JP2024019096A - Paper container, manufacturing method of top seal paper container and paper container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper container high in a top sealing property and a manufacturing method of the top seal paper container and the paper container.

SOLUTION: The paper container mainly consists of: a bottom portion; a sidewall portion connected to the bottom portion; a flange portion connected to the upper end of the sidewall portion and extending horizontally outward; and an edge-wrapping portion connected to the outer edge of the flange portion. The flange portion has a plurality of wrinkles 6 (including a crushing wrinkle 7) formed by folding in from the bottom surface thereof to the top surface by press molding. Furthermore, the wrinkles 6 (including the crushing wrinkle 7) of the flange portion have flattened portions 28 formed at least partially. This configuration results in a paper container with improved top sealing when top sealing is performed using a lidding material such as top sealing film, because the flange portion is flattened and the presence or absence of fine voids 25 inside the crease 6 has no effect on the top sealing. In addition, the strength of the container increases compared to conventional paper containers that do not have flattened wrinkles.

SELECTED DRAWING: Figure 4

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a paper container, a top-seal paper container, and a method for manufacturing a paper container, and particularly relates to a paper container, a top-seal paper container, and a method for manufacturing a paper container formed from a single sheet of paperboard by press molding only. .

There is a paper container shown in Patent Document 1 that is formed from a single sheet of paperboard only by press molding.

FIG. 8 is a perspective view showing the external appearance of a conventional paper container shown in Patent Document 1.

Referring to FIG. 8, the paper container 51 includes a bottom portion 52 having a substantially rectangular shape with rounded corners, a side wall portion 53 connected to the periphery of the bottom portion 52 and rising diagonally upward, and connected to the upper end of the side wall portion 53. It is composed of a flange portion 54 extending in the horizontal direction, and a hem wrap portion 55 connected to the outer peripheral end of the flange portion 54. Note that the corner portions of the side wall portion 53 and the flange portion 54 are a side wall corner portion 57 and a curved flange portion 58 in which a plurality of wrinkles 56 are formed radially from the inside toward the outer periphery.

FIG. 9 is a plan view showing the overall shape of a base paperboard for press-molding the paper container shown in FIG. 8.

Referring to FIG. 9, the paperboard base paper 70 has a substantially rectangular shape with four rounded corners, a central portion 72 of which corresponds to the bottom 52 of the paper container, and an outer peripheral portion 73 of the paper container 51. These portions correspond to the side wall portion 53, flange portion 54, and edge wrapping portion 55 of. Note that a plurality of radially extending ruled lines 71 are formed at the four corners of the outer peripheral portion 73 in portions corresponding to the side wall corner portions 57 and the curved flange portions 58.

In the above-described paper container 51 shown in Patent Document 1, irregular wrinkles that tend to occur at the corners during press forming are absorbed by the ruled lines 71 formed on the paperboard base paper 70, thereby improving the forming process. Occasional occurrence of irregular wrinkles can be suppressed.

However, since the wrinkles 56 are formed in the press-formed paper container 51 as described above, it is assumed that the formation of the wrinkles 56 can be controlled regularly by forming a plurality of ruled lines 71 on the paperboard base paper 70 and press-forming it. However, the wrinkles 56 themselves become uneven. Therefore, in the case of a plastic container, it is possible to create a top-sealed container with high sealing performance by forming a flat flange on the container and top-sealing the flange with a plastic film having top-sealing properties. However, in the case of a paper container 51 in which wrinkles 56 are formed by press molding, even if the flange portion 54 is formed and the plastic film is top-sealed, complete sealing cannot be achieved due to the unevenness of the wrinkles 56. For this reason, it has been difficult to perform top sealing using a plastic film that has top sealing properties.

Therefore, Patent Document 2 discloses that after press-forming a deep-drawn paper container having a flange using paperboard base paper with a thermoplastic resin layer laminated on one side of the paperboard, the flange is made into a smooth surface by ultrasonic processing. A technology has been disclosed for a deep-drawn paper container with high sealing properties using a top seal, in which the flange portion is crushed using heat and pressure by ultrasonic processing to form a smooth surface with few irregularities.

Japanese Patent Application Publication No. 10-43027 Japanese Patent Application Publication No. 2000-33927

Figure 10 is a diagram showing how the ruled lines formed on the base paperboard change during the manufacturing of paper containers; (1) is before the pressing process, (2) is after the pressing process, and (3) is the wrinkles caused by ultrasonic processing. After the pressing process, (4) is a diagram showing the state after top seal packaging.

Referring to FIG. 10 (1), a paperboard base paper 80 has a resin layer (not shown) formed on the inner surface of the container, and is folded from the inner surface of the container to the outer surface of the container to form ruled lines 81. That is, the concave portion 82 and convex portion 83 of the ruled line 81 are formed on the inner surface of the container and the outer surface of the container, respectively.

Next, referring to FIG. 10(2), when such a base paperboard 80 is pressed, wrinkles 86 are formed around the protrusions 83 of the ruled lines 81 on the outer surface of the container. At this time, the recess 82 of the ruled line 81 formed on the inner surface of the container is compressed from both sides thereof, and a space 84 is formed inside the wrinkle 86.

Referring to FIG. 10 (3), when the wrinkle 86 is pressed from above and below by ultrasonic processing, the resin layer on the surface of the wrinkle 86 on the inner surface of the container melts and becomes a fusion layer. try to fuse together. As a result, the unevenness that has occurred in the wrinkles 86 of the flange portion can be flattened to some extent.

However, in the paper container described in Patent Document 2, the wrinkles 86 formed on the side wall portion and the flange portion are formed by being folded from the inner surface to the outer surface of the paper container. When the wrinkles 86 are formed in this way, even if the wrinkles 86 at the flange portion are flattened by crushing using heat and pressure by ultrasonic processing as in Patent Document 2, the inner side of the wrinkles 86 The fine spaces 84 of the wrinkles 86 cannot be completely melted and fused, and a void 85 remains inside the wrinkles 86. Even if food (contents) containing moisture is stored in such a paper container and the flange portion of the paper container is top-sealed with a plastic film 87, as shown in (4) of FIG. , since the moisture etc. of the contents seeps out or leaks from the minute voids 85 existing inside the wrinkles 86, it cannot be said that the top sealing performance is sufficient. This is presumably because liquid such as moisture is absorbed into the fine voids 85 existing inside the wrinkles 86 by capillary action. A similar problem occurs even with gas.

In addition, in order to eliminate such voids 85, it is possible to increase the energy applied during ultrasonic processing to the flange part or to lengthen the time of ultrasonic processing, but if such measures are taken, In this case, the wrinkles 86 become overheated, causing problems such as burning of the resin and paper, making it difficult to control the processing.

This invention was made to solve the above-mentioned problems, and an object thereof is to provide a paper container with high top-sealability, a top-seal paper container, and a method for manufacturing the paper container.

In order to achieve the above-mentioned object, the invention according to claim 1 is formed only by press molding from a sheet of paperboard on which a resin layer is formed on at least the inner surface of the container, and the bottom part and the bottom part are connected to each other. A paper container comprising a side wall portion having a flat surface and a flange portion connected to the upper end of the side wall portion and extending horizontally outward, the side wall portion and the flange portion having a plurality of wrinkles formed by press molding. However, the wrinkles on the flange portion are formed by folding from the lower surface to the upper surface of the flange portion, and the wrinkles appearing on the upper surface of the flange portion have a flat portion formed at least in part.

With this configuration, the flange portion is flattened, and the presence or absence of minute voids on the inner side of the wrinkles does not affect the top seal, which is the first effect.

The invention according to claim 2 is the structure of the invention according to claim 1, in which the outer peripheral edge of the flange portion is provided with an edge wrapping portion, and the highest part of the edge wrapping portion is at the same height as the upper surface of the flange portion. Or located below.

