JPH0142292B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to ion exchange membranes that operate at low voltages and high current densities, thus having low power consumption and good tear resistance, and their use. Fluorinated ion exchange polymers containing carboxylic acid and/or sulfonic acid functional groups or salts thereof are known in the art. One major use of such polymers is as a membrane component used to isolate the anode and cathode compartments of chlor-alkali electrolyzers. Such membranes may be in the form of reinforced or unreinforced films or laminated structures. For use in chlor-alkali baths, the membranes can operate at low voltages and high current densities and therefore with low power consumption, giving high quality products at low prices in view of today's increasing energy costs. desirable.
It is further desirable that the membrane be tough and resistant to damage during its manufacture and use in such vessels. The best existing ion-exchange polymer films have low tear strengths, so membranes can be reinforced with
It has proven necessary to strengthen it, for example by producing it with reinforcing fibers. However, the use of reinforcement in the membrane is not entirely beneficial. One drawback is that the use of reinforcing materials such as textile fabrics makes the membranes thicker, resulting in membranes that can only be used at high voltages because the increased thickness increases electrical resistance. be. Efforts to lower resistance by using thinner films in manufacturing reinforced membranes have resulted in membrane tears in some of the fabric windows during membrane manufacture, resulting in leaky membranes. They are often unsuccessful because of this. (Here, "window" means
(meaning the open area between adjacent threads of a textile fabric). Leaky membranes are undesirable in that they allow anolyte and catholyte to flow into opposite cell chambers, reducing current efficiency and impure the product produced. Additionally, the polymer layer becomes thicker at the intersections of the reinforcing fiber fabric yarns, creating high resistance regions. (The "intersection" here means the point where the weft and warp threads overlap). The second drawback, also common to high voltage applications, is the "shadow" of the reinforced membrane.
induced by action. The shortest path for ions through the membrane is a vertical straight path from one surface to the other. The reinforced membrane is uniformly made of a material that is not permeable to ions. Portions of the membrane where ions cannot pass vertically and in a straight line through the membrane, and where ions must take a circuitous route around the reinforcing member, are referred to as "shadow regions."
It is called. When a "shadow zone" is introduced into a membrane through the use of reinforcement, the
The effective ion transport capacity is reduced and the operating voltage of the membrane is therefore increased. The portion of the membrane's shadow zone that is adjacent to the downstream side of the reinforced membrane, ie, adjacent to the "downstream" side with respect to the direction of cation flow through the membrane, is referred to as the "blind zone." The main object of the present invention is to provide an ion exchange membrane that operates at low voltage and high current efficiency, and therefore with low power consumption, and yet has good tear resistance. Another objective is to provide a thin and strong ion exchange membrane. Other purposes will become apparent from the description below. In summary, according to the invention there is provided a reinforced membrane with a high aspect ratio as defined below, a polymer layer with carboxylic acid functional groups downstream of the reinforced membrane, and a conduit in the membrane leading to the blind area. An ion exchange membrane having (channels) is provided. More particularly, fluorinated polymers in which adjacent layers with -COOM and/or _-SO3W functional groups [where M is H, NA, K or _NH4 ] are in adhesive contact with each other. an ion exchange membrane impermeable to hydraulic flow of a liquid, comprising at least two layers and a web of support material embedded therein, the membrane comprising: a first membrane having -COOM functional groups; at least one layer and a second said layer having _SO3M functional groups are present, and the total thickness of the at least two layers of fluorinated polymer is used in the production of the membrane.
When measured on a layer of precursor polymer with COOR and/or _-SO2W functionality [where R is lower alkyl and W is F or Cl], 50
~250 microns, the web of support material having a thickness of about 25 to 125 microns and an openness of at least 50% and comprising reinforcing members; a member defines a window area therebetween, and a channel within the membrane extends from the window area to a blind area, where the reinforcing member is located near the first layer. An ion exchange membrane is provided. Further, according to the present invention, there are provided a precursor membrane for producing an ion exchange membrane, an electrochemical cell containing the ion exchange membrane as a component, and an electrolysis method using the ion exchange membrane. The membranes of the present invention are typically made of 2 fluorinated polymers having -COOR and/or _-SO2W functional groups, where R is lower alkyl and W is F or Cl. Manufactured from one or more layers and a web of support material. The first layer of polymer with which this invention pertains is typically a carboxylic acid polymer having a fluorinated hydrocarbon chain to which are attached functional groups or pendant side chains containing functional groups. This pendant side chain can be e.g. [wherein Z is F or _CF3 , t is 1 to 12, and V is -COOR or -CN, where R is lower alkyl]. Typically, the functional groups in the side chains of polymers are It will exist at the base. Examples of fluorinated polymers of this type are British Patent No. 1145445, US Patent No. 4116888
and US Pat. No. 3,506,635.
More specifically, the polymer is prepared from monomers that 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, such as vinyl fluoride, hexafluoropropylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, perfluoro(alkyl vinyl ether), tetrafluoroethylene, and mixtures thereof. It is. For copolymers used in brine electrolysis, the precursor vinyl monomer will desirably be hydrogen-free.
Furthermore, at least one monomer is a fluorinated monomer containing in its side chain a group hydrolysable to a carboxylic acid group, such as a carbalkoxy or nitrile group, as described above. The term "fluorinated polymer" as used herein means a polymer that loses its R group through hydrolysis and becomes an ion-exchange type polymer, in which the number of F atoms is at least 90% of the number of F atoms and H atoms. . The monomer preferably contains no hydrogen other than the R group of -COOR, especially when the polymer is used for brine electrolysis, and most preferably contains no hydrogen for maximum stability in harsh environments. and chlorine, ie perfluorinated; the R group need not be fluorinated since it is lost during hydrolysis where the functional group is converted to an ion exchange group. One suitable type of carboxyl-containing monomer is, illustratively, of the formula [Wherein, R is lower alkyl, Y is F or
CF ₃ and s is 0, 1 or 2]. These monomers with s 1 can be prepared and separated in good yields when s is 0.
