JPS604769B2 - Molding method for composite moldings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a composite molded article by injecting two or more synthetic resins into a mold cavity, and more specifically to a sandwich structure molded article whose surface layer and inner core are made of different synthetic resins. In the molding process, the method mainly involves molding a molded article in which the first synthetic resin constituting the surface layer has a uniform surface layer.

- In injection molding etc. in which synthetic resin is injected into the mold cavity, the first synthetic resin is injected into the mold cavity, and then the second synthetic resin is injected, so that the surface layer is made of the first synthetic resin,
A method of molding a sandwich structure whose inner core is made of a second synthetic resin is described in US Pat. No. 2,996,764 and the like.

However, with the conventional method of molding a sandwich structure mold, it was possible to obtain a molded product whose surface layer uniformly covers the inner core only in the case of molded products of very limited shapes. For example, it was possible to mold a disk-shaped object or a cone-shaped object with a gate for injecting resin in the center, but with other shapes, the surface layer may become partially thick, or the inner core may break through the surface layer and reach the surface. It was exposed. There is a strong demand for a method for molding sandwich structures having complex shapes and uniform surface layers.

The present invention answers these needs. We placed two types of synthetic resins at the injection port into the mold cavity, with the first synthetic resin forming the surface layer and the second synthetic resin forming the inner core separated so as not to surround each other. It was discovered that when injected, each resin flows into the mold cavity in the form of a stream, and the proportion of mutual mixing in the injection port and mold cavity is extremely low.

As a result of various studies utilizing this phenomenon, the present invention was arrived at.
In the present invention, two types of synthetic resins are injected into a mold cavity whose distance from the injection port of the mold cavity to the end of the mold cavity is uneven, and the surface layer of the first synthetic resin and the inner core of the second synthetic resin are injected into the mold cavity. In a method for molding a composite molded article consisting of, first, a first synthetic resin is injected in an amount necessary to form the surface layer on the side where the distance from the injection port of the mold cavity to the end of the mold cavity is short; Next, at the injection port of the mold cavity, the second synthetic resin is applied to the side with the shorter distance to the end of the mold cavity, and the first synthetic resin is added in an amount necessary to form a surface layer on the longer side, so as not to surround each other. If there is an intermediate side, switch from the first synthetic resin to the second synthetic resin in order of shortest distance to the end of the mold cavity, and then inject the second synthetic resin. A method of molding uniform sandwich structures characterized by injection to fill the entire mold cavity.

The present invention will be explained with reference to the drawings.

Figure 1 shows a sandwich structure molded using the conventional molding method.
FIG. 2 shows a sandwich structure formed by the method of the present invention.
FIG. 3 shows each step of filling the mold cavity with synthetic resin in the method of the present invention. If the gate 3 cannot be placed in the center of the molded product, the conventional sandwich injection molding method, that is, the molding method in which the first synthetic resin is injected into the mold cavity, and then the second synthetic resin is injected to flow the mold cavity, As shown in FIG. 1, the first synthetic resin 1 cannot form a uniform surface layer, and the second synthetic resin 2 is unevenly distributed on one side.

In contrast, the method of the present invention, in which two types of synthetic resins are injected into the mold cavity, is arranged so that the first synthetic resin forming the surface layer and the second synthetic resin forming the inner core are not surrounded by each other. By injecting each resin into the mold cavity at the same time in a separated state, and injecting each resin individually, it is possible to create a uniform surface layer 4 and a uniform inner core 5 as shown in Fig. 2. A sandwich structure is obtained. The method of the present invention will be explained with reference to FIG.

The first synthetic resin 1 is injected into the mold cavity 6 through the gate 3 (3-1), and then the first synthetic resin 1 and the second synthetic resin 2 are poured into the mold cavity at a short distance from the gate opening to the end of the mold cavity. The second synthetic resin 2 is injected into the mold cavity 6 at the same time, and the first synthetic resin 1 in an amount necessary to form a surface layer on the long side is placed separately so as not to surround each other (3-2
), then inject only the second synthetic resin 2 (3-3),
If necessary, a minute amount of the first synthetic resin 1 is injected,
A sandwich structure consisting of a uniform surface layer 4 made of a first synthetic resin and a uniform inner core 5 made of a second synthetic resin is molded (3-4). In this case, it is necessary to adjust the amount of resin injected individually and the amount of resin injected simultaneously depending on the shape of the molded product. It is necessary that the position and volume of the inlet be adjusted to each other. In the case of the shape shown in FIG. 3, each resin to be injected at the same time may be divided into two halves by a gate and then injected at the same time. As the shape of the molded product becomes more complex, the correlation between the resins injected at the same time becomes more complex.

FIG. 4 shows an example of the positional relationship of resins to be injected at the same time. FIG. 4 shows the state of injection of two types of synthetic resin into the mold cavity 6, and shows each step of injection from the gate 3. The nozzle 7 of the molding machine that injects synthetic resin has a structure that allows two types of synthetic resin to be freely injected from eight locations A, B, C, D, E, F, G, and 1, as shown in Figure 4. The resin injected from the nozzle is separated at a predetermined position by the gate 3 and simultaneously injected into the mold cavity. FIG. 4 shows the step of injecting the first synthetic resin and the second synthetic resin into the mold cavity 6 shown in FIG. 4 to form a sandwich-structure molded product having a uniform surface layer and an inner core. The thickness of the mold cavity 6 in FIG. 4 is uniform on the 5 side.
First, the first resin is injected from each location of A, B, C, D, E, F, G, and day, and is injected into the mold cavity 6 through the gate 3 (4-1), and then to the end of the mold cavity. The second resin is injected from the side E where the distance is shorter, and the first resin is simultaneously injected from the other seven locations (4-2). Next, the second resin is injected from five locations A, B, C, and D on the intermediate side and E on the side where the distance to the end of the mold cavity is short, and at the same time, from F on the side where the distance to the end of the mold cavity is long. The first resin is injected from three locations: , G, and day (4-3). In this way, if there is an intermediate side where the distance from the injection port to the end of the mold cavity is neither long nor short, the first synthetic resin is applied to the second synthetic resin in order of shortest distance to the end of the mold cavity. Switch and inject into the mold cavity. Furthermore, A, B, C, D
, E, F, G, and the second resin is injected from 8 locations (
4-4), drip the mold cavity 4-5). On the other hand, if a conventional sandwich structure molding method is used, that is, a molding method in which a first resin is injected and then a second resin is injected, a non-uniform structure as shown in (4-6) is obtained. FIGS. 5, 6 and 7 show a molding apparatus for carrying out the method of the present invention.
As shown in the figure. Figures 5 and 6 show an apparatus for injecting two types of synthetic resins using two injection cylinders. In Figure 5,
From the screw 101 of the first injection cylinder 8, the first
The synthetic resin is heat-plasticized and accumulated in the front part 12 of the first injection cylinder 8, and the second synthetic resin is heat-plasticized and accumulated in the front part 12 of the first injection cylinder 9.
in the front part 13 of the injection cylinder 9. The injection nozzle 14 has a conduit 1 having a conduit 16 for guiding the second synthetic resin.
5, and the conduit 15 has a notch 17 that connects the conduit 16 and the nozzle port 18. When a high pressure forward force is applied to the screw 10, the first synthetic resin passes through a passage within the injection nozzle 14 and is injected from the nozzle opening 18. When a high-pressure forward force is applied to the screw 11, the second synthetic resin is injected from the nozzle port 18 through the conduit 16 and the notch 17. When the first synthetic resin and the second synthetic resin are simultaneously injected, the two synthetic resins are separated at a desired arrangement by the position of the notch 17 and are simultaneously injected from the nozzle opening 18. It is necessary to adjust the position of the notch 17 depending on the shape of the molded product to be molded. FIG. 6 shows the hydraulic cylinders, drive hydraulic piping, etc. that drive the two injection cylinders shown in FIG. 5.

