JP7853473B1 - Oil leak detection material - Google Patents

Abstract

[Problem] To provide an oil leak detection material that can reliably detect only oil leaks even when wet with rainwater or other water, can accurately detect the location of an oil leak in a short time regardless of the viscosity or amount of the oil leak to be detected, and has excellent weather resistance and water resistance.
[Solution] The oil leak detection material 10 comprises a colored layer 11 colored with a predetermined color, and a white discoloration layer provided in contact with at least a part of the upper surface of the colored layer 11, in which white powder 12, which is white particles or white powder, has a coating 12a made of silicone resin or silicone rubber on at least a part of its surface, and the white powder 12 is bound together by the coating 12a, while having gaps that absorb oil leaks and repel water.
[Selection Diagram] Figure 1

Description

This invention relates to an oil leak detection material that can reliably detect oil leaks and has excellent weather resistance and water resistance.

Oil leaks in welded joints of oil storage tanks and containers, and in joints of oil piping, were previously detected during periodic inspections when the tanks and containers were empty and no oil was flowing through the piping. This involved filling the empty tanks, containers, and piping with nitrogen gas to a specified pressure and observing the rate of pressure drop to check for leaks. However, while oil leaks in tanks, containers, and piping carrying oil must be detected visually, small leaks may not be detected visually.

As a detection material capable of detecting oil leaks from tanks and containers where oil is stored, or from oil pipes through which oil flows, Patent Document 1 discloses an oil leak detection material made of synthetic resin having water permeability and oil-retaining properties that absorb and retain oil, formed from a nonwoven fabric with a thickness of 200 μm or more, having a colored layer in which the nonwoven fabric is colored, and a white layer with a thickness of at least 150 μm laminated on one side of the colored layer, in which a white powder with a refractive index of 1.5 to 1.6 is dispersed in a transparent resin so that the color of the colored layer is opaque when the colored layer is wet with water, and transparent when the colored layer is wet with oil, allowing the hue of the colored layer to be seen.
However, with conventional oil leak detection materials, the white layer becomes slightly transparent when wet with water such as rainwater, which can lead to misidentification as an oil leak. Furthermore, if the white layer does not dry sufficiently after getting wet, the oil leak will not penetrate the white layer sufficiently, resulting in insufficient transparency of the white layer and making reliable detection of the oil leak impossible. Moreover, since the refractive index of the white powder in the white layer is 1.5 to 1.6, the white layer does not become sufficiently transparent with silicone oil, which has a refractive index of 1.4, making it difficult to detect silicone oil leaks.

Therefore, the applicant has already provided, as in Patent Document 2, an oil leak detection material comprising: a colored layer having oil absorption properties and colored with a predetermined color; a white layer having oil absorption properties provided in contact with at least a part of the upper surface of the colored layer and containing or having white particles or white powder attached to a transparent resin layer; a protective layer made of a transparent hydrophobic resin provided so as to cover the upper surface of the white layer; and an oil absorption layer provided on the lower side of the colored layer and being made of a material having oil absorption and oil retention properties and being water-repellent or having been treated with a water-repellent coating, wherein the colored layer and the white layer contain water To prevent penetration, the colored layer and the white layer are sandwiched between the protective layer and the oil-absorbing layer. Furthermore, the refractive index difference between the oil (the target of oil leak detection) with a refractive index of 1.40 to 1.55 and the white particles or white powder is 0.1 or less. When oil leaks or oil leaks and water come into contact with at least a portion of the surface of the oil-absorbing layer, only the oil leaks are absorbed by the oil-absorbing layer and penetrate the colored and white layers, causing the white layer to become transparent or semi-transparent, and allowing the hue of the colored layer to be visually observed through the protective layer. This oil leak detection material has been developed.

The oil leak detection material developed in this way is resistant to rainwater and can detect silicone oil. However, because the oil leak seeps into the oil-absorbing layer from the side via capillary action, penetrates through the colored layer, and reaches the white layer, the white layer becomes transparent or semi-transparent, and the color of the colored layer gradually becomes visible, causing a change in color and thus detecting the oil leak. Therefore, detecting an oil leak can take several minutes to tens of minutes or more even for low-viscosity oils like gasoline, and several hours for high-viscosity oils, resulting in the problem of not being able to quickly detect oil leaks.

Furthermore, this oil leak detection material requires a sufficient amount of oil to penetrate the oil-absorbing layer in the layer-plane direction and diffuse not only into the colored layer but also into the interlayer direction of the white layer. Therefore, there was a risk that small amounts of droplet-like oil leaks might not cause discoloration and thus go undetected, or that extremely small amounts of mist-like oil leaks might not be detected.

Furthermore, this oil leak detection material had a problem in that it could not accurately detect the location of the oil leak because the oil leaked from the leak point penetrated and diffused into the oil-absorbing layer, colored layer, and white layer, and the direction of penetration and diffusion was influenced by the fiber orientation of the oil-absorbing layer, colored layer, and white layer.

