Food storage containers

Abstract

To provide a food storage container that does not require an adhesive layer between polymer layers and has excellent stain resistance and moldability. [Solution] A container body having an opening, The container body has a laminated structure comprising a polymethylpentene-containing layer having a contact surface with food, and a polyolefin-containing layer directly disposed on the polymethylpentene-containing layer. At least a portion of the edge of the container body defining the opening is bent or curved, and the laminated structure is maintained at that edge. A food storage container in which the sum of the thickness of the polymethylpentene-containing layer and the thickness of the polyolefin-containing layer is 0.2 mm to 1.8 mm.

Description

Technical Field

[0001] The present disclosure relates to a container for food preservation.

Background Art

[0002] As a container used for storing foods and the like, a plastic container composed of a plurality of polymer layers is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technology described in Patent Document 1, there is room for improvement from the viewpoint of the balance between antifouling properties and moldability (hereinafter, including suppression of wrinkles in the sheet, ensuring the self-standing property of the container, suppression of thickness unevenness, suppression of bridges, etc., and these performances are collectively referred to as "moldability"). In addition, an adhesive layer is essential between the polymer layers, and the production method is limited.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a food preservation container that does not require an adhesive layer between polymer layers and is excellent in both antifouling properties and moldability.

Means for Solving the Problems

[0006] As a result of intensive studies, the present inventor has found that the above problems can be solved by a specific laminated structure, and has completed the present invention.

[0007] That is, the present invention includes the following aspects. [1] Comprising a container body having an opening, The container body has a laminated structure comprising a polymethylpentene-containing layer having a contact surface with food, and a polyolefin-containing layer directly disposed on the polymethylpentene-containing layer. At least a portion of the edge of the container body defining the opening is bent or curved, and the laminated structure is maintained at that edge. A food storage container in which the sum of the thickness of the polymethylpentene-containing layer and the thickness of the polyolefin-containing layer is 0.2 mm to 1.8 mm. [2] The food storage container according to [1], wherein the ratio of the thickness of the polymethylpentene-containing layer to the thickness of the polyolefin-containing layer is 1.0:1.0 to 1.0:9.0. [3] At least a portion of the aforementioned edge is bent, A food storage container according to [1] or [2], wherein the edge angle at the edge is 0° or more and 75° or less. [4] At least a portion of the aforementioned edge is curved, A food storage container according to any one of [1] to [3], wherein the edge angle at the edge is 0° or more and 75° or less. [5] A food storage container according to any one of [1] to [4], further comprising a lid configured to fit onto the container body via at least a portion of the rim. [Effects of the Invention]

[0008] According to the present invention, a food storage container is provided that does not require an adhesive layer between polymer layers and is excellent in both stain resistance and moldability. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a perspective view showing an example of a food storage container. [Figure 2] Figure 2 is a plan view showing an example of a food storage container. [Figure 3] Figure 3 is a cross-sectional view taken along line A-A' in Figure 2. [Figure 4] Figure 4 is a diagram showing an example of edge angle measurement. [Figure 5] Figure 5 is a diagram showing an example of edge angle measurement. [Figure 6] Figure 6 is a diagram showing an example of edge angle measurement. [Figure 7] Figure 7 is a diagram showing an example of edge angle measurement. [Figure 8] Figure 8 is a diagram showing an example of edge angle measurement. [Figure 9] Figure 9 is a diagram showing an example of edge angle measurement. [Figure 10] Figure 10 is a diagram showing an example of edge angle measurement. [Figure 11] Figure 11 is a diagram for explaining a modified example of the food storage container. [Figure 12] Figure 12 is a diagram showing a cross-sectional view of the food storage container in Example 1. [Figure 13] Figure 13 is a diagram showing a cross-sectional view of the food storage container in Example 6. [Figure 14] Figure 14 is a diagram showing a cross-sectional view of the food storage container in Example 9.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments for carrying out the present invention (hereinafter also referred to as "the present embodiment") will be described in detail with appropriate reference to the drawings. The present invention is not limited to the present embodiment and can be variously modified and implemented within the scope of its gist. Hereinafter, the same elements are denoted by the same reference numerals, and redundant explanations are omitted.

