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EP-4046795-B1 - MULTILAYER POLYMER PACKAGING LINER

EP4046795B1EP 4046795 B1EP4046795 B1EP 4046795B1EP-4046795-B1

Inventors

  • VERSCHAEREN, PATRICK CORNEEL MATHILDE
  • Hanegraaf, Joan Antonius Adrianus Maria

Dates

Publication Date
20260513
Application Date
20210223

Claims (14)

  1. Multilayer polymer packaging liner for packaging of expandable polystyrene (EPS) granulates, wherein the liner is comprised of at least one inner layer, preferably at least two inner layers, comprised of a polymer consisting of polyamide (PA) or ethylene vinyl alcohol (EVOH), preferably PA and wherein the at least one inner layer comprises between 10 to 35 wt% of PA, or comprises between 2 to 10 wt% of EVOH based on the total weight of the liner, wherein the liner further comprises two or more adhesive polymer layers, and at least two outer layers comprised of a thermoplastic ethylene copolymer encapsulating said at least one inner layer and two or more adhesive polymer layers, wherein the adhesive polymer layers provide adhesion between the at least one inner layer and two or more outer layers of thermoplastic ethylene copolymer, and wherein the two or more adhesive polymer layers comprise between 10 to 20 wt%, preferably 12 to 17 wt%, more preferably at least 14 to 16 wt% of the total weight of the liner and wherein the two or more adhesive polymer layers each further comprise at least 80 wt% of a plastomer in combination with polyethylene (PE), preferably at least 85 wt%, based on the total weight of each of the adhesive polymer layers, and wherein the two or more adhesive polymer layers are selected from the group consisting of maleic anhydride (MAH)-grafted PE polymer wherein the PE is of low density PE (LDPE) or linear low density PE (LLDPE), ethylene acrylic acid (EAA), ethylene methacrylic acid (EMAA), EMA (ethyl methacrylate), ethylene vinyl acetate (EVA), or blends thereof with LLDPE, preferably maleic anhydride (MAH)-grafted PE polymers, more preferably maleic anhydride (MAH)-grafted LLDPE, wherein the liner has an Oxygen Transmission Rate (OTR) of at most 150 cc/m 2 /24h, preferably at most 125 cc/m 2 /24h, more preferably at most 100 cc/m 2 /24h, as determined according to ASTM E398, and has a Water Vapor Transmission Rate (WVTR) of at least 7.5 g/m2/24h, preferably at least 10 g/m2/24h, more preferably at least 15 g/m2/24h, as determined according to ASTM D3985, and has a surface resistance of at most 10 12 Ω·m, preferably at most 10 11 Ω·m, more preferably at most 10 10 Ω·m as determined according to ASTM D257.
  2. Multilayer polymer packaging liner according to claim 1, wherein the at least one inner layer comprises between 20 to 30 wt%, more preferably 24 to 28 wt% of PA, or comprises between 4 to 9 wt%, more preferably 5 to 8 wt% of EVOH, , based on the total weight of the liner.
  3. Multilayer polymer packaging liner according to claim 1 or 2, wherein the at least two outer layers are comprised of thermoplastic ethylene copolymer comprise at least 35 wt%, preferably at least 50 wt%, more preferably at least 55 wt%, based on the total weight of the liner.
  4. Multilayer polymer packaging liner according to any of the claims 1 to 3, wherein the at least two outer layers comprised of thermoplastic ethylene copolymer are one or more selected from the group consisting of ethylene vinyl acetate (EVA), ethylene butyl acrylate (EBA), ethylene methyl acrylate (EMA), ethylene ethyl acrylate (EEA), ethylene acrylic acid (EAA), ethylene methacrylic acid (EMAA), and ionomer, preferably EVA.
  5. Multilayer polymer packaging liner according to any of the claims 1 to 4, wherein the at least two outer layers comprised of thermoplastic ethylene copolymer each further comprise between 2 to 10 wt% of an antistatic additive, based on the total weight of each of the thermoplastic ethylene copolymer outer layers.
  6. Multilayer polymer packaging liner according to any of the claims 1 to 5, wherein the at least one inner layer has a total thickness of between 1 to 50 µm, preferably 10 to 30 µm, more preferably 15 to 20 µm.
  7. Multilayer polymer packaging liner according to any of the claims 1 to 6, wherein the liner has a hot seal strength at a temperature of between 120 to 160 °C of at least 1.2 N/15mm, preferably at least 1.4 N/15mm as determined in machine direction by standard test method ASTM F1921.
  8. Multilayer polymer packaging liner according to any of the claims 1 to 7, wherein the at least one inner layer is comprised of PA, the two or more adhesive polymer layers are comprised of a mixture of LLDPE and a plastomer, and the at least two outer layers are comprised of a mixture of EVA and an antistatic additive.
  9. Multilayer polymer packaging liner to any of the claims 1 to 8, wherein the multilayer polymer packaging liner is comprised of at least two inner layers, at least five layers of adhesive polymers and at least four outer layers of thermoplastic ethylene copolymer, wherein the two or more layers of adhesive polymers alternate with the inner layers and outer layers in a multilayer construction of the multilayer polymer packaging liner, wherein the multilayer polymer packaging liner has a symmetric multiplayer structure..
  10. Multilayer polymer packaging liner according to any of the claims 1 to 9, wherein the liner has a total thickness of 50 to 150 µm, preferably 70 to 125 µm, more preferably 80 to 100 µm.
  11. A method for producing a multilayer polymer packaging liner according to any of the claims 1 to 10, wherein the method comprises the steps of, a) melting of polyamide (PA) or ethylene vinyl alcohol (EVOH), a thermoplastic ethylene copolymer, and adhesive polymer to obtain a homogenous polymer melt per polymer, b) co-extrusion and joining of multiple polymer films to form a single film structure with multiple layers of the polymer melt providing a multilayer polymer liner, wherein the liner is comprised of at least one inner layer, preferably at least two inner layers, comprised of a polymer selected from the group consisting of polyamide (PA), ethylene vinyl alcohol (EVOH), preferably PA, wherein the liner further comprises two or more adhesive polymer layers, and at least two outer layers comprised of a thermoplastic ethylene copolymer encapsulating said at least one inner layer and two or more adhesive polymer layers, and wherein the multilayer polymer packaging liner has a symmetric multiplayer structure, c) cooling of the multilayer polymer liner by air to below 100 °C.
  12. Method for producing a multilayer polymer packaging liner according to claim 11, wherein the melting is performed at 160 to 240 °C, preferably 180 to 220 °C, most preferably 195 to 205 °C, and/or wherein the melting is performed at a pressure of 200 to 500 bar, preferably 250 to 400 bar, more preferably 300 to 350 bar.
  13. Packaging material for EPS granules comprised of multilayer polymer packaging liner according to any of the claims 1 to 10.
  14. Use of multilayer polymer packaging liner according to any of the claims 1 to 10 for packaging of EPS granules.

