Fluorescent inspection liquid

Abstract

This fluorescent inspection liquid is obtained by dissolving, in water, a composition that contains: a fluorochrome that is easily broken down by microorganisms, light or oxygen; and a preservative that prevents putrefaction of the fluorochrome. The preservative contains a parahydroxybenzoic acid ester or an isothiazolinone derivative.

Description

Fluorescent inspection liquid

[0001] The present invention relates to a fluorescent inspection liquid used in leak inspection.

[0002] Leak inspections are sometimes performed on equipment or piping that require a certain level of airtightness. One method of leak inspection is to use a test liquid containing a fluorescent dye (hereinafter referred to as a fluorescent test liquid).

[0003] For example, Japanese Patent Application Laid-Open No. 2018-132305 discloses a system for supplying a mist containing a fluorescent test liquid into a pharmaceutical work chamber to test for leaks in the work chamber. The above document also discloses the use of a solution of riboflavin or riboflavin phosphate sodium as the fluorescent test liquid.

[0004] When a fluorescent dye in a fluorescent test solution is a substance that is safe for the human body, it is difficult to store the fluorescent dye for a long period of time because the fluorescent dye may decay.

[0005] Furthermore, in leak inspections, any fluorescent inspection liquid that has leaked from the leaking location must be wiped up by an operator with a rag or the like after the inspection, which poses a problem of labor-intensive cleaning work.

[0006] Therefore, there is a need for a fluorescent inspection liquid that uses fluorescent dyes that are safe for the human body, prevents the fluorescent dyes from decaying, allows for long-term storage, and further, once released into the environment, the fluorescent dyes are quickly decomposed, thereby reducing the amount of cleaning work required.

[0007] An object of the present invention is to solve the above-mentioned problems.

[0008] One aspect of the following disclosure is a fluorescent test solution in which a composition containing a fluorescent dye that is easily decomposed by microorganisms, light, or oxygen, and a preservative that prevents the fluorescent dye from spoiling is dissolved in water.

[0009] The fluorescent test solution of the above aspect prevents deterioration of the fluorescent dye during storage, and after being released into the environment, the fluorescent dye is decomposed and the fluorescence disappears within a few hours to a few days. As a result, the fluorescent test solution of the above aspect can simplify the work of adjusting the fluorescent test solution before a leak test and the cleaning work after a leak test, thereby enabling labor savings in leak tests.

[0010] Fig. 1 is a table showing example compositions of the first to sixth fluorescent test solutions according to the experimental examples, their fluorescent colors, and the evaluation results of the sewage discharge standards. Fig. 2A is a photograph taken by irradiating the leak location with ultraviolet light during a leak test, and Fig. 2B is a photograph taken one week after the photograph of Fig. 2A was taken by irradiating the leak location with ultraviolet light.

[0011] The fluorescent inspection liquid according to this embodiment is used, for example, to inspect leaks in piping systems in factories. The fluorescent inspection liquid is sprayed as a mist onto compressed air and introduced into the piping system together with the compressed air. The mist of the fluorescent inspection liquid is carried along with the compressed air and spreads to each part of the piping. For example, if a part such as a pipe joint becomes loose, compressed air will leak from that part. The fluorescent inspection liquid flows out from the leaking point, such as the pipe joint, along with the leaking compressed air, and stains the leak point with a fluorescent dye. The leak point stained with the fluorescent inspection liquid can be easily detected visually by irradiating it with ultraviolet light, such as a black light.

[0012] The above example does not limit the use of the fluorescent inspection liquid to piping systems. The fluorescent inspection liquid can also be used to inspect leaks in water pipes, food manufacturing equipment, building air conditioning ducts, and other equipment that requires airtightness. Furthermore, the fluorescent inspection liquid may not only be added to high-pressure air in the form of a mist, but may also be introduced into pipes as a liquid diluted at a predetermined ratio.

[0013] The fluorescent inspection liquid of this embodiment is an aqueous solution in which a fluorescent dye and a preservative are dissolved in water as a solvent. The fluorescent dye is made of a substance that is susceptible to degradation by microorganisms, decomposition by reaction with oxygen in the atmosphere, or decomposition by visible or ultraviolet light in the environment, and is highly safe for the human body. Depending on the application, the fluorescent dye may be selected from, for example, food dyes or substances contained in food. Depending on the application, the fluorescent dye may be selected from substances that are less irritating to the skin when in contact with the skin. Blue fluorescent dyes, green fluorescent dyes, and red fluorescent dyes may be used.

[0014] The blue fluorescent dye is a dye that absorbs ultraviolet light and emits blue fluorescence in the wavelength range of 360 to 500 nm. Examples of blue fluorescent dyes that can be used in the fluorescent test solution of this embodiment include flavin derivatives, quinine, pyrene, anthocyanin, and umbelliferone, which will be described later. These blue fluorescent dyes may be used alone or in combination.

[0015] Among blue fluorescent dyes, a mixture of quinine and a flavin derivative is suitable because it is safe for humans and emits a bright, highly visible blue fluorescence. Quinine is used, for example, as a bittering agent in soft drinks (tonic water). It is highly safe for humans even when taken orally, and is also highly biodegradable and easily decomposed in the atmosphere. The flavin derivative of this embodiment is derived from riboflavin, which has a flavin skeleton. Such a flavin derivative is, for example, a fluorescent dye obtained by photolyzing riboflavin, and contains formylmethylflavin and lumichrome as its main components. The flavin derivative of this embodiment is obtained by irradiating an aqueous solution of riboflavin with light for a sufficient amount (length of time), and emits a strong blue fluorescence. Photodecomposition products of riboflavin (vitamin B2) are substances contained in foods, are safe when taken orally, and are rapidly decomposed in the environment.

[0016] The green fluorescent dye is a dye that absorbs ultraviolet light and emits green fluorescence in the wavelength range of 500 to 570 nm. Examples of green fluorescent dyes include riboflavin (vitamin B2), fluorescein, acridine orange, phloxine B (Red No. 104), and lycopene. These green fluorescent dyes may be used alone or in combination. Of these, riboflavin is contained in foods as vitamin B2, and is highly safe for the human body and has excellent biodegradability and atmospheric decomposition properties, making it suitable for the fluorescent inspection solution of this embodiment.

[0017] Red fluorescent dyes are dyes that absorb ultraviolet light and emit red fluorescence in the wavelength range of 590 to 830 nm. Examples of red fluorescent dyes include chlorophyll, rhodamine B, acid red (Red No. 106), eosin, cochineal pigment, tannin, phycocyanin (spirulina pigment), carthamin (safflower pigment), phycoerythrin, erythrosine (Red No. 3), and rose bengal (Red No. 105). These red fluorescent dyes may be used alone or in combination.

[0018] The fluorescent test liquid may be prepared so as to emit blue-green fluorescence by containing a blue fluorescent dye and a green fluorescent dye. The fluorescent test liquid may also be prepared so as to emit orange or yellow fluorescence by combining a green fluorescent dye and a red fluorescent dye. Furthermore, the fluorescent test liquid may also be prepared so as to emit pink or purple fluorescence by combining a blue fluorescent dye and a red fluorescent dye. The fluorescent test liquid of this embodiment can be appropriately selected to have the fluorescent color most highly visible under the test environment.

[0019] The preservative prevents deterioration of the fluorescent dye contained in the fluorescent test solution due to putrefaction, and parahydroxybenzoic acid esters or isothiazolinone derivatives can be used as the preservative.

[0020] In one embodiment, a parahydroxybenzoic acid ester may be used as a preservative. Examples of parahydroxybenzoic acid esters that can be used in the fluorescent test solution include methyl parahydroxybenzoate (methylparaben), ethyl parahydroxybenzoate (ethylparaben), propyl parahydroxybenzoate (propylparaben), isopropyl parahydroxybenzoate (isopropylparaben), butyl parahydroxybenzoate (butylparaben), isobutyl parahydroxybenzoate (isobutylparaben), heptyl parahydroxybenzoate (heptylparaben), and benzyl parahydroxybenzoate (benzylparaben). One or a combination of the parahydroxybenzoic acid esters listed above may be used as the preservative.

[0021] In another embodiment, an isothiazolinone derivative may be used as the preservative, and the isothiazolinone derivative may be any one or a combination of methylisothiazolinone (MI), methylchloroisothiazolinone (MCI), octylisothiazolinone (OI), dichlorooctylisothiazolinone (DOCI), and benzisothiazolinone (BI).

[0022] In the fluorescent test solution, the preservative can be used in a concentration range of 10 ppm or less or 100 ppm or less, depending on the application. Methylparaben in a concentration range of 10 ppm or less meets the standards acceptable for food additives and is highly safe for oral ingestion, making it suitable for fluorescent test solutions for food processing equipment, for example. Furthermore, a preservative concentration of 100 ppm or less meets the standards acceptable for pharmaceuticals and medical devices, does not irritate the skin even when in contact with it, and can achieve a highly safe fluorescent test solution. Furthermore, a preservative concentration of 100 ppm or less does not hinder the rapid decomposition of the fluorescent dye in the environment after use.

[0023] (Experimental Example) Hereinafter, an example of the composition of the fluorescent test liquid, the evaluation results of the sewage discharge standards, and the evaluation results of the fluorescence quenching property will be described.

[0024] Figure 1 is a table showing example compositions, fluorescent colors, and sewage discharge standard evaluation results for the first through sixth fluorescent test solutions in the experimental examples. The first fluorescent test solution is an aqueous solution containing 27 ppm of riboflavin (vitamin B2) as the first fluorescent dye. The first fluorescent test solution also contains 100 ppm of methylparaben as a preservative. The first fluorescent test solution emits a pale yellow fluorescence with a slight greenish tinge. The COD (chemical oxygen demand) and BOD (biochemical oxygen demand), which indicate the degree of water pollution, of the first fluorescent test solution were below the 160 mg / L standard value for discharge as sewage. Therefore, it was confirmed that the first fluorescent test solution can be discharged into the sewer.

[0025] The second fluorescent test solution is an aqueous solution containing 18 ppm of riboflavin as a first fluorescent dye, 6 ppm of quinine, a blue fluorescent dye, as a second fluorescent dye, and 100 ppm of methylparaben as a preservative. The second fluorescent test solution emits yellow-green fluorescence. It was confirmed that the COD and BOD of the second fluorescent test solution were both below 160 mg / L, making it suitable for disposal in sewer systems.

[0026] The third fluorescent test solution is an aqueous solution containing 27 ppm of riboflavin as the first fluorescent dye and 2.7 ppm of the red fluorescent dye acid red as the second fluorescent dye. The third fluorescent test solution also contains 100 ppm of methylparaben as a preservative. The third fluorescent test solution emits a slightly reddish yellow fluorescence. The third fluorescent test solution had COD and BOD both below 160 mg / L, and it was confirmed that it could be poured into the sewer.

[0027] The fourth fluorescent test solution is an aqueous solution containing 20 ppm of a flavin derivative, a blue fluorescent dye, as the first fluorescent dye, 7 ppm of quinine, a blue fluorescent dye, as the second fluorescent dye, and 100 ppm of methylparaben as a preservative. The fourth fluorescent test solution emits blue fluorescence. It was confirmed that the fourth fluorescent test solution had COD and BOD both below 160 mg / L and was therefore suitable for disposal in sewerage.

[0028] The fifth fluorescent test solution contains 123 ppm of rhodamine B, a red fluorescent dye, as the first fluorescent dye, and 100 ppm of methylparaben as a preservative. The fifth fluorescent test solution emits orange (yellowish red) fluorescence. The fifth fluorescent test solution had COD and BOD levels both below 160 mg / L, confirming that it can be poured into sewer systems.

[0029] The sixth fluorescent test solution contains 210 ppm of the red fluorescent dye Acid Red as the first fluorescent dye and 100 ppm of methylparaben as a preservative. The sixth fluorescent test solution emits red fluorescence. The sixth fluorescent test solution had COD and BOD both below 160 mg / L, and it was confirmed that the sixth fluorescent test solution can be poured into sewerage.

[0030] Next, we will explain the results of an investigation into the decomposition of fluorescent dyes in the atmosphere. A mist of fluorescent test solution was supplied along with compressed air to a test pipe with a loose joint that could become a leak point. In this experiment, the fluorescent test solution used contained riboflavin as the fluorescent dye at a concentration of 5 ppm and methyl parahydroxybenzoate as a preservative at a concentration of 10 ppm.

[0031] In the area indicated by the white oval frame in Figure 2A, fluorescent test liquid is leaking from a pipe joint. The leaking area is illuminated with ultraviolet light from a black light. As shown in the figure, bright fluorescence is emitted from the leaking fluorescent test liquid, making the leaking area easily visible.

[0032] Next, the pipe and joint shown in Figure 2A were left for one week without cleaning with the fluorescent inspection liquid, and then the same locations were irradiated with ultraviolet light to check for the presence or absence of fluorescence. The results are shown in Figure 2B. As shown in Figure 2B, the fluorescence of the fluorescent inspection liquid disappeared in the joint, and the fluorescent dye (riboflavin) was quickly decomposed. Thus, it was confirmed that the fluorescent dye of the fluorescent inspection liquid of this embodiment is decomposed in a short time, within one week.

[0033] It should be noted that the present embodiment is not limited to the above disclosure, and various configurations can be adopted without departing from the gist of the present invention.

[0034] (Supplementary Note 1) One aspect of the above disclosure is a fluorescent test solution obtained by dissolving in water a composition containing a fluorescent dye that is easily decomposed by microorganisms, light, or oxygen, and a preservative that prevents the fluorescent dye from spoiling. The fluorescent test solution can prevent deterioration of the fluorescent dye during storage.

[0035] (Appendix 2) In the fluorescent test liquid according to Appendix 1, the preservative may include a parahydroxybenzoic acid ester or an isothiazolinone derivative. After this fluorescent test liquid is released into the environment, the fluorescent dye decomposes and the fluorescence disappears within a few hours to a few days. This simplifies the preparation of the fluorescent test liquid before a leak test and the cleaning work after the leak test, thereby reducing the labor required for leak testing.

[0036] (Appendix 3) In the fluorescent test solution according to Appendix 2, the preservative may contain at least one of methyl parahydroxybenzoate, ethyl parahydroxybenzoate, propyl parahydroxybenzoate, isopropyl parahydroxybenzoate, butyl parahydroxybenzoate, isobutyl parahydroxybenzoate, heptyl parahydroxybenzoate, and benzyl parahydroxybenzoate. This fluorescent test solution is safe for the human body because the preservative is less irritating to the human body.

[0037] (Appendix 4) In the fluorescent test liquid according to Appendix 2, the preservative may include at least one of methylisothiazolinone and methylchloroisothiazolinone. This fluorescent test liquid has excellent anti-corrosion properties for the fluorescent dye and is relatively low in irritation to the human body.

[0038] (Appendix 5) The fluorescent inspection liquid according to any one of Appendices 1 to 4 may contain the preservative at a concentration of 100 ppm or less. This fluorescent inspection liquid is less irritating to human skin, and the preservative does not interfere with decomposition of the fluorescent dye in the environment.

[0039] (Appendix 6) In the fluorescent test solution according to any one of Appendices 1 to 5, the fluorescent dye may include at least one of quinine, pyrene, anthocyanin, umbelliferone, and a flavin derivative derived from riboflavin having a flavin skeleton, and may include a blue fluorescent dye that emits blue fluorescence when irradiated with ultraviolet light. This fluorescent test solution can further produce blue or bluish fluorescence, and can realize various fluorescent colors by mixing with fluorescent dyes of other colors.

[0040] (Supplementary Note 7) In the fluorescent test solution according to any one of Supplementary Notes 1 to 6, the fluorescent dye may include at least one of riboflavin, fluorescein, acridine orange, phloxine B, and lycopene, and may include a green fluorescent dye that emits green fluorescence when irradiated with ultraviolet light. This fluorescent test solution can further produce green or greenish fluorescence, and can realize various fluorescent colors by mixing with fluorescent dyes of other colors.

[0041] (Appendix 8) In the fluorescent test solution according to any one of Appendices 1 to 7, the fluorescent dye may include at least one of chlorophyll, rhodamine B, acid red, eosin, cochineal pigment, tannin, phycocyanin, carthamin, phycoerythrin, erythrosine, and rose bengal, and may include a red fluorescent dye that emits red fluorescence when irradiated with ultraviolet light. This fluorescent test solution can further produce red or reddish fluorescence, and by mixing with fluorescent dyes of other colors, various fluorescent colors can be realized.

Claims

1. A fluorescence test solution obtained by dissolving in water a composition containing a fluorescent dye that is easily decomposed by microorganisms, light, or oxygen, and a preservative that prevents spoilage of the fluorescent dye.

2. The fluorescence test solution according to claim 1, wherein the preservative contains a paraoxybenzoic acid ester or an isothiazolinone derivative.

3. The fluorescence test solution according to claim 2, wherein the preservative contains at least one of methyl paraoxybenzoate, ethyl paraoxybenzoate, propyl paraoxybenzoate, isopropyl paraoxybenzoate, butyl paraoxybenzoate, isobutyl paraoxybenzoate, heptyl paraoxybenzoate, and benzyl paraoxybenzoate.

4. The fluorescence test solution according to claim 2, wherein the preservative contains at least one of methylisothiazolinone and methylchloroisothiazolinone.

5. The fluorescence test solution according to claim 2, wherein the preservative is contained at a concentration of 100 ppm or less.

6. The fluorescence test solution according to any one of claims 1 to 5, wherein the fluorescent dye contains at least one of quinine, pyrene, anthocyanin, umbelliferone, and a flavin derivative starting from riboflavin having a flavin skeleton, and contains a blue fluorescent dye that emits blue fluorescence upon irradiation with ultraviolet light.

7. The fluorescence test solution according to any one of claims 1 to 5, wherein the fluorescent dye contains at least one of riboflavin, fluorescein, acridine orange, phloxine B, and lycopene, and contains a green fluorescent dye that emits green fluorescence upon irradiation with ultraviolet light.

8. The fluorescence test solution according to any one of claims 1 to 5, wherein the fluorescent dye contains at least one of chlorophyll, rhodamine B, acid red, eosin, cochineal dye, tannin, phycocyanin, curcumin, phycoerythrin, erythrosine, and rose bengal, and contains a red fluorescent dye that emits red fluorescence upon irradiation with ultraviolet light.

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