JPS6155812A - Flame resistant electric insulator and method of producing same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to fire-resistant vL electrical insulation. The insulator of the present invention exhibits excellent performance especially as an insulator for [9c wiring of emergency equipment] in preventing dielectric breakdown caused by heat of fire.

As fire-resistant electrical insulators, materials whose main component is asbestos have been used for a long time, but in addition to lacking fire resistance, they also have the disadvantage of being carcinogenic, so they have been used less and less in recent years. It's starting to disappear.

In place of this, electric wires using various ceramic hollow moldings as insulators, V-shaped wires, and wires coated with ceramics, etc., have come into use, but they lack flexibility and are difficult to install. There are some serious drawbacks.

Electrical insulators made from various flame-retardant organic materials and glass fibers are used as heat-resistant electrical insulators under limited conditions. However, flame-retardant organic materials gradually carbonize and lose their insulating properties at high temperatures. Glass fibers also become electrically conductive when melted. These materials exhibit sufficient performance as electrical insulators for emergency equipment only when they are embedded in thick heat insulators.

However, it is desirable that the electrical insulators in emergency equipment do not lose their insulating properties until the conductive material (e.g., copper wire) reaches its melting temperature and do not cause short circuits or grounding. Various proposals have been made regarding insulating materials having such performance.

US Pat. No. 3,095,336 describes a glass fiber fabric coated with a thermosetting resin filled with ceramic particles. Although this material is considered as an intermediate for ceramic moldings, it could also be used as a refractory insulator. Japanese Patent Publication No. 7897/1989 describes a wire coating in which alumina, silica, etc. are dispersed in an insulating phenol. The disadvantages of this method are that workability deteriorates rapidly when the amount of ceramic particles dispersed is increased, and that the strength of the coating layer is almost lost when the face part is thermally decomposed. This is because fire resistance cannot be obtained. Japanese Patent Publication No. 49-12061 describes a method of coating an insulating face with inorganic powder, but this method also has the disadvantage that the coating layer loses almost all of its strength when the face is thermally decomposed. . Also, JP-A-56
No. 162,416 describes using glass A fiber as a base fabric and coating it with ceramic particles with an organic binder containing colloidal silica. The problem with this method is that the bonding strength between the ceramic particles is insufficient, and if the coating layer is exposed to a temperature below the softening temperature of glass fibers for a long time at the temperature at which the organic binder decomposes, the coating layer loses its integrity, resulting in vibrations, etc. It becomes extremely weak against fire and exhibits no fire resistance.

As a result of studying the problems of the prior art, we have found a combination of materials with good integrity of the coating layer, excellent visibility and moldability, and arrived at the present invention.

The electrical insulator of the present invention is produced by coating an electrically insulating refractory powder on a base fabric containing glass H1 fibers with an intermediate coating layer having a thickness of 0.5 μm to 200 μm containing an organic polymer as a main component. It is characterized in that the granular sintered material layers are in close contact with each other, and the apparent volume resistivity at 950° C. is 10 6 Ω·α or more.

The electrical insulator of the present invention is produced by forming a coating layer mainly composed of an organic polymer on a base fabric mainly composed of gaffus m-fibers, solidifying it, and then thermally spraying it using electrically insulating refractory powder. The refractory is manufactured by forming a coating layer of powdered sintered material by a method.

Thermal spraying of refractories onto glass fibers is extremely difficult because the fibers are severely degraded by the heat brought by the particles. Deterioration of glass fibers due to thermal spray particles decreases as the fiber diameter increases, but there is a problem in that the strength of glass fibers decreases rapidly as the fiber diameter increases. Furthermore, as the diameter of the glass fibers increases, the glass fiber cloth becomes less hard and less flexible, resulting in poor secondary processability. Making the spray particles smaller tends to reduce the deterioration of the glass fibers, but since the cooling rate of the spray particles increases, it becomes necessary to place the glass fibers in close proximity to the heating fluid such as the plasma flame, so the effect of reducing the particle size is It's not very big. Moreover, the smaller the particle size is, the more difficult it is to make the particle size uniform, and the yield rate during thermal spray processing becomes worse.

