JPS6161202B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention has a low viscosity that allows it to be cast before curing;
The extremely long pot life significantly improves workability during casting and impregnation, and after curing, the liquid rubber flame-retardant composition has rubber-like elasticity, high electrical insulation properties, and flame retardant properties. The present invention relates to cast-molded electrical devices. In traditional cast or molded electrical devices, when an electrical discharge occurs, the organic material used as an insulator decomposes and forms carbonaceous deposits that eventually form a low-resistance conductive path that can destroy the electrical device. It's summery. Furthermore, in environments such as high temperature, high humidity, and a dusty atmosphere, tracking failure may occur, and furthermore, sudden arcs from other devices may cause combustion accidents. Therefore, insulating materials are required to have a high degree of electrical insulation, arc resistance, tracking resistance, and flame retardancy in order to prevent the above-mentioned accidents. As a method to satisfy these required properties, we have used cast molding using epoxy resin or unsaturated polyester resin, and butyl rubber or EPT.
There are those molded using rubber or the like, and those that use a combination of casting and molding, but each of these has the following drawbacks. (1) Electrical equipment cast with epoxy resin, etc. Cast insulating materials such as epoxy resin or unsaturated polyester resin have poor elongation and impact resistance, so shrinkage during curing and thermal or mechanical Cracks may occur in the resin layer due to the stress caused by physical impact, and the required performance may not be obtained because the magnetic properties of products with an internal iron core change due to the shrinkage stress of the resin.
It was electrically and mechanically unstable and lacked reliability. (2) Electrical devices molded with butyl rubber, etc. Molding materials such as butyl rubber or EPT rubber have high extensibility and are unlikely to cause cracks, but their viscosity during molding is high, so they must be press-fitted into the entire mold with considerable pressure. For this reason, for example, the shapes and relative positions of internal embedded items such as coils and iron cores were changed, resulting in electrical and mechanical instability and lack of reliability. FIG. 1 is an example of a conventional molded electrical device.
Here, a fully molded current transformer is shown. In Figure 1, 1 is an iron core, 2 is a base, 3 is a primary coil, 4 is a secondary coil, 5 is a primary terminal, 6 is a secondary terminal, 7 is a molded insulator such as butyl rubber or EPT rubber, and 8 is the same. A fixed insulator such as butyl rubber or EPT rubber, 9 is an inner insulator. That is, the primary coil 3, the secondary coil 4 and the iron core 1
In order to maintain the prescribed insulation dimensions and withstand the pressure during molding the entire body, a fixed insulator 8 is pre-molded in advance, and then the primary coil 3 is wound on the fixed insulator 8 and the iron core 1 is assembled, and other parts are The primary terminal 5, the secondary terminal 6, the base 2, and other parts were attached and the whole was molded with a molded insulator 7. In the case of such a conventional device, since the molded insulator 7 has a high viscosity, it must be press-fitted into the mold with a very large pressure. For this reason, it is necessary to change the iron core 1 to deteriorate the electrical characteristics, or to make the molding press-fit path unnecessarily large.In addition, the primary terminal 5, secondary terminal 6, base 2, etc. must be designed to withstand the molding pressure. There was a tendency for the shape to become larger. (3) Electrical devices using both casting and molding Rubber molding has the disadvantage that the molding material cannot fill minute gaps due to its high viscosity. In order to compensate for this drawback, there are cases where the details are filled with epoxy resin etc. in advance and then rubber molded, or the outer shell is formed by rubber molding and then epoxy resin etc. is injected inside. In either case, the manufacturing process was complicated, the workability was poor, and the shape became large. This invention was made to solve the above-mentioned problems. It can be cast with low viscosity, has a very long pot life, has extremely excellent rubber elasticity after curing, and has electrical insulation properties. To provide a compact and inexpensive cast-molded electrical device with good electrical and mechanical performance by using a liquid rubber flame-retardant composition having excellent arc resistance, tracking resistance, and flame retardancy. With the goal. That is, the inventors of this invention conducted intensive studies on casting materials, and found that 100 parts by weight of a hydrogenated polyhydroxybutadiene polymer and 10 to 150 parts by weight of castor oil, preferably 20 to 150 parts by weight, were used as casting materials.
