Bromine-phosphorus-nitrogen synergistic flame-retardant PBT (polybutylene terephthalate) modified material as well as preparation method and application thereof

Abstract

The invention provides a bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material as well as a preparation method and application thereof, and belongs to the technical field of new materials. The brominated flame retardant and the phosphorus-nitrogen flame retardant are compounded according to a specific ratio, so that the balance between excellent flame retardance and electrical insulation performance is realized, the high-grade flame retardant standard can be reached under the condition of relatively thin thickness, and meanwhile, the flame retardant has good glowing filament resistance and tracking resistance; and good mechanical properties and processing stability of the glass fiber reinforced PBT material are maintained. The material can be widely applied to various electrical and electronic equipment with strict requirements on flame retardance, heat resistance and electrical safety, and has remarkable application value and market prospect.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, and in particular to a bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material, its preparation method, and its application. Background Technology

[0002] Polybutylene terephthalate (PBT) is a semi-crystalline thermoplastic engineering plastic with excellent mechanical properties, heat resistance, chemical resistance, and electrical insulation properties. It is widely used in electrical and electronic industries, the automotive industry, and home appliances. To further improve its mechanical strength and heat distortion temperature, PBT is typically reinforced with glass fiber. Glass fiber reinforced PBT has become a common material for manufacturing electrical and electronic components such as connectors, relays, circuit breakers, switches, and coil bobbins.

[0003] In the electrical and electronic fields, materials must meet stringent flame retardant safety standards, such as the UL94 flame retardant rating and glow wire ignition temperature (GWIT) requirements. Traditional flame retardant modification typically employs a compound system of brominated flame retardants and antimony trioxide. This system enables glass fiber reinforced PBT to achieve the UL94 V-0 flame retardant rating. However, under high glow wire testing conditions, its char structure is not dense and stable enough, making it prone to continuous combustion or drip ignition. Simultaneously, in humid or dusty environments, the material's tracking resistance (CTI) is also a crucial indicator of electrical safety, and traditional brominated antimony systems often struggle to achieve high CTI values. Furthermore, in glass fiber reinforced systems, achieving a good balance between flame retardant efficiency, mechanical properties, and processing stability is often difficult, especially for thin-walled parts where both flame retardant performance and high glow wire requirements are challenging to meet simultaneously.

[0004] Therefore, developing a glass fiber reinforced PBT material that can balance high flame retardancy, high glow wire ignition temperature, high tracking resistance index, and good mechanical properties is of great practical significance. Summary of the Invention

[0005] The purpose of this invention is to provide a bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material, its preparation method and application, which solves the technical problems of insufficient carbon layer stability of existing glass fiber reinforced PBT materials under high glow wire conditions and difficulty in simultaneously meeting the requirements of thin-wall flame retardancy and high resistance to leakage current tracking.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material, comprising PBT resin, bromine-based flame retardant, phosphorus-nitrogen-based flame retardant and alkali-free glass fiber, wherein the weight ratio of the bromine-based flame retardant to the phosphorus-nitrogen-based flame retardant is 2.5:1 to 3.5:1.

[0008] Preferably, the above-mentioned bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material further includes one or more of the following: toughening agent, antioxidant, lubricant, color masterbatch, nucleating agent, anti-dripping agent, coupling agent, release agent, anti-hydrolysis agent, light stabilizer, or antistatic agent.

[0009] Preferably, by weight, the above-mentioned bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material comprises 40-50 parts of PBT resin, 10-20 parts of bromine-based flame retardant, 5-15 parts of phosphorus-nitrogen-based flame retardant, and 25-35 parts of alkali-free glass fiber.

[0010] Preferably, by weight, the above-mentioned bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material includes 1 to 5 parts toughening agent, 0.1 to 0.5 parts antioxidant, 0.1 to 0.8 parts lubricant and 0.5 to 2 parts color masterbatch.

[0011] Preferably, the amount of the above-mentioned bromine-based flame retardant is 16 to 19 parts, and the amount of the above-mentioned phosphorus-nitrogen-based flame retardant is 5 to 7 parts.

[0012] Preferably, the above-mentioned bromine-based flame retardant is a brominated epoxy resin flame retardant, and the above-mentioned phosphorus-nitrogen-based flame retardant is melamine polyphosphate.

[0013] The present invention also provides a method for preparing the above-mentioned bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material, comprising the following steps: adding PBT resin, bromine-based flame retardant, phosphorus-nitrogen-based flame retardant and alkali-free glass fiber into a twin-screw extruder, and then performing melt blending, extrusion granulation to obtain the bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material.

[0014] Preferably, the preparation method specifically includes: mixing PBT resin with toughening agent and color masterbatch and adding it from the main feed port; mixing brominated flame retardant, phosphorus-nitrogen flame retardant, antioxidant and lubricant evenly and adding it from the side feed port; and adding alkali-free glass fiber from the other side feed port.

[0015] Preferably, the temperature of the melt-extruded barrel is 220~260℃; The melt extrusion is carried out in a twin-screw extruder with a length-to-diameter ratio of 48:1, a screw speed of 300-500 rpm, a production capacity of 800-900 kg / h, and a vacuum pressure of 0.06-0.10 MPa. The molten extrudate is cooled by water, and the water cooling process has a flow length of 0.5 to 1.2 meters.

[0016] The present invention also provides an application of the above-mentioned bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material or the bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material prepared by the above preparation method in the preparation of power transmission and distribution equipment, household appliances, automotive parts, communication equipment, industrial automation equipment, medical devices or power tools.

[0017] The beneficial effects of this invention are: The bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material provided by this invention achieves a balance between excellent flame-retardant and electrical insulation properties through a specific ratio of bromine-based and phosphorus-nitrogen-based flame retardants. It can achieve high-level flame-retardant standards at relatively thin thicknesses, while possessing good glow wire resistance and tracking resistance, and maintaining the good mechanical properties and processing stability of glass fiber reinforced PBT materials. This material can be widely used in various electrical and electronic equipment with strict requirements for flame retardancy, heat resistance, and electrical safety, and has significant application value and market prospects. Specifically, this invention has the following advantages: the bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material provided by this invention can still achieve a UL94V-0 flame-retardant rating at an ultra-thin thickness of 0.4mm, and the glow wire ignition temperature reaches 875℃, demonstrating excellent thin-wall flame-retardant performance, which can meet the safety requirements of smaller and lighter products; the tracking resistance index reaches 250V, which can meet the safety requirements of electrical equipment for insulation materials. In terms of mechanical properties, the material exhibits a tensile strength of 140-150 MPa, a flexural strength of 230-240 MPa, a flexural modulus of 10,000-11,000 MPa, and an impact strength of 7-8 MPa, maintaining the excellent comprehensive mechanical properties of glass fiber reinforced PBT materials. Furthermore, the material has a moderate melt flow index and good processing fluidity, making it suitable for injection molding of various precision parts. These comprehensive properties make the material of this invention particularly suitable for applications requiring strict flame retardancy, heat resistance, electrical safety, and mechanical properties, such as power transmission and distribution equipment, household appliances, automotive parts, communication equipment, industrial automation equipment, medical devices, and power tools. Detailed Implementation

[0018] This invention provides a bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material, comprising PBT resin, bromine-based flame retardant, phosphorus-nitrogen-based flame retardant and alkali-free glass fiber, wherein the weight ratio of the bromine-based flame retardant to the phosphorus-nitrogen-based flame retardant is 2.5:1 to 3.5:1.

[0019] In this invention, the PBT resin, or polybutylene terephthalate, is a semi-crystalline thermoplastic engineering plastic with excellent mechanical properties, heat resistance, chemical corrosion resistance, and electrical insulation properties. PBT resin can be obtained through transesterification or direct esterification polycondensation, with a melting point of 220-230°C and a glass transition temperature of approximately 40-60°C. This invention does not impose special restrictions on the source of the PBT resin; commercially available industrial-grade PBT resin can be used, such as products with an intrinsic viscosity of 0.7-1.2 dL / g, or different viscosity grades can be selected according to actual needs.

[0020] In this invention, the brominated flame retardant refers to an organic flame retardant containing bromine in its molecular structure. Its flame retardant mechanism primarily involves the decomposition of hydrogen bromide during combustion, which captures active free radicals generated during the combustion of polymeric materials, thereby interrupting the chain reaction. Brominated flame retardants usable in this invention include, but are not limited to, brominated epoxy resin, decabromodiphenyl ethane, brominated polystyrene, tetrabromobisphenol A and its derivatives. Brominated flame retardants have advantages such as high flame retardant efficiency, good compatibility with PBT resin, and minimal impact on the mechanical properties of materials. The phosphorus-nitrogen flame retardant refers to a flame retardant containing both phosphorus and nitrogen. Its flame retardant mechanism primarily involves promoting the formation of a dense char layer on the material surface during combustion, isolating oxygen and heat transfer. Simultaneously, the presence of nitrogen enhances the charring effect of phosphorus. Phosphorus-nitrogen flame retardants usable in this invention include, but are not limited to, melamine polyphosphate, melamine cyanurate, and ammonium polyphosphate. Phosphorus-nitrogen flame retardants are characterized by low smoke, low toxicity, and anti-dripping properties, making them particularly suitable for applications requiring high glow wire performance. This invention achieves a synergistic effect of gas-phase and condensed-phase flame retardancy by compounding brominated flame retardants with phosphorus-nitrogen flame retardants at a weight ratio of 2.5:1 to 3.5:1. This significantly improves the glow wire ignition temperature and tracking resistance of the material while ensuring flame retardant efficiency. Within the above ratio range, a further preferred ratio is 2.8:1 to 3.2:1, and more preferably 3:1.

