JP6774254B2 - Heat resistant paper container - Google Patents

Description

The present invention relates to an improvement of a heat-resistant paper container such as a heat-resistant paper cup having a body and a bottom.

Conventionally, when a paper material is used as a paper container material for applications where heat resistance is required for the paper container, such as for baking by heating at a low temperature of about 130 ° C. in an oven, a heat resistant resin is laminated on the inner surface or both inner and outer surfaces of the base paper. The composition is known.
At this time, as the heat-resistant resin, polypropylene (PP) having a relatively high heat-resistant temperature, polyethylene terephthalate (PET), and the like are mainly used.

On the other hand, in the shape of a paper container such as a paper cup or a paper cup composed of two pieces, a tubular body and a bottom that closes the bottom surface of the body, the body blank is tubular in order to maintain the sealing property of the container. Adhesion of the bottom part to the body and the overlapping part attached to the paper is important. Conventionally, a polyethylene film having a relatively low melting point and good resin fluidity was laminated on the inner surface or both inner and outer surfaces of the base paper. The configuration is known (see Patent Documents 1 and 2).

Therefore, for example, when a paper cup in which a polyethylene film is laminated as a general two-piece paper cup is filled with raw materials for baked goods such as steamed pudding and cooked in an oven, an oven at 130 ° C. is used. When the paper cup was heated, the heat-resistant temperature of the polyethylene film was low, so that pinholes were generated and the laminated polyethylene film was foamed, so that the paper cup could not be used for cooking by oven heating.

Therefore, in addition to a paper cup made of a base paper laminated with a polyethylene film (abbreviated as PE lami base paper), a paper cup made of a base paper laminated with a polypropylene film (abbreviated as PP lami base paper) and a base paper laminated with a PET resin film are used. A pinhole generation test was conducted with a paper cup (abbreviated as PET lami base paper) (see Table 1).

即ち、各温度におけるオーブン加熱（４０分間加熱）によるピンホールの発生テストを行った。テスト方法は、空容器をオーブンに入れ、指定温度（１１０℃〜１７０℃）で４０分加熱後、容器胴部内面に浸透性の高い試験液（例えば３％ヨウ素‐エタノール溶液）を塗布し、ピンホールの有無を確認した。その結果、ＰＰラミ原紙やＰＥＴラミ原紙はＰＥラミ原紙に比べて耐熱温度が高いため、ＰＰラミ原紙では１６０℃、ＰＥＴラミ原紙では１７０℃のオーブン加熱でもピンホールは発生しなかった。

That is, a pinhole generation test was performed by oven heating (heating for 40 minutes) at each temperature. The test method is to put an empty container in an oven, heat it at a specified temperature (110 ° C to 170 ° C) for 40 minutes, and then apply a highly permeable test solution (for example, 3% iodine-ethanol solution) to the inner surface of the container body. The presence or absence of pinholes was confirmed. As a result, since the PP Lami base paper and the PET Lami base paper have a higher heat resistant temperature than the PE Lami base paper, pinholes did not occur even when the PP Lami base paper was heated at 160 ° C. and the PET Lami base paper at 170 ° C.

On the other hand, since the melting points of the PP lami base paper and the PET lami base paper are higher than those of the PE lami base paper, the adhesive portion tends to be unattached during paper cup molding, and the contents leak or bleed. There was a risk that it could not be used (see Table 2).
In addition, an excessive amount of heat is required to bond the PP lami base paper and the PET lami base paper, and even if they can be adhered, the base paper will be burnt and the appearance will be deteriorated.

上記接着性に関しては、スコアロール水溶液による漏れ確認テストを行った。い、テストの方法は、０．０５％スコアロール水溶液を容器の満杯容量の２／３程充填し、２０分間静置後、漏れが無いか確認した。その結果、前記ＰＰラミ原紙を用いた紙コップや、ＰＥＴラミ原紙を用いた紙コップでは漏れがあることが確認され、ＰＥラミ原紙を用いた紙コップでは漏れが無いことが確認された。

For the above adhesiveness, a leak confirmation test with an aqueous score roll solution was performed. In the test method, a 0.05% scoreroll aqueous solution was filled with about 2/3 of the full capacity of the container, allowed to stand for 20 minutes, and then checked for leakage. As a result, it was confirmed that there was a leak in the paper cup using the PP Lami base paper and the paper cup using the PET Lami base paper, and it was confirmed that there was no leakage in the paper cup using the PE Lami base paper.

Japanese Unexamined Patent Publication No. 2007-23592 JP-A-2013-6631)

The present inventors form a blend layer in which a film blended with polypropylene and polyethylene is laminated on both the inner and outer surfaces of the base paper, and further, by laminating a polyethylene film on the blend layer, the inner blend layer is heat resistant. To complete the present invention, it was found that the temperature can be made higher than that of the polyethylene film to enable oven heating at about 130 ° C., and the melting point of the outer polyethylene film layer can be made lower than that of the inner blend layer to improve the adhesiveness. I arrived.
That is, the problem to be solved by the present invention is to provide a heat-resistant paper container that has both heat resistance and adhesiveness of the paper container and satisfies the moldability of the paper container.

