High-flame-retardant reinforced PBT (polybutylene terephthalate) composition and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a high-flame-retardant reinforced PBT (polybutylene terephthalate) composition and a preparation method thereof. The high-flame-retardant reinforced PBT composition is prepared from the following raw materials in parts by mass: 70 to 80 parts of PBT resin, 5 to 7 parts of a composite flame retardant, 0.7 to 1 part of a flame-retardant synergist, 20 to 25 parts of flame-retardant reinforced modified chopped glass fibers, 3 to 5 parts of a lubricant, 0.3 to 0.5 part of a silane coupling agent and 0.3 to 0.5 part of an antioxidant, and the composite flame retardant is prepared from a phosphorus-silicon flame retardant and melamine ammonium polyphosphate. Through composite flame-retardant design, fiber functional modification and multi-component collaborative optimization, the flame retardance, mechanical strength and processability are comprehensively improved, the problems that a traditional PBT material is low in flame-retardant efficiency and contradictory in mechanical property and processability are solved, and the PBT material is particularly suitable for the high-end industrial field with strict performance requirements.

Description

Technical Field

[0001] The present application relates to the technical field of polymer materials, and in particular to a highly flame-retardant reinforced PBT composition and a preparation method thereof. Background Art

[0002] Glass fiber-reinforced PBT composites offer advantages such as low density, excellent corrosion resistance, high specific stiffness and strength, excellent fatigue resistance, high dimensional stability, and excellent electrical insulation properties. They are widely used in automobiles, home appliances, lighting fixtures, electronic appliances, coil bobbins, cooling fans, and electrical connectors. However, due to the inherent flammability of PBT resin, glass fiber-reinforced PBT composites exhibit poor fire performance, severely limiting their application in applications requiring high flame retardancy and mechanical properties. Glass fiber exhibits a "wick effect" in PBT resin. When a glass fiber-reinforced PBT composite burns, the PBT resin melts, softens, and decomposes, infiltrating and rapidly and directionally flowing along the glass fiber surface into the flame zone, accelerating fuel supply and intensifying combustion. To achieve high flame retardancy, the current industry standard is to add larger amounts of flame retardants to the composite. However, increasing the amount of flame retardants in glass fiber-reinforced PBT composites increases costs and reduces the composite's mechanical properties.

[0003] Therefore, the development of glass fiber reinforced PBT composite materials with low flame retardant content and high flame retardancy has become the focus of the industry. Summary of the Invention

[0004] This application aims to address the shortcomings of current technologies by providing a highly flame-retardant, reinforced PBT composition and its preparation method. By adding a composite flame retardant and flame-retardant, reinforced, modified chopped glass fibers, along with a silane coupling agent, this application improves the dispersibility and compatibility of the composite flame retardant and flame-retardant, reinforced, modified chopped glass fibers in PBT resin, significantly enhancing the flame retardant and mechanical properties of the highly flame-retardant, reinforced PBT composition.

[0005] In the first aspect, the present application provides a highly flame retardant reinforced PBT composition, which adopts the following technical solution: A highly flame-retardant reinforced PBT composition comprises the following raw materials in parts by mass: 70-80 parts of PBT resin, 5-7 parts of a composite flame retardant, 0.7-1 part of a flame retardant synergist, 20-25 parts of flame-retardant reinforced modified chopped glass fibers, 3-5 parts of a lubricant, 0.3-0.5 parts of a silane coupling agent, and 0.3-0.5 parts of an antioxidant, wherein the composite flame retardant comprises a phosphorus silicon flame retardant and melamine ammonium polyphosphate.

