JPH044119A - Injection blow molding method of vessel - Google Patents

Abstract

PURPOSE:To control favorably a thickness of a circumferential surface of a hollow vessel at the time of blow molding, by a method wherein a gate casting resin within an injection mold is provided as a resin flow control gate controlling a resin flow extending from the bottom to the circumferential surface of a bottomed parison at the time of injection molding. CONSTITUTION:An injection mold 20 possesses an injection core 24 and injection mold 22 and a hot liner nozzle 40 is connected with a resin casting gate 26 of the injection mold 20 through a heat insulation agent 42. Since molten resin is cast within the injection mold 20 from a runner 40a by passing through the gate 26, a bottomed parison 10 is formed. In this instance, a flow of the molten resin to be cast within the mold 20 is controlled by making use of a gate 26 and a distribution of a potential amount of heat corresponding to a form of a synthetic resin vessel 10 of a final molded product is given to the bottomed parison, especially extending from its bottom 16 to the circumferential surface 17. With this construction, air is blown into the parison 10 and even in case of blow forming of a flat synthetic resin vessel 110 where expansion ratios are different from each other in length and breadth, a difference in aspect ratios can be replenished with the distribution of the potential amount of heat.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an injection blow molding method for containers, particularly to an improvement in an injection blow molding method for forming a hollow synthetic resin container from a cylindrical bottomed parison.

[Prior Art] An injection blow molding method is well known in which a cylindrical bottomed parison is formed by injection molding, and the bottomed parison is expanded by blowing gas to form a synthetic resin container in a predetermined shape. Containers for cosmetics and detergents.

It is used to form various hollow containers such as beverage bottles.

In this injection molding method, it is extremely important to properly control the expansion ratio of each part of the bottomed parison during blow molding, or to make the thickness distribution of the hollow container formed uniform.

In other words, when a cylindrical hollow container is formed from a cylindrical bottomed parison, the wall thickness distribution of the container is such that as long as the wall thickness and temperature distribution of the bottomed parison are constant, the expansion ratio that occurs there is also constant. Therefore, since there is no difference in the elongation of each part, it is said to be uniform throughout.

However, when forming a hollow container with a rectangular cross-sectional shape, a flat hollow container with a flat circular shape, an elliptical shape, etc. from a cylindrical bottomed parison, differences occur in the coefficient of linear expansion of each part of the parison.
The wall thickness distribution of the container, especially the wall thickness distribution on the circumferential surface (side surface) of the container is uneven, resulting in uneven wall thickness.

This uneven wall thickness may appear as a slight difference when the container is formed with a thick wall, or as a significant difference in wall thickness when the container is formed with a thin wall. In some cases, the container is formed as thin as a film, and its function as a container is completely impaired.

In order to solve these problems, proposals have been made regarding injection blow molding methods for flat containers (Japanese Patent Publication No. 5
9-42925). In this molding method, the first
Air is blown into a bottomed parison 1 having a circular cross section as shown in FIG. 1 to form a flat container 2 having significantly different vertical and horizontal expansion ratios in the planar cross section as shown in FIG. 12.

At this time, as shown in FIG. 13, the bottomed parison 1 has a flat or circular cross section, and has opposing portions 1a.

1a is formed to be slightly thicker than the other portions 1b, 1b. As shown in FIG. 14, the thick portions 1a, la have front and rear surfaces 2a, 2 with a large expansion ratio of the flat container 2.
The other portion 1b1b forms both circumferential surfaces 2b2b of the flat container 2 with a smaller expansion ratio.

That is, the thick portion 1a1a of the bottomed parison 1 is as follows:
Since the heat capacity is larger than that of the other portions 1b and 1b, even if the blow molding has different vertical and horizontal expansion ratios, the difference in the expansion ratios is compensated for by the difference in heat capacity, and as a result, uniform expansion is possible. Thereby, although the cylindrical bottomed parison 1 is used, it is possible to form a flat hollow container 2 with a uniform wall thickness distribution.

[Problems to be Solved by the Invention] However, in this conventional method, it is necessary to form parisons 1 with slightly different wall thickness distributions. For this reason, there was a problem in that the processing of the mold used for injection molding was complicated.

In particular, the above-mentioned prior art requires complicated processing to form the core mold of the injection mold into a flat shape that matches the inner shape of the parison, which has the problem of making the entire manufacturing equipment expensive.

Furthermore, in such conventional techniques, the injection-molded bottomed parison 1 is often sent to a heating furnace to adjust the parison temperature, and then the flat container is blow-molded. In this case, the temperature control core mold installed in the heating furnace also requires complicated processing to match the inner shape of the bottomed parison, which also raises the problem of increasing the cost of the entire manufacturing equipment. there were.

