Multilayered hollow container and method for producing multilayered hollow container

Abstract

Provided is a multilayered hollow container comprising: a poly(ethylene terephthalate) layer including poly(ethylene terephthalate); and a poly(ethylene furanoate) layer including poly(ethylene furanoate). When the height of the multilayered hollow container is expressed by H, the lower end of the poly(ethylene furanoate) layer is positioned in the range of 0.05H-0.15H in terms of distance from the grounding portion of the multilayered hollow container and the upper end of the poly(ethylene furanoate) layer is positioned in the range of 0.90H-1.00H in terms of distance from the grounding portion of the multilayered hollow container.

Description

Multilayer hollow container and method for manufacturing multilayer hollow container

[0001] The present invention relates to a multi-layer hollow container and a method for manufacturing the same.

[0002] Polyethylene terephthalate (PET) is characterized by excellent transparency, mechanical properties, melt stability, solvent resistance, aroma retention, recyclability, etc. Therefore, polyethylene terephthalate is widely used in various packaging materials such as films, sheets, and hollow containers. Although polyethylene terephthalate has relatively high gas barrier properties, these properties are not necessarily sufficient for applications requiring better gas barrier properties against oxygen, carbon dioxide, etc. Therefore, methods for improving the gas barrier properties of polyethylene terephthalate have been used, such as vapor deposition of aluminum oxide or silicon oxide onto molded articles or packaging containers made of polyester resin, or coating, laminating, or melt-mixing a resin having high gas barrier properties onto molded articles or packaging containers made of polyethylene terephthalate.

[0003] Examples of gas barrier resins include polyamide resins such as nylon 6 and nylon 66, and polyester resins such as ethylene-vinyl alcohol copolymers, polyethylene furanoate (PEF), and polyglycolic acid. Among polyester resins, PEF and PGA, which use monomers derived from biomass, have excellent gas barrier properties and are superior to other barrier resins in terms of reducing environmental impact.

[0004] For example, Patent Document 1 discloses a multilayer container having at least a layer containing polyethylene furanoate, the polyethylene furanoate being a polycondensate of biomass-derived polyethylene glycol and biomass-derived furandicarboxylic acid, with the aim of obtaining a multilayer container having gas barrier properties using a carbon-neutral material.

[0005] Japanese Patent Application Laid-Open No. 2018-199258

[0006] In Patent Document 1, polyethylene furanoate is used as a gas barrier layer, but the multilayer container described in Patent Document 1 was insufficient in terms of barrier properties, particularly against carbon dioxide. Furthermore, while a longer shelf life is required to reduce food waste, the multilayer container of Patent Document 1 was also insufficient in terms of shelf life. For these reasons, there has been a demand for a container that is excellent in both barrier properties against carbon dioxide and shelf life. Therefore, an object of the present invention is to provide a multilayer hollow container that has high barrier properties against carbon dioxide and a long shelf life.

[0007] As a result of intensive research in light of the above-mentioned problems, the present inventors have found that a multilayer hollow container having a polyethylene furanoate layer containing a specific polyethylene furanoate at a specific position can solve the above-mentioned problems, and have completed the present invention. The present invention provides the following [1] to [9].

[0008] [1] A multi-layer hollow container having a polyethylene terephthalate layer containing polyethylene terephthalate and a polyethylene furanoate layer containing polyethylene furanoate, wherein, when the height of the multi-layer hollow container is H, the lower end of the polyethylene furanoate layer is located within a range of 0.05H to 0.15H from the ground portion of the multi-layer hollow container and the upper end of the polyethylene furanoate layer is located within a range of 0.90H to 1.00H from the ground portion of the multi-layer hollow container. [2] The multi-layer hollow container according to [1], wherein the polyethylene furanoate layer covers 50 to 95% of the area of ​​the outer surface of the multi-layer hollow container. [3] The multi-layer hollow container according to [1] or [2], wherein the content of the polyethylene furanoate layer is 0.05 to 10.0 mass% of the total amount of the polyethylene terephthalate layer and the polyethylene furanoate layer. [4] The multi-layer hollow container according to any one of [1] to [3], wherein the polyethylene furanoate is a polycondensate of biomass-derived ethylene glycol and biomass-derived furan dicarboxylic acid. [5] The multi-layer hollow container according to any one of [1] to [4], wherein the bio-based content is 4% by mass or more. [6] The multi-layer hollow container according to any one of [1] to [5], wherein the multi-layer hollow container has a three-layer structure consisting of a polyethylene terephthalate layer, a polyethylene furanoate layer, and a polyethylene terephthalate layer, in that order. [7] The multi-layer hollow container according to any one of [1] to [6], wherein the polyethylene furanoate layer is formed substantially continuously over the entire circumference in the height direction and circumferential direction of the multi-layer hollow container. [8] A carbonated beverage product in which a carbonated beverage is contained in the multi-layer hollow container according to any one of [1] to [7].[9] A method for producing a multilayer hollow container, comprising: Step 1, in which polyethylene terephthalate or a resin composition containing polyethylene terephthalate and polyethylene furanoate or a resin composition containing polyethylene furanoate are co-injection molded to obtain a multilayer preform having a three-layer structure composed, in this order, of a polyethylene terephthalate layer containing polyethylene terephthalate, a polyethylene furanoate layer containing polyethylene furanoate, and a polyethylene terephthalate layer containing polyethylene terephthalate; and Step 2, in which the multilayer preform is blow molded, wherein, when the total length of the multilayer preform is h, the lower end of the polyethylene furanoate layer is located in a range of 0.05 h to 0.15 h from the tip of the multilayer preform, and the upper end of the polyethylene furanoate layer is located in a range of 0.90 h to 1.00 h from the tip of the multilayer preform.

