JP2544630B2 - Manufacturing method for plastic containers - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a method for manufacturing a plastic container, and more specifically, it has a shape and strength that can withstand the conventional metal can filling, double winding of a metal lid by a sealing machine, and can reduce the weight. The present invention relates to a manufacturing method for obtaining a plastic container having excellent properties such as resilience upon impact and storability.

[Prior art]

There are various types of metal cans, but they can be classified into three-piece cans and two-piece cans depending on the structure of the can body. A three-piece can is also called a tin solder can, and has a structure in which a cylindrical can body, a lid, and a bottom are sealed by double winding, and a two-piece can is also called a tin punching can. It has a structure in which the lid is double wound. These metal cans are used as food packaging containers for various food canned foods, juices, soft drinks, jams, dried foods, etc., and are rigid containers with excellent sealing and storage functions. However, the metal can has the following points to be improved. That is, since it is a metal can, there is a limit to weight reduction. When it receives a shock, once it is crushed there is no restoration and it deforms. The energy cost of its production is higher than that of a plastic container. If the display effect of the container exterior is metal, it cannot be changed freely, and the exterior means is only by printing. It is impossible to make a transparent container that allows the contents to be checked without opening the can.

[Problems to be Solved by the Invention]

The drawbacks of the conventional metal can as described above can be solved by using a plastic can and double-tightening the metal lid. The most suitable method for inexpensively mass-producing plastic cans is a thermoforming method using compressed air or vacuum. To double tighten the metal lid onto the flange of the thermoformed plastic container, the thickness of the flange is
It must be thinned to about 0.5 mm. However, when thermoformed by sheet forming, the thickness of the flange is determined by the thickness of the sheet used. The plastic can requires sufficient buckling strength because a pressing force is applied to the container when the metal lid is double-fastened. In order to have such strength, it is necessary to increase the thickness of the plastic sheet used for molding, but if a thick sheet is used, the flange thickness will inevitably increase. Then, how to make the molded product strong and to reduce the flange thickness becomes a problem. Further, the flange is required to have dimensional stability in the thickness and width of the flange because the metal lid is wound on the flange. It has been difficult to achieve such a point by thermoforming. An object of the present invention is to solve the above problems and to provide a method for manufacturing a plastic container having a double-wound flange.

[Means for solving problems]

INDUSTRIAL APPLICABILITY The present invention uses a plastic sheet having a sufficient thickness suitable for forming a container to form a container having a flange by forming by a general thermoforming method, and then presses the flange thickness of the formed plastic container by press heat. The present invention relates to a method of manufacturing a plastic container by molding again so as to have a thickness suitable for double winding, and simultaneously with press thermoforming or by removing a flange after press thermoforming. If necessary, a printed label is inserted into the mold during press thermoforming of the flange, and the label is fused on the side surface of the container.

[Action]

The entire container is molded by thermoforming with a plastic sheet having a sufficient thickness, and only the thickness of the flange is adjusted by press thermoforming to a thickness suitable for double winding. Despite having thickness and strength, the thickness of the flange portion can be set arbitrarily and the dimensional stability is good.

