Long-lasting flame-retardant reinforced pbt material and method for producing the same

Abstract

The application discloses a long-acting flame-retardant reinforced PBT material and a preparation method thereof, and relates to the technical field of polymer materials. The material comprises the following components in parts by weight: 45-70 parts of polybutylene terephthalate, 15-35 parts of reinforcing fibers, 8-18 parts of phosphorus-containing flame retardants, 2-8 parts of nitrogen-containing flame retardants, 1-6 parts of inorganic flame-retardant synergists, 2-8 parts of toughening compatilizers, 0.1-0.6 parts of anti-dripping agents, 0.1-0.5 parts of antioxidants and 0.1-0.8 parts of lubricants; and the inorganic flame-retardant synergists are prepared from layered silicates, zinc borate, aluminum hydroxide, silica sol and aluminum dihydrogen phosphate. The material is improved in the problems of inorganic powder agglomeration and insufficient interface bonding through the dispersion coating of the composite inorganic components, the phosphorus-containing and nitrogen-containing flame-retardant systems and the glass fiber reinforcing effect, and is provided with good flame-retardant retention, mechanical properties and processing stability.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a long-lasting flame-retardant reinforced PBT material and its preparation method. Background Technology

[0002] Polybutylene terephthalate (PBT) possesses good processability, electrical insulation, and dimensional stability, and is commonly used in electronics, connectors, appliance components, and structural parts. To meet requirements for load-bearing capacity, heat resistance, and safe use, PBT materials typically require fiber reinforcement and flame-retardant modification to form a composite system. Existing reinforced flame-retardant PBT materials often employ a combination of glass fiber and phosphorus- or nitrogen-containing flame retardants to improve the material's mechanical and flammability properties. However, in actual processing and use, insufficient interfacial compatibility between the flame retardant, reinforcing fibers, and resin matrix can easily affect melt flow, dispersion uniformity, and product appearance quality. While phosphorus- and nitrogen-containing flame retardants can create a synergistic effect in flame-retardant systems, relying solely on organic flame retardants can lead to problems such as localized decomposition, migration, or decreased flame-retardant efficiency during high-temperature shearing processes, resulting in insufficient flame-retardant stability. Inorganic flame retardant synergists can improve char formation, heat insulation, and smoke suppression. However, conventional inorganic powders have strong surface polarity, limiting their bonding ability with the PBT matrix. They are prone to agglomeration during melt mixing, making particle size control difficult and weakening their synergistic effect, potentially leading to a decrease in material impact resistance. Adding glass fibers to reinforced PBT materials increases rigidity and strength, but also complicates the system interface. When flame retardants, inorganic powders, and glass fibers coexist, uneven dispersion or insufficient interfacial bonding among components can lead to a mismatch between mechanical and flame retardant properties. While anti-dripping agents, toughening compatibilizers, antioxidants, and lubricants can improve processing and performance, improper matching of the additive system can affect extrusion stability, flame retardancy, and the overall performance of the final material. Summary of the Invention

[0003] The purpose of this invention is to address the problems existing in the prior art, such as insufficient compatibility between flame retardants and resin matrices in reinforced flame-retardant PBT materials, easy agglomeration and poor dispersion stability of inorganic flame retardant synergists, insufficient flame retardant efficiency and durability of flame retardant systems during processing and use, and difficulty in simultaneously achieving material mechanical properties, flame retardant properties and processing performance. This invention provides a long-lasting flame-retardant reinforced PBT material and its preparation method, characterized by uniform dispersion of inorganic flame retardant synergists, good interfacial bonding, and a combination of long-lasting flame retardant properties, reinforcing effect, and good processing stability.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: a long-lasting flame-retardant reinforced PBT material, composed of the following components in parts by weight: 45-70 parts of polybutylene terephthalate, 15-35 parts of reinforcing fiber, 8-18 parts of phosphorus-containing flame retardant, 2-8 parts of nitrogen-containing flame retardant, 1-6 parts of inorganic flame retardant synergist, 2-8 parts of toughening compatibilizer, 0.1-0.6 parts of anti-dripping agent, 0.1-0.5 parts of antioxidant, and 0.1-0.8 parts of lubricant.

[0005] Furthermore, the inorganic flame retardant synergist is prepared from the following raw materials in parts by weight: 30-55 parts of layered silicate, 15-35 parts of zinc borate, 15-35 parts of aluminum hydroxide, 3-12 parts of silica sol (calculated as colloidal silica), and 2-10 parts of aluminum dihydrogen phosphate.

