Low-water-absorption glass bead modified PBT (polybutylene terephthalate) material and preparation method thereof

Abstract

The invention provides a low-water-absorption glass bead modified PBT (polybutylene terephthalate) material and a preparation method thereof. The low-water-absorption glass bead modified PBT material comprises the following components in parts by weight: 70-100 parts of PBT resin; 0 to 30 parts of solid glass beads; 0-5 parts of a toughening agent; 0-2 parts of an antioxidant; 0-2 parts of a lubricant; 0-2 parts of black color master batch; 0-2 parts of a coupling agent; 0-5 parts of polytetrafluoroethylene wax; wherein the average particle size of the solid glass beads is 1-50 [mu] m; the average particle size of the polytetrafluoroethylene wax is 3-15 [mu] m, and the weight-average molecular weight of the polytetrafluoroethylene wax is 10000-30000 g / mol; the weight ratio of the solid glass beads to the polytetrafluoroethylene wax is (5-10): 1. According to the invention, the polytetrafluoroethylene wax is added into the solid glass bead modified PBT material, so that the shrinkage difference between the material flow direction and the vertical flow direction is effectively reduced, the water absorption rate of the material is remarkably reduced, the preparation process is simple, and the production process is easy to control.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite material technology, and relates to a low water absorption glass microsphere modified PBT material and its preparation method. Specifically, it relates to a solid glass microsphere modified PBT composite material with low water absorption, small difference in flow / vertical shrinkage rate, and good mechanical properties. Background Technology

[0002] Polybutylene terephthalate (hereinafter referred to as PBT), as an important thermoplastic engineering plastic, has been widely used in many fields such as automobiles, electronics, and industrial machinery since the 1970s due to its excellent heat resistance, chemical resistance, electrical insulation, dimensional stability and good molding and processing performance. Especially in high-end application scenarios such as automotive electronics and communication equipment, higher requirements are put forward for the comprehensive performance of materials.

[0003] However, pure PBT resin has some inherent defects, such as generally low mechanical strength, low heat distortion temperature under load, easy crystallization leading to large shrinkage, and easy warping of products. These problems seriously affect its assembly and use in precision structural parts. To improve the performance of PBT, glass fiber reinforcement is traditionally used. Although glass fiber can significantly improve the mechanical strength of the material, it also brings a series of problems, such as reduced flowability, exposed glass fibers, uneven shrinkage, and severe warping, which are particularly prominent in complex components and products with high surface quality requirements.

[0004] To overcome the aforementioned problems, materials engineers began exploring the use of various fillers to modify PBT. Among them, glass microspheres, due to their unique spherical structure and isotropic physical properties, can effectively homogenize the shrinkage behavior of PBT and significantly reduce warpage, making them one of the ideal fillers for modification. Hollow glass microspheres, in particular, not only possess excellent dimensional stability and low shrinkage but also exhibit low density and high strength. This allows for enhanced mechanical properties while simultaneously achieving material weight reduction and lower water absorption, expanding the application range of PBT in humid environments.

[0005] CN104987677A discloses a hollow glass microsphere-modified PBT composite material and its preparation method. The PBT-modified material is composed of the following components by weight percentage: 100 parts PBT resin, 3-40 parts hollow glass microspheres, 0.1-2 parts antioxidant, 0.1-5 parts lubricant, and 3-15 parts toughening agent. Specifically, the material density is reduced and the mechanical properties are improved through optimized formulation.

[0006] CN115403899A discloses a modified PBT material and its preparation method. The raw materials include: 50-90 parts of PBT base material, 0-30 parts of fiber material, 0-20 parts of particulate filler, 10-30 parts of modifier, 0-10 parts of compatibilizer, and 0.1-2 parts of additives. Specifically, hollow glass microspheres are used as the modifier. By compounding hollow glass microspheres with other fillers, the comprehensive performance of low dielectric, low loss and lightweight is achieved.

[0007] However, the PBT materials prepared by the aforementioned patents failed to meet expectations in terms of dimensional stability and electrical properties in high humidity or underwater environments, making them unsuitable for high humidity environments such as automotive housing sensors and underwater equipment. In other words, the existing technology still lacks systematic optimization for the key performance of "low water absorption rate of PBT materials," especially in terms of maintaining the dimensional stability and electrical properties of PBT materials in high humidity environments, which still requires further breakthroughs.

[0008] In view of this, developing a glass microsphere-modified PBT material with low water absorption, high dimensional stability, good mechanical properties, and adaptability to the needs of high-end electronic and electrical fields has important industrial application value and technical significance. Summary of the Invention

[0009] The purpose of this invention is to solve the problem that PBT materials in the prior art fail to achieve the expected dimensional stability and electrical performance retention under high humidity environments, and to provide a low water absorption glass microsphere modified PBT material and its preparation method.

[0010] To achieve the above objectives, the present invention proposes the following technical solution: Firstly, a low-water-absorption glass microsphere-modified PBT material is proposed, specifically comprising the following components in parts by weight: PBT resin: 70~100 parts; Solid glass microspheres: 0~30 parts; Toughening agent: 0-5 parts; Antioxidant: 0-2 parts; Lubricant: 0-2 parts; Black masterbatch: 0-2 parts; Coupling agent: 0-2 parts; Polytetrafluoroethylene wax: 0~5 parts; The solid glass microspheres have an average particle size of 1~50 μm; The average particle size of the polytetrafluoroethylene wax is 3~15 μm, and the weight-average molecular weight of the polytetrafluoroethylene wax is 10000~30000 g / mol. The weight ratio of the solid glass microspheres to the polytetrafluoroethylene wax is (5~10):1.

[0011] Furthermore, it includes the following components in parts by weight: PBT resin: 70-90 parts; Solid glass microspheres: 10-30 parts; Toughening agent: 0-5 parts; Antioxidant: 0.1~0.5 parts; Lubricant: 0.1~0.5 parts; Black masterbatch: 0.5~1.0 parts; Coupling agent: 0~1 part; Polytetrafluoroethylene wax: 3-5 parts.

[0012] Furthermore, the intrinsic viscosity of the PBT resin is 0.80~1.20 dL / g; The melting point of the PBT resin is 220~230 ℃; The PBT resin has a terminal carboxyl group content of ≤30 mmol / kg.

[0013] Furthermore, the solid glass microspheres are made of materials including soda-lime silicate glass and borosilicate glass; The density of the solid glass microspheres is 2.5 g / cm³. 3 .

