Silicone rubber material for LED and preparation method thereof

Abstract

The invention provides a silicone rubber material for an LED and a preparation method thereof, and the preparation method comprises the following steps: adding a silicon-based polymer and a part of functional filler into deionized water, heating to 50-65 DEG C, stirring, adding a silane monomer, and uniformly stirring to obtain a mixed glue solution; adding a release agent and the remaining functional filler into the mixed glue solution, stirring, cooling to room temperature, and standing for 8-10 hours to obtain a prefabricated colloid; and putting the prefabricated rubber body into an internal mixer, carrying out primary mixing for 2-6 hours, then carrying out secondary mixing for 30-60 minutes at the temperature higher than that of the primary mixing for 30-60 minutes, and cooling to obtain the silicone rubber material for the LED. The weather resistance and the service life of the silicon rubber material for the LED are effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of silicone rubber materials, and in particular relates to a silicone rubber material for LED and a preparation method thereof. Background Art

[0002] LED light strips are mainly composed of LED lamp beads, circuit boards, power supplies and shells. The shell protects the internal structure of the LED light strip. Common shell materials for light strips mainly include silicone rubber. LEDs generate high heat during operation. When the heat cannot be effectively dissipated, the temperature of the LED chip will rise, the light efficiency will be reduced, and even the life will be shortened. LED packaging needs to prevent the intrusion of water vapor and external current to ensure circuit safety and long-term stable operation. Silicone rubber has excellent insulation properties and thermal stability, can effectively isolate the LED chip from the external environment, has waterproof and dustproof functions, and protects internal electronic components. It also helps to dissipate heat and keep the LED operating temperature stable.

[0003] Although traditional silicone rubber is flexible, its hardness is relatively low, and its mechanical tear resistance and wear resistance may be insufficient. Especially in high-frequency extrusion and long-term use, it is prone to aging, resulting in a shortened service life. Under long-term ultraviolet radiation and thermal oxidation, silicone rubber is prone to yellowing and aging. Poor weather resistance affects the product appearance and optical performance, thereby reducing the lighting quality of LEDs. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a silicone rubber material for LED and a preparation method thereof, aiming to solve the problem that silicone rubber is easy to age and has poor weather resistance.

[0005] To solve the above technical problems, the present invention is implemented as follows: a method for preparing a silicone rubber material for LED, the steps comprising: S1. Add the silicon-based polymer and some functional fillers into deionized water, heat it to 50-65°C and stir it, then add the silane monomer and stir until mixed to obtain a mixed glue solution; S2, adding a release agent and the remaining functional filler to the mixed glue solution, cooling to room temperature after stirring and standing for 8 to 10 hours to obtain a prefabricated colloid; S3, placing the prefabricated colloid in an internal mixer, performing a first mixing, the first mixing time is 2 to 6 hours, and then performing a second mixing, the mixing time is 30 to 60 minutes, the first mixing temperature is higher than the second mixing temperature, and after cooling, a silicone rubber material for LED is obtained.

[0006] In some embodiments of the present invention, in step S1, the silicon-based polymer includes at least one of methyl vinyl silicone rubber, vinyl polydimethylsiloxane, vinyl phthalimide silicone rubber, and phenyl modified silicone rubber, the functional filler includes at least one of fumed silica nanopowder, precipitated silica powder, fused silica powder, white carbon black, and nano titanium dioxide, and the silane monomer includes at least one of tetramethyldivinyldisilazane, dimethyldimethoxysilane, and hexamethyldisilazane.

[0007] In some embodiments of the present invention, in step S1, calculated according to the mass ratio, the silicon-based polymer: the functional filler: the silane monomer = 10: (5-7): (1-4).

[0008] In some embodiments of the present invention, step S1 comprises: S1.1. Add the silicon-based polymer and 30-50% of the functional filler into deionized water, slowly raise the temperature to 50-65°C, adjust the speed to 200-300 rpm and stir for 10-15 minutes to obtain a premixed solution; S1.2, add silane monomer to the premixed liquid, continue stirring at 50-65°C for 5-10 minutes, until the pH of the premixed liquid reaches 4.5 and the viscosity reaches 3000-3500 cP, then stop stirring to obtain a mixed glue solution.

[0009] In some embodiments of the present invention, in step S2, the release agent includes at least one of a silane-modified polysiloxane release agent, a fluorosilicone composite release agent, and a silicone polymer release agent, and the release agent accounts for 1-10% of the mass of the mixed glue.

[0010] In some embodiments of the present invention, step S2 comprises: S2.1, adding a release agent to the mixed glue, and adding the remaining functional filler in batches, adjusting the stirring speed to 250-350 rpm, maintaining the temperature at 50-65°C, and stirring for 20-25 minutes; S2.2. After stirring, slowly cool to room temperature and keep it at room temperature for 8 to 10 hours to obtain a prefabricated colloid.

