Novel disubstituted oxygen / thioxanthone efficient visible light initiator, preparation method and application of novel disubstituted oxygen / thioxanthone efficient visible light initiator in thiol-olefin photopolymerization system

Abstract

The invention discloses a disubstituted oxygen / thioxanthone efficient visible light initiator and a preparation method of the disubstituted oxygen / thioxanthone efficient visible light initiator. Meanwhile, the invention discloses a preparation method of the novel disubstituted oxygen / thioxanthone efficient visible light initiator. The prepared disubstituted oxygen / thioxanthone efficient visible light initiator is used as a photoacid generator molecule to be applied to a photoinitiator of a prepolymer containing mercaptan-olefin free radical photopolymerization system. The structural formula of the disubstituted oxygen / thioxanthone efficient visible light initiator is shown in the specification.

Description

Technical Field

[0001] This invention relates to a method for preparing a novel class of highly efficient visible light initiators of the disubstituted oxygen / thioxanthrone type and their application in thiol-olefin photopolymerization systems, belonging to the field of free radical photoinitiators. Background Technology

[0002] Photoreaction is a rapid chemical process triggered by light, playing a crucial role in polymer synthesis and cross-linking curing. Photopolymerization technology is a green and environmentally friendly technology with advantages such as high polymerization rate, spatiotemporal controllability, good wavelength selectivity, mild polymerization conditions, and environmental friendliness. It is widely used in traditional and emerging fields such as surface coating, photosensitive adhesives, tissue repair, and 3D printing. Photoinitiators are one of the key components in photopolymerization and photocuring formulations. Based on the wavelength of the light source absorbed by the photoinitiator, they can be divided into ultraviolet photoinitiators and visible light photoinitiators. Considering the safety and environmental issues, high energy consumption, and harm to human health of ultraviolet radiation sources, the use of ultraviolet lamps in industrial production will be gradually reduced or prohibited. Therefore, safer, lighter, and longer-lasting light sources—visible light LEDs—are being used to replace ultraviolet radiation sources. LED is short for light-emitting diode. Visible light LEDs have strong light transmission capabilities and good monochromatic bandwidth behavior, leading to widespread attention and application of visible light curing technology.

[0003] Heterocyclic anthrones and their derivatives are a class of heterocyclic anthrone compounds containing heteroatoms. Due to their low triplet energy and high quantum yield, they exhibit good absorption in the 360-420 nm wavelength range, making it easy to match the emission spectrum of light sources through absorption spectrum modulation, thus possessing enormous development and application potential. The heteroatoms in heterocyclic anthrones all contain lone pairs of electrons, resulting in an electron-rich molecule that can act as a typical electron donor unit in push-pull structures. Furthermore, in the anthracene ring conformation of heterocyclic anthrones, the benzene rings on both sides of the central heterocycle are almost in the same plane, allowing the lone pairs of electrons from the heteroatoms to form conjugated π bonds for delocalization, which is beneficial for intramolecular charge transfer effects. They can also form π bridges connecting electron donors and acceptors, resulting in long-absorption push-pull dyes. Therefore, heterocyclic anthrones can be modified to act as the electron-donating D portion in push-pull dyes or as π bonds in push-pull dyes, yielding long-wavelength, strongly absorbing visible light initiators with different structures. As a class of highly efficient photoinitiators, oxygen / thioxanthrone derivatives are widely used in free radical and cationic photopolymerization technologies. Summary of the Invention

[0004] This invention designs a novel class of disubstituted oxygen / thioheterocyclic anthrone visible light initiators by combining them with functional acyl groups, using disubstituted oxygen / thioheterocyclic 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 thiol-olefin radical photopolymerization systems.

[0005] The objective of this invention is achieved through the following solution: A novel class of highly efficient visible light initiators, derived from disubstituted oxygen / thioheterocyclic anthrones, has the following specific structural formula.

[0006]

[0007] in: R 1 and R 2 It is oxygen or sulfur; R 3 Includes, but is not limited to, one of the following groups: ; R 4 It is oxygen or sulfur; R 5 It is nitrogen or phosphorus; R 6 It is methyl or ethyl; The above-mentioned novel disubstituted oxygen / thioheterocyclic anthrone high-efficiency visible light initiator is prepared by using 2,4-disubstituted oxygen / thioheterocyclic anthrone compounds and acyl chloride compounds as raw materials, and synthesizing them using the synthetic route shown in the following formula.

[0008] ; The preparation method includes the following steps: Under inert gas protection, 2,4-disubstituted oxygen / thiocyclic 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 heterocyclic anthrone compounds.

[0009] The 2,4-disubstituted oxy / thioheterocyclic anthrone compounds mentioned include, but are not limited to: .

[0010] Where R 1 and R 2 It is oxygen or sulfur; The sulfonyl chloride compound is: R 3 COCl, R 3 Includes, but is not limited to, one of the following groups: ; Where R 4 For oxygen or sulfur; R 5 For nitrogen or phosphorus; R 6 It can be methyl or ethyl.

[0011] 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.

[0012] In the preparation method described above, the reactions in each step are carried out at room temperature.

[0013] The novel disubstituted oxygen / thioheterocyclic anthrone high-efficiency visible light initiator is applied to the initiation and curing of prepolymers containing thiol-olefin free radical photopolymerization systems.

[0014] In some preferred embodiments, the prepolymer contains thiol-olefin polymerization systems in which thiol groups include TMPMP and PETMP; and vinyl groups include HPMA and ST. Further preferred are the prepolymer containing thiol-olefin polymerization systems, where the thiol groups include a mixture of thiol-based TMPMP and vinyl-based HPMA, and a mixture of thiol-based PETMP and vinyl-based ST.

[0015] In this field, TMPMP is a typical thiol polymerizing monomer, and HPMA is a typical vinyl polymerizing monomer. The novel disubstituted oxygen / thioheterocyclic anthrone compounds obtained in this application can copolymerize the thiol groups in thiol polymerizing monomers with the double bonds in vinyl polymerizing monomers. This also demonstrates that the novel disubstituted oxygen / thioheterocyclic anthrone compounds obtained in this application can initiate the curing of prepolymers containing thiol-olefin radical photopolymerization systems.

[0016] These novel, bisubstituted oxygen / thioheterocyclic 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.

[0017] 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 oxygen / thioheterocyclic anthrone-based high-efficiency visible-light photoinitiator can efficiently initiate free radical monomer polymerization under ultraviolet LED light irradiation. In a preferred embodiment, the disubstituted oxygen / thioheterocyclic anthrone-based high-efficiency visible-light photoinitiator achieves a thiol group conversion rate of ≥55% and an olefin double bond conversion rate of ≥60% in the polymerization monomers of a mixed system of thiol and vinyl groups; more preferably, a thiol group conversion rate of ≥70% and an olefin double bond conversion rate of ≥80%; further preferably, a thiol group conversion rate of ≥75% and an olefin double bond conversion rate of ≥80%; further preferably, a thiol group conversion rate of ≥70% and an olefin double bond conversion rate of ≥85%; further preferably, a thiol group conversion rate of ≥85% and an olefin double bond conversion rate of ≥85%; and further preferably, a thiol group conversion rate of ≥87% and an olefin double bond conversion rate of ≥90%. Attached Figure Description

[0018] Figure 1 The FT-IR spectrum of 2,4-bis(acetoxy)thioxanthonone prepared in Example 1.

[0019] Figure 2 The 2,4-bis(acetoxy)thioxanthonone prepared in Example 1 1 H-NMR spectrum.

[0020] Figure 3 The 2,4-bis(acetoxy)thioxanthonone prepared in Example 1 13 C-NMR spectrum.

[0021] Figure 4 The UV-vis spectrum of 2,4-bis(acetoxy)thionone prepared in Example 1.

[0022] Figure 5 The kinetic curves are for the 2,4-bis(acetoxy)thioxanthraquinone-initiated TMPMP and HPMA mixed system prepared in Example 1. Detailed Implementation

[0023] 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.

[0024] Example 1. Visible light initiator Preparation 2.44 g (10 mmol) of 2,4-dihydroxythioxanthrone, 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. 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 g of the target compound 1.

[0025] Figures 1-3 The provided FT-IR, 1 H and 13 C10 NMR provided evidence for the structure of target compound 1.

[0026] Appendix Figure 1 The FT-IR spectra appear at 2970 and 2921 cm⁻¹. -1 The absorption peak can be attributed to the characteristic absorption peak of the CH stretching vibration on the benzene ring skeleton in its molecular structure; 1721 cm⁻¹ -1 and 1635 cm -1 The absorption peaks at 1601 and 1437 cm⁻¹ can be attributed to the stretching vibrations of the ester carbonyl group of the acetate ester and the ketone carbonyl group of the thioxanthone in its molecular structure; -1 The characteristic absorption peak for the C=C stretching vibration of the anthracene ring skeleton is located at 1268 cm⁻¹. -1 The peak at this location represents the characteristic peak of the COC stretching vibration of the acetate group.

[0027] Depend on Figure 2 As can be seen, the proton peaks of the benzene ring skeleton near the acetoxy group are at chemical shifts of 8.2 and 7.4 ppm, the proton peaks of the benzene ring skeleton on the thioxanthone are in the range of 7.4-7.7 ppm, and the proton peaks of the methyl group on the disubstituted acetoxy group are at 2.5 and 2.4 ppm.

[0028] Figure 3 The data shows that the chemical shift at 173.9 ppm is the C=O carbon peak in the thioxanthone structure, the peaks at 163.2 and 164.2 ppm are the O=C carbon peaks in the disubstituted acetoxy group, the peaks at 143.7 and 141.2 ppm are the resonance absorption peaks of the two C atoms bonded to the adjacent ether bond in the thioxanthone structure, and the peaks at 16.2 and 16.1 ppm are the methyl absorption peaks in the disubstituted acetoxy group. These results indicate that the target compound 1 has been successfully prepared.

[0029] from Figure 4The UV-vis spectrum shows that the maximum absorption wavelength of target compound 1 is located at 405 nm, which is in the visible light region, and its effective absorption range covers 275-450 nm.

[0030] Appendix Figure 5 The kinetic curves for initiating the TMPMP and HPMA mixed system 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 the TMPMP and HPMA mixed system as the polymerization monomers, different concentrations of target compound 1 ([PI] = 2 × 10⁻⁶) were prepared. -5 A sample solution of (mol / g) / (TMPMP+HPMA) was dropped onto the center of a potassium bromide salt sheet to form a uniform liquid film. After 15 min of LED UV irradiation, the changes in the absorption peak areas of carbon-carbon double bonds and thiol groups were recorded using an infrared spectrometer to obtain the conversion rate of the corresponding monomers. The results show that 2,4-di(acetoxy)thioxanthanone can also successfully initiate the free radical polymerization of polyacrylic acid thiol carbonate resin. These photopolymerization experimental results demonstrate that 2,4-di(acetoxy)thioxanthanone is an excellent visible light initiator.

[0031] Example 2. Visible light initiator Preparation 2.60 g (10 mmol) of 2,4-dimercaptoxanthone, 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 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 3.7 g of the target compound 2.

[0032] Kinetic application testing of a mixed system of thiol-based PETMP and vinyl-based AN initiated by 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 the PETMP and AN mixed system as the polymerization monomers, target compound 2 ([PI] = 2 × 10⁻⁶) was added. -5 A sample solution of (mol / g) / (PETMP+AN) was added dropwise to the center of a potassium bromide salt plate to form a uniform liquid film. After irradiation with LED ultraviolet light for 15 min, the changes in the absorption peak areas of carbon-carbon double bonds and thiol bonds were recorded by an infrared spectrometer. The conversion rates of monomers PETMP and AN were detected to be 65% and 70%, respectively.

[0033] Example 3. Visible light initiator Preparation 2.60 g (10 mmol) of 2,4-dimercaptoxanthone, 0.20 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 4.91 g of the target compound 3.

[0034] Kinetic application testing of a mixed system of thiol-based GDMP and vinyl-based HEA 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. Using the GDMP and HEA mixed system as the polymerization monomers, target compound 3 ([PI] = 2 × 10⁻⁶) was added. -5 A sample solution of (mol / g) / (GDMP+HEA) was added dropwise to the center of a potassium bromide salt plate to form a uniform liquid film. After irradiation with LED ultraviolet light for 15 min, the changes in the absorption peak areas of carbon-carbon double bonds and thiol bonds were recorded by an infrared spectrometer. The conversion rates of monomers GDMP and HEA were detected to be 58% and 67%, respectively.

[0035] Example 4. Visible light initiator Preparation 2.44 g (10 mmol) of 2,4-dihydroxythioxanthrone, 0.21 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 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 4.64 g of the target compound 4.

[0036] Kinetic application testing of a mixed system of thiol-based BDMP and vinyl-based HEMA initiated by compound 4: 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 the BDMP and HEMA mixed system as the polymerization monomers, target compound 4 ([PI] = 2 × 10⁻⁶) was added. -5A sample solution of (mol / g) / (BDMP+HEMA) was added dropwise to the center of a potassium bromide salt plate to form a uniform liquid film. After irradiation with LED ultraviolet light for 15 min, the changes in the absorption peak areas of carbon-carbon double bonds and thiol bonds were recorded using an infrared spectrometer. The conversion rates of monomers BDMP and HEMA were detected to be 56% and 66%, respectively.

[0037] Example 5. Visible light initiator Preparation 2.44 g (10 mmol) of 2,4-dihydroxythioxanthone, 0.18 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 4.58 g of the target compound 5.

[0038] Kinetic application testing of a thiol-based PETMP and vinyl-based HPA mixed system 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 the PETMP and HPA mixed system as the polymerization monomers, target compound 5 ([PI] = 2 × 10⁻⁶) was added. -5 A sample solution of (mol / g) / (PETMP+HPA) was added dropwise to the center of a potassium bromide salt plate to form a uniform liquid film. After irradiation with LED ultraviolet light for 15 min, the changes in the absorption peak areas of carbon-carbon double bonds and thiol bonds were recorded by infrared spectroscopy. The conversion rates of monomers PETMP and HPA were detected to be 62% and 77%, respectively.

[0039] Example 6. Visible light initiator Preparation 2.44 g (10 mmol) of 2,4-dihydroxythioxanthrone, 0.14 g (25 mmol) of potassium hydroxide, and 40 mL of N,N-dimethylacetamide 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-dimethylacetamide and 0.44 g (25 mmol) of P-methylphosphacyclopentadiene-2-carboxyl 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 5.20 g of the target compound 6.

[0040] Kinetic application testing of a mixed system of thiol-based PETMP and vinyl-based ST initiated by compound 6: 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 the PETMP and ST mixture as the polymerization monomers, target compound 6 ([PI] = 2 × 10⁻⁶) was added. -5 A sample solution of (mol / g) / (PETMP+ST) was added dropwise to the center of a potassium bromide salt plate to form a uniform liquid film. After irradiation with LED ultraviolet light for 15 min, the changes in the absorption peak areas of carbon-carbon double bonds and thiol bonds were recorded using an infrared spectrometer. The conversion rates of monomers PETMP and ST were detected to be 87% and 89%, respectively.

[0041] The kinetic application test of the mixed system of thiol-based TMPMP and vinyl-based HPMA prepared above was conducted: the change in absorption intensity of a certain characteristic peak under illumination was recorded using real-time infrared spectroscopy and a high-speed recorder. Using the TMPMP and HPMA mixed system as the polymerization monomer, target compound 1-6 ([PI] = 2 × 10⁻⁶) was added. -5 A sample solution of (mol / g) / (TMPMP+HPMA) was added dropwise to the center of a potassium bromide salt plate to form a uniform liquid film. After irradiation with LED ultraviolet light for 15 min, the changes in the absorption peak areas of carbon-carbon double bonds and thiol bonds were recorded using an infrared spectrometer. The monomer conversion distribution is as follows: .

Claims

1. A class of disubstituted oxoxanthone-based high-efficiency visible light initiators, characterized in that, The visible light initiator has an oxygen / thioxanthrone as its main skeleton, and its structural formula is as follows: 。 2. The visible light initiator structure according to claim 1, characterized in that: R 1 For oxygen or sulfur; R 2 For oxygen or sulfur; R 3 Includes, but is not limited to, one of the following groups: .

3. The visible light initiator structure according to claim 2, characterized in that: R 4 For oxygen or sulfur; R 5 For nitrogen or phosphorus; R 6 It can be methyl or ethyl.

4. A method for preparing a visible light initiator as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: Under inert gas protection, 2,4-disubstituted oxygen / thiocyclic anthrone compounds were dissolved in an organic solvent, excess alkali was added, and excess organic solution of acyl chloride compounds was slowly added dropwise under an ice-water bath. The reaction was carried out at room temperature, and the reaction was stopped by TLC detection. The mixture was then filtered, the filtrate was concentrated, and purified to obtain a novel, highly efficient visible light initiator of disubstituted heterocyclic anthrone compounds.

5. The method for preparing the visible light initiator according to claim 4, characterized in that, The 2,4-disubstituted oxygen / thioheterocyclic anthrone compounds include the following compounds: R 1 For oxygen or sulfur; R 2 It is oxygen or sulfur.

6. The method for preparing the visible light initiator according to claim 5, characterized in that, The acyl chloride compound is R 3 C(O)Cl, R 3 Includes one of the following groups: ;R 4 For oxygen or sulfur; R 5 For nitrogen or phosphorus; R 6 It can be methyl or ethyl.

7. The method for preparing the visible light initiator according to claim 4, characterized in that, The organic solvent includes any one of ethanol, methanol, acetone, tetrahydrofuran, acetonitrile, N,N-dimethylformamide, or N,N-dimethylacetamide.

8. The method for preparing the visible light initiator according to claim 4, characterized in that, The bases mentioned include, but are not limited to, sodium hydroxide, potassium hydroxide, pyridine, triethylamine, piperidine, or tetrahydropyrrole.

9. The visible light initiator according to any one of claims 1-3 or the visible light initiator prepared by the method according to any one of claims 4-8, as a photo-acid-generating molecule, is used as a photoinitiator in the prepolymer-containing thiol-olefin free radical photopolymerization system.

10. The application according to claim 9, characterized in that, The prepolymer contains thiol-olefin polymerization systems, where thiol groups include TMPMP, PETMP, GDMP, and BDMP; and vinyl groups include HPMA, ST, AN, HEA, HEMA, and HPA. Further preferred are the prepolymer containing thiol-olefin polymerization systems, where the thiol groups include a mixture of thiol-based TMPMP and vinyl-based HPMA, and a mixture of thiol-based PETMP and vinyl-based ST.

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