A method for continuously preparing a photoinitiator using a microreactor

Abstract

This invention discloses a method for the continuous preparation of photoinitiators using a microreactor, comprising the following steps: Step 1: Under ultrasonic vibration and light-protected conditions, a pump continuously delivers the initiator raw material solution and acyl chloride dilution solution from two ports of a T-shaped tee into the T-shaped tee to achieve mixing of the raw materials; Step 2: After the initiator raw material solution and acyl chloride dilution solution are mixed in the T-shaped tee, they flow out from the third port of the T-shaped tee and enter a microchannel to continue the reaction for a period of time; Step 3: After the microchannel stabilizes, the photoinitiator product is collected at the outlet of the microchannel. This invention also discloses a microreactor for the continuous preparation of photoinitiators. This invention enables the continuous preparation of the photoinitiator HMEM, effectively overcoming the problems existing in batch synthesis and its industrial scale-up, and significantly improving production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of microreactor technology, specifically, it is a method for the continuous preparation of photoinitiators using a microreactor. Background Technology

[0002] Photopolymerization refers to the rapid polymerization of monomers or prepolymers into macromolecules under the radiation of light (ultraviolet, visible light, etc.). It is now widely used in UV coatings, inks, adhesives, photosensitive printing plates, photoresists, and photo-rapid prototyping materials. Photoinitiators are important components of photopolymerization systems; they are compounds that can absorb light energy of a certain wavelength, undergo excitation transitions to an excited state, generate free radical reactive intermediates, and thus further initiate monomer polymerization.

[0003] In 1999, Guo Xuhong first achieved the preparation of nanospherical polyelectrolyte brushes by photoemulsion polymerization in Germany. The photoinitiator HMEM was attached to the surface of polystyrene core and the monomer was polymerized in situ under ultraviolet light to form nanospherical polyelectrolyte brushes. Spherical polystyrene-based polyacrylic acid brushes with a size of 100-200 nm were synthesized.

[0004] Currently, the most mature method for preparing the photoinitiator HMEM is carried out in a closed reactor, which is an indirect preparation method. This involves adding the initiator raw materials and catalyst to a closed reactor, slowly adding acyl chloride dropwise, and stirring the reaction for a certain period to obtain the photoinitiator. However, this preparation method still has some insurmountable problems: First, the traditional dropwise addition method suffers from localized overheating, requiring a low-temperature environment to ensure the conversion rate of the photoinitiator, making it difficult to directly scale up to industrial production; second, the reaction time required in the traditional closed batch reactor is long, making it difficult to achieve large-scale continuous production.

[0005] In recent years, the country has placed increasing emphasis on environmental protection and safe production, making the research and development of clean, environmentally friendly, and safe chemical processes crucial. Advanced processes require equipment with advanced concepts to achieve their realization. Microreactors are a new type of equipment developed in recent years for chemical synthesis. Microreactors possess excellent heat and mass transfer capabilities, enabling rapid and uniform mixing of materials and efficient heat transfer. Therefore, many reactions that cannot be achieved in conventional reactors can be realized in microreactors. Utilizing this emerging technology to achieve continuous production of photoinitiators not only improves production efficiency but also ensures process controllability, possessing significant research value and economic benefits. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for the continuous preparation of photoinitiators using microreactors, thereby solving the current challenge of continuous production of photoinitiators.

[0007] To achieve the above objectives, a first aspect of the present invention provides a method for continuously preparing a photoinitiator, comprising the following steps:

[0008] Step 1: Under ultrasonic vibration and light-protected conditions, the initiator raw material solution and acyl chloride dilution solution in the raw material container are continuously pumped into the T-shaped tee from the two ports to achieve mixing of the raw materials;

[0009] Step 2: After the initiator raw material solution and the acyl chloride dilution solution are mixed in the T-shaped tee, they flow out from the third port of the T-shaped tee and enter the microchannel to continue the reaction for a period of time;

[0010] Step 3: After the microchannel has stabilized, collect the photoinitiator product at the outlet of the microchannel;

[0011] In step 1, a catalyst is added to the initiator raw material solution, and the catalyst is pyridine.

[0012] According to the present invention, the initiator raw material is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone (HMP), and the acyl chloride is methacryloyl chloride.

[0013] Furthermore, the initiator feed solution mentioned in step 1 is prepared by diluting HMP to 0.24 mol / L using acetone as a solvent;

[0014] Furthermore, the acyl chloride diluent mentioned in step 1 is prepared by diluting the acyl chloride to 0.58–0.72 mol / L using acetone as a solvent.

[0015] According to the present invention, the amount of pyridine catalyst added is 240% to 300% of the amount of HMP.

[0016] Preferably, the flow rate ratio of the initiator raw material solution and the acyl chloride dilution solution in step 1 is 1:1.

[0017] Preferably, the total flow rate of the reaction solution in step 1 is 1 to 2 mL / min.

[0018] A second aspect of the present invention provides a microreactor for the continuous preparation of photoinitiators, comprising:

[0019] The pump is used to continuously and quantitatively deliver the initiator raw material solution and the acyl chloride dilution solution stored in the raw material container to the T-shaped tee;

[0020] The T-shaped tee has two of its three ports connected to containers storing the initiator raw material solution and the acyl chloride dilution solution via pipelines, while the third port is connected to a microchannel.

[0021] The microchannel is connected at one end to the third interface of the T-shaped tee, and at the other end to the product's outlet.

[0022] The T-shaped tee and microchannel are both placed in an ultrasonic water tank, and the entire microreactor is protected from light.

[0023] Furthermore, the inner diameter of the microchannel is 0.5–2 mm, and the length is 0.5–25 m.

[0024] Furthermore, the inner diameter of the T-shaped tee is 0.5–5 mm.

[0025] The present invention has the following beneficial effects:

[0026] 1. This invention provides a photoinitiator prepared according to the above preparation method, wherein the conversion rate of the photoinitiator is 27.7% to 35.8%. The conversion rate and yield of the photoinitiator can be controlled by adjusting the inner diameter and length of the pipe in the microreactor and the reaction residence time, exhibiting good controllability.

[0027] 2. Compared with batch reactors, this invention enables continuous preparation of the photoinitiator HMEM, effectively overcoming the problems existing in batch synthesis and its industrial scale-up, and significantly improving production efficiency. By using microfluidics for mixing and reaction in a microreactor, heat control and a simplified reaction environment are achieved, along with continuous production, while ensuring the controllability and safety of the production process. This simple and efficient preparation method helps to facilitate the large-scale continuous production of photoinitiators. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the microreactor used in this invention. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. It should be understood that the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of the present invention.

[0030] The microreactor used in this invention for preparing photoinitiators is as follows: Figure 1 As shown, it includes:

[0031] Pump 1 is used to continuously and quantitatively deliver the initiator raw material solution and acyl chloride dilution solution stored in the raw material container to the T-shaped tee 2;

[0032] The T-shaped tee 2 has two of its three ports connected to containers storing the initiator raw material solution and the acyl chloride dilution solution respectively via pipelines, and the third port is connected to the microchannel 3;

[0033] Microchannel 3 is connected at one end to the third interface of the T-shaped tee 2, and at the other end is the product outlet.

[0034] The T-shaped tee 2 and the microchannel 3 are both placed in the ultrasonic water tank 4, and the entire microreactor is protected from light.

[0035] Preferably, the inner diameter of the T-shaped tee 2 is 0.5–5 mm. The inner diameter of the microchannel 3 is 0.5–2 mm, and its length is 0.5–25 m.

[0036] The principle of the microreactor device of the present invention for preparing photoinitiators is as follows:

[0037] Pump 1 delivers the initiator raw material solution and acyl chloride dilution solution from the raw material container into the T-shaped tee 2 through the two ports of the T-shaped tee 2 for mixing. Then, the mixture enters the microchannel 3 through the third port of the T-shaped tee 2 for reaction, and the reaction product flows out from the other end of the microchannel 3.

