Methyl methacrylate polymers, processes for their preparation and use

Abstract

The application relates to the field of high polymer material preparation, and discloses a methyl methacrylate polymer and a preparation method and application thereof. The polymer comprises structural unit A and optionally structural unit B; the structural unit A has the structure shown in formula I; the structural unit B has the structures shown in formula II and / or formula III; R1 is selected from C2-C4 linear or branched alkyl, and R2 is selected from H or C1-C3 linear or branched alkyl; the isotacticity of the polymer is 4-10%; the melt index of the polymer is 4-8 g / 10 min under the conditions of 230 DEG C and 3.8 kg. The methyl methacrylate polymer has the characteristics of uniform molecular weight, low isotacticity and good processing performance.

Description

Technical Field

[0001] This invention relates to the field of polymer material preparation, specifically to a methyl methacrylate polymer, its preparation method, and its applications. Background Technology

[0002] Polymethyl methacrylate (PMMA), also known as plexiglass or acrylic, is a polymer compound made from methacrylates. This material is renowned for its smooth surface, high transparency, lightweight, high strength, corrosion resistance, UV aging resistance, good insulation, and sound insulation properties. PMMA is mainly produced through bulk polymerization, suspension polymerization, and solution polymerization. Bulk polymerization offers significant advantages due to its pure, uniform, and highly transparent product, which can be directly used for casting or granulation. It also boasts high production efficiency, eliminates the need for complex separation and devolatilization processes, and results in low energy consumption and minimal pollution.

[0003] China is the largest consumer of PMMA, with annual apparent consumption approaching 800,000 tons, driven by the continued growth in demand for high-end PMMA products from the domestic electronics and LCD display sectors. However, despite this large demand, China still relies heavily on imports of high-end PMMA products, with approximately 200,000 tons imported annually. Therefore, developing high-performance PMMA products is of significant strategic importance for meeting domestic market demand. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of non-uniform weight-average molecular weight, high isotacticity, and poor processing performance of methyl methacrylate polymers in the prior art, and to provide a methyl methacrylate polymer, its preparation method, and its application. This methyl methacrylate polymer has uniform molecular weight, low isotacticity, and good processing performance.

[0005] To achieve the above objectives, a first aspect of the present invention provides a methyl methacrylate polymer, wherein the polymer comprises structural unit A and optionally structural unit B;

[0006] Wherein, the structural unit A has the structure shown in Equation I,

[0007]

[0008] Wherein, the structural unit B has the structure shown in Formula II and / or Formula III,

[0009]

[0010] Wherein, R1 is selected from C2-C4 straight-chain or branched alkyl groups, and R2 is selected from H or C1-C3 straight-chain or branched alkyl groups;

[0011] The isotacticity of the polymer is 4-10%;

[0012] The polymer has a melt index of 4-8 g / 10 min at 230°C and 3.8 kg.

[0013] Preferably, the isotacticity of the polymer is 4-7%.

[0014] Preferably, the polymer has a melt index of 4.5-7.5 g / 10 min at 230°C and 3.8 kg.

[0015] A second aspect of the present invention provides a method for preparing a methyl methacrylate polymer, comprising the following steps:

[0016] (1) In the presence of a protective gas, methyl methacrylate, optionally functional monomer X, chain transfer agent and initiator I are subjected to a prepolymerization reaction in reactor I to obtain a prepolymer;

[0017] (2) In the presence of a protective gas, the prepolymer is subjected to a final polymerization reaction in reactor II to obtain the methyl methacrylate polymer;

[0018] Steps (1) and / or (2) are carried out in the presence of initiator II;

[0019] Wherein, the initiator II is a compound represented by formula IV.

[0020]

[0021] Preferably, the temperature of the final polymerization reaction is higher than the temperature of the prepolymerization reaction.

[0022] The third aspect of the present invention provides a methyl methacrylate polymer prepared by the preparation method described in the second aspect above.

[0023] The fourth aspect of the present invention provides the use of the methyl methacrylate polymer described in the first or third aspect above in at least one of liquid crystal displays, optical materials and electronic products.

[0024] Through the above technical solution, the methyl methacrylate polymer provided by the present invention has uniform molecular weight, low isotacticity and good processing performance, which is conducive to the application of methyl methacrylate polymer in at least one of liquid crystal displays, optical materials and electronic products, and effectively meets the domestic market demand for high-quality methyl methacrylate polymer.

[0025] In the preparation process, this invention employs a highly efficient polymerization method that achieves precise control over the polymerization of methyl methacrylate by contacting methyl methacrylate, optionally functionalized monomer X, chain transfer agent, initiator I, and initiator II. This method simplifies the preparation process, ensures the controllability of the polymerization process, optimizes mass and heat transfer, and reduces the occurrence of gelation.

[0026] In particular, initiator II used in this invention is more conducive to obtaining methyl methacrylate polymers with uniform molecular weight, low isotacticity, and excellent processing properties. The use of this initiator not only improves the quality of the polymer but also further enhances its potential in high-end applications, providing strong support for the development of related industries. Detailed Implementation

[0027] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this invention are based on weight, unless being based on weight would not be in accordance with the common understanding of those skilled in the art.

