Monovinylaromatic polymer with improved stress crack resistance
OwnerRaghava Reddy, Kenneth Blackmoninventors
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Abstract
The present invention discloses a composition of matter consisting of a high impact polystyrene exhibiting improved environmental stress crack resistance. The HIPS material is formed utilizing polybutadiene, polyisoprene, and copolymers thereof with styrene, having a Mooney viscosity exceeding about 35 and a gel content of up to about 28%. The present invention discloses the use of a combination of lubricant additives to obtain a HIPS material with higher ESCR values than either additive alone could provide, and also discloses the optimum level of each additive.
Claims10
A high impact monovinylaromatic polymer compound comprising:
- a rubber-modified polymer formed by the polymerization of a monovinylaromatic monomer in the presence of a rubber selected from the group consisting of natural rubbers, polybutadienes, polyisoprenes, and copolymers of butadienes or isoprene with styrene;
- and
- from about 1 wt. % to about 4 wt. % of an ESCR enhancing additive consisting essentially of polyisobutylene having a viscosity range of 196-233 cst at 99° C.
A process for producing a composition, comprising:
- polymerizing a mixture of a monovinylaromatic monomer and rubber, the monovinylaromatic monomer being selected from the group consisting of styrene, alphamethyl styrene and ring-substituted styrenes, and the rubber being selected from the group consisting of polybutadiene, polyisoprene, copolymers of butadiene or isoprene with styrene, and natural rubbers;
- and
- adding to the mixture of monomer and rubber, prior to or during the polymerizing process, at least one ESCR enhancing additive selected from alpha-olefins having the formula RCH═CH2, wherein R is a C4 to C50 alkyl group or mixtures of alpha-olefins, vinylidene compounds, internal olefins or saturated hydrocarbons.
Dependencies are inferred from the claim text.