[0011] The food storage container of this embodiment comprises a container body having an opening, the container body having a laminated structure including a polymethylpentene-containing layer having a contact surface with food, and a polyolefin-containing layer directly disposed on the polymethylpentene-containing layer, at least a portion of the edge of the container body defining the opening is bent or curved, the laminated structure is maintained at the edge, and the sum of the thickness of the polymethylpentene-containing layer and the polyolefin-containing layer is 0.2 mm to 1.8 mm. Because the food storage container of this embodiment is constructed in this way, it does not require an adhesive layer between polymer layers and has excellent stain resistance and moldability.

[0012] The food storage container of this embodiment is configured as a container for storing food. In this embodiment, "storage" means storage under various environmental conditions, for example, storage in the low-temperature environment of a refrigerator, or storage in the even lower-temperature environment of a freezer. Furthermore, the food storage container of this embodiment may be configured to be usable at room temperature or higher temperatures, and may be configured to withstand heating by microwave heating using a microwave oven or other heating means.

[0013] Figure 1 is a perspective view showing an example of a food storage container. Figure 2 is a plan view showing an example of a food storage container. Figure 3 is a cross-sectional view taken along line A-A' in Figure 2, illustrating an example of the configuration of the cross-section of a food storage container (particularly the container body).

[0014] The food storage container 100 comprises a container body 10 having an opening OP. The shape of the container body 10 may be such that it can store various foods, for example, a square, rectangle, circle, oval, bowl shape, etc., when viewed from above. Regardless of the shape of the container body 10, it has a laminated structure LS including a polymethylpentene-containing layer 10a and a polyolefin-containing layer 10b.

[0015] The polymethylpentene-containing layer 10a has a contact surface CS with food. Generally, containers used for food storage are exposed to food containing acids, pigments, oils, odor components, etc., at room temperature, high temperature, or low temperature. Such containers are stored in refrigerators or freezers with food inside, and then heated in microwave ovens after being removed. After that, dirt tends to adhere to the container before the food is removed. Furthermore, after washing the container with a sponge and detergent, or after washing it with hot water in a dishwasher and then drying it by air drying or in a dryer at high temperature, dirt that cannot be completely removed tends to become fixed. In addition, repeated use of the container exposes it to temperature changes and sponge friction many times, which further tends to cause dirt to adhere. In the food storage container 100, the polymethylpentene-containing layer 10a is provided on the contact surface CS with food. Therefore, due to the surface tension of polymethylpentene, food adhesion tends to be suppressed. Polymethylpentene tends to exhibit higher stain resistance compared to other polyolefins such as polypropylene. Thus, the food storage container 100 has excellent stain resistance.

[0016] The contact surface CS constitutes the inner surface of the container body 10, and may, for example, form the bottom or side surface of the inner surface of the container body 10. The bottom surface of the container body 10 may have an uneven surface. Such an uneven surface can be utilized when stacking multiple food storage containers 100.

[0017] The polymethylpentene-containing layer 10a may be a polymer layer composed of a polymer of 4-methylpentene-1. The polymer of 4-methylpentene-1 may be a homopolymer of 4-methyl-1-pentene, or a copolymer of 4-methyl-1-pentene with another monomer. Examples of such copolymers include copolymers of 4-methyl-1-pentene with other α-olefins. Examples of α-olefins include ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. In the case of copolymers, it is preferable that the copolymer contains 50% by mass or more of 4-methyl-1-pentene. The α-olefin used in copolymerization may be used alone or in combination of two or more types.

[0018] The melt flow rate (MFR) of polymethylpentene may be between 0.1 and 220 g / 10 min. An MFR within this range provides a resin composition with excellent rigidity, cold impact strength, and transparency, and is suitable for high production rates derived from the molding temperature. An MFR below 0.1 g / 10 min makes molding difficult, while an MFR exceeding 220 g / 10 min may result in a resin composition with insufficient cold impact strength. The above MFR can be measured in accordance with ASTM D1238 under conditions of a load of 5.0 kg and a temperature of 260°C. The above MFR can be adjusted to the specified range, for example, by controlling the molecular weight of the polymer.