[0011] In some embodiments of the present invention, step S3 includes: S3.1, add the preformed colloid and the crosslinking agent into an internal mixer, heat to 150-200°C for the first mixing, maintain the first mixing for 2-6 hours, evacuate to 0.06-0.08MPa, and stir at a speed of 250-350rpm for the first mixing; S3.2, cooling to 80-100°C, and performing the second mixing, the second mixing time is controlled within 30-60 minutes, and the stirring speed of the second mixing is 200-300rpm; S3.3. After cooling to room temperature, irradiate with 365nm ultraviolet light for 10 to 15 minutes to obtain silicone rubber material for LED.

[0012] In some embodiments of the present invention, in step S3.1, the crosslinking agent includes at least one of dimethyl siloxane diacrylate, tripropylene silane, and methoxyethyl silane methacrylate.

[0013] The present invention provides a silicone rubber material for LED, which is made by the preparation method of the silicone rubber material for LED as described above, wherein the silicone rubber material for LED comprises a silicon-based polymer, a functional filler, a silane monomer and a release agent; wherein: The silicon-based polymer is used to form a cross-linked network in the silicone rubber material for LED; The functional filler is used to improve the UV resistance, heat resistance and aging resistance of the silicone rubber material for LED; The silane monomer is used to generate siloxane bonds to enhance the weather resistance and yellowing resistance of the silicone rubber material for LEDs; The release agent is used to prevent the silicone rubber material for LED from adhering to the surface of processing equipment.

[0014] Compared with the prior art, the LED silicone rubber material and the preparation method thereof in the present invention have the following beneficial effects: In the S1 stage, the silicon-based polymer and some functional fillers are uniformly dispersed in deionized water, and then silane monomers are added to form hydrolysis and condensation reactions on the surface of the silicon-based polymer and the filler, and a uniform cross-linked network is initially constructed. The uniform cross-linked network not only improves the mechanical strength and flexibility of the material, but also reduces the aging phenomenon caused by local overreaction or uneven cross-linking, thereby delaying the degradation of silicone rubber. The functional filler can significantly improve the reinforcing effect of the filler through effective interface bonding with the silicon-based polymer. After the modified filler is evenly dispersed, it not only plays a reinforcing role, but also can shield part of the ultraviolet rays, reduce yellowing and cross-linked network damage caused by ultraviolet irradiation, and extend the service life of LED products. In the S3 stage, the first mixing is carried out at a high temperature of 150-200°C, and low-boiling substances and residual water are removed by vacuum, effectively preventing the formation of bubbles and impurities, and ensuring the integrity of the final cross-linked network. Through this process, the internal cross-linked structure is more stable, reducing local aging caused by residual solvents or moisture, thereby improving the weather resistance of the material under long-term ultraviolet irradiation and temperature changes. The second mixing is carried out at a lower temperature, which can relieve internal stress and improve surface smoothness. The structure of the cured silicone rubber material is tighter and more stable, and can effectively resist degradation caused by environmental factors such as high temperature and ultraviolet rays, thereby extending the service life of the LED package. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic flow chart of a method for preparing a silicone rubber material for LED in one embodiment of the present invention. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0017] The present invention provides a method for preparing a silicone rubber material for LED, the steps comprising: S1. Add the silicon-based polymer and some functional fillers into deionized water, heat it to 50-65°C and stir it, then add the silane monomer and stir until mixed to obtain a mixed glue solution.

[0018] In step S1, the silicon-based polymer includes at least one of methyl vinyl silicone rubber, vinyl polydimethylsiloxane, vinyl phthalimide silicone rubber, and phenyl modified silicone rubber, the functional filler includes at least one of fumed silica nanopowder, precipitated silica powder, fused silica powder, white carbon black, and nano titanium dioxide, and the silane monomer includes at least one of tetramethyldivinyldisilazane, dimethyldimethoxysilane, and hexamethyldisilazane.

[0019] Methyl vinyl silicone rubber provides the main framework of the polymer matrix, contains vinyl functional groups, can undergo cross-linking reactions with silane monomers to construct a three-dimensional cross-linked network; it gives the material good electrical insulation, flexibility and basic mechanical strength, and is the core component of the silicone rubber system. Methyl vinyl silicone rubber raw rubber includes the first methyl vinyl silicone rubber raw rubber, the second methyl vinyl silicone rubber raw rubber and the third methyl vinyl silicone rubber raw rubber in a weight ratio of 5-20:80-90:0-5, and the first methyl vinyl silicone rubber raw rubber, the second methyl vinyl silicone rubber raw rubber and the third methyl vinyl silicone rubber raw rubber have different vinyl contents. For example, the first methyl vinyl silicone rubber raw rubber has a vinyl mass content of 0.07% and a molecular weight of 600,000-700,000; the second methyl vinyl silicone rubber raw rubber has a vinyl mass content of 0.24% and a molecular weight of 600,000-700,000; the third methyl vinyl silicone rubber raw rubber has a vinyl mass content of 5% and a molecular weight of 600,000-700,000.

