Heat-resistant methyl methacrylate copolymer as well as preparation method and application thereof

Abstract

The invention relates to the technical field of chemical engineering, and discloses a heat-resistant methyl methacrylate copolymer and a preparation method and application thereof.The preparation method comprises the following steps that S1, under the action of a chain transfer agent, methyl methacrylate and styrene are subjected to a polymerization reaction in an organic solvent, and polymerization slurry A is obtained; wherein the sum of the parts by mass of the methyl methacrylate and the styrene is 100 parts, the methyl methacrylate accounts for 60-99 parts by mass, and the styrene accounts for 1-40 parts by mass; s2, performing first-stage devolatilization treatment on the polymerized slurry A, and controlling the devolatilization temperature to be 110-180 DEG C and the devolatilization pressure to be 20-90 KPa to obtain polymerized slurry B; s3, mixing the polymerization slurry B with a primary amine substance, and carrying out a reaction at 210-280 DEG C for 1-50 min to obtain a slurry C; and S4, carrying out second-stage devolatilization treatment on the slurry C, and carrying out molding treatment on the obtained slurry D, thereby obtaining the product. According to the preparation method, extrusion equipment is not needed, the operation is simple and convenient, and the obtained copolymer has excellent heat resistance.

Description

Technical Field

[0001] The present application relates to the field of chemical technology, and in particular to a heat-resistant methyl methacrylate copolymer and a preparation method and application thereof. Background Art

[0002] Polymethyl methacrylate (PMMA) is a transparent thermoplastic material primarily composed of methyl methacrylate. It exhibits excellent optical properties, weather resistance, surface hardness, dimensional stability, and electrical insulation. Consequently, PMMA is widely used in a variety of applications, including automotive, display, electronics, lighting, and billboards.

[0003] PMMA's heat resistance is particularly important in applications requiring high thermal stability, such as automotive headlight lenses, plastic optical fibers, and optical displays. However, the glass transition temperature of general-purpose PMMA is generally below 115°C, making it susceptible to performance degradation in high-temperature environments and difficult to meet the demands of these high-performance applications. Therefore, improving PMMA's heat resistance has become a pressing technical challenge within the industry.

[0004] In order to improve the heat resistance of PMMA, the existing technology mainly adopts the following methods:

[0005] Copolymerization modification: Improves the thermal and hygroscopic properties of PMMA by copolymerizing it with monomers with rigid structures or strong polarity. However, certain highly polar cyclic monomers used in this method exhibit significant differences in copolymerization properties with methyl methacrylate, resulting in an uneven copolymer structure. This often requires the introduction of a third aromatic vinyl monomer for ternary copolymerization, complicating the composition. Furthermore, these cyclic monomers are often difficult to remove, and any residues in the material may affect its performance stability.

[0006] Blending modification method: By blending PMMA with other resins with good heat resistance, a synergistic improvement in performance can be achieved; however, in this process, the compatibility issues between different resins are more prominent, which can easily lead to uneven material properties or processing difficulties.

[0007] In this context, imidization modification has attracted attention because it can directly introduce a thermally stable structure into the polymer backbone without changing the main monomer system. This method reacts amine reagents with the ester groups in PMMA to form an imide structure, significantly improving the material's heat resistance. However, existing imidization modification processes often rely on extrusion reactions under high temperature and high pressure, which not only requires high equipment requirements but also has complex operational procedures, affecting process stability and economic viability.

[0008] Therefore, developing a method for preparing a heat-resistant methyl methacrylate copolymer that does not require extrusion equipment, is easy to operate, and can be combined with the existing PMMA resin production process has become a focus of attention and a direction of technological development for those skilled in the art. Summary of the Invention

[0009] In view of this, the technical problem to be solved by the present invention is to overcome the defects of the prior art that imidization modification relies on an extrusion reaction process under high temperature and high pressure conditions, has high equipment requirements, and has a complicated operation process, and to provide a heat-resistant methyl methacrylate copolymer and its preparation method and application.

[0010] According to an embodiment of the present application, in a first aspect, a method for preparing a heat-resistant methyl methacrylate copolymer is provided, comprising the following steps:

[0011] S1. Under the action of a chain transfer agent, methyl methacrylate and styrene undergo polymerization reaction in an organic solvent to obtain a polymer slurry A;

[0012] Wherein, the total mass parts of the methyl methacrylate and the styrene is 100 parts, the methyl methacrylate is 60 to 99 parts by mass, and the styrene is 1 to 40 parts by mass;

[0013] S2. Performing a first-stage devolatilization treatment on the polymer slurry A, controlling the devolatilization temperature to be 110-180° C. and the devolatilization pressure to be 20 KPa-90 KPa, to obtain polymer slurry B;

[0014] S3, mixing the polymer slurry B with a primary amine substance, and reacting at 210° C. to 280° C. for 1 minute to 50 minutes to obtain slurry C;

[0015] S4, performing a second-stage devolatilization treatment on the slurry C, and forming the obtained slurry D.

[0016] This application integrates imide modification into the polymerization devolatilization process, avoiding the complex process of traditional methods that rely on dedicated reaction extrusion equipment. The equipment used (such as heat exchangers and conventional devolatilizers) is compatible with existing general production lines, facilitating industrial promotion.

[0017] This application uses copolymerization of styrene and methyl methacrylate to increase the proportion of rigid groups in the polymer. At the same time, after polymerization, an amine modifier is used to undergo an imidization reaction with the ester group in the polymer to introduce an imide structure with higher thermal stability, giving the material a higher glass transition temperature (Tg≥120°C) to meet the requirements of high-temperature usage scenarios such as car lights and optical displays.

[0018] The devolatilization process is designed in stages. The first stage devolatilization removes most of the monomers, and the second stage devolatilization removes the remaining volatile components, which significantly reduces the residual monomers and oligomers in the system and improves the purity and stability of the finished resin.

[0019] The copolymer obtained in the present application can maintain high light transmittance and low haze while maintaining good melt fluidity, has excellent transparency and molding performance, and can be widely used in the processing of optical-grade products such as injection molding and extrusion.

[0020] Furthermore, in some embodiments, in step S3, the primary amine substance is selected from one or more of methylamine, ethylamine, propylamine, butylamine, cyclohexylamine, and aniline; preferably, methylamine or cyclohexylamine;

[0021] This application uses primary amines as imide modifiers, enabling efficient imidization reactions with ester groups on the polymer backbone under high-temperature conditions. This reaction is a nucleophilic substitution mechanism. Primary amines offer minimal steric hindrance and high reactivity, effectively reacting with polymer ester groups to form amide structures within a short timeframe. This further ring-closes at high temperatures to form imides, significantly enhancing the rigidity and heat resistance of the polymer segments.

[0022] Different primary amines can also impart different application properties to polymers. For example, methylamine modification significantly increases the Tg of polymers, making them suitable for applications requiring high thermal stability. Cyclohexylamine, due to its hydrophobicity, can further improve the material's moisture resistance and dimensional stability. Aniline, with its conjugated structure, helps adjust the material's optical properties and yellowing resistance. Therefore, by selecting the appropriate primary amine based on different performance requirements, multi-dimensional optimization of material properties can be achieved while ensuring heat resistance.

[0023] Furthermore, primary amine modifiers are common small-molecule amine compounds with simple reaction systems, a wide range of raw material sources, and ease of operation and continuous production. The modification process can be performed in conventional reactors and heat exchangers, eliminating the need for costly and complex reactive extrusion equipment, further enhancing the process's applicability and affordability.

