JPS6350192B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method of manufacturing a food packaging container.

More specifically, the present invention relates to an improvement in a method for manufacturing food packaging containers that enables retort sterilization and significantly enriches the variety of filling materials.

In recent years, containers for food packaging such as liquid beverages, whose main body is a cylindrical body made by laminating and bonding laminated sheets of synthetic resin, paper, and aluminum foil as appropriate, are rolled up, stacked, and welded at both ends. It is being used in large numbers because of its light weight, excellent display properties as a container, printability, and ease of incineration.

However, such food packaging containers
Most containers use low-density polyethylene resin alone, which has good sealing properties, for both outer layers of the cylindrical body, which is the main body of the container, and the joints of the cylindrical bodies are simply overlapped and welded. No special efforts were made.

On the other hand, retort sterilization is known as a relatively inexpensive device and harsh sterilization conditions under high temperature and pressure.

However, if retort sterilization is performed at a temperature of about 120°C with a conventional container configured as described above, the low-density polyethylene resin on the surface of the container will melt, and the outer surface of the container will melt. When sterilized by placing a large amount of them side by side, they fuse together, and when they are separated after sterilization, the film peels off. On the other hand, on the inner surface of the container, rough skin and pinholes occur, causing problems in terms of appearance and food hygiene. In addition, the strength of the joints between the container cylinder and the lid and container cylinder decreases dramatically due to the melting of the low-density polyethylene resin, and the slight pressure inside and outside the container during retort sterilization Fluctuations easily caused joints to shift and bags to break. Furthermore, the paper absorbs water from the joint end surface of the container cylinders that are simply overlapped and welded together.
The strength of the paper decreased, which caused the container itself to buckle and cause wrinkles and other deformations.

Therefore, when conventional containers are used for distribution at room temperature, heat sterilization at about 90° C. is the limit, and the types of contents to be filled are extremely limited.

Therefore, in order to increase the variety of filling materials, it is necessary to increase the heat sterilization conditions, and the general indicator for this is Fo value of 4 or more.

The Fo value represents the heating time required to kill a certain concentration of bacteria (spores) at a certain temperature, and is the lethal time in minutes at 250°C (121°C). Other temperatures are also expressed in terms of 250〓. For example, Clostridium botulinum is said to be killed in 250 × 4 minutes in a phosphate buffer, and is expressed as Fo=4.

In order to solve these drawbacks of conventional containers, the present inventors used thermoplastic resin as the material for both outer layers of the container cylindrical body, excluding low-density polyethylene resin alone, and also devised a method for the joints of the cylindrical body (waterproofing treatment). ) was proposed.

In addition, the cylindrical body is designed to prevent scratches on the paper beyond the synthetic resin of the outer layer during the conveyance system such as a belt conveyor during container manufacturing, the conveyance system into the retort sterilization pot, and the movement of the container during retort sterilization. We also proposed that the laminated sheets constituting the paper have a laminated structure with aluminum foil placed on both sides of the paper. but,
It turns out that even these proposals still have some shortcomings.

In other words, no matter how well selected the materials for the outer layers of the container cylinder, the joints of the cylinders, and the laminated structure of the laminated sheets are, it is still necessary to close both the upper and lower openings of the cylinder with a lid. In some cases, if traces such as seams that are inevitably formed by the capping jig used are inadvertently created, hot water will enter during subsequent retort sterilization, and the paper will absorb this water. As a result, the strength of the paper decreased, which caused the container itself to buckle and cause deformations such as wrinkles.

The present inventors have solved these drawbacks of the conventional technology, retaining the advantages of using a laminated sheet made of synthetic resin, paper, and aluminum foil as the main body of the container, and making retort sterilization possible. We have worked diligently to provide a method for manufacturing food packaging containers that not only allows for a marked increase in the variety of filling materials, but also prevents deformation of the container due to water seepage through marks such as seams that are inevitably formed in the lid material. As a result of our studies, we found that this object could be achieved by selecting the materials for both outer layers of the container cylinder, devising the joining part of the cylinder, and specifying the form of the lid fastening jig as described above, and arrived at the present invention. Ivy.

In other words, the gist of the present invention is to waterproof a laminated sheet made of a synthetic resin, paper, and aluminum foil, with both outer layers made of a thermoplastic resin other than a low-density polyethylene resin alone, and then weld the ends of the laminated sheet rolled and stacked one on top of the other. A method of producing a container by forming a cylinder, and closing both the upper and lower openings of the cylinder with a lid made of aluminum foil whose inner surface is coated with a synthetic resin of the same type as the synthetic resin in the laminated sheet. In closing the opening of the cylindrical body with the lid, a block-shaped hot stamp that advances into the opening from the longitudinal direction of the cylindrical body and holds the central part of the lid, and a block-shaped hot stamp around the hot stamp. The cylindrical body converges radially from the circumferential direction, and the adjacent side ends engage with each other and become integrated, thereby pressing the peripheral part of the lid material between the outer peripheral surface of the hot stamp. Then, a lid tightening jig is used, which is composed of a plurality of jaws forming an outer rim protruding from the outer circumferential surface of the end of the cylinder, and the side ends of the jaws hold the thin plate-like body against the outer circumferential surface of the cylinder. A substantially comb-shaped cross section is formed by stacking a plurality of sheets at appropriate intervals in the longitudinal direction, and the height of the joint formed by converging and integrating these joints is less than half the height of the outer rim of the lid material. A method of manufacturing a food packaging container is provided.

The present invention will be explained in more detail below.

The food packaging container manufactured according to the present invention is the first
As shown in the figure, it basically consists of a cylindrical body 1 and upper and lower lids 3.

The cylindrical body 1 is formed by welding both ends of laminated sheets 2 made of synthetic resin, paper, and aluminum foil rolled up and stacked one on top of the other.

Both outer layers of the laminated sheet 2 are thermoplastic resins excluding low density polyethylene resin alone.

Examples of this thermoplastic resin include commonly used thermoplastic resins other than those containing low-density polyethylene resin alone, such as polyethylene resins mainly consisting of high-density polyethylene resins, polypropylene resins,
Examples include polyethylene terephthalate resin. Among these, polyethylene resins, mainly consisting of high-density polyethylene resins, are preferably used.

Here, the high-density polyethylene resin generally refers to a resin with a density of 0.941 g/cm ³ or more.

"Mainly composed of high-density polyethylene resin" includes high-density polyethylene resin alone or a blend with other resins.

However, if high-density polyethylene resin is used alone, there are some disadvantages in the extrusion laminate molding method that is often used for molding the laminated sheet 2 as described below, so blends with other resins are preferred. used.

Therefore, the processability required for the extrusion lamination method is the ability to form thin objects (the ability to make the resin thinner, that is, the ability to form thinner films at higher speeds as the processing speed increases). Good quality and low net-in (a phenomenon in which the width of the extruded film is much smaller than the effective width of the die when forming a film using a T-die, and the thickness of the film at both ends becomes large) is required. be done.

Although it was not possible to satisfy all of the above requirements using a high-density polyethylene resin alone, it was found that this could be improved by blending a low-density polyethylene resin with good fluidity.

The blending amount of the low-density polyethylene resin is 10% to 25% by weight based on the high-density polyethylene resin, and the high-density polyethylene resin is the main component.

If the blend amount is less than this, the effect of blending will not be produced, and if it is too large, the heat resistance will be extremely reduced.

By the way, in retort sterilization under heat conditions of 120°C, the blended amount of low density polyethylene resin is limited to 25% by weight as mentioned above.

Note that the low-density polyethylene resin here refers to one having a density of 0.925 or less, as usual.

For example, the laminated structure of the laminated sheet 2 is, from the outer surface side of the cylinder, thermoplastic synthetic resin/paper/aluminum foil/
There are thermoplastic synthetic resins.

Further, as another example, there are thermoplastic synthetic resin/aluminum foil/paper/aluminum foil/thermoplastic synthetic resin from the outer surface side of the cylinder. Of course, the structure is not limited to this example, and may have a laminated structure with more layers, and may be changed as desired.

