JPH0724916A - Manufacture of plastic container - Google Patents

Abstract

PURPOSE:To prevent a pinhole from being generated by a method wherein a welded part of a plastic sheet is protected, and certainly welded to a container body. CONSTITUTION:A surface of a plastic sheet 2A is covered with a heat-resisting release sheet 7. A heating metal mold 4 pushes a surface of the plastic sheet 2A via the heat-resisting release sheet 7 and welded that by heating. The heat- resisting release sheet 7 covering a container body in welding is kept in a covering state, and a melt part of the plastic sheet in a covering state, and a melt part of the plastic sheet 2A is cooled. Since the surface of the melt part of the heat-resisting release sheet 7 is protected from heating to cooling thereby, the surface of the plastic sheet 2A is protected with the heat-resisting release sheet 7, and a pinhole can be prevented from being generated. Further, since heating temperature of the plastic sheet 2A can be set at high temperature, the plastic container can be certainly welded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a plastic container mainly filled with a chemical solution, and more particularly, to manufacturing a plastic container in which a peripheral edge of a plastic sheet is melted to form a container body and a spout is welded to the container body. Regarding the method. The mouth plug is cylindrical and has a central hole that is hermetically sealed.

[0002]

2. Description of the Related Art There is a container shown in FIG. 1 in which a container body is welded with a spigot. This container is made of plastic. The contact surface between the spout 1 and the container body 2 is made of thermoplastic plastic so that the spout 1 and the container body 2 are melted and tightly adhered to each other. Usually, the inner surface of the container body 2 is made of a thermoplastic plastic sheet, and the entire spout is made of a thermoplastic such as polyethylene.

The container shown in FIG. 1 is manufactured by welding a peripheral edge of a plastic sheet to manufacture a container body 2 and then welding a spout 1 to the container body 2. The upper end edge of the container body 2 is open without being welded in FIG. The stopper 1 is inserted into the opening of the container body 2 and welded.

The container body 2 is manufactured as follows. Two plastic sheets are laminated, and the peripheral edge thereof is pressed by a heating die, heated, melted, and welded. The melted portion is sandwiched between cooling molds and forcedly cooled.

The container body manufactured as described above is
The spout 1 is welded as shown in FIGS. As shown in FIG. 2, the tip of the plug 1 is inserted into the ring-shaped preheating heater 3. The preheating heater 3 preheats the surface of the plug 1 to be inserted. As shown in FIG. 3, the container body 2 is opened and the spout 1 is inserted. The container body 2 can open by adsorbing both sides of the opening. FIG. 4 shows a state in which the spout 1 is inserted into the container body 2. The connection portion of the container body 2 with the spout 1 is transferred between the heating molds 4, and the heating mold 4 shown in FIGS. 4 and 5 clamps the upper end surface of the container body 2 in a heated state. In this state, the container body 2 is heated from the surface, and the spout 1 is welded. After the spout 1 is welded to the container body 2, the surface of the container body 2 is clamped by a cooling mold 5 to forcibly cool it.

As described above, in the method of welding the spigot to the container body and the plastic sheet to form the container body, it is important to melt the plastic so that pin holes cannot be formed. . In particular, the container filled with the chemical solution is required to have no pinhole at the welded portion. It is important that the container filled with the liquid is not limited to the chemical liquid, and that it tightly adheres to each other in order to prevent leakage due to pinholes and to prevent bacteria from entering.

[0007]

Various methods have been proposed in order to prevent the formation of pinholes by eliminating the gap between the spout and the container body. For example, JP-A-3-
Japanese Patent No. 49762 and Japanese Utility Model Laid-Open No. 61-194638 describe a technique of welding to a container body using a unique spigot. As shown in FIG. 6, the containers described in these publications are provided with projecting portions 6 along the container body 2 on both sides of the spout 1. This method has a feature that it can be closely attached to the container body without a gap as compared with a cylindrical stopper.

