Low-precipitation and high-performance red phosphorus flame-retardant PBT composite material

Abstract

The invention relates to the field of high polymer materials, in particular to a low-precipitation and high-performance red phosphorus flame-retardant PBT (polybutylene terephthalate) composite material. The low-precipitation and high-performance red phosphorus flame-retardant PBT composite material is obtained by selecting the specific synergistic flame retardant. According to the low-precipitation and high-performance red phosphorus flame-retardant PBT composite material provided by the invention, the hydrogen phosphide release is far lower than the maximum allowable concentration (0.42 ppm) of hydrogen phosphide in air of a specified working place; meanwhile, the material has excellent flame retardance, the UL-94 can reach 0.8 mm V0 level, the CTI value is high, the CTI can reach 600V, and the material also has good processability and mechanical properties; the red phosphorus flame-retardant PBT composite material has excellent comprehensive performance.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, and more specifically, to a low-exudation, high-performance red phosphorus flame-retardant PBT composite material. Background Technology

[0002] Polybutylene terephthalate (PBT) has been widely used in the electronics, automotive, and home appliance industries due to its excellent mechanical properties, chemical resistance, and processing performance. When PBT is used in low-voltage vacuum contactors, residual current devices (RCDs), charging pile housings, and thin-walled electronic components, extremely high requirements are placed on its flame retardancy and electrical performance. Typically, it must simultaneously meet the UL94 (0.8mm) V-0 flame retardancy rating and the relative tracking index (CTI) ≥600 V standard.

[0003] Red phosphorus, as a highly efficient halogen-free flame retardant, is introduced into PBT modification. It exerts its flame-retardant effect by promoting matrix charring and isolating heat and oxygen, offering advantages such as low dosage and low cost. However, the inherent chemical instability of red phosphorus leads to its tendency to absorb moisture and release acidic substances such as phosphoric acid in humid and hot environments. These acidic substances corrode the PBT matrix, resulting in a decline in the material's mechanical properties, flame-retardant properties, and electrical properties (especially CTI). More seriously, red phosphorus slowly releases highly toxic phosphine (PH3) gas, posing safety and environmental hazards.

[0004] While microencapsulation technology (which involves encapsulating red phosphorus) can improve the compatibility and hygroscopicity of red phosphorus with PBT to some extent, the release of phosphine remains consistently low below the maximum permissible concentration in workplace air (0.42 ppm), failing to meet the stringent safety requirements of high-end applications. Currently, research on how to fundamentally inhibit the release of acidic substances and phosphine from red phosphorus in polymers is insufficient, and technical solutions are lacking.

[0005] Therefore, there is an urgent need in this field to develop an innovative modification scheme that can completely solve the problems of acid precipitation and phosphine release while retaining the high flame retardant advantages of red phosphorus, thereby preparing PBT composite materials that simultaneously meet the requirements of high flame retardancy, high electrical performance, high safety and environmental friendliness, and broaden its application in high-requirement electronic and electrical fields. Summary of the Invention

[0006] To address the technical problem of high phosphine release in existing PBT composite materials containing red phosphorus, this invention provides a low-release, high-performance red phosphorus flame-retardant PBT composite material.

[0007] This invention obtains a red phosphorus flame-retardant PBT composite material with excellent flame retardant effect and significantly reduced phosphine release and phosphate content by selecting specific synergistic flame retardants.

[0008] One of the objectives of this invention is to provide a low-exudation, high-performance red phosphorus flame-retardant PBT composite material.

[0009] The low-exudation, high-performance red phosphorus flame-retardant PBT composite material comprises: 100 parts by weight of PBT; The alkali-free glass fiber is 20 to 40 parts by weight, for example 25, 30, or 35 parts by weight, preferably 25 to 35 parts by weight; 6 to 20 parts by weight of red phosphorus masterbatch, for example 8, 10, 12, 14, 15, or 18 parts by weight, preferably 10 to 16 parts by weight; The synergistic flame retardant is 3 to 15 parts by weight, for example, 4, 5, 6, 8, 10, 12, or 14 parts by weight, preferably 4 to 8 parts by weight; The filler is 1 to 5 parts by weight, for example, 2, 2.3, 2.5, 2.8, 3.0, 3.5, or 4.0 parts by weight, preferably 1 to 3 parts by weight; The toughening agent is 2 to 8 parts by weight, for example, 3, 4, 5, 6, or 7 parts by weight, preferably 3 to 6 parts by weight; The lubricant is used in amounts of 0.5 to 3 parts by weight, such as 0.8, 1.0, 1.2, 1.4, 1.8, 2.0, or 2.5 parts by weight, preferably 1 to 1.5 parts by weight; The antioxidant is used in amounts of 0.2 to 1 part by weight, such as 0.3, 0.4, 0.5, or 0.8 parts by weight, preferably 0.2 to 0.4 parts by weight.

[0010] The PBT resin can be any one or more existing PBT resins. Preferably, the intrinsic viscosity of the PBT resin is 0.7 dl / g to 1.7 dl / g, for example 0.8 dl / g, 0.9 dl / g, 1.0 dl / g, 1.2 dl / g, or 1.5 dl / g, and more preferably 0.8 dl / g to 1.0 dl / g.

[0011] The glass fiber can be any one or more existing types of glass fiber. As a preferred option, the glass fiber is selected from alkali-free glass fiber.

[0012] The red phosphorus masterbatch can be any one or more existing red phosphorus masterbatches. As a preferred embodiment, the red phosphorus masterbatch is an in-situ coated red phosphorus masterbatch with a polyester plastic carrier and a red phosphorus content of 25wt% to 65wt%. The red phosphorus content of the red phosphorus masterbatch can be 30wt%, 35wt%, 40wt%, 42wt%, 45wt%, 48wt%, 50wt%, 52wt%, 55wt%, 58wt%, or 60wt%, preferably 40wt% to 60wt%. Specifically, the red phosphorus masterbatch is at least one of RPM440, RPM440A, RPM450H, and RPM440T, all produced by Zhonglan Chenguang Chemical Research and Design Institute Co., Ltd.

[0013] The synergistic flame retardant can be any one or more existing flame retardants that can be used to prepare red phosphorus flame-retardant PBT composite materials. The synergistic flame retardant is selected from at least one of melamine urate, hydroxides, and metal oxides. Preferably, the hydroxide is selected from at least one of magnesium hydroxide and aluminum hydroxide. Preferably, the metal oxide is selected from at least one of magnesium oxide and aluminum oxide. For example, the synergistic flame retardant is selected from at least one of melamine urate, magnesium oxide, aluminum oxide, magnesium hydroxide, and aluminum hydroxide.

[0014] Compared to selecting one of melamine urate, hydroxide, or metal oxide as a synergistic flame retardant, when the synergistic flame retardant is composed of hydroxide and melamine urate or metal oxide and melamine urate, the phosphine release and phosphate content of the prepared low-emission, high-performance red phosphorus flame-retardant PBT composite material are further reduced. Therefore, as a more preferred embodiment, the synergistic flame retardant is composed of flame retardant A and flame retardant B; flame retardant A is melamine urate, and flame retardant B is selected from at least one of hydroxide and metal oxide. As a further preferred embodiment, the synergistic flame retardant is composed of melamine urate and alumina, or the synergistic flame retardant is composed of melamine urate and magnesium hydroxide, or the synergistic flame retardant is composed of melamine urate and aluminum hydroxide, or the synergistic flame retardant is composed of melamine urate and magnesium hydroxide.

[0015] When the synergistic flame retardant is composed of flame retardant A and flame retardant B, the mass ratio of flame retardant A to flame retardant B can be any ratio. As a preferred embodiment, the mass ratio of flame retardant A to flame retardant B is 3-8:1, for example 4:1, 5:1, 6:1, 7:1, and preferably 5:1.

[0016] The filler can be any one or more existing fillers suitable for preparing red phosphorus flame-retardant PBT composite materials. As a preferred embodiment, the filler is selected from at least one of montmorillonite, hydrotalcite, talc, calcium carbonate, wollastonite, and boehmite. Compared to other fillers, talc and wollastonite, when combined with other components in this invention, improve the CTI (Combined Thermal Intensity).

[0017] The toughening agent can be any one or more existing toughening agents that can be used to prepare red phosphorus flame-retardant PBT composite materials. As a preferred embodiment, the toughening agent is selected from maleic anhydride graft copolymers.

[0018] The lubricant can be any one or more existing lubricants suitable for preparing red phosphorus flame-retardant PBT composite materials. As a preferred embodiment, the lubricant is selected from at least one of calcium stearate, TAF, and calcium lignite.

[0019] The antioxidant can be any one or more existing antioxidants that can be used to prepare red phosphorus flame-retardant PBT composite materials. As a preferred embodiment, the antioxidant is selected from at least one of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 626, antioxidant DLTP, and antioxidant DSTP, and preferably consists of antioxidant 1010 and antioxidant 626.