[0009] According to the present invention, it is possible to provide a multilayer hollow container having high barrier properties against carbon dioxide and a long shelf life.

[0010] [Multilayer hollow container] The multilayer hollow container of the present invention is a multilayer hollow container having a polyethylene terephthalate layer containing polyethylene terephthalate and a polyethylene furanoate layer containing polyethylene furanoate, in which, when the height of the multilayer hollow container is H, the lower end of the polyethylene furanoate layer is located in a range of 0.05H to 0.15H from the ground portion of the multilayer hollow container, and the upper end of the polyethylene furanoate layer is located in a range of 0.90H to 1.00H from the ground portion of the multilayer hollow container.

[0011] The reason why the multilayer hollow container of the present invention having the above-described configuration has high barrier properties against carbon dioxide and a long shelf life is unclear, but it is thought to be as follows. Structurally, the body of a hollow container such as a bottle is stretched at a high ratio, and it is thought that the thickness of the barrier layer made of polyethylene furanoate is likely to be thin. However, by concentrating the barrier layer in the body portion, it is thought that barrier properties can be efficiently imparted to the hollow container. Therefore, it is thought that the multilayer hollow container of the present invention has excellent barrier properties against carbon dioxide and can also have a long shelf life.

[0012] <Polyethylene Terephthalate Layer> The polyethylene terephthalate layer contains polyethylene terephthalate.

[0013] (Polyethylene terephthalate) The polyethylene terephthalate (PET) contained in the polyethylene terephthalate layer is a polyester mainly having structural units derived from a dicarboxylic acid containing structural units derived from terephthalic acid and structural units derived from a diol containing structural units derived from ethylene glycol. The polyethylene terephthalate preferably has structural units derived from a dicarboxylic acid containing 80 mol% or more of structural units derived from terephthalic acid and structural units derived from a diol containing 80 mol% or more of structural units derived from ethylene glycol, more preferably structural units derived from a dicarboxylic acid containing 90 mol% or more of structural units derived from terephthalic acid and structural units derived from a diol containing 90 mol% or more of structural units derived from ethylene glycol, and even more preferably structural units derived from a dicarboxylic acid containing 98 mol% or more of structural units derived from terephthalic acid and structural units derived from a diol containing substantially 100 mol% of structural units derived from ethylene glycol. In this specification, "polyethylene terephthalate" refers to the polyethylene terephthalate forming the polyethylene terephthalate layer and the polyethylene terephthalate used as a raw material for the polyethylene terephthalate layer.

[0014] Polyethylene terephthalate may contain structural units derived from an aromatic dicarboxylic acid other than terephthalic acid. The aromatic dicarboxylic acid other than terephthalic acid is preferably one or more selected from isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, and 4,4'-biphenyldicarboxylic acid. These are low cost, and copolymerized polyesters containing these are easy to produce. Of these, isophthalic acid and naphthalenedicarboxylic acid are preferred as aromatic dicarboxylic acids other than terephthalic acid, with isophthalic acid being more preferred. Polyethylene terephthalate containing structural units derived from isophthalic acid is excellent in moldability and, due to its slower crystallization rate, prevents whitening of molded articles. Furthermore, polyethylene terephthalate containing structural units derived from naphthalenedicarboxylic acid increases the glass transition point of the resin, improving heat resistance and absorbing ultraviolet light, making it suitable for use in the production of multilayer containers requiring ultraviolet resistance. Among naphthalenedicarboxylic acids, 2,6-naphthalenedicarboxylic acid is preferred due to its ease of production and high economic efficiency. When polyethylene terephthalate contains constituent units derived from aromatic dicarboxylic acids other than terephthalic acid, the proportion of constituents derived from aromatic dicarboxylic acids other than terephthalic acid is preferably 1 to 20 mol %, more preferably 1 to 10 mol %, even more preferably 1 to 5 mol %, and still more preferably 1 to 2 mol %, of the dicarboxylic acid units.

[0015] Polyethylene terephthalate can be produced by known methods such as direct esterification and transesterification.

[0016] The intrinsic viscosity of polyethylene terephthalate is preferably 0.5 to 2.0 dL / g, more preferably 0.6 to 1.5 dL / g. An intrinsic viscosity of 0.5 dL / g or higher results in excellent mechanical properties of the container. The intrinsic viscosity is measured by dissolving polyethylene terephthalate in a phenol / 1,1,2,2-tetrachloroethane (6 / 4 mass ratio) mixed solvent to prepare 0.2, 0.4, or 0.6 g / dL solutions, and measuring the solutions at 25°C using an automatic viscosity measuring device (Viscotek, manufactured by Malvern Instruments). Bio-based polyethylene terephthalate may also be used. The use of bio-based polyethylene terephthalate is preferred because it can improve the bio-based content of the entire multilayer hollow container. Recycled polyethylene terephthalate may also be used. Examples of recycled polyethylene terephthalate include mechanically recycled polyethylene terephthalate and chemically recycled polyethylene terephthalate. One type of polyethylene terephthalate may be used alone, or two or more types may be used in combination.

