JPS5840487B2 - Manufacturing method for epoxy resin cast products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an epoxy resin cast article, and particularly to a novel method for producing an epoxy resin cast article having embedded electrodes.

Metal electrodes such as copper and aluminum are often embedded in epoxy resin castings used for power equipment and power transmission and distribution equipment.

As shown in FIG. 1, conventional methods for manufacturing epoxy resin cast products having embedded electrodes include casting resin 3 into a mold 1 in which embedded electrodes 2 are installed in required parts in advance. This is then placed in a curing tank 4, cured under predetermined temperature conditions, and then cured and demolded to obtain a product.

This method is an effective method because it allows products of various shapes to be obtained relatively easily.

However, epoxy resin has the property of shrinking during the curing reaction process.

Therefore, in the conventional method described above, as the size of the product increases and the amount of resin increases, the epoxy resin hardens and shrinks, causing damage to the surface of the product, the interior of the product, or the interface between the embedded electrode and the resin. In this case, defects such as dents, voids, and cracks may occur.

Recently, research has been carried out in various places to solve these problems, and several new techniques have been proposed.

One example is a method generally called pressure gelling method, in which resin is poured into a casting mold with embedded electrodes installed in the required parts in advance, and when the resin is hardened, the resin is poured into a mold. By raising the temperature of the mold and making the resin composition relatively high in reactivity, a curing reaction is caused in the order of the resin in contact with the casting mold, the resin in the center, and then the resin in the injection hole, In addition, the volume reduction of the resin due to curing shrinkage is replenished by injecting uncured resin under pressure through the injection hole.

The product obtained by this method has a glossy surface and good dimensional stability.

However, in the pressurized gelation method, there are limits to the size of the product and the amount of resin, and it is impossible to use a product that is too large. This cannot be said to be satisfactory with respect to defects at the interface between the embedded electrode and the resin.

Another example is a method of creating a temperature gradient from the top to the bottom of the casting mold.

This implementation method includes a method of providing a heating device in the mold;
Alternatively, a method has been proposed in which a heating device is brought into contact with the mold; in both cases, the injection hole is located at the top of the mold ω, and the temperature is adjusted so that it increases from the top to the bottom of the mold.
Therefore, it is characterized in that the curing reaction progresses from the bottom to the top.

According to this method, relatively large parts can be manufactured, and the surface condition and dimensional stability of the product are also good.

However, even in this method, the curing reaction proceeds from the resin in contact with the mold, so it is not satisfactory for defects at the interface between the embedded electrode and the resin.The present invention is suitable for manufacturing epoxy resin cast products. Disadvantages: This is a new manufacturing method that eliminates defects such as voids, peeling, and cracks, especially at the interface between the embedded electrode and the resin. Provided is a manufacturing method characterized in that when resin is cast and cured, the temperature of the embedded electrode is raised higher than that of the mold or the casting resin, and a curing reaction is initiated from the resin near the embedded electrode. It is something to do.

To explain the present invention with reference to FIG. 2, a casting resin 3 is poured into a casting mold 1 in which an embedded electrode 2 has been incorporated in a required part,
The heating element 5 in contact with the embedded electrode 2 heats the embedded electrode, causing a curing reaction from the resin near the embedded electrode, and sequentially moves from the embedded electrode toward the casting mold surface by heating the resin in the center, then pouring. The resin near the mold surface and the resin near the injection hole are cured in this order.

Further, if necessary, the casting mold 1 is placed in a curing tank 4 to adjust the temperature of the resin and the temperature of the casting mold during the process of heating the embedded metal fittings, or to perform secondary curing.

Further, the manufacturing method of the present invention will be explained using FIG. 3 as an example of the manufacturing method of a power cable connection body. The conductor 11 is heated by the heating cylinder 14.
is heated to harden the epoxy resin injected into the injection space 16 from the injection hole 15 from the point where it contacts the conductor 11.

Further, the casting mold is transferred to a heating tank; after hardening, the mold is demolded to obtain a product.