[0020] The second objective of this invention is to provide a method for preparing the red phosphorus flame-retardant PBT composite material described in the first objective of this invention.

[0021] The preparation method of the red phosphorus flame-retardant PBT composite material includes: mixing the components according to the weight parts and melt extruding; the melt extrusion temperature is 180~250℃.

[0022] One specific method for preparing the red phosphorus flame-retardant PBT composite material includes: drying PBT and red phosphorus masterbatch at 110~120℃ for 2~3h according to weight parts; then mixing the components evenly in a mixer; and then adding them to a twin-screw extruder for extrusion granulation at an extrusion temperature of 180~250℃ and a screw speed of 250~350r / min.

[0023] The third objective of this invention is to provide the application of the red phosphorus flame-retardant PBT composite material described in the first objective of the invention or the red phosphorus flame-retardant PBT composite material prepared by the preparation method described in the second objective of the invention in the field of electronics and electrical engineering.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: The low-release, high-performance red phosphorus flame-retardant PBT composite material provided by this invention has low phosphine release and phosphate content, and features low release, high mechanical properties, and high flame-retardant performance. It is a red phosphorus flame-retardant PBT composite material with excellent comprehensive performance.

[0025] The low-emission, high-performance red phosphorus flame-retardant PBT composite material provided by this invention has phosphine release far below the maximum permissible concentration of phosphine in workplace air (0.42 ppm); it also has excellent flame retardancy, achieving a UL-94 rating of 0.8 mm V0 and a high CTI value, with a CTI of up to 600V.

[0026] The low-extraction, high-performance red phosphorus flame-retardant PBT composite material provided by this invention solves the problems of red phosphorus leaching from polymers corroding the matrix and generating phosphine, which negatively impact the environment and human health. It also achieves good processability, flame retardancy, and mechanical properties while maintaining low extraction. This type of material possesses excellent mechanical properties, is stable during processing, and exhibits low red phosphoric acid extraction, making it widely applicable in fields such as electronics, automotive, and electrical equipment. Detailed Implementation

[0027] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0028] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available products. Among them: PBT GX112 is sourced from Sinopec Yizheng; Both red phosphorus masterbatches RPM450H and RPM440A are from Zhonglan Chenguang. Melamine urate (MCA) was sourced from the Sichuan Institute of Fine Chemicals. Both aluminum hydroxide and aluminum oxide are from Luoyang Rheinheide. Magnesium hydroxide is from Shandong Juke Polymer. The talc and wollastonite both come from Quanzhou Xufeng Powder Co., Ltd. The toughening agent comes from Shanghai Yexin; The lubricant is from Brügmann; Antioxidant from Albemarle; The alkali-free glass fiber comes from Taishan Fiberglass.

[0029] Examples 1-8 The raw materials used and their weight proportions are shown in Table 1.

[0030] PBT and red phosphorus masterbatch were dried at 120℃ for 2 hours. According to the weight proportions shown in Table 1, the raw materials were mixed evenly in a high-speed mixer at 2000 r / min, and then extruded and granulated using a twin-screw extruder to obtain red phosphorus flame-retardant PBT granules. The extrusion temperatures were: zone 1 180℃, zone 2 220℃, zone 3 230℃, zone 4 240℃, zone 5 240℃, zone 6 250℃, zone 7 250℃, zone 8 240℃, and zone 9 240℃; the screw speed was 300 r / min.

[0031] Comparative Example 1 The raw materials used and their weight proportions are shown in Table 1.

[0032] PBT and red phosphorus masterbatch were dried at 120℃ for 2 hours. According to the weight proportions shown in Table 1, the raw materials were mixed evenly in a high-speed mixer at 2000 r / min, and then extruded and granulated using a twin-screw extruder to obtain red phosphorus flame-retardant PBT granules. The extrusion temperatures were: zone 1 180℃, zone 2 220℃, zone 3 230℃, zone 4 240℃, zone 5 240℃, zone 6 250℃, zone 7 250℃, zone 8 240℃, and zone 9 240℃; the screw speed was 300 r / min.

[0033] Table 1. Formulation composition of red phosphorus flame-retardant reinforced PBT composite material

[0034] Performance testing Red phosphorus flame-retardant PBT particles were prepared according to Examples 1-8 and Comparative Example 1. Tensile strength, notched beam impact strength, flame retardancy, CTI, polymer phosphorus precipitation, and phosphine release were tested respectively.