[0017] (Components Other Than Polyethylene Terephthalate) The polyethylene terephthalate layer may contain components other than polyethylene terephthalate. Examples of such other components include antioxidants, aldehyde catchers, heat stabilizers, light stabilizers, moisture-proofing agents, waterproofing agents, lubricants, and spreading agents. The polyethylene terephthalate layer may contain resins other than polyethylene terephthalate, which is the main component, to the extent that the effects of the present invention are not impaired. The content of polyethylene terephthalate is preferably 80 to 100% by mass, and more preferably 90 to 100% by mass, relative to the total resin amount of the polyethylene terephthalate layer. The resin constituting the polyethylene terephthalate layer may consist solely of polyethylene terephthalate.

[0018] <Polyethylene furanoate Layer> The polyethylene furanoate layer contains polyethylene furanoate (PEF). The content of polyethylene furanoate in the polyethylene furanoate layer is preferably 70 to 100% by mass, based on the total amount of the polyethylene furanoate layer. From the viewpoints of gas barrier properties and shelf life, it is more preferably 90 to 100% by mass, even more preferably 95 to 100% by mass, and even more preferably 99 to 100% by mass. The polyethylene furanoate layer may be composed of polyethylene furanoate or may consist solely of polyethylene furanoate. The content of polyethylene furanoate in the polyethylene furanoate layer is preferably 0.05 to 10.0% by mass, based on the total amount of the polyethylene furanoate layer and the polyethylene terephthalate layer. From the viewpoints of gas barrier properties and shelf life, it is more preferably 1.0 to 10.0% by mass, even more preferably 3.0 to 9.0% by mass, even more preferably 5.0 to 9.0% by mass, and even more preferably 6.0 to 8.5% by mass. The content of the polyethylene furanoate layer is preferably 0.05 to 10.0% by mass, based on the total amount of the polyethylene furanoate layer and the polyethylene terephthalate layer, and from the viewpoints of gas barrier property and shelf life, it is more preferably 1.0 to 10.0% by mass, even more preferably 3.0 to 9.0% by mass, still more preferably 5.0 to 9.0% by mass, and still more preferably 6.0 to 8.5% by mass.

[0019] The polyethylene furanoate layer contains polyethylene furanoate, which is preferably a resin produced from bio-derived raw materials. The bio-based content of the polyethylene furanoate layer is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. There is no upper limit, as long as it is 100% by mass or less. Having the bio-based content of the polyethylene furanoate layer in the above range is preferable because it enables the resulting multilayer hollow container to address environmental issues.

[0020] (Polyethylene furanoate) Polyethylene furanoate is a polyester having primarily structural units derived from a dicarboxylic acid containing structural units derived from 2,5-furandicarboxylic acid and structural units derived from a diol containing structural units derived from ethylene glycol. The polyethylene furanoate preferably has structural units derived from a dicarboxylic acid containing 80 mol% or more of structural units derived from 2,5-furandicarboxylic acid and structural units derived from a diol containing 80 mol% or more of structural units derived from ethylene glycol, more preferably has structural units derived from a dicarboxylic acid containing 90 mol% or more of structural units derived from 2,5-furandicarboxylic acid and structural units derived from a diol containing 90 mol% or more of structural units derived from ethylene glycol, and more preferably has structural units derived from a dicarboxylic acid containing substantially 100 mol% of structural units derived from 2,5-furandicarboxylic acid. %, and structural units derived from a diol containing substantially 100 mol% structural units derived from ethylene glycol; even more preferably, structural units derived from a dicarboxylic acid containing 100 mol% structural units derived from 2,5-furandicarboxylic acid and structural units derived from a diol containing substantially 100 mol% structural units derived from ethylene glycol; and even more preferably, structural units derived from a dicarboxylic acid containing 100 mol% structural units derived from 2,5-furandicarboxylic acid and structural units derived from a diol containing 100 mol% structural units derived from ethylene glycol. Furthermore, from the viewpoint of increasing the bio-based content of the polyethylene furanoate layer and the multilayer hollow container, the polyethylene furanoate contained in the polyethylene furanoate layer is preferably a polycondensate of biomass-derived ethylene glycol and biomass-derived furandicarboxylic acid, and more preferably a polycondensate of ethylene glycol obtained from a plant-derived raw material and 2,5-furandicarboxylic acid obtained from a carbohydrate.

[0021] Polyethylene furanoate can be produced by known methods such as direct esterification and transesterification.

[0022] The glass transition point of polyethylene furanoate is preferably 80 to 90°C. The intrinsic viscosity of polyethylene furanoate is preferably 0.4 to 1.5 dL / g, more preferably 0.5 to 0.8 dL / g. Polyethylene furanoate has excellent gas barrier properties, and its oxygen permeability is preferably 0.40 cc mm / m. ２ The polyethylene furanoate may be used alone or in combination of two or more types.

[0023] (Other Components) The polyethylene furanoate layer may contain other components. Examples of other components include antioxidants, aldehyde catchers, heat stabilizers, light stabilizers, moisture-proofing agents, waterproofing agents, lubricants, and spreading agents. The polyethylene furanoate layer may contain resins other than polyethylene furanoate, which is the main component, to the extent that the effects of the present invention are not impaired. The content of polyethylene furanoate is preferably 80 to 100% by mass, and more preferably 90 to 100% by mass, based on the total resin amount of the polyethylene furanoate layer. The resin constituting the polyethylene furanoate layer may consist solely of polyethylene furanoate.