【Example】

Next, the present invention will be described in more detail in the order of steps. The outline of the process of the present invention is shown in FIG. Step (A) A plastic sheet 1 having a thickness necessary for forming a container is heated 2 by a general thermoforming method, and a molded product 4 is molded by a general molding method using a mold 3. The molding method may be pressure molding, vacuum molding, or a combination thereof. As shown in FIG. 3, the cross-section of one container 5 constituting the obtained molded product 4 has a side surface 6 and a bottom portion 7 having a thickness and strength sufficient to withstand the pressure applied during double winding. However, the flange 8 is not suitable for double winding because the thickness d1 is too large. As a plastic sheet forming the container, when manufacturing a food storage container, a plastic laminated sheet configured to have a low permeability of oxygen gas and water vapor is used. As a food storage container, the oxygen gas barrier property of the container is 0.8cc / ke ・ 24hrs ・ atm (20 ℃, 90% RH) or less, and the H ₂ O barrier is 0.2g / ke ・ 24hrs ・ atm (40 ℃ , 90% R
H) It is desirable that it is below. Step (B) The molded product 4 formed in the step (A) is hot pressed to reduce the flange thickness d1 and at the same time improve the accuracy. That is, the molded container 5 is put into the mold 9 as shown in FIG. The inside of the mold 9 is heated, and the surface is treated with Teflon or the like in order to improve the releasability. Next, the heated plug 10 descends from the upper part and crushes the flange 8. The drive of the plug 10 may be hydraulic or pneumatic. When the flange reaches a predetermined thickness, the plug 10 moves up and the pressing of the flange is completed. The thickness d2 of the flange is preferably 0.25 to 0.9 mm. Flange thickness d2 is the general clearance for hot press molding.
The thickness of the flange lower part 11 is set to 0.5 mm and 0.8 mm. Further, as shown in FIG. 4, the label 12 or the like printed on the side surface or bottom portion of the container under the flange at the time of the hot pressing can be inserted into a mold to fuse the label 12 together with the flange formation. For the label 12, the same resin as that of the previously molded container or a layer that can be fused by heat is positioned on the inner layer of the label and fused on the container. Step (C) The molded product 4 in which the flange 8 is adjusted to have a predetermined thickness in the step (B) is pulled out by the mold 14 having the blade 13 so that the flange width w becomes a predetermined width. The flange width w is generally 1.0 to 2.5 mm. This step of removing can also be performed together with the step (B). That is, if a plug 16 having a blade 15 attached to the pressing surface of the plug as shown in FIG. 6 is used, steps (B) and (C) can be carried out simultaneously to manufacture the desired container. Example Made of polypropylene / adhesive layer / ethylene vinyl alcohol polymer / adhesive layer / polypropylene, the thickness of each layer is 640μ / 40μ / 40μ / 40μ / 640μ, the total thickness is 1400μ
Using a raw sheet consisting of the contact layer sheet, the container having the dimensions of a = 65 mm, b = 30.0 mm, d1 = 1300 μ in FIG. 3 was heat-molded. Molding was performed by plug-assisted pressure molding. Next, heat press to perform flange thickness d2 = 500μ
At the same time, printed polyethylene terephthalate / polypropylene / polypropylene (cast) is 12
The label 12 laminated with a thickness of μ / 100 μ / 60 μ was inserted into the mold and fused to the side surface 6 of the container. The container in which the flange thickness was adjusted to a predetermined dimension was pulled out so that the flange width w = 2.0 mm. The obtained container was filled with water, and a 211-type metal lid was double wound around the container flange with a seamer. This was sterilized by retort sterilization at 120 ° C for 30 minutes, but the shape of the container and the storage condition of the contents did not change, and good results were obtained.

【The invention's effect】

The method for producing a plastic container in the present invention is a method of molding a container from a sheet by a thermoforming method and then adjusting the thickness of the flange only to a thickness suitable for double winding by press thermoforming. Suitable for
The thickness of the flange portion can be set arbitrarily and accurately. The plastic container obtained by the present invention,
The metal lid can be double-wound onto the flange and sealed, which is suitable for storing various foods.

[Brief description of drawings]

FIG. 1 is an explanatory view showing each step of the manufacturing method of the present invention, FIG. 2 is a perspective view showing a molded product, FIG. 3 is a sectional view of a container constituting the molded product, and FIG. 4 is a hot press molding of a flange. FIG. 5 is a partial sectional explanatory view showing a process, FIG. 5 is a sectional view showing a flange removing process, and FIG. 6 is a partial sectional explanatory view showing another embodiment of the flange removing. 1 …… Plastic sheet, 4 …… Molded product, 5 …… Container, 8 …… Flange, 12 …… Label, d1 …… Flange thickness of molded product, d2 …… Flange thickness after press thermoforming, w …… Flange width

Claims (3)

(57) [Claims] 1. A double winding, wherein a plastic container having a flange portion is thermoformed by sheet forming, then the flange thickness of the molded plastic container is thinned by press thermoforming, and the plastic container is drawn to have a constant flange width. A method of manufacturing a plastic container having a tightenable flange. 2. The method for producing a plastic container according to claim 1, wherein a label is inserted into the mold and the label is attached to the side surface of the container during press thermoforming. 3. The thickness of the flange is reduced to 0 by press thermoforming.
The method for producing a plastic container according to claim 1, wherein the plastic container has a thickness of 25 to 0.9 mm, and the flange width is 1.0 to 2.5 mm.