Process for the preparation of methyl methacrylate polymers and methyl methacrylate polymers and their use

Abstract

The application relates to the technical field of high polymer material preparation, and discloses a preparation method of a methyl methacrylate polymer, the methyl methacrylate polymer and application thereof. The method comprises the following steps: (1) pre-polymerization reaction of methyl methacrylate, optionally functional monomer X, chain transfer agent and initiator I in a reaction kettle I in the presence of a protective gas to obtain a pre-polymer; (2) final polymerization reaction of the pre-polymer in a reaction kettle II in the presence of the protective gas to obtain the methyl methacrylate polymer; wherein, step (1) and / or step (2) are carried out in the presence of initiator II; wherein, the initiator II is a compound shown in formula I. The method provided by the application can orderly decompose the initiator into free radicals in polymerization, the free radical concentration is relatively stable, the polymerization is good in controllability, the mass and heat transfer effects are good, and the gel phenomenon is not prone to occurring.

Description

Technical Field

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

[0002] Polymethyl methacrylate (PMMA), also known as plexiglass, is a versatile thermoplastic resin material primarily obtained through the polymerization of methyl methacrylate (MMA) monomers. PMMA is widely used in numerous fields due to its excellent optical and mechanical properties, particularly in industries such as liquid crystal displays, automotive, aerospace, and fiber optics.

[0003] PMMA can be produced through various polymerization processes, including bulk polymerization, suspension polymerization, and solution polymerization. Each process has its own characteristics and significantly impacts the performance of the final product. Bulk polymerization is particularly valued for its ability to produce PMMA materials with high transmittance (over 92.5%) and low haze (less than 0.3%), making it a preferred choice for high-end optical materials. However, bulk polymerization suffers from high viscosity, low mass and heat transfer efficiency, and a tendency for self-acceleration, which negatively affects the material's optical and mechanical properties. Compared to bulk polymerization, suspension and solution polymerization are more mature processes with better mass and heat transfer, but the PMMA materials produced by these methods have relatively low transmittance, making them unsuitable for high-end optical applications. Therefore, although these processes are widely used industrially, the PMMA products they produce are typically classified as conventional materials.

[0004] Currently, the key technologies for bulk polymerization are mainly controlled by some foreign companies, which has led to a relative lag in the technological development of this field in China. As the world's largest consumer of PMMA, China's annual apparent consumption is close to 800,000 tons, but most of its high-end PMMA products rely on imports, with approximately 200,000 tons of high-end PMMA products needing to be imported from abroad each year.

[0005] With the increasing domestic demand for high-end PMMA products, the synthesis of high-end optical-grade PMMA materials using continuous bulk polymerization processes is gradually becoming a focus of research. This process can meet the domestic market's demand for high-performance PMMA and promote the upgrading and development of the domestic PMMA industry. Therefore, developing and optimizing continuous bulk polymerization processes to improve the performance of PMMA materials is of great significance for reducing dependence on imported high-end PMMA and enhancing the competitiveness of the domestic PMMA industry. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of poor polymerization controllability, poor mass and heat transfer, and easy gelation in the polymerization of methyl methacrylate in the prior art. This invention provides a method for preparing methyl methacrylate polymer, the methyl methacrylate polymer and its application. This method has the characteristics of good polymerization controllability, good mass and heat transfer, and less tendency to gel.

[0007] To achieve the above objectives, the first aspect of the present invention provides a method for preparing methyl methacrylate polymer, comprising the following steps:

[0008] (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;

[0009] (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;

[0010] Steps (1) and / or (2) are carried out in the presence of initiator II;

[0011] Wherein, the initiator II is a compound represented by formula I.

[0012]

[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 the present invention provides the application of the methyl methacrylate polymer described in the second aspect above in liquid crystal displays or optical materials.

[0015] Through the above technical solution, this invention achieves highly efficient initiation by combining initiator I and initiator II. Specifically, initiator II used in this invention can decompose into free radicals in an orderly manner, maintaining a relatively stable free radical concentration, which significantly improves the controllability of the polymerization reaction rate. Under suitable reaction conditions, initiator II has a stable and controllable free radical generation capability. Compared to initiators with excessively low activity, it can fully ensure the smooth progress of the polymerization reaction within a reasonable time period. Compared to initiators with excessively high activity, it can effectively avoid adverse phenomena such as local overheating and explosive polymerization caused by overly vigorous reactions. 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] To achieve the above objectives, the first aspect of the present invention provides a method for preparing 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 to achieve efficient initiation and effective control of the polymerization reaction. Initiator I is beneficial to the prepolymerization process, enabling the stable polymerization of methyl methacrylate.