[0014] Furthermore, the toughening agent is one or a mixture of more than one of ethylene-alkyl acrylate-glycidyl methacrylate copolymer, ethylene-butyl acrylate copolymer, and glycidyl methacrylate-grafted polyethylene elastomer.

[0015] Furthermore, the coupling agent is a silane coupling agent.

[0016] Furthermore, the polytetrafluoroethylene wax is a powdered polytetrafluoroethylene micro powder obtained by thermal decomposition. The average particle size of the polytetrafluoroethylene wax is 5~7 μm, and the particle size distribution index is ≤1.8. The heat of melting of the polytetrafluoroethylene wax is 30~45 J / g.

[0017] Secondly, a method for preparing the aforementioned low-water-absorption glass microsphere modified PBT material is proposed, comprising the following steps: S1. Mix PBT resin, toughening agent, antioxidant, lubricant, black masterbatch, coupling agent, and polytetrafluoroethylene wax in a high-speed mixer for 5-10 minutes to obtain a uniform premix. S2. The premixed material is fed into the main feed port of the twin-screw extruder. During the melt extrusion process of the twin-screw extruder, solid glass microspheres are added from the side feed port of the twin-screw extruder. After melt extrusion, the material is cooled and pelletized after passing through a water tank. The processing temperature of the twin-screw extruder is set to 200~260 ℃ from the feeding section to the die head; The side feed port is located at 25-40% of the total length of the twin-screw extruder barrel.

[0018] Furthermore, in S2, the twin-screw extruder has at least nine temperature zones; The temperature of the twin-screw extruder is 200~220 ℃ in zone 1, 220~240 ℃ in zone 2, 240~260 ℃ in zones 3, 4 and 5, 220~240 ℃ in zones 6, 7, 8 and 9, and 230~250 ℃ at the die head.

[0019] Furthermore, in S2, the screw speed of the twin-screw extruder is 300~500 r / min; The screw configuration of the twin-screw extruder is configured such that, after the side feed port, it consists of a conveying element and at least one set of toothed disc assembly blocks; The total conveying time of the premix and the solid glass microspheres in the screw is 25~60 s.

[0020] The beneficial effects of this invention are: This invention adds low molecular weight polytetrafluoroethylene wax to solid glass microsphere modified PBT material, which effectively reduces the difference in shrinkage rate between the material flow direction and the perpendicular flow direction, and significantly reduces the water absorption rate of the material. The preparation process is simple and the production process is easy to control.

[0021] On the one hand, this invention achieves a significant synergistic effect by employing a specific combination of solid glass microspheres and polytetrafluoroethylene wax, and optimizing their ratio. Solid glass microspheres provide high rigidity, isotropic dimensional stability, and a low coefficient of thermal expansion; while polytetrafluoroethylene wax not only improves processing fluidity as a lubricant, but also migrates to the glass microsphere interface during processing, forming an effective coating layer with PBT resin, greatly improving the interfacial compatibility of the material. This results in the material of this invention simultaneously possessing high rigidity, low warpage, extremely low water absorption, excellent wear resistance, and surface smoothness.

[0022] On the other hand, the composite phase coating layer formed by polytetrafluoroethylene wax and PBT resin reduces the path of water penetration, and the selected PBT resin has a low carboxyl content. The material of this invention exhibits excellent stability, with a water absorption rate consistently below 0.2%, specifically below 0.06%; shrinkage rates in the flow direction and vertical direction consistently below 1.8%, specifically below 1.5%; and heat distortion consistently above 155°C, making it very suitable for harsh environments such as automotive sensors and outdoor electronic devices.

[0023] On the other hand, this invention, through the use of a premix comprising PBT resin and polytetrafluoroethylene wax, and the synergistic process of adding solid glass microspheres from a side feed port with a mild shear screw configuration, ultimately forms a stable microstructure within the material characterized by uniform dispersion and tight interfacial bonding of solid glass microspheres. In this material, the breakage rate of the solid glass microspheres is controlled to an extremely low level of less than 3%. The intact microspheres effectively avoid stress concentration, ensuring long-term mechanical properties. Simultaneously, their spherical structure helps reduce the dielectric constant and dielectric loss, making them suitable for applications requiring specific electrical performance.

[0024] On the other hand, based on the above-mentioned synergistic process combination, the present invention, by precisely controlling the total conveying time of the material in the screw and setting the temperature of each zone of the twin-screw extruder and matching specific temperature curves, ensures that the material is fully melted and mixed while maximizing the protection of the integrity of the filler material, greatly improving the production efficiency of the process, resulting in good product consistency, high yield, and easy large-scale industrial production.

[0025] In summary, this invention, through the rational proportioning of each component in the formula, specifically by using solid glass microspheres and polytetrafluoroethylene wax in a synergistic effect, reduces the water absorption rate of the material system and further reduces the difference in shrinkage rate in the injection molding flow direction and vertical direction. This systematically optimizes the reduction of water absorption rate of PBT material, making it applicable to high humidity environments while maintaining good dimensional stability and electrical performance, and enabling large-scale industrial production.

[0026] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below can be considered part of the inventive subject matter of this disclosure, provided that such concepts do not contradict each other. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the described 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. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0028] The terms "comprising" or "including" or similar words used in the patent application specification and claims of this invention mean that the elements or objects preceding "comprising" or "including" encompass the features, integrals, steps, operations, elements and / or components listed after "comprising" or "including", and do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0029] Unless otherwise stated, the abbreviations used in this invention have the following meanings: In this invention, PBT refers to polybutylene terephthalate; PETS refers to pentaerythritol stearate; PTFE refers to polytetrafluoroethylene; and PTFE wax refers to polytetrafluoroethylene wax.

[0030] DSC refers to Differential Scanning Calorimetry.

[0031] This invention discloses a method for preparing a PBT material modified with low water absorption glass microspheres, comprising the following steps: S1. Mix 70-100 parts by weight of PBT resin, 0-5 parts by weight of toughening agent, 0-2 parts by weight of antioxidant, 0-2 parts by weight of lubricant, 0-2 parts by weight of black masterbatch, 0-2 parts by weight of coupling agent, and 0-5 parts by weight of polytetrafluoroethylene wax in a high-speed mixer for 5-10 minutes to obtain a uniform premix. S2. The premixed material is fed into the main feed port of the twin-screw extruder. During the melt extrusion process of the twin-screw extruder, 0-30 parts by weight of solid glass microspheres are added from the side feed port of the twin-screw extruder. After melt extrusion, the material is cooled and pelletized after passing through a water tank.

[0032] Preferably, the mixing time of the high-speed mixer is 5 to 8 minutes to ensure that the remaining powdered components can be fully mixed with the PBT resin during premixing, without causing the materials to clump or the performance to deteriorate due to excessive time.

[0033] The processing temperature of the twin-screw extruder is set to 200~260 ℃ from the feeding section to the die head; the side feed port is located at 25~40% of the total length of the twin-screw extruder barrel, specifically corresponding to the positions of the 4th to 6th barrel sections.

[0034] The twin-screw extruder has at least nine temperature zones. The temperature of zone one is 200~220 ℃, the temperature of zone two is 220~240 ℃, the temperature of zones three, four and five is 240~260 ℃, the temperature of zones six, seven, eight and nine is 220~240 ℃, and the temperature of the die head is 230~250 ℃.

[0035] Specifically, setting the processing temperature of the twin-screw extruder from the feeding section to the die head to a precise temperature curve with a lower temperature at the beginning and a higher temperature at the end can ensure the stable melting of PBT material, avoid bridging, and provide a suitable melt environment for solid glass microspheres.

[0036] The screw speed of the twin-screw extruder is 300~500 r / min.

[0037] The screw configuration of the twin-screw extruder is configured such that, after the side feed port, it consists of a conveying element and at least one set of toothed discs, which can work with solid glass microspheres to ensure their breakage rate, so that the total conveying time of the premix and solid glass microspheres in the screw is 20~60 s.

[0038] Preferably, the total conveying time of the premix and solid glass microspheres in the screw is 25~60 s.

[0039] Specifically, the total conveying time mentioned above refers to the total time from when the premixed material from the main feed port and the solid glass microspheres from the side feed port all enter the screw until they are extruded from the die head. This time covers the entire process of melting, dispersing, and homogenizing the solid glass microspheres in the material, thereby ensuring a low breakage rate.

[0040] Further preferably, the total conveying time of the premix and solid glass microspheres in the screw is 30-40 seconds, which limits the residence time of the material in the screw and avoids insufficient melting and mixing due to too short a residence time, or PBT degradation or breakage of solid glass microspheres due to excessive shearing due to too long a residence time. At the same time, the configuration structure of the screw element is limited, and high-shear processes are clearly excluded. The use of toothed discs can achieve gentle and effective distribution mixing, ensuring that the solid glass microspheres are uniformly dispersed and not damaged, thereby ensuring a high integrity rate of solid glass microspheres in the final product, with the breakage rate controlled to an extremely low level of less than 3%.

[0041] The following detailed description, with reference to specific embodiments, further illustrates the low water absorption glass microsphere-modified PBT material and its preparation method disclosed in this invention. Unless otherwise specified, the reagents and materials used in the examples and comparative examples are commercially available. Specific product models and other information in the examples are as follows: The intrinsic viscosity of PBT resin is 0.80~1.20 dL / g. The intrinsic viscosity test method is GB / T 14190-2017, specifically using a mixed solvent of phenol and 1,1,2,2-tetrachloroethane at a weight ratio of 1:1 to dissolve the PBT resin and prepare a solution of a specified concentration. The intrinsic viscosity is measured using an Ubbelohde viscometer under constant temperature conditions of 25.0 ± 0.1℃.

[0042] The intrinsic viscosity of PBT resin directly affects the overall performance of the composite material. Too low a viscosity results in short molecular chains and insufficient matrix strength, impacting the mechanical properties of the final part. Too high a viscosity leads to poor melt flow, requiring more intense shearing of the solid glass microspheres and PTFE wax during processing. This increases the risk of microsphere breakage and excessive shearing of the PTFE wax, hindering the achievement of the desired dimensional stability and surface properties. The specific components of this invention achieve an optimal balance between processability and performance within the aforementioned viscosity range.

[0043] The melting point of PBT resin is 220~230 ℃. The melting point test method is GB / T 19466.3-2004. Specifically, 5~10 mg of sample is weighed and heated from 30 ℃ to 280 ℃ at a rate of 10 ℃ / min under a nitrogen atmosphere. The peak temperature of the melting endothermic peak is recorded as the melting point.

[0044] The melting point of PBT resin reflects its crystallinity and regularity. Limiting the melting point range ensures that PBT resin has appropriate crystallization ability. A melting point that is too low results in insufficient resin purity or crystallinity, affecting the material's heat distortion temperature and dimensional stability. A melting point that is too high results in a narrow processing temperature window or compatibility issues with other components. The specific components of this invention exhibit excellent crystallization behavior and thermal stability within the aforementioned melting point range.

[0045] The end carboxyl group content of PBT resin is ≤30 mmol / kg. The test method for end carboxyl group content is GB / T 14190-2017. End carboxyl groups are the terminal groups of PBT molecular chains, and their content directly affects the thermal stability, hydrolytic stability and molecular weight growth potential of the resin. Excessive content will accelerate the degradation of the material during high-temperature processing and use, while low end carboxyl group content makes the resin itself less prone to hydrolytic degradation, thereby effectively ensuring the low water absorption rate of the material.

[0046] In this example, the PBT resin used was a commercially available product, model MY08, with an intrinsic viscosity of 0.83 dL / g, a melting point of 226℃, and a terminal carboxyl group content of less than 30 mmol / kg.

[0047] Solid glass microspheres, made of materials including soda-lime silicate glass and borosilicate glass; average particle size 1~50 μm, density 2.5 g / cm³. 3 Solid glass microspheres differ from hollow glass microspheres. Hollow glass microspheres can reduce density, but their thin walls make them brittle and prone to breakage under high shear processing or stress conditions, affecting the long-term stability of the material. This invention uses solid glass microspheres, which have higher strength and better pressure resistance, better ensuring the dimensional stability of the material under humid heat and load, thereby ensuring its low water absorption and high stability.

[0048] In this embodiment, the solid glass microspheres used are commercially available products, model SWARCOFORCE 1-50 Type 1 C3, made of soda-lime silicate glass, with an average particle size of 30-40 μm and a density of 2.5 g / cm³. 3 .

[0049] Toughening agent: One or more of the following are used: ethylene-alkyl acrylate-glycidyl methacrylate copolymer, ethylene-butyl acrylate copolymer, and glycidyl methacrylate grafted polyethylene elastomer.

[0050] In the examples, the toughening agent is glycidyl methacrylate grafted polyethylene elastomer, a commercially available product, model KT-22; the toughening agent in the examples is ethylene-alkyl acrylate-glycidyl methacrylate copolymer, a commercially available product, model PTW; the toughening agent in the examples is ethylene-butyl acrylate copolymer, a commercially available product, model 35BA40T.

[0051] In the examples, the toughening agent used is KT-22.

[0052] Antioxidant: A compound of hindered phenolic antioxidants and phosphite antioxidants is used, specifically one or a mixture of more than one of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and tris(2,4-di-tert-butylphenyl) phosphite.

[0053] In this embodiment, the antioxidant is a combination of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester and tris(2,4-di-tert-butylphenyl) phosphite. β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester is the main antioxidant, a commercially available product, model 1076; tris(2,4-di-tert-butylphenyl) phosphite is the auxiliary antioxidant, a commercially available product, model 168.

[0054] The primary antioxidant and secondary antioxidant are compounded in a weight ratio of 1:2.

[0055] Lubricant: One or a mixture of one or more of pentaerythritol stearate, ethylene bis-stearamide, and polydimethylsiloxane.

[0056] In this example, the lubricant used is commercially available PETS.

[0057] The black masterbatch uses carrier-free carbon black masterbatch.

[0058] In this embodiment, the black mother-of-pearl is a commercially available product, model 3300.

[0059] The coupling agent used is a silane coupling agent.

[0060] In the examples, the coupling agent used is a commercially available product, model 560.

[0061] The polytetrafluoroethylene wax is made from powdered polytetrafluoroethylene micro powder obtained by thermal decomposition.

[0062] Specifically, polytetrafluoroethylene wax is produced by thermal decomposition, which is a conventional technology. This method mainly involves heating high molecular weight polytetrafluoroethylene in a high-temperature, oxygen-free environment to break its molecular chains, thereby reducing its molecular weight.

[0063] The specific preparation method of polytetrafluoroethylene wax is as follows: PTFE raw material is pulverized to 20-100 mesh, thoroughly dried to remove moisture, and then added to a fluidized bed reactor. The reactor is sealed, and high-purity nitrogen gas is introduced. Once the oxygen content in the reactor drops below 50 ppm, nitrogen gas is continuously introduced. The reactor temperature is gradually increased to 420-500 °C, initiating a cracking reaction in PTFE. After the reaction continues for a predetermined time, such as 1-4 hours, heating is stopped, and the reactor temperature is lowered to below 200 °C while continuously introducing nitrogen gas. The cooled PTFE wax powder is then transferred to a collection container under an inert atmosphere.

[0064] In some alternative embodiments, in order to improve the compatibility or surface properties of PTFE wax powder, PTFE wax is subjected to short-term oxygen treatment at 250~350°C to introduce a small amount of oxygen-containing groups on its surface.

[0065] The morphology of polytetrafluoroethylene wax affects its dispersibility and friction properties. In order to ensure that polytetrafluoroethylene wax can protect solid glass microspheres from excessive shearing and breakage during extrusion, while promoting its uniform dispersion in the PBT matrix and reducing stress concentration points, the type of polytetrafluoroethylene wax is limited to polymer powder.

[0066] The average particle size of polytetrafluoroethylene (PTFE) wax is 3–15 μm, and the particle size distribution index is ≤1.8. The particle size of PTFE wax directly affects its dispersion uniformity in the PBT matrix, the surface smoothness of the product, and its protective effect on solid glass microspheres. If the particle size is too large, it will lead to surface defects; if it is too small, it will be difficult to disperse due to its high surface energy, thus affecting the formulation and processing effect.

[0067] Preferably, the polytetrafluoroethylene wax has an average particle size of 5~7 μm and a particle size distribution index ≤1.8.

[0068] The heat of fusion of polytetrafluoroethylene (PTFE) wax is 30–45 J / g, determined by DSC in the second heating scan according to GB / T 19466.3-2004. Limiting the heat of fusion of PTFE wax can indirectly characterize its crystallinity and lubrication efficiency. The heat of fusion of PTFE wax is closely related to its crystallinity. Low molecular weight PTFE wax powder undergoes random chain breakage, leading to a significant decrease in crystallinity and a significantly lower heat of fusion than standard PTFE.

[0069] The weight-average molecular weight of polytetrafluoroethylene (PTFE) wax ranges from 10,000 to 30,000 g / mol. This weight-average molecular weight was determined by gel permeation chromatography, based on the difference in hydrodynamic volume of the polymers in solution. Larger molecules are eluted first, followed by smaller molecules. The molecular weight of PTFE wax determines its lubricating properties and stability during processing. This invention uses powdered, low-molecular-weight PTFE wax to ensure its synergistic effect with solid glass microspheres.

[0070] Specifically, due to its ultra-high molecular weight and non-melting properties, conventional PTFE cannot melt and flow at processing temperatures when used as an additive in PBT composites. It is difficult to disperse evenly in the PBT matrix and cannot effectively migrate to the filler interface to form a functional coating layer. As a result, the modification effect is limited, and it may become a stress concentration point due to uneven dispersion.

[0071] This invention creatively uses polytetrafluoroethylene wax to overcome the inherent defects of conventional PTFE. Specifically, it utilizes the migration and interfacial coating capabilities of polytetrafluoroethylene wax to allow it to work together with PBT resin on the surface of solid glass microspheres during melt blending.

[0072] On the one hand, the composite phase of polytetrafluoroethylene wax and PBT resin effectively reduces the interfacial energy between solid glass microspheres and the PBT matrix, reducing defects and stress concentration caused by poor interfacial bonding, thereby significantly improving the interfacial compatibility of the materials. On the other hand, the polytetrafluoroethylene wax layer coated on the surface of the solid glass microspheres can provide continuous and stable lubrication when the material is subjected to force or friction, thereby significantly reducing the coefficient of friction and wear rate of the composite material. Furthermore, the dense interfacial coating layer effectively blocks the penetration path of moisture along the solid glass microsphere-matrix interface, ensuring that the material has excellent low water absorption.

[0073] In the examples, the polytetrafluoroethylene wax used is a commercially available product, model PTFE L5 powder, which is prepared by thermal decomposition.

[0074] Preferably, the ratio of solid glass microspheres to polytetrafluoroethylene wax is (5~10):1.

[0075] A further preferred embodiment is that the weight ratio of solid glass microspheres to polytetrafluoroethylene wax is (6~7):1.

[0076] Solid glass microspheres are uniformly dispersed in the material, and their surfaces are coated with a composite phase formed by PBT resin and the polytetrafluoroethylene wax. The ratio of the number of complete solid glass microspheres to their total number is greater than or equal to 95%.

[0077] Specifically, during the processing, some low molecular weight PTFE micropowders, due to their compatibility differences with the matrix polymer, will gradually migrate to the surface of the composite material, forming an extremely thin, PTFE-rich hydrophobic layer that prevents water molecules from penetrating. The tiny PTFE particles, uniformly dispersed in the PBT resin and the interface between the PBT resin and the glass microspheres, will physically block the gaps between polymer molecular chains, the interface between the resin and the glass microspheres, and the pathways through which water molecules can penetrate.

[0078] When the relative amount of PTFE wax is too small, there is insufficient PTFE wax in the system to effectively migrate and coat the surface of all solid glass microspheres. On the one hand, this results in some glass microspheres not being fully coated, leaving weak points at the interface with the PBT matrix, which become channels for water penetration and sources of stress concentration, leading to increased water absorption and decreased mechanical properties. On the other hand, it results in insufficient "in-situ lubrication" at the microsphere interface, resulting in an insignificant reduction in the coefficient of friction of the composite material.

[0079] When the relative amount of PTFE wax is excessive, after the PTFE wax has completed the interfacial coating of glass microspheres, there is still a large amount of excess PTFE wax. The excess PTFE wax will form macroscopic agglomerates or an excessively thick lubricating layer in the PBT matrix. On the one hand, the excessive PTFE wax, as a low-modulus and low-strength component, significantly reduces the rigidity, strength and heat resistance of the composite material. On the other hand, it causes the material to slip during extrusion, affecting the stability of conveying, and may cause phase separation due to excessive compatibility differences, affecting the surface quality of the product.

[0080] In summary, within the specific ratio range mentioned above, the solid glass microspheres and polytetrafluoroethylene wax achieve optimal synergistic balance in conjunction with the preparation process. That is, the amount of polytetrafluoroethylene wax is sufficient to form a complete, dense, and robust coating film on the surface of each solid glass microsphere, maximizing the improvement of interfacial compatibility and blocking moisture, and providing microscale lubrication points. At the same time, its amount is insufficient to damage the continuous phase and overall mechanical properties of the PBT matrix, thereby ensuring that the composite material prepared by this invention can simultaneously achieve the optimal comprehensive effect of low water absorption and high dimensional stability.

[0081] The specific product models and other information in the comparison examples are as follows: In the comparative example, the polytetrafluoroethylene used was a commercially available product, model M-111, with an average particle size of 25 μm, a particle size distribution index ≤1.8, a heat of melt of 75 J / g, and a weight-average molecular weight of 1.08 × 10⁻⁶. 7 g / mol.

[0082] The hollow glass microspheres used in the comparative example were commercially available products, model HL38, made of soda-lime borosilicate glass, with an average particle size of 40 μm and a density of 0.36 ~ 0.40 g / cm³. 3 .

[0083] Example 1 A method for preparing a low-water-absorption glass microsphere-modified PBT material includes the following steps: S1. Mix 73.2 parts by weight of PBT resin, 4.5 parts by weight of toughening agent, 0.3 parts by weight of antioxidant, 0.5 parts by weight of lubricant, 0.5 parts by weight of black masterbatch, and 1 part by weight of coupling agent in a high-speed mixer for 5 min to obtain a uniform premix. S2. The premixed material is fed into the main feed port of a twin-screw extruder and extruded through the twin-screw extruder at a melting temperature of 200~250 ℃. During the extrusion process, 20 parts by weight of solid glass microspheres are added from the side feed port of the twin-screw extruder. After melt extrusion, cooling in a water tank, and pelleting, a low water absorption glass microsphere modified PBT material is obtained.

[0084] The total conveying time of the premixed material and solid glass microspheres in the screw is 35 s.

[0085] Example 2 A method for preparing a low-water-absorption glass microsphere-modified PBT material includes the following steps: S1. Mix 70.2 parts by weight of PBT resin, 4.5 parts by weight of toughening agent, 0.3 parts by weight of antioxidant, 0.5 parts by weight of lubricant, 0.5 parts by weight of black masterbatch, 1 part by weight of coupling agent and 3 parts by weight of polytetrafluoroethylene wax in a high-speed mixer for 5 min to obtain a uniform premix. S2. The premixed material is fed into the main feed port of a twin-screw extruder and extruded through the twin-screw extruder at a melting temperature of 200~250 ℃. During the extrusion process, 20 parts by weight of solid glass microspheres are added from the side feed port of the twin-screw extruder. After melt extrusion, cooling in a water tank, and pelleting, a low water absorption glass microsphere modified PBT material is obtained.

[0086] The total conveying time of the premixed material and solid glass microspheres in the screw is 35 s.

[0087] Example 3 A method for preparing a low-water-absorption glass microsphere-modified PBT material includes the following steps: S1. Mix 63.2 parts by weight of PBT resin, 4.5 parts by weight of toughening agent, 0.3 parts by weight of antioxidant, 0.5 parts by weight of lubricant, 0.5 parts by weight of black masterbatch, and 1 part by weight of coupling agent in a high-speed mixer for 5 min to obtain a uniform premix. S2. The premixed material is fed into the main feed port of a twin-screw extruder and extruded through the twin-screw extruder at a melting temperature of 200~250 ℃. During the extrusion process, 30 parts by weight of solid glass microspheres are added from the side feed port of the twin-screw extruder. After melt extrusion, cooling in a water tank, and pelleting, a low water absorption glass microsphere modified PBT material is obtained.

[0088] The total conveying time of the premixed material and solid glass microspheres in the screw is 35 s.

[0089] Example 4 A method for preparing a low-water-absorption glass microsphere-modified PBT material includes the following steps: S1. Mix 60.2 parts by weight of PBT resin, 4.5 parts by weight of toughening agent, 0.3 parts by weight of antioxidant, 0.5 parts by weight of lubricant, 0.5 parts by weight of black masterbatch, 1 part by weight of coupling agent and 3 parts by weight of polytetrafluoroethylene wax in a high-speed mixer for 5 min to obtain a uniform premix. S2. The premixed material is fed into the main feed port of a twin-screw extruder and extruded through the twin-screw extruder at a melting temperature of 200~250 ℃. During the extrusion process, 30 parts by weight of solid glass microspheres are added from the side feed port of the twin-screw extruder. After melt extrusion, cooling in a water tank, and pelleting, a low water absorption glass microsphere modified PBT material is obtained.

[0090] The total conveying time of the premixed material and solid glass microspheres in the screw is 35 s.

[0091] Comparative Example 1 A method for preparing a low water absorption PBT material includes the following steps: S1. Mix 94.2 parts by weight of PBT resin, 4.5 parts by weight of toughening agent, 0.3 parts by weight of antioxidant, 0.5 parts by weight of lubricant, and 0.5 parts by weight of black masterbatch in a high-speed mixer for 5 min to obtain a uniform premix. S2. The premixed material is fed into the main feed port of a twin-screw extruder and extruded through a twin-screw extruder with a melting temperature of 200~250 ℃. After passing through a water tank, it is cooled and pelletized to obtain low water absorption PBT material.

[0092] The total conveying time of the premixed material in the screw is 35 seconds.

[0093] The difference between Comparative Example 1 and Example 1 above is that the amount of PBT resin is changed to 93.7 parts by weight, and solid glass microspheres, polytetrafluoroethylene wax, and coupling agent are not added.

[0094] Comparative Example 2 A method for preparing a PBT material modified with low water absorption glass microspheres includes the following steps: S1. Mix 70.2 parts by weight of PBT resin, 4.5 parts by weight of toughening agent, 0.3 parts by weight of antioxidant, 0.5 parts by weight of lubricant, 0.5 parts by weight of black masterbatch, 1 part by weight of coupling agent and 3 parts by weight of polytetrafluoroethylene in a high-speed mixer for 5 min to obtain a uniform premix. S2. The premixed material is fed into the main feed port of a twin-screw extruder and extruded through the twin-screw extruder at a melting temperature of 200~250 ℃. During the extrusion process, 20 parts by weight of solid glass microspheres are added from the side feed port of the twin-screw extruder. After melt extrusion, cooling in a water tank, and pelleting, a low water absorption glass microsphere modified PBT material is obtained.

[0095] The total conveying time of the premixed material and solid glass microspheres in the screw is 35 s.

[0096] The difference between Comparative Example 2 and Example 2 above is that the polytetrafluoroethylene wax is replaced with polytetrafluoroethylene.

[0097] Comparative Example 3 A method for preparing a PBT material modified with low water absorption glass microspheres includes the following steps: S1. Mix 70.2 parts by weight of PBT resin, 4.5 parts by weight of toughening agent, 0.3 parts by weight of antioxidant, 0.5 parts by weight of lubricant, 0.5 parts by weight of black masterbatch, 1 part by weight of coupling agent and 3 parts by weight of polytetrafluoroethylene wax in a high-speed mixer for 5 min to obtain a uniform premix. S2. The premixed material is fed into the main feed port of a twin-screw extruder and extruded through the twin-screw extruder at a melting temperature of 200~250 ℃. During the extrusion process, 20 parts by weight of solid glass microspheres are added from the side feed port of the twin-screw extruder. After melt extrusion, cooling in a water tank, and pelleting, a low water absorption glass microsphere modified PBT material is obtained.

[0098] The total conveying time of the premixed material and solid glass microspheres in the screw is 25 s.

[0099] The difference between Comparative Example 3 and Example 2 above is that the total conveying time of the premix and solid glass microspheres in the screw is changed to 25 s.

[0100] Comparative Example 4 A method for preparing a PBT material modified with low water absorption glass microspheres includes the following steps: S1. Mix 70.2 parts by weight of PBT resin, 4.5 parts by weight of toughening agent, 0.3 parts by weight of antioxidant, 0.5 parts by weight of lubricant, 0.5 parts by weight of black masterbatch, 1 part by weight of coupling agent and 3 parts by weight of polytetrafluoroethylene wax in a high-speed mixer for 5 min to obtain a uniform premix. S2. The premixed material is fed into the main feed port of a twin-screw extruder and extruded through the twin-screw extruder at a melting temperature of 200~250 ℃. During the extrusion process, 20 parts by weight of solid glass microspheres are added from the side feed port of the twin-screw extruder. After melt extrusion, cooling in a water tank, and pelleting, a low water absorption glass microsphere modified PBT material is obtained.

[0101] The total conveying time of the premixed material and solid glass microspheres in the screw is 50 s.

[0102] The difference between Comparative Example 4 and Example 2 above is that the total conveying time of the premix and solid glass microspheres in the screw is changed to 50 s.

[0103] Comparative Example 5 A method for preparing a low-water-absorption glass microsphere-modified PBT material includes the following steps: S1. Mix 70.2 parts by weight of PBT resin, 4.5 parts by weight of toughening agent, 0.3 parts by weight of antioxidant, 0.5 parts by weight of lubricant, 0.5 parts by weight of black masterbatch, 1 part by weight of coupling agent and 3 parts by weight of polytetrafluoroethylene wax in a high-speed mixer for 5 min to obtain a uniform premix. S2. The premixed material is fed into the main feed port of a twin-screw extruder and extruded through the twin-screw extruder at a melting temperature of 200~250 ℃. During the extrusion process, 20 parts by weight of hollow glass microspheres are added from the side feed port of the twin-screw extruder. After melt extrusion, cooling in a water tank, and pelleting, a low water absorption glass microsphere modified PBT material is obtained.

[0104] The total conveying time of the premixed material and hollow glass microspheres in the screw is 35 s.

[0105] The difference between Comparative Example 5 and Example 2 above is that the solid glass microspheres are replaced with hollow glass microspheres.

[0106] Comparative Example 6 A method for preparing a low water absorption PBT material includes the following steps: S1. Mix 94.2 parts by weight of PBT resin, 4.5 parts by weight of toughening agent, 0.3 parts by weight of antioxidant, 0.5 parts by weight of lubricant, 0.5 parts by weight of black masterbatch, and 1 part by weight of coupling agent in a high-speed mixer for 5 min to obtain a uniform premix. S2. The premixed material is fed into the main feed port of a twin-screw extruder and extruded through a twin-screw extruder with a melting temperature of 200~250 ℃. After passing through a water tank, it is cooled and pelletized to obtain low water absorption PBT material.

[0107] The total conveying time of the premixed material in the screw is 35 seconds.

[0108] The difference between Comparative Example 6 and Example 1 above is that the amount of PBT resin is changed to 93.7 parts by weight, and solid glass microspheres and polytetrafluoroethylene wax are not added.

[0109] Comparative Example 7 A method for preparing a PBT material modified with low water absorption glass microspheres includes the following steps: S1. Mix 70.2 parts by weight of PBT resin, 4.5 parts by weight of toughening agent, 0.3 parts by weight of antioxidant, 0.5 parts by weight of lubricant, 0.5 parts by weight of black masterbatch and 3 parts by weight of polytetrafluoroethylene wax in a high-speed mixer for 5 min to obtain a uniform premix. S2. The premixed material is fed into the main feed port of a twin-screw extruder and extruded through the twin-screw extruder at a melting temperature of 200~250 ℃. During the extrusion process, 20 parts by weight of solid glass microspheres are added from the side feed port of the twin-screw extruder. After melt extrusion, cooling in a water tank, and pelleting, a low water absorption glass microsphere modified PBT material is obtained.

[0110] The total conveying time of the premixed material and solid glass microspheres in the screw is 35 s.

[0111] The composition and dosage of the low water absorption glass microsphere modified PBT materials of Examples 1-4 and Comparative Examples 1-7 are summarized in Tables 1 and 2, respectively.

[0112] Table 1. Weight ratio of each component in Examples 1-4 Component Name Example 1 Example 2 Example 3 Example 4 PBT resin 73.2 70.2 63.2 60.2 Solid glass microbeads 20 20 30 30 Hollow glass microspheres —— —— —— —— toughening agent 4.5 4.5 4.5 4.5 antioxidants 0.3 0.3 0.3 0.3 lubricant 0.5 0.5 0.5 0.5 Black mother 0.5 0.5 0.5 0.5 Coupling agent 1 1 1 1 Polytetrafluoroethylene wax —— 3 —— 3 polytetrafluoroethylene —— —— —— —— Table 2. Weight proportions of each component in Comparative Examples 1-7 Component Name Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 PBT resin 94.2 70.2 70.2 70.2 70.2 94.2 70.2 Solid glass microbeads —— 20 20 20 —— —— 20 Hollow glass microspheres —— —— —— —— 20 —— —— toughening agent 4.5 4.5 4.5 4.5 4.5 4.5 4.5 antioxidants 0.3 0.3 0.3 0.3 0.3 0.3 0.3 lubricant 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Black mother 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Coupling agent —— 1 1 1 1 1 —— Polytetrafluoroethylene wax —— —— 3 3 3 —— 3 polytetrafluoroethylene —— 3 —— —— —— —— —— Performance testing

[0113] To better verify the performance of the low water absorption glass microsphere modified PBT materials obtained in the above embodiments and comparative examples, the materials prepared in the above comparative examples and embodiments were subjected to performance testing.

[0114] The materials obtained in Examples 1-4 and Comparative Examples 1-7 were dried at 100 °C for 4 hours, and injection molded according to the corresponding index testing standards. After injection molding, the samples were conditioned in a standard laboratory environment with a temperature of 23 ± 2 °C and a relative humidity of 50 ± 10% for no less than 48 hours to eliminate the effects of internal stress and moisture absorption. Subsequently, initial mechanical properties and water absorption properties were tested, including tensile strength test, flexural strength test and flexural modulus test.

[0115] The above performance indicators were all tested using existing known methods, and the specific test methods are as follows: Density test standard: ISO 1183-1:2019, test conditions: 23 ± 2 ℃, unit is g / cm³ 3 ; Tensile strength test: ISO 527-2:2012 Test conditions: 23±2 °C, 50±5 % RH, loading speed 50mm / min, unit is MPa; the specimen specification is type 1A.

[0116] Bending strength test: ISO 178:2019, test conditions: 23±2 °C, 50±5 % RH, loading speed 10 mm / min, unit is MPa; spline size is 80mm×10mm×4mm.

[0117] Flexural modulus test: ISO 178:2019, test conditions: 23±2 °C, 50±5 % RH, loading speed 10 mm / min, unit is MPa; spline size is 80mm×10mm×4mm.

[0118] Heat distortion temperature (0.45 MPa): ISO 75-2:2013, flat test, maximum bending stress applied is 0.45 MPa, heating rate is 120 °C / h, unit is °C; the sample size is 80 mm × 10 mm × 4 mm.

[0119] Shrinkage: ISO 294-4:2018, test conditions: within 24 hours after injection molding, at 23 ℃, measure the dimensional changes in the flow direction (MD) and vertical direction (TD) respectively, in %; the sample size is 60mm×60mm×2mm or 120mm×120mm×2mm.

[0120] Water absorption rate: ISO 62:2008. After weighing the dried sample, immerse it completely in distilled water at 23 °C. After soaking until saturation, i.e., mass change <0.1 mg / 24h, remove it, wipe off the surface moisture, and weigh it immediately. The unit is %; the sample size is 60mm×60mm×2mm.

[0121] The specific test results of Examples 1-4 and Comparative Examples 1-7 are shown in Tables 3 and 4, respectively.

[0122] Table 3. Performance test results of PBT materials modified with low water absorption glass microspheres obtained in Examples 1-4 Testing items unit Example 1 Example 2 Example 3 Example 4 density <![CDATA[g / cm 3 ]]> 1.408 1.412 1.468 1.471 Tensile strength MPa 47.8 48.5 43.9 43.7 Bending strength MPa 73.3 72.9 64.8 65.2 Flexural modulus MPa 2760 2650 3150 3100 Heat distortion temperature (0.45 MPa) °C 158.4 159.8 164.2 163.8 Shrinkage rate (MD) % 1.66 1.40 1.48 1.37 Shrinkage rate (TD) % 1.77 1.44 1.64 1.42 Water absorption rate % 0.16 0.06 0.14 0.07 Table 4. Performance test results of PBT materials modified with low water absorption glass microspheres obtained from Comparative Examples 1-7 Testing items unit Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 density <![CDATA[g / cm 3 ]]> 1.285 1.415 1.417 1.412 1.187 1.287 1.411 Tensile strength MPa 51.7 47.9 48.1 49.2 46.6 52.1 46.1 Bending strength MPa 68.8 73.1 71.7 73.3 71.1 70.3 70.9 Flexural modulus MPa 2120 2770 2590 2620 2570 2170 2590 Heat distortion temperature (0.45 MPa) °C 138.9 161.7 158.8 157.2 159.2 140.3 156.8 Shrinkage rate (MD) % 2.01 1.42 1.38 1.41 1.41 2.11 1.47 Shrinkage rate (TD) % 2.39 1.49 1.51 1.43 1.46 2.27 1.54 Water absorption rate % 0.17 0.23 0.07 0.15 0.33 0.15 0.09 As shown in Tables 3 and 4, the higher the amount of solid glass microspheres added, the greater the rigidity of the material, the higher the heat distortion temperature, and the lower the shrinkage rate. The addition of polytetrafluoroethylene wax reduces the difference in shrinkage rate between the flow direction and the direction perpendicular to the flow direction, and also reduces the water absorption rate of the material. When the amount of solid glass microspheres is 20 parts by weight, the cost and performance advantages are more obvious.

