Benzotriazole-diazonaphthoquinone type photoinitiators with bridging structures as well as synthesis and application of benzotriazole-diazonaphthoquinone type photoinitiators

Abstract

The invention discloses a benzotriazole-diazo naphthoquinone photoinitiator with a bridging structure, which belongs to the field of near ultraviolet photoinitiators, the chemical structural general formula of the benzotriazole-diazo naphthoquinone photoinitiator is as follows: in the structural formula, R represents hydrogen, hydroxyl and a diazo naphthoquinone ester group, and at least one substituent of R is the diazo naphthoquinone ester group. The benzotriazole-diazonaphthoquinone type photoinitiator with a bridging structure is synthesized through a simple and efficient method, the ultraviolet visible absorption peak value of the photoinitiator is subjected to red shift to 360 nm, the half-peak width is about 60 nm and extends to about 450 nm, the requirement for near ultraviolet absorption is completely met, and the photoinitiator has the advantages that the photoinitiator is simple and efficient, and the photoinitiator is suitable for industrial production. The near ultraviolet light initiator can be used as a photocuring material by initiating monomer polymerization under the irradiation of near ultraviolet light.

Description

Technical Field

[0001] This invention belongs to the field of near-ultraviolet photoinitiators, particularly benzotriazole-diazonaphthoquinone type photoinitiators with bridging structures and their synthesis and application. Background Technology

[0002] Photoinitiators are a crucial component of UV curing systems. Under UV irradiation, photoinitiators decompose into reactive intermediates (free radicals or cationic compounds). These intermediates initiate cross-linking of the functional groups of oligomers (resins) or reactive diluents (monomers) through free radical polymerization. Compared to traditional thermosetting, UV curing offers advantages such as shorter curing time, higher curing efficiency, and environmental friendliness, and is widely used in coatings, food packaging, pharmaceuticals, and 3D printing. Photoinitiators typically account for 3%-5% of UV curing formulations, playing a vital role in the speed and quality of curing and influencing the surface finish, adhesion, and hardness of the cured film. Photoinitiators can be classified into free radical photoinitiators and cationic photoinitiators, depending on the reactive intermediates produced under UV irradiation. Among the most commonly used photoinitiators, benzophenone (BP) has advantages such as simple synthesis, low cost, and good solubility. However, benzophenone has inherent limitations, such as short UV absorption, small molecule migration during the photoreaction process, off-odor during curing, yellowing of the film, and long curing time. These problems have spurred the rapid development of novel photoinitiators. In recent years, more efforts have been devoted to developing new photoinitiators with a wider light absorption range and addressing the aforementioned challenges. This invention develops a novel hybrid photoinitiator based on a benzotriazole-diazonaphthoquinone backbone. This cationic-radical hybrid photoinitiator exhibits good initiation efficiency and excellent photocuring properties.

[0003] In summary, developing novel photoinitiators with extended conjugation, strong light absorption, high molecular weight, and good solubility is a prerequisite for achieving highly efficient photoinitiators. This paper synthesizes a series of novel benzotriazole-diazonaphthoquinone derivatives with functional groups through the esterification reaction of benzotriazole with sulfonyl chloride on diazonaquinone. Using these derivatives as photoinitiators, coatings cured under ultraviolet light exhibit faster curing speed and deeper curing depth, thereby improving the performance of the cured film. Summary of the Invention

[0004] The purpose of this invention is to synthesize a benzotriazole-diazonaphthoquinone type photoinitiator with a bridging structure through a simple method, so that its UV-Vis absorption peak is red-shifted to 360 nm, its half-maximum width is about 60 nm, and it extends to around 450 nm, which fully meets the requirements of near-ultraviolet absorption. The photosensitive system composed of this near-ultraviolet photoinitiator can initiate monomer polymerization under near-ultraviolet light irradiation or be used as a photocurable material.

[0005] The benzotriazole-diazonaphthoquinone type photoinitiator with a bridging structure involved in this invention has the following general chemical structural formula:

[0006] In the structural formula, R represents hydrogen, hydroxyl group and diazonoquinone ester group, where at least one of the substituents of R is a diazonoquinone ester group.

[0007] The synthesis method of the above-mentioned benzotriazole-diazonaphthoquinone type photoinitiator with bridging structure is as follows: The reaction equation is: .

[0008] In the structural formula, D represents: hydrogen group, hydroxyl group (where D has at least one substituent that is hydroxyl); R represents: hydrogen, hydroxyl group, diazonaphthoquinone ester group (where R has at least one substituent that is diazonaphthoquinone ester group). Specific steps: The molar ratio of compound a (diazonaphthoquinone sulfonyl chloride) and compound b (benzotriazole derivative) is 1:1-4; in some examples, it is 1:1, 1:1, 1:2, 1:3, or 1:4.

[0009] Compound a (diazonaphthoquinone sulfonyl chloride) and compound b (benzotriazole derivative) are dissolved in 1,4-dioxane and stirred until completely dissolved at 30-35°C. At the same time, a mixed solution of 1,4-dioxane containing 5-15% by mass of triethylamine is added dropwise at 30-35°C, preferably with a triethylamine mass concentration of 10%, to carry out the reaction.

[0010] In the examples, the reaction temperature was 30-40°C, the reaction time was 10-30 min, heating was stopped after the reaction was completed, and post-processing was performed.

[0011] The post-processing of this invention includes neutralizing excess triethylamine with acid, then adding the reaction solution containing 1,4-dioxane to water to precipitate crystals, filtering the solution until the pH of the filtrate is 6.0-7.0, collecting the filter cake, drying it, and obtaining the target compound.

[0012] In the embodiments, the addition of acid to neutralize excess triethylamine involves adding 30-31% hydrochloric acid.

[0013] The advantages and beneficial effects of this invention are as follows: (1) The synthesis method and separation of the benzotriazole-diazonaphthoquinone type photoinitiator with bridging structure of the present invention are simple and the raw materials are readily available.

[0014] (2) The benzotriazole-diazonaphthoquinone type photoinitiator of the present invention with a bridging structure red-shifts the peak of its ultraviolet-visible absorption to 360 nm, with a half-peak width of about 60 nm and an extension to around 450 nm, which fully meets the requirements of near-ultraviolet absorption. The photoinitiator together forms a photosensitive system to initiate monomer polymerization under near-ultraviolet light irradiation or as a photocurable material.

[0015] (3) Benzotriazole compounds have special photochemical properties and can absorb in the near-ultraviolet region; diazonoquinone compounds can be used as photosensitive compounds; the photoinitiator synthesized from both has excellent photocuring properties. Attached Figure Description

[0016] Figure 1 shows a 1×10 in Embodiment 1 of the present invention. -6 The relationship between absorbance and wavelength of compound c dissolved in acetonitrile at a concentration of mol / L. Detailed Implementation

[0017] The features and advantages of the present invention can be further understood through the following detailed description in conjunction with the accompanying drawings. The provided embodiments are merely illustrative of the method of the present invention and do not limit the rest of the content disclosed herein in any way.

[0018] The present invention will be further described below with reference to embodiments and accompanying drawings: Example 1 Synthesis of compound c1

[0019] Where R has at least one diazononaphthoquinone sulfonyl group, that is, the result is a mixture in which there are compounds with 1 R being a diazononaphthoquinone sulfonyl group and compounds with 2 R being diazononaphthoquinone sulfonyl groups.

[0020] Weigh compound a (diazonaphthoquinone sulfonyl chloride) (3.7 mmol, 1.0 g) and compound b (benzotriazole derivative) (3.7 mmol, 0.84 g) into a three-necked ground glass flask. Add 30 ml of 1,4-dioxane to the flask, add a magnetic stir bar, and heat in a water bath until the system temperature reaches 30 °C. After the solid raw materials are completely dissolved, slowly add a mixture of triethylamine (5.5 mmol, 0.56 g) and 5 ml of 1,4-dioxane solution dropwise at 30 °C, maintaining the temperature between 30-31 °C. The addition should be completed within 30 min. After the addition was complete, the temperature was raised to 35 °C, and the reaction was allowed to proceed for 30 min. Heating was then stopped, and 10 ml of 1,4-dioxane solution was added during the cooling process. Once the system cooled to 30 °C, 30% hydrochloric acid was added (slowly). During the addition, pale yellow solid crystals were observed to precipitate. The mixture was stirred at room temperature for 10 min, filtered, and the filter cake was washed with 10 ml of 1,4-dioxane solvent. The filtrate was collected. The filtrate was added to a mixture of 200 ml of ultrapure water and 10 ml of 30% hydrochloric acid. During the addition, a large amount of yellow solid precipitated. After the filtrate was completely added, the mixture was stirred at room temperature for 10 min, filtered, and the filter cake was washed with ultrapure water until the pH of the final filtrate was 6-7. The mixture was then dried at 40 °C to obtain the target compound in 99% yield.

[0021] The compound from Example 1 was reduced from 1 × 10 -6 A concentration of mol / L was added to acetonitrile, and the absorption wavelength was analyzed. The results were obtained. Figure 1 Figure 1 shows a 1×10⁻⁶ ohmmeter in Embodiment 1 of the present invention. -6 The absorbance and wavelength relationship curve of compound c dissolved in acetonitrile at mol / L is shown. It can be seen that the photoinitiator of the present invention has a UV-Vis absorption peak red-shifted to 360 nm, a half-maximum width of about 60 nm, and extends to around 450 nm, which fully meets the requirements of near-ultraviolet absorption. This photoinitiator, together with other photosensitive systems, can initiate monomer polymerization under near-ultraviolet light irradiation or be used as a photocurable material.

[0022] Example 2 Synthesis of compound c

[0023] Where R has at least one diazononaphthoquinone sulfonyl group, that is, the result is a mixture in which there are compounds with 1 R being a diazononaphthoquinone sulfonyl group and compounds with 2 R being diazononaphthoquinone sulfonyl groups.

[0024] Weigh compound a (diazonaphthoquinone sulfonyl chloride) (3.7 mmol, 1.0 g) and compound b (benzotriazole derivative) (3.7 mmol, 0.84 g) into a three-necked ground glass flask. Add 30 ml of 1,4-dioxane to the flask, add a magnetic stir bar, and heat in a water bath until the system temperature reaches 30 °C. After the solid raw materials are completely dissolved, slowly add a mixture of triethylamine (5.5 mmol, 0.56 g) and 5 ml of 1,4-dioxane solution dropwise at 30 °C, maintaining the temperature between 30-31 °C. The addition should be completed within 30 min. After the addition was complete, the temperature was raised to 35 °C, and the reaction was allowed to proceed for 30 min. Heating was then stopped, and during the cooling process, 10 ml of 1,4-dioxane solution was added. Once the system cooled to 30 °C, 30% hydrochloric acid was added (slowly). During the addition, pale yellow solid crystals were observed to precipitate. The mixture was stirred at room temperature for 10 min, filtered, and the filter cake was washed with 10 ml of 1,4-dioxane solvent. The filtrate was collected. The filtrate was added to a mixture of 200 ml ultrapure water and 10 ml of 30% hydrochloric acid. During the addition, a large amount of yellow solid precipitated. After the filtrate was completely added, the mixture was stirred at room temperature for 10 min, filtered, and the filter cake was washed with ultrapure water until the final filtrate pH was 6-7. The filtrate was then dried at 40 °C to obtain the target compound in 98% yield.

[0025] Example 3 Synthesis of compound c

[0026] Where R has at least one diazonoquinone sulfonyl group, that is, the result is a mixture in which the mixture contains compounds with 1 R being a diazonoquinone sulfonyl group, compounds with 2 R being a diazonoquinone sulfonyl group, and compounds with 3 R being a diazonoquinone sulfonyl group.

[0027] Weigh compound a (diazonaphthoquinone sulfonyl chloride) (3.7 mmol, 1.0 g) and compound b (benzotriazole derivative) (3.7 mmol, 0.90 g) into a three-necked ground glass flask. Add 30 ml of 1,4-dioxane to the flask, add a magnetic stir bar, and heat in a water bath until the system temperature reaches 30 °C. After the solid raw materials are completely dissolved, slowly add a mixture of triethylamine (5.5 mmol, 0.56 g) and 5 ml of 1,4-dioxane solution dropwise at 30 °C, maintaining the temperature between 30-31 °C. The addition should be completed within 30 min. After the addition was complete, the temperature was raised to 35 °C, and the reaction was allowed to proceed for 30 min. Heating was then stopped, and 10 ml of 1,4-dioxane solution was added during the cooling process. Once the system cooled to 30 °C, 30% hydrochloric acid was added (slowly). During the addition, pale yellow solid crystals were observed to precipitate. The mixture was stirred at room temperature for 10 min, filtered, and the filter cake was washed with 10 ml of 1,4-dioxane solvent. The filtrate was collected. The filtrate was added to a mixture of 200 ml of ultrapure water and 10 ml of 30% hydrochloric acid. During the addition, a large amount of yellow solid precipitated. After the filtrate was completely added, the mixture was stirred at room temperature for 10 min, filtered, and the filter cake was washed with ultrapure water until the pH of the final filtrate was 6-7. The mixture was then dried at 40 °C to obtain the target compound in 99% yield.

[0028] Example 4 Synthesis of compound c

[0029] Where R has at least one diazononaphthoquinone sulfonyl group, that is, the result is a mixture in which the mixture contains compounds with 1 R being a diazononaphthoquinone sulfonyl group, compounds with 2 R being a diazononaphthoquinone sulfonyl group, compounds with 3 R being a diazononaphthoquinone sulfonyl group, and compounds with 4 R being a diazononaphthoquinone sulfonyl group.

[0030] Weigh compound a (diazonaphthoquinone sulfonyl chloride) (3.7 mmol, 1.0 g) and compound b (benzotriazole derivative) (3.7 mmol, 0.96 g) into a three-necked ground glass flask. Add 30 ml of 1,4-dioxane to the flask, add a magnetic stir bar, and heat in a water bath until the system temperature reaches 30 °C. After the solid raw materials are completely dissolved, slowly add a mixture of triethylamine (5.5 mmol, 0.56 g) and 5 ml of 1,4-dioxane solution dropwise at 30 °C, maintaining the temperature between 30-31 °C. The addition should be completed within 30 min. After the addition was complete, the temperature was raised to 35 °C, and the reaction was allowed to proceed for 30 min. Heating was then stopped, and 10 ml of 1,4-dioxane solution was added during the cooling process. Once the system cooled to 30 °C, 30% hydrochloric acid was added (slowly). During the addition, pale yellow solid crystals were observed to precipitate. The mixture was stirred at room temperature for 10 min, filtered, and the filter cake was washed with 10 ml of 1,4-dioxane solvent. The filtrate was collected. The filtrate was added to a mixture of 200 ml of ultrapure water and 10 ml of 30% hydrochloric acid. During the addition, a large amount of yellow solid precipitated. After the filtrate was completely added, the mixture was stirred at room temperature for 10 min, filtered, and the filter cake was washed with ultrapure water until the pH of the final filtrate was 6-7. The mixture was then dried at 40 °C to obtain the target compound c, with a yield of 99%.

[0031] Example 5 Synthesis of compound c

[0032] Where R has at least one diazononaphthoquinone sulfonyl group, the resulting mixture contains compounds with 1 R being a diazononaphthoquinone sulfonyl group, compounds with 2 R being a diazononaphthoquinone sulfonyl group, compounds with 3 R being a diazononaphthoquinone sulfonyl group, compounds with 4 R being a diazononaphthoquinone sulfonyl group, and compounds with 5 R being a diazononaphthoquinone sulfonyl group.

[0033] Weigh compound a (diazonaphthoquinone sulfonyl chloride) (3.7 mmol, 1.0 g) and compound b (benzotriazole derivative) (3.7 mmol, 1.02 g) into a three-necked ground glass flask. Add 30 ml of 1,4-dioxane to the flask, add a magnetic stir bar, and heat in a water bath until the system temperature reaches 30 °C. After the solid raw materials are completely dissolved, slowly add a mixture of triethylamine (5.5 mmol, 0.56 g) and 5 ml of 1,4-dioxane solution dropwise at 30 °C, maintaining the temperature between 30-31 °C. The addition should be completed within 30 min. After the addition was complete, the temperature was raised to 35 °C, and the reaction was allowed to proceed for 30 min. Heating was then stopped, and 10 ml of 1,4-dioxane solution was added during the cooling process. Once the system cooled to 30 °C, 30% hydrochloric acid was added (slowly). During the addition, pale yellow solid crystals were observed to precipitate. The mixture was stirred at room temperature for 10 min, filtered, and the filter cake was washed with 10 ml of 1,4-dioxane solvent. The filtrate was collected. The filtrate was added to a mixture of 200 ml of ultrapure water and 10 ml of 30% hydrochloric acid. During the addition, a large amount of yellow solid precipitated. After the filtrate was completely added, the mixture was stirred at room temperature for 10 min, filtered, and the filter cake was washed with ultrapure water until the pH of the final filtrate was 6-7. The mixture was then dried at 40 °C to obtain the target compound c, with a yield of 99%.

[0034] Example 6 The photoinitiator benzotriazole-diazonaphthoquinone prepared in the examples and commercially available TPO (2,4,6-trimethylbenzoyl diphenylphosphine oxide) were added at a ratio of 5% (mass ratio) to the acrylic epoxy resin sample system (formulation: 35% bisphenol A epoxy acrylate; 8% amino acrylate; 25% propoxylated glycerol triacrylate; 24% hexanediol diacrylate; 0.5% polysiloxane acrylate; 3.5% ethoxypentaerythritol tetraacrylate). The mixture was uniformly coated on a cleaned and dried copper-clad board and irradiated with a 1 kW high-pressure mercury lamp to allow the liquid film to polymerize and solidify. The measurement results are shown in Table 1 below.

[0035] Table 1. Photocuring effect of the photoinitiator of the present invention on acrylic epoxy resin. .

Claims

1. A class of benzotriazole-diazonaphthoquinone type photoinitiators with a bridging structure, whose general chemical formula is as follows: In the structural formula, R represents hydrogen, hydroxyl group and diazonoquinone ester group, where at least one of the substituents of R is a diazonoquinone ester group.

2. The method for synthesizing the benzotriazole-diazonaphthoquinone type photoinitiator with a bridging structure as described in claim 1, characterized by the following: In the reaction formula, R represents hydrogen, diazonaphthoquinone ester group; TEA represents triethylamine. Diazonoquinone sulfonyl chloride compound a and benzotriazole derivative compound b were dissolved in 1,4-dioxane solvent and stirred until completely dissolved to obtain a reaction solution. A mixed solution of 1,4-dioxane containing triethylamine was added dropwise to the reaction solution to carry out the reaction. After the reaction was completed, hydrochloric acid was added dropwise to neutralize the excess triethylamine. The reaction solution was then added to water to crystallize. The crystals were obtained by filtration and washing to obtain a benzotriazole-diazonaphthoquinone type photoinitiator.

3. The synthesis method according to claim 2, characterized in that, The mass concentration of the 1,4-dioxane mixed solution containing triethylamine is 5-15%, preferably 10%.

4. The synthesis method according to claim 2, characterized in that, The reaction temperature is 30-40℃, and the reaction time is 10-30 min.

5. The application of the benzotriazole-diazonaphthoquinone type photoinitiator with a bridging structure as described in claim 1 in initiating monomer polymerization under near-ultraviolet light irradiation, wherein the monomer comprises acrylic epoxy resin.

6. A photocurable material, characterized in that, Includes the benzotriazole-diazonaphthoquinone type photoinitiator with a bridging structure as described in claim 1.

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