Heat-resistant container

Abstract

To provide a container having heat resistance up to 130°C and excellent transparency.SOLUTION: A container 10 is a heat-resistant container having a container body 11 formed from a polypropylene-based resin composition containing a polypropylene resin and a nucleating agent, and the volume change rate of the container body after heating at 130°C for 60 minutes is within ±1%. The total haze value of the container body is 60.0% or less when measured according to JIS K7136. A sheet is made from a polypropylene-based resin composition containing a polypropylene resin and a nucleating agent, and has a total haze value of 60.0% or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present technology relates to heat-resistant containers. [Background technology]

[0002] Conventionally, plastic containers made from petroleum resources and the like have been used in large quantities as containers for storing fresh foods such as meat, fish, and vegetables, or processed foods such as boxed lunches, prepared meals, frozen foods, confectioneries, and noodles, because they are easy to mold, can be mass-produced, and have low manufacturing costs. Materials used for these plastic containers include, for example, polypropylene resin, polyethylene resin, and polystyrene resin. Among these, polypropylene resin has a heat resistance of around 120°C, is excellent in moisture resistance and chemical resistance, and is inexpensive, so it is widely used as a material for heat-resistant containers.

[0003] In recent years, food manufacturers have come to widely use steam convection ovens, which can heat ingredients using steam in addition to the functions of a regular oven (Patent Documents 1 and 2).

[0004] However, when cooking in a steam convection oven, the temperature rises to about 130° C., and conventional polypropylene resins have insufficient heat resistance. In order to improve heat resistance, it has been proposed to add a filler to the polypropylene resin (Non-Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2002-335927 A [Patent Document 2] JP 2005-110570 A [Non-patent literature]

[0006] [Non-Patent Document 1] Plastic Materials Lecture [7] Polypropylene Resin (Takagi Kenyuki, Sasaki Heizo, editors, Nikkan Kogyo Shimbun), published February 1, 1982, first edition, 8th printing, 86 pages Summary of the Invention [Problem to be solved by the invention]

[0007] The food ingredients stored in the container are cooked in a steam convection oven at a food manufacturer and sealed in the container with a fitting lid or the like. The containers storing the food ingredients are transported to convenience stores, supermarkets, etc. while maintaining the refrigerated or frozen state. In convenience stores, supermarkets, etc., the containers storing the food ingredients are usually displayed for sale. For this reason, the containers are required to have excellent transparency so that purchasers can fully see the food ingredients stored in the container. However, there is a problem that containers molded from polypropylene resins containing fillers to improve heat resistance have poor transparency.

[0008] An object of the present invention is to provide a heat-resistant container that has heat resistance up to 130° C. and excellent transparency. [Means for solving the problem]

[0009] This technology is Polypropylene resin, A container body formed from a polypropylene-based resin composition containing a nucleating agent, The heat-resistant container has a volume change rate of ±1% or less after heating at 130°C for 60 minutes. A heat-resistant container, wherein the total haze value of the container body is 60% or less when measured in accordance with JIS K7136. The polypropylene resin may have a meso pentad fraction (mmmm) of 96.0 to 99.5 mol %. The nucleating agent may be a metal salt of a cyclic fatty acid. The nucleating agent may be a metal hexahydrophthalate. The heat-resistant container may be a heat-resistant food container for containing food. In addition, this technology: Polypropylene resin, A sheet formed from a polypropylene-based resin composition containing a nucleating agent, Also provided is a sheet having a total haze value of 60.0% or less. In addition, this technology: A first outer layer, a second outer layer, and an intermediate layer provided between the first outer layer and the second outer layer, the first outer layer is made of a first resin composition containing a first polyolefin-based resin, the second outer layer is made of a second resin composition containing a second polyolefin-based resin, A multi-layer sheet, wherein at least the intermediate layer is made of a polypropylene-based resin composition containing a polypropylene resin and a nucleating agent, Also provided is a multilayer sheet having a total haze value of 60.0% or less. In addition, this technology: A polypropylene resin composition preparation step of mixing a polypropylene resin and a nucleating agent to prepare a polypropylene resin composition; a sheet molding step of extruding the polypropylene-based resin preparation as is or after pelletization into a sheet; a container body forming step of forming a container body from the sheet; A method for manufacturing a heat-resistant container comprising the steps of: Furthermore, this technology: A polypropylene resin composition preparation step of mixing a polypropylene resin and a nucleating agent to prepare a polypropylene resin composition; a sheet molding step of extruding the polypropylene-based resin preparation as is or after pelletization into a sheet; A method for producing a sheet is also provided. Effect of the Invention

[0010] This technology can provide a heat-resistant container that has heat resistance up to 130°C and excellent transparency. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view showing an example of a heat-resistant container according to a first embodiment. [Diagram 2] FIG. 2 is a perspective view showing an example of a heat-resistant container body according to the first embodiment. [Diagram 3] FIG. 1 is a front view showing an example of a heat-resistant container according to a first embodiment. [Figure 4] FIG. 2 is a plan view showing an example of a heat-resistant container body according to the first embodiment. [Diagram 5] FIG. 4 is a front view showing another example of the heat-resistant container according to the first embodiment. [Figure 6] FIG. 6 is a plan view showing the heat-resistant container body of FIG. 5. [Figure 7] 6 is a front view showing a state in which the heat-resistant container body in FIG. 5 is covered with a fitting lid. [Figure 8] FIG. 8 is a plan view of the fitting lid of FIG. [Figure 9] 8 is an enlarged view of a fitting portion between the fitting lid and the heat-resistant container body shown in FIG. 7. [Figure 10] FIG. 2 is a perspective view showing how to measure a volume change rate of a heat-resistant container according to the embodiment. [Figure 11] FIG. 13 is a diagram showing a dedicated jig used when measuring the volumetric change rate of a heat-resistant container. [Figure 12] FIG. 2 is a diagram showing a flat plate with a hole in the center used when measuring the volume change rate of a heat-resistant container. [Figure 13] FIG. 11 is a cross-sectional view showing an example of a multilayer sheet according to a third embodiment. [Figure 14] FIG. 11 is a schematic diagram showing an example of a multilayer co-extrusion molding machine used in the manufacturing method of a multilayer sheet according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Preferred embodiments for carrying out the present technology will be described below. Note that the embodiments described below are representative embodiments of the present technology, and the scope of the present technology is not limited to these embodiments.

[0013] This technology will be described in the following order. 1. First embodiment (example of heat-resistant container) (1) Heat-resistant container structure (2) Manufacturing method of heat-resistant containers (3) Physical properties of heat-resistant containers 2. Second embodiment (example of sheet) (1) Seat configuration (2) Seat manufacturing method (3) Physical properties of the sheet 3. Third embodiment (example of multilayer sheet) (1) Structure of the multi-layer sheet (2) Manufacturing method of multilayer sheet (3) Physical properties of multilayer sheets 4. Fourth embodiment (example of multilayer sheet) (1) Structure of the multi-layer sheet (2) Manufacturing method of multilayer sheet (3) Physical properties of multi-layer sheets 5. Working Example

[0014] 1. First embodiment (an example of a heat-resistant container)

[0015] (1) Heat-resistant container structure

[0016] Hereinafter, the configuration of the heat-resistant container according to this embodiment will be described with reference to the drawings. In this specification, "the direction perpendicular to an object (e.g., a container, etc.) placed on a horizontal plane with the surface on which food or the like is placed facing upward" is referred to as "thickness direction," and "any direction in a plane perpendicular to the thickness direction" is referred to as "planar direction." Also, "viewing an object (e.g., a container, etc.) placed on a horizontal plane with the surface on which food or the like is placed facing upward in the thickness direction from above in the vertical direction" is referred to as "planar view." Furthermore, of the two surfaces facing each other in the thickness direction of a packaging container, the surface on which food or the like is placed is referred to as the "inner surface," and the other surface opposite thereto is referred to as the "outer surface."

[0017] The heat-resistant container of this embodiment is composed of a heat-resistant container body (hereinafter, abbreviated as "container body") and a lid. The container body is formed from a polypropylene-based resin composition, and has, for example, a bottom part, a side part extending upward from the periphery of the bottom part, and an opening surrounded by the upper end of the side part. The container body may further have, for example, a flange part formed toward the outside at the opening. The lid is, for example, fitted inside the container body to close the opening of the container body. The heat-resistant container of this embodiment may also be used as a heat-resistant container for food to store food, or may be used for steam convection.

[0018] In the container body, the shape of the bottom surface and the opening may be, for example, a circle, an ellipse, a polygon, or a substantially polygonal shape, but is not particularly limited. The shape of the bottom surface and the opening may be the same or different. The side surface may be perpendicular to the bottom surface, or may be tapered. The shape of the container body having the bottom surface, the side surface, and the opening may be, for example, a bottomed cylindrical shape or a bottomed inverted truncated cone shape, but is not particularly limited.

[0019] The container body of this embodiment may be, for example, a container body formed by thermoforming using the polypropylene-based resin composition. The thermoforming may be, for example, deep-draw thermoforming. That is, the container body of this embodiment may be a deep-draw container body. In this specification, a deep-draw container body means a container body having an expansion ratio of 2.5 or more. In this specification, the expansion ratio of the container body is the ratio of the total area of ​​the side and bottom parts to the area of ​​the opening, and is a value calculated by the following formula. The larger the expansion ratio, the deeper the draw of the container body.

