Acrylic plate and preparation method thereof

Abstract

The invention discloses an acrylic plate and a preparation method thereof, and relates to the technical field of acrylic plate preparation, and the preparation method comprises the steps of S1, raw material pretreatment, S2, prepolymer preparation, S3, molding and curing, and S4, post-treatment process. The nano-particles are distributed in an acrylic matrix in a gradient mode, specifically, in the pre-polymerization stage, a high-density nano-particle enrichment layer is formed in a surface layer area through concentration gradient regulation and control in the time dimension, and the material is endowed with excellent ultraviolet resistance and photocatalytic self-cleaning performance; the interior of the matrix is kept in a low-concentration dispersion state, high light transmittance and impact toughness of the material are maintained, the surfaces of the nanoparticles are modified by the silane coupling agent and then form covalent bond connection with an acrylic molecular chain, and then the interface bonding strength can be enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of acrylic plate preparation, and particularly relates to an acrylic plate and a preparation method thereof. Background Art

[0002] Acrylic, also known as PMMA or plexiglass, is derived from the English word acrylic (acrylic plastic), and its chemical name is polymethyl methacrylate. Acrylic is a relatively early developed high molecular thermoplastic material, and its processing and molding are relatively convenient. The molding methods of acrylic materials mainly include casting molding and extrusion molding. After the acrylic material is molded, it can also be softened by reheating to form various shapes as needed. Acrylic has good transparency and light transmittance, and its light transmittance can reach 92%. It has good chemical stability and weather resistance, and has strong adaptability to the natural environment.

[0003] The preparation of acrylic plates often adopts the blending method. The conventional blending method is prone to cause agglomeration of nanoparticles, which will not only weaken the light transmittance, but also cause stress concentration points, reduce the toughness of the material, and the requirements for surface anti-ultraviolet and matrix toughening cannot be met simultaneously. In view of the above problems, the following solutions are proposed. Summary of the Invention

[0004] The purpose of the present invention is to provide an acrylic plate and a preparation method thereof. Through staged gradient injection and chemical bonding, the gradient distribution of nanoparticles in the acrylic matrix is achieved, maintaining the toughness and anti-ultraviolet ability of the material, and solving the problem of the decrease in light transmittance caused by existing nanoparticle agglomeration.

[0005] To solve the above technical problems, the present invention is realized through the following technical solutions:

[0006] The present invention provides an acrylic plate, which is composed of the following raw materials in parts by weight: 85 - 95 parts of methyl methacrylate, 0.5 - 3.0 parts of nano-titanium dioxide, 0.5 - 2.0 parts of silane coupling agent, 0.05 - 0.15 parts of AIBN, 1.0 - 3.0 parts of dibutyl phthalate, 0.1 - 0.5 parts of ammonium polyacrylate, 0.2 - 0.8 parts of nano-zinc oxide, and 1.0 - 5.0 parts of fluorosilicone resin;

[0007] The preparation method of the acrylic plate includes the following steps:

[0008] Step S1, raw material pretreatment: Methyl methacrylate is filtered through a filter membrane and dehydrated by a molecular sieve to ensure purity, graft-modified under a buffer solution and temperature, a gradient dispersion liquid is prepared and ultrasonically treated;

[0009] Step S2, prepolymer preparation: The initiator is mixed with the raw materials for prepolymerization. The oxygen content is controlled by a nitrogen bubbling device and a sensor. The nano-slurry is accurately injected in a gradient manner using a double-plunger metering pump and a spiral deflector, and the rotation speed is adjusted according to the viscosity.

[0010] Step S3, molding and curing: After the mold is polished, a release agent is sprayed and the film thickness is controlled. The liquid material is injected into the mold at a specific temperature and polymerized according to a gradient heating program. The internal stress is eliminated through multiple temperature compensation zones and staged pressure release.

[0011] Step S4, post-treatment process: Ultrasonic waves are applied during hot pressing, the distance is adjusted during plasma treatment, a surface energy gradient is constructed by stepwise heating during the curing of fluorosilicone resin, and finally UV curing is performed.

