Process for the preparation of photoinitiator tpo

Abstract

The application discloses a preparation method of a photoinitiator TPO and belongs to the field of photoinitiators. The preparation method of the photoinitiator TPO comprises the following steps: carrying out chlorination reaction on diphenyl phosphoric acid and a chlorinating agent to generate diphenyl phosphinic chloride; carrying out condensation reaction on the diphenyl phosphinic chloride and 2,4,6-trimethylbenzyl magnesium chloride to obtain (2,4,6-trimethylbenzyl) diphenyl phosphine oxide; and carrying out oxidation addition reaction on the (2,4,6-trimethylbenzyl) diphenyl phosphine oxide and an oxidizing agent to obtain the photoinitiator TPO. The diphenyl phosphoric acid originally as solid waste is fully utilized, waste is turned into treasure, energy is fully utilized, environmental protection pressure is reduced, the synthesis mode of the photoinitiator TPO is expanded, and the production cost of the photoinitiator TPO is reduced, and the economic and environmental friendliness of the photoinitiator TPO makes the preparation method convenient for large-scale popularization and application.

Description

Technical Field

[0001] This invention relates to the field of photoinitiators, and particularly to a method for preparing the photoinitiator TPO. Background Technology

[0002] (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TPO) is a highly efficient free radical photoinitiator (TPO for short). It can achieve efficient absorption in a long wavelength range and is widely used in the field of ultraviolet curing.

[0003] Diphenylphosphine chloride is an important intermediate in the production of photoinitiator TPO. Currently, the industrial synthesis method of diphenylphosphine chloride is as follows: phenylphosphine chloride is generated by reacting benzene and phosphorus trichloride under the action of Lewis acid, and then obtained by disproportionation reaction, decomposition with a decomposition agent, and vacuum distillation.

[0004] However, current methods for synthesizing diphenylphosphine chloride produce large amounts of low-purity diphenylphosphine, which is currently treated as solid waste. This not only causes environmental pollution but also increases environmental protection costs. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing the photoinitiator TPO, which can solve the above-mentioned technical problems.

[0006] Specifically, the following technical solutions are included:

[0007] A method for preparing a photoinitiator TPO, the method comprising:

[0008] Diphenylphosphoric acid is reacted with a chlorinating agent to produce diphenylphosphonic chloride;

[0009] The diphenylphosphonic chloride was subjected to a condensation reaction with 2,4,6-trimethylbenzylmagnesium chloride to obtain (2,4,6-trimethylbenzyl)diphenylphosphine oxide;

[0010] The (2,4,6-trimethylbenzyl)diphenylphosphine oxide was subjected to an oxidative addition reaction with an oxidant to obtain the photoinitiator TPO.

[0011] In some possible implementations, the chlorinating agent includes at least one of oxaloyl chloride and thionyl chloride.

[0012] In some possible implementations, the chlorination reaction of diphenylphosphonic acid with a chlorinating agent to generate diphenylphosphonic chloride includes:

[0013] In the presence of a chlorination accelerator, the diphenylphosphoric acid and the chlorinating agent are subjected to the chlorination reaction in a first solvent;

[0014] The chlorination aid includes at least one of N,N-dimethylformamide and N,N-diethylformamide.

[0015] In some possible implementations, the chlorination reaction is carried out at a temperature of 0°C to 120°C.

[0016] In some possible implementations, the 2,4,6-trimethylbenzyl magnesium chloride is prepared by the following method:

[0017] Under anhydrous and oxygen-free conditions, a solution of 2,4,6-trimethylbenzyl chloride was added to a magnesium solution containing an initiator, and after stirring and reaction, the 2,4,6-trimethylbenzyl magnesium chloride was generated.

[0018] In some possible implementations, the initiator includes iodine crystals.

[0019] In some possible implementations, the reaction temperature of the condensation reaction is 0°C-150°C.

[0020] In some possible implementations, the oxidant is sodium periodate.

[0021] In some possible implementations, the oxidative addition reaction of the (2,4,6-trimethylbenzyl)diphenylphosphine oxide with an oxidant includes:

[0022] In the presence of a catalyst, the (2,4,6-trimethylbenzyl)diphenylphosphine oxide is subjected to an oxidative addition reaction with an oxidant.

[0023] In some possible implementations, the catalyst is selected from at least one of ferric chloride, ruthenium chloride, nickel chloride, copper chloride, cuprous chloride and its pyridine mixtures, iodine and its pyridine mixtures, tetraisopropyl titanate, triisopropyl vanadate, acetylacetonate vanadium oxyacetyl ketone, Salen-type copper, Salen-type nickel, Salen-type cobalt, and Salen-type iron.

[0024] The oxidant is selected from at least one of hydrogen peroxide, tert-butyl hydrogen peroxide, oxygen, and air.

