High-cold-resistance flame-retardant PC / PBT polyester alloy and preparation method thereof

Abstract

This invention discloses a high cold-resistant and flame-retardant PC / PBT polyester alloy and its preparation method, relating to the field of polymer materials technology. The PC / PBT polyester alloy comprises, by weight: 50-80 parts PC resin, 10-30 parts silicone PC resin, 10-30 parts PBT resin, 3-15 parts main flame retardant, 2-5 parts synergistic flame retardant, 4-8 parts toughening agent, 0.2-0.8 parts anti-low-temperature aging agent, 0.5-2 parts transesterification inhibitor, 1-2 parts compatibilizer, 0.1-1 part antioxidant, and 0.6-1.5 parts composite lubricant. The addition of an anti-low-temperature aging agent to the PC / PBT polyester alloy, which is a compound of hindered amine antioxidants and organophosphate antioxidants, effectively inhibits molecular chain breakage and oxidation reactions under low-temperature conditions, thereby improving the molecular structural stability of the material under low-temperature conditions.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a high cold-resistant and flame-retardant PC / PBT polyester alloy and its preparation method. Background Technology

[0002] PC resin (polycarbonate resin) is a thermoplastic engineering plastic polymerized from bisphenol A and diphenyl carbonate through transesterification. It has excellent transparency, mechanical properties, and heat resistance. PBT resin (polybutylene terephthalate) is a thermoplastic engineering plastic formed by the condensation polymerization of terephthalic acid and 1,4-butanediol. It has a milky white or light yellow appearance and a glossy surface. PC / PBT polyester alloy is a plastic alloy formed by blending polycarbonate (PC) and polybutylene terephthalate (PBT), combining the excellent properties of both. It is widely used in the automotive, electronics, and home appliance industries.

[0003] However, the low-temperature impact performance and flame retardancy of PC and PBT materials still have certain limitations. In some low-temperature environments, the impact strength of PC and PBT decreases significantly, affecting their normal use. In the automotive, electronics, electrical and home appliance industries, some products also require flame retardancy, which ordinary PC and PBT are insufficient to meet. This results in significant limitations in the production of PC / PBT polyester alloys made from PC and PBT materials, making it difficult to meet product needs. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a high cold-resistant and flame-retardant PC / PBT polyester alloy and its preparation method, thus solving the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a high cold-resistant and flame-retardant PC / PBT polyester alloy, wherein the PC / PBT polyester alloy comprises, by weight: 50-80 parts of PC resin, 10-30 parts of silicone PC resin, 10-30 parts of PBT resin, 3-15 parts of main flame retardant, 2-5 parts of synergistic flame retardant, 4-8 parts of toughening agent, 0.2-0.8 parts of low-temperature aging resistant agent, 0.5-2 parts of transesterification inhibitor, 1-2 parts of compatibilizer, 0.1-1 parts of antioxidant, and 0.6-1.5 parts of composite lubricant.

[0006] Preferably, the synergistic flame retardant is nano-magnesium hydroxide modified with a silane coupling agent, and the amount of the silane coupling agent used in the modification treatment is 1% to 3% of the weight of the nano-magnesium hydroxide.

[0007] Preferably, the primary flame retardant is one or two of bromotriazine and phenoxytetrabromobisphenol A carbonate oligomer, and the weight ratio of the primary flame retardant to the synergistic flame retardant is 3:1.

[0008] Preferably, the toughening agent is one or more of the following: silicone-acrylate toughening agents, core-shell butadiene-methyl methacrylate copolymers, and ethylene-butyl acrylate-glycidyl methacrylate terpolymers.

[0009] Preferably, the transesterification inhibitor is one of mono- or di-dodecyl phosphate, and the alkyl carbon chain length in the molecular structure of the transesterification inhibitor is 12-18.

[0010] Preferably, the compatibilizer is one of maleic anhydride-grafted polypropylene or ethylene-butyl acrylate-glycidyl methacrylate terpolymer, and the grafting rate of the compatibilizer is 0.5% to 2%.

