Yellowing-resistant light-cured organic silicon resin and preparation method thereof

Abstract

The invention discloses yellowing-resistant light-cured organic silicon resin and a preparation method thereof, and belongs to the technical field of light-cured resin. The resin is prepared from the following raw materials in parts by weight: 80 to 100 parts of vinyl-terminated polysiloxane, 15 to 25 parts of trimethylolpropane tri (3-mercaptopropionate), 1 to 3 parts of yellowing-resistant aid, 2 to 4 parts of photoinitiator and 0.5 to 1 part of flatting agent. When the resin is prepared, the raw materials are uniformly mixed under a dark condition, and the resin is obtained after vacuum defoaming. Wherein the yellowing-resistant auxiliary agent is a benzotriazole ultraviolet light absorber and is synthesized through a multi-step reaction, the structure simultaneously contains a benzotriazole ring and anthryl, and the benzotriazole ring and the anthryl have a synergistic effect so that ultraviolet rays can be efficiently absorbed and yellowing can be inhibited. The obtained resin has excellent yellowing resistance and high curing speed, and is suitable for the fields of coatings, printing ink, adhesives, electronic packaging and the like.

Description

Technical Field

[0002] This invention belongs to the field of photocurable resin technology, specifically, it relates to a yellowing-resistant photocurable silicone resin and its preparation method. Background Technology

[0003] Currently, with the rapid development of polymer materials science and the continuous expansion of downstream applications, UV-curable resins have been widely used in many industrial fields such as coatings, inks, adhesives, 3D printing, and electronic packaging due to their outstanding advantages such as high efficiency, energy saving, and environmental friendliness. Under irradiation with UV light of a specific wavelength, the photoinitiator within these materials rapidly generates active free radicals or cations, initiating a chain reaction of polymerization between the prepolymer with unsaturated double bonds and the reactive diluent. This process transforms the liquid state into a solid state in a very short time, forming a cross-linked network structure. Compared with traditional thermosetting processes, UV curing technology has significant advantages such as extremely low energy consumption, fast curing rate, small equipment footprint, and almost zero volatile organic compound emissions, aligning with the current trend of green manufacturing and sustainable development.

[0004] However, existing UV-curable resins generally suffer from poor resistance to yellowing during use. Yellowing refers to the irreversible changes in the chemical structure of a material under the influence of factors such as oxygen, ultraviolet light, visible light, and even heat in the natural environment, leading to a gradual yellowing of the product's color, decreased transparency, and loss of gloss, severely affecting the product's appearance and lifespan. Traditional UV-curable resins, such as acrylates and epoxy resins, often contain unsaturated double bonds and amine groups. Unsaturated double bonds are easily oxidized under light and high temperatures, generating colored products such as conjugated ketones, leading to yellowing. Secondly, some amine curing accelerators remaining in the resin synthesis process easily react with oxygen to generate colored oxidation products, accelerating yellowing.

[0005] Therefore, in view of the shortcomings of existing photocurable resins in long-term yellowing resistance, there is an urgent need to invent a yellowing-resistant photocurable resin and its preparation method to meet the higher technical requirements of the photocurable resin technology field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a yellowing-resistant photocurable silicone resin and its preparation method.

[0007] The objective of this invention can be achieved through the following technical solutions: A yellowing-resistant light-curing silicone resin comprises the following raw materials in parts by weight: 80-100 parts vinyl-terminated polysiloxane, 15-25 parts trimethylolpropane tris(3-mercaptopropionate), 1-3 parts yellowing-resistant additive, 2-4 parts photoinitiator, and 0.5-1 part leveling agent.

[0008] Preferably, the anti-yellowing agent is prepared by the following steps: S1. Add 3-amino-p-cresol, 2-anthracarboxylic acid and 4-dimethylaminopyridine to a dry three-necked flask equipped with a magnetic stirrer and a reflux condenser, then add N,N-dimethylformamide as a solvent, start stirring until the solids are completely dissolved, add dicyclohexylcarbodiimide, after the addition is complete, heat the apparatus to 30-35℃, and continue stirring the reaction for 8-12 hours. After the reaction is complete, after post-processing, anthracene compounds are obtained. The reaction formula for the preparation of anthracene compounds in step S1 is as follows:

[0009] S2. Add o-nitroaniline to a round-bottom flask equipped with a magnetic stirrer, then add water and dropwise concentrated hydrochloric acid solution. After the addition is complete, place the apparatus under ice bath conditions, dissolve sodium nitrite in water and gradually dropwise into the flask. After the addition is complete, turn on the stirrer and react for 30-40 minutes to obtain a diazonium salt solution. S3. Add the anthracene compound to a dry three-necked flask equipped with a magnetic stirrer and a dropping funnel. Then add N,N-dimethylformyl as a solvent, start stirring, place the apparatus under ice bath conditions, and add concentrated hydrochloric acid solution and diazonium salt solution prepared in step S2 dropwise through the dropping funnel. After the addition is complete, continue the reaction for 3-4 hours. After the reaction is complete, the coupling product is obtained after post-processing. S4. Add the coupling product to a round-bottom flask equipped with a magnetic stirrer, then add N,N-dimethylformamide as a solvent, start stirring, and slowly add sodium hydroxide solution dropwise until the system becomes strongly alkaline (pH=12). After the addition is complete, heat the apparatus to 70-75℃, and then add thiourea dioxide in batches. After the addition is complete, continue the reaction for 3-4 hours. After the reaction is complete, the anti-yellowing additive is obtained after post-treatment.

[0010] The reaction formula for preparing the anti-yellowing agent of this invention is as follows:

[0011] Preferably, the ratio of the amounts of 3-amino-p-cresol, 2-anthracarboxylic acid, 4-dimethylaminopyridine and dicyclohexylcarbodiimide in step S1 is 12.3g:23.3g:1.2g:22.7g.

[0012] Preferably, in step S2, the ratio of o-nitroaniline, concentrated hydrochloric acid solution, and sodium nitrite is 15.4g:30mL:6.9g.

[0013] Preferably, the ratio of anthracene compound to concentrated hydrochloric acid solution in step S3 is 32.7 g: 30 mL.

[0014] Preferably, the ratio of the coupling product to thiourea dioxide in step S4 is 50.7g:35.6g.

[0015] This invention produces a benzotriazole-based UV absorber through a four-step reaction. Its molecular structure consists of a benzotriazole ring linked to a benzene ring containing hydroxyl groups. Hydrogen bonds between the nitrogen atom and the adjacent hydroxyl group create a stable cyclic structure, significantly improving the yellowing resistance of the matrix. Furthermore, the molecule contains anthracene groups, which have a long excited-state lifetime and a large conjugated system. These groups can accept energy from benzotriazole units or other excited-state molecules through intramolecular energy transfer and release it via fluorescence or non-radiative means, reducing the risk of photodegradation. Therefore, the two groups work synergistically, and their complementary spectra further enhance the yellowing resistance of the matrix. Finally, this invention integrates functional groups into a single molecule. Compared to adding various additives individually, this method avoids phase separation or local aggregation due to differences in polarity and solubility between the two molecules during mixing, resulting in higher efficiency and better stability.

[0016] Preferably, the vinyl-terminated polysiloxane is prepared by the following steps: Under dry nitrogen protection, α,ω-dihydroxypolydimethylsiloxane and anhydrous toluene were added to a four-necked flask equipped with a stirrer, thermometer, reflux condenser and dropping funnel. The temperature was raised to 80-85℃, stirring was started, and 3-(meth)acryloyloxypropylmethyldimethoxysilane was added dropwise. After the addition was complete, a catalyst was added, and the temperature was slowly raised to 110-115℃. The reaction was refluxed for 6-8 hours. After the reaction was completed, toluene and byproducts were removed by distillation under reduced pressure to obtain vinyl-terminated polysiloxane.

[0017] Preferably, the raw materials are as follows by weight: 90-100 parts α,ω-dihydroxypolydimethylsiloxane, 50-60 parts anhydrous toluene, 25-30 parts 3-(meth)acryloyloxypropylmethyldimethoxysilane and 0.1-0.2 parts catalyst.

[0018] This invention also provides a method for preparing a yellowing-resistant photocurable silicone resin, comprising the following steps: A1. Under light-protected conditions, first add vinyl-terminated polysiloxane to the reactor, then add trimethylolpropane tris(3-mercaptopropionate), and stir (300-500 rpm) in a water bath until the system is completely homogeneous and transparent. A2. Add the yellowing resistant agent, photoinitiator and leveling agent to the reaction vessel of step A1, and continue stirring for 20-40 minutes until the photoinitiator is completely dissolved. Then degas under vacuum and filter to obtain the yellowing resistant light-curing silicone resin.

