Methyl methacrylate copolymer as well as preparation method and application thereof

Abstract

The invention discloses a methyl methacrylate copolymer as well as a preparation method and application thereof. The methyl methacrylate copolymer is mainly obtained by polymerizing 20-90 parts by mass of a methyl methacrylate monomer a), 10-80 parts by mass of an aromatic unsaturated hydrocarbon monomer b) and 0-20 parts by mass of other vinyl monomers c). A phosphite antioxidant is added before resin devolatilization, and a hindered phenol antioxidant is added in a resin extrusion granulation stage, so that the resin has relatively good optical performance and aging resistance.

Description

Technical Field

[0001] The invention relates to a copolymer, in particular to a methyl methacrylate copolymer and a preparation method thereof. Background Art

[0002] With the improvement of people's living standards, people have higher aesthetic requirements for various electronic products. Taking televisions as an example, "large screen and narrow frame" has become a development trend. In order to adapt to this change in demand, higher requirements are also placed on the quality of raw materials. They not only need to have high optical performance and high purity, but also be environmentally stable, not easy to deform, and easy to form and process to meet various needs.

[0003] MS (methyl methacrylate-styrene copolymer) is obtained by free radical polymerization of methyl methacrylate and styrene. In some application fields, it has better performance than polymethyl methacrylate (PMMA), such as good processability, low moisture absorption, solvent resistance, good dimensional stability, and also has excellent light transmittance, so it has been widely used in the large-size display light guide plate market.

[0004] For methyl methacrylate copolymers, whether PMMA or MS resin, when used for display light guide plates, very high requirements are placed on the optical properties of the plates. In terms of optical performance indicators, in addition to requiring transmittance, haze, yellowing index, etc. to meet basic requirements, the light guide plate is also required to have good aging resistance and be able to minimize appearance color changes and performance degradation under long-term light exposure.

[0005] Due to the introduction of aromatic styrene monomers into MS resin, its color appearance and aging resistance are somewhat inferior to those of methyl methacrylate polymer (PMMA). Therefore, it is very important to develop MS resin with good color appearance and excellent UV aging resistance.

[0006] The inventors of this application have found that the color appearance and aging performance of MS are mainly affected by its copolymer composition. Increasing the proportion of methyl methacrylate will make its various properties close to PMMA, but the solvent resistance and hygroscopicity are not improved enough. Therefore, it is hoped to find a method to improve its application performance without changing the copolymer composition of the resin. Summary of the invention

[0007] In order to solve the above technical problems, the present invention first proposes a methyl methacrylate copolymer in one aspect, which has good performance in terms of transmittance, haze, color, aging resistance and other properties, and is used to display light guide plates with better optical effects and longer service life.

[0008] Based on the second aspect of the present invention, a preparation method and application of a methyl methacrylate copolymer are also provided.

[0009] To achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0010] A methyl methacrylate copolymer is obtained by polymerization reaction of 20-90 parts by mass (for example, including but not limited to 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 parts by mass) of a methyl methacrylate monomer component A, 10-80 parts by mass (for example, including but not limited to 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 parts by mass) of an aromatic unsaturated hydrocarbon monomer component B, and 0-20 parts by mass (for example, including but not limited to 5, 10, 15, 20 parts by mass) of a vinyl monomer component C different from component A and component B; and a phosphite antioxidant is added before devolatilization of the resin, and a hindered phenol antioxidant is added during the resin extrusion granulation stage;

[0011] The methyl methacrylate copolymer has a melt flow rate of 2-15 g / 10 min at 230° C. / 3.8 kg, such as 3 g / 10 min, 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min, 9 g / 10 min, 10 g / 10 min, 11 g / 10 min, 12 g / 10 min, 13 g / 10 min, 14 g / 10 min, etc., and an injection molded product with a thickness of 3 mm has a total light transmittance of ≥90%, such as 91%, 92%, 93%, 94%. , 95%, 96%, 97%, 98%, 99%, etc., haze ≤1%, for example 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, etc., yellowing index YI≤1, for example 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, etc., yellowing index YI change value ΔYI before and after 30 days UV aging resistance is 1.5, for example 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, etc.

[0012] In a specific embodiment, the total amount of the hindered phenol antioxidant and the phosphite antioxidant added is 10-2000 ppm, based on the mass of the resin, for example 20 ppm, 50 ppm, 80 ppm, 100 ppm, 300 ppm, 500 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, etc., preferably 100-1000 ppm;

[0013] In a preferred embodiment, the mass ratio of the hindered phenol antioxidant to the phosphite antioxidant is 5:1-1:5, for example, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, etc., preferably 3:1-1:3.

