Naphthalimide photoinitiators, photopolymerizable liquid compositions, methods and uses

Abstract

The application discloses a naphthalimide photoinitiator, and has the general structure I, wherein the structure of R1 is shown in general structure II, n is an arbitrary positive integer, R2 is selected from Br, H, NH2, a substituted or unsubstituted phenyl, aziridine, azetidine, tetrahydropyrrole, morpholine, piperidine, hexamethyleneimine or dimethylamine, and R3 is a substituent at an uncertain position of a benzene ring. The naphthalimide photoinitiator disclosed by the application is based on a diethylaminobenzophthalimide with an intersystem crossing of a spin-orbital charge transfer system, and can realize effective visible light polymerization without heavy atoms.

Description

Technical Field

[0001] This invention relates to the field of photocurable materials, and more particularly to a class of naphthalimide photoinitiators, their preparation methods and applications, and photopolymerizable liquids containing photoinitiators. Background Technology

[0002] Traditional curing technologies primarily rely on thermosetting techniques, typically carried out in autoclaves or high-temperature ovens (~200℃), characterized by low energy efficiency. However, limitations in size, energy, and material costs pose significant challenges to the future development of cured materials. Therefore, there is a new demand for environmentally friendly, efficient curing technologies that are not limited by space or time. Photocuring refers to the process of monomers or oligomers transforming from a liquid to a solid state under light irradiation via a photoinitiator. It offers advantages such as high efficiency, environmental friendliness, and energy saving, and exhibits superior spatial and temporal selectivity. Generally, the photocuring process typically involves a light source, a photoinitiator (PI), and a polymerizable medium. Compared to traditional mercury lamps, visible light-emitting diodes (LEDs), with their negligible radiation, harmlessness, low cost, and high efficiency, have received more extensive research. However, the absorption of PIs is difficult to match the narrow wavelength range of LEDs, leading to low excitation efficiency. Furthermore, based on the type of initiation mechanism, PIs can be classified into radical PIs and cationic PIs. Compared to cationic PIs, radical PIs have advantages such as rapid initiation, simple preparation, and low cost. Therefore, visible light-triggered radical initiators are more suitable for photocuring.

[0003] Based on their mechanism of action in free radical photopolymerization (FRP), free radical photoinitiators (PIs) can generally be classified into type I and type II. Type I initiators undergo homolytic cleavage of chemical bonds under irradiation, generating active free radicals for polymerization. During this process, these initiators inevitably produce toxic pyrolysis products, irritating odors, and volatile substances, causing harmful environmental impacts. Type II free radical photoinitiators, with their hydrogen transfer mechanism, avoid the possibility of homolytic cleavage and fragmentation associated with type I free radical photoinitiators, making them safer and more environmentally friendly. However, type II photoinitiators are currently suffering from low hydrogen transfer efficiency. The electron / hydrogen extraction efficiency involved in the hydrogen transfer mechanism needs to be improved by increasing the excited-state lifetime and shortening the donor-acceptor distance. To date, a common strategy is to incorporate heavy atoms (such as Pt, Ir, Ru, Br, and I) into the chromophore to improve the efficiency of generating triplet excited states. However, this method leads to low initiator solubility, poor photostability, and high cytotoxicity, limiting practical applications. Intersystem crossing (SOCT-ISC) of spin-orbit charge transfer systems without heavy atoms can occur in molecules with significant charge transfer (CT) properties, and can also increase triplet yields. In summary, to improve intersystem crossing (ISC) efficiency and shorten donor-acceptor distances, it is essential to develop and design highly efficient photoinitiators with self-supplied hydrogen from heavy atoms to facilitate the processing of new materials. Summary of the Invention

[0004] To address the problems of existing photoinitiators relying on heavy atoms doped with noble metals or toxic halogens, resulting in increased dark toxicity, short three-state lifetime, and poor photostability, this invention provides a class of naphthalimide photoinitiators based on diethylaminophenylbenzine imide with cross-linked spin-orbit charge transfer systems, achieving efficient visible light polymerization without heavy atoms.

[0005] To achieve the above objectives, the technical solution of the present invention is: a type of naphthalimide photoinitiator, the structure of which is shown in general formula I:

[0006]

[0007] In general formula I,

[0008] The structure of R1 is shown in General Formula II, where n takes any positive integer value.

[0009] R2 is selected from one of Br, H, NH2, substituted or unsubstituted phenyl, aziridine, azacyclobutane, tetrahydropyrrole, morpholine, piperidine, hexamethyleneimine or dimethylamine;

[0010] R3 is selected from a substituent at an undetermined position on the benzene ring.

[0011] Furthermore, the substituents referred to in the substituted phenyl group are selected from H, OH, SH, NH2, NO2, CN, COOH, C 1-8 Alkoxy, C 1-8 Alkylamino, C 1-8 Amide group, halogen or C 1-8 One of the haloalkyl groups;

[0012] The substituents at the uncertain positions on the benzene ring are selected from H, OH, SH, NH2, NO2, CN, COOH, and C. 1-8 Alkoxy, C 1-8 Alkylamino, C 1-8 Amide group, halogen or C 1-8 One of the haloalkyl groups.

[0013] Furthermore, in general formula II, n takes the value 1, 2, or 3;

[0014] R2 is selected from aziridine, morpholine, piperidine, or dimethylamine.

[0015] The photopolymerizable liquid composition comprises 0.01-0.1 wt% of a naphthaleneimide photoinitiator, with the balance being tripropylene glycol diacrylate;

[0016] It may be composed of amine compounds, onium salt compounds and naphthalimide photoinitiators, wherein the weight of the naphthalimide photoinitiator accounts for 0.1-5 wt% of the initiator, the weight of the amine compounds is 1-10 times the weight of the naphthalimide photoinitiator, and the balance is onium salt compounds.

[0017] Furthermore, the amine compound is selected from one or any combination of several of the following: L-phenylglycine, N-phenylglycine, 2-amino-2-phenylacetic acid, N-(2-carboxy)phenylglycine, N-phenyl-N-methylglycine, ethyl 4-dimethylaminobenzoate, N,N-dimethylaniline, N-methyldiethanolamine, N-ethyldiethanolamine, triethanolamine, and triisopropanolamine.

[0018] Furthermore, the onium salt compound is selected from one or any combination of iodonium salt compounds and thiodonium salt compounds.

[0019] Furthermore, the iodonium salts are selected from one or any combination of diphenyliodonium hexafluorophosphate, bis(tert-butylphenyl)iodonium hexafluorophosphate, bis(p-tolyl)iodonium hexafluorophosphate, triaryliodonium salt, diaryliodonium salt, and alkyliodonium salt;

[0020] The thioonium salts are selected from one or any combination of triarylthioonium salts, diarylthioonium salts, and alkylthioonium salts.

[0021] The preparation method of naphthalimide photoinitiator includes the following steps:

[0022] (1) Under an inert atmosphere, 4-bromo-1,8-naphthalenedicarboxylic anhydride containing R3 substitution and aniline containing R1 substitution are refluxed in an organic solvent for 3-12 h at a reaction temperature of 120 °C; the preferred time is determined according to different reaction processes.

[0023] (2) Under an inert atmosphere, the compound obtained in step (1) and compound R2 are refluxed in a reaction solvent for 3-12 h at a reaction temperature of 125 °C to obtain the target product.

[0024] The process is as follows:

[0025]

[0026]

[0027] Further, in step (1), the molar ratio of 4-bromo-1,8-naphthalenedicarboxylic anhydride containing R3 substitution to aniline containing R1 substitution is 1:1-4; preferably, the molar ratio is 1:1-2.

[0028] The organic solvent is selected from at least one of anhydrous ethanol, acetic acid, or formic acid; preferably ethanol.

[0029] Furthermore, in step (2), the molar ratio of the compound obtained in step (1) to compound R2 is 1:1-1:1.5; the optimal molar ratio is 1:1.5.

[0030] The reaction solvent is selected from at least one of dimethyl sulfoxide, dichloromethane, dichloroethane, chloroform, carbon tetrachloride, benzene, toluene, xylene, acetonitrile, chlorobenzene, dichlorobenzene, anisole, petroleum ether, dioxane, tetrahydrofuran, pyridine, N,N-dimethylformamide, N-methylpyrrolidone, methyl tert-butyl ether, ethylene glycol dimethyl ether, acetone, butanone, methanol, ethanol, or propanol, with ethylene glycol monomethyl ether being the preferred solvent.

[0031] The aforementioned naphthalimide photoinitiator has low cytotoxicity in the field of photocuring technology, which is beneficial for promoting the application of coatings, inks or 3D printing in food packaging and biomedicine.

[0032] Furthermore, the main material cured in the photocuring technology described in this application is selected from at least one of the following acrylate monomers: diethylene glycol diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, triethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tripropylene glycol dimethacrylate, tetraethylene glycol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, 1,6-hexanediol diacrylate, and trimethylolpropane triacrylate.

[0033] In summary, the present invention has the following beneficial effects:

[0034] First, the imine derivative provided in this application has a D (electron donor)-T (conjugated electron bridge)-A (electron acceptor) structure. In this application, diethylamino is used as the electron acceptor, -Ph-R is used as the electron donor, and coumarin core is used as the bridge. According to density function theory analysis, HOMO electrons are mainly distributed in diethylamino, and LUMO electrons are mainly distributed in the bridge and electron acceptor positions, indicating that intramolecular charge transfer can occur, causing the absorption peak to redshift to the visible light region, which is compatible with LED light sources.

[0035] Second, because the hydrogen donor and hydrogen acceptor are on the same parent nucleus structure, the photoinitiation activity is high. Experiments have shown that only 0.05 wt% can make the acrylate monomer polymerization rate about 90%.

[0036] Third, it contains co-initiating groups, which can initiate polymerization without the addition of additives;

[0037] Fourth, it has low toxicity and is environmentally friendly. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 The images show the UV-Vis spectra of the photoinitiators in Examples 1-5 of this invention, all at a concentration of 1×10⁻⁶. -5 mol / L, the test system is acetonitrile solution;

[0040] Figure 2 The graphs show the absorbance changes of the photoinitiators in Examples 1-5 of this invention under LED irradiation at a wavelength of 405 nm. The concentration of the photoinitiator molecules is 1 × 10⁻⁶. -5 mol / L, LED light intensity is 100mW / cm 2 ;

[0041] Figure 3 This is a schematic diagram showing the thermal stability of the photoinitiators in Examples 1-5 of this invention under nitrogen protection.

[0042] Figure 4 This is a schematic diagram of the curing conversion rate of a single-component photopolymerizable liquid containing photoinitiators from Examples 1-5 disclosed in this invention;

[0043] Figure 5 This is a schematic diagram of the curing conversion rate of a multi-component photopolymerizable liquid containing photoinitiators from Examples 1-5 disclosed in this invention;

[0044] Figure 6 The kinetics of photopolymerization of TPGDA monomers with the NPG / IOD mixture at the optimal concentration are shown. The initiator / co-initiator ratio is expressed as a percentage of the monomer mass. The irradiation wavelength was 405 nm, and the optical density was 100 mW / cm². 2 . Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, 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 protection of the present invention.

[0046] The purification method for the naphthalimide photoinitiator of the present invention employs conventional methods and is not particularly limited. Typically, after purification, a small amount of solvent is added to precipitate the precipitate.

[0047] The following detailed description of the naphthalimide photoinitiator represented by general formula I is provided in conjunction with specific examples.

[0048] A class of naphthalimide photoinitiators, the structure of which is shown in general formula I:

[0049]

[0050] In general formula I,

[0051] R1 is selected from the structure shown in General Formula II or -OC n H m n and m can take any positive integer values;

[0052] R2 is selected from one of Br, H, NH2, substituted or unsubstituted phenyl, aziridine, azacyclobutane, tetrahydropyrrole, morpholine, piperidine, hexamethyleneimine or dimethylamine;

[0053] R3 is selected from a substituent at an undetermined position on the benzene ring.

[0054] Preferably, R2 is selected from -N(CH3)2, -N(CH2CH3)2, -NCH3C4H8CH3, -Ph-OCH3 or -Ph-OC3H7;

[0055] The following are specific examples of compounds represented by general formula I, but the present invention is not limited to these specific examples.

[0056]

[0057] The general synthesis process of the compound represented by formula I in this invention is as follows:

[0058]

[0059] The present invention relates to the synthesis of compounds represented by general formula I by the methods described below.

[0060] Example

[0061] Example 1

[0062] A class of N-Br naphthalimide photoinitiators has the following structural formula:

[0063]

[0064] Its preparation method includes the following steps:

[0065] 4-Bromo-1,8-naphthoic anhydride (3.26 g, 11.78 mmol) was added to a 100 mL double-sided flask and dissolved in 25 mL of ethanol. The mixture was stirred for 10 min, and then N,N-diethyl-p-phenylenediamine (2.52 g, 15.5 mmol) was added. The mixture was then refluxed under a nitrogen atmosphere for 2.5 h. After cooling the mixture overnight, a large amount of needle-like crystals precipitated. These crystals were washed repeatedly with water to give 4.6 g of a brownish-yellow solid, with a yield of 93.6%, which was named N-Br.

[0066] The 1H NMR spectrum data of the photoinitiator N-Br are as follows:

[0067] 1 HNMR (400MHz, CDCl3) δ8.70(dd,J=7.3,1.1Hz,1H),8.61(dd,J=8.5,1.1Hz,1H),8.46(d,J=7.8Hz,1H),8.06(d,J=7.8H z,1H),7.87(dd,J=8.5,7.3Hz,1H),7.14–7.06(m,2H),6.81–6.74(m,2H),3.40(q,J=7.1Hz,4H),1.20(t,J=7.0Hz,6H).

[0068] The mass spectrometry data for the photoinitiator N-Br are: C calculated at m / z. 19 H 18 BrNO2[M+H] + :422.0630, Test:423.03.

[0069] Example 2

[0070] A class of N-PD naphthalimide photoinitiators has the following structural formula:

[0071]

[0072] Its preparation method includes the following steps:

[0073] The NP-Br (4.22 g, 10 mmol) prepared in Example 1 was placed in a 100 mL two-necked flask, and 40 mL of ethylene glycol monomethyl ether was added as a solvent, along with 0.5 mL of piperidine. The mixture was then refluxed under a nitrogen atmosphere for 3 h. After the reaction was complete, the product was purified by petroleum ether / dichloroethylene column chromatography to obtain the target product, named N-PD, 3.98 g, with a yield of 93.2%. The structure was identified by mass spectrometry and nuclear magnetic resonance spectroscopy.

[0074] The 1H NMR spectrum data of the photoinitiator N-PD are as follows:

[0075] 1HNMR (400MHz, CDCl3) δ8.61(d,J=7.3Hz,1H),8.53(d,J=8.1Hz,1H),8.42(d,J=8.4Hz,1H),7.69(t,J=7.8Hz,1H),7.20(d,J=8.1Hz,1H),7.10(d,J= 8.4Hz,2H),6.76(d,J=8.4Hz,2H),3.39(q,J=7.1Hz,4H),3.24(q,J=6.4Hz ,4H),1.90(p,J=5.5Hz,4H),1.74(d,J=6.6Hz,2H),1.19(t,J=7.0Hz,6H).

[0076] The mass spectrometry data for the photoinitiator N-PD are: C calculated at m / z. 27 H 29 N3O2[M+H] + :427.2260, Test:428.2339.

[0077] Example 3

[0078] A class of N-ML naphthalimide photoinitiators has the following structural formula:

[0079]

[0080] The only difference from Example 2 is the solvent R2; specifically,

[0081] The NP-Br (4.22 g, 10 mmol) provided in Example 1 was placed in a 100 mL two-necked flask, and 40 mL of ethylene glycol monomethyl ether was added as a solvent, along with 0.5 mL of morpholine. The mixture was then refluxed under a nitrogen atmosphere for 3 h. After the reaction was complete, the product was purified by petroleum ether / dichlorocarbon column chromatography to obtain the target product, named N-ML, 3.79 g, with a yield of 88.3%. The structure was identified by mass spectrometry and nuclear magnetic resonance spectroscopy.

[0082] The 1H NMR spectrum data of the photoinitiator N-ML are as follows:

[0083] 1HNMR (400MHz, CDCl3) δ8.63(d,J=7.2Hz,1H),8.57(d,J=8.0Hz,1H),8.46(d,J=8.4Hz,1H),7.73(t,J=7.8Hz,1H),7.24(d,J=7.8Hz,1H) 7.10(d,J=8.4Hz,2H),6.77(d,J=8.4Hz,2H),4.04(t,J=4.5Hz,4H),3.40(q,J=7.1Hz,4H),3.29(t,J=4.5Hz,4H),1.20(t,J=7.0Hz,6H).

[0084] The mass spectrometry data for the photoinitiator N-ML are: C calculated at m / z. 26 H 27 N3O3[M+H] + :427.2260, Test:428.2339.

[0085] Example 4

[0086] A class of NP-ML naphthalimide photoinitiators has the following structural formula:

[0087]

[0088] Its preparation method includes the following steps:

[0089] (1) 4-Bromo-1,8-naphthoic anhydride (3.26 g, 11.78 mmol) was added to a 100 mL double-sided flask and dissolved in 25 mL of ethanol. After stirring for 10 min, aniline (1.457 g, 15.5 mmol) was added. Subsequently, the mixture was refluxed under a nitrogen atmosphere for 2.5 h. After cooling the mixture overnight, a large amount of needle-like crystals precipitated. After washing with water several times, a brownish-yellow solid was obtained, named NP-Br, 4.05 g, with a yield of 96%.

[0090] (2) The NP-Br (3.51 g, 10 mmol) obtained in step (1) was placed in a 100 mL two-necked flask, and 40 mL of ethylene glycol monomethyl ether was added as solvent, along with 0.5 mL of morpholine. The mixture was then refluxed under a nitrogen atmosphere for 3 h. After the reaction was complete, the product was purified by petroleum ether / dichlorocarbon column chromatography to obtain the target product, named NP-ML, 3.16 g, with a yield of 88.3%. The structure was identified by mass spectrometry and nuclear magnetic resonance spectroscopy.

[0091] The 1H NMR spectrum data of the photoinitiator NP-ML are as follows:

[0092] 1HNMR (400MHz, DMSO) δ8.56 (dd, J=8.5, 1.3Hz, 1H), 8.49 (dd, J=7.3, 1.2Hz, 1H), 8.42 (d, J=8.1Hz, 1H), 7.85 (dd, J=8.5, 7.2Hz, 1H),7.56–7.49(m,2H),7.48–7.42(m,1H),7.40(d,J=8.1Hz,1H),7.38–7.33(m,2H),3.93(t,J=4.5Hz,4H),3.30–3.22(m,4H).

[0093] The mass spectrometry data for the photoinitiator NP-ML are as follows: C calculated at m / z 22 H 18 N₂O₃[M+H] + :358.1317, Test:359.1393.

[0094] Example 5

[0095] A class of NOP-ML naphthalimide photoinitiators has the following structural formula:

[0096]

[0097] Its preparation method includes the following steps:

[0098] (1) 4-Bromo-1,8-naphthoic anhydride (3.26 g, 11.78 mmol) was added to a 100 mL double-sided flask and dissolved in 25 mL of ethanol. The mixture was stirred for 10 min, and then p-methoxyaniline (1.922 g, 15.5 mmol) was added. The mixture was then refluxed under a nitrogen atmosphere for 2.5 h. After cooling the mixture overnight, a large amount of needle-like crystals precipitated. These crystals were washed repeatedly with water to obtain a brownish-yellow solid, named NOP-Br, 3.95 g, with a yield of 88%.

[0099] (2) The NOP-Br (3.81 g, 10 mmol) provided in step (1) was placed in a 100 mL two-necked flask, and 40 mL of ethylene glycol monomethyl ether was added as a solvent, along with 0.5 mL of morpholine. The mixture was then refluxed under a nitrogen atmosphere for 3 h. After the reaction was complete, the product was purified by petroleum ether / dichlorocarbon column chromatography to obtain the target product, named NOP-ML, 3.58 g, with a yield of 92.3%. The structure was identified by mass spectrometry and nuclear magnetic resonance spectroscopy.

[0100] The 1H NMR spectrum data of the photoinitiator NOP-ML are as follows:

[0101] 1HNMR (400MHz, DMSO) δ8.55(dd,J=8.4,1.2Hz,1H),8.48(dd,J=7.3,1.1Hz,1H),8.42(d,J=8.1Hz,1H),7.85(dd,J=8.4,7.3H z,1H),7.40(d,J=8.1Hz,1H),7.28–7.22(m,2H),7.08–7.03(m,2H),3.97–3.89(m,4H),3.83(s,3H),3.25(t,J=4.5Hz,4H).

[0102] The mass spectrometry data for the photoinitiator NOP-ML are as follows: C calculated at m / z 23 H 20 N₂O₄[M+H] + :388.1423, test:389.1495.

[0103] Test case

[0104] Test Example 1

[0105] To demonstrate the application of the naphthalimide photoinitiators prepared in Examples 1-5 in the field of photocuring technology, exhibiting low cytotoxicity and facilitating their application in food packaging and biomedicine, such as in coatings, inks, or 3D printing, the naphthalimide photoinitiators prepared in Examples 1-5 were formulated into a 1×10⁻⁶ solution using dichloromethane. -5 mol / L naphthimide solution was used for the following tests:

[0106] (1) Absorption test

[0107] The absorbance of the compound solutions from Examples 1-5 was measured using a UV spectrophotometer, and the results are shown in [the table / image / data]. Figure 1 middle.

[0108] from Figure 1 It can be seen that the absorption range of N-Br is 250–375 nm, while the absorption peaks of N-PD, N-ML, NP-ML, and NOP-ML cover 350–475 nm. This is to illustrate that changing the group at the 2-position affects its absorption; introducing an electron-donating group causes a red shift in absorption. Compared to N-ML, NP-ML, and NOP-ML, changing the group at the 1-position does not significantly change the initiator.

[0109] (2) Steady-state photolysis test

[0110] Take 2 mL of naphthalimide dichloromethane solution and place it in a cuvette for irradiation under different LED light sources (light intensity 100 mW / cm²). 2 The absorbance of the solution was measured at different times using a UV spectrophotometer, and the results are shown in [the table / data]. Figure 2middle.

[0111] from Figure 2 It can be seen that as the illumination time increases, the absorption peak of the photoinitiator molecule gradually decreases. Compared with NP-ML and NOP-ML, N-PD and N-ML undergo slower photodegradation, indicating that changing the R1 group is beneficial to adjusting the photostability of the photoinitiator. N-PD and N-ML have better photostability, which is beneficial to photoinitiation.

[0112] (3) Photo-induced thermal stability test

[0113] Thermogravimetric analysis (TGA) was used to evaluate the thermal stability of the synthetic dyes. Under nitrogen protection, the synthetic dyes were heated from 50°C to 600°C at a heating rate of 10°C / min, and their thermal decomposition temperature was determined based on a weight loss of 5 wt%. The dyes were then heated from 50°C to 100°C at a heating rate of 10°C / min and held at that temperature for 10 min, followed by a further heating to 600°C at a rate of 10°C / min. The test results are as follows: Figure 3 As shown.

[0114] from Figure 3 As can be seen, the temperature at which N-PD, N-ML, NP-ML, and NOP-ML lose 5 wt% of thermal weight is approximately 400℃, and the temperature at which N-PD, N-ML, NP-ML, and NOP-ML lose 50 wt% of thermal weight is 450℃. The developed initiator has good thermal stability and is easy to store and transport.

[0115] Test Example 2

[0116] To demonstrate that the naphthalimide photoinitiator prepared in Examples 2-5 can initiate polymerization in the environment without the addition of additives under 405nm LED light source irradiation; and that its initiation activity is higher than that of existing photoinitiators such as benzophenone and naphthalimide.

[0117] (1) Prepare a single-component photosensitive solution containing naphthalimide photoinitiator, with the following ratio:

[0118] A: Tripropylene glycol diacrylate (99.99%-99.90% by weight)

[0119] B: The initiator includes 0.01-0.1 wt% of naphthimide photoinitiator.

[0120] (2) Prepare a composite photosensitive solution containing naphthalimide photoinitiator, with the following proportions:

[0121] The product comprises an amine compound, an onium salt compound, and a naphthalimide photoinitiator, wherein the naphthalimide photoinitiator accounts for 0.05 wt% of the total initiator weight, the amine compound accounts for 1-10 times the weight of the naphthalimide photoinitiator, the onium salt compound accounts for 1-10 times the weight of the naphthalimide photoinitiator, and the balance is TPGDA monomer. Preferably, the amine compound is selected from N-phenylglycine, and the onium salt compound is selected from diphenyliodonium hexafluorophosphate.

[0122] (3) Photoinitiation ability test of single-component photosensitive liquid

[0123] The tripropylene glycol diacrylate in (1) was mixed with the compounds prepared in Examples 1-5 (0.03 wt%, 0.05 wt%, 0.1 wt%), and a homogeneous resin mixture was obtained by ultrasonic vibration and mechanical stirring to prepare a photocurable formulation. Based on the FRP process, the studied resin was coated on a thin KBr sheet (thickness = 2 mm). Then, it was covered with another glass slide for photopolymerization. After irradiation, the decrease in TPGDA double bond content was monitored using a Nicolet 5700FT-IR spectrometer. The test results showed that... Figure 4 , Figure 5 and Figure 6 .

[0124] Figure 4 This is a schematic diagram of the curing conversion rate in step (3), intended to illustrate that the single-component N-ML still possesses extremely high photoinitiation capabilities. Figure 4 As can be seen, when N-PD / N-ML is used alone, only 0.03wt% is needed to initiate curing. When the concentration is increased to 0.05wt%, the conversion rate of acrylate double bonds can reach 85%. When the concentration is increased to 0.1wt%, the conversion rate is nearly 90%.

[0125] Figure 5 The diagram shows the curing conversion rate of Examples 1-5. The purpose is to illustrate the excellent performance of the developed initiator. With only 0.05wt%, it can exceed the commercially available Type II BP photoinitiator (0.3%, Anage, 99% pure).

[0126] from Figure 6 As can be seen, when N-PD / N-ML (0.05wt%) is used in conjunction with commercially available NPG / IOD (0.3wt%) (NPG: N-phenylglycine, 98% pure, Anage; IOD: diphenyliodohexafluorophosphate, 97% pure, Anage), the conversion rate of acrylate double bonds can reach 90%. The addition of the additive did not significantly increase the conversion rate of acrylate double bonds, but only improved the polymerization rate. This indicates that the developed single-component initiator preferentially initiates the process by absorbing hydrogen intramolecularly, with intermolecular hydrogen absorption as a supplement, further verifying the effectiveness of the single-component photoinitiator.

[0127] The existing non-patent literature (Recent advances on naphthalic anhydrides and 1,8-naphthalimide-based photoinitiators of polymerization, Guillaume Noirbent, Frédéric Dumur, European Polymer Journal, 132, 109702, 2020. (https: / / doi.org / 10.1016 / j.eurpolymj.2020.109702.) on page 18, Table 7, NAPHT-43 / Iod (0.5% / 2%, w / w) at 405 nm, 110 Mw / cm 2 The conversion rate under irradiation is only about 60%. It can be seen that the photoinitiator provided in the prior art has a large amount of light and high light density, but low conversion rate. The naphthalimide photoinitiator disclosed in this application has better initiation ability than the existing naphthalimide photoinitiators. The naphthalimide photoinitiator disclosed in this application still has a high conversion rate under low dosage and low light density.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photopolymerizable liquid composition using naphthalimide photoinitiator, characterized in that, The photopolymerizable liquid composition comprises 0.01-0.1 wt% of a naphthalimide photoinitiator, with the balance being tripropylene glycol diacrylate; The structure of the naphthalimide photoinitiator is shown in general formula I: ； General formula I is selected from the following compounds: 。 2. The photopolymerizable liquid composition according to claim 1, characterized in that, The preparation method of the aforementioned naphthalimide photoinitiator includes the following steps: The target product was obtained by reacting 4-bromo-1,8-naphthalenedicarboxylic anhydride containing R3 substitution with aniline containing R1 substitution in an organic solvent for 3-12 h at a reaction temperature of 120 °C under an inert atmosphere. The process is as follows: ； The target product is the naphthimide photoinitiator N-Br.

3. The photopolymerizable liquid composition according to claim 2, characterized in that, The preparation method of the aforementioned naphthalimide photoinitiator further includes the following steps: Under an inert atmosphere, the target product and compound R2 were reacted in a reaction solvent at a molar ratio of 1:1-1:1.5 for 3-12 h at a reaction temperature of 125 °C to obtain a photoinitiator containing a naphthalimide derivative. The process is as follows: ； R2 is selected from morpholine and piperidine; the photoinitiator containing the naphthalimide derivative is either N-PD or N-ML.

4. The photopolymerizable liquid composition according to claim 3, characterized in that, The molar ratio of 4-bromo-1,8-naphthoic anhydride containing R3 substitution to aniline containing R1 substitution is 1:1-4. The organic solvent is selected from at least one of anhydrous ethanol, acetic acid, or formic acid; The reaction solvent is selected from dimethyl sulfoxide, dichloromethane, dichloroethane, chloroform, carbon tetrachloride, benzene, toluene, xylene, acetonitrile, chlorobenzene, dichlorobenzene, anisole, petroleum ether, dioxane, tetrahydrofuran, pyridine, N,N dimethylformamide, N At least one of methylpyrrolidone, methyl tert-butyl ether, ethylene glycol dimethyl ether, acetone, butanone, methanol, ethanol, or propanol.

5. The application of the photopolymerizable liquid composition according to claim 1 in the field of photocuring technology, characterized in that, It is used in coatings, inks, 3D printing, and biomedicine.

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