[0024] <Structure and Properties of Multilayer Hollow Container> The multilayer hollow container of the present invention has a polyethylene terephthalate layer containing polyethylene terephthalate and a polyethylene furanoate layer containing polyethylene furanoate, wherein, when the height of the multilayer hollow container is H, the lower end of the polyethylene furanoate layer is located in a range of 0.05H to 0.15H from the ground portion of the multilayer hollow container, and the upper end of the polyethylene furanoate layer is located in a range of 0.90H to 1.00H from the ground portion of the multilayer hollow container. The multilayer hollow container of the present invention may contain resin layers other than the polyethylene terephthalate layer and the polyethylene furanoate layer. However, from the viewpoints of improving the appearance, recyclability, and bio-based content of the container while maintaining gas barrier properties, it is preferable that the content of resin layers other than the polyethylene terephthalate layer and the polyethylene furanoate layer is low, and it is preferable that the container is substantially free of resin layers other than the polyethylene terephthalate layer and the polyethylene furanoate layer. In addition, an adhesive layer made of an adhesive or an inorganic layer made of an inorganic material may be provided, but the content of the adhesive layer or inorganic layer is preferably small, and it is preferable that the adhesive layer or inorganic layer is not substantially included.

[0025] The multilayer hollow container of the present invention has a multilayer structure of two or more layers, preferably a 2- to 5-layer structure, more preferably a 3- to 5-layer structure, even more preferably a 3-layer or 5-layer structure, and even more preferably a 3-layer structure. The outermost layer of the multilayer hollow container of the present invention is preferably a polyethylene terephthalate layer. The innermost layer is also preferably a polyethylene terephthalate layer, and more preferably the outermost and innermost layers are polyethylene terephthalate layers. When the outermost layer is a polyethylene terephthalate layer, the multilayer hollow container has excellent impact resistance, appearance, and design. Therefore, the structure of the multilayer hollow container is preferably a 2- to 5-layer structure with the outermost layer being a polyethylene terephthalate layer, more preferably a 3- to 5-layer structure with the outermost and innermost layers being polyethylene terephthalate layers, and even more preferably a 3-layer structure with the outermost and innermost layers being polyethylene terephthalate layers. Therefore, it is even more preferable that the multilayer hollow container has a three-layer structure consisting of a polyethylene terephthalate layer, a polyethylene furanoate layer, and a polyethylene terephthalate layer in this order.

[0026] When the multilayer hollow container has a three-layer structure consisting of a polyethylene terephthalate layer, a polyethylene furanoate layer, and a polyethylene terephthalate layer in this order, the ratio of the thickness of the polyethylene terephthalate layer on the outside of the container to the thickness of the polyethylene terephthalate layer on the inside of the container in the body (outside / inside) is preferably 30 / 70 to 70 / 30, more preferably 35 / 65 to 65 / 35, even more preferably 40 / 60 to 60 / 40, and still more preferably 45 / 55 to 55 / 45.

[0027] In the case of a two-layer structure, the structure is preferably a polyethylene furanoate layer / polyethylene terephthalate layer from the innermost layer, and in the case of a five-layer structure, the structure is preferably a polyethylene terephthalate layer / polyethylene furanoate layer / polyethylene terephthalate layer / polyethylene furanoate layer / polyethylene terephthalate layer from the innermost layer.

[0028] In the multilayer hollow container of the present invention, when the height of the multilayer hollow container is H, the lower end of the polyethylene furanoate layer is located within a range of 0.05H to 0.15H from the grounding portion of the multilayer hollow container, and the upper end of the polyethylene furanoate layer is located within a range of 0.90H to 1.00H from the grounding portion of the multilayer hollow container. "When the height of the multilayer hollow container is H, the lower end of the polyethylene furanoate layer is located within a range of 0.05H to 0.15H from the grounding portion of the multilayer hollow container" means that the polyethylene furanoate layer is not contained within a range from the grounding portion (position 0H) to a height 0.05 to 0.15 times the height of the container. Preferably, the range from the grounding portion of the multilayer hollow container to the lower end of the polyethylene furanoate layer consists solely of polyethylene terephthalate layer. Similarly, "where the height of the multilayer hollow container is H, the upper end of the polyethylene furanoate layer is located within a range of 0.90H to 1.00H from the ground contact portion of the multilayer hollow container" means that the polyethylene furanoate layer is included from the ground contact portion (position 0H) to a height of 0.90 to 1.00 times the height of the container. The "ground contact portion" is the portion that comes into contact with a horizontal surface when the multilayer hollow container of the present invention is placed on the horizontal surface. Note that the "ground contact portion" and "container height" do not include decorative portions, handles, etc. that do not affect the storage of the contents. Furthermore, the "ground contact portion" and "container height" do not include lids, skirts, etc. that are molded separately from the multilayer hollow container and attached to the multilayer hollow container.

[0029] From the viewpoint of improving the gas barrier properties and shelf life, when the height of the multilayer hollow container is H, the lower end of the polyethylene furanoate layer is preferably located in the range of 0.06H to 0.15H from the ground contact portion of the multilayer hollow container, more preferably in the range of 0.06H to 0.14H, even more preferably in the range of 0.07H to 0.13H, even more preferably in the range of 0.08H to 0.12H, and even more preferably in the range of 0.09H to 0.11H.

