Preparation method and application of linear chain modified hyperbranched polyester and polybutylene terephthalate composite material

Abstract

This invention belongs to the field of polymer composite materials technology and discloses a method for preparing and applying a linear chain-modified hyperbranched polyester and polybutylene terephthalate (PBT) composite material. The method involves esterifying a carboxyl-terminated hyperbranched polyester, a diol, and a diacid monomer under the action of a catalyst to obtain a linear chain-modified carboxyl-terminated hyperbranched polyester. This hyperbranched polyester is then compounded with PBT and glass fiber, and the mixture is subjected to high-speed mixing and twin-screw extrusion granulation to obtain a glass fiber reinforced PBT composite material. This invention can efficiently enhance the interfacial bonding strength between PBT and glass fiber, significantly improve the dispersibility of high glass fiber systems, eliminate defects such as fiber floating, delamination, and agglomeration, and comprehensively improve the tensile strength, flexural strength, and impact strength of ultra-high glass fiber reinforced composite materials.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials technology, and more specifically, relates to a method for preparing and applying a linear chain modified hyperbranched polyester and polybutylene terephthalate composite material. Background Technology

[0002] In response to the upgrading needs of the automotive lightweighting industry, glass fiber reinforced polybutylene terephthalate (PET) composites have become a highly competitive core material in the automotive lightweighting field due to their comprehensive performance advantages. This composite material not only retains the excellent melt processability, chemical corrosion resistance, and insulation properties of the PET matrix itself, but also achieves significant improvements in heat resistance and mechanical properties through glass fiber modification. The dimensional accuracy and long-term stability of molded parts are also significantly optimized. As a lightweight engineering material that can replace non-ferrous metals and ordinary steel, glass fiber reinforced PET can achieve a weight reduction of 35%-50% for automotive parts. This effectively reduces fuel consumption and hydrocarbon emissions, and plays a crucial role in optimizing vehicle handling, extending component service life, and improving reliability under various operating conditions.

[0003] Glass fiber reinforced polybutylene terephthalate (PET) composites, as ideal structural materials to replace traditional metals, not only significantly reduce vehicle weight and powertrain load, but also demonstrate irreplaceable technological advantages in improving component temperature resistance, optimizing electromagnetic shielding effectiveness, and meeting stringent electrical reliability requirements. However, with increasing glass fiber filler ratios, PET matrix systems encounter bottlenecks such as decreased melt flowability, injection molding difficulties, and reduced surface gloss. Uneven fiber dispersion in the matrix, insufficient interfacial bonding strength leading to "floating fiber" and exposure, and excessive fiber breakage during high-speed shearing resulting in insufficient fiber length remain key obstacles hindering the development of PET composites towards higher rigidity and higher surface quality. Furthermore, existing high-flowability composites often exhibit poor toughness and impact resistance. Currently, there is no glass fiber reinforced PET composite that combines both high flowability and high mechanical properties.

[0004] Currently, most existing publicly available technologies focus on modifying the conventional glass fiber content. Patent application CN119708626A discloses a hydrolysis-resistant, low-fouling glass fiber reinforced PBT material with a glass fiber content of 14-32 wt%; patent CN120271970B discloses a light-transmitting, laser-weldable glass fiber reinforced PBT material with a glass fiber content of 30-50 wt%; patent application CN121517682A discloses a low-warpage, hydrolysis-resistant glass fiber reinforced PBT material with a glass fiber content of 10-40 wt%; and patent CN113956598 B discloses a glass fiber reinforced ASA / PBT alloy material with a glass fiber content of only 5-30 wt%. In existing technologies, the glass fiber content of glass fiber reinforced PBT is generally concentrated in the range of 10-50 wt%, generally not exceeding 50 wt%, which is insufficient to meet the requirements of high-end structural components for higher rigidity, higher dimensional stability, lower creep, and higher heat resistance. PBT materials with ultra-high glass fiber content of 50~70 wt% are rarely reported in existing patents. Problems such as uneven dispersion, poor interfacial bonding, difficult processing, increased mold fouling, and fluctuations in mechanical properties caused by ultra-high glass fiber have not yet been effectively solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing and applying a linear chain-modified hyperbranched polyester and polybutylene terephthalate (PBT) composite material. By using linear chain-modified end-carboxyl hyperbranched polyester, the interfacial bonding strength between PBT and glass fiber is improved, thereby achieving ultra-high glass fiber load while ensuring uniform dispersion of glass fiber in the matrix and strong interfacial bonding, thus improving the overall performance of the composite material.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a linear chain-modified end-carboxyl hyperbranched polyester, comprising: subjecting the end-carboxyl hyperbranched polyester, a diol, and a diacid monomer to an esterification reaction under the action of a catalyst to obtain a linear chain-modified end-carboxyl hyperbranched polyester; wherein the molar ratio of the end-carboxyl hyperbranched polyester, the diol, and the diacid monomer is 1:10~50:10~40.

