JP2022110341A - paper tray - Google Patents

Abstract

To provide a three-dimensional paper tray having a flat flange part and an excellent twist resistance.SOLUTION: A paper tray 1 is formed by three-dimensional moulding of a laminate 2 formed of a paper substitute 3 with a basis weight of 30 g/m2 or more and 700 g/m2 or less, and a liner material 4. The paper tray includes a horizontal bottom part 5, a side wall part 6 rising from the bottom part, a horizontal flange part 7 extended from an upper part of the side wall part, and a ribs 8 continued from a tip end of the flange part diagonally downward.SELECTED DRAWING: Figure 1

Description

The present invention relates to a paper tray having a three-dimensional shape, and in particular, having a flat flange improves the sealing performance of the lid member, and having ribs connected from the flange improves rigidity against twisting. Regarding paper trays.

Plastic containers made from fossil resources are widely used, but from the viewpoint of global environmental protection, such as the problem of marine pollution caused by waste plastic, wood, which is a renewable resource and biodegradable, is used as a raw material. Containers made of paper that is easy to store are attracting attention.

The paper container described in Patent Document 1 is a paper container in which a paper base that has been punched into a predetermined shape in advance is mounted in a vacuum pressure molding die, covered with a plastic sheet as a liner from above, and integrated by vacuum pressure molding. be. According to this method, a paper container having a three-dimensional shape can be obtained, but it cannot be manufactured at a low cost due to poor productivity. Also, the three-dimensional shape is a polyhedral shape that is a set of planes, and is not a three-dimensional shape with curved surfaces.

The paper tray described in Patent Document 2 is a paper tray composed of a bottom portion, a side wall portion, and a flange portion. A plurality of ruled lines of two types with different lengths extending from the edge of the blank to the middle of the side wall portion are provided at a location corresponding to Half or full cuts are provided in the thickness direction of the paper extending from the middle of the ruled line to the interface between the bottom and the side wall, and the blank is formed into the shape of the bottom, side wall and flange by pressing. A paper tray characterized by being formed.

The paper tray described in Patent Document 2 has a three-dimensional shape by adding ruled lines and cuts to the corners. It also adversely affects the strength of the tray. In addition to the paper tray described in Patent Document 2, three-dimensional trays made of paper have been known for some time. It could not be used for applications that required sealing with material.

A paper tray that does not use a lid does not require a flange in the first place, and it is possible to increase the torsional rigidity by curling the edges. However, curling causes extra process costs, lowers production speed, and increases costs.

On the other hand, in a tray-shaped container made of plastic rather than paper, it is easy to form a flat and smooth flange. is also commonly done. Conventionally, however, it has been difficult to combine all of these characteristics in paper trays.

WO2019/177652 Japanese Patent No. 5083813

The problem to be solved by the present invention is to propose a three-dimensional paper tray having a flat flange portion and excellent torsional rigidity.

As a means for solving the above problems, the invention according to claim 1 provides a three-dimensional laminate comprising a paper base material having a basis weight of 30 g/m ² or more and 700 g/m ² or less and a liner material. A molded paper tray comprising a horizontal bottom, side walls rising from the bottom, horizontal flanges extending from the upper ends of the side walls, and obliquely downward from the tip of the flanges. A paper tray characterized by having ribs.

Since the paper tray according to the present invention has ribs extending obliquely downward from the tip of the horizontal flange, the torsional rigidity is improved.

The tip of the rib that is continuously provided obliquely downward from the tip of the flange portion may further extend in the horizontal direction.

More preferably, the basis weight of the paper substrate used for the paper tray according to the present invention is 100 g/m ² or more and 400 g/m ² or less.

The paper substrate has a tensile elongation at break of 2% or more and 12% or less in the MD direction (machine direction), 0.5% or more and 15% or less in the TD direction (perpendicular direction), and a tensile strength of 50 N/15 mm in the MD direction. 500 N/15 mm or less, and 30 N/15 mm or more and 400 N/15 mm or less in the TD direction.

