CN114315807B - Pyridinium salt photoinitiator and preparation method and application thereof - Google Patents
Pyridinium salt photoinitiator and preparation method and application thereof Download PDFInfo
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- CN114315807B CN114315807B CN202210007834.XA CN202210007834A CN114315807B CN 114315807 B CN114315807 B CN 114315807B CN 202210007834 A CN202210007834 A CN 202210007834A CN 114315807 B CN114315807 B CN 114315807B
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Abstract
The invention relates to a pyridinium salt photoinitiator and application thereof in photo-curing, and belongs to the technical field of photoinitiators. The pyridinium salt photoinitiator has the following structural general formula (1), wherein X is SbF 6 、BF 4 、PF 6 Or AsF 6 ；R 1 、R 2 Is hydrogen, alkyl, alkoxy, amino, cyano, acyl, halogen or amino. The photoinitiator can initiate the polymerization reaction of the free radical monomer without adding other auxiliary agents. The photoinitiator structure has the advantages of coumarin compounds, has a larger conjugated structure, has stronger absorption near 360nm, and can induce photolysis by an LED light source to generate active free radicals so as to initiate monomer polymerization. The photoinitiator has good initiation efficiency in experiments, and the single-component photoinitiator can simplify the production process of the photo-curing technology, reduce the use of chemicals and meet the development requirements of environment-friendly society.
Description
Technical Field
The invention relates to a pyridinium salt photoinitiator and application thereof in photo-curing, and belongs to the technical field of photoinitiators.
Background
The photo-curing technology is a radiation processing technology for curing liquid resin by polymerization reaction under the radiation of a light source with a specific wavelength. Compared with the traditional heat curing, the photo-curing technology has the advantages of energy conservation, economy, environmental protection, high efficiency, wide adaptability and the like, so that the photo-curing technology has wide application in the fields of printing ink, digital storage, photoresist, additive manufacturing and the like.
The coumarin derivative has strong fluorescence emission, and can be used as a fluorescent color body for various purposes. Meanwhile, coumarin also has a characteristic of high molar extinction coefficient in the near ultraviolet and visible light ranges. Coumarin is therefore often used as a chromophore in the synthesis of photoinitiators. At present, coumarin derivatives are widely reported as photosensitizers and coinitiators for initiating photopolymerization. However, the addition of co-initiators may have some negative effects, such as: the addition of the ammonia co-initiator brings problems of odor, easy yellowing of the polymer and the like.
Disclosure of Invention
The invention provides a single-component pyridinium salt photoinitiator with ultraviolet-visible light absorption, a preparation method and application thereof.
Under the irradiation of ultraviolet-visible light, the photoinitiator can initiate the polymerization reaction of the free radical monomer under the condition of not adding other auxiliary agents, thereby avoiding the problem caused by the addition of the third component. The photoinitiator structure has the advantages of coumarin compounds, has a larger conjugated structure, has stronger absorption near 360nm, and can generate active free radicals by the photolysis initiated by an LED light source so as to initiate the polymerization of monomers. Such photoinitiators show good initiation efficiency in experiments.
The first object of the present invention is to provide a pyridinium salt photoinitiator having the following structural formula:
x is SbF 6 、BF 4 、PF 6 Or AsF 6 ；
R 1 、R 2 Is hydrogen, alkyl, alkoxy, amino, cyano, acyl, or halogen or amino;
the C-S bond of the alpha-position of the carbonyl group is easy to break to generate active species, can directly initiate the polymerization of the acrylic double bond monomer, and can initiate the polymerization without a third component.
In one embodiment, the pyridinium salt photoinitiator structure is as follows
The second object of the present invention is to provide a method for preparing a pyridinium ultraviolet-visible light photoinitiator, which comprises the following steps:
step 1, R 1 Preparing coumarin derivatives from substituted salicylaldehyde and ethyl acetoacetate through Knoevenagel condensation reaction, wherein the structural formula is shown in the specification 2-1;
step 2, the coumarin derivative in step 1 and liquid bromine undergo electrophilic substitution reaction to obtain bromide, wherein the structural formula is shown in the specification
Formula 2-2;
step 3, step 2 the bromide with R 2 Substituted pyridines in the presence of salts of X acids by S N1 The pyridinium salt photoinitiator is prepared by reaction.
In one embodiment, when X is hexafluoroantimonate, the specific preparation steps are:
step 1-1, correspond to R 1 Dissolving substituted salicylaldehyde and ethyl acetoacetate in ethanol, adding piperidine and a trace of glacial acetic acid into the solution for treatment and refluxing; cooling the mixture to room temperature, and separating and purifying to obtain a product of the first step;
step 1-2, dissolving the product of the first step obtained in the step 1-1 in chloroform, slowly dropwise adding a chloroform solution of bromine under ice bath conditions, and separating and purifying after the reaction is completed to obtain a second step of product;
step 1-3, dissolving the second-step product obtained in the step 1-2 and silver hexafluoroantimonate in acetonitrile, and adding R 2 Stirring and heating substituted pyridine until the raw materials reactAnd (3) cooling to room temperature when the reaction is completed, and separating and purifying to obtain a solid product. The reaction was carried out in a dark environment.
In one embodiment, the method is characterized in that,
in step 1-1, the corresponding R 1 The molar ratio of the substituted salicylaldehyde to the acetoacetic ester is 1:10-10:1;
in the step 1-2, the molar ratio of the product of the first step to liquid bromine is 1:10-10:1;
in steps 1-3, the second step product is reacted with the corresponding R 2 The molar ratio of the substituted pyridine is 1:10-10:1, and the molar ratio of the second step product to the onium salt is 1:10-10:1.
Bromide readily reacts with pyridine under mild conditions to form S N1 The reaction is easy to obtain the product, so the preparation method is simple and has better industrialized application prospect.
The third object of the invention is to provide an application of the pyridinium salt photoinitiator, which can initiate the photolysis of the pyridinium salt under the radiation of ultraviolet-visible light to generate active free radicals, so as to realize the curing of the free radical monomers.
In one embodiment, the pyridinium photoinitiator absorbs at 365nm, 405nm and is compatible with 365nm and 405nm LED light sources.
In one embodiment, the radical monomers include trimethylolpropane triacrylate (TMPTA), tripropylene glycol diacrylate (TPGDA).
In one embodiment, the method of application is: in the curing of the free radical monomer, 0.05 to 2wt% of the pyridinium photoinitiator is added to the free radical monomer.
The invention has the beneficial effects that:
(1) The pyridinium salt photoinitiator provided by the invention has good initiation efficiency for a free radical initiation system, and the double bond conversion rate of the initiated tripropylene glycol diacrylate (TPGDA) can reach 78%.
(2) The pyridinium salt photoinitiator provided by the invention has good photophysical and photochemical properties in an ultraviolet-visible light region, and can be subjected to photolysis by a wavelength-matched LED light source to generate active free radicals so as to initiate free radical monomer polymerization. The defects of large heat quantity, low efficiency, easy ozone generation and the like of the traditional mercury lamp can be avoided.
(3) Compared with the common coumarin skeleton photosensitizer, the pyridinium salt photoinitiator provided by the invention can be directly cracked to generate active species to initiate free radical monomer polymerization under ultraviolet-visible light irradiation, and a co-initiator is not needed to be added, so that the problems of odor, easy yellowing of polymers and the like caused by the addition of the co-initiator are avoided. Meanwhile, the single-component photoinitiator can simplify the production process of the photo-curing technology, reduce the use of chemicals and meet the development requirements of environment-friendly society.
(4) The pyridinium salt photoinitiator provided by the invention can be widely applied to the fields of photo-curing coating, photo-curing ink, photoresist, 3D printing and the like.
Drawings
FIG. 1 is a scheme showing the synthesis of photoinitiators according to example 1 of the present invention;
FIG. 2 is a nuclear magnetic resonance spectrum of the photoinitiator according to example 1 of the present invention;
FIG. 3 is a UV-visible absorption spectrum of the photoinitiator according to example 2 of the present invention;
FIG. 4 is a graph showing steady state photolysis profile of a photoinitiator according to example 2 of the present invention under 405nm LED irradiation;
FIG. 5 is a graph showing the real-time double bond conversion of the photoinitiator-initiated tripropylene glycol diacrylate (TPGDA) cure in example 3 of the present invention.
Detailed Description
The present invention will be described in detail below with reference to the drawings and examples.
Example 1: synthesis of pyridinium salt photoinitiator P1
The synthetic route of P1 is shown in FIG. 1.
Step 1, 3.04g of 4-methoxysalicylaldehyde (20 mmol) and 3.8ml of ethyl acetoacetate (30 mmol) were dissolved in 30ml of ethanol, 40ul of piperidine (0.39 mmol) and four drops of glacial acetic acid were added to the solution, and the mixture was refluxed with stirring at 80 ℃. The reaction was monitored by TLC plate and after complete salicylaldehyde consumption, the mixture was cooled to room temperature, and the reaction was subsequently filtered to give product a as a yellow solid. The yield thereof was found to be 86%.
Step 2, 2.18g of yellow solid product A (10 mmol) was dissolved in 20ml of chloroform and added to a round bottom flask. A long needle was extended into the bottom of the liquid bromine bottle to aspirate 1.6g of liquid bromine (10 mmol) and added to the dropping funnel, followed by dissolution with 5mL of chloroform and slow dropwise addition to the round bottom flask over 3 h. The mixture was stirred under ice bath conditions and, after complete reaction, was dried by spinning. The solid was washed with diethyl ether and recrystallized from acetic acid to give solid product B. The yield thereof was found to be 87%.
Step 3, 171mg of silver hexafluoroantimonate (0.5 mmol), 148.5mg of solid product (0.5 mmol) and 40ul of pyridine (0.5 mmol) are added into a 50ml round bottom flask, 30ml of acetonitrile is added, heating and stirring are carried out at 50 ℃, a TLC plate is used for monitoring, the reaction system is filtered after the reaction is completely reacted, filter residues are washed by diethyl ether, and a yellow solid product pyridinium salt photoinitiator P1 is obtained after vacuum drying. The yield thereof was found to be 48%.
Nuclear magnetic hydrogen spectrum data of P1: 1 H NMR(400MHz,DMSO-d 6 )δ8.98–8.94(m,2H),8.93(s,1H),8.81–8.67(m,1H),8.33–8.10(m,2H),8.02(d,J＝8.8Hz,1H),7.20(d,J＝2.4Hz,1H),7.12(dd,J＝8.8,2.4Hz,1H),6.29(s,2H),3.96(s,3H).
example 2: performance detection of P1
1. Ultraviolet-visible absorption test: formulation 7.4X10 -5 The UV-visible absorption of the acetonitrile solution of P1 prepared in example 1 was measured in mol/L by using a TU1901 type UV-visible spectrophotometer of the Japanese Lambda company. The ultraviolet-visible absorption spectrum is shown in FIG. 3, and can be seen in FIG. 3The photoinitiator has absorption at 365nm and 405nm, which indicates that the photoinitiator can be used as a photoinitiator in the ultraviolet-visible light region.
2. Photolysis test: formulation 7.4X10 -5 3mL of the acetonitrile solution of P1 prepared in example 1 in mol/L was placed in a quartz cuvette, and magneton was added. The RUNLED-UVP60 type point light source is adopted for irradiation, the distance between a fixed point light source optical fiber and the cuvette is measured, and the irradiation power at the cuvette is 150mW/cm by a blue light irradiation meter 2 . UV-visible absorption was measured using a TU1901 type UV-visible spectrophotometer from Lambda, japan. The change curve of the ultraviolet visible absorption of photolysis is shown in fig. 4, and it can be seen from fig. 4 that: p1 undergoes photolysis under 405nm LED radiation.
Example 3: p1 polymerization kinetics test
1. Tripropylene glycol diacrylate (TPGDA) free radical polymerization kinetics test.
FIG. 5 shows the real-time conversion curve of the polymerization of TPGDA double bonds initiated by the P1 photoinitiator prepared in example 1.
The specific implementation method comprises the following steps: 1wt% of a pyridinium salt photoinitiator P1 was added to a resin tripropylene glycol diacrylate (TPGDA) and mixed by mechanical agitation and ultrasound to obtain a uniformly mixed resin. It was applied between two KBr salt plates and subsequently tested. Real-time infrared spectrometer (spectrum range: 500-4000 cm) with Nicolet 6700 -1 Resolution of 8cm -1 ) The change of infrared absorption of the groups with time during the initiation of polymerization was monitored and polymerization kinetics studies were performed by monitoring the decrease of double bonds in TPGDA. Conversion was calculated by the following formula.
A t Representing the characteristic peak area of the double bond at time t, A 0 Representing the initial peak area.
As shown in fig. 5, P1 initiates TPGDA polymerization with final double bond conversion of 78% using 365nm LED light source irradiation; the final double bond conversion of the polymerization of TPGDA initiated by P1 was 71% by irradiation with a 405nm LED light source.
Claims (7)
1. A pyridinium salt photoinitiator, characterized by the following structural formula:
x is SbF 6 、BF 4 、PF 6 Or AsF 6 ；
R1 is methoxy, and R2 is H.
2. The method for preparing a pyridinium salt photoinitiator according to claim 1, wherein:
step 1, R 1 Preparing coumarin derivatives by a Knoevenagel condensation reaction of substituted salicylaldehyde and ethyl acetoacetate, wherein the structure of the coumarin derivatives is shown as the formula (2-1);
step 2, preparing coumarin halide by electrophilic substitution reaction of the coumarin derivative and liquid bromine in the step 1, wherein the structure is shown as the formula (2-2);
step 3, step 2 the coumarin halide with R 2 Substituted pyridines are prepared by reacting S in the presence of silver X-acid N1 The pyridinium salt photoinitiator is prepared by reaction.
3. The method for preparing a pyridinium salt photoinitiator according to claim 2, wherein:
when X is hexafluoroantimonate, the specific preparation steps are as follows:
step 1-1, R is taken as 1 Substituted salicylaldehyde and ethyl acetoacetateDissolving in ethanol, adding piperidine and a trace of glacial acetic acid into the solution, treating and refluxing; cooling the mixture to room temperature, and separating and purifying to obtain a product of the first step;
step 1-2, dissolving the product of the first step obtained in the step 1-1 in chloroform, slowly dropwise adding a chloroform solution of bromine under ice bath conditions, and separating and purifying after the reaction is completed to obtain a second step of product;
step 1-3, dissolving the second-step product obtained in the step 1-2 and silver hexafluoroantimonate in acetonitrile, and adding R 2 And (3) stirring and heating the substituted pyridine, cooling to room temperature when the raw materials react completely, separating and purifying to obtain a solid product, and carrying out the reaction in a light-proof environment.
4. A process for preparing a pyridinium salt photoinitiator according to claim 3, wherein,
in step 1-1, the R 1 The molar ratio of the substituted salicylaldehyde to the acetoacetic ester is 1:10-10:1,
in the step 1-2, the molar ratio of the product of the first step to liquid bromine is 1:10-10:1.
In step 1-3, the second step product is reacted with R 2 The molar ratio of the substituted pyridine is 1:10-10:1, and the molar ratio of the second step product to the onium salt is 1:10-10:1.
5. Use of a pyridinium salt photoinitiator according to claim 1 or a pyridinium salt photoinitiator according to claim 2, said pyridinium salt photoinitiator allowing curing of free radical monomers under uv-visible light irradiation.
6. The use of a pyridinium salt photoinitiator according to claim 5 wherein the free radical monomers comprise trimethylolpropane triacrylate, tripropylene glycol diacrylate.
7. Use of a pyridinium salt photoinitiator according to claim 6 wherein the pyridinium salt photoinitiator is added to the free radical monomer in the curing of the free radical monomer in an amount of 0.05wt% to 2wt%.
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Citations (2)
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| WO2010042225A2 (en) * | 2008-10-10 | 2010-04-15 | Dana Farber Cancer Institute | Chemical modulators of pro-apoptotic bax and bcl-2 polypeptides |
| CN104244944A (en) * | 2011-12-30 | 2014-12-24 | Ptc医疗公司 | Compounds for treating spinal muscular atrophy |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010042225A2 (en) * | 2008-10-10 | 2010-04-15 | Dana Farber Cancer Institute | Chemical modulators of pro-apoptotic bax and bcl-2 polypeptides |
| CN104244944A (en) * | 2011-12-30 | 2014-12-24 | Ptc医疗公司 | Compounds for treating spinal muscular atrophy |
Non-Patent Citations (2)
| Title |
|---|
| An efficient synthesis and antimicrobial screening of new hybrid molecules containing coumarin and indenopyridine moiety;Dinkar I. Brahmbhatt 等;《Med Chem Res》;第24卷;第1596-1604页 * |
| One-pot synthesis of novel (E)-3-(3,8a-dihydro-2H-oxazolo [3,2-a]pyridin-2-ylidene)chroman-2-one derivatives;Abolfazl Olyaei 等;《J Heterocyclic Chem》;第58卷(第3期);第757-765页 * |
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