Paper-made container

Abstract

To provide a paper-made container which is excellent in both productivity and leakage prevention.SOLUTION: A paper-made container includes a cylindrical trunk part formed of trunk paper, and a bottom which is formed of bottom paper and blocks the lower end of the trunk part. A bottom paper upper surface resin layer is provided on the upper surface of the bottom paper. The bottom paper upper surface resin layer is formed of polyethylene for a bottom paper upper surface having a density of less than 0.930 (g / cm3) and an MFR of 10 to 18 (g / 10 min).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a paper container. [Background technology]

[0002] Paper containers such as paper cups are known that have a body formed from a body paper and a bottom formed from a bottom paper. Among such paper cups, there is known one in which a resin layer is formed on the top surface of the bottom paper to prevent leakage of contents, etc.

[0003] For example, Patent Document 1 (Example) describes a specific linear low-density polyethylene resin layer (density 0.90 g / cm ) as the innermost layer. 3 The document discloses a paper cup made using a base material formed by extrusion coating with a special body material (a cellulose rubber base with a melt index of 21 g / 10 min and a melting point of 103°C). The document also describes that when the paper cup was subjected to a sealing suitability evaluation, good results were obtained. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4713187 Summary of the Invention [Problem to be solved by the invention]

[0005] There is an increasing demand for paper containers to prevent leakage. The part of a paper container where leakage is likely to occur is the joint between the bottom paper and the body paper. If a gap is formed at the joint between the bottom paper and the body paper, the risk of leakage increases.

[0006] The inventors believe that if the resin layer formed on the top surface of the base paper has appropriate physical properties, the gap at the joint between the base paper and the body paper will be filled with resin, and leakage can be prevented. From this perspective, the physical properties of the resin formed on the base paper are being investigated.

[0007] However, the physical properties of the resin formed on the base paper are also limited from the viewpoint of productivity. For example, extrusion lamination is considered as a method for forming a resin layer on the base paper. In order to perform extrusion lamination stably, a resin with physical properties that allow stable extrusion lamination must be selected. Therefore, a resin with suitable physical properties is required not only to prevent leakage but also from the viewpoint of productivity.

[0008] That is, an object of the present invention is to provide a paper container that is excellent in both productivity and leakage prevention. [Means for solving the problem]

[0009] In one aspect, the present invention relates to a paper container. This paper container comprises a tubular body formed from body paper, and a bottom formed from bottom paper that closes the lower end of the body. A bottom paper upper surface resin layer is provided on the upper surface of the bottom paper. The outer periphery of the bottom paper is provided with a folded portion that is folded downward. The folded portion is bonded to the inner surface of the body paper via the bottom paper upper surface resin layer. The bottom paper upper surface resin layer is made of a resin having a viscosity of 0.930 (g / cm 3 The polyethylene for the upper surface of the bottom paper has a density of less than 1000 kJ / 10 min and an MFR of 10 to 18 (g / 10 min).

[0010] In another aspect, the present invention relates to a method for manufacturing the above-mentioned paper container. This manufacturing method includes the steps of forming a bottom paper upper surface resin layer made of polyethylene for the bottom paper upper surface on a base paper of the bottom paper by extrusion lamination, producing a bottom paper having a folded portion folded downward on the outer periphery using the base paper of the bottom paper on which the bottom paper upper surface resin layer has been formed, molding the body paper into a cylindrical shape, and heating and pressing the folded portion of the bottom paper to the inner surface of the lower end of the molded body paper. The polyethylene for the top surface of the bottom paper has a viscosity of 0.930 (g / cm 3 ) and an MFR of 10 to 18 (g / 10 min). [Effects of the Invention]

[0011] According to the present invention, a paper cup that is excellent in both productivity and leak prevention is provided. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing a paper cup according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional side view of a paper cup, showing a cross section passing through a side seam portion. [Figure 3] FIG. 3 is a diagram schematically showing a cross section taken along line AA′ in FIG. [Figure 4] FIG. 4 is a cross-sectional view showing a schematic configuration of the bonded portion during and after pressure is applied. [Figure 5] FIG. 5 is a diagram showing an example of the configuration of the joining portion at the time of joining. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] (Summary) The paper container according to this embodiment will be described below using a paper cup as an example. Fig. 1 is a schematic diagram showing a paper cup 1 according to this embodiment. This paper cup 1 has a body 2 and a bottom 3.

