Patent GB-1453516-A (GB)
Title: Method for continuous extrusion moulding of thermosetting resins
IPC: B29C48/12
Filed: 1974-01-18
Abstract: 1453516 Moulding thermosetting compositions DAI NIPPON TORYO CO Ltd 18 Jan 1974 02521/74 Heading B5A A composition comprising a thermosetting resin, a thermoplastic resin in an amount of up to 50% of the total weight of resin, a filler, a fibrous material, and a curing agent, is continuously delivered to the outlet of a screw extruder in an uncured condition, and is cured under pressure within moulding means during continued continuous delivery from the outlet. At the outlet, the resin has a "needle penetration" (as defined) of at least 20, and the curing is effected for 1 second to 5 minutes at a resin temperature of 80 to 250 C., and a pressure of not higher than 200 kg./cm.<SP>2</SP>. In the Fig. 2 embodiment, for the production of a tube 21, the resin is frictionally heated by the extruder screw 3, during passage through the extruder barrel which may be cooled, or heated, by medium in passages 4, 5, 6. The extruder die 11 is heated by medium in passages 12 to obtain the desired needle penetration, prior to delivery into the moulding means comprising opposed mould parts 14, 15, which are heated by fluid medium passages 18, 19, and between which the required pressure is maintained by cylinders 16, 17. The mould parts 14, 15 may remain stationary, or may be reciprocated away from and towards the die by cylinders 22, 23, with simultaneous transverse reciprocation by cylinders 16, 17 to respectively engage and disengage the extrudate. In the Fig. 3 embodiment (not shown) a sheet is extruded between moulding means comprising a pair of opposed heated endless belts, which move in the extrusion direction. In the Fig. 4 embodiment, a tube 44 is extruded through a heated die 43 comprising the moulding means, within which the required pressure is maintained by compressed air admitted from location 45, and retained by a plug 46 in the tube end. In the Fig. 5 embodiment (not shown) the pressure is alternatively maintained within the extruded tube by the moulding means comprising an open-ended die, through perforations of which a reduced pressure is applied to the tube exterior. The heating to effect curing may also be effected by hot air, infra red, or induction. Further curing may also be effected after the moulding means. The extrusion may also comprise a coating. The resin may comprise numerous unsaturated polyester, phenolic, epoxy, urethane (which may be foamed) and allyl resins, or mixtures of two or more thereof. Various additives are specified, including the fillers, lubricants, blowing agents, and the fibrous material may comprise glass, steel, organic fibres or carbon or asbestos. The thermoplastic resins, with polyester resins, are of average molecular weight of at least 10,000, e.g. 25,000 to 500,000 and preferably comprise 1 to 20% and preferably 5 to 15% by weight. In the Examples: (1) a tube is extruded and passed through a die attached to the extruder, the composition comprising a specified polyester resin incorporating polyvinyl chloride, barium sulphate and asbestos fibres; (2) a tube is extruded using the apparatus of Example (1), and the same polyester resin incorporating polyvinyl chloride, calcium carbonate, and organic fibres; Figs. 6 and 7 (not shown), illustrate the relationship between needle penetration and temperature, respectively for a phenolic and an unsaturated polyester resin.