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 method comprises the following steps: (1) performing a prepolymerization reaction on methyl methacrylate, optionally a functional monomer X, a chain transfer agent and an initiator I in a reaction kettle I in the presence of a protective gas to obtain a prepolymer; (2) performing a final polymerization reaction on the prepolymer in a reaction kettle II in the presence of the protective gas to obtain the methyl methacrylate polymer; wherein, the step (1) and / or the step (2) are performed in the presence of an initiator II; wherein, the initiator II is a compound shown in formula I, and the methyl methacrylate polymer has the characteristics of narrow molecular weight distribution.

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] Methyl methacrylate (PMMA), also known as plexiglass, is a polymer material with excellent transparency, boasting a light transmittance more than 10% higher than ordinary glass. In addition to its high transparency, PMMA also possesses good mechanical and processing properties, making it widely used in various fields such as optical glass, lighting equipment, optical fibers, bulletproof glass for aircraft and automobiles, and medical devices.

[0003] Among the many physical properties of PMMA, molecular weight and its distribution are crucial. Molecular weight distribution directly affects the mechanical properties, processing characteristics, and transparency of PMMA. Studies show that the thermal properties, tensile properties, and film-forming properties of PMMA improve with decreasing molecular weight distribution. Therefore, preparing PMMA with a narrow molecular weight distribution is of great significance for improving the performance of related products.

[0004] Specifically, PMMA with a narrow molecular weight distribution can further improve light transmittance, making it an ideal choice for optical materials. Optical fibers made using this PMMA exhibit lower light loss during transmission, as low as 167 dB / km. Furthermore, the narrower the molecular weight distribution, the better the thermal stability and impact strength of PMMA, expanding its application range in fields such as outdoor heat-resistant materials. Therefore, there is an urgent need to develop PMMA with a narrow molecular weight distribution and superior performance to meet market demand for high-performance PMMA. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of wide molecular weight distribution of polymethyl methacrylate in the prior art, and to provide a methyl methacrylate polymer, its preparation method and application, wherein the polymer has the characteristic of narrow molecular weight distribution.

[0006] The first aspect of this invention provides a method for preparing a methyl methacrylate polymer, comprising the following steps:

[0007] (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;

[0008] (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;

[0009] Steps (1) and / or (2) are carried out in the presence of initiator II;

[0010] Wherein, the initiator II is a compound represented by formula I.

[0011]

[0012] Preferably, the temperature of the final polymerization reaction is higher than the temperature of the prepolymerization reaction.

[0013] The second aspect of the present invention provides a methyl methacrylate polymer prepared by the preparation method described in the first aspect above.

[0014] The third aspect of this invention provides the application of the methyl methacrylate polymer described in the second aspect above in the field of optics.

[0015] Through the above technical solution, this invention employs a highly efficient polymerization method, innovatively using initiator II to initiate the polymerization reaction, simplifying the preparation process, ensuring the controllability of the polymerization process, and simultaneously optimizing mass and heat transfer effects to reduce the occurrence of gelation. During the polymerization process, the relative proportions of chain growth and chain termination reactions can be controlled by adjusting the rate of free radical generation, thereby obtaining optical-grade methyl methacrylate polymers with a narrow molecular weight distribution. Polymers with a narrow molecular weight distribution exhibit high light transmittance and good thermal stability. Detailed Implementation

[0016] 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.

[0017] 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.

[0018] The first aspect of this invention provides a method for preparing a methyl methacrylate polymer, comprising the following steps:

[0019] (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;

[0020] (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;

[0021] Steps (1) and / or (2) are carried out in the presence of initiator II;

[0022] Wherein, the initiator II is a compound represented by formula I.

[0023]

[0024] This invention employs initiator I and initiator II for segmented polymerization, effectively controlling the polymerization rate and avoiding gelation, resulting in a methyl methacrylate polymer with a narrow molecular weight distribution and superior optical properties, exhibiting higher light transmittance and thermal stability.

[0025] This invention employs initiator II, as shown in Formula I, to primarily initiate the polymerization of methyl methacrylate at high temperatures, effectively reducing the probability of thermal initiation and disproportionation termination, and lowering the molecular weight distribution. Due to its specific chemical structure, initiator I can generate a relatively stable concentration of free radicals during polymerization. This stable free radical concentration facilitates uniform initiation of monomer polymerization, resulting in a narrow molecular weight distribution in the generated polymer. During prepolymerization and final polymerization, it can control the relative proportions of chain growth and chain termination reactions by adjusting the rate of free radical generation, thereby obtaining a methyl methacrylate polymer with a narrow molecular weight distribution. Polymers with a narrow molecular weight distribution exhibit high light transmittance and good thermal stability.

[0026] 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, or any range between any two values. By controlling the amount of initiator I, the present invention is beneficial to controlling the prepolymerization reaction process and efficiency, and to achieving effective and stable polymerization of methyl methacrylate.

[0027] Furthermore, based on the total weight of methyl methacrylate and functional monomer X, the amount of initiator I is 0.2-0.4% by weight.

[0028] 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% 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. By controlling the amount of initiator II, the present invention is beneficial to controlling the final polymerization reaction efficiency and process.

[0029] Furthermore, based on the total weight of methyl methacrylate and functional monomer X, the amount of initiator II is 0.2-0.6% by weight.

[0030] This invention, by controlling the content of initiator I and initiator II, is more conducive to achieving segmented polymerization, improving the performance of methyl methacrylate polymers and controlling the polymerization process, and is more conducive to obtaining polymers with narrow molecular weight distribution, resulting in polymers with higher light transmittance.

[0031] 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.

[0032] According to the present invention, preferably, based on the total weight of methyl methacrylate and functional monomer X, the amount of methyl methacrylate is 85-100% by weight, and the amount of functional monomer X is 0-15% by weight. Using the above range is beneficial to obtaining a polymer with a narrow molecular weight distribution.

[0033] Furthermore, based on the total weight of methyl methacrylate and functional monomer X, the amount of methyl methacrylate is more preferably 90-100% by weight, and the amount of functional monomer X is more preferably 0-10% by weight.

[0034] 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 to controlling the weight-average molecular weight of the polymer in the present invention.

[0035] Furthermore, based on the total weight of methyl methacrylate and functional monomer X, the amount of the chain transfer agent is 0.2-0.5% by weight.

[0036] According to the present invention, preferably, in step (1), the functional monomer X is selected from the structure shown in Formula II and / or Formula III.

[0037]

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] In this invention, using the above-mentioned groups and methyl methacrylate for polymerization is more conducive to obtaining products with narrow molecular weight distribution and high light transmittance.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] The present invention does not impose any particular limitation on 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 0-10℃, more preferably 2-8℃.

[0048] 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.

[0049] 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, optionally 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.

[0050] This invention does not particularly limit the mixing method and order of methyl methacrylate, optional functional monomer X, chain transfer agent, initiator I and initiator II. For example, methyl methacrylate, optional functional monomer X, chain transfer agent, initiator I and initiator II can be mixed independently with other substances, as long as the above 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 optional 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 they are completely dissolved. After the above substances are dissolved, they are injected into a storage tank, and after nitrogen gas is introduced, they are transferred to reaction vessel I.

[0051] 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.

[0052] 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 select according to actual needs.

[0053] 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 vertical polymerization reactor I.

[0054] The vertical polymerization reactor I used in this invention has a high-torque stirring paddle, which effectively transfers mass and heat, precisely controls the temperature, avoids gel formation, and prevents the polymerization from automatically accelerating and widening the molecular weight distribution, thus giving the product high light transmittance.

[0055] 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 0.5-1.5 L / min.

[0056] It should be noted that the present invention does not particularly limit the rate at which the chain transfer agent, initiator I, and optionally 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 0.5-1.5 L / min.

[0057] 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.

[0058] This invention does not impose any particular limitation on the type of pump; any pump that meets the requirements of this invention is acceptable. Those skilled in the art can select the appropriate pump based on actual needs.

[0059] 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.

