Resin Sheet for Thermoforming and Molded Product

Abstract

To provide a resin sheet for thermoforming which is excellent in rigidity, heat resistance and cold resistance, and a container.SOLUTION: A resin sheet for thermoforming contains high density polyethylene, block polypropylene, homopolypropylene, and an inorganic filler, in which the high density polyethylene contains high density polyethylene (I) having a flow rate ratio measured according to JIS K 7210 of 10-13, a content of the high density polyethylene is 20-55 wt.% based on whole material blending, a content of the high density polyethylene (I) is 10-30 wt.% based on whole material blending, and Dupont impact strength at -30°C is 0.5 J or more. A molded article is obtained by molding the resin sheet for thermoforming.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a resin sheet for thermoforming and a molded article that are excellent in heat resistance, rigidity, and cold resistance.

Background Art

[0002] Polyolefin resin sheets such as polyethylene (hereinafter referred to as "PE") and polypropylene (hereinafter referred to as "PP") are widely used as various molded articles, for example, containers for food and drink, because of their excellent physical properties. For example, Patent Document 1 describes a polyolefin resin sheet composed of a PP-based resin, high-density polyethylene, and talc.

[0003] Hitherto, resin containers for storing heat-cooked foods have been required to have heat resistance during microwave heating in addition to rigidity. However, in recent years, in order to reduce food loss, foods cooked by microwave heating are generally stored and transported in the frozen temperature range. As the use of containers for food and drink at frozen or chilled temperatures increases, cold resistance is also required so that the container does not crack when an external impact is applied to the container even at low temperatures. Patent Document 2 discloses that the cold impact strength of a laminate is improved by laminating a composition composed of a polypropylene-based polymer, an ethylene-based polymer, and a nucleating agent.

[0004] In recent years, as plastics are being used and discarded in large quantities, the problems associated with their landfill and incineration treatments have been regarded as issues. The combustion treatment of plastics causes environmental burdens such as the generation of harmful gases during combustion and global warming due to a large amount of combustion heat. In order to reduce such environmental burdens, it is known to use biopolyethylene as a resin material derived from non-petroleum sources. However, Patent Document 3 points out that simply blending polypropylene with biopolyethylene results in poor durability of the obtained molded article, etc., and it is relatively easily damaged by dropping or the like. In order to solve this problem, Patent Document 3 describes a resin molded article comprising biopolyethylene, polypropylene, and at least one of an olefin-based thermoplastic elastomer and an α-olefin-based copolymer.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] As described above, in recent years, molded products and resin sheets for manufacturing them are required to be excellent in heat resistance, rigidity, and cold resistance. However, Patent Document 1 aims to overcome drawbacks such as drawdown during thermoforming in a PP-based resin sheet, and does not mention technical knowledge regarding cold resistance. Further, Patent Document 2 discloses that when the density of an ethylene-based polymer is high, the cold impact strength is inferior, and it has been shown that a resin sheet using high-density PE (HZ5000H) is inferior in cold impact strength compared to a resin sheet blended with linear low-density PE or an ethylene elastomer.

[0007] An object of the present invention is to provide a resin sheet for thermoforming and a molded article that are excellent in heat resistance and rigidity and also excellent in cold resistance.

Means for Solving the Problems

[0008] The resin sheet for thermoforming of the present invention is a resin sheet for thermoforming containing high-density polyethylene, block polypropylene, homopolypropylene, and an inorganic filler, wherein the high-density polyethylene contains high-density polyethylene (I) having a flow rate ratio measured in accordance with JIS K7210 in the range of 10 to 13, the content of the high-density polyethylene is 20 to 55% by weight of the total material formulation, the content of the high-density polyethylene (I) is 10 to 30% by weight of the total material formulation, and the Dupont impact strength of the resin sheet for thermoforming at -30°C is 0.5 J or more.

[0009] The molded article of the present invention is obtained by thermoforming the resin sheet for thermoforming of the present invention.