In particular, when using a laminated structure in which aluminum foil is placed on both sides of the paper, the synthesis of the outer layer is difficult in conveyance systems such as belt conveyors during container manufacturing, conveyance systems into retort sterilization pots, and movement of containers during retort sterilization. This is preferable because it eliminates inconveniences such as hot water soaking due to flaws that often occur in resins. There is essentially an adhesive layer between each layer of thermoplastic synthetic resin, paper and aluminum foil. This adhesive layer is interposed between the thermoplastic synthetic resin, which is mainly made of high-density polyethylene resin, which is the outer layer, and the aluminum foil, and between the aluminum foil and the paper to ensure good adhesion between each layer. For this purpose, low density polyethylene resin can be used as the adhesive layer.

Paperboard is also referred to as paper and paperboard in the JIS terminology, and is a general term for thick paper made mainly of wood chemical pulp, ground wood pulp, straw pulp, waste paper, etc., and is made using a paperboard machine.

This paper is hard and stiff, so it is often used as a packaging material, and there are cardboard base paper, yellow paperboard, and white paperboard, but white paperboard made by combining white paper stock is particularly preferred. used.

The basis weight of paper is usually about 180 to 400 g/m ² .

Furthermore, aluminum foil is a common material often used for packaging materials, etc., and its thickness is 5 to 150 μm.
That's about it.

In particular, the cylindrical body of the container is preferably 5 to 20 microns, and the lid is preferably about 100 to 150 microns.

The laminated sheet 2 made of such a material is molded by an appropriate molding method such as the extrusion lamination method as described above.

To obtain a food packaging container according to the present invention, first, the laminated sheets 2 are rolled up and overlapped, and both ends are waterproofed and welded to form a cylindrical body.
This "waterproofing treatment" refers to a treatment that prevents both ends of the rolled and stacked laminated sheet 2 from coming into direct contact with the contents or being exposed to the outside air, and various forms can be considered. The preferred embodiments thereof will be described below.

That is, a tape-shaped aluminum foil 4 coated on both sides with the same type of synthetic resin as the synthetic resin in the laminated sheet 2 is used.

Here, the synthetic resin of the same type as the synthetic resin in the laminated sheet 2 is basically a thermoplastic resin excluding low-density polyethylene resin alone, as described above, and also includes differences in density within regulations. It is something that

The tape-shaped aluminum foil 4 is shown in (a) to (d) in Fig. 2.
This process is applied to both side edges of the laminated sheet.

That is, in FIG. 2 A to B, both ends of the laminated sheet 2 are surrounded by tape-shaped aluminum foil 4 from the outside in a substantially dogleg shape with a gap, and at least one tape-shaped aluminum foil is 4 is bent inward within one side of the laminated sheet 2 and inserted.

In the case where both ends of the laminated sheet 2 are surrounded by tape-shaped aluminum foil 4 in a substantially doglegged shape, the "doglegged" shape is intended to ensure effective heating and melting in the subsequent stage. The bending angle may be obtuse or acute, but is preferably around 90 degrees. At such an angle, it is preferable that the tape-shaped aluminum foil 4 is not offset as much as possible with respect to the laminated sheet 2, and furthermore, it is surrounded from the outside with a suitable gap as shown in the figure.

In addition, bending one end of the tape-shaped aluminum foil 4 inward on one side of the laminated sheet 2 and inserting the aluminum foil 4 in a tape shape surrounding both side ends of the laminated sheet 2 in a substantially dogleg shape. Of the aluminum foils 4, one or both may be used. In particular, in the case of both, one side of the laminated sheet 2 should be in the same plane.

Next, in step (c), the burner 5 heats both sides of the tape-shaped aluminum foil 4 and the laminate sheet 2 through the acute-angled gap between the top and bottom of the tape-shaped aluminum foil 4 and the laminate sheet 2. can be welded.

This special heating method almost eliminates the stringy phenomenon in the subsequent pressing process, but
To ensure this, the following considerations should be made.

That is, the flame from the burner 5
It is preferable to provide a shielding plate 6 made of a suitable material such as metal so that the aluminum foil 4 does not protrude outside the tape-shaped aluminum foil 4 surrounding the aluminum foil 4 in a substantially dogleg shape.