[0015] The body 2 is cylindrical and made of body paper. The body 2 has a side seam 4. The side seam 4 is a portion where both ends of the body paper in the circumferential direction are joined. In other words, in the side seam 4, both ends of the body paper overlap. The side seam 4 is provided from the top end to the bottom end of the body 2.

[0016] The bottom part 3 closes the lower end of the body part 2. The bottom part 3 is formed by a bottom paper.

[0017] Fig. 2 is a side cross-sectional view of the paper cup 1, showing a cross section passing through the side seam portion 4. The structure of the joint between the body paper 10 and the bottom paper 11 will be described with reference to Fig. 2. For convenience, Fig. 2 depicts a gap at the joint between the body paper 10 and the bottom paper 11. However, in reality, no gap exists at the joint between the two.

[0018] As shown in Figure 2, the bottom paper 11 has a bottom surface portion 12 and a folded portion 13. The bottom surface portion 12 is the portion that forms the bottom of the paper cup 1. The folded portion 13 is a portion provided on the outer periphery of the bottom paper 11 and extends downward. In other words, the bottom paper 11 is folded downward at its outer periphery.

[0019] The folded portion 13 is sandwiched by the lower end of the body paper 10. In other words, the lower end of the body paper 10 is folded back so as to sandwich the folded portion 13. As a result, a layered structure is formed at the bottom of the paper cup 1 by the folded portion 13 and the body paper 10 sandwiching the folded portion 13. At the lower end of the side seam portion 4, a layered structure is formed in which the folded portion 13 is sandwiched between two layers of body paper 10. In other words, a layered structure of five layers in total is formed.

[0020] Although not explicitly shown in Figure 2, a bottom paper upper surface resin layer is provided on the upper surface of the bottom paper 11. The bottom paper upper surface resin layer is also provided in the folding portion 13. In the folding portion 13, the surface facing outward corresponds to the upper surface of the bottom paper 11. In the folding portion 13, the bottom paper 11 is bonded to the inner surface of the body paper 10 via the bottom paper upper surface resin layer.

[0021] In this embodiment, the physical properties of the resin forming the bottom paper upper surface resin layer are devised from the viewpoints of productivity and leakage prevention. The bottom paper upper surface resin layer will be described below.

[0022] (1) Bottom paper top resin layer The bottom paper upper surface resin layer is formed from a polyethylene for the top surface of the bottom paper, which has specific physical properties, as described below. In this specification, "formed from" means that most of the constituent components are specific components. In other words, the bottom paper upper surface resin layer may contain other components, as long as they are in small amounts. Specifically, 80% by mass or more, preferably 95% by mass or more, and more preferably 99% by mass or more of the bottom paper upper surface resin layer is polyethylene for the top surface of the bottom paper, as described below.

[0023] (density and type of polyethylene) The polyethylene for the top surface of the base paper is 0.930 (g / cm 3 ) The use of polyethylene with such a density ensures good productivity. Specifically, when a bottom paper upper surface resin layer is formed on the bottom paper by extrusion lamination, delamination is unlikely to occur. Delamination refers to the resin layer peeling off from the substrate. The polyethylene for the top surface of the bottom paper may be either low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE). Low-density polyethylene (LDPE) is preferred.

[0024] (MFR) The MFR of the polyethylene for the upper surface of the bottom paper is 10 to 18 (g / 10 min). The MFR value in this specification is a value determined in accordance with Japanese Industrial Standards (K7210-1:2014 (ISO 1133-1:2011)) under conditions of 190°C and a load of 2.16 kg.

[0025] MFR is an index that indicates the fluidity of a resin. When the MFR of the polyethylene for the top surface of the bottom paper is within the above range, a paper cup 1 that is excellent in both productivity and leakage prevention is provided. This point will be explained below.

[0026] First, an MFR of 10 (g / 10 min) or more facilitates the polyethylene filling of gaps at the joint between the body paper and the bottom paper. Figure 3 is a schematic diagram of the AA' cross section of Figure 2. Specifically, Figure 3 shows the structure of the joint between the bottom paper 11 (folded portion 13) and the body paper 10 in the side seam portion 4. As shown in Figure 3, a step occurs at the end of the side seam portion 4. At the step, a gap 5 is likely to form between the bottom paper 11 and the body paper 10. Therefore, leakage is likely to occur through the gap 5. In contrast, using polyethylene for the top surface of the bottom paper with an MFR of 10 (g / 10 min) or more facilitates filling of the gap 5 when the bottom paper 11 and the body paper 10 are joined. Specifically, heat treatment during joining fluidizes the bottom paper top surface resin layer 6 to the extent that it fills the gap 5. This eliminates the gap 5 and prevents leakage.

