Patent GB-777894-A (GB)
Title: An improved method of preparing a composition comprising a synthetic resin and a natural or synthetic rubber
IPC: B29C48/67
Filed: 1955-06-24
Abstract: A composition is prepared by blending synthetic rubber latex with a compatible dry particulate synthetic resin, at a temperature below that at which the resin and rubber fuse into a single phase, to form a granular free-flowing mixture which is masticated at an elevated temperature, e.g. 150 DEG  to 475 DEG  F., to fuse the resin and rubber into a single phase, removing water and any other volatiles from the mixture prior to completion of the mastication, and extruding the resulting mixture.  The original mixture preferably comprises 4 to 60 per cent by weight of water derived from the latex, and 4 to 55 parts by weight of rubber per 96 to 45 parts of synthetic resin, and 0 to 60 per cent of a filler based on the total weight of rubber and resin.  The latex may be that of butadiene-acrylonitrile copolymer, or a copolymer containing at least 25 per cent by weight of a diolefin, e.g. butadiene, copolymerized with a monoethylenically unsaturated monomer, e.g. methacrylonitrile, a lower alkyl acrylate, methacrylate, maleate, or fumarate, styrene, a -methyl styrene, para-methyl styrene, a -paradimethyl styrene, 2-, 3- or 4-vinyl pyridine, or a mono-lower alkyl mono-vinyl pyridine.  Neoprene latex may also be used.  The synthetic resin may comprise a phenol-aldehyde resin of the Novolac type which is rendered insoluble and infusible on heating with a hardening agent, such as hexamethylene tetramine, e.g. a cashew-nut shell oil-modified phenolformaldehyde resin, or it may comprise a thermoplastic resin, e.g. polyvinyl acetal, a copolymer of styrene and acrylonitrile or butadiene, polyvinyl chloride, or a copolymer of vinyl chloride and a minor proportion of vinyl acetate.  In one example 17.12 parts by weight of wood flour are mixed with 36.47 parts of butadiene-acrylonitrile latex, 33.18 parts cashew nut shell oil-modified phenol-formaldehyde resin containing 8 per cent hexamethylenetetramine, 6.77 parts cryolite, 2.92 parts yellow iron oxide, and 1.12 parts paraffin wax.  The resulting mixture is heated in an oven at about 115 DEG  F. to evaporate the major proportion of water, and is then masticated in a twin-screw extruder with removal of the remaining water and other volatiles prior to extrusion.  The mixture is extruded in the required form, e.g. as a pipe or rod, and may be fed to a pelletizing apparatus.  In other examples the mixtures comprise (a) butadiene-acrylonitrile copolymer latex, polyvinyl formal, antioxidant and pigment; (b) butadiene-acrylonitrile copolymer latex, cashew nut shell oil-modified-phenolformaldehyde resin containing 8 per cent hexamethylenetetramine, diatomaceous earth, pigment, and carnauba and paraffin waxes; (e) butadiene-acrylonitrile copolymer latex, styrene-acrylonitrile copolymer, pigment, 2,6-di-t-butyl-cresol, antioxidant and zinc stearate; and (d) butadiene-acrylonitrile copolymer latex, polyvinyl chloride, resin stabilizers, zinc stearate and white mineral oil.  Specifications 632,722, 670,131, 721,340 and 766,429 and U.S.A.  Specifications 2,598,289, 2,615,199 and 2,669,485 are referred to.