JP2003211498A - Method for manufacturing dichroic molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a dichroic molded product capable of forcibly removing the product when a mold is opened by utilizing an elastic force or a repulsion force of a thermoplastic elastomer and raising a molding efficiency by enabling to automatically cut a gate almost unnecessary for a postworking. <P>SOLUTION: A gate 5 is provided on a rear surface side of a preform 2. The method for manufacturing the dichroic molded product comprises the step of casting a molten thermoplastic elastomer in the cavity 4 via a through-hole 6 formed at the preform 2. The method further comprises the steps of connecting the gate 5 directly to an undercut part 8 without gate land for increasing a gap to the undercut part 8, forming a sectional shape of a sub-runner 7 to the gate 5 in an elliptical shape, and thereby utilizing an elastic action of the elastomer in the sub-runner 7. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention enables automatic gate cutting with almost no traces, and uses the elasticity of a thermoplastic elastomer to allow forcible removal during mold opening to improve molding efficiency. The present invention relates to a method for producing a two-color molded product that is made possible.

[0002]

2. Description of the Related Art A thermoplastic elastomer having a core formed of a hard synthetic resin such as ABS resin and having an appropriate shape is produced and the surface of the primary molded article exhibits excellent abrasion resistance and the like. A two-color molded product obtained by thermally fusing a polymer material having remarkable elasticity as described above to obtain a finished product is often used, for example, as an operation button for a game machine.

FIGS. 4 and 5 show a conventional example for obtaining a two-color molded product, in which the cavity 21 for injecting a molten thermoplastic elastomer is a mold element in the one shown in FIG. A side gate 22 that is formed in the mold 20a and communicates with the cavity 21 is provided in the mold element 20a.

In the space formed by the mold element 20b and the mold element 20c, the primary molded product 23 serving as a core is formed.
Since the cavity 21 also serves as the upper surface of the primary molded product 23, the thermoplastic elastomer injected into the cavity 21 through the side gate 22 is the upper surface of the primary molded product 23. A two-color molded product is obtained by heat-sealing and opening the mold.

In the conventional example shown in FIG. 5, the mold element 20a is used.
Further, a cavity 21 for injecting the molten thermoplastic elastomer is provided, and a kind of submarine gate 24 communicating with the cavity 21 is provided so as not to be conspicuous in a region adjacent to the primary molded product 23. In this conventional example, an ejector pin 25 that acts when the mold is opened is provided in the mold element 20c.

[0006]

Among the above-mentioned conventional examples, in the one shown in FIG. 4, the structure of the mold element 20a is simple and economically advantageous, but the primary molding as the core is performed. There are problems that secondary gate marks are left in relatively conspicuous portions of the side edges of the elastic layer formed of the thermoplastic elastomer formed on the upper surface of the product 23, which impairs the external appearance and requires gate treatment.

Further, in the case of the submarine gate 24 shown in FIG. 5, the ejector pin 2 is required even if the labor required for the remaining gate processing is less than in the case of the conventional example shown in FIG.
There is a problem that the die structure such as providing 5 in the die becomes complicated, which is economically disadvantageous, and at least gate finishing is indispensable and requires some labor.

In order to reduce the gate residue due to automatic gate cutting, a small-diameter gate land has been provided around the gate portion of the mold. According to this method, a separation distance is provided between the gate land and the undercut. Therefore, when the thermoplastic elastomer is cut at the undercut portion, the gate land portion remains in the secondary molded product, which requires post-treatment and deteriorates molding efficiency.

Therefore, the present invention solves the above-mentioned problems associated with the conventional method for producing a two-color molded article, and makes it possible to force the die-opening during mold opening by utilizing the elasticity of the thermoplastic elastomer. It is an object of the present invention to provide a method for producing a two-color molded product, which enables automatic gate cutting that requires almost no processing to improve molding efficiency.

[0010]

Means for Solving the Problems To elaborate the constitution of the present invention for achieving the above object, the invention according to claim 1 is
In the method for producing a two-color molded product in which an elastic layer made of a thermoplastic elastomer is formed on the surface of a primary molded product made of a hard synthetic resin to be a core, a gate portion for injecting a molten thermoplastic elastomer into a cavity is provided. It is set on the back surface side of the primary molded product, and the molten thermoplastic elastomer is injected into the cavity through the through hole formed in the primary molded product, and the gate part is provided with an undercut part. To use the elasticity of the thermoplastic elastomer in the sub-runner by eliminating the gate land part to increase the gap and connecting it directly to the undercut part, and making the cross-sectional shape of the sub-runner reaching the gate part oval. The method for producing a two-color molded product is characterized in that the molded product can be forcibly removed by performing the above process.

The invention according to claim 2 is the method for producing a two-color molded product according to claim 1, wherein the primary molded product made of a hard synthetic resin as a core is a game machine operation button having a bowl shape. is there.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The specific construction of the method for producing a two-color molded article according to the present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is an explanatory view showing an example of a mold structure used in the manufacturing method of the present invention, FIG. 2 is an enlarged explanatory view of the periphery of a gate portion, and FIG. 3 is a sectional view of the sub-runner portion of FIG.

