A weather-resistant, wear-resistant and flexural-resistant white PMMA transparent film and its preparation method

Abstract

The present invention relates to the technical field of laminated composite film materials, and particularly relates to a weather-resistant, wear-resistant, and anti-fold white PMMA transparent film and a preparation method thereof. The preparation method comprises the following steps: toluene diisocyanate, polyether polyol, and hydroxyethyl acrylate react to obtain polyurethane acrylate; the polyurethane acrylate reacts with 4-propenoxy-2-hydroxybenzophenone to obtain a modified polyurethane acrylate; polymethyl methacrylate, the modified polyurethane acrylate, a transparent epoxy resin, and an antioxidant are mixed and melted to obtain a surface layer melt, polymethyl methacrylate and the modified polyurethane acrylate are mixed and melted to obtain an intermediate layer melt, and polymethyl methacrylate, the modified polyurethane acrylate, and an antioxidant are melted to obtain a bottom layer melt; the surface layer melt, the intermediate layer melt, and the bottom layer melt are extruded to obtain a PMMA transparent film. The PMMA transparent film has good weather resistance, wear resistance, and anti-fold white performance, and can be used for protecting color-coated plates.

Description

Technical Field

[0001] The present invention relates to the technical field of laminated composite film materials, and particularly relates to a weather-resistant, wear-resistant, anti-fold white PMMA transparent film and a preparation method thereof. Background Art

[0002] Color-coated plates, also known as color-coated steel plates, are generally made with metal coils as the substrate and a color-coated material is coated on the surface of the substrate. As the service time extends, under the action of various external factors, the coating will fade, and even the adhesion between the coating and the substrate will decrease and peeling will occur, thus directly exposing the metal substrate to the air environment and making it prone to corrosion.

[0003] Since PMMA (polymethyl methacrylate) has high transparency, making a PMMA film and laying it on the surface of a color-coated plate can not only effectively protect the color-coated plate but also not cover the display of the original color of the color-coated plate. However, PMMA is a brittle material, and during the laying and use of the PMMA film, it is prone to brittle fracture under external force impact. Therefore, a toughening material needs to be added to PMMA to improve the impact resistance of the PMMA film. However, after adding the toughening material, a large number of microcrack aggregation regions will be generated in the PMMA film under stress, and due to the decrease in the refractive index, a stress whitening (fold whitening) phenomenon will occur in the microcrack aggregation regions, and the fold whitening phenomenon of the PMMA film will affect the color display of the color-coated plate.

[0004] Chinese Patent CN104203574B discloses a co-extruded impact-modified PMMA film. The PMMA film at least includes an inner layer and an outer layer. The outer layer contains a matting agent, and the inner layer contains an anti-blocking agent. Both the matting agent and the anti-blocking agent are inorganic particles. However, the addition of inorganic particles will affect the transparency of the PMMA film; in addition, the weather resistance, wear resistance, and anti-fold white performance of the PMMA film also need to be improved. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a weather-resistant, wear-resistant, anti-fold white PMMA transparent film to solve the problems that the transparency, weather resistance, wear resistance, and anti-fold white performance of the PMMA film in the prior art need to be improved.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A preparation method of a weather-resistant, wear-resistant, anti-fold white PMMA transparent film includes the following steps:

[0008] Step 1: Add toluene diisocyanate, polyether polyol, and dibutyltin dilaurate to benzene, stir until dissolved, then raise the temperature to a first set temperature and react. After the reaction ends, raise the temperature to a second set temperature, dropwise add hydroxyethyl acrylate, and continue to react after the dropping is completed. After the reaction ends, cool to obtain a polyurethane acrylate solution;

[0009] Step 2: Add 4 - allyloxy - 2 - hydroxybenzophenone into toluene, stir until dissolved to obtain a 4 - allyloxy - 2 - hydroxybenzophenone solution;

[0010] Add the 4 - allyloxy - 2 - hydroxybenzophenone solution and benzoyl peroxide into the polyurethane acrylate solution, heat up to the third set temperature, react. After the reaction is completed, carry out rotary evaporation, purification, and drying to obtain modified polyurethane acrylate;

[0011] Step 3: Mix polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and antioxidant pentaerythritol tetrakis[β - (3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate], and melt to obtain a surface layer melt;

[0012] Mix polymethyl methacrylate and modified polyurethane acrylate, and melt to obtain an intermediate layer melt;

[0013] Mix polymethyl methacrylate, modified polyurethane acrylate, and antioxidant pentaerythritol tetrakis[β - (3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate], and melt to obtain a bottom layer melt;

[0014] Step 4: Extrude the surface layer melt, intermediate layer melt, and bottom layer melt through a three - layer co - extrusion extruder to form a weather - resistant, wear - resistant, and flexure - resistant white PMMA transparent film.

[0015] Preferably, in Step 1: The molar ratio of toluene diisocyanate, polyether polyol, and hydroxyethyl acrylate is (1.1 - 1.2):1:(0.2 - 0.4); the dosage of benzene is 6 - 10 times the sum of the masses of toluene diisocyanate and polyether polyol; the addition amount of dibutyltin dilaurate is 0.1% - 0.3% of the sum of the masses of toluene diisocyanate and polyether polyol.

[0016] Preferably, in Step 1: The reaction conditions are to react at the first set temperature for 2.5 - 3.5 h, and the first set temperature is 55 - 65°C;

[0017] The conditions for the continued reaction are to react at the second set temperature for 3.5 - 4.5 h, and the second set temperature is 70 - 80°C.

[0018] Preferably, the dropping time of hydroxyethyl acrylate is 30 min.

