Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Ion-exchange polymer or process of preparing
Patent
1983-03-25
1984-11-06
Schofer, Joseph L.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Ion-exchange polymer or process of preparing
20415915, C08F 800, C08F25908, B01J 100
Patent
active
044813066
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to novel cation exchange resins, their preparation and their use; in particular it relates to cation exchange materials suitable for use as permselective membranes in electrolytic cells such as are used in the manufacture of alkali metal hydroxide solutions and chlorine.
BACKGROUND ART
Alkali metal hydroxide solutions and chlorine are generally manufactured in mercury cells or diaphragm cells. Mercury cells have the advantage of producing concentrated alkali metal hydroxide solutions but give rise to problems associated with the disposal of mercury-containing effluents. On the other hand, diaphragm cells, in which the anodes and cathodes are separated by porous diaphragms which permit the passage of both positive and negative ions and of electrolyte, avoid the aforesaid effluent problem, but have the disadvantage that: which results in increased evaporation costs; and becoming mixed.
Attempts have been made to overcome disadvantages of both mercury cells and diaphragm cells by the use of cells in which the anodes and cathodes are separated by cation-active permselective membranes; these are membranes which are selectively permeable so as to allow the passage of only positively charged ions and not the passage of bulk electrolyte. Cation-active permselective membranes which are suitable for this use in chlorine cells include, for example, those made of synthetic organic copolymeric material containing cation-exchange groups, for example sulfonate, carboxylate and phosphonate.
In particular, synthetic fluoropolymers which will withstand cell conditions for long periods of time are useful, for example, the perfluorosulfonic acid membranes manufactured and sold by E I DuPont de Nemours and Company under the trade mark "NAFION" and which are based upon hydrolyzed copolymers of perfluorinated hydrocarbons (for example polytetrafluoroethylene) and fluorosulfonated perfluorovinyl ethers.
The active sites in the molecular structure of the resins from which these membranes are made are provided by the fluorosulfonated perfluorovinyl ether component. These sites are present on side chains attached by an ether linkage to the skeletal structure of the resin. Such membranes are described for example in U.S. Pat. Nos. 2,636,851; 3,017,338; 3,496,077; 3,560,568; 2,967,807; 3,282,875 and UK Patent No. 1,184,321.
Generally these fluoropolymers are made by the polymerization or copolymerization of fluorocarbon monomers in an emulsion or suspension containing a radical polymerization catalyst. The resulting polymers are moulded into membranes by conventional moulding procedures such as melt fabrication.
DISCLOSURE OF INVENTION
We have now discovered a novel process of making fluoropolymers suitable for use in cation-active permselective membranes. This process differs from the prior art processes in that monomers containing active sites, or functional groups that can be converted to active sites, are grafted directly onto perhalogenated polymeric skeletal substrates by a process of radiation grafting. It is a particular feature of our process that the polymeric skeletal substrates may be in powder or film form.
More particularly, we have found that when a functional monomer as hereinafter defined, a nonfunctional linking monomer as hereinafter defined, and a perhalogenated fluorine-containing hydrocarbon polymer skeletal substrate are together subjected to a radiation grafting process the functional monomer and the nonfunctional linking monomer simultaneously copolymerize and graft to the polymer to form a cation exchange resin having a fluorine-containing hydrocarbon polymeric substrate with pendant side chains containing functional groups. These functional groups may themselves be active sites for cation exchange or may readily be converted to such active site by conventional processes, such as hydrolysis.
Accordingly we provide a process of preparing cation exchange resins which process comprises radiation grafting with copolymerization onto a perhalogenated fluorine-con
REFERENCES:
patent: 3839172 (1974-10-01), Chapiro et al.
patent: 4094826 (1978-06-01), Tatemoto et al.
patent: 4278777 (1981-07-01), Jakabhazy et al.
patent: 4385130 (1983-05-01), Molinski et al.
Barnett George H.
Markus Michael V.
ICI Australia Limited
Kulkosky Peter F.
Schofer Joseph L.
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