[0021] In this invention, the alkali-free glass fiber refers to glass fiber with an alkali metal oxide content of less than 0.8%, characterized by high strength, high modulus, and strong bonding with PBT resin. The addition of glass fiber can significantly improve the tensile strength, flexural strength, and flexural modulus of the material, while also improving its heat distortion temperature and dimensional stability. This invention does not impose special restrictions on the morphology of the alkali-free glass fiber; continuous glass fiber, chopped glass fiber, or glass fiber powder can be used, preferably chopped glass fiber. The fiber diameter is generally 5-20 μm, and the length is generally 2-5 mm. In one specific embodiment of this invention, the alkali-free glass fiber used is 10 μm alkali-free glass fiber (Chongqing International, model: ECS303-3-H). The alkali-free glass fiber can be surface-treated with a coupling agent to improve the interfacial bonding strength with PBT resin. The coupling agent includes, but is not limited to, silane coupling agents and titanate coupling agents.

[0022] Preferably, the above-mentioned bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material further includes at least one of a toughening agent, antioxidant, lubricant, color masterbatch, nucleating agent, anti-dripping agent, coupling agent, release agent, anti-hydrolysis agent, light stabilizer, or antistatic agent. In this invention, the toughening agent refers to an additive capable of improving the impact resistance of the material. Its mechanism of action is to form an elastomeric dispersed phase in the matrix resin, absorb impact energy, and prevent crack propagation. Toughening agents usable in this invention include, but are not limited to, ethylene-butyl acrylate copolymer, ethylene-vinyl acetate copolymer, methyl methacrylate-butadiene-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, and polyester elastomers. The antioxidants refer to additives that can inhibit or delay the oxidative degradation of polymeric materials, including primary antioxidants and secondary antioxidants. Primary antioxidants include hindered phenolic antioxidants, such as pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; secondary antioxidants include phosphite antioxidants, such as tris(2,4-di-tert-butylphenyl) phosphite. The lubricants refer to additives that can reduce friction and adhesion during material processing, including internal lubricants and external lubricants. Internal lubricants mainly reduce internal friction between resin molecules, such as stearic acid, stearate esters, and PETS (pentaerythritol stearate); external lubricants mainly reduce the adhesion between the melt and the equipment surface, such as polyethylene wax, paraffin wax, rice bran wax, and montmorillonite wax. In this invention, internal and external lubricants, including rice bran wax, montmorillonite wax, and PETS, are preferred. These can effectively improve the processing fluidity of the material, reduce extrusion torque, improve the surface finish of the product, and have little impact on the flame retardant and mechanical properties of the material.

[0023] The masterbatch refers to a granular colorant made by uniformly dispersing pigments or dyes in a carrier resin, used to impart a specific color to a material. The nucleating agent refers to an additive that promotes the crystallization of polymer materials, increases the crystallization rate and crystallinity, including inorganic nucleating agents such as talc and calcium carbonate, and organic nucleating agents such as sodium benzoate and sorbitol derivatives. The anti-dripping agent refers to an additive that prevents molten dripping during material combustion, typically a polytetrafluoroethylene-based substance, which forms a fibrous network structure during processing, increasing melt strength. The coupling agent refers to an additive that improves the interfacial bonding between inorganic fillers and organic resins, including silane coupling agents, titanate coupling agents, and aluminate coupling agents. The release agent refers to an additive that reduces the adhesion between the product and the mold, including zinc stearate, calcium stearate, and silicone oil. The anti-hydrolysis agent refers to an additive that improves the hydrolysis resistance of polyester materials, including carbodiimide anti-hydrolysis agents and epoxy compound anti-hydrolysis agents. The light stabilizer refers to an additive that can inhibit or delay the photoaging of polymer materials, including ultraviolet absorbers and hindered amine light stabilizers. The antistatic agent refers to an additive that can reduce the surface resistance of materials and prevent static electricity accumulation, including cationic antistatic agents, anionic antistatic agents, and nonionic antistatic agents. All of the above-mentioned additives are commercially available. Without affecting the core performance of the modified material of this invention, those skilled in the art can select appropriate types and amounts according to actual needs.

[0024] Preferably, by weight, the above-mentioned bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material comprises 40-50 parts of PBT resin, 10-20 parts of bromine-based flame retardant, 5-15 parts of phosphorus-nitrogen-based flame retardant, and 25-35 parts of alkali-free glass fiber.

[0025] In this invention, the amount of PBT resin is 40-50 parts by weight, more preferably 42-45 parts by weight, and even more preferably 43-44 parts by weight. The amount of the brominated flame retardant is 10-20 parts by weight, more preferably 16-19 parts by weight, and even more preferably 18 parts by weight. The amount of the phosphorus-nitrogen flame retardant is 5-15 parts by weight, more preferably 5-7 parts by weight, and even more preferably 6 parts by weight. The amount of the alkali-free glass fiber is 25-35 parts by weight, more preferably 28-33 parts by weight, and even more preferably 30 parts by weight. Within the above ranges, the material can achieve the best balance between flame retardant performance and mechanical properties.

[0026] Preferably, by weight, the above-mentioned bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material includes 1 to 5 parts toughening agent, 0.1 to 0.5 parts antioxidant, 0.1 to 0.8 parts lubricant and 0.5 to 2 parts color masterbatch.

[0027] In this invention, the toughening agent is used in an amount of 1-5 parts by weight, more preferably 2-4 parts by weight, and even more preferably 2.5-3.5 parts by weight. The antioxidant is used in an amount of 0.1-0.5 parts by weight, more preferably 0.2-0.4 parts by weight, and even more preferably 0.3 parts by weight. The lubricant is used in an amount of 0.1-0.8 parts by weight, more preferably 0.2-0.6 parts by weight, and even more preferably 0.3-0.4 parts by weight. The masterbatch is used in an amount of 0.5-2 parts by weight, more preferably 0.8-1.5 parts by weight, and even more preferably 1.0-1.2 parts by weight. The amounts of the above-mentioned additives can be adjusted according to actual needs to achieve optimal processing performance and product appearance.

[0028] Preferably, the amount of the above-mentioned bromine-based flame retardant is 16 to 19 parts, and the amount of the above-mentioned phosphorus-nitrogen-based flame retardant is 5 to 7 parts.

[0029] In this invention, it is further preferred that the amount of brominated flame retardant is 16-19 parts by weight and the amount of phosphorus-nitrogen flame retardant is 5-7 parts by weight. Within this preferred range, the total amount of brominated and phosphorus-nitrogen flame retardants added is 23-26 parts by weight, and the weight ratio of the two is about 2.3:1 to 3.8:1. When the amount of brominated flame retardant is 18 parts by weight and the amount of phosphorus-nitrogen flame retardant is 6 parts by weight, the weight ratio of the two is 3:1, at which point the material can achieve an optimal balance of flame retardant performance, glow wire ignition temperature, and resistance to tracking.

[0030] Preferably, the aforementioned brominated flame retardant is a brominated epoxy resin flame retardant, and the aforementioned phosphorus-nitrogen flame retardant is melamine polyphosphate. In this invention, the brominated epoxy resin flame retardant refers to a brominated flame retardant prepared by reacting epoxy resin with a brominating agent. Its molecular structure contains both bromine and epoxy groups, exhibiting excellent compatibility and dispersibility with PBT resin while having minimal impact on the mechanical properties of the material. The bromine content of the brominated epoxy resin flame retardant is generally 40-60%, the molecular weight is generally 6000-30000, and the softening point is generally 80-150℃. The melamine polyphosphate refers to a salt compound formed by the reaction of melamine with phosphoric acid or polyphosphoric acid. Its molecular structure contains a triazine ring and polyphosphate groups. During combustion, it can rapidly decompose to form a dense char layer while releasing non-combustible gases to dilute oxygen, exhibiting good flame retardant and smoke suppression effects. Melamine polyphosphate typically has a phosphorus content of 10-20%, a nitrogen content of 40-50%, and a decomposition temperature of 300-350℃.

[0031] This invention also provides a method for preparing the above-mentioned bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material, comprising the following steps: adding PBT resin, brominated flame retardant, phosphorus-nitrogen flame retardant, and alkali-free glass fiber into a twin-screw extruder, followed by melt blending and extrusion granulation to obtain the bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material. More preferably, the preparation method includes: adding PBT resin mixed with toughening agent and color masterbatch through the main feed inlet; adding brominated flame retardant, phosphorus-nitrogen flame retardant, antioxidant, and lubricant after uniform mixing through the side feed inlet; and adding alkali-free glass fiber through the other side feed inlet. This preparation method employs a step-by-step mixing approach, aiming to first mix PBT resin with toughening agent and color masterbatch, then with flame retardant, antioxidant, and lubricant, and finally add glass fiber. This facilitates the uniform dispersion of each component, avoids the decomposition of the flame retardant due to prolonged high-temperature residence, and reduces shear damage to the glass fiber, thereby obtaining a modified material with excellent performance.

[0032] Preferably, the barrel temperature of the melt extrusion is 220~260℃; the melt extrusion is carried out in a twin-screw extruder with a length-to-diameter ratio of 48:1, a screw speed of 300~500 rpm, a production capacity of 800~900 kg / h, and a vacuum pressure of 0.06~0.10 MPa.

[0033] In this invention, the barrel temperature refers to the set temperature of each section of the extruder barrel, which can be set in sections according to the length of the extruder barrel and the characteristics of the material. Generally, the temperature gradually increases or remains constant from the feed port to the die head. The preferred barrel temperature is 230~250℃, more preferably 235~245℃. The length-to-diameter ratio (L / D) of the twin-screw extruder is 48:1, which is beneficial for the full melting, mixing and venting of the material. The preferred screw speed is 350~450 rpm, more preferably 400 rpm. The preferred output is 820~880 kg / h, more preferably 850 kg / h. The preferred vacuum pressure is 0.07~0.09 MPa, more preferably 0.08 MPa. By coordinating the above process parameters, stable production and good quality consistency of the material can be achieved. Preferably, the molten extrudate is water-cooled, and the water cooling length is 0.5~1.2 meters. In this invention, water cooling refers to cooling the molten extruded strip through a cooling water tank to rapidly cool and solidify it, facilitating subsequent granulation. The water passage length refers to the length of the strip in contact with water in the tank. A water passage length that is too short will result in insufficient cooling and adhesion of the strip surface; a water passage length that is too long may cause over-cooling of the strip, affecting the pelletizing effect. The water passage length is preferably 0.7~1.0 meters, more preferably 0.8~0.9 meters. The temperature of the cooling water is generally from room temperature to 40°C, and can be adjusted appropriately according to the ambient temperature and production speed.

[0034] The present invention also provides an application of the above-mentioned bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material or the bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material prepared by the above preparation method in the preparation of power transmission and distribution equipment, household appliances, automotive parts, communication equipment, industrial automation equipment, medical devices or power tools.

[0035] In this invention, the power transmission and distribution equipment includes, but is not limited to, circuit breakers, contactors, terminals, fuse holders, meter housings, relay housings, and switch cabinet insulation components. The household appliances include, but are not limited to, internal structural components and housings of products such as air conditioners, washing machines, refrigerators, vacuum cleaners, microwave ovens, rice cookers, air fryers, and hair dryers. The automotive parts include, but are not limited to, headlight housings, sensor housings, connectors, coil frames, motor end covers, battery brackets, fuse boxes, and wiring harness fasteners. The communication equipment includes, but is not limited to, base station housings, router housings, switch housings, fiber optic terminal boxes, antenna covers, and power adapter housings. The industrial automation equipment includes, but is not limited to, PLC housings, servo driver housings, frequency converter housings, sensor housings, industrial controller housings, and robot components. The medical devices include, but are not limited to, patient monitor housings, ultrasound equipment housings, diagnostic equipment housings, portable medical device housings, and medical sensor housings. The power tools include, but are not limited to, electric drill housings, electric saw housings, angle grinder housings, electric hammer housings, garden tool housings, and electric screwdriver housings. The aforementioned application areas all have high requirements for the flame retardancy, heat resistance, electrical safety, and mechanical properties of materials. The material of this invention can meet these requirements and has good application prospects.

[0036] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0037] Example 1 This embodiment provides a bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material, the components and weight parts of which are as follows: PBT resin: 43.2 parts Brominated epoxy resin flame retardant (bromine-based): 18 parts Melamine polyphosphate (phosphorus-nitrogen based): 6 parts Alkali-free glass fiber: 30 parts Toughening agent (EBA type): 1.0 part Antioxidant: 0.3 parts Lubricant: 0.3 parts Masterbatch: 1.2 parts The weight ratio of the above-mentioned bromine-based flame retardant to the phosphorus-nitrogen-based flame retardant is 3:1, and the total amount of flame retardant added is 24 parts.

[0038] The preparation method is as follows: PBT resin, toughening agent, and color masterbatch were added to a high-speed mixer and mixed at room temperature for 5 minutes to obtain the first mixture. Brominated flame retardants, phosphorus-nitrogen flame retardants, antioxidants, and lubricants were pre-mixed evenly in another mixer to obtain a flame retardant mixture. The first mixture was fed into a twin-screw extruder with a length-to-diameter ratio of 48:1 through the main feed port. The flame retardant mixture was fed into the extruder through a side feed port, and alkali-free glass fiber was fed into the extruder through another side feed port. The barrel temperatures of each section of the extruder were set as follows: C0 = 0℃, C1 = 250℃, C2 = 250℃, C3 = 250℃, C4 = 250℃, C5 = 240℃, C6 = 240℃, C7 = 240℃, C8 = 230℃, C9 = 230℃, C10 = 240℃, C11 = 230℃, G1 = 240℃, and G2 = 240℃. The screw speed is 400 rpm, the output is 850 kg / h, and the vacuum pressure is 0.08~0.09 MPa. The melt-extruded strip is cooled by water with a water passage length of 0.9 meters. After cooling, it is granulated by a pelletizer with a speed of 85 rpm to obtain granular product, which is the bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material.

[0039] Example 2 This embodiment provides a bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material, the components and weight parts of which are as follows: PBT resin: 45 parts Brominated epoxy resin flame retardant (bromine-based): 17.5 parts Melamine polyphosphate (phosphorus-nitrogen based): 7 parts Alkali-free glass fiber: 30 parts Toughening agent (EBA type): 1.0 part Antioxidant: 0.3 parts Lubricant: 0.3 parts Masterbatch: 1.2 parts The weight ratio of the above-mentioned bromine-based flame retardant to the phosphorus-nitrogen-based flame retardant is 2.5:1, and the total amount of flame retardant added is 24.5 parts.

[0040] The preparation method is as follows: PBT resin, toughening agent, and color masterbatch were added to a high-speed mixer and mixed at room temperature for 5 minutes to obtain the first mixture. Brominated flame retardants, phosphorus-nitrogen flame retardants, antioxidants, and lubricants were pre-mixed evenly in another mixer to obtain a flame retardant mixture. The first mixture was fed into a twin-screw extruder with a length-to-diameter ratio of 48:1 through the main feed port. The flame retardant mixture was fed into the extruder through a side feed port, and alkali-free glass fiber was fed into the extruder through another side feed port. The barrel temperatures of each section of the extruder were set as follows: C0 = 0℃, C1 = 250℃, C2 = 250℃, C3 = 250℃, C4 = 250℃, C5 = 240℃, C6 = 240℃, C7 = 240℃, C8 = 230℃, C9 = 230℃, C10 = 240℃, C11 = 230℃, G1 = 240℃, and G2 = 240℃. The screw speed is 400 rpm, the output is 850 kg / h, and the vacuum pressure is 0.08~0.09 MPa. The melt-extruded strip is cooled by water with a water passage length of 0.9 meters. After cooling, it is granulated by a pelletizer with a speed of 85 rpm to obtain granular product, which is the bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material.

[0041] Example 3 This embodiment provides a bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material, the components and weight parts of which are as follows: PBT resin: 43 parts Brominated epoxy resin flame retardant (bromine-based): 21 parts Melamine polyphosphate (phosphorus-nitrogen based): 6 parts Alkali-free glass fiber: 30 parts Toughening agent (EBA type): 1.0 part Antioxidant: 0.3 parts Lubricant: 0.3 parts Masterbatch: 1.2 parts The weight ratio of the above-mentioned bromine-based flame retardant to the phosphorus-nitrogen-based flame retardant is 3.5:1, and the total amount of flame retardant added is 27 parts.

[0042] The preparation method is as follows: PBT resin, toughening agent, and color masterbatch were added to a high-speed mixer and mixed at room temperature for 5 minutes to obtain the first mixture. Brominated flame retardants, phosphorus-nitrogen flame retardants, antioxidants, and lubricants were pre-mixed evenly in another mixer to obtain a flame retardant mixture. The first mixture was fed into a twin-screw extruder with a length-to-diameter ratio of 48:1 through the main feed port. The flame retardant mixture was fed into the extruder through a side feed port, and alkali-free glass fiber was fed into the extruder through another side feed port. The barrel temperatures of each section of the extruder were set as follows: C0 = 0℃, C1 = 250℃, C2 = 250℃, C3 = 250℃, C4 = 250℃, C5 = 240℃, C6 = 240℃, C7 = 240℃, C8 = 230℃, C9 = 230℃, C10 = 240℃, C11 = 230℃, G1 = 240℃, and G2 = 240℃. The screw speed is 400 rpm, the output is 850 kg / h, and the vacuum pressure is 0.08~0.09 MPa. The melt-extruded strip is cooled by water with a water passage length of 0.9 meters. After cooling, it is granulated by a pelletizer with a speed of 85 rpm to obtain granular product, which is the bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material.

[0043] Experimental Example The sample obtained in Example 1 was used as experimental group 1, and the following control group was set up. The only difference between the control group and Example 1 was the difference in the formulation components and dosages. The preparation method and process parameters were the same as those in Example 1.

[0044] Comparison 1 The difference from Example 1 is that: the amount of PBT resin is 41.2 parts, the amount of PET resin is 8 parts, the amount of brominated flame retardant is 12 parts, the amount of phosphorus-nitrogen flame retardant is 6 parts, and the weight ratio of brominated flame retardant to phosphorus-nitrogen flame retardant is 2:1. The remaining components (30 parts of alkali-free glass fiber, 1.0 part of toughening agent, 0.3 parts of antioxidant, 0.3 parts of lubricant, and 1.2 parts of color masterbatch) and the preparation process are the same as in Example 1.

[0045] Comparison 2 The difference from Example 1 is that: the PBT resin is 46.2 parts, PET resin is not added, the brominated flame retardant is 14 parts, the phosphorus-nitrogen flame retardant is 7 parts, and the weight ratio of the brominated flame retardant to the phosphorus-nitrogen flame retardant is 2:1. The remaining components and preparation process are the same as in Example 1.

[0046] Comparison 3 The difference from Example 1 is that: the PBT resin is 47.7 parts, PET resin is not added, the brominated flame retardant is 13 parts, the phosphorus-nitrogen flame retardant is 6.5 parts, and the weight ratio of the brominated flame retardant to the phosphorus-nitrogen flame retardant is 2:1. The remaining components and preparation process are the same as in Example 1.

[0047] Compare with 4 The difference from Example 1 is that: the PBT resin is 43.2 parts, no PET resin is added, the brominated flame retardant is 12 parts, the phosphorus-nitrogen flame retardant is 12 parts, and the weight ratio of the brominated flame retardant to the phosphorus-nitrogen flame retardant is 1:1. The remaining components and preparation process are the same as in Example 1.

[0048] Performance testing methods: 1. Melt Flow Index Test according to ASTM D1238 standard. After drying the sample to the required moisture content, heat the melt flow indexer to 250°C and hold at that temperature for at least 30 minutes. Add approximately 5-10g of sample to the heating chamber and compact it with a pressure bar to remove air. Apply a 2.16kg standard weight to the pressure bar to melt and extrude the sample. After the sample has been stably extruded, use a blade to cut off the extrudate at specified time intervals. Weigh the mass of the extrudate and calculate the melt flow index value.

