JPH02178019A - Method and apparatus for manufacturing container - Google Patents

Abstract

PURPOSE:To manufacture a container having excellent optical characteristics and especially transparency by a method wherein preforming is done by pushing polypropylene sheet or polypropylene-based multi-layer sheet, which is heated up to a specified temperature, with a forming plug equipped with outlets of pressure fluid in a mold and, after that, the sheet is pressed against the inner wall surface of the mold by puffing out pressure fluid through the outlets. CONSTITUTION:The temperature of polypropylene sheet or polypropylene-based multi-layer sheet elevated by heating normally lies within the range from the one, which is lower than the melting point of polypropylene by 30 deg.C, to the melting point of polypropylene and preferably lies within the range of 150-164 deg.C. The production equipment is equipped with a mold 1 and a forming plug 2, the opening part 3 of which is made at the projecting part 2 of the plug. Forming material such as polypropylene sheet, polypropylene-based multi-layer sheet or the like, abuts against the contact part 25, which is made by the outer and inner peripheral edges of the opening part 3. Accordingly, since the contact area between the forming plug 2 and the forming material becomes smaller than that in the conventional production equipment, a container excellent in heat resistance and transparency can be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method and apparatus for manufacturing a container, and more specifically, the present invention relates to a container manufacturing method and a manufacturing apparatus, and more specifically, it relates to a container manufacturing method and a manufacturing apparatus, and more specifically, a method and apparatus for manufacturing a container, which improves the uniformity of wall thickness during molding near the melting point in the solid molding range. A container which can obtain a container, and which can maximize the characteristics of polypropylene or polypropylene-based resin end layers without reducing the excellent optical properties, especially the transparency, of these materials. The present invention relates to a manufacturing method and a manufacturing device that can be suitably used in this method, can accommodate various shapes, and is capable of deep drawing.

[Prior art and issues to be solved by the invention WU] For example, in the food packaging field, polypropylene sheets,
Containers made from polypropylene resin laminate sheets are widely used.

Such containers are generally manufactured by plug-assisted molding in which a sheet of molding material such as a polypropylene sheet or a polypropylene resin laminate sheet is forced into a mold using a molding plug.

Specifically, the molding material sheet heated to the ripening temperature is pushed into the mold using a molding plug, and the space formed by the molding material sheet and the inner wall of the mold is evacuated to remove the molding material sheet. The vacuum forming method involves pressing the mold against the inner wall surface of the mold using atmospheric pressure, the forming method performs this operation in the solid phase range below the thermoforming temperature of the molding material sheet, and the molding material sheet is placed inside the mold using a molding plug. A molding method has been put into practical use in which a sheet of molding material, which has been pushed into a mold, is pressed against the inner wall surface of the mold using a pressurized fluid such as compressed air.

However, in these conventional molding methods, it is difficult to obtain containers with uniform wall thickness, so there is a problem that the resulting containers have uneven transparency and strength.

Therefore, various attempts have been made to solve this problem.

For example, in Japanese Patent Publication No. 53-1790, as shown in No. 512, a mold A having an open molding cavity a is
a clamping device C for clamping the sheet B of thermoplastic material around the opening of the molding cavity a; and a molding plug mounted to be inserted into the molding cavity a to squeeze the sheet B into the molding cavity a. D, and means E for generating a fluid pressure difference on both sides of the wall of the squeezed sheet a to compress the sheet B against the wall surface of the molding cavity a; A molding device is disclosed in which a portion of the molding plug located at the rear of the molding plug has a shape including a concave side surface in its cross section.

However, this device has a disadvantage in that, because the shape of the molding plug is special, it is difficult to quickly adapt to all container shapes, and it is especially difficult to adapt to round containers.

In addition, in the container obtained using this device, the wall thickness near the point of contact with the molding plug is thin, so the strength of this area is not sufficient.

In particular, when a BOPP propylene sheet or a polypropylene resin laminate sheet is used as a material, there is a problem that the transparency of this portion is reduced.

The present invention has been made based on the above circumstances.

An object of the present invention is to obtain a container with improved wall thickness uniformity when molded near the melting point in the solid molding range, and to improve the optical properties, especially transparency, of polypropylene or polypropylene resin laminates. A method for producing a container that maximizes the features of these materials without degrading the quality of the material, and a container that can be suitably used in this method and that can be made into various shapes and have a depth. The object of the present invention is to provide a manufacturing device capable of drawing.

[Means for Solving the Problems] In order to solve the above problems, the inventors have made extensive studies and found that in plug assist molding, a polypropylene sheet or a polypropylene resin laminate sheet is heated to a specific temperature. After.

If a pressure fluid is introduced by a specific means to press a polypropylene sheet or a polypropylene resin laminate sheet against the wall of a mold to form a container, a container with improved wall thickness uniformity can be obtained, and the polypropylene or The excellent optical properties of polypropylene resin laminates, especially the fact that the characteristics of these materials can be brought out to the maximum without reducing their transparency, and that this method is suitable for molding with a specific structure. The present invention has been arrived at by discovering that a particular manufacturing device equipped with a plug can be advantageously used.

The structure of the invention according to claim 1 is a method for manufacturing a container by plug assist molding using a polypropylene sheet or polypropylene multilayer sheet as a material, wherein the polypropylene sheet or polypropylene multilayer sheet is 30° C. lower than the melting point of polypropylene. After heating the polypropylene sheet or polypropylene multilayer sheet to a temperature within a range from the temperature to the melting point of the polypropylene, the polypropylene sheet or polypropylene multilayer sheet is pressed against a molding plug equipped with a pressurized fluid discharge port. A method for manufacturing a container, characterized in that the polypropylene sheet or polypropylene multilayer sheet is pressed against the inner wall surface of the mold by pressing the polypropylene sheet or polypropylene multilayer sheet against the inner wall surface of the mold by pressing the polypropylene sheet or polypropylene multilayer sheet into the mold for preforming by pressing the polypropylene sheet into a mold and then discharging a pressure fluid from the discharge port. can be.

The structure of the invention according to claim 2 includes a mold and a molding plug provided with a plug protrusion inserted into the mold, and a molding material in the plug protrusion of the molding plug. 913 is a container manufacturing apparatus, characterized in that an opening is provided on a surface in contact with the opening, and a pressurized fluid discharge port facing the opening; The container manufacturing apparatus according to claim 2, wherein the ratio of the diameter of the stopper to the diameter of the inner peripheral edge is 0.80 to 0.97, and the structure of the invention according to claim 4 is such that 4. A bag for manufacturing a container according to claim 2 or 3, wherein the contour is linear.

In the method of the present invention, first, a polypropylene sheet or polypropylene multilayer sheet is heated to a temperature within a range from 30° C. lower than the melting point of polypropylene to the melting point of polypropylene.

The polypropylene multilayer sheet to be used is composed of a resin laminate mainly composed of polypropylene.

Specifically, for example, polypropylene/adhesive/ethylene/vinyl alcohol copolymer/adhesive/polypropylene, high density polyethylene/polypropylene/, high density polyethylene/polypropylene/adhesive/ethylene/
Vinyl alcohol copolymer/adhesive/polypropylene, polyethylene terephthalate/polypropylene, polyethylene terephthalate/polypropylene/l! i-adhesive/ethylene-vinyl alcohol copolymer/adhesive/laminated sheet of thermoplastic resin mainly composed of polypropylene such as polypropylene.

Regarding the means for heating the polypropylene sheet or polypropylene multilayer sheet, these sheets can be heated by
There is no particular restriction as long as it can be heated to a temperature within the range of 30°C lower than the melting point of polypropylene to the melting point of polypropylene. A radiation heating method in which a polypropylene sheet or a polypropylene multilayer sheet is indirectly heated from both upper and lower surfaces can be suitably employed.

In the method of the present invention, the temperature reached by heating the polypropylene sheet or polypropylene multilayer sheet is usually in the range from 30°C lower than the melting point of polypropylene to the melting point of polypropylene, preferably 150°C to 164°C. It is ℃.

If this temperature does not exceed 30"C lower than the melting point of polypropylene, the heat resistance of the resulting container may decrease,
This results in a decrease in the wall thickness of the bottom surface of the resulting container, resulting in a decrease in the rigidity of the container. On the other hand, when the melting point of polypropylene is exceeded, the transparency of the resulting container decreases.

In the method of the present invention, after heating the polypropylene sheet or polypropylene multilayer sheet to a temperature within the above range, the polypropylene sheet or polypropylene multilayer sheet is moved to a molding zone of a mold, and then, Shape.

There is no particular restriction on the means for moving the polypropylene sheet or polypropylene multilayer sheet to the molding zone of the mold, and known means can be suitably employed.

The polypropylene sheet or polypropylene multilayer sheet moved to the molding zone of the mold is molded by pressing the molding plug onto the polypropylene sheet or polypropylene multilayer sheet to mold the polypropylene sheet or polypropylene multilayer sheet into a metal. This is carried out by a preforming step of pushing it into a mold, and a step of discharging a pressure fluid from the discharge port of the molding plug to press the polypropylene sheet or polypropylene multilayer sheet against the inner wall surface of the mold to shape it.

The molding plug is provided with a pressure fluid discharge port, and in the method of the present invention, the manufacturing apparatus according to any one of claims 2 to 4, which is provided with a specific molding plug, is particularly preferably used. Can be done.

For example, the polypropylene sheet or polypropylene multilayer sheet is placed inside the mold by discharging the pressure fluid from around the molding plug using a manufacturing device equipped with a conventional molding plug that does not have the discharge port. When the polypropylene sheet or polypropylene multilayer sheet is pressed against the wall surface and shaped, the thickness of the polypropylene sheet or multilayer polypropylene sheet is pressed against the inner wall surface of the mold while maintaining almost the same thickness as in the preforming process, so that the thickness of the bottom surface of the resulting container is reduced. becomes extremely thick, and the wall thickness near the contact portion with the molding plug becomes thinner, making it impossible to manufacture a container with excellent wall thickness uniformity.

The pressure fluid is capable of generating a fluid pressure difference sufficient to press the polypropylene sheet or polypropylene multilayer sheet pushed into the mold by the operation of the preforming process against the inner wall surface of the mold. For example, compressed air can be suitably used.

In the method of the present invention, after the above-mentioned shaping is performed using the pressure fluid, cooling is performed using a mold to obtain a container.

The container thus obtained has excellent uniformity in wall thickness distribution, has excellent rigidity and heat resistance, and has excellent optical properties, especially transparency, which the polypropylene sheet or polypropylene multilayer sheet has. It can be suitably used, for example, in the food packaging field.

Next, the manufacturing apparatus of the present invention will be explained with reference to the drawings.

As shown in FIG. 1, the manufacturing apparatus of the present invention includes a mold l,
A molding plug 2 is provided.

As shown in FIG. 2, the opening 3 of the molding plug 2 is formed in the plug projection 2G, and the molding material, such as the polypropylene sheet or polypropylene multilayer sheet, is formed between the outer peripheral edge 21 of the opening 3 and the inner surface. The contact portion 25 formed by the peripheral edge 22 comes into contact with the contact portion 25 . Therefore, the contact area between the molding plug and the molding material in the manufacturing apparatus of the present invention is:
Since the contact area between the molding plug and the molding material in conventional manufacturing equipment is reduced, the manufacturing equipment of the present invention can provide a container that is superior in terms of heat resistance and transparency.

Furthermore, the molding plug 2 has a pressure fluid discharge port 4 facing the opening 3.

