A branched structure toughening agent and a preparation method and application thereof

Abstract

The application provides a branched structure toughening agent and a preparation method and application thereof, and relates to the technical field of polymer modification, and particularly relates to a branched structure toughening agent and a preparation method and application thereof. The branched structure toughening agent is prepared by mixing an aromatic vinyl monomer, an acrylic ester monomer, an initiator and water, and then heating and polymerizing to obtain an intermediate; and then mixing the intermediate with a polyolefin elastomer, an initiator and an antioxidant, and then performing double-screw extrusion granulation. Compared with the existing linear structure toughening agent, the branched structure toughening agent has a larger free volume and a higher toughening efficiency; compared with the core-shell structure toughening agent, the preparation method is simpler, and the structure has a large degree of freedom. The branched structure toughening agent has the advantages of no need of using a solvent, less investment, easy acquisition of equipment, less discharge of a process route, simple process control, low residual monomer content of a product, stable composition, simple use of the product, and wide application in toughening modification of polylactic acid, polyester and polyamide materials, and wide use in medical treatment, packaging, household appliances, automobiles, aviation and other fields. The branched structure toughening agent has a very wide application prospect and industrial value.

Description

Technical Field

[0001] This invention relates to a method for preparing a toughening agent with a multi-branched structure and its application, which can be used for the modification of polylactic acid, polyester and polyamide polymers, and belongs to the field of polymer materials. Background Technology

[0002] Toughening modification is a crucial part of polymer modification, and toughening agents are a core technology. Currently, most toughening agents on the market are linear in structure, such as POE-g-MAH for nylon toughening and POE-g-GMA and EMA-g-GMA for polyester toughening. These toughening agents can effectively improve the impact strength of nylon or polyester; however, while improving toughness, linear toughening agents often negatively impact other properties, such as flowability and strength.

[0003] Existing technology discloses a high-flowability nylon toughening agent prepared by reactive extrusion of a propylene-based elastomer, a vinyl elastomer, a first grafted monomer, and a second grafted monomer. This toughening agent exhibits good toughening effect and high flowability, and can improve the notched impact strength of nylon products while maintaining their processing flowability to a maximum extent. Existing technology introduces a method based on polyolefin elastomers, which, by introducing specific crosslinking aids, generates micro-crosslinks during the grafting of grafted monomers with the polyolefin elastomer, forming an interwoven coating structure with the unreacted polyolefin elastomer, thus balancing interfacial compatibility, processing flowability, and toughening effect. This type of technology, prepared by reactive extrusion, still mainly produces a linear structure, and while toughening, it inevitably has an adverse effect on the modulus of nylon and polyester materials. Due to process limitations, the grafting rate of reactive extrusion is generally less than 1%, and the ungrafted small molecule monomers are prone to volatilization, generating TVOCs, which affect the production environment.

[0004] Existing technology describes a method for preparing a cryogenic nylon toughening agent by adding an elastomer, initiator, and polar monomer to a blending device for melt blending, followed by the addition of amino silicone oil for further blending. This toughening agent possesses a certain branched structure. When applied to nylon products, the polar monomers can react with the amino or carboxyl groups of the nylon chain segments, enhancing compatibility. Simultaneously, the addition of amino silicone oil further improves the cryogenic impact resistance and toughness of nylon, resulting in cryogenic impact-resistant nylon with excellent cryogenic impact resistance. While the introduction of the branched structure brings some performance advantages, the method of introducing branches through the reaction of functional groups with the branches reduces the effective grafting rate, which is detrimental to compatibility and dispersion in nylon or polyester. Existing technology also describes a polyolefin toughening agent prepared using low-temperature plasma technology, which improves the grafting rate while reducing the side reactions of peroxides and the problem of residual active monomers caused by reactive extrusion processes. However, this method is difficult to implement, has high investment costs, and does not optimize the structure of the toughening agent. The prior art introduces a PMMA toughening agent prepared by solution copolymerization of caprolactone-modified acrylate and MMA monomer, which significantly improves its low-temperature flexibility; however, this process requires a large amount of solvent and causes significant environmental pollution. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing and applying a branched toughening agent, which can be used for toughening modification of engineering plastics such as nylon and polyester. The toughening agent of this invention improves the toughness of materials such as nylon and polyester, while overcoming the conventional technical bias that toughening agents negatively impact strength and modulus during toughening. Furthermore, the toughening agent of this invention has low steric hindrance and high reactivity. Further, this invention first prepares an intermediate with a certain degree of polymerization and viscosity through polymerization, and then uses a reactive extrusion process, which facilitates easier distribution and dispersion of the intermediate with the polyolefin elastomer in conventional equipment, and allows for grafting reactions. This effectively increases the content of active functional groups while reducing the presence of residual monomers. In particular, the intermediate of this invention is produced using suspension polymerization with water as the medium, making the reaction easy to control, avoiding environmental pollution, and utilizing common and readily available reaction and extrusion equipment.