[0020] Container body expansion ratio = (side area + bottom area) / opening area

[0021] The expansion ratio of the container body may be, for example, preferably 1.1 to 5.5, more preferably 1.2 to 5.3, and even more preferably 1.3 to 5.0. By having the expansion ratio in such a range, the content volume can be ensured and the thickness of the side part of the heat-resistant container can be prevented from becoming excessively thin to an extent that it cannot withstand practical use.

[0022] Hereinafter, the heat-resistant container of this embodiment will be described with reference to the drawings.

[0023] FIG. 1 is a perspective view of an example of a heat-resistant container of this embodiment (hereinafter, also referred to as "container 10"). As shown in FIG. 1, the container 10 is composed of a container body 11 and a lid 12. FIG. 2 is a perspective view of the container body 11 showing a state in which the lid 12 is separated from the container 10 of this embodiment. As shown in FIG. 2, the container body 11 includes a bottom surface portion 15, a container body side surface portion 16 that extends and spreads upward from the outer edge of the bottom surface portion 15, and a flange portion 14 that extends outward from the upper end of the container body side surface portion 16. Also, as shown in FIG. 2, the container body 11 includes an opening portion 13 surrounded by the upper end of the container body side surface portion 16.

[0024] Fig. 3 is a front view of the container 10 of this embodiment. As shown in Fig. 3, a stacking protrusion 19 may be formed in the vicinity of the upper end of the container body side portion 16 of the container body 11.

[0025] A container body fitting portion 17 into which a lid material fitting portion (not shown) fits is preferably formed on the upper portion of the container body side surface portion 16. The container body fitting portion 17 may be provided around the entire periphery.

[0026] The shape of the container body fitting portion 17 may be various. For example, the container body fitting portion 17 may be an inverted taper shape that gradually reduces in diameter toward the upper side, or may be a vertical shape (straight shape) or a forward taper shape with a fitting recess recessed outward. In this embodiment, the container body fitting portion 17 may be configured to have a fitting recess recessed outward. The cross-sectional shape of the fitting recess may be various, but it is preferable that the fitting recess is curved outward and is an arc-shaped or trapezoidal shape in cross section.

[0027] As shown in FIG. 3, the container body fitting portion 17 is provided at the upper end of the container body side portion 16. The container body fitting portion 17 extends substantially vertically (vertically or with a slight reverse taper or slight forward taper) along the up-down direction. It is preferable that a step portion 18 is provided below the container body fitting portion 17. The step portion 18 is inclined upward toward the outside or extends substantially horizontally. The container body fitting portion 17 extends upward from the outer edge of the step portion 18.

[0028] The flange portion 14 may be provided with a knob (not shown) for facilitating the lid opening operation. A container body border 21 is formed on the outer edge of the flange portion 14, extending outward, for example, horizontally or slightly downward. From the viewpoint of obtaining a reinforcing effect for the container body, it is preferable to form a large number of extremely fine irregularities in the outer region of the entire width of the container body border 21 in the inward and outward directions. These irregularities are wavy when viewed enlarged from the front, and the direction in which the numerous peaks and valleys extend is the width direction (inward and outward direction).

[0029] Fig. 4 is a plan view of the container body 11 of this embodiment. As shown in Fig. 4, a plurality of stacking protrusions 19 may be formed along the circumferential direction. The container bodies 11 are transported in a stacked state (also referred to as a stacked state) to a line for filling the contents such as foodstuffs. The stacking protrusions 19 ensure gaps between the stacked container bodies 11, making it easier to remove the container bodies 11. As shown in Fig. 4, the opening 13 and bottom surface portion 15 of the container body 11 are circular in shape. As shown in Fig. 4, the bottom surface portion 15 has recesses 20 arranged concentrically.

[0030] As shown in Figs. 2 and 3, the shape of the container body 11 including the bottom portion 15, the container body side portion 16, and the opening portion 13 is an inverted truncated cone shape.

[0031] As shown in FIG. 3, the lid material 12 covers the opening 13 of the container body 11 and may be a top seal composed of a single layer or multiple layers having gas barrier properties that is attached to the flange portion 14 of the container body 11, and such a top seal may be attached to the flange portion 14 by thermal welding (fusion) or with a specified adhesive.

[0032] FIG. 5 is a front view of another example of the heat-resistant container of this embodiment. As shown in FIG. 5, the container body includes a bottom surface portion 55, a container body side surface portion 56 that extends from the outer edge of the bottom surface portion 55 while expanding upward, and a flange portion 54 that extends outward from the upper end of the container body side surface portion 56. The flange portion 54 may be provided with a knob portion (not shown) for facilitating the lid opening operation. The outer edge of the flange portion 54 is formed with a container body border portion 51 that extends outward, for example, horizontally or slightly downward. From the viewpoint of obtaining a reinforcing effect of the container body, it is preferable to form a large number of extremely fine irregularities in the outer region of the entire width of the container body border portion 51 in the inward and outward directions. The irregularities are wavy when viewed enlarged from the front, and the direction in which the many peaks and valleys extend is the width direction (inward and outward direction). As shown in FIG. 5, the container body includes an opening portion 53 surrounded by the upper end of the container body side surface portion 56.

[0033] As shown in FIG. 5, a stacking protrusion 59 is formed near the upper end of the container body side portion 56 of the container body. FIG. 6 is a plan view of another example of the container of this embodiment. As shown in FIG. 6, the stacking protrusion 59 may be formed along the circumferential direction. The container bodies are transported to a line in which a large number of container bodies are stacked (also called a stacked state) and filled with contents such as foodstuffs. The stacking protrusion 59 ensures a gap between the stacked container bodies, making it easy to remove the container bodies. As shown in FIG. 6, the shape of the opening 53 and the bottom surface portion 55 of the container body is a square with four arc-shaped corners. As shown in FIG. 6, the bottom surface portion 55 is provided with a recess 60 along the entire circumferential direction.

[0034] As shown in Figs. 5 and 6, the shape of the container body including the bottom surface portion 55, the container body side surface portion 56, and the opening portion 53 is substantially an inverted truncated pyramid shape.

[0035] As shown in Fig. 5, the lid material 52 covers the opening 53 of the container body, and may be a top seal composed of a single layer or multiple layers having gas barrier properties that are attached to the flange part 54 of the container body, and such a top seal may be attached to the flange part 54 by heat welding (fusion) or with a predetermined adhesive. In the case of a top-sealed container, if the container body changes in dimension during high-temperature treatment such as steam convection treatment, the container body cannot be fixed in the sealing bucket when sealing with the lid material, and seal misalignment may occur. Therefore, it is desirable that the volume change rate is as small as possible, preferably 1% or less.

[0036] A fitting lid may be used instead of the lid material 52 shown in FIG. 5. FIG. 7 is a front view showing the state in which the fitting lid is placed on the container body. FIG. 8 is a plan view of the fitting lid. FIG. 9 is an enlarged view of the fitting portion between the fitting lid and the container body shown in FIG. 7. As with the container body, the fitting lid may be formed from a polypropylene resin composition containing a polypropylene resin and a nucleating agent, and the total haze value of the fitting lid may be 60% or less when measured according to JIS K7136. The physical properties of the fitting lid and the manufacturing method of the fitting lid are the same as those of the container body, so the explanation will be omitted.

[0037] As shown in Figure 7, the fitting lid comprises a fitting lid convex portion 80, a fitting lid top portion 70, a fitting lid side portion 71 extending downward from the outer edge of the fitting lid top portion 70, a fitting lid extension portion 81 extending approximately horizontally outward from the lower end of the fitting lid side portion 71, a fitting lid fitting portion 72 extending upward from the outer edge of the fitting lid extension portion 81, and a fitting lid flange portion 73 extending outward from the upper end of the fitting lid fitting portion 72.

[0038] As shown in Fig. 7, the upper end of the container body side portion 77 is provided with a container body fitting portion 75 into which the fitting portion 72 of the fitting lid is fitted. The container body fitting portion 75 may be provided around the entire circumference. The container body fitting portion 75 extends substantially vertically along the up-down direction. Furthermore, the flange portion 74 extends outward from the container body fitting portion 75.

[0039] The cross-sectional shape of the fitting lid fitting portion 72 preferably corresponds to the cross-sectional shape of the container body fitting portion 75. The fitting lid fitting portion 72 and the container body fitting portion 75 preferably have curved surfaces with approximately the same curvature in their cross-sectional shapes. At least one of the cross-sectional shape of the fitting lid fitting portion 72 corresponding to the cross-sectional shape of the container body fitting portion 75 and the fitting lid fitting portion 72 and the container body fitting portion 75 having curved surfaces with approximately the same curvature in their cross-sectional shapes allows surface contact between the fitting lid fitting portion 72 and the container body fitting portion 75, thereby increasing the fitting strength. In the case of the fitting lid method, if the container body changes in dimensions under high-temperature treatment such as steam convection treatment, the fitting lid cannot be fitted, so it is desirable that the volume change rate is as small as possible, preferably 1% or less.

[0040] As shown in FIG. 8, a lid knob 82 may be provided on the outer edge of the fitting lid flange 73 to facilitate the lid opening operation. The container body of the present embodiment is formed from a polypropylene-based resin composition containing a polypropylene resin and a nucleating agent. The polypropylene-based resin composition will be described below.

