Process for preparing normally crystalline vinylidene halide polymers having superior flow properties employing a combination of colloidal silica and non-ionic water soluble cellulose ether having a viscosity of about 5 cp or less as stabilizing agents
AssigneeThe Dow Chemical Company
InventorsRalph M. Wiley, Merritt R. Meeks, Burke A. Beebe
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Abstract
Normally crystalline vinylidene halide polymers are prepared by an improved limited coalescence suspension polymerization reaction wherein colloidal silica is used as a solid particle emulsifier, and a low molecular weight, non-ionic, water-soluble cellulose ether, having a viscosity grade less than about 35 centipoise, is used as the stabilizing agent. Spheroidal polymer particles are obtained having a generally uniform, small size and superior flow properties.
Claims7
In a process of making solid bodies of normally crystalline vinylidene halide polymers in the form of spheroidal globules comprising the steps of forming a mixture of a polymerizable liquid and an aqueous non-solvent liquid medium, the non-solvent liquid medium containing a water-dispersible, water-insoluble, colloidal solid particle emulsifier;
- mechanically agitating the mixture to disperse the polymerizable liquid as smaller-than-stable droplets in the non-solvent liquid medium;
- bringing the resulting unstable dispersion to a condition of quiescence, whereby the unstable droplets undergo a limited coalescence to form a stable suspension of droplets;
- treating the stable suspension with a stabilizing agent to prevent agglomeration of the droplets;
- and thereafter subjecting the suspension to polymerization conditions without high turbulence;
- the improvement which comprises employing in combination colloidal silica as the solid particle emulsifier, and a low molecular weight, non-ionic, water-soluble cellulose ether, having a viscosity grade of about 5 centipoise or less, as the stabilizing agent.
Dependencies are inferred from the claim text.