In order to solve the above problems, the present invention uses the heat-resistant paper cup according to claim 1.
In a heat-resistant paper container whose bottom is heat-sealed on a tubular body with the ends bonded together.
The body of the container is formed by laminating a blend film layer in which polypropylene and polyethylene are blended on both the inner and outer surfaces of the base paper, and laminating a polyethylene film layer on the blend film layer.
The blend film layer has a ratio of polypropylene: polyethylene = 60 to 70:40 to 30.
The bottom of the container is characterized by laminating a low melting point polyethylene layer on the inner and outer surfaces of the base paper.
In the invention of claim 2,
The polypropylene-polyethylene blend film layer is characterized by having a polypropylene: polyethylene = 70:30 ratio.

In the heat-resistant paper container of the present invention, the heat-resistant temperature is raised by the inner layer of the film blended with polypropylene and polyethylene to enable oven heating at about 130 ° C., and the outer layer of the polyethylene film has adhesiveness at a low melting point. It can be enhanced, there is no leakage, and the moldability of the container is improved.

It is an exploded perspective view of the heat-resistant paper cup of Example 1. (A) is a cross-sectional view showing a laminated structure of a body portion, and (b) is a sectional view showing a laminated structure of a bottom portion. It is an exploded perspective view of the heat-resistant paper cup which shows the attachment state of the lid part of Example 2. FIG. (A) is a cross-sectional view of the state before the lid and the body are bonded, and (b) is a cross-sectional view of the state where the lid is peeled off.

Hereinafter, preferred examples in which the heat-resistant paper container of the present invention is applied to a heat-resistant paper cup will be described with reference to the drawings.

In the heat-resistant paper cup 10 of this embodiment, the end portion of the fan-shaped blank is bonded to form a substantially tubular body portion 1, and the end portion is closed on the lower inner surface of the body portion 1 by closing the bottom opening of the body portion 1. It consists of two pieces of a substantially circular bottom 7 to be bonded (see FIGS. 1 to 2).

The body 1 is laminated with a blend film layer 3 in which polypropylene and polyethylene are blended on both the inner and outer surfaces of the base paper 2, and the polyethylene film layer 4 is laminated on the innermost surface side or the outer surface side of the blend film layer 3. It has a configuration (see FIG. 2 (a)).
Further, the bottom portion 7 is configured to have a polyethylene film layer 9 in which a low melting point polyethylene film 9 is laminated on both the inner and outer surfaces of the base paper 8 for the bottom portion (see FIG. 2B). The blend layer 3 may be laminated between the base paper 8 for the bottom and the polyethylene layer 9. With this configuration, heat resistance is also imparted to the bottom paper, so that the heat resistance of the container is further improved.

In this example, as the polyethylene (PE), a low melting point polyethylene LW-01 (manufactured by Tosoh Corporation) having a melting point of 128 ° C. was used as an example, but polyethylene having a high melting point or other melting points may be used.
Further, as the polypropylene (PP), an F109V (manufactured by Prime Polymer Co., Ltd.) having a melting point of 162 ° C. was used as an example, but the polypropylene (PP) is not limited to this.

The blend film layer 3 in which polypropylene and polyethylene are blended is a resin in which polypropylene and polyethylene are blended in order to increase heat resistance, adhesive strength between paper / resin, and adhesive strength between the blend layer and the polyethylene layer laminated on the blend layer. Therefore, as the blend ratio, in this example, a polypropylene: polyethylene = 70:30 ratio was adopted in order to achieve both heat resistance and adhesive strength.

When baking in an oven, cooking of steamed pudding or the like requires heating at around 130 ° C. Therefore, based on the polypropylene and polyethylene, the heat resistance and heat-sealing property of the blend ratio at 130 ° C. I investigated the relationship.
The heat resistance test method is as follows: after heating an empty container in an oven at 130 ° C. for 40 minutes, fill the container with 0.05% scoreroll aqueous solution to about 2/3 of the full capacity of the container, leave it for 20 minutes, and then pinhole. I confirmed the presence or absence of. The evaluation was ○ if there was no pinhole, and × if there was.
The heat sealability test method is to prepare a sample by heat-sealing the lami surfaces of two base papers with a hot air sealer, etc., peel off the sample after sealing, and apply food coloring water etc. to the peeled surface. The peeled area was confirmed. The evaluation was performed according to the following criteria.
Evaluation criteria: ○… Paper peeling area (colored area) is 70 to 100%
△… Paper peeling area is 30 to 69%
×… Paper peeling area is 0 to 29%

As a result of Table 3, it was confirmed that when the ratio of polypropylene is high, for example, when it is 80% or more, the influence of the melting point of polypropylene appears strongly, so that the melting point temperature becomes high and the heat resistant temperature is high, but the heat sealability is slightly impaired. It was.
Further, when the ratio of polyethylene is high, the influence of the heat-resistant temperature of polyethylene appears strongly, so that the heat-resistant temperature becomes low, and it cannot withstand oven heating at 130 ° C. If it is within 30%, the influence of polypropylene having a high heat-resistant temperature It was confirmed that the oven could be heated at 130 ° C.