This is preferable because it can be achieved more easily than in case 2 or 2. Compound are particularly useful monomers. Such monomers may have, for example, the formula [wherein s and Y have the same meanings as above] From a compound having (1) the terminal vinyl group is saturated with chlorine and converted into a CF ₂ Cl−CFCl− group, in a subsequent step. (2) oxidation with nitrogen dioxide to convert -OCF ₂ CF ₂ SO ₂ F groups to -OCF ₂ COF groups; (3) esterification with an alcohol such as methanol to generate -OCF ₂ COOCH ₃ groups; , and (4)
It can be produced by dechlorinating with zinc dust to regenerate the terminal CF ₂ =CF- group. However, instead of this _sequence of steps (2) and ( ₃ ), (a) sulfinic acid, _-OCF2CF2SO2H , by treatment of the -OCF2 _{- CF2SO2F} group with sulphite or _hydrazine ; or its reduction to an alkali metal or alkaline earth metal salt; (b) formation of -OCF ₂ COOH group or its metal salt by oxidizing sulfuric acid or its salt with oxygen or chromic acid; and (c) known Depending on the method
Esterification to OCF ₂ COOCH ₃ can also be used. This sequence is described in further detail in US Pat. No. 4,267,364 in connection with the preparation of copolymers of such monomers. Other suitable types of carboxy-containing monomers have the formula [Wherein, V is -COOR or -CN, R is lower alkyl, Y is F or _CF3 , and Z
is F or CF ₃ and s is 0, 1 or 2]. The most preferred monomers, due to their ease of conversion to polymeric and ionic forms, are -COOR, where R is lower, generally C ₁ -
It is C ₅ alkyl. Monomers in which s is 1 are also preferred because their production and separation in good yields is easier to achieve than when s is 0 or 2. The preparation of these monomers and copolymers thereof where V is -COOR and R is lower alkyl is described in U.S. Pat. No. 4,131,740.
a compound whose method of manufacture is indicated therein; as well as are particularly useful monomers. A method for making monomers in which V is -CN is described in US Pat. No. 3,852,326. Yet other suitable types of carboxyl-containing monomers have terminal groups of -O( _CF2 ) _vCOOCH3 , where v is from 2 to 20, such as _CF2 =CFO( _CF2 ) _{3COOCH3 and} CF ₂ = _CFOCF2CF ( _CF3 ) _O ( _CF2 ) _3COOCH3 . Methods for producing such monomers and copolymers thereof are described in Japanese Patent Publication No. 52-38486 and Japanese Patent Publication No. 52-28586, and British Patent No.
Described in No. 1145445. Other types of carboxyl-containing polymers are repeating units [wherein q is 3 to 15, r is 1 to 10, s is 0, 1 or 2, t is 1 to 12, and x taken together are 4 fluorine or 3 fluorine and 1 chlorine, Y is F or _CF3 , and Z
is F or CF ₃ and R is lower alkyl]. A preferred group of copolymers are tetrafluoroethylene and [where n is 0, 1 or 2, m is 1,
₂ , 3 or 4 _, Y is F or _CF3 , and R is _CH3 , _C2H5 or _C3H7 ]. Such copolymers to which the present invention relates can be prepared by known techniques, such as US Pat. No. 3,528,954, US Pat. No. 4,131,740 and South African Patent No. 78/2225. The sulfonyl polymers to which this invention relates are typically polymers having a fluorohydrocarbon chain further attached with a functional group or pendant side chains bearing a functional group. The pendant side chain can be e.g. [wherein Rf is F, Cl or a _C1 - _C10 perfluoroalkyl group, and W is F or Cl, preferably F]. The functional groups in the side chains of polymers are usually terminal groups.

[Formula] will be present in [Formula]. Examples of fluorinated polymers of this type are U.S. Pat.
Disclosed in No. 3718627. More specifically,
The polymers can be made from fluorinated monomers or fluorine-substituted vinyl compounds. The polymer is made from at least two monomers, with at least one monomer from each of the two groups below. At least one monomer is a fluorinated vinyl compound such as vinyl fluoride, hexafluoropropylene,
Vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, perfluoro(alkyl vinyl ether), tetrafluoroethylene, and mixtures thereof. For copolymers used in brine electrolysis, the precursor vinyl monomer desirably does not contain hydrogen. The second group is the precursor group

It is a sulfonyl-containing monomer containing [Formula]. A further example is the general formula _CF2 =CF-Tk- _CF2SO2F , where T is a difunctional _{difluorinated} group having 1 to 8 carbon atoms, and k is 0 or 1. It can be expressed as: The substituent atomic group in T includes fluorine, chlorine, or hydrogen, but hydrogen is generally excluded when the copolymer is used for ion exchange in a chloralkali tank. The most preferred polymers have no hydrogen and chlorine bonded to carbon, ie they are perfluorinated for maximum stability in harsh environments. The T group in the above formula may be branched or unbranched, i.e. linear;
It may have one or more ether bonds. The vinyl group in the group of copolymers containing sulfonyl fluorides is attached to the T group through an ether linkage, i.e. the copolymer has the formula CF ₂ =CF-O-T
_-CF2 - _SO2F is preferred.
Examples of such sulfonyl fluoride-containing comonomers are It is. The most preferred sulfonyl fluoride-containing comonomer is perfluoro(3,6-dioxer-4
-methyl-7-octensulfonyl fluoride), It is. Sulfonyl-containing monomers are disclosed in U.S. Pat. No. 3,282,875.
No. 3,041,317, No. 3,718,627 and No. 3,560,568. Suitable types of such polymers include repeating units [wherein h is 3 to 15, j is 1 to 10, p is 0, 1 or 2, and X together represent 4 fluorine or 3 fluorine and 1 chlorine] and
Y is F or CF ₃ and Rf is F, Cl or C ₁
~ _C10 perfluoroalkyl group]. The most preferred copolymer is of tetrafluoroethylene and perfluoro(3,6-dioxa-4-methyl-7-octensulfonyl fluoride).
It is a copolymer containing 20 to 65% by weight, preferably 25 to 50% by weight of the latter. Such copolymers used in the present invention are compatible with general polymerization methods developed for the homopolymerization and copolymerization of fluorinated ethylene, particularly for tetrafluoroethylene, which are described in the literature. It can be manufactured by a method. A non-aqueous method for making the copolymer is that of U.S. Pat. No. 3,041,317, in which a mixture of main monomers, e.g., tetrafluoroethylene and fluorinated ethylene containing sulfonyl fluoride groups, is combined with a radical initiator, Preferably in the presence of a perfluorocarbon peroxide or an azo compound, at a temperature of 0 to 200°C and a pressure of
Includes methods in which polymerization is carried out at ¹⁰⁵ to 2× ¹⁰⁷ Pascals (1 to 200 atmospheres) or higher. The non-aqueous polymerization reaction can be carried out in the presence of a fluorinated solvent if desired. Suitable fluorinated solvents include inert liquid perfluorinated hydrocarbons such as perfluoromethylcyclohexane, perfluorodimethylcyclobutane, perfluorooctane, perfluorobenzene, etc., and inert liquid chlorofluorocarbons such as 1, 1,2-trichloro-1,2,2-trifluoroethane and the like. Aqueous methods for making copolymers involve contacting the monomers with an aqueous medium containing a radical initiator and forming a non-aqueous wet or particulate polymer as disclosed in U.S. Pat. No. 2,393,967. Obtaining a slurry of coalesced particles or contacting the monomers with an aqueous medium containing both a radical initiator and a telogenically inert dispersant, e.g., U.S. Pat. No. 2,559,752
and coagulating the dispersion. Copolymers containing different types of functional groups can also be used as one of the component films in making the membranes of the invention. For example, produced from monomers selected from the group of non-functional monomers mentioned above, monomers from the group of carboxylic acid monomers mentioned above and also monomers from the group of sulfonyl monomers mentioned above. The terpolymers prepared can be prepared and used as one of the film components in making membranes. Additionally, films that are mixtures of two or more polymers can be used as one of the component films of the membrane. For example, a mixture of a melt-processable form of a polymer having sulfonyl groups and a melt-processable form of a polymer having carboxyl groups can be prepared and used as one of the component films of the membranes of the present invention. . Furthermore, it is also possible to use the laminated film as one of the component films in producing the membrane. For example, a film having a melt-processable copolymer layer having sulfonyl groups and a melt-processable copolymer layer having carboxyl groups can be used as one of the component films in the production of the membranes of the present invention. . When used in a film or membrane for separating the anode and cathode compartments of an electrolytic cell, such as a chlor-alkali cell, the sulfonate polymers covered by this invention, after being converted to an ionizable form, have a
milliequivalents/g, preferably at least 0.6 milliequivalents/g and more preferably 0.8 to 1.4 milliequivalents/g.
