Multilayer resin sheet and container formed using the same

Abstract

To provide a multilayer resin sheet that reduces the amount of fossil fuel-derived resin used compared to conventional products, maintains the same moldability as conventional products, and improves drop impact resistance in low-temperature environments. [Solution] The present invention provides a resin multilayer sheet having a resin layer laminated therein, wherein the resin multilayer sheet has a thickness of 250 to 500 μm, and the resin multilayer sheet has at least (1) to (7) layers laminated in the following order from the outer surface, the biomass-derived polyethylene content in the (1) layer is 1 to 10% by mass, the biomass-derived polyethylene content in the (2) layer and the (6) layer is 10 to 30% by mass, and the biomass-derived polyethylene content relative to the entire resin multilayer sheet is 10 to 30% by mass.

Description

Technical Field

[0001] The present invention relates to a resin multilayer sheet and a container formed using the same. The resin multilayer sheet of the present invention is a resin multilayer sheet for molding processing suitable for secondary molding such as vacuum molding and pressure-air molding.

Background Art

[0002] In recent years, consideration for the environment has become necessary for raw materials of resin products. Biomass-derived plastics manufactured using renewable organic resources as raw materials are expected to contribute to the prevention of global warming from the perspective of carbon neutrality, and there is a movement to replace fossil fuel-derived plastics as much as possible. For example, there is a polyolefin resin film in which a part of the raw material fossil fuel-derived polyethylene is replaced with biomass-derived polyethylene (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a resin multilayer sheet that reduces the amount of fossil fuel-derived resin used compared to conventional products, maintains moldability equivalent to that of conventional products, and improves drop impact resistance in a low-temperature environment.

Means for Solving the Problems

[0005] In order to achieve the above objective, the inventors of the present invention have found, through various studies, that by specifying the mixing of biomass-derived polyethylene (PE) into a specific layer of a resin multilayer sheet, the amount of mixing, and the thickness of the resin multilayer sheet, it is possible to replace a portion of conventional products containing fossil fuel-derived polypropylene (PP) with biomass-derived PE while maintaining the same moldability as conventional products and improving drop impact resistance in low-temperature environments, thus arriving at the present invention. That is, the present invention is as follows. [1] A multilayer resin sheet in which resin layers are laminated, The thickness of the aforementioned resin multilayer sheet is 250 to 500 μm. The aforementioned resin multilayer sheet has at least the following layers (1) to (7) laminated in the order shown below from the outer surface: (1) Surface layer containing a mixed resin of fossil fuel-derived polypropylene and biomass-derived polyethylene (2) Intermediate layer containing a mixed resin of fossil fuel-derived polypropylene and biomass-derived polyethylene (3)Adhesive resin layer (4) Gas barrier resin layer (5)Adhesive resin layer (6) Intermediate layer containing a mixed resin of fossil fuel-derived polypropylene and biomass-derived polyethylene (7) Surface layer made of fossil fuel-derived polypropylene resin The content ratio of biomass-derived polyethylene in the above (1) layer is 1 to 10% by mass, The content ratio of biomass-derived polyethylene in the aforementioned layer (2) and layer (6) is 10 to 30% by mass, The biomass-derived polyethylene content ratio to the entire resin multilayer sheet is 10 to 30% by mass. A multi-layered sheet made of resin. [2] The resin multilayer sheet according to [1], wherein the thickness of the (1) layer is 20 to 50 μm, and the thicknesses of the (2) and (6) layers are each 70 to 210 μm. [3] The resin multilayer sheet according to [1] or [2], wherein the (1) layer and the (7) layer do not contain coloring raw materials, and the (2) layer and the (6) layer further contain coloring raw materials. [4] A container formed using a resin multilayer sheet as described in any one of the above items [1] to [3]. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a resin multilayer sheet and a container molded using the same, which reduces the amount of fossil fuel-derived resin used compared to conventional products, maintains the same moldability as conventional products, and improves drop impact resistance in low-temperature environments. [Modes for carrying out the invention]

