Flame-retardant reinforced PBT (polybutylene terephthalate) material with high glowing filament initiation temperature and preparation method thereof

Abstract

The invention relates to the technical field of flame-retardant reinforced PBT (Polybutylene Terephthalate) materials, in particular to a flame-retardant reinforced PBT material with a high glowing filament initiation temperature and a preparation method of the flame-retardant reinforced PBT material. The reinforced PBT material is prepared from the following raw materials in percentage by weight: 10 to 35 percent of glass fiber, 7 to 13 percent of microencapsulated flame retardant, 1 to 3 percent of tris (2, 3-dibromopropyl) phosphate, 1 to 3 percent of tris (dichloro isopropyl) phosphate, 3 to 7 percent of flexibilizer, 3.5 to 4.5 percent of silicon synergist, 0.5 to 1.5 percent of lubricant and the balance of PBT resin. The microencapsulated flame retardant is prepared by coating an organic shell layer with a nano inorganic flame retardant, the nano inorganic flame retardant is a mixture of magnesium hydroxide and zinc borate, and the mass ratio of the magnesium hydroxide to the zinc borate is (2-4): 1; the PBT material has the advantage that the high glowing filament ignition temperature and the tensile strength of the PBT material are improved at the same time.

Description

Technical Field

[0001] This application relates to the technical field of flame-retardant reinforced PBT materials, and particularly relates to a high glow wire ignition temperature flame-retardant reinforced PBT material and a preparation method thereof. Background Art

[0002] PBT (polybutylene terephthalate) is a thermoplastic engineering plastic with excellent properties and is widely used. PBT has good comprehensive properties such as heat resistance, flame retardancy, electrical insulation, etc. and good processing properties, and is widely used in industries such as electrical appliances, automobiles, aircraft manufacturing, communications, household appliances, and transportation.

[0003] In the prior art, halogen flame retardants are added to improve the high glow wire ignition temperature of PBT materials. However, when solid waste containing halogen flame retardants is incinerated, toxic substances will be generated, which will cause persistent harm to the environment and humans. And generally, the compatibility of halogen-free flame retardants with the PBT matrix is poor, resulting in a reduction in the mechanical properties and processing properties of PBT materials. Therefore, developing a PBT material with a high glow wire ignition temperature and good mechanical properties still faces great challenges. Summary of the Invention

[0004] In order to simultaneously improve the high glow wire ignition temperature and tensile strength of PBT materials, this application provides a high glow wire ignition temperature flame-retardant reinforced PBT material and a preparation method thereof.

[0005] In the first aspect, this application provides a high glow wire ignition temperature flame-retardant reinforced PBT material, adopting the following technical solution: A high glow wire ignition temperature flame-retardant reinforced PBT material, which comprises raw materials with the following weight percentages: 10 - 35% of glass fiber, 7 - 13% of microencapsulated flame retardant, 1 - 3% of tris(2,3-dibromopropyl) phosphate, 1 - 3% of tris(dichloroisopropyl) phosphate, 3 - 7% of toughening agent, 3.5 - 4.5% of silicon-based synergist, 0.5 - 1.5% of lubricant, and the balance is PBT resin; The microencapsulated flame retardant is prepared by coating an organic shell layer with a nano-inorganic flame retardant. The nano-inorganic flame retardant is a mixture of magnesium hydroxide and zinc borate, and the mass ratio of magnesium hydroxide to zinc borate is (2 - 4):1.

[0006] By adopting the above technical solutions, magnesium hydroxide can be decomposed at high temperature to generate magnesium oxide. The magnesium oxide can form a porous but dense carbon layer on the surface of the material, isolating heat conduction and oxygen penetration, and playing a flame retardant effect. The advantage of its good coverage can effectively inhibit the release of volatile products during the carbonization process, reduce smoke, and the endothermic decomposition of magnesium hydroxide can delay the thermal degradation and combustion of the material. The generated water vapor dilutes the combustible gas and enhances the flame retardant effect. Zinc borate can dehydrate at high temperature, with the functions of heat absorption and foaming, forming a glassy inorganic expansion layer. It synergizes with magnesium hydroxide to make the formed barrier layer dense and complete. And in this application, through the organic microencapsulation of magnesium hydroxide and zinc borate, on the one hand, its stability is improved, and on the other hand, the compatibility between the inorganic flame retardant and the PBT matrix is greatly improved, the interfacial tension between the two is greatly reduced, the binding force between the inorganic flame retardant and the PBT matrix is improved, and the inorganic flame retardant can be evenly dispersed even when its particle size is at the nanometer level. Under the combined action of various aspects, by preparing the microencapsulated flame retardant in this application, the dosage of the halogen-containing flame retardant is greatly reduced, and the glow wire ignition temperature and mechanical properties of the reinforced PBT material are greatly improved.