[0041] [Polypropylene resin composition]

[0042] The polypropylene-based resin composition forming the container body of this embodiment contains a polypropylene resin and a nucleating agent.

[0043] (Polypropylene resin)

[0044] In the present embodiment, the polypropylene resin contained in the polypropylene-based resin composition is preferably homopolypropylene. Homopolypropylene refers to a polypropylene resin obtained by polymerizing only propylene, but also includes those in which 99.5 wt% to 100 wt% of the total structural units constituting the resin are propylene units.

[0045] The mesopentad fraction (mmmm) is an index representing the isotactic stereoregularity of a polypropylene resin, and as the mesopentad fraction (mmmm) increases, the isotactic stereoregularity increases. From the viewpoint of improving heat resistance, the polypropylene resin preferably has a high isotactic stereoregularity, and the mesopentad fraction (mmmm) is preferably 96.0 to 99.5 mol%, more preferably 97.0 to 99.5 mol%, and even more preferably 98.0 to 99.5 mol%. The mesopentad fraction (mmmm) is determined according to the method disclosed by A. Zambelli. 13 The measurements were performed in accordance with C-NMR (Macromolecules, vol. 6 (1973), p. 925) and Macromolecules, vol. 8 (1975), p. 687.

[0046] The polypropylene resin may be a commercially available polypropylene resin. Examples of such polypropylene resins include "Novatec (registered trademark) EA9HD" (meso pentad fraction [mmmm] in the range of 96.0 to 99.5 mol%) manufactured by Japan Polypropylene Corporation, "VS200A" (meso pentad fraction [mmmm] in the range of 96.0 to 99.5 mol%) and "VS200M" (meso pentad fraction [mmmm] in the range of 96.0 to 99.5 mol%) manufactured by SunAllomer Corporation.

[0047] The content of the polypropylene resin in the resin component is preferably 85% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less, based on the mass of the polypropylene resin composition.

[0048] (Nucleating agent)

[0049] In the present embodiment, the nucleating agent contained in the polypropylene resin composition is a component added to improve the crystallization rate and generate uniform and fine crystals in the polypropylene resin contained in the polypropylene resin composition. Examples of such nucleating agents include cyclic fatty acid metal salts and hexahydrophthalic acid metal salts.

[0050] The fatty acid metal salt is preferably a cyclic fatty acid metal salt, for example, a hexahydrophthalic acid metal salt represented by the following general formula (1).

[0051] [ka]

[0052] (In the general formula (1), M1 and M2 are each independently selected from the group consisting of calcium, sodium, strontium, lithium, zinc, magnesium, and monobasic aluminum; R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 are each independently selected from the group consisting of hydrogen and C1-C9 alkyl; and any two adjacent R3-R10 alkyl groups may be optionally bonded to form a carbon ring.)

[0053] Examples of metal salts of hexahydrophthalic acid include calcium salts of hexahydrophthalic acid and sodium salts of hexahydrophthalic acid, and preferably calcium 1,2-cyclohexanedicarboxylate. Examples of commercially available products of metal salts of hexahydrophthalic acid include HYPERFORM HPN-20E (manufactured by Milliken Japan LLC).

[0054] The amount of the nucleating agent is preferably 100 ppm or more and 10,000 ppm or less, more preferably 100 ppm or more and 5,000 ppm or less, and further preferably 100 ppm or more and 3,000 ppm or less, based on the mass of the polypropylene resin composition.

[0055] (Additives)

[0056] The polypropylene-based resin composition forming the container body of the present embodiment may further contain additives, such as antioxidants, neutralizing agents, light stabilizers, ultraviolet absorbers, lubricants, antistatic agents, flame retardants, dispersants, and plasticizers.

[0057] The additives may be used alone or in combination of two or more kinds.

[0058] For example, the blending amount of the antioxidant or neutralizing stabilizer is preferably 0.01 to 2 parts by weight, more preferably 0.01 to 1 part by weight, and further preferably 0.01 to 0.5 parts by weight, based on 100 parts by weight of the polypropylene resin composition.

[0059] (2) Manufacturing method of heat-resistant containers

[0060] The method for producing a heat-resistant container according to this embodiment will be described below. The method for producing a heat-resistant container according to this embodiment includes a polypropylene resin composition preparation step of mixing a polypropylene resin and a nucleating agent to prepare a polypropylene resin composition, a sheet molding step of extruding the polypropylene resin preparation to form a sheet, and a container body molding step of molding the sheet into a container body. Each step will be described below.

[0061] [Polypropylene resin composition preparation process]

[0062] In the polypropylene resin composition preparation process, the polypropylene resin and the nucleating agent are heated and mixed at 300°C or less. In this process, the raw materials such as the polypropylene resin and the nucleating agent may be mixed first. After the raw materials are mixed, the mixed raw materials may be heated and kneaded. In this process, the polypropylene resin may be heated to a temperature at which it can melt. The temperature may be appropriately selected by a person skilled in the art depending on the type of nucleating agent used and its content.

[0063] In the above step, for example, when the nucleating agent is a cyclic fatty acid metal salt, the kneading is preferably performed at a temperature equal to or higher than the melting point of the polypropylene resin, more preferably equal to or higher than 180° C., and even more preferably equal to or higher than 200° C. Also, the kneading is preferably performed at a temperature equal to or lower than 300° C., more preferably equal to or lower than 280° C., and even more preferably equal to or lower than 260° C.

[0064] The mixing of raw materials such as polypropylene resin and nucleating agent may be performed by a mixer such as a high-temperature agitator, a Henschel mixer, a tumbler mixer, a Banbury mixer, or a kneader mixer. The mixed raw materials may be heated and kneaded by, for example, a single-screw kneading extruder or a twin-screw kneading extruder. As these kneading extruders, devices known in the art may be used. Preferably, the process includes at least a heating and kneading treatment by a twin-screw kneading extruder. As the twin-screw kneading extruder, a co-rotating twin-screw kneading extruder or a counter-rotating twin-screw kneading extruder may be used. By performing the kneading treatment by the twin-screw kneading extruder, a polypropylene-based resin composition, which is a kneaded product in which the raw materials are more uniformly dispersed, can be obtained.

[0065] The polypropylene resin composition obtained in the above step as a kneaded product may be directly subjected to a sheet molding step without being pelletized, thereby making it possible to omit the pelletizing step. The polypropylene resin composition obtained as a kneaded product in the above step may be pelletized. The pelletized polypropylene resin composition as a kneaded product may be subjected to a sheet molding step.

[0066] [Sheet forming process]

[0067] In the sheet molding step, the polypropylene resin composition obtained in the polypropylene resin composition preparation step is molded to obtain a sheet. For example, the polypropylene resin composition obtained in the polypropylene resin composition preparation step is transferred to a sheet molding machine, and the polypropylene resin composition is molded using the sheet molding machine to form a sheet. The temperature during molding of the sheet may be set preferably to a melting temperature of the polypropylene resin composition or higher, for example, to a melting point of the polypropylene resin to 300°C. The molding pressure may also be set appropriately.

[0068] When forming the sheet, various molding machines such as a T-die extruder and a calendar molding machine can be used. After the sheet is formed by the molding machine, the temperature of the take-up roll may be appropriately set immediately after the sheet is formed to a predetermined thickness, and the sheet may be cooled and taken up as a raw roll and wound up. The thickness of the sheet may be, for example, 100 μm or more.

[0069] In the molding, for example, the polypropylene resin composition may be extruded from a molding machine as it is without being pelletized, or the pelletized polypropylene resin composition may be melted and the molten polypropylene resin composition may be extruded from a molding machine. The extrusion temperature may be appropriately selected by a person skilled in the art depending on the type and content of the nucleating agent contained in the polypropylene resin composition.

[0070] [Container body forming process]

[0071] In the container body forming process, the sheet obtained in the sheet forming process is softened by heating, and the softened sheet is attached to a forming die by suction to form a recess in which the packaged item is accommodated, thereby forming the container body. Vacuum forming or vacuum pressure forming is used as the forming method. Plug assist is also performed depending on the expansion ratio. The depth of the recess can be appropriately set according to the application, and for example, the depth of the recess may be preferably 1 to 5 cm. Deep drawing molding with an expansion ratio of 2.5 or more may also be performed. The sheet surface temperature immediately before forming in the forming machine measured with a non-contact radiation thermometer is preferably heated to 140°C to 170°C, the heating time is preferably set to 6 to 15 seconds, and the forming time is preferably set to 6 to 15 seconds. Here, a higher sheet surface temperature immediately before forming is advantageous in terms of heat resistance, since the stress remaining in the formed container is less, but the optimal sheet surface temperature is selected from the viewpoint of the thickness deviation balance of a multi-cavity container. According to the present invention, a container can be produced that satisfies a volume change rate of ±1% or less after heating at 130° C. for 60 minutes, even when the sheet surface temperature is below the melting point of PP.

[0072] In addition, the container body molding process is not limited to the thermoforming method, and may be an injection molding method in which a compound of the specific polypropylene resin and a nucleating agent is melted and plasticized by heating and kneading, and then the container is obtained by injecting the compound into a mold, holding the pressure, cooling, opening the mold, removing the compound, and closing the mold.