With this configuration, effect 2 is obtained in that the hem wrap portion is not located on the outward extension of the mounting surface of the lid member.

The invention according to claim 3 is the structure of the invention according to claim 1 or claim 2, in which the cross-sectional thickness (S1) of a wrinkled paper container having a flat portion and the cross-sectional thickness of a wrinkled paper container having no flat portion are provided. The ratio (S1/S2) to (S2) is 0.7 or less.

With this configuration, effect 3 can be obtained in that wrinkles having flat portions are more reliably flattened than wrinkles having no flat portions.

The invention according to claim 4 is the structure of the invention according to claim 1 or claim 2, in which the wrinkles of the flange portion are formed based on a plurality of ruled lines formed on a portion of the paperboard base paper corresponding to the flange portion. It is something.

With this configuration, effect 4 can be obtained in that wrinkles that tend to occur irregularly during press molding are absorbed by the ruled lines.

According to a fifth aspect of the invention, in the structure of the first or second aspect of the invention, the wrinkles on the side wall portion are formed by being folded from the inner surface to the outer surface of the side wall portion.

With this configuration, the wrinkle recess is located on the inner surface of the side wall, and the wrinkle that is folded from the inner surface to the outer surface of the paper container extends to the top of the side wall, so that the crease is located inside the wrinkle. Effect 5 is obtained in that even if capillary action occurs due to minute voids, moisture absorbed by the capillary action only reaches the upper part of the side wall part and does not reach the flange part.

The invention according to claim 6 is a top-seal paper container comprising the paper container according to claim 1 or 2 and a lid material having top-sealing properties.

With this configuration, effect 6 can be obtained in that the flange portion is top-sealed without leakage.

The invention according to claim 7 provides a step of preparing a base paperboard and pressing the base paperboard to form a bottom part, a side wall part connected to the bottom part, and a horizontal part connected to the upper end of the side wall part and extending outwardly. a pressing step for forming a paper container including a flange portion extending in the direction and having wrinkles formed by folding the upper surface from the lower surface to the upper surface; and a wrinkle pressing step for forming a flat portion in at least a part of the wrinkles. A method for manufacturing a paper container comprising:

With this configuration, the flange portion is flattened and a paper container can be obtained in which the presence or absence of minute voids on the inside of the wrinkles does not affect the top seal.

According to an eighth aspect of the invention, in the seventh aspect of the invention, the wrinkle pressing step includes ultrasonic processing on the wrinkles.

With this configuration, effect 8 can be obtained in that the flange portion can be easily flattened.

According to the ninth aspect of the present invention, in the configuration of the eighth aspect of the present invention, a resin layer is formed on at least the surface of the paperboard that is the inner surface of the container, and the resin layer is melted by ultrasonic processing.

With this configuration, the effect 9 can be obtained in that the gaps inside and around the wrinkles are filled with the resin layer, and a paper container with a flattened flange portion can be obtained.

The invention according to claim 10 is the structure of the invention according to claim 9, in which the wrinkle pressing step is performed by applying ultrasonic processing to wrinkles having flat portions with respect to 100% cross-sectional thickness of the wrinkled paper container before ultrasonic processing. The cross-sectional thickness of the paper container is 70% or less.

With this configuration, effect 10 can be obtained in that a paper container whose wrinkles on the flange portion are reliably flattened compared to the wrinkles before ultrasonic processing is obtained.

The invention set forth in claim 11 is the structure of the invention set forth in claim 6, in which a resin layer having barrier properties is formed on the paper container and the lid material.

With this configuration, the effect 11 that the flange portion is top-sealed without leakage can be obtained.

As explained above, since the invention according to claim 1 can obtain the above effect 1, when top sealing is performed using a lid material such as a top seal film, it is possible to use a paper container with improved top sealing properties. Become. Moreover, the strength is improved compared to conventional paper containers whose wrinkles are not flattened.

The invention set forth in claim 2 provides the above-mentioned effect 2 in addition to the effect of the invention set forth in claim 1, so that attachment of the lid material becomes easy and yield is improved.

The invention according to claim 3 provides the above-mentioned effect 3 in addition to the effects of the invention according to claim 1 or 2. Therefore, when top sealing is performed using a top seal film, the top sealing property is improved. Further improvement.

The invention according to claim 4 provides the above-mentioned effect 4 in addition to the effects of the invention according to claim 1 or 2. Therefore, when top sealing is performed using a top seal film, the top sealing property is improved. Variations in quality are less likely to occur, and the aesthetic appearance is improved.

The invention set forth in claim 5 provides the above-mentioned effect 5 in addition to the effect of the invention set forth in claim 1 or 2, so that the ease of eating is improved, and the top seal film is used to seal the top seal. When doing so, it is possible to achieve both good top sealing properties and ease of eating.

In the invention as set forth in claim 6, since the above effect 6 can be obtained, the sealing performance of the top seal paper container is improved.

The invention as set forth in claim 7 provides the above-mentioned effect 7, so when top sealing is performed using a top seal film, a paper container with improved top sealing properties can be obtained.

The invention set forth in claim 8 provides the effect 8 described above in addition to the effect of the invention set forth in claim 7, so that the productivity of paper containers is improved.

The invention according to claim 9 provides the above-mentioned effect 9 in addition to the effect of the invention according to claim 8, so that when top sealing is performed using a top seal film, the paper with further improved top sealing properties can be obtained. A container is obtained.

The invention according to claim 10 provides the above-mentioned effect 10 in addition to the effect of the invention according to claim 9, so when top sealing is performed using a top seal film, the paper with further improved top sealing properties can be obtained. A container is obtained.

The invention according to claim 11 provides the above-mentioned effect 11 in addition to the effect of the invention according to claim 6, so that the sealing performance of the top-seal paper container is improved and the top-seal paper container has high gas barrier properties. .

FIG. 1 is a plan view showing the overall shape of a paper container according to an embodiment of the present invention. FIG. 2 is a sectional view showing the overall structure of the paper container shown in FIG. 1. FIG. FIG. 2 is a plan view showing the overall shape of a base paperboard for press-molding the paper container shown in FIG. 1. FIG. FIG. 4 is a diagram showing how the ruled lines formed on the paperboard base paper shown in FIG. 3 change during paper container manufacturing, in which (1) is before the pressing process, (2) is after the pressing process, and (3) is after ultrasonic processing. After the wrinkle pressing process, (4) is a diagram showing the state after top seal packaging. FIG. 2 is a schematic cross-sectional view showing a wrinkle pressing step according to the paper container manufacturing method shown in FIG. 1. FIG. FIG. 2 is a schematic diagram showing a measurement test performed on the paper container shown in FIG. 1. FIG. 7 is a graph showing the results of the measurement test shown in FIG. 6, where (1) is a graph in the longitudinal direction and (2) is a graph in the transverse direction. 1 is a perspective view showing the external appearance of a conventional paper container shown in Patent Document 1. FIG. FIG. 9 is a plan view showing the overall shape of a base paperboard for press-molding the paper container shown in FIG. 8; It is a diagram showing how the ruled lines formed on the paperboard base paper change during the manufacturing of paper containers, (1) before the pressing process, (2) after the pressing process, and (3) after the wrinkle pressing process by ultrasonic processing. , (4) is a diagram showing the state after top seal packaging.

FIG. 1 is a plan view showing the overall shape of a paper container according to an embodiment of the present invention, and FIG. 2 is a sectional view showing the overall structure of the paper container shown in FIG.

Referring to FIGS. 1 and 2, a paper container 1 has an oval bottom 2, a side wall 3 connected to the bottom 2, and a side wall 3 connected to the upper end of the side wall 3 and extending outward in a horizontal direction. It is composed of a flange portion 4 and a hem wrap portion 5 connected to the outer peripheral edge of the flange portion 4.