Effects of the Invention

[0010] The resin sheet for thermoforming and the molded article of the present invention are excellent in heat resistance and rigidity and also excellent in low-temperature impact strength.

Modes for Carrying Out the Invention

[0011] Embodiments of the present invention will be described below. This embodiment is an example of carrying out the present invention, and the present invention is not limited to this embodiment.

[0012] (1) Resin Sheet for Thermoforming The resin sheet for thermoforming according to an embodiment of the present invention (hereinafter simply referred to as "this sheet") contains high-density PE. Here, "high-density PE" means PE having a density of 0.94 g / cm 3 or more, preferably 0.942 to 0.970 g / cm 3 .

[0013] The high-density PE includes high-density PE (I) with a flow rate (FR) ratio measured in accordance with JIS K7210 in the range of 10 to 13, and the content of the high-density PE (I) is 10 to 30% by weight of the total material formulation. By including the high-density PE (I), it is excellent in rigidity and heat resistance, and can improve the low-temperature impact strength of the resin sheet and the molded product. If the content is less than 10% by weight, the rigidity and low-temperature impact strength of the resin sheet and the molded product will decrease, which is not preferable. If the content exceeds 30% by weight, the heat resistance will decrease, which is not preferable. Here, "total material formulation" means the total of high-density PE, block PP, homo PP, and inorganic filler.

[0014] The FR ratio is calculated by the method described in the Examples section, that is, in accordance with JIS K7210, measuring the MFR value (unit: g / 10 min) of high-density PE under Conditions 1 and 2, and dividing the MFR value under Condition 2 by the MFR value under Condition 1. A small FR ratio indicates a narrow molecular weight distribution of PE, and a large FR ratio indicates a wide molecular weight distribution of PE. If the FR ratio is outside the above range, the low-temperature impact strength of the resin sheet and the molded product will decrease, which is not preferable.

[0015] The high-density PE may contain only the high-density PE (I), or may contain one or more other high-density PEs. As the other high-density PE, for example, PE (plant-derived high-density PE) obtained by polymerization (homopolymerization or copolymerization) of non-petroleum-derived ethylene, such as plant-derived ethylene, is preferably mentioned. By using plant-derived high-density PE, it is possible to suppress the generation of CO2 from fossil-derived raw materials during combustion and reduce the environmental load, which is preferable. The plant-derived ethylene as a raw material can be obtained, for example, by distilling and separating the alcohol component, especially ethyl alcohol, from the fermentation product of sugar or the cellulose fermentation product extracted from plant raw materials (such as sugarcane and corn), and then performing a dehydration reaction. The plant-derived high-density PE can be obtained by polymerizing the plant-derived ethylene alone by a normal polymerization method or copolymerizing it with other monomers.

[0016] When the high-density PE contains non-petroleum-derived ethylene such as plant-derived high-density PE, its content is not particularly limited and can be appropriately determined. The content of the high-density PE derived from the plant raw material can be 3 to 20% by weight of the total material formulation. When the content of the non-petroleum-derived ethylene is within the above range, it is preferable because it is excellent in rigidity and low-temperature impact strength and can reduce the environmental load.

[0017] The content of the high-density PE is 20 to 55% by weight, preferably 25 to 55% by weight, of the total material formulation. If the content is less than 20% by weight, the low-temperature impact strength and rigidity of the resin sheet and molded product will decrease, which is not preferable. If the content exceeds 55% by weight, the heat resistance of the resin sheet and molded product will decrease, which is not preferable.

[0018] The content ratio of the high-density PE to the block PP and the homopolymer PP is not particularly limited and can be appropriately determined. The weight ratio of the high-density PE to the total of the block PP and the homopolymer PP can be (0.2 to 1.5):1, preferably (0.2 to 1):1, and more preferably (0.3 to 0.8):1. When the weight ratio is within the above range, it is preferable because the resin sheet and molded product are excellent in rigidity, low-temperature impact strength, and heat resistance.

