JP2005179501A - Conductive coating, conductive coated film, coating for monitoring cracks, and coated film for detecting cracks - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive coating, a conductive coated film, a crack detecting coating, and a crack detecting coated film, which have a volume resistivity optimum for detecting cracks, which are easy to install at a site, and with which cracks can be acculately detected. <P>SOLUTION: The crack detecting coating film 1 is formed by applying a conductive coating containing a carbon black and an epoxy resin. If a pair of electrodes 2a and 2b are arranged on the crack detecting coated film 1 and a crack C is introduced between the electrodes, the increase amount of the resistance between the electrodes is larger when the length of the crack C is longer, and a crack C of a very small length can be detected when the width W of the crack detecting coated film 1 is narrower. For example, in the case of applying the crack detecting coated film 1 in a width W=5 mm or smaller, a crack C of 1 mm or shorter can be detected, and in the case of applying the crack detecing coated film 1 in a width W=about 1 mm or smaller, a crack C of about 0.5 mm or shorter in length can be detected. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is applied to a conductive paint containing a conductive pigment and an organic resin, a conductive coating applied on the surface of the object to be coated, and applied to the surface of the object to be detected where cracks are expected to occur. The present invention relates to a crack detection paint for detecting cracks in an object and a crack detection coating film for detecting cracks.

  In steel structures, fatigue cracks occur at sites where tensile loads are applied due to repeated loads, and serious conditions such as loosening or dropping of rivets and bolts at joints occur. If such a serious condition grows to a size that affects the proof stress of the structure, the structure will be destroyed. Construction is being done for. The seriousness of steel structures develops over multiple years under normal conditions, so there is no need to repair or reinforce immediately when deformation occurs. Moreover, since the progress may stop in the middle of the deformation, it is necessary to monitor the progress after the occurrence of the deformation in order to determine the necessity of repair or reinforcement.

  For inspection of steel structures, periodic inspections that are conducted within two years, irregular inspections that are performed when a large load is received during an abnormality such as an earthquake, and abnormalities that are assumed by periodic inspections, etc. There are detailed inspections conducted. The periodic inspection and the irregular inspection mainly consist of visual inspection from the inspection passage by patrol, and in this visual inspection, the breakage portion of the anticorrosion coating film is visually observed in the vicinity of the portion where the occurrence of cracks is assumed. The coating film rupture accompanying the occurrence of cracks in the steel material grows linearly from the portion assumed to be the stress concentration portion, and can be easily distinguished from other coating film rupture causes. Moreover, it is known from past experience that the anticorrosion coating film breaks at the time of fatigue cracking of the steel material. Rupture of rivets and bolts can be easily detected using binoculars if the joint can be observed. Looseness of rivets and bolts can be detected by a hammering test in which the rupture state of the coating film around them is closely observed and a change in the hammering sound is confirmed with a hammer or the like. On the other hand, the detailed inspection may involve the construction of a scaffold for the inspection, although it varies depending on the inspection purpose. Deformation is discovered by visual inspection only at the site close to the inspection passage. In many cases, it is necessary to construct a scaffold and observe it closely, but it requires a lot of cost to construct the scaffold. Become. For this reason, except for highly urgent detailed inspections, inspection is carried out by using the coating scaffolding of the repainting work carried out every 10 to 15 years.

  In recent years, a method has been proposed in which a conductive thin film is arranged in a structure and the crack is detected by breaking the conductive thin film when a crack occurs in the structure. For example, a conventional crack detection material has a base layer formed by applying a waterproof insulating paint to the wall surface of a tunnel, and a conductive paint on the surface of the base layer so as to form a linear pattern electric circuit. A conductive layer formed by coating, and a protective layer formed by coating the conductive layer and the base layer with the same insulating paint as the base layer are provided (see Patent Document 1). In such a conventional crack detection material, if a crack occurs on the wall surface and an abnormality occurs, the periphery of this abnormal part is peeled off, the conductive layer is disconnected, and the conductive layer is in a non-energized state. An abnormal state of the wall surface can be detected by detecting a non-energized state.

