GB1572863A

GB1572863A - Phosphonated fluorotelomers

Info

Publication number: GB1572863A
Application number: GB854577A
Authority: GB
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1976-03-02
Filing date: 1977-03-01
Publication date: 1980-08-06
Also published as: BR7701283A; JPS61353B2; FR2343000B1; DK62277A; FR2343000A1; AU508300B2; IT1086214B; JPS52118431A; LU76864A1; DE2709097A1; AU2282177A; NL7702186A; CA1096093A

Description

(54) PHOSPHONATED FLUOROTELOMERS (71) We, E.I. DU PONT DE NEMOURS AND COMPANY, a Corporation organised and existing under the laws of the State of Delaware, United States of America, located at Wilmington, State of Delaware, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to phosphonated fluorotelomers and their uses.

In commercial chlor-alkali cells used for the production of chlorine, hydrogen and sodium hydroxide from brine, asbestos diaphragms are ordinarily used to separate the anolyte and catholyte compartments. Diaphragms of this sort are generally satisfactory, but their electrical resistance is high and cells which use such diaphragms therefore require more electric current for operation than is desirable. Furthermore, asbestos diaphragms treated with certain ion-exchange resins are described in U.S. Patent 3,853,721- Darlington and Foster (1974).

The phosphonated fluorotelomers of the invention are those represented by the formula

where Y1, Y2, Y3 and Y4 are the same or different and are alkyl radicals of 1-10 carbon atoms, alkyl radicals of 1-10 carbon atoms substituted with at least one alkyl radical of 1-4 carbon atoms, or monovalent metal cations; X is a homo- or cotelomeric moiety of at least one of (a) one or more monoethylenically unsaturated monomers fully substituted with fluorine atoms or with a combination of at least one fluorine atom and chlorine or bromine atoms, and (b) a perfluoroalkyl vinyl ether whose alkyl group contains 1-10 carbon atoms; Z1 and Z2 are the same of different and are divalent metal cations, alkylene radicals of 1-10 carbon atoms, or alkylene radicals of 1-10 carbon atoms substituted with at least one alkyl radical of 1-4 carbon atoms, or Z2 is made up of Yt and Y2; and n is 2-500.

As used in the definition of formulae (1) and (2), "cotelomeric moiety" means a telomeric moiety composed of two or more different types of monomer units, and "homotelomeric moiety" means a telomeric moiety composed of one type of monomer units.

The telomers of formula (1) can also be in the form of trivalent metal salts, which have a cross-linked structure in which one or two of the metal valences are taken by one fluorotelomer molecule and the remaining valences are taken by other fluorotelomer molecules. The monovalent, divalent and trivalent metal salts of the fluorotelomers can be formed in situ in a chloralkali cell where the fluorotelomer is used.

Those fluorotelomers of formulas (1) and (2) which are not hydrophilic or are only marginally hydrophilic can be made hydrophilic by converting them to the free acid forms or to metal salts. as will be described.

The phosphonated fluorotelomers preferred for use according to the invention because they are easy to prepare and because they have good ion-exchange characteristics and low solubility in cell liquors are those of formula (1) where X is a teleomeric moiety of tetrafluoroethylene (TFE); Y1, Y2, Y3 and Y4 are all ethyl or all butyl, or where Yl and Y2 are ethyl and Y3 and Y4 are butyl; and n is 20-100.

Also preferred for their low melting points and the ease with which diaphragms can be fabricated with them are fluorotelomers of formula (1) where X is a cotelomeric moiety of TFE and a perfluoropropyl vinyl ether in a weight ratio of 83/17, or a telomeric moiety of hexafluoropropylene; Y1, Y2, Y3 and Y4 are all ethyl; and n is 20-100.

Also preferred in some circumstances are fluorotelomers of formula (2) where Xis a cotelomeric moiety of TFE and hexafluoropropylene (HFP) in a weight ratio of 5/ 1; Zl is ethylene and Z2 is diethyl; and n is 20-100.