[0019] This sheet contains block PP. The block PP is a propylene-ethylene block copolymer in which a polymer mainly composed of ethylene and an ethylene-propylene rubber-like copolymer are dispersed in a linear polymer mainly composed of propylene to form a sea-island structure. The block PP can usually be obtained by polymerizing homopolymer PP and then copolymerizing propylene and ethylene in the presence of homopolymer PP. There are no particular limitations on the specific physical properties of the block PP. For example, as the block PP, a block PP having an MFR value of 0.5 to 1 g / 10 min can be used. The block PP may be used alone or in combination of two or more.

[0020] This sheet contains homopolymer polypropylene (homoPP). As long as it is a homopolymer of propylene, there are no particular limitations on specific physical properties. As the homoPP resin, for example, a homoPP resin with a melt flow rate (MFR) value of 0.4 to 3.0 g / 10 min can be used. The homoPP may be used alone or in combination of two or more.

[0021] As the homoPP, a homoPP containing a nucleating agent may be used. Using a homoPP containing a nucleating agent as the homoPP is preferable because it can enhance rigidity and low-temperature impact strength. There are no particular limitations on the content of the nucleating agent in the homoPP, and it can be appropriately determined as needed. When the content of the nucleating agent increases, rigidity and low-temperature impact strength can be enhanced.

[0022] The type of the nucleating agent is not particularly limited as long as it can promote the crystallization of homoPP. As the nucleating agent, a nucleating agent known in the technical field of resins can be used. The nucleating agent may be either an organic nucleating agent or an inorganic nucleating agent. Specifically, examples of the organic nucleating agent include acetal-based (sorbitol-based), phosphorus-based, carboxylic acid or its metal salt, polymer-based, amide compound, and saccharides. Specifically, examples of the inorganic nucleating agent include disodium hydrogen phosphate, sodium dihydrogen phosphate, magnesium oxide, titanium oxide, zinc oxide, calcium carbonate, sodium carbonate, calcium silicate, magnesium silicate, magnesium sulfate, barium sulfate, talc, kaolin, alumina, silica, clay, etc. The nucleating agent may be used alone or in combination of two or more.

[0023] The MFR values of the block PP and homoPP are the values measured for the PP resin under the conditions of a measurement temperature of 230°C and a load of 2.16 kg based on the method of JIS K7210.

[0024] There are no particular limitations on the contents of the block PP and the homopolymer PP, and they can be appropriately determined as needed. In this sheet, the total content of the block PP and the homopolymer PP can be 15 to 50% by weight in the total material formulation. When the total content is within the above range, it is preferable because it has an excellent balance between low-temperature impact strength and rigidity.

[0025] There are no particular limitations on the ratio of the block PP to the homopolymer PP, and they can be appropriately determined as needed. When the proportion of the block PP is large, the low-temperature impact strength is improved, and when the proportion of the homopolymer PP is large, the rigidity is improved. The weight ratio of the block PP to the homopolymer PP is preferably 50 to 75:50 to 25. When the weight ratio is within the above range, it is preferable because it has an excellent balance between low-temperature impact strength and rigidity.

[0026] This sheet contains the inorganic filler. Thereby, the rigidity can be improved. There are no particular limitations on the content of the inorganic filler, and it can be appropriately determined as needed. The content of the inorganic filler can be 10 to 45% by weight, preferably 20 to 40% by weight in the total material formulation.

[0027] There are no particular limitations on the type of the inorganic filler. Specific examples of the inorganic filler include, for example, talc, calcium carbonate, silica, diatomaceous earth, alumina, titanium oxide, magnesium oxide, aluminum hydroxide, magnesium hydroxide, calcium silicate, glass beads, bentonite, glass flakes, glass fibers, carbon fibers, aluminum powder, molybdenum sulfide, boron fibers, potassium titanate, calcium titanate, hydrotalcite, carbon fibers, pumice powder, mica, calcium phosphate, and aluminum phosphate. The inorganic filler may be used alone or in combination of two or more.

