JPH06246779A - Method for manufacturing hollow resin molded product - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a method for manufacturing a hollow resin molded product, which can accurately and easily mold a desired hollow resin molded product by using a core that can be accurately molded into a predetermined shape and does not deform. [Structure] First, a core 1 having a predetermined shape in the hollow portion of a hollow resin molded product is molded with a resin having a relatively low melting point. next,
The core 1 is placed in an injection molding die having a hollow portion of a predetermined shape, and a resin having a relatively higher melting point than the core is injected between the core 1 and the hollow portion to form the core 1 and the hollow portion. A molded product 25 including the resin molded product 23 is molded. Next, the molded product 25 is heated to the melting temperature of the core 1 to elute and remove the core. The resin core 1 has a low thermal conductivity, does not cause resin improperness in injection molding, is light in weight and does not deform, and thus is easy to manufacture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hollow resin molded product such as an intake manifold for an automobile, and more particularly to a product having a predetermined shape obtained by injection molding using a resin core and eluting the core. About what you got to.

[0002]

2. Description of the Related Art Hollow resin moldings include, for example, synthetic resin manifolds used for automobile intake manifolds and the like. This has a complicated shape in which a gas suction part, a cylinder head joint part, and a branch pipe connecting both parts are integrated. This product is conventionally manufactured by a method as shown in FIGS. 11 and 12, for example. First, the core 101 having a predetermined shape in the hollow portion of the hollow resin molded product is molded with a low melting point alloy. Next, the core 101 is placed in an injection molding die 105 having a hollow portion 103 of a predetermined shape, and a resin 107 is injected between the core 101 and the hollow portion 103 to form the core 101 and the hollow resin molded product. 10
A molded product 111 composed of 9 is molded. Next, the molded product 111 is heated to elute and remove the core 101 of the low melting point alloy to obtain a hollow resin molded product 109.

[0003]

The above-mentioned conventional structure has the following problems. First, the core 1 of the low melting point alloy
Since 01 is a metal and has a high thermal conductivity, the injected resin 107
Has a problem that it is apt to cause a whirl due to a temperature drop. For example, when the core 101 having an uneven portion as shown in FIG. 12 is placed in the molding die 105 and injection molding is performed,
The resin 107 is not injected into the concave portion and stops in front of the resin 107, so that the hollow resin molded product 109 having a predetermined shape cannot be manufactured. This phenomenon also occurs when the molding distance is long. or,
Although it is conceivable to increase the injection pressure in order to eliminate such non-rotation, the core 101 of the low melting point alloy is deformed and it becomes impossible to manufacture the hollow resin molded product 109 having a predetermined shape. Also, the core 101 of the low melting point alloy
Since it is heavy, it is difficult to handle, and even if it is molded into a predetermined shape, it is easily deformed by bending after molding and the curvature of the curved portion is changed, and it is difficult to manage until molding.

The present invention has been made on the basis of the above points, and its object is to ensure that a desired hollow resin molded product can be reliably and easily formed by a core that can be accurately molded into a predetermined shape and does not deform. It is to provide a method for producing a hollow resin molded product that can be produced.

[0005]

In order to achieve the above object, a method for producing a hollow resin molded product according to the present invention is such that a core having a predetermined shape in the hollow portion of the hollow resin molded product is made of a resin having a relatively low melting point. Molding step, the core is placed in an injection mold having a hollow portion of a predetermined shape, and a resin having a relatively higher melting point than the core is injected between the core and the hollow portion. And a step of molding a molded product consisting of a hollow resin molded product, and a step of heating the molded product to elute and remove the core having a low melting point,
It is characterized by having. In the above manufacturing method, it is conceivable that the core is hollow. Further, it is conceivable that the core is a mixture of conductive whiskers.