[0019] Preferably, in Step 2: The mass ratio of the polyurethane acrylate solution, 4 - allyloxy - 2 - hydroxybenzophenone solution, and benzoyl peroxide is (800 - 1000):(50 - 80):(0.4 - 0.6).

[0020] Preferably, in the 4 - allyloxy - 2 - hydroxybenzophenone solution, the mass ratio of 4 - allyloxy - 2 - hydroxybenzophenone to toluene is 25:(300 - 500).

[0021] Preferably, in the second step: the reaction condition is to react for 1 - 2 h at the third set temperature, and the third set temperature is 90 - 100 °C.

[0022] Preferably, purification includes washing the product after rotary evaporation with ethanol.

[0023] Preferably, in the third step: when preparing the surface melt, the mass ratio of polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and antioxidant pentaerythritol tetrakis[β-(3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate] is 100:(20 - 25):(6 - 10):(0.2 - 0.4), and the melting temperature is 170 - 180 °C.

[0024] Preferably, in the third step: when preparing the intermediate layer melt, the mass ratio of polymethyl methacrylate to modified polyurethane acrylate is 100:(20 - 25), and the melting temperature is 170 - 180 °C.

[0025] Preferably, in the third step: when preparing the bottom layer melt, the mass ratio of polymethyl methacrylate, modified polyurethane acrylate, and antioxidant pentaerythritol tetrakis[β-(3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate] is 100:(20 - 25):(0.2 - 0.4), and the melting temperature is 170 - 180 °C.

[0026] Preferably, in the fourth step: the head temperature of the three - layer co - extrusion extruder is 190 - 200 °C.

[0027] Preferably, the thickness of the PMMA transparent film is 30 - 50 μm.

[0028] The present invention also discloses a weather - resistant, wear - resistant, and anti - folding white PMMA transparent film prepared by using the preparation method of the weather - resistant, wear - resistant, and anti - folding white PMMA transparent film as described above.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] In the present invention, PMMA is used as the resin matrix to prepare the film material. The obtained PMMA film has high transparency. The PMMA film has a three-layer structure, and polyurethane acrylate is added as a toughening material in all three layers. Since the polyurethane acrylate structure has extremely polar groups, it has good compatibility with PMMA, which can effectively improve the impact resistance of the PMMA film. At the same time, due to the good compatibility between polyurethane acrylate and PMMA, the phase separation of polyurethane acrylate is restricted, enabling the PMMA film to maintain high transparency; in the surface layer film, the addition of epoxy resin can improve the surface hardness of the PMMA film, thereby improving the wear resistance of the PMMA film; antioxidants are added to the surface layer film and the bottom layer film, which can improve the thermal oxidation aging resistance of the PMMA film surface, thereby improving the weather resistance of the PMMA film;

[0031] The polyurethane acrylate in the present invention is prepared from toluene diisocyanate, polyether polyol and hydroxyethyl acrylate. The molecular chain is mainly composed of a long-chain polyether as the soft segment and a hard segment formed by rigid urethane bonds and aromatic rings. The long-chain polyether of the soft segment is easy to rotate and has good flexibility. It can not only toughen but also easily entangle with the PMMA molecular chain. It can not only destroy the regularity of the PMMA molecular chain, reduce the crystallinity of PMMA, effectively terminate the silver streaks, prevent them from growing into microcracks, and thus improve the whitening phenomenon of the PMMA film; at the same time, when subjected to stress, it can inhibit the generation of silver streaks and cavities through chain segment migration and deformation, and consume energy at the same time, further reducing the whitening phenomenon of the PMMA film;

[0032] The polyurethane acrylate in the present invention is modified. Through the carbon-carbon double bonds contained in the polyurethane acrylate, under the action of an initiator, it reacts with the carbon-carbon double bonds in the molecule of the ultraviolet absorber 4-propenyloxy-2-hydroxybenzophenone, and the low-molecular-weight ultraviolet absorber is connected to the polyurethane acrylate molecule by chemical bonding. The introduction of the ultraviolet absorber can improve the ultraviolet aging resistance of the PMMA film, and the compatibility and dispersion uniformity of the ultraviolet absorber in PMMA are high, improving the weather resistance of the PMMA film. At the same time, the migration of the ultraviolet absorber is effectively prevented, further improving the weather resistance of the PMMA film;

[0033] The antioxidant pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] in the present invention is a high-molecular-weight hindered phenol antioxidant, which has good compatibility with PMMA and low volatility and is not easy to migrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is the process flow chart for the preparation of the modified polyurethane acrylate in the present invention;

[0035] Figure 2Bar chart of the wear resistance test results of the PMMA transparent films prepared in Examples 1-5 and Comparative Examples 1-3 of the present invention;

[0036] Figure 3 Bar chart of the weather resistance test results of the PMMA transparent films prepared in Examples 1-5 and Comparative Examples 1-3 of the present invention;

[0037] Figure 4 Bar chart of the anti-fold whitening performance test results of the PMMA transparent films prepared in Examples 1-5 and Comparative Examples 1-3 of the present invention. Detailed implementation manners

[0038] Example 1

[0039] This example discloses a preparation method of a weather-resistant, wear-resistant and anti-fold whitening PMMA transparent film, which includes the following steps:

[0040] Step 1: Add toluene diisocyanate, polyether polyol, and dibutyltin dilaurate into benzene, stir at a stirring speed of 100 r / min until the dibutyltin dilaurate is completely dissolved, heat up to 55 °C, react at 55 °C for 3.5 h. After the reaction is completed, heat up to 70 °C, dropwise add hydroxyethyl acrylate, and the dropping time is 30 min. After the dropping is completed, continue to react at 70 °C for 4.5 h. After the reaction is completed, cool to room temperature to obtain a polyurethane acrylate solution;