A plurality of wrinkles 6 (including crush wrinkles 7 to be described later) extending radially toward the outer circumference are formed around the entire circumference of the side wall portion 3, flange portion 4, and hem wrap portion 5 of the paper container 1. Details of the wrinkles 6 will be described later.

The edge wrapping portion 5 is located downward from the outer peripheral edge of the flange portion 4, and the end portion of the edge wrapping portion 5 is formed so as to be wound inside the edge wrapping portion 5, and the end portion of the edge wrapping portion 5 is formed so as to be wound inside the edge wrapping portion 5. It is formed along the entire circumference, and the cross section of the edge wrapping part 5 is formed in an annular shape. Further, the hem wrap portion 5 is formed such that the annular portion with the highest height is located at the same height as the upper surface of the flange portion 4.

With this configuration, when the lid material is used, the edge wrapping portion 5 is not located on the outward extension of the mounting surface of the lid material so as to protrude above the upper surface of the flange portion 4. When performing top sealing using a lid material, especially a lid material such as a top seal film, the hem 5 does not get in the way during top sealing, making it easier to top seal, making it easier to attach the lid material. Therefore, the yield is improved.

Next, the paperboard base paper for press-molding the paper container 1 will be explained.

FIG. 3 is a plan view showing the overall shape of a base paperboard for press-molding the paper container shown in FIG. 1.

Referring to FIG. 3, a paperboard base paper 10 is formed by punching out a sheet having resin layers formed on both sides of a paper base material by an extrusion lamination method, and has an oval shape. The central part of the paperboard base paper 10 is a bottom corresponding part 12 that corresponds to the bottom part 2 of the paper container 1, and the outer peripheral side thereof is a part corresponding to the side wall part 3, flange part 4, and edge wrapping part 5 of the paper container 1. These are the side wall portion corresponding portion 13, the flange portion corresponding portion 14, and the edge wrapping portion corresponding portion 15.

A plurality of radially extending ruled lines 21 are formed in the side wall portion corresponding portion 13, the flange portion corresponding portion 14, and the edge wrapping portion corresponding portion 15.

Next, a method for manufacturing the paper container 1 will be described, focusing on the wrinkles 6 in the paper container 1.

FIG. 4 is a diagram showing how the ruled lines formed on the base paperboard shown in FIG. 3 change during the manufacture of paper containers; (1) is before the pressing process, (2) is after the pressing process, and (3) is After the wrinkle pressing process by ultrasonic processing, (4) is a diagram showing the state after top seal packaging.

First, paperboard base paper 10 is prepared. Referring to FIG. 4(1), the ruled lines 21 formed on the base paperboard 10 are formed by folding from the inner surface of the container to the outer surface of the container. That is, the protrusions 23 and recesses 22 of the ruled lines 21 are formed on the inner surface of the container and the outer surface of the container, respectively.

Next, the base paperboard 10 is pressed from above and below by a mold member of a molding device to perform press molding. As a result, from the paperboard base paper 10, a bottom part 2, a side wall part 3 connected to the bottom part 2, a side wall part 3 connected to the upper end of the side wall part 3, extending outward in the horizontal direction and folded from the bottom surface to the top surface are formed. A paper container 1 including a flange portion 4 having wrinkles 6 is formed.

In this way, when the ruled lines 21 are formed on the side wall corresponding portion 13, flange portion corresponding portion 14, and edge wrapping portion corresponding portion 15 of the paperboard base paper 10, irregular wrinkles that are likely to occur during press forming can be prevented from forming on the ruled lines 21. absorbed and compressed. Therefore, the aesthetic appearance of the paper container 1 is improved. In addition, since the occurrence of irregular wrinkles on the flange portion 4 can be suppressed, when top sealing is performed using a top seal film on the flange portion 4, variations in the quality of top sealing properties are less likely to occur.

Referring to FIG. 4(2), wrinkles 6 are formed on the side wall portion 3 and flange portion 4 of the paper container 1 after the pressing process, centered around the convex portion 23 on the inner surface of the container. In the flange portion 4 of the paper container 1, wrinkles 6 are formed so as to be folded in from the lower surface to the upper surface of the flange portion 4.

The outer peripheral edge of the flange portion 4 is hem-wrapped to form an hem-wrap portion 5 around the entire periphery. The hem winding part 5 is formed in an annular shape on the outer peripheral edge of the flange part 4, and the upper end (highest part) of the hem winding part 5 is located above the upper surface of the flange part 4.

Next, after the pressing process, the wrinkles 6 of the flange portion 4 are further pressed by ultrasonic processing.

FIG. 5 is a schematic cross-sectional view showing the wrinkle pressing process according to the paper container manufacturing method shown in FIG.

Referring also to FIG. 5, after the pressing process, the paper container 1 is placed on the pedestal 41 of the ultrasonic processing device, the ultrasonic horn 42 is lowered from above the paper container 1, and the pedestal 41 and the ultrasonic The flange portion 4 of the paper container 1 is sandwiched between the horn 42 and the horn 42 . Then, it is pressed from above and below while applying a predetermined ultrasonic vibration. Then, the resin layer of the flange portion 4 is locally heated by ultrasonic processing. Since the resin layer has thermoplasticity, the portion folded together with the ruled lines 21 melts to form a fusion layer and are fused together. When pressed in this state, the wrinkles 6 on the flange portion 4 are flattened as a whole.

Note that the portion of the pedestal 41 of the ultrasonic processing device corresponding to the edge wrap 5 is notched, and the entire surface of the ultrasonic horn 42 that comes into contact with the paper container 1, including the portion corresponding to the edge wrap 5, is flat. Therefore, when the ultrasonic horn 42 is lowered to the upper surface of the flange portion 4, the highest part of the hemline portion 5, which was located above the upper surface of the flange portion 4, is moved downward by the ultrasonic horn 42. However, since the part of the pedestal 41 corresponding to the edge wrap 5 is notched, the edge wrap 5 will not be crushed even by the pressure by the ultrasonic horn 42, and the edge will be pushed down as the ultrasonic horn 42 descends. The winding portion 5 is pushed down to the same height as the upper surface of the flange portion 4. In this way, the paper container 1 shown in FIG. 1 is manufactured. In the embodiment, the paper container 1 was installed and subjected to ultrasonic processing so that the ultrasonic horn 42 was in contact with the upper surface of the flange portion 4 as shown in FIG. Even if the paper container 1 is placed in a direction in contact with the lower surface of the portion 4 (that is, in a direction in which the opening of the paper container 1 faces downward) and ultrasonic processing is performed, the same effect as that of the present invention can be obtained.

Next, a description will be given of how the wrinkles 6 of the flange portion 4 change during the manufacture of a paper container.

Referring to FIG. 4 (2), as described above, when the paperboard base paper 10 is pressed, wrinkles centering around the convex portion 23 of the ruled line 21 on the inner surface side of the container (the upper surface of the flange portion 4) 6 is formed. At this time, a pair of gaps 26a and 26b are formed on both sides of the convex portion 23 of the ruled line 21 formed on the inner surface of the container (the upper surface of the flange portion 4). Further, the recess 22 of the ruled line 21 formed on the outer surface of the container (lower surface of the flange portion 4) is compressed from both sides thereof, and a space 24 is formed inside the wrinkle 6.

Next, referring to FIG. 4(3), after the pressing process, the wrinkles 6 are heated by ultrasonic processing while being pressed. Then, the gaps 26a and 26b are closed, and the resin layer around the gaps 26a and 26b melts and becomes a fusion layer that is fused to each other so as to fill the gaps 26a and 26b, so that a pair of gap marks 27a and 27b are formed. Become. As a result, the wrinkles 6 are flattened, and a flat portion 28 is formed between the pair of gap marks 27a and 27b on the inner surface of the container (the upper surface of the flange portion 4). That is, the flat portion 28 refers to the surface portion of the crushed wrinkles 7 formed on the inner surface of the container (the upper surface of the flange portion 4) by crushing the wrinkles 6 through a process of pressing the wrinkles such as ultrasonic processing. say. Furthermore, flatness refers to a state in which there is no change in height such as unevenness as a whole to the extent that the top seal is not obstructed. Note that, in this embodiment, a flat portion is formed at least in part of the upper part of the wrinkle 6.

