JPH0453041B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention relates to an inorganic insulated wire with excellent electrical properties at high temperatures. [Prior Art] Inorganic insulated wires in which a vitreous composition is baked onto a metal conductor have been known. (Tokuko Showa 37
-2124 Publication, Japanese Patent Publication No. 39-2124 Publication (1985) Such inorganic insulated wires are made of, for example, 20 to 50% SiO ₂ ,
A frit slurry with a composition of 10 to 60% PbO and 10 to 30% _K2O is applied onto the metal conductor wire, fired at 500 to 800℃,
It is manufactured by forming a glassy inorganic insulating film on a conductor. [Problems to be Solved by the Invention] However, the inorganic insulated wire obtained by such a manufacturing method has the following problems, and it is desired to solve them. Since the inorganic insulating coating is formed of a continuous glassy coating and there is a large difference in thermal expansion coefficient between the insulating coating and the metal conductor, thermal strain accumulates in the coating and peeling of the coating is likely to occur. This tendency is especially noticeable when coil-wound, and usually 500
When the film is taken out from a temperature of approximately 20°C to a room temperature of 20°C, the coating may peel off after two or three heat shock tests. As the conductor diameter becomes smaller, the degree of accumulation of the thermal strain increases, and coating peeling becomes more likely to occur.
For this reason, it has not been possible to form an insulating film on a conductor with a diameter of 0.5 mm or less. Therefore, if we try to change the glass composition to reduce the difference in thermal expansion diameter between the metal conductor and the insulating coating or to improve the adhesion to the conductor, it is difficult to change the original characteristics of inorganic insulated wire. High-temperature insulation properties will be greatly reduced. [Means for solving the problem] Therefore, in this invention, lead-containing frit with excellent flexibility and high-melting point inorganic material with good high-temperature insulation properties are used as main ingredients, and in addition to these, lead-containing frit with excellent flexibility and a high-melting point inorganic material with good high-temperature insulation properties are used. coating a metal conductor with a slurry-like coating liquid consisting of a certain bond oxide and a pyrolyzable resin soluble in water or an organic solvent that prevents the solid particles of each of the above components from settling;
By firing to form a porous insulating film with good adhesion, the above problems were solved, and at the same time, variations in film properties during long-term continuous production due to sedimentation of solid particles were avoided. The inorganic insulation of this invention contains 35 to 75 parts by weight of lead-containing frit on a conductor, Al ₂ O ₃ , SiO ₂ , MgO, TiO ₂ ,
25 to 65 parts by weight of one or more high melting point inorganic substances selected from the group consisting of ZrO ₂ and Fe, Ni, Co, Sb, Mo
0.05 to 5 parts by weight of a thermally decomposable resin soluble in water or an organic solvent per 100 parts by weight of a composition consisting of 0.5 to 10 parts by weight of one or more combined oxides selected from the group consisting of oxides of A porous insulating screen is formed by coating with a coating liquid containing 30% of the above resin, adding this to a temperature higher than the thermal decomposition temperature of the resin, causing the resin to thermally decompose and disappear, and then firing at a high temperature. It is. First, the lead-containing frit used in the present invention contains PbO and B ₂ O ₃ , has a predominant PbO content of 50% by weight or more, and has a softening melting point of 700° C. or less. Examples of such frits include those having the compositions shown below. PbO 50-85% (weight%, same below) B ₂ O ₃ 3-9% SiO ₂ 1-4% ZnO 4-15% PbO 50-85% B ₂ O ₃ 3-9% SiO ₂ 2-15% Al ₂ O ₃ 1-8% ZrO ₂ or TiO ₃ 2-10% PbO 50-80% B ₂ O ₃ 2-9% SiO ₂ 1.5-8% Al ₂ O ₃ 0.5-4% ZnO 15-28% This The lead-containing frit is used by melting the glass raw material having the above composition, quenching it in water, and pulverizing it to a density of about 200 mesh, as in the conventional method. In addition, the highly advantageous inorganic substances include Fl ₂ O ₃ ,
One or more of the following oxides are used: SiO ₂ MgO, TiO, TrO ₂ . All of these high melting point inorganic substances have a melting point of
It is an oxide with a high melting point of 1000℃ or higher, and is mainly responsible for the high-temperature insulation properties of the resulting insulating film.Furthermore, during firing, it partially melts into the molten glass of the lead-containing frit, lowering the melting point of the glass itself. It has the function of raising the temperature. Furthermore, the combined oxides include Fe, Ni, Co,
One type or a mixture of two or more types of oxides of Sb and Mo can be used in an arbitrary ratio. This bonding oxide reacts with the conductor during firing to form a strong bonding layer between the insulating coating and the metal conductor, thereby increasing adhesion. The resin used to prevent sedimentation of these inorganic substances and as a binder is one that is soluble in water or an organic solvent and is thermally decomposable. Examples of such resins include polyethylene oxide (molecular weight 100,000 to 3 million).