[0024] In some embodiments, a tertiary amine catalyst is further added to the polymerization slurry B, preferably triethylamine;

[0025] Tertiary amine compounds possess strong basicity and excellent Lewis base catalytic ability, effectively promoting the nucleophilic substitution process between primary amines and ester groups in methyl methacrylate polymers during the imidization reaction. The introduction of tertiary amine catalysts can reduce the activation energy of the reaction and increase the reaction rate, thereby achieving efficient formation of imide structures within a relatively short high-temperature residence time.

[0026] Triethylamine, a tertiary amine with moderate volatility, strong catalytic activity, and good thermal stability, is preferred. It exhibits excellent solubility and dispersibility, quickly forming a homogeneous system with the amine modifier in the slurry, ensuring a thorough and uniform reaction. Triethylamine exhibits excellent thermal stability at high temperatures, avoiding the risk of catalyst decomposition affecting product performance.

[0027] In industrial operations, triethylamine exhibits low corrosivity and excellent process compatibility, facilitating continuous addition and reaction control in conventional equipment without the need for complex pre- or post-treatment processes. Furthermore, its controllable volatility facilitates the removal of residuals during the subsequent devolatilization step, ensuring the purity and thermal stability of the final copolymer. The introduction of triethylamine as a catalyst enables rapid and efficient completion of the imidization reaction, improving the polymer's heat resistance and structural stability while ensuring the safety, controllability, and applicability of the overall process.

[0028] In some embodiments, the mass fraction of the primary amine substance in the polymer slurry B is 0.1 to 10%, preferably 0.5 to 5%;

[0029] When the amount of amine modifier added is too low (less than 0.1%), the degree of imidization reaction is insufficient, the imide structure content in the polymer is low, and the molecular chain segment rigidity cannot be significantly improved, resulting in the copolymer glass transition temperature (Tg) unable to reach the target value required for high-heat-resistant materials, making it difficult to meet the performance requirements of high-temperature usage scenarios such as car lights and liquid crystal optical components.

[0030] If the amount of amine modifier added is too high (over 10%), although the degree of reaction may be further improved, it will bring multiple side effects. First, too many amine components in the system are prone to self-condensation, degradation or side reactions, thereby affecting the stability of the polymer backbone. Secondly, the increase in by-products in the reaction may cause color change, causing the copolymer to appear yellow, increase the yellowing index and other problems, affecting optical transparency. More importantly, although the excessive imide structure improves thermal stability, it may cause brittleness of the material, reduce its impact resistance, and affect its usability in applications requiring mechanical toughness.

[0031] In some embodiments, the mass fraction of the catalyst in the polymerization slurry B is 0.01 to 3%, preferably 0.1 to 1%.

[0032] Adding a catalyst in an amount of no less than 0.01% effectively promotes the formation of the imide ring, improves modification efficiency, and ensures the reaction is completed under short-term, high-temperature conditions. However, excessive catalyst can make residues difficult to remove, resulting in a darker color and increased impurity content in the final product, which in turn affects optical properties and long-term stability. Therefore, controlling the catalyst addition amount to 0.01-3%, and particularly within the preferred range of 0.1-1%, maximizes catalytic efficiency without introducing unnecessary side effects, thereby ensuring the polymer has good thermal properties, color stability, and structural controllability.

[0033] Furthermore, in some embodiments, in step S3, the reaction is carried out at 230° C. to 250° C. for 5 min to 30 min to obtain slurry C.

[0034] This application ensures that the amine modifier has sufficient reactivity to efficiently react with the ester group in the polymer to form an imide structure by reasonably controlling the reaction temperature range, while avoiding excessively high temperatures that cause thermal degradation or coloring of the polymer. By reasonably controlling the reaction time, both the sufficiency of the reaction and the rhythm of industrial production are taken into account. A time shorter than 1 minute will result in incomplete reaction, while a time longer than 50 minutes will pose risks of overheating and low production efficiency. By reasonably controlling the time range, a high conversion rate modification reaction can be achieved under continuous process conditions, ensuring the unity of improved material performance and process stability.

[0035] Furthermore, in some embodiments, in step S2, the devolatilization temperature is controlled to be 120° C. to 160° C., and the devolatilization pressure is controlled to be 40 KPa to 80 KPa;

[0036] By rationally controlling the devolatilization temperature and the devolatilization pressure of the first stage devolatilization in step S2, it is helpful to effectively remove most of the unreacted monomers and low-boiling volatile components in the system without causing thermal degradation of the materials.

[0037] In some embodiments, in step S4, the devolatilization temperature is controlled to be 230° C. to 250° C., and the devolatilization pressure is less than or equal to 5 KPa, preferably less than or equal to 3 KPa.

[0038] During the second-stage devolatilization process in step S4 of this application, high temperature and low pressure conditions help to further and efficiently remove residual monomers, low molecular weight byproducts, and unreacted modifiers and catalysts from the system after the imide modification reaction is completed. The higher temperature ensures that the volatiles have sufficient vapor pressure, while the lower system pressure increases the driving force for devolatilization of the material, thereby achieving deep devolatilization, improving the purity and thermal stability of the final copolymer, and reducing the impact of residual impurities on the color, odor, and performance consistency of the finished product.

[0039] Furthermore, in some embodiments, in the polymerization step, 70 to 95 parts by mass of methyl methacrylate and 5 to 30 parts by mass of styrene are used for polymerization.

[0040] The mass ratio of methyl methacrylate and styrene in this application can take into account the optical properties, weather resistance, and heat resistance of the copolymer. When the proportion of methyl methacrylate is high, it is beneficial to maintain the high transparency and excellent weather resistance of the polymer; and the introduction of an appropriate amount of styrene as a rigid comonomer can effectively increase the glass transition temperature and chemical resistance of the polymer. The copolymer system within the above ratio range can obtain a heat-resistant methyl methacrylate copolymer with uniform structure and balanced performance, which is suitable for applications that require both optical properties and thermal stability.

[0041] Furthermore, in some embodiments, in step S1, an initiator is added to carry out a polymerization reaction, and the half-life of the initiator is 3 to 30 minutes, preferably 5 to 15 minutes.

[0042] Preferably, based on the total mass of the methyl methacrylate and styrene, the mass fraction of the initiator is 10 to 1000 ppm, preferably 50 to 300 ppm.

[0043] Preferably, the initiator is selected from one or more of organic peroxides and azo compounds; preferably, one or more of 1,1-bis-(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis-(tert-butylperoxy)cyclohexane, tert-butyl peroxy-3,5,5-trimethylhexanoate, 2,2-di(tert-butylperoxy)butane, tert-butylperoxycarbonate-2-ethylhexyl ester, tert-amyl perbenzoate, tert-butyl perbenzoate, diisopropyl benzene peroxide, and di-tert-butyl peroxide.

[0044] The half-life of the initiator is 3 to 30 minutes, preferably 5 to 15 minutes, at the polymerization reaction temperature. Initiators with a half-life within this range can maintain the polymerization rate while reducing chain termination reactions caused by excessively rapid release of free radicals, thereby facilitating the production of copolymers with balanced molecular weight and stable structure.

[0045] The amount of initiator added is 10 to 1000 ppm, preferably 50 to 300 ppm, based on the total mass of methyl methacrylate and styrene. An appropriate amount of initiator ensures a sufficient free radical concentration to initiate the polymerization reaction while avoiding problems such as increased thermal polymerization side reactions, decreased molecular weight, or decreased product thermal stability caused by excessive initiator addition, thereby balancing polymerization efficiency and product performance.