FIG. 6 shows an injection cylinder 8 for injecting the first synthetic resin.
and a screw 10, an injection cylinder 9 and a screw 11 for injecting the second synthetic resin, a member 19 for rotating each screw (not shown in detail), and hydraulic cylinders 20 and 21 for advancing each screw at high pressure. Hydraulic piping 23 to be driven, electromagnetic switching valve 24 relief valve 25, backflow prevention valve 26, flow control valve 2
7. Limit switch 2 that operates each electromagnetic switching valve 24
2 shows a device consisting of two parts. By operating each electromagnetic switching valve 24, the first synthetic resin and the second synthetic resin can be injected individually or simultaneously. In particular, the hydraulic systems that drive the hydraulic cylinders 20 and 21 can be injected in series. By connecting them, the ratio of the injection amounts of the first synthetic resin and the second synthetic resin that are injected simultaneously can be kept constant. If the two hydraulic cylinders 20, 21 have the same inner diameter, the forward speed of the two hydraulic cylinders 20, 21 can be controlled by connecting another hydraulic cylinder with the same diameter in series between the two hydraulic cylinders. can be made equal.

Depending on the shape of the molded product, the limit switch 22 is adjusted to determine the order in which each resin is injected individually or simultaneously. FIG. 7 shows another example of implementing the method of the invention.

FIG. 7 shows an apparatus for injecting two types of synthetic resins using one injection cylinder 28. The injection cylinder 28 has a movable mandrel 31 which can move back and forth in the injection cylinder, - a front chamber 33 at the front of the movable mandrel 31 stores a first synthetic resin and a rear chamber 34 stores a second synthetic resin; accumulate. The first synthetic resin heated and plasticized in the extruder 29 passes through the check valve 32 and then passes through the extension nozzle 35 and the movable mandrel 3.
1 and is accumulated in the front chamber 33. The second synthetic resin heated and plasticized by the screw 30 is accumulated in the rear chamber 34 between the movable mandrel 31 and the screw 30, and moves back to the movable mandrel 31 and the screw 3 depending on the accumulated amount of each resin. The movable mandrel 31 has a passage in the center through which the second synthetic resin passes, an extension tube 36 that enters an extension nozzle 35 at the tip, and a conduit 37 through which the first synthetic resin passes. When the high pressure forward force of three screws is applied,
When the first synthetic resin accumulated in the front part 33 of the injection cylinder 28 is injected and the extension tube 36 of the movable mandrel enters the extension nozzle 35, the first synthetic resin is continuously transferred through the notch 38 provided in the extension tube 36. Synthetic resin is injected,
At the same time, a second synthetic resin is injected through the central passage of the movable mandrel. When the notch 38 of the extension tube 36 finishes entering the extension nozzle 35, injection of the first synthetic resin stops and only the second synthetic resin is injected. When all of the second synthetic resin has been injected, the last remaining first synthetic resin is injected through the conduit 37. In this device, it is necessary to adjust the size of each passage in advance so that the injections are carried out in this order. The position and amount of the first synthetic resin to be injected at the same time is determined by the position and size of the notch 38 provided in the extension tube 36. In the present invention, the first synthetic resin and the second synthetic resin are injected at the same time while being separated so as not to surround each other. As shown in FIG. 8, this means that the first synthetic resin forming the surface layer does not surround the second synthetic resin forming the inner core, but is injected at the same time so that they are separated from each other.

FIG. 8 shows various examples of injection ports that are arranged separately so as not to surround the first synthetic resin 41 and the second synthetic resin 42 and simultaneously inject them. In the present invention, two types of synthetic resins include not only synthetic resins with different structures, but also synthetic resins with different additives, such as different colorants.