[0006] By adopting the above technical solution, PBT resin serves as the main component of the composite, providing the material's basic mechanical properties (such as strength and toughness) and processability. Its ester structure can form hydrogen bonds or covalent bonds with the silane coupling agent, promoting interfacial bonding. The phosphorus-silicon flame retardant in the composite flame retardant combines organic phosphorus elements with vapor-phase flame retardant (decomposition to produce phosphoric acid that coats the burning surface), while organic silicon elements provide condensed-phase flame retardant (promoting the formation of a char layer). Silicon and phosphorus are covalently bonded to prevent decomposition and failure at high temperatures. Melamine ammonium polyphosphate (MPP) decomposes at high temperatures to produce polyphosphoric acid and ammonia, which catalyze the dehydration of PBT to char, isolate oxygen, and suppress smoke release during combustion. Flame retardant synergists (such as antimony trioxide) and phosphorus-based flame retardants form a phosphorus-antimony synergistic system, generating high-boiling-point antimony compounds (such as SbPO4), which prolong the capture time of gas-phase free radicals. This also enhances the strength of the char layer and reduces melt dripping during combustion. Flame-retardant reinforced modified chopped glass fiber, modified with flame retardant and vinyl triethoxysilane, significantly improves its dispersibility and compatibility in PBT resin, thereby enhancing the flame retardancy and mechanical properties of the highly flame-retardant reinforced PBT composition. Lubricants (such as pentaerythritol stearate) reduce melt viscosity, reduce inter-molecular friction during processing, and improve fluidity. This prevents melt adhesion to the mold, improving demolding efficiency. Antioxidants capture free radicals, blocking oxidative chain reactions during PBT processing and use. This prevents high-temperature yellowing and maintains the product's appearance. The flame retardant system works synergistically: the phosphorus-based flame retardant phase extinguishes fire, the silicon-based phase promotes carbon layer strengthening, and the MPP releases nitrogen to dilute oxygen. The porous carbon layer formed by silicon and MPP exhibits enhanced thermal stability. Synergistically at the fiber-matrix interface, the amino groups of the modified glass fiber hydrolyze with the ethoxy groups of the silane coupling agent to form Si-O-Si bonds. Surface phosphonate groups form polar adsorption with PBT ester groups, forming a physical and chemical bond. In short, this system combines fiber functionalization with multi-scale flame-retardant design, and is suitable for scenarios such as new energy vehicle battery brackets that have strict requirements on temperature resistance, flame retardancy, and strength.

[0007] Preferably, the mass ratio of the phosphorus silicon flame retardant to melamine ammonium polyphosphate is 2:3-4.

[0008] By employing the above-mentioned technical solution, the phosphorus-silicon flame retardant forms a silicon-phosphorus crosslinked network: during combustion, a continuous Si-OPC carbon layer is formed, increasing the residual weight and thermal stability of the carbon layer. Si-O bonds bond with the PBT ester groups, enhancing interfacial bonding strength. Melamine ammonium polyphosphate decomposes at high temperatures to produce NH3, diluting the oxygen concentration. The released polyphosphoric acid catalyzes the dehydration and crosslinking of the PBT, promoting the formation of a dense carbon layer and reducing the release of toxic gases such as CO and benzene. The synergistic mechanism of the two is as follows: 1. Collaborative construction of multi-scale carbon layers. The primary carbon layer (phosphorus-silicon flame retardant): The Si-OPC network forms the skeleton, creating a micron-sized porous structure that reflects radiant heat. The secondary carbon layer (MPP): Nanoscale carbon particles generated by polyphosphoric acid fill the pores and increase the density of the carbon layer. 2. The flame retardant elements react in relay mode. During the initial combustion phase (300-400°C), MPP decomposes first, releasing phosphoric acid and NH3, inhibiting the initial thermal decomposition of PBT (delaying the peak thermal weight loss rate by 20 seconds). In the middle stage of combustion (400-600℃): the phosphorus silicon flame retardant begins to form carbon, and the Si-OP network stabilizes the carbon layer structure to prevent cracking. In the late stage of combustion (>600℃): the silicon element forms a SiO2 glassy covering layer, isolating oxygen and continuing to act. 3. Nitrogen-phosphorus-silicon ternary synergy: NH3 (MPP) dilutes oxygen, PO· (phosphorus silicon flame retardant) captures free radicals to form a double gas phase fire extinguishing barrier. The Si-OP network (phosphorus silicon) and polyphosphate (MPP) jointly enhance the oxidation resistance of the carbon layer. This ratio design achieves the best balance between flame retardant efficiency and mechanical properties by precisely controlling the temporal and spatial effects of different flame retardant phases. It is suitable for fields such as electrical housings and automotive interiors that have strict requirements on flame retardancy and mechanical properties.

[0009] Preferably, the preparation method of the phosphorus silicon flame retardant is as follows: according to the mass parts, at room temperature and under nitrogen protection, 500 parts of toluene, 29.5 parts of 1,3,5-tris(dimethylchlorosilyl)benzene and 30.3 parts of triethylamine are added to the reactor, and the mixture is placed in an ice-water bath and stirred for 60-70 minutes. Then, 102 parts of dry toluene diphenyl phosphate are slowly added to the reactor within 30 minutes, the temperature is raised to 28-30°C, the reaction is kept warm for 26-30 hours, the solvent is removed under reduced pressure, and then washed with distilled water 3 times. Finally, the mixture is placed in a vacuum drying oven and dried at 115°C for 24 hours to obtain the phosphorus silicon flame retardant.

