JP7068055B2 - Manufacturing method of thin-walled hollow container, thin-walled hollow container - Google Patents

Description

The present invention relates to a method for manufacturing a thin-walled hollow container made of a thermoplastic resin, and more particularly to a method for manufacturing a thin-walled hollow container in which all or part of the thin-walled hollow container is an ultrafine hollow tube.

So-called blow molding is widely known as a method for manufacturing a hollow container made of a thermoplastic resin such as plastic. Blow molding includes direct blow molding, injection blow molding, stretch blow molding, etc., but direct blow molding is widely used for low-cost mass production of products having a relatively simple shape. Direct blow molding involves a parison extrusion process in which a thermoplastic resin in a heated and melted state is extruded vertically downward from an extruder called a die as a tubular parison (hot parison), and the parison is sandwiched between a pair of dies and closed. After that, air is blown into the parison through the nozzle to inflate it, and after pressing the parison against the inner surface of the mold, the mold is opened and the solidified parison is taken out. It consists of a post-processing process that cuts and removes (burrs and waste bags) to make the final product.

FIG. 1 is a cross-sectional view showing a general direct blow molding process. First, as a parison extrusion step, the separately heated and melted parison P is sent to the extruder E (a), the extruder E fills the accumulator A with the parison P (b), and the die D is operated by the blanger B. The parison P sent inward becomes tubular from the gap between the die ring R of the die D and the outer periphery of the core C and is pushed downward (c). Next, as a blow molding process, the pair of forming dies M is closed, the extruded tubular parison P is sandwiched (d), and air is blown from the core C into the inside of the parison P (blow) to inflate the parison P. Press against the inner surface (cavity) of the mold M. The parison P pressed against the cooled mold M is solidified and formed into the shape of the product (e). Next, the mold is opened and the product is taken out (f), and then, if necessary, the process proceeds to a post-processing process such as deburring.
Process diagram of general direct blow molding (Fig. 1)

In recent years, a shuttle type blow molding machine has become widespread, in which a mold sandwiching a parison is moved up and down or left and right in the blow molding process, and then air is blown into the parison with a separately provided blow nozzle. There is. In the shuttle type blow molding machine, by moving the mold to make space under the die, the next parison extrusion process can be started without waiting for the end of the blow molding process, so that the manufacturing efficiency is improved.

By the way, direct blow molding is generally used for manufacturing bottle-type or tank-type hollow containers, but it is difficult to mold ultra-fine hollow tubes. Conventionally, in direct blow molding, when a tubular parison is extruded vertically downward in a molten state in the parison extrusion process, "drawdown" occurs in which the tubular parison hangs down due to its own weight, resulting in uneven wall thickness. rice field. Measures have been taken to deal with this problem, such as applying a material with resin characteristics (melt tension and extensional viscosity) that does not easily cause uneven thickness. Meat can be suppressed.

Even so, for example, when trying to form an ultrafine hollow tube having an inner diameter of 3 mm or less, even a slight drawdown may cause blockage in the tube. Further, in the above-mentioned shuttle type blow molding machine, the moment due to the movement of the mold acts on the parison before solidification, which may cause the inside of the pipe to be blocked. Therefore, even if there is no problem if the length of the medium space is short, it has been extremely difficult to manufacture a container having a structure having a long hollow tube having a length exceeding 10 cm by direct blow molding.

FIG. 2 is a perspective view of a product called an ice stick for swallowing training, and FIG. 3 is a schematic cross-sectional view along the axis thereof. This is a tool used for rehabilitation of patients with dysphagia such as elderly people. Water is filled inside a polyethylene hollow body having a hollow tube S coaxially with the hollow head H and frozen in a refrigerator. , Hold the hollow tube S and stimulate the oral cavity with the hollow head H (ice massage) to improve dysphagia. In the past, at medical institutions, etc., cut cotton was wrapped around the tip of disposable chopsticks, and an ice massage stick that was chilled with water was handmade. ..

Such ice sticks are used disposable from the viewpoint of hygiene, and there is a great demand for cost reduction. In addition, if the hollow head of the ice stick falls off in the oral cavity during use and the user accidentally swallows it, there is a risk of suffocation, so the hollow head and hollow tube must be integrally molded. Therefore, it is desirable to manufacture by direct blow molding. However, since the hollow tube has an extremely fine length of 14 to 15 cm and an inner diameter of 3 mm, as described above, when manufactured by conventional direct blow molding, the occurrence of blockage in the hollow tube becomes a problem.

