JPS6112314A - Method and apparatus for preparing resin molded product - Google Patents

Abstract

PURPOSE:To prevent the generation of a sink mark, by making it possible to evenly pressing a synthetic resin held under an uncured state ot a cavity surface under uniform pressure by the emission of a fluid. CONSTITUTION:A heated molten synthetic resin 9 such as polyvinyl choliride is allowed to fill a cavity space 3 through the runner 9 and the gate 10 of a mold. When the molten resin P is injected in the cavity spece 3, a solenoid valve 8 is operated to drive a fluid pressure feed apparatus 7 and a fluid is sent into the cavity space 3 so as to be emitted from the surface of a plate body 4 exposed to said cavity space 3. Because the fluid is supplied through the plate body 4, it is heated to a certain degree and further expanded to develop uniform dispersing action while the syntheric resin P present in the cavity space 3 under an uncured state is pressed to the molding surface of a cavity mold 2 from the side of a core mold 1 to impatt the shape with high fidelity corresponding to the molding surface to the synthetic resin P while the molded resin can be solidified under cooling.

Description

Detailed Description of the Invention: Industrial Field of Application The present invention is a method of heating and melting a thermoplastic or thermosetting synthetic resin and injecting it into a cavity space in a mold, or mixing at least two unreacted synthetic resins. The present invention relates to a method and apparatus for manufacturing a resin molded product that can be widely applied to injection molding, in which resin molded products are injected into a cavity space in a mold and cured by reaction within the cavity space.

Conventionally, for example, when resin molding an end cap on the terminal of an automobile body side molding, the molding terminal is inserted into a predetermined position facing the cavity space of an openable and closable mold, and heated molten heat is applied to the cavity space. Inject plastic or thermosetting synthetic resin through the runner,
The resin is integrally fixed to the end of the molding in a shape that corresponds to the cavity space.

Problems to be Solved by the Invention This injection molding machine suppresses the injection pressure of the resin to a certain extent, since there is a risk that the molten resin may overflow from the gap between the cavity space and the end of the molding to the flat side of the molding body, causing cracks. However, on the other hand, there is a high possibility that recesses called "sink marks" may partially occur on the outer surface of the molded product due to molding shrinkage of the resin material used. These sink marks are likely to occur in uneven thickness areas, flat plate parts, etc. of molded products, and are particularly preferable for sink marks that are exposed to the outside for exterior use, such as the sink mark a that occurs on the end cap C of the body side molding M, because they significantly impair decorative properties. No (see Figure 6).

Means for Solving the Problems In the method and apparatus for manufacturing a resin molded product according to the present invention, a liquid synthetic resin is filled into a cavity space, and a fluid such as air is discharged into the cavity from one side. By using this fluid pressure, the uncured synthetic resin in the cavity space is forcibly pressed against the inner wall of the cavity space from one side, thereby preventing the occurrence of so-called sink marks. By installing a fine continuous porous plate in a part of the cavity with its surface exposed inside the cavity, and connecting this plate with a fluid pumping device placed outside the mold through a series of holes. It is constructed so that it can press the uncured synthetic resin with uniform pressure from one side.

This will be explained below with reference to FIGS. 1 to 5.

The mold shown in Figures 1 to 4 is used to mold an end cap at the end of an automobile molding.It consists of a core mold 1 and a cavity mold 2.Normally, the core fil is the mold plate of the injection molding machine (Fig. On the other hand, the cavity mold 2 is fixed to another guide plate and moved up and down, so that it can be opened and closed between it and the core mold 1. In addition, in this injection mold, when both molds are closed, a cavity space 3 having a shape corresponding to a desired end cap is formed in the core mold 1. Cavity type 2
In addition to the cut end surface of the molding body inserted into the mold. A plate-shaped body 4 made of a fine continuous porous material is attached to the cavity space 3 by being fitted into the recess of the core mold 1 and fixed thereto so that one surface thereof is exposed. As this plate-like body 4, for example, sintered alloys such as copper and aluminum, ceramics, etc.
Materials such as gypsum can be used. In addition, the size is wider than the outer circumferential shape of resin molded products such as end caps.
A vertical hole 5 is connected to the plate-like body 4, which may be small in both length, and a fluid pumping device 7 outside the mold is connected to the vertical hole 5 through a communication hole 6 formed in the core mold l. connected.

