MULTILAYER FILM FOR RECLOSABLE PACKAGING WITH POLYPROPYLENE LAYER OBTAINED BY FLAT SHEET CO-EXTRUSION
A multilayer film comprises an adhesive layer A comprising an HMPSA composition (a); a complexable thin layer B comprising a PolyPropylene (PP) composition (b); and a heat-sealable and breakable layer C comprising a PolyPropylene (PP) composition (c). Layers B and C are bonded together by layer A and the film is characterized in that the melt flow indices of compositions (a), (b) and (c), denoted MFI(a), MFI(b) and MFI(c), respectively, are such that the ratios MFI(a)/MFI(b) and MFI(a)/MFI(c) are each between 0.3 and 3.5. A process for manufacturing the film comprises flat sheet coextrusion of composition (a) and of compositions (b) and (c) at a temperature of between 150° C. and 250° C. Resealable packaging can comprise the multilayer film.
1 - 14 . (canceled)
15 . A multilayer film comprising:
an adhesive layer A consisting of an extrudable HMPSA composition (a);
a complexable thin layer B consisting of a PolyPropylene (PP) composition (b) denoted PP(b); and
a heat-sealable and breakable layer C consisting of a PolyPropylene (PP) composition (c) denoted PP(c);
wherein layers B and C are bonded together by layer A and said film is characterized in that the melt flow indices:
of the HMPSA composition (a), measured in g/10 minutes at a temperature of 190° C. and a total weight of 2.16 kg, and denoted MFI(a), and
of compositions (b) and (c), measured in g/10 minutes at a temperature of 230° C. and a total weight of 2.16 kg, and denoted MFI(b) and MFI(c), respectively,
are such that the ratios MFI(a)/MFI(b) and MFI(a)/MFI(c) are each between 0.3 and 3.5.
16 . The multilayer film as claimed in claim 15 , characterized in that the melt flow indices MFI(b) and MFI(c) are each between 2.5 and 30 g/10 minutes.
17 . The multilayer film as claimed in claim 15 , characterized in that the MFI(a) is in a range from 4 to 100 g/10 minutes.
18 . The multilayer film as claimed in claim 15 , characterized in that the extrudable HMPSA composition (a) comprises, 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, on the basis of its total weight:
of 10% to 90% by weight of at least one diblock copolymer selected from the group consisting of SI, SBI, SIB, SB, SEB and SEP, and
of 10% to 90% by weight of at least one triblock copolymer selected from the group consisting of SIS, SIBS, SBS, SEBS and SEPS;
wherein the total content of styrene units of said composition (a1) ranges 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).
19 . The multilayer film as claimed in claim 15 , characterized in that compositions (b) and (c) are compositions of the same PolyPropylene PP.
20 . The multilayer film as claimed in claim 15 , characterized in that compositions (b) and (c) consists of a PP.
21 . The multilayer film as claimed in claim 15 , characterized in that compositions (b) and (c) are PP-based compositions which comprise, in addition to said PP, an additive comprising an anti-fogging agent, a processing aid, a slip agent and/or an antiblocking agent.
22 . The multilayer film as claimed in claim 15 , characterized in that it consists of three layers A, B and C.
23 . The multilayer film as claimed in claim 15 , characterized in that it comprises, in addition to the three layers A, B and C, additional thin layers comprising:
a rigid layer,
a printable layer, and/or
a layer with a barrier effect against oxygen, water vapor or carbon monoxide.
24 . The multilayer film as claimed in claim 15 , characterized in that its total thickness varies in a range from 20 to 300 μm.
25 . The multilayer film as claimed in claim 15 , characterized in that the thickness of the adhesive layer A varies in a range from 5 to 50 μm and the thickness of the heat-sealable and breakable layer C varies in a range from 5 to 25 μm.
26 . A process for manufacturing the multilayer film as defined in claim 15 , comprising flat sheet coextrusion of the HMPSA composition (a) and of compositions (b) and (c) at a temperature of between 150° C. and 250° C.
27 . Resealable packaging comprising the multilayer film as defined in claim 15 .
28 . The resealable packaging of claim 15 , wherein the multiplayer film is a cover film of a resealable tray.