JPH04147518A - Heat-proof insulated electric wire and manufacture thereof - Google Patents

Abstract

PURPOSE:To realize the forming of a heat-proof insulated electric wire having an excellent heat-proof ability and a highly excellent insulating ability as well by coating a base material for an electric wire with ceramics having a silicon nitride quality or its precursor body which is induced from polysilasane and has a specific carbon containing ratio. CONSTITUTION:A heat-proof insulated electric wire is formed by coating a base material for an electric wire with ceramics having a silicon nitride quality or its precursor body which is induced from polysilasane and has carbon containing ratio of not more than 5weight%. In order to manufacture the electric wire coated with the ceramics having the silicon nitride quality or its precursor body, the polysilasane is used as a coating material, and this is coated with the base material for the electric wire, and after a polysilasane coat is formed on the surface of the electric wire, heat treatment is carried out on this. If the polysilasane is in liquid condition, after this is coated on the surface of the base material of the electric wire, it is kept at a temperature between the normal temperature and about 400 deg.C, preferably at 80-200 deg.C for a prescribed time under the atmosphere of air, inactive gas or reducing gas. Thereby, a coat consisting of solid state polysilasane having a cross-linking structure can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a heat-resistant insulated wire that can be used even in a high temperature range of 300° C. or higher, and a method for manufacturing the same.

(Prior art and its problems) Traditionally, polyimide wires have been used as heat-resistant insulated wires.

Polyamide-imide wires are known, but these
Since the constituent material of the insulating layer is an organic material, there is a natural limit to its heat resistance, and its maximum operating temperature is usually up to about 250°C. Also, what is known as heat-resistant wire is glass winding wire, which is insulated by wrapping glass thread around the conductor once or twice.
The glass thread itself is an inorganic material and has excellent heat resistance, but an organic substance, such as an insulating paint such as alkyd resin, is usually applied between the glass threads to improve insulation and prevent the threads from fraying or fuzzing. To be there.

Its heat resistance was at most 180°C.

In response to this, studies have been conducted to use various inorganic-containing paints as insulating layer constituent materials, but the inorganic insulating wires obtained in this case are generally hard and brittle, and have poor flexibility and require coil winding. For example, ^a, 0. or Cr, 0. An inorganic wire made by dispersing inorganic substances such as in a solvent and coating and firing it on a conductor has been studied (Japanese Patent Application No. 2-86008), but it has poor flexibility and adhesion to the conductor, and the coating is generally porous. To become.

It has poor insulation properties and has not been put into practical use yet.

Furthermore, heat-resistant electric wires using organometallic polymers such as polycarbosilane, polysilastyrene, polytitanocarbosilane, and polyborosiloxane have been developed (Japanese Patent Application No. 2-86013); Due to the presence of free carbon (usually greater than IO weight S), there is a limit to the insulation properties. Similarly, these organic polymers have low thermal decomposition yields (usually 70% by weight or less),
There was a limit to how dense or thick the film could be.

(Problem of the Invention) An object of the present invention is to solve the above-mentioned problems found in conventional heat-resistant electric wires and to provide a heat-resistant electric wire that can be used in a high temperature range of 300°C or higher even at %%, and a method for manufacturing the same. shall be.

(Means for Solving the Problems) The present inventors have conducted extensive research to solve the above problems, and as a result, have completed the present invention.

According to one aspect of the present invention, there is provided a heat-resistant insulated wire in which a wire base material is coated with a silicon nitride ceramic derived from polysilazane and having a carbon content of 5% by weight or less, or a precursor thereof.

Further, according to the present invention, after forming a film of nitrogen-containing polysilazane on the surface of an electric wire base material, the film is converted by heating into a silicon nitride ceramic having a carbon content of 5% by weight or less or a precursor thereof. A method of manufacturing a characteristic heat-resistant insulated wire is provided.

In addition, the silicon nitride ceramic precursor referred to in this specification is a heat-resistant material containing hydrogen and l or carbon in the molecule, which is generated during the ceramic formation process when polysilazane is heated and raised to form a ceramic. means a cured polysilazane product.

In the present invention, various conventionally known polysilazane can be used as the raw material for coating the silicon nitride ceramic or its precursor, but the following polysilazane is preferable.

(1) Number average molecular weight having a repeating unit of the general formula is 100-50,
000 cyclic inorganic polysilazane, linear inorganic polysilazane or a mixture thereof.

(2) Polysilazane or A as described above as a raw material.

5tock, Ber, 54. p740 (1921), V
, M, 5cantlin, Inorganic Che
mistry, 11 (1972), A, 5eyFert
h, the silazane polymer disclosed in U.S. Pat. No. 4,397,328, etc., is combined with tertiary amines such as trialkylamine, secondary amines having a sterically hindered group, phosphine, etc. Number average molecular weight 200-SOO obtained by using a basic compound as a solvent or adding it to a non-basic solvent such as hydrocarbons and heating at -78°C to 300°C to perform a dehydration condensation reaction.

000, preferably from 500 to 100,000.