An object of the present invention is to solve such a problem and to provide a manufacturing method capable of manufacturing a thin-walled hollow container having an ultra-fine hollow tube by direct blow molding. Therefore, the invention according to claim 1 is a manufacturing method by direct blow molding of a thin-walled hollow container having an ultrafine hollow tube having an inner diameter of 3 mm or less and a length of 10 cm or more with one end opened. Consists of at least a parison extrusion process and a blow molding process,
In the parison extrusion step, the thickness of the tubular parison extruded is increased by moving the core provided in the die upward to change the size of the gap between the tip of the core and the die ring at the opening of the die. Along with the continuous increase, a preliminary blow is performed inside the parison through the parison extrusion process.
In the blow molding step, a tubular parison is sandwiched between a pair of molds having a cavity corresponding to a thin-walled hollow container having an ultrafine hollow tube at least above, the upper end is cut with a cutter, and then a nozzle pin is inserted inside the parison. It is inserted and the main blow is performed, and after the main blow air expands the parison in the cavity, it is discharged to the outside of the mold through the gap between the parison and the nozzle pin.
It is characterized by.

As the direct blow molding machine used in the present invention, the shuttle type blow molding machine described above is suitable, but the direct blow molding machine is not always limited to this. On the other hand, the mold to be used has a cavity having a shape in which the hollow tube portion of a thin-walled hollow container having an ultra-fine hollow tube having one end opened, which is a product, is located above, and is medium in a state where the mold is closed. The shape is such that the cross section of the empty tube opens on the upper surface of the closed mold, but the shape is not limited to this, and the final product can be applied to all thin-walled hollow containers having a long ultrafine hollow tube. In the blow molding process, after the mold sandwiches the parison, the parison is cut above the mold by a cutter separately provided in the direct blow molding machine. Next, the mold is moved in the horizontal direction, for example, and a ventilable nozzle pin separately provided in a direct blow molding machine is inserted into the opening of the parison exposed on the upper part of the mold to perform a main blow to blow air into the mold. Inflate the parison within.

In the direct blow molding machine that has become widespread in recent years, "Parison control" (commonly known as "Paricon") is used as a means to control the wall thickness of the parison that is tubular and pushed downward from the gap between the diling and the outer circumference of the core. A mechanism called is known. The parison control controls the wall thickness by adjusting the amount of the parison to be extruded by moving the position of the core up and down during the extruding of the parison to change the gap between the tip of the core and the outer circumference of the die ring. It is used when blow molding final products with different wall thicknesses depending on the part. The direct blow molding machine used in the present invention shall be equipped with a parison control.

As mentioned above, in blow molding of an ultra-fine hollow tube with an inner diameter of 3 mm or less, it is necessary to reduce the wall thickness of the hollow tube, and the inside of the tube is blocked by the moment that drawdown and mold movement exert on the parison. Becomes a problem. Therefore, in the invention according to claim 1, the core provided in the die is moved upward by the parison control during the parison extrusion step, and the gap between the tip of the core and the die ring at the opening of the die is gradually increased. Continuously increases the wall thickness of the extruded tubular parison. At this time, the extrusion amount of the parison is continuously changed so as to be the smallest at the start of extrusion and the predetermined thickness at the end of extrusion in consideration of the increase in the wall thickness due to the drawdown. As a result, the wall thickness of the parison can be made uniform in the ultrafine hollow tube of the mold at the time when the main blow is started in the next blow molding step, and the blockage in the tube can be prevented.

However, when the inner diameter of the hollow tube is extremely small, even if the wall thickness of the parison is controlled, the inside of the tube may be blocked. Therefore, in the invention according to claim 1, a preliminary blow is further performed in which a small amount of air is blown through the core nozzle through the parison extrusion step. Since the parison is extruded into a tubular shape, the air in the preliminary blow passes through the inside of the parison being extruded and continues to be discharged from the lower end, thus preventing blockage inside the parison.

Further, in the blow molding step, a tubular parison is sandwiched between a pair of molds having a cavity corresponding to a thin-walled hollow container having an ultrafine hollow tube at least above, the upper end is cut with a cutter, and then the inside of the parison is formed. Insert the nozzle pin and perform this blow. The diameter of the nozzle pin shall be smaller than the inner diameter of the tubular parison in the cavity of the hollow tube portion.

When the tubular parison is sandwiched between the molds, the lower end of the parison is closed to form a blind tube, and the parison below the cavity is compressed by the mold to become burrs. On the other hand, since the lower end portion of the parison is blocked, the air supply of the preliminary blow cannot enter the cavity, so that the parison above the mold expands momentarily. Then, when the cutter cuts the parison at the bulging portion, the cut surface becomes a tubular opening without being blocked, and the opening moves directly under the nozzle pin by the horizontal movement of the mold.