[0006] Furthermore, the preparation method of the inorganic flame retardant synergist includes the following steps:

[0007] S1. Add layered silicate to deionized water, control the solid content to 25-40 wt%, and shear disperse at 1200-2500 r / min for 20-45 min to obtain layered silicate dispersion slurry; then keep the layered silicate dispersion slurry at 50-70℃ and stir for 30-60 min at a stirring speed of 300-600 r / min.

[0008] S2. Add zinc borate and aluminum hydroxide to the layered silicate dispersion slurry obtained in step S1, control the solid content of the system to be 35-55 wt%, and wet grind in a ball mill for 1.5-4 hours. The ball milling media is zirconia balls with a diameter of 2-8 mm and a ball-to-material mass ratio of 2:1-5:1. The grinding speed is 250-450 r / min. After grinding, a composite inorganic slurry is obtained.

[0009] S3. Add silica sol to the composite inorganic slurry obtained in step S2, adjust the system temperature to 55-80℃, and stir at 400-800 r / min; then add aluminum dihydrogen phosphate aqueous solution with a mass concentration of 10-25 wt% for 20-50 min; after the addition is complete, continue the reaction at 55-80℃ for 1-3 h to obtain the reaction-coated slurry.

[0010] S4. The reaction coating slurry obtained in step S3 is dried at 90-120℃ for 6-12h to obtain a dried product; the dried product is pulverized and then subjected to air classification to control the D50 particle size of the obtained inorganic flame retardant synergist to be 1.5-6.0μm, the D90 particle size to be ≤12μm, and the moisture content to be ≤0.5wt%.

[0011] The inorganic flame retardant synergist improves the powder interface and dispersion defects through a multi-level composite configuration. Layered silicates, possessing two-dimensional elongation characteristics, act as a framework carrier, driving the shear force of wet milling to uniformly anchor zinc borate and aluminum hydroxide particles between layers and on the surface, effectively reducing the surface energy and hard agglomeration of individual inorganic particles. Silica sol and aluminum dihydrogen phosphate then undergo a condensation reaction around the composite particles, constructing a dense, glassy, ​​inert coating layer rich in silicon-phosphorus bonds. During polymer processing and subsequent humid heat service, this inorganic coating layer acts as a physical barrier, blocking moisture intrusion and inhibiting the release or migration of internal active elements, maintaining the flame retardant retention rate during the material's aging process. When exposed to high-temperature combustion, the outer shell and internal active particles simultaneously undergo dehydration, endothermic reaction, and nucleation cross-linking on the silicate framework, catalyzing the rapid transformation of the surrounding resin melt into a highly dense, high-strength inorganic reinforced carbon layer network. This micro-composite configuration not only eliminates stress concentration points at the powder-matrix interface to ensure the material's mechanical toughness, but also enables the char-forming sites for heat insulation and oxygen barrier to be uniformly distributed within the system.

[0012] Furthermore, the layered silicate is selected from one or more of montmorillonite, kaolinite, talc, and mica powder.

[0013] Furthermore, the reinforcing fiber is glass fiber.

[0014] Furthermore, the phosphorus-containing flame retardant is selected from one or more of aluminum diethylphosphonate, aluminum phosphonate, and ammonium polyphosphate.

[0015] Furthermore, the nitrogen-containing flame retardant is one or more of melamine cyanurate, melamine, melamine orthophosphate, melamine pyrophosphate, and bismelamine pyrophosphate.

[0016] Furthermore, the toughening compatibilizer is selected from glycidyl methacrylate and maleic anhydride.

[0017] Furthermore, the anti-dripping agent is polytetrafluoroethylene powder.

[0018] Furthermore, the antioxidant is a combination of pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate) and tris(2,4-di-tert-butylphenyl) phosphite, and the mass ratio of the two is 1:1 to 3:1.

[0019] Furthermore, the lubricant is selected from one or more of pentaerythritol stearate, ethylene bis-stearamide, calcium stearate, and zinc stearate.

[0020] A method for preparing a long-lasting flame-retardant reinforced PBT material includes the following steps:

[0021] (1). The polybutylene terephthalate is dried at 110-130℃ for 3-6 hours to make its moisture content ≤0.05wt% to obtain dried polybutylene terephthalate.