[0049] 2. Tensile strength and elongation at break Test according to ASTM D638 standard. Prepare standard dumbbell-shaped specimens and place them at 23℃±2℃ and 50%±5% relative humidity for at least 40 hours. Set the tensile speed of the universal testing machine to 5 mm / min, clamp both ends of the specimen in the upper and lower fixtures of the machine, start the machine, and record the force-displacement curve until the specimen breaks. Tensile strength is the maximum tensile force divided by the original cross-sectional area of ​​the specimen. Elongation at break is the gauge length at break minus the original gauge length divided by the original gauge length multiplied by 100%.

[0050] 3. Bending strength and bending modulus Test according to ASTM D790 standard. Prepare rectangular specimens of 127mm × 12.7mm × 3.2mm and place them at 23℃ ± 2℃ and 50% ± 5% relative humidity for at least 40 hours. Use a three-point bending test fixture, setting the span to 16 times the specimen thickness (approximately 50mm), and the test speed to 2mm / min. Place the specimen on two support points, ensuring the load application point is at the center of the span, apply a bending load, and record the load-deflection curve until the specimen breaks or reaches the specified deflection. Calculate the bending strength using the formula (3 × maximum load × span) ÷ (2 × specimen width × specimen thickness²). Calculate the bending modulus using the formula (span³ × load difference) ÷ (4 × specimen width × specimen thickness³ × deflection difference).

[0051] 4. Impact strength Tested according to ASTM D256 standard. The material was machined into V-notch specimens measuring 63.5 mm × 12.7 mm × 3.2 mm, with a notch depth of 1 / 3 of the specimen thickness. These specimens were placed in an environment of 23℃ ± 2℃ and 50% ± 5% relative humidity for at least 40 hours. Using a simply supported beam impact testing machine, the impact pendulum energy was set to 2.75 J. The specimen was placed on a simply supported beam support with the notch facing the impact direction. The pendulum was released, and the energy absorbed at impact fracture was recorded. The impact strength is calculated by dividing the absorbed impact energy by the cross-sectional area of ​​the notch in the specimen.

[0052] 5. Flame retardant rating Refer to UL94 standard testing. Process the material into standard strip specimens measuring 127mm × 12.7mm × corresponding thicknesses (3.2mm, 1.6mm, 0.8mm, 0.4mm), with at least 5 specimens per group. Place the specimens at 23℃±2℃ for at least 48 hours. Using a vertical burning tester, fix the specimens vertically, ignite a Bunsen burner with a flame height of 20mm from the bottom of the specimen, and remove the flame after 10 seconds. Record the flaming burning time (T1) and the flameless burning time (T2) of the specimen, observing whether the specimen drips burning material and whether it ignites the cotton below. Determine the flame retardancy rating based on the T1 and T2 times and the amount of burning material dripping.

[0053] 6. Compared to the tracking index (CTI) Test according to IEC 60112 standard. Process the material into 100mm × 100mm × 3.2mm samples and place them in an environment of 23℃ ± 2℃ and 50% ± 5% relative humidity for at least 24 hours. Using a tracking index tester, press platinum electrodes (4mm spacing) onto the sample surface, apply an initial voltage, and drip one drop of 0.05ml of 0.1% ammonium chloride electrolyte every 30 seconds, continuing for 50 drops. Observe whether tracking occurs on the sample surface (current ≥ 0.5A and lasting for more than 2 seconds). If no tracking occurs, increase the voltage (increase by 25V each time) and repeat the test until tracking occurs. The CTI value is the highest voltage at which the material does not exhibit tracking.

[0054] 7. Glow wire ignition temperature (GWIT) Test according to IEC 60695 standard. Process the material into specimens of 60mm × 60mm × corresponding thicknesses (3.2mm, 1.6mm, 0.8mm), with at least 3 specimens per group. Place the specimens in an environment of 23℃±2℃ and 50%±5% relative humidity for at least 24 hours. Using a glow wire tester, heat a 4mm diameter nickel-chromium alloy glow wire to the set temperature, hold it at that temperature for 10 minutes, then press it onto the specimen surface at a speed of 10mm / s. After a contact time of 30 seconds, remove the wire and observe whether the specimen ignites. Record the flaming and non-flaming combustion times. If the combustion time is ≤30 seconds, increase the temperature (by 25℃ each time) and repeat the test until the combustion time is >30 seconds. The GWIT value is the highest temperature at which the material meets the combustion time requirement.

[0055] The test results are shown in Table 1 below: Table 1 Performance Test Results

[0056] Note: Melt index, tensile strength, elongation at break, flexural strength, flexural modulus, and impact strength: " / " in the table indicates the results of three independent tests on the same sample.

[0057] UL94 (3.2mm) T1 / T2: The values ​​in the table are the first burn time (T1) and the second burn time (T2), in seconds. For example, "0 / 5" means T1=0 seconds and T2=5 seconds.

[0058] UL94 (1.6mm) T1 / T2: Controls 1, 2, and 3 have two test results, separated by commas, such as "6 / 5, 7 / 6" indicating that the first test had T1=6 seconds and T2=5 seconds, and the second test had T1=7 seconds and T2=6 seconds. In Experiment 1, both T1 and T2 tests were 0 seconds. Control 4 failed the flame retardancy test at a thickness of 1.6mm, therefore no T1 / T2 data is available.

