Hydrolysis-resistant PBT modified engineering plastic and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to hydrolysis-resistant PBT (polybutylene terephthalate) modified engineering plastic and a preparation method thereof. The plastic comprises the following raw materials: PBT resin, a brominated flame retardant, a flame retardant synergist, a glowing filament synergist compound, a flexibilizer, an antioxidant, a lubricant, a chain extender and glass fibers, according to the glowing filament synergist compound, melamine cyanurate, 1, 3-phenylene phosphate tetra (2, 6-dimethylphenyl) ester (condensation polymer) and magnesium hydroxide are compounded to form a synergistic barrier layer. And a chain extender and a toughening agent synergistically improve material molecules, the material molecules are processed by adopting a melt extrusion process, and V0-level quantity and damp-heat stability are realized through dual effects of a brominated flame-retardant system and an expanded carbon layer. The hydrolysis-resistant PBT modified engineering plastic prepared by the invention has the characteristics of high rigidity, excellent hydrolysis resistance and environmental protection, and is suitable for the fields of new energy automobile parts, electronic connectors and other harsh working conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a hydrolysis-resistant PBT modified engineering plastic and a preparation method thereof. Background Art

[0002] Polybutylene terephthalate (PBT) is an engineering plastic with excellent comprehensive properties, having excellent mechanical properties, high rigidity, high hardness, good toughness, impact resistance, wear resistance, creep resistance, and good chemical resistance.

[0003] With the rapid development of industries such as electronics and electrical appliances, new energy, etc., higher requirements are put forward for the flame retardant performance and hydrolysis resistance of PBT materials. A high glow wire flame retardant enhanced hydrolysis-resistant PBT modified material has emerged to meet these needs.

[0004] Patent CN111303388B discloses a preparation method of a hydrolysis-resistant PBT polyester resin. First, terephthalic acid, 1,4-butanediol, an organic titanate compound, and magnesium phosphate are mixed to form a slurry, and an esterification reaction is carried out to obtain a prepolymer. Then, a melt polycondensation reaction is carried out to obtain a PBT polyester resin substrate. Finally, the PBT polyester resin substrate is mixed with a capping modifier and an organic phosphate compound in a twin-screw extruder to obtain a hydrolysis-resistant PBT polyester resin, which belongs to the production of PBT raw materials by upstream polymerization reaction and is not in the field of modified engineering plastics.

[0005] Patent CN115073893B discloses a hydrolysis-resistant polybutylene terephthalate composition and a preparation method thereof, including the following components and parts by weight: polybutylene terephthalate (PBT resin): 70 - 90 parts, aliphatic polyamide polymer: 10 - 25 parts, polytetrafluoroethylene (PTFE resin): 2 - 5 parts, antioxidant: 0.1 - 2 parts; it is prepared by the following steps: adding the PBT resin, aliphatic polyamide polymer, PTFE resin, and antioxidant into a mixing blender for mixing, and subjecting the obtained mixture to co-blending granulation through a twin-screw extruder, and granulating after melt extrusion to obtain the hydrolysis-resistant polybutylene terephthalate composition. However, currently, environmental protection regulations control per- and polyfluoroalkyl substances (PFAS) and ban PTFE, which does not meet the requirements of environmental protection regulations. Summary of the Invention

[0006] The purpose of the present invention is to solve the disadvantages and deficiencies existing in the prior art, and to propose a hydrolysis-resistant PBT modified engineering plastic and a preparation method thereof.

[0007] For the above purposes, the present invention provides a hydrolytic-resistant PBT modified engineering plastic, and its raw materials include the following components by weight: PBT resin: 30-58.6%, brominated flame retardant: 9-13%, flame retardant synergist: 2-5%, glow wire synergist complex: 8-12%, toughening agent: 1-4%, antioxidant: 0.2-1%, lubricant: 0.2-1%, chain extender: 1-4%, glass fiber: 20%-30%; The glow wire synergist complex is made by mixing melamine cyanurate, tetra(2,6-dimethylphenyl) 1,3-phenylene phosphonate (condensate) and magnesium hydroxide in a weight ratio of 8:1-2:1-2 in a powder mixer for 3-7 minutes.