[0011] Preferably, the anti-low-temperature aging agent is a mixture of hindered amine antioxidant GW-540 and organophosphate antioxidant 168 in a mass ratio of 1:1, and the composite lubricant is a mixture of polytetrafluoroethylene micro powder and stearic acid amine or pentaerythritol stearate.

[0012] A method for preparing a high cold-resistant and flame-retardant PC / PBT polyester alloy, applicable to the aforementioned high cold-resistant and flame-retardant PC / PBT polyester alloy, the method comprising the following steps:

[0013] The PC resin and the PBT resin are baked at 120°C for 3-4 hours. The synergistic flame retardant and the baked PC resin are pre-dispersed in a high-speed mixer to obtain a pre-dispersed synergistic flame retardant. The anti-low-temperature aging agent, the antioxidant and the composite lubricant are stirred and mixed to prepare a composite additive.

[0014] The baked PBT resin and the toughening agent are added to a twin-screw extruder, and the twin-screw extruder is used to granulate the PBT toughening masterbatch.

[0015] The PBT toughening masterbatch, the pre-dispersed synergistic flame retardant, the composite additive package, the silicone PC resin, the transesterification inhibitor, the main flame retardant, the compatibilizer, and the transesterification inhibitor are stirred and mixed to obtain a mixture;

[0016] The mixture is fed into the twin-screw extruder at a screw speed of 350-400 rpm, and the twin-screw extruder is used for granulation to obtain the PC / PBT polyester alloy granules.

[0017] Preferably, the temperature control settings of the twin-screw extruder are as follows: zone 1-2 temperature is 120-140℃, zone 3-4 temperature is 245-265℃, zone 5-6 temperature is 250-275℃, zone 7-8 temperature is 240-270℃, zone 9-10 temperature is 235-270℃, zone 11-12 temperature is 235-245℃, and zone 13-14 temperature is 235-245℃; the die head temperature of the twin-screw extruder is 255-265℃.

[0018] Preferably, when the high-speed mixer mixes and disperses the synergistic flame retardant and the PC resin, it is stirred at a speed of 3000 rpm for 5 minutes, and the stirring speed of the anti-low temperature aging agent, the antioxidant, and the composite lubricant is 1500 rpm for 10 minutes.

[0019] This invention provides a high cold-resistant and flame-retardant PC / PBT polyester alloy and its preparation method. It has the following beneficial effects:

[0020] (1) A low-temperature aging agent was added to the PC / PBT polyester alloy. This low-temperature aging agent is composed of hindered amine antioxidants and organophosphate antioxidants. It can effectively inhibit the breakage and oxidation reaction of molecular chains under low temperature conditions, improve the molecular structure stability of the material under low temperature conditions, and at the same time, by optimizing the dispersibility and interfacial compatibility of the toughening agent, the material can still maintain good toughness and impact resistance under low temperature conditions, avoiding the embrittlement and cracking problems that are prone to occur in ordinary PC / PBT polyester alloys at low temperatures.

[0021] (2) Nano-magnesium hydroxide modified with silane coupling agent is used as a synergistic flame retardant, which significantly improves the compatibility and dispersibility with PC / PBT matrix and effectively inhibits the migration and precipitation of flame retardant during long-term use. This synergistic flame retardant not only enhances the initial flame retardant effect of the material, but also ensures the long-term stability of flame retardant performance in complex environments such as humid heat and high temperature through the dual effects of physical barrier and chemical flame retardant.

