JP2001225354A - Injection molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the appearance of a molded article, in molding the molded article wherein projected parts are provided on the rear surface of a plate part having a smooth surface using a synthetic resin containing a brilliant material, by avoiding such a state that a large restriction is applied to the shape of the molded article or a mold to prevent the generation of a flow mark or weld line. SOLUTION: A first semi-molded article integrally having a thin-walled plate part 11 thinner than a plate part and the projected parts 9, 10 formed on the thin-walled plate part 11 is injection molded in a first step and a plate-shaped second semi-molded article 7 constituting the plate part 8 together with the thin-walled plate part 11 is injection molded in a second step so as to be integrally bonded to the surface of the thin-walled plate part 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method for molding a molded product in which a projection is provided on the back surface of a plate portion having a smooth surface, using a synthetic resin containing a glittering material.

[0002]

2. Description of the Related Art When such a molded product is molded at a time by injecting a molten resin into a molding die, the molten resin flowing ahead of the protruding portion and the molten resin flowing behind the other portion are merged. Flow marks and weld lines may be formed on the surface of the molded product and impair the appearance of the molded product.In particular, in the case of synthetic resins containing glittering materials such as aluminum foil, glass beads and pearl mica, When the flow of the resin is relatively slow, the flow mark and the weld line tend to be formed on the surface of the molded product.

A technique for preventing the occurrence of such flow marks and weld lines is disclosed in, for example, Japanese Patent Laid-Open No. 4-3751.
No. 6, JP-A-8-276453, and the like, and in these prior arts, a gas pressure is applied to a portion corresponding to a projection.

[0004]

However, in the techniques disclosed in the above publications, it is difficult to apply a required amount of gas pressure to a required position, and there is no resin in a compressed state in a molding die. Even if the gas pressure is considerably increased, it is difficult to press-fit the gas, which imposes great restrictions on the shape of the molded product and the design of the mold.

The present invention has been made in view of such circumstances, and it is possible to prevent a flow mark or a weld line from being generated by avoiding a large restriction on a shape and a mold of a molded product. An object of the present invention is to provide an injection molding method capable of improving the appearance.

[0006]

In order to achieve the above object, according to the present invention, there is provided a molded product comprising a plate portion having a smooth surface and a projection provided on the back surface thereof, containing a glittering material. Injection molding method for molding with a synthetic resin, comprising: a first semi-molded product having a thin plate portion thinner than the plate portion and the protrusion integrally projecting from the back surface of the thin plate portion. And a second step of injection-molding such that the plate-shaped second semi-molded product forming the plate portion in cooperation with the thin plate portion is integrally joined to the surface side of the thin plate portion. And characterized in that:

[0007] According to the method of the first aspect,
Even if a flow mark or a weld line is formed on the surface of the thin plate portion in the first semi-molded product, the surface of the thin plate portion is covered with the second semi-molded product. No flow mark or weld line remains on the surface of the molded product, and the appearance of the molded product can be improved. Moreover, since it does not apply gas pressure,
There are no significant restrictions on the shape of the molded article and the design of the mold.

[0008] In order to achieve the above object, a second aspect is provided.
The described invention is an injection molding method for molding a molded product having a plurality of protrusions provided on the back surface of a plate portion having a smooth surface, using a synthetic resin containing a glittering material, wherein each of the protrusions is A first step of injection-molding a first semi-molded product connected by a connecting portion, and a plate-shaped second semi-molded product constituting the plate portion being integrally joined to the first semi-molded product. A second step of injection-molding, and a third step of cutting off the connecting portion.
And a step of:

According to such a method of claim 2,
In the first step, a first semi-molded product in which a plurality of protrusions are integrally connected at the connection portion can be injection-molded so as to secure the passage of the molten resin at the connection portion, and at the second step, Since the plate-shaped second half-molded product is integrally joined to the first half-molded product while being injection-molded, there is no flow mark or weld line on the surface of the second half-molded product, and connection is performed in the third step. The appearance of the molded article formed by cutting off the part can be improved, and this is particularly effective when the thickness of the plate part in the molded article is small. Moreover, since no gas pressure is applied, no significant restrictions are imposed on the shape of the molded product and the design of the molding die.

