Monoazo-based dye for acid detection

Abstract

The present invention relates to a monoazo-based dye for acid detection, which changes color upon addition of or exposure to acid and, more specifically, to a dye which changes color within a few seconds upon exposure to a trace amount of a strong acidic material, and a fiber product using the same. The monoazo-based dye for acid detection according to the present invention has an effect of reacting with a trace amount of strong acid to change color, and returning to the original color when the acid is removed. Also, a fiber dyed with the dye of the present invention exhibits high color fastness and thus is not discolored and faded by laundering or sunlight. In addition, there is an effect of preventing secondary contamination at an accident scene and serious accidents from harmful environmental factors, when protective or working clothes are manufactured applying the effect, thereby providing a function enabling workers to recognize an exposure to acid in real time in the case of an exposure to an acid-contaminated environment.

Claims

1. A method of detecting acid upon exposure to acid gas, comprising detecting a color change on a fiber dyed with a monoazo-based dye of the following Formula 1, when exposed to acid gas having an acid concentration of 3 ppm or above: ##STR00017## wherein n is an integer of 2 to 11.

2. The method of claim 1, wherein the acid is a strong acid in the range of pH 0.1 to pH 5.

3. The method of claim 1, wherein the acid is hydrochloric acid, hydrofluoric acid, sulfuric acid, or a mixture thereof.

4. The method of claim 1, wherein the dye changes its color upon exposure to acid gas and returns to its original color when the acid gas is removed.

5. The method of claim 1, wherein the dye changes its color within 5 seconds to 30 seconds upon exposure to the acid gas.

6. The method of claim 1, wherein the fiber is at least one fiber selected from the group consisting of polyester fiber, nylon fiber, acetate fiber, acrylic fiber, polypropylene fiber, and polyethylene fiber, or a blended fiber thereof.

7. The method of claim 1, wherein the fiber is comprised in a yarn.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the color change behavior when protective clothes are manufactured dying the dye prepared in Example 1 of the present invention to polypropylene fiber.

(2) FIG. 2 shows the result of HPLC of the compound prepared in Example 1 of the present invention.

(3) FIG. 3 shows the result of GC-MS of the compound prepared in Example 1 of the present invention.

(4) FIG. 4 shows the result of NMR of the compound prepared in Example 1 of the present invention.

(5) FIG. 5 shows the measurement result of K/S values when the structure of the terminal amino group substituent of the N,N-diC.sub.3-12 alkylaniline azobenzene, according to Experimental Example 1, is a C.sub.1-15 alkyl.

DETAILED DESCRIPTION OF THE INVENTION

(6) Hereinafter, the present invention will be described in detail with reference to the following Examples. However, the Examples of the present invention may be embodied in many different forms and these Examples should not be construed as limiting the scope of the present invention.

(7) The starting materials and reaction reagents among the compounds used below were the reagents from Aldrich, and all solvents were pure and thus used without drying or purification.

Example 1: Preparation of (E)-N,N-dihexyl-4-(phenyldiazenyl)benzenamine Compound (General Name: N,N-dihexylanilineazobenzene) Dye

(8) Aniline (0.01 mole) was added into water (5 mL), added with hydrochloric acid (35%; 2.19 g) and dissolved. Sodium nitrite (0.01 mole) was dissolved in water (5 mL) and slowed added into the dissolved aniline while maintaining the temperature at 0 C. to 5 C. to proceed with a diazotization reaction. The resulting diazotized solution was added with propionic acid (1.5 mL) and acetic acid (8.5 mL).

(9) N,N-dihexylaniline (0.01 mole) as a coupler was dissolved/emulsified in ethanol (40 mL) and the coupler solution was added to the diazotized solution and reacted.

(10) In about 2 hours thereafter, the reaction was completed, added with distilled water (200 mL), and allowed to stand for 24 hours for the phase separation of the synthesized dye. The separated distilled water in the lower layer was removed by release and placed thereat using an excess amount of distilled water, and this whole process was repeated 3 times for purification.

(11) Upon completion of the purification using distilled water, the synthesized dye was obtained by dissolving in benzene, which has high solubility for the dye, and the distilled water contained in part of the benzene was removed, and finally, the benzene was evaporated to obtain the title compound represented by Formula 2 below (yield; 75%).

