Process for crosslinking thermoplastic polymers with silanes employing peroxide blends and the resulting crosslinked thermoplastic polymers
View Patent ↗A composition comprising at least one silane possessing an unsaturated organic function; at least two free radical initiators, and a process for producing silane-crosslinked thermoplastic polymers comprising providing a cross-linkable compound; at least one thermoplastic polymer; and, reacting the crosslinkable compound under reactive mechanical-working conditions and exposing the crosslinkable compound to moisture to provide crosslinked thermoplastic polymers.
1. A composition comprising:
(i) at least one silane possessing an unsaturated organic function;
(ii) at least two free radical initiators, the first initiator having a first 0.1 hour half-life temperature and the second initiator having a second 0.1 hour half-life temperature, said second half-life temperature being between 30° C. and 90° C. higher than said first half-life temperature;
(iii) optionally one or more condensation catalysts;
(iv) optionally, one or more stabilizers, stabilizer packages, inhibitors or free radical scavengers;
(v) optionally, additives such as fillers, colorants and processing aids; and,
(vi) at least one thermoplastic polyolefin selected from the group consisting of high-pressure low-density polyethylene, medium/low-pressure high-density polyethylene, low-pressure low-density polyethylene, medium-density polyethylene, an ethylene-α-olefin copolymer, polypropylene, an ethylene-ethyl acrylate copolymer, an ethylene-vinyl acetate copolymer, an ethylene-propylene copolymer, an ethylene-propylene-diene terpolymer, an ethylene-butene copolymer, polymethyl-pentene-1, polybutene, chlorinated polyethylene, an ethylene-vinyl acetate-chlorine terpolymer, and mixtures thereof.
2. The composition of claim 1 wherein the silane possesses the general formula RR′SiY 2 wherein R represents a monovalently olefinically unsaturated hydrocarbon radical or a radical selected from the group consisting of
each Y represents a hydrolysable organic radical and R′ represents an R radical or a Y radical.
3. The composition of claim 2 wherein the R radical is selected from the group consisting of vinyl, allyl, butenyl, cyclohexenyl, cyclopentadienyl, and cyclohexadienyl.
4. The composition of claim 2 wherein the group Y represents a hydrolysable organic radical selected from the group consisting of alkoxy radicals, acyloxy radicals, oximato radicals and amino radicals.
5. The composition of claim 2 wherein the silane is vinyl triethoxysilane and/or vinyl trimethoxysilane.
6. The composition of claim 1 wherein the 0.1 hour half-life temperature of the first free radical initiator is from about 80° to about 160° C.
7. The composition of claim 1 wherein the 0.1 hour half-life temperature of the first free radical initiator is from about 90° to about 155° C.
8. The composition of claim 1 wherein the 0.1 hour half-life temperature of the second free radical initiator is from about 125° to about 190° C.
9. The composition of claim 1 wherein the 0.1 hour half-life temperature of the second free radical initiator is from about 140° to about 170° C.
10. The composition of claim 6 wherein the first free radical initiator is selected from the group consisting of di(2,4-dichlorobenzoyl) peroxide, tertbutyl peroxypivalate, dilauroyl peroxide, dibenzoyl peroxide, tert-butyl peroxy-2-ethylhexanoate, 1,1 -di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, di(tert-butyl peroxy)cyclohexane, tert-butyl peroxy-3,5,5 -trimethylhexanoate, tert-butyl peroxyacetate, tert-butyl peroxybenzoate, di-tert-amyl peroxide, dicumyl peroxide, di(tert-butylperoxyisopropyl)benzene and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.
11. The composition of claim 8 wherein the second free radical initiator is selected from the group consisting of tert-butyl peroxyacetate, tert-butyl peroxybenzoate, di-tert-amyl peroxide, dicumyl peroxide, di(tert-butyl peroxyisopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl cumyl peroxide, 2,5-dimethyl-2,5 -di(tert-butylperoxy)hexyne-3 and di-tert-butyl peroxide.
12. The composition of claim 1 further comprising at least one additional component selected from the group consisting of oils, plasticizers, pigments and lubricants.
13. The composition of claim 1 where catalyst is a metal carboxylate, an organic metal compound, an organic base, or an acid.
14. The composition of claim 13 where metal carboxylate is dibutyltindilaurate, stannous acetate, stannous octoate, lead naphthenate, zinc octoate, iron-2-ethylhexoate, or cobalt naphthenate.
15. The composition of claim 13 where organic metal compound is a titanium ester or a titanium chelate.
16. The composition of claim 15 where a titanium ester or a titanium chelate is a tetrabutyl titanate, tetranonyl titanate, or bis-(acetylacetonyl) di-isopropyl titanate.
17. The composition of claim 13 where an organic base is ethylamine, hexylamine, dibutylamine or piperidine.
18. The composition of claim 13 where an acid is a mineral acid or a fatty acid.