[0025] In some possible implementations, the oxidative addition reaction occurs at 0°C-100°C.

[0026] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0027] The method for preparing photoinitiator TPO provided in this invention uses diphenylphosphoric acid as a raw material, and prepares the photoinitiator TPO through a series of chlorination, condensation, and oxidative addition reactions. This method fully utilizes diphenylphosphoric acid, which is originally considered solid waste, turning waste into treasure, achieving full energy utilization, reducing environmental pressure, expanding the synthesis methods of photoinitiator TPO, and reducing the production cost of photoinitiator TPO. Its economic and environmental benefits make this method of preparing photoinitiator TPO suitable for large-scale promotion and application. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The H-NMR spectrum of the photoinitiator TPO prepared in Example 1 provided in this embodiment of the invention;

[0030] Figure 2 The image shows the H-NMR spectrum of the photoinitiator TPO prepared in the comparative example. Detailed Implementation

[0031] To make the technical solutions and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0032] (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TPO) is a highly efficient free radical photoinitiator (TPO for short), which has at least the following advantages:

[0033] (1) The wavelength absorption peaks are at 269nm, 298nm, 379nm, and 393nm, and the absorption wavelength width can reach 430nm, which is particularly suitable for the photocuring of colored systems; (2) Its photolysis products are trimethylbenzoyl free radical and diphenylphosphonyl free radical, both of which are free radicals with high polymerization activity, and the photocuring speed is relatively fast; (3) The absorption wavelength of the photolysis products shifts to short wavelengths, which has a photobleaching effect and is conducive to the transmission of ultraviolet light, and can be used for the curing of thick coatings; (4) It has excellent thermal stability, and no chemical reaction occurs when heated to 180℃, and it has good storage stability; (5) Although it is light yellow, it becomes colorless after photolysis, has a photobleaching effect, and does not yellow; (6) The post-polymerization effect is low and there is no residue; (7) It is widely used in the field of ultraviolet curing, for example, it can be used in ultraviolet curing coatings, printing inks, ultraviolet curing adhesives, optical fiber coatings, photoresists, photopolymer printing plates, stereolithography resins, composite materials, dental fillings, etc.

[0034] Diphenylphosphine chloride is an important intermediate in the production of photoinitiator TPO. Currently, the industrial synthesis method of diphenylphosphine chloride is as follows: phenylphosphine chloride is generated by reacting benzene and phosphorus trichloride under the action of Lewis acid, and then obtained by disproportionation reaction, decomposition with a decomposition agent, and vacuum distillation.

[0035] However, current methods for synthesizing diphenylphosphine chloride produce large amounts of low-purity diphenylphosphine, which is currently treated as solid waste. This not only causes environmental pollution but also increases environmental protection costs.

[0036] The chemical structural formula of diphenylphosphine chloride is shown below:

[0037]

[0038] The chemical structural formula of diphenylphosphoric acid is shown below:

[0039]

[0040] This invention provides a method for preparing a photoinitiator TPO, the method comprising:

[0041] Step 101: React diphenylphosphoric acid with a chlorinating agent to produce diphenylphosphonic chloride.

[0042] The synthetic route for synthesizing diphenylphosphonic chloride from diphenylphosphonic chloride is shown below:

[0043]

[0044] Step 102: Diphenylphosphonic chloride is condensed with 2,4,6-trimethylbenzyl magnesium chloride to obtain (2,4,6-trimethylbenzyl)diphenylphosphine oxide.

[0045] The synthetic route for (2,4,6-trimethylbenzyl)diphenylphosphine oxide is shown below:

[0046]

[0047] Step 103: Perform an oxidative addition reaction between (2,4,6-trimethylbenzyl)diphenylphosphine oxide and an oxidant to obtain the photoinitiator TPO.

[0048] The synthetic route for synthesizing the photoinitiator TPO using (2,4,6-trimethylbenzyl)diphenylphosphine oxide is shown below:

[0049]

[0050] The method for preparing photoinitiator TPO provided in this invention uses diphenylphosphoric acid as a raw material, and prepares the photoinitiator TPO through a series of chlorination, condensation, and oxidative addition reactions. This method fully utilizes diphenylphosphoric acid, which is originally considered solid waste, turning waste into treasure, achieving full energy utilization, reducing environmental pressure, expanding the synthesis methods of photoinitiator TPO, and reducing the production cost of photoinitiator TPO. Its economic and environmental benefits make this method of preparing photoinitiator TPO suitable for large-scale promotion and application.

[0051] The preparation steps described above are further described below:

[0052] For step 101, diphenylphosphoric acid is chlorinated with a chlorinating agent to produce diphenylphosphonic chloride. In some examples, the suitable chlorinating agent includes at least one of oxaloyl chloride (i.e., oxaloyl chloride) and thionyl chloride.

[0053] In some examples, the molar ratio of diphenylphosphonic acid to chlorinating agent is 1:(1-5), more commonly 1:(1-2), and more commonly 1:(1-1.5). Examples include, but are not limited to, 1:1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, and 1:4.5. Within these ranges, the proportion of chlorinating agent not only ensures sufficient reaction with diphenylphosphonic acid but also avoids waste and reduces the need for subsequent evaporation treatment.

[0054] Step 101 involves reacting diphenylphosphonic acid with a chlorinating agent to produce diphenylphosphonic chloride. In some examples, the diphenylphosphonic acid and the chlorinating agent can be reacted directly in a first solvent without the presence of other auxiliaries, such as the chlorinating auxiliaries described below. That is, diphenylphosphonic acid can be reacted with a chlorinating agent to produce diphenylphosphonic chloride even in the absence of chlorinating auxiliaries.

[0055] In other examples, diphenylphosphoric acid is reacted with a chlorinating agent in a first solvent in the presence of a chlorinating accelerator; wherein the chlorinating accelerator includes at least one of N,N-dimethylformamide and N,N-diethylformamide. Using the above-mentioned types of chlorinating accelerators, the chlorination reaction can be catalyzed to increase the reaction rate.

[0056] Based on the above examples, it can be seen that the molar ratio of diphenylphosphonic acid to chlorination auxiliaries is 1:(0-5), further 1:(0-1), and further 1:0.02-0.05. For example, this includes, but is not limited to: 1:0.01, 1:0.015, 1:0.02, 1:0.025, 1:0.03, 1:0.035, 1:0.04, 1:0.045, 1:0.05, 1:0.1, 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.5, etc.

[0057] In some examples, the chlorination reaction temperature is 0℃-120℃, and more specifically 90℃-120℃. For example, this includes, but is not limited to, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, and 120℃. Chlorination reactions within this temperature range not only have a high reaction rate but also result in a relatively mild reaction, strong controllability, and a safer process.

[0058] In some examples, the first solvent suitable for the above chlorination reaction includes, but is not limited to, at least one of the following solvents: toluene, xylene, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, ethylene glycol dimethyl ether, dichloromethane, 1,2-dichloroethane, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, etc.

[0059] The mass of the first solvent is 3 to 10 times the mass of diphenylphosphoric acid, for example, 4, 5, 6, 7, 8, 9 times, etc.

[0060] In some examples, step 101 above may include, but is not limited to, the following operational steps:

[0061] Under room temperature and stirring conditions, diphenylphosphoric acid is added to the first solvent and stirred until homogeneous. Then, chlorinating agent and chlorinating auxiliaries are added until homogeneous. The reaction system is then slowly heated to the set chlorination reaction temperature and refluxed. This reflux reaction is carried out under reflux with stirring for a set time, for example, 5-10 hours.

[0062] After the above reflux reaction is complete, the reaction product system is subjected to vacuum distillation at 40℃~50℃ to remove volatiles, yielding an intermediate product system. The first solvent is then added to the intermediate product system, and vacuum distillation is performed again at 40℃~50℃ (this process can be repeated multiple times) until the residual chlorinating agent is completely separated, yielding high-purity diphenylphosphonic chloride.

[0063] To facilitate the preservation and application of diphenylphosphonic chloride, the diphenylphosphonic chloride obtained above can be stored in tetrahydrofuran solution or toluene solution. For example, it can be stored in tetrahydrofuran solution, which does not require further separation and purification and can be directly used for subsequent condensation reactions.

[0064] In step 102, diphenylphosphonic chloride is condensed with 2,4,6-trimethylbenzyl magnesium chloride to obtain (2,4,6-trimethylbenzyl)diphenylphosphine oxide.

[0065] The chemical structural formula of 2,4,6-trimethylbenzyl magnesium chloride is shown below:

[0066]

[0067] In some examples, 2,4,6-trimethylbenzylmagnesium chloride is prepared by the following method:

[0068] Under anhydrous and oxygen-free conditions, a solution of 2,4,6-trimethylbenzyl chloride is added to a magnesium solution containing an initiator, and after stirring, 2,4,6-trimethylbenzyl magnesium chloride is generated. Exemplarily, the initiator includes iodine crystals as an initiator for the Grignard reaction.

[0069] For example, the synthesis steps of 2,4,6-trimethylbenzyl magnesium chloride are as follows:

[0070] Mix 2,4,6-trimethylbenzyl chloride and tetrahydrofuran to obtain a tetrahydrofuran solution of 2,4,6-trimethylbenzyl chloride; and mix magnesium (e.g., magnesium strips) with tetrahydrofuran to obtain a tetrahydrofuran solution of magnesium.

[0071] An initiator (e.g., 1-2 crystals of iodine of common size) is added to a solution of magnesium in tetrahydrofuran. Then, under anhydrous and oxygen-free conditions, at 40-45°C and with stirring, a solution of 2,4,6-trimethylbenzyl chloride in tetrahydrofuran is slowly added to the solution of magnesium in tetrahydrofuran. The reaction is then stirred for a set time, for example, 5-8 hours, until the magnesium shavings disappear, finally yielding a solution of 2,4,6-trimethylbenzyl magnesium chloride in tetrahydrofuran.

[0072] The tetrahydrofuran solution of 2,4,6-trimethylbenzylmagnesium chloride can be used directly for subsequent condensation reactions without further separation and purification.

[0073] When diphenylphosphonochloride undergoes a condensation reaction with 2,4,6-trimethylbenzylmagnesium chloride, the reaction temperature is -20℃ to 200℃, more specifically 0℃ to 150℃, and even more specifically 50℃ to 70℃, including but not limited to: 50℃, 55℃, 58℃, 60℃, 62℃, 65℃, and 68℃. Within this temperature range, the condensation reaction not only exhibits a high reaction rate but also results in a relatively mild reaction, strong controllability, and a safer reaction process.

[0074] In some examples, the molar ratio of diphenylphosphochloride to 2,4,6-trimethylbenzylmagnesium chloride is 1:1 to 5, and more specifically 1:1 to 2. For example, this includes, but is not limited to, 1:1, 1:1.2, 1:1.5, 1:1.7, 1:2, etc. The ratio of the two is within the above range, which not only ensures that the two react fully and completely, but also avoids additional waste of the reaction raw materials and simplifies the post-processing.

[0075] The condensation reaction is carried out under solvent conditions. In some examples, diphenylphosphochloride is condensed with 2,4,6-trimethylbenzylmagnesium chloride in a second solvent, which includes, but is not limited to, at least one of toluene, xylene, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, ethylene glycol dimethyl ether, dichloromethane, and 1,2-dichloroethane.

[0076] In some examples, the total mass ratio of diphenylphosphochloride and 2,4,6-trimethylbenzylmagnesium chloride to the mass ratio of the second solvent is 1:(1-10), such as including but not limited to: 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc.

[0077] In some examples, step 102 above may include, but is not limited to, the following operational steps:

[0078] Under stirring conditions, a tetrahydrofuran solution of diphenylphosphochloride is slowly added to a tetrahydrofuran solution of 2,4,6-trimethylbenzylmagnesium chloride, raising the temperature of the reaction system to the set condensation reaction temperature, and then refluxing is carried out, for example, for 10-20 hours.

[0079] After the reaction is complete, the reaction product system is cooled to room temperature, and then the pH of the product system is adjusted to neutral using an acid solution (e.g., dilute hydrochloric acid). Tetrahydrofuran is removed by vacuum distillation, and then dichloromethane and water are added (dichloromethane is used to dissolve (2,4,6-trimethylbenzyl)diphenylphosphine oxide, and water is used to dissolve 2,4,6-trimethylbenzyl magnesium chloride). After stirring for a certain period of time, the mixture is allowed to stand and separate into layers. Dichloromethane is removed by vacuum distillation to obtain high-purity (2,4,6-trimethylbenzyl)diphenylphosphine oxide.

[0080] To facilitate the preservation and application of (2,4,6-trimethylbenzyl)diphenylphosphine oxide, the isolated (2,4,6-trimethylbenzyl)diphenylphosphine oxide can be stored in toluene to obtain a toluene solution of (2,4,6-trimethylbenzyl)diphenylphosphine oxide. This solution can be directly used for subsequent oxidative addition reactions without further separation and purification. Toluene was chosen as the solvent for (2,4,6-trimethylbenzyl)diphenylphosphine oxide because it has advantages such as high solubility, high boiling point, insolubility in water, and ease of post-processing.

[0081] For step 103, (2,4,6-trimethylbenzyl)diphenylphosphine oxide and an oxidant are subjected to an oxidative addition reaction to obtain the photoinitiator TPO.

[0082] In some examples, the oxidizing agent is sodium periodate.

[0083] In some examples, (2,4,6-trimethylbenzyl)diphenylphosphine oxide is subjected to an oxidative addition reaction with an oxidant in the presence of a catalyst.

[0084] For example, the catalyst is selected from at least one of ferric chloride, ruthenium chloride, nickel chloride, copper chloride, cuprous chloride and its pyridine mixtures, iodine and its pyridine mixtures, tetraisopropyl titanate, triisopropyl vanadate, acetylacetonate vanadium oxyacetate, Salen-type copper, Salen-type nickel, Salen-type cobalt, and Salen-type iron. The oxidant is selected from at least one of hydrogen peroxide, tert-butyl hydrogen peroxide, oxygen, and air.

[0085] Catalysts and oxidants can exist in the form of a composition, for example, compositions consisting of oxidants and catalysts include, but are not limited to, the following:

[0086] Ferric chloride-hydrogen peroxide, ferric chloride-tert-butyl peroxide, ferric chloride-oxygen, ferric chloride-air, ruthenium chloride-hydrogen peroxide, ruthenium chloride-tert-butyl peroxide, ruthenium chloride-oxygen, ruthenium chloride-air, nickel chloride-hydrogen peroxide, nickel chloride-tert-butyl peroxide, nickel chloride-oxygen, nickel chloride-air, copper chloride-hydrogen peroxide, copper chloride-tert-butyl peroxide, copper chloride-oxygen, copper chloride-air, cuprous chloride-hydrogen peroxide, chlorine Cuprous chloride-tert-butyl hydrogen peroxide, cuprous chloride-oxygen, cuprous chloride-air, cuprous chloride-pyridine-hydrogen peroxide, cuprous chloride-pyridine-tert-butyl hydrogen peroxide, cuprous chloride-pyridine-oxygen, cuprous chloride-pyridine-air, iodine-pyridine-hydrogen peroxide, iodine-pyridine-tert-butyl hydrogen peroxide, iodine-pyridine-oxygen, iodine-pyridine-air, tetraisopropyl titanate-hydrogen peroxide, tetraisopropyl titanate-tert-butyl hydrogen peroxide, tetraisopropyl titanate-oxygen Tetraisopropyl titanate-air, triisopropyl vanadate-hydrogen peroxide, triisopropyl vanadate-tert-butyl hydrogen peroxide, triisopropyl vanadate-oxygen, triisopropyl vanadate-air, acetylacetone vanadium oxy-hydrogen peroxide, acetylacetone vanadium oxy-tert-butyl hydrogen peroxide, acetylacetone vanadium oxy-oxygen, acetylacetone vanadium oxy-air, Salen-type copper-hydrogen peroxide, Salen-type copper-tert-butyl hydrogen peroxide, Salen-type copper-oxygen, Salen-type copper-air, Salen-type nickel-hydrogen peroxide, Salen-type nickel-tert-butyl hydrogen peroxide, Salen-type nickel-oxygen, Salen-type nickel-air, Salen-type cobalt-hydrogen peroxide, Salen-type cobalt-tert-butyl hydrogen peroxide, Salen-type cobalt-oxygen, Salen-type cobalt-air, Salen-type iron-hydrogen peroxide, Salen-type iron-tert-butyl hydrogen peroxide, Salen-type iron-oxygen, Salen-type iron-air, etc.

[0087] The oxidant can be selected from sodium periodate or used in combination with the above-mentioned catalyst, both of which can promote the above-mentioned oxidation reaction to proceed fully and efficiently.

[0088] In some examples, the oxidative addition reaction temperature is 0℃-100℃, and more specifically 50℃-80℃, including but not limited to: 50℃, 55℃, 58℃, 60℃, 62℃, 65℃, 68℃, 70℃, 75℃, etc. Oxidative addition reactions within this temperature range not only have high reaction rates but also result in milder reactions, greater controllability, and a safer reaction process.

[0089] In some examples, the molar ratio of (2,4,6-trimethylbenzyl)diphenylphosphine oxide to the oxidant is 1:(1-10), and more commonly 1:(1-5). Examples include, but are not limited to, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, and 1:10. Maintaining this ratio within the above range ensures a full and complete reaction without causing additional waste of reactants, thus simplifying the post-processing.

[0090] The molar amount of the catalyst is 1%-5% of the molar amount of (2,4,6-trimethylbenzyl)diphenylphosphine oxide, including but not limited to 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, etc.

[0091] The oxidative addition reaction is carried out under solvent conditions. In some examples, (2,4,6-trimethylbenzyl)diphenylphosphine oxide and an oxidant are condensed in a third solvent, which includes, but is not limited to, at least one of toluene, o-xylene, m-xylene, p-xylene, chlorobenzene, tetrahydrofuran, 2-methyltetrahydrofuran, dichloromethane, 1,2-dichloroethane, acetonitrile, propionitrile, methyl tert-butyl ether, isopropyl ether, dioxane, ethylene glycol dimethyl ether, methanol, ethanol, isopropanol, and water.

[0092] In some examples, the total mass ratio of (2,4,6-trimethylbenzyl)diphenylphosphine oxide and oxidant to the mass ratio of the third solvent is 1:(1-10), such as including but not limited to: 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc.

