JPS60192615A - Vacuum-molding method of both surfaces of container - Google Patents

Abstract

PURPOSE:To obtain a molded container having the highest strength within the limit height heaped by the given base material by taking the limited free blowing structure accomplished by keeping the space between molds in a vacuum atmosphere. CONSTITUTION:Plasticized, softened, expanded and heated sheet is guided to a forming station, and stretched by the molds 2, 3. When air tightness is made by mold clamping between the circumference of the mold and an expansible sheet, vacuum pressure is applied by a vacuum pump to the expansible sheet through the piping 5 and the fine pores 4 perforating both surfaces of each mold. Therefore, the stretched sheet which is kept still in a plasticized state is expanded between the molds under balanced tension caused by the gas pressure in independent foams and the viscoelastic force of thermoplastic resin forming foams and the viscoelastic force of thermoplastic resin forming foams and finally the resin heat is taken from the mold surfaces 2, 3 and the resin is cooled and hardened to obtain a molded body.

Description

Detailed Description of the Invention: Expansion ratio produced by incorporating low-boiling point organic substances such as propane, butane, and Freon in a copolymer resin such as polystyrene or styrene-based copolymer resin such as butadiene or methyl acrylate that can be copolymerized with styrene. A thermoplastic foam resin sheet of about 8 to 18 times the size, or a non-foamed sheet made of polystyrene (ps) #high-impact polystyrene (RIP8) on one or both sides of the same, unstretched polypropylene (○pp), polyethylene (pg), etc. Molded product containers based on foamed composite sheets made by laminating thermoplastic films generally have sharp dimensions and shapes as quality characteristics, as well as stable stacking height maintenance and bending deflection deformation. sufficient repulsion strength is required.

Ordinary molded containers have a defined angle of sidewall rise due to their shape design, but in this case, it is important to have a structure in which the sidewalls are in contact with each other when stacked. Regardless, the stacking height is simply determined by the influence of the side wall thickness. That is, if the side wall thickness is made thick, the stacking height must be maintained high, and conversely, if the side wall thickness is made thin, the stacking height can be maintained low.

Although the stacking height of molded product containers made from foamed sheets is generally much larger than those made from non-foamed sheets, the sag is greater than that of lightweight, thickened foamed sheet molded products. Due to its nature, it cannot be avoided.

However, from the viewpoint of transportation and inventory, it is better to keep the stacking height as low as possible because the number of items loaded will increase and the inventory space will be kept smaller for the same number of items. Although it is easy to see that it will have a favorable effect economically, on the other hand, when considering the deflection deformation strength required for molded product containers, it is important to consider the type and area weight of the base material, and the foaming degree. etc., it is advantageous in the opposite aspect because it is possible to simply make the shape as thick as possible so that the overall rigidity can be maintained high, but in the end, the two exhibit superiority and inferiority in opposite directions. Become. Under such circumstances, the present invention has been developed to solve the problem that the deflection deformation strength acting around the mouth of a molded product container is not only affected by the overall thick-walled shape, but also depends on the wall thickness around the mouth and the bottom riser. There is a particularly strong correlation with the wall thickness at the periphery, and this tendency is especially noticeable for containers with a relatively low stretching ratio and rectangular shapes, such as meat F-rays and lunch boxes. This invention was achieved by discovering that. That is, as a means of increasing the thickness, the thickness of the formed stretched sheet also has large voids, and the structure allows for air tightness at the peripheral line, so that both surfaces of the base material are coated with a pressure of 9-509-5O0 gauge pressure or more. Apply a vacuum pressure of, for example, -600mHf (gauge pressure), -650smT1f (gauge pressure), and apply a vacuum pressure of 50 to 60°C for the male mold.
The heated sheet is introduced into a molding mold with a male and female mating mold that enables foaming inside the mold with a controlled temperature.When molding this, the area to be reinforced is the area excluding the side wall part that affects the stacking height. In other words, the inside of the mold is maintained under a vacuum atmosphere in order to make the parts around the mouth part, the bottom part, and the part or all around the bottom rising part more highly foamed and thick. Improvements in the molding process to obtain molded containers with the highest strength within stacking height limitations for a given substrate by shaping the material into a marginally free-foamed structure. This is what was done.

This invention molds a container in a male-female mold that heats and plasticizes a thermoplastic foamed resin sheet or a composite foamed resin sheet in which a non-foamed thermoplastic resin layer is laminated on a thermoplastic foamed resin sheet and vacuum-forms the same. In the method of J-5001'jlH on both sides of the male and female molds so that the critical free foaming degree of internal foaming is greater than the wall thickness.
The content includes a double-sided vacuum forming method by applying a vacuum pressure of more than g.

FIG. 1 shows a schematic cross-sectional view of an example of the mold according to the invention in a state where the shape of the molded product is finally achieved.
Figure 5 is also for the purpose of comparison, and although it is a conventional mold that involves in-mold foaming for a thermoplastic foamed resin sheet, the wall thickness of the molded product is regulated on both surfaces of the mold. A schematic cross-sectional view of the case where it is received is shown.

In order to clearly show the difference in specific content between the two, enlarged views of the bubble shape and negative surface shape of the heat-stretched foam sheet around the mouth are shown below. etc. will be explained.

Generally, the molding operation itself involves leading the heated sheet, which has been plasticized, softened, and foamed, to the molding station and at the same time
and 3 (2' and 3'), stretch molding is first performed, and with air tightness created between the mold mouth area and the foamed sheet by mold clamping,
By applying vacuum pressure to the pores 4 and 4' that communicate with both surfaces of the mold, the stretched material is maintained in a vermilion plasticized state (V-) i
, 1' causes foaming within the mold under the balance between the gas pressure within the closed cells and the tension caused by the viscoelastic force of the thermoplastic resin forming the bubbles, and finally mold surfaces 2, 3 (2', 3')
The molded shape is achieved by removing the resin temperature and cooling and solidifying, and there is no particular difference between the two in terms of the molding operation itself.