[0006]

First, the core of the hollow resin molded article having a predetermined shape is molded from a resin having a relatively low melting point. Next, the core is placed in an injection molding die having a hollow portion of a predetermined shape, and a resin having a relatively higher melting point than that of the core is injected between the core and the hollow portion to form the core and the hollow portion. A molded product consisting of a resin molded product is molded. Next, the molded product is heated to the melting temperature of the core to elute and remove the core. The resin core has a low thermal conductivity, does not cause improper rotation of the resin in injection molding, is lightweight and does not deform, and thus is easy to manufacture. Further, the hollow core makes it easier to elute the core. In addition, by using a conductive whisker mixed in the core, the core can be reinforced so that it can withstand the pressure at the time of injection molding, and high frequency is irradiated when the core is dissolved. It is possible to shorten the elution time of the core.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present invention will be described below with reference to FIGS.
An example will be described. First, as shown in FIG. 1, a core 1 having a predetermined shape in the hollow portion of a hollow resin molded product is molded with a resin having a relatively low melting point. What is shown in the figure is an injection mold, in which a cavity 7 having the shape of a hollow portion of a hollow resin molded product is formed between the upper mold 3 and the lower mold 5, and a resin 11 is injected into the cavity 7 from an injection device 9. To do. Resin 1
No. 1 needs to have a relatively low melting point with respect to the resin of the hollow resin molded product described later, and PS resin, ABS resin and the like are used as those satisfying this condition. The solid core 1 is molded by the above molding.

Next, as shown in FIG. 2, the core 1 is placed in an injection molding die having a hollow portion of a predetermined shape, and the space between the core and the hollow portion is relatively higher than that of the core. A resin having a melting point is injected to form a molded product including a core and a hollow resin molded product. The one shown is an insert injection mold, and the upper mold 1
3, a cavity 17 having an outer shape of a hollow resin molded product is formed between the lower mold 15 and the lower mold 15, the core 1 is arranged in the cavity 17, and an injection device is provided in a space between the cavity 17 and the core 1. Resin 21 is injected from 19. Resin 21 is core 1
It is necessary to have a relatively high melting point, and PPS resin (polyphenylene sulfide) is used to satisfy this condition. By the above molding, a molded product 25 including the core 1 and the hollow resin molded product 23 is molded.

Next, as shown in FIG.
Is heated to the melting temperature of the core 1 to elute and remove the core 1. The illustrated one is an oil bath, and oil 29 is filled in oil tank 27 and heated by heater 31. The molded product 25 is put in this oil 29, and the core 1 is eluted by setting the oil temperature to the melting point temperature of the core 1 to obtain a hollow resin molded product 23 as shown in FIG.

According to this embodiment, the following effects can be obtained. First, the resin core 1 has a low thermal conductivity and the temperature of the resin does not drop during injection molding. Therefore, the hollow resin molded product 23 having an accurate shape can be manufactured.
Moreover, since the resin core 1 is lightweight and does not deform, the hollow resin molded product 23 can be easily manufactured, and
Management up to molding becomes easy. Further, the resin core 1 is cheaper than the one made of the low melting point alloy, and the thermoplastic resin can be repeatedly used, so that the manufacturing cost can be reduced.

Next, a second embodiment will be described with reference to FIGS. In the case of this embodiment, a hollow core is used instead of the solid core 1 of the first embodiment.
FIG. 5 shows a gas-assisted injection molding die, in which a cavity 37 having the shape of a hollow portion of a hollow resin molded product is formed between an upper die 33 and a lower die 35, and a cavity 37 is formed.
While injecting the resin 41 from the injecting device 39, gas is introduced from the nozzle 43 in the injecting device 39 to hollow the molten resin to form the hollow core 45.

Next, as shown in FIG. 6, the core 45 is placed in an insert injection molding die 47 and injection molding is carried out to obtain a molded product 51 consisting of the core 45 and a hollow resin molded product 49. Next, as shown in FIG.
Then, the core 45 is eluted by setting the oil temperature to the melting point of the core 45 to obtain a hollow resin molded product 49.

According to this embodiment, the core 45 is made of resin to obtain the core 45 having an accurate shape, and the hollow resin molded product 49 having an accurate shape is manufactured by injection molding using the core 45. be able to. Further, the hollow core 45 further reduces the weight and convenience of handling, and when the core 45 is eluted, the absolute amount of the resin is small and the surface area is large. Heat is applied to the inside, and elution becomes easier.

Next, a third embodiment will be described with reference to FIGS. In the case of this embodiment, the core is mixed with conductive whiskers. First, as shown in FIG. 8, a gas-assisted injection molding die is used to form a cavity 37 having the shape of the hollow portion of the hollow resin molded product between the upper die 33 and the lower die 35, and the cavity 37 is formed in the cavity 37. Injection device 3
When the resin 41 is injected from No. 9, the conductive whiskers 55 are mixed into the resin 41. The conductive whiskers 55 have conductivity and reinforcement. Thereby, the core 57 is molded.

