Multilayer thermoplastic resin sheet

Abstract

To provide a plant-derived polyethylene-resin-containing multilayer thermoplastic resin sheet having much the same mechanical characteristics, especially cold impact resistance as a resin sheet produced from a raw material obtained from conventional fossil fuel and having a low oxygen permeation degree necessary for a food container or the like.SOLUTION: A multilayer thermoplastic resin sheet includes a core layer containing plant-derived polyethylene on both sides of one or two oxygen barrier resin layers each with an adhesive layer in-between and a skin layer containing no plant-derived polyethylene on the outside of the core layer. The multilayer thermoplastic resin sheet contains polypropylene of 80 mass%. The core layer contains block polypropylene of 25 mass% or more. The skin layer has a thickness ratio to the core layer of 10-45%. The multilayer thermoplastic resin sheet has an oxygen permeation degree of 2.0 cc / m2 day atm at 20°C, 65% Rh.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multilayer thermoplastic resin sheet including a resin layer containing plant-derived polyethylene, more specifically, a resin layer containing plant-derived polyethylene obtained by polymerizing a monomer or monomer mixture containing plant-derived ethylene, and an oxygen barrier resin layer. In particular, the present invention relates to a multilayer thermoplastic resin sheet having excellent cold impact resistance and oxygen permeability, a molded article molded from the multilayer thermoplastic resin sheet, and a manufacturing method thereof. [Background technology]

[0002] Plant-derived resin is a resin derived from organic compounds photosynthesized from carbon dioxide and water, and when used, it turns back into carbon dioxide and water, making it a so-called carbon-neutral renewable energy source. Compared to molded products made from conventional fossil fuel-derived resins, it can reduce the environmental impact. In other words, by using plant-derived resins in combination with fossil fuel-derived resins, it is possible to reduce the amount of fossil fuel used. Therefore, in order to reduce the environmental impact, studies are being conducted to replace some of the resins derived from fossil fuels with resins derived from biomass resources such as plants. However, even if plant-derived resins are used, it is still necessary to obtain molded products that are at least comparable to conventional fossil fuel-derived resins in terms of mechanical properties such as cold impact resistance.

[0003] On the other hand, to maintain the quality of food, it is important to prevent oxidation, and packaging materials with low oxygen permeability are used. Ethylene-vinyl alcohol copolymers or poly(metaxylylene adipamide), which are used as resin components with low oxygen permeability, have excellent gas barrier properties and are therefore used in food packaging materials.

[0004] However, as shown in Patent Document 1, in a product including an ethylene-vinyl alcohol polymer layer and a fossil fuel-derived polyethylene resin layer, if part of the raw polyethylene resin is replaced with a plant-derived polyethylene resin, the interlaminar adhesion tends to decrease and the mechanical properties, etc. also tend to decrease. Furthermore, Patent Document 2 discloses an invention that aims to provide a laminated sheet that uses block polypropylene, a conventional resin derived from fossil fuels, and that has heat resistance and excellent impact resistance in a freezing environment. However, no plant-derived resin is used, the sheet is three layers or less, and there is no description that a sheet with excellent oxygen permeability or cold impact resistance has been obtained. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-177531 [Patent Document 2] Patent Publication No. 2021-37748 Summary of the Invention [Problem to be solved by the invention]

[0006] In conventional multilayer thermoplastic resin sheets made from fossil fuel-derived resins, if part of the fossil fuel-derived resin is replaced with plant-derived resin, the oxygen permeability and mechanical properties decrease due to the increase in the blending ratio, and the interlayer adhesive strength also decreases. To solve these problems, each layer can be made thicker, but this makes production and processing more difficult and does not improve the mechanical properties, especially cold impact resistance. Therefore, the present invention aims to improve the adhesiveness between the layers and to provide excellent mechanical properties to the entire multi-layer thermoplastic resin sheet, even when a part of the fossil fuel-derived multi-layer thermoplastic resin sheet is replaced with a plant-derived resin. The objective of the present invention was to provide a multilayer thermoplastic resin sheet that is strong enough to withstand high temperatures and has low oxygen permeability, which is necessary for packaging materials for food, etc. In terms of mechanical properties, the objective was to provide a multilayer thermoplastic resin sheet that is particularly excellent in cold impact resistance, taking into account storage and transportation in a frozen state, assuming a container for frozen foods. [Means for solving the problem]

[0007] The inventors discovered that oxygen permeability can be reduced by using a multilayer structure of seven or more layers, including an oxygen barrier resin layer, and that cold impact resistance can be improved by adjusting the materials of the layer containing plant-derived resin and the layer made of fossil fuel-derived resin and placing a layer made of fossil fuel-derived resin on the outside of the layer containing plant-derived resin, and by setting the thickness ratio of the two layers to an appropriate value, thereby completing the present invention.

[0008] That is, the present invention provides: 1. An oxygen barrier resin layer is provided, and an adhesive layer is provided on both sides of the oxygen barrier resin layer. It has a core layer containing plant-derived polyethylene, The core layer has skin layers that do not contain plant-derived polyethylene on both outer sides thereof, An adhesive layer may be provided on the outside of one or both of the skin layers, and a polyolefin-based resin layer may be provided on the outside of the adhesive layer. A multilayer thermoplastic resin sheet consisting of 7 to 11 layers in total, The adhesive layers on both sides of the oxygen barrier resin layer and the adhesive layer on the outside of the skin layer may be the same or different, The skin layer contains 80% by mass or more of polypropylene including propylene homopolymer and / or block polypropylene, The core layer contains 25% by mass or more of block polypropylene, the thickness of the skin layer is 10 to 45% of the thickness of the core layer; The oxygen permeability of the multilayer thermoplastic resin sheet is 2.0 cc / m at 20°C and 65% Rh. 2 Multilayer thermoplastic resin sheet, which is below 10 ... 2. The multilayer thermoplastic resin sheet according to 1, wherein the content of plant-derived polyethylene in the core layer is 1% by mass to 20% by mass of the entire multilayer thermoplastic resin sheet. 3. The multilayer thermoplastic resin sheet according to 1, wherein the plant-derived polyethylene is a biomass-derived high-density polyethylene composed of a polymer of a monomer containing biomass-derived ethylene or a copolymer of the monomer and another monomer. 4. The multilayer thermoplastic resin sheet according to 1, wherein the oxygen barrier resin layer is a layer of an ethylene-vinyl alcohol copolymer or poly(metaxylylene adipamide). 5. The overall density of the multilayer thermoplastic resin sheet is 0.85 to 1.30 g / cm 3 1. The multilayer thermoplastic resin sheet according to 1, 6. The multilayer thermoplastic resin sheet according to 1, wherein the multilayer thermoplastic resin sheet has a total thickness of 0.25 to 1.2 mm. 7. A container made of the multilayer thermoplastic resin sheet according to any one of 1 to 6. 8. A method for producing the multilayer thermoplastic resin sheet according to any one of 1 to 6 by coextrusion molding, coextrusion lamination or dry lamination. [Effects of the Invention]

[0009] The multilayer thermoplastic resin sheet of the present invention can have a thick layer containing plant-derived polyethylene, and can also have excellent cold impact resistance and reduced oxygen permeability. According to the present invention, by incorporating polypropylene as a component of the skin layer and block propylene into the core layer, and by making the thickness of the skin layer within the range of 10 to 45% of the thickness of the core layer, it is possible to obtain a multilayer thermoplastic resin sheet with excellent cold impact resistance, even if the core layer contains plant-derived polyethylene. In other words, the present invention allows for the production of a multi-layer thermoplastic resin sheet containing a large amount of plant-derived polyethylene, which can reduce the amount of fossil fuel used and the environmental impact. Furthermore, even though the multi-layer thermoplastic resin sheet contains plant-derived polyethylene, it has excellent cold impact resistance compared to conventional fossil fuel-derived resins, making it possible to replace conventional fossil fuel-derived resin sheets. 。 Book According to the present invention, oxygen permeation is suppressed throughout the entire multilayer thermoplastic resin sheet, making it possible to produce a container for food and the like that has excellent cold impact resistance. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of one embodiment of the multilayer thermoplastic resin sheet of the present invention. [Figure 2] FIG. 2 shows the shape of the container used in the "Evaluation of Cold Impact Resistance of Containers." DETAILED DESCRIPTION OF THE INVENTION

[0011] One aspect of the present invention will be described in detail below. [Oxygen barrier resin layer] The oxygen barrier resin layer contains at least one oxygen barrier resin, for example, ethylene-vinyl alcohol copolymer (EVOH), poly(metaxylylene adipamide) (MXD6), polyvinyl alcohol, polyacrylonitrile, polyamides such as nylon 6 and nylon 6,6, polyester, polyurethane, and (meth)acrylic resin, and among these, EVOH and MXD6 are preferred in terms of oxygen barrier properties. In order to obtain excellent oxygen permeability, the content of the oxygen barrier resin in the oxygen barrier resin layer is preferably 60% by mass or more, more preferably 70% by mass or more, or 80% by mass or more. By making the content of the oxygen barrier resin in the oxygen barrier resin layer 60% by mass or more, the oxygen barrier property can be further improved. The content of the oxygen barrier resin in the multilayer thermoplastic resin sheet is preferably 20% by mass or less, and may be 18% by mass or less, 15% by mass or less, 13% by mass or less, 10% by mass or less, 8% by mass or less, or 5% by mass or less. The oxygen barrier resin may be one layer or multiple layers. In the case of multiple layers, the components may be the same or different, the oxygen barrier resin layers may be in contact with each other or may be in contact with each other via an adhesive layer, and an olefin-based resin layer may be present between the two oxygen barrier resin layers in addition to the adhesive layer.