Japanese Unexamined Patent Publication No. 2001-201477 (paragraph numbers 0010 to 0015 and FIG. 2)

  In such a conventional crack monitoring material, it is necessary to form a conductive layer with a conductive paint having a low electrical resistance capable of detecting a crack. In recent years, conductive coatings with low electrical resistance for the purpose of preventing electrification, electromagnetic shielding, prevention of condensation and the like are known. For example, in a conventional conductive paint (prior art 1), carbon black and graphite are mixed and dispersed in an acrylic resin aqueous dispersion (see Patent Document 2). In this prior art 1, the additive mixing ratio of carbon black and graphite is adjusted so as to minimize the electric resistance value, thereby preventing the occurrence of condensation. Moreover, the conventional conductive paint (conventional technology 2) mix | blends the carbon black pigment and the epoxy resin (refer patent document 3). In this prior art 2, the mixing ratio of the carbon black pigment and the epoxy resin is adjusted to reduce the variation in electric resistance value and improve the coating strength.

JP 2003-238881 (paragraph numbers 0018 to 0024)

JP 2002-302625 A (paragraph numbers 0010 to 0019)

  In the prior art 1, it is necessary to adjust two types of conductive pigments, carbon black and graphite, at a mixing ratio that lowers the volume resistivity. For this reason, it is difficult to adjust compared to the case of one kind of conductive pigment, and when used as a crack detection paint, the volume resistivity is too low to sufficiently detect the progress of cracks. There's a problem. Moreover, in the prior art 2, a carbon black pigment and an epoxy resin are mixed, but when used as a crack detection paint, the volume resistivity is too high, so that the occurrence of cracks and the progress of the cracks are fully detected. There is a problem that you can not.

  An object of the present invention is to provide a conductive coating, a crack detection coating, and a crack detection coating film that have an optimum volume resistivity for crack detection, are easy to perform on-site, and can accurately detect cracks. That is.

The present invention solves the above-mentioned problems by the solving means described below.
In addition, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this embodiment.
The invention of claim 1 is a conductive paint containing a conductive pigment and an organic resin, wherein the conductive pigment contains carbon black, the organic resin contains an epoxy resin, and the organic resin has a mass relative to the mass of the conductive pigment. A conductive paint characterized by having a mass of 300 to 700 wt%.

  The invention of claim 2 is a conductive paint containing a conductive pigment and an organic resin, wherein the conductive pigment contains nickel powder, the organic resin contains an epoxy resin, and the organic resin has a mass relative to the mass of the conductive pigment. A conductive paint characterized by having a mass of 20 to 80 wt%.

  The invention of claim 3 is a conductive coating film formed by being applied to the surface of the object to be coated, and formed by applying the conductive paint according to claim 1 or claim 2 to the surface of the object to be coated. It is a conductive coating film characterized by being made.

  According to a fourth aspect of the present invention, in the conductive coating film according to the third aspect, the surface of the object to be coated is an insulating layer surface of a steel structure or a surface of a concrete structure. It is a membrane.

  The invention according to claim 5 is a crack detection coating material that is applied to the surface of a detection object to be predicted to generate a crack and detects a crack of the detection object. A crack detection coating material comprising a conductive coating material.

  The invention of claim 6 is the crack detection paint according to claim 5, wherein the surface of the detection object is an insulating layer surface of a steel structure or a surface of a concrete structure. It is a paint.

  The invention of claim 7 is a crack detecting coating film for detecting cracks (C), and the resistance value between the electrodes (2a, 2b; 4) of the conductive coating film of claim 3 or claim 4. Is a crack-detecting coating film (1; 3), characterized by having a resistance of 200 to 10,000 Ω.

  The invention of claim 8 is the crack detection coating film according to claim 7, wherein the conductive coating film has a thickness of 10 to 100 μm.