[0006] This invention is achieved through the following technical solution:

[0007] A branched toughening agent is prepared by the following steps: aromatic vinyl monomers, acrylate monomers, polymerization initiators, molecular weight regulators, and water are mixed and then polymerized under heat to obtain an intermediate; the intermediate is then melt-mixed with a polyolefin elastomer, an extrusion initiator, and an antioxidant to obtain the branched toughening agent. Specifically, twin-screw extrusion is used to achieve melt mixing and prepare the branched toughening agent.

[0008] In this invention, after the heating polymerization is completed, the polymerization intermediate is mixed with polyolefin elastomer, initiator, and antioxidant in a certain proportion, and then granulated by reactive extrusion using a twin-screw extruder to prepare a branched toughening agent. Preferably, the twin-screw extruder has an aspect ratio of not less than 48 and the equipment has a vacuum function. Specifically, the preparation method of the branched toughening agent includes the following steps: aromatic vinyl monomers, acrylate monomers, initiators, molecular weight regulators, and water are mixed and heated for polymerization. The resulting intermediate is then dried and mixed with polyolefin elastomer, initiator, and antioxidant in a certain proportion, and then granulated by reactive extrusion using a twin-screw extruder to obtain the branched toughening agent.

[0009] This invention provides a branched toughening agent that overcomes the shortcomings of existing technologies, such as low grafting rate, high residual monomer content, and limited configuration. It is a green, environmentally friendly, simple-to-process, and conveniently used toughening agent with a suitable molecular weight. It can be used for toughening and modifying engineering plastics such as nylon and polyester, improving the toughness of these materials while mitigating the negative impact of toughening agents on strength and modulus. Furthermore, the toughening agent of this invention has low steric hindrance and higher reactivity.

[0010] In this invention, by first polymerizing an intermediate in the absence of organic solvents, the problem of organic solvent recovery and treatment in the prior art is effectively solved. Then, through reactive extrusion, the intermediate with functional groups has a certain degree of polymerization and viscosity, which makes it easier to distribute and disperse with polyolefin elastomers in the basic equipment and to undergo grafting reactions. This can effectively increase the content of active functional groups while keeping the residual monomer content low.

[0011] In this invention, the total mass of aromatic vinyl monomers and acrylate monomers is 100%, wherein the mass percentage of aromatic vinyl monomers is 45-95%, preferably 50-85%, and the remainder is acrylate monomers. The raw material ratio significantly affects the structure of the intermediate, the reactive extrusion process, and the performance of the toughening agent, especially the degree of branching and grafting rate of the toughening agent, thus influencing its application. It is well known that when the viscosities are matched, the mixing of the two polymer melts is more likely to achieve uniformity. This uniform mixing state is more suitable for reacting under peroxide initiation to form uniform grafting points, resulting in a "brush-like" branched structure. Too low a degree of polymerization, due to the large viscosity difference with conventional polymers, makes uniform mixing difficult. Although the free radical reactivity is higher, it is also more prone to local aggregation, forming a grafted structure. Too high a molecular weight reduces grafting efficiency, making it easier to form a "star-shaped" grafted structure. Although both are conventional branched structures, neither structure is conducive to improving the toughening effect. In addition, intermediates can also affect the performance of toughening agents. Changes in intermediate processing technology can lead to a decrease in the processability of the product and an increase in the risk of gelation, which has a significant negative impact on the processing and mechanical properties of the polymer. It can also lead to insufficient reactivity of the product, which is not conducive to the dispersion of toughening agents in the modification process, and has a negative impact on toughness. At the same time, the reduced compatibility will affect the stability of the modification production.

[0012] In preparing the intermediates according to the present invention, the amount of molecular weight regulator is 0.1-5% of the monomer mass, preferably 1-5%, and most preferably 3-5%; the amount of polymerization initiator is 0.1-2% of the monomer mass, preferably 0.1-1%, and most preferably 0.3-0.6%. The monomer mass is the sum of the masses of the aromatic vinyl monomer and the acrylate monomer.

[0013] In this invention, the mass percentage of the intermediate and the polyolefin elastomer is 100%, wherein the mass percentage of the intermediate is 2-15%, preferably 5-10%. With the mass percentage of the intermediate and the polyolefin elastomer being 100%, the amount of the extrusion initiator is 0.5-15%, preferably 0.5-2%; and the amount of the antioxidant is 0.5-1%, preferably 0.5-0.8%.

[0014] In this invention, the heating polymerization temperature is 65–110°C, and the time is 2–10 hours. Preferably, the heating polymerization is carried out at 65–80°C for 2–6 hours, followed by heating to 90–110°C for another 0.5–2 hours. After drying, the product yields an intermediate that can be used for the second step of reactive extrusion. This invention avoids the problem of using organic solvents in solution polymerization and, compared with existing reactive extrusion processes, improves the degree of reaction, significantly reduces the content of residual monomers, and the equipment is readily available. The obtained product has a branched structure, and when extruded with an elastomer, it becomes a toughening agent. The reactive functional groups are located in the branches, and the branch length and grafting rate are reasonably controllable, resulting in less residual monomers, which is more beneficial for subsequent processing and downstream use.

[0015] This invention provides the application of the above-mentioned branched toughening agent as a toughening agent in the preparation of toughened modified polymers, such as the application of the branched toughening agent in the preparation of ultra-tough nylon, PC / PBT alloy, or the application of the above-mentioned branched toughening agent in the preparation of biodegradable polymers. That is, the branched toughening agent of this invention can be used as a toughening modifier for nylon, polyester and polylactic acid materials, especially to improve toughness, while hardly affecting other properties such as processability and strength.

[0016] In this invention, the aromatic vinyl monomers include styrene monomers, such as styrene monomer, α-methylstyrene monomer, α-chlorostyrene monomer, or p-methylstyrene monomer; the acrylate monomers include methacrylate, glycidyl methacrylate, and / or glycidyl methacrylate ether. Preferably, the acrylate monomers are a mixture of methacrylate (MMA) and glycidyl methacrylate (GMA) in a mass ratio of methacrylate to glycidyl methacrylate of 1–3:10, which facilitates the formation of a multi-branched structure during the second-step reactive extrusion. The molecular weight regulator includes dodecyl mercaptan, and the polymerization initiator includes azobisisobutyronitrile (AIBN) or benzoyl peroxide (BPO).

[0017] In this invention, the polyolefin elastomer in the reactive extrusion stage is one or a mixture of several of the following: ethylene-octene copolymer, ethylene-propylene binary copolymer, ethylene-propylene-norbornene terpolymer, and propylene-based elastomer, preferably ethylene-octene copolymer; the initiator is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane masterbatch, and the initiator content is 40 wt%.

[0018] The branched toughening agent of the present invention has branches that are random copolymers formed by copolymerization of aromatic vinyl monomers and acrylate monomers; as a preferred embodiment, the weight average molecular weight of the branches is 2000-10000, preferably 3000-7000; as a preferred embodiment, the reactive functional group is a mixture of methacrylate and glycidyl methacrylate.

[0019] In the branched toughening agent of this invention, the molecular chain contains multiple epoxy functional groups. When polymerized with polymers such as polyester, it can connect the polyester molecular chains and form a multi-branched state. In particular, it does not produce problems such as gelation. The branched structure is conducive to the slippage of molecular chains and is beneficial to modification and processing. At the same time, the rigid branches and the flexible main chain form a rigid-toughness balanced structure, which basically does not reduce the strength and modulus while toughening.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The toughening agent of this invention has a rationally controllable branched structure with rigid branches, achieving a good balance between rigidity and toughness. Reactive functional groups are located in the branches, exhibiting high reactivity. The functional group density is suitable, with no mutual interference, and gelation is unlikely. It also exhibits low residual monomer content and good thermal stability, which is beneficial for later use.

