| 摘要 |
Foams of decreased inflammability are produced by foaming or sintering mixtures of combustible synthetic macromolecular substances, or precursors thereof, with elemental sulphur so that at least 2% by weight of sulphur is retained in a surface layer 1 mm. deep, irrespective of the elemental sulphur content in other parts of the cellular structure. The sulphur is preferably present in this layer in proportions between 5 and 35% by weight, and it may be evenly distributed up to a maximum of 50% in the mixture from which the foam is prepared. The macromolecular substance may be polystyrene, polyurethane, a polyolefin, a polyacetal, a polyether or a polyester. Examples include the addition of sulphur to prefoamed polystyrene beads in a mould and subsequent expansion, and the suspension of sulphur in a polyhydric alcohol and subsequent reaction with a polyisocyanate to produce a polyurethane foam. Other flame retardants may also be incorporated, e.g. organic halogen compounds and organic phosphorus compounds, especially tris (2,3-dibromopropyl) phosphate, and antimony compounds. The sulphur may be dispersed in a plasticizer before addition, or may be mixed with or adsorbed on an inert material, e.g. clay or kieselguhr, or may be dissolved in a solvent, e.g. CS2 or naphthalene, or may be coated with substances such as starch, polyvinyl alcohol and polyvinyl acetate, or mixed with molten polystyrene, solidified and ground. |