[0038] The T-shaped channel 2 and microchannel 3 of this microreactor device need to be placed in the ultrasonic water tank 4. This is because the reaction will produce a certain amount of white precipitate, and the accumulation of precipitate may cause blockage of the pipeline. Ultrasonic vibration can prevent the precipitate from clumping and clear the pipeline. Therefore, placing the T-shaped channel 2 and microchannel 3 in the ultrasonic water tank 4 can ensure the normal operation of the microreactor and ensure the safety of the production process.

[0039] When preparing the photoinitiator, turn on the ultrasonic vibration, start the pump to feed, and after the inside of the microreactor is stable, collect the photoinitiator product at the outlet of microchannel 2.

[0040] In this invention, the initiator raw material is HMP, and the acyl chloride is methacryloyl chloride. The photoinitiator is prepared using pyridine as a catalyst. The hydroxyl group of HMP reacts with methacryloyl chloride via a Schotten-Baumann reaction to introduce a terminal double bond, thereby synthesizing the photoinitiator HMEM. The chemical reaction formula for preparing the photoinitiator is as follows:

[0041] Preferably, the initiator raw material solution is prepared by diluting the raw material HMP to 0.24 mol / L with acetone as the solvent; the acyl chloride dilution solution is prepared by diluting the acyl chloride to 0.58-0.72 mol / L with acetone as the solvent.

[0042] Preferably, the amount of pyridine catalyst added is 240% to 300% of the molar amount of the HMP. Pyridine is used as a catalyst because, as an organic base, it can neutralize the hydrogen chloride produced in the reaction, thereby helping to improve the conversion rate of the photoinitiator.

[0043] Preferably, the flow rate ratio of the initiator raw material solution to the acyl chloride dilution solution is 1:1; the total flow rate of the reaction solution is 1-2 mL / min.

[0044] Example 1

[0045] The initiator raw material HMP was diluted with acetone to 0.24 mol / L, and then a certain amount of pyridine (240% of the HMP volume) was added. Acyl chloride was diluted with acetone to 0.58 mol / L and pumped into a T-type tee. The materials were mixed using a T-type tee with an inner diameter of 3.2 mm. The microchannel used had an inner diameter of 1.6 mm, a length of 5 m, and a total microchannel volume of 10 mL. The two materials were fed and mixed at a 1:1 flow ratio, with a total reaction flow rate of 2.0 mL / min and a reaction residence time of 5 min. The product was collected at the microchannel outlet.

[0046] The collected products were analyzed using liquid chromatography to detect the reaction products, and the calculated reaction conversion rate was 29.6%.

[0047] Example 2

[0048] The initiator raw material HMP was diluted with acetone to 0.24 mol / L, and then a certain amount of pyridine (260% of the HMP volume) was added. Acyl chloride was diluted with acetone to 0.62 mol / L and pumped into a T-type tee. The materials were mixed using a T-type tee with an inner diameter of 3.2 mm. The microchannel used had an inner diameter of 1.6 mm, a length of 5 m, and a total microchannel volume of 10 mL. The two materials were fed and mixed at a 1:1 flow ratio, with a total reaction flow rate of 2.0 mL / min and a reaction residence time of 5 min. The product was collected at the microchannel outlet.

[0049] The collected products were analyzed using liquid chromatography to detect the reaction products, and the calculated reaction conversion rate was 35.8%.

[0050] Example 3

[0051] The initiator raw material HMP was diluted with acetone to 0.24 mol / L, and then a certain amount of pyridine (280% of the HMP volume) was added. Acyl chloride was diluted with acetone to 0.67 mol / L and pumped into a T-type tee. The materials were mixed using a T-type tee with an inner diameter of 3.2 mm. The microchannel used had an inner diameter of 1.6 mm, a length of 5 m, and a total microchannel volume of 10 mL. The two materials were fed and mixed at a 1:1 flow ratio, with a total reaction flow rate of 2.0 mL / min and a reaction residence time of 5 min. The product was collected at the microchannel outlet.

[0052] The collected products were analyzed using liquid chromatography to detect the reaction products, and the calculated reaction conversion rate was 32.3%.

[0053] Example 4

[0054] The initiator raw material HMP was diluted with acetone to 0.24 mol / L, and then a certain amount of pyridine (300% of the HMP volume) was added. Acyl chloride was diluted with acetone to 0.72 mol / L and pumped into a T-type tee. The materials were mixed using a T-type tee with an inner diameter of 3.2 mm. The microchannel used had an inner diameter of 1.6 mm, a length of 5 m, and a total microchannel volume of 10 mL. The two materials were fed and mixed at a 1:1 flow ratio, with a total reaction flow rate of 2.0 mL / min and a reaction residence time of 5 min. The product was collected at the microchannel outlet.

[0055] The collected products were analyzed using liquid chromatography to detect the reaction products, and the calculated reaction conversion rate was 27.7%.

[0056] Example 5

[0057] The initiator raw material HMP was diluted with acetone to 0.24 mol / L, and then a certain amount of pyridine (300% of the HMP volume) was added. Acyl chloride was diluted with acetone to 0.72 mol / L and pumped into a T-type tee. The materials were mixed using a T-type tee with an inner diameter of 3.2 mm. The microchannel used had an inner diameter of 1.6 mm, a length of 5 m, and a total microchannel volume of 10 mL. The two materials were fed and mixed at a 1:1 flow ratio, with a total reaction flow rate of 1.0 mL / min and a reaction residence time of 10 min. The product was collected at the microchannel outlet.

[0058] The collected products were analyzed using liquid chromatography to detect the reaction products, and the calculated reaction conversion rate was 35.1%.

Claims

1. A method for continuous preparation of photoinitiators using a microreactor, characterized in that, Includes the following steps: Step 1: Under ultrasonic vibration and light-protected conditions, the initiator raw material solution and acyl chloride dilution solution in the raw material container are continuously pumped from the two ports of the T-shaped tee into the T-shaped tee to achieve mixing of the raw materials; Step 2: After the initiator raw material solution and the acyl chloride dilution solution are mixed in the T-shaped tee, they flow out from the third port of the T-shaped tee and enter the microchannel to continue the reaction for a period of time; Step 3: After the microchannel has stabilized, collect the photoinitiator product at the outlet of the microchannel; In step 1, a catalyst is added to the initiator raw material solution, and the catalyst is pyridine; the initiator raw material is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, and the acyl chloride is methacryloyl chloride.

2. The method according to claim 1, characterized in that, The initiator feedstock solution is prepared by diluting 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone to 0.24 mol / L using acetone as a solvent.

3. The method according to claim 1, characterized in that, The acyl chloride diluent is prepared by diluting the acyl chloride to 0.58–0.72 mol / L using acetone as a solvent.

4. The method according to claim 1, characterized in that, The amount of pyridine catalyst added is 240% to 300% of the amount of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone.

5. The method according to claim 1, characterized in that, The flow rate ratio of the initiator raw material solution and the acyl chloride dilution solution in step 1 is 1:

1.

6. The method according to claim 1, characterized in that, The total flow rate of the reaction solution in step 1 is 1 to 2 mL / min.

7. A microreactor for the continuous preparation of photoinitiators, used in the method of claim 1, characterized in that... include: The pump is used to continuously and quantitatively deliver the initiator raw material solution and the acyl chloride dilution solution stored in the raw material container to the T-shaped tee; The T-shaped tee has two of its three ports connected to containers storing the initiator raw material solution and the acyl chloride dilution solution via pipelines, while the third port is connected to a microchannel. The microchannel is connected at one end to the third interface of the T-shaped tee, and at the other end to the product's outlet. The T-shaped tee and the microchannel are both placed in an ultrasonic water tank, and the entire microreactor is protected from light.

8. The microreactor according to claim 7, characterized in that, The microchannel has an inner diameter of 0.5–2 mm and a length of 0.5–25 m.

9. The microreactor according to claim 7, characterized in that, The inner diameter of the T-shaped tee is 0.5–5 mm.

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