[0010] By employing the above technical solution, 1,3,5-tris(dimethylsilylchloro)benzene provides a silicon source, containing three active chlorosilyl groups, which facilitate reaction with the phosphorus source. Cresyl diphenyl phosphate serves as a phosphorus source, and its presence in a benzene ring structure enhances thermal stability. Nitrogen protection prevents side reactions such as oxidation or hydrolysis of the silane groups, ensuring the directional nature of the reaction. Triethylamine absorbs the HCl generated by the reaction (released by the silicon-chloride bond reacting with the phosphate), driving the reaction forward. Ice bath temperature control suppresses side reactions at an initial low temperature, ensuring the orderly formation of silicon-phosphorus bonds. Slow heating: Maintaining the temperature at 28-30°C for 26-30 hours promotes the condensation reaction between silicon and phosphorus to form a covalent bond (Si-OP bond). Reduced pressure solvent removal removes toluene and unreacted monomers, improving product purity. Water washing and drying thoroughly remove residual triethylamine hydrochloride to avoid the introduction of impurities. The silicon (Si) and phosphorus (P) in the phosphosilicate flame retardant form a three-dimensional crosslinked structure through Si-OP bonds, resulting in high thermal stability. The benzene ring skeleton: 1,3,5-trisubstituted phenyl groups provide rigid support, and the flame retardant itself has a strong charring ability. The role of the phosphosilicate flame retardant in the composition is as follows: 1. A dual-phase synergistic flame retardant mechanism. During combustion, silicon promotes the formation of a dense char layer, isolating oxygen and heat. The Si-OP network in the char layer reflects radiant heat, reducing the pyrolysis rate of the matrix. Phosphorus release: Decomposition produces PO· free radicals, which capture H· and OH· free radicals in the combustion chain reaction. Silicon reduces the release of toxic gases (such as CO) and reduces smoke density. 2. Enhanced interfacial bonding: The Si-O bonds on the surface of the phosphosilicate flame retardant undergo an ester exchange reaction with the PBT ester groups (-COO-) during processing, forming Si-OC bonds. This enhances interfacial bonding and reduces phase separation. Synergistically with melamine polyphosphate (MPP), MPP decomposes at high temperatures to produce polyphosphoric acid, which catalyzes the dehydration of PBT into char, while the silicon in the phosphosilicate flame retardant enhances the mechanical strength of the char layer. A Si-OPN multi-element synergistic network is formed in the carbon layer, which improves the oxygen index (LOI). Nitrogen-phosphorus-silicon ternary synergy: MPP releases NH3 to dilute the oxygen concentration, and the gas phase / condensed phase action of the phosphorus silicon flame retardant forms a three-dimensional fire barrier. In collaboration with antimony trioxide, Sb2O3 reacts with phosphorus in the phosphorus silicon flame retardant to form high-boiling point compounds such as SbPO4, which prolongs the gas phase flame retardant time. Antimony-silicon synergistically improves the antioxidant capacity of the carbon layer. 3. In collaboration with modified glass fiber, the phosphonate groups grafted on the surface of the glass fiber form POP bonds with the phosphorus silicon flame retardant to construct a through-type flame retardant network. The silane coupling agent (vinyl triethoxysilane) simultaneously bonds the fiber and the flame retardant to improve the interface heat transfer efficiency. In short, this preparation method achieves a high degree of matching between the structure and performance of the flame retardant through precise molecular design, meeting the requirements of extreme working conditions such as high-voltage components in new energy vehicles.

