JPH0156896B2 - - 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, have become popular, with containers mainly consisting of cylinders made by appropriately laminating synthetic resin, paper, and aluminum foil, rolling up laminated sheets, and welding the ends of the laminated sheets together. is being used in large numbers because it is lightweight, has excellent display properties as a container, is printable, and is easily incinerated. However, such food packaging containers
Most containers use low-density polyethylene resin alone, which has good sealing properties, for the outer layer 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 the container cylinder is extremely reduced due to the melting of the low-density polyethylene resin, resulting in slight damage to the inside and outside of the container during retort sterilization. Pressure fluctuations easily caused the joints to shift or break the bag. 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, heating sterilization by hot filling at about 90° C. is the limit, and the types of filling materials 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 potulinum is said to die in 4 minutes in a phosphate buffer, and is expressed as Fo=4. The present inventors have solved the drawbacks of the conventional technology by using thermoplastic resin as the material for both outer layers of the container cylindrical body, excluding low-density polyethylene resin alone, and by improving the joints of the cylindrical body (waterproofing treatment). ) made a proposal. 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. That is, in order to manufacture the proposed container, the cylindrical body made of a laminated sheet and the lid material are integrated by heat fusion. At this time, the cylindrical body is made of laminated sheets made of synthetic resin, paper, and aluminum foil that are rolled up and stacked one on top of the other, and both ends are welded together.Aluminium foil and synthetic resin are laminated on both the upper and lower openings of the cylindrical body. A container is manufactured by closing the lid material and heating and compressing it.
Here, heating is carried out by a block-shaped hot stamp that advances into the opening from the longitudinal direction of the cylinder and contacts and holds the central part of the lid. Furthermore, the pressing is performed on the hot stamp and around the hot stamp, converging radially from the circumferential direction of the cylindrical body, and the adjacent side ends are engaged with each other and integrated, so that the hot stamp This is done using a plurality of jaws that press the peripheral portion of the lid material between the outer circumferential surface of the cylinder body and form an outer rim projecting from the outer circumferential surface of the end of the cylinder. The heat from the hot stamp during heating and pressing is conducted through the aluminum foil of the lid material, which heats the outer rim (folded outward) of the lid material itself, and the laminated sheet of the cylinder. The heat conduction is divided into two parts: heat conduction from the thickness direction, and the synergistic effect of both allows the lid material and the cylinder to be well welded. However, the welded part of the laminated sheet in the cylinder,
In other words, the two side edges of the stacked sheets (the two laminated sheets
Although there is no difference in heat conduction between the lid material itself (the part where the sheets are overlapped), the heat conduction from the thickness direction of the laminated sheet of the cylinder is significantly reduced, and therefore, as will be described later, there is a difference in heat conduction between the lid material and the cylinder. Welding of the body becomes insufficient. That is, there is inevitably a level difference in the welded part of the laminated sheet in the cylinder, and it is necessary to perform sufficient welding to fill the slight gap created between the level difference and the surface of the lid material with molten resin. However, as mentioned above, when the heat conduction from the thickness direction of the laminated sheet decreases, the amount of resin melted at that point naturally decreases, so the gap between the step at the welded part of the laminated sheet and the surface of the lid material is reduced. The amount of melted resin is insufficient for embedding, resulting in poor welding. Therefore, during retort sterilization, hot water enters from the defective welding locations. Due to this water intrusion, the paper in the cylindrical body absorbs water, and the strength of the paper is extremely reduced. For this reason, the strength required for containers after retort sterilization during distribution processes such as cardboard packaging, stacked storage, and transportation is reduced, resulting in wrinkles, buckling, etc. on the outer surface of the container. For this reason, not only does the product lose its appearance, but also
It has also been found that there is a risk of contents leaking. 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. Not only can the types of filling materials be greatly expanded, but also the food packaging container can be created without deformation of the container due to water seepage from the insufficiently welded part formed at the overlapping part of the cylinders in the lid fastening part of the container. As a result of intensive studies to provide a manufacturing method, we found that this objective can be achieved by selecting the materials for both outer layers of the container cylindrical body, devising the joint of the cylindrical body, and specifying the form of the lid tightening jig as described above. We discovered this and arrived at the present invention. 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 consisting of a plurality of jaws forming an outer rim protruding from the outer peripheral surface of the end of the cylinder is used, and among the plurality of jaws, the laminated sheets are rolled up and overlapped. The present invention resides in a method for manufacturing a food packaging container, characterized in that only the containers corresponding to both end portions are heated and held. 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. Further, the polypropylene resin similarly includes a polypropylene resin alone or a blend with other resins having improved extrusion lamination properties. Therefore, the processability required for the extrusion lamination method is the ability to form thin objects (the ability to make thinner resins, 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 at both ends of the film becomes large) is required. be done. For example, when high density polyethylene resin alone was used, all of the above requirements could not be satisfied, but it was found that the improvement could be achieved by blending 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 body. If the blend amount is too small, the effect of blending will not be achieved, 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. The laminated structure of the laminated sheet 2 is, for example, thermoplastic resin/paper/aluminum foil/thermoplastic synthetic resin from the outer surface side of the cylinder. 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 substantially a connecting layer between each layer of thermoplastic, paper and aluminum foil. This connection 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. In addition, paper is 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 corrugated cardboard materials, yellow paperboards, and white paperboards, but white paperboard made from 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 thereof are waterproofed and welded to form a cylinder. 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.
