container

Abstract

A container (1) mainly comprises a paper substrate layer (10) and a resin layer (11) that is laminated on the inner surface of the substrate layer (10). A copolymerized polyethylene terephthalate resin constituting the resin layer (11) is a copolymerized polyethylene terephthalate resin obtained by copolymerization with an isophthalic acid, and the copolymerization ratio of the isophthalic acid in the copolymerized polyethylene terephthalate resin is at least 1 mol% and less than 10 mol%. The copolymerized polyethylene terephthalate resin has a melting point of 234°C to 250°C. Due to the above configuration, a container having high adhesion between the substrate layer (10) and the resin layer (11) and high heat resistance can be obtained. As a result, container (1) molding defects can be prevented and the container is suitable for use even in cases where an object in the container reaches a high temperature or the object undergoes a firing step.

Description

[Technical Field]

[0001] The present invention relates to a container, and more particularly to a container used as a paper cup or case for storing beverages, food, etc. [Background technology]

[0002] BACKGROUND ART Conventionally, there have been containers for storing beverages, foods, and the like, which use a composite substrate in which a synthetic resin is laminated on one or both sides of a paper substrate.

[0003] Japanese Patent No. 4750909 discloses a container using homopolyethylene terephthalate (PET) as the resin.

[0004] Furthermore, Japanese Patent No. 5680917 discloses a container using a copolymerized PET resin (copolymerization component ratio is 10 mol % to 40 mol %) as the resin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent No. 4750909 [Patent Document 2] Japanese Patent No. 5680917

[0006] Homo-PET resins, such as those used in Japanese Patent No. 4750909, generally have a relatively high melting point of around 255°C. Therefore, to form a uniform film on the surface of a paper substrate by extrusion lamination, the resin must be extruded at temperatures exceeding 310°C. However, PET resins are prone to hydrolysis under high temperatures. Therefore, while it is often assumed that homo-PET resins, which have a high melting point, will have higher heat resistance, excessively high extrusion temperatures can cause hydrolysis in some of the PET resin on the surface of the container formed after extrusion lamination, resulting in reduced heat resistance for that portion and the entire container. On the other hand, lowering the extrusion temperature to reduce the effects of hydrolysis increases heat resistance, but the increased melt viscosity during extrusion lamination makes it difficult to form a uniform film on the paper surface. Even if a film is successfully formed, the high melt viscosity of the resin results in poor adhesion to the paper during extrusion. Therefore, when such composite substrates are used to form containers, poor container formation due to reduced adhesion and delamination between the paper and PET resin are likely to occur.

[0007] Furthermore, the copolymerized PET resin of Japanese Patent No. 5680917 has a relatively low melting point of 230°C or below, allowing the resin to be extruded at a low temperature, reducing hydrolysis at high temperatures and reducing the loss of adhesion to paper during extrusion onto the paper surface. However, the low melting point of 230°C or below results in poor heat resistance for the resulting container after molding. In particular, when filling a container with a food that requires cooking, such as a gratin, a baking process under high temperatures is required to brown the surface after filling the container, resulting in localized high temperatures, requiring high heat resistance. Furthermore, when the food is baked, packaged, and distributed to the market as a food product, the container also becomes hot when heated in a microwave oven and consumed by consumers, requiring similar high heat resistance. However, the container of Japanese Patent No. 5680917, with its poor heat resistance, fails to fully meet these requirements.

[0008] The present invention has been made to solve the above-mentioned problems, and has an object to provide a container in which the adhesion between the substrate layer and the resin layer is high and which has high heat resistance. DISCLOSURE OF THE INVENTION

[0009] In order to achieve the above object, a container in a first aspect of the present invention is a container composed of a composite substrate having a base layer made of paper and a resin layer made of copolymerized polyethylene terephthalate resin laminated on at least one side of the base layer, wherein the copolymerized polyethylene terephthalate resin is a copolymerized polyethylene terephthalate resin obtained by copolymerization with isophthalic acid, the copolymerization ratio of isophthalic acid in the copolymerized polyethylene terephthalate resin is 1 mol% or more and less than 10 mol%, and the copolymerized polyethylene terephthalate resin has a melting point of 234°C or more and 250°C or less.

