB8201004A patent/GB2091167B/en not_active Expired
- 1982-01-14 CA CA000394201A patent/CA1189828A/en not_active Expired
- 1982-01-15 DE DE19823201119 patent/DE3201119A1/en not_active Withdrawn
- 1982-01-15 BE BE0/207067A patent/BE891795A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| GB2091167A (en) | 1982-07-28 |
| US4341605A (en) | 1982-07-27 |
| GB2091167B (en) | 1984-09-19 |
| FR2498116A1 (en) | 1982-07-23 |
| DE3201119A1 (en) | 1982-09-02 |
| BE891795A (en) | 1982-07-15 |
| FR2498116B1 (en) | 1986-01-31 |
| JPS57139127A (en) | 1982-08-27 |
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