High-efficiency fluorine-free anti-dripping agent and preparation method thereof

Abstract

The present application relates to the technical field of fluorine-free anti-dripping agent, and particularly relates to a high-efficiency fluorine-free anti-dripping agent and a preparation method thereof, which comprises high-aspect-ratio silicon nanotubes, low-aspect-ratio silicon nanotubes, modified PVP-b-PCL and a composite stabilizer. The high-aspect-ratio silicon nanotubes are grafted with PEG, which effectively prevents PBT molecules from approaching the surface of the silicon nanotubes, thereby controlling the shrinkage of the material after molding. The low-aspect-ratio silicon nanotubes are added to prevent the high-aspect-ratio silicon nanotubes from directly contacting and tightly winding to cause agglomeration, and the introduction of the low-aspect-ratio silicon nanotubes can significantly improve the zero-shear viscosity of the polymer melt, thereby avoiding the warping and distortion of the product. The PCL segment of the modified PVP-b-PCL helps the high-aspect-ratio silicon nanotubes to better integrate into the PBT matrix, and the PVP segment prevents the short nanotubes from being aggregated due to polarity, so that the low-aspect-ratio silicon nanotubes can stably exist around the high-aspect-ratio silicon nanotubes to form a uniform mixture.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fluorine-free anti-dripping agents, and particularly relates to a high-efficiency fluorine-free anti-dripping agent and a preparation method thereof. BACKGROUND

[0002] Anti-dripping agents are key additives for improving the flame-retardant safety of polymer materials, and can effectively prevent the materials from producing melt dripping during combustion to avoid secondary fire. At present, silicon-based nanomaterials are attracting much attention as potential fluorine-free substitutes. However, the introduction of silicon nanotubes can significantly affect the shrinkage and warping behavior of crystalline polymer (such as PBT) products. On the one hand, as an efficient nucleating agent, silicon nanotubes provide a large number of additional nucleation points for the crystallization of PBT, which in turn leads to an increase in the crystallinity of the polymer and the shrinkage of the material after molding. On the other hand, during the PBT injection molding process, the melt undergoes strong shearing and flow, and the high aspect ratio silicon nanotubes are prone to orientation in the flow direction, which in turn induces the arrangement of PBT molecular chains and crystals along the flow direction, resulting in different shrinkage rates parallel and perpendicular to the flow direction. This anisotropic shrinkage causes the product to warp and twist. Moreover, the silicon nanotubes are not uniformly dispersed, forming agglomerates, which become stress concentration points and do not shrink uniformly with the matrix during cooling, further exacerbating warping. SUMMARY

[0003] (1) Technical problem to be solved

[0004] The purpose of the present application is to provide a high-efficiency fluorine-free anti-dripping agent and a preparation method thereof to solve the problems of increased shrinkage and warping behavior caused by the introduction of silicon nanotubes in PBT.

[0005] (2) Technical scheme

[0006] To achieve the above-mentioned purpose, on the one hand, the present application provides a high-efficiency fluorine-free anti-dripping agent, which comprises silicon nanotubes, modified PVP-b-PCL, and a composite stabilizer.

[0007] The silicon nanotubes comprise PEG-grafted high-aspect-ratio silicon nanotubes and surface-hydroxylated low-aspect-ratio silicon nanotubes.

[0008] The aspect ratio of the high-aspect-ratio silicon nanotubes is 80-100, and the aspect ratio of the low-aspect-ratio silicon nanotubes is 10-30.

[0009] The mass ratio of the high-aspect-ratio silicon nanotubes to the low-aspect-ratio silicon nanotubes is 2-4:1.

[0010] The modified PVP-b-PCL accounts for 20-25% of the total mass of the silicon nanotubes.

[0011] The modified PVP-b-PCL is a product of modified PVP and PCL block copolymerization;

[0012] The preparation method of the modified PVP comprises the following steps:

[0013] S11. Mix NVP, NVF, RAFT chain transfer agent and AIBN, add anhydrous DMF, perform oxygen removal treatment on the obtained mixed system, stir and react in an oil bath, drop the obtained reaction liquid into cold ethanol for precipitation, filter and collect the solid, wash with methanol, and vacuum dry to obtain the modified PVP;

[0014] The composite stabilizer accounts for 1-1.5% of the total mass of the silicon nanotube.

[0015] Further, the preparation method of the high aspect ratio silicon nanotube comprises the following steps:

[0016] S21. Add CTAB, PEG-4000 and ammonia water to deionized water, stir until completely dissolved, slowly drop TEOS, stir and react, centrifugally collect the product, wash and centrifugally separate with deionized water and anhydrous ethanol alternately, and vacuum dry to obtain mesoporous silica nanorods;

[0017] S22. Ultrasonically disperse the mesoporous silica nanorods in deionized water, add PEI, mechanically stir, transfer to a high-pressure reaction kettle for reaction, centrifugally collect the solid, wash with deionized water, vacuum dry, add magnesium powder, grind the mixture in a mortar, load the obtained mixture into a corundum boat, place it in a tube furnace, heat to 660℃ for reduction reaction, immerse the obtained product in HCl, centrifugally collect the solid, wash with deionized water, and vacuum dry to obtain silicon nanotubes;

[0018] S23. Vacuum dry the silicon nanotubes, ultrasonically disperse them in anhydrous toluene, slowly drop KH-550, reflux and stir to react, centrifugally wash the obtained reaction with toluene and ethanol alternately, and vacuum dry to obtain aminated silicon nanotubes;

[0019] S24. Dissolve mPEG-COOH in anhydrous dichloromethane, add DCC and DMAP, stir in an ice bath for 1 hour, continue to react when the temperature is raised to room temperature, filter and collect the filtrate, precipitate in ice ethyl ether, filter and collect the solid, and vacuum dry to obtain activated PEG;

[0020] S25. Ultrasonically disperse the aminated silicon nanotubes in anhydrous DMF, add activated PEG and triethylamine, react under nitrogen protection, centrifugally wash the obtained product with DMF and deionized water alternately, and freeze-dry to obtain high-aspect-ratio silicon nanotubes.

[0021] Further, the preparation method of the low-aspect-ratio silicon nanotube comprises the following steps:

[0022] S31. Add CTAB, PEG-4000, ammonia water into deionized water, stir until completely dissolved, slowly add TEOS, stir the reaction, centrifugal collection of product, with deionized water and anhydrous ethanol alternately wash centrifugal, vacuum drying, get mesoporous silica nanorod;

[0023] S32. Ultrasonic dispersion of mesoporous silica nanorod in deionized water, add PEI, mechanical stirring, to the high pressure reactor, centrifugal collection of solid, deionized water washing, vacuum drying, add magnesium powder, grinding mixture in mortar, the mixture obtained is loaded into corundum boat, placed in tube furnace, heating to 660 DEG C reduction reaction, the product obtained with HCl immersion, centrifugal collection of solid, deionized water washing, vacuum drying, get silicon nanotube;

[0024] S33. Silicon nanotube dispersion in H2O2 solution, water bath stirring, centrifugal washing, vacuum drying, get surface hydroxylated silicon nanotube;

[0025] S34. Surface hydroxylated silicon nanotube dispersion in isopropanol, with ultrasonic cell disruptor ultrasonic treatment, the suspension 3000rmp centrifugal, collection supernatant 15000rmp centrifugal, the product obtained with anhydrous ethanol washing, vacuum drying, get low aspect ratio silicon nanotube.

[0026] Further, the preparation method of the modified PVP-b-PCL comprises the following steps:

[0027] S41. The modified PVP, epsilon caprolactone monomer, stannous octoate are mixed, anhydrous toluene is added, the obtained mixed system is deoxygenated, the reaction is stirred in oil bath, glacial acetic acid is added to terminate the reaction, the reaction liquid obtained is slowly added to cold methanol for precipitation, the solid is collected by filtration, washed with methanol, and vacuum dried to obtain the modified PVP-b-PCL.

[0028] Further, the composite stabilizer comprises Joncryl ADR-4370S, carbodiimide, Irganox 1010, zinc stearate.

[0029] In another aspect, based on the same inventive concept, the application also provides a preparation method of high-efficiency fluorine-free anti-dripping agent, which is applied to the high-efficiency fluorine-free anti-dripping agent and comprises the following steps:

[0030] S1. The modified PVP-b-PCL is stirred and dissolved in DMF, low aspect ratio silicon nanotubes are added, ultrasonic treatment is performed, high aspect ratio silicon nanotubes are added, ultrasonic treatment is performed, and mechanical stirring is performed to obtain a first mixture.

[0031] S2. Stir Joncryl ADR-4370S into DMF, add into the first mixture, stir at 400-450 rpm for 15-25 min, continue to add carbodiimide, Irganox 1010, zinc stearate, stir at 400-450 rpm for 25-35 min, to obtain the second mixture;

[0032] S3. Put the second mixture into a spray dryer, set the inlet temperature to 150 DEG C and the outlet temperature to 80 DEG C, and the obtained product is aged at 78-82 DEG C for 2 hours to obtain a fluorine-free anti-dripping agent.

[0033] When the silicon nanotube is blended as a fluorine-free anti-dripping agent with PBT, its unique tubular structure constructs a three-dimensional network in the material, thereby improving the melt strength and preventing melt dripping during combustion. However, in actual operation, the introduction of the silicon nanotube significantly affects the shrinkage and warping behavior of the crystalline polymer (such as PBT) product.

[0034] Therefore, the present application grafts PEG on the high aspect ratio silicon nanotube, and in the PBT melt, the grafted PEG long chain stretches to form a dense "polymer brush" layer, effectively hinders the PBT molecules from approaching the surface of the silicon nanotube, so that the silicon nanotube cannot provide a large number of additional nucleation points for the crystallization of PBT, and it is difficult to form ordered crystal nuclei, thereby controlling the shrinkage of the material after molding. However, the high aspect ratio silicon nanotube is easy to entangle and agglomerate, and is difficult to disperse, which will further exacerbate the warping of the material.

[0035] The present application adds low aspect ratio silicon nanotubes, on the one hand, in the system, the high aspect ratio silicon nanotube serves as the main trunk, and the low aspect ratio silicon nanotube is inserted between the high aspect ratio silicon nanotubes and acts as a spacer to prevent the high aspect ratio silicon nanotubes from directly contacting and tightly entangling to cause agglomeration. On the other hand, the introduction of the low aspect ratio silicon nanotube can significantly improve the zero shear viscosity of the polymer melt, to a certain extent, the free rotation and swing of the high aspect ratio silicon nanotube is bound, and a large number of low aspect ratio silicon nanotubes exist to interfere with and disrupt the original smooth laminar flow lines of the melt, so that the high aspect ratio silicon nanotube cannot be in a stable, unified directional torque, and finally the orientation degree of the high aspect ratio silicon nanotube is reduced, thereby avoiding the warping and distortion of the product caused by the introduction of the silicon nanotube.

[0036] Meanwhile, the application introduces an amphiphilic block copolymer dispersant, modified PVP-b-PCL, into the system, which has good compatibility with PEG on the high aspect ratio silicon nanotube and PBT groups, can spontaneously adsorb or wrap around the PEG brush layer, and help the high aspect ratio silicon nanotube to better integrate into the PBT matrix. The PVP segment is a strong polar segment, which is strongly combined with the hydroxyl on the surface of the low aspect ratio silicon nanotube through dipole-dipole interaction and hydrogen bond, thereby preventing the short nanotube from being aggregated due to polarity, so that the low aspect ratio silicon nanotube can stably exist around the high aspect ratio silicon nanotube, forming a uniform mixture. In order to prevent the degradation of the PVP segment at the processing temperature of PBT, by introducing more stable amide bonds into the PVP backbone, replacing part of the easily degradable pyrrolidone ring, the thermal decomposition temperature of PVP is improved.

[0037] The Joncryl ADR-4370S in the composite stabilizer can enhance the PEG interface stability, the carbodiimide prevents the hydrolysis of the PEG chain, the Irganox 1010 prevents thermal oxidative degradation, and the zinc stearate serves as a lubricant to improve the processability.

[0038] In summary, due to the adoption of the above technical solutions, the application has the following beneficial effects:

[0039] 1. The PEG grafted high aspect ratio silicon nanotube effectively hinders the PBT molecular chain from approaching the surface of the silicon nanotube, so that the silicon nanotube cannot provide a large number of additional nucleation points for the crystallization of PBT, and it is difficult to form ordered crystal nuclei, thereby controlling the shrinkage rate of the material after forming.

[0040] 2. The addition of the low aspect ratio silicon nanotube prevents the high aspect ratio silicon nanotube from directly contacting and tightly winding to cause agglomeration, and the introduction of the low aspect ratio silicon nanotube can significantly improve the zero shear viscosity of the polymer melt, interfere with and disrupt the original smooth laminar flow lines of the melt, so that the orientation degree of the high aspect ratio silicon nanotube decreases, avoiding the occurrence of warping and distortion of the product.

[0041] 3. The PCL segment of the modified PVP-b-PCL spontaneously adsorbs or wraps around the PEG brush layer, helping the high aspect ratio silicon nanotube to better integrate into the PBT matrix. The PVP segment is strongly combined with the hydroxyl on the surface of the low aspect ratio silicon nanotube through dipole-dipole interaction and hydrogen bond, preventing the short nanotube from being aggregated due to polarity, so that the low aspect ratio silicon nanotube can stably exist around the high aspect ratio silicon nanotube, forming a uniform mixture. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0043] The formulations of the embodiments described below are shown in the following table:

[0044]

[0045] Embodiment 1: The embodiment discloses a high-efficiency fluorine-free anti-dripping agent, comprising silicon nanotubes, modified PVP-b-PCL, and a composite stabilizer.

[0046] The silicon nanotubes comprise PEG-grafted high-aspect-ratio silicon nanotubes and surface-hydroxylated low-aspect-ratio silicon nanotubes.

[0047] The high-aspect-ratio silicon nanotubes have an aspect ratio of 80, and the low-aspect-ratio silicon nanotubes have an aspect ratio of 10.

[0048] The mass ratio of the high-aspect-ratio silicon nanotubes to the low-aspect-ratio silicon nanotubes is 3:1.

[0049] The modified PVP-b-PCL accounts for 20% of the total mass of the silicon nanotubes.

[0050] The modified PVP-b-PCL is a product of copolymerization of modified PVP and PCL blocks.

[0051] The preparation method of the modified PVP comprises the following steps:

[0052] S11. 50 g of NVP, 5.6 g of NVF, 0.55 g of a RAFT chain transfer agent, and 0.16 g of AIBN are mixed, 200 mL of anhydrous DMF is added, the obtained mixed system is subjected to oxygen removal treatment, and the system is stirred in an oil bath at 70°C for 24 hours to obtain a reaction solution, which is added dropwise into 1000 mL of cold ethanol for precipitation, the solid is collected by filtration, washed with methanol, and vacuum dried at 40°C for 24 hours to obtain modified PVP.

[0053] The composite stabilizer accounts for 1% of the total mass of the silicon nanotubes.

[0054] It should be noted that the modified PVP-b-PCL is modified polyvinylpyrrolidone-b-poly caprolactone, PEG is polyethylene glycol, NVP is N-vinyl pyrrolidone, NVF is N-vinyl formamide, the RAFT chain transfer agent is cetyl pyridine bromide, AIBN is azobisisobutyronitrile, and DMF is N,N dimethylformamide.