[0019] The polyolefin-containing layer 10b is directly disposed on the polymethylpentene-containing layer 10a. Here, "directly disposed" means that no adhesive layer is formed between the polymethylpentene-containing layer 10a and the polyolefin-containing layer 10b. The polyolefin constituting the polyolefin-containing layer 10b may be a polyolefin different from polymethylpentene. The polyolefin-containing layer 10b is preferably a polymer layer composed of a polypropylene polymer, from the viewpoint of obtaining heat resistance to microwave heating and hot water washing in a dishwasher. The polypropylene polymer may be a homopolymer of propylene, or a copolymer of propylene and another monomer. Such a copolymer is a copolymer of propylene and α-olefin, and may be either a random copolymer or a block copolymer, but a random copolymer is preferable from the viewpoint of transparency. Examples of α-olefins used in copolymerization include α-olefins with 2 to 20 carbon atoms other than propylene, such as ethylene, butene-1, hexene-1, and octene-1. One or more types of α-olefins copolymerized with propylene may be used. Of these, ethylene and butene-1 are preferred. Ethylene is more preferred. Specific examples of copolymers include propylene-ethylene copolymer, propylene-ethylene-diene copolymer, propylene-ethylene-butene-1 copolymer, propylene-butene-1 copolymer, propylene-hexene-1 copolymer, and propylene-octene-1 copolymer. Of these, propylene-ethylene copolymer, propylene-butene-1 copolymer, and propylene-ethylene-butene-1 copolymer are particularly preferred.

[0020] The MFR of polypropylene may be 0.1 to 100 g / 10 min. More preferably, it is 0.2 to 80 g / 10 min, even more preferably 0.3 to 70 g / 10 min, particularly preferably 0.5 to 50 g / 10 min, and most preferably 1.0 to 40 g / 10 min. When the MFR is within this range, it provides a resin composition that is excellent in rigidity, cold impact strength, and transparency, and is suitable for high production rates derived from the molding temperature. If the MFR is less than 0.1 g / 10 min, molding becomes difficult, while if it exceeds 100 g / 10 min, there is a risk that the resin composition will not be able to obtain good cold impact strength. The above MFR can be measured in accordance with JIS K7210 under conditions of a load of 2.16 kg and a temperature of 230 °C. The above MFR can be adjusted to the above range, for example, by controlling the molecular weight of the polymer.

[0021] As described above, polymethylpentene generally tends to have higher fluidity than polypropylene. When a container is made solely of polymethylpentene, injection molding can be used as the molding method, but even then, the dimensional accuracy tends to decrease (thickness unevenness increases) compared to when the container is made solely of polypropylene. In this embodiment, by using polymethylpentene and polypropylene in combination, the moldability tends to improve, preventing a decrease in dimensional accuracy and ensuring the self-supporting ability of the container. Furthermore, by making the sum of the thickness of the polymethylpentene-containing layer 10a and the thickness of the polypropylene-containing layer 10b 0.2 mm or more, the self-supporting ability can be further improved. On the other hand, by making the sum of the thickness of the polymethylpentene-containing layer 10a and the thickness of the polypropylene-containing layer 10b 1.8 mm or less, the bending (bent part) or curvature (curved part) of the edge of the container body can be molded with high precision. In particular, when a food storage container is further equipped with a lid as described later, uneven thickness between the bottom and the rim can affect the fit between the container body and the lid. In this embodiment, by using polymethylpentene and polypropylene in combination, and by making the sum of the thickness of the polymethylpentene-containing layer 10a and the thickness of the polypropylene-containing layer 10b 1.8 mm or less, not only can the fit between the container body and the lid be favorably ensured, but the occurrence of bridging during molding (a phenomenon in which uneven thickness occurs in a wrinkled manner when the parts of the resin sheet that do not adhere closely to the mold and bend together become one) tends to be suppressed, and as a result, it becomes easier to stack the containers together. From this viewpoint, the sum of the thickness of the polymethylpentene-containing layer 10a and the thickness of the polypropylene-containing layer 10b is 0.2 mm to 1.8 mm, preferably 0.3 mm to 1.3 mm, and more preferably 0.5 mm to 1.0 mm. In this embodiment, the sum of the thickness of the polymethylpentene-containing layer 10a and the thickness of the polypropylene-containing layer 10b can match the thickness of the container body 10. From the same viewpoint as above, the ratio of the thickness of the polymethylpentene-containing layer 10a to the thickness of the polypropylene-containing layer 10b is preferably 1.0:1.0 to 1.0:9.0.

