MBS resin for improving low-temperature tensile strength and preparation method thereof

Abstract

The invention relates to the technical field of MBS resin preparation, in particular to MBS resin with improved low-temperature tensile strength and a preparation method thereof. The MBS resin for improving the low-temperature tensile strength is prepared from the following main raw materials: butadiene, styrene, methyl methacrylate, butyl acrylate, N-phenylmaleimide, BAPT, a silane coupling agent and an auxiliary reinforcing monomer, the composition also comprises the following auxiliary agents: an emulsifier, an initiator, a molecular weight regulator and an antioxidant. Through gradient introduction and step-by-step reaction of a rigid monomer N-PMI, a flexible monomer THFA and a cross-linking agent BAPT, a fine structure of'in-core rigidity increasing, shell layer rigidity and softness and interface strengthening 'is realized in polymer particles. By means of the collaborative structure from inside to outside, optimal distribution of rigidity and toughness of the material on the molecular level is achieved in advance, and the root reason for breaking through the low-temperature performance balance bottleneck macroscopically is achieved.

Description

Technical Field

[0001] This invention relates to the field of MBS resin preparation technology, specifically to MBS resin with improved low-temperature tensile strength and its preparation method. Background Technology

[0002] Methyl methacrylate-butadiene-styrene (MBS) resin, as an important core-shell structure impact modifier, is widely used in the toughening modification of engineering plastics such as polyvinyl chloride (PVC) and polycarbonate (PC) due to its excellent transparency, impact resistance and processing compatibility, and occupies a key position, especially in transparent PVC products.

[0003] However, the performance of traditional MBS resins is heavily dependent on temperature. Their toughening mechanism primarily relies on the formation of crazing and shear bands in the rubber particles (the "core") under stress, thereby absorbing and dissipating impact energy. At room temperature, the rubber phase is in a highly elastic state, and this mechanism is highly effective. However, when temperatures drop to extremely cold environments such as -20°C or even -40°C and below, traditional MBS resins face severe challenges: on the one hand, the glass transition temperature (Tg) of the styrene-butadiene rubber (SBR), which forms the core, is relatively high. At low temperatures, the rubber phase gradually loses elasticity, tends to harden and become brittle, and its ability to initiate and terminate crazing decreases sharply; on the other hand, the interfacial bond strength between the polymethyl methacrylate (PMMA) resin (the "shell") and the rubber phase may also weaken at low temperatures, causing stress to be unable to be effectively transferred from the rigid matrix to the rubber phase, making interfacial delamination highly likely. As a result, the material exhibits a double decrease in tensile strength and elongation at break at low temperatures, which cannot meet the stringent requirements for low-temperature mechanical properties of materials in cold-region infrastructure, such as cold-resistant pipes, cable sheaths, special vehicle parts, and outdoor equipment.

[0004] Existing technologies have explored ways to improve the low-temperature toughness of MBS resins, mainly including the following two approaches: First, increasing the rubber phase content to provide more stress concentration points, but this usually significantly reduces the material's modulus, tensile strength, and heat distortion temperature, impairing its rigidity. Second, introducing flexible monomers into the shell or rubber phase, which can reduce the overall Tg and improve low-temperature toughness, but often at the cost of severely sacrificing the material's hardness, tensile strength, and heat resistance, leading to a performance imbalance.

[0005] Patent CN108997534A discloses a method for preparing small-particle-size styrene-butadiene latex via low-temperature polymerization, followed by grafting styrene and methyl methacrylate resin phases into MBS resin. This technology aims to improve the low-temperature transparency and impact resistance of the resin by precisely controlling the physical size of the rubber particles. However, this approach relies entirely on physical structure control, and its chemical composition is identical to traditional MBS, lacking low-temperature strengthening design for the phase interface and resin matrix. Therefore, while achieving low-temperature toughness, it is difficult to maintain and even less able to improve the tensile strength and modulus of the material in extremely cold environments, exhibiting significant limitations in meeting the stringent requirements of high strength and high toughness below -40°C.

[0006] Patent CN107304241A discloses a low-temperature resistant MBS resin, which adds a crosslinking agent to the rubber phase to strengthen the network and introduces acrylonitrile monomers into the shell to improve rigidity. This approach aims to improve the overall strength and low-temperature dimensional stability of the material through chemical crosslinking and copolymerization of rigid monomers. However, this technology fails to simultaneously address the issues of low-temperature toughness and interface weakening. The introduction of acrylonitrile sacrifices transparency and increases low-temperature brittleness. Furthermore, the lack of targeted low-temperature toughening components and interface strengthening designs means that it still faces the risk of insufficient toughness or strength-toughness imbalance under extremely cold conditions, failing to meet the stringent requirements of low-temperature comprehensive performance in application scenarios.