[0012] [Oxygen permeability] Oxygen permeability is one of the physical properties of the sheet. It is measured at 1 atm (1 atmosphere) through 1 m of the sheet. 2It indicates the amount of oxygen passing through per day. It is greatly affected by temperature and humidity, so when comparing, tests must be conducted under the same conditions. The unit is cc / m 2 ·24h·atm. The higher the value, the easier it is for oxygen to pass through, and the lower the value, the more difficult it is for oxygen to pass through. One device that can be used for measurement is the OX-TRAN 1 / 50 (manufactured by MOCON). This device complies with oxygen permeability measurement standards such as JIS K7126-2 (constant pressure method) as well as ASTM and ISO. Measurements are performed by sandwiching the resin sheet between test cells and flowing oxygen into one of the test cells. The oxygen that then diffuses through the resin sheet is introduced into the other cell, where the sensor is located, and the amount of oxygen introduced is converted into oxygen permeability. The oxygen permeability of the multi-layer thermoplastic resin sheet is 2.0cc / m at 20℃ and 65% Rh. 2 ·day·atm or less, 1.5cc / m 2 ·day·atm or less, 0.7cc / m 2 ·day·atm or less is preferable, and 0.5cc / m 2 ·day·atm or less is preferable.

[0013] [Thermoplastic resin] Olefin resins are thermoplastic resins. Examples of thermoplastic resins include polyethylene. Examples of the resin include acrylic resins, polyolefin resins such as polypropylene resins, halogen-containing resins such as vinyl chloride, EVOH, vinyl alcohol resins such as polyvinyl alcohol, (meth)acrylic resins, styrene resins, polyester resins, polyamide resins, polycarbonate resins, polysulfone resins, polyphenylene ether resins, and cellulose ester resins.

[0014] [polypropylene] It is a polymer of propylene and a thermoplastic resin of the olefin-based resin family. Polypropylene has good heat resistance, the lowest specific gravity, and floats on water. It also has relatively high strength, excellent chemical resistance (including acids and alkalis), and no moisture absorption. In the form of copolymerization, polypropylene includes propylene homopolymer, random copolymer, and block polypropylene.

[0015] [Propylene homopolymer] Homopolymers are polymers made solely from propylene. They are polymerized using only propylene and hydrogen as a chain transfer agent. They have excellent rigidity, heat resistance, chemical resistance, and transparency.

[0016] [Block polypropylene] Block polypropylene is a copolymer that has a polymer block made of propylene and a polymer block made of an α-olefin other than propylene. It also includes impact copolymers, which are a mixture of propylene homopolymer and EPR (ethylene propylene rubber). When considering the impact resistance, a mechanical property of packaging containers, it is preferable to include block polypropylene.

[0017] [Plant-based polyethylene] Plant-derived polyethylene is polyethylene obtained by chemical or biological synthesis using renewable biomass resources. Even if plant-derived polyethylene is incinerated, it does not increase the concentration of carbon dioxide in the atmosphere due to the carbon-neutral nature of biomass. The layer containing plant-derived polyethylene preferably uses plant-derived ethylene polymerized from bioethanol obtained from plant raw materials. The layer containing plant-derived polyethylene may also contain biomass-derived high-density polyethylene obtained by polymerizing a monomer containing biomass-derived ethylene. From the viewpoint of environmental impact, the lower limit of the plant-derived polyethylene content is 0.05% by mass or more of the entire multilayer thermoplastic resin sheet, and preferably 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more, and can be 3% by mass or more, 5% by mass or more, 8% by mass or more, or 10% by mass or more. From the viewpoint of mechanical properties, the upper limit of the content is preferably 25% by mass or less, and can be 20% by mass or less, 18% by mass or less, 15% by mass or less, 13% by mass or less, or 10% by mass or less.

[0018] [polyethylene] The plant-derived polyethylene is, for example, high-density polyethylene (HDPE, density 0.940 g / cm 3 Medium density polyethylene (MDPE, density 0.925 to 0.940 g / cm 3 or less), low-density polyethylene (LDPE, density 0.911 or more and 0.925 g / cm 3 or less), linear low-density polyethylene (LLDPE, density 0.911 or more and 0.925 g / cm 3 These may be used alone or in combination of two or more. Among them, when taking into consideration the mechanical properties of packaging containers and the like, such as rigidity and impact resistance, it is preferable that the material contains a large amount of high-density polyethylene.

[0019] [density] The density was measured according to the method specified in Method A of JIS K7112-1999 after annealing as specified in JIS K6760-1995. The density of the multilayer thermoplastic resin sheet was, for example, 0.85 to 1.30 g / cm 3 , preferably 0.88 to 1.20 g / cm 3 , and 0.9 to 1.15 g / cm 3 The density of the entire layer of the multilayer thermoplastic resin sheet can also be calculated based on the density of the resin used in each layer. If the density is 0.85 or more, the rigidity and impact resistance of the multilayer thermoplastic resin sheet can be increased. If the density is 1.30 or less, the formability of the multilayer thermoplastic resin sheet can be increased. If the density is within the above range, the rigidity and impact resistance of the multilayer thermoplastic resin sheet can be increased, and the formability can also be improved.