[0022] The container body 10 has an edge portion EP that defines the opening OP. At least a portion of the edge portion EP is bent or curved, and the laminated structure LS is maintained at the edge portion EP. Generally, polymethylpentene does not have a high affinity with polyolefins such as polypropylene, and an adhesive layer is interposed when the two materials are integrated. In contrast, in this embodiment, the polymethylpentene-containing layer 10a and the polypropylene-containing layer 10b are bent or curved at the edge portion EP of the container body 10, thereby promoting the integration of the polymethylpentene-containing layer 10a and the polypropylene-containing layer 10b. Therefore, in this embodiment, the polymethylpentene-containing layer 10a and the polypropylene-containing layer 10b can be integrated without the interposition of an adhesive layer, and separation of these layers can be suppressed. In this embodiment, even if some layer separation occurs in parts of the container body 10 other than the edge portion EP, it is considered that the product can be used for practical purposes as long as the laminated state is maintained without layer separation at least at the edge portion EP (the end of the polymethylpentene-containing layer 10a and the polypropylene-containing layer 10b). In this embodiment, it is preferable that the laminated structure LS is maintained throughout the entire container body 10.

[0023] In this embodiment, from the viewpoint of suppressing layer separation, it is preferable that the edge angle at the edge EP is 0° or more and 150° or less. In this embodiment, even if at least a part of the edge EP is bent or curved, the edge angle may be 0° or more and 150° or less. It is more preferable that the edge angle is 0° or more and 75° or less, and if it is 75° or less, layer separation can be further suppressed. The edge angle can be specified as follows.

[0024] When the container is viewed from the side (for example, as observed in the A-A' section in Figure 2 (the same applies hereafter)), a bent portion 351 formed by straight lines 301 and 302 can be observed, as illustrated in Figure 4. In this case, the edge angle is the angle θ1 between straight lines 301 and 302 at the edge EP.

[0025] The case where there are two or more bends will be explained. When the container is viewed from the side, as illustrated in Figure 5, a bend 353 formed by straight lines 303 and 304, a bend 354 formed by straight lines 304 and 305, and a bend 355 formed overall from straight line 303 to straight line 305 can be observed. In this case, three edge angles can be considered: the angle θ1 between straight lines 303 and 304, the angle θ2 between straight lines 304 and 305, and the angle θ3 between straight lines 303 and 305. In this embodiment, the smallest of these is taken as the edge angle of edge EP. That is, in this case, the edge angle at edge EP is θ3.

[0026] When the container is viewed from the side, a curved section formed by a straight line 306, a curved line 308, and a straight line 307 can be observed, as illustrated in Figure 6. In this case, at the intersection point 356 of the tangent line A at the inflection point X between the straight line 306 and the curved line 308 and the tangent line B at the inflection point Y between the straight line 307 and the curved line 308, the angle θ1 between tangent line A and tangent line B becomes the edge angle at the edge EP.

[0027] The case where there are two or more curved sections will be described. When the container is viewed from the side, as illustrated in Figure 7, one curved section formed by the straight line 309, the curved line 311, and the straight line 310 can be observed, as can another curved section formed by the straight line 310, the curved line 313, and the straight line 312, and a curved section formed overall from the straight line 309 to the straight line 312. In this case, three edge angles can be considered: θ1, the angle between tangent A at the inflection point X between the straight line 309 and the curved line 311, and θ2, the angle between tangent C at the inflection point Z between the straight line 310 and the curved line 313, and θ2, the angle between tangent C and tangent D at the intersection point 360 between the straight line 312 and the curved line 313, and θ3, the angle between tangent A and tangent D at the intersection of tangent A and tangent D. In this embodiment, the smallest of all edge angles is taken as the edge angle of the edge; therefore, in this case, the edge angle at edge EP is θ3. If θ3 is negative, it is taken as 0 degrees.

[0028] When the container is viewed from the side, a curved portion formed by a straight line 314 and a curved line 315 can be observed, as illustrated in Figure 8. In this case, at the intersection point 364 of the tangent line A at the inflection point X of the straight line 314 and the curved line 315 and the tangent line B at the endpoint Y of the curved line 315, the angle θ1 between tangent line A and tangent line B becomes the edge angle at the edge portion EP.