Although various aspects are conceivable, preferred aspects 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 applied to both side ends of the laminated sheet by steps A to D shown in FIG. That is, in FIG. 2 A to B, both ends of the laminated sheet 2 are surrounded by tape-shaped aluminum foil 4 in a substantially dogleg shape from the outside with a gap, and at least one tape-shaped aluminum foil 4 is One end of the laminate sheet 2 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, both sides of the tape-shaped aluminum foil 4 and the laminated sheet 2 are heated by the burner 5 through the acute-angled gap between the top and bottom of the tape-shaped aluminum foil 4 and the laminated sheet 2 to weld them together. possible. 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. At this time, it is particularly preferable to install an edge roller (not shown) for adhering the outside of the dogleg shape of the tape-shaped aluminum foil 4 to the end surface of the laminated sheet 2. 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 2, the tape-shaped aluminum foil 4 heated in step 3 and the laminated sheet 2 are welded together by the upper and lower pressure of the pressure 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 of the laminated sheet 2 located inside the overlapping part of the cylinder obtained in this way is completely softened, and water is absorbed from the inside of the cylinder (from the water content of the filling material).
The inconvenience caused by this will be resolved. 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. When the outer rim 10 is formed to protrude, 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 preferably less than half the height (width) of the outer rim 10 of the lid member 3. This seam should not be less than half of the outer rim 10 of the lid 3, and when the container is retort sterilized after filling with contents, water will mostly seep through the lid, although there will be slight differences depending on the retort conditions. This 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 of the height of the outer rim 10. Furthermore, in the present invention, it is preferable that the jaw 9 has a special shape in consideration of the following points. That is, by compressing and welding the aluminum foil of the lid 3 to the outer rim 10 of the lid 3 by pressing the hot stamp 8 and the jaw 9, the aluminum foil is applied to the non-pressed portion formed at the seam 12. Not only does it escape, but the aluminum foil also folds inwards. This aspect is shown in FIG. 6B. In the case of a rectangular container, this folding often occurs at the corners. This folding breaks the synthetic resin surface layer of the laminated sheet of the cylinder, creating pinholes. Due to the occurrence of pinholes, water will be absorbed when the container is sterilized by retort, which is extremely inconvenient as a container for retort sterilization. In the present invention, in order to prevent such inconveniences due to folding, it is preferable to take the following considerations. That is, as shown in FIG. A plurality of elongated escape grooves 13 are provided. The escape groove 13 is not limited to the embodiment shown in FIG. 5A, and may extend obliquely to the width direction (height direction) of the jaw 9, for example. The cross-sectional shape of the relief groove 13 is, for example, semicircular, triangular, or rectangular, and when it is particularly rectangular, the side corresponding to the inner circumferential surface of the jaw 9 is the longest side, so that it is a so-called wide-open groove. It is preferable to do so. A plurality of relief grooves 13 are provided in consideration of slight deviations that occur when the plurality of jaws 9 converge and engage with each other at their side ends to become integrated. FIG. 5A shows a case where five relief grooves 13 are provided for convenience. Among the plurality of relief grooves 13, the groove corresponding to the corner tip of the outer rim 10 of the lid member 3 (corresponding to the center groove in FIG. 5A) is made larger than the other adjacent relief grooves. is preferable. The large relief groove 13 at the center has a depth that accommodates the bent tip of the outer rim 10 of the lid 3, and the other adjacent relief grooves 13 accommodate the bent aluminum foil portion of the lid 3. It is sufficient to have a depth that accommodates the If the size of the relief groove 13 is too large than these settings, it may cause internal water seepage, and conversely the relief groove 1