  The invention according to claim 9 is the crack detecting coating film according to claim 7 or claim 8, wherein the conductive coating film has a physical property that the elongation at break by a tensile test is 10 to 30%. It is a coating film for crack detection.

  According to the present invention, it has an optimal volume resistivity for detecting cracks, is easy to perform on-site, and can detect cracks with high accuracy.

Hereinafter, embodiments of the present invention will be described in detail.
The crack detection coating film according to the embodiment of the present invention is a coating film for detecting cracks in a steel structure or the like, and is formed by applying a crack detection coating to the surface of an insulating layer of a steel structure. Here, the insulating layer of the steel structure is formed of an insulating paint or the like that causes a crack to occur at the same time when a crack occurs in the steel structure. The crack detection coating is a coating that is applied to the surface of an insulating layer of a steel structure where cracks are expected to occur and detects cracks in the steel structure. It is a conductive coating that contains a conductive pigment and an organic material. is there. As the conductive pigment, carbon black, graphite, nickel, copper, silver and the like are preferable, and as the organic resin, an epoxy resin, a polyurethane resin, an acrylic resin, a phenol resin, an alkyl silicate resin, and the like are preferable.

  If the thickness of the crack detection coating film is 10 μm or less, there is a risk that a continuous coating film may not be obtained by on-site construction, and if it is 100 μm or more, many coating film defects such as sagging occur when applied. If the viscosity is increased in order to prevent this, workability may be sacrificed. For this reason, the thickness of the crack detection coating film is preferably 10 to 100 μm, particularly preferably 30 to 60 μm. The physical properties of the crack detection coating film may break due to other factors such as expansion and contraction due to the temperature difference of the steel structure when the elongation at break by tensile test is 10% or less, and cracking of the steel structure occurs when it is 30% or more. There is a risk that the crack detection coating film will not be destroyed at the same time when the bolt is loosened. For this reason, as for the physical property of the coating film for a crack detection, it is preferable that the elongation at the time of the fracture | rupture by a tensile test is 10 to 30%. When detecting the progress of cracks, the crack detection coating film has a volume resistivity of 1 to 10 Ω · cm, and a resistance between electrodes after application of 200 to 10,000 Ω, preferably 200 to 2000 Ω, It is formed by adjusting the blending amount of the conductive pigment and the organic resin. The crack detection coating film has a lower volume resistivity of 0.01 to 1 Ω · cm when detecting the occurrence of cracks and a resistance between electrodes after coating of 200 to 200 when compared to the detection of crack growth. It is preferably formed by adjusting the blending amount of the conductive pigment and the organic resin so as to be 10000Ω, preferably 200 to 2000Ω. It is preferable to adjust the viscosity of the crack detection coating material to such an extent that it can be applied on site with a brush, roller, spray, or the like.

The crack detection coating film according to the embodiment of the present invention has the following effects.
(1) In this embodiment, the conductive paint contains carbon black and an epoxy resin, and the mass of the epoxy resin is 300 to 700 wt% with respect to the mass of the carbon black. As a result, since the volume resistivity is about 1 to 10 Ω · cm, the progress of a crack generated in a steel structure or the like can be detected. In this embodiment, the conductive paint contains nickel powder and an epoxy resin, and the mass of the epoxy resin with respect to the mass of the nickel powder is 20 to 80 wt%. As a result, since the volume resistivity is about 0.01 to 1 Ω · cm, it is possible to detect a crack generated in a steel structure or the like and the progress of the crack.

(2) In this embodiment, since the resistance value between the electrodes of the conductive coating film is 200-10000Ω, preferably 200-2000Ω, the occurrence of cracks and the progress of cracks can be detected with high accuracy. Further, in this embodiment, since the thickness of the conductive coating film is 10 to 100 μm, the coating film can be continuously formed on site and the occurrence of coating film defects such as dripping can be prevented. Furthermore, in this embodiment, since the elongation at break by a tensile test of the conductive coating film is 10 to 30%, the coating film can be broken almost simultaneously with the occurrence of a crack in a steel structure or the like. It is possible to prevent the coating film from cracking due to shrinkage due to temperature change of a steel structure or the like.