The molding plug 2 is installed in a compressed air box 40 having a pressure fluid supply means (not shown), for example, as shown in FIG. From there, pressure fluid is discharged toward the molding material 50 pushed into the molding recess 30 of the mold 1 by the contact portion 25 . Specifically, for example, if a compressed air supply device is used as a pressure fluid supply means (not shown), compressed air is discharged toward the molding material 50.

Therefore, in the manufacturing apparatus of the present invention, pressure fluid is discharged from inside the molding plug 2.

It is no longer necessary to introduce pressure fluid along the outer wall of the molding plug as in the molding plug in conventional manufacturing equipment, and the outline of the outer wall of the plug protrusion 20 in the molding plug 2 is made straight. Can be done. That is, in the manufacturing apparatus of the present invention, it is possible to simplify the shape of the molding plug 2, and it is easy to adapt to various container shapes.

In the present invention, for example, the ratio d, /d between the diameter d of the outer peripheral edge 21 shown in FIG. 2 and the diameter d of the opening end 15 of the molding recess of the mold 1 shown in FIG. 3 is 0.75. -0.95 is preferable. If this ratio is smaller than 0.75, the opening of the container molded using this molding plug will not be sufficiently elongated, and the resulting container will be different from other containers. The wall thickness may become thinner or the appearance may become poor. On the other hand, if it is larger than 0.95, the opening of a container molded using this molding plaque will be too elongated, and the resulting container will have a thin wall near the opening.

Furthermore, the ratio d t / d between the diameter d of the outer peripheral edge 21 and the diameter d2 of the inner peripheral edge 22 of the molding plug 2 shown in FIG.
l is preferably in the range of 0.80 to 0.97,
If this ratio is less than 0.80, the area of the contact portion 25 increases, leading to an increase in the contact area between the molding material such as a polypropylene sheet or polypropylene multilayer sheet and the molding plug, resulting in an increase in transparency and It becomes difficult to obtain a container that is advantageous in terms of heat resistance.

Furthermore, for example, the length fLI of the mold insertion portion of the plug protrusion 20 in the molding plug 2 shown in FIG.
The ratio of the depth of the molding recess 30 of the mold 1 shown in the figure to the pattern 2 is 12
/1. is preferably in the range of 0.10 to 0.70. If this ratio is less than 0.10, the bottom wall of the resulting container will become thinner, making it difficult to obtain a container with sufficient strength. It becomes difficult.

On the other hand, if it exceeds 0.70, the molded plug 2 will be pushed too deeply into the molded recess 30, and the plug marks will become obvious on the resulting container, making it difficult to obtain a container with a good appearance. become.

In the present invention, it is preferable that the molding plug 2 is formed of a heat insulating material.

When the molding plug 2 is made of a heat insulating material, the temperature at the time of contact between the molding plug 2 and the molding material such as the polypropylene sheet or polypropylene multilayer sheet is stabilized, making it possible to create a container with excellent heat resistance. Because you can get it. Such an effect can also be achieved, for example, by forming the molding plug 2 from metal and controlling the surface temperature of the molding plug 2.
This has the drawbacks of making the device more complex and larger, as well as increasing costs. In addition, if the molding plug 2 is made of a heat insulating material, the slippage between the molding plug 2 and the molding material such as the polypropylene sheet or polypropylene multilayer sheet will be improved, thereby improving the uniformity of the wall thickness and the surface of the molding plug 2. A container with an excellent appearance can be obtained.

Examples of the heat insulating material include foamed glass.

The contact portion 25 of the molding plug 2 can be formed using a heat insulating material such as glass fiber, carbon fiber, alumina/silica fiber, alumina powder, basic magnesium carbonate powder, etc. Preferably, the peripheral edge is formed into a curved surface.

As described above, the manufacturing apparatus of the present invention is equipped with a specific molding plug that is provided with a pressurized fluid discharge port inside, and can be particularly preferably used in the manufacturing method according to claim 1. can.