(3) A polymer obtained by a modification reaction of inorganic polysilazane, which has a cross-linked bond (NH)-n (n = 1 or 2), and has an atomic ratio of nitrogen bonded to silicon atoms and silicon (N/Si
) is 0.8 or more and the number average molecular weight is 200 to soo, oo
o, preferably between 500 and 100,000. This modified polysilazane can be produced by carrying out a dehydrogenation condensation reaction of polysilazane using ammonia or hydrazine (Japanese Patent Application No. 62-202767).

(4) Composition formula (R5iHN)I) x ((R5iH),
,,N), -x (wherein R is an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, or a group other than these groups in which the atom directly connected to Si is carbon, an alkylsilyl group, an alkyl group) Represents an amino group, an alkoxy group,
and 0.4<x<1) (Japanese Patent Application No. 60-293472). -26881) and polymetallosilazane (patent application 1986-
223790), polyborosilazane reacted with an organic boron compound (Japanese Patent Application No. 1-69169), etc. may also be used. The various types of polysilazane described above, depending on the type,
Shows liquid to solid state at room temperature.

In order to manufacture the silicon nitride ceramic or its precursor coated wire of the present invention, the polysilazane is used as a coating material, and the wire base material is coated with the polysilazane to form a polysilazane coating on the wire surface, which is then heat-treated. do. If the polysilazane is in liquid form, after coating the surface of the wire base material, it is coated in an atmosphere of air, inert gas (for example, N2, argon, etc.), or reducing gas (for example, ammonia, hydrazine, etc.). Temperature between room temperature and about 400°C, preferably 80-200”C
The temperature is maintained for a certain period of time. As a result, a film made of crosslinked solid polysilazane is obtained. Also,
If the polysilazane is solid (powder), it is dissolved in an organic solvent, this solution is coated on the surface of the wire base material, and the used organic solvent is removed by evaporation to form a solid polysilazane coating. be able to.

Coating materials containing polysilazane include organic amines, carboxylic anhydrides, isocyanates, thiols, carboxyimides, and metal alkoxides.

A hardening agent such as a metal halide can be added, and the ceramic powder 1 can be added with a hardening agent such as a metal nitride, oxide,
An appropriate amount of carbide or the like can be added, and a suitable amount of silicone resin can also be added.

The heat treatment of the polysilazane coating is carried out at 100°C or higher in an atmosphere of air, inert gas, or reducing gas as described above.
Preferably it is carried out at a temperature of 200 to 1300°C. In this case, the temperature increase rate is 100°C/min or less, preferably 20°C
/minute or less. By heat treatment, the polysilazane film becomes 5
The film is made of silicon nitride ceramics or its precursor having i-N bonds. In this case, in the heat treatment under air or oxygen atmosphere, the condensation or decomposition of polysilazane is promoted by the action of oxygen, and when heated at a temperature of about 100 to 300 ° C., a ceramic precursor containing hydrogen and/or carbon is produced. When heated above about 300° C., a ceramic is formed that substantially does not contain hydrogen or carbon. The ceramics thus formed are 5i-N and 5i-
It mainly includes a bond consisting of 0. On the other hand, when heating under an inert gas or reducing atmosphere, 500
When heated to about ℃, dehydrogenation condensation of polysilazane mainly occurs, and ceramic precursors containing hydrogen and/or carbon are produced, and at higher temperatures, polysilazane mainly decomposes and has -5i-N bonds. Ceramics are formed.

Further, by preheating the polysilazane film and then heat-treating it in an oxidizing gas atmosphere, at least the surface layer of the silicon nitride ceramic film can be formed into an oxide layer. This surface layer has 5i-N-0 bonds, and specifically, this surface oxide layer has (
a) Amorphous consisting essentially of SxpN*O; or (b) an aggregate consisting of solid-quality SiO□ and Si□N,0; or (c
) Consists of a mixed system of the above (a) and (b).

The thickness of the surface oxide layer can be controlled by the type of oxidizing gas, firing temperature, and firing time, but is usually 0.0
1-5, preferably 0.11-3p.

The temperature of the preliminary heat treatment is 400 to 1300°C, preferably 400 to 1000°C, and the firing temperature in an oxidizing gas atmosphere is 300°C or higher, preferably 400 to 140°C.
It is 0°C. This method also makes it possible to obtain a ceramic coating having an oxide layer on one surface.

In the present invention, when forming a silicon nitride ceramic coating having an oxide layer on the surface, the ratio of oxygen atoms to silicon atoms in the oxide layer (0/Si) is 0.
．． 1-1.95, preferably 0.2-1.9.

In the present invention, when the polysilazane coating is made into a ceramic, the free carbon content in the ceramic is 5 parts by weight or less, preferably 3 parts by weight or less. Such ceramics with a low free carbon content or containing no carbon can be formed by using polysilazane with a low carbon content or containing no carbon, and also by using an inert gas during the heat treatment of the polysilazane coating. It can be formed by using a non-oxidizing atmosphere such as ammonia gas or the like.

