JP2002309042A - Electroconductive rubber sheet and antifouling device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antifouling device capable of preventing a structure, a ship or a piping, contacting with seawater from being fouled by the attachment of organisms, constituted of (A) an electroconductive rubber sheet obtained by lining a parts of a body to be prevented from being fouled, comprising an electroconductive or nonconductive material and requiring the antifouling, directly or through a feeding body, (B) an electrode material arranged in the sea so as not to directly contact with the electroconductive sheet, and (C) a direct current source, connected so that the electroconductive rubber sheet may be an anode and the electrode material may be a cathode, and having high electroconductivity in the thickness direction of the rubber sheet to enable a sufficient antifouling electric current to flow. SOLUTION: A rubber sheet obtained by lining a composition obtained by kneading each 15-30 wt.% (total 30-60 wt.%) of an amorphous graphite having 1-20 μm particle diameter and a carbon black having 5-100 μm particle diameter with a butyl rubber, and having <=500 Ω.cm volume resistivity in the thickness direction is used as the electroconductive sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive rubber sheet having improved conductivity. The present invention also relates to an improvement in an antifouling device using the conductive rubber sheet to prevent fouling due to marine organisms adhering to structures or pipes that come into contact with seawater.

[0002]

2. Description of the Related Art In facilities that use large amounts of seawater, such as seaside thermal and nuclear power plants, steel and steel, petrochemicals, and desalination plants, barnacles and mussels are installed in facilities such as intake pipes. Such marine organisms attach to the pipes, causing problems such as clogging of pipes, reduction of heat exchange efficiency, and corrosion.

At present, as a countermeasure for preventing such contamination, seawater is electrolyzed to produce sodium hypochlorite, which is then injected into a seawater cooling water system to prevent marine organisms from adhering. And a chemical injection method in which an oxidizing agent such as hydrogen peroxide or copper ions is injected, or a cleaning method in which mechanical removal is periodically performed.

However, in recent years, the electrolysis method and the chemical injection method are often shunned due to the growing public interest in environmental issues, and the cleaning method requires a great deal of labor, and also involves the removal of shellfish and the like. There is a secondary problem of how to treat the kimono.

[0005] As an antifouling method for solving such a problem, the inventors have previously proposed a technique described in Japanese Patent Publication No. Hei 7-24822. The technology consists of applying a conductive rubber or conductive resin lining layer or a conductive paint film on the surface that requires antifouling, and using these conductive coating layers as anodes and placing them separately in seawater. It is a gist of the invention that a direct current is passed using the electrode material thus formed as a cathode to apply an electric shock to marine organisms that come into contact with the surface to be contaminated, thereby preventing adhesion. This electrical antifouling has an advantage that no environmental problem arises because it acts only on organisms that are to adhere to the surface and does not release harmful substances.

In addition, when the present inventors adopt a lining made of a conductive sheet as a conductive film, they knead butyl rubber with graphite and carbon black at a specific ratio to form a sheet, and have a volume resistivity of 1 to 20 Ω. ·cm
The most suitable conductive sheet was found, and this was also disclosed in JP-A-11-123382.

However, the value of the volume resistivity of 1 to 20 Ω · cm is a very high conductivity as a conductive rubber,
The powders having high conductivity per se that have been used to achieve this have been extremely expensive among the conductive powders. Specifically, graphite having such high conductivity has a particle size of 0.1 to 1.0 μm.
And, it is the smallest class of graphite, it takes a long time to pulverize to reduce the particle size, so the cost is very high, and the amount supplied is small,
It was not easily available.

An antifouling device used for large-scale equipment such as a seawater intake channel in a power plant or the like applies a large area to a conductive rubber coating. Therefore, all materials used are inexpensive. Of course, something easy to do is desirable. Graphite and carbon black (carbon black is necessary as a reinforcing agent for rubber as described later) as conductive powders are also more versatile and inexpensive.
Moreover, it is desired that the composition kneaded with the rubber has good workability. However, when a conductive rubber sheet is manufactured using inexpensive graphite and carbon black, depending on the properties of the selected graphite and carbon black, the conductivity is not sufficient or the composition becomes flexible at the time of kneading rubber. And the sheet processability is very poor.

Although the volume resistivity of the conductive sheet is in the range of 1 to 20 Ω · cm in the plane direction, the resistance is higher in the thickness direction. In such a case, a sufficient current does not flow through the antifouling device, which is often inconvenient.

