Patent GB-743866-A (GB)
Title: Improvements in or relating to hollow particles
IPC: C08J9/32
Filed: 1953-05-11
Abstract: Gas-filled hollow particles are formed from film-forming material by a process which includes sub-dividing into individual droplets a solution comprising a volatile solvent having dissolved therein film-forming material and a latent gas material, and subjecting the droplets to a drying temperature at which the solvent is volatilized at a rate to form a tough, gas-impervious surface skin coincident with particle formation, and the latent gas material is converted into a gas, whereby gas liberated within said forming particle is trapped by the surface skin within the space thereof, thus forming particles having a continuous hole-free-skin surface.  Specified film-forming materials are polyvinyl alcohol, polyvinyl chloride, copolymers of vinyl chloride and vinyl acetate, polyvinyl butyral, polystyrene, polyvinylidene chloride, polymethyl methacrylate, polyethylene, polyamide resins, alkyds, polysiloxane, phenolformaldehyde, urea-formaldehyde, melamine-formaldehyde, cellulose acetate, cellulose acetate-butyrate, acetate-propionate, xanthate, cuprammonium cellulose, methyl and ethyl cellulose, soybean protein, zein protein and alginates.  The latent gas material may be a dissolved gas, e.g. ammonia, methyl chloride, dimethyl ether, ethylene oxide, methylamine, methyl bromide, dimethylamine or carbon dioxide or a substance which is decomposed at drying temperatures with formation of a gas, a large number of the usual flowing agents being specified for this purpose.  Specified solvents are water, alcohols, ethers, esters, organic acids, hydrocarbons, and chlorinated hydrocarbons.  In general, the film-forming material in solution is spray dried.  The product may be used as insulating material or as a filler for such articles as linoleum and floor tiles or as aggregate for concrete or plaster. The particles may be adhered together either by softening under pressure or by using a binder to form rigid or non-rigid materials and may then be used as the core of three-ply laminates.  They may also be used as compressible lubricants when bonded with polyethylene, oils and greases.ALSO:Hollow particles are formed from sodium aluminate or silicate by a process which includes subdividing into individual droplets a solution comprising a volatile solvent having dissolved therein the aluminate or silicate and a latent gas material and subjecting the drops to a drying temperature at which the solvent is volatilized at a rate to form a tough, gas-impervious surface skin coincident with particle formation, and the latent gas mixture is converted into a gas, whereby gas liberated within said forming particle is trapped by the surface skin thus forming particles having a continuous hole-free skin surface.  The latent gas material may be a dissolved gas, e.g. ammonia, methyl chloride, dimethyl ether, ethyleneoxide methyl amine, methyl bromide, dimethyl amine or carbon dioxide or a substance which is decomposed of drying temperatures with formation of a gas, a large number of the usual flowing agents being specified for this purpose.  Specified solvents are water, alcohols, ethers, esters, organic acids, hydrocarbons and chlorinated hydrocarbons.  In general the aluminate or silicate in solution is sprayed.  The product may be used as insulating materialALSO:Cements and plasters incorporate hollow particles formed from film-forming material by subdividing into individual droplets a solution of the film-forming material in a volatile solvent and a latent gas material and subjecting the drops to a drying temperature at which the solvent is volatilized at a rate to form a gas-impervious surface skin and then the latent gas material gasified, this gas being trapped by the surface skin.  In examples: (1) one part of Portland cement and from 3 to 9 parts of hollow particles made from phenol-formaldehyde or polyvinyl alcohol resin, with, if desired, a small proportion of sand were mixed and used to make light-weight concrete; (2) one part fibrous gypsum plaster and from 2-4 parts phenol-formaldehyde resin hollow particles were used to produce light-weight plaster.