Next, examples of the present invention will be described.
(Resistance measurement experiment 1)
FIG. 1 is a configuration diagram of resistance measurement experiment 1 for a crack detection coating film according to an embodiment of the present invention, FIG. 1 (A) is a plan view, and FIG. 1 (B) is a front view.
FIG. 1 is a diagram showing a state in which an insulating layer is applied on a detection target in which the occurrence of cracks is predicted, and a crack detection coating film 1 is applied thereon. This crack detection coating film 1 is a coating film for detecting cracks in the detection object. The crack-detecting coating film 1 is formed by applying a crack-detecting coating material in a strip shape, and the electrical resistance changes according to the occurrence of a crack. The crack detection coating film 1 is formed by applying a conductive paint having a resin / pigment ratio of 500% containing carbon black as a conductive pigment and liquid epoxy as an organic material. The electrodes 2a and 2b are portions through which an electric current is passed through the crack detection coating film 1, and are formed on the surface of the crack detection coating film 1 with a distance L ₁ = 700 mm. The crack detection coating film 1 shown in FIG. 1 is formed with a length L = 720 mm and a thickness t = 0.06 mm, and the crack detection coating film 1 is changed to a width W = 1 to 300 mm. A crack C was introduced from one of the long sides, and the electrical resistance between the electrodes 2a and 2b was measured.

FIG. 2 is a graph showing the measurement results of resistance measurement experiment 1 of the crack detection coating film according to the example of the present invention. FIG. 3 is a graph showing the relationship between the crack length and the amount of increase in resistance value when the crack detection coating film according to the example of the present invention is applied at a width = 50 mm.
The graphs shown in FIGS. 2 and 3 show the relationship between the crack length of the crack detection coating film 1 and the amount of increase in the resistance value, the horizontal axis is the length (mm) of the crack C, and the vertical axis is the electrode 2a. , 2b, the increase in resistance value (Ω). 2 and 3, as the length of the crack C increases, the amount of increase in the resistance value between the electrodes 2a and 2b increases, and the width W of the crack detection coating film 1 is narrow as shown in FIG. It is considered that the crack C having a very small length can be detected. For example, as shown in FIG. 2, when the crack detection coating film 1 is applied with a width W = 5 mm or less, a crack C of 1 mm or less can be detected, and the crack detection coating film 1 has a width W = When applied at about 1 mm, a crack C having a length of about 0.5 mm can be detected. Further, when the crack detection coating film 1 is applied with a width W of about 10 mm, a crack length of nearly 10 mm can be detected with an accuracy of about 5 mm in length.

(Resistance measurement experiment 2)
4A and 4B are configuration diagrams of resistance measurement experiment 2 of the crack detection coating film according to the embodiment of the present invention, FIG. 4A is a plan view, and FIG. 4B is a front view.
The crack detection coating film 3 shown in FIG. 4 is a coating film that is applied on the insulating layer of the detection target that is predicted to generate cracks and detects cracks in the detection target. The crack detection coating 3 is formed by applying a crack detection coating to the surface of a 3.0 mm thick substrate with a length L = 1800 mm and a width W = 900 mm in a thickness of t = 0.06 mm. The electrical resistance changes according to the occurrence of cracks. The crack detection coating film 3 is formed by applying the same conductive paint as the crack detection coating film 1 shown in FIG. The electrode 4 is a portion for passing an electric current through the crack detection coating 3 and is spaced at a distance of L ₁ = 400 mm from the short side of the crack detection coating 3 and a distance L ₂ = 225 mm from the long side. It is formed with D ₁ = 225 mm and a lateral distance D ₂ = 500 mm. A crack C was introduced into the center of the crack detection coating film 3 shown in FIG. 4 and the electrical resistance between the electrodes 4 was measured.

