Toughened PMMA material and method of manufacture

Abstract

This invention discloses a toughened PMMA material and its preparation method. The preparation method includes the following steps: 1) mixing methyl methacrylate and a chain transfer agent to obtain a first mixture; 2) mixing dicyclopentadiene and an initiator to obtain a second mixture; 3) mixing the first mixture and the second mixture through a pipe mixer, and then adding the mixture to a continuous screw reactor for polymerization to form the toughened PMMA material. The toughened PMMA material prepared using this method exhibits significantly improved impact strength while maintaining its light transmittance, tensile strength, and other key properties without significant decrease. Furthermore, the raw materials used in this preparation are inexpensive, reducing production costs.

Description

Technical Field

[0001] This invention relates to the field of acrylic glass technology, and in particular to a toughened PMMA material and its preparation method. Background Technology

[0002] Polymethyl methacrylate (PMMA), also known as plexiglass, is the transparent polymer material with the highest light transmittance. It weighs half that of glass and possesses advantages such as insulation, weather resistance, and ease of processing. It can be used to produce a variety of products, including automotive lights, consumer electronics, and electrical appliances. Although PMMA has relatively higher toughness than glass, it is still insufficient in some thin-walled applications, such as tempered glass films, making it prone to brittle cracking.

[0003] Existing chemical toughening methods can effectively improve the impact resistance of PMMA, but it is difficult to ensure that the light transmittance, tensile strength and flexural strength do not decrease significantly while improving the impact strength of PMMA. In addition, it requires the use of expensive polymer monomers, which is costly and complicated in preparation process. Summary of the Invention

[0004] This invention provides a toughened PMMA material and its preparation method. The toughened PMMA material prepared using this method has significantly improved impact strength while maintaining its other key properties, such as light transmittance and tensile strength, without significant decrease. Furthermore, the raw materials used in the preparation are inexpensive, thus reducing production costs.

[0005] In a first aspect, the present invention provides a method for preparing toughened PMMA material, comprising the following steps:

[0006] 1) Methyl methacrylate and a chain transfer agent are mixed to obtain a first mixture;

[0007] 2) Dicyclopentadiene and the initiator are mixed to obtain a second mixture;

[0008] 3) The first mixture and the second mixture are mixed through a pipe mixer and then added to a continuous screw reactor for polymerization to form the toughened PMMA material.

[0009] Furthermore, based on the mass of the methyl methacrylate, the mass percentage of the dicyclopentadiene is 15% to 30%.

[0010] Furthermore, based on the mass of the methyl methacrylate, the chain transfer agent accounts for 0.05% to 0.2% by mass.

[0011] Furthermore, based on the mass of the methyl methacrylate, the mass percentage of the initiator is 0.001% to 0.05%.

[0012] Furthermore, the mixing temperature of the dicyclopentadiene and the initiator is 5°C to 25°C.

[0013] Furthermore, the reaction temperature of the continuous screw reactor is 150℃~200℃, the pressure is 1.0MPaG~3.0MPaG, the reaction residence time is 4h~6h, and the screw speed is 30r / min~100r / min.

[0014] Furthermore, the polymerization reaction is followed by a molding process, which includes vacuum melt extrusion, wherein the vacuum degree of the vacuum melt extrusion is -0.095MPaG to -0.07MPaG and the temperature is 160℃ to 190℃.

[0015] Furthermore, the chain transfer agent is at least one of n-dodecyl mercaptan, tert-dodecyl mercaptan, and α-methylstyrene dimer, and the initiator is at least one of tert-butyl hydroperoxide, di-tert-butyl hydroperoxide, cumene hydroperoxide, and dicumene peroxide.

[0016] Secondly, the present invention provides a toughened PMMA material prepared by the method for preparing toughened PMMA material described in the first aspect, wherein the notched impact strength of the toughened PMMA material is 8 kJ / m at 23°C. 2 ~12kJ / m 2 .

[0017] Furthermore, at least one of the following conditions must be met:

[0018] a. The tensile strength of the toughened PMMA material is 65MPa~70MPa;

[0019] b. The flexural strength of the toughened PMMA material is 105MPa~115MPa;

[0020] c. When the thickness of the toughened PMMA material is 3mm, the light transmittance is 90%~92%.

[0021] This invention provides a toughened PMMA material and its preparation method. Through precise premixing design and synergistic subsequent processes, the reaction system is stabilized and the material properties are optimized. Specifically, a mismatched premixing strategy is used to prepare two mixtures: the first mixture is a mixture of methyl methacrylate (MMA) and a chain transfer agent, and the second mixture is a mixture of dicyclopentadiene (DCPD) and an initiator. This design can establish a stable reaction foundation in advance. The chain transfer agent is pre-dispersed in MMA, establishing a dispersed chain length control system in advance, ensuring uniform chain length distribution throughout the subsequent polymerization reaction. The initiator is pre-mixed with low-activity DCPD, allowing the initiator to be dispersed within the second mixture system before the polymerization reaction, thereby reducing the initial activity of the initiator and decreasing the proportion of MMA self-polymerization (without DCPD participation). This ensures uniform polymerization of DCPD and MMA upon contact, guaranteeing a controllable reaction process. Synergistic Process and Toughening Effect after Premixing: Two premixes are rapidly and uniformly mixed at the molecular level using a pipe mixer. The initiator diffuses uniformly into the MMA phase simultaneously with DCPD, thereby initiating the polymerization of MMA and DCPD. Simultaneously, the fully dispersed chain transfer agent precisely controls molecular chain growth during polymerization, generating flexible segments. These segments can absorb impact energy through rotation and slip under impact and maintain tensile strength by controlling chain length distribution. DCPD forms chemical bonds with MMA through the polymerization reaction, and its rigid ring structure is embedded in the polymerized segments, maintaining the structural strength of the material while preventing phase separation and ensuring light transmittance. Polymerization Reaction Control and Final Effect: The polymerization reaction is precisely controlled using a continuous screw reactor, ensuring complete polymerization and uniform molecular structure, without agglomeration and uniform dispersion, achieving toughening while ensuring uniform light transmission. The final toughened PMMA material shows significantly improved impact strength, with no significant decrease in key properties such as light transmittance and tensile strength. Furthermore, DCPD raw materials are readily available and inexpensive, significantly reducing production costs. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the accompanying drawings used in the description of the embodiments of the present invention or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic flowchart illustrating a method for preparing a toughened PMMA material provided by the present invention. Detailed Implementation

[0024] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In a first aspect, the present invention provides a method for preparing toughened PMMA material, comprising the following steps:

[0026] 1) Methyl methacrylate and a chain transfer agent are mixed to obtain a first mixture;

[0027] 2) Dicyclopentadiene and the initiator are mixed to obtain a second mixture;

[0028] 3) After mixing the first mixture and the second mixture through a pipe mixer, the mixture is added to a continuous screw reactor for polymerization to form toughened PMMA material.

[0029] This invention achieves stable reaction system and optimized material properties through precise premixing design and synergy with subsequent processes. The precise premixing design involves separately configuring a first mixture and a second mixture, allowing the initiator to first contact the low-reactivity monomer—dicyclopentadiene (DCPD)—in the second mixture, and only after mixing in a pipeline mixer does it contact the high-reactivity monomer—methyl methacrylate (MMA), with both monomers, DCPD and MMA, being initiated simultaneously.

[0030] The above preparation method first uniformly disperses the chain transfer agent in MMA to pre-construct a uniform and stable chain length control environment, avoiding subsequent local chain length unevenness. By premixing the initiator with DCPD, not only is the dispersibility of the initiator adjusted, but the low reactivity of DCPD is also used to inhibit the initial initiation efficiency of the initiator, reducing the initial activity of the initiator and achieving a match between the initiation activity and the polymerization rate of the monomers (highly reactive monomer MMA and low-reactive monomer DCPD). This allows for a stable and uniform polymerization reaction after the initiator contacts MMA. Simultaneously, after mixing the first and second mixtures through a pipeline, the initiator can uniformly diffuse into the MMA phase along with DCPD, simultaneously initiating the polymerization of MMA and DCPD. DCPD is uniformly distributed with the initiator without agglomeration. At the same time, the chain transfer agent is fully dispersed, allowing for precise control of chain length, ultimately stabilizing the polymerization system and ensuring that DCPD is uniformly embedded in the molecular chain, guaranteeing the toughening effect.

[0031] By introducing a chain transfer agent into the first mixture, the molecular chain length of the polymethyl methacrylate (PMMA) backbone generated after the polymerization reaction can be controlled, forming shorter segments with better flexibility. These shorter segments are the first type of toughening segments (i.e., short-chain PMMA segments generated under the control of the chain transfer agent). These short segments can absorb impact energy through segment rotation and slippage when the toughened PMMA material is impacted, laying the foundation for improved toughness. At the same time, controlling the chain length distribution maintains the molecular chain length, thereby maintaining the tensile strength of the toughened PMMA material. In the second mixture, DCPD is selected. The unsaturated double bonds in the DCPD molecule can undergo a polymerization reaction with the double bonds of MMA, so that the DCPD segments and MMA are tightly bonded by chemical bonds to form the second type of toughening segments (i.e., MMA-DCPD polymerized segments containing DCPD structural units). These segments not only further enhance the toughened PMMA material's ability to absorb impact energy with the help of the flexible segments of DCPD, but also maintain the overall structural strength with its rigid ring structure, without phase separation. The process avoids issues related to light transmittance. Subsequent use of a pipe mixer enables rapid and uniform molecular-level mixing of the first and second mixtures, resulting in a uniform concentration distribution of DCPD throughout the reaction system. This ensures that the second type of toughening segment (MMA-DCPD polymeric segment containing DCPD structural units) and the first type of toughening segment (short-chain PMMA segment) remain uniformly dispersed within the PMMA matrix (a continuous PMMA molecular network formed by the polymerization of MMA monomers). This allows the toughening segments to exert a consistent toughening effect throughout the toughened PMMA material, ensuring a uniform improvement in overall toughness while allowing light to penetrate uniformly without affecting transmittance. Furthermore, a continuous screw reactor precisely controls the polymerization reaction, ensuring complete polymerization and a uniform molecular structure. Ultimately, the prepared toughened PMMA material exhibits significantly improved impact strength without a noticeable decrease in transmittance, tensile strength, or other key properties. Moreover, the DCPD used is a readily available and inexpensive raw material, significantly reducing production costs.

[0032] In step 1) of this invention, after MMA and chain transfer agent are mixed, the chain transfer agent is only dissolved in MMA and does not have the activity to initiate the polymerization reaction. Therefore, it will not cause MMA to undergo homopolymerization. The resulting first mixture has a stable system, which provides a basis for the uniformity of the subsequent polymerization reaction between MMA and DCPD.

[0033] In step 2) of this invention, DCPD has significantly lower homopolymerization activity than MMA. When mixed with the initiator, the small amount of free radicals generated by the decomposition of the initiator can only initiate a very small amount of DCPD oligomerization reaction to generate a small amount of oligomers (the proportion of these oligomers is extremely low and does not affect the effect of subsequent polymerization reaction). As a result, the second mixture obtained has a relatively stable system, making DCPD evenly distributed.