This ratio can be determined experimentally because it changes depending on the melting point and heat-resistant temperature of the specifications of polypropylene and polyethylene actually used, but polypropylene is less than 80% and has a higher heat-resistant temperature property than polyethylene. Polypropylene is preferably in the range of 60 percent to 70 percent, and polyethylene is preferably in the range of 40 percent to 30 percent.
Therefore, in this example, a film blended in a ratio of polypropylene: polyethylene = 70:30 was used.

Since the melting point of the polypropylene / polyethylene blend film layer 3 alone is higher than that of the polyethylene single layer, an excessive amount of heat is required to melt the resin when molding and adhering the paper cup, resulting in pinholes and pinholes around the heated portion. There was a fear that the paper would be scorched.
Therefore, by providing the polyethylene film layer 4 on the blend film layer 3, the polyethylene film layer 4 having a low melting point is melted when the paper cup is molded, and adhesion is possible with a small amount of heat, and pinholes and paper are charred. Can be suppressed.

Table 4 shows the test results of the presence or absence of pinholes between the heat-resistant paper cup of this example and the heat-resistant paper cup using various conventional lami base papers with respect to the heating temperature of the oven. The polyethylene lami base paper has a temperature of 120 ° C. However, it was confirmed that the heat-resistant paper cup of this example does not generate pinholes until the temperature reaches 140 ° C.

Further, in the leakage test using the scoreroll aqueous solution, it was confirmed that leakage occurred in both the PP lami paper cup and the PET lami paper cup, but there was no leakage in the heat-resistant paper cup 7 of this example.

In the body portion 1, the polyethylene film layer 4 on the inner surface of one end of the body portion 1 and the polyethylene film layer 4 on the outer surface of the other end surface of the body portion 1 are overlapped and adhered to each other. Since they are attached to each other, they can be firmly bonded with a small amount of heat.
Further, in the bottom portion 7, the low melting point polyethylene film layer 9 and the polyethylene film layer 4 on the inner surface side of the body portion 2 are adhered by heat sealing, and since they are both polyethylene films, they are firmly adhered to each other. be able to.

In the above embodiment, the heat-resistant paper cup 10 is not provided with the lid, but the lid 15 may be sealed in the opening of the heat-resistant paper cup 10 (see FIGS. 3 to 4).
In this embodiment, the lid portion 15 has a low melting point polyethylene film 17 laminated on at least the inner surface of the base paper 16 for the lid portion, and is firmly adhered to the polyethylene film layer 4 at the upper end of the body portion 2 (FIG. 4 (FIG. 4). a) See).

Therefore, the low melting point polyethylene film layer 16 of the lid portion 15 and the polyethylene film layer 4 of the body portion 1 are adhered to the same type of polyethylene film, and the adhesive strength is strong, but the polyethylene film layer 4 and polypropylene and polyethylene are blended. Since the type is different from that of the film layer 3, the adhesive strength is relatively weak.
As a result, when the lid portion 15 is peeled off, the lid portion 15 can be peeled off between the polyethylene film layer 4 and the blend film layer 3 in a state of being adhered to the polyethylene film layer 4, and it is easy peeling. Stable opening strength (see FIG. 4B).

In the above embodiment, a paper cup has been described as an example of a heat-resistant paper container, but it can be applied to a paper cup having a wide opening and other paper containers.
Further, the present invention is not limited to the above-described embodiment, and in short, various design changes can be made without changing the gist of the present invention.

1 Body 2 Base paper for body 3 Blend film layer 4 Polyethylene film layer 7 Bottom 8 Base paper for bottom 9 Low melting point polyethylene film layer 10 Heat resistant paper cup 15 Lid 16 Base paper for lid 17 Low melting point polyethylene film

Claims (2)

In a heat-resistant paper container whose bottom is heat-sealed on a tubular body with the ends bonded together.
The body of the container is formed by laminating a blend film layer in which polypropylene and polyethylene are blended on both the inner and outer surfaces of the base paper, and laminating a polyethylene film layer on the blend film layer.
The blend film layer has a ratio of polypropylene: polyethylene = 60 to 70:40 to 30.
A heat-resistant paper container characterized in that the bottom of the container is formed by laminating a low-melting point polyethylene layer on the inner and outer surfaces of the base paper. The heat-resistant paper container according to claim 1, wherein the blend film layer has a ratio of polypropylene: polyethylene = 70:30.

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