[0025] This invention employs initiator II, as shown in Formula I, which is more conducive to effectively controlling the polymerization reaction. The initiator structure of Formula I contains multiple peroxy groups (-OO-). These peroxy bonds have high activation energies and, under relatively high reaction temperatures, will generate free radicals stepwise to initiate the polymerization reaction. Its unique structure allows it to generate free radicals gradually in a relatively stable and controllable manner, maintaining a relatively stable free radical concentration in the system, thus facilitating precise control of the polymerization reaction. Compared to initiators with excessively low activity, it ensures the reaction proceeds within a reasonable timeframe; compared to initiators with excessively high activity, it avoids problems such as excessively vigorous reactions leading to localized overheating and explosive polymerization. This effectively improves production efficiency and product 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 0.05-1% by weight, for example, it can be 0.05, 0.15, 0.25, 0.35, 0.45, 0.55, 0.65, 0.75, 0.85, 0.95, 1% by weight, or any range between any two values. The present invention controls the amount of initiator I to ensure stable polymerization in the prepolymerization reaction process, more preferably 0.1-0.4% by weight.

[0027] According to the present invention, preferably, based on the total weight of methyl methacrylate and functional monomer X, the amount of initiator II is 0.02-1.2% by weight, for example, it can be 0.02, 0.12, 0.22, 0.32, 0.42, 0.52, 0.62, 0.72, 0.82, 0.92, 1, 1.1, 1.2% by weight, and any range between any two values. The present invention, by controlling the amount of initiator II, is beneficial to controlling the final polymerization reaction process, and more preferably 0.1-0.4% by weight.

[0028] This invention improves the performance of methyl methacrylate polymers by controlling the content of initiator I and initiator II, thereby facilitating the polymerization reaction, controlling the polymerization process, reducing gelation, and enhancing the properties of the polymer.

[0029] According to the present invention, preferably, based on the total weight of methyl methacrylate and functional monomer X, the amount of methyl methacrylate is 80-100% by weight, and the amount of functional monomer X is 0-20% by weight. Using the above range is beneficial to improving the performance of the polymer.

[0030] Furthermore, based on the total weight of methyl methacrylate and functional monomer X, the amount of methyl methacrylate is preferably 90-100% by weight, and the amount of functional monomer X is preferably 0-10% by weight.

[0031] 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 0.05-0.8% by weight, for example, it can be 0.05, 0.15, 0.25, 0.35, 0.45, 0.55, 0.65, 0.75, 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.

[0032] 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.

[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] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] In this invention, using the above-mentioned groups and methyl methacrylate for polymerization is more conducive to obtaining products with a narrow molecular weight distribution.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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 0-20℃, more preferably 0-10℃.

[0044] 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.

[0045] 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.

[0046] 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, functional monomer X, chain transfer agent, and initiator I for polymerization.

[0047] 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 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 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 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] The vertical polymerization reactor I used in this invention has a high-torque stirring paddle to enhance mass and heat transfer. A gas phase condenser is installed at the top of the polymerization reactor to achieve precise temperature control of bulk polymerization and improve the controllability of polymerization.

[0052] 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.

[0053] 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 the appropriate rate 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 functional monomer X at a rate of 0.1-1 L / min.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] According to the present invention, preferably, the prepolymerization reaction in step (1) is carried out under stirring conditions.

[0058] 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 20-100 rpm.

[0059] 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.

[0060] The polymerization temperature described above in this invention enables stable polymerization of methyl methacrylate and avoids gelation.

[0061] According to the present invention, preferably, the yield of the prepolymer in the prepolymerization reaction in step (1) is 20-40% by weight, which helps to avoid the problem caused by the sharp increase in viscosity of the polymerization system in the final polymerization reaction, and more preferably 25-35% by weight, which is more conducive to the final polymerization reaction.

[0062] 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%.

[0063] In this invention, the prepolymer solution refers to the solution after the prepolymerization reaction.

[0064] 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 polymerization reactor II.

[0065] The horizontal self-cleaning polymerization reactor II used in this invention is equipped with circulating heat transfer medium in the stirring paddle and jacket, which can effectively and quickly transfer heat and control the polymerization reaction temperature, and avoid automatic acceleration of polymerization.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] According to the present invention, preferably, the final polymerization reaction in step (2) is carried out under stirring conditions.

[0070] 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 5-20 rpm.

[0071] 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 20-40 minutes.

