Process for forming non-woven webs from highly oriented melt blown fibers

Claim 1

A process for producing a tubular sleeve of non-woven fibers, which comprises: (a) heating a thermoplastic condensation polymer selected from the group consisting of polyethylene terephthalate and nylon 6,6 to a molten state to a temperature sufficient to attain an apparent melt viscosity of less than 50 poise; (b) spinning by melt blowing said molten thermoplastic condensation polymer in the presence of a first gaseous medium heated to melt blowing conditions to form oriented, heat shrinkable, melt blown fibers, said melt blown fibers exhibiting a shrinkage of at least about 19%; (c) collecting said melt blown fibers on a rotating mandrel to form a loose tubular sleeve of said oriented melt blown fibers; (d) contacting said tubular sleeve with a second gaseous medium heated to a temperature of from 70° to 265° C. to thereby shrink and entangle said melt blown fibers and form a rigid cartridge having a density of at least 0.1 gram/cc; and (e) removing said cartridge from said rotating mandrel.