The paper substrate has a tensile elongation at break of 3% or more and 11% or less in the MD direction and 1% or more and 14% or less in the TD direction, and a tensile strength of 100 N/15 mm or more and 400 N/15 mm or less in the TD direction. More preferably, it is 80 N/15 mm or more and 300 N/15 mm or less.

The paper tray according to the present invention is formed by three-dimensionally forming a laminate consisting of a paper base material and a liner material, and has a wrinkle-free horizontal flange, so that it can be used as an airtight container by sealing the lid material. be able to.

In the paper tray according to the present invention, the torsional rigidity of the tray is improved by providing the rib extending obliquely downward at the tip of the flange portion. It works more effectively when the tip of the rib, which is continuously provided obliquely downward from the tip of the flange portion, extends further in the horizontal direction.

The paper tray according to the present invention can realize a smooth three-dimensional shape with a corresponding depth by selecting the paper base material and the liner material, so that the range of design is widened.

The paper tray according to the present invention can be efficiently produced using a molding method such as a pressure forming method, a vacuum pressure forming method, a hot plate pressure forming method, or the like.

FIG. 1 is a perspective explanatory view showing one embodiment of a paper tray according to the present invention. FIG. 2 is a cross-sectional explanatory view showing the AA' cross section of FIG. FIG. 3 is a perspective explanatory view showing another embodiment of the paper tray according to the present invention. FIG. 4 is a cross-sectional explanatory view showing a BB′ cross section of FIG. FIG. 5 is a perspective explanatory view showing an example of a conventional ribless paper tray. FIG. 6 is a cross-sectional explanatory view showing a CC' cross section of FIG.

A paper tray according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a perspective explanatory view showing one embodiment of a paper tray 1 according to the present invention. FIG. 2 is a cross-sectional explanatory view showing the AA' cross section of FIG.

A paper tray 1 according to the present invention is a paper tray obtained by three-dimensionally forming a laminate 2 comprising a paper base material 3 having a basis weight of 30 g/m ² or more and 700 g/m ² or less and a liner material 4. It comprises a horizontal bottom portion 5, a side wall portion 6 rising from the bottom portion 5, a horizontal flange portion 7 extending from the upper end of the side wall portion 6, and an end of the flange portion 7 extending obliquely downward. The paper tray is characterized by having ribs 8. In addition, the bottom portion 5 does not need to be a simple flat surface, and may have rib-like unevenness.

The basis weight of the paper base material 3 must be 30 g/m ² or more and 700 g/m ² or less, and more preferably 100 g/m ² or more and 400 g/m ² or less. If it is less than 30 g/m ² , it will be difficult to bond it with the liner material, and if it exceeds 700 g/m ² , the paper will be too strong and difficult to form into a tray shape.

The tensile elongation at break of the paper substrate is 2% or more and 12% or less in the MD direction (machine direction), 0.5% or more and 15% or less in the TD direction (perpendicular direction), and the tensile strength is 50 N/15 mm or more in the MD direction. It is desirable to be 500 N/15 mm or less, 30 N/15 mm or more and 400 N/15 mm or less in the TD direction.

In this way, the grammage, tensile elongation at break, and tensile strength of the paper base material 3 are calculated based on the respective values in the MD direction (Machine Direction = machine direction, papermaking direction) and TD direction (Transverse Direction = vertical direction, width direction). Three-dimensional moldability is ensured by defining the range.

The tensile elongation at break of the paper substrate 3 is desirably 2% or more and 12% or less in the MD direction (machine direction) and 0.5% or more and 15% or less in the TD direction (perpendicular direction), more preferably in the MD direction. They are 3% or more and 11% or less, and 1% or more and 14% or less in the TD direction. When the MD direction is less than 2% and the TD direction is less than 0.5%, elongation is insufficient during molding, and the film may break. It is difficult and unrealistic to produce paper that exceeds 12% in the MD direction and 15% in the TD direction.