[0030] From the viewpoint of improving gas barrier properties and shelf life, the upper end of the polyethylene furanoate layer is preferably located in the range of 0.91H to 1.00H from the ground portion of the multilayer hollow container, where H is the height of the multilayer hollow container, more preferably in the range of 0.93H to 1.00H, even more preferably in the range of 0.95H to 1.00H, even more preferably in the range of 0.97H to 1.00H, and even more preferably in the range of 0.99H to 1.00H. It is believed that barrier properties can be improved by concentrating the polyethylene furanoate layer in the body portion, where the stretch ratio is high, rather than in the bottom portion or near the lower portion of the body, where the stretch ratio is low and the thickness is high. Furthermore, carbon dioxide gas generated from the contents tends to accumulate in the upper part of the container, and it is believed that barrier properties can be further improved by arranging the polyethylene furanoate layer in this area as well.

[0031] From the viewpoint of improving the gas barrier properties and shelf life, the vertical width of the polyethylene furanoate layer is preferably in the range of 0.85H to 0.95H, more preferably in the range of 0.86H to 0.94H, even more preferably in the range of 0.87H to 0.93H, still more preferably in the range of 0.88H to 0.92H, and even more preferably in the range of 0.89H to 0.91H, where H is the height of the multilayer hollow container.

[0032] The polyethylene furanoate layer may have a thickness within the above ranges at its upper and lower ends. However, it is preferable that the polyethylene furanoate layer be formed substantially continuously around the entire height and circumferential direction of the multilayer hollow container, and more preferably, it is formed continuously around the entire height and circumferential direction of the multilayer hollow container. The continuous presence of the polyethylene furanoate layer enhances gas barrier properties. Furthermore, it is preferable that the polyethylene furanoate layer be provided over 50 to 95% of the outer surface area of ​​the multilayer hollow container. In other words, when the area of ​​all the outer surfaces of the multilayer hollow container that are in contact with the outside air, such as the body, tip (mouth), shoulder, and bottom, is taken as 100%, the area of ​​the polyethylene furanoate layer is preferably 50 to 95%, more preferably 60 to 95%, even more preferably 60 to 90%, even more preferably 70 to 90%, and even more preferably 70 to 80%.

[0033] In the body of the multilayer hollow container of the present invention, the ratio of the thickness of the polyethylene furanoate layer to the total thickness of the polyethylene terephthalate layer and the polyethylene furanoate layer is preferably 0.5 to 40%, more preferably 0.5 to 20%, even more preferably 1 to 15%, even more preferably 3 to 15%, even more preferably 5 to 10%, and even more preferably 6 to 10%. The thickness of the polyethylene terephthalate layer refers to the average thickness, and when the body contains multiple polyethylene terephthalate layers, it refers to the total thickness of the multiple layers. The same applies to the thickness of the polyethylene furanoate layer. When the thickness ratio of the polyethylene furanoate layer is within the above range, the hollow container has excellent gas barrier properties and can store the contents for a long period of time. In this specification, the "body" of a multilayer hollow container refers to the portion that forms the side surface of the multilayer hollow container that holds the contents and is primarily responsible for holding the contents. Therefore, the body typically has a larger area when cut horizontally than other portions. Furthermore, the shape of the body when cut horizontally is usually a circle, oval, square, rectangle, or the like.

[0034] The thickness of the body of the multilayer hollow container (total thickness of all layers of the body) is preferably 100 μm to 5 mm, more preferably 100 μm to 3 mm, even more preferably 100 μm to 2 mm, and even more preferably 200 μm to 2 mm. The thickness of each polyethylene terephthalate layer is preferably 30 μm to 2 mm, more preferably 40 μm to 1 mm, and even more preferably 50 μm to 500 μm. The thickness of each polyethylene furanoate layer is preferably 1 to 200 μm, more preferably 3 to 100 μm, and even more preferably 8 to 50 μm. In the present invention, by setting the thickness of the polyethylene furanoate layer within this range, the gas barrier properties and shelf life can be improved.

[0035] The multilayer hollow container of the present invention is not limited in shape as long as it has the above-mentioned configuration, but is preferably a so-called bottle shape. Specifically, the multilayer hollow container preferably has a mouth provided with an opening through which contents can be put in and taken out, a tubular body having a cross-sectional area larger than that of the mouth, a shoulder connecting the mouth and the body, and a bottom (bottom) closing the tubular end of the body opposite the shoulder.

[0036] The polyethylene furanoate layer contains polyethylene furanoate, which is preferably a resin produced from bio-derived raw materials. The bio-based content of the polyethylene furanoate layer is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. There is no upper limit, as long as it is 100% by mass or less. Having the bio-based content of the polyethylene furanoate layer in the above range is preferable because it enables the resulting multilayer hollow container to address environmental issues. The bio-based content of the polyethylene furanoate layer is the mass ratio of biomass raw materials to the total amount (100% by mass) of raw materials contributing to the resin structure contained in the polyethylene furanoate layer.

