mikroporoese gegenstaende from resin and method of manufacture

摘要

1296545 Extruding porous articles INTERNATIONAL PLASTICS Inc 31 Oct 1969 53596/69 Heading B5A [Also in Divisions B1 C3 and F2] A porous article having 5000 to 200,000 apertures per sq. inch, each of 0À2 to 10 microns, e.g. 2 to 4 microns, is extruded under heat and pressure from a mixture of moulding powder of polymethylmethacrylate, or polyvinyl chloride, or at least 50% (by weight of the moulding powder) of acrylonitrile/butadiene/styrene copolymer, and of 0À5 to 25 weight per cent of the mixture, of decomposable chemical compound particles, to cause decomposition of the compound during extrusion, and the products whereof are removed through the surface of the unsolidified extrudate. The article may comprise a conduit having 6000 to 25,000 apertures p.s.i. or a sheet of 6000 to 150,000 apertures p.s.i., each of 0À3 to 5 micron diameter. The decomposable particles may comprise 0À5 to 10% by weight of particles of 0À2 to 10 microns diameter, e.g. of 0À3 to 6 microns when of sodium carbonate. The compound is preferably ground to a size, e.g. 2 micron, approximating the size of the desired pores. The resin may comprise a 50% mixture of acrylonitrile-butadiene-styrene terpolymer with polystyrene, and examples are given of various per cent mixtures of the resins with sodium carbonate compound. The compound may also comprise the carbonates and bicarbonates of alkali and alkaline earth metals such as lithium, potassium, calcium, or of ammonia, or hydrated salts such as sodium sulphate (or carbonate) decahydrate, or organic materials which decompose into inert grass, e.g. nitrogen from organic oxides, or metal hydrides such as of lithium from which hydrogen is liberated. The mixing of sodium bicarbonate with acrylonitrile / styrene / butadiene particles is facilitated by a small amount of partially polymerized liquid of the resin. The article may comprise a pipe, buried below ground level for distributing fertilizer and water to crops, a tubular filter for the removal of solid matter from water, a filter for removal of soot or smoke from an air stream, or a sheet for use as a filter or evaporative cooler, and which sheets may be extruded with interior channels for conveyance of a suspension or a filtrate. In the described embodiment, the mixture supplied at a hopper 18 is screw extruded, e.g. at up to 7000 lbs./sq. inch, through a barrel 13 provided with an inlet 21 (for the admission of gas to present collapse of the extrudate) and heated by hot oil circulated through a jacket 16, the die 23 being at 15-20‹ F. less than the barrel 13. The molten tubular extrudate is drawn off at a factor of two or four and passes through a chamber 26, at flexible rubber seals 34, in which chamber vacuum, e.g. of 2 to 3 inches of water is applied at 31 to remove gas or vapour through the extrudate surface, with simultaneous cooling and removal of solid compound residue being effected by sprays 31 of water, which drains via a trap 30.