[0007] In summary, existing technologies have failed to fundamentally resolve the contradictory requirement of simultaneously maintaining high rigidity and high toughness at extremely low temperatures. Therefore, developing an MBS resin capable of achieving synergistic optimization of strength and toughness in low-temperature environments has become a pressing technical challenge in this field. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the purpose of this invention is to provide an MBS resin with improved low-temperature tensile strength, high transparency, and the ability to achieve a balance between high strength and high toughness at low temperatures.

[0009] The present invention also provides a preparation method that is simple, easy to implement, and suitable for large-scale production.

[0010] The MBS resin for improving low-temperature tensile strength described in this invention is prepared from the following main raw materials in parts by weight: Butadiene: 62-78 parts; Styrene: 22-38 parts; Methyl methacrylate (MMA): 38-52 parts; Butyl acrylate (BA): 6-14 parts; N-Phenylanimide (N-PMI): 3-9 parts; Crosslinking agent: 1,3-bis(3-acryloyloxypropyl)-1,1,3,3-tetramethyldisiloxane (BAPT), 0.4-1.6 parts; Low-temperature interface activator: silane coupling agent, 0.7-2.3 parts; Auxiliary enhancer monomers: 1-4 parts; It also includes the following adjuvants: Emulsifier: 2.8-4.2% of the total mass of the main raw materials; Initiator: 0.35-0.75% of the total mass of the main raw materials; Molecular weight regulator: 0.07-0.22% of the total mass of the main raw materials; Antioxidant: 0.45-0.85% of the total mass of the main raw materials.

[0011] The silane coupling agent is γ-glycidyl etheroxypropyltrimethoxysilane (KH-560), and the auxiliary reinforcing monomer is tetrahydrofuran acrylate (THFA).

[0012] The emulsifier is a compound of sodium dicyclohexyl sulfosuccinate (Aerosol A-196 40) and octylphenol polyoxyethylene ether (OP-10) in a mass ratio of 1:1.2.

[0013] The initiator is a composite system of ammonium persulfate and tert-butyl hydroperoxide.

[0014] The molecular weight regulator is n-dodecyl mercaptan.

[0015] The antioxidant is a compound of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010) and tris(2,4-di-tert-butylphenyl) phosphite (antioxidant 168) in a mass ratio of 1:1.

[0016] The method for preparing MBS resin with improved low-temperature tensile strength according to the present invention comprises the following steps: Step 1: Preparation of N-phenylmaleimide pre-assembled styrene-butadiene latex Water, a portion of emulsifier, a low-temperature interface activator, butadiene, styrene, and a molecular weight regulator were added to a reaction vessel for pre-emulsification to obtain a homogeneous emulsion. The mixture was heated, and a portion of a methanol solution of N-phenylmaleimide (20 wt.%) was added dropwise. The reaction was then maintained at this temperature. In a separate vessel, the initiator and water were mixed evenly to obtain an initiator solution. A portion of the initiator solution was added, and the reaction was continued until the conversion rate reached over 90%, resulting in N-phenylmaleimide pre-assembled styrene-butadiene latex. The particle size was measured to be 90-125 nm using a laser particle size analyzer. Step 2: Preparation of pre-emulsion Methyl methacrylate, butyl acrylate, the remaining N-phenylmaleimide solution, auxiliary reinforcing monomers, and part of the crosslinking agent are mixed evenly to obtain a monomer mixture; the monomer mixture is mixed with part of the initiator solution, and water and the remaining emulsifier are added for emulsification to obtain a stable pre-emulsion; Step 3: Core-shell grafting polymerization The N-phenylmaleimide pre-assembled styrene-butadiene latex was transferred into a reaction vessel and heated to 68.5-69.5℃. Then, the remaining initiator solution was added as a seed initiator. The pre-emulsion was added dropwise in three batches. The first batch of pre-emulsion is added at a rate of 35-45% of its total mass over a period of 120-140 minutes, with the temperature controlled at 69-71℃. This ensures that the monomer feed rate is lower than the polymerization rate, maintaining a monomer-starved state. The second batch of pre-emulsion is added at 35-45% of its total mass over a period of 100-120 minutes, with the temperature controlled at 71-73°C. The dropping rate is appropriately increased to maintain a high polymerization rate and control the viscosity of the system to prevent gel formation. The third batch of the remaining pre-emulsion is added dropwise over a time of 80-100 minutes at a temperature of 71-73°C. The dropwise rate is reduced to ensure complete reaction and control the final particle size distribution. Step 4: Drying the reaction mixture at low temperature After the addition is complete, keep the temperature at 74-78℃, raise the temperature to 83-87℃ and add the remaining crosslinking agent, keep the temperature for reaction, lower the temperature to 46-50℃, add the antioxidant and mix evenly, cool to room temperature, demulsify, filter to separate the solid material, wash, and spray dry to obtain a white powder with a particle size distribution D50=120-150μm.

