Disubstituted halogenated azaanthrone visible light initiator, preparation method and application of disubstituted halogenated azaanthrone visible light initiator in acrylate photopolymerization system

Abstract

The invention discloses a disubstituted halogenated azaanthrone visible light initiator, a preparation method and application of the disubstituted halogenated azaanthrone visible light initiator in an acrylate photopolymerization system. The method comprises the following steps: dissolving a 2, 4-disubstituted halogenated azacyclo-anthrone compound in an organic solvent under the protection of inert gas, adding excessive alkali, slowly dropwise adding excessive organic solution of an acyl chloride compound in an ice-water bath, reacting at room temperature, detecting that the reaction is complete by TLC (Thin Layer Chromatography), stopping the reaction, performing suction filtration, concentrating filtrate, and drying to obtain the 2, 4-disubstituted halogenated azacyclo-anthrone compound. And purifying to obtain the novel disubstituted halogenated azacyclo-anthrone high-efficiency visible light initiator. The novel disubstituted halogenated azacyclo-anthrone high-efficiency visible light initiator not only shows better solubility in an organic solvent and resin, but also shows higher polymerization efficiency in a photocuring system, so that the application range of the novel disubstituted halogenated azacyclo-anthrone high-efficiency visible light initiator in a free radical photocuring system is widened.

Description

Technical Field

[0001] This invention relates to a method for preparing a class of highly efficient visible light initiators of disubstituted halothanethones and their application in acrylate photopolymerization systems, belonging to the field of free radical photoinitiators. Background Technology

[0002] Photopolymerization technology, as an environmentally friendly green process, has been widely applied in many key fields such as coatings, inks, electronic communications, photoresists, dental restorative materials, and additive manufacturing (3D printing). Given the significant advantages of visible light curing technology and its supporting LED light sources in terms of light source stability, environmental compatibility, and operational safety, the development of novel high-efficiency visible light initiators (VLPIs) has important research value and industrialization significance. As the core functional component of the visible light curing system, the performance of VLPIs directly determines the curing rate and final conversion rate (degree of curing) of the photosensitive material.

[0003] N-xanthones are a typical class of carbonyl photosensitive compounds. These molecules typically exhibit low triplet energy levels (T) and high intersystem crossing quantum yields (ΦISC). Their characteristic absorption peaks in the UV-Vis absorption spectra are located in the 370-385 nm region, and the absorption band can extend to approximately 420 nm. These excellent photophysical properties make it easy to control the absorption spectrum through molecular design, thereby achieving efficient matching with the emission spectrum of target light sources (especially visible light LEDs), demonstrating great potential for application development.

[0004] N-Xanthones are classic Type II photoinitiators, whose mechanism of action relies on the extraction of hydrogen from coexisting hydrogen donors (such as tertiary amines or thiols) to generate active free radicals. However, traditional small-molecule tertiary amine co-initiators, due to their strong migration, easily lead to problems such as odor, yellowing, and even biotoxicity in cured materials. To overcome this technical bottleneck, an effective strategy is to directly introduce groups such as ether bonds (-O-) or thioether bonds (-S-) into the molecular backbone of N-Xanthones, constructing a multifunctional single-component photoinitiator system that integrates photosensitive units and hydrogen donor groups. This molecular design not only endows the initiator with highly efficient visible light response characteristics but also significantly improves its stability in polymer matrices (such as thin films). Therefore, functionalized derivatives based on the N-Xanthones backbone have become an important research direction for high-efficiency VL PIs and have shown broad application prospects in radical photopolymerization and cationic photopolymerization technologies. Summary of the Invention

[0005] This invention designs a novel class of disubstituted halo-alumino heterocyclic anthrone visible light initiators by combining them with functional acyl groups, using disubstituted halo-alumino heterocyclic anthrones as the basic conjugated backbone structure. These visible light initiators exhibit excellent light absorption performance in the ultraviolet-visible region and demonstrate highly efficient initiation effects on acrylate-containing free radical photopolymerization systems.

[0006] The objective of this invention is achieved through the following solution: A novel class of highly efficient visible light initiators, consisting of disubstituted halo-nitrogen heterocyclic anthrones, has the following specific structural formula.

[0007]

[0008] in: R 1 It is chlorine or bromine; R 2 It is oxygen or sulfur; R 3 Includes one of the following groups: ; R 4 It is oxygen or sulfur; R 5 It is nitrogen; R 6 It can be methyl or ethyl.

[0009] The above-mentioned method for preparing novel disubstituted halo-acid heterocyclic anthrone high-efficiency visible light initiators uses 2,4-disubstituted halo-acid heterocyclic anthrone compounds and acyl chloride compounds as raw materials and is synthesized using the synthetic route shown in the following formula.

[0010]

[0011] The preparation method includes the following steps: Under inert gas protection, 2,4-disubstituted haloazonic heterocyclic anthrone compounds were dissolved in an organic solvent, and an excess of alkali was added. An excess organic solution of the acyl chloride compound was slowly added dropwise under an ice-water bath. The reaction was carried out at room temperature, and TLC analysis confirmed complete reaction. The reaction was then stopped. The mixture was filtered, the filtrate was concentrated, and purified to obtain a novel, highly efficient visible-light initiator of disubstituted haloazonic heterocyclic anthrone compounds.

[0012] The 2,4-disubstituted halo-azo-containing anthrone compounds mentioned above include, but are not limited to: .

[0013] Where R 1 It is chlorine or bromine, R 2 It is oxygen or sulfur; The sulfonyl chloride compound is: R 3 COCl, R 3Includes, but is not limited to, one of the following groups: ; Where R 4 For oxygen or sulfur; R 5 For nitrogen; R 6 It can be methyl or ethyl.

[0014] The solvents include, but are not limited to, ethanol, methanol, acetone, tetrahydrofuran, acetonitrile, N,N-dimethylformamide or N,N-dimethylacetamide; the bases include, but are not limited to, sodium hydroxide (NaOH), potassium hydroxide (KOH), pyridine, triethylamine ((C2H5)3N), piperidine or pyrrolidine.

[0015] In the preparation method described above, the reactions in each step are carried out at room temperature.

[0016] The novel bisubstituted halo-nitrogen heterocyclic anthrone-based high-efficiency visible light initiator can be applied to initiate the curing of acrylate-containing free radical photopolymerization systems of prepolymers.

[0017] The prepolymer contains acrylate polymer systems including PDDA, TPGDA, HDDA, DPGDA, NPGDA, and TEGDA systems.

[0018] These novel, bisubstituted halo-nitrogen heterocyclic anthrone-based high-efficiency visible light initiators not only exhibit better solubility in organic solvents and resins, but also demonstrate higher polymerization efficiency in photocuring systems, thus broadening their application range in free radical photocuring systems.

[0019] The advantages and beneficial effects of this invention are as follows: High photoinitiation efficiency. Photopolymerization kinetics studies of this invention show that the novel disubstituted halo-nitrogen heterocyclic anthrone-based high-efficiency visible light initiator can efficiently initiate free radical monomer polymerization under ultraviolet LED light irradiation. Attached Figure Description

[0020] Figure 1 The kinetic curve of HDDA initiated by 2,4-bis(acetoxy)-(N-chloro)azanthone prepared in Example 1. Detailed Implementation

[0021] 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.

[0022] Example 1. Visible light initiator Preparation 2.71 g (10 mmol) of 2,4-dihydroxy(N-chloro)azanthone, 2.50 g (25 mmol) of triethylamine, and 40 mL of anhydrous tetrahydrofuran were added to a 100 mL single-necked flask. The mixture was purged with argon gas and kept under argon protection. The mixture was stirred in an ice-water bath until completely dissolved. After stirring for 10 min in an ice-water bath, 5 mL of freshly distilled tetrahydrofuran and 0.20 g (25 mmol) of chloroacetyl were slowly added dropwise using a constant-pressure dropping funnel. The addition was completed over 10 min, and the mixture was stirred in an ice-water bath for 2 h. The reaction was monitored by TLC to ensure complete reaction. The reaction mixture was filtered, diluted with an appropriate amount of ethyl acetate, washed three times with water, and the organic phase was concentrated to obtain 3.28 g of the target compound 1.

[0023] Figure 1 The kinetic curves for inducing HDDA are presented. The change in absorption intensity of a characteristic peak under illumination was recorded using real-time infrared spectroscopy and a high-speed recorder. Using HDDA as the monomer, target compound 1 ([PI] = 2 × 10⁻⁶) at different concentrations was prepared. -5 A mol / g HDDA sample solution was dropped into the middle of a potassium bromide salt sheet to form a uniform liquid film. After irradiation with 405 nm LED ultraviolet light for 15 min, the change in the absorption peak area of ​​the carbon-carbon double bond was recorded using an infrared spectrometer, thus obtaining the conversion rate of the corresponding monomer. The results show that 4-di(acetoxy)-(N-chloro)azanthone can also successfully initiate the free radical polymerization of polyurethane acrylic resins. These photopolymerization experimental results demonstrate that 4-di(acetoxy)-(N-chloro)azanthone is an excellent visible light initiator.

[0024] Example 2. Visible light initiator Preparation 2.91 g (10 mmol) of 2,4-dimercapto(N-chloro)azanthone, 1.00 g (25 mmol) of sodium hydroxide, and 40 mL of anhydrous ethanol were added to a 100 mL single-necked flask. The mixture was purged with argon gas and kept under argon protection. The mixture was stirred in an ice-water bath until completely dissolved. After stirring for 10 min in an ice-water bath, 5 mL of anhydrous ethanol and 0.24 g (25 mmol) of chloropropionyl were slowly added dropwise over a constant-pressure dropping funnel over 10 min. The mixture was stirred in an ice-water bath for 2 h, and the reaction was monitored by TLC to confirm completion. The reaction mixture was filtered, diluted with an appropriate amount of ethyl acetate, washed three times with water, and the organic phase was concentrated to obtain 3.45 g of the target compound 2.

[0025] Kinetic application testing of acrylate-based TPGDA using compound 2: Real-time infrared spectroscopy combined with a high-speed recorder was used to record the change in absorption intensity of a characteristic peak under illumination. Using TPGDA as the polymerization monomer, target compound 2 ([PI] = 2 × 10⁻⁶) was added. -5A mol / g TPGDA sample solution was dropped into the middle of a potassium bromide salt plate to form a uniform liquid film. After irradiation with 405 nm LED ultraviolet light for 15 min, the change in the absorption peak area of ​​the carbon-carbon double bond was recorded by infrared spectroscopy. The conversion rate of the monomer TPGDA was detected to be 78%.

[0026] Example 3. Visible light initiator Preparation 2.91 g (10 mmol) of 2,4-dimercapto(N-chloro)azanthone, 2.0 g (25 mmol) of pyridine, and 40 mL of anhydrous acetone were added to a 100 mL single-necked flask. The mixture was purged with argon gas and kept under argon protection. The mixture was stirred in an ice-water bath until completely dissolved. After stirring for 10 min in an ice-water bath, 5 mL of anhydrous acetone and 0.33 g (25 mmol) of furan-2-formyl chloride were slowly added dropwise using a constant-pressure dropping funnel. The addition was completed over 10 min. The mixture was stirred in an ice-water bath for 2 h, and the reaction was monitored by TLC to confirm completion. The reaction mixture was filtered, diluted with an appropriate amount of ethyl acetate, washed three times with water, and the organic phase was concentrated to obtain 4.78 g of the target compound 3.

[0027] Kinetic application testing of acrylate DPGDA initiated by compound 3: Real-time infrared spectroscopy combined with a high-speed recorder was used to record the change in absorption intensity of a characteristic peak under illumination. DPGDA was used as the polymerization monomer, and target compound 3 ([PI] = 2 × 10⁻⁶) was added. -5 A mol / g DPGDA sample solution was dropped into the middle of a potassium bromide salt plate to form a uniform liquid film. After irradiation with 405 nm LED ultraviolet light for 15 min, the change in the absorption peak area of ​​the carbon-carbon double bond was recorded by infrared spectroscopy. The conversion rate of the monomer DPGDA was detected to be 83%.

[0028] Example 4. Visible light initiator Preparation 3.55 g (10 mmol) of 2,4-dihydroxy(N-bromo)azanthone, 2.1 g (25 mmol) of piperidine, and 40 mL of anhydrous acetonitrile were added to a 100 mL single-necked flask. The mixture was purged with argon gas and kept under argon protection. The mixture was stirred in an ice-water bath until completely dissolved. After stirring for 10 min in an ice-water bath, 5 mL of freshly distilled acetonitrile and 0.37 g (25 mmol) of thiophene-2-formyl chloride were slowly added dropwise using a constant-pressure dropping funnel. The addition was completed over 10 min, and the mixture was stirred in an ice-water bath for 2 h. The reaction was monitored by TLC to ensure complete reaction. The reaction mixture was filtered, diluted with an appropriate amount of ethyl acetate, washed three times with water, and the organic phase was concentrated to obtain 5.26 g of the target compound 4.

[0029] Kinetic application testing of compound 4-initiated NPGDA acrylate: Real-time infrared spectroscopy combined with a high-speed recorder was used to record the change in absorption intensity of a characteristic peak under illumination. Using NPGDA as the polymerization monomer, target compound 4 ([PI] = 2 × 10⁻⁶) was added. -5 A sample solution of NPGDA (mol / g) was added dropwise to the center of a potassium bromide salt plate to form a uniform liquid film. After irradiation with 405 nm LED ultraviolet light for 15 min, the change in the absorption peak area of ​​the carbon-carbon double bond was recorded by infrared spectroscopy. The conversion rate of the monomer NPGDA was found to be 73%.

[0030] Example 5. Visible light initiator Preparation 3.41 g (10 mmol) of 2,4-dihydroxy(N-bromo)azanthone, 1.8 g (25 mmol) of tetrahydropyrrole, and 40 mL of N,N-dimethylformamide were added to a 100 mL single-necked flask. The mixture was purged with argon gas and kept under argon protection. The mixture was stirred in an ice-water bath until completely dissolved. After stirring for 10 min in an ice-water bath, 5 mL of N,N-dimethylformamide and 0.36 g (25 mmol) of N-methylpyrrole-2-formyl chloride were slowly added dropwise using a constant-pressure dropping funnel. The addition was completed over 10 min. The mixture was stirred in an ice-water bath for 2 h, and the reaction was monitored by TLC to confirm completion. The reaction mixture was filtered, diluted with an appropriate amount of ethyl acetate, washed three times with water, and the organic phase was concentrated to obtain 5.38 g of the target compound 5.

[0031] Kinetic application testing of acrylate-based TEGDA initiated by compound 5: Real-time infrared spectroscopy combined with a high-speed recorder was used to record the change in absorption intensity of a characteristic peak under illumination. Using TEGDA as the polymerization monomer, target compound 5 ([PI] = 2 × 10⁻⁶) was added. -5 A mol / g TEGDA sample solution was dropped into the middle of a potassium bromide salt plate to form a uniform liquid film. After irradiation with 405 nm LED ultraviolet light for 15 min, the change in the absorption peak area of ​​the carbon-carbon double bond was recorded by infrared spectroscopy. The conversion rate of the monomer TEGDA was detected to be 82%.

[0032] The kinetic applications of compounds 1-5 prepared above in initiating acrylate-based PDDA and vinyl-based ST were tested: Real-time infrared spectroscopy combined with a high-speed recorder was used to record the change in absorption intensity of a characteristic peak under illumination. Using PDDA or ST as the polymerization monomer, target compound 1-5 ([PI] = 2 × 10⁻⁶) was added. -5A mol / g PDDA or ST sample solution was added dropwise to the center of a potassium bromide salt plate to form a uniform liquid film. After irradiation with 405 nm LED UV light for 15 min, the changes in the carbon-carbon double bond absorption peak area were recorded using an infrared spectrometer. The conversion rates of PDDA and ST monomers are as follows:

Claims

1. A class of disubstituted halogenated azaxanthone visible light initiators characterized by, The visible light initiator has halogenated azaxanthone as a main skeleton, and has the following structural formula: ; R 1 is halogen; R 2 is oxygen or sulfur; R 3 comprises one of the following groups: .

2. The disubstituted halogenated azaxanthone visible light initiator according to claim 1, characterized in that: R 4 is oxygen or sulfur; R 5 is nitrogen; R 6 is methyl or ethyl.

3. A process for the preparation of a disubstituted halogenated azaxanthone visible light initiator according to any one of claims 1-2, characterized in that, The preparation method comprises the following steps: Under the protection of inert gas, the 2,4-disubstituted halogenated azaxanthone compound is dissolved in an organic solvent, an excessive amount of base is added, an excessive amount of acyl chloride compound is slowly added dropwise under an ice water bath, reaction is carried out at room temperature, the reaction is stopped after TLC detection, the reaction is stopped, filtration is carried out, the filtrate is concentrated, and the double-substituted halogenated azaxanthone visible light initiator is obtained after purification.

4. The method for preparing the disubstituted haloazonanone visible light initiator according to claim 3, characterized in that, The 2,4-disubstituted halogenated azaxanthone compound comprises the following compounds: , R 1 is halogen; R 2 is oxygen or sulfur.

5. The method for preparing the disubstituted haloazonanone visible light initiator according to claim 4, characterized in that, The acyl chloride compound is R 3 C(O)Cl, R 3 comprises one of the groups shown below: ; R 4 is oxygen or sulfur; R 5 is nitrogen; R 6 is methyl or ethyl.

6. The method for preparing the disubstituted haloazonanone visible light initiator according to claim 3, characterized in that, The organic solvent comprises any one of ethanol, methanol, acetone, tetrahydrofuran, acetonitrile, N, N-dimethylformamide or N, N-dimethylacetamide.

7. The method for preparing the disubstituted haloazonanone visible light initiator according to claim 3, characterized in that, The base comprises any one of sodium hydroxide, potassium hydroxide, pyridine, triethylamine, piperidine or tetrahydropyrrole.

8. Application of the double-substituted halogenated azaxanthone visible light initiator in claim 1-2 or the double-substituted halogenated azaxanthone visible light initiator prepared by the method in claim 3-7 to a photoinitiated prepolymer containing acrylate radical photopolymerization system.

9. Use according to claim 8, characterized in that, The prepolymer containing acrylate polymerization system comprises a PDDA, TPGDA, HDDA, DPGDA, NPGDA and TEGDA system.

10. A photoacid generator characterized in that, The double-substituted halogenated azaxanthone visible light initiator in claim 1-2 or the double-substituted halogenated azaxanthone visible light initiator prepared by the method in claim 3-7.

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