All synthetic resins commonly used in injection molding can be used in the present invention. In the molding method of the present invention, first, a first synthetic resin is injected into the mold cavity, then two types of resin are injected, and finally, a small amount of the first synthetic resin is injected again, and the nozzle part of the molding device is injected into the mold cavity. It is preferable to replace the resin with a synthetic resin when performing continuous molding.

Example Using a mold in which the mold cavity is disc-shaped with a diameter of 260 mm and a thickness of 15 mm, and the synthetic resin injection port into the mold cavity is offset by 4 ribs from the center, the molding apparatus shown in FIG. 7 is used. Sandwich molding was performed using

Using polystyrene as the first synthetic resin and rubber-reinforced polystyrene as the second synthetic resin, a sandwich structure is formed in which the surface layer is made of the first synthetic resin and the inner core is made of the second synthetic resin. The ratio between the surface layer and the inner core was measured when the second synthetic resin was injected at the maximum amount without appearing on the surface layer. Molded by the conventional sandwich molding method, that is, the molding method in which the first synthetic resin is injected and then the second synthetic resin, and the molding method of the present invention, that is, the molding method explained in FIG. 3, The surface layer/inner core ratio was measured.

As a result, the surface layer/inner core ratio of the conventional sandwich molding method was 1/0.8, and the surface layer was nonuniform.

On the other hand, the surface layer/inner core ratio of the molding method of the present invention was 1/2.9, resulting in a sandwich structure consisting of a uniform surface layer.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a sandwich structure molded by the conventional molding method, FIG. 2 is a cross-sectional view of a sandwich structure molded by the method of the present invention, and FIGS. Explanatory cross-sectional views showing each step of filling the mold cavity with resin; FIGS. 5, 6, and 7 show a molding apparatus for carrying out the method of the present invention; and FIG. 8 shows an injection port into the mold cavity. FIG. 2 is an explanatory diagram showing a state in which two types of synthetic resins are injected at the same time. In the figure: 1: First synthetic resin, 2: Second synthetic resin.
3: Gate "Mother: Uniform surface layer, 5: Uniform inner core, 6:
Mold cavity, 7: nozzle, 8: first injection cylinder, 9: second injection cylinder, 0, 11: screw, 12: front of first injection cylinder, 13: front of second injection cylinder part, 14: injection nozzle, 15: conduit,
16: Guide path, 11: Notch, 18: Nozzle port, 19: Material for rotating the screw, 20, 21: Hydraulic cylinder L 22: Limit switch, 23: Hydraulic piping, 24
: Solenoid switching valve, 25: Relief valve, 26: Non-return valve,
27: Flow control valve, 28: Injection cylinder,
29: Extruder, 30: Screw, 31: Movable mandrel, 32: Non-return valve, 33: Front chamber, 34: Back chamber, 35
: Extension nozzle, 36: Extension pipe, 37: Conduit, 38: Notch, 39: First synthetic resin layer, 40: Second synthetic resin layer, 41: First synthetic resin, 42: Second Synthetic resin. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1. Two types of synthetic resins are injected into a mold cavity whose distance from the injection port of the mold cavity to the end of the mold cavity is uneven, so that the mold cavity consists of a surface layer of the first synthetic resin and an inner core of the second synthetic resin. In the method of molding a composite molded article, first, the first synthetic resin is injected in an amount necessary to form the surface layer on the side where the distance from the injection port of the mold cavity to the end of the mold cavity is short, and then the first synthetic resin is injected into the mold cavity. At the injection port, the second synthetic resin is placed on the side with the shortest distance to the end of the mold cavity, and the first synthetic resin is placed in an amount necessary to form the surface layer on the long side so as not to surround each other. If there is an intermediate side, inject from the first synthetic resin to the second synthetic resin in order of shortest distance to the end of the mold cavity, and then inject the second synthetic resin. A method for forming uniform sanderch structure moldings characterized by filling the entire mold cavity.