[0072] According to the present invention, preferably, the temperature fluctuation of the final polymerization reaction is less than 3°C.

[0073] According to the present invention, preferably, the temperature of the final polymerization reaction is higher than the temperature of the prepolymerization reaction.

[0074] The polymerization temperature used in this invention is more conducive to the stable polymerization of methyl methacrylate.

[0075] 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.

[0076] This invention improves polymer performance by using a protective gas to remove dissolved oxygen from the system.

[0077] According to the present invention, preferably, after the final polymerization reaction, the methyl methacrylate polymer is further subjected to discharge, devolatilization and extrusion.

[0078] 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.

[0079] According to the present invention, preferably, the discharge temperature is 180-200℃.

[0080] 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.

[0081] According to the present invention, preferably, the devolatilization temperature is 190-230℃, the devolatilization rate is 100-200rpm, and the devolatilization pressure is less than or equal to 10Pa.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] The second aspect of the present invention provides a methyl methacrylate polymer prepared by the preparation method described in the first aspect above.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] According to the present invention, preferably, the weight-average molecular weight of the methyl methacrylate polymer is 8 × 10⁻⁶. 4 -13×10 4 g / mol, more preferably 9×10 g / mol 4 -12.2×10 4 g / mol.

[0090] According to the present invention, preferably, the molecular weight distribution of the methyl methacrylate polymer is 1.85-2.15, more preferably 1.88-2.02.

[0091] This invention uses gel permeation chromatography (PL-GPC20) to measure the weight-average molecular weight and its distribution of polymers.

[0092] According to the present invention, preferably, the T of the methyl methacrylate polymer g The temperature is 108-120℃, more preferably 110-118℃.

[0093] This invention uses a differential scanning calorimeter (DSC8500) to test the glass transition temperature T of the polymer. g .

[0094] According to the present invention, preferably, the methyl methacrylate polymer has a melt index of 5-9 g / 10 min at 230°C and 3.8 kg, more preferably 5.2-8.8 g / 10 min.

[0095] The polymer melt index was tested according to ISO 1133-1:2022 at 230°C and 3.8 kg.

[0096] According to the present invention, preferably, the methyl methacrylate polymer comprises structural unit A and optionally structural unit B;

[0097] Wherein, the structural unit A has the structure shown in Equation 1,

[0098]

[0099] Wherein, the structural unit B has the structure shown in Equation 2 and / or Equation 3,

[0100]

[0101] 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.

[0102] 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.

[0103] According to the present invention, preferably, based on the total weight of the polymer, the content of structural unit A is 80-100% by weight, and the content of structural unit B is 0-20% 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.

[0104] The third aspect of the present invention provides the application of the methyl methacrylate polymer described in the second aspect above in liquid crystal displays or optical materials.

[0105] This invention tests the transmittance and haze of methyl methacrylate polymers according to ISO 13468-2:2021 and ISO 14782:2021. The transmittance of the methyl methacrylate polymer products is greater than or equal to 92.5%, and the haze is less than or equal to 0.29%.

[0106] The present invention will be described in detail below through embodiments.

[0107] 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.

[0108] 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%.

[0109] 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.

[0110] In the following examples and comparative examples, the glass transition temperature T of the polymers was tested using a differential scanning calorimeter (DSC8500). g .

[0111] 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.

[0112] 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.

[0113] In the following examples and comparative examples, the hydrogen spectra of the polymers were measured using a Swiss Bruker AV 300 nuclear magnetic resonance spectrometer, and the residual amount of polymer monomers was calculated based on the integrated area of ​​the hydrogen spectra.

[0114] In the following examples and comparative examples, the yield of the final polymer in the final polymerization reaction of the present invention was calculated by the precipitation method. The mass of the polymer solution taken out was m2, and the mass of the precipitated polymer after drying was m3. The yield of the final polymer = (m3 / m2)×100%.

[0115] Example 1

[0116] 100 kg of methyl methacrylate was metered into the preparation vessel by a pump, stirred and mixed evenly, and then cooled to 10°C.

[0117] Add 0.2 kg of chain transfer agent n-dodecyl mercaptan, 0.2 kg of benzoyl peroxide, and 0.3 kg of initiator II to the preparation vessel, and stir until completely dissolved;

[0118] 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;

[0119] The material is continuously injected into a vertical high-torque polymerization reactor at a rate of 0.5 L / min, with an internal temperature of 105°C, a stirring rate of 60 rpm, and a material residence time of 20 min. Then, it is continuously fed from the bottom of the reactor into a horizontal self-cleaning polymerization reactor at a rate of 0.5 L / min to continue polymerization at a temperature of 145°C, a stirring rate of 10 rpm, and a material residence time of 30 min.