[0029] Another example of a case where there are two or more curved sections will be described. When the container is viewed from the side, as illustrated in Figure 9, one curved section formed by the straight line 316 and the curved line 317 can be observed, as can another curved section formed by the straight line 318 and the curved line 319, and another curved section formed overall from the straight line 316 to the straight line 318. In the example in Figure 9, the curved line 317 and the curved line 319 are connected at the inflection point Y. In this case, three edge angles can be considered: θ1, the angle between tangent A at inflection point X of the straight line 316 and curved line 317, and θ2, the angle between tangent C at inflection point Z of the straight line 318 and curved line 319, and θ3, the angle between tangent A and tangent D at intersection point 368 of the straight line 318 and curved line 319. The smallest of all edge angles is taken as the edge angle of the edge; therefore, in this case, the edge angle at edge EP is θ3. If θ3 is negative, it is taken as 0 degrees.

[0030] The case where there are bent and curved sections will be explained. When the container is viewed from the side, as illustrated in Figure 10, a bent section 369 is formed by straight lines 319 and 320, a curved section 322 is formed by straight line 320, curved line 322 and straight line 321, and an edge section is formed overall from straight line 319 to straight line 321. In this case, the edge angle is the angle θ1 between straight line 319 and straight line 320, the angle θ2 between tangent C at the inflection point Y between straight line 320 and curved line 322 and tangent D at the inflection point Z between straight line 321 and curved line 322 is the edge angle, and the angle θ3 between straight line 319 and tangent D at the intersection point of straight line 319 and tangent D is the edge angle. Since the smallest of all edge angles is taken as the edge angle of the edge, in this case the edge angle at edge EP is θ3. If θ3 is negative, it is taken as 0 degrees.

[0031] Furthermore, the above-mentioned measurements and determination of the edge angle can also be performed automatically using methods such as those described in the examples.

[0032] The food storage container 100 may further include a lid 11. The lid 11 may be configured to close the opening OP in the container body 10. In this embodiment, the lid 11 may be configured to fit onto at least a portion of the edge EP of the container body 10. When the lid 11 is configured to fit onto at least a portion of the edge EP, it is preferable that it provides a suitable seal when fitted. This prevents as much air from outside the container body 10 as possible from entering the container body 10, and also tends to prevent leakage of food inside the container body 10 in the event that the food storage container 100 is tipped over. The material of the lid 11 is not particularly limited and may be made of a plastic material such as polypropylene.

[0033] The method for manufacturing the food storage container 100 is not particularly limited, as long as the above-described configuration of the food storage container 100 can be obtained. For example, the container body 10 can be obtained by co-extruding the raw materials for the polymethylpentene-containing layer 10a and the raw materials for the polypropylene-containing layer 10b into a sheet, and then forming it into a container shape by vacuum pressure forming. The sheet thickness is preferably 0.2 mm to 2.0 mm. If the sheet thickness is 0.2 mm or more, the occurrence of wrinkles and wave patterns due to the thinning of the polymethylpentene-containing layer can be reduced. If the sheet thickness is 2.0 mm or less, the amount of polymethylpentene used during container molding can be reduced, resulting in more cost-effective container molding. The ratio of the thickness of the polymethylpentene-containing layer 10a to the thickness of the polypropylene-containing layer 10b can be adjusted by appropriately adjusting the amount of raw materials used during co-extrusion. The conditions for vacuum pressure forming may be adjusted as appropriate, including the upper heater temperature, lower heater temperature, heating time, upper mold time, upper mold delay time, lower mold time, lower mold delay time, upper mold compression delay, upper mold compression time, lower mold vacuum delay, lower mold vacuum time, lower mold demolding delay, lower mold demolding time, clearance, etc. The lid 11 can be manufactured in the same manner as the container body 10. [Examples]

[0034] The embodiment will be described in detail below with reference to examples, but this embodiment is not limited to these examples.

[0035] [Example 1] A two-layer sheet with a thickness ratio of 1.0:1.0 between a polymethylpentene-containing layer (hereinafter also referred to as "Layer A") made of polymethylpentene (Mitsui Chemicals, Inc., MX002O) and a polypropylene-containing layer (hereinafter also referred to as "Layer B") made of polypropylene (Sun Allomer Co., Ltd., PL500A) was obtained as follows. Specifically, the two-layer sheet was manufactured by extrusion molding (Labtech, Inc., LCR-350+LE25-30 / C-HA) of polymethylpentene and polypropylene under the molding conditions shown in Table 1.