[0073] In the in-line molding method, a container body is molded, the contents to be packed are filled therein, and then a top film is placed as a lid material as shown in Fig. 1, heat sealed, and then cut. Such a top film is not particularly limited, and may be made of a polyethylene resin, a polypropylene resin, a polyamide resin, an ethylene-vinyl alcohol copolymer resin, a polyethylene terephthalate resin, or the like, suitably in a single layer or multiple layers. Also, a fitting lid as shown in Figs. 7, 8, and 9 may be used instead of the top film.

[0074] (3) Physical properties of heat-resistant containers

[0075] The physical properties of the heat-resistant container according to this embodiment will be described below.

[0076] [Volume change rate]

[0077] The heat-resistant container of this embodiment satisfies a volumetric change rate of ±1% or less after heating at 130° C. for 60 minutes, preferably ±0.9% or less, more preferably ±0.8% or less. The volumetric change rate of the heat-resistant container after heating at 120° C. for 60 minutes is ±0.9% or less, preferably ±0.8% or less, more preferably ±0.7% or less.

[0078] (Measurement of volume change rate)

[0079] The rate of volume change is measured by measuring the volume of the container before heating and the volume of the heat-resistant container after heating. The heat-resistant container is placed in a high-temperature incubator heated to the specified temperature, and the heat-resistant container is heated with the damper open to 75 degrees. After the specified temperature is reached, the heat-resistant container is heated for an additional hour. After one hour has passed, the heat-resistant container is exposed to room temperature and left for at least one day, after which the rate of volume change of the heat-resistant container is measured.

[0080] The volume change rate of the heat-resistant container is measured by the following procedure. (i) First, the container water filling amount Wb(g) before heating is measured. FIG. 10 is a perspective view showing how to measure the volume change rate of a heat-resistant container. FIG. 11 is a diagram showing a dedicated jig. FIG. 12 is a diagram showing a flat plate with a hole in the center. First, as shown in FIG. 10, the heat-resistant container 103 is placed on a dedicated jig 104 on an electronic balance 101 (FX-2000i, manufactured by A&D Co., Ltd.) with the bottom surface of the heat-resistant container 103 as the bottom, and a flat plate 102 with a hole of φ7 mm in the center that is larger than the top surface of the heat-resistant container 103 is placed on the top surface and fixed with masking tape, and the zero point is adjusted. (ii) Water is added from the hole in the center of the flat plate 102 using a dropper or the like, and the amount of water filled in the container when it is full, Wb (g), is measured (to cancel the surface tension of the water). The measurement is performed for n=5. The obtained values ​​are arithmetically averaged to obtain Wb ave Let us assume that. (iii) Set the high-temperature incubator "LP-201" (manufactured by Espec Corporation) to the specified temperature and heat it. Place the heat-resistant container 103 in the heated high-temperature incubator and heat the heat-resistant container 103 with the damper open to 75. After the specified temperature is reached, heat it for one hour. After one hour has passed, expose the heat-resistant container 103 to room temperature and leave it for one day or more, and then measure the container water fill amount Wa(g) after heating in the same manner as the container water fill amount Wb(g) before heating. (iv) The volume change rate is calculated from the following formula. Note that the measurement is performed for n=5, and the obtained values ​​are arithmetically averaged to obtain Wa ave Let us assume that. Volume change rate (%) = [1-Wa ave / Wb ave ] x 100

[0081] [Total Haze Value]

[0082] The heat-resistant container of this embodiment has a total haze value of 60% or less, preferably 55% or less, more preferably 53% or less, and even more preferably 50% or less, when measured according to JIS K 7136. The total haze value (total haze) refers to a haze value obtained by adding up the external haze value (surface haze) and the internal haze value (inner haze), and is expressed by the following formula: Total haze value (%) = External haze value (%) + Internal haze value (%) The measurement principle of internal haze is the same as for total haze, but by applying silicone to both outer surfaces of the sample and sandwiching it between glass plates, the cause of external haze caused by unevenness on the outer surface of the sample can be eliminated. The external haze can be calculated from the measured total haze and internal haze values ​​using the above formula.

[0083] (Total haze measurement)

[0084] Using a haze meter "HZ-V3" (manufactured by Suga Test Instruments Co., Ltd.), measure the center part of the side of the heat-resistant container before heat treatment in accordance with JIS K7136. The measurement is performed by measuring four or more points on the side of the heat-resistant container, and the total haze value is plotted against the thickness of the measured part. The total haze value for a specific thickness is calculated from the approximation line of the plot.

[0085] 2. Second embodiment (example of sheet)

[0086] (1) Seat configuration

[0087] The configuration of the sheet according to this embodiment will be described below: The sheet according to this embodiment is a single-layer sheet. The sheet according to this embodiment is formed from a polypropylene-based resin composition containing a polypropylene resin and a nucleating agent. All of the explanations regarding the polypropylene-based resin composition described in the above 1. "(1) Configuration of the container" also apply to the second embodiment. Therefore, the explanation of the polypropylene-based resin composition is omitted.

[0088] (2) Seat manufacturing method

[0089] The sheet manufacturing method according to this embodiment includes a polypropylene resin composition preparation step of mixing a polypropylene resin and a nucleating agent to prepare a polypropylene resin composition, and a sheet molding step of extruding the polypropylene resin composition to form a sheet. Note that, with regard to the polypropylene resin composition preparation step and the sheet molding step, all of the descriptions regarding the polypropylene resin composition preparation step and the sheet molding step described in "(2) Container manufacturing method" in 1 above also apply to the second embodiment. Therefore, the description of the polypropylene resin composition preparation step and the sheet molding step according to the second embodiment will be omitted.

[0090] (3) Physical properties of the sheet

[0091] [Total Haze Value]

[0092] The sheet of the present embodiment has a total haze value of 60% or less, preferably 55% or less, more preferably 53% or less, and further preferably 50% or less, when measured according to JIS K7136.

[0093] (Total haze measurement)

[0094] Using a haze meter "HZ-V3" (manufactured by Suga Test Instruments Co., Ltd.), the sheet before heat treatment is measured in accordance with JIS K7136. The total haze value % and thickness are measured at four or more points on the sheet, and the total haze value is plotted against the thickness of the measured part. The total haze value for a specific thickness is calculated from the approximation line of the plot.

[0095] 3. Third embodiment (example of multilayer sheet)

[0096] (1) Structure of the multi-layer sheet

[0097] Here, a three-type three-layer sheet is shown, but there is no particular limitation on the number of layers, as long as it is a multilayer sheet formed by laminating at least one layer having "homopolypropylene with a mesopentad fraction of 96.0 to 99.5 mol % and a nucleating agent" and a thermoplastic resin. As shown in FIG. 13, the multilayer sheet of this embodiment has a first outer layer 111, a second outer layer 113, and an intermediate layer 112 disposed between the first outer layer and the second outer layer.

[0098] [First outer layer]

[0099] The first outer layer 111 is made of a first resin composition containing a first polyolefin resin. The first polyolefin resin is preferably a polymer obtained by polymerization of olefins (e.g., α-olefins) as a main monomer. The polyolefin resin may be, for example, a polyethylene (PE) resin, a polypropylene (PP) resin, or a combination thereof.

[0100] The polyethylene resin may be, for example, a low density polyethylene resin (LDPE: Low Density Polyethylene), a high density polyethylene resin (HDPE: High Density Polyethylene), a very low density polyethylene resin (VLDPE: Very Low Density Polyethylene), a linear low density polyethylene resin (LLDPE: Linear Low Density Polyethylene), an ethylene copolymer such as an ethylene-vinyl acetate copolymer (EVA: Ethylene-Vinyl Acetate Copolymer), an ultra high molecular weight polyethylene resin (UHMW-PE: Ultra High Molecular Weight-Polyethylene), or a combination thereof.

[0101] The polyolefin resin may be, if necessary, preferably a biomass-derived polyolefin resin (e.g., a biomass-derived polyethylene resin, etc.), for example, a biomass polyethylene resin. The biomass polyethylene resin may be, for example, LDPE, LLDPE, or HDPE. Biomass polyethylene can be considered carbon neutral and can reduce CO2 emissions compared to petroleum-derived polyethylene.

[0102] The polyolefin resin may be a metallocene-catalyzed polyolefin resin, i.e., the thermoplastic resin may be, for example, a metallocene-catalyzed polyethylene resin or polypropylene resin, or a combination thereof.

[0103] The polyester resin as the other first resin composition is a polymer in which monomers are polymerized by ester bonds. The polyester resin may be, for example, polyethylene terephthalate resin (PET), polyethylene naphthalate resin (PEN), polybutylene terephthalate resin (PBT), polylactic acid resin (PLA), polycarbonate resin (PC), polybutylene adipate terephthalate resin (PBAT), polybutylene succinate resin (PBS), polyhydroxyalkanoate resin (PHA), or a combination of two or more of these.

[0104] The polystyrene resin as the other first resin composition is a polymer obtained by polymerizing a styrene monomer, and may be a metallocene catalyst-based polystyrene resin. The polystyrene resin may be, for example, a polystyrene resin, a rubber-reinforced polystyrene resin (high impact polystyrene resin, HIPS), a syndiotactic polystyrene resin, an acrylonitrile-styrene copolymer (AS resin), a methacrylate ester-styrene copolymer, an acrylonitrile-acrylic rubber-styrene copolymer, an acrylonitrile-ethylene propylene-styrene copolymer, or a combination of two or more of these.

