Tie based on grafted polyethylene and on high-impact or crystal polystyrene with cohesive failure
The invention relates to a tie comprising a blend of grafted polyethylene (PE), of grafted or ungrafted high-impact or crystal polystyrene and optionally of ungrafted PE. The grafted PE is preferably composed of two different cografted PEs. This tie is of use in the manufacture of multilayer structures intended for the field of Civil Engineering Works (CEW), more particularly for the fields of aluminium panels, of multilayer pipes, but also for the field of packaging.
1 . Tie comprising, (% by total weight of the said tie):
from 10 to 79% of a polyethylene (PE) (A) which is a very low density polyethylene (VLDPE) with a density of between 0.870 and 0.910 g/cm 3 or of a blend of at least two polyethylenes, PE (A1) and PE(A2), where:
PE (A2), which is a VLDPE with a density of between 0.870 and 0.910 g/cm 3 , is different from PE (A1),
PE (A) is grafted or the blend PE (A1) and (A2) is grafted or co-grafted,lend
PE(A), PE(A1) or PE(A2) are chosen from PE homopolymers and copolymers, said copolymers comprising at least 51 mole % of ethylene and a comonomer selected from the group consisting of: an alpha-olefin chosen from propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene, 1-dococene, 1-tetracocene, 1-hexacocene, 1-octacocene, 1-triacontene and mixtures thereof; and wherein said PE (A) or blend of at least two polyethylenes, PE (A1) and PE(A2) is not selected from the group consisting of esters of unsaturated carboxylic acids, vinylesters of saturated carboxylic acids, and dienes;
from 21 to 50% of a grafted or ungrafted high-impact PS(B) or a grafted or ungrafted crystal PS (B); and
from 0 to 70% of an ungrafted PE(C) obtained by Ziegler-Natta catalysis.
2 . Tie according to claim 1 , wherein said tie comprises:
15-70% of a PE (A) or of a blend of at least two polyethylenes, PE (A1) and PE(A2);
21-30% of a grafted or ungrafted crystal or high-impact PS (B);
0-60% of an ungrafted PE(C) obtained by Ziegler-Natta catalysis.
3 . Tie according to claim 1 , wherein the PE (A1) is chosen from a linear low density polyethylene (LLDPE), a low density polyethylene (LDPE) and a metallocene polyethylene (PEm).
4 . Tie according to claim 3 , wherein PE(A1) is an LLDPE.
5 . Tie according to claim 1 , wherein the PE (C) is chosen from an LDPE, an LLDPE and a VLDPE.
6 . Tie according to claim 5 , wherein PE(C) is an LLDPE.
7 . Tie according to claim 1 , wherein the grafted polymers are grafted with a grafting monomer selected from the group consisting of unsaturated carboxylic acids having 2 to 20 carbon atoms and their derivatives, and unsaturated dicarboxylic acids having 4 to 10 carbon atoms and their derivatives.
8 . Tie according to claim 7 , wherein the grafting monomer is maleic anhydride.
9 . Tie according to claims 7 , wherein the amount of grafting monomer is from 0.01 to 10% by weight of grafted polymer.
10 . Tie according to claim 1 , wherein copolymers comprising PE(A), PE(A1) or PE(A2) comprise at least 75 mole % of ethylene.
11 . A multilayer structure comprising aluminium layer/tie layer/PE layer, wherein said tie layer is the tie of claim 1 .
12 . The multiplayer structure of claim 11 , wherein the PE layer is an LDPE layer.
13 . The multiplayer structure of claim 11 , wherein the PE layer further comprises flame-retardant fillers.