[0028] In this sheet, the Dupont impact strength at -30°C is 0.5 J or more. Since the Dupont impact strength is within the above range, this sheet is excellent in low-temperature impact strength. The Dupont impact strength is a value measured according to JIS K7124 under the condition of -30°C. The Dupont impact strength can be increased, for example, by adjusting the weight ratio of block PP and homo PP, specifically by increasing the ratio of the block PP to the homo PP, by using, as the homo PP, a homo PP containing the above-mentioned nucleating agent, or by adding elastomers.

[0029] There is no particular limitation on the layer structure of this sheet. This sheet may have a single-layer structure or a laminated sheet of two or more layers. As this sheet which is a laminated sheet of two or more layers, for example, on at least one side of a base sheet containing the above-mentioned high-density PE (I), the above-mentioned high-density PE, the block PP, the homo PP, and an inorganic filler, and having a content of the high-density PE of 20 to 55% by weight of the total material formulation and a content of the high-density PE (I) of 10 to 30% by weight of the total material formulation, one or more other layers mainly composed of a polyolefin resin are laminated. More specifically, a laminated sheet in which one or more of the other layers are laminated on both sides of the base sheet can be mentioned. When there are two or more of the other layers, the other layers may be the same layer or layers having different types or physical properties.

[0030] As long as the other layer is mainly composed of a polyolefin resin, there is no particular limitation on the type and physical properties. There is no particular limitation on the type and physical properties of the polyolefin resin. The polyolefin resin may be a homopolymer or a copolymer. Specifically, examples of the polyolefin resin include a PE resin and a PP resin. The PP resin may be either a homo PP resin or a block PP resin. Also, the PE resin includes a high-density PE resin, a low-density PE (LDPE; density 0.910 to 0.930 g / cm 3 ), and a linear low-density polyethylene (LLDPE; density 0.910 to 0.925 g / cm 3) can be mentioned. The polyolefin resin may be used alone or in combination of two or more. In addition, "main component" means that the proportion of the polyolefin resin is 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more in 100% by weight of all the resins constituting the other layer.

[0031] There is no limitation on the manufacturing method of the laminated sheet. The laminated sheet can be manufactured by general lamination molding methods such as coextrusion method, injection molding method, and thermoforming. In the coextrusion method, any single-screw extruder and twin-screw extruder can be used. In the coextrusion method, as long as these layers are laminated in a molten state immediately before being extruded from the die, there is no limitation on the specific method. Specifically, as the coextrusion method, for example, a multi-manifold method in which the raw materials of the base sheet and the other layer are melt-kneaded by an extruder and then laminated in a die, and a feed block method (combining adapter method) in which the foamed layer and the non-foamed layer are laminated immediately before flowing into the die can be mentioned. Any of a T-die, a coat hanger type, or an annular die can be used as the die. In the coextrusion method, the foamed resin laminated sheet extruded from the die is cooled and solidified by a known method, for example, a polishing roll, an air knife, or a mandrel. Thereafter, it is wound by a winder or cut into a predetermined size by a cutting machine.

[0032] In the production of the laminated sheet, post-treatment may be carried out after cooling and solidification as necessary. There are no particular restrictions on the post-treatment. Specifically, the post-treatment includes, for example, polarity-imparting treatment steps such as corona treatment, flame treatment, frame treatment, plasma treatment, etc., coating steps such as coating with an anti-fogging agent or an antistatic agent using a coater roll, film lamination, printing, and painting. In particular, film lamination includes a pre-thermoforming lamination method that laminates before secondary forming, a thermal lamination method that laminates during cooling when forming a foamed resin laminated sheet, a method that once cools the foamed resin laminated sheet and then reheats it with a heating roll or the like for lamination, etc. It is possible to laminate by any known method. The type of film to be laminated is not particularly limited, such as a CPP film, a printed film thereof, a film laminated with EVOH, etc. However, it is preferable to use a film that is easily adhered to a polyolefin-based material, a film having a polyolefin-based resin disposed on the bonding surface, or a film coated with an ink, an adhesive, etc. mixed with chlorinated polypropylene or a low-molecular-weight polyolefin.