[0007] The present invention will be described in detail below. 1. Thickness and layer structure of resin multilayer sheets The resin multilayer sheet of the present invention is a sheet in which multiple resin layers are laminated, and the thickness of the sheet is 250 to 500 μm, preferably 250 to 420 μm. The sheet thickness is the thickness measured in the sheet state, that is, the thickness of the sheet before secondary molding. After secondary molding, the thickness may become uneven due to molding, and parts of it may fall outside the above range. The resin layer of the multilayer resin sheet of the present invention consists of two surface layers and an intermediate layer between them. The inner surface layer when the sheet is molded into a container is a resin layer of fossil fuel-derived PP. The outer surface layer when the sheet is molded into a container is a resin layer containing a mixture of fossil fuel-derived PP and biomass-derived PE. The intermediate layer has a gas barrier resin layer and a resin layer (hereinafter sometimes referred to as the intermediate mixed resin layer) which is a mixture of fossil fuel-derived PP and biomass-derived PE. The gas barrier resin layer is sandwiched between the two intermediate mixed resin layers. Furthermore, because resin layers with low affinity are bonded together, an adhesive resin layer is provided between the gas barrier resin layer and the intermediate mixed resin layer. When increasing the thickness of the sheet within the above range, it is more preferable to increase the thickness so that the proportion of the intermediate mixed resin layer increases. The layer structure of the resin multilayer sheet is as follows, from the outer surface: (1) a surface layer containing a mixed resin of fossil fuel-derived PP and biomass-derived PE, (2) an intermediate layer containing a mixed resin of fossil fuel-derived PP and biomass-derived PE, (3) an adhesive resin layer, (4) a gas barrier resin layer, (5) an adhesive resin layer, (6) an intermediate layer containing a mixed resin of fossil fuel-derived PP and biomass-derived PE, and (7) a surface layer made of fossil fuel-derived PP resin.

[0008] 2.Outer surface layer ((1) surface layer) The outer surface layer of the resin multilayer sheet of the present invention is a mixture of fossil fuel-derived PP and biomass-derived PE. Fossil fuels are fuels such as coal, oil, and natural gas that are formed from the remains of plants and animals from the past. Fossil fuel-derived PP is PP that is chemically or biologically synthesized from these. The outer surface layer PP may be homoPP, which is a homopolymer; random PP, which is a random copolymer containing 1 to 7% by mass of ethylene or butene-1; or block PP, which contains 20% by mass or less of ethylene propylene rubber component, but block PP is more preferred. Furthermore, considering secondary moldability, the melt flow rate of the PP base material is more preferably 0.3 to 2.0 g / 10 min (230°C), even more preferably 0.3 to 1.0 g / 10 min (230°C), and particularly preferably 0.3 to 0.6 g / 10 min (230°C). Biomass-derived PE refers to PE obtained by chemical or biological synthesis from raw materials containing substances derived from renewable organic resources. Biomass-derived PE preferably has a density of 0.94 to 0.97 g / cm³ 3 High-density polyethylene (hereinafter referred to as HDPE), more preferably 0.950 to 0.965 g / cm³ 3It is HDPE. Furthermore, the melt flow rate of the biomass-derived PE is preferably 0.3 to 10.0 g / 10 min, more preferably 0.3 to 5.0 g / 10 min, still more preferably 0.3 to 2.0 g / 10 min, and particularly preferably 0.3 to 1.0 g / 10 min. The melt flow rate is the value measured by the standard test method ASTM D1238 for the melt flow rate of thermoplastic resins using an extrusion plastometer. The temperature is measured at 190 °C and the load is 2.16 kg weight. A small amount of additives such as coloring raw materials may be mixed in the outer surface layer. Examples of the coloring raw materials include titanium oxide, iron oxide, etc. Also, it is preferable that the outer surface layer does not contain coloring raw materials.

[0009] 3. Inner surface layer ((7) surface layer) The inner surface layer of the resin multi-layer sheet of the present invention is made of fossil fuel-derived PP. The fossil fuel-derived PP is the same as described in the section of the outer surface layer. The PP of the inner surface layer is preferably block PP. A small amount of additives such as coloring raw materials may be mixed in the inner surface layer. The coloring raw materials are the same as described in the section of the outer surface layer. Also, it is preferable that the inner surface layer does not contain coloring raw materials.

