JP2753057B2 - Manufacturing method of liquid container by blow molding - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a liquid container by hollow molding used for medical, food, chemical, general industrial products, household goods and the like. In particular, the present invention relates to a method for manufacturing a liquid container in which the thickness of the wall of the opening is significantly different from the thickness of the wall of the container and the container is flat by a hollow molding method.

[Related Art] In recent years, in medical treatment such as infusion, a closed system has been used to prevent a content liquid from coming into contact with the outside world. The medical liquid container used in this closed system needs to discharge the content liquid due to gravity, the structure of the container, and the flexibility of the material of the container. Further, it is preferably formed of a transparent material so that the content liquid can be monitored from the outside. In addition, the opening must be sealed with a rubber stopper or cap, and the wall thickness of the opening must be increased so that when the bottle needle of the infusion set is accidentally pierced into the opening wall, it does not penetrate. There is. For such a purpose, in the conventional medical liquid container, the wall of the opening needs to be thick, the wall of the container needs to be thin, and the container needs to be flat. .

In order to form such a container by the hollow molding method, the thickness corresponding to the container is thin, the thickness corresponding to the opening is thick, and a parison having a large outer diameter is formed. Had been hollow molded. The mold used for the hollow molding is divided into three sections: an upper section, a middle section, and a lower section. First, a large parison whose lower end is sealed is sandwiched between the upper and lower parts of the mold, and the parison is flattened. The liquid container engraved in the mold was molded.

[Problems to be Solved by the Invention] In the conventional blow molding method, when a parison having a small outer diameter and a large thickness is used, it is necessary to increase the blow ratio in order to produce a predetermined container. A parison with a small outside diameter is sandwiched between the upper and lower sections of the mold, the parison is cut, and then a predetermined amount of air is blown from the cutting opening to expand the parison into a large cylindrical shape, and then tighten the middle section of the mold. When blow molding, the large expanded cylindrical parison comes into contact with the mold near the center of the stand first, the parison cools and the wall thickness increases. It was easy to be uniform.

When a thin parison having a large outer diameter and a small thickness is used, the blow ratio may be small in order to produce a predetermined container. A parison having a large outer diameter is sandwiched between the upper and lower portions of the mold, and the parison is cut. At this time, the parison has a flat shape. Next, when the middle part of the mold is tightened and hollow-molded, the parison is in a flat shape and almost uniformly contacts the mold, so that the wall thickness of the molded container is substantially uniform. However, when a thin parison is extruded at a high speed, the shear rate increases, melt fracture easily occurs, and the molded container becomes extremely poor. Furthermore, when a parison having a large outer diameter is used, the portion corresponding to the opening has many unnecessary portions as burrs,
A lot of resin was used, and the cost was high.

[Means for Solving the Problems] An object of the present invention is to provide a liquid container suitable as an infusion bag or the like. However, the present inventors have conducted various studies on a method of manufacturing a container by a hollow molding method. As a result, the hollow mold is divided into at least four sections, a parison having a small outer diameter is formed by an extruder, and the parison is inflated by preliminary blowing of air to increase the outer diameter. The present invention has been achieved by finding that a suitable container can be obtained by partially sandwiching the parison to form a flat shape, and then tightening the entire mold and performing full blowing.

That is, the present invention relates to a method for manufacturing a liquid container having an opening formed by hollow molding, a flat container portion, and a hanging port, wherein a hollow molding die for molding the liquid container forms the opening. At least four of an opening division mold, a container division mold for forming the flat container section, an upper flat division mold and a lower flat division mold vertically adjacent to the container division mold. A parison having a lower end sealed by an extruder is formed by a split mold, and the opening split mold cuts the upper part of the parison after sandwiching the parison, and then cuts the parison. After blowing a predetermined amount of air from the part to inflate the parison, further tightening the upper flat split mold and the lower flat split mold to deform the parison flat, then tightening the container split mold, and Almost at the same time A method for manufacturing a liquid container according to blow molding, wherein the blowing pressure air from the cutting opening of the Son.

[Operation] Next, the present invention will be specifically described based on the drawings.

FIG. 1 shows a liquid container manufactured according to the present invention.
The liquid container 1 is a hollow molded product having a small-diameter opening 2 at an upper end and a hanging port 4 at a lower end, and the container 3 having a flat shape.