[0022] The process route selected in this invention does not require the use of organic solvents, requires less investment, and the equipment and raw materials are readily available. The process route has low emissions, simple formulation, and stable composition. The monomers selected in this invention are non-toxic or low-toxic, the raw material monomers are readily available, and the process route helps to further reduce residual monomers. It is applicable to high-end applications related to medical device and food and drug packaging.

[0023] The chain extender of this invention has a wide range of applications: it has excellent toughening effects on polyester alloy materials such as polycarbonate (PC) / polyethylene terephthalate (PET) and polycarbonate (PC) / polybutylene terephthalate (PBT), as well as engineering plastics such as polylactic acid (PLA), polyamide, and polyphenylene ether. The toughening agent of this invention is simple to use and can be widely used in medical devices, packaging, home appliances, automobiles, aerospace and other fields, with very broad application prospects and industrialization value. Attached Figure Description

[0024] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0025] Figure 1 The infrared image is of the intermediate.

[0026] Figure 2 Infrared image of the toughening agent.

[0027] Figure 3 This is a diagram of the branched structure of the toughening agent.

[0028] Figure 4 Comparison of flow lengths for toughening agent-modified PBT.

[0029] Figure 5 Comparison of mechanical properties of PBT toughening modification.

[0030] Figure 6 Comparison of mechanical properties of PC / PBT toughened modification. Detailed Implementation

[0031] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0032] The preparation method of the branched toughening agent of this invention is as follows: aromatic vinyl monomers, acrylate monomers, polymerization initiators, molecular weight regulators, and water are added to a reaction vessel and reacted at 65-80°C for 2-8 hours under conventional stirring. Then, the reaction is continued at 90-110°C for 0.5-2 hours. After discharge, the mixture is filtered and dried to obtain an intermediate for branching and grafting. The intermediate is mixed with polyolefin elastomers, extrusion initiators, and antioxidants in a specific ratio, and then granulated by twin-screw extrusion to obtain the branched toughening agent. The preparation process requires no organic solvents, no pressure, and no special atmosphere protection. The branched toughening agent has a multi-branched structure, in which reactive functional groups are located in the branches, and the branch length and grafting rate are controllable. The twin-screw extruder has a length-to-diameter ratio (L / D) greater than 48, the reaction extrusion temperature is set to 80-210°C, and the screw speed is set to 180-400 rpm.

[0033] The toughening agent of this invention has a wide range of applications: it exhibits excellent toughening effects on polyester alloy materials such as polycarbonate (PC) / polyethylene terephthalate (PET) and polycarbonate (PC) / polybutylene terephthalate (PBT), as well as engineering plastics such as polylactic acid (PLA), polyamide, and polyphenylene ether. This invention discloses a method for preparing a toughening polymer, which involves mixing polymer raw materials and the aforementioned branched toughening agent, followed by extrusion to obtain the toughening polymer. Preferably, the amount of the branched toughening agent is 3-20% of the mass of the polymer raw materials. The polymer raw materials can be virgin pure particles or recycled plastics; it can be applied to polyester materials and their alloys such as polycarbonate (PC), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT), polyamide materials, and can also be applied to the toughening modification of unused biodegradable plastics such as polylactic acid (PLA).

[0034] POE, density 0.88, MI 0.5 (190℃ / 2.16Kg); PBT, Chang Chun, Taiwan, grade: 6200; PC, Hunan Petrochemical, grade: 1100.

[0035] The test conditions are as follows:

[0036] Infrared structure: Tested using a Fourier transform infrared spectrometer.

[0037] Branching structure characterization: A rotational rheometer (TA, USA) was used. The test sample had a diameter of 25 mm and a thickness of 0.9 mm. The sample was pressed into a sheet (1 mm thick) at 180 °C and 12 MPa to obtain the sample for rheological testing. The measured storage modulus and loss modulus were fitted using a "cole-cole" method to analyze the presence and degree of branching structure.

[0038] Functional group content: calculated based on the mass ratio of the feed ingredients.