FIG. 5 is a graph showing a measurement result of resistance measurement experiment 2 of the crack detection coating film according to the example of the present invention.
The graph shown in FIG. 5 shows the relationship between the crack length of the crack detection coating film 3 and the amount of increase in the resistance value, and the horizontal axis represents the crack length with respect to the short side length (mm) of the crack detection coating film 3. (mm) ratio, and the vertical axis represents the amount of resistance increase (Ω) between the electrodes 4. Here, α is an average value of resistance increase amounts between the electrode positions P _I and P _{i and} between the electrode positions P _III and P _{iii shown} in FIG. β is an average value of the resistance increase amount between the electrode positions P _II and P _i, between the electrode positions P _II and P _iii, between the electrode positions P _I and P _{ii, and} between the electrode positions P _III and P _ii . γ is the average value of the resistance increase between the electrode positions P _I and P _{iii and} between the electrode positions P _III and P _i . As shown in FIG. 5, there is no change in the amount of increase in the resistance value between the electrode positions P _A and P _B facing each other in the same direction as the progress direction of the crack C regardless of the size of the crack C. On the other hand, between the electrode positions P _II and P _ii facing each other in a direction crossing the direction of propagation of the crack C, the resistance change amount increases as the crack C increases. As a result, the generation of the crack C and the length of the crack C are detected by detecting a change in the resistance value between the electrode positions P _II and P _ii arranged in the direction intersecting the propagation direction of the crack C. It is possible to detect the progress direction of the crack C.

(Example 1)
FIG. 6 is a graph showing the relationship between the resin / pigment ratio and the volume resistivity of the crack detection coating material according to Example 1 of the present invention.
The horizontal axis shown in FIG. 6 is the resin / pigment ratio (wt%), and the vertical axis is the volume resistivity (specific resistivity) (Ω · cm). Here, the resin / pigment ratio indicates the ratio of the mass of the resin to the mass of the pigment, and the smaller the value, the smaller the amount of resin. Example 1 includes carbon black (manufactured by Denki Black Co., Ltd., trade name: Denka Black) as a conductive pigment, and a liquid epoxy resin (trade name: Epicron, produced by Dainippon Ink & Chemicals, Inc.) as an organic material. It is a crack detection coating material containing.

  Table 1 shows the measurement results of the volume resistivity of carbon black / liquid epoxy resin. In Example 1, as shown in FIG. 6 and Table 1, when the resin content decreases, the volume resistivity decreases and the conductivity is improved. When the crack detection coating material of Example 1 is used as a crack growth detection coating film for detecting the crack growth, the volume resistivity is about 1 to 10 Ω · cm with respect to the mass of the conductive pigment. It is desirable to adjust the mass of the organic resin to about 300 to 700 wt%.

(Example 2)
FIG. 7 is a graph showing the relationship between the resin / pigment ratio and the volume resistivity of the crack detection coating material according to Example 2 of the present invention.
The horizontal axis shown in FIG. 7 is the resin / pigment ratio (wt%), and the vertical axis is the volume resistivity (mΩ · cm). Example 2 is for crack detection, which contains nickel powder (reagent manufactured by Kanto Chemical Co., Inc.) as a conductive pigment, and liquid epoxy resin (trade name: Epicron, manufactured by Dainippon Ink & Chemicals, Inc.) as an organic material. It is a paint.

  Table 2 shows the measurement results of the volume resistivity of the nickel powder / liquid epoxy resin. In Example 2, as shown in FIG. 7 and Table 2, when the resin content decreases, the volume resistivity decreases and the conductivity is improved as in Example 1. In the case of using the crack detection coating material of Example 2 as a crack growth detection coating film for detecting the progress of cracks or a crack generation detection coating film for detecting the occurrence of cracks, the volume resistivity is 0.01 to It is desirable to adjust the mass of the organic resin to about 20 to 80 wt% with respect to the mass of the conductive pigment so as to be about 0.04 Ω · cm.