If 3 is too small or the number is too small, folding 14 into the surface layer of the cylinder 3 will occur on the inside, resulting in water absorption due to pinpole formation. The mutual spacing between the relief grooves 13 depends on factors such as the thickness of the cover material 3, but generally it may be several millimeters. Furthermore, each relief groove 13 may be tapered so that it becomes a deeper groove as it goes downwards in the jaw 9. Furthermore, in the present invention, some of the plurality of jaws are specially designed in consideration of the following points. That is, in manufacturing the container of the present invention, the lid material 3 is compressed and welded to the cylindrical body made of the laminated sheet by pressing with the hot stamp 8 and the jaw 9. At this time, poor welding occurs in the welded portion of the laminated sheet of the cylinder body to be welded to the lid material 3, that is, in part of the overlapped side end portions (the portion where two laminated sheets are overlapped). The reason for this is that, as described above, in the welded portion of the laminated sheet, the heat of the hot stamp 8 is difficult to conduct from the thickness direction of the laminated sheet, and therefore, this portion becomes insufficiently heated. When the hot stamp 8 is heated to a higher temperature in an attempt to eliminate these inconveniences, the single layer portion (the portion other than the welded portion of the laminated sheet) becomes overheated, and the thermoplastic resin in that portion flows out. This results in a loss of sealing effect. In the present invention, in order to solve the problem of poor welding due to insufficient heating at both ends of stacked laminate sheets, in addition to heating with a hot stamp, the laminate sheets are stacked in a Only the joints corresponding to the opposite ends are heated and held. Heat and hold the JIYO in such a way as to obtain a sufficient amount of melted resin to fill the step at the welded part of the laminated sheet (the overlapping part of the cylinders) in the lid fastening part and the gap in the surface of the lid material. For example, if the outer layer resin of the cylinder of the container is polyethylene resin, the temperature of the hot stamp is 200°C, and the heating temperature of the thermometer is about 60 to 100°C, although this varies somewhat depending on the thickness and other factors. Similar to the heating and holding of a hot stamp, the heating and holding of the JIYO may take any form as long as it can be set and adjusted to a desired temperature. The food packaging container obtained according to the present invention is applied to ordinary 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. Not only is there a wide variety of types available, but also containers are manufactured that are free from deformation due to water seepage from the insufficiently welded portion formed at the overlapping portion of the cylindrical bodies in the lid fastening portion of the container. The present invention will be further described below based on Examples, but the present invention is not limited to the following 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 into the following configuration by an extrusion lamination method or the like. Laminated sheet for cylinder formation (width 240mm): outer layer side,
Polyethylene resin ⁽¹⁾ (20μ) / LDPE ⁽²⁾ (20μ) / Aluminum foil ⁽³⁾ (12μ) / LDPE ⁽²⁾ (20μ) / Paperboard (270
g/m ² )/LDPE ⁽²⁾ (20μ)/Aluminum foil ⁽³⁾ (12μ)/
LDPE ⁽²⁾ (20μ) / Polyethylene resin ⁽¹⁾ (45μ), Inner layer tape aluminum foil (width 20mm): Polyethylene resin ⁽¹⁾ (25μ) / LDPE ⁽²⁾ (25μ) / Aluminum foil ⁽³⁾
(25μ) / LDPE ⁽²⁾ (25μ) / Polyethylene resin ⁽¹⁾
(25μ) Lid material (width 90mm): Inner layer side, polyethylene resin ⁽¹⁾
(50μ) / LDPE ⁽²⁾ (30μ) / Aluminum foil ⁽³⁾ ′ (130μ) (1) High-density polyethylene resin (Novatec
JVO40, MI.-5.0, ρ=0.968, Novatec is a registered trademark of Mitsubishi Chemical Industries, Ltd.) 80% by weight and low density polyethylene resin (Novatec-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, Novatec-
(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. A container with top and bottom lids as shown in FIG. 1, filled with 700 ml of water, was manufactured from these materials. (Manufactured by F, L, Hetsselmaschinenfabrik AG, HYPA system equipment.) The joints of the cylinders of the resulting containers were made as shown in Figure 3. Note that the tape-shaped aluminum foil 4 at the joint portion
(Width: 20 mm) The width at the bent 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. Furthermore, the jaw is provided with five relief grooves as shown in FIG. The cross-sectional shape of the relief groove is a right triangle, and the center relief groove has a depth of
0.5mm, base 1mm, other clearance grooves depth 0.3mm, base
0.6 mm, and the clearance between the relief grooves is 3 mm each. Among these plurality of Jyo, heating heaters (manufactured by Wattslow Co., Ltd., USA,
