Silicone-thermoplastic polymer reactive blends and copolymer products
Silicone-thermoplastic polymer reactive blends and copolymer products are prepared using economical post-reactor reactive mixing, e.g., extrusion. The procedure is based on the ring-opening polymerization of cyclic siloxanes within a thermoplastic polymer matrix. In a preferred mode, the thermoplastic polymer is a polyolefin, optionally containing silane groups that are available for reaction with the silicone polymer that is formed in situ. The resulting materials provide hybrid performance that can extend the range of applications beyond those which are served by thermoplastic polymers or silicones alone, or their physical blends.
1. A process for making a copolymer product comprising units derived from a polyethylene, a silane crosslinker and a silicone polymer, the process comprising the step of simultaneously contacting within a matrix of the polyethylene and under grafting and ring-opening and polymerization conditions, the polyethylene, the silane crosslinker and a cyclic siloxane such that the silane crosslinker grafts to the polyethylene, the cyclic siloxane polymerizes to form the silicone polymer that in turn combines with the silane-grafted polyethylene to form the copolymer product, wherein the silane crosslinker is at least one of vinyl trimethoxy silane, vinyl triethoxy silane, γ-(meth)acryloxy propyl trimethoxy silane and mixtures of two or more of these silanes.
2. The process of claim 1 in which the polymerization of the cyclic siloxane is facilitated with a catalyst.
3. The process of claim 2 in which the catalyst is a phosphazene base.
4. The process of claim 3 in which the cyclic siloxane is at least one of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, penta(methylvinyl)-cyclopentasiloxane, tetra(phenylmethyl)cyclotetrasiloxane and pentamethylhydro-cyclopentasiloxane.