The present invention has been made in view of such conventional problems, and its purpose is to provide an injection blow molding method for containers that can solve the above-mentioned problems and form containers with good wall thickness distribution. It is about providing.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method for blow-molding a bottomed parison injection-molded using an injection mold to form a hollow container. By providing a gate for injecting the resin inside as a resin flow control gate that controls the resin flow from the bottom surface to the circumferential surface of the bottomed parison during injection molding, it is possible to control the retained heat distribution according to the shape of the final molded product. It is characterized by forming a bottomed parison so as to control the wall thickness distribution on the circumferential surface of the hollow container during blow molding.

[Work] Next, the present invention will be explained in detail.

The bottomed parison is formed by injecting molten resin from a runner into an injection mold through a gate. At this time, the resin present in the gate formed in the injection mold cools and solidifies on the bottom surface of the bottomed parison, forming a protrusion called a Kate part.

A feature of the present invention is that by providing the gate as a resin control cage that controls the resin flow from the bottom surface of the bottomed parison to the circumferential surface during injection molding, The objective is to provide a retained heat distribution that corresponds to the shape of the hollow container that is the final molded product. As a result, the circumferential surface of the hollow container (
This makes it possible to control the wall thickness distribution on the side surfaces.

That is, when resin is injected from the gate of the injection mold, the injected resin passes through the resin flow control gate and flows from a portion corresponding to the bottom surface of the bottomed parison to a portion corresponding to the circumferential surface. At this time, by forming the cross-sectional shape of the gate formed in the injection mold as an elliptical, star-shaped, or flat plate-shaped resin flow control gate, the runner passes through this resin flow control gate. The flow of the resin flowing into the mold is controlled according to the shape of the resin flow control gate, and an arbitrary heat distribution can be given to the bottomed parison.

As described above, according to the present invention, the shape of the control gate is formed to give a retained heat distribution corresponding to the shape of the container to be blow molded, so that it can be molded into a rectangular hollow container, an oval shape, an oval shape, etc. A flat hollow container can be formed so that its circumferential surface has a substantially uniform wall thickness distribution.

In particular, in the present invention, instead of controlling the thickness of the circumferential surface of the bottomed parison to provide a distribution of retained heat as in the past, the gate of the injection mold is used to control the flow of resin during injection molding. This was created based on a completely new idea of forming a flow control gate and providing a distribution of retained heat by the flow of the resin. Therefore, the injection mold and the temperature control mold do not require complicated machining corresponding to the complicated wall thickness distribution as in the past, and the cost of the entire device can be reduced.

[Example] Next, a preferred example of the present invention will be described in detail based on the drawings.

A first preferred embodiment of the invention is shown in FIGS. 1-7.

In the injection blow molding method of this embodiment, air is blown into the cylindrical bottomed parison 10 shown in FIG. 1 to form a flat hollow synthetic resin container 110 as shown in FIG. 2.

FIG. 3(a) shows an injection mold 20 used for injection molding of the bottomed parison 10.

This injection mold 20 has an injection core mold 24 and an injection mold 22. A hot runner nozzle 40 is connected to the resin injection gate 26 of the injection mold 20 via a heat insulating material 42.

Then, by injecting the molten resin from the runner 40a through the gate 26 into the injection mold 20, the bottomed parison 10 is formed. At this time, the resin present in the gate 26 formed in the injection mold 20 is cooled and solidified, and a protrusion called a gate portion 12 is formed.

A feature of the present invention is that the flow of molten resin injected into the mold 20 is controlled using the gate 26, and the flow of the molten resin injected into the mold 20 is controlled using the gate 26, and the synthetic resin container 110, which is the final molded product, is The purpose is to provide a distribution of retained heat according to the shape. As a result, air is blown into the parison 10, and a flat synthetic resin container 110 with different vertical and horizontal expansion ratios is created.
Even when blow-forming, it is possible to compensate for the difference in expansion ratio with the retained heat distribution. As a result, despite using the cylindrical bottomed parison 10, the peripheral surface 1
It is possible to obtain a flat synthetic resin container 110 in which the thickness distribution of the walls 10a and 110b is uniform.

As shown in FIGS. 3(b) and (-c), the gate 2 of the embodiment
Reference numeral 6 comprises a pore gate 26a as an initial injection port and a resin flow control gate 26b following the pore gate 26a.
6a and 26b, a protruding initial gate portion 26a
A plate-shaped control gate portion 26b connected thereto is formed.

With the above configuration, the molten resin flow injected into the mold from the initial gate 26a through the resin flow control gate 26b flows into the bottom forming space 28a.

It flows toward the back of the mold while passing through the peripheral surface forming space 28b. It is presumed that the flow of the resin at this time is controlled as shown in FIG.

