JPS5929416B2 - TASOUSEIKEIHINNOSEIZOUHOU - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a multi-layered container, a bottomed Parylin, etc. by injecting two types of synthetic resin into a mold cavity in which the distance from the gate to the tip of the mold cavity is equal.

In general, containers are required to have excellent shielding properties, mechanical properties, stress crack resistance, appearance, hygiene, cost, etc.

When manufacturing containers using synthetic resins, it is difficult to meet these requirements with one type of resin. In such cases, it is common practice to use two or more resins in a layered manner. In that case, for example, a laminated structure using a resin with excellent shielding properties and stress crack resistance in the inner layer and a resin with excellent mechanical properties and appearance in the outer layer is preferable. Many methods have been proposed for forming the above-described laminated structure by injection molding. For example, U.S. Patent No. 3,339,240
A method of obtaining a molded product with a two-layer structure by simultaneously injecting two types of synthetic resins into a mold cavity is described in the patent specification.
However, in those methods, when two types of synthetic resins are simultaneously injected into a mold cavity, it is necessary that the two types of resins be injected at approximately the same rate from beginning to end, and therefore the resulting molded products are approximately equal. This results in a two-layer structure (see Figure 1). Depending on the application of the molded product, the thickness of each layer of the two-layer structure may be
One may be required to be thick and the other thin (see Figure 2). For example, some containers have a structure that has a thin inner layer 2 made of expensive resin with excellent shielding properties and a thick outer layer 1 that is relatively inexpensive and has excellent physical properties (Figure (2-2)), or the opposite. Structure No. 2-1 is required. 2nd-
Figure 3 is an example of a molded product with the structure shown in Figure 2-2.
Figure 4 shows an enlarged cross-section of part 3. In order to obtain such a molded product, conventionally, the inner layer resin is first injection molded, then the molded product is placed in a larger mold cavity, and the outer layer resin is injection molded on the outside of the molded product, or the inner layer, They have been made only by separately molding the outer layer and gluing it together. However, these molding methods are complicated and the molded products are therefore expensive. The present inventor has further improved the method described in US Pat. No. 3,339,240 in a method for manufacturing molded articles having a multilayer structure of two or more layers, and the thickness of each layer can be adjusted to a desired degree. The present invention was achieved by intensive research on methods that can be changed arbitrarily. That is, the present invention provides a method for molding a multilayered container or the like by injecting two types of synthetic resin into a mold cavity having the same distance from the gate to the tip of the mold cavity.
of the synthetic resin are separated concentrically into an inner layer and an outer layer at the injection port of the mold cavity in approximately equal amounts, and
Simultaneously inject a total amount that fills part of the mold cavity, then inject the first or second synthetic resin, pressing the previously injected first and second synthetic resins against the mold wall surface,
A multilayer molded product characterized by filling the extruded mold cavity at the tip of the mold cavity, and injecting an appropriate amount of the same type of resin as the synthetic resin that will become the outer layer into the mold cavity in advance, and then carrying out the above method. This is the manufacturing method.

Next, the method of the present invention will be explained with reference to FIG. 3 and subsequent figures.

In Figure 3, two types of synthetic resins are concentrically separated into an inner layer and an outer layer from the injection port 5 of the mold cavity 4 into the mold cavity 4, and the same amounts are simultaneously added to the mold cavity so that the total amount is equal to that of the mold cavity. 3-1, then stop the injection of the resin for the inner layer and inject only the resin for the outer layer, and as shown in FIG. 3-2, the resin 6 for the outer layer is formed. The inner layer resin 7 is forced to the tip of the mold cavity 4 and fills the mold cavity Tj to obtain a two-layer structure molded product consisting of a thin inner layer 7 and a thick outer layer 6 as shown in FIG. 3-3. In this case, it is necessary to adjust the injection amount of the inner layer resin to an amount that will form a thin and uniform inner layer as shown in FIG. 3-3. Further, the thickness of the inner layer 7 can be adjusted to some extent by adjusting the viscosity of the resin, the temperature of the mold, the injection speed of the resin, etc. When injecting into the two-layer structure shown in FIG. 3-1, it is preferable to first inject a small amount of the inner layer resin, and then simultaneously inject equal amounts of the inner layer and outer layer resins. In order to mold a two-layer molded product with a thick inner layer 7 and a thin outer layer 6 shown in Fig. 3-4, the third
This is obtained by stopping the injection of the resin 6 for the outer layer and injecting only the resin 7 for the inner layer from the state shown in Fig.-1. Next, in the method of the second invention, the first synthetic resin and the second synthetic resin are concentrically separated into an inner layer and an outer layer at the injection port of the mold cavity, and are injected into the mold cavity in almost equal amounts each and in total amount. Prior to the method of simultaneously injecting an amount to fill a part of the resin and then injecting the first or second synthetic resin to fill the mold cavity, an appropriate amount of synthetic resin that will become the outer layer is injected into the mold cavity in advance. This relates to a method characterized by the following, and will be explained below with reference to FIG. The first synthetic resin 21 is injected into the mold cavity 4, as shown in FIG. 4-1, and then the first synthetic resin 21 and the second synthetic resin 22 are injected simultaneously, as shown in FIG. When the resin is injected to fill the mold cavity, the second synthetic resin 22 is thinly and uniformly encapsulated in the first synthetic resin 21, as shown in FIG. 4-3. In this case, it is preferable to use a colored resin or a resin with excellent shielding properties as the second synthetic resin. FIG. 5 shows a longitudinal section of an injection molding apparatus for carrying out the method of the invention, which injection molding apparatus consists of two injection cylinders.