[0011] Preferably, the method for preparing the flame retardant reinforced modified chopped glass fiber comprises the following steps: S41. Place 50 parts by mass of chopped glass fibers in 400 parts by mass of a 60% sodium hydroxide solution, and then heat the mixture at 105-110° C. for 3-4 hours. After the reaction is complete, filter and dry the mixture to obtain hydroxylated chopped glass fibers. S42, placing 50 parts by mass of hydroxylated chopped glass fibers in 500 parts by mass of xylene, ultrasonically dispersing the fibers for 30-40 minutes, adding 10 parts of glycine, and reacting the mixture under reflux for 12-14 hours, then filtering the mixture, washing the mixture, and drying the mixture to obtain pretreated chopped glass fibers; S43. Place 50 parts by mass of pretreated chopped glass fibers in 500 parts of tetrahydrofuran, ultrasonically disperse for 40-50 minutes, and place in an ice bath at 0°C. Add 10 parts of diethyl 2-bromoethylphosphonate and 1 part of triethylamine, and stir thoroughly for 6-7 hours. Filter, wash, and dry to obtain flame-retardant modified chopped glass fibers. S44. Disperse 50 parts of flame retardant modified chopped glass fibers in a solution consisting of 200 parts of ethanol and 100 parts of water, stir for 20 minutes, then add 6 parts of vinyltriethoxysilane, adjust the pH of the solution to 4.5-5, stir for 4-5 hours, filter, wash and dry to obtain flame retardant reinforced modified chopped glass fibers.

[0012] By adopting the above technical solution, S41: Preparation of hydroxylated chopped glass fibers: 60% NaOH etches the SiO2 network on the glass fiber surface at high temperature (105-110°C) to generate silanol (-Si-OH) groups, which provide active sites for subsequent grafting. This enhances the polarity of the fiber surface and improves its reactivity with organic reagents. S42: Glycine amination treatment: The carboxyl group (-COOH) of glycine connects with the -Si-OH of the hydroxylated fiber through an esterification reaction, releasing water molecules and providing nucleophilic sites for subsequent phosphonate grafting. The amino group acts as a "chemical anchor" to guide the subsequent flame retardant grafting. Ultrasonic dispersion in xylene makes the fibers monofilamentous and prevents agglomeration. S43: Phosphonate flame retardant grafting: The amino group (-NH2) attacks the bromine atom of diethyl 2-bromoethylphosphonate to form a POC bond. Triethylamine acts to neutralize the generated HBr and promote the forward reaction. Flame retardant function is imparted: Phosphorus is grafted onto the surface, releasing PO· free radicals during combustion, interrupting the chain reaction. The polar groups of the phosphonate form hydrogen bonds with the PBT ester groups, improving compatibility. S44: Surface modification with a silane coupling agent. Vinyltriethoxysilane hydrolyzes to silanol (Si-OH) under acidic conditions (pH 4.5-5), which condenses with the hydroxyl groups on the fiber surface to form Si-O-Si bonds. The vinyl groups (-CH=CH2) of the silane graft with the PBT ester groups during melt processing. This chemical bonding significantly improves the shear strength of the fiber-resin interface. Through an integrated flame retardant-reinforcement design, the phosphonate on the fiber surface releases phosphorus free radicals during the initial combustion phase, inhibiting gas-phase combustion. At high temperatures, it forms a SiO2 protective layer, delaying thermal degradation. In conjunction with a composite flame retardant, the phosphorus element on the fiber surface forms a POP network with the phosphorus-silicon flame retardant, doubling the flame retardant efficiency. The silane coupling agent forms a strong interface between the fiber and PBT, improving mechanical properties. In summary, this preparation method achieves a high degree of integration of fiber reinforcement and flame retardancy through precise chemical modification and interface design, significantly improving the flame retardant and mechanical properties of the PBT composite.

[0013] Preferably, the chopped glass fibers have a length of 3-4 mm and a diameter of 9-12 μm.

[0014] Preferably, the silane coupling agent is composed of vinyltri(β-methoxyethoxy)silane and vinyltriethoxysilane in a mass ratio of 1:1.

[0015] By adopting the above technical solution, the silane coupling agent is composed of vinyl tri(β-methoxyethoxy) silane and vinyl triethoxy silane in a 1:1 ratio. Its main function is to improve the dispersibility and compatibility of the flame-retardant reinforced modified chopped glass fiber and the composite flame retardant in the PBT resin, thereby improving the flame retardancy and mechanical properties of the PBT composition. Specifically, vinyl triethoxy silane forms a dense chemical bonding layer, improving interfacial shear strength. Vinyl tri(β-methoxyethoxy) silane continuously couples, filling micro-defects at the interface and improving interfacial stability. Vinyl tri(β-methoxyethoxy) silane: The long chain structure fills micro-gaps and forms an elastic buffer layer. Vinyl triethoxy silane: The short chain structure provides rigid support and enhances interfacial shear resistance. In summary, the two silanes complement each other and effectively improve the overall performance of the highly flame-retardant reinforced PBT composition.