[0007] Furthermore, the esterification reaction is carried out in a microwave reactor, heated to 110-160°C at a microwave power of 80-500W for 1-3 hours. The microwave power is preferably 100-200W.

[0008] Furthermore, the end-carboxyl hyperbranched polyester has an acid value of 120-300 mgKOH / g, a molecular weight of 2500-8000 g / mol, and a branching degree of 0.4-0.7. The diol is any one or more of aliphatic and aromatic diols with 2-10 carbon atoms; the diacid monomer is a diacid or diacid anhydride, preferably any one or more of aliphatic and aromatic diacids or anhydrides with 4-10 carbon atoms. The catalyst is any one of methanesulfonic acid, p-toluenesulfonic acid, sulfuric acid, phosphoric acid, n-butyl titanate, ethyl propylene titanate, and zinc acetate.

[0009] Furthermore, the end-carboxyl hyperbranched polyester is one or more of the HyPerC102, HyPer C103, HyPer C202, HyPer C203, HyPer C302, HyPer C303, HyPer C402 and HyPer C403 series products from Wuhan Hyperbranched Resin Technology Co., Ltd.; the diol is one or more of ethylene glycol, 1,3-propanediol, terephthalic acid, isophthalic acid, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanediol. The dicarboxylic acid is one or more of glutaric acid, octanoic acid, azelaic acid, maleic acid, adipic acid, 1,4-cyclohexanedicarboxylic acid, phthalic acid, and terephthalic acid; the dicarboxylic acid anhydride is succinic anhydride.

[0010] In a second aspect, the present invention provides a linear chain-modified terminal carboxyl hyperbranched polyester, which is prepared by the above-described preparation method.

[0011] In a third aspect, the present invention provides a polybutylene terephthalate composite material comprising polybutylene terephthalate, glass fiber, and the linear chain modified end-carboxyl hyperbranched polyester.

[0012] Furthermore, the glass fiber content in the composite material is 50-70% by mass; And / or, the linear chain modified end-carboxyl hyperbranched polyester has a mass content of 0.1% to 1% in the composite material.

[0013] Furthermore, the polybutylene terephthalate is any one of B4520, B4500, B4450, 1200-211D, S 4090G6, B 4300 G6, 1200-211M, DR48-1001, KH2083, and 357 BK1066; the glass fiber is one or more of alkali-free glass fiber, medium-alkali glass fiber, high-alkali glass fiber, alkali-resistant glass fiber, and high-strength glass fiber.

[0014] According to a fourth aspect of the present invention, a method for preparing the polybutylene terephthalate composite material is provided, comprising: mixing polybutylene terephthalate, glass fiber, and linear chain modified end-carboxyl hyperbranched polyester in a high-speed mixer until uniform, and then feeding the mixture into a twin-screw extruder for extrusion granulation to obtain the polybutylene terephthalate composite material; wherein the extrusion granulation temperature is controlled at 200-270°C.

[0015] According to a fifth aspect of the present invention, an application of the aforementioned polybutylene terephthalate composite material is provided, wherein the composite material can be used in the preparation of structural components in the fields of power equipment, machinery manufacturing, automotive industry and / or aerospace.

[0016] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following advantages and beneficial effects: (1) The linear chain modified end-carboxyl hyperbranched polyester used in this invention can effectively enhance the interfacial bonding strength between PBT and glass fiber, greatly improve the dispersibility of high glass fiber system, eliminate defects such as floating fiber, delamination, and agglomeration, and comprehensively improve the tensile strength, flexural strength and impact strength of ultra-high glass fiber reinforced composite material.