Further, Japanese Patent Laid-Open No. 3-268925 discloses a technique of heating a spigot to a temperature higher than its melting point, inserting it into a container body, and welding it. The method described in this publication can make the contact with the container body more effective by heating the spout. However, these manufacturing methods have a drawback in that molten plastic adheres to the heating mold when the heating mold is separated from the welding surface. When the plastic adheres to the heating mold, a part of the container body becomes thin and causes pinholes. Further, the plastic heated and melted by the heating mold may flow before being cooled by the cooling mold. This is because it is heated and melted in a state where it easily flows. Particularly, since it is necessary to weld the plastic to the inside of the heating die rather than the pressing surface, the surface of the plastic that comes into contact with the heating die is melted in a state in which it easily flows. When the plastic flows, the wall thickness is partially deformed, causing pinholes. This state is the same not only when the spout is connected to the container body but also when the container body is manufactured by welding the plastic sheet, which causes a pinhole.

Further, in the conventional method of manufacturing a plastic container, when the plastic sheet is heated and pressed by the heating die, the convex portion 9 is formed on the periphery of the heating die 4 as shown by the chain line as shown in FIG. it can. If this convex portion 9 is sandwiched between cooling molds 5 and molded to have the same thickness, a thin portion is formed, which causes a pinhole. The heated plastic is melted and flows as shown by the arrow in FIG. Since it is necessary to heat weld the plastic sheet on the inner surface of the heating mold,
The surface of the plastic sheet is heated above the melting temperature. The plastic in this state is in a state in which it easily flows. Further, in the heating die, in order to surely weld the welding surface, it is necessary to press the surface of the plastic sheet with a considerable pressure. Molten plastic is
The convex portion 9 is pressed by the heating mold 4 and pushed out to the periphery thereof.
Becomes

When the temperature of the heating mold is lowered and the pressing force is weakened, the convex portion becomes small. However, this makes it difficult to reliably weld the plastic sheet. This is because the welded surface cannot be completely melted by heat.

As shown in FIG. 7, when plastic having projections 9 formed on the periphery of the heating mold 4 is sandwiched by cooling molds 5 and forcedly cooled, the projections 9 are pressed and corrected to the same thickness. To be done. At this time, a thin portion is formed on the right side of the convex portion 9 and causes a pinhole. It seems that this problem can be eliminated by using a narrow cooling die that does not press the convex portion. However, in reality, it is not possible to use a cooling mold that does not press the convex portion. This is because the heated plastic of the convex portion cannot be cooled efficiently. Since the convex portion is in the vicinity of the heating die and is the molten plastic extruded by the heating die, this portion also needs to be forcibly cooled.

A method has also been developed in which the structure of the cooling mold is devised so that the convex portion of the plastic is not pressed.
This is a method of fixing a cushioning material such as rubber to the pressing surface of the cooling mold. In this method, since the plastic is pressed through the cushioning material, the protrusions are not modified to have the same thickness. However,
This method has a drawback in that the plastic sheet cannot be cooled efficiently because of the buffer material. This is because the thermal conductivity of the cushioning material is poor. Therefore, there is a drawback that the plastic sheet cannot be cooled in a short time and the productivity is reduced.

The adverse effect of pinholes formed by thinly correcting the convex portion of the cooling mold can be eliminated by a natural cooling method without using the cooling mold. However, this method does not forcibly cool the plastic sheet, so that the cooling time becomes long.
Not only that, but there is a drawback that the convex portions remain as a product. The convex portion remaining on the product transforms the welded portion of the plastic sheet into a wavy shape and further reduces the commercial value without forming a clean welded surface. This method cannot be practically used because the welded product is not clean and it takes a long time to cool.

The present invention was developed for the purpose of solving this drawback. An important object of the present invention is to manufacture a plastic container that prevents molten plastic from adhering to a heating mold and further prevents molten plastic from flowing to effectively prevent pinholes. To provide a method.

[0015]

In order to achieve the above object, the method of manufacturing a container of the present invention welds a spigot to a container body as follows. Insert the stopper 1 into the container body 2,
This is an improved method in which the surface of the container body 2 is pressed by a heating mold 4 to be heated from the outside, the container body 2 is pressed against the inserted plug 1 to be welded, and then the molten portion is cooled.

In the method for manufacturing a container of the present invention, the surface of the container 1 connecting portion of the spout 1 is covered with a heat-resistant release sheet 7, and the surface of the container body 2 is heated with the heating die 4 through the heat-resistant release sheet 7. By pressing and heating, the contact surface between the container body 2 and the spout 1 is welded. The heat-resistant peeling sheet 7 covering the container body 2 does not peel off when the container body is heated. After the welded portion of the container body 2 is cooled, it is peeled off from the container body.

Further, in the method for producing a plastic container according to the second aspect of the present invention, the container body is produced as follows. The plastic sheets 2A are laminated and the surface thereof is pressed by the heating mold 4 and heated from the outside, and the plastic sheets 2A are melted and welded to form a container body.

Further, in order to prevent the formation of pinholes in the welded portion of the container body 2, the method of the present invention covers the surface of the plastic sheet 2A with a heat-resistant peeling sheet 7 through which the heat-resistant peeling sheet 7 is interposed. Then, the surface of the plastic sheet 2A is pressed by the heating die 4 to heat, melt, and weld. The heat-resistant release sheet 7 that covers the surface of the plastic sheet 2A does not release when the plastic is heated. The plastic sheet 2A is held in a covered state to cool the melted portion, and after cooling, the heat resistant release sheet is released from the plastic sheet 2A.

Further, in the method of manufacturing a plastic container according to a third aspect of the present invention, the heat-resistant peeling sheet 7 for covering the surface of the container body 2 or the plastic sheet 2A is held in a covered state and the molten portion is cooled by the mold 5. Or cooled by spraying pressurized air, and after cooling, heat-resistant release sheet 7
Peel off. In the method of cooling the melted portion covered with the cooling mirror heat-resistant release sheet 7 with the cooling die 5 or the pressurized air, both the cooling die and the pressurized air can be used together to cool the melted portion. Further, in the production method of the present invention, the melted portion coated with the heat resistant release sheet can be cooled with pressurized air without using a cooling mold.

[0020]

The method of manufacturing the plastic container of the present invention is as shown in FIG.
As shown in, the heat-resistant release sheet 7 is sandwiched and the surface of the plastic sheet 2A of the container body 2 is heated and pressed by a heating die. The heat-resistant release sheet 7 covers the surface of the plastic sheet 2A pressed by the heating die 4. The heat-resistant release sheet 7 that covers the surface of the plastic sheet 2A is
As shown in FIG. 8, the plastic pressed and melted by the heating mold 4 is prevented from flowing to the peripheral edge of the heating mold 4. The plastic pressed by the heating die 4 tends to flow out to the periphery of the heating die 4 as indicated by the arrow. When the melted plastic moves to the peripheral edge of the heating mold 4, the protrusion 9
You can The heat resistant release sheet 7 presses the convex portions 9 to suppress the flow of the melted plastic. Therefore, the heat-resistant peeling sheet 7 is used to form the convex portions 9 formed on the periphery of the heating mold 4.
Will be lower.

Further, in the method for manufacturing a plastic container of the present invention, the heat resistant peeling sheet 7 is peeled off after cooling the welded portion. Therefore, it is possible to effectively prevent the molten plastic from adhering to the heating mold 4. A heating mold 4 having a heat-resistant peeling layer formed on its surface has already been developed. However, even if this heating die 4 is used, it is difficult to reliably prevent the molten plastic from adhering to the heating die 4. This is because the heat-resistant peeling layer needs to be peeled off from the surface of the plastic while the plastic is molten. The molten plastic is extremely easy to adhere to the surface of the heating mold 4 and can be freely deformed. Therefore, it is difficult to completely prevent the plastic from being adhered to the heating mold 4.

