A pp resin foamed optical diffusion plate and a method for manufacturing the same

Abstract

The application discloses a kind of PP resin foamed optical diffusion plate and preparation method thereof, wherein diffusion plate includes upper layer, middle layer and lower layer, upper layer and lower layer are located on both sides of middle layer, the thickness ratio of upper, middle, lower layer is 1:(7-9):1, upper layer and lower layer are the same composition, upper layer includes the following component ingredients according to mass fraction:PP resin, PP-g-MAH resin, copolymer microspheres, flame retardant, antioxidant, mineral oil, light stabilizer, ultraviolet absorber, whitening agent;Middle layer includes the following component ingredients according to mass fraction:GPPS resin, foaming agent, antioxidant, mineral oil, light stabilizer, ultraviolet absorber, whitening agent, the diffusion plate, the overall structure of the diffusion plate is stable, optical performance is good, and manufacturing cost is low.

Description

Technical Field

[0001] This invention relates to the field of optical diffusion plate manufacturing technology, specifically to a PP resin foamed optical diffusion plate and its preparation method. Background Technology

[0002] Light diffusers, also known as light-diffusing plates, are now widely used in LCD displays and LED lighting. Their main function is to fully scatter incident light, achieving a softer and more uniform illumination effect. However, the GPPS materials currently used to manufacture optical diffusers generally suffer from poor heat resistance and impact resistance. During long-term use, the heat from the light source can easily cause the diffuser to deform, affecting its lifespan. Furthermore, it is easily damaged by impacts during transportation, resulting in defects.

[0003] Polypropylene (PP) is a general-purpose thermoplastic obtained by polymerizing propylene. Due to its abundant raw material sources and relatively simple synthesis process, it has advantages over other general-purpose thermoplastics, including low price, high impact resistance, good heat and chemical resistance, and high mechanical strength. Therefore, it is widely used in the automotive, electrical appliance, packaging, and daily necessities industries. Patent document CN220320523U discloses a corrosion-resistant polypropylene (PP) pipe, and patent document CN213200686U discloses an environmentally friendly recycled PP woven bag. However, no reports have been found regarding a PP resin foamed optical diffusion plate. Summary of the Invention

[0004] To address the aforementioned challenges, this invention provides a PP resin foamed optical diffusion plate with stable overall structure, good optical performance, and low manufacturing cost. The plate comprises an upper layer, a middle layer, and a lower layer, with the upper and lower layers located on either side of the middle layer. The thickness ratio of the upper, middle, and lower layers is 1:(7-9):1. The upper and lower layers have the same composition. The upper layer comprises the following components by weight: 69-85 parts PP resin, 10-20 parts PP-g-MAH resin, 1-3 parts copolymer microspheres, 3-5 parts flame retardant, and 0. The intermediate layer comprises the following components by weight: 3-0.7 parts antioxidant, 0.08-0.16 parts mineral oil, 0.4-1.2 parts light stabilizer, 0.2-0.9 parts ultraviolet absorber, and 0.02-0.04 parts whitening agent; 83-93 parts GPPS resin, 5-13 parts foaming agent, 0.4-1.2 parts antioxidant, 0.23-0.27 parts mineral oil, 0.6-1 part light stabilizer, 0.4-1.1 parts ultraviolet absorber, and 0.37-0.43 parts whitening agent.

[0005] Preferably, the antioxidant is at least one of antioxidant 1024, antioxidant 1010, or antioxidant 1076.

[0006] Preferably, the mineral oil is silicone oil or liquid paraffin.

[0007] Preferably, the light stabilizer is any one or more selected from light stabilizer 622, light stabilizer 770, and light stabilizer 944.

[0008] Preferably, the ultraviolet absorber is selected from one or more of the ultraviolet absorbers UV-327, UV-329, and UV-531.

[0009] Preferably, the brightener is the fluorescent whitening agent CBS-127.

[0010] This invention also provides a method for preparing a PP resin foamed optical diffuser plate, comprising the following steps:

[0011] Preparation of copolymer microspheres;

[0012] Mixture a is prepared by uniformly mixing 1-3 parts of copolymer microspheres with 69-85 parts of PP resin, 10-20 parts of PP-g-MAH resin, 3-5 parts of flame retardant, 0.3-0.7 parts of antioxidant, 0.08-0.16 parts of mineral oil, 0.4-1.2 parts of light stabilizer, 0.2-0.9 parts of ultraviolet absorber, and 0.02-0.04 parts of whitening agent.

[0013] Mixture b is prepared by uniformly mixing 83-93 parts of GPPS resin, 5-13 parts of foaming agent, 0.4-1.2 parts of antioxidant, 0.23-0.27 parts of mineral oil, 0.6-1 part of light stabilizer, 0.4-1.1 parts of ultraviolet absorber, and 0.37-0.43 parts of whitening agent.

[0014] Mixture a and mixture b are fed into a single screw extruder at a mass ratio of 2:(3-5), heated and melted, co-extruded in three layers, and then pressed to obtain the finished product;

[0015] The temperatures of each zone of the single-screw extruder are as follows: Zone 1: 180–190℃; Zone 2: 190–200℃; Zone 3: 210–220℃; Zone 4: 210–220℃; Zone 5: 225–235℃; Zone 6: 215–225℃; Zone 7: 210–220℃; and the die temperature is 205–215℃. The production rate is 310 kg / h.

[0016] Preferably, the preparation of copolymer microspheres includes the following steps:

[0017] Dissolve 30-50 parts of maleic anhydride, 45-55 parts of styrene, and 5-15 parts of azobisisobutyronitrile in 150-250 parts of isoamyl acetate. After purging with nitrogen for 30-40 minutes, heat in a water bath at 70°C for 4-6 hours. Centrifuge the resulting suspension, remove the supernatant, disperse the solid in n-hexane, wash, filter, collect the filter residue, and dry the filter residue to obtain copolymer microspheres.

[0018] Preferably, the centrifugation rate is 2000–4000 r / min and the centrifugation time is 20–30 min.

[0019] Preferably, the drying temperature is 90–110℃ and the drying time is 6–8 hours.

[0020] The beneficial effects are as follows: This application provides a PP resin foamed optical diffuser plate, comprising three layers: upper, middle, and lower. The middle layer uses GPPS resin as the substrate. Due to the high transparency of GPPS resin, combined with a brightening agent, the middle layer can be ensured to have high light transmittance. Secondly, the addition of a foaming agent to the middle layer can form a microporous structure to uniformly and effectively scatter light. Furthermore, this microporous structure can also significantly reduce the weight of the middle layer. The upper and lower layers use PP resin, which has good mechanical properties and chemical resistance, as the substrate, making the diffuser plate more weather-resistant and aging-resistant, providing better protection and support for the middle layer.

[0021] Furthermore, since GPPS resin is an amorphous thermoplastic and PP resin is a semi-crystalline thermoplastic, the two differ significantly in molecular chain structure, polarity, and crystallization behavior, resulting in poor compatibility between GPPS and PP resins. Direct mixing easily leads to delamination. Therefore, solving the compatibility and interfacial adhesion between GPPS and PP resins is the key to preparing optical diffusion plates. After extensive experimentation, the inventors discovered that adding PP-g-MAH resin to the system can significantly improve the compatibility and interfacial adhesion between the upper and lower layers and the middle layer. This is because the maleic anhydride groups in PP-g-MAH resin can react with the benzene rings in GPPS, thereby improving the interfacial bonding force between the upper and lower layers and the middle layer, and enhancing the overall structural stability of the diffusion plate.

[0022] In addition, self-developed copolymer microspheres are added to the upper and lower layers to further improve the light diffusion effect of the upper and lower layers. These copolymer microspheres have good compatibility with PP resin, so they can form good dispersion in PP resin. The refractive index of the copolymer microspheres is 1.4897, which is not much different from the refractive index of PP resin (1.5076). Using these copolymer microspheres as light diffusing agents can significantly improve the haze and light transmittance of the upper and lower layers.

[0023] Finally, this application designs the thickness ratio of the upper, middle and lower layers to be 1:(7~9):1, based on the fact that the middle layer has good light transmittance, and the upper and lower layers have excellent light diffusion function and mechanical strength. In this way, when the thickness ratio of the upper, middle and lower layers is reasonable, it can not only ensure that the diffuser plate has excellent optical performance, but also ensure the overall structural stability and durability of the diffuser plate, while also saving manufacturing costs to the greatest extent. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention.

[0025] The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. All other embodiments obtained by those skilled in the art based on the specific embodiments of the invention without inventive effort are within the protection scope of the invention.

[0026] In the embodiments of the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art; in the embodiments of the present invention, unless specifically specified, the technical means used are conventional means well known to those skilled in the art.

[0027] Raw material source:

[0028] Polystyrene (GPPS) resin, model GPPS-300NT, purchased from China National Petroleum Corporation Dushanzi Petrochemical Company;

[0029] Polypropylene (PP), model M60ET, purchased from Zhenhai Refining & Chemical Branch of China Petroleum & Chemical Corporation;

[0030] Polypropylene grafted maleic anhydride (PP-g-MAH) resin, model Mitsui ADMER from Japan, purchased from Jiangsu Weirun High Plastic Chemical Co., Ltd.

[0031] Flame retardant (melamine), purchased from Yunsheng Chemical (Shandong) Co., Ltd.;

[0032] Foaming agent (sodium bicarbonate), purchased from Foshan Sanzhong Environmental Protection Technology Co., Ltd.;

[0033] Antioxidant, purchased from Shandong Xuxiang Chemical Co., Ltd.;

[0034] Silicone oil, purchased from Jinan Xuchuang Chemical Technology Co., Ltd.

[0035] Liquid paraffin, purchased from Hefeng New Energy Co., Ltd.

[0036] Light stabilizer, purchased from Shanghai Tiandui New Materials Co., Ltd.;

[0037] Ultraviolet absorber, purchased from Jinan Xiangfeng Weiye Chemical Co., Ltd.

[0038] Fluorescent whitening agent, model CBS-127, purchased from Guangzhou Yuanda New Materials Co., Ltd.

[0039] Maleic anhydride, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0040] Styrene was purchased from Shandong Chuangying Chemical Co., Ltd.

[0041] Azobisisobutyronitrile (AIBN) was purchased from Zibo Tongyizhai Chemical Co., Ltd.

[0042] Isoamyl acetate, purchased from Xiamen Minghuiyang Chemical Co., Ltd.;

[0043] n-Hexane, purchased from Jinan Mingxin Chemical Co., Ltd.;

[0044] All other reagents were commercially available.

[0045] Example 1

[0046] This embodiment provides a PP resin foamed optical diffusion plate, comprising an upper layer, a middle layer, and a lower layer. The upper and lower layers are located on both sides of the middle layer, and the thickness ratio of the upper, middle, and lower layers is 1:7:1. The upper and lower layers have the same composition. The upper layer comprises the following components by weight: 85 parts PP resin, 10 parts PP-g-MAH resin, 1 part copolymer microspheres, 3 parts flame retardant, 0.3 parts antioxidant, 0.08 parts mineral oil, 0.4 parts light stabilizer, and 0.2 parts ultraviolet absorber. The intermediate layer comprises the following components by weight: 93 parts GPPS resin, 5 parts foaming agent, 0.4 parts antioxidant, 0.23 parts mineral oil, 0.6 parts light stabilizer, 0.4 parts ultraviolet absorber, and 0.37 parts whitening agent; wherein, the antioxidant is antioxidant 1024; the mineral oil is silicone oil; the light stabilizer is light stabilizer 622; the ultraviolet absorber is ultraviolet absorber UV-327; and the whitening agent is fluorescent whitening agent CBS-127.

[0047] The method for preparing the PP resin foamed optical diffuser plate includes the following steps:

[0048] Preparation of copolymer microspheres: 30 parts maleic anhydride, 55 parts styrene, and 15 parts azobisisobutyronitrile were dissolved in 150 parts isoamyl acetate, respectively. After purging with nitrogen for 30 min, the mixture was heated in a water bath at 70 °C for 4 h. The resulting suspension was centrifuged, the supernatant was removed, the solid was dispersed in n-hexane and washed, the filter residue was collected, and the residue was dried to obtain copolymer microspheres. The centrifugation rate was 2000 r / min, the centrifugation time was 20 min, the drying temperature was 90 °C, and the drying time was 6 h.

[0049] Mixture a is prepared by uniformly mixing 1 part copolymer microspheres with 85 parts PP resin, 10 parts PP-g-MAH resin, 3 parts flame retardant, 0.3 parts antioxidant, 0.08 parts mineral oil, 0.4 parts light stabilizer, 0.2 parts ultraviolet absorber and 0.02 parts whitening agent;

[0050] Mixture b is prepared by uniformly mixing 93 parts GPPS resin, 5 parts foaming agent, 0.4 parts antioxidant, 0.23 parts mineral oil, 0.6 parts light stabilizer, 0.4 parts ultraviolet absorber, and 0.37 parts whitening agent.

[0051] Mixture a and mixture b are fed into a single screw extruder at a mass ratio of 2:3, heated and melted, co-extruded in three layers, and then pressed to obtain the finished product.

[0052] The temperatures of each zone of the single-screw extruder are as follows: Zone 1: 180℃, Zone 2: 190℃, Zone 3: 210℃, Zone 4: 210℃, Zone 5: 225℃, Zone 6: 215℃, Zone 7: 210℃, and the die head temperature is 205℃; the production rate is 310 kg / h.

[0053] Example 2

[0054] This embodiment provides a PP resin foamed optical diffusion plate, comprising an upper layer, a middle layer, and a lower layer. The upper and lower layers are located on both sides of the middle layer, and the thickness ratio of the upper, middle, and lower layers is 1:8:1. The upper and lower layers have the same composition. The upper layer comprises the following components by weight: 77 parts PP resin, 15 parts PP-g-MAH resin, 2 parts copolymer microspheres, 4 parts flame retardant, 0.5 parts antioxidant, 0.12 parts mineral oil, 0.8 parts light stabilizer, and 0.55 parts ultraviolet absorber. The intermediate layer comprises the following components by weight: 88 parts GPPS resin, 9 parts foaming agent, 0.8 parts antioxidant, 0.25 parts mineral oil, 0.8 parts light stabilizer, 0.75 parts ultraviolet absorber, and 0.4 parts whitening agent; wherein, the antioxidant is antioxidant 1010; the mineral oil is liquid paraffin; the light stabilizer is light stabilizer 770; the ultraviolet absorber is ultraviolet absorber UV-329; and the whitening agent is fluorescent whitening agent CBS-127.

[0055] The method for preparing the PP resin foamed optical diffuser plate includes the following steps:

[0056] Preparation of copolymer microspheres: 40 parts maleic anhydride, 50 parts styrene, and 10 parts azobisisobutyronitrile were dissolved in 200 parts isoamyl acetate, respectively. After purging with nitrogen for 35 min, the mixture was heated in a water bath at 70 °C for 5 h. The resulting suspension was centrifuged, the supernatant was removed, the solid was dispersed in n-hexane and washed, the filter residue was collected, and the residue was dried to obtain copolymer microspheres. The centrifugation rate was 3000 r / min, the centrifugation time was 25 min, the drying temperature was 100 °C, and the drying time was 7 h.

[0057] Mixture a was prepared by uniformly mixing 2 parts copolymer microspheres with 77 parts PP resin, 15 parts PP-g-MAH resin, 4 parts flame retardant, 0.5 parts antioxidant, 0.12 parts mineral oil, 0.8 parts light stabilizer, 0.55 parts ultraviolet absorber and 0.03 parts whitening agent.

[0058] Mixture b is prepared by uniformly mixing 88 parts GPPS resin, 9 parts foaming agent, 0.8 parts antioxidant, 0.25 parts mineral oil, 0.8 parts light stabilizer, 0.75 parts ultraviolet absorber, and 0.4 parts whitening agent.

[0059] Mixture a and mixture b are fed into a single screw extruder at a mass ratio of 2:4, heated and melted, co-extruded in three layers, and then pressed to obtain the finished product.

[0060] The temperatures of each zone of the single-screw extruder are as follows: Zone 1: 185℃, Zone 2: 195℃, Zone 3: 215℃, Zone 4: 215℃, Zone 5: 230℃, Zone 6: 220℃, Zone 7: 215℃, and the die head temperature is 210℃; the production rate is 310 kg / h.

[0061] Example 3

[0062] A PP resin foamed optical diffusion plate includes an upper layer, a middle layer, and a lower layer. The upper and lower layers are located on both sides of the middle layer. The thickness ratio of the upper, middle, and lower layers is 1:9:1. The upper and lower layers have the same composition. The upper layer includes the following components by weight: 69 parts PP resin, 20 parts PP-g-MAH resin, 3 parts copolymer microspheres, 5 parts flame retardant, 0.7 parts antioxidant, 0.16 parts mineral oil, 1.2 parts light stabilizer, and 0.9 parts ultraviolet absorber. 0.04 parts whitening agent; the intermediate layer comprises the following components by weight: 83 parts GPPS resin, 13 parts foaming agent, 1.2 parts antioxidant, 0.27 parts mineral oil, 1 part light stabilizer, 1.1 parts ultraviolet absorber, and 0.43 parts whitening agent; wherein, the antioxidant is antioxidant 1076; the mineral oil is silicone oil; the light stabilizer is light stabilizer 944; the ultraviolet absorber is ultraviolet absorber UV-531; and the whitening agent is fluorescent whitening agent CBS-127.

[0063] The method for preparing the PP resin foamed optical diffuser plate includes the following steps:

[0064] Preparation of copolymer microspheres: 50 parts maleic anhydride, 45 parts styrene, and 5 parts azobisisobutyronitrile were dissolved in 250 parts isoamyl acetate, respectively. After purging with nitrogen for 40 min, the mixture was heated in a water bath at 70 °C for 6 h. The resulting suspension was centrifuged, the supernatant was removed, the solid was dispersed in n-hexane and washed, the filter residue was collected, and the residue was dried to obtain copolymer microspheres. The centrifugation rate was 4000 r / min, the centrifugation time was 30 min, the drying temperature was 110 °C, and the drying time was 8 h.

[0065] Mixture a was prepared by uniformly mixing 3 parts copolymer microspheres with 69 parts PP resin, 20 parts PP-g-MAH resin, 5 parts flame retardant, 0.7 parts antioxidant, 0.16 parts mineral oil, 1.2 parts light stabilizer, 0.9 parts UV absorber and 0.04 parts whitening agent.

[0066] Mixture b is prepared by uniformly mixing 83 parts GPPS resin, 13 parts foaming agent, 1.2 parts antioxidant, 0.27 parts mineral oil, 1 part light stabilizer, 1.1 parts UV absorber and 0.43 parts whitening agent.

[0067] Mixture a and mixture b are fed into a single screw extruder at a mass ratio of 2:5, heated and melted, co-extruded in three layers, and then pressed to obtain the finished product.

[0068] The temperatures of each zone of the single-screw extruder are as follows: Zone 1: 190℃, Zone 2: 200℃, Zone 3: 220℃, Zone 4: 220℃, Zone 5: 235℃, Zone 6: 225℃, Zone 7: 220℃, and the die head temperature is 215℃; the production rate is 310 kg / h.

[0069] Comparative Example 1

[0070] The difference between this comparative example and Example 2 is that the PP resin in both the upper and lower layer formulations was increased from 77 parts to 92 parts, and PP-g-MAH resin was not added. All other components and experimental steps were the same as in Example 2.

[0071] Comparative Example 2

[0072] The difference between this comparative example and Example 2 is that the PP resin in both the upper and lower layer formulations was increased from 77 parts to 79 parts, and copolymer microspheres were not added. All other components and experimental steps were the same as in Example 2.

[0073] Comparative Example 3

[0074] The difference between this comparative example and Example 2 is that 2 parts of silica were replaced with 2 parts of copolymer microspheres in both the upper and lower layer formulations, while the other components and experimental steps were the same as in Example 2.

[0075] Comparative Example 4

[0076] The difference between this comparative example and Example 2 is that the GPPS resin in the intermediate layer formulation was increased from 88 parts to 95 parts, and the foaming agent was reduced from 9 parts to 2 parts. All other components and experimental steps were the same as in Example 2.

[0077] Comparative Example 5

[0078] The difference between this comparative example and Example 2 is that in the preparation method of the PP resin foamed optical diffusion plate, mixture a and mixture b are fed into a single screw extruder and heated to melt at a mass ratio of 2:1. Other components and experimental steps are the same as in Example 2.

[0079] The diffusion plates prepared in Examples 1-3 and Comparative Examples 1-5 were tested.

[0080] Test method:

[0081] Light transmittance and haze were tested according to ASTM D1003 standard;

[0082] Center brightness and average brightness were tested according to GY / T 326-2019 standard;

[0083] Impact strength was tested according to ASTM D256 standard;

[0084] The heat distortion temperature was tested according to ASTM D648 standard;

[0085] Flame retardancy was tested according to UL94 standard;

[0086] Density was tested according to ASTM D792;

[0087] The test results are shown in Table 1.

[0088] Table 1. Performance Test Results of Diffuser Plate

[0089]

[0090] As shown in Table 1, the PP resin foamed optical diffusion plates prepared in each embodiment of this application all have a heat distortion temperature above 110℃, indicating that the diffusion plates prepared in each embodiment are not prone to softening and deformation at high temperatures and have good stability; the impact strength is greater than 85Kg / cm. 2 This indicates that the diffuser plates prepared in each embodiment have high impact resistance, good mechanical properties, and are safe and durable; their flame retardancy all reach V0 level; their light transmittance is all above 65%, their haze is all greater than 80%, their center brightness is all greater than 1800, and their average brightness is all greater than 1100, with little difference between the center brightness and the average brightness. This shows that the diffuser plates prepared in the embodiments have good optical performance, high light transmittance, and can be effectively scattered, resulting in a bright lighting effect. They can achieve uniform light distribution and effectively reduce glare while maintaining high brightness. Their density is all below 1.0 g / cm³. 3 The material is lightweight and easy to transport. The thickness ratio of the upper, middle and lower layers is within the range of 1:(7~9):1, which ensures the overall structural stability.

[0091] Further comparison and analysis of the data from Example 2 and the comparative examples revealed that in Comparative Example 1, the amount of PP resin in both the upper and lower layers increased from 77 parts to 92 parts. Furthermore, without the addition of PP-g-MAH resin, the impact strength of the diffuser plate decreased, its mechanical properties deteriorated, and its transmittance and haze were also affected, resulting in poor optical performance. This indicates that PP-g-MAH resin has a significant impact on both the mechanical and optical properties of the diffuser plate. In Comparative Example 2, the amount of PP resin in both the upper and lower layers increased from 77 parts to 79 parts. Without the addition of copolymer microspheres, the transmittance, haze, center brightness, and average brightness of the diffuser plate all decreased significantly, resulting in extremely poor optical performance. This indicates that the copolymer microspheres have a very significant impact on the optical performance of the diffuser plate. In Comparative Example 3, replacing 2 parts of copolymer microspheres with 2 parts of silica in the upper and lower layers resulted in a decrease in the density of the diffuser plate. With increased density, the diffuser plate becomes heavier, and its optical performance is significantly worse than when copolymer microspheres are used. In Comparative Example 4, the amount of GPPS resin in the intermediate layer formulation was increased from 88 parts to 95 parts, and the amount of foaming agent was reduced from 9 parts to 2 parts. The transmittance, haze, center brightness, and average brightness of the diffuser plate all decreased, but the decrease was not as significant as in Comparative Example 2. The ratio of upper / middle / lower layer thickness also decreased, and the impact strength decreased, indicating that the proportion of foaming agent in the system has a certain impact on the optical and mechanical properties of the diffuser plate. In Comparative Example 5, in the preparation method of PP resin foamed optical diffuser plate, mixing mixture a and mixture b in a mass ratio of 2:1 was added to a single screw extruder and heated to melt. This significantly changed the ratio of upper / middle / lower layer thickness of the diffuser plate, and the impact strength decreased significantly, indicating that it had a great impact on the mechanical strength and overall structural stability of the diffuser plate.

[0092] In summary, this application provides a formulation and process for successfully applying PP resin to a light diffusion plate, which has overall structural stability, excellent optical performance, and low manufacturing cost.

[0093] The above are merely embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A PP resin foamed optical diffusion plate, characterized in that, The material comprises an upper layer, a middle layer, and a lower layer, with the upper and lower layers located on either side of the middle layer. The thickness ratio of the upper, middle, and lower layers is 1:(7~9):

1. The upper and lower layers have the same composition. The upper layer comprises the following components by weight: 69~85 parts PP resin, 10~20 parts PP-g-MAH resin, 1~3 parts copolymer microspheres, 3~5 parts flame retardant, 0.3~0.7 parts antioxidant, and 0.08~0.1 parts [unclear - possibly a specific component or ingredient]. The intermediate layer comprises, by weight, 6 parts mineral oil, 0.4-1.2 parts light stabilizer, 0.2-0.9 parts ultraviolet absorber, and 0.02-0.04 parts whitening agent; the intermediate layer comprises, by weight, the following components: 83-93 parts GPPS resin, 5-13 parts foaming agent, 0.4-1.2 parts antioxidant, 0.23-0.27 parts mineral oil, 0.6-1 part light stabilizer, 0.4-1.1 parts ultraviolet absorber, and 0.37-0.43 parts whitening agent; The preparation of the copolymer microspheres includes the following steps: Dissolve 30-50 parts of maleic anhydride, 45-55 parts of styrene, and 5-15 parts of azobisisobutyronitrile in 150-250 parts of isoamyl acetate. After purging with nitrogen for 30-40 minutes, heat in a water bath at 70°C for 4-6 hours. Centrifuge the resulting suspension, remove the supernatant, disperse the solid in hexane, wash, filter, collect the filter residue, and dry the filter residue to obtain copolymer microspheres.

2. The PP resin foamed optical diffuser plate according to claim 1, characterized in that, The antioxidant is at least one of antioxidant 1024, antioxidant 1010, or antioxidant 1076.

3. The PP resin foamed optical diffusion plate according to claim 1, characterized in that, The mineral oil is either silicone oil or liquid paraffin.

4. The PP resin foamed optical diffuser plate according to claim 1, characterized in that, The light stabilizer is selected from any one or more of light stabilizer 622, light stabilizer 770, and light stabilizer 944.

5. The PP resin foamed optical diffusion plate according to claim 1, characterized in that, The ultraviolet absorber is selected from one or more of the ultraviolet absorbers UV-327, UV-329, and UV-531, in combination.

6. The PP resin foamed optical diffuser plate according to claim 1, characterized in that, The brightening agent is the fluorescent whitening agent CBS-127.

7. A method for preparing a PP resin foamed optical diffusion plate as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Prepare the copolymer microspheres; Mix 1-3 parts of the copolymer microspheres with 69-85 parts of PP resin, 10-20 parts of PP-g-MAH resin, 3-5 parts of flame retardant, 0.3-0.7 parts of antioxidant, 0.08-0.16 parts of mineral oil, 0.4-1.2 parts of light stabilizer, 0.2-0.9 parts of ultraviolet absorber, and 0.02-0.04 parts of whitening agent to obtain mixture a; Mixture b is prepared by uniformly mixing 83-93 parts of GPPS resin, 5-13 parts of foaming agent, 0.4-1.2 parts of antioxidant, 0.23-0.27 parts of mineral oil, 0.6-1 part of light stabilizer, 0.4-1.1 parts of ultraviolet absorber, and 0.37-0.43 parts of whitening agent. The mixture a and the mixture b are fed into a single screw extruder at a mass ratio of 2:(3~5), heated and melted, co-extruded in three layers, and then pressed to obtain the finished product; The temperatures of each zone of the single-screw extruder are as follows: Zone 1: 180~190℃, Zone 2: 190~200℃, Zone 3: 210~220℃, Zone 4: 210~220℃, Zone 5: 225~235℃, Zone 6: 215~225℃, Zone 7: 210~220℃, and the die head temperature is 205~215℃; the production rate is 310 kg / h.

8. The method for preparing a PP resin foamed optical diffusion plate according to claim 7, characterized in that, The centrifugation rate is 2000~4000 r / min, and the centrifugation time is 20~30 min.

9. The method for preparing a PP resin foamed optical diffuser plate according to claim 7, characterized in that, Drying temperature 90~110℃, drying time 6~8h.

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