Method of preparing vinyl halide polymers and copolymers with polyolefins

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS THEREOF Except for the above-defined improvements of the invention, the reactants and reaction conditions, e.
g.
reaction temperature and pressure, are substantially the same as those of the polymerization disclosed in the aforementioned U.
S.
applications, Ser.
Nos.
746,046 and 674,202, the disclosures of which are incorporated herein by reference.
The vinyl halide utilized in the present process is preferably vinyl chloride, although other vinyl halides such as vinyl fluoride and vinyl bromide can be employed also.
In carrying out the present improved process the vinyl halide monomer can be removed from the thick paste state of the agitated polymerization reaction mass in any suitable way.
For example, the liquid monomer may be filtered from the bulk reaction mass e.
g.
by passage through a pressure filter.
The filtrate is then distilled outside the reaction vessel with the distillation residue containing initiator and unreacted polyolefin being returned to the reaction vessel.
However, since the polymerization is generally carried out under at least autogeneous superatmospheric pressure, especially when vinyl chloride is employed as the vinyl halide reactant, removal of the vinyl halide is preferably achieved by venting the reaction mixture to a pressure zone e.
g.
the atmosphere, wherein the pressure is substantially below the reaction pressure.
Removal by venting is especially desirable since it promotes rapid removal of heat from the reaction mass.
Vinyl halide monomer removal is commenced during the above-described thick paste state of the reaction the duration of which corresponds to conversion to polymer of about 25% to about 45%, more typically about 30% to about 40% by weight of vinyl halide, based on vinyl halide charged.
The onset of the thick paste state is generally accompanied by a rapid increase in the heat evolved from the reaction, i.
e.
by a rapid increase in the reaction isotherm as evidenced by a sharp increase in reaction pressure