JP3571375B2 - Injection molding method, injection mold and injection molded product - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a thermoplastic resin injection molding method, an injection mold, and an injection molded product.
[0002]
[Prior art]
Molecules and fillers in injection molded articles have a strong tendency to orient in the direction of resin flow during filling, and this is particularly noticeable in thin molded articles.
The flow direction of the resin can be controlled to some extent by changing the position and size of the gate and devising the shape of the molded product.
However, it was impossible to control the orientation freely or to provide a plurality of orientations in any direction by using only these techniques.
[0003]
[Problems to be solved by the invention]
Since the strength in the direction intersecting with the orientation direction is extremely low as compared with the orientation direction, it is pointed out that a thin plate-shaped molded product has insufficient strength in the direction orthogonal to the orientation direction.
The shrinkage in the direction perpendicular to the orientation direction is larger than the shrinkage in the orientation direction, which is one factor that causes deformation such as warpage.
[0004]
[Means for Solving the Problems]
According to the present invention, a resin filling gate is provided on one side of a peripheral edge of a rectangular thin plate-shaped cavity, and a variable volume resin reservoir communicating with the cavity is provided on one adjacent edge orthogonal to the side on which the gate is provided. Injecting a mold for injection molding and a thermoplastic resin, characterized in that using the mold for injection molding, first stop the injection immediately before the resin is completely filled in the cavity, and then Injection molding method in which the volume of the resin pool is reduced, resin pressure is applied in a direction intersecting the injection direction, and the unsolidified core layer is caused to flow in that direction to cross the orientation with the skin layer. And a plate-shaped injection-molded product formed so that the respective orientations of the skin layer and the core layer intersect with each other. The resin pool is formed by enlarging a part of the cavity in the thickness direction, thereby reducing the cavity. And it can be formed in one piece.
[0005]
[Action]
ADVANTAGE OF THE INVENTION According to the method and apparatus of this invention, the core layer can be made to have the orientation which cross | intersected the skin layer, and the anisotropic and the warpage were eased by the molded article with the different orientation, and it was formed by the method. The product has high strength and little deformation.
[0006]
【Example】
An example in which the injection molding method, the injection molding die, and the injection molded product according to the present invention are implemented on a lid of a rectangular thin plate-shaped case will be described with reference to the drawings.
First, the mold for injection molding will be described. In the mold 1 shown in FIG. 1, a cavity 2 is formed, and a slit-shaped gate 3 as an injection port is opened on one side of the cavity 2.
The gate 3 is generally called a film gate, and is communicated with a sprue 3b via a runner 3a. The molten resin is uniformly and rapidly injected into the cavity 2.
[0007]
In the mold 1, a resin reservoir 4 communicating with the cavity 2 and having a wider gap in the thickness direction than the cavity 2 is formed on an adjacent edge orthogonal to the side where the gate 3 is provided.
The resin reservoir 4 is composed of a blank 5 recessed in the inner wall of the upper surface of the cavity 2 and a block body 6 pushed into the blank 5. By setting the volume of 5 to 0, only the shape of the cavity 2 can be obtained.
[0008]
First, the molten resin M is injected from the gate 3 into the cavity 2 by using such a mold 1, and the injection is stopped immediately before the filling is completed.
At the time of this injection, since the thickness of the resin reservoir 4 is larger than that of the cavity 2 by the thickness of the blank 5, the resin filling into the resin reservoir 4 precedes due to the resin filling thickness dependency, and as a result, the resin reservoir 4 is separated from the resin reservoir 4. An unfilled portion 7 occurs on the opposite side (FIG. 2).
In the injected resin M, the molecules are oriented in the injection direction, the skin layer in contact with the inner surface of the cavity 2 is instantaneously solidified, and the core layer sandwiched between the skin layers is not solidified, but the molecules are not solidified. Like the layers, they are oriented in the emission direction.
Then, while the core layer is in an unsolidified state, when the block body 6 is pushed into the blank 5 and the resin in the blank 5 is pushed into the cavity 2, the unfilled material generated on the opposite side to the resin pool 4 is formed. The resin flows into the portion 7 (FIG. 3), so that the resin flows in the core layer in a direction intersecting the injection direction, and the unfilled portion is filled with the resin M, and a layer oriented in the flow direction is formed. (FIG. 4).
Therefore, as shown in FIG. 5, a three-layer structure in which some orientations of molecules (including a filler) of the skin layer 8 and the core layer 9 cross each other is obtained.
[0009]
Next, a remarkable effect of the present invention is demonstrated by using a molded article using a liquid crystal polymer mixed with 30% of glass fiber as an example.
The dimensions of the product were 70 mm in width, 100 mm in length, 1 mm in thickness, and the height of the rising wall was 4 mm. .
If not flow, flexural strength, injection direction 3200kgf / cm ^2, the cross direction is 1500 kgf / cm ^2. If allowed to flow thereto, the injection direction is 3000 kgf / cm ² and a slight decrease was observed in the cross direction was confirmed to be remarkably improved and 2400kgf / cm ^2.
Further, in a 50% breaking energy test by falling weight impact, a high strength of 0.83 joules or more was confirmed in the case of the punch diameter of 13.5 mm compared to 0.46 joules in the conventional example.
Further, the magnitude of the warpage due to the deformation was greatly reduced to 1.0 mm from 2.2 mm in the related art.
[0010]
The above values are test results of a molded product of a liquid crystal polymer mixed with 30% of glass fibers, and the effect of the crystalline thermoplastic resin was remarkable, and it was confirmed that it was preferable. Thermoplastic resins are not limited to liquid crystal polymers, and similar effects have been confirmed for these thermoplastic resins including a filler material.
The resin reservoir can be formed not only integrally with the cavity but also separately.
Further, in order to promote the flow of the resin, a vibrating function for applying a vibration of 10 Hz or less was added to the extruding operation portion of the block body, or the block body was operated in the flow direction, that is, in the plate thickness direction in the above embodiment. The present invention is not limited to the embodiment, for example, by changing the direction to the plate surface direction.
[0011]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the synthetic resin thin molded article which ensured the intensity | strength with respect to the direction which intersected the injection direction and prevented deformation by the injection molding method using an improved metal mold | die is provided.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an injection mold according to the present invention.
FIG. 2 is an explanatory view showing steps of an injection molding method according to the present invention.
FIG. 3 is an explanatory view showing steps of an injection molding method according to the present invention.
FIG. 4 is an explanatory view showing steps of an injection molding method according to the present invention.
FIG. 5 is an explanatory view showing the structure of an injection molded product according to the present invention.
[Explanation of symbols]
1. Mold, 2. Cavity, 3. Gate, 4. Resin pool, 5. Blank, 6. Block, 7. Unfilled part, 8. Skin layer, 9. Core layer , M ... resin.

Claims (4)

A resin filling gate is provided on one side of the peripheral edge of the rectangular thin plate-shaped cavity, and a variable volume resin reservoir communicating with the cavity is provided on one adjacent edge orthogonal to the side where the gate is provided. Mold for injection molding. The injection molding die according to claim 1, wherein the resin reservoir is formed by enlarging a part of the cavity in a thickness direction. In the injection molding of the thermoplastic resin, the injection is stopped immediately before the resin is completely filled in the cavity, and then the volume of the resin reservoir is reduced by using the injection molding die according to claim 1. An injection molding method in which a resin pressure is applied in a direction intersecting the injection direction at least and the unsolidified core layer is caused to flow in that direction so as to intersect the orientation with the skin layer. A plate-shaped injection-molded article formed by the injection molding method according to claim 2 so that each orientation of the skin layer and the core layer intersect.

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