It should have a total ion exchange capacity of g. If the ion exchange capacity is less than 0.5 meq/g, the electrical resistance will be too high, and if it exceeds 2 meq/g, the polymer will swell excessively, resulting in poor mechanical properties. The relative amounts of the components that make up the polymer, when used as an ion exchange barrier in an electrolyzer, are
The polymer should be adjusted or selected to have an equivalent weight of no greater than about 2000. The equivalent weight at which the resistance of the film or membrane is too high for practical use in an electrolytic cell varies somewhat with the thickness of the film or membrane. For thin films and membranes, equivalent weights up to about 2000 can be tolerated. Usually the equivalent weight should be at least 600, preferably at least 900. The polymeric film having sulfonyl groups in ion-exchanged form will preferably have an equivalent weight within the range of 900-1500. However, for many purposes, and for films of normal thickness, values of no greater than about 1400 are preferred. In the carboxylate polymers addressed herein, when used to isolate the chambers of chloralkali baths, the requirements regarding ion exchange capacity are different from those of the sulfonate polymers. The carboxylate polymer has an ion exchange capacity of at least 0.6 meq/g, preferably at least 0.7 meq/g, and most preferably at least 0.8 meq/g so as to have an acceptably low resistance. Must be. Such values have a thickness range of 10 to
Particularly acceptable for films having a thickness on the lower end of 100 microns, and for films in the middle and upper end of this range, an ion exchange capacity of at least 0.7 meq/g, preferably 0.8 meq/g. /
It should be g. The ion exchange capacity is 2 meq/g or less, preferably 1.5 meq/g or less,
And more preferably it should be 1.3 milliequivalents/g or less. In terms of equivalent weight, the carboxylate polymer most preferably has an equivalent weight within the range of 770-1250. The membranes of the present invention are made from component polymer films having a thickness of from about 13 microns (0.5 mils) to about 150 microns (6 mils). Since membranes are generally made from two or three such polymer films, the total thickness of the polymer films used in making the membrane is generally about 50 to 250 microns (2 to 10 mils), preferably about 2 to 10 mils. will be 75-200 microns (3-8 mils), most preferably about 75-150 microns (3-6 mils). Conventional methods for specifying the structural composition of membranes in this art include determining the polymer composition, equivalent weight and thickness of the polymeric film in melt-processable form, and the type of reinforcing fabric with which the membrane is made. It is to stipulate. This is done both in the case of the intermediate product membranes of the lamination process and the hydrolyzed ion exchange membranes made therefrom. The reasons for this are: (1) the thickness of the reinforced membrane is not uniform, i.e. it is thicker at the intersections of the reinforcing fibers and thinner elsewhere, and the measurements taken with a caliper or micrometer are only at the highest thickness; and (2) measurement of the cross section using micrographs and photographs is cumbersome and time consuming. Furthermore, in the case of hydrolyzed ion exchange membranes, the measured thickness depends on whether the membrane is dry or swollen with water or electrolyte, or even if the amount of polymer is constant, the ions of the electrolyte Varies depending on species and ionic strength. Since membrane function is in part a function of the amount of polymer, the most convenient way to define the structural composition is as described immediately above. The web of support material is suitably a woven or non-woven paper. In either case, the web consists of both reinforcing and sacrificial members. In the case of woven fabrics, weaves such as conventional basket weave and leno weave are suitable. Both reinforcing yarns and temporary reinforcing yarns can be monofilament or multi-stranded. The reinforcing member is a perhalocarbon polymer thread. "Perhalocarbon polymer" used here
The term is used to denote a polymer having a carbon chain that may or may not contain ether oxygen linkages and is substituted entirely with fluorine or fluorine and chlorine atoms. Preferred perhalocarbon polymers are perfluorocarbon polymers due to their greater chemical inertness. Typically, such polymers include homopolymers made from tetrafluoroethylene and tetrafluoroethylene and hexafluoropropylene and/or perfluoro(alkyl vinyl ethers) having from 1 to 10 carbon atoms in the alkyl group. ), for example copolymers with perfluoro(propyl vinyl ether).
An example of the most suitable reinforcing material is polytetrafluoroethylene. Reinforcing threads made from chlorotrifluoroethylene polymers are also useful. In order to provide adequate strength to the fiber cloth prior to lamination and to the membrane after lamination, the reinforcing yarn should be 50 to 600
It should be of denyl, preferably from 200 to 400 denyl (denyl is grams per 9000 m of yarn). However, such denier threads with typical round cross-sections are particularly thick enough that the thread overlap makes the reinforcement up to twice the thickness of the thread, thus making it leak-free. It is necessary to use a film layer of a fluorinated polymer, resulting in a thickness that necessitates operation at high voltages and thus provides an unsatisfactory membrane. According to the invention,
The reinforcing member has a particular denier but is non-circular. That is, fiber fabrics with a cross-sectional shape having an aspect ratio of 2 to 20, preferably 5 to 10 are used. By aspect ratio is meant the ratio of the width of the reinforcing member to its thickness. Typical suitable cross-sectional shapes include rectangular, oval and oval. The rectangular member may be in the form of a thin, narrow ribbon slit from the film, or may be extruded as such;
In this case, the corners can be rounded. oval,
Ovals and other shapes may be extruded or made by calendering fibers or yarns. It is also possible to calender the woven fabric to obtain the required aspect ratio. A rectangular cross section as described above is preferred. The support material web is
25-125 microns (1-5 mil), preferably 50-125 microns (1-5 mil)
Having a thickness in the range of 75 microns (2-3 mils), the reinforcing member is 12-63 microns (0.5-2.5 mils), preferably 25-38 microns (1-1.5 mils).
It should have a thickness of . In each of the warp and weft of the fiber cloth,
It should have a thread count in the range of 1.6 to 16 reinforcing threads/cm (4 to 40 threads/inch). A thread count in the range of 6 to 8 reinforcing threads/cm is preferred. The temporary reinforcing member of the textile fabric is threads of any of a number of suitable materials, natural or synthetic. Suitable materials include cotton, linen, silk, rayon, 6-6
Included are nylon, polyethylene terephthalate, and polyacrylonitrile. Cellulosic materials are preferred. The primary requirement for temporary reinforcing fibers is that they can be removed without adversely affecting the polymer matrix. Under this condition,
Chemical properties of temporary reinforcing fibers
makeup) is not strict. Similarly, the method of removing the temporary reinforcing fibers is not critical so long as its removal does not interfere with the ion exchange capacity of the final polymer in the cation-permeable separator. By way of example, removal of temporary reinforcing fibers from cellulosic materials such as rayon can be accomplished using sodium hypochlorite. Temporary reinforcing fibers are fibers that can be removed without adversely affecting either the intermediate polymer, which is a precursor to the polymer having ion exchange sites, or the polymer having ion exchange sites. The temporary reinforcing fibers are removed from the polymer, leaving voids, without interfering with the ion exchange capacity of the final polymer. The method of removal of the temporary reinforcing fibers must not affect the support fibers used to reinforce the separator. The temporary reinforcing member, such as a narrow ribbon cut from rayon thread or regenerated cellulose film, is suitably about 40 to 100 denier. They are,
can have an aspect ratio in the range 1 to 20, i.e. can have a rectangular, oval or oval cross-section, or if of a sufficiently low denier an aspect ratio of 1;
That is, the cross section can be circular. As in the case of reinforcing threads, the temporary reinforcing threads should have a thickness of 12 to 63 microns, preferably 25 to 38 microns. In each of the warp and fill yarns, the ratio of temporary reinforcing yarns to reinforcing yarns in the fabric should be within the range of 10:1 to 1:1. A preferred ratio of temporary reinforcing fibers to reinforcing fibers is from 2:1 to 6:1, most preferably from 2:1 to 4:1. Furthermore, it is preferred that for each reinforcing fiber there is an even number of temporary reinforcing fibers. Fabrics having an odd number of temporary reinforcing fibers for each reinforcing fiber can also be used, but they are not the preferred type. The reason for this preference can be seen by observing what happens in the case of textile fabrics of normal weave with one temporary reinforcing fiber for each reinforcing fiber: textile fabric. When the temporary reinforcing fibers of are removed, the remaining reinforcing fibers are not in the form of a textile fabric: one set of fibers only remains on top of the other set of fibers, and such are not tolerated in the present invention. Yes, but it's not suitable. Of course, in such cases it is also possible to use special weaves that remain woven after removing the temporary reinforcing fibers. To avoid the need to create such special weaves, fabrics having an even number of temporary reinforcing fibers for each reinforcing fiber are preferred. Reinforcing fiber fabrics can be made with or without twisting existing high aspect ratio yarns. When twisting,
Reduce the number of twists and maintain a high aspect ratio. After the reinforcing fiber cloth is removed with temporary reinforcing thread,
At least 50% fiber fabric, preferably at least 65%
It should be such that it has an aperture ratio of .
Here, the "open area ratio" refers to the total area of the window relative to the total area of the fiber cloth, expressed as a percentage. In the case of nonwoven paper, thin open sheets of suitable component fibers can be used. The reinforcing member is a perhalocarbon polymer fiber. The term "fiber" as used herein with respect to nonwoven papers includes chopped fibers cut from filaments as well as fibrids and fibrils. Perhalocarbon has the same meaning as defined above with respect to perhalocarbon polymer yarn, and in this case too it is preferably perfluorocarbon. These fibers are 5~
10 denyl, 3-20mm, preferably 5-10mm
It has a length of The temporary reinforcing member is a fiber of cellulosic or other material as described above in connection with the temporary reinforcing yarn. Paper fibers are characterized by standard tests that define the "freeness" of pulp, such as TAPPI standard T227m.
It can be defined by the "Canadian Standards Degrees of Freedom" defined in 58. Suitable degrees of freedom values for paper temporary reinforcing members are within the 300-750 ml Canadian standard range. A preferred example is kraft fiber. The paper consists of 10-90% by weight of perhalocarbon fibers and 90-10% by weight of temporary reinforcing fibers, preferably 25-75% by weight of perhalocarbon fibers and 75-25% by weight of temporary reinforcing fibers. The paper should have a basis weight of 25 to 125 g/m ² , preferably less than 50 g/m ² . As in the case of woven paper, the thickness of the paper is between 25 and 125 microns (1 and 5 mils), preferably between 50 and 75 microns (2 and 3 mils).
and should have an open area of at least 50%, preferably at least 65% after removal of the temporary reinforcing fibers. Membranes can be made from a web of component layers of film and support material with the aid of heat and pressure. To fuse the polymeric films used together to form a single membrane structure with the support material, and to fuse adjacent film sheets together when more than two films are used. Usually requires a temperature of about 200-300°C. However, the required temperature may be above or below this range and depends on the polymer used. The selection of an appropriate temperature in that case is important because if the temperature is too low, the films will fail to adhere properly to the reinforcing member and to each other and/or large voids will form between the films adjacent to the reinforcing member. , and if the temperature is too high, it will be evident because excessive polymer fluidization will result in leakage and non-uniform polymer thickness. The pressure is about 2x
It can be used from pressures as low as ¹⁰⁴ Pascals to pressures exceeding ¹⁰⁷ Pascals. A suitable type of equipment for batch operations is a hydraulic press, usually using pressures in the range of 2×10 ⁵ to 10 ⁷ Pascals. The apparatus suitable for the continuous production of membranes and used in the examples unless otherwise specified consists of a hollow roll with an internal heater and an internal vacuum source. The hollow roll includes a series of circumferential slots on its surface, and an internal vacuum source draws the component material toward the hollow roll. A curved stationary plate with a radiant heater is connected to the upper surface of the hollow roll by approximately 6 mm (1/4 inch)
facing at an interval of During the lamination operation, a porous release paper is used as a support material in contact with the hollow roll to prevent adhesion of the component material to the roll surface, and a vacuum source draws the component material towards the hollow roll. Supply and removal means are provided for component materials and products. The feeding means uses Andler rolls with a smaller diameter than the hollow rolls.
Place the roll against the release paper and component materials.
The supply and removal means are positioned such that the component material passes around the hollow roll over a length of approximately 5/6 of its circumference. A further Andler roll is placed against the release paper to separate it from the other materials. Removal means are provided for the release paper and the product film. When used for ion exchange purposes and in electrolytic cells, such as chloralkali cells for the electrolysis of brine, the membrane should have all functional groups converted to ionizable functional groups. Usually and preferably these are sulfonic and carboxylic acid groups, or alkali metal salts thereof. Such conversion is usually and conveniently carried out by acid or base hydrolysis such that the various functional groups mentioned above for the melt processable polymer are converted to the free acid or alkali metal salt thereof, respectively. achieved. Such hydrolysis can be carried out using mineral acids or aqueous solutions of alkali metal hydroxides. Hydrolysis with a base is preferred because it proceeds quickly and completely.
