JP2000355366A - Easy-open lid material for paper containers - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and inexpensively manufacture a lid member which is excellent in openability while being made only of a resin which is high in safety by a method wherein an emboss processing is applied to the interior side of a base paper constituting the lid member and a thermoplastic synthetic resin layer is laminated on the processed surface with the surface roughness measured by a tracer method at the laminated surface specified. SOLUTION: A paper container is formed in a cup-like shape with its upper part opened and a synthetic resin layer is provided at the interior side of the container mnain body 1, and a flat flange part 2 is formed at the opening. Then, a lid body 4 is heat sealed to the flange part 2 through a heat sealing part 3 and the opening is sealed up therewith. The lid body 4 is made up by using a base paper similar to that used for the container main body 1. The thickness of the base paper is set as 0.05-2 mm and a specified emboss processing is applied to the base paper. While the depth of embossment is set as 0.01-5 mm, the surface roughness measured by a tracer method at the surface of the synthetic resin layer is set as 10-200 μm by R max. Thereby, a desired easiness for opening is ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper-made lid material for a container in which snack foods, frozen foods, liquid foods and the like are put and a lid is heat-sealed on a flange portion or a top curl portion.

[0002]

2. Description of the Related Art Paper containers are widely used because they are inexpensive and can be mass-produced, and because they are easy to incinerate and landfill for disposal as waste and have high safety. When used for contents such as foods, a synthetic resin layer is often laminated not on paper alone but on the inner side of the container. In the present invention, since this type of paper container is targeted, a case having a synthetic resin layer on the inner surface is hereinafter referred to simply as "paper container" or "paper container".

[0003] As a form of a container for storing and packing food and the like in a paper container having the above-mentioned synthetic resin layer on the inner surface, a flat flange portion is provided at an opening portion (top portion) of the container or a top portion is provided. A shape having a curled portion is usual. In some cases, after the top curl portion is formed, it is formed into a shape like a flange portion by press molding. These are collectively referred to as “flange portion or the like” below in the present invention.

When the contents are put into a paper container having a flange or the like and the lid is closed, a sheet-like lid obtained by laminating a synthetic resin layer on the base paper is placed so that the synthetic resin layer becomes the inner surface of the container (flange). A method of heat-sealing the lid and the container flange portion so as to make contact with the synthetic resin layer of the portion, etc.) is adopted as the simplest method. The present invention is directed to a lid that is heat-sealed in such a manner. Hereinafter, even when the cover is made of paper, it has a synthetic resin layer.

In this case, the opening (top part) of the container is
Since it is necessary to seal to the extent that the contents do not leak, it is desired to increase the temperature and pressure of the lid seal. However, it was difficult to open the lid when the consumer tried to peel off the lid by hand with a strong seal.

In a plastic container, there is no problem that the container is distorted or the paper layer is not broken even if the container is strongly peeled. However, in the case of a paper container, if the container is peeled off with a strong force, the container may be crushed. However, there is a problem that the paper layer peels off and becomes messy. For this reason, methods such as selecting a hot-melt agent that can be peeled off with an appropriate force and using a peeling agent such as silicone have been proposed, but have problems such as high manufacturing cost, safety, and odor. is there.

[0007]

SUMMARY OF THE INVENTION The present invention proposes an easy-to-open lid material for paper containers which can be manufactured very simply at a low cost, can be manufactured simply with a highly safe resin, and can be opened with an appropriate force. That is the task.

[0008]

In order to solve the above problems, the present invention employs the following constitution. (1) A tray-shaped or cup-shaped paper container having a synthetic resin layer on the side to be the inner surface of the container and having an open top,
The opening portion is a sheet-like lid material that is heat-sealed to a container having a flat flange portion or a top curl portion, and the lid material is embossed on a side to be the inner surface of the base paper container, and the surface is made of a thermoplastic material. The synthetic resin layer is laminated, and the stylus type surface roughness of the surface of the synthetic resin layer is R
An easily openable lid material for a paper container having a maximum of 10 μm to 200 μm.

(2) In the invention of the above (1), the thickness of the base paper is 0.05 to 2 mm, and the base paper has a depth of 0.01 mm.
An easily-openable lid material for a paper container, which is embossed to a thickness of 0.2 mm and a thickness of the thermoplastic synthetic resin layer is smaller than the emboss depth.

(3) An easy-opening lid for a paper container according to the invention (1), wherein the thermoplastic synthetic resin is a polyolefin resin.

(4) In each of the present inventions, the shape of the peak of the emboss is preferably a square or a circle, and the side or diameter is preferably about 0.5 mm to 2 mm. The vertical and horizontal pitch (interval) between each emboss is 0.2
It is desirably about 1.0 mm.

(5) In each of the present inventions, it is preferable that the embossed concavo-convex area ratio is 9: 1 to 1: 9.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The form of the paper container to which the present invention is applied includes, for example, a rectangular container with a flange as shown in FIG. 1 and a paper cup type container as shown in FIG. As the configuration of the container, at least one paper layer and at least one synthetic resin layer are required. As the paper layer, paperboard having a basis weight of about 100 to 700 g / m ² is preferable, and as a pulp type, NBKP is most preferable. However, LBKP, deinked waste paper pulp and the like may be used, and there is no particular limitation.

The synthetic resin layer laminated on the paper layer has a thickness of 5 to 5.
It is about 100 μm. The synthetic resin is most preferably a polyolefin resin, but may be any of commonly used resins such as polyester, nylon, polystyrene and polycarbonate. As the polyolefin resin, those obtained by homopolymerizing or copolymerizing monomers such as ethylene, propylene, butene, and methylpentene can be used.