That is, from the control gate 26b to the bottom surface forming space 28a
The molten resin flow that has flowed into the control gate 26b obediently flows from both ends of the control gate 26b toward the peripheral surface forming space 28b as shown by the arrow 100a, but flows into the bottom surface forming space 28a near the center of the control gate 26b. The resin flow hits the injection core mold 24 and flows sideways, as shown by arrow 100b, and then flows into the peripheral surface forming space 28b.

FIG. 5(a) shows an estimated diagram of the resin flow in the section Va-Va of FIG. 4, and FIG.
An estimated diagram of the resin flow in the vb-vb cross section perpendicular to a-Va is shown. As can be understood from these estimated figures, the bottomed parison 10 formed by injection molding of the example has a resin flow that obediently enters <10a, 1
It is presumed that the amount of heat retained in the 0a region is large, and the amount of heat retained in the 10b-10b region becomes low as the resin flow flows in. This is because the resin flow of 100a is
This is because the resin is cooled by the mold in the process of flowing toward the resin flow b, and as a result, it is estimated that the amount of heat retained in the region 10a is higher than that in the region 10b.

Therefore, it can be understood that in the regions 10a and 10a where the retained heat amount is large, the resin is easy to stretch in the blow molding process described below, and in the regions 10b and 10b where the retained heat amount is low, the resin is difficult to stretch in the blow molding process.

Then, the bottomed parison 10 is blow-molded into a flat synthetic resin container 110 using a blow mold 30 shown in FIG. At this time, the parison 10 is transferred to the blowing mold 30 after being released from the injection mold 20, or it is transferred to the blowing mold 30 immediately after being released from the injection mold 20, or it is sent to a heating furnace and the parison temperature is re-adjusted. There are cases where the material is transferred to the blowing mold 30 after adjustment, but the present invention can adopt either of these methods.

FIG. 6 shows the bottomed parison 10 in the blow mold 30.
location is shown. In the example, the bottomed parison 1
0 is a mold surface 32a located at the center of the flat cavity 32 and forming the front and rear peripheral surfaces 110g and 110a of the flat container 110.

32a faces the regions 10a, 10a having a high amount of retained heat. By blowing air into the bottomed parison 10, a region 10a with a high retained heat amount is formed.

10a in the direction in contact with the mold surfaces 32a, 32a, and regions 10b, 10b with low retained heat amount in the mold surfaces 32b, 3 for molding both the left and right peripheral surfaces 110b, 110b of the flat container 110.
Expand in the direction of contact with 2b.

At this time, the area 1 where the retained heat of the bottomed parison 10 is larger
0a and 10a are regions with small retained heat], Ob, 10
It extends sufficiently compared to b. As a result, a flat hollow container 110 with a uniform wall thickness distribution on the circumferential surface 140a110b can be obtained from the cylindrical bottomed parison 10 as shown in FIG. 1, as shown in FIG.

In particular, according to the present invention, unlike the conventional case, both circumferential surfaces 1.10b and 110b of the flat container 110 are formed thin like a film, resulting in insufficient strength or stress whitening, which significantly impairs the aesthetic appearance. There is no problem, and a good flat synthetic resin container can be obtained.

Further, after forming the synthetic resin container 110 in this manner, the gate portion 112a of the bottom surface 116 of the synthetic resin container 110 is removed.

112b may get in the way. In this case, the gate portions 112a, 112b may be crushed during blow molding, and then the gate portions 112a, 112b may be crushed.
You may remove only the part.

Furthermore, the resin flow control gate portion 112b on the bottom surface 116 of the synthetic resin container 110 may be actively utilized. For example, by making a hole 120 etc. in the control gate portion 112b, the container 110 can be hung as a hanging device. can also be used.

In this embodiment, the explanation has been given by taking as an example a case in which a fairly large control cage portion 12b is formed on the bottom surface of the bottomed parison 10. However, even if the control cage portion 12b is not so large, it may be A sufficient effect can be obtained even with a small device as shown in Fig. 7.

In this embodiment, the resin flow control gate 26b is explained by taking as an example a case in which a plate-shaped control gate part 12b is provided on the bottom surface 16 of a bottomed parison, but the present invention is not limited to this. Depending on the shape of the synthetic resin container 110 to be formed, the resin flow control gate 26b may be formed so that the control gate portion 12b has an arbitrary shape, for example, a star shape or an oval shape.

For example, when forming a prismatic hollow synthetic resin container 110 as shown in FIG.
As shown in FIG. 8, a star-shaped control gate portion 12b having a cross shape may be formed on the bottom surface by using the cross-shaped control gate portion 12b. This results in
As shown in FIG. 8(C), the bottomed parison 10, especially its bottom surface 16, is formed alternately with regions 10a into which the resin flow easily flows and which have a large amount of heat, and regions 10b into which the resin flow does not easily flow and which have a low amount of heat. be done. Therefore, by blowing air into the bottomed parison 10, the region 10a with a high retained heat amount forms the peripheral surface 110a of the synthetic resin container 110, and the region 10b with a low retained heat amount forms a corner part 110b of the container 110. will be formed.

