Filled Glass fiber separators for batteries and method for making such separators

A sheet useful as a separator in a valve regulated lead acid battery, said sheet comprising at least a first layer of substantially binder free glass fibers and a second layer of substantially binder free glass fibers and a powder that is inert to battery reactions and to materials that are present in batteries, said sheet being produced by the method consisting of the steps of

• depositing a first, substantially binder free furnish consisting essentially of glass, fibers onto the wire of a paper making machine to form the first layer and
• depositing onto the fibers from the first furnish while they are on the wire of the paper making machine a second, substantially binder free furnish consisting essentially of glass fibers and a powder that is inert to battery reactions and to materials that are present in batteries to form the second layer, said powder having a mean particle size ranging from 0.001 .mu.m to 20 .mu.m,
• said powder having a particle size and density, and being present in said second layer in an amount such that a significant portion of the powder from a layer formed by depositing the second furnish onto the wire of the paper making machine would pass through the wire, and said first layer having a sufficiently small pore size that substantially all of the powder in said second furnish either remains in a layer formed by depositing, the second furnish on the first layer, while on the wire of the paper making machine, or is filtered from the liquid of said furnish by the fibers of the first layer while on the wire of the paper making machine, and substantially all of the powder in the second furnish is retained in the sheet.