Preparation method of high-whiteness thermosensitive color developing agent containing sulfonylurea structure

Abstract

A preparation method of a high-whiteness thermosensitive color developing agent containing a sulfonylurea structure comprises the following steps: dissolving MAP in an organic solvent, slowly dropwise adding PTSI into the organic solvent, and carrying out heat preservation to a reaction endpoint to obtain an intermediate product N-p-toluenesulfonyl-N '-(3-hydroxyphenyl) urea system; adding alkali liquor into the obtained intermediate product system for dissolving, then slowly dropwise adding an organic solution of PTSC, simultaneously dropwise adding the alkali liquor to control the pH value of the system, and carrying out heat preservation reaction to the end point to obtain a product N-p-toluenesulfonyl-N '-(3-p-toluenesulfonyloxyphenyl) urea system; adding an alcohol solvent into the prepared N-p-toluenesulfonyl-N-(3-p-toluenesulfonyloxy phenyl) urea system, neutralizing with acid, and filtering to obtain a filter cake; and carrying out post-treatment and vacuum drying on the filter cake to obtain a final product. According to the preparation method disclosed by the invention, the sulfonylurea color developing agent with high yield, high purity, whiter color and less solvent residue can be obtained, and the process operation is more suitable for industrial production.

Description

technical field [0001] The invention relates to a preparation method of a heat-sensitive color developer, in particular to a preparation method of a high-whiteness heat-sensitive color developer containing a sulfonylurea structure. Background technique [0002] N-p-toluenesulfonyl-N'-(3-p-toluenesulfonyloxyphenyl) urea is a new type of thermosensitive chromogenic agent, which releases hydrogen ions (H + ) to make the heat-sensitive coupler color base develop color. Compared with the carcinogenic phenolic coupler, which is controversial in terms of carcinogenicity, its photostability is higher, and the image is more suitable for long-term storage. [0003] In recent years, the research on N-p-toluenesulfonyl-N'-(3-p-toluenesulfonyloxyphenyl) urea only focuses on the research on the preparation method, and there is little research on the post-treatment of the target product. [0004] Since the production process of thermal paper is to directly compound and coat the color deve...

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Problems solved by technology

[0004] Since the production process of thermal paper is to directly compound and coat the color developer, color coupler, stabilizer and other functional components on the surface of the paper base, the entire use process does not involve the color developer purification or similar purification process, so the obvious The purity and whiteness of the colorant will directly affect the quality of thermal paper; at the same time, in industrial production, since most of the sulfonylurea color developers are synthesized in a highly polar solvent, the residual solvent will cause the color developer to be separated from the color developer in advance. Chromogenic effect, resulting in dark and gray thermal paper stored for a long time

[0005] The above problems can be solved by decolorizing and recrystallizing the finished chromogenic agent before application, but the purification operation makes the preparation process more complicated and complicated, and the yield is lost. Therefore, while changing and controlling the preparation process, the post-treatment process of the target product should be studied is the best way to solve the problems existing in the application

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