[0037] The biobased content of the multilayer hollow container of the present invention is preferably 4% by mass or more, more preferably 5% by mass or more, even more preferably 6% by mass or more, and even more preferably 7% by mass or more. There is no upper limit, as long as it is 100% by mass or less. Having a biobased content within the above range is preferable because the resulting multilayer hollow container can address environmental issues. The biobased content of the multilayer hollow container is the mass ratio of biomass raw materials to the total amount (100% by mass) of raw materials contributing to the resin structure that constitutes the multilayer hollow container.

[0038] [Uses of multilayer hollow container and carbonated beverage product] The multilayer hollow container of the present invention is more preferably a liquid packaging container that is filled with a liquid, and even more preferably a beverage packaging container. Examples of the liquid to be filled include beverages, liquid seasonings, chemicals, pharmaceuticals, detergents, etc., with beverages being preferred. Examples of liquid seasonings include sauces, soy sauce, syrup, mirin, dressings, etc. Examples of chemicals include pesticides, insecticides, etc.

[0039] Examples of beverages include water, carbonated water, oxygenated water, hydrogenated water, milk, dairy products, juice, coffee, coffee drinks, carbonated soft drinks, tea, alcoholic drinks, etc. Among these, carbonated drinks are preferred, as deterioration can be effectively prevented by the barrier properties of the multilayer hollow container of the present invention against carbon dioxide.

[0040] The present invention also includes a carbonated beverage product in which a carbonated beverage is contained in the multi-layer hollow container. The carbonated beverage product of the present invention has the polyethylene terephthalate layer and the polyethylene furanoate layer, and where the height of the multi-layer hollow container is H, the lower end of the polyethylene furanoate layer is located 0.05H to 0.15H from the ground edge of the multi-layer hollow container and the upper end of the polyethylene furanoate layer is located 0.90H to 1.00H from the ground edge of the multi-layer hollow container. Because the carbonated beverage is contained in the multi-layer hollow container, which has excellent barrier properties against carbon dioxide, the carbonated beverage product of the present invention has a long shelf life and is also preferable from the perspective of reducing food waste.

[0041] <Method for manufacturing multi-layer hollow container> The method for manufacturing a multi-layer hollow container of the present invention is not particularly limited as long as it is a method for manufacturing a multi-layer hollow container having the polyethylene terephthalate layer and the polyethylene furanoate layer, wherein, when the height of the multi-layer hollow container is H, the lower end of the polyethylene furanoate layer is located in a range of 0.05H to 0.15H from the ground part of the multi-layer hollow container and the upper end of the polyethylene furanoate layer is located in a range of 0.90H to 1.00H from the ground part of the multi-layer hollow container. However, the following manufacturing method is preferred.

[0042] The method for producing a multilayer hollow container of the present invention includes Step 1 of co-injecting polyethylene terephthalate or a resin composition containing polyethylene terephthalate with polyethylene furanoate or a resin composition containing polyethylene furanoate to obtain a multilayer preform having a three-layer structure composed, in this order, of a polyethylene terephthalate layer containing polyethylene terephthalate, a polyethylene furanoate layer containing polyethylene furanoate, and a polyethylene terephthalate layer containing polyethylene terephthalate, and Step 2 of blow molding the multilayer preform, wherein, when the total length of the multilayer preform is h, the lower end of the polyethylene furanoate layer is preferably located 0.05 h to 0.15 h from the tip of the multilayer preform and the upper end of the polyethylene furanoate layer is preferably located 0.90 h to 1.00 h from the tip of the multilayer preform. Here, the tip of the multilayer preform refers to the end that will become the bottom of the multilayer hollow container after blow molding.

[0043] (Step 1 (Step of Obtaining a Multilayer Preform)) In step 1, polyethylene terephthalate or a resin composition containing polyethylene terephthalate and a resin composition containing polyethylene furanoate or polyethylene furanoate are co-injection molded to obtain a multilayer preform having a three-layer structure composed, in this order, of a polyethylene terephthalate layer containing polyethylene terephthalate, a polyethylene furanoate layer containing polyethylene furanoate, and a polyethylene terephthalate layer containing polyethylene terephthalate. The resin composition containing polyethylene terephthalate is a composition containing polyethylene terephthalate as the main component and containing resins other than polyethylene furanoate and other components, etc., as described in the section <Polyethylene Terephthalate Layer>. The resin composition containing polyethylene furanoate is a composition containing polyethylene furanoate as the main component and containing resins other than polyethylene furanoate and other components, etc., as described in the section <Polyethylene Furanoate Layer>. Note that the resin composition also includes mixtures obtained by dry-blending resins and other components, etc. These mixtures become uniform compositions by melt-mixing the respective components in this step. In co-injection molding, polyethylene terephthalate or a resin composition containing polyethylene terephthalate and polyethylene furanoate or a resin composition containing polyethylene furanoate are each extruded into a mold and co-injection molded to form a multilayer preform.

[0044] In addition, when the total length of the multilayer preform obtained in this step is h, it is preferable that the lower end of the polyethylene furanoate layer is located in a range of 0.05 h to 0.15 h from the tip of the multilayer preform, and the upper end of the polyethylene furanoate layer is located in a range of 0.90 h to 1.00 h from the tip of the multilayer preform.

[0045] From the viewpoint of improving the gas barrier properties and shelf life, when the total length of the multilayer preform is h, the lower end of the polyethylene furanoate layer is preferably located in the range of 0.06 h to 0.15 h from the tip of the multilayer preform, more preferably in the range of 0.06 h to 0.14 h, even more preferably in the range of 0.07 h to 0.13 h, even more preferably in the range of 0.08 h to 0.12 h, and even more preferably in the range of 0.09 h to 0.11 h.

[0046] From the viewpoint of improving gas barrier properties and shelf life, when the total length of the multilayer preform is h, the upper end of the polyethylene furanoate layer is preferably located in the range of 0.91 h to 1.00 h from the tip of the multilayer preform, more preferably in the range of 0.93 h to 1.00 h, even more preferably in the range of 0.95 h to 1.00 h, even more preferably in the range of 0.97 h to 1.00 h, and even more preferably in the range of 0.99 h to 1.00 h. In a multilayer hollow container obtained using the multilayer preform, it is believed that barrier properties can be improved by concentrating the polyethylene furanoate layer in the body portion, where the stretching ratio is high, rather than in the bottom portion or near the lower portion of the body, where the stretching ratio is low and the thickness is high. Furthermore, carbon dioxide gas generated from the contents tends to stagnate in the upper part of the container, and it is believed that arranging the polyethylene furanoate layer in this area can further improve barrier properties.

[0047] From the viewpoint of improving gas barrier properties and shelf life, the vertical width of the polyethylene furanoate layer is preferably in the range of 0.85h to 0.95h, more preferably in the range of 0.86h to 0.94h, even more preferably in the range of 0.87h to 0.93h, even more preferably in the range of 0.88h to 0.92h, and even more preferably in the range of 0.89h to 0.91h, where h is the total length of the multilayer preform.

[0048] (Step 2 (Blow Molding Step)) In Step 2, the multilayer preform is blow molded. In the method for producing a multilayer hollow container of the present invention, it is preferable to mold the multilayer preform (multilayer parison) obtained in Step 1 by stretch blow molding. Among these, in Step 2, it is preferable to stretch blow mold the multilayer preform obtained by coinjection molding, and it is more preferable to biaxially stretch blow mold the multilayer preform obtained by coinjection molding. Note that the conditions for biaxial stretch blow molding are preferably a preform heating temperature of 95 to 110°C, a primary blow pressure of 0.5 to 1.2 MPa, and a secondary blow pressure of 2.0 to 2.6 MPa, which suppresses the occurrence of thickness unevenness and stretch unevenness and makes it possible to obtain a multilayer hollow container that is excellent in strength and gas barrier properties.

[0049] EXAMPLES The present invention will be explained in more detail below using examples and comparative examples, but the present invention is not limited to these examples.

[0050] [Raw Materials] The polyethylene terephthalate and polyethylene furanoate used in the Examples and Comparative Examples are as follows: <Polyethylene terephthalate> PET 1101: Polyclear Refresh PET 1101, polyethylene terephthalate (manufactured by Indorama) <Polyethylene furanoate> PEF: polyethylene furanoate: glass transition point 86°C, intrinsic viscosity 0.67 dL / g, oxygen permeability 0.33 cc mm / m ２·day·atm The polyethylene furanoate was produced as follows: 1.5 kg of biomass-derived furan distillate and 1.5 kg of biomass-derived ethylene glycol were introduced into a reaction vessel equipped with a packed column rectification column, a partial condenser, a total condenser, a cold trap, a stirrer, a heating device, and a nitrogen inlet tube. The mixture was heated to 200°C using an oil bath under a nitrogen flow and allowed to stand for 1.5 hours. Then, zinc acetate calculated to give 400 ppm zinc was added, and the mixture was heated to 260°C while gradually reducing the pressure to 0.1 kPa. After stirring for 4 hours, nitrogen was again introduced and the mixture was cooled to obtain polyethylene furanoate. The biobased content in Table 1 indicates the biobased content of the multi-layer hollow container and represents the mass proportion (mass %) of the biomass raw material relative to the total amount of the raw materials contributing to the structure of the polyethylene terephthalate and polyethylene furanoate resins constituting the multi-layer hollow container, where the total amount of the raw materials is taken as 100 mass %.

[0051] Examples 1 and 2 and Comparative Examples 1 to 4 [Production of multilayer hollow containers] (Preform molding) Using an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd., model DU130CI) having two injection cylinders and a two-cavity mold (manufactured by Kortec), polyethylene furanoate was injected from one injection cylinder and polyethylene terephthalate from the other injection cylinder, and three-layer preforms (weight equivalent to 25 g per preform) consisting of a polyethylene terephthalate layer / polyethylene furanoate layer / polyethylene terephthalate layer were produced by injection molding under the conditions shown below.

[0052] The mass ratio of the total polyethylene terephthalate layer to the polyethylene furanoate layer in the preform was as shown in Table 1, and the position of the polyethylene furanoate layer after bottle molding was as shown in Table 1. Specifically, the position of the polyethylene furanoate layer was adjusted by shifting the start and end times of polyethylene terephthalate filling and the start and end times of polyethylene furanoate filling. The shape of the preform was 95 mm in total length, 22 mm in outer diameter, and 4.0 mm in wall thickness. The molding conditions for the three-layer preform were as shown below.