[0010] With this configuration, the base material layer and the resin layer have high adhesion and the container has high heat resistance.

[0011] A container according to a second aspect of the present invention is one in which, in the configuration of the invention according to the first aspect, the copolymerization ratio of isophthalic acid in the copolymerized polyethylene terephthalate resin is 4.0 mol % or less.

[0012] This configuration provides favorable adhesion between the base layer and the resin layer and favorable heat resistance of the container.

[0013] A container according to a third aspect of the present invention has the configuration of the first or second aspect of the invention, wherein the adhesion of the resin layer to the substrate layer is 4 N / 50 mm or more.

[0014] This configuration provides good adhesion.

[0015] A container in a fourth aspect of the present invention has the configuration of any one of the first to third aspects of the invention, wherein the copolymerization ratio of isophthalic acid in the copolymerized polyethylene terephthalate resin is 1.5 mol % or more and 2.2 mol % or less.

[0016] This configuration improves the adhesion between the base layer and the resin layer and the heat resistance of the container.

[0017] A container in a fifth aspect of the present invention is one in which, in the configuration of the invention in any one of the first to fourth aspects, the copolymerized polyethylene terephthalate resin is a biologically derived biomass polyethylene terephthalate resin with a bio-based carbon content of 5% or more.

[0018] This configuration reduces the amount of fossil fuels used and improves carbon neutrality.

[0019] A container in a sixth aspect of the present invention has the configuration of any one of the first to fifth aspects of the invention, and includes a bottom and a side wall rising from the periphery of the bottom, and the bottom and the side wall are connected by thermal bonding.

[0020] With this configuration, the bottom and the sidewall are firmly bonded together.

[0021] A container in a seventh aspect of the present invention is formed by press molding or folding molding of a single sheet of base paper obtained from the composite substrate in the configuration of the invention in any one of the first to fifth aspects.

[0022] With this configuration, the container becomes a press-molded product or a molded product formed by bending.

[0023] As described above, the container in the first aspect of the present invention has high adhesion between the base layer and the resin layer and is highly heat-resistant, which prevents defective molding of the container and makes it suitable for use when the contents become hot or when they undergo a baking process.

[0024] The container according to the second aspect of the present invention has the same effects as the first aspect of the invention, and is therefore convenient to use because it has good adhesion between the substrate layer and the resin layer and good heat resistance.

[0025] In addition to the effects of the first or second aspect of the present invention, the container according to the third aspect of the present invention has good adhesion, and therefore molding defects of the container can be suitably prevented.

[0026] The container according to the fourth aspect of the present invention has the same effects as the first to third aspects of the invention, and in addition, the adhesion between the base layer and the resin layer and the heat resistance of the container are more favorable, making it more convenient to use.

[0027] In addition to the effects of the invention in any one of the first to fourth aspects, the container in the fifth aspect of the present invention can reduce the amount of fossil fuel-derived materials used and improve carbon neutrality, thereby improving sustainability and contributing to environmental conservation.

[0028] In addition to the effects of the invention in any one of the first to fifth aspects, the container in the sixth aspect of the present invention has a bottom and a side wall that are firmly bonded together, resulting in a stably molded container.

[0029] In addition to the effects of the invention according to any one of the first to fifth aspects, the container according to a seventh aspect of the present invention is a stably molded container because the container is a press-molded product or a molded product by bending. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a cross-sectional view showing the overall structure of a container according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view of the "X" portion shown in FIG. [Figure 3] FIG. 4 is a cross-sectional view showing the overall structure of a container according to a second embodiment of the present invention. [Figure 4]FIG. 10 is a perspective view showing a container according to a third embodiment of the present invention used in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0031] FIG. 1 is a cross-sectional view showing the overall structure of a container according to a first embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view of the "X" portion shown in FIG.