  The present invention is not limited to the embodiments described above, and various modifications or changes are possible, and these are also within the scope of the present invention. For example, in this embodiment, the steel structure has been described as an example of the detection target, but the present invention can also be applied to other structures such as a concrete structure. In this case, the crack detection paint can be applied to the surface of the concrete structure. Also, in this embodiment, the case where the crack detection coating material is manufactured using a liquid epoxy resin whose resin itself is liquid has been described as an example. However, the solid epoxy which has a higher molecular weight than that of the liquid epoxy resin and is solid at room temperature. It is also possible to produce a crack detection coating material with a resin. Furthermore, in this embodiment, the case where the crack detection coating material is manufactured using nickel powder has been described as an example, but the present invention is not limited to this. For example, even if other metal pigments other than nickel powder whose surface is covered with an oxide can be formed into a conductive coating film by being pulverized in a resin, cracks are caused by such other metal pigments. A detection paint can also be produced.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the resistance measurement experiment 1 of the coating film for a crack detection which concerns on the Example of this invention, (A) is a top view, (B) is a front view. It is a graph which shows the measurement result of the resistance measurement experiment 1 of the coating film for a crack detection which concerns on the Example of this invention. It is a graph which shows the relationship between the crack length when the coating film for a crack detection based on the Example of this invention is apply | coated by width = 50mm, and the increase amount of resistance value. It is a block diagram of the resistance measurement experiment 2 of the coating film for crack detection which concerns on the Example of this invention, (A) is a top view, (B) is a front view. It is a graph which shows the measurement result of the resistance measurement experiment 2 of the coating film for a crack detection which concerns on the Example of this invention. It is a graph which shows the relationship between the resin / pigment ratio and volume resistivity of the crack detection coating material which concerns on Example 1 of this invention. It is a graph which shows the relationship between resin / pigment ratio of the coating material for crack detections based on Example 2 of this invention, and volume resistivity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coating film for crack detection 2a, 2b Electrode 3 Coating film for crack detection 4 Electrode

Claims (9)

A conductive paint containing a conductive pigment and an organic resin,
Carbon black is included as the conductive pigment,
Including an epoxy resin as the organic resin,
The weight of the organic resin with respect to the weight of the conductive pigment is 300 to 700 wt%,
Conductive paint characterized by A conductive paint containing a conductive pigment and an organic resin,
Including nickel powder as the conductive pigment,
Including an epoxy resin as the organic resin,
The mass of the organic resin relative to the mass of the conductive pigment is 20 to 80 wt%,
Conductive paint characterized by A conductive coating applied to the surface of the object to be painted,
The conductive paint according to claim 1 or 2 is applied and formed on the surface of the object to be coated.
Conductive coating film characterized by In the electroconductive coating film of Claim 3,
The surface of the object to be painted is an insulating layer surface of a steel structure or a surface of a concrete structure;
Conductive coating film characterized by A crack detection coating that is applied to the surface of a detection object where cracks are predicted to occur and detects a crack in the detection object,
Including the conductive paint according to claim 1 or 2,
A paint for crack detection. In the crack detection paint according to claim 5,
The surface of the detection object is an insulating layer surface of a steel structure or a surface of a concrete structure;
A paint for crack detection. A crack detection coating for detecting cracks,
The resistance value between the electrodes of the conductive coating film according to claim 3 or claim 4 is 200 to 10,000Ω,
A coating for crack detection, characterized by In the crack detection coating film according to claim 7,
The thickness of the conductive coating film is 10-100 μm,
A coating for crack detection, characterized by In the coating film for crack detection according to claim 7 or claim 8,
The physical property of the conductive coating film is that the elongation at break by a tensile test is 10 to 30%,
A coating for crack detection, characterized by

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