[0055] The preparation method of the high aspect ratio silicon nanotube comprises the following steps:

[0056] S21. 2 g of CTAB, 0.3 g of PEG-4000, 8 g of ammonia water are added into 800 mL of deionized water, stirred until completely dissolved, 8 g of TEOS is slowly added dropwise, stirred at 35°C for 24 hours, the product is collected by centrifugation, washed and centrifuged alternately with deionized water and anhydrous ethanol, and vacuum dried at 60°C for 12 hours to obtain mesoporous silica nanorods;

[0057] S22. 5 g of mesoporous silica nanorods are ultrasonically dispersed in 500 mL of deionized water, 1 g of PEI is added, mechanically stirred, transferred to a high-pressure reaction kettle, and reacted at 120°C for 8 hours, the solid is collected by centrifugation, washed with deionized water, and vacuum dried at 80°C for 8 hours, 3 g of magnesium powder is added, ground in a mortar, the obtained mixture is loaded into a corundum boat, placed in a tube furnace, and heated to 660°C at a rate of 5°C / min, and kept for 3 hours for reduction reaction, the obtained product is soaked in 2M HCl for 24 hours, the solid is collected by centrifugation, washed with deionized water, and vacuum dried at 60°C for 12 hours to obtain silicon nanotubes;

[0058] S23. 10 g of silicon nanotubes are vacuum dried at 120°C for 6 hours, ultrasonically dispersed in 800 mL of anhydrous toluene, 2 g of KH-550 is slowly added dropwise, and stirred at 85°C for 16 hours for reflux reaction, the obtained reaction is centrifuged and washed alternately with toluene and ethanol, and vacuum dried at 60°C for 12 hours to obtain aminated silicon nanotubes;

[0059] S24. 30 g of mPEG-COOH is dissolved in 400 mL of anhydrous dichloromethane, 6 g of DCC and 0.6 g of DMAP are added, stirred in an ice bath for 1 hour, and then the temperature is increased to room temperature for continuous reaction for 6 hours, the filtrate is collected by filtration, precipitated in ice ethanol, the solid is collected by filtration, and vacuum dried to obtain activated PEG;

[0060] S25. 10 g of aminated silicon nanotubes are ultrasonically dispersed in 600 mL of anhydrous DMF, 30 g of activated PEG and 1 mL of triethylamine are added, and reacted at 85°C for 36 hours under nitrogen protection, the obtained product is centrifuged and washed alternately with DMF and deionized water, and freeze-dried to obtain high aspect ratio silicon nanotubes.

[0061] It should be noted that CTAB is cetyltrimethylammonium bromide, PEG-4000 is polyethylene glycol-4000, TEOS is tetraethyl orthosilicate, PEI is polyethyleneimine, KH-550 is 3-aminopropyl triethoxysilane, mPEG-COOH is monomethoxy polyethylene glycol-carboxylic acid, DCC is N,N'-dicyclohexyl carbodiimide, and DMAP is 4-dimethylaminopyridine.

[0062] It should be noted that, according to the different retention time of silicon nanotubes with different aspect ratios in the asymmetric flow field flow fractionation device, the high-aspect-ratio silicon nanotubes prepared above are collected by the asymmetric flow field fractionation device, and the silicon nanotubes with a retention time of 15-18 minutes are collected, the aspect ratio is 80, and the size accuracy is ± 6%.

[0063] The preparation method of the low-aspect-ratio silicon nanotube comprises the following steps:

[0064] S31. 2g CTAB, 0.3g PEG-4000, 8g ammonia water are added to 800mL deionized water, stirred until completely dissolved, 8g TEOS is slowly added, stirred at 35℃ for 24 hours, the product is collected by centrifugation, washed and centrifuged with deionized water and anhydrous ethanol alternately, and vacuum dried at 60℃ for 12 hours to obtain mesoporous silica nanorods;

[0065] S32. 5g mesoporous silica nanorods are ultrasonically dispersed in 500mL deionized water, 1g PEI is added, mechanically stirred, and transferred to a high-pressure reaction kettle for reaction at 120℃ for 8 hours, the solid is collected by centrifugation, washed with deionized water, and vacuum dried at 80℃ for 8 hours, 3g magnesium powder is added, ground in a mortar, the obtained mixture is loaded into a corundum boat, placed in a tube furnace, and heated to 660℃ at a rate of 5℃ / min, and kept for 3 hours for reduction reaction, the obtained product is soaked in 2M HCl for 24 hours, the solid is collected by centrifugation, washed with deionized water, and vacuum dried at 60℃ for 12 hours to obtain silicon nanotubes;

[0066] S33. 5 silicon nanotubes are dispersed in 500mL 10%H2O2 solution, stirred in a water bath at 70℃ for 6 hours, washed by centrifugation, and vacuum dried at 60℃ for 8 hours to obtain surface-hydroxylated silicon nanotubes;

[0067] S34. The surface-hydroxylated silicon nanotubes are dispersed in 800mL isopropanol, treated with an ultrasonic cell crusher for 90 minutes, the obtained suspension is centrifuged at 3000rmp, the supernatant is collected and centrifuged at 15000rmp, the obtained product is washed with anhydrous ethanol, and vacuum dried at 40℃ for 24 hours to obtain low-aspect-ratio silicon nanotubes.

[0068] It should be noted that, according to the different migration distances of silicon nanotubes with different aspect ratios in zone electrophoresis, the low-aspect-ratio silicon nanotubes prepared above are collected by zone electrophoresis separation technology, and the silicon nanotubes with a migration distance of 8-10cm are collected, the aspect ratio is 10, and the size accuracy is ± 10%.