[0046] Furthermore, in some embodiments, in step S1, the mass fraction of the chain transfer agent is 0.01 to 0.3%, preferably 0.05 to 0.15%, based on the total mass of methyl methacrylate and styrene;

[0047] Preferably, the chain transfer agent is selected from one or more of n-butyl mercaptan, isobutyl mercaptan, n-octyl mercaptan, isooctyl mercaptan, n-dodecyl mercaptan, tert-dodecyl mercaptan, and mercaptoethanol.

[0048] The introduction of the chain transfer agent in the present application can effectively regulate the molecular weight of the polymer in the polymerization slurry A, wherein the weight-average molecular weight of the polymer is 50,000 to 300,000, thereby preventing excessive growth of the molecular chain during the polymerization reaction, thereby improving the melt fluidity and enhancing the stability and controllability of the material during subsequent processing and molding.

[0049] The amount of chain transfer agent used balances molecular chain termination efficiency with product performance stability. Too low an addition will result in excessively high molecular weight, high melt viscosity, and processing difficulties; while too high an addition may cause polymer structural inhomogeneity or degrade mechanical properties. Therefore, properly controlling the mass fraction of the chain transfer agent can optimize the balance between polymer chain growth and processing performance.

[0050] Furthermore, in some embodiments, in step S1, the polymerization reaction temperature is 100°C to 180°C, preferably 120°C to 160°C.

[0051] In some embodiments, the polymerization reaction time is 1 to 6 hours, preferably 1.5 to 4 hours.

[0052] By properly controlling the polymerization reaction temperature, this application can ensure the effective release of free radicals while avoiding side reactions or system instability caused by excessively high temperatures. Setting the temperature within this range helps achieve a dynamic balance between reaction rate, molecular weight control, and slurry viscosity.

[0053] In some optional embodiments, according to the embodiments of the present application, in a second aspect, a heat-resistant methyl methacrylate copolymer is provided, which is prepared by the preparation method described in any of the above embodiments.

[0054] Preferably, the heat-resistant methyl methacrylate copolymer satisfies at least one of the following characteristics:

[0055] Glass transition temperature greater than or equal to 113°C;

[0056] At 230℃ / 3.8kg, the melt index is 2-4.5g / 10min;

[0057] The weight average molecular weight is 50,000 to 300,000, preferably 105,000 to 148,000;

[0058] Water vapor permeability: 146~198g / m 2 ·day;

[0059] The yellowing index measured on samples with a thickness of 3 mm is 0.35 to 0.43;

[0060] The haze measured at a sample thickness of 3 mm was 0.3%.

[0061] In some optional embodiments, according to the embodiments of the present application, the third aspect provides the use of the heat-resistant methyl methacrylate copolymer as described in any of the above embodiments in automotive materials, aviation materials, building materials, agricultural materials, liquid crystal materials, optical materials, medical materials or packaging materials.

[0062] The technical solution of this application has the following advantages:

[0063] The present application introduces a rigid structure through copolymerization of methyl methacrylate and styrene, and performs imide modification after the first-stage devolatilization, thereby synergistically improving the heat resistance and moisture resistance of the copolymer; the first-stage devolatilization of the present application can reduce the concentration of volatiles in the system to facilitate the uniform progress of the modification reaction, and the second-stage devolatilization deeply purifies the material, achieving overall optimization of heat resistance, moisture resistance, and structural uniformity, and solving the problems of low modification efficiency, high residue, and complex process existing in a single modification path.

[0064] The heat-resistant methyl methacrylate copolymer described in this application is prepared through a specific copolymerization combination, imide modification, and optimized reaction and devolatilization processes. It exhibits a high glass transition temperature, moderate melt fluidity, and a weight-average molecular weight controlled between 50,000 and 300,000, achieving a comprehensive balance of heat resistance, moisture resistance, processability, and molecular structure stability. This copolymer material is not only suitable for use in high-temperature environments, but also maintains excellent molding and processing properties and physical stability. It is particularly well-suited for applications such as optics, automotive, and electronics, which require both high thermal stability and formability.

[0065] The heat-resistant methyl methacrylate copolymer disclosed herein exhibits excellent thermal stability, optical transparency, and processing fluidity, making it widely applicable in a variety of fields, including automotive, aviation, construction, liquid crystal displays, optical components, medical devices, and packaging. The copolymer material disclosed herein is resistant to deformation in high-temperature environments, exhibits structural stability, and combines low hygroscopicity with good formability. It can meet the comprehensive requirements of these applications for heat resistance, dimensional stability, and appearance, possessing significant practical application value and potential for widespread adoption.

[0066] Additional aspects and advantages of the embodiments of the present application will be described and shown in part in the subsequent description, or explained through the implementation of the embodiments of the present application. DETAILED DESCRIPTION

[0067] The following is a clear and complete description of the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0068] The sources of the main raw materials involved in the examples and comparative examples of this application are shown in Table 1:

[0069] Table 1. Main raw material information

[0070]

[0071]

[0072] Specific experimental steps or conditions not specified in the examples and comparative examples of this application can be carried out according to the conventional experimental steps or conditions described in the literature in this field. The reagents or instruments used without indicating the manufacturer are all conventional reagent products that can be obtained through commercial purchase.

[0073] The relevant structure and performance testing methods of the copolymer in this application are as follows:

[0074] Molecular weight test: The molecular weight was tested by gel permeation chromatography (GPC) with tetrahydrofuran (THF) as the mobile phase, a parallax refractometer as the detector, and monodisperse polymethyl methacrylate (PMMA) as the standard sample.

[0075] Glass transition temperature test: glass transition temperature differential scanning calorimeter (DSC) test, nitrogen atmosphere, heating rate 10K / min.

[0076] Conversion rate test: During the continuous polymerization process, it is calculated based on the ratio of the mass of the outlet polymer to the amount of reaction liquid fed per unit time.

[0077] Moisture resistance test: Methyl methacrylate copolymer is cast into a 40 micron film, and the water vapor transmission rate (water vapor permeability) within 24 hours is tested.

[0078] Other relevant performance test methods are shown in Table 2:

[0079] Table 2. Polymer performance test standards and conditions

[0080] Test items Test standards Experimental conditions Melt index ISO 1133 230℃、3.8kg Light transmittance ISO 13486 3mm Haze ISO 14782 3mm Yellowing index ISO 13468 3mm

[0081] A method for preparing a methyl methacrylate copolymer comprises the following steps:

[0082] S101, Ingredients

[0083] Add methyl methacrylate, styrene, an optional initiator and an optional chain transfer agent into a batching tank and mix to prepare a reaction solution;

[0084] The total mass of methyl methacrylate and styrene is 100 parts by mass; methyl methacrylate is 60 to 99 parts by mass, and styrene is 1 to 40 parts by mass; preferably, methyl methacrylate is 70 to 95 parts by mass, and styrene is 5 to 30 parts by mass.

[0085] For the optional initiator, the half-life of the initiator at the polymerization reaction temperature is 3-30 minutes, such as 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, etc., preferably 5-15 minutes. The mass fraction of the initiator, based on the total mass of the methyl methacrylate and styrene, is 10-1000 ppm, such as 20 ppm, 50 ppm, 80 ppm, 100 ppm, 300 ppm, 500 ppm, 800 ppm, 1000 ppm, etc., preferably 50-300 ppm.

[0086] Among them, the initiator is selected from one or more of organic peroxides and azo compounds; preferably, one or more of 1,1-bis-(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis-(tert-butylperoxy)cyclohexane, peroxy-3,5,5-trimethylhexanoate, 2,2-di(tert-butylperoxy)butane, tert-butylperoxycarbonate-2-ethylhexyl ester, tert-amyl perbenzoate, tert-butyl perbenzoate, diisopropyl benzene peroxide, and di-tert-butyl peroxide.