[0020] [Resin composition] The resin composition may contain not only a plant-derived resin but also a fossil fuel-derived resin. The fossil fuel-derived resin may contain a fossil fuel-derived polyolefin. Examples of polyolefins include polyethylene, polypropylene, polymethylpentene, an ethylene-propylene copolymer, and a propylene-butene copolymer. Among these, polyethylene and polypropylene are preferred in terms of physical properties such as mechanical properties. The lower limit of the fossil fuel-derived polyolefin content in the entire resin composition of the multilayer thermoplastic resin sheet may be 50 mass% or more, 60 mass% or more, 70 mass% or more, or 80 mass% or more from the viewpoint of mechanical properties, and the upper limit of the fossil fuel-derived polyolefin content may be 99 mass% or less, 95 mass% or less, 90 mass% or less, or 85 mass% or less from the viewpoint of environmental impact. In addition to the polyolefin that is the main component, various additives may be added to the resin composition of the multilayer thermoplastic resin sheet. Examples of the additives include colorants, plasticizers (aliphatic polyhydric alcohols such as ethylene glycol, glycerin, and hexanediol), oxygen absorbers, heat stabilizers, light stabilizers, ultraviolet absorbers, antistatic agents, surfactants, antibacterial agents, antiblocking agents, fillers (e.g., inorganic fillers), etc. These additives may be used alone or in combination of two or more.

[0021] [Core layer] The core layer is an olefin-based resin containing plant-derived polyethylene. In one embodiment of the present invention, in the case of a seven-layer multilayer thermoplastic resin sheet, these are the second and sixth layers. These two layers contain polypropylene as a component and further contain plant-derived polyethylene. By including plant-derived polyethylene in these two layers, the environmental impact can be reduced and the formability of the multilayer thermoplastic resin sheet can be improved. The polypropylene that makes up these two layers includes propylene homopolymer and block polypropylene. From the viewpoint of cold impact resistance, the polypropylene content of the core layer can be 30% by mass or more, preferably 35% by mass or more, and further can be 40% by mass or more, 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, or 85% by mass or more. From the viewpoint of cold impact resistance, the content of propylene homopolymer in the core layer can be 10% by mass or more, preferably 15% by mass or more, and further can be 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, or 40% by mass or more. From the viewpoint of cold impact resistance, the content of block polypropylene in the core layer can be 10% by mass or more, preferably 15% by mass or more, and further can be 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, or 40% by mass or more. From the viewpoint of environmental impact, the content of plant-derived polyethylene in the core layer may be 3% by mass or more, preferably 5% by mass or more, and may further be 8% by mass or more, 10% by mass or more, 13% by mass or more, 15% by mass or more, 18% by mass or more, or 20% by mass or more. From the viewpoint of environmental impact, the content of fossil fuel-derived polyethylene in the core layer may be 25% by mass or less, preferably 20% by mass or less, and further may be 18% by mass or less, 15% by mass or less, 13% by mass or less, 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less. Furthermore, in terms of the blending of plant-derived polyethylene and fossil fuel-derived polyethylene, it is preferable that the blending amount of plant-derived polyethylene is greater than the blending amount of fossil fuel-derived polyethylene relative to the total amount of the core layer from the viewpoint of environmental impact, and further, the blending amount may be 3% by mass or more, 5% by mass or more, 8% by mass or more, 10% by mass or more, 13% by mass or more, 15% by mass or more, 18% by mass or more, 20% by mass or more, or 25% by mass or more.

[0022] Skin Layer The skin layer is an olefin-based resin that does not contain plant-derived polyethylene. A case will be described in which a core layer is provided on both sides of the oxygen barrier resin layer in contact with the core layer via an adhesive layer, and skin layers are provided on both outer sides of the core layer. In one embodiment of the present invention, in the case of a seven-layered multilayer thermoplastic resin sheet, it is used for the first and seventh layers. These two outer layers contain polypropylene and polyethylene as components. The polypropylene includes propylene homopolymer and / or block polypropylene. The polyethylene is fossil fuel-derived polyethylene, including LLDPE (linear low-density polyethylene) and / or HDPE (high-density polyethylene). Each layer of the present invention can contain plant-derived polyethylene, but the skin layers are configured to not contain plant-derived polyethylene. The polypropylene content of the skin layer can be 30% by mass or more, preferably 40% by mass or more, and can further be 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, or 85% by mass or more. The polyethylene content of the skin layer may be 30% by mass or less, preferably 25% by mass or less, and may further be 23% by mass or less, 20% by mass or less, 18% by mass or less, 15% by mass or less, 13% by mass or less, 10% by mass or less, 8% by mass or less, or 5% by mass or less. The content of propylene homopolymer is not particularly limited, but from the viewpoint of improving rigidity, it can be 10% by mass or more of the core layer, preferably 15% by mass or more, and further, it can be 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, or 40% by mass or more. The content of the block polypropylene is not particularly limited, but from the viewpoint of cold impact resistance, it can be 10% by mass or more of the core layer, preferably 15% by mass or more, and further, it can be 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, or 40% by mass or more.