[0069] The preparation method of the modified PVP-b-PCL comprises the following steps:

[0070] S41. 20g modified PVP, 30g ε-caprolactone monomer, 0.03g stannous octoate were mixed, 150mL anhydrous toluene was added, the obtained mixed system was subjected to oxygen removal treatment, and was stirred in an oil bath at 110℃ for 12 hours. Glacial acetic acid was added to terminate the reaction. The obtained reaction liquid was slowly added into 800mL cold methanol for precipitation. The solid was collected by filtration, washed with methanol, and vacuum dried at 40℃ for 36 hours to obtain modified PVP-b-PCL.

[0071] The composite stabilizer comprises Joncryl ADR-4370S, carbodiimide, Irganox 1010, and zinc stearate.

[0072] It should be noted that the mass ratio of Joncryl ADR-4370S, carbodiimide, Irganox 1010, and zinc stearate is 4:3:2:1.

[0073] A preparation method of a high-efficiency fluorine-free anti-dripping agent, comprising the following steps:

[0074] S1. 20g modified PVP-b-PCL was stirred and dissolved in DMF, 25g low aspect ratio silicon nanotubes were added and ultrasonically treated, and then 75g high aspect ratio silicon nanotubes were added and ultrasonically treated, and mechanical stirring was performed to obtain a first mixture;

[0075] S2. 0.4g Joncryl ADR-4370S was stirred and dissolved in DMF and added to the first mixture, and stirring was performed at 400-450rmp for 15-25min, and then 0.3g carbodiimide, 0.2g Irganox 1010, and 0.1g zinc stearate were continuously added, and stirring was performed at 400-450rmp for 25-35min to obtain a second mixture;

[0076] S3. The second mixture was placed in a spray dryer, the inlet temperature was set to 150℃, and the outlet temperature was set to 80℃, and the obtained product was subjected to aging treatment at 78-82℃ for 2 hours to obtain a fluorine-free anti-dripping agent.

[0077] Example 2: This example is based on Example 1, and differs from Example 1 in that the high aspect ratio silicon nanotubes in this example have an aspect ratio of 100.

[0078] It should be noted that the high aspect ratio silicon nanotubes prepared in Example 1 were collected by using an asymmetric flow field fractionation device to fractionate silicon nanotubes with a retention time of 18-22min, and the aspect ratio was 100 and the size accuracy was ±5%.

[0079] The other components and preparation methods are the same as those in Example 1.

[0080] Example 3: This example is based on Example 1, except that the low aspect ratio silicon nanotubes of this example have an aspect ratio of 30.

[0081] It should be noted that the low aspect ratio silicon nanotubes prepared in Example 1 were collected by zone electrophoresis separation technology for the silicon nanotubes with a migration distance of 11-13 cm, an aspect ratio of 30, and a size accuracy of 9%.

[0082] The other components and preparation methods are the same as those of Example 1.

[0083] Example 4: This example is based on Example 1, except that the high aspect ratio silicon nanotubes of this example have a mass ratio of 4:1 to the low aspect ratio silicon nanotubes.

[0084] The other components and preparation methods are the same as those of Example 1.

[0085] Example 5: This example is based on Example 1, except that the high aspect ratio silicon nanotubes of this example have a mass ratio of 2:1 to the low aspect ratio silicon nanotubes.

[0086] The other components and preparation methods are the same as those of Example 1.

[0087] Example 6: This example is based on Example 1, except that the modified PVP-b-PCL of this example accounts for 25% of the total mass of the silicon nanotubes.

[0088] The other components and preparation methods are the same as those of Example 1.

[0089] Example 7: This example is based on Example 1, except that the composite stabilizer of this example accounts for 1.5% of the total mass of the silicon nanotubes.

[0090] The other components and preparation methods are the same as those of Example 1.

[0091] Comparative Example 1: This comparative example is based on Example 1, except that the high aspect ratio silicon nanotubes of this comparative example have an aspect ratio of 50.

[0092] It should be noted that the high aspect ratio silicon nanotubes prepared in Example 1 were collected by asymmetric flow field flow fractionation equipment for the silicon nanotubes with a retention time of 12-15 minutes, an aspect ratio of 50, and a size accuracy of ±8%.

[0093] The other components and preparation methods are the same as those of Example 1.

[0094] Comparative Example 2: This comparative example is based on Example 1, except that the low aspect ratio silicon nanotubes of this comparative example have an aspect ratio of 5.

[0095] It should be noted that the low aspect ratio silicon nanotubes prepared in Example 1 are collected by zone electrophoresis separation technology for the silicon nanotubes with a migration distance of 5-7 cm, an aspect ratio of 5, and a size accuracy of 12%.

[0096] The other components and preparation methods are the same as those in Example 1.

[0097] Comparative Example 3: This comparative example is based on Example 1, and is different from Example 1 in that the high aspect ratio silicon nanotubes in this comparative example are not grafted with PEG.