[0087] The chain transfer agent may be selected from one or more of n-butyl mercaptan, isobutyl mercaptan, n-octyl mercaptan, isooctyl mercaptan, n-dodecyl mercaptan, tert-dodecyl mercaptan, and mercaptoethanol, preferably n-octyl mercaptan. The mass fraction of the chain transfer agent, based on the total mass of the methyl methacrylate and styrene, is 0.01 to 0.3%, preferably 0.05 to 0.15%.

[0088] S102, polymerization reaction

[0089] The reaction solution of step S101 is added into a polymerization reactor to react to prepare a polymerization slurry A;

[0090] The methyl methacrylate polymer can be polymerized by heat or by an initiator during the polymerization stage. In order to accelerate the polymerization reaction rate and facilitate the regulation of the conversion rate, it is preferred to use an initiator to initiate the polymerization.

[0091] During the polymerization process, an organic solvent may be added as needed to reduce the viscosity of the materials in the reactor. Available solvents include, but are not limited to, one or more of toluene, ethylbenzene, xylene, acetone, butanone, ethyl acetate, butyl acetate, tetrahydrofuran, and N,N-dimethylformamide, with toluene or ethylbenzene being preferred. The amount of solvent added is 5-30% of the total mass of methyl methacrylate, styrene, initiator, and chain transfer agent, for example, 8%, 10%, 15%, 18%, 20%, 23%, 25%, 27%, etc., preferably 10-20%.

[0092] In the polymerization reaction stage, the reaction temperature is 100°C to 180°C, for example, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, etc., preferably 120 to 160°C.

[0093] The polymerization reaction time is controlled within the range of 1 to 6 hours, for example, 1.5 h, 2 h, 2.5 h, 3 h, 4 h, 5 h, 6 h, etc., preferably 1.5 to 4 h.

[0094] The polymerization reactor can be a fully mixed flow reactor, a plug flow reactor, or a combination of the two, preferably a fully mixed flow reactor, more preferably a stirred reactor equipped with a jacket temperature control device. The reactor should be provided with a raw material supply port, a product extraction port and a stirring device, and the stirring device preferably has an efficient mixing capacity covering the entire reaction zone to ensure the temperature uniformity and material dispersion of the reaction process. In addition to the jacket temperature control, a draft tube, a heating coil or other heat transfer structure can also be provided inside the reactor, and further temperature control is achieved by circulating the heat carrier to improve the heat distribution uniformity and temperature control accuracy in the reaction zone.

[0095] During the polymerization reaction stage, the monomer conversion rate at the outlet of the polymerization reactor is controlled within the range of 50% to 85%, for example, 55%, 60%, 65%, 70%, 75%, 80%, 85%, etc., preferably 65% to 75%. When the conversion rate is too low, it is not conducive to improving production efficiency; while when the conversion rate is too high, the viscosity of the slurry may increase significantly, affecting the heat transfer and transportation stability of subsequent processes and reducing the controllability of the production process.

[0096] S201, first stage devolatilization

[0097] The polymer slurry A obtained in step S102 is fed into a first devolatilizer to remove 50-95% of unreacted monomers and other volatile components therein to obtain a devolatilized polymer slurry B.

[0098] The devolatilization temperature of the first stage devolatilization is 110°C to 180°C, and the devolatilization pressure is 20KPa to 90KPa; preferably, the devolatilization temperature is 120 to 160°C, and the devolatilization pressure is 40KPa to 80KPa; under these conditions, 50 to 95 wt% of the volatile components in the polymer slurry can be effectively removed, and the preferred removal ratio is 70 to 90% to ensure the uniformity of the subsequent modification reaction and the stability of the system.

[0099] The first devolatilizer can be selected from any one of a venting extruder, a falling strand devolatilizer, a falling film devolatilizer, a thin film evaporator, a single-shaft devolatilizer, or a double-shaft devolatilizer, or a combination thereof, preferably a falling strand devolatilizer, and more preferably a combined system consisting of two stages of falling strand devolatilizers.

[0100] S301, imide modification

[0101] The polymerized slurry B of step S201 is uniformly mixed with the primary amine substance and the catalyst, and then fed into a preheater, where it stays for 1 min to 50 min, preferably 5 min to 30 min; the temperature of the preheater outlet is 210° C. to 280° C., preferably 230° C. to 250° C.; thereby obtaining a modified slurry C;

[0102] The primary amine is selected from one or more of methylamine, ethylamine, propylamine, butylamine, cyclohexylamine, and aniline, preferably methylamine or cyclohexylamine. The catalyst is a tertiary amine catalyst, preferably triethylamine.

[0103] Based on the mass of the polymerization slurry B, the mass fraction of the primary amine substance is 0.1-10%, preferably 0.5-5%; the mass fraction of the catalyst is 0.01-3%, preferably 0.1-1%.

[0104] S401, second stage devolatilization

[0105] The slurry C modified in step S301 is further fed into a second devolatilizer to remove the remaining monomers and other volatile components to obtain slurry D;

[0106] The preheater is set on the top of the second devolatilizer. The preheater is a shell and tube heat exchanger with a static mixing element inside and a distribution plate with a hole diameter of 2-6 mm at the bottom. The bottom distribution plate can make the slurry B full in the static mixer, which is conducive to the reaction of methyl methacrylate polymer and amine modifier.

[0107] The modified slurry from step (4) is fed into a second devolatilizer, where unreacted monomers and impurities are removed. The second stage devolatilization temperature is 230°C to 250°C, and the devolatilization pressure is less than or equal to 5 kPa, preferably less than or equal to 3 kPa. The residence time of the modified slurry in the second devolatilizer is less than or equal to 15 minutes, preferably 2 to 5 minutes.

[0108] S402, Molding

[0109] The slurry D is extruded and pelletized to obtain the final product, a heat-resistant methyl methacrylate copolymer.

[0110] The unreacted monomers and other volatile components generated during the devolatilization process of this application are condensed in a condenser and then recovered. Preferably, the recovered volatiles are distilled to separate and remove high-boiling-point impurities (such as oligomers). The resulting low-boiling-point recyclable components are primarily original monomers such as methyl methacrylate and styrene, which can be reused as raw materials in the polymerization reaction process, thereby achieving raw material recycling and improving production efficiency.

[0111] In the process of preparing the methyl methacrylate copolymer by the above method, an appropriate amount of auxiliary agents can be added to the melt or formed particles after devolatilization as needed. The auxiliary agents may include but are not limited to release agents, ultraviolet absorbers, antioxidants, colorants and antistatic agents to further improve the processing performance, optical stability or performance of the product.

[0112] The heat-resistant methyl methacrylate copolymer prepared by the method of this application not only retains the excellent optical transparency and weather resistance of general-purpose methyl methacrylate materials, but also significantly improves its heat and moisture resistance, enabling it to adapt to a wider range of environments. This copolymer is suitable for use in a variety of fields, including automotive glass, aviation materials, building materials, agricultural materials, liquid crystal materials, optical components, medical devices, and packaging materials, and has excellent application prospects and industrial promotion value.

[0113] Example 1

[0114] S101, Ingredients

[0115] To a batching tank, add 80 parts by mass of methyl methacrylate, 20 parts by mass of styrene, 0.018 parts by mass of tert-butylperoxy-3,5,5-trimethylhexanoate (TBPMH), and 0.1 parts by mass of n-octyl mercaptan and mix thoroughly to prepare a reaction solution. The initiator, tert-butylperoxy-3,5,5-trimethylhexanoate (TBPMH), has a half-life of 8 minutes at 135°C. Nitrogen is then introduced to completely eliminate oxygen from the system to prevent it from inhibiting the polymerization reaction.

[0116] S102, polymerization reaction

[0117] The reaction liquid of step (1) was continuously added to a fully mixed flow reactor (effective volume of 30 L) at a flow rate of 10 kg / h, the temperature in the reactor was controlled at 135° C., and the average residence time of the reaction liquid was 2.5 h to obtain a polymer slurry A; the monomer conversion rate at the outlet was 70%.

[0118] S201, first stage devolatilization

[0119] The polymer slurry A is continuously fed into a first-stage falling strip devolatilizer and subjected to devolatilization treatment at a devolatilization pressure of 60 KPa and a devolatilization temperature of 150° C. to remove about 85% of the volatile components to obtain a devolatilized polymer slurry B.

[0120] S301, imide modification

[0121] Based on the mass of the polymerization slurry B, 9% cyclohexylamine and 0.5% triethylamine were injected into the polymerization slurry B, mixed evenly, and sent to a preheater. The temperature of the heat transfer oil in the preheater jacket was controlled to be 260°C, the material residence time in the preheater was 20 minutes, and the outlet slurry temperature was 240°C; thereby obtaining a modified slurry C.

[0122] S401, second stage devolatilization

[0123] The modified slurry C was sent to the second devolatilizer and devolatilized at a devolatilization temperature of 230°C and a devolatilization pressure of 3 kPa. The slurry stayed in the devolatilizer for 2 minutes to remove the remaining volatile components to obtain slurry D.

[0124] S402, Molding

[0125] The devolatilized slurry D is extruded and pelletized to obtain the final product, a heat-resistant methyl methacrylate copolymer.

[0126] Example 2

[0127] S101, Ingredients

[0128] 80 parts by mass of methyl methacrylate, 20 parts by mass of styrene, 0.02 parts by mass of dicumyl peroxide (DCP), and 0.05 parts by mass of n-octyl mercaptan were added to a batching tank and thoroughly mixed to prepare a reaction solution. The initiator, dicumyl peroxide (DCP), has a half-life of 8 minutes at 145°C. Nitrogen was then introduced to provide a protective atmosphere to completely eliminate oxygen from the system to prevent it from inhibiting the polymerization reaction.

[0129] S102, polymerization reaction

[0130] The reaction liquid of step (1) was continuously added to a fully mixed flow reactor (effective volume of 30 L) at a flow rate of 10 kg / h, the temperature in the reactor was controlled at 145° C., and the average residence time of the reaction liquid was 3 h to obtain a polymer slurry A; the monomer conversion rate at the outlet was 70%.

[0131] S201, first stage devolatilization

[0132] The polymer slurry A is continuously fed into a first-stage falling strip devolatilizer and subjected to devolatilization treatment at a devolatilization pressure of 60 KPa and a devolatilization temperature of 150° C. to remove about 80% of the volatile components to obtain a devolatilized polymer slurry B.

[0133] S301, imide modification

[0134] Based on the mass of the polymerization slurry B, 3% methylamine and 0.5% triethylamine were injected into the polymerization slurry B, mixed evenly, and sent to a preheater. The temperature of the heat transfer oil in the preheater jacket was controlled to be 260°C, the material residence time in the preheater was 20 minutes, and the outlet slurry temperature was 240°C; thereby obtaining a modified slurry C.

[0135] S401, second stage devolatilization

[0136] The modified slurry C was sent to the second devolatilizer and devolatilized at a devolatilization temperature of 230°C and a devolatilization pressure of 3 kPa. The slurry stayed in the devolatilizer for 2 minutes to remove the remaining volatile components to obtain slurry D.

[0137] S402, Molding

[0138] The devolatilized slurry D is extruded and pelletized to obtain the final product, a heat-resistant methyl methacrylate copolymer.

[0139] Example 3

[0140] S101, Ingredients

[0141] To a batching tank, add 95 parts by mass of methyl methacrylate, 5 parts by mass of styrene, 0.015 parts by mass of tert-butyl peroxy-3,5,5-trimethylhexanoate (TBPMH), and 0.15 parts by mass of n-octyl mercaptan and mix thoroughly to prepare a reaction solution. The initiator (TBPMH) has a half-life of 8 minutes at 135°C. Nitrogen is then introduced to completely eliminate oxygen from the system to prevent it from inhibiting the polymerization reaction.

[0142] S102, polymerization reaction

[0143] The reaction liquid of step (1) was continuously added to a fully mixed flow reactor (effective volume of 30 L) at a flow rate of 10 kg / h, the temperature in the reactor was controlled at 135° C., and the average residence time of the reaction liquid was 3 h to obtain a polymer slurry A; the monomer conversion rate at the outlet was 64%.

[0144] S201, first stage devolatilization

[0145] The polymer slurry A is continuously fed into a first-stage falling strip devolatilizer and subjected to devolatilization treatment at a devolatilization pressure of 55 KPa and a devolatilization temperature of 150° C. to remove about 90% of the volatile components to obtain a devolatilized polymer slurry B.

[0146] S301, imide modification

[0147] Based on the mass of the polymerization slurry B, 5% cyclohexylamine and 0.5% triethylamine were injected into the polymerization slurry B, mixed evenly, and sent to a preheater. The temperature of the heat transfer oil in the preheater jacket was controlled to be 260°C, the material residence time in the preheater was 20 minutes, and the outlet slurry temperature was 240°C; thereby obtaining a modified slurry C.

[0148] S401, second stage devolatilization

[0149] The modified slurry C was sent to the second devolatilizer and devolatilized at a devolatilization temperature of 230°C and a devolatilization pressure of 3 kPa. The slurry stayed in the devolatilizer for 2 minutes to remove the remaining volatile components to obtain slurry D.

[0150] S402, Molding

[0151] The devolatilized slurry D is extruded and pelletized to obtain the final product, a heat-resistant methyl methacrylate copolymer.

[0152] Example 4

[0153] S101, Ingredients

[0154] To a batching tank, add 70 parts by mass of methyl methacrylate, 30 parts by mass of styrene, 0.015 parts by mass of tert-butylperoxy-3,5,5-trimethylhexanoate (TBPMH), and 0.05 parts by mass of n-octyl mercaptan and mix thoroughly to prepare a reaction solution. The initiator (TBPMH) has a half-life of 8 minutes at 135°C. Nitrogen is then introduced to completely eliminate oxygen from the system to prevent it from inhibiting the polymerization reaction.

[0155] S102, polymerization reaction

[0156] The reaction liquid of step (1) was continuously added to a fully mixed flow reactor (effective volume of 30 L) at a flow rate of 10 kg / h, the temperature in the reactor was controlled at 135° C., and the average residence time of the reaction liquid was 3 h to obtain a polymer slurry A; the monomer conversion rate at the outlet was 67%.

[0157] S201, first stage devolatilization

[0158] The polymer slurry A is continuously fed into a first-stage falling strip devolatilizer and subjected to devolatilization treatment at a devolatilization pressure of 60 KPa and a devolatilization temperature of 150° C. to remove about 75% of volatile components to obtain a devolatilized polymer slurry B.

[0159] S301, imide modification

[0160] Based on the mass of the polymerization slurry B, 5% methylamine and 0.5% triethylamine were injected into the polymerization slurry B, mixed evenly, and sent to a preheater. The temperature of the heat transfer oil in the preheater jacket was controlled to be 260°C, the material residence time in the preheater was 20 minutes, and the outlet slurry temperature was 240°C; thereby obtaining a modified slurry C.

[0161] S401, second stage devolatilization

[0162] The modified slurry C was sent to the second devolatilizer and devolatilized at a devolatilization temperature of 230°C and a devolatilization pressure of 3 kPa. The slurry stayed in the devolatilizer for 2 minutes to remove the remaining volatile components to obtain slurry D.

[0163] S402, Molding

[0164] The devolatilized slurry D is extruded and pelletized to obtain the final product, a heat-resistant methyl methacrylate copolymer.

[0165] Example 5

[0166] The only difference between this embodiment and embodiment 3 is that the amine modifier added in step S301 is different. In this embodiment, 1% methylamine is added, while in embodiment 3, 5% cyclohexylamine is added.

[0167] Example 6

[0168] The only difference between this embodiment and embodiment 1 is that the amount of cyclohexylamine added in step S301 is larger, that is, 12% cyclohexylamine is injected in this embodiment; while in embodiment 1, 9% cyclohexylamine is added.

[0169] Example 7

[0170] The only difference between this embodiment and embodiment 1 is that the ingredients include 70 parts by mass of methyl methacrylate and 30 parts by mass of styrene.

[0171] Example 8

[0172] The only difference between this embodiment and embodiment 1 is that the ingredients include 95 parts by mass of methyl methacrylate and 5 parts by mass of styrene.

[0173] Example 9

[0174] The only difference between this embodiment and embodiment 1 is that in step (4), the injection amount of cyclohexylamine is different. In this embodiment, 0.1% cyclohexylamine is injected into slurry B.

[0175] Example 10

[0176] The only difference between this embodiment and embodiment 1 is that in step (4), the injection amount of cyclohexylamine is different. In this embodiment, 0.5% cyclohexylamine is injected into slurry B.

[0177] Example 11

[0178] The only difference between this embodiment and embodiment 1 is that in step (4), the injection amount of cyclohexylamine is different. In this embodiment, 3% cyclohexylamine is injected into slurry B.

[0179] Example 12

[0180] The only difference between this embodiment and embodiment 1 is that in step (4), the injection amount of cyclohexylamine is different. In this embodiment, 5% cyclohexylamine is injected into slurry B.

[0181] Example 13

[0182] The only difference between this embodiment and embodiment 1 is that in step (4), the type of amine modifier is different. The amine modifier in this embodiment is butylamine.

[0183] Example 14

[0184] The only difference between this embodiment and embodiment 1 is that in step (4), the type of amine modifier is different. The amine modifier in this embodiment is propylamine.

[0185] Example 15

[0186] The only difference between this embodiment and embodiment 1 is that in step S301 , no catalyst is injected into the polymerization slurry B.

[0187] Example 16

[0188] S101, Ingredients

[0189] To a batching tank, add 60 parts by mass of methyl methacrylate, 40 parts by mass of styrene, 0.001 parts by mass of an initiator, and 0.01 parts by mass of a chain transfer agent and mix thoroughly to prepare a reaction solution. The initiator has a half-life of 3 minutes at 120°C. Nitrogen is then introduced to provide a protective atmosphere to completely eliminate oxygen from the system to prevent it from inhibiting the polymerization reaction.

[0190] S102, polymerization reaction

[0191] The reaction liquid of step (1) was continuously added into a fully mixed flow reactor (effective volume of 30 L) at a flow rate of 10 KG / h, the temperature in the reactor was controlled at 120°C, and the average residence time of the reaction liquid was 1 hour to obtain polymerization slurry A.

[0192] S201, first stage devolatilization

[0193] The polymer slurry A was continuously fed into a first-stage falling strip devolatilizer and subjected to devolatilization treatment under the conditions of a devolatilization pressure of 20 KPa and a devolatilization temperature of 110° C. to obtain a devolatilized polymer slurry B.

[0194] S301, imide modification

[0195] Based on the mass of the polymerization slurry B, 10% cyclohexylamine and 0.01% triethylamine were injected into the polymerization slurry B, mixed evenly, and sent to a preheater. The temperature of the heat transfer oil in the preheater jacket was controlled to 230° C. The material stayed in the preheater for 5 minutes to obtain a modified slurry C.

[0196] S401, second stage devolatilization

[0197] The modified slurry C was sent to the second devolatilizer and devolatilized at a devolatilization temperature of 250°C and a devolatilization pressure of 5 kPa. The slurry stayed in the devolatilizer for 2 minutes to remove the remaining volatile components to obtain slurry D.

[0198] S402, Molding

[0199] The devolatilized slurry D is extruded and pelletized to obtain the final product, a heat-resistant methyl methacrylate copolymer.

[0200] Example 17

[0201] S101, Ingredients

[0202] To a batching tank, add 99 parts by mass of methyl methacrylate, 1 part by mass of styrene, 0.1 part by mass of an initiator, and 0.3 part by mass of a chain transfer agent and mix thoroughly to prepare a reaction solution. The initiator has a half-life of 30 minutes at 100°C. Nitrogen is then introduced to provide a protective atmosphere to completely eliminate oxygen from the system to prevent it from inhibiting the polymerization reaction.

[0203] S102, polymerization reaction

[0204] The reaction solution of step (1) was continuously added to a fully mixed flow reactor (effective volume of 30 L) at a flow rate of 10 kg / h, the temperature in the reactor was controlled at 100° C., and the average residence time of the reaction solution was 6 h to obtain a polymer slurry A;

[0205] S201, first stage devolatilization

[0206] The polymer slurry A was continuously fed into a first-stage falling strip devolatilizer and subjected to devolatilization treatment under the conditions of a devolatilization pressure of 90 KPa and a devolatilization temperature of 180° C. to obtain a devolatilized polymer slurry B.

[0207] S301, imide modification

[0208] Based on the mass of the polymerization slurry B, 5% cyclohexylamine and 0.1% triethylamine were injected into the polymerization slurry B, mixed evenly, and sent to a preheater. The temperature of the heat transfer oil in the preheater jacket was controlled to 250° C. The material stayed in the preheater for 30 minutes to obtain a modified slurry C.

[0209] S401, second stage devolatilization

[0210] The modified slurry C was sent to the second devolatilizer and devolatilized at a devolatilization temperature of 240°C and a devolatilization pressure of 4 kPa. The slurry stayed in the devolatilizer for 2 minutes to remove the remaining volatile components to obtain slurry D.

[0211] S402, Molding

[0212] The devolatilized slurry D is extruded and pelletized to obtain the final product, a heat-resistant methyl methacrylate copolymer.

[0213] Example 18

[0214] S101, Ingredients

[0215] To a batching tank, add 80 parts by mass of methyl methacrylate, 20 parts by mass of styrene, 0.005 parts by mass of an initiator, and 0.1 parts by mass of a chain transfer agent and mix thoroughly to prepare a reaction solution. The initiator has a half-life of 5 minutes at 160°C. Nitrogen is then introduced to provide a protective atmosphere to completely eliminate oxygen from the system to prevent it from inhibiting the polymerization reaction.

[0216] S102, polymerization reaction

[0217] The reaction liquid of step (1) was continuously added into a fully mixed flow reactor (effective volume of 30 L) at a flow rate of 10 KG / h, the temperature in the reactor was controlled at 160°C, and the average residence time of the reaction liquid was 1.5 h to obtain polymer slurry A.

[0218] S201, first stage devolatilization

[0219] The polymer slurry A was continuously fed into a first-stage falling strip devolatilizer and subjected to devolatilization treatment under the conditions of a devolatilization pressure of 40 KPa and a devolatilization temperature of 120° C. to obtain a devolatilized polymer slurry B.

[0220] S301, imide modification

[0221] Based on the mass of the polymer slurry B, 9% cyclohexylamine and 1% triethylamine were injected into the polymer slurry B, mixed evenly, and sent to a preheater. The temperature of the heat transfer oil in the preheater jacket was controlled to be 210° C. The material stayed in the preheater for 1 minute to obtain a modified slurry C.

