JPH0146808B2 - - Google Patents

Description

[Detailed description of the invention] [Purpose of the invention]

[Industrial Application Field] The present invention relates to a temperature rise alarm sensor for facilitating the detection of distribution lines, connections between distribution lines and electrical equipment, bearings, and other locations that are likely to generate heat when an abnormality occurs. . [Prior Art] Conventionally, when a break occurs in a covered wire, there is no easy way to detect the break through the covering.
For this reason, a method is generally used in which the coating is sequentially peeled off and the location of the disconnection is identified using a continuity tester. However, when the current is large or the voltage is high, this work is not only dangerous but also complicated. In particular, the difficulty in detecting flaws in locations where many wires are intricately intertwined, when an accident occurs at night, or when the wires are located at a high place is particularly significant, and is a source of worry for those engaged in track maintenance work. It was hot. Of course, overcurrent interrupting devices called breakers have been widely used, but in reality, they only indicate the section where an overcurrent has flowed, and do not specifically indicate the location of the disconnection. Therefore, the difficulty of flaw detection work is hardly alleviated. Therefore, it can be said that the development of a means for easily detecting the location where a disconnection has occurred is an important issue in power distribution. In addition to the cases related to power distribution maintenance described above, there are many other cases in which failures are difficult to detect from the outside. For example, the same applies if the bearings in the bearings that support the rotating parts are damaged or the lubrication system malfunctions, or if the electrodes in the electrolytic cell are abnormally worn out or the cooling water system malfunctions. It is. [Problems to be Solved by the Invention] Therefore, the present invention solves problems such as disconnections in power distribution lines,
The purpose of this invention is to provide a means to facilitate the discovery of locations where failures are difficult to detect from the outside.

[Structure of the invention]

(1) Progress of the invention As a result of conducting various studies on the phenomena accompanying the breakage of electric wires, the inventor found that in many cases, a strong heat generation occurs at the point immediately before the breakage occurs, and that this heat generation is caused by: It has been found that even if an overcurrent interrupting device is installed, an overcurrent can occur at a defective wire connection or coating before the overcurrent interrupting device is activated. Therefore, as a result of further studies and experiments on a method for visualizing this heat generation phenomenon, we came up with the idea of adopting a specific foamable material as a heat generation alarm material, and finally arrived at the present invention. (2) Based on the above findings, the temperature increase notification sensor according to the present invention is characterized by containing a thermoplastic resin, a foaming agent, and potassium titanate fibers. Hereinafter, the structure of the invention and related matters will be explained in sections. (3) Thermoplastic resin In the above configuration, the "thermoplastic resin" can be any type as long as it has the property of melting or softening near the intended designated temperature;
Considering various points such as electrical insulation, strength and formability, aging resistance, and self-fusion properties, polyethylene or ethylene copolymers (for example, copolymers of ethylene and vinyl acetate, vinyl chloride, or acrylic ester) or Blends of ethylene-propylene-diene terpolymer (EPDM) and butyl rubber or polyisobutylene are optimal. In particular, isotactic polyethylene made using a Ziegler-Natsuta catalyst exhibits sharp melting characteristics due to its high crystallinity. However, other thermoplastic resins can be used as well, and specific examples include the following. Vinyl resins such as vinyl acetate resins, styrene resins, and vinyl chloride resins, vinylidene chloride resins and copolymers thereof, acrylic resins, methacrylic resins and copolymers thereof, and combinations of acrylonitrile and acrylic acid or methacrylic acid esters. Binary or ternary copolymers, binary or ternary copolymers of vinyl acetate and acrylic acid or methacrylic ester, binary or ternary copolymers of styrene and acrylic acid or methacrylic ester, etc. Copolymers of vinyl compounds and acrylic compounds, polyolefin resins such as polypropylene resins or polybutylene resins, or copolymers of various olefins, vinylidene chloride resins, vinyl butyral resins, polyvinylpyrrolidone or blends thereof, polyamides, silicone resins , alkylcelluloses such as methylcellulose and ethylcellulose,
Modified celluloses such as carboxymethylcellulose and cellulose phosphate, natural or synthetic rubber, and blends of the above. (4) Foaming agent Next, as the foaming agent, any foaming agent can be used as long as it is stable at ambient temperature and has the property of foaming at a constant temperature. These include pyrolytic foaming agents that decompose and generate gas when exposed to heat, microballoon foaming agents that trap gas in a thermofusible shell, and microscopic thermoplastic foaming agents that adsorb gas or vaporizable solvents. There are adsorption blowing agents made of resin particles and reactive blowing agents in which the isocyanate group of an isocyanate compound is blocked with a thermally decomposable group. The first pyrolytic blowing agent is, for example, ammonium carbonate (decomposition temperature (decomposition temperature) 58
°C), 2,2'-azobisisobutyronitrile (85-90 °C), azohexahydrobenzonitrile (103-104 °C), azodicarboxylic acid amide (190 °C)
~230℃), diazoaminobenzene (90~100
°C), benzene sulfohydrazide (90-100 °C),
P-toluenesulfonyl hydrazide (110°C),
Diphenyl sulfone-3,3'-disulfohydrazide (148℃), diphenyl oxide-4,4'-
Disulfohydrazide (150℃), N,N'-dinitrosopentamethylenetetramine (160-200℃)
C), N,N'-dinitroso-N,N'-dimethylterephthalamide (105C), and terephthalazide (90 to 110C). However, the thermal decomposition temperature of the above-mentioned decomposable blowing agent can be changed significantly by adding a suitable decomposition aid. For example, when oxalic acid or zinc acetate is used in combination with azodicarboxylic acid amide, the decomposition point is 100
~150℃ or 120-130℃. In addition, stabilizers for vinyl chloride resin can lower the decomposition temperature of this product to 20~20°C.
Reduce temperature by 30℃. Furthermore, the decomposition temperature of N,N'-dinitrosopentamethylenetetramine (DNPT) can be increased from 200℃ by adding salicylic acid or urea.
It can be adjusted over a wide range of 70°C. The second microballoon foaming agent is one in which a gas or easily vaporized liquid such as propane, butane, or pentane is sealed in a microscopic hollow body made of a material with high gas barrier properties such as polyvinylidene chloride. There is. These balloon-type foaming agents usually foam at 100-110℃,
Since it is stable in organic solvents and water, it is suitable for the purpose of the invention. The third adsorption type blowing agent is, for example, one in which a gas or liquid such as carbon dioxide gas, butane, pentane, or trichlorofluoromethane is adsorbed onto fine particles of polystyrene, polyvinyl chloride, or the like. Although the application of this type of foaming agent is limited by the type of thermoplastic resin that is the main material, it is inexpensive and has excellent foaming efficiency. The last reactive blowing agent is, for example, tolylene diisocyanate, xylylene diisocyanate,
Hexamethylene diisocyanate, diphenylmethane-4,4'-diisocyanate, 1,5-
The active isocyanate group of an isocyanate compound such as naphthalene diisocyanate is masked using a masking agent such as ethanol, phenol, m-cresol, o-nitrophenol, ε-caprolactam, benzenedithiol, or ethylmalonate. When the masking agent is removed by heat, urea bonds are formed due to moisture in the air, and the carbon dioxide gas produced at this time acts as a blowing agent. (5) Calcium titanate The present inventor has found that even more preferable results can be obtained by blending short fibers of potassium titanate in addition to the above thermoplastic resin and blowing agent. In other words, when short fibers of potassium titanate coexist, the brittleness of a compound consisting only of a thermoplastic resin and a blowing agent is greatly improved. Or when applied to covered electric wires, etc., it prevents the occurrence of cracks due to bending of the part, and in particular, the excellent infrared reflection effect of this fiber suppresses the temperature rise of the composition due to sunlight. Therefore, even when exposed to intense direct sunlight in the summer, erroneous foaming due to temperature rise is completely prevented. Incidentally, the blending of this fiber is also effective in improving the dimensional stability, etc. of molded articles. Potassium titanate short fiber has the general formula _K2O
( _TiO2 )n (n=2-8), average fiber length 5-70μ,
A fiber having an average fiber diameter of 0.1 to 0.7μ is suitable. The appropriate blending amount of this fiber for the sensor of the present invention cannot be unambiguously determined because it changes depending on various conditions, but it is generally 20 parts (by weight) for the total amount of thermoplastic resin and constant temperature foamable material.
It is appropriate that the amount is within 1 part (weight). If the amount of the present fiber added significantly exceeds the upper limit, the blend will become brittle. (6) Preparation of sensor In the sensor of the present invention, since the foaming temperature means the indicated temperature, it is preferable that this temperature is within the narrowest possible range. Generally, thermally decomposable blowing agents may dissolve in the solvent for preparing the formulation described below and lose their foaming properties. Although it is necessary to perform insolubilization treatment on the solvent, generally speaking, organic solvents tend to reduce the foaming properties of the thermally decomposable foaming agent. however,
When water is used as a solvent, a relatively stable constant-temperature foaming compound can be prepared by dispersing foaming agent powder in mineral oil, liquid oil, etc., and then emulsifying and dispersing it in an aqueous solvent. sell. If there is a sufficient difference between the plasticizing temperature of the thermoplastic resin and the foaming start temperature of the blowing agent, then kneading the blowing agent and potassium titanate fibers into the softened thermoplastic material will be the easiest way to create the sensor of the invention. A formulation is obtained. However, the melting point (first transition temperature, Tm) of ordinary thermoplastics is 150
℃ or higher, this method cannot be applied except in special cases. Therefore, usually (a) a resin with rubber-like properties (for example, EPDM) is used as the thermoplastic resin, or a foaming agent and potassium titanate fiber are added to the resin mixed with raw rubber, and the resin is heated at a low temperature. Extrude with or
(b) Dissolving the thermoplastic resin in a solvent, blending a blowing agent and potassium titanate fibers and spreading the mixture, and then evaporating the solvent; or (c) emulsion polymerizing the monomer of the thermoplastic resin at a low temperature; One of the methods employed is to mix a foaming agent and potassium titanate fibers with the mixture, and then spread and harden the mixture. In method (a), by adding a small amount of a vulcanizing agent and a vulcanization accelerator, a tape-shaped molded product with excellent self-bonding properties can be obtained. However, care must be taken not to destroy the balloon-type foaming agent during extrusion. Method
In the case of (b), consideration must be given to avoid deteriorating the performance of the decomposable blowing agent added as described above. Balloon blowing agents are safe as long as the shell membrane does not dissolve or swell in the solvent. Method (c) can be applied to foamable materials other than reactive blowing agents. The film obtained by evaporation of the medium is peeled off and then cut to a certain size. In addition, according to this method, since the compound before evaporation of the solvent is in a liquid state, it is most suitable when it is desired to apply the sensor of the present invention in the form of a paint. Copolymers of vinyl acetate and acrylic esters or dibutyl maleate, various acrylic monomers, or copolymer latexes obtained from acrylic monomers and small amounts of vinyl monomers mixed with foaming materials are particularly excellent constant-temperature foaming coatings. Forms a film. Although the ratio of the blowing agent in the sensor formulation according to the present invention is not critical, if the blowing agent is too small, sufficient foaming will not occur, making it difficult to detect the foaming phenomenon with the naked eye.
On the other hand, if the content of the foaming agent is too high, it tends to reduce the mechanical strength and adhesiveness of the tape and coating used as a sensor. For this reason, it is usually preferable to select the weight ratio (dry weight ratio) of the thermoplastic resin and the blowing agent within the range of 45:5 to 30:20. (7) Other additives The sensor formulation of the present invention may further contain other additives, such as pigments, anti-aging agents, antioxidants, ultraviolet absorbers, vulcanizing agents, vulcanization accelerators, and preservatives, as desired. It may contain agents, fillers, thickeners, and the like. (8) Other forms The sensor composition of the present invention can be formed into a sheet or paint by any of the methods a to c described above. It may be impregnated into a fabric-like base material such as cotton cloth, synthetic fiber cloth, or nonwoven fabric, and after cutting the impregnated material into a tape shape, an adhesive may be applied to one side of the impregnated material. The sensor supported on the fabric tape in this manner has a characteristic of being highly flexible. (9) Applications A tape or paint made from a mixture of thermoplastic resin, foamable material, and potassium titanate fibers can be wrapped around electric wires, connections between electric wires and electrical equipment, or breakers. When applied, the foaming agent in the tape or coating foams and expands due to the heat generated by the overcurrent, changing its appearance, making it possible to immediately visually detect a malfunctioning part. In addition, if the above tape or paint is pasted, wrapped, or painted on the outside of the bearing part, this tape or paint film will be used even if frictional heat generation occurs due to damage to the bearing or insufficient supply of lubricant. As the foaming agent inside expands, abnormalities can be detected early. Therefore, repairs can be made before a major failure such as burnout occurs. In addition to the above, the property that the sensor of the present invention foams due to heat is effective in finding faults in resistors, capacitors, rectifying elements, etc. in complex electronic circuits. [Function] The sensor of the present invention can be applied in advance to electric wires, electric wire connections, bearings of rotating equipment, etc. in the form of tapes or coatings.
By simply applying it to a target part of an electronic component, etc., the part where an abnormality accompanied by heat generation has occurred can be irreversibly displayed through a bubbling phenomenon. Therefore, flaw detection of abnormal wires and wire connections,
This not only provides great benefits in repairing and predicting abnormalities in rotating equipment, electronic components, and saving labor in maintenance, but also contributes to the prevention of industrial accidents. [Example] Below, examples are given to describe the mode of carrying out the invention.
The examples are merely illustrative and are not intended to limit the scope of the invention. Example 1 Ethylene-propylene-diene terpolymer 30
Parts by weight (the same applies hereinafter), 70 parts of butyl rubber, 15 parts of Micropearl F-30 (trade name for butane gas-containing microballoons), and 15 parts of potassium titanate short fibers are kneaded in a kneader, mixed well, and passed through a roll. It was rolled into a sheet with a thickness of 0.6 mm, and this sheet was further cut into a tape with a width of 40 mm. In order to evaluate it as a self-bonding tape, the above tape was stretched 100-200% and wound around a 10m/m glass rod to form a tape roll, and after being left for 24 hours, the roll was checked for cracks. As a result of observation, no cracks were observed, and no peeling was observed in the overlapping convoluted layer. Next, a nichrome wire was inserted into the upper glass rod and electricity was applied. When the surface temperature reached 100 to 150°C, the wound material began to foam, forming an irregular linear foam. This foam did not shrink even when the electricity was turned off, and its volumetric expansion rate was about 900%. Example 2 20 parts of polyvinyl butyral, 60 parts of isopropyl alcohol, 20 parts of n-butyl alcohol, 5 parts of potassium titanate short fibers, micro pearl (listed above)
10 parts of the mixture and 15 parts of the viscosity imparting agent were heated to 40°C, stirred for 2 hours using a propeller type stirrer, mixed, and then kneaded using three rolls to obtain a uniform blend. This mixture is coated on release paper and dried to a thickness of approx.
A 0.2 mm sheet-like molded product was obtained. After cutting this molded product (sensor) into a tape shape, it was wrapped around the connecting part of an overhead electric wire with a simulated connection failure and the coating surface, and when a 250A electric wire was passed through it, the temperature of the connected part rose to 170℃. , the tape showed irregular foaming. On the other hand, the surface temperature of the covered portion was 85° C., and the wrapped tape was a foam with a thickness of about 2 mm with irregularities. Example 3 80 parts of an ethylene/vinyl acetate copolymer emulsion (solid content approximately 50%) made by emulsion polymerization method, 10 parts of Micro Pearl (listed above), and 10 parts of a viscosity imparting agent were uniformly mixed with a propeller stirrer. After being dispersed, it was spread uniformly on release paper and dried to obtain a sheet with a thickness of about 0.2 mm. An adhesive was applied to the surface of this sheet, and the sheet was wound to form a tape with the release paper still attached. When this tape was pasted on the bearing part of a rotating shaft with simulated rotational resistance and operated for a day and night, the temperature of the bearing part reached 130°C, and the pasted tape was foaming, indicating that the tape was foaming. It was confirmed that the bearing part was generating heat. However, the rotating shaft continued to rotate, warning of the need for early repairs.

【Effect of the invention】

As explained above, the present invention provides a simple and reliable method for easily detecting the location of heat generation when an abnormality accompanied by heat generation occurs in power distribution lines, connections between power distribution lines and electrical equipment, bearings, etc. By providing a temperature rise alarm sensor, maintenance and
It can contribute widely to industry through various effects such as easier inspection, early detection of failures, labor saving in flaw detection work, and increased safety.

Claims (1)

[Claims] 1. A temperature rise alarm sensor characterized by containing a thermoplastic resin, a foaming agent, and potassium titanate fibers. 2 The weight ratio of thermoplastic resin and blowing agent is 45:5 to
2. The sensor according to claim 1, wherein the ratio is 35:20. 3. The sensor according to claim 1 or 2, wherein the thermoplastic resin is a blend of polyethylene, an ethylene copolymer, or an ethylene-propylene-diene terpolymer and butyl rubber or polyisobutylene. 4. The sensor according to claim 1, wherein the amount of potassium titanate is 20 parts by weight or less based on 100 parts by weight of the total amount of the thermoplastic synthetic resin and the blowing agent. 5. Claims 1 to 4, wherein the shape is in the form of a tape.
The sensor described in any of the above. 6. The sensor according to claim 1, wherein the shape is in the form of paint.