[0023] To reduce the environmental impact, the core layer needs to be thicker. However, based on previous patent documents, it was determined that a layer containing plant-derived polyethylene (core layer) alone would not provide the same mechanical properties as fossil fuel-derived resins. Therefore, the core layer was sandwiched between skin layers on both sides to create a multilayer thermoplastic resin sheet with excellent mechanical properties. The thickness of the core layer is desirably thicker than the thickness of the skin layer from the viewpoint of mechanical properties and environmental load. The lower limit of the ratio of the thickness of the skin layer to the core layer is desirably 1% or more, and may be 3% or more, 5% or more, 8% or more, 10% or more, 15% or more, 18% or more, or 20% or more. The upper limit of the thickness ratio is desirably 60% or less, and may be 58% or less, 55% or less, 53% or less, 50% or less, 48% or less, 45% or less, 43% or less, 40% or less, 38% or less, or 49% or less. % or less, 35% or less, 33% or less, 30% or less, or 28% or less.

[0024] [Adhesive layer] In one embodiment of the present invention, in the case of a seven-layer multilayer thermoplastic resin sheet, the oxygen barrier resin layer is Layer 4, and the third and fifth layers are Layers 3 and 5. In the case of the seven-layer sheet, the oxygen barrier resin layer is Layer 4. In the case of the seven-layer sheet, the oxygen barrier resin layer is an adhesive layer formed to bond Layers 2 and 4, and Layers 4 and 6 together. Furthermore, in the case of a 9-layer structure, the outer surface of one of the first and seventh skin layers of the seven layers mentioned above serves as an adhesive layer. In the case of an 11-layer structure, the outer surfaces of both the first and seventh skin layers of the seven layers mentioned above serve as adhesive layers. The adhesive layers bonding the second and fourth layers, and the fourth and sixth layers, and the adhesive layers on both sides of the skin layers, that is, the first and seventh layers, may be the same or different. The adhesive layer contains at least one resin material, for example, polyolefin, modified polyolefin, polyester, vinyl resin, polyamide, etc. Among these, modified polyolefin is preferred from the viewpoint of adhesion. The thickness of the adhesive layer can be 3 to 40 μm, and preferably 5 to 30 μm. By making the thickness of the adhesive layer 3 μm or more, the adhesiveness can be improved, and by making it 40 μm or less, the processability of the multilayer thermoplastic resin sheet can be improved.

[0025] [7 or more layers of multi-layer thermoplastic resin sheet] An example of a seven-layered multilayer thermoplastic resin sheet has been shown, but an example of a multilayered thermoplastic resin sheet with eight or more layers will be described below. In the seven-layer example, a polyolefin resin layer can be provided on one outer side of the skin layer to make it eight layers, and polyolefin resin layers can be provided on both outer sides of the skin layer to make it nine layers. In addition, in the seven-layer example, an adhesive layer and a polyolefin-based resin layer can be provided on one side of the outer skin layer, making it nine layers, and an adhesive layer and a polyolefin-based resin layer can be provided on both sides of the outer skin layer, making it eleven layers. Furthermore, in the seven-layer example, a polyolefin resin layer may be provided on one outer side of the skin layer, and an adhesive layer and a polyolefin resin layer may be provided on the other outer side of the skin layer, resulting in a ten-layer structure. The polyolefin resin layers in the above case may be of the same composition or different compositions, and preferably made of unstretched polypropylene. Furthermore, although the oxygen barrier resin layer in the seven-layer example is a single layer, the oxygen barrier resin layer may be two layers made of two different materials or two layers made of the same material. Furthermore, the two layers may be three layers in total, with an adhesive layer interposed between them. The adhesive layer in this case is the same as the "adhesive layer" described above. The total number of layers will be eight if two oxygen barrier resin layers are added to the seven mentioned above, and nine if the adhesive layer is added to the two oxygen barrier resin layers. Furthermore, if there are two oxygen barrier resin layers in addition to the 11 layers, the total number of layers will be 12, and if the adhesive layer is added to the two oxygen barrier resin layers, the total number of layers will be 13. In other words, in the case of a multilayer thermoplastic resin sheet having a total of 7 to 11 layers, if the number of oxygen barrier resin layers is two, it becomes +1 layer, and if the adhesive layer is added to the two oxygen barrier resin layers, it becomes +2 layers.