[0033] There are no particular restrictions on the specific shape of the sheet, and it can be appropriately determined as necessary. Therefore, the term "sheet" includes a film shape. The thickness of the sheet can be, for example, 0.1 to 3 mm, or 0.5 to 2 mm.

[0034] The sheet may contain other components as necessary, as long as the performance is not significantly impaired. Specifically, the other components include, for example, additives used in known resin sheets, such as flame retardants, ultraviolet absorbers, fluorescent brighteners, antistatic agents, anti-fogging agents, lubricants, anti-blocking agents, fluidity improvers, plasticizers, dispersants, and antibacterial agents. As described above, when the sheet is the laminated sheet, the other components may be contained in all of the layers constituting the laminated sheet, or may be contained in any of them.

[0035] There are no particular restrictions on the specific use of the sheet. As described later, the sheet can be used to obtain molded products such as containers by various molding methods.

[0036] (2) Molded Product This molded product is obtained by thermoforming this sheet. There are no particular limitations on the specific method of this thermoforming, and known thermoforming methods can be used, such as hot plate forming, vacuum forming, pressure air forming, vacuum pressure air forming, double-sided vacuum forming, plug forming, or press forming. Also, the conditions of thermoforming are not particularly limited. The forming conditions can be appropriately determined as needed.

[0037] There are no particular limitations on the shape, dimensions, and specific uses of this molded product. Examples of the uses of this molded product include containers such as packaging containers, for example, containers for packaging food and beverages, such as packaging containers for storing food and beverages for heated dishes. Since this sheet is excellent in low-temperature impact strength as described above, as the packaging container for food and beverages, a packaging container for food and beverages stored or transported at low temperature is preferably mentioned. Note that the "container" includes not only the entire container but also a part of the container. For example, the "container" includes not only the main body of the container but also the lid of the container.

Examples

[0038] Hereinafter, the present invention will be specifically described by way of examples. Note that the present invention is not limited to the forms shown in the examples. The embodiments of the present invention can be variously changed within the scope of the present invention according to the purpose, use, etc.

[0039] 1. Manufacture of Resin Sheet for Thermoforming The following components were used as raw materials.

[0040] <Block PP> "EC9GD" manufactured by Japan Polypropylene Co., Ltd. (MFR; 0.5 g / 10 min) <Homo PP> "EA9" manufactured by Japan Polypropylene Co., Ltd. (MFR; 0.5 g / 10 min) <Nucleating Agent-Containing Homo PP> "EA9FTD" manufactured by Japan Polypropylene Co., Ltd. (containing an inorganic nucleating agent, MFR; 0.4 g / 10 min) <High-Density PE (HDPE)> "E8040" manufactured by Kyoeisha Polyethylene Co., Ltd. (fossil fuel-derived HDPE, MFR measured at 190°C / 2.16 kg: 0.35 g / 10 min, FR ratio: 11.4) "B5803" manufactured by Kyoeisha Polyethylene Co., Ltd. (fossil fuel-derived HDPE, MFR measured at 190°C / 2.16 kg: 0.3 g / 10 min, FR ratio: 20.0) <Plant-derived HDPE> "SGM9450F" manufactured by Braskem (MFR measured at 190°C / 5 kg: 0.33 g / 10 min) <HDPE containing inorganic filler> "HFS60-5R" manufactured by Sankyo Chemical Industry Co., Ltd. (contains 40.0 parts by weight of fossil fuel-derived HDPE and 60.0 parts by weight of talc). <Colorant> "PEONY F-33000MMR" manufactured by DIC Corporation

[0041] The MFR value of the fossil fuel-derived HDPE was measured under the following conditions in accordance with JIS K7210. Then, the FR ratio of the fossil fuel-derived HDPE was calculated by dividing the MFR value of Condition 2 by the MFR value of Condition 1. Condition 1: MFR value measured at 190°C and 2.16 kg load (unit: g / 10 min) Condition 2: MFR value measured at 190°C and 10.0 kg load (unit: g / 10 min)

[0042] The MFR values of the block PP and homo PP were measured in accordance with JIS K7210 at 230°C and 2.16 kg load.

