A green thermal-sensitive colorant and its preparation method

Abstract

The present invention aims to disclose a green thermal colorant and a preparation method thereof. The green thermal colorant is 3-dibutylamino-7-dibenzylfluoran. Compared with the prior art, the reaction raw materials are readily available, the production process is simple, and the product is stable. Not only can green thermal paper, film, and thermal color-forming materials be produced, but also thermal color-forming materials of any color can be produced by color matching, thereby achieving the purpose of the present invention.

Description

Technical Field

[0001] The present invention relates to a thermosensitive colorant and a preparation method thereof, in particular to a green thermosensitive colorant and a preparation method thereof. Background Art

[0002] Currently, thermal printing is widely used in many industries due to its simplicity and convenience.

[0003] Thermal colorants are special compounds that, unlike traditional dyes, are inherently colorless. When applied or distributed on various substrates, such as paper, plastic film, metal film, textiles, and solvents, they react chemically with thermal developers under the influence of heat, pressure, and additives to produce colored compounds, achieving color development. These compounds are used in the production of thermal and pressure-sensitive paper, color-shifting coatings, and are widely used in a variety of applications, including labels, fax machines, receipts, documents, color-shifting coatings, and writing materials.

[0004] Existing thermal couplers rarely produce orange color. Existing green thermal couplers primarily include 3-diethylamino-7-phenylaminofluoran and 3-diethylamino-7-diphenylaminofluoran. However, these green thermal couplers are difficult to obtain from raw materials, have complex synthesis processes, and are expensive. They also suffer from drawbacks such as high thermal color development temperatures, low color density, and unstable color development.

[0005] Therefore, there is a particular need for a green thermal-sensitive coloring agent and a preparation method thereof, which can print all the colors required by the user to solve the above-mentioned existing problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a green thermosensitive color-forming agent and a preparation method thereof, which addresses the deficiencies of the prior art and has readily available raw materials, a simple process, low production cost, stable products and bright colors.

[0007] The technical problem solved by the present invention can be achieved by adopting the following technical solutions:

[0008] In a first aspect, the present invention provides a green thermal coupler, wherein the green thermal coupler is 3-dibutylamino-7-dibenzylfluoran, and its molecular formula is as follows:

[0009] .

[0010] In a second aspect, the present invention provides a method for preparing a green thermosensitive coupler, comprising the following steps:

[0011] Dibutyl dibenzoic acid is dissolved in concentrated sulfuric acid, and 4-methoxy-N,N-dibenzylaniline is added. After the condensation is completed, it is precipitated with water. Under alkaline conditions, a ring-closure reaction is performed to generate a crude product, which is dissolved in an organic solvent, decolorized with activated carbon, cooled, crystallized, filtered, and dried to obtain a green thermosensitive colorant.

[0012] In a preferred embodiment of the present invention, the ratio of concentrated sulfuric acid to dibutyl benzoic acid is 2-8:1, preferably 3-5:1; and the concentration of concentrated sulfuric acid is 95-110%, preferably 100-105%.

[0013] In a preferred embodiment of the present invention, the temperature of the condensation reaction is 5-60°C, and optimally 10-30°C.

[0014] In a preferred embodiment of the present invention, the molar ratio of dibutylbenzoic acid to 4-methoxy-N,N-dibenzylaniline is 0.95-1.5:1, and optimally 1.05-1.2:1.

[0015] In a preferred embodiment of the present invention, the temperature of the ring-closing reaction is 60-100°C, and optimally 80-90°C.

[0016] In a preferred embodiment of the present invention, the organic solvent is benzene, toluene, ethanol or methanol.

[0017] Compared with the prior art, the green thermal colorant and preparation method of the present invention have readily available reaction raw materials, a simple production process, and a stable product. Not only can green thermal paper, film, and thermal color-forming materials be produced, but also thermal color-forming materials of any color can be produced by color matching, thereby achieving the purpose of the present invention.

[0018] The features of the present invention can be clearly understood by referring to the detailed description of the preferred embodiments below. DETAILED DESCRIPTION

[0019] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further explained below in combination with specific details.

[0020] The green thermal coupler of the present invention is 3-dibutylamino-7-dibenzylfluoran, and its molecular formula is as follows:

[0021] . Example 1

[0022] To a 2000ml three-necked flask, add 1200g of concentrated sulfuric acid and 400g of fuming sulfuric acid. Slowly add 350g of dibutyl benzoic acid at 30-35°C while stirring. Continue stirring at 30-35°C until completely dissolved, then cool to below 20°C. Add 300g of 4-methoxy-N,N-dibenzylaniline within 2 hours. After addition, allow to react at 30-35°C for 2 hours, then heat to 50±2°C and react for 4 hours. Slowly add the mixture to 1000g of ice water, stir for 0.5 hour, filter, add 500ml of toluene to the filter cake, adjust the pH to >10 with 30% caustic soda, heat at reflux for 3 hours, maintain the pH at >10, drain, wash with water, add 5g of activated carbon, reflux, drain, filter the activated carbon, cool, crystallize, and dry to yield 520g of the finished product. Example 2

[0023] To a 2000ml three-necked flask, add 1600g of concentrated sulfuric acid and 400g of fuming sulfuric acid. Slowly add 350g of dibutyl benzoic acid at 30-35°C while stirring. Continue stirring at 30-35°C until completely dissolved, then cool to below 20°C. Add 300g of 4-methoxy-N,N-dibenzylaniline within 2 hours. After addition, allow to react at 30-35°C for 2 hours, then heat to 50±2°C and react for 4 hours. Slowly add the mixture to 1000g of ice water, stir for 0.5 hour, filter, add 500ml of toluene to the filter cake, adjust the pH to >10 with 30% caustic soda, heat under reflux for 3 hours, maintain the pH at >10, drain, wash with water, add 5g of activated carbon, reflux, drain, filter the activated carbon, cool, crystallize, and dry to yield 560g of the finished product. Example 3

[0024] To a 2000ml three-necked flask, add 1600g of concentrated sulfuric acid and 400g of fuming sulfuric acid. Slowly add 350g of dibutyl benzoic acid at 30-35°C while stirring. Continue stirring at 30-35°C until completely dissolved, then cool to below 20°C. Add 300g of 4-methoxy-N,N-dibenzylaniline within 2 hours. After addition, allow to react at 20-25°C for 2 hours, then heat to 40±2°C and react for 4 hours. Slowly add the mixture to 1000g of ice water, stir for 0.5 hours, filter, and add 500ml of toluene to the filter cake. Adjust the pH to >10 with 30% caustic soda. Heat under reflux for 3 hours to maintain the pH >10, drain, and wash with water. Add 5g of activated carbon, reflux, drain, filter, and cool to crystallize and dry to yield 460g of the finished product. Example 4

[0025] To a 2000ml three-necked flask, add 1600g of concentrated sulfuric acid and 400g of fuming sulfuric acid. Slowly add 350g of dibutyl benzoic acid at 30-35°C while stirring. Continue stirring at 30-35°C until completely dissolved, then cool to below 20°C. Add 350g of 4-methoxy-N,N-dibenzylaniline within 2 hours. After addition, allow to react at 30-35°C for 2 hours, then heat to 40±2°C and react for 4 hours. Slowly add the mixture to 1000g of ice water, stir for 0.5 hours, filter, and add 500ml of toluene to the filter cake. Adjust the pH to >10 with 30% caustic soda. Heat under reflux for 3 hours to maintain the pH >10. Drain the water, wash with water, add 5g of activated carbon, reflux the mixture, drain the water, filter the activated carbon, and cool, crystallize, and dry to yield 570g of the finished product.

[0026] Thermal coating experiment:

[0027] Mix 10g of the product with 20g of 10% PVA solution, add 0.5g of emulsifier (sodium acrylate), and grind into an emulsion with a particle size of 0.8um using a ball mill.

[0028] Mix 15g of bisphenol S and 30g of 10% PVA, add 1.0g of emulsifier (sodium acrylate), and grind with a ball mill to an emulsion with a particle size of 1.0um.

[0029] Mix the above two emulsions at 6g / m 2 The coating amount is applied on the paper, and the thermal paper begins to emit green statically when heated to 80 degrees.

[0030] The basic principles, main features and advantages of the present invention are shown and described above. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention, which is defined by the appended claims and their equivalents.

Claims

1. Application of 3-dibutylamino-7-dibenzylfluoran as a green thermal coupler. The molecular formula of the 3-dibutylamino-7-dibenzylfluoran is as follows:

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