[0008] Preferably, the intrinsic viscosity of the PBT resin is 0.80-0.86 dl / g, and the melt flow rate is 50-80 g / (10 min) under the test conditions of 250°C / 2.16 kg.

[0009] Preferably, the brominated flame retardant is one or more of brominated epoxy, brominated polystyrene and bromotriazine.

[0010] Preferably, the flame retardant synergist is one or two of antimony trioxide and sodium antimonate.

[0011] Preferably, the toughening agent is one or more of polyester toughening agent POE-g-GMA, maleic anhydride grafted POE, ethylene-methyl acrylate-glycidyl methacrylate and ethylene-butyl acrylate-glycidyl methacrylate.

[0012] Preferably, the antioxidant is one or more of antioxidant 1010, antioxidant 168 and antioxidant 1098.

[0013] Preferably, the lubricant is one or more of pentaerythritol stearate PETS, Honeywell 540A and silicone powder.

[0014] Preferably, the chain extender can be a chain extender with the model Sanulater HK250. Appearance of Sanulater HK250: white powder, particle size: >800 mesh, melting point: >120°C, material: organic and inorganic composite, addition amount: 0.1-0.3%; Sanulater HK250 is a mixture, and by weight, its composition components are: polyamide wax: CAS NO is 63428-84-2, content is 30-60 parts; long carbon chain stearate: CAS NO is 3159-62-4, content is 40-70 parts; talc powder: CAS NO is 14807-96-6, content is 10-30 parts.

[0015] Preferably, the diameter of the glass fiber is 8-16 μm.

[0016] Furthermore, the present invention also provides a preparation method of the above-mentioned hydrolysis-resistant PBT modified engineering plastic, which specifically includes the following steps: S1. Put PBT resin, brominated flame retardant, flame retardant synergist, glow wire synergist complex, toughening agent, antioxidant, lubricant, and chain extender into a blender, and mix and stir for 10-20 min to obtain a mixture A; S2. Put the mixture A and glass fiber into a twin-screw extruder, heat to melt and extrude, and then obtain a hydrolysis-resistant PBT modified engineering plastic.

[0017] Preferably, the melt extrusion temperature in S2 is 220-250 °C, and the screw speed is 300-550 r / min.

[0018] The beneficial effects of the present invention: 1. Through the scientific compatibility of the brominated flame retardant, flame retardant synergist and glow wire synergist complex, a multi-level barrier protection mechanism is formed during the combustion process of the material. The brominated flame retardant efficiently captures free radicals in the gas phase and blocks the combustion chain reaction; the synergist further enhances the flame retardancy efficiency and reduces the smoke generation. The glow wire synergist complex forms a dense expanded carbon layer at high temperature, isolates oxygen and delays heat transfer, significantly improving the glow wire tolerance of the material and ensuring no ignition and no dripping in an extremely high temperature environment. At the same time, the formulation system strictly avoids harmful substances such as polybrominated biphenyls, meets the restrictions on toxic substances in international environmental protection regulations, and has both high-efficiency flame retardancy and green environmental protection characteristics, and is suitable for the electronic and electrical fields with strict requirements for safety and environmental protection.

[0019] 2. By introducing a chain extender and a blending modification technology, the molecular chain length and molecular weight of the material are effectively increased. The chain extender repairs the broken molecular chains during the processing and forms a stable network structure, greatly enhancing the anti-degradation ability of the material in a humid and hot environment. Even when exposed to high temperature and high humidity conditions for a long time, the molecular chains can still maintain integrity, and the mechanical property attenuation rate is significantly reduced. The synergistic effect of the toughening agent further improves the toughness of the material and avoids brittle fracture caused by environmental stress. This optimized design at the molecular level enables the material to maintain excellent mechanical strength and dimensional stability under harsh working conditions such as humidity and hot humidity.

