Methyl methacrylate copolymer, method for preparing the same, and use thereof

Abstract

The application discloses a methyl methacrylate copolymer and a preparation method and application thereof. The methyl methacrylate copolymer is mainly obtained by polymerization of 20-90 mass parts of methyl methacrylate monomer a), 10-80 mass parts of aromatic unsaturated hydrocarbon monomer b) and 0-20 mass parts of other vinyl monomer c). By adding phosphite antioxidant before resin devolatilization and adding hindered phenolic antioxidant in the resin extrusion granulation stage, the resin has good optical performance and aging resistance.

Description

Technical Field

[0001] This invention relates to a copolymer, and more particularly to a methyl methacrylate copolymer and its preparation method. Background Technology

[0002] As people's living standards improve, they have higher aesthetic requirements for various electronic products. Taking televisions as an example, "large screen and narrow bezel" has become a development trend. In order to adapt to this change in demand, there are also higher requirements for the quality of raw materials. They not only need to have high optical performance and high purity, but also need to have characteristics such as environmental stability, resistance to deformation, and easy molding and processing to meet various needs.

[0003] MS (methyl methacrylate-styrene copolymer) is obtained by free radical polymerization of methyl methacrylate and styrene. In some applications, it has superior properties compared to polymethyl methacrylate (PMMA), such as good processability, low moisture absorption, solvent resistance, and good dimensional stability. It also has relatively good light transmittance, and therefore has been widely used in the large-size display light guide plate market.

[0004] For methyl methacrylate copolymers, whether PMMA or MS resin, the optical properties of the substrate are subject to very high requirements when used in display light guide plates. In addition to meeting basic requirements such as transmittance, haze, and yellowing index, the light guide plate must also have good aging resistance, minimizing changes in appearance and performance degradation under long-term illumination.

[0005] Due to the introduction of aromatic styrene monomers, the color appearance and aging resistance of MS resin are somewhat degraded compared to PMMA polymers. Therefore, developing MS resins with good color appearance and excellent UV aging resistance is of great significance.

[0006] The inventors of this application have discovered that the color appearance and aging properties of MS are mainly affected by its copolymer composition. Increasing the proportion of methyl methacrylate (MMA) makes its various properties close to those of PMMA, but the improvement in solvent resistance and moisture absorption is insufficient. Therefore, we hope to find a method to improve its application performance without changing the copolymer composition of the resin. Summary of the Invention

[0007] To address the above technical problems, this invention first proposes a methyl methacrylate copolymer, which exhibits excellent performance in terms of light transmittance, haze, color, and aging resistance, and is used to display light guide plates with better optical effects and a longer service life.

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

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

[0010] A methyl methacrylate copolymer is obtained by polymerization of 20-90 parts by weight (e.g., including but not limited to 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 parts by weight) of methyl methacrylate monomer component A, 10-80 parts by weight (e.g., including but not limited to 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 parts by weight) of aromatic unsaturated hydrocarbon monomer component B, and 0-20 parts by weight (e.g., including but not limited to 5, 10, 15, 20 parts by weight) of vinyl monomer component C, which is different from components A and B; and a phosphite antioxidant is added before resin devolatilization, and a hindered phenolic 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℃ / 3.8 kg, for example, 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 the total light transmittance of the injection-molded product with a thickness of 3 mm is ≥90%, for example, 91%, 92%, 93%, 94%. 95%, 96%, 97%, 98%, 99%, etc.; haze ≤1%, such as 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, etc.; yellowing index YI ≤1%, such as 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 ≤1.5 before and after 30 days of UV aging, such as 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 one specific embodiment, the total amount of the hindered phenolic antioxidant and phosphite antioxidant added is 10-2000 ppm, based on the quality of the resin, such as 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 phenolic antioxidant to the phosphite antioxidant is 5:1 to 1:5, such as 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, etc., preferably 3:1 to 1:3.

[0014] In a preferred embodiment, a methyl methacrylate copolymer is obtained by polymerization of 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; and a phosphite antioxidant is added before resin devolatilization, and a hindered phenolic 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℃ / 3.8 KG, and the injection molded product has a total light transmittance of ≥91%, haze of ≤0.5%, yellowing index YI value of ≤0.7 and a yellowing index YI change value ΔYI ≤1.0 before and after 30 days of UV aging.