[0105] The first polyolefin resin may preferably be the polypropylene resin composition of the first embodiment. The first resin composition may be composed only of a resin other than the polypropylene resin.

[0106] The first resin composition may preferably comprise the nucleating agent of the first embodiment.

[0107] [Second outer layer]

[0108] The second outer layer 113 is made of a second resin composition containing a second polyolefin resin. The same description as for the first polyolefin resin applies to the second polyolefin resin. Therefore, the description of the second polyolefin resin is omitted. The second polyolefin resin may be the same type as the first polyolefin resin, or may be a different type. The second resin composition may be composed only of a resin other than polypropylene resin.

[0109] [Middle layer]

[0110] 13, the intermediate layer 112 is provided between the first outer layer and the second outer layer. The intermediate layer is made of a polypropylene resin composition containing a polypropylene resin and a nucleating agent.

[0111] The polypropylene resin composition and nucleating agent forming the intermediate layer are all the same as those in the first embodiment, and therefore the description thereof will be omitted.

[0112] (2) Manufacturing method of multilayer sheet

[0113] The method for producing the multilayer sheet of the present embodiment can include, for example, a resin composition preparation step and a multilayer extrusion molding step.

[0114] [Resin composition preparation process]

[0115] In the resin composition preparation step, a first resin composition, a second resin composition, and a polypropylene-based resin composition are prepared, respectively. The explanation of the polypropylene-based resin composition preparation step in the first embodiment is applicable to the first resin composition and the second resin composition, except that the first resin composition and the second resin composition are used instead of the polypropylene-based resin composition, and therefore the explanation is omitted.

[0116] [Multi-layer extrusion molding process]

[0117] In the multilayer extrusion process, the first resin composition, the polypropylene-based resin composition, and the second resin composition are extruded and molded so that the resin layers are laminated to each other to obtain a multilayer sheet. The multilayer sheet can be obtained, for example, by using a multilayer co-extrusion molding machine 300 shown in FIG. 14. The multilayer co-extrusion molding machine 300 may have a first outer layer extruder 301, an intermediate layer extruder 302, a second outer layer extruder 303, a feed block 304, and a die 305. The multilayer co-extrusion molding machine 300 co-extrudes a three-layer structure multilayer sheet 306 in which the first outer layer, the intermediate layer, and the second outer layer are laminated, with the intermediate layer containing the polypropylene-based resin composition as the middle layer and the first outer layer and the second outer layer as the surface layers. The intermediate layer extruder 302 extrudes the polypropylene-based resin composition prepared in the resin composition preparation step, and each of the first outer layer extruder 301 and the second outer layer extruder 303 may extrude a different type of resin composition from the polypropylene-based resin composition extruded from the intermediate layer extruder 302, or may extrude the same polypropylene-based resin composition.

[0118] (3) Physical properties of multi-layer sheets

[0119] [Total Haze Value]

[0120] The multilayer sheet of the present embodiment has a total haze value of 60% or less, preferably 55% or less, more preferably 53% or less, and even more preferably 50% or less, when measured according to JIS K7136.

[0121] (Total haze measurement)

[0122] The measurement of the total haze value of the multilayer sheet is the same as that described in 2. (3) Physical properties of the sheet, and therefore the description thereof is omitted.

[0123] 4. Fourth embodiment (example of multilayer sheet)

[0124] (1) Structure of the multi-layer sheet

[0125] The multilayer sheet of the present embodiment may be a multilayer sheet according to a third embodiment shown in FIG. 13, in which the first outer layer 111 and the second outer layer 113 may be made of a polypropylene-based resin composition containing a polypropylene resin and a nucleating agent, and the intermediate layer 112 provided between the first outer layer and the second outer layer may be made of a first resin composition containing the first polyolefin-based resin or a second resin composition containing the second polyolefin-based resin. The multilayer sheet of the present embodiment may be a two-layer sheet having either the first outer layer 111 or the second outer layer 113 and the intermediate layer 112, in which the first outer layer 111 or the second outer layer 113 may be made of a polypropylene-based resin composition containing a polypropylene resin and a nucleating agent, and the intermediate layer 112 provided between the first outer layer and the second outer layer may be made of a first resin composition containing the first polyolefin-based resin or a second resin composition containing the second polyolefin-based resin.

[0126] The present technology can also adopt the following configuration. [1] Polypropylene resin, A container body formed from a polypropylene-based resin composition containing a nucleating agent, The heat-resistant container has a volume change rate of ±1% or less after heating at 130°C for 60 minutes. A heat-resistant container, wherein the total haze value of the container body is 60% or less when measured in accordance with JIS K7136. [2] The heat-resistant container according to [1], wherein the polypropylene resin has a meso pentad fraction (mmmm) of 96.0 to 99.5 mol %. [3] The heat-resistant container according to [1] or [2], wherein the nucleating agent is a metal salt of a cyclic fatty acid. [4] The heat-resistant container according to any one of [1] to [3], wherein the nucleating agent is a metal salt of hexahydrophthalic acid. [5] The heat-resistant container according to any one of [1] to [4], which is a heat-resistant container for food for storing food. [6] The heat-resistant container is intended for steam convection use and has a container body formed from a polypropylene-based resin composition containing a polypropylene resin and a nucleating agent. [7] A first outer layer, a second outer layer, and an intermediate layer provided between the first outer layer and the second outer layer, the first outer layer is made of a first resin composition containing a first polyolefin-based resin, the second outer layer is made of a second resin composition containing a second polyolefin-based resin, At least the intermediate layer is made of a polypropylene-based resin composition containing a polypropylene resin and a nucleating agent, A heat-resistant container in which the volumetric change rate of the container body after heating at 130°C for 60 minutes is within ±1%, and the total haze value is 60.0% or less. [8] Polypropylene resin, A sheet formed from a polypropylene-based resin composition containing a nucleating agent, A sheet having a total haze value of 60.0% or less. [9] A first outer layer, a second outer layer, and an intermediate layer provided between the first outer layer and the second outer layer, the first outer layer is made of a first resin composition containing a first polyolefin-based resin, the second outer layer is made of a second resin composition containing a second polyolefin-based resin, A multi-layer sheet, wherein at least the intermediate layer is made of a polypropylene-based resin composition containing a polypropylene resin and a nucleating agent, A multilayer sheet having a total haze value of 60.0% or less.

[10] A polypropylene resin composition preparation step of mixing a polypropylene resin and a nucleating agent to prepare a polypropylene resin composition; a sheet molding step of extruding the polypropylene-based resin preparation as is or after pelletization into a sheet; a container body forming step of forming a container body from the sheet; A method for manufacturing a heat-resistant container comprising the steps of:

[11] A polypropylene resin composition preparation step of mixing a polypropylene resin and a nucleating agent to prepare a polypropylene resin composition; a sheet molding step of extruding the polypropylene-based resin preparation as is or after pelletization into a sheet; A method for manufacturing a sheet comprising the steps of:

[0127] 5. Working Example

[0128] The present invention will be described in more detail below based on examples. Note that the examples described below are representative examples of the present invention, and the scope of the present invention is not limited to these examples. The evaluation methods used in the examples are the same as those described in 1.(3) Properties of the container and 3.(3) Properties of the multilayer sheet above.

[0129] Example 1

[0130] A polypropylene resin (product name: EA9HD, manufactured by Japan Polypropylene Corporation, homopolypropylene having a mesopentad fraction in the range of 96.0 to 99.5 mol%) was supplied to a first outer layer single screw extruder 301 of a multi-layer co-extrusion molding machine 300 shown in FIG. 14 via a hopper so that the amount of the polypropylene resin (product name: EA9HD, manufactured by Japan Polypropylene Corporation, homopolypropylene having a mesopentad fraction in the range of 96.0 to 99.5 mol%) was 97.5 mass% relative to the mass of the first resin composition, and a hexahydrophthalic acid metal salt masterbatch (product name: HYPERFORM HPN-20E, manufactured by Milliken Japan LLC, containing 4% nucleating agent component) was 2.5 mass%. A polypropylene resin (product name: EA9HD, manufactured by Japan Polypropylene Corporation) was supplied to an intermediate layer twin screw extruder 302 via a loss-in type weight feeder (not shown) so that the amount of the hexahydrophthalic acid metal salt masterbatch (product name: HYPERFORM HPN-20E, manufactured by Milliken Japan LLC, containing 4% nucleating agent component) was 97.5 mass% relative to the mass of the polypropylene resin composition. HPN-20E, manufactured by Milliken Japan LLC, containing 4% nucleating agent component) was supplied to the second outer layer single screw extruder 303 via a hopper so that 97.5% by mass of polypropylene resin (trade name: EA9HD, manufactured by Japan Polypropylene Corporation) and 2.5% by mass of hexahydrophthalic acid metal salt masterbatch (trade name: HYPERFORM HPN-20E, manufactured by Milliken Japan LLC, containing 4% nucleating agent component) were supplied to the second outer layer single screw extruder 303, and the resin compositions supplied to the first outer layer single screw extruder, intermediate layer twin screw extruder, and second outer layer single screw extruder were co-extruded, cooled with a three-roll take-up machine (not shown) with each roll temperature of 50 ° C., and film-formed at a take-up speed of 26.0 m / min. After edge trimming, a roll of a three-layer structure multilayer sheet with a sheet width of 775 mm was obtained.