[0098] The preparation method of the high aspect ratio silicon nanotubes includes the following steps:

[0099] S11. 2 g of CTAB, 0.3 g of PEG-4000, and 8 g of ammonia water are added to 800 mL of deionized water, stirred until completely dissolved, 8 g of TEOS is slowly added dropwise, and stirred at 35°C for 24 hours. The product is collected by centrifugation, washed and centrifuged alternately with deionized water and anhydrous ethanol, and vacuum dried at 60°C for 12 hours to obtain mesoporous silica nanorods;

[0100] S12. 5 g of mesoporous silica nanorods are ultrasonically dispersed in 500 mL of deionized water, 1 g of PEI is added, mechanically stirred, and transferred to a high-pressure reaction kettle for reaction at 120°C for 8 hours. The solid is collected by centrifugation, washed with deionized water, and vacuum dried at 80°C for 8 hours. 3 g of magnesium powder is added and ground in a mortar. The obtained mixture is loaded into a corundum boat and placed in a tube furnace. The temperature is raised to 660°C at a rate of 5°C / min and held for 3 hours for reduction reaction. The obtained product is soaked in 2M HCl for 24 hours, the solid is collected by centrifugation, washed with deionized water, and vacuum dried at 60°C for 12 hours to obtain high aspect ratio silicon nanotubes.

[0101] The other components and preparation methods are the same as those in Example 1.

[0102] Comparative Example 4: This comparative example is based on Example 1, and is different from Example 1 in that the low aspect ratio silicon nanotubes in this comparative example are not subjected to hydroxyl treatment on the surface.

[0103] The preparation method of the low aspect ratio silicon nanotubes includes the following steps:

[0104] S21. 2 g of CTAB, 0.3 g of PEG-4000, and 8 g of ammonia water are added to 800 mL of deionized water, stirred until completely dissolved, 8 g of TEOS is slowly added dropwise, and stirred at 35°C for 24 hours. The product is collected by centrifugation, washed and centrifuged alternately with deionized water and anhydrous ethanol, and vacuum dried at 60°C for 12 hours to obtain mesoporous silica nanorods;

[0105] S22. 5 g of mesoporous silica nanorods were ultrasonically dispersed in 500 mL of deionized water, 1 g of PEI was added, mechanically stirred, transferred to a high-pressure reaction kettle at 120°C for 8 hours, the solid was collected by centrifugation, washed with deionized water, and vacuum dried at 80°C for 8 hours, 3 g of magnesium powder was added, the mixture was ground in a mortar, the obtained mixture was loaded into a corundum boat, and placed in a tube furnace, and heated to 660°C at a rate of 5°C / min, and kept for 3 hours for reduction reaction, the obtained product was soaked in 2M HCl for 24 hours, the solid was collected by centrifugation, washed with deionized water, and vacuum dried at 60°C for 12 hours to obtain silicon nanotubes;

[0106] S23. The silicon nanotubes were dispersed in 800 mL of isopropanol and treated with an ultrasonic cell crusher for 90 minutes, the obtained suspension was centrifuged at 3000 rpm, the supernatant was collected and centrifuged at 15000 rpm, the obtained product was washed with anhydrous ethanol, and vacuum dried at 40°C for 24 hours to obtain low aspect ratio silicon nanotubes.

[0107] The other components and preparation methods are the same as in Example 1.

[0108] Comparative Example 5: This comparative example is based on Example 1, and differs from Example 1 in that the modified PVP of this comparative example does not contain NVF.

[0109] The preparation method of the modified PVP comprises the following steps:

[0110] S11. 55.6 g of NVP, 0.55 g of a RAIT chain transfer agent, and 0.16 g of AIBN were mixed, 200 mL of anhydrous DMF was added, the obtained mixed system was subjected to oxygen removal treatment, and stirred in an oil bath at 70°C for 24 hours of reaction, the obtained reaction solution was added dropwise into 1000 mL of cold ethanol for precipitation, the solid was collected by filtration, washed with methanol, and vacuum dried at 40°C for 24 hours to obtain the modified PVP.

[0111] The other components and preparation methods are the same as in Example 1.

[0112] Comparative Example 6: This comparative example is based on Example 1, and differs from Example 1 in that this comparative example does not contain high aspect ratio silicon nanotubes.

[0113] The other components and preparation methods are the same as in Example 1.

[0114] Comparative Example 7: This comparative example is based on Example 1, and differs from Example 1 in that this comparative example does not contain low aspect ratio silicon nanotubes.

[0115] The other components and preparation methods are the same as in Example 1.

[0116] Comparative Example 8: This comparative example is based on Example 1, and differs from Example 1 in that this comparative example does not contain modified PVP-b-PCL.

[0117] Other components and preparation methods are the same as Example 1.

[0118] Comparative Example 9: This comparative example is a blank control group.

[0119] The preparation method of the fluorine-free anti-dripping agent comprises the following steps:

[0120] S1. 2 g of CTAB, 0.3 g of PEG-4000, 8 g of ammonia water were added to 800 mL of deionized water, stirred until completely dissolved, 8 g of TEOS was slowly added, stirred at 35°C for 24 hours, the product was collected by centrifugation, washed and centrifuged with deionized water and anhydrous ethanol alternately, vacuum dried at 60°C for 12 hours, and mesoporous silica nanorods were obtained;

[0121] S2. 5 g of mesoporous silica nanorods were ultrasonically dispersed in 500 mL of deionized water, 1 g of PEI was added, mechanically stirred, and transferred to a high-pressure reaction kettle for reaction at 120°C for 8 hours, the solid was collected by centrifugation, washed with deionized water, and vacuum dried at 80°C for 8 hours, 3 g of magnesium powder was added, and the mixture was ground in a mortar. The obtained mixture was loaded into a corundum boat and placed in a tube furnace, and the temperature was raised to 660°C at a rate of 5°C / min, and the temperature was kept for 3 hours for reduction reaction. The obtained product was soaked in 2M HCl for 24 hours, the solid was collected by centrifugation, washed with deionized water, and vacuum dried at 60°C for 12 hours to obtain a fluorine-free anti-dripping agent.