[0059] UL94 (0.8mm) T1 / T2: Only test group 1 passed at a thickness of 0.8mm, with both T1 and T2 taking 0 seconds. All others failed.

[0060] UL94 (0.4mm) T1 / T2: Only test group 1 passed at a thickness of 0.4mm, with both T1 and T2 taking 0 seconds. All others failed.

[0061] UL94 rating: V-0 is the highest rating, determined by a combination of T1 and T2 times and the amount of dripping during combustion.

[0062] The experimental results above show that the bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material provided in Example 1 of this invention can achieve a UL94 V-0 flame retardant rating at a thickness of 0.8 mm, with a glow wire ignition temperature of 875°C, and a tracking resistance index of 250V, demonstrating the best overall flame retardant and electrical insulation performance. While controls 1-3 achieved V-0 at thicknesses of 3.2 mm and 1.6 mm, a thickness of 0.8 mm failed the test, with a GWIT of only 850°C and a CTI of 250V. Control 4 passed the CTI at 250V, but failed the flame retardant test at thicknesses of 1.6 mm and 0.8 mm, with a GWIT of only 850°C. Furthermore, experimental group 1 maintained a V-0 flame retardant rating and a GWIT of 875°C at an ultra-thin thickness of 0.4 mm, while all controls failed the 0.4 mm flame retardant test, further demonstrating the superiority of the technical solution of this invention.

[0063] As can be seen from the above embodiments, the present invention provides a bromine-phosphorus-nitrogen synergistic flame-retardant modified PBT material. By adjusting the ratio of bromine-based flame retardant to phosphorus-nitrogen-based flame retardant, the flame-retardant and electrical insulation properties of the material can be significantly affected. When the ratio is within the range defined by the present invention, the material can still achieve a high level of flame retardancy even at a relatively thin thickness, while also possessing a high glow wire ignition temperature and good resistance to tracking. In contrast, in the comparative examples, when the ratio of bromine-based flame retardant to phosphorus-nitrogen-based flame retardant deviates from the range of the present invention, the thin-wall flame-retardant properties, glow wire ignition temperature, and resistance to tracking all show varying degrees of decline. Therefore, the present invention effectively optimizes the overall performance of the material through a specific flame retardant compounding ratio.

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A PBT modified material with synergistic bromine-phosphorus-nitrogen flame retardancy, characterized in that, It includes PBT resin, brominated flame retardant, phosphorus-nitrogen flame retardant and alkali-free glass fiber, wherein the weight ratio of brominated flame retardant to phosphorus-nitrogen flame retardant is 2.5:1 to 3.5:

1.

2. The bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material according to claim 1, characterized in that, It also includes one or more of the following: toughening agents, antioxidants, lubricants, color masterbatches, nucleating agents, anti-dripping agents, coupling agents, release agents, anti-hydrolysis agents, light stabilizers, or antistatic agents.

3. The bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material according to claim 1, characterized in that, By weight, it comprises 40-50 parts PBT resin, 10-20 parts brominated flame retardant, 5-15 parts phosphorus-nitrogen flame retardant, and 25-35 parts alkali-free glass fiber.

4. The bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material according to claim 3, characterized in that, By weight, it includes 1 to 5 parts toughening agent, 0.1 to 0.5 parts antioxidant, 0.1 to 0.8 parts lubricant and 0.5 to 2 parts color masterbatch.

5. The bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material according to claim 3, characterized in that, The bromine-based flame retardant is 16-19 parts, and the phosphorus-nitrogen-based flame retardant is 5-7 parts.

6. The bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material according to claim 1, characterized in that, The bromine-based flame retardant is a brominated epoxy resin flame retardant, and the phosphorus-nitrogen-based flame retardant is melamine polyphosphate.

7. The preparation method of the bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material according to any one of claims 1 to 6, characterized in that, Includes the following steps: PBT resin, brominated flame retardant, phosphorus-nitrogen flame retardant and alkali-free glass fiber are added to a twin-screw extruder, and then melt-blended, extruded and granulated to obtain the bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material.

8. The preparation method according to claim 7, characterized in that, The preparation method includes: mixing PBT resin with toughening agent and color masterbatch and adding it from the main feed port; mixing bromine flame retardant, phosphorus-nitrogen flame retardant, antioxidant and lubricant evenly and adding them from the side feed port; and adding alkali-free glass fiber from the other side feed port.

9. The preparation method according to claim 8, characterized in that, The barrel temperature of the melt extrusion is 220~260℃; The melt extrusion is carried out in a twin-screw extruder with a length-to-diameter ratio of 48:1, a screw speed of 300-500 rpm, a production capacity of 800-900 kg / h, and a vacuum pressure of 0.06-0.10 MPa. The molten extrudate is cooled by water, and the water cooling process has a flow length of 0.5 to 1.2 meters.

10. The application of the bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material according to any one of claims 1 to 6 or the bromine-phosphorus-nitrogen synergistic flame-retardant PBT modified material prepared by the preparation method according to any one of claims 7 to 9 in the preparation of power transmission and distribution equipment, household appliances, automotive parts, communication equipment, industrial automation equipment, medical devices or power tools.

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