[0022] (3) The introduction of composite lubricant, through the synergistic effect of polytetrafluoroethylene micro powder and traditional lubricant, effectively reduces melt viscosity without reducing material mechanical properties, improves the flow characteristics of alloy in molten state, and optimizes lubrication effect so that melt flow is more uniform and stable during twin-screw extrusion and injection molding, significantly reduces molding defects such as melt fracture, surface shrinkage and blemishes, and improves surface gloss and dimensional accuracy of products. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the preparation steps of a high cold-resistant and flame-retardant PC / PBT polyester alloy and its preparation method according to the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0025] Please see Figure 1 This invention provides a high cold-resistant and flame-retardant PC / PBT polyester alloy and its preparation method. To achieve the above objectives, this invention is implemented through the following technical solution: The PC / PBT polyester alloy comprises, by weight, 50-80 parts of PC resin, 10-30 parts of silicone PC resin, 10-30 parts of PBT resin, 3-15 parts of main flame retardant, 2-5 parts of synergistic flame retardant, 4-8 parts of toughening agent, 0.2-0.8 parts of anti-low-temperature aging agent, 0.5-2 parts of transesterification inhibitor, 1-2 parts of compatibilizer, 0.1-1 parts of antioxidant, and 0.6-1.5 parts of composite lubricant.

[0026] The PC resin is bisphenol A aromatic polycarbonate (300℃ / 1.2kg) with MI=6~10, the PBT resin is polybutylene terephthalate with a viscosity of 1.0-1.2, and the silicone PC resin is silicone copolycarbonate with a silicone content of 15%~26%.

[0027] The synergistic flame retardant is nano-magnesium hydroxide with surface modification of silane coupling agent. The amount of silane coupling agent used in the modification treatment is 1% to 3% of the weight of nano-magnesium hydroxide.

[0028] The main flame retardant is one or two of the following: bromotriazine, phenoxytetrabromobisphenol A carbonate oligomer, and brominated polystyrene, and the weight ratio of the main flame retardant to the synergistic flame retardant is 3:1.

[0029] The toughening agent is one or more of the following: silicone-acrylate toughening agents, core-shell butadiene-methyl methacrylate copolymer, and ethylene-butyl acrylate-glycidyl methacrylate terpolymer.

[0030] The transesterification inhibitor is one of mono- or di-dodecyl phosphate, and the alkyl carbon chain length in the molecular structure of the transesterification inhibitor is 12-18.

[0031] The compatibilizer is one of maleic anhydride-grafted polypropylene or ethylene-butyl acrylate-glycidyl methacrylate terpolymer, and the grafting rate of the compatibilizer is 0.5% to 2%.

[0032] The low-temperature aging resistant agent is a mixture of hindered amine antioxidant GW-540 and organophosphate antioxidant 168 in a mass ratio of 1:1. The composite lubricant is a mixture of polytetrafluoroethylene micro powder and stearic acid amine or pentaerythritol stearate.

[0033] The preparation method of PC / PBT polyester alloy includes the following steps:

[0034] PC resin and PBT resin were baked at 120℃ for 3-4 hours. The synergistic flame retardant was pre-dispersed with the baked PC resin in a high-speed mixer to obtain the pre-dispersed synergistic flame retardant. The low-temperature aging agent, antioxidant and composite lubricant were stirred and mixed to prepare the composite additive.

[0035] The baked PBT resin and toughening agent are added to a twin-screw extruder, and the twin-screw extruder is used to granulate the PBT toughening masterbatch.

[0036] PBT toughening masterbatch, pre-dispersed synergistic flame retardant, composite additive package, silicone PC resin, transesterification inhibitor, main flame retardant, compatibilizer and transesterification inhibitor are stirred and mixed to obtain a mixture;

[0037] The mixture is fed into a twin-screw extruder at a screw speed of 350-400 rpm, and granulated by extrusion to obtain PC / PBT polyester alloy granules.

[0038] The temperature control settings for the twin-screw extruder are as follows: Zones 1-2: 120-140℃; Zones 3-4: 245-265℃; Zones 5-6: 250-275℃; Zones 7-8: 240-270℃; Zones 9-10: 235-270℃; Zones 11-12: 235-245℃; Zones 13-14: 235-245℃; and the die head temperature is 255-265℃.