[0039] Weight-average molecular weight (Mw): GPC test was performed using PS as a standard.

[0040] RTVM: Tested according to ASTM D790 standard using GC-MS.

[0041] Melt flow index: Tested according to ASTM D1238 standard.

[0042] Thermogravimetric analysis: Tested according to ASTM D6370-99 standard using TGA.

[0043] Impact strength (Charpy notch): Tested according to GB / T 1843-2008 standard, impact energy 4J;

[0044] Bending strength: Tested according to GB / T 9341-2008 standard, 2 mm / min.

[0045] Tensile strength: tested according to GB / T 1040.1-2018 standard, 50 mm / min.

[0046] Table 1. Formulation table of intermediate polymerization examples and control examples, kg

[0047] Material Example 1 Example 2 Example 3 Compare with Example 1 Compare with Example 2 Compare with Example 3 Compare with Example 4 Compare with Example 5 styrene 85 50 50 50 55 50 50 50 GMA 12 45 40 50 5 45 45 45 MMA 3 5 10 40 5 5 5 Initiator 0.4 0.4 0.5 0.4 0.3 0.4 0.4 0.4 Molecular weight regulator 3 3 5 3 5 0.5 7 3 Preparation process ① ① ① ① ① ① ①

[0048] The preparation process is as follows:

[0049] ① Styrene, glycidyl methacrylate (GMA), methyl methacrylate (MMA), azobisisobutyronitrile (AIBN) initiator, dodecyl mercaptan (DIM) molecular weight regulator, and 200 kg of deionized water are mixed in a reactor and reacted at 80°C for 5 hours under conventional stirring. The temperature is then raised to 100°C and the reaction continues for 2 hours. The mixture is then discharged into a discharge tank, filtered conventionally, and the resulting particles are dried at 95°C to constant weight.

[0050] Styrene, GMA, MMA, initiator azobisisobutyronitrile, molecular weight regulator dodecyl mercaptan, and 200 kg of deionized water were mixed in a reactor and reacted at 70°C for 5 hours under conventional stirring. The reaction was then continued for 2 hours. The mixture was then discharged into a discharge tank, filtered conventionally, and the resulting particles were dried at 95°C to constant weight.

[0051] This invention copolymerizes styrene, MMA, and GMA into a St-MMA-GMA random copolymer structure. The GMA groups in this structure can react with the end groups of polyesters and polyamides, thereby aiding in the elastic dispersion of the polyolefin and achieving a toughening effect. In particular, the introduction of MMA monomers allows for the ring-opening reaction between the ester groups of MMA and the epoxy groups of GMA, introducing double bonds that can initiate grafting. Figure 1 Infrared structural diagrams of Example 1 (low functional group content) and Example 2 (high functional group content) are shown. The 1720 cm⁻¹ structure is also shown. -1 The characteristic peaks indicate the presence of GMA functional groups. The peak intensity increases with the increase of the GMA ratio as the monomer ratio is adjusted. The molecular weight (Mw) and residual monomer content (RTVM) of the chain extenders in the above examples and control examples were tested under the above conventional testing conditions. The test results are shown in Table 2. As shown in Table 2, when process 2 is used, the residual monomer content is relatively high, which is due to the excessively low ripening temperature in the later stages of polymerization.

[0052] Table 2. Molecular weight and residual monomers of intermediate examples and control examples

[0053]

[0054] Intermediates 1-7 were mixed with polyolefin elastomer, initiator, and antioxidant according to the proportions in Table 3, and then granulated by twin-screw extrusion. The reaction extrusion temperature was 190-200℃, the extruder L / D was 52, and the screw speed was set to 300 rpm to prepare a branched toughening agent. The initiator was 2,5-dimethyl-2,5-bis(tert-butadiene)hexane masterbatch with an initiator content of 40 wt%. The antioxidant was a compound of 168 and 1313 in equal mass. Figure 2 The infrared spectrum of the toughening agent product from Example 5 was compared with that of commercially available conventional POE-g-GMA. The intermediate of this invention underwent a grafting reaction with the polyolefin elastomer, and the infrared structure diagram showed the characteristic peak (720 cm⁻¹) of the long carbon chain of the elastomer. -1 ), and the characteristic peak of styrene (1600 cm⁻¹). -1 3000~3100cm -1 (Multiple peaks), the characteristic peak of the functional group is 1720 cm⁻¹. -1 Nearby. It is evident that the grafting reaction was successfully carried out via reactive extrusion. Figure 3The branched structure of the toughening agent products prepared in Examples 5 and 6 of conventional commercially available POE-g-GMA was characterized by rotational rheology. Figure 3 It is evident that commercially available POE-g-GMA has a linear structure, thus exhibiting stress-strain softening properties. In contrast, the toughening agent samples prepared in Examples 5 and 6 have a branched structure, exhibiting stress-strain hardening properties. Furthermore, the larger the molecular weight of the branched chain, the more pronounced the "tailing" phenomenon becomes.