[0014] In a preferred embodiment, a methyl methacrylate copolymer is obtained by polymerizing 40-65 parts by mass of methyl methacrylate monomer, 35-60 parts by mass of aromatic unsaturated hydrocarbon monomer, and 0-10 parts by mass of vinyl monomer different from component A and component B; and a phosphite antioxidant is added before the resin is devolatilized, and a hindered phenol antioxidant is added during the resin extrusion granulation stage;

[0015] The methyl methacrylate copolymer has a melt flow rate of 4-10 g / 10 min at 230° C. / 3.8 kg, a total light transmittance of 3 mm thick injection molded products ≥91%, a haze ≤0.5%, a yellowing index YI value ≤0.7, and a yellowing index YI change value ΔYI≤1.0 before and after 30 days of UV aging.

[0016] The methyl methacrylate resin copolymer of the present invention, in addition to methyl methacrylate, also contains an aromatic unsaturated hydrocarbon monomer component B. Copolymerization of the aromatic unsaturated monomer and methyl methacrylate can improve the hygroscopicity, solvent resistance, injection molding processability, etc. of the methyl methacrylate polymer.

[0017] The aromatic unsaturated hydrocarbon monomer in the component B is selected from one or more of styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, dibromostyrene, α-methylstyrene, α-ethylstyrene, dimethylstyrene and vinylnaphthalene, preferably styrene.

[0018] In the methyl methacrylate resin copolymer of the present invention, in addition to methyl methacrylate and aromatic unsaturated hydrocarbon monomers, other vinyl monomer components C can be selected as needed. The optional vinyl monomer component C can be a methacrylate monomer, including any one of ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, and isobornyl methacrylate; or it can be an alkyl acrylate monomer, including any one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, and isooctyl acrylate; or it can be an acid monomer, including any one of acrylic acid, methacrylic acid, and itaconic acid; or it can be an anhydride monomer, including any one of maleic anhydride and glutaric anhydride; or it can be an imide monomer, including any one of N-phenylmaleimide and N-cyclohexylmaleimide; or it can be a nitrile monomer, including any one of acrylonitrile and methacrylonitrile.

[0019] In another aspect of the present invention, the method for preparing the aforementioned methyl methacrylate copolymer comprises the following steps:

[0020] 1) Polymerization: adding methyl methacrylate monomer component A, aromatic unsaturated hydrocarbon monomer component B, and optionally vinyl monomer component C different from component A and component B into a polymerization reactor, and performing polymerization reaction to obtain slurry;

[0021] 2) Devolatilization: The obtained slurry is sent to a devolatilizer to remove unreacted monomers and other volatile components;

[0022] 3) Post-treatment: extruding and granulating the devolatilized resin to obtain a methyl methacrylate copolymer;

[0023] Among them, a phosphite antioxidant is added before the slurry enters the devolatilizer, and a hindered phenol antioxidant is added before the resin is granulated.

[0024] Experiments have found that in the preparation process of the methyl methacrylate polymer of the present invention, adding an antioxidant in two steps at different stages can simultaneously improve the optical properties (especially the yellowing index YI) and aging resistance of the resin.

[0025] First, after the polymerization is completed, a phosphite antioxidant is added before the reaction liquid enters the devolatilizer; secondly, after the resin is devolatilized, a hindered phenol antioxidant B is added before the melt is extruded and granulated. The addition amount of the two antioxidants is 10-2000ppm based on the total mass of the resin, preferably 100-1000ppm. The mass ratio of hindered phenol to phosphite is in the range of 5:1-1:5, preferably in the range of 3:1-1:3.

[0026] The methyl methacrylate polymer of the present invention can be thermally initiated polymerization or initiator initiated polymerization in the polymerization stage. In order to accelerate the polymerization reaction rate and facilitate the regulation of conversion rate, it is preferred to use an initiator to initiate the polymerization. For the initiator that can be selected, the half-life of the initiator at the polymerization reaction temperature is 3-30min, which is more suitable, and is more conducive to controlling the polymerization reaction rate and regulating the production cycle within a suitable time, such as 5min, 10min, 15min, 20min, 25min, etc., preferably 5-15min.

[0027] The amount of initiator added is 10-1000ppm based on the total mass of components A, B, and C, such as 20ppm, 50ppm, 80ppm, 100ppm, 300ppm, 500ppm, 800ppm, 1000ppm, etc., preferably 50-300ppm. It is known to those skilled in the art that the appropriate amount of initiator added is conducive to regulating the production efficiency and the thermal stability of the resin.