[0017] (2) In response to the problem that PBT with ultra-high glass fiber content of 50-70 wt% has high melt viscosity, poor fluidity and is difficult to process and form, the present invention introduces hyperbranched polyester, which can significantly reduce melt viscosity, improve processing fluidity and correspondingly reduce processing temperature while achieving ultra-high glass fiber load, making it easier to form, reducing equipment load and improving production stability.

[0018] (3) The high glass fiber content PBT composite material prepared by the present invention maintains ultra-high rigidity and dimensional stability, while also possessing excellent processing fluidity, high temperature creep resistance, thermal stability and wear resistance. Its comprehensive performance is significantly better than that of conventional 10-50wt% glass fiber reinforced PBT, and can meet the stringent requirements of high-end structural components in fields such as power equipment, machinery manufacturing, automobiles, and aerospace.

[0019] (4) The present invention preferably uses microwave high-efficiency synthesis technology to prepare hyperbranched polyester, which greatly shortens the 4-20 hours required for traditional esterification reaction to 2-3 hours, increases the reaction rate by more than 5 times, significantly shortens the production cycle, reduces energy consumption, and is more suitable for industrial high-efficiency production.

[0020] (5) The present invention has a simple overall process, low raw material cost, significant modification effect and high product added value. While achieving 50-70 wt% ultra-high glass fiber reinforcement, it solves the industry pain points such as difficult processing, unstable strength and poor appearance caused by high glass fiber, and has extremely high industrial promotion value. Attached Figure Description

[0021] Figure 1 The TG curve is shown for the GF68 / PBT composite material with a glass fiber content of 68wt% in Example 1.

[0022] Figure 2 In the figures, (a) and (b) are SEM images of the interlaminar cross section and cross section of the C103-H / GF68 / PBT composite material prepared in Example 1, respectively; (c) and (d) are SEM images of the interlaminar cross section and cross section of the GF68 / PBT composite material prepared in Comparative Example 1, respectively.

[0023] Figure 3 The infrared spectrum of the linear chain-modified terminal carboxyl hyperbranched polyester C202-H prepared in Example 2. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0025] The method for preparing the linear chain modified high-temperature hyperbranched polyester of the present invention includes: esterifying the carboxyl-terminated hyperbranched polyester, the diol and the diacid monomer under the action of a catalyst to obtain the linear chain modified carboxyl-terminated hyperbranched polyester, wherein the diacid monomer is a diacid or anhydride.

[0026] Specifically, the following steps are included: Diol, diacid or anhydride and carboxyl-terminated hyperbranched polyester are mixed evenly in a dehydrating agent, an esterification catalyst is added, and then the mixture is placed in a microwave reactor and stirred at 110-160℃ for 1-3 hours. After cooling to room temperature, the mixture is crushed and ground to obtain white linear chain modified carboxyl-terminated hyperbranched polyester powder.

[0027] Preferably, the end-carboxyl hyperbranched polyester is one or more of the HyPer C102, HyPer C103, HyPer C202, HyPer C203, HyPer C302, HyPer C303, HyPer C402 and HyPer C403 series products from Wuhan Hyperbranched Resin Technology Co., Ltd.

[0028] Table 1 Properties of carboxyl-terminated hyperbranched polyesters

[0029] Preferably, the diol is one or more of ethylene glycol, 1,3-propanediol, terephthalic acid, isophthalic acid, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanediol.

[0030] Preferably, the dicarboxylic acid or anhydride is one or more of glutaric acid, octanoic acid, azelaic acid, maleic acid, adipic acid, 1,4-cyclohexanedicarboxylic acid, phthalic acid, terephthalic acid, and succinic anhydride. The esterification catalyst is any one of methanesulfonic acid, p-toluenesulfonic acid, phosphoric acid, sulfuric acid, n-butyl titanate, ethyl propyl titanate, and zinc acetate; the dehydrating agent is toluene or xylene.

[0031] The linear chain-modified end-carboxyl hyperbranched polyester of the present invention can be used in polybutylene terephthalate composites.