The tensile strength of the paper substrate 3 is preferably 50 N/15 mm or more and 500 N/15 mm or less in the MD direction, and 30 N/15 mm or more and 400 N/15 mm or less in the TD direction, and more preferably 100 N/15 mm or more in the MD direction. 400 N/15 mm or less, 80 N/15 mm or more and 300 N/15 mm or less in the TD direction. If it is less than 50 N/15 mm in the MD direction and less than 30 N/15 mm in the TD direction, the strength may be insufficient and the film may break during molding. Moreover, paper exceeding 500 N/15 mm in the MD direction and 400 N/15 mm in the TD direction is too hard and difficult to mold, which is not realistic.

The shape of the paper container is not limited to the example shown in FIG. 1, and may be circular, elliptical, square, rectangular, star-shaped, or any other shape that can be formed. In relation to the drawing depth, it is necessary that the flange portion, bottom portion, side wall portion, etc. have a shape that does not cause wrinkles.

It has been experimentally confirmed that the paper tray 1 according to the present invention has ribs 8 extending obliquely downward from the tip of the flange portion 7, thereby improving the rigidity against twisting. The angle and length of the ribs 8 are not particularly restricted.

FIG. 3 is a perspective explanatory view showing another embodiment of the paper tray 1 according to the present invention. FIG. 4 is a cross-sectional explanatory view showing a BB′ cross section of FIG. This example is characterized in that the tip 9 of the rib 8 that extends obliquely downward from the tip of the flange portion 7 further extends in the horizontal direction.

By doing so, the rigidity against twisting of the paper tray 1 is further improved. The length of the horizontal portion of the tip 9 of the rib 8 is not particularly restricted. As for the shape of the rib 8, other than the shape shown in FIGS.

The material of the paper base material 3 constituting the laminate 2 is not particularly limited as long as it has moldability for the desired shape. Examples include white paperboard such as manila balls and white balls, yellow chipboard, colored paperboard, base paper for corrugated board, art paper, coated paper, base paper for cards, kraft paper, and base paper for cups. For example, fiber foam paper made for molding can also be suitably used. A material obtained by bonding two sheets of paper together with a thermoformable synthetic resin such as polyethylene resin can also be used.

As the material of the liner material 4, a moldable synthetic resin film can be used singly or in combination. Examples include polyethylene resin (PE), polypropylene resin (PP), unstretched polypropylene resin (CPP), heat-sealable polyethylene terephthalate resin (HS-PET), polyvinylidene chloride resin (PVDC), ethylene vinyl alcohol copolymer. Coalescing (EVOH), polyacrylonitrile resin (PAN), various biodegradable resins can be used. Examples of biodegradable resins include polybutylene succinate resin (PBS), polylactic acid resin (PLA), polyhydroxyalkanoic acid resin (PHA), poly(butylene adipate/terephthalate) resin (PBAT), polycaprolactone resin ( PCL), poly(hydroxybutyrate/hydroxyhexanoate) resin (PHBH (registered trademark)), and the like.

As the liner material 4, a sealant having a barrier property in the innermost layer such as paper substrate/adhesive resin/barrier sealant may be used. Examples of barrier sealants include Diamilon MF (manufactured by Mitsubishi Chemical Corporation) and Multitron ZEX (manufactured by Tamapoly Corporation).

As the liner material 4, a multilayer film formed by co-extrusion of two or more layers such as PE/EVOH/PE can be used.

As a method for forming the paper tray according to the present invention, a forming method such as a press forming method, a vacuum forming method, a pressure forming method, a vacuum pressure forming method, or a hot plate pressure forming method can be used. Even so, in order to prevent wrinkling of the flange portion, it is necessary to hold or fix the flange portion during molding so that the paper is not drawn from the flange portion into the concave portion of the container during molding.

Specifically, in pressure forming, vacuum pressure forming, and hot-plate pressure forming, the front, rear, left, and right sides of the paper substrate are clamped at the height of the flanges, and then formed. In press molding, good results can be obtained by pressing the flange face presser with a part of the convex mold or a separately driven plate prior to the convex mold entering from the plane of the flange of the concave mold.