[0060] According to the present invention, preferably, the prepolymerization reaction in step (1) is carried out under stirring conditions.

[0061] 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 80-120 rpm.

[0062] According to the present invention, preferably, the conditions for the prepolymerization reaction include: a reaction temperature of 100-130°C and a reaction time of 15-30 minutes.

[0063] The polymerization temperature described above in this invention enables stable polymerization of methyl methacrylate and avoids gelation.

[0064] According to the present invention, preferably, the yield of the prepolymer in the prepolymerization reaction in step (1) is 20-40% by weight, which is conducive to the smooth progress of the final polymerization reaction, and more preferably 25-35% by weight, which is more conducive to avoiding the problem caused by the sharp increase in viscosity of the polymerization system in the final polymerization reaction.

[0065] In this invention, the yield of the prepolymer in the prepolymerization reaction is calculated by precipitation. 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%.

[0066] In this invention, the prepolymer solution refers to the solution after the prepolymerization reaction.

[0067] In this invention, the yield of the prepolymer in the prepolymerization reaction is within the above-mentioned range, and controlling the viscosity of the prepolymer reactant is more conducive to the final polymerization reaction.

[0068] The present invention does not particularly limit the type of reactor II, as long as it can enable 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 vertical polymerization reactor II.

[0069] The vertical polymerization reactor II used in this invention has a high-torque stirring paddle, which effectively transfers mass and heat, precisely controls the temperature, avoids gel formation, and prevents the polymerization from automatically accelerating and widening the molecular weight distribution, so that the product has a moderate melt index and excellent processing performance.

[0070] The continuous bulk polymerization process using a dual vertical polymerization reactor ensures the polymerization system has good fluidity, preventing coking and yellowing of the reactor walls and guaranteeing the optical properties of polymethyl methacrylate.

[0071] 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 0.5-1.5 L / min.

[0072] 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.

[0073] 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 via the same pipeline at a rate of 0.5-1.5 L / min.

[0074] According to the present invention, preferably, the final polymerization reaction in step (2) is carried out under stirring conditions.

[0075] The present invention does not particularly limit the stirring rate of the final polymerization reaction, as long as the substances in the final polymerization reaction 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 50-100 rpm.

[0076] According to the present invention, preferably, the conditions for the final polymerization reaction include: a reaction temperature of 140-180°C and a reaction time of 10-50 minutes.

[0077] According to the present invention, preferably, the temperature of the final polymerization reaction is higher than the temperature of the prepolymerization reaction.

[0078] 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, which effectively reduces the probability of thermal initiation and disproportionation termination, resulting in a polymer with a narrow molecular weight distribution, which is more conducive to improving light transmittance.

[0079] 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.

[0080] This invention improves polymer performance by using a protective gas to remove dissolved oxygen from the system.

[0081] According to the present invention, preferably, after the final polymerization reaction, the methyl methacrylate polymer is further subjected to discharge, devolatilization and extrusion.

[0082] 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.

[0083] According to the present invention, preferably, the discharge temperature is 180-200℃.

[0084] 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.

[0085] According to the present invention, preferably, the devolatilization temperature is 200-230°C, the devolatilization rate is 80-150 rpm, and the devolatilization pressure is less than or equal to 10 Pa.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] The second aspect of the present invention provides a methyl methacrylate polymer prepared by the preparation method described in the first aspect above.

[0091] According to the present invention, preferably, the content of residual monomer in the methyl methacrylate polymer is less than or equal to 0.35% by weight, more preferably less than or equal to 0.3% by weight.

[0092] 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.

[0093] 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.

[0094] According to the present invention, preferably, the weight-average molecular weight of the methyl methacrylate polymer is 7.5 × 10⁻⁶. 4 -12×10 4 g / mol, more preferably 9×10 g / mol 4 -11.8×10 4 g / mol.

[0095] According to the present invention, preferably, the molecular weight distribution of the methyl methacrylate polymer is 1.6-2, more preferably 1.7-1.8.

[0096] This invention uses gel permeation chromatography (PL-GPC20) to measure the weight-average molecular weight and its distribution of polymers.