[0032] Referring to these figures, a container 1 is mainly composed of a bottom portion 2 and a side wall portion 3 rising from the peripheral edge of the bottom portion 2.

[0033] Referring to Figure 2, the side wall portion 3 is composed of a composite substrate 7 having a base layer 10 made of paper and a resin layer 11 made of copolymer polyethylene terephthalate resin laminated on the inner surface of the base layer 10 (the surface in the direction in which the contents are stored).

[0034] The bottom 2 is also made of a composite substrate 7 having the same configuration as the side wall 3, and the bottom 2 and side wall 3 are connected by thermal bonding. Specifically, the container shape is formed by punching out a side wall member (unfolded shape of the side wall 3) and a bottom member (unfolded shape of the bottom 2) of a predetermined shape from the composite substrate 7, and then bonding the ends of both members together by a known method such as thermal bonding.

[0035] The copolymerized polyethylene terephthalate resin in the present invention is a copolymerized polyethylene terephthalate resin obtained by copolymerization with isophthalic acid (IPA), and the copolymerization ratio of isophthalic acid in the copolymerized polyethylene terephthalate resin is 1 mol % or more and less than 10 mol %.

[0036] By configuring it in this manner, the container has high adhesion between the base material layer 10 and the resin layer 11 and is highly heat-resistant, which prevents defective molding of the container 1 and makes it suitable for use when the contents become hot or when they undergo a baking process.

[0037] The upper limit of the copolymerization ratio of isophthalic acid is preferably 8 mol% or less, more preferably 4.0 mol% or less, and even more preferably 2.2 mol% or less. The lower limit is preferably 1.5 mol% or more. Therefore, the range of the upper and lower limits is preferably 1.5 mol% to 2.2 mol%. This more preferably achieves both improved adhesion and improved heat resistance. Generally, polyethylene terephthalate resins are obtained by polycondensation of an acid component primarily composed of terephthalic acid and a glycol component primarily composed of ethylene glycol. However, the copolymerized polyethylene terephthalate resin used in the present invention contains isophthalic acid in addition to terephthalic acid as an acid component, and the copolymerized polyethylene terephthalate resin is obtained by copolymerizing this isophthalic acid in a predetermined ratio. Other acid components may be contained within a range that does not impair the effects of the present invention, and the glycol component may include diethylene glycol in addition to ethylene glycol. The copolymerized polyethylene terephthalate resin used in the present invention may be a mixture of polyethylene terephthalate resins having different copolymerization ratios, adjusted to a predetermined copolymerization ratio suitable for the present invention. For example, a homopolyethylene terephthalate resin and a copolymerized polyethylene terephthalate resin may be mixed in a predetermined ratio to adjust to a predetermined copolymerization ratio suitable for the present invention, or a mixture of polyethylene terephthalate resins having different copolymerization ratios may be mixed in a predetermined ratio to adjust to a predetermined copolymerization ratio suitable for the present invention. The copolymerization ratio of isophthalic acid is determined by the copolymerized polyethylene terephthalate resin. 1 It can be calculated by qualitative and quantitative analysis using H-NMR spectroscopy. 1The monomer units composed of terephthalic acid and the monomer units composed of isophthalic acid in the copolymerized polyethylene terephthalate resin are estimated from the spectrum obtained by H-NMR spectrum measurement, and the composition ratio (molar ratio) of each monomer unit in the copolymerized polyethylene terephthalate resin is calculated from the peak area ratio of the spectrum, and the ratio (%) of the "isophthalic acid monomer unit molar ratio" to the "total of the terephthalic acid monomer unit molar ratio and the isophthalic acid monomer unit molar ratio" can be calculated.