This fluid pressure feeding device 7 supplies air into the cavity space 3 through the plate-shaped body 4, and its operation is controlled by a solenoid valve 8. The vertical hole 5 may be provided with a check valve to prevent backflow of fluid.

Function When using this mold, first, the end portion of the molding body M is inserted and placed in the core mold 1, and then the cavity mold 2 is lowered and the mold is clamped and fixed. Thereafter, the heated and melted synthetic resin P, such as polyvinyl chloride, is passed through the nozzle (not shown) of the injection molding machine to the runner 9 of the mold. The cavity space 3 is filled through the gas pipe 10. When the molten resin P is injected into the cavity space 3, the solenoid valve 8
operates to drive the fluid pumping device 7, and the fluid is transferred from the surface of the plate-shaped body 4 exposed to the cavity space 3 to the cavity space 3.
Since the fluid is supplied through the plate-shaped body 4, it is heated to some extent and expands further, and becomes uniformly dispersed. By pressing the synthetic resin P against the mold surface of the cavity mold 2 from the core mold l side and shaping the synthetic resin P into a shape faithful to the mold surface, it becomes possible to cool and solidify. The fluid is applied to the core mold 1 so as to surround the entire circumference of the plate-shaped body 4.
By providing teeth 11 that protrude into the cavity space, leakage can be prevented (see Figure 3!).

In addition, in the above-mentioned example, the end cap c was 1200°C.
Synthetic resin heated and melted to a certain degree! Although it has been applied to molds for molding, it can also be applied to molding using reaction-curing resins such as polyurethane resins and polyamide resins that do not use heated and melted synthetic resins, and can also be applied to various resin molded products. Fluid pressure can also be applied to the part where B and rib R are formed from the tip end side of post B and rib R.
Also, depending on the shape of the resin molded product, the plate-like body 4 may be not only flat but also block-like, and the plate-like body 4 can be installed near the Venus gate 10 (see Fig. 4). (See Figure 5).

Effects of the Invention As described above, according to the method and apparatus for manufacturing a resin molded product according to the present invention, the uncured synthetic resin can be evenly pressed against the cavity surface with uniform pressure by discharging the fluid. ,
To easily obtain a highly decorative molded product without causing any sink marks on the surface of the molded product. In addition, since the occurrence of sink marks can be prevented, the wall thickness can be increased during molding of ribs, posts, etc., and secondary effects such as increasing the strength of the molded product can also be achieved.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view showing an apparatus for manufacturing a resin molded product according to the present invention, Fig. 2 is an explanatory diagram showing the molding state of a resin molded product in the same equipment, and Fig. 3 is a toothed structure that prevents fluid leakage. FIG. 4 is a perspective view showing another resin molded product to which the present invention can be applied, FIG. 5 is an explanatory diagram of a mold with a plate-shaped body attached near the gate, and FIG. FIG. 2 is a perspective view of a resin molded product manufactured by a conventional method. l, 2: mold, 3: cavity space, 4: plate-shaped body, 5,
6: Fluid passage, 7: Fluid pressure feeding device.

Claims (3)

[Claims] (1) Fill the cavity space of an openable and closable mold with liquid synthetic resin, forcefully discharge fluid into the cavity space from one side, and use the fluid pressure to fill the uncured synthetic resin into the cavity space. A method for producing a resin molded product, characterized in that the resin molded product is cooled and solidified while being pressed from one side to the other side. (2) A fine continuous porous plate is installed in a part of the cavity formed by the openable and closable mold, with the surface exposed inside the cavity, and the plate has a communication channel in the mold. 1. A manufacturing apparatus for a resin molded product, characterized in that the apparatus is connected to an externally provided fluid pumping device via a. (3) The apparatus for manufacturing a resin molded product according to claim 2, wherein the plate-like body is made of a hard continuous porous material such as sintered metal, ceramic, or gypsum.