Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1993-03-04
1995-06-20
Gorgos, Kathryn
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204296, 20415715, 429192, 429249, 521 27, 427243, 427244, 427336, 4273935, 4274301, C25B 1304, C25B 1308, H01M 618, B05D 500
Patent
active
054258650
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to polymer membranes. The invention relates in particular to a composite polymer membrane, a method of making a composite polymer membrane, and a method of crosslinking the material of a microporous polymer matrix.
BACKGROUND OF THE INVENTION
A composite polymer membrane, which comprises a microporous matrix formed from a first polymeric material and a second polymeric material within the pores of the matrix, can be used as a selective barrier. For example, such a membrane may be used to separate components of a liquid. By use of an ion exchange material as the second polymeric material, such a membrane may be used as a selective barrier for ions in solution; for example, such a membrane may be used as an electrode separator in an electrochemical device, in which ionic conduction between electrodes of the device is required and in which a barrier is required to prevent migration of certain dissolved species (such as ions) and of electrode material in particulate form. The barrier is also required in secondary cells on recharging, when loosely attached material is deposited on the anode, often in the form of dendrites, which is required not to make contact with the cathode. A composite polymer membrane can be used to separate materials by other mechanisms, for example by ultrafiltration.
A suitable composite polymer membrane for use as an electrode separator in an electrochemical device is disclosed in our U.S. Pat. No. 5,256,503 the disclosure of which is incorporated herein by reference thereto. The membrane comprises a porous matrix of polyethylene which has been formed from a blend of polyethylene and polyethylene oxide ;by removal of the polyethylene oxide.
The pores in the matrix contain polyacrylic acid which preferably has been polymerized in situ in the pores, and which blocks, and preferably fills, the pores of the matrix. The acrylic acid is supplied to the pores of the matrix in solution with a crosslinking agent and a photoinitiator. Polymerization and crosslinking of the acrylic acid are initiated by exposure to ultraviolet radiation.
The polymerization and crosslinking reactions of the acrylic acid in the composite membrane disclosed in U.S. Pat. No. 5,256,503 compete for the acrylic acid, and by selecting the relative rates of the competing reactions, it is possible to control the degrees of crosslinking and polymerization of the acrylic acid. It has been found possible to vary the properties of the known membrane by appropriate selection of the crosslink density of the acrylic acid impregnant, for example to provide a membrane with a low resistance and relatively weak barrier performance using a low crosslink density, and to provide a membrane with relatively high resistance and good barrier performance using a high crosslink density. The degree of crosslinking can be selected by for example providing the impregnant with an appropriate quantity of crosslinking agent for reaction. However, a remaining difficulty lies in producing a membrane by the technique disclosed in U.S. Pat. No. 5,256,503 which has a good barrier performance towards certain dissolved species (such as silver or mercury ions).
Another approach to producing a composite polymer membrane is the subject of U.S. Pat. No. 3,427,206, and involves grafting a polymer of an ethylenically unsaturated carboxylic acid such as acrylic acid onto a non-porous sheet of a material such as polyethylene. This approach can be contrasted to that discussed above, in that ion migration takes place through the bulk polymer of the sheet to which acrylic acid has been grafted, rather than through regions of polyacrylic acid contained within pores in a microporous sheets.
Membranes which are formed by grafting an ion exchange material onto the polymeric material of a continuous sheet may be crosslinked, generally before the ion exchange material is supplied. It has been found that crosslinking of such membranes has effects which are similar to those in the membranes disclosed in WO-A-87/06395,
REFERENCES:
patent: Re31824 (1985-02-01), D'Agostino et al.
patent: 2965697 (1960-12-01), Duddy
patent: 3376168 (1968-02-01), Horowitz
patent: 3427206 (1969-02-01), Scardaville et al.
patent: 4230463 (1980-10-01), Henis et al.
patent: 4346142 (1982-08-01), Lazear
patent: 4468441 (1984-08-01), D'Agostino et al.
patent: 4547411 (1985-10-01), Bachot et al.
patent: 4613544 (1986-09-01), Burleigh
patent: 4804598 (1989-02-01), Jackovitz et al.
W. H. Philipp et al., "New Ion Exchange Membranes," NASA Technical Memorandum 81670. Oct. 1980.
D'Agostino et al., "Grafted Membranes," Zinc-Silver Oxide Batteries, Wiley and Sons, Inc.; New York, N.Y.; 1971; pp. 271-281.
Cook John A.
Gargan Kenneth
Singleton Raymond W.
Gorgos Kathryn
Scimated Limited
LandOfFree
Polymer membrane does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polymer membrane, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polymer membrane will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1842382