A method for preparing flame-retardant PA6@SiO2 composite powder

Abstract

This invention relates to a method for preparing flame-retardant PA6@SiO2 composite powder. First, nano-SiO2 is modified with phosphoric acid and N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid to obtain modified SiO2. Then, the modified SiO2, PA6, a neutral solvent, and diethylamine are mixed, and the flame-retardant PA6@SiO2 composite powder is prepared by a dissolution-precipitation method. The content of diethylamine in the mixture of modified SiO2, PA6, neutral solvent, and diethylamine is 7-9 wt%. This invention utilizes waste PA6 to prepare flame-retardant PA6@SiO2 composite powder, which is beneficial to environmental protection and resource utilization. Furthermore, the prepared composite powder improves the dimensional stability of pure PA6 powder while further forming a P / S / Si / N flame-retardant system, thus imparting flame-retardant properties to the PA6 powder.

Description

Technical Field

[0001] This invention belongs to the field of thermoplastic powders and relates to a method for preparing flame-retardant PA6@SiO2 composite powder. Background Technology

[0002] Nylon powder is a thermoplastic powder with many excellent properties, such as electrical insulation, lubricity, abrasion resistance, and impact resistance. It can be used alone or mixed with lubricants, fillers, and other additives. The manufacturing methods of nylon powder are mainly divided into direct polymerization, mechanical pulverization, and solution precipitation. Direct polymerization has strict process requirements, mechanical pulverization requires pre-freezing the material with liquid nitrogen, while solution precipitation has certain advantages.

[0003] The basic principle of the dissolution-precipitation method is: the polymer is dissolved by the solvent at high temperature but not at low temperature. Then, by changing the temperature or adding a non-solvent, the free polymer macromolecular chains aggregate to form particles. The literature "Ananosilica / nylon-12 composite powder for selective laser sintering[J]. Journal of Reinforced Plastics and Composites, 2009, 28(23):2889-2902." uses a dissolution-precipitation method to prepare silica / PA12 composite powder to improve the dimensional stability of PA12. The specific process is as follows: First, silica is modified with silane coupling agent 3-aminopropyltriethoxysilane coupling agent. Then, the modified nano-SiO2 is dispersed in a solvent of ethanol / butanone / water to prepare SiO2 emulsion. Finally, PA12 particles, solvent and SiO2 emulsion are added to a 10L reactor. The reactor is evacuated and N2 gas is added to protect the reactants from oxidation. The temperature is raised to 145℃ to completely dissolve PA12. The mixture is stirred vigorously and cooled to about 105℃ at a rate of 10℃ / h. At this time, PA12 begins to precipitate. The temperature is maintained until precipitation is complete and the solvent is distilled off.

[0004] However, during the preparation of nylon powder using the dissolution-precipitation method, the nylon macromolecular chains are unstable during precipitation on the surface of the nucleating agent, exhibiting a random entangled state. This results in the nylon powder having an irregular and complex shape, leading to poor flowability and hindering its application.

[0005] PA6 powder, a type of nylon powder, possesses advantages such as a wide operating temperature range, good physical properties, excellent wear resistance, and a low coefficient of friction, thus leading to its broad application. Therefore, it is necessary to prepare a PA6 powder with a regular morphology using a solution-precipitation method. Summary of the Invention

[0006] The purpose of this invention is to solve the problems existing in the prior art and provide a method for preparing flame-retardant PA6@SiO2 composite powder.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing flame-retardant PA6@SiO2 composite powder involves first modifying nano-SiO2 with phosphoric acid and N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid to obtain modified SiO2. Then, the modified SiO2, PA6, neutral solvent, and diethylamine are mixed, and the flame-retardant PA6@SiO2 composite powder is prepared by a dissolution-precipitation method. The content of diethylamine in the mixture of modified SiO2, PA6, neutral solvent, and diethylamine is 7-9 wt%.

[0009] The purpose of modifying nano-SiO2 with phosphoric acid and N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid before preparing flame-retardant PA6@SiO2 composite powder is: ① To combine multiple flame-retardant elements to achieve better flame-retardant effects and improve the dimensional stability of PA6 material. Nano-SiO2 contains Si, which has a smoke-suppressing effect; N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid contains N and S elements, showing potential as a flame retardant; and phosphoric acid contains P, a commonly used synthetic raw material for flame retardants. The P-... The OH bond can react with -OH, which can link nano-SiO2 with N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid and provide flame retardant elements, so that the modified nano-SiO2 forms a P / S / Si / N flame retardant system; ② It ensures that PA6 precipitates faster on modified SiO2. The S=O of N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid can form hydrogen bonds with the NH of the PA6 macromolecular chain, promoting the precipitation of the PA6 macromolecular chain on modified SiO2, so that the PA6 macromolecular chain can better encapsulate the modified SiO2.

[0010] The principle of this invention for preparing flame-retardant PA6@SiO2 composite powder via a dissolution-precipitation method is as follows: During the dissolution-precipitation process, the solvent has good solubility for PA6 at high temperatures. After complete dissolution, the temperature is lowered. As the temperature decreases, the solvent's solubility for PA6 decreases, so PA6 gradually precipitates during the cooling process. This precipitation process is the gradual entanglement and aggregation of macromolecular chains. The modified SiO2 used can cause PA6 macromolecular chains to aggregate on the surface through heterogeneous nucleation, forming a core-shell structure. However, the PA6 macromolecular chains are unstable during the precipitation process on the SiO2 surface, exhibiting a random entanglement state, resulting in an irregular and complex shape for the entire composite powder. To avoid this phenomenon, diethylamine is added to the system. The NH3 in diethylamine can form hydrogen bonds with the C=O of the PA6 macromolecular chains, preventing the PA6 macromolecular chains from violently entangled and contacting each other, thereby avoiding… To prevent irregular and rapid precipitation, the methylene groups on the diethylamine molecule replace the hydrogen bonds between different PA6 macromolecular chains with van der Waals forces, stabilizing the PA6 macromolecular chains and preventing them from being in a relatively free state. This allows them to uniformly cover the modified SiO2 surface and form a regular shape. The amount of diethylamine needs to be controlled within a suitable range. In this invention, the content of diethylamine in the mixture of modified SiO2, PA6, neutral solvent, and diethylamine is controlled within the range of 7-9 wt%. If the content is too high, it will cause diethylamine to form hydrogen bonds with the S=O on the modified SiO2 surface, thereby affecting the aggregation of PA6 macromolecular chains on the modified SiO2 and causing PA6 macromolecular chains to aggregate in non-modified SiO2 areas, failing to encapsulate the modified SiO2. If the content is too low, the stability of the PA6 macromolecular chains during precipitation will be poor, resulting in uneven precipitation of PA6 macromolecular chains on each modified SiO2 and an increase in PDI.

[0011] In preparing flame-retardant PA6@SiO2 composite powder by the dissolution-precipitation method, a neutral solvent is used in this invention because this avoids the release of hydrogen ions from the sulfonic acid groups in the modified SiO2, which would accelerate the degradation of PA6.

[0012] As a preferred technical solution:

[0013] The preparation method of flame-retardant PA6@SiO2 composite powder as described above, which modifies nano-SiO2 with phosphoric acid and N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid to obtain modified SiO2, is as follows: First, nano-SiO2 is impregnated in phosphoric acid solution and dried to obtain nano-SiO2 adsorbed with phosphoric acid. Then, the nano-SiO2 adsorbed with phosphoric acid is mixed with N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid solution and reacted to obtain modified SiO2.

[0014] The method for preparing flame-retardant PA6@SiO2 composite powder as described above involves a mass ratio of phosphoric acid solution to nano-SiO2 of 10–15:1; a concentration of phosphoric acid solution of 10–15 wt%; and an impregnation temperature of 120–130 °C and a time of 24–36 h for the nano-SiO2 in the phosphoric acid solution.

[0015] The preparation method of the flame-retardant PA6@SiO2 composite powder described above involves drying at a temperature of 60–70°C for 20–24 hours.

[0016] The method for preparing flame-retardant PA6@SiO2 composite powder as described above involves a mass ratio of nano-SiO2 adsorbing phosphoric acid to N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid of 1:1 to 2; the solvent in the N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid solution is formamide, and the mass ratio of N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid to formamide is 1:13 to 15; the reaction temperature is 130 to 150°C, and the reaction time is 3 to 5 hours.