[0029] The first aspect of the present invention provides a methyl methacrylate polymer, wherein the polymer includes structural unit A and optionally structural unit B;

[0030] Wherein, the structural unit A has the structure shown in Equation I,

[0031]

[0032] Wherein, the structural unit B has the structure shown in Formula II and / or Formula III,

[0033]

[0034] Wherein, R1 is selected from C2-C4 straight-chain or branched alkyl groups, and R2 is selected from H or C1-C3 straight-chain or branched alkyl groups;

[0035] The isotacticity of the polymer is 4-10%;

[0036] The polymer has a melt index of 4-8 g / 10 min at 230°C and 3.8 kg.

[0037] This invention controls the isotacticity and melt index of the polymer within the above-mentioned range, successfully achieving both uniformity of polymer weight-average molecular weight and low isotacticity characteristics, while also possessing excellent processing performance.

[0038] According to the present invention, preferably, the isotacticity of the polymer is 4-7%.

[0039] According to the present invention, preferably, the polymer has a melt index of 4.5-7.5 g / 10 min at 230°C and 3.8 kg.

[0040] In this invention, polymer isotacticity and melt index within the above-mentioned preferred ranges are more conducive to improving the processing performance of the polymer.

[0041] This invention uses a Swiss Bruker AV 300 nuclear magnetic resonance spectrometer to measure the proton spectrum of a polymer, calculates the isotacticity of the polymer based on the integral area of ​​the proton spectrum, and tests the polymer melt index according to ISO 1133-1:2022 at 230°C and 3.8 kg.

[0042] In this invention, the isotacticity of a polymer refers to the proportion of isotactic isomers to all isomers in the polymer chain. The methyl methacrylate polymer in this invention has a low isotacticity, which is more beneficial for improving the polymer's processing performance.

[0043] In this invention, the melt index of a polymer refers to the mass (in grams) of polymer melt that passes through a standard capillary tube within 10 minutes under certain temperature and pressure conditions. It is an important indicator for measuring the flowability of polymer melts. The methyl methacrylate polymer in this invention has a high melt index, which is more conducive to improving the polymer's processing performance.

[0044] In this invention, "optionally" means that the polymer may include structural unit A and structural unit B, or may include only structural unit A. Those skilled in the art can make the selection according to actual needs, and this invention does not have any particular limitation.

[0045] In this invention, C2-C4 straight-chain or branched alkyl groups refer to saturated hydrocarbon groups containing 2 to 4 carbon atoms. These alkyl groups can be straight-chain or branched, and for example, can be at least one of ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl.

[0046] In this invention, C1-C3 straight-chain or branched alkyl refers to alkyl groups containing 1 to 3 carbon atoms. These alkyl groups can be straight-chain or branched, for example, at least one of methyl, ethyl, n-propyl, and isopropyl.

[0047] The present invention does not particularly limit the relative position of R2 to the benzene ring. Those skilled in the art can select it according to actual needs. For example, R2 can be at least one of the ortho, meta and para positions of the benzene ring.

[0048] According to the present invention, preferably, based on the total weight of the polymer, the content of structural unit A is 70-100% by weight, and the content of structural unit B is 0-30% by weight; the content of methyl methacrylate is preferably 90-100% by weight, and the content of structural unit B is preferably 0-10% by weight.

[0049] In this invention, the contents of structural unit A and structural unit B were determined by measuring the integral area of ​​the proton spectrum of special groups in structural unit A and structural unit B using a Swiss Bruker AV 300 nuclear magnetic resonance spectrometer.

[0050] In this invention, the content of structural unit A and structural unit B within the above-mentioned range is more conducive to improving the performance of methyl methacrylate polymer.

[0051] According to the present invention, preferably, the glass transition temperature of the polymer is 107-120°C, more preferably 110-120°C.

[0052] This invention uses a differential scanning calorimeter (DSC8500) to test the glass transition temperature T of the polymer. g .

[0053] In this invention, the polymer has a moderate glass transition temperature, which is more conducive to maintaining good processing performance.

[0054] According to the present invention, preferably, the polymer has a weight-average molecular weight of 9 × 10⁻⁶. 4 -14×10 4 g / mol, more preferably 9×10 g / mol. 4 -12×10 4 gg / mol.

[0055] According to the present invention, preferably, the molecular weight distribution of the polymer is 1.9-2.2, more preferably 1.9-2.

[0056] This invention uses gel permeation chromatography (PL-GPC20) to measure the molecular weight and distribution of polymers.

[0057] In this invention, the polymer has a higher molecular weight and a narrower molecular weight distribution range, which is more conducive to improving processing performance.

[0058] In this invention, the polymer has a high melt index, which is more conducive to product processing and application.

[0059] According to the present invention, preferably, the content of residual monomer in the polymer is less than or equal to 0.35% by weight, more preferably less than or equal to 0.3% by weight.

[0060] This invention uses a Swiss Bruker AV 300 nuclear magnetic resonance spectrometer to measure the hydrogen spectrum of polymers, and calculates the residual monomer content of polymers based on the integral area of ​​the hydrogen spectrum.

[0061] It should be noted that, in this invention, residual monomer refers to the remaining amount of all raw material monomers used to prepare methyl methacrylate polymers.

[0062] A second aspect of the present invention provides a method for preparing a methyl methacrylate polymer, comprising the following steps:

[0063] (1) In the presence of a protective gas, methyl methacrylate, optionally functional monomer X, chain transfer agent and initiator I are subjected to a prepolymerization reaction in reactor I to obtain a prepolymer;

[0064] (2) In the presence of a protective gas, the prepolymer is subjected to a final polymerization reaction in reactor II to obtain the methyl methacrylate polymer;

[0065] Steps (1) and / or (2) are carried out in the presence of initiator II;

[0066] Wherein, the initiator II is a compound represented by formula IV.

[0067]

[0068] This invention employs initiator I and initiator II to achieve multi-stage, multi-functionality initiation, thereby improving production efficiency and product performance.

[0069] The present invention employs initiator II as shown in Formula IV, which is more conducive to providing stable free radicals and initiating the polymerization reaction of methyl methacrylate monomers. It can effectively control the weight-average molecular weight of the polymer. Initiator II can promote the polymerization reaction, reduce the residue of unreacted monomers, and is more conducive to improving the performance of the product.

[0070] According to the present invention, preferably, based on the total weight of methyl methacrylate and functional monomer X, the amount of initiator I is 0.1-1% by weight, for example, it can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1% by weight and any range between any two values. The present invention, by controlling the amount of initiator I, is beneficial to the prepolymerization reaction process, and more preferably 0.2-0.6% by weight.

[0071] According to the present invention, preferably, based on the total weight of methyl methacrylate and functional monomer X, the amount of initiator II is 0.1-1.5% by weight, for example, it can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5% by weight, and any range between any two values. The present invention, by controlling the amount of initiator II, is beneficial to the final polymerization reaction process, and more preferably 0.2-0.5% by weight.

[0072] This invention, by adjusting the content of initiator I and initiator II, is more conducive to achieving multi-stage, multi-functional initiation, thereby improving the performance of methyl methacrylate polymers and controlling the polymerization process.

[0073] According to the present invention, preferably, based on the total weight of methyl methacrylate and functional monomer X, the amount of methyl methacrylate is 70-100% by weight, and the amount of functional monomer X is 0-30% by weight. Using the above range is beneficial for improving the performance of the polymer. Preferably, the amount of methyl methacrylate is 90-100% by weight, and the amount of functional monomer X is preferably 0-10% by weight.

[0074] According to the present invention, preferably, based on the total weight of methyl methacrylate and functional monomer X, the amount of chain transfer agent is 0.1-0.8% by weight, for example, it can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8% by weight and any range between any two values. The use of chain transfer agent within the above range is beneficial for controlling the weight-average molecular weight of the polymer in the present invention, and more preferably 0.1-0.3% by weight.

[0075] According to the present invention, preferably, in step (1), the functional monomer X is selected from the structure shown in Formula 1 and / or Formula 2.

[0076]

[0077] Wherein, R1 is selected from C2-C4 straight-chain or branched alkyl groups, and R2 is selected from H or C1-C3 straight-chain or branched alkyl groups.

[0078] It should be noted that in this invention, when there is more than one type of functional unit X, there is no particular limitation on the specific amount of each unit, as long as the total amount of functional unit X meets the scope of this invention. Those skilled in the art can make selections according to actual needs.

[0079] The present invention does not particularly limit the type of chain transfer agent, as long as the weight-average molecular weight of the polymer in the present invention can be controlled. Those skilled in the art can select according to actual needs. Preferably, the chain transfer agent is selected from at least one of n-dodecyl mercaptan, tert-dodecyl mercaptan, n-butanethiol, n-octyl mercaptan and tert-butanethiol.

[0080] The present invention does not particularly limit the type of initiator I, as long as it can initiate the prepolymerization reaction of the polymer. Those skilled in the art can select it according to actual needs. Preferably, the initiator I is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, lauroyl peroxide, tert-butyl peroxide, diisopropyl peroxide, cumene hydrogen peroxide, diisopropylbenzene peroxide, and cyclohexanone peroxide.

[0081] According to the present invention, preferably, the method further includes cooling the methyl methacrylate, functional monomer X, chain transfer agent, initiator I and initiator II.

[0082] The present invention does not particularly limit the cooling temperature of methyl methacrylate, functional monomer X, chain transfer agent, initiator I and initiator II, as long as the reaction can proceed smoothly. Those skilled in the art can select according to actual needs. Preferably, the cooling temperature is 0-20°C, more preferably 10-15°C.

[0083] In this invention, cold material is introduced into the polymerization reactor, which can achieve effective mass and heat transfer of high-viscosity fluid in bulk polymerization, and is more conducive to precise temperature control.

[0084] In this invention, the optional functional unit X means that functional unit X may or may not be added, and this invention does not have any particular limitation on this.

[0085] In this invention, steps (1) and / or (2) are carried out in the presence of initiator II, meaning that it can be introduced at any stage of the polymerization process to promote the reaction. Specifically, initiator II can be added to reactor I together with methyl methacrylate, functional monomer X, chain transfer agent, and initiator I for prepolymerization. Alternatively, it can be added to reactor II together with the prepolymer after the prepolymerization stage for final polymerization. Furthermore, initiator II can be added in both reaction stages to ensure the smooth progress of the entire polymerization process. This invention does not particularly limit the timing of initiator II addition, as long as it can trigger the polymerization reaction; those skilled in the art can choose according to actual needs. Preferably, this invention uses initiator II added to reactor I together with methyl methacrylate, optionally functional monomer X, chain transfer agent, and initiator I for polymerization.

[0086] This invention does not particularly limit the mixing method and order of methyl methacrylate, functional monomer X, chain transfer agent, initiator I, and initiator II. For example, methyl methacrylate, functional monomer X, chain transfer agent, initiator I, and initiator II can be mixed independently with other substances, as long as the substances can be fully contacted. Those skilled in the art can select according to actual needs. Preferably, this invention involves first mixing methyl methacrylate and optionally functional monomer X evenly in a preparation vessel, then adding chain transfer agent, initiator I, and initiator II to the preparation vessel after cooling and stirring until completely dissolved. After the substance is dissolved, it is injected into a storage tank, and after nitrogen gas is introduced, it is transferred to reaction vessel I.

[0087] The present invention does not particularly limit the types of configuration vessels and storage tanks mentioned above, as long as they can meet the requirements of the present invention, those skilled in the art can select them according to actual needs.

[0088] The present invention does not particularly limit the stirring method and rate described above, as long as methyl methacrylate, functional monomer X, chain transfer agent, initiator I and initiator II can be fully mixed or completely dissolved. Those skilled in the art can choose according to actual needs.

[0089] The present invention does not particularly limit the type of reactor I, as long as it can enable the reaction described in step (1) to proceed. Those skilled in the art can select according to actual needs. Preferably, the reactor I described in step (1) is a horizontal self-cleaning reactor I.

[0090] The horizontal self-cleaning reactor I used in this invention has a high-torque stirring paddle, which can realize effective mass and heat transfer of high-viscosity fluids in bulk polymerization. Furthermore, the stirring paddle and jacket of the horizontal self-cleaning reactor I are equipped with a circulating heat transfer medium, which is more conducive to achieving rapid heat transfer over a large area and precise temperature control, and avoids gel formation.

[0091] The present invention does not particularly limit the rate at which methyl methacrylate and functional monomer X are introduced into reactor I, as long as the reaction proceeds smoothly. Those skilled in the art can select the rate according to actual needs. Preferably, the rates at which methyl methacrylate and functional monomer X are introduced into reactor I are each 0.1-1 L / min independently.

[0092] It should be noted that the present invention does not particularly limit the rate at which the chain transfer agent, initiator I, and initiator II are introduced into reactor I, and those skilled in the art can select them according to actual needs. According to a specific embodiment of the present invention, preferably, the chain transfer agent, initiator I, and initiator II are introduced into reactor I together with methyl methacrylate and optionally functional monomer X at a rate of 0.1-1 L / min.

[0093] The present invention does not particularly limit the feeding method. The materials can be fed independently through multiple pipelines at the above-mentioned speed, or they can be mixed and fed through one pipeline. Those skilled in the art can choose according to actual needs. Preferably, the present invention uses a pump to feed the chain transfer agent, initiator I and initiator II together with methyl methacrylate and optionally functional monomer X into reactor I through one pipeline.

[0094] This invention does not impose any particular limitation on the type of pump; any pump that can meet the requirements of this invention is acceptable. Those skilled in the art can select the appropriate type based on actual needs.

[0095] The above-mentioned rate is more conducive to the full contact of methyl methacrylate, functional monomer X, chain transfer agent, initiator I and initiator II, resulting in a stable reaction and improved performance of methyl methacrylate polymer.

[0096] According to the present invention, preferably, the prepolymerization reaction in step (1) is carried out under stirring conditions.

[0097] The present invention does not particularly limit the stirring rate of the prepolymerization reaction, as long as the substances in the prepolymerization reaction can react fully. Those skilled in the art can select according to actual needs. Preferably, the stirring rate of the prepolymerization reaction in step (1) is 5-20 rpm.

[0098] According to the present invention, preferably, the conditions for the prepolymerization reaction include: a reaction temperature of 90-130°C and a reaction time of 15-40 minutes.

[0099] According to the present invention, preferably, the temperature fluctuation of the prepolymerization reaction is less than 3°C.

[0100] The polymerization temperature described above in this invention enables the stable polymerization of methyl methacrylate.

[0101] According to the present invention, preferably, the yield of the prepolymer in the prepolymerization reaction in step (1) is 20-40% by weight, more preferably 25-35% by weight.

[0102] In this invention, the yield of the prepolymer is calculated by precipitation method. The mass of the prepolymer solution is m0, and the mass of the precipitated polymer after drying is m1. The yield of the prepolymer is (m1 / m0)×100%.

[0103] In this invention, the prepolymer solution refers to the solution after the prepolymerization reaction.

[0104] The yield of the prepolymer in the prepolymerization reaction of this invention is within the above-mentioned range, which is more conducive to the final polymerization reaction in continuous polymerization.

[0105] The present invention does not particularly limit the type of reactor II, as long as it enables the reaction described in step (2) to proceed. Those skilled in the art can select according to actual needs. Preferably, the reactor II described in step (2) is a horizontal self-cleaning reactor II.

[0106] The horizontal self-cleaning reactor II used in this invention has a high-torque stirring paddle, which can realize effective mass and heat transfer of high-viscosity fluids in bulk polymerization. Furthermore, the stirring paddle and jacket of the horizontal self-cleaning reactor II are equipped with a circulating heat transfer medium, which is more conducive to achieving rapid heat transfer over a large area and precise temperature control, and avoids gel formation.

[0107] The present invention does not impose any particular limitation on the rate at which the prepolymer is introduced into reactor II in step (2), as long as the reaction in step (2) proceeds smoothly. Those skilled in the art can make the selection according to actual needs. Preferably, the rate at which the prepolymer is introduced into reactor II is 0.1-1 L / min.

[0108] The method of introducing the material in step (2) is the same as that described in step (1) above, and will not be repeated here.

[0109] It should be noted that when initiator II is added in step (2), the present invention does not particularly limit the rate at which initiator II is introduced into reactor I, and those skilled in the art can select the rate according to actual needs. Preferably, in the present invention, initiator II and prepolymer are introduced into reactor I together through the same pipeline at a rate of 0.1-1 L / min.

[0110] According to the present invention, preferably, the final polymerization reaction in step (2) is carried out under stirring conditions.

[0111] The present invention does not particularly limit the stirring rate of the final polymerization reaction, as long as the substances in step (2) can react fully. Those skilled in the art can select according to actual needs. Preferably, the stirring rate of the final polymerization reaction in step (2) is 5-20 rpm.

[0112] According to the present invention, preferably, the conditions for the final polymerization reaction include: a reaction temperature of 130-170°C and a reaction time of 10-40 minutes.

[0113] According to the present invention, preferably, the temperature fluctuation of the final polymerization reaction is less than 3°C.

[0114] According to the present invention, preferably, the temperature of the final polymerization reaction is higher than the temperature of the prepolymerization reaction.

[0115] The polymerization temperature used in this invention is more conducive to the stable polymerization of methyl methacrylate. By using multifunctional initiator II at this temperature, the polymerization of methyl methacrylate is mainly initiated by high temperature, and a methyl methacrylate polymer with uniform molecular weight, low isotacticity and good processability is prepared.

[0116] The present invention does not particularly limit the type of protective gas in step (1) and / or step (2), as long as it can meet the requirements of the present invention. Those skilled in the art can select according to actual needs. Preferably, the protective gas is nitrogen.

[0117] This invention improves polymer performance by using a protective gas to remove dissolved oxygen from the system.

[0118] According to the present invention, preferably, after the final polymerization reaction, the methyl methacrylate polymer is further subjected to discharge, devolatilization and extrusion.

[0119] The present invention does not particularly limit the equipment for polymer discharge, devolatilization and extrusion. Those skilled in the art can select according to actual needs. According to a specific embodiment of the present invention, preferably, polymer discharge, devolatilization and extrusion are carried out in a screw extruder.

[0120] According to the present invention, preferably, the discharge temperature is 170-190°C.

[0121] The present invention does not have a particular limitation on the discharge rate, which can be adjusted according to the size of the reactor. Those skilled in the art can select according to actual needs. Preferably, the discharge rate is 8-20 rpm.

[0122] According to the present invention, preferably, the devolatilization temperature is 190-230℃, the devolatilization rate is 80-180rpm, and the devolatilization pressure is less than 20Pa.

[0123] This invention does not impose any particular limitation on the number of temperature settings during the devolatilization process, as long as the volatile substances in the polymerization reaction process can be effectively removed. Those skilled in the art can select the appropriate settings according to actual needs.

[0124] The present invention employs the above-mentioned discharge temperature and rate, as well as devolatilization temperature and rate, which are more conducive to obtaining pure polymers.

[0125] The present invention further includes discharging, devolatilization and extrusion of the methyl methacrylate polymer, followed by stranding, cooling, pelletizing and drying to obtain methyl methacrylate polymer granules.

[0126] This invention does not impose any particular limitations on the equipment and temperature for stretching, cooling, pelletizing, and drying, as long as the methyl methacrylate polymer pellets described in this invention can be obtained. Those skilled in the art can select the appropriate equipment based on actual needs.

[0127] The third aspect of the present invention provides a methyl methacrylate polymer prepared by the preparation method described in the second aspect above.

[0128] The fourth aspect of the present invention provides the use of the methyl methacrylate polymer described in the first or third aspect above in at least one of liquid crystal displays, optical materials and electronic products.

[0129] The present invention will be described in detail below through embodiments.

[0130] Unless otherwise specified, all examples and comparative examples below are based on conventional methods; and all reagents and materials used, unless otherwise specified, are commercially available and / or prepared using methods known in the art.

[0131] In the following examples and comparative examples, the contents of structural unit A and structural unit B were obtained by measuring the integral area of ​​the proton spectrum of special groups in structural unit A and structural unit B using a Swiss Bruker AV 300 nuclear magnetic resonance spectrometer.

[0132] In the following examples and comparative examples, the yield of the prepolymer in the prepolymerization reaction was calculated by the precipitation method. The mass of the prepolymer solution was m0, and the mass of the precipitated polymer after drying was m1. The yield of the prepolymer was (m1 / m0)×100%.

[0133] In the following examples and comparative examples, gel permeation chromatography (PL-GPC20) was used to measure the weight-average molecular weight and its distribution of the polymers.

[0134] In the following examples and comparative examples, the glass transition temperature T of the polymers was tested using a differential scanning calorimeter (DSC8500). g .

[0135] In the following examples and comparative examples, the transmittance of the polymer was determined according to ISO 13468-2:2021 and the haze of the polymer was determined according to ISO 14782:2021.

[0136] In the following examples and comparative examples, the polymer melt index was tested according to ISO 1133-1:2022 at 230°C and 3.8 kg.

[0137] In the following examples and comparative examples, the proton NMR spectra of the polymers were measured using a Swiss Bruker AV 300 NMR spectrometer, and the isotacticity and residual monomer content of the polymers were calculated based on the integral area of ​​the proton NMR spectra.

[0138] Example 1

[0139] 100 kg of methyl methacrylate was metered into the preparation vessel by a pump, stirred and mixed evenly, and then cooled to 12°C.

[0140] Add 0.25 kg of chain transfer agent n-dodecyl mercaptan, 0.2 kg of benzoyl peroxide, and 0.5 kg of multifunctional initiator II to the preparation vessel, and stir until completely dissolved;

[0141] The solution in the preparation vessel is injected into the monomer storage tank by a pump metering, and high-purity nitrogen gas is blown in through the bottom tube in the tank;

[0142] The material is continuously injected into the horizontal self-cleaning reactor I at a rate of 0.6 L / min, with an internal temperature of 100°C, a stirring rate of 8 rpm, and a material residence time of 30 min. Then, it is continuously pumped from reactor I to the horizontal self-cleaning reactor II at a rate of 0.6 L / min to continue polymerization at a polymerization temperature of 140°C, a stirring rate of rpm, and a material residence time of 30 min.

[0143] The material is continuously fed into the twin-screw devolatilization section via a discharge screw. The discharge screw temperature is 175℃, the discharge screw speed is 10rpm, the six devolatilization temperatures are 190℃, 200℃, 210℃, 210℃, 215℃ and 220℃ respectively, the twin-screw devolatilization speed is 110rpm, and the devolatilization section pressure is less than 20Pa.

[0144] After devolatilization, the methyl methacrylate polymer granules were obtained by extrusion through a twin-screw extruder, forming, cooling, pelletizing, and drying. The performance test results are shown in Tables 1 and 2.

[0145] Example 2

[0146] 95 kg of methyl methacrylate and 5 kg of styrene (R2 is H in Formula 2) were metered into the preparation vessel by a pump, stirred and mixed evenly, and then cooled to 10°C.

[0147] Add 0.1 kg of chain transfer agent tert-dodecyl mercaptan, 0.6 kg of azobisisobutyronitrile, and 0.2 kg of multifunctional initiator II to the preparation vessel, and stir until completely dissolved;

[0148] The solution in the preparation vessel is injected into the monomer storage tank by a pump metering, and high-purity nitrogen gas is blown in through the bottom tube in the tank;

[0149] The material is continuously injected into the horizontal self-cleaning reactor I at a rate of 0.3 L / min by a pump. The internal temperature of the reactor is 90℃, the stirring rate is 12 rpm, and the material residence time is 40 min. Then, it is continuously fed from reactor I to the horizontal self-cleaning reactor II at a rate of 0.3 L / min to continue polymerization. The polymerization temperature is 170℃, the stirring rate is 14 rpm, and the material residence time is 20 min.

[0150] The material is continuously fed into the twin-screw devolatilization section via a discharge screw. The discharge screw temperature is 190℃, the discharge screw speed is 13rpm, the six devolatilization temperatures are 200℃, 205℃, 210℃, 215℃, 215℃ and 220℃ respectively, the twin-screw devolatilization speed is 80rpm, and the devolatilization section pressure is less than 20Pa.

[0151] After devolatilization, the methyl methacrylate polymer granules were obtained by extrusion through a twin-screw extruder, forming, cooling, pelletizing, and drying. The performance test results are shown in Tables 1 and 2.

[0152] Example 3

[0153] 90 kg of methyl methacrylate and 10 kg of styrene (R2 is H in Formula 2) are metered into the preparation vessel by a pump, stirred and mixed evenly, and then cooled to 12°C.

[0154] Add 0.3 kg of chain transfer agent n-dodecyl mercaptan, 0.30 kg of benzoyl peroxide, and 0.4 kg of multifunctional initiator II to the preparation vessel, and stir until completely dissolved;

[0155] The solution in the preparation vessel is injected into the monomer storage tank by a pump metering, and high-purity nitrogen gas is blown in through the bottom tube in the tank;

[0156] The material is continuously injected into the horizontal self-cleaning reactor I at a rate of 0.6 L / min, with an internal temperature of 100°C, a stirring rate of 8 rpm, and a material residence time of 30 min. Then, it is continuously pumped from reactor I to the horizontal self-cleaning reactor II at a rate of 0.6 L / min to continue polymerization at a polymerization temperature of 140°C, a stirring rate of rpm, and a material residence time of 30 min.

[0157] The material is continuously fed into the twin-screw devolatilization section via a discharge screw. The discharge screw temperature is 175℃, the discharge screw speed is 10rpm, the six devolatilization temperatures are 190℃, 200℃, 210℃, 210℃, 215℃ and 220℃ respectively, the twin-screw devolatilization speed is 110rpm, and the devolatilization section pressure is less than 20Pa.

[0158] After devolatilization, the methyl methacrylate polymer granules were obtained by extrusion through a twin-screw extruder, forming, cooling, pelletizing, and drying. The performance test results are shown in Tables 1 and 2.

[0159] Example 4

[0160] 85 kg of methyl methacrylate and 15 kg of tert-butyl methacrylate (R1 in Formula 1 is tert-butyl) were metered into the preparation vessel by a pump, stirred and mixed evenly, and then cooled to 20°C.

[0161] Add 0.2 kg of chain transfer agent dodecyl mercaptan, 0.6 kg of tert-butyl peroxide, and 0.3 kg of multifunctional initiator II to the preparation vessel, and stir until completely dissolved;

[0162] The solution in the preparation vessel is injected into the monomer storage tank by a pump metering, and high-purity nitrogen gas is blown in through the bottom tube in the tank;

[0163] The material is continuously injected into the horizontal self-cleaning reactor I at a rate of 0.4 L / min by a pump. The internal temperature of the reactor is 110℃, the stirring rate is 20 rpm, and the material residence time is 35 min. Then, it is continuously fed from reactor I to the horizontal self-cleaning reactor II at a rate of 0.4 L / min to continue polymerization. The polymerization temperature is 130℃, the stirring rate is 20 rpm, and the material residence time is 40 min.

[0164] The material is continuously fed into the twin-screw devolatilization section via a discharge screw. The discharge screw temperature is 170℃, the discharge screw speed is 20rpm, the six devolatilization temperatures are 190℃, 195℃, 200℃, 210℃, 220℃ and 230℃ respectively, the twin-screw devolatilization speed is 180rpm, and the devolatilization section pressure is less than 20Pa.

[0165] After devolatilization, the methyl methacrylate polymer granules were obtained by extrusion through a twin-screw extruder, forming, cooling, pelletizing, and drying. The performance test results are shown in Tables 1 and 2.

[0166] Example 5

[0167] 70 kg of methyl methacrylate and 30 kg of butyl methacrylate (R1 in Formula 1 is butyl) were metered into the preparation vessel by a pump, stirred and mixed evenly, and then cooled to 0°C.

[0168] Add 0.8 kg of chain transfer agent n-octyl mercaptan, 0.1 kg of azobisisobutyronitrile, and 1.5 kg of multifunctional initiator II to the preparation vessel, and stir until completely dissolved;

[0169] The solution in the preparation vessel is injected into the monomer storage tank by a pump metering, and high-purity nitrogen gas is blown in through the bottom tube in the tank;

[0170] The material is continuously injected into the horizontal self-cleaning reactor I at a rate of 0.8 L / min by a pump. The reactor temperature is 130°C, the stirring rate is 5 rpm, and the material residence time is 20 min. Then, it is continuously fed from reactor I to the horizontal self-cleaning reactor II at a rate of 0.8 L / min to continue polymerization. The polymerization temperature is 152°C, the stirring rate is 5 rpm, and the material residence time is 25 min.

[0171] The material is continuously fed into the twin-screw devolatilization section via a discharge screw. The discharge screw temperature is 175℃, the discharge screw speed is 8 rpm, the six devolatilization temperatures are 190℃, 200℃, 205℃, 210℃, 215℃ and 220℃ respectively, the twin-screw devolatilization speed is 160 rpm, and the pressure in the devolatilization section is less than 20 Pa.

[0172] After devolatilization, the methyl methacrylate polymer granules were obtained by extrusion through a twin-screw extruder, forming, cooling, pelletizing, and drying. The performance test results are shown in Tables 1 and 2.

[0173] Example 6

[0174] 80 kg of methyl methacrylate and 20 kg of ethyl methacrylate (R1 in Formula 1 is ethyl) were metered into the preparation vessel by a pump, stirred and mixed evenly, and then cooled to 5°C.

[0175] Add 0.35 kg of chain transfer agent n-butanethiol, 0.3 kg of dicumyl peroxide, and 0.8 kg of multifunctional initiator II to the preparation vessel, and stir until completely dissolved;

[0176] The solution in the preparation vessel is injected into the monomer storage tank by a pump metering, and high-purity nitrogen gas is blown in through the bottom tube in the tank;

[0177] The material is continuously injected into the horizontal self-cleaning reactor I at a rate of 1 L / min by a pump. The reactor temperature is 120℃, the stirring rate is 15 rpm, and the material residence time is 15 min. Then, it is continuously fed from reactor I to the horizontal self-cleaning reactor II at a rate of 1 L / min to continue polymerization. The polymerization temperature is 160℃, the stirring rate is 14 rpm, and the material residence time is 18 min.

[0178] The material is continuously fed into the twin-screw devolatilization section via a discharge screw. The discharge screw temperature is 180℃, the discharge screw speed is 16rpm, the six devolatilization temperatures are 190℃, 200℃, 210℃, 215℃, 220℃ and 225℃ respectively, the twin-screw devolatilization speed is 135rpm, and the pressure in the devolatilization section is less than 20Pa.

[0179] After devolatilization, the methyl methacrylate polymer granules were obtained by extrusion through a twin-screw extruder, forming, cooling, pelletizing, and drying. The performance test results are shown in Tables 1 and 2.

[0180] Example 7

[0181] The method was the same as in Example 1, except that the amount of multifunctional initiator II added was 0.1 kg. The performance test results are shown in Tables 1 and 2.

[0182] Example 8

[0183] The method was the same as in Example 1, except that 97 kg of methyl methacrylate and 3 kg of styrene were used. The performance test results are shown in Tables 1 and 2.

[0184] Example 9

[0185] The method was followed in Example 1, except that the prepolymerization temperature was 140°C, which was the same as the final polymerization temperature. The performance test results are shown in Tables 1 and 2.

[0186] Comparative Example 1

[0187] The properties of methyl methacrylate polymer with the grade Mitsubishi VH001 were tested, and the results are shown in Tables 1 and 2.

[0188] Comparative Example 2

[0189] The method of Example 1 was followed, except that initiator II was replaced with an equal amount of cumene hydrogen peroxide. The performance test results are shown in Tables 1 and 2.

[0190] Comparative Example 3

[0191] The method of Example 1 was followed, except that initiator II was not added. The performance test results are shown in Tables 1 and 2.

[0192] Table 1

[0193]

[0194]

[0195] Table 2

[0196]

[0197] The monomer residue in Table 2 refers to the content of residual monomers in the methyl methacrylate polymer.

[0198] As can be seen from the results in Tables 1 and 2, compared with the comparative example, the polymer of the present invention has significant advantages in terms of molecular characteristics, exhibiting higher uniformity in weight-average molecular weight and lower isotacticity. The polymer provided by the present invention demonstrates superior processing performance.