[0020] 3. The present invention achieves a comprehensive balance of mechanical properties, flame retardancy, processability and weather resistance through component innovation and process control. The high content of glass fiber reinforcement gives the material excellent rigidity and deformation resistance, while the introduction of toughening agent effectively improves the impact resistance and avoids the defect of large brittleness of traditional flame retardant materials. The optimized melt fluidity ensures that there are no problems such as mold sticking and flow marks during the processing process, and the surface finish of the product is high and the dimensional accuracy is stable. The material has the characteristics of high strength and toughness, fire safety, and environmental aging resistance, meeting the comprehensive performance requirements under complex working conditions.

[0021] 4. The production process adopted by the present invention adopts efficient blending and melt extrusion technology, which does not require complex pretreatment or multi-stage reaction, and significantly reduces production energy consumption and equipment investment. The components are evenly mixed through a one-step method to avoid performance fluctuations caused by multi-stage processing, and the product batch stability is excellent. The formula design takes into account processing friendliness, a wide melting temperature range, high screw speed adaptability, and can seamlessly connect to existing engineering plastic production lines. This technology greatly simplifies the production process, shortens the production cycle, reduces the overall cost, and ensures the product yield, providing reliable support for large-scale industrial production and facilitating the rapid market application of high-performance modified engineering plastics. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0023] Table 1 Distribution ratio of each group in the embodiment (unit: g) Table 2 Distribution ratio of each group in the comparative example (unit: g) The modified engineering plastics described in Examples 1-4 are prepared by the above-mentioned method for preparing the hydrolysis-resistant PBT modified engineering plastics, which specifically comprises the following steps: (1) Mix melamine cyanurate, 1,3-phenylene phosphate tetrakis (2,6-dimethylphenyl) ester (condensation product) and magnesium hydroxide in a powder grinder for 3-7 minutes to prepare a glow-wire synergist compound; (2) PBT resin, brominated flame retardant, flame retardant synergist, glow-wire synergist compound, toughening agent, antioxidant, lubricant, and chain extender are placed in a blender and mixed for 10-20 minutes to obtain a mixture A; (3) The mixture A and glass fiber are fed into a twin-screw extruder and heated to melt and extrude to obtain a hydrolysis-resistant PBT modified engineering plastic, wherein the melt extrusion temperature is 220-250° C. and the screw speed is 300-550 r / min.

[0024] Comparative Examples 1-12 were prepared using the above preparation method.

[0025] Performance Test: Tensile Strength: The test method refers to the ISO527 / 2-93 standard; Flexural Modulus: The test method refers to the ISO178 standard; Notched Impact Strength: The test method refers to the ISO180-2000 standard; Flame Retardant Grade: The test method refers to the ISO1210 standard; Glow Wire Test: The test method refers to the GB / T5169.10-2021, GB / T5169.11-2021, and GB / T5169.12-2021 standards. The glow wire temperature is 750 °C, and each example and comparative example are tested five times respectively; High Temperature and High Humidity Aging Resistance Test: The plastics prepared in Examples 1-4 and Comparative Examples 1-12 were made into specimens of 60 mm × 60 mm × 2 mm, placed in a high temperature and high humidity aging chamber, with the temperature set at 85 °C and the humidity at 85%. The test time was 500 h and 1000 h, and the surface changes of the specimens were observed; The above experimental results are shown in Table 3.

[0026] Table 3 Performance Test Results Performance Analysis: From the experimental data in Table 3, it can be seen that the hydrolysis-resistant PBT modified engineering plastics prepared by the formulations of each group of the present invention in the examples have good mechanical properties and flame retardant ability, and at the same time have good hydrolysis resistance and stability under high temperature and high pressure. Among them, Example 2 has the best comprehensive performance.