The first synthetic resin that will become the inner layer of the molded product is accumulated in the first injection cylinder 9 using the screw 10, and the second synthetic resin that will become the outer layer of the molded product is accumulated in the second injection cylinder 11 using the screw 12. After that, the first hydraulic cylinder 13 and the second
Pressure oil is injected into the hydraulic cylinder 14, the screws 10 and 12 move forward, and the first synthetic resin and the second synthetic resin simultaneously pass through the check valves 16 and 16' and exit the nozzle 15 into the mold cavity (Fig. (not shown). Nozzle 15
Then, the first synthetic resin is separated into an inner layer and the second synthetic resin is separated into an outer layer. After a certain amount of the first and second synthetic resins, which together fill a portion of the mold cavity, have been injected, the injection of the first synthetic resin is stopped and only the second synthetic resin is injected. The first hydraulic cylinder 13 and the second hydraulic cylinder 14 are connected in series, the first and second hydraulic cylinders are driven simultaneously, and the proportions of the first and second synthetic resins injected are kept constant. As a result, a molded article having a uniform two-layer structure as shown in FIG. 3-1 is molded. Next, the hydraulic pressure is connected to drive only the second hydraulic cylinder 14, and when the second synthetic resin is injected in an amount sufficient to fill the chisel mold cavity, the molded product shown in FIG. 3-3 is molded. Fifth
In the figure, 17 is a hydraulic pipe, 19 is a switching valve, and 18 is an auxiliary hydraulic cylinder. If the first, second and auxiliary hydraulic cylinders are of the same diameter, the forward speed of each screw of the two injection cylinders will be the same. FIG. 6 shows an example in which the drive hydraulic piping system of FIG. 5 is modified. In the auxiliary hydraulic cylinder 20, the rods of the two hydraulic cylinders are mechanically connected and have the same stroke. As shown in the figure, oil is discharged from each cylinder according to the amount of oil injected into the auxiliary hydraulic cylinder 20, and the first hydraulic cylinder 13 and the second hydraulic cylinder 14 are driven. Auxiliary hydraulic cylinder 2
0 is an auxiliary hydraulic cylinder 20 because the rods of the two hydraulic cylinders are mechanically connected as described above.
The amounts of oil discharged from each other are kept at a constant ratio. As another molding apparatus for carrying out the present invention, an apparatus in which one injection cylinder is divided into two chambers by a movable mandrel can be similarly used.

Note that all resins that can be generally injection molded can be used in the present invention.

In particular, when used as a container, it is preferable to use a resin with excellent shielding properties. Moreover, 2 injection molded by the method of the present invention
Injection blow molding, in which a layer or three layer structural molded article is transferred to a larger mold cavity and then blow molded, is likewise suitably used. As described above, according to the method of the present invention, a molded product having a multilayer structure in which the inner and outer layers or the intermediate layer have different thicknesses can be easily obtained, and a synthetic resin having desired physical properties is used in combination for the inner and outer layers or the intermediate layer. The industrial effect is extremely large.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of a two-layer structure molded product obtained by the conventional molding method, Fig. 2 is an example of a longitudinal cross-sectional view of a two-layer structure molded product obtained by the method of the present invention, and Figs. Fig. 5 is a partial vertical cross-sectional explanatory view showing an example of an injection molding apparatus embodying the present invention, and Fig. 6 is another example of a drive hydraulic piping system. FIG. 1, 6...Exterior, 2,7...Inner layer, 4
...Mold cavity, 5...Injection port, 9
...First injection cylinder, 10, 12...
...Screw 1, 11...Second injection cylinder, 13...First hydraulic cylinder 14...
・Second hydraulic cylinder, 15...Nozzle, 17
...Hydraulic piping, 19...Switching valve, 18
,20...Auxiliary hydraulic cylinder.

Claims (1)

[Claims] 1. In a method for molding a multilayered container or the like by injecting two types of synthetic resin into a mold cavity having an equal distance from the gate to the tip of the mold cavity, the first synthetic resin and the second Separate the synthetic resin concentrically into an inner layer and an outer layer at the injection port of the mold cavity and simultaneously inject them in approximately equal amounts and in a total amount that fills a part of the mold cavity,
Multi-layer molding characterized in that the first or second synthetic resin is then injected and extruded to the tip of the mold cavity to fill the mold cavity while pressing the previously injected first and second synthetic resins against the mold wall surface. method of manufacturing the product. 2. In a method of molding multilayered containers, etc. by injecting two types of synthetic resin into a mold cavity with equal distances from the gate to the tip of the mold cavity, an appropriate amount of the same type of resin as the outer layer is poured into the mold in advance. inject into the cavity,
Next, the first synthetic resin and the second synthetic resin are concentrically separated into an inner layer and an outer layer at the injection port of the mold cavity, and approximately equal amounts are added to a part of the mold cavity. The first or second synthetic resin is injected at the same time, and the previously injected first and second synthetic resins are pressed against the mold wall surface and extruded to the tip of the mold cavity to fill the mold cavity. A method for producing a multilayer molded product characterized by: