Polyester composition as well as preparation method and application thereof

Abstract

The invention discloses a polyester composition and a preparation method and application thereof, and belongs to the technical field of high polymer materials, the polyester composition comprises the following components by weight: 18-62 parts of polyester resin, 9-42 parts of glass fiber, 8-21 parts of a flame retardant, 0.4-5.5 parts of a nanotube material, 0-1.2 parts of a lubricant, and 0-1.2 parts of an antioxidant; the nanotube material comprises a first carbon nanotube and a second carbon nanotube in a weight ratio of (0.6-2.2): 1; the average length of the first carbon nanotubes is 0.5 to 10 [mu] m; and the average length of the second carbon nanotubes is 50-250 [mu] m. The polyester composition disclosed by the invention has excellent low-temperature resistance, has excellent ductility and toughness at low temperature, is suitable for preparing automobile parts and electronic and electrical parts, and is particularly suitable for preparing the automobile parts and the electronic and electrical parts with metal insert structures.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to a polyester composition and a preparation method and application thereof. BACKGROUND

[0002] As common engineering plastics, polyester materials such as polybutylene terephthalate (PBT) and polyethylene terephthalate (PET) are widely used in the fields of electronics, lighting, household appliances and automobiles after modification due to excellent processing performance, solvent resistance, electrical properties and heat resistance. PBT and PET both exhibit poor ductility at low temperatures, and are prone to cracking in the application scenario of plastic-coated metal, showing poor low-temperature resistance of the polyester-modified composition.

[0003] At present, the methods for improving the low-temperature resistance of polyester materials mainly include copolymerization modification, blending modification and addition of plasticizers. Copolymerization modification improves the low-temperature resistance of polyester materials by introducing flexible segments, but may affect the thermal stability and mechanical properties of polyester materials; for example, patent CN102115533A discloses a polyester elastomer with mixed soft segment low-temperature resistance and a preparation method thereof, which improves the elasticity and low-temperature resistance of the polyester material by introducing polydimethylsiloxane with more flexible molecular chains, but affects the mechanical properties and thermal stability of the polyester material; although the addition of plasticizers can improve the flexibility of the material, the plasticizers are prone to migration and precipitation, affecting the long-term performance of the material, for example, CN106632981A discloses a three-component low-temperature-resistant polyester-based polyurethane elastomer and a preparation method thereof, which improves the low-temperature resistance of the material by adding 988-SG plasticizer, which tends to form a glass body or super-cooled liquid at-30℃, and cannot be used at low temperatures below-30℃, and has the risk of migration and precipitation at high temperatures; therefore, how to improve the low-temperature resistance of polyester materials has become a technical problem to be solved by those skilled in the art. SUMMARY

[0004] The purpose of the present application is to overcome the deficiencies in the prior art and provide a polyester composition, a preparation method and application thereof. The polyester composition disclosed by the present application has excellent low-temperature resistance, and the polyester composition has excellent ductility and toughness at low temperatures.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: A polyester composition, comprising the following components by weight: 18-62 parts of polyester resin, 9-42 parts of glass fiber, 8-21 parts of flame retardant, 0.4-5.5 parts of nanotube material, 0-1.2 parts of lubricant, 0-1.2 parts of antioxidant; The nanotube material comprises the first carbon nanotube and the second carbon nanotube in a weight ratio of (0.6-2.2):1; the average length of the first carbon nanotube is 0.5-10 μm; and the average length of the second carbon nanotube is 50-250 μm.

[0006] The application creatively combines the above raw materials to obtain a polyester composition with excellent low-temperature resistance by taking polyester resin as a matrix and under the joint action of glass fiber, flame retardant, nanotube material, lubricant and antioxidant.

[0007] The first carbon nanotube (short carbon nanotube) can enhance interface bonding and disperse stress, and the high specific surface area and dispersibility of the short carbon nanotube help to uniformly distribute stress, avoid local crack propagation of the material, and thus improve the toughness at low temperature; the second carbon nanotube (long carbon nanotube) provides high strength and rigidity, forms a more stable micro support structure; the nanometer reinforcing effect of the glass fiber and the carbon nanotube is combined, which can be more uniformly dispersed in the system, avoid agglomeration, reduce stress concentration, form a three-dimensional network structure in the polyester composition, effectively disperse stress at low temperature, delay or reduce the occurrence of embrittlement at low temperature, reduce crack propagation caused by low temperature, enhance the polyester resin from the micro-nano scale, and effectively improve the ductility and toughness of the polyester composition at low temperature.

[0008] The polyester resin is used in an amount of 18-62 parts, for example, 18 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 62 parts or a range formed by any two of the above values.

[0009] Preferably, the polyester resin is used in an amount of 20-60 parts.

[0010] Preferably, the polyester resin comprises at least one of PBT (polybutylene terephthalate), PET (polyethylene terephthalate), PETG (polyethylene terephthalate-1,4-cyclohexane dimethyl ester), PCT (poly-1,4-cyclohexane dimethyl terephthalate), and PCTG (polyethylene-1,4-cyclohexane dimethyl terephthalate).

[0011] The glass fiber is preferably used in an amount of 9 to 42 parts, for example, 9 parts, 10 parts, 15 parts, 18 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 42 parts, or a range defined by any two of them.

[0012] The glass fiber is preferably used in an amount of 10 to 40 parts.

[0013] The flame retardant is preferably used in an amount of 8 to 21 parts, for example, 8 parts, 9 parts, 10 parts, 12 parts, 14 parts, 15 parts, 16 parts, 18 parts, 20 parts, 21 parts, or a range defined by any two of them.

[0014] The flame retardant is preferably used in an amount of 9 to 20 parts.

[0015] The nanotube material is preferably used in an amount of 0.4 to 5.5 parts, for example, 0.4 parts, 0.5 parts, 0.8 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, or a range defined by any two of them.

[0016] The nanotube material is preferably used in an amount of 0.5 to 5 parts.

[0017] The nanotube material preferably has a weight percentage content of 0.2 to 10% in the polyester composition, for example, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range defined by any two of them.

[0018] The nanotube material preferably has a weight percentage content of 0.4 to 7.5% in the polyester composition.

[0019] The nanotube material preferably has a weight percentage content of 0.5 to 6% in the polyester composition.

[0020] The lubricant is preferably used in an amount of 0 to 1.2 parts, for example, 0 parts, 0.1 parts, 0.2 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.8 parts, 1 part, 1.2 parts, or a range defined by any two of them.

[0021] The lubricant is preferably used in an amount of 0 to 1 part.

[0022] The antioxidant is preferably used in an amount of 0 to 1.2 parts, for example, 0 parts, 0.1 parts, 0.2 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.8 parts, 1 part, 1.2 parts, or a range defined by any two of them.

[0023] Preferably, the amount of antioxidant used is 0 to 1 part.

[0024] In the polyester composition, the polyester resin has a weight percentage of not less than 25%.

[0025] Preferably, in the polyester composition, the polyester resin has a weight percentage of 25-65%, for example, it can be 25%, 28%, 30%, 32%, 35%, 36%, 38%, 40%, 42%, 45%, 46%, 48%, 50%, 55%, 60%, 65% or any two of these values.

[0026] Preferably, the PBT resin in the polyester composition has a weight percentage of 27-65%.

[0027] Preferably, the PBT resin in the polyester composition has a weight percentage of 30-55%.

[0028] Preferably, the polyester composition comprises the following components in parts by weight: 20-60 parts polyester resin, 10-40 parts glass fiber, 9-20 parts flame retardant, 0.5-5 parts nanotube material, 0-1 part lubricant, and 0-1 part antioxidant.

[0029] Preferably, the polyester composition comprises the following components in parts by weight: 30-50 parts polyester resin, 20-30 parts glass fiber, 12-18 parts flame retardant, 2-4 parts nanotube material, 0.4-0.8 parts lubricant, and 0.4-0.8 parts antioxidant. In particular, when the amount of each raw material is within this range, the toughness and ductility of the polyester composition at low temperatures can be improved more significantly.

[0030] Preferably, the average diameter of the first carbon nanotube is 4~50nm, for example, it can be 4nm, 5nm, 6nm, 8nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm or any two of these values.

[0031] Preferably, the average diameter of the first carbon nanotube is 10~30 nm.

[0032] Preferably, the average diameter of the second carbon nanotube is 7~12nm, for example, it can be 7nm, 8nm, 9nm, 10nm, 11nm, 12nm or any two of these values.

[0033] The average diameter and average length of the carbon nanotubes can be confirmed using a two-dimensional optical microscope. At least 100 carbon nanotubes are collected, and the average diameter and length are determined using measurement software.

[0034] Preferably, the intrinsic viscosity of the polyester resin is 0.6~1.4 dl / g, for example, it can be 0.6 dl / g, 0.7 dl / g, 0.8 dl / g, 0.9 dl / g, 1 dl / g, 1.1 dl / g, 1.2 dl / g, 1.3 dl / g, 1.4 dl / g or any two of these values. The intrinsic viscosity of the polyester resin is tested according to Method A (capillary viscometer method) in GB / T14190-2017.

[0035] Preferably, the intrinsic viscosity of the polyester resin is 0.8~1 dl / g.

[0036] Preferably, the polyester includes at least one of PBT resin and PET resin.

[0037] Preferably, the average diameter of the glass fiber is 10~17μm, for example, it can be 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm or any two of these values.

[0038] Preferably, the average diameter of the glass fiber is 13~14μm.

[0039] Preferably, the average length of the glass fiber is 3 to 4.5 mm, for example, it can be 3 mm, 3.2 mm, 3.5 mm, 3.8 mm, 4 mm, 4.2 mm, 4.5 mm or any two of these values.

[0040] The average diameter and average length of the glass fiber can be confirmed using the two-dimensional method of optical microscopy. At least 100 glass fibers are collected, and the diameter and length are determined by measurement software. Finally, the average value is calculated.

[0041] Preferably, the flame retardant comprises a brominated flame retardant and an antimony flame retardant in a weight ratio of (2~9):1, for example, it can be a range of 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or any two of these values.

[0042] Preferably, the flame retardant comprises a brominated flame retardant and an antimony flame retardant in a weight ratio of (3~8):1.

[0043] Preferably, the brominated flame retardant includes at least one of tetrabromobisphenol A, brominated triazine, brominated epoxy resin, decabromodiphenyl ethane, decabromodiphenyl ether, brominated polyimide, brominated polystyrene, polybrominated styrene, brominated polycarbonate, and brominated polyacrylate.

[0044] Preferably, the antimony-based flame retardant includes at least one of antimony trioxide, antimony pentoxide, and sodium antimonate.

[0045] Preferably, the lubricant comprises at least one of aliphatic carboxylic acid esters, erucamide, ethylene bis-stearamide, montan esters, polyethylene wax, and oxidized polyethylene wax.

[0046] The aliphatic carboxylic acid esters include at least one of ethylene glycol stearate and pentaerythritol stearate.

[0047] Preferably, the antioxidant includes at least one of thioester antioxidants, hindered phenolic antioxidants, hydroxylamine antioxidants, phosphite antioxidants, and phosphate antioxidants.

[0048] Preferably, the thioester antioxidant includes at least one of dialkyl thiodipropionate or pentaerythritol tetra(3-lauryl thiopropionate).

[0049] Preferably, the hindered phenolic antioxidant comprises at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, vinyl bis(oxyvinyl)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate] or 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane.

[0050] Preferably, the hydroxylamine antioxidant includes bis(octadecyl)hydroxylamine.

[0051] Preferably, the phosphite antioxidant includes at least one of tris(2,4-di-tert-butylphenyl) phosphite and pentaerythritol dibis(2,4-tert-butylphenyl) phosphite.

[0052] Preferably, the phosphate antioxidant includes bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate.

[0053] The polyester composition of the present invention may include antioxidants, and suitable antioxidants may include, but are not limited to, thioester antioxidants, hindered phenolic antioxidants, hydroxylamine antioxidants, phosphite antioxidants, phosphate antioxidants, and combinations thereof.

[0054] Preferably, the polyester composition of the present invention may further include at least one of mineral powder, colorant, weathering agent, antistatic agent, ultraviolet absorber, and processing aid.

[0055] The polyester composition of the present invention may include colorants, and suitable colorants include, but are not limited to, carbon black, titanium dioxide, zinc sulfide, iron oxide red, titanium yellow, bismuth yellow, and combinations thereof.

[0056] The polyester composition of the present invention may include weathering agents, and suitable weathering agents include, but are not limited to, hindered amine light stabilizers.

[0057] The polyester composition of the present invention may include an antistatic agent, and suitable antistatic agents include, but are not limited to, zinc oxide, manganese dioxide, chromium trioxide, and combinations thereof.

[0058] The polyester composition of the present invention may include ultraviolet light absorbers, suitable ultraviolet light absorbers including but not limited to hydroxybenzophenones, benzotriazoles, hydroxybenzotriazines, cyanoacrylates, nanoscale inorganic materials (e.g., titanium oxide, cerium oxide, and zinc oxide), and combinations thereof.

[0059] The polyester composition of the present invention can be processed with aids, and suitable processing aids include, but are not limited to, solid paraffin, liquid paraffin, calcium stearate, magnesium stearate, zinc stearate, barium stearate, and combinations thereof.

[0060] The present invention also provides a method for preparing a polyester composition, comprising the following steps: The components are mixed evenly, melt-extruded, and granulated to obtain a polyester composition.

[0061] During melt extrusion, the feeding speed is 450~800 kg / h.

[0062] During melt extrusion, the screw temperatures of each section of the twin-screw extruder from the feed port to the die head are 220~230℃, 230~240℃, 230~240℃, 240~250℃, 250~260℃, 240~250℃, 240~250℃, 230~240℃, and 230~240℃, respectively, and the screw speed is 250~400 rpm.

[0063] The present invention also provides an application of the described polyester composition in the preparation of automotive parts, electronic and electrical components, household goods, household appliances, gardening equipment, and medical technology equipment.

[0064] The present invention also provides an automotive part made from the polyester composition described above.

[0065] The beneficial effects of this invention are as follows: This invention uses polyester resin as a matrix, and with the combined action of glass fiber, flame retardant, nanotube material, lubricant and antioxidant, a polyester composition with excellent low-temperature resistance is obtained. The polyester composition has excellent ductility and toughness at low temperatures. The polyester composition is suitable for preparing automotive parts and electronic and electrical components, especially suitable for preparing automotive parts and electronic and electrical components with metal insert structures. Detailed Implementation

[0066] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0067] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0068] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0069] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0070] The raw materials used in the examples and comparative examples are described below: PBT-1: Intrinsic viscosity 0.80 dl / g, grade PBTGX112, Sinopec Yizheng Chemical Fiber Co., Ltd.

[0071] PBT-2: Intrinsic viscosity 1.0 dl / g, grade PBT GX121, Sinopec Yizheng Chemical Fiber Co., Ltd.

[0072] PBT-3: Intrinsic viscosity 0.72 dl / g, grade PBT GX111, Sinopec Yizheng Chemical Fiber Co., Ltd.

[0073] PBT-4: Intrinsic viscosity 1.37 dl / g, grade PBT GL236, Sinopec Yizheng Chemical Fiber Co., Ltd.

[0074] PET: Intrinsic viscosity 0.675 dl / g, grade PET FG600, Sichuan Dongfang Insulation Materials Co., Ltd.

[0075] Glass fiber-1: average diameter 13μm, average length 3mm, ECS13-3-534A, Jushi Group.

[0076] Glass fiber-2: average diameter 14μm, average length 4.5mm, ECS14-4.5-508S, Jushi Group.

[0077] Glass fiber-3: average diameter 10μm, average length 3mm, ECS10-3-534A, Jushi Group.

[0078] Glass fiber-4: average diameter 17μm, average length 3mm, ECS17-3-508S, Jushi Group.

[0079] Brominated epoxy resin: Grade F-2100, Israel Chemicals.

[0080] Decabromodiphenyl ethane: Commercially available.

[0081] Antimony trioxide: Commercially available.

[0082] Sodium antimonate: Commercially available.

[0083] Carbon nanotube-1: average length 2 μm, average diameter 30 nm, Beijing Deco Island Gold Technology, CNT405.

[0084] Carbon nanotube-2: average length 0.5 μm, average diameter 20 nm, Beijing Deco Island Gold Technology, CNT404.

[0085] Carbon nanotube-3: average length 10 μm, average diameter 10 nm, Jiangsu Tiannai Technology, FT9000.

[0086] Carbon nanotube-4: average length 250 μm, average diameter 7 nm, Jiangsu Tiannai Technology, FT6000.

[0087] Carbon nanotube-5: average length 50 μm, average diameter 12 nm, Jiangsu Tiannai Technology, 6800 series.

[0088] Carbon nanotube-6: average length 2 μm, average diameter 4 nm, Jiangsu Xianfeng Nano, XFM70.

[0089] Carbon nanotube-7: average length 2 μm, average diameter 50 nm, Beijing Deco Island Gold Technology, CNT406.

[0090] Carbon nanotube-8: average length 20 μm, average diameter 10 nm, Jiangsu Tiannai Technology, 6100 series.

[0091] Carbon nanotube-9: average length 30μm, average diameter 10nm, Shanghai Xiangtian Nano, XT-C1-07.

[0092] Carbon nanotubes-10, average length 500 μm, average diameter 2.2 nm, Jiangsu Tiannai Technology, 2000 series.

[0093] Lubricant-1: Pentaerythritol stearate, commercially available.

[0094] Lubricant-2: Erucamide, commercially available.

[0095] Antioxidant-1: Antioxidant 1010, commercially available.

[0096] Antioxidant-2: Antioxidant 168, commercially available.

[0097] Unless otherwise specified, all components, raw materials, or instruments used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0098] Examples 1-18, Comparative Examples 1-9 The formulations of the polyester compositions of Examples 1-18 and Comparative Examples 1-9 are shown in Tables 1 and 2 (all figures are parts by weight).

[0099] The preparation methods of the polyester compositions in Examples 1-18 and Comparative Examples 1-9 all include the following steps: (1) The polyester resin is pre-dried at 130°C for 5 hours. The dried polyester resin is then mixed with other components in a high-speed mixer in proportion. (2) The above mixture is fed into a twin-screw extruder. Under the conveying and shearing action of the twin-screw extruder, it is fully melted and plasticized, kneaded and mixed, extruded through the die head, and granulated to obtain a polyester composition.

[0100] In the above preparation method, the feed rate of the twin-screw extruder is 500 kg / hour; the screw temperatures of each section of the twin-screw extruder from the feed port to the die head are 220℃, 230℃, 230℃, 240℃, 250℃, 240℃, 240℃, 230℃, and 230℃, respectively, and the screw speed is 350 rpm.

[0101] Table 1 Table 2 Performance testing Low-temperature elongation at break: Tested according to GB / T 528-2009 test standard, temperature -30℃, dumbbell shape type 1, tensile rate 50mm / min.

[0102] Low-temperature notched impact strength: Cantilever beam notched impact strength (Type A notch): according to ISO 180-2000, 4mm, -30℃.

[0103] High and low temperature impact test (cracking time): The metal is coated with a polyester composition. The metal is solid and the outer plastic coating is 1.5 mm thick. It is injection molded. The metal commonly used is iron. The polyester-coated metal insert is placed in an environment of -40℃ and 80℃ for 30 min each. The temperature change is completed by the movement of a robotic arm. One cycle is completed every hour. The sample is observed once every 10 cycles and the cracking time is recorded (the total test time is 500 h).

[0104] Table 3 As can be seen from Table 3, the polyester composition of the present invention has excellent low-temperature resistance. The polyester composition exhibits excellent ductility and toughness at low temperatures, specifically, the elongation at break at -30°C is ≥3.4%, and the notched impact strength at -30°C is ≥8.1 kJ / m. 2 The high and low temperature impact test cracking time is ≥350h. The polyester composition has excellent ductility and toughness at low temperatures. The polyester composition is suitable for preparing automotive parts and electronic and electrical components, especially suitable for preparing automotive parts and electronic and electrical components with metal insert structures (e.g., cooling fans, connectors, electric vehicle distribution boxes).

[0105] Comparing Example 2 with Comparative Examples 1 and 2, it can be seen that by controlling the weight ratio of the first carbon nanotube and the second carbon nanotube to (0.6~2.2):1, the low-temperature resistance of the polyester composition can be significantly improved.

[0106] As can be seen from the comparison of Example 2 with Comparative Examples 3-9, the addition of first carbon nanotubes and second carbon nanotubes of specific lengths in this application synergistically improves the low-temperature resistance of the polyester composition.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A polyester composition, characterized in that, It includes the following components in parts by weight: 18-62 parts polyester resin, 9-42 parts glass fiber, 8-21 parts flame retardant, 0.4-5.5 parts nanotube material, 0-1.2 parts lubricant, and 0-1.2 parts antioxidant; The nanotube material comprises a first carbon nanotube and a second carbon nanotube in a weight ratio of (0.6~2.2):1; the average length of the first carbon nanotube is 0.5~10μm; and the average length of the second carbon nanotube is 50~250μm.

2. The polyester composition according to claim 1, characterized in that, It includes the following components by weight: 30-50 parts polyester resin, 20-30 parts glass fiber, 12-18 parts flame retardant, 2-4 parts nanotube material, 0.4-0.8 parts lubricant, and 0.4-0.8 parts antioxidant.

3. The polyester composition according to claim 1, characterized in that, The diameter of the first carbon nanotube is 4~50nm, preferably 10~30nm; the average diameter of the second carbon nanotube is 7~12nm.

4. The polyester composition according to claim 1, characterized in that, The intrinsic viscosity of the polyester resin is 0.7~1.4 dl / g, preferably 0.8~1 dl / g.

5. The polyester composition according to claim 1, characterized in that, The glass fiber has an average diameter of 10~17μm and an average length of 3~4.5mm.

6. The polyester composition according to claim 1, characterized in that, The flame retardant includes bromine-based flame retardants and antimony-based flame retardants in a weight ratio of (2~9):

1.

7. The polyester composition according to claim 6, characterized in that, The brominated flame retardant includes at least one of tetrabromobisphenol A, brominated triazine, brominated epoxy resin, decabromodiphenyl ethane, decabromodiphenyl ether, brominated polyimide, brominated polystyrene, polybrominated polystyrene, brominated polycarbonate, and brominated polyacrylate. The antimony-based flame retardant includes at least one of antimony trioxide, antimony pentoxide, and sodium antimonate.

8. A method for preparing the polyester composition according to any one of claims 1 to 7, characterized in that, Includes the following steps: The components are mixed evenly, melt-extruded, and granulated to obtain a polyester composition.

9. The use of the polyester composition according to any one of claims 1 to 7 in the preparation of automotive parts, electronic and electrical components, household goods, household appliances, gardening equipment, and medical technology equipment.

10. An automotive component, characterized in that, It is prepared using the polyester composition according to any one of claims 1 to 7.

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