100 parts by weight, 5 to 60 parts by weight of magnesium hydroxide, preferably 20 to 50 parts by weight, 60 to 180 parts by weight of hydrated alumina, preferably 100 to 150 parts by weight, and an isocyanate represented by the following structural formula as a hardening agent. Compound 11.2-73.9 parts by weight (In the formula, R ₁ , R ₂ and R ₃ are lower alkyl groups n is 1 to
By using a liquid rubber flame retardant composition preferably formulated in the range of 21.9 to 41 parts by weight, it has a low viscosity before curing, a very long pot life, and an extremely excellent after curing. It has been discovered that it has rubber elasticity and is also excellent in electrical insulation, arc resistance, tracking resistance, and flame retardancy. Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 2 is an embodiment of a cast electric device according to the present invention. This is a partially sectional front view showing a fully molded current transformer, and in the figure, 1 to 6 and 9 are the same as the conventional one. 10 is a liquid rubber flame retardant composition. That is, the primary coil 3 and the secondary coil 4 are wound in advance, and the primary coil 3 and the primary terminal 5 are connected and fixed, and the base 2, the iron core 1, and the inner peripheral insulator 9 are set to the secondary coil. 4 is assembled at the same time, and fixed in the mold using the base 2, primary terminal 5, etc. while maintaining the specified insulation dimensions, and then the whole is cast with liquid rubber flame retardant composition 10. It is formed by hardening. According to such a casting electric device, since the mechanical force during casting of the liquid rubber flame retardant composition 10 used as a casting material is very small, it is mechanically stable, and therefore the iron core 1 is stable. Cast-molded electrical equipment that does not deform, does not require the large molding press-fitting path of conventional equipment, can be made smaller and lighter, and has excellent electrical insulation, arc resistance, tracking resistance, and flame retardancy. It is effective in manufacturing. Specific examples of the liquid rubber flame retardant composition 10 and measurement results of its electrical and mechanical properties will be listed below as reference examples. Reference example Hydrogenated product of polyhydroxybutadiene polymer
After kneading 25 g of magnesium hydroxide, 125 g of hydrated alumina, and 3 g of carbon black into a mixture of 100 g and 20 g of castor oil using three rolls,
It was heated to ℃ to make a homogeneous solution. Then, 3-isocyanate methyl-3.5.
5-trimethylcyclohexyl isocyanate
After adding 7.6 g and mixing by heating at 85°C, viscosity measurement was started. The initial viscosity was 71 poise, and it took 52 minutes to reach 1000 poise, so it had a viscosity and pot life that allowed for easy pouring. The electrical and mechanical properties of such a mixture after curing are shown in the table below. 【table】

[Brief explanation of the drawing]

FIG. 1 is a partially sectional front view of a conventional cast electric device, and FIG. 2 is a partially sectional front view showing an embodiment of the cast electric device according to the present invention. In the figure, 10 is a liquid rubber flame retardant composition. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Claims] 1. 100 parts by weight of hydrogenated polyhydroxybutadiene polymer, 10 to 150 parts by weight of castor oil, 60 to 180 parts by weight of hydrated alumina, 5 to 60 parts by weight of magnesium hydroxide.
The structural formula below (in the formula
R ₁ , R ₂ and R ₃ are lower alkyl groups, n is 1 to 4
) 1. A cast-molded electrical device characterized in that it is cast with a liquid rubber flame-retardant composition containing an isocyanate compound represented by the formula in a range of 11.2 to 78.9 parts by weight. 2 The blending ratio of the liquid rubber flame retardant composition is 100% hydrogenated polyhydroxybutadiene polymer.
Parts by weight, 20-100 parts by weight of castor oil, hydrated alumina
The cast electric device according to claim 1, wherein the content is 100 to 150 parts by weight, magnesium hydroxide 20 to 50 parts by weight, and said isocyanate compound 21.9 to 41 parts by weight.