When the wrinkle 6 is heated by ultrasonic processing while being pressed, the resin layer on the surface of the wrinkle 6 on the outside of the container melts and the space 24 formed on the outer surface of the container (lower surface of the flange portion 4) melts. The neighboring resin layers form an adhesion layer and fuse to each other, and the wrinkles 6 on the outer surface of the container are flattened to some extent. However, since the space 24 is considerably larger than the gaps 26a and 26b, the wrinkles 6 are The inner space 24 cannot be completely eliminated, and a void 25 remains inside the wrinkle 6 (crushed wrinkle 7).

Next, referring to (4) in FIG. 4, food containing moisture (contents) is stored in such a paper container 1, and the flange portion 4 of the paper container 1 is used as a lid material 29 having top sealing properties. When top-seal packaging is performed using a plastic film, the upper surface of the flange portion 4 has a flat portion 28 formed after the wrinkle pressing process by ultrasonic processing, so the flange portion is flattened and the top surface is sealed without leaking into the flange portion 4. Can be sealed. Moreover, since the minute voids 25 on the inner side of the wrinkles 6 (the crushed wrinkles 7) appear on the lower surface of the flange portion 4, they do not affect the top seal. Therefore, the paper container 1 has improved top sealing properties. Since the flange portion 4 is flattened, the strength is improved compared to conventional paper containers in which wrinkles are not flattened. In particular, since the wrinkle pressing step includes ultrasonic processing on the wrinkles, the flange portion can be easily flattened, and the productivity of the paper container is improved.

In the above embodiments, the paper container has an oval outer edge, but the shape is not particularly limited as long as it has a flange. For example, when viewed from above the opening of the container, the shape may be circular, square, polygonal, or approximately elliptical including a straight portion. The size of the container is also not particularly limited. Further, the container shape includes a container having a partition on the inside.

Further, in the above embodiment, the plurality of wrinkles formed by press forming were formed based on the plurality of ruled lines formed on the base paperboard, but the wrinkles were formed based on the plurality of ruled lines formed on the base paperboard. Similarly, it has the effect of improving strength and top sealing performance.

Furthermore, in the above embodiment, the wrinkles that appear on the upper surface of the flange portion are formed as a flat portion from the end of the upper surface of the flange portion on the side wall side to the end on the hemline side. It is sufficient that a flat portion is formed in at least a portion of the edge portion from the side end portion to the edge portion side end portion. Further, among the plurality of wrinkles appearing on the upper surface of the flange portion, flat portions may be formed only in some of the wrinkles, and flat portions may not be formed in the other wrinkles. For example, when the outer edge of a paper container is oval, it is possible to improve the strength of the container in the longitudinal direction by forming a flat part only at the wrinkles of the flange in the longitudinal direction. It is also possible to improve the strength in specific directions or parts.

Further, in the above embodiment, the flat portion is formed around the entire periphery of the flange portion, but it may be formed on at least a portion of the flange portion. Alternatively, it may be formed on the side wall portion. That is, ultrasonic processing may be performed on (the wrinkles of) the side wall portion.

Furthermore, with reference to FIGS. 4(2) and 4(3), in the above embodiment, the paper container cross-sectional thickness (S1) of wrinkles having a flat portion and the wrinkles having no flat portion It is preferable that the ratio of S2 to the cross-sectional thickness of the paper container (S2) is 0.7 or less. With this configuration, the crushed wrinkles, which are wrinkles that have flat portions, are more reliably flattened than the wrinkles that do not have flat portions, so that the top sealability is further improved. Incidentally, S2 can also be measured as the cross-sectional thickness of the wrinkled paper container in the side wall portion that has not been subjected to ultrasonic processing.

Furthermore, in the above embodiment, the flange extends horizontally, but the horizontal direction does not mean only the horizontal direction when the paper container is placed on a horizontal surface, but also the flange extending diagonally upward or diagonally toward the horizontal direction. This includes cases where it extends downward. Also, it includes unavoidable errors due to the molding process and paper characteristics.

Further, in the above embodiment, the highest part of the hem wrap portion is located at the same height as the top surface of the flange portion, but it may be located above the top surface of the flange portion. , may be located below.

Furthermore, in the embodiments described above, the paper container is provided with an edge wrap, but the paper container may not have an edge wrap.

Further, in the above embodiment, the wrinkles on the side wall portion are formed by being folded from the outer surface of the container to the inner surface of the container, but they may be formed by being folded from the inner surface to the outer surface. In this case, in the paperboard base paper, a portion may be provided where the ruled lines are not connected to each other between the ruled line corresponding to the wrinkle of the side wall portion and the ruled line corresponding to the wrinkle of the flange portion.

With this configuration, the wrinkled recess is located on the inner surface side of the side wall. Then, when food is stored and eaten using a spoon or the like, since there are no wrinkled protrusions on the inner surface, the spoon or the like will not get caught on the wrinkled protrusions on the inner surface of the container. In addition, since the wrinkles that are folded from the inner surface to the outer surface of the paper container extend to the top of the side wall, even if capillary action occurs due to the minute voids that exist inside the wrinkles, the moisture absorbed by the capillary action etc., only reach the upper part of the side wall part and not the flange part. Therefore, both good top sealability and ease of eating can be achieved.

Further, in the above embodiment, the top seal is performed using a lid material such as a top seal film, but a lid material made of paper, plastic, metal such as aluminum, etc. may be fitted. Moreover, it may be shrink-wrapped.

In addition, when using a top seal film, there are no particular limitations on the type, configuration, or sealing mode, as long as the paper container can be sealed by sealing with the top seal film that serves as the lid. It does not matter whether it is a complete seal type or an easy peel type. Of course, a commonly used top seal film with heat sealability can also be used. Therefore, the top seal film may be a film composed of a single layer of resin as long as it has sealing properties, or it may be a film composed of not only a single layer but also multiple layers of resin to provide heat resistance and barrier properties. It doesn't matter if there is. In particular, when a top seal film with high gas barrier properties is used as the lid material for the paper container of the present invention, it is possible to obtain a top seal paper container with high gas barrier properties.

The resin used for the top seal film is not particularly limited, but examples include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyolefin resins such as polypropylene, polyethylene, and polymethylpentene, and polyamides such as nylon. Examples include thermoplastic resins such as polycarbonate resins, acrylic (methacrylic) resins, diene resins such as polybutadiene, and polycarbonate resins. For paper containers that are more environmentally friendly, for example, the above-mentioned thermoplastic resin may be manufactured as biomass resin derived from living organisms, polybutylene succinate (PBS), polylactic acid (PLA), cellophane, etc. It is also possible to use biodegradable resins. Among them, it is particularly preferable to use a resin having heat resistance that can withstand high-temperature heating in an oven or a microwave oven when used as a top seal film of a packaging container for storing food. Furthermore, if it is desired to provide a paper container with barrier properties that block or suppress the permeation of gas such as oxygen or water vapor, a resin having such barrier properties may be laminated with a film or coating. The type of resin having barrier properties is not particularly limited, but examples thereof include polyvinyl alcohol resin, ethylene vinyl alcohol copolymer resin, polyvinylidene chloride resin, and the like. Furthermore, films made of polyethylene terephthalate or polypropylene on which a metal vapor-deposited film such as aluminum or an inorganic vapor-deposited film such as silica or alumina are formed can also be used for the purpose of imparting barrier properties. Alternatively, a top seal film may be made by laminating a combination of a plurality of resins as described above. For example, a top layered with at least a polyolefin resin such as polypropylene or polyethylene, or a polyester resin such as polyethylene terephthalate or polybutylene terephthalate, and a resin with high gas barrier properties such as ethylene vinyl alcohol copolymer resin or polyvinyl alcohol resin. An example is a sealing film. In particular, when using a top seal film in which polyethylene terephthalate and ethylene vinyl alcohol copolymer resin are laminated at least, it is possible to impart high gas barrier properties and a high heat resistance when top sealing the paper container of the present invention. This is preferable because it allows it to be made into a paper container. Of course, this does not exclude laminating other resins (for example, a sealant layer in the case of heat sealing) or laminating other structures (for example, paper or metal foil such as aluminum foil) in the configuration. do not have. Further, the sealant layer may also be formed of an adhesive such as a lacquer-type adhesive, an easy-peel adhesive, or a hot-melt adhesive, in addition to a known sealant film. The thickness of such a top seal film is also not particularly limited, and examples thereof include those having a thickness of about 5 μm to 200 μm. Preferably, the thickness may be about 20 μm to 80 μm.