The basic method for forming a polysilazane film on the wire base material is to apply a coating solution containing polysilazane to the wire base material by dipping, etc., but ceramic fibers such as glass fibers and alumina fibers containing polysilazane There are two methods: applying a coating liquid by dipping, etc., and wrapping it around the wire base material; or wrapping ceramic fibers such as glass fibers or alumina fibers around the wire base material, and then applying a coating liquid containing polysilazane to the wire base material, by dipping, etc. There are various methods of applying it.

Various metal wires including copper wire are used as the wire base material.

(Effects of the Invention) The electric wire of the present invention has a silicon nitride ceramic coating on its surface and has excellent heat resistance, and furthermore, the carbon content in the ceramic coating is specified to be 5% by weight or less. From, I! The relationship is also very good.

The heat-resistant insulated wire of the present invention is suitable for use in nuclear power generation, geothermal power generation, and other special high-temperature environments.

As described above, the method for manufacturing a heat-resistant insulated wire of the present invention includes:
Since it consists of a coating process and a heating process, it is easy to carry out, and has the advantage that the yield of ceramic coatings from polysilazane coatings is extremely high, at 85% by weight or more.

(Example) Next, the present invention will be explained in more detail with reference to Examples.

Example 1 A copper wire with a diameter of 1 mm was impregnated with a 20 wt % ortho-xylene solution of inorganic polysilazane (number average molecular weight: 1450, Si/N ratio: 1.33), and left at room temperature for 2 hours to dry.

Next, the inorganic polysilazane was heated to 500°C in a ~2 atmosphere to form a ceramic. The thickness of the obtained insulating ceramic layer was 1-, and its carbon content was 0.4% by weight. .

Example 2 A copper wire with a diameter of 1 was impregnated with a 20w1J ortho-xylene solution of an inorganic polysilazane (number average molecular weight 1450, Si/N ratio 1.33) and left at room temperature for 2 hours to dry.

Next, the inorganic polysilazane was heated to 500° C. in an air atmosphere to form a ceramic. The thickness of the obtained insulating ceramic layer is IIIm, and its carbon content is 0.3
% by weight.

Example 3 A copper wire with a diameter of b + 100 mm was impregnated with a 20 wt % ortho-xylene solution of inorganic polysilazane (number average molecular weight: 1450, Si/N ratio: 1.33) and allowed to stand at room temperature for 2 hours to dry.

Next, the inorganic polysilazane was heated to 200° C. in the air to form a ceramic. The thickness of the obtained insulating ceramic layer was IIIa, and its carbon content was 0.8
% by weight.

Example 4 Eleven diameter wires were impregnated with a 40-t% ortho-xylene solution of inorganic polysilazane (number average molecular weight 1450, Si ratio 1.33) and left at room temperature for 2 hours to dry.

Next, the inorganic polysilazane was turned into a ceramic by heating to 200° C. in an air atmosphere. Obtained. Il! The thickness of the neutral ceramic layer was 1.5 and the carbon content was 1.0 by weight.

Example 5 A copper wire with a diameter of 1 mm was impregnated with a 20 wt % ortho-xylene solution of inorganic polysilazane (number average molecular weight 1630, SL/NLiNO2) and left at room temperature for 2 hours to dry.

Next, the inorganic polysilazane was heated to 200° C. in an air atmosphere to form a ceramic. The thickness of the obtained insulating ceramic layer was l/j11, and its carbon content was 0.
It was 7% by weight.

Example 6 0.05 wt% ortho-xylene solution of inorganic polysilazane (number average molecular weight 1450, Si/N ratio 1°33)
Is MgO fine powder was added 3 times the weight ratio to polysilazane and mixed in a ball mill to form a slurry. A copper wire with a diameter of 111ffl was impregnated with this slurry and heated at room temperature for 2
Leave it for a while to dry. Next, in an N2 atmosphere, 500
The inorganic polysilazane was turned into a ceramic by heating to ℃. The thickness of the obtained insulating ceramic layer was soIlm, and its carbon content was 0.3% by weight.

Next, the I! of the electric wire obtained in the above example will be explained. The results of the edge characteristic evaluation are shown in the table below.

Claims (5)

[Claims] (1) A heat-resistant insulated wire comprising a wire base material coated with a silicon nitride ceramic derived from polysilazane and having a carbon content of 5% by weight or less, or a precursor thereof. (2) A heat-resistant insulated wire characterized by forming a polysilazane film on the surface of the wire base material and then converting the film into silicon nitride ceramic or its precursor with a carbon content of 5% by weight or less by heating. Production method. (3) The method according to claim 2, wherein a polysilazane coating is formed on the surface of the wire base material by applying a coating liquid containing polysilazane to the wire base material. (4) The method according to claim 2, wherein a polysilazane coating is formed on the surface of the electric wire base material by winding ceramic fibers having a polysilazane coating on the surface of the electric wire base material. (5) The method according to claim 2, wherein a polysilazane coating is formed on the surface of the wire base material by winding ceramic fibers on the surface of the wire base material and then applying a coating solution containing polysilazane.