[0123] Therefore, considering all the test results and factors such as cost, Example 2 is a superior technical solution, thus yielding the preferred preparation method of the present invention.

[0124] As can be seen from Example 2 and Comparative Example 2 and the corresponding test results, the water absorption performance of the material provided in Example 2 of the present invention is better than that of Comparative Example 2. This is because the molecular weight of polytetrafluoroethylene in Comparative Example 2 is too large compared with that of polytetrafluoroethylene wax, resulting in insufficient interfacial compatibility of the material and poor water absorption performance.

[0125] As can be seen from Examples 2 and Comparative Examples 3 and 4 and their corresponding test results, the material provided in Example 2 of this invention exhibits a smaller difference in shrinkage rate between the flow direction and the vertical direction compared to Comparative Example 3, and a lower water absorption rate compared to Comparative Example 4. This is because the total conveying time of the mixture composed of premix and solid glass microspheres in the screw is shorter in Comparative Example 3 and longer in Comparative Example 4, respectively, which affects the melting effect of each component in Comparative Example 3 and the relatively high breakage rate of the solid glass microspheres in Comparative Example 4, thus affecting the material's water absorption performance. Therefore, the preferred total conveying time of the mixture composed of premix and solid glass microspheres in the screw is 35 s.

[0126] As can be seen from Example 2 and Comparative Example 5 and the corresponding test results, the water absorption performance of the material provided in Example 2 of the present invention is better than that of Comparative Example 5, because the hollow glass microspheres in Comparative Example 5 are damaged, which affects the long-term stability of the material and thus affects the water absorption performance of the material.

[0127] The results from Examples 2 and Comparative Examples 1, 6, and 7, along with their corresponding test results, show that the coupling agent has a relatively small impact on unfilled systems. In systems containing fillers, the coupling agent can significantly improve the tensile, flexural strength, and heat distortion temperature of the material.

[0128] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0129] The preparation method of a low water absorption glass microsphere modified PBT material provided in the embodiments of this application has been described in detail above. Specific examples have been used to illustrate the principle and implementation of this application. The description of the above embodiments is only for the purpose of helping to understand the technical solution and core idea of ​​this application. Those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A PBT material modified with low water absorption glass microspheres, characterized in that, The components include the following parts by weight: PBT resin: 70~100 parts; Solid glass microspheres: 0~30 parts; Toughening agent: 0-5 parts; Antioxidant: 0-2 parts; Lubricant: 0-2 parts; Black masterbatch: 0-2 parts; Coupling agent: 0-2 parts; Polytetrafluoroethylene wax: 0~5 parts; The solid glass microspheres have an average particle size of 1~50 μm; The average particle size of the polytetrafluoroethylene wax is 3~15 μm, and the weight-average molecular weight of the polytetrafluoroethylene wax is 10000~30000 g / mol. The weight ratio of the solid glass microspheres to the polytetrafluoroethylene wax is (5~10):

1.

2. The low water absorption glass microsphere modified PBT material according to claim 1, characterized in that, It includes the following components in parts by weight: PBT resin: 70-90 parts; Solid glass microspheres: 10-30 parts; Toughening agent: 0-5 parts; Antioxidant: 0.1~0.5 parts; Lubricant: 0.1~0.5 parts; Black masterbatch: 0.5~1.0 parts; Coupling agent: 0~1 part; Polytetrafluoroethylene wax: 3-5 parts.

3. A low-water-absorption glass microsphere modified PBT material according to claim 1 or 2, characterized in that, The intrinsic viscosity of the PBT resin is 0.80~1.20 dL / g; The melting point of the PBT resin is 220~230 ℃; The PBT resin has a terminal carboxyl group content of ≤30 mmol / kg.

4. A low-water-absorption glass microsphere modified PBT material according to claim 1 or 2, characterized in that, The solid glass microspheres are made of materials including soda-lime silicate glass and borosilicate glass; The density of the solid glass microspheres is 2.5 g / cm³. 3 .

5. A low-water-absorption glass microsphere modified PBT material according to claim 1 or 2, characterized in that, The toughening agent is one or a mixture of more than one of the following: ethylene-alkyl acrylate-glycidyl methacrylate copolymer, ethylene-butyl acrylate copolymer, and glycidyl methacrylate-grafted polyethylene elastomer.

6. A low-water-absorption glass microsphere modified PBT material according to claim 1 or 2, characterized in that, The coupling agent is a silane coupling agent.

7. A low-water-absorption glass microsphere modified PBT material according to claim 1 or 2, characterized in that, The polytetrafluoroethylene wax is a powdered polytetrafluoroethylene micro powder obtained by thermal decomposition. The average particle size of the polytetrafluoroethylene wax is 5~7 μm, and the particle size distribution index is ≤1.

8. The heat of melting of the polytetrafluoroethylene wax is 30~45 J / g.

8. A method for preparing a low-water-absorption glass microsphere modified PBT material as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Mix PBT resin, toughening agent, antioxidant, lubricant, black masterbatch, coupling agent, and polytetrafluoroethylene wax in a high-speed mixer for 5-10 minutes to obtain a uniform premix. S2. The premixed material is fed into the main feed port of the twin-screw extruder. During the melt extrusion process of the twin-screw extruder, solid glass microspheres are added from the side feed port of the twin-screw extruder. After melt extrusion, the material is cooled and pelletized after passing through a water tank. The processing temperature of the twin-screw extruder is set to 200~260 ℃ from the feeding section to the die head; The side feed port is located at 25-40% of the total length of the twin-screw extruder barrel.

9. The method for preparing a low-water-absorption glass microsphere modified PBT material according to claim 8, characterized in that, In S2, the twin-screw extruder has at least nine temperature zones; The temperature of the twin-screw extruder is 200~220 ℃ in zone 1, 220~240 ℃ in zone 2, 240~260 ℃ in zones 3, 4 and 5, 220~240 ℃ in zones 6, 7, 8 and 9, and 230~250 ℃ at the die head.

10. The method for preparing a low-water-absorption glass microsphere modified PBT material according to claim 8, characterized in that, In S2, the screw speed of the twin-screw extruder is 300~500 r / min; The screw configuration of the twin-screw extruder is configured such that, after the side feed port, it consists of a conveying element and at least one set of toothed disc assembly blocks; The total conveying time of the premix and the solid glass microspheres in the screw is 25~60 s.