[0022] (2) Weigh out dry polybutylene terephthalate, phosphorus-containing flame retardant, nitrogen-containing flame retardant, inorganic flame retardant synergist, toughening compatibilizer, anti-dripping agent, antioxidant and lubricant, mix for 3-10 min to obtain premix.

[0023] (3). The premix obtained in step (2) is added to the main feed port of a twin-screw extruder, and the reinforcing fiber is added from the side feed port. After melt mixing, extrusion, cooling and pelletizing, the long-lasting flame-retardant reinforced PBT material is obtained.

[0024] Furthermore, the temperatures from zone one to the die head of the twin-screw extruder are sequentially controlled as 210-230℃, 220-240℃, 225-250℃, 230-255℃, 230-255℃, 225-250℃, and 220-245℃, the screw speed is 250-500 r / min, and the vacuum exhaust pressure is -0.06--0.09 MPa.

[0025] Furthermore, in step (2), the phosphorus-containing flame retardant, nitrogen-containing flame retardant, inorganic flame retardant synergist, anti-dripping agent, antioxidant and lubricant are first premixed to obtain a flame retardant additive premix, which is then mixed with polybutylene terephthalate and toughening compatibilizer.

[0026] Furthermore, in step (3), the reinforcing fiber is added from the feed port on the rear side of the twin-screw extruder.

[0027] This invention utilizes a modified system comprised of polybutylene terephthalate (PET), reinforcing fibers, a phosphorus-containing flame retardant, a nitrogen-containing flame retardant, and an inorganic flame retardant synergist. During heating or combustion, the phosphorus-containing flame retardant promotes the formation of a char layer on the matrix surface, while the nitrogen-containing flame retardant participates in the expansion into char and dilutes combustible gases. The layered silicates, zinc borate, and aluminum hydroxide in the inorganic flame retardant synergist, together with the coating components, enhance the density and stability of the char layer, slowing heat transfer and the release of combustible decomposition products. This improves the insufficient flame retardant efficiency and unstable flame retardant durability of traditional reinforced flame-retardant PBT materials. The composite inorganic components, after treatment with silica sol and aluminum dihydrogen phosphate, exhibit improved surface conditions and particle dispersibility, reducing the agglomeration tendency of inorganic powders in the resin matrix and enhancing their bonding stability with the PBT system. Reinforcing fibers play a skeletal reinforcing role in the material, while toughening compatibilizers help mitigate interfacial differences between glass fibers, flame retardants, and resins. Anti-dripping agents, antioxidants, and lubricants work together to improve melt processing stability, anti-dripping effect, and processing fluidity, enabling the material to maintain its reinforcing effect while also taking into account flame retardant and processing properties. This approach has a targeted improvement effect on the problems of insufficient interfacial compatibility, uneven dispersion of inorganic synergists, and difficulty in coordinating mechanical properties and flame retardant properties in the prior art.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. In the long-lasting flame-retardant reinforced PBT material obtained by the present invention, the inorganic flame-retardant synergist is more uniformly dispersed, which can reduce the tendency of powder agglomeration and improve processing stability.

[0030] 2. This invention forms a carbon layer barrier by combining phosphorus- and nitrogen-containing flame retardants with composite inorganic components, thereby improving the flame retardancy retention of the material and alleviating the problem of decreased flame retardancy efficiency.

[0031] 3. In this invention, the interfacial bonding between glass fiber, toughening compatibilizer and flame retardant filler is good, so that the material maintains a relatively balanced state between reinforcement, flame retardancy and impact resistance. Detailed Implementation

[0032] The following will provide a clear and complete description of the technical solutions of this invention. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] Preparation Example 1

[0034] Preparation of the inorganic flame retardant synergist:

[0035] 1. Components by weight:

[0036] The layered silicate was 45 parts, selected from montmorillonite K10, Sigma-Aldrich, catalog number 281522, in powder form.

[0037] The zinc borate was 25 parts, selected from zinc borate 3,5-hydrate.

[0038] The amount of aluminum hydroxide is 20 parts.

[0039] The silica sol is 20 parts based on colloidal silica, LUDOX ® AS-30 colloidal silica, Sigma-Aldrich, catalog number 420832, silica content 30wt%, pH 9.1, density 1.2g / mL, 6.0 parts as colloidal silica.

[0040] Aluminum dihydrogen phosphate is 8 parts.

[0041] 122 parts of deionized water.