Further, the paperboard base paper used for the paper container of the present invention is not particularly limited in type, but includes, for example, pure white roll paper, kraft paper, coated cardboard, parchment paper, ivory paper, manila paper, card paper, and cup paper. In addition to paper, glassine paper, etc., water-resistant or oil-resistant treated paperboard or synthetic paper can be used, and the desired material may be selected depending on the purpose. Further, depending on the purpose of use, a combination of a resin film laminated onto a paperboard, a resin extruded by an extrusion lamination method, a resin-coated paperboard, etc. can be used. In particular, when used for food storage, it is preferable that a resin layer is formed on at least one side of the paperboard (the side that comes into contact with food) by an extrusion lamination method, and it is more preferable to use a paperboard that has resin layers formed on both sides.

Further, the thickness of the above-mentioned paperboard base paper is not particularly limited, but a thickness of about 0.1 to 0.5 mm (basis weight 100 to 500 g/m ² ) can be preferably used. In the paper container of the present invention, when wrinkles on the flange portion are flattened by ultrasonic processing or the like, the strength of the flange portion is improved, so that the strength against deformation of the entire container is increased. Therefore, it is possible to form a base paperboard with a thickness thinner than that of the conventional paperboard, and even when such a thin paperboard is used, it is possible to ensure strength comparable to that of the conventional paperboard.

Further, the interlayer strength of the paperboard base paper is preferably 500 mN/cm or more, more preferably 700 mN/cm or more in the case of the T-peel method. When using the test method according to the internal bond tester method (JAPAN TAPPI No. 18-2 "Paper and paperboard - Internal bond strength test method - Part 2: Internal bond tester method"), it must be 200 J/m ² or more is preferable, and more preferably 290 J/m ² or more. Paperboard base paper, which is normally used for forming paper containers, is composed of multiple pulp layers created by papermaking, so if the interlayer strength is low, delamination between the pulp layers is likely to occur, and buckling may occur during forming. It becomes easier. If the interlaminar strength of the base paperboard is 500 mN/cm or more in the case of the T-peel method or 200 J/ ^m2 or more in the case of the internal bond tester method, buckling of the base paperboard during paper container forming, especially at the hem wrap, can be avoided. It is possible to suppress the occurrence of buckling of the base paperboard during forming. There is no particular upper limit to the interlayer strength of the paperboard base paper, but in the case of the T-peel method, it is preferably 1500 mN/cm or less, more preferably 1000 mN/cm or less. In the case of the internal bond tester method, it is preferably 800 J/m ² or less, more preferably 500 J/m ² or less. When the interlaminar strength exceeds the above upper limit, the rigidity of the paperboard base paper becomes too high, which may reduce moldability or cause springback after molding. Here, the interlayer strength refers to the interlayer peel strength between the first layer and the second layer and between the second layer and the third layer. By controlling the interlaminar strength within the above range, delamination can be suppressed, and it becomes possible to particularly improve the formability of the hemline portion. In addition, when the paperboard base paper is composed of multiple pulp layers such as three or five layers, it is more preferable that the interlayer strength between any of the layers is within the above range.

Furthermore, it is desirable that the paperboard base paper has a predetermined folding strength. In the case of a paper container obtained by press-forming a sheet of paperboard base paper, the paper tends to tear easily on the side walls of the paper container, particularly at the corners where many wrinkles gather. This is because the portions of the base paper corresponding to the corners are three-dimensionally bent in the vertical direction by a mold during press molding, and external forces are applied from multiple directions to form multiple wrinkles. Therefore, the paperboard base paper used in this example has a folding resistance of 800 times or more in both the vertical and horizontal directions, as measured in accordance with JIS P8115 (2001) ``Test method for folding strength using MIT tester for paper and paperboard.'' It shall be 2000 times or less. More preferably, the number of folding cycles is 1000 or more and 1800 or less. If the paperboard base paper has a folding resistance of less than 800 times, there is a risk that the paper will tear during press molding, especially at the side walls of the paper container, especially at the corner parts. For paperboard base paper that can withstand more than 2,000 folds, the foldability of the paper is too strong, so springback tends to occur in the hem after press forming, which may reduce the shape retention of the paper container.

Furthermore, a resin film or coating may be laminated on the surface of the paperboard base paper. When forming a resin layer on at least one side of paperboard, the type of resin is not particularly limited. ) type resins, diene type resins such as polybutadiene, and thermoplastic resins such as polycarbonate type resins. In order to make a paper container more environmentally friendly, for example, the thermoplastic resin mentioned above may be manufactured as a biologically derived biomass resin, or a paper container made of biomass resin such as polybutylene succinate (PBS) or polylactic acid (PLA) may be used. Degradable resins can also be used. Among these, thermoplastic resins that are suitable for ultrasonic processing after forming paper containers are preferred, and in particular, thermoplastic resins that can withstand high-temperature heating in ovens and microwaves when used as packaging containers for food storage are preferred. More preferably, it is a thermoplastic resin having properties. Furthermore, if it is desired to provide a paper container with barrier properties that block or suppress the permeation of gas such as oxygen or water vapor, a resin having such barrier properties may be laminated with a film or coating. The type of resin having barrier properties is not particularly limited, but examples thereof include polyvinyl alcohol resin (PVA), ethylene vinyl alcohol copolymer resin (EVOH), polyvinylidene chloride resin (PVDC), and the like. Furthermore, films made of polyethylene terephthalate or polypropylene on which a metal vapor-deposited film such as aluminum or an inorganic vapor-deposited film such as silica or alumina are formed can also be used for the purpose of imparting barrier properties. Furthermore, a combination of a plurality of the various resins described above may be laminated on the surface of the paperboard base paper. For example, starting from the surface of the paperboard, the first resin layer is a polyolefin resin such as polypropylene or polyethylene, or the polyester resin such as polyethylene terephthalate or polybutylene terephthalate, and the second resin layer is ethylene vinyl. Laminate multiple resins, such as a resin with high gas barrier properties such as alcohol copolymer resin or polyvinyl alcohol resin, and a polyolefin resin or polyester resin as the third resin layer in the same way as the first layer. This can be exemplified. In particular, from the surface of the paperboard base paper, the first resin layer is polypropylene, the second resin layer is ethylene vinyl alcohol copolymer resin, and the third resin layer is polypropylene. In this case, it is preferable because it is possible to provide the paper container with high gas barrier properties, high heat resistance, good workability, and low raw material costs. Of course, this does not exclude laminating other resins or laminating other structures (for example, metal foil such as aluminum foil) in this configuration. Examples of methods for forming the resin layer include extrusion lamination, dry lamination, wet lamination, and coating with a resin solution. By laminating the resin, properties such as heat resistance, water resistance, and gas/liquid permeability can be imparted to the paper container after molding. In addition, if you want to impart high gas barrier properties to paper containers as described above, you can prepare a gas barrier resin film in advance, and when extrusion laminating another resin layer on the surface of the paperboard, you can apply it on top of that resin layer. It is also possible to adopt a method in which the gas barrier resin film is laminated on the gas barrier resin film. When such a method is used, a plurality of resin layers can be formed on the surface of the paperboard without using a separate adhesive. For example, as mentioned above, starting from the surface of the base paperboard, the first resin layer is a polyolefin resin such as polypropylene or polyethylene, or the polyester resin such as polyethylene terephthalate or polybutylene terephthalate, and the second layer is a polyolefin resin such as polypropylene or polyethylene, or a polyester resin such as polyethylene terephthalate or polybutylene terephthalate. The resin layer can be made of a resin with high gas barrier properties such as ethylene vinyl alcohol copolymer resin or polyvinyl alcohol resin, and the third resin layer can be made of polyolefin resin or polyester resin like the first layer. When laminating resins of When extrusion laminating a polyolefin resin such as polypropylene or polyethylene or a polyester resin such as polyethylene terephthalate or polybutylene terephthalate as a layer, this gas barrier resin film is laminated on the first resin layer. This makes it possible to easily impart gas barrier properties to paper containers. Therefore, it is also possible to use a known gas barrier resin film that is commercially available as a gas barrier resin film.