[0020] Vinyl polydimethylsiloxane has low surface tension and excellent optical transparency, which improves the flexibility and thermal stability of the material. After modification, it can improve processing performance while enhancing the low-temperature elasticity and overall weather resistance of the material. Phthalimide groups are introduced into the molecular structure of vinyl phthalimide silicone rubber. These polar groups help to improve the thermal stability and mechanical strength of silicone rubber. At the same time, the vinyl functional group enables it to react with crosslinking agents, enhance the crosslinking density, and improve aging resistance. The phenyl group of phenyl-modified silicone rubber can improve the rigidity, oil resistance, and chemical resistance of the material while improving thermal stability. In addition, the phenyl structure can enhance the resistance of silicone rubber to ultraviolet rays, reduce photo-induced yellowing, and extend the service life.

[0021] As a reinforcing agent, fumed silica nanopowder can significantly improve the mechanical strength and wear resistance of silicone rubber; its ultrafine particle size and high specific surface area help improve the interface bonding between fillers and polymers, and can also reduce the thermal expansion coefficient after uniform dispersion, while playing a partial UV shielding role. Precipitated silica powder has good reinforcement effect and rheological control ability, which can improve the shear stability of the rubber; its particle size and morphology help improve the processing performance and surface flatness of silicone rubber and prevent the formation of excessive cross-linking areas. Fused silica powder has high purity and excellent thermal stability, which can improve the material's high temperature resistance and anti-aging properties; at the same time, fused silica powder can improve the mechanical properties of silicone rubber and enhance overall rigidity and weather resistance. White carbon black can improve the mechanical strength and tear resistance of the material; its good dispersibility and surface activity, after appropriate modification, can help improve the optical transparency and UV resistance of silicone rubber and reduce the risk of yellowing. Nano titanium dioxide has excellent ultraviolet absorption and scattering capabilities, can effectively shield ultraviolet rays and prevent the material from yellowing due to UV irradiation; at the same time, nano titanium dioxide can also play a reinforcing role and improve the weather resistance and aging resistance of silicone rubber.

[0022] Tetramethyldivinyldisilazane contains vinyl and silicon nitrogen structures in its molecules, which can undergo hydrolysis and condensation reactions with silicon-based polymers and filler surfaces; it promotes the formation of a cross-linked network, improves the overall mechanical strength and heat resistance of the material, and helps improve interfacial compatibility. Dimethyldimethoxysilane, as a cross-linking agent, generates silanol after hydrolysis, which undergoes a condensation reaction with the hydroxyl groups in the matrix to form siloxane bonds; it helps to build a uniform cross-linked network, improves the weather resistance and anti-yellowing properties of the material, and ensures the long-term stability of silicone rubber. Hexamethyldisilazane has a low polarity, which can reduce the hydroxyl content on the filler surface and improve the compatibility of the filler with silicon-based polymers; at the same time, it plays an auxiliary role in the cross-linking reaction, helps to form a stable cross-linked network, and enhances the thermal stability and weather resistance of the material.

[0023] In step S1, according to the mass ratio, silicon-based polymer: functional filler: silane monomer = 10: (5-7): (1-4).

[0024] Step S1 includes: S1.1. Add the silicon-based polymer and 30-50% of the functional filler into deionized water, slowly raise the temperature to 50-65°C, adjust the speed to 200-300 rpm and stir for 10-15 minutes to obtain a premixed solution.

[0025] During the temperature increase, deionized water reduces the viscosity of the silicon-based polymer, making the molecular chain more flexible. At the same time, the water medium helps the functional filler to be fully dispersed in the liquid, avoiding the problem of local uneven concentration due to aggregation. The formation of a uniformly dispersed premix lays the foundation for the uniform addition of the subsequent silane monomer and the hydrolysis cross-linking reaction, ensuring full contact between the matrix and the filler interface in the composite material, and improving the efficiency and uniformity of the subsequent cross-linking reaction. When the temperature rises to 50~65℃, some functional groups on the surface of the silicon-based polymer (such as some vinyl or other reactive groups) begin to be slightly hydrolyzed or activated by water, which is conducive to the subsequent silane monomer to participate in the condensation reaction. The pre-activated silicon-based polymer is more likely to react chemically with the silane monomer, ensuring the initial formation of the cross-linking network, thereby providing a basis for the overall weather resistance, mechanical strength and anti-yellowing of the material. In the aqueous phase, functional fillers such as silicon dioxide nanopowder or nano-titanium dioxide are fully stirred to form a uniform micro-suspension state, reducing local concentration differences. It is beneficial to the subsequent interface reaction between fillers and silicon-based polymers and silane monomers, improves the reinforcing effect of the fillers and the overall uniformity of the materials, and improves the optical transparency and aging resistance of the composite materials.

[0026] S1.2. Add silane monomer to the premixed liquid, continue stirring at 50-65°C for 5-10 minutes, until the pH of the premixed liquid reaches 4.5 and the viscosity reaches 3000-3500 cP, then stop stirring to obtain a mixed adhesive solution.

[0027] Under weakly acidic conditions (pH about 4.5), the silane monomer first undergoes a hydrolysis reaction to generate a silanol group, and then the silanol reacts with the hydroxyl group on the surface of the silicon-based polymer or filler to form a stable siloxane bond (–Si–O–Si–). Through hydrolysis and condensation reactions, a preliminary three-dimensional cross-linked network is established, which improves the mechanical strength and weather resistance of the composite material, and helps prevent yellowing and deterioration during subsequent processing. The pH value in the premix drops to 4.5, indicating that the hydrolysis reaction of the silane monomer is under ideal acid-catalyzed conditions, and the viscosity reaches 3000-3500cP, reflecting that the cross-linking reaction between the molecular chains has been initially formed. Through online detection of pH and viscosity, it is ensured that the cross-linking reaction reaches the predetermined degree and avoids excessive or incomplete reaction, thereby ensuring that the mixed glue has stable processing performance and long-term storage, while ensuring the smooth progress of subsequent processing steps (such as mixing, degassing, and curing). After uniform dispersion of S1.1, the silane monomer can fully contact with the silicon-based polymer and functional filler, and form a chemical bond connection during the hydrolysis and condensation reaction, making the interface bonding between the filler and the matrix stronger. The interface structure is optimized, the overall mechanical properties and weather resistance of the composite material are improved, and the transparency and optical effect of the material are improved, providing a guarantee for the long-term stable operation of the LED.

[0028] In one embodiment, by controlling the ratio of the silicon-based polymer to the functional filler (such as nano-titanium dioxide, fumed silica nanopowder, etc.) in step S1 and controlling the stirring temperature, the mixing free energy of the system can be kept negative, ensuring that the components are uniformly mixed without adverse phase separation. The control equation is: in, is the mixing free energy (J / mol), which determines whether the mixed system is spontaneously mixed evenly and can be between -5 and -20. is the Boltzmann constant, and its value is 8.314 J / (mol·K). is the absolute temperature, unit is K. is the volume fraction of the silicon-based polymer in the mixed gel (dimensionless), which is calculated using the volume fraction equation. and They are the degree of polymerization (dimensionless) of the silicon-based polymer and the remaining components (components other than the silicon-based polymer), which can be obtained by gel permeation chromatography or nuclear magnetic resonance, and are usually in the range of 100 to 10,000. is the interaction parameter (dimensionless), which measures the incompatibility between the two phases and ranges from 0.1 to 1.0.

[0029] Gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) are two commonly used polymer characterization techniques, mainly used to determine the molecular weight, molecular weight distribution and structural information of polymers. The following is a detailed introduction to their basic principles and practical operation methods. Gel permeation chromatography (GPC), also known as size exclusion chromatography, is based on the "permeation" behavior of polymer molecules in the stationary phase gel for separation. Larger molecules are less restricted in their movement, and smaller molecules can more easily enter the gel pores, resulting in longer retention time in the column. By detecting the signal of molecules at different exclusion volumes, a calibration curve of molecular weight distribution can be established to determine the average molecular weight and distribution range of the sample. Dissolve the sample in an appropriate solvent (e.g., tetrahydrofuran, dichloromethane or other solvent suitable for the sample). Filter the sample solution through a filter (e.g., 0.45µm filter membrane) to remove insoluble impurities and particles. Use a pre-calibrated GPC system, which usually includes a solvent pump, a chromatographic column (usually multiple cascaded columns), a detector (such as a differential refractive index detector or UV detector), and a data acquisition system. Calibrate with known molecular weight standards to establish a calibration curve. Inject the filtered sample solution into the GPC system. As the sample solution passes through the chromatographic column, components of different molecular weights elute in sequence at different retention times. The detector records the elution curve and converts it into molecular weight distribution data through the calibration curve. The degree of polymerization of the sample is calculated using dedicated software.

[0030] Nuclear magnetic resonance (NMR) uses the resonance phenomenon of atomic nuclei in an external magnetic field. By applying radio frequency pulses to excite magnetic atomic nuclei in the sample, the resonance frequency, chemical shift, coupling constant and integrated area are recorded. These parameters can reflect the chemical environment and structure within the molecule, and are then used for structural analysis, monomer composition and degree of polymerization. The polymer sample is dissolved in an appropriate deuterated solvent, which helps to eliminate the interference of the solvent peak. The sample concentration is usually between 10 and 30 mg / mL and is adjusted according to the requirements of the instrument. The prepared sample solution is transferred to a dedicated NMR tube to ensure that the sample is uniform and free of bubbles. The NMR tube is placed in the NMR spectrometer and the magnetic field, temperature (usually room temperature or set temperature) and frequency parameters are adjusted. Select the appropriate measurement mode and set the corresponding pulse sequence and number of scans to obtain a spectrum with sufficient signal-to-noise ratio. After collecting the signal, Fourier transform is performed to obtain the NMR spectrum. Analyze the chemical shift signals in the spectrum to determine the existence, structure and relative proportion of each group in the polymer. The degree of polymerization can be calculated by comparing the integrated area with the known signal.

[0031] S2. Add a release agent and the remaining functional filler into the mixed glue solution, cool to room temperature after stirring and let stand for 8 to 10 hours to obtain a prefabricated colloid.

[0032] In step S2, the release agent includes at least one of a silane-modified polysiloxane release agent, a fluorosilicone composite release agent, and an organic silicon polymer release agent, and the release agent accounts for 1-10% of the mass of the mixed glue solution.

[0033] Step S2 includes: S2.1. Add the release agent to the mixed glue solution, and add the remaining functional filler in batches. Adjust the stirring speed to 250-350 rpm, maintain the temperature at 50-65°C, and stir for 20-25 minutes.

[0034] The release agent has low surface energy and good lubrication in the silane-modified polysiloxane system. The silicone chain in its molecular structure can be physically adsorbed or chemically bonded to the surface of the silicon-based polymer and the filler, thereby forming a thin release protective layer in the mixed glue. Adding functional fillers in batches can avoid the local concentration of fillers being too high when added all at once, which leads to agglomeration, thereby ensuring that the fillers are uniformly dispersed in the glue. Achieving full mixing of the release agent and the functional filler improves the interface bonding between the filler and the matrix, reduces the overall surface energy of the system, and ensures that the material is smoothly separated from the processing equipment during the subsequent molding process; uniformly dispersed fillers can effectively enhance the reinforcement effect of composite materials, improve anti-aging, weather resistance and mechanical properties, and improve the rheological properties of the colloid, which is beneficial to improving optical transparency and reducing haze.

[0035] During the stirring process, the release agent not only improves the interface dispersion, but also participates in part of the auxiliary cross-linking reaction, helping to generate more uniform siloxane bond connections. At the same time, the fillers added in batches make the contact between the components in the premixed system more complete, promoting the uniform formation of the cross-linking network. Making the cross-linking reaction more complete helps to improve the overall weather resistance and long-term storage stability of the material; avoiding physical defects or stress concentration caused by excessively high local filler concentrations, and further ensuring the mechanical properties and optical uniformity of the product.

[0036] S2.2. After stirring, slowly cool to room temperature and keep it at room temperature for 8 to 10 hours to obtain a prefabricated colloid.

[0037] Slow cooling allows for a smooth transition of the temperature gradient in the system, avoiding internal thermal stress and local over-crosslinking caused by rapid cooling. At the same time, during the static process, the incompletely reacted silane monomers continue to slowly condense with silanols, making the crosslinking network more stable and uniform; in addition, the static process helps the natural volatilization of residual low-boiling substances and volatile components inside, reducing the risk of bubbles in subsequent processing. A prefabricated colloid with uniform structure and low internal stress is formed, providing high-quality raw materials for subsequent mixing and molding; improving the storage stability of the material to ensure that the ideal processability and physical properties can be maintained after long-term storage. During the static stage, the lubricating effect of the release agent between the matrix and the filler is fully exerted, further stabilizing the physical adsorption and chemical bonding between the two, thereby optimizing the interface state. Effectively reduce interface defects, improve the mechanical properties, anti-aging and weather resistance of the composite material; enhance the overall consistency of the material to meet the surface finish requirements of LED products.

[0038] In the S2.1 stage, the mold release agent and the remaining functional fillers are added to the mixed glue in batches, and the mixture is fully mixed at a stirring speed of 250-350rpm at 50-65℃, so that the functional fillers are fully and evenly dispersed in the glue to avoid local over-concentration and agglomeration; the mold release agent forms a low surface energy protective layer between the filler and the silicon-based polymer, improves the interface adhesion, and promotes uniform cross-linking; it is helpful for the efficient subsequent cross-linking reaction and the stability of the composite material performance. In the S2.2 stage, slow cooling and static treatment are carried out to ensure that low-temperature curing and static allow the internal cross-linking reaction to continue, forming a uniform three-dimensional cross-linked network; avoid stress concentration and bubble residue caused by rapid cooling, improve the storage stability of the material and the quality of subsequent processing; further strengthen the combination of filler and matrix, and improve the overall mechanical and optical properties.

[0039] S3. Place the prefabricated colloid in an internal mixer and perform the first mixing. The first mixing time is 2 to 6 hours, and then perform the second mixing. The mixing time is 30 to 60 minutes. The first mixing temperature is higher than the second mixing temperature. After cooling, the silicone rubber material for LED is obtained.

[0040] Step S3 includes: S3.1. Add the prefabricated colloid into an internal mixer, heat it to 150-200°C for the first mixing, maintain the first mixing for 2-6 hours, evacuate to 0.06-0.08MPa, stir at 250-350rpm for the first mixing, and add part of the crosslinking agent during the first mixing. The crosslinking agent includes at least one of dimethyl siloxane diacrylate, tripropylene silane, and methoxyethyl methacrylate, and the concentration of the crosslinking agent is 0.01-0.1mol / L.

[0041] Under high temperature conditions of 150-200°C, the silane monomers in the prefabricated colloid undergo further hydrolysis and condensation reactions with the silicon-based polymers and the hydroxyl groups on the surface of the functional filler to generate siloxane (–Si–O–Si–) bonds, forming a high-density, uniform three-dimensional cross-linked network. This improves the overall mechanical strength, heat resistance, and weather resistance of the material, provides a solid foundation for LED products, and prevents performance degradation due to high-temperature aging. The high temperature and vacuum conditions work together to rapidly volatilize and remove the low-boiling substances (such as incompletely reacted silane or water) remaining in the prefabricated colloid. This eliminates potential bubbles and impurities, avoids the occurrence of voids, bubbles, and uneven cross-linking during subsequent processing, and ensures a smooth surface and stable structure of the final product.

[0042] Under high temperature and high vacuum, the internal mixer provides sufficient shear force to fully mix the components, break the local agglomeration phenomenon, and facilitate the uniform dispersion of nano-scale functional fillers (such as fumed silica nanopowder, nano-titanium dioxide, etc.) in the matrix. It ensures the formation of a stable interface interaction between the filler and the matrix, and further enhances the mechanical fatigue resistance and weather resistance of the composite material.

[0043] S3.2, cool down to 80~100℃, and carry out the second mixing. The second mixing time is controlled within 30~60 minutes, the stirring speed of the second mixing is 200~300rpm, and the remaining cross-linking agent is added during the second mixing. The second mixing is carried out at a lower temperature. The main purpose is to eliminate the local thermal stress and uneven areas generated during the first mixing process, and to improve the rheological properties of the material through gentle mechanical shearing. The internal cross-linking network is further homogenized, and the surface of the material is smoother and more uniform, which helps to avoid burrs or particle defects during subsequent molding processing, thereby improving the optical and mechanical properties of the product. In the low-temperature mixing stage, through continuous stirring and appropriate shearing, the tiny bubbles that may remain in the previous stage are effectively dispersed or discharged. Bubbles that may affect transparency and mechanical properties are eliminated to ensure that the final product has high uniformity and optical effects in the LED light strip.

[0044] S3.3. After cooling to room temperature, irradiate with 365nm ultraviolet light for 10 to 15 minutes to obtain silicone rubber material for LED.

[0045] After high-temperature and low-temperature mixing to form a uniform cross-linked network, 365nm ultraviolet light irradiation can trigger the cross-linking agent to cure rapidly and fix the existing network structure. The curing process freezes the cross-linked structure, further preventing subsequent heat or environmental stress from causing network rearrangement and performance degradation, thereby improving the material's weather resistance and anti-yellowing properties. UV irradiation can stimulate and accelerate the photosensitive cross-linking reaction, while some UV absorbers will also absorb part of the UV energy, slowing down the degradation process of the silicon-based polymers in the material. After UV curing, the material's anti-ultraviolet aging and weather resistance are significantly improved, which helps the LED light strip maintain stable optical and mechanical properties in long-term outdoor environments and extend its service life.

[0046] In the S3.1 stage, high temperature, high shear and vacuum extraction are used to fully promote the hydrolysis and condensation reaction between the silane monomer in the prefabricated colloid and the silicon-based polymer and the hydroxyl group on the surface of the filler, thereby constructing a uniform and high-density cross-linked network, while removing low-boiling substances and moisture to ensure the stability and purity of the material structure. In the S3.2 stage, refining and mixing are carried out at low temperatures to relieve internal stress, improve rheology and eliminate residual bubbles, ensuring that the product surface is smooth and uniform, meeting the requirements of high-end LED light strips for appearance and performance. In the S3.3 stage, 365nm ultraviolet light curing is used to quickly freeze the cross-linked network, further improving the yellowing resistance and weather resistance, and ensuring the stability and high performance of LED silicone rubber materials in long-term outdoor use.

[0047] The present invention provides a silicone rubber material for LED, which is made by a preparation method of the silicone rubber material for LED. The silicone rubber material for LED includes a silicon-based polymer, a functional filler, a silane monomer and a release agent; wherein: Silicon-based polymers are used to form cross-linked networks in silicone rubber materials for LEDs; Functional fillers are used to improve the UV resistance, heat resistance and aging resistance of silicone rubber materials for LEDs; Silane monomers are used to generate siloxane bonds to enhance the weather resistance and yellowing resistance of silicone rubber materials for LEDs; Release agents are used to prevent LED silicone rubber materials from adhering to the surface of processing equipment.

[0048] In one embodiment, the silicon-based polymer is composed of the following silicon-based polymers in proportion, which ensures reactivity while taking into account weather resistance and transparency: 6 parts of methyl vinyl silicone rubber raw rubber, which constructs the main chain network and provides basic flexibility, electrical insulation and reactivity. 2 parts of vinyl polydimethylsiloxane, which improves low-temperature elasticity, increases optical transparency, and reduces surface tension. 1 part of vinyl phthalimide silicone rubber, which introduces polar groups, enhances thermal stability and mechanical strength, and improves anti-aging performance.

[0049] The functional fillers are selected from the following filler combinations: 4 parts of fumed silica nanopowder, whose ultrafine particle size and high specific surface area help to disperse evenly, and can reduce the thermal expansion coefficient and light scattering, and maintain transparency. 2 parts of nano titanium dioxide, with excellent ultraviolet absorption and scattering effects, can shield part of the UV, prevent the material from yellowing, and have a certain reinforcement effect, but the amount is controlled at a low level to avoid affecting transparency.

[0050] The silane monomers are selected from the following components: 2 parts of dimethyldimethoxysilane, which generates silanol after hydrolysis, and undergoes condensation reaction with the silicon-based polymer and the hydroxyl groups on the surface of the filler to construct a siloxane cross-linking network, thereby improving the overall weather resistance and mechanical stability.

[0051] Release agent: 1.5 parts, silane-modified polysiloxane release agent, which forms a low surface energy film during processing, improves the release between materials and equipment during mixing and molding, ensures a smooth surface and no burrs on the product, and has a positive impact on storage performance. This formula design not only meets the requirements of LED packaging for high transparency, weather resistance and mechanical strength, but also solves the problems of easy aging, yellowing and bubbles in processing of traditional silicone rubber through reasonable chemical cross-linking and filler dispersion, thereby ensuring the stability and excellent performance of LED light strips in long-term outdoor use.

[0052] In this formula, for the mixing process in step S3, it is determined whether the reaction degree of the LED silicone rubber material meets the requirements, and a calculation equation group of the reaction degree is designed: in, is the conversion rate of the reaction (dimensionless), is the conversion rate of the first mixing (dimensionless), is the conversion rate of the second mixing (dimensionless). is the reaction rate constant of the first mixing ( ), can be . is the reaction rate constant of the second mixing (L / mol·s), which can be . and The results are obtained by repeated tests on small-scale samples of LED silicone rubber materials in combination with the Arrhenius equation. The frequency factor and activation energy in the Arrhenius equation can be obtained by curve fitting during repeated tests, which is well known to those skilled in the art and will not be described in detail here. and It can also be calculated by the half-life of the mixing process, which refers to the time required for the concentration of vinyl groups to decrease to half of the initial concentration, so .

[0053] is the vinyl group concentration (mol / L), indicating the concentration of unreacted vinyl groups during the reaction, and is monitored by FTIR (infrared spectroscopy) at 1590–1650 The C=C stretching vibration peak is integrated and calculated. Both the preformed colloid and the cross-linking agent contain vinyl groups, or a sample is taken for calculation by titration. The vinyl consumption is determined by iodine addition reaction. The vinyl group can react with iodine. During the titration process, the vinyl group consumes iodine. At the end of the reaction, the unreacted iodine is back-titrated with sodium thiosulfate to calculate the vinyl consumption. is the concentration of added cross-linker (mol / L). is the initial concentration of vinyl groups at the beginning of the reaction (mol / L), calculated by initial integration using NMR or FTIR, or theoretically calculated based on the feed ratio. and are the reaction times (min) for the first mixing and the second mixing, respectively. A is the reaction degree of silicone rubber material for LED (dimensionless), 2≤A≤5.

[0054] The degree of crosslinking determines the hardness and elasticity of the material. As the crosslinking density increases, the hardness, heat resistance and weather resistance of the material improve. However, excessive crosslinking may cause the material to become brittle. Insufficient crosslinking will result in better elasticity of the material, but weaker mechanical properties. The more complete the crosslinking reaction is, the more uniform the crosslinking points are, and the higher the optical transparency of the material is. If the crosslinking is insufficient, unreacted vinyl may exist in the system, resulting in a decrease in optical properties.

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

Claims

1. A method for preparing a silicone rubber material for LED, characterized in that the steps include: S1. Add the silicon-based polymer and some functional fillers into deionized water, heat it to 50-65°C and stir it, then add the silane monomer and stir until mixed to obtain a mixed glue solution; S2, adding a release agent and the remaining functional filler to the mixed glue solution, cooling to room temperature after stirring and standing for 8 to 10 hours to obtain a prefabricated colloid; S3, placing the prefabricated colloid in an internal mixer, performing a first mixing, the first mixing time is 2 to 6 hours, and then performing a second mixing, the mixing time is 30 to 60 minutes, the first mixing temperature is higher than the second mixing temperature, and after cooling, a silicone rubber material for LED is obtained.

2. The method for preparing a silicone rubber material for LED according to claim 1, characterized in that: In step S1, the silicon-based polymer includes at least one of methyl vinyl silicone rubber, vinyl polydimethylsiloxane, vinyl phthalimide silicone rubber, and phenyl modified silicone rubber; the functional filler includes at least one of fumed silica nanopowder, precipitated silica powder, fused silica powder, white carbon black, and nano titanium dioxide; and the silane monomer includes at least one of tetramethyldivinyldisilazane, dimethyldimethoxysilane, and hexamethyldisilazane.

3. The method for preparing a silicone rubber material for LED according to claim 1 or 2, characterized in that: In step S1, according to the mass ratio, the silicon-based polymer: the functional filler: the silane monomer = 10: (5-7): (1-4).

4. The method for preparing a silicone rubber material for LED according to claim 1, characterized in that: Step S1 includes: S1.

1. Add the silicon-based polymer and 30-50% of the functional filler into deionized water, slowly raise the temperature to 50-65°C, adjust the speed to 200-300 rpm and stir for 10-15 minutes to obtain a premixed solution; S1.2, add silane monomer to the premixed liquid, continue stirring at 50-65°C for 5-10 minutes, until the pH of the premixed liquid reaches 4.5 and the viscosity reaches 3000-3500 cP, then stop stirring to obtain a mixed glue solution.

5. The method for preparing a silicone rubber material for LED according to claim 1, characterized in that: In step S2, the release agent includes at least one of a silane-modified polysiloxane release agent, a fluorosilicone composite release agent, and a silicone polymer release agent, and the release agent accounts for 1-10% of the mass of the mixed glue.

6. The method for preparing a silicone rubber material for LED according to claim 1, characterized in that: Step S2 includes: S2.1, adding a release agent to the mixed glue, and adding the remaining functional filler in batches, adjusting the stirring speed to 250-350 rpm, maintaining the temperature at 50-65°C, and stirring for 20-25 minutes; S2.

2. After stirring, slowly cool to room temperature and keep it at room temperature for 8 to 10 hours to obtain a prefabricated colloid.

7. The method for preparing a silicone rubber material for LED according to claim 1, characterized in that: Step S3 includes: S3.1, add the preformed colloid and the crosslinking agent into an internal mixer, heat to 150-200°C for the first mixing, maintain the first mixing for 2-6 hours, evacuate to 0.06-0.08MPa, and stir at a speed of 250-350rpm for the first mixing; S3.2, cooling to 80-100°C, and performing the second mixing, the second mixing time is controlled within 30-60 minutes, and the stirring speed of the second mixing is 200-300rpm; S3.

3. After cooling to room temperature, irradiate with 365nm ultraviolet light for 10 to 15 minutes to obtain silicone rubber material for LED.

8. The method for preparing a silicone rubber material for LED according to claim 7, characterized in that: In step S3.1, the crosslinking agent includes at least one of dimethyl siloxane bisacrylate, tripropylene silane, and methoxyethyl silane methacrylate.

9. A silicone rubber material for LED, characterized in that: It is made by the preparation method of a silicone rubber material for LED according to any one of claims 1 to 8, wherein the silicone rubber material for LED comprises a silicon-based polymer, a functional filler, a silane monomer and a release agent; wherein, The silicon-based polymer is used to form a cross-linked network in the silicone rubber material for LED; The functional filler is used to improve the UV resistance, heat resistance and aging resistance of the silicone rubber material for LED; The silane monomer is used to generate siloxane bonds to enhance the weather resistance and yellowing resistance of the silicone rubber material for LEDs; The release agent is used to prevent the silicone rubber material for LED from adhering to the surface of processing equipment.

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