[0042] 2. Preparation method:

[0043] S1. Under an air atmosphere, 45.0 parts of montmorillonite K10 were added to 105.0 parts of deionized water, and the solid content of the slurry was controlled to be 30 wt%. The slurry was sheared and dispersed at 1800 r / min for 30 min. During the dispersion process, the temperature of the slurry was controlled not to exceed 35℃ to obtain a layered silicate dispersion slurry. Then, the layered silicate dispersion slurry was heated to 60℃ and stirred at 450 r / min for 45 min. The resulting slurry had a pH of 3.8 ± 0.3 and a grayish-white uniform appearance.

[0044] S2. Add 25.0 parts of zinc borate and 20.0 parts of aluminum hydroxide to the layered silicate dispersion slurry obtained in step S1, and then add 5.0 parts of deionized water to control the solid content of the system to 45wt%; then add 270.0 parts of zirconia balls with a diameter of 5mm, and perform wet grinding at a mass ratio of zirconia balls to solid materials of the system of 3:1, with a grinding speed of 350r / min, a grinding time of 3h, and a grinding temperature controlled between 25-40℃. After grinding, filter and separate the zirconia balls to obtain a composite inorganic slurry with a pH of 5.8±0.5 and an appearance of milky white suspension slurry.

[0045] S3. The composite inorganic slurry obtained in step S2 is heated to 70℃, and 20.0 parts of silica sol are added at 600 r / min for 10 min. Separately, 8.0 parts of approximately 50 wt% aluminum dihydrogen phosphate aqueous solution are mixed with 12.0 parts of deionized water and stirred at 500 r / min for 10 min to obtain an aluminum dihydrogen phosphate aqueous solution with a mass concentration of 20 wt%. This aluminum dihydrogen phosphate aqueous solution is added dropwise to the composite inorganic slurry containing silica sol at a rate of 0.50 parts / min for 40 min. During the dropwise addition, the system temperature is maintained at 70℃ and the stirring speed is 600 r / min. After the dropwise addition is completed, the reaction is continued at 70℃ for 2 h to obtain a reactive coated slurry with a pH of 4.2 ± 0.4 and a solid content of 41.7 wt%.

[0046] S4. The reaction-coated slurry obtained in step S3 is directly dried at 105°C for 8 hours without washing before drying; after drying, a block-shaped dried material is obtained, which is then crushed and sieved through a 200-mesh sieve, followed by air classification to obtain an inorganic flame retardant synergist. The obtained inorganic flame retardant synergist is a grayish-white powder.

[0047] Preparation Example 2

[0048] The inorganic flame retardant synergist was prepared by referring to the preparation method in Preparation Example 1, except that the layered silicate montmorillonite K10 was replaced with kaolin, and everything else remained the same as in Preparation Example 1.

[0049] Preparation Example 3

[0050] The inorganic flame retardant synergist was prepared by referring to the preparation method in Preparation Example 1, except that the layered silicate montmorillonite K10 was replaced with mica powder, and everything else remained the same as in Preparation Example 1.

[0051] Preparation Example 4

[0052] The preparation of the inorganic flame retardant synergist was carried out by referring to the preparation method in Preparation Example 1, except that the wet grinding time of 3h in step S2 was replaced with 2h, and the rest remained the same as in Preparation Example 1.

[0053] Comparative Preparation Example 1

[0054] The inorganic flame retardant synergist was prepared by referring to the preparation method in Preparation Example 1, except that 45.0 parts of layered silicate montmorillonite K10 were replaced with 45.0 parts of commercially available precipitated silica, and the rest remained the same as in Preparation Example 1.

[0055] Comparative Preparation Example 2

[0056] The inorganic flame retardant synergist was prepared by referring to the preparation method in Preparation Example 1, except that 25.0 parts of zinc borate 3,5-hydrate was replaced with 25.0 parts of commercially available zinc oxide, and the rest remained the same as in Preparation Example 1.

[0057] Comparative preparation example 3

[0058] The inorganic flame retardant synergist was prepared by referring to the preparation method in Preparation Example 1, except that 20.0 parts of aluminum hydroxide were replaced with 20.0 parts of commercially available magnesium hydroxide, and the rest remained the same as in Preparation Example 1.

[0059] Comparative preparation example 4

[0060] The inorganic flame retardant synergist was prepared by referring to the preparation method in Preparation Example 1, except that 20.0 parts of silica sol were replaced with 20.0 parts of fumed silica aqueous dispersion with a solid content of 30 wt%, wherein the fumed silica aqueous dispersion was 6.0 parts based on silica, and the rest remained the same as in Preparation Example 1.

[0061] Comparative preparation example 5

[0062] The inorganic flame retardant synergist was prepared by referring to the preparation method in Preparation Example 1, except that 8.0 parts of approximately 50 wt% aluminum dihydrogen phosphate aqueous solution was replaced with 8.0 parts of 50 wt% ammonium dihydrogen phosphate aqueous solution, and mixed with 12.0 parts of deionized water as in Preparation Example 1 to prepare an ammonium dihydrogen phosphate aqueous solution with a mass concentration of 20 wt%. Everything else remained the same as in Preparation Example 1.

[0063] Comparative preparation example 6

[0064] The inorganic flame retardant synergist was prepared by referring to the preparation method in Preparation Example 1, except that the aluminum dihydrogen phosphate aqueous solution in step S3 was added dropwise at a rate of 0.50 parts / min for 40 min, and then 20.0 parts of aluminum dihydrogen phosphate aqueous solution with a mass concentration of 20 wt% were added at once. The rest remained the same as in Preparation Example 1.

[0065] Example 1

[0066] Preparation of a long-lasting flame-retardant reinforced PBT material:

[0067] 1. Raw material components by weight:

[0068] 53.5 parts of polybutylene terephthalate, BASF, Ultradur ® B 4520, viscosity 130cm 3 / g; MVR at 250℃ / 2.16kg is 20cm 3 / 10min, melting temperature approximately 223℃.

[0069] 25 parts of reinforcing fiber, selected from glass fiber, China Jushi Co., Ltd., 988A, glass fiber roving for thermoplastics, treated with silane sizing agent.

[0070] 11.5 parts of phosphorus-containing flame retardant, selected from aluminum diethylphosphonate.

[0071] Four parts of nitrogen-containing flame retardant, selected from melamine cyanurate.

[0072] Three parts of the inorganic flame retardant synergist were prepared as shown in Example 1.

[0073] Two parts of toughening compatibilizer, selected from glycidyl methacrylate.

[0074] 0.3 parts of anti-dripping agent, selected from polytetrafluoroethylene.

[0075] 0.1-0.5 parts of antioxidant, selected from a composition of pentaerythritol tetra(3,5-di-tert-butyl-4-hydroxyhydrocinnamate) and tris(2,4-di-tert-butylphenyl) phosphite in a mass ratio of 2:1;

[0076] 0.4 parts of lubricant, selected from pentaerythritol stearate.

[0077] 2. Preparation method:

[0078] (1) 53.5 parts of polybutylene terephthalate were dried at 120°C for 4 hours. The drying atmosphere was hot air. No solvent was added or the pH was adjusted during the drying process.

[0079] (2) Weigh out 11.5 parts by weight of aluminum diethylphosphinate, 4.0 parts by weight of melamine cyanurate, 3.0 parts by weight of the inorganic flame retardant synergist obtained in Preparation Example 1, 0.3 parts by weight of polytetrafluoroethylene powder, 0.20 parts by weight of pentaerythritol tetra(3,5-di-tert-butyl-4-hydroxyhydrogenated cinnamate), 0.10 parts by weight of tris(2,4-di-tert-butylphenyl) phosphite and 0.4 parts by weight of pentaerythritol stearate, mix them in air at 600 r / min for 5 min, and control the mixing temperature at 25-35℃ to obtain the flame retardant premix. The dried polybutylene terephthalate obtained in step (1) was then added to a mixing device and stirred at 300 r / min. 2.0 parts of glycidyl methacrylate were added dropwise or sprayed onto the surface of the polybutylene terephthalate at a rate of 0.40 parts / min for 5 minutes, with the material temperature controlled at 25-35℃ during the addition process. After the addition was complete, mixing continued at 300 r / min for 3 minutes. Then, the above-mentioned flame retardant premix was added, and mixing continued at 600 r / min for 5 minutes to obtain the premix.