(12) ##STR00002##

(13) In order to confirm whether the above compound of the present invention was prepared, HPLC, GC-MS, and NMR analyses were performed. As a result of the HPLC analysis, the peak, which appeared when the retention time was about 6.5 minutes, was the peak for the above title compound, and the purity of the compound after synthesis and purification was about 95% (FIG. 2). Additionally, as a result of the GC-MS analysis, it was confirmed that the predicted molecular weight of the title compound was 365 and also confirmed that the title compound was obtained exactly at 365 as a result of the GC-MS analysis. The peaks which appeared below 365 were confirmed to be peaks occurring due to fragmentation (FIG. 3).

(14) Additionally, the synthesis of the title compound was confirmed by observing the appearances of the peaks of 5 kinds of aliphatic hydrogen and the peaks of 5 kinds of aromatic hydrogen as a result of NMR analysis (FIG. 4).

Example 2: Preparation of (E)-N,N-dipropyl-4-(phenyldiazenyl)benzenamine Compound (General Name: N,N-dipropylanilineazobenzene) Dye

(15) The dye of the title compound represented by Formula 3 below was obtained in the same manner as described in Example 1, except that N,N-dipropylaniline was used as the coupler.

(16) ##STR00003##

(17) In order to confirm whether the above compound of the present invention was prepared, GC-MS analysis was performed. As a result of the GC-MS analysis, it was confirmed that the predicted molecular weight of the title compound was 281 and also confirmed that the title compound was obtained exactly at 281 as a result of the GC-MS analysis. The peaks which appeared below 281 were confirmed to be peaks occurring due to fragmentation.

Example 3: Preparation of (E)-N,N-dibutyl-4-(phenyldiazenyl)benzenamine Compound (General Name: N,N-dibutylanilineazobenzene) Dye

(18) The dye of the title compound represented by Formula 4 below was obtained in the same manner as described in Example 1, except that N,N-dibutylaniline was used as the coupler.

(19) ##STR00004##

(20) In order to confirm whether the above compound of the present invention was prepared, GC-MS analysis was performed. As a result of the GC-MS analysis, it was confirmed that the predicted molecular weight of the title compound was 309 and also confirmed that the title compound was obtained exactly at 309 as a result of the GC-MS analysis. The peaks which appeared below 309 were confirmed to be peaks occurring due to fragmentationdivision.

Example 4: Preparation of (E)-N,N-dipentyl-4-(phenyldiazenyl)benzenamine Compound (General Name: N,N-dipentylanilineazobenzene) Dye

(21) The dye of the title compound represented by Formula 5 below was obtained in the same manner as described in Example 1, except that N,N-dipentylaniline was used as the coupler.

(22) ##STR00005##

(23) In order to confirm whether the above compound of the present invention was prepared, GC-MS analysis was performed. As a result of the GC-MS analysis, it was confirmed that the predicted molecular weight of the title compound was 337 and also confirmed that the title compound was obtained exactly at 337 as a result of the GC-MS analysis. The peaks which appeared below 337 were confirmed to be peaks occurring due to fragmentation.

Example 5: Preparation of (E)-N,N-diheptyl-4-(phenyldiazenyl)benzenamine Compound (General Name: N,N-diheptylanilineazobenzene) Dye

(24) The dye of the title compound represented by Formula 6 below was obtained in the same manner as described in Example 1, except that N,N-diheptylaniline was used as the coupler.

(25) ##STR00006##

(26) In order to confirm whether the above compound of the present invention was prepared, GC-MS analysis was performed. As a result of the GC-MS analysis, it was confirmed that the predicted molecular weight of the title compound was 393 and also confirmed that the title compound was obtained exactly at 393 as a result of the GC-MS analysis. The peaks which appeared below 393 were confirmed to be peaks occurring due to fragmentationdivision.

Example 6: Preparation of (E)-N,N-dioctyl-4-(phenyldiazenyl)benzenamine Compound (General Name: N,N-dioctylanilineazobenzene) Dye

(27) The dye of the title compound represented by Formula 7 below was obtained in the same manner as described in Example 1, except that N,N-dioctylaniline was used as the coupler.

(28) ##STR00007##

(29) In order to confirm whether the above compound of the present invention was prepared, GC-MS analysis was performed. As a result of the GC-MS analysis, it was confirmed that the predicted molecular weight of the title compound was 421 and also confirmed that the title compound was obtained exactly at 421 as a result of the GC-MS analysis. The peaks which appeared below 421 were confirmed to be peaks occurring due to fragmentation.

Example 7: Preparation of (E)-N,N-dinonyl-4-(phenyldiazenyl)benzenamine Compound (General Name: N,N-dinonylanilineazobenzene) Dye

(30) The dye of the title compound represented by Formula 8 below was obtained in the same manner as described in Example 1, except that N,N-dinonylaniline was used as the coupler.

(31) ##STR00008##

(32) In order to confirm whether the above compound of the present invention was prepared, GC-MS analysis was performed. As a result of the GC-MS analysis, it was confirmed that the predicted molecular weight of the title compound was 449 and also confirmed that the title compound was obtained exactly at 449 as a result of the GC-MS analysis. The peaks which appeared below 449 were confirmed to be peaks occurring due to fragmentation.

Example 8: Preparation of (E)-N,N-didecyl-4-(phenyldiazenyl)benzenamine Compound (General Name: N,N-didecylanilineazobenzene) Dye

(33) The dye of the title compound represented by Formula 9 below was obtained in the same manner as described in Example 1, except that N,N-didecylaniline was used as the coupler.

(34) ##STR00009##

(35) In order to confirm whether the above compound of the present invention was prepared, GC-MS analysis was performed. As a result of the GC-MS analysis, it was confirmed that the predicted molecular weight of the title compound was 477 and also confirmed that the title compound was obtained exactly at 477 as a result of the GC-MS analysis. The peaks which appeared below 477 were confirmed to be peaks occurring due to fragmentation.

Example 9: Preparation of (E)-4-(phenyldiazenyl)-N,N-diundecylbenzenamine Compound (General Name: N,N-diundecylanilineazobenzene) Dye

(36) The dye of the title compound represented by Formula 10 below was obtained in the same manner as described in Example 1, except that N,N-diundecylaniline was used as the coupler.

(37) ##STR00010##

(38) In order to confirm whether the above compound of the present invention was prepared, GC-MS analysis was performed. As a result of the GC-MS analysis, it was confirmed that the predicted molecular weight of the title compound was 505 and also confirmed that the title compound was obtained exactly at 505 as a result of the GC-MS analysis. The peaks which appeared below 505 were confirmed to be peaks occurring due to fragmentation.

Example 10: Preparation of (E)-N,N-didodecyl-4-(phenyldiazenyl)benzenamine Compound (General Name: N,N-didodecylanilineazobenzene) Dye

(39) The dye of the title compound represented by Formula 11 below was obtained in the same manner as described in Example 1, except that N,N-didodecylaniline was used as the coupler.

(40) ##STR00011##

(41) In order to confirm whether the above compound of the present invention was prepared, GC-MS analysis was performed. As a result of the GC-MS analysis, it was confirmed that the predicted molecular weight of the title compound was 533 and also confirmed that the title compound was obtained exactly at 533 as a result of the GC-MS analysis. The peaks which appeared below 533 were confirmed to be peaks occurring due to fragmentation.

Comparative Example 1: Preparation of (E)-N,N-dimethyl-4-(phenyldiazenyl)benzenamine Compound (General Name: N,N-dimethylanilineazobenzene) Dye

(42) The dye of the title compound represented by Formula 12 below was obtained in the same manner as described in Example 1, except that N,N-dimethylaniline was used as the coupler.

(43) ##STR00012##

(44) In order to confirm whether the above compound of the present invention was prepared, GC-MS analysis was performed. As a result of the GC-MS analysis, it was confirmed that the predicted molecular weight of the title compound was 225 and also confirmed that the title compound was obtained exactly at 225 as a result of the GC-MS analysis. The peaks which appeared below 225 were confirmed to be peaks occurring due to fragmentation.

Comparative Example 2: Preparation of (E)-N,N-diethyl-4-(phenyldiazenyl)benzenamine Compound (General Name: N,N-diethylanilineazobenzene) Dye

(45) The dye of the title compound represented by Formula 13 below was obtained in the same manner as described in Example 1, except that N,N-diethylaniline was used as the coupler.

(46) ##STR00013##

(47) In order to confirm whether the above compound of the present invention was prepared, GC-MS analysis was performed. As a result of the GC-MS analysis, it was confirmed that the predicted molecular weight of the title compound was 253 and also confirmed that the title compound was obtained exactly at 253 as a result of the GC-MS analysis. The peaks which appeared below 253 were confirmed to be peaks occurring due to fragmentation.

Comparative Example 3: Preparation of (E)-4-(phenyldiazenyl)-N,N-ditridecylbenzenamine Compound (General Name: N,N-ditridecylanilineazobenzene) Dye

(48) The dye of the title compound represented by Formula 14 below was obtained in the same manner as described in Example 1, except that N,N-ditridecylaniline was used as the coupler.

(49) ##STR00014##

(50) In order to confirm whether the above compound of the present invention was prepared, GC-MS analysis was performed. As a result of the GC-MS analysis, it was confirmed that the predicted molecular weight of the title compound was 561 and also confirmed that the title compound was obtained exactly at 561 as a result of the GC-MS analysis. The peaks which appeared below 561 were confirmed to be peaks occurring due to fragmentation.

Comparative Example 4: Preparation of (E)-4-(phenyldiazenyl)-N,N-ditetradecylbenzenamine Compound (General Name: N,N-ditetradecylanilineazobenzene) Dye

(51) The dye of the title compound represented by Formula 15 below was obtained in the same manner as described in Example 1, except that N,N-ditetradecylaniline was used as the coupler.

(52) ##STR00015##

(53) In order to confirm whether the above compound of the present invention was prepared, GC-MS analysis was performed. As a result of the GC-MS analysis, it was confirmed that the predicted molecular weight of the title compound was 589 and also confirmed that the title compound was obtained exactly at 589 as a result of the GC-MS analysis. The peaks which appeared below 589 were confirmed to be peaks occurring due to fragmentation.

Comparative Example 5: Preparation of (E)-N,N-dipentadecyl-4-(phenyldiazenyl)benzenamine Compound (General Name: N,N-dipentadecylanilineazobenzene) Dye

(54) The dye of the title compound represented by Formula 16 below was obtained in the same manner as described in Example 1, except that N,N-dipentadecylaniline was used as the coupler.

(55) ##STR00016##

(56) In order to confirm whether the above compound of the present invention was prepared, GC-MS analysis was performed. As a result of the GC-MS analysis, it was confirmed that the predicted molecular weight of the title compound was 617 and also confirmed that the title compound was obtained exactly at 617 as a result of the GC-MS analysis. The peaks which appeared below 617 were confirmed to be peaks occurring due to fragmentation.

Experimental Example 1: Experiment on Measurement of Color Intensity During Dyeing of a Chromic Dye for Acid Detection

(57) Dyeing was performed on polypropylene fiber using the dye prepared in Examples 1 to 10 and Comparative Examples 1 to 5 at a dye concentration of 5% owf at 130 C. for 1 hour.

(58) The color intensity of the fiber dyed with the dye according to the present invention was indicated after measuring the K/S value at 420 nm, which is the maximum absorption wavelength of the fiber, using the datacolor SF 600 plus. Specifically, the surface reflection rate (R) was measured at 420 nm, which is the maximum absorption wavelength of the fiber, and the result was indicated in color intensity K/S using Equation 1 below.

(59) $\begin{array}{cc}K/S=\frac{{\left(1-R\right)}^2}{2R}& \left[\mathrm{Equation}1\right]\end{array}$

(60) The K/S values when terminal amino group substituent of the N,N-dialkylaniline azobenzene structure is a C.sub.1-15 alkyl were measured and are shown in FIG. 5.

Experimental Example 2: Dyeability of a Chromic Dye for Acid Detection According to Fiber Types

(61) Dyeing was performed on polyester fiber, nylon fiber, acetate fiber, acrylic fiber, polypropylene fiber, and polyethylene fiber using the dye prepared in Example 1 at a dye concentration of 5% owf at the dyeing temperature (the dyeing temperature is variably determined according to fiber type and thus follows as described in Table 1 below) for 1 hour.

(62) The fibers dyed with the dyes according to the present invention showed much higher concentrated colors, and in particular, on polypropylene and polyethylene fibers, which are commonly used in anti-chemical clothes, thus indicating extremely concentrated yellow color.

(63) TABLE-US-00001 TABLE 1 Polyethylene Fiber (high Type Polyester Nylon Acetate Acryl Polypropylene strength) Dyeing 130 C. 100 C. 100 C. 100 C. 130 C. 130 C. Temp. Intensity 20 16 19 13 25 24 of Dye Color (Single Wavelength K/S) Visual Concentrated Moderately Concentrated Concentrated Extremely Extremely Color Color Concentrated Color Color Concentrated Concentrated Intensity Color Color Color *single wavelength K/S: the color intensity (thickness) of a dyed fiber is indicated in value *intermediate color: dyeing to a color with an intermediate level of thickness *moderately concentrated color: dyeing to a color with an intermediate level to a thick color *concentrated color: dyeing to a thick color *extremely concentrated color: dyeing to a very thick color

(64) In particular, dyeing was performed on polyester fiber, nylon fiber, acetate fiber, acrylic fiber, polypropylene fiber, and polyethylene fiber using the N,N-dimethylaniline azobenzene (Comparative Example 1) or N,N-diethylaniline azobenzene (Comparative Example 2) dye, prepared in a similar manner to that described in Example 1, using N,N-dimethylaniline (0.01 mole) or N,N-diethylaniline (0.01 mole) as a coupler instead of N,N-dihexylaniline, at a dye concentration of 5% owf at the dyeing temperature (the dyeing temperature is variably determined according to fiber type and thus follows as described in Table 1 below) for 1 hour. As a result, it was confirmed that the polyester fiber, nylon fiber, acetate fiber, and acrylic fiber were dyed, but, due to the extremely poor color fastness to regarding washing, abrasion, and sublimation of the dyes (almost a level of the 1.sup.st to 2.sup.nd degree), the yellow color immediately disappeared upon washing, and also the polypropylene fiber and the polyethylene fiber could hardly be dyed.

Experimental Example 3: Chromic Property of a Polypropylene Fiber Dyed with a Chromic Dye for Acid Detection According to an Acid Gas Concentration

(65) The concentration of a hydrochloric acid gas was adjusted to 0 ppm to 1000 ppm, and the color change behavior of the polypropylene fibers dyed with the chromic dye in Experimental Example 2 was measured. The results are shown in Table 2 below.

(66) The chromic property was shown in extremely diluted concentrations of the hydrochloric acid gas, and showed a color difference before and after color change (E) of 10. Since anyone with a normal vision could easily recognize the color change in the case of color change (E) of 1, it was confirmed that it is possible to recognize color change in 3 ppm, which is the minimum concentration of the experiment.

(67) Additionally, the color changed from the initial yellow color before the detection of the hydrochloric acid gas to a red color after the detection.

(68) TABLE-US-00002 TABLE 2 Conc. of 0 3 5 10 20 50 100 500 1000 Acid Gas (ppm) Chromic 0 10 12 15 17 20 22 25 30 Property (E) Possibility possible possible possible possible possible possible possible possible of Naked- Eye Recognition *chromic property (E): value indicating the difference due to the color change between the initial yellow color before the detection of an acid gas and the red color after the detection of an acid gas

Experimental Example 4: Rate of Color Change of a Polypropylene Fiber Dyed with a Chromic Dye for Acid Detection According to the Detection of an Acid Gas (3 ppm)

(69) The time for color change was examined in 3 ppm, which is the minimum experimental concentration of the hydrochloric acid gas. As a result, the chromic property (E) was shown to be 3 or higher within 5 seconds after being exposed to the hydrochloric acid gas, and the color difference was 9 or higher in about 30 seconds after the exposure, and thus normal people could recognize the color change.

(70) TABLE-US-00003 TABLE 3 Time (sec) 0 5 10 15 20 30 50 100 200 Chromic 0 3 5 7 8 9 9 10 10 Property (E) Possibility possible possible possible possible possible possible possible possible of Naked- Eye Recognition *chromic property (E): value indicating the difference due to the color change between the initial yellow color before the detection of an acid gas and the red color after the detection of an acid gas

Experimental Example 5: Rate of Color Return Upon Removal of an Acid Gas (Natural Ventilation) after Detection of the Acid Gas (3 ppm) by a Polypropylene Fiber Dyed with a Chromic Dye for Acid Detection

(71) The dye prepared in Example 1 showed a phenomenon that its original yellow color changed upon detection of a hydrochloric acid gas into a red color, and upon removal of the hydrochloric acid gas (by natural ventilation) returned to its original yellow color. In this regard, the rate of color return was examined and the results are shown in Table 4 below. Although the color return to the original color required slightly more time compared to the rate of color change upon detection of a hydrochloric acid gas, the chromic property to return to the original color (yellow) by natural ventilation for about 5 minutes (300 seconds).

(72) TABLE-US-00004 TABLE 4 Time (sec) 0 30 60 90 120 180 240 300 600 Chromic 10 9 8 7 6 5 3 0 0 Property (E)

Experimental Example 6: Reversible Repetition of Detection of an Acid Gas (3 ppm) by a Polypropylene Fiber Dyed with a Chromic Dye for Acid Detection

(73) The dye prepared in Example 1 showed a phenomenon that its original yellow color changed upon detection of a hydrochloric acid gas into a red color, and upon removal of the hydrochloric acid gas (by natural ventilation) returned to its original yellow color. In this regard, for the measurement of reversible repetition of the dye prepared in Example 1, the chromic property (E) was examined by repeating the exposure to a hydrochloric acid and ventilation up to 50 times. As a result, even if repeating the exposure to a hydrochloric acid and ventilation was conducted up to 50 times, it was confirmed that the initial color change behavior was almost not changed as shown in Table 5 below.

(74) TABLE-US-00005 TABLE 5 No. of Repetition (No.) 1 5 10 Exposure Exposure Exposure to Natural to Natural to Natural Gas Ventilation Gas Ventilation Gas Ventilation Chromic 10 0 10 0 10 0 Property (E) Possibility possible possible possible of Naked- Eye Recognition No. of Repetition (No.) 20 30 50 Exposure Exposure Exposure to Natural to Natural to Natural Gas Ventilation Gas Ventilation Gas Ventilation Chromic 10 0 10 0 10 0 Property (E) Possibility possible possible possible of Naked- Eye Recognition

Experimental Example 7: Measurement of Durability (Color Fastness) of a Polypropylene Fiber Dyed with a Chromic Dye for Acid Detection

(75) The durability of the dye prepared in Example 1 in response to washing, abrasion, and sunlight described below, on the fiber after dyeing with a polypropylene fiber, was examined. In color fastness, the higher the degree the more excellent the property and the 5.sup.th degree, which is the possible highest degree, may be obtained. However, in real cases, it is rare to determine the 5.sup.th degree, and the commercially highest degree of color fastness is indicated as between the 4.sup.th degree and the 5.sup.th degree.

(76) The polypropylene fiber dyed with a chromic dye for acid detection of the present invention showed the 4.sup.th degree to the 5.sup.th degree of color fastness in all aspects of washing, abrasion, and sunlight, as shown in Table 6, thus confirming its extremely excellent durability.

(77) TABLE-US-00006 TABLE 6 Color Fastness Degree Washing Discoloration/Fading 4 to 5 Contamination Acetate 4 to 5 Cotton 4 to 5 Nylon 4 to 5 Polyester 4 to 5 Acryl 4 to 5 Wool 4 to 5 Abrasion Contamination Dry 4 to 5 Wet 4 to 5 Sunlight Discoloration/Fading 4 to 5

(78) Additionally, the chromic property or dyeing behavior of polypropylene fiber and polyethylene fiber are almost the same, and thus it was confirmed that if the same experiment is performed using the polyethylene fiber dyed with a chromic dye for acid detection of Example 1, instead of the polypropylene fiber dyed with a chromic dye for acid detection of Example 1, the same as/similar to the experimental result described above could be obtained.

(79) As a result of analyzing the color fastness by dyeing using the dye prepared in Example 1, the color fastness of the dye was shown to be excellent both in washing and abrasion having the 4.sup.th degree or higher, and the color fastness regarding the sublimation was between the 2.sup.nd degree to the 3.sup.rd degree. In color fastness to sunlight, the dye showed to be excellent having the 4.sup.th degree or higher.

(80) When the polypropylene fiber dyed with the dye prepared in Example 1 was exposed to a hydrochloric acid gas, it was visually observed that the initial yellow color of the polypropylene fiber was changed to a red color upon detection, and upon removal of the hydrochloric acid gas, the polypropylene fiber returned to a yellow color.

(81) Based on the above results, it can be confirmed that the application of the finally synthesized dye to protective clothes can help workers to immediately recognize their exposure to an acid gas thereby capable of preventing injuries while working in harmful environments.