Description

The present invention relates to a multilayer polymer packaging liner for packaging of expandable polystyrene (EPS) granulates. The present invention further relates to a method for producing the multilayer polymer packaging liner, and packaging material for EPS granules comprised of the multilayer polymer packaging liner and its use for packaging of EPS granules. Polystyrene (C8H8)n is a synthetic aromatic hydrocarbon thermoplastic polymer. Polystyrene can be solid or foamed, and is one of the most widely used plastics and include protective packaging using expanded polystyrene (EPS). EPS is a rigid, tough, closed-cell foam made of pre-expanded polystyrene beads. The manufacturing process for EPS starts with the production of polystyrene beads (~200 um in diameter) by suspending styrene monomers in water, where they undergo free-radical addition polymerization. The beads are then permeated with a blowing agent, often pentane, that enables the beads to be expanded forming EPS (also know as Styrofoam) which is commonly used as building insulation and packing material. The EPS beads or EPS granulate are subsequently packed in industrial packaging material. Expandable polystyrene beads are a moulding material in the form of granules or beads, approximately 3 mm in diameter. The EPS granules may contain between 5% to 10% of a volatile hydrocarbon, most often pentane. During the polystyrene moulding process, the EPS granules are heated causing expansion and fusion, forming the familiar polymeric packaging material. However, during storage or transport, the material will release a portion of the pentane i.e. losing the blowing agent with which the EPS beads were permeated and which is needed during the moulding process to provide for the expanded polymeric packaging material. Furthermore, risks associated with EPS are related to the flammable blowing agent and the combustible nature of the polymeric material. Explosion and/or fire are significant risks that must be prevented when storing EPS beads. The pentane blowing agent is liberated very slowly during storage. It is a highly flammable gas and can form explosive mixtures with air at concentrations between 1.4 % and 7.8 % volume. EPS granules being packaged have been found to generate flammable concentrations of gas in enclosed spaces, and have been involved in several major explosions in storage containers such as container ships. The release rate and thus loss of this pentane is increased with a rise in temperature and is affected by the quality and type of the packaging material and if this packaging material provides a sufficient gas barrier that reduces or prevents the pentane to be released from the EPS granules. Furthermore, packaging material for EPS should have antistatic properties to prevent the creation of spark or ignition during (un)loading of the EPS in the packaging material. The EPS packaging material has a surface resistance of at most 1012 Ohm. Liners are mostly comprised of polyethylene (PE) which is non-polar. Therefore present PE liners have been mixed with antistatic additives or compounds, for example internally incorporated amine compounds, that migrates to the surface of the liner allowing for atmospheric dissipation of the static charge. At present EPS granules are packaged and transported in specific octagonal packaging made of very strong corrugated cardboard (octa-bin), which consists of a base, sleeve and a lid, and comprises a polyethylene polyamide liner (PE + PA polymer film) that helps to preserve the quality of the EPS beads as long as possible, including a degree of prevention of pentane loss from the EPS granules. Many plastic liners are used as a polymer liner for packaging, depending on the permeability of the material to gases. However, during the production of the EPS granules and in order to reduce the loss of blowing agent (pentane), the warm extruded EPS granules (after being permeated with blowing agent) are packaged as quickly as possible into the container (e.g. an octa-bin) providing a gas barrier and reducing loss of the blowing agent. This results in that next to the warm EPS also air will be included that holds water vapor and will lead to condensation of water over time inside the container holding the warm EPS granules. This water condensation affects the quality of the EPS granules over time. The often used materials for films such as polyethylene (PE), polypropylene (PP) and polyamide (PA) form a barrier to water vapor and are therefore not optimal for use as packaging material for EPS. Furthermore, small proportions of the pentane are still being released to the atmosphere and this proportion is increased at elevated temperatures Prior art liners are disclosed in BE1025049B1, US6087020A and EPO907508A1. Considering the above, there is a need in the art for a packaging material suitable for EPS granules that provides an optimal gas barrier that prevents or strongly reduces the blowing agent being released