[0019] Preferably, the temperature of the water bath is 50-60℃.

[0020] Preferably, the vacuum degree of the vacuum degassing is -0.1 MPa, and the degassing time is 15-20 min.

[0021] The beneficial effects of this invention are: Advantage 1: This invention introduces benzotriazole ultraviolet absorbers as anti-yellowing additives, which can efficiently absorb ultraviolet rays and convert them into heat energy, thereby effectively inhibiting the yellowing phenomenon of resin under environmental factors such as light, oxygen, and heat. Advantage 2: It uses vinyl-terminated polysiloxane as the main prepolymer, combined with trimethylolpropane tris(3-mercaptopropionate), to form a highly efficient photocurable system that cures rapidly under UV irradiation and forms a dense cross-linked network structure. Advantage 3: It adopts ultraviolet curing technology, which does not require high-temperature heating, has low energy consumption, fast curing speed, and meets environmental protection requirements; In summary, this invention, by combining the design of anti-yellowing additives with a highly efficient photocuring system, successfully solves the technical problem of easy yellowing of traditional photocurable resins, and has good industrial application prospects and market competitiveness. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0023] Example 1 Preparation of anti-yellowing additives: S1. 12.3 g of 3-amino-p-cresol, 23.3 g of 2-anthracarboxylic acid, and 1.2 g of 4-dimethylaminopyridine were added to a dry three-necked flask equipped with a magnetic stirrer and a reflux condenser. 100 mL of N,N-dimethylformamide was added as a solvent, and stirring was started until the solids were completely dissolved. 22.7 g of dicyclohexylcarbodiimide was added. After the addition was complete, the apparatus was heated to 35 °C and the reaction was stirred continuously for 12 h. After the reaction was complete, the mixture was filtered, and the reaction solution was cooled to room temperature and filtered under vacuum. The filter cake was washed with DCM, and the filtrates were combined and washed successively with saturated sodium carbonate solution, dilute hydrochloric acid solution (mass fraction 5%), and deionized water. The organic phase was dried with anhydrous sodium sulfate, filtered, and the filtrate was concentrated by rotary evaporation. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate, volume ratio 2:1). Rotary evaporation was performed to obtain anthracene compounds. S2. Add 15.4 g of o-nitroaniline to a round-bottom flask equipped with a magnetic stirrer, then add 30 mL of water and dropwise add 30 mL of concentrated hydrochloric acid solution (mass fraction 36%). After the addition is complete, place the apparatus under ice bath conditions, dissolve 6.9 g of sodium nitrite in 10 mL of water and gradually add it dropwise to the flask. After the addition is complete, turn on the stirrer and react for 40 min to obtain a diazonium salt solution. S3. Add 32.7 g of anthracene compound to a dry three-necked flask equipped with a magnetic stirrer and a dropping funnel. Then add 100 mL of N,N-dimethylformyl as a solvent, start stirring, and place the apparatus under ice bath conditions. Add 30 mL of concentrated hydrochloric acid solution (36% by mass) and the diazonium salt solution prepared in step S2 dropwise through the dropping funnel. After the addition is complete, continue the reaction for 4 h. When the reaction is complete, slowly pour the reaction solution into an ice-water mixture and wait for the solid to precipitate. Filter and wash several times with ethanol solution to obtain the coupling product. S4. Add 50.7g of the coupling product to a round-bottom flask equipped with a magnetic stirrer, then add 150mL of N,N-dimethylformamide as a solvent, start stirring, and slowly add sodium hydroxide solution (20% by mass) dropwise until the system is strongly alkaline (pH=12). After the addition is complete, heat the apparatus to 70℃, and then add 35.6g of thiourea dioxide in batches. After the addition is complete, continue the reaction for 4 hours. After the reaction is complete, pour the reaction solution into ice water to precipitate the product. Adjust the pH to neutral with dilute hydrochloric acid solution (5% by mass). At this time, a large amount of solid will precipitate. Filter, collect the solid, wash with ethyl acetate, and dry to obtain the anti-yellowing agent. Preparation of vinyl-terminated polysiloxanes: Under dry nitrogen protection, 90 parts of α,ω-dihydroxypolydimethylsiloxane and 50 parts of anhydrous toluene were added to a four-necked flask equipped with a stirrer, thermometer, reflux condenser and dropping funnel. The temperature was raised to 80°C, stirring was started, and 25 parts of 3-(meth)acryloyloxypropylmethyldimethoxysilane were added dropwise. After the addition was complete, 0.1 parts of stannous octoate were added, the temperature was slowly raised to 110°C, and the reaction was refluxed for 6 hours. After the reaction was completed, toluene and byproducts were removed by distillation under reduced pressure to obtain vinyl-terminated polysiloxane. A method for preparing a yellowing-resistant, light-curing silicone resin includes the following steps: A1. Under light-protected conditions, first add 80 parts of vinyl-terminated polysiloxane to the reactor, then add 15 parts of trimethylolpropane tris(3-mercaptopropionate), and stir (300 rpm) in a 50°C water bath until the system is completely homogeneous and transparent. A2. Add 1 part of anti-yellowing agent, 2 parts of photoinitiator 1173 and 0.5 parts of leveling agent (BYK-307) to the reactor of step A1, continue stirring for 20 minutes until the photoinitiator is completely dissolved, then degas under vacuum at -0.1MPa for 15 minutes, filter, and obtain anti-yellowing photocurable silicone resin.

