Low equivalent weight ionomer
AssigneeGore Enterprise Holdings, Inc.
InventorsHuey Shen Wu, Charles W. Martin, Xin Kang Chen
Life of this patent
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Abstract
An ionomer and a process for forming the ionomer such that the ionomer has (1) low equivalent weight; below 950, preferably between 625 and 850, and most preferably between about 700 and about 800; and (2) high conductivity, (greater than 0.15 S/cm). In an alternative embodiment, the ionomer has (1) low equivalent weight; below 950, preferably between 625 and 850, and most preferably between about 700 and about 800; and (2) acceptably low hydration, (less than about 75 weight percent). These ionomers are adapted to be processed into thin films that have acceptable physical stability. They are thus extremely well-suited for low humidity or high temperature fuel cell applications.
Claims16
A fluorinated ionomeric co-polymer comprising
- (a) a substantially fluorinated backbone;
- (b) pendant groups derived from an ionomeric monomer of the formula
- where X is F, Cl or Br or mixtures thereof;
- n is an integer equal to zero, one or two;
- Rf and Rf′ are independently selected from the group of F, Cl, perfluoroalkyl radical, and chloroperfluoroalkyl radical;
- Y is an acid group or a functional group convertible to an acid group a is zero or an integer greater than zero;
- and b is an integer greater than zero;
- and
- (c) pendant groups derived from a vinyl ether monomer that has at least two vinyl ether groups of the form, CA2═CB—O—, where the vinyl groups are separated by greater than four atoms;
- A is independently selected from the group containing F, Cl, and H;
- and B is independently selected from F, Cl, H and ORi, where Ri is a branched or straight chain alkane that may be partially, substantially or completely fluorinated or chlorinated;
- wherein the concentration of the pendant groups derived from the ionomeric monomer and the vinyl ether monomer is between about 10 mole percent and about 45 mole percent of the final product, and wherein the concentration of the pendant groups derived from the vinyl ether monomer is present in the final product between about 0.05 and about 2 mole percent.
A process for making a fluorinated polymer comprising the steps of:
- (i) forming a mini-emulsion in an agitated reactor with at least one substantially fluorinated alkene gas;
- (ii) pressurizing said mini-emulsion in an agitated reactor with at least one
- substantially fluorinated alkene gas;
- (iii) initiating polymerization with a free radical initiator in said reactor;
- (iv) maintaining a known pressure of the substantially fluorinated alkene
- gas for a period of time;
- and
- (v) adding, during one or more of the process steps (i) through (iv), a vinyl
- either monomer having at least two vinyl ether groups of the form,
- CA2═CB—O—, where the vinyl groups are separated by greater than four
- atoms;
- A is independently selected from the group containing F, Cl, and
- H;
- and B is independently selected from F, Cl, H and ORi, where Ri is a
- branched or straight chain alkane that may be partially, substantially or
- completely fluorinated or chlorinated.
The product produced by the process of
- (i) forming a mini-emulsion of a mixture of deionized water, a
- perfluorinated surfactant, optionally dissolved in an aqueous solution;
- a
- liquid perfluorinated hydrocarbon having a molecular weight below
- 2000 and an ionomeric monomer;
- (ii) pressurizing said mini-emulsion in an agitated reactor with at least one substantially fluorinated alkene gas;
- (iii) initiating polymerization with a free radical initiator in said reactor;
- (iv) maintaining a known pressure of the substantially fluorinated alkene
- gas for a period of time;
- and
- (v) adding, during one or more of the process steps (i) through (iv), a vinyl
- ether monomer having at least two vinyl ether groups of the form,
- CA2═CB—O—, where the vinyl groups are separated by greater than four
- atoms;
- A is independently selected from the group containing F, Cl,
- and H;
- and B is independently selected
- from F, Cl, H and ORi, where Ri is a branched or straight chain alkane
- that may be partially, substantially or completely fluorinated or chlorinated.
Dependencies are inferred from the claim text.