[0097] According to the present invention, preferably, the T of the methyl methacrylate polymer g The temperature is 112-117℃, more preferably 113-117℃.

[0098] This invention uses a differential scanning calorimeter (DSC8500) to test the glass transition temperature T of the polymer. g .

[0099] According to the present invention, preferably, the methyl methacrylate polymer has a melt index of 5-9.5 g / 10 min at 230°C and 3.8 kg, more preferably 5.8-9.2 g / 10 min.

[0100] The polymer melt index was tested according to ISO 1133-1:2022 at 230°C and 3.8 kg.

[0101] According to the present invention, preferably, the methyl methacrylate polymer comprises structural unit A and optionally structural unit B;

[0102] Wherein, the structural unit A has the structure shown in Equation 1,

[0103]

[0104] Wherein, the structural unit B has the structure shown in Equation 2 and / or Equation 3,

[0105]

[0106] 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.

[0107] In this invention, the methyl methacrylate polymer including structural unit A and optionally structural unit B means that, according to a specific embodiment, the methyl methacrylate polymer obtained by homopolymerization of methyl methacrylate monomers contains only structural unit A, while the methyl methacrylate polymer obtained by copolymerization of methyl methacrylate monomers and functional monomer X contains both structural unit A and structural unit B.

[0108] According to the present invention, preferably, based on the total weight of the polymer, the content of structural unit A is 84-100% by weight, and the content of structural unit B is 0-16% 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.

[0109] 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.

[0110] The third aspect of this invention provides the application of the methyl methacrylate polymer described in the second aspect above in the field of optics.

[0111] The present invention will be described in detail below through embodiments.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] In the following examples and comparative examples, the glass transition temperature T of the polymers was tested using a differential scanning calorimeter (DSC8500). g .

[0116] 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.

[0117] In the following examples and comparative examples, the yield of the prepolymer in the prepolymerization reaction of the present invention 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%.

[0118] 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 residual monomer content was calculated based on the integral area of ​​the proton NMR spectra.

[0119] Example 1

[0120] 100 kg of methyl methacrylate was metered into the preparation vessel using a pump, stirred until homogeneous, and then cooled to 8°C.

[0121] Add 0.3 kg of chain transfer agent n-dodecyl mercaptan, 0.4 kg of benzoyl peroxide, and 0.3 kg of multifunctional initiator II to the preparation vessel, and stir until completely dissolved;

[0122] 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;

[0123] The material is continuously injected into vertical polymerization reactor I at a rate of 1L / min by a pump. The reactor temperature is 110℃, the stirring rate is 100rpm, and the material residence time is 20min. Then, it is continuously fed from vertical polymerization reactor I to vertical polymerization reactor II at a rate of 1L / min to continue polymerization. The polymerization temperature is 140℃, the stirring rate is 70rpm, and the material residence time is 30min.

[0124] 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 12rpm, the six devolatilization temperatures are 190℃, 195℃, 200℃, 210℃, 220℃ and 225℃ respectively, the twin-screw devolatilization speed is 80rpm, and the pressure in the devolatilization section is less than 5Pa.

[0125] 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.

[0126] Example 2

[0127] 90 kg of methyl methacrylate and 10 kg of tert-butyl methacrylate (R1 in Formula II is tert-butyl) were metered into the preparation vessel by a pump, stirred and mixed evenly, and then cooled to 6°C.

[0128] Add 0.5 kg of chain transfer agent n-octyl mercaptan, 0.2 kg of tert-butyl peroxide, and 0.6 kg of multifunctional initiator II to the preparation vessel, and stir until completely dissolved;

[0129] 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;

[0130] The material is continuously injected into vertical polymerization reactor I at a rate of 1.2 L / min, with an internal temperature of 120°C, a stirring rate of 110 rpm, and a material residence time of 30 min. Then, it is continuously transferred from vertical polymerization reactor I to vertical polymerization reactor II at a rate of 1.2 L / min to continue polymerization at a temperature of 150°C, a stirring rate of 90 rpm, and a material residence time of 20 min.