[0007] Preferably, the preparation method of the microencapsulated flame retardant is as follows: S1. Add 1.5 - 2.5 parts by weight of polyvinylpyrrolidone to water, stir until dissolved, and then add 160 - 200 parts by weight of the flame retardant, and stir for dispersion; S2. Then add 20 - 30 parts by weight of melamine, heat up to 70 - 78 °C while stirring, then adjust the pH to 8 - 9, add 130 - 170 parts by weight of a formaldehyde solution with a mass fraction of 30 - 40%, keep the pH unchanged during the addition, after the addition is completed, continue to react for 30 - 60 min, then adjust the pH to 5 - 6, continue to react for 20 - 40 min, filter, wash, and dry to obtain the microencapsulated flame retardant.

[0008] By adopting the above technical solutions, the preparation method of microencapsulation in this application is simple and easy to operate, can be prepared in large quantities, and can save a large amount of cost compared with the organic polymer modification in the prior art. And it is generally difficult to prepare a large amount of organic polymer modification, and its loading amount is more difficult to control. Compared with the modification with silane coupling agent, the modification effect of microencapsulation in this application is better.

[0009] Preferably, when adjusting the pH to 8 - 9 in S2, it is adjusted by an aqueous solution of one or more of isopropanolamine, N - methylethanolamine, and triethanolamine.

[0010] By adopting the above technical solutions, adjusting with a weak base can reduce the dissolution of magnesium hydroxide.

[0011] Preferably, when adjusting the pH to 5 - 6 in S2, it is adjusted by an aqueous solution of one or more of methacrylic acid, acrylic acid, citric acid, malic acid, oxalic acid, and tartaric acid.

[0012] By adopting the above technical solution, using weak acids can reduce the dissolution of magnesium hydroxide.

[0013] Preferably, the average particle size of the magnesium hydroxide and the zinc borate is 50 - 200 nm.

[0014] By adopting the above technical solution, in actual experiments, as the particle size gradually decreases, the flame retardant effect is better. However, when the particle size drops below 50 nm, the microencapsulation is incomplete, and the flame retardant effect decreases instead. Therefore, the particle size of 50 - 200 nm is a preferable particle size.

[0015] Preferably, the reinforced PBT material further includes 1 - 3% by weight of nano - sepiolite.

[0016] By adopting the above technical solution, adding nano - sepiolite, which has a layered structure and a large specific surface area, is beneficial for the PBT matrix to enter the interlayer, thereby improving the compatibility between sepiolite and the PBT matrix. And the presence of silane coupling agent in the system can also reduce the surface tension between the two; at high - temperature environments, nano - sepiolite can promote the formation of a carbon layer, and it can fill into the barrier layer formed by magnesium hydroxide and zinc borate, improving the compactness of the barrier layer; and the fibrous network structure of sepiolite can effectively restrict the flow of polymer molecular chains, further preventing the spread of combustion, reducing the formation of flame drips, and also improving the toughness of the material; more importantly, nano - sepiolite can absorb the water generated by magnesium hydroxide and zinc borate at high temperatures, and the sepiolite becomes soft when encountering water, thereby effectively improving the ductility of the barrier layer, increasing the coverage rate of the carbon layer, and further increasing the glow - wire ignition temperature of the reinforced PBT material.

[0017] Preferably, the PBT resin is a mixture of PBT resins with intrinsic viscosities of 0.75 dL / g, 0.98 dL / g, and 1.25 dL / g at 25°C in a mass ratio of 1:(3 - 5):1.

[0018] By adopting the above technical solution, with the compounding of PBT resins of multiple viscosities, low - viscosity PBT (0.75 dL / g) can improve the melt fluidity, high - viscosity PBT (1.25 dL / g) can enhance the crystallinity and final strength; medium - viscosity PBT (0.98 dL / g) serves as the main body to balance the processability and mechanical properties; the blending of multi - level viscosities can also reduce the anisotropy of the material and reduce warpage deformation.

[0019] Second aspect, the present application provides a preparation method of a flame-retardant reinforced PBT material with a high glow wire ignition temperature, adopting the following technical solutions: A preparation method of a flame-retardant reinforced PBT material with a high glow wire ignition temperature, which comprises the following steps: S1. Mix PBT resin and a toughening agent evenly to obtain mixture A; S2. Stir and mix the remaining raw materials except glass fiber to obtain mixture B; S3. Transfer mixture A, mixture B and glass fiber to a twin-screw extruder for melt extrusion and pelletizing to obtain a reinforced PBT material.

[0020] By adopting the above technical solutions, adding glass fiber at the end can reduce the high-temperature residence time, prevent fiber length loss, and retain the reinforcement effect of long fibers.

[0021] In summary, the present application includes at least one of the following beneficial technical effects: 1. By organically microencapsulating magnesium hydroxide and zinc borate, on the one hand, the stability is improved, and on the other hand, the compatibility between the inorganic flame retardant and the PBT matrix is greatly improved, the interfacial tension between the two is greatly reduced, the binding force between the inorganic flame retardant and the PBT matrix is improved, and the inorganic flame retardant can be evenly dispersed even when the particle size is in the nanometer range. Under the combined action of multiple aspects, by preparing the microencapsulated flame retardant, the dosage of the halogen-containing flame retardant is greatly reduced, and the glow wire ignition temperature and mechanical properties of the reinforced PBT material are greatly improved.

[0022] 2. The tensile strength of the reinforced PBT material prepared in the present application is between 129-147 MPa, the GWIT is between 840-878 °C, and at the same time T 1% is between 375-407 °C, and the flame retardancy can reach above V-0; it shows that the reinforced PBT material prepared in the present application has excellent mechanical properties and a high glow wire ignition temperature at the same time. Specific Embodiments

[0023] The following further elaborates on the present application in detail in combination with specific content.

[0024] Raw Materials All raw materials used in the embodiments of the present application are commercially available products. Among them, the average particle size of nano-sepiolite is 70 nm, and the manufacturer is Hunan Sepiolite Technology Co., Ltd.; the silicon-based synergist is Dow Corning Organic Silicon F-202; the glass fiber is alkali-free chopped glass fiber, with a length range of 3-5 mm and a diameter range of 7-13 μm; the toughening agent is purchased from Dow Chemical, and the model is ENGAGE™ 8450; the lubricant is purchased from Tiger Petrochemical, and it is polyethylene wax, with the model TG-PE 301.

[0025] Preparation Example 1 A microencapsulated flame retardant, and its preparation method is as follows: S1. Add 2 g of polyvinylpyrrolidone PVP K30 to 500 g of water, stir until dissolved, and then add 180 g of flame retardant and stir to disperse. The flame retardant is a mixture of magnesium hydroxide and zinc borate, and the mass ratio of magnesium hydroxide to zinc borate is 3:1. The average particle sizes of magnesium hydroxide and zinc borate are both 50 nm; S2. Then add 25 g of melamine, heat up to 75 °C while stirring, then adjust the pH to 8 with isopropanolamine, and dropwise add 150 g of a 35% formaldehyde solution. During the dropping, keep the pH unchanged. After the dropping is completed, continue to react for 50 min, then adjust the pH to 5.5 with a 40% methacrylic acid solution, continue to react for 30 min, filter, wash with water, and dry to obtain the microencapsulated flame retardant.

[0026] Example 1. A high glow wire ignition temperature flame retardant reinforced PBT material, the raw materials and their dosages are shown in Table 1, and its preparation method is as follows: S1. Weigh each raw material according to the dosage in Table 1, mix the PBT resin and the toughening agent evenly at a rotation speed of 750 r / min to obtain mixture A. The PBT resin is a mixture of mixtures with intrinsic viscosities of 0.75 dL / g, 0.98 dL / g, and 1.25 dL / g at 25 °C in a ratio of 1:4:1; S2. Stir and mix the remaining raw materials except glass fiber at a mixing rotation speed of 800 r / min to obtain mixture B; S3. Transfer mixture A, mixture B, and glass fiber to a twin-screw extruder for melt extrusion granulation. The melting temperature is 250 °C, and the screw rotation speed is maintained at 300 - 400 r / min to obtain the reinforced PBT material.

[0027] Table 1. Raw materials and their dosages (kg) of Example 1

[0028] Example 2 A high glow wire ignition temperature flame retardant reinforced PBT material, which is different from Example 1 in that the addition amount of the microencapsulated flame retardant is 7 kg, and the remaining steps are the same as those in Example 1.

[0029] Example 3 A high glow wire ignition temperature flame retardant reinforced PBT material, which is different from Example 1 in that the addition amount of the microencapsulated flame retardant is 13 kg, and the remaining steps are the same as those in Example 1.

[0030] Example 4 A high glow wire ignition temperature flame-retardant reinforced PBT material, which is different from that of Example 1 in that when the microencapsulated flame retardant is prepared, the average particle sizes of magnesium hydroxide and zinc borate are both 100 nm, and the remaining steps are the same as those of Example 1.