[0038] Furthermore, the copolymerized polyethylene terephthalate resin of the present invention has a melting point of 234°C or higher and 250°C or lower. The melting point is preferably 240°C or higher and 250°C or lower, and more preferably 243°C or higher and 250°C or lower. This configuration ensures that the melting point falls within a suitable range, allowing the extrusion temperature during extrusion lamination to be kept relatively low while the melting point itself is sufficiently high, resulting in favorable adhesion between the base layer 10 and the resin layer 11 and favorable heat resistance of the container 1. The melting point can be measured by differential scanning calorimetry (DSC).

[0039] Furthermore, the crystalline fraction (%) of the copolymerized polyethylene terephthalate resin in the present invention is preferably 2% to 15% and more preferably 3% to 10%. This configuration provides favorable adhesion between the base layer 10 and the resin layer 11, and reduces molding defects in the container 1. In particular, when the container of the present invention is manufactured by press-molding a single sheet of base paper obtained from the composite substrate 7, the shape retention of the container may decrease over time due to springback of the paper after press-molding. However, if the crystalline fraction (%) of the copolymerized polyethylene terephthalate resin constituting the composite substrate 7 is within the above range, the adhesion between the base layer 10 and the resin layer 11 and between the resin layers 11 themselves is favorable, thereby preventing a decrease in shape retention after press-molding. The crystalline fraction (%) of the copolymerized polyethylene terephthalate resin can be determined, for example, by removing only the resin layer 11 from the composite substrate 7, measuring its dissolution behavior by differential scanning calorimetry (DSC), and calculating the crystalline fraction (%) based on the following formula 1: The portion other than the crystalline portion is assumed to be an amorphous portion, and the amorphous portion can be calculated as follows: amorphous portion (%) = 100 - crystalline portion (%). Formula 1:

[0040]

number

[0041] Furthermore, the polyethylene terephthalate resin in the present invention is preferably a biomass polyethylene terephthalate resin derived from living organisms (biomass resources) and having a bio-based carbon content of 5% or more. Polyethylene terephthalate resin is a resin obtained by polycondensation of ethylene glycol and terephthalic acid as its main components, but most of it (including those disclosed in the aforementioned Japanese Patents Nos. 4750909 and 5680917) is derived from fossil resources. By converting this into a biomass polyethylene terephthalate resin derived from living organisms such as sugarcane, the amount of fossil resources used can be reduced and carbon neutrality improved, thereby improving sustainability and contributing to environmental conservation.

[0042] In the present invention, the biobased carbon content, which is an indicator of the proportion of biologically derived materials in a polyethylene terephthalate copolymer resin, is preferably 5% or more, and more preferably 15% or more. The higher the biobased carbon content, the lower the proportion of fossil-derived materials, resulting in a container that is more environmentally friendly. On the other hand, a higher biobased carbon content also increases costs, so it is preferable for it to be within an appropriate range. The biobased carbon content can be expressed as the C14 content obtained by a radiocarbon (C14) measurement method in accordance with ISO-16620-2 (equivalent to the ASTM-D6866 standard). Fossil-derived materials contain very little C14, while biological sources contain a certain proportion (105.5 pMC). Therefore, if the C14 content in the polyethylene terephthalate copolymer resin is designated as PC14, the biobased carbon content can be calculated using the following formula:

[0043] Bio-based carbon content (%) = PC14 / 105.5 x 100 Next, FIG. 3 is a cross-sectional view showing the overall structure of a container according to a second embodiment of the present invention.

[0044] Since the container 21 according to the second embodiment of the present invention has a structure basically similar to that of the container 1 according to the first embodiment described above, the following description will focus on the differences.

[0045] Referring to the figure, container 21 is formed by press molding a sheet of base paper obtained from composite substrate 27 (having the same configuration as composite substrate 7 in the first embodiment described above). Specifically, container 21 is formed by punching out a sheet of base paper of a predetermined shape obtained from composite substrate 27 and then press molding it, thereby forming container 21 having bottom 22 and side wall 23 rising from the periphery of bottom 22.

