Light diffusion polypropylene material for LED lampshade and preparation method thereof

Abstract

This invention provides a light-diffusing polypropylene material for LED lampshades and its preparation method. By weight, the raw materials include: 60-75 parts of transparent random copolymer polypropylene, 15-25 parts of transparent homopolymer polypropylene, 2.0-4.5 parts of reactive porous silica microspheres, 0.8-2.0 parts of rosin-based macromolecular compatibilizer, 0.3-0.8 parts of nucleating agent, 0.08-0.18 parts of initiator, 0.1-0.3 parts of co-crosslinking agent, 0.5-1.0 parts of antioxidant, 0.4-0.8 parts of light stabilizer, 0.5-1.2 parts of nano zinc oxide, 0.4-1.0 parts of lubricant, and 0.1-0.3 parts of surface treatment agent. The light-diffusing polypropylene material provided by this invention possesses excellent comprehensive properties such as mechanical properties, processing fluidity, and heat resistance, and can effectively extend the service life of LED lampshades made from this material.

Description

Technical Field

[0001] This invention relates to the field of LED lampshade technology, specifically to a light-diffusing polypropylene material for LED lampshades and its preparation method. Background Technology

[0002] LEDs, as energy-saving lighting sources, have become the mainstream light source for general indoor and outdoor lighting due to their advantages such as low energy consumption, long lifespan, and high luminous efficacy. LED lampshades, as key components of lighting equipment, directly affect light uniformity, lighting comfort, overall lighting effect, and lifespan. Therefore, the materials used in LED lampshades must possess good light diffusion, optical transmittance, mechanical properties, and processing compatibility. Polypropylene, due to its moderate cost, good processing fluidity, and excellent mechanical properties, is gradually being promoted as a substrate for LED lampshades. However, ordinary polypropylene materials themselves have insufficient light diffusion capabilities, making it difficult to directly meet the uniform light output requirements of LEDs.

[0003] Currently, the light-diffusing polypropylene materials used in LED lampshades mostly achieve light diffusion effects through physical blending modification. However, they generally suffer from the problem of difficulty in synergistically optimizing light diffusion efficiency and optical transmittance, which easily leads to defects such as uneven light output and obvious glare. At the same time, the poor compatibility of the components results in poor stability of the material system. Long-term use is prone to performance degradation and aging and yellowing, which not only affects the lighting effect but also shortens the lifespan of the lampshade. This makes it difficult to meet the requirements of energy-saving lighting equipment for high performance, long lifespan, and high stability of lampshade materials. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a light-diffusing polypropylene material for LED lampshades and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a light-diffusing polypropylene material for LED lampshades. By weight, the raw materials for its preparation include: 60-75 parts of transparent random copolymer polypropylene, 15-25 parts of transparent homopolymer polypropylene, 2.0-4.5 parts of reactive porous silica microspheres, 0.8-2.0 parts of rosin-based macromolecular compatibilizer, 0.3-0.8 parts of nucleating agent, 0.08-0.18 parts of initiator, 0.1-0.3 parts of co-crosslinking agent, 0.5-1.0 parts of antioxidant, 0.4-0.8 parts of light stabilizer, 0.5-1.2 parts of nano zinc oxide, 0.4-1.0 parts of lubricant, and 0.1-0.3 parts of surface treatment agent.

[0006] Using the above technical solution, transparent random copolymer polypropylene and transparent homopolymer polypropylene are compounded as the matrix resin, providing the material with basic mechanical properties and processing fluidity, ensuring that the material is easy to process and mold into LED lampshades, meeting the requirements of LED energy-saving lighting; reactive porous silica microspheres, through interface modification and multiple light scattering synergistic effect, can achieve efficient light diffusion and improve the light emission uniformity of LED light source; rosin-based macromolecular compatibilizer can improve the interfacial compatibility between inorganic particles and polypropylene matrix, improving the overall stability of the material; nucleating agent can refine crystal structure and optimize the optical and mechanical properties of the material; initiator and co-crosslinking agent synergistic effect can improve the melt strength and heat resistance of the material; antioxidant and light stabilizer can delay material aging and extend the life of lampshade; surface-modified nano zinc oxide has the functions of ultraviolet shielding, auxiliary light scattering and interface enhancement, and synergistic effect with hindered amine light stabilizer to further improve the material's resistance to light aging and anti-yellowing performance; lubricant can improve the material's processing fluidity and processability; surface treatment agent can improve the surface properties of inorganic filler, improve filler dispersibility and product dimensional stability.

[0007] Preferably, the nucleating agent is a compound of sorbitol-based nucleating agent and aromatic carboxylate nucleating agent in a mass ratio of (1.5-2.5):1; the sorbitol-based nucleating agent is dibenzyl sorbitol or bis(p-methylbenzyl)sorbitol, and the aromatic carboxylate nucleating agent is sodium benzoate or aluminum benzoate; the antioxidant is a compound of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010) and tris(2,4-di-tert-butylphenyl) phosphite (antioxidant 168) in a mass ratio of 1:(1.2-2.0).

[0008] Using the above technical solution, dibenzyl sorbitol or bis(p-methylbenzyl)sorbitol, as sorbitol-based nucleating agents, can induce polypropylene to form a refined α-crystal form, improving the transparency and rigidity of the material; sodium benzoate or aluminum benzoate, as aromatic carboxylate nucleating agents, can provide rapid nucleation sites and optimize the crystallization rate of the material; the nucleating agent formed by the two in a mass ratio of (1.5~2.5):1 can produce a synergistic nucleation effect, refine the size of polypropylene spherulites, reduce internal heterogeneous scattering, and improve the uniformity of light diffusion while ensuring light transmittance; antioxidant 1010, as the main antioxidant, can inhibit the thermo-oxidative degradation of polypropylene and delay the aging of the material; antioxidant 168, as the auxiliary antioxidant, can decompose the hydroperoxides generated during thermo-oxidative aging, and work synergistically with the main antioxidant to further improve the material's resistance to thermo-oxidative aging and extend the material's service life.

[0009] Preferably, the initiator is at least one of dicumyl peroxide and di-tert-butyl peroxide; the co-crosslinking agent is at least one of triallyl isocyanurate and trimethylolpropane trimethacrylate; the light stabilizer is light stabilizer 944 or light stabilizer 622; the lubricant is polydimethylsiloxane; and the surface treatment agent is γ-glycidoxypropyltrimethoxysilane (KH-560).

[0010] Using the above technical solution, dicumyl peroxide and di-tert-butyl peroxide, as initiators, can decompose at high temperatures to generate free radicals, which can capture tertiary hydrogen atoms on the polypropylene molecular chain to form macromolecular free radicals; triallyl isocyanurate and trimethylolpropane trimethacrylate, as co-crosslinking agents, can react with polypropylene macromolecular free radicals to form grafting points, promote the branching of polypropylene long chains and the formation of moderately mild crosslinked structures, and improve melt strength and dimensional stability; high molecular weight hindered amine light stabilizer 944 and high molecular weight hindered amine light stabilizer 622 can inhibit material photo-oxidation and delay material aging by capturing free radicals and decomposing hydrogen peroxide; polydimethylsiloxane, as a lubricant, can improve the processing fluidity of the material and enhance the compatibility between the components; KH-560 can modify the surface of nano-zinc oxide and reactive porous silica microspheres, enhance the interfacial bonding force between nano-zinc oxide and reactive porous silica microspheres and the polypropylene matrix, and improve the system compatibility and dispersion stability.

