Patent GB-983405-A (GB)
Title: Improvements relating to fibre-reinforced polyester structures
IPC: E04C2/22
Filed: 1961-06-23
Abstract: 983,405. Laminates. E. I. DU PONT DE NEMOURS & CO. June 23, 1961 [June 24, 1960], No. 22883/61. Heading B5N. A composite structure consists essentially of a substrate of cured, fibre-reinforced organic polyesters and a surface of polyvinyl fluoride film chemically bonded to said substrate. The substrate may consist of a cured glass-fibre-reinforced organic polyester which may contain an ultraviolet light-absorbing compound. The polyvinyl fluoride film may be biaxially oriented and, prior to bonding, may exhibit a shrinkage on being held without restraint at 60 C. for 3 minutes in a circulating air oven, of 0À2 to 5% in each direction of stretch and it, also, or alternatively, may contain an ultra-violet light absorbent compound. Such structures may be made by a process wherein a mixture consisting essentially of (a) at least one organic linear polymeric ester containing recurring ethylenic unsaturation, (b) at least one addition polymerizable ethylenically unsaturated organic monomer, and (c) reinforcing fibres is subjected to addition-polymerization conditions effective to produce from it a cured fibre-reinforced polyester structure in a mould surfaced with a mould-release agent consisting essentially of a preformed solid film of polyvinyl fluoride having a chemically reactive free surface (that is, the surface of the film which is not in contact with the mould.) The polyvinyl fluoride film may be biaxially oriented. Unsaturated polymeric esters suitable for use in the invention may be obtained by condensing under polymerizing conditions either (a) an ethylenically unsaturated dicarboxylic acid with a diol containing no ethylenic unsaturation, (b) a dicarboxylic acid containing no ethylenic unsaturation with an ethylenically unsaturated diol, or (c) a mixture of ethylenically unsaturated dicarboxylic acid and dicarboxylic acids containing no ethylenic unsaturation, with a diol containing no ethylenic unsaturation. Stable dichlorides, diesters or anhydrides of the dicarboxylic acids, where available, may be substituted for the free acids. Suitable ethylenically unsaturated dicarboxylic acids or derivatives are fumaric acid, maleic acid and its anhydride, citraconic acid, mesaconic acid, itaconic acid and endomethylene tetrahydrophthalic acid. Suitable dicarboxylic acids or derivatives thereof containing no ethylenic unsaturation are phthalic acid and its anhydride, adipic acid, sebacic acid, isophthalic acid, terephthalic acid, malonic acid, succinic acid and glutaric acid. A suitable ethylenically unsaturated diol is 2-butene-1,4 diol. Suitable diols containing no ethylenic unsaturation are ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol. Suitable addition monomers are styrene, diallyl phthalate, methyl methacrylate, triallyl cyanurate, α-methylstyrene, divinyl benzene, vinyl toluene, allyl diglycollate, methyl acrylate, ethyl acrylate, ethyl methacrylate, vinyl acetate, acrylonitrile, diallyl maleate, vinyl phenol and allyl carbamate. Specified fibres are glass, asbestos, nylon, cellulosic and like mineral and organic fibres. Glass fibres may be used in the form of cloth, yarns, mats, rovings, milled fibres, parallel strands, surfacing mats and loose fibres. Fillers such as pigments, clays, mica, silica and talc may be incorporated into the mixtures prior to curing. Heat may be used to accelerate the reaction, and also accelerators such as cobalt naphthenate, phenyl phosphinic acid, p-toluene sulphonic acid, and dimethylaniline. Catalytic initiators such as benzoyl peroxide, t-butyl peroxide, di-t-butyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, organic azo compounds and lauryl peroxide may also be used. The structures may be made by lowpressure moulding techniques including the use of vacuum bag, pressure bag and matched metal dies. Suitable polyvinyl fluoride film may be made by feeding a mixture of a latent solvent and particulate polyvinyl fluoride to a heated extruder connected to a slotted casting hopper whence a tough coalesced gel polyvinyl fluoride film is continuously extruded. This film may be stretched longitudinally over heated rolls and then transversely in a tenter frame, in which it is held while the remaining latent solvent is volatilized. An ultra-violet lightabsorbing compound may be incorporated into the polyvinyl fluoride film or be chemically bonded on to the surface thereof by the use of polyisocyanates. Suitable ultra-violet light absorbent compounds are 2,2<SP>1</SP>-dihydroxy-4,4<SP>1</SP>- dimethoxy - benzophenone, 2,2<SP>1</SP> - 4,41 - tetrahydroxy - benzophenone, 2 - hydroxy - 4,4<SP>1</SP> - dimethoxy - benzophenone, 2,4 - dihydroxy - benzophenone, 2-hydroxy-4-decyloxybenzophenone and phenyl-1, 3-benzotriazole. The preformed solid polyvinyl fluoride film must have a chemically reactive free surface, i.e. at least one of its surfaces should contain one or more functional groups consisting of ethylenic carbon: carbon double bonds, or hydroxyl, carboxyl, carbonyl, amino or amido groups. The chemically reactive surface may be obtained (a) by passing the film through a chamber containing a gaseous mixture containing boron trifluoride followed by a water wash and drying in air or heating briefly; or (b) by contacting the film with concentrated sulphuric acid, fuming sulphuric acid or sulphur trioxide, followed by water wash and air-drying; or (c) by immersing the film briefly in liquid phase boron trifluoride etherate complexes followed by a water-wash or ether-wash and heating in air; or (d) by passing the film over a chilled metal drum while the surface away from the drum passes through the flame of a gas burner; or (e) by H.F. spark discharge treatment by passing the film in an atmosphere of nitrogen, over an earthed metal drum while the surface away from the drum passes under and in close proximity to a rod or bar serving as an electrode and connected to a source of H.F. alternating voltage. Examples disclose the preparation of structures by placing a piece of polyvinyl fluoride film on a flat glass plate, forming a dam around the edges of the film with a length of twine, pouring on to the film a degassed blend of polyester composition and allowing it to spread evenly over the area bounded by the twine. Next a piece of chopped strand fibre glass mat is placed in the polyester layer and when the resin mixture has welled up through the interstices of the mat a second piece of polyvinyl fluoride film is placed on top followed by another glass plate and sufficient extra weight to establish a suitable pressure over the area. The entire sandwich is then placed in an oven and subjected to the curing cycle. The resulting panels exhibited unbroken surfaces of polyvinyl fluoride film over a substrate of cured polyester. A typical panel is illustrated in cross-sectional view in the Figure. Structures producible by the invention include boats and parts thereof, life rafts and containers therefor, automobile and other vehicle bodies and parts, radomes, shelters, kiosks, buoys, aircraft rotor and wing parts, furniture, swimming pools, tanks, signs, safety helmets, skis, sleds and the like, luggage, and roofing and other building components. Specifications 845,634, 892,264, and 936,398 are referred to.