, polymethyl methacrylate, methyl methacrylate-n-butyl methacrylate copolymer, n
-Butyl methacrylate-isobutyl methacrylate copolymer, ethyl methacrylate-methyl acrylate copolymer, and the like. The mixing ratio of the lead-containing frit, the high-melting point inorganic substance, and the combined oxide is 35 to 75 parts by weight of the lead-containing frit, 25 to 65 parts by weight of the high-melting point inorganic substance, and 0.5 to 10 parts by weight of the combined oxide. It is considered a percentage. If the lead-containing frit is less than 35 parts by weight, the adhesion of the insulation coating to the conductor
It does not have sufficient flexibility, and if it exceeds 75 parts by weight, it becomes difficult to dissipate decomposed gas, causing foaming and blistering, which causes flaking when coiled, which has the disadvantage of not becoming porous. It becomes insufficient, and the thermal shock resistance deteriorates. In addition, if the high melting point inorganic substance is less than 25 parts by weight, the film will lack high-temperature insulation and will not be able to become porous, and if it exceeds 65 parts by weight, the porosity will progress too much and the film will become dangerous. ,
cause inconvenience. Further, the bonding oxide is added in an amount of 0.5 to 10 parts by weight per 100 parts by weight of the mixture of lead-containing frit and pore melting point mineral. If it is less than 0.5 parts by weight, the adhesion of the insulating coating to the conductor will be insufficient, and if it exceeds 10 parts by weight, although the adhesion will be sufficient, there will be a significant tendency for the insulation to deteriorate, which is disadvantageous. and a mixture of a lead-containing frit, a high melting point inorganic substance, and a combined oxide.
The above resin is added in an amount of 0.05 to 5 parts by weight per 100 parts by weight. If the amount added is less than 0.05 parts by weight, the desired effect of preventing sedimentation of solid particles cannot be obtained, and if it exceeds 5 parts by weight, the time required for the resin to decompose and disappear becomes longer and blisters and foaming due to decomposed gas are likely to occur. Therefore, if a sufficient sedimentation prevention effect cannot be obtained even after adding 5 parts by weight, or if blistering or foaming is likely to occur due to decomposed gas, inorganic sediments such as gyrome clay, bentonite, montmorillonite, etc. may be added in addition to the above resins. A combination of inhibitors may also be used. The metal conductor used in this invention is preferably one that has good corrosion resistance at high temperatures, such as nickel-clad copper, stainless steel-clad copper, nickel-clad silver, nickel-iron-clad copper, chromel, constantan, nichrome, tungsten, titanium, A silver-palladium alloy or the like is selected depending on the purpose and use. In addition, the wire diameter of the conductor is not particularly limited, but since the insulating coating is porous, it is possible to reduce thermal strain.
