JPS6392419A - Method of molding synthetic resin hollow body - Google Patents

Abstract

PURPOSE:To facilitate the control of temperature in a short time and at the same time at low cost by a method wherein a resin molding is molded by employing a core made of low melting metal as an insert and, after that, inert heating medium, which is heated up to about the melting point of the core, is fed under pressure in the core and recover the low melting metal by high frequency heating in order to completely remove core metal. CONSTITUTION:A core 17 is made of low melting metal. A synthetic resin member 16 is molded by internally chilling the core. The leading-on ports 3 and a recovery pipe 4 of inert heating medium 6 are connected to a synthetic resin molded item 1. Under the condition that the inert heating medium 6, which is heated up to about the melting point of the constituting the core 17, is fed in the core 17 under pressure, only the core 17 is heated and melted through high frequency heating given by a high frequency heater 2 so as to be removed by being run out of the synthetic resin molding 1 together with the inert heating medium 6. High frequency heating heats only the metal core 17 without giving any bad effect to the synthetic resin molding 16. The molten core metal is easily and completely washed away in a short time by means of the pressure of the inert heating medium 6 from the interior of the molding 16. In addition, because the inert heating medium 6 circulatingly washes the interior of the molding item 16, the washing can be done with small amount of the inert heating medium and consequently the heating of the inert heating medium is done in a short time and, at the same time, at low cost and consequently the control of the temperature of the inert heating medium becomes easy.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of molding a synthetic resin hollow body using a core of a low-melting metal, and particularly relates to a method for molding a synthetic resin hollow body using a core of a low-melting metal. This is a molding method suitable for molding structural products, and is mainly used in the molding field of the automobile industry.

[Conventional technology]

A method of manufacturing an intake manifold with a complex three-dimensional structure using a low-melting point metal was proposed in JP-A-5
No. 8-82059.

In this known method, as schematically shown in FIGS. 2 to 5, after the upper mold A and the lower mold B are clamped, a low melting point metal (tin-bismuth alloy) solution is introduced into the mold through a pipe 13. Press fit,
A core 17 made of a low melting point metal is molded, and then an upper mold C
After setting the core in a mold consisting of a lower mold and a lower mold, a molten synthetic resin material (melting point 220°C to 240°C) whose melting point is higher than that of a low melting point metal (melting point 170°C) is placed into the mold using a piston P. The core 17 is molded at an engineering college, and then heated to a set temperature (higher than the melting point of the core metal but lower than the molded synthetic resin material).
In a container 20 containing oil 6 heated to 190°C),
The molded product with a core is immersed, the core is melted and removed in a container, only the molded product 16 is taken out, and the molten low melting point metal is poured into a valve.
It is collected through

[Problems to be solved by the invention] Removal of the core is carried out by immersing the molded product in a heated oil tank, which requires a relatively large container and the heating of a large amount of oil.
In addition, it takes time to melt the low-melting point metal, resulting in a two-liter strike in terms of space and heating energy, and the molding process requires completely removing the core from the molded product in an oil tank. A large number of man-hours were required for the means for shaking the product and the means for recovering the molten metal diffused at the bottom of the large container, resulting in high manufacturing costs.

[Means and actions for solving the problem] After molding the synthetic resin material, the inlet 3' of the inert heat medium 6 and the recovery pipe 4 are connected to the synthetic resin molded product, and the metal forming the core is connected to the synthetic resin molded product. While an inert heating medium 6 heated to around the melting point of This solves the problem of.

In high-frequency heating, only the metal core is heated without adversely affecting the synthetic resin molded product, and the molten core metal is easily and completely washed away from the inside of the molded product in a short time by the pressure of the inert heating medium. .

In addition, since the inert heat medium 6 circulates and cleans the inside of the molded product, it can be achieved with a smaller amount of liquid than melting and removing by immersion, and because of the small amount of liquid, heating can be done in a short time and at low cost. This makes it easier to control the temperature of the inert heat medium.

〔Example〕

As a low melting point metal, the trade name of tin-bismuth alloy (J Alloy 138 (manufactured by Osaka Asahi Metal Industries, melting point 138°) is used.
C) was used to melt and inject the upper mold A and the lower mold B into a clamped core mold as shown in FIG. 2 to form the core of the intake manifold.

Next, as shown in Fig. 3, after setting the core 17 in the 4-mold C and the lower mold and clamping the mold, the glass fiber 3
The intake manifold 1 was obtained by injection molding 6 nylon mixed with 0% by weight.

Next, as shown in FIG. 1, the molded product 1 with a core was
0W, frequency 27KH2O high frequency heater 2, connect the inlet 3' of the pipe 3 to the core molded product, and connect the other end to the
A recovery pipe 4 was connected, and a separation tank 5 for separating low-melting point metals was received below the recovery pipe.