A hollow mold for producing the liquid container 1 is a second mold.
Shown in the figure. The hollow molding die 21 is composed of four split dies: an opening split die 22, an upper flat split die 23, a container split die 24, and a lower flat split die 25. These split molds can operate independently.

Next, a method of manufacturing the liquid container 1 using the hollow molding die 21 will be sequentially described.

First, a molten parison 5 having a closed lower end is formed by an extruder. In order to seal the lower end portion, the pinch portion 6 may be provided by sandwiching the parison 5 with a pinch device. The parison 5 has an upper part 10 corresponding to the opening 2.
The parison central part 9 corresponding to the container part 3 becomes thicker
Is preferably formed so that the thickness of the metal is reduced. In addition, when the outer diameter of the parison 5 is small, the amount of unnecessary burrs around the opening 2 is reduced when the hollow molding is performed, and the amount of resin used for manufacturing one liquid container can be reduced. . If the outer diameter of the parison 5 is smaller than the outer diameter of the opening 2 of the liquid container, no burr will be generated around the opening 2 when hollow molding is performed.

Next, as shown in FIG. 3, the parison 5 whose lower end is hermetically closed is sandwiched by the opening division mold 22 and the upper part of the parison 5 is cut. FIG. 4 shows the shape of the parison as viewed from the cross section taken along the line II of FIG. At this time, the parison has a substantially cylindrical shape.

Next, as shown in FIG. 5, a predetermined amount of air is blown from a cutting opening 7 of the parison 5 by a blowing device 8. The parison 5 swells, the outer diameter increases, and the wall thickness decreases. FIG. 6 shows the shape of the parison as viewed from the cross section taken along line II-II of FIG. The parison at this time has a rugby ball-like shape.

Next, as shown in FIG. 7, the parison 5 swollen like a rugby ball is divided into an upper flat split mold 23 and a lower flat split mold.
Tighten 25 to sandwich parison 5 to make it flat.
The shape of the parison viewed from the cross section taken along the line III-III in FIG.
Shown in the figure. The parison at this time has a flat shape. The flat part 9 of the parison 5 corresponds to the container part 3 of the liquid container 1.

Next, as shown in FIG. 9, the container part split mold 24 is tightened, high-pressure air is blown by the blowing device 10, and the parison 5 is formed into a shape engraved in the hollow forming die 21. When the container part split mold 24 is closed, the parison 5 has a flat shape, so that the entire parison comes into contact with the container part split mold almost at the same time. Tends to be uniform. FIG. 9 shows the shape of the parison as viewed from the section taken along line IV-IV in FIG. The parison 5 is formed into a desired hollow molding 12. By cutting and removing unnecessary portions of the hollow molded article 12, the liquid container 1 is completed.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1 Using a linear low-density polyethylene (density: 0.924 g / cm ² ), an opening having an outer diameter of 20 mm, a flat container having a major axis of 80 mm and a minor axis of 20 mm, and a hanging opening were used. In order to produce a liquid container having the above configuration, hollow molding is performed using a four-part mold shown in FIG. First, a parison having an outer diameter of 20 mm was formed. At this time, the thickness of the upper part of the parison was 2 mm, and the thickness of the central part was 0.8 mm.

Next, the opening division mold that forms the opening is tightened to sandwich the parison. The upper part of the parison is cut almost at the same time as the opening division mold is tightened. Then, with the blowing device,
Air was blown into the parison so that the outer diameter of the parison was approximately 45 mm.

Next, the parison was deformed into a flat shape by tightening the upper flat split mold forming the shoulder of the container portion and the lower flat split mold forming the suspension port.

Next, the container part forming die forming the container part was tightened, and high-pressure air was blown from a blowing device to form a shape engraved in the hollow forming die. The weight of the hollow molded product thus obtained was 16.5 g. Unnecessary burrs around the suspension opening of the hollow molded product were cut and removed to obtain a liquid container. The weight of the liquid container was 13 g.

The thickness of the wall of the opening of the liquid container was 2 mm, and the thickness of the wall of the container was almost uniform at 0.25 to 0.35 mm.