[0131] The material is continuously fed into the twin-screw devolatilization section via a discharge screw. The discharge screw temperature is 195℃, the discharge screw speed is 15rpm, the six devolatilization temperatures are 210℃, 215℃, 215℃, 220℃, 225℃ and 230℃ respectively, the twin-screw devolatilization speed is 150rpm, and the pressure in the devolatilization section is less than 5Pa.

[0132] 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.

[0133] Example 3

[0134] 85 kg of methyl methacrylate and 15 kg of ethyl methacrylate (R1 in Formula II is ethyl) were metered into the preparation vessel by a pump, stirred and mixed evenly, and then cooled to 2°C.

[0135] Add 0.6 kg of chain transfer agent n-butanethiol, 0.15 kg of azobisisobutyronitrile, and 0.5 kg of multifunctional initiator II to the preparation vessel, and stir until completely dissolved;

[0136] 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;

[0137] The material is continuously injected into vertical polymerization reactor I at a rate of 0.7 L / min by a pump. The internal temperature of the reactor is 125℃, the stirring rate is 90 rpm, and the material residence time is 25 min. Then, it is continuously fed from vertical polymerization reactor I to vertical polymerization reactor II at a rate of 0.7 L / min to continue polymerization. The polymerization temperature is 160℃, the stirring rate is 100 rpm, and the material residence time is 15 min.

[0138] 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 8 rpm, the six devolatilization temperatures are 200℃, 205℃, 210℃, 215℃, 220℃ and 225℃ respectively, the twin-screw devolatilization speed is 130 rpm, and the pressure in the devolatilization section is less than 5 Pa.

[0139] 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.

[0140] Example 4

[0141] 89 kg of methyl methacrylate and 11 kg of styrene (R2 is H in Formula III) were metered into the preparation vessel by a pump, stirred and mixed evenly, and then cooled to 10°C.

[0142] Add 0.1 kg of chain transfer agent tert-dodecyl mercaptan, 1 kg of dicumyl peroxide, and 0.1 kg of multifunctional initiator II to the preparation vessel, and stir until completely dissolved;

[0143] 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;

[0144] The material is continuously injected into vertical polymerization reactor I at a rate of 1.5 L / min, with an internal temperature of 100°C, a stirring rate of 120 rpm, and a material residence time of 10 min. Then, it is continuously transferred from vertical polymerization reactor I to vertical polymerization reactor II at a rate of 1.5 L / min to continue polymerization at a temperature of 140°C, a stirring rate of 80 rpm, and a material residence time of 40 min.

[0145] 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 20rpm, the six devolatilization temperatures are 205℃, 210℃, 215℃, 215℃, 220℃ and 225℃ respectively, the twin-screw devolatilization speed is 110rpm, and the pressure in the devolatilization section is less than 5Pa.

[0146] 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.

[0147] Example 5

[0148] 87 kg of methyl methacrylate and 13 kg of butyl methacrylate (R1 in Formula II is butyl) were metered into the preparation vessel by a pump, stirred and mixed evenly, and then cooled to 0°C.

[0149] Add 0.8 kg of chain transfer agent dodecyl mercaptan, 0.1 kg of azobisisobutyronitrile and 1 kg of multifunctional initiator II to the preparation vessel, and stir until completely dissolved;

[0150] 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;

[0151] The material is continuously injected into vertical polymerization reactor I at a rate of 0.5 L / min by a pump. The reactor temperature is 130°C, the stirring rate is 80 rpm, and the material residence time is 18 min. Then, it is continuously fed from vertical polymerization reactor I to vertical polymerization reactor II at a rate of 0.5 L / min to continue polymerization. The polymerization temperature is 180°C, the stirring rate is 50 rpm, and the material residence time is 50 min.

[0152] The discharge screw continuously feeds the material into the twin-screw devolatilization section. The discharge screw temperature is 200℃, the discharge screw speed is 13rpm, the six devolatilization temperatures are 210℃, 215℃, 220℃, 220℃, 225℃ and 230℃ respectively, the twin-screw devolatilization speed is 100rpm, and the pressure in the devolatilization section is less than 5Pa.