According to a third aspect of the present invention, in addition to the configuration of the first or second aspect of the present invention, there is provided a molding die having a fixed die and a movable die capable of moving back and forth with respect to the fixed die. Injecting the synthetic resin into a first cavity formed between the fixed mold and the movable mold corresponding to the first semi-molded product, performing the first step, and placing the first semi-molded product in the molding die The second step is performed by injecting the synthetic resin into a second cavity formed in the mold corresponding to the second semi-molded product by moving the movable mold away from the fixed mold by a predetermined distance while storing the movable mold. According to such a method, the first and second cavities are respectively formed by adjusting the advance and retreat positions of the movable mold with respect to the fixed mold, and the first and second semi-molded articles are formed in the same mold. Can be injection molded In, it is possible to reduce the installation space of the mold by eliminating the need for multiple molds, it is possible to reduce equipment costs.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on embodiments of the present invention shown in the accompanying drawings.

1 to 5 show a first embodiment of the present invention. FIG. 1 is a perspective view of a molded product, and FIG. 2 is 2-2 of FIG.
FIG. 3 is a longitudinal sectional view of the molding die when the first step is executed, and FIG. 4 is a molding die corresponding to FIG. 3 before the second step is executed. Longitudinal sectional view of the
FIG. 5 is a longitudinal sectional view of the molding die corresponding to FIG. 3 at the time of executing the second step.

First, in FIGS. 1 and 2, this molded product 5 is made of AAS or AES containing, for example, 0.1 to 7% of a glittering material such as aluminum foil, glass beads and pearl mica.
A first semi-molded product 6 injection-molded with a synthetic resin such as
The first molded product 6 and the second semi-molded product 7 that is injection-molded with the same material are integrally joined, and are formed on the back surface of the plate portion 8 having a smooth surface, for example, as a boss. A cylindrical projection 9 that functions, and a flat projection 10 that functions as, for example, a rib are provided.

The first semi-molded product 6 has a thin plate portion 11 thinner than the plate portion 8 of the molded product 5 and the projections 9 and 10 projecting from the back surface of the thin plate portion 11 integrally. The second semi-molded product 7 is injection-molded into a plate shape constituting the plate portion 8 in cooperation with the thin plate portion 11 of the first semi-molded product 6, and It is integrally joined to the surface side of the plate portion 11.

In order to form such a molded product 5, a molding die 12 as shown in FIG. 3 is used. The molding die 12 is capable of moving forward and backward with respect to the stationary die 13. And a movable mold 14 having the above configuration.

The fixed die 13 is integrally provided with a projection 15 protruding toward the movable die 14, and the movable die 14 is provided with a fitting recess 16 for fitting the projection 15 so as to be relatively slidable. The fixed mold 13 has the protrusions 15 of the fixed mold 13.
A gate 17 for injecting the molten synthetic resin between the fitting recesses 16 of the movable mold 14; a pin 18 for opening and closing the gate 17; and a cylinder for driving the pin 18 in the axial direction. 19 are provided.

In molding the molded article 5 by using the molding die 12, the first and second steps are sequentially performed. First, in the first step, FIG.
As shown in the figure, a first cavity 20 corresponding to the first semi-molded product 6 is formed between the fixed mold 13 and the movable mold 14. That is, the advance / retreat position of the movable mold 14 is adjusted so that the interval between the fixed mold 13 and the movable mold 14 corresponds to the thickness t1 of the thin plate portion 11 in the first semi-molded product 6, and the gate 17 is opened to melt. A resin is injected into the first cavity 20.

