JPH07142136A - Grounding resistance reducing agent and grounding electrode - Google Patents

Abstract

PURPOSE:To maintain high conductivity for a long time even in the case where a crack or the like is generated, and to improve the mechanical strength by using grounding resistance reducing agent. CONSTITUTION:The grounding resistance reducing agent includes conductive fiber such as carbon fiber and hygroscopic material such as zeolite and bentonite. The conductive fiber has an aspect ratio at 10-5000, and the conductive fiber, which is curled, can be used. The grounding resistance reducing agent, which includes inorganic hardening material such as hydraulic agent, which includes In relation to inorganic hardening material at 100 parts by weight, conductive fiber at 0.1-10 parts by weight and hygroscopic material at 5-200 parts by weight are included. The grounding resistance reducing agent, which is formed by forming and hardening, can be utilized as a grounding electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground resistance reducing agent useful for grounding power transmission towers, lightning rods and the like.

[0002]

2. Description of the Related Art In order to ground a power transmission tower, a lightning rod, etc., a method is known in which a mixture of a conductive substance and hydraulic cement is sprinkled around a ground electrode and water is sprinkled to form a grounded body. . However, in this method, the conductivity decreases as the hydraulic cement hardens.

Japanese Unexamined Patent Publication (Kokai) No. 62-35479 proposes a ground resistance reducing agent in which stone powder obtained by crushing highly conductive stone such as serpentine is mixed with particulate carbon.
Further, in JP-A-3-265556, (1) hydraulic cement, (2) clay mineral as a water retention agent such as bentonite, (3) superabsorbent polymer, (4) conductivity of carbon powder and the like. A ground resistance-reducing agent has been proposed, which contains a substance and (5) an adsorbent and retains an electrolyte solution and contains limestone, silica stone or dolomite powder in a specific ratio.

However, since these ground resistance reducing agents use carbon powder as a conductive substance, they not only have low conductivity but also low mechanical strength. When the ground electrode composed of the ground resistance reducing agent is laid or buried in the ground, particularly in a sandy ground or a sandy layer where the ground is weak, the ground electrode may be damaged due to an earthquake, vibration accompanying traveling of the vehicle, or uneven settlement. Cracks occur and the conductivity is further reduced. Therefore, high conductivity cannot be maintained for a long time.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a ground resistance reducing agent and a ground electrode which can maintain high conductivity for a long period of time even if cracks occur.

Another object of the present invention is to provide a ground resistance reducing agent and a ground electrode which have high mechanical strength, can suppress the occurrence of cracks, and can maintain high conductivity.

[0007]

As a result of intensive studies to achieve the above object, the present inventors have found that the use of a composition in which a conductive fiber and a hygroscopic substance are combined or an inorganic curable substance is used together results in mechanical It was found that a grounding body having high strength and capable of maintaining high conductivity was obtained, and the present invention was completed.

That is, the ground resistance reducing agent of the present invention contains a conductive fiber and a hygroscopic substance. This ground resistance reducing agent may contain an inorganic curable substance.

Further, the ground electrode of the present invention is formed of the ground resistance reducing agent.

As the conductive fiber, various highly conductive fibers, for example, metal fibers such as aluminum, copper and iron; conductive organic fibers; polymers such as polyacrylonitrile, phenol resin, copna resin and rayon, Examples thereof include carbon fibers made from fibers that can be made into carbon fibers such as petroleum or coal pitch. These conductive fibers may be used alone or in combination of two or more.

The use of such a conductive fiber not only reinforces the grounding body composed of the grounding resistance reducing agent, but also
Even if the grounding body is cracked or cracked, the conductive fiber does not reduce the conductivity. Further, when the conductive fiber is used, it is possible to secure high conductivity even in a small amount, unlike the conductive material in the form of powder.

Among these conductive fibers, preferred conductive fibers include carbon fibers. The carbon fiber is a fiber that can be made into a carbon fiber, and is 800
Carbonized fibers fired at a temperature of about 1500 ° C. may be used, but graphitized fibers having high conductivity are preferable.
Graphitized fibers have temperatures above 1500 ° C., for example 20
It can be obtained by firing at about 00 to 3500 ° C, preferably about 2500 to 3500 ° C. The graphitized fiber may not have the crystal structure of graphite.

The conductive fibers may be straight fibers, but are preferably fibrillated fibers, especially curled crimped fibers. If fibrillated fibers or crimped fibers are used, the contact ratio of the conductive fibers can be increased due to the entanglement of the fibers, and compared with straight fibers,
The conductivity can be significantly increased.

The aspect ratio of the conductive fiber can be selected within a range that does not impair the conductivity and the mixing and dispersibility.
It is 10 to 5000, preferably 25 to 3500, and more preferably 50 to 2500. Aspect ratio is 1
When it is less than 0, the conductivity is lowered, and when it exceeds 5000, the mixing and dispersibility is apt to be lowered.

The wire diameter of the conductive fiber can be appropriately selected from the range of about 1 μm to 0.5 mm, depending on the type of the fiber. The strand diameter of the carbon fiber is, for example, 5 to
It is about 30 μm, preferably about 10 to 25 μm.

Conductive fibers are often used as short fibers. The length of the short fibers can be selected within a range not impairing the conductivity and the mixing dispersibility including the length in the crimped state,
For example, it is about 0.1 to 40 mm, preferably about 1 to 30 mm, and short fibers of about 3 to 25 mm are frequently used.

As the hygroscopic substance, various substances having water retention property can be used. For example, starch-based polymer, cellulose-based polymer, acrylic acid-based polymer, methacrylic acid-based polymer, maleic acid-based polymer, isobutylene-maleic anhydride copolymer can be used. Super absorbent polymers such as polymers; activated carbon, acid clay, activated clay, activated alumina, titanium oxide, clay minerals (eg kaolin, bentonite, diatomaceous earth, kibushi clay, gyrome clay, etc.), zeolite, perlite,
Examples include hygroscopic porous inorganic substances such as vermiculite, shirasu balloon, calcined kaolin, and magnesium silicate. These hygroscopic substances may be used alone or in combination of two or more.

Preferred hygroscopic substances include highly hygroscopic substances having high hygroscopicity, for example, diatomaceous earth, zeolite,
Porous inorganic substances such as bentonite and clay minerals, especially clay minerals are included. Hygroscopic substances are often used as powders. The particle size of the hygroscopic substance is often, for example, 150 mesh or less, and the specific surface area is 5 to 300.
It is often about 0 m ² / g.

When a hygroscopic substance is used, water can be held appropriately and high conductivity can be maintained. Further, since it is rich in viscosity and toughness as a grounding body and reinforced with conductive fibers,
Even a simple construction method can withstand long-term use. If a clay mineral is used as a hygroscopic substance, it will be viscous while retaining water, but since it is reinforced with fibers,
The form as a grounding body can be maintained in the soil.

In the ground resistance reducing agent, the ratio of the conductive fibers to the hygroscopic substance can be appropriately selected within a range that does not impair the conductivity. 0.1 to 20 parts by weight of fiber, preferably 0.
The amount is 5 to 10 parts by weight, more preferably 1 to 5 parts by weight. If the ratio of the conductive fibers is less than 0.1 part by weight, the conductivity and mechanical strength are not improved so much, and if it exceeds 20 parts by weight, the mixing and dispersibility of the conductive fibers tends to be lowered.

In order to improve the strength of the ground resistance reducing agent, it is useful to use an inorganic curable substance together. Examples of the inorganic curable substance include gypsum; lime such as slaked lime and dolomite plaster; and hydraulic substance. As the hydraulic material, hydraulic cement such as cement (for example, Portland cement, early strength Portland cement, alumina cement, rapid hardening high strength cement, self-hardening cement such as gypsum; lime slag cement, blast furnace cement; mixed cement) Is mentioned. Preferred inorganic curable substances include, for example, gypsum, slaked lime, dolomite plaster, hydraulic cement and the like. One kind or two or more kinds of inorganic curable substances can also be used.

When such an inorganic curable substance is contained, the strength of the grounding body made of the ground resistance reducing agent can be further improved by the curing of the inorganic curable substance in combination with the reinforcing effect of the conductive fiber. In addition, with the curing of the inorganic curable substance, usually, the conductivity is often reduced, but since the conductive substance is fibrous, even if the inorganic curable substance is cured, the conductivity is lowered. Can be suppressed.

In the composition containing an inorganic curable substance, the proportion of each component can be selected within a range that does not impair the electrical conductivity and mechanical strength. For example, 100 parts by weight of the inorganic curable substance can be used for the conductive fiber. 0.1 to 15 parts by weight (preferably 0.
5 to 10 parts by weight, more preferably 1 to 5 parts by weight), and a hygroscopic substance 5 to 200 parts by weight (preferably 10 to 1).
50 parts by weight, more preferably about 25 to 100 parts by weight). If the ratio of the conductive fibers is less than 0.1 parts by weight, the conductivity and mechanical strength of the ground resistance reducing agent will decrease, and
If it exceeds 5 parts by weight, the uniform dispersibility of the conductive fibers tends to decrease. Further, if the proportion of the hygroscopic substance is less than 5 parts by weight, the conductivity tends to decrease, and if it exceeds 200 parts by weight, the mechanical strength tends to decrease.

The ground resistance reducing agent is, in addition to the above-mentioned components, reinforcing fibers (for example, glass fibers; ceramic fibers such as aluminum silicate fibers, alumina fibers and silicon carbide fibers; polyethylene fibers, polypropylene fibers, cellulose fibers). , Rayon fiber, acetate fiber,
Polymer fibers such as nylon fibers, polyester fibers, polyvinyl alcohol-based synthetic fibers (vinylon fibers), polyether sulfone fibers, aromatic polyamide fibers (aramid fibers, etc.) may be added.

The ground resistance reducing agent may be an aggregate which may be fine particles such as sand, silica sand and perlite; a colorant, a curing agent, a set retarder such as an organic acid salt and an inorganic acid salt, calcium chloride. Various accelerators, water reducing agents such as sodium naphthalene sulfonate, coagulants, thickeners such as carboxymethyl cellulose, methyl cellulose, polyvinyl alcohol, foaming agents, waterproofing agents such as synthetic resin emulsions, and various additives such as plasticizers. May be included.

The ground resistance reducing agent of the present invention is a kneaded material (mortar) kneaded with water, and is ground or grounded by a method such as spraying or placing around a ground electrode composed of a conductive wire material such as copper or aluminum. Can be formed and the ground electrode can be grounded. In addition, the ground electrode may be grounded together with the grounding body by injecting the kneaded material into a hole provided in the ground where the ground electrode is arranged. When it contains an inorganic curable substance, a ground resistance reducing agent should be placed around the ground electrode or injected into the hole where the ground electrode is placed without sprinkling with water, without forming a kneaded product with water. Alternatively, the grounded body may be formed by curing with water in soil or soil.

Further, as described above, the ground resistance reducing agent of the present invention has a high reinforcing property and contains conductive fibers capable of suppressing a decrease in conductivity even if cracks or the like occur. It is also possible to use the ground electrode itself. Particularly, the ground resistance reducing agent containing the inorganic curable substance is useful for forming a ground electrode. In this case, a fluid composition or mortar composed of a mixture of the ground resistance reducing agent and water is poured into a hole in the ground (for example, a hole having a diameter of 10 cm and a depth of 5 m) and solidified. A ground electrode can be formed. The proportion of water in the kneaded product,
It can be appropriately selected within a range where a pourable or pourable flowable composition is obtained.

The cross-sectional shape of the ground electrode may be any of a polygonal shape, an elliptical shape, a circular shape, etc., and is not particularly limited. In addition, the shape of the ground electrode can be selected according to the strength of the ground, and may be a columnar ground electrode in a place where the ground is weak, such as a sandy ground, a sandy layer, a wetland, etc. It may be a ground electrode having a shape such as a shape.
Due to earthquakes, vibrations associated with the running of the vehicle, uneven settlement, etc.
Even when stress is applied to the grounded or laid ground electrode, the occurrence of cracks and cracks and the decrease in conductivity can be significantly suppressed.

[0029]

Since the ground resistance reducing agent and the ground electrode of the present invention contain the conductive fiber and the hygroscopic substance, the high conductivity can be maintained for a long time and the mechanical strength of the grounding body can be enhanced. . Further, since the conductive substance is fibrous, high conductivity can be maintained even if cracks occur. Furthermore, when an inorganic curable substance is included, the mechanical strength of the grounding body can be further increased, the occurrence of cracks can be suppressed, and high conductivity can be maintained.

[0030]

EXAMPLES The present invention will be described in more detail based on the following examples.

Example 1 Pitch-based graphitized carbon fiber (fiber diameter 18 μm, fiber length 25 mm) 2 crimped with 100 parts by weight of bentonite
1 part by weight and 100 parts by weight of water are added and mixed, and the resulting kneaded product is placed in a mold (4 cm × 4 cm × 16 cm) and dried at 23 ° C. and 50% relative humidity for 3 days to give a specimen. It was made.

Comparative Example 1 A specimen was prepared in the same manner as in Example 1, except that 100 parts by weight of bentonite was used and 2 parts by weight of carbon powder made of conductive carbon black was used.

Example 2 100 parts by weight of ordinary Portland cement was mixed with 2 parts by weight of crimped pitch-based graphitized carbon fiber (fiber diameter 18 μm, fiber length 25 mm), bentonite 50 parts by weight, and water 60 parts by weight. Cement mortar was prepared by adding and mixing. Form the obtained cement mortar into a mold (4 cm x 4
(cm × 16 cm) and cured in air at 23 ° C. and 50% relative humidity for 1 week to prepare a test piece.

Example 3 A specimen was prepared in the same manner as in Example 2 except that 50 parts by weight of zeolite was used instead of 50 parts by weight of bentonite.

Example 4 The procedure of Example 2 was repeated, except that 2 parts by weight of straight-pitch pitch-based graphitized carbon fiber (fiber diameter 18 μm, fiber length 25 mm) was used in place of the crimped carbon fiber. A sample was prepared.

Example 5 Instead of 2 parts by weight of crimped graphitized carbon fiber, crimped pitch-based graphitized carbon fiber (fiber diameter 18 μm, fiber length 25 m)
m) A sample was prepared in the same manner as in Example 2 except that 5 parts by weight was used.

Example 6 Instead of 2 parts by weight of crimped graphitized carbon fiber, crimped pitch-based graphitized carbon fiber (fiber diameter 18 μm, fiber length 25 m)
m) A test piece was prepared in the same manner as in Example 2 except that 0.5 part by weight was used.

Comparative Example 2 A sample was prepared in the same manner as in Example 2 except that 2 parts by weight of carbon powder made of conductive carbon black was used instead of the graphitized carbon fiber.

Comparative Example 3 To 100 parts by weight of ordinary Portland cement, 2 parts by weight of straight hair type pitch-based graphitized carbon fibers (fiber diameter 18 μm, fiber length 25 mm) and 50 parts by weight of water were added and mixed. A specimen was prepared in the same manner as in Example 2 except that cement mortar was prepared.

Then, a conductive adhesive (dotite) was applied to both ends of the specimens obtained in the above Examples and Comparative Examples, and the electrical resistance was measured using a tester. In addition, a crack was generated in the test piece by a three-point bending test, and the electrical resistance when the crack was generated was also measured. Further, the bending strength of the test piece was measured by a three-point bending test. The results are shown in the table.

[0041]

[Table 1] As is clear from the table, not only the strength of the test piece of the example is large, but also the electric resistance value thereof is extremely smaller than that of the test piece of the comparative example. In particular, even if cracks occur, the electric resistance value hardly decreases.

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Claims (8)

[Claims] 1. A ground resistance reducing agent containing a conductive fiber and a hygroscopic substance. 2. The conductive fiber has an aspect ratio of 10 to 50.
The ground resistance reducing agent according to claim 1, which is 00. 3. The conductive fiber is curled.
The ground resistance reducing agent described. 4. The conductive fiber is a carbon fiber.
The ground resistance reducing agent described. 5. The ground resistance reducing agent according to claim 1, which contains 0.1 to 20 parts by weight of conductive fibers with respect to 100 parts by weight of the hygroscopic substance. 6. The ground resistance reducing agent according to claim 1, which contains an inorganic curable substance. 7. With respect to 100 parts by weight of the inorganic curable substance,
Conductive fiber 0.1 to 10 parts by weight, and hygroscopic substance 5 to
The ground resistance reducing agent according to claim 6, which comprises 200 parts by weight. 8. A ground electrode formed of the ground resistance reducing agent according to claim 1.