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EP-4562106-B1 - HOT-MELT PRESSURE-SENSITIVE ADHESIVES FOR RESEALABLE PACKAGING

EP4562106B1EP 4562106 B1EP4562106 B1EP 4562106B1EP-4562106-B1

Inventors

  • ROBERT, CHRISTOPHE
  • WIEGERT, Barbara

Dates

Publication Date
20260513
Application Date
20230724

Claims (15)

  1. 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.
  2. Composition according to Claim 1, characterized in that it comprises from 45% to 80% by weight of copolymer(s) A, preferably from 50% to 80%, more preferentially still from 50% to 70%, by weight of copolymer(s) A, with respect to the total weight of said composition.
  3. Composition according to either one of Claims 1 and 2, characterized in that the copolymer A has a polydispersity index (Mw/Mn) of less than or equal to 3, preferably ranging from 2 to 3.
  4. Composition according to any one of Claims 1 to 3, characterized in that the copolymer A has a Shore A hardness of less than or equal to 90, preferably of less than or equal to 70 and more preferentially still of less than or equal to 65.
  5. Composition according to any one of Claims 1 to 4, characterized in that the copolymer A comprises at most 20% by weight of units derived from ethylene, preferably at most 18% by weight of units derived from ethylene and more preferentially still at most 10% by weight of units derived from ethylene.
  6. Composition according to any one of Claims 1 to 5, characterized in that it comprises from 1.8% to 4.3% by weight of copolymer(s) T, preferentially from 2.0% to 4.0% and more preferentially still from 2.0% to 3.5% by weight, with respect to the total weight of said composition.
  7. Composition according to any one of Claims 1 to 6, characterized in that the copolymer T comprises more than 60% by weight of units derived from propylene, more preferentially more than 70% by weight of units derived from propylene and more preferentially still more than 80% by weight of units derived from propylene.
  8. Composition according to any one of Claims 1 to 7, characterized in that the copolymer T can comprise from 1% to 25% by weight of units derived from ethylene, preferably from 1% to 10% by weight of units derived from ethylene and more preferentially still from 1% to 5% by weight of units derived from ethylene.
  9. Composition according to any one of Claims 1 to 8, characterized in that the copolymer T comprises from 1% to 25% by weight of units derived from butene, preferably from 2% to 15% by weight of units derived from butene and more preferentially still from 5% to 12% by weight of units derived from butene.
  10. Composition according to any one of Claims 1 to 9, characterized in that the total content of tackifying resin(s) iii) ranges from 18.5% to 58.5% by weight, preferably from 18.5% to 53.5% by weight, preferentially from 18.5% to 48.5% by weight and more preferentially still from 28.5% to 48.5% by weight, with respect to the total weight of said composition.
  11. Composition according to any one of Claims 1 to 10, characterized in that it does not comprise a tackifying resin other than the tackifying resin(s) iii).
  12. Composition according to any one of Claims 1 to 11, characterized in that it is provided in the form of granules of ellipsoidal shape, the mean dimensions of the major axis and of the minor axis of which are preferably as follows: - mean dimension of the major axis of between 1 and 10 mm, preferably between 2 and 6 mm; - mean dimension of the minor axis of between 1 and 10 mm, preferably between 2 and 6 mm.
  13. 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 one of Claims 1 to 12.
  14. Multilayer film according to Claim 13, 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.
  15. Use of the multilayer film as defined in Claim 13 or 14, for the manufacture of reclosable packagings.

Description

FIELD OF INVENTION The present invention relates to a new self-adhesive hot melt composition, as well as a multilayer film intended for the manufacture of resealable packaging (or trays), which includes an adhesive layer made up of said composition. TECHNOLOGICAL BACKGROUND Resealable trays are used in the food processing industry and large retailers to package food products, particularly fresh produce. Such packaging is described by the patent US 4673601 and the patent application EP 1053952 (And WO2021127351A1 , EP3260512A1 And US2013202836A1 ). After the initial opening of the packaging and consumption of some of the food product inside, the user can manually reseal the packaging in a substantially airtight manner, thus ensuring, if necessary after refrigeration, the preservation of the remaining portion of the product. Repeated opening and resealing is also possible. These packages generally include a container (or receptacle) and a lid, which are hermetically sealed together by welding. The container, which is more or less deep and relatively rigid, consists of a multilayer (also called complex or composite) sheet with a minimum thickness of 200 µm, generally between 200 and 1000 µm. This sheet is thermoformed to present a flat base on which the food product rests and a flat, band-shaped perimeter. This perimeter, generally parallel to the base, is welded to the flexible, flat lid, which is made of a multilayer (also called complex or composite) film generally between 40 and 150 µm thick, and is sometimes referred to as the lidding film. When the packaging is opened, the lidding film is manually separated from the receptacle at the level of the flat strip around the edge. This operation reveals an adhesive layer on this flat strip, both on the lidding strip and on the receptacle strip, which were previously in contact. These two adhesive layers (continuous or discontinuous), referred to as "daughter" layers, result from the rupture of an initial or "parent" adhesive layer or, possibly, from its separation (or detachment) from one of the two adjacent layers of the multilayer complex film. The initial adhesive layer is therefore one of the layers of this multilayer complex film, which is itself a component comprising either in the composite sheet which constitutes the receptacle or, possibly, in the sealing film. The two adhesive strips present on the edges of the receptacle and lid, located after opening the packaging, are therefore aligned. Simply reposition the lid on the receptacle, matching its position in the packaging before opening, to bring the two adhesive strips back into contact. A light press by hand then reseals the packaging. The adhesive composition that makes up the mother and daughter adhesive layers is therefore necessarily a pressure-sensitive adhesive (also called self-adhesive or PSA, from the English "Pressure Sensitive Adhesive"). Hot melt adhesive compositions typically include tackifying resins and styrenic block copolymers with an elastomer block. These adhesive compositions are also commonly referred to as HMPSA, short for Hot Melt Pressure Sensitive Adhesive. They are solid at room temperature and contain neither water nor solvents. Applied in a molten state, they solidify upon cooling, forming an adhesive layer that bonds the two thin layers of thermoplastic polymer material to be assembled, while also providing the packaging with advantageous opening and resealing properties. A "stick-slip" phenomenon can occur when peeling the adhesive backing while opening the packaging. This jerky, jerky movement creates an unpleasant sensation for the consumer, who prefers a smooth and even opening. The quality of the adhesive break is therefore an important factor that impacts the consumer's experience. Therefore, there is a need for a self-adhesive hot-melt composition that can remedy at least partially at least one of the aforementioned drawbacks. There is a particular need for a self-adhesive hot-melt compound that offers a good compromise between adhesive properties and break quality. Specifically, there is a need for a self-adhesive hot-melt compound that provides a good balance between sufficient initial opening force, maximum resealing force, and good adhesive break quality. DESCRIPTION OF THE INVENTION COMPOSITION The present invention relates to a self-adhesive, hot-melt composition comprising: (i) 40% to 80% by weight of at least one copolymer A but-1-ene-ethylene, said copolymer comprising more than 80% by weight of but-1-ene derived units; 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 propylene-derived units; iii) at least one non-hydrogenated tackifying resin obtained by polymerization, or copolymerization with an aromatic hydrocarbon, of mixtures of unsaturated aliphatic hydrocarbons having 4 to 6 carbon atoms from petroleum cuts. The percentages by weight of the ingredients a