GB1604176A

GB1604176A - Perfluorovinyl compounds and copolymers thereof

Info

Publication number: GB1604176A
Application number: GB41259/80A
Authority: GB
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1977-04-20
Filing date: 1978-04-19
Publication date: 1981-12-02
Also published as: BR7802434A; BE866122A; IT1094088B; IL54539A; IL54539A0; FR2485024A1; ZA782224B; GB1604173A; NL7804220A; FR2388013B1; GB1604174A; GB1604175A; AU3516878A; SU784786A3; FR2388013A1; FR2485024B1; AU525395B2; JPS53132094A; NZ187022A; IT7822495A0

Abstract

Fluorinated ion exchange polymers which have both pendant side chains containing carboxylic groups and pendant side chains which contain sulfonyl groups, when used in the form of membranes to separate the anode and cathode compartments of an electrolysis cell, permit operation at high current efficiency. They are made by oxidation of flourinated polymers which have pendant side chains containing sulfinic groups, or both sufinic and sulfonyl groups. The fluorinated polymers which have pendant side chains containing sulfinic groups, or both sufinic and sulfonyl groups, are in turn made from fluorinated polymers which have pendant side chains containing sulfonyl halide groups by reduction with, for example, hydrazine. Fluorinated ion exchange polymers which have pendant side chains containing -OCF2COOR groups and also pendant side chains which contain sulfonyl groups can also be made by copolymerization of a mixture of monomers, one of which is a vinyl monomer which contains the indicated carboxylic group; and also by treatment of a polymer which contains -OCF2CF2SO3H or salts thereof with a combination of fluorine and oxygen.

Description

PATENT SPECIFICATION ( 11) 1 604 176

\Z ( 21) Application No41259/80 ( 22) Filed 19 Apr1978 ( 19) .% ( 62) Divided Out of No 1604173 ( 31) Convention Application No 789726 ( 32) Filed 20 Apr 1977 in ( 33) United States of America (US) ( 44) Complete Specification Published 2 Dec 1981 - ( 51) INT CL 3 C 07 C 69/708 143/70 ii C 08 F 214/18 C 25 B 13/08 ( 52) Index at Accpetance C 2 C 200 20 Y 21 X 231 240 304 311 313 318 31 Y 339 364 366 368 36 Y 39 Y 409 440 491 628 634 AA CW QC C 3 P DF C 3 Y B 262 B 284 B 360 B 362 F 102 G 320 C 7 B145 551 552 553 CB ( 54) PERFLUOROVINYL COMPOUNDS AND COPOLYMERS THEREOF ( 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: 5

The present invention relates to perfluorovinyl compounds.

The compounds of the invention are of the formula:CF 2 =CFO CF 2-CF -Om CF 2 COOR 1 10 F 3 wherein m is 0, 1 or 2, and R' is lower alkyl, generally C,-C 5, or M(v), where M is H, alkali 15 metal or alkaline earth metal, and N is the valence of M.

The most preferred compounds are those wherein R' is lower alkyl, generally C 1-C 5, or M where M is H, because of their ease of polymerization Those compounds wherein m is 1 are also preferred because their preparation and isolation in good yield is more easily accomplished than when m is 0 or 2 20 The compounds of the invention can be used to provide polymers which possess pendant side chains which contain carboxylic groups and pendant side chains which contain sulfonyl groups by copolymerizing a mixture of the appropriate monomers, one monomer of which mixture is a carboxyl-containing compound of the invention The novel compounds 25 CF 2 =CFOCF 2 CFOCF 2 COOCH 3 CF 3 30 and the corresponding free carboxylic acid are especially useful monomers.

Monomers of the invention can be prepared for example, from compounds having the formula 35 CF 2 =CF(OCF 2 CF +"m OCF 2 CF 25 02 F CF 3 2 1 604 176 2 by ( 1) saturating the terminal vinyl group with chlorine to protect it in subsequent steps by converting it to a CF 2 C 1-CF Cl group; ( 2) oxidation with nitrogen dioxide to convert the -OCF 2 CF 2 SO 2 F group to an OCF 2 COF group; ( 3) esterification with an alcohol such as methanol to form an -OCF 2 COOCH 3 group; and ( 4) dechlorination with zinc dust to regenerate the terminal CF 2 =CF group It is also possible to replace steps ( 2) and ( 3) of 5 this sequence by the steps (a) reduction of the -OCF 2 CF 2 SO 2 F group to a sulfinic acid -OCF 2 CF 2 SO 2 H or alkali metal or alkaline earth metal salt thereof by treatment with a sulfite salt or hydrazine; (b) oxidation of the sulfinic acid or salt thereof with oxygen or chromic acid, whereby -OCF 2 COOH groups or metal salts thereof are formed as described and claimed in Application No 80-41257 Serial No 1604174 and (c) esterification to 10 -OCF 2 COOCH 3 by known methods.

