Preparation method of carbazole free radical-cation coupling type visible light photoinitiator

Abstract

The present invention discloses a preparation method and application of a carbazole free radical-cation coupling type visible light photoinitiator. The carbazole free radical-cation coupling type visible light photoinitiator of the present invention is prepared by Suzuki coupling reaction and nucleophilic substitution of carbazole and bromo-oxime ester pyridine derivatives. As a visible light photoinitiator, it has the dual characteristics of free radical photoinitiator and cationic photoinitiator, can be used for visible light above 450 nm to initiate free radical and cationic polymer systems, has the advantages of visible light absorption, high photoinitiation efficiency, good anti-oxidation and inhibition effect, and has broad application prospects in light-curing industrial fields such as coatings, inks, and 3D printing.

Description

Technical Field

[0001] The invention belongs to the field of new chemical materials, and specifically relates to a preparation method and application of a carbazole free radical-cation coupling type visible light photoinitiator. Background Art

[0002] As the leader of new infrastructure and the core general technology of the new round of scientific and technological revolution, 5G will promote the construction of my country's network power and high-quality economic development. As the key raw material for the preparation of high-performance photoresists, the performance of high-end photoinitiators directly determines the integration, power consumption performance, yield and reliability of downstream application products [Fine & Specialty Chemicals 2020, 28(6): 1-10; Polym Bull, 2021: 1-35]. However, most of the current photoinitiators are ultraviolet (UV) light initiators, which have the following challenging scientific problems: (1) low curing depth; (2) low sensitivity; (3) radiation safety, which makes it difficult to meet the process requirements of 5G semiconductor devices; compared with UV, visible light LED initiation has the advantages of low energy consumption, high safety, low cost and long service life [Nat Commun 2019, 10(1): 1-9]. Therefore, the development of high-performance visible light LED photoinitiators has important scientific significance and practical value.

[0003] According to the photoinitiator properties and initiation mechanism, it is mainly divided into: (1) free radical type. Including derivatives such as benzoin, benzophenone, acylphosphine oxide, etc., it has the advantages of fast curing rate, easy performance adjustment and low cost [Prog Org Coat 2010, 67 (3): 225-232]. However, its photosensitivity and initiation activity are low, the influence of oxygen inhibition is large, and it needs to be compounded with hydrogen donors or sulfonium salts, which limit its application in the field of deep photocurable materials. In comparison, the development of cleavage-type oxime ester photoinitiators has largely solved the above problems [Adv Synth Catal 2021, 363 (10): 2502-2528]. BASF in Germany took the lead in developing commercial oxime ester photoinitiators OXE-01 and OXE-02 with high stability, which are used in the preparation of photosensitive materials in the electronics industry. The use of photoresist can achieve higher resolution and meet the process requirements of fine processing in the current electronics industry. However, OXE-01 and OXE-02 are still in the UV initiation region, and the field of deep photocurable materials is still limited. Due to its larger conjugated system and stronger intramolecular charge transfer characteristics, carbazole chromophores can red-shift the wavelength of the photoinitiator to the visible light region, while improving its photosensitivity and initiation activity [Prog Org Coat 2021, 157: 106306]. Therefore, the development of carbazole oxime ester photoinitiators has broad application prospects in the field of industrial photopolymerization. (2) Cationic type. Including aromatic diazonium salts, ferrocenium aromatic complexes, onium salts, etc., it has the advantages of deep curing, low toxicity, and small oxygen inhibition effect [Angew Chem Int Edit 2021, 60 (31): 16917-16921]. However, its disadvantages such as slow curing speed and high cost limit its practical application value. (3) Free radical / cation coupling type. This type of photoinitiator has the advantages of both, and has a good coupling effect in terms of photoinitiation, volume change complementarity, and performance regulation [Macromolecules 2019, 53 (1): 112-124]. Taking phenylphosphine dibenzophenone salts as an example, its curing film-forming time is less than 8s, which has extremely high industrial production and commercial value. Chinese patents CN202010942193.8, CN202010976789.X and CN202011286177.4 have publicly reported a series of free radical-cation coupling photoinitiators and applied them to the field of multi-system photopolymerization. However, ultraviolet or even extreme ultraviolet light initiation results in defects such as low photoinitiation efficiency, high energy consumption, and harm to human health. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems existing in the prior art, provide the light reaction characteristics of coupled oxime ester photoinitiators and onium salt cationic photoinitiators, and design and synthesize a series of carbazole free radical / cation coupled visible light photoinitiators that are efficiently matched with commercial LED light sources; firstly, by introducing carbazole chromophores, the photosensitivity is increased, and the absorption wavelength of the photoinitiator is red-shifted to the visible light region; secondly, oxime esters and iodonium salts are used as free radical and cationic initiating groups, respectively, and the advantages of the two are combined to exert a coupling effect and enhance the initiating activity.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] The preparation method and application of a carbazole free radical-cation coupling type visible light photoinitiator, the general structural formula of which is shown in formula (I):

[0007]

[0008] The synthetic route of the preparation method of the carbazole free radical-cation coupling type visible light photoinitiator is as follows:

[0009]

[0010] To further achieve the purpose of the present invention, the specific steps include:

[0011] The synthesis of the intermediate monomer S2 is carried out by reacting with hydroxylamine hydrochloride under the catalytic action of a base to produce the oxime structure S2;

[0012] Preferably, the base is one or more of sodium hydroxide, potassium hydroxide, sodium acetate, potassium acetate;

[0013] Preferably, the solvent is one or more of ethanol, methanol, isopropanol, and n-butanol.

[0014] The intermediate product S2 is further esterified with bromoacetyl chloride under the action of a base acid-binding agent to prepare an oxime ester compound S3;

[0015] Preferably, the alkaline acid-binding agent is one or more of triethylamine, sodium carbonate, sodium bicarbonate, potassium carbonate, and sodium hydride;

[0016] Preferably, the solvent is one or more of dichloromethane, chloroform, and tetrahydrofuran.

[0017] The synthesis process of the intermediate monomer S5 is to sequentially add phenyl-substituted 3,6-dibromocarbazole, pyridine boronic acid, acid-binding agent, catalyst, and organic solvent into a container equipped with a stirring device, react in an oil bath at 65-85° C., and after the reaction is completed, separate the liquids for extraction, remove the organic solvent with a rotary evaporator, and purify the pure product by silica gel column chromatography to obtain the intermediate monomer S5;

[0018] Preferably, the acid binding agent is one or more of sodium carbonate, potassium carbonate, and cesium carbonate;

[0019] Preferably, the catalyst is one or more of Pd(PPh3)4, Pd(PPh3)2Cl2, NiCl2(dppf), PdCl2(dppf), Pd(OAc)2;

[0020] Preferably, the organic solvent is one or more of toluene, tetrahydrofuran, and acetonitrile;

[0021] Preferably, the molar ratio of the pyridine boronic acid to the phenyl-substituted 3,6-dibromocarbazole is (2.1-2.8):1.

[0022] The intermediate monomer S3 and the intermediate monomer S5 are subjected to reflux reaction in an organic solvent according to a measured molar ratio. After the reaction is completed, the solid is filtered and collected to obtain the carbazole free radical-cation coupling type visible light photoinitiator in the general formula (I).

[0023] Preferably, the molar ratio of the intermediate monomer S3 to the intermediate monomer S5 is (2.1-2.8):1;

[0024] Preferably, the solvent is one or more of acetonitrile, toluene, and N,N-dimethylformamide.

[0025] The use of carbazole free radical-cation coupling type visible light photoinitiator is characterized in that it is used as a photoinitiator in a free radical or cationic photocuring polymerization formulation system, and the absorption wavelength of this type of photoinitiator is above 450nm.

[0026] Preferably, the free radical photocuring system is a polymerization system containing C=C double bonds such as trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, etc.

[0027] Preferably, the cationic photocuring system is a polymerization system containing epoxy monomers such as 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclomethyl ester, 1,2,3-propylene glycol glycidyl ether, 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ether, epoxy resin E51, epoxy resin E44, etc.

[0028] Preferably, in the photopolymerization system, the amount of the carbazole free radical-cation coupling type visible light photoinitiator is 0.1 to 10 parts by weight of the photocurable polymerization formula system.

[0029] Compared with the prior art, the preparation method and application of the carbazole free radical-cation coupling type visible light photoinitiator of the present invention have the following advantages and beneficial effects:

[0030] (1) From the perspective of structural design, by introducing carbazole chromophores, the initiation wavelength is red-shifted to above 455 nm, increasing the photosensitivity. At the same time, the absorption wavelength of the photoinitiator is red-shifted to the visible light region, realizing the application of visible light photopolymerization above 450 nm.

[0031] (2) Oxime esters and onium salts are used as free radical and cationic initiating groups, respectively, combining the advantages of both, exerting a coupling effect, and improving the initiation activity. This method can be applied to free radical, cationic, and hybrid photopolymerization.

[0032] (3) This type of photoinitiator has the advantages of visible light absorption, high photoinitiation efficiency, and good antioxidant and polymerization inhibition effect. It has broad application prospects in photocuring industrial fields such as coatings, inks, and 3D printing. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with embodiments, but the scope of protection claimed by the present invention is not limited to the scope described in the embodiments.

[0034] Example 1

[0035] Example 1 The synthesis route of the photoinitiator is as follows:

[0036]

[0037] Under N2 protection, trifluoromethylbenzaldehyde (20 mmol), hydroxylamine hydrochloride (30 mmol), sodium acetate (50 mmol), and ethanol (50 mL) were added to a container equipped with a stirring device in sequence and reacted at room temperature for 24 h. The reaction progress was tracked by TLC. After the reaction was completed, the liquids were separated and extracted, and the organic solvent was removed by a rotary evaporator. The pure product was purified by silica gel column chromatography to obtain the intermediate monomer S2 with a yield of 90.23%;

[0038] (2) Under N2 protection, the intermediate monomer S2 (10 mmol), bromoacetyl chloride (15 mmol), sodium hydride (15 mmol), and tetrahydrofuran (50 mL) were added in sequence to a container equipped with a stirring device and reacted at room temperature for 24 h. The reaction progress was tracked by TLC. After the reaction was completed, the liquids were separated and extracted, and the organic solvent was removed by a rotary evaporator. The pure product was purified by silica gel column chromatography to obtain the intermediate monomer S3 with a yield of 89.34%;

[0039] (3) Under N2 protection, phenyl-substituted 3,6-dibromocarbazole (10 mmol), pyridine boronic acid (22 mmol), potassium carbonate (25 mmol), Pd(PPh3)4 (0.5 mmol), toluene (50 mL), and ethanol (25 mL) were added in sequence to a container equipped with a stirring device, and the reaction was refluxed in an oil bath at 85°C. After the reaction was completed, the liquids were separated and extracted, and the organic solvent was removed by a rotary evaporator. The pure product was purified by silica gel column chromatography to obtain the intermediate monomer S5 with a yield of 75.18%.

[0040] (4) Under N2 protection, the intermediate monomer S3 (12 mmol), the intermediate monomer S5 (5 mmol) and 20 mL of acetonitrile were added in sequence to a container equipped with a stirring device, and the reaction was refluxed overnight. The progress of the reaction was tracked by TLC. After the reaction was completed, the solid phase was collected by filtration and rinsed with acetonitrile three times to obtain a red solid photoinitiator with a yield of 94.37%.

[0041] Example 2

[0042] The only difference from Example 1 is that the trifluoromethylbenzaldehyde in step (1) is replaced by benzaldehyde. Yield: 95.12%.

[0043] Example 3

[0044] The only difference from Example 1 is that trifluoromethylbenzaldehyde in step (1) is replaced by thiophenecarboxaldehyde. Yield: 93.78%.

[0045] Example 4

[0046] The only difference from Example 1 is that pyridine boronic acid in step (3) is replaced by quinoline boronic acid. Yield: 91.21%.

[0047] Example 5

[0048] The only difference from Example 1 is that the pyridine boronic acid in step (3) is replaced by acridine boronic acid. Yield: 90.39%. Preparation of photocuring system: The photoinitiators in Examples 1 to 5 are respectively reacted with an acrylic free radical photocuring system and an epoxy cationic photocuring system to prepare a resin composition.

[0049] Application Example 1:

[0050] The photoinitiator in Example 1 is mixed with acrylic resin, pentaerythritol triacrylate and BASF EFKA 3777 fluorine-modified leveling agent to prepare a resin composition, and the amount of the photoinitiator is 2 parts by weight of the photocurable polymerization formula system, the acrylic resin is 89 parts by weight, and the pentaerythritol triacrylate is 9 parts by weight. Use a 7cm*7cm blank glass plate to coat on a rotary glue machine, the speed is 350rpm, the front baking is 100℃ / 5min, the exposure machine is exposed, the exposure amount is 100mJ, and the post baking is 280℃ / 40min to prepare a cured film. The cured film is dissolved in an acetonitrile solution, and the filtrate is obtained by extraction and purification. The mobility is tested by gas chromatography-mass spectrometry (GC-MS) "Shimadzu GCMS-TQ8040 NX". The mobility of the test results of the embodiment is better than that of the comparative item. The cured film is dissolved in an acetonitrile solution, and the filtrate is obtained by extraction and purification. The absorption spectrum is tested by ultraviolet visible absorption spectroscopy (UV-VIS) "Shimadzu UV-2450".

[0051] Application Example 2:

[0052] The only difference from Application Example 1 is that the amount of photoinitiator used in Example 1 is 5 parts by weight of the photocurable polymerization formula system.

[0053] Application Example 3:

[0054] The only difference from Application Example 1 is that the photoinitiator is the photoinitiator in Example 5.

[0055] Application Example 4:

[0056] The only difference from Application Example 1 is that the photopolymerizable resin composition is a 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclomethyl ester system.

[0057] Application Example 5:

[0058] The only difference from Application Example 1 is that the photopolymerizable resin composition is a mixed system of 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclic methyl ester and acrylic resin, wherein the weight ratio of 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclic methyl ester to acrylic resin is 2:8.

[0059] Application Example 6:

[0060] The only difference from Application Example 1 is that the photopolymerizable resin composition is a mixed system of epoxy resin E51 and acrylic resin, wherein the weight ratio of epoxy resin E51 to acrylic resin is 2:8.

[0061] Application Example 7:

[0062] The only difference from Application Example 1 is that the photopolymerizable resin composition is a mixed system of 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclic methyl ester and acrylic resin, wherein the weight ratio of 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclic methyl ester to acrylic resin is 3:7.

[0063] Application Comparative Example 1:

[0064] The only difference from Comparative Example 1 is that the photoinitiator is the commercial photoinitiator isopropylthioxanthone (ITX).

[0065] Application Comparative Example 2:

[0066] The only difference from Comparative Example 1 is that the photoinitiator is a commercial photoinitiator ethyl 4,4-dimethylaminobenzoate (EDB).

[0067] Application Comparative Example 3:

[0068] The only difference from Comparative Example 1 is that the amount of photoinitiator added is 20 parts by weight.

[0069] Application Comparative Example 4:

[0070] The only difference from Comparative Application Example 1 is that the polymerization system is an alkyd resin.

[0071] Application Comparative Example 5:

[0072] The only difference from Comparative Application Example 1 is that the polymerization system is a polyurethane resin.

[0073] The photoinitiator effects are shown in Table 1 below.

[0074] Table 1 Photoinitiator test results

[0075]

[0076]

[0077] The implementation methods of the present invention are not limited to the above-mentioned embodiments. Any other modifications, changes, substitutions, combinations and simplifications that deviate from the spirit and principles of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A carbazole free radical-cation coupling type visible light photoinitiator, the general chemical structure of which is shown in the following formula (I): （I） In formula (I): R is independently selected from electron donating and withdrawing substituted aromatic rings; in, The aromatic ring is a benzene ring, a furan ring, or a thiophene ring; The electron donating and withdrawing substituents are H, trifluoromethyl, and methoxy.

2. The method for preparing the carbazole free radical-cation coupling type visible light photoinitiator according to claim 1, characterized in that: The synthetic route is as follows: The preparation process of carbazole free radical-cation coupling type visible light photoinitiator includes the following steps: (1) Monomer S1 reacts with hydroxylamine hydrochloride in an organic solvent 1 under alkaline conditions to obtain an intermediate product S2; (2) The intermediate product S2 is further esterified with bromoacetyl chloride in the presence of an organic solvent 2 and an alkaline acid-binding agent to prepare an oxime ester compound S3; (3) Phenyl-substituted 3,6-dibromocarbazole, pyridine boronic acid, an acid-binding agent, a catalyst, and an organic solvent are reacted in an oil bath at 65-85° C. After the reaction is completed, the liquids are separated and extracted, and the organic solvent is removed by a rotary evaporator. The intermediate monomer S5 is purified by silica gel column chromatography; (4) The intermediate monomer S3 and the intermediate monomer S5 are subjected to reflux reaction in an organic solvent 3 according to a measured molar ratio. After the reaction is completed, the solid is filtered and collected to obtain the carbazole free radical-cation coupling type visible light photoinitiator in the general formula (I).

3. The method for preparing the carbazole free radical-cation coupling type visible light photoinitiator according to claim 2, characterized in that: The solvent in step (1) is one or more of ethanol, methanol, isopropanol, and n-butanol; the alkaline environment is a reaction environment with a pH of 9 to 14 formed by reacting one or more of sodium hydroxide, potassium hydroxide, sodium acetate, and potassium acetate; The molar ratio of monomer S1 to hydroxylamine hydrochloride is 1:1.1-1.

8.

4. The method for preparing the carbazole free radical-cation coupling type visible light photoinitiator according to claim 2, characterized in that: The alkaline acid-binding agent described in step (2) is one or more of triethylamine, sodium carbonate, sodium bicarbonate, potassium carbonate, and sodium hydride; The organic solvent 2 is one or more of dichloromethane, chloroform, and tetrahydrofuran; The molar ratio of the intermediate product S2 to bromoacetyl chloride is 1:1.1-1.

8.

5. The method for preparing the carbazole free radical-cation coupling type visible light photoinitiator according to claim 2, characterized in that: The acid binding agent in step (3) is one or more of sodium carbonate, potassium carbonate and cesium carbonate; The catalyst is one or more of Pd(PPh3)4, Pd(PPh3)2Cl2, NiCl2(dppf), PdCl2(dppf), Pd(OAc)2; The organic solvent is one or more of toluene, tetrahydrofuran and acetonitrile; The molar ratio of the pyridine boronic acid and the phenyl-substituted 3,6-dibromocarbazole is (2.1-2.8):1; The pyridine boric acid includes pyridine boric acid, acridine boric acid and quinoline boric acid.

6. The method for preparing the carbazole free radical-cation coupling type visible light photoinitiator according to claim 2, characterized in that: The molar ratio of the intermediate monomer S3 to the intermediate monomer S5 in step (4) is (2.1-2.8):1; The organic solvent 3 is one or more of acetonitrile, toluene, and N,N-dimethylformamide, and the reflux reaction temperature is 65-85°C.

7. Use of the carbazole free radical-cation coupling visible light photoinitiator according to claim 1 in the preparation of a free radical or cationic photocurable polymerization formulation system, wherein the absorption wavelength of the photoinitiator is above 450 nm.

8. The use according to claim 7, characterized in that: The free radical photocuring system is a polymerization system containing C=C double bonds of trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate or triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione.

9. The use according to claim 7, characterized in that: The cationic photocuring system is a polymerization system containing epoxy monomers of 3,4-epoxycyclohexylcarboxylic acid-3',4'epoxycyclomethyl ester, 1,2,3-propanetriol glycidyl ether, 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ether, epoxy resin E51 or epoxy resin E44.

10. The use according to claim 7, characterized in that: In the photopolymerization system, the amount of the carbazole free radical-cation coupling type visible light photoinitiator is 0.1 to 10 parts by weight of the photocurable polymerization formula system.

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