[0028] In the preparation process of the methyl methacrylate copolymer of the present invention, a solvent can be added as needed to reduce the viscosity of the material in the reactor. The solvents that can be selected include but are not limited to toluene, ethylbenzene, xylene, acetone, butanone, ethyl acetate, butyl acetate, tetrahydrofuran, N, N-dimethylformamide, preferably toluene or ethylbenzene. The amount of solvent added is 5-30% of the total mass of components A, B, and C, such as 8%, 10%, 15%, 18%, 20%, 23%, 25%, 27%, etc., preferably 10-20%. It is known to those skilled in the art that when the amount of solvent added is too much, the solid content of the material at the outlet of the reactor is too low, which is not conducive to the increase in output. At the same time, a large amount of solvent needs to be removed, which is not cost-effective in terms of energy consumption. When the amount of solvent added is too low or no solvent is added, the viscosity of the reaction solution will be high, and there may be certain problems in mass transfer and heat transfer.

[0029] In terms of the polymerization reactor, the methyl methacrylate polymer of the present invention can be selected from a full mixed flow reactor or a plug flow reactor or a combination of the two, preferably a full mixed flow reactor, and more preferably a stirred reactor with jacket temperature control. The polymerization reactor is equipped with a supply port, an extraction port and a stirring device, and the stirring device preferably has a mixing performance that roughly covers the entire reaction zone. In addition to the jacket temperature control, a draft tube or a coil can also be set inside the reactor to further control the temperature by circulating a heat carrier.

[0030] In the polymerization reaction stage, the reaction temperature is 100-180° C., for example, 110° C., 120° C., 130° C., 140° C., 150° C., 160° C., 170° C., 180° C., etc., preferably 120-160° C. Those skilled in the art will appreciate that when the reaction temperature is too low, the viscosity of the reaction liquid is high, which is not conducive to mass transfer and heat transfer; when the reaction temperature is too high, the proportion of side reaction oligomers will increase, which is not conducive to improving product quality.

[0031] In the polymerization reaction stage, the reactor outlet conversion rate is 50-85%, such as 55%, 60%, 65%, 70%, 75%, 80%, 85%, etc., preferably 65-75%. When the outlet conversion rate is too low, it is not conducive to the improvement of production efficiency. When the outlet conversion rate is too high, it is not conducive to production control due to the large viscosity. In order to control the outlet conversion rate, the polymerization reaction time is controlled within the range of 1-6h, such as 1.5h, 2h, 2.5h, 3h, 2.5h, 4h, 4.5h, 5h, 5.5h, 6h, etc., preferably 1.5-4h. The polymerization reaction temperature and the reactor residence time jointly determine the outlet conversion rate. It will be appreciated by those skilled in the art that the outlet conversion rate is basically only related to production efficiency and has little to do with the performance indicators of the copolymer.

[0032] The devolatilizer used in the preparation process of the methyl methacrylate copolymer of the present invention can be a venting extruder, a falling strip devolatilizer, a falling film devolatilizer, a thin film evaporator, a single-shaft or double-shaft devolatilizer, or any combination thereof, preferably a falling strip devolatilizer or a venting extruder or a combination thereof, and more preferably a venting twin-screw extruder.

[0033] The screw-type devolatilization device preferably has a rear volatile component outlet, a reaction liquid supply port, a front volatile component outlet, and a polymer outlet arranged from the driving part side of the screw to the front end side. The reaction liquid supplied from the reaction liquid supply port releases the heat accumulated as latent heat at the reaction liquid supply port to quickly evaporate the volatile component. In order to quickly remove the vapor of the volatile component from the extruder, it is preferred to set the rear volatile component outlet on the side opposite to the flow direction of the resin relative to the reaction liquid supply port. Furthermore, in order to suppress the generation of carbides and the coloring of the resin, it is preferred to use a metal other than iron such as chromium and titanium to coat the inner wall of the cylinder and the surface of the screw.

[0034] In the devolatilization stage, unreacted monomers and impurities are removed in the devolatilizer. The melt temperature of the devolatilizer is controlled to be 210°C-280°C, for example, 210°C, 220°C, 230°C, 240°C, 250°C, etc., preferably 220-250°C. The devolatilization pressure is lower than 5KPaA, for example, 4KPaA, 3KPaA, 2KPaA, 1KPaA, etc., preferably lower than 3KPa. The residence time of the resin in the melt pool is not higher than 15min, for example, 14min, 13min, 12min, 11min, 10min, 9min, 8min, 7min, 6min, 5min, 4min, 3min, etc., preferably 5-10min. When the devolatilization temperature is too low and the residence time is short, the volatile matter is not easily fully removed. When the devolatilization temperature is too high and the residence time is too long, the polymer is easily colored by heat.