[0039] When mixing the synergistic flame retardant and PC resin in a high-speed mixer, stir at 3000 rpm for 5 minutes. The stirring speed for the low-temperature aging agent, antioxidant, and composite lubricant is 1500 rpm, and the stirring time is 10 minutes.

[0040] By adjusting the ratio of PC to PBT, a PC / PBT blend with excellent low-temperature impact performance can be obtained. Melt blending using a twin-screw extruder ensures uniform dispersion of PBT and toughening agents, producing a PBT toughening masterbatch. PC, PBT toughening masterbatch, flame retardant, toughening agent, and other additives are then uniformly mixed under twin-screw extrusion conditions to improve the dispersibility of the blend. This PC / PBT ratio enables the PBT polyester alloy to exhibit advantages such as high impact resistance at low temperatures, good flame retardancy, and good surface gloss. It has a wide range of applications, and the preparation method is low-cost and highly efficient, making it suitable for industrial production. Example

[0041] The PC / PBT polyester alloy comprises the following raw materials by weight: 60 parts PC resin (bisphenol A aromatic polycarbonate), 10 parts silicone PC resin (silicone copolycarbonate), 20 parts PBT resin (polybutylene terephthalate), 12 parts main flame retardant (bromotriazine), 4 parts synergistic flame retardant (silane coupling agent modified nano magnesium hydroxide, modification amount 2%), 4 parts toughening agent (silicone-acrylate toughening agent), 0.5 parts low-temperature aging resistant agent (GW-540 and 168 compounded, 1:1), 1 part transesterification inhibitor (monododecyl phosphate), 1.5 parts compatibilizer (maleic anhydride grafted polypropylene, grafting rate 1%), 0.5 parts antioxidant, and 1 part composite lubricant (polytetrafluoroethylene micro powder and stearic acid amine compounded).

[0042] The preparation method of PC / PBT polyester alloy specifically includes the following steps:

[0043] PC resin and PBT resin were baked at 120℃ for 3 hours. The synergistic flame retardant was pre-dispersed with the baked PC resin in a high-speed mixer and stirred at 3000 rpm for 5 minutes to obtain the pre-dispersed synergistic flame retardant. The low-temperature aging agent, antioxidant and composite lubricant were stirred and mixed at 1500 rpm for 10 minutes to prepare the composite compound additive.

[0044] The baked PBT resin and toughening agent are added to a twin-screw extruder, and the twin-screw extruder is used to granulate the PBT toughening masterbatch.

[0045] PBT toughening masterbatch, pre-dispersed synergistic flame retardant, composite additive package, silicone PC resin, transesterification inhibitor, main flame retardant, compatibilizer and transesterification inhibitor are stirred and mixed to obtain a mixture;

[0046] The mixture is fed into a twin-screw extruder at a screw speed of 380 rpm. The temperatures for zones 1-2 are set to 130℃, zones 3-4 to 255℃, zones 5-6 to 265℃, zones 7-8 to 255℃, zones 9-10 to 250℃, zones 11-12 to 240℃, and zones 13-14 to 240℃. The die temperature of the twin-screw extruder is set to 260℃. The mixture is extruded and granulated to obtain PC / PBT polyester alloy granules. Example

[0047] PC / PBT polyester alloy comprises the following raw materials by weight: 55 parts PC resin, 15 parts silicone PC resin, 20 parts PBT resin, 12 parts main flame retardant, 4 parts synergistic flame retardant, 4 parts toughening agent, 0.5 parts low-temperature aging resistant agent, 1 part transesterification inhibitor, 1.5 parts compatibilizer, 0.5 parts antioxidant, and 1 part composite lubricant.