According to the manufacturing method according to the present invention, the silicification reaction is started by the force of the epoxy resin in the vicinity of the buried electrode, so that the buried electrode and the resin can be bonded without causing voids, peeling, cracks, etc. , residual reactions in the resin at the interface are also reduced.

In epoxy resin cast products used in power equipment and power transmission and distribution equipment, the potential near the embedded electrode is generally high at around 1, and the performance of the interface between the embedded electrode and the resin is extremely important for product quality. However, according to the manufacturing method of the present invention, no defects occur at the interface as described above, and the residual stress in the resin near the interface is small, so the reliability of the product can be significantly improved. .

Note that the method of heating the embedded electrode is arbitrary, and for example, an electric heating device or a heating medium device may be used.

When incorporating the embedded electrode into the casting mold, if necessary to clearly control the temperature of the embedded electrode and the temperature of the casting mold,
It is necessary to interpose a heat insulating material between the embedded electrode and the casting mold.

The curing reaction of the resin begins near the embedded electrode,
The process proceeds sequentially from the embedded electrode toward the surface of the casting mold, but in order to maintain a good surface finish of the product, there is a means of replenishing uncured resin through the injection hole, etc. by increasing the pressure during the curing process. It is also possible to take

Examples of the manufacturing method of the present invention will be described.

Covering a copper rod with a thickness of 101nrILφ and a length of 400cm,
An aluminum pipe with an inner diameter of 18 mmφ, an outer diameter of 20 mmφ, and a length of 300 mm was installed concentrically at both ends of the aluminum pipe with a 4 mm thick annular spacer interposed therebetween, and in the gap between the aluminum pipe and the copper rod, An epoxy resin composition was injected and experiments of Examples and Comparative Examples were conducted under the following conditions.

The formulation of the epoxy resin composition is Araldite XB.
2793 (100 parts by weight of CIBA (E-E I GY epoxy resin trade name), Araldite XB2794
(CIBAGEIGY epoxy resin curing agent product name)
was set at 110 parts by weight.

〔Example〕

Wrap the flexible tape heak around the end of the copper rod, and
40~150℃, and aluminum pipes at 50~60℃
The above composition was injected and cured while heated to .degree.

Furthermore, it was transferred to a constant temperature bath at 140° C. for secondary curing.

[Comparative example]

The entire copper rod and aluminum pipe assembly to 140°C
The whole was placed in a constant temperature bath and preheated to the same temperature, and the above composition was injected and cured.

In the above examples and comparative examples, when the aluminum pipe was removed and the finished product was checked, the cast product of the example had a good finish, but the molded product of the comparative example had a good finish. Peeling was observed at the interface.

In the method of manufacturing an epoxy resin cast article of the present invention, the embedded electrode is heated and cured by making the temperature of the embedded electrode higher than that of the mold and resin, so the resin near the embedded electrode is cured first. It is possible to obtain a highly reliable product that is free from defects such as peeling, voids, and cracks at the interface between the embedded electrode and the resin.

[Brief explanation of the drawing]

Fig. 1 and Fig. 2 are explanatory diagrams of a conventional method of manufacturing an epoxy resin casting amount and a method according to the present invention, respectively, and Fig. 3 is an explanatory diagram of a method of manufacturing an electric cable connection body by the method of the present invention. . 1...Casting mold, 2...Embedded electrode, 3.
...Casting resin, 4...Curing tank, 5...
... Heating body, 11 ... Copper rod, 12 ...
・Casting mold, 13...01J, 14...
... Heating cylinder, 15 ... Injection hole, 16 ...
・Injection space.

Claims (1)

[Claims] 1. Epoxy resin is poured into a casting mold in which embedded electrodes have been provided in the required areas in advance, and when the epoxy resin is cured, the temperature of the embedded electrodes is set to be higher than the temperature of the casting mold and the epoxy resin. A method for producing an epoxy resin cast product, characterized in that curing is started from the resin near the embedded electrode.