The use of hot solutions, such as solutions near the boiling point, is preferred for fast hydrolysis. The time required for hydrolysis increases with the thickness of the structure. It is also advantageous for the hydrolysis bath to contain organic compounds that are miscible with water, such as dimethyl sulfoxide. Removal of the temporary reinforcing fibers from the membrane can occur at any stage before, during, or after converting the original membrane in melt-processable form into an ion exchange membrane. This can be done during the conversion if the temporary reinforcing element is one that is destroyed by the hydrolysis bath used in the conversion. An example of this is the caustic hydrolysis of nylon polymers. Also, in the case of temporary reinforcing elements of rayon, for example, removal can be effected before the conversion by treatment with aqueous sodium hypochlorite before the conversion. At this time, the temporary reinforcing fibers are removed and a membrane is produced in which the functional groups of the polymer layer remain in the -COOR and _-SO2W form. Hydrolysis may first be carried out, in which case the functional groups are converted to -COOH and -SO ₃ H or salts thereof, producing a membrane in ion-exchange form that still contains temporary reinforcing fibers. temporary reinforcing fibers are later removed;
In the case of rayon or other cellulosic materials or polyester materials, this can be accomplished if the membrane is used in a chloralkali bath by the action of the hypochlorous acid formed in the bath during electrolysis. Removal of the temporary reinforcing member from the membrane leaves a conduit in the membrane at the location originally occupied by the temporary reinforcing member. These conduits generally extend from the window area to the shadowed or blind area, while the reinforcing member is located near the functional polymer having carboxyl functionality. The conduits have a nominal diameter of 1 to 50 microns. This nominal diameter is the same as that of the temporary reinforcing fiber, the removal of which results in the creation of a conduit. The actual diameter of the conduit will vary due to shrinkage or collapse of the membrane when it is dehydrated and swelling when the membrane itself swells. Typically, the conduits remaining after removal of temporary reinforcing threads from textile fabrics are in the range of 10 to 50 microns in diameter, and in removal of temporary reinforcing members from paper are in the range of 1 to 20 microns in diameter. . The membranes of the invention are characterized in that the support material is not impregnated with a first layer of fluorinated polymers having carboxyl functional groups, but at least other layers of fluorinated polymers having primarily carboxyl and/or sulfonyl functional groups. layer and preferably present in a second layer, usually the surface layer of the membrane, of a fluorinated polymer having sulfonyl functionality. As a result, the conduits are also present at least primarily in layers other than the first layer of polymer and preferably in the second layer of polymer having sulfonyl functionality. The ion exchange membrane conduits created by the removal of the temporary reinforcing member do not penetrate the membrane from one surface to the opposite surface, so the membrane is free of liquid flow at the typical low pressures encountered in chloralkyl baths. Impermeable to hydraulic flow. (A diaphragm that is porous does not cause any change in the composition of the hydraulic flow of liquid passing through it, whereas an ion exchange membrane is such that the substances that permeate differ in composition from that of the liquid that contacts the membrane.
Allows selective permeation by ions and permeation of liquids by diffusion. ) It is easy to determine the presence or absence of a line passing through the membrane by a leak test using gas or liquid. However, the conduit may or may not be open or closed, ie, permeable through the second layer of fluorinated polymer to the surface of the membrane. In each case, the conduit extends from the window area of the membrane to the blind area. Preferably, the conduits in the second layer open to the surface of the membrane.
The reason is that such membranes work at lower voltages than membranes with occluded channels. When the ion exchange membrane is used for the electrolysis of saline water, the membrane is positioned with the layer with carboxyl functionality towards the catholyte and the second layer preferably with sulfonic acid functionality towards the anolyte (saline solution). If the conduit is open, the reinforcing member serves to transport the brine to the blind area in the membrane near the layer with carboxyl functionality, or similarly if it is occluded, it It serves to transport the liquid penetrating into the surface area of the second layer up to the blind area. The ratio of temporary reinforcing yarns to reinforcing yarns in the textile fabric is 1:1.
, the conduit after removal of the temporary reinforcing thread extends from the window region to the blind region adjacent to half of the thread segment. Here is the "thread segment"
means the length of reinforcing yarn extending from the intersection of one yarn to the intersection of the adjacent yarn. If the ratio of temporary reinforcing yarns to reinforcing yarns is 2:1, the conduit after removal of the temporary reinforcing yarns runs from the window area to the blind area adjacent to all yarn segments. As the ratio of temporary reinforcing yarns to reinforcing yarns is further increased, the number of conduits to the blind areas that are subsequently created increases. Therefore, fabrics with a ratio of temporary reinforcing yarns to reinforcing yarns of at least 2:1 are preferred. For paper support materials, the paper portion remaining in the membrane after removal of the temporary reinforcing fibers has a basis weight of 2.5 to 112.5 g/m ² , preferably 45 g/m ² or less. The channels formed when the temporary reinforcing fibers of the paper support material are removed appear to be interconnected. Preferred membranes of the invention include as one surface layer -
A first layer of fluorinated polymer with only COOR functional groups, a second layer of fluorinated polymer with only _−SO2F functional groups as the other surface layer, and embedded in the second layer It consists of a web of support material. The first layer has a thickness in the range of about 25-75 microns and the second layer has a thickness in the range of about 75-150 microns. After hydrolysis to the ion-exchange form and removal of the temporary reinforcement of the support material, the resulting ion-exchange membrane is a suitable membrane for chlor-alkali baths. More preferably, this latter membrane conduit is an open conduit as described above. Although such membranes have two layers of fluorinated polymer, they may have three or more layers of polymer, such as a polymer layer with -COOR,
From a layer of polymer with -SO ₂ W, a web of support material and another layer of polymer with -SO ₂ W groups, the web of support material is as seen in some of the examples below. The above-mentioned sequence is processed in such a way that it is completely or at least almost completely embedded in a matrix with --SO ₂ W groups. In the claims, the thickness of the component layer is the nominal thickness,
That is, the thickness of the layers used before they are combined to make a membrane, whereas the total thickness of the membrane refers to its thickness after production of the membrane. The main application of the ion exchange membrane of the present invention is in electrochemical cells. Such a cell consists of an anode, an anode chamber, a cathode, a cathode chamber and a membrane located to separate the two chambers. One example is a chloralkali bath. In this case, the membrane should have functional groups in salt form; in such a bath, a layer of membrane with carboxyl functional groups would be placed towards the cathode chamber. Electrochemical baths, especially chlor-alkali baths, are usually
The space or spacing between the anode and cathode is narrow, i.e. about 3
It will be made no wider than mm. It is also often advantageous to operate the cell and carry out the electrolysis process with the membrane in contact with either the anode or the cathode; Open mesh or grid
This can be achieved by using a separator. Furthermore, zero-gap arrangement (zero-gap
It is often advantageous to have the membrane in contact with both the anode and the cathode. Such an arrangement offers the advantage of minimizing the resistance introduced by the anolyte and catholyte, thus allowing operation at low voltages. Even without such an arrangement, either or both electrodes may have a suitable catalytically active surface layer of the type known in the art for reducing overvoltages at the electrodes. The membranes described herein can be used as a substrate to carry an electrocatalyst composition on either or both surfaces, thereby forming a composite membrane/electrode. can do. Such electrocatalysts are of the type known in the art, such as U.S. Pat. No. 4,224,125 and U.S. Pat.
and published British patent application GB2009788A. Suitable cathode electrocatalysts include platinum black, Raney nickel, and ruthenium black. Suitable anode electrocatalysts include platinum black and ruthenium and iridium mixed oxides. The membranes described herein are also designed to enhance gas release properties, e.g. by providing optimal surface roughness or smoothness, or preferably with gas- and liquid-permeable porous structures thereon. By providing a non-electrode layer, either one surface or both surfaces can be modified. Such non-electrode layers can be in the form of thin hydrophilic coatings or spacers and are usually comprised of inert, electrically inactive or non-electrocatalytic materials. Such a non-electrode layer has a porosity of 10-99%, preferably 30-70%, and a porosity of 0.01-2000 microns, preferably 0.1-70%.
It should have an average pore size of 1000 microns and a thickness typically in the range 0.1-500 microns, preferably 1-300 microns. The non-electrode layer usually consists of an inorganic component and a binder; the inorganic component is of the type as described in published British patent application GB2064586A, preferably tin oxide, titanium oxide, zirconium oxide, or Fe ₂ O ₃ or Fe ₃ It can be an iron oxide like _O4 . Other information regarding non-electrode layers on ion exchange membranes can be found in published European patent application no. The binder component in the non-electrode layer and in the electrocatalyst composition is, for example, polytetrafluoroethylene,
At least the surface may be introduced with functional groups such as -COOH or -SO ₃ H by treatment with ionizing radiation in air or by modifiers (e.g. published UK patent application
GB2060703A) or fluorocarbon polymers made hydrophilic by treatment with reagents such as sodium in liquid ammonia,
They can be functionalized fluorocarbon polymers or copolymers with carboxylate or sulfonate functional groups, or polytetrafluoroethylene particles whose surface has been modified with fluorinated polymers with acid-type functional groups ( GB2064586A) Such binders are suitably used in an amount of 10 to 50% by weight of the non-electrode layer or electrocatalyst composition layer. Composite structures having a non-electrode layer and/or an electrocatalyst composition layer thereon can be made by a variety of methods known in the art, such as decals that are then pressed onto the membrane surface. preparation of
Application of a slurry (e.g. dispersion) in a liquid composition of the binder, followed by drying, screen or gravure printing of the pasty composition, hot pressing of the powder distributed on the membrane surface, and GB2064586A
Other methods are included, such as those described in . Such structures can be made by applying the layers described above in melt-processable form onto the membrane and in ion-exchange form by certain methods; When the combined components are in a melt processable form, they can be hydrolyzed into ion exchange form by known methods. The non-electrode layer and the electrocatalyst composition layer can be used on the membrane in a variety of combinations. For example, the surface of the membrane can be modified with a non-electrode layer, and an electrocatalytic composition layer can be placed on the latter. On top of the membrane it is also possible to provide a layer containing both an electrocatalyst and a conductive non-electrode material, such as a metal powder with a higher overvoltage than the electrocatalyst, combined in a single layer with a binder. A preferred type of membrane is one having a cathodic electrocatalyst composition on one surface and a non-electrode layer on its opposite back surface. Membranes having one or more electrocatalytic layers, or one or more non-electrode layers, or a combination thereof on their surface, are used in electrochemical cells with narrow gap or zero-gap configurations as described above. be able to. The copolymers used in the layers described herein have molecular weights high enough to produce at least moderately strong films, both in the melt-processable precursor form and in the hydrolyzed ion-exchange form. Should. The following examples are presented to further illustrate the innovative aspects of the invention. Each abbreviation in the examples is as follows. PTFE means polytetrafluoroethylene; TFE/EVE means a copolymer of tetrafluoroethylene and methyl perfluoro (4,7-dioxa-5-methyl-8-nonenoate); TFE/PSEPVE means tetrafluoroethylene EW means equivalent weight. EXAMPLES Example 1 A reinforced cation exchange membrane was produced by thermally bonding together the following layers under heat and pressure: A TFE/TFE with an equivalent weight (EW) of 1080
Cathode surface layer consisting of EVE's 25 micron (1 mil) film. B TFE/PSEPVE with equivalent weight of 1100
76 micron (3 mil) layer. C. Support fabric containing both reinforcing yarns and temporary reinforcing yarns. The reinforcing yarn was a 200 denier monofilament of torn PTFE film 19 microns (0.75 mils) thick and 508 microns (20 mils) wide, twisted at 3.5 twists per inch and flattened. 7.87 threads/cm (20
The yarn had a warp and weft count of 1000 yarns/inch). This yarn had an aspect ratio of 6.7.
Temporary reinforcing threads: 15.75 threads/cm (40 threads/inch)
The yarn was a 50 denier rayon yarn with a warp and weft count of . The total thickness of the cloth is 76 microns (3
Mill). Anode surface layer consisting of a 25 micron (1 mil) film of TFE/PSEPVE copolymer with an equivalent weight of D 1100. First, layers A and B were crimped together without heat, being careful to exclude air trapped between the layers. The four layers were then passed through a thermal laminator with layer D supported on a web of porous release paper. In the heating zone, vacuum is applied from the underside of the porous release paper and the TFE/
The air trapped between the two layers of PSEPVE was drawn through the thin molten bottom layer (D layer), thereby completely surrounding the reinforcing fabric. The temperature of the polymer leaving the heating zone is measured by an infrared measuring device.
The temperature of the heating zone was adjusted to be 230-235°C. After lamination, the composite membrane was incubated at 90°C in an aqueous bath containing 30% dimethyl sulfoxide and 11% KOH.
Hydrolyzed for 20 minutes. The film was then rinsed and mounted in a damp state in a small chloralkali bath with an active area of 45 cm ² between a dimensionally stable anode and a soft iron stretched metal cathode. tank
It was operated at 90°C with a current of 3.1KA/ ^m2 . The salt content at the anolyte outlet was maintained at 200g/. Adding water to the anolyte reduces the concentration of the produced caustic to 32±1%
I kept it. After 8 days, the cell was operating at 3.55 volts and 97% current efficiency. This ability remained unchanged after 36 days of operation. Example 2 “A” layer has an equivalent weight of 1080 TFE/
Apart from consisting of a 50 micron (2 mil) layer of EVE,
Example 1 was repeated. After 8 days of testing in a small chloralkali bath, the membrane
It was running at 3.65 volts and 97% current efficiency. This performance remained unchanged after 37 days of operation. Example 3 "B" layer has an equivalent weight of 1100 TFE/
Example 1 was repeated except with a 101 micron (4 mil) layer of PSEPVE. After 8 days of testing in a small chloralkali bath, the membrane
It was running at 3.65 volts and 97% current efficiency. This performance remained unchanged after 37 days of operation. Example 4 "A" layer has an equivalent weight of 1080 TFE/
TFE/
Example 1 was repeated except with a 101 micron (4 mil) layer of PSEPVE. This membrane was tested in a small chloralkali bath under the same conditions as Example 1, except that the bath temperature was 80°C. After 6 days of operation, the membrane was operating at 3.70 volts and a current efficiency of 95.2%. Comparative Example A This comparative example shows the effect on the electrolytic cell potential when using a reinforcing fabric containing monofilaments with a low aspect ratio and no temporary reinforcing threads. The membrane was fabricated by thermally bonding the following layers: A TFE with equivalent weight (EW) of 1080/
The cathode surface layer consists of a 25 micron (1 mil) layer of EVE. B TFE/PSEPVE with equivalent weight of 1100
101 micron (4 mil) layer. C. Fabric with only reinforcing yarns without temporary reinforcing yarns. The reinforcing thread is tetrafluoroethylene 96
% by weight and 4% by weight perfluoro(propylene vinyl ether) copolymer (U.S. Pat. No. 4,029,868)
No. 1, Comparative Example C), diameter 127 microns (5
It consisted of a 200 denier extruded monofilament with a circular cross section (mill).
It had an aspect ratio of 1. Cloth is warp count
13.8 threads/cm (34 threads/inch) and weft count
It was a leno weave with 6.7 threads/cm (17 threads/inch). The fabric was heat calendered to an overall thickness of 239 microns (9.4 mils). The yarn flattened slightly at the intersection point and the aspect ratio of the yarn increased from 1 to 1.13. Anode surface layer consisting of a 51 micron (2 mil) film of TFE/PSEPVE copolymer with an equivalent weight of D 1100. The above components were thermally bonded, hydrolyzed and their performance evaluated as in Example 1. After 9 days in a small chlor-alkali bath, the membrane showed 3.80 volts and a current efficiency of 95.2% (average of 3 bath tests).
It was operating in Attempts to make thinner membranes with the same reinforced woven fabric using less than 25 microns (1 mil) of either layer A, B, or D will result in: (1) attempts at high processing temperatures; or (2) in the case of attempts at low processing temperatures, films B and D are placed next to the threads of fabric C.
This was unsuccessful due to the formation of large voids in between. Both conditions made the membrane unsuitable for long-term use in chloralkali baths. Comparative Example B This comparative example shows the effect on cell voltage when using a reinforcing fabric comprising monofilaments with high aspect ratios and no temporary reinforcing threads. Layer C consists of a monofilament of 300 denier slit PTFE film with a thickness of 50.4 microns (2
It consists of yarns twisted to a width of 305 microns (mil) and a width of 12 microns, with a warp and weft count of 15.75/
cm (40 pieces/inch), except for the reinforcement cloth.
The structure was the same as Example B. The aspect ratio of the yarns in layer C was 6/1, and no temporary reinforcing yarns were included. After 6 days in a small chloralkali bath, the membrane
It was operating at 4.0 volts and a current efficiency of 94.5%. Example 5 This example illustrates the method of the present invention by using a reinforcing fabric consisting of a monofilament with a high aspect ratio and a temporary reinforcing yarn. The membrane layers were: A 51 micron (2 mil) layer of 1050EW TFE/EVE. B 1100EW 101 micron (4 mil) layer of TFE/PSEPVE. C. Fabrics containing both reinforcing and temporary reinforcing yarns. The reinforcing yarn has a fiber width of 305 microns (12 mils).
and 200 denier calendered or flattened to a thickness of 56 microns (2.2 mils).
It consisted of PTFE multifilament yarn. The aspect ratio was 5.5. Thread count in both warp and weft directions is 5.9 threads/cm
(15 pieces/inch). The temporary reinforcing yarn consisted of 50 denier rayon yarn with a warp and weft count of 23.6 threads/cm (60 threads/inch). The total thickness of the fabric was 112 microns (4.4 mils). Anode surface layer consisting of 25 microns (1 mil) of TFE/PSEPVE copolymer with an equivalent weight of D 1100. The structural components were thermally bonded, hydrolyzed, and evaluated in a small chloralkali bath as in Example 1, except that the bath temperature was 80°C. After 9 days of operation, the current efficiency was 96.7% and the potential was 3.68 volts. After 53 days, the value was 95.5% and 3.62 volts. Comparative Example C This comparative example shows the effect on cell voltage when using a reinforcing fabric having high aspect ratio multifilament yarns but without interwoven temporary reinforcing fibers. The composition of the laminate was the same as Example 5, except that the reinforcing fiber fabric was as follows: Layer C was a fabric containing only reinforcing yarns without temporary reinforcing yarns. . This is 200 denier
PTFE multifilament warp 20 pieces/cm (51 pieces/cm)
inch) and 400 denier weft threads 10.2/cm (26
It was a leno weave consisting of 1 inch/inch). The fabric was calendered so that the thread width was 508 microns (20 mils) and the thickness was 63.5 microns (2.5 mils) at the intersection of the threads. This had an aspect ratio of 8.0. The total thickness of the fabric was 127 microns (5.0 mils). The structural components were thermally bonded and hydrolyzed.
Approximately half of the area was leaked. This indicated that the thickness of the polymer layer was a limit. the temperature of the tank
Leak-free areas were evaluated in a small chloralkali bath as in Example 1, except at 80°C. After 7 days in the bath, the membrane has a current efficiency of 96.5% and
It operated on 3.99 volts. This was 310 millivolts higher than Example 5, which had temporary reinforcing threads. Example 6 This example illustrates the method of the present invention using a nonwoven reinforcing material containing a mixture of fluorocarbon polymer fibers and temporary reinforcing fibers. A TFE with equivalent weight (EW) of 1080/
Cathode surface layer consisting of a 51 micron (2 mil) layer of EVE copolymer. B TFE/PSEPVE with equivalent weight of 1100
152 micron (6 mil) layer. C The reinforcing material is 6 mm long and 6.7 denier.
Made of bleached kraft pulp with PTFE filament and 630ml Canadian standard freedom
It was a porous paper made from a 50/50 weight percent mixture. Its thickness was 119 microns (4.7 mils) and it weighed 33.8 g/m ² (1 oz/square yard). A laminate was prepared as in Example 1. In the heating zone, a vacuum was applied from the underside of the porous release paper to draw the molten TFE/PSEPVE down through the porous reinforcement paper, thereby completely surrounding the reinforcing fabric. The laminate did not leak even after hydrolysis. This membrane was evaluated in a small chloralkali bath as in Example 1, except that the temperature of the bath was 80°C. After 7 days of operation, the current efficiency is 96% and the voltage is 3.68 volts. Example 7 U.S. patent application filed February 14, 1980
Laminates were made using the same reinforcing materials as in the previous example, except that the laminator described in No. 121461 was used. The layers were: A 51 micron (2 mil) layer of 1080EW TFE/EVE. B 51 micron (2 mil) layer of TFE/PSEPVE in 1100EW. C 50/50 PTFE/Kraft as in Example 6. D. 51 micron (2 mil) layer of TFE/PSEPVE in 1100EW. The laminates were hydrolyzed and evaluated in a small chloralkali bath at a temperature of 80°C. Other conditions were the same as in Example 1. After 13 days of operation, the current efficiency was 96.5% and the voltage was 3.62 volts. Comparative Example D This comparative example uses TFE that does not contain temporary reinforcing fibers.
Figure 3 shows the effect on cell voltage when using non-woven reinforcing material from filaments only. The structural components were similar to Example 6 except that the PTFE paper did not contain temporary reinforcing fibers. The paper is 110 microns (4.3 mils) thick and 110 g/m ² (3.26
g/square yard). After hydrolysis, it was evaluated in a small chloralkali bath. After 7 days, this has a current efficiency of 93.1% and
It showed a potential of 4.16 volts. Industrial Applicability The ion exchange membrane of the present invention is technologically more advanced than conventional membranes. It exhibits improved performance characteristics when used as a membrane in chlor-alkali baths, including low voltage and high current efficiency, ie, operation with low power consumption. Thus, there is a substantial savings in operating costs associated with lower power consumption.

Claims (1)

[Claims] 1 -COOR and/or -SO ₂ W functional group [where R is lower alkyl and W is F or
at least two layers in which adjacent layers of fluorinated polymer having Cl] are in adhesive contact with each other;
and a web of support material embedded therein, wherein at least a first said layer having -COOR groups and a second said layer having -SO ₂ W functional groups are present; wherein the total thickness of the at least two layers of fluorinated polymer used in the production of is in the range of about 50 to 250 microns, and the web of support material has a thickness of about 25 to 125 microns. and impermeable to hydraulic flow of liquids, characterized in that it comprises both a reinforcing member and a temporary reinforcing member that is removable after production of the membrane without substantially adversely affecting the polymer constituting the membrane. A membrane that is. 2. The membrane of claim 1, wherein said layer comprises a perfluorinated polymer. 3 The -COOR functional group is -O-( _CF2 )m-
is part of a COOR residue, where m is 2 or 3, and the _-SO2W functional group is _-CF2-
The membrane according to claim 2, which is a part of _CF2 - _SO2W residues. 4. The web of support material is a woven fabric, the reinforcing member is a perhalocarbon polymer yarn having a denier of 50 to 600 and an aspect ratio in the range of 2 to 20; reinforcement member
40 to 100 denier, the woven fabric has a yarn count in the range of 1.6 to 16 perhalocarbon polymer yarns/cm in each of the warp and weft; 1 in each:
Claim 3 having a ratio of temporary reinforcing yarn to perhalocarbon polymer yarn in the range of 1 to 10:1.
Membrane described in section. 5. The membrane according to claim 4, wherein the perhalocarbon polymer thread is a perfluorocarbon polymer thread. 6. The woven fabric has a thickness of 50 to 100 microns, and the perfluorocarbon polymer yarn has a denyl of 200 to 400 and an aspect ratio in the range of 5 to 10. The membrane described. 7. The woven fabric has a yarn count in the range of 6 to 8 perfluorocarbon polymer yarns/cm in each of the warp and weft and a temporary reinforcement of 2:1 to 4:1 in each of the warp and weft. 7. The membrane of claim 6 having a ratio of threads to perfluorocarbon polymer threads. 8. The membrane of claim 7, wherein the perfluorocarbon polymer yarn is a monofilament of polytetrafluoroethylene. 9. The perfluorocarbon polymer thread has a substantially rectangular cross section, an aspect ratio within the range of 6 to 8, and a
9. The membrane of claim 8 having a thickness of 35 to 40 microns and having a ratio of temporary reinforcing yarns to perfluorocarbon polymer yarns of 4:1 in each of the warp and fill yarns. 10. The membrane of claim 7, wherein each membrane perfluorocarbon polymer yarn is multistrand. 11 -O-( _CF2 )m-COOR and/or _-CF2
There are two layers of a fluorinated polymer having _-CF2 - _SO2W , the first layer having a thickness in the range of 13 to 75 microns and the second layer having a thickness in the range of 50 to 125 microns. 8. A membrane according to claim 7, having a thickness within the range of 100 to 150 microns, and wherein the total thickness of said layer of fluorinated polymer is within the range of 75 to 150 microns. 12 m is 2 and the -SO ₂ W functional group is -
The membrane according to any one of claims 8 to 11, which is a part of O- _CF2 - _CF2 - _SO2W residues. 13. Claim 8, wherein said woven fabric is present at least primarily in said second layer of perfluorinated polymer.
The membrane according to any one of items 1 to 11. 14. The membrane according to any one of claims 8 to 11, wherein the temporary reinforcing thread is a rayon thread. 15 the web of support material is nonwoven paper;
The reinforcing member is perhalocarbon polymer fiber 10~
90% by weight and the temporary reinforcing member is 90-10% by weight temporary reinforcing fibers, and the paper has about 25-10% by weight temporary reinforcing fibers.
A membrane according to claim 3 having a basis weight of 125 g/cm ² . 16. The membrane of claim 15, wherein the perhalocarbon polymer fibers are perfluorocarbon polymer fibers. 17 The nonwoven paper has a thickness of 50 to 75 microns and a thickness of 25 to 75 microns.
A membrane according to claim 16 having a basis weight of 50 g/m ² . 18 The perfluorocarbon polymer fiber is 5-
18. A membrane according to claim 17, which is 10 denyl and has a length of 3 to 20 mm. 19. The membrane of claim 18, wherein the temporary reinforcing fibers are cellulosic kraft fibers having a freeness within the Canadian Standard range of 500 to 700 ml. 20. The membrane of claim 19, wherein said nonwoven paper comprises 25-75% by weight of said perfluorocarbon polymer fibers and 75-25% by weight of said kraft fibers. 21 -O-( _CF2 )m-COOR and/or _-CF2
There are two layers of fluorinated polymer with _-CF2 - _SO2W , the first layer having a thickness in the range of 13-75 microns and the second layer having a thickness in the range of 50-125 microns. 20. The membrane of claim 19 having a thickness in the range of microns, and wherein the total thickness of said layer of fluorinated polymer is in the range of 75 to 150 microns. 22 m is 2 and the -SO ₂ W functional group is -
22. The membrane according to claim 20 or 21, which is a part of O- _CF2 - _CF2 - _SO2W residues. 23. A membrane according to claim 20 or 21, wherein the nonwoven paper is at least predominantly present in the second layer of perfluorinated polymer. 24 -COOR and/or _-SO2W functional group [where R is lower alkyl and W is F or
at least two layers in which adjacent layers of fluorinated polymer having Cl] are in adhesive contact with each other;
A membrane consisting of a web of support material embedded therein and a gas- and liquid-permeable porous non-electrode layer on at least one surface, comprising:
At least a first said layer having a COOR group and a second said layer having an -SO ₂ W functional group are present, and all of said at least two layers of fluorinated polymer used in the production of said membrane are present. The thickness ranges from approximately 50 to 250 microns;
a temporary reinforcing member wherein the web of support material has a thickness of about 25 to 125 microns and is removable after production of the membrane without substantially adversely affecting the reinforcing member and the polymer comprising the membrane; A membrane impermeable to hydraulic flow of liquid, characterized in that it consists of both.