[0048] The difference from Example 1 is that the proportion of raw material components is adjusted, but the preparation process is the same as that of Example 1. Example

[0049] The PC / PBT polyester alloy comprises the following raw materials by weight: 60 parts PC resin, 10 parts silicone PC resin, 20 parts PBT resin, 12 parts main flame retardant, 4 parts synergistic flame retardant, 4 parts toughening agent (core-shell structured butadiene-methyl methacrylate copolymer), 0.5 parts anti-low temperature aging agent, 1 part transesterification inhibitor, 1.5 parts compatibilizer, 0.5 parts antioxidant, and 1 part composite lubricant.

[0050] The difference from Example 1 is that the type of toughening agent is adjusted, while the other components and preparation process are the same as in Example 1. Example

[0051] The PC / PBT polyester alloy comprises the following raw materials by weight: 60 parts PC resin, 10 parts silicone PC resin, 20 parts PBT resin, 12 parts main flame retardant (phenoxytetrabromobisphenol A carbonate oligomer), 4 parts synergistic flame retardant, 4 parts toughening agent, 0.5 parts anti-low temperature aging agent, 1 part transesterification inhibitor, 1.5 parts compatibilizer, 0.5 parts antioxidant, and 1 part composite lubricant.

[0052] The difference from Example 1 is that the type of main flame retardant is adjusted, while the remaining components and preparation process are the same as in Example 1. Example

[0053] PC / PBT polyester alloy comprises the following raw materials by weight: 60 parts PC resin, 10 parts silicone PC resin, 20 parts PBT resin, 12 parts main flame retardant, 4 parts synergistic flame retardant, 4 parts toughening agent, 0.5 parts low-temperature aging resistant agent, 1 part transesterification inhibitor, 1.5 parts compatibilizer, 0.5 parts antioxidant, and 1 part composite lubricant.

[0054] The difference from Example 1 lies in adjusting the parameters of the twin-screw extruder in the process. Specifically, the screw speed is 350 rpm, the temperature of zone 1-2 is set to 120°C, the temperature of zone 3-4 is 245°C, the temperature of zone 5-6 is 250°C, the temperature of zone 7-8 is 240°C, the temperature of zone 9-10 is 235°C, the temperature of zone 11-12 is 235°C, and the temperature of zone 13-14 is 235°C. The die temperature of the twin-screw extruder is 255°C. The remaining components and processes are the same as in Example 1.

[0055] Comparative Example 1

[0056] PC / PBT polyester alloy comprises the following raw materials by weight: 60 parts PC resin, 10 parts silicone PC resin, 20 parts PBT resin, 12 parts main flame retardant, 4 parts synergistic flame retardant, 0.5 parts low-temperature aging resistant agent, 1 part transesterification inhibitor, 1.5 parts compatibilizer, 0.5 parts antioxidant, and 1 part composite lubricant.

[0057] The difference from Example 1 is that no toughening agent was added, while the remaining components and preparation process are the same as in Example 1.

[0058] Comparative Example 2

[0059] PC / PBT polyester alloy comprises the following raw materials by weight: 60 parts PC resin, 10 parts silicone PC resin, 20 parts PBT resin, 8 parts main flame retardant, 4 parts synergistic flame retardant, 4 parts toughening agent, 0.5 parts low-temperature aging resistant agent, 1 part transesterification inhibitor, 1.5 parts compatibilizer, 0.5 parts antioxidant, and 1 part composite lubricant.

[0060] The difference from Example 1 is that the ratio of the main flame retardant to the synergistic flame retardant is adjusted to 2:1, while the remaining components and preparation process are the same as in Example 1.

[0061] Comparative Example 3

[0062] The PC / PBT polyester alloy comprises the following raw materials by weight: 60 parts PC resin, 10 parts silicone PC resin, 20 parts PBT resin, 12 parts main flame retardant, 4 parts synergistic flame retardant, 4 parts toughening agent, 1 part transesterification inhibitor, 1.5 parts compatibilizer, 0.5 parts antioxidant, and 1 part composite lubricant.

[0063] The difference from Example 1 is that no anti-low-temperature aging agent was added, while the remaining components and preparation process are the same as in Example 1.

