Chromone oxime ester photoinitiators, methods of making and using the same

Abstract

The application discloses a class of aurone oxime ester photoinitiators, a preparation method and application thereof. The photoinitiator has ultraviolet absorption in the wavelength range of 250-450 nm, has a large molar extinction coefficient under common LED light wavelengths, has high photosensitive activity, can be well matched with an LED light source, can quickly and efficiently initiate double bond polymerization of a free radical monomer, and solves the problem that a traditional photoinitiator cannot initiate double bond polymerization of a monomer under an LED light source or has low initiation efficiency. The photoinitiator takes an aurone compound as a matrix, has simple synthesis, is easy to prepare, has low cytotoxicity, and has certain application potential in the fields of biological medicines, photocuring coatings, inks, 3D printing materials and UV-LED curing systems.

Description

Technical Field

[0001] This invention relates to the field of photoinitiators, and particularly to a class of orange ketone oxime ester photoinitiators, their preparation methods and applications. Background Technology

[0002] Photopolymerization technology utilizes light or electron beams as energy to rapidly cure and crosslink chemically active liquid materials into solid materials through the action of photoinitiators. Compared with other curing methods, such as solvent evaporation curing, air oxidation curing, and thermal curing, photopolymerization technology has advantages such as fast curing speed, high energy efficiency, and safety and environmental friendliness. It is widely used in furniture decoration, printed circuit boards, 3D printing, biomedical materials, automotive industry, inks, and other fields, and is hailed as a new technology for green industry towards sustainable development in the 21st century.

[0003] Photoinitiators are photosensitive compounds that absorb light energy of a certain wavelength in the ultraviolet or visible light region, generating active species such as free radicals and cations capable of initiating polymerization, thereby initiating cross-linking and curing of oligomers. Although used in small quantities in photocurable formulations, photoinitiators significantly influence the polymerization rate and conversion rate, making them a crucial component of the photocurable system. Based on the manner, type, and mechanism of action of generating active particles, photoinitiators can be classified into free radical photoinitiators and non-free radical photoinitiators. Free radical photoinitiators are the most widely used, and can be further divided into cleavage-type (Norrish I) photoinitiators and hydrogen-abstraction-type (Norrish II) photoinitiators. Norrish I photoinitiators break their relatively weak chemical bonds upon light exposure, generating active free radicals. This eliminates the need for external co-initiators and other additives, reducing the impact of external additives on the curing system. They offer advantages such as simple formulation, cost-effectiveness, and environmental friendliness, and are therefore widely used.

[0004] Currently, the main light source used in the photopolymerization field is the high-pressure mercury lamp. However, high-pressure mercury lamps have many drawbacks, such as long start-up time, high energy consumption, and the potential for ozone and mercury pollution, especially mercury pollution, which is severe. In the future, the production and use of mercury products will be gradually controlled and reduced. Compared with high-pressure mercury lamps, LED light sources have many advantages, such as speed and efficiency, economy, safety and environmental friendliness, and stable output. Therefore, LED light sources will replace mercury lamps as the mainstream light source for the photopolymerization industry in the near future. However, unlike the continuous spectrum of traditional mercury arc lamps, the spectral distribution of LED light sources is concentrated in a narrow spectral band; they are single-wavelength light sources. Only when the excitation wavelength of the photoinitiator is within the spectral range can photopolymerization be effectively and rapidly initiated.

[0005] However, most commercially available photoinitiators are developed based on traditional mercury lamps, leading to a mismatch between the traditional photoinitiator and the LED emission wavelength, which severely affects the initiation efficiency of the photoinitiator. The few traditional photoinitiators that can be excited by LED light sources suffer from low initiation efficiency, high toxicity, and poor biocompatibility. Examples include the commercially available Norrish type I photoinitiator Irgacure 369 (2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone) and the oxime ester photoinitiator OXE-01 (2-((benzoyloxy)imino)-1-(4-(phenylthio)phenyl)oct-1-one), whose chemical structures are shown below.

[0006]

[0007] Irgacure 369 absorbs at common LED emission wavelengths of 365nm and 405nm, making it compatible with LED light sources. However, its photosensitivity is poor, its initiation activity is low, and its synthesis process is complex and expensive, which limits its use to some extent. OXE-01 absorbs at common LED emission wavelengths, has good photosensitivity, and excellent thermal stability. However, its synthesis process is complex and its production cost is high, which also limits its use to some extent.

[0008] Therefore, there is an urgent need to develop a highly efficient photoinitiator that is simple to synthesize, inexpensive, highly photosensitive, adaptable to the emission wavelength of LED light sources, and has good biocompatibility. Summary of the Invention

[0009] To address the above problems, this invention provides a class of orange ketone oxime ester photoinitiators, their preparation method, and their applications.

[0010] The photoinitiator described in this invention uses an orange ketone structure as the parent compound to red-shift the absorption wavelength of the initiator to above 400 nm, better matching the emission wavelength of common LED light sources. Furthermore, orange ketones belong to the flavonoid family and are natural compounds found in plants. The introduction of the orange ketone structure effectively reduces the toxicity of the photoinitiator, resulting in an initiator with good biocompatibility. An oxime ester structure is introduced as the reactive group. The NO bond in the oxime ester structure has a low bond energy, making it easy to break after light exposure. Through decarboxylation, it releases CO2 and generates a free radical with polymerization initiation activity, effectively initiating double bond polymerization. The photoinitiator described in this invention absorbs in the wavelength range of 250 nm-450 nm and has high molar extinction coefficients at common LED emission wavelengths of 385 nm and 405 nm, exhibiting high photosensitivity and compatibility with LED light sources. Moreover, its synthesis method is simple, the raw materials are readily available, and its application performance is excellent, making it a novel, low-toxicity, and highly efficient Norrish type I photoinitiator.

[0011] The orange ketone oxime ester photoinitiator of the present invention has the following general structural formula (Ⅰ):

[0012]

[0013] in,

[0014] R1 is selected from One of them;

[0015] R2 is selected from C1-C 20 Straight-chain or branched alkyl groups, C3-C 20 cycloalkyl, C4-C 20 alkyl cycloalkyl or cycloalkylalkyl, C2-C 20 Straight-chain or branched alkenyl groups, C3-C 20 Cycloalkenyl, C4-C 20 alkylcycloalkenyl or cycloalkenylalkyl, C6-C 20 aryl or C7-C 20 One of the aralkyl groups; more preferably, the R2 is selected from C1-C1. 10 Straight-chain or branched alkyl groups, C3-C 10 cycloalkyl, C4-C 10 alkyl cycloalkyl or cycloalkylalkyl, C2-C 10 Straight-chain or branched alkenyl groups, C3-C 10 Cycloalkenyl, C4-C 10 alkylcycloalkenyl or cycloalkenylalkyl, C6-C 10 aryl or C7-C 10 One of the aralkyl groups; particularly preferred, the R2 is selected from methyl or phenyl.

[0016] Any one or more hydrogen atoms in R2 can be replaced by the following substituents: halogens (-F, -Cl, -Br, -I), hydroxyl groups, nitro groups, cyano groups, aldehyde groups, C1-C... 10 carbonyl group, sulfonic acid group, C1-C 10 alkoxy groups, C1-C 10 alkylthio groups, mono(C1-C) 10 alkyl)amino, di(C1-C 10 Alkyl)amino.

[0017] For the technical solution described above, preferably, the orange ketone oxime ester photoinitiator of the present invention is selected from one of the following structural formulas:

[0018]

[0019] This invention also provides a chemical preparation method for this type of orange ketone oxime ester photoinitiator, characterized by comprising the following steps:

[0020]

[0021] 3-Benzofurone and a dialdehyde compound react under the action of a catalyst to generate intermediate A with an aldehyde group; intermediate A reacts with hydroxylamine hydrochloride under the action of a base to generate intermediate B with an oxime group; intermediate B reacts with an acyl chloride compound in the presence of an acid-binding agent to generate an orange ketone oxime ester photoinitiator CT.

[0022] Specifically, the chemical preparation method of the orange ketone oxime ester photoinitiator includes the following steps:

[0023] (1) Synthesis of intermediate product A:

[0024] 3-Benzofurone, dialdehyde compound and catalyst were mixed and reaction solvent I was added. Under nitrogen protection and light protection, the mixture was stirred at room temperature until the reaction was complete. The intermediate product A was obtained by filtration, vacuum distillation and purification.

[0025] For the technical solution described above, preferably, the dialdehyde compound is selected from at least one of terephthalaldehyde, 2,5-dicarboxyfuran, and thiophene-2,5-dicarboxaldehyde; the catalyst is activated alumina; and the reaction solvent I is dichloromethane.

[0026] For the technical solution described above, preferably, the molar ratio of the 3-benzofuranone, the dialdehyde compound, and the catalyst is 1:(1.1-1.3):(4.5-5.5); a more preferably molar ratio is 1:1.2:(4.8-5.2);

[0027] (2) Synthesis of intermediate product B:

[0028] Hydroxylamine hydrochloride and an appropriate amount of base were mixed and reaction solvent II was added. After complete dissolution, intermediate product A was added. Under nitrogen protection, the mixture was refluxed and stirred at (85-110)℃ until the reaction was complete. Then, intermediate product B was obtained by vacuum distillation, extraction and purification.

[0029] For the above-described technical solution, preferably, the alkali is anhydrous sodium acetate; the reaction solvent II is a mixed solvent of ethanol, tetrahydrofuran and water, and more preferably a mixed solvent of ethanol, tetrahydrofuran and water in a volume ratio of 5:1:1.

[0030] For the technical solution described above, preferably, the molar ratio of intermediate product A, hydroxylamine hydrochloride and base is 1:(1.5-2.0):(1.5-2.0); a more preferred molar ratio is 1:(1.8-2.0):(1.8-2.0).

[0031] (3) Synthesis of CT, a photoinitiator of orange oxime esters:

[0032] Intermediate product B was added to reaction solvent III. Under nitrogen protection and light protection, an acid-binding agent was slowly added and the reaction was stirred. Then, an acyl chloride compound was slowly added under ice bath conditions and the reaction was stirred at room temperature. After the reaction was complete, the crude product was obtained by extraction and vacuum distillation. The crude product was purified by silica gel column chromatography to obtain the orange oxime ester photoinitiator CT.

[0033] For the above-described technical solution, preferably, the reaction solvent III is anhydrous dichloromethane; the acid-binding agent is at least one of anhydrous triethylamine and anhydrous pyridine; and the acyl chloride compound is at least one of acetyl chloride, benzoyl chloride, and cinnamoyl chloride.

[0034] For the technical solution described above, preferably, the molar ratio of the intermediate product B, the acyl chloride compound and the acid-binding agent is 1:(1.5-2.0):(1.5-2.0); a more preferably molar ratio is 1:(1.8-2.0):(1.8-2.0).

[0035] This invention also protects the application of the orange oxime ester photoinitiators described above, including applications in biomedicine, photocurable coatings, inks, 3D printing materials, and UV-LED curing systems.

[0036] The inks include: printing inks and inkjet inks;

[0037] The photocurable coatings include: wood coatings and coatings for electronic devices;

[0038] The 3D printing materials include: photopolymer 3D printing, rapid prototyping parts, and additive manufacturing models;

[0039] The UV-LED curing system includes: acrylate resin, epoxy resin, and polyurethane UV curing.

[0040] For the above-described technical solution, preferably, the UV-LED curing system of the application is characterized by: (1) the wavelength range of the LED light source used in the curing system is 365-450nm; (2) the curing system contains at least one compound described by general formula (Ⅰ) as a photoinitiator; (3) the prepolymer monomer used in the curing system contains at least one unsaturated compound containing an olefin bond (C=C).

[0041] For the technical solution described above, preferably, the prepolymer monomer is selected from at least one of tripropylene glycol diacrylate (TPGDA), 1,6-hexanediol diacrylate (HDDA), polyethylene glycol diacrylate (PEGDA), and trimethylolpropane triacrylate (TMPTA).

[0042] For the technical solution described above, preferably, the wavelength of the LED light source is 385-415nm.

[0043] For the technical solution described above, preferably, when the photoinitiator in the photocuring system is a single component of an orange ketone oxime ester photoinitiator, the mass ratio of the prepolymer monomer to the orange ketone oxime ester photoinitiator is 100:(0.1-1); more preferably, the mass ratio of the prepolymer monomer to the orange ketone oxime ester photoinitiator is 100:(0.3-0.5).

[0044] For the technical solution described above, preferably, when the photoinitiator in the photocuring system is a two-component combination of an orange ketone oxime ester photoinitiator and a diaryl iodine salt compound, the mass ratio of the prepolymer monomer, the orange ketone oxime ester photoinitiator and the diaryl iodine salt compound is 100:(0.1-1):(0.1-2); more preferably, the mass ratio of the prepolymer monomer, the orange ketone oxime ester photoinitiator and the diaryl iodine salt compound is 100:(0.3-0.5):(0.5-1).

[0045] More preferably, the diaryliodomonium salt compound is selected from at least one of diphenyliodohexafluorophosphate (IOD) and 4,4'-dimethyliodohexafluorophosphate.

[0046] The beneficial technical effects of this invention are as follows:

[0047] (1) The photoinitiator described in this invention has ultraviolet absorption in the wavelength range of 250-450nm and has a large molar extinction coefficient at common LED emission wavelengths (such as 385nm and 405nm). Compared with the two commercially available Norrish type I photoinitiators (Irgacure 369 and OXE-01), the absorption wavelengths have a significant red shift, and the photosensitivity is higher, which can better match the LED light source.

[0048] (2) When used alone, the photoinitiator described in this invention can effectively initiate the double bond polymerization of free radical monomers, and the final double bond conversion rate can reach 93%, which is superior to the commercial Norrish type I photoinitiator Irgacure 369 and OXE-01. When the photoinitiator described in this invention is combined with diaryliodonium salt compounds to form a two-component photoinitiation system, the double bond conversion rate of free radical polymerization monomers can be further increased to 97%.

[0049] (3) The photoinitiator described in this invention has a simple molecular structure, a simple synthesis method, readily available raw materials, and is easy to prepare.

[0050] (4) The photoinitiator described in this invention has low toxicity and good biocompatibility, and has certain application potential in fields such as biomedicine or inkjet printing (especially food packaging labels). Attached Figure Description

[0051] Figure 1 The molecular structural formulas and names of the four orange ketone oxime ester photoinitiators described in this invention are as follows.

[0052] Figure 2 This is the proton NMR spectrum of CT-1.

[0053] Figure 3 This is a high-resolution mass spectrum of CT-1.

[0054] Figure 4 This is the 1H NMR spectrum of CT-B.

[0055] Figure 5 This is a high-resolution mass spectrum of CT-B.

[0056] Figure 6 This is the 1H NMR spectrum of CT-2.

[0057] Figure 7 This is a high-resolution mass spectrum of CT-2.

[0058] Figure 8 This is the 1H NMR spectrum of CT-3.

[0059] Figure 9 This is a high-resolution mass spectrum of CT-3.

[0060] Figure 10 The images show the UV-Vis absorption spectra of the four orange ketone oxime ester photoinitiators described in this invention.

[0061] Figure 11 The UV-Vis absorption spectra of two commercially available Norrish type I photoinitiators are shown.

[0062] Figure 12 This is the UV-Vis absorption spectrum of CT-2 during its photodegradation process under LED illumination.

[0063] Figure 13 The figure shows the cytotoxicity test results of the four orange oxime ester photoinitiators described in this invention.

[0064] Figure 14 Double bond conversion curves for TPGDA polymerization initiated by CT-1, CT-B, and two commercial photoinitiators when used alone.

[0065] Figure 15 Double bond conversion curves for TPGDA polymerization initiated by a binary photoinitiation system composed of CT-1 and IOD. Detailed Implementation

[0066] The technical solution of the present invention will be further described in detail below through specific embodiments. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any modifications or alterations made to the present invention will fall within the protection scope of the present invention.

[0067] Unless otherwise specified, all raw materials used in the chemical preparation methods of this invention are commercially available, and all reagents, methods and equipment used in this invention are conventional reagents, methods and equipment in the technical field; all parts and percentages are in units of weight.

[0068] Example 1: Preparation of CT-1

[0069] The synthetic route and specific preparation method of CT-1 are as follows:

[0070]

[0071] (a) Synthesis of CT-1-CHO

[0072] In a 250 mL two-necked round-bottom flask, 1.34 g (10.00 mmol) of 3-benzofuranone, 1.61 g (12.00 mmol) of terephthalaldehyde, and 5.10 g (50.00 mmol) of activated alumina were added sequentially. 100 mL of dichloromethane was added as the reaction solvent. The mixture was stirred at room temperature for 8 h under nitrogen protection and in the dark. The reaction was monitored by thin-layer chromatography. After the reaction was complete, the activated alumina solid was removed by filtration, and the solvent was removed by vacuum distillation to obtain the crude product. The crude product was loaded onto silica gel and purified by silica gel column chromatography to obtain a pale yellow solid product CT-1-CHO (1.58 g, yield 63.2%).

[0073] Nuclear magnetic resonance characterization confirmed that the CT-1-CHO structure was correct.

[0074] 1 HNMR(600MHz,DMSO-d6)δ10.06(s,1H),8.20(d,J=8.1Hz,2H),8.05–8.00(m,2H),7.8 8–7.81(m,2H),7.61(dd,J=8.2,0.9Hz,1H),7.36(td,J=7.5,0.8Hz,1H),7.03(s,1H).

[0075] (b) Synthesis of CT-1-OH

[0076] Hydroxylamine hydrochloride (0.69 g, 10.00 mmol) and anhydrous sodium acetate (0.82 g, 10.00 mmol) were added sequentially to a 250 mL two-necked round-bottom flask. Ethanol (80 mL), tetrahydrofuran (16 mL), and water (16 mL) were added as reaction solvents. The mixture was stirred until the solid was completely dissolved. Then, CT-1-CHO (1.25 g, 5.00 mmol) was added. The mixture was refluxed and stirred at 100 °C for 12 h under nitrogen protection. The reaction was monitored by thin-layer chromatography. After the reaction was complete, the solvent was removed by vacuum distillation, and the solid was redissolved in ethyl acetate (100 mL). The solid was extracted three times with saturated brine (200 mL), and the solvent was removed by vacuum distillation to obtain the crude product. The crude product was loaded onto silica gel and purified by silica gel column chromatography to obtain a pale yellow solid product CT-1-OH (0.75 g, yield 56.6%).

[0077] Nuclear magnetic resonance characterization confirmed that the CT-1-OH structure is correct.

[0078] 1 H NMR(400MHz, DMSO-d6)δ9.83(s,1H),8.16(s,1H),7.97(dd,J=9.1,1.3Hz,1H),7.78–7.72(m, 2H),7.67–7.59(m,3H),7.52(td,J=9.0,1.4Hz,1H),7.42(dd,J=6.7,1.4Hz,1H),6.82(s,1H).

[0079] (c) Synthesis of CT-1

[0080] CT-1-OH (0.53 g, 2.00 mmol) was added to a dry 100 mL three-necked round-bottom flask, along with anhydrous dichloromethane (40 mL) as the reaction solvent. Under nitrogen protection and in the dark, triethylamine (0.56 mL, 4.00 mmol) was slowly added, and the mixture was stirred for 20 minutes. Then, acetyl chloride (0.28 mL, 4.00 mmol) was slowly added under ice bath conditions. After the addition was complete, the mixture was stirred at room temperature for 8 hours. The reaction was monitored by thin-layer chromatography. After the reaction was complete, the reaction solution was extracted three times with saturated saline (200 mL), and the solvent was removed by vacuum distillation to obtain the crude product. The crude product was loaded onto silica gel and purified by silica gel column chromatography to obtain the yellow solid product CT-1 (0.53 g, yield 86.3%).

[0081] The CT-1 structure was confirmed to be correct by nuclear magnetic resonance and high-resolution mass spectrometry characterization.

[0082] 1H NMR (600MHz, DMSO-d6) δ8.73(s,1H),8.11(d,J=8.3Hz,2H),7.92–7.79(m,4H),7.60(d,J=8.3Hz,1H),7.35(t,J=7.5Hz,1H),6.99(s,1H),2.22(s,3H).

[0083] HRMS(ESI, m / z): C 18 H 13 NO4[M+Na] + Calculated value: 330.0742; Test value: 330.0742.

[0084] Example 2: Preparation of CT-B

[0085] The synthetic route and specific preparation method of CT-B are as follows:

[0086]

[0087] (a) The synthesis of CT-1-CHO and CT-1-OH is the same as above.

[0088] (b) Synthesis of CT-B

[0089] CT-1-OH (0.53 g, 2.00 mmol) was added to a dry 100 mL three-necked round-bottom flask, along with anhydrous dichloromethane (40 mL) as the reaction solvent. Under nitrogen protection and in the dark, triethylamine (0.56 mL, 4.00 mmol) was slowly added, and the mixture was stirred for 20 minutes. Then, benzoyl chloride (0.46 mL, 4.00 mmol) was slowly added under ice bath conditions. After the addition was complete, the mixture was stirred at room temperature for 8 hours. The reaction was monitored by thin-layer chromatography. After the reaction was complete, the reaction solution was extracted three times with saturated saline (200 mL), and the solvent was removed by vacuum distillation to obtain the crude product. The crude product was loaded onto silica gel and purified by silica gel column chromatography to obtain the yellow solid product CT-B (0.62 g, yield 84.0%).

[0090] The CT-B structure was confirmed to be correct by NMR and high-resolution mass spectrometry.

[0091] 1H NMR (600MHz, DMSO-d6) δ8.99(s,1H),8.15(d,J=8.0Hz,2H),8.09(d,J=7.7Hz,2H),7.95(d,J=8.0Hz,2H ),7.85(t,J=8.3Hz,2H),7.77–7.72(m,1H),7.62(t,J=7.3Hz,3H),7.36(t,J=7.4Hz,1H),7.02(s,1H).,

[0092] HRMS(ESI, m / z): C 23 H 15 NO4[M+Na] + Calculated value: 392.0898; Test value: 392.0895.

[0093] Example 3: Preparation of CT-2

[0094] The synthetic route and specific preparation method of CT-2 are as follows:

[0095]

[0096] (a) Synthesis of CT-2-CHO

[0097] In a 250 mL two-necked round-bottom flask, 3-benzofuranone (1.34 g, 10.00 mmol), 2,5-diformylfuran (1.49 g, 12.00 mmol), and activated alumina (5.10 g, 50.00 mmol) were added sequentially. Dichloromethane (100 mL) was added as the reaction solvent. The mixture was stirred at room temperature for 8 h under nitrogen protection and in the dark. The reaction was monitored by thin-layer chromatography. After the reaction was complete, the activated alumina solid was removed by filtration, and the solvent was removed by vacuum distillation to obtain the crude product. The crude product was loaded onto silica gel and purified by silica gel column chromatography to obtain a pale yellow solid product CT-2-CHO (1.51 g, yield 62.9%).

[0098] Nuclear magnetic resonance characterization confirmed that the CT-2-CHO structure is correct.

[0099] 1 H NMR (400MHz, DMSO-d6) δ9.70 (s, 1H), 7.89–7.79 (m, 2H), 7.72 (d, J = 3.8Hz, 1H), 7.57 (d d,J=8.3,0.9Hz,1H),7.41(d,J=3.8Hz,1H),7.36(td,J=7.5,0.8Hz,1H),6.94(s,1H).

[0100] (b) Synthesis of CT-2-OH

[0101] Hydroxylamine hydrochloride (0.69 g, 10.00 mmol) and anhydrous sodium acetate (0.82 g, 10.00 mmol) were added sequentially to a 250 mL two-necked round-bottom flask. Ethanol (80 mL), tetrahydrofuran (16 mL), and water (16 mL) were added as reaction solvents. The mixture was stirred until the solid was completely dissolved. Then, CT-2-CHO (1.20 g, 5.00 mmol) was added. The mixture was refluxed and stirred at 100 °C for 12 h under nitrogen protection. The reaction was monitored by thin-layer chromatography. After the reaction was complete, the solvent was removed by vacuum distillation, and the solid was redissolved in ethyl acetate (100 mL). The solid was extracted three times with saturated brine (200 mL), and the solvent was removed by vacuum distillation to obtain the crude product. The crude product was loaded onto silica gel and purified by silica gel column chromatography to obtain a pale yellow solid product CT-2-OH (0.68 g, yield 53.3%).

[0102] Nuclear magnetic resonance characterization confirmed that the CT-2-OH structure is correct.

[0103] 1 H NMR (400MHz, DMSO-d6) δ11.69(s,1H),7.97(dd,J=9.1,1.3Hz,1H),7.75(s,1H),7.63(ddd,J=8.8,6.7,1.3Hz,1H), 7.52(td,J=9.0,1.4Hz,1H),7.42(dd,J=6.7,1.4Hz,1H),7.28(d,J=5.1Hz,1H),7.01(d,J=5.1Hz,1H),6.92(s,1H).

[0104] (c) Synthesis of CT-2

[0105] CT-2-OH (0.51 g, 2.00 mmol) was added to a dry 100 mL three-necked round-bottom flask, along with anhydrous dichloromethane (40 mL) as the reaction solvent. Under nitrogen protection and in the dark, triethylamine (0.56 mL, 4.00 mmol) was slowly added, and the mixture was stirred for 20 minutes. Then, acetyl chloride (0.28 mL, 4.00 mmol) was slowly added under ice bath conditions. After the addition was complete, the mixture was stirred at room temperature for 8 hours. The reaction was monitored by thin-layer chromatography. After the reaction was complete, the reaction solution was extracted three times with saturated saline (200 mL), and the solvent was removed by vacuum distillation to obtain the crude product. The crude product was loaded onto silica gel and purified by silica gel column chromatography to obtain the yellow solid product CT-2 (0.52 g, yield 87.5%).

[0106] The CT-2 structure was confirmed to be correct by nuclear magnetic resonance and high-resolution mass spectrometry characterization.

[0107] 1 H NMR (600MHz, DMSO-d6) δ8.64 (s, 1H), 7.82 (ddd, J = 14.1, 7.7, 1.4Hz, 2H), 7.54 (d, J=8.3Hz,1H),7.39(d,J=3.7Hz,1H),7.37–7.30(m,2H),6.93(s,1H),2.22(s,3H).

[0108] HRMS(ESI, m / z): C 16 H 11 NO5[M+Na] + Calculated value: 320.0535; Test value: 320.0534.

[0109] Example 4: Preparation of CT-3

[0110] The synthetic route and specific preparation method of CT-3 are as follows:

[0111]

[0112] (a) Synthesis of CT-3-CHO

[0113] In a 250 mL two-necked round-bottom flask, 3-benzofuranone (1.34 g, 10.00 mmol), thiophene-2,5-dicarboxaldehyde (1.68 g, 12.00 mmol), and activated alumina (5.10 g, 50.00 mmol) were added sequentially. Dichloromethane (100 mL) was added as the reaction solvent. The reaction was carried out under nitrogen protection and in the dark at room temperature with stirring for 8 h. The reaction was monitored by thin-layer chromatography. After the reaction was complete, the activated alumina solid was removed by filtration, and the solvent was removed by vacuum distillation to obtain the crude product. The crude product was loaded onto silica gel and purified by silica gel column chromatography to obtain the pale yellow solid product CT-3-CHO (1.59 g, yield 62.1%).

[0114] Nuclear magnetic resonance characterization confirmed that the CT-3-CHO structure was correct.

[0115] 1 H NMR(400MHz, DMSO-d6)δ9.84(s,1H),7.98(dd,J=9.1,1.3Hz,1H),7.84(d,J=7.0Hz,1H),7.6 3(ddd,J=8.8,6.7,1.3Hz,1H),7.55–7.48(m,2H),7.42(dd,J=6.7,1.4Hz,1H),7.18(s,1H).

[0116] (b) Synthesis of CT-3-OH

[0117] Hydroxylamine hydrochloride (0.69 g, 10.00 mmol) and anhydrous sodium acetate (0.82 g, 10.00 mmol) were added sequentially to a 250 mL two-necked round-bottom flask. Ethanol (80 mL), tetrahydrofuran (16 mL), and water (16 mL) were added as reaction solvents. The mixture was stirred until the solid was completely dissolved. Then, CT-3-CHO (1.28 g, 5.00 mmol) was added, and the mixture was refluxed at 100 °C for 12 h under nitrogen protection. The reaction was monitored by thin-layer chromatography. After the reaction was complete, the solvent was removed by vacuum distillation, and the solid was redissolved in ethyl acetate (100 mL). The solid was extracted three times with saturated brine (200 mL), and the solvent was removed by vacuum distillation to obtain the crude product. The crude product was loaded onto silica gel and purified by silica gel column chromatography to obtain a pale yellow solid product CT-3-OH (0.75 g, yield 55.4%).

[0118] Nuclear magnetic resonance characterization confirmed that the CT-3-OH structure is correct.

[0119] 1 H NMR (400MHz, DMSO-d6) δ11.54(s,1H),8.39(s,1H),7.81(dd,J=8.3,6.8Hz,2H),7.69( d,J=3.9Hz,1H),7.60(dd,J=8.2,1.2Hz,1H),7.39(d,J=3.9Hz,1H),7.37–7.31(m,2H).

[0120] (c) Synthesis of CT-3

[0121] CT-3-OH (0.54 g, 2.00 mmol) was added to a dry 100 mL three-necked round-bottom flask, along with anhydrous dichloromethane (40 mL) as the reaction solvent. Under nitrogen protection and in the dark, triethylamine (0.56 mL, 4.00 mmol) was slowly added, and the mixture was stirred for 20 minutes. Then, acetyl chloride (0.28 mL, 4.00 mmol) was slowly added under ice bath conditions. After the addition was complete, the mixture was stirred at room temperature for 8 hours. The reaction was monitored by thin-layer chromatography. After the reaction was complete, the reaction solution was extracted three times with saturated saline (200 mL), and the solvent was removed by vacuum distillation to obtain the crude product. The crude product was loaded onto silica gel and purified by silica gel column chromatography to obtain the yellow solid product CT-3 (0.55 g, yield 87.9%).

[0122] The CT-3 structure was confirmed to be correct by nuclear magnetic resonance and high-resolution mass spectrometry.

[0123] 1H NMR(600MHz,DMSO-d6)δ8.93(d,J=1.8Hz,1H),7.84–7.79(m,2H),7.76(dd,J=4.2,1.8Hz,1H) ,7.69–7.65(m,2H),7.39(d,J=1.9Hz,1H),7.35(td,J=7.5,1.7Hz,1H),2.20(d,J=1.6Hz,3H).

[0124] HRMS(ESI, m / z): C 16 H 11 NO4S[M+Na] + Calculated value: 336.0306; Test value: 336.0305.

[0125] Example 5: Ultraviolet-Visible Absorption Spectroscopy Test

[0126] Weigh out the four orange ketone oxime ester photoinitiators described in this invention and two commercially available Norrish type I photoinitiators (Irgacure 369 and OXE-01) respectively, and prepare a concentration of 2.5 × 10⁻⁶. -5 mol·L -1 Anhydrous acetonitrile solution. The absorbance (A) of the solution in the wavelength range of 250-500 nm was measured using a UV-Vis spectrophotometer (model: Lambda 1050+). According to Lambert-Beer law: A = ε × c × L (where A is the absorbance of the solution; ε is the molar extinction coefficient, in L·mol⁻¹). -1 ·cm -1 c represents the solution concentration, in mol·L⁻¹. -1 (L represents the thickness of the absorption layer in cm; in this test, L is 1 cm). Calculate the molar extinction coefficient of the photoinitiator in anhydrous acetonitrile solution. Unless otherwise specified, the default slit width of the optical path is used during the test.

[0127] The UV-Vis absorption spectra of the four orange ketone oxime ester photoinitiators and two commercially available Norrish type I photoinitiators described in this invention are as follows: Figure 10 and Figure 11 As shown, its maximum absorption wavelength λ max Maximum molar extinction coefficient ε max The molar extinction coefficients at common LED light source emission wavelengths (365nm, 385nm, 405nm, 420nm) are shown in Tables 1 and 2 below. Figure 10As shown in Table 1, all four orange oxime ester photoinitiators exhibit ultraviolet absorption in the wavelength range of 250-450 nm and possess large molar extinction coefficients at common LED emission wavelengths, demonstrating high photosensitivity and good compatibility with LED light sources. (Comparison) Figure 11 As shown in Table 2, the maximum absorption wavelength of the four orange oxime ester photoinitiators described in this invention is significantly red-shifted compared to the two selected commercial Norrish type I photoinitiators, which can better adapt to LED light sources. At the same time, their molar extinction coefficients at common LED emission wavelengths are significantly greater than those of commercial Norrish type I photoinitiators, indicating higher photosensitivity and significant advantages over commercial photoinitiators.

[0128] Table 1. Maximum absorption wavelength and molar extinction coefficient of four orange ketone oxime ester photoinitiators

[0129]

[0130] Table 2. Maximum absorption wavelength and molar extinction coefficient of two commercially available Norrish type I photoinitiators

[0131]

[0132] Example 6: Steady-state photodegradation test

[0133] Weigh out appropriate amounts of the four orange ketone oxime ester photoinitiators and prepare them to a concentration of 2.5 × 10⁻⁶. -5 mol·L -1 Anhydrous acetonitrile solution was injected into a cuvette with a path length of 1 cm. Nitrogen gas was bubbled into the solution for 15 min, and then the cuvette was sealed. The solution was measured at a wavelength of 405 nm and an intensity of 110 mW·cm⁻¹. -2 Under an LED light source, the absorbance at different times of illumination was measured, and the changes in the ultraviolet-visible absorption spectrum of the solution under LED illumination were observed.

[0134] The UV-Vis absorption spectrum of CT-2 during its photodegradation process under 405nm LED illumination is shown below. Figure 12 As shown in the figure, the orange ketone oxime ester photoinitiator of this invention undergoes a significant change in its ultraviolet-visible absorption spectrum within a short time under LED illumination. This indicates that the photoinitiator molecules underwent a photochemical reaction within a short period of time under light illumination, exhibiting high photosensitivity and photodegradation activity. Under LED illumination, it can rapidly initiate the polymerization of the photocurable system.

[0135] Example 7: Cytotoxicity Test

[0136] HaCat cells (human immortalized keratinocytes) were seeded in 96-well plates, approximately 8000 cells per well, and cultured for 24 hours at 37°C and 5% CO2. Then, photoinitiator solutions of different concentrations (4, 8, 16, and 32 μM) were added and incubated for 12 hours. After incubation, 100 μL of 3-(4,5-dimethylthiazol-2)-2,5-diphenyltetrazolium bromide (MTT, 5 mg / mL) was added to each well, and incubation was continued for 4 hours. Finally, the MTT solution was removed, 100 μL of DMSO solution was added, and the absorbance of each well was measured using a microplate reader.

[0137] The cytotoxicity test results of the four orange ketone oxime ester photoinitiators described in this invention are as follows: Figure 13 As shown in the figure, after culturing in a medium containing the orange oxime ester photoinitiator described in this invention for 12 hours, the survival rate of all cells remained above 90%. This indicates that the photoinitiator described in this invention has low toxicity and good biocompatibility, and has certain application potential in fields such as biomedicine or inkjet printing (especially food packaging labels).

[0138] Example 8: Real-time Infrared Dynamics Testing

[0139] Using tripropylene glycol diacrylate (TPGDA) as the polymerizing monomer, the orange ketone oxime ester photoinitiators CT-1 and CT-B, as well as two commercially available Norrish type I photoinitiators (Irgacure 369 and OXE-01), were formulated into 0.3 wt% photosensitive solutions. A small amount of the photosensitive solution was applied to a potassium bromide salt plate. To eliminate the influence of oxygen in the air, another potassium bromide salt plate was used to cover the sample for testing. The sample was irradiated under a 385 nm LED point light source, and the light intensity was determined to be 90 mW·cm using a UV-Vis radiometer. -2 The changes in the double bonds of the polymer monomers were tested and recorded in real time using a real-time infrared spectrometer (model: Nicolet5700FT-IR spectroscope). The changes were then calculated using 810 cm⁻¹. -1 The change in the area of ​​the infrared characteristic absorption peak of the acrylate double bond near the double bond characterizes the double bond conversion rate of TPGDA. The final double bond conversion rate is calculated by the following formula:

[0140] Conversion% = (1-S) t / S0)×100%

[0141] Among them, S t S0 and S0 represent the peak areas of the characteristic peaks of the double bonds of acrylate at time t (when the light exposure time is t) and when there is no light exposure, respectively.

[0142] The double bond conversion curves of the TPGDA monomer polymerization initiated by the photoinitiators CT-1 and CT-B, as well as two commercially available Norrish type I photoinitiators, when used alone, are shown in the figure below. Figure 14 As shown in the test results, the orange ketone oxime ester photoinitiator CT-1 described in this invention can effectively initiate the double bond polymerization of the monomer TPGDA under a 385nm LED light source, achieving a final double bond conversion rate of 93% with a very small initiator dosage (0.3wt%). Under the same conditions, the final double bond conversion rates of two commercially available Norrish type I photoinitiators, Irgacure 369 and OXE-01, are 86% and 89%, respectively, lower than that of CT-1. This demonstrates that the orange ketone oxime ester photoinitiator described in this invention can achieve a higher final double bond conversion rate under the same conditions.

[0143] The photoinitiator described in this invention has an oxime ester structural unit, in which the NO bond has a low bond energy and is easily broken after light irradiation. Subsequently, CO2 is released through a decarboxylation reaction, generating a free radical with polymerization initiation activity. CT-1, after photodecarboxylation, generates a methyl free radical to initiate polymerization. To compare the initiation effects of different types of free radicals, the effect of CT-B (which generates a phenyl free radical after photodecarboxylation) on initiating the polymerization of the TPGDA double bond was synthesized and tested. CT-B exhibits a significant redshift in its maximum absorption wavelength and a high molar extinction coefficient at common LED emission wavelengths, but from... Figure 14 As can be seen from the data, under the same initiation conditions as CT-1, the final double bond conversion rate of CT-B was only 83%, which was significantly lower than that of CT-1. This indicates that methyl radicals have a better initiation effect on the acrylate monomer TPGDA than phenyl radicals. Therefore, methyl radicals were used for the design and synthesis of molecules in CT-2 and CT-3.

[0144] A two-component photoinitiating system was constructed by combining CT-1, which exhibits good polymerization initiation effects, with diaryliodomonium salts to investigate the effect of this system on initiating the double bond polymerization of free radical monomers. Tripropylene glycol diacrylate (TPGDA) was used as the monomer, and CT-1 and diphenyliodohexafluorophosphate (IOD) were added to prepare a photosensitive solution. The mass fractions of CT-1 and IOD were 0.3 wt% and 1 wt%, respectively. A photosensitive solution with 1 wt% IOD and no photoinitiator was prepared as a control. A small amount of the photosensitive solution was applied to a potassium bromide plate, and then another potassium bromide plate was used to cover the sample for testing. The sample was irradiated under a 385 nm LED point light source, and the light intensity was determined to be 90 mW·cm using a UV-Vis radiometer. -2 The changes in the double bonds of the polymer monomers were tested and recorded in real time using a real-time infrared spectrometer. The changes were then calculated using 810 cm⁻¹.-1 The change in the area of ​​the infrared characteristic absorption peak of the nearby acrylate double bond characterizes the double bond conversion rate of TPGDA.

[0145] The double bond conversion curve of the monomer TPGDA polymerization initiated by the two-component photoinitiating system composed of the photoinitiator CT-1 and the diaryl iodine salt compound IOD described in this invention is shown in the figure below. Figure 15 As shown in the figure, when a two-component photoinitiation system is formed, the final double bond conversion rate of the radical monomer TPGDA is further improved, increasing from 93% to 97%, and IOD alone cannot quickly and effectively initiate double bond polymerization. This indicates that the synergistic effect of CT-1 and IOD can further enhance the effect of the photoinitiator, initiating the double bond polymerization of radical monomers more quickly and efficiently.

[0146] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A class of orange ketone oxime ester photoinitiators, characterized in that, The general structural formula of the initiator is shown in the following formula (Ⅰ): (Ⅰ) in, R1 is selected from , , One of them; R2 is selected from methyl or phenyl.

2. The photoinitiator according to claim 1, characterized in that: The initiator is selected from one of the following structural formulas: 。 3. The method for preparing the orange ketone oxime ester photoinitiator according to claim 1, characterized in that, Includes the following steps: 3-Benzofurone and a dialdehyde compound react under the action of a catalyst to generate intermediate A with an aldehyde group; intermediate A reacts with hydroxylamine hydrochloride under the action of a base to generate intermediate B with an oxime group; intermediate B reacts with an acyl chloride compound in the presence of an acid-binding agent to generate an orange ketone oxime ester photoinitiator CT.

4. The preparation method according to claim 3, characterized in that, The chemical preparation method of the orange ketone oxime ester photoinitiator includes the following steps: (1) Synthesis of intermediate product A: 3-Benzofurone, a dialdehyde compound, and a catalyst were mixed, and reaction solvent I was added. Under nitrogen protection and in the dark, the mixture was stirred at room temperature until the reaction was complete. The product A was then obtained by filtration, vacuum distillation, and purification. The dialdehyde compound is selected from at least one of terephthalaldehyde, 2,5-dicarboxyfuran, and thiophene-2,5-dicarboxaldehyde; the catalyst is activated alumina; and the reaction solvent I is dichloromethane. The molar ratio of the 3-benzofuranone, the dialdehyde compound, and the catalyst is 1:(1.1-1.3):(4.5-5.5); (2) Synthesis of intermediate product B: Hydroxylamine hydrochloride and an appropriate amount of base were mixed and reaction solvent II was added. After complete dissolution, intermediate product A was added. Under nitrogen protection, the mixture was refluxed and stirred at 85-110℃ until the reaction was complete. Then, intermediate product B was obtained by vacuum distillation, extraction and purification. The alkali is anhydrous sodium acetate; the reaction solvent II is a mixed solvent of ethanol, tetrahydrofuran and water; The molar ratio of intermediate product A, hydroxylamine hydrochloride, and base is 1:(1.5-2.0):(1.5-2.0). (3) Synthesis of CT, a photoinitiator of orange ketone oxime esters: Reaction solvent III was added to intermediate product B. Under nitrogen protection and light protection, an acid-binding agent was slowly added and the reaction was stirred. After stirring, an acyl chloride compound was slowly added under ice bath conditions and the reaction was stirred at room temperature. After the reaction was complete, the crude product was obtained by extraction and vacuum distillation. The crude product was purified by silica gel column chromatography to obtain the orange ketone oxime ester photoinitiator CT. The reaction solvent III is anhydrous dichloromethane; the acid-binding agent is at least one of anhydrous triethylamine and anhydrous pyridine; the acyl chloride compound is at least one of acetyl chloride, benzoyl chloride, and cinnamoyl chloride. The molar ratio of the intermediate product B, the acyl chloride compound, and the acid-binding agent is 1:(1.5-2.0):(1.5-2.0).

5. The application of the orange ketone oxime ester photoinitiator according to claim 1, characterized in that, The applications include biomedicine, photocurable coatings, inks, 3D printing materials, and UV-LED curing systems.

6. The application according to claim 5, characterized in that, (1) The wavelength range of the LED light source used in the curing system is 365-450 nm; (2) The curing system contains at least one compound described by general formula (I) as a photoinitiator; (3) The prepolymer monomer used in the curing system contains at least one unsaturated compound containing an olefin bond.

7. The application according to claim 6, characterized in that, The prepolymer monomer is selected from at least one of tripropylene glycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, and trimethylolpropane triacrylate.

8. The application according to claim 6, characterized in that, When the photoinitiator in the photocuring system is a single component of an orange oxime ester photoinitiator, the mass ratio of the prepolymer monomer to the orange oxime ester photoinitiator is 100:(0.1-1); When the photoinitiator in the photocuring system is a two-component system of orange ketone oxime ester photoinitiator and diaryl iodomonium salt compound, the mass ratio of the prepolymer monomer, orange ketone oxime ester photoinitiator and diaryl iodomonium salt compound is 100:(0.1-1):(0.1-2).

9. The application according to claim 6, characterized in that, The diaryliodomonium salts are selected from at least one of diphenyliodohexafluorophosphate (IOD) and 4,4'-dimethyliodohexafluorophosphate.

Images