[0093] In some examples, step 103 above may include, but is not limited to, the following operational steps:

[0094] An oxidant was added to a toluene solution of (2,4,6-trimethylbenzyl)diphenylphosphine oxide at room temperature with stirring, and the mixture was stirred until homogeneous. The reaction system was heated to the set oxidative addition reaction temperature, and the reaction was stirred for a set time (e.g., 8-15 hours). After the reaction was complete, the reaction product system was cooled to room temperature and filtered. The filter cake was then recrystallized (e.g., using toluene) and vacuum dried to obtain the photoinitiator TPO.

[0095] Some specific embodiments of the present invention will be described in more detail below. While specific embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0096] Example 1

[0097] This embodiment 1 provides a photoinitiator TPO, the preparation method of which is shown below:

[0098] (1-1) The synthetic route and steps for preparing diphenylphosphochloride are shown below:

[0099]

[0100] (1) Under stirring conditions at room temperature, 110 g of diphenylphosphoric acid was added to 500 mL of toluene and stirred evenly. Then, 90 g of thionyl chloride and 1 g of N,N-dimethylformamide were added. The temperature was slowly raised to 100 °C and refluxed. The reaction was stirred under reflux for 6 hours.

[0101] (2) The above reaction product system was subjected to vacuum distillation at 45°C to remove volatiles. Then, 500 mL of toluene was added to the reaction product system, and vacuum distillation was carried out again at 45°C to completely remove residual thionyl chloride, so as to obtain diphenylphosphine chloride.

[0102] (3) Add 500 mL of tetrahydrofuran to diphenylphosphine chloride to obtain a tetrahydrofuran solution of diphenylphosphine chloride. This tetrahydrofuran solution of diphenylphosphine chloride does not need to be separated and purified, and can be used directly for subsequent condensation reactions.

[0103] (1-2) Preparation of (2,4,6-trimethylbenzyl)diphenylphosphine oxide

[0104] The synthetic route and steps for (2,4,6-trimethylbenzyl)diphenylphosphine oxide are shown below:

[0105]

[0106] (1) Mix 100 g of 2,4,6-trimethylbenzyl chloride with 100 mL of tetrahydrofuran to obtain a tetrahydrofuran solution of 2,4,6-trimethylbenzyl chloride; and mix 15 g of magnesium strip with 200 mL of tetrahydrofuran to obtain a tetrahydrofuran solution of magnesium.

[0107] Add 1-2 iodine crystals to a magnesium tetrahydrofuran solution, and then slowly add a 2,4,6-trimethylbenzyl chloride tetrahydrofuran solution to the magnesium tetrahydrofuran solution under anhydrous, oxygen-free, 40-45°C and stirring conditions. Stir the reaction for 6 hours until the magnesium shavings disappear, and finally obtain a 2,4,6-trimethylbenzyl magnesium chloride tetrahydrofuran solution.

[0108] (2) Under stirring conditions, the prepared tetrahydrofuran solution of diphenylphosphine chloride was slowly added to the tetrahydrofuran solution of 2,4,6-trimethylbenzyl magnesium chloride, and the temperature of the reaction system was raised to 60°C. Then the reaction was refluxed for 16 hours, wherein the molar ratio of diphenylphosphine chloride to 2,4,6-trimethylbenzyl magnesium chloride was 1:1.5.

[0109] (3) After the reaction is complete, the reaction product system is cooled to room temperature. The pH of the product system is adjusted to neutral using dilute hydrochloric acid. Tetrahydrofuran is removed by vacuum distillation. Then, 300 mL of dichloromethane and 100 mL of water are added. After stirring for a certain period of time, the mixture is allowed to stand and separate into layers. Dichloromethane is removed by vacuum distillation to obtain high-purity (2,4,6-trimethylbenzyl)diphenylphosphine oxide.

[0110] (4) Add 300 mL of toluene to (2,4,6-trimethylbenzyl)diphenylphosphine oxide to obtain a toluene solution of (2,4,6-trimethylbenzyl)diphenylphosphine oxide, which does not require further separation and purification and can be directly used for subsequent oxidation reactions.

[0111] (1-3) Preparation of photoinitiator TPO

[0112] The synthetic route and steps of the photoinitiator TPO are shown below:

[0113]

[0114] (1) Under room temperature and stirring conditions, an oxidant was added to a toluene solution of (2,4,6-trimethylbenzyl)diphenylphosphine oxide and stirred until homogeneous. The combination of oxidant and catalyst consisted of 5 g of vanadium acetylacetonate (IV) and 64 g of an aqueous solution of 70% tert-butyl hydroperoxide; the molar ratio of (2,4,6-trimethylbenzyl)diphenylphosphine oxide to oxidant was 1:2.5.

[0115] (2) Heat the reaction system to 50°C and stir for 10 hours. After the reaction is complete, cool the reaction product system to room temperature and filter it. Use 150 ml of toluene to recrystallize the filter cake and then vacuum dry it at 50°C for 6 hours to prepare the photoinitiator TPO.

[0116] The prepared photoinitiator TPO was tested and found to be a white solid with a mass of 141 grams, a purity of over 99%, and a yield of over 77%.

[0117] Example 2

[0118] This embodiment 2 provides a photoinitiator TPO, the preparation method of which is shown below:

[0119] (1-1) The synthetic route and steps for preparing diphenylphosphochloride are shown below:

[0120]

[0121] (1) Under stirring conditions at room temperature, 59 g of diphenylphosphoric acid was added to 300 mL of dioxane and stirred evenly. Then, 52 g of oxaloyl chloride and 1 g of N,N-dimethylformamide were added. The temperature was slowly raised to 100 °C and refluxed. The reaction was stirred under reflux for 7 hours.

[0122] (2) The above reaction product system was subjected to vacuum distillation at 50°C to remove volatiles. Then, 300 mL of toluene was added to the reaction product system, and vacuum distillation was carried out again at 50°C to completely remove residual thionyl chloride, so as to obtain diphenylphosphine chloride.

[0123] (3) Add 250 mL of tetrahydrofuran to diphenylphosphine chloride to obtain a tetrahydrofuran solution of diphenylphosphine chloride. This tetrahydrofuran solution of diphenylphosphine chloride does not need to be separated and purified, and can be used directly for subsequent condensation reactions.

[0124] (1-2) Preparation of (2,4,6-trimethylbenzyl)diphenylphosphine oxide

[0125] The synthetic route and steps for (2,4,6-trimethylbenzyl)diphenylphosphine oxide are shown below:

[0126]

[0127] (1) Mix 54 g of 2,4,6-trimethylbenzyl chloride with 100 mL of tetrahydrofuran to obtain a tetrahydrofuran solution of 2,4,6-trimethylbenzyl chloride; and mix 8 g of magnesium strip with 100 mL of tetrahydrofuran to obtain a tetrahydrofuran solution of magnesium.

[0128] Add 1-2 iodine crystals to a magnesium tetrahydrofuran solution, and then slowly add a 2,4,6-trimethylbenzyl chloride tetrahydrofuran solution to the magnesium tetrahydrofuran solution under anhydrous, oxygen-free, 45°C and stirring conditions. Stir the reaction for 6 hours until the magnesium shavings disappear, and finally obtain a 2,4,6-trimethylbenzyl magnesium chloride tetrahydrofuran solution.

[0129] (2) Under stirring conditions, the prepared tetrahydrofuran solution of diphenylphosphochloride was slowly added to the tetrahydrofuran solution of 2,4,6-trimethylbenzyl magnesium chloride, so that the temperature of the reaction system was raised to 70°C, and then refluxed for 16 hours, wherein the molar ratio of diphenylphosphochloride to 2,4,6-trimethylbenzyl magnesium chloride was 1:2.

[0130] (3) After the reaction is complete, the reaction product system is cooled to room temperature. The pH of the product system is adjusted to neutral by dilute hydrochloric acid. Tetrahydrofuran is removed by vacuum distillation. Then, 200 mL of dichloromethane and 100 mL of water are added. After stirring for a certain period of time, the mixture is allowed to stand and separate into layers. Dichloromethane is removed by vacuum distillation to obtain high-purity (2,4,6-trimethylbenzyl)diphenylphosphine oxide.

[0131] (4) Add 200 mL of toluene to (2,4,6-trimethylbenzyl)diphenylphosphine oxide to obtain a toluene solution of (2,4,6-trimethylbenzyl)diphenylphosphine oxide, which does not require further separation and purification and can be used directly for subsequent oxidation reactions.

[0132] (1-3) Preparation of photoinitiator TPO

[0133] The synthetic route and steps of the photoinitiator TPO are shown below:

[0134]

[0135] (1) Under room temperature and stirring conditions, an oxidant was added to a toluene solution of (2,4,6-trimethylbenzyl)diphenylphosphine oxide and stirred until homogeneous. The combination of oxidant and catalyst consisted of 630 mg of iodine, 200 mg of pyridine, and 60 g of an aqueous solution of 70% tert-butyl hydroperoxide; the molar ratio of (2,4,6-trimethylbenzyl)diphenylphosphine oxide to oxidant was 1:4.

[0136] (2) Heat the reaction system to 80°C and stir for 12 hours. After the reaction is complete, cool the reaction product system to room temperature and filter it. Recrystallize the filter cake with 100 ml of toluene and then vacuum dry it at 50°C for 6 hours to prepare the photoinitiator TPO.