[0027] On the other hand, an MFR of 18 (g / 10 min) or less improves productivity. Specifically, extrusion lamination can be used when producing the bottom paper 11. To perform extrusion lamination, molten polyethylene must be extruded from a die into a film. At this time, the extruded polyethylene must have a certain degree of melt tension. According to the inventors' findings, the smaller the MFR, the higher the melt tension. Furthermore, if the MFR is 18 (g / 10 min) or less, the melt tension necessary for performing extrusion lamination can be ensured. Therefore, it becomes possible to stably produce the bottom paper 11 using extrusion lamination, improving productivity.

[0028] The melt tension of the polyethylene for the top surface of the bottom paper is, for example, 8 mN or more, preferably 10 mN or more. There is no particular upper limit to the melt tension, but it is, for example, 20 mN or less. The melt tension in this specification is a value measured under the following conditions. Measuring equipment: Capillograph Heating temperature: 190℃, L (capillary length) = 10 mm, D (capillary diameter) = Φ1 mm, Measurement method: Gradually increase the take-up speed in the range of 15 to 45 mm / min, and measure the melt tension when the resin breaks.

[0029] As described above, in this embodiment, by using polyethylene for the upper surface of the bottom paper having a specific density and a specific MFR, a paper cup that is excellent in both productivity and leakage prevention is provided.

[0030] Preferably, the MFR of the polyethylene for the upper surface of the bottom paper is less than 15 (g / 10 min), and more preferably, 12 (g / 10 min) or more and less than 15 (g / 10 min).

[0031] (tanδ) In a preferred embodiment, the polyethylene for the upper surface of the bottom paper has a tan δ of 3.0 or less. In this embodiment, tan δ indicates the value of "loss modulus / storage modulus" at 160°C. The loss modulus and storage modulus can be determined by measuring the dynamic viscoelasticity of the resin using a rheometer. Specifically, they can be determined by measuring the dynamic viscoelasticity under the following conditions. Vibration frequency: 1.59Hz Distortion: 1% Cooling rate: 5℃ / min Measurement temperature range: 90 to 160°C

[0032] The use of polyethylene for the top surface of the bottom paper having a tan δ of 3.0 or less more reliably prevents the occurrence of gaps. This point will be explained below.

[0033] Tan δ is an index showing the viscoelastic properties of polyethylene. A small tan δ indicates a strong elastic tendency. A strong elastic tendency makes it easier for polyethylene to follow the springback of the base paper 11. As a result, the occurrence of voids is more reliably prevented.

[0034] More specifically, when the body paper 10 and the bottom paper 11 are joined, pressure is applied to the joint. Figure 4 is a cross-sectional view showing the structure of the joint during and after pressurization, showing the structure of the side seam portion 4. As shown in Figure 4(a), when pressurization is applied, the bottom paper 11 deforms to conform to the step. At this time, the gap 5 is filled by the upper surface resin layer 6 of the bottom paper, which has been rendered fluid by heating. However, after the pressurization is completed, springback generates a force that pulls the bottom paper 11 away from the body paper 10. If the polyethylene for the upper surface of the bottom paper has low elasticity, the polyethylene filled in the gap 5 may adhere to and be pulled by the bottom paper 11, creating a gap, as shown in Figure 4(b). In contrast, if the polyethylene for the upper surface of the bottom paper has high elasticity, the polyethylene will easily follow the deformation of the bottom paper 11. Therefore, as shown in Figure 4(c), gaps due to springback are unlikely to occur.

[0035] According to the findings of the present inventors, if tan δ is 3.0 or less, a sufficient elastic tendency can be obtained in terms of preventing the occurrence of voids due to springback. In a more preferred embodiment, the tan δ of the polyethylene for the top surface of the bottom paper is 2.0 or less. However, there is no particular lower limit for the tan δ of the polyethylene for the top surface of the bottom paper. For example, the tan δ is 1.1 or more.

