A thioxanthone-chalcone photoinitiator and its application

Abstract

The present invention provides a thioxanthone-chalcone photoinitiator and its application. The thioxanthone-chalcone photoinitiator comprises a compound having the structural formula shown in formula (I), wherein, in formula (I), R is -OMe or -SMe. The thioxanthone-chalcone photoinitiator provided by the present invention has a good photoinitiating effect, particularly a high double bond conversion rate and / or epoxy conversion rate in the polymerization reaction, and the resulting photocurable product has good photobleaching performance and a lighter color.

Description

Technical Field

[0001] The present invention relates to the field of photoinitiators, and more particularly to a thioxanthone-chalcone photoinitiator and applications thereof. Background Art

[0002] A photoinitiator is a substance that absorbs light energy and converts it into chemical energy. It typically has a certain absorption capacity in the ultraviolet or visible light regions. After absorbing light energy, it can produce active fragments that can initiate monomer polymerization. These active fragments can be free radicals, cations, anions, etc. Based on their initiation mechanism, photoinitiators can be divided into free radical polymerization photoinitiators and cationic photoinitiators. Based on the wavelength of light energy absorbed, photoinitiators can be divided into ultraviolet photoinitiators and visible light photoinitiators. As an efficient and environmentally friendly light source, LEDs have great development potential. LED photoinitiators need to have high absorbance within the wavelength range of the LED light source and high conversion efficiency.

[0003] Thioxanthone initiators are a class of highly efficient photoinitiators. Existing thioxanthone initiators have poor compatibility with photocuring systems and usually require the addition of a hydrogen donor to achieve high initiation activity, which causes problems such as migration, yellowing, and toxicity to photocurable materials. In order to meet the needs of various developments, the existing technology and the applicant's research team have made various improvements to thioxanthone initiators. The effect of existing thioxanthone photoinitiators (including the thioxanthone-chalcone photoinitiator previously applied for by this research team) in LED photoinitiated polymerization reactions needs to be further improved. At the same time, the products obtained by curing with existing thioxanthone photoinitiators have poor photobleaching properties, and the obtained photocured products are dark in color. Existing thioxanthone photoinitiators cannot give both good photoinitiation effects and a lighter color to the obtained photocured products. Summary of the Invention

[0004] The first object of the present invention is to provide a thioxanthone-chalcone photoinitiator, which has good photoinitiating effect and can make the obtained photocurable product have good photobleaching performance and lighter color.

[0005] The thioxanthone-chalcone photoinitiator includes a compound having the structural formula shown in the following formula (I):

[0006]

[0007] Wherein, in formula (I), R is -OMe or -SMe.

[0008] The thioxanthone-chalcone photoinitiator provided by the present invention, comprising a compound having the structural formula represented by Formula (I), is a single-component photoinitiator. This type of photoinitiator does not require an external solvent to dissolve the photoinitiator, nor does it require an auxiliary agent, and can more quickly and effectively initiate free radical polymerization of monomers. Furthermore, when compounded with an iodonium salt, it can effectively initiate cationic polymerization and free radical-cationic polymerization to form an interpenetrating polymer network structure even at a relatively low dosage.

[0009] The thioxanthone-chalcone photoinitiator provided by the present invention has high initiation activity, and the obtained photocurable product has good photobleaching performance and lighter color.

[0010] In one embodiment of the present invention, in formula (I), R is preferably -OMe, that is, the compound has the structural formula shown in (II):

[0011]

[0012] In one embodiment of the present invention, in formula (I), R may be -SMe, that is, the compound has the structural formula shown in (III):

[0013]

[0014] In a preferred embodiment of the present invention, the thioxanthone-chalcone photoinitiator provided by the present invention is an LED photoinitiator. In a specific embodiment of the present invention, the wavelength of the LED light source can be 365-405 nm.

[0015] In one embodiment of the present invention, when the thioxanthone-chalcone photoinitiator provided by the present invention is used for photoinitiated polymerization, the light intensity can be 50-200 mW / cm 2 .

[0016] Another object of the present invention is to provide a method for preparing the above-mentioned thioxanthone-chalcone photoinitiator, which comprises the following steps:

[0017] Mix sodium hydroxide, ethanol and water, add 2-formylthioxanthone and 4-methoxyacetophenone, and react at room temperature for 10-20 hours.

[0018] The preparation method of the thioxanthone-chalcone photoinitiator provided by the invention is simple.

[0019] Another object of the present invention is to provide the use of the above-mentioned thioxanthone-chalcone photoinitiator in the field of photocuring.

[0020] In a preferred embodiment of the present invention, the thioxanthone-chalcone photoinitiator is used to initiate cationic polymerization or free radical-cationic polymerization. The cationic polymerization is preferably the polymerization of epoxy monomers. The free radical-cationic polymerization is preferably the polymerization of acrylate / epoxy hybrid monomers.

[0021] In a preferred embodiment of the present invention, the epoxy monomer is 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate or 2-(propylene-2-enyloxymethyl)oxirane, preferably 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate.

[0022] In a preferred embodiment of the present invention, the acrylic acid ester monomer is methyl methacrylate, butyl methacrylate, methyl acrylate, n-butyl acrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, β-hydroxyethyl methacrylate or β-hydroxyethyl acrylate, preferably 1,6-hexanediol diacrylate.

[0023] In a preferred embodiment of the present invention, the thioxanthone-chalcone photoinitiator provided by the present invention is compounded with an iodonium salt when initiating cationic polymerization and free radical-cationic polymerization. When used in combination with an iodonium salt, it can trigger cationic polymerization of epoxy monomers with high initiation activity. At the same time, it can also trigger a mixture of acrylate monomers / epoxy monomers to undergo free radical-cationic polymerization to form an interpenetrating polymer network structure. Among them, the epoxy monomer is preferably 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate or 2-(propylene-2-enyloxymethyl)oxirane. Among them, the acrylate monomer in the free radical-cationic polymerization is preferably trimethylolpropane triacrylate, and the epoxy monomer is preferably 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate.

[0024] The iodonium salt can be diphenyliodonium hexafluorophosphate, bis(tert-butylphenyl)iodonium hexafluorophosphate, or bis(p-tolyl)iodonium hexafluorophosphate, preferably bis(tert-butylphenyl)iodonium hexafluorophosphate. When used in combination, the molar mass ratio of the thioxanthone-chalcone photoinitiator to the iodonium salt is preferably 1:1-1:3. Only a very small amount of photoinitiator is required to effectively and efficiently initiate cationic polymerization and free radical-cationic polymerization when combined with the iodonium salt.

[0025] In a preferred embodiment of the present invention, in the polymerization initiated by the thioxanthone-chalcone photoinitiator of the present invention, the wavelength of the light in the photocuring process may be preferably 365 nm to 405 nm. The curing time is preferably 30 s to 600 s. The light intensity is preferably 50 to 200 mW / cm 2 .

[0026] The thioxanthone-chalcone photoinitiator provided by the present invention is suitable for initiating free radical polymerization of acrylate and methacrylate monomers. It does not require the addition of a solvent to dissolve the photoinitiator, and can effectively initiate monomer polymerization without the need for other auxiliary agents, and has high initiation activity. When the thioxanthone-chalcone photoinitiator of the present invention is used in combination with an iodonium salt, only a very small amount of photoinitiator is required to very effectively initiate cationic polymerization of epoxy monomers. It can also initiate free radical-cationic polymerization of a mixture of acrylate monomers / epoxy monomers to form an interpenetrating polymer network structure.

[0027] The thioxanthone-chalcone photoinitiator provided by the present invention has good photoinitiating effect (especially high double bond conversion rate and / or epoxy conversion rate in the polymerization reaction), and can also make the obtained photocurable product have good photobleaching performance and lighter color. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a graph showing the irradiation time-epoxy monomer conversion rate when the photoinitiator / iodonium salt-induced EPOX / TMPTA hybrid photocuring is obtained in Experimental Example 1;

[0029] Figure 2 This is a graph showing the conversion rate of double bonds of acrylate monomers over illumination time when the photoinitiator / iodonium salt-induced EPOX / TMPTA hybrid light curing is obtained in Experimental Example 1;

[0030] Figure 3 This is a graph showing the irradiation time-epoxy monomer conversion rate when the photoinitiator / iodonium salt obtained in Experimental Example 2 initiates EPOX photocuring;

[0031] Figure 4 is the H NMR spectrum of the photoinitiator compound (II) obtained in Example 1;

[0032] Figure 5 This is the H NMR spectrum of the photoinitiator compound (III) obtained in Example 2;

[0033] Figure 6 This is a picture of the mixed light-cured product in Experimental Example 1. DETAILED DESCRIPTION

[0034] The following examples are provided to further illustrate the present invention, but are not intended to limit the scope of the present invention.

[0035] Example 1

[0036] Preparation method of compound of formula (II) (TX-AP-OMe)

[0037] In a 50mL single-necked flask, 0.2g of sodium hydroxide, 10mL of anhydrous ethanol, and 10mL of water were added. The mixture was cooled to room temperature, and 0.24g of 2-formylthioxanthone and 0.165g of 4-methoxyacetophenone were added with stirring. The mixture was stirred at room temperature for 12 hours. Thin-layer chromatography analysis indicated that the reaction was stopped when the 2-formylthioxanthone had completely reacted. The filter cake was collected by filtration and washed with icy ethanol to obtain a yellow solid. Vacuum drying gave 0.329g of the product with a yield (yield = actual product mass / theoretical mass * 100%) of 88.4%.

[0038] The H NMR spectrum data of the product obtained in this example is 1 H NMR (CDCl3, 400MHz): 3.83 (s, 3H, OCH3), 6.90-6.90 (m, 2H, J = 8.8Hz), 7.41-7.46 (td, 1H, J1 = 7.4Hz, J2 = 1.6Hz), 7.48-7.65 (m, 4H), 7.72-7.82 (m, 2H), 7.96-8.04 (d, 2H, J = 8.8Hz), 8.53-8.57 (dd, 1H, J1 = 8.4Hz, J2 = 1.2Hz), 8.78-8.81 (d, 1H, J = 1.6Hz). The hydrogen nuclear magnetic resonance spectrum of the product is Figure 4 .

[0039] Example 2

[0040] Preparation method of compound of formula (III) (TX-AP-SMe)

[0041] In a 50mL single-necked flask, add 0.2g of sodium hydroxide, 10mL of anhydrous ethanol, and 10mL of water. Cool and add 0.24g of 2-formylthioxanthone and 0.183g of 4-methylthioacetophenone with stirring. Stir at room temperature for 12 hours. Thin-layer chromatography analysis indicates that the reaction is complete when the 2-formylthioxanthone reacts. The filter cake is collected by filtration and washed with icy ethanol to obtain a yellow solid. Vacuum drying yields 0.354g of the product, with a yield of 91.2%.

[0042] The H NMR spectrum data of the product obtained in this example is 1 H NMR (CDCl3, 400MHz): 2.49 (s, 3H, SCH3), 7.23-7.30 (d, 2H, J = 8.4Hz), 7.42-7.48 (t, 1H, J = 7.6Hz), 7.49-7.63 (m, 4H), 7.74-7.84 (m, 2H), 7.90-7.95 (d, 2H, J = 8.4Hz), 8.54-8.58 (d, 1H, J = 8.4Hz), 8.79-8.83 (d, 1H, J = 1.2Hz). The H NMR spectrum of the product is Figure 5 .

[0043] Experimental Example 1

[0044] Preparation of hybrid light-curing photoinitiator system samples

[0045] Weigh 3×10 -5 0.0161 g of bis-tert-butylphenyl iodonium hexafluorophosphate (Iod) as the photoinitiator provided in the mol example was transferred to a 10 mL centrifuge tube. 1.5000 g of trimethylolpropane triacrylate (TMPTA) and 1.5000 g of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate (EPOX) were weighed into the tube and ultrasonically mixed until uniform. The mass of the photoinitiator TX-DMAP in the TX-DMAP system was 0.0115 g; the mass of the photoinitiator TX-AP-OMe in the TX-AP-OMe system was 0.0112 g; and the mass of the photoinitiator TX-AP-SMe in the TX-AP-SMe system was 0.0116 g. 2-Isopropylthioxanthone (ITX) was used as a comparative photoinitiator; the mass of ITX in this system was 0.0076 g.

[0046] Real-time infrared detection of photoinduced kinetics steps:

[0047] The above samples were tested for their photocuring dynamics in air using real-time infrared method, where the light source was LED @ 385nm and the light intensity was 180mW / cm 2 The obtained EPOX monomer epoxy functional group conversion rate-time curve is as follows: Figure 1 As shown, the conversion rate-time curve of the carbon-carbon double bond functional group of the TMPTA monomer obtained over time is as shown in Figure 2 As shown. Figure 1 and Figure 2 It can be seen that when the photoinitiator / iodonium salt photoinitiator system triggers TMPTA / EPOX to undergo hybrid photocuring, all three have faster photoinitiation speeds, but compared with the TX-DMAP system, the TX-AP-SMe and TX-AP-OMe photoinitiator systems have higher epoxy conversion rates and double bond conversion rates.

[0048] Photobleaching test steps:

[0049] 0.2000 g of the mixed light-curing photoinitiator system sample was weighed in a small glass bottle and the mixture was heated under air with a LED @ 385 nm light source (light intensity of 130 mW / cm 2 ) Irradiate for 5 minutes and solidify the sample. Figure 6 shown. Figure 6From left to right, these are photocurable products using TX-DMAP, TX-AP-SMe, and TX-AP-OMe as photoinitiators. The color of the photocurable materials shows that compared to the TX-DMAP system, the TX-AP-SMe and TX-AP-OMe systems are significantly lighter in color, demonstrating that the TX-AP-SMe and TX-AP-OMe systems exhibit superior photobleaching performance.

[0050] Experimental Example 2

[0051] Preparation of Cationic Polymerization Photoinitiator System Samples

[0052] Weigh 3×10 -5 0.0161 g of bis-tert-butylphenyl iodonium hexafluorophosphate (Iod) provided in the mol example was transferred to a 10 mL centrifuge tube. 3.0000 g of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate (EPOX) was weighed into the tube and ultrasonically mixed until uniform. The mass of the TX-DMAP photoinitiator in the TX-DMAP system was 0.0115 g; the mass of the TX-AP-OMe photoinitiator in the TX-AP-OMe system was 0.0112 g; and the mass of the TX-AP-SMe photoinitiator in the TX-AP-SMe system was 0.0116 g.

[0053] Real-time infrared method to detect the photoinitiated kinetics: The above samples were respectively tested for their photocuring kinetics in air using the real-time infrared method, where the light source was LED @ 385nm and the light intensity was 180mW / cm 2 The obtained EPOX monomer epoxy functional group conversion rate-time curve is as follows: Figure 3 shown.

[0054] from Figure 3 It can be seen that when the photoinitiator / iodonium salt photoinitiator system initiates cationic polymerization of EPOX, the TX-AP-SMe and TX-AP-OMe photoinitiator systems have higher photoinitiation rates and higher epoxy conversion rates than the TX-DMAP system.

[0055] Finally, the method of the present invention is only a preferred embodiment and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A thioxanthone-chalcone photoinitiator, characterized in that The thioxanthone-chalcone photoinitiator is a compound having the structural formula shown in the following formula (I): ； Wherein, in formula (I), R is -OMe or -SMe.

2. The thioxanthone-chalcone photoinitiator according to claim 1, characterized in that The thioxanthone-chalcone photoinitiator is an LED photoinitiator.

3. Use of the thioxanthone-chalcone photoinitiator according to claim 1 or 2 in the field of photocuring, characterized in that: The thioxanthone-chalcone photoinitiator is used to initiate cationic polymerization or free radical-cationic polymerization.

4. The use according to claim 3, characterized in that The cationic polymerization is the polymerization of epoxy monomers.

5. The use according to claim 4, characterized in that The epoxy monomer is 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate or 2-(propylene-2-enyloxymethyl)ethylene oxide.

6. The use according to claim 3, characterized in that The free radical-cationic polymerization is the polymerization of acrylate / epoxy mixed monomers.

7. The use according to claim 6, characterized in that The epoxy monomer is 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate or 2-(propylene-2-enyloxymethyl)oxirane; The acrylic acid ester monomer is methyl methacrylate, butyl methacrylate, methyl acrylate, n-butyl acrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, β-hydroxyethyl methacrylate or β-hydroxyethyl acrylate.

8. The use according to any one of claims 4 to 7, characterized in that The cationic polymerization and free radical-cationic polymerization are initiated by combining the thioxanthone-chalcone photoinitiator with an iodonium salt; the iodonium salt is diphenyliodonium hexafluorophosphate, bis(tert-butylphenyl)iodonium hexafluorophosphate or bis(p-tolyl)iodonium hexafluorophosphate.

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