Dynamically cured thermoplastic olefin polymers

DETAILED DESCRIPTION This invention relates to improved TPO compositions.
In particular it relates to compositions of a specific type of polyolefin resin and two rubbers, one of which is a halogenated butyl rubber and the other rubber is a polychloroprene.
The vulcanization or curing (i.
e.
, crosslinking) of the rubber is accomplished by dynamic vulcanization.
As used in the specification and claims, the term "dynamic vulcanization" means a vulcanization process for effecting crosslinking of a rubber-containing TPO composition wherein the rubber is vulcanized under conditions of high shear.
As a result, the rubber is simultaneously crosslinked and dispersed as fine particles of a "micro-gel" within a polyolefin matrix.
Dynamic vulcanization is effected by mixing the TPO ingredients at a temperature which is at or above the curing temperature of the rubber in equipment such as roll mills, Banbury mixers, continuous mixers, kneaders or mixing extruders, e.
g.
, twin screw extruders.
The unique characteristic of the dynamically cured compositions is that, notwithstanding the fact that the rubber component is fully cured, the compositions can be processed and reprocessed by conventional rubber and/or thermoplastic processing techniques such as extrusion, injection molding, compression molding, etc.
Scrap or flashing can be salvaged and reprocessed.
The term "dynamically vulcanized alloy" (DVA) as used in the specification and claims means a composition comprising a thermoplastic resin and a rubber wherein the rubber component has been dynamically vulcanized to a fully cured state.
The compositions are generally prepared by blending together the polyolefin resin and rubbers with curatives and fillers under conditions of dynamic vulcanization.
In preparing the preferred DVA compositions of this invention at least one ethylene copolymer polyolefin resin is blended with a halogenated butyl rubber and a polychloroprene rubber.
The term "ethylene copolymer resin" as used in the specification and claims means copolymers of ethylene with an alkyl ester of an alpha, beta monoethylenically unsaturated monocarboxylic acid as well as copolymers with the acid per se