[0026] [Oxygen barrier resin layer of multi-layer thermoplastic resin sheet] In one embodiment of the present invention, in the case of a seven-layer multilayer thermoplastic resin sheet, the oxygen barrier resin layer is the fourth layer. This layer is an oxygen barrier resin layer formed to impart oxygen barrier properties to the entire multilayer thermoplastic resin sheet. The thickness of the oxygen barrier resin layer affects the oxygen barrier properties of the entire multilayer thermoplastic resin sheet. In order to impart barrier properties to the multilayer thermoplastic resin sheet, the lower limit of the thickness of the oxygen barrier resin layer can be 3 μm or more, and 5 μm or more. The upper limit of the thickness can be 150 μm or less, preferably 130 μm or less, and can be 100 μm or less, 80 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, or 50 μm or more. The upper limit of the thickness can be 150 μm or less, preferably 130 μm or less, and can be 100 μm or less, 80 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less. When the oxygen barrier resin layer is an ethylene-vinyl alcohol copolymer, the lower limit of the thickness in order to impart barrier properties can be set to 3 μm or more, preferably 5 μm or more, and furthermore, 8 μm or more, 10 μm or more, 15 μm or more, 20 μm or more, 30 μm or more, 40 μm or more, or 50 μm or more; and the upper limit of the thickness can be set to 150 μm or less, preferably 130 μm or less, and furthermore, 100 μm or less, 80 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less. When the oxygen barrier resin layer is MXD6, the lower limit of the thickness in order to impart barrier properties can be set to 90 μm or more, preferably 98 μm or more, and further can be set to 100 μm or more, 103 μm or more, 105 μm or more, 108 μm or more, 110 μm or more, 113 μm or more, or 115 μm or more, and the upper limit of the thickness can be set to 200 μm or less, preferably 180 μm or less, and further can be set to 160 μm or less, 150 μm or less, 140 μm or less, or 130 μm or less.

[0027] [Whole layer] When each layer is laminated by extrusion molding or the like, this is referred to as the entire layer. The thickness of the entire layer can be 0.1 to 2.0 mm, preferably 0.15 to 1.5 mm, and more preferably 0.25 to 1.2 mm. A multilayer thermoplastic resin sheet with a thickness within the above range can be used for various applications, such as thermoformed products such as resin plates and trays, and is particularly suitable for containers.

[0028] [Manufacturing method] The method for producing the multilayer thermoplastic resin sheet is not particularly limited, and the sheet can be produced by a conventionally known method. In the present invention, the multilayer thermoplastic resin sheet is preferably produced by coextrusion molding, coextrusion lamination, or dry lamination, and more preferably by a T-die method such as extrusion molding.

[0029] [Application] The multilayer thermoplastic resin sheet according to the present invention can be suitably used for various applications such as thermoformed products such as resin plates and trays, particularly containers, and thermoformed products are particularly preferred. [Example]

[0030] The materials used in the examples and their abbreviations are shown below. BPP: Fossil fuel-derived block polypropylene (Prime Polymer Co., Ltd., product name: E702G, biomass content: 0%, density: 0.9 g / cm3, MFR: 0.9 g / 10 min) HPP: Fossil fuel-derived propylene homopolymer (Prime Polymer Co., Ltd., product name: E-100GPL, biomass content: 0%, density: 0.90 g / cm3, MFR: 0.9 g / 10 min) Petrochemical HD: High-density polyethylene derived from fossil fuels (Prime Polymer Co., Ltd., product name: 5000S, biomass content: 0%, density: 0.949 g / cm3, MFR: 0.82 g / 10 min) Bio HD: Plant-derived high-density polyethylene (manufactured by Braskem, product name: SHE150, biomass content: 94%, density: 0.948 g / cm3, MFR: 1.0 g / 10 min) EVOH: Ethylene-vinyl alcohol copolymer (manufactured by Mitsubishi Chemical Corporation, product name: DT2904RB, biomass content: 0%, density: 1.21 g / cm3, MFR: 3.8 g / 10 min at 210°C) MXD6: Poly(metaxylylene adipamide) (manufactured by Mitsubishi Gas Chemical Company, Inc., trade name: S6007, density: 1.22) CPP: Non-oriented polypropylene (manufactured by Futamura Chemical Co., Ltd., product name: FCMSOK) LLDPE: Linear low-density polyethylene (Prime Polymer Co., Ltd., product name: 2022L, density: 0.919) Colored MB: White masterbatch (manufactured by Sankyo Chemical Industry Co., Ltd.)

[0031] [Example 1] In this example, a seven-layer multilayer thermoplastic resin sheet was fabricated. The core layer was a dry blend of 40.0 parts by mass of fossil-fuel-derived block polypropylene, 40.0 parts by mass of fossil-fuel-derived propylene homopolymer, and 20.0 parts by mass of plant-derived high-density polyethylene. The skin layers were made of a resin consisting of 80 parts by mass of the same fossil-fuel-derived polypropylene and 20 parts by mass of LLDPE. The oxygen barrier resin layer was made of a resin consisting of 100 parts by mass of EVOH. The thickness of each layer and the blending ratio between the core and skin layers were melt-extruded to obtain a 600 μm-thick multilayer thermoplastic resin sheet. Table 1 shows the thickness of each layer and the blending ratio between the core and skin layers.

