Encapsulating metal parts with thermoplastic by injection moulding - has metal part first coated with heat-reactivatable adhesive which is activated by heat and pressure of thermoplastic during moulding

摘要

Metal part is coated with a heat-reactivatable adhesive (I) and the coating is allowed to dry to a solid. The metal part is then encapsulated with a thermoplastic (II), whereby (I) is activated by temp. and pressure of (I) introduced into the mould, a firm bond being formed between metal part and (II). Metal part is of steel, steel alloy, Al, or light metal alloy and its surface has been pretreated by brushing, sand blasting, filing with roughening, and/or by applying inorganic, nonmetallic coating by chemical means, partic. phosphatising, epoxidising, anodising, or chromatising. (I) is crystallising polyurethane dissolved in ethyl methyl ketone and diluted with Et acetate in ratio 1:2 to 1:5 applied in 1 or more coatings. Max. 20 wt.% of polyisocyanate, dissolved in Et acetate in ratio 1:2 to 1:4, is added to this soln.. Before metal part is coated with (I) it is coated with conventional primer soln. of organic resins and/or polymers in organic solvent. Encapsulation is carried out at latest 2 hours after last coating with (I). (II) is polyurethane, polyester-block-amide, ABS, polycarbonate, or polyoxymethylene. (II) contains up to 30 wt.% mineral filler, partic. glass or C fibres, rock flour, or metal powder. ADVANTAGE - Good bonding is obtd. between metal part and coating of (II) on encapsulating parts by injection moulding (rapid process, suitable for mass prodn.), and is retained on cooling.