As the base paper for the lid material of the present invention, the same paper as the paper for the above-mentioned container can be used. The thickness of the cover base paper is about 0.05 to 2 mm. In addition, both the container and the lid may have an aluminum foil layer, a film layer, or the like on the outer surface of the paper, and may be printed. Further, a coating layer or the like for improving adhesion may be provided between the paper layer and the synthetic resin layer on the inner surface of the container.

The embossing of the cover base paper can be carried out by a device usually used in the field of paper and paperboard, such as a molding machine or an embossing calendar. For example, a method is possible in which paper is passed while applying pressure between two rolls, at least one of which is an engraving roll. As a combination of rolls, there are a combination of two steel rolls with one another, a combination of one roll with an engraving roll and the other with an elastic roll, and the like. The combination of the embossing depths can be the deepest, but there is a processing limit that does not cause any breakage depending on the size, material, and density of the base paper. Generally, two embossing rolls related to a paper container are used, and a continuous pattern engraved on a metal roll by a combination of a metal roll and a rubber roll is stamped on a base paper surface after roll pressing.

The embossing depth is preferably about 0.01 to 0.5 mm, and the value of Rmax is 10 μm to 200 μm in the measurement of the stylus type surface roughness on the surface of the synthetic resin after laminating the synthetic resin. Then, the object of the present invention is achieved. The average thickness of the synthetic resin layer is smaller than the value of the emboss depth, and is 0.005 mm to 0.49 mm.
mm.

The operation of the present invention will be described below.
The phenomenon that occurs when the lid material is peeled from the container is (1)
Three modes of interfacial peeling, (2) cohesive failure, and (3) delamination can be considered. Interfacial delamination is the separation between the synthetic resin layer of the lid material and the synthetic resin layer of the container, and cohesive failure occurs when the cohesive force of either synthetic resin is weak. The case where the synthetic resin layer laminated on the paper layer of the container is separated from the paper layer of the container is delamination. In the case (4), the synthetic resin layer of the lid may be peeled off from the paper layer of the lid.
This phenomenon is generally poor opening.

The present invention is characterized in that the cover base paper is preliminarily embossed and then a synthetic resin laminate is formed on the uneven surface of the base paper. As a result, the thin and thick portions of the laminate layer are partially scattered, so that the adhesion between the thin protrusion of the lid resin and the container can be weakened, and the lid and the container are made of the same material (such as PE). Even if there was, it was confirmed that the lid had easy-openability. That is, in the case of the present invention, the opening torque of the container lid can be reduced to 1 kgf or less due to the partial occurrence of the phenomenon (2) or (3). In some cases, the phenomenon (4) may occur microscopically. However, in the case of the embodiment of the present invention, since the phenomenon does not occur continuously, there is an advantage that opening failure does not occur.

[0020]

EXAMPLE A pulp made of NBKP, having a thickness of 0.1 mm.
A material obtained by extruding and laminating 50 μm of polyethylene on a paperboard for a food container having a density of 5 mm and a density of 0.7 was cup-formed into a normal paper cup having a bottom plate so that the polyethylene layer became the inner surface of the container, and top curling was performed. Separately from this, a single-sided embossing process is performed on a 200 μm-thick paper of the same material as shown in FIG. 5 to a depth of 0.05 mm, and polyethylene is extruded on the embossed surface to a thickness of 30 g / m ^2. Lamination was performed and punched to a predetermined size to prepare a lid material. The contact surface roughness of the polyethylene surface was 20 μm in Rmax. Place the lid on the cup container so that the polyethylenes are in contact with each other.
Heat sealing was performed at a pressure of g / m ² . The seal portion was cut into a predetermined size to prepare a sample having a width of 10 mm, and the peel strength was measured with Tensilon. Peel strength is 0.8kg
f / 10 mm, and was smooth after peeling.
For comparison, a comparative example was prepared in the same manner as in the example except that embossing was not performed. The peel strength of the comparative example was 1.2 kgf / 10 mm, and the paper layer of the container was exposed and could not be peeled cleanly.

[0021]

Conventionally, if the container resin is an olefin-based resin such as PE, the outermost surface of the lid material in contact with the container can be easily opened unless a special easy-opening hot melt or a special synthetic resin is used. However, the use of the present invention makes it possible to obtain a necessary easy-opening function using a relatively inexpensive general-purpose PE or the like.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the shape of a container to which the present invention is applied.

FIG. 2 is a schematic sectional view showing the shape of a container to which the present invention is applied.

FIG. 3 is a schematic sectional view of a conventional lid.

FIG. 4 is a schematic sectional view of a lid according to the present invention

FIG. 5 shows an example of an emboss pattern

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container main body 2 Flange part 3 Heat seal part 4 Lid material 5 Thermoplastic resin layer 6 Emboss part 7 Emboss pitch

Claims (3)

[Claims] 1. A tray-shaped or cup-shaped paper container having an open top and having a synthetic resin layer on the inner surface side of the container, the opening having a flat flange portion or a top curl portion. In a sheet-like lid material which is heat-sealed, the lid material is formed by embossing the side of the base paper which is to be the inner surface of the container, and laminating a thermoplastic synthetic resin layer on the surface, and An easily-openable lid material for a paper container, wherein a stylus type surface roughness of the resin layer surface is 10 μm to 200 μm in Rmax. 2. A base paper having a thickness of 0.05 to 2 mm,
2. The paper container according to claim 1, wherein the base paper is embossed to a depth of 0.01 to 0.5 mm, and the thickness of the thermoplastic synthetic resin layer is smaller than the emboss depth. Lid material. 3. The easy-opening lid material for a paper container according to claim 1, wherein the thermoplastic synthetic resin is a polyolefin resin.