Crosslinked porous skinless particles of PVC resin and process for producing same
AssigneeThe B. F. Goodrich Company
InventorRoss J. Cozens
Life of this patent
Estimating the term…
Abstract
Porous particles of crosslinked PVC are disclosed. the particles are skinless and have a fast powder mix time. Processes to produce the novel particles are also disclosed.
Claims32
An agitated aqueous suspension process for producing porous, skinless, agglomerated, crosslinked polyvinyl chloride resin particles comprising polymerizing vinyl chloride monomer together with at least one crosslinking agent in the presence of from about 0.01 part by weight to about 0.1 part by weight per 100 parts by weight of polymerizable monomer of at least one ionic sensitive primary dispersant capable of thickening water, and at least one secondary dispersant, wherein an a monovalent inorganic or organic ionic compound in amounts sufficient to desorb a substantial amount of said primary dispersant off the monomer droplets, is charged to the polymerization medium at from about 1% to about 5% conversion of monomer to polymer, thereby producing a skinless, agglomerated, crosslinked, porous PVC resin in particulate form, said resin particles having a mercury porosity of from about 0.1 cc/g to about 0.8 cc/g, and a particle size of from about 70 microns to about 1000 microns, and a friability of less than about 2, and a powder mix time of less than about 400 seconds, and a shape factor less than about 0.85 and wherein greater than about 20% of the area of surface of said particle is PVC as measured by ESCA.
A process for producing porous, crosslinked, skinless, agglomerated vinyl resin particles in an aqueous medium comprising:
- (a) charging water and at least one ion sensitive primary dispersant(s) capable of thickening water to polymerization vessel equipped with agitation and cooling means;
- (b) agitating said water and said dispersant(s);
- (c) reducing or stopping said agitation such that non-turbulent flow is achieved;
- (d) charging at least one vinyl monomer together with at least one crosslinking agent to the polymerization vessel such that there is formed two liquid layers in the polymerization vessel, a bottom thickened aqueous layer and a top vinyl monomer layer;
- (e) charging to the top vinyl monomer layer a solution comprising at least one catalyst, at least one solvent, and at least one secondary dispersant, wherein said solvent has a density equal to or less than the vinyl monomer(s) being polymerized and said catalyst solution has a density less than 1.0 gg/cc;
- (f) allowing said catalyst to diffuse through the vinyl monomer top layer;
- (g) increasing the agitation such that the entire polymerization medium is emulsified to form monomer droplets suspended in an aqueous polymerization medium;
- (h) conducting the polymerization of the vinyl monomer to a conversion of from about 1% to about 5%;
- (i) charging an a monovalent inorganic or organic ionic compound to the polymerization medium in amounts sufficient to substantially desorb the primary dispersant off the monomer droplets;
- (j) continuing the polymerization of the vinyl monomer to form porous, crosslinked, agglomerated, skinless resin particles;
- (k) removing the polymerized resin from the reaction vessel, said resin particles having a mercury porosity of from about 0.1 cc/g to about 0.8 cc/g, and a particle size of from about 70 microns to about 1000 microns, and a friability of less than about 2, and a powder mix time of less than about 400 seconds, and a shape factor less than about 0.85 and wherein greater than about 20% of the area of the surface of said particle is PVC as measured by ESCA.
Dependencies are inferred from the claim text.