[0122] Test verification:

[0123] The fluorine-free anti-dripping agent prepared by the examples and comparative examples was blended and extruded with PBT in a twin-screw extruder to prepare samples.

[0124] 1. The anti-dripping performance, rheological property, and melt flow rate of the samples prepared in Examples 1-3, Comparative Examples 1-2, and Comparative Examples 6-7 were detected respectively.

[0125] (1). Anti-dripping performance: tested according to UL94 vertical burning test standard;

[0126] (2). Rheological property: dynamic frequency scanning was performed using a rotary rheometer, and the zero shear viscosity and storage modulus at 0.1 rad / s were recorded;

[0127] (3). Melt flow rate: the melt flow rate was detected according to test standard ASTM D1238.

[0128]

[0129] The effect of silicon nanotubes with different aspect ratios on the basic properties of the fluorine-free anti-dripping agent is shown in Table 1. From the table, it can be seen that the comparative examples 1, 6-7 do not meet the anti-dripping performance requirements, indicating that the anti-dripping agent needs a higher aspect ratio to form an effective network. The low aspect ratio silicon nanotubes act as spacers to prevent the high aspect ratio silicon nanotubes from directly contacting and tightly winding to cause agglomeration. It can be known from the comparison of the examples 1-3 that with the increase of the aspect ratio, the zero shear viscosity and the storage modulus are increased. The greater the storage modulus represents the enhancement of the network structure, but the zero shear viscosity of the examples 2-3 is too high, exceeding 3000 Pa·s, which will make the processing difficult. The solubility flow rate is moderate, generally in the range of 10-20 g / 10 min. Therefore, in summary, the high aspect ratio silicon nanotubes and the low aspect ratio silicon nanotubes with the aspect ratios of 80 and 10 in the example 1 are the best combination of the present application.

[0130] 2. The shrinkage (flow direction shrinkage and vertical direction shrinkage) and warpage of the samples prepared from the examples 1, 4-7, the comparative examples 3-5, 6-9 are respectively detected.

[0131] (1). Shrinkage: The flow direction shrinkage and the vertical direction shrinkage are tested according to ASTM D955;

[0132] (2). Warpage: The warpage is tested according to ASTM D5947.

[0133]

[0134] The shrinkage and warpage of the samples of each test group are shown in Table 2. According to the data, the shrinkage of the material prepared by Example 1 is increased compared with that of Comparative Example 3, which is not modified by PEG. The silicon nanotubes provide a large number of additional nucleation points for the crystallization of PBT, thereby resulting in the increase of the shrinkage of the material prepared. According to the data in Table 1 and Table 2, the high aspect ratio silicon nanotubes in the system act as the main stem of the network, and the low aspect ratio silicon nanotubes prevent the agglomeration of the high aspect ratio silicon nanotubes. The low aspect ratio silicon nanotubes can significantly improve the zero shear viscosity of the polymer melt, thereby reducing the orientation degree of the high aspect ratio silicon nanotubes and avoiding the warpage and distortion of the product caused by the introduction of the silicon nanotubes. According to the comparison between Example 1 and Comparative Examples 4-5 and 8, it is shown that the modified PVP-b-PCL has an important influence on the shrinkage and warpage of the fluorine-free anti-dripping agent. The PCL segment of the modified PVP-b-PCL spontaneously adsorbs or winds around the PEG brush layer, which helps the high aspect ratio silicon nanotubes to better integrate into the PBT matrix. The PVP segment is strongly combined with the hydroxyl groups on the surface of the low aspect ratio silicon nanotubes through dipole-dipole interaction and hydrogen bonding, so that the low aspect ratio silicon nanotubes can stably exist around the high aspect ratio silicon nanotubes to form a uniform mixture. The PVP segment is easily degraded at the processing temperature of PBT, and it is necessary to introduce more stable amide bonds into the PVP backbone to replace part of the easily degradable pyrrolidone ring, thereby improving the thermal decomposition temperature of PVP.

[0135] The above only describes the preferred embodiments of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement and improvement made by any person skilled in the art within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A high efficiency fluorine-free anti-dripping agent, characterized by comprising: The silicon nanotube comprises PEG grafted high aspect ratio silicon nanotube and surface hydroxylated low aspect ratio silicon nanotube. The high aspect ratio silicon nanotube has an aspect ratio of 80-100. The high aspect ratio silicon nanotube has an aspect ratio of 80-100. The high aspect ratio silicon nanotube has an aspect ratio of 80-100. The high aspect ratio silicon nanotube has an aspect ratio of 80-100. The modified PVP-b-PCL accounts for 20-25% of the total mass of the silicon nanotube. The modified PVP-b-PCL is a product of copolymerization of modified PVP and PCL blocks. The preparation method of the modified PVP comprises the following steps: S11. Mix NVP, NVF, RAFT chain transfer agent and AIBN, add dehydrated DMF, perform oxygen removal treatment on the obtained mixed system, stir and react in an oil bath, add the obtained reaction solution dropwise into cold ethanol for precipitation, collect the solid by filtration, wash with methanol, and vacuum dry to obtain modified PVP.