By this first step, the thin plate portion 11
Then, the first semi-molded product 6 integrally having the projections 9 and 10 projecting from the back surface of the thin plate portion 11 is injection-molded. Thus, the thickness t1 of the thin plate portion 11 is 0.1 m
It is desirable to set m ≦ t2 ≦ 5 mm.

After the execution of the first step, for example, 1
After cooling for ~ 180 seconds, the second step is performed. In the second step, first, as shown in FIG. By moving the movable mold 14 away from the fixed mold 13 by a predetermined distance, the second cavity 2 corresponding to the second semi-molded product 7 is formed.
1 is formed in a mold 12. That is, the thin plate portion 11 of the second semi-molded product 7 moved together with the movable die 14 and the fixed die 1
3 is adjusted so as to correspond to the thickness t2 of the second semi-molded product 7, and the gate 17 is opened and the molten resin is placed in the second cavity 21 as shown in FIG. Inject.

In the second step, the second semi-molded article 7 is injection-molded so as to be integrally joined to the surface side of the thin plate portion 11 of the first semi-molded article 6. The thickness t2 of the semi-molded product 7 is 0.1 mm ≦ t1 ≦ 5
mm.

After the process of the second step is completed, the mold is cooled, for example, for 1 to 180 seconds, and then the mold 12 is cooled.
The molded article 5 can be obtained by opening.

Next, the operation of the first embodiment will be described. In molding the molded article 5 with a synthetic resin containing a glittering material, the thin plate portion 11 and the projections projecting from the back surface of the thin plate portion 11 are formed. In a first step, a first semi-molded product 6 integrally including 9 and 10 is injection-molded, and a plate-shaped second semi-molded product forming the plate portion 8 of the molded product 5 in cooperation with the thin plate portion 11 is formed. In the second step, the product 7 is integrally molded to the surface side of the thin plate portion 11 and injection-molded.

According to such an injection molding method, even if a flow mark or a weld line is formed on the surface of the thin plate portion 11 in the first semi-molded product 6, the surface of the thin plate portion 11 is formed by the second half molding. Since it is covered with the article 7, no flow mark or weld line remains on the surface of the second semi-molded article 7, that is, the surface of the molded article 5. Therefore, the appearance of the molded article 5 can be improved, and since no gas pressure is applied, no great restrictions are imposed on the shape of the molded article 5 and the design of the molding die 12.

In the first step, the first semi-molded product 6 is formed by injecting a synthetic resin into the first cavity 20 formed between the fixed mold 13 and the movable mold 14,
In the step, the synthetic resin is injected into the second cavity 21 formed by moving the movable mold 14 away from the fixed mold 13 by a predetermined distance while the first semi-molded product 6 is housed in the molding die 12, and the second semi-molding is performed. Since the molding of the article 7 and the integral joining to the first semi-molded article 6 are performed, a plurality of molding dies are not required, so that the installation space for the molding dies 12 can be reduced and the equipment cost can be reduced. Can be achieved.

FIGS. 6 and 7 show a second embodiment of the present invention. FIG. 6 is a perspective view of a molded product, and FIG. 7 is an exploded perspective view of first and second semi-molded products constituting the molded product. FIG.

First, in FIG. 6, this molded article 5 'is molded from a synthetic resin such as AAS or AES containing 0.1 to 7% of a glittering material such as aluminum foil, glass beads and pearl mica. On the back surface of the plate portion 8 having a smooth surface, for example, a cylindrical protrusion 9 functioning as a boss or a flat protrusion 1 functioning as a rib, for example.
0 is provided.

In molding the molded article 5 ', the first
The third step is executed sequentially. In the first step, as shown in FIG. 7, a first semi-molded product 6 'formed by connecting the projections 9 and 10 by a connecting portion 22 is injected. Molded,
In the second step, the plate-shaped second semi-molded product 7 ′ constituting the plate portion 8 is injection-molded so as to be integrally joined to the first semi-molded product 6 ′. Part 22
Cut off.