[Example] Next, Examples and Comparative Examples of the present invention will be shown to further specifically explain the present invention.

(Example 1) A polypropylene sheet (trade name "Pure Ray"; manufactured by Idemitsu Petrochemical Co., Ltd., thickness 0.85") was heated from both sides of the sheet using a radiant heating method using a ceramic heater.
Heated to 45°C.

Next, the polypropylene sheet is moved onto the mold l of the manufacturing apparatus shown in FIG. 1, and the molding plug 2 (outer diameter d, =80mm, diameter d of inner periphery
, =76ms, dz/d+=0.95. Diameter d of outer periphery
1 and the diameter d of the molding four-part open end of the mold d, /
d = 0.87) toward the molding recess 30 of the mold 1 while inserting the molding plug 2 into the BOPP propylene sheet.
The polypropylene sheet was pushed into the molding recess 30 of the mold I to a position where the drawing ratio was 0.20.

In this example, a mold with a diameter of 91.5 mm, a depth of 41.21 mm, and a drawing ratio of 0.45 was used.

Subsequently, pressure 4 is released from the pressure fluid discharge port 4 of the molding plug 2.
The polypropylene sheet was pressed against the inner wall surface of the molding recess 30 by discharging compressed air of kg/cm2, and then cooled to obtain a container.

The wall thickness of the resulting container was measured at seven locations shown in FIG. In addition, the optical properties, heat resistance, and mold reproducibility of this container were evaluated.

The results are shown in Table 1.

The optical properties, heat resistance, and mold reproducibility were evaluated as follows.

Optical properties: Haze at the center of the side of the container was measured.

Heat resistance: A heat resistance test was conducted under the conditions of a temperature of 120° C. and a pressure of 2 kg/cm”·G for 30 minutes.

Evaluated by visual observation into the following three stages: Ta.

O: No deformation observed.

Δ: Slight deformation is observed.

×: Deformation is observed.

Mold reproducibility; ○: Good Δ: Slightly poor (no problem in use) X: Poor (Example 2) In Example 1, the heating temperature of the polypropylene sheet was changed from 145°C to 155°C. It was carried out in the same manner as in Example 1.

(Example 3) The same procedure as in Example 1 was carried out except that the heating temperature of the polypropylene sheet was changed from 145°C to 162°C.

(Comparative Example 1) Example 1 except that the heating temperature of the polypropylene sheet was changed from 145°C to 130°C.

A container was manufactured in the same manner as in Example 1, and the wall thickness of the obtained container was measured, and the optical properties, heat resistance, and mold reproducibility were evaluated.

The results are shown in Table 1.

(Comparative Example 2) A container was manufactured in the same manner as in Example 1, except that the heating temperature of the polypropylene sheet was changed from 145°C to 170°C, and the wall thickness of the resulting container was measured. At the same time, optical properties, heat resistance, and mold reproducibility were evaluated.

The results are shown in Table 1.

(Comparative Example 3) In Example 1, instead of using the manufacturing apparatus of the present invention having a molding plug as shown in FIG. 2, a conventional molding plug D (diameter 73) as shown in FIG. A container was manufactured under the same conditions as in Example 1, except that a manufacturing device with a radius of curvature of 451) at the tip was used, and the wall thickness of the resulting container was measured, and the optical properties were measured. , heat resistance and mold reproducibility were evaluated.

The results are shown in Table 1.

(Comparative Example 4) Comparative Example 3 except that the heating temperature of the polypropylene sheet was changed from 145°C to 155°C.

A container was manufactured in the same manner as in Example 1, and the wall thickness of the obtained container was measured, and the optical properties, heat resistance, and mold reproducibility were evaluated.

The results are shown in Table 1.

(Comparative Example 5) A container was manufactured in the same manner as in Example 1, except that the heating temperature of the polypropylene sheet was changed from 145°C to 162°C in Comparative Example 3, and the wall thickness of the resulting container was measured. At the same time, optical properties, heat resistance, and mold reproducibility were evaluated.