[0017] The emulsifier mentioned in step one accounts for 80-85 wt.% of the total emulsifier usage, the N-phenylmaleimide mentioned in step one accounts for 25-35 wt.% of the total N-phenylmaleimide usage, and the initiator mentioned in step one accounts for 35-45 wt.% of the total initiator usage.

[0018] The crosslinking agent described in step two accounts for 65-70 wt.% of the total crosslinking agent usage, and the initiator described in step two accounts for 45-55 wt.% of the total initiator usage.

[0019] The temperature increase mentioned in step one is to raise the temperature to 62-64℃.

[0020] The benzene ring of N-phenylmaleimide (N-PMI) provides rigid support to maintain low-temperature strength. The maleimide ring has strong polarity, which can enhance the interfacial bonding force between internal phases. At the same time, the N-substituent reduces steric hindrance and effectively improves low-temperature toughness.

[0021] The crosslinking agent 1,3-bis(3-acryloyloxypropyl)-1,1,3,3-tetramethyldisiloxane (BAPT) possesses low-temperature flexibility in its siloxane backbone, while the acryloyloxy group provides reactivity and the propyl linkage acts as a moderately flexible buffer. In the early stage of step two, BAPT is added to participate in copolymerization during the shell monomer polymerization. Its double bonds contribute to chain growth, while the long-chain siloxane portion acts as a flexible spacer. This creates moderate and uniform chemical crosslinking points between the shell polymer chains of PMMA / BA / THFA / N-PMI, thus constructing a lightly crosslinked network. This network significantly improves the cohesive strength, temperature resistance, and creep resistance of the shell, and is key to enhancing overall tensile strength and low-temperature dimensional stability. In the later stage of step four, BAPT is added to initiate the reaction of the remaining crosslinking agent within the core-shell polymerized particles at 83-87°C. This step can induce deeper secondary crosslinking within the formed polymer particles, creating a denser and more robust interpenetrating network, thereby locking in the optimized structure and making the performance more stable.

[0022] This invention introduces N-phenylmaleimide (N-PMI) in step one for pre-assembly: it is added at the initial stage of styrene-butadiene rubber chain polymerization, allowing N-PMI molecular chain segments to chemically bond into the rubber network. This is equivalent to embedding tiny rigid structures into flexible rubber, significantly improving the strength and glass transition temperature (Tg) of the rubber phase itself. This prevents the rubber particles from excessively softening at extremely low temperatures, still providing effective stress support, which is one of the fundamental sources of low-temperature strength. Then, N-PMI is introduced into the shell layer in step two: it is added during PMMA shell layer polymerization. Its rigid structure effectively compensates for the decrease in shell layer strength caused by the introduction of flexible monomers such as BA and THFA, maintaining the overall strength and temperature resistance of the shell layer. At the same time, the N-PMI segments distributed in the shell layer have strong polar interactions with the N-PMI segments in the rubber phase, further enhancing the intrinsic bonding force at the core-shell interface.

[0023] γ-glycidyl etheroxypropylsilane (KH-560) molecules possess methoxy and epoxy groups. The methoxy group hydrolyzes in the presence of water to generate silanol groups, which then undergo condensation or strong hydrogen bonding with the rubber phase or inorganic surface. The epoxy group can open its ring under heated reaction conditions, interacting with ester groups in the PMMA shell, unsaturated bonds in the rubber chain, or residual double bonds. Through chemical bridging—anchoring the rubber core at one end and bonding the resin shell at the other—the bonding strength between the two phases under low-temperature shrinkage stress is significantly enhanced. This ensures that stress can be efficiently transferred from the rigid shell to the rubber core under low-temperature stress, avoiding interfacial debonding, a major failure mode leading to low-temperature brittle fracture.

[0024] Tetrahydrofuran acrylate (THFA) monomers contain both polymerizable acrylate double bonds and flexible tetrahydrofuran cyclic ether structures. The ether bonds endow its chain segments with excellent flexibility and low-temperature flexibility. When introduced into shell copolymerization, it can effectively plasticize the PMMA matrix and improve the low-temperature flexibility and crack resistance of the shell and even the whole.