2. The high efficiency fluorochemical anti-drip agent according to claim 1, characterized in that, The composite stabilizer accounts for 1-1.5% of the total mass of the silicon nanotube. The preparation method of the high aspect ratio silicon nanotube comprises the following steps: S21. Add CTAB, PEG-4000 and ammonia water to deionized water, stir until completely dissolved, slowly drop TEOS, stir and react, collect the product by centrifugation, wash and centrifuge with deionized water and anhydrous ethanol alternately, and vacuum dry to obtain mesoporous silica nanorods; S22. Ultrasonically disperse the mesoporous silica nanorods in deionized water, add PEI, mechanically stir, transfer to a high-pressure reaction kettle for reaction, collect the solid by centrifugation, wash with deionized water, vacuum dry, add magnesium powder, grind the mixture in a mortar, load the obtained mixture into a corundum boat, place it in a tube furnace, heat to 660℃ for reduction reaction, immerse the obtained product in HCl, collect the solid by centrifugation, wash with deionized water, and vacuum dry to obtain silicon nanotubes; S23. Vacuum dry the silicon nanotubes, ultrasonically disperse them in anhydrous toluene, slowly drop KH-550, reflux and stir to react, centrifugally wash the obtained reaction product with toluene and ethanol alternately, and vacuum dry to obtain aminated silicon nanotubes; S24. Dissolve mPEG-COOH in anhydrous dichloromethane, add DCC and DMAP, stir in an ice bath for 1 hour, continue to react at room temperature, collect the filtrate by filtration, precipitate in ice ethyl ether, collect the solid by filtration, and vacuum dry to obtain activated PEG; 3. The high efficiency fluorochemical anti-drip agent according to claim 1, wherein, S25. Ultrasonically disperse the aminated silicon nanotubes in anhydrous DMF, add activated PEG and triethylamine, react under nitrogen protection, centrifugally wash the obtained product with DMF and deionized water alternately, and freeze-dry to obtain high aspect ratio silicon nanotubes. The preparation method of the low aspect ratio silicon nanotube comprises the following steps: S31. Add CTAB, PEG-4000 and ammonia water to deionized water, stir until completely dissolved, slowly drop TEOS, stir and react, collect the product by centrifugation, wash and centrifuge with deionized water and anhydrous ethanol alternately, and vacuum dry to obtain mesoporous silica nanorods; S32. Ultrasonic dispersion of mesoporous silica nanorods in deionized water, adding PEI, mechanical stirring, into the high-pressure reaction kettle, centrifugal collection of solids, deionized water washing, vacuum drying, adding magnesium powder, grinding mixture in a mortar, the resulting mixture into corundum boat, placed in a tube furnace, heating to 660 ℃ reduction reaction, the resulting product with HCl immersion, centrifugal collection of solids, deionized water washing, vacuum drying, to obtain silicon nanotubes; S33. Silicon nanotubes dispersed in H2O2 solution, water bath stirring, centrifugal washing, vacuum drying, to obtain surface hydroxylated silicon nanotubes; S34. Surface hydroxylated silicon nanotubes dispersed in isopropanol, ultrasonic cell disruptor ultrasonic treatment, the resulting suspension 3000rmp centrifugal, collection of supernatant 15000rmp centrifugal, the resulting product anhydrous ethanol washing, vacuum drying, to obtain low aspect ratio silicon nanotubes.

4. The high efficiency fluorochemical anti-drip agent according to claim 1, wherein, The preparation method of the modified PVP-b-PCL comprises the following steps: S41. Mixing modified PVP, ε-caprolactone monomer and stannous octoate, adding anhydrous toluene, deoxygenating the resulting mixed system, stirring in an oil bath, adding glacial acetic acid to terminate the reaction, slowly dropping the resulting reaction solution into cold methanol to precipitate, filtering to collect solids, washing with methanol, and vacuum drying to obtain modified PVP-b-PCL.

5. The high efficiency fluorochemical anti-drip agent according to claim 1, wherein, The composite stabilizer comprises Joncryl ADR-4370S, carbodiimide, Irganox 1010, and zinc stearate.

6. A preparation method of high-efficiency fluorine-free anti-dripping agent, applied to the preparation of the high-efficiency fluorine-free anti-dripping agent according to any one of claims 1-5, characterized in that, The method comprises the following steps: S1. Stirring modified PVP-b-PCL in DMF, adding low aspect ratio silicon nanotubes, ultrasonic treatment, then adding high aspect ratio silicon nanotubes, ultrasonic treatment, and mechanical stirring to obtain a first mixture; S2. Stirring Joncryl ADR-4370S in DMF, adding to the first mixture, stirring at 400-450rmp for 15-25min, continuously adding carbodiimide, Irganox 1010, and zinc stearate, stirring at 400-450rmp for 25-35min to obtain a second mixture; S3. Placing the second mixture in a spray dryer, setting the inlet temperature to 150℃ and the outlet temperature to 80℃, and aging the resulting product at 78-82℃ for 2 hours to obtain a fluorine-free anti-dripping agent.

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