[0131] The cylinder temperatures and adapter temperatures of the first outer layer single screw extruder 301 (L / D=30, φ75mm), the intermediate layer twin screw extruder 302 (L / D=30, φ113mm), and the second outer layer single screw extruder 303 (L / D=30, φ75mm) were set to 220 to 250°C. The intermediate layer twin screw extruder 302 had a discharge rate of 620kg / h, and the first outer layer single screw extruder 301 and the second outer layer single screw extruder 303 had a discharge rate of 30kg / h. The resin temperatures of the first outer layer single screw extruder 301 were 224°C, the intermediate layer twin screw extruder 302 was 248°C, and the second outer layer single screw extruder 303 was 224°C.

[0132] The multilayer extrusion molding gave a multilayer sheet having a thickness of 552 μm (hereinafter also referred to as "multilayer sheet of Example 1"), which was aimed at a thickness of 550±27.5 μm. In the multilayer sheet of Example 1, the first outer layer had a thickness of 22 μm, which was aimed at a thickness of 30±10.0 μm, the intermediate layer had a thickness of 508 μm, which was aimed at a thickness of 490±20.0 μm, and the second outer layer had a thickness of 22 μm, which was aimed at a thickness of 30±10.0 μm. The obtained multilayer sheet had a total haze value of 51.0% at a thickness of 550 μm. The measurement results are shown in Table 1 below.

[0133] [Table 1]

[0134] The multilayer sheet obtained was heated to 150°C using a radiation thermometer of a molding machine, and then vacuum-pressure molded into multiple cup-shaped containers. The expansion ratio of the resulting cup-shaped container was 2.6. The volume change rate of the resulting cup-shaped container after heating at 120°C for 60 minutes was -0.2%, and the volume change rate after heating at 130°C for 60 minutes was -0.5%. The total haze value at a thickness of 210 μm on the side of the resulting cup-shaped container before heating was 44.3%. The measurement results are shown in Table 2 below.

[0135] [Table 2]

[0136] Example 2

[0137] A polypropylene resin (product name: VS200M, manufactured by Sunallomer Co., Ltd., homopolypropylene having a mesopentad fraction in the range of 96.0 to 99.5 mol%) was supplied to the first outer layer single screw extruder 301 and the second outer layer single screw extruder 303 via a hopper so as to be 100.0 mass% based on the mass of the resin composition, and a polypropylene resin (product name: EA9HD, manufactured by Japan Polypropylene Corporation, homopolypropylene having a mesopentad fraction in the range of 96.0 to 99.5 mol%) was supplied to the intermediate layer twin screw extruder 302 via a loss-in type weight feeder (not shown) so as to be 97.5 mass% based on the mass of the polypropylene resin composition, and a hexahydrophthalic acid metal salt masterbatch (product name: HYPERFORM HPN-20E, Milliken Japan LLC, containing 4% nucleating agent component) was supplied to the first outer layer single screw extruder, the intermediate layer twin screw extruder, and the second outer layer single screw extruder, respectively, and the resin compositions supplied thereto were co-extruded and film-formed at a take-up speed of 25.9 m / min. After edge trimming, a roll with a sheet width of 775 mm was obtained. As a result, a three-layered multilayer sheet (hereinafter also referred to as "multilayer sheet of Example 2") having a thickness of 548 μm was obtained, with the target thickness being 550±27.5 μm. In the multilayer sheet of Example 2, the thickness of the first outer layer was 21 μm, the thickness of the intermediate layer was 507 μm, and the thickness of the second outer layer was 21 μm.

[0138] The film-forming equipment, equipment temperature, and extrusion rate were the same as in Example 1. The resin temperatures of the first outer layer single-screw extruder 301 were 225°C, the intermediate layer twin-screw extruder 302 was 248°C, and the second outer layer single-screw extruder 303 was 225°C.

[0139] The multilayer sheet obtained in Example 2 had a total haze value of 51.3% at a thickness of 550 μm. The measurement results are shown in Table 1.

[0140] The multilayer sheet obtained was then vacuum-pressurized into a cup-shaped container of the same shape as in Example 1 (expansion ratio 2.6) by the same method as in Example 1. The volume change rate of the obtained cup-shaped container after heating at 120°C for 60 minutes was -0.3%, and the volume change rate after heating at 130°C for 60 minutes was -0.6%. The total haze value at a thickness of 210 μm on the side of the obtained cup-shaped container before heating was 45.0%. The measurement results are shown in Table 2.

[0141] Example 3

[0142] The same procedure as in Example 1 was carried out except that a polypropylene resin (product name: VS200M, manufactured by SunAllomer Co., Ltd., homopolypropylene with a mesopentad fraction in the range of 96.0 to 99.5 mol%) was supplied to the first outer layer single screw extruder 301, the intermediate layer twin screw extruder 302, and the second outer layer single screw extruder 303 in an amount of 97.5 mass% relative to the mass of the resin composition, and a hexahydrophthalic acid metal salt masterbatch (product name: HYPERFORM HPN-20E, manufactured by Milliken Japan LLC, containing 4% nucleating agent component) was supplied in an amount of 2.5 mass%. A multilayer sheet having a three-layer structure (hereinafter also referred to as the "multilayer sheet of Example 3") was obtained. In the multilayer sheet of Example 3, the thickness of the first outer layer was 22 μm, the thickness of the intermediate layer was 510 μm, and the thickness of the second outer layer was 21 μm.

[0143] The film-forming equipment, set temperature, and extrusion rate were the same as in Example 1. The resin temperatures were 227° C. for the first outer layer single screw extruder 301, 249° C. for the intermediate layer twin screw extruder 302, and 227° C. for the second outer layer single screw extruder 303. The resin was formed into a film at a drawing speed of 25.7 m / min, and after edge trimming, a roll with a sheet width of 775 mm was obtained.

[0144] The multilayer sheet obtained in Example 3 had a total haze value of 52.8% at a thickness of 550 μm. The measurement results are shown in Table 1.

[0145] The multilayer sheet obtained was then vacuum-pressurized into a cup-shaped container of the same shape as in Example 1 (expansion ratio 2.6) by the same method as in Example 1. The volume change rate of the obtained cup-shaped container after heating at 120°C for 60 minutes was 0.1%, and the volume change rate after heating at 130°C for 60 minutes was -0.2%. The total haze value at a thickness of 210 μm on the side of the obtained cup-shaped container before heating was 47.3%. The measurement results are shown in Table 2.

[0146] Example 4

[0147] The same procedure as in Example 1 was carried out except that a polypropylene resin (trade name: EA9HD, manufactured by Japan Polypropylene Corporation, homopolypropylene with a mesopentad fraction in the range of 96.0 to 99.5 mol%) was supplied to the first outer layer single screw extruder 301, the intermediate layer twin screw extruder 302, and the second outer layer single screw extruder 303 so as to be 98.5 mass% relative to the mass of the resin composition, and a hexahydrophthalic acid metal salt masterbatch (trade name: HYPERFORM HPN-20E, manufactured by Milliken Japan LLC, containing 4% nucleating agent component) was supplied to be 1.5 mass%. A multilayer sheet having a three-layer structure (hereinafter also referred to as "multilayer sheet of Example 4") was obtained. In the multilayer sheet of Example 4, the thickness of the first outer layer was 23 μm, the thickness of the intermediate layer was 503 μm, and the thickness of the second outer layer was 22 μm.

[0148] The manufacturing equipment and set temperatures were the same as in Example 1, the output of the twin-screw extruder 302 for the intermediate layer was 420 kg / h, and the output of each of the first single-screw extruder 301 for the outer layer and the second single-screw extruder 303 for the outer layer was 20 kg / h. The resin temperatures of the first single-screw extruder 301 for the outer layer were 222° C., the twin-screw extruder 302 for the intermediate layer was 250° C., and the second single-screw extruder 303 for the outer layer was 222° C. The resin was formed into a film at a drawing speed of 17.8 m / min, and after edge trimming, a roll with a sheet width of 775 mm was obtained.

[0149] The multilayer sheet obtained in Example 4 had a total haze value of 44.9% at a thickness of 550 μm. The measurement results are shown in Table 1.

[0150] The multilayer sheet obtained was then vacuum-pressurized into a cup-shaped container of the same shape as in Example 1 (expansion ratio 2.6) by the same method as in Example 1. The volume change rate of the obtained cup-shaped container after heating at 120°C for 60 minutes was -0.3%, and the volume change rate after heating at 130°C for 60 minutes was -0.6%. The total haze value at a thickness of 210 μm on the side of the obtained cup-shaped container before heating was 50.6%. The measurement results are shown in Table 2.

[0151] Example 5

[0152] The first outer layer single screw extruder 301, the intermediate layer twin screw extruder 302, and the second outer layer single screw extruder 303 were fed with 87.5% by mass of polypropylene resin (trade name: EA9HD, manufactured by Japan Polypropylene Corporation, homopolypropylene with a mesopentad fraction in the range of 96.0 to 99.5 mol%), 10.0% by mass of polyethylene resin (trade name: KS260, manufactured by Japan Polyethylene Corporation), and 2.5% by mass of hexahydrophthalic acid metal salt master batch (trade name: HYPERFORM HPN-20E, manufactured by Milliken Japan LLC, containing 4% nucleating agent component) to the resin composition, respectively, in the same manner as in Example 1, to obtain a multilayer sheet having a three-layer structure (hereinafter also referred to as the "multilayer sheet of Example 5"). In the multilayer sheet of Example 5, the thickness of the first outer layer was 21 μm, the thickness of the intermediate layer was 505 μm, and the thickness of the second outer layer was 21 μm.