Furthermore, these oil leak detection materials used a lipophilic transparent resin in the white layer, such as ethylcellulose (a cellulose-based resin). However, sunlight and ultraviolet light easily broke the carbon-carbon bonds in the main chain, causing it to become hydrophilic in a short period, making it prone to discoloration from rainwater and water leaks. Therefore, there was a need for an oil leak detection material with excellent weather and water resistance, that did not discolor with water, and only discolored in the event of an oil leak.

Patent No. 6609085 Patent No. 7546125

The present invention aims to provide an oil leak detection material that can reliably detect only oil leaks even when wet with rainwater or other water, can accurately detect the location of the oil leak in a short time regardless of the viscosity or amount of the oil leak to be detected, and has excellent weather resistance and water resistance.

The oil leak detection material of the present invention, which was made to achieve the above objective,
A colored layer that has been colored with a predetermined color,
A white discoloration layer is provided in contact with at least a portion of the upper surface of the colored layer, and the white powder, which is white particles or white powder, has a coating made of silicone resin or silicone rubber on at least a portion of its surface, and the white powder particles are bound together by the coating, while having gaps that absorb oil and repel water.
They are prepared.

This oil leak detection material works by having the oil leak absorbed into the gap, causing the discoloration layer to become transparent and making the color of the colored layer visible.

This oil leak detection material preferably contains the white particles or white powder having a refractive index of 1.40 to 1.50.

This oil leak detection material is made of a silicone resin or silicone rubber having, for example, a polydimethylsiloxane skeleton, a polydiphenylsiloxane skeleton, or a polymethylphenylsiloxane skeleton.

This oil leak detection material contains, for example, 30 to 90 parts by mass of the white powder and 10 to 70 parts by mass of the silicone resin or silicone rubber in the discoloration layer.

This oil leak detection material is such that, for example, the discolored layer is a coating layer of a composition containing the white powder, binder, and solvent, and the gaps represent traces of the solvent's disappearance within the coating layer.

This oil leak detection material may have the underside of the colored layer covered with an oil-absorbing or non-oil-absorbing base layer, such as an oil-absorbing base layer selected from woven fabric, non-woven fabric, and paper, or a film.

This oil leak detection material may also include an oil-absorbing and/or oil-permeable protective layer, selected from woven fabric, non-woven fabric, paper, and mesh, covering the upper surface of the discoloration layer.

In this oil leak detection material, it is preferable that the protective layer is made of a hydrophobic material.

Preferably, this oil leak detection material has an adhesive layer or a tacky layer on the underside of the colored layer that can adhere to the object to which the oil leak is to be detected.

This oil leak detection material may have a structure in which the adhesive layer or the adhesive layer and the colored layer are permeable to the oil leak.

This oil leak detection material is characterized in that the white powder is, for example, white particles or white powder selected from organic compounds, metal soaps, plastic powders, metal inorganic salts, minerals, glass beads, and glass fillers.

This oil leak detection material is more preferably composed of white particles or a white powder containing the metal soap and/or amorphous silica.

This oil leak detection material is even more preferably composed of white particles or a white powder containing amorphous silica.

This oil leak detection material is characterized in that the colored layer is colored with one of the following colors, for example, black, navy blue, red, orange, blue, green, brown, and purple, as well as any intermediate color therein.

This oil leak detection material may have the colored layer and/or the discoloration layer shaped into letters, symbols, and/or figures, or the colored layer may be printed in the shape of letters, symbols, and/or figures.

Preferably, the difference in refractive index between the white particles or white powder and the oil leak in this oil leak detection material is 0.1 or less.

The oil leak detection material of the present invention does not change color to transparent or semi-transparent even when wet with water from leaks or rainwater. Even when wet, the color-changing layer, which is made of silicone resin or silicone rubber, changes color to transparent or semi-transparent only when exposed to oil from a leak, allowing the color of the colored layer to become visible. Therefore, oil leaks can be reliably detected without misidentification.

Furthermore, this oil leak detection material can detect oil leaks in a timely manner, whether large quantities or small amounts such as droplets or oil mist. As long as the oil seeps into the discoloration layer, the layer changes color extremely quickly—from white to transparent or semi-transparent—within tens of seconds at the latest, revealing the color of the colored layer.

Furthermore, this oil leak detection material allows for accurate identification of the leak location and enables rapid repairs, as only the areas wet with oil become transparent or semi-transparent, revealing the color of the underlying oil leak.

Furthermore, because the silicone resin or silicone rubber in the discoloration layer of this oil leak detection material does not decompose or become hydrophilic due to sunlight or ultraviolet rays, it has excellent weather resistance and water resistance, and can maintain its performance for a long period of time. Therefore, it does not require frequent replacement, reducing troublesome labor.

These are a front view and a schematic cross-sectional view showing the state before and after use of one embodiment of an oil leak detection material to which the present invention is applied. This is a schematic cross-sectional view showing a partially enlarged view of the discolored layer of an oil leak detection material to which the present invention is applied. These are a front view and a schematic cross-sectional view showing the state of an oil leak detection material before and after use in another embodiment to which the present invention is applied. These are a front view and a schematic cross-sectional view showing the state of an oil leak detection material before and after use in another embodiment to which the present invention is applied. This is a schematic cross-sectional view showing the state of an oil leak detection material before use in another embodiment to which the present invention is applied.

Figure 1(a1) shows a front view of an example of the oil leak detection material 10 to which the present invention is applied before use, and Figure 1(b1) shows a schematic cross-sectional view of the material along the X-X line. Figure 1(a2) shows a front view of an example of the material in use, attached to an object 30 to be detected for oil leak detection, with the oil leak 20 adhering to it, and Figure 1(b2) shows a schematic cross-sectional view of the material along the X-X line.

As shown in Figures 1(a1) and (b1), this oil leak detection material 10 has a rectangular colored layer 13 colored with a predetermined color, a white discoloration layer 11 containing white powder 12 of the same size and rectangular shape as the colored layer 13, and a release paper 16 bonded to it via a release paper adhesive layer 15. In the discoloration layer 11, as shown in Figure 2, at least a portion of the surface of the white powder 12 has a coating 12a made of silicone resin or silicone rubber, and the white powder 12 particles are connected to each other by the coating 12a. This creates gaps 12b that absorb the leaked oil 20 (see Figures 1(a2) and (b2)) and repel water, preventing water absorption.

As shown in Figures (a2) and (b2), the oil leak detection material 10 works by absorbing the leaked oil 20 into the gap 12b, wetting the white powder 12. This causes the discoloration layer 11 to become transparent, allowing the color of the colored layer 13 to be visible, thus enabling detection of oil leaks and their locations.

A white discoloration layer 11 is provided in close contact with the upper surface of the colored layer 13. The discoloration layer 11 is formed by a coating layer of a composition containing white powder 12, a silicone resin or silicone rubber raw material binder, and a solvent. After coating with the composition, as the solvent evaporates, the raw material binder, or the cured silicone resin or silicone rubber (if necessary, heat-cured or photo-cured), forms a film 12a on at least a portion of the surface of the white powder 12, binding the white powder particles 12 together. However, gaps 12b are formed as traces of the solvent's disappearance within the coating layer due to the evaporation of the solvent. At this time, the discoloration layer 11 and the colored layer 13 bond together due to the bonding properties of the raw material binder. Because the gaps 12b are formed between the individual white particles or white powder of the white powder 12, the discoloration layer 11 is a porous layer.

To form the gap 12b, it is important to adjust the ratio of the white powder 12 to the silicone resin or silicone rubber raw material binder in the composition by weight to 30-90:70-10, preferably 50-80:50-20. Such a composition may optionally contain additives such as a silicone crosslinking agent.

If the mass ratio of the white powder 12 to the silicone resin or silicone rubber binder falls outside the range of 30-90:70-10, and the proportion of the white powder 12 is low, the whiteness decreases due to a reduction in porosity and a relative decrease in the white component of the white powder. This results in a smaller color change with the colored layer 13 during oil leakage. On the other hand, if the mass ratio of the silicone resin or silicone rubber binder is low, the water repellency and coating strength decrease, leading to discoloration due to water absorption, or a brittle coating that easily peels off.

The mass ratio of the white powder 12 to the raw material binder of silicone resin or silicone rubber is adjusted as appropriate depending on the characteristics of the white powder 12 (for example, physical properties such as particle size and specific surface area).
For example, if the white powder 12 is mainly silica-based powder with an average particle size of about 10 μm, a ratio of about 40 parts by mass of white powder to 60 parts by mass of silicone resin or silicone rubber is preferred. On the other hand, if the white powder 12 is zinc stearate with an average particle size of about 10 μm, a ratio of about 75 parts by mass of white powder to 25 parts by mass of silicone resin or silicone rubber is preferred.

Suitable materials for use as white powders are those with a refractive index in the range of 1.40 to 1.50, that are resistant to decomposition by sunlight and ultraviolet light, are poorly soluble in water, and have a melting point (above 100°C) that does not melt at ambient temperature. Materials that meet these characteristics include metal soaps and silica, which are preferred. Silica, in particular, is preferred over metal soaps with similar refractive indices because it becomes clearer and more transparent upon contact with oil, and also has a higher melting point.

The white powder 12 is made visible as white due to diffuse reflection, provided its average particle size is 20 μm or less, preferably 20 to 1 μm. A particle size of 10 μm or less is particularly preferable, as it enhances the light scattering effect and increases the whiteness of the discoloration layer 11. The particle size of the white powder or white particles is measured, for example, using a grindometer. Since the silicone resin or silicone rubber coating 12a is extremely thin and almost transparent, the white powder 12 continues to diffusely reflect light regardless of its thickness, even if at least a portion of its surface is coated with silicone resin or silicone rubber. Therefore, the discoloration layer 11 is visible as white unless it comes into contact with the leaked oil 20.

When the discolored layer 11 comes into contact with the leaked oil, the high permeability of the leaked oil to the gap 12b due to the silicone resin and silicone rubber in the coating 12a allows the leaked oil to penetrate the gap 12b, overcoming the oil-repellent properties of the silicone resin and silicone rubber. Once the gap 12b is filled, the white powder 12 can no longer diffusely reflect light, becoming transparent or semi-transparent. This phenomenon occurs because light that has passed through the permeated leaked oil can pass through the discolored layer 11 without being significantly bent at the boundary with the white powder or white particles.

However, because silicone resins and silicone rubbers have high water repellency and therefore low affinity for water, moisture such as rainwater, leaks, and humidity cannot penetrate the gaps 12b. Therefore, even when wet with these moisture, the discoloration layer 11 remains white, rather than becoming transparent or semi-transparent. Thus, the oil leak detection material 10 is capable of selectively detecting oil leaks.

However, silicone resins and silicone rubbers do not decompose in sunlight or ultraviolet light, are resistant to hydrophilicity, and are highly resistant to high temperatures and humidity, making them excellent materials in terms of weather resistance and water resistance. Therefore, this oil leak detection material 10 does not change color with water, only with oil leaks, and does not deteriorate even under harsh indoor and outdoor conditions, maintaining high weather resistance, water resistance, and oil leak detection selectivity.

Examples of such white particles or white powders include those that are solid at room temperature, specifically fatty acid derivatives such as stearic acid and palmitic acid and their calcium salts such as metal soaps, alcohol derivatives, ether derivatives, aldehyde derivatives, ketone derivatives, amine derivatives, amide derivatives, nitrile derivatives, hydrocarbon derivatives, thiol derivatives, sulfide derivatives, and other organic compound powders or particles, as well as polyvinyl chloride, polyethylene, polypropylene, polystyrene, acrylonitrile butadiene styrene, acrylonitrile styrene, polymethyl methacrylic, polyvinyl alcohol, polyvinylidene chloride, polyethylene terephthalate, polyamide, polyacetal, and poly Examples include plastic powders or particles such as recarbonates, polyphenylene ethers, polybutylene terephthalate, polyvinylidene fluoride, polysulfones, polyethersulfones, polyphenylene sulfides, polyarylates, polyamide-imides, polyetherimides, polyetheretherketones, polyimides, liquid crystal polymers, polytetrafluoroethylenes, phenolic resins, urea resins, melamine resins, unsaturated polyesters, epoxy resins, silicone resins, and polyurethanes; alkaline earth metal salts such as magnesium carbonate and calcium carbonate; inorganic metal salt powders or particles such as aluminum hydroxide, talc, and silica; mineral powders or particles; glass beads; and glass fillers.

It is preferable to select such white powders or particles such that the refractive index difference between them and the oil being detected is 0.1 or less. The oil being detected is a hydrophobic oil derived from minerals such as petroleum, animals, or plants, that floats on water and is liquid at room temperature, with a refractive index of 1.40 to 1.55, such as insulating oil, kerosene, light oil, heavy oil, linseed oil, paraffin oil, silicone oil, or hydraulic oil. When such oil is used as the target of oil detection, preferred white powders or particles include stearic acid (refractive index 1.43), talc (refractive index 1.54), urea resin powder (refractive index 1.57), calcium carbonate (refractive index 1.50 to 1.64), aluminum hydroxide (refractive index 1.57), magnesium carbonate (refractive index 1.52 to 1.53), glass beads (refractive index 1.52 to 1.57), and glass filler (refractive index 1.50 to 1.58).

These white powders or white particles may be used individually or in combination of several types, such as two or three types.

The thickness of the discolored layer 11 should be 1 μm or more to ensure sufficient opacity, which is preferable. The upper limit of the discolored layer 11 should preferably be 260 μm or less, considering its relationship to the flexibility of the oil leak detection material 10.

In the oil leak detection material 10, the colored layer 13 can be made of an oil-absorbing material, such as paper, nonwoven fabric, woven fabric, porous cement, porous ceramics, porous metal, or other porous inorganic materials, foamed plastic, or an ink coating. These materials are colored to a predetermined color. The coloring is preferably done with a coloring agent such as a pigment, dye, or mixture thereof that is resistant to fading in sunlight and has excellent lightfastness. A hue that is easily recognizable by the naked eye or image sensor and has a clear contrast with white is preferred, and among these, chromatic colors such as black, navy blue, red, orange, blue, green, brown, or purple, or intermediate colors of any of these, are even more preferred. Black and navy blue are prone to changes in brightness and may be mistaken for shadows, so red, which is a dangerous color due to changes in saturation, is practical and even more preferred.
The coloring may be applied to the material constituting the oil-absorbing material, or to the material molded into a predetermined shape. The thickness of the colored layer 13 is preferably 1 to 150 μm.

The oil leak detection material 10 shown in Figure 1 is manufactured as follows. First, a composition containing white powder 12, a silicone resin or silicone rubber raw material binder, a solvent, and various additives as needed is prepared. This composition is applied to the upper surface of a colored layer 13, which has a release paper attached to an adhesive layer 15 on its lower side, to form a coating layer. The resulting coating layer is air-dried or air-dried to evaporate the solvent, and then heat-treated or light-irradiated as needed to cross-link and harden into silicone resin or silicone rubber. The hardened material forms a film 12a on at least a portion of the surface of the white powder 12, binding the white powder particles together, and gaps 12b are formed as the solvent evaporates, resulting in the oil leak detection material 10.

As shown in Figure 1(b2), the oil leak detection material 10 is used by attaching the adhesive layer 15 to the object 30 to be detected for oil leaks, such as flanges and pipes. When oil leaks onto the discolored layer 11, it penetrates into the gap 12b, and at the point of penetration, the discolored layer 11 becomes transparent or semi-transparent, making the colored layer 13 visible. This allows for the rapid detection of both the fact of an oil leak and the location of the leak. Since this penetration of oil into the gap 12b is more of a filling phenomenon than capillary action, the oil does not diffuse to areas other than the leak location, making it possible to identify the discolored area retrospectively.

The mechanism by which the oil leak detection material 10 changes color is presumed to be as follows. When the oil leak detection material 10 is not in contact with an oil leak, only the white color of the discolored layer 11 is visible, as shown in Figure 1(a1), and the hue of the colored layer 13 is not visible. The refractive index difference between the white particles or white powder dispersed in the discolored layer 11 and the air in the gaps, i.e., microscopic spaces, surrounding the white particles or white powder is large, and the light that has passed through the discolored layer 11 is greatly bent and dispersed at the boundary between the white particles or white powder and the microscopic spaces. On the other hand, when an oil leak comes into contact with the oil leak detection material 10, the oil penetrates into the discolored layer 11. The discolored layer 11 becomes transparent or semi-transparent, and the hue of the colored layer 13 becomes visible, as shown in Figure 1. The refractive index difference between the oil that has penetrated the discolored layer 11 and filled the microscopic space surrounding the white particles or white powder and the white particles or white powder is smaller than the refractive index difference between air and the white particles or white powder. This allows light that has passed through the discolored layer 11 to pass through without significant refraction at the boundary between the white particles or white powder and the oil in the microscopic space. Therefore, it is preferable to select the white powder or white particles such that their refractive index difference with the oil in the oil-detection target is 0.1 or less.

Although not shown in Figure 1(b2), this oil leak detection material 10 may also be used in a way that allows oil seeping from the object to be detected 30 to penetrate the adhesive layer 15, colored layer 13, and discoloration layer 11, causing the discoloration layer 11 to change to a transparent or semi-transparent state, making the color of the colored layer 13 visible. It is preferable that the adhesive layer 15 be formed from an adhesive such as rubber, acrylic, silicone, polyvinyl, or polyurethane, so that the oil leak penetrates the adhesive layer 15 and reaches the colored layer 13 and discoloration layer 11.

Another embodiment of the oil leak detection material 10 is shown in Figure 3. A schematic cross-sectional view of an example before use is shown in Figure 3(a1), and a schematic cross-sectional view of the material in use, after being attached to the object to be detected for oil leaks 30 and with the oil leak 20 adhering to it, is shown in Figure 3(a2). This embodiment of the oil leak detection material 10 has a base layer 14 between the colored layer 13 and the adhesive layer 15 of the oil leak detection material in Figure 1. This oil leak detection material 10 can be used in the same manner as shown in Figure 1.

The base material layer 14 may be, for example, an oil-permeable nonwoven or woven fabric made of a hydrophobic resin, preferably a nonwoven fabric. Examples of hydrophobic resins include cellulose, cellulose derivatives, polyolefins, polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, hydrochloric acid rubber, polyamide, fluororesin, polybutene, polyvinyl butyral, polyethylene oxide, polyurethane, cellulose acetate butyrate, hydroxyethylcellulose, and polyimide.

The colored layer 13 may be made of the aforementioned materials and may be attached to the base layer 14 via adhesives such as heat welding, rubber-based, acrylic-based, silicone-based, polyvinyl-based, polyurethane-based adhesives, or composites thereof. Alternatively, the colored layer 13 may be printed onto the base layer 14 using a colorant-containing ink.

The base layer 14 may be made of a hydrophobic resin and, by making it an oil-impermeable film, detect only oil leaks from the discoloration layer 11 side. Examples of such hydrophobic resins include cellulose, cellulose derivatives, polyolefins, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyester, polystyrene, hydrochloric acid rubber, polyamide, fluororesin, polybutene, polyvinyl butyral, polyethylene oxide, polyurethane, cellulose acetate butyrate, hydroxyethylcellulose, and polyimide.

Another embodiment of the oil leak detection material 10 is shown in Figure 4. A schematic cross-sectional view of an example before use is shown in Figure 4(a1), and a schematic cross-sectional view of the material in use, after being attached to the object to be detected for oil leaks 30 and with oil leaks 20 adhering to it, is shown in Figure 4(a2). This embodiment of the oil leak detection material 10 has a protective layer 17 made of nonwoven fabric on the upper surface of the discolored layer 11 of the oil leak detection material in Figure 1. This oil leak detection material 10 can be used in the same manner as shown in Figure 1.

The discoloration layer 11 consists of a white powder 12 and a coating 12a, and because it has gaps, it is easily peeled off by physical contact such as scratching with a fingernail or rubbing against tools. Therefore, covering and protecting it with an oil-absorbing and/or oil-permeable nonwoven fabric protective layer 17 does not affect oil leak detection, but also provides protection against physical contact.

The protective layer 17 may be made of nonwoven fabric, or of any other material such as woven fabric, paper, or mesh, as long as it is oil-absorbing and/or oil-permeable. Examples of materials for the protective layer 17 include hydrophobic resins, specifically cellulose, cellulose derivatives, polyolefins, polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, hydrochloric acid rubber, polyamide, fluororesin, polybutene, polyvinyl butyral, polyethylene oxide, polyurethane, cellulose acetate butyrate, hydroxyethylcellulose, and polyimide.

The adhesive layer 22 for the release paper is preferably formed from an adhesive that is both lipophilic and hydrophobic, specifically a rubber-based adhesive, an acrylic-based adhesive, a silicone-based adhesive, a polyvinyl-based adhesive, a polyurethane-based adhesive, or a composite adhesive thereof.

Another embodiment of the oil leak detection material 10 is shown in Figure 5. While the oil leak detection material 10 shown in Figures 1 and 3-4 has an adhesive layer 15, as shown in Figure 5, it does not necessarily have to have an adhesive layer.

Furthermore, instead of the shape of the oil leak detection material 10 shown in Figures 1 and 3-5, the shapes of the discoloration layer 11 and the colored layer 13 can be various shapes such as rectangles and circles, or any shape such as letters or symbols. For example, the discoloration layer 11 itself can be made into the shape of letters indicating an oil leak, such as "oil," so that the letters become visible when oil leaks, or conversely, it can be designed to be invisible. Alternatively, the colored layer 13 can be made into the shape of letters or symbols to be displayed or hidden.

For example, if the colored layer 13 itself is shaped like letters indicating an oil leak, when there is no oil leak, the letters are hidden by the discolored layer 11 and are not visible. When an oil leak occurs, the discolored layer 11 becomes transparent or semi-transparent, revealing the letters on the colored layer 13, making them visible and displayed. On the other hand, if the discolored layer 11 itself is shaped like letters indicating an oil leak, when there is no oil leak, the colored layer 13 is visible through the non-letter-shaped parts of the discolored layer 11, while the letter shape hides the colored layer 13, making the letters visible. However, when an oil leak occurs, the discolored layer 11 becomes transparent or semi-transparent and no longer hides the colored layer 13, so the letters become invisible and appear not to be displayed.

This oil leak detection material 10 can be easily attached to areas prone to oil leaks, such as flanges, and can reliably detect oil leaks even if the material 10 gets wet from rainwater or leaks. Alternatively, this oil leak detection material 10 can reliably detect oil leaks only when oil alone or a water-oil mixture containing both water and oil comes into contact with the material 10.

The following describes in detail examples to which the present invention is applied and comparative examples to which the present invention is not applied.
(Example 1)
The oil leak detection material shown in Figure 3 was prepared as follows. First, a black ink was prepared by kneading 10 parts by mass of carbon black as a black pigment, 25 parts by mass of transparent silicone resin (Shin-Etsu Chemical Co., Ltd., KR-220L), and 65 parts by mass of 1-butanol. This black ink was screen printed onto a tacky white polyester film (Lintec Corporation, PETWH50(A)PAT1 8LK2) used as a base layer/adhesive layer/release paper to a coating thickness of approximately 5 μm, and then dried to form a colored layer. Next, a white ink was prepared by kneading 35 parts by mass of zinc stearate (refractive index 1.45-1.50) as a white powder, 12 parts by mass of transparent silicone resin (Shin-Etsu Chemical Co., Ltd., KR-220L), and 53 parts by mass of 1-butanol. This white ink was screen printed to a thickness of approximately 15 μm onto the colored layer/substrate layer/adhesive layer/release paper side, and then dried to form a discolored layer. Afterward, it was cut into 50 mm x 50 mm squares to obtain the oil leak detection material shown in Figure 3. The resulting oil leak detection material had an opaque discolored layer that made the hue of the colored layer almost invisible.

(Example 2)
The oil leak detection material shown in Figure 4 was prepared as follows. First, a white ink was prepared by kneading 35 parts by mass of zinc stearate (refractive index 1.45-1.50) as a white powder, 12 parts by mass of transparent silicone resin (Shin-Etsu Chemical Co., Ltd., KR-220L), and 53 parts by mass of 1-butanol. This white ink was applied to a polyester nonwoven fabric, which served as the nonwoven fabric layer, by screen printing to a thickness of approximately 15 μm, and then dried to form a discolored layer. Next, a black ink was prepared by kneading 10 parts by mass of carbon black as a black pigment, 25 parts by mass of transparent silicone resin (Shin-Etsu Chemical Co., Ltd., KR-220L), and 65 parts by mass of 1-butanol. This black ink was applied to the discolored layer side of the discolored layer/nonwoven fabric layer by screen printing to a thickness of approximately 5 μm, and then dried to form a colored layer. An acrylic adhesive and release paper were applied to the colored layer side of the colored layer/discolored layer/nonwoven fabric layer as an adhesive layer/release paper. Then, the material was cut into 50 mm x 50 mm squares to obtain the oil leak detection material shown in Figure 4. The resulting oil leak detection material had an opaque discolored layer that made the hue of the colored layer almost invisible.

(Comparative Example 1)
An oil leak detection material as shown in Example 1 of Patent Document 2 was prepared. First, a white ink was prepared by kneading 30 parts by mass of stearic acid (refractive index 1.43) as a white powder, 5 parts by mass of transparent ethylcellulose resin, and 65 parts by mass of xylene. This white ink was applied to one side of a black-colored high-quality paper to a coating thickness of 150 μm using a coater applicator, and then dried to form a discoloration layer. Next, the substrate with the discoloration layer formed on one side of the colored layer was cut into a 40 mm x 40 mm square. In addition, an oil-permeable acrylic adhesive was applied to both sides of a polyethylene nonwoven fabric (Tyvek 1056DR (trade name), basis weight 54 g/ ^m² , manufactured by Asahi DuPont Flashspun Products Co., Ltd.) to form a first hydrophobic adhesive layer and a release paper adhesive layer, and then cut into a 50 mm x 50 mm square. A cut colored layer was attached to the center of the cut first hydrophobic adhesive layer, with the discolored layer facing upwards. Furthermore, a 50 mm x 50 mm transparent polyethylene terephthalate film was attached as a protective layer so that the top surface of the discolored layer and the sides of both the discolored and colored layers were covered. Subsequently, a 50 mm x 50 mm release paper was attached to the release paper adhesive layer 22 to obtain an oil leak detection material. In the obtained oil leak detection material, the hue of the colored layer could not be seen from the protective layer due to the opaque discolored layer.

(Comparative Example 2)
An oil leak detection material was prepared in the same manner as in Example 1, except that the resin of the discoloration layer was a cellulose-based resin. First, a black ink was prepared by kneading 10 parts by mass of carbon black as a black pigment, 25 parts by mass of transparent silicone resin (Shin-Etsu Chemical Co., Ltd., KR-220L), and 65 parts by mass of 1-butanol. This black ink was applied to a tacky white polyester film (Lintec Corporation, PETWH50(A)PAT1 8LK2) used as a base layer/adhesive layer/release paper with a coating thickness of approximately 5 μm by screen printing, and then dried to form a colored layer. Next, a white ink was prepared by kneading 35 parts by mass of zinc stearate (refractive index 1.45-1.50) as a white powder, 5 parts by mass of ethyl cellulose resin, and 60 parts by mass of 1-butanol. This white ink was screen printed to a thickness of approximately 15 μm onto the colored layer/substrate layer/adhesive layer/release paper side, and then dried to form a discolored layer. Afterward, it was cut into 50 mm x 50 mm squares to obtain the oil leak detection material shown in Figure 1. The resulting oil leak detection material had an opaque discolored layer that made the hue of the colored layer almost invisible.

(Example 3)
Test specimens were prepared by attaching the oil leak detection materials 10 obtained in Examples 1 and 2 and the oil leak detection materials obtained in Comparative Examples 1 and 2 to aluminum plates. These test specimens were placed outdoors (south-facing, 45-degree angle, no shade) for one month. After that, they were immersed in a tray containing water (refractive index 1.33), hydraulic oil (refractive index 1.5; ENEOS Corporation, High-Pressure Insulating Oil K), or silicone oil (refractive index 1.44; Shin-Etsu Chemical Co., Ltd., KF-96-500CS), and the time until the discoloration layer began to change was measured. The measurement results are shown in Table 1 below.

As is clear from Table 1, the oil leak detection material 10 of Examples 1 and 2 did not change color when immersed in water, but when immersed in hydraulic oil and silicone oil, it clearly changed color in 1 second, 10 seconds, and 30 seconds, allowing for instantaneous visual detection of oil wetting. On the other hand, the oil leak detection material of Comparative Example 1 did not change color when immersed in water, but it took 600 seconds when immersed in hydraulic oil and 8 hours when immersed in silicone oil, making instantaneous visual detection of oil wetting impossible. Furthermore, Comparative Example 2 immediately changed color when immersed in water. This was because the cellulose resin in the discoloration layer deteriorated due to ultraviolet light, increasing its hydrophilicity, resulting in discoloration upon contact with water. Therefore, it became clear that it could not be used outdoors.

The oil leak detection material of the present invention does not change color with rainwater alone, but only changes color when oil is leaking. It can reliably detect oil leaks even with silicone oil, which has a refractive index close to that of water, and can detect oil leaks from various oil tanks, pipe flanges, etc.

10 is the oil leak detection material, 11 is the discolored layer, 12 is the white powder, 12a is the coating, 12b is the gap, 13 is the colored layer, 14 is the base layer, 15 is the adhesive layer, 16 is the release paper, 20 is the oil leak, and 30 is the object to be detected by the oil leak.

Claims (17)

A colored layer that has been colored with a predetermined color,
A white discoloration layer is provided in contact with at least a portion of the upper surface of the colored layer, and the white powder, which is white particles or white powder, has a coating made of silicone resin or silicone rubber on at least a portion of its surface, and the white powder particles are bound together by the coating, while having gaps that absorb oil and repel water.
An oil leak detection material characterized by having the following features. The oil leak detection material according to claim 1, characterized in that the oil leak is absorbed into the gap, causing the discolored layer to become transparent and making the color of the colored layer visible. The oil leak detection material according to claim 2, characterized in that the white powder contains white particles or white powder having a refractive index of 1.40 to 1.50. The oil leak detection material according to claim 1, characterized in that the silicone resin or silicone rubber has a polydimethylsiloxane skeleton, a polydiphenylsiloxane skeleton, or a polymethylphenylsiloxane skeleton. The oil leak detection material according to claim 1, characterized in that the discoloration layer contains, for example, 30 to 90 parts by mass of the white powder and 10 to 70 parts by mass of the silicone resin or silicone rubber. The oil leak detection material according to claim 1, characterized in that the discolored layer is a coating layer of a composition containing the white powder, the silicone resin or silicone rubber raw material binder, and a solvent, and the gaps are traces of the solvent disappearing within the coating layer. The oil leak detection material according to claim 1, characterized in that the lower surface of the colored layer is covered with an oil-absorbing or non-oil-absorbing base layer made of an oil-absorbing base layer selected from woven fabric, non-woven fabric, and paper, or a film. The oil leak detection material according to claim 1, characterized in that it comprises an oil-absorbing and/or oil-permeable protective layer, selected from woven fabric, nonwoven fabric, paper, and mesh, covering the upper surface of the discoloration layer. The oil leak detection material according to claim 8, characterized in that the protective layer is made of a hydrophobic material. The oil leak detection material according to claim 1, characterized in that the lower surface of the colored layer is provided with an adhesive layer or a tacky adhesive layer that can be adhered to an object to which oil leaks should be detected. The oil leak detection material according to claim 10, characterized in that the adhesive layer or the adhesive layer and the colored layer are permeable to the oil leak. The oil leak detection material according to claim 1, characterized in that the white powder is white particles or white powder containing at least one selected from organic compounds, metal soaps, plastic powders, metal inorganic salts, minerals, silica, glass beads, and glass fillers. The oil leak detection material according to claim 12, characterized in that the white powder is the white particles or white powder containing the metal soap and/or amorphous silica. The oil leak detection material according to claim 12, characterized in that the white powder is the white particles or white powder containing amorphous silica. The oil leak detection material according to claim 1, characterized in that the colored layer is colored with one of the following colors: black, navy blue, red, orange, blue, green, brown, and purple, or any intermediate color therebetween. The oil leak detection material according to claim 1, characterized in that the colored layer and/or the discoloration layer are shaped into the form of letters, symbols, and/or figures, or the colored layer is printed in the form of letters, symbols, and/or figures. The oil leak detection material according to claim 1, characterized in that the difference in refractive index between the white particles or white powder and the oil leak is 0.1 or less.