[0027] From the data of Comparative Examples 1-2 and Example 2, it can be seen that in Comparative Example 1, the content of PBT resin only accounts for 15%, which is much lower than 44% in Example 2. As the matrix material, too low content of PBT leads to poor material continuity, weak interfacial bonding between glass fiber and resin, significant decrease in tensile strength and notched impact strength. At the same time, insufficient resin matrix makes the flame retardant unevenly dispersed, and the flame retardant grade only reaches HB; in Comparative Example 2, the content of PBT accounts for 80%, squeezing the space of the flame retardant system and glass fiber. Excessive PBT makes the material too rigid, but insufficient flame retardant components cause some failures in the glow wire test, and the glass fiber reinforcement effect is limited, resulting in a decrease in impact strength. Both verify that the PBT resin needs to maintain the component balance range of the present invention, ensuring both matrix continuity and leaving space for the flame retardant and reinforcement systems.

[0028] It can be seen from the data of Comparative Examples 3-4 and Example 2 that the content of brominated flame retardant in Comparative Example 3 is only 6%, and it is impossible to form a sufficient free radical capture layer, the flame retardancy level is reduced to V2, and the glow-wire test shows "full ignition"; while the content of brominated flame retardant in Comparative Example 4 is as high as 16%. Although the flame retardancy level remains V0, excessive bromide causes the thermal stability of the material to decrease: during the 750°C glow-wire test, bromide may decompose to produce HBr gas, which suppresses the flame but causes "severe carbonization and cracking" on the surface of the material. At the same time, excessive brominated flame retardant interferes with the crystallization of PBT, and the tensile strength and notched impact strength decrease. This shows that the brominated flame retardant needs to be strictly controlled at 9-13%, which can not only ensure the flame retardant efficiency, but also avoid negative effects on mechanical properties and thermal stability.

[0029] From the data of Comparative Examples 5-6 and Example 2, it can be seen that the synergist content of Comparative Example 5 is only 1.5%, and the synergistic effect with the brominated flame retardant is insufficient, resulting in a decrease in gas phase flame retardant efficiency, a "surface smoke" phenomenon in the glow wire test, and a flame retardant rating of V-2; while the synergist content of Comparative Example 6 is as high as 7%, which will form agglomerated particles during processing, become stress concentration points, and the impact strength drops sharply. At the same time, too much flame retardant synergist increases the material density and deteriorates the melt fluidity, resulting in "surface roughness" during extrusion. Experiments have shown that the flame retardant synergist needs to be maintained at 2-5%, at which time the best synergistic effect can be achieved, which can form a dense gas phase barrier layer without destroying the homogeneity of the material.

[0030] It can be seen from the data of Comparative Examples 7-8 and Example 2 that the content of the glow-wire synergistic compound in Comparative Example 7 is only 6%, of which the effective ingredient MCA (melamine cyanurate) is insufficient, and a complete expanded carbon layer cannot be formed during the glow-wire test, resulting in only 3 passes out of 5 tests; while the content of the glow-wire synergistic compound in Comparative Example 8 is as high as 15%, and the excess magnesium hydroxide absorbs moisture during processing, causing PBT to hydrolyze, resulting in a decrease in tensile strength. At the same time, the excess MCA decomposes to produce too much gas, causing micropores inside the material and a decrease in impact strength; the content of the glow-wire synergistic compound in Example 2 can balance the gas phase / condensed phase flame retardant mechanism to form a stable expanded carbon layer.

[0031] It can be seen from the data of Comparative Examples 9-10 and Example 2 that the chain extender content in Comparative Example 9 is only 0.5%, which cannot effectively repair the molecular chain breakage in PBT processing, resulting in insufficient melt strength, uneven dispersion of glass fibers, and a decrease in bending modulus; the chain extender content in Comparative Example 10 is 6%, which causes excessive chain extension and even cross-linking, resulting in a decrease in melt flow rate, an increase in torque during processing, and an increase in material brittleness; the chain extender content in Example 2 can stabilize the intrinsic viscosity within a suitable range, thereby ensuring processing fluidity and maintaining sufficient molecular weight.

