JPH06278179A - Injection molding method, injection molding die and product - Google Patents

Abstract

PURPOSE:To secure high accuracy and strength of a resin molded product manufactured by injection molding. CONSTITUTION:Resin pressure is applied from one side of a cavity to the other side in the direction crossing the injection direction after filling resin into a cavity, and a core layer 14 is flowed in the applying direction of resin pressure while the core layer 14 is unsolidified to manufacture a three-layer structure in which the orientation of a skin layer 13 crosses the orientation of the core layer 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin injection molding method, an injection molding die and an injection molded article.

[0002]

2. Description of the Related Art Molecules and fillers in injection-molded products tend to be oriented in the resin flow direction during filling. This tendency is remarkable especially in thin-walled molded products. Therefore, in order to change the orientation in an arbitrary direction, the resin flow direction at the time of filling is controlled by changing the position and size of the gate or designing the shape of the molded product. However, it has been impossible to give a plurality of orientations in arbitrary directions only by these techniques.

[0003]

The strength in the direction orthogonal to the alignment direction is extremely low as compared with the alignment direction. Therefore, it is pointed out that the thin plate-shaped molded product lacks strength in the direction orthogonal to the orientation direction. Also, the shrinkage ratio in the direction orthogonal to the alignment direction is larger than the shrinkage ratio in the alignment direction,
That is one of the factors that cause deformation such as warpage.

[0004]

According to the present invention, a resin filling gate is provided on one side edge of a cavity, and an openable and closable resin reservoir communicated with the cavity is provided on one side intersecting the injection direction of the gate. On the other side, injection molding dies each provided with a variable volume resin reservoir that communicates with the cavity, and when the thermoplastic resin is injection-molded using the dies, the cavity is filled with resin. Immediately after that, a resin pressure is applied from one side of the cavity to the other side in a direction intersecting the injection direction, and the core layer is allowed to flow in the acting direction of the indicated pressure while the core layer is not solidified, and its injection molding method. It is an injection-molded article having a layer in which the skin layer and the orientation are crossed depending on the method.

[0005]

According to the method and apparatus of the present invention, a layer having an orientation intersecting with the skin layer can be provided, and a molded article having a different orientation has reduced anisotropy and warpage and has a higher strength. High deformation amount.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example in which an injection molding method, an injection molding die, and an injection molded article according to the present invention are carried out on a lid of a case having a thin plate shape will be described with reference to the drawings. First, a mold for injection molding will be described. A cavity 2 is formed in the mold 1, and a slit-shaped gate 3 which is an injection port is opened at one side of the cavity 2. The gate 3 is generally called a film gate, and is communicated with the sprue 3b through the runner 3a, and the molten resin is uniformly and rapidly injected into the cavity 2.

In the mold 1, resin reservoirs 4 and 5 communicating with the cavity 2 are formed respectively on the adjacent sides orthogonal to the side on which the gate 3 is provided. One of these resin pools 4 is composed of a blank 6 recessed in the inner wall of the cavity 2 and a block body 7 that is pushed into the blank 6, and the volume depending on the pushing amount of the block body 7. Can be controlled. The other resin pool 5
Is a blank 8 recessed next to the cavity 2
And a block body 10 that is pushed into the blank 8 by a spring 9, and a push rod 11 that pushes the block body 10 out of the blank 8 against the pressing force of the spring 9. , The push-out operation and the push-in operation are the piston rod 1
It is interlocked with the pushing operation of 2, and both resin pools 4, 5
The volume change amounts of are the same.

First, the molten resin M is injected into the cavity 2 by using such a die (FIG. 2), and the block body 7 and the block body 10 are pushed out in both resin reservoirs 4 and 5 immediately (see FIG. 2). 3 and 4). The molecules of the injected resin are oriented in the injection direction, and the cavity 2
The skin layer in contact with the inner surface of the solidified instantly. The molecules of the core layer sandwiched between the skin layers are also oriented in the injection direction. However, while the core layer is in an unsolidified state, the block body 7 is pushed into the blank 6 by pushing out the piston rod 12. The resin in the blank 6 is pushed back into the cavity 2, and the block body 10 is pushed out of the blank 8 against the pressing force of the spring 9 to perform the blank 8 operation.
By increasing the volume of the resin, the resin flows in the core layer in a direction orthogonal to the injection direction, and a layer oriented in the flowing direction is generated. Therefore, as shown in FIG. 5, a part of the molecules of the skin layer 13 and the core layer 14 (including the filler) are aligned with each other.
It has a three-layer structure that intersects at an angle of 0 degree.