The results are shown in Table 1.

(Comparative Example 6) A container was manufactured in the same manner as in Example 1 except that the molding plug was not used, and the wall thickness of the obtained container was measured, and the optical properties and Heat resistance and mold reproducibility were evaluated.

The results are shown in Table 1.

(Comparative Example 7) A container was manufactured in the same manner as in Example 1, except that the molding plug was not used in Example 2, and the wall thickness of the obtained container was measured, and the optical properties and Heat resistance and mold reproducibility were evaluated.

The results are shown in Table 1.

(Comparative Example 8) A container was manufactured in the same manner as in Example 1, except that the molding plug was not used in Example 3, and the wall thickness of the obtained container was measured, and the optical properties and Heat resistance and mold reproducibility were evaluated.

The results are shown in Table 1.

(Gourd, hereafter blank) (Evaluation) As is clear from Table 1, the containers obtained by the manufacturing method of the present invention have excellent uniformity in wall thickness, and little deterioration in optical properties. When heated to a temperature range of 164° C., a container with good heat resistance and mold reproducibility can be obtained.

[Effects of the Invention] (1) According to the invention of claim 1, it is possible to improve the uniformity of the wall thickness, and the excellent optical properties of the polypropylene or polypropylene resin laminate,
In particular, it is possible to provide a method for manufacturing containers that does not reduce transparency and can maximize the features of these materials in terms of heat resistance and mold reproducibility.

(2) Furthermore, according to the inventions of claims 2 to 4, it can be suitably used in this manufacturing method, has a simple shape, can be deep drawn, and can be easily formed into various container shapes. It is possible to provide an industrially useful container manufacturing apparatus equipped with a molding plug that can handle the following.

[Brief explanation of the drawing]

11N is an explanatory view showing an example of the manufacturing apparatus of the present invention, FIG. 2(A) is a plan view showing an example of a molding plug in the manufacturing apparatus of the present invention, and FIG. FIG. 3 is an explanatory view showing an example of a mold in the manufacturing apparatus of the present invention, FIG. 4 is a sectional view showing an example of a container obtained by the manufacturing method of the present invention, and FIG. The figure is an explanatory diagram showing an example of a conventional container manufacturing apparatus, and the sixth
The figure is an explanatory diagram showing an example of a molding plug in a conventional container manufacturing apparatus. l... Mold, 2... Molding plug, 3... Opening, 4... Pressure fluid discharge port, 20... Plug protrusion,
21...Outer peripheral edge, 22...Inner peripheral edge Fig. 1 Fig. 2 (A) (B) Fig. 3 Fig. 4 IVVVI■ Fig. 5 Fig. 6 Heater φ73.2--→

Claims (4)

[Claims] (1) In a method of manufacturing a container by plug assist molding using a polypropylene sheet or polypropylene multilayer sheet as a material, the polypropylene sheet or polypropylene multilayer sheet is heated from a temperature 30°C lower than the melting point of polypropylene to a temperature of 30°C lower than the melting point of polypropylene. After heating the polypropylene sheet or polypropylene multilayer sheet to a temperature within a range of A method for producing a container, which comprises performing preforming, and then discharging a pressure fluid from the discharge port to press the polypropylene sheet or polypropylene multilayer sheet against the inner wall surface of a mold. (2) A molding plug comprising a mold and a plug protrusion inserted into the mold, and an opening on a surface of the plug protrusion of the molding plug that contacts the molding material. What is claimed is: 1. An apparatus for manufacturing a container, comprising: a pressure fluid discharge port facing the opening; (3) The container manufacturing apparatus according to claim 2, wherein the ratio of the diameter of the outer peripheral edge of the opening to the diameter of the inner peripheral edge is 0.80 to 0.97. (4) The container manufacturing apparatus according to claim 2 or 3, wherein the outer wall of the plug protrusion has a linear outline.