Battery separator manufacturing process
AssigneeExxon Research & Engineering Co.
InventorsRobert R. Buntin, Walter A. Morgan
Life of this patent
Estimating the term…
Abstract
Battery separators are produced from nonwoven mats of thermoplastic fibers by wetting the fibers with a surfactant-water mixture to modify the surface properties of the fibers in the nonwoven mat, vaporizing the water while depositing the surfactant on the fibers, heating the nonwoven mat prior to compressing and then compressing to increase the fiber-to-fiber bonding as well as to form the desired structure. During compressing, ribs may be formed by using appropriate embossed rolls or press plate patterns. After the compressing step, slitting, cooling and cutting steps are carried out to produce a battery separator of the desired dimensions.
Claims5
A method for producing a battery acid wettable nonwoven battery separator from nonwoven mats of polypropylene thermoplastic fibers, which mats before treatment are not wettable by at least a 35% sulfuric acid battery acid, which method comprises:
- wetting a nonwoven mat of said thermoplastic fibers with a surfactant-water solution at a temperature of 60.degree. to 170.degree. F., wherein said surfactant is cationic or nonionic and is present as a 0.2 to about 1.0 wt. % solution in said water by contacting only one side of said mat and permitting said solution to spread through said mat;
- vaporizing the water from the surfactantwater solution within said mat in a hot air countercurrent oven whereby said surfactant is evenly deposited in an amount of 0.3 to 1.0% by weight based on fibers of said nonwoven mat which is now essentially dry;
- then heating said nonwoven mat to a temperature in excess of the softening point of said thermoplastic fibers but insufficient to melt, shrink or degrade said fibers;
- and subsequently compressing said heated nonwoven mat to a void fraction of at least 0.4.
Dependencies are inferred from the claim text.