HOT-MELT PRESSURE-SENSITIVE ADHESIVES FOR RESEALABLE PACKAGING
The present invention relates to a hot-melt self-adhesive composition comprising: i) from 40% to 80% by weight of at least one but-1-ene-ethylene copolymer A, said copolymer comprising more than 80% by weight of units derived from but-1-ene; ii) from 1.5% to 4.5% by weight of at least one propylene-ethylene-butene copolymer T, said copolymer T comprising more than 50% by weight of units derived from propylene; iii) at least one nonhydrogenated tackifying resin obtained by polymerization, or copolymerization with an aromatic hydrocarbon, of mixtures of unsaturated aliphatic hydrocarbons having from 4 to 6 carbon atoms resulting from petroleum cuts.
1 - 19 . (canceled)
20 . A hot-melt self-adhesive composition comprising:
i. from 40% to 80% by weight of at least one but-1-ene-ethylene copolymer A, said copolymer comprising more than 80% by weight of units derived from but- 1-ene;
ii. from 1.5% to 4.5% by weight of at least one propylene-ethylene-butene copolymer T, said copolymer T comprising more than 50% by weight of units derived from propylene;
iii. at least one nonhydrogenated tackifying resin obtained by polymerization, or copolymerization with an aromatic hydrocarbon, of mixtures of unsaturated aliphatic hydrocarbons having from 4 to 6 carbon atoms resulting from petroleum cuts.
21 . The composition as claimed in claim 20 , characterized in that it comprises from 45% to 80% by weight of copolymer(s) A, with respect to the total weight of said composition.
22 . The composition as claimed in claim 20 , characterized in that the copolymer A has a polydispersity index (M w /M n ) of less than or equal to 3.
23 . The composition as claimed in claim 20 , characterized in that the copolymer A has a Shore A hardness of less than or equal to 90.
24 . The composition as claimed in claim 20 , characterized in that the copolymer A comprises at most 20% by weight of units derived from ethylene.
25 . The composition as claimed in claim 20 , characterized in that it comprises from 8% to 4.3% by weight of copolymer(s) T, with respect to the total weight of said composition.
26 . The composition as claimed in claim 20 , characterized in that the copolymer T comprises more than 60% by weight of units derived from propylene.
27 . The composition as claimed in claim 20 , characterized in that the copolymer T can comprise from 1% to 25% by weight of units derived from ethylene.
28 . The composition as claimed in claim 20 , characterized in that the copolymer T comprises from 1% to 25% by weight of units derived from butene.
29 . The composition as claimed in claim 20 , characterized in that the total content of tackifying resin(s) iii) ranges from 18.5% to 58.5% by weight, with respect to the total weight of said composition.
30 . The composition as claimed in claim 20 , characterized in that it does not comprise a tackifying resin other than the tackifying resin(s) iii).
31 . The composition as claimed in claim 20 , characterized in that it has a melt flow index (MFI) ranging from 5 to 50 g/10 min.
32 . The composition as claimed in claim 20 , characterized in that it has a total content of polymers (copolymer A+copolymer T) ranging from 41.5% to 84.5%.
33 . The composition as claimed in claim 20 , characterized in that it comprises a polymers (copolymer A+copolymer T): tackifying resin(s) iii) ratio by weight ranging from 40:60 to 90:10.
34 . The composition as claimed in claim 20 , characterized in that it comprises less than 0.1% by weight of styrene block copolymer (SBC), with respect to the total weight of said composition.
35 . The composition as claimed in claim 20 , characterized in that it is provided in the form of granules of ellipsoidal shape, the mean dimensions of a major axis and of a minor axis of which are as follows:
mean dimension of the major axis of between 1 and 10 mm;
mean dimension of the minor axis of between 1 and 10 mm.
36 . A multilayer film comprising two thin layers B and C of thermoplastic material bonded together by an adhesive layer A, characterized in that said layer A consists of the hot- melt self-adhesive composition as defined in claim 20 .
37 . The multilayer film as claimed in claim 36 , characterized in that it comprises five layers consisting of the adhesive layer A, two additional layers D and E and the two thin layers B and C, according to the sequence B/D/A/E/C in which the “/” sign signifies that the faces of the layers in question are in direct contact.
38 . Reclosable packagings comprising the multilayer film as defined in claim 36 .