[0222] S401, second stage devolatilization

[0223] The modified slurry C was sent to the second devolatilizer and devolatilized at a devolatilization temperature of 250°C and a devolatilization pressure of 3 kPa. The slurry stayed in the devolatilizer for 2 minutes to remove the residual volatile components to obtain slurry D.

[0224] S402, Molding

[0225] The devolatilized slurry D is extruded and pelletized to obtain the final product, a heat-resistant methyl methacrylate copolymer.

[0226] Example 19

[0227] S101, Ingredients

[0228] To a batching tank, add 80 parts by mass of methyl methacrylate, 20 parts by mass of styrene, 0.03 parts by mass of initiator, and 0.1 parts by mass of chain transfer agent and mix thoroughly to prepare a reaction solution. The initiator has a half-life of 15 minutes at 180°C. Nitrogen is then introduced to provide a protective atmosphere to completely eliminate oxygen from the system to prevent it from inhibiting the polymerization reaction.

[0229] S102, polymerization reaction

[0230] The reaction liquid of step (1) was continuously added into a fully mixed flow reactor (effective volume of 30 L) at a flow rate of 10 KG / h, the temperature in the reactor was controlled at 180°C, and the average residence time of the reaction liquid was 4 h to obtain polymer slurry A.

[0231] S201, first stage devolatilization

[0232] The polymer slurry A was continuously fed into a first-stage falling strip devolatilizer and subjected to devolatilization treatment under the conditions of a devolatilization pressure of 80 KPa and a devolatilization temperature of 160° C. to obtain a devolatilized polymer slurry B.

[0233] S301, imide modification

[0234] Based on the mass of the polymer slurry B, 9% cyclohexylamine and 3% triethylamine were injected into the polymer slurry B, mixed evenly, and sent to a preheater. The temperature of the heat transfer oil in the preheater jacket was controlled to 210° C. The material resided in the preheater for 50 minutes to obtain a modified slurry C.

[0235] S401, second stage devolatilization

[0236] The modified slurry C was sent to the second devolatilizer and devolatilized at a devolatilization temperature of 230°C and a devolatilization pressure of 3 kPa. The slurry stayed in the devolatilizer for 2 minutes to remove the remaining volatile components to obtain slurry D.

[0237] S402, Molding

[0238] The devolatilized slurry D is extruded and pelletized to obtain the final product, a heat-resistant methyl methacrylate copolymer.

[0239] Comparative Example 1

[0240] The difference between this comparative example and Example 1 is that the imide modification in step S301 is not performed, and the second stage devolatilization is directly performed after the first stage devolatilization.

[0241] Comparative Example 2

[0242] The difference between this comparative example and Example 1 is that in step S101, all monomers are methyl methacrylate, no styrene is added, the added amount of the chain transfer agent n-octyl mercaptan is 0.15 parts by mass, and the added amount of the initiator is 0.015 parts by mass.

[0243] Comparative Example 3

[0244] This comparative example differs from Example 2 in that, in step S101, 50 parts by mass of methyl methacrylate, 50 parts by mass of styrene, and 0.015 parts by mass of tert-butylperoxy-3,5,5-trimethylhexanoate (TBPMH) were added to a batching tank and thoroughly mixed to prepare a reaction solution. Nitrogen was then introduced for protection to fully remove oxygen from the system to prevent oxygen from inhibiting the polymerization reaction.

[0245] In step (2), the polymerization reaction was carried out at 135° C., with an average residence time of the reaction solution of 2.5 h, to obtain a polymer slurry A; the monomer conversion rate at the outlet was 65%.

[0246] Comparative Example 4

[0247] The only difference between this comparative example and Example 1 is that the first-stage devolatilization process in step S201 is omitted, that is, cyclohexylamine and triethylamine are directly injected after the polymerization reaction is completed and sent to the preheater for imide modification.

[0248] Experimental Example 1

[0249] This experimental example tested the weight average molecular weight, melt index, light transmittance, haze, glass transition temperature, yellowing index, and water vapor permeability of the products of Examples 1 to 15 and Comparative Examples 1 to 4. The results are shown in Table 3 below:

[0250] Table 3:

[0251]

[0252]

[0253] As can be seen from the above table, the heat-resistant methyl methacrylate copolymer in this application has a weight-average molecular weight of 105,000 to 148,000; a melt index of 2.0 g / 10 min to 4.5 g / 10 min, a transmittance of 92.10% to 92.70%, a haze of 0.30%, a glass transition temperature of 113 to 130°C, a yellowing index (YI, 3mm) of 0.35 to 0.43, and a moisture permeability of 146 g / m 2 ·Day~198g / m 2 day. It can be seen that the heat-resistant methyl methacrylate copolymer prepared in this application not only maintains excellent optical properties (high transmittance and low haze) but also exhibits good thermal performance and hygrothermal stability. The high glass transition temperature and moderate melt index facilitate structural stability during high-temperature processing or use, while the low yellowing index and moisture permeability indicate good color retention and moisture resistance.

[0254] Further analysis and comparison of Examples 1, 7, and 8 show that a moderate styrene ratio yields the most balanced material properties. A higher styrene ratio improves hygroscopicity and processability, but slightly reduces heat resistance and increases the risk of yellowing. A lower styrene ratio improves heat resistance and transparency, but degrades hygroscopicity. Therefore, maintaining a reasonable styrene content is crucial to achieving an optimal balance between heat resistance, transparency, and hygroscopicity.

[0255] Further, analysis and comparison of Examples 1 and 9 through 14 demonstrate that, using the same imidization conditions, adjusting only the amount of amine modifier added can modulate the heat resistance and hygroscopicity of the copolymer. Specifically, when the amine addition level is too low, the degree of imidization is limited, resulting in a low glass transition temperature and insufficient heat resistance. However, adding an appropriate amount of amine modifier effectively introduces an imide structure, improving heat resistance and structural stability, and exhibiting superior overall performance.

[0256] Comparison of Example 1, Example 13 and Example 14 shows that the use of different amine modifiers has a significant impact on the performance of the copolymer. The cyclohexylamine used in Example 1 gives the material better comprehensive properties, while ensuring a glass transition temperature of 126°C, maintaining a low yellowing index (0.38) and good moisture permeability (160g / m 2day), demonstrating excellent thermal stability, color stability, and hygroscopicity. However, the use of butylamine (Example 13) and propylamine (Example 14) increased the Tg to 128°C and 130°C, respectively, but increased the yellowing index to 0.42 and 0.43, and also reduced moisture permeability, indicating that while these improved heat resistance came at the expense of some optical stability and hygroscopicity.

[0257] Comparing Example 1 with Example 15, it can be seen that the addition of a catalyst has a significant impact on the imidization modification effect. Example 1 added triethylamine as a catalyst in the imidization step, and its copolymer had a higher glass transition temperature, a lower yellowing index, and excellent moisture permeability. In Example 15, no catalyst was added. Although other process parameters were the same, its Tg dropped to 122°C, the yellowing index increased to 0.42, and the moisture permeability also increased to 198g / m 2 ·day, indicating that the imidization reaction is incomplete, resulting in decreased heat resistance and hygroscopicity. Therefore, catalysts are important in improving reaction efficiency and promoting the formation of imide structures, and are a key factor in ensuring the overall performance of the material.

