Patent GB-1112896-A (GB)
Title: Polyolefine-coated, reticulated polyurethane foams
IPC: C08J9/42
Filed: 1965-05-06
Abstract: Reticulated polymeric structures are produced by wetting reticulated polyurethane foam with a liquid, distributing throughout said reticulated polyurethane foam polyolefine resin powder and melting in a heating zone said polyolefine powder at a temperature below the decomposition point of the polyurethane and polyolefine to conform the molten polyolefine to the outlines of said reticulated polyurethane foam, and if desired repeating the above steps.  The foam may be a polyester or a polyether polyurethane.  The polyolefine may be polyethylene or polypropylene, The powder may be dusted on the reticulated polyurethane foam, and the structure then heated in an oven or a heating zone using infrared, radiant or convection heating. The polyurethane core may be removed from the polyolefine to form a reticulated polyolefine structure by soaking in polyurethane hydrolyzing solution, or cutting the strands or nexae of the structure or simply cutting the structure, and immersing in a hydrolysing solution such as acid or alkali solution at elevated temperature and high concentration of treating agent.  Acids and alkalies mentioned are sulphuric, hydrochloric or phosphoric acids, sodium, potassium and lithium hydroxide.  Alternatively the polyolefine may be melted to expose a part of the strands or nexae of the polyurethane structure. Polyolefin powder may be admixed with the polyurethane foam-forming starting material to obtain a structure having a smaller hollow core.  The structures having a hollow core may be treated by explosion-glazing techniques by subjecting the structures to an explosive flame front.  A polyurethane reticulated foam structure may first be treated with a polypropylene powder, then treated to remove the polyurethane and then recoated with a polyethylene powder.  The structures may be heat-formed into various shapes, and may be bonded to any surface possessing sufficient affinity for molten polyethylene.  The structures are useful in such applications as acid, or alkali filters, heating plant filters, humidifier and evaporative cooler pads in which connection surface modifiers such as glass, asbestos, feldspar and pumice alumina, may be deposited on the structures with the aid of an adhesive. Composite filters of varying pore sizes may be prepared by melting the polyethylene on the surface of one structure, and joining it to another structure having less pores.  The pressure drop characteristics of the structures may be controlled by densification of the structures.ALSO:Reticulated polymeric structures are produced by wetting reticulated polyurethane foam with a liquid, distributing throughout said reticulated polyurethane foam polyolefine resin powder and melting in a heating zone said polyolefine powder at a temperature below the decomposition point of the polyurethane and polyolefine to conform the molten polyolefine to the outlines of said reticulated polyurethane foam, and if desired repeating the above steps.  The foam may be a polyester or a polyether polyurethane.  The polyolefine may be polyethylene, polypropylene, polybutene polypentene or copolymers thereof, and mixtures thereof.  The powder may be dusted on the reticulated polyurethane foam, and the structure then heated in an oven or a heating zone using infrared, radiant or convection heating.  The polyurethane core may be removed from the polyolefine to form a reticulated polyolefine structure by soaking in polyurethane hydrolyzing solution, or cutting the strands or nexae of the structure or simply cutting the structure, and immersing in a strong hydrolyzing solution such as strong acid or alkali solution say at elevated temperature and high concentration of treating agent. Acids and alkalies mentioned are sulphuric, hydrochloric or phosphoric acids, sodium, potassium and lithium hydroxide. Weak acids and alkalis may also be used.  Alternatively the polyolefine may be melted to expose a part of the strands or nexae of the polyurethane structure.  Polyolefin powder may be admixed with the polyurethane foam-forming starting material to obtain a structure having a smaller hollow core.  The structures having a hollow core may be treated by explosion-glazing techniques by subjecting the structures to an explosive flame front.  A polyurethane reticulated foam structure may first be treated with a polypropylene powder, then treated to remove the polyurethane and then recoated with a polyethylene powder.  The structures may be heat-formed into various shapes, and may be bonded to any surface possessing sufficient affinity for molten polyethylene. The structures are useful in such applications as acid, or alkali filters, heating plant filters, humidifier and evaporative cooler pads in which connection surface modifiers such as glass, asbestos, feldspar and punice alumina, may be deposited on the structures with the aid of an adhesive.  Composite filters of varying pore sizes may be prepared by melting the polyethylene on the surface of one structure, and joining it to another structure having less pores.  The pressure drop characteristics of the structures may be controlled by densification of the structures.