Furthermore, the thickness of the resin on the surface of the paperboard base paper is not particularly limited, but may range from 10 μm to 50 μm, for example. Particularly preferably, the thickness is within the range of 20 μm to 30 μm. However, in the case of laminating a plurality of resin layers as the resin layer as described above, this range may be exceeded. For example, in the case of laminating a plurality of resin layers, the total thickness is in the range of 10 μm to 200 μm. It is particularly preferably 30 μm to 100 μm, and even more preferably 50 μm to 70 μm. Within this range, desired effects can be provided by forming the resin layer. Furthermore, by forming a thick resin layer, when the flange portion is flattened, paper irregularities are less likely to appear on the surface of the flange portion, which contributes to further flattening of the flange portion. If the thickness of the resin layer is less than this range, there is a possibility that the desired effect of forming the resin layer cannot be expected, and if the thickness of the resin layer exceeds this range, the cost will increase. Furthermore, if the total thickness of a plurality of resin layers exceeds 200 μm, there is a risk that the container can no longer be called a paper container due to the thickness or weight of the paperboard base paper.

Furthermore, the surface of the above paperboard base paper may be printed. This makes it possible to improve the design.

Furthermore, although the above-mentioned base paperboard has ruled lines formed all around the parts corresponding to the side walls, flanges, and edge wraps, it is sufficient that they are formed in at least part of the side walls and flanges. . Further, it is also possible that no ruled lines are formed.

Furthermore, with reference to FIG. 4 (2) and FIG. 4 (3), the wrinkle pressing step is performed to form a flat portion by ultrasonic processing with respect to 100% of the cross-sectional thickness of the wrinkled paper container before ultrasonic processing. It is more preferable that the cross-sectional thickness of the wrinkled paper container is 70%. With this configuration, the wrinkles on the flange portion are reliably flattened compared to the wrinkles before ultrasonic processing, resulting in a paper container with further improved top sealability.

Furthermore, although the paper container according to the embodiment of the present invention is manufactured by a specific manufacturing method, it may be manufactured by another manufacturing method.

Furthermore, although the flange portion of the paper container according to the embodiment of the present invention was manufactured by pressing wrinkles using ultrasonic processing to form a flat portion, the flat portion was formed by pressing using a method other than ultrasonic processing. It may be a manufacturing method for forming.

The present invention will be specifically described below based on Examples. Note that the embodiments of the present invention are not limited to the examples.

Test specimens of Examples and Comparative Examples of the present invention were prepared, and these test specimens were tested to measure the thickness of the wrinkled paper container cross section, and to evaluate the adhesion of the top seal. A strength measurement test was conducted to measure the strength of the paper container.
<Preparation of test specimen>
・Example 1
First, a base paperboard is prepared on which a resin layer is formed on both sides and ruled lines are formed on the side wall corresponding part, the flange part corresponding part, and the edge wrapping part corresponding part (preparation process), and this paperboard base paper is press-formed. A paper container was formed by this (pressing process). The paperboard base paper has a thickness of about 0.3 mm, a basis weight of about 260 g/m ² , and is extrusion laminated with about 20 μm of polypropylene resin on each side. The paper container has a length of approximately 179 mm in the long side direction (including the flange) in plan view, a length of approximately 120 mm in the short side direction (including the flange), and a height of approximately 30 mm from the bottom to the flange. , the diameter of the hemline portion was approximately 3 mm. In addition, since the ruled lines of the paperboard are folded from the outer side of the container to the inner side of the container, the side wall and flange of the paper container after press forming are folded from the outer side of the container (lower surface of the flange) to the inner side of the container. Wrinkles are formed so as to be folded into the inner surface (upper surface of the flange portion) (hereinafter, a state in which wrinkles are formed so as to be folded from the outer surface of the container to the inner surface of the container is referred to as "reverse stitch").

