Patent GB-877220-A (GB)
Title: Improvements in electric storage battery vent plugs
IPC: H01M2/36
Filed: 1959-05-05
Abstract: A material permeable to gases but not liquids consists of a microporous synthetic resin the pores of which have deposited on them a layer of silicone.  The resin may be polyethylene, polypropylene, polystyrene or polyvinyl chloride.  A high density polymer of ethylene is preferred, and it may be extruded in the form of a tube for use as a gas venting plug which prevents the passage of liquid. The resin may be made porous by mixing it with starch, sugar or other soluble substance which is removed by immersing the finished article in a 3% solution of hydrochloric acid, then in a 3% solution of potassium hydroxide, and finally in repeated baths of water of decreasing temperatures.  The pores have diameters ranging from 0,84 micron to 9,6 microns and are given a coating of silicone by vacuum impregnation of hydrolysable silanes or by immersing the article in a 1% aqueous solution of acetone, evaporating the acetone and subjecting the article to the vapour of the silanes.  Hydrolysis occurs and the silicone deposit is polymerized by heat.ALSO:A material permeable to gases but not liquids consists of a microporous synthetic resin the pores of which have deposited on them a layer of silicone.  The resin may be polyethylene, polypropylene, polystyrene or polyvinyl chloride.  A high density polymer of ethylene is preferred, and it may be extruded in the form of a tube for use as a gas venting plug which prevents the passage of liquid.  The resin may be made porous by mixing it with starch, sugar or other soluble substance which is removed by immersing the finished article in a 3% solution of hydrochloric acid, then in a 3% solution of potassium hydroxide, and finally in repeated baths of water of decreasing temperatures.  The pores have diameters ranging from 0.84 micron to 9.6 microns and are given a coating of silicone by vacuum impregnation of hydrolysable silanes or by immersing the article in a 1% aqueous solution of acetone, evaporating the acetone and subjecting the article to the vapour of the silanes.  Hrydrolysis occurs and the silicone deposit is polymerized by heat.ALSO:A material permeable to gases but not liquids consists of a microporous synthetic resin the pores of which have deposited on them a layer of silicone.  The resin may be polyethylene, polypropylene, polystyrene or polyvinyl chloride.  A high density polymer of ethylene is preferred, and it may be extruded in the form of a tube for use as gas venting plug which prevents the passage of liquid.  The resin may be made porous by mixing it with starch, sugar or other soluble substance which is removed by immersing the finished article in a 3% solution of hydrochloric acid, then in a 3% solution of potassium hydroxide, and finally in repeated baths of water of decreasing temperatures.  The pores have diameters ranging from 0,84 micron to 9,6 microns and are given a coating of silicone by vacuum impregnation of hydrolysable silanes or by immersing the article in a 1% aqueous solution of acetone, evaporating the acetone and subjecting the article to the vapour of the silanes.  Hydrolysis occurs and the silicone deposit is polymerized by heat.