[0064] Comparative Example 4

[0065] PC / PBT polyester alloy comprises the following raw materials by weight: 60 parts PC resin, 10 parts silicone PC resin, 20 parts PBT resin, 12 parts main flame retardant, 4 parts synergistic flame retardant, 4 parts toughening agent, 0.5 parts low-temperature aging resistant agent, 1 part transesterification inhibitor, 0.5 parts antioxidant, and 1 part composite lubricant.

[0066] The difference from Example 1 is that no compatibilizer was added, while the remaining components and preparation process are the same as in Example 1.

[0067] Test case

[0068] Test content and methods

[0069] Mechanical property testing

[0070] Tensile strength: The size of the specimen is strictly set to 150mm×10mm×4mm. During the test, a tensile force is applied to the specimen at a constant tensile speed of 50mm / min until the specimen breaks. The maximum tensile force value is recorded and used to calculate the tensile strength. The formula for calculating the tensile strength is σ=F / A (where F is the maximum tensile force and A is the original cross-sectional area).

[0071] Bending strength: The specimen size is determined to be 80mm×10mm×4mm, the span is set to 64mm, and a bending force is applied to the specimen at a speed of 2mm / min until the specimen reaches the specified bending degree or fails. The bending strength is calculated by the recorded data.

[0072] Notched impact strength: The specimen size is 80mm×10mm×4mm, and the notch depth is precisely machined to 2mm. The test is carried out at ambient temperatures of 23℃ and -40℃ respectively. The specimen is placed on an impact testing machine and impacted with a specified pendulum. The energy absorbed when the specimen breaks is recorded, and the notched impact strength is calculated.

[0073] Table 1 shows the test results of the mechanical properties of PC / PBT polyester alloy materials.

[0074]

[0075] Flame retardant performance test

[0076] UL-94 Vertical Burning Test: The specimen dimensions are 125mm × 13mm × 1.6mm. The specimen is vertically fixed on the test apparatus, and the bottom of the specimen is ignited using a Bunsen burner with a specific flame height (20±1mm) for 10±0.5s. After ignition, the Bunsen burner is removed, and the afterflame time t1 and afterburner time t3 are recorded. The specimen is then re-ignited for 10±0.5s, and the afterflame time t2 is recorded after the Bunsen burner is removed. The flame retardancy rating of the specimen is determined according to the V-0, V-1, and V-2 rating criteria specified in the standard.

[0077] Oxygen Index (LOI): The sample size is 80mm×10mm×4mm. The sample is installed in the oxygen index tester. By adjusting the mixing ratio of oxygen and nitrogen, the mixed gas flows through the sample at a specified flow rate. The sample is ignited with an ignition source, and the combustion of the sample is observed. The oxygen concentration is gradually changed until the lowest oxygen concentration that can just maintain the stable combustion of the sample is found. This oxygen concentration is the oxygen index.

[0078] Table 2 shows the test results of the flame retardant properties of PC / PBT polyester alloy materials.

[0079]

[0080] Thermal performance test

[0081] Heat distortion temperature (HDT): The sample size is 80mm×10mm×4mm. Under the load of 1.82MPa, the sample is placed in a heat distortion temperature tester and heated at a certain heating rate. The deformation of the sample is observed. When the sample reaches the specified deformation, the temperature at this time is recorded, which is the heat distortion temperature.

[0082] Melt Flow Index (MI): Under a temperature of 260℃ and a load of 2.16 kg, a certain amount of sample is added to the barrel of the melt flow indexer. After preheating, the sample is melted under a specified temperature and load and extruded through a standard die. The extruded material is collected within a certain time, and the melt flow index is calculated by measuring the mass of the extruded material.

[0083] Table 3 shows the thermal performance test results of PC / PBT polyester alloy materials.