[0034] In step 3) of this invention, the pipeline mixer is a static mixing instrument installed in a fluid delivery pipeline without external power drive. Through the shearing, segmentation, recombination, and convection diffusion effects generated by the fluid's own flow, it is used to gradually refine two or more materials from macroscopic dispersion to microscopic mixing, achieving a rapid and uniform molecular-level dispersion effect for different materials. The pipeline mixer, through rapid segmentation and recombination, enables the first and second mixtures to reach a microscopically uniform state within milliseconds, ensuring that the concentrations of MMA, DCPD, initiator, and chain transfer agent in each fluid unit are completely consistent. Subsequently, after entering the continuous screw reactor, the initiator initiates the polymerization reaction. The free radicals from the initiator decomposition simultaneously contact MMA and DCPD. MMA, as the main monomer, forms the PMMA backbone, and DCPD is uniformly incorporated into the PMMA molecular chain, achieving toughening. This preparation process avoids premature reaction through group mixing and ensures uniformity through a synergistic continuous polymerization reaction. It utilizes the diene structure of DCPD to introduce rigid and flexible balanced segments, alleviating the brittle fracture of PMMA and improving impact strength. Furthermore, because DCPD and PMMA have a small difference in refractive index and the polymerization reaction is uniform, the toughened PMMA material formed has an amorphous structure, ensuring that the light transmittance does not decrease significantly. At the same time, DCPD does not destroy the rigid skeleton of the PMMA main chain, so that properties such as tensile strength remain stable. Moreover, all raw materials used are low-cost materials, which effectively reduces production costs.

[0035] This method enables toughened PMMA materials prepared with this method to achieve a significant increase in impact strength while maintaining other key properties such as light transmittance and tensile strength without a significant decrease. Furthermore, the raw materials used in this preparation are inexpensive, reducing production costs.

[0036] In some preferred embodiments, methyl methacrylate and a chain transfer agent are uniformly mixed to obtain a first mixture; dicyclopentadiene and an initiator are uniformly mixed to obtain a second mixture; both the first and second mixtures are uniformly dispersed systems without stratification. The uniform dispersion system formed by methyl methacrylate and the chain transfer agent ensures that the chain transfer agent is uniformly dispersed throughout the first mixture, providing a stable prerequisite for precise control of the formation of short-chain PMMA segments (first-type toughening segments) during subsequent polymerization, and ensuring the uniformity of the material's tensile strength; the uniform dispersion system formed by the initiator and dicyclopentadiene (DCPD) ensures that DCPD does not agglomerate in the premix, laying the foundation for subsequent molecular-level mixing with the first mixture and simultaneous initiation of the MMA-DCPD polymerization reaction.

[0037] The synergistic effect of the first and second mixtures in the uniformly dispersed system can reduce the process burden of subsequent pipeline mixing, ensure uniform concentration of each component in the reaction system after mixing, and thus enable the two types of toughening segments (short-chain PMMA segments and MMA-DCPD polymer segments) to be uniformly distributed in the matrix. This avoids the toughness fluctuation of the toughened PMMA material caused by the absence or agglomeration of local toughening segments, while ensuring the stability of key properties such as light transmittance and tensile strength.

[0038] In some embodiments, the mass percentage of dicyclopentadiene is 15% to 30% based on the mass of methyl methacrylate.

[0039] For example, the amount of DCPD added is any value or a range of any two of 15%, 20%, 25%, 30% of the mass of MMA.

[0040] Within this range, DCPD can provide sufficient polymeric segments to ensure the formation of a uniformly distributed toughened structure in the PMMA molecular chain, fully absorbing impact energy and significantly improving the material's impact resistance. At the same time, this dosage will not excessively occupy the polymerization sites of the PMMA main molecular chain, ensuring that key properties such as light transmittance and tensile strength are maintained at their original levels, achieving a balance between toughening and other key properties such as light transmittance and tensile strength.

[0041] In some embodiments, the chain transfer agent is 0.05% to 0.2% by mass of methyl methacrylate.

[0042] For example, the mass percentage of the chain transfer agent is any value or a range of any two of 0.05%, 0.1%, 0.15%, 0.2%, etc.

[0043] This dosage of chain transfer agent allows for precise control of the molecular weight, viscosity, and properties of the polymerized product. It can regulate the molecular weight and viscosity of the polymerized product to the target range, ensuring the stability of continuous production and reducing the coating residue of unreacted monomers within the system. Specifically, it can precisely adjust the growth length of active chains in the polymerization reaction, resulting in a more concentrated and uniform molecular weight distribution. The synergistic effect between the PMMA matrix and DCPD polymerized chain segments is better, giving the polymerized product a suitable molecular chain length distribution. This ensures the material's processing fluidity while enhancing the binding force between molecular chains, allowing the material to maintain stable mechanical properties such as tensile strength while improving impact strength, without compromising light transmittance.

[0044] In some embodiments, the initiator is 0.001% to 0.05% by mass of methyl methacrylate.

[0045] For example, the mass percentage of the initiator is any value or a range of any two of the following: 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%.

[0046] The initiator provides free radicals to initiate the polymerization reaction between MMA and DCPD. Initiator dosage within this range ensures efficient and complete polymerization with a stable reaction rate, reducing unreacted monomers and facilitating subsequent separation. The free radical concentration at this dosage ensures uniform DCPD incorporation into the PMMA molecular backbone, guaranteeing the uniformity of the toughened PMMA material's properties. This avoids problems such as explosive polymerization, inability to remove reaction heat in a timely manner, and reactor blockage.