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

[0017] The aromatic unsaturated hydrocarbon monomer in 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 selectable vinyl monomer component C can be any one of methacrylate monomers, including ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, and isobornyl methacrylate; or it can be any one of alkyl acrylate monomers, including methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, and isooctyl acrylate; or it can be any one of acid monomers, including acrylic acid, methacrylic acid, and itaconic acid; or it can be any one of acid anhydride monomers, including maleic anhydride and glutaric anhydride; or it can be any one of imide monomers, including N-phenylmaleimide and N-cyclohexylmaleimide; or it can be any one of nitrile monomers, including acrylonitrile and methacrylonitrile.

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

[0020] 1) Polymerization: Methyl methacrylate monomer component A, aromatic unsaturated hydrocarbon monomer component B, and optional vinyl monomer component C (different from components A and B) are added to the polymerization reactor, and the polymerization reaction yields a slurry.

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

[0022] 3) Post-treatment: The devolatilized resin is extruded and granulated to obtain methyl methacrylate copolymer;

[0023] Specifically, phosphite antioxidants are added before the slurry enters the devolatilizer, and hindered phenolic antioxidants are added before resin granulation.

[0024] Experiments have shown that in the preparation process of the methyl methacrylate polymer of the present invention, adding antioxidants 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 polymerization, a phosphite antioxidant is added before the reaction solution enters the devolatilizer; second, after resin devolatilization, a hindered phenolic antioxidant B is added before melt extrusion granulation. The amount of both antioxidants added is 10-2000 ppm based on the total mass of the resin, preferably 100-1000 ppm. 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 or initiated by an initiator during the polymerization stage. To accelerate the polymerization rate and facilitate conversion control, initiation by an initiator is preferred. For the selected initiator, a half-life of 3-30 min at the polymerization temperature is suitable, as it is more beneficial for controlling the polymerization rate and regulating the production cycle within a suitable time, such as 5 min, 10 min, 15 min, 20 min, or 25 min, preferably 5-15 min.

[0027] The initiator addition amount is 10-1000 ppm based on the total mass of components A, B, and C, such as 20 ppm, 50 ppm, 80 ppm, 100 ppm, 300 ppm, 500 ppm, 800 ppm, 1000 ppm, etc., preferably 50-300 ppm. As is known to those skilled in the art, a suitable initiator addition amount is beneficial for controlling 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. Selectable solvents include, but are not limited to, toluene, ethylbenzene, xylene, acetone, butanone, ethyl acetate, butyl acetate, tetrahydrofuran, and N,N-dimethylformamide, with toluene or ethylbenzene being preferred. The amount of solvent added is 5-30% of the total mass of components A, B, and C, for example, 8%, 10%, 15%, 18%, 20%, 23%, 25%, 27%, etc., preferably 10-20%. Those skilled in the art will understand that when too much solvent is added, the solid content of the material at the reactor outlet is too low, which is not conducive to increasing production. At the same time, a large amount of solvent needs to be removed, which is not energy-efficient. When the amount of solvent added is too low or no solvent is added, the viscosity of the reaction liquid will be too high, which may cause problems in mass and heat transfer.

[0029] Regarding the polymerization reactor, the methyl methacrylate polymer of this invention can be produced using a fully stirred-flow reactor, a plug flow reactor, or a combination of both, preferably a fully stirred-flow reactor, and more preferably a stirred reactor with jacketed temperature control. The polymerization reactor has a feed port, an exhaust port, and a stirring device, which preferably has mixing capabilities that cover approximately the entire reaction zone. In addition to jacketed temperature control, the reactor can also be equipped with a flow guide pipe or coil, etc., for further temperature control through heat transfer fluid circulation.

[0030] During the polymerization stage, the reaction temperature is 100-180℃, such as 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, etc., preferably 120-160℃. Those skilled in the art will understand that when the reaction temperature is too low, the viscosity of the reaction liquid is high, which is detrimental to mass and heat transfer; when the reaction temperature is too high, the proportion of by-reaction oligomers will increase, which is detrimental to product quality improvement.

[0031] During the polymerization stage, the reactor outlet conversion rate is 50-85%, such as 55%, 60%, 65%, 70%, 75%, 80%, 85%, etc., preferably 65-75%. A conversion rate that is too low is detrimental to improving production efficiency, while a conversion rate that is too high results in high viscosity, which is unfavorable for production control. To control the outlet conversion rate, the polymerization reaction time is controlled within the range of 1-6 hours, such as 1.5 hours, 2 hours, 2.5 hours, 3 hours, 2.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, etc., preferably 1.5-4 hours. The polymerization reaction temperature and reactor residence time jointly determine the outlet conversion rate. Those skilled in the art will understand that the outlet conversion rate is essentially only related to production efficiency and has almost no bearing on 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 one or any combination of a vented extruder, a drop-screw devolatilizer, a falling film devolatilizer, a thin film evaporator, a single-shaft or twin-shaft devolatilizer, preferably a drop-screw devolatilizer or a vented extruder or a combination thereof, and more preferably a vented 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 drive section side of the screw towards the front end side. The reaction liquid supplied from the reaction liquid supply port causes the volatile components to evaporate rapidly by releasing heat accumulated as latent heat at the reaction liquid supply port. To quickly remove the vapor of this volatile component from the extruder, it is preferable to provide the rear volatile component outlet on the side opposite to the resin flow direction, relative to the reaction liquid supply port. Furthermore, to suppress the formation of carbides and resin coloring, it is preferable to coat the cylinder inner wall and screw surface with a metal other than iron, such as chromium or titanium.

[0034] In the devolatilization stage, unreacted monomers and impurities are removed within the devolatilizer. The melt temperature in the devolatilizer is controlled between 210℃ and 280℃, such as 210℃, 220℃, 230℃, 240℃, and 250℃, preferably 220-250℃. The devolatilization pressure is below 5 kPaA, such as 4 kPaA, 3 kPaA, 2 kPaA, and 1 kPaA, preferably below 3 kPa. The residence time of the resin in the melt pool is no more than 15 minutes, such as 14 minutes, 13 minutes, 12 minutes, 11 minutes, 10 minutes, 9 minutes, 8 minutes, 7 minutes, 6 minutes, 5 minutes, 4 minutes, and 3 minutes, preferably 5-10 minutes. When the devolatilization temperature is too low and the residence time is too short, volatile components are not easily and completely removed. When the devolatilization temperature is too high and the residence time is too long, the polymer is prone to heat-induced coloration.

[0035] From an economic perspective, it is preferable to recover and reuse unreacted monomers and other volatiles by condensing them in a condenser. More preferably, high-boiling-point components such as oligomers contained in the volatiles can be separated and removed by distillation and then reused as monomers.

[0036] The methyl methacrylate copolymer prepared by the method of this invention has a weight-average molecular weight range of 50,000 to 300,000, preferably 80,000 to 200,000. A molecular weight that is too low is detrimental to improving resin performance, while a molecular weight that is too high is detrimental to resin production and processing.

[0037] When producing methyl methacrylate copolymers using the above method, mold release agents, ultraviolet absorbers, antioxidants, colorants, antistatic agents, and other additives can be added to the devolatilized melt or particles as needed. The types and amounts of these additives are 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 Implementation

[0039] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

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

[0041] Table 1. Information on Main Raw Materials

[0042]

[0043]

[0044] The following are the methods for testing the structure and properties of polymers:

[0045] <Molecular Weight Test>

[0046] Molecular weight was determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as the mobile phase and a parallax refractive index detector. Monodisperse PMMA was used as the standard.

[0047] Conversion Rate Test

[0048] In a continuous polymerization reaction, the ratio of the mass of polymer exiting the extruder to the amount of reaction liquid fed per unit time is used for calculation.

[0049] <UV Aging Resistance Test>

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

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

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

[0053] 4) Cyclic conditions: 8 hours of UV light irradiation, 4 hours of condensation at 50°C

[0054] Other relevant performance testing methods are shown in Table 2:

[0055] Table 2. Polymer Performance Testing Standards and Conditions

[0056] Melt Flow Index ISO 1133 230℃, 3.8KG Light transmittance ISO 13486 3mm Haze ISO 14782 3mm Yellowing Index ISO 13468 3mm

[0057]

Example 1

[0058] Add 60 parts by weight of methyl methacrylate, 40 parts by weight of styrene, 0.018 parts by weight of tert-butylperoxide-3,5,5-trimethylhexanoate (TBPMH), 15 parts by weight of toluene, and 0.15 parts by weight of tert-dodecyl mercaptan to the mixing tank and mix thoroughly to prepare the reaction solution. Purge with nitrogen to completely remove oxygen.