[0153] 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.

[0154] Example 6

[0155] The method of Example 1 was followed, except that benzoyl peroxide was added in an amount of 0.1 kg. The performance test results are shown in Tables 1 and 2.

[0156] Example 7

[0157] The method was followed 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.

[0158] Example 8

[0159] The method is the same as in Example 1, except that the prepolymerization temperature is 140°C, which is the same as the final polymerization temperature.

[0160] Comparative Example 1

[0161] The method was the same as in Example 1, except that the amount of multifunctional initiator II added was 0.05 kg. The performance test results are shown in Tables 1 and 2.

[0162] Comparative Example 2

[0163] The method of Example 1 was followed, except that initiator II was replaced with an equal amount of di-tert-butyl peroxide. The performance test results are shown in Tables 1 and 2.

[0164] Comparative Example 3

[0165] 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.

[0166] Table 1

[0167]

[0168] Table 2

[0169]

[0170] The monomer residue in Table 2 refers to the content of residual monomers in the methyl methacrylate polymer.

[0171] As can be seen from the results in Tables 1 and 2, compared with the comparative examples, the examples using the efficient polymerization method of the present invention and the examples using initiator II to initiate the polymerization reaction have better thermal stability and a narrower molecular weight distribution of the polymer.

[0172] 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 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 I.

2. The preparation method according to claim 1, wherein, Based on the total weight of methyl methacrylate and functional monomer X, the amount of methyl methacrylate is 85-100% by weight, preferably 90-100% by weight; the amount of functional monomer X is 0-15% by weight, preferably 0-10% by weight; the amount of chain transfer agent is 0.1-0.8% by weight, preferably 0.2-0.5% by weight; the amount of initiator I is 0.1-1% by weight, preferably 0.2-0.4% by weight; and the amount of initiator II is 0.1-1% by weight, preferably 0.2-0.6% by weight.

3. The preparation method according to claim 1 or 2, wherein, In step (1), the functional monomer X is selected from the structures 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.

4. The preparation method according to claims 1-3, wherein, 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.

5. The preparation method according to any one of claims 1-4, wherein, The reactor I mentioned in step (1) is a vertical polymerization 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 0-10℃; And / or, the rates at which methyl methacrylate and functional monomer X are introduced into reactor I are each independently 0.5-1.5 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 80-120 rpm; And / or, the conditions for the prepolymerization reaction include: a reaction temperature of 100-130°C and a reaction time of 15-30 minutes; And / or, the yield of the prepolymer in the prepolymerization reaction described in step (1) is 20-40% by weight.

6. The preparation method according to any one of claims 1-5, wherein, The reactor II mentioned in step (2) is a vertical polymerization reactor II; And / or, the rate at which the prepolymer is introduced into reactor II is 0.5-1.5 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 50-100 rpm; And / or, the conditions for the final polymerization reaction include: a reaction temperature of 140-180°C and a reaction time of 10-50 minutes; And / or, the final polymerization temperature is higher than the prepolymerization temperature.

7. The preparation method according to any one of claims 1-6, wherein, The process after the final polymerization reaction also includes discharging, devolatilizing, and extruding the methyl methacrylate polymer. Preferably, the discharge temperature is 180-200℃ and the discharge rate is 8-20 rpm; Preferably, the devolatilization temperature is 200-230℃, the devolatilization rate is 80-150rpm, and the devolatilization pressure is less than or equal to 10Pa.

8. A methyl methacrylate polymer prepared by the preparation method according to any one of claims 1-7; Preferably, the content of residual monomer in the methyl methacrylate polymer is less than or equal to 0.35% by weight.

9. The polymer according to claim 8, wherein, The polymer has a weight-average molecular weight of 7.5 × 10⁻⁶. 4 -12×10 4 g / mol, preferably 9×10 g / mol 4 -11.8×10 4 g / mol; And / or, the molecular weight distribution of the polymer is 1.6-2, preferably 1.7-1.

8.

10. The application of the methyl methacrylate polymer of claim 8 or 9 in the field of optics.

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