[0036] (others) The polyethylene for the upper surface of the bottom paper preferably has a loss modulus (160°C) of 9000 Pa or less. With such a loss modulus, the occurrence of voids due to springback can be more reliably prevented. The loss modulus of the polyethylene for the upper surface of the bottom paper is more preferably 8500 Pa or less. The loss modulus is even more preferably 5000 to 8500 Pa, and most preferably 7000 to 8000 Pa.

[0037] The polyethylene for the upper surface of the bottom paper preferably has a storage modulus of 2000 Pa or more. If the storage modulus is in this range, the occurrence of voids due to springback can be more reliably prevented. The storage modulus of the polyethylene for the upper surface of the bottom paper is preferably 3000 Pa or more, more preferably 3000 to 7000 Pa.

[0038] The melting point of the polyethylene for the upper surface of the bottom paper is preferably 100 to 115°C, more preferably 100 to 110°C. Within this range, problems such as delamination are unlikely to occur during extrusion lamination. The melting point of polyethylene can be measured, for example, by differential scanning calorimetry (DSC).

[0039] As mentioned above, the density of the polyethylene for the top surface of the base paper is 0.930 (g / cm 3 Within this range, delamination is unlikely to occur when forming the resin layer on the top surface of the bottom paper. The density of polyethylene is preferably 0.910 to 0.920 (g / cm 3 )

[0040] The thickness of the resin layer on the top surface of the bottom paper is, for example, 20 to 100 μm, and preferably 40 to 80 μm.

[0041] (2) Bottom paper Next, we will explain the bottom paper itself, which serves as the base material for the bottom paper upper surface resin layer. The bottom paper may be any material as long as it is possible to form a bottom paper upper surface resin layer on its upper surface, and there are no particular restrictions on its material. As the bottom paper, one made of base paper commonly used for paper cups can be used.

[0042] The base paper for the base paper is, for example, 50 to 500 g / m 2 The base paper for the base paper preferably has a basis weight of 100 to 300 g / m 2 The thickness of the base paper for the base paper is, for example, 130 to 380 μm.

[0043] The bottom paper may be a laminate of base paper and another film material. For example, the bottom paper may have a structure in which base paper and a barrier film (such as an aluminum film) are laminated together via an internal polyethylene layer (a polyethylene layer for adhesion that is different from the resin layer on the top surface of the bottom paper). The resin layer on the top surface of the bottom paper may be provided on the barrier film. Another resin layer may also be provided on the bottom surface of the bottom paper.

[0044] (3) Trunk paper Next, the body paper will be described. The material of the body paper is not particularly limited. As with the bottom paper, the body paper can also be made of base paper that is generally used for paper cups.

[0045] The base paper for the body paper is, for example, 100 to 700 g / m 2 The basis weight of the base paper for the body paper is preferably 200 to 500 g / m 2 The thickness of the base paper for the body paper is, for example, 200 to 600 μm.

[0046] Preferably, the inner surface of the body paper is provided with a body paper inner surface resin layer made of polyethylene. The provision of the body paper inner surface resin layer further increases the strength of the joint between the body paper and the bottom paper, more reliably preventing leakage. Leakage of the contents is also more reliably prevented. The thickness of the body paper inner surface resin layer is, for example, 5 to 100 μm, preferably 10 to 50 μm.

[0047] Preferably, a resin layer made of polyethylene is also provided on the outer surface of the cardboard. The provision of a resin layer on the outer surface of the cardboard more reliably prevents leakage of the contents. The thickness of the resin layer on the outer surface of the cardboard is, for example, 5 to 100 μm, preferably 5 to 30 μm.

[0048] The physical properties of the polyethylene forming the inner resin layer of the body paper and the polyethylene forming the outer resin layer of the body paper (hereinafter, both may be collectively referred to as body paper polyethylene) are not particularly limited. In a preferred embodiment, the body paper polyethylene has a viscosity of 0.930 (g / cm3 More preferably, the density of the polyethylene for the body paper is 0.910 to 0.920 (g / cm 3 In a preferred embodiment, LDPE is used as the polyethylene for the body paper.

[0049] The melting point of the polyethylene for the body paper is, for example, 100 to 120°C, and preferably 105 to 115°C.

[0050] The MFR of the polyethylene for the body paper is, for example, 3 to 15 (g / 10 min), and preferably 5 to 10 (g / 10 min).

[0051] The storage modulus of the polyethylene for the body paper is, for example, 2,000 to 15,000 Pa, and preferably 5,000 to 10,000 Pa.