[0016] Preferably, the antioxidant consists of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0017] Preferably, the flame retardant synergist is antimony trioxide.

[0018] Preferably, the lubricant is pentaerythritol stearate.

[0019] In a second aspect, the present application provides a method for preparing a highly flame-retardant reinforced PBT composition, which adopts the following technical solution: A method for preparing a highly flame-retardant reinforced PBT composition, using the raw materials of the highly flame-retardant reinforced PBT composition, comprising the following steps: S101, pouring the dried raw materials into a high-speed mixer according to the mass fraction and mixing them evenly to obtain a mixture; S102. The obtained mixture is put into a twin-screw extruder and granulated, and subjected to extrusion, strip drawing, cooling, and pelletizing to obtain a highly flame-retardant reinforced PBT composition, wherein the temperatures of the screws of the twin-screw extruder from the feed port to the die are 220-230°C, 230-240°C, 240-250°C, 250-260°C, 240-250°C, 230-240°C, and 220-230°C, respectively; and the screw speed is 300-350rpm.

[0020] In summary, the beneficial technical effects of this application are: 1. Highly effective flame retardant performance Multi-mechanism synergistic flame retardancy: Phosphorus silicon flame retardant (condensed phase carbonization) and melamine ammonium polyphosphate (gas phase oxygen inhibition) form a dual flame retardant barrier, significantly improving the limiting oxygen index (LOI ≥ 42%). Phosphonate grafted onto the surface of the modified glass fiber works synergistically with the flame retardant to create a three-dimensional flame retardant network, suppressing melt dripping and reducing smoke release.

[0021] 2.Excellent mechanical properties Reinforced fiber and interface optimization: Modified glass fiber is treated with chemical grafting and silane coupling agent to form a strong interface bond with PBT resin, making the tensile strength reach 120-130MPa. Bissilane coupling agent (1:1 ratio) balances the toughness and rigidity of the material through the design of a rigid and flexible interface (notched impact strength 8.5-9.5kJ / m 2 ).

[0022] 3. Processing performance optimization Improved Dispersion and Flowability: Silane coupling agents and lubricants synergistically improve the dispersion of flame retardants and fibers in PBT, achieving a melt index of 25-30g / 10min, making it suitable for injection molding of complex structures. Pentaerythritol stearate reduces melt viscosity, improving demolding efficiency and reducing processing energy consumption.

[0023] 4. Environmental protection and applicability Low toxicity and environmental protection: The flame retardant system is halogen-free, and the harmful gases released during combustion (such as CO and benzene) are reduced by more than 50%, which complies with RoHS and automotive interior material environmental protection standards.

[0024] Wide applicability: The comprehensive performance meets the high-demand scenarios such as electrical appliance housings, new energy vehicle battery brackets, 5G communication equipment, etc., and has the characteristics of lightweight, high temperature resistance, and high flame retardancy. DETAILED DESCRIPTION

[0025] The embodiments of the present application will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0026] In the following examples and preparation examples, 1 part means 100 g.

[0027] Preparation Example 1 Preparation of Phosphorus Silicon Flame Retardant The preparation method of the phosphosilicate flame retardant is as follows: according to the mass parts, at room temperature and under nitrogen protection, 500 parts of toluene, 29.5 parts of 1,3,5-tris(dimethylsilylchloro)benzene and 30.3 parts of triethylamine are added to a reactor, the mixture is placed in an ice-water bath and stirred for 65 minutes, and 102 parts of dry toluene diphenyl phosphate are slowly added to the reactor within 30 minutes. The temperature is raised to 29°C, the reaction is kept warm for 28 hours, the solvent is removed under reduced pressure, and then the mixture is washed with distilled water 3 times. Finally, the mixture is placed in a vacuum drying oven and dried at 115°C for 24 hours to obtain the phosphosilicate flame retardant.

