Patent GB-808421-A (GB)
Title: Composite structures and methods for producing same
IPC: C08J9/34
Filed: 1955-08-04
Abstract: 808,421. Laminates. FARBENFABRIKEN BAYER A.G. Aug. 4, 1955 [Aug. 5, 1954 (2) ; Sept. 17, 1954], No. 22473/55. Drawings to Specification. Class 140. A composite structure comprises a core of plastic foam whose outer layer is reinforced by the inclusion in the foam of randomly arranged fibres or of fibrous flock and a skin bonded to the surface of the outer layer, said foam increasing stepwise in density from the centre of the core to the inner surface of the skin and the skin decreasing in density stepwise from its outer surface to its inner, core-contacting surface. The skins may be a combination of metal with plastic, plywood, a perforated hard fibre plate, or a perforated plate of wood shavings, or a combination of metal, plastic or wood with paper such as blotting paper, or a combination of steel plate and vulcanized fibre sheet, or thin metal such as aluminium-magnesium-copper alloy with polyester resin strengthened glass fabric (the polyester resins used being copolymerized with e.g. styrene), or aluminium combined with plywood. Acids, acid halides, inorganic or organic acid salts, e.g. p. toluenesulphonic acid, acetic acid or acetyl chloride may be added to the foam mixture to delay the foaming process. Lists of suitable acids, polyhydroxy compounds and polyisocyanates for forming polyurethane foams are given. Glass, synthetic, metallic or curled fibres e.g hair may be used to reinforce the foam as well as cotton, rayon and wool fibres. The fibres or flocks may be deposited by electrostatic precipitation on to the adhesively coated skins or may be affixed by adhesive thereto. The adhesive used may comprise copolymers of maleic acid-phthalic acidglycol polyester and styrene or phthalic acidadipic acid-glycol polyesters in conjunction with polyisocyanates with the possible addition of accelerators such as tertiary amines, or polyester isocyanates having a basis of adipic acid and glycols and stabilized with hydrogen chloride or acetyl chloride. The sprayed adhesive may be infra red heated to hasten copolymerization. The skin surfaces are degreased or, if metal, pickled before addition of the adhesive. Where paper or plywood is used as the skin material air permeable moulds may be used in the foam blowing process to enable the foam to penetrate the skin material. The inner foam core may be strengthened by the provision of local filling blocks of metal, wood, or plastic. In making the structures the assembled skins with fleeces adhesively in place on their inner sides are placed in a mould and foamable mixture applied to them, the mould is closed and the foam blown. For large area members, the skins may be given their adhered fibre coating and retarded foamable mixture applied to them by spatula and prevented from expanding by continuous smoothing until a uniform layer of fibre insert and polyurethane is formed. The structural units are then assembled and the hollow structure filled with foamable mixture, final foaming being effected before the initially applied foamable mixture has reacted completely. In examples: ( 1 ) aluminium-magnesium-copper alloy is bonded to a perforated hard fibre plate by means of an adhesive made by reacting an ethyl acetate solution with an adipic acid-1,3 butylene glycol-trimethylol propane polyester with tolylene diisocyanate. Glass fibre fleeces are stuck to these covering layers with the above adhesive and the cavity between the layers is filled with a foamable mixture of a polyester of adipic acid, phthalic anhydride, trimethylol propane and 1,3 butanediol ; a polyester of adipic acid, hexanetriol and butanediol ; bis-(diethylaminoethanol) adipate ; diethylamine oleate; sulphonated castor oil containing water ; tolylene diisocyanate. (2) Plywood or a polyester resin plate is bonded to aluminium by means of an adhesive consisting of malefic acid-glycol polyester, styrene, benzoyl peroxide, dibutyl phthalate and dimethyl anilene diluted with methylene chloride. This covering layer is sprayed with the above adhesive and provided electrostatically with polyamide flock. The structural members are assembled and filled with a mixture of a polyester of adipic acid, hexanetriol and phthalic acid ; a polyester of adipic acid, 1,3 butylene glycol and trimethylol propane; silicic chalk; an activator mixture consisting of bis-(N-diethylaminoethanol) adipate, sulphonated castor oil containing water and diethylamine oleate; tolylene diisocyanate The structures may be used as construction members for refrigerators, motor vehicles, ships, aircraft, houses, as floating equipment, e.g. buoys, water-skis, in doors, window frames, roof constructions, tanks, as insulating plates, and in radio and television cabinets.