[0047] In some embodiments, the mixing temperature of dicyclopentadiene and the initiator is 5°C to 25°C.

[0048] For example, the mixing temperature of DCPD and initiator is any value or a range of any two of the following: 5°C, 10°C, 15°C, 20°C, 25°C.

[0049] This temperature range effectively stabilizes the chemical properties of the initiator, preventing premature decomposition and the generation of numerous free radicals that could lead to initiator deactivation. This, in turn, prevents DCPD from undergoing a chemical reaction in the second mixture, ensuring the efficiency of subsequent polymerization reactions. Simultaneously, at this temperature, the reaction induction period is moderate, enhancing the controllability of the reaction residence time. This allows DCPD and the initiator to achieve uniform mixing, ensuring that when the initiator comes into contact with the first mixture, it can simultaneously initiate the polymerization reaction of the two monomers. This ensures the uniform distribution of DCPD in the PMMA molecular backbone, guaranteeing the toughening effect of the material and improving the stability of the toughened PMMA material.

[0050] In some embodiments, the reaction temperature of the continuous screw reactor is 150℃~200℃, the pressure is 1.0MPaG~3.0MPaG, the reaction residence time is 4h~6h, and the screw speed is 30r / min~100r / min.

[0051] For example, the reaction temperature is any value or a range of any two of the following: 150°C, 160°C, 170°C, 180°C, 190°C, 200°C.

[0052] For example, the pressure is any value or a range of any two of 1.0 MPaG, 1.5 MPaG, 2 MPaG, 2.5 MPaG, 3.0 MPaG, etc.

[0053] For example, the reaction residence time is any value or a range of any two of the following: 4h, 4.5h, 5h, 5.5h, 6h.

[0054] For example, the screw speed is any value or a range of any two of the following: 30 r / min, 40 r / min, 50 r / min, 60 r / min, 70 r / min, 80 r / min, 90 r / min, 100 r / min.

[0055] The polymerization temperature of 150℃~200℃ is adapted to the reaction kinetics of MMA and DCPD, which can promote the efficient initiation of free radical polymerization, ensure the full reaction of the polymerization reaction, and at the same time ensure the uniform release of reaction heat, maintain the stable state of monomers and the reactivity of initiators.

[0056] A pressure environment of 1.0 MPaG to 3.0 MPaG can maintain the stability of the monomer, avoid the large amount of monomer volatilization affecting the polymerization efficiency, stabilize the molecular weight of the toughened PMMA material, and thus ensure that the mechanical properties such as tensile strength do not decrease. Moreover, if the polymerization reaction pressure is too high, the cost of reactor equipment and production energy consumption will increase significantly, resulting in poor economic efficiency. This pressure range can balance production costs.

[0057] In some embodiments, the material has a relatively high boiling point at pressures of 1.0 MPaG to 3.0 MPaG, not yet reaching vapor-liquid equilibrium (i.e., boiling state), but close to boiling. At this point, the saturated vapor pressure of the material in the reaction system is high, and some material will vaporize, thus carrying away a large amount of reaction heat. The vaporized material is then recycled back to the reactor through an external condenser. This heat transfer method improves heat transfer capacity, thereby avoiding the thermal decomposition reaction of MAA or DCPD, ensuring that the polymerization reaction occurs and stable products are generated.

[0058] A reaction residence time of 4 to 6 hours ensures that the two monomers are fully polymerized, avoids side reactions such as high-temperature degradation caused by excessive residence time, and improves conversion rate. Within this reaction residence time range, no pigment impurities will be generated, and the transmittance will not be affected.

[0059] The actual screw speed is 30~100r / min, which enables the continuous screw reactor to provide moderate shear force to break up the small aggregates that DCPD may form, further ensuring its uniform dispersion. At the same time, it promotes the heat conduction of polymerization, making the overall heating uniform, and ultimately achieving stable and uniform product performance, ensuring mechanical properties such as tensile strength. Moreover, the power consumption of the polymerization reactor is low within this screw speed range, which can reduce production costs.

[0060] In some embodiments, the continuous screw reactor includes, but is not limited to, a single-screw reactor or a twin-screw reactor. The continuous screw reactor is a high-shear, narrow-channel reactor. This invention does not limit the rotation method of the twin-screw reactor; co-rotation or counter-rotation can be selected.

[0061] The continuous screw reactor of the present invention includes a feed inlet, a reaction zone, a screw, and a discharge outlet. The polymerization reaction of the present invention is carried out in the reaction zone within the continuous screw reactor; wherein, the total length of the screw is k, and the reaction zone is divided into n connected segments according to the screw length, where n≥1.

[0062] In some preferred embodiments, the reaction zone is divided into two interconnected sections. The first mixture and the second mixture are mixed by a pipe mixer and then enter a continuous screw reactor, passing sequentially through a feed inlet, a first reaction zone, a second reaction zone, and a discharge outlet. The length of the first reaction zone is h, and the length of the second reaction zone is kh.

[0063] For example, the length of the first reaction region is equal to the length of the second reaction region.

[0064] The reaction temperatures of the first and second reaction regions mentioned above are each independently between 150°C and 200°C.

[0065] In some implementations, the temperatures of the first reaction region and the second reaction region are different; the temperature of the second reaction region is 5 to 15°C higher than that of the first reaction region.

[0066] For example, the reaction temperature of the first reaction zone is any value of 150°C, 155°C, 160°C, or a range of any combination of both.

[0067] For example, the reaction temperature of the second reaction zone is any value or a range of any two of the following: 160°C, 170°C, 180°C, 190°C, 200°C.