[0028] Preparation Example 2 Preparation of flame retardant reinforced modified chopped glass fibers The method for preparing flame-retardant reinforced modified chopped glass fibers comprises the following steps: S41. Place 50 parts by mass of chopped glass fibers having a length of 3-4 mm and a diameter of 9-12 μm in 400 parts by mass of a 60% sodium hydroxide solution, and heat the mixture at 107° C. for 3.4 hours. After the reaction is complete, filter and dry the mixture to obtain hydroxylated chopped glass fibers. S42, placing 50 parts by mass of hydroxylated chopped glass fibers in 500 parts by mass of xylene, ultrasonically dispersing the fibers for 35 minutes, adding 10 parts of glycine, and reacting the mixture under reflux for 13 hours, then filtering, washing, and drying the mixture to obtain pretreated chopped glass fibers; S43. Place 50 parts by mass of pretreated chopped glass fibers in 500 parts of tetrahydrofuran, ultrasonically disperse for 43 minutes, and place in an ice bath at 0°C. Then, add 10 parts of diethyl 2-bromoethylphosphonate and 1 part of triethylamine, stir thoroughly for 6.7 hours, filter, wash, and dry to obtain flame-retardant modified chopped glass fibers. S44. Disperse 50 parts of flame-retardant modified chopped glass fibers in a solution consisting of 200 parts of ethanol and 100 parts of water, stir for 20 minutes, then add 6 parts of vinyltriethoxysilane, adjust the pH of the solution to 4.7, stir for 4.5 hours, filter, wash, and dry to obtain flame-retardant reinforced modified chopped glass fibers.

[0029] Example 1 A highly flame-retardant reinforced PBT composition comprises the following raw materials in parts by mass: 70 parts of PBT resin, 5 parts of a composite flame retardant, 0.7 parts of antimony trioxide, 20 parts of flame-retardant reinforced modified chopped glass fiber, 3 parts of pentaerythritol stearate, 0.3 parts of a silane coupling agent, and 0.3 parts of an antioxidant, wherein the composite flame retardant comprises a phosphosilicate flame retardant and melamine ammonium polyphosphate in a mass ratio of 2:3; the silane coupling agent comprises vinyl tris(β-methoxyethoxy) silane and vinyl triethoxy silane in a mass ratio of 1:1; and the antioxidant comprises antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0030] The raw materials of the above-mentioned highly flame-retardant reinforced PBT composition include the following steps: S101, pouring the dried raw materials into a high-speed mixer according to the mass fraction and mixing them evenly to obtain a mixture; S102. The obtained mixture is put into a twin-screw extruder granulator for extrusion, strip drawing, cooling and pelletizing to obtain a highly flame retardant reinforced PBT composition, wherein the temperatures of each section of the screw of the twin-screw extruder granulator from the feed port to the die are 220°C, 230°C, 240°C, 250°C, 240°C, 230°C and 220°C respectively; the screw speed is 350rpm.

[0031] Example 2 A highly flame-retardant reinforced PBT composition comprises the following raw materials in parts by mass: 80 parts of PBT resin, 7 parts of a composite flame retardant, 1 part of antimony trioxide, 25 parts of flame-retardant reinforced modified chopped glass fiber, 4 parts of pentaerythritol stearate, 0.5 part of a silane coupling agent, and 0.5 part of an antioxidant, wherein the composite flame retardant comprises a phosphosilicate flame retardant and melamine ammonium polyphosphate in a mass ratio of 2:4; the silane coupling agent comprises vinyl tris(β-methoxyethoxy) silane and vinyl triethoxy silane in a mass ratio of 1:1; and the antioxidant comprises antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0032] The raw materials of the above-mentioned highly flame-retardant reinforced PBT composition include the following steps: S101, pouring the dried raw materials into a high-speed mixer according to the mass fraction and mixing them evenly to obtain a mixture; S102. The obtained mixture is put into a twin-screw extruder granulator for extrusion, drawing, cooling and pelletizing to obtain a highly flame-retardant reinforced PBT composition, wherein the temperatures of each section of the screw of the twin-screw extruder granulator from the feed port to the die are 230°C, 240°C, 250°C, 260°C, 250°C, 240°C and 230°C respectively; the screw speed is 300rpm.

[0033] Example 3 A highly flame-retardant reinforced PBT composition comprises the following raw materials in parts by mass: 75 parts of PBT resin, 6 parts of a composite flame retardant, 0.8 parts of antimony trioxide, 23 parts of flame-retardant reinforced modified chopped glass fiber, 5 parts of pentaerythritol stearate, 0.4 parts of a silane coupling agent, and 0.4 parts of an antioxidant, wherein the composite flame retardant comprises a phosphosilicate flame retardant and melamine ammonium polyphosphate in a mass ratio of 2:3.5; the silane coupling agent comprises vinyl tris(β-methoxyethoxy) silane and vinyl triethoxy silane in a mass ratio of 1:1; and the antioxidant comprises antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0034] The raw materials of the above-mentioned highly flame-retardant reinforced PBT composition include the following steps: S101, pouring the dried raw materials into a high-speed mixer according to the mass fraction and mixing them evenly to obtain a mixture; S102. The obtained mixture is put into a twin-screw extruder granulator for extrusion, strip drawing, cooling and pelletizing to obtain a highly flame-retardant reinforced PBT composition, wherein the temperatures of the screws of the twin-screw extruder granulator from the feed port to the die are 225°C, 236°C, 245°C, 256°C, 245°C, 234°C and 225°C respectively; the screw speed is 330rpm.

[0035] Comparative Example 1 The same as Example 3, except that equal weight portions of unmodified chopped glass fibers are used instead of the flame retardant reinforced modified chopped glass fibers.

[0036] Comparative Example 2 The same as Example 3, except that the composite flame retardant is a phosphorus silicon flame retardant.

[0037] Comparative Example 3 The same as Example 3, except that the composite flame retardant is melamine ammonium polyphosphate.

[0038] Comparative Example 4 The same as Example 3, except that the silane coupling agent is vinyl tris (β-methoxyethoxy) silane.

[0039] Comparative Example 5 The same as Example 3, except that the silane coupling agent is vinyltriethoxysilane.

[0040] Performance Testing The highly flame retardant reinforced PBT compositions prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were sampled, and standard test strips were made and performance tests were performed. The results are shown in Table 1.

[0041] Melt index: mass (260°C, 2.16 kg) tested according to ASTM D1238; Tensile strength: tested according to ASTM / D638, 50mm / min; Bending strength: tested according to ASTM / D790, 1.3mm / min; Izod beam notched impact strength: tested in accordance with GB1843-2008 standard; Flame retardant performance (limiting oxygen index): According to the GB / T2406.2-2009 standard test, the limiting oxygen index of the sample is measured using an oxygen index meter. The sample size is 100mm*6.5mm*1.6mm.

[0042] Table 1 Performance test Analyzing the data in Table 1, we can see that: 1) The highly flame-retardant reinforced PBT compositions prepared in Examples 1 to 3 achieve comprehensive improvements in flame retardancy, mechanical strength, and processability through composite flame-retardant design, fiber functionalization modification, and multi-component synergistic optimization. This solves the problems of low flame retardancy efficiency and the contradiction between mechanical properties and processability of traditional PBT materials, and is particularly suitable for high-end industrial fields with stringent performance requirements.

[0043] 2) A comparative analysis of the performance of the highly flame retardant reinforced PBT composition prepared in Example 3 and Comparative Example 1 shows that the flame retardant reinforced modified chopped glass fiber prepared in the present application, after flame retardant and vinyltriethoxysilane modification, can significantly improve the dispersibility and compatibility of the flame retardant reinforced modified chopped glass fiber in the PBT resin, thereby achieving a high degree of integration of fiber reinforcement and flame retardant functions, and significantly improving the flame retardant and mechanical properties of the PBT composition.

[0044] 3) A comparative analysis of the properties of the highly flame-retardant reinforced PBT compositions prepared in Example 3 and Comparative Examples 2-3 showed that the composite flame retardant consisted of a phosphosilicate flame retardant and melamine ammonium polyphosphate in a mass ratio of 2:3.5. The synergistic effect between the phosphosilicate flame retardant and the melamine ammonium polyphosphate was utilized to achieve an optimal balance between the flame retardant efficiency and mechanical properties of the PBT composition.

[0045] 4) A comparative analysis of the properties of the highly flame retardant reinforced PBT compositions prepared in Example 3 and Comparative Examples 4-5 shows that the silane coupling agent is composed of vinyl tris (β-methoxyethoxy) silane and vinyl triethoxy silane in a mass ratio of 1:1. These two silanes complement each other to enhance the dispersibility and compatibility of the flame retardant reinforced modified chopped glass fiber and the composite flame retardant in the PBT resin, thereby improving the flame retardant and mechanical properties of the PBT composition.

[0046] The above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the above embodiments provide a detailed description of the present application, relevant technical personnel should understand that the specific implementation methods of the present application can still be modified or replaced by equivalents. Any modifications and equivalent replacements that do not depart from the spirit and scope of the present application should be included in the scope of the claims of the present application.

