Environmentally friendly PC / PMMA composite sheet and preparation method thereof

Abstract

The present application discloses an environmentally friendly PC / PMMA composite sheet and a preparation method thereof, and relates to the field of composite materials. The environmentally friendly PC / PMMA composite sheet comprises an environmentally friendly PC layer and a PMMA layer composited up and down, wherein the PMMA layer is made of PMMA resin, and the raw materials for preparing the environmentally friendly PC layer include 100 parts by weight of PC resin doped with post-consumer recycled materials, 10-15 parts by weight of toughening agent, 0.8-1.2 parts by weight of antioxidant, and 3-5 parts by weight of anti-ultraviolet agent; the toughening agent includes an organic toughening agent and an inorganic toughening agent, and the weight ratio of the organic toughening agent to the inorganic toughening agent is (8-9): (1-2). The present application can effectively improve the utilization rate of post-consumer recycled PC resin, while ensuring that the mechanical properties of the environmentally friendly PC / PMMA composite sheet meet the needs of downstream manufacturers, and can also reduce production costs.

Description

Technical Field

[0001] The present application relates to the field of composite materials, and in particular to an environmentally friendly PC / PMMA composite sheet and a preparation method thereof. Background Art

[0002] PC / PMMA composite sheet is obtained by co-extrusion of PC and PMMA. PMMA is polymethyl methacrylate, which has good hardness and transmittance, and PC is polycarbonate, which has good toughness. Among them, PC / PMMA composite sheet includes upper and lower composite PC layer and PMMA layer, which has the advantages of both PC and PMMA, can meet the requirements of rigidity and decoration, and can meet the requirements of wireless charging without shielding, and has lower cost than 3D glass and ceramics, and meets the radio frequency requirements of 5G communication for signals, so it is widely used in mobile phone back covers.

[0003] As environmental protection requirements have become increasingly stringent in recent years, mobile phone manufacturers have become increasingly strict with cost control. Using PCR (post-consumer recycled) PC resin doped with post-consumer recycled materials (i.e. environmentally friendly PC) to replace part of the PC resin to prepare the PC layer can not only reduce costs but also comply with environmental protection concepts. Therefore, it is imperative to develop an environmentally friendly PC / PMMA composite sheet.

[0004] However, the mechanical properties of PC resin doped with post-consumer recycled materials are inferior to those of undoped PC resin. The mechanical properties of environmentally friendly PC / PMMA composite sheets are also lower than those of PC / PMMA composite sheets, making it difficult to meet the needs of downstream manufacturers. Summary of the invention

[0005] In order to improve the problem in the related art that the environmentally friendly PC / PMMA composite sheet has poor mechanical properties and is difficult to meet the needs of downstream manufacturers, the present application provides an environmentally friendly PC / PMMA composite sheet and a preparation method thereof to solve the problem of low mechanical properties of the environmentally friendly PC / PMMA composite sheet.

[0006] In the first aspect, the present application provides an environmentally friendly PC / PMMA composite sheet adopts the following technical solution: an environmentally friendly PC / PMMA composite sheet, comprising an environmentally friendly PC layer and a PMMA layer composited upper and lower, wherein the PMMA layer is made of PMMA resin, and the raw materials for preparing the environmentally friendly PC layer include 100 parts by weight of PC resin doped with post-consumer recycled materials, 10-15 parts by weight of toughening agent, 0.8-1.2 parts by weight of antioxidant and 3-5 parts by weight of anti-ultraviolet agent; in the PC resin doped with post-consumer recycled materials, the proportion of post-consumer recycled materials is 18-25%, the toughening agent includes an organic toughening agent and an inorganic toughening agent, and the weight ratio of the organic toughening agent to the inorganic toughening agent is (8-9): (1-2).

[0007] In the present application, before preparing the environmentally friendly PC / PMMA composite sheet, the PC resin doped with post-consumer recycled materials is first modified by using a composite toughening agent composed of an organic toughening agent and an inorganic toughening agent, so as to improve the toughness of the PC resin doped with post-consumer recycled materials and improve the strength performance, thereby improving some defects in the mechanical properties of the PC resin doped with post-consumer recycled materials, so that the mechanical properties of the environmentally friendly PC / PMMA composite sheet can meet the needs of downstream manufacturers. In addition, the addition of an antioxidant can reduce the thermal degradation of the raw materials during the processing process, which is also conducive to the improvement of the mechanical properties of the environmentally friendly PC / PMMA composite sheet.

[0008] In some specific embodiments, the organic toughening agent is at least one of methyl methacrylate-butadiene-styrene copolymer, ethylene-acrylate copolymer, polybutyl acrylate / polymethyl methacrylate, ethylene-butyl acrylate-glycidyl acrylate copolymer, and polydimethylsiloxane-polybutyl methacrylate diblock copolymer.

[0009] Methyl methacrylate-butadiene-styrene copolymer, ethylene-acrylate copolymer, polybutyl acrylate / polymethyl methacrylate, ethylene-butyl acrylate-glycidyl acrylate copolymer, polydimethylsiloxane-polybutyl methacrylate diblock copolymer, etc. all have the characteristics of good toughness. Adding them to PC resin doped with post-consumer recycled materials can improve the toughness of PC resin doped with post-consumer recycled materials, improve the brittleness and difficult molding of PMMA resin, and obtain environmentally friendly PC / PMMA composite sheets with good toughness and good molding performance.

[0010] In some specific embodiments, the organic toughening agent is a composition of ethylene-butyl acrylate-glycidyl acrylate copolymer and polydimethylsiloxane-polybutyl methacrylate diblock copolymer, and the weight ratio of the ethylene-butyl acrylate-glycidyl acrylate and polydimethylsiloxane-polybutyl methacrylate diblock copolymer is (3-4):1.

[0011] In the present application, the organic toughening agent is further preferably a composition having a weight ratio of (3-4):1 of ethylene-butyl acrylate-glycidyl acrylate and polydimethylsiloxane-polybutyl methacrylate diblock copolymer, wherein the combination of ethylene-butyl acrylate-glycidyl acrylate and polydimethylsiloxane-polybutyl methacrylate diblock copolymer can further improve the dispersibility of the inorganic toughening agent in the PC resin doped with post-consumer recycled materials on the basis of improving the toughness performance of the environmentally friendly PC / PMMA composite sheet, which is beneficial to improving the thickness uniformity of the environmentally friendly PC / PMMA composite sheet.

[0012] In some specific embodiments, in the ethylene-butyl acrylate-glycidyl acrylate, the mass fraction of butyl acrylate is 23-28%, and the mass fraction of glycidyl acrylate is 6-9%.

[0013] In the present application, ethylene-butyl acrylate glycidyl acrylate is preferably ethylene-butyl acrylate glycidyl acrylate having a mass fraction of butyl acrylate in the range of 23-28% and a mass fraction of glycidyl acrylate in the range of 6-9%, which is beneficial to further improve the mechanical properties of the environmentally friendly PC / PMMA composite sheet.

[0014] In some specific embodiments, the molecular weight of the polydimethylsiloxane-poly(n-butyl methacrylate) diblock copolymer is 30,000-35,000, and the mass percentage of the polydimethylsiloxane is 20-25%.

[0015] In the present application, the polydimethylsiloxane-polybutyl methacrylate diblock copolymer preferably has a molecular weight of 30,000-35,000 and a mass percentage of polydimethylsiloxane of 20-25%, which is conducive to the uniform dispersion of the polydimethylsiloxane-polybutyl methacrylate diblock copolymer in the PC resin doped with post-consumer recycled materials, and can further improve the mechanical properties of the environmentally friendly PC / PMMA composite sheet.

[0016] In some specific embodiments, the inorganic toughening agent is at least one of aminosilane coupling agent modified silica whiskers, aminosilane coupling agent modified nano calcium carbonate, and aminosilane coupling agent modified nano alumina.

[0017] In some specific embodiments, the antioxidant includes a primary antioxidant and a secondary antioxidant, and the weight ratio of the primary antioxidant to the secondary antioxidant is (1.5-2):1; wherein the primary antioxidant is at least one of antioxidant 1010 or antioxidant 1076, and the secondary antioxidant is at least one of antioxidant 168 and antioxidant DLTDP.

[0018] In the present application, the antioxidant adopts a composition of a main antioxidant and an auxiliary antioxidant in a specific ratio. Through the combination of the main antioxidant and the auxiliary antioxidant, thermal degradation of the raw materials during processing is prevented, which is beneficial to further improve the mechanical properties of the environmentally friendly PC / PMMA composite sheet.

[0019] In some specific embodiments, the anti-ultraviolet agent is at least one of the anti-ultraviolet agent UV-P, the anti-ultraviolet agent BHT, and the anti-ultraviolet agent TBHQ.

[0020] Anti-ultraviolet agent UV-P, anti-ultraviolet agent BHT, and anti-ultraviolet agent TBHQ can absorb ultraviolet rays and delay the ultraviolet aging and degradation of environmentally friendly PC / PMMA composite sheets.

[0021] In some specific embodiments, the thickness ratio of the environmentally friendly PC layer to the PMMA layer is (15-20):1.

[0022] In the second aspect, the present application provides a method for preparing an environmentally friendly PC / PMMA composite sheet using the following technical solution:

[0023] A method for preparing an environmentally friendly PC / PMMA composite sheet comprises the following steps:

[0024] After drying the raw materials for preparing the environmentally friendly PC layer, extrusion granulation is performed at a temperature of 270-280°C to obtain environmentally friendly PC masterbatch;

[0025] After melting PMMA resin at 250-260°C to obtain PMMA melt and melting environmentally friendly PC masterbatch at 270-280°C to obtain environmentally friendly PC melt, the PMMA melt and the environmentally friendly PC melt are distributed to a die head for double-layer composite co-extrusion, followed by plasticization, calendering, traction cooling and shaping to obtain an environmentally friendly PC / PMMA composite sheet.

[0026] In the present application, the raw materials of the environmentally friendly PC layer are first dried and melt-extruded to prepare an environmentally friendly PC masterbatch, and then the environmentally friendly PC masterbatch and PMMA resin are melted and co-extruded to prepare an environmentally friendly PC / PMMA composite sheet. This can effectively improve the utilization rate of post-consumer recycled PC resin, while ensuring that the mechanical properties of the environmentally friendly PC / PMMA composite sheet meet the needs of downstream manufacturers, and can also reduce production costs.

[0027] In summary, this application at least includes the following beneficial technical effects:

[0028] (1) In the present application, before preparing the environmentally friendly PC / PMMA composite sheet, a composite toughening agent composed of an organic toughening agent and an inorganic toughening agent is first used to modify the PC resin doped with post-consumer recycled materials, thereby improving the toughness of the PC resin doped with post-consumer recycled materials and improving the strength performance, thereby improving some defects in the mechanical properties of the PC resin doped with post-consumer recycled materials, so that the mechanical properties of the environmentally friendly PC / PMMA composite sheet can meet the needs of downstream manufacturers. In addition, the addition of an antioxidant can reduce the thermal degradation of the raw materials during the processing process, which is also conducive to improving the mechanical properties of the environmentally friendly PC / PMMA composite sheet.

[0029] (2) In the present application, the organic toughening agent is further preferably a composition of ethylene-butyl acrylate-glycidyl acrylate and polydimethylsiloxane-polybutyl methacrylate diblock copolymer in a weight ratio of (3-4):1, wherein the combination of ethylene-butyl acrylate-glycidyl acrylate and polydimethylsiloxane-polybutyl methacrylate diblock copolymer can further improve the dispersibility of the inorganic toughening agent in the PC resin doped with post-consumer recycled materials on the basis of improving the toughness performance of the environmentally friendly PC / PMMA composite sheet, which is beneficial to improving the thickness uniformity of the environmentally friendly PC / PMMA composite sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic structural diagram of an environmentally friendly PC / PMMA composite sheet according to an embodiment of the present application.

[0031] Description of reference numerals:

[0032] 1. PMMA layer; 2. Environmentally friendly PC layer. DETAILED DESCRIPTION

[0033] The present application is further described below in conjunction with specific experiments.

[0034] Example

[0035] [Example 1]

[0036] An environmentally friendly PC / PMMA composite sheet, referring to Figure 1 , including an environmentally friendly PC layer 2 and a PMMA layer 1 connected in a composite manner, the thickness of the environmentally friendly PC layer 2 is 600μm, and the thickness of the PMMA layer 1 is 40μm. Among them, the PMMA layer 1 is made of PMMA resin (Rohm Chemical 8N), and the raw materials for preparing the environmentally friendly PC layer 2 include 100kg of PC resin doped with post-consumer recycled materials (LG Chemical's LUPOYER1000A, with a recycled PC material ratio of 20%), 10kg of toughening agent, 0.8kg of antioxidant and 3kg of anti-ultraviolet agent.

[0037] The toughening agent includes 8 kg of organic toughening agent and 2 kg of inorganic toughening agent. The organic toughening agent is specifically methyl methacrylate-butadiene-styrene copolymer (Japan's Kaneka M-732). The inorganic toughening agent is specifically aminosilane coupling agent modified silica whisker. The preparation method of aminosilane coupling agent modified silica whisker is as follows:

[0038] Aminosilane coupling agent KH550 and silica whiskers were added to an ethanol solution, and then the temperature was raised to 30° C. and stirred for reaction for 3 hours, followed by centrifugal separation, washing, and drying to obtain aminosilane coupling agent-modified silica whiskers.

[0039] The antioxidant is specifically antioxidant 1010, and the anti-ultraviolet agent is specifically anti-ultraviolet agent UV-P.

[0040] In this embodiment, the preparation method of the environmentally friendly PC / PMMA composite sheet comprises the following steps:

[0041] After drying the raw materials for preparing the environmentally friendly PC layer 2, the raw materials are extruded and granulated at a temperature of 270° C. to obtain environmentally friendly PC masterbatch;

[0042] After the PMMA resin is melted at 250°C to obtain a PMMA melt and the environmentally friendly PC masterbatch is melted at 270°C to obtain an environmentally friendly PC melt, the PMMA melt and the environmentally friendly PC melt are distributed to a die head for double-layer composite co-extrusion, followed by plasticization, calendering, and traction cooling to obtain an environmentally friendly PC / PMMA composite sheet.

[0043] [Example 2]

[0044] An environmentally friendly PC / PMMA composite sheet, referring to Figure 1 , including an environmentally friendly PC layer 2 and a PMMA layer 1 connected in a composite manner, the thickness of the environmentally friendly PC layer 2 is 600μm, and the thickness of the PMMA layer 1 is 40μm. Among them, the PMMA layer 1 is made of PMMA resin (Rohm Chemical 8N), and the raw materials for preparing the environmentally friendly PC layer 2 include 100kg of PC resin doped with post-consumer recycled materials (LG Chemical's LUPOY ER1000A, with a recycled PC material ratio of 20%), 15kg of toughening agent, 1.2kg of antioxidant and 5kg of anti-ultraviolet agent.

[0045] The toughening agent includes 13.5 kg of an organic toughening agent and 1.5 kg of an inorganic toughening agent. The organic toughening agent specifically uses methyl methacrylate-butadiene-styrene copolymer (Japan's Kaneka M-732), and the inorganic toughening agent specifically uses aminosilane coupling agent-modified silica whiskers. The preparation method of aminosilane coupling agent-modified silica whiskers is as follows:

[0046] Aminosilane coupling agent KH550 and silica whiskers were added to an ethanol solution, and then the temperature was raised to 40° C. and stirred for reaction for 2 hours, followed by centrifugal separation, washing, and drying to obtain aminosilane coupling agent-modified silica whiskers.

[0047] The antioxidant is specifically antioxidant 1070, and the anti-ultraviolet agent is specifically anti-ultraviolet agent UV-P.

[0048] In this embodiment, the preparation method of the environmentally friendly PC / PMMA composite sheet comprises the following steps:

[0049] After drying the raw materials for preparing the environmentally friendly PC layer 2, the raw materials are extruded and granulated at a temperature of 280° C. to obtain environmentally friendly PC masterbatch;

[0050] After the PMMA resin is melted at 260°C to obtain a PMMA melt and the environmentally friendly PC masterbatch is melted at 280°C to obtain an environmentally friendly PC melt, the PMMA melt and the environmentally friendly PC melt are distributed to a die head for double-layer composite co-extrusion, followed by plasticization, calendering, and traction cooling to obtain an environmentally friendly PC / PMMA composite sheet.

[0051] [Example 3]

[0052] An environmentally friendly PC / PMMA composite sheet, which differs from [Example 1] in that the organic toughening agent is different.

[0053] In this embodiment, the organic toughening agent is ethylene-butyl acrylate-glycidyl acrylate (Arkema, AX8700). In the ethylene-butyl acrylate-glycidyl acrylate, the mass fraction of butyl acrylate is 23-28%, and the mass fraction of glycidyl acrylate is 6-9%.

[0054] [Example 4]

[0055] An environmentally friendly PC / PMMA composite sheet, which differs from [Example 1] in that the organic toughening agent is different.

[0056] In this embodiment, the organic toughening agent is a polydimethylsiloxane-polybutyl methacrylate diblock copolymer, the molecular weight of the polydimethylsiloxane-polybutyl methacrylate diblock copolymer is about 32,000, and the mass percentage of polydimethylsiloxane is 22%.

[0057] [Example 5]

[0058] An environmentally friendly PC / PMMA composite sheet, which differs from [Example 1] in that the organic toughening agent is different.

[0059] In this embodiment, the organic toughening agent includes ethylene-butyl acrylate-glycidyl acrylate (Arkema, AX8700) and polydimethylsiloxane-polybutyl methacrylate diblock copolymer (the same as the polydimethylsiloxane-polybutyl methacrylate diblock copolymer in Example 4), and the weight ratio of ethylene-butyl acrylate-glycidyl acrylate (Arkema, AX8700) to polydimethylsiloxane-polybutyl methacrylate diblock copolymer is 1:1.

[0060] [Example 6]

[0061] An environmentally friendly PC / PMMA composite sheet, which differs from [Example 1] in that the organic toughening agent is different.

[0062] In this embodiment, the organic toughening agent includes ethylene-butyl acrylate-glycidyl acrylate (Arkema, AX8700) and polydimethylsiloxane-polybutyl methacrylate diblock copolymer (the same as the polydimethylsiloxane-polybutyl methacrylate diblock copolymer in Example 4), and the weight ratio of ethylene-butyl acrylate-glycidyl acrylate (Arkema, AX8700) to polydimethylsiloxane-polybutyl methacrylate diblock copolymer is 3:1.

[0063] Comparative Example

[0064] [Comparative Example 1]

[0065] An environmentally friendly PC / PMMA composite sheet, which differs from [Example 1] in that the organic toughening agent of the present application is replaced by an equal amount of aminosilane coupling agent-modified silica whiskers.

[0066] [Comparative Example 2]

[0067] An environmentally friendly PC / PMMA composite sheet, which differs from [Example 1] in that the inorganic toughening agent of the present application is replaced by an equal amount of methyl methacrylate-butadiene-styrene copolymer.

[0068] [Comparative Example 3]

[0069] An environmentally friendly PC / PMMA composite sheet, which differs from [Example 1] in that: in the present application, the organic toughening agent and the inorganic toughening agent are both 5 kg.

[0070] Performance test data

[0071] 1. Light transmittance: The light transmittance (%) of the PMMA films in the examples and comparative examples was measured according to GB / T 2410-2008 “Determination of light transmittance and haze of transparent plastics”. The higher the light transmittance value, the better the light transmittance performance of the film.

[0072] 2. Tensile strength: The tensile strength (MPa) of the PMMA films in the examples and comparative examples at 23°C was tested according to GB / T 1040.3-2006 "Determination of tensile properties of plastics Part 3: Films and sheets" at a test speed of 50 mm / min; wherein, the higher the tensile strength value, the better the mechanical properties of the film.

[0073] 3. Elongation at break: GB / T 1040.3-2006 "Determination of tensile properties of plastics Part 3: Films and sheets" tests the elongation at break (%) of PMMA films at 23°C in the examples and comparative examples, with a test speed of 50 mm / min; wherein, the higher the value of the elongation at break, the better the toughness performance of the film.

[0074] 4. Film thickness uniformity test: The thickness of the films in Examples 1-14 and Comparative Examples 1-2 was measured according to the mechanical measurement method for thickness determination of plastic films and sheets in GB / T 6672-2001, wherein the length and width of the sample were cut into 60 cm*40 cm, the thickness was tested at 20 scattered points, and the standard deviation σ was calculated.

[0075] Table 1

[0076] Sample Light transmittance / % Tensile strength / MPa Elongation at break / % Standard Deviation Example 1 89.16 56.8 82.4 0.43 Example 2 88.69 60.6 85.9 0.51 Example 3 89.09 56.4 83.1 0.45 Example 4 88.88 56.1 83.8 0.49 Example 5 89.01 56.8 83.6 0.38 Example 6 89.05 59.4 84.7 0.21 Comparative Example 1 89.56 52.2 75.4 0.89 Comparative Example 2 88.10 49.5 78.1 0.41 Comparative Example 3 88.78 50.6 79.2 0.76

[0077] According to Example 1 and Comparative Examples 1-3 and the test data in Table 1, it can be seen that when the toughening agent is an organic toughening agent or an inorganic toughening agent alone, the tensile strength and elongation at break of the environmentally friendly PC / PMMA composite sheet are reduced, and when the ratio of the organic toughening agent to the inorganic toughening agent exceeds the range of (8-9): (1-2), the tensile strength and elongation at break of the environmentally friendly PC / PMMA composite sheet are also reduced. It can be seen that when the environmentally friendly PC layer is prepared by using PC resin doped with post-consumer recycled materials, the use of a specific ratio of organic toughening agent and inorganic toughening agent to toughen the PC resin doped with post-consumer recycled materials is more conducive to the improvement of the mechanical properties of the environmentally friendly PC / PMMA composite sheet. In addition, when the inorganic toughening agent is used alone to toughen the PC resin doped with post-consumer recycled materials, the problem of large thickness differences of the environmentally friendly PC / PMMA composite sheet is likely to occur. The reason is that the inorganic toughening agent is excessive and partially agglomerated, resulting in the inability to evenly disperse the inorganic toughening agent.

[0078] According to Example 1 and Example 3-6 and the test data in Table 1, it can be seen that the difference between Example 1 and Example 3-6 is that the composition of the organic toughening agent is different. Among them, when other conditions remain the same as in Example 1, the organic toughening agent uses a composition of ethylene-butyl acrylate-glycidyl acrylate and polydimethylsiloxane-polymethacrylate diblock copolymer with a weight ratio in the range of (3-4):1, which is conducive to further improving the mechanical properties of the environmentally friendly PC / PMMA composite sheet and at the same time, improving the thickness uniformity of the environmentally friendly PC / PMMA composite sheet.

[0079] This specific implementation manner is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the specific implementation manner as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. An environmentally friendly PC / PMMA composite sheet, characterized in that: The invention comprises an environmentally friendly PC layer (2) and a PMMA layer (1) which are composited on top and bottom, wherein the PMMA layer (1) is made of PMMA resin, and the raw materials for preparing the environmentally friendly PC layer (2) include 100 parts by weight of PC resin doped with post-consumer recycled materials, 10-15 parts by weight of a toughening agent, 0.8-1.2 parts by weight of an antioxidant, and 3-5 parts by weight of an anti-ultraviolet agent; in the PC resin doped with post-consumer recycled materials, the proportion of post-consumer recycled materials is 18-25%, the toughening agent includes an organic toughening agent and an inorganic toughening agent, and the weight ratio of the organic toughening agent to the inorganic toughening agent is (8-9):(1-2); The organic toughening agent is a composition of ethylene-butyl acrylate-glycidyl acrylate copolymer and polydimethylsiloxane-polybutyl methacrylate diblock copolymer, wherein the weight ratio of the ethylene-butyl acrylate-glycidyl acrylate and the polydimethylsiloxane-polybutyl methacrylate diblock copolymer is (3-4):1; In the ethylene-butyl acrylate-glycidyl acrylate, the mass fraction of butyl acrylate is 23-28%, and the mass fraction of glycidyl acrylate is 6-9%; The molecular weight of the polydimethylsiloxane-polybutyl methacrylate diblock copolymer is 30000-35000, and the mass percentage of the polydimethylsiloxane is 20-25%; The inorganic toughening agent is at least one of aminosilane coupling agent modified silicon dioxide whisker, aminosilane coupling agent modified nano calcium carbonate, and aminosilane coupling agent modified nano alumina.

2. The environmentally friendly PC / PMMA composite sheet according to claim 1, characterized in that: The antioxidant includes a primary antioxidant and a secondary antioxidant, and the weight ratio of the primary antioxidant to the secondary antioxidant is (1.5-2):1; wherein the primary antioxidant is at least one of antioxidant 1010 or antioxidant 1076, and the secondary antioxidant is at least one of antioxidant 168 and antioxidant DLTDP.

3. The environmentally friendly PC / PMMA composite sheet according to claim 1, characterized in that: The anti-ultraviolet agent is at least one of the anti-ultraviolet agent UV-P, the anti-ultraviolet agent BHT and the anti-ultraviolet agent TBHQ.

4. The environmentally friendly PC / PMMA composite sheet according to claim 1, characterized in that: The thickness ratio of the environmentally friendly PC layer (2) to the PMMA layer (1) is (15-20):

1.

5. The method for preparing an environmentally friendly PC / PMMA composite sheet according to any one of claims 1 to 4, characterized in that: The following steps are involved: After drying the raw materials for preparing the environmentally friendly PC layer, extrusion granulation is performed at a temperature of 270-280°C to obtain environmentally friendly PC masterbatch; After melting PMMA resin at 250-260°C to obtain PMMA melt and melting environmentally friendly PC masterbatch at 270-280°C to obtain environmentally friendly PC melt, the PMMA melt and the environmentally friendly PC melt are distributed to a die head for double-layer composite co-extrusion, followed by plasticization, calendering, traction cooling and shaping to obtain an environmentally friendly PC / PMMA composite sheet.

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