Next, the nozzle pin is lowered and inserted into the parison through the opening to perform the main blow. As described above, since the outer diameter of the nozzle pin is smaller than the inner diameter of the tubular parison in the cavity of the hollow tube portion, the nozzle pin can be inserted into the parison without touching the inner surface of the parison. Here, when air is blown from the tip of the nozzle pin to perform the main blow, the air expands the parison in order from the lower part to the upper part and presses it against the inner surface of the cavity, and finally is discharged from the opening. During this blow, air flows between the parison and the nozzle pin, and the parison cooled by the mold and the air solidifies during that time, so that the parison does not stick to the nozzle pin. After that, if the nozzle pin is raised and removed from the mold and the mold is opened, the molded thin-walled hollow container can be taken out and the process proceeds to a post-processing step such as deburring.

Next, the invention according to claim 2 is the method for manufacturing a thin-walled hollow container according to claim 1 , wherein the mold has a substantially cylindrical hollow head and an inner diameter of 3 mm or less with one end opened. It is characterized by having a cavity corresponding to a thin-walled hollow container composed of an ultra-fine hollow tube having a size of 10 cm or more . By using a mold having a cavity having such a shape, the above-mentioned ice stick for swallowing training can be manufactured.

According to the method for manufacturing a thin-walled hollow container according to the present invention, all of the ultrafine hollow tubes having a total length of 10 cm or more and an inner diameter of 3 mm or less, which was difficult in the conventional direct blow molding due to the possibility of internal blockage. Alternatively, a thin-walled hollow container made of a thermoplastic resin, which is partially contained, can be manufactured by direct blow molding.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. 4 to 7 are schematic cross-sectional views showing a parison extrusion step in the method for manufacturing a thin-walled hollow container according to an embodiment of the present invention. 8 to 10 are schematic cross-sectional views showing the blow molding process. The direct blow molding machine in the figure is shown by simplifying only the part related to the present invention, and the configurations of other extruders, accumulators, blangers, etc. are omitted. In addition, the figure of the part related to the mold is shown by omitting a part of the length in the vertical direction.

In the parison extrusion step, first, as shown in FIG. 4, the parison P is fed into the die D from the accumulator. The die D has a hollow inside, has an opening provided with a die ring R on the lower surface, and has a core C in the cavity that can be raised and lowered in the axial direction. The core C has a through hole on the axis. A gap is provided between the inner wall of the die D and the outer surface of the core C, and the parison P sent into the die D descends in the die D along the gap, and the lower end of the core C and the die ring R. It is extruded into a tubular shape through the gap between the wall and the wall. The extruded tubular parison p descends between a pair of molds M placed below the die D. The mold M is provided with a cavity corresponding to a thin-walled hollow container having an ultra-fine hollow tube on the inner surface thereof. Also, during the parison extrusion step, a preliminary blow is performed to blow air into the tubular parison p through the through hole of the core C.

Next, as shown in FIG. 5, when the core C is raised in the die D in response to the descent of the tubular parison p, the gap between the tip of the core C and the die ring R gradually expands, and the tubular parison p Continuously increase the thickness of. The speed and width of the increase of the core C shall be appropriately controlled according to the physical properties such as the viscosity of the parison P by the parisonn control (not shown) equipped in the direct blow molding machine. As a result, the wall thickness of the tubular parison p gradually increases from the lower end to the upper end, and the increase in the wall thickness due to the drawdown is offset to equalize the wall thickness of the tubular parison p.

Next, as shown in FIG. 6, when the tip of the tubular parison p descends to a predetermined length, the mold M is closed. At this time, since the lower portion of the mold M is closed, the lower end portion of the tubular parison p is closed to form a blind tube. Further, the tubular parison p below the mold M is cut and dropped, and the tubular parison p sandwiched between the mold M below the cavity is compressed and becomes a burr. As described above, the preliminary blow is performed throughout the parison extrusion process, and since air is constantly flowing in the tubular parison p, even when the mold M is closed, the ultrafine hollow tube portion The inside of the tubular parison p is kept hollow in the cavity, and obstruction is prevented.

On the other hand, the lower end of the tubular parison p is obstructed and becomes a blind tube, so that the air supply by the preliminary blow has no place to go, and the tubular parison p above the mold expands momentarily and becomes a "throwing bag". Will be. Here, as shown in FIG. 7, a cutter B is inserted from the side between the die D and the mold M, and the tubular parison p is cut at the waste bag portion. As a result, the cut surface becomes a tubular opening at the upper part of the mold M without being blocked. After this, the process moves to the blow molding process.