Applicable to relatively small diameter objects, with a minimum diameter of 0.05
Thin wire up to mmφ can be used. Then, a slurry-like composition consisting of a lead-containing frit, a high melting point inorganic substance, a bonded oxide, and a resin is prepared. Specifically, first, a resin is dissolved in water or an organic solvent such as an ester, a ketone, or an aromatic hydrocarbon to prepare a high clay resin liquid. The concentration of the resin liquid is appropriately determined depending on the type of resin and the clay used in the solution, but is usually 7% by weight or less. Next, a lead-containing frit, a high-melting point inorganic substance, and a combined oxide are added to this resin liquid, and the coating liquid is prepared by stirring or kneading in a ball mill, or the lead-containing frit, a high-melting point inorganic substance, a combined oxide, and water or The resin liquid is added to a slurry obtained by mixing and pulverizing a composition consisting of an organic solvent and an organic solvent in a ball mill in advance, and the mixture is mixed to adjust the viscosity, and then used as a coating liquid. The solid content of this slurry-like coating liquid is not particularly limited, but is determined appropriately by taking into account the clay, sedimentation properties of solid particles, coating thickness on the metal conductor, etc., and is usually about 55 to 70% by weight. Ru. Next, the slurry-like coating liquid thus obtained is applied to the surface of the metal conductor and fired at a high temperature to form a film. This coating may be formed by immersing the metal conductor in the coating solution, and the coating thickness may be adjusted by repeating the coating and baking process multiple times as necessary to match the coating thickness of the book. You may do so. Furthermore, prior to firing, the resin is thermally decomposed to disappear. First, the resin is placed in a heating furnace maintained at a temperature at which it can be thermally decomposed, and the resin is heated to be thermally decomposed and volatilized from the coating film as thermal decomposition gas. The heating time is usually in the range of about 1 to 5 minutes, and is determined by the resin content in the coating film, the coating thickness, etc. Once the resin has disappeared from the coating film, the temperature is further increased to a firing temperature of 800 to 1000°C, and firing is performed. The firing time is determined as appropriate depending on the thickness of the coating film, the diameter and type of the conductor, the composition of the coating liquid, etc.
It is usually in the range of 1 to 5 minutes. Through this firing, the glass of the molten lead-containing frit adheres to the surface of the high-melting point inorganic particles, and this glass acts as a binder to bind the high-melting point inorganic particles to each other and fix them on the conductor. It becomes a porous inorganic film. To put it in an analogy, it would be similar to the state of "Awa Okosi". Further, during firing, the bonded oxide causes a reaction between the metal conductor surface and the inorganic coating to form a strong bond, thereby ensuring good adhesion. The thickness of the insulating coating thus fired is usually about 2.5 to 25 μm, but is not limited to this range and can be determined as appropriate depending on the use of the inorganic insulated wire. Note that, if necessary, a resin coating mainly made of silicone resin, fluororesin, uretown resin, etc. can be formed on this insulating coating. [Function] Since the insulating coating obtained from such inorganic insulated wires is porous, the insulating coating does not peel off from the metal conductor even when the wire is wound. It exhibits high resistance to thermal shock. In addition, since the actual constituent material of the coating is a high melting point oxide, it has excellent insulation properties at high temperatures, and some of the high melting point oxides dissolve into the glass of the lead-containing frit during firing. Since the melting point of the glass itself becomes high, even if a glass with a low melting point is used, it can be used up to a high temperature above the melting point of the frit. Furthermore, since it is a porous coating, there is little accumulation of thermal strain even if it is coated on a small diameter conductor, so it can be applied to a thin wire of about 0.05 mmφ. In addition, since resin is used to increase the viscosity of the coating liquid and prevent solid particles from settling, solid particles are uniformly dispersed in the coating liquid regardless of their specific gravity, so the coating process This prevents variations in the properties of the insulating coating or deterioration of the properties due to changes in the composition of the coating. Basic salts such as soda carbonate, sodium nitrite, and barium chloride, so-called "tomegusuri", are used to raise the clay of the coating solution, but when such salts are added, the high-temperature insulation of the insulation coating is It has the disadvantage of decreasing performance. In this regard, in the present invention, since a resin is used and the resin is thermally decomposed and disappeared during firing, no resin remains in the coating, and such inconvenience does not occur. [Examples] Hereinafter, examples will be shown to clarify the effects of this invention. Example 1 A mixture having the composition shown in Table 1 was dispersed in a 1% by weight aqueous solution of polyethylene oxide having an average molecular weight of about 1 million to obtain a dispersion with a solid content of 60%, which was pulverized in a ball mill for 70 hours. all solids
The coating liquid was prepared so that the thickness was 10μ or less. This coating liquid was applied to a Nickelrad copper wire with a diameter of 0.25 mm, and then introduced into a furnace whose temperature was controlled within the range of 500 to 550°C, and heated for 5 minutes to thermally decompose the polyethylene oxide, which caused the coating film to deteriorate. Make it disappear more,
Then, it was fired for 3 minutes in a firing furnace whose temperature was controlled at 800 to 900°C to form an inorganic porous insulation coating with a thickness of 13 μm. The lead-containing frit in Table 1 has the composition shown above, the high-melting point inorganic substance consists of 85 parts by weight of Al ₂ O ₃ and 15 parts by weight of TiO ₂ , and the combined oxides include CoO, NiO, etc. A mixture of amounts was used. Regarding the inorganic insulated wires obtained in this way, ○A adhesion and flexibility of the insulation coating ○B High-temperature insulation properties ○C Thermal shock resistance ○D Variations in the properties of the insulation coating were investigated. Regarding adhesion and flexibility,
An insulated wire was wound into a coil with a diameter 10 times its outer diameter, and the presence or absence of peeling of the insulating coating was evaluated by microscopic observation. High temperature insulation is 500 by JIS 2-stranded sample.