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

[0060] The slurry obtained above is continuously fed into a drop-type devolatilizer. Before entering the devolatilizer, RIANOX 168, a phosphite antioxidant, is added to the slurry and mixed uniformly in a static mixer. Unreacted monomers and other volatiles are removed under conditions of vacuum of -3 kPa, temperature of 230°C, and residence time of 10 min. Before the devolatilized resin enters the die, RIANOX 1076, a hindered phenol antioxidant, is added and statically mixed. The addition amounts of the two antioxidants are based on a resin mass of 100 ppm and a hindered phenol to phosphite ratio of 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 weight of methyl methacrylate, 50 parts by weight of styrene, 0.02 parts by weight of tert-butylperoxide-3,5,5-trimethylhexanoate (TBPMH), 15 parts by weight of ethylbenzene, and 0.1 parts by weight of tert-dodecyl mercaptan to the mixing tank and mix thoroughly to prepare the reaction solution. Purge with nitrogen to completely remove oxygen.

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

[0064] The slurry obtained above is continuously fed into a drop-type devolatilizer. Before entering the devolatilizer, RIANOX 168, a phosphite antioxidant, is added to the slurry and mixed uniformly in a static mixer. Unreacted monomers and other volatiles are removed under vacuum conditions of -3 kPa, temperature of 230°C, and residence time of 10 min. RIANOX 1076 is added to the devolatilized resin before it enters the die and is statically mixed. The addition amounts of the two antioxidants are based on a resin mass of 500 ppm and a hindered phenol to phosphite ratio of 1:1. The devolatilized melt is extruded and pelletized to obtain the final product, methyl methacrylate copolymer.

[0065]

Example 3

[0066] Add 35 parts by weight of methyl methacrylate, 65 parts by weight of styrene, 0.01 parts by weight of dicumyl peroxide (DCP), 15 parts by weight of ethylbenzene, and 0.05 parts by weight of tert-dodecyl mercaptan to the mixing tank and mix thoroughly to prepare the reaction solution. Purge with nitrogen to completely remove oxygen.

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

[0068] The slurry obtained above is continuously fed into a drop-type devolatilizer. Before entering the devolatilizer, RIANOX 168, a phosphite antioxidant, is added to the slurry and mixed uniformly in a static mixer. Unreacted monomers and other volatiles are removed under conditions of -3 kPa vacuum, 230°C temperature, and 10 min residence time. Before the devolatilized resin enters the die, RIANOX 1076, a hindered phenol antioxidant, is added and statically mixed. The addition amounts of the two antioxidants are based on a resin mass of 1000 ppm and a hindered phenol to phosphite ratio of 1:3. The devolatilized melt is extruded and pelletized to obtain the final product, methyl methacrylate copolymer.

[0069]

Example 4

[0070] Add 75 parts by weight of methyl methacrylate, 15 parts by weight of styrene, 10 parts by weight of maleic anhydride, 0.02 parts by weight of tert-butyl peroxide-3,5,5-trimethylhexanoate (TBPMH), 15 parts by weight of toluene, and 0.2 parts by weight of n-octylthiol to the mixing tank and mix thoroughly to prepare the reaction solution. Purge with nitrogen to completely remove oxygen.

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

[0072] The slurry obtained above is continuously fed into a strip-type devolatilizer. Before entering the devolatilizer, RIANOX 168, a phosphite antioxidant, is added to the slurry and mixed uniformly in a static mixer. Unreacted monomers and other volatiles are removed under vacuum conditions of -3 kPa, temperature of 230°C, and residence time of 10 min. Before the devolatilized resin enters the die, RIANOX 1076, a hindered phenol antioxidant, is added and statically mixed. The addition amounts of the two antioxidants are based on a resin mass of 500 ppm and a hindered phenol to phosphite ratio of 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 weight of methyl methacrylate, 50 parts by weight of styrene, 0.02 parts by weight of tert-butylperoxide-3,5,5-trimethylhexanoate (TBPMH), 15 parts by weight of ethylbenzene, and 0.1 parts by weight of tert-dodecyl mercaptan to the mixing tank and mix thoroughly to prepare the reaction solution. Purge with nitrogen to completely remove oxygen.

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

[0076] The slurry obtained above is continuously fed into a drop-type devolatilizer. Before entering the devolatilizer, RIANOX 168, a phosphite antioxidant, is added to the slurry and mixed uniformly in a static mixer. Unreacted monomers and other volatiles are removed under vacuum conditions of -3 kPa, temperature of 230°C, and residence time of 10 min. RIANOX 1010 is added to the devolatilized resin before it enters the die and is statically mixed. The addition amounts of the two antioxidants are based on a resin mass of 500 ppm and a hindered phenol to phosphite ratio of 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 weight of methyl methacrylate, 50 parts by weight of styrene, 0.02 parts by weight of tert-butylperoxide-3,5,5-trimethylhexanoate (TBPMH), 15 parts by weight of ethylbenzene, and 0.1 parts by weight of tert-dodecyl mercaptan to the mixing tank and mix thoroughly to prepare the reaction solution. Purge with nitrogen to completely remove oxygen.

[0079] The reaction solution after batching was continuously added to a fully mixed flow reactor (effective volume 30L) at a flow rate of 10KG / h. The reactor temperature was controlled at 140℃, 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-type devolatilizer. Before entering the devolatilizer, RIANOX 138, a phosphite antioxidant, is added to the slurry and mixed uniformly in a static mixer. Unreacted monomers and other volatiles are removed under conditions of vacuum -3 kPa, temperature 230°C, and residence time 10 min. RIANOX 1076 is added to the devolatilized resin before it enters the die and is statically mixed. The addition amounts of the two antioxidants are based on a resin mass of 600 ppm and a hindered phenol to phosphite ratio of 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 weight of methyl methacrylate, 80 parts by weight of styrene, 0.005 parts by weight of tert-butylperoxide-3,5,5-trimethylhexanoate (TBPMH), and 10 parts by weight of ethylbenzene to the mixing tank, and mix thoroughly to prepare the reaction solution. Purge with nitrogen to completely remove oxygen.

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

[0084] The slurry obtained above is continuously fed into a drop-type devolatilizer. Before entering the devolatilizer, RIANOX 168, a phosphite antioxidant, is added to the slurry and mixed uniformly in a static mixer. Unreacted monomers and other volatiles are removed under vacuum of -3 kPa, temperature of 230°C, and residence time of 10 min. Before the devolatilized resin enters the die, RIANOX 1076, a hindered phenol antioxidant, is added and statically mixed. The addition amounts of the two antioxidants are based on a resin mass of 1000 ppm and a hindered phenol to phosphite ratio of 1:1. The devolatilized melt is extruded and pelletized to obtain the final product, methyl methacrylate copolymer.

[0085]

Example 8

[0086] Add 70 parts by weight of methyl methacrylate, 10 parts by weight of styrene, 20 parts by weight of glutaric anhydride, 0.02 parts by weight of tert-butyl peroxide-3,5,5-trimethylhexanoate (TBPMH), 15 parts by weight of toluene, and 0.2 parts by weight of n-octyl mercaptan to a mixing tank and mix thoroughly to prepare the reaction solution. Purge with nitrogen to completely remove oxygen.

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

[0088] The slurry obtained above is continuously fed into a strip-type devolatilizer. Before entering the devolatilizer, RIANOX 138, a phosphite antioxidant, is added to the slurry and mixed uniformly in a static mixer. Unreacted monomers and other volatiles are removed under vacuum of -3 kPa, temperature of 230°C, and residence time of 10 min. Before the devolatilized resin enters the die, RIANOX 1010, a hindered phenol antioxidant, is added and statically mixed. The addition amounts of the two antioxidants are based on a resin mass of 800 ppm and a hindered phenol to phosphite ratio of 1:1. The devolatilized melt is extruded and pelletized to obtain the final product, methyl methacrylate copolymer.