[0024] Example 2 The only difference between this embodiment and Embodiment 1 is that, in this embodiment, the vinyl-terminated polysiloxane is processed through the following steps: Under dry nitrogen protection, 100 parts of α,ω-dihydroxypolydimethylsiloxane and 60 parts of anhydrous toluene were added to a four-necked flask equipped with a stirrer, thermometer, reflux condenser and dropping funnel. The temperature was raised to 85°C, stirring was started, and 30 parts of 3-(meth)acryloyloxypropylmethyldimethoxysilane were added dropwise. After the addition was complete, 0.2 parts of stannous octoate were added, the temperature was slowly raised to 115°C, and the reaction was refluxed for 8 hours. After the reaction was completed, toluene and byproducts were removed by distillation under reduced pressure to obtain vinyl-terminated polysiloxane. A method for preparing a yellowing-resistant, light-curing silicone resin includes the following steps: A1. Under light-protected conditions, first add 90 parts of vinyl-terminated polysiloxane to the reactor, then add 20 parts of trimethylolpropane tris(3-mercaptopropionate), and stir (500 rpm) in a 60°C water bath until the system is completely homogeneous and transparent. A2. Add 2 parts of anti-yellowing agent, 3 parts of photoinitiator 1173 and 0.75 parts of leveling agent (BYK-307) to the reactor of step A1, and continue stirring for 40 minutes until the photoinitiator is completely dissolved. Then, degas under vacuum at a vacuum degree of -0.1MPa for 20 minutes, filter, and obtain anti-yellowing photocurable silicone resin.

[0025] Example 3 The only difference between this embodiment and Embodiment 2 is that, in this embodiment, a method for preparing a yellowing-resistant light-curing silicone resin includes the following steps: A1. Under light-protected conditions, first add 100 parts of vinyl-terminated polysiloxane to the reactor, then add 25 parts of trimethylolpropane tris(3-mercaptopropionate), and stir (500 rpm) in a 60°C water bath until the system is completely homogeneous and transparent. A2. Add 3 parts of anti-yellowing agent, 4 parts of photoinitiator 1173 and 1 part of leveling agent (BYK-307) to the reaction vessel of step A1, continue stirring for 40 minutes until the photoinitiator is completely dissolved, then degas under vacuum at -0.1MPa for 20 minutes, filter, and obtain anti-yellowing photocurable silicone resin.

[0026] Comparative Example 1 The difference between this comparative example and Example 3 is that, in this comparative example, an equal amount of 2-(2-hydroxy-5-benzyl)benzotriazole (UV-P) was used to replace the yellowing resistance additive to prepare the resin. Comparative Example 2 The difference between this comparative example and Example 3 is that no yellowing-resistant additive was added to obtain the resin.

[0027] The resins obtained in Examples 1, 2, and 3, and Comparative Examples 1 and 2, were subjected to the following performance tests: Using GB / T 1865 standard, with a wavelength of 340nm as the reference, the irradiance is set at 0.5W / m. 2 The color difference of the sample after aging for 500 hours was measured.

[0028] The performance test results are shown in Table 1: Table 1

[0029] As can be seen from the performance test results in the table above, the resin prepared in the embodiments of the present invention has small color difference and strong resistance to yellowing after aging. Therefore, the present invention has important application value in the field of photocurable resin technology.

[0030] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A yellowing-resistant photocurable silicone resin, characterized by comprising: The raw materials include the following components by weight: 80-100 parts of vinyl-terminated polysiloxane, 15-25 parts of trimethylolpropane tris(3-mercaptopropionate), 1-3 parts of yellowing-resistant auxiliary agent, 2-4 parts of photoinitiator, and 0.5-1 part of leveling agent.

2. The yellowing resistant photocured silicone resin according to claim 1, wherein The yellowing-resistant auxiliary agent is prepared by the following steps: S1, 3-amino-p-cresol, 2-anthracene carboxylic acid, and 4-dimethylamino pyridine are added to a flask, N,N-dimethylformamide is added, stirring is started, dicyclohexyl carbodiimide is added, and after the addition is completed, the reaction is carried out at 30-35 DEG C for 8-12 h, and after the reaction is completed, an anthryl compound is obtained; S2, o-nitroaniline is added to a flask, water is then added, and concentrated hydrochloric acid solution is added dropwise, after the dropwise addition is completed, sodium nitrite is dissolved in water under ice bath conditions, and the solution is gradually added dropwise to the flask, after the dropwise addition is completed, stirring is started, and after the reaction is carried out for 30-40 min, a diazonium salt solution is obtained; S3, the anthryl compound is added to a flask, N,N-dimethylformamide is then added as a solvent, stirring is started, concentrated hydrochloric acid solution and the diazonium salt solution prepared in step S2 are added dropwise in sequence under ice bath conditions, after the dropwise addition is completed, the reaction is continued for 3-4 h, and after the reaction is completed, a coupling product is obtained; S4, the coupling product is added to a flask, N,N-dimethylformamide is then added, stirring is started, sodium hydroxide solution is added dropwise slowly until the pH is 12, heating is carried out to 70-75 DEG C, and thiourea dioxide is added, and the reaction is continued for 3-4 h, and after the reaction is completed, a yellowing-resistant auxiliary agent is obtained.

3. The yellowing resistant photocured silicone resin according to claim 2, wherein The ratio of the amounts of 3-amino-p-cresol, 2-anthracene carboxylic acid, 4-dimethylamino pyridine, and dicyclohexyl carbodiimide used in step S1 is 12.3 g:23.3 g:1.2 g:22.7 g.

4. The yellowing resistant photocured silicone resin according to claim 2, wherein The ratio of the amounts of o-nitroaniline, concentrated hydrochloric acid solution, and sodium nitrite used in step S2 is 15.4 g:30 mL:6.9 g.

5. The yellowing resistant photocured silicone resin according to claim 2, wherein The ratio of the amounts of anthryl compound and concentrated hydrochloric acid solution used in step S3 is 32.7 g:30 mL.

6. The yellowing resistant photocured silicone resin according to claim 2, wherein The ratio of the amounts of coupling product and thiourea dioxide used in step S4 is 50.7 g:35.6 g.

7. A process for the preparation of a yellowing resistant photocurable silicone resin according to any one of claims 1 to 6, characterized in that, The following steps are included: A1, under light-proof conditions, the vinyl-terminated polysiloxane is first added to a reaction kettle, the trimethylolpropane tris(3-mercaptopropionate) is then added, and stirring is started under water bath conditions until the system is completely uniform and transparent; A2, the yellowing-resistant auxiliary agent, the photoinitiator, and the leveling agent are added to the reaction kettle of step A1, stirring is continued for 20-40 min, and then vacuum degassing is carried out, filtration is carried out, and a yellowing-resistant photocurable silicone resin is obtained.

8. The method for preparing a yellowing-resistant light-curing silicone resin according to claim 7, characterized in that, The temperature of the water bath is 50-60 DEG C.

9. The method for preparing a yellowing-resistant light-curing silicone resin according to claim 7, characterized in that, The vacuum degree of the vacuum degassing is -0.1 MPa, and the degassing time is 15-20 min.

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