Without this shielding plate 6, the flame that protrudes outward may heat and melt the surface side directly in contact with the pressure roller in the latter stage, causing stringiness. It is preferable that the shielding plate 6 be placed very close to the tape-shaped aluminum foil 4 without coming into contact with it.

In addition, when heating the tape-shaped aluminum foil 4 and the laminated sheet 2, an infrared heater, a hot air blowing device, etc. may be appropriately employed instead of the burner 5.

In step (d), the tape-shaped aluminum foil 4 heated in step (c) and the laminated sheet 2 are welded together by the upper and lower pressure of the pressing roller 7. The surface of the pressure roller 7 is preferably subjected to a surface treatment such as "Teflon" coating.

After welding the tape-shaped aluminum foil 4 to both ends of the laminated sheet 2 in this way, the tape-shaped aluminum foil 4 is rolled up so that the bent side becomes the inner surface of the container, and then stacked. Both ends are welded to form a cylinder.

For this welding, if one end of the tape-shaped aluminum foil 4 at both ends of the laminated sheet is bent, for example, as shown in FIG. Tape-shaped aluminum foil 4
Simply place them next to each other and weld them together without overlapping them.

When the bending process on one end of the tape-shaped aluminum foil 4 is performed on both tape-shaped aluminum foils 4 as shown in FIG. In this case, the welded portion becomes thick, which is not practical.

The end portion of the laminated sheet 2 located inside the overlapping portion of the cylinder obtained in this way is completely softened, and the inconvenience caused by water absorption from the inside of the cylinder (from the water content of the filling) is eliminated.

Furthermore, since the ends of the tape-shaped aluminum foil 4 do not come into contact with the filling material, there is no problem in terms of food hygiene.

Both the upper and lower openings of the cylindrical body are welded and closed by lid members made of aluminum foil whose insides are coated with a synthetic resin of the same type as the synthetic resin in the laminated sheet.

In the present invention, the following considerations are taken when closing the opening of the cylindrical body with the lid material.

That is, to close the opening of the cylindrical body with the lid material, a lid tightening jig consisting of a combination of a hot stamp 8 and a jaw 9 as shown in FIG. 4 is used.

The hot stamp 8 is block-shaped and extends from the longitudinal direction of the cylinder into both the upper and lower openings and holds the central portion of the lid.

The external shape and size of the hot stamp 8 are similar to the internal shapes of both the upper and lower openings of the cylindrical body, and are slightly smaller. That is, the configuration is such that a lid material can be interposed between the outer surface of the hot stamp 8 and the inner surfaces of both the upper and lower openings of the cylindrical body. The hot stamp 8 can be heated to a desired temperature as appropriate.

As shown in FIG. 4, a plurality of jaws 9 are provided around the hot stamp 8, converge radially from the circumferential direction of the cylinder, and are integrated by engaging adjacent side ends. Become.

The jaws 9 converge radially from the circumferential direction of the cylindrical body, and their adjacent side ends engage with each other to form an integral body, thereby tightening the peripheral portion of the lid material between the outer circumferential surface of the hot stamp 8 and the outer circumferential surface of the hot stamp 8. Pressing is performed to form an outer rim 10 protruding from the outer circumferential surface of the end of the cylindrical body.

FIG. 4C shows a form in which the jaws 9 converge radially from the circumferential direction of the cylindrical body, and their adjacent side ends engage with each other to form an integral body. That is, the side end portion of the jaw 9 forms a substantially comb-shaped cross section in which a plurality of thin plate-like bodies 11 are stacked at appropriate intervals in the vertical direction, that is, in the longitudinal direction of the cylindrical body. The side end portions of adjacent jaws 9 may be adjusted so as to closely rub against each other, and may be provided with a spacer or the like as appropriate.

In this way, the plurality of jaws 9 converge and engage with each other at their side ends to become an integral body, pressing the peripheral part of the lid member with the outer peripheral surface of the hot stamp 8, and pressing the outer peripheral part of the end of the cylindrical body. an outer rim 10 that protrudes into the
When this is formed, a seam 12 (a portion not pressed by the jaw 9) is generated. This seam 12 is a trace that is inevitably formed in order to exert a pressing force against the lid material by converging and integrating the plurality of jaws 9.

In the present invention, the height of this seam 12 (along the longitudinal direction of the cylinder) is less than half the height (width) of the outer rim 10 of the lid member 3.

If this seam is not made less than half of the outer rim 10 of the lid material 3, when the container is retort sterilized after being filled with contents, there will be slight differences depending on the retort conditions.
Most of the water leaks through the lid, which is extremely inconvenient as a container for retort sterilization.

In order to make the height of the seam 12 caused by the convergence and integration of a plurality of joints 9 to be less than half the height of the outer rim of the lid, thin plate-like bodies at adjacent side ends of the joints 9 that engage with each other are used. Thickness (height) of itself
This is achieved by making the height less than half the height of the outer rim 10. There is no particular need to heat and maintain the JIYO 9.

The food packaging container of the present invention has such a structure, and is applied to normal retort sterilization after being filled with food, such as a liquid beverage.

As detailed above, according to the present invention, the advantages of mainly using a laminated sheet made of synthetic resin, paper, and aluminum foil are retained, and retort sterilization is possible, so that the contents can be easily sterilized. Of course, the variety of
A container is manufactured that is free from deformation due to water seepage through the seams and other marks that are inevitably formed in the lid.

The present invention will be further explained below based on Examples, but the present invention is not limited to the Examples unless the gist of the invention is exceeded.

Example 1 A laminated sheet for forming a cylindrical body, a tape-shaped aluminum foil for covering the joints of the laminated sheets, and a lid material were manufactured by extrusion lamination to have the following configuration.

Laminated sheet for cylinder formation (width 240mm): outer layer side,
Polyethylene resin1 ⁾ (40μ) / Aluminum foil3 ⁾ (12μ) /
LDPE ²⁾ (20μ) / Paperboard (270g/m ² ) / LDPE ²⁾
(20μ) / Aluminum foil ³⁾ (12μ) / LDPE ²⁾ (20μ) / Polyethylene resin ¹⁾ (45μ), inner layer side Tape-shaped aluminum foil (width 20mm): Polyethylene resin ¹⁾ (25μ) / LDPE ²⁾ ( 25μ) / Aluminum foil ³⁾ (25μ) /
LDPE ²⁾ (25μ) / Polyethylene resin ¹⁾ (25μ) Lid material: Inner layer side, polyethylene resin (50μ) /
LDPE (30μ) / Aluminum foil 3)' (130μ) 1 High-density polyethylene resin (Novatec
JVO40, MI=5.0, ρ=0.968, Novatek is a registered trademark of Mitsubishi Chemical Industries, Ltd.) 80% by weight and low density polyethylene resin (Novatek-L, L-300,
MI=3.5, ρ=0.922) 20% by weight blend.

2 Low density polyethylene resin (Novatec-L,
L-300, MI=3.5, ρ=0.922, Novatek
(L is a registered trademark of Mitsubishi Chemical Industries, Ltd.) 3 Both sides are treated with a regular urethane anchor coating agent.

3' Only one side in contact with LDPE is treated with a regular urethane anchor coating agent.

From these parts, the Agricultural Cooperative Coffee Cafe O.
A container with lids on the top and bottom as shown in FIG. 1 was prepared, filled with 700 ml of LE (manufactured by Zenkoku Nokyo Direct Sales Co., Ltd.). (Manufactured by F, L, Hetzselmaschinenfabrik AG, HYPA system equipment.) The joints of the cylinders of the resulting container were made as shown in Figure 3.

Note that the tape-shaped aluminum foil 4 at the joint portion
(Width: 20 mm) The width on the unbent end side was approximately 7 mm.
Furthermore, the height (width) of the outer rim of the lid was 3 mm.

The following considerations were made when blocking the lid material.

That is, there are four block-shaped hot stamps that are similar in shape to the inner surface shape of the upper and lower openings of the cylinder and are slightly smaller, and four hot stamps are arranged around the hot stamp and converge radially from the circumferential direction of the cylinder. A lid tightening jig consisting of an integrated jig was used.
(As shown in Figure 4 A to C) The Jyo is made of five stainless steel plates with a thickness of 1 mm stacked one on top of the other in the vertical direction, so that the side edges of adjacent Jyo are interlocked with each other. be.

