US-20260124824-A1 - COEXTRUDED MULTILAYER FILM, LAMINATE, AND PACKAGING BAG

Abstract

A coextruded multilayer film according to one aspect of the present disclosure is a coextruded multilayer film including a first layer and a second layer, in which the second layer includes a polyethylene resin, the first layer includes a resin having a melting point higher than that of the polyethylene resin, and a thickness of the first layer is 0.3 μm or more and 6 μm or less.

Inventors

• Yuki EJIMA
• Ryo Takei

Assignees

• TOPPAN HOLDINGS INC.

Dates

Publication Date

20260507

Application Date

20231031

Priority Date

20221102

Claims (10)

1. 1 . A coextruded multilayer film comprising a first layer and a second layer, wherein the second layer includes a polyethylene resin, the first layer includes a resin having a melting point higher than that of the polyethylene resin, and a thickness of the first layer is 0.3 μm or more and 6 μm or less.
2. 2 . The coextruded multilayer film according to claim 1 , further comprising a third layer formed on a side of the second layer opposite to the first layer, wherein the third layer includes a resin having a melting point higher than that of the polyethylene resin.
3. 3 . A laminate comprising the coextruded multilayer film according to claim 1 , a first adhesive layer provided on the second layer side of the coextruded multilayer film, and a sealant layer in this order, wherein the sealant layer includes a polyethylene resin, and a content of the polyethylene resin in the laminate is 90 mass % or more based on a total amount of the laminate.
4. 4 . The laminate according to claim 3 , wherein a difference between a heat-seal onset temperature of a front layer of the coextruded multilayer film and a heat-seal onset temperature of the sealant layer is 40° C. or higher.
5. 5 . The laminate according to claim 4 , further comprising a polyethylene film and a second adhesive layer formed between the first adhesive layer and the sealant layer from the first adhesive layer side.
6. 6 . The laminate according to claim 5 , wherein an absolute value of a molecular orientation degree of the polyethylene film is less than 1.07.
7. 7 . The laminate according to claim 5 , wherein the polyethylene film includes a front layer, an intermediate layer, and a back layer in this order, in the polyethylene film, a probe descending temperature of the intermediate layer is higher than a probe descending temperature of the front layer and is equal to or higher than a probe descending temperature of the back layer, and the front layer of the polyethylene film includes a polyethylene resin having a density of 0.926 g/cm 3 or more.
8. 8 . The laminate according to claim 5 , further comprising a gas barrier layer formed between the coextruded multilayer film and the polyethylene film.
9. 9 . The laminate according to claim 5 , further comprising a gas barrier layer formed between the polyethylene film and the sealant layer.
10. 10 . A packaging bag formed using the laminate according to claim 3 .

Description

TECHNICAL FIELD The present disclosure relates to a coextruded multilayer film, a laminate, and a packaging bag. BACKGROUND ART In a packaging bag, various materials are used in combination according to the nature of contents to be packaged, the amount of the contents, a post-treatment for preventing deterioration of the contents, a form of transporting the packaging bag, a method of opening the packaging bag, a method of discarding the packaging bag, and the like. For example, in a packaging bag of a flexible package using a laminated film, a biaxially stretched film such as a polypropylene resin or a polyester resin is used in order to obtain the mechanical strength of the packaging bag, and a combination with a polyethylene resin, a polypropylene resin, an ethylene-vinyl acetate copolymer, or the like as a heat sealing material is used in order to seal the contents as the packaging bag. In addition, in order to suppress deterioration of the contents, an aluminum foil or an ethylene vinyl alcohol copolymer is also laminated. The laminate using the various functionally separated materials described above is designed with emphasis on suitability in each process such as transportation, storage, and opening from the packaging of the contents. However, due to growing awareness of environmental problems in recent years, emphasis has been put on functions such as resource saving and recyclability of various products, and similar functions have been required for a laminate used for a packaging bag. In general, it is considered that when a ratio of a main resin included in a packaging material is 90 mass % or more, recyclability is high. However, a lot of conventional packaging materials include a plurality of resin materials and, in some cases, paper and a metal material, and do not satisfy this standard, and therefore, are not recycled at present. Therefore, Patent Literature 1 describes that in a laminate including a base material, an adhesive layer, and a heat seal layer, the base material and the heat seal layer are formed of a polyethylene resin. When the base material and the heat seal layer are formed of the same material, the standard of recyclability is easily cleared. CITATION LIST Patent Literature Patent Literature 1: Japanese Unexamined Patent Publication No. 2020-55157 SUMMARY OF INVENTION Technical Problem However, when the laminate described in Patent Literature 1 is applied to a packaging bag, in a bag formation step of forming the packaging bag, there is a step of heat-welding (heat-sealing) the laminate by causing the heat seal layers (sealant layers) of the laminate to face each other and sandwiching the laminate by applying a pressure from an outer surface side of a base material layer of the laminate with a high-temperature jig. A jig of a heat sealing machine has a high temperature, and the outer surface of the base material layer in direct contact with the jig is exposed to a high temperature, and therefore, in the conventional laminate, the base material layer may be affected by heat or adhere to the jig, or the heat sealing portion may be wrinkled, and heat sealability is not sufficient. Therefore, there are problems such as narrow preferred conditions of a bag production temperature, poor productivity, and insufficient strength of the packaging bag. The present disclosure provides a laminate having excellent recyclability and excellent heat sealability and a packaging bag using the same. In addition, the present disclosure provides a coextruded multilayer film by which a resulting laminate has excellent recyclability and excellent heat sealability when used as a material for a laminate. Solution to Problem One aspect of the present disclosure relates to a coextruded multilayer film including a front layer and a back layer, in which the back layer includes a polyethylene resin, the front layer includes a resin having a melting point higher than that of the polyethylene resin, and a thickness of the front layer is 0.3 μm or more and 6 μm or less. When such a coextruded multilayer film is used as a material for a laminate, a resulting laminate has excellent recyclability and excellent heat sealability. In addition, since such a coextruded multilayer film can be produced in one step by a coextrusion method, production efficiency is excellent. One aspect of the present disclosure relates to a coextruded multilayer film including a front layer, an intermediate layer, and a back layer, in which the intermediate layer includes a polyethylene resin, the front layer and the back layer include a resin having a melting point higher than that of the polyethylene resin, and a thickness of the front layer is 0.3 μm or more and 6 μm or less. Such a coextruded multilayer film is less likely to curl, and when used as a material for a laminate, a resulting laminate has excellent recyclability and excellent heat sealability. In addition, since such a coextruded multilayer film can be produced in one step b