[0025] The flexible ether bonds of THFA, the rigid imide rings of N-PMI, and the flexible siloxane chains of BAPT form a clever rigid-flexible complementarity. This not only offsets some of the brittleness risk brought by N-PMI, but also avoids excessive softening due to the constraint of the cross-linking network and rigid components. This multi-level structure of "rigid skeleton + flexible hinge + chemical cross-linking" is the essence of molecular-level design for achieving both high strength and high toughness at low temperatures.

[0026] This application employs anionic / nonionic compound emulsifiers added in stages, utilizing their different spatial and electrostatic stabilization mechanisms to synergistically control micelle formation and growth, laying the physical foundation for preparing core-shell particles with uniform particle size, narrow distribution, and good stability. Combined with a batch-by-batch gradient addition of shell monomers, the shell thickness, compositional gradient, and grafting rate can be precisely controlled, resulting in a core-shell structure with a smooth interface transition and optimal stress distribution.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention uses N-phenylmaleimide to enhance the rigidity of the rubber phase and 1,3-bis(3-acryloyloxypropyl)-1,1,3,3-tetramethyldisiloxane to construct a crosslinking network, so that the material still maintains high tensile strength at -40℃; at the same time, with the help of the flexibility toughening of tetrahydrofuran acrylate and the interface strengthening of KH-560, excellent low-temperature impact resistance and elongation at break are ensured, overcoming the problem of low-temperature failure in traditional materials where strength and toughness are difficult to achieve at the same time.

[0028] (2) The refractive indices of the functional monomers N-phenylmaleimide and tetrahydrofuran acrylate match those of the matrix PMMA / PVC, and the KH-560 coupling agent reduces light scattering at the phase interface, enabling the material to achieve high performance at low temperatures while fully meeting the requirements of high-end transparent products.

[0029] (3) The chemical bond formed by KH-560 at the core-shell interface significantly improves the bonding strength of the two phases under low temperature thermal stress, avoids the performance degradation caused by interface peeling, and makes the material stable in low temperature cycling environment.

[0030] (4) Through the gradient introduction and stepwise reaction of rigid monomer N-PMI, flexible monomer THFA and crosslinking agent BAPT, a fine structure of "intrinsic stiffness, shell rigidity and flexibility, and interface strengthening" is achieved inside the polymer particles. This synergistic structure from the inside out enables the material to achieve an optimized distribution of rigidity and toughness at the molecular level in advance, which is the fundamental reason for its breakthrough in the bottleneck of low-temperature performance balance on a macroscopic level. Detailed Implementation

[0031] The present invention will be further described below with reference to the embodiments.

[0032] Unless otherwise specified, all raw materials used in the examples were commercially available.

[0033] Example 1 The MBS resin for improving low-temperature tensile strength is prepared from the following main raw materials in parts by weight: Butadiene: 70 parts; Styrene: 30 parts; Methyl methacrylate (MMA): 45 parts; Butyl acrylate (BA): 10 parts; N-Phenylanimide (N-PMI): 6 parts; Crosslinking agent: 1,3-bis(3-acryloyloxypropyl)-1,1,3,3-tetramethyldisiloxane (BAPT), 1.0 part; Low-temperature interface activator: KH-560, 1.5 parts; Auxiliary reinforcing monomer: Tetrahydrofuran acrylate (THFA), 2.5 parts; It also includes the following additives: (based on a total mass of 166 parts of the main raw material) Emulsifier: A compound of sodium dicyclohexyl sulfonate (Aerosol A-196 40) and octylphenol polyoxyethylene ether (OP-10) in a mass ratio of 1:1.2, used at 3.5% of the total mass of the main raw materials; Initiator: A composite system of ammonium persulfate and tert-butyl hydroperoxide in a mass ratio of 2:1, used at a rate of 0.55% of the total mass of the main raw materials; Molecular weight regulator: n-Dodecyl mercaptan, used at 0.15% of the total mass of the main raw materials; Antioxidant: A compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, with a dosage of 0.65% of the total mass of the main raw materials.

[0034] The method for preparing the MBS resin with improved low-temperature tensile strength comprises the following steps: Step 1: Preparation of N-phenylmaleimide pre-assembled styrene-butadiene latex Water, 82 wt.% of the total emulsifier, low-temperature interface activator, butadiene, styrene, and molecular weight regulator were added to the reaction vessel for pre-emulsification for 30 min. The mixture was stirred at 400 rpm at room temperature to obtain a homogeneous emulsion. The temperature was raised to 63°C, and a methanol solution of N-phenylmaleimide (20 wt.%), accounting for 30 wt.% of the total N-phenylmaleimide, was added dropwise. The reaction was then maintained at this temperature for 1.5 h. In a separate container, the initiator and water were mixed evenly to obtain an initiator solution (3.3 wt.%). 40 wt.% of the total initiator solution was added to the initiator solution, and the reaction was carried out until the conversion rate reached 93%, resulting in N-phenylmaleimide pre-assembled styrene-butadiene latex. The particle size was measured to be 112 nm using a laser particle size analyzer. Step 2: Preparation of pre-emulsion Methyl methacrylate, butyl acrylate, the remaining N-phenylmaleimide solution, auxiliary reinforcing monomers, and 68 wt.% of the total crosslinking agent were mixed evenly to obtain a monomer mixture. The monomer mixture was then mixed with 45 wt.% of the total initiator solution, the remaining emulsifier was added, and deionized water was added to achieve a water-to-oil ratio of 2:1. The mixture was then emulsified at 10,000 rpm for 20 minutes using a high-pressure homogenizer to obtain a stable pre-emulsion. Step 3: Core-shell grafting polymerization The N-phenylmaleimide pre-assembled styrene-butadiene latex was transferred into a reaction vessel, heated to 69°C, and then the remaining initiator solution was added as a seed initiator. The pre-emulsion was added dropwise in three batches. The first batch of pre-emulsion was added at a constant rate, with a dripping time of 130 minutes and the temperature controlled at 70℃. The second batch of pre-emulsion was added at a constant rate, with a dripping time of 110 minutes and a temperature controlled at 72℃. The third batch of the remaining pre-emulsion was added dropwise at a uniform rate over a time of 90 minutes, with the temperature controlled at 72°C. Step 4: Drying the reaction mixture at low temperature After the addition was complete, the mixture was kept at 76℃ for 2.5 hours, then heated to 85℃ to add the remaining crosslinking agent. The mixture was kept at this temperature for 1.5 hours, then cooled to 48℃. The antioxidant was added and stirred for 1.2 hours to ensure uniform mixing. The mixture was cooled to room temperature, and 10 wt.% calcium chloride solution was added to break the emulsion. The amount added was 5% of the emulsion volume. The mixture was allowed to stand for 30 minutes to separate into layers. The solid material was separated by filtration, washed three times with deionized water, and spray-dried to obtain a white powder with a particle size distribution D50 = 135 μm.

[0035] Example 2 The MBS resin for improving low-temperature tensile strength is prepared from the following main raw materials in parts by weight: Butadiene: 65 parts; Styrene: 25 parts; Methyl methacrylate (MMA): 40 parts; Butyl acrylate (BA): 7 parts; N-Phenylanimide (N-PMI): 4 parts; Crosslinking agent: 1,3-bis(3-acryloyloxypropyl)-1,1,3,3-tetramethyldisiloxane (BAPT), 0.6 parts; Low-temperature interface activator: KH-560, 1.0 part; Auxiliary reinforcing monomer: Tetrahydrofuran acrylate (THFA), 1.5 parts; It also includes the following additives: (based on a total mass of 144.1 parts of the main raw material) Emulsifier: A compound of sodium dicyclohexyl sulfonate (Aerosol A-196 40) and octylphenol polyoxyethylene ether (OP-10) in a mass ratio of 1:1.2, used at 3.0% of the total mass of the main raw materials; Initiator: A composite system of ammonium persulfate and tert-butyl hydroperoxide in a mass ratio of 2:1, used at a rate of 0.40% of the total mass of the main raw materials; Molecular weight regulator: n-Dodecyl mercaptan, used at 0.10% of the total mass of the main raw materials; Antioxidant: A compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, used at a rate of 0.50% of the total mass of the main raw materials.

