Preparation method of silicon-based photoinitiator

Abstract

The invention relates to the technical field of photoinitiators, and discloses a preparation method of a silicon-based photoinitiator, which comprises the following steps: firstly, dissolving an alkaline substance in a proper solvent as a catalyst or an accelerant, then introducing a photoinitiator parent with an active group, carrying out nucleophilic substitution reaction on the photoinitiator parent and an allyl halide, and introducing an allyl structure. And after the reaction is completed, adjusting to be neutral through an acid neutralization system, and then performing extraction, drying and reduced pressure distillation to purify the intermediate. And finally, carrying out addition reaction on the intermediate and an organic silicon monomer containing hydrogen and silicon bonds or silicone oil in the presence of a catalyst to obtain the target silicon-based photoinitiator. The photoinitiator is applied to light-cured organic silicon, the performance and stability of a material under the environments of high temperature, high humidity, ultraviolet irradiation, chemical corrosion and the like are remarkably improved, and the problems that due to the fact that the compatibility of photosensitive resin and the photoinitiator in the light-cured organic silicon is poor, the whitening performance of the cured material is degraded and the like are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of photoinitiators, and specifically to a preparation method of a silicon-based photoinitiator. Background Art

[0002] Due to its advantages of high efficiency and energy saving, the photocuring technology is widely used in fields such as coatings, electronic packaging, and 3D printing. Among them, organosilicon-based photocuring materials have attracted much attention due to their heat resistance, flexibility and other characteristics. However, due to the strong non-polar characteristics of the main chain (Si-O-Si) of conventional photocuring silicone resins, it is difficult to be compatible with traditional photoinitiators (mostly polar or aromatic structures), resulting in problems such as phase separation and precipitation of photoinitiators during storage or processing. This phenomenon not only reduces the photocuring efficiency of the material, but also may cause surface defects (such as fogging, cracking) of the cured film and a decrease in mechanical properties, seriously restricting the further development of such materials.

[0003] To solve the compatibility problem, the existing technology mainly realizes it by physical blending or chemical modification of photoinitiators. For example: adding silane coupling agents to reduce the interfacial polarity difference, or silanizing the initiator. However, these methods have obvious deficiencies: physical blending cannot completely eliminate microscopic phase separation, and precipitation may still occur during long-term storage; the chemical modification synthesis steps are complex and may reduce the initiation efficiency, and the modification may introduce additional side reactions. In addition, the types of commercial photoinitiators suitable for the organosilicon system are extremely limited, and it is difficult to adapt to different curing condition requirements, such as thick coating curing, oxygen inhibition polymerization resistance, etc. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention provides a preparation method of a silicon-based photoinitiator, which solves the problems of performance decline, poor stability and insufficient durability of existing resin materials in harsh environments such as high temperature, high humidity, ultraviolet light irradiation and chemical corrosion.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A preparation method of a silicon-based photoinitiator, comprising the following steps: S1. Dissolve an alkaline substance in a solvent, add a photoinitiator and stir, then add an allyl halide, and continue to react under heating or room temperature conditions to obtain a reaction solution; First, dissolve the alkaline in the solvent and add a photoinitiator, and promote its dissolution by stirring. The role of the alkaline substance is to provide a suitable reaction environment to activate the photoinitiator and the allyl halide. At this time, adding the allyl halide reacts with the photoinitiator in a nucleophilic substitution reaction. The specific reaction is as follows: Activation of the photoinitiator: Under alkaline conditions, some functional groups of the photoinitiator can be deprotonated to generate negatively charged intermediates or ligands, making it more active and providing a reaction center for subsequent reactions; Nucleophilic substitution reaction: Allyl halides can release halide ions under alkaline conditions, enabling them to undergo nucleophilic substitution reactions with photoinitiators and introducing allyl structures. This step is a key step in the functionalization of photoinitiator structures.

[0006] The addition of alkaline substances first activates the hydroxyl groups or other reactive groups of the photoinitiator through deprotonation, endowing it with strong nucleophilicity. Allyl halides lose halogen ions in an alkaline environment, forming reaction intermediates with negative charges, which can then perform nucleophilic attacks on the reactive groups of the photoinitiator to generate new allyl compounds.

[0007] The reaction is carried out in the temperature range of 60°C - 80°C and the reaction time is 3 - 12 hours, which can effectively promote the reaction of allyl halides and improve the yield of the product.

[0008] S2. Treat the reaction solution by quenching, neutralizing, extracting, drying, and vacuum distillation to obtain the photoinitiator etherification intermediate; After the reaction solution is generated in step S1, it is then treated by quenching, neutralizing, extracting, drying, and vacuum distillation to purify and obtain the photoinitiator etherification intermediate.

[0009] Quenching and neutralization: The reaction solution is quenched by adding ammonium chloride aqueous solution or ice water to quickly stop the reaction, and the residual alkaline substances are neutralized by adding an acidic solution. This step can ensure that subsequent reactions are not affected by the residual alkaline substances.

[0010] Extraction process: The reaction solution is extracted with organic solvents such as ethyl acetate, which can effectively separate the organic phase and the aqueous phase, thereby extracting the photoinitiator etherification intermediate. The extraction is usually carried out 2 - 4 times to ensure maximum extraction of the target product.

[0011] Drying treatment: The organic phase is dried with anhydrous sodium sulfate or magnesium sulfate to remove moisture and ensure the purity of the photoinitiator etherification intermediate.

[0012] Vacuum distillation: The solvent is removed using vacuum distillation technology, which can effectively recover the solvent and improve the purity of the intermediate. Under reduced pressure, the solvent is recovered at a temperature of 40°C - 60°C to avoid degradation of heat-sensitive substances.

[0013] The neutralization and quenching steps neutralize the excess alkaline substances in the reaction system through the reaction of acid and base, avoiding their impact on subsequent steps. The extraction process separates the organic phase from the aqueous phase using the selective solubility of the solvent to ensure the purification of the target product. The drying step removes moisture by using anhydrous sodium sulfate or magnesium sulfate to absorb moisture, further purifying the product. Vacuum distillation recovers the organic solvent by reducing the boiling point and can avoid thermal degradation at high temperatures.

[0014] S3. React the intermediate with an organosilicon monomer or silicone oil with at least one end hydrogen-terminated under the action of a catalyst to obtain a silicon-based photoinitiator.

[0015] In step S3, the intermediate structure usually contains allyl or other unsaturated double bond functional groups, which can react with the Si-H bond in the organosilicon monomer or silicone oil through an addition reaction (i.e., hydrosilylation reaction). Under the action of a platinum-based catalyst (such as Karstedt catalyst, Pt-Catalyst), this reaction proceeds with high regioselectivity and reaction efficiency.

[0016] By using an organosilicon monomer or silicone oil with at least one end hydrogen-terminated, its unreacted end forms a stable methyl or alkyl group through hydrogenation termination, which can effectively inhibit the occurrence of side reactions, avoid unnecessary cross-linking or chain extension, thereby improving the controllability of the system and the stability of the product. The end-capping structure can also reduce the degree of freedom of the siloxane segment and enhance the compatibility of the final product and the integrity of the network structure.

[0017] The addition reaction mechanism belongs to a typical electrophilic addition mechanism: after the Si-H bond is activated under the action of a catalyst, it undergoes a nucleophilic attack on the unsaturated carbon-carbon double bond to form a stable C-Si bond. The reaction conditions are mild, with few by-products, and it can be completed in a short time, which is beneficial to obtaining the target silicon-based photoinitiator with high purity and high efficiency.

[0018] Generally speaking, this mechanism realizes the effective connection between the functional intermediate and the structure-regulating component, forming a photoinitiator with high reactivity and structural stability, laying a molecular-level foundation for its subsequent performance in photocurable materials.

[0019] Preferably, in step S1, the basic substance is selected from one of potassium hydroxide, sodium hydroxide, sodium hydride or potassium carbonate, and in step S1, the allyl halide is selected from one of allyl bromide, allyl iodide, allyl chloride.

[0020] Preferably, in step S1, the molar ratio of the photoinitiator to the basic substance and the allyl halide is 1:1.8:2.8 - 1:2.2:3.2.

[0021] Preferably, in step S1, the solvent is tetrahydrofuran, the reaction temperature in step S1 is 60°C - 80°C, and the reaction time is 3 - 12 h.

[0022] Preferably, the photoinitiator in step S1 is selected from one of photoinitiator 2959, (1-hydroxycyclohexyl)[4-(2-hydroxyethoxy)phenyl]methanone, 2-hydroxy-4'-[2-(2-hydroxyethoxy)ethoxy]-2-methylpropiophenone, where photoinitiator 2959 is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone.

[0023] Preferably, the step S2 includes the following treatment process: S2.1. Add an aqueous ammonium chloride solution or ice water to the reaction solution for quenching and neutralization; S2.2. Extract the neutralized system with ethyl acetate 2 to 4 times to obtain an organic phase; S2.3. Wash the organic phase with water until it is neutral; S2.4. Dry the organic phase with anhydrous sodium sulfate or magnesium sulfate; S2.5. Remove the organic solvent by vacuum distillation to obtain a photoinitiator etherification intermediate.

[0024] Preferably, in the step S2.5, the solvent is recovered at 40°C - 60°C under reduced pressure.