[0035] From the viewpoint of economic efficiency, it is preferred that volatiles such as unreacted monomers are condensed using a condenser and recovered before being reused. In this case, it is more preferred that high boiling point components such as oligomers contained in the volatiles are separated and removed by distillation and then reused as monomers.

[0036] The methyl methacrylate copolymer prepared by the method of the present invention has a weight average molecular weight range of 50,000 to 300,000, preferably 80,000 to 200,000. When the molecular weight is too low, it is not conducive to improving the performance of the resin, and when the molecular weight is too high, it is not conducive to the production and processing of the resin.

[0037] When the methyl methacrylate copolymer is produced by the above method, auxiliary agents such as release agents, ultraviolet absorbers, antioxidants, colorants, antistatic agents, etc. can be added to the melt or particles after devolatilization as needed. The types and amounts of these additives are well known to those skilled in the art.

[0038] On the other hand, the aforementioned methyl methacrylate copolymer or the methyl methacrylate copolymer prepared by the aforementioned preparation method is used in the fields of display light guide plates, lighting light guide plates, automobiles, daily necessities, and cosmetic packaging. DETAILED DESCRIPTION

[0039] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0040] The sources of the main raw materials involved in the following examples and comparative examples of the present invention are shown in Table 1:

[0041] Table 1. Main raw material information

[0042]

[0043]

[0044] The polymer related structure and performance test methods are as follows:

[0045] <Molecular weight test>

[0046] The molecular weight was tested by liquid gel chromatography (GPC), with tetrahydrofuran (THF) as the mobile phase and a parallax refractometer as the detector. Monodisperse PMMA was used as the standard sample.

[0047] <Conversion rate test>

[0048] During the continuous polymerization process, it is calculated based on the ratio of the mass of polymer at the extruder outlet to the amount of reaction liquid fed per unit time.

[0049] <UV aging test>

[0050] 1) Reference standard GB / T 16422.3-2022

[0051] 2) Light source: UVA-340nm

[0052] 3)Radiance: 0.76W / m 2

[0053] 4) Cycle conditions: UV illumination for 8 hours, condensation at 50°C for 4 hours

[0054] Other related performance test methods are shown in Table 2:

[0055] Table 2. Polymer performance test standards and conditions

[0056] Test items Test Standards Experimental conditions Melt index ISO 1133 230℃、3.8KG Light transmittance ISO 13486 3mm Haze ISO 14782 3mm Yellowing Index ISO 13468 3mm

[0057] [Example 1]

[0058] 60 parts by mass of methyl methacrylate, 40 parts by mass of styrene, 0.018 parts by mass of tert-butyl peroxy-3,5,5-trimethylhexanoate (TBPMH), 15 parts by mass of toluene, and 0.15 parts by mass of tert-dodecyl mercaptan were added to a batching tank and mixed thoroughly to prepare a reaction solution. Nitrogen was passed through to fully exclude oxygen.

[0059] The reaction liquid after batching was continuously added into the full mixed flow reactor (effective volume 30L) at a flow rate of 10KG / h, the temperature in the reactor was controlled at 140°C, the average residence time was 2.5h, and the outlet conversion rate was 70%.

[0060] The slurry obtained above is continuously fed into a strip devolatilizer. Before entering the devolatilizer, add the phosphite antioxidant RIANOX 168 to the slurry and mix it evenly in a static mixer, and remove the unreacted monomers and other volatile components under the conditions of vacuum degree -3KPa, temperature 230°C, and residence time 10min. Before the devolatilized resin enters the die head, add the hindered phenol antioxidant RIANOX 1076 and mix it statically. The addition amount of the two antioxidants is 100ppm based on the resin mass, and the ratio of hindered phenol to phosphite is 3:1. The devolatilized melt is extruded and pelletized to obtain the final product, methyl methacrylate copolymer.

[0061] [Example 2]

[0062] Add 50 parts by mass of methyl methacrylate, 50 parts by mass of styrene, 0.02 parts by mass of tert-butyl peroxy-3,5,5-trimethylhexanoate (TBPMH), 15 parts by mass of ethylbenzene, and 0.1 parts by mass of tert-dodecyl mercaptan into a batching tank, mix well to prepare a reaction solution, and pass nitrogen to fully exclude oxygen.

[0063] The reaction liquid after batching was continuously added into the full mixed flow reactor (effective volume 30L) at a flow rate of 10KG / h, the temperature in the reactor was controlled at 140°C, the average residence time was 2.5h, and the outlet conversion rate was 70%.

[0064] The slurry obtained above is continuously fed into a strip devolatilizer. Before entering the devolatilizer, add the phosphite antioxidant RIANOX 168 to the slurry and mix it evenly in a static mixer. Unreacted monomers and other volatile components are removed under the conditions of vacuum degree -3KPa, temperature 230°C, and residence time 10min. Before the devolatilized resin enters the die head, add RIANOX 1076 and mix it statically. The addition amount of the two antioxidants is 500ppm based on the resin mass, and the ratio of hindered phenol to phosphite is 1:1. The devolatilized melt is extruded and pelletized to obtain the final product, methyl methacrylate copolymer.

[0065] [Example 3]

[0066] 35 parts by mass of methyl methacrylate, 65 parts by mass of styrene, 0.01 parts by mass of dicumyl peroxide (DCP), 15 parts by mass of ethylbenzene, and 0.05 parts by mass of tert-dodecyl mercaptan were added to a batching tank and mixed thoroughly to prepare a reaction solution. Nitrogen was passed through to fully exclude oxygen.

[0067] The reaction liquid after batching was continuously added into a fully mixed flow reactor (effective volume 30L) at a flow rate of 10KG / h, the temperature in the reactor was controlled at 150°C, the average residence time was 2h, and the outlet conversion rate was 69%.

[0068] The slurry obtained above is continuously fed into a strip devolatilizer. Before entering the devolatilizer, add the phosphite antioxidant RIANOX 168 to the slurry and mix it evenly in a static mixer, and remove the unreacted monomers and other volatile components under the conditions of vacuum degree -3KPa, temperature 230°C, and residence time 10min. Before the devolatilized resin enters the die head, add the hindered phenol antioxidant RIANOX 1076 and mix it statically. The addition amount of the two antioxidants is 1000ppm based on the resin mass, and the ratio of hindered phenol to phosphite is 1:3. The devolatilized melt is extruded and pelletized to obtain the final product, methyl methacrylate copolymer.

[0069] [Example 4]

[0070] 75 parts by mass of methyl methacrylate, 15 parts by mass of styrene, 10 parts by mass of maleic anhydride, 0.02 parts by mass of tert-butyl peroxy-3,5,5-trimethylhexanoate (TBPMH), 15 parts by mass of toluene, and 0.2 parts by mass of n-octyl mercaptan were added to a batching tank and mixed thoroughly to prepare a reaction solution. Nitrogen was passed through to fully exclude oxygen.

[0071] The reaction liquid after batching was continuously added into a fully mixed flow reactor (effective volume 30L) at a flow rate of 10KG / h, the temperature in the reactor was controlled at 140°C, the average residence time was 2h, and the outlet conversion rate was 65%.

[0072] The slurry obtained above is continuously fed into a strip devolatilizer. Before entering the devolatilizer, add the phosphite antioxidant RIANOX 168 to the slurry and mix it evenly in a static mixer, and remove the unreacted monomers and other volatile components under the conditions of vacuum degree -3KPa, temperature 230°C, and residence time 10min. Before the devolatilized resin enters the die, add the hindered phenol antioxidant RIANOX 1076 and mix it statically. The addition amount of the two antioxidants is 500ppm based on the resin mass, and the ratio of hindered phenol to phosphite is 3:1. The devolatilized melt is extruded and pelletized to obtain the final product, methyl methacrylate copolymer.

[0073] [Example 5]

[0074] Add 50 parts by mass of methyl methacrylate, 50 parts by mass of styrene, 0.02 parts by mass of tert-butyl peroxy-3,5,5-trimethylhexanoate (TBPMH), 15 parts by mass of ethylbenzene, and 0.1 parts by mass of tert-dodecyl mercaptan into a batching tank, mix well to prepare a reaction solution, and pass nitrogen to fully exclude oxygen.

[0075] The reaction liquid after batching was continuously added into the full mixed flow reactor (effective volume 30L) at a flow rate of 10KG / h, the temperature in the reactor was controlled at 140°C, the average residence time was 2.5h, and the outlet conversion rate was 70%.

[0076] The slurry obtained above is continuously fed into a strip devolatilizer. Before entering the devolatilizer, add the phosphite antioxidant RIANOX 168 to the slurry and mix it evenly in a static mixer. Unreacted monomers and other volatile components are removed under the conditions of vacuum degree -3KPa, temperature 230°C, and residence time 10min. Before the devolatilized resin enters the die head, add RIANOX 1010 and mix it statically. The addition amount of the two antioxidants is 500ppm based on the resin mass, and the ratio of hindered phenol to phosphite is 1:1.5. The devolatilized melt is extruded and pelletized to obtain the final product, methyl methacrylate copolymer.

