JPS5916710B2 - Sea heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the insulation resistance characteristics of a sheathed heater due to moisture absorption.

In a conventional sheathed heater, as shown in FIG. 1, an electrically insulating material 4 is generally filled between a metal pipe 1 and a coiled heater 3 to which a terminal bar 2 is welded.

In this case, magnesia 5 powder is most widely used as the electrical insulating material 4, but since magnesia powder is hygroscopic, it has the disadvantage that it easily absorbs moisture in the indoor atmosphere and deteriorates the insulation resistance. Therefore, by mixing silicone resin with this magnesia powder and heating it to form a silicone resin film '0 on the surface of the magnesia powder, the surface of the filler becomes water repellent, does not easily absorb moisture from the outside, and has insulation performance. Methods have been proposed to prevent the deterioration of However, with this method, the heat resistance of the silicone resin is approximately 35.
Because of its low temperature of 0'C, '5 had the disadvantage that after high temperature use, its water repellency deteriorated due to the decomposition of the silicone resin, and the filler absorbed moisture in the indoor atmosphere, causing deterioration of its insulation properties. The present invention is intended to overcome such drawbacks, that is, to prevent the insulation properties j0 from deteriorating even when the sheathed heater is used at high temperatures, the surface of the magnesia powder used as an electrical insulating material itself has a repellent material that does not deteriorate even after high-temperature heating. To provide a sheathed heater that is water-based and does not deteriorate even after long-term use. Hereinafter, one embodiment of the present invention will be explained based on FIG.
In the figure, reference numeral 5 denotes a metal pipe constituting the outer casing of the sheathed heater, which has a heater 6 at its center, and terminal rods 1 protruding from the metal pipe 5 at both ends of the heater 6, respectively. Reference numeral 8 denotes an electrical insulating material in which a borazole polymer is mixed with magnesia 0 powder filled in the metal pipe 5.

By energizing the sheathed heater made as above, V)
The mixed and applied borazole polymer is heated to lower its viscosity and adheres to the magnesia surface to form a borazole polymer layer, thereby making the filler water repellent.

The borazole polymer is an inorganic polymer compound obtained by polymerizing borazole, and is a water-repellent polymer that is stable up to about 600°C, as its general formula is shown below.

A sheathed heater using magnesia coated with the above polymer as an insulating material has improved heat resistance and water repellency than one coated with silicone resin, and can withstand use up to approximately 600°C. Ta.

As described above, the sheathed heater of the present invention has a borazole polymer layer on the surface of the particles of the filling material that insulates and holds the heater and the terminal part in the metal pipe, so it has water repellency and the filling material does not resist at high temperatures. It does not lose its water repellency even after being heated. Furthermore, even when the polymer decomposes, it becomes an electrical insulator and retains its electrical insulation properties, making it of great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional sheathed heater, and FIG. 2 is a sectional view of a sheathed heater according to an embodiment of the present invention. 5... Metal pipe, 6... Heater, r
...Terminal bar, 8...Electrical insulating material.

Claims (1)

[Scope of Claims] 1. In a sheathed heater in which an electrical insulating material such as magnesia powder is filled between a coiled heater equipped with a terminal bar and a metal pipe, the filling material contains a general formula ▲mathematical formula, chemical formula, or table. etc.▼ A sheathed heater characterized in that a borazole polymer represented by the following formula (R in the formula is an organic group) is mixed and filled into the metal pipe.