A core metal recovery vibe 13 is pulled out from the bottom of the separation tank 5, and the pipe 13 is connected to a pump 8. It was connected to a storage tank 10 via a heater 9. A take-out pipe 13' extended upward from the bottom of the storage tank 10 and was connected to the core mold 12 via a pressure regulator 11 provided with a heater.

In addition, the vibrator 3 is connected to the pump 8 from the middle part of the separation tank 6.
, and extended upwardly through heater 9 to the point of introduction ``]3'.

Using ζ silicone oil as an inert heat medium, heat the silicone oil to 150°C and pressurize it with the pump 8.
- The core metal 17 was heated by high frequency heating with an output of 500 W and a frequency of 27 KHz from the high frequency heater 2 while circulating between the separation tank 5 and the pump 8.

Low melting point metal used for core (product name 1. J Alloy 138)
has a melting point of 138°C, which is higher than the melting point of nylon 6 (220°C).
During the core melting and outflow process, the nylon molded product is not subjected to any thermal stress (~240°C), and the core inside the molded product is exposed to a pressurized flow of silicone oil. In addition, when molding the intake manifold, since the core metal 17 has a greater heat capacity than the injected resin, molding was possible without any particular melting and deformation. It took about 4 hours to melt and remove using heated silicone oil using a molded article with a child, but in this example it was possible to melt and remove it in 30 minutes.

The silicone oil and the molten core metal flow down together, but the layers are separated in the separation tank 5 due to the difference in specific gravity, and the silicone oil in the upper layer is circulated as shown by arrow A2 and can be used semi-permanently. The molten metal 7 in the lower layer was sequentially collected from the separation tank in the pipe 13 as shown by arrow A3 so as not to accumulate more than a certain standard.

Since the molten metal 7 is put into the storage tank 10 in a molten state via a pump 8 and a heater 9, it can be injected into the core mold 12 via a pressure regulator if necessary, and the separation tank is small. Therefore, it could be reused quickly and efficiently.

Note that the scale and frequency of the high-frequency heater may be appropriately selected depending on the target workpiece.

Further, when using U alloy 138 with a melting point of 138° C., it is possible to use ordinary mineral oil as an inert heat medium, but silicone oil is preferable from the viewpoint of deterioration.

〔Effect of the invention〕

Since the inert heat transfer medium is circulated under pressure inside the molded product with core,
The melted portions of the core metal can be removed one after another, the melting action of the core can be achieved quickly, and the core metal can be completely removed from the molded product.

In addition, since there is no need to immerse the molded product with a core in an inert heating medium, only a small amount of inert heating medium is required, and the separation tank can be made smaller, making it easier to recover the molten core metal from the separation tank. Yes, it is suitable for recycling.

The inert heating medium is circulated at a temperature approximately equivalent to the melting point of the core metal (1
Since the core metal is heated to about 40°C (approximately 40°C), compared to methods that remove the core metal by immersion (heating temperature is about 190°C),
Heating can be done in a short time and at low cost, making temperature control easier. Additionally, deterioration of the inert heat medium is suppressed, making maintenance easier.

Furthermore, since the core metal can be melted and removed at a temperature sufficiently lower than the melting point of the synthetic resin material, deformation of the resin molded product due to external stress can be eliminated.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of an apparatus used in one embodiment of the present invention. FIG. 2 is an explanatory diagram of metal core molding used in carrying out the present invention. FIG. 3 is an explanatory diagram of a molding method used to implement the present invention. FIGS. 4 and 5 are explanatory diagrams of conventional manufacturing methods, respectively. 1: Molded product with core, 2: High frequency heating, 3: Pipe,
4: Recovery pipe, 5: Separation tank, 6: Inert heat medium, 7: Melting low melting point metal, 8: Pump, 9: Heater, 10: Storage tank, 11: Pressure regulator, 12: Core mold, 13 : Pipe, 16: Molded product, 17: Core. 'l Figure 2 Figure 4 Figure 1 Day Figure 5

Claims (1)

[Claims] 1. A core (17) is formed of a low melting point metal;
) is inserted and a resin molded product (1) is molded with a synthetic resin material, and then an inert heat medium (6) is inserted into the resin molded product (1).
The inert heat medium (6) heated around the melting point of the core is passed through the inlet (3') and the recovery pipe (4).
) A method for forming synthetic resin hollow bodies in which only low-melting point metals are heated and melted and recovered by high-frequency heating. 2. Pressurized inflow from the inlet (3') of the inert heat medium (6) is carried out in a circulation system equipped with a recovery pipe (4), a separation tank (5), a pump (8) and a heater (9). A method for molding a synthetic resin hollow body according to claim 1, which is carried out.