GB856943A - Drying of wet powdery materials - Google Patents

Abstract

A process for drying polymeric materials containing water which comprises introducing such a material by means of a gas stream into a cylindrical stream of hot gas externally confined by the walls of a tube system in such a manner that both streams have the same direction and the gas stream carrying the material is surrounded by the cylindrical stream of hot gas whereby the material is entrained by the combined cylindrical gas stream, keeping the material in the combined gas stream until the water has been substantially evaporated and thereafter removing the material from the combined gas stream. Polymeric materials specified are mixtures of thermoplastic polymers or co-polymers such as styrene-acrylonitrile co-polymers, and elastomeric co-polymers of butadiene and acrylonitrile and/or styrene, particularly co-polymers of butadiene and acrylonitrile may be used as elastomeric components of said mixtures, these co-polymers additionally containing monomers with self-crosslinking groups incorporated therein by polymerization, e.g., ethylenically unsaturated carboxylic acids, amides of ethylenically unsaturated carboxylic acids, ethylenically unsaturated aldehydes, co-polymerizable ethylenically unsaturated monomers containing at least one methylol or methylolether group, co-polymerizable ethylenically unsaturated monomers, containing at least one dioxolane residue in the molecule, co-polymerizable ethylenically unsaturated monomers containing at least one ureido radical and monomers having the formula <FORM:0856943/IV(a)/1> In the above polymeric materials the following substitutions may be made: (i) in the elastic copolymers butadiene may be replaced by isoprene, styrene by a chlorostyrene and part of the monomers by vinylchloride; and (ii) the thermoplastic polymer may be replaced by polyvinyl chloride or by copolymers of vinyl chloride with vinylidene chloride or vinyl acetate. The blending of the elastic and of the thermoplastic copolymers is preferably carried out by mixing the latices of said co-polymers as they are obtained by emulsion polymerization. These mixtures are then subjected to coagulation by well known methods. Other polymeric materials specified are a graft polymer produced from an aliphatic conjugated diene having 4 to 6 carbon atoms and a monoethylenically unsaturated monomer such as a monovinylaromatic compound, acrylonitrile and/or methacrylonitrile, and acrylonitrile polymers or co-polymers of acrylonitrile with about 1-20% of monomers. The example describes the drying of a polymeric material obtained by the co-coagulation of a latex of a co-polymer obtained by emulsion polymerization from butadiene with 35% by weight of acrylonitrile, 0,5% by weight of divinyl benzene and by 1,5% by weight of methacrylic acid and a latex of a co-polymer produced in aqueous emulsion from styrene with 25,2% by weight of acrylonitrile, which mixture of latices contains a dispersion of titanium dioxide. Specifications 358,534, 632,722, 636,965, 695,169, 744,455, 747,184, 754,722, 761,901, 792,874, 822,266, and U.S.A. Specifications 2,505,349, 2,550,139, 2,600,024, 2,680,735 2,802,808 and 2,802,809 are referred to.