[0032] [Examples 2, 4 to 9] A core layer was made from a resin dry-blended according to the "core layer compounding ratio (% by mass)" in Table 1, a skin layer was made from a resin consisting of 80 parts by mass of the above-mentioned fossil fuel-derived polypropylene and 20 parts by mass of LLDPE, and an oxygen barrier resin layer was made from a material shown as barrier material (oxygen barrier resin) in Table 1. A multilayer thermoplastic resin sheet was obtained by melt extrusion to the thickness shown in the sheet layer configuration in Table 1. The thickness of each layer and the compounding ratio of the core layer to the skin layer are shown in Table 1.

[0033] [Example 3] In this example, a nine-layer multilayer thermoplastic resin sheet was fabricated. The core layer was a dry blend of 40.0 parts by mass of fossil-fuel-derived block polypropylene, 40.0 parts by mass of fossil-fuel-derived propylene homopolymer, and 20.0 parts by mass of plant-derived high-density polyethylene. The skin layers were a resin consisting of 80 parts by mass of the above fossil-fuel-derived polypropylene and 20 parts by mass of LLDPE. The oxygen barrier resin layers were a resin consisting of 100 parts by mass of EVOH. The eighth layer was an adhesive layer, and the ninth layer was a polyolefin (CPP) layer. These layers were coextrusion laminated to a thickness of 650 μm. The thickness of each layer and the composition ratio of the core and skin layers are shown in Table 1.

[0034] [Examples 13 to 23] A multilayer thermoplastic resin sheet was obtained by melt extrusion using a resin dry-blended at the "core layer compounding ratio (% by mass)" in Table 2 as the core layer, a resin having the "skin layer compounding ratio (% by mass)" in Table 2 as the skin layer, and EVOH as the oxygen barrier resin layer, with the thickness shown in the sheet layer configuration in Table 2. The thickness of each layer and the compounding ratio of the core layer and skin layer are shown in Table 2.

[0035] [Comparative Example 1] In this example, a seven-layer thermoplastic resin sheet was fabricated. The core layer consisted of a dry blend of 40.0 parts by mass of fossil-fuel-derived block polypropylene, 40.0 parts by mass of fossil-fuel-derived propylene homopolymer, and 15.0 parts by mass of fossil-fuel-derived high-density polyethylene. The skin layers consisted of 80 parts by mass of the same fossil-fuel-derived polypropylene and 20 parts by mass of LLDPE. The oxygen barrier layer consisted of 100 parts by mass of the same fossil-fuel-derived block polypropylene. The thickness of each layer and the blending ratio between the core and skin layers were melt-extruded to obtain a 600 μm-thick multilayer thermoplastic resin sheet. Table 1 shows the thickness of each layer and the blending ratio between the core and skin layers.

[0036] [Comparative Examples 2 to 6] The resin dry-blended according to the "Core layer compounding ratio (mass parts %)" in Table 1 was used as the core layer. A resin consisting of 80 parts by mass of fossil fuel-derived polypropylene and 20 parts by mass of LLDPE or 100 parts by mass of fossil fuel-derived polypropylene was used as the skin layer, and a material shown as barrier material (oxygen barrier resin) in Table 1 was used as the oxygen barrier resin layer, and a multilayer thermoplastic resin sheet was obtained by melt extrusion to the thickness shown in the sheet layer configuration in Table 1. The thickness of each layer and the blending ratio between the core layer and the skin layer are shown in Table 1.

[0037] [Comparative Examples 7 to 14] A multilayer thermoplastic resin sheet was obtained by melt extrusion using a resin dry-blended at the "core layer compounding ratio (% by mass)" in Table 2 as the core layer, a resin having the "skin layer compounding ratio (% by mass)" in Table 2 as the skin layer, and EVOH as the oxygen barrier resin layer, with the thickness shown in the sheet layer configuration in Table 2. The thickness of each layer and the compounding ratio of the core layer and skin layer are shown in Table 2.

[0038] [Evaluation of sheets or containers made of resin compositions] The resin compositions of the Examples and Comparative Examples were evaluated for (1) the barrier properties of the sheets and (2) the cold impact resistance of the containers. [(1) Evaluation of the barrier properties of the sheet] The oxygen barrier properties of the multilayer thermoplastic resin sheet were evaluated by measuring its oxygen permeability. The oxygen permeability measurement device used was an OX-TRAN1 / 50 (manufactured by MOCON). The sheet layer structure of the multilayer thermoplastic resin sheet and the evaluation results are shown in Table 1. [Table 1] Skin: skin layer, Core: core layer, Adhesion: adhesive layer, Barrier material: oxygen barrier resin, Barrier property: Barrier property evaluation, Skin / Core%: Skin layer / Core layer ratio (%) Barrier property rank (unit: [cc / m 2 ·day·atm] (20℃, 65%Rh) A: 0.5 or less, B: more than 0.5 to 0.7 or less, C: more than 0.7 to 2.0 or less, D: more than 2.0

[0039] [Evaluation results] From Table 1, the thickness of the oxygen barrier resin layer is 4 μm or less for EVOH, 100 μm or less for MXD6, and 2.0 cc / m for materials other than EVOH or MXD6. 2 It was found that the oxygen barrier properties were poor, exceeding 1000kJ / day atm.