In the manufacturing method of the present invention, the heat-resistant release sheet is not peeled off when the plastic is melted. When the plastic cools and hardens, it peels from the container body. The cooled plastic does not deform and does not adhere to the heat resistant release sheet when it is released. Therefore, the plastic does not adhere to the heat-resistant release sheet and the container does not become partially thin. Further, the heat-resistant release sheet that protects the surface until the plastic is cooled prevents the surface of the plastic from being deformed before the heating mold is opened to cool the molten portion.

If the heat-resistant release sheet is peeled off immediately after heating the container body, the surface of the container body is heated to a high temperature up to the melting temperature, so that the container body is in a state of being easily deformed. Therefore, when peeling the heat-resistant release sheet before cooling the plastic, the container body is easily deformed, and even when the heat-resistant release sheet is peeled off, the wall thickness of the container body due to the movement of the molten resin is deformed. It may cause pinholes and uneven thickness.

In the method of the present invention, in order to prevent deformation of the heated container body, the heat-resistant release sheet coated with the plastic sheet of the container body is not peeled at the time of heating, but is peeled after cooling. Therefore, even if the container body is heated to a high temperature, pinholes can be reduced. This is
By increasing the heating temperature of the container body, the welding can be performed more reliably. That is, the manufacturing method of the present invention has an excellent feature that the plastic can be surely welded to prevent the generation of pinholes in the container body.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. However, the following examples illustrate a manufacturing method for embodying the technical idea of the present invention,
The present invention does not specify the method for manufacturing the plastic container as the following method.

Further, in this specification, for easy understanding of the claims, the numbers corresponding to the members shown in the embodiments are referred to as "claims column", "action column", and "action column". It is added to the members shown in the section of "Means for Solving the Problems". However, the members shown in the claims are
It is by no means specific to the members of the examples.

A specific example of the method of manufacturing the container shown in FIG. 1 will be described in detail below. The container shown in FIG. 1 is manufactured by welding the spout 1 to the container body 2. The container body 2 is formed by heat-sealing the periphery of the plastic sheet 2A into a bag shape. The plastic sheet 2A is a single-layer plastic film,
Alternatively, multiple layers of plastic film are used.
In order to heat-weld the periphery of the plastic sheet 2A and to weld the spout 1 to it, at least the inner surface of the container body 2 is made of a thermoplastic film, or the whole is made of a thermoplastic film. Mouth plug 1
It is formed of a thermoplastic such as polyethylene into a cylindrical shape, and the central hole can be closed with a cap having a rubber plug embedded therein.

The container body 2 is manufactured by welding a plastic sheet 2A. The plastic sheet 2A is manufactured by heat-welding a portion excluding a portion where the spout 1 is welded, that is, both side edges and a lower edge. After that, the stopper 1 is inserted into the opening which is not welded, and this is welded to complete the product.

The plastic sheet of the container body is welded at the three peripheral edges as follows. As shown in FIG. 9, the peripheral edges of the two-layered plastic sheets 2A laminated with each other are sandwiched by a heating die 4 and heated from the surface. At this time, the heat-resistant peeling sheet 7 is disposed between the surface of the plastic sheet 2A and the heating die 4.

The heat-resistant peeling sheet 7 includes a heat-welding film 7
Use a Teflon sheet that freely deforms along the surface of the. As the heat-resistant release sheet 7, any sheet that has heat resistance and flexibility and that can be easily released from the plastic sheet 2A can be used instead of the Teflon sheet. The heat-resistant release sheet 7 heats the plastic sheet 2A and then covers the surface of the plastic sheet 2A until it is cooled.

Further, the heat-resistant release sheet 7 presses the surface of the plastic sheet 2A to reduce the protrusions on the periphery of the heating die 4. The plastic sheet 2A sandwiched between the heating molds 4 tends to flow as indicated by the arrow in FIG. This is because the molten plastic sheet 2A is pressed by the heating mold 4. When the molten plastic flows in the direction of the arrow, it is extruded to the side edge of the heating die 4 to form the convex portion 9. The heat-resistant release sheet 7 presses the surface of the molten plastic pressed by the heating mold 4,
The convex portion 9 is reduced in size.

