Method for producing a recyclable and easily tearable multi-layer plastic having a good barrier effect
According to an aspect of the present disclosure, a method for producing a multi-layer plastic may include coextruding a first laminate with a substrate layer having an HDPE content of at least 60% by volume; a barrier layer having a barrier polymer and having a thickness of at most 20% of a total thickness of the first laminate; and a connecting layer between the substrate layer and the barrier layer; stretching the coextruded first laminate in a machine direction only; and connecting a second laminate having a polyethylene content of at least 80% by volume to the barrier layer of the stretched first laminate.
1 . A method for producing a multi-layer plastic film, comprising the steps of:
coextruding a first laminate with:
a substrate layer having an HDPE content of at least 60% by volume;
a barrier layer having a barrier polymer and having a thickness of at most 20% of a total thickness of the first laminate; and
a connecting layer between the substrate layer and the barrier layer;
stretching the coextruded first laminate in a machine direction only; and
connecting a second laminate having a polyethylene content of at least 80% by volume to the barrier layer of the stretched first laminate.
2 . The method according to claim 1 , further comprising printing and/or metallizing and/or coating the first laminate before connecting to the second laminate.
3 . The method according to claim 2 , wherein the substrate layer is at least partially transparent such that a printed image and/or metallization and/or coating is visible through the substrate layer.
4 . The method according to claim 1 , further comprising the step of connecting the substrate layer to a further single-layer or multi-layer laminate having a polyethylene content of at least 80% by weight.
5 . The method according to claim 4 , further comprising the step of printing and/or metallizing and/or coating the barrier layer and/or the substrate layer before connecting the substrate layer to the further laminate.
6 . The method according to claim 5 , further comprising the step of pre-treating the barrier layer with a corona treatment or a flame treatment.
7 . The method according to claim 4 , further comprising the step of printing and/or metallizing and/or coating at least one layer of the further laminate.
8 . The method according to claim 1 , further comprising the steps of:
providing another multi-layer laminate comprising:
a substrate layer having an HDPE content of at least 60% by volume;
a barrier layer comprising a barrier polymer; and
a connecting layer in between,
stretching the another multi-layer laminate in the machine direction; and
connecting the barrier layer of the stretched another multi-layer laminate to the substrate layer of the stretched first laminate.
9 . The method according to claim 1 , further comprising the steps of:
coextruding the second laminate with a substrate layer comprising:
an HDPE content of at least 60% by volume,
a connecting layer,
a barrier layer comprising a barrier polymer and having a thickness of at most 20% of a total thickness of the second laminate, and
a sealing layer, wherein the connecting layer is between the substrate layer and the barrier layer of the second laminate, and the sealing layer is arranged on the substrate layer;
stretching the second laminate in the machine direction; and
connecting the barrier layer of the stretched second laminate to the barrier layer of the stretched first laminate.
10 . The method according to claim 9 , wherein at least two layers form the sealing layer.
11 . The method according to claim 1 , wherein the barrier layer comprises polyamide and/or ethylene-vinyl alcohol copolymer.
12 . The method according to claim 1 , wherein the connecting layer comprises at least one of polyolefin modified with a maleic anhydride, ethylene-vinyl acetate copolymer, ethylene acid copolymer, acrylic acid copolymer, or ethylene-butyl acrylate copolymer.
13 . The method according to claim 1 , wherein the first laminate is connected to the second laminate by a laminating adhesive, the laminating adhesive including at least one of a polyurethane adhesive or a polyolefin copolymer.
14 . The method according to claim 1 , further comprising the step of protecting the first laminate from water absorption before connecting the second laminate.
15 . The method according to claim 1 , wherein the machine direction is a direction of extrusion.
16 . The method according to claim 1 , wherein the connecting layer is configured to connect the barrier layer with the substrate layer to resist delamination of the first laminate.
17 . The method according to claim 1 , wherein the barrier polymer has barrier properties against at least one of oxygen, hydrogen or aroma.
18 . The method according to claim 1 , wherein the first laminate is coextruded via a blown film extrusion process or a flat film extrusion process.
19 . The method according to claim 1 , wherein the first laminate has an asymmetrical structure.
20 . The method according to claim 1 , wherein stretching the first laminate is performed while the first laminate is at a temperature below a melting point of a polymer thereof.