[0046] Furthermore, although not shown, the container according to the third embodiment is formed by folding a sheet of base paper obtained from a composite substrate (having the same configuration as the composite substrate 7 in the first embodiment described above) and forming it into a predetermined container shape. Specifically, a sheet of base paper of a predetermined shape obtained from the composite substrate is punched out, and then the base paper is folded or otherwise formed into a bottom and side walls rising from the periphery of the bottom, thereby forming a container having a bottom and side walls rising from the periphery of the bottom.

[0047] The containers according to the embodiments of the present invention can be used for a variety of purposes, including, but not limited to, food storage. They are particularly suitable for storing food that is heated under high-temperature conditions after being filled into the container. Specifically, they can be used under high-temperature heating conditions of 100°C or higher, and can be called heat-resistant paper containers. They can also be used for cooking in ovens (including toasters, grills, etc.) at temperatures of 200°C or higher.

[0048] In the containers according to the embodiments of the present invention, the composition of the paper constituting the composite substrate is not particularly limited, and pure white roll paper, kraft paper, parchment paper, ivory paper, Manila paper, card paper, cup paper, etc. can be used depending on the desired application. In addition, the basis weight of the paper is 150 g / m 2 ~500g / m 2 By configuring in this way, molding of the container becomes easy and the cost of the container can be reduced.

[0049] Furthermore, in the containers according to the embodiments of the present invention, the method for laminating the polyethylene terephthalate resin onto the paper is not particularly limited, and examples include extrusion lamination, heat lamination, dry lamination, wet lamination, etc. In the present invention, the use of extrusion lamination is preferred because it is suitable for mass production, is cost-effective, and allows direct lamination without an anchor coat, etc. However, this does not exclude the formation of an anchor coat layer on the paper beforehand during extrusion lamination.

[0050] Furthermore, in the containers according to the embodiments of the present invention, the thickness of the resin layer is not particularly limited, but is preferably 6 μm to 50 μm. Within this range, the desired heat resistance can be imparted to the container. Furthermore, when the resin layers of the composite substrate are thermally bonded together during container molding, the resin temperature can be easily raised uniformly, making it possible to achieve uniform adhesion. Furthermore, the occurrence of tunneling and pinholes in the resin layer during thermal bonding can be suppressed.

[0051] Furthermore, in the containers according to each embodiment of the present invention, the resin layer is formed on the inner surface of the base material layer, but it is sufficient that it is formed on at least one surface, or it may be formed on both surfaces.

[0052] Furthermore, in the container according to each embodiment of the present invention, an anchor coat layer may be interposed between the base layer and the resin layer as described above, or a printed layer may be formed, as long as the object of the present invention is not impaired. Also, the paper of the base layer may be subjected to corona treatment.

[0053] Furthermore, in the containers according to each embodiment of the present invention, the copolymerized polyethylene terephthalate resin may contain appropriate amounts of various additives such as chain extenders, ultraviolet absorbers, lubricants, antistatic agents, heat stabilizers, antioxidants, pigments, dyes, hydrolysis inhibitors, light stabilizers, and plasticizers, within the scope of not impairing the object of the present invention.

[0054] Furthermore, in the containers according to the respective embodiments of the present invention, the method for producing the copolymerized polyethylene terephthalate resin obtained by copolymerization with isophthalic acid is not particularly limited, and the copolymerization may be carried out by a known method and under known conditions, and as described above, a plurality of polyethylene terephthalate resins may be mixed to adjust the copolymerization ratio. [Example]

[0055] The present invention will be described in detail below based on examples, but the embodiments of the present invention are not limited to these examples.