After welding the plastic sheet 2A, the heating mold 4 is opened. Then, the container body 2 is stopped at a fixed position without moving, the heating die 4 is moved from the sandwiching position to the outside, and the cooling die 5 is moved to a position where the welded portion of the container body is sandwiched. At this time, the heat-resistant peeling sheet 7 is not peeled off from the surface of the container body, and the surface of the molten portion of the container body 2 remains covered.

As shown in FIG. 10, the molten portion of the container body is sandwiched by the cooling mold 5. The cooling mold 5 forcibly cools the molten portion of the container body. At this time as well, the heat-resistant peeling sheet 7 is not peeled from the surface of the container body. Cooling mold 5
Holds the molten portion of the container body with the heat-resistant release sheet 7 interposed therebetween. The container body sandwiched between the cooling molds 5 is forcibly cooled, and the molten plastic cools and becomes hard.

The molten plastic can be cooled by reducing the convex portion 9 as follows. Immediately after opening the heating mold 4 or before opening the heating mold 4, pressurized air is jetted from the nozzle 10 toward the convex portion 9 formed on the side edge of the heating mold 4 as shown in FIG. To do. The heat-resistant peeling sheet 7 reduces the convex portion 9 formed on the periphery of the heating die 4,
Depending on the type of plastic sheet, the heating temperature of the heating die, and the clamping force, a convex portion is formed on the periphery of the heating die. Pressurized air comfortably presses the surface of the convex portion to make it smaller. Since the convex portion 9 pressed by the pressurized air is in a molten or softened state, it flows as shown by the arrow in FIG. The convex portion 9 pressed through the heat-resistant peeling sheet 7 is uniformly pressed by the pressurized air and is corrected to be small.

The action of the pressurized air to correct the convex portion 9 to a lower level becomes stronger when the injection pressure of the pressurized air is increased and the flow rate is increased. In addition, it becomes stronger even if the nozzle that injects the pressurized air approaches the convex portion. The injection pressure and the flow rate of the pressurized air are adjusted to optimum values in consideration of the distance between the nozzle 10 and the convex portion 9.
When the convex portion 9 becomes higher, the convex portion 9 approaches the nozzle. The nozzle 10 approaching the convex portion 9 effectively corrects the convex portion to be smaller than the nozzle 10 away from the convex portion. For this reason, the convex portion protruding higher is corrected more effectively than the convex portion lower, and the height is corrected uniformly.

Since the protrusion 9 is formed by extruding plastic on the peripheral edge of the heating die 4, it can be formed continuously along the peripheral edge of the heating die 4. In order to uniformly correct the convex portions 9 formed continuously, the pressurized air is jetted toward the convex portions 9 from a plurality of nozzles arranged along the convex portions 9. Instead of a plurality of nozzles, it is also possible to inject pressurized air toward the convex portion 9 from a slit opened in parallel with the convex portion 9.

The convex portion formed by welding the plastic sheet causes a pinhole of the container. However, the convex portion formed outside the welded portion does not cause a pinhole. This is because the pinhole caused by the outer convex portion is located outside the container. Therefore, in the method of injecting pressurized air to correct the convex portion small, it is important to correct the convex portion formed on the inner edge 2b of the melted portion welded by the heating mold to be low. The convex portion formed on the outer edge of the container body 2 can be removed by cutting along the outer periphery of the container body after welding.
Therefore, it is important to inject the pressurized air to the inner edge of the welded portion. It is not always necessary to inject pressurized air to the outer edge of the welded portion. However, it is preferable that the convex portion formed on the outer peripheral edge of the welded portion is also blown with pressurized air to reduce the size.
This is because the convex portion can be made smaller and the container body can be neatly molded without cutting the outer peripheral edge of the container body.