[0068] In the aforementioned continuous screw reactor, during the initial stage of polymerization in the first reaction zone, the initiator concentration is relatively high, and the reaction temperature can be 5-15°C lower than that in the second reaction zone to quickly initiate the polymerization reaction and promote the rapid polymerization of monomers. When the reactants enter the second reaction zone, due to the deactivation of a small amount of initiator, the reaction temperature in the second reaction zone is increased by 5-15°C, which can improve the conversion rate of the second reaction zone, enhance the controllability of the polymerization reaction, ensure that the reaction proceeds fully, and thus obtain high-quality polymer products.

[0069] In some embodiments, a catalyst is added to the second reaction zone to improve the conversion rate of the second reaction zone, enhance the controllability of the polymerization reaction, ensure that the reaction proceeds fully, and thus obtain a high-quality polymer product.

[0070] In some embodiments, the polymerization reaction is followed by a molding process, which includes vacuum melt extrusion at a vacuum level of -0.095 MPaG to -0.07 MPaG and a temperature of 160°C to 190°C.

[0071] For example, the vacuum degree of vacuum melt extrusion is any value or a range of any two of -0.095MPaG, -0.09MPaG, -0.085MPaG, -0.08MPaG, -0.075MPaG, and -0.07MPaG.

[0072] For example, the vacuum melt extrusion temperatures are 160°C, 170°C, 180°C, and 190°C.

[0073] Vacuum melt extrusion under these conditions can efficiently remove residual unreacted MMA monomers, DCPD monomers, and small oligomer impurities from the polymerization product, improving product purity. Simultaneously, the molten state further eliminates trace amounts of gel that may be generated during polymerization, optimizing product uniformity and improving the impact strength and light transmittance of the toughened PMMA material. Furthermore, the conditions for the above-mentioned vacuum melt extrusion step have moderate energy consumption, do not increase equipment costs, and improve the economics of the production line.

[0074] In some embodiments, the extrusion process further includes pelleting; the extruded reaction product is pelletized to obtain granules for subsequent packaging.

[0075] The present invention does not limit the shape of the toughened PMMA material. For example, the toughened PMMA material can be in the form of granules, sheets, rods, plates, or films.

[0076] In some embodiments, the molding process is followed by a drying process, with a drying temperature of 60°C to 120°C and a drying time of 4 to 8 hours.

[0077] For example, the drying temperature is any value or a range of any two of the following: 60°C, 80°C, 100°C, 120°C, etc.

[0078] For example, the drying time is any value or a range of any two of the following: 4h, 5h, 6h, 7h, 8h, etc.

[0079] The above-mentioned drying process can further remove volatiles such as unreacted monomers and moisture remaining on the surface and inside the product, controlling the moisture content within an ideal range. Moisture removal prevents defects such as bubbles, silver streaks, and surface dents caused by moisture evaporation during subsequent processing, thus avoiding impacts on properties like light transmittance. Simultaneously, it prevents moisture-induced degradation of the PMMA molecular chains, further ensuring the stability of key properties such as impact strength, tensile strength, surface finish, and light transmittance, and improving the processing adaptability and reliability of toughened PMMA materials. It also features low energy consumption and good economic efficiency.

[0080] In some embodiments, the chain transfer agent is at least one of n-dodecyl mercaptan, tert-dodecyl mercaptan, and α-methylstyrene dimer, and the initiator is at least one of tert-butyl hydroperoxide, di-tert-butyl hydroperoxide, cumene hydroperoxide, and dicumene peroxide.

[0081] The above-mentioned chain transfer agent has good chain transfer activity, can accurately adjust the molecular weight of the product, and has excellent compatibility with MMA and DCPD, without introducing impurities that affect the material performance. The decomposition temperature of the above-mentioned initiator is compatible with the polymerization temperature of the present invention, which can efficiently start the polymerization reaction and leave little residue after the reaction. At the same time, the raw materials are inexpensive and in abundant supply, further reducing the preparation cost.

[0082] Secondly, the present invention provides a toughened PMMA material prepared by the method for preparing toughened PMMA material in the first aspect, wherein the notched impact strength of the toughened PMMA material is 8 kJ / m at 23°C. 2 ~12kJ / m 2 .

[0083] For example, the notched impact strength is 8 kJ / m. 2 9kJ / m 2 10kJ / m 2 11kJ / m 2 12kJ / m 2 The range of any value in the range, or any combination of both.

[0084] The aforementioned toughened PMMA material uses a short-chain PMMA molecular backbone generated under the regulation of a chain transfer agent as the basic framework to form a continuous three-dimensional network PMMA matrix. DCPD undergoes a polymerization reaction with MMA through unsaturated double bonds, uniformly embedding itself in the PMMA molecular backbone as monomer units to form MMA-DCPD polymeric segments with rigid ring structures containing DCPD. The toughened PMMA material of this invention contains two types of toughening segments (short-chain PMMA segments and MMA-DCPD polymeric segments). These two types of toughening segments do not agglomerate in the matrix, are uniformly dispersed throughout, and form an integrated network structure through chemical bonding and intermolecular chain entanglement. They have no obvious phase separation interface and have a uniform molecular chain length distribution, which can achieve efficient absorption of impact energy and stable maintenance of structural strength.

[0085] In some implementations, the number-average molecular weight of the toughened PMMA material is 700 kDa to 800 kDa.

[0086] For example, the number-average molecular weight of the toughened PMMA material is any value or a range of any combination of 700kDa, 730kDa, 750kDa, 770kDa, 800kDa, etc.

[0087] In some embodiments, the molecular weight distribution (PDI) of the toughened PMMA material is 1.3 to 1.8.