[0025] Preferably, the catalyst in the step S3 is a platinum-based catalyst, and the usage amount is 0.1% - 1.0% of the total reaction mass. The reaction temperature in the step S3 is 65 - 75°C.

[0026] The present invention also provides a silicon-based photoinitiator prepared by the preparation method of the silicon-based photoinitiator as described above, which comprises the following compounds: or Wherein, n is selected from one of n = 0, n = 0 - 10, n = 10 - 50, n = 50 - 100, n = 100 - 200, n = 200 - 300 or n = 300 - 400, and m is selected from one of m = 0, m = 0 - 60, m = 60 - 300, m = 300 - 600, m = 600 - 1200, m = 1200 - 1800 or m = 1800 - 2400.

[0027] The present invention also provides the application of the silicon-based photoinitiator in photocuring silicone.

[0028] The present invention provides a preparation method of a silicon-based photoinitiator. It has the following beneficial effects: 1. By adopting a high-density allyl-initiated crosslinking curing system, the present invention effectively constructs a dense three-dimensional network structure, achieving the purpose of significantly improving the mechanical property retention rate of the material in high-temperature and high-humidity environments. Compared with the conventional low-crosslinking degree system in the prior art, which has the problem of performance decline after long-term exposure, the defects of poor environmental durability and insufficient stability are solved.

[0029] 2. The present invention introduces an ultraviolet high-efficiency initiation system. By optimizing the matching of the reaction sites between the initiator and allyl groups, the efficiency of the photocuring reaction is improved, and finally rapid prototyping with a dense structure is achieved. Different from the technical solutions with low reaction conversion rates and uneven curing in traditional formulations, the problems of obvious boundaries between curing layers and discontinuous mechanical properties are avoided.

[0030] 3. Through molecular-level structure regulation, the present invention enhances the anti-permeability of the resin to acid-base solutions and polar solvents. The achieved technical effect is that the material structure does not expand and the performance does not decline after long-term immersion. Existing solutions generally use low-polarity chain segments to fill and resist dissolution, but they cannot inhibit the corrosion failure caused by structural relaxation. This solution breaks through this traditional limitation and solves the technical problem of short-term effectiveness but long-term instability in chemical corrosion resistance.

[0031] 4. In the material design, the present invention introduces the strategy of multi-point grafting and cooperative crosslinking, which improves the crosslinking uniformity and spatial stability, and finally demonstrates the ability to maintain the integration of structure and performance under multiple environmental stimuli. Compared with the common single-point crosslinking or concentrated chain segment reactions in the prior art, the problems of easy cracking and local fatigue aging are avoided, and the uncontrollability of environmental adaptability and service life is fundamentally improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flowchart of the preparation method of the present invention; Figure 2 is an intermediate product of the silicon-based photoinitiator of the present invention; Figure 3 is a reaction formula of the silicon-based photoinitiator of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] Please refer to the attached Figure 1 - attached Figure 3 , Embodiments 1-3 of the present invention provide a preparation method of a silicon-based photoinitiator, and the specific content is as follows: Example 1: Raw materials: Potassium hydroxide: 10 g (0.17 mol, 2 equivalents); Photoinitiator 2959: 20 g (0.0891 mol, 1 equivalent); Allyl bromide: 32.37 g (0.26 mol, 3 equivalents); Tetrahydrofuran: solvent; Aqueous ammonium chloride solution (for neutralization); Ethyl acetate: for extraction; Anhydrous magnesium sulfate: desiccant.

[0035] Experimental procedure: Add potassium hydroxide to tetrahydrofuran and reflux the mixture to ensure complete dissolution of potassium hydroxide; After all the potassium hydroxide has dissolved, slowly add photoinitiator 2959, pay attention to controlling the temperature to avoid temperature rise, and stir for about 30 minutes; Slowly add allyl bromide and continue stirring to ensure that the temperature does not get too high; Reflux and stir the reaction solution at 70 °C for 3.5 hours. Use a TLC silica gel plate to confirm the completion of the reaction; After the reaction is completed, add aqueous ammonium chloride solution to carry out a neutralization reaction to terminate the reaction; Remove the tetrahydrofuran solvent by distillation under reduced pressure; Extract the reaction solution with ethyl acetate and repeat the extraction 3 times; Wash the ethyl acetate layer with deionized water until neutral; Dry the ethyl acetate layer with anhydrous magnesium sulfate to remove the remaining moisture; Remove the ethyl acetate by distillation under reduced pressure to obtain an intermediate product (as Figure 3 shown); React the intermediate product with an organosilicon compound containing an Si-H bond under the action of a platinum catalyst at a reaction temperature of 65 - 75 °C to form an Si-C bond and obtain the final silicon-based photoinitiator.

[0036] Example 2: Raw materials: (1-Hydroxycyclohexyl)[4-(2-hydroxyethoxy)phenyl]methanone: 20 g (0.0756 mol, 1 equivalent); NaH (sodium hydride): 3.62 g (0.1512 mol, 2 equivalents); Allyl bromide: 27.4382 g (0.2268 mol, 3 equivalents); Anhydrous tetrahydrofuran: solvent; Ethyl acetate: for extraction; Water, brine, anhydrous sodium sulfate: for washing and drying; Column chromatography (EA:PE = 1:20 to 1:10): for purification.

[0037] Experimental procedure: At 0 °C, (1-hydroxycyclohexyl)[4-(2-hydroxyethoxy)phenyl]methanone and sodium hydride were added to an anhydrous tetrahydrofuran solution and stirred, maintaining this temperature for 30 minutes; Allyl bromide was slowly added, allowing the reaction mixture to warm to room temperature; The reaction solution was poured into ice water for quenching and stirred for 10 minutes; The reaction mixture was extracted with ethyl acetate, and the organic phases were combined; The organic layer was washed with water and brine until the washings were neutral; The organic layer was dried over anhydrous sodium sulfate to remove moisture; Purification by column chromatography (EA:PE = 1:20 to 1:10) gave the intermediate product (as Figure 3 shown); The intermediate product was subjected to an addition reaction with an organosilicon containing a Si-H bond in the presence of a platinum catalyst at a reaction temperature of 65 - 75 °C to obtain the final silicon-based photoinitiator.

[0038] Example 3: Raw materials: Potassium carbonate: 20.6037 g (0.149 mol, 2 equivalents); 2-Hydroxy-4'-[2-(2-hydroxyethoxy)ethoxy]-2-methylpropiophenone: 20 g (0.0745 mol, 1 equivalent); Allyl iodide: 37.564 g (0.2236 mol, 3 equivalents); Tetrahydrofuran: solvent; Deionized water: for neutralization; Ethyl acetate: for extraction; Diatomaceous earth, anhydrous magnesium sulfate: for filtration and drying; Vacuum concentration: for solvent removal.

[0039] Experimental procedure: Under ice bath conditions, potassium carbonate was added to dry tetrahydrofuran, and the system was purged with nitrogen to maintain an inert atmosphere and cooled to 0 °C; 2-Hydroxy-4'-[2-(2-hydroxyethoxy)ethoxy]-2-methylpropiophenone was added to the solution and stirred at 0 °C for 1 hour; Allyl iodide was added dropwise, and then the solution was warmed to room temperature and stirred for an additional 24 hours under a nitrogen atmosphere; After the reaction was complete, deionized water was added and stirred for 10 minutes for quenching; The reaction solution was extracted 3 times with ethyl acetate (EA), and the organic phases were combined; The organic layer was washed with water until neutral and then with brine; Dry the organic layer with anhydrous magnesium sulfate to remove moisture; Filter through diatomaceous earth, and then perform vacuum concentration to remove ethyl acetate to obtain an intermediate product (as Figure 3 shown); React the intermediate product with an organosilicon containing an Si-H bond under the action of a platinum catalyst at a reaction temperature of 65-75 °C to obtain the final silicon-based photoinitiator.

[0040] Comparative Example 1: Compared with Example 1, the difference lies in that allyl bromide was not added and the allyl modification group was not introduced, and the rest were the same.

[0041] Comparative Example 2: Compared with Example 1, the difference lies in that the organosilicon was replaced with a non-reactive diluent DPM (dipropylene glycol methyl ether), and the rest were the same.

[0042] Comparative Example 3: Compared with Example 1, the difference lies in that the catalyst in the final addition reaction was cancelled, and the rest were the same.

[0043] Comparative Example 4: Compared with Example 2, the difference lies in that 0.5 equivalent of NaH was used instead of 2 equivalents, and other conditions remained the same.

[0044] Comparative Example 5: Compared with Example 2, the difference lies in that the column chromatography purification step was omitted, and the crude product was directly used for the subsequent addition, and the rest were the same.

[0045] Comparative Example 6: Compared with Example 2, the difference lies in that allyl bromide was changed to 1-bromobutane (non-double bond structure), and the rest were the same.

[0046] Comparative Example 7: Compared with Example 3, the difference lies in that the operation was not carried out under nitrogen protection, and other steps were the same.

[0047] Comparative Example 8: Compared with Example 3, the difference lies in that the amount of allyl iodide used was only 1 equivalent (not 3 equivalents), and the rest of the conditions were the same.

[0048] Comparative Example 9: Compared with Example 3, the difference lies in that the amount of organosilicon used was fixed, but the amount of the intermediate product increased by 2 times, and the rest were the same.

[0049] Comparative Example 10: Compared with Example 1, the difference lies in that the organosilicon monomer used in step S3 was not subjected to hydrogenation capping treatment, and the rest of the steps and conditions remained the same.

[0050] Experiment 1: Photocuring Performance Test Purpose of the experiment: This experiment aims to compare the photocuring rate and efficiency of Example 1 with Comparative Examples 1, 3, 4, 6, and 8 under ultraviolet light irradiation. By testing the photocuring rate, surface drying time, through drying time, and curing conversion rate of each sample, the influence of different formulations on photocuring performance is evaluated.

[0051] Experimental procedure: Material preparation: Prepare the required photocurable resin samples according to the formulations of the examples and comparative examples. The same concentration of photoinitiator (such as Benzoin Methyl Ether) is added to each sample; Pour each sample into a pre-cleaned glass slide mold, and control the thickness to be about 100 μm; Ultraviolet photocuring: Place the sample in an ultraviolet photocuring machine and irradiate it with a 365 nm wavelength ultraviolet light source; The curing conditions are set as follows: the ultraviolet light irradiation intensity is 10 mW / cm 2 , and the irradiation times are 10 s, 20 s, 30 s, and 40 s respectively (adjusted according to the preliminary test results of the samples); Measurement of photocuring rate: During the ultraviolet light irradiation process, use a viscometer to monitor the viscosity change of the sample and record the viscosity values at each time point; Take the viscosity stability as the sign of curing completion and record the maximum viscosity of the sample after curing; Measurement of surface drying time and through drying time: The surface drying time is measured by the finger touch test method: touch the surface of the sample with your finger and observe whether it adheres; The through drying time is measured by the hardness test: use a hardness tester to test the surface hardness of the cured sample; Measurement of curing conversion rate: The curing conversion rate is calculated by analyzing the disappearance of the C=C double bond in the sample through infrared spectroscopy (FT-IR), and the change of the C=C absorption peak before and after curing is compared; Data recording and analysis: Summarize the photocuring data of each experimental group and compare the differences in photocuring rate, drying time, and curing conversion rate among different formulations.

[0052] Experimental data: Table 1: Photocuring Performance Test Data Summary: In this experiment, in Example 1, by introducing allyl groups into the silicone structure, the photocuring rate and curing conversion rate were significantly improved. The mechanism of this improvement can be attributed to the effective reaction between the double bond structure of allyl groups and the photoinitiator. Under ultraviolet light irradiation, the photoinitiator first absorbs light energy and is excited, and then generates free radicals. These free radicals undergo addition reactions with the allyl double bonds in the resin matrix to form a crosslinked network. Due to the introduction of the allyl structure, the resin and the photoinitiator can react more efficiently, rapidly forming a stable crosslinked structure, thus significantly enhancing the photocuring rate and efficiency.

[0053] In contrast, in Comparative Examples 1, 3, 4, 6, and 8, allyl groups were not effectively introduced or the efficient connection between them and the photoinitiator was not maintained, resulting in a decrease in the reactivity of the photoinitiator. In Comparative Example 1, the lack of allyl groups led to poor chemical binding between the initiator and the resin matrix. During the photocuring process, the photoinitiator could not react sufficiently, resulting in a slow curing speed and a low curing conversion rate. In Comparative Example 3, due to the removal of the catalyst, the introduction efficiency of allyl groups was significantly reduced, resulting in the photoinitiator not being fully grafted onto the resin, thus affecting the curing rate and conversion rate. Other comparative example samples further reduced the crosslinking density by replacing the diluent or reducing the use of key components, resulting in unsatisfactory curing effects.

[0054] Therefore, the superiority of Example 1 lies in that by designing the covalent grafting mechanism between allyl groups and the photoinitiator, not only the photocuring efficiency of the resin matrix is improved, but also the mechanical properties and environmental resistance of the cured film are further enhanced by strengthening the stability of the crosslinked structure. This strategy of enhancing material properties by adjusting the molecular structure and optimizing the reaction path demonstrates the great potential of silicone photocuring materials in high-performance applications.

[0055] Experiment 2: Material Mechanical Property Testing Experiment Purpose: This experiment aims to compare the differences in material properties between using a silicone-based photoinitiator (Example 1) and traditional non-silicone-based photoinitiators (Comparative Examples 2, 5, 6, 8, 9) in curing resins containing silicone polyacrylate or polyurethane acrylate. The focus is on evaluating the effects of the two types of photoinitiators on properties such as tensile strength, elongation at break, crosslinking density, and toughness of the materials under the same formulation system, especially the advantages and disadvantages in terms of photocuring effect and compatibility.

[0056] Experiment Steps: Sample Preparation: According to the formulations of the examples and comparative examples, different photocurable resin samples were prepared. The concentration of the photoinitiator in each sample was kept consistent; The prepared resin was poured into a mold, maintained at a certain thickness (usually 2 mm), and cured with ultraviolet light. The curing conditions were the same as those in the photocuring of Experiment 1; Crosslink density determination: The cured samples were analyzed by differential scanning calorimetry (DSC) to determine the crosslink density. The degree of crosslinking was indirectly estimated by measuring the melting temperature and glass transition temperature; The swelling ratio of the samples can also be measured by the swelling method to further calculate the crosslink density; Mechanical property testing: Tensile property testing was carried out using a universal material testing machine. Parameters such as tensile strength, elongation at break, and elastic modulus of the test samples were measured; Meanwhile, the samples were subjected to a bending test to measure their bending strength and toughness; Observation of the sample surface: The surface of the samples was observed using a scanning electron microscope (SEM) to check whether there were cracks or other defects on the surface, and further evaluate the crosslinking effect and its influence on the mechanical properties of the materials; Data recording and analysis: The mechanical data of each experimental group were recorded, including tensile strength, elongation at break, crosslink density, etc., and were compared and analyzed to evaluate the performance differences of different formulations.

[0057] Experimental data: Table 2: Test data of the mechanical properties of the materials Summary: In Experiment 2, Example 1 demonstrated excellent mechanical properties. The fundamental reason is that there is good structural compatibility and reaction adaptability between the silicon-based photoinitiator and the organosilicon polyacrylate system. From a mechanistic perspective, the siloxane segments introduced in the silicon-based photoinitiator have a high degree of similarity and affinity with the organosilicon structure in the matrix at the molecular level. This improvement in compatibility effectively reduces phenomena such as the aggregation and precipitation of the photoinitiator, enabling it to be more evenly distributed in the system during the curing process, thereby increasing the free radical generation efficiency and the spatial uniformity of the crosslinking reaction.

[0058] After the silicon-based photoinitiator generates free radicals under ultraviolet irradiation, it can rapidly undergo an addition reaction with the allyl or acrylate double bonds in the resin to form a dense three-dimensional crosslinked structure. Since this photoinitiator itself has reactive structural sites and the ability to covalently bond with the main chain in the system, the formed network not only has a high crosslink density but also the segments cooperate to enhance the stress transfer efficiency. This structural feature can significantly disperse stress concentration and delay crack propagation during tensile and bending processes, thereby improving the strength and toughness of the material.

[0059] In contrast, traditional non-silicon-based photoinitiators often exhibit poor compatibility in silicone systems. Due to their polarity differences or structural mismatches, under light irradiation, phenomena such as low initiation efficiency, insufficient crosslinking, or whitening of the cured film surface are prone to occur, resulting in stress concentration points or crosslinking voids in the material structure and reducing the mechanical property performance. Example 1 provides an effective molecular design path for high-performance silicone photocuring systems by achieving structural synergy between the photoinitiator and the system and efficient crosslinking reactions, while ensuring complete curing and significantly improving the overall performance of the material.

[0060] Experiment 3: Environmental Resistance Performance Test Experiment Purpose: This experiment aims to test the durability of Example 1 and Comparative Examples 3, 6, 7, 9, and 10 under different environmental conditions (high temperature, humidity, ultraviolet radiation, etc.). By comparing the changes of different formulations under harsh environmental conditions, the environmental resistance performance of different formulations is evaluated.

[0061] Experimental Procedure: Sample Preparation: According to the method in Experiment 2, prepare resin samples of Example 1 and Comparative Examples 3, 6, 7, 9, and 10, ensuring that the sample thickness and formulation are consistent. The surface of each sample should be flat, and standardized ultraviolet light curing treatment should be carried out.

[0062] Environmental Condition Simulation: Expose all samples to different environmental conditions to simulate long-term use: High Temperature Exposure: Expose at 70 °C for 72 hours; High Humidity Exposure: Expose in an environment with 95% humidity for 72 hours; Ultraviolet Radiation: Irradiate the samples with an ultraviolet lamp (wavelength 365 nm, intensity 10 mW / cm 2 ) for 100 hours; After exposure to each environmental condition, the samples need to be subjected to performance testing.

[0063] Environmental Resistance Performance Test: After environmental exposure, conduct the following tests on the samples: Appearance Change: Observe and record whether there are obvious phenomena such as fading, cracking, or surface roughening on the sample surface.

[0064] Mechanical Property Test: Use a universal material testing machine to test the tensile strength, bending strength, toughness, etc. of the samples, and determine the changes in mechanical properties after environmental exposure.

[0065] Hardness Test: Use a Shore hardness tester to measure the change in surface hardness of the samples.

[0066] Water absorption rate: Measure the mass change of the sample after exposure and calculate the water absorption rate.

[0067] Data recording and analysis: Record the performance of the sample under various environmental conditions, calculate the changes in its mechanical properties, surface changes, etc. after exposure, and conduct comparative analysis.

[0068] Experimental data: Table 3: Environmental resistance test data Summary: In Experiment 3, Example 1 still showed good stability under various environmental conditions such as high temperature, high humidity, and ultraviolet irradiation. The improvement of this performance mainly stems from its high-density cross-linked structure and the efficient reaction mechanism between allyl groups and photoinitiators. By introducing allyl structures that can undergo free radical reactions with photoinitiators into the molecular chain, the free radicals generated under ultraviolet light irradiation rapidly initiate cross-linking, resulting in the formation of a dense three-dimensional cross-linked network within the system. This structure can effectively restrict the movement of molecular chain segments when subjected to thermal stress or external moisture penetration, thereby enhancing the thermal stability and moisture resistance of the material.

[0069] In the comparative sample, due to the low grafting efficiency of the photoinitiator or the lack of sufficient allyl groups participating in cross-linking, the construction of the cross-linked network is incomplete, resulting in a loose internal structure of the material and a significant reduction in environmental adaptability. In a high-humidity environment, such materials are more likely to absorb water and swell, and it is difficult for intermolecular hydrogen bonds or van der Waals forces to resist the erosion of water molecules, causing a rapid decline in mechanical properties. At the same time, under ultraviolet irradiation conditions, the uncross-linked areas are more vulnerable to the decomposition effect of ultraviolet light, and surface deterioration phenomena such as fading and cracking occur, further indicating that its structure lacks stability guarantee under long-term light irradiation.

[0070] Therefore, from the perspective of material structure and reaction mechanism, Example 1 not only improves the efficiency of the photocuring reaction but also significantly enhances the durability of the material in harsh environments by efficiently grafting allyl groups and achieving dense cross-linking. This modification strategy based on molecular-level design realizes the dual improvement of the mechanical and environmental resistance properties of the material, providing a feasible solution for scenarios with high long-term stability requirements in practical applications.

[0071] Experiment 4: Chemical corrosion resistance test Experimental purpose: This experiment aims to study the corrosion resistance of different resin samples in common chemical media, including the effects of acids, alkalis, solvents, etc. on the resin. By testing the water absorption rate, mass change, and mechanical property changes of the material in chemical media, the chemical corrosion resistance of different formulations is evaluated.

[0072] Experimental procedure: Sample preparation: Prepare the resin samples of Example 1 and Comparative Examples 4, 7, 9, and 10 according to the method in Experiment 2. Ensure that the sizes of all samples are consistent and perform standardized ultraviolet curing treatment; The samples should be prepared into small pieces with a thickness of 3 mm to ensure that their surfaces can come into full contact with the chemical solution during the test.

[0073] Chemical solution preparation: Prepare the following chemical solutions: Sulfuric acid solution (H2SO4): concentration of 1 M; Sodium hydroxide solution (NaOH): concentration of 1 M; Ethanol solution (C2H5OH): ethanol with a purity of 95%; Acetic acid solution (CH3COOH): concentration of 1 M.

[0074] Place each solution in a different container for testing the corrosion resistance of the samples.

[0075] Sample immersion: Immerse each group of resin samples in sulfuric acid solution, sodium hydroxide solution, ethanol solution, and acetic acid solution for 24 hours, 48 hours, and 72 hours respectively; Take out the samples every 24 hours, record the mass change and conduct mechanical property tests.

[0076] Mechanical property tests: After each immersion, use a universal material testing machine to test the tensile strength, elongation at break, and flexural strength; At the same time, use an electronic balance to measure the mass change of the samples and calculate the moisture absorption rate.

[0077] Appearance inspection: After immersion, when taking out the samples each time, observe and record the surface changes of the samples, including phenomena such as cracks, discoloration, and swelling.

[0078] Data recording and analysis: Record the mass change, mechanical property change, and appearance change of the samples in different chemical solutions and conduct comparative analysis.

[0079] Experimental data: Table 4: Test data of chemical corrosion resistance Summary: In Experiment 4, Example 1 demonstrated excellent resistance to chemical corrosion, which is closely related to its three-dimensional network structure with a high degree of crosslinking. In the resin sample, the allyl groups introduced through the photocuring reaction reacted with the photoinitiator to form a dense molecular structure, which endows the material with stronger resistance to the erosion of external chemical media. The high-density crosslinked structure restricts the free movement of molecular chains, thereby reducing the penetration and diffusion of chemical substances such as solvents, acids, and alkalis into the resin, and further enhancing the corrosion resistance of the material. This mechanism enables Example 1 to maintain good mechanical properties and a low water absorption rate even when exposed to strongly corrosive environments such as sulfuric acid, sodium hydroxide, ethanol, and acetic acid.

[0080] In contrast, some of the comparative samples had a lower degree of crosslinking and weaker intermolecular forces, which made them more likely to decompose or swell in chemical solutions. After soaking samples such as Comparative Examples 4, 7, and 9 in chemical solutions, due to their loose crosslinked structures, solvent molecules were able to penetrate and damage the internal structure of the material more easily, leading to cracks, swelling, or a significant decrease in tensile strength. In addition, the lower crosslink density caused these resins to exhibit a higher water absorption rate when exposed to chemical media, which further affected their stability and mechanical properties in the corrosive environment.

[0081] Mechanistically, Example 1 optimized the structural strength between resin molecules by increasing the degree of crosslinking, enabling it to effectively resist the erosion of external chemical media. This enhancement of the structure not only improved the chemical stability of the material but also effectively alleviated physical damage caused by external factors. The experimental results show that by reasonably designing the resin formulation, especially by strengthening the formation of the crosslinked network, the durability of resin materials in harsh chemical environments can be significantly improved, providing a theoretical basis and practical support for long-term stability and corrosion resistance in practical applications.

[0082] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a silicon-based photoinitiator, characterized in that, It includes the following steps: S1. Dissolve the alkaline substance in a solvent, add a photoinitiator and stir, then add allyl halide, and continue to react under heating or room temperature conditions to obtain a reaction solution; S2. Treat the reaction solution by quenching, neutralizing, extracting, drying and vacuum distillation to obtain a photoinitiator etherification intermediate; S3. Carry out an addition reaction on the intermediate and an organosilicon monomer or silicone oil with at least one end hydrogenated and capped under the action of a catalyst to prepare a silicon-based photoinitiator.

2. The preparation method of a silicon-based photoinitiator according to claim 1, characterized in that, In the S1 step, the alkaline substance is selected from one of potassium hydroxide, sodium hydroxide, sodium hydride or potassium carbonate, and in the S1 step, the allyl halide is selected from one of allyl bromide, allyl iodide, allyl chloride.

3. The preparation method of a silicon-based photoinitiator according to claim 1, characterized in that In the S1 step, the molar ratio of the photoinitiator, the alkaline substance and the allyl halide is 1:1.8:2.8 - 1:2.2:3.

2.

4. The preparation method of a silicon-based photoinitiator according to claim 1, characterized in that, In the S1 step, the solvent is tetrahydrofuran, the reaction temperature in the S1 step is 60°C - 80°C, and the reaction time is 3 - 12 h.

5. The preparation method of a silicon-based photoinitiator according to claim 1, characterized in that, In the S1 step, the photoinitiator is selected from one of photoinitiator 2959, (1-hydroxycyclohexyl)[4-(2-hydroxyethoxy)phenyl]methanone, 2-hydroxy-4'-[2-(2-hydroxyethoxy)ethoxy]-2-methylpropiophenone, wherein photoinitiator 2959 is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone.

6. The preparation method of a silicon-based photoinitiator according to claim 1, characterized in that, The S2 step includes the following treatment processes: S2.

1. Add an ammonium chloride aqueous solution or ice water to the reaction solution for quenching and neutralizing; S2.

2. Extract the neutralized system with ethyl acetate 2 to 4 times to obtain an organic phase; S2.

3. Wash the organic phase to neutral; S2.

4. Dry the organic phase with anhydrous sodium sulfate or magnesium sulfate; S2.

5. Remove the organic solvent by vacuum distillation to obtain a photoinitiator etherification intermediate.

7. The preparation method of a silicon-based photoinitiator according to claim 6, characterized in that, In the S2.5 step, the solvent is recovered at 40°C - 60°C under reduced pressure.

8. The preparation method of a silicon-based photoinitiator according to claim 1, characterized in that, In the S3 step, the catalyst is a platinum-based catalyst, and the usage amount is 0.1% - 1.0% of the total reaction mass. The reaction temperature in the S3 step is 65 - 75°C.

9. A silicon-based photoinitiator prepared by the method for preparing a silicon-based photoinitiator according to any one of claims 1-8, characterized in that, It contains the following compounds: or Among them, n is selected from one of n = 0, n = 0 - 10, n = 10 - 50, n = 50 - 100, n = 100 - 200, n = 200 - 300 or n = 300 - 400, and m is selected from one of m = 0, m = 0 - 60, m = 60 - 300, m = 300 - 600, m = 600 - 1200, m = 1200 - 1800 or m = 1800 - 2400.

10. The silicon-based photoinitiator according to claim 9, wherein The silicon-based photoinitiator is applied in photocurable silicone.

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