When the pressurized air jetted to the convex portion is cooled,
It can be used together to forcefully cool the molten portion of plastic. In this method, it is not necessary to sandwich the welded portion with the cooling mold after correcting the convex portion. The manufacturing process is significantly simplified. However, it is also possible to correct the convex portion to a low level with pressurized air, and then sandwich it with a cooling die for forced cooling. In the method of forcibly cooling the melted portion with pressurized air, strong pressured air may be blown onto the convex portion to correct the melted portion low, and pressurized air may be jetted weakly to the other portion for forced cooling.

To cool the pressurized air, the jet cooler 11 shown in FIG. 16 is used. Jet cooler 11
Causes the supplied pressurized air to spirally flow at high speed inside. High-speed flowing air internally generates vortices. The vortex lowers the pressure in the central part and adiabatically expands the air to cool it. Jet cooler 11 that cools air with this mechanism
Has the advantages that it has no mechanical moving parts, has a simple structure, and can reduce failures. The jet cooler 11 having this structure has the ability to cool the supplied air by 10 to 35 ° C. The jet cooler 11 is supplied with clean air in which dust is filtered by a filter. As the device for cooling the pressurized air, any device that can cool the air can be used.

The timing of starting to inject the pressurized air toward the convex portion is usually set immediately after the heating die is opened. At this time, the convex portion 9 formed on the peripheral edge of the heating die 4 is in a molten state and can be corrected to a low level by pressing it with pressurized air. However, when the heating die 4 presses the plastic sheet 2A, it is also possible to inject pressurized air to the portion where the convex portion 9 is formed. In this state, when pressurized air is jetted to the portion where the convex portion 9 is formed, the molten plastic flowing toward the portion where the convex portion 9 is formed is pressed in the direction opposite to the flowing direction to reduce the flow of the plastic and reduce the convex portion. This is because 9 can be lowered. That is, it is possible to lower the height by pressing the convex portion 9 with the pressurized air through the heat resistant release sheet 7. Therefore, the ideal method for injecting pressurized air is to start the injection from the state where the heating die 4 presses the plastic sheet 2A, and to inject even after the heating die 4 is opened to correct the convex portion 9 small. Is the way.

The timing for stopping the injection of pressurized air is
This is when the convex portion 9 is corrected to be small and the cooling of the molten portion is completed. The method in which the molten portion of the plastic is not cooled by the pressurized air, that is, the method in which the pressurized air is heated air, is when the convex portion 9 is modified by the pressurized air. In the method of heating the pressurized air and not sufficiently cooling the convex portion 9, the convex portion 9 is made small and the plastic sheet 2A is cooled by the mold 5.
And then forcibly cool it. In order to effectively cool the container body 2, the cooling mold 5 circulates cold water or a coolant (not shown) to forcibly cool it, or forcibly blows air to forcibly cool it.

After cooling the melted portion of the plastic sheet, the heat-resistant peeling sheet 7 is peeled off. The heat-resistant release sheet 7 prevents the heated and melted plastic sheet 2A from adhering to the heating die 4 when the heating die 4 is removed from the plastic sheet 2A, and then the plastic sheet 2A is cooled until cooled. Protect the surface of. When the heat-resistant peeling sheet 7 is peeled off, since the plastic sheet 2A is cooled and hardened, the molded plastic sheet 2A can be peeled off quickly without deformation. Therefore, the method of injecting pressurized air using the heat-resistant release sheet 7 has a feature that the generation of pinholes can be further reduced to an ideal state. However, in the manufacturing method of the present invention, it is not always necessary to inject pressurized air to cool the container body. It is also possible to cool the molten portion of the plastic with the cooling die 5 without using the pressurized air.