[0043] As raw materials for forming the base sheet, each of the above raw materials was dry-blended at the ratios shown in Tables 1 to 5 and supplied to an extruder. Further, as the raw material for forming the surface layer, homopolymer PP "FY6C" (manufactured by Japan Polypropylene Corporation, MFR; 2.4 g / 10 min) was supplied to the extruder. The raw materials dry-blended in each extruder were heated and melted, and the molten and mixed resins were co-extruded to obtain resin sheets for thermoforming of Examples and Comparative Examples (thickness: 0.35 mm, laminated structure: surface layer / base sheet / surface layer). In Tables 1 to 5, the blending amounts of polyolefins (PP and PE) are in wt%. Also, the blending amount of the colorant is in parts by weight based on the total amount of polyolefins.

[0044]

Table 1

[0045]

Table 2

[0046]

Table 3

[0047]

Table 4

[0048]

Table 5

[0049] 2. Performance Test of Resin Sheet For the resin sheets of Examples and Comparative Examples, performance tests were conducted by the following methods. The results are also shown in Tables 1 to 5.

[0050] (1) DuPont Impact Strength Test pieces measuring 50 mm in length and 50 mm in width were prepared from the resin sheets of the examples and comparative examples. For these test pieces, the 50% fracture energy (E50, unit: J) was measured in accordance with JIS K7124 using a DuPont impact tester (manufactured by Mize Testing Machine Co., Ltd.). (2) Flexural modulus Using an "Autograph AGS-X" (manufactured by Shimadzu Corporation), the measurement was carried out in accordance with JIS K7171 under the conditions of a support span of 30 mm and a bending speed of 20 mm / min.

[0051] 3. Manufacture of containers Using a vacuum pressure forming apparatus (manufactured by Asano Laboratory), the resin sheets of the examples and comparative examples were vacuum pressure formed under the conditions of an upper heater temperature of 435 °C and a lower heater temperature of 425 °C to manufacture rectangular containers (upper part: 232 mm × 195 mm × depth 34 mm) of the examples and comparative examples.

[0052] 4. Performance test of containers Performance tests were conducted on the containers of the examples and comparative examples by the following methods. The results are also shown in Tables 1 to 5.

[0053] (1) Container drop crack test A 250 g weight was placed in the containers of the examples and comparative examples, and a lid (rectangular shape with a long side of 232 mm, a short side of 195 mm, and a depth of 17 mm) obtained by separately thermoforming was put on. Then, the containers were stacked in 5 layers and stored in a corrugated cardboard box in 2 rows (10 in total) and stored at the set temperature (-20 °C or -30 °C) for 24 hours. After that, in that atmosphere, the corrugated cardboard was dropped from a height of 40 cm, the cracks in the containers were visually inspected, and the number of cracked containers was counted. (2) Container waist strength (g) Using a "Tensilon universal testing machine RTC-1310A" (manufactured by Orientec Co., Ltd.), the container was clamped in a state of standing in the short side direction, and the entire long side side wall part of the container was compressed by 18 mm in the width direction (compression speed: 400 mm / min), and the maximum stress at this time was taken as the waist strength. (3) Container range deflection (mm) 250 g of cooked rice was stored in the container body, and the change in the deflection amount of the container before and after microwave heating (500 W, 5 minutes) with the long side of the container fixed at 95 mm was measured. (4) Container heat resistance test The container body was placed face down in the "Gear Oven GPH-100" manufactured by Espec, and a 170 g weight was placed on it. It was stored for 1 minute at each set temperature (120 °C, 130 °C, 140 °C), and the degree of container deformation was visually confirmed.