[0017] The method for preparing flame-retardant PA6@SiO2 composite powder as described above, wherein PA6 is PA6 waste filament, PA6 plastic, PA6 fabric or PA6 powder.

[0018] In the preparation method of the flame-retardant PA6@SiO2 composite powder described above, the neutral solvent is a mixture of methanol and ethanol in a volume ratio of 3:1.

[0019] In the preparation method of flame-retardant PA6@SiO2 composite powder as described above, in the mixture of modified SiO2, PA6, neutral solvent, and diethylamine, the mass ratio of neutral solvent to PA6 is 7-8:1. Under this ratio, the macromolecular chains of PA6 dissolved in the neutral solvent are more freely distributed, resulting in more uniform precipitation. When the mass ratio of PA6 to modified SiO2 is 10-12:1, the effect of diethylamine in fixing PA6 macromolecular chains during precipitation is limited. If the mass ratio of PA6 to modified SiO2 is too large, too many PA6 macromolecular chains will aggregate on the surface of modified SiO2, and some PA6 molecular chains will still slip, which is not conducive to obtaining PA6 powder with a regular morphology. Therefore, this invention controls the mass ratio of PA6 to modified SiO2 to be 10-12:1, thereby reducing the number of PA6 macromolecular chains coated on each modified SiO2.

[0020] The preparation method of flame-retardant PA6@SiO2 composite powder as described above, the specific process of preparing flame-retardant PA6@SiO2 composite powder by dissolution precipitation is as follows: a mixture of modified SiO2, PA6, neutral solvent and diethylamine is heated to 145-170℃ and held for 1-2 hours, then cooled to below 40℃ at a cooling rate of 0.2-1℃ / min to obtain precipitated particles. Finally, the particles are washed (using water) and dried (60℃, 24 hours) to obtain flame-retardant PA6@SiO2 composite powder.

[0021] This invention controls the dissolution temperature at 145–170°C and the dissolution time at 1–2 hours. This is to ensure complete dissolution of PA6 and to allow sufficient contact between diethylamine and the PA6 macromolecular chains. Because diethylamine is a small molecule and readily soluble in ethanol and methanol, it can only mix with the PA6 macromolecular chains after PA6 has dissolved. While PA6 can be dissolved at 145°C, the dissolution capacity increases with temperature. As the temperature rises, the PA6 macromolecular chains move more vigorously, resulting in more thorough mixing with diethylamine. The dissolution time varies with temperature; at lower temperatures, a longer time is required for complete mixing, while at higher temperatures, a shorter time is needed.

[0022] The preparation method of flame-retardant PA6@SiO2 composite powder as described above involves washing and drying PA6 before dissolving it. The specific process is as follows: first, PA6 is immersed in a soaping solution with a bath ratio of 1:30 to 50 and a soaping solution concentration of 2 g / L. Then, it is soaked and washed at 25 to 35°C for 1 hour, and finally dried at 25 to 35°C for 12 to 24 hours.

[0023] The method for preparing flame-retardant PA6@SiO2 composite powder as described above has a yield of 70-80%, where the yield is calculated as: (mass of dried flame-retardant PA6@SiO2 composite powder / (mass amount of PA6 added + mass amount of modified SiO2 added)) × 100%. The average particle size of the flame-retardant PA6@SiO2 composite powder is 20-30 μm, the PDI is 0.08-0.12, the limiting oxygen index is 29.9-30.5%, and the flowability index is 64-66°.

[0024] The flame-retardant PA6@SiO2 composite powder obtained by this invention has a smaller average particle size and a smaller PDI. This is because the mass of PA6 and modified SiO2 is relatively small, and diethylamine is a small molecule compound. Under high temperature conditions, the PA6 macromolecular chain can be fully mixed and contacted with diethylamine, so that the PA6 macromolecular chain is uniformly fixed by diethylamine.

[0025] The flame-retardant PA6@SiO2 composite powder obtained by this invention has a high limiting oxygen index because the final composite powder is a flame-retardant system composed of multiple flame-retardant elements (P / S / Si / N). The multiple flame-retardant elements work synergistically to achieve higher flame-retardant efficiency.