[0031] Example 5 A high glow wire ignition temperature flame-retardant reinforced PBT material, which is different from that of Example 1 in that when the microencapsulated flame retardant is prepared, the average particle sizes of magnesium hydroxide and zinc borate are both 200 nm, and the remaining steps are the same as those of Example 1.

[0032] Example 6 A high glow wire ignition temperature flame-retardant reinforced PBT material, which is different from that of Example 1 in that its raw materials further include 2 kg of nano-sepiolite, and the remaining steps are the same as those of Example 1.

[0033] Comparative Example 1 A high glow wire ignition temperature flame-retardant reinforced PBT material, which is different from that of Example 1 in that the microencapsulated flame retardant in its raw materials is replaced with a mixture of magnesium hydroxide and zinc borate of equal mass, the average particle sizes of magnesium hydroxide and zinc borate are both 50 nm, and the mass ratio of magnesium hydroxide to zinc borate is 3:1, and the remaining steps are the same as those of Example 1.

[0034] Comparative Example 2 A high glow wire ignition temperature flame-retardant reinforced PBT material, which is different from that of Example 1 in that when the microencapsulated flame retardant in its raw materials is prepared, magnesium hydroxide is replaced with zinc borate of equal mass, and the remaining steps are the same as those of Example 1.

[0035] Comparative Example 3 A high glow wire ignition temperature flame-retardant reinforced PBT material, which is different from that of Example 1 in that when the microencapsulated flame retardant in its raw materials is prepared, zinc borate is replaced with magnesium hydroxide of equal mass, and the remaining steps are the same as those of Example 1.

[0036] Performance detection test Detection method / Test method Prepare the reinforced PBT materials according to the preparation methods of Examples 1-6 and Comparative Examples 1-3 respectively, and then detect them according to the following detection methods. The detection results are shown in Table 2.

[0037] Tensile strength: Detect according to the detection method in TSO 527; Glow wire ignition temperature (GWIT): Detect according to the detection method in ICE 60695-2-2013, and conduct different temperature tests for confirmation; Flame retardant performance: Detect according to the UL94 vertical burning standard; Thermogravimetric analysis: The reinforced PBT material was subjected to thermogravimetric analysis, and the temperature (T 1% ) at which its mass loss was 1% was recorded. The higher the T 1% temperature, the better its high-temperature resistance.

[0038] Table 2 Detection results of Examples 1-6 and Comparative Examples 1-3

[0039] From Examples 1-6, Comparative Examples 1-3, and the detection data in Table 2, it can be seen that the tensile strength of the reinforced PBT material prepared in this application is between 129-147 MPa, the GWIT is between 840-878 °C, and at the same time, T 1% is between 375-407 °C, and the flame retardant performance can reach above V-0; it shows that the reinforced PBT material prepared in this application has excellent mechanical properties and a high glow wire ignition temperature at the same time.

[0040] Magnesium hydroxide can decompose at high temperature to form magnesium oxide. Magnesium oxide can form a porous but dense carbon layer on the material surface, isolating heat conduction and oxygen penetration, and playing a flame retardant effect. Its good covering property can effectively inhibit the release of volatile products during the carbonization process, reduce smoke, and magnesium hydroxide decomposes endothermically, which can delay the thermal degradation and combustion of the material. The water vapor generated by decomposition dilutes the combustible gas and enhances the flame retardant effect; while zinc borate can dehydrate at high temperature, has the functions of endothermic absorption and foaming, and forms a glassy inorganic expansion layer. It synergizes with magnesium hydroxide to make the formed barrier layer dense and complete; and in this application, by organically microencapsulating magnesium hydroxide and zinc borate, on the one hand, its stability is improved, and on the other hand, the compatibility between the inorganic flame retardant and the PBT matrix is greatly improved, the interfacial tension between the two is greatly reduced, the binding force between the inorganic flame retardant and the PBT matrix is improved, and the inorganic flame retardant can be evenly dispersed even when its particle size is at the nanometer level. Under the combined action of multiple aspects, the glow wire ignition temperature of the reinforced PBT material is greatly improved. This can be verified by the detection data of Example 1 and Comparative Example 1. And combined with Comparative Examples 1-2, magnesium hydroxide and zinc borate have a synergistic effect on each other. On this basis, combined with Examples 2-3, when the addition amount of the microencapsulated flame retardant in this application is 10 kg, the comprehensive performance of the prepared reinforced PBT material is stronger.

