JPH0698640B2 - Multilayer molding nozzle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a multilayer molding nozzle used when injection molding a synthetic resin molded product having a multilayered cross-sectional structure.

[Prior Art] A conventional multilayer molding nozzle is provided with a plurality of resin passages in a concentric circle in a nozzle body having a mouth at the center of the tip, and different molten resin in each resin passage is caved from the nozzle mouth. It consists of multiple nozzles that can be fired.

[Problems to be Solved by the Invention] The multi-layering of synthetic resin molded products can further improve the quality of thin molded products as beverage containers by the resin interposed as the intermediate layer. Due to the interposition, there are problems that the impact resistance is lower than that of the single layer, and the cost is high.

Therefore, using conventional double nozzles or triple nozzles, the injection pressure, time, injection timing, etc. of the molten resin forming the intermediate layer were controlled, and injection molding of a molded article partially having the intermediate layer was attempted. Due to the resin pressure, it was extremely difficult to mold the intermediate layer within a predetermined range.

Also, as described in JP-A-60-34819, a multiple nozzle for controlling the molten resin by moving the central path of multiple resin paths and selectively opening and closing the orifices of each resin path is also available. However, it requires a special valve device to control the flow of molten resin through the orifice and into the central passage for injection,
The valve device is mechanically operated and has a very complicated structure as a nozzle.

The present invention was conceived in order to solve the problems of the above-mentioned conventional multiple nozzles, and its object is to provide a valve member that operates with a resin pressure in the flow path of the molten resin to be the intermediate layer with a simple structure. It is an object of the present invention to provide a new multi-layer molding nozzle which can be opened and closed and thereby injection-molded a molten resin to always accurately perform switching from multi-layer to single-layer or from single-layer to multi-layer.

[Means for Solving the Problems] According to the present invention according to the above object, a triple nozzle in which a first resin passage, a second resin passage, and a third resin passage having the same injection port are provided concentrically inside a nozzle body. At the central portion of the third resin passage located inside the mouth portion of the second resin passage, the second resin passage is moved forward and backward by the resin pressure between the third resin passage and the second resin passage.
It is configured by a valve member that opens and closes the resin passage, or the mouth portion of the intermediate second resin passage located inside the first resin passage is moved forward and backward by the resin pressure of the second resin passage and the first resin passage. Then, the second resin passage is constituted by a valve member that opens and closes, thereby solving the conventional problems.

[Operation] The molten resin of each resin passage to which the injection pressure is applied is simultaneously injected into the cavity from the mouth portion of each resin passage through the nozzle mouth portion. If the injection pressure of the second resin passage is removed during this injection, the valve member moves forward or backward by the resin pressure of the first resin passage or the third resin passage to close the second resin passage,
The outflow of the molten resin from the second resin passage is prevented. Therefore, only the molten resin in the first and third resin passages can be injected into the cavity.

When an injection pressure is applied to the second resin passage, the valve member moves backward or forward to open the second resin passage due to the difference in pressure receiving area of the valve member, and the molten resin is cavities together with the molten resin in the other resin passages. Is injected into.

Therefore, the molten resins in the first and third resin paths are of the same type,
When the molten resin in the second resin passage is made of another type, the molded product produced there is composed of the type 2, 3 layer portion and the single layer portion.

Further, the present invention will be described in detail with reference to the illustrated example.

[Embodiment] 1 is a nozzle body in which an injection port 2 is opened at the center of the front end surface, and each has a first resin passage 3, a second resin passage 4, and a third resin passage 5 concentrically inside.

Each of the resin paths is formed by sequentially inserting hollow core members 6 and 7 having spacers on the side portions into the nozzle body from the rear end opening of the nozzle body 1.

The triple nozzle shown in FIG. 1 is provided with an opening 41 of the second resin passage 4 inside the opening 31 of the first resin passage 3 connected to the injection port 2, and further has an opening 41 of the third resin passage 5. 51 to the mouth portion 41 of the second resin passage 4
And the mouth portion 51 is constituted by the valve member 8.

The valve member 8 is formed of a ring body that is inserted into and retracted from the inside of the tip portion of the core member 7. The inner diameter of the valve member 8 is substantially equal to the inner diameter of the mouth of the first resin passage 3 and smaller than the diameter of the third resin passage 5, and the front end surface 8a and the rear end surface 8b are formed into tapered surfaces. , And the resin pressure acts on each.

