Preparation method and application of a new type of thermal color developer

Abstract

The present invention relates to the field of IPC C07C311 / 60, and in particular to a preparation method and application of a novel thermosensitive developer. The preparation step of the novel thermosensitive developer includes mixing a diamine compound with a sulfonyl halide and reacting it with a compound containing NCO to obtain a novel thermosensitive developer product. The novel thermosensitive developer provided by the present invention has the following advantages: while optimizing the efficiency and safety of the developer production process, a novel structure of a ternary benzene ring non-phenol type thermosensitive developer is provided to improve the separation effect of the target product and impurities, significantly improve the yield and purity of the thermosensitive developer, and provide a feasible solution for the subsequent preparation of thermal paper; the obtained thermosensitive developer has wide adaptability to the substrate, can be applied to a variety of thermal papers, has high color sensitivity, high color density, strong image stability, strong environmental tolerance, and has broad application prospects.

Description

Technical Field

[0001] The invention relates to the field of IPC C07C311 / 60, and in particular to a preparation method and application of a novel thermosensitive developer. Background Art

[0002] Thermal paper is an information carrier that can present different patterns on paper. Since its development, it has been rapidly applied to various work scenarios such as fax communications, securities, labels, ticketing, instrument recording terminals, etc. It is a new type of information recording material. The color development principle of thermal paper is to combine the base paper with a reagent with a specific color development function, so the characteristics of the color developer directly affect the color development performance of thermal paper. Traditional phenolic color developers have poor color development sensitivity, and when applied to thermal paper, it is difficult to meet the high requirements of thermal paper for image quality and image stabilization; at the same time, phenolic color developers are highly volatile, and both the preparation process and the use process have a negative impact on human health, and have been gradually eliminated in the field of color developers for thermal paper.

[0003] Chinese patent CN202010157164.0 discloses a novel non-phenolic thermosensitive color developer, a preparation method and its application in thermal recording materials. Benzenesulfonyl isocyanate and meta-phenylenediamine are reacted to obtain N,N'-(((1,3-phenylenebis(azadiyl))bis(carbonyl)))dibenzenesulfonamide. However, the meta-phenylenediamine in its synthetic raw material is a "three-hazard" substance recognized by the industry. It can cause mutagenicity, carcinogenicity and teratogenicity during use. Thermal paper is used in direct contact with the human body in daily life, and this method has great safety hazards.

[0004] Chinese patent CN201710175990.6 discloses a method for preparing a thermal developer containing a sulfonylurea structure, wherein m-aminophenol and p-toluenesulfonyl chloride are esterified under alkaline conditions to obtain 3-aminophenyl p-toluenesulfonate, which is then reacted with p-toluenesulfonyl isocyanate, and further acidified and refined to obtain a finished thermal developer. The developer obtained by this method has excellent performance, but has high requirements for process operation and still cannot meet the demand for large quantities of thermal paper. Summary of the invention

[0005] In order to solve the above problems, the first aspect of the present invention provides a method for preparing a novel thermosensitive color developer. The preparation steps of the novel thermosensitive color developer include mixing a diamine compound with a sulfonyl halide and then reacting with a -NCO-containing compound to obtain a novel thermosensitive color developer product.

[0006] In some preferred embodiments, at least two of the diamine compound, the sulfonyl halide, and the -NCO-containing compound contain a benzene ring structure.

[0007] In some preferred embodiments, the diamine compound is an aromatic diamine compound, and the number of primary amines in the aromatic diamine compound is ≥1.

[0008] More preferably, the aromatic diamine compound contains two primary amines, preferably at least one of 1,2-phenylenediamine, 1,3-phenylenediamine and 1,4-phenylenediamine.

[0009] More preferably, the aromatic diamine compound is 1,2-phenylenediamine.

[0010] In some preferred embodiments, the sulfonyl halide is specifically benzenesulfonyl halide, and the number of electron layers of the halogen element in the benzenesulfonyl halide is 2 to 5; that is, the halogen element is selected from any one of chlorine, bromine, iodine and fluorine.

[0011] Further preferably, the halogen element in the sulfonyl halide is chlorine; the sulfonyl halide includes a combination of one or more of benzenesulfonyl chloride, 2,4,6-trichlorobenzenesulfonyl chloride, 4-methylsulfonyl chloride, 4-chloro-2,5-dimethylbenzenesulfonyl chloride and 2,4,6-trimethylbenzenesulfonyl chloride.