However, the molding method shown in Fig. 1 for the thermoplastic foamed resin sheet in this case is called a mated mold, in which both male and female molds are fitted together. In this case, the shape of the gap should be the same as the target cross-sectional shape of the molded product, and in that case, the wall thickness of each part of the molded product should be less than the critical foaming degree achieved by in-mold foaming. Therefore, the inner and outer shapes of the molded product and its wall thickness are completely controlled by the mold surface, whereas in the method of the present invention, as shown in Figure 1, the stacking height is affected. The shape of the mouth area, bottom area, and surrounding area, excluding the side wall thickness dimension, is restricted only from one side of the mold. In other words, whether the shape of the molded product is to follow the male mold or the female mold will be determined depending on the market requirements in each case, but the vacuum applied to both sides of the stretching V-) Since a pressure difference is applied to the pressure by a pressure regulating valve, any shape can be selected. Since the molded product is made of thick, free-foamed material, the main feature of this book is that it is designed to strengthen the bending deformation strength that occurs at the mouth.

Example 1 After curing a compressed sheet made of polystyrene with Freon as a foaming agent and having a foaming ratio of 11.3 times and a thickness of 2 tones, it was heated for 10 minutes in a far-infrared heating furnace with an internal temperature of 180°C.
The average foaming thickness when heated for seconds was 4.2 m. This is in order of vertical and horizontal external dimensions 160 x 160, depth 2211
111E% rising angle 35.5°, side wall mold gap 5.
37mg, top and bottom of mouth? ) Meat molded using a meat tray mold with a free-foam structure in the 5.5 am height range, applying a vacuum level of -650 mHj' (gauge pressure) on the male mold side and a vacuum level of -600 mHfc gauge pressure on the female mold side.・The tray has a wall thickness around the mouth of 4.7 rMlr s, a side wall thickness of 3.37 mm, a bottom riser wall thickness of 4.6 mm, and an inner shape of the tan that matches the surface shape of the male mold. C, ioo
The stacking height of the sheets is 5801RI++%, and the repulsion strength is 390f when 5 concentrated deformation strains are applied to the center around the opening.
It had a

In order to deal with this, a vacuum degree of 1600 smHg was applied to a conventional mold in which the mold gap of each part was S, '57wm, and the wall thickness of the molded product was regulated by the mold surface shape on both the inner and outer surfaces. The molded product has a wall thickness of 3, S 7 WJRs.
'Stacking height of 100 sheets is 580m+, mouth area F
C5WjnL: 15 The repulsion strength when subjected to concentrated deformation strain was 340 g.

Example 2 Thickness 2 based on polystyrene using Freon as a blowing agent If! After curing an extruded sheet with an Iff N foaming ratio of 14 times, the average foaming thickness was 3.7.
Met. The vertical and horizontal external dimensions are 35.501, the side wall mold gap is 3.37 all, and the top and bottom of the mouth are p5.
．． 8. The meat tray was molded using a meat tray mold with a free foam structure in the height range, applying a vacuum level of -650 mHf (gauge pressure) on the male mold side and -600 #IIHf (gauge pressure) on the female mold side. The wall thickness around the mouth is 4.5. , side wall thickness 3.57111% bottom riser thickness 4.8 ttua
The inner shape of the mold must match the surface shape of the male mold,
The stacking height for 100 sheets is 580 m5 center F around the opening.
Repulsion strength 3 when intensive deformation strain is applied to C5lIII
It had a diameter of 75 f.

On the other hand, a conventional mold with a mold gap of 3.37 mg at each part and a molded product wall thickness of both the inner and outer surfaces, which are regulated by the mold surface shape, requires a vacuum of -600 aam Tlfl (gauge pressure). The thickness of each part is 1! +711! I, stacking height of 100 sheets is 58
01101!A concentrated deformation strain of 5 cities was applied around the 10th section, and the repulsion strength during running was 325F.

Fig. 1-1 is an explanatory sectional view showing the state of the molding die of the present invention at the end of molding, Fig. 1-2 is an enlarged sectional view of the vicinity of the mouth of the molded container, and Fig. 5-1 is FIG. 5-2 is an explanatory cross-sectional view showing the state of a conventional conventional molding die at the end of molding, and FIG. 5-2 is an enlarged cross-sectional view of the vicinity of the mouth of the molding container.

1.1' is a molded thermoplastic foam resin sheet), 2. ! ! 2' and 3' are molds, 4 and 4' are vacuum holes, and 5, 6, and 5' and 6' are piping for the vacuum pump.

Patent applicant Kanebuchi Chemical Industry Co., Ltd. Representative Patent Attorney Makoto Asano 1st! ! -1

Claims (2)

[Claims] (1) After heating and layering a thermoplastic foamed resin sheet or a composite foamed resin sheet in which a non-foamed thermoplastic resin layer is laminated on a thermoplastic foamed resin sheet, a container is formed in a male-female mold. In this method, the wall thickness of the side wall of the container is controlled on the mold surface so that it is below the critical free foaming wall thickness achieved by in-mold foaming, and the thickness of some or all of the other parts is controlled by the mold surface. A double-sided vacuum forming method for containers, characterized in that a vacuum pressure of 1500 wHg or more is applied from both sides of male and female molds to achieve the critical free foaming degree and wall thickness of in-mold foaming without restricting the surface. (2) The double-sided vacuum forming method according to claim 1, wherein the portion other than the side wall of the container is the bottom of the container, a rising portion around the bottom, and/or the periphery of the mouth.