[0052] The loss modulus of the polyethylene for the body paper is, for example, 2,000 to 15,000 Pa, and preferably 6,000 to 13,000 Pa.

[0053] The tan δ of the polyethylene for the body paper is, for example, 1.0 to 3.0, and preferably 1.0 to 2.0.

[0054] (4) Manufacturing method The method for manufacturing the paper cup according to the present embodiment is not particularly limited, and the manufacturing method will be described below by giving an example.

[0055] First, the base paper is prepared. Specifically, a resin layer is formed on the base paper by extrusion lamination. The base paper is then punched into a desired shape to obtain the base paper. Note that by using a die that performs drawing during punching, folded portions can be formed around the periphery of the base paper.

[0056] On the other hand, the body paper is prepared. For example, a polyethylene resin layer is formed on both sides of the base paper by extrusion lamination. Then, the base paper is punched out into, for example, a fan shape. This gives the body paper (blank).

[0057] Next, the body paper is molded into a cylindrical shape around the bottom paper. Specifically, a mold is prepared having an outer peripheral surface corresponding to the body portion. The bottom paper having a folded portion is placed at the lower end of the prepared mold. The body paper is then molded by wrapping the bottom paper and the mold. At this time, both ends of the body paper in the circumferential direction are joined to form a side seam portion. The both ends of the body paper in the circumferential direction can be joined, for example, by ultrasonic sealing. Alternatively, the both ends of the body paper can be joined by melting the polyethylene layer on the body paper with hot air.

[0058] Next, the folded portion of the base paper is pressed against the inner surface of the body paper, which has a side seam. Specifically, the lower end of the body paper is folded back so as to sandwich the folded portion. The joint between the folded portion and the body paper is then heated with a burner or the like, causing the resin layer on the top surface of the base paper to become fluid. Pressure is then applied to the heated joint. As a result, the fluidized resin layer on the top surface of the base paper fills the gaps that form on the sides of the side seam.

[0059] The method of applying pressure to the joint portion is not particularly limited. Fig. 5 is a diagram showing an example of the configuration of the joint portion during joining. Fig. 5(a) shows a side cross-sectional view of the joint portion. Fig. 5(b) is a diagram of the paper cup 1 viewed from below. In the example shown in Fig. 5, during joining, the bottom end of the paper cup 1 is placed inside the annular pilot ring 7. A bottom roller 8 is also placed inside the joint portion between the body paper 10 and the bottom paper 11. The bottom roller 8 then presses the joint portion against the pilot ring 7, applying pressure. Instead of a bottom roller, pressure may be applied to the joint portion using other means, such as an expander.

[0060] Thereafter, if necessary, a curling process or the like is carried out on the opening of the paper cup 1. In this way, the paper cup according to this embodiment is obtained. [Example]

[0061] Next, the results of experiments conducted by the inventors will be described in order to explain the present invention in more detail, although the present invention should not be construed as being limited to the examples described below.

[0062] (Comparative Example 1) Base paper: 200g / m 2 Ordinary paper (thickness 280 μm) with a basis weight of 1000 μm was prepared. Then, a 60 μm polyethylene layer was formed as a bottom paper top surface resin layer on one side (top surface) of the base paper by extrusion lamination. Table 1 shows the physical properties of the polyethylene used to form the bottom paper top surface resin layer. After the bottom paper top surface resin layer was formed, the base paper was punched into a circle using a mold. At this time, a drawing process was performed to obtain a bottom paper with a folded portion formed on the outer periphery.

[0063] On the other hand, the base paper for the body is 330 g / m 2 Ordinary paper (thickness 380 μm) having a basis weight of 10 ... Type:LDPE Density: 0.922(g / cm 3 ) Melting point: 108℃ MFR: 7g / 10min Storage modulus: 7549 (Pa) Loss modulus: 9735 (Pa) tanδ: 1.3

[0064] Next, a cylindrical mold for forming the body was prepared. Then, a bottom paper having a folded portion was placed on the bottom of the mold. Next, a fan-shaped body paper (blank) was formed by wrapping the bottom paper and the mold. At this time, both ends of the body paper in the circumferential direction were joined using ultrasonic sealing. Next, the bottom was heated using a burner. In addition, the lower end of the body paper was folded back so as to sandwich the folded portion of the bottom paper. Then, a pilot ring and a bottom roller were used to press the joint between the folded portion and the body paper in the heated state. After that, a curling process was performed to obtain the paper cup of Comparative Example 1.