[0036] [Table 1]

[0037] The obtained two-layer sheet was vacuum-formed (using a Wakisaka Engineering Co., Ltd. FVT400) under the molding conditions described in Table 2 to produce stackable food storage containers with a thickness of 0.6 mm (see Figure 12), as described later. The deflection of the container (evaluation of self-support) was evaluated as having no problems with practical performance, and other evaluation items also yielded good results.

[0038] [Table 2]

[0039] [Example 2] A two-layer sheet was obtained in the same manner as in Example 1, except that the conditions were changed in the extrusion molding process so that the thickness of layer A:layer B was 3.0:7.0. A food storage container was obtained in the same manner as in Example 1, except that this two-layer sheet was used. Good results were obtained for all evaluation items described later.

[0040] [Example 3] A two-layer sheet was obtained in the same manner as in Example 1, except that the conditions were changed in the extrusion molding process so that the thickness of layer A:layer B was 2.0:8.0. A food storage container was obtained in the same manner as in Example 1, except that this two-layer sheet was used. Good results were obtained for all evaluation items described later.

[0041] [Example 4] A two-layer sheet was obtained in the same manner as in Example 1, except that the conditions were changed in the extrusion molding process so that the thickness of layer A:layer B was 1.5:8.5. A food storage container was obtained in the same manner as in Example 1, except that this two-layer sheet was used. Good results were obtained for all evaluation items described later.

[0042] [Example 5] A two-layer sheet was obtained in the same manner as in Example 1, except that the conditions were changed in the extrusion molding process to have a thickness ratio of 1.0:9.0 between the thickness of layer A and the thickness of layer B. A food storage container was obtained in the same manner as in Example 1, except that this two-layer sheet was used. Because layer A was thin, some wave-like wrinkles occurred in the center of the sheet, and as a result, a wave pattern was visible on the container. However, the thickness variation was within an acceptable range, and it was evaluated that there were no problems with practical performance (see Table 4).

[0043] [Example 6] A two-layer sheet was obtained in the same manner as in Example 1, except that the conditions were changed in the extrusion molding process to have a thickness ratio of 3.0:7.0 between layer A and layer B. A food storage container (see Figure 13) was obtained in the same manner as in Example 1, except that the conditions were changed in the vacuum forming process using the two-layer sheet to have a larger edge angle than in Example 1. Good results were obtained for all evaluation items described later.

[0044] [Example 7] A two-layer sheet was obtained in the same manner as in Example 1, except that the conditions were changed in the extrusion molding process to have a thickness ratio of 3.0:7.0 between layer A and layer B. A food storage container (see Figure 13) was obtained in the same manner as in Example 1, except that the conditions were changed in the vacuum forming process using the above two-layer sheet to have an even larger edge angle than in Example 6. Good results were obtained for all evaluation items described later.

[0045] [Example 8] A two-layer sheet was obtained in the same manner as in Example 1, except that the conditions were changed in the extrusion molding process to have a thickness ratio of 5.0:95.0 for layer A and 95.0 for layer B. A food storage container was obtained in the same manner as in Example 1, except that this two-layer sheet was used. Because layer A was thinner than in Example 5, wrinkles in the sheet were more noticeable, and a wave pattern was visible on the container. However, the wrinkles and thickness variations in the sheet were within acceptable limits, and it was evaluated that there were no problems with practical performance (see Table 4).

[0046] [Example 9] A two-layer sheet was obtained in the same manner as in Example 1, except that the conditions were changed in the extrusion molding process to have a thickness ratio of 6.0:4.0 between layer A and layer B. A food storage container was obtained in the same manner as in Example 1, except that this two-layer sheet was used. Due to the thickness of layer A, some deflection and thickness variations were observed in the container, but these were within acceptable limits and were evaluated as having no problems with practical performance (see Table 4).

[0047] [Example 10] A two-layer sheet was obtained in the same manner as in Example 1, except that the conditions were changed in the extrusion molding process in Example 1 so that the thickness of layer A:layer B was 3.0:7.0. A food storage container (see Figure 14) was obtained in the same manner as in Example 1, except that the conditions were changed in the vacuum forming process in Example 1 so that the edge angle was larger than that of Example 7, using the above two-layer sheet. Due to the large edge angle, in the stain resistance evaluation, a part of the edge of the container body contracted during microwave heating, and after the evaluation, delamination between layers began to be observed, but it was evaluated that there was no problem with practical performance (see Table 4).