[0089]

Example 9

[0090] Add 70 parts by weight of methyl methacrylate, 20 parts by weight of α-methylstyrene, 10 parts by weight of maleic anhydride, 0.03 parts by weight of tert-butyl peroxide-3,5,5-trimethylhexanoate (TBPMH), and 15 parts by weight of toluene to a mixing tank and mix thoroughly to prepare the reaction solution. Purge with nitrogen to completely remove oxygen.

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

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

[0093] Comparative Example 1

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

[0095] Comparative Example 2

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

[0097] Comparative Example 3

[0098] The methyl methacrylate copolymer was prepared in essentially the same manner as in Example 2, except that no antioxidants were added.

[0099] Comparative Example 4

[0100] Methyl methacrylate copolymers were prepared in essentially the same manner as in Example 2, except that no phosphite antioxidants were added, and only the hindered phenolic antioxidant RIANOX 1076 was added at a rate of 500 ppm during the extrusion granulation stage.

[0101] Comparative Example 5

[0102] The methyl methacrylate copolymer was prepared in essentially the same manner as in Example 2, except that: no hindered phenolic antioxidants were added, and only 500 ppm of phosphite antioxidant RIANOX 168 was added before melt devolatilization.

[0103] Comparative Example 6

[0104] The methyl methacrylate copolymer was prepared in essentially the same manner as in Example 2, except that hindered phenolic antioxidant RIANOX 1076 and phosphite antioxidant RIANOX 168 were added during the monomer formulation stage, with the amount and proportion of addition remaining unchanged.

[0105] The performance tests of the methyl methacrylate copolymers prepared in each embodiment and comparative example were performed as shown in Table 3, and the results are shown in Table 3.

[0106] As can be seen from the comparison of the examples and comparative examples, when phosphite antioxidants are added before resin devolatilization and hindered phenolic antioxidants are added during the resin extrusion granulation stage, the methyl methacrylate copolymer of the present invention exhibits excellent performance in terms of light transmittance, haze, color, and aging resistance.

[0107] Table 3. Formulations and performance test results of the examples and comparative examples.

[0108]

Claims

1. A methyl methacrylate copolymer, characterized in that, It is obtained by polymerization reaction comprising 20-90 parts by mass of methyl methacrylate monomer component A, 10-80 parts by mass of aromatic unsaturated hydrocarbon monomer component B, and 0-20 parts by mass of vinyl monomer component C, which is different from components A and B. Phosphite antioxidants are added before resin devolatilization, and hindered phenolic antioxidants are added during the resin extrusion granulation stage; the total amount of hindered phenolic antioxidants and phosphite antioxidants added is 10-2000 ppm, and the mass ratio of hindered phenolic antioxidants to phosphite antioxidants is 5:1-1:5 based on the mass of the resin. The methyl methacrylate copolymer has a melt flow rate of 2-15 g / 10 min at 230℃ / 3.8 KG. The injection molded product has a total light transmittance of ≥90%, haze of ≤1%, yellowing index YI≤1 and yellowing index YI change value ΔYI≤1.5 before and after 30 days of UV aging.

2. The methyl methacrylate copolymer according to claim 1, characterized in that, It is obtained by polymerization of 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. The methyl methacrylate copolymer has a melt flow rate of 4-10 g / 10 min at 230℃ / 3.8 KG, and the injection molded product has a total light transmittance of ≥91%, haze of ≤0.5%, yellowing index YI value of ≤0.7 and a yellowing index YI change value ΔYI of ≤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 hindered phenolic antioxidants and phosphite antioxidants added is 100-1000 ppm, based on the mass of the resin.

4. The methyl methacrylate copolymer according to claim 3, characterized in that, The mass ratio of the hindered phenolic antioxidant to the phosphite antioxidant is 3:1 to 1:

3.

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

6. The methyl methacrylate copolymer according to claim 5, characterized in that, The aromatic unsaturated hydrocarbon monomer in component B is styrene.

7. The methyl methacrylate copolymer according to claim 3, characterized in that, The vinyl monomer in component c) is selected from at least one of methacrylate monomers, alkyl acrylate monomers, acid monomers, acid anhydride monomers, imide monomers, and nitrile monomers.

8. The methyl methacrylate copolymer according to claim 7, characterized in that, 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 monomers are selected from any one of acrylic acid, methacrylic acid, and itaconic acid; and / or The anhydride monomers are selected from 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 either acrylonitrile or methacrylonitrile.

9. A method for preparing the methyl methacrylate copolymer according to any one of claims 1-8, characterized in that, Includes the following steps: 1) Polymerization: Methyl methacrylate monomer component A, aromatic unsaturated hydrocarbon monomer component B, and optional vinyl monomer component C (different from components A and B) are added to the polymerization reactor, and the polymerization reaction yields a slurry; 2) Deviation: The obtained slurry is sent to a devolatilizer to remove unreacted monomers and other volatiles; 3) Post-treatment: The devolatilized resin is extruded and granulated to obtain methyl methacrylate copolymer; Specifically, phosphite antioxidants are added before the slurry enters the devolatilizer, and hindered phenolic antioxidants are added before resin granulation.

10. The preparation method according to claim 9, characterized in that, The polymerization step 1) is carried out by adding an initiator, which is an organic peroxide or an azo compound.

11. The preparation method according to claim 10, characterized in that, The initiator is an organic peroxide.

12. The preparation method according to claim 11, characterized in that, The initiator is any one or more of the following: 1,1-bis-(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis-(tert-butylperoxy)cyclohexane, tert-butyl peroxide-3,5,5-trimethylhexanoate, 2,2-bis(tert-butylperoxy)butane, tert-butylperoxycarbonate-2-ethylhexyl, tert-amyl peroxide, tert-butyl peroxide, dicumyl peroxide, and di-tert-butyl peroxide.

13. The preparation method according to claim 10, characterized in that, The half-life of the initiator at the polymerization reaction temperature is 3-30 min; the amount of initiator added is 10-1000 ppm based on the total mass of components A, B, and C.

14. The preparation method according to claim 13, characterized in that, The amount of initiator added is 50-300 ppm based on the total mass of components A, B, and C.

15. The preparation method according to claim 13, characterized in that, The polymerization reaction temperature is 100-180℃; the polymerization reaction time is 1-6h; and the reactor outlet conversion rate is 50-85%.

16. The preparation method according to claim 15, characterized in that, The polymerization reaction temperature is 120-160℃; the polymerization reaction time is 1.5-4h; and the reactor outlet conversion rate is 65-75%.

17. The preparation method according to any one of claims 9-16, characterized in that, Step 1) The polymerization reaction is carried out in the presence of a solvent.

18. The preparation method according to claim 17, characterized in that, Step 1) During the polymerization reaction, add solvent accounting for 5-30% of the total mass of components A, B, and C.

19. The preparation method according to claim 18, characterized in that, Step 1) During the polymerization reaction, add solvent accounting for 10-20% of the total mass of components A, B, and C.

20. The preparation method according to claim 17, characterized in that, The solvent is one or more of toluene, ethylbenzene, xylene, acetone, butanone, ethyl acetate, butyl acetate, tetrahydrofuran, and N,N-dimethylformamide.

21. The preparation method according to claim 20, characterized in that, The solvent is toluene or ethylbenzene.

22. The preparation method according to any one of claims 9-16, characterized in that, The devolatilizer mentioned in step 2) is selected from one or more combinations of vented extruders, drop strip devolatilizers, falling film devolatilizers, thin film evaporators, single-shaft devolatilizers, and bi-shaft devolatilizers.

23. The preparation method according to claim 22, characterized in that, The devolatilizer mentioned in step 2) is selected from a drop-type devolatilizer, a vented extruder, or a combination thereof.

24. The preparation method according to claim 23, characterized in that, The devolatilizer mentioned in step 2) is a strip devolatilizer.

25. The preparation method according to claim 22, characterized in that, In the post-processing stage of step 3), an auxiliary agent may also be added, which is selected from at least one of release agents, blueing agents, and ultraviolet absorbers.

26. The application of the methyl methacrylate copolymer according to any one of claims 1-8 or the methyl methacrylate copolymer prepared by the preparation method according to any one of claims 9-25 in the fields of display light guide plates, lighting light guide plates, automobiles, daily necessities, and cosmetic packaging.

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