The ratio of the pressure receiving areas on the both end faces 8a, 8b is preferably in the range of 0.5 <second resin passage / third resin passage <4. As long as the above relational expression is satisfied, the valve member 8 is the second resin passage at the time of injection. Even if the resin pressure of the third resin passage 5 is applied to the rear end face 8b by the resin pressure of 4, the second resin passage 4 is retained in the front end portion of the core member 7 and the opening of the second resin passage 4 is maintained. The injection pressure of 4 is controlled,
When the resin pressure is remarkably reduced, the valve member 8 immediately advances due to the resin pressure of the third resin passage 5 acting on the rear end surface 8b to close the second resin passage 4.

Therefore, the valve member 8 opens and closes the second resin passage 4 in accordance with the difference in resin pressure acting on both end surfaces, and controls the injection of the molten resin from the second resin passage 4.

The triple nozzle shown in FIG. 2 is configured so that the second resin passage 4 can be opened and closed by the resin pressure of the first resin passage 3, and the valve member 8 is provided in the tip portion of the core member 6. It is inserted and retracted freely.

Further, in this case, since the second resin passage 4 is closed by retreating the valve member 8, the diameter of the tip portion 7a of the core member 7 is reduced and the tip is extended to the first resin passage 3, and the mouth portion is formed. The opening 51 of the third resin passage 5 is exposed to the inside of the first resin passage 31 and the second resin passage 4 is opened at the side surface of the tip portion, and the opening 41 is formed so that the opening 41 is formed in the core member 6.
The valve member 8 is inserted into the tip of the valve member 8, and the rear end surface 8b of the valve member 8 contacts the tapered shoulder portion 9 formed in the core member 7 to close the second resin passage 4. .

Further, the ratio of the pressure receiving area between the front end surface 8a and the rear end surface 8b of the valve member 8 formed on the tapered surface is preferably 0.5 <second resin passage / first resin passage <4.

The material resin supplied to each of the resin paths is arbitrarily selected according to the molded product, and in the case of three kinds of five layers, different material resins are supplied to each resin path. When injection molding a two-kind three-layer molded product, the material resins of the first resin passage 3 and the third resin passage 5 are of the same type.

As shown in FIG. 3, the above-mentioned triple nozzle is used by mounting the required number on the hot runner block 10. In this embodiment, a molded product of two types and three layers is molded, and inside the hot runner block 10, the hot runners 13, 12 connected to the sprue bushes 11, 12 arranged side by side, respectively,
14 is provided, the hot runner 13 and the second resin path 4
And the hot runner 14 and the third resin path 5, and the branch path 15 of the hot runner 14 and the first resin path 3 are connected to each other.
The same material resin can be injected from the third resin paths 3 and 5, and the different material resin can be injected from the second resin path 4.

Next, molding of a three-layer molded product having an intermediate layer using the triple nozzle shown in FIG. 1 will be described.

First, when injection pressure is applied to the first resin passage 3 and the third resin passage 5 to inject the same molten resin A, A, the second resin passage 4 and the third resin passage 4 are injected.
Due to the pressure difference with the resin passage 5, the valve member 8 advances together with the molten resin simultaneously with the injection, and closes the second resin passage 4 as shown in FIG.

As a result, only the same molten resins A, A are injected into the cavity, and different molten resins B in the second resin passage 4 are not injected.

Next, when the injection of the predetermined amount of the molten resin A, A is completed and the injection pressure is applied to the second resin passage 4 while continuing the injection,
Due to the difference in the pressure receiving area of the valve member 8, the valve member 8 is retracted to open the second resin passage 4 as shown in FIG. 4, and different molten resin B is supplied to the first and third resin passages 3,5. The molten resin A, A flows out so as to be interposed between them, and is further injected from the injection port 2 into the cavity together with the molten resin A, A.

When the injection is performed to the end, a molded product having three layers as a whole is molded. However, if the injection pressure of the second resin passage 4 is cut off in the middle, the valve member 8 is As shown in FIG. 5, the second resin passage 4 is closed by advancing again by the resin pressure in the third resin passage 5.

For this reason, the injection is made only of the same molten resins A, A again from the middle, and is molded into a single layer. Further, since the molten resin B injected from the second resin passage 4 comes to be located at the center of the molten resins A, A, the molten resin A, A which comes into contact with the mold surface while being filled and moved in the cavity. Even if a skin layer is formed on the surface of the resin, it is slow to be affected by the skin layer, and it is difficult for the molten resin B to form the skin layer on the way.

In the molded product 20 shown in FIG. 6, the molten resin B in the second resin passage 4 is injection-filled only in the mouth portion 21 to form three layers, the body portion 22 and the bottom portion.
23 is a bottomed preform in which 23 is a single layer made of only the molten resin A, and a chain line indicates a container 30 stretch-blow molded from the bottomed preform.