[0080] (3) The premix obtained in step (2) is added through the main feed port of the twin-screw extruder, and 25.0 parts of glass fiber are added through the side feed port of the middle and rear section of the twin-screw extruder. Based on a total feed rate of 20 kg / h, the main feed rate is 15.0 kg / h, and the glass fiber side feed rate is 5.0 kg / h. No solvent is added, the pH is not adjusted, and no inert protective gas is introduced during the melt extrusion process; the pressure of the vacuum exhaust section is controlled at -0.08 MPa. The temperatures from zone one to the die head are controlled sequentially at 220℃, 230℃, 240℃, 245℃, 245℃, 238℃, and 230℃, the screw speed is 350 r / min, and the average residence time of the material in the barrel is controlled at 2 min. After melt mixing and extrusion, the resulting continuous strips are cooled with deionized water at 25°C for 25 seconds, then the surface moisture is dried and pelletized to obtain cylindrical particles. The particles are dried at 80°C for 2 hours and then sieved through a 20-mesh sieve to remove fine powder and clumps, thus obtaining long-lasting flame-retardant reinforced PBT material.

[0081] Examples 2-4

[0082] The preparation of a long-lasting flame-retardant reinforced PBT material is carried out by referring to the preparation method in Example 1, except that the inorganic flame-retardant synergist is replaced with the inorganic flame-retardant synergist prepared in Preparation Examples 2-4, and the rest is the same as in Example 1.

[0083] Comparative Examples 1-6

[0084] The preparation of a long-lasting flame-retardant reinforced PBT material is carried out by referring to the preparation method in Example 1, except that the inorganic flame-retardant synergist is replaced with the inorganic flame-retardant synergist prepared in Comparative Preparation Examples 1-6 in turn, and the rest is the same as in Example 1.

[0085] Comparative Example 7

[0086] The preparation of a long-lasting flame-retardant reinforced PBT material is carried out by referring to the preparation method in Example 1, except that the inorganic flame-retardant synergist obtained in Example 1 is replaced with an equal mass of commercially available zinc borate 3,5-hydrate, and the rest remains the same as in Example 1.

[0087] Comparative Example 8

[0088] The preparation of a long-lasting flame-retardant reinforced PBT material is carried out by referring to the preparation method in Example 1, except that the inorganic flame-retardant synergist obtained in Example 1 is replaced with an equal mass of commercially available aluminum hydroxide, wherein the particle size of the commercially available aluminum hydroxide is 1-3 μm, and the rest is the same as in Example 1.

[0089] Comparative Example 9

[0090] The preparation of a long-lasting flame-retardant reinforced PBT material is carried out by referring to the preparation method in Example 1, except that the inorganic flame-retardant synergist obtained in Example 1 is replaced with an equal mass of commercially available montmorillonite K10, and the rest is the same as in Example 1.

[0091] Performance testing

[0092] A1. Sample Preparation: The granules obtained from each example and comparative example were dried at 120℃ for 4 hours to ensure the moisture content of the granules did not exceed 0.05wt%. Standard samples were then prepared using an injection molding machine with a barrel temperature of 260℃, a mold temperature of 80±5℃, a holding time of 10s, and a cooling time of 25s. The resulting samples were conditioned for 48 hours at 23±2℃ and a relative humidity of 50±10% before testing.

[0093] A2. Tensile strength test: The test was conducted in accordance with GB / T1040.2-2022 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics", using type 1A specimens and a tensile speed of 5 mm / min. The data are shown in Table 1.

[0094] A3. Cantilever beam notched impact strength test: The test was conducted in accordance with GB / T1843-2008 "Standard for Determination of Impact Strength of Plastic Cantilever Beams". The sample size was 80mm×10mm×4mm. A type A notch was machined in the middle of the sample. The bottom radius of the notch was 0.25±0.05mm. The data are shown in Table 1.

[0095] A4. Oxygen Index Test Before Damp Heat Treatment: The oxygen index was tested according to GB / T2406.2-2009 "Determination of Combustion Behavior by Oxygen Index Method for Plastics - Part 2: Room Temperature Test". The sample size was 80mm×10mm×4mm. The untreated sample from A1 after condition conditioning was taken, with a sample size of 80mm×10mm×4mm. The sample was vertically fixed in a combustion chamber with a mixture of oxygen and nitrogen. The upper part of the sample was ignited, and the oxygen volume fraction was adjusted. The minimum oxygen concentration required to maintain the combustion of the sample under the specified combustion criteria was measured. The data are shown in Table 1.

[0096] A5. Oxygen Index Test after Damp Heat Treatment: The sample after condition conditioning in A1 was placed in a constant temperature and humidity chamber at 85±2℃ and 85±5% relative humidity for 168h. After removal, the surface moisture was wiped off, and the sample was placed at 23±2℃ and 50±10% relative humidity for 4h. Subsequently, the oxygen index was tested according to GB / T2406.2-2009 "Determination of Combustion Behavior by Oxygen Index Method for Plastics - Part 2: Room Temperature Test". The sample size was 80mm×10mm×4mm, and the data are shown in Table 1.