[0084]

[0085] As shown in Tables 1 to 3, Example 1 exhibits a tensile strength of 65.86 MPa and a flexural strength of 90.46 MPa, demonstrating excellent structural load-bearing capacity. Even at an extreme low temperature of -40℃, its notched impact strength still reaches 61.42 kJ / m². 2 It exhibits excellent low-temperature toughness, achieves a flame retardant rating of V-0, and has an oxygen index of 28.24%, indicating good flame retardant properties. The heat distortion temperature is 130℃, indicating that the material can maintain good dimensional stability at high temperatures. Under these optimal composition and process conditions, the prepared PC / PBT polyester alloy has good comprehensive performance and can meet the needs of various application scenarios.

[0086] In Example 2, increasing the content of silicone PC resin slightly decreased the tensile and flexural strengths, while other properties remained largely unchanged, indicating that adjusting the silicone PC resin within a certain range has little impact on performance. In Example 3, changing the type of toughening agent slightly decreased the performance but kept it basically stable, indicating that different toughening agents have a certain degree of compatibility and synergistic effect in this system. In Example 4, adjusting the type of main flame retardant slightly decreased the flame retardant performance and oxygen index, but still met the V-0 rating, indicating that there are differences in the flame retardant efficiency of different main flame retardants. In Example 6, adjusting the process parameters slightly increased the melt flow index and decreased the heat distortion temperature, indicating that process parameters with low rotation speed and lower temperature have a certain impact on the thermal properties of the alloy.

[0087] Comparative Example 1, without toughening agent, had a notched impact strength of only 30.47 kJ / m² at -40°C, compared to Example 1 (61.42 kJ / m²). 2 The low-temperature impact strength decreased by 50.4%, while in Examples 1-5, different toughening agents such as silicone-acrylate and core-shell butadiene-methyl methacrylate copolymer were used respectively, and the low-temperature impact strength was maintained above 57 kJ / m². This shows that the toughening agent can significantly improve the low-temperature toughness of the material by optimizing the dispersibility and interfacial compatibility, and different types of toughening agents have good compatibility in this system with little difference in performance.

[0088] When the main flame retardant and synergistic flame retardant in Examples 1-5 were mixed in a 3:1 ratio, the UL-94 rating was V-0 and the oxygen index was ≥26.88%. However, when the ratio in Comparative Example 2 was adjusted to 2:1, the flame retardant rating dropped to V-2 and the oxygen index was only 22.12%, resulting in a significant decline in flame retardant performance. At the same time, the synergistic flame retardant (silane coupling agent modified nano magnesium hydroxide) can improve the compatibility with the matrix, prevent the migration and precipitation of the flame retardant, and further ensure long-term flame retardant stability.

[0089] Comparative Example 3, without the addition of anti-low-temperature aging agent, had a notched impact strength of 45.86 kJ / m² at -40°C, which was 25.3% lower than that of Example 1. However, Examples 1-5, after adding the anti-low-temperature aging agent of "hindered amine GW-540 + organophosphate 168 (1:1)", could effectively inhibit molecular chain breakage and oxidation reaction at low temperature, significantly improve molecular structure stability, and ensure low-temperature mechanical properties.

[0090] Comparative Example 4, without compatibilizer, exhibited a tensile strength of 55.32 MPa, a flexural strength of 75.71 MPa, and a notched impact strength at -40°C of 35.22 kJ / m², which were 16.0%, 16.3%, and 42.7% lower than those of Example 1, respectively. This indicates that the compatibilizer can improve the interfacial compatibility between PC and PBT, reduce phase separation, and thus enhance the overall mechanical properties of the material.

[0091] This high cold-resistant and flame-retardant PC / PBT polyester alloy combines excellent low-temperature toughness (impact strength ≥60kJ / m² at -40℃), high flame retardancy (V-0 grade), good thermal stability (heat distortion temperature ≥125℃), and good formability (melt index ≥14g / 10min). It can meet the needs of automobiles (parts in low-temperature environments), electronics and electrical appliances (housing and connectors with high flame retardancy requirements), and home appliances (structural parts that need to balance toughness and heat resistance). Moreover, the manufacturing process is low-cost and efficient, and has the potential for industrial production.