As the material used as the cover material of the paper tray according to the present invention, an easy peel film capable of cohesive peeling, interfacial peeling, or interlaminar peeling is preferable. An easy peel layer may also be provided on the tray side. Examples of the easy peel film include CF film 9501A and 9501F (manufactured by Toray Industries, Inc.), SMX (manufactured by J Film Co., Ltd.), and the like. The paper container 1 according to the present invention will be specifically described below based on Examples and Comparative Examples.

<Example 1>
As the paper base material, two sheets of paper having a basis weight of 150 g/m ² were laminated together by extrusion lamination using polyethylene resin. A multilayer barrier film (ZEX101, 50 μm, manufactured by Tamapoly Co., Ltd.) as a liner material was similarly laminated by extrusion lamination using a polyethylene resin to obtain a laminate.

Using this laminate, a paper tray having a cross-sectional shape as shown in FIGS. 3 and 4 was produced by hot platen pressure molding. The dimensions of the tray are 117 mm short side, 154 mm long side, and 20 mm deep. This tray was evaluated for liquid leakage (sealing property), impact resistance, and twist resistance.

<Evaluation method>
Leakage: Pour in the penetrant, seal it with a lid, and check for leaks after storage over time (temperature 40°C, humidity 75%, 1 month).
Impact resistance: 200 g of content is put into the container, and a drop and vibration test is carried out based on JIS Z0200 to confirm the shape change.
Twisting resistance: A paper tray was set in a torque meter (TNP-10 manufactured by Nidec-Shimpo Co., Ltd.), and the value was measured when the flange surface was twisted by 45°. Measured in each of the long side direction and the short side direction.

<Comparative Example 1>
As Comparative Example 1, using the same material and method as those used in the Examples, a conventional paper tray without ribs as shown in FIGS. 5 and 6 was produced. This paper tray was evaluated in the same manner as in Examples.

<Comparative Example 2>
A paper tray was produced in the same manner as in Examples, except that the flange portion was not fixed during molding. Since the molding was performed without fixing the flange portion, wrinkles were generated in the flange portion. This paper tray was evaluated in the same manner as in Examples.

<Comparative Example 3>
As a result of molding the rib-free paper tray used in Comparative Example 1 without fixing the flange portion, a paper tray was produced in which wrinkles were generated in the flange portion. This paper tray was evaluated in the same manner as in Examples.
Table 1 summarizes the above evaluation results.

From Table 1, it can be seen that the provision of the ribs nearly doubles the torque value and helps improve the impact resistance in addition to the resistance to torsion. It was found that the paper tray according to the present invention has higher rigidity against twisting, better sealing performance, and better impact resistance than conventional products.

REFERENCE SIGNS LIST 1 Paper tray 2 Laminate 3 Paper substrate 4 Liner material 5 Bottom 6 Side wall 7 Flange 8 Rib 9・・・Rib tip

Claims (5)

A paper tray formed by three-dimensionally forming a laminate consisting of a paper substrate having a basis weight of 30 g/m ² or more and 700 g/m ² or less and a liner material, and has a horizontal bottom and side walls rising from the bottom. a horizontal flange portion extending from the upper end of a side wall portion; and ribs extending obliquely downward from the tip of the flange portion. 2. The paper tray according to claim 1, wherein the tip of the rib extending obliquely downward from the tip of the flange further extends in the horizontal direction. The paper tray according to claim 1 or 2, wherein the paper base material has a basis weight of 100 g/ ^m2 or more and 400 g/ ^m2 or less. The paper substrate has a tensile elongation at break of 2% or more and 12% or less in the MD direction (machine direction), 0.5% or more and 15% or less in the TD direction (perpendicular direction), and a tensile strength of 50 N/15 mm in the MD direction. 4. The paper tray according to any one of claims 1 to 3, wherein the tension is 500 N/15 mm or less and 30 N/15 mm or more and 400 N/15 mm or less in the TD direction. The paper substrate has a tensile elongation at break of 3% or more and 11% or less in the MD direction and 1% or more and 14% or less in the TD direction, and a tensile strength of 100 N/15 mm or more and 400 N/15 mm or less in the TD direction. 5. The paper container according to any one of claims 1 to 4, wherein the paper container has a tensile strength of 80 N/15 mm or more and 300 N/15 mm or less.

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