The carboxyl-containing compounds of this invention can be copolymerized with fluorinated vinyl compounds from each of first and second groups of comonomers as described below, and under non-aqueous polymerization techniques also described below.

The first group is of fluorinated vinyl monomers of the formula CX 2 =CX 2, wherein each 15 X, which may be the same or different, is H, Cl, F, CF 3 or perfluoroalkoxy subject to the proviso that at least one X is F such as vinyl fluoride, hexafluoropropylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, perfluro (alkyl vinyl ether), tetrafluoroethylene and mixtures thereof In the case of copolymers which will be used in electrolysis of brine, the precursor vinyl monomer desirably will not contain hydrogen, and 20 preferably the X's taken together are four fluorines or three fluorines and one chlorine.

The second group is of the sulfonyl-containing monomers containing the precursor group -CF-CF 2-SO 2 A, 25 I Rf wherein Rf is F, Cl or Cl-C 10 perfluoroalkyl and A is F or Cl, preferably F Additional 30 examples can be represented by the general formula CF 2 =CF-Tk-CF 2 SO 2 F wherein T is a bifunctional perfluorinated radical comprising 1 to 8 carbon atoms, and k is 0 or 1.

The particular chemical content or structure of the radical T is not critical, but it must have a fluorine atom attached to the carbon atom to which the -CF 2 SO 2 F group is attached Other atoms connected to this carbon can include fluorine, chlorine, or hydro 35 gen although generally hydrogen will be excluded in use of the copolymer for ion exchange in a chlor-alkali cell The T radical of the formula above can be either branched or unbranched, i e, straight-chain, and can have one or more ether linkages It is preferred that the vinyl radical in this group of sulfonyl fluoride containing comonomers be joined to the T group through an ether linkage, i e, that the comonomer be of the formula 40 CF 2 =CF-O-T-CF 2-SO 2 F Illustrative of such sulfonyl fluoride containing comonomers are CF 2 =CFOCF 2 CF 25 O 2 F, CF 2 =CFOCF 2 CFOCF 2 CF 2 SO 2 F 45 CF 3 CF 2 =CFOCF 2 CFOCF 2 CFOCF 2 CF 2 SO 2 F, 50 I i CF 3 CF 3 CF 2 =CFCF 2 CF 2 SO 2 F, and 55 CF 2 =CFOCF 2 C 1 FOCF 2 CF 25 O 2 F CF 2 60 C CF 3.

1 604 176 The most preferred sulfonyl fluoride containing comonomer is perfluoro ( 3,6-dioxa-4methyl-7-octenesulfonyl fluoride), CF 2 =CFOCF 2 CFOCF 2 CF 2 SO 2 F 5 1 CF 3 The sulfonyl-containing monomers are disclosed in such references as U S P 3,282,875, 10 U.S P 3,041,317, U S P 3,718,627 and U S P 3,560,568.

The preferred copolymers prepared in this way are perfluorocarbon although others can be utilised as long as the T group has a fluorine atom attached to the carbon atom which is attached to the -CF 2 SO 2 F group.

The copolymers can be prepared by general polymerization techniques developed for 15 homo and copolymerizations of fluorinated ethylenes, particularly those employed for tetrafluoroethylene which are described in the literature Nonaqueous techniques for preparing the copolymers of the present invention include that of U S P 3, 041,317, that is, by the polymerization of a mixture of the major monomer therein, such as tetrafluoroethylene, a monomer of the invention and a fluorinated ethylene containing a 20 sulfonyl fluoride group in the presence of a free radical initiator, preferably a perfluorocarbon peroxide or azo compound, at a temperature in the range 0200 C and at pressures in the range 1-200, or more atmospheres The nonaqueous polymerization may, if desired, be carried out in the presence of a fluorinated solvent Suitable fluorinated solvents are inert, liquid, perfluorinated hydrocarbons, such as perfluoromethylcyclohexane, 25 perfluorodimethylcyclobutane, perfluorooctane and perfluorobenzene, and inert, liquid chlorofluorocarbons such as 1,1,2-trichloro-1,2,2-trifluoroethane.