Next, a remarkable effect of the present invention will be demonstrated with a molded product of a liquid crystal polymer in which 30% of glass fiber is mixed. The dimensions of the product are: width 70 mm, length 100 mm, thickness 1
mm, the height of the rising wall was 4 mm, and the case where the resin of the core layer was made to flow in the direction orthogonal to the injection direction immediately after injection was compared with the case where it was not made to flow. If not flowed, the bending strength is
Injection direction is 3200kgf / cm ² , crossing direction is 1500kgf /
It is 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 2600kgf / cm ^2. Further, in the 50% breaking energy test by falling weight impact, when the punch diameter was 13.5 mm, high strength of 0.83 joule or more was confirmed as compared with 0.46 joule of the conventional example. Furthermore, the magnitude of warpage due to deformation was significantly reduced to 0.7 mm compared to the conventional 2.2 mm.

The above numerical values are test results for a molded product of a liquid crystal polymer in which 30% of glass fiber is mixed, and the effect of the crystalline thermoplastic resin is remarkable, and it was confirmed that it is suitable. The thermoplastic resin used for is not limited to a liquid crystal polymer, and similar effects have been confirmed with these thermoplastic resins containing a filler material. Although this embodiment describes a thin plate-shaped molded product, it can also be applied to a block-shaped, cylindrical, rod-shaped, or other complicated shape. Furthermore, in order to promote the desired flow, the piston rod that controls the push-out operation and the push-in operation of the block body is provided with a vibrating function of giving a vibration of 10 Hz or less, or a resin is applied in a direction intersecting the injection direction. The means for causing the flow is not limited to the embodiment, for example, the operation is performed by retracting the piston rod.

The embodiment has a three-layer structure in which the orientations of the layers intersecting with the skin layer intersect with each other at an angle of 90 degrees, but the orientation with the skin layer intersects at an angle of 90 degrees. Not only may the orientations intersect at an angle of, for example, 45 degrees. Further, the thick-walled molded article may have a five-layer structure by allowing the resin to flow in the direction intersecting with the injection direction and then further allowing the resin to flow in the direction intersecting with the direction.

[0012]

Industrial Applicability According to the present invention, it is possible to provide a synthetic resin molded article having high accuracy and uniform strength in different directions.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an injection molding die according to the present invention.

FIG. 2 is an explanatory view showing steps of the injection molding method according to the present invention.

FIG. 3 is an explanatory view showing steps of the injection molding method according to the present invention.

FIG. 4 is an explanatory view showing steps of the 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, 4.5
..Resin puddle, 6 ... Blank, 7 ... Block, 8
・ Blank, 9 ・ ・ Spring, 10 ・ ・ Block body,
11 ... Extrusion rod, 12 ... Piston rod, 1
3 ... Skin layer, 14 ... Core layer.

Claims (3)

[Claims] 1. When injection molding a thermoplastic resin,
After filling the cavity with resin, the core layer was not solidified,
An injection molding method characterized in that the core layer is caused to flow in a direction intersecting the injection direction. 2. A gate for resin filling is provided on one side edge of the cavity, and an openable and closable resin reservoir communicating with the cavity is provided on one side intersecting the injection direction of the gate, and a cavity is provided on the other side. A mold for injection molding that is provided with a variable volume resin reservoir that communicates with each. 3. In injection molding a thermoplastic resin,
After the resin is filled into the cavity, a resin pressure is applied from one side of the cavity to the other side in a direction that intersects the injection direction, causing the unsolidified core layer to flow in that direction and having a layer that intersects with the skin layer. Injection molded product.