| 摘要 |
1,194,492. Tobacco smoke filters. ROBERT L. STRICKMAN FOUNDATION Inc. 3 May, 1968, No. 21206/68. Heading A2C. [Also in Division C3] A filter for aerosols (particularly tobacco smoke) containing as filtering material rigid polyurethane particles essentially devoid of celullar structure. The filter material may be produced by reacting a polyisocyanate and a polyol in amounts sufficient to provide a ratio of reactive isocyanate groups to organic hydroxyl groups of between 0.75 and 1.25 to produce a rigid polyurethane in the presence of sufficient blowing agent that the rigid polyurethane shall be produced as a foam having a density of less than 3 pounds per cubic foot, granulating the resulting rigid foam to produce particles essentially devoid of cellular structure, perferably having a particle size of less than 750 microns, subjecting the granules to a treatment with hot water or steam, and drying the product. It is preferred to employ water-soluble acid salts of metals of groups VA and VIA of the Periodic Table, e.g. alkane tungstates, molybdates, vanadates and chromates and alkyl silicates in the preparation of the intermediate polyurethane foam. The particulate polyurethane filter material is desirably mixed with inorganic additives such as aluminium hydroxide, magnesium trisilicate and carbonates, silicates or hydroxides of alkaline earth metals. These additives may have the same particle size as for the polyurethane particles. Mixtures of aluminium hydroxide and magnesium trisilicate are preferably employed as a 1 : 1 mixture by weight in amounts of between 3 and 15% by weight of the filter material. The dried granules of filter material with or without inorganic additives may be filled into the open tubular end of a cigarette and are prevented from falling out by a small plug of cotton or other suitable material. |