Aqueous techniques for preparing copolymers include contacting the monomers with an aqueous medium containing a free-radical initiator to obtain a slurry of polymer particles in non-water-wet or granular form, as disclosed in U S Patent, 2,393,967, or contacting the 30 monomers with an aqueous medium containing both a free-radical initiator and a telogenically inactive dispersing agent, to obtain an aqueous colloidal dispersion of polymer particles, and coagulating the dispersion, as disclosed, for example, in U S P 2,559,752 and U.S P 2,593,583.

Copolymers produced in accordance with the invention can be used, after conversion of 35 the -SO 2 A group to a sulfonic acid or sulfonate group and in film or membrane form, in chlor-alkali cells to separate the anode and cathode sections of the cells as described more particularly in Application No 15539/78 (Specification No 1604173), from which this

Application has been divided.

The following Example will illustrate the invention 40 EXAMPLE

Preparation of CF 2 =CFOCF 2 CF(CF 3)OCF 2 COOCH 3, Methyl perfluoro-4-methyl-3,6-dioxa-7-octenoate A 2-liter 3-necked flask was fitted with a stirrer, gas inlet tube and dry ice cooled 45 condenser The apparatus was blanketed with nitrogen, 3276 1 g of perfluorol 2-( 2fluorosulfonylethoxy)-propyl vinyl etherl added and chlorine bubbled into the flask while irradiating with a sunlamp until no more chlorine was absorbed Distillation yielded 2533 8 g ( 66 7 %) of perfluorol 2-( 2-fluorosulfonylethoxy)-propyl-1,2dichloroethyl etherl, bp 165 C 50 To a quartz tube ( 1-inch outside diameter and 1 foot long) heated to 550 C were added nitrogen dioxide at a rate of approximately 0 2 g/min and 37 6 g perfluorol 2-( 2fluorosulfonylethoxy)-propyl-1,2-dichloroethyl etherl at a rate of 0 33 mrl/min The product was trapped in a dry ice cooled trap, allowed to come to room temperature, treated with 20 ml methanol, and washed with 250 ml water to give 19 3 g of product The combined 55 distillation of a number of similar runs yielded methyl perfluoro-7,8dichloro-4-methyl-3,6dioxaoctanoate, bp 167 C, whose structure was confirmed by infrared and NMR spectroscopy.

A mixture of 10 g crude methyl perfluoro-7,8-dichloro-4-methyl-3,6dioxaoctanoate, 5 g zinc dust, 50 ml anhydrous diethylene glycol dimethyl ether and 0 1 g iodine was heated to 60 C, and then distilled The distillate was washed with water and the product chromatographed to yield appreciable amounts of CF 2 =CFOCF 2 CF(CF 3)OCF 2 COOCH 3.

The structure of the final product was proven by IR spectroscopy and by conversion with bromine to CF 2 Br CF Br OCF 2 CF(CF 3)OCF 2 COOCH 3 The structure of the vinyl ether was further confirmed by its boiling point, 75 C at 50 mm of Hg, and its NMR spectrum 65 4 1 604 176 4

Claims

WHAT WE CLAIM IS:

1 A compound of the formula:

CF 2 =CFO ' CF 2-CF-O 'm CF 2 COOR 1 5 CF 3 wherein m is 0, 1 or 2, and R 1 is lower alkyl or M(), where M is H, alkali metal or alkaline 10 earth metal, and N is the valence of M.

2 A compound according to claim 1 wherein m is 1 and R' is CH 3.

3 A fluorinated polymer prepared by copolymerising a compound as claimed in claim 1 with (i) a fluorinated vinyl monomer of the formula CX 2 =CX 2, wherein each X, which may be the same or different, is H, Cl, F, CF 3 or perfluoroalkoxy, subject to the proviso that at 15 least one X is F, and (ii) a sulfonyl-containing monomer containing a group -CF-CF 2-SO 2 A, l 20 Rf wherein Rf is F, Cl or C 1-Clo O perfluoroalkyl, and A is F or Cl.

4 A fluorinated polymer according to claim 3 wherein the X's taken together are four 25 fluorines or three fluorines and one chlorine and A is F.

A film or membrane of a fluorinated ion exchange polymer obtained by converting the -SO 2 A group of a polymer as claimed in claim 3 or 4 to a sulfonic acid or sulfonate group.

6 An electrolytic cell comprising a housing with separate anode and cathode sections, 30 said cell being separated by a film or membrane as claimed in claim 5.

J.A KEMP & CO, Chartered Patent Agents, 14, South Square, 35 Gray's Inn, London WC 1 R 5 EU.

Printed for Her Majesty's Stationery Office by Croydon Printing Company Limited Croydon Surrey 1981.

Published by The Patent Office, 25 Southampton Buildings London WC 2 A l AY from which copies may be obtained.