[0010]

SUMMARY OF THE INVENTION A first object of the present invention is to solve the above-mentioned problems and to provide a conductive material, particularly in the thickness direction, which is made of a material which is highly workable, inexpensive and easily available. An object of the present invention is to provide an economical conductive rubber sheet having excellent conductivity.

A second object of the present invention is to provide an antifouling device having excellent performance using such a conductive rubber sheet.

[0012]

A conductive rubber sheet which achieves the first object of the present invention is obtained by molding a composition obtained by kneading a natural or synthetic rubber with a conductive powder into a sheet. In the conductive rubber sheet, as conductive powder, amorphous graphite having a particle size of 1 to 20 μm and a particle size of 5 to 100 nm
And carbon black of each of the compositions 15 to 3
It is characterized in that it is used in an amount occupying 0% by weight (a total amount of 30 to 60% by weight) and has a volume resistivity in the thickness direction of 10 to 500 Ω · cm.

The antifouling device using the above-mentioned conductive rubber sheet which achieves the second object of the present invention is a device which prevents fouling due to organisms adhering to structures, ships or pipes which come into contact with seawater. Then, as shown in FIGS. 1 to 3,
(A ₁ ) A conductive rubber sheet (2) directly lined with a portion of the antifouling body made of a conductive substance which requires antifouling, or (A ₂ ) a conductive rubber sheet made of a conductive or nonconductive substance. (B) the conductive rubber sheet (2), which is one of a power supply body disposed close to a portion of the antifouling body requiring antifouling and a conductive rubber sheet (2) lined on the surface of the power supply body; And (C) a DC power supply (4). The conductive rubber sheet (2) serves as an anode and the electrode material (3).
An antifouling device connected to a DC power supply (4) such that the negative electrode is a cathode, the conductive rubber sheet described above;
That is, in a conductive rubber sheet formed by kneading a composition obtained by kneading a natural or synthetic rubber with a conductive powder into a sheet shape, as the conductive powder, amorphous graphite having a particle size of 1 to 20 μm and a particle size of 5 to 100 nm of carbon black, each of which occupies 15 to 30% by weight (30 to 60% by weight in total) of the composition, and has a volume resistivity in the thickness direction of 10 to 500 Ω · cm. The conductive rubber sheet is used.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION As described above with respect to the above-mentioned invention, butyl rubber is optimal, and it is recommended to use this to produce a conductive rubber sheet.

The total amount of the conductive powder in the conductive rubber composition is preferably in the range of 40 to 50% by weight, from the viewpoint of satisfying the required conductivity and the workability. .

A simple method of providing a conductive rubber sheet on the surface of the antifouling material is a rubber lining method, that is, a method in which conductive powder is mixed with rubber and formed into a sheet shape, and the resultant is pasted. The thickness of the conductive rubber sheet is selected from the range of 1 to 10 mm in order to provide durability. Usually 3
~ 5 mm is appropriate.

As the material of the electrode material, various metals can be used since it is a cathode, but steel or stainless steel is suitable in view of workability and cost.

The antifouling device of the present invention can have several modes. For example, when the object to be contaminated is a seawater channel using a steel pipe having a relatively small diameter, as shown in FIG. 1, the inside of the steel pipe (1) to be contaminated is made of a conductive rubber sheet (2). Using the lining as an anode, an electrode material (3) insulated from the steel pipe by an insulating material is sandwiched between flanges (12) of the steel pipe to form a conduit. In FIG. 1, (4) is a DC power supply. Needless to say, in this embodiment, the steel pipe (1), which is a good conductor of electricity, can be used as a power feeder.

When the body to be soiled cannot be directly lined with a conductive rubber sheet, such as a concrete channel, as shown in FIG. 2, the seawater intake channel (5) which is the body to be soiled, as shown in FIG. , A power supply panel is provided as a conductive support structure, and a conductive rubber sheet (2) serving as an anode is lined thereon. As the power supply, a metal plate or net including steel or stainless steel may be used.

When the body to be soiled is a large-diameter steel pipe and is buried underground or installed in the sea, the inside and outside of the pipe are entirely covered with a conductive rubber sheet. Therefore, it is not possible to use the steel pipe itself as a feeder serving as an anode in order to prevent corrosion of the steel pipe. Therefore, as shown in FIG. 3, similarly to the case of a concrete water channel, a power supply panel (21) in which a conductive rubber sheet (2) is lined with a power supply body is prepared, and a large-diameter insulating coating is applied. Attachment bolts (not shown) are provided on the surface of the steel pipe (6) to be soiled in such a manner that the insulation between the conductive rubber sheet (2) and the large-diameter steel pipe to be soiled is maintained. Fixed by. In FIG. 3, reference numeral (7) denotes a sacrificial anode for cathodic protection.