[0088] For example, the molecular weight distribution (PDI) of the toughened PMMA material is any value or a range of any two of the following: 1.3, 1.4, 1.5, 1.6, 1.7, 1.8.

[0089] The aforementioned number-average molecular weight (Mn) range effectively balances the mechanical and optical properties of the material. Furthermore, by controlling the molecular weight distribution (PDI), the overall performance is further optimized, ensuring adaptability for downstream applications. This range of number-average molecular weights allows PMMA molecular chains to form sufficient chain entanglement density, significantly improving the material's notched impact strength and mitigating its inherent brittleness, thus meeting the core requirements of toughening modification. Simultaneously, it avoids the problem of impeded molecular chain movement caused by excessively high molecular weights, ensuring the material possesses excellent tensile strength and processing stability, and is less prone to defects such as stress cracking and uneven deformation during molding. At the same time, rationally controlling the PDI within this molecular weight range can reduce the impact of differences in molecular chain length on light scattering, maintaining the light transmittance of the PMMA material and ensuring its clear and bright appearance in optical scenarios. These balanced properties, conferred by specific molecular weights and distributions, directly address the core requirements of downstream applications—the need for materials to simultaneously possess sufficient impact resistance, structural strength, and optical transparency. This application improves the performance of toughened PMMA materials, expands application scenarios, and enhances the market applicability and reliability of the product through precise control of the number-average molecular weight and PDI parameters.

[0090] In some implementations, at least one of the following conditions is also met:

[0091] a. The tensile strength of toughened PMMA material is 65MPa~70MPa;

[0092] b. The flexural strength of toughened PMMA material is 105MPa~115MPa;

[0093] c. When the thickness of the toughened PMMA material is 3mm, the light transmittance is 90%~92%.

[0094] For example, the tensile strength is any value or a range of any two of the following: 65MPa, 66MPa, 67MPa, 68MPa, 69MPa, 70MPa.

[0095] For example, the bending strength is any value or a range of any two of the following: 105MPa, 106MPa, 107MPa, 108MPa, 109MPa, 110MPa, 111MPa, 112MPa, 113MPa, 114MPa, 115MPa.

[0096] For example, the light transmittance at a thickness of 3 mm is any value of 90%, 90.5%, 91%, 91.5%, 92%, or any combination of both.

[0097] The toughened PMMA material of this invention significantly improves impact strength while maintaining other key properties such as light transmittance and tensile strength without significant decrease. Furthermore, the raw materials used in its preparation are inexpensive, thus reducing production costs.

[0098] To further understand the present invention, the technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0099] Unless otherwise specified, all reagents involved in the embodiments of this invention are commercially available products and can be obtained through commercial channels.

[0100] A schematic diagram of the preparation method of toughened PMMA material is shown below. Figure 1 As shown. The examples and comparative examples used a tubular mixer and a continuous screw reactor, respectively, using a twin-screw reactor, specifically a Shanghai Zhongye Venturi type and a Nanjing Ruixin SHJ-20 parallel twin-screw compressor.

[0101] Example 1

[0102] 100g of MMA and 0.15g of α-methylstyrene dimer chain transfer agent were mixed evenly to obtain a first mixture. 25g of DCPD and 0.02g of cumene hydroperoxide initiator were mixed evenly at 15°C to obtain a second mixture. The first and second mixtures were pumped separately to a pipeline mixer for mixing, and then added to a twin-screw reactor for polymerization. In the twin-screw reactor, the material passed through a connected inlet, a first reaction zone, a second reaction zone, and an outlet. The total length of the screw was 1.2m, the length of the first reaction zone was 0.6m, and the length of the second reaction zone was 0.6m. The reaction temperature of the first reaction zone was set at 160°C, the reaction temperature of the second reaction zone was set at 180°C, the reaction pressure was set at 2MPaG, the reaction residence time was controlled at 5h, and the screw speed was set at 60r / min.

[0103] The reaction product at the outlet of the polymerization reactor was conveyed to an extruder via a screw conveyor under closed conditions for melt extrusion. The extruder vacuum was set to -0.08 MPaG and the temperature to 175℃. The melt-extruded product was cooled and shaped under nitrogen protection and cut into particles with an average diameter of 5 mm. After drying with hot nitrogen at 80℃ for 8 hours, toughened PMMA material was obtained. The toughened PMMA material had a molecular weight of 756 kDa and a PDI of 1.38.

[0104] Example 2

[0105] 100g MMA and 0.15g tert-dodecyl mercaptan chain transfer agent were mixed evenly to obtain the first mixture. 15g DCPD and 0.01g tert-butyl hydrogen peroxide initiator were mixed evenly at 15°C to obtain the second mixture. The first and second mixtures were pumped to a pipeline mixer for mixing and then added to a twin-screw reactor for polymerization. The reaction temperature was set to 180°C, the reaction pressure was set to 1.7MPaG, the reaction residence time was controlled to be 4.5h, and the screw speed was set to 40r / min.

[0106] The reaction product at the outlet of the polymerization reactor was conveyed to an extruder via a screw conveyor under closed conditions for melt extrusion. The extruder vacuum was set to -0.085 MPaG and the temperature to 165℃. The melt-extruded product was cooled and shaped under nitrogen protection and cut into particles with an average diameter of 5 mm. After drying with hot nitrogen at 120℃ for 6 hours, toughened PMMA material was obtained. The toughened PMMA material had a molecular weight of 784 kDa and a PDI of 1.52.

[0107] Example 3

[0108] The results were essentially the same as in Example 1, except that the amount of α-methylstyrene dimer chain transfer agent added was 0.2 g. The toughened PMMA material obtained had a molecular weight of 734 kDa and a PDI of 1.60.

