JPS61274912A - Nozzle apparatus for multilayer molding - Google Patents

Abstract

PURPOSE:To obtain a thin walled container excellent in heat resistance and gas barrier property by preventing the offsetting of an intermediate layer by equalizing the wall thicknesses of inner and outer layers, by doubly combining an outer nozzle having an injection orifice at the leading end thereof and an inner nozzle having a first flow passage formed therein in a concentric state and forming the second flow passage communicated with the injection orifice between the outer nozzle and the inner nozzle and further providing a third flow passage communicated with an outflow port in a branched state in the inner nozzle. CONSTITUTION:When different resins A, B are supplied to a first flow passage 23 and a second flow passage 15 in such a state that an injection orifice 11 is contacted with the gate 33 of a mold 32, resin A of the first flow passage 23 is flowed out from the ring shaped outflow port of an inner nozzle 2 while the resin B is flowed out from the second flow passage 15 to flow to the injection orifice 11 but a part of the resin B is branched toward the central part of the inner nozzle 2 by a third flow passage 31 and flowed to the injection orifice 11 from an outflow port 21. By this method, the resins A, B injected in a cavity 34 from the gate 33 are impinged to a core 35 to be brought to a concentric circular state to mold a molded product having a three-layered structure having the resin A as an intermediate layer at the core part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a nozzle device used for injection molding of a multilayer synthetic resin molded product having an intermediate layer.

[Prior Art] In order to compensate for the shortcomings of the resin used to form an article, it is common practice to form a multilayer article using another resin as an intermediate layer. In particular, when the molded product is a container, multilayering is required for the purpose of improving heat resistance and gas barrier properties.

Generally, when forming a multi-layer molded product by injection molding, when the layer 311 is formed therein, a double structure nozzle device in which an outer nozzle and an inner nozzle are concentrically combined is used. For example, the molding of multilayer bottomed parisons used in stretch-blow molding of containers was published in Japanese Patent Publication No. 59-29416.
As described in the publication, a double nozzle with an inner channel communicating with the nozzle opening and an inner channel opening at the tip of the outer channel is used to form a parison. The resin is injected into the cavity from the outer channel, and the intermediate layer forming resin is injected from the inner channel.

To inject the resin, first inject one parison-forming resin from the outer channel, then inject the intermediate layer-forming resin from the inner channel together with the parison-forming resin in the outer channel, and finally inject the parison-forming resin again. The molding has been completed.

[Problems to be Solved by the Invention] In molding using such a double nozzle, the resin injected into the cavity first forms the inner layer of the molded product, so the resin that forms the intermediate layer is subsequently injected into the cavity. The thickness of the inner layer becomes extremely thin compared to the outer layer, which receives resin injection, and accordingly, the position of the intermediate layer shifts inward from the center.

On the other hand, when injection is performed from the inner flow path, the outer layer side becomes thinner for the same reason as above, and the middle 1IV11 is biased toward the outside.

By the way, ethylene vinyl alcohol copolymer (EVOH) and polyamide (P
With resins such as A), permeable acids such as oxygen and carbon dioxide gas also increase as the amount of moisture absorbed increases.

On the other hand, the two-wheel stretched polyester resin used for carbonated beverage bottles has a lower moisture permeability than the above resins, but
As with all resins, its moisture permeability depends on its thickness.

For this reason, in multilayer containers with thin inner or outer layers, even if the resin used to form the container is double-stretched polyethylene terephthalate, the gas barrier properties of the intermediate layer are significantly reduced due to moisture absorption from inside and outside the container. However, the permeability of oxygen and carbon dioxide increases. For this reason, it is not suitable for long-term storage of beer, carbonated drinks, etc., and it is said that it is most preferable for the middle layer to be located in the center for containers for foods and drinks that do not want oxygen to pass through.

In order to meet such a demand, that is, to position the middle layer in the center of the molded product by injection molding, a triple-structure nozzle device that can mold the inner and outer layers at the same time as the middle ties and to the same thickness is required. Although it would be possible to use a nozzle device with a triple structure, it is not only more complicated than a double structure, but also makes it difficult to control the temperature of each resin flow path.
There is a problem in that it is difficult to use when a large number of molded products are injection molded at the same time.

[Means for Solving the Problems] This invention was devised to solve the above problems, and the points f and I6 are that although the nozzle structure is double, the thickness of the inner and outer layers is Molded to the same thickness to make medium Wi
The layer can be located in the center and, if desired,
It is an object of the present invention to provide a nozzle device for multilayer molding with a new structure that can also change the thickness distribution of each layer.

The present invention for the above purpose concentrically combines an outer nozzle having an injection port at its tip and an inner nozzle having an outlet at the center of the conical tip and a first flow path inside. The outflow port is located within the projection plane of the injection port, and a second flow path communicating with the injection port is formed between the outer nozzle and the inner nozzle, and the second flow path is provided inside the inner nozzle. The outlet of the first flow path is provided in an annular shape around the tip of the inner nozzle, and the resin from the first flow path is transferred to the second and third flow paths. It is arranged so that multilayer molding can be performed by positioning it between the same resins coming from the flow path.

[Function] In the above structure, two flows of the same resin are generated from the periphery of the inner nozzle and the center of the inner nozzle toward the opposite outlet, and the resin from the first flow path exists in an annular shape between the resins. As a result, these resins flow toward the injection port while maintaining concentric circles without mixing with each other. As a result, the resin from the first channel is located in the center of the same resin as an intermediate layer. Also the flow of each flow path! By changing the dimensions of the outflow gap or outflow port, the thickness of the layer formed by each resin can be changed, and the position of the middle layer can be set somewhere other than the center depending on the difference in thickness distribution. You can also do that.