[0199] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A methyl methacrylate polymer, characterized in that, The polymer includes structural unit A and optionally structural unit B; Wherein, the structural unit A has the structure shown in Equation I, Wherein, the structural unit B has the structure shown in Formula II and / or Formula III, Wherein, R1 is selected from C2-C4 straight-chain or branched alkyl groups, and R2 is selected from H or C1-C3 straight-chain or branched alkyl groups; The isotacticity of the polymer is 4-10%; The polymer has a melt index of 4-8 g / 10 min at 230°C and 3.8 kg.

2. The polymer according to claim 1, wherein, The isotacticity of the polymer is 4-7%; And / or, the polymer has a melt index of 4.5-7.5 g / 10 min at 230°C and 3.8 kg; And / or, based on the total weight of the polymer, the content of structural unit A is 70-100% by weight, preferably 90-100% by weight, and the content of structural unit B is 0-30% by weight, preferably 0-10% by weight.

3. The polymer according to claim 1 or 2, wherein, The glass transition temperature of the polymer is 107-120℃; And / or, the weight-average molecular weight of the polymer is 9 × 10⁻⁶. 4 -14×10 4 g / mol; And / or, the molecular weight distribution of the polymer is 1.9-2.2, preferably 1.9-2; And / or, the content of residual monomers in the polymer is less than or equal to 0.35% by weight.

4. A method for preparing a methyl methacrylate polymer, characterized in that, Includes the following steps: (1) In the presence of a protective gas, methyl methacrylate, optionally functional monomer X, chain transfer agent and initiator I are subjected to a prepolymerization reaction in reactor I to obtain a prepolymer; (2) In the presence of a protective gas, the prepolymer is subjected to a final polymerization reaction in reactor II to obtain the methyl methacrylate polymer; Steps (1) and / or (2) are carried out in the presence of initiator II; Wherein, the initiator II is a compound represented by formula IV.

5. The preparation method according to claim 4, wherein, Based on the total weight of methyl methacrylate and functional monomer X, the amount of methyl methacrylate is 70-100% by weight, preferably 90-100% by weight; the amount of functional monomer X is 0-30% by weight, preferably 0-10% by weight; the amount of chain transfer agent is 0.1-0.8% by weight, preferably 0.1-0.3% by weight; the amount of initiator I is 0.1-1% by weight, preferably 0.2-0.6% by weight; and the amount of initiator II is 0.1-1.5% by weight. % by weight, preferably 0.2-0.5% by weight.

6. The preparation method according to claim 4 or 5, wherein, In step (1), the functional unit X is selected from the structure shown in Formula 1 and / or Formula 2. Wherein, R1 is selected from C2-C4 straight-chain or branched alkyl groups, and R2 is selected from H or C1-C3 straight-chain or branched alkyl groups; And / or, the chain transfer agent is selected from at least one of n-dodecyl mercaptan, tert-dodecyl mercaptan, n-butanethiol, n-octyl mercaptan, and tert-butanethiol; And / or, the initiator I is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, lauroyl peroxide, tert-butyl peroxide, diisopropyl peroxide, cumene hydroperoxide, diisopropylbenzene peroxide, and cyclohexanone peroxide.

7. The preparation method according to any one of claims 4-6, wherein, The reactor I mentioned in step (1) is a horizontal self-cleaning reactor I; And / or, the method further includes cooling methyl methacrylate, functional monomer X, chain transfer agent, initiator I and initiator II; Preferably, the cooling temperature is 0-20°C; And / or, the rates at which methyl methacrylate and functional monomer X are introduced into reactor I are each independently 0.1-1 L / min; And / or, the prepolymerization reaction described in step (1) is carried out under stirring conditions; Preferably, the stirring rate of the prepolymerization reaction in step (1) is 5-20 rpm; And / or, the conditions for the prepolymerization reaction include: a reaction temperature of 90-130°C and a reaction time of 15-40 minutes; Preferably, the temperature fluctuation of the prepolymerization reaction is less than 3°C; And / or, the yield of the prepolymer in the prepolymerization reaction described in step (1) is 20-40% by weight.

8. The preparation method according to any one of claims 4-7, wherein, The reactor II mentioned in step (2) is a horizontal self-cleaning reactor II; And / or, the rate at which the prepolymer is introduced into reactor II is 0.1-1 L / min; And / or, the final polymerization reaction described in step (2) is carried out under stirring conditions; Preferably, the stirring rate of the final polymerization reaction in step (2) is 5-20 rpm; And / or, the conditions for the final polymerization reaction include: a reaction temperature of 130-170°C and a reaction time of 10-40 minutes; Preferably, the temperature fluctuation of the final polymerization reaction is less than 3°C; And / or, the final polymerization temperature is higher than the prepolymerization temperature.

9. The preparation method according to any one of claims 4-8, wherein, The process after the final polymerization reaction also includes discharging, devolatilizing, and extruding the methyl methacrylate polymer. Preferably, the discharge temperature is 170-190℃ and the discharge rate is 8-20 rpm; Preferably, the devolatilization temperature is 190-230℃, the devolatilization rate is 80-180rpm, and the devolatilization pressure is less than or equal to 20Pa.

10. The methyl methacrylate polymer prepared by the preparation method according to any one of claims 4-9.

11. The use of a methyl methacrylate polymer according to any one of claims 1-3 and 10 in at least one of liquid crystal displays, optical materials and electronic products.

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