[0053] Skin side injection cylinder temperature: 285°C Core side injection cylinder temperature (3 layers only): 265°C Mold resin flow path temperature: 285°C Mold cooling water temperature: 15°C Cycle time: 40 seconds

[0054] (Bottle Molding) The preform obtained in the (Preform Molding) step was biaxially stretched and blow molded using a blow molding machine (EFB1000ET, manufactured by Frontier) to obtain a multilayer bottle (multilayer hollow container). The multilayer bottle had a total length of 223 mm, an outer diameter of 65 mm, an internal volume of 500 mL, and a petaloid bottom. No dimples were provided on the body. The biaxial stretch blow molding conditions were as follows: Preform heating temperature: 103°C, stretch rod pressure: 0.7 MPa, primary blow pressure: 1.1 MPa, secondary blow pressure: 2.5 MPa, primary blow delay time: 0.30 seconds, primary blow time: 0.30 seconds, secondary blow time: 2.0 seconds, blow exhaust time: 0.6 seconds, mold temperature: 30°C.

[0055] [Evaluation Methods] <Evaluation 1: Shelf Life> The multilayer bottles (multilayer hollow containers, internal volume 500 mL) obtained in the Examples and Comparative Examples were filled with 500 mL of carbonated water containing carbon dioxide in an amount (standard conditions) approximately four times the internal volume of the bottle, and after the caps were closed, the bottles were stored in an environment of 23°C and 50% RH, and the change in the internal pressure of the bottle over time was continuously measured. Carbon dioxide inside the bottle permeates through the bottle wall over time, so the pressure decreases over time. The shelf life was defined as the number of days until the pressure decreased to 80%, assuming the initial pressure to be 100%. The higher the shelf life (days (s)), the better the shelf life, and this is preferable because when the multilayer bottles (multilayer hollow containers) are used for carbonated beverages, they can be stored in stores for long periods of time, reducing food waste.

[0056] <Evaluation 2: Carbon Dioxide Barrier Property> The multilayer bottles (multilayer hollow containers, internal volume 500 mL) obtained in the Examples and Comparative Examples were filled with 500 mL of carbonated water containing carbon dioxide in an amount (standard conditions) approximately four times the internal volume of the bottle, and after the caps were closed, the bottles were stored in an environment of 23°C and 50% RH. Carbon dioxide permeability was measured using a gas barrier tester Permatran C10 (manufactured by MOCON Corporation). The smaller the carbon dioxide permeability (cc / day), the better the carbon dioxide barrier property, and the more effectively carbon dioxide leakage can be prevented when the multilayer bottles (multilayer hollow containers) are used for carbonated beverages, which is preferable.

[0057]

[0058] As shown in Table 1, the multilayer bottles of the examples have excellent gas barrier properties against carbon dioxide and a long shelf life. This demonstrates that the multilayer hollow container of the present invention has high barrier properties against carbon dioxide and a long shelf life. Because the multilayer hollow container of the present invention has the excellent properties described above, it is particularly useful as a container for storing carbonated beverages.

Claims

1. A multi-layer hollow container having a polyethylene terephthalate layer containing polyethylene terephthalate and a polyethylene furanoate layer containing polyethylene furanoate, wherein, when the height of the multi-layer hollow container is H, the lower end of the polyethylene furanoate layer is located within a range of 0.05H to 0.15H from the ground part of the multi-layer hollow container, and the upper end of the polyethylene furanoate layer is located within a range of 0.90H to 1.00H from the ground part of the multi-layer hollow container.

2. The multi-layer hollow container according to claim 1, wherein the polyethylene furanoate layer is provided over 50 to 95% of the area of ​​the outer surface of the multi-layer hollow container.

3. A multilayer hollow container according to claim 1 or 2, wherein the content of the polyethylene furanoate layer is 0.05 to 10.0 mass% relative to the total amount of the polyethylene terephthalate layer and the polyethylene furanoate layer.

4. The multilayer hollow container according to any one of claims 1 to 3, wherein the polyethylene furanoate is a polycondensate of biomass-derived ethylene glycol and biomass-derived furan dicarboxylic acid.

5. A multilayer hollow container according to any one of claims 1 to 4, having a bio-based content of 4% by mass or more.

6. A multilayer hollow container according to any one of claims 1 to 5, which has a three-layer structure consisting of a polyethylene terephthalate layer, a polyethylene furanoate layer, and a polyethylene terephthalate layer in that order.

7. A multi-layer hollow container according to any one of claims 1 to 6, wherein the polyethylene furanoate layer is formed substantially continuously over the entire circumference of the multi-layer hollow container in the height direction and circumferential direction.

8. A carbonated beverage product comprising a multilayer hollow container according to any one of claims 1 to 7, and a carbonated beverage contained therein.

9. A method for producing a multilayer hollow container, comprising: Step 1 of co-injecting polyethylene terephthalate or a resin composition containing polyethylene terephthalate with polyethylene furanoate or a resin composition containing polyethylene furanoate to obtain a multilayer preform having a three-layer structure consisting of a polyethylene terephthalate layer containing polyethylene terephthalate, a polyethylene furanoate layer containing polyethylene furanoate, and a polyethylene terephthalate layer containing polyethylene terephthalate, in that order; and Step 2 of blow molding the multilayer preform, wherein, when the overall length of the multilayer preform is h, the lower end of the polyethylene furanoate layer is located within a range of 0.05h to 0.15h from the tip of the multilayer preform, and the upper end of the polyethylene furanoate layer is located within a range of 0.90h to 1.00h from the tip of the multilayer preform.

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