[0097] A6. Residual mass rate test of thermogravimetric analysis: Cut a 6mg sample from the middle of the injection molded sample and place it in a thermogravimetric analyzer. Test under nitrogen atmosphere with a nitrogen flow rate of 50mL / min, a heating range of 30-800℃ and a heating rate of 10℃ / min. Record the residual mass rate at 700℃. The data are shown in Table 1.

[0098] Table 1. Performance test data of the examples and comparative examples

[0099] Tensile strength (MPa) <![CDATA[Izod impact strength of cantilever beam (kJ / m 2 )]]> Oxygen index (%) before hydrothermal treatment Oxygen index (%) after hydrothermal treatment Residual mass percentage of thermal weight loss (%) Example 1 115.2 8.6 31.5 30.8 33.5 Example 2 112.5 8.2 31 29.8 32.8 Example 3 114 7.9 30.8 29.5 33.1 Example 4 110.6 8.1 31.2 29.6 32.5 Comparative Example 1 108.4 7.5 29.5 27.2 30.6 Comparative Example 2 106.5 7.7 28.6 26.5 30.3 Comparative Example 3 107.2 7.4 29.1 27 31.1 Comparative Example 4 105.8 6.8 29.8 26.2 30.8 Comparative Example 5 104.5 7.1 30.6 24.5 30.1 Comparative Example 6 106.2 7 30.1 25.8 31 Comparative Example 7 98.5 5.8 28.5 24.2 29.6 Comparative Example 8 95.4 6.1 28 23.6 29.1 Comparative Example 9 100.2 6.3 28.3 24.8 29.9

[0100] The PBT material prepared in this invention exhibits significant performance advantages in terms of mechanical strength, flame retardant efficiency, and resistance to damp heat. This is mainly because the layered silicate, zinc borate, and aluminum hydroxide, after wet grinding and in-situ coating treatment, reduce the surface energy and hard agglomeration tendency of the powder, improve their dispersion state and interfacial compatibility in the PBT resin matrix, thereby alleviating the stress concentration defects caused by the introduction of inorganic particles and maintaining the tensile and notched impact toughness of the material. The composite inorganic synergist and the phosphorus- and nitrogen-containing flame retardant exert a positive synergistic effect when heated, promoting the rapid formation of a dense and robust char layer skeleton on the matrix surface, effectively blocking heat transfer and the leakage of combustible gases; at the same time, the inorganic coating layer constructed by silica sol and aluminum dihydrogen phosphate has excellent barrier and hydration resistance properties, inhibiting the migration or hydrolytic failure of flame retardant components during damp heat aging, enabling the material to maintain a high oxygen index even after undergoing harsh temperature and humidity cycles. Conversely, when the inorganic composite system is changed or untreated single inorganic powder is added, the agglomeration and interfacial debinding of the filler are significantly aggravated, making it difficult to form a continuous and stable char network during combustion. This results in damage to the mechanical toughness of the material and a significant decline in its flame retardant properties after aging.

[0101] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A long-lasting flame-retardant reinforced PBT material, characterized in that, It is composed of the following components in parts by weight: 45-70 parts polybutylene terephthalate, 15-35 parts reinforcing fiber, 8-18 parts phosphorus-containing flame retardant, 2-8 parts nitrogen-containing flame retardant, 1-6 parts inorganic flame retardant synergist, 2-8 parts toughening compatibilizer, 0.1-0.6 parts anti-dripping agent, 0.1-0.5 parts antioxidant, and 0.1-0.8 parts lubricant; The inorganic flame retardant synergist is prepared from the following raw materials in parts by weight: 30-55 parts of layered silicate, 15-35 parts of zinc borate, 15-35 parts of aluminum hydroxide, 3-12 parts of silica sol (calculated as colloidal silica), and 2-10 parts of aluminum dihydrogen phosphate. The preparation method of the inorganic flame retardant synergist includes the following steps: S1. Add layered silicate to deionized water, control the solid content to 25-40 wt%, and shear disperse at 1200-2500 r / min for 20-45 min to obtain layered silicate dispersion slurry; then keep the layered silicate dispersion slurry at 50-70℃ and stir for 30-60 min at a stirring speed of 300-600 r / min; S2. Add zinc borate and aluminum hydroxide to the layered silicate dispersion slurry obtained in step S1, control the solid content of the system to be 35-55 wt%, and wet grind in a ball mill for 1.5-4 h. The ball milling media is zirconia balls with a diameter of 2-8 mm and a ball-to-material mass ratio of 2:1-5:

1. The grinding speed is 250-450 r / min. After grinding, a composite inorganic slurry is obtained. S3. Add silica sol to the composite inorganic slurry obtained in step S2, adjust the system temperature to 55-80℃, and stir at 400-800 r / min; then add aluminum dihydrogen phosphate aqueous solution with a mass concentration of 10-25 wt% for 20-50 min; after the addition is complete, continue to react at 55-80℃ for 1-3 h to obtain the reaction-coated slurry; S4. The reaction coating slurry obtained in step S3 is dried at 90-120℃ for 6-12h to obtain a dried product; the dried product is pulverized and then subjected to air classification to control the D50 particle size of the obtained inorganic flame retardant synergist to be 1.5-6.0μm, the D90 particle size to be ≤12μm, and the moisture content to be ≤0.5wt%.

2. The long-lasting flame-retardant reinforced PBT material according to claim 1, characterized in that, The layered silicate is selected from one or more of montmorillonite, kaolin, talc, and mica.

3. The long-lasting flame-retardant reinforced PBT material according to claim 1, characterized in that, The reinforcing fiber is glass fiber.

4. The long-lasting flame-retardant reinforced PBT material according to claim 1, characterized in that, The phosphorus-containing flame retardant is selected from one or more of aluminum diethylphosphonate, aluminum phosphonate, and ammonium polyphosphate.

5. The long-lasting flame-retardant reinforced PBT material according to claim 1, characterized in that, The nitrogen-containing flame retardant is one or more of melamine cyanurate, melamine, melamine orthophosphate, melamine pyrophosphate, and bismelamine pyrophosphate.

6. The long-lasting flame-retardant reinforced PBT material according to claim 1, characterized in that, The toughening compatibilizer is selected from glycidyl methacrylate and maleic anhydride.

7. The long-lasting flame-retardant reinforced PBT material according to claim 1, characterized in that, The anti-dripping agent is polytetrafluoroethylene powder; The antioxidant is a combination of pentaerythritol tetra(3,5-di-tert-butyl-4-hydroxyhydrocinnamate) and tris(2,4-di-tert-butylphenyl) phosphite, and the mass ratio of the two is 1:1-3:

1. The lubricant is selected from one or more of pentaerythritol stearate, ethylene bis-stearamide, calcium stearate, and zinc stearate.

8. A method for preparing a long-lasting flame-retardant reinforced PBT material as described in any one of claims 1-7, characterized in that, Includes the following steps: (1). The polybutylene terephthalate is dried at 110-130℃ for 3-6 hours to make its moisture content ≤0.05wt% to obtain dried polybutylene terephthalate; (2) Weigh out dry polybutylene terephthalate, phosphorus-containing flame retardant, nitrogen-containing flame retardant, inorganic flame retardant synergist, toughening compatibilizer, anti-dripping agent, antioxidant and lubricant, mix for 3-10 min to obtain premix; (3). The premix obtained in step (2) is added to the main feed port of a twin-screw extruder, and the reinforcing fiber is added from the side feed port. After melt mixing, extrusion, cooling and pelletizing, the long-lasting flame-retardant reinforced PBT material is obtained.

9. The method for preparing a long-lasting flame-retardant reinforced PBT material according to claim 8, characterized in that, The temperatures from zone one to the die head of the twin-screw extruder are controlled sequentially as follows: 210-230℃, 220-240℃, 225-250℃, 230-255℃, 230-255℃, 225-250℃, and 220-245℃. The screw speed is 250-500 r / min, and the vacuum exhaust pressure is -0.06 to 0.09 MPa.

10. The method for preparing a long-lasting flame-retardant reinforced PBT material according to claim 8, characterized in that, In step (2), the phosphorus-containing flame retardant, nitrogen-containing flame retardant, inorganic flame retardant synergist, anti-dripping agent, antioxidant and lubricant are first premixed to obtain flame retardant additive premix, and then mixed with polybutylene terephthalate and toughening compatibilizer. In step (3), the reinforcing fiber is added from the feed port on the middle and rear section of the twin-screw extruder.