[0011] Preferably, the raw materials for preparing the reactive porous silica microspheres, by weight, include: 80-120 parts of porous silica microspheres, 4-10 parts of 3-isocyanate-propyltriethoxysilane, 0.3-0.7 parts of diethylenetriamine, and 400-600 parts of anhydrous ethanol.

[0012] Using the above technical solution, porous silica microspheres serve as the substrate for reactive porous silica microspheres, providing a basic porous structure and specific surface area, thus providing a carrier for subsequent functional group grafting. 3-Isocyanate-propyltriethoxysilane can graft isocyanate groups onto the surface of the porous silica microspheres through a reaction, giving the prepared reactive porous silica microspheres interfacial reactivity. Diethylenetriamine acts as a crosslinking agent, reacting with the surface isocyanate groups to improve surface grafting stability. Anhydrous ethanol, as a solvent, can uniformly disperse the porous silica microspheres, 3-isocyanate-propyltriethoxysilane, and diethylenetriamine, providing a stable dispersion system for the reaction and ensuring that the reaction is uniform and complete.

[0013] Preferably, the method for preparing the reactive porous silica microspheres includes the following steps: 1) Add porous silica microspheres to 60%–75% anhydrous ethanol, add 1%–3% deionized water (by mass of the anhydrous ethanol), and ultrasonically disperse for 20–40 minutes at a power of 300–500W and a frequency of 35–45kHz to form a suspension. 2) Dissolve 3-isocyanate-propyltriethoxysilane in 15%–20% anhydrous ethanol and add it dropwise to the suspension at a constant rate over 1–2 hours, stirring at a speed of 200–250 r / min. After the addition is complete, raise the temperature to 50–70°C and adjust the pH to 4.0–5.0 with glacial acetic acid under nitrogen protection. Continue the reaction for 3–5 hours. 3) Dissolve diethylenetriamine in the remaining anhydrous ethanol and add it dropwise over 30-40 min to the system obtained in step 2), and continue the reaction for 1-2 h; 4) After the reaction is complete, centrifuge at 6000-7000 r / min for 10-15 min, wash with anhydrous ethanol and deionized water 3-5 times respectively, and then dry at 80-90℃ and vacuum degree -0.08--0.09MPa for 8-12 h to obtain reactive porous silica microspheres.

[0014] Using the above technical solution, this preparation method can uniformly disperse porous silica microspheres in anhydrous ethanol system, providing a uniform environment for the grafting reaction of 3-isocyanate-propyltriethoxysilane. After being dissolved and added dropwise, 3-isocyanate-propyltriethoxysilane reacts with the porous silica microspheres under suitable temperature, nitrogen protection, and specific pH conditions to achieve the grafting of isocyanate groups on the surface of the microspheres. Diethylenetriamine continues to participate in the reaction after being dissolved and added dropwise, which can regulate the reaction system and ensure the sufficiency and stability of the isocyanate group grafting reaction. After the reaction, the centrifugation and washing steps can remove unreacted small molecules and impurities in the system, and the drying step can remove the solvent in the product, finally obtaining high-purity reactive porous silica microspheres.

[0015] Preferably, the raw materials for preparing the rosin-based macromolecular compatibilizer, by weight, include: 80-120 parts of dehydroabsic acid, 12-25 parts of maleic anhydride, 25-50 parts of amino-terminated polydimethylsiloxane, 0.03-0.08 parts of dibutyltin dilaurate, and 200-400 parts of acetone; wherein the amino-terminated polydimethylsiloxane has a molecular weight of 2000-3000 and an ammonia value of 0.6-0.8 mmol / g.

[0016] Using the above technical solution, dehydroabietic acid and maleic anhydride can react to generate maleic anhydride-dehydroabietic acid, providing reactants containing anhydride groups for subsequent amidation reactions; terminal amino polydimethylsiloxane can undergo amidation reactions with maleic anhydride-dehydroabietic acid, and its specific molecular weight and ammonia value can ensure the smooth progress of the reaction and the stability of the product structure; dibutyltin dilaurate can act as a catalyst to promote the reaction between dehydroabietic acid and maleic anhydride, and between maleic anhydride-dehydroabietic acid and terminal amino polydimethylsiloxane; acetone can act as a solvent to uniformly disperse the raw materials, and can also be used to extract and remove unreacted small molecules from the product, thereby improving the product purity.

[0017] Preferably, the preparation method of the rosin-based macromolecular compatibilizer includes the following steps: (1) Add dehydroabietic acid and maleic anhydride to the reaction vessel, heat to 180-200℃, stir at 200-250r / min for 15-20min, and react for 3-4h under nitrogen protection to obtain maleic anhydride-modified dehydroabietic acid. (2) Cool maleic anhydride dehydroabietic acid to 80-90℃, add amino-terminated polydimethylsiloxane and dibutyltin dilaurate, and control the molar ratio of the amino group of the amino-terminated polydimethylsiloxane to the anhydride group of maleic anhydride dehydroabietic acid to be (0.85-0.95):1 (so that the anhydride group is slightly in excess to ensure complete amidation reaction). Stir at 200-250 r / min for 15-20 min and react under vacuum of -0.05 to -0.07 MPa for 2-3 h. Take a sample every 20 min during the reaction to measure the acid value. Stop the reaction when the acid value drops to 20-30 mg KOH / g. (3) After extracting the product obtained in step (2) with acetone for 12 to 18 hours, it is then dried at 75 to 85°C and vacuum of -0.08 to -0.09 MPa for 6 to 10 hours to obtain rosin-based macromolecular compatibilizer.

[0018] Using the above technical solution, this preparation method allows dehydroabietic acid to react with maleic anhydride to generate maleic anhydride-dehydroabietic acid, and nitrogen protection ensures the smooth progress of the reaction. Maleic anhydride-dehydroabietic acid undergoes an amidation reaction with amino-terminated polydimethylsiloxane under the action of dibutyltin dilaurate. Acid value detection can control the reaction endpoint and ensure the stability of the product structure. Acetone extraction can remove unreacted small molecules from the product, and vacuum drying can remove solvents and moisture from the product, finally yielding a rosin-based macromolecular compatibilizer.

[0019] The present invention also provides a method for preparing a light-diffusing polypropylene material for LED lamp covers, comprising the following steps: S1. Add nano zinc oxide and surface treatment agent to a high-speed mixer and stir at 800-1000 r / min for 10-15 min at 60-70℃ to obtain surface-modified nano zinc oxide; S2. Add 50%–70% of the total mass of transparent random copolymer polypropylene, transparent homopolymer polypropylene, rosin-based macromolecular compatibilizer, nucleating agent, lubricant, 50%–70% of the total mass of antioxidant, and surface-modified nano zinc oxide to a high-speed mixer and stir at 800–1000 r / min at 25–30°C for 8–10 min to obtain premix A. S3. Add reactive porous silica microspheres to a high-speed mixer. Dissolve the initiator and crosslinking agent in 5 to 8 times their weight of acetone. Spray the solution evenly onto the surface of the reactive porous silica microspheres. Stir at 300 to 400 r / min at 40 to 50°C for 15 to 20 minutes. Then dry at 60 to 70°C and a vacuum of -0.08 to -0.09 MPa for 30 to 40 minutes to obtain premix B. S4. Using a twin-screw extruder with a length-to-diameter ratio (40-48):1 and a screw diameter of 35-50mm, the material is extruded by partitioned feeding. After water cooling and pelletizing, it is dried at 80-85℃ for 4-6 hours to obtain light-diffusing polypropylene material.

[0020] Using the above technical solution, this preparation method can achieve surface modification of nano-zinc oxide and improve its compatibility with the system; the premixing treatment ensures uniform mixing of each component and guarantees the uniformity of subsequent reactions; loading the initiator and co-crosslinking agent onto the surface of reactive porous silica microspheres can achieve uniform dispersion of the two; using twin-screw partitioned feeding extrusion and subsequent drying treatment can obtain a stable light-diffusing polypropylene material, ensuring that each component plays its full role and is tightly bound.

[0021] Preferably, in step S4, the twin-screw extruder uses a zoned feeding method as follows: premix A is added to the main feed port, premix B is added to the third barrel side feed port, and the remaining antioxidant, light stabilizer, and remaining lubricant are added to the sixth barrel side feed port.

[0022] Using the above technical solution, this zoned feeding method allows premix A to be fully melted in the twin-screw extruder first, providing a stable polypropylene matrix for subsequent reactions; premix B is added in the melting section, which allows the reactive porous silica microspheres and their loaded initiators and crosslinking agents to be uniformly mixed with the molten matrix, ensuring that the interfacial reaction and branching reaction proceed in an orderly manner; the remaining antioxidants, light stabilizers, and remaining lubricants are added in the reaction section, which can reduce their loss during the high-temperature melting process, ensuring that each component fully exerts its own role and ensuring the stable performance of the final light-diffusing polypropylene material.

[0023] Preferably, in step S4, the temperatures of each section of the extruder are set as follows: Zone 1 165-175℃, Zone 2 175-185℃, Zone 3 175-185℃, Zone 4 185-195℃, Zone 5 190-200℃, Zone 6 185-195℃, Zone 7 180-190℃, and the die head 180-185℃; the screw speed is 250-350 r / min; and the vacuum degree is -0.08 to -0.09 MPa.

[0024] Using the above technical solution, the extrusion temperature setting forms a gradient temperature control system. The temperatures in zones one and two allow premix A to melt fully, while the temperatures in zones three to seven and the die head ensure the orderly conduct of the interfacial reaction between the reactive porous silica microspheres and the rosin-based macromolecular compatibilizer, as well as the polypropylene branching reaction initiated by the initiator and the co-crosslinking agent, while ensuring uniform mixing of all components. A screw speed of 250–350 r / min provides suitable shear strength, promoting the dispersion of all components and ensuring sufficient reaction. A vacuum degree of -0.08 to -0.09 MPa reduces air bubbles in the system during extrusion, ensuring the molding quality and performance stability of the light-diffusing polypropylene material.

[0025] The beneficial effects of this invention are as follows: Transparent random copolymer polypropylene and transparent homopolymer polypropylene are blended as the matrix resin, providing the material with basic mechanical properties and processing fluidity, ensuring that the material is easily processed and molded into LED lampshades, meeting the requirements of LED energy-saving lighting. Reactive porous silica microspheres, through interface modification and multiple light scattering synergy, can achieve efficient light diffusion and improve the light emission uniformity of LED light sources. Rosin-based macromolecular compatibilizers can improve the interfacial compatibility between inorganic particles and the polypropylene matrix, enhancing the overall stability of the material. Nucleating agents can refine the crystal structure and optimize the optical and mechanical properties of the material. Initiators and co-crosslinking agents work synergistically to improve the melt strength and heat resistance of the material. Antioxidants and light stabilizers can delay material aging and extend the lifespan of the lampshade. Surface-modified nano zinc oxide has the functions of ultraviolet shielding, auxiliary light scattering, and interface enhancement. In synergy with hindered amine light stabilizers, it further improves the material's resistance to light aging and yellowing. Lubricants can improve the material's processing fluidity and processability. Surface treatment agents can improve the surface properties of inorganic fillers, enhance filler dispersibility, and improve the dimensional stability of the product. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The specific information on the raw materials used in the embodiments of the present invention is shown in Table 1.

[0028] Table 1 Raw material specifications and sources

[0029] Example 1: This embodiment provides a light-diffusing polypropylene material for LED lampshades. By weight, the raw materials for its preparation include: 60 parts of transparent random copolymer polypropylene, 15 parts of transparent homopolymer polypropylene, 2 parts of reactive porous silica microspheres, 0.8 parts of rosin-based macromolecular compatibilizer, 0.3 parts of nucleating agent, 0.08 parts of initiator, 0.1 parts of co-crosslinking agent, 0.5 parts of antioxidant, 0.4 parts of light stabilizer, 0.5 parts of nano zinc oxide, 0.4 parts of lubricant, and 0.1 parts of surface treatment agent.

[0030] The nucleating agent is a compound of sorbitol-based nucleating agent and aromatic carboxylate nucleating agent at a mass ratio of 1.5:1; the sorbitol-based nucleating agent is dibenzyl sorbitol, and the aromatic carboxylate nucleating agent is sodium benzoate; the antioxidant is a compound of antioxidant 1010 and antioxidant 168 at a mass ratio of 1:1.2. The initiator is dicumyl peroxide; the co-crosslinking agent is triallyl isocyanurate; the light stabilizer is light stabilizer 944; the lubricant is polydimethylsiloxane; and the surface treatment agent is KH-560.

[0031] The raw materials for preparing reactive porous silica microspheres, by weight, include: 80 parts of porous silica microspheres, 4 parts of 3-isocyanate-propyltriethoxysilane, 0.3 parts of diethylenetriamine, and 400 parts of anhydrous ethanol.

[0032] The preparation method of reactive porous silica microspheres includes the following steps: 1) Add porous silica microspheres to 60% anhydrous ethanol, add 1% deionized water (by mass of the anhydrous ethanol) and ultrasonically disperse for 20 minutes at 300W power and 35kHz frequency to form a suspension. 2) Dissolve 3-isocyanate-propyltriethoxysilane in 15% anhydrous ethanol and add it dropwise to the suspension at a constant rate over 1 hour, while stirring at 200 r / min. After the addition is complete, raise the temperature to 50°C and adjust the pH to 4.0 with glacial acetic acid under nitrogen protection, and continue the reaction for 3 hours. 3) Dissolve diethylenetriamine in the remaining anhydrous ethanol and add it dropwise over 30 min to the system obtained in step 2), and continue the reaction for 1 h; 4) After the reaction was completed, the mixture was centrifuged at 6000 r / min for 10 min, washed three times with anhydrous ethanol and deionized water respectively, and then dried at 80℃ and vacuum degree -0.08MPa for 8 h to obtain reactive porous silica microspheres.

[0033] The raw materials for preparing the rosin-based macromolecular compatibilizer, by weight, include: 80 parts of dehydroabsic acid, 12 parts of maleic anhydride, 25 parts of amino-terminated polydimethylsiloxane, 0.03 parts of dibutyltin dilaurate, and 200 parts of acetone; the amino-terminated polydimethylsiloxane has a molecular weight of 2000 and an ammonia value of 0.6 mmol / g.

[0034] The preparation method of rosin-based macromolecular compatibilizer includes the following steps: (1) Dehydroabietic acid and maleic anhydride were added to the reaction vessel, heated to 180°C, stirred at 200 r / min for 15 min, and reacted for 3 h under nitrogen protection to obtain maleic anhydride-derived dehydroabietic acid. (2) Cool maleic anhydride dehydroabietic acid to 80°C, add amino-terminated polydimethylsiloxane and dibutyltin dilaurate, control the molar ratio of the amino group of amino-terminated polydimethylsiloxane to the anhydride group of maleic anhydride dehydroabietic acid to be 0.85:1, stir at 200 r / min for 15 min, react under vacuum of -0.05 MPa for 2 h, take a sample every 20 min during the reaction to measure the acid value, and stop the reaction when the acid value drops to 20 mg KOH / g; (3) The product obtained in step (2) was extracted with acetone for 12 hours and then dried at 75°C and vacuum degree -0.08MPa for 6 hours to obtain rosin-based macromolecular compatibilizer.

[0035] This embodiment also provides a method for preparing a light-diffusing polypropylene material for LED lamp covers, comprising the following steps: S1. Add nano zinc oxide and surface treatment agent to a high-speed mixer and stir at 800 r / min for 10 min at 60℃ to obtain surface-modified nano zinc oxide; S2. Add 50% of the total mass of transparent random copolymer polypropylene, transparent homopolymer polypropylene, rosin-based macromolecular compatibilizer, nucleating agent, lubricant, 50% of the total mass of antioxidant, and surface-modified nano zinc oxide to a high-speed mixer and stir at 800 r / min for 8 min at 25°C to obtain premix A. S3. Add reactive porous silica microspheres to a high-speed mixer, dissolve the initiator and crosslinking agent in acetone at 5 times their respective weights, and spray them evenly onto the surface of the reactive porous silica microspheres by spraying. Stir at 300 r / min for 15 min at 40℃, and then dry at 60℃ and vacuum degree -0.08 MPa for 30 min to obtain premix B. S4. A twin-screw extruder with a length-to-diameter ratio of 40:1 and a screw diameter of 35mm is used for zoned feeding extrusion. The zoned feeding method of the twin-screw extruder is as follows: premix A is added from the main feed port of the twin-screw extruder, premix B is added from the side feed port of the third section of the barrel, and the remaining antioxidant, light stabilizer, and remaining lubricant are added from the side feed port of the sixth section of the barrel. The temperature settings of each section of the extruder are as follows: Zone 1 165℃, Zone 2 175℃, Zone 3 180℃, Zone 4 185℃, Zone 5 190℃, Zone 6 185℃, Zone 7 180℃, and the die head 180℃. The screw speed is 250r / min, and the vacuum degree is -0.08MPa. After water cooling and pelletizing, the extrudate is dried at 80℃ for 4 hours to obtain light-diffusing polypropylene material.

[0036] Example 2: This embodiment provides a light-diffusing polypropylene material for LED lampshades. By weight, the raw materials for its preparation include: 75 parts of transparent random copolymer polypropylene, 25 parts of transparent homopolymer polypropylene, 4.5 parts of reactive porous silica microspheres, 2 parts of rosin-based macromolecular compatibilizer, 0.8 parts of nucleating agent, 0.18 parts of initiator, 0.3 parts of co-crosslinking agent, 1.0 part of antioxidant, 0.8 parts of light stabilizer, 1.2 parts of nano zinc oxide, 1 part of lubricant, and 0.3 parts of surface treatment agent.

[0037] The nucleating agent is a compound of sorbitol-based nucleating agent and aromatic carboxylate nucleating agent at a mass ratio of 2.5:1; the sorbitol-based nucleating agent is bis(p-methylbenzyl)sorbitol, and the aromatic carboxylate nucleating agent is aluminum benzoate; the antioxidant is a compound of antioxidant 1010 and antioxidant 168 at a mass ratio of 1:2. The initiator is di-tert-butyl peroxide; the co-crosslinking agent is trimethylolpropane trimethacrylate; the light stabilizer is light stabilizer 622; the lubricant is polydimethylsiloxane; and the surface treatment agent is KH-560.

[0038] The raw materials for preparing reactive porous silica microspheres, by weight, include: 120 parts porous silica microspheres, 10 parts 3-isocyanate-propyltriethoxysilane, 0.7 parts diethylenetriamine, and 600 parts anhydrous ethanol.

[0039] The preparation method of reactive porous silica microspheres includes the following steps: 1) Add porous silica microspheres to 75% anhydrous ethanol, add 3% deionized water (by mass of the anhydrous ethanol in this step), and ultrasonically disperse for 40 minutes at a power of 500W and a frequency of 45kHz to form a suspension. 2) Dissolve 3-isocyanate-propyltriethoxysilane in 20% anhydrous ethanol and add it dropwise to the suspension at a constant rate over 2 hours, while stirring at 250 r / min. After the addition is complete, raise the temperature to 70°C and adjust the pH to 5.0 with glacial acetic acid under nitrogen protection, and continue the reaction for 5 hours. 3) Dissolve diethylenetriamine in the remaining anhydrous ethanol and add it dropwise over 40 min to the system obtained in step 2), and continue the reaction for 2 h; 4) After the reaction was completed, the mixture was centrifuged at 7000 r / min for 15 min, washed 5 times with anhydrous ethanol and deionized water respectively, and then dried at 90℃ and vacuum degree -0.09MPa for 12 h to obtain reactive porous silica microspheres.

[0040] The raw materials for preparing the rosin-based macromolecular compatibilizer, by weight, include: 120 parts of dehydroabietic acid, 25 parts of maleic anhydride, 50 parts of amino-terminated polydimethylsiloxane, 0.08 parts of dibutyltin dilaurate, and 400 parts of acetone; the amino-terminated polydimethylsiloxane has a molecular weight of 2000 and an ammonia value of 0.8 mmol / g.

[0041] The preparation method of rosin-based macromolecular compatibilizer includes the following steps: (1) Dehydroabietic acid and maleic anhydride were added to the reaction vessel, heated to 200°C, stirred at 250 r / min for 20 min, and reacted for 4 h under nitrogen protection to obtain maleic anhydride-derived dehydroabietic acid. (2) Cool maleic anhydride dehydroabietic acid to 90°C, add amino-terminated polydimethylsiloxane and dibutyltin dilaurate, control the molar ratio of the amino group of the amino-terminated polydimethylsiloxane to the anhydride group of maleic anhydride dehydroabietic acid to be 0.95:1, stir at 250 r / min for 20 min, and react for 3 h under vacuum of -0.07 MPa. Take a sample every 20 min during the reaction to measure the acid value. Stop the reaction when the acid value drops to 30 mg KOH / g. (3) The product obtained in step (2) was extracted with acetone for 18 hours and then dried at 85°C and vacuum degree -0.09MPa for 10 hours to obtain rosin-based macromolecular compatibilizer.

[0042] This embodiment also provides a method for preparing a light-diffusing polypropylene material for LED lamp covers, comprising the following steps: S1. Add nano zinc oxide and surface treatment agent to a high-speed mixer and stir at 1000 r / min for 15 min at 70℃ to obtain surface-modified nano zinc oxide. S2. Add 70% of the total mass of transparent random copolymer polypropylene, transparent homopolymer polypropylene, rosin-based macromolecular compatibilizer, nucleating agent, lubricant, 70% of the total mass of antioxidant, and surface-modified nano zinc oxide to a high-speed mixer and stir at 1000 r / min for 10 min at 30°C to obtain premix A. S3. Add reactive porous silica microspheres to a high-speed mixer, dissolve the initiator and crosslinking agent in acetone at 8 times their respective weights, and spray them evenly onto the surface of the reactive porous silica microspheres by spraying. Stir at 400 r / min for 20 min at 50℃, and then dry at 70℃ and vacuum degree -0.09 MPa for 40 min to obtain premix B. S4. A twin-screw extruder with a length-to-diameter ratio of 48:1 and a screw diameter of 50mm is used for zoned feeding extrusion. The zoned feeding method of the twin-screw extruder is as follows: premix A is added from the main feed port of the twin-screw extruder, premix B is added from the side feed port of the third section of the barrel, and the remaining antioxidant, light stabilizer, and remaining lubricant are added from the side feed port of the sixth section of the barrel. The temperature settings of each section of the extruder are as follows: Zone 1 175℃, Zone 2 185℃, Zone 3 185℃, Zone 4 195℃, Zone 5 200℃, Zone 6 195℃, Zone 7 190℃, and the die head 185℃. The screw speed is 350r / min, and the vacuum degree is -0.09MPa. After water cooling and pelletizing, the extrudate is dried at 85℃ for 6 hours to obtain light-diffusing polypropylene material.

[0043] Example 3: This embodiment provides a light-diffusing polypropylene material for LED lampshades. By weight, its raw materials include: 68 parts of transparent random copolymer polypropylene, 20 parts of transparent homopolymer polypropylene, 3.5 parts of reactive porous silica microspheres, 1.4 parts of rosin-based macromolecular compatibilizer, 0.5 parts of nucleating agent, 0.13 parts of initiator, 0.2 parts of co-crosslinking agent, 0.8 parts of antioxidant, 0.6 parts of light stabilizer, 0.8 parts of nano zinc oxide, 0.7 parts of lubricant, and 0.2 parts of surface treatment agent.

[0044] The nucleating agent is a mixture of sorbitol-based nucleating agent and aromatic carboxylate nucleating agent at a mass ratio of 2:1; the sorbitol-based nucleating agent is dibenzyl sorbitol, and the aromatic carboxylate nucleating agent is sodium benzoate. The antioxidant is a mixture of antioxidant 1010 and antioxidant 168 at a mass ratio of 1:1.5. The initiator is dicumyl peroxide; the co-crosslinking agent is triallyl isocyanurate; the light stabilizer is light stabilizer 944; the lubricant is polydimethylsiloxane; and the surface treatment agent is KH-560.

[0045] The raw materials for preparing reactive porous silica microspheres, by weight, include: 100 parts porous silica microspheres, 7 parts 3-isocyanate-propyltriethoxysilane, 0.5 parts diethylenetriamine, and 500 parts anhydrous ethanol.

[0046] The preparation method of reactive porous silica microspheres includes the following steps: 1) Add porous silica microspheres to 68% anhydrous ethanol, add 2% deionized water (by mass of the anhydrous ethanol in this step), and ultrasonically disperse for 30 minutes at a power of 400W and a frequency of 40kHz to form a suspension. 2) Dissolve 3-isocyanate-propyltriethoxysilane in 18% anhydrous ethanol and add it dropwise to the suspension at a constant rate over 1.5 hours, stirring at 230 r / min. After the addition is complete, raise the temperature to 60°C and adjust the pH to 4.5 with glacial acetic acid under nitrogen protection. Continue the reaction for 4 hours. 3) Dissolve diethylenetriamine in the remaining anhydrous ethanol and add it dropwise over 35 min to the system obtained in step 2), and continue the reaction for 1.5 h; 4) After the reaction was completed, the mixture was centrifuged at 6500 r / min for 12 min, washed 4 times with anhydrous ethanol and deionized water respectively, and then dried at 85℃ and vacuum degree -0.085 MPa for 10 h to obtain reactive porous silica microspheres.

[0047] The raw materials for preparing the rosin-based macromolecular compatibilizer, by weight, include: 100 parts of dehydroabietic acid, 18 parts of maleic anhydride, 35 parts of amino-terminated polydimethylsiloxane, 0.05 parts of dibutyltin dilaurate, and 300 parts of acetone; the amino-terminated polydimethylsiloxane has a molecular weight of 2500 and an ammonia value of 0.7 mmol / g.

[0048] The preparation method of rosin-based macromolecular compatibilizer includes the following steps: (1) Dehydroabietic acid and maleic anhydride were added to the reaction vessel, heated to 190°C, stirred at 230 r / min for 18 min, and reacted under nitrogen protection for 3.5 h to obtain maleic anhydride-modified dehydroabietic acid. (2) Cool maleic anhydride dehydroabietic acid to 85°C, add amino-terminated polydimethylsiloxane and dibutyltin dilaurate, control the molar ratio of the amino group of the amino-terminated polydimethylsiloxane to the anhydride group of maleic anhydride dehydroabietic acid to be 0.9:1, stir at 230 r / min for 18 min, and react for 2.5 h under vacuum of -0.06 MPa. Take a sample every 20 min during the reaction to measure the acid value. Stop the reaction when the acid value drops to 25 mg KOH / g. (3) The product obtained in step (2) was extracted with acetone for 15 hours and then dried at 80°C and vacuum degree -0.085MPa for 8 hours to obtain rosin-based macromolecular compatibilizer.

[0049] This embodiment also provides a method for preparing a light-diffusing polypropylene material for LED lamp covers, comprising the following steps: S1. Add nano zinc oxide and surface treatment agent to a high-speed mixer and stir at 900 r / min for 12 min at 65℃ to obtain surface-modified nano zinc oxide. S2. Add 60% of the total mass of transparent random copolymer polypropylene, transparent homopolymer polypropylene, rosin-based macromolecular compatibilizer, nucleating agent, lubricant, 60% of the total mass of antioxidant, and surface-modified nano zinc oxide to a high-speed mixer and stir at 900 r / min for 9 min at 28℃ to obtain premix A. S3. Add reactive porous silica microspheres to a high-speed mixer, dissolve the initiator and crosslinking agent in acetone at 6 times their respective weights, and spray them evenly onto the surface of the reactive porous silica microspheres by spraying. Stir at 350 r / min for 18 min at 45℃, and then dry at 65℃ and vacuum degree -0.085 MPa for 35 min to obtain premix B. S4. A twin-screw extruder with a length-to-diameter ratio of 44:1 and a screw diameter of 45mm is used for zoned feeding extrusion. The zoned feeding method of the twin-screw extruder is as follows: premix A is added from the main feed port of the twin-screw extruder, premix B is added from the side feed port of the third section of the barrel, and the remaining antioxidant, light stabilizer, and remaining lubricant are added from the side feed port of the sixth section of the barrel. The temperature settings of each section of the extruder are as follows: Zone 1 170℃, Zone 2 180℃, Zone 3 180℃, Zone 4 190℃, Zone 5 195℃, Zone 6 190℃, Zone 7 185℃, and Die head 182℃. The screw speed is 300r / min, and the vacuum degree is -0.085MPa. After water cooling and pelletizing, the extrudate is dried at 82℃ for 5h to obtain light-diffusing polypropylene material.

[0050] Comparative Example 1: A light-diffusing polypropylene material for LED lampshades and its preparation method are disclosed. The only difference between this material and Example 3 is that reactive porous silica microspheres are not added, and an equal mass of commercially available organosilicon light-diffusing agent (Shin-Etsu KMP-590 from Japan, which has no porous structure and isocyanate groups) is used instead.

[0051] Comparative Example 2: A light-diffusing polypropylene material for LED lampshades and its preparation method are disclosed. The only difference between this material and Example 3 is that no rosin-based macromolecular compatibilizer is added, and it is replaced by commercially available maleic anhydride-grafted polypropylene (PP-g-MAH, grafting rate 0.8%, model DuPont 50E662, purchased from Dongguan Bailing New Materials Co., Ltd.).

[0052] Comparative Example 3: A light-diffusing polypropylene material for LED lampshades and its preparation method are disclosed, which differ from Example 3 only in that reactive porous silica microspheres and rosin-based macromolecular compatibilizers are not added.

[0053] Comparative Example 4: A light-diffusing polypropylene material for LED lampshades and its preparation method are disclosed, the only difference between this material and Example 3 is that dicumyl peroxide and triallyl isocyanurate are not added.

[0054] Comparative Example 5: A light-diffusing polypropylene material for LED lampshades and its preparation method are disclosed. The only difference between this material and Example 3 is that the nucleating agent is replaced with a single sorbitol-based nucleating agent (dibenzylsorbitol), and the amount used is the same as the total mass of the nucleating agent in Example 3.

[0055] Comparative Example 6: A light-diffusing polypropylene material for LED lampshades and its preparation method are disclosed, the only difference between this material and Example 3 is that nano zinc oxide is not added.

[0056] Comparative Example 7: A light-diffusing polypropylene material for LED lampshades and its preparation method differ from Example 3 only in that: the partitioned feeding process is not used, and all components are added to the main feed port for extrusion at once.

[0057] Comparative Example 8: A light-diffusing polypropylene material for LED lampshades and its preparation method are disclosed. The only difference between this material and Example 3 is that light stabilizer 944 is not added, and it is replaced by a low molecular weight light stabilizer (light stabilizer 770, molecular weight approximately 480) in equal mass.

[0058] The light-diffusing polypropylene materials obtained in Examples 1-3 and Comparative Examples 1-8 were injection molded into standard specimens and 100×100×2mm square plates using an injection molding machine. The injection temperature was 200-220℃, and the mold temperature was 40-60℃. After being placed in an environment of 23℃ and 50% relative humidity for 24 hours, performance tests were performed. Light transmittance and haze According to GB / T 2410-2008 Determination of transmittance and haze of plastic films and sheets, a haze meter was used to test a 2mm thick square plate, with light source C and a standard illuminator, and the transmittance (%) and haze (%) were recorded.

[0059] Tensile strength According to ISO 527-2:2012 Determination of tensile properties of plastics – Part 2: Test conditions for molded and extruded plastics, the tensile speed is 50 mm / min, and the tensile strength (MPa) is recorded.

[0060] Notched impact strength According to ISO 179-1:2010 "Determination of impact properties of simply supported beams made of plastics - Part 1: Non-instrumental impact testing", an A-notch was used, and the notched impact strength (kJ / m) was recorded. 2 ).

[0061] Heat distortion temperature (HDT) According to ISO 75-2:2013 Determination of heat distortion temperature under load for plastics – Part 2: Plastics and hard rubber, with a load of 0.45 MPa, record the heat distortion temperature (°C).

[0062] silicone bond strength According to GB / T 2791-1995 "Test Method for T-Peel Strength of Adhesives - Flexible Materials to Flexible Materials", a T-peel test was adopted; the substrates were injection-molded square plates and anodized aluminum plates, and the adhesive was Dow Corning DOWSIL. TM 7091 silicone, curing conditions 23℃ / 50%RH×72h, test width 25mm, peel speed 100mm / min, record peel strength (N / 25mm); peel strength of all samples was tested before xenon lamp aging to ensure consistent test conditions.

[0063] Yellowing index (ΔYI) According to the "Standard Implementation Procedure for Instrumental Measurement of White and Yellow Indices of Color Coordinates" (ASTM E313-20), the xenon lamp was aged for 2000 hours (irradiance 0.55 W / m²). 2 Yellowing index was tested after exposure to light at 340nm, blackboard temperature 65℃, relative humidity 50%, and continuous illumination.

[0064] Antibacterial properties According to GB / T 31402-2015 "Test Method for Antibacterial Properties of Plastic Surfaces", the antibacterial rate against Escherichia coli and Staphylococcus aureus was tested; test conditions: bacterial concentration 1.0 × 10⁻⁶. 6 The concentration of CFU / mL was measured, the contact time was 24 hours, the sample surface was disinfected with ethanol and then sterilized with ultraviolet light for 30 minutes, and the antibacterial rate (%) was recorded.

[0065] β crystal content X-ray diffraction (XRD) was used for testing. The test conditions were Cu Kα radiation, scanning range 2θ = 10-35°, step size 0.02°, scanning rate 2° / min. Gaussian peak fitting was performed using PeakFit software, and the K value was calculated according to the Turner-Jones formula (K = H(300) / [H(300) + H(040) + H(130)], where H is the diffraction peak intensity). The β crystal content (%) was recorded.

[0066] The results are shown in Tables 2 and 3.

[0067] Table 2. Results of Optical and Mechanical Performance Tests

[0068] Table 3. Results of weather resistance, adhesion and antibacterial properties tests

[0069] Using Example 3 as the control group, the performance differences and causes of Comparative Examples 1-8 are analyzed as follows: Comparative Example 1 (non-reactive porous silica microspheres, replaced with commercially available silicone light diffusing agent): Haze decreased from 95.8% to 78.5% (a decrease of 18.1%), silicone peel strength decreased from 12.8 N / 25 mm to 5.8 N / 25 mm (a decrease of 54.7%), and notched impact strength decreased from 10.5 kJ / m 2 Reduced to 7.5 kJ / m 2 (A decrease of 28.6%), β-crystal content decreased from 68% to 58% (a decrease of 14.7%), yellowing index increased from 1.5 to 3.2 (an increase of 113.3%), and transmittance retention decreased from 95% to 90% (a decrease of 5.3%). Ordinary organosilicon light diffusing agents lack a porous structure with a gradient refractive index design, resulting in a significant reduction in light scattering efficiency and a substantial decrease in haze. Simultaneously, the lack of isocyanate groups prevents them from reacting with the carboxyl / amino groups at the ends of rosin-based macromolecular compatibilizers to form urea or amide bonds, thus lacking chemical anchoring with silica gel. Furthermore, the absence of a gradient refractive index structure and reactive groups in ordinary organosilicon light diffusing agents leads to decreased light scattering efficiency and interfacial bonding. Delamination at the inorganic-organic interface creates defect points, accelerating photo-oxidative degradation during xenon lamp aging, resulting in intensified yellowing and faster transmittance decay.

[0070] Comparative Example 2 (without rosin-based macromolecular compatibilizer, replaced by PP-g-MAH): Notched impact strength increased from 10.5 kJ / m 2 Reduced to 7.2 kJ / m 2(Decrease of 31.4%), β crystal content decreased from 68% to 42% (decrease of 38.2%), heat distortion temperature decreased from 116℃ to 108℃ (decrease of 6.9%), silicone peel strength decreased from 12.8N / 25mm to 8.5N / 25mm (decrease of 33.6%), tensile strength decreased from 33.2MPa to 31.5MPa (decrease of 5.1%), and yellowing index increased from 1.5 to 2.2 (increase of 46.7%). Although PP-g-MAH can provide polar groups, it lacks the β-crystal induction ability of the dehydroabsic acid framework, and cannot form a high-content β-crystal structure, resulting in a significant decrease in the material's ability to absorb impact energy. Its molecular chain lacks polydimethylsiloxane segments, resulting in weak interfacial compatibility with reactive porous silica microspheres, and it cannot form a dual interfacial anchoring structure of "chemical bonds + physical entanglement", thus reducing the interfacial bonding strength. At the same time, the interfacial interaction between PP-g-MAH and nano zinc oxide and silicone lubricant is insufficient, leading to a decrease in heat resistance and long-term weather resistance.

[0071] Comparative Example 3 (non-reactive porous silica microspheres and rosin-based macromolecular compatibilizer): Haze decreased from 95.8% to 72.0% (a decrease of 24.8%), silicone peel strength decreased from 12.8 N / 25 mm to 3.2 N / 25 mm (a decrease of 75.0%), and notched impact strength decreased from 10.5 kJ / m 2 Reduced to 7.0 kJ / m 2 The heat distortion temperature decreased from 116℃ to 105℃ (a decrease of 9.5%), the β crystal content decreased from 68% to 28% (a decrease of 58.8%), the yellowing index increased from 1.5 to 5.5 (an increase of 266.7%), the light transmittance retention decreased from 95% to 80% (a decrease of 15.8%), the light transmittance increased from 83.5% to 89.2% (an increase of 6.8%), the tensile strength increased from 33.2MPa to 35.0MPa (an increase of 5.4%), the antibacterial rate against Escherichia coli decreased from 95.0% to 72% (a decrease of 24.2%), and the antibacterial rate against Staphylococcus aureus decreased from 96.8% to 70% (a decrease of 27.7%). When both non-reactive porous silica microspheres and rosin-based macromolecular compatibilizers are absent, the system loses the gradient refractive index scattering centers provided by the light diffusing agent, resulting in a significant decrease in haze and an increase in transmittance. However, without the interfacial reactive compatibilizing network, the interfacial bonding between the inorganic filler and the matrix is ​​almost lost, leading to a sharp decrease in stress transfer efficiency and a significant reduction in impact strength and heat distortion temperature. At the same time, the lack of β-crystal induction and the synergistic effect of the branching network cause a comprehensive deterioration in the material's heat resistance and toughness. More seriously, the micro-defects formed by interfacial debonding become degradation initiation points under the influence of light, heat, and oxygen, accelerating yellowing and transmittance decay. Furthermore, due to the decreased dispersibility of nano-zinc oxide and the reduction in interfacial contact area, the antibacterial properties are significantly reduced.

[0072] Comparative Example 4 (without dicumyl peroxide and triallyl isocyanurate): The heat distortion temperature decreased from 116℃ to 98℃ (a decrease of 15.5%), the silicone peel strength decreased from 12.8 N / 25 mm to 6.5 N / 25 mm (a decrease of 49.2%), the tensile strength decreased from 33.2 MPa to 30.5 MPa (a decrease of 8.1%), and the yellowing index increased from 1.5 to 3.0 (an increase of 100.0%). The absence of dicumyl peroxide and triallyl isocyanurate prevented the polypropylene matrix from forming a long-chain branched and slightly cross-linked network. Insufficient melt strength led to increased molecular chain slippage during processing, a significant decrease in heat distortion temperature, and a decrease in interfacial stress transfer efficiency. In addition, linear polypropylene molecules are more prone to thermo-oxidative degradation during high-temperature processing and long-term use, resulting in an increased yellowing index.

[0073] Comparative Example 5 (nucleating agent replaced with a single sorbitol-based nucleating agent): β-crystal content decreased from 68% to 38% (a decrease of 44.1%), and notched impact strength decreased from 10.5 kJ / m. 2 Reduced to 8.8 kJ / m 2 (Decrease of 16.2%), the silicone peel strength decreased from 12.8 N / 25 mm to 11.0 N / 25 mm (decrease of 14.1%), and the yellowing index increased from 1.5 to 1.8 (increase of 20.0%). Single sorbitol nucleating agents primarily induce α-crystals and lack high β-crystal induction ability. While the crystallization rate is fast, the spherulite morphology is uniform, leading to a significant decrease in β-crystal content, resulting in reduced optical uniformity and toughness. Simultaneously, the reduced β-crystal content prevents the β-crystal toughening mechanism of rosin-based macromolecular compatibilizers from being fully utilized, slightly decreasing interfacial stress transfer efficiency. Furthermore, the α-crystal-dominated crystal structure is more prone to crystalline defects during photo-oxidation, leading to a slight decrease in weather resistance.

[0074] Comparative Example 6 (without nano zinc oxide): Yellowing index increased from 1.5 to 4.2 (an increase of 180.0%), light transmittance retention decreased from 95% to 87% (a decrease of 8.4%), silicone peel strength decreased from 12.8 N / 25 mm to 11.2 N / 25 mm (a decrease of 12.5%), silicone peel strength after aging decreased from 12.0 N / 25 mm to 6.0 N / 25 mm (a decrease of 50.0%), antibacterial rate against Escherichia coli decreased from 95.0% to 38% (a decrease of 60.0%), and antibacterial rate against Staphylococcus aureus decreased from 96.8% to 42% (a decrease of 56.6%). The absence of nano zinc oxide causes the material to lose its ultraviolet shielding layer. The hindered amine light stabilizer is directly exposed to ultraviolet irradiation and is rapidly consumed. Furthermore, it cannot capture the reactive oxygen species generated by photocatalysis, leading to accelerated yellowing and decreased light transmittance. At the same time, ultraviolet light directly damages the polypropylene molecular chains and interfacial chemical bonds, resulting in a sharp decrease in interfacial bonding strength after aging. In addition, the loss of the contact antibacterial mechanism of nano zinc oxide almost completely destroys the antibacterial properties of the material surface.

[0075] Comparative Example 7 (without zoned feeding process): Haze decreased from 95.8% to 90.5% (a decrease of 5.5%), silicone peel strength decreased from 12.8 N / 25 mm to 7.5 N / 25 mm (a decrease of 41.4%), and notched impact strength decreased from 10.5 kJ / m 2 Reduced to 8.2 kJ / m 2 (Decrease of 21.9%), heat distortion temperature decreased from 116℃ to 109℃ (decrease of 6.0%), β crystal content decreased from 68% to 52% (decrease of 23.5%), yellowing index increased from 1.5 to 3.5 (increase of 133.3%), light transmittance retention decreased from 95% to 89% (decrease of 6.3%), and tensile strength decreased from 33.2MPa to 30.8MPa (decrease of 7.2%). One-time feeding prevents the reactive porous silica microspheres from fully undergoing the addition reaction of isocyanate groups with carboxyl / hydroxyl / amino groups within the suitable temperature range (150~165℃). This results in insufficient interfacial chemical anchoring, increased particle size of the light diffusing agent, and reduced haze. Simultaneously, premature decomposition of dicumyl peroxide in the conveying section triggers premature degradation of polypropylene, leading to a wider molecular weight distribution, uneven melt strength, and a decrease in heat distortion temperature. Furthermore, the free radicals generated during degradation cause chain breakage, reducing notched impact strength and tensile strength. In addition, incomplete reaction leads to decreased interfacial stability and accelerated performance degradation after xenon lamp aging.

[0076] Comparative Example 8 (Replacing Light Stabilizer with Low Molecular Weight Light Stabilizer): The peel strength of silicone (after aging) decreased from 12.0 N / 25 mm to 2.8 N / 25 mm (a decrease of 76.7%), the yellowing index increased from 1.5 to 7.8 (an increase of 420.0%), and the transmittance retention decreased from 95% to 76% (a decrease of 20.0%). Light stabilizer 770, with a molecular weight of only about 480, is prone to migration, volatilization, and precipitation loss during high-temperature processing and long-term light exposure, failing to form a durable "absorption-capture" dual protection system. After 2000 hours of xenon lamp aging, almost no effective light stabilizer remained on the material surface. Ultraviolet light directly damaged the polypropylene molecular chains and interfacial chemical bonds, leading to a sharp increase in yellowing, a significant decrease in transmittance, and almost complete loss of interfacial adhesion strength after aging.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A light-diffusing polypropylene material for LED lampshades, characterized in that, The raw materials for its preparation, by weight, include: 60-75 parts of transparent random copolymer polypropylene, 15-25 parts of transparent homopolymer polypropylene, 2.0-4.5 parts of reactive porous silica microspheres, 0.8-2.0 parts of rosin-based macromolecular compatibilizer, 0.3-0.8 parts of nucleating agent, 0.08-0.18 parts of initiator, 0.1-0.3 parts of co-crosslinking agent, 0.5-1.0 parts of antioxidant, 0.4-0.8 parts of light stabilizer, 0.5-1.2 parts of nano zinc oxide, 0.4-1.0 parts of lubricant, and 0.1-0.3 parts of surface treatment agent.

2. The light-diffusing polypropylene material for LED lampshades according to claim 1, characterized in that, The nucleating agent is a compound of sorbitol-based nucleating agent and aromatic carboxylate nucleating agent in a mass ratio of (1.5-2.5):1; the sorbitol-based nucleating agent is dibenzyl sorbitol or bis(p-methylbenzyl)sorbitol, and the aromatic carboxylate nucleating agent is sodium benzoate or aluminum benzoate; the antioxidant is a compound of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite in a mass ratio of 1:(1.2-2.0).

3. The light-diffusing polypropylene material for LED lampshades according to claim 1, characterized in that, The initiator is at least one of dicumyl peroxide and di-tert-butyl peroxide; the co-crosslinking agent is at least one of triallyl isocyanurate and trimethylolpropane trimethacrylate; the light stabilizer is light stabilizer 944 or light stabilizer 622; the lubricant is polydimethylsiloxane; and the surface treatment agent is γ-glycidoxypropyltrimethoxysilane.

4. The light-diffusing polypropylene material for LED lampshades according to claim 1, characterized in that, The raw materials for preparing the reactive porous silica microspheres, by weight, include: 80-120 parts of porous silica microspheres, 4-10 parts of 3-isocyanate-propyltriethoxysilane, 0.3-0.7 parts of diethylenetriamine, and 400-600 parts of anhydrous ethanol.

5. The light-diffusing polypropylene material for LED lampshades according to claim 4, characterized in that, The preparation method of the reactive porous silica microspheres includes the following steps: 1) Add porous silica microspheres to 60%–75% anhydrous ethanol, add 1%–3% deionized water (by mass of the anhydrous ethanol), and ultrasonically disperse for 20–40 minutes at a power of 300–500W and a frequency of 35–45kHz to form a suspension. 2) Dissolve 3-isocyanate-propyltriethoxysilane in 15%–20% anhydrous ethanol and add it dropwise to the suspension at a constant rate over 1–2 hours, stirring at a speed of 200–250 r / min. After the addition is complete, raise the temperature to 50–70°C and adjust the pH to 4.0–5.0 with glacial acetic acid under nitrogen protection. Continue the reaction for 3–5 hours. 3) Dissolve diethylenetriamine in the remaining anhydrous ethanol and add it dropwise over 30-40 min to the system obtained in step 2), and continue the reaction for 1-2 h; 4) After the reaction is complete, centrifuge at 6000-7000 r / min for 10-15 min, wash with anhydrous ethanol and deionized water 3-5 times respectively, and then dry at 80-90℃ and vacuum degree -0.08--0.09MPa for 8-12 h to obtain reactive porous silica microspheres.

6. The light-diffusing polypropylene material for LED lampshades according to claim 1, characterized in that, The raw materials for preparing the rosin-based macromolecular compatibilizer, by weight, include: 80-120 parts of dehydroabietic acid, 12-25 parts of maleic anhydride, 25-50 parts of amino-terminated polydimethylsiloxane, 0.03-0.08 parts of dibutyltin dilaurate, and 200-400 parts of acetone; the amino-terminated polydimethylsiloxane has a molecular weight of 2000-3000 and an ammonia value of 0.6-0.8 mmol / g.

7. The light-diffusing polypropylene material for LED lampshades according to claim 6, characterized in that, The preparation method of the rosin-based macromolecular compatibilizer includes the following steps: (1) Add dehydroabietic acid and maleic anhydride to the reaction vessel, heat to 180-200℃, stir at 200-250r / min for 15-20min, and react for 3-4h under nitrogen protection to obtain maleic anhydride-modified dehydroabietic acid. (2) Cool maleic anhydride dehydroabietic acid to 80-90℃, add amino-terminated polydimethylsiloxane and dibutyltin dilaurate, control the molar ratio of the amino group of the amino-terminated polydimethylsiloxane to the anhydride group of maleic anhydride dehydroabietic acid to be (0.85-0.95):1, stir at 200-250 r / min for 15-20 min, react under vacuum of -0.05 to -0.07 MPa for 2-3 h, and stop the reaction when the acid value drops to 20-30 mg KOH / g; (3) After extracting the product obtained in step (2) with acetone for 12 to 18 hours, it is then dried at 75 to 85°C and vacuum of -0.08 to -0.09 MPa for 6 to 10 hours to obtain rosin-based macromolecular compatibilizer.

8. A method for preparing a light-diffusing polypropylene material for LED lampshades according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Add nano zinc oxide and surface treatment agent to a high-speed mixer and stir at 800-1000 r / min for 10-15 min at 60-70℃ to obtain surface-modified nano zinc oxide; S2. Add 50%–70% of the total mass of transparent random copolymer polypropylene, transparent homopolymer polypropylene, rosin-based macromolecular compatibilizer, nucleating agent, lubricant, 50%–70% of the total mass of antioxidant, and surface-modified nano zinc oxide to a high-speed mixer and stir at 800–1000 r / min at 25–30°C for 8–10 min to obtain premix A. S3. Add reactive porous silica microspheres to a high-speed mixer. Dissolve the initiator and crosslinking agent in 5 to 8 times their weight of acetone. Spray the solution evenly onto the surface of the reactive porous silica microspheres. Stir at 300 to 400 r / min at 40 to 50°C for 15 to 20 minutes. Then dry at 60 to 70°C and a vacuum of -0.08 to -0.09 MPa for 30 to 40 minutes to obtain premix B. S4. Using a twin-screw extruder with a length-to-diameter ratio (40-48):1 and a screw diameter of 35-50mm, the material is extruded by partitioned feeding. After water cooling and pelletizing, it is dried at 80-85℃ for 4-6 hours to obtain light-diffusing polypropylene material.

9. The method for preparing the light-diffusing polypropylene material for LED lampshades according to claim 8, characterized in that, In step S4, the twin-screw extruder is fed in the following sections: premix A is added to the main feed port, premix B is added to the third barrel side feed port, and the remaining antioxidant, light stabilizer, and remaining lubricant are added to the sixth barrel side feed port.

10. The method for preparing the light-diffusing polypropylene material for LED lampshades according to claim 8, characterized in that, In step S4, the temperatures of each section of the extruder are set as follows: Zone 1 165-175℃, Zone 2 175-185℃, Zone 3 175-185℃, Zone 4 185-195℃, Zone 5 190-200℃, Zone 6 185-195℃, Zone 7 180-190℃, and the die head 180-185℃. The screw speed is 250-350 r / min, and the vacuum degree is -0.08 to -0.09 MPa.

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