A stopper is welded to a container body manufactured by heat-welding three sides of a plastic sheet. The process of welding the spigot to the container body is as follows. As shown in FIG. 2, the outer circumference of the spout 1 is preheated.
That is, the tip of the stopper 1 is inserted into the ring-shaped preheating heater 3, and the surface of the stopper 1 is preheated by the preheating heater 3. As shown in FIG. 12, both sides of the container body 2 are sucked by the suction cups 8 and the openings are opened by the suction cups 8. Insert the plug 1 into the opening. As shown in FIGS. 13 and 14, a heat-resistant release sheet 7 is arranged between the container body 2 having the spout 1 inserted in the opening and the heating mold 4. The surface of the container body 2 is sandwiched by the heating mold 4 via the heat-resistant release sheet 7 and heated from the surface.
At this time, the heat-resistant release sheet 7 covers the surface of the container body 2 and prevents the heating die 4 from directly contacting the container body 2. The heat-resistant release sheet 7 is the same as that used for molding the plastic sheet of the container body.

The heat-resistant release sheet 7 is held in a state of covering the surface of the container body 2, and as shown in FIG. 15, the surface of the container body 2 is forcibly cooled by being sandwiched by a cooling mold 5. That is, the cooling mold 5 sandwiches the container main body 2 via the heat-resistant peeling sheet 7 to cool it. Since the cooling mold 5 forcibly cools the container body 2, the heating mold 4 clamps the connecting portion of the spout 1 that clamps the container body 2. In order to effectively cool the container body 2, the cooling mold 5 circulates cold water or a coolant (not shown) to forcibly cool it, or forcibly blows air to forcibly cool it.

The heat-resistant release sheet 7 covers the surface of the container body 2 until the container body 2 is heated and cooled. In this way, the heat-resistant release sheet 7 that covers the surface of the container body 2
Regulates the movement of the resin that is heated by the heating mold 4 and is in a molten state, and prevents the occurrence of pinholes and the like.

After the surface of the container body 2 is forcibly cooled by the cooling mold 5, the heat-resistant peeling sheet 7 is peeled from the surface of the container body 2. The heat-resistant release sheet 7 that has been released is used many times.

When cooling the spout of the container body, it is also possible to inject pressurized air to the convex portion 9 formed on the peripheral edge of the heating mold 4 in the same manner as welding the plastic sheet 2A to form the container body. it can.

[0048]

The method of manufacturing a plastic container of the present invention has the features that the stopper can be surely welded to the container body without a gap, and that uneven thickness and pin holes can be minimized on the container body. This is because the manufacturing method of the present invention protects the surface of the container body with the heat-resistant release sheet from the time when the container body is heated and the spout is welded until the container body is forcibly cooled. The heat-resistant peeling sheet that protects the surface of the container body prevents the plastic that has been melted by being heated by the heating mold from moving until it is heated and cooled. When the molten plastic moves in this state, the plastic covering the top of the spout
It flows in both directions of the mouth plug and the upper part becomes thin, making it easier to form pinholes. However, in the container manufacturing method of the present invention, the container body heated by the heating mold is covered with the heat-resistant release sheet until it is cooled. For this reason, the heat-resistant release sheet prevents the molten plastic from flowing and prevents the formation of pinholes in the container body.

The pinhole of the container manufactured by the method of the present invention can be measured by the measuring device shown in FIG. This device
Use as follows. Fill the container with a conductive liquid such as water. Place the container on a grounded table. Place the electrode close to the pinhole. The electrodes are brought as close as possible to, for example, about 0.5 to 1 mm. However, the electrode does not contact the container. Apply a predetermined voltage to the electrodes. If there are pinholes in the container, discharge will occur at a voltage that is considerably lower than in normal conditions. This is because pinholes destroy the insulation.

As a result of measuring the discharge voltage of the containers manufactured by the method of the present invention using the pinhole measuring device shown in FIG. 11, the discharge voltage of all the containers was 20 kV or more,
It was proven that there were no pinholes.

As described above, the method for producing a container of the present invention is
In addition to being able to effectively prevent the occurrence of pinholes in the container body, it also has the feature that the spigot can be reliably welded to the container body. This is because the heat-resistant release sheet protects the container body until it is heated and cooled, so the container body can be protected and the spout can be reliably welded even if the heating temperature of the container body is set slightly higher. Is. The conventional manufacturing method has a drawback that the plastic of the heated container body flows when the heating temperature of the container body is increased in order to securely weld the spout and the container body. However, in the production method of the present invention, the heat-resistant release sheet protects the container body and welds the spigot until heating and cooling, so even if the heating temperature of the container body is set to be slightly higher, This has the advantage that the adverse effect of pinholes on the container body can be prevented and the spigot can be reliably welded to the container body.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a container manufactured by the method of the present invention.

FIG. 2 is a side view showing a state in which a spout is preheated in a method of manufacturing a plastic container.

FIG. 3 is a side view showing a state in which a stopper is inserted into a container body in a conventional manufacturing method.

FIG. 4 is a cross-sectional view showing a state in which a heating die clamps and heats a container body to weld a spigot.

FIG. 5 is a side view showing a state in which a container body is heated by a heating mold and cooled by a cooling mold.

FIG. 6 is a sectional view showing a conventional example in which a protruding piece is provided on the container body.

FIG. 7 is a side view showing a state where the heating mold and the cooling mold press the container body.

FIG. 8 is a sectional view showing a specific example of the present invention in which a plastic sheet using a heat-resistant release sheet is heated and melted.

FIG. 9 is a cross-sectional view showing a state in which plastic sheets are laminated and welded using a heat-resistant release sheet.

FIG. 10 is a cross-sectional view showing a state in which a welded plastic sheet is sandwiched by cooling molds and cooled.

FIG. 11 is a schematic side view of an apparatus for measuring a pinhole of a container.

FIG. 12 is a sectional view showing a state in which a spout is inserted into the container body.

FIG. 13 is a sectional view showing a state in which a spout is welded to a container body.

FIG. 14 is a cross-sectional view showing a state in which a spout is welded to a container body.

FIG. 15 is a cross-sectional view showing a state in which the mouth plug welding portion of the container body is cooled by a cooling mold.

FIG. 16 is a schematic cross-sectional view of a jet cooler that cools air jetted to a welded portion.

[Explanation of symbols]

1 ... Mouth plug 2 ... Container body 2A ... Plastic sheet
2b ... inside 3 ... preheating heater 4 ... heating die 5 ... cooling die 6 ... projection 7 ... heat-resistant peeling sheet 8 ... sucker 9 ... projection 10 ... nozzle 11 ... jet cooler

Claims (3)

[Claims] 1. A container main body (2) is inserted with a spout (1), and the surface of the container main body (2) is pressed by a heating mold (4) to heat it from the outside.
In the method of manufacturing a plastic container in which the container body (2) is pressed against the inserted spout (1) and welded, the surface of the connection part of the spout (1) of the container body (2) is heat-resistant peeling sheet.
Heated mold (4) covered with (7) and heat resistant release sheet (7)
Press the surface of the container body (2) to heat it, weld the contact surface between the container body (2) and the spigot (1), and coat the heat-resistant release sheet (7) that covers the container body (2). A method for producing a plastic container, characterized in that the heat-resistant peeling sheet (7) is peeled off from the container body after cooling the welded portion while maintaining the state. 2. A plastic sheet (2A) is laminated and its surface is pressed by a heating mold (4) and externally heated to melt and weld the plastic sheet (2A) to form a container body (2). In the method of manufacturing a plastic container, the surface of the welded part of the plastic sheet (2A) is covered with a heat-resistant release sheet (7), and a heating mold is placed through the heat-resistant release sheet (7).
Press the surface of the plastic sheet (2A) with (4) to heat it,
Melt, weld, heat-resistant peeling sheet (7) that covers the surface of plastic sheet (2A) is held in a covered state to cool the melted portion, and after cooling, peel heat-resistant peeling sheet (7) from plastic sheet (2A) A method of manufacturing a plastic container, comprising: 3. The heat-resistant release sheet (7) is held in a covered state, the melted portion is cooled by either or both of a cooling mold (5) and pressurized air, and then the heat-resistant release sheet (7) is released. The method for producing a plastic container according to claim 1 or 2, characterized in that: