Free radical photoinitiator composition and application thereof

Abstract

The invention discloses a free radical photoinitiator composition and application thereof. The free radical photoinitiator composition comprises modified thioxanthone and an auxiliary initiator, the modified thioxanthone has a structure as shown in a formula A. The free radical photoinitiator composition provided by the invention has excellent thermal stability and storage stability by mixing the modified thioxanthone and the co-initiator, is high in photoreaction activity, and can be widely applied to the fields of resins, coatings, printing inks, pressure-sensitive adhesives, photoresists, 3D printing materials and the like. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the technical field of photoinitiator materials, and particularly relates to a free radical photoinitiator composition and its application. Background Art

[0002] The photocuring technology is a surface treatment technology that uses ultraviolet light to initiate the rapid polymerization and crosslinking of chemically active liquid materials, and instantaneously cures them into solid materials. It has the advantages of being economical and efficient, having a wide range of adaptability, being energy-saving and environmentally friendly, and is known as a new technology for the green industry in the 21st century. It is widely used in the fields of printing, packaging, advertising, building materials, electronics, computers, aerospace, etc.

[0003] The photocuring system mainly consists of a prepolymer, a diluent, and a photoinitiator. The prepolymer and the diluent contain acrylate groups or epoxy groups that can undergo UV curing and can participate in the photocuring reaction during the photocuring process to form part of the crosslinked network. Among them, the photoinitiator is a key component of the photocuring material, and it plays a decisive role in the photocuring speed of the photocuring material. Photoinitiators can be divided into two major categories: free radical photoinitiators and cationic photoinitiators due to the different active intermediates generated. Free radical photoinitiators can be further divided into two major categories: cleavage-type photoinitiators and hydrogen abstraction-type photoinitiators due to the different mechanisms of generating free radicals.

[0004] Among the hydrogen abstraction-type photoinitiators, benzophenone and thioxanthone have strong designability, and the photoinitiating performance of some of their derivatives is better than themselves. Therefore, people modify them by introducing different groups at different sites of benzophenone and thioxanthone to improve solubility, extend the absorption wavelength, increase the initiation efficiency, and endow the ability of self-initiation.

[0005] Thioxanthone-based photoinitiators are a classic type of free radical photoinitiators that generate active free radicals through intermolecular hydrogen abstraction. After absorbing light energy of a specific wavelength, the thioxanthone molecule will jump from the ground state to the excited state, and then reach the triplet state through intersystem crossing. The thioxanthone molecule in the triplet state will take away the hydrogen on the co-initiator to generate a thioxanthone free radical and an amine alkyl free radical. The absorption wavelength of thioxanthone photoinitiators is around 380 nm, and the molar extinction coefficient is large. The most common wavelength of UV-LED light sources is 395 nm, and the two are relatively well-matched. Therefore, it has great potential in the field of LED photocuring. However, the thioxanthone-based photoinitiators in the prior art have poor thermal stability and storage stability, and their photoreaction activity still needs to be improved.

[0006] Therefore, there is an urgent need for a free radical photoinitiator with excellent thermal stability and storage stability and high photoreaction activity at present. Summary of the Invention

[0007] Object of the Invention: Aiming at the defects of the prior art, the object of the present invention is to provide a free radical photoinitiator composition with excellent thermal stability and storage stability and high photo-reaction activity, and its application.

[0008] Technical Solution:

[0009] To achieve the above object of the invention, the present invention provides a free radical photoinitiator composition, comprising a modified thioxanthone and a co-initiator;

[0010] The modified thioxanthone has a structure shown in the following formula A:

[0011]

[0012] The present invention uses the modified thioxanthone as the main photoinitiator. After the main structure of thioxanthone is excited, thioxanthone free radicals and amide free radicals are generated. After combining with the co-initiator, it has excellent photo-reaction activity and can efficiently initiate polymerization reactions.

[0013] Further, the co-initiator is selected from one of N-phenylglycine, ethyl 4-dimethylaminobenzoate, N,N-di(hydroxyethyl)aniline or N,N-di(hydroxyethyl)-p-methylaniline.

[0014] Further, the modified thioxanthone is prepared by the following steps:

[0015] (1) Reacting N-methylbenzamide with 5-bromopentyltrimethoxysilane to obtain a siloxane-substituted benzene;

[0016] (2) Reacting thiosalicylic acid with the siloxane-substituted benzene to obtain the modified thioxanthone.

[0017] Further, the siloxane-substituted benzene has a structure shown in the following formula B:

[0018]

[0019] By introducing a siloxane structure into thioxanthone, the present invention can improve the dispersibility and stability of the photoinitiator in the photocuring system and further improve the photocuring efficiency.

[0020] Further, the specific method of step (1) is as follows: In a reactor, add N-methylbenzamide, sodium hydroxide and absolute ethanol. Under the protection of an inert gas, dropwise add 5-bromopentyltrimethoxysilane and then heat to 80-90 °C. Stir and react for 8-12 hours, then cool, filter, wash and dry to obtain the siloxane-substituted benzene.

[0021] Further, the molar ratio of N-methylbenzamide to 5-bromopentyltrimethoxysilane is 1.2-1.4:1.

[0022] Further, the specific method of step (2) is as follows: in a reactor, thiosalicylic acid, phosphorus pentoxide, and concentrated sulfuric acid are added. After stirring evenly, siloxane-substituted benzene is added. After heating to 80 - 90 °C and reacting for 2 - 4 hours, it is cooled, filtered, washed, and dried to obtain the modified thioxanthone.

[0023] In the present invention, thiosalicylic acid is added to react with siloxane-substituted benzene to obtain modified thioxanthone. On the one hand, due to the temperature resistance and weather resistance of the siloxane structure in siloxane-substituted benzene, the thermal stability and storage stability of the photoinitiator composition can be significantly improved; on the other hand, by combining siloxane with the amide group structure, having multiple chromophore groups and hydrogen-donating sites, the photo-reaction activity of the photoinitiator composition can be further improved.

[0024] Further, the mass ratio of thiosalicylic acid to siloxane-substituted benzene is 2 - 3:4; the mass concentration of the concentrated sulfuric acid is 90 - 99%.

[0025] Further, the mass ratio of the modified thioxanthone to the co-initiator is 1:3 - 5.

[0026] Use of any of the above free radical photoinitiator compositions in resins, coatings, inks, pressure-sensitive adhesives, photoresists, and 3D printing materials.

[0027] Beneficial effects:

[0028] (1) The free radical photoinitiator composition provided by the present invention, by using modified thioxanthone and mixing it with a co-initiator, has excellent thermal stability and storage stability, and high photo-reaction activity, and can be widely used in fields such as resins, coatings, inks, pressure-sensitive adhesives, photoresists, and 3D printing materials.

[0029] (2) In the free radical photoinitiator composition provided by the present invention, using modified thioxanthone as the main photoinitiator, after the main structure of thioxanthone is excited, thioxanthone radicals and amide radicals are generated, and after combining with the co-initiator, it has excellent photo-reaction activity and can efficiently initiate polymerization reactions.

[0030] (3) In the free radical photoinitiator composition provided by the present invention, thiosalicylic acid is added to react with siloxane-substituted benzene to obtain modified thioxanthone. On the one hand, due to the temperature resistance and weather resistance of the siloxane structure in siloxane-substituted benzene, the thermal stability and storage stability of the photoinitiator composition can be significantly improved; on the other hand, by combining siloxane with the amide group structure, having multiple chromophore groups and hydrogen-donating sites, the photo-reaction activity of the photoinitiator composition can be further improved.

[0031] (4) The free radical photoinitiator composition provided by the present invention can improve the dispersibility and stability of the photoinitiator in the photocuring system by introducing a siloxane structure into thioxanthone, and can further improve the photocuring efficiency. Detailed implementation manners

[0032] The present invention will be described below in conjunction with specific implementation manners. It should be noted that the following examples are examples of the present invention, only for illustrating the present invention, and not for limiting the present invention. Without departing from the gist or scope of the present invention, other combinations and various improvements within the concept of the present invention can be made.

[0033] The commercially available photoinitiator is photoinitiator 754 purchased from Shanghai Yinchang New Materials Co., Ltd.; the commercially available thioxanthone photoinitiator is photoinitiator DETX purchased from Hubei Jianchu Biopharmaceutical Co., Ltd.; the remaining reagents and equipment are conventional reagents and equipment in the technical field.

[0034] Preparation of silane-substituted benzene

[0035] The silane-substituted benzene is prepared through the following steps:

[0036] In a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen protection device, 0.012 mol of N-methylbenzamide, 8 g of sodium hydroxide and 50 ml of absolute ethanol are added. Under nitrogen protection, 0.01 mol of 5-bromopentyltrimethoxysilane is added dropwise, and then the temperature is raised to 90 °C. After stirring and reacting for 12 hours, it is cooled, filtered, washed and dried to obtain the siloxane-substituted benzene.

[0037] Mass spectrometry data of siloxane-substituted benzene: The product was analyzed by LC-MS. The m / z of the product was 325.17 (100.0%), 326.21 (23.9%), 327.18 (6.1%).

[0038] Preparation of modified thioxanthone-1

[0039] The modified thioxanthone-1 is prepared through the following steps:

[0040] In a three-necked flask equipped with a stirrer and a nitrogen protection device, 2.5 g of thiosalicylic acid, 1.5 g of phosphorus pentoxide and 20 ml of concentrated sulfuric acid with a mass concentration of 98% are added. After stirring evenly, 4 g of siloxane-substituted benzene is added. After heating to 85 °C and reacting for 3 hours, it is cooled, filtered, washed and dried to obtain the modified thioxanthone-1.

[0041] Mass spectrometry data of modified thioxanthone-1: The product was analyzed by LC-MS. The m / z of the product was 459.15 (100.0%), 460.31 (36.2%), 461.23 (10.5%), 462.24 (2.1%).

[0042] Preparation of Modified Thioxanthone-2

[0043] It is basically the same as the preparation of modified thioxanthone-1, except that the siloxane-substituted benzene is changed to an equal amount of N-methylbenzamide.

[0044] Example 1

[0045] A radical photoinitiator composition was prepared by uniformly mixing modified thioxanthone-1 and N-phenylglycine in a mass ratio of 1:4.

[0046] Example 2

[0047] A radical photoinitiator composition was prepared by uniformly mixing modified thioxanthone-1 and ethyl 4-dimethylaminobenzoate in a mass ratio of 1:3.

[0048] Example 3

[0049] A radical photoinitiator composition was prepared by uniformly mixing modified thioxanthone-1 and N,N-di(hydroxyethyl)aniline in a mass ratio of 1:5.

[0050] Comparative Example 1

[0051] Commercially available photoinitiator.

[0052] Comparative Example 2

[0053] It is basically the same as Example 1, except that N-phenylglycine is changed to an equal amount of modified thioxanthone-1.

[0054] Comparative Example 3

[0055] It is basically the same as Example 1, except that modified thioxanthone-1 is changed to an equal amount of commercially available thioxanthone photoinitiator.

[0056] Comparative Example 4

[0057] It is basically the same as Example 1, except that modified thioxanthone-1 is changed to an equal amount of modified thioxanthone-2.

[0058] Performance Test

[0059] 1. Thermal stability detection: Take 15 mg of the products of Examples 1-3 and Comparative Examples 1-4, place them in a crucible for testing, with a heating rate of 10 °C / min and a temperature range of 50-500 °C. Detect the change in product quality with temperature by programmed heating, and record the temperature when the sample loses 5% of its weight.

[0060] 2. Photo-reaction activity detection: Respectively take 3 wt% of the products of Examples 1-3 and Comparative Examples 1-4 and conduct a photocuring experiment with 40 wt% ethyl acrylate and 57 wt% hexanediol diacrylate. The light source power is 160 mW / cm2 The absorption peak intensities of the organic film before and after curing near 1635 cm -1 (C═C) and 1720 cm -1 (C═O) were detected using FT-IR (Nicolet iS50, Thermo-Fisher), and the photocuring rate was calculated.

