| 摘要 |
A foam forming composition comprises a resin, e.g. copolymer of vinyl acetate and vinyl stearate or an alkyl acrylate and N-tert-butyl acrylamide, dissolved in a solvent propellent, e.g. trichlorofluoromethane, dichlorodifluoromethane, dichlorofluoromethane, 1,1,2-trichloro - 1,2,2 -difluoroethane, 1,1 - difluoro - 1 -chloroethane, vinyl chloride or dimethyl ether, with an inert filler, e.g. absorbent cotton or rayon fibres, derivatives of montmorillonite, microcrystalline cellulose, silica gel, silica or titanium dioxide. The components are placed in a can chilled in a dry ice-acetone bath, the can being then closed with a dispensing valve and agitated for 20 hours at 75 DEG F. to dissolve the resin in the solvent-propellent and dispense the filler. Paraffin, e.g. paraffin wax is added to produce a flexible foamed product, brittle resins being used to produce rigid foamed products.ALSO:Acrylic esters, e.g. 2-ethyl hexyl and n-butyl acrylates, are polymerized with acrylamides, e.g. N-tert-butylacrylamide, in ethyl acetate in the presence of benzoyl peroxide.ALSO:A wound cover comprising an air-pervious sheet of non-tacky, solvent-free foamed resin containing an inert filler is formed in situ or before application from a foam-forming composition comprising the resin dissolved in a solvent propellent with the filler suspended therein. The components are placed in a can chilled in a dry iceacetane bath, the can being then closed with a dispensing valve and agitated for 20 hours at 75 DEG F. to dissolve the resin in the solvent-propellent and disperse the filler. Resins which may be used are copolymers of vinyl acetate and vinyl stearate containing 10-30% by weight of vinyl stearate, or copolymers of an alkyl acrylate and N-tert-butyl acrylamide containing 30-70% of the alkyl acrylate by weight. Preferred solvent-propellents are trichlorofluoromethane, dichlorodifluoromethane or dichlorofluoromethane or mixtures of these, but 1, 1, 2-trichloro-1, 2, 2-difluoroethane, 1, 1-difluoro-1-chloroethane, vinyl chloride or dimethyl ether may be used. The resin may be placed in the can in the form of cut pieces of film. Flexible foam dressings are formed by using flexible resins and may include 1% to 3.7% paraffin e.g. paraffin wax. Rigid foam dressings are formed from brittle resins e.g. copolymers of 50% n-butyl acrylate and 50% N-tert-butyl acrylamide. The rigidity of the dressing is increased by increasing the proportion of n-butyl acrylate in the copolymer. For a rigid dressing the foam composition is applied over a polyurethane foam sheet on the body and is moulded by hand. Inert fillers used are chosen from absorbent cotton or rayon fibres, derivatives of martmorillonite, microcrystalline cellulose, silica gel, fine silica or titanium dioxide, the filler comprising 10-50% by weight of the solids in the preparation.
|