In the figure, 1a, 1b and 1c are all mold elements, and 2 is a primary molded product set in a recess formed by the mold element 1b and the mold element 1c. The primary molded product 2 is a core of a finished two-color molded product, and is excellent in heat resistance, impact resistance, chemical resistance, etc.
It is made of a hard synthetic resin such as a BS resin, and in the present invention, an elastic layer made of a thermoplastic elastomer having excellent properties such as abrasion resistance and slip resistance is formed on the surface 3 of the primary molded product 2. It is about how to do it.

The cavity 4 for receiving the molten thermoplastic elastomer is provided in the mold element 1a corresponding to the upper surface of the primary molded product 2, and the gate portion 5 communicating with the cavity 4 is the primary molded product. It is provided in the mold element 1c corresponding to the back surface side of 2. In addition, a through hole 6 for guiding the molten elastomer injected from the gate portion 5 into the cavity 4 is formed at substantially the center of the primary molded product 2.

The mold elements 1a and 1b are provided with a sub-runner 7 communicating with the above-mentioned gate portion 5, and the molten elastomer is provided through the sub-runner 7 provided in the mold elements 1a and 1b. 5 is injected into the cavity 4, but the gate portion 5 has a large gap with the undercut portion 8 so as to be directly connected to the undercut portion 8 without the gate land portion as shown in FIG. I am doing it.

Conventionally, a small-diameter gate land portion is provided between the gate portion and the undercut portion in order to make the gate cut well. However, the elastomer that has been cooled and cured during mold opening is undercut portion. In many cases, the elastomer cured in the gate land remains in the secondary molded product, which requires post-processing. However, in the method of the present invention, since the gate land portion is not provided between the gate portion 5 and the undercut portion 8 and the undercut portion 8 is directly connected to the gate portion 5, a gap with the undercut portion 8 is formed. The effect can be utilized and the gate part 5 enables automatic gate cutting without leaving a trace.

Further, in the present invention, the elastic force or the repulsive force of the thermoplastic elastomer remaining in the sub-runner 7 in the mold elements 1a and 1b is applied so that the mold can be smoothly opened. The cross-sectional shape is elliptical as shown in FIG.

That is, when the sub-runner 7 has a circular shape similar to the conventional one, it is impossible to obtain sufficient elasticity or repulsive force of the elastomer remaining in the sub-runner 7 when the mold is opened. However, if the cross-sectional shape of the sub-runner 7 is elliptical as in the method of the present invention, the elastic force or repulsive force inherent in the elastomer should be fully utilized. In addition to the fact that the gate land portion is eliminated and the undercut portion 8 is directly connected to the gate portion 5 as described above, the mold opening is easy, and the automatic gate cut leaves almost no trace. Became possible.

According to the method of the present invention, even if the primary molded article made of a hard synthetic resin as the core has a bowl shape like an operation button for a game machine, its surface has good abrasion resistance. An elastic layer having wear resistance and anti-slip effect can be efficiently formed. In particular, the primary molded product 2 is provided with a through hole 6 serving as a passage for the molten elastomer injected into the cavity 4 through the gate portion 5, and the molten elastomer also naturally enters the through hole 6 so that the primary molded product 2 It is possible to provide a two-color molded product which is highly reliable in terms of strength.

[0020]

As described above, according to the method of the present invention, it is possible to perform automatic gate cutting with almost no traces, and it is possible to forcefully remove the elastomer during the mold opening without breaking the elastomer in the sub-runner on the way. As a result, it is possible to provide a two-color molded product that is extremely efficient, has a small number of defective products, has a good appearance, and has sufficient strength. Also,
According to the method of the present invention, the primary molded product is provided with through holes communicating with the front and back, and the thermoplastic elastomer is fused with the primary molded product in the through holes, so that the game machine is highly reliable in strength. It is possible to provide operation buttons and the like.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a mold structure used in a manufacturing method of the present invention.

FIG. 2 is an enlarged explanatory diagram around a gate portion.

3 is a cross-sectional view of the sub-runner portion of FIG.

FIG. 4 is an explanatory diagram showing an example of a conventional method.

FIG. 5 is an explanatory diagram showing another example of a conventional method.

[Explanation of symbols]

1a: Mold element 1b: Mold element 1c: Mold element 2: Primary molded product 3 :: Surface 4: Cavity 5: Gate part 6: Through hole 7: Sub-runner 8: Undercut part

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazushi Yamauchi             147-1 Hanajima-cho, Hanamigawa-ku, Chiba City, Chiba Prefecture             Yoshiyama Plastic Industry Co., Ltd. F-term (reference) 4F202 AA13 AD05 AG03 AH71 CA01                       CA11 CB01 CB12 CB28 CK03                       CK06 CL02 CM31 CQ01

Claims (2)

[Claims] 1. A method for producing a two-color molded article in which an elastic layer made of a thermoplastic elastomer is formed on the surface of a primary molded article made of a hard synthetic resin as a core, wherein a molten thermoplastic elastomer is placed in a cavity. The gate part to be injected is set on the back surface side of the primary molded product, and the molten thermoplastic elastomer is injected into the cavity through the through hole formed in the primary molded product. In order to make a large gap with the undercut part, the gate land part is removed and it is directly connected to the undercut part, and the cross-sectional shape of the sub-runner reaching the gate part is elliptical so that the thermoplastic elastomer A method for producing a two-color molded article, characterized in that the molded article can be forcibly removed by utilizing elasticity. 2. The method for producing a two-color molded product according to claim 1, wherein the primary molded product made of a hard synthetic resin as a core is an operation button for a game machine having a bowl shape.