[0258] Comparing Example 1 with Comparative Example 1, the glass transition temperature (Tg) of Example 1 is 126°C, which is significantly higher than 110°C of Comparative Example 1, and the moisture permeability is increased from 180g / m2 of Comparative Example 1 to 110g / m2. 2 ·day down to 160g / m2 of Example 1 2 The results show that the modified material exhibits significant improvements in both heat resistance and moisture resistance. This is evident from the introduction of an imide structure into the polymer backbone. The imide group's strong conjugation and rigid ring system significantly restrict the free movement of polymer segments, thereby increasing the polymer's glass transition temperature (Tg). Furthermore, the imide structure's less polar, dense molecular arrangement helps reduce the permeation pathway and diffusion rate of water in the material, effectively reducing moisture absorption.

[0259] Comparing Example 1 with Comparative Example 2, it can be seen that although the glass transition temperature (Tg) of Comparative Example 2 (PMMA homopolymer) is slightly higher, its moisture permeability is as high as 200g / m 2 day, significantly higher than 160g / m2 in Example 1 2 day, indicating that the monomer structure significantly affects the material's hygroscopicity. In Example 1, by introducing a highly hydrophobic styrene monomer for copolymerization, the polarity of the material was effectively reduced, inhibiting the adsorption and diffusion of moisture. Simultaneously, the copolymer structure enhanced the chain segment rigidity and bulk density, helping to form a denser moisture barrier. Styrene copolymerization not only maintained a high glass transition temperature but also significantly improved moisture resistance.

[0260] Comparing Example 2 with Comparative Example 3 reveals that, while the polymerization temperature and reaction time are essentially identical, the styrene content in Comparative Example 3 is as high as 50%, resulting in a drop in the glass transition temperature to 112°C and a failure to achieve improved heat resistance. Furthermore, the yellowing index increases to 0.56, and the transmittance decreases to 91.5%, significantly inferior to that of Example 2. This indicates that excessive styrene content can disrupt the uniformity of the copolymer segment structure, reduce the thermal stability and optical purity of the material, and easily lead to a darker color and decreased transparency. Therefore, while the introduction of styrene can improve certain properties, its dosage must be precisely controlled within a reasonable range to achieve a balanced balance of heat resistance, color stability, and optical properties.

[0261] Comparison of Example 1 and Comparative Example 4 shows that the introduction of a first-stage devolatilization treatment before the imide modification step has a significant effect on improving product performance. Comparative Example 4 omits the devolatilization step, resulting in an increase in the yellowing index to 0.41, an increase in haze to 0.50%, a decrease in light transmittance to 92.10%, and an increase in moisture permeability to 168 g / m 2 day, indicating that the material's optical transparency, color stability, and moisture resistance were all affected. In contrast, Example 1, which performed imide modification after the first-stage devolatilization, exhibited superior properties across the board. Its Tg was raised to 126°C, its YI was only 0.38, and its haze was maintained at 0.30%, demonstrating excellent modification uniformity and overall performance. This demonstrates that the first-stage devolatilization not only helps reduce residual volatiles and improve reaction efficiency, but also improves the thermal, optical, and environmental stability of the final material.

[0262] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of this application.

Claims

1. A method for preparing a heat-resistant methyl methacrylate copolymer, characterized in that: The steps include: S1. Under the action of a chain transfer agent, methyl methacrylate and styrene undergo polymerization reaction in an organic solvent to obtain a polymer slurry A; Wherein, the total mass parts of the methyl methacrylate and the styrene is 100 parts, the methyl methacrylate is 60 to 99 parts by mass, and the styrene is 1 to 40 parts by mass; S2, performing a first-stage devolatilization treatment on the polymer slurry A, controlling the devolatilization temperature to be 110-180° C. and the devolatilization pressure to be 20 KPa-90 KPa, to obtain polymer slurry B; S3, mixing the polymer slurry B with a primary amine substance, and reacting at 210° C. to 280° C. for 1 minute to 50 minutes to obtain slurry C; S4, performing a second-stage devolatilization treatment on the slurry C, and forming the obtained slurry D.

2. The method for preparing a heat-resistant methyl methacrylate copolymer according to claim 1, wherein In step S3, the primary amine substance is selected from one or more of methylamine, ethylamine, propylamine, butylamine, cyclohexylamine, and aniline; preferably, methylamine or cyclohexylamine; And / or, a tertiary amine catalyst is further added to the polymerization slurry B, preferably triethylamine; Preferably, the mass fraction of the primary amine substance in the polymerization slurry B is 0.1-10%, preferably 0.5-5%; the mass fraction of the catalyst in the polymerization slurry B is 0.01-3%, preferably 0.1-1%.

3. The method for preparing a heat-resistant methyl methacrylate copolymer according to claim 1 or 2, wherein: In the step S3, the reaction is carried out at 230° C. to 250° C. for 5 to 30 minutes to obtain slurry C.

4. The method for preparing a heat-resistant methyl methacrylate copolymer according to any one of claims 1 to 3, characterized in that: In step S2, the devolatilization temperature is controlled to be 120° C. to 160° C., and the devolatilization pressure is controlled to be 40 KPa to 80 KPa; And / or, in step S4, the devolatilization temperature is controlled to be 230° C. to 250° C., and the devolatilization pressure is less than or equal to 5 KPa, preferably less than or equal to 3 KPa.

5. The method for preparing a heat-resistant methyl methacrylate copolymer according to any one of claims 1 to 4, characterized in that: In step S1, an initiator is added to carry out a polymerization reaction, and the half-life of the initiator is 3 to 30 minutes, preferably 5 to 15 minutes; Preferably, based on the total mass of the methyl methacrylate and styrene, the mass fraction of the initiator is 10 to 1000 ppm, preferably 50 to 300 ppm.

6. The method for preparing a heat-resistant methyl methacrylate copolymer according to claim 5, wherein: The initiator is selected from one or more of organic peroxides and azo compounds; Preferably, the initiator is selected from one or more of 1,1-bis-(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis-(tert-butylperoxy)cyclohexane, tert-butyl peroxy-3,5,5-trimethylhexanoate, 2,2-di(tert-butylperoxy)butane, tert-butylperoxycarbonate-2-ethylhexyl ester, tert-amyl peroxybenzoate, tert-butyl peroxybenzoate, diisopropyl benzene peroxide, and di-tert-butyl peroxide.

7. The method for preparing a heat-resistant methyl methacrylate copolymer according to any one of claims 1 to 6, characterized in that: In step S1, the mass fraction of the chain transfer agent is 0.01 to 0.3%, preferably 0.05 to 0.15%, based on the total mass of methyl methacrylate and styrene; Preferably, the chain transfer agent is selected from one or more of n-butyl mercaptan, isobutyl mercaptan, n-octyl mercaptan, isooctyl mercaptan, n-dodecyl mercaptan, tert-dodecyl mercaptan, and mercaptoethanol.

8. The method for preparing a heat-resistant methyl methacrylate copolymer according to any one of claims 1 to 7, characterized in that: In step S1, the polymerization reaction temperature is 100°C to 180°C, preferably 120°C to 160°C; And / or, the polymerization reaction time is 1 to 6 hours, preferably 1.5 to 4 hours.

9. A heat-resistant methyl methacrylate copolymer, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8 above; Preferably, the heat-resistant methyl methacrylate copolymer satisfies at least one of the following characteristics: Glass transition temperature greater than or equal to 113°C; At 230℃ / 3.8kg, the melt index is 2-4.5g / 10min; The weight average molecular weight is 50,000 to 300,000, preferably 105,000 to 148,000; Water vapor permeability: 146~198g / m 2 ·day; The yellowing index measured on samples with a thickness of 3 mm is 0.35 to 0.43; The haze measured at a sample thickness of 3 mm was 0.3%.

10. Use of the heat-resistant methyl methacrylate copolymer according to claim 9 in automotive materials, aviation materials, building materials, agricultural materials, liquid crystal materials, optical materials, medical materials or packaging materials.

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