JPS61213118A - Two-color injection molding method - Google Patents

Abstract

PURPOSE:To contrive an improvement in adhesion of a joint part between a primary molded article and secondary molded article, by a method wherein an uneven part is formed on a joint surface of the primary molded article with the secondary molded article by a primary molding and a protrusion group on the joint surface is molten by heat of molten resin of secondary molding. CONSTITUTION:A core 6 for formation of a window opening part 5 on a main body case 1 is set up on a top force 3. A fine uneven surface in a satiny state has been processed on a circumferential surface 6a of the lower edge of the core 6. A primary molding material is injected within a cavity in a top and bottom forces 3, 4, the core 6 is retreated by cooling and shaping in a semicured state, the main body case 1 which is a primary molded article is obtained and a fine uneven parts 5a, 5b are formed on an inner circumferential surface of the window opening part 5. Then a molten resin which is a transparent secondary material is injected into a secondary molding cavity formed between the main body case 1 and the retreating core 6, through heat of which a protrusion 5b group on the inner circumferential surface of the window opening part 5 of the main body case 1 is molten and a see-through window plate 2 is joined and molded unitarily with the inside of the window opening part 5 of the main body case 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-color injection molding method, and more specifically, to an improved method for adhering a primary molded product and a secondary molded product.

[Conventional technology]

Conventionally 9 For example, tape cartridges are made by processing a see-through window for visualizing the amount of tape rolled into a plastic main body case, but in this process, the main body case with the window opening and the see-through window plate are separated. After that, a see-through window plate is fitted into the window opening of the main body case, and the two are joined together by ultrasonic welding or the like. However, the processing of such a see-through window requires many steps such as a process for molding the main body case, a process for forming the see-through window plate, and an ultrasonic welding process for both, so productivity does not improve much.

Therefore, recently, a two-color injection molding method has emerged in which the 9-body case is firstly molded and the transparent window plate is secondarily molded. According to this two-color injection molding method, productivity can be significantly improved because primary molding and secondary molding are performed continuously.

[Problem that the invention seeks to solve]

In the conventional two-color injection molding method described above, the main body case, which is the primary molded product, and the see-through window plate, which is the secondary molded product, are simply joined and molded together by simply butting the thick cross sections of the main body case and the transparent window plate, which are the secondary molded products. Therefore, during secondary molding, it is necessary that the thick sections of the main body case, which is the primary molded product, and the see-through window plate, which is the secondary molded product, are sufficiently welded together.

However, when selecting the primary molding material and the secondary molding material, it is particularly desirable to use a material with high thermal conductivity as the primary molding material in order to improve the cooling solidification rate and molding speed. In such a case, the primary molded product is likely to solidify before the secondary molding.2. Because of this, the joint surface of the primary molded product with the secondary molded product cannot be sufficiently melted by the heat of the molten resin of the secondary molding, and as a result, complete fusion of the two becomes difficult to achieve. For this reason, after molding.

The joint between the main case, which is the primary molded product, and the see-through window plate, which is the secondary molded product, receives loads from inside and outside the case.

It is easy to separate due to deformation caused by temperature changes.

This invention solves these problems, improves molding speed,
Another object of the present invention is to provide a two-color injection molding method that can improve the adhesion between the primary molded product and the secondary molded product.

[Means for solving problems]

In order to achieve the above object, the present invention is characterized in that the primary molded product and the secondary molded product are integrally joined and molded by melting the convex portions on the primary surface. As molded products, it is commonly used for tape cartridge main cases and hubs. However, the present invention can be applied not only to Phillips type tape cartridges but also to video tape cartridges and other various tape cartridges.

〔Effect of the invention〕

According to the two-color injection molding method of the present invention as described above, 1
1. The joining surfaces of the secondary molded products are reliably and firmly joined together by melting the convex portions of the joining surfaces of the next molded product. In addition, since the convex parts on the joint surface of the primary molded product are melted only by the heat of the molten resin in the secondary molding, the material of the primary molded product has good thermal conductivity and a low cooling solidification rate. It becomes possible to use a fast molding material, and even if the primary molded product is semi-solidified by the time of secondary molding, it is possible to join and integrate the two, and as a result, the molding speed can be improved. especially.

It has now become possible to completely fuse thin cross-sections such as the main body case of a tape cartridge and the see-through window plate.

[Embodiment 1] A first embodiment of the present invention will be described based on FIGS. 1 to 3. In Figures 2 and 3, 1 is the main body case of the tape cartridge, which is a primary molded product, and 2 is a transparent window plate, which is a secondary molded product, and these are integrally assembled by two-color injection molding as follows. Bonded and molded.