[0012] The specific steps of the raw material pretreatment in the step S1 are as follows:

[0013] Step S11, purification of methyl methacrylate: Filter methyl methacrylate through a PTFE filter membrane with a pore size of 0.22 μm to remove the inhibitor. At the same time, use an online viscometer to control the filtration speed ≤ 0.5 L / min, add 3‰ of 4A molecular sieve for dehydration for 24 hours. The molecular sieve needs to be calcined at 350 °C for 4 hours in advance and then cooled under nitrogen protection to ensure that the monomer purity reaches the polymerization grade (moisture ≤ 50 ppm, inhibitor ≤ 3 ppm).

[0014] Step S12, surface modification of nano-TiO2: The surface of nano-TiO2 is grafted through a silane coupling agent KH570. The silane is hydrolyzed in an acetic acid buffer solution with pH = 4.5 for 45 min, and the grafting reaction is carried out under the condition of constant temperature magnetic stirring at 60 ± 2 °C to ensure that the hydroxyl grafting rate ≥ 85%, preventing the secondary aggregation of nanoparticles.

[0015] Step S13, preparation of concentration gradient dispersion liquid: Prepare nano-TiO2 dispersion liquids with concentrations of 0.5 wt%, 1.0 wt%, and 1.5 wt% respectively, ultrasonically treat for 30 minutes. The ultrasonic probe uses a titanium alloy horn, and 0.1% ammonium polyacrylate dispersant is added to make the Zeta potential of the slurry stable above -35 mV, and there is no sedimentation after storage for 72 hours.

[0016] Furthermore, the online viscometer adopts the model Brookfield DV2T and is installed on the pipeline downstream of the PTFE filter membrane group, 15 ± 2 cm away from the inlet of the molecular sieve filling tank.

[0017] The ultrasonic treatment uses a power of 500 W and a frequency of 40 kHz.

[0018] The diameter Φ of the titanium alloy horn is 20 mm.

[0019] The weight-average molecular weight Mw of the ammonium polyacrylate dispersant is 5000.

[0020] Furthermore, the preparation of the prepolymer in step S2 specifically includes the following steps:

[0021] Step S21, construction of the initiation system: Premix 0.08% AIBN initiator with purified methyl methacrylate, add 0.5% dibutyl phthalate plasticizer, stir in a 75°C water bath, and pre-polymerize until the conversion rate reaches 35%;

[0022] Step S22, oxygen inhibition elimination system: The prepolymerization reaction kettle is equipped with a three-channel nitrogen bubbling device, and the oxygen content is monitored in real time by a Mettler Toledo InPro6050 sensor to ensure that the oxygen concentration in the kettle ≤ 10 ppm, avoiding premature gelation of the prepolymer;

[0023] Step S23, gradient dispersion process: Inject the nano-slurry in three stages. Add 0.5 wt% low-concentration slurry at the initial stage of prepolymerization; inject 1.0 wt% medium-concentration slurry when the conversion rate reaches 15%; add 1.5 wt% high-concentration slurry when the conversion rate reaches 25%. After each injection, perform high-speed shear dispersion at 2000 rpm for 10 minutes, use a double-plunger metering pump for gradient injection, and set a spiral deflector at the injection port, thereby controlling the gradient difference of nanoparticle distribution within ±5%;

[0024] Step S24, viscosity closed-loop regulation: Online monitor the viscosity of the prepolymer. When the viscosity rises by 100 cP each time, increase the rotation speed by 200 rpm to maintain the viscosity of the system within the optimal processing window of 800 - 1200 cP.

[0025] Furthermore, the Mettler Toledo InPro6050 sensor is installed in the center of the reaction kettle top cover, and the end of the probe is 50 ± 5 mm away from the liquid level;

[0026] The flow accuracy of the double-plunger metering pump is ±0.1 mL / min;

[0027] The lead angle of the spiral deflector is 55°;

[0028] In step S24, viscosity closed-loop regulation, the online viscometer used for online monitoring of the prepolymer viscosity is of the Rheonics SRV model and is installed in the pipeline between the reaction kettle outlet and the static mixer.

[0029] Furthermore, the molding and curing in step S3 specifically includes the following steps:

[0030] Step S31. Mold pretreatment: Select a chromium-plated stainless steel mold, perform electrochemical polishing until the surface roughness Ra = 0.08 μm, then spray a silicone oil emulsion containing 0.1% nano-zinc oxide as a release agent, and use a white light interferometer to detect the film thickness of the release agent, controlling it within 12 ± 2 μm to obtain a mirror-level surface (glossiness ≥ 95 GU);

[0031] Step S32. Pouring and polymerization: Inject the material into the mold when the material temperature is controlled at 40 - 45 °C, and adopt a gradient heating program: maintain at a temperature of 50 °C for 2 hours, then raise the temperature to 60 °C and maintain for 4 hours, and finally raise the temperature to 80 °C and maintain for 2 hours; Set 6 temperature compensation zones to control the polymerization reaction kinetics, pressurize to 0.8 MPa to eliminate interfacial defects, and then release the pressure in stages, from 0.8 MPa to 0.5 MPa and maintain for 30 minutes, from 0.5 MPa to 0.2 MPa and maintain for 30 minutes, and finally completely release to atmospheric pressure to eliminate internal stress (birefringence ≤ 30 nm / cm).

[0032] Furthermore, the post-treatment process in step S4 specifically includes the following steps:

[0033] Step S41. Hot pressing and strengthening: Perform three-stage hot pressing at 120 °C, that is, the initial pressure of 5 MPa is maintained for 10 min, the final pressure of 12 MPa is maintained for 15 min, and finally the pressure is released and rebounds. During the hot pressing process, ultrasonic waves of 20 kHz are applied synchronously with an amplitude of 15 μm, and a porous template is used to assist in exhaust, which can reduce the porosity and improve the tensile strength;

[0034] Step S42. Surface functionalization: Perform plasma treatment, and dynamically adjust the treatment distance during the treatment process; then spray a fluorosilicone resin protective layer with a thickness of 50 μm. The fluorosilicone resin is cured using a stepped temperature increase, so that the surface gradually transitions from 38 mN / m to 22 mN / m, and finally UV curing is performed.

[0035] Furthermore, the pore diameter Φ of the porous template is 0.5 mm, and the porosity is 30%;

[0036] The gas used for the plasma treatment is argon, the power is set to 200 watts, and it lasts for 5 min;

[0037] The treatment distance changes dynamically, gradually adjusting from the initial 10 mm to 5 mm, and finally becoming 2 mm;

[0038] The stepped temperature increase means that when the fluorosilicone resin is cured, it passes through three temperature stages of 80 °C, 100 °C, and 120 °C in sequence;

[0039] The UV curing uses ultraviolet light with a wavelength of 365 nm and an energy density of 800 mJ / cm 2 。

[0040] The present invention has the following beneficial effects:

[0041] 1. Through staged gradient injection and chemical bonding operations, the present invention realizes the gradient distribution of nanoparticles in the acrylic matrix. Specifically, in the pre-polymerization stage, through the concentration gradient regulation in the time dimension, a high-density nanoparticle enrichment layer is formed in the surface layer region, endowing the material with excellent anti-ultraviolet and photocatalytic self-cleaning properties; while the interior of the matrix maintains a low-concentration dispersion state, maintaining the high light transmittance and impact resistance of the material. After the surface of the nanoparticles is modified with a silane coupling agent, covalent bonds are formed with the acrylic molecular chains, thereby enhancing the interfacial bonding strength.

[0042] 2. By combining gradient temperature rise polymerization and staged pressure relief processes, the present invention can effectively eliminate the internal stress generated by polymerization shrinkage, inhibit the initiation of microcracks, and ensure the dimensional stability of the plate under extreme temperature differences or mechanical loads; in addition, the composite surface treatment technology of plasma activation and fluorosilicone resin coating constructs an energy gradient transition interface from the matrix to the outer layer: plasma etching forms micro-nano structures to enhance the coating adhesion, while the fluororesin endows the material with superhydrophilic and antifouling functions through its low surface energy characteristics; this dual surface engineering enables the plate to maintain self-cleaning efficiency during long-term outdoor exposure, avoids the performance decline caused by interface failure of traditional coatings, and extends the service life.