Claims

1. A highly flame retardant reinforced PBT composition, characterized in that: The invention comprises the following raw materials in parts by mass: 70-80 parts of PBT resin, 5-7 parts of composite flame retardant, 0.7-1 part of flame retardant synergist, 20-25 parts of flame retardant reinforced modified chopped glass fiber, 3-5 parts of lubricant, 0.3-0.5 parts of silane coupling agent, and 0.3-0.5 parts of antioxidant, wherein the composite flame retardant is composed of phosphorus silicon flame retardant and melamine ammonium polyphosphate.

2. A highly flame retardant reinforced PBT composition according to claim 1, characterized in that: The mass ratio of the phosphorus silicon flame retardant to melamine ammonium polyphosphate is 2:3-4.

3. A highly flame retardant reinforced PBT composition according to claim 1, characterized in that: The preparation method of the phosphorus silicon flame retardant comprises the following steps: adding 500 parts by mass of toluene, 29.5 parts of 1,3,5-tris(dimethylsilylchloro)benzene and 30.3 parts of triethylamine to a reactor at room temperature under nitrogen protection, placing the mixture in an ice-water bath and stirring for 60-70 minutes, slowly adding 102 parts of dry toluene diphenyl phosphate to the reactor within 30 minutes, heating the mixture to 28-30° C., keeping the temperature for reaction for 26-30 hours, removing the solvent under reduced pressure, washing the mixture with distilled water three times, and finally placing the mixture in a vacuum drying oven and drying it at 115° C. for 24 hours to obtain the phosphorus silicon flame retardant.

4. A highly flame retardant reinforced PBT composition according to claim 1, characterized in that: The method for preparing the flame-retardant reinforced modified chopped glass fiber comprises the following steps: S41. Place 50 parts by mass of chopped glass fibers in 400 parts by mass of a 60% sodium hydroxide solution, and then heat the mixture at 105-110° C. for 3-4 hours. After the reaction is complete, filter and dry the mixture to obtain hydroxylated chopped glass fibers. S42, placing 50 parts by mass of hydroxylated chopped glass fibers in 500 parts by mass of xylene, ultrasonically dispersing the fibers for 30-40 minutes, adding 10 parts of glycine, and reacting the mixture under reflux for 12-14 hours, then filtering the mixture, washing the mixture, and drying the mixture to obtain pretreated chopped glass fibers; S43. Place 50 parts by mass of pretreated chopped glass fibers in 500 parts of tetrahydrofuran, ultrasonically disperse for 40-50 minutes, and place in an ice bath at 0°C. Add 10 parts of diethyl 2-bromoethylphosphonate and 1 part of triethylamine, and stir thoroughly for 6-7 hours. Filter, wash, and dry to obtain flame-retardant modified chopped glass fibers. S44. Disperse 50 parts of flame retardant modified chopped glass fibers in a solution consisting of 200 parts of ethanol and 100 parts of water, stir for 20 minutes, then add 6 parts of vinyltriethoxysilane, adjust the pH of the solution to 4.5-5, stir for 4-5 hours, filter, wash and dry to obtain flame retardant reinforced modified chopped glass fibers.

5. A highly flame retardant reinforced PBT composition according to claim 4, characterized in that: The length of the chopped glass fibers is 3-4 mm and the diameter is 9-12 μm.

6. A highly flame retardant reinforced PBT composition according to claim 1, characterized in that: The silane coupling agent is composed of vinyl tris (β-methoxyethoxy) silane and vinyl triethoxy silane in a mass ratio of 1:

1.

7. A highly flame retardant reinforced PBT composition according to claim 1, characterized in that: The antioxidant consists of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:

1.

8. The highly flame retardant reinforced PBT composition according to claim 1, characterized in that: The flame retardant synergist is antimony trioxide.

9. The highly flame retardant reinforced PBT composition according to claim 1, characterized in that: The lubricant is pentaerythritol stearate.

10. A method for preparing the highly flame retardant reinforced PBT composition according to any one of claims 1 to 9, characterized in that: The following steps are involved: S101, pouring the dried raw materials into a high-speed mixer according to the mass fraction and mixing them evenly to obtain a mixture; S102. The obtained mixture is put into a twin-screw extruder granulator for extrusion, drawing, cooling and pelletizing to obtain a highly flame-retardant reinforced PBT composition, wherein the temperatures of each section of the screw of the twin-screw extruder granulator from the feed port to the die are 220-230°C, 230-240°C, 240250°C, 250-260°C, 240-250°C, 230-240°C and 220-230°C respectively; the screw speed is 300-350rpm.

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