Example 2 Five-part five-piece hollow molding die as shown in FIG.
A liquid container was prepared using 31. An opening division mold for forming an opening by molding the same parison as in the first embodiment.
Tighten 32 and the lower split mold 36 (corresponding to the fifth split mold), and sandwich the parison. When the upper and lower sides of the parison are sandwiched by the split molds as described above, the parison can be prevented from swaying when the mold is moved from the parison forming station to the blowing station. From now on,
A hollow molded article was formed in the same manner as in Example 1. Since the parison was less shaken during the movement of the mold, the mold could be moved at a higher speed than in Example 1.

Comparative Example 1 FIG. 2 shows a three-part mold composed of an opening part mold, a container part mold, and a lower part mold, in which the upper flat mold and the container part mold are integrated. Was used to form the same parison as in Example 1, the opening division mold was closed, the parison was sandwiched, and the upper part of the parison was cut. In the same manner as in Example 1, air was blown into the parison from the cutting opening by a blowing device so that the parison had an outer diameter of about 45 mm.

Next, the parison was sandwiched by tightening the lower flat mold that forms the suspension opening, but the parison did not become flat.

Next, the container part forming die forming the container part was tightened, and high-pressure air was blown from a blowing device to form a shape engraved in the hollow forming die. Unnecessary burrs around the suspension opening of the hollow molded product were cut and removed to obtain a liquid container.

The wall thickness of the container portion of this liquid container was 0.15 to 0.45 mm. In particular, looking at the cross-sectional shape of the container portion, the corrugation was severe, and the thick portion had poor transparency.

[Effects of the Invention] As described above, the method for manufacturing a liquid container of the present invention has the following advantages.

Since a flat liquid container can be obtained with a parison having a small outer diameter, unnecessary burrs are reduced, so that the cost of the liquid container can be reduced.

Since a flat parison is obtained with a thick parison, melt fracture hardly occurs even when the parison is extruded at a high speed. Therefore, the number of production per equipment increases, and the cost of the liquid container can be reduced.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of a liquid container manufactured by the manufacturing method of the present invention, FIG. 2 is a cross-sectional view of a hollow molding die for manufacturing the liquid container, and FIG. FIG. 4 is a cross-sectional view showing a state of a hollow molding die and a parison for explaining a method of manufacturing the liquid container of FIG. 4; FIG. FIG. 6 is a cross-sectional view showing a state of a hollow mold and a parison for explaining a method of manufacturing a liquid container according to the present invention. FIG. FIG. 7 is a sectional view showing a state of a hollow mold and a parison for explaining a method of manufacturing a liquid container of the present invention, and FIG. 8 is II in FIG.
FIG. 9 is a side view showing the state of the parison as viewed from the cross section taken along the line I-III, FIG. FIG. 9 is a side view showing the state of the parison as viewed from the cross section taken along line IV-IV of FIG. 9, and FIG. DESCRIPTION OF SYMBOLS 1 ... Liquid container, 2 ... Opening part, 3 ... Container part, 4 ... Hanging mouth part, 5 ... Parison, 6 ... Pinch part, 7 ... Cutting opening part, 8
... Blow-in device, 9 ... Parison central part, 10 ... Parison upper part, 12 ... Hollow molded product, 21 ... Hollow molded die, 22 ... Opening part split die, 23 ... Upper flat split die, 24 ... Container part split die Type, 25
... lower flat split mold, 31 ... 5 split hollow molding die, 32 ... opening split mold, 33 ... upper flat split mold, 34 ... container part split mold, 35 ... lower flat split mold, 36 ... Lower split mold

Claims (1)

(57) [Claims] In a method for manufacturing a liquid container having an opening formed by hollow molding, a flat container portion, and a suspension opening, a hollow molding die for molding the liquid container forms the opening. At least four of an opening division mold, a container division mold for forming the flat container section, an upper flat division mold and a lower flat division mold vertically adjacent to the container division mold. A parison having a lower end sealed by an extruder is formed by a split mold, and the opening split mold cuts the upper part of the parison after sandwiching the parison, and then cuts the parison. After blowing a predetermined amount of air from the part to inflate the parison, further tightening the upper flat split mold and the lower flat split mold to deform the parison flat, then tightening the container split mold, and Almost at the same time the parison Method of manufacturing a liquid container according to blow molding, wherein the blowing pressure air from the cutting opening.