[0055] Table 3 Formulation table of toughening agent examples and control examples, Kg

[0056]

[0057] Table 4 Functional group content and residual monomer content of toughening agent products

[0058]

[0059] As shown in Table 4, the process employed in this invention demonstrates significantly superior performance in terms of residual monomers in the toughening agent compared to commercially available POE-g-GMA. This is because commercially available products utilize reactive extrusion, making residual monomer control difficult. While post-processing thermal devolatilization can effectively reduce unreacted residual monomers, it is not suitable for elastomers as it causes the toughening agent to stick, hindering its later use. The process of this invention, however, can control residual monomers at very low levels, meeting the needs of specialized fields such as food packaging and medical applications. Furthermore, this process overcomes the limitations of traditional reactive extrusion on functional group grafting rates, achieving a higher level of control.

[0060] Application Examples

[0061] Toughening agent samples and commercially available POE-g-MAH structural toughening agents (Comparative Example 10) were added to PA6 to prepare toughened modified PA6. The toughening agent was added at 10% of the weight of PA6. PA6 and toughening agent were extruded using a conventional twin-screw extruder. The mechanical properties of the prepared samples were tested after injection molding, as shown in Table 5.

[0062] Table 5. Physical properties of toughened modified PA6

[0063]

[0064] As shown in Table 5, comparing Example 4 and Example 5, the toughening efficiency of Example 4 is lower than that of Example 5 because the elastomer ratio is reduced. However, compared to Example 8, the toughening efficiency is actually lower in Example 8 because the content of branched functional groups is higher, resulting in excessively vigorous local reactions. This is consistent with the performance of Comparative Example 6, where the excessively high content of branched functional groups negatively impacted the dispersion of the toughening agent in PA6, thus reducing the impact strength. Although local crosslinking is beneficial to strength, the strength of Comparative Example 6 is also lower than that of the examples due to dispersion issues.

[0065] In Comparative Example 7, the GMA / MMA ratio was too low, resulting in a final effective content of only 0.3%, which failed to achieve the desired effect in toughening modification. Compared with Example 5, Comparative Examples 8 and 9 had similar final effective contents of active functional groups and similar molecular weights. However, the branch length of Comparative Example 8 was too large, which was not conducive to the dispersion of the toughening agent; while the branch length of Comparative Example 9 was too low, and the advantages of the branched structure were not reflected. Therefore, except for the melt index, its performance was similar to that of commercially available products, showing only a slight advantage.

[0066] Example 5 was added to polylactic acid at an addition amount of 0.8%, and twin-screw granulation was carried out at 140-210°C. The melt index (210°C / 5Kg) was 58.3, which did not reduce the fluidity compared with the 54.2 of the polylactic acid raw material.

[0067] Examples 5, 9, and 10 were added to polybutylene terephthalate (PBT) at an addition amount of 20 wt% to obtain toughened modified PBT; and added to polycarbonate (PC) / polybutylene terephthalate (PBT) polyester alloy material at an addition amount of 5 wt% to obtain toughened modified PC / PBT. The obtained modified particles were injection molded and then tested.

[0068] Figure 4 Examples 5, 9, and 10 demonstrate the addition of 20% of polybutylene terephthalate (PBT) to toughened modified PBT, achieving good flowability. Compared to commercially available products (Comparative Example 10), the toughening agents in Examples 5 and 9 had almost no effect on flowability, showing no difference from PBT. However, commercially available POE-g-MAH differs from PBT. This is similar to PA modification. Figure 5 The results of mechanical property tests on PBT toughening modification and PC / PBT alloy toughening modification are shown in Example 5. Both examples demonstrate excellent toughening performance and a balance between stiffness and toughness.

