Method for preparing asbestos-free chlor-alkali diaphragm
AssigneePPG Industries, Inc.
InventorsDonald W. DuBois, Colonel R. Dilmore, Jr.
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Abstract
A method for preparing asbestos-free diaphragms for chlor-alkali electrolytic cells is described. The comprises establishing a liquid permeable diaphragm base mat of fibrous synthetic polymeric material and ion-exchange material on the cathode structure, treating the base mat with strongly alkaline aqueous alkali metal hydroxide having a concentration of from about 15 to about 40 weight percent, and providing a coating of inorganic particulate material on the base mat before the base mat has dried. Preferably, the base mat is coated with the inorganic particulate material using a slurry of the inorganic particulate material suspended in the strongly alkaline aqueous alkali metal hydroxide.
Claims23
A method for forming an electrolyte-permeable asbestos-free diaphragm on a foraminous cathode structure for use in a chlor-alkali electrolyte cell, comprising:
- (a) forming on a surface of said cathode structure from a liquid slurry a liquid permeable diaphragm base mat of asbestos-free material comprising fibrous synthetic polymeric material resistant to the chlor-alkali cell environment and ion-exchange material,
- (b) treating said diaphragm base mat with aqueous alkali metal hydroxide having a concentration of from about 15 to about 40 weight percent alkali metal hydroxide before the base mat has dried,
- (c) providing a coating of inorganic particulate material on the surface of said diaphragm base mat, said pre-dried diaphragm having alkali metal hydroxide present from step (b), and
- (d) drying the resultant coated diaphragm.
A method for forming an electrolyte permeable asbestos-free diaphragm on a foraminous cathode structure for use in a chlor-alkali electrolytic cell comprising:
- (a) forming on a surface of said cathode structure from a liquid slurry a liquid-permeable diaphragm base mat of asbestos-free material comprising fibrous synthetic polymeric material resistant to the chlor-alkali cell environment and ion-exchange material,
- (b) depositing a coating of inorganic particulate material on the surface of said diaphragm base mat before the base mat has dried by drawing through said diaphragm base mat a liquid slurry comprising said inorganic particulate material dispersed in aqueous alkali metal hydroxide solution, said alkali metal hydroxide solution having a concentration of from about 15 to about 40 weight percent, and
- (c) drying the resultant coated diaphragm at temperatures below the sintering or melting temperature of the synthetic polymeric material.
A method for forming an electrolyte-permeable asbestos-free diaphragm on a foraminous cathode structure for use in a chlor-alkali electrolytic cell, comprising:
- (a) forming on a surface of said cathode structure from a liquid slurry a liquid permeable diaphragm base mat of asbestos-free material comprising fibrous synthetic polymeric material resistant to the chlor-alkali cell environment and ion-exchange material,
- (b) treating said diaphragm base mat before the base mat has dried with aqueous sodium hydroxide having a concentration of from about 15 to about 40 weight present,
- (c) providing a coating of inorganic particulate material on the surface of said treated diaphragm base mat before said treated base mat has dried, said pre-dried diaphragm having sodium hydroxide present from step (b), and
- (d) drying the resultant coated diaphragm.
Dependencies are inferred from the claim text.