[0061] Photocuring rate (%) = |1 - (F / S)| × 100;

[0062] where F is the ratio of the absorption peak intensity of the cured organic film near 1635 cm -1 to the absorption peak intensity near 1720 cm -1 ; S is the ratio of the absorption peak intensity of the uncured organic film near 1635 cm -1 to the absorption peak intensity near 1720 cm -1 .

[0063] 3. Storage stability test: Take 2 g of the products of Examples 1-3 and Comparative Examples 1-4, add them to 50 ml of diethylene glycol diacrylate respectively, stir evenly, and store at room temperature for 3 days, and observe the solution state.

[0064] The above test results are shown in Table 1 below:

[0065] Table 1 shows the test results of Examples 1-3 and Comparative Examples 1-4

[0066] Table 1

[0067]

[0068]

[0069] From the comparison of the test results of Examples 1-3 and Comparative Example 1, it can be seen that the free radical photoinitiator composition provided by the present invention can improve the photoreaction activity of the initiator composition and has excellent thermal stability and storage stability by combining modified thioxanthone with a co-initiator.

[0070] From the comparison of the test results of Examples 1-3 and Comparative Example 2, it can be seen that in the free radical photoinitiator composition provided by the present invention, although the single-component modified thioxanthone has better thermal stability, its photoreaction activity is insufficient. By combining with a co-initiator, it can have higher photoreaction activity while maintaining excellent thermal stability and storage stability.

[0071] According to the comparison of the detection results of Examples 1-3 and Comparative Examples 3 and 4, it can be seen that in the free radical photoinitiator composition provided by the present invention, by introducing a siloxane structure into thioxanthone, the thermal stability and storage stability of the photoinitiator can be significantly improved, and it has excellent photoreaction activity.

[0072] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it. However, the protection scope of the present invention cannot be limited thereby. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A free radical photoinitiator composition, characterized in that, It contains modified thioxanthone and a co-initiator; The modified thioxanthone has the structure shown in Formula A below:

2. The free radical photoinitiator composition according to claim 1, characterized in that, The co-initiator is selected from one of N-phenylglycine, ethyl 4-dimethylaminobenzoate, N,N-di(hydroxyethyl)aniline, or N,N-di(hydroxyethyl)-p-methylaniline.

3. The free radical photoinitiator composition according to claim 1, characterized in that, The modified thioxanthone is prepared by the following steps: (1) N-methylbenzamide reacts with 5-bromopentyltrimethoxysilane to obtain a siloxane-substituted benzene; (2) Thiosalicylic acid reacts with the siloxane-substituted benzene to obtain the modified thioxanthone.

4. The free radical photoinitiator composition according to claim 3, wherein The siloxane-substituted benzene has the structure shown in Formula B below:

5. The radical photoinitiator composition according to claim 3, characterized in that, The specific method of step (1) is as follows: In a reactor, add N-methylbenzamide, sodium hydroxide, and absolute ethanol. Under the protection of an inert gas, dropwise add 5-bromopentyltrimethoxysilane, then heat to 80 - 90 °C, stir and react for 8 - 12 hours, then cool, filter, wash, and dry to obtain the siloxane-substituted benzene.

6. The radical photoinitiator composition according to claim 5, characterized in that, The molar ratio of N-methylbenzamide to 5-bromopentyltrimethoxysilane is 1.2 - 1.4:

1.

7. The radical photoinitiator composition according to claim 3, wherein The specific method of step (2) is as follows: In a reactor, add thiosalicylic acid, phosphorus pentoxide, and concentrated sulfuric acid. After stirring evenly, add the siloxane-substituted benzene, heat to 80 - 90 °C and react for 2 - 4 hours, then cool, filter, wash, and dry to obtain the modified thioxanthone.

8. The free radical photoinitiator composition according to claim 7, characterized in that, The mass ratio of thiosalicylic acid to the siloxane-substituted benzene is 2 - 3:4; the mass concentration of the concentrated sulfuric acid is 90 - 99%.

9. The radical photoinitiator composition according to claim 1, characterized in that, The mass ratio of the modified thioxanthone to the co-initiator is 1:3 - 5.

10. Use of the radical photoinitiator composition according to any one of claims 1 - 9 in resins, coatings, inks, pressure-sensitive adhesives, photoresists, and 3D printing materials.

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