Synthesis and application method of water-soluble blue light photoinitiator

Abstract

The invention provides a synthesis method of a water-soluble blue light photoinitiator and application of the water-soluble blue light photoinitiator in a blue light 3D printer. The photoinitiator has a low blue light initiation threshold, high initiation efficiency and good water solubility, and can efficiently initiate a photopolymerization reaction under low radiation intensity. Through a specific chemical synthesis path, the high-performance photoinitiator is successfully prepared and is applied to preparation of blue light 3D printing ink. Experimental results show that the blue light 3D printing ink using the photoinitiator can realize high-precision three-dimensional forming under the condition of low blue light radiation, and meanwhile, good printing stability and forming quality are kept. The photoinitiator provided by the invention not only improves the 3D printing efficiency and precision, but also reduces the energy consumption in the printing process, and has remarkable economic and environmental benefits.

Description

Technical Field

[0001] The present invention belongs to the technical field of 3D printing material chemistry and relates to a synthesis method of a water-soluble blue light photoinitiator and an application method thereof. Background Art

[0002] Photoinitiators are core components in photocuring technology. They generate reactive free radicals or cations under ultraviolet or visible light, initiating polymerization reactions of monomers or oligomers. They are widely used in coatings, inks, adhesives, 3D printing, and other fields. Traditional photoinitiators are mostly oil-soluble and suitable for organic systems. However, their compatibility and dispersibility in water-based photocuring systems are poor, limiting their application in environmentally friendly water-based materials.

[0003] In recent years, with the increasingly stringent environmental regulations and the development of green chemistry, water-based photocuring technology has attracted widespread attention due to its advantages such as low volatile organic compound (VOC) emissions and safety and non-toxicity. However, the types of existing water-soluble photoinitiators are limited, and they generally have problems such as low photoinitiation efficiency, poor stability, migration and precipitation. In particular, water-soluble photoinitiators for the blue light (400-500nm) region are more difficult to develop, but the demand is urgent. For example, in emerging fields such as biocompatible materials, electronic device packaging, and flexible printing, blue light curing technology has the advantages of high energy efficiency, strong penetration, and little damage to the substrate.

[0004] Faced with this challenge, current research on water-soluble blue light photoinitiators focuses on modifying small molecules (such as thioxanthones and camphorquinones) or introducing hydrophilic groups (such as quaternary ammonium salts, sulfonates, and polyethylene glycol chains) to enhance water solubility and photoactivity. Reference 1 developed water-based thioxanthones by introducing water-soluble structures such as carboxyl groups, sulfonic acid groups, and quaternary ammonium salts into the thioxanthones. These compounds exhibit strong absorption between 370 and 385 nm, with a peak absorption extending to around 450 nm. Furthermore, these compounds are highly water-soluble, making them suitable for aqueous photopolymerization systems and exhibiting high activity, particularly under relatively long-wavelength UV light. However, this method often faces challenges such as complex synthesis steps, high costs, or insufficient initiation efficiency (Lin Yiqing, Qian Zhen, Wang Jindi, et al. Synthesis of novel aqueous thioxanthone photoinitiators III [J]. Journal of East China University of Science and Technology, 2000, 26(2): 212-214, 220.). Reference 2 synthesized several MAPO and BAPO salts and tested their solubility in aqueous solution, storage stability, cytotoxicity, and photopolymerization reactivity. Not only did they outperform existing photoinitiators in terms of water solubility, but they also performed well in terms of biocompatibility, storage stability, and reactivity. Although significant progress has been made in the research of water-soluble visible light photoinitiators, there are still deficiencies in the comprehensiveness of cytotoxicity testing, long-term stability evaluation, in vivo verification of biocompatibility, in-depth research in specific application fields, and cost and environmental impact analysis. These limitations may affect their widespread promotion and long-term use in practical applications (Benedikt S, Wang J, Markovic M, et al. Highly Efficient Water-Soluble Visible Light Photoinitiators [J]. Journal of Polymer Science Part A: Polymer Chemistry, 2015, 54 (4): 473-479). Therefore, the development of a water-soluble photoinitiator that is simple to synthesize, efficient and stable, and suitable for the blue light region is of great significance to promoting the development of water-based photocuring technology. Summary of the Invention

[0005] The purpose of the present invention is to provide a synthesis and application of a water-soluble blue light photoinitiator.

[0006] The technical solution for achieving the purpose of the present invention is:

[0007] In response to the shortcomings of the existing technology, this application proposes a molecular design and synthesis method for a water-soluble blue light photoinitiator. By optimizing the structure of the photosensitive group and the hydrophilic group, it achieves the comprehensive performance of high water solubility, high initiation efficiency and low mobility, and expands its application in water-based coatings, biomedical materials, electronic packaging and other fields.

[0008] A method for synthesizing a water-soluble blue light photoinitiator comprises: dextran (DT2000) of formula I, acryloyl chloride of formula II, and 1,1′-bis(1-(2,4,6-trimethylphenyl)methanone)phosphite (BAP-H) of formula III as raw materials. First, dextran (DT2000) and acryloyl chloride are reacted in N-methylpyrrolidone, which serves as both a solvent and an acid-binding agent, for 72 hours. After completion of the reaction, the reaction solution is purified with ethanol to obtain acryloyl-substituted dextran (DT2000-AC) of formula IV. DT2000-AC and BAP-H are then reacted in the presence of tetramethylguanidine as a base and N-methylpyrrolidone as a solvent at a reaction temperature of 60°C for 24 hours. Finally, 30% hydrogen peroxide is added as an oxidant at 0°C and the reaction is continued for 6 hours. After the reaction is completed, the reaction solution is purified with ethanol to obtain a photoinitiator structure (DT2000-BAPO) of Formula V. Formulas I, II, III, IV and V are as follows:

[0009]

[0010] The reaction formula is:

[0011]

[0012] The molar ratio of DT2000 represented by formula I and acryloyl chloride represented by formula II of the present invention is 1:3.

[0013] The DT2000-AC separation and purification method of the present invention is as follows: after the reaction is completed, the reaction solution is diluted with a large amount of ethanol and filtered. Then, ethanol is added again and the filtration is repeated three times. Finally, the DT2000-AC represented by formula (IV) is obtained by filtration.

[0014] The molar ratio of DT2000-AC represented by formula IV and BAP-H represented by formula III of the present invention is 1:3.

[0015] The DT2000-BAPO separation and purification method of the present invention comprises: after the reaction is completed, the reaction solution is diluted with a large amount of ethanol and filtered. Then, ethanol is added and the filtration is repeated three times. Finally, the photoinitiator represented by formula (V) is obtained by filtration.

[0016] Compared with the prior art, the present invention has the following significant advantages:

[0017] (1) The process conditions of the present invention are reasonable, and the operation is simple and safe.

[0018] (2) The present invention avoids the use of toxic reagents, produces less three wastes, and is environmentally friendly.

[0019] (3) The present invention is easy to post-process and produces few by-products. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It's DT2000 1 H NMR spectrum.

[0021] Figure 2 It's DT2000 13 C NMR spectrum.

[0022] Figure 3 It is DT2000-BAPO 1 H NMR spectrum.

[0023] Figure 4 It is DT2000-BAPO 13 C NMR spectrum.

[0024] Figure 5 It is DT2000-BAPO 31 P NMR spectrum.

[0025] Figure 6 This is a real picture of a Blu-ray printer.

[0026] Figure 7 Structure diagram printed by a blue-ray printer. a. Cage-like structure; b. Protractor; c. Castle; d. Tweezers.

[0027] Figure 8 At 450nm (light intensity: 42.3mW / cm 2 ) In situ infrared (IR) spectra of the formulations at different exposure times under irradiation.

[0028] Figure 9 The relationship between the double bond conversion rate of the formula and the illumination time. DETAILED DESCRIPTION

[0029] In order to better understand the present invention, the technical solutions of the present invention are described in detail below through specific embodiments.

[0030] The present invention provides a method for preparing a multifunctional photoinitiator, comprising the following steps:

[0031] (1) Vacuum drying and activation of 2000 molecular weight dextran DT2000: Place DT2000 in a container and dry it under vacuum and heating conditions;

[0032] (2) 2-1 Substitution reaction of DT2000 and acryloyl chloride: DT2000 is dissolved in solvent 1, and then acryloyl chloride is added under certain conditions for reaction. After the reaction is completed, solvent 2 is poured in, and then filtered and dried to obtain the intermediate DT2000-AC;

[0033] 2-2 Subsequently, the bisacylphosphine oxide precursor and solvent 1 were added to the reaction flask containing DT2000-AC, followed by dropwise addition of organic base 1 as an acid-binding agent, and the reaction was carried out under heating conditions;

[0034] After 2-3, solvent 3 is added at low temperature and reacted under certain conditions; after the reaction is completed, solvent 2 is poured in, and then filtered and dried to obtain the photoinitiator.

[0035] The present invention provides a specific implementation as follows: in step (1), the drying temperature is 80-90° C. and the drying time is 24 hours.

[0036] The present invention provides a specific implementation as follows: in step (2),

[0037] Solvent 1 is N-methylpyrrolidone;

[0038] Solvent 1 is ethanol;

[0039] Solvent 3 is a 30% mass fraction hydrogen peroxide solution;

[0040] The present invention provides a specific embodiment as follows: in step (2), the organic base 1 is one or both of 1,1,3,3-tetramethylguanidine and triethylamine;

[0041] The molar ratio of DT2000 to acryloyl chloride is 1:3; the molar ratio of DT2000 to bisacylphosphine oxide precursor is 1:3.

[0042] The present invention provides a specific embodiment as follows: in step (2) 2-1, the inert gas is argon or nitrogen; the reaction is carried out at 0° C. for 72 hours;

[0043] In 2-2, the bisacylphosphine oxide precursor is 1,1′-bis[1-(2,4,6-trimethylphenyl)methanone]phosphite; the heating condition reaction temperature is 60° C.; the heating condition reaction time is 24 hours;

[0044] In 2-3, the reaction temperature under low temperature conditions is an ice bath at 0°C; the reaction time under low temperature conditions is 6 hours; and the drying method is drying under high vacuum at 60°C for 1 day.

[0045] Example 1

[0046] To a 250mL anhydrous and oxygen-free tube, add 20g (10mmol) of dextran (DT2000), followed by 200mL of N-methylpyrrolidone (NMP) as both a solvent and an acid binder. Finally, add acryloyl chloride (3eq, 30mmol, 2.41mL) at 0°C. Stir and react at 25°C for 72h. After the reaction is complete, dilute the reaction solution with a large amount of ethanol and filter. Repeat the addition of ethanol and filtration three more times. Finally, filter to obtain DT2000-AC, the acryloyl-substituted dextran. Dry to obtain 18.3g of DT2000-AC, with a yield of 85%. NMR characterization data are as follows:

[0047] 1 H NMR (500MHz, D2O, 298K): δ [ppm] = 6.49-6.53 (d, 3H, CH2 = CH, 3 J HH =7.2Hz)),6.24-6.29(d,3H,CH2=CH, 3 J HH =12.5Hz),6.04-6.11(d,3H,CH2=CH, 3 J HH =10Hz),5.23-5.25(s,OH),5.04-5.05(s,OH),4.97-4.99(s,OH),3.97-4.00(s,12H,DT2000),4.91-4.9 2(s,12H,DT2000),3.85-3.87(s,12H,DT2000),3.72-3.74(s,12H,DT2000),3.58-3.60(s,12H,DT2000).

[0048] 13 C{ 1 H}NMR (126MHz, D2O): δ [ppm] = 167.4, 133.8, 127.3, 97.8, 73.5, 71.5, 70.3, 69.7, 65.6.

[0049] Example 2

[0050] In a 250mL anhydrous and oxygen-free tube, 10g (4.6mmol) of DT2000-AC and 4.84g (3.2eq, 14.8mmol) of BAP-H were added, followed by 200mL of N-methylpyrrolidone (NMP) as a solvent, and finally, tetramethylguanidine (TMG, 10% mmol, 2mL) as a catalyst. The reaction was stirred at 60°C for 24h. After the reaction, 30% hydrogen peroxide solution (H2O2, 1.1eq, 5mmol, 0.2mL) was added as an oxidant at 0°C. After the reaction, the reaction solution was diluted with a large amount of ethanol and filtered. Ethanol was then added and the filtration was repeated three times. Finally, DT2000-BAPO was filtered. Drying gave 11.82g of the photoinitiator with a yield of 80%. The NMR characterization data are as follows:

[0051] 1 H NMR (500MHz, DMSO-d6, 298K) δ [ppm] = 6.62 (s, 12H, Har Mes),4.70(s,12H,DT2000),4.46(s,12H,DT2000),3.42(s,12H,DT2000),3.1(s,12H,DT2000),3.00(s,12H,DT2000),1.99(s,54H,p-CH3 Mes,o-CH3 Mes).

[0052] 13 C{1H}NMR(126MHz,DMSO-d6,298K)δ[ppm]=162.6(d,COCH2CH2),138.0((s,C 4 Mes),133.7(s,C 2,6 Mes),128.1(s,C 1 Mes),106.8(s,C 3,5 Mes),98.9(s,DT2000),76.3(s,DT2000),72.0(s,DT2000),70.5(s,DT2000),64.4(s,DT2000),36.0(s,CH2CH2P),29.8(d,CH2P),21.9(s,p-CH3 Mes),17.1(s,o-CH3 Mes).

[0053] 31 P NMR (202MHz, DMSO-d6) δ [ppm] = 20.4.

[0054] Example 3

[0055] (1) 2.4 g of multifunctional photoinitiator DT2000-BAPO, 8 mg of Sudan I and 77.6 g of ethylene glycol monomethyl ether acrylate (Mn=550) were added to a 100 mL sample bottle, stirred overnight, and then ultrasonicated for 10 min to obtain a photosensitive resin.

[0056] (2) Use Solidwork 3D software to create an additive 3D model, and then export the created 3D model file in STL format for subsequent layering processing and support establishment.

[0057] (3) Construct reasonable supports and slices, mainly for overhanging and thin-walled structures, to prevent deformation by adding corresponding support structures; the slice thickness is 0.01-0.05mm, and the appropriate layer thickness is selected according to the size and shape of the device. The Asiga digital light processing 3D printer supporting software composer can automatically slice the created STL file for subsequent layer-by-layer printing to build precise hydrogel structures, and the software generates slice simulation layers at each level for subsequent structural enhancement and improvement, which are transmitted wirelessly to the printer.

[0058] (4) According to the preset model parameters of the structure, the photosensitive resin was placed in a homemade blue light 3D printer for 3D printing to obtain the printed structure. The printing parameters were as follows: printer light wavelength: 450nm; printing layer thickness: 0.05mm; base light intensity: 42mW / cm2; remaining layer light intensity: 42mW / cm2; base exposure time: 6s; remaining layer exposure time: 4s; platform separation speed: 4mm / s; waiting time after separation: 5s; post-curing time: 15min. Using the above printing parameters, the resolution of the printed structure can be greatly improved and the defect rate can be reduced.

[0059] In this embodiment, the photoinitiator is used in a blue light DLP 3D printer, and the printed structure can have high resolution and low defect rate. Figure 7 shown.

[0060] experiment:

[0061] Fourier transform infrared (FT-IR) spectra were collected using a NICOLETIS20 Fourier transform infrared spectrometer (ThermoFisher Scientific) equipped with an attenuated total reflectance (ATR) accessory. The diamond crystal of the ATR accessory was placed in contact with the sample area (approximately 1.5 mm in diameter) for analysis. All spectra were acquired at 4 cm -1 The resolution was recorded and 32 scans were averaged, covering the wavenumber range from 4000 to 525 cm -1 .

[0062] The double bond conversion rate of the multifunctional photoinitiator obtained in this embodiment reached 92%. Figure 8 、9 shown.

[0063] The above embodiments do not limit the present invention in any way, and any technical solutions obtained by equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A multifunctional photoinitiator, characterized in that The structural formula is as follows:

2. A method for preparing a multifunctional photoinitiator, characterized in that: The following steps are involved: (1) Vacuum drying and activation of 2000 molecular weight dextran DT2000: Place DT2000 in a container and dry it under vacuum and heating conditions; (2) 2-1 Substitution reaction of DT2000 and acryloyl chloride: DT2000 is dissolved in solvent 1, and then acryloyl chloride is added under certain conditions for reaction. After the reaction is completed, solvent 2 is poured in, and then filtered and dried to obtain the intermediate DT2000-AC; 2-2 Subsequently, the bisacylphosphine oxide precursor and solvent 1 were added to the reaction flask containing DT2000-AC, followed by dropwise addition of organic base 1 as an acid-binding agent, and the reaction was carried out under heating conditions; After 2-3, solvent 3 is added at low temperature and reacted under certain conditions; after the reaction is completed, solvent 2 is poured in, and then filtered and dried to obtain the photoinitiator.

3. The method for preparing a multifunctional photoinitiator according to claim 2, wherein: In step (1), the drying temperature is 80-90° C. and the drying time is 24 hours.

4. The method for preparing a multifunctional photoinitiator according to claim 2, wherein: In step (2), Solvent 1 is N-methylpyrrolidone; Solvent 1 is ethanol; Solvent 3 is a 30% by mass hydrogen peroxide solution.

5. The method for preparing a multifunctional photoinitiator according to claim 2, wherein: In step (2), The organic base 1 is one or both of 1,1,3,3-tetramethylguanidine and triethylamine; The molar ratio of DT2000 to acryloyl chloride is 1:3; the molar ratio of DT2000 to bisacylphosphine oxide precursor is 1:

3.

6. The method for preparing a multifunctional photoinitiator according to claim 2, wherein: Step (2) 2-1 In the reaction, the inert gas is argon or nitrogen; the reaction is carried out at 0°C for 72 hours; In 2-2, the bisacylphosphine oxide precursor is 1,1′-bis[1-(2,4,6-trimethylphenyl)methanone]phosphite; the heating reaction temperature is 60° C.; the heating reaction time is 24 hours; In 2-3, the reaction temperature under low temperature conditions is an ice bath at 0°C; the reaction time under low temperature conditions is 6 hours; and the drying method is drying under high vacuum at 60°C for 1 day.

7. An initiator, characterized in that A photoinitiator obtained by the method according to any one of claims 2 to 6.

8. A method for using a photoinitiator in a blue-light printer, characterized in that: The method comprises the following specific steps: preparing a photosensitive resin: uniformly mixing 0.02 wt% of a multifunctional photoinitiator, 0.01 wt% of Sudan I and a monofunctional acrylate to form a photosensitive resin; Blue light 3D printing: According to the preset structural model parameters, the photosensitive resin is placed in the 3D printer for 3D printing to produce a 3D printed structure.

9. The method for using a photoinitiator in a blue-light printer according to claim 8, characterized in that: The monofunctional acrylate is one or more of butyl acrylate, polyethylene glycol monomethyl ether acrylate (Mn=550), benzyl acrylate and cyclohexyl acrylate.

10. The method for using a photoinitiator in a blue-ray printer according to claim 8, characterized in that: The printing parameters of blue light 3D printing are as follows: printer light wavelength: 450nm; printing layer thickness: 0.05mm; substrate light intensity: 42mW / cm 2 ; The light intensity of the remaining layers is 42mW / cm 2 ; Exposure time for substrate: 6s; Exposure time for other layers: 4s; Platform separation speed: 4mm / s; Waiting time after separation: 5s; Post-curing time: 15min.

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