Hooker Chemicals & Plastics Corporation

Occidental Chemical Corporation

Christine A Lazarz

Edward H Cook, Jr

Lesleigh V Scripa

Eng-Pi Chang

Ursula I Keller

Arthur C Schulz

Richard D Darling

A porous polyfluoroalkylene sheet, preferably of polytetrafluoroethylene, which is suitable for use as a stable low voltage separator or diaphragm in an electrolytic cell, such as one employed for the electrolysis of brine, without being subject to an objectionable voltage increase upon use, is of a thickness in the range of about 0.2 to 2 mm., a porosity in the range of about 70 to 90% and of pore sizes within a range up to about one mm. in diameter, with a pore size distribution such that the pores of a diameter about 0.1 micron (or less) are less than 10% of the total pore volume and the volume of those of about one to ten microns is a substantial part, e.g. 50%, of the total pore volume, and with the ratio of the numbers of such pores in the lower size range to those in the upper range being less than about 30. Limiting the 0.1 micron diameter pores in the microporous sheet helps to prevent the cell from 'going high voltage' during operation and the presence of one to ten micron diameter pores improves diaphragm action while still maintaining a low resistance thereof. Also disclosed are: a diaphragm made from a portion of such sheet material; an electrolytic cell including such a diaphragm; a method of electrolyzing brine, utilizing such a cell, and a method for testing of such sheets so as to determine suitability for use thereof as stable low voltage diaphragms in electrolytic cells.

Method of electrolyzing brine with stable low voltage microporous

A porous polyfluoroalkylene sheet, very preferably of polytetrafluoroethylene, which is suitable for use as a separator in an electrolytic cell, such as one used for the electrolysis of brine, has a porosity in the range of 70 to 90%, a thickness in the range of 0.2 to 3.5 mm. and at least one of (a) an A X-ray ratio in the range of 0.1 to 0.35 and (b) a B X-ray ratio in the range of 0.75 to 0.98. Preferably the A X-ray ratio is in the range of 0.1 to 0.3, the B.sub.2 X-ray ratio is in the range of 0.75 to 0.98 and the B.sub.1 X-ray ratio is in the range of 0.1 to 0.32. The porous sheets are incorporated in separators or diaphragms for electrolytic cells and the uses of such separators and cells in electrolysis processes, preferably in the electrolysis of brine, are described. Also shown in the specification are a method for the manufacture of the porous sheets and a method for ascertaining which milled, sintered and leached porous sheets are more suitable for use in electrolytic processes.

Process for forming a porous polyfluoroalkylene sheet useful for

A porous polyfluoroalkylene sheet, preferably of polytetrafluoroethylene, which is suitable for use as a stable low voltage separator or diaphragm in an electrolytic cell, such as one employed for the electrolysis of brine, without being subject to an objectionable voltage increase upon use, is of a thickness in the range of about 0.2 to 2 mm., a porosity in the range of about 70 to 90% and of pore sizes within a range up to about one mm. in diameter, with a pore size distribution such that the pores of a diameter about 0.1 micron (or less) are less than 10% of the total pore volume and the volume of those of about one to ten microns is a substantial part, e.g. 50%, of the total pore volume, and with the ratio of the numbers of such pores in the lower size range to those in the upper range being less than about 30. Limiting the 0.1 micron diameter pores in the microporous sheet helps to prevent the cell from 'going high voltage' during operation and the presence of one to ten micron diameter pores improves diaphragm action while still maintaining a low resistance thereof. Also disclosed are: a diaphragm made from a portion of such sheet material; an electrolytic cell including such a diaphragm; a method of electrolyzing brine, utilizing such a cell; and a method for testing of such sheets so as to determine suitability for use thereof as stable low voltage diaphragms in electrolytic cells.

Stable low voltage microporous diaphragm for electrolytic cells

A porous polyfluoroalkylene sheet, very preferably of polytetrafluoroethylene, which is suitable for use as a separator in an electrolytic cell, such as one used for the electrolysis of brine, has a porosity in the range of 70 to 90%, a thickness in the range of 0.2 to 3.5 mm. and at least one of (a) an A X-ray ratio in the range of 0.1 to 0.35 and (b) a B X-ray ratio in the range of 0.75 to 0.98. Preferably the A X-ray ratio is in the range of 0.1 to 0.3, the B.sub.2 X-ray ratio is in the range of 0.75 to 0.98 and the B.sub.1 X-ray ratio is in the range of 0.1 to 0.32. The porous sheets are separators or diaphragms for electrolytic cells and the uses of such separators and cells in electrolysis processes, preferably in the electrolysis of brine, are described. Also known in the specification are a method for the manufacture of the porous sheets and a method for ascertaining which milled, sintered and leached porous sheets are more suitable for use in electrolytic processes.

Porous polyfluoroalkylene sheet useful for separating anolyte from

Microporous membrane materials suitable for use in electrolytic cells, such as cells for the electrolysis of brine to produce chlorine, are formed from a mixture of polytetrafluoroethylene, a particulate pore forming material and an organic fluorinated lubricant. Such materials are preferably formed into a sheet, which is rolled to a desired thickness, sintered and subjected to leaching out of the pore forming material.

Microporous membrane materials

A separator for an electrolytic cell or similar cell is made of a porous polymeric material, preferably porous polytetrafluoroethylene, and comprises a plurality of tubular portions of such material with one or two flange(s) at end(s) thereof for sealing to other such flanges and to the cell. The flanges are so constructed that when being sealed in place they do not strain or tear and do not strain or tear the material of the tubular portions. The separator is especially useful as a replacement for deposited asbestos diaphragms in electrolytic cells for the manufacture of chlorine and caustic.

Electrolytic cell separator, tubular member component thereof and

Hydrophobic polymeric separators are made wettable to electrolytic cell fluids by a post-manufacturing process of treating with fluorinated surface-active agents. The application of a hydrophilic film of fluorosurfactant onto separator surfaces followed by drying renders the separator permanently wettable. The hydrophilic surfaces rendered inert by drying are reactivated in-situ after installation of the separator by contacting the separator surfaces with heated aqueous solution. The pre-installation process provides a convenient means for shipping fully manufactured separators and for their storage by users until actually needed. From an operational standpoint, the pre-installation process eliminates fouling of the cell with foam occurring with conventional in-situ wetting procedures.

Processes of wetting hydrophobic fluoropolymer separators

The invention disclosed herein relates to a polymeric microporous electrolytic cell separators for producing alkali metal hydroxide at high current efficiencies, said separator having:

Polymeric microporous separators for use in electrolytic processes and

Microporous membrane materials suitable for electrolytic cell utilization are formed from the blend of particulate polytetrafluoroethylene, a dry pore forming particulate material, and an organic lubricant. The materials are milled and formed into a sheet, which is rolled to the desired thickness, sintered, and subjected to leaching of the pore forming materials.

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Niagara Falls, NY, United States of America

Christine A Lazarz