[0043] Of course, it is not necessary for any product implementing the present invention to achieve all the above-mentioned advantages simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0045] Figure 1 It is a schematic flow chart of an acrylic plate and its preparation method according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0047] Please refer to Figure 1As shown in the figure, the present invention relates to an acrylic plate, which is composed of the following raw materials by weight: 85-95 parts of methyl methacrylate, 0.5-3.0 parts of nano-titanium dioxide, 0.5-2.0 parts of silane coupling agent, 0.05-0.15 parts of AIBN, 1.0-3.0 parts of dibutyl phthalate, 0.1-0.5 parts of ammonium polyacrylate, 0.2-0.8 parts of nano-zinc oxide, and 1.0-5.0 parts of fluorosilicone resin;

[0048] A method for preparing an acrylic plate includes the following steps:

[0049] Step S1, raw material pretreatment: Methyl methacrylate is filtered through a filter membrane and dehydrated by a molecular sieve to ensure purity, graft-modified under buffer solution and temperature conditions, a gradient dispersion liquid is prepared and ultrasonic treatment is carried out;

[0050] Step S2, prepolymer preparation: The initiator is mixed with the raw materials for prepolymerization, the oxygen content is controlled by a nitrogen bubbling device and a sensor, the nano-slurry is accurately injected in a gradient manner by a double-plunger metering pump and a spiral deflector, and the rotation speed is adjusted according to the viscosity;

[0051] Step S3, molding and curing: After the mold is polished, a release agent is sprayed and the film thickness is controlled. The liquid material is injected into the mold at a specific temperature, polymerized according to a gradient heating program, and the internal stress is eliminated through a multi-temperature compensation zone and staged pressure release;

[0052] Step S4, post-treatment process: Ultrasonic waves are applied during hot pressing, the distance is adjusted during plasma treatment, the fluorosilicone resin is cured by stepwise heating to construct a surface energy gradient, and finally UV curing is carried out;

[0053] Step S1, the raw material pretreatment specifically includes the following steps:

[0054] Step S11, purification of methyl methacrylate: Methyl methacrylate is filtered through a PTFE filter membrane with a pore size of 0.22 μm to remove the inhibitor. At the same time, an online viscometer is used to control the filtration speed ≤ 0.5 L / min, and 3‰ of 4A molecular sieve is added for dehydration for 24 hours. The molecular sieve is pre-calcined at 350 °C for 4 hours and then cooled under nitrogen protection;

[0055] Step S12, surface modification of nano-TiO2: The surface of nano-TiO2 is grafted through silane coupling agent KH570. The silane is hydrolyzed in an acetic acid buffer solution with pH = 4.5 for 45 min, and the grafting reaction is carried out under the condition of constant temperature magnetic stirring at 60 ± 2 °C;

[0056] Step S13, preparation of concentration gradient dispersion liquid: Nano-TiO2 dispersion liquids with concentrations of 0.5 wt%, 1.0 wt%, and 1.5 wt% are prepared, ultrasonic treatment is carried out for 30 minutes, the ultrasonic probe uses a titanium alloy horn, and 0.1% ammonium polyacrylate dispersant is added.

[0057] The on-line viscometer uses the model Brookfield DV2T and is installed on the pipeline downstream of the PTFE filter membrane group, 15 ± 2 cm away from the inlet of the molecular sieve filling tank;

[0058] The ultrasonic treatment uses a power of 500 W and a frequency of 40 kHz;

[0059] The diameter Φ of the titanium alloy horn is 20 mm;

[0060] The weight-average molecular weight Mw of the ammonium polyacrylate dispersant is 5000.

[0061] Step S2, the preparation of the prepolymer specifically includes the following steps:

[0062] Step S21, construction of the initiation system: Premix 0.08% AIBN initiator with purified methyl methacrylate, add 0.5% dibutyl phthalate plasticizer, stir in a 75 °C water bath, and pre-polymerize until the conversion rate reaches 35%;

[0063] Step S22, oxygen inhibition elimination system: The prepolymerization reaction kettle is equipped with a three-channel nitrogen bubbling device, and the oxygen content is monitored in real time by a Mettler Toledo InPro6050 sensor;

[0064] Step S23, gradient dispersion process: Inject the nano-slurry in three stages. At the initial stage of prepolymerization, incorporate 0.5 wt% low-concentration slurry; inject 1.0 wt% medium-concentration slurry when the conversion rate reaches 15%; add 1.5 wt% high-concentration slurry when the conversion rate reaches 25%. After each injection, perform high-speed shear dispersion at 2000 rpm for 10 minutes, use a double-plunger metering pump for gradient injection, and set a spiral flow guide at the injection port;

[0065] Step S24, viscosity closed-loop regulation: Monitor the viscosity of the prepolymer online. When the viscosity rises by 100 cP each time, increase the rotation speed by 200 rpm to maintain the system viscosity at 800 - 1200 cP.

[0066] The Mettler Toledo InPro6050 sensor is installed in the center of the reaction kettle top cover, and the end of the probe is 50 ± 5 mm away from the liquid level;

[0067] The flow accuracy of the double-plunger metering pump is ±0.1 mL / min;

[0068] The lead angle of the spiral flow guide is 55°;

[0069] Step S24, in the viscosity closed-loop regulation, the on-line viscometer used for on-line monitoring of the prepolymer viscosity is of the model Rheonics SRV and is installed on the pipeline between the reaction kettle outlet and the static mixer.

[0070] Step S3, molding and curing specifically includes the following steps:

[0071] Step S31, Mold pretreatment: Select a chromium-plated stainless steel mold, perform electrochemical polishing until the surface roughness Ra = 0.08 μm, then spray a silicone oil emulsion containing 0.1% nano-zinc oxide as a release agent, and use a white light interferometer to detect the film thickness of the release agent, controlling it within 12 ± 2 μm;

[0072] Step S32, Pouring and polymerization: Inject into the mold when the material temperature is controlled at 40 - 45 °C, and adopt a gradient heating program: maintain at 50 °C for 2 hours, then raise the temperature to 60 °C and maintain for 4 hours, and finally raise the temperature to 80 °C and maintain for 2 hours; Set 6 temperature compensation zones to control the polymerization reaction kinetics, pressurize to 0.8 MPa to eliminate interface defects, and then release the pressure in stages, from 0.8 MPa to 0.5 MPa and maintain for 30 minutes, from 0.5 MPa to 0.2 MPa and maintain for 30 minutes, and finally completely release to atmospheric pressure.

[0073] Step S4, The post-treatment process specifically includes the following steps:

[0074] Step S41, Hot pressing and strengthening: Perform three-stage hot pressing at 120 °C, that is, the initial pressure of 5 MPa is maintained for 10 min, the final pressure of 12 MPa is maintained for 15 min, and finally the pressure is released and rebounds. During the hot pressing process, apply 20 kHz ultrasonic waves with an amplitude of 15 μm, and use a porous template to assist in exhausting air;

[0075] Step S42, Surface functionalization: Perform plasma treatment, and dynamically adjust the treatment distance during the process; Then spray a fluorosilicone resin protective layer with a thickness of 50 μm. The curing of the fluorosilicone resin adopts a stepped temperature increase, so that the surface gradually transitions from 38 mN / m to 22 mN / m, and finally perform UV curing.

[0076] The pore diameter Φ of the porous template is 0.5 mm, and the porosity is 30%;

[0077] The gas used for plasma treatment is argon, the power is set at 200 watts, and it lasts for 5 min;

[0078] The treatment distance is dynamically changed, gradually adjusted from the initial 10 mm to 5 mm, and finally becomes 2 mm;

[0079] Stepped temperature increase means that during the curing of the fluorosilicone resin, it successively passes through three temperature stages of 80 °C, 100 °C, and 120 °C;

[0080] UV curing uses ultraviolet light with a wavelength of 365 nm and an energy density of 800 mJ / cm 2 。

[0081] A specific application of this embodiment is:

[0082] Step S1. Raw material pretreatment:

[0083] Step S11. Purification of methyl methacrylate: Filter methyl methacrylate through a PTFE membrane with a pore size of 0.22 μm to remove inhibitors. At the same time, use an online viscometer to control the filtration rate ≤ 0.5 L / min, add 3‰ of 4A molecular sieve for dehydration for 24 hours. The molecular sieve is pre-calcined at 350 °C for 4 hours and then cooled under nitrogen protection.

[0084] Step S12. Surface modification of nano-TiO₂: Graft the surface of nano-TiO₂ through silane coupling agent KH570. Hydrolyze the silane in an acetic acid buffer solution with pH = 4.5 for 45 min, and carry out the grafting reaction under the condition of constant temperature magnetic stirring at 60 ± 2 °C.

[0085] Step S13. Prepare concentration gradient dispersions: Prepare nano-TiO₂ dispersions with concentrations of 0.5 wt%, 1.0 wt%, and 1.5 wt% respectively, ultrasonically treat for 30 minutes. The ultrasonic probe uses a titanium alloy horn, and add 0.1% ammonium polyacrylate dispersant.

[0086] Step S2. Preparation of prepolymer:

[0087] Step S21. Construction of initiation system: Premix 0.08% AIBN initiator with purified methyl methacrylate, add 0.5% dibutyl phthalate plasticizer, stir in a 75 °C water bath, and pre-polymerize to a conversion rate of 35%.

[0088] Step S22. Oxygen inhibition elimination system: The pre-polymerization reaction kettle is equipped with a three-channel nitrogen bubbling device, and use a Mettler Toledo InPro6050 sensor to monitor the oxygen content in real time.

[0089] Step S23. Gradient dispersion process: Inject nano-slurry in three stages. Inject 0.5 wt% low-concentration slurry at the initial stage of pre-polymerization; inject 1.0 wt% medium-concentration slurry when the conversion rate reaches 15%; add 1.5 wt% high-concentration slurry when the conversion rate reaches 25%. After each injection, carry out high-speed shear dispersion at 2000 rpm for 10 minutes, use a double-plunger metering pump for gradient injection, and set a spiral flow guide at the feeding port.

[0090] Step S24. Viscosity closed-loop regulation: Monitor the viscosity of the prepolymer online. When the viscosity rises by 100 cP each time, increase the rotation speed by 200 rpm to maintain the system viscosity at 800 - 1200 cP.

[0091] Step S3. Molding and curing:

[0092] Step S31, Mold pretreatment: Select a chromium-plated stainless steel mold, electrochemically polish it until the surface roughness Ra = 0.08 μm, then spray a silicone oil emulsion containing 0.1% nano-zinc oxide as a release agent, and use a white light interferometer to detect the film thickness of the release agent, controlling it within 12 ± 2 μm;

[0093] Step S32, Pouring and polymerization: Inject the material into the mold when the material temperature is controlled at 40 - 45 °C, and adopt a gradient heating program: maintain at a temperature of 50 °C for 2 hours, then raise the temperature to 60 °C and maintain for 4 hours, and finally raise the temperature to 80 °C and maintain for 2 hours; Set 6 temperature compensation zones to control the polymerization reaction kinetics, pressurize to 0.8 MPa to eliminate interface defects, and then release the pressure in stages, from 0.8 MPa to 0.5 MPa and maintain for 30 minutes, from 0.5 MPa to 0.2 MPa and maintain for 30 minutes, and finally completely release to atmospheric pressure;

[0094] Step S4, Post-treatment process:

[0095] Step S41, Hot pressing and strengthening: Conduct three-stage hot pressing at 120 °C, that is, the initial pressure of 5 MPa is maintained for 10 min, the final pressure of 12 MPa is maintained for 15 min, and finally the pressure is released and rebounds. During the hot pressing process, apply 20 kHz ultrasonic waves with an amplitude of 15 μm, and use a porous template to assist in exhausting air;

[0096] Step S42, Surface functionalization: Conduct plasma treatment and dynamically adjust the treatment distance during the process; Then spray a fluorosilicone resin protective layer with a thickness of 50 μm. The fluorosilicone resin is cured using a stepped temperature rise to make the surface transition from 38 mN / m to 22 mN / m in a gradient manner, and finally conduct UV curing;

[0097] Taking the preparation of a 1m × 2m × 5mm plate as an example:

[0098] Raw material treatment: Co-hydrolyze tetrabutyl titanate (0.5 mol / L) and silane coupling agent KH570 (3 wt%) in ethanol / water (volume ratio 4:1), and disperse it by 40 kHz ultrasonic for 30 minutes to form a modified nano-TiO2 slurry (particle size D50 = 50 nm);

[0099] Gradient pre-polymerization: Under nitrogen protection at 75 °C, pre-polymerize purified methyl methacrylate with 0.08% AIBN initiator to a conversion rate of 15%, and inject 0.5%, 1.0%, and 1.5% TiO2 slurry in three times. After each injection, perform high-speed shearing at 2000 rpm for 10 minutes;

[0100] Hydrothermal forming: Inject the pre-polymer into a chromium-plated mold, and polymerize for 8 hours using a gradient temperature rise (50 °C → 80 °C). Apply a pressure of 0.8 MPa during the period to eliminate bubbles;

[0101] Function enhancement: The cured plate is subjected to hot pressing treatment at 120 °C / 12 MPa, and then the surface is activated with Ar plasma (200 W, 5 min), sprayed with fluorosilicone resin (thickness 50 μm) and UV cured.

[0102] The obtained plate has a light transmittance of ≥ 92% (550 nm), a yellowing index ΔYI = 1.8 after 3000 hours of QUV aging, and a water contact angle of 12°. Through gradient dispersion and interface regulation, a functional gradient distribution of nanoparticles is achieved.

[0103] In the description of this specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0104] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. An acrylic sheet, characterized in that, By weight, it consists of the following raw materials: 85 - 95 parts of methyl methacrylate, 0.5 - 3.0 parts of nano-titanium dioxide, 0.5 - 2.0 parts of silane coupling agent, 0.05 - 0.15 parts of AIBN, 1.0 - 3.0 parts of dibutyl phthalate, 0.1 - 0.5 parts of ammonium polyacrylate, 0.2 - 0.8 parts of nano-zinc oxide, and 1.0 - 5.0 parts of fluorosilicone resin.

2. A preparation method of an acrylic plate, adopting the preparation method of an acrylic plate described in claim 1, characterized in that, It includes the following steps: Step S1, raw material pretreatment: Methyl methacrylate is filtered through a membrane filter and dehydrated with a molecular sieve to ensure purity, graft-modified under buffer solution and temperature conditions, a gradient dispersion liquid is prepared and ultrasonically treated; Step S2, prepolymer preparation: The initiator is mixed with the raw materials for prepolymerization, the oxygen content is controlled by a nitrogen bubbling device and a sensor, nano-slurry is accurately injected in a gradient manner using a double-plunger metering pump and a spiral flow guide, and the rotation speed is adjusted according to the viscosity; Step S3, molding and curing: After the mold is polished, a release agent is sprayed and the film thickness is controlled. The liquid material is injected into the mold at a specific temperature, polymerized according to a gradient heating program, and internal stress is eliminated through a multi-temperature compensation zone and staged pressure release; Step S4, post-treatment process: Ultrasonic waves are applied during hot pressing, the distance is adjusted during plasma treatment, the fluorosilicone resin is cured by stepwise heating to construct a surface energy gradient, and finally UV curing is carried out; The specific steps of the said Step S1, raw material pretreatment include the following steps: Step S11, purification of methyl methacrylate: Methyl methacrylate is filtered through a PTFE filter membrane with a pore size of 0.22 μm to remove the inhibitor, and at the same time, an online viscometer is used to control the filtration speed ≤ 0.5 L / min. 3‰ of 4A molecular sieve is added for dehydration for 24 hours. The molecular sieve is pre-calcined at 350 °C for 4 hours and then cooled under nitrogen protection; Step S12, surface modification of nano-TiO2: The surface of nano-TiO2 is grafted through the silane coupling agent KH570. The silane is hydrolyzed in an acetic acid buffer solution with pH = 4.5 for 45 min, and the grafting reaction is carried out under the condition of constant temperature magnetic stirring at 60 ± 2 °C; Step S13, preparation of concentration gradient dispersion liquid: Nano-TiO2 dispersion liquids with concentrations of 0.5 wt%, 1.0 wt%, and 1.5 wt% are prepared, ultrasonically treated for 30 minutes, the ultrasonic probe uses a titanium alloy horn, and 0.1% ammonium polyacrylate dispersant is added.

3. The preparation method of an acrylic board according to claim 2, wherein The said online viscometer adopts the model Brookfield DV2T, and is installed on the pipeline downstream of the PTFE filter membrane group, 15 ± 2 cm away from the inlet of the molecular sieve filling tank; The said ultrasonic treatment adopts a power of 500 W and a frequency of 40 kHz; The diameter Φ of the said titanium alloy horn is 20 mm; The weight-average molecular weight Mw of the said ammonium polyacrylate dispersant is 5000.

4. The preparation method of an acrylic board according to claim 2, characterized in that, The specific steps of the said Step S2, prepolymer preparation include the following steps: Step S21, construction of the initiation system: 0.08% AIBN initiator is premixed with purified methyl methacrylate, 0.5% dibutyl phthalate plasticizer is added, and stirred in a 75 °C water bath until the conversion rate reaches 35%; Step S22, Oxygen Inhibition Elimination System: The prepolymerization reactor is equipped with a three-channel nitrogen bubbling device, and the oxygen content is monitored in real time using a Mettler Toledo InPro6050 sensor; Step S23, Gradient Dispersion Process: The nano-slurry is injected in three stages. At the initial stage of prepolymerization, 0.5 wt% of the low-concentration slurry is incorporated; when the conversion rate reaches 15%, 1.0 wt% of the medium-concentration slurry is injected; when the conversion rate reaches 25%, 1.5 wt% of the high-concentration slurry is added. After each injection, high-speed shear dispersion is carried out at 2000 rpm for 10 minutes. A double-plunger metering pump is used for gradient injection, and a spiral flow guide is set at the feeding port; Step S24, Viscosity Closed-Loop Regulation: The viscosity of the prepolymer is monitored online. When the viscosity rises by 100 cP each time, the rotation speed is increased by 200 rpm to maintain the system viscosity at 800 - 1200 cP.

5. The preparation method of an acrylic board according to claim 4, characterized in that, The Mettler Toledo InPro6050 sensor is installed in the center of the reactor top cover, and the end of the probe is 50 ± 5 mm away from the liquid surface; The flow accuracy of the double-plunger metering pump is ±0.1 mL / min; The lead angle of the spiral flow guide is 55°; In the step S24, Viscosity Closed-Loop Regulation, the online viscometer model used for online monitoring of the prepolymer viscosity is Rheonics SRV, which is installed in the pipeline between the reactor outlet and the static mixer.

6. The preparation method of an acrylic plate according to claim 2, wherein, The step S3, Molding and Curing specifically includes the following steps: Step S31, Mold Pretreatment: A chrome-plated stainless steel mold is selected, electrochemically polished to a surface roughness Ra = 0.08 μm, and then a silicone oil emulsion containing 0.1% nano-zinc oxide is sprayed as a release agent. The film thickness of the release agent is detected using a white light interferometer and controlled at 12 ± 2 μm; Step S32, Pouring and Polymerization: When the material temperature is controlled at 40 - 45 °C, it is injected into the mold. A gradient heating program is adopted: it is maintained at 50 °C for 2 hours, then heated to 60 °C and maintained for 4 hours, and finally heated to 80 °C and maintained for 2 hours; 6 temperature compensation zones are set to control the polymerization reaction kinetics, pressurized to 0.8 MPa to eliminate interface defects, and then the pressure is released in stages, from 0.8 MPa to 0.5 MPa and maintained for 30 minutes, from 0.5 MPa to 0.2 MPa and maintained for 30 minutes, and finally completely released to atmospheric pressure.

7. The preparation method of an acrylic board according to claim 2, wherein The step S4, Post-treatment Process specifically includes the following steps: Step S41, Hot Pressing Enhancement: Three-stage hot pressing is carried out at 120 °C, that is, the initial pressure of 5 MPa is maintained for 10 min, the final pressure of 12 MPa is maintained for 15 min, and finally the pressure is released and rebounds. During the hot pressing process, 20 kHz ultrasonic waves are applied synchronously with an amplitude of 15 μm, and a porous template is used to assist in exhaust; Step S42, Surface Functionalization: Plasma treatment is carried out, and the treatment distance is dynamically adjusted during the treatment process; then a fluorosilicone resin protective layer is sprayed, and the thickness of the protective layer is 50 μm. The fluorosilicone resin is cured using a stepped temperature rise to make the surface transition from 38 mN / m to 22 mN / m in a gradient manner, and finally UV curing is carried out.

8. A method for preparing an acrylic sheet according to claim 7, characterized in that, The pore diameter Φ of the porous template is 0.5 mm, and the porosity is 30%; The gas used in the plasma treatment is argon, the power is set at 200 watts, and it lasts for 5 minutes; The treatment distance is dynamically changed, gradually adjusted from the initial 10 mm to 5 mm, and finally becomes 2 mm; The fluorosilicone resin contains 0.1 - 0.3 parts by mass of a UV curing agent; The stepwise temperature increase means that when the fluorosilicone resin is cured, it successively passes through three temperature stages of 80 °C, 100 °C, and 120 °C; The UV curing uses ultraviolet light with a wavelength of 365 nm and an energy density of 800 mJ / cm 2 .

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