Garanu I! For these reasons, it is extremely difficult to thermally spray refractories on c-fibers, but on the other hand, the thermally sprayed coating layer has many advantages that cannot be obtained with other methods, and exhibits desirable properties as an electrical insulator. For example, it is possible to obtain a higher level of fire resistance than conventionally used ceramic insulators. This is because the heating medium used in thermal spraying is extremely high temperature, such as arc plasma, so there is a large degree of freedom in material selection. It also has the advantage of being less corrosive to conductive materials such as copper wire.

This is because it does not contain organic substances, alkalis, halogens, etc. that cause corrosion. Another advantage is that it has a small coefficient of thermal expansion and is resistant to thermal shock.

Although the cause of this has not been fully elucidated, this property is considered to be extremely desirable as a material for emergency electrical equipment.

As a result of various studies on ways to reduce the deterioration of glass fibers when thermal spraying them with refractories, we found that it is effective to coat the glass fibers with an organic polymer layer and then process them. We have arrived at the present invention.

The thickness of the coating layer is 0.5 μm to 200 μm.

If the thickness is less than 0.5 μm, the protective effect for glass fibers will be insufficient, and if it is more than 200 μm, when heated as an electrical insulator, the gap between the base fabric and the sprayed layer will be too large. This is undesirable because it is not possible to fill the gap due to shrinkage, making it more likely to be damaged by vibrations. The thickness of the coating layer is 5μm to 50μm
m is preferred. The polymer material for the coating layer may be any material as long as it adheres to the glass fibers, but in particular polyolefins, methacrylic acid polymers,
Particularly preferred are acrylic acid polymers, PVA, polystyrene polymers, polyesters, aliphatic polyamides, polystyrene polymers, and the like. It is preferable that an inorganic filler is added to the coating layer in order to reduce the amount of heat generated during heating. As fillers, aluminum hydroxide, alumina, chestnut, magnesia, titania, zirconia,
Calcium carbonate, magnesium carbonate, mica, and clay, which is a raw material for refractories, can be used. Any filler can be used as long as it does not react with the sprayed refractory to produce a substance with a low softening point.

Methods for forming the coating layer include methods of dissolving the organic polymer in a solvent and coating it, coating a dispersion of the organic polymer, coating a melt of the organic polymer, and coating the organic polymer by dissolving it in a solvent. A method of coating by heating the powder of a polymer at high temperature VCj A method is used in which the base fabric is coated with a polymer using the above-mentioned coating method and then polymerized to form a polymer.

In the present invention, the base fabric mainly composed of glass fibers includes woven fabrics, knitted fabrics, nonwoven fabrics, and paper made of glass fibers. This base fabric can contain sizing agents, oils, adhesives, flameproofing agents, and colorants, and can also contain various organic Rm, inorganic fibers other than glass Rm, and various powders. It is possible.

In the present invention, any method applicable to refractories can be used for thermal spraying, but among them, a method using arc plasma is most preferred. The operating conditions of the thermal spray gun are almost the same as in the normal case, but the base fabric needs to be strongly cooled in the area that is being thermally sprayed. Further, it is preferable to perform thermal spraying in small amounts at intervals. During thermal spraying, the base fabric is brought into close contact with a support device made of a material with high thermal conductivity that is subjected to forced cooling. Since it is difficult to use a device that presses the support device, the support device is made to have a cylindrical or other convex curved surface and is press-bonded by applying tension to the base fabric. The magnitude of the tension may be such that the base fabric does not flutter due to the flow of thermal spray fluid. It is preferable that the support device is cooled by flowing a fluid therein, and it is more preferable to adjust the temperature of the support device by adjusting the flow rate or the like.

Preferably, the part that is being thermally sprayed is cooled separately by an air stream. This cooling air flow is measured at a distance of 1 m/sea to 50 m/sea at a location 1z closer to the cooling air outlet from the location where the thermal spraying process is performed, with the movement of the support device and the operation of the thermal spray gun stopped. Preferably, it is δec.

When performing thermal spraying, it is preferable to move the support device and the thermal spray gun at high speed to reduce the amount of heat that the base fabric receives during one thermal spraying process. The contact time with the thermal spraying fluid during one thermal spraying is preferably 1/1000 second to 1/10.

If the contact time is too short, the sprayed refractory particles will be cooled too quickly, making sintering difficult, and the adhesion of the sprayed layer will deteriorate. The weight of the sprayed layer coated by one thermal spraying is 5 mg for the area of the base fabric 10I, os, g or 5 mg.
is preferred.

The refractory to be thermally sprayed is one that has good insulation properties at high temperatures. Although alumina refractories exhibit excellent properties, mullite refractories such as chamotte, silica, zirconia, zircon, and mixtures thereof can also be used.

If the refractory powder sintered material layer produced by thermal spraying is too thin, it will suffer erosion from the molten glass when heated above the flow temperature of the glass fibers and its electrical insulation will deteriorate. If it is too thick, flexibility will be poor and secondary processing and molding will be difficult. In particular, in the case of electric wire coatings, it is desirable that they have high flammability since they can be bent with a small radius of curvature. The thickness of the refractory powder sintered material layer is from 10 g/m to 1000 g/m as the surface density based on the area of the sheet-like electrical insulator.
g/m is preferred. A wire coating of 20 g/rn to 200 y/m is particularly preferred.

There is also a suitable range for the ratio of the thickness of the powder sintered material layer of the refractory to the thickness of the base fabric whose main component is glass fiber, and the thickness of the sintered material layer is the same as the thickness of the base material. If the thickness is smaller than that, the sintered material layer generally tends to be easily damaged. If it is too large, the effect of thermal deterioration of glass R#: during thermal spraying processing may be small in relative value, but the absolute value will be so large that it cannot be ignored, which is not preferable because the secondary processing will be short. The weight ratio of the sintered material layer to the base fabric is preferably between 1:20 and 5:1.

The fire-resistant electrical insulator of the present invention can be coated with another type of electrical insulating material before or after being formed into electrical equipment, wiring, etc. Such coatings improve the mechanical and electrical strength of the refractory electrical insulation of the present invention. The materials used for these processes do not necessarily have to be flame retardant. Rather, it is preferable to use a material that easily decomposes and vaporizes in a heated environment such as a fire, and does not leave any carbide. Specifically, phenolic resins that easily carbonize, melamine jutsuji, aramid, Selerose, polyacrylonitrile, etc. are not preferred, and polyolefins that do not easily carbonize, soft vinyl chloride, polyvinyl alcohol, polyester, aliphatic polyamide, acrylic acid derivative polymers, Preferred are methacrylic acid derivative polymers, polystyrene, and the like.

The fire-resistant electrical insulator of the present invention can be produced by heating at 950°C for 1 hour! There is very little change in gas insulation properties. It also exhibits sufficient insulation properties even when heated. Therefore, in the event of a fire, the heat will not cause a short circuit or grounding, so it exhibits excellent performance as an insulator for emergency power supplies. 9
The decrease in insulation properties is not noticeable in the temperature range of 50℃ or higher, but in the range of 950 to 1050℃, oxidation of the copper wire rapidly progresses and it becomes difficult to conduct electricity, so the heat resistance of the insulator is 950℃. considered to be sufficient.

Next, the present invention will be explained by examples.

Example 1 Polyvinyl alcohol-1v (polymerized pi17o,
.

Completely saponified product) 5 parts, hydroxide aluminum aluminum worm 5 parts, water 9 parts
Apply a solution consisting of 0 parts, dry at 70'(1'),
A coating layer of 45/l/rrL was formed. The coating layer is mainly formed on one side of the fabric, so that the fabric has a thickness of about 10 μm.
It got thicker. Note that if the same amount of coating layer is formed on a plate without pores, the thickness will be about 25 μm.

Alumina powder (105 manufactured by MeLco) was sprayed onto this sheet by a plasma method. Argon plasma containing a small amount of hydrogen was used as plasma. The sheet material was attached under tension to a metal roller with forced ventilation in the center cavity, rotated at a surface speed of 140 m/min, and the distance 11L between the sheet material and the spray gun was set to 200 m/min.
Thermal spraying was performed using mrn.

The contact time between the plasma flame and the sheet material is approximately 4×
IO paper, the amount coated in one spray is 2 x 1
It was 0.09 parts cm. 25 times ab by moving the spray gun
The spray was then sprayed again to form a sintered material layer of 5097 m2.

The sheet-like material after thermal spraying exhibits an electrical resistance of 9×10 Ω/cm. This sheet was sandwiched between platinum electrodes and pressed between chamotte bricks, and the temperature was increased at a rate of 5 to 10<6 >C/min under a pressure of 0.5 kg/Cm to measure changes in electrical resistance. The results are shown in Table 1.

Although the stain resistance decreases to approximately 1150 by heating at 950'C for 1 hour, the apparent volume resistivity is still 10Ω.
・It is on the order of 200 yen, and is within the range that can be used as an insulating material.

This sheet-like material was slit to a width of about 20 mm and wound around a copper wire bundle having a diameter of 2 mm. When wrapped with a refractory powder sintered layer on the inside, the coating layer does not crack during the wrapping process, and does not catch fire even when heated in air up to 950°C.
There was very little smoke.

The one heated at 9500G for 1 hour has grains remaining even though the temperature is at which the glass fiber melts, the glass fiber is in an incompletely melted state, and a part of the inner refractory powder sintered layer is The prototype was stopped.

This sheet-like material was heat-treated in air at 300° C. for 3 hours, which is a condition in which the organic component Polyvinyl Fluco-P is decomposed and the glass fibers are not deteriorated. Although the strength of the sheet did not change much, the sintered material layer was slightly easier to peel off. Regarding the degree of ease of peeling, when the sheet is heat treated in a flat state, peeling due to sellotape or brushing occurs locally, which did not occur at all before treatment, but when the sheet is wrapped around copper wire, peeling occurs locally. No particular change was observed when heated, and it is considered to be a minor change.

Example 2 When chamotte refractory powder having approximately the same particle size was used as a base for the alumina powder in Example 1, a similarly excellent refractory electrical insulator was obtained.

Example 3 When a Si-Conia material with approximately the same particle size was used for the 7-lumina powder powder in Example 1, a similarly excellent fire-resistant electrical insulator was obtained.

Example 4 Polymethyl methacrylate (molecular weight approximately 800) was used instead of the aqueous polyvinyl alcohol solution of Example 1 as a coating material mainly consisting of an organic polymer to form the intermediate coating layer.
When a solution containing 4 parts of silica powder, 8 parts of finely divided silica (average particle size 50 mμ, surface treated to make it lipophilic), and 88 parts of methyl ethyl ketone was used, a similarly excellent fire-resistant electrical insulator was obtained.

Example 5 On the same base fabric as in Example 1, the same intermediate coating layer and the same sintered powder layer were formed with different weights to form a sheet-like article. Table 2 shows the performance of this sheet-like material.

Claims (1)

[Scope of Claims] 1) An electrically insulating refractory material is formed on a base fabric mainly composed of glass fibers through an intermediate coating layer having a thickness of 0.5 μm to 200 μm and mainly composed of an organic polymer. A fire-resistant electrical insulator characterized by having a layer of sintered powder and granular material in close contact and having an apparent volume resistivity of 10^6 Ωcm or more at 950°C 2) Main component is glass fiber After forming and solidifying a coating layer mainly composed of an organic polymer on the base fabric, a coating of the refractory is formed by a thermal spraying method using electrically insulating refractory powder and sintered, When adhering to the coating layer whose main component is the organic polymer, thermal spraying is performed by applying tension to the base fabric and making it adhere to a support device made of a material with high thermal conductivity, whose back surface is forcedly cooled. A method for producing a fire-resistant insulator characterized by performing the following steps: