A high-impact and aging-resistant PC sheet and its co-extrusion molding process

Abstract

This invention provides a high-impact, aging-resistant PC sheet and its co-extrusion molding process, specifically relating to the field of sheet materials. The core layer comprises aromatic polycarbonate resin, siloxane-polycarbonate copolymer, organosilicon core-shell toughening agent, composite antioxidant, composite light stabilizer, nano-inorganic particles, and processing aids. The upper and lower surface layers comprise polymethyl methacrylate (PMMA) resin, polyvinylidene fluoride (PVDF) resin, reactive compatibilizer, UV absorber, and light stabilizer. This invention employs a composite toughening system of siloxane copolymerized PC and organosilicon core-shell toughening agent, solving the problem of easy aging and degradation of traditional toughening agents, and simultaneously achieving toughening and aging resistance. Aging resistance is improved through synergistic effects; and the reactive compatibilizer undergoes in-situ chemical bonding at the interface during co-extrusion thermal processes, resulting in high interlayer bonding strength. Furthermore, the use of large amounts of inorganic fillers is avoided, ensuring the overall light transmittance of the core layer and the sheet material.

Description

Technical Field

[0001] This invention belongs to the field of sheet materials, specifically relating to a high-impact, aging-resistant PC sheet and its co-extrusion molding process. Background Technology

[0002] PC sheet, also known as polycarbonate sheet, is a plastic sheet made primarily of polycarbonate using co-extrusion technology. Due to its excellent transparency, impact resistance, and heat resistance, PC sheet is widely used in various fields. However, PC sheet has the following drawbacks with long-term use: 1. Due to its high molecular chain rigidity, its low-temperature toughness and stress cracking resistance are poor, leading to a significant decline in mechanical properties after long-term use and aging; 2. Outdoor exposure to ultraviolet radiation easily causes photo-oxidative aging, resulting in yellowing and a decrease in overall strength.

[0003] To address these shortcomings, traditional processes often employ single-formula modification, such as: improving PC performance solely by adding toughening agents and weather-resistant additives; while this increases strength, it significantly reduces the light transmittance of the sheet; or by co-extruding a functional layer onto the PC core surface, but this technique suffers from large temperature variations, resulting in insufficient bonding and delamination over long-term use; or by applying UV or nano-coatings after PC sheet molding, but the adhesion between the coating and the substrate is limited, and the coating is easily damaged; among these, CN104448756A discloses a coated PC sheet and its preparation method. The coated PC sheet prepared by this method has a low proportion of infrared additives, a simple preparation method, good thermal insulation effect, guaranteed light transmittance, and low product cost; however, it still does not improve high impact resistance and aging resistance. Summary of the Invention

[0004] The purpose of this invention is to provide a high-impact and aging-resistant PC sheet and its co-extrusion molding process, which can improve the high impact resistance and aging resistance of PC sheets, making them possess both high impact resistance and aging resistance.

[0005] This invention provides the following technical solution:

[0006] A high-impact and aging-resistant PC board comprises a core layer, and an upper surface layer and a lower surface layer covering the upper and lower sides of the core layer; the upper surface layer accounts for 5-15% of the thickness, the core layer accounts for 70-90% of the thickness, and the lower surface layer accounts for 5-15% of the thickness.

[0007] The core layer is composed of the following parts by weight:

[0008] 60-80 parts aromatic polycarbonate resin, 10-25 parts siloxane-polycarbonate copolymer, 5-15 parts organosilicon core-shell toughening agent, 0.3-1.0 parts composite antioxidant, 0.3-1.0 parts composite light stabilizer, 1-5 parts nano-inorganic particles, and 0.2-0.8 parts processing aid;

[0009] The upper and lower surface layers are composed of the following substances in parts by mass:

[0010] 60-80 parts of polymethyl methacrylate (PMMA) resin, 10-30 parts of polyvinylidene fluoride (PVDF) resin, 3-10 parts of reactive compatibilizer, 2-8 parts of ultraviolet absorber, and 0.5-2 parts of light stabilizer.

[0011] Preferably, in the core layer: the organosilicon core-shell toughening agent is Mitsubishi Chemical Metalatn S2001;

[0012] The compound antioxidant consists of 1 part by weight of hindered phenolic primary antioxidant and 2 parts by weight of phosphite secondary antioxidant;

[0013] The composite light stabilizer consists of 3 parts by mass of benzotriazole UV absorber and 1 part by mass of hindered amine HALS;

[0014] The nano-inorganic particles are nano-silica; the processing aid is pentaerythritol stearate.

[0015] Preferably, in the upper and lower surface layers: the reactive compatibilizer is an ethylene-acrylate-glycidyl methacrylate (GMA) terpolymer;

[0016] The ultraviolet absorber is a benzotriazole ultraviolet absorber;

[0017] The light stabilizer is a high molecular weight polymeric hindered amine light stabilizer with a thermal weight loss temperature ≥270℃.

[0018] A co-extrusion molding process for high-impact and aging-resistant PC sheets, the specific steps of which are as follows:

[0019] S1. Material drying: Use a dehumidifying dryer to dry the core layer material at 115-125℃ for 4-6 hours to reduce the material moisture content to less than 0.02%; dry the upper and lower surface materials at 80-90℃ for 3-4 hours.

[0020] After drying, the core material is fed into the main extruder; the upper and lower surface materials are fed into the two extruders respectively.

[0021] S2: Core layer processing: A single-screw extruder is used with a length-to-diameter ratio (L / D) ≥ 30. The barrel temperature is controlled in sections from the feeding section to the metering section. The temperature setting range is 250~280℃. The screw speed range is 40~80rpm. The melt pressure is controlled at 12~18MPa.

[0022] S3: Upper and lower surface layer processing: The upper and lower surface layers each use a single-screw extruder for simultaneous melt plasticization. Temperature setting range: 220~250℃; Screw speed range: 20~50rpm, which needs to be matched and adjusted according to the target layer thickness ratio and core layer extrusion amount.

[0023] S4: Molding: The core layer, upper and lower surface layer melts are fed into the distributor and merged; the distributor adopts a gradient temperature flow channel and has independently temperature-controlled core layer flow channel area, transition zone and surface layer flow channel area:

[0024] Among them, the core layer flow channel temperature zone is 265~280℃; the transition temperature zone between the core layer and the surface layer flow channel is 245~255℃; the surface layer flow channel temperature zone is 240~250℃; and the overall temperature control range of the die head is 260~275℃.

[0025] S5: Shaping: The three-layer composite sheet extruded from the die head enters the three-roll calender unit vertically; Roller temperature setting range: 80~130℃, gradient temperature control is adopted, and the ratio of lead-out speed to extrusion line speed is 1.00~1.05;

[0026] S6: Finished product preparation: After cooling and shaping, the continuous sheet material is trimmed at both sides by an edge trimmer, pulled at a constant speed by traction rollers, and finally cut to a fixed length to obtain the target product.

[0027] The beneficial effects of this invention are:

[0028] 1. This invention adopts a composite toughening system, which solves the problem of easy aging and degradation of traditional toughening agents, and simultaneously achieves toughening and aging resistance.

[0029] 2. This invention improves aging resistance through synergistic effect; and the reactive compatibilizer undergoes in-situ chemical bonding at the interface during co-extrusion thermal process, resulting in high interlayer bonding strength.

[0030] 3. This invention avoids the use of a large amount of inorganic fillers, thus ensuring the overall light transmittance of the core layer and the board. Detailed Implementation

[0031] Example 1:

[0032] A high-impact and aging-resistant PC board comprises a core layer, and an upper and lower surface layer covering the upper and lower sides of the core layer; it uses a 3 mm thick PC board, with the upper surface layer accounting for 15% of the thickness, the core layer accounting for 70% of the thickness, and the lower surface layer accounting for 15% of the thickness;

[0033] The core layer is composed of the following parts by weight:

[0034] The composition includes 60 parts aromatic polycarbonate resin, 10 parts siloxane-polycarbonate copolymer, 5 parts organosilicon core-shell toughening agent, 0.3 parts composite antioxidant, 0.3 parts composite light stabilizer, 1 part nano-inorganic particles, and 0.2 parts processing aid. The organosilicon core-shell toughening agent is Mitsubishi Chemical Metalatn S2001; the composite antioxidant consists of 1 part by mass of hindered phenolic primary antioxidant and 2 parts by mass of phosphite secondary antioxidant; the composite light stabilizer consists of 3 parts by mass of benzotriazole UV absorber and 1 part by mass of hindered amine HALS; the nano-inorganic particles are nano-silica; and the processing aid is pentaerythritol stearate.

[0035] The upper and lower surface layers are composed of the following components in parts by weight: 60 parts polymethyl methacrylate (PMMA) resin, 10 parts polyvinylidene fluoride (PVDF) resin, 3 parts reactive compatibilizer, 2 parts ultraviolet absorber, and 0.5 parts light stabilizer; wherein the reactive compatibilizer is an ethylene-acrylate-glycidyl methacrylate (GMA) terpolymer; the ultraviolet absorber is a benzotriazole ultraviolet absorber, preferably BASF Tinuvin 234 (UV-234); and the light stabilizer is a high molecular weight polymeric hindered amine light stabilizer (light stabilizer TH-944) with a thermogravimetric temperature ≥270℃.

[0036] A co-extrusion molding process for high-impact and aging-resistant PC sheets, the specific steps of which are as follows:

[0037] S1. Material Drying: The core layer material is dried in a dehumidifying dryer at 115℃ for 4 hours to reduce the moisture content to less than 0.02%; the upper and lower surface layer materials are dried at 80℃ for 3 hours; after drying, the core layer material is fed into the main extruder; the upper and lower surface layer materials are fed into two extruders respectively.

[0038] S2: Core layer processing: A single-screw extruder is used with a length-to-diameter ratio (L / D) ≥ 30. The barrel is temperature-controlled in sections from the feeding section to the metering section. Temperature settings: feeding section 250℃ / compression section 265℃ / metering section 275℃ / connector 275℃; screw speed range: 40 rpm; melt pressure is controlled at 12 MPa.

[0039] S3: Upper and lower surface processing: The upper and lower surface layers each use a single-screw extruder for simultaneous melt plasticization. Temperature settings: feeding section 220℃ / compression section 235℃ / metering section 245℃ / connecting body 245℃; screw speed range: 20rpm.

[0040] S4: Molding: The core layer, upper and lower surface layer melts are fed into the distributor and merged; the distributor adopts a gradient temperature flow channel and has independently temperature-controlled core layer flow channel area, transition zone and surface layer flow channel area:

[0041] The core layer flow channel temperature zone is 265℃; the transition temperature zone between the core layer and the surface layer flow channel is 245℃; the surface layer flow channel temperature zone is 240℃; and the overall die head temperature control range is 260℃. This design reduces the temperature difference between the two melts with significant temperature variations before they come into contact, effectively lowering interfacial thermal stress. The multi-layered melt, after being combined by the distributor, enters the coat hanger-type T-die head, ensuring uniform flow velocity across each layer (outlet flow velocity deviation ≤5%).

[0042] S5: Shaping: The three-layer composite sheet extruded from the die head enters the three-roll calender unit vertically; Roller temperature setting range: 80℃, with gradient temperature control, upper roll 105℃ / middle roll 115℃ / lower roll 120℃; The ratio of lead-out speed to extrusion line speed is 1.00.

[0043] S6: Finished product preparation: After cooling and shaping, the continuous sheet material is trimmed at both sides by an edge trimmer, pulled at a constant speed by traction rollers, and finally cut to a fixed length to obtain the target product.

[0044] Example 2:

[0045] A high-impact and aging-resistant PC board comprises a core layer, and an upper and lower surface layer covering the upper and lower sides of the core layer; it uses a 3 mm thick PC board, with the upper surface layer accounting for 10% of the thickness, the core layer accounting for 80% of the thickness, and the lower surface layer accounting for 10% of the thickness;

[0046] The core layer is composed of the following parts by weight:

[0047] The composition includes 70 parts aromatic polycarbonate resin, 15 parts siloxane-polycarbonate copolymer, 10 parts organosilicon core-shell toughening agent, 0.6 parts composite antioxidant, 0.6 parts composite light stabilizer, 3 parts nano-inorganic particles, and 0.5 parts processing aid. The organosilicon core-shell toughening agent is Mitsubishi Chemical Metalatn S2001; the composite antioxidant consists of 1 part by mass of hindered phenolic primary antioxidant and 2 parts by mass of phosphite secondary antioxidant; the composite light stabilizer consists of 3 parts by mass of benzotriazole UV absorber and 1 part by mass of hindered amine HALS; the nano-inorganic particles are nano-silica; and the processing aid is pentaerythritol stearate.

[0048] The upper and lower surface layers are composed of the following substances in parts by mass:

[0049] The mixture comprises 70 parts of polymethyl methacrylate (PMMA) resin, 20 parts of polyvinylidene fluoride (PVDF) resin, 6 parts of reactive compatibilizer, 5 parts of ultraviolet absorber, and 1 part of light stabilizer. The reactive compatibilizer is an ethylene-acrylate-glycidyl methacrylate (GMA) terpolymer; the ultraviolet absorber is a benzotriazole ultraviolet absorber, preferably BASF Tinuvin 234 (UV-234); and the light stabilizer is a high molecular weight polymeric hindered amine light stabilizer (light stabilizer TH-944) with a thermal weight loss temperature ≥270℃.

[0050] A co-extrusion molding process for high-impact and aging-resistant PC sheets, the specific steps of which are as follows:

[0051] S1. Material Drying: The core layer material is dried in a dehumidifying dryer at 120°C for 5 hours to reduce the moisture content to less than 0.02%; the upper and lower surface layer materials are dried at 85°C for 3.5 hours; after drying, the core layer material is fed into the main extruder; the upper and lower surface layer materials are fed into the two extruders respectively.

[0052] S2: Core layer processing: A single-screw extruder is used with a length-to-diameter ratio (L / D) ≥ 30. The barrel is temperature-controlled in sections from the feeding section to the metering section. Temperature settings: feeding section 250℃ / compression section 265℃ / metering section 275℃ / connector 275℃; screw speed range: 60 rpm; melt pressure is controlled at 15 MPa.

[0053] S3: Upper and lower surface processing: The upper and lower surface layers each use a single-screw extruder for simultaneous melting and plasticizing. Temperature settings: feeding section 220℃ / compression section 235℃ / metering section 245℃ / connector 245℃; screw speed range: 35rpm, which needs to be matched and adjusted according to the target layer thickness ratio and core layer extrusion amount.

[0054] S4: Molding: The core layer, upper and lower surface layers of melt are fed into a distributor and combined. The distributor uses a gradient temperature flow channel and has independently temperature-controlled core layer flow channel, transition zone, and surface layer flow channel: the core layer flow channel temperature zone is 273℃; the transition temperature zone between the core layer and surface layer flow channels is 250℃; the surface layer flow channel temperature zone is 245℃; the overall die head temperature control range is 273℃. This reduces the temperature difference between the two melts with large temperature differences before they come into contact, effectively reducing interfacial thermal stress. The multi-layered melt, after being combined by the distributor, enters a coat hanger-type T-die head, ensuring uniform flow velocity in each layer (outlet flow velocity deviation ≤5%).

[0055] S5: Shaping: The three-layer composite sheet extruded from the die head enters the three-roll calender unit vertically; Roller temperature setting range: 105℃, with gradient temperature control: upper roll 105℃ / middle roll 115℃ / lower roll 120℃; The ratio of lead-out speed to extrusion line speed is 1.02.

[0056] S6: Finished product preparation: After cooling and shaping, the continuous sheet material is trimmed at both sides by an edge trimmer, pulled at a constant speed by traction rollers, and finally cut to a fixed length to obtain the target product.

[0057] Example 3:

[0058] A high-impact and aging-resistant PC board comprises a core layer, and an upper and lower surface layer covering the upper and lower sides of the core layer; it uses a 3 mm thick PC board, with the upper surface layer accounting for 5% of the thickness, the core layer accounting for 90% of the thickness, and the lower surface layer accounting for 5% of the thickness;

[0059] The core layer is composed of the following components by weight: 80 parts aromatic polycarbonate resin, 25 parts siloxane-polycarbonate copolymer, 15 parts organosilicon core-shell toughening agent, 1.0 part composite antioxidant, 1.0 part composite light stabilizer, 5 parts nano-inorganic particles, and 0.8 parts processing aid. Specifically, the organosilicon core-shell toughening agent is Mitsubishi Chemical Metalatn S2001; the composite antioxidant consists of 1 part by weight of hindered phenolic primary antioxidant and 2 parts by weight of phosphite secondary antioxidant; the composite light stabilizer consists of 3 parts by weight of benzotriazole UV absorber and 1 part by weight of hindered amine HALS; the nano-inorganic particles are nano-silica; and the processing aid is pentaerythritol stearate.

[0060] The upper and lower surface layers are composed of the following components in parts by weight: 80 parts polymethyl methacrylate (PMMA) resin, 30 parts polyvinylidene fluoride (PVDF) resin, 10 parts reactive compatibilizer, 8 parts ultraviolet absorber, and 2 parts light stabilizer; wherein the reactive compatibilizer is an ethylene-acrylate-glycidyl methacrylate (GMA) terpolymer; wherein the ultraviolet absorber is a benzotriazole ultraviolet absorber, preferably BASF Tinuvin 234 (UV-234); and the light stabilizer is a high molecular weight polymeric hindered amine light stabilizer (light stabilizer TH-944) with a thermogravimetric temperature ≥270℃.

[0061] A co-extrusion molding process for high-impact and aging-resistant PC sheets, the specific steps of which are as follows:

[0062] S1. Material Drying: The core layer material is dried in a dehumidifying dryer at 125°C for 6 hours to reduce the moisture content to less than 0.02%; the upper and lower surface layer materials are dried at 90°C for 4 hours; after drying, the core layer material is fed into the main extruder; the upper and lower surface layer materials are fed into the two extruders respectively.

[0063] S2: Core layer processing: A single-screw extruder is used with a length-to-diameter ratio (L / D) ≥ 30. The barrel is temperature-controlled in sections from the feeding section to the metering section. Temperature settings: feeding section 250℃ / compression section 265℃ / metering section 275℃ / connector 275℃; screw speed range: 80 rpm; melt pressure is controlled at 18 MPa.

[0064] S3: Upper and lower surface processing: The upper and lower surface layers each use a single-screw extruder for simultaneous melting and plasticizing. Temperature settings: feeding section 220℃ / compression section 235℃ / metering section 245℃ / connector 245℃; screw speed range: 50rpm, which needs to be matched and adjusted according to the target layer thickness ratio and core layer extrusion amount.

[0065] S4: Molding: The core layer, upper and lower surface layers of melt are fed into a distributor and combined. The distributor uses a gradient temperature flow channel and has independently temperature-controlled core layer flow channel, transition zone, and surface layer flow channel: Core layer flow channel temperature zone: 280℃; transition zone between core and surface layer flow channels: 255℃; surface flow channel temperature zone: 250℃; overall die head temperature control range: 275℃. This reduces the temperature difference between the two melts with large temperature differences before they come into contact, effectively reducing interfacial thermal stress. The multi-layered melt, after being combined by the distributor, enters a coat hanger-type T-die head, ensuring uniform flow rate for each layer (outlet flow rate deviation ≤5%).

[0066] S5: Shaping: The three-layer composite sheet extruded from the die head enters the three-roll calender unit vertically; Roller temperature setting range: 130℃, with gradient temperature control, upper roll 105℃ / middle roll 115℃ / lower roll 120℃; The ratio of lead-out speed to extrusion line speed is 1.05.

[0067] S6: Finished product preparation: After cooling and shaping, the continuous sheet material is trimmed at both sides by an edge trimmer, pulled at a constant speed by traction rollers, and finally cut to a fixed length to obtain the target product.

[0068] Experimental test:

[0069] The 3mm PC boards produced in Examples 1-3 were used as experimental groups 1-3 for testing, and commercially available 3mm PC boards were randomly purchased as comparative examples. The experimental tests were conducted as follows:

[0070] 1. Room temperature impact strength (23℃), the test standard is ASTM D256, adopts the plastic cantilever beam (Izod) impact test standard, method A (notched specimen), pendulum energy 2.75~5.5J, specimen size 63.5×12.7×3.2mm, notch depth 2.54mm;

[0071] 2. Low-temperature impact strength (−30℃), the test standard is ASTM D256, using the plastic cantilever beam (Izod) impact test standard, method A (notched specimen), pendulum energy 2.75~5.5J, specimen size 63.5×12.7×3.2mm, notch depth 2.54mm, the specimen is subjected to impact immediately after being conditioned in an environment of −30℃±2℃ for at least 4 hours;

[0072] 3. Light transmittance test, the test standard is ASTM D1003, standard test method for light transmittance and haze of transparent plastic, using an integrating sphere haze meter, wavelength 550nm, 3mm plate thickness;

[0073] 4. Interlayer peel strength test, the test standard is ASTM D903, the standard test method for peel strength of adhesive joints, T-type peel, peel speed 100mm / min, sample width 25mm;

[0074] 5. Aging yellowing index ΔYI test: First, accelerated aging under a xenon lamp. The test standard is ISO4892-2, Plastics Laboratory Light Source Exposure Method, Part 2 Xenon Arc Lamp, Cycle 1 (dry state), Irradiance 0.51W / (m²·nm)@340nm, black panel temperature 65℃±3℃, chamber temperature 38℃±3℃, relative humidity 50%±10%.

[0075] Then, the yellowing index ΔYI test was performed, and the test standard was ASTM E313. The CIE tristimulus value was measured by a spectrophotometer and then calculated as follows: YI = [100 × (1.2769X − 1.0592Z)] / Y, ΔYI = YI (after aging) − YI (before aging).

[0076] 6. Impact retention test after aging: After aging for the specified time according to ISO 4892-2 conditions, samples are taken and the impact strength is determined according to ASTM D256 test standard. The result is (impact strength after aging / impact strength before aging) × 100%.

[0077] The specific mean experimental data are shown in the table below:

[0078] Impact strength at room temperature (23℃) 62kJ / m² 88kJ / m² 95kJ / m² 90kJ / m² Low-temperature impact strength (−30℃) 10kJ / m² 50kJ / m² 56kJ / m² 49kJ / m² Light transmittance 87% 84.5% 86.3% 85.1% interlayer peel strength <5N / cm 13.5 N / cm 15.8 N / cm 14.9 N / cm ΔYI after aging for 4000 hours 5 2.5 2.0 2.3 Impact retention rate after 4000 hours of aging 40% 85% 88% 83%

[0079] The PC board of the present invention only has a slightly lower light transmittance. In other aspects, the performance standards of the present invention are significantly improved compared with the traditional PC board. It can be seen that the present invention cannot achieve the comprehensive performance of room temperature impact, low temperature toughness, interlayer bonding and aging resistance.

[0080] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-impact, aging-resistant PC board, comprising a core layer, and an upper and lower surface layer covering the upper and lower sides of the core layer; characterized in that: The thickness of the upper surface layer accounts for 5-15%, the thickness of the core layer accounts for 70-90%, and the thickness of the lower surface layer accounts for 5-15%. The core layer is composed of the following components by mass: 60-80 parts aromatic polycarbonate resin, 10-25 parts siloxane-polycarbonate copolymer, 5-15 parts organosilicon core-shell toughening agent, 0.3-1.0 parts composite antioxidant, 0.3-1.0 parts composite light stabilizer, 1-5 parts nano-inorganic particles, and 0.2-0.8 parts processing aid; The upper and lower surface layers are composed of the following substances in parts by mass: 60-80 parts of polymethyl methacrylate (PMMA) resin, 10-30 parts of polyvinylidene fluoride (PVDF) resin, 3-10 parts of reactive compatibilizer, 2-8 parts of ultraviolet absorber, and 0.5-2 parts of light stabilizer.

2. A high impact and weather resistant PC sheet and its co-extrusion process as claimed in claim 1 wherein: In the core layer: the organosilicon core-shell toughening agent is Mitsubishi Chemical Metalatn S2001; the composite antioxidant consists of 1 part by mass of hindered phenolic primary antioxidant and 2 parts by mass of phosphite secondary antioxidant; the composite light stabilizer consists of 3 parts by mass of benzotriazole UV absorber and 1 part by mass of hindered amine HALS; the nano-inorganic particles are nano-silica; and the processing aid is pentaerythritol stearate.

3. A high impact and weather resistant PC sheet and its co-extrusion process as claimed in claim 1 wherein: In the upper and lower layers: the reactive compatibilizer is an ethylene-acrylate-glycidyl methacrylate (GMA) terpolymer; the ultraviolet absorber is a benzotriazole ultraviolet absorber; and the light stabilizer is a high molecular weight polymeric hindered amine light stabilizer with a thermal weight loss temperature ≥270℃.

4. A high impact and weather resistant PC sheet as claimed in claim 1, wherein the co-extrusion process is characterized by: The specific steps are as follows: S1. Material drying: Use a dehumidifying dryer to dry the core layer material at 115-125℃ for 4-6 hours to make the material moisture content less than 0.02%; dry the upper and lower surface materials at 80-90℃ for 3-4 hours. After drying, the core layer material is fed into the main extruder; the upper and lower surface layer materials are fed into the two extruders respectively. S2. Core layer processing: A single-screw extruder is used with a length-to-diameter ratio (L / D) ≥ 30. The barrel temperature is controlled in sections from the feeding section to the metering section. The temperature setting range is 250~280℃. The screw speed range is 40~80rpm. The melt pressure is controlled at 12~18MPa. S3. Upper and lower surface layer processing: The upper and lower surface layers each use a single-screw extruder for simultaneous melt plasticization. Temperature setting range: 220~250℃; Screw speed range: 20~50rpm, which needs to be matched and adjusted according to the target layer thickness ratio and core layer extrusion amount. S4: Molding: The core layer, upper and lower surface layer melts are fed into the distributor and merged; the distributor adopts a gradient temperature flow channel and has independently temperature-controlled core layer flow channel area, transition zone and surface layer flow channel area: Among them, the core layer flow channel temperature zone is 265~280℃; the transition temperature zone between the core layer and the surface layer flow channel is 245~255℃; the surface layer flow channel temperature zone is 240~250℃; and the overall temperature control range of the die head is 260~275℃. S5. Shaping: The three-layer composite sheet extruded from the die head enters the three-roll calender unit; the roller temperature setting range is 80~130℃, with gradient temperature control, and the ratio of the lead-out speed to the extrusion line speed is 1.00~1.05; S6. Finished product preparation: After cooling and shaping, the continuous sheet material is trimmed at both sides by an edge trimmer, pulled at a constant speed by traction rollers, and finally cut to a fixed length to obtain the target product.

5. The co-extrusion molding process for high-impact and aging-resistant PC sheets according to claim 4, characterized in that: In step S1, the core layer material is dried in a dehumidifying dryer at 120°C for 5 hours to reduce the material moisture content to less than 0.02%; the upper and lower surface layer materials are dried at 85°C for 3.5 hours; after drying, the core layer material is fed into the main extruder; the upper and lower surface layer materials are fed into two extruders respectively.

6. A high impact and weather resistant PC sheet co-extrusion process as claimed in claim 4 wherein: In step S2, a single-screw extruder with a length-to-diameter ratio (L / D) ≥ 30 is used. The barrel temperature is controlled in sections from the feeding section to the metering section. The temperature settings are: feeding section 250℃ / compression section 265℃ / metering section 275℃ / connecting body 275℃; screw speed range: 60 rpm; melt pressure is controlled at 15 MPa.

7. A co-extrusion process for high impact and weatherable PC sheet as claimed in claim 4 wherein: In step S3, a single-screw extruder is used for both the upper and lower surface layers to simultaneously melt and plasticize. The temperature settings are: feeding section 220℃ / compression section 235℃ / metering section 245℃ / connector 245℃; the screw speed range is 35 rpm, which needs to be matched and adjusted according to the target layer thickness ratio and the core layer extrusion amount.

8. A co-extrusion process for high impact and weatherable PC sheet as claimed in claim 4 wherein: In step S4, the three melt streams—core layer, upper layer, and lower surface layer—are fed into a distributor to converge. The distributor employs a gradient temperature flow channel and has independently temperature-controlled core layer flow channel, transition zone, and surface layer flow channel: the core layer flow channel temperature zone is 273℃; the transition temperature zone between the core layer and surface layer flow channels is 250℃; and the surface layer flow channel temperature zone is 245℃.

9. A co-extrusion process for high impact and weatherable PC sheet as claimed in claim 4 wherein: In step S5, the three-layer composite sheet extruded from the die head enters the three-roll calender unit; the roller temperature setting range is 105℃, and gradient temperature control is adopted: upper roller 105℃ / middle roller 115℃ / lower roller 120℃; the ratio of the extraction speed to the extrusion line speed is 1.02.