[0012] More preferably, the sulfonyl halide is benzenesulfonyl chloride.

[0013] In some preferred embodiments, the -NCO-containing compound contains a benzene ring structure, including phenyl isocyanate, 4-isocyanatobutylbenzoate, p-phenylene diisocyanate, 1-isocyanato-4-pentylbenzene, diisocyanatomethyl-benzene, 2,3-dimethylphenylisocyanate, and a combination of one or more of 2-(methoxycarbonyl)phenylisocyanate.

[0014] More preferably, the -NCO-containing compound has a melting point of -15 to -45°C and a surface tension of 30 to 50 dyne / cm.

[0015] More preferably, the -NCO-containing compound is phenyl isocyanate, which has a melting point of -31±1° C. and a surface tension of 38.6 dyne / cm.

[0016] In order to balance the color development performance and safety of the color developer, the applicant aims to explore a new color development material that can effectively replace the phenolic color developer. In the process of studying thermal paper technology, it was found that the material with NH2-C(=O)-NH-RS(=O)2 structure has the characteristics of high sensitivity and high color density when applied to paper substrates. The use of multifunctional amine compounds as the starting synthetic raw materials, reacting with sulfonyl halides and -NCO-containing compounds, can achieve the preparation of a new type of thermal color developer. However, the raw materials used in this synthetic route are all characterized by high reactivity. The reaction process is difficult to control in the actual synthesis process, and the yield and purity of the synthetic product are low, resulting in low clarity of subsequent color development imaging. After a lot of attempts and explorations, the applicant found that by reacting diamine compounds containing a benzene ring structure, sulfonyl halides and -NCO-containing compounds, especially selecting 1,2-phenylenediamine with benzenesulfonyl chloride and phenyl isocyanate, a high-yield, high-purity ternary benzene ring color-developing structure can be obtained under relatively mild process conditions; the reason may be that under these conditions, each reactant can have both reaction activity and appropriate steric hindrance, which promotes the interaction between the reactive groups, thereby improving the yield and purity of the synthetic product.

[0017] In some preferred embodiments, the preparation steps of the novel thermosensitive developer are specifically as follows:

[0018] S1. Add the diamine compound into a reaction vessel containing a mixed solvent, set the temperature to 10-16°C under a nitrogen atmosphere, then add the sulfonyl halide, raise the temperature to 50-60°C for reaction for 1-2h, and collect the intermediate product;

[0019] S2. The intermediate product is cooled to 30-37°C, a compound containing -NCO is added, the reaction is kept warm for 1-2 hours, and the product is purified to obtain a novel thermosensitive color developer.

[0020] In some preferred embodiments, the operation of collecting the intermediate product is specifically as follows: after the reaction in step S1 is completed, a second solvent is added to the reaction vessel, the temperature is raised to 55-65° C. to dissolve all the materials, the liquid is allowed to stand and separate into an organic layer and an aqueous layer, the aqueous layer is removed, and the organic layer is subjected to azeotropic dehydration to obtain the intermediate product.

[0021] In some preferred embodiments, the mixed solvent comprises a combination of an organic solvent and an inorganic solvent; the inorganic solvent is water, and the organic solvent comprises at least one of ethyl acetate, methanol, acetonitrile, acetone, cyclohexane, N,N-dimethylformamide, and toluene.

[0022] More preferably, the mixed solvent is water and toluene, and the volume ratio of toluene to water is (2-5):1.

[0023] In some preferred embodiments, in the step S1, when the diamine compound is added into the reaction container, an alkali metal carbonate is added simultaneously; the molar ratio of the diamine compound to the alkali metal carbonate is 2:(1-1.5).

[0024] In some preferred embodiments, the alkali metal carbonate includes but is not limited to sodium carbonate and potassium carbonate.

[0025] The applicant discovered during the experimental operation that in the reaction of 1,2-phenylenediamine and benzenesulfonyl chloride, the use of an organic-inorganic mixed solvent and the addition of a specific amount of alkali metal carbonate can effectively promote the formation of an -NHSO2- structure between the primary amine molecule and the sulfonyl group; the normal S1 step requires more than 2 hours to react from room temperature to 50°C. The present invention unexpectedly discovered that when the mixed solvent is water and toluene in a volume ratio of (2-5):1, the initial temperature is controlled at 10-16°C and then the temperature is raised for the reaction, which can significantly improve the reactivity of the aromatic diamine and benzenesulfonyl chloride, so that the reaction in the S1 step can be completed in 1.5 hours, and the intermediate product obtained is easy to separate from the impurities, thereby improving the process efficiency and the yield of the finished color developer.

[0026] In some preferred embodiments, the purification treatment is specifically as follows: after the reaction in step S2 is completed, the reaction container is cooled to below 10°C, the solid product is collected by filtration, and dried under negative pressure to obtain a novel thermosensitive color developer product.

[0027] The applicant also found during the research process that the water content of the intermediate product is likely to interfere with the subsequent reaction process, generate by-products that affect the smooth progress of the reaction, and consume reactants to reduce the yield of the final product. After the liquid separation of the organic layer and the water layer, the present invention further performs azeotropic dehydration on the organic layer before the start of step S2, which can significantly inhibit the occurrence of side reactions, so that step S2 can be carried out smoothly at a lower temperature. After the reaction is completed, a new color developer with a yield of up to 95% and a purity of more than 98% can be obtained through simple suction filtration and drying operations.

[0028] In some preferred embodiments, the addition rate of the sulfonyl halide is 0.05-1 mol / min.

[0029] In some preferred embodiments, the addition rate of the -NCO-containing compound is 0.1-0.2 mol / min.

[0030] In some preferred embodiments, the addition rate of the sulfonyl halide is 0.5 to 3 times the addition rate of the -NCO-containing compound.

[0031] The structural formula of the novel thermosensitive developer provided by the present invention is as follows:

[0032]

[0033] The second aspect of the present invention provides a method for preparing a novel thermosensitive developer and its application in the field of thermosensitive materials.

[0034] During the research process of thermal color developers, the applicant found that the thermal color developer with the above structure obtained according to the above preparation method has the characteristics of high sensitivity, high color density and high image stability, and can exert excellent color development effect when combined with various paper materials. In actual application, it can be used for thermal paper with various color development requirements such as thermal fax paper, thermal film, boarding pass, thermal label paper, lottery ticket, ticket, etc., and the color development is clear and long-lasting. It is not easy to be distorted even in harsh environments such as humidity and stuffiness. The pattern of thermal paper is not easy to deform or migrate after folding. The application range of the color developer of the present invention is extremely wide, and the process flow is simple and practical, which can meet the use needs of large quantities of thermal paper.

[0035] Beneficial effects:

[0036] The novel thermosensitive developer provided by the present invention has the following advantages:

[0037] (1) 1,2-phenylenediamine is reacted with benzenesulfonyl chloride and phenyl isocyanate to obtain a non-phenolic thermosensitive developer having an active color-developing group under mild reaction conditions, thereby optimizing the efficiency and safety of the developer production process and providing a novel structure of a ternary benzene ring non-phenolic thermosensitive developer;

[0038] (2) By controlling the amount of each raw material and coordinating a specific heating program and impurity removal step, the occurrence of side reactions during the reaction is suppressed, and the separation effect of the target product and impurities is improved, and the yield and purity of the thermal color developer are significantly improved, providing a feasible solution for the subsequent preparation of thermal paper;

[0039] (3) The obtained thermal color developer has wide adaptability to substrates and can be applied to various types of thermal papers. It has the characteristics of high color development sensitivity, high color density, strong image stability, and strong environmental tolerance, and has broad application prospects. DETAILED DESCRIPTION

[0040] Example 1.

[0041] This embodiment provides a method for preparing a novel thermosensitive color developer. The preparation steps of the novel thermosensitive color developer are as follows:

[0042] S1. 2 mol of diamine compound was placed in a reaction vessel containing 1500 mL of a mixed solvent, the temperature was set to 14 ° C under a nitrogen atmosphere, and then 1.8 mol of sulfonyl halide was added, the temperature was raised to 53 ° C for reaction for 1.5 h, and the intermediate product was collected;

[0043] S2. The intermediate product was cooled to 35°C, 1.9 mol of a compound containing -NCO was added, the reaction was kept warm for 1.5 hours, and the product was purified to obtain a new type of thermosensitive color developer.

[0044] The aromatic diamine compound is 1,2-phenylenediamine, and its CAS number is 95-54-5.

[0045] The sulfonyl halide is specifically benzenesulfonyl chloride, and its CAS number is 98-09-9.

[0046] The -NCO-containing compound is phenyl isocyanate, with a CAS number of 103-71-9; its melting point is -31±1° C., and its surface tension is 38.6 dyne / cm.

[0047] The operation of collecting the intermediate product is specifically as follows: after the reaction in step S1 is completed, 700 mL of the second solvent is added to the reaction container, the temperature is raised to 62° C. to dissolve all the materials, the liquid is allowed to stand and separate into an organic layer and an aqueous layer, the aqueous layer is removed, and the organic layer is subjected to azeotropic dehydration to obtain the intermediate product.

[0048] The mixed solvent is water and toluene, and the volume ratio of toluene to water is 0.3:1.

[0049] In the step S1, when the diamine compound is added into the reaction container, the alkali metal carbonate is added simultaneously; the molar ratio of the diamine compound to the alkali metal carbonate is 2:1.4.

[0050] The alkali metal carbonate is sodium carbonate.

[0051] The second solvent is toluene.

[0052] The purification treatment is specifically as follows: after the reaction in step S2 is completed, the reaction container is cooled to 5° C., the solid product is collected by suction filtration, and vacuum dried for 12 hours to obtain a novel thermosensitive color developer product.

[0053] The addition rate of the sulfonyl halide is 0.2 mol / min.

[0054] The addition rate of the -NCO-containing compound is 0.1 mol / min.

[0055] The structural formula of the novel thermosensitive developer provided in this embodiment is as follows:

[0056]

[0057] The second aspect of this embodiment provides an application of a method for preparing a novel thermosensitive color developer, and the application of the method for preparing the novel thermosensitive color developer in the field of thermosensitive materials.

[0058] Example 2.

[0059] This embodiment provides a method for preparing a novel thermosensitive color developer. The preparation steps of the novel thermosensitive color developer are as follows:

[0060] S1. 2 mol of diamine compound was placed in a reaction vessel containing 1500 mL of a mixed solvent, the temperature was set to 10°C under a nitrogen atmosphere, and then 1.8 mol of sulfonyl halide was added, the temperature was raised to 53°C for reaction for 1.5 h, and the intermediate product was collected;

[0061] S2. The intermediate product was cooled to 35°C, 1.9 mol of a compound containing -NCO was added, the reaction was kept warm for 1.5 hours, and the product was purified to obtain a new type of thermosensitive color developer.

[0062] The aromatic diamine compound is 1,2-phenylenediamine, and its CAS number is 95-54-5.

[0063] The sulfonyl halide is specifically benzenesulfonyl chloride, and its CAS number is 98-09-9.

[0064] The -NCO-containing compound is phenyl isocyanate, with a CAS number of 103-71-9; its melting point is -31±1° C., and its surface tension is 38.6 dyne / cm.

[0065] The operation of collecting the intermediate product is specifically as follows: after the reaction in step S1 is completed, 700 mL of the second solvent is added to the reaction container, the temperature is raised to 62° C. to dissolve all the materials, the liquid is allowed to stand and separate into an organic layer and an aqueous layer, the aqueous layer is removed, and the organic layer is subjected to azeotropic dehydration to obtain the intermediate product.

[0066] The mixed solvent is water and toluene, and the volume ratio of toluene to water is 0.4:1.

[0067] In the step S1, when the diamine compound is added into the reaction container, the alkali metal carbonate is added simultaneously; the molar ratio of the diamine compound to the alkali metal carbonate is 2:1.2.

[0068] The alkali metal carbonate is sodium carbonate.

[0069] The second solvent is toluene.

[0070] The purification treatment is specifically as follows: after the reaction in step S2 is completed, the reaction container is cooled to 5° C., the solid product is collected by suction filtration, and vacuum dried for 12 hours to obtain a novel thermosensitive color developer product.

[0071] The addition rate of the sulfonyl halide is 0.2 mol / min.

[0072] The addition rate of the -NCO-containing compound is 0.15 mol / min.

[0073] The structural formula of the novel thermosensitive developer provided in this embodiment is as follows:

[0074]

[0075] The second aspect of this embodiment provides an application of a method for preparing a novel thermosensitive color developer, and the application of the method for preparing the novel thermosensitive color developer in the field of thermosensitive materials.

[0076] Comparative Example 1.

[0077] This comparative example provides a method for preparing a novel thermosensitive color developer, and the specific implementation method is the same as that of Example 1; the difference is that in step S1, 2 mol of diamine compound is put into a reaction container containing 1500 mL of mixed solvent, the temperature is set to 24°C under a nitrogen atmosphere, and then 1.8 mol of sulfonyl halide is added, the temperature is raised to 50°C for reaction for 1.5 hours, and the intermediate product is collected;.

[0078] Comparative Example 2.

[0079] This comparative example provides a method for preparing a novel thermosensitive color developer, and the specific implementation manner is the same as that of Example 1; the difference is that the mixed solvent is water and ethyl acetate, and the volume ratio of ethyl acetate to water is 0.5:1.

[0080] Performance Testing Methods

[0081] 1. Target product performance

[0082] (1) Yield: The thermosensitive developer products obtained in the examples and comparative examples were weighed, and the yield of the thermosensitive developer was calculated according to the following formula:

[0083] Yield = (theoretical production - actual production) / theoretical production × 100%

[0084] (2) Purity: The purity of the thermosensitive color developing agents obtained in the examples and comparative examples was analyzed by HPLC (Agilent 1260).

[0085] The results are recorded in Table 1.

[0086] 2. Color rendering performance

[0087] Thermosensitive color developing liquid was prepared according to the formula of 4% thermosensitive color developer, 3% color former, 8% sensitizer, 5% binder, and water to make up the balance. The dry coating weight was 4g / m 2 The product was coated on a thermal base paper, and then placed in a thermal color development instrument under the conditions of a voltage of 15V and a pulse width of 2ms to develop color, thereby obtaining a thermal paper sample.

[0088] The thermosensitive color developer is the thermosensitive color developer provided in Example 1-2 and Comparative Example 1-2, the color former is 3-(N-ethyl-4-toluidine)-6-methyl-7-anilinofluoran (ETAC), the sensitizer is 1,2-diphenoxyethane (DPE), and the adhesive is polyvinyl alcohol (brand name JVP VP-18).

[0089] The thermal paper sample was immersed in 30°C water for 48 hours, and the optical density before and after immersion was measured using an optical densitometer (Lin Shang LS117), and the loss amount δ was calculated.

[0090] δ = (optical concentration before immersion - optical concentration after immersion) / optical concentration before immersion × 100%

[0091] It is defined that δ≤3% is qualified for color rendering, and δ>3% is unqualified for color rendering; the results are recorded in Table 1.

[0092] Performance test data

[0093] Table 1. Performance test results

[0094] Yield % purity% Color rendering Example 1 95.4 98.9 qualified Example 2 94.2 97.2 qualified Comparative Example 1 90.5 95.4 Failure Comparative Example 2 92.6 94.8 Failure

Claims

1. A method for preparing a thermosensitive developer, characterized in that: The preparation steps of the thermosensitive developer are specifically as follows: S1. 2 mol of diamine compound was placed in a reaction vessel containing 1500 mL of a mixed solvent. Under a nitrogen atmosphere, the temperature was set to 14°C, and then 1.8 mol of sulfonyl halide was added. The temperature was raised to 53°C for reaction for 1.5 hours, and the intermediate product was collected. S2. The intermediate product was cooled to 35°C, 1.9 mol of a -NCO-containing compound was added, the reaction was kept warm for 1.5 hours, and the product was purified to obtain a thermosensitive developer; The diamine compound is 1,2-phenylenediamine; The sulfonyl halide is specifically benzenesulfonyl chloride; The -NCO-containing compound is phenyl isocyanate; its melting point is -31±1°C and its surface tension is 38.6 dyne / cm; The operation of collecting the intermediate product is specifically as follows: after the reaction in step S1 is completed, 700 mL of the second solvent is added to the reaction container, the temperature is raised to 62° C. to dissolve all the materials, the liquid is allowed to stand and separate into an organic layer and an aqueous layer, the aqueous layer is removed, and the organic layer is subjected to azeotropic dehydration to obtain the intermediate product; The mixed solvent is water and toluene, and the volume ratio of toluene to water is 0.3:1; In the step S1, when the diamine compound is added into the reaction container, an alkali metal carbonate is added at the same time; the molar ratio of the diamine compound to the alkali metal carbonate is 2:1.4; The alkali metal carbonate is sodium carbonate; The second solvent is toluene; The purification treatment is specifically as follows: after the reaction in step S2 is completed, the reaction container is cooled to 5°C, the solid product is collected by suction filtration, and vacuum dried for 12 hours to obtain a thermosensitive color developer product; The addition rate of the sulfonyl halide is 0.2 mol / min; The addition rate of the -NCO-containing compound is 0.1 mol / min.

2. An application of the preparation method of the thermosensitive developer according to claim 1 in the field of thermosensitive materials.

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