[0054] 5. Performance evaluation of the resin sheet and the container Based on the results of the above performance tests, the performance of the resin sheet and the container was evaluated according to the following criteria. The results are also shown in Tables 1 to 5.

[0055] (1) Sheet evaluation criteria For the resin sheets of the examples and comparative examples, those that satisfied both Condition 1 (the Dupont impact strength at -30 °C is 0.5 J or more) and Condition 2 (the flexural modulus is 2700 MPa or more) were evaluated as "〇". Also, those that satisfied either one of Condition 1 and Condition 2 were evaluated as "△", and those that satisfied neither Condition 1 nor Condition 2 were evaluated as "×". (2) Container evaluation criteria For the containers of the examples and comparative examples, those that satisfied both Condition 1 (the number of cracks in the container drop test at -30 °C is 2 or less) and Condition 2 (no deformation at 130 °C in the container heat resistance test) were evaluated as "〇". Also, those that satisfied either one of Condition 1 and Condition 2 were evaluated as "△", and those that satisfied neither Condition 1 nor Condition 2 were evaluated as "×". (3) Comprehensive evaluation criteria Those with both the sheet evaluation and the container evaluation being "〇" were regarded as "〇", and the others were regarded as "×".

[0056] 6. Results From Table 1 (composition ratio; PP / PE / inorganic filler = 20 / 50 / 30 (Examples 1 to 12), 30 / 40 / 30 (Examples 13 and 14)), all the resin sheets of the examples have a DuPont impact strength of 0.5 J or more at -30°C and a flexural modulus of 2700 MPa or more, and thus are excellent in rigidity and low-temperature impact strength. Also, all the containers of the examples have 2 or fewer cracks in the container at -30°C and no deformation was observed at 130°C, and thus are excellent in cold resistance and heat resistance.

[0057] From Table 2 (composition ratio; PP / PE / inorganic filler = 40 / 30 / 30), when only homopolymer PP is used as PP (Comparative Examples 2-1 to 2-5), the flexural modulus is high and it is excellent in rigidity, but the DuPont impact strength at -30°C is low and sufficient low-temperature impact strength is not obtained. Also, the number of cracks in the container at -30°C is large and the cold resistance is not sufficient. On the other hand, when only block PP is used as PP (Comparative Examples 2-6 to 2-10), although the DuPont impact strength at -30°C is improved, sufficient low-temperature impact strength is not obtained, and also the flexural modulus decreases and the rigidity is not sufficient. Furthermore, although the number of cracks in the container also decreases, it is still large and the cold resistance is not sufficient. The same tendency is observed in any case when "E8040" (FR ratio; 11.4) and "B5803" (FR ratio; 20.0) are used as high-density PE.

[0058] From Table 3 (composition ratio; PP / PE / inorganic filler = 30 / 40 / 30), even when the content of PE was increased, the same tendency as in Table 2 was observed. That is, when only homopolymer PP was used as PP (Comparative Examples 3-1 to 3-4), the flexural modulus was high and the rigidity was excellent. On the other hand, although the Dupont impact strength at -30°C showed an improving tendency compared to Table 2, it was still low and sufficient low-temperature impact strength was not obtained. When nucleating agent-containing homopolymer PP was used as the homopolymer PP (Comparative Examples 3-5 to 3-8), although the Dupont impact strength at -30°C showed an improving tendency, sufficient low-temperature impact strength was still not obtained. Also, when only block PP was used as PP (Comparative Examples 3-9 to 3-14), although the Dupont impact strength at -30°C improved, sufficient low-temperature impact strength was still not obtained, and the flexural modulus decreased and the rigidity was not sufficient. The same tendency was observed in either case when "E8040" (FR ratio; 11.4) and "B5803" (FR ratio; 20.0) were used as the high-density PE.

