Polymer compositions comprising mixtures of polyolefins
The invention provides a polyolefin composition comprising (i) a polyolefin (A) comprising epoxy groups; and (ii) a polyolefin (B) comprising carboxylic acid groups and/or precursors thereof, with the proviso that at least one of (A) and (B) is polyethylene. Preferably one of (A) and (B) is a low density polyethylene (LDPE) and the other is a polypropylene.
1. A polyolefin composition comprising:
(i) 50 to 98 wt % relative to the total weight of the composition as a whole of a polyolefin (A) comprising epoxy groups; and
(ii) 2 to 50 wt % relative to the total weight of the composition as a whole of a polyolefin (B) comprising carboxylic acid groups and/or precursors thereof,
wherein polyolefin (A) is a low density polyethylene (LDPE) and polyolefin (B) is a polypropylene.
2. The polyolefin composition as claimed in claim 1 , wherein the carboxylic acid groups and/or precursors thereof are grafted to said polyolefin (B).
3. The polyolefin composition as claimed in claim 1 , wherein the carboxylic acid groups and/or precursor thereof is at least one of acrylic acid, maleic anhydride (MAH), or an alkyl (meth)acrylate.
4. The polyolefin composition as claimed in claim 1 , wherein component (i) is present in an amount of 90 to 98 wt % and component (ii) is present in an amount of 2 to 10 wt %, relative to the total weight of the composition as a whole.
5. The polyolefin composition as claimed in claim 1 , wherein the epoxy groups are present in the form of an epoxy-group-containing comonomer.
6. The polyolefin composition as claimed in claim 5 , wherein said epoxy-group-containing comonomer is selected from the group consisting of 1,2-epoxy-9-decene, 1,2-epoxy-5-hexene, 3,4-epoxy-1-butene, glycidyl methacrylate, glycidyl acrylate, and allyl glycidyl ether.
7. The polyolefin composition as claimed in claim 1 , wherein said LDPE has an MFR 2 (2.16 kg, 190° C.) of 0.1 to 10 g/10 min.
8. The polyolefin composition as claimed in claim 1 , wherein said LDPE has a density of 917 to 935 kg/m 3 .
9. The polyolefin composition as claimed in claim 1 , wherein said polypropylene has a melting temperature (Tm) of greater than 140° C.
10. The polyolefin composition as claimed in claim 1 , wherein said composition is substantially free of peroxide.
11. A process for crosslinking the polyolefin composition as defined in claim 1 , wherein said process comprises heating said polyolefin composition to a temperature greater than the melting point of at least the major polymer component(s) of the composition.
12. The process as claimed in claim 11 , wherein said process does not use peroxide.
13. A cable comprising one or more conductors surrounded by at least one layer, wherein said layer comprises the polyolefin composition as defined in claim 1 .
14. The cable as claimed in claim 13 , wherein said one or more conductors are surrounded by at least an inner semiconductive layer, an insulation layer, and an outer semiconductive layer, in that order.
15. The cable as claimed in claim 13 , wherein said layer comprising said polyolefin composition is an insulation layer.
16. The cable as claimed in claim 13 , wherein said cable is crosslinked.
17. A process for producing a cable comprising the steps of: applying on one or more conductors, a layer comprising the polyolefin composition as defined in claim 1 .
18. A method of use of the polyolefin composition as defined in claim 1 , the method comprising using the polyolefin composition in an insulation layer or semi-conductive layer in a cable.