The contents were filled at a liquid temperature of 85°C, then the lid was tightened at a lid tightening temperature of 200°C, and then cooled with water to produce a filled container.

The lid tightening portion was schematically shown in FIG. 5, and the lid surface portion corresponding to the joint of the lid tightening jig (jiyo) had little curling up and had a good appearance.

This container was retort sterilized under the following conditions.

The sterilizer used was ROTORZWERG・
It is a hot water rotary retort (manufactured by Stock, West Germany).
Retort sterilization conditions: Heating time from initial product temperature of 18℃
Reach 125℃ in 1.5 minutes and hold at 125℃ for 18 minutes. Set pressure 2.5Kg/cm ² (gauge pressure), cooling 11 minutes (under the same set pressure), rotation speed of the container holding cage in the retort pot 8r.pm, After retort sterilization, the container is placed at the joint of the lid. There was no water seepage due to the bag turning over, and the bag was normal with no breakage, deformation, water absorption, or leakage of contents.

The weight increase of the container after sterilization was 0.3 (most likely due to moisture absorption by the outer layer resin). In addition,
The Fo value during main sterilization was 18.

Comparative Example 1 Example 1 except that a JI-O having a structure in which 2 mm thick stainless steel plates were stacked alternately in the vertical direction was used.
A retort sterilized filled container was obtained by performing the same operation as above. The appearance of the lid tightening part is as shown in Figure 6.
The seam of the lid was approximately 2 mm square.

The outer rim of the lid is 3mm long, but the outer rim only has a maximum clearance of 1mm. For this reason,
Approximately 1 in 20 retort-sterilized containers flooded with water due to the peeling of the aluminum part, which corresponds to the joint of the joint. At this time, the weight increase of the container before and after retort sterilization was 3.5 g, and the area that was flooded was approximately 1/2 of the total area, and the appearance was unfavorable due to ink bleeding and wrinkles in the film.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view of a container obtained by the present invention;
Fig. 2 is a schematic diagram showing how the tape-shaped aluminum foil and the laminated sheet are welded, Fig. 3 is an enlarged partial cross-sectional view of the joint of the container cylinder, and Fig. 4 is the lid fastening method used in the present invention. FIG. 5 is a schematic diagram showing the aspect of the jig, FIG. 5 is a schematic diagram showing the aspect of the seam occurring in Example 1 of the present invention, and FIG. 6 is a schematic diagram showing the aspect of the seam occurring in the comparative example. 1: cylindrical body, 2: laminated sheet constituting the cylindrical body,
3: Lid material, 4: Tape-shaped aluminum foil, 8: Hot stamp, 9: Jyo, 10: Outer rim, 12: Seam.

Claims (1)

[Claims] 1 Laminated sheets made of synthetic resin, paper, and aluminum foil with both outer layers made of thermoplastic resin (excluding low-density polyethylene resin alone) are rolled up and stacked on top of each other, and both ends are waterproofed and welded to form a cylinder. , a method for manufacturing a container by closing both upper and lower openings of the obtained cylinder with a lid material made of aluminum foil whose inner surface is coated with a synthetic resin of the same type as the synthetic resin in the laminated sheet, the method comprising: When closing the opening of the cylindrical body, a block-shaped hot stamp that advances from the long axis direction of the cylindrical body into the opening and holds the central part of the lid material, and around the hot stamp, the cylindrical body By converging radially from the circumferential direction of the cylinder body and engaging with each other to form an integral unit, the peripheral part of the lid member is pressed between the outer peripheral surface of the hot stamp and the cylindrical body is heated. A lid tightening jig is used, which includes a plurality of jaws forming an outer rim protruding from the outer circumferential surface of the end, and the side ends of the jaws are arranged so that the thin plate-like body is spaced appropriately in the longitudinal direction of the cylinder. A food product characterized in that a plurality of sheets are stacked to form a substantially comb-shaped cross section, and the height of the joint formed by convergence and integration of these sheets is less than half the height of the outer rim of the lid material. Method for manufacturing packaging containers.