The second embodiment is effective when the same molding method as in the first embodiment cannot be performed due to the small thickness of the plate portion 8 in the molded product 5 '. In this case, the first semi-molded product 6 ′ in which the plurality of protrusions 9 and 10 are integrally connected by the connecting portion 22 can be injection-molded so that the passage of the molten resin is secured by the connecting portion 22.
In the second step, the plate-shaped second half-molded product 7 'is integrally joined to the first half-molded product 6' while being injection-molded, so that a flow mark or a weld line is formed on the surface of the second half-molded product 7 '. Does not occur, and the appearance of the molded product 5 'formed by cutting off the connecting portion 22 in the third step can be improved, and there are great restrictions on the shape of the molded product 5' and the design of the mold. Is not added.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the appended claims. It is possible.

[0030]

As described above, according to the first aspect of the present invention, the appearance of a molded product can be improved, and no significant restrictions are imposed on the shape of the molded product and the design of a molding die.

According to the second aspect of the present invention, when the thickness of the plate portion of the molded product is small, the appearance of the molded product can be effectively improved, and the shape of the molded product and the design of the molding die are large. There are no restrictions.

Further, according to the third aspect of the present invention, a plurality of molding dies are not required, so that the space for installing the molding dies can be reduced, and the equipment cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of a molded product according to a first embodiment.

FIG. 2 is a cross-sectional view of the molded product viewed from a direction along line 2-2 in FIG.

FIG. 3 is a vertical cross-sectional view of a molding die when a first step is performed.

FIG. 4 is a longitudinal sectional view of a molding die corresponding to FIG. 3 in a state before execution of a second step.

FIG. 5 is a longitudinal sectional view of the molding die corresponding to FIG. 3 at the time of executing the second step.

FIG. 6 is a perspective view of a molded product according to a second embodiment.

FIG. 7 is an exploded perspective view of first and second semi-molded articles constituting the molded article.

[Explanation of symbols]

 5, 5 ... molded article 6, 6 '... first semi-molded article 7, 7' ... second semi-molded article 8 ... plate part 9, 10 ... projection 11 ... Thin plate portion 12: molding die 13: fixed die 14: movable die 20: first cavity 21: second cavity 22: connecting portion

Claims (3)

[Claims] 1. An injection molding method for molding a molded product (5) having a projection (9, 10) on the back surface of a plate portion (8) having a smooth surface using a synthetic resin containing a glittering material. A first semi-molded product (1) having a thin plate portion (11) thinner than the plate portion (8) and the projections (9, 10) integrally projecting from the back surface of the thin plate portion (11). 6) a first step of injection molding, and a second plate-shaped semi-finished product (7) constituting the plate portion (8) in cooperation with the thin plate portion (11). A second step of performing injection molding so as to be integrally joined to a surface side of the injection molding. 2. A molded product (5 ') having a plurality of projections (9, 10) provided on the back surface of a plate portion (8) having a smooth surface is molded from a synthetic resin containing a glittering material. A first step of injection-molding a first semi-molded product (6 ') comprising the projections (9, 10) connected by a connecting portion (22); 8) A second injection molding is performed so that the plate-shaped second half-molded product (7 ′) constituting the above-mentioned 8) is integrally joined to the first half-molded product (6 ′).
And a third step of cutting off the connecting portion (22). 3. A molding die (1) comprising a fixed die (13) and a movable die (14) capable of moving back and forth with respect to the fixed die (13).
2) is prepared, and the synthetic resin is injected into a first cavity (20) formed between the fixed mold (13) and the movable mold (14) corresponding to the first semi-molded product (6, 6 '). Performing the first step, moving the movable mold (14) away from the fixed mold (13) by a predetermined distance while the first semi-molded product (6, 6 ') is housed in the mold (12); The molding die (1) corresponding to the second semi-molded product (7, 7 ')
The injection molding method according to claim 1 or 2, wherein the second step is performed by injecting the synthetic resin into a second cavity (21) formed in (2).