Patent GB-950218-A (GB)
Title: Improvements in or relating to production of pulverized resins and polymers
IPC: B29B13/00
Filed: 1961-09-12
Abstract: A process of pulverizing a normally solid synthetic polymer comprises forming a solid polymer by the incorporation therein during polymerization or after polymerization of an organic solvent, treating the resultant swollen polymer with steam to remove the imbibed organic solvent and to displace the same with water, and mechanically crushing the resultant porous water-containing polymer at a temperature below its softening point.  The polymer may also be dried after the steam treatment and in that event is pulverized in the presence of an added liquid.  The process is applicable to the treatment of polystyrene, or polyvinyl chloride but is particularly useful for the preparation of finely divided powders of polymers of 1-olefins having up to 8 carbon atoms in the molecule. Swelling agents specified are aliphatic, aromatic, hydroaromatic, oxygenated and chlorinated hydrocarbons.  In Examples (1) to (6) a polymer is prepared by solution polymerization in mineral spirits of the appropriate monomers in the presence of a solid catalyst.  The solvent-containing polymer obtained, (after removal of the catalyst) is subjected to steam distillation for removal of solvent.  The products, containing imbibed water, are then pulverized. Polyethylene and ethylene-propylene copolymer are treated by this method. In example (4) isopropyl alcohol is also incorporated before the pulverization. In other examples (7) polyvinyl chloride which has been swollen with dioxane and then subjected to steam-distillation and drying, is pulverized in contact with alcohol; (8) polystyrene which has been swollen with benzene followed by steam-stripping and drying is pulverized in the presence of added water.  Specifications 734,501 and 748,634 are referred to.ALSO:A process of pulverizing a normally solid synthetic polymer comprises forming a solid polymer by the incorporation therein during polymerization or after polymerization of an organic solvent, treating the resultant swollen polymer with steam to remove the imbibed organic solvent and to displace the same with water, and mechanically crushing the resultant porous water-containing polymer at a temperature below its softening point.  The polymer may also be dried after the steam treatment and is then pulverized in the presence of an added liquid.  The process is applicable to the treatment of polyvinyl chloride or polystyrene but is particularly useful for the preparation of finely divided powders of polymers of 1-olefins having up to 8 carbon atoms in the molecule.  Swelling agents specified are aliphatic, aromatic, hydroaromatic, oxygenated and chlorinated hydrocarbons.  In Examples (1) to (6) a polymer is prepared by solution polymerization in mineral spirits of the appropriate monomers in the presence of a solid catalyst.  The solvent-containing polymer obtained (after removal of the catalyst) is subjected to steam distillation for removal of solvent.  The products are then mechanically pulverized. Polyethylene and ethylene-propylene copolymers are treated by this method.  In Example (4) isopropyl alcohol is also incorporated before the polymerization.  In other examples (7) polyvinyl chloride which has been swollen with dioxane and then subjected to steam distillation and drying, is pulverized in contact with alcohol; (8) polystyrene which has been swollen with benzene followed by steam-stripping and drying is pulverized in the presence of added water.  Specifications 734,501 and 748,634 are referred to.