[0056] (Example Preparation 1) First, several types of copolymerized polyethylene terephthalate resins were prepared by copolymerizing them with isophthalic acid at different ratios, or by mixing several polyethylene terephthalate resins with different copolymerization ratios to adjust them to a predetermined copolymerization ratio. Note that a biomass polyethylene terephthalate resin was prepared as the resin used in Examples 1 and 3, and a homopolyethylene terephthalate resin was prepared as the resin used in Comparative Example 1. 1 The ratio (%) of the "isophthalic acid monomer unit molar ratio" to the "total of the terephthalic acid monomer unit molar ratio and the isophthalic acid monomer unit molar ratio" was calculated by qualitative and quantitative analysis using H-NMR. As a result, the copolymerization ratio of isophthalic acid in each copolymerized polyethylene terephthalate resin was 2.0% (Example 1), 1.6% (Example 2), 5.0% (Example 3), 7.5% (Example 4), 9.2% (Example 5), 3.0% (Example 6), 3.9% (Example 7), 14.1% (Comparative Example 2), and 10.5% (Comparative Example 3). The copolymerization ratio of isophthalic acid in the homopolyethylene terephthalate resin was 0% (Comparative Example 1). The melting points of each resin were measured using a commercially available differential scanning calorimeter. Furthermore, the biobased carbon content was measured using the radiocarbon (C14) measurement method in accordance with ISO-16620-2 (equivalent to the ASTM-D6866 standard) and calculated using the biobased carbon content calculation formula described above.

[0057] Basis weight 230g / m 2 Each composite substrate was prepared by coating one side of the paper used as a substrate layer with the above-mentioned polyethylene terephthalate resin by extrusion lamination to a thickness of 30 μm in Examples 1, 2, 4, 6, 7, and Comparative Examples 1 to 3, a thickness of 40 μm in Example 3, and a thickness of 20 μm in Example 5. The thickness of the polyethylene terephthalate resin was measured by observing the cross section of the composite substrate with a commercially available microscope.

[0058] Side wall members and bottom members of a predetermined shape were punched out from each type of composite substrate to form containers large enough to hold 300 g of the white sauce described below, and these were then combined and thermally bonded to produce the containers of Examples 1 to 7 and Comparative Examples 1 to 3.

[0059] (Adhesion test) Test pieces measuring 50 mm × 150 mm were cut out from each of the composite substrates prepared above, and a peel test was performed at a 180° peel angle and a speed of 100 mm / min to test the adhesion between the substrate layer and the resin layer of the composite substrate.

[0060] The measuring device used was a MAX-R2KN-B model manufactured by Japan Measurement Systems Co., Ltd. The ideal adhesion is complete peeling between the paper layers, but it was determined that there was no problem if there was enough strength to cause partial peeling between the paper layers. Adhesion was evaluated as follows: less than 4N / 50mm was x (unsuitable), 4N / 50mm to 7N / 50mm was △ (acceptable), and 7N / 50mm or more was ○ (suitable).

[0061] (Heat resistance test) Using each type of container prepared above, the following two types of heat resistance tests were carried out. (1) Microwave oven heating test Each container was filled with 100 g of water and heated at 500 W for 3 minutes in a microwave oven (manufactured by SANYO Electric Co., Ltd., model number: EMO-FM23C, without turntable). The containers were then removed and left to stand for 12 hours with the water still in them. The presence or absence of water leakage from the container and the surface condition of the resin layer constituting the container were then visually inspected. The test was conducted with five containers per container. The water leakage evaluation was judged as ◯ (good) if no water leakage occurred in any of the five containers, and × (unacceptable) if water leakage occurred in even one of the five containers. The surface condition of the resin layer was also evaluated as ◯ (good) if no abnormalities such as bubbles or tears were found on the surface of the resin layer constituting the five containers, and × (unacceptable) if abnormalities such as bubbles or tears were found on the surface of the resin layer constituting the five containers. (2) Baking test after filling the container with white sauce Each container was filled with 300 g of Heinz Japan white sauce, and the filled containers were then baked in a Fujimac oven (model number: FSCC101) at 200°C for 5 minutes and at 260°C for 5 and 10 minutes, respectively, for a baking test. The test was conducted with 5 samples at each temperature. After the baking test, the white sauce was removed from the container, and the presence or absence of delamination (peeling at the interface between the paper substrate and the resin layer) between the base layer and the resin layer of the composite substrate constituting the container was visually confirmed. A case in which no delamination occurred anywhere on the container was judged as ◯ (good), and a case in which delamination occurred anywhere on the container was judged as × (bad).