The feature of the antifouling technique of the present invention lies in the realization of high conductivity in the thickness direction of the sheet by the structure of the conductive rubber sheet, particularly by the combination of the conductive powder. In the present invention, an antifouling body using a metal material that is a good conductor is used as a power feeder, or a power feeder is separately provided, and a conductive rubber sheet is formed on the power feeder. Adhesion is performed so that DC current flows from the power feeder through the conductive rubber sheet to the electrode material arranged in seawater.High conductivity is required so that the current flow is not obstructed. It is the thickness direction.

The conductive rubber sheet is produced by extruding an unvulcanized rubber composition with an extruder or rolling it with a calender roll, and the directions of rubber molecules and fillers are aligned according to the direction of extrusion or rolling. In other words, anisotropy based on the so-called “grain” occurs. Especially flat,
When the needle-like or fibrous filler is kneaded, the anisotropy becomes more remarkable. The properties that make such notable differences are mechanical strength, such as tensile strength and tear strength, gas permeability, and electrical properties.

The graphite used for the conductive rubber sheet constituting the antifouling device of the present invention is selected from the group consisting of a scale-like powder having a planar crystal structure typical of graphite and an amorphous earth-like powder. is there. Here, the term "amorphous" does not refer to completely amorphous, but because a large number of fine crystals are aggregated in random directions to form particles, they appear to be amorphous in appearance. Meaning.

Since the conductivity of the graphite crystal is high in the direction parallel to the crystal plane and low in the direction perpendicular to the plane (axial direction), flake graphite having a high degree of crystallinity is kneaded into rubber to form a sheet. In this case, the conductivity in the plane direction of the sheet in which the flaky powder is arranged in a plane is sufficiently high, but the conductivity in the thickness direction is low.

On the other hand, since the ground graphite has the above-described particle structure, the conductivity of each particle shows almost no anisotropy. Due to this fact and the fact that the particles of soil-like graphite are not flat in themselves, and the influence of the grain formed during the molding of the sheet is small, the conductivity of the conductive rubber sheet obtained by kneading it with rubber is in the plane direction. There is not so much difference between the thickness direction. That is, the conductivity in the thickness direction is higher than that of the conductive rubber sheet obtained by kneading scale-like graphite into rubber. Thus, suitable for use in the present application is amorphous earth graphite.

When soil graphite is used, its particle size and filling amount are important points. If the particle size is very small, there is a problem of cost and production amount as described above, and as a cheaper and more easily obtainable one, it is possible to select earth graphite having a large particle size, although the conductivity is slightly inferior. It is a good idea. However, in order to reach the desired level of conductivity of the conductive rubber composition using only graphite having a large particle size, it is necessary to knead the rubber composition at a high filling rate.

Since graphite has no reinforcing effect on rubber, a conductive rubber composition containing only graphite has insufficient strength and is not suitable as a lining sheet. Therefore, carbon black, which is the same carbonaceous material as graphite and has a small contribution to conductivity, but has a reinforcing effect when kneaded with rubber, should be used in combination.

The inventors kneaded rubber with a combination of various types of earth graphite and carbon black, and tested the performance of the resulting conductive rubber sheet. As a result, it has been found that a combination of earthy graphite having a slightly larger particle diameter and carbon black having a very small particle diameter has the best balance between conductivity and workability with respect to rubber. Suitable particle size is 1-20 μm for graphite,
The carbon black is 5 to 100 nm, and the appropriate loading is 15 to 30% by weight based on the conductive rubber composition, respectively, and the total amount of graphite and carbon is 30 to 60% by weight. I understand. The preferred total amount of graphite and carbon is 40 to 50% by weight.

As described above, the conductivity of the conductive rubber sheet used in the apparatus of the present invention is important not in the direction of the sheet surface but in the thickness direction. It should be in the thickness direction, not the direction.
Based on this idea, as a result of pursuing the level to be realized as the volume resistivity in the thickness direction of the conductive rubber sheet, in obtaining the effect of preventing the adhesion of microorganisms on the surface of the conductive rubber sheet,
The volume resistivity in the thickness direction that allows a sufficient current to flow is 500Ω · cm at the upper limit, and preferably 200Ω · cm.
cm or less. There is no particular lower limit for the volume resistivity in the thickness direction, but in practice, those having a volume resistivity of less than 10 Ω · cm are difficult to manufacture, and usually will exceed 10 Ω · cm.

The upper limit of the volume resistivity is larger than the volume resistivity in the plane direction of 1 to 20 Ω · cm, which was previously determined to be appropriate in JP-A-11-123382, and is low in conductivity. This difference is caused by the influence of the grain in the processing of the rubber sheet. In the conductive rubber sheet, the ratio of the volume resistivity in the thickness direction to the surface direction is:
When flaky graphite is used, sometimes 1,000
More than double. Therefore, the volume resistivity in the plane direction is 1
Even within the range of ~ 20Ωcm, the volume resistivity in the thickness direction may be a high value of 1,000Ωcm or more,
In this case, it was found that a sufficient antifouling current might not flow. On the other hand, in the case of a conductive rubber sheet using earth graphite, the ratio of the volume resistivity between the thickness direction and the surface direction is from 5 times to at most 50 times. In any case, by selecting earth graphite, a high volume resistivity in the thickness direction, which cannot be obtained by using flake graphite, has been realized.

In addition to the above description, the antifouling of the present invention is basically carried out in accordance with the antifouling techniques disclosed in the above-mentioned Japanese Patent Publication No. Hei 7-24822 and Japanese Patent Laid-Open Publication No. H11-123382. The matters described in the prior art documents are all applied to the present invention with necessary changes.

[0032]

EXAMPLES Four kinds of graphites having properties shown in Table 1 and carbon black were prepared. As for graphite,
Table 1 shows the production volume and price.

Table 1 Average particle size Particle size range Shape Production Price Graphite A 0.4-0.7 μm 0.1-1.0 μm Earthy powder Small High Graphite B 2-3 μm 1-10 μm Earthy powder Medium Medium Graphite C 2-3 μm 1 10 μm scale-like powder Medium Medium Graphite D 5-7 μm 1-30 μm Earthy powder Multi Low carbon black 40-50 nm 5-90 nm

The graphite and carbon black were kneaded with butyl rubber at the ratio shown in Table 2 to obtain a conductive rubber composition. This composition is applied to a width of 30c.
An antifouling panel was prepared by lining a steel plate of mx 45 cm in length and having a thickness of 1.5 mm with a thickness of 1.5 mm and an insulating rubber lining on the back surface. Table 2 shows the evaluation of the processability when the composition is processed into a sheet.

Table 2 Conductive rubber composition No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 Graphite A 50% 25% Graphite B 25% 25% Graphite C 25% Graphite D 25% Carbon black 25% 25% 25% 25% Workability evaluation × × ○ ○ ○ ○

For these antifouling panels, first, the volume resistivity of the lining was measured in the thickness direction and the surface direction. The volume resistivity in the thickness direction is based on the Japan Rubber Association Standard S
Performed on a test piece according to the test piece specified in RIS2304,
The volume resistivity in the plane direction was measured according to the method specified in the standard SRIS2301.

Next, each antifouling panel is immersed in seawater at 25 ° C. and connected to a constant potential control DC power supply so that the conductive rubber sheet as an anode has a potential of 1.2 V vs. Ag / AgCl. Thus, the density of the current flowing at that time was measured. After energization was continued for one week, it was examined whether a microbial film (slime) was formed on the surface of the conductive rubber sheet, and the antifouling performance was evaluated. Table 3 shows the results.

Table 3 Antifouling panel No.1 No.2 No.3 No.4 No.5 No.6 Volume resistivity (Ω · cm) Thickness direction − − 16.7 57.0 3,230 640 Surface direction − − 2.5 4.6 2.8 15.0 Current density (μA / cm ² )--13.0 11.6 0.1 3.0 Microbial film formation--None None Yes Slight antifouling performance evaluation--○ ○ × △ Evaluation ○: Good △: Possible ×: Poor-: Measurement / Evaluation Can not.

Antifouling panel No. 3, 50% of fine earth-like graphite (graphite A) powder having an average particle size of 0.4 to 0.7 μm and a particle size range of 0.1 to 1.0 μm
Although the performance was good, the material was expensive and could not be implemented economically. In contrast,
Antifouling panel No. 4, that is, 25% of ground graphite (graphite B) powder having an average particle size of 2 to 3 μm and a particle size range of 1 to 10 μm used in combination with 25% of carbon black having an average particle size of 40 to 50 nm, This was the best in terms of good sheet workability, good conductivity in the thickness direction, and the fact that the material was not particularly expensive and could be implemented economically.

[0040]

According to the antifouling device of the present invention, the benefits provided by the antifouling device disclosed in Japanese Patent Publication No. Hei 7-24822 by the present inventors, that is, without generating harmful substances polluting the environment, It enjoys the benefit of effectively preventing the attachment of organisms, and additionally has the economic benefit of the conductive sheet used as an anode, which is disclosed in Japanese Patent Application Laid-Open No. H11-123382, in which the durability is significantly improved. After doing
An economical effect was further enhanced by using a cheaper and more readily available conductive material for the conductive sheet. Thereby, antifouling by the marine organisms in the flow path using the seawater as the cooling water can be realized at a lower cost.

[Brief description of the drawings]

FIG. 1 shows one embodiment of an antifouling device according to the invention,
Sectional view of the device.

FIG. 2 is a sectional view of the antifouling device according to the present invention, showing another embodiment of the device.

FIG. 3 is a cross-sectional view of an antifouling device according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel pipe 12 Flange 2 Conductive rubber sheet 21 Power supply panel lined with conductive rubber 3 Electrode material 4 DC power supply 5 Seawater intake channel (made of concrete) 6 Large diameter steel pipe 7 Sacrificial anode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) E02B 1/00 301 E02B 1/00 301A H01B 5/00 H01B 5/00 L 5/16 5/16 (72 ) Inventor Naoya Kumagai 11 Shinjyoji, Kashiwa City, Chiba Prefecture Inside Daiki Engineering Co., Ltd. (72) Inventor Kanjo Takahashi 2-1-2, Watanabe-dori, Chuo-ku, Fukuoka City, Fukuoka Prefecture Inside Kyushu Electric Power Company (72 ) Inventor Masaru Shimizu 2-182 Watanabe-dori, Chuo-ku, Fukuoka City Inside Kyushu Electric Power Company (72) Inventor Masahiro Yoshinaga 2-182 Watanabe-dori, Chuo-ku Fukuoka City, Fukuoka Kyushu Electric Power Company (72) Inventor Hidetoshi Yano 2091-1, Shirahama, Shisahama, Shisa-cho, Matsuura-city, Nagasaki Prefecture Inside the Matsuura Power Station, Kyushu Electric Power Co., Inc. No. 2091, Shirahama Duty Developing No. 1 F-term in Matsuura Power Station, Kyushu Electric Power Co., Inc. 5G307 AA02 HB01 HB02 HC02

Claims (7)

[Claims] 1. A conductive rubber sheet formed by kneading a composition obtained by kneading a natural or synthetic rubber with a conductive powder into a sheet, wherein the conductive powder has a particle size of 1 to 20 μm.
Of amorphous graphite and carbon black having a particle size of 5 to 100 nm, each of which occupies 15 to 30% by weight (30 to 60% by weight in total) of the composition, and has a volume resistivity in the thickness direction. A conductive rubber sheet having a resistivity of 500 Ω · cm or less. 2. The conductive rubber sheet according to claim 1, wherein butyl rubber is used as the rubber. 3. The composition according to claim 1, wherein the total amount of the conductive powder is from 40 to 40% of the composition.
3. The conductive rubber sheet according to claim 1, which accounts for 50% by weight. 4. The conductive rubber sheet according to claim 1, wherein a volume resistivity in a thickness direction is 200 Ω · cm or less. 5. An apparatus for preventing fouling of a structure, a pipe, or a ship coming into contact with seawater due to organisms adhering thereto,
(A ₁₎ conducting directly lined conductive rubber sheet antifouling portion that requires of the antifouling body made of material or (A ₂₎ conductive or non-conductive a substance to be antifouling member, Either a power feeder disposed in proximity to a portion requiring antifouling or a conductive rubber sheet lined on the surface of the power feeder; (B) a submersible so as not to come into direct contact with the conductive rubber sheet; And (C) an antifouling device essentially consisting of a DC power supply and connected to a DC power supply such that the conductive rubber sheet serves as an anode and the electrode material serves as a cathode. An antifouling device using the conductive rubber sheet according to any one of claims 1 to 4. 6. The antifouling device according to claim 5, comprising a reference electrode, a constant potential control DC power supply for detecting a potential of the anode and supplying a DC current so that the potential is constant. 7. The antifouling device according to claim 5, wherein the structure or piping that comes into contact with seawater is a small- or large-diameter seawater intake pipe or a concrete seawater intake channel.