JPH0132262B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a coloring agent that can be repeatedly decolored and decolored depending on pH.

(Prior art and problems to be solved by the invention) Conventionally, phthalein-based indicators have been used as colorants that can be repeatedly decolored and developed by pH, but since they are dye-type, they have poor water resistance. When applied to paper, etc., there was a problem that the dye would wash out if water came on it.

Therefore, in order to make the phthalein indicator water resistant, the present applicant created a color-discoloring coloring material in the Showa era, in which a phthalein indicator into which a dialkylaminomethyl group was introduced was cationized with acid and bonded to clay through ion exchange.
Filed on April 30, 1955 (Japanese Unexamined Patent Publication No. 152879/1983)
However, although this product had improved water resistance, its solvent resistance was somewhat inadequate.

(Means for Solving the Problems) The present invention is an attempt to solve the above-mentioned problems by basically bonding the phthalein indicator and the clay more firmly. The gist of this product is a decolorizable colorant made by converting a phthalein indicator into which an aminomethyl group has been introduced into a quaternary ammonium salt and ion-exchange bonding it with the cations of clay containing cations in its crystal structure.

Hereinafter, the composition of the present invention will be explained in detail.

Examples of phthalein indicators include phenolphthalein, o-cresol phthalein, p-xylenophthalein, α-naphthol phthalein,
Examples include bromothymol phthalein, bromophenolphthalein, nitrophenolphthalein, and the like, which can be used alone or in combination of two or more.

As the clay containing cations in its crystal structure, bentonite, montmorillonite, zeolite, and kaolinite can be used.

The manufacturing method will be described.

First, in order to obtain a phthalein indicator into which a dialkylaminomethyl group has been introduced with quaternary ammonium chloride, various methods are used to introduce a dialkylaminomethyl group into a phthalein indicator. Representative examples include the Mannich reaction and the Reimer-Tiemann reaction. (especially considering the ease of operation)
A method using Mannich reaction is preferred. ) After introducing a dialkylaminomethyl group into a phthalein indicator, it is converted into a quaternary ammonium salt by the action of dialkyl sulfate, alkyl halide, etc.

Next, a phthalein indicator with a quaternary ammonium chloride dialkylaminomethyl group introduced is mixed with clay containing cations in its crystal structure such as bentonite, montmorillonite, zeolite, and kaolinite, and heated to 30 to 70°C. The mixture is stirred to form an ion-exchange bond, which is then filtered and dried to obtain the desired coloring material.

(Action) Since the phthalein indicator into which a dialkylaminomethyl group has been introduced is converted into a quaternary ammonium salt, the phthalein indicator is cationized.
Therefore, it is presumed that the clay and the clay containing cations in the crystal structure are more strongly bonded through ion exchange bonding, and the solvent resistance is also improved.

(Example) Hereinafter, a more detailed explanation will be given according to examples.

Example 1 (using Mannich reaction) 0.03 mol of phenolphthalein was placed in a 200 ml four-neck flask equipped with a stirrer and a thermometer, and 20
0.06 mol of diethylamine was added dropwise with stirring at °C. Further, 0.06 mol of formalin (35% aqueous solution) was added dropwise to this mixture, and the mixture was stirred for 1 hour.The temperature was then raised to 80°C, and the mixture was stirred for 2 hours, and then poured into water to obtain a rubber-like substance. This was dissolved in 30 ml of concentrated salt and filtered. The filtrate was neutralized with sodium carbonate, and the resulting precipitate was filtered and dried.

Next, take 0.01 mol of this product and use a stirring device.
Pour into a 100ml four-necked flask equipped with a thermometer.
Furthermore, add 50 ml of isopropanol and add methyl iodide.
0.025 mol was added dropwise. After dropping, raise the temperature to 80℃,
Stirred for about 2 hours. Thereafter, the mixture was cooled, and the precipitate formed was filtered and dried.

0.5 g of this product was taken, dissolved in 200 g of water, 50 g of bentonite was added thereto, and the mixture was stirred at 30 to 70° C. for 1 hour, then filtered and dried to obtain a white decolorizable colorant.

Example 2 A white decolorizable coloring material was obtained in the same manner as in Example 1 except that diethyl sulfate was used in place of iodination and montmorillonite was used in place of bentonite.

(Effects) The coloring materials of Examples 1 and 2 were applied to plain paper, and when the PH was made alkaline with sodium carbonate, the color developed, and when the PH was made acidic with hydrochloric acid, the color disappeared. By sequentially repeating this process, decoloring and coloring were achieved.

Furthermore, when these colorants were applied to plain paper, colored with alkaline, and then immersed in methanol, no elution of the colorant was observed.

On the other hand, when phenolphthalein into which a dimethylaminomethyl group was introduced was cationized with concentrated hydrochloric acid and combined with bentonite, a colorant was applied to plain paper, developed with alkalinity, and then dipped in methanol. Elution was observed.

As described above, it can be seen that the coloring material of the present invention can be repeatedly decolored and colored, and has excellent solvent resistance.

Claims (1)

[Claims] 1. A decolorizing coloring material made by converting a phthalein indicator into which a dialkylaminomethyl group has been introduced into a quaternary ammonium salt and ion exchange bonding with the cation of clay containing a cation in its crystal structure.