[0048] [Example 11] A two-layer sheet was obtained in the same manner as in Example 2, except that the conditions were changed in the extrusion molding process to make the container thickness 1.8 mm. A food storage container was obtained in the same manner as in Example 1, except that this two-layer sheet was used. Good results were obtained for all evaluation items described later.

[0049] [Comparative Example 1] A single-layer sheet consisting only of layer B was obtained in the same manner as in Example 1, except that the conditions were changed in the extrusion molding process to prevent the formation of layer A. A food storage container was obtained in the same manner as in Example 1, except that this single-layer sheet was used. The stain resistance was deemed insufficient and unsuitable for practical use (see Table 4).

[0050] [Comparative Example 2] A single-layer sheet consisting only of layer A was obtained in the same manner as in Example 1, except that the conditions were changed in the extrusion molding process to prevent the formation of layer B. A food storage container was obtained in the same manner as in Example 1, except that this single-layer sheet was used. The deflection of the container was within an acceptable range, but the thickness of the container was significantly uneven and was evaluated as unsuitable for practical use (see Table 4).

[0051] [Comparative Example 3] A two-layer sheet was obtained in the same manner as in Example 1, except that the conditions were changed in the extrusion molding process so that the thickness of the container was 0.1 mm. A food storage container was obtained in the same manner as in Example 1, except that this two-layer sheet was used. The container exhibited significant deflection and was deemed unsuitable for practical use (see Table 4).

[0052] [Comparative Example 4] In Example 2, a two-layer sheet was obtained in the same manner as in Example 2, except that the conditions were changed so that the thickness of the container was 2.0 mm during the extrusion molding process. A food storage container was obtained in the same manner as in Example 1, except that this two-layer sheet was used. As a result of insufficient vacuum pressure in the sheet and distortion of the edges due to bridging, the containers could not be stacked and were therefore evaluated as unsuitable for practical use (see Table 4).

[0053] <Measuring the thickness of food storage containers> The thickness of the food storage container was measured at the center point P1 on the bottom surface, at points P2, P3, P4, and P5 on each side, and at points P6, P7, P8, and P9 on each edge (see Figure 12) using a magnetic thickness gauge (Olympus Magna-Mike8600). The average value of the measurement results at these nine points was defined as the thickness of the food storage container. Points P2 to P5 were identified as being 2 cm below the midpoint of each side of the container edge, and edge points P6 to P9 were identified as being 2 mm outside the midpoint of each side of the container edge. Since the food storage containers in the above-mentioned examples and comparative examples are composed of layer A and / or layer B, the measured thickness of the food storage container is shown in Table 4 as being equal to the total thickness (mm) of layer A and layer B.

[0054] <Measuring the edge angle of food storage containers> A food storage container was sprayed with Scanningspray (AESUB blue, manufactured by Scanningspray Vertriebs GmbH) and scanned entirely with a 3D scanner (VL-700, manufactured by Keyence Corporation). Focusing on the inner surface of the container (the surface in contact with food), the two straight lines forming all the bends, or the two straight lines located at both ends of all the curves, were extracted using the two-point specification command in the cross-sectional analysis, and then the two straight lines located at both ends of all the curves were extracted using the one-line auxiliary tool command. The angles formed between these straight lines were measured using the angle measurement tool command, and the smallest of all measured values ​​was rounded to the first decimal place to determine the edge angle.

[0055] <Method for evaluating the presence or absence of wrinkles in the sheet> The sheets were visually inspected to determine if wave-like resin wrinkles had formed, and evaluated according to the following criteria. A score of △ or higher was considered acceptable for practical use, while a score of × was considered unsuitable for practical use. ○: None △: Slightly present ×: Yes

[0056] <Evaluation of the self-supporting ability of food storage containers> A 260g retort pouch of meat sauce (manufactured by Nisshin Flour Milling Co., Ltd.) was placed in a food storage container to a filling ratio of 37 wt / vol%. The container was lifted with enough force to prevent it from falling, with both palms resting on the sides of the container, and the deflection was judged and evaluated according to the following criteria. A score of △ or higher was considered to be practically acceptable, while a score of × was considered unsuitable for practical use. ○: 5mm or less △: More than 5mm but less than 10mm ×: More than 10mm

