Patent GB-1061337-A (GB)
Title: Fibrillated plexifilamentary material
Inventor: ANDERSEN RONALD DEAN
IPC: D01F6/04
Filed: 1965-09-22
Abstract: Tobacco smoke filters may be made from plexifilaments produced by flash-spinning a fibrilated plexilfilamentary material.  A synthetic, crystallizable organic polymer and a solvent therefor are supplied under pressure into a dissolution zone, and the polymer dissolved to form a solution having a temperature of at least the critical temperature of the solvent minus 45 DEG C. and a pressure above the two-liquid-phase pressure boundary for the solution, the concentration of polymer in the solution being 2 to 20% by weight. The solution is forwarded through a transfer zone, and the solution passed into a pressure reduction zone for p  lowering the pressure of the solution to below the two-liquid-phase pressure boundary for the solution, a constant pressure being maintained in the transfer zone preceding the pressure reduction zone by keeping the heat balance in the transfer zone at the same level as in the dissolution zone and by regulating the rates of supply of polymer and solvent to the dissolution zone inversely in relation to the pressure in the transfer zone and in a fixed ratio to one another.  The solution is discharged through a spinneret orifice of restricted size into a gaseous zone which is at atmospheric pressure and temperature. The polymer may be supplied to the dissolution zone as a molten stream. The polymer and solvent may be supplied to this zone as a slurry. The solvent may have a boiling point at least 25 DEG C. below the melting point of the polymer and dissolve less than 1% by weight of the polymer at that boiling point.  The polymer may be a crystalline polyhydrocarbon such as polyethylene and the solvent may be trichlorofluorosmethane.  Specification 891,943 discloses similar plexifilamentary strands and a process for their preparation.ALSO:A process for flash-spinning a fibrilated plexifila-mentary material comprises supplying under pressure into a dissolution zone a synthetic crystallizable organic polymer and a solvent therefor, dissolving the polymer to form a solution having a temperature of at least the critical temperature of the solvent minus 45 DEG C and a pressure above the two-liquid-phase pressure boundary for the solution, the concentration of polymer in the solution being 2 to 20% by weight, forwarding the solution through a transfer zone, passing the solution into a pressure reduction zone for lowering the pressure of the solution to below the two-liquid-phase pressure boundary for the solution, maintaining a constant pressure in the transfer zone preceding the pressure reduction zone by keeping the heat balance in the transfer zone at the same level as in the dissolution zone and by regulating the rates of supply of polymer and solvent to the dissolution zone inversely in relation to the pressure in the transfer zone and in a fixed ratio to one another, and discharging the solution through a spinneret orifice of restricted size into a gaseous zone which is at atmospheric pressure and temperature.  The polymer may be supplied to the dissolution zone as a molten stream. The polymer and solvent may be supplied to this zone as a slurry. The solvent may have a boiling point at least 25 DEG C below the melting point of the polymer and dissolve less than 1% by weight of the polymer at that boiling point.  The polymer may be a crystalline polyhydrocarbon such as polyethylene and the solvent may be trichlorofluoroamethane.  Specification 891,943 discloses similar plexifilamentary strands and a process for their preparation. The product of the present invention may be used in paper manufacture.