[0109] Example 4

[0110] The results were essentially the same as in Example 1, except that the amount of cumene hydroperoxide initiator added was 0.01 g. The toughened PMMA material obtained had a molecular weight of 790 kDa and a PDI of 1.35.

[0111] Example 5

[0112] The results were largely the same as in Example 1, except that the mixing temperature of DCPD and the initiator was 25°C. The toughened PMMA material obtained had a molecular weight of 762 kDa and a PDI of 1.44.

[0113] Example 6

[0114] The reaction was essentially the same as in Example 1, except that the reaction temperature for the first half of the polymerization reaction was adjusted to 180°C, and the reaction temperature for the second half was adjusted to 160°C. The toughened PMMA material obtained had a molecular weight of 742 kDa and a PDI of 1.62.

[0115] Example 7

[0116] The results were essentially the same as in Example 1, except that the screw speed was 100 r / min. The toughened PMMA material obtained had a molecular weight of 756 kDa and a PDI of 1.36.

[0117] Example 8

[0118] The results were essentially the same as in Example 1, except that the extruder temperature was adjusted to 190°C. The toughened PMMA material obtained had a molecular weight of 756 kDa and a PDI of 1.38.

[0119] Example 9

[0120] The process was essentially the same as in Example 1, except that the drying temperature was adjusted to 100°C. The toughened PMMA material obtained had a molecular weight of 757 kDa and a PDI of 1.37.

[0121] Example 10

[0122] The results were essentially the same as in Example 1, except that the amount of DCPD added was 30g. The toughened PMMA material obtained had a molecular weight of 742kDa and a PDI of 1.31.

[0123] Example 11

[0124] The results were largely consistent with Example 1, except that the amount of α-methylstyrene dimer chain transfer agent added was 0.05 g. The toughened PMMA material obtained had a molecular weight of 792 kDa and a PDI of 1.39.

[0125] Example 12

[0126] The results were essentially the same as in Example 1, except that the amount of cumene hydroperoxide initiator added was 0.001 g. The toughened PMMA material obtained had a molecular weight of 786 kDa and a PDI of 1.75.

[0127] Example 13

[0128] The results were largely the same as in Example 1, except that the mixing temperature of DCPD and the initiator was 5°C. The toughened PMMA material obtained had a molecular weight of 756 kDa and a PDI of 1.38.

[0129] Example 14

[0130] The reaction was essentially the same as in Example 1, except that the reaction temperature in the continuous screw reactor was 150°C. The toughened PMMA material obtained had a molecular weight of 776 kDa and a PDI of 1.66.

[0131] Example 15

[0132] The reaction was essentially the same as in Example 1, except that the reaction temperature in the continuous screw reactor was 200°C. The toughened PMMA material obtained had a molecular weight of 752 kDa and a PDI of 1.33.

[0133] Example 16

[0134] The reaction was essentially the same as in Example 1, except that the residence time in the continuous screw reactor was 4 hours. The toughened PMMA material obtained had a molecular weight of 748 kDa and a PDI of 1.50.

[0135] Example 17

[0136] The results were largely the same as in Example 1, except that the screw speed in the continuous screw reactor was 30 r / min. The toughened PMMA material obtained had a molecular weight of 746 kDa and a PDI of 1.45.

[0137] Example 18

[0138] The results were essentially the same as in Example 1, except that the vacuum degree of the vacuum melt extrusion was -0.07 MPaG. The toughened PMMA material obtained had a molecular weight of 754 kDa and a PDI of 1.52.

[0139] Example 19

[0140] The results were essentially the same as in Example 1, except that the vacuum melt extrusion temperature was 160°C. The toughened PMMA material obtained had a molecular weight of 752 kDa and a PDI of 1.58.

[0141] Comparative Example 1

[0142] Mix 100g MMA and 0.02g cumene hydroperoxide initiator uniformly to obtain mixture 1. Mix 25g DCPD and 0.15g α-methylstyrene dimer chain transfer agent uniformly at 15℃ to obtain mixture 2. Mixture 1 and mixture 2 are pumped to a pipeline mixer for mixing and then added to a twin-screw reactor for polymerization. In the twin-screw reactor, the material passes through a connected inlet, a first reaction zone, a second reaction zone, and an outlet in sequence. The total length of the screw is 1.2m, the length of the first reaction zone is 0.6m, and the length of the second reaction zone is 0.6m. The reaction temperature of the first reaction zone is set to 160℃, the reaction temperature of the second reaction zone is set to 180℃, the reaction pressure is set to 2MPaG, the reaction residence time is controlled to 5h, and the screw speed is set to 60r / min.

[0143] The reaction product at the outlet of the polymerization reactor is conveyed to an extruder via a screw conveyor under closed conditions for melt extrusion. The extruder vacuum is set to -0.08 MPaG and the temperature is set to 175℃. The melt-extruded product is cooled and shaped under nitrogen protection and cut into particles with an average diameter of 5 mm. After drying with hot nitrogen at 80℃ for 8 hours, PMMA material is obtained, denoted as PMMA-1. PMMA-1 has a molecular weight of 76.8 kDa and a PDI of 2.2.

[0144] Comparative Example 2

[0145] 100g MMA and 0.15g α-methylstyrene dimer chain transfer agent were mixed evenly to obtain a mixture. This mixture and 0.02g cumene hydroperoxide initiator were pumped separately to a pipeline mixer for mixing, and then added to a twin-screw reactor for polymerization. In the twin-screw reactor, the material passed through a connected inlet, a first reaction zone, a second reaction zone, and an outlet in sequence. The total length of the screw was 1.2m, the length of the first reaction zone was 0.6m, and the length of the second reaction zone was 0.6m. The reaction temperature of the first reaction zone was set to 160℃, the reaction temperature of the second reaction zone was set to 180℃, the reaction pressure was set to 2MPaG, the reaction residence time was controlled to 5h, and the reactor screw speed was set to 60r / min.

[0146] The reaction product at the outlet of the polymerization reactor is conveyed to an extruder via a screw conveyor under closed conditions for melt extrusion. The extruder vacuum is set to -0.08 MPaG and the temperature is set to 175℃. The melt-extruded product is cooled and shaped under nitrogen protection and cut into particles with an average diameter of 5 mm. After drying with hot nitrogen at 80℃ for 8 hours, PMMA material is obtained, denoted as PMMA-2. PMMA-2 has a molecular weight of 778 kDa and a PDI of 1.51.

[0147] Comparative Example 3

[0148] 100g MMA, 0.15g α-methylstyrene dimer chain transfer agent, 25g DCPD, and 0.02g cumene hydroperoxide initiator were added to the same beaker at 15°C and mixed thoroughly. The mixture was then added to a twin-screw reactor for polymerization. The twin-screw reactor was connected to a feed inlet, a first reaction zone, a second reaction zone, and a discharge outlet. The total length of the screw was 1.2m, the length of the first reaction zone was 0.6m, and the length of the second reaction zone was 0.6m. The reaction temperature in the first reaction zone was set to 160°C, the reaction temperature in the second reaction zone was set to 180°C, the reaction pressure was set to 2MPaG, the reaction residence time was controlled to 5h, and the reactor screw speed was set to 60r / min.

[0149] The reaction product at the outlet of the polymerization reactor is conveyed to an extruder via a screw conveyor under closed conditions for melt extrusion. The extruder vacuum is set to -0.08 MPaG and the temperature is set to 175℃. The melt-extruded product is cooled and shaped under nitrogen protection and cut into particles with an average diameter of 5 mm. After drying with hot nitrogen at 80℃ for 8 hours, PMMA material is obtained, denoted as PMMA-3. PMMA-3 has a molecular weight of 771 kDa and a PDI of 1.92.

[0150] Test Example 1

[0151] The number-average molecular weight (Mn), molecular weight distribution (PDI), tensile strength, flexural strength, notched beam impact strength, and light transmittance of the materials obtained in Examples 1-9 and Comparative Examples 1-3 were tested. The performance testing methods included: determining Mn and PDI according to GB / T21863-2008 standard; tensile strength according to ISO527 standard; flexural strength according to ISO178 standard; notched beam impact strength according to ISO179 / 1eA standard; and light transmittance according to ISO13486 standard. The test results are shown in Table 1.

[0152] Table 1 Test Results

[0153]

[0154] As can be seen from the comparison between Examples 1-19 and Comparative Examples 1-3, the toughened PMMA material obtained by the method of the present invention has a better toughening effect, and while the impact strength is significantly improved, other key properties such as light transmittance and tensile strength do not decrease significantly.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a toughened PMMA material, characterized in that, Includes the following steps: 1) Methyl methacrylate and a chain transfer agent are mixed to obtain a first mixture; 2) Dicyclopentadiene and the initiator are mixed to obtain a second mixture; 3) The first mixture and the second mixture are mixed through a pipe mixer and then added to a continuous screw reactor for polymerization to form the toughened PMMA material.

2. The method for preparing the toughened PMMA material according to claim 1, characterized in that, The mass percentage of dicyclopentadiene is 15% to 30% based on the mass of the methyl methacrylate.

3. The method for preparing the toughened PMMA material according to claim 1, characterized in that, The chain transfer agent has a mass percentage of 0.05% to 0.2% based on the mass of the methyl methacrylate.

4. The method for preparing the toughened PMMA material according to claim 1, characterized in that, The initiator has a mass percentage of 0.001% to 0.05% based on the mass of the methyl methacrylate.

5. The method for preparing the toughened PMMA material according to claim 1, characterized in that, The mixing temperature of the dicyclopentadiene and the initiator is 5°C to 25°C.

6. The method for preparing the toughened PMMA material according to any one of claims 1-5, characterized in that, The continuous screw reactor has a reaction temperature of 150℃~200℃, a pressure of 1.0MPaG~3.0MPaG, a reaction residence time of 4h~6h, and a screw speed of 30r / min~100r / min.

7. The method for preparing the toughened PMMA material according to any one of claims 1-5, characterized in that, The polymerization reaction is followed by a molding process, which includes vacuum melt extrusion. The vacuum degree of the vacuum melt extrusion is -0.095 MPaG to -0.07 MPaG, and the temperature is 160℃ to 190℃.

8. The method for preparing the toughened PMMA material according to any one of claims 1-5, characterized in that, The chain transfer agent is at least one of n-dodecyl mercaptan, tert-dodecyl mercaptan, and α-methylstyrene dimer, and the initiator is at least one of tert-butyl hydroperoxide, di-tert-butyl hydroperoxide, cumene hydroperoxide, and dicumene peroxide.

9. A toughened PMMA material prepared by the method for preparing toughened PMMA material according to any one of claims 1-8, characterized in that, The notched impact strength of the toughened PMMA material is 8 kJ / m 2 at 23 °C 2 12 kJ / m 10. The toughened PMMA material according to claim 9, characterized in that, It also meets at least one of the following conditions: a. The tensile strength of the toughened PMMA material is 65MPa~70MPa; b. The flexural strength of the toughened PMMA material is 105MPa~115MPa; c. When the thickness of the toughened PMMA material is 3mm, the light transmittance is 90%~92%.

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