KR-20260065800-A - Laminated films, covering materials, and packaging containers

Abstract

The present invention aims to provide a laminated film that enables weight reduction of packaging materials, has excellent impact resistance and puncture resistance, and also has excellent ease of opening. The laminated film of the present invention comprises a biaxially stretched polyester film and a sealant film, wherein the biaxially stretched polyester film contains 30 to 55 mass% of polybutylene terephthalate resin and 45 to 70 mass% of polyethylene terephthalate resin, the thermal insulation resistance of the laminated film is 100 to 200 N, the tear strength is 200 to 600 mN, and the ratio of the tear strength TSa in the longitudinal direction and the tear strength TSb in the transverse width direction of the laminated film, TSb/TSa, is 0.6 to 1.1.

Inventors

• 마나베, 노부유키
• 고토, 다카미치

Assignees

• 도요보 가부시키가이샤

Dates

Publication Date

20260511

Application Date

20240830

Priority Date

20230904

Claims (4)

1. A laminated film comprising a biaxially oriented polyester film and a sealant film, The above-mentioned biaxially stretched polyester film comprises 30 to 55 mass% of polybutylene terephthalate resin and 45 to 70 mass% of polyethylene terephthalate resin, has a puncture strength per film thickness of 0.60 to 1.00 N/μm, and has a ratio of BEa/BEb of the elongation at break in the film length direction and the elongation at break in the perpendicular width direction of BEb of 0.65 to 1.50. The above laminated film is characterized by satisfying the conditions of (a) to (c) below. (a) The thermal insulation resistance of the laminated film is 100 to 200 N. (b) The tear strength of the laminated film is 200 to 600 mN. (c) The ratio of the longitudinal tear strength TSa of the laminated film to the longitudinal tear strength TSb is 0.6 to 1.1, TSb/TSa.
2. A laminated film according to claim 1, wherein the laminated film further comprises an aluminum foil layer.
3. A cover material comprising a laminated film as described in paragraph 1 or 2.
4. A packaging container comprising the laminated film described in paragraph 1 or 2.

Description

Laminated films, covering materials, and packaging containers The present invention relates to a biaxially stretched polyester film comprising polybutylene terephthalate resin and polyethylene terephthalate resin, a laminated film having a sealant film, a cover material using the same, and a packaging container. In the field of container packaging for food, pharmaceuticals, etc., packaging is required to protect the contents, and high sealability that prevents easy opening by resisting external forces such as sterilization processes during food manufacturing, vibrations during transportation, and cargo handling is important. On the other hand, it is required to be easily opened during use, and "ease of opening" is required for containers, lids, and packaging. In recent years, due to social backgrounds such as women's entry into the workforce, the rise of nuclear families, and the aging of the population, there is a growing demand for packaging that is highly convenient and easy to open. For example, various types of packaging materials with ease of opening have been proposed, including containers equipped with easy-opening lids that facilitate the opening of cup or tray-shaped container bodies, as well as easy-open type sealed packaging containers. Among these, packaging materials known as "easy peel" utilize a sealant film that provides opening properties and are widely used as lids for side dishes, desserts, and dairy products; in this context, a balance between stable sealing performance and ease of opening is crucial. Furthermore, as these sealed packaging containers are increasingly packaged in boxes for transport and retail sales in recent years, they are required to be resistant to breakage even if dropped during transport. These easy-open type sealed packaging containers often have an opening formed to allow for easy opening. In the case of containers with fixed shapes, such as hard trays or cups, the container body can be opened by gripping the container body with one hand and the opening with the other. However, in the case of trays formed from thin sheets, the container itself deforms if force is applied to open it by gripping the container body. Therefore, a non-sealing section is provided at the corner, adjacent to the seal that is typically easy to open, and the container is opened by gripping both the lid material and the bottom material of the non-sealing section as the opening. However, in order to ensure a design that safely and sufficiently considers the sealing performance of the packaging container, the peel strength of the easy-open mechanism is usually set to be strong. Furthermore, in the case of cotton seals, since the peel boundary gradually widens as it peels away from the opening, tearing forces are prone to occur in the seal material during peeling, which can cause the seal to crack and prevent a clean opening. When the contents include paste-like or liquid substances, problems such as the contents overflowing due to container deformation occur as soon as the seal cracks; this poses a risk of contaminating hands or clothing with the food contents, or causing burns if the contents are heated. Patent Document 1 discloses a polyester laminated film containing a thermoplastic copolymer polyester resin and a polyolefin resin in a seal layer. According to this technology, the crystal melting peak temperature or ratio of the polyethylene terephthalate resin and the thermoplastic copolymer polyester resin included in the seal layer, and the ratio of the polyolefin resin are placed within a specific range, and by laminating a polyester laminated film composed of a support layer containing a polyethylene terephthalate resin with a substrate layer, a packaging body with improved ease of opening and impact resistance is obtained. It is stated that by using a polyester film as the base layer, it is possible to provide a cover material or packaging with excellent single-material properties while possessing ease of peeling, ease of opening, heat sealability, and orientation. However, the biaxially stretched polyester film used as the base layer has the problem of low impact strength, puncture strength, and pinhole resistance, leaving room for improvement. Furthermore, in order to stably produce a polyester laminated film and ensure good handling properties such as winding, it is necessary to make the support layer a thick film. Consequently, it is difficult to reduce the volume of the packaging including the base layer. Consequently, there are issues regarding the decrease in mechanical strength and puncture strength, which become challenges associated with volume reduction, and the lack of impact resistance, which pose problems in terms of resource conservation and environmental impact. Meanwhile, it is known that a biaxially stretched polyester film with polybutylene terephthalate resin as the main component possesses heat resistance and flexibility (Patent Document 2). According to this tec