[0032] The polybutylene terephthalate (PBT) composite material of this invention comprises PBT, glass fiber GF68, and the aforementioned linear chain-modified end-carboxyl hyperbranched polyester. The linear chain-modified hyperbranched polyester prepared by this invention can significantly reduce the melt viscosity of the high glass fiber reinforced PBT system, improve processing fluidity, effectively improve the dispersion and interfacial bonding ability of glass fibers in the matrix, eliminate floating fiber defects, and significantly improve the tensile, flexural, and impact resistance mechanical properties of the composite material; simultaneously, it reduces the processing temperature of the composite material, saves energy, and lowers production costs. The product combines the advantages of high glass fiber content, excellent thermal stability, and high dimensional accuracy. The composite material preparation process is simple, suitable for large-scale industrial production, and can be widely used in power equipment, machinery manufacturing, automotive industry, and aerospace fields.

[0033] Preferably, in the composite material, the mass percentage of glass fiber is 50-70%, and the mass percentage of linear chain modified end-carboxyl hyperbranched polyester is 0.1%-1%.

[0034] This invention achieves ultra-high glass fiber load while ensuring uniform dispersion of glass fiber in the matrix and strong interfacial bonding, giving the material both high strength and excellent processability. It breaks through the performance bottleneck of traditional medium and low glass fiber reinforced PBT and has significant technical value and application prospects.

[0035] Preferably, the polybutylene terephthalate is one of B4520, B4500, 310SE0, 1200-211D, S600F10, 200FP, 1200-211M, KH2083, and VALOX 325.

[0036] Preferably, the glass fiber is one or more of alkali-free glass fiber, medium-alkali glass fiber, high-alkali glass fiber, alkali-resistant glass fiber, and high-strength glass fiber.

[0037] The preparation method of the polybutylene terephthalate composite material of the present invention includes the following steps: first, polybutylene terephthalate, glass fiber and linear chain modified end-carboxyl hyperbranched polyester are mixed evenly by a high-speed mixer, and then extruded and granulated by a twin-screw extruder to obtain the polybutylene terephthalate composite material; wherein, the extrusion granulation temperature is 200-270°C.

[0038] In the preparation of the polybutylene terephthalate composite material of the present invention, the temperature of the extruder can be reduced to below 270°C, which effectively reduces the manufacturing temperature compared with the prior art.

[0039] The beneficial effects of the above solution are illustrated below through specific embodiments: Example 1

[0040] 320.00 g HyPer C103, 62.01 g ethylene glycol, 73.00 g adipic acid, 0.68 g methanesulfonic acid catalyst, and 40 mL xylene were added to a 1000 mL three-necked flask and refluxed at 250 W (130 °C) for 2.5 h. After the reaction was completed, the mixture was cooled to room temperature to obtain linear chain-modified terminal carboxyl hyperbranched polyester C103-H with a yield of 95.32%. The product was crushed, ground, and stored. GPC analysis showed that its number-average molecular weight was 8750 g / mol.

[0041] 320.00 g of dried polybutylene terephthalate (KH2083), 680.00 g of high-alkali glass fiber, and 5.00 g of hyperbranched polyester C103-H were mixed in a high-speed mixer for 5 minutes until homogeneous. The mixture was then extruded and granulated using a twin-screw extruder. The extrusion temperatures were sequentially set to 240℃, 260℃, 270℃, 270℃, and 260℃, with the main screw speed at 50 rpm. The resulting granules were then used to prepare standard test specimens (GF68 / PBT composite material) for mechanical property testing using an injection molding machine. The mechanical properties of the composite material were tested using a universal testing machine and an impact tester, and the flowability of the composite material was tested using a melt flow indexer.

[0042] Figure 1 The TG curve is for a glass fiber content of 68 wt%. The thermal decomposition temperature is 371.1℃ when the mass loss is 5%, indicating good thermal stability. Figure 2 (a) is a SEM image of the interlaminar cross-section of the GF68 / PBT composite material, and (b) is a SEM image of the cross-section of the composite material. It can be observed that the glass fibers are neatly and tightly arranged, with small gaps between the fibers and the matrix, indicating a tight interfacial bond. This demonstrates that the modifier effectively improves the interfacial compatibility between the glass fibers and the PBT matrix.

[0043] Example 2

[0044] 210.00 g HyPer C202, 260.38 g neopentyl glycol, 264.24 g glutaric acid, 2.62 g phosphoric acid, and 40 mL xylene were added to a 1000 mL three-necked flask and refluxed at 250 W (130 °C) for 3 h. After the reaction was complete, the mixture was cooled to room temperature to obtain linear chain-modified terminal carboxyl hyperbranched polyester C202-H with a yield of 96.15%. The product was then crushed, ground, and stored. The infrared spectrum of C202-H is shown below. Figure 3 1725-1735 cm -1 Corresponding peak for the C=O stretching vibration of the ester group, 2964 cm⁻¹ -1 Corresponding to the stretching vibration peak of saturated alkyl CH, 1000-1300 cm⁻¹ -1 The sample exhibits multiple strong CO peaks. GPC analysis revealed a number-average molecular weight of 6630 g / mol, indicating that this embodiment successfully prepared a linear chain-modified terminal carboxyl hyperbranched polyester C202-H.

[0045] 320.00 g of dried polybutylene terephthalate (KH2083), 680.00 g of high-alkali glass fiber, and 5.00 g of hyperbranched polyester C202-H were mixed in a high-speed mixer for 5 minutes until homogeneous. The mixture was then extruded and granulated using a twin-screw extruder. The extrusion temperatures were sequentially set to 240℃, 260℃, 270℃, 270℃, and 260℃, with the main screw speed at 40 rpm. The resulting granules were then used to prepare standard test specimens for mechanical properties using an injection molding machine. The mechanical properties of the composite material were tested using a universal testing machine and an impact tester, and the flowability of the composite material was tested using a melt flow indexer.

[0046] Example 3

[0047] 280.00 g HyPer C302, 60.87 g 1,3-propanediol, 72.10 g 1,4-butanediol, 215.23 g 1,4-cyclohexanedicarboxylic acid, 1.74 g p-toluenesulfonic acid, and 40 mL xylene were added to a 1000 mL three-necked flask and refluxed at 250 W (130 °C) for 3 h. After the reaction was completed, the mixture was cooled to room temperature to obtain linear chain-modified terminal carboxyl hyperbranched polyester C302-H with a yield of 95.78%. The product was crushed, ground, and stored. GPC analysis showed that its number-average molecular weight was 5835 g / mol.

[0048] 320.00 g of dried polybutylene terephthalate (KH2083), 680.00 g of high-alkali glass fiber, and 5.00 g of hyperbranched polyester C302-H were mixed for 5 minutes and then extruded and granulated using a twin-screw extruder. The extrusion temperatures were set sequentially to 240℃, 260℃, 270℃, 270℃, and 260℃, with the main screw speed at 50 rpm. The resulting granules were then used to prepare standard test specimens for mechanical properties using an injection molding machine. The mechanical properties of the composite material were tested using a universal testing machine and an impact tester, and the flowability of the composite material was tested using a melt flow indexer.

[0049] Example 4

[0050] 130.00 g of HyPer C102, 216.32 g of 1,4-cyclohexanediethanol, 150.11 g of succinic anhydride, 1.83 g of n-butyl titanate, and 40 mL of xylene were added to a 1000 mL three-necked flask and refluxed at 250 W (130 °C) for 3 h. After the reaction was completed, the mixture was cooled to room temperature to obtain linear chain-modified terminal carboxyl hyperbranched polyester C102-H with a yield of 95.16%. The product was then crushed, ground, and stored. GPC analysis showed that its number-average molecular weight was 9390 g / mol.

[0051] 320.00 g of dried polybutylene terephthalate (KH2083), 680.00 g of high-alkali glass fiber, and 5.00 g of hyperbranched polyester C102-H were mixed for 5 minutes and then extruded and granulated using a twin-screw extruder. The extrusion temperatures were set sequentially to 240℃, 260℃, 270℃, 270℃, and 260℃, with the main screw speed at 40 rpm. The resulting granules were then used to prepare standard test specimens for mechanical properties using an injection molding machine. The mechanical properties of the composite material were tested using a universal testing machine and an impact tester, and the flowability of the composite material was tested using a melt flow indexer.

[0052] Example 5

[0053] 260.00 g HyPer C203, 207.24 g isophthalic acid, 130.65 g octanoic acid, 1.69 g ethyl propylene titanate, and 40 mL xylene were added to a 1000 mL three-necked flask and refluxed at 250 W (130 °C) for 3 h. After the reaction was complete, the mixture was cooled to room temperature to obtain linear chain-modified terminal carboxyl hyperbranched polyester C203-H with a yield of 96.02%. The product was crushed, ground, and stored. GPC analysis showed that its number-average molecular weight was 11420 g / mol.

[0054] 320.00 g of dried polybutylene terephthalate (KH2083), 680.00 g of high-alkali glass fiber, and 5.00 g of hyperbranched polyester C203-H were mixed for 5 minutes and then extruded and granulated using a twin-screw extruder. The extrusion temperatures were set sequentially to 240℃, 260℃, 270℃, 270℃, and 260℃, with the main screw speed at 40 rpm. The resulting granules were then used to prepare standard test specimens for mechanical properties using an injection molding machine. The mechanical properties of the composite material were tested using a universal testing machine and an impact tester, and the flowability of the composite material was tested using a melt flow indexer.

[0055] Example 6

[0056] 285.00 g HyPer C303, 144.57 g 1,3-propanediol, 54.80 g adipic acid, 62.30 g terephthalic acid, 1.31 g zinc acetate, and 40 mL xylene were added to a 1000 mL three-necked flask and refluxed at 250 W (130 °C) for 3 h. After the reaction was completed, the mixture was cooled to room temperature to obtain linear chain-modified terminal carboxyl hyperbranched polyester C303-H with a yield of 96.35%. The product was crushed, ground, and stored. GPC analysis showed that its number-average molecular weight was 10395 g / mol.

[0057] 320.00 g of dried polybutylene terephthalate (KH2083), 680.00 g of high-alkali glass fiber, and 5.00 g of hyperbranched polyester C303-H were mixed for 5 minutes and then extruded and granulated using a twin-screw extruder. The extrusion temperatures were set sequentially to 240℃, 260℃, 270℃, 270℃, and 260℃, with the main screw speed at 40 rpm. The resulting granules were then used to prepare standard test specimens for mechanical properties using an injection molding machine. The mechanical properties of the composite material were tested using a universal testing machine and an impact tester, and the flowability of the composite material was tested using a melt flow indexer.

[0058] Example 7

[0059] 170.00 g HyPer C402, 138.16 g terephthalic acid, 112.93 g azelaic acid, 1.26 g phosphoric acid, and 40 mL xylene were added to a 1000 mL three-necked flask and refluxed at 250 W (130 °C) for 3 h. After the reaction was completed, the mixture was cooled to room temperature to obtain linear chain-modified terminal carboxyl hyperbranched polyester C402-H with a yield of 95.48%. The product was crushed, ground, and stored. GPC analysis showed that its number-average molecular weight was 7996 g / mol.

[0060] 320.00 g of dried polybutylene terephthalate (KH2083), 680.00 g of high-alkali glass fiber, and 5.00 g of hyperbranched polyester C402-H were mixed for 5 minutes and then extruded and granulated using a twin-screw extruder. The extrusion temperatures were set sequentially to 240℃, 260℃, 270℃, 270℃, and 260℃, with the main screw speed at 40 rpm. The resulting granules were then used to prepare standard test specimens for mechanical properties using an injection molding machine. The mechanical properties of the composite material were tested using a universal testing machine and an impact tester, and the flowability of the composite material was tested using a melt flow indexer.

[0061] Example 8

[0062] 380.00 g of HyPer C403, 346.10 g of 1,4-cyclohexanediethanol, 232.58 g of terephthalic acid, 2.89 g of p-toluenesulfonic acid, and 40 mL of xylene were added to a 1000 mL three-necked flask and refluxed at 250 W (130 °C) for 3 h. After the reaction was completed, the mixture was cooled to room temperature to obtain linear chain-modified terminal carboxyl hyperbranched polyester C403-H with a yield of 95.92%. The product was crushed, ground, and stored. GPC analysis showed that its number-average molecular weight was 18170 g / mol.

[0063] 320.00 g of dried polybutylene terephthalate (KH2083), 680.00 g of high-alkali glass fiber, and 5.00 g of hyperbranched polyester C403-H were mixed for 5 minutes and then extruded and granulated using a twin-screw extruder. The extrusion temperatures were set sequentially to 240℃, 260℃, 270℃, 270℃, and 260℃, with the main screw speed at 40 rpm. The resulting granules were then used to prepare standard test specimens for mechanical properties using an injection molding machine. The mechanical properties of the composite material were tested using a universal testing machine and an impact tester, and the flowability of the composite material was tested using a melt flow indexer.

[0064] Example 9 170.00 g HyPer C402, 345.40 g isophthalic acid, 261.30 g octanoic acid, 1.92 g phosphoric acid, and 40 mL xylene were added to a 1000 mL three-necked flask and refluxed at 250 W (130 °C) for 3 h. After the reaction was completed, the mixture was cooled to room temperature to obtain linear chain-modified terminal carboxyl hyperbranched polyester C402-H with a yield of 95.81%. The product was crushed, ground, and stored. GPC analysis showed that its number-average molecular weight was 13520 g / mol.

[0065] 320.00 g of dried polybutylene terephthalate (B4500), 680.00 g of high-alkali glass fiber, and 5.00 g of hyperbranched polyester C403-H were mixed for 5 minutes and then extruded and granulated using a twin-screw extruder. The extrusion temperatures were set sequentially to 240℃, 260℃, 270℃, 270℃, and 260℃, with the main screw speed at 40 rpm. The resulting granules were then used to prepare standard test specimens for mechanical properties using an injection molding machine. The mechanical properties of the composite material were tested using a universal testing machine and an impact tester, and the flowability of the composite material was tested using a melt flow indexer.

[0066] Example 10

[0067] 285.00 g HyPer C303, 95.18 g 1,3-propanediol, 264.24 g glutaric acid, 1.86 g p-toluenesulfonic acid, and 40 mL xylene were added to a 1000 mL three-necked flask and refluxed at 250 W (130 °C) for 3 h. After the reaction was complete, the mixture was cooled to room temperature to obtain linear chain-modified terminal carboxyl hyperbranched polyester C303-H with a yield of 96.37%. The product was crushed, ground, and stored. GPC analysis showed that its number-average molecular weight was 11250 g / mol.

[0068] 320.00 g of dried polybutylene terephthalate (1200-211D), 680.00 g of high-alkali glass fiber, and 5.00 g of hyperbranched polyester C303-H were mixed for 5 minutes and then extruded and granulated using a twin-screw extruder. The extrusion temperatures were set sequentially to 240℃, 260℃, 270℃, 270℃, and 260℃, with the main screw speed at 50 rpm. The resulting granules were then used to prepare standard test specimens for mechanical properties using an injection molding machine. The mechanical properties of the composite material were tested using a universal testing machine and an impact tester, and the flowability of the composite material was tested using a melt flow indexer.

[0069] Comparative Example 1 320.00 g of dried polybutylene terephthalate (KH2083) and 680.00 g of high-alkali glass fiber were mixed for 5 minutes and then extruded and granulated using a twin-screw extruder. The extrusion temperatures were set sequentially to 280℃, 290℃, 300℃, 300℃, and 290℃, with the main screw speed at 50 rpm. The resulting granules were then used to prepare standard test specimens for mechanical property testing via an injection molding machine. The mechanical properties of the composite material were tested using a universal testing machine and an impact tester, and the flowability of the composite material was tested using a melt flow indexer. The tensile strength and flexural strength of the specimens were tested according to GB / T 1040.2-2006 and GB / T9341-2008. The impact performance of the material was tested using a GT-7045-MDL impact testing machine.

[0070] from Figure 2 As can be seen from (c) and (d), the interfacial compatibility between glass fiber and PBT matrix is ​​poor when the linear chain modified end-carboxyl hyperbranched polyester of the present invention is not added.

[0071] Table 2 Performance test results of polybutylene terephthalate composite materials in each example and comparative example

[0072] As can be seen from the test results in Table 2, the composite materials of Examples 1-8 of the present invention have higher tensile strength and melt flow index than the comparative materials without hyperbranched polyester, especially Examples 1-5, which are significantly higher than the comparative materials. Therefore, the composite materials of Examples 1-8 have good strength and flowability. Meanwhile, the flexural strength and notched impact strength of the composite materials of Examples 1-8 are higher than those of the comparative materials, especially Examples 1-7, which are significantly higher than the comparative materials, indicating that the composite materials of Examples 1-8 also have good toughness and impact resistance. The end-carboxyl group structure of the hyperbranched polyester of the present invention endows it with high-temperature resistance, the highly branched structure improves the flowability of polybutylene terephthalate, and the carboxyl functional groups improve the interfacial bonding between glass fiber and matrix. Therefore, the hyperbranched polyester of the present invention can significantly improve the tensile strength, flexural strength, impact strength, and melt flow index of the composite materials.