[0120] 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 10rpm, the six devolatilization temperatures are 190℃, 200℃, 200℃, 210℃, 210℃ and 220℃ respectively, the twin-screw devolatilization speed is 140rpm, and the devolatilization section pressure is less than or equal to 10Pa.

[0121] 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.

[0122] Example 2

[0123] 80 kg of methyl methacrylate and 20 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 20°C.

[0124] Add 0.8 kg of chain transfer agent n-dodecyl mercaptan, 0.05 kg of lauroyl peroxide, and 1.2 kg of initiator II to the preparation vessel, and stir until completely dissolved;

[0125] 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;

[0126] The material is continuously injected into a vertical high-torque polymerization reactor at a rate of 0.2 L / min. The reactor temperature is 100℃, the stirring rate is 40 rpm, and the material residence time is 30 min. Then, it is continuously fed from the bottom of the reactor into a horizontal self-cleaning polymerization reactor at a rate of 0.2 L / min to continue polymerization. The polymerization temperature is 160℃, the stirring rate is 16 rpm, and the material residence time is 40 min.

[0127] 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 18rpm, the six devolatilization temperatures are 190℃, 200℃, 210℃, 210℃, 210℃ and 215℃ respectively, the twin-screw devolatilization speed is 120rpm, and the devolatilization section pressure is less than or equal to 10Pa.

[0128] 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.

[0129] Example 3

[0130] 97.5 kg of methyl methacrylate and 2.5 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.

[0131] Add 0.05 kg of chain transfer agent n-butanethiol, 1 kg of azobisisobutyronitrile, and 0.1 kg of initiator II to the preparation vessel, and stir until completely dissolved;

[0132] 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;

[0133] The material is continuously injected into a vertical high-torque polymerization reactor at a rate of 0.8 L / min, with an internal temperature of 120°C, a stirring rate of 85 rpm, and a material residence time of 25 min. Then, it is continuously fed from the bottom of the reactor into a horizontal self-cleaning polymerization reactor at a rate of 0.8 L / min to continue polymerization at a temperature of 170°C, a stirring rate of 18 rpm, and a material residence time of 25 min.

[0134] The material is continuously fed into the twin-screw devolatilization section via a discharge screw. The discharge screw temperature is 185℃, the discharge screw speed is 16rpm, the six devolatilization temperatures are 190℃, 200℃, 210℃, 220℃, 220℃ and 230℃ respectively, the twin-screw devolatilization speed is 150rpm, and the devolatilization section pressure is less than or equal to 10Pa.

[0135] 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.

[0136] Example 4

[0137] 95 kg of methyl methacrylate and 5 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 15°C.

[0138] Add 0.3 kg of chain transfer agent tert-dodecyl mercaptan, 0.25 kg of diisopropyl peroxide dicarbonate, and 0.4 kg of initiator II to the preparation vessel, and stir until completely dissolved;

[0139] 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;

[0140] The material is continuously injected into a vertical high-torque polymerization reactor at a rate of 0.6 L / min. The reactor temperature is 130°C, the stirring rate is 35 rpm, and the material residence time is 15 min. Then, it is continuously fed from the bottom of the reactor into a horizontal self-cleaning polymerization reactor at a rate of 0.6 L / min to continue polymerization. The polymerization temperature is 150°C, the stirring rate is 12 rpm, and the material residence time is 35 min.

[0141] The material is continuously fed into the twin-screw devolatilization section via a discharge screw. The discharge screw temperature is 185℃, the discharge screw speed is 11 rpm, the six devolatilization temperatures are 190℃, 200℃, 210℃, 210℃, 220℃ and 225℃ respectively, the twin-screw devolatilization speed is 160 rpm, and the devolatilization section pressure is less than or equal to 10 Pa.

[0142] 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.

[0143] Example 5

[0144] 90 kg of methyl methacrylate and 10 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 8°C.

[0145] Add 0.4 kg of chain transfer agent n-octyl mercaptan, 0.4 kg of cyclohexanone peroxide, and 0.6 kg of initiator II to the preparation vessel, and stir until completely dissolved;

[0146] 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;

[0147] The material is continuously injected into a vertical high-torque polymerization reactor at a rate of 0.9 L / min, with an internal temperature of 115°C, a stirring rate of 70 rpm, and a material residence time of 20 min. Then, it is continuously fed from the bottom of the reactor into a horizontal self-cleaning polymerization reactor at a rate of 0.9 L / min to continue polymerization at a temperature of 180°C, a stirring rate of 20 rpm, and a material residence time of 20 min.