In the molded product 40 shown in FIG. 7, the molten resin B in the second resin passage 4 is injected and filled only in the body portion 42 to form three layers, and the mouth portion 41 and the bottom portion 43 are formed as a single layer made of only the molten resin A. With the bottomed preform made, the dashed line shows the container 50 stretch blow molded from the bottomed preform.

Further, in the molded product 60 shown in FIG. 8, only the bottom portion 63 is injected and filled with the molten resin B of the second resin passage 4 to form three layers, and the mouth portion 61 and the body portion 62 are formed as a single layer of only the molten resin A. With the bottomed preform made, the dashed line shows the container 70 stretch blow molded from the bottomed preform.

The material resin used as the molten resin A may be a resin that can be injection stretch blow molded such as polyethylene terephthalate, and the molten resin B is excellent in barrier properties such as meta-xylene group-containing polyamide, ethylene vinyl alcohol, and high nitrile. A resin having heat resistance such as a resin or a polycarbonate or a U polymer is used depending on the application of the container molded therein.

For example, the mouth portion 31 of the container 30 can be formed into a multi-layer structure by using
When polycarbonate is used as the resin forming 34, the heat resistance is remarkably improved as compared with the case where only polyethylene terephthalate is used, and the mouth portion change during heating and filling is prevented.

Similarly, when the bottom portion 73 of the container 70 is multilayered by the intermediate layer 74 of U polymer, the heat resistance of the bottom portion 73 is improved, and even if the bottom portion 73 of the container 70 is heat treated after being filled with carbonated juice, the bottom portion of the bottom portion of the container becomes like the bottom portion of a single layer. The part does not project and deform.

Furthermore, like the container 50, in the case where only the body portion 52 is multilayered with an intermediate layer 54 such as a meta-xylene group-containing polyamide,
The barrier property is improved, delamination is prevented when the bottom part is made multi-layered, and the expensive resin used for the intermediate layer 54 can be saved.

Next, one example of molding conditions by the triple nozzle shown in FIG. 1 is shown below.

Cross-sectional area of each resin path 1st resin path 34.56mm ² 2nd resin path 59.69mm ² 3rd resin path 21.23mm ² Injection port diameter 2.0 to 3.0mm Pressure receiving area (projected area) of valve member ^2nd resin path side (tip) Surface) 25.13mm ² 3rd resin road side (rear end surface) 21.23mm ² Material Resin 1st and 3rd resin passage Polyethylene terephthalate 2nd resin passage SM nylon Injection pressure 1st and 3rd resin passage Primary pressure 140Kg / cm ² 2 Next pressure 58Kg / cm ² Second resin passage 100Kg / cm ² [Effect of the invention] As described above, the present invention can be applied to the first to the third inside the nozzle body.
Is provided in a concentric circle, and the second resin passage is closed by a valve member operated by the resin pressure of another resin passage to control the injection of the molten resin from the second resin passage. Since the formation position of the layers can be arbitrarily set, only the mouth portion, the body portion or the bottom portion of the molded product can be multilayered. It also has the advantage that the position of the intermediate layer can be set at the center.

[Brief description of drawings]

The drawings show an embodiment of a multi-layer molding nozzle according to the present invention. FIG. 1 is a sectional view of the first embodiment, FIG. 2 is a sectional view of the second embodiment, and FIG. 3 is a hot runner block. The attached sectional view, FIGS. 4 and 5 are sectional views showing the molding process, and FIGS. 6 to 8 are sectional views of the bottomed preform and the container. 1 ... Nozzle body, 2 ... Injection port 3 ... First resin path, 4 ... Second resin path 5 ... Third resin path, 6, 7 ... Core member 8 ... Valve member, 8a. Front face 8b …… Rear end face

Claims (2)

[Claims] 1. A triple nozzle having a first resin passage, a second resin passage, and a third resin passage having the same injection port inside a nozzle body, which are concentrically arranged, and located inside the mouth of the second resin passage. The opening portion of the central third resin passage is configured by a valve member that opens and closes the second resin passage by advancing and retreating by the resin pressure of the third resin passage and the second resin passage. Multi-layer molding nozzle. 2. A triple nozzle provided concentrically with a first resin passage, a second resin passage, and a third resin passage having the same injection port inside a nozzle body, and an intermediate portion located inside the first resin passage. Of the second resin passage is configured by a valve member that opens and closes the second resin passage by advancing and retracting by the resin pressure of the second resin passage and the first resin passage. Nozzle.