Parts, percentages and proportions herein are by weight except where indicated otherwise.

In actual use, the preferred telomers are converted to the corresponding sodium salts in an electrolytic cell.

In addition to the fluorotelomers themselves, the invention also comprises processes for their preparation in the ester, acid and salt forms, diaphragms and membranes made using them, and the use of such diaphragms and membranes.

Unlike ordinary fluorotelomers, the fluorotelomers of this invention are hydrophilic or can easily be made to be hydrophilic. "Hydrophilic" in this sense means the telomers absorb water rather than repel it. More specifically, "hydrophilic" means that the telomer has a water contact angle of O" to 50 , as measured by the method and apparatus described on page 137 of "Contact Angle, Wettability and Adhesion" American Chemical Society, 1964.

The claimed hydrophilic fluorotelomers, when blended with inert fibrous materials and binders and fabricated into diaphragms, or when formed into a membrane preferably supported by an inert fabric, can be used in ion-exchange procedures, especially where hydrophilicity is desirable or essential. Such diaphragms used in chloroalkali cells, surprisingly have far less electrical resistance than conventional asbestos diaphragms. As a result, cells using diaphragms containing the hydrophilic fluorotelomers of the invention can maintain chlorine, hydrogen and caustic production at the same levels obtained when asbestos diaphragms are used even though the cells operate at lower voltages. In addition, diaphragms made with these fluorotelomers in general are more resistant to attack by electrolytic cell liquors, last longer and are more dimensionally stable than prior art asbestos diaphragms.

The invention therefore also includes a process for the electrolytic production of chlorine from brine comprising keeping the chlorine produced at the anode separated from the hydrogen and sodium hydroxide produced at the cathode with a diaphragm as described above.

How the Phosphated Fluorotelomers are Made The phosphonated fluorotelomers of the invention can be made by reacting a suitable monoethylenically unsaturated fluoromonomer selected from (a) or (b) with a compound capable of generating a phosphorous-containing free radical of the structure

where Yl and Y2 are the same or different and preferably are alkyl radicals of 1-10 carbon atoms or alkyl radicals of 1-10 carbon atoms substituted with at least one alkyl radical of 1-4 carbon atoms.

Illustrative of the fluoromonomers which can be used are tetrafluoroethylene (TFE) monochlorotrifluoroethylene dichlorodifluoroethylene monobromotrifluoroethylene dibromodifluoroethylene hexafluoropropylene (HFP) perfluoroalkyl vinyl ethers (whose alkyl groups contain 1-10 carbon atoms) These fluoromonomers can be used singly to produce homotelomeric forms, or can be used in combinations of two or more to form cotelomeric forms of the phosphonated fluorotelomers.

Illustrative of the compounds capable of generating the requisite phosphorous-containing free radical are tetraalkyl hypophosphates (whose alkyl groups contain 1-10 carbon atoms) tetraalkyl pyrophosphites (whose alkyl groups contain 1-10 carbon atoms) cycloalkyl hypophosphates (whose alkyl groups contain 1-10 carbon atoms) cycloalkyl pyrophosphites (whose alkyl groups contain 1-10 carbon atoms) and compounds of the formula

where Y1, Y2, Y3 and Y4 are defined as in formula (1). Mixtures of such compounds can also be used.

The reaction of the fluoromonomer and free radical generating compound proceeds according to the following illustrative equations:

OR OR O I I Ii (4) 2RO-P-O-P-OR initiator > 2R0-P OR tetraalkyl free radical pyrophosphite O 0 0 II II 2RO-P- + fluoromonomer--) RO-PX P-OR OR OR OR free radical telomer O O 0 II n II (5) 2RO-P- P-OR initiator > 2R0-P.