[0062] Table 1 below shows the composition of each type of container (resin, composite substrate) and the results of each test.

[0063] [Table 1] As shown in Table 1, Examples 1 to 7, in which the copolymerization ratio and melting point of isophthalic acid were within the preferred ranges, exhibited suitable adhesion and showed no problems with heat resistance in a baking test at a heating temperature of 200°C. In particular, Examples 1 to 4, 6, and 7, in which the copolymerization ratio of isophthalic acid was 1.5 mol% or more and 8 mol% or less, also showed suitable results in heat resistance in a baking test at a heating temperature of 260°C for a heating time of 5 minutes. Furthermore, Examples 1, 2, 6, and 7, in which the copolymerization ratio of isophthalic acid was 4.0 mol% or less, also showed suitable results in heat resistance in a baking test at a heating temperature of 260°C for a heating time of 10 minutes.

[0064] Furthermore, it was confirmed that Example 1, which had a bio-based carbon content of 17%, Example 3, which had a bio-based carbon content of 6.2%, Example 6, which had a bio-based carbon content of 21.1%, and Example 7, which had a bio-based carbon content of 18.7%, also had favorable adhesion and heat resistance, similar to the other Examples with a bio-based carbon content of 0%.

[0065] (Example Preparation 2) In the same manner as in the above-mentioned "Preparation of Example 1," several types of copolymerized polyethylene terephthalate resins and homopolyethylene terephthalate resins were prepared. 2 The paper was used as the substrate layer, and each of the above-mentioned types of polyethylene terephthalate resin was coated on both sides of the substrate to a thickness of 30 μm by extrusion lamination to produce each composite substrate. The melting point, thickness, and bio-based carbon content of the polyethylene terephthalate resin were measured using the same methods as in "Example Preparation 1." These values ​​are shown in Table 2.

[0066] [Table 2] In Table 2, Examples 1-1, 2-1, 6, 7, and Comparative Example 1 use the same resins as in Examples 1, 2, 6, 7, and Comparative Example 1 in Table 1, and extrusion lamination was performed under the same extrusion conditions. On the other hand, in Examples 1-2 and 2-2, the same resins as in Examples 1 and 2 were used, but extrusion conditions were appropriately adjusted, such as by slowing the extrusion speed, to obtain a crystalline fraction (%) different from that in Examples 1 and 2. The crystalline fraction (%) of the copolymerized polyethylene terephthalate resin was calculated using the above-mentioned formula 1, by removing the resin layer from the composite substrate constituting the paper container after press molding, as described below, for example, and measuring its dissolution behavior by differential scanning calorimetry (DSC).

[0067] Then, a sheet of base paper having a predetermined shape was punched out from each type of composite substrate, and press-molded to produce a container having a rolled edge around the periphery as shown in FIG.

[0068] FIG. 4 is a perspective view showing a container according to a third embodiment of the present invention, which is used in the examples.

[0069] Referring to the figure, the dimensions of the container after press molding are as follows: Length D (including flange): approx. 177 mm Width (including flange) in the short direction: approx. 123 mm Height H: approx. 27mm Diameter of the edge roll: approx. 3 mm Flange width (including rolled edge) x2: approx. 7 mm (shape retention test) For the press-molded containers, (1) the width in the short direction of the container immediately after molding (W in Figure 4), (2) the width in the short direction of the container 30 minutes after molding, and (3) the width in the short direction of the container 24 hours after molding were measured, and compared with the container immediately after molding, the change in the width in the short direction of the container over time due to springback of the paper was confirmed after 30 minutes and 24 hours. Specifically, the percentage of dimensional change was calculated using Equation 2.