The insulation resistance and breakdown voltage (BDV) at ℃ were evaluated. Thermal shock resistance is measured by repeatedly testing a coil wound around a 20x diameter bobbin at 600°C for 15 minutes, then immediately taking it out into the air at 20°C, and determining the cycle in which the coating layer of the coiled wire peels off. Evaluated by number. In addition, variations in the characteristics of the insulation coating can be determined by measuring the breakdown voltage (BDV) at 500°C for a total of 30 samples taken from every 100 m of wire length, and calculating the average value of these,
Evaluation was performed by finding the standard deviation. The results are shown together with the first vote.

[Table] For comparison, we measured the dielectric breakdown voltage of the mixture of Formulation Example 3 dispersed in water, and calculated the average value and standard deviation.
It was 160V, 11.3. Example 2 The coating liquid of Formulation Example 3 in Example 1 was
Nickel clad copper wires of 0.1 mm, 0.2 mm, 0.3 mm, 0.5 mm, and 1.0 mm were coated and fired in the same manner as in Example 1. These inorganic insulated wires were coil-wound onto a bobbin with a diameter 20 times larger, and their thermal shock resistance was examined under the same conditions as in Example 1. The results are shown in Table 2.

〔Effect of the invention〕

As explained above, according to the inorganic insulated wire of the present invention, the mixing ratio of the lead-containing frit and the high melting point inorganic material is such that a continuous glass coating cannot be formed, so the resulting insulating coating is porous. This results in an insulating coating that has good flexibility and is resistant to thermal shock. Furthermore, since a bonded oxide and a flexible lead-containing frit are used, the adhesion of the coating is increased. Furthermore, since a high melting point inorganic substance with a high melting point and high insulation properties is used as a substantial constituent material of the coating, the insulation properties at high temperatures are also excellent. Furthermore, since the insulating coating is porous and made of a high-melting-point inorganic material such as silica or alumina that has high hardness, an inorganic insulated wire with good wear resistance can be obtained.
Furthermore, water is used to increase the viscosity of the coating liquid by adding a thermally decomposable resin soluble in an organic solvent to uniformly disperse solid particles with different specific gravities. Since there is little variation in the temperature and the resin added has excellent thermal decomposition properties, excellent effects can be obtained without causing problems such as decomposition products remaining during firing and deterioration of insulation properties.

Claims (1)

[Claims] 1. 35 to 75 parts by weight of a lead-containing frit containing PbO and B ₂ O ₃ and having a softening and melting point of 700°C or less, and from Al ₂ O ₃ , SiO ₂ , MgO, TiO ₂ , ZrO ₂ 25 to 65 parts by weight of one or more high melting point inorganic substances selected from the group consisting of; and 0.5 to 10 parts by weight of one or more combined oxides selected from the group consisting of oxides of Fe, Ni, Co, Sb, and Mo. 0.05 to 100 parts by weight of a pyrolyzable resin soluble in water or an organic solvent,
1. An inorganic insulated wire characterized in that a porous inorganic insulating coating is formed by firing a mixture in which 5 parts by weight is added.