[0092] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A high cold-resistant and flame-retardant PC / PBT polyester alloy, characterized in that: The PC / PBT polyester alloy comprises, by weight: 50-80 parts PC resin, 10-30 parts silicone PC resin, 10-30 parts PBT resin, 3-15 parts main flame retardant, 2-5 parts synergistic flame retardant, 4-8 parts toughening agent, 0.2-0.8 parts anti-low-temperature aging agent, 0.5-2 parts transesterification inhibitor, 1-2 parts compatibilizer, 0.1-1 part antioxidant, and 0.6-1.5 parts composite lubricant; The synergistic flame retardant is nano-magnesium hydroxide modified with a silane coupling agent, and the amount of the silane coupling agent used in the modification treatment is 1% to 3% of the weight of the nano-magnesium hydroxide; The main flame retardant is one or two of bromotriazine and phenoxytetrabromobisphenol A carbonate oligomer, and the weight ratio of the main flame retardant to the synergistic flame retardant is 3:

1. The toughening agent is one or more of the following: silicone-acrylate toughening agents, core-shell butadiene-methyl methacrylate copolymer, and ethylene-butyl acrylate-glycidyl methacrylate terpolymer. The transesterification inhibitor is one of mono-dodecyl phosphate or di-dodecyl phosphate; The compatibilizer is one of maleic anhydride-grafted polypropylene or ethylene-butyl acrylate-glycidyl methacrylate terpolymer, and the grafting rate of the compatibilizer is 0.5% to 2%. The low-temperature aging resistant agent is a mixture of hindered amine antioxidant GW-540 and organophosphate antioxidant 168 in a mass ratio of 1:

1. The composite lubricant is a mixture of polytetrafluoroethylene micro powder and stearic acid amine or pentaerythritol stearate.

2. A method for preparing a high cold-resistant and flame-retardant PC / PBT polyester alloy, applied to the high cold-resistant and flame-retardant PC / PBT polyester alloy as described in claim 1, characterized in that: The preparation method of the PC / PBT polyester alloy includes the following steps: The PC resin and the PBT resin are baked at 120°C for 3-4 hours. The synergistic flame retardant and the baked PC resin are pre-dispersed in a high-speed mixer to obtain a pre-dispersed synergistic flame retardant. The anti-low-temperature aging agent, the antioxidant and the composite lubricant are stirred and mixed to prepare a composite additive. The baked PBT resin and the toughening agent are added to a twin-screw extruder, and the twin-screw extruder is used to granulate the PBT toughening masterbatch. The PBT toughening masterbatch, the pre-dispersed synergistic flame retardant, the composite mixing additive, the silicone PC resin, the transesterification inhibitor, the main flame retardant, the compatibilizer, and the transesterification inhibitor are stirred and mixed to obtain a mixture; The mixture is fed into the twin-screw extruder at a screw speed of 350-400 rpm, and the twin-screw extruder is used for granulation to obtain the PC / PBT polyester alloy granules.

3. The method for preparing a high cold-resistant and flame-retardant PC / PBT polyester alloy according to claim 2, characterized in that: The temperature control settings of the twin-screw extruder are as follows: zone 1-2: 120-140℃; zone 3-4: 245-265℃; zone 5-6: 250-275℃; zone 7-8: 240-270℃; zone 9-10: 235-270℃; zone 11-12: 235-245℃; and zone 13-14: 235-245℃. The die head temperature of the twin-screw extruder is 255-265℃.

4. The method for preparing a high cold-resistant and flame-retardant PC / PBT polyester alloy according to claim 2, characterized in that: When the high-speed mixer mixes and disperses the synergistic flame retardant and the PC resin, it is stirred at a speed of 3000 rpm for 5 minutes. The stirring speed of the anti-low temperature aging agent, the antioxidant, and the composite lubricant is 1500 rpm, and the stirring time is 10 minutes.

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