[0065] (Comparative Examples 2 to 5, Examples 1 to 2) The physical properties of the polyethylene forming the upper resin layer of the bottom paper were changed as shown in Table 1. Paper cups according to Comparative Examples 2 to 5 and Examples 1 and 2 were obtained in the same manner as Comparative Example 1 in other respects. Note that for Comparative Examples 3 to 5, it was not possible to properly form a polyethylene layer on the bottom paper using the extrusion lamination method.

[0066] (suitable for lamination) The obtained samples were evaluated for lamination suitability when forming the resin layer on the top surface of the bottom paper. The results of the lamination suitability are summarized in Table 1. As mentioned above, for Comparative Examples 3 and 4, the polyethylene layer could not be properly formed on the bottom paper using the extrusion lamination method. Therefore, the lamination suitability was evaluated as "×". Specifically, for Comparative Example 3, the polyethylene layer shrunk significantly after lamination and peeled off from the bottom paper. In other words, delamination occurred. Furthermore, for Comparative Examples 4 and 5, the melt tension during extrusion of the polyethylene was not sufficient to perform extrusion lamination. On the other hand, for Comparative Example 2 and Examples 1 and 2, the lamination properties were good. Therefore, the lamination suitability was evaluated as "○". The melt tension of the polyethylene used in each sample is also shown in Table 1.

[0067] (Leak test) Leakage tests were conducted on Comparative Examples 1 and 2 and Examples 1 and 2. Specifically, a test liquid was filled into a paper cup. A liquid colored with crimson was used as the test liquid. After filling with the test liquid, the paper cup was left to stand for 20 minutes. Then, the presence or absence of leakage was confirmed visually. Leakage tests were conducted on 50 samples, and the number of samples in which leakage was observed was recorded as the result. The results are shown in Table 1.

[0068] (Watermark inspection) After the leak test, the test liquid was discarded. Then, illumination light was irradiated onto the bottom of the paper cup from below. With the illumination light irradiated, the paper cup was visually observed from the side to check whether the test liquid had penetrated into the bottom edge of the paper cup. 50 samples were tested, and the number of samples in which penetration was observed was recorded as the result. The results are shown in Table 1.

[0069] (Air leak inspection) An air leak test was conducted using an air leak test device. Specifically, the paper cup was set in the test device so that the inside of the paper cup became an airtight space and an airtight space was also formed below the bottom of the paper cup. Air was then sealed in the airtight space inside the paper cup at a predetermined pressure for a predetermined time. The amount of air leaking through the bottom was then measured by measuring the pressure in the airtight space formed below the paper cup. An air leak test was conducted on 200 samples, and the maximum amount of air leaking was taken as the result. The results are shown in Table 1.

[0070] (Cross-section observation) The cross section of the joint between the bottom paper and the body paper was observed using X-ray CT. The size of the voids formed at the joint between the bottom paper and the body paper was evaluated from the obtained images. The size of the voids was evaluated according to the following criteria. The results are shown in Table 1. 〇: No voids ×: With voids

[0071] (Discussion of results) In Comparative Example 3, in which HDPE (high density polyethylene) was used as the polyethylene forming the upper resin layer of the bottom paper, delamination occurred, as mentioned above, and extrusion lamination could not be carried out. Furthermore, in Comparative Examples 4 and 5, in which the MFR was greater than 18 (g / 10 min), appropriate melt tension could not be obtained, as mentioned above, and extrusion lamination could not be carried out. In contrast, in Comparative Examples 4 and 5, in which the MFR was 10 to 18 (g / 10 min) and the density was 0.930 (g / cm 3 In Examples 1 and 2, in which polyethylene having a viscosity of less than 1000 ppm was used, suitability for lamination was good. Specifically, a melt tension was obtained that was sufficient for extrusion lamination, and delamination did not occur.

[0072] In Comparative Examples 1 and 2, in which the MFR was less than 10, no defects were found in the leak test, but penetration of the test liquid was confirmed by the watermark test. The amount of air leakage was also large. Furthermore, large voids were observed in the cross-sectional observation. In contrast, Examples 1 and 2, in which the MFR was 10 to 18 (g / 10 min), obtained better results in the watermark test, the amount of air leakage, and the cross-sectional observation than Comparative Examples 1 and 2. From this, it can be seen that an MFR of 10 to 18 (g / 10 min) can more reliably prevent leakage.

[0073] Comparing Example 1 and Example 2, the amount of air leakage and the results of cross-sectional observation showed better results in Example 1. This confirmed that the smaller tan δ is, the more the generation of voids due to springback is suppressed.

[0074] [Table 1]

[0075] [Note] Representative configurations included in the present invention are summarized below as appendices.

[0076] (Appendix 1) The container has a cylindrical body formed from body paper and a bottom formed from bottom paper that closes the lower end of the body, and a bottom paper upper surface resin layer is provided on the upper surface of the bottom paper, and a folded portion that is folded downward is provided on the outer periphery of the bottom paper, and the folded portion is bonded to the inner surface of the body paper via the bottom paper upper surface resin layer, and the bottom paper upper surface resin layer has a viscosity of 0.930 (g / cm 3 ) and an MFR of 10 to 18 (g / 10 min). (Appendix 2) A paper container according to Appendix 1, wherein the lower end of the body paper is folded back so as to sandwich the folded portion. (Appendix 3) A paper container according to Appendix 1 or 2, wherein the body portion has a side seam portion, and the side seam portion is an area where both ends of the body paper overlap in the circumferential direction. (Appendix 4) 4. The paper container according to any one of claims 1 to 3, wherein the polyethylene for the upper surface of the bottom paper has an MFR of less than 15 (g / 10 min). (Appendix 5) 5. The paper container according to any one of claims 1 to 4, wherein the polyethylene for the upper surface of the bottom paper has a tan δ of 3.0 or less. (Appendix 6) 6. The paper container according to any one of appendices 1 to 5, wherein the polyethylene for the upper surface of the bottom paper has a tan δ of 2.0 or less. (Appendix 7) 7. The paper container according to any one of appendices 1 to 6, wherein the polyethylene for the upper surface of the bottom paper has a loss modulus of elasticity of 9000 (Pa) or less. (Appendix 8) 8. The paper container according to any one of appendices 1 to 7, wherein the polyethylene for the upper surface of the bottom paper is low-density polyethylene (LDPE). (Appendix 9) The method comprises the steps of: forming a bottom paper upper surface resin layer made of polyethylene for the bottom paper upper surface on a base paper of the bottom paper by extrusion lamination; producing a bottom paper having a folded portion folded downward on the outer periphery using the base paper of the bottom paper on which the bottom paper upper surface resin layer has been formed; forming a body paper into a cylindrical shape; and pressing the folded portion of the bottom paper against the inner surface of the lower end of the formed body paper while heating. The polyethylene for the bottom paper upper surface is 0.930 (g / cm 3 A method for producing a paper container having a density of less than 10 (g / 10 min) and an MFR of 10 to 18 (g / 10 min). [Explanation of symbols]

[0077] 1 Paper cup, 2 Body, 3 Bottom, 4 Side seam, 5 Gap, 6 Upper resin layer of bottom paper, 7 Pilot ring, 8 Bottom roller, 10 Body paper, 11 Bottom paper, 12 Bottom, 13 Folding section

Claims

1. a cylindrical body portion formed by a body paper; a bottom portion formed by a bottom paper and closing a lower end portion of the body portion; Equipped with A bottom paper upper surface resin layer is provided on the upper surface of the bottom paper, The bottom paper has a folded portion that is folded downward on the outer periphery thereof, The folded portion is bonded to the inner surface of the body paper via the upper surface resin layer of the bottom paper, The resin layer on the top surface of the bottom paper has a viscosity of 0.930 (g / cm ３ The bottom paper is made of polyethylene for the upper surface having a density of less than 1000 kJ / 10 min and an MFR of 10 to 18 g / 10 min. Paper container.

2. The paper container according to claim 1, The polyethylene for the upper surface of the bottom paper has an MFR of less than 15 (g / 10 min). Paper container.

3. The paper container according to claim 1, The polyethylene for the upper surface of the bottom paper has a tan δ of 3.0 or less. Paper container.

4. The paper container according to claim 1, The polyethylene for the upper surface of the bottom paper has a loss modulus of 9000 (Pa) or less. Paper container.

5. The paper container according to claim 1, The polyethylene for the top surface of the bottom paper is low-density polyethylene (LDPE); Paper container.

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