[0032] From the data of Comparative Examples 11-12 and Example 2, it can be seen that in Comparative Example 11, the glass fiber content is only 15%, the strengthening effect is insufficient, the flexural modulus decreases, and at the same time, it will also cause an increase in the shrinkage rate of the resin matrix and poor dimensional stability; in Comparative Example 12, the glass fiber content is as high as 45%. Although the flexural modulus is improved, the excessive fibers lead to deteriorated melt fluidity, and the stress concentration at the fiber ends causes a decrease in impact strength; the glass fiber content in Example 2 can achieve the best strengthening effect, which can not only effectively transfer stress but also not overly hinder the melt flow.

[0033] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A hydrolytic resistant PBT modified engineering plastic, characterized in that, Its raw materials include the following components by weight: PBT resin: 30 - 58.6%, brominated flame retardant: 9 - 13%, flame retardant synergist: 2 - 5%, glow wire synergist complex: 8 - 12%, toughening agent: 1 - 4%, antioxidant: 0.2 - 1%, lubricant: 0.2 - 1%, chain extender: 1 - 4%, glass fiber: 20% - 30%; The glow wire synergist complex is made by mixing melamine cyanurate, tetra(2,6 - dimethylphenyl) 1,3 - phenylenediphosphate (condensate) and magnesium hydroxide in a weight ratio of 8:1 - 2:1 - 2 in a powder mixer and mixing evenly for 3 - 7 min.

2. The hydrolytic resistance PBT modified engineering plastic according to claim 1, characterized in that, The intrinsic viscosity of the PBT resin is 0.80 - 0.86 dl / g, and the melt flow rate is 50 - 80 g / (10 min) under the test conditions of 250 °C / 2.16 kg.

3. The hydrolytic resistance PBT modified engineering plastic according to claim 1, characterized in that, The brominated flame retardant is one or more of brominated epoxy, brominated polystyrene and bromotriazine; the flame retardant synergist is one or two of antimony trioxide and sodium antimonate.

4. The hydrolytic resistance PBT modified engineering plastic according to claim 1, characterized in that, The toughening agent is one or more of polyester toughening agent POE - g - GMA, maleic anhydride grafted POE, ethylene - methyl acrylate - glycidyl methacrylate and ethylene - butyl acrylate - glycidyl methacrylate.

5. The hydrolytic-resistant PBT modified engineering plastic according to claim 1, wherein The antioxidant is one or more of antioxidant 1010, antioxidant 168 and antioxidant 1098.

6. The hydrolytic resistance PBT modified engineering plastic according to claim 1, characterized in that The lubricant is one or more of pentaerythritol stearate PETS, Honeywell 540A and silicone powder.

7. The hydrolytic resistant PBT modified engineering plastic according to claim 1, characterized in that, The diameter of the glass fiber is 8 - 16 μm.

8. The preparation method of the hydrolysis-resistant PBT modified engineering plastic according to any one of claims 1-7, characterized in that, It includes the following steps: S1. Put the PBT resin, brominated flame retardant, flame retardant synergist, glow wire synergist complex, toughening agent, antioxidant, lubricant and chain extender into a mixer, mix and stir for 10 - 20 min to obtain mixture A; S2. Put mixture A and glass fiber into a twin - screw extruder, heat to melt and extrude to obtain a hydrolysis - resistant PBT modified engineering plastic.

9. The preparation method of the hydrolysis-resistant PBT modified engineering plastic according to claim 8, characterized in that, The melt extrusion temperature in S2 is 220 - 250 °C, and the screw speed is 300 - 550 r / min.

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