[0153] The film-forming equipment, set temperature, and extrusion rate were the same as in Example 4. The resin temperatures were 223° C. for the first outer layer single screw extruder 301, 250° C. for the intermediate layer twin screw extruder 302, and 222° C. for the second outer layer single screw extruder 303. The resin was formed into a film at a drawing speed of 18.2 m / min, and after edge trimming, a roll with a sheet width of 775 mm was obtained.

[0154] The multilayer sheet obtained in Example 5 had a total haze value of 38.6% at a thickness of 550 μm. The measurement results are shown in Table 1.

[0155] The multilayer sheet obtained was then vacuum-pressurized into a cup-shaped container of the same shape as in Example 1 (expansion ratio 2.6) by the same method as in Example 1. The volume change rate of the obtained cup-shaped container after heating at 120°C for 60 minutes was -0.4%, and the volume change rate after heating at 130°C for 60 minutes was -0.5%. The total haze value at a thickness of 210 μm on the side of the obtained cup-shaped container before heating was 44.4%. The measurement results are shown in Table 2.

[0156] Example 6

[0157] A polypropylene resin (product name: EA9HD, manufactured by Japan Polypropylene Corporation, homopolypropylene with a mesopentad fraction in the range of 96.0 to 99.5 mol%) was fed to the first outer layer single screw extruder 301, the intermediate layer twin screw extruder 302, and the second outer layer single screw extruder 303 in an amount of 97.5 mass% relative to the mass of the resin composition, and a hexahydrophthalic acid metal salt masterbatch (product name: HYPERFORM HPN-20E, manufactured by Milliken Japan LLC, containing 4% nucleating agent component) was fed to 2.5 mass%. The same procedure was followed as in Example 1, except that the take-up speed was 17.8 m / min. A roll of a three-layered multilayer sheet (hereinafter also referred to as "multilayer sheet of Example 6") having a thickness of 798 μm and a sheet width of 795 mm after edge trimming was obtained, compared to a target thickness of 800 ± 40.0 μm. In the multilayer sheet of Example 6, the target thickness of the first outer layer was 30±10.0 μm, while the thickness of the first outer layer was 31 μm; the target thickness of the intermediate layer was 740±20.0 μm, while the thickness of the intermediate layer was 737 μm; and the target thickness of the second outer layer was 30±10.0 μm, while the thickness of the second outer layer was 30 μm.

[0158] The resin temperatures of the first outer layer single screw extruder 301, the intermediate layer twin screw extruder 302, and the second outer layer single screw extruder 303 were 224°C, 248°C, and 224°C, respectively.

[0159] The multilayer sheet obtained in Example 6 had a total haze value of 59.1% at a thickness of 800 μm. The measurement results are shown in Table 1.

[0160] Furthermore, the obtained multilayer sheet was vacuum-pressure molded into a cup-shaped container having a different shape from that of Example 1 with an expansion ratio of 3.8 by the same method as in Example 1. The obtained cup-shaped container had a volume change rate of -0.3% after heating at 120°C for 60 minutes, and a volume change rate of -0.7% after heating at 130°C for 60 minutes, even though the expansion ratio was large at 3.8. In addition, the total haze value at a thickness of 210 μm on the side of the obtained cup-shaped container before heating was 45.2%. The measurement results are shown in Table 2.

[0161] Comparative Example 1

[0162] A multilayer sheet having a three-layer structure (hereinafter also referred to as "multilayer sheet of Comparative Example 1") was obtained in the same manner as in Example 4, except that a polypropylene resin (product name: EA9HD, manufactured by Japan Polypropylene Corporation, homopolypropylene with a mesopentad fraction in the range of 96.0 to 99.5 mol%) was supplied to the first outer layer single screw extruder 301, the intermediate layer twin screw extruder 302, and the second outer layer single screw extruder 303 so as to be 100.0 mass% relative to the mass of the resin composition. In the multilayer sheet of Comparative Example 1, the thickness of the first outer layer was 25 μm, the thickness of the intermediate layer was 498 μm, and the thickness of the second outer layer was 24 μm.

[0163] The film-forming equipment, set temperature, and extrusion rate were the same as those in Example 4. The resin temperatures were 222° C. for the first outer layer single screw extruder 301, 249° C. for the intermediate layer twin screw extruder 302, and 222° C. for the second outer layer single screw extruder 303. The resin was formed into a film at a drawing speed of 18.0 m / min, and after edge trimming, a roll having a sheet width of 775 mm was obtained.

[0164] The multilayer sheet obtained in Comparative Example 1 had a total haze value of 50.2% at a thickness of 550 μm. The measurement results are shown in Table 1.

[0165] Furthermore, the obtained multilayer sheet was vacuum-pressure molded into a cup-shaped container of the same shape as in Example 1 (expansion ratio 2.6) by the same method as in Example 1. The volume change rate of the obtained cup-shaped container after heating at 120°C for 60 minutes was 1.1%, and the volume change rate after heating at 130°C for 60 minutes was 1.3%. In addition, the container after heating at 120°C and 130°C showed swelling and deformation at the bottom, etc., making it difficult to use in practice. In addition, the total haze value at a thickness of 210 μm on the side of the obtained cup-shaped container before heating was 56.0%. The measurement results are shown in Table 2.

[0166] Comparative Example 2

[0167] The same procedure as in Example 4 was carried out except that a polypropylene resin (trade name: E-304GP, manufactured by Prime Polymer Co., Ltd., homopolypropylene with a mesopentad fraction in the range of 90.0 to 93.0 mol%) was supplied to the first outer layer single screw extruder 301, the intermediate layer twin screw extruder 302, and the second outer layer single screw extruder 303 in an amount of 97.5 mass% relative to the mass of the resin composition, and a hexahydrophthalic acid metal salt master batch (trade name: HYPERFORM HPN-20E, manufactured by Milliken Japan LLC, containing 4% nucleating agent component) was supplied in an amount of 2.5 mass%. A multilayer sheet having a three-layer structure (hereinafter also referred to as the "multilayer sheet of Comparative Example 2") was obtained. In the multilayer sheet of Comparative Example 2, the thickness of the first outer layer was 22 μm, the thickness of the intermediate layer was 503 μm, and the thickness of the second outer layer was 22 μm.

[0168] The film-forming equipment, set temperature, and extrusion rate were the same as in Example 4. The resin temperatures were 222° C. for the first outer layer single screw extruder 301, 249° C. for the intermediate layer twin screw extruder 302, and 222° C. for the second outer layer single screw extruder 303. The resin was formed into a film at a drawing speed of 17.7 m / min, and after edge trimming, a roll having a sheet width of 775 mm was obtained.

[0169] The multilayer sheet obtained in Comparative Example 2 had a total haze value of 37.1% at a thickness of 550 μm. The measurement results are shown in Table 1.

[0170] Furthermore, the obtained multilayer sheet was vacuum-pressure molded into a cup-shaped container of the same shape as in Example 1 (expansion ratio 2.6) by the same method as in Example 1. The volume change rate of the obtained cup-shaped container after heating at 120°C for 60 minutes was 0.9%, and the volume change rate after heating at 130°C for 60 minutes was 1.1%. In addition, the container after heating at 120°C and 130°C showed swelling and deformation at the bottom, etc., making it difficult to use in practice. In addition, the total haze value at a thickness of 210 μm on the side of the obtained cup-shaped container before heating was 41.5%. The measurement results are shown in Table 2.

[0171] Comparative Example 3

[0172] The same procedure as in Example 1 was carried out except that a polypropylene resin (trade name: EA9HD, manufactured by Japan Polypropylene Corporation, homopolypropylene with a mesopentad fraction in the range of 96.0 to 99.5 mol%) was supplied to the first outer layer single screw extruder 301, the intermediate layer twin screw extruder 302, and the second outer layer single screw extruder 303 so as to be 98.0 mass% relative to the mass of the resin composition, and a dispersion-type nucleating agent (registered trademark: RiKACRYSTA P1, manufactured by New Japan Chemical Co., Ltd., containing 5% nucleating agent component) was supplied to 2.0 mass%. A multilayer sheet having a three-layer structure (hereinafter also referred to as "multilayer sheet of Comparative Example 3") was obtained. In the multilayer sheet of Comparative Example 3, the thickness of the first outer layer was 23 μm, the thickness of the intermediate layer was 504 μm, and the thickness of the second outer layer was 22 μm.

[0173] The film-forming equipment, set temperature, and extrusion rate were the same as in Example 1. The resin temperatures were 224° C. for the first outer layer single screw extruder 301, 249° C. for the intermediate layer twin screw extruder 302, and 224° C. for the second outer layer single screw extruder 303. The resin was formed into a film at a drawing speed of 26.0 m / min, and after edge trimming, a roll with a sheet width of 775 mm was obtained.

[0174] The multilayer sheet obtained in Comparative Example 3 had a total haze value of 54.8% at a thickness of 550 μm. The measurement results are shown in Table 1.