[0057] <Evaluation of thickness variations in food storage containers> After performing the aforementioned thickness measurement, the thickness uniformity evaluation value was calculated using the following formula (1). Thickness unevenness evaluation value = Thickness of the center P1 of the base / Average thickness of the edges P6, P7, P8, P9 ... (1) Based on the thickness unevenness evaluation value calculated using the above formula (1), the following criteria were used for evaluation. A score of △ or higher was considered acceptable for practical use, while a score of × was considered unsuitable for practical use. ◎: Thickness ratio < 3.1 ○: 3.1 ≤ Thickness ratio < 3.5 △: 3.5 ≤ Thickness ratio < 4.0 ×: 4.0 ≤ Thickness ratio

[0058] <Bridge evaluation of food storage containers> We visually inspected the food storage containers for bridging and evaluated whether the bridging affected the stacking of multiple food storage containers according to the following criteria. Since the mold is smooth, even slight resin wrinkles were considered bridging. If there was one or more noticeable bridgings that acted as an obstacle to stacking (marked with × below), the container was evaluated as unsuitable for practical use. If there was a ○ or higher, the container was evaluated as having no practical problems. ◎: No bridge, easily stackable. ○: There is one small bridge, but it can be stacked. ×: There is a large bridge, or multiple small bridges, and when they are stacked, there are areas that lift up, or force needs to be applied.

[0059] <Evaluation of delamination in food storage containers> After conducting the stain resistance evaluation described below, the layer boundaries of the same or different resins at the end of the container were visually inspected. Precision tweezers were inserted into the layer boundaries to determine whether the layers could be separated into two or more layers, according to the following criteria. A score of △ or higher indicated that the material was practically acceptable, while a score of × indicated that it was unsuitable for practical use. ◎: Not possible ○: Not easy, but possible. △: Possible ×: Easily possible

[0060] <Evaluation of stain resistance of food storage containers> A 260g retort pouch of meat sauce (manufactured by Nisshin Flour Milling Co., Ltd.) was placed in a food storage container to a filling ratio of 37 wt / vol%, and heated in a microwave oven (Sharp, RE-S26A) for twice the time indicated on the back (500w, 4 minutes). It was then allowed to cool in a 23°C room for 10 minutes, and then washed with a dishwashing sponge (3M, Scotch-Brite® antibacterial urethane sponge S-21KS) soaked in tap water and 3 drops of dish soap (Asahi Kasei Home Products Corporation, Frosch® aloe vera) added. This series of operations was repeated four times. Sensory evaluations were conducted by 100 housewives aged 20 to 50 regarding discoloration, lingering odor, and sliminess after washing. The food storage container before use was scored as 5 points, and the evaluation was based on a scale of 1 to 5 points. The evaluation criteria are shown in Table 3. The average value of the evaluations from the 100 panelists was calculated and evaluated according to the following criteria. ○: 3 points < average ≤ 5 points △: 2 points ≤ average ≤ 3 points ×: 1 point ≤ average < 2 points

[0061] [Table 3]

[0062] The results of each of the measurements and evaluations described above are summarized in Table 4.

[0063] [Table 4] [Explanation of Symbols]

[0064] 100…Food storage containers 10…Container body 10a...Polymethylpentene-containing layer 10b...Polyolefin-containing layer OP...Opening LS…Laminated structure EP…Edge CS…Contact surface 11... Lid

Claims

1. A container body having an opening, The container body has a laminated structure comprising a polymethylpentene-containing layer having a contact surface with food, and a polyolefin-containing layer directly disposed on the polymethylpentene-containing layer. At least a portion of the edge of the container body defining the opening is bent or curved, and the laminated structure is maintained at that edge. A food storage container in which the sum of the thickness of the polymethylpentene-containing layer and the thickness of the polyolefin-containing layer is 0.2 mm to 1.8 mm.

2. The food storage container according to claim 1, wherein the ratio of the thickness of the polymethylpentene-containing layer to the thickness of the polyolefin-containing layer is 1.0:1.0 to 1.0:9.

0.

3. At least a portion of the aforementioned edge is bent, The food storage container according to claim 1, wherein the edge angle at the edge is 0° or more and 75° or less.

4. At least a portion of the aforementioned edge is curved, The food storage container according to claim 1, wherein the edge angle at the edge is 0° or more and 75° or less.

5. A food storage container according to any one of claims 1 to 4, further comprising a lid configured to fit onto the container body via at least a portion of the rim.

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