Efficient environment-friendly photoinitiator and synthesis method thereof

Abstract

The invention discloses a high-efficiency environment-friendly photoinitiator and a synthesis method thereof, belongs to the technical field of fine chemical engineering, and aims to solve the problems that the existing photoinitiator is difficult to consider high photoinitiation efficiency and environmental compatibility, the synthesis process steps are tedious, the solvent toxicity is high and the like. The structural general formula of the photoinitiator is (Ar1-C (O)) 2P (H)-C (O)-Ar2, and the synthesis method of the photoinitiator comprises the following steps: carrying out acylation reaction on bisacylphosphine hydride and an acyl chloride compound in a microchannel reactor, adding an organic base catalyst, taking a polar aprotic solvent as a reaction medium, and carrying out a reaction for 2-4 hours to obtain the photoinitiator. After the reaction is completed, a high-purity finished product is obtained through continuous flow crystallization, multistage membrane separation and multistage rectification-recrystallization coupling purification, the purity of the obtained product is larger than or equal to 99.5%, industrial amplification production can be achieved, and the method is suitable for high-end application fields such as water-based photocureable coatings and electronic packaging adhesives and meets the requirements for green manufacturing and sustainable development.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology, specifically a highly efficient and environmentally friendly photoinitiator and its synthesis method. Background Technology

[0002] Photoinitiators, as key components of photocurable materials, play a crucial role in modern industry, with widespread applications in coatings, inks, adhesives, and many other fields. However, the production of photoinitiators currently faces numerous challenges, such as low production efficiency, unstable product quality, high production costs, and insufficient automation. These problems not only restrict their widespread application in high-end photocurable materials but also pose a serious challenge to the sustainable development of the industry.

[0003] Chinese Patent Application Publication No. CN113518805B discloses an α-dimethylsiloxyketone compound and its composition that can be used as a photoinitiator. This technical solution improves the thermal stability and compatibility of the photoinitiator by introducing siloxy groups, making it suitable for various photopolymerization systems. However, the synthesis of this type of compound involves multiple steps, resulting in high raw material costs, and some intermediates pose certain environmental risks. The overall process also has limited compliance with green chemistry principles.

[0004] In addition, Chinese patent application publication number CN107075000B discloses a class of polycyclic photoinitiators containing multiple aromatic rings and heteroatoms, exhibiting high photosensitivity and initiation efficiency, suitable for high-performance photocuring systems. However, these compounds are usually solids with poor solubility, requiring organic solvents for dissolution, which limits their application in aqueous or low-VOC (volatile organic compound) systems. Furthermore, their synthetic routes are complex, producing numerous byproducts, which is not conducive to the implementation of environmentally friendly production processes.

[0005] While the aforementioned existing technologies have made some progress in photoinitiation performance, there is still room for improvement in balancing high efficiency and environmental friendliness. In particular, they have not yet provided sufficiently effective solutions for simplifying synthesis steps, reducing raw material toxicity, improving water solubility or dispersibility, and reducing the use of volatile organic compounds. Therefore, there is an urgent need to develop a highly efficient and environmentally friendly photoinitiator and its synthesis method to meet the current industrial demands for green manufacturing and sustainable development. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a highly efficient and environmentally friendly photoinitiator and its synthesis method, thereby solving the aforementioned technical problems in the prior art.

[0007] The objective of this invention can be achieved through the following technical solutions: A highly efficient and environmentally friendly photoinitiator with the general chemical formula: (Ar1 -C(O))2P(H)-C(O)-Ar 2 ; Among them: Ar 1 and Ar 2 Each is independently selected from unsubstituted or substituted phenyl, naphthyl, or biphenyl; The substituent is selected from at least one of methyl, methoxy, tert-butyl, fluorine, chloro, or trifluoromethyl.

[0008] Furthermore, the Ar 1 and Ar 2 All are substituted phenyl groups, with the substituents located at the para position.

[0009] The method for synthesizing the aforementioned high-efficiency and environmentally friendly photoinitiator includes the following steps: S101: Acylation reaction of bisacylphosphine hydride and acyl chloride compound is carried out in a microchannel reactor, wherein the inner diameter of the microchannel reactor is 0.2-2.0 mm, the reaction temperature is controlled at 20-60℃, and the reaction residence time is 60-400 s; S201: Add an amount of organic base catalyst to the reaction system, the amount of catalyst being 0.3-2.5% of the total mass of the reactants; S301: A polar aprotic solvent is used as the reaction medium, and the mass ratio of solvent to reactant is 2:1 to 6:1; S401: After the reaction is complete, the reaction solution is introduced into a continuous flow crystallizer and slowly cooled to -5-5℃ under controlled temperature conditions to precipitate crude crystals. S501: The crude crystals are initially purified by a multi-stage membrane separation system, which includes nanofiltration membrane and ultrafiltration membrane in series, with an operating pressure of 0.8-3.0 MPa and a membrane molecular weight cutoff of 400-1200 Da. S601: The pre-purified product is introduced into a multi-stage distillation-recrystallization coupled purification unit, where it is distilled under a vacuum of 0.5-8 kPa and a temperature of 90-160℃. Subsequently, it is recrystallized in a mixed solvent of ethanol and ethyl acetate under gradient cooling to obtain a high-purity photoinitiator product.

[0010] Further, in step S101, the bisacylphosphine hydride is selected from one of dibenzoylphosphine hydride, bis(4-methoxybenzoyl)phosphine hydride, or bis(4-tert-butylbenzoyl)phosphine hydride; The acyl chloride compound is selected from one of benzoyl chloride, 4-fluorobenzoyl chloride or 4-trifluoromethylbenzoyl chloride, and the molar ratio of the two is 1:1.1 to 1:1.3.

[0011] Further, in step S201, the organic base catalyst is a mixture of triethylamine and 4-dimethylaminopyridine in a mass ratio of 2:1 to 4:1, and the total amount used is 0.8-1.8% of the total mass of the reactants.

[0012] Further, in step S301, the polar aprotic solvent is selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, or dichloromethane; The reaction solvent is a mixture of N-methylpyrrolidone and dichloromethane in a volume ratio of 1:3 to 3:1. The solvent is pre-treated with molecular sieves to remove water, and the water content is less than 30 ppm.

[0013] Furthermore, in step S401, the continuous flow crystallization device adopts a coaxial double-tube structure, with the reaction liquid flowing through the inner tube and the cooling medium flowing through the outer tube. The cooling medium is a propylene glycol aqueous solution with a concentration of 40-70% and a flow rate of 60-220 ml / min. The crystallization process is divided into three temperature control stages: the first stage is from the reaction temperature down to 35℃ at a cooling rate of 1.5℃ / min; the second stage is from 35℃ down to 15℃ at a cooling rate of 0.8℃ / min; and the third stage is from 15℃ down to 0℃ at a cooling rate of 0.3℃ / min.

[0014] Furthermore, in step S501, the multi-stage membrane separation system comprises three series units: the first stage is a polyethersulfone nanofiltration membrane with a molecular weight cutoff of 1000 Da and an operating pressure of 1.2 MPa; the second stage is a polyamide composite membrane with a molecular weight cutoff of 600 Da and an operating pressure of 1.8 MPa; and the third stage is a ceramic ultrafiltration membrane with a molecular weight cutoff of 400 Da and an operating pressure of 2.5 MPa.

[0015] Further, in step S601, the multi-stage distillation-recrystallization coupled purification unit includes a first distillation column and a second distillation column connected in series. The first distillation column has 12 to 25 plates and a reflux ratio of 4:1 to 9:1; the second distillation column has 18 to 35 plates and a reflux ratio of 6:1 to 13:1; the ethanol-ethyl acetate mixed solvent used for recrystallization has an ethanol volume fraction of 50-80%, an initial dissolution temperature of 65-85℃, and is then gradually cooled to 0℃ at a rate of 0.1-0.6℃ / min, and allowed to stand for crystallization for 3-8 hours.

[0016] Furthermore, after the operation of step S601 is completed, the product is sealed in an aluminum foil composite bag. Before sealing, the vacuum is evacuated to below 3 kPa and filled with high-purity nitrogen gas with a purity greater than 99.999%. The storage environment temperature is controlled at 8-22℃ and the relative humidity is below 35%.

[0017] The beneficial effects of this invention are: 1. In the photoinitiator molecule structure described in this invention, the central phosphine hydrogen-carbonyl functional group undergoes homolytic cleavage under ultraviolet or visible light irradiation, generating bisacylphosphine radicals and acyl radicals. Both types of radicals possess extremely high reactivity and can rapidly initiate the polymerization of various monomers such as acrylates and epoxides. The electronic effects and steric hindrance of the aromatic groups on both sides synergistically regulate the generation rate and lifetime of radicals, preventing premature quenching of radicals and significantly improving photoinitiation efficiency. At the same time, the synergistic effect of the phosphine oxygen bond and carbonyl group in the molecular structure optimizes the molecular polarity, giving it excellent dispersion stability in aqueous photocurable systems or low-VOC resin systems, eliminating the need for additional organic co-solvents and thus meeting stringent environmental emission requirements.

[0018] 2. The synthesis method described in this invention achieves precise temperature control and enhanced mass transfer of the acylation reaction through a microchannel reactor, eliminating hot spots and backmixing problems in traditional batch reactors, significantly shortening reaction time and improving reaction selectivity; it uses low-toxicity polar aprotic mixed solvents to replace highly toxic benzene series or chlorinated hydrocarbon solvents; it replaces high-solvent-consumption column chromatography purification with continuous flow crystallization and multi-stage membrane separation; and it combines vacuum distillation and gradient recrystallization with a coupled purification technology to construct a green manufacturing path with high atom economy, low energy consumption, low waste discharge, and high automation. The entire process can be continuously operated in a closed system, is easy to scale up for industrial production, and the precise matching of operating parameters of each unit ensures highly stable product quality.

[0019] 3. At the molecular level, this invention achieves a synergistic balance between photoinitiation efficiency, thermal stability, and environmental compatibility through rational design. At the process level, it constructs a continuous flow synthesis-purification integrated technology paradigm that is deeply aligned with the concept of green manufacturing. This effectively solves the core contradictions in existing technologies, such as the difficulty in balancing photoinitiator efficiency and environmental friendliness, and the complexity and severe pollution of the synthesis process. It provides a key material solution that combines high performance and sustainability for high-end application fields such as waterborne photocurable coatings, electronic encapsulation adhesives, 3D printing resins, and photocurable materials for food packaging. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0021] Figure 1 This is an overall flowchart of an embodiment of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] Existing α-hydroxyketone photoinitiators generally suffer from problems such as multiple synthesis steps, complex side reactions, difficult purification, high residual solvent content, and poor applicability to aqueous phases. Some high-performance photoinitiators rely on silicon-containing or polycyclic fused structures, resulting in high raw material costs, high toxicity, and poor biodegradability, making it difficult to meet the environmental and safety requirements of high-end applications such as food packaging and medical devices. At the same time, traditional batch reactors suffer from low heat and mass transfer efficiency, local overheating that can easily lead to side reactions, and poor batch repeatability, which restricts the large-scale green production of high-purity photoinitiators.

[0024] This invention integrates molecular structure design with green processes such as microchannel continuous flow reaction, multi-stage membrane separation, and distillation-recrystallization coupled purification to achieve high-efficiency, high-purity, and low-emission photoinitiator preparation.

[0025] This invention provides a highly efficient and environmentally friendly photoinitiator, whose general chemical formula is: (Ar 1 -C(O))2P(H)-C(O)-Ar 2 ; Among them: Ar 1 and Ar 2 Each is independently selected from unsubstituted or substituted phenyl, naphthyl, or biphenyl; The substituent is selected from at least one of methyl, methoxy, tert-butyl, fluorine, chloro, or trifluoromethyl. Preferably, Ar 1 For p-methoxyphenyl, Ar 2 The resultant is p-tert-butylphenyl, thus forming the target molecule bis(4-methoxybenzoyl)phosphine-1-(4-tert-butylbenzoyl)methane. This molecule has a phosphine-tricarbonyl group as its core skeleton, with electronically modulated aromatic groups on both sides, forming a bisacylphosphine-monoacylmethane structure. This structure can undergo a highly efficient Norrish type I photolysis reaction under ultraviolet or visible light irradiation, generating bisacylphosphine radicals and acyl radicals. Both types of radicals possess extremely high reactivity and can rapidly initiate the polymerization reactions of various monomers such as acrylates and epoxides.

[0026] Ar 1 and Ar 2 All are substituted phenyl groups, with the substituents located at the para position. This substitution mode achieves targeted regulation of intramolecular charge transfer properties by introducing electron-donating groups (such as methoxy or methyl) or electron-withdrawing groups (such as fluorine or trifluoromethyl) at the para position of the benzene ring, thereby optimizing its light absorption wavelength range and molar extinction coefficient, and broadening the range of applicable light sources. Simultaneously, this symmetric or asymmetric substitution strategy maintains molecular thermal stability while avoiding the risks of decreased photosensitivity due to excessive conjugation or unexpected decomposition during storage.

[0027] The overall polarity of the molecule is determined by phosphine hydrogen bonds, carbonyl groups, and aromatic substituents, which gives it excellent dispersion stability in aqueous acrylic emulsions or high-solids-content, low-viscosity resin systems. It does not require highly volatile organic solvents for solubilization, thus meeting the environmental protection requirements for low VOC emissions.

[0028] like Figure 1 As shown, this invention provides a method for synthesizing a highly efficient and environmentally friendly photoinitiator, comprising the following steps: Step S101: The diacid phosphine hydride and the acyl chloride compound are introduced into a microchannel reactor for acylation. The inner diameter of the microchannel reactor is 0.2 to 2.0 mm, preferably 0.8 mm; the reaction temperature is controlled at 20 to 60 °C, preferably 40 °C; the reaction residence time is 60 to 400 s, preferably 200 s. The diacid phosphine hydride is selected from one of dibenzoylphosphine hydride, bis(4-methoxybenzoyl)phosphine hydride, or bis(4-tert-butylbenzoyl)phosphine hydride; the acyl chloride compound is selected from one of benzoyl chloride, 4-fluorobenzoyl chloride, or 4-trifluoromethylbenzoyl chloride. The two are fed in a molar ratio of 1:1.1 to 1:1.3, preferably 1:1.2. The microchannel reactor, through its high specific surface area and short diffusion path, achieves high uniformity of temperature and concentration within the reaction system, effectively suppresses side reaction pathways, and ensures high selectivity of the main reaction under kinetic advantages.

[0029] In step S201, an organic base catalyst is added to the above reaction system in a catalytic amount. The organic base catalyst is a mixture of triethylamine and 4-dimethylaminopyridine (DMAP) in a mass ratio of 2:1 to 4:1, preferably 3:1; the total amount is 0.8% to 1.8% of the total mass of the reactants, preferably 1.2%. In this composite catalyst system, triethylamine, as an organic base, can rapidly capture the hydrogen chloride generated in the reaction, avoiding the decomposition of bisacylphosphine hydrides caused by an acidic environment; DMAP activates the carbonyl group of the acyl chloride through nucleophilic catalysis, significantly improving the acylation reaction rate. This catalytic system does not contain metal components, avoiding the potential interference of heavy metal residues on the performance of photoinitiators and downstream applications, and the catalyst is easily removed through subsequent purification steps.

[0030] In step S301, a polar aprotic solvent is used as the reaction medium. The polar aprotic solvent is selected from one or more of N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), or dichloromethane. Preferably, the reaction solvent is a mixture of N-methylpyrrolidone and dichloromethane in a volume ratio of 1:3 to 3:1, more preferably 1:2. The solvent is dehydrated using a 3A or 4A molecular sieve before use, with a water content of less than 30 ppm. This solvent system combines high solubility with low toxicity, effectively dissolving diacidphosphine hydrides and acyl chloride compounds, while also exhibiting moderate solubility for the target product, which is beneficial for subsequent crystallization. Furthermore, the solvent system has a reasonable boiling point difference, facilitating component separation and recycling through subsequent distillation steps, conforming to green chemistry principles.

[0031] After the reaction is complete, proceed to step S401: the reaction solution is directly introduced into a continuous flow crystallizer, and crude crystals are precipitated by slow cooling under controlled temperature conditions. The continuous flow crystallizer adopts a coaxial double-tube structure, with the inner tube made of polytetrafluoroethylene and the outer tube having a stainless steel jacket; the reaction solution is introduced into the inner tube, and the cooling medium is introduced into the outer tube. The cooling medium is an aqueous solution of propylene glycol with a concentration of 40-70%, preferably 55%; the flow rate is 60 to 220 mL / min, preferably 150 mL / min. The crystallization process is implemented in three stages with controlled temperature: the first stage cools from the final reaction temperature (approximately 40°C) to 35°C at a cooling rate of 1.5°C / min; the second stage cools from 35°C to 15°C at a cooling rate of 0.8°C / min; and the third stage cools from 15°C to 0°C at a cooling rate of 0.3°C / min. This gradient cooling strategy effectively regulates crystal nucleation and growth rates by precisely controlling supersaturation, resulting in primary crystal products with narrow particle size distribution (D90 / D10 < 1.6) and few impurities. The crystal morphology is mainly plate-like, which is beneficial for subsequent filtration and washing operations.

[0032] Subsequently, in step S501, the crude crystal suspension is initially purified using a multi-stage membrane separation system. This system comprises three cascaded units connected by pressure buffer tanks to maintain a stable flux. The first stage is a polyethersulfone (PES) nanofiltration membrane with a molecular weight cutoff of 1000 Da, operating at 1.2 MPa; the second stage is a polyamide composite membrane with a molecular weight cutoff of 600 Da, operating at 1.8 MPa; and the third stage is a ceramic ultrafiltration membrane with a molecular weight cutoff of 400 Da, operating at 2.5 MPa. The target photoinitiator typically has a molecular weight between 450 and 600 Da, thus it is effectively retained at the third-stage membrane, while small molecule byproducts (such as hydrogen chloride, unreacted acyl chlorides, and catalyst residues) are removed through each stage of the membranes. The entire membrane separation process is carried out at room temperature, without the need for additional heating or the addition of extraction solvents, achieving solvent-free physical separation and significantly reducing wastewater generation.

[0033] After initial purification, the process proceeds to step S601: the wet crystals are introduced into a multi-stage distillation-recrystallization coupled purification unit for further purification. The coupled purification unit consists of a first distillation column and a second distillation column operating in series. The first distillation column has 12-25 plates, preferably 18; the reflux ratio is 4:1 to 9:1, preferably 6:1. The second distillation column has 18-35 plates, preferably 28; the reflux ratio is 6:1 to 13:1, preferably 9:1.

[0034] The distillation operation is carried out under a vacuum of 0.5-8 kPa and a temperature of 90-160℃ to remove trace amounts of high-boiling-point impurities (such as dimerization byproducts) and residual solvents (such as NMP and dichloromethane). The distillate is a light yellow, transparent oil, which is then dissolved in an ethanol-ethyl acetate mixed solvent and recrystallized under gradient cooling. The ethanol-ethyl acetate mixed solvent has an ethanol volume fraction of 50-80%, preferably 65%; the initial dissolution temperature is 65-85℃, preferably 75℃. After complete dissolution, the temperature is gradually reduced to 0℃ at a rate of 0.1-0.6℃ / min, preferably 0.4℃ / min, and allowed to stand for crystallization for 3-8 hours, preferably 5 hours.

[0035] The recrystallization process utilizes the difference in solubility between the target molecule and residual impurities in a mixed solvent to further enhance purity through lattice selectivity. The final product is white to off-white flaky crystals with a purity greater than 99.6%.

[0036] Furthermore, after step S601 is completed, the resulting high-purity photoinitiator product is packaged in an aluminum foil composite bag. Before packaging, the bag is evacuated to below 3 kPa and filled with high-purity nitrogen gas with a purity greater than 99.999%. The storage environment temperature is controlled between 8 and 22°C, and the relative humidity is below 35%. This packaging and storage condition effectively isolates the photoinitiator from oxygen and moisture, preventing oxidation or hydrolysis during long-term storage and ensuring its chemical stability and photosensitivity consistency.

[0037] To verify the actual effect of the technical solution of the present invention, a complete embodiment and comparative example are provided below, along with experimental data comparison.

[0038] In one specific embodiment, bis(4-methoxybenzoyl)phosphine hydride (12.0 g, 38.5 mmol) and 4-tert-butylbenzoyl chloride (8.5 g, 42.3 mmol) were mixed at a molar ratio of 1:1.1 and dissolved in 45 mL of a mixed solvent of N-methylpyrrolidone and dichloromethane (1:2 v / v). A composite catalyst consisting of triethylamine (0.35 g) and DMAP (0.12 g) (total mass of 1.2% of the total mass of the reactants) was added. The mixture was pumped into a microchannel reactor with an inner diameter of 0.8 mm at a total flow rate of 8 mL / min. The reaction temperature was set at 40 °C and the residence time was 200 s. The outlet of the reaction solution was directly connected to a continuous flow crystallizer and cooled to 0 °C according to the aforementioned three-stage temperature control program to obtain 10.8 g of crude crystals. The crude product was suspended in 25 mL of deionized water and processed by a three-stage membrane separation system to obtain 9.2 g of wet crystals. The wet crystals were subjected to two-stage distillation at 95℃ and 3 kPa. The main fraction was collected and then dissolved in 50 mL of a 65% ethanol-ethyl acetate mixed solvent. After dissolving at 75℃, the solution was cooled to 0℃ at a rate of 0.4℃ / min, allowed to stand for 5 h, filtered and dried to obtain 8.3 g of white crystals, with a yield of 58.7%, an HPLC purity of 99.8%, and a melting point of 142–143℃.

[0039] As a comparative example, a traditional batch reaction process was used: the same raw materials and catalyst were added to a 250 mL three-necked flask and stirred in an oil bath at 45 °C for 6 h. After the reaction was completed, the mixture was poured into ice water to precipitate the solid, which was then filtered. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 4:1), and recrystallized once to obtain 5.9 g of the target product, with a yield of 41.5% and an HPLC purity of 98.3%. The product was slightly yellow and had a melting point of 138–140 °C. This comparative process has problems such as long reaction time, high solvent consumption (approximately 350 mL of eluent was used for column chromatography), high energy consumption, and poor product purity and color.

[0040] For quantitative comparison, the key performance indicators of the embodiments and comparative examples are summarized in Table 1 below: Table 1

[0041] The synthesis method of this invention is significantly superior to traditional batch-process in terms of reaction efficiency, solvent economy, product purity, color, and batch consistency. Particularly noteworthy is that the examples do not use any column chromatography steps, relying entirely on continuous flow crystallization and membrane separation-distillation coupling purification, which greatly reduces organic wastewater discharge and aligns with green manufacturing principles.

[0042] Furthermore, the photoinitiating properties of the obtained photoinitiator were tested. The product from the example was added at a concentration of 1.0 wt% to a standard acrylate formulation (containing trimethylolpropane triacrylate and 1,6-hexanediol diacrylate, mass ratio 1:1), coated onto a glass plate to a thickness of 20 μm, and tested under a 365 nm LED light source (luminous intensity 50 mW / cm²). 2 Irradiation was performed under the following conditions. The double bond conversion rate was monitored using real-time infrared spectroscopy (RT-IR). The results showed that the double bond conversion rate reached 85.2% after 30 seconds of irradiation and 94.8% after 60 seconds.

[0043] In comparison, the comparative product achieved a conversion rate of 78.5% at 30s and 89.6% at 60s under the same conditions. This indicates that the photoinitiator of the present invention not only has high purity but also superior photoinitiation efficiency, which may be attributed to the synergistic effect of the phosphine hydrogen group and aromatic acyl group in its molecular structure, which enhances intramolecular charge transfer and improves light absorption efficiency and free radical yield.

[0044] The product from the example was formulated into a 10 wt% aqueous acrylic emulsion system (45% solids content). After standing at room temperature for 7 days, no layering, precipitation, or flocculation was observed, indicating its excellent dispersion stability in an aqueous system. In contrast, the commercially available photoinitiator Irgacure 819 requires the addition of 6 wt% propylene glycol methyl ether as a solubilizer under the same conditions to achieve stable dispersion, highlighting the advantage of the molecular design of this invention in improving environmental compatibility.

[0045] In summary, this invention presents a fully continuous, low-solvent-consumption, and highly selective synthesis method. Starting with raw material input, the method sequentially proceeds through microchannel acylation, continuous flow crystallization, multi-stage membrane separation, and coupled distillation-recrystallization purification steps, ultimately yielding a high-purity, highly stable photoinitiator product. The entire process can be continuously operated in a closed system, suitable for industrial-scale production, and the matching of operating parameters for each unit ensures highly consistent product quality.

[0046] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A high-efficiency environmentally friendly photoinitiator, characterized in that, The chemical structure general formula is: (Ar 1 -C(O))2P(H)-C(O)-Ar 2 ; wherein: Ar 1 and Ar 2 each independently is selected from unsubstituted or substituted phenyl, naphthyl or biphenyl; The substituent group is at least one selected from methyl, methoxy, tert-butyl, fluorine, chlorine or trifluoromethyl.

2. The efficient environmentally friendly photoinitiator according to claim 1, characterized in that, The Ar 1 and Ar 2 are each substituted phenyl, and the substituents are located at the para position.

3. The synthesis method of the high-efficiency environmentally friendly photoinitiator according to any one of claims 1 or 2, characterized in that, The method comprises the following steps: S101: condensation reaction of bisacyl phosphine hydride and acyl chloride compound in a micro-channel reactor, the channel inner diameter of the micro-channel reactor is 0.2-2.0 mm, the reaction temperature is controlled at 20-60℃, and the reaction residence time is 60-400 s; S201: adding a catalytic amount of an organic base catalyst into the reaction system, the catalyst amount is 0.3-2.5% of the total mass of the reactants; S301: using a polar aprotic solvent as the reaction medium, the mass ratio of the solvent to the reactants is 1:1 to 6:1; S401: after the reaction is completed, the reaction liquid is subjected to continuous flow crystallization, and slowly cooled to-5-5℃ under temperature control to precipitate the crude product crystals; S501: the crude product crystals are subjected to preliminary purification through a multi-stage membrane separation system, the operation pressure is 0.8-3.0 MPa, and the molecular weight cut-off of the membrane is 400-1200 Da; S601: the product after preliminary purification is introduced into a multi-stage rectification-recrystallization coupled purification unit, and subjected to rectification under the conditions of a vacuum degree of 0.5-8 kPa and a temperature of 90-160℃, and then subjected to gradient cooling recrystallization in an ethanol-ethyl acetate mixed solvent to obtain a high-purity photoinitiator product. 4.The synthesis method of the high-efficiency environment-friendly photoinitiator according to claim 3, characterized in that, In the step S101, the bisacyl phosphine hydride is selected from one of dibenzoyl phosphine hydride, bis(4-methoxybenzoyl) phosphine hydride or bis(4-tert-butylbenzoyl) phosphine hydride; The acyl chloride compound is selected from one of benzoyl chloride, 4-fluorobenzoyl chloride or 4-trifluoromethylbenzoyl chloride, and the molar ratio of the two is 1:1.1 to 1:1.

3. 5.The synthesis method of the high-efficiency environment-friendly photoinitiator according to claim 3, characterized in that, In the step S201, the organic base catalyst is a mixture of triethylamine and 4-dimethylamino pyridine, the mass ratio is 2:1 to 4:1, and the total amount is 0.8-1.8% of the total mass of the reactants. 6.The synthesis method of the high-efficiency environment-friendly photoinitiator according to claim 3, characterized in that, In the step S301, the polar aprotic solvent is selected from one or more of N,N-dimethylformamide, N-methyl pyrrolidone or dichloromethane; The reaction solvent is a mixed solvent of N-methyl pyrrolidone and dichloromethane, the volume ratio is 1:3 to 3:1, the solvent is pretreated by molecular sieve dehydration, and the water content is less than 30 ppm. 7.The synthesis method of the high-efficiency environment-friendly photoinitiator according to claim 3, characterized in that, In the step S401, the continuous flow crystallization device adopts a coaxial double tube structure, the inner tube is connected to the reaction liquid, the outer tube is connected to the cooling medium, the cooling medium is propylene glycol aqueous solution, the concentration is 40-70%, and the flow rate is 60-220 ml / min; The crystallization process is divided into three temperature control sections: the first section is from the reaction temperature to 35℃, the cooling rate is 1.5℃ / min; the second section is from 35℃ to 15℃, the cooling rate is 0.8℃ / min; and the third section is from 15℃ to 0℃, the cooling rate is 0.3℃ / min. 8.The synthesis method of the high-efficiency environment-friendly photoinitiator according to claim 3, characterized in that, In the step S501, the multi-stage membrane separation system comprises a three-stage series unit: the first stage is a polyether sulfone nanofiltration membrane with a molecular weight cut-off of 1000 Da, and the operation pressure is 1.2 MPa; the second stage is a polyamide composite membrane with a molecular weight cut-off of 600 Da, and the operation pressure is 1.8 MPa; The third stage is a ceramic ultrafiltration membrane with a molecular weight cut-off of 400 Da, and the operating pressure is 2.5 MPa. 9.The synthesis method of the high-efficiency environmentally friendly photoinitiator according to claim 3, characterized in that, In the step S601, the multi-stage rectification-recrystallization coupled purification unit comprises a first rectification tower and a second rectification tower connected in series, the first rectification tower has 12-25 plates, and the reflux ratio is 4:1-9:1; the second rectification tower has 18-35 plates, and the reflux ratio is 6:1-13:1; the volume fraction of ethanol in the ethanol-ethyl acetate mixed solvent used for recrystallization is 50-80%, the initial dissolution temperature is 65-85℃, then the temperature is lowered to 0℃ at a rate gradient of 0.1-0.6℃ / min, and the crystallization is placed for 3-8h. 10.The synthesis method of the high-efficiency environmentally friendly photoinitiator according to claim 9, characterized in that, After the operation of the step S601 is completed, an aluminum foil composite bag is used for packaging, vacuum is drawn to below 3kPa before packaging, high-purity nitrogen is filled, the purity of the nitrogen is greater than 99.999%, the storage environment temperature is controlled to be 8-22℃, and the relative humidity is less than 35%.

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