Next, the paper container after press forming (after the pressing process) is placed on the pedestal of the ultrasonic processing device as shown in Fig. 5, and the ultrasonic horn is lowered from above the paper container, and the pedestal and the ultrasonic horn The flange of the paper container was sandwiched between the two, and ultrasonic vibration of 3.0 kW was applied to the flange for 0.5 seconds, and a pressure of 0.4 Mpa/cm ² was applied to crush the wrinkles from above and below (wrinkle pressing step). This paper container was designated as Example 1.
・Example 2
A paper container press-formed in the same manner as in Example 1 was subjected to ultrasonic vibration of 3.0 kW for 1.0 seconds on the flange using the same ultrasonic processing equipment as in Example 1, and was 0.4 Mpa/cm ² . Pressure was applied to crush wrinkles from above and below. This paper container was designated as Example 2.
・Example 3
A paper container press-formed in the same manner as in Example 1 was subjected to ultrasonic vibration of 3.0 kw for 1.5 seconds on the flange using the same ultrasonic processing device as in Example 1, and was 0.4 Mpa/cm ² Pressure was applied to crush wrinkles from above and below. This paper container was designated as Example 3.
・Example 4
In place of the paperboard base paper used in Example 1, the paperboard thickness is approximately 0.3 mm and the basis weight is approximately 260 g/m ² , and one side of the paperboard base paper is extrusion laminated with approximately 20 μm of polypropylene resin, and the other side is coated with paperboard. Starting from the surface of the base paper, the first resin layer is a polypropylene resin of about 20 μm, the second resin layer is an ethylene vinyl alcohol copolymer resin of about 20 μm, and the third resin layer is a polypropylene of about 20 μm. A paper container was press-molded in the same manner as in Example 1, except that a resin-layered paperboard base paper was used, so that the side of the paperboard base paper on which only polypropylene resin was formed was the outer surface of the container. Ultrasonic vibration of 3.0 kW was applied to the flange portion for 1.0 seconds using an ultrasonic processing device, and wrinkles were crushed from above and below by applying a pressure of 0.4 Mpa/cm ² . This paper container was designated as Example 4. In addition, the formation of the first to third resin layers on the paperboard base paper is performed using a composite film (gas barrier resin film) in which the second resin layer and the third resin layer are laminated. This gas barrier resin film was prepared in advance, and when extrusion laminating polypropylene resin as the first resin layer on the surface of the paperboard base paper, this gas barrier resin film was laminated on top of the first resin layer. .
・Example 5
In place of the paperboard base paper used in Example 1, the paperboard thickness is approximately 0.3 mm and the basis weight is approximately 260 g/m ² , and one side of the paperboard base paper is extrusion laminated with approximately 20 μm of polypropylene resin, and the other side is coated with paperboard. Starting from the surface of the base paper, the first resin layer is a polypropylene resin of about 20 μm, the second resin layer is an ethylene vinyl alcohol copolymer resin of about 20 μm, and the third resin layer is a polypropylene of about 20 μm. A paper container was press-molded in the same manner as in Example 1, except that a resin-layered paperboard base paper was used, so that the side of the paperboard base paper on which only polypropylene resin was formed was the inner surface of the container. Ultrasonic vibration of 3.0 kW was applied to the flange portion for 1.5 seconds using an ultrasonic processing device, and wrinkles were crushed from above and below by applying a pressure of 0.4 Mpa/cm ² . This paper container was designated as Example 5. Note that the formation of the first to third resin layers on the paperboard base paper was performed in the same manner as in Example 4.
・Example 6
A paper container was press-formed in the same manner as in Example 1, except that the formation of ruled lines on the base paperboard in the preparation process of Example 1 was performed in the manner described below, using the same ultrasonic processing device as in Example 1. Ultrasonic vibration of 3.0 kW was applied to the flange portion for 1.0 seconds, and a pressure of 0.4 Mpa/cm ² was applied to crush wrinkles from above and below. This paper container was designated as Example 6. Here, in obtaining the paper container of Example 6, the ruled lines of the paperboard base paper were formed such that the ruled lines of the portion corresponding to the side wall of the paper container after press molding were folded from the inner surface of the container to the outer surface of the container. At the same time, the ruled lines of the part corresponding to the flange of the paper container after press forming are formed so as to be folded from the outer side of the container to the inner side of the container, and the ruled lines corresponding to the wrinkles on the side wall and the wrinkles on the flange are formed. Between the ruled lines, there are places where the ruled lines are not connected to each other. As a result, the paper container after the pressing process but before the wrinkle pressing process using the ultrasonic processing device has wrinkles formed on its side wall so as to be folded from the inner surface of the container to the outer surface of the container (hereinafter referred to as , the state in which wrinkles are formed so as to be folded from the inner surface of the container to the outer surface of the container is called "sequential"), and the flange part has wrinkles with a reverse pattern, and the ultrasonic processing equipment The wrinkles on the flange part are crushed by the wrinkle pressing process using.
・Example 7
A paper container press-formed in the same manner as in Example 6 was subjected to ultrasonic vibration of 3.0 kW for 1.5 seconds on the flange using the same ultrasonic processing device as in Example 6, and was 0.4 Mpa/cm ² . Pressure was applied to crush wrinkles from above and below. This paper container was designated as Example 7.
・Comparative example 1
Comparative Example 1 was a paper container press-molded in the same manner as in Example 1. In other words, it is a paper container that has not been subjected to a wrinkle pressing process using an ultrasonic processing device.
・Comparative example 2
A paper container press-formed in the same manner as in Example 1 was wrinkled by simply applying a pressure of 0.4 Mpa/cm ² to the flange without applying a wrinkle pressing process using an ultrasonic processing device to the flange. I crushed it. This paper container was designated as Comparative Example 2. In other words, it is a paper container that has not been subjected to a wrinkle pressing process using an ultrasonic processing device.
・Comparative example 3
A paper container was formed by press-molding a paperboard base paper in which resin layers were formed on both sides and ruled lines were formed in the side wall corresponding portion, the flange portion corresponding portion, and the edge wrapping portion corresponding portion. The paperboard base paper has a thickness of about 0.3 mm, a basis weight of about 260 g/m ² , and is extrusion laminated with about 20 μm of polypropylene resin on each side. The paper container has a length of approximately 179 mm in the long side direction (including the flange) in plan view, a length of approximately 120 mm in the short side direction (including the flange), and a height of approximately 30 mm from the bottom to the flange. , the diameter of the hemline portion was approximately 3 mm. Furthermore, since the ruled lines of the paperboard are formed by folding from the inner surface of the container to the outer surface of the container, regular wrinkles are formed on the side wall and flange of the paper container after press molding. This paper container was designated as Comparative Example 3. That is, this is a paper container in which the direction of wrinkle formation is different from that in Example 1, and the paper container is not subjected to the wrinkle pressing process using an ultrasonic processing device.
・Comparative example 4
A paper container press-formed in the same manner as in Comparative Example 3 was subjected to ultrasonic vibration of 3.0 kW for 1.0 seconds on the flange using the same ultrasonic processing equipment as in Example 1, and 0.4 Mpa/cm ² pressure was applied to crush the wrinkles. This paper container was designated as Comparative Example 4. That is, this is a paper container in which the wrinkle formation direction is different from that in Example 1, and the wrinkle pressing process was performed using an ultrasonic processing device under the same conditions as in Example 2.
・Comparative example 5
A paper container press-formed in the same manner as in Comparative Example 3 was subjected to ultrasonic vibration of 3.0 kW for 1.5 seconds on the flange using the same ultrasonic processing device as in Example 1, and was 0.4 Mpa/cm ² . pressure was applied to crush the wrinkles. This paper container was designated as Comparative Example 5. That is, this is a paper container in which the wrinkle formation direction is different from that in Example 1, and the wrinkle pressing process was performed using an ultrasonic processing device under the same conditions as in Example 3.
・Comparative example 6
A paper container press-molded in the same manner as in Example 4 was designated as Comparative Example 6. In other words, it is a paper container that has not been subjected to a wrinkle pressing process using an ultrasonic processing device.
<Thickness measurement test, air leakage test, and strength measurement test of wrinkled paper container cross section>
・Test 1-1. Test for measuring the cross-sectional thickness of a wrinkled paper container The cross-sectional thickness of a paper container with wrinkles at four points on the flange was measured using a micrometer.

A micrometer manufactured by Mitutoyo Co., Ltd., product number: M110-25 was used.

Referring to FIG. 1, the measurement points were two on both sides in the longitudinal direction of the flange portion (measurement point A and measurement point C) and two points on both sides in the transverse direction (measurement point B and measurement point D).

The results were as shown in Table 1 below.

Next, the thickness (S2) of the cross section of the paper container at the wrinkles on the side wall connected below the measurement points A to D of each Example and Comparative Example was measured.

In order to compare the thickness of the wrinkled paper container cross section before and after ultrasonic processing on the flange part, we calculated the thickness of the paper container cross section with wrinkles on the flange part (S1)/thickness of the paper container cross section with wrinkles on the side wall part. The thickness (S2) was calculated. In this test, since the side wall was not subjected to ultrasonic processing, the cross-sectional thickness of the wrinkled paper container on the side wall was used as the thickness of the wrinkled paper container cross-section before the ultrasonic processing on the flange.

The results were as shown in Table 2 below.

Referring to Table 2, the four-point average of Examples 1 to 7, which were subjected to ultrasonic processing, was S1/S2<0.7. Further, the four-point average of Examples 2 to 7, in which ultrasonic processing was performed for 1.0 seconds or more, was S1/S2≦0.59. From the above measurement results, it was found that ultrasonic processing reliably flattens wrinkles. In addition, the four-point average of Comparative Example 4 and Comparative Example 5, which were subjected to ultrasonic processing, was S1/S2≦0.57.
・Test 1-2. Air Leakage Test A sample for the thickness measurement test of the cross-section of a wrinkled paper container was top-sealed, compressed air of 0.1 MPa was sealed and submerged in water, and air leakage from the sealing surface was visually confirmed. The sealing conditions were as follows: the heating temperature was 180 degrees, the heating time was 2 seconds, the pressure was 0.5 MPa/cm ² , and the number of times of sealing was 1.

Also, those with no air leakage were rated as ◎, those with a slight amount of air leakage that was less than those without ultrasonic processing and no compression, and those with air leakage that were defective were evaluated as ×.