[0010] 4. Gas barrier resin layer The resin multi-layer sheet of the present invention is assumed to be used as a food packaging material and has a gas barrier resin layer. Examples of the gas barrier resin include ethylene vinyl alcohol copolymer resin (hereinafter, EVOH), polyvinylidene chloride (PVDC), etc. The gas barrier resin layer is a resin layer mainly composed of these.

[0011] 5. Intermediate mixed resin layer The resin multi-layer sheet of the present invention has an intermediate layer containing a resin obtained by mixing fossil fuel-derived PP and biomass-derived PE. The fossil fuel-derived PP and biomass-derived PE are the same as described in the section of the outer surface layer. The PP of the intermediate mixed resin layer is preferably block PP. The intermediate mixed resin layer may contain a small amount of additives such as coloring raw materials and anti-gelling agents, and may also contain crushed and recovered materials of end materials and recycled products as raw materials. The coloring raw materials are preferably contained in the intermediate mixed resin layer, not contained in the inner surface layer, more preferably contained in the outer surface layer and the intermediate mixed resin layer, not contained in the inner surface layer and the outer surface layer, and even more preferably contained in the intermediate mixed resin layer.

[0012] 6. Mixing ratio of biomass-derived PE The content ratio of biomass-derived PE in the outer surface layer is 1 to 10% by mass, more preferably 1 to 5% by mass, and even more preferably 1 to 3% by mass. The content ratio of fossil fuel-derived PP in the outer surface layer is preferably 90 to 99% by mass, more preferably 95 to 99% by mass, and even more preferably 97 to 99% by mass. The combined content ratio of fossil fuel-derived PP and biomass-derived PE is more preferably 95% by mass or more. The content ratio of biomass-derived PE in the intermediate mixed resin layer is 10 to 30% by mass, more preferably 15 to 25% by mass, and even more preferably 20 to 24% by mass. The content ratio of fossil fuel-derived PP in the intermediate mixed resin layer is preferably 60 to 90% by mass, more preferably 60 to 85% by mass, and even more preferably 60 to 80% by mass. The combined content ratio of fossil fuel-derived PP and biomass-derived PE is more preferably 80 to 95% by mass. For the entire resin multi-layer sheet, the biomass-derived PE is 10 to 30% by mass, more preferably 10 to 20% by mass, and even more preferably 10 to 17% by mass. The content ratio of fossil fuel-derived PP for the entire resin multi-layer sheet is preferably 60 to 90% by mass, more preferably 60 to 87% by mass. The combined content ratio of fossil fuel-derived PP and biomass-derived PE is more preferably 80 to 95% by mass. If the proportion of biomass-derived PE is too high, dispersibility decreases, physical properties such as hardness (i.e., elastic modulus) decrease, and it may also cause appearance defects, making it impossible to meet the required characteristics of the product. If the proportion of biomass-derived PE is too low, the objective of increasing the biomass content of the product will not be achieved. Furthermore, the resin that forms the base material of this invention is fossil fuel-derived PP, and in order to maintain the required characteristics, it is necessary to include a certain proportion or more of fossil fuel-derived PP. It is preferable that the biomass-derived PE content in the outer surface layer is less than the biomass-derived PE content in the intermediate mixed resin layer. Fossil fuel-derived PP and biomass-derived PE are immiscible, and if a large amount of immiscible raw materials is contained in the outer surface layer, it will increase the generation of die residue at the lip of the T-die exit, which will reduce productivity. Therefore, it is preferable that the biomass-derived PE content in the outer surface layer is less than that in the intermediate mixed resin layer. When adding coloring raw materials to the inner surface layer, outer surface layer, and intermediate mixed resin layer, it is preferable that the amount is approximately 3 to 10 parts by mass per 100 parts by mass of fossil fuel-derived PP contained in the layer to which the coloring raw material is added. The mass percentage indicating the mixing ratio of each resin is a theoretical value calculated from the mass mixed during manufacturing. Naturally, when using scraps or crushed recycled materials as raw materials, the individual components such as fossil fuel-derived PP and biomass-derived PE are included in the calculation.

[0013] 7.Adhesive resin layer For the adhesive resin layer, a resin mainly composed of polyolefins such as polyethylene or polypropylene may be used. Besides between the gas barrier resin layer and the intermediate mixed resin layer, an adhesive resin layer may also be provided between resin layers with low affinity when bonding them together.

[0014] 8. Example of a layer configuration In the resin multilayer sheet of the present invention, the thickness of each layer is preferably 20 to 50 μm for layers (1) and (7), 70 to 210 μm for layers (2) and (6), and 5 to 15 μm for layer (4). More preferably, layers (1) and (7) are 20 to 30 μm, layers (2) and (6) are 90 to 110 μm, and layer (4) is 5 to 15 μm. There are no particular restrictions on the thickness of the adhesive resin layer, but it is particularly preferably 5 to 15 μm. The thickness of each layer is the thickness before secondary processing. The thickness of each layer can be calculated by observing the cross-section of the sheet with a microscope or similar device, and comparing the ratio of the thicknesses of each layer in the cross-sectional image with the total thickness of the sheet.

[0015] 9. (1) Method for manufacturing a resin multilayer sheet of the present invention The resin multilayer sheets of the present invention can be manufactured by extrusion molding or calendering. In the case of extrusion molding, the material can be manufactured using a co-extrusion multilayer T-die method, such as a feed block method in which the resin is combined before the die, or a multi-manifold method in which the resin is combined near the discharge port of the T-die. Inside the die, all layers of the multilayer sheet are integrated, extruded from the discharge port into a single sheet, solidified by passing through a cooling roll or cooling tank, and the sheet is wound up to manufacture the resin multilayer sheet of the present invention. Calendering is a method of manufacturing sheets by rolling resin between rolls. Depending on the arrangement of the rolls, there are various types such as the straight three-roll type, the inverted L-type, and the Z-type, but any type can be used. (2) Secondary molding process of the resin multilayer sheet of the present invention The manufactured resin multilayer sheets can be further processed by methods such as vacuum forming and pressure forming to create containers for food, cosmetics, pharmaceuticals, and industrial applications.

[0016] 10. Physical properties and processability of manufactured resin multilayer sheets The modulus of elasticity of the resin multilayer sheet is more preferably 700 to 1800 MPa. [Examples]

[0017] (Example 1) (1) Manufacturing of resin multilayer sheets (I) Raw materials The following were used as raw materials. • PP: Fossil fuel-derived PP (block PP), MFR 0.5g / 10min, density 0.90g / cm³ 3 • PE: Biomass-derived PE (HDPE): MFR 0.34g / 10min, density 0.961g / cm³ 3 ·Coloring raw materials • Gelling inhibitor (II) Manufacturing method (i) Preparation of the resins that make up each layer • Outer surface layer: The raw materials were mixed so that PP accounted for 99% by mass and PE accounted for 1% by mass. The mixing was performed using a kneader. • Inner surface layer: The PP material, as indicated in the raw materials, is made to be 100% by mass. • Intermediate mixed resin layer: The raw materials were mixed so that PP accounted for 69% by mass, PE for 22% by mass, and other gelling inhibitors and coloring agents totaled 9% by mass. The mixing was performed using a kneader. • Adhesive resin layer: A polypropylene-based adhesive resin was used. • Gas barrier resin layer: EVOH was used. (ii) Manufacturing of resin multilayer sheets (i) Using the resins that make up each layer prepared in (i), a multilayer resin sheet was manufactured by the feed-block method of the co-extrusion multilayer T-die method, which is a type of extrusion molding. The arrangement of the resin layers was as follows: (1) A mixed resin layer (outer surface layer) of fossil fuel-derived PP and biomass-derived PE (2) A mixed resin layer of fossil fuel-derived PP and biomass-derived PE (intermediate mixed resin layer) (3)Adhesive resin layer (4) EVOH resin layer (gas barrier resin layer) (5)Adhesive resin layer (6) A mixed resin layer of fossil fuel-derived PP and biomass-derived PE (intermediate mixed resin layer) (7) Fossil fuel derived PP resin layer (inner surface layer) The thickness of the resin multilayer sheet was set to 270 μm. (2) Manufacturing of food containers by secondary molding process The multilayer resin sheet manufactured in (1) was formed by vacuum / pressure forming into a container with a flange having a short side of approximately 90 mm, a long side of approximately 200 mm, and a depth of approximately 22 mm, thereby manufacturing a food container.

[0018] (Example 2) A multilayer resin sheet was manufactured in the same manner as in Example 1, except that the raw materials for the intermediate mixed resin layer were crushed and mixed from scraps and recycled materials of the multilayer resin sheet manufactured in Example 1. A food container was then manufactured using this multilayer resin sheet.

[0019] (Comparative Example 1) A multilayer resin sheet was manufactured in the same manner as in Example 2, except that biomass-derived PE was replaced with fossil fuel-derived PP, and a food container was manufactured using this sheet.

[0020] (evaluation) (1) Evaluation of resin multilayer sheets Table 1 shows the overall thickness of the resin multilayer sheets and the thickness of each layer for Example 2 and Comparative Example 1. The biomass-derived PE content of the resin multilayer sheet in Example 1 was 15% by mass.

[0021] [Table 1]

[0022] (2) Evaluation of drop impact resistance in low-temperature environments (I) Method of verification The contents were filled into the food containers of Example 2 and Comparative Example 1, and the lid film was heat-sealed. Twenty-five of each were then packed into cartons measuring approximately 100 mm on the short side, 200 mm on the long side, and 24 mm in height, and prepared as Example samples and Comparative Example samples. The example samples and comparative example samples were cooled at 5°C for at least 24 hours. Then, under 5°C conditions, the cartons were dropped once from a height of 150 cm with the short side facing downwards, and the presence or absence of cracks or bends in the containers was visually inspected. (II) Results and Discussion Table 2 shows the number of cracks and bends observed in the example sample and the comparative example sample. The example sample exhibited fewer cracks and bends than the comparative example sample, demonstrating superior resistance to drop impact in low-temperature environments.

[0023] [Table 2] [Industrial applicability]

[0024] According to the present invention, it is possible to manufacture a multilayer resin sheet with a high biomass content that has moldability equivalent to conventional products and superior physical properties compared to conventional products. The demand for environmentally friendly resin and plastic products is expected to continue to grow, making this invention useful for the resin and plastics industry.

Claims

1. A multilayer resin sheet in which resin layers are laminated, The thickness of the aforementioned resin multilayer sheet is 250 to 500 μm. The aforementioned resin multilayer sheet has at least the following layers (1) to (7) laminated in the order shown below from the outer surface: (1) Surface layer containing a mixed resin of fossil fuel-derived polypropylene and biomass-derived polyethylene (2) Intermediate layer containing a mixed resin of fossil fuel-derived polypropylene and biomass-derived polyethylene (3) Adhesive resin layer (4) Gas barrier resin layer (5) Adhesive resin layer (6) Intermediate layer containing a mixed resin of fossil fuel-derived polypropylene and biomass-derived polyethylene (7) Surface layer made of fossil fuel-derived polypropylene resin The content ratio of biomass-derived polyethylene in the above (1) layer is 1 to 10% by mass, The content ratio of biomass-derived polyethylene in the (2) layer and the (6) layer is 10 to 30% by mass, The content ratio of biomass-derived polyethylene to the entire resin multilayer sheet is 10 to 30% by mass. A multi-layered sheet made of resin.

2. The resin multilayer sheet according to claim 1, wherein the thickness of the (1) layer is 20 to 50 μm, and the thicknesses of the (2) and (6) layers are each 70 to 210 μm.

3. The resin multilayer sheet according to claim 1, wherein the (1) layer and the (7) layer do not contain coloring raw materials, and the (2) layer and the (6) layer further contain coloring raw materials.

4. A container formed using a resin multilayer sheet as described in any one of claims 1 to 3.

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