A photoinitiator and a method for preparing the same

Abstract

The application relates to the technical field of photoinitiators, in particular to a photoinitiator and a preparation method thereof, and a structural formula of the photoinitiator is shown in the following formula 1: wherein R1 and R2 are the same or different, and each is independently selected from hydrogen, deuterium, a hydroxyl group, a C1-C4 alkyl group or a group shown in formula 2; R3 and R4 are the same or different, and each is independently selected from hydrogen, a C1-C4 alkyl group, a C6-C30 aromatic group and a C6-C30 aromatic amine group; the photoinitiator has a photoinitiation activity much higher than that of benzophenone, does not need to add a tertiary amine co-initiator and is a high-efficiency photoinitiator.

Description

Technical Field

[0001] This invention relates to the field of photoinitiator technology, specifically to a photoinitiator and its preparation method. Background Technology

[0002] Photopolymerization technology boasts advantages such as rapid reaction speed, green operation, environmental friendliness, and economy, making it a crucial technology in today's industrial era. It has been widely applied in coatings, inks, adhesives, microelectronics, and photoresists. In photopolymerization technology, the photoinitiator plays a decisive role. It absorbs light energy and undergoes a photochemical reaction to generate active fragments, thereby initiating monomer polymerization. It directly determines whether the monomer can rapidly transform from a liquid state to a solid polymer upon light irradiation.

[0003] Benzophenone is one of the most widely used hydrogen-abstracting photoinitiators. After absorbing light energy under ultraviolet light, benzophenone transitions to an excited state and then reacts with a co-initiator to form an excitosome complex. Through electron transfer and hydrogen abstraction reactions, it can generate amine alkyl radicals with high initiation activity and benzyl alcohol radicals with lower activity. However, because the photoinitiation activity of benzophenone is still somewhat lacking, and tertiary amine co-initiators need to be added during its use, with the development of the industry, people have put forward higher requirements for the initiation performance of benzophenone photoinitiators. Summary of the Invention

[0004] Purpose of the invention: To address the above-mentioned technical problems, this invention proposes a photoinitiator and its preparation method.

[0005] The technical solution adopted is as follows:

[0006] A photoinitiator, the structural formula of which is shown in Formula 1 below:

[0007]

[0008]

[0009] Wherein, R1 and R2 may be the same or different, and each is independently selected from hydrogen, deuterium, hydroxyl, C1-C4 hydrocarbon group or the group shown in Formula 2;

[0010]

[0011] R3 and R4 may be the same or different, and each is independently selected from hydrogen, C1-C4 hydrocarbon group, C6-C30 aromatic group, and C6-C30 aromatic amine group.

[0012] Furthermore, the functional groups shown in Formula 2 are specifically as follows:

[0013]

[0014] R3 and R4 may be the same or different, and each is independently selected from hydrogen, C1-C4 hydrocarbon group, C6-C30 aromatic group, and C6-C30 aromatic amine group.

[0015] Furthermore, R1 and R2 may be the same or different, and each may be independently selected from hydrogen or the group shown in Formula 2.

[0016] Furthermore, R3 and R4 may be the same or different, and each is independently selected from hydrogen, methyl, ethyl, n-propyl, isopropyl, phenyl, biphenyl, and diphenylamino.

[0017] Furthermore, R1 and R2 are different.

[0018] Furthermore, at least one of R3 and R4 is a diphenylamino group.

[0019] Furthermore, the photoinitiator is any one of the following compounds:

[0020]

[0021] This invention also provides a method for preparing the above-mentioned photoinitiator:

[0022]

[0023] Under nitrogen protection, SM-1 and SM-2 were added to an organic solvent, stirred until homogeneous, and heated to react for more than 5 hours. After returning to room temperature, the organic solvent was removed by vacuum distillation. Water and dichloromethane were added for extraction, and the dichloromethane phase was separated. After drying, the crude product was obtained by vacuum distillation. The crude product was then dissolved in dichloromethane, and petroleum ether was added dropwise until turbidity appeared. The mixture was cooled to below 5°C to crystallize naturally. Finally, it was filtered and dried under vacuum.

[0024] Furthermore, the reaction temperature is ≥50℃.

[0025] Furthermore, the organic solvent is any one of methanol, ethanol, or isopropanol.

[0026] The beneficial effects of this invention are:

[0027] This invention provides a photoinitiator that, by introducing a tertiary amine unit into the benzophenone structure, achieves higher photoinitiation efficiency through efficient intramolecular electron and proton transfer. Furthermore, due to the increased conjugation system, the excitation energy required is reduced, the wavelength is lengthened, a redshift is generated, and its molar absorptivity is enhanced. This allows for excellent matching with visible LED light sources, broadening its industrial applications. Moreover, it eliminates the need for tertiary amine co-initiators, and its photoinitiation activity is far greater than that of benzophenone, making it a highly efficient photoinitiator. Attached Figure Description

[0028] Figure 1The graph shows a comparison of double bond conversion rate curves in the performance test. It can be seen that the final conversion rate of the photoinitiator prepared in Examples 1-2 after 600s is significantly higher than that of benzophenone, indicating that it has a higher photoinitiation efficiency. Detailed Implementation

[0029] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Techniques not mentioned in this invention refer to existing technologies. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters.

[0030] Example 1:

[0031] A method for preparing a photoinitiator:

[0032]

[0033] Under nitrogen protection, 25.4g of SM-1 (CAS: 19533-07-4) and 50.4g of... SM-2 (CAS: 1309601-63-5) was added to 500 ml of ethanol, stirred until homogeneous, and heated to reflux for 6 h. The addition was stopped, and the mixture was allowed to cool naturally to room temperature. Ethanol was removed by vacuum distillation. The reaction was quenched by adding 5 L of deionized water, followed by extraction with 5 L of dichloromethane. The mixture was separated, and the dichloromethane phase was dried over anhydrous sodium sulfate. Dichloromethane was then removed by vacuum distillation to obtain 6.3 g of crude product. The crude product was dissolved in 50 ml of dichloromethane. Petroleum ether was added dropwise to the resulting solution until turbidity appeared (365 ml of petroleum ether was added). The solution was cooled to 0 ± 5 °C and allowed to crystallize naturally for 36 h. After filtration, the product was dried in a vacuum oven at 60 °C for 10 h in the dark to finally obtain the target product A-1 (37.1 g, yield 48.9%). ESI-MS (m / z) (M + Theoretical value 757.93, measured value 757.46, elemental analysis results (molecular formula C): 52 H 43 N3O3): Theoretical values: C, 82.40; H, 5.72; N, 5.54; O, 6.33; Measured values: C, 82.13; H, 5.44; N, 5.69; O, 6.07.

[0034] Example 2:

[0035] A method for preparing a photoinitiator:

[0036]

[0037] Under nitrogen protection, 25.4g SM-1 (CAS: 19533-07-4) and 33.6g... SM-2 (CAS: 19606-98-5) was added to 500 ml of ethanol, stirred until homogeneous, and heated to reflux for 6 h. The addition was stopped, and the mixture was allowed to cool naturally to room temperature. Ethanol was removed by vacuum distillation. The reaction was quenched by adding 5 L of deionized water, followed by extraction with 5 L of dichloromethane. The mixture was separated, and the dichloromethane phase was dried over anhydrous sodium sulfate. Dichloromethane was then removed by vacuum distillation to obtain 5.9 g of crude product. The crude product was dissolved in 50 ml of dichloromethane. Petroleum ether was added dropwise to the resulting solution until turbidity appeared (406 ml of petroleum ether was added). The solution was cooled to 0 ± 5 °C and allowed to crystallize naturally for 36 h. After filtration, the product was dried in a vacuum oven at 60 °C for 10 h in the dark to finally obtain the target product A-2 (36.5 g, yield 61.8%). ESI-MS (m / z) (M + Theoretical value: 590.72, measured value: 590.16, elemental analysis results (molecular formula C): 40 H 34 N2O3): Theoretical values: C, 81.33; H, 5.80; N, 4.74; O, 8.13; Measured values: C, 81.62; H, 5.65; N, 4.33; O, 8.26.

[0038] Performance testing:

[0039] ① Maximum absorption wavelength and maximum molar absorptivity test: The photoinitiator prepared in Examples 1-2 of this invention and commercially available benzophenone were respectively prepared to a concentration of 5×10 -5 A 1 mol / L chloroform solution was used, designated as Test Example 1, Test Example 2, and Comparative Example, respectively. The ultraviolet absorption spectra of the test solutions in the 245-500 nm range were analyzed, and the wavelength at the maximum absorption peak was defined as the maximum absorption wavelength λ. max The corresponding maximum molar absorptivity E max Calculated using equation (1).

[0040] E max =A / (b×c)————Equation (1)

[0041] In equation (1), A is the absorbance at the maximum absorption peak; b is the optical path length in mm; and c is the concentration of the photoinitiator in mol / L.

[0042] The test results are shown in Table 1:

[0043] Table 1:

[0044]

[0045] As shown in Table 1, the photoinitiator prepared in this invention exhibits a red shift in maximum ultraviolet absorption compared to benzophenone, and also has a higher molar absorptivity and a significantly improved absorbance. Its photoinitiating activity is far greater than that of benzophenone, making it a highly efficient photoinitiator.

[0046] ② Double bond conversion rate test: The photoinitiator prepared in Examples 1-2 of this invention and commercially available benzophenone were added to the monomer trimethylolpropane triacrylate (TMPTA) at a ratio of 1 wt% and stirred evenly; a drop of the mixture was evenly spread on a potassium bromide salt sheet, and a thin and transparent potassium bromide salt sheet was then covered on the upper surface to prevent oxygen inhibition of polymerization. The mixture was irradiated with LED point light sources with wavelengths of 385 nm and 420 nm, and the double bond conversion rate was tested using a Nico Leti S50 Fourier transform real-time infrared spectrometer. The test results are as follows: Figure 1 As shown, it can be seen that the final conversion rate of the photoinitiator prepared in Examples 1-2 after 600s is significantly higher than that of benzophenone, indicating a higher photoinitiation efficiency.

[0047] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photoinitiator characterized by, For any one of the following compounds: 。

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