The results were as shown in Table 3 below.

Referring to Table 3, it was confirmed that in all Examples 1 to 7, air leakage was reduced and top sealability was improved.

Further, in Examples 2 to 7 in which S1/S2<0.7, it was confirmed that air leakage was eliminated and the top sealing performance was further improved.
・Test 1-3. Oxygen gas permeability measurement test 1. Preparation of measurement samples The paper containers of Example 4 and Example 5 were prepared as measurement samples. In addition, as Example 5-2, in the paper container of Example 5, a paper obtained in the same manner as in Example 5 except that the second resin layer was an ethylene vinyl alcohol copolymer resin with a thickness of about 10 μm was prepared. Prepared the container. It should be noted that all paper containers have undergone a wrinkle pressing process. Next, a laminated film (manufactured by Mitsubishi Chemical Corporation, trade name Diamilon VM60) having a total thickness of 50 μm and having an easy-peel sealant layer configuration for EVOH (ethylene vinyl alcohol copolymer resin) / nylon / PP (polypropylene resin) was used. By dry laminating a 12 μm PET (polyethylene terephthalate resin) film, a lid material with top-sealing properties having a structure of PET/EVOH/nylon/easy-peel sealant layer was produced, and Example 4 and Example 5 And for the paper container of Example 5-2, the easy peel sealant layer of this lid material faces the paper container and is top-sealed to the flange portion of the paper container by heat sealing. A sealed paper container was prepared.
2. Measurement Test Using Measurement Samples The oxygen gas permeability of the top-sealed paper containers of Example 4, Example 5, and Example 5-2 obtained in 1 above was measured by a method based on JIS K7126-2.

The measuring device and measurement conditions were as follows, and the top-sealed paper container itself was used as a measurement sample for measurement.
Measuring device: OX-TRAN2/21 (manufactured by MOCON)
Temperature and humidity: 23°C 50% RH air (outer test gas), 23°C dry nitrogen (inner carrier gas)
Permeated gas: Air (21% oxygen)
Transmission direction: from outside to inside The transmission results are as shown in Table 4 below.

Referring to Table 4, it was confirmed that the top-sealed paper containers of Example 4, Example 5, and Example 5-2 obtained in 1 above all had good oxygen gas permeability. In addition, Examples 4 and 5, in which the second resin layer is an ethylene vinyl alcohol copolymer resin with a thickness of about 20 μm, have a higher oxygen gas content than Example 5-2, in which the second resin layer is an ethylene vinyl alcohol copolymer resin with a thickness of about 10 μm. It was confirmed that the permeability was improved.
・Test 2. Strength measurement test I. Preparation for measurement test As examples, Examples 1 to 3 described above were prepared.

As a comparative example, Comparative Example 1 described above was prepared.

Using these Examples and Comparative Examples, the respective circumferential strengths (longitudinal direction, transverse direction) were measured.

As a measuring device, a material testing machine "Autograph" (registered trademark) manufactured by Shimadzu Corporation and its data processing software "TRAPEZIUM" (registered trademark) were used.

The measurement test was based on the circumferential direction test of "TRAPEZIUM" (registered trademark), but the value of the switching stroke was changed from 10 mm to 20 mm.
II. Longitudinal Direction Measurement Test FIG. 6 is a schematic diagram showing a measurement test performed on the paper container shown in FIG. 1.

Referring to FIG. 6, the paper container 1 was pressed from the direction indicated by the arrow in the figure while the lower end was fixed by the measuring device 30, and the stress was measured by the measuring device 30.

The measurement test was performed on three samples each of the examples and comparative examples, and the arithmetic mean of the three tests was calculated and used as the result of the measurement test.

FIG. 7 is a graph showing the results of the measurement test shown in FIG. 6, where (1) is the result in the longitudinal direction and (2) is the result in the transverse direction.

Referring to (1) in FIG. 7, when the same test force [N] is applied to the paper containers of the example and comparative example in the longitudinal direction, the amount of deformation [mm] of the example is greater than that of the comparative example. It was found that it decreased. Further, among Examples 1 to 3, it was found that Example 3, in which the ultrasonic machining time was the longest, had the greatest reduction in the amount of deformation [mm].
III. Measurement test in the transverse direction The measurement method was the same as the measurement test in the longitudinal direction described above, except that the paper container was tilted at 90 degrees.

Referring to (2) in FIG. 7, it was found that when the same test force was applied to the paper containers of the example and the comparative example in the transverse direction, the amount of deformation of the example was lower than that of the comparative example. Ta. Further, among Examples 1 to 3, it was found that Example 3, in which the ultrasonic machining time was the longest, had the greatest reduction in the amount of deformation [mm].

From the results of the above measurement tests, it was confirmed that the strength of the ultrasonically processed paper container of the present invention is improved.

1... Paper container 2... Bottom part 3... Side wall part 4... Flange part 5... Edge wrapping part 6... Wrinkle 10... Paperboard base paper 14... Flange part corresponding part 21... Ruled line 28... Flat part 29... Lid material having top sealing property S1...Cross-sectional thickness of wrinkled paper container with flat portion S2...Cross-sectional thickness of wrinkled paper container without flat portion Note that the same reference numerals in each figure indicate the same or equivalent portions.

Claims (11)

It is formed only by press molding from a sheet of paperboard with a resin layer formed on at least the inner surface of the container, and has a bottom, a side wall connected to the bottom, an upper end of the side wall, and an outer surface. A paper container comprising a flange portion extending horizontally toward the side,
The side wall portion and the flange portion have a plurality of wrinkles formed by press molding,
The wrinkles of the flange portion are formed by folding from the lower surface to the upper surface of the flange portion,
A paper container, wherein the wrinkles appearing on the upper surface of the flange portion have a flat portion formed at least in part. The outer peripheral edge of the flange portion is provided with an edge wrapping portion,
The paper container according to claim 1, wherein the highest portion of the hemline portion is located at the same height as or below the upper surface of the flange portion. The ratio (S1/S2) of the cross-sectional thickness (S1) of the wrinkled paper container having the flat portion to the cross-sectional thickness (S2) of the wrinkled paper container not having the flat portion is 0.7 or less. , the paper container according to claim 1 or claim 2. The paper container according to claim 1 or 2, wherein the wrinkles of the flange portion are formed based on a plurality of ruled lines formed on a portion of the base paperboard corresponding to the flange portion. The paper container according to claim 1 or 2, wherein the wrinkles on the side wall are formed by folding from the inner surface to the outer surface of the side wall. A top-seal paper container comprising the paper container according to claim 1 or 2 and a lid material having top-sealing properties. a preparation process for preparing paperboard base paper;
By pressing the paperboard base paper, a bottom part, a side wall part connected to the bottom part, and a side wall part connected to the upper end of the side wall part, extending outward in the horizontal direction and folded into the top surface from the bottom surface to the top surface are formed. a pressing step of forming a paper container comprising a flange portion having wrinkles formed therein;
A method for manufacturing a paper container, comprising a wrinkle pressing step of forming a flat portion in at least a portion of the wrinkle. 8. The method for manufacturing a paper container according to claim 7, wherein the wrinkle pressing step includes ultrasonic processing on the wrinkles. 9. The method for manufacturing a paper container according to claim 8, wherein a resin layer is formed on at least a surface of the paperboard that is the inner surface of the container, and the resin layer is melted by the ultrasonic processing. 9 . The wrinkle pressing step reduces the cross-sectional thickness of the wrinkled paper container having the flat portion by the ultrasonic processing to 70% or less with respect to 100% of the cross-sectional thickness of the wrinkled paper container before the ultrasonic processing. A method for producing the paper container described above. 7. The top seal paper container according to claim 6, wherein a resin layer having barrier properties is formed on the paper container and the lid material.

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