[0036] The method for preparing the MBS resin with improved low-temperature tensile strength comprises the following steps: Step 1: Preparation of N-phenylmaleimide pre-assembled styrene-butadiene latex Water, 80 wt.% of the total emulsifier, low-temperature interface activator, butadiene, styrene, and molecular weight regulator were added to the reaction vessel for pre-emulsification for 30 min. The mixture was stirred at 400 rpm at room temperature to obtain a homogeneous emulsion. The temperature was raised to 62 °C, and a methanol solution of N-phenylmaleimide (20 wt.%), which was 25 wt.% of the total N-phenylmaleimide, was added dropwise. The reaction was then maintained at this temperature for 1.5 h. In a separate container, the initiator and water were mixed evenly to obtain an initiator solution (3.3 wt.%). 35 wt.% of the total initiator solution was added to the initiator solution and the reaction was carried out until the conversion rate reached 91%, resulting in N-phenylmaleimide pre-assembled styrene-butadiene latex. The particle size was measured to be 105 nm using a laser particle size analyzer. Step 2: Preparation of pre-emulsion Methyl methacrylate, butyl acrylate, the remaining N-phenylmaleimide solution, auxiliary reinforcing monomers, and 65 wt.% of the total crosslinking agent were mixed evenly to obtain a monomer mixture. The monomer mixture was then mixed with 45 wt.% of the total initiator solution, the remaining emulsifier was added, and deionized water was added to achieve a water-to-oil ratio of 2:1. The mixture was then emulsified at 10,000 rpm for 20 minutes using a high-pressure homogenizer to obtain a stable pre-emulsion. Step 3: Core-shell grafting polymerization The N-phenylmaleimide pre-assembled styrene-butadiene latex was transferred into a reaction vessel, heated to 68.5°C, and then the remaining initiator solution was added as a seed initiator. The pre-emulsion was added dropwise in three batches: The first batch of pre-emulsion was added at a constant rate of 35% of its total mass, over a period of 125 minutes, with the temperature controlled at 69°C. The second batch of pre-emulsion was added at a constant rate, with a dripping time of 110 minutes and a temperature controlled at 71℃. The third batch of the remaining pre-emulsion was added dropwise at a uniform rate over a time of 90 minutes, with the temperature controlled at 71°C. Step 4: Drying the reaction mixture at low temperature After the addition was complete, the mixture was kept at 74℃ for 2.5 hours, then heated to 83℃ to add the remaining crosslinking agent. The mixture was kept at this temperature for 1.5 hours, then cooled to 46℃. The antioxidant was added and stirred for 1.2 hours to ensure uniform mixing. The mixture was cooled to room temperature, and 10 wt.% calcium chloride solution was added to break the emulsion. The amount added was 5% of the emulsion volume. The mixture was allowed to stand for 30 minutes to separate into layers. The solid material was separated by filtration, washed three times with deionized water, and spray-dried to obtain a white powder with a particle size distribution D50 = 128 μm.

[0037] Example 3 The MBS resin for improving low-temperature tensile strength is prepared from the following main raw materials in parts by weight: Butadiene: 75 parts; Styrene: 35 parts; Methyl methacrylate (MMA): 50 parts; Butyl acrylate (BA): 12 parts; N-Phenylanimide (N-PMI): 8 parts; Crosslinking agent: 1,3-bis(3-acryloyloxypropyl)-1,1,3,3-tetramethyldisiloxane (BAPT), 1.4 parts; Low-temperature interface activator: KH-560, 2.0 parts; Auxiliary reinforcing monomer: Tetrahydrofuran acrylate (THFA), 3.5 parts; It also includes the following additives: (based on a total mass of 186.9 parts of the main raw material) Emulsifier: A compound of sodium dicyclohexyl sulfonate (Aerosol A-196 40) and octylphenol polyoxyethylene ether (OP-10) in a mass ratio of 1:1.2, used at 4.0% of the total mass of the main raw materials; Initiator: A composite system of ammonium persulfate and tert-butyl hydroperoxide in a mass ratio of 2:1, used at a rate of 0.7% of the total mass of the main raw materials; Molecular weight regulator: n-Dodecyl mercaptan, used at 0.20% of the total mass of the main raw materials; Antioxidant: A compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, with a dosage of 0.80% of the total mass of the main raw materials.

[0038] The method for preparing the MBS resin with improved low-temperature tensile strength comprises the following steps: Step 1: Preparation of N-phenylmaleimide pre-assembled styrene-butadiene latex Water, 85 wt.% of the total emulsifier, low-temperature interface activator, butadiene, styrene, and molecular weight regulator were added to the reaction vessel for pre-emulsification for 30 min. The mixture was stirred at 400 rpm at room temperature to obtain a homogeneous emulsion. The temperature was raised to 64 °C, and a methanol solution of N-phenylmaleimide (20 wt.%), 35 wt.% of the total N-phenylmaleimide, was added dropwise. The reaction was then maintained at this temperature for 1.8 h. In a separate vessel, the initiator and water were mixed evenly to obtain an initiator solution (3.3 wt.%). 45 wt.% of the total initiator solution was added to the initiator solution and the reaction was carried out until the conversion rate reached 94%, resulting in N-phenylmaleimide pre-assembled styrene-butadiene latex. The particle size was measured to be 118 nm using a laser particle size analyzer. Step 2: Preparation of pre-emulsion Methyl methacrylate, butyl acrylate, the remaining N-phenylmaleimide solution, auxiliary reinforcing monomers, and 70 wt.% of the total crosslinking agent were mixed evenly to obtain a monomer mixture. The monomer mixture was then mixed with 55 wt.% of the total initiator solution, the remaining emulsifier was added, and deionized water was added to achieve a water-to-oil ratio of 2:1. The mixture was then emulsified at 10,000 rpm for 20 minutes using a high-pressure homogenizer to obtain a stable pre-emulsion. Step 3: Core-shell grafting polymerization The N-phenylmaleimide pre-assembled styrene-butadiene latex was transferred into a reaction vessel, heated to 69.5°C, and then the remaining initiator solution was added as a seed initiator. The pre-emulsion was added dropwise in three batches: The first batch of pre-emulsion was added at a constant rate, with a dripping time of 140 minutes and the temperature controlled at 71℃. The second batch of pre-emulsion was added at a constant rate, with a dripping time of 120 minutes and a temperature controlled at 73℃. The remaining pre-emulsion was added in the third batch at a uniform rate over a time of 85 minutes, with the temperature controlled at 73°C. Step 4: Drying the reaction mixture at low temperature After the addition was complete, the mixture was kept at 78℃ for 2.5 hours, then heated to 87℃ to add the remaining crosslinking agent. The mixture was kept at this temperature for 1.5 hours, then cooled to 50℃. The antioxidant was added and stirred for 1.2 hours to ensure uniform mixing. The mixture was cooled to room temperature, and 10 wt.% calcium chloride solution was added to break the emulsion. The amount added was 5% of the emulsion volume. The mixture was allowed to stand for 30 minutes to separate the layers. The solid material was separated by filtration, washed three times with deionized water, and spray-dried to obtain a white powder with a particle size distribution D50 = 145 μm.

[0039] Comparative Example 1 Same as Example 1, except that all special functional components are removed: N-PMI, KH-560, BAPT, and THFA are not added.

[0040] Comparative Example 2 Same as Example 1, except that N-PMI is removed.

[0041] Comparative Example 3 Same as Example 1, except that KH-560 is removed.

[0042] Comparative Example 4 Same as Example 1, except that the crosslinking agent BAPT is removed.

[0043] Comparative Example 5 Same as Example 1, except that all crosslinking agents are used in step 2 when preparing the pre-emulsion, and the step 4 of adding crosslinking agents for reaction is omitted.

[0044] Comparative Example 6 Same as Example 1, except that THFA is not added, and its mass fraction is made up by an equal amount of MMA.

[0045] Comparative Example 7 Similar to Example 1, except that all N-PMIs are added in step two, and pre-assembly is not performed in step one.

[0046] The MBS resins obtained in Examples 1-3 and Comparative Examples 1-7 were processed into PVC / MBS blends. The raw materials and formulations are shown in Table 1 below. Table 1 Raw Materials and Formulation

[0047] Detailed preparation process High-speed mixing: Add all raw materials sequentially to the high-speed mixer (SHR-50A type), mix at low speed for 2 minutes, then switch to high speed. During the mixing process, the material temperature automatically rises, controlling the final discharge temperature to 95±2℃, with a total mixing time of 12 minutes. The material is then transferred to a low-speed cold mixer and cooled to below 45℃ before discharge.

[0048] Melt granulation: The cooled mixture is melt-extruded and granulated using a co-rotating parallel twin-screw extruder (TSE-35 type, L / D=40:1). The temperatures for each zone are set as follows: Zone 1 150℃, Zone 2 165℃, Zone 3 175℃, Zone 4 175℃, and the die head 170℃. The screw speed is 200 rpm, and the feed rate is matched with the speed to ensure stable mains current.

[0049] Injection Molding: The extruded granules were placed in a forced-air drying oven and dried at 80±2℃ for 4 hours. Standard specimens conforming to the requirements of various national testing standards were prepared using an injection molding machine (HTF80X2 type). The injection temperature was set as follows: 165℃ for zone 1 of the barrel, 170℃ for zone 2, 175℃ for zone 3, and 170℃ for the nozzle; the mold cooling water temperature was controlled at 40±2℃; the injection pressure and holding pressure were adjusted appropriately according to the specimen filling situation.

[0050] Conditioning: All injection-molded specimens were placed in a standard laboratory environment at 23±2℃ and 50±5% relative humidity for 24 hours before testing. The performance test data of the PVC / MBS blend are shown in Table 2 below. Table 2 Performance Test Data of PVC / MBS Blend Materials

Claims

1. An MBS resin for improving low-temperature tensile strength, characterized in that, It is prepared from the following main raw materials in parts by weight: Butadiene: 62-78 parts; Styrene: 22-38 parts; Methyl methacrylate: 38-52 parts; Butyl acrylate: 6-14 parts; N-Phenylonmaleimide: 3-9 parts; Crosslinking agent: 1,3-bis(3-acryloyloxypropyl)-1,1,3,3-tetramethyldisiloxane, 0.4-1.6 parts; Low-temperature interface activator: silane coupling agent, 0.7-2.3 parts; Auxiliary enhancer monomers: 1-4 parts; It also includes the following adjuvants: Emulsifier: 2.8-4.2% of the total mass of the main raw materials; Initiator: 0.35-0.75% of the total mass of the main raw materials; Molecular weight regulator: 0.07-0.22% of the total mass of the main raw materials; Antioxidant: 0.45-0.85% of the total mass of the main raw materials.

2. The MBS resin for improving low-temperature tensile strength according to claim 1, characterized in that, The silane coupling agent is γ-glycidoxypropyltrimethoxysilane, and the auxiliary reinforcing monomer is tetrahydrofuran acrylate.

3. The MBS resin for improving low-temperature tensile strength according to claim 1, characterized in that, The emulsifier is a compound of sodium dicyclohexyl sulfosuccinate and octylphenol polyoxyethylene ether.

4. The MBS resin for improving low-temperature tensile strength according to claim 1, characterized in that, The initiator is a composite system of ammonium persulfate and tert-butyl hydroperoxide.

5. The MBS resin for improving low-temperature tensile strength according to claim 1, characterized in that, The molecular weight regulator is n-dodecyl mercaptan.

6. The MBS resin for improving low-temperature tensile strength according to claim 1, characterized in that, The antioxidant is a compound of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl) phosphite.

7. A method for preparing MBS resin with improved low-temperature tensile strength according to any one of claims 1 to 6, characterized in that, It is prepared by the following steps: Step 1: Preparation of N-phenylmaleimide pre-assembled styrene-butadiene latex Water, a portion of emulsifier, a low-temperature interface activator, butadiene, styrene, and a molecular weight regulator were added to a reaction vessel for pre-emulsification to obtain a homogeneous emulsion. The temperature was raised, and a portion of N-phenylmaleimide solution was added dropwise. The reaction was then kept at the temperature. In a separate container, the initiator and water were mixed evenly to obtain an initiator solution. A portion of the initiator solution was added to react to obtain N-phenylmaleimide pre-assembled styrene-butadiene latex. Step 2: Preparation of pre-emulsion Methyl methacrylate, butyl acrylate, the remaining N-phenylmaleimide solution, auxiliary reinforcing monomers, and part of the crosslinking agent are mixed evenly to obtain a monomer mixture; the monomer mixture is mixed with part of the initiator solution, and water and the remaining emulsifier are added for emulsification to obtain a stable pre-emulsion; Step 3: Core-shell grafting polymerization The N-phenylmaleimide pre-assembled styrene-butadiene latex was transferred into a reaction vessel and heated to 68.5-69.5℃. Then, the remaining initiator solution was added as a seed initiator. The pre-emulsion was added dropwise in three batches. The first batch of pre-emulsion is added at 35-45% of its total mass, with a dropping time of 120-140 minutes and a temperature controlled at 69-71℃. The second batch of pre-emulsion is added at 35-45% of its total mass, with a dropping time of 100-120 minutes and a temperature controlled at 71-73℃. The third batch of the remaining pre-emulsion is added dropwise over a time of 80-100 minutes at a temperature of 71-73°C. Step 4: Drying the reaction mixture at low temperature After the addition is complete, keep the temperature at 74-78℃, raise the temperature to 83-87℃ and add the remaining crosslinking agent, keep the temperature for reaction, lower the temperature to 46-50℃, add the antioxidant and mix evenly, cool to room temperature, demulsify, filter to separate the solid material, wash, and spray dry to obtain a white powder.

8. The method for preparing MBS resin with improved low-temperature tensile strength according to claim 7, characterized in that, The emulsifier mentioned in step one accounts for 80-85 wt.% of the total emulsifier usage, the N-phenylmaleimide mentioned in step one accounts for 25-35 wt.% of the total N-phenylmaleimide usage, and the initiator mentioned in step one accounts for 35-45 wt.% of the total initiator usage.

9. The method for preparing MBS resin with improved low-temperature tensile strength according to claim 8, characterized in that, The crosslinking agent described in step two accounts for 65-70 wt.% of the total crosslinking agent usage, and the initiator described in step two accounts for 45-55 wt.% of the total initiator usage.

10. The method for preparing MBS resin with improved low-temperature tensile strength according to claim 8, characterized in that, The temperature increase mentioned in step one is to raise the temperature to 62-64℃.

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