[0148] 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 15rpm, the six devolatilization temperatures are 200℃, 200℃, 200℃, 210℃, 210℃ and 220℃ respectively, the twin-screw devolatilization speed is 145rpm, and the devolatilization section pressure is less than or equal to 10Pa.

[0149] 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.

[0150] Example 6

[0151] The method of Example 1 was followed, except that the amount of initiator II added was 0.02 kg. The performance test results are shown in Tables 1 and 2.

[0152] Example 7

[0153] Following the method of Example 1, except that samples were taken at a sampling port reserved in the middle of the horizontal self-cleaning polymerization reactor at 20 min, 40 min, 60 min, 80 min, 100 min, and 120 min of polymerization, respectively, to test the process yield in the final polymerization reactor. The test results were 79.8%, 80.2%, 79.9%, 79.1%, 80.3%, and 80.2%, respectively. This indicates that initiator II can decompose into free radicals in an orderly manner, the polymerization reaction is stable, and the polymerization rate is controllable.

[0154] Example 8

[0155] Following the method of Example 3, except that samples were taken at a sampling port reserved in the middle of the horizontal self-cleaning polymerization reactor at 20 min, 40 min, 60 min, 80 min, 100 min, and 120 min of polymerization, respectively, to test the process yield in the final polymerization reactor. The test results were 76.2%, 76.3%, 76.1%, 76.1%, 76.3%, and 76.1%, respectively. This indicates that initiator II can decompose into free radicals in an orderly manner, the polymerization reaction is stable, and the polymerization rate is controllable.

[0156] Example 9

[0157] The method was followed in Example 1, except that the prepolymerization temperature was 145°C, which was the same as the final polymerization temperature. The performance test results are shown in Tables 1 and 2.

[0158] Comparative Example 1

[0159] The method of Example 1 was followed, except that initiator II was replaced with an equal amount of benzoyl peroxide. The performance test results are shown in Tables 1 and 2.

[0160] Comparative Example 2

[0161] Following the method of Example 1, except that initiator II was not added, and samples were taken at a sampling port reserved in the middle of the horizontal self-cleaning polymerization reactor at 20 min, 40 min, 60 min, 80 min, 100 min, and 120 min of polymerization to test the monomer conversion rate. The test results were 44.7%, 38.8%, 48.5%, 40.7%, 42.5%, and 45.6%, respectively. This indicates that without initiator II, the conversion rate is low, the polymerization reaction is unstable, the polymerization rate is uncontrollable, and local overheating occurs. The performance test results are shown in Tables 1 and 2.

[0162] Table 1

[0163]

[0164]

[0165] Table 2

[0166]

[0167] The monomer residue in Table 2 refers to the content of residual monomers in the methyl methacrylate polymer.

[0168] As can be seen from the results in Tables 1 and 2, the polymer prepared in the embodiments of the present invention significantly outperforms the comparative example in terms of performance. During the polymerization process, this method demonstrates excellent control capabilities, effectively ensuring that the reaction proceeds along a precise and stable path. Simultaneously, it greatly enhances mass and heat transfer efficiency, promoting the rapid and uniform distribution and exchange of matter and energy within the reaction system. This creates more ideal environmental conditions for the polymerization reaction, effectively reducing the risk of gelation and avoiding product quality fluctuations and performance degradation caused by gelation problems.

[0169] 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 80-100% by weight, preferably 90-100% by weight; the amount of functional monomer X is 0-20% by weight, preferably 0-10% by weight; the amount of chain transfer agent is 0.05-0.8% by weight, preferably 0.1-0.3% by weight; the amount of initiator I is 0.05-1% by weight, preferably 0.1-0.4% by weight; and the amount of initiator II is 0.02-1.2% by weight, preferably 0.1-0.4% 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 any one of 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 0-20°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 20-100 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 horizontal self-cleaning polymerization 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 140-180°C and a reaction time of 20-40 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.

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 190-230℃, the devolatilization rate is 100-200rpm, and the devolatilization pressure is less than or equal to 10Pa.

8. A methyl methacrylate polymer prepared by any one of claims 1-7.

9. The polymer according to claim 8, wherein, The content of residual monomers in the polymer is less than or equal to 0.35% by weight.

10. The use of the methyl methacrylate polymer of claim 8 or 9 in liquid crystal displays or optical materials.

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