[0073] The modified high-content glass fiber reinforced polybutylene terephthalate composite material of the present invention, while ensuring tensile strength and high fluidity, also has high toughness and impact resistance, which greatly improves the performance of the material itself, thus enabling it to be used in a wider range of more demanding fields.

[0074] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a linear chain-modified terminal carboxyl hyperbranched polyester, characterized in that, include: A carboxyl-terminated hyperbranched polyester, a diol, and a diacid monomer are subjected to an esterification reaction under the action of a catalyst to obtain a linear chain modified carboxyl-terminated hyperbranched polyester; the molar ratio of the carboxyl-terminated hyperbranched polyester, the diol, and the diacid monomer is 1:10~50:10~40.

2. The method for preparing linear chain-modified terminal carboxyl hyperbranched polyester according to claim 1, characterized in that, The esterification reaction is carried out in a microwave reactor, heated to 110-160°C by microwave heating at 80-500W for 1-3 hours.

3. The method for preparing linear chain-modified terminal carboxyl hyperbranched polyester according to any one of claims 1-2, characterized in that, The end-carboxyl hyperbranched polyester has an acid value of 120-300 mgKOH / g, a molecular weight of 2500-8000 g / mol, and a degree of branching of 0.4-0.

7. The diol is any one or more of aliphatic and aromatic diols with 2-10 carbon atoms; the diacid monomer is a diacid or diacid anhydride, specifically any one or more of aliphatic and aromatic diacids or anhydrides with 4-10 carbon atoms. The catalyst is any one of methanesulfonic acid, p-toluenesulfonic acid, phosphoric acid, sulfuric acid, n-butyl titanate, ethyl propyl titanate, and zinc acetate.

4. The method for preparing linear chain-modified terminal carboxyl hyperbranched polyester according to claim 3, characterized in that, The end-carboxyl hyperbranched polyester is one or more of the HyPer C102, HyPer C103, HyPer C202, HyPer C203, HyPer C302, HyPer C303, HyPer C402 and HyPer C403 series products from Wuhan Hyperbranched Resin Technology Co., Ltd. The diol is one or more selected from ethylene glycol, 1,3-propanediol, terephthalic acid, isophthalic acid, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanediol. The dicarboxylic acid is one or more of glutaric acid, octanoic acid, azelaic acid, maleic acid, adipic acid, 1,4-cyclohexanedicarboxylic acid, phthalic acid, and terephthalic acid; the dicarboxylic acid anhydride is succinic anhydride.

5. A linear chain-modified terminal carboxyl hyperbranched polyester, characterized in that, It is prepared by the preparation method according to any one of claims 1-4.

6. A polybutylene terephthalate composite material, characterized in that, It includes polybutylene terephthalate, glass fiber, and the linear chain modified terminal carboxyl hyperbranched polyester as described in claim 5.

7. The polybutylene terephthalate composite material according to claim 6, characterized in that, The glass fiber content in the composite material is 50-70% by mass. And / or, the linear chain modified end-carboxyl hyperbranched polyester has a mass content of 0.1% to 1% in the composite material.

8. The polybutylene terephthalate composite material according to claim 6, characterized in that, The polybutylene terephthalate is any one of B4520, B4500, B4450, 1200-211D, 1200-211M, DR48-1001, and KH2083; the glass fiber is one or more of alkali-free glass fiber, medium-alkali glass fiber, high-alkali glass fiber, alkali-resistant glass fiber, and high-strength glass fiber.

9. A method for preparing the polybutylene terephthalate composite material according to any one of claims 6-8, characterized in that, include: Polybutylene terephthalate, glass fiber, and linear chain-modified end-carboxyl hyperbranched polyester are mixed evenly in a high-speed mixer and then fed into a twin-screw extruder for granulation to obtain polybutylene terephthalate composite material; wherein the extrusion granulation temperature is controlled at 200-270℃.

10. The application of the polybutylene terephthalate composite material according to any one of claims 6-8, characterized in that, The application is to use the composite material in the fabrication of structural components in the fields of power equipment, machinery manufacturing, automotive industry and / or aerospace.

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