First, as shown in FIG. 1(a), upper and lower molds 3 and 4 are set for primary molding of the main body case 1. A core 6 for forming a window opening 5 in the main body case 1 is set in the upper mold 3. The lower end circumferential surface 6a of the core 6 is machined with a satin-like fine uneven surface.

In this way, the primary molding material is injected into the cavities in the upper and lower molds 3 and 4, cooled and shaped into a semi-solidified state, and the core 6 is retreated. As shown in Fig. 1, the main body case 1 having a window opening 5 as a primary molded product is obtained by retreating the core 6, and minute irregularities 5a and 5b are formed on the inner peripheral surface of the window opening 5.
is formed. The inner circumferential surface of the window opening 5 having the fine uneven parts 5a and 5b becomes the joint surface with the transparent window plate 2, which is a secondary molded product.

Next, as shown in FIG. 1(e), molten resin, which is a transparent secondary molding material, is injected into the cavity of the secondary molding formed between the main body case 1, which is the primary molded product, and the retreating core 6. The heat of the molten resin melts the convex portions 5b on the inner peripheral surface of the window opening 5 of the main body case 1, which is the primary molded product, and the see-through window plate 2 is integrally joined within the window opening 5 of the main body case 1. molded.

As the primary molding material, a filler composite plastic is used to improve the mechanical and thermal properties of the main body case 1 itself. A specific example is a composite of polypropylene with a filler of calcium carbonate (33 wt%). For Kone J2, polypropylene alone is used as the secondary molding material.

In this way, when a plastic composite of polypropylene and calcium carbonate is used as the molding material for the main body case 1, which is the primary molded product, it has excellent rigidity and heat resistance, as well as high thermal conductivity (8.3 x 10 caj! / cm - 5
ec-'C), the cooling solidification rate increases and the molding rate improves. Then, as a secondary molding material, polypropylene (3X 10 c
al /cta-sec-'C) is used, but the heat of this molten resin can sufficiently melt the group of fine protrusions 5b on the joint surface of the main body case 1, which is the primary molded product, and it is completely melted. It has now been possible to fuse to.

[Embodiment 2] FIG. 4 shows a second embodiment of the present invention, in which uneven portions 5a and 5b are formed on the joint surface of the main body case 1 with the transparent window plate 2.
In forming the core 6, an elongated linear convex portion 5b is formed on the joint surface thereof along the direction of the retreating movement of the core 6. According to this, the relatively large convex portion 5b can be formed without interfering with the backward movement of the core 6.

[Embodiment 3] FIG. 5 shows a third embodiment of the present invention, in which a hub on which the tape of a tape cartridge is wound is shown as a molded article. The inner ring part 11 having the pawls 10 of this hub is first formed, and the outer ring part 12 on which the tape is directly wound is second formed. In this molding, as in the case of the above embodiment,
The inner ring part 11 and the outer ring part 12 are integrally joined by forming minute irregularities on the outer peripheral surface of the inner ring part 11 in the primary molding, and then melting the raised parts with the heat of the molten resin in the secondary molding. It is molded.

In addition, in the above example, a core-back method is adopted in two-color injection molding, but instead of this, the mold is opened after primary molding,
Leave the primary molded product attached to the core.

It is also possible to adopt an inversion method in which the material is inverted and moved to the secondary forming position.

[Brief explanation of the drawing]

Figures 1 to 3 show the first embodiment of the present invention, Figures 1 (a), middle), and (C) are cross-sectional views of the two-color injection molded state, and Figure 2 is a cross-sectional view of the molded product. A plan view of the main body case of a tape cartridge, which is an example, and Fig. 3 shows ■-■ in Fig. 2.
Line enlarged cross-sectional view. FIG. 4(a) (mountain) shows a second embodiment of the present invention, and FIG. 4 (al is a plan view of the joint surface of the primary molded product with the secondary molded product, FIG. is a sectional view thereof. FIG. 5 shows a third embodiment of the present invention, and is a plan view showing a hub of a tape cartridge as a molded product. ■・・・The main case of the tape cartridge. 2...Transparent window board. 5b...Protrusion. Inventor Shigeo Sasaki Toshiharu Nakatamari Figure 3 Figure 5

Claims (1)

[Claims] (1) It consists of a primary molding process in which a primary molded product is molded, and a secondary molding process in which a secondary molded product is integrally bonded to the primary molded product. A two-color injection molding method, characterized in that an uneven portion is formed on a surface to be joined to a molded product, and a group of convex portions on the joint surface are melted by heat of molten resin during secondary molding.