In particular, when conventionally forming such a rectangular hollow container 110, the corner part 110b tends to stretch during blow molding and tends to lack strength, but according to the present invention, this corner part 110b It is possible to maintain good wall thickness.

Further, in the above embodiment, the gate 26 is composed of the fine hole gate 26a as an initial injection port and the resin flow control gate 26b following this, but the present invention is not limited to this, and the fine hole gate 26a can be used as necessary. A configuration may be adopted in which only the resin flow control gate 26b is provided without providing the hole gate 26a. In this case, the resin flow control gate 26b may be formed so that the control cage portion 12b of the bottomed parison 10 has the shape shown in FIG. 10, for example.

Note that the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present invention.

E. Effects of the Invention As explained above, according to the present invention, the gate for injecting resin into the injection mold is used for controlling the resin flow from the bottom surface to the circumferential surface of the bottomed parison during injection molding. By providing it as a gate, it is possible to form a bottomed parison so that it has a retained heat distribution that corresponds to the shape of the final molded product, which allows good control of the wall thickness of the circumferential surface of the hollow container during blow molding. be able to.

In particular, according to the present invention, the wall thickness of the hollow container circumferential surface during blow molding can be controlled without using a bottomed parison whose circumferential wall thickness is accurately controlled, so injection molds, temperature control molds, etc. The mold does not require complicated processing as in the past, making it possible to reduce the cost of the injection molding apparatus itself.

[Brief explanation of drawings]

FIG. 1 is an explanatory view of a bottomed parison used in the present invention, in which (a) is an explanatory view of its circumferential surface, and (b) is a circumferential surface viewed from the direction of the arrow in (a). An explanatory diagram. Figure (C) is an explanatory diagram of the bottom of Figure (a) viewed from the direction of arrow C. Figure 2 is a flat hollow synthetic resin formed by blowing air into the bottomed parison shown in Figure 1. It is an explanatory diagram of a container,
FIG. 3 is an explanatory diagram of an injection mold used for molding the bottomed parison shown in FIG. The same figure (a) is an explanatory longitudinal cross-sectional view of the whole, the same figure (b) is an explanatory longitudinal cross-sectional view of the main part,
FIG. 4(c) is an explanatory longitudinal cross-sectional view in a direction orthogonal to FIG. 4(b), FIGS. 4(a) and (b) are explanatory views showing the flow of resin in the mold shown in FIG. FIGS. 5(a) and 5(b) are explanatory diagrams of the flow of resin in the mold shown in FIGS. 3(b) and (c), and FIG. 6 is the position of the bottomed parison and the blowing mold. A cross-sectional explanatory diagram showing the relationship, FIG. 7 is an explanatory diagram showing an example of a case where the resin flow control gate portion formed on the bottom surface of the bottomed parison is formed smaller, and FIG. An explanatory diagram of the resin flow control gate part seen from the side, Figure (b) is an explanatory diagram seen from the front, and Fig. 8 shows a bottomed parison with a control gate part with a star-shaped cross section formed on the bottom surface. FIG. 3(a) is an explanatory view of its peripheral surface, FIG. 2(b) is an explanatory perspective view of the bottomed parison as seen diagonally from below, and FIG. 1(C) is an explanatory view of its bottom surface. , FIG. 9 is an explanatory diagram of a square hollow synthetic resin container formed using the bottomed parison shown in FIG. 8, and FIG.
10 is an explanatory diagram of a bottomed parison in which only a control gate portion is formed on the bottom surface. FIGS. FIG. 2 is an explanatory diagram showing an example of an injection blow molding method. 10... Bottomed parison, 10a, 10b... Area, 1
2b... Control cage part, 16... Bottom surface, 26...
・Cate, 26b...Cate for resin flow control, 110・
・Synthetic resin container. Agent Patent attorney Inoue - (2 others) Part (a) Zuru = 103 24 core type / Fig. (a) (b) Fig. (a) (b) Fig. (a) (b) Busy) 0a Figure 30 Blow mold = Figure (b) Figure (○) Figure Figure Figure Figure Figure

Claims (1)

[Claims] (1) In a method of blow-molding a bottomed parison injection molded using an injection mold to form a hollow container, a gate for injecting resin into the injection mold is placed on the bottom surface of the bottomed parison during injection molding. By providing a resin flow control gate that controls the resin flow from the surface to the circumferential surface,
A method for injection blow molding a container, characterized by forming a bottomed parison so as to have a heat retention distribution according to the shape of the final molded product, and controlling the wall thickness distribution on the circumferential surface of the hollow container during blow molding.