JPH08160030A - Printing ink composition for detecting water leak - Google Patents

Abstract

PURPOSE: To discriminate a water leak by using a printing ink compsn. containing sodium fluoresceine of specific concn. and a weak basic substance of which the carboxyl group being a substituent is an alkali metal salt and showing a dark orange color under a normal temp. and normal humidity condition not to change in hue but generating a hue change upon the direct contact with water to show a fluorescent yellow color. CONSTITUTION: Sodium fluoresceine (uranine) is a hygroscopic orangish red powder and emits a strong fluorescent color in a neutral-alkaline aq. soln. usually. The concn. of uranine is set to 0.050.3wt.%. Other than uranine, a weak basic substance of which the carboxyl group being a substituent is an alkali metal salt is added. As the weak basic substance, for example, a sodium salt of a high-molecular compd. having a carboxyl group such as polysaccharide is used. As polysaccharide, for example, sodium carboxymethylcellulose is used. A soln. containing the weak basic substance having the carboxyl group as a substituent in desired concn. is prepared and a predetermined amt. of uranine is dissolved therein to prepare a compsn. which is, in turn, printed on a base material and dried to form a film.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a dry state (normal temperature and normal humidity).
The present invention relates to a printing ink composition which can be distinguished from each other by a remarkable change in color tone when wet with water.

[0002]

2. Description of the Related Art Conventionally, fluorescein test paper has been known as a test paper for detecting alkali or ammonia. This fluorescein test paper is a neutral black paper dyed with a neutral solution of fluorescein and then dried.
Since it exhibits a fluorescent (yellow-green) color extremely sensitive to alkali, alkali or ammonia can be easily detected. However, the fluorescein test strip is
When wet with an alkali-free aqueous solution, it does not change so much that it can be visually confirmed.

On the other hand, fluorescein sodium (uranin), which is a sodium salt of fluorescein, is known as a reagent exhibiting a fluorescent (yellowish green) color in an aqueous solution.
When the aqueous solution is acidic, the fluorescence disappears and it becomes difficult to detect water wetting. Further, when the above-mentioned uranin is used, it is necessary to make the uranin have a high concentration in order to make the color tone change remarkably when dried and when wet. However, when an ink composition containing a high concentration of uranin is formed in a pattern, there is a problem that the uranin exudes when wet with water and the pattern is crushed.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a printing ink composition for detecting water wetting, which is less affected by the pH of an aqueous solution and shows a stable fluorescent (yellowish green) color when exposed to water, and a pattern. It is to provide a printing ink composition for detecting water wetting, in which a pattern does not bleed or collapse when wet with water even when formed into a shape.

[0005]

As a result of earnest research in view of the above problems, the present inventors have found that a weak basic substance having a substituent carboxyl group as an alkali metal salt is added to uranine which is a water-wetting detection reagent. Therefore, they have found that good water wetting can be detected even if the aqueous solution to be detected is acidic, and completed the present invention.

That is, the present invention is a printing ink composition for water wetting detection containing sodium fluorescein and a weakly basic substance in which the carboxyl group of the substituent is an alkali metal salt. Hereinafter, the present invention will be described in detail. The water wetting detection reagent used in the printing ink composition for water wetting of the present invention is fluorescein sodium (uranin). Uranine is a hygroscopic tow red powder, which normally emits a strong fluorescent (yellowish green) color in neutral to alkaline aqueous solutions.

The concentration of uranine in the ink composition is 0.05.
It is preferably from 0.3 to 0.3% by weight, particularly preferably from 0.10 to 0.20% by weight. If it exceeds 0.3% by weight, when the ink composition is patterned, uranin may ooze out when wet, and the pattern may be crushed. On the other hand, if it is less than 0.05% by weight, it is difficult to detect water wetting.

The printing ink composition for detecting water wetting of the present invention contains, in addition to the above-mentioned uranin, a weakly basic substance in which the carboxyl group of the substituent is an alkali metal salt. Examples of such weakly basic substances include sodium salts of polymer compounds having a carboxyl group such as polysaccharides and acrylic resins, and sodium salts of organic acids such as sodium citrate and sodium tartrate. Examples of the polysaccharide include sodium carboxymethyl cellulose, sodium carboxymethyl starch, gum arabic, sodium alginate and the like. Examples of the acrylic resin include sodium polyacrylate, sodium polymethacrylate, methyl vinyl ether / sodium oleate copolymer, vinyl alcohol / sodium acrylate copolymer and the like. Other examples include polyvinylpyrrolidone / vinyl acetate copolymers, which are vinyl acetate resins.

When patterning the ink composition,
As the weakly basic substance, it is preferable to use a polymer compound having a thickening effect on the ink composition, for example, a binder resin or a coating resin. The specific molecular weight is preferably about 1,000 to 1,000,000,
Particularly preferred is 5,000 to 500,000. By using such a polymer compound, uranine is included in the resin, and even when wet with water, uranin does not exude, and there is no risk of the pattern being crushed.

The concentration of the weakly basic substance in the ink composition is preferably 5 to 50% by weight, more preferably 10 to 30% by weight. When it exceeds 50% by weight, the printing suitability of the ink composition is deteriorated, and when it is less than 5% by weight, the fluorescence exhibited by uranine disappears when the aqueous solution to be detected is acidic. To prepare the printing ink composition for detecting water wetting of the present invention, first, a solution containing a weakly basic substance in which the carboxyl group of the substituent is an alkali metal salt at a desired concentration is prepared. As the solvent used at this time, water or cyclohexanone, ethanol, acetone, ethyl acetate,
An organic solvent such as chloroform can be used. Water is preferably used as the solvent.

Next, a predetermined amount of uranine is dissolved in the obtained weakly basic substance solution. To dissolve, ultrasonic treatment may be performed. In addition, it is preferable that the printing ink composition of the present invention for detecting wetness does not contain a medium such as a dry offset medium that is generally used for printing inks. Since the above-mentioned medium usually has water repellency, when it is used, water wettability is lowered.

The printing ink composition for detecting water wetting thus obtained can be used by printing (patterning) on a desired substrate and then drying to remove the solvent to form a coating film. Examples of the base material include paper products such as disposable diapers and toilet sheets for pets, tent canopies, cloth products such as sun and rain caps, plastic films, wood, concrete, wall cloth, wallpaper and other building materials, and packaging materials. , A very wide range of materials can be used.

Printing (patterning) may be carried out by a conventional method, for example, screen printing or transfer printing. The water-wetting detection printing ink composition of the present invention exhibits a stable dark orange color that does not exhibit a fluorescent color when dried at room temperature and normal humidity, and exhibits a yellow-green fluorescent color when directly contacted with water (when wet with water). . This printing ink composition for detecting water wetting can detect from an alkaline aqueous solution to an acidic aqueous solution having a pH of 2 to 5.

[0014]

The present invention will be described below in detail with reference to examples. However, the present invention is not limited to these examples. (Example 1) To 100 g of a 25% aqueous sodium polyacrylate solution (manufactured by Wako Pure Chemical Industries, low polymerization type), 0.2 g of uranine (manufactured by Junsei Kagaku) was added and dissolved by ultrasonication.

The resulting printing ink composition for detecting water wetting was applied to the surface of paper (manufactured by Honshu Paper Co., Ltd., Dissolve CD-2) by a silk printing method so as to have a slit shape with a thickness of 20 μm and an interval of 5 mm. Patterned. The printing ink composition for water wet detection formed on paper showed a dark orange color when dried at room temperature and normal humidity. When an aqueous solution of pH 3, pH 6 and pH 10 was added dropwise to this water-wetting detection printing ink composition, in each case, the portion to which the aqueous solution adhered exhibited a yellowish green fluorescent color and showed a remarkable change in color tone. Further, uranin did not exude from the printing ink composition for detecting water wetting and the pattern was not crushed.

Example 2 0.2 g of uranine (manufactured by Junsei Kagaku) was added to 100 g of 20% sodium carboxymethyl cellulose aqueous solution (manufactured by Daicel Chemical Co., Ltd., water-based adhesive) and dissolved by ultrasonic treatment. The obtained printing ink composition for detecting water wetting was applied to the surface of a paper (Honshu Paper Co., Ltd., Dissolve CD-2) by a silk printing method at a thickness of 10 μm to form 3
The patterning was performed so as to have a slit shape with mm intervals. The printing ink composition for detecting water wetting formed on paper showed a dark orange color when dried at room temperature and normal humidity.

The pH of the printing ink composition for detecting water wetting is
When an aqueous solution of pH 3, pH 6 and pH 10 was dropped, the portion to which the aqueous solution adhered exhibited a yellow-green fluorescent color and showed a remarkable change in color tone in all cases. Further, uranin did not exude from the printing ink composition for detecting water wetting and the pattern was not crushed.

[0018]

EFFECTS OF THE INVENTION According to the present invention, the dark orange color does not show a color change at room temperature and normal humidity, and when it is directly touched with water, the wet color can be identified by a remarkable color change from a dark orange color to a fluorescent yellow color, and pH 2 ~
A printing ink composition for water wetting detection, in which the fluorescent color does not disappear even with the acidic aqueous solution of 5, can be obtained.

Claims (3)

[Claims] 1. A printing ink composition for water wetting detection, which comprises sodium fluorescein and a weakly basic substance in which a substituent carboxyl group is an alkali metal salt. 2. The concentration of sodium fluorescein is 0.
The printing ink composition for detecting water wetting according to claim 1, wherein the printing ink composition is from 05 to 0.3% by weight. 3. The printing ink composition for detecting water wetting according to claim 1, wherein the weakly basic substance is a polymer compound.