[0040] [(2) Evaluation of container cold shock resistance] For the resin compositions of Examples and Comparative Examples having the constitutions shown in Table 2, (2) cold impact resistance of the container was evaluated. Multilayer thermoplastic resin sheets with a thickness of 600 μm or 650 μm were thermoformed into rectangular container shapes, and their cold impact resistance was evaluated. The evaluation was performed according to JIS Z0200, with the impact test classification being Level II. The containers used for the evaluation were the above-mentioned Comparative Examples 1 to 4 and Examples 1 to 3, with container dimensions of approximately 30 mm deep, approximately 150 mm long, and approximately 100 mm short. The evaluation test method involved placing 150 g of water in the recess of each container, heat-sealing the opening with a multilayer film dry-laminated with ONy (manufactured by Unitika Ltd., Emblem ONU, thickness 25 μm) and easy-peel film (manufactured by J-Film Inc., VMX LMX, thickness 35 μm), and placing the containers in a cardboard box with three layers, eight per layer, and sealing the cardboard box. The packaged cardboard box weighed approximately 3.6 kg. Ten cases of packed cardboard boxes (240 evaluation samples) were prepared and left to stand in a freezer at -18°C for 24 hours, after which they were dropped 10 times from a height of 0.6 m onto a concrete floor at an ambient temperature of -18°C. The containers were then evaluated for cracks and leakage of contents after the cardboard boxes were dropped. The evaluation method was to score the largest crack (penetrating crack) that occurred in each container using the following points, and the total scores are shown in Table 2. score 1: Cracks less than 5mm 2: Cracks between 5mm and 10mm 3: Cracks of 10 mm or more In the cold shock resistance rating, a score of 20 or less was judged as "good" and 21 or more was judged as "bad." [Table 2] Skin: Skin layer, Core: Core layer, Adhesive: Adhesive layer, Skin / Core%: Skin layer / Core layer ratio (%)

[0041] [Evaluation results] When the "skin layer / core layer ratio" is 7.7% or less or 47.4% or more, the cold impact resistance evaluation is "Fail." Even if plant-derived high-density polyethylene is contained, and fossil fuel-derived high-density polyethylene is not contained, even if only plant-derived high-density polyethylene is contained, the "skin layer / core layer ratio" is 7.7%. exceed ~47. 4 % less than If the temperature is within this range, the cold shock resistance rating will be "good." Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these, and various modifications can be made without departing from the spirit of the invention.

[0042] [Total layer density] The overall layer density of Examples 1 and 2 was measured according to the method specified in Method A of JIS K7112-1999 after annealing as specified in JIS K6760-1995. As a result, Example 1 had a density of 0.928 g / cm 3 , and Example 2 is 0.922 g / cm 3 This is what happened. [Industrial Applicability]

[0043] The multilayer thermoplastic resin sheet according to the present invention can be suitably used for various applications, such as thermoformed products such as resin plates and trays, and is particularly suitable for thermoformed products. Specifically, it can be used for food packaging containers, etc. [Explanation of symbols]

[0044] 1. Multilayer thermoplastic resin sheet 2. Skin layer 3 Core layer 4 Adhesive layer 5. Oxygen barrier resin layer 6 containers

Claims

1. an oxygen barrier resin layer, and an adhesive layer on both sides of the oxygen barrier resin layer, Each of the core layers comprises a plant-derived polyethylene. The core layer has skin layers that do not contain plant-derived polyethylene on both outer sides thereof, A multilayer thermoplastic resin sheet having excellent cold impact resistance and consisting of a total of 7 to 13 layers, The skin layer contains 80% by mass or more of polypropylene including propylene homopolymer and / or block polypropylene, The core layer contains 30% by mass or more of polypropylene, the thickness of the skin layer relative to the thickness of the core layer is 12.0 to 40.0%; the oxygen barrier resin layer is an ethylene-vinyl alcohol copolymer layer having a thickness of 10 μm or more and 150 μm or less, or a poly(metaxylylene adipamide) layer having a thickness of 120 μm or more and 200 μm or less, The oxygen permeability of the multilayer thermoplastic resin sheet is 2.0 cc / m at 20°C and 65% Rh. ２ A multi-layer thermoplastic resin sheet with excellent cold impact resistance of 10 ...

2. 2. The multilayer thermoplastic resin sheet according to claim 1, wherein the content of the plant-derived polyethylene in the core layer is 1% by mass to 20% by mass of the entire multilayer thermoplastic resin sheet.

3. 2. The multilayer thermoplastic resin sheet having excellent cold impact resistance according to claim 1, wherein the plant-derived polyethylene is a biomass-derived high-density polyethylene composed of a polymer of a monomer containing biomass-derived ethylene or a copolymer of the monomer with another monomer.

4. A container made of the multilayer thermoplastic resin sheet having excellent cold impact resistance according to any one of claims 1 to 3.

5. A method for producing the multilayer thermoplastic resin sheet having excellent cold impact resistance according to any one of claims 1 to 3 by coextrusion molding, coextrusion lamination or dry lamination.

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