[0070] Formula 2: Width of the container in the shortest direction after a certain time has elapsed since molding (mm) ÷ Width of the paper container in the shortest direction immediately after molding (mm) × 100 = % of the degree of opening due to springback of the paper container over time The shape retention test was carried out using five samples for each paper container, and the arithmetic mean value of the five paper container samples was calculated.

[0071] As shown in Table 2 above, in all of the Examples, the dimensional change in the width of the container in the shortest direction after 30 minutes and 24 hours from press molding was small, at 103%, indicating good shape retention. On the other hand, in the Comparative Examples, the change was 105% after 30 minutes and 110% after 24 hours, indicating poor shape retention. This is presumably because the crystalline fraction (%) of the resin layer in the Examples was within the specified range, resulting in good adhesion of the resin layer to the wrinkled and rolled portions of the container formed by squeezing during press molding, and minimizing paper springback after press molding. On the other hand, in the Comparative Examples, the crystalline fraction (%) of the resin layer was high, resulting in poor adhesion of the resin layer to the wrinkled and rolled portions of the container, presumably preventing paper springback after press molding and resulting in poor shape retention. [Industrial Applicability]

[0072] As described above, the container according to the present invention is suitable as, for example, a paper cup or case for storing beverages, food, etc.

Claims

1. A container (1) comprising a composite substrate (7) including a base layer (10) made of paper and a resin layer (11) made of copolymerized polyethylene terephthalate resin laminated on at least one surface of the base layer, The copolymerized polyethylene terephthalate resin is a copolymerized polyethylene terephthalate resin obtained by copolymerization with isophthalic acid, a copolymerization ratio of the isophthalic acid in the copolymerized polyethylene terephthalate resin is 1 mol% or more and less than 10 mol%, The copolymerized polyethylene terephthalate resin has a melting point of 234°C or higher and 250°C or lower, A container in which 100 g of water is placed in the container, heated in a microwave oven at 500 W for 3 minutes, and then removed. The container is left with the water in it for 12 hours, after which there is no water leakage from the container and no abnormalities such as bubbles or tears on the surface of the resin layer. The container is filled with 300 g of white sauce, and then heated in an oven at a heating temperature of 200°C and 260°C for a heating time of 5 minutes in both cases, and in both cases no delamination occurs between the base material layer and the resin layer of the composite base material that constitutes the container.

2. A container (1) comprising a composite substrate (7) including a base layer (10) made of paper and a resin layer (11) made of copolymerized polyethylene terephthalate resin laminated on at least one surface of the base layer, The copolymerized polyethylene terephthalate resin is a copolymerized polyethylene terephthalate resin obtained by copolymerization with isophthalic acid, a copolymerization ratio of the isophthalic acid in the copolymerized polyethylene terephthalate resin is 1 mol% or more and less than 10 mol%, The copolymerized polyethylene terephthalate resin has a melting point of 234°C or higher and 250°C or lower, The copolymerized polyethylene terephthalate resin has a crystalline portion (%) of 2% or more and 15% or less, The resin layer has an adhesion to the base layer of 4 N / 50 mm or more.

3. 3. The container according to claim 1, wherein the copolymerization ratio of said isophthalic acid in said copolymerized polyethylene terephthalate resin is 4.0 mol % or less.

4. 2. The container according to claim 1, wherein the resin layer has an adhesion to the base material layer of 4 N / 50 mm or more.

5. 5. The container according to claim 1, wherein a copolymerization ratio of the isophthalic acid in the copolymerized polyethylene terephthalate resin is 1.5 mol % or more and 2.2 mol % or less.

6. 6. The container according to claim 1, wherein the copolymerized polyethylene terephthalate resin is a biologically derived biomass polyethylene terephthalate resin having a bio-based carbon content of 5% or more.

7. It comprises a bottom (2) and a side wall (3) rising from the periphery of the bottom, 7. The container according to claim 1, wherein the bottom and the side wall are connected by thermal bonding.

8. A container described in any one of claims 1 to 6, wherein the container is a press-molded product or a bent-molded product.

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