A cartridge heater TYPE) and a temperature controller (67000 Series Midget Thermoswitch, manufactured by Phenol, USA) were embedded to maintain heating at the desired temperature. Filling with the contents was carried out at a liquid temperature of 85°C, then the temperature of the hot stamp was set at 200°C, and the surface temperature of the heating jacket (the jacket corresponding to both ends of the laminated sheet rolled up and stacked) was measured as shown in Table 1. Filled containers were manufactured by changing the temperatures shown in 8 to 8 and tightening the lids and further cooling with water. The appearance of the lid tightening part is as shown in Figure 5 (b), and there is no inward folding on the outer rim of the lid material, which corresponds to the corner part of the lid, and the folding is absorbed by the escape groove. Because of this, the folds were sticking out to the outside. In order to check the water resistance (good or bad welding) of the overlapping part of the cylinders in the capping part of the obtained filled container, the container was immersed in a methylene blue alcohol solution. If the welding is poor, it can be easily determined because the paper of the laminated sheet of the cylinder absorbs water and turns blue. The number of containers that absorbed water was counted depending on the heating temperature. The results are shown in Table-1. In addition, the surface temperature of the heating tube was set at 90° C., and a filled container manufactured in the same manner was retort sterilized under the following conditions. The sterilizer used was ROTOMAT.
RSE, type 2, hot water rotary retort (West Germany, stock)
company). Retort sterilization conditions: Initial product temperature 19℃
The temperature was raised from 122℃ to 122℃ in 3 minutes.
Hold for a minute. Set pressure 2.2Kg/cm ² (gauge pressure),
After cooling for 15 minutes (under the same set pressure), the rotation speed of the container holding cage in the retort pot was 8 rpm. After retort sterilization, the containers showed no water seepage, bag breakage, deformation, or leakage of contents, and the appearance before sterilization was There was no change at all and it was normal. The weight increase of the container after sterilization was 0.4 g (most likely due to moisture absorption by the outer layer resin). Furthermore, the containers were packed in a cardboard box (containing 20 bottles) and stored in four stacks for one week, and the appearance was re-inspected, but no abnormality was found. Comparative Example Eight filled containers were obtained by carrying out exactly the same operation as in the example except that JIYO was not heated and held at all. The filled containers thus obtained were immersed in a methylene blue alcohol solution in the same manner as in Examples, and the number of containers that had absorbed water was counted. The results are shown in Table-1. Furthermore, 100 filled containers were obtained in exactly the same manner as in this comparative example, and then retort sterilized under the same conditions as in the example. After retort sterilization, 82 out of 100 containers had water seepage in the overlapping part of the cylinders at the lid tightening part. The weight increase of the retort sterilization container is 0.6 to 1.7 g.
It was hot. In total, the area of the areas flooded with water was less than about 10% of the entire container, and the container appeared normal in appearance, with no ink bleeding or wrinkles in the film. However, when the containers were packed in a cardboard box (containing 20 bottles) and stored in four stacks for a week, and the appearance was re-inspected, 5 of the 20 containers were in the bottom cardboard box. There were also wrinkles and small creases on the outer surface of the container.

【table】

[Table] As is clear from Table 1, the effect of using heated Jyo is remarkable. When the surface temperature of the heating tube was 100°C, no water was observed in the container, but the outer resin layer was pricked when the lid was tightened, indicating that the container was slightly overheated.

[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. 5A is a schematic diagram showing the aspect of the jig; FIG. The figure is a schematic diagram showing the manner of seams and folds that occur in the conventional 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, 13: Relief groove, 14: Fold.

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 consisting of a plurality of jiyos forming an outer rim protruding from the outer circumferential surface of the end portion is used, and among the plurality of jiyos, the lid tightening jig is adapted to correspond to both end portions of the laminated sheet rolled and overlapped. A method for producing a food packaging container characterized by heating and holding only the container for food packaging.