JPH0148846B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a laminated injection molded article of a long object such as a steering wheel for an automobile. The present invention provides a laminated injection molded product that is lightweight and has the same flexibility in all parts. Conventionally, long items such as automobile steering wheels have a large ratio L/T between the length (L) from the gate of the molded product to the weld part and the average wall thickness (T) between the gate and the weld part. Laminated injection molding was not put to practical use because the core layer was difficult to fill in the weld area. In addition, in laminated injection molding of such long objects, the weld part of the molded product is mostly made of the skin layer forming resin because the skin layer forming resin is pushed from two directions by the core layer forming resin and there is no place for it to escape. was. Especially when there are a large number of welds with multi-point gates, it is difficult to obtain a lightweight laminated injection molded product.
This was a major drawback in the marketability of laminated injection molded products. In order to make a lightweight and flexible foam by injection molding a foamable resin into the core layer, compared to injection molding of a non-foamable resin, it is necessary to short shot and use the foaming pressure of the core resin. However, since a laminated structure is formed, it is difficult to form a uniform foam core layer even at the weld portion. The present invention compensates for these drawbacks and provides a laminated injection molded product that is lighter and has similar flexibility in all parts. In the method of manufacturing a steering wheel for an automobile, the present invention provides that when molding a long object having a large L/T and difficult to fill with a core layer, (1) the number of gates is 2 to 8 multi-point gates. (2) The position of each gate in a multi-point gate is determined by each L/T.
position so that they are equal. (3) Apply skin to the weld part of the desired molded product.
An extension part that can be filled with core layer forming resin is provided, a laminated injection molded product of the skin and core layer is formed in the desired molded part and the extension part, and after the resin has solidified, the laminated injection molded product is molded in the extension part. This is a method for manufacturing a steering wheel for an automobile, characterized in that the molded product is removed from the intended molded product. The number of gates used in the present invention is 2 to 8 multi-point gates. The number of gates is experimentally determined depending on the materials of the skin and core layer, whether the core layer is foamed or non-foamed, the sizes of L and T of the molded product, the shape of the molded product, etc. Further, each gate of the multi-point gate needs to be positioned so that each L/T is equal. The mold extension used in the present invention can be easily separated from the molded product even after the molded product and the extension are removed from the mold or during the molding process that they are in the mold. For example, the resin is guided through a hole of about φ8 (mm) to the extension part, torn off as the movable plate moves when opening the mold, and after the molded product is removed from the mold, a knife is passed along the outer periphery of the molded product. You can cut it out with etc. The filling amount of the molded article and the extension part is such that the molded part has a laminated structure with as many core layers as possible, and the extension part also has a laminated structure consisting of a skin layer and a core layer. The volume of the extension depends on the resin material used and the shape and size of the molded product. However, since the extension part is recycled or discarded, it is desirable that the extension part be as small as possible while still providing a satisfactory molded product. This size can be easily determined experimentally by means of volumetrically adjustable extensions. The shape of the extension part is not particularly limited as long as it is sufficiently filled with the core layer. In addition, by providing an extension part, a part of the outer peripheral surface of the molded product will be scratched for separation, so the connecting cross-sectional area between the molded product and the extension part is such that the core layer sufficiently fills the extension part with low pressure. It is desirable that it be as small as possible within the range that allows a satisfactory molded product to be obtained. Furthermore, it is necessary to ensure that the gate and weld are located in inconspicuous locations from the time of mold design. Of course, it is also possible to use a non-foamed material for the core layer. In addition, the method of the present invention can be applied not only to polyvinyl chloride but also to thermoplastic resins.
It can be used without any problems and is not restricted in any way. Next, typical examples of the present invention will be explained. An automobile steering wheel with an iron core was molded using an injection molding machine for forming laminated products with a clamping force of 200 tons and having two cylinder units that meet at the nozzle. A polyvinyl chloride skin layer-forming resin is injected into the mold in an insufficient amount to fill the mold space, and before the inner surface of the skin layer-forming resin solidifies, a blowing agent containing foaming agent is injected into the mold. A polyvinyl chloride core layer forming resin was then injected. As a result, a handle was obtained in which the skin layer of a molded article containing an iron core was made of polyvinyl chloride and the core layer was made of foamed polyvinyl chloride. The number of gates is 1 point, 2 points, 4 points,
Molding was performed with each of the 8-point gates. Further, the gate position and the position of the extension part of the weld part are shown in FIGS. 1 to 4. Diameter φ8 from the back of the outer circumference of the handle at the weld part
(mm), length 10 (mm) hole, length 30 (mm), width 30 (mm)
,
The resin is guided to the extension part with a height of 30 (mm) and a volume of 27 (cm ³ ), and is torn off as the movable side plate moves when the mold is opened, and after the handle is removed from the mold, it is spread along the outer periphery of the molded product. and post-processed with a knife.
Of course, after the molded article has been removed from the mold, it may be treated with a suitable cutting instrument such as a knife. Of course, the extension made of the polyvinyl chloride skin layer and the foamed polyvinyl chloride core layer can be shredded into pellets and mixed with the foamed polyvinyl chloride core layer forming resin for recycling. The materials used in this example had the following composition:
After mixing in a super mixer, the mixture was kneaded in a Hanbury mixer to form pellets. Skin layer forming resin Weight part polyvinyl chloride (=1100) 100 DOP 70 Epoxidized soybean oil 5 Ba-Zn stabilizer 5 Core layer forming resin polyvinyl chloride (=1400) 100 DOP 50 Epoxidized soybean oil 10 Ba-Zn System stabilizer 5 ADCA (foaming agent) 3 The dimensions of the handle obtained in this example are:
It is as follows. Diameter of handle: 380 (mm) Diameter of outer grip: 28 (mm) Diameter of core material (made of iron): 14 (mm) Table 1 shows a comparison of molded products for 2-point, 4-point, and 8-point gates. show.

【table】

[Table] ○...Excellent ×...Slightly inferior As described above, the manufacturing method according to the present invention dramatically improves the performance and uses of laminated injection molded products.

[Brief explanation of drawings]

Figures 1, 2, 3, and 4 show that when forming the handle, the number of gates is 1, 2, 4,
FIG. 7 is a plan view showing the positions of each gate and the position of the guide hole to the extension in the case of an eight-point gate. 1...Arm part of the insert, 2...Outer grip part of the handle part, G...Gate, O...Guidance hole to the extension part.

Claims (1)

[Claims] 1. A core material for an automobile steering wheel is placed in a mold, and an insufficient amount of skin layer forming resin is injected to fill the mold space, and before the inner surface of the skin layer forming resin hardens. , in a method for manufacturing an automobile steering wheel in which a core layer forming resin containing a foaming agent is continuously injected, the number of gates is a multi-point gate of 2 to 8, and the position of each gate of the multi-point gate is set to each L/ T is set at a position where T is equal, an extension part that can be filled with the skin and core layer forming resin is provided in the weld part, a laminated injection molded product of the skin and core layer is formed in the desired molded part and the extension part, and the resin is 1. A method for manufacturing an automobile steering wheel, comprising: solidifying the resin, and then removing the laminated injection molded product formed by the extension from the intended molded product.