FIELD: manufacturing technology.
SUBSTANCE: invention relates to multi-layer moisture and gas barrier with rather thick-walled thermoformable films and relates to a biaxially oriented and thermally fixed flat coextruded barrier film and a method for its manufacturing, that can be used in food industry. Contains an external heat-sealing layer made of (co)polyolefin with a Wiki softening temperature not higher than 130 °C; a heat-resistant layer made of at least one polar (co)polymer selected from the group consisting of aliphatic (co)polyamides and aromatic (co)polyesters; a core adhesive layer of a material having an adhesion simultaneously to (co)polyolefins and polar (co)polymers, wherein the heat-resistant layer made of aliphatic (co)polyamides contains at least 15 % of at least one predominantly aliphatic copolyamide with melting point not higher than 205 °C. Method includes the steps of coextrusion, biaxial stretching, thermofixing and winding of the finished film into roll, wherein the degree of surface stretching with biaxial stretching is at least 8 and the thermofixing stage is accompanied by linear relaxation with shrinkage at least in one of the directions, including longitudinal (machinery) and transverse direction by more than 25 % and surface relaxation with a shrinkage of more than 40 %.
EFFECT: invention provides a film production that can be used for thermoforming by deep drawing in harsh conditions, while manufactured items made of it have the necessary mechanical reliability.
20 cl, 2 dwg, 3 tbl, 7 ex