In the blow molding step, as shown in FIG. 8, the mold M is horizontally moved from under the die D, and the opening of the tubular parison p is set so as to be directly under the nozzle pin N for blowing. Next, the nozzle pin N is lowered and inserted into the tubular parison p through the opening so that the tip of the nozzle pin N penetrates into the cavity corresponding to the substantially cylindrical head below the mold M and through the nozzle pin N. Perform a book blow that blows air. At this time, since the diameter of the nozzle pin N is smaller than the inner diameter of the tubular parison p in the cavity of the hollow tube portion, the nozzle pin N does not come into contact with the tubular parison p. By this blow, the tubular parison p swells in the mold M and is pressed against the inner surface of the cavity to be cooled and solidified. Further, the air of this blow is discharged from the upper opening through the gap between the tubular nozzle pin N and the parison p.

Finally, as shown in FIG. 10, when the nozzle pin N is moved upward and removed from the mold M to open the mold M, a thin hollow head composed of a substantially cylindrical hollow head and an extra-fine hollow tube is formed. A container is obtained. After that, the thin-walled hollow container is sent to a post-processing process for cutting and removing unnecessary parts (burrs and waste bags) generated when the parison is sandwiched, and becomes a final product.

In the present embodiment, a thin-walled hollow container for the ice stick for swallowing training, which is composed of a substantially cylindrical hollow head and an ultra-fine hollow tube having a total length of 14 to 15 cm, is assumed as a final product and a mold. The cavity of M has a corresponding shape, but the final product is not limited to this, and a thin-walled hollow container having another shape may be used as long as it has a long ultrafine hollow tube.

Although the method for manufacturing a thin-walled hollow container according to the present invention has been described above, the present invention is not limited to the above embodiment, and can be improved or modified within the scope of the technical idea of the present invention. Belongs to the technical scope of the present invention. In the manufacturing method according to the embodiment, a shuttle type blow molding machine is assumed. For example, in a fixed type direct blow molding machine, a nozzle pin that can be raised and lowered is provided in the through hole of the core, and preliminary blow is performed through the nozzle pin. It is also possible to start the blow molding process with the position of the mold M as it is after cutting the upper part by sandwiching the tubular parison p with the mold M by making the configuration capable of both the main blow and the main blow.

According to the method for manufacturing a thin-walled hollow container according to the present invention, a thin-walled hollow container having an ultra-fine hollow tube can be efficiently manufactured by direct blow molding.

Cross-sectional view showing a general direct blow molding process Perspective view of ice stick for swallowing training Cross section of ice stick for swallowing training Schematic cross-sectional view showing the parison extrusion process (Part 1) Schematic cross-sectional view showing the parison extrusion process (Part 2) Schematic cross-sectional view showing the parison extrusion process (Part 3) Schematic cross-sectional view showing the parison extrusion process (No. 4) Schematic cross-sectional view showing the blow molding process (Part 1) Schematic cross-sectional view showing the blow molding process (Part 2) Schematic cross-sectional view showing the blow molding process (Part 3)

A accumulator B blanger C core c cutter D die E extruder N nozzle pin P parison p tubular parison R diling H hollow head M mold S hollow tube

Claims (2)

It is a manufacturing method by direct blow molding of a thin-walled hollow container having an ultrafine hollow tube having an inner diameter of 3 mm or less and a length of 10 cm or more with one end open, and the manufacturing method comprises at least a parison extrusion step and a blow molding step. ,
In the parison extrusion step, the thickness of the tubular parison extruded is increased by moving the core provided in the die upward to change the size of the gap between the tip of the core and the die ring at the opening of the die. Along with the continuous increase, a preliminary blow is performed inside the parison through the parison extrusion process.
In the blow molding step, a tubular parison is sandwiched between a pair of molds having a cavity corresponding to a thin-walled hollow container having an ultrafine hollow tube at least above, the upper end is cut with a cutter, and then a nozzle pin is inserted inside the parison. It is inserted and the main blow is performed, and after the main blow air expands the parison in the cavity, it is discharged to the outside of the mold through the gap between the parison and the nozzle pin.
A method for manufacturing a thin-walled hollow container. The mold is characterized by having a cavity corresponding to a thin-walled hollow container composed of a substantially cylindrical hollow head and an ultra-fine hollow tube having an inner diameter of 3 mm or less and an inner diameter of 10 cm or more with one end open. Item 2. The method for manufacturing a thin-walled hollow container according to Item 1.

Images