[0137] The prepared photoinitiator TPO was tested and found to be a white solid with a mass of 76 grams, a purity of over 99%, and a yield of over 75%.

[0138] Comparative Example

[0139] The comparative example provides a method for preparing the photoinitiator TPO that has been disclosed in the prior art. The synthetic route and synthetic steps are shown below:

[0140]

[0141] Under stirring conditions at room temperature, 200 ml of toluene, 22 g of diphenylphosphine chloride, 13 g of N,N-dimethylaniline, and 4 g of methanol were added to a reaction flask and stirred for 4 hours to obtain methyl diphenylphosphite. Methyl diphenylphosphite was not further processed. Then, 20 g of 2,4,6-trimethylbenzoyl chloride was added to the reaction flask, and the reaction was continued with stirring for 10 hours. After the reaction was complete, the mixture was filtered and washed with water to obtain an organic layer. Toluene was removed from the organic layer by vacuum distillation to obtain an oily substance. The oily substance was recrystallized from 100 ml of isopropyl ether to prepare 25 g of a white solid, which was the photoinitiator TPO.

[0142] Depend on Figure 1 and Figure 2 It can be seen that the chemical structural formulas of the compounds prepared in Example 1 and the comparative example are the same, which indicates that the photoinitiator TPO was successfully prepared using the method provided in the examples of the present invention. Furthermore, the prepared photoinitiator TPO has high purity and high yield, which is convenient for large-scale promotion and application.

[0143] The above description is merely for the purpose of enabling those skilled in the art to understand the technical solutions of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a photoinitiator TPO, characterized in that, The preparation method of the photoinitiator TPO includes: Diphenylphosphoric acid is reacted with a chlorinating agent to produce diphenylphosphonic chloride; The diphenylphosphonic chloride was subjected to a condensation reaction with 2,4,6-trimethylbenzylmagnesium chloride to obtain (2,4,6-trimethylbenzyl)diphenylphosphine oxide; The (2,4,6-trimethylbenzyl)diphenylphosphine oxide was subjected to an oxidative addition reaction with an oxidant to obtain the photoinitiator TPO.

2. The method for preparing the photoinitiator TPO according to claim 1, characterized in that, The chlorinating agent is selected from at least one of oxalyl chloride and thionyl chloride.

3. The method for preparing the photoinitiator TPO according to claim 1, characterized in that, The process of reacting diphenylphosphonic acid with a chlorinating agent to produce diphenylphosphonic chloride includes: In the presence of a chlorination accelerator, the diphenylphosphoric acid and the chlorinating agent are subjected to the chlorination reaction in a first solvent; The chlorination aid is selected from at least one of N,N-dimethylformamide and N,N-diethylformamide.

4. The method for preparing the photoinitiator TPO according to claim 1, characterized in that, The chlorination reaction is carried out at a temperature of 0℃-120℃.

5. The method for preparing the photoinitiator TPO according to claim 1, characterized in that, The 2,4,6-trimethylbenzyl magnesium chloride was prepared by the following method: Under anhydrous and oxygen-free conditions, a solution of 2,4,6-trimethylbenzyl chloride was added to a magnesium solution containing an initiator, and after stirring and reaction, the 2,4,6-trimethylbenzyl magnesium chloride was generated.

6. The method for preparing the photoinitiator TPO according to claim 5, characterized in that, The initiator is selected from iodine crystals.

7. The method for preparing the photoinitiator TPO according to claim 1, characterized in that, The reaction temperature for the condensation reaction is 0℃-150℃.

8. The method for preparing the photoinitiator TPO according to any one of claims 1-7, characterized in that, The oxidant is sodium periodate.

9. The method for preparing the photoinitiator TPO according to any one of claims 1-7, characterized in that, The step of causing the (2,4,6-trimethylbenzyl)diphenylphosphine oxide to undergo an oxidative addition reaction with an oxidant includes: In the presence of a catalyst, the (2,4,6-trimethylbenzyl)diphenylphosphine oxide is subjected to an oxidative addition reaction with an oxidant.

10. The method for preparing the photoinitiator TPO according to claim 9, characterized in that, The catalyst is selected from at least one of ferric chloride, ruthenium chloride, nickel chloride, copper chloride, cuprous chloride and its pyridine mixture, iodine and its pyridine mixture, tetraisopropyl titanate, triisopropyl vanadate, acetylacetonate vanadium oxyacetyl ketone, Salen-type copper, Salen-type nickel, Salen-type cobalt, and Salen-type iron. The oxidant is selected from at least one of hydrogen peroxide, tert-butyl hydrogen peroxide, oxygen, and air.

11. The method for preparing the photoinitiator TPO according to claim 9, characterized in that, The reaction temperature for the oxidative addition reaction is 0℃-100℃.

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