[0059] From Table 4 (composition ratio; PP / PE / filler = 30 / 40 / 30), it can be seen that even when containing high-density PE, block PP, homopolymer PP, and an inorganic filler and the contents of high-density PE and high-density PE (I) are within a specific range, the Dupont impact strength at -30°C is low and it does not necessarily meet the requirements of the present invention.

[0060] However, when comparing Comparative Examples 4-1 and 4-2 with Examples 13 and 14, it can be seen that by using nucleating agent-containing homopolymer PP as the homopolymer PP, the Dupont impact strength at -30°C is improved and the requirements of the present invention can be met. Also, when comparing Comparative Examples 4-7 and 4-8 with Examples 13 and 14, it can be seen that by increasing the compounding amount of block PP and adjusting the weight ratio of block PP to homopolymer PP, the Dupont impact strength at -30°C is improved and the requirements of the present invention can be met. These results indicate that the Dupont impact strength at -30°C of the present invention can be appropriately adjusted by using nucleating agent-containing homopolymer PP as the homopolymer PP, or by increasing the compounding amount of block PP and adjusting the weight ratio of block PP to homopolymer PP.

[0061] From Table 5 (composition ratio; PP / PE / filler = 10 / 60 / 30), it can be seen that when the proportion of high-density PE is too high, deformation at 130 °C is observed, indicating inferior heat resistance. When using "E8040" (FR ratio; 11.4) as the high-density PE (Comparative Examples 5-7 to 5-9), the low-temperature impact strength is improved compared to when using "B5803" (FR ratio; 20.0) (Comparative Examples 5-1 to 5-6), but the heat resistance is not improved. The same tendency was observed whether the content of "E8040" (FR ratio; 11.4) was within the scope of the present invention (Comparative Examples 5-8 and 5-9) or outside the scope (Comparative Example 5-7).

Claims

1. A thermoformable resin sheet containing high-density polyethylene, block polypropylene, homopolypropylene, and an inorganic filler, wherein the high-density polyethylene contains high-density polyethylene (I) having a flow rate ratio measured in accordance with JIS K7210 in the range of 10 to 13, when the homopolypropylene contains a nucleating agent, the content of the high-density polyethylene is 40 to 55% by weight of the total material formulation, and when the homopolypropylene does not contain a nucleating agent, the content of the high-density polyethylene is 50 to 55% by weight of the total material formulation, the content of the high-density polyethylene (I) is 10 to 30% by weight of the total material formulation, the weight ratio of the block polypropylene to the homopolypropylene is 50 to 75:50 to 25, and the thermoformable resin sheet has a Dupont impact strength at -30°C of 0.5 J or more. A thermoformable resin sheet characterized by this.

2. The thermoformable resin sheet according to claim 1, wherein the high-density polyethylene contains high-density polyethylene derived from plant raw materials, and the content of the high-density polyethylene derived from plant raw materials is 3 to 20% by weight of the total material formulation.

3. The thermoformable resin sheet according to claim 1 or 2, wherein the homopolypropylene contains a nucleating agent.

4. A laminated sheet in which one or more other layers mainly composed of a polyolefin resin are laminated on at least one side of a base sheet containing high-density polyethylene, block polypropylene, homopolypropylene, and an inorganic filler, the high-density polyethylene containing high-density polyethylene (I) having a flow rate ratio measured in accordance with JIS K7210 in the range of 10 to 13, wherein the content of the high-density polyethylene is 40 to 55% by weight of the total material composition when the homopolypropylene contains a nucleating agent, 50 to 55% by weight of the total material composition when the homopolypropylene does not contain a nucleating agent, and the content of the high-density polyethylene (I) is 10 to 30% by weight of the total material composition. The resin sheet for thermoforming according to any one of claims 1 to 3.

5. A molded article obtained by thermoforming the resin sheet for thermoforming according to any one of claims 1 to 4.

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