Patent ID: 11912000
Assignee: BOSTIK SA
Field: Surface technology, coating (Chemistry)
Classification: CPC B | IPC B

Claim 0:
1. A multilayer film comprising 2 thin layers D and E of a thermoplastic material bonded together by a continuous layer A which has a thickness ranging from 7 to 50 μm, and consists of a hot-melt pressure-sensitive adhesive (HMPSA) composition (a) comprising, on the basis of the total weight of said composition:
from 40% to 70% by weight of a composition (a1) of styrene block copolymers comprising at least one elastomer block, said composition (a1) consisting of, on the basis of its total weight:
30% to 90% by weight of at least one diblock copolymer selected from the group consisting of polystyrene-polyisoprene (SI), polystyrene-polybutadiene-polyisoprene (SBI), polystyrene-polyisoprene-polybutadiene (SIB), polystyrene-polybutadiene (SB), polystyrene-poly(ethylenebutylene) (SEB) and polystyrene-poly(ethylenepropylene) (SEP), and
10% to 70% by weight of at least one triblock copolymer selected from the group consisting of polystyrene-polyisoprene-polystyrene (SIS), polystyrene-polyisoprene-polybutadiene-polystyrene (SIBS), polystyrene-polybutadiene-polystyrene (SBS), polystyrene-poly(ethylenebutylene)-polystyrene (SEBS) and polystyrene-poly(ethylenepropylene)-polystyrene (SEPS);
the total content of styrene units of said composition (a1) ranging from 10% to 40% by weight on the basis of the total weight of (a1); and

from 30% to 60% by weight of one or more tackifying resins (a2);
wherein, the adhesive layer A is:
connected to the layer D by a tie layer B, and
connected to the layer E by a tie layer C;

each of the 2 layers B and C respectively consisting of a composition (b) and (c) each comprising:
a polyolefin (P) selected from the group consisting of a polyethylene (PE) and a polypropylene (PP), optionally modified with an unsaturated carboxylic anhydride which is either a ring comprising 4 or 5 carbon atoms or a linear chain comprising 6 or 8 carbon atoms; and
at least one elastomer compound (EL) selected from the group consisting of a copolymer of ethylene and of propylene (EL1) and a styrene block copolymer (EL2) comprising at least one elastomer block, the styrene block copolymer (EL2) being in the form of a diblock and triblock composition as defined for the composition (a1).