[0026] The flame-retardant PA6@SiO2 composite powder obtained by this invention has a high flowability index because the final composite powder has a regular shape, good rolling properties, small gaps between particles, and low friction.

[0027] Beneficial effects:

[0028] (1) The present invention provides a method for preparing flame-retardant PA6@SiO2 composite powder, which can prepare flame-retardant PA6@SiO2 composite powder with regular shape by dissolution precipitation method, and has excellent flame-retardant properties.

[0029] (2) The present invention provides a method for preparing flame-retardant PA6@SiO2 composite powder, which uses waste PA6 as raw material to prepare flame-retardant PA6@SiO2 composite powder, effectively solving the problem of solid waste accumulation and pollution caused by waste PA6, and is conducive to environmental protection and resource utilization. Attached Figure Description

[0030] Figure 1 This is a schematic diagram comparing the TG values ​​of the P / S / Si / N flame-retardant composite powder and PA6 after soaping in Example 1 of this invention.

[0031] Figure 2 This is a schematic diagram comparing the DTG of the P / S / Si / N flame retardant composite powder and PA6 after soaping in Example 1 of the present invention.

[0032] Figure 3 This is a distribution diagram of Si element in the P / S / Si / N flame retardant composite powder of Example 1 of the present invention;

[0033] Figure 4 This is a distribution diagram of the S element in the P / S / Si / N flame-retardant composite powder of Example 1 of the present invention;

[0034] Figure 5 This is a distribution diagram of the P element in the P / S / Si / N flame-retardant composite powder of Example 1 of the present invention;

[0035] Figure 6 This is a schematic diagram showing the P, Si, and S contents of the P / S / Si / N flame-retardant composite powder in Example 1 of the present invention;

[0036] Figure 7 This is a SEM image of the P / S / Si / N flame-retardant composite powder in Example 1 of the present invention. Detailed Implementation

[0037] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0038] The test methods for the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0039] Average particle size: The average particle size was obtained by selecting 200 particles using Nano Measure 1.2 software based on the scanning electron microscope image with a scale bar.

[0040] PDI: Accurately weigh 0.1g of the flame-retardant PA6@SiO2 composite powder to be tested, disperse the composite powder in 50mL of deionized water, dilute until transparent, and equilibrate for 10s on a Nano-ZS90 nanoparticle size analyzer at 25℃ to obtain the PDI of the composite powder.

[0041] Limiting oxygen index: The composite powder is poured into a polytetrafluoroethylene mold with a thickness of 10 mm and a size of 200×20×10 mm in a molten state. After cooling, it is cut into test samples with a thickness of 4 mm and a size of 120×10×4 mm. The test is carried out in accordance with the national standard for limiting oxygen index, GB / T 2406-2009 Determination of combustion behavior of plastics by oxygen index method.

[0042] Flowability index: The angle of repose of the composite powder was measured using a JHY-1004X angle of repose measuring instrument according to GB / T 31057.3—2018 "Physical Properties Testing of Particulate Materials Part 3: Measurement of Flowability Index of Flow Samples". Approximately 150 mL of sample was placed in a graduated cylinder, the funnel was plugged, and the composite powder was placed in the funnel. The valve stem was opened, and the powder was slowly stirred with a stirrer to allow it to flow through. After 2 minutes, the height of the powder cone tip from the base was measured. Five tests were performed, and the average of the five test results was taken.

[0043] Molecular weight determination: The molecular weight of different PA6 raw materials was determined by the viscosity method. The viscosity was determined using an Ubbelohde viscometer with a capillary inner diameter of 0.6 mm. An 85% formic acid aqueous solution was used as the solvent. The concentration of the formic acid solution for PA6 raw materials was 10 mg / mL. The test temperature was 25 ± 0.1℃.