[0041] Among them, the molar ratio of toluene diisocyanate, polyether polyol, and hydroxyethyl acrylate is 1.1:1:0.2; the dosage of benzene is 6 times the sum of the masses of toluene diisocyanate and polyether polyol; the addition amount of dibutyltin dilaurate is 0.1% of the sum of the masses of toluene diisocyanate and polyether polyol;

[0042] Step 2: Add 4-propenyloxy-2-hydroxybenzophenone into toluene, stir at a stirring speed of 100 r / min until it is completely dissolved, and the mass ratio of 4-propenyloxy-2-hydroxybenzophenone to toluene is 25:300 to obtain a 4-propenyloxy-2-hydroxybenzophenone solution;

[0043] Add the 4-propenyloxy-2-hydroxybenzophenone solution and benzoyl peroxide into the polyurethane acrylate solution. The mass ratio of the polyurethane acrylate solution, the 4-propenyloxy-2-hydroxybenzophenone solution, and benzoyl peroxide is 800:50:0.4. Heat up to 90 °C and react at 90 °C for 2 h. After the reaction is completed, first remove benzene by rotary evaporation at 55 °C, then remove toluene by rotary evaporation at 75 °C. The rotary-evaporated product is washed 3 times with ethanol and placed in a vacuum drying oven at 50 °C for drying for 10 h to obtain a modified polyurethane acrylate;

[0044] Step 3: Mix polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and antioxidant tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] pentaerythritol ester. The mass ratio of polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and antioxidant tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] pentaerythritol ester is 100:20:6:0.2. Melt them at 170 °C to obtain a surface layer melt;

[0045] Mix polymethyl methacrylate and modified polyurethane acrylate. The mass ratio of polymethyl methacrylate to modified polyurethane acrylate is 100:20. Melt them at 170 °C to obtain an intermediate layer melt;

[0046] Mix polymethyl methacrylate, modified polyurethane acrylate, and antioxidant tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] pentaerythritol ester. The mass ratio of polymethyl methacrylate, modified polyurethane acrylate, and antioxidant tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] pentaerythritol ester is 100:20:0.2. Melt them at 170 °C to obtain a bottom layer melt;

[0047] Step 4: Extrude and mold the surface layer melt, intermediate layer melt, and bottom layer melt through a three-layer co-extrusion extruder. The head temperature is 190 °C to obtain a weather-resistant, wear-resistant, and flexure-resistant white PMMA transparent film;

[0048] The thickness of the PMMA transparent film is 40 μm;

[0049] The PMMA transparent film includes a surface layer, an intermediate layer, and a bottom layer. The thicknesses of the surface layer, intermediate layer, and bottom layer are 15 μm, 10 μm, and 15 μm respectively.

[0050] Example 2

[0051] This example discloses a preparation method of a weather-resistant, wear-resistant, and flexure-resistant white PMMA transparent film, including the following steps:

[0052] Step 1: Add toluene diisocyanate, polyether polyol, and dibutyltin dilaurate to benzene. Stir at a stirring speed of 100 r / min until the dibutyltin dilaurate is completely dissolved. Heat up to 65 °C and react at 55 °C for 2.5 h. After the reaction is completed, heat up to 80 °C and dropwise add hydroxyethyl acrylate. The dropping time is 30 min. After the dropping is completed, continue to react at 80 °C for 3.5 h. After the reaction is completed, cool to room temperature to obtain a polyurethane acrylate solution;

[0053] Among them, the molar ratio of toluene diisocyanate, polyether polyol, and 2-hydroxyethyl acrylate is 1.2:1:0.4; the dosage of benzene is 10 times the sum of the masses of toluene diisocyanate and polyether polyol; the addition amount of dibutyltin dilaurate is 0.3% of the sum of the masses of toluene diisocyanate and polyether polyol;

[0054] Step 2: Add 4-allyloxy-2-hydroxybenzophenone into toluene, and stir until completely dissolved at a stirring speed of 100 r / min. The mass ratio of 4-allyloxy-2-hydroxybenzophenone to toluene is 25:500 to obtain a 4-allyloxy-2-hydroxybenzophenone solution;

[0055] Add the 4-allyloxy-2-hydroxybenzophenone solution and benzoyl peroxide into the polyurethane acrylate solution. The mass ratio of the polyurethane acrylate solution, 4-allyloxy-2-hydroxybenzophenone solution, and benzoyl peroxide is 1000:80:0.6. Heat up to 100 °C and react at 100 °C for 1 h. After the reaction, first rotate and evaporate to remove benzene at 55 °C, then rotate and evaporate to remove toluene at 75 °C. The product after rotary evaporation is washed 3 times with ethanol and placed in a vacuum drying oven at 50 °C for drying for 10 h to obtain the modified polyurethane acrylate;

[0056] Step 3: Mix polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. The mass ratio of polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is 100:25:10:0.4, and melt at 180 °C to obtain a surface layer melt;

[0057] Mix polymethyl methacrylate and modified polyurethane acrylate. The mass ratio of polymethyl methacrylate to modified polyurethane acrylate is 100:25, and melt at 180 °C to obtain an intermediate layer melt;

[0058] Mix polymethyl methacrylate, modified polyurethane acrylate, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. The mass ratio of polymethyl methacrylate, modified polyurethane acrylate, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is 100:25:0.4, and melt at 180 °C to obtain a bottom layer melt;

[0059] Step 4: Extrude and mold the surface layer melt, intermediate layer melt, and bottom layer melt through a three-layer co-extrusion extruder. The head temperature is 200 °C to obtain a weather-resistant, wear-resistant, and anti-flexural white PMMA transparent film;

[0060] The thickness of the PMMA transparent film is 40 μm;

[0061] The PMMA transparent film includes a surface layer, a middle layer, and a bottom layer, and the thicknesses of the surface layer, the middle layer, and the bottom layer are 15 μm, 10 μm, and 15 μm respectively.

[0062] Example 3

[0063] This example discloses a preparation method of a weather-resistant, wear-resistant, and fold-resistant white PMMA transparent film, which includes the following steps:

[0064] Step 1: Add toluene diisocyanate, polyether polyol, and dibutyltin dilaurate into benzene, stir at a stirring speed of 100 r / min until the dibutyltin dilaurate is completely dissolved, heat up to 60 °C, react at 60 °C for 3 h. After the reaction is completed, heat up to 75 °C, dropwise add hydroxyethyl acrylate, and the dropping time is 30 min. After the dropping is completed, continue to react at 75 °C for 3 h. After the reaction is completed, cool to room temperature to obtain a polyurethane acrylate solution;

[0065] Among them, the molar ratio of toluene diisocyanate, polyether polyol, and hydroxyethyl acrylate is 1.13:1:0.25; the dosage of benzene is 8 times the sum of the masses of toluene diisocyanate and polyether polyol; the addition amount of dibutyltin dilaurate is 0.2% of the sum of the masses of toluene diisocyanate and polyether polyol;

[0066] Step 2: Add 4 - allyloxy - 2 - hydroxybenzophenone into toluene, stir at a stirring speed of 100 r / min until it is completely dissolved, and the mass ratio of 4 - allyloxy - 2 - hydroxybenzophenone to toluene is 25:350 to obtain a 4 - allyloxy - 2 - hydroxybenzophenone solution;

[0067] Add the 4 - allyloxy - 2 - hydroxybenzophenone solution and benzoyl peroxide into the polyurethane acrylate solution. The mass ratio of the polyurethane acrylate solution, the 4 - allyloxy - 2 - hydroxybenzophenone solution, and benzoyl peroxide is 850:60:0.45. Heat up to 95 °C and react at 95 °C for 1.5 h. After the reaction is completed, first remove benzene by rotary evaporation at 55 °C, then remove toluene by rotary evaporation at 75 °C. The product after rotary evaporation is washed 3 times with ethanol and placed in a vacuum drying oven at 50 °C for drying for 10 h to obtain a modified polyurethane acrylate;

[0068] Step 3: Mix polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. The mass ratio of polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is 100:21:7:0.25. Melt them at 175 °C to obtain a surface layer melt;

[0069] Mix polymethyl methacrylate and modified polyurethane acrylate. The mass ratio of polymethyl methacrylate to modified polyurethane acrylate is 100:21. Melt them at 175 °C to obtain an intermediate layer melt;

[0070] Mix polymethyl methacrylate, modified polyurethane acrylate, and pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. The mass ratio of polymethyl methacrylate, modified polyurethane acrylate, and pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is 100:21:0.25. Melt them at 180 °C to obtain a bottom layer melt;

[0071] Step 4: Extrude and shape the surface layer melt, intermediate layer melt, and bottom layer melt through a three-layer co-extrusion extruder. The head temperature is 195 °C to obtain a weather-resistant, wear-resistant, and flexure-resistant white PMMA transparent film;

[0072] The thickness of the PMMA transparent film is 40 μm;

[0073] The PMMA transparent film includes a surface layer, an intermediate layer, and a bottom layer. The thicknesses of the surface layer, intermediate layer, and bottom layer are 15 μm, 10 μm, and 15 μm, respectively.

[0074] Example 4

[0075] This example discloses a preparation method of a weather-resistant, wear-resistant, and flexure-resistant white PMMA transparent film, which includes the following steps:

[0076] Step 1: Add toluene diisocyanate, polyether polyol, and dibutyltin dilaurate to benzene. Stir at a stirring speed of 100 r / min until dibutyltin dilaurate is completely dissolved. Heat up to 60 °C and react at 60 °C for 3 h. After the reaction ends, heat up to 75 °C and dropwise add hydroxyethyl acrylate. The dropping time is 30 min. After the dropping is completed, continue to react at 75 °C for 3 h. After the reaction ends, cool to room temperature to obtain a polyurethane acrylate solution;

[0077] Among them, the molar ratio of toluene diisocyanate, polyether polyol, and 2-hydroxyethyl acrylate is 1.15:1:0.3; the dosage of benzene is 8 times the sum of the masses of toluene diisocyanate and polyether polyol; the addition amount of dibutyltin dilaurate is 0.2% of the sum of the masses of toluene diisocyanate and polyether polyol;

[0078] Step 2: Add 4-propenyloxy-2-hydroxybenzophenone to toluene and stir until completely dissolved at a stirring speed of 100 r / min. The mass ratio of 4-propenyloxy-2-hydroxybenzophenone to toluene is 25:400 to obtain a 4-propenyloxy-2-hydroxybenzophenone solution;

[0079] Add the 4-propenyloxy-2-hydroxybenzophenone solution and benzoyl peroxide to the polyurethane acrylate solution. The mass ratio of the polyurethane acrylate solution, 4-propenyloxy-2-hydroxybenzophenone solution, and benzoyl peroxide is 900:65:0.5. Heat up to 95 °C and react at 95 °C for 1.5 h. After the reaction, first remove benzene by rotary evaporation at 55 °C, then remove toluene by rotary evaporation at 75 °C. Wash the rotary-evaporated product with ethanol 3 times and dry it in a vacuum drying oven at 50 °C for 10 h to obtain the modified polyurethane acrylate;

[0080] Step 3: Mix polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. The mass ratio of polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is 100:22.5:8:0.3 and melt at 175 °C to obtain a surface layer melt;

[0081] Mix polymethyl methacrylate and modified polyurethane acrylate. The mass ratio of polymethyl methacrylate to modified polyurethane acrylate is 100:22.5 and melt at 175 °C to obtain an intermediate layer melt;

[0082] Mix polymethyl methacrylate, modified polyurethane acrylate, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. The mass ratio of polymethyl methacrylate, modified polyurethane acrylate, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is 100:22.5:0.3 and melt at 180 °C to obtain a bottom layer melt;

[0083] Step 4: Extrude and mold the surface layer melt, intermediate layer melt, and bottom layer melt through a three-layer co-extrusion extruder with the head temperature at 195 °C to obtain a weather-resistant, wear-resistant, and anti-flexural white PMMA transparent film;

[0084] The thickness of the PMMA transparent film is 40 μm;

[0085] The PMMA transparent film includes a surface layer, a middle layer, and a bottom layer, and the thicknesses of the surface layer, the middle layer, and the bottom layer are 15 μm, 10 μm, and 15 μm respectively.

[0086] Example 5

[0087] This example discloses a preparation method of a weather-resistant, wear-resistant, and flexure-resistant white PMMA transparent film, which includes the following steps:

[0088] Step 1: Add toluene diisocyanate, polyether polyol, and dibutyltin dilaurate into benzene, stir at a stirring speed of 100 r / min until the dibutyltin dilaurate is completely dissolved, raise the temperature to 60 °C, react at 60 °C for 3 h. After the reaction is completed, raise the temperature to 75 °C, dropwise add hydroxyethyl acrylate, and the dropping time is 30 min. After the dropping is completed, continue to react at 75 °C for 3 h. After the reaction is completed, cool to room temperature to obtain a polyurethane acrylate solution;

[0089] Among them, the molar ratio of toluene diisocyanate, polyether polyol, and hydroxyethyl acrylate is 1.18:1:0.35; the dosage of benzene is 8 times the sum of the masses of toluene diisocyanate and polyether polyol; the addition amount of dibutyltin dilaurate is 0.2% of the sum of the masses of toluene diisocyanate and polyether polyol;

[0090] Step 2: Add 4 - allyloxy - 2 - hydroxybenzophenone into toluene, stir at a stirring speed of 100 r / min until it is completely dissolved, and the mass ratio of 4 - allyloxy - 2 - hydroxybenzophenone to toluene is 25:450 to obtain a 4 - allyloxy - 2 - hydroxybenzophenone solution;

[0091] Add the 4 - allyloxy - 2 - hydroxybenzophenone solution and benzoyl peroxide into the polyurethane acrylate solution. The mass ratio of the polyurethane acrylate solution, the 4 - allyloxy - 2 - hydroxybenzophenone solution, and benzoyl peroxide is 950:70:0.55. Raise the temperature to 95 °C and react at 95 °C for 1.5 h. After the reaction is completed, first remove benzene by rotary evaporation at 55 °C, then remove toluene by rotary evaporation at 75 °C. The product after rotary evaporation is washed 3 times with ethanol and placed in a vacuum drying oven at 50 °C for drying for 10 h to obtain a modified polyurethane acrylate;

[0092] Step 3: Mix polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. The mass ratio of polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is 100:24:9:0.35. Melt them at 175 °C to obtain the surface layer melt;

[0093] Mix polymethyl methacrylate and modified polyurethane acrylate. The mass ratio of polymethyl methacrylate to modified polyurethane acrylate is 100:24. Melt them at 175 °C to obtain the intermediate layer melt;

[0094] Mix polymethyl methacrylate, modified polyurethane acrylate, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. The mass ratio of polymethyl methacrylate, modified polyurethane acrylate, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is 100:24:0.35. Melt them at 180 °C to obtain the bottom layer melt;

[0095] Step 4: Extrude and mold the surface layer melt, intermediate layer melt, and bottom layer melt through a three-layer co-extrusion extruder. The head temperature is 195 °C to obtain a weather-resistant, wear-resistant, and anti-flexural white PMMA transparent film;

[0096] The thickness of the PMMA transparent film is 40 μm;

[0097] The PMMA transparent film includes a surface layer, an intermediate layer, and a bottom layer. The thicknesses of the surface layer, intermediate layer, and bottom layer are 15 μm, 10 μm, and 15 μm, respectively.

[0098] Comparative Example 1

[0099] This comparative example discloses a preparation method of a PMMA transparent film, including the following steps:

[0100] Step 1: Add toluene diisocyanate, polyether polyol, and dibutyltin dilaurate to benzene. Stir at a stirring speed of 100 r / min until dibutyltin dilaurate is completely dissolved. Raise the temperature to 65 °C and react at 55 °C for 2.5 h. After the reaction is completed, raise the temperature to 80 °C and dropwise add hydroxyethyl acrylate. The dropping time is 30 min. After the dropping is completed, continue to react at 80 °C for 3.5 h. After the reaction is completed, rotary evaporate to remove benzene at 55 °C and place it in a vacuum drying oven at 50 °C for 10 h to obtain polyurethane acrylate;

[0101] Among them, the molar ratio of toluene diisocyanate, polyether polyol, and hydroxyethyl acrylate is 1.2:1:0.4; the amount of benzene used is 10 times the sum of the masses of toluene diisocyanate and polyether polyol; the addition amount of dibutyltin dilaurate is 0.3% of the sum of the masses of toluene diisocyanate and polyether polyol;

[0102] Step 2: Mix polymethyl methacrylate, polyurethane acrylate, 4 - allyloxy - 2 - hydroxybenzophenone, transparent epoxy resin, and pentaerythritol tetrakis[β-(3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate]. The mass ratio of polymethyl methacrylate, polyurethane acrylate, 4 - allyloxy - 2 - hydroxybenzophenone, transparent epoxy resin, and pentaerythritol tetrakis[β-(3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate] is 100:24:1:10:0.4. Melt at 180 °C to obtain the surface layer melt;

[0103] Mix polymethyl methacrylate, polyurethane acrylate, and 4 - allyloxy - 2 - hydroxybenzophenone. The mass ratio of polymethyl methacrylate, polyurethane acrylate, and 4 - allyloxy - 2 - hydroxybenzophenone is 100:24:1. Melt at 180 °C to obtain the intermediate layer melt;

[0104] Mix polymethyl methacrylate, polyurethane acrylate, 4 - allyloxy - 2 - hydroxybenzophenone, and pentaerythritol tetrakis[β-(3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate]. The mass ratio of polymethyl methacrylate, polyurethane acrylate, 4 - allyloxy - 2 - hydroxybenzophenone, and pentaerythritol tetrakis[β-(3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate] is 100:24:1:0.4. Melt at 180 °C to obtain the bottom layer melt;

[0105] Step 3: Extrude and mold the surface layer melt, intermediate layer melt, and bottom layer melt through a three - layer co - extrusion machine. The head temperature is 200 °C to obtain a weather - resistant, wear - resistant, and flexure - resistant white PMMA transparent film;

[0106] The thickness of the PMMA transparent film is 40 μm;

[0107] The PMMA transparent film includes a surface layer, an intermediate layer, and a bottom layer. The thicknesses of the surface layer, intermediate layer, and bottom layer are 15 μm, 10 μm, and 15 μm, respectively.

[0108] Comparative Example 2

[0109] This comparative example discloses a preparation method of a PMMA transparent film, which includes the following steps:

[0110] Step 1: Mix polymethyl methacrylate, 4 - allyloxy - 2 - hydroxybenzophenone, transparent epoxy resin, and pentaerythritol tetrakis[β-(3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate]. The mass ratio of polymethyl methacrylate, 4 - allyloxy - 2 - hydroxybenzophenone, transparent epoxy resin, and pentaerythritol tetrakis[β-(3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate] is 124:1:10:0.4. Melt at 180 °C to obtain the surface layer melt;

[0111] Mix polymethyl methacrylate and 4 - allyloxy - 2 - hydroxybenzophenone. The mass ratio of polymethyl methacrylate to 4 - allyloxy - 2 - hydroxybenzophenone is 124:1. Melt at 180 °C to obtain the intermediate layer melt;

[0112] Mix polymethyl methacrylate, 4 - allyloxy - 2 - hydroxybenzophenone, and pentaerythritol tetrakis[β-(3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate]. The mass ratio of polymethyl methacrylate, 4 - allyloxy - 2 - hydroxybenzophenone, and pentaerythritol tetrakis[β-(3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate] is 124:1:0.4. Melt at 180 °C to obtain the bottom layer melt;

[0113] Step 2: Extrude the surface layer melt, intermediate layer melt, and bottom layer melt through a three - layer co - extrusion machine. The head temperature is 200 °C to obtain a weather - resistant, wear - resistant, and flexural - resistant white PMMA transparent film;

[0114] The thickness of the PMMA transparent film is 40 μm;

[0115] The PMMA transparent film includes a surface layer, an intermediate layer, and a bottom layer. The thicknesses of the surface layer, intermediate layer, and bottom layer are 15 μm, 10 μm, and 15 μm, respectively.

[0116] Comparative Example 3

[0117] This comparative example discloses a preparation method of a PMMA transparent film, which includes the following steps:

[0118] Step 1: Add toluene diisocyanate, polyether polyol, and dibutyltin dilaurate to benzene. Stir at a stirring speed of 100 r / min until the dibutyltin dilaurate is completely dissolved. Heat up to 65 °C and react at 55 °C for 2.5 h. After the reaction ends, heat up to 80 °C and dropwise add hydroxyethyl acrylate. The dropping time is 30 min. After the dropping is completed, continue to react at 80 °C for 3.5 h. After the reaction ends, cool to room temperature to obtain a polyurethane acrylate solution;

[0119] Among them, the molar ratio of toluene diisocyanate, polyether polyol, and hydroxyethyl acrylate is 1.2:1:0.4; the dosage of benzene is 10 times the sum of the masses of toluene diisocyanate and polyether polyol; the addition amount of dibutyltin dilaurate is 0.3% of the sum of the masses of toluene diisocyanate and polyether polyol;

[0120] Step 2: Add 4 - allyloxy - 2 - hydroxybenzophenone to toluene and stir at a stirring speed of 100 r / min until completely dissolved. The mass ratio of 4 - allyloxy - 2 - hydroxybenzophenone to toluene is 25:500 to obtain a 4 - allyloxy - 2 - hydroxybenzophenone solution;

[0121] Add the 4 - allyloxy - 2 - hydroxybenzophenone solution and benzoyl peroxide to the polyurethane acrylate solution. The mass ratio of the polyurethane acrylate solution, 4 - allyloxy - 2 - hydroxybenzophenone solution, and benzoyl peroxide is 1000:200:0.8. Heat up to 100 °C and react at 100 °C for 1 h. After the reaction, first rotary evaporate to remove benzene at 55 °C, then rotary evaporate to remove toluene at 75 °C. Wash the rotary - evaporated product with ethanol 3 times and dry it in a vacuum drying oven at 50 °C for 10 h to obtain the modified polyurethane acrylate;

[0122] Step 3: Mix polymethyl methacrylate, modified polyurethane acrylate, and pentaerythritol tetra[β - (3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate]. The mass ratio of polymethyl methacrylate, modified polyurethane acrylate, and pentaerythritol tetra[β - (3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate] is 110:25:0.4, and melt it at 180 °C to obtain a surface layer melt;

[0123] Mix polymethyl methacrylate and modified polyurethane acrylate. The mass ratio of polymethyl methacrylate and modified polyurethane acrylate is 100:25, and melt it at 180 °C to obtain an intermediate layer melt;

[0124] Mix polymethyl methacrylate, modified polyurethane acrylate, and pentaerythritol tetra[β - (3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate]. The mass ratio of polymethyl methacrylate, modified polyurethane acrylate, and pentaerythritol tetra[β - (3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate] is 100:25:0.4, and melt it at 180 °C to obtain a bottom layer melt;

[0125] Step 4: Extrude and mold the surface layer melt, intermediate layer melt, and bottom layer melt through a three - layer co - extrusion extruder. The head temperature is 200 °C to obtain a weather - resistant, wear - resistant, and flexural - resistant white PMMA transparent film;

[0126] The thickness of the PMMA transparent film is 40 μm;

[0127] The PMMA transparent film includes a surface layer, a middle layer, and a bottom layer, and the thicknesses of the surface layer, the middle layer, and the bottom layer are 15 μm, 10 μm, and 15 μm, respectively.

[0128] In the above examples and comparative examples, the polyether polyol was purchased from Hai'an Petrochemical Factory, Jiangsu Province, with the specification: PPG-1500; the polymethyl methacrylate was purchased from Shanghai Kewanjia Plastic Co., Ltd., with the product number: CM-207; the transparent epoxy resin was bisphenol A type epoxy resin E-44, purchased from Wuxi Changgan Chemical Co., Ltd., with the viscosity: 18000-25000 (mPas).

[0129] Test Example

[0130] Perform performance tests on the PMMA transparent films prepared in Examples 1-5 and Comparative Examples 1-3:

[0131] (1) Abrasion resistance: The surface layer melts of Examples 1-5 and Comparative Examples 1-3 were injection molded to form circular specimens with a diameter of 100 mm. The thickness of the specimens was 10 mm. The surfaces of the specimens were smooth, flat, without bubbles, mechanical damage, and impurities. Referring to the standard GB / T 5478-2008 "Plastics - Method of Test for Rolling Wear", the wear rate of the specimens was measured, and the measurement results are shown in Table 1:

[0132] Table 1

[0133]

[0134] As can be seen from Table 1, when epoxy resin is added, the abrasion resistance of the surface layer can be effectively improved, and thus the abrasion resistance of the PMMA transparent film is improved. Compared with Example 2, in Comparative Examples 1 and 2, the amount of epoxy resin in the surface layer is the same, which has no effect on the wear rate. In Comparative Example 3, since no epoxy resin is added, the wear rate is significantly reduced, and the abrasion resistance is the worst.

[0135] (2) Weather resistance

[0136] The PMMA transparent film samples prepared in Examples 1-5 and Comparative Examples 1-3 were placed in a xenon light aging test chamber for a light aging test. A total of 168 h of cyclic treatment was carried out, with each cycle being 30 min (15 min of spraying water and irradiating with light, 15 min of irradiating with light without spraying water). After the light aging test was completed, the initial thermal degradation temperature of the samples was measured, and the measurement results are shown in Table 2:

[0137] Table 2

[0138]

[0139] As can be seen from Table 2, the PMMA transparent film prepared by the present invention has good weather resistance. The addition of the ultraviolet absorber 4-allyloxy-2-hydroxybenzophenone can effectively improve the photoaging resistance of the PMMA transparent film. Compared with Example 2, in Comparative Example 1 and Comparative Example 2, the ultraviolet absorber 4-allyloxy-2-hydroxybenzophenone is not connected to the polyurethane acrylate molecule by chemical bonding, resulting in a decrease in the compatibility and dispersion uniformity in MMA, a decrease in the photoaging resistance, a decrease in the initial thermal degradation temperature, and an acceleration of the thermal decomposition process.

[0140] (3) Flexural whitening resistance: Referring to the German Volkswagen PV3966 standard, the flexural whitening (anti-flexural whitening) performance of the PMMA transparent films prepared in Examples 1-5 and Comparative Examples 1-3 was measured. The specimen size was 70×70 mm, and an iron ball of 500 g was dropped from a height of 1 m to impact the specimen. The color difference ΔL of the specimen before and after the ball drop was compared under a standard light source. The smaller ΔL indicates better flexural whitening resistance. The measurement results are shown in Table 3.

[0141] Table 3

[0142] ΔL ΔL Example 1 1.36 Example 5 1.25 Example 2 1.21 Comparative Example 1 1.22 Example 3 1.32 Comparative Example 2 4.53 Example 4 1.29 Comparative Example 3 1.21

[0143] As can be seen from Table 3, the PMMA transparent film prepared by the present invention has good flexural whitening resistance. When preparing the PMMA transparent film, polyurethane acrylate is added. The molecular chain of polyurethane acrylate is mainly composed of a long-chain polyether as a soft segment and a hard segment formed by a rigid urethane bond and an aromatic ring. The long-chain polyether of the soft segment is prone to rotation and has good flexibility. It can not only toughen and improve the toughness of the PMMA transparent film, but also the molecular chain of polyurethane acrylate is prone to entanglement with the PMMA molecular chain, destroying the regularity of the PMMA molecular chain, reducing the crystallinity of PMMA, effectively terminating silver streaks, preventing them from growing into microcracks, and improving the stress whitening phenomenon of the PMMA film. At the same time, when subjected to stress, it can inhibit the generation of silver streaks and cavities through chain segment migration and deformation, and consume energy at the same time, further reducing the stress whitening phenomenon of the PMMA film. Compared with Example 2, in Comparative Example 2, polyurethane acrylate was not added, and the flexural whitening resistance decreased significantly.

[0144] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a weather-resistant, wear-resistant and flexure-resistant white PMMA transparent film, characterized in that, It includes the following steps: Step 1: Add toluene diisocyanate, polyether polyol, and dibutyltin dilaurate into benzene. After stirring until dissolved, raise the temperature to the first set temperature and react. After the reaction ends, raise the temperature to the second set temperature, dropwise add hydroxyethyl acrylate. After the dropping is completed, continue the reaction. After the reaction ends, cool to obtain a polyurethane acrylate solution; Step 2: Add 4 - acryloxy - 2 - hydroxybenzophenone into toluene. The mass ratio of 4 - acryloxy - 2 - hydroxybenzophenone to toluene is 25:(300 - 500). Stir until dissolved to obtain a 4 - acryloxy - 2 - hydroxybenzophenone solution; Add the 4 - acryloxy - 2 - hydroxybenzophenone solution and benzoyl peroxide into the polyurethane acrylate solution. Raise the temperature to the third set temperature and react. After the reaction ends, perform rotary evaporation, purification, and drying to obtain a modified polyurethane acrylate; Among them, the mass ratio of the polyurethane acrylate solution, the 4 - acryloxy - 2 - hydroxybenzophenone solution, and benzoyl peroxide is (800 - 1000):(50 - 80):(0.4 - 0.6); The reaction condition is to react at the third set temperature for 1 - 2 h, and the third set temperature is 90 - 100 °C; Step 3: Mix polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and pentaerythritol tetrakis[β - (3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate] and melt to obtain a surface layer melt; Mix polymethyl methacrylate and modified polyurethane acrylate and melt to obtain an intermediate layer melt; Mix polymethyl methacrylate, modified polyurethane acrylate, and pentaerythritol tetrakis[β - (3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate] and melt to obtain a bottom layer melt; Step 4: Extrude the surface layer melt, the intermediate layer melt, and the bottom layer melt through a three - layer co - extrusion extruder to form a weather - resistant, wear - resistant, and flexure - resistant white PMMA transparent film.

2. The preparation method of a weather-resistant, wear-resistant and flexure-resistant white PMMA transparent film according to claim 1, characterized in that, In the said Step 1: The molar ratio of toluene diisocyanate, polyether polyol, and hydroxyethyl acrylate is (1.1 - 1.2):1:(0.2 - 0.4); the dosage of benzene is 6 - 10 times the sum of the masses of toluene diisocyanate and polyether polyol; the addition amount of dibutyltin dilaurate is 0.1% - 0.3% of the sum of the masses of toluene diisocyanate and polyether polyol.

3. The preparation method of a weather-resistant, wear-resistant and flexural-resistant white PMMA transparent film according to claim 1, characterized in that, In the said Step 1: The reaction condition is to react at the first set temperature for 2.5 - 3.5 h, and the first set temperature is 55 - 65 °C; The condition for continuing the reaction is to react at the second set temperature for 3.5 - 4.5 h, and the second set temperature is 70 - 80 °C.

4. The preparation method of a weather-resistant, wear-resistant and flexural-resistant white PMMA transparent film according to claim 1, characterized in that, When preparing the surface layer melt in the said Step 3, the mass ratio of polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and pentaerythritol tetrakis[β - (3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate] is 100:(20 - 25):(6 - 10):(0.2 - 0.4), and the melting temperature is 170 - 180 °C.

5. The preparation method of a weather-resistant, wear-resistant and flexural-resistant white PMMA transparent film according to claim 1, characterized in that, In step three: when preparing the intermediate layer melt, the mass ratio of polymethyl methacrylate to modified polyurethane acrylate is 100:(20 - 25), and the melting temperature is 170 - 180°C.

6. The preparation method of a weather-resistant, wear-resistant and flexure-resistant white PMMA transparent film according to claim 1, characterized in that, In step three: when preparing the bottom layer melt, the mass ratio of polymethyl methacrylate to modified polyurethane acrylate to pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is 100:(20 - 25):(0.2 - 0.4), and the melting temperature is 170 - 180°C.

7. The preparation method of a weather-resistant, wear-resistant and flexure-resistant white PMMA transparent film according to claim 1, characterized in that, In step four: the head temperature of the three-layer co-extrusion extruder is 190 - 200°C; The thickness of the obtained PMMA transparent film is 30 - 50 μm.

8. A weather-resistant, wear-resistant and flexure-resistant white PMMA transparent film prepared by using the preparation method of the weather-resistant, wear-resistant and flexure-resistant white PMMA transparent film according to any one of claims 1 - 7.

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