[0035] in, Tensile strength shall conform to GB / T1040.2-2022; The notched impact strength of simply supported beams shall be in accordance with GB / T1043.1-201; Flame retardancy was tested according to the UL-94-1985 standard, with sample thicknesses of 3.2 mm, 1.6 mm, and 0.8 mm prepared for each group of samples. Phosphate content test: First, the red phosphorus flame retardant PBT particles were prepared into 125mm×13mm×1.6mm strips and placed in deionized water at 50℃ for 28 days. Then, the phosphate content in the solution was determined according to GB 11893-89. Phosphine precipitation test: 0.5g of red phosphorus flame-retardant PBT particles were placed in the pyrolysis unit of a GC-MS instrument. The pyrolysis gas from the particles was then absorbed by the GC-MS instrument using the external standard method to accurately determine the phosphine content in the sample. The test results are shown in Table 2.

[0036] Table 2. Test performance results of red phosphorus flame-retardant reinforced PBT composite materials

[0037] The only difference between Example 8 and Comparative Example 1 is that Example 8 added MCA to the Comparative Example 1. Compared to Comparative Example 1, Example 8 showed a 38.4% reduction in phosphine release, a 21.9% reduction in phosphate content, an improvement in flame retardancy rating from 1.6 mm V0 to 0.8 mm V0, a ​​14.3% increase in CTI, and no significant change in mechanical properties. It is evident that MCA, in the formulation of this invention, works in combination with other components to reduce phosphine release and phosphate content, and improve CTI and flame retardancy. However, the phosphate content in Example 8 was 3.2 mg / L, which is still relatively high; the phosphine release in Example 8 was 1.65 ppm, which is still far above the maximum permissible concentration in workplace air (0.42 ppm).

[0038] Compared to Comparative Example 1, Example 6 differs only in that aluminum hydroxide is added to the composition of Comparative Example 1. Compared to Comparative Example 1, Example 6 showed a 90.67% reduction in phosphine release, a 70.73% reduction in phosphate content, no change in flame retardant rating and CTI, and no significant change in mechanical properties. It is evident that in the formulation of this invention, aluminum hydroxide, in the absence of MCA, reduces phosphine release and phosphate content through its combination with other components, but does not affect CTI and flame retardant properties; therefore, its CTI and flame retardant properties still need improvement.

[0039] The only difference between Example 1 and Example 8 is that Example 1 uses an equal amount of aluminum hydroxide to replace MCA (replacing 1 part of the 6 parts of MCA with 1 part of aluminum hydroxide). Compared to Example 8, the phosphine release in Example 1 is reduced by 86.1%, and the phosphate content is reduced by 65.6%. Compared to Example 8, the flame retardant rating, CTI, and mechanical properties of Example 1 show no significant changes. Therefore, aluminum hydroxide, in the formulation of this invention, plays a role in reducing phosphine release and phosphate content by combining with other components.

[0040] Compared to Example 8, Example 3 differs only in that it uses an equal amount of alumina instead of MCA. Compared to Example 8, Example 3 shows a 67.9% reduction in phosphine release and a 34.4% reduction in phosphate content; however, the flame retardant rating, CTI, and mechanical properties of Example 3 show no significant changes compared to Example 8. Therefore, alumina, in the formulation of this invention, plays a role in reducing phosphine release and phosphate content through its combination with other components.

[0041] Compared to Example 8, Example 4 differs only in that it uses an equal amount of magnesium hydroxide instead of MCA. Compared to Example 8, the phosphine release in Example 1 decreased by 84.2%, and the phosphate content decreased by 50.0%. Compared to Example 8, the flame retardant rating, CTI, and mechanical properties of Example 4 showed no significant changes. Therefore, magnesium hydroxide, in the formulation of this invention, plays a role in reducing phosphine release and phosphate content through its combination with other components.

[0042] Comparing the effects of aluminum hydroxide, aluminum oxide, and magnesium hydroxide in the formulation of this invention, in combination with other components, it can be concluded that their effects differ in reducing phosphine release and phosphate content. The order of their inhibitory effects on phosphorus and phosphine precipitation is: aluminum hydroxide is stronger than magnesium hydroxide, which is stronger than aluminum oxide.

[0043] The only difference between Example 1 and Comparative Example 1 is that Example 1 adds MCA and aluminum hydroxide to the existing Comparative Example 1. Compared with Comparative Example 1, Example 1 shows a 91.4% reduction in phosphine release, a 73.2% reduction in phosphate content, an improvement in flame retardancy rating from 1.6 mm V0 to 0.8 mm V0, and a 12.5% ​​increase in CTI, while maintaining no significant change in mechanical properties.

[0044] Comparing the results of Example 6 with Comparative Example 1, Example 8 with Comparative Example 1, and Example 1 with Comparative Example 1, it can be found that MCA and aluminum hydroxide have a synergistic effect in the formulation of the present invention.

[0045] Compared with Example 7, Example 1 differs only in that talc powder is added to the formula of Example 7. Compared with Example 7, the phosphine release, phosphate content, and mechanical properties of Example 1 show no significant changes, except that the CTI is increased by 8.3%. It is evident that talc powder, in combination with other components in the formulation of this invention, plays a role in improving the CTI.

[0046] Compared to Example 7, Example 5 differs only in that it adds wollastonite to the formula of Example 7. Compared to Example 7, Example 5 shows no significant changes in phosphine release, phosphate content, or mechanical properties; only the CTI (chemical iodine content) is increased by 8.3%. This demonstrates that wollastonite, in combination with other components, enhances the CTI in the formulation of this invention.

[0047] Comparative examples and comparative examples show that synergistic flame retardants and fillers have a significant impact on the phosphine release, phosphorus precipitation release, flame retardant properties, and CTI of PBT composite materials. Comparison of Examples 1, 2, 4, and 5 shows that, compared to oxides, hydroxides have a greater impact on the phosphine release and phosphorus precipitation release of the composite materials. Examples 1, 2, 4, and 5 show significantly lower phosphorus precipitation and phosphine release, and the phosphine release is far below the permissible concentration in the working environment air (0.43 PPM). Furthermore, comprehensive comparison indicates that hydroxides in the system not only act as flame retardant synergists but also as reactants for red phosphorus precipitation.

Claims

1. A low-exudation, high-performance red phosphorus flame-retardant PBT composite material, comprising: 100 parts by weight of PBT; 20-40 parts by weight of glass fiber, preferably 25-35 parts by weight; 6-20 parts by weight of red phosphorus masterbatch, preferably 10-16 parts by weight; 3-15 parts by weight of synergistic flame retardant, preferably 4-8 parts by weight; The filler is 1 to 5 parts by weight, preferably 1 to 3 parts by weight; 2-8 parts by weight of toughening agent, preferably 3-6 parts by weight; Lubricant: 0.5 to 3 parts by weight, preferably 1 to 1.5 parts by weight; Antioxidant: 0.2 to 1 part by weight, preferably 0.2 to 0.4 parts by weight.

2. The red phosphorus flame-retardant PBT composite material as described in claim 1, characterized in that, The intrinsic viscosity of the PBT resin is 0.7 dl / g-1.7 dl / g, preferably 0.8 dl / g-1.0 dl / g.

3. The red phosphorus flame-retardant PBT composite material as described in claim 1, characterized in that, The glass fiber is selected from alkali-free glass fiber.

4. The red phosphorus flame-retardant PBT composite material as described in claim 1, characterized in that, The synergistic flame retardant is selected from at least one of melamine urate, hydroxide, and metal oxide. Preferably, the hydroxide is selected from at least one of magnesium hydroxide and aluminum hydroxide, and the metal oxide is selected from at least one of magnesium oxide and aluminum oxide.

5. The red phosphorus flame-retardant PBT composite material as described in claim 1, characterized in that, The filler is selected from at least one of montmorillonite, hydrotalcite, talc, calcium carbonate, wollastonite, and boehmite.

6. The red phosphorus flame-retardant PBT composite material as described in claim 1, characterized in that, The toughening agent is selected from maleic anhydride graft copolymer.

7. The red phosphorus flame-retardant PBT composite material as described in claim 1, characterized in that, The lubricant is selected from at least one of calcium stearate, TAF, and calcium lignite.

8. The red phosphorus flame-retardant PBT composite material as described in claim 1, characterized in that, The antioxidant is selected from at least one of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 626, antioxidant DLTP, and antioxidant DSTP, and is preferably composed of antioxidant 1010 and antioxidant 626.

9. A method for preparing a red phosphorus flame-retardant PBT composite material as described in any one of claims 1-8, comprising: Mix the components according to their weight parts and melt extrude them; the melt extrusion temperature is 180~250℃.

10. The application of a red phosphorus flame-retardant PBT composite material as described in any one of claims 1-8 or a red phosphorus flame-retardant PBT composite material prepared by the preparation method described in claim 9 in the field of electronics and electrical engineering.

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