[0041] It can be seen from the detection data of Example 1 and Examples 4-5 that as the particle size gradually decreases, the flame retardant effect is better. However, when the particle size drops below 50 nm (it is difficult to achieve microencapsulation under the same experimental conditions in actual experiments), the microencapsulation is incomplete and the flame retardant effect decreases instead. Therefore, the particle size of 50 nm is the optimal particle size. On this basis, in order to further increase the glow wire ignition temperature of the reinforced PBT material, nano-sepiolite is added. Nano-sepiolite has a layered structure and a large specific surface area, which is beneficial for the PBT matrix to enter the interlayer, thereby improving the compatibility between sepiolite and the PBT matrix. And the system contains a silicon-based synergist, which can also reduce the surface tension between the two; under high-temperature environments, nano-sepiolite can promote the formation of a carbon layer, and it can fill into the barrier layer formed by magnesium hydroxide and zinc borate to improve the compactness of the barrier layer; and the fibrous network structure of sepiolite can effectively restrict the flow of polymer molecular chains, further prevent the spread of combustion, reduce the formation of flame drips, and can also improve the toughness of the material; more importantly, nano-sepiolite can absorb the water generated by magnesium hydroxide and zinc borate at high temperatures. The texture of sepiolite becomes soft when it meets water, so it can effectively improve the ductility of the barrier layer and the coverage rate of the carbon layer, thereby further increasing the glow wire ignition temperature of the reinforced PBT material.

[0042] This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions according to needs, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A flame retardant reinforced PBT material with high glow-wire ignition temperature, characterized in that: The invention comprises the following raw materials in percentage by weight: 10-35% glass fiber, 7-13% microencapsulated flame retardant, 1-3% tris(2,3-dibromopropyl) phosphate, 1-3% tris(dichloroisopropyl) phosphate, 3-7% toughening agent, 3.5-4.5% silicon-based synergist, 0.5-1.5% lubricant, and the balance is PBT resin; The microencapsulated flame retardant is prepared by coating an organic shell layer with a nano inorganic flame retardant. The nano inorganic flame retardant is a mixture of magnesium hydroxide and zinc borate. The mass ratio of magnesium hydroxide to zinc borate is (2-4):

1.

2. The high glow-wire ignition temperature flame-retardant reinforced PBT material according to claim 1, characterized in that: The preparation method of the microencapsulated flame retardant is as follows: S1. Add 1.5-2.5 parts by weight of polyvinyl pyrrolidone to water, stir until dissolved, then add 160-200 parts by weight of flame retardant, stir and disperse; S2. Then add 20-30 parts by weight of melamine, raise the temperature to 70-78°C while stirring, then adjust the pH to 8-9, add 130-170 parts by weight of a 30-40% formaldehyde solution, keep the pH unchanged during the addition, continue to react for 30-60 minutes after the addition is completed, adjust the pH to 5-6, continue to react for 20-40 minutes, filter, wash, and dry to obtain a microencapsulated flame retardant.

3. The high glow-wire ignition temperature flame retardant reinforced PBT material according to claim 2, characterized in that: When the pH in S2 is adjusted to 8-9, it is adjusted by using an aqueous solution of one or more of isopropanolamine, N-methylethanolamine, and triethanolamine.

4. The high glow-wire ignition temperature flame retardant reinforced PBT material according to claim 2, characterized in that: When the pH in S2 is adjusted to 5-6, it is adjusted by using an aqueous solution of one or more of methacrylic acid, acrylic acid, citric acid, malic acid, oxalic acid, and tartaric acid.

5. The high glow-wire ignition temperature flame retardant reinforced PBT material according to claim 1, characterized in that: The average particle size of the magnesium hydroxide and the zinc borate is 50-200 nm.

6. The high glow-wire ignition temperature flame retardant reinforced PBT material according to claim 1, characterized in that: The reinforced PBT material also includes nano-sepiolite with a weight percentage of 1-3%.

7. The high glow-wire ignition temperature flame retardant reinforced PBT material according to claim 1, characterized in that: The PBT resin is a mixture of resins having intrinsic viscosities of 0.75 dL / g, 0.98 dL / g and 1.25 dL / g at a mass ratio of 1:(3-5):1 at 25°C.

8. A method for preparing the high glow-wire ignition temperature flame-retardant reinforced PBT material according to any one of claims 1 to 7, characterized in that: It includes the following steps: S1, mixing PBT resin and toughening agent uniformly to obtain mixture A; S2, stirring and mixing the remaining raw materials except the glass fiber to obtain a mixture B; S3, moving the mixture A, the mixture B and the glass fiber into a twin-screw extruder for melt extrusion and granulation to obtain a reinforced PBT material.

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