[0044] Example 1

[0045] A method for preparing flame-retardant PA6@SiO2 composite powder, comprising the following steps:

[0046] (1) Preparation of raw materials;

[0047] PA6: PA6 fabric, manufactured by Wujiang Fuhua Textile Co., Ltd. of Suzhou City, Jiangsu Province, with a molecular weight of 18000 g / mol;

[0048] Nano SiO2;

[0049] Phosphoric acid solution: concentration 15 wt%, solvent is water;

[0050] N,N-Di(2-hydroxyethyl)-2-aminoethanesulfonic acid solution: a mixture of N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid and formamide in a mass ratio of 1:15;

[0051] Neutral solvent: a mixture of methanol and ethanol in a volume ratio of 3:1;

[0052] Diethylamine;

[0053] Liquid soap: composed of water and soap flakes;

[0054] (2) At 25°C, PA6 was immersed in a soaping solution with a concentration of 2 g / L and washed for 1 h, and then dried at 25°C for 24 h; wherein the bath ratio of PA6 to soaping solution was 1:50.

[0055] (3) Nano SiO2 was immersed in phosphoric acid solution at 130°C for 36 h and then dried at 60°C for 24 h to obtain nano SiO2 adsorbed with phosphoric acid. Finally, the nano SiO2 adsorbed with phosphoric acid was mixed with N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid solution and reacted at 150°C for 5 h to obtain modified SiO2. The mass ratio of phosphoric acid solution to nano SiO2 was 15:1, and the mass ratio of nano SiO2 adsorbed with phosphoric acid to N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid was 1:2.

[0056] (4) After mixing modified SiO2, PA6, neutral solvent and diethylamine, the mixture is heated to 145℃ and held for 2 hours. Then it is cooled to 35℃ at a cooling rate of 1℃ / min. After drying in a vacuum at 60℃ for 24 hours, flame-retardant PA6@SiO2 composite powder is obtained. The mass ratio of neutral solvent to PA6 is 8:1, the mass ratio of PA6 to modified SiO2 is 12:1, and the content of diethylamine in the mixture of modified SiO2, PA6, neutral solvent and diethylamine is 9wt%.

[0057] The final flame-retardant PA6@SiO2 composite powder (such as...) Figure 7 The average particle size (as shown) is 30 μm, the yield is 80%, the PDI is 0.08, the limiting oxygen index of the flame-retardant PA6@SiO2 composite powder is 30.5%, and the flowability index is 66°.

[0058] Because nitrogen (N) is already present in PA6, P, Si, and S are all successfully present in the prepared flame-retardant PA6@SiO2 composite powder, and their distribution is as follows: Figures 3-5 As shown, the contents of P, Si, and S are as follows: Figure 6 As shown;

[0059] Meanwhile, a comparison of TG and DTG of the flame-retardant PA6@SiO2 composite powder prepared above and the PA6 after soaping in step (2) shows that, as Figure 1 , Figure 2 As shown, the final residual mass of PA6 after soaping is only 0.2%, while the residual mass of the composite powder is close to 10%, and the residual mass of silica at 700℃ is at least 85%. Therefore, the reason for the residual mass of the composite powder is the combined thermal protection effect of phosphorus and sulfur elements on the surface of silica. The introduced flame retardant elements are effective, which improves the thermal stability of the composite powder and reduces the degree of thermal decomposition. Moreover, the maximum thermal decomposition temperature of the composite powder is earlier than that of PA6 after soaping, which can promote the heat release and play a flame retardant role, further improving the flame retardant performance of the composite powder.

[0060] Comparative Example 1

[0061] A method for preparing flame-retardant PA6@SiO2 composite powder is basically the same as in Example 1, except that the content of diethylamine in step (4) is 6 wt%.

[0062] The final flame-retardant PA6@SiO2 composite powder had an average particle size of 34 μm, a PDI of 0.31, a limiting oxygen index of 30.5%, and a flowability index of 43°.

[0063] Comparative Example 2

[0064] A method for preparing flame-retardant PA6@SiO2 composite powder is basically the same as in Example 1, except that the content of diethylamine in step (4) is 10wt%.

[0065] The final flame-retardant PA6@SiO2 composite powder had an average particle size of 40 μm, a PDI of 0.43, a limiting oxygen index of 30.5%, and a flowability index of 32°.

[0066] Comparing Comparative Examples 1, 2, and 1, it can be seen that when the diethylamine content is low, the PA6 macromolecular chains are unstable in the aggregated state of the modified SiO2 during precipitation. The surface PA6 macromolecular chains are prone to slippage, causing the outermost layers of adjacent surface-aggