Weather-resistant wear-resistant fracture-resistant white PMMA transparent film and preparation method thereof

Abstract

The invention relates to the technical field of layered composite film materials, in particular to a weather-resistant wear-resistant fracture-resistant white PMMA transparent film and a preparation method thereof. The preparation method comprises the following steps: carrying out a reaction on toluene diisocynate, polyether polyol and hydroxyethyl acrylate to prepare urethane acrylate; the preparation method comprises the following steps: reacting polyurethane acrylate with 4-propenyloxy-2-hydroxybenzophenone, so as to obtain modified polyurethane acrylate; the preparation method comprises the following steps: mixing and melting polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin and an antioxidant to obtain a surface-layer melt, mixing and melting polymethyl methacrylate and modified polyurethane acrylate to obtain a middle-layer melt, and melting polymethyl methacrylate, modified polyurethane acrylate and an antioxidant to obtain a bottom-layer melt; and extruding the surface layer melt, the middle layer melt and the bottom layer melt to obtain the PMMA transparent film. The PMMA transparent film has good weather resistance, wear resistance and folding and whitening resistance, and can be used for protecting the color-coated sheet.

Description

Technical Field

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

[0002] Color coated steel sheet, also known as color coated steel sheet, is generally made of metal coil as the base material, and a color coating material is applied on the surface of the base material. With the extension of service time, under the influence of various external factors, the coating will fade, and even the adhesion between the coating and the base material will decrease and fall off, thus exposing the metal base material directly to the air environment, which is prone to corrosion.

[0003] PMMA (polymethyl methacrylate) has high transparency. When PMMA is made into a film and spread on the surface of the color-coated plate, it can not only effectively protect the color-coated plate, but also will not cover the color display of the color-coated plate. However, PMMA is a brittle material. During the spreading and use process, the PMMA film is prone to brittle fracture under external force impact. Therefore, it is necessary to add toughening materials to PMMA to improve the impact resistance of the PMMA film. However, after adding toughening materials, the PMMA film will produce a large number of microcrack aggregation areas under stress, and the microcrack aggregation areas will show stress whitening (folding whitening) due to the decrease in refractive index. The folding whitening phenomenon of the PMMA film will affect the color development of the color-coated plate.

[0004] Chinese patent CN104203574B discloses a co-extruded impact-resistant modified PMMA film, wherein the PMMA film comprises at least an inner layer and an outer layer, wherein the outer layer comprises a matting agent, and the inner layer comprises an anti-adhesion agent, wherein both the matting agent and the anti-adhesion agent are inorganic particles, but the addition of inorganic particles will affect the transparency of the PMMA film; in addition, the weather resistance, abrasion resistance, and anti-whitening properties of the PMMA film also need to be improved. Summary of the invention

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

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

[0007] A method for preparing a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film comprises the following steps:

[0008] Step 1, adding toluene diisocyanate, polyether polyol, and dibutyltin dilaurate into benzene, stirring until dissolved, heating to a first set temperature, reacting, and after the reaction is completed, heating to a second set temperature, dripping hydroxyethyl acrylate, continuing the reaction, and cooling after the reaction is completed to obtain a polyurethane acrylate solution;

[0009] Step 2, adding 4-propyleneoxy-2-hydroxybenzophenone to toluene, stirring until dissolved, to obtain a 4-propyleneoxy-2-hydroxybenzophenone solution;

[0010] Adding 4-propyleneoxy-2-hydroxybenzophenone solution and benzoyl peroxide to the polyurethane acrylate solution, heating to a third set temperature, reacting, and after the reaction is completed, rotary evaporating, purifying, and drying to obtain modified polyurethane acrylate;

[0011] Step 3, polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and antioxidant tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester are mixed and melted to obtain a surface melt;

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

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

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

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

[0016] Preferably, in step 1: the reaction condition is to react at a first set temperature for 2.5-3.5 hours, and the first set temperature is 55-65° C.;

[0017] The condition for continuing the reaction is to react at the second set temperature for 3.5-4.5 hours, and the second set temperature is 70-80°C.

[0018] Preferably, the dripping time of hydroxyethyl acrylate is 30 minutes.

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

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

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

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

[0023] Preferably, in the step three: 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 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.

[0025] Preferably, in the step three, 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 step 4: 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 invention also discloses a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film prepared by adopting the method for preparing the weather-resistant, wear-resistant and fold-resistant white PMMA transparent film.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] In the present invention, PMMA is used as a resin matrix to prepare a film material, and the prepared PMMA film has high transparency. The PMMA film has a three-layer structure, and polyurethane acrylate is added to the three-layer film as a toughening material. Since the polyurethane acrylate structure has a highly polar group, it has good compatibility with PMMA and 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 limited, and the PMMA film can maintain a high transparency; the addition of epoxy resin in the surface film can improve the surface hardness of the PMMA film, thereby improving the wear resistance of the PMMA film; the addition of antioxidants in the surface film and the bottom film can improve the heat-oxidative 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, and the molecular chain 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 easy to rotate and has good flexibility. It can not only increase toughness, but also easily entangle with the PMMA molecular chain, which can not only destroy the regularity of the PMMA molecular chain and reduce the crystallinity of PMMA, but also effectively terminate silver streaks and prevent them from growing into microcracks, thereby improving the whitening phenomenon of the PMMA film; at the same time, when subjected to stress, it can be deformed by segment migration, inhibiting the generation of silver streaks and holes, while consuming energy, and further reducing the whitening phenomenon of the PMMA film;

[0032] The polyurethane acrylate in the present invention is subjected to modification treatment, and the carbon-carbon double bond contained in the polyurethane acrylate reacts with the carbon-carbon double bond in the ultraviolet absorber 4-propyleneoxy-2-hydroxybenzophenone molecule under the action of an initiator, so that 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 ultraviolet absorber has high compatibility and uniform dispersion in PMMA, thereby improving the weather resistance of the PMMA film, and effectively preventing the migration of the ultraviolet absorber, thereby further improving the weather resistance of the PMMA film.

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

[0034] Figure 1 is a process flow chart for preparing the modified polyurethane acrylate of the present invention;

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

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

[0037] Figure 4 It is a bar chart showing the test results of the anti-whitening performance of the PMMA transparent films prepared in Examples 1-5 of the present invention and Comparative Examples 1-3. DETAILED DESCRIPTION

[0038] Example 1

[0039] This embodiment discloses a method for preparing a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film, comprising the following steps:

[0040] Step 1, adding toluene diisocyanate, polyether polyol and dibutyltin dilaurate to benzene, stirring at a stirring speed of 100 r / min until dibutyltin dilaurate is completely dissolved, heating to 55°C, reacting at 55°C for 3.5 hours, and after the reaction is completed, heating to 70°C, adding hydroxyethyl acrylate dropwise for 30 minutes, and after the addition is completed, continuing to react at 70°C for 4.5 hours. After the reaction is completed, cooling to room temperature to obtain a polyurethane acrylate solution;

[0041] The molar ratio of toluene diisocyanate, polyether polyol and hydroxyethyl acrylate is 1.1:1:0.2; the amount of benzene is 6 times the mass of toluene diisocyanate and polyether polyol; the amount of dibutyltin dilaurate added is 0.1% of the mass of toluene diisocyanate and polyether polyol;

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

[0043] Adding 4-propyleneoxy-2-hydroxybenzophenone solution and benzoyl peroxide to the polyurethane acrylate solution, the mass ratio of the polyurethane acrylate solution, the 4-propyleneoxy-2-hydroxybenzophenone solution, and the benzoyl peroxide is 800:50:0.4, heating to 90°C, reacting at 90°C for 2 hours, and after the reaction, firstly removing benzene by rotary evaporation at 55°C, and then removing toluene by rotary evaporation at 75°C, washing the product after rotary evaporation with ethanol 3 times, and drying it in a vacuum drying oven at 50°C for 10 hours to obtain modified polyurethane acrylate;

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

[0045] Mixing polymethyl methacrylate and modified polyurethane acrylate in a mass ratio of 100:20, and melting them at 170° C. to obtain an intermediate layer melt;

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

[0047] Step 4: Extruding the surface layer melt, the middle layer melt and the bottom layer melt through a three-layer co-extruder at a die head temperature of 190° C. to obtain a weather-resistant, wear-resistant and anti-folding white PMMA transparent film;

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

[0049] The PMMA transparent film comprises 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.

[0050] Example 2

[0051] This embodiment discloses a method for preparing a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film, comprising the following steps:

[0052] Step 1, adding toluene diisocyanate, polyether polyol and dibutyltin dilaurate to benzene, stirring at a stirring speed of 100 r / min until dibutyltin dilaurate is completely dissolved, heating to 65°C, reacting at 55°C for 2.5 hours, and after the reaction is completed, heating to 80°C, and dripping hydroxyethyl acrylate for 30 minutes. After the dripping is completed, continuing to react at 80°C for 3.5 hours, and after the reaction is completed, cooling to room temperature to obtain a polyurethane acrylate solution;

[0053] The molar ratio of toluene diisocyanate, polyether polyol and hydroxyethyl acrylate is 1.2:1:0.4; the amount of benzene is 10 times the mass of toluene diisocyanate and polyether polyol; the amount of dibutyltin dilaurate added is 0.3% of the mass of toluene diisocyanate and polyether polyol;

[0054] Step 2, adding 4-propyleneoxy-2-hydroxybenzophenone to toluene, stirring at a stirring speed of 100 r / min until completely dissolved, the mass ratio of 4-propyleneoxy-2-hydroxybenzophenone to toluene is 25:500, to obtain a 4-propyleneoxy-2-hydroxybenzophenone solution;

[0055] Adding 4-propyleneoxy-2-hydroxybenzophenone solution and benzoyl peroxide to the polyurethane acrylate solution, the mass ratio of the polyurethane acrylate solution, the 4-propyleneoxy-2-hydroxybenzophenone solution, and the benzoyl peroxide is 1000:80:0.6, heating to 100°C, reacting at 100°C for 1 hour, after the reaction is completed, firstly removing benzene by rotary evaporation at 55°C, and then removing toluene by rotary evaporation at 75°C, washing the product after rotary evaporation with ethanol 3 times, and drying it in a vacuum drying oven at 50°C for 10 hours to obtain modified polyurethane acrylate;

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

[0057] Mixing polymethyl methacrylate and modified polyurethane acrylate in a mass ratio of 100:25, and melting them at 180° C. to obtain an intermediate layer melt;

[0058] The polymethyl methacrylate, modified polyurethane acrylate, antioxidant tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester and the polymethyl methacrylate, modified polyurethane acrylate, antioxidant tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester are melted at a temperature of 180° C. to obtain a bottom layer melt;

[0059] Step 4: Extruding the surface layer melt, the middle layer melt and the bottom layer melt through a three-layer co-extruder at a die head temperature of 200° C. to obtain a weather-resistant, wear-resistant and anti-folding white PMMA transparent film;

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

[0061] The PMMA transparent film comprises 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 embodiment discloses a method for preparing a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film, comprising the following steps:

[0064] Step 1, adding toluene diisocyanate, polyether polyol and dibutyltin dilaurate to benzene, stirring at a stirring speed of 100 r / min until dibutyltin dilaurate is completely dissolved, heating to 60°C, reacting at 60°C for 3 hours, and after the reaction is completed, heating to 75°C, adding hydroxyethyl acrylate dropwise for 30 minutes, and after the addition is completed, continuing to react at 75°C for 3 hours. After the reaction is completed, cooling to room temperature to obtain a polyurethane acrylate solution;

[0065] The molar ratio of toluene diisocyanate, polyether polyol and hydroxyethyl acrylate is 1.13:1:0.25; the amount of benzene is 8 times the mass of toluene diisocyanate and polyether polyol; the amount of dibutyltin dilaurate added is 0.2% of the mass of toluene diisocyanate and polyether polyol;

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

[0067] Adding 4-propyleneoxy-2-hydroxybenzophenone solution and benzoyl peroxide to the polyurethane acrylate solution, the mass ratio of the polyurethane acrylate solution, the 4-propyleneoxy-2-hydroxybenzophenone solution, and the benzoyl peroxide is 850:60:0.45, heating to 95°C, reacting at 95°C for 1.5 hours, and after the reaction is completed, firstly removing benzene by rotary evaporation at 55°C, and then removing toluene by rotary evaporation at 75°C, washing the product after rotary evaporation with ethanol three times, and drying it in a vacuum drying oven at 50°C for 10 hours to obtain modified polyurethane acrylate;

[0068] Step 3, polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and antioxidant tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester are mixed, and the mass ratio of polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and antioxidant tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester is 100:21:7:0.25, and melt at a temperature of 175° C. to obtain a surface melt;

[0069] Mixing polymethyl methacrylate and modified polyurethane acrylate in a mass ratio of 100:21, and melting them at a temperature of 175° C. to obtain an intermediate layer melt;

[0070] The polymethyl methacrylate, modified polyurethane acrylate, antioxidant tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester and the polymethyl methacrylate, modified polyurethane acrylate, antioxidant tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester in a mass ratio of 100:21:0.25 are melted at a temperature of 180° C. to obtain a bottom layer melt;

[0071] Step 4: Extruding the surface layer melt, the middle layer melt and the bottom layer melt through a three-layer co-extruder at a die head temperature of 195° C. to obtain a weather-resistant, wear-resistant and anti-folding white PMMA transparent film;

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

[0073] The PMMA transparent film comprises 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.

[0074] Example 4

[0075] This embodiment discloses a method for preparing a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film, comprising the following steps:

[0076] Step 1, adding toluene diisocyanate, polyether polyol and dibutyltin dilaurate to benzene, stirring at a stirring speed of 100 r / min until dibutyltin dilaurate is completely dissolved, heating to 60°C, reacting at 60°C for 3 hours, and after the reaction is completed, heating to 75°C, adding hydroxyethyl acrylate dropwise for 30 minutes, and after the addition is completed, continuing to react at 75°C for 3 hours. After the reaction is completed, cooling to room temperature to obtain a polyurethane acrylate solution;

[0077] The molar ratio of toluene diisocyanate, polyether polyol and hydroxyethyl acrylate is 1.15:1:0.3; the amount of benzene is 8 times the mass of toluene diisocyanate and polyether polyol; the amount of dibutyltin dilaurate added is 0.2% of the mass of toluene diisocyanate and polyether polyol;

[0078] Step 2, adding 4-propyleneoxy-2-hydroxybenzophenone to toluene, stirring at a stirring speed of 100 r / min until completely dissolved, the mass ratio of 4-propyleneoxy-2-hydroxybenzophenone to toluene is 25:400, to obtain a 4-propyleneoxy-2-hydroxybenzophenone solution;

[0079] Adding 4-propyleneoxy-2-hydroxybenzophenone solution and benzoyl peroxide to the polyurethane acrylate solution, the mass ratio of the polyurethane acrylate solution, the 4-propyleneoxy-2-hydroxybenzophenone solution, and the benzoyl peroxide is 900:65:0.5, heating to 95°C, reacting at 95°C for 1.5 hours, and after the reaction is completed, firstly removing benzene by rotary evaporation at 55°C, and then removing toluene by rotary evaporation at 75°C, washing the product after rotary evaporation with ethanol 3 times, and drying it in a vacuum drying oven at 50°C for 10 hours to obtain modified polyurethane acrylate;

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

[0081] Mixing polymethyl methacrylate and modified polyurethane acrylate in a mass ratio of 100:22.5, and melting them at a temperature of 175° C. to obtain an intermediate layer melt;

[0082] The polymethyl methacrylate, modified polyurethane acrylate, antioxidant tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester and the polymethyl methacrylate, modified polyurethane acrylate, antioxidant tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester are melted at a temperature of 180° C. to obtain a bottom layer melt;

[0083] Step 4: Extruding the surface layer melt, the middle layer melt and the bottom layer melt through a three-layer co-extruder at a die head temperature of 195° C. to obtain a weather-resistant, wear-resistant and anti-folding white PMMA transparent film;

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

[0085] The PMMA transparent film comprises 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 embodiment discloses a method for preparing a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film, comprising the following steps:

[0088] Step 1, adding toluene diisocyanate, polyether polyol and dibutyltin dilaurate to benzene, stirring at a stirring speed of 100 r / min until dibutyltin dilaurate is completely dissolved, heating to 60°C, reacting at 60°C for 3 hours, and after the reaction is completed, heating to 75°C, adding hydroxyethyl acrylate dropwise for 30 minutes, and after the addition is completed, continuing to react at 75°C for 3 hours. After the reaction is completed, cooling to room temperature to obtain a polyurethane acrylate solution;

[0089] The molar ratio of toluene diisocyanate, polyether polyol and hydroxyethyl acrylate is 1.18:1:0.35; the amount of benzene is 8 times the mass of toluene diisocyanate and polyether polyol; the amount of dibutyltin dilaurate added is 0.2% of the mass of toluene diisocyanate and polyether polyol;

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

[0091] Adding 4-propyleneoxy-2-hydroxybenzophenone solution and benzoyl peroxide to the polyurethane acrylate solution, the mass ratio of the polyurethane acrylate solution, the 4-propyleneoxy-2-hydroxybenzophenone solution, and the benzoyl peroxide is 950:70:0.55, heating to 95°C, reacting at 95°C for 1.5 hours, and after the reaction is completed, firstly removing benzene by rotary evaporation at 55°C, and then removing toluene by rotary evaporation at 75°C, washing the product after rotary evaporation with ethanol three times, and drying it in a vacuum drying oven at 50°C for 10 hours to obtain modified polyurethane acrylate;

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

[0093] Mixing polymethyl methacrylate and modified polyurethane acrylate in a mass ratio of 100:24, and melting them at a temperature of 175° C. to obtain an intermediate layer melt;

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

[0095] Step 4: Extruding the surface layer melt, the middle layer melt and the bottom layer melt through a three-layer co-extruder at a die head temperature of 195° C. to obtain a weather-resistant, wear-resistant and anti-folding white PMMA transparent film;

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

[0097] The PMMA transparent film comprises 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.

[0098] Comparative Example 1

[0099] This comparative example discloses a method for preparing a PMMA transparent film, comprising 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, heat to 65°C, react at 55°C for 2.5 hours, after the reaction is completed, heat to 80°C, add hydroxyethyl acrylate dropwise for 30 minutes, after the addition is completed, continue to react at 80°C for 3.5 hours, after the reaction is completed, remove benzene by rotary evaporation at 55°C, place in a 50°C vacuum drying oven and dry for 10 hours to obtain polyurethane acrylate;

[0101] The molar ratio of toluene diisocyanate, polyether polyol and hydroxyethyl acrylate is 1.2:1:0.4; the amount of benzene is 10 times the mass of toluene diisocyanate and polyether polyol; the amount of dibutyltin dilaurate added is 0.3% of the mass of toluene diisocyanate and polyether polyol;

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

[0103] Mixing polymethyl methacrylate, polyurethane acrylate, and 4-propyleneoxy-2-hydroxybenzophenone in a mass ratio of 100:24:1, and melting at a temperature of 180° C. to obtain an intermediate layer melt;

[0104] Melting polymethyl methacrylate, polyurethane acrylate, 4-propyleneoxy-2-hydroxybenzophenone, antioxidant tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] pentaerythritol ester in a mass ratio of 100:24:1:0.4 at a temperature of 180° C. to obtain a bottom layer melt;

[0105] Step 3: Extruding the surface layer melt, the middle layer melt and the bottom layer melt through a three-layer co-extruder at a die head temperature of 200° C. to obtain a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film;

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

[0107] The PMMA transparent film comprises 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.

[0108] Comparative Example 2

[0109] This comparative example discloses a method for preparing a PMMA transparent film, comprising the following steps:

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

[0111] Mixing polymethyl methacrylate and 4-propyleneoxy-2-hydroxybenzophenone in a mass ratio of 124:1, and melting at a temperature of 180° C. to obtain an intermediate layer melt;

[0112] The mass ratio of polymethyl methacrylate, 4-propyleneoxy-2-hydroxybenzophenone, and antioxidant tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] pentaerythritol ester is 124:1:0.4, and they are melted at a temperature of 180° C. to obtain a bottom layer melt;

[0113] Step 2: Extruding the surface layer melt, the middle layer melt and the bottom layer melt through a three-layer co-extruder at a die head temperature of 200° C. to obtain a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film;

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

[0115] The PMMA transparent film comprises 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.

[0116] Comparative Example 3

[0117] This comparative example discloses a method for preparing a PMMA transparent film, comprising the following steps:

[0118] Step 1, adding toluene diisocyanate, polyether polyol and dibutyltin dilaurate to benzene, stirring at a stirring speed of 100 r / min until dibutyltin dilaurate is completely dissolved, heating to 65°C, reacting at 55°C for 2.5 hours, and after the reaction is completed, heating to 80°C, and dripping hydroxyethyl acrylate for 30 minutes. After the dripping is completed, continuing to react at 80°C for 3.5 hours, and after the reaction is completed, cooling to room temperature to obtain a polyurethane acrylate solution;

[0119] The molar ratio of toluene diisocyanate, polyether polyol and hydroxyethyl acrylate is 1.2:1:0.4; the amount of benzene is 10 times the mass of toluene diisocyanate and polyether polyol; the amount of dibutyltin dilaurate added is 0.3% of the mass of toluene diisocyanate and polyether polyol;

[0120] Step 2, adding 4-propyleneoxy-2-hydroxybenzophenone to toluene, stirring at a stirring speed of 100 r / min until completely dissolved, the mass ratio of 4-propyleneoxy-2-hydroxybenzophenone to toluene is 25:500, to obtain a 4-propyleneoxy-2-hydroxybenzophenone solution;

[0121] Adding 4-propyleneoxy-2-hydroxybenzophenone solution and benzoyl peroxide to the polyurethane acrylate solution, the mass ratio of the polyurethane acrylate solution, the 4-propyleneoxy-2-hydroxybenzophenone solution, and the benzoyl peroxide is 1000:200:0.8, heating to 100°C, reacting at 100°C for 1 hour, and after the reaction, firstly removing benzene by rotary evaporation at 55°C, and then removing toluene by rotary evaporation at 75°C, washing the product after rotary evaporation with ethanol 3 times, and drying it in a vacuum drying oven at 50°C for 10 hours to obtain modified polyurethane acrylate;

[0122] Step 3, polymethyl methacrylate, modified polyurethane acrylate, and antioxidant tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester are mixed, the mass ratio of polymethyl methacrylate, modified polyurethane acrylate, and antioxidant tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester is 110:25:0.4, and melted at a temperature of 180° C. to obtain a surface melt;

[0123] Mixing polymethyl methacrylate and modified polyurethane acrylate in a mass ratio of 100:25, and melting them at 180° C. to obtain an intermediate layer melt;

[0124] The polymethyl methacrylate, modified polyurethane acrylate, antioxidant tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester and the polymethyl methacrylate, modified polyurethane acrylate, antioxidant tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester are melted at a temperature of 180° C. to obtain a bottom layer melt;

[0125] Step 4: Extruding the surface layer melt, the middle layer melt and the bottom layer melt through a three-layer co-extruder at a die head temperature of 200° C. to obtain a weather-resistant, wear-resistant and anti-folding white PMMA transparent film;

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

[0127] The PMMA transparent film comprises 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 embodiments and comparative examples, polyether polyol was purchased from Hai'an Petrochemical Plant in Jiangsu Province, specification: PPG-1500; polymethyl methacrylate was purchased from Shanghai Kewanjia Plastics Co., Ltd., item number: CM-207; transparent epoxy resin is bisphenol A type epoxy resin E-44, purchased from Wuxi Changgan Chemical Co., Ltd., viscosity: 18000-25000 (mPas).

[0129] Test example

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

[0131] (1) Wear resistance: The surface melts in Examples 1-5 and Comparative Examples 1-3 were injection molded into circular specimens with a diameter of 100 mm. The specimens were 10 mm thick and had smooth, flat surfaces without bubbles, mechanical damage or impurities. The wear rates of the specimens were measured in accordance with the standard GB / T 5478-2008 "Test method for rolling wear of plastics". The results are shown in Table 1.

[0132] Table 1

[0133]

[0134] It can be seen from Table 1 that the addition of epoxy resin can effectively improve the wear resistance of the surface layer, thereby improving the wear resistance of the PMMA transparent film. 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 wear 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 light aging test. The total cycle treatment was 168 hours, with each 30 minutes being one cycle (15 minutes of water spraying and light irradiation, and 15 minutes of no water spraying and light irradiation). After the light aging test was completed, the initial thermal degradation temperature of the sample was measured. The measurement results are shown in Table 2:

[0137] Table 2

[0138]

[0139] As shown in Table 2, the PMMA transparent film prepared by the present invention has good weather resistance. The addition of the ultraviolet absorber 4-propyleneoxy-2-hydroxybenzophenone can effectively improve the light aging resistance of the PMMA transparent film. Compared with Example 2, in Comparative Examples 1 and 2, the ultraviolet absorber 4-propyleneoxy-2-hydroxybenzophenone is not connected to the polyurethane acrylate molecule by chemical bonding, and its compatibility and dispersion uniformity in MMA are reduced, the light aging resistance is reduced, the initial thermal degradation temperature is reduced, and the thermal decomposition process is accelerated.

[0140] (3) Anti-whitening performance: The stress whitening (anti-whitening) performance of the PMMA transparent films prepared in Examples 1-5 and Comparative Examples 1-3 was measured with reference to the German Volkswagen PV3966 standard. The sample size was 70×70 mm. A 500 g iron ball was dropped from a height of 1 m to impact the sample. The color difference ΔL of the sample before and after the ball was dropped was compared under a standard light source. The smaller the ΔL, the better the stress whitening performance. 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 anti-whitening performance. 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 easy to rotate 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 easy to entangle with the PMMA molecular chain, destroying the regularity of the PMMA molecular chain, reducing the crystallinity of PMMA, and can effectively terminate silver streaks and prevent them from growing into microcracks, thereby improving the stress whitening phenomenon of the PMMA film. At the same time, when subjected to stress, it can be deformed by segment migration, suppressing the generation of silver streaks and holes, and consuming 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 anti-whitening performance was significantly reduced.

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

Claims

1. A method for preparing a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film, characterized in that: The steps include: Step 1, adding toluene diisocyanate, polyether polyol, and dibutyltin dilaurate into benzene, stirring until dissolved, heating to a first set temperature, reacting, and after the reaction is completed, heating to a second set temperature, dripping hydroxyethyl acrylate, continuing the reaction, and cooling after the reaction is completed to obtain a polyurethane acrylate solution; Step 2, adding 4-propyleneoxy-2-hydroxybenzophenone to toluene, stirring until dissolved, to obtain a 4-propyleneoxy-2-hydroxybenzophenone solution; Adding 4-propyleneoxy-2-hydroxybenzophenone solution and benzoyl peroxide to the polyurethane acrylate solution, heating to a third set temperature, reacting, and after the reaction is completed, rotary evaporating, purifying, and drying to obtain modified polyurethane acrylate; Step 3, polymethyl methacrylate, modified polyurethane acrylate, transparent epoxy resin, and antioxidant tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester are mixed and melted to obtain a surface melt; Mixing polymethyl methacrylate and modified polyurethane acrylate, and melting them to obtain an intermediate layer melt; Melting polymethyl methacrylate, modified polyurethane acrylate, and antioxidant pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate to obtain a bottom melt; Step 4: Extrude the surface layer melt, the middle layer melt and the bottom layer melt through a three-layer co-extrusion extruder to obtain a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film.

2. The method for preparing a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film according to claim 1, characterized in that: In the step 1, the molar ratio of toluene diisocyanate, polyether polyol and hydroxyethyl acrylate is (1.1-1.2):1:(0.2-0.4); the amount of benzene used is 6-10 times the mass sum of toluene diisocyanate and polyether polyol; the amount of dibutyltin dilaurate added is 0.1%-0.3% of the mass sum of toluene diisocyanate and polyether polyol.

3. The method for preparing a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film according to claim 1, characterized in that: In the step 1: the reaction condition is to react at the first set temperature for 2.5-3.5 hours, 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 hours, and the second set temperature is 70-80°C.

4. The method for preparing a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film according to claim 1, characterized in that: In the step 2: the mass ratio of polyurethane acrylate solution, 4-propyleneoxy-2-hydroxybenzophenone solution, and benzoyl peroxide is (800-1000):(50-80):(0.4-0.6); In the 4-propyleneoxy-2-hydroxybenzophenone solution, the mass ratio of 4-propyleneoxy-2-hydroxybenzophenone to toluene is 25:(300-500).

5. The method for preparing a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film according to claim 1, characterized in that: In the step 2: the reaction condition is to react at the third set temperature for 1-2 hours, and the third set temperature is 90-100°C.

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

7. The method for preparing a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film according to claim 1, characterized in that: In the step 3, 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.

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

9. The method for preparing a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film according to claim 1, characterized in that: In the step 4: the head temperature of the three-layer co-extrusion extruder is 190-200° C.; The thickness of the prepared PMMA transparent film is 30-50 μm.

10. A weather-resistant, wear-resistant and fold-resistant white PMMA transparent film prepared by the method for preparing a weather-resistant, wear-resistant and fold-resistant white PMMA transparent film according to any one of claims 1 to 9.

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