I I 2 OR OR OR tetraalkyl free radical hypophosphate O 0 0 II II 2RO-P + fluoromonomer 5 RO-PX (X)n P OR OR OR OR free radical telomer The same reactions can be used to prepare the telomers of formula (2), using cycloalkyl hypophosphates or cycloalkyl pyrophosphites as free radical generating compounds.

The reactions described in equations 04) and (5) are carried out by first dissolving enough of the hypophosphate or pyrophosphite reactant in a halogenated hydrocarbon solvent to make a 1-50% by weight solution. To this solution is then added 0.1%-10 by by weight, of a free radical initiator like di-t.butyl peroxide or azobisisobutyronitrile.

The solution is then placed in a pressure vessel and the fluoromonomer gas or liquid is added. The amount of fluoromonomer added will depend on the telomer chain length desired [i.e. the value of n in formulas (1) and (2)] and ordinarily is in the range of 2-500 moles for each two moles of pyrophosphite or hypophosphate.

The vessel is then sealed, heated to 50-3000C, preferably 60-120"C and held there, with rocking, until the pressure in the vessel drops, which indicates completion of the reaction. The vessel is then opened, the dispersion of phosphonated fluorotelomer removed and the solvent stripped from the dispersion by evaporation. The resulting product is washed in methanol, dried and is then ready for use.

The fluorotelomer thus isolated can vary in physical state from a viscous liquid to a waxy solid.

The mixed telomers of the invention, i.e., those in which Yl and Y2 are different from Y3 and Y4, can be prepared according to the following illustrative equations:

o o (6) CHJ P 30--P II Ii CR3 (CR2) 30-P-p OCH2CR3 initiator\ CH3 (CR2)3-O OCH2CH3 mixed tetraalkyl hypophosphate

o 0 0 II Ii CH3 (CH2 ) + CH3CH20-P .

CR3 (CR2) 3O CH3CR2-O free radical free radical

0 0 II II CH3(CH2)3-O-P. + CR3CR2O-P. + fluoromonomer CE3(CH2)3 CH3CR2-O 0 0 II II CH3 (CH2)3- - O - IP Pr t IP - O - CH2CH3 CH3(CH2)3 o 0-CH2CH3 telomer The reaction described in equation (6) is carried out in the same way as those of equations (4) and (5).

In the formation of the free radicals, some different terminal groups, such as carboxyl groups, may be introduced. However, this would not affect the ability of the described fluorotelomers which are still present to provide the advantages of the invention.

The mixed tetraalkyl hypophosphate reactant used in equation (6) can be prepared as described in Bull, Acad. Polon. Sci., Ser. Sci, Chim., 13, 253 (1965) and in Z. Anorg. Allg, Che., 288, 171(1956).

The metal salts of the phosphonated flurotelomers can be prepared by hydrolyzing a telomer to the free acid form, then replacing the hydrogens of the carboxyl groups with metals by metathesis.

Monovalent, divalent or trivalent metals can be used to form a fluorotelomer salt. Illustrative of such metals are sodium manganese potassium iron lithium cobalt calcium copper barium zinc magnesium cadmium aluminium Ordinarily, the fluorotelomers are used in the ester form to make diaphragms for chloralkali cells. The ester form is converted to the sodium salt form when the diaphragm comes into contact with sodium hydroxide in the cell liquor. The ester form is also readily converted to the acid form by hydrolysis such as with suitable acids.

How Diaphragms of the Telomers are Made For whatever use, a diaphragm using a phosphonated fluorotelomer of the invention can be prepared from a composition which comprises a) one or more fluorotelomers of formula (1); b) a fibrous material which will act as a base for the diaphragm; c) a fluoropolymer binder material; and d) a liquid carrier.

This composition can also contain conventional adjuncts such as wetting agents, surfac- tants, and defoamers in the usual amounts.

A diaphragm can be made from such a composition by first deagglomerating the fibers of (b) and then forming a mat of the fibers by removing the carrier, preferably by a papermaking technique. The mat is then heated to the binder fusion temperature, to give a coherent structure which can be used directly for whatever purpose intended.

The diaphragm mat can be formed directly on the cathode screen of the electrolytic cell in which it is to be used and then heated to fuse the binder. The diaphragm thus made can be used directly, without further treatment. Diaphragms made in this way must meet manufacturer's specifications regarding permeability, current efficiency and dimensional stability.

These specifications vary with the manufacturer, the type of cell being used, electrical current demands of the cell, and like factors. One skilled in the diaphragm making art will use the same skills in preparing diaphragms from the compositions of this invention that he does in preparing conventional asbestos diaphragms.

Any fibrous material can be used which can withstand the baking temperature to be used and which resists attack by the environment in which the membrane is to be used. Illustrative of such materials are asbestos glass fibers fibers of such fluoropolymers as polytetrafluoroethylene (PTFE) or TFE/HFP copolymers potassium titanate fibers.

Mixtures of such fibrous materials can also be used. Asbestos is the preferred fibrous material for use in electrolytic cell diaphragms. Especially preferred is a chrysotile asbestos whose fibers have an average diameter of about 200A (as measured by electron microscopy) and an average length of about 70 mm. Preferably, the asbestos fibers are completely or substantially completely coated with fluorotelomers of the invention.

Similarly, the fluoropolymer to be used as a binder material can be any which resists attack by the environment in which it is to be used. Illustrative are PTFE TFE/HFP copolymers (all monomer ratios).

polyvinyl fluoride polyvinylidene fluoride vinylidene fluoride/HFP copolymers (all monomer ratios).

Mixtures of binder materials can also be used.

In electrolytic cell diaphragms, the TFE/HFP copolymers are preferred as binder materials because of their inert nature.

The carrier can be any liquid which will not significantly affect the chemical or physical characteristics of the diaphragm. Illustrative of such liquids are water chlorinated hydrocarbons methanol hexane brine.

When the composition is to be used to make an electrolytic cell diaphragm, brine solution of 15% NaCl in water is preferred as a carrier because it helps keep the fibrous material in suspension.

The components of the composition are preferably present in the following concentrations: (a) Telomer- 10-90%by weight of the total of (a) and (b), even more preferably 40-60%; (b) Binder - 10-90% by weight of the total of (a) and (b), even more preferably 40-60%; (a) plus (b) constituting 10-90 o, preferably 20-25 O/o, byweight of the total of (a), (b), and (c); (c) Fibrous material - 10-90% by weight of the total of (a), (b), (c), preferably 70-80%; (d) Carrier - the remainder.

The composition will usually contain 0.01-3%, by weight, of solids, preferably about 1%.

In a variant of this composition, an appropriate amount of the telomer and binder can be mixed together, and the fibrous material and carrier can be added to this mixture just before the resulting composition is to be used to prepare a diaphram.

In such a composition, the telomer and binder each each present in concentrations of 1-99 o, preferably 10-90%, by weight of the total of telomer and binder.

Although it is expected that the phosphonated fluorotelomers of the invention will be used primarily to fabricate diaphragms for electrolytic cells, especially chlor-alkali cells, they can also be used to prepare membranes for use as the separating means for separating diverse substances, either electrolytically or nonelectrolytically. For instance, they may be used in ion-exchange procedures such as the desalination of sea water, and to prepare semipermeable membranes for use in osmotic procedures and in dialysis, including Donnan dialysis. The telomers can also be used to prepare battery separators, especially for use in alkaline cells.

Fluorotelomers of formulas (1) and (2) where n is 2-20 can also be used to passivate metals.

Membranes differ from diaphragms in that membranes are substantially hydrolytically impermeable, selectively passing either cations or anions, depending on the perm-selectivity of the membrane. Semipermeable membranes also have minute porosity permitting the passage of liquids but inhibiting the passage of relatively large species such as some colloids.

Diaphragms do pass substantial amounts of fluid while inhibiting the passage of anions or cations.

Membranes may be formed and used according to techniques known in the art. Phosphonated fluorotelomers of the invention may be formed into membranes, preferably about 0.1-0.25 mm thick in contrast to typical diaphragm thicknesses of 2.5 mm. Such thin membranes would normally be formed on a fabric, preferably of open mesh design, of material which is inert to the operating environment. Fluorocarbon polymers such as PTFE are suitable to support phosphonated fluorotelomers of the invention to be used in chloralkali cells.

The following examples illustrate the invention. In each example, the diaphragms prepared were used with a cathode-to-anode spacing of 0.635 cm (i in). Typical asbestos diaphragm cells of the prior art require 3.5-3.7 volts to obtain a current density of 0.204 amperes per square centimeter with that spacing. Although the diaphragms of the examples are formed as sheets and then placed into electrolytic cells, similar results are obtained when the diaphragms are formed on a cathode screen in the cell.

EXAMPLE ONE (A) A pressure vessel was charged with (1) trichlorotrifluoroethane 160 parts (2) a solution of 6.45 parts of tetraethyl pyrophosphite in 20 parts of trichloro trifluoroethane (3) a solution of 2 parts of ditertiary butyl peroxide in 20 parts of trichloro trifluoroethane (4) tetrafluoroethylene 50 parts The charge was blanketed with nitrogen, the vessel sealed and the temperature of the charge raised to 1000C and held there for two hours. The temperature of the charge was then raised to 1200C, held there for two hours, then raised still again to 1400C and held at that temperature for two hours. At that point, a drop in pressure inside the vessel indicated completion of the reaction.

The vessel was opened, the contents removed and placed in a still, where the solvent was distilled off at 40-50 C.

The resulting waxy solid was washed twice with methanol and then dried under vacuum.

(B) The following were prepared: (1) a solution of 363 parts of sodium chloride in 2420 parts of distilled water.

(25 a mixture of (a) 5.5 parts of a TFE/HFP 85/15 copolymer dispersion, 55% solids in water, and (b) 3.03 parts of the product of (A) in 30 parts of isopropanol.

Solution (1) was placed in a blender, to which was then added 24.2 parts of asbestos fibers (average diameter 200An, average length 70 mm, sold by Johns-Manville Co. as Chlorbestos SP-25). Mixture (2) was then added. The charge was blended at medium speed for 2 minutes and then sparged with air for two hours to deagglomerate the asbestos fibers.

This mixture was then diluted with an equal volume of distilled water and poured into a sheet mold, where the liquid was drawn off under a vacuum of 250 mm. The resulting mat was washed by drawing 2000 parts of distilled water through it and was then dried at 950C for one hour and then baked at 275"C for 30 minutes, to give a product 2.5 mm thick.

The mat was then boilded in 5% aqueous sodium hydroxide for 2.75 hours and dried.

(C) The mat prepared in (B) was put in the diaphragm position on the cathode of a chlor-alkali cell, where, in operation, it required an average voltage of 3.7 to achieve a current density of 0.204 amperes per square centimeter of diaphragm area.

EXAMPLE TWO (A) A fluorotelomer was prepared as described in Example 1 (A) using the following charge (1) a solution of 16.5 parts of dibutyl-diethyl hypophosphate in 200 parts of trichloro trifluoroethane (2) azobisisobutyronitrile 4.1 parts (3) tetrafluoroethylene 50 parts and holding the reaction temperature at 650C for three hours followed by 90"C for three hours.

(B) Asbestos fibers of the type used in Example 1 (B), 3.7 parts, and 370 parts of distilled water were placed in a blender. To this was then added a mixture of dispersion of (A) 6.95 parts methanol 40 parts dispersion of a TFE/HFP 85/15 copolymer in water (55% solids) 1.11 parts distilled water 20 parts the charge was blended at low speed for 10 minutes and the resulting slurry was then diluted with 1558 parts of distilled water. The liquid was drawn from this slurry in a Buechner funnel under a vacuum of 250 mm.

The resulting mat was dried under light pressure at 250C for 5 minutes, then at 950C for 30 minutes, and finally baked at 275"C for 30 minutes, to give a product 2.5 mm thick.

The mat was then boiled for 90 minutes in 5% aqueous sodium hydroxide.

(C) The mat prepared in (B) was put in the diaphragm position on the cathode of a chxor-alkali cell, where, in operation, it required an average voltage of 3.26 to achieve a current density of 0.204 amperes per square centimeter of diaphragm area.

Example 2 can be repeated except that the tetrafluoroethylene used in (A) is replaced with an equal amount of a 50/16 mixture of tetrafluoroethylene and bromotrifluoroethylene.

Results will be substantially the same.

EXAMPLE THREE (A) A fluorotelomer was prepared as described in Example 1 (A) using the following charge (1) a solution of 12 parts of tetraethyl pyrophosphite in 120 parts of trichlorotrif- luoroethane (2) a solution of 3.65 parts of di-t. butyl peroxide in 40 parts of trichlorotrifluoroethane (3) a mixture of 50 parts of tetrafluoro ethylene and 10 parts of perfluoropropyl vinyl ether and holding the reaction temperature at 1000C for two hours, at 1200C for another two hours, and then at 140"C for two hours.

(B) A slurry of Distilled water 2420 parts Sodium chloride 263 parts Asbestos (same type as in Example 1) 24.2 parts was sparged with air for two hours. To the slurry was added a dispersion of (1) Dispersion of the telomer of (A), 3.03 parts in 14.91 parts of methanol (2) TFE/HFP 85/15 copolymer powder 3.03 parts The slurry was sparged with air for 30 minutes and then blended in a blender for one minute at medium speed.

A mat was prepared from the slurry by drawing off the liquid in a sheet mold under a vacuum of 250 mm of mercyry. The mat was washed by drawing 2000 parts of distilled water through it, was pressed between sheets of absorbent paper and then held at 1350C for five minutes, still between the sheets of paper.

The resulting dry mat, 1.5 mm thick, was then baked for 30 minutes at 275 C.

(C) The mat prepared in (B) was put in the diaphragm position on the cathode of a chlor-alkali cell, where, in operation, it required an average voltage of 2.96 to achieve a current density of 0.129 amperes per square centimeter.

Example three can be repeated except that the fluoromonomer charge in (A) is replaced with an equimolar amount of an 80/20 mixture of tetrafluoroethylene and hexafluorop ropylene. Results will be substantially the same.

EXAMPLE FOUR (A) A fluorotelomer was prepared as described in Example 1 (A) using the following charge (1) a solution of 12 parts of tetraethyl pyrophosphite in 120 parts of trichlorotrif luoroethane 2 a solution of 3.65 parts oft. butyl perpivalate in 40 parts of trichlorotrifluoroethane 3 a mixture of 50 parts of TFE and 15 parts of HFP and holding the reaction temperature at 600C for 2 hours and then at 800C for 2 hours.

(B) A slurry of Distilled Water 2420 parts Sodium chloride 263 parts Asbestos (same type as in Example 1) 24.2 parts was sparged with air for two hours. To the slurry was added a dispersion of (1) a dispersion of the telomer of (A), 4.54 parts in 50 parts of methanol (2) TFE/HFP 18/15 copolymer powder 1.90 parts The slurry was sparged with air for two hours and then blended for one minute in a blender at medium speed.

A mat was prepared from the slurry as in Example 3(B).

(C) The mat prepared in (B) was put in the diaphragm position on the cathode of a chloralkali cell, where, in operation, the average voltages indicated below were required to achieve the current densities indicated.

Volts Amperes/cm2 2.86 0.129 3.04 0.182 3.10 0.204 Such results are also obtained when the diaphragm is formed by similar techniques directly on the cathode.

WHAT WE CLAIM IS: 1. A fluorotelomer represented by the structure

where Y1, Y2, Y3 and Y4 are the same of different and are alkyl radicals of 1-10 carbon atoms, alkyl radicals of 1-10 carbon atoms substituted with at least one alkyl radical of 1-4 carbon atoms, or monovalent metal cations; X is a homo-or cotelomeric moiety of at least one of (a) one or more monoethylenically unsaturated monomers fully substituted with fluorine atoms or with a combination of at least one fluorine atom and chlorine or bromine atoms, and (b) a perfluoroalkyl vinyl ether whose alkyl group contains 1-10 carbon atoms; Z1 and Z2 are the same or different and are divalent metal cations, alkylene radicals of 1-10 carbon atoms, or alkylene radicals of 1-10 carbon atoms substituted with at least one alkyl radical of 1-4 carbon atoms, or Z2 is made up of Y1 and Y2; n is 2-500; and salts of such fluorotelomers with one or more trivalent metals.

2. The fluorotelomer of Claim 1 wherein X is a telomeric moiety of tetrafluoroethylene.

3. The fluorotelomer of Claim 1 wherein X is a cotelomeric moiety of tetrafluoroethylene and perfluoropropyl vinyl ether.

4. The fluorotelomer of Claim 1, 2 or 3 wherein Y1, Y2, Y3 and Y4 are ethyl.

5. The fluorotelomer of Claim 1, 2 or 3 wherein Y1, Y2, Y3 and Y4 are butyl.

6. The fluorotelomer of Claim 1, 2 or 3, wherein Y1 and Y2 are ethyl and Y3 and Y4 are butyl.

7. The fluorotelomer of Claim 1, 2 or 3 wherein Y1, Y2, Y3 and Y4 are sodium.

8. The fluorotelomer of any one of Claims 1 to 7 wherein n is 20-100.

9. A salt of the fluorotelomer of formula (1), of Claim 1 in accordance with any one of Claims 1 to 8 with a trivalent metal.

10. A composition suitable for preparing a diaphragm for an electrolytic cell containing a cell liquor. comprising (a) 10-90%, by weight of the total of (a) and (b), of at least one telomer according to any one of the preceding claims; (b) 10-90%, by weight of the total of (a) and (b), of a fluoropolymer binder; (a) plus (b) constituting 10-90% by weight of the total of (a), (b) and (c), (c) 10-90 O/o, by weight of the total of (a), (b) and (c) of a fibrous material resistant to attack by the cell liquor; and

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. (1) a dispersion of the telomer of (A), 4.54 parts in 50 parts of methanol (2) TFE/HFP 18/15 copolymer powder 1.90 parts The slurry was sparged with air for two hours and then blended for one minute in a blender at medium speed. A mat was prepared from the slurry as in Example 3(B). (C) The mat prepared in (B) was put in the diaphragm position on the cathode of a chloralkali cell, where, in operation, the average voltages indicated below were required to achieve the current densities indicated. Volts Amperes/cm2 2.86 0.129 3.04 0.182 3.10 0.204 Such results are also obtained when the diaphragm is formed by similar techniques directly on the cathode. WHAT WE CLAIM IS:

1. A fluorotelomer represented by the structure

4. The fluorotelomer of Claim 1, 2 or 3 wherein Y1, Y2, Y3 and Y4 are ethyl.

5. The fluorotelomer of Claim 1, 2 or 3 wherein Y1, Y2, Y3 and Y4 are butyl.

7. The fluorotelomer of Claim 1, 2 or 3 wherein Y1, Y2, Y3 and Y4 are sodium.

8. The fluorotelomer of any one of Claims 1 to 7 wherein n is 20-100.

(d) a liquid carrier.

11. The composition of Claim 10 wherein the fibrous material in (c) is asbestos.

12. The composition of Claim 10 or 11 wherein the carrier in (d) is brine.

13. The composition of Claim 10, 11 or 12, wherein the binder in (b) is a tetrafluoroethylene/hexafluoropropylene copolymer.

14. A composition consisting essentially of (a) 1 99 %, by weight of the total of (a) and (b), of a fluorotelomer according to any one of Claims 1 to 9; and (b) 1%-99%, by weight of the total of (a) and (b), of a fluoropolymer.

15. An electrolytic cell diaphragm prepared from the composition of Claim 10, 11, or 12 by forming a mat from the composition by removing the carrier, heating the mat to a temperature at which the fluoropolymer fuses, and then bringing the resulting product into contact with an aqueous solution of sodium hydroxide.

16. The electrolytic cell diaphragm of Claim 15 prepared directly on the cathode of the cell.

17. A process for preparing the fluorotelomer of Claim 1, comprising bringing into contact under conditions suitable for reaction in the presence of a free radical initator at least one of (a) one or more monoethylenically unsaturated monomers fully substituted with fluorine atoms or with a combination of at least one fluorine atom and chlorine or bromine atoms, and (b) a perfluoroalkyl vinyl ether whose alkyl group contains 1-10 carbon atoms, with a compound capable of generating a free radical of the structure

where Y1 and Y2 are the same or different and are alkyl radicals of 1-10 carbon atoms or alkyl radicals of 1-10 carbon atoms substituted with at least one alkyl radical of 1-4 carbon atoms.

18. A process according to Claim 17 wherein the fluorotelomer is subsequently hydrolyzed to convert Y1 and Y2 to hydrogens by contact with acids.

19. A process according to Claim 17 wherein the fluorotelomer is subsequently converted to the salt form wherein Y1 and Y2 are metals by contact with a salt of the selected metals.

20. A process for the electrolytic production of chlorine from brine, comprising keeping the chlorine produced at the anode separated from the hydrogen and sodium hydroxide produced at the cathode with a diaphragm of Claim 15 or 16.

21. An electrolytic cell having a diaphragm of Claim 15 or 16.

22. An electrolytic cell membrane comprising a phosphonated fluorotelomer of any one of Claims 1 to 9 supported by a fabric of polyfluorocarbon.

23. A process for separating diverse substances from each other by dialysis, osmosis or ion-exchange, comprising using as the separating means a membrane prepared from the composition of Claim 10, 11 or 12 by forming a mat from the composition by removing the carrier and then heating the mat to the fluoropolymer binder fusion temperature.

24. A modification of the process claimed in Claim 17 wherein Y1 and Y2 are linked together to form an alkylene radical of 1 to 10 carbon atoms or an alkylene radical of 1 to 10 carbon atoms substituted with at least one alkyl radical of 1 to 4 carbon atoms.

25. A fluorotelomer according to Claim 1 substantially as described herein.

26. A fluorotelomer substantially as described herein with reference to any one of Examples 1 to 4.

27. A composition according to Claim 10 substantially as described herein.

28. A composition for preparing a diaphragm for an electrolytic cell substantially as described herein with reference to any one of Examples 1 to 4.

29. An electrolytic cell diaphragm substantially as described herein with reference to any one of Examples 1 to 4.

30. A process for preparing a fluorotelomer according to Claim 17 substantially as described herein.

31. A process for preparing a fluorotelomer substantially as described herein with reference to any one of Examples 1 to 4.

32. A fluorotelomer when prepared by the process of any one of Claims 17, 18, 19,24,30 or 31.

33. A process for the electrolytic production of chlorine from brine according to Claim 20 substantially as described herein.

34. An electrolytic cell or an electrolytic cell membrane according to Claim 21 or 22 substantially as described herein.

35. A process for separating diverse substances according to Claim 23 substantially as described herein.