[0175] The multilayer sheet obtained was then vacuum-pressurized into a cup-shaped container of the same shape as in Example 1 (expansion ratio 2.6) by the same method as in Example 1. The volume change rate of the obtained cup-shaped container after heating at 120°C for 60 minutes was -0.5%, and the volume change rate after heating at 130°C for 60 minutes was -1.5%. The total haze value at a thickness of 210 μm on the side of the obtained cup-shaped container before heating was 54.3%. The measurement results are shown in Table 2.

[0176] Comparative Example 4

[0177] The same procedure as in Example 4 was carried out except that a polypropylene resin (trade name: EA9HD, manufactured by Japan Polypropylene Corporation, homopolypropylene with a mesopentad fraction in the range of 96.0 to 99.5 mol%) was supplied to the first outer layer single screw extruder 301, the intermediate layer twin screw extruder 302, and the second outer layer single screw extruder 303 so as to be 98.0 mass% relative to the mass of the resin composition, and a phosphate metal salt master batch (registered trademark: ADKSTAB NA11, manufactured by ADEKA Corporation, containing 5% nucleating agent component) was supplied to be 2.0 mass%. A multilayer sheet having a three-layer structure (hereinafter also referred to as "multilayer sheet of Comparative Example 4") was obtained. In the multilayer sheet of Comparative Example 4, the thickness of the first outer layer was 22 μm, the thickness of the intermediate layer was 504 μm, and the thickness of the second outer layer was 21 μm.

[0178] The film-forming equipment, set temperature, and extrusion rate were the same as those in Example 4. The resin temperatures were 223° C. for the first outer layer single screw extruder 301, 250° C. for the intermediate layer twin screw extruder 302, and 223° C. for the second outer layer single screw extruder 303. The resin was formed into a film at a drawing speed of 17.7 m / min, and after edge trimming, a roll with a sheet width of 775 mm was obtained.

[0179] The multilayer sheet obtained in Comparative Example 4 had a total haze value of 32.4% at a thickness of 550 μm. The measurement results are shown in Table 1.

[0180] The multilayer sheet obtained was then vacuum-pressurized into a cup-shaped container of the same shape as in Example 1 (expansion ratio 2.6) by the same method as in Example 1. The volume change rate of the obtained cup-shaped container after heating at 120°C for 60 minutes was -1.1%, and the volume change rate after heating at 130°C for 60 minutes was -1.2%. The total haze value at a thickness of 210 μm on the side of the obtained cup-shaped container before heating was 45.2%. The measurement results are shown in Table 2.

[0181] Comparative Example 5

[0182] The same procedure as in Example 4 was carried out except that a polypropylene resin (trade name: EA9HD, manufactured by Japan Polypropylene Corporation, homopolypropylene with a mesopentad fraction in the range of 96.0 to 99.5 mol%) was supplied to the first outer layer single screw extruder 301, the intermediate layer twin screw extruder 302, and the second outer layer single screw extruder 303 in an amount of 97.5 mass% relative to the mass of the resin composition, and a fatty acid metal salt master batch (registered trademark: AL-PTBBA, manufactured by Oxalis Chemicals Corporation, containing 4% nucleating agent component) was supplied in an amount of 2.5 mass%. A multilayer sheet having a three-layer structure (hereinafter also referred to as "multilayer sheet of Comparative Example 5") was obtained. In the multilayer sheet of Comparative Example 5, the thickness of the first outer layer was 21 μm, the thickness of the intermediate layer was 505 μm, and the thickness of the second outer layer was 22 μm.

[0183] The film-forming equipment, set temperature, and extrusion rate were the same as those in Example 4. The resin temperatures were 224° C. for the first outer layer single screw extruder 301, 250° C. for the intermediate layer twin screw extruder 302, and 223° C. for the second outer layer single screw extruder 303. The resin was formed into a film at a drawing speed of 17.9 m / min, and after edge trimming, a roll having a sheet width of 775 mm was obtained.

[0184] The multilayer sheet obtained in Comparative Example 5 had a total haze value of 40.4% at a thickness of 550 μm. The measurement results are shown in Table 1.

[0185] The multilayer sheet obtained was then vacuum-pressurized into a cup-shaped container of the same shape as in Example 1 (expansion ratio 2.6) by the same method as in Example 1. The volume change rate of the obtained cup-shaped container after heating at 120°C for 60 minutes was -1.1%, and the volume change rate after heating at 130°C for 60 minutes was -1.5%. The total haze value at a thickness of 210 μm on the side of the obtained cup-shaped container before heating was 49.6%. The measurement results are shown in Table 2.

[0186] Comparative Example 6

[0187] The same procedure as in Example 4 was carried out except that polypropylene resin (trade name: EA9HD, manufactured by Japan Polypropylene Corporation, homopolypropylene with mesopentad fraction in the range of 96.0 to 99.5 mol%) was supplied to the first outer layer single screw extruder 301, the intermediate layer twin screw extruder 302, and the second outer layer single screw extruder 303 so as to be 97.5 mass% relative to the mass of the resin composition, and benzylidene sorbitol compound master batch (registered trademark: Mirado 3988, manufactured by Milliken Japan LLC, containing 10% nucleating agent component) was supplied to 2.5 mass%. A multilayer sheet having a three-layer structure (hereinafter also referred to as "multilayer sheet of Comparative Example 6") was obtained. In the multilayer sheet of Comparative Example 6, the thickness of the first outer layer was 23 μm, the thickness of the intermediate layer was 502 μm, and the thickness of the second outer layer was 24 μm.

[0188] The film-forming equipment, set temperature, and extrusion rate were the same as those in Example 4. The resin temperatures were 223° C. for the first outer layer single screw extruder 301, 250° C. for the intermediate layer twin screw extruder 302, and 223° C. for the second outer layer single screw extruder 303. The resin was formed into a film at a drawing speed of 18.2 m / min, and after edge trimming, a roll having a sheet width of 775 mm was obtained.

[0189] The multilayer sheet obtained in Comparative Example 6 had a total haze value of 22.5% at a thickness of 550 μm. The measurement results are shown in Table 1.

[0190] The multilayer sheet obtained was then vacuum-pressurized into a cup-shaped container of the same shape as in Example 1 (expansion ratio 2.6) by the same method as in Example 1. The volume change rate of the obtained cup-shaped container after heating at 120°C for 60 minutes was -1.6%, and the volume change rate after heating at 130°C for 60 minutes was -1.6%. The total haze value at a thickness of 210 μm on the side of the obtained cup-shaped container before heating was 38.0%. The measurement results are shown in Table 2. [Explanation of symbols]

[0191] 10 containers 11 Container body 12 Lid material 13 Opening 14 Flange section 15 Bottom part 16 Container body side part 17 Container body fitting part 18 Step section 19 Stacking protrusion 21 Container body edge S / C: Screen changer G / P: Gear pump F / B: Feed block Die: T-die

Claims

1. Polypropylene resin, A container body formed from a polypropylene-based resin composition containing a nucleating agent, The heat-resistant container has a volume change rate of ±1% or less after heating at 130° C. for 60 minutes. A heat-resistant container, wherein the total haze value of the container body is 60% or less when measured in accordance with JIS K7136.

2. The heat-resistant container according to claim 1, wherein the polypropylene resin has a meso pentad fraction (mmmm) of 96.0 to 99.5 mol%.

3. The heat-resistant container according to claim 1 , wherein the nucleating agent is a metal salt of a cyclic fatty acid.

4. The heat-resistant container according to claim 1 , wherein the nucleating agent is a metal salt of hexahydrophthalic acid.

5. The heat-resistant container according to claim 1 , wherein the heat-resistant container is a heat-resistant container for food to contain food.

6. The heat-resistant container is a heat-resistant container for steam convection use, and has a container body formed from a polypropylene-based resin composition containing a polypropylene resin and a nucleating agent.

7. A first outer layer, a second outer layer, and an intermediate layer provided between the first outer layer and the second outer layer, the first outer layer is made of a first resin composition containing a first polyolefin-based resin, the second outer layer is made of a second resin composition containing a second polyolefin-based resin, At least the intermediate layer is made of a polypropylene-based resin composition containing a polypropylene resin and a nucleating agent, A heat-resistant container in which the volumetric change rate of the container body after heating at 130° C. for 60 minutes satisfies ±1% or less, and the total haze value is 60.0% or less.

8. Polypropylene resin, A sheet formed from a polypropylene-based resin composition containing a nucleating agent, A sheet having a total haze value of 60.0% or less.

9. A first outer layer, a second outer layer, and an intermediate layer provided between the first outer layer and the second outer layer, the first outer layer is made of a first resin composition containing a first polyolefin-based resin, the second outer layer is made of a second resin composition containing a second polyolefin-based resin, A multi-layer sheet, wherein at least the intermediate layer is made of a polypropylene-based resin composition containing a polypropylene resin and a nucleating agent, A multilayer sheet having a total haze value of 60.0% or less.

10. A polypropylene resin composition preparation step of mixing a polypropylene resin and a nucleating agent to prepare a polypropylene resin composition; a sheet molding step of extruding the polypropylene-based resin preparation as is or after pelletization into a sheet; a container body forming step of forming a container body from the sheet; A method for manufacturing a heat-resistant container comprising the steps of:

11. A polypropylene resin composition preparation step of mixing a polypropylene resin and a nucleating agent to prepare a polypropylene resin composition; a sheet molding step of extruding the polypropylene-based resin preparation as is or after pelletization into a sheet; A method for manufacturing a sheet comprising the steps of:

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