[0069] The specific embodiments of the present invention have been described above. The specific methods for toughening and modifying PA, PBT, and PC / PBT alloys are conventional techniques, and conventional extrusion processes can be selected according to the plastic. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the substantive content of the present invention.

[0070] Compared with the prior art, the present invention has the following beneficial effects: 1. The toughening agent of the present invention has a controllable branched structure, and the branches are rigid, which can achieve a better balance between rigidity and toughness. 2. The reactive functional groups are located in the branched chain, resulting in higher reactivity than conventional structures located in the main chain. The functional group density is suitable, with no mutual interference, and gelation is not easily formed. 3. Low residual monomer content and good thermal stability are beneficial for later use. 4. The process route selected in this invention does not require solvents, requires less investment, and the equipment and raw materials are readily available. The process route has low emissions, simple formulation, and stable composition. 5. The monomers selected in this invention are non-toxic or low-toxic, the raw material monomers are readily available, and the process route is conducive to further reducing residual monomer content, making it suitable for high-end applications related to medical devices and food and pharmaceutical packaging. 6. The toughening agent of this invention has a wide range of applications: it has excellent toughening effects on polyester alloy materials such as polycarbonate (PC) / polyethylene terephthalate (PET) and polycarbonate (PC) / polybutylene terephthalate (PBT), as well as engineering plastics such as polylactic acid (PLA), polyamide, and polyphenylene ether. 7. The toughening agent of this invention is simple to use and can be widely used in medical devices, packaging, home appliances, automobiles, aerospace, and other fields, with very broad application prospects and industrialization value.

[0071] The successful implementation of this invention can break the foreign technological monopoly, lead technological progress and green production in this field, realize the upgrading of the domestic related industrial chain structure and technology, improve the technological support and innovation capabilities of the circular economy, and play a positive role in guiding the chemical industry towards refinement and high added value. At the same time, the technical route of this invention is a synthetic route that can achieve industrialized production, is environmentally friendly, and has a high yield.

Claims

1. A method for preparing a branched toughening agent, characterized in that, The process includes the following steps: Aromatic vinyl monomers, acrylate monomers, polymerization initiators, molecular weight regulators, and water are mixed and polymerized under heat to prepare an intermediate. The polymerization is carried out at 65–80°C for 2–6 hours, followed by further polymerization at 90–110°C for 0.5–2 hours. Then, the intermediate is melt-mixed with a polyolefin elastomer, an extrusion initiator, and an antioxidant to prepare a branched toughening agent. The total mass of the aromatic vinyl monomers and acrylate monomers is 100%, with the aromatic vinyl monomers comprising 50–85% of the total mass. The polymerization initiator is used at 0.1–2% of the monomer mass, and the molecular weight regulator is used at 0.1–5% of the monomer mass. The acrylate monomers are a mixture of methacrylate and glycidyl methacrylate, with a mass ratio of methacrylate to glycidyl methacrylate of 1–3:

10. The total mass of the intermediate and the polyolefin elastomer is 100%, with the intermediate comprising 2–12% of the total mass. The extrusion initiator is used at 0.5–15% of the total mass.

2. The method for preparing the branched toughening agent as described in claim 1, characterized in that, The weight-average molecular weight of the intermediate is 2000 to 10000.

3. The method for preparing the branched toughening agent as described in claim 1, characterized in that, After the heating polymerization is completed, the intermediate obtained is mixed with polyolefin elastomer, extrusion initiator and antioxidant in proportion, and then granulated by twin-screw extrusion to prepare branched toughening agent.

4. The branched toughening agent prepared by the method described in claim 1.

5. The application of the branched toughening agent according to claim 4 in the toughening of plastics.

6. A method for preparing a toughened modified polymer, characterized in that, The process includes the following steps: mixing polymer raw materials and the branched toughening agent described in claim 4, followed by extrusion, to obtain a toughened modified polymer.

7. The method for preparing the toughened modified polymer as described in claim 6, characterized in that, The amount of the branched toughening agent is 3 to 20% of the polymer raw material mass.

Images