Further, the present invention will be explained in detail using illustrated examples.

(Example) In the figure, 1 is an outer nozzle that can be heated and heated on its outer periphery, and has an injection port 11 at the center of the tip.
A nozzle head 12 having a tapered inner peripheral side in contact with the nozzle body 13 is connected to the nozzle body 13.

Consisting of

2' is an inner nozzle, the tip of which is formed into a conical shape having the same angle as the tapered surface, a nozzle tip 22 having an outlet 21 in the center of the tip, and a tube with an inner space as a first flow path 23. It is embedded within the tip of the body 24.

The inner nozzle 2 is installed concentrically inside the outer nozzle 1, with the outlet 21 located within the projection plane of the injection port 11, so that there is no injection between the outer nozzle 1 and the inner nozzle 2. A second flow path 15 is formed that connects the outlet 11 and an inlet 14 formed in the nozzle body 13. Note that the end of the second flow path 15 is closed by the intrusive end 24a of the tube body 24. Further, 16 is a spacer.

At the center of the interior of the nozzle chip 22, the first flow path 2 is provided.
A through hole 25 forming a part of the inner nozzle 2 and a passage 26 of the outlet 21 are bored in front and behind each other, and the passage 2G is a part of the second flow passage 15 which is bored inward from the side of the inner nozzle 2. A third flow path 31 is formed therein by connecting to a plurality of branch paths 27 .

Further, around the tip of the inner nozzle 2, there is an annular outlet 28 formed at the boundary between the nozzle tip 22 and the tip edge 24b of the tube body 24 made of a tapered surface. A channel 23 is connected via a channel 29 around the chip. Note that 30 is the passage 29 and the through hole 25 in the chip.
There are multiple passages that span the area.

In the nozzle device, different resins A are applied to the first flow path 23 and the second flow path 15 with the injection port 11 in contact with the gate 33 of the mold 32, as shown in FIG.

When B is supplied, the resin A in the first flow path 23 flows through the inner nozzle 2.
It flows out from the annular outlet 28 to the injection port 11 along the distal end surface.

Further, the resin B flows out through the second flow path 15 to the injection port 11, but a part of the resin is diverted to the center of the inner nozzle 2 by the third flow path 31 at the tip of the nozzle, and the resin B flows through the third flow path 31 at the tip of the nozzle. Exit 2
1 to the injection port 11. Therefore, the resin A is sandwiched between the resin B flowing between the center and the outside, and is injected into the cavity 34 from the injection port 11 as it is.

Resin A injected into cavity 34 from Genit 33.

B hits the core 35 and the cavity 34 is in a concentric state.
A three-layered molded product 36 (see FIG. 6) having resin A from the first flow path 23 as an intermediate layer is molded therein.

Further, the intermediate layer made of resin A is formed in the second and third channels 15 and 3.
If the flow rates of resin B in No. 1 are the same, the resin B will always be located in the center. Furthermore, the third flow path 31 allows the gap between the first flow path 23 and the outflow port 28 and the outflow port 2
The thickness distribution of each layer in the molded product 36 and the position of the intermediate layer can also be arbitrarily set by adjusting the diameter of the molded article 1 or by selecting the injection speed.

[Effects of the Invention] As described above, the present invention branches part of the second flow path formed between the outer nozzle and the inner nozzle into the third flow path that flows out from the center of the tip of the inner nozzle, and , the outlet of the first flow path is formed in an annular shape at the tip of the inner nozzle formed on the tapered surface, so that the flow of resin forming an intermediate layer in the resin flowing out from the second and third flow paths is formed. The cross-sectional shape of the nozzle device is better than that of a double-structure nozzle device that requires the injection of resin for the inner or outer layer in advance. A three-layer molded product with uniform properties can be easily molded. In addition, since the position of the intermediate layer and the thickness distribution of each layer can be set arbitrarily, problems caused by unevenness of the intermediate layer can be solved, and the intermediate layer can also be used to form thin containers with excellent heat resistance or gas barrier properties. In addition to being useful for this purpose, the structure is not particularly complicated compared to conventional ones, and the temperature of the flow path during injection molding can be easily controlled.

[Brief explanation of drawings]

The drawings show an embodiment of the nozzle device for multilayer molding according to the present invention, in which FIG. 1 is a vertical side view, FIG. 2 is a vertical side view of the nozzle tip and mold during molding, and FIG. 3 is a vertical side view of the nozzle tip and mold during molding. Figure 2■-
4 is an enlarged sectional view of the gate portion, FIG. 5 is a sectional view of the inside of the mold, and FIG. 6 is a longitudinal sectional front view of the molded product. 1...Outer nozzle 2...Inner nozzle 11...
Injection port 15...Second flow path 21...Injection port
23...First channel 31...Third channel Fig. 2 Fig. 3

Claims (1)

[Claims] An outer nozzle having an injection port at the tip and an inner nozzle having an outlet at the center of the conical tip and a first flow path inside are combined in a double manner, and the injection port is placed within the projection plane of the injection port. In a nozzle device in which an outflow port is located and a second flow path communicating with the injection port is formed between an outer nozzle and an inner nozzle, the second flow path is branched into the inner nozzle and connected to the outflow port. A nozzle device for multilayer molding, characterized in that a communicating third flow path is formed, and the outlet of the first flow path is provided in an annular shape on the tip surface of an inner nozzle.