Next, as shown in FIG. 9, the core 57 is placed in the insert injection molding die 47 and injection molding is performed to obtain a molded product 61 composed of the core 57 and the hollow resin molded product 59. Next, as shown in FIG. 10, the molded product 61 is put into the oil 65 in the oil tank 63, and the oil temperature is heated to the melting point temperature of the core 57. A high frequency generator 67 is arranged around the oil tank 63, and the core 57 is irradiated with a high frequency. Since the core 57 is made conductive by the conductive whiskers 55, it is heated from the inside by a high frequency. As a result, the core 57 is eluted and the hollow resin molded product 59 is obtained.

As described above, according to the present embodiment, the core 57 is made of resin to obtain a core having an accurate shape, and the hollow resin molded product 59 having an accurate shape is formed by injection molding using this core.
Can be manufactured. Further, the core 57 is reinforced when the hollow resin molded product 59 is injection-molded by mixing the conductive whiskers 55.
The deformation of 7 can be prevented. Further, since the oil bath and high-frequency heating can be used together when the core 57 is eluted, the time required for the elution can be shortened.

The present invention is not limited to the above embodiments. For example, it is possible to mix conductive whiskers even when the core is solid. As a means for eluting the core, a heating method using a heater or a hot air heating method may be used in addition to the oil bath. Further, the method of molding the core into a hollow shape is not limited to gas-assisted injection molding, but blow molding or the like may be used. The conductive whiskers mixed in the core have conductivity and reinforcement,
It is also possible to mix a filler having a reinforcing property.

[0018]

As described in detail above, according to the method for producing a hollow resin molded product according to the present invention, the core is made of resin, so that the thermal conductivity of the core becomes low, and the resin is Accurately shaped hollow resin molded product 2 with no temperature drop
3 can be manufactured. Further, since the resin core is lightweight and does not deform, the hollow resin molded product can be easily manufactured, and the management up to the molding can be facilitated. Further, when the core is hollow, the weight is further reduced, the handling is improved, and the core is more easily eluted. or,
When conductive whiskers are mixed in the core, deformation of the core due to injection pressure can be prevented due to its reinforcing property, and high-frequency heating can be used during elution of the core, so that elution time can be shortened.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a mold for a core according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an injection molding die of a molded product including a core and a hollow resin molded product in the first embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a first embodiment of the present invention when the core is eluted.

FIG. 4 is a sectional view showing a hollow resin molded product in the first embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a molding die for a core according to a second embodiment of the present invention.

FIG. 6 is a sectional view showing an injection molding die of a molded product including a core and a hollow resin molded product in a view showing a second embodiment of the present invention.

FIG. 7 is a view showing a second embodiment of the present invention and is a cross-sectional view showing a state where a core is eluted.

FIG. 8 is a cross-sectional view showing a molding die of a core according to a third embodiment of the present invention.

FIG. 9 is a sectional view showing an injection-molding die of a molded product including a core and a hollow resin molded product in a view showing a third embodiment of the present invention.

FIG. 10 is a cross-sectional view showing a third embodiment of the present invention during elution of a core.

FIG. 11 is a cross-sectional view showing an injection molding die of a molded product including a core and a hollow resin molded product in a view showing a conventional example.

FIG. 12 is a cross-sectional view showing an injection molding die of a molded product including a core and a hollow resin molded product in a view showing a conventional example.

[Explanation of symbols]

 1 Core 3 Hollow Part 9 Injection Device 7 Adhesive 11 Resin 23 Hollow Resin Molded Product 25 Molded Product 27 Oil Tank

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Claims (3)

[Claims] 1. A step of molding a core having a predetermined shape of a hollow portion of a hollow resin molded product with a resin having a relatively low melting point, and the core is placed in an injection molding die having a hollow portion having a predetermined shape. A step of injecting a resin having a relatively higher melting point than the core between the core and the hollow portion to form a molded article composed of the core and the hollow resin molded article, and heating the molded article. And a step of eluting and removing the core having a low melting point, the method for producing a hollow resin molded product. 2. The method for producing a hollow resin molded product according to claim 1, wherein the core is formed in a hollow shape. 3. The method for producing a hollow resin molded product according to claim 1 or 2, wherein the core is a mixture of conductive whiskers.