Process for molecular weight lowering of vinyl halide polymers employing saturated carbon to carbon bonded aldehydes
AssigneeHooker Chemicals & Plastics Corporation
InventorLeigh E. Walker
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Abstract
Vinyl halide homopolymers, copolymers and graft polymers of substantially lower molecular weight are obtained when polymerization is carried out in bulk in the presence of a small concentration in the polymerization reaction mass of an aldehyde which is devoid of ethylenic and acetylenic unsaturation and which contains at least one carbon to carbon bond. The polymers are obtained without substantial lowering of the polymerization conversion rate and are characterized by excellent fusion properties and improved solubility in organic solvents, which properties render the products useful in molding, extrusion, coating and solution casting applications.
Claims11
In the process for preparation of a vinyl halide homopolymer, vinyl halide copolymer or vinyl halide graft polymer containing up to about 50% by weight of comonomer devoid of aldehyde substituents and/or a compatible back-bone polymer by bulk liquid phase polymerization which comprises:
- 1. polymerizing a vinyl halide monomer composition comprising 0% to about 50% by weight of said comonomer and/or said back-bone polymer at a temperature of about -60.degree. C to about 90.degree. C;
- 2. recovering the resulting vinyl halide polymer from said monomer or monomers, the improvement which comprises carrying out at least part of the polymerization in the presence of a small molecular weight-lowering amount of an aldehyde which is devoid of ethylenic and acetylenic unsaturation and which contains at least one carbon to carbon bond, whereby the molecular weight of the vinyl halide polymer product is substantially lowered without substantial lowering of the rate of conversion of vinyl halide to polymer, said amount of aldehyde being less than about 10 weight percent based on the weight of polymerization mixture.
A two-stage liquid phase bulk process for the preparation of a low molecular weight vinyl chloride polymer wherein said bulk polymerization is carried out at about -60.degree. C to about 90.degree. C and comprises the steps of
- 1. polymerizing in the first stage a vinyl chloride composition comprising 0% to 50% by weight of a comonomer devoid of aldehyde substituents while subjecting the reaction mixture to high speed agitation until about 3 weight percent to about 15 weight percent of said monomer or monomers have polymerized,
- 2. subjecting the resultant reaction mixture to low speed agitation in the second stage to complete the polymerization in the presence of a small molecular weight lowering amount of an aldehyde of 2 to 30 carbon atoms devoid of ethylenic and acetylenic unsaturation and,
- 3. recovering the resulting polymer from unreacted monomer or monomers, whereby the vinyl chloride polymer product is of lower molecular weight than the corresponding polymer obtained by polymerization in absence of said aldehyde but the conversion rate of vinyl chloride to polymer is at least substantially the same as that of the polymerization carried out in absence of said aldehyde.
Dependencies are inferred from the claim text.