[0077] [Example 6]

[0078] Add 50 parts by mass of methyl methacrylate, 50 parts by mass of styrene, 0.02 parts by mass of tert-butyl peroxy-3,5,5-trimethylhexanoate (TBPMH), 15 parts by mass of ethylbenzene, and 0.1 parts by mass of tert-dodecyl mercaptan into a batching tank, mix well to prepare a reaction solution, and pass nitrogen to fully exclude oxygen.

[0079] The reaction liquid after batching was continuously added into the full mixed flow reactor (effective volume 30L) at a flow rate of 10KG / h, the temperature in the reactor was controlled at 140°C, the average residence time was 2.5h, and the outlet conversion rate was 70%.

[0080] The slurry obtained above is continuously fed into a strip devolatilizer. Before entering the devolatilizer, add the phosphite antioxidant RIANOX 138 to the slurry and mix it evenly in a static mixer, and remove the unreacted monomers and other volatile components under the conditions of vacuum degree -3KPa, temperature 230°C, and residence time 10min. Before the devolatilized resin enters the die head, add RIANOX 1076 and mix it statically. The addition amount of the two antioxidants is 600ppm based on the resin mass, and the ratio of hindered phenol to phosphite is 1:2. The devolatilized melt is extruded and pelletized to obtain the final product, methyl methacrylate copolymer.

[0081] [Example 7]

[0082] Add 20 parts by mass of methyl methacrylate, 80 parts by mass of styrene, 0.005 parts by mass of tert-butyl peroxy-3,5,5-trimethylhexanoate (TBPMH), and 10 parts by mass of ethylbenzene into a batching tank, mix well to prepare a reaction solution, and pass nitrogen to fully exclude oxygen.

[0083] The reaction liquid after batching was continuously added into a fully mixed flow reactor (effective volume 30L) at a flow rate of 10KG / h, the temperature in the reactor was controlled at 140°C, the average residence time was 2h, and the outlet conversion rate was 68%.

[0084] The slurry obtained above is continuously fed into a strip devolatilizer. Before entering the devolatilizer, add the phosphite antioxidant RIANOX 168 to the slurry and mix it evenly in a static mixer, and remove the unreacted monomers and other volatile components under the conditions of vacuum degree -3KPa, temperature 230°C, and residence time 10min. Before the devolatilized resin enters the die head, add the hindered phenol antioxidant RIANOX 1076 and mix it statically. The addition amount of the two antioxidants is 1000ppm based on the resin mass, and the ratio of hindered phenol to phosphite is 1:1. The devolatilized melt is extruded and pelletized to obtain the final product, methyl methacrylate copolymer.

[0085] [Example 8]

[0086] 70 parts by mass of methyl methacrylate, 10 parts by mass of styrene, 20 parts by mass of glutaric anhydride, 0.02 parts by mass of tert-butyl peroxy-3,5,5-trimethylhexanoate (TBPMH), 15 parts by mass of toluene, and 0.2 parts by mass of n-octyl mercaptan were added to a batching tank and mixed thoroughly to prepare a reaction solution. Nitrogen was passed through to fully exclude oxygen.

[0087] The reaction liquid after batching was continuously added into a fully mixed flow reactor (effective volume 30L) at a flow rate of 10KG / h, the temperature in the reactor was controlled at 140°C, the average residence time was 2h, and the outlet conversion rate was 68%.

[0088] The slurry obtained above is continuously fed into a strip devolatilizer. Before entering the devolatilizer, add the phosphite antioxidant RIANOX 138 to the slurry and mix it evenly in a static mixer, and remove the unreacted monomers and other volatile components under the conditions of vacuum degree -3KPa, temperature 230°C, and residence time 10min. Before the devolatilized resin enters the die, add the hindered phenol antioxidant RIANOX 1010 and mix it statically. The addition amount of the two antioxidants is 800ppm based on the resin mass, and the ratio of hindered phenol to phosphite is 1:1. The devolatilized melt is extruded and pelletized to obtain the final product, methyl methacrylate copolymer.

[0089] [Example 9]

[0090] 70 parts by mass of methyl methacrylate, 20 parts by mass of a-methylstyrene, 10 parts by mass of maleic anhydride, 0.03 parts by mass of tert-butylperoxy-3,5,5-trimethylhexanoate (TBPMH), and 15 parts by mass of toluene were added to a batching tank and mixed thoroughly to prepare a reaction solution. Nitrogen was passed through to fully exclude oxygen.

[0091] The reaction liquid after batching was continuously added into a fully mixed flow reactor (effective volume 30L) at a flow rate of 10KG / h, the temperature in the reactor was controlled at 140°C, the average residence time was 2h, and the outlet conversion rate was 63%.

[0092] The slurry obtained above is continuously fed into a strip devolatilizer. Before entering the devolatilizer, add the phosphite antioxidant RIANOX 138 to the slurry and mix it evenly in a static mixer. Unreacted monomers and other volatile components are removed under the conditions of vacuum degree -3KPa, temperature 230°C, and residence time 10min. Before the devolatilized resin enters the die head, add the hindered phenol antioxidant RIANOX 1076 and mix it statically. The addition amount of the two antioxidants is 2000ppm based on the resin mass, and the ratio of hindered phenol to phosphite is 1:2. The devolatilized melt is extruded and pelletized to obtain the final product, methyl methacrylate copolymer.

[0093] [Comparative Example 1]

[0094] A methyl methacrylate copolymer was prepared in substantially the same manner as in Example 2, except that the compound antioxidants RIANOX 1076 and RIANOX 168 were added after devolatilization and before melt extrusion granulation.

[0095] [Comparative Example 2]

[0096] A methyl methacrylate copolymer was prepared in substantially the same manner as in Example 2, except that the compound antioxidants RIANOX 1076 and RIANOX 168 were added after the polymerization reaction and before devolatilization.

[0097] [Comparative Example 3]

[0098] A methyl methacrylate copolymer was prepared in substantially the same manner as in Example 2, except that no antioxidant was added.

[0099] [Comparative Example 4]

[0100] A methyl methacrylate copolymer was prepared in substantially the same manner as in Example 2, except that no phosphite antioxidant was added, and only a hindered phenol antioxidant RIANOX 1076 was added in an amount of 500 ppm during the extrusion granulation stage.

[0101] [Comparative Example 5]

[0102] A methyl methacrylate copolymer was prepared in substantially the same manner as in Example 2, except that no hindered phenol antioxidant was added, and only a phosphite antioxidant RIANOX 168 was added before melt devolatilization in an amount of 500 ppm.

[0103] [Comparative Example 6]

[0104] A methyl methacrylate copolymer was prepared in substantially the same manner as in Example 2, except that a hindered phenol antioxidant RIANOX 1076 and a phosphite antioxidant RIANOX 168 were added during the monomer formulation stage, and the added amounts and proportions remained unchanged.

[0105] The methyl methacrylate copolymers prepared in the embodiments and comparative examples were subjected to the performance tests shown in Table 3. The results are shown in Table 3.

[0106] From the comparison between the embodiments and the comparative examples, it can be seen that when the phosphite antioxidant is added before the resin devolatilization and the hindered phenol antioxidant is added during the resin extrusion granulation stage, the methyl methacrylate copolymer of the present invention has very excellent performance in terms of transmittance, haze, color, aging resistance, etc.

[0107] Table 3 Examples and Comparative Examples Formulations and Performance Test Results

[0108]

Claims

1. A methyl methacrylate copolymer, characterized in that: The monomer is obtained by polymerization reaction of 20-90 parts by weight of methyl methacrylate monomer component A, 10-80 parts by weight of aromatic unsaturated hydrocarbon monomer component B, and 0-20 parts by weight of vinyl monomer component C different from component A and component B; Phosphite antioxidants are added before the resin is devolatilized, and hindered phenol antioxidants are added during the resin extrusion granulation stage; The methyl methacrylate copolymer has a melt flow rate of 2-15 g / 10 min at 230° C. / 3.8 kg, a total light transmittance of 3 mm thick injection molded products ≥90%, a haze ≤1%, a yellowing index YI ≤1, and a yellowing index YI change value ΔYI ≤1.5 before and after 30 days of UV aging resistance.

2. The methyl methacrylate copolymer according to claim 1, characterized in that The polymer is obtained by polymerizing 40-65 parts by weight of methyl methacrylate monomer, 35-60 parts by weight of aromatic unsaturated hydrocarbon monomer, and 0-10 parts by weight of vinyl monomer different from component A and component B; The methyl methacrylate copolymer has a melt flow rate of 4-10 g / 10 min at 230° C. / 3.8 kg, a total light transmittance of 3 mm thick injection molded products ≥91%, a haze ≤0.5%, a yellowing index YI value ≤0.7, and a yellowing index YI change value ΔYI≤1.0 before and after 30 days of UV aging.

3. The methyl methacrylate copolymer according to claim 1 or 2, characterized in that The total amount of the hindered phenol antioxidant and the phosphite antioxidant added is 10-2000 ppm, based on the mass of the resin, preferably 100-1000 ppm; Preferably, the mass ratio of the hindered phenol antioxidant to the phosphite antioxidant is 5:1-1:5, preferably 3:1-1:

3.

4. The methyl methacrylate copolymer according to claim 3, characterized in that The aromatic unsaturated hydrocarbon monomer in the component B is selected from one or more of styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, dibromostyrene, α-methylstyrene, α-ethylstyrene, dimethylstyrene and vinylnaphthalene, preferably styrene.

5. The methyl methacrylate copolymer according to claim 3, characterized in that The vinyl monomer in the component c) is selected from at least one of methacrylate monomers, alkyl acrylate monomers, acid monomers, anhydride monomers, imide monomers, and nitrile monomers; Preferably, the methacrylate monomer is selected from any one of ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate and isobornyl methacrylate; and / or The alkyl acrylate monomer is selected from any one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate and isooctyl acrylate; and / or The acid monomer is selected from any one of acrylic acid, methacrylic acid and itaconic acid; and / or The anhydride monomer is selected from any one of maleic anhydride and glutaric anhydride; and / or The imide monomer is selected from any one of N-phenylmaleimide and N-cyclohexylmaleimide; and / or The nitrile monomer is selected from any one of acrylonitrile and methacrylonitrile.

6. A method for preparing a methyl methacrylate copolymer according to any one of claims 1 to 5, characterized in that: The following steps are involved: 1) Polymerization: adding methyl methacrylate monomer component A, aromatic unsaturated hydrocarbon monomer component B, and optionally vinyl monomer component C different from component A and component B into a polymerization reactor, and performing polymerization reaction to obtain slurry; 2) Devolatilization: The obtained slurry is sent to a devolatilizer to remove unreacted monomers and other volatile components; 3) Post-treatment: extruding and granulating the devolatilized resin to obtain a methyl methacrylate copolymer; Among them, a phosphite antioxidant is added before the slurry enters the devolatilizer, and a hindered phenol antioxidant is added before the resin is granulated.

7. The preparation method according to claim 6, characterized in that: The polymerization step 1) is carried out by adding an initiator, wherein the initiator is an organic peroxide or an azo compound, preferably an organic peroxide, and more preferably any one or more of 1,1-bis-(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis-(tert-butylperoxy)cyclohexane, peroxy-3,5,5-trimethylhexanoate, 2,2-di(tert-butylperoxy)butane, tert-butylperoxycarbonate-2-ethylhexyl, tert-amyl peroxybenzoate, tert-butyl peroxybenzoate, diisopropylbenzene peroxide, and di-tert-butyl peroxide; Preferably, the half-life of the initiator at the polymerization reaction temperature is 3-30 min; the amount of the initiator added is 10-1000 ppm, preferably 50-300 ppm, based on the total mass of components A, B, and C; More preferably, the reaction temperature of the polymerization reaction is 100-180° C., preferably 120-160° C.; the polymerization reaction time is 1-6 h, preferably 1.5-4 h; and the reactor outlet conversion rate is 50-85%, preferably 65-75%.

8. The preparation method according to claim 6 or 7, characterized in that: Step 1) The polymerization reaction is carried out in the presence of a solvent; preferably, 5-30%, more preferably 10-20% of the total mass of components A, B, and C is added; Preferably, the solvent is one or more of toluene, ethylbenzene, xylene, acetone, butanone, ethyl acetate, butyl acetate, tetrahydrofuran, and N,N-dimethylformamide, preferably toluene or ethylbenzene.

9. The preparation method according to claim 6 or 7, characterized in that: The devolatilizer in step 2) is selected from a combination of one or more of a venting extruder, a falling strip devolatilizer, a falling film devolatilizer, a thin film evaporator, a single-shaft devolatilizer, and a double-shaft devolatilizer, preferably a falling strip devolatilizer, a venting extruder or a combination thereof, and more preferably a falling strip devolatilizer; Preferably, in the post-treatment stage of step 3), an auxiliary agent is optionally added, and the auxiliary agent is selected from at least any one of a release agent, a blueing agent, and a UV absorber.

10. Use of the methyl methacrylate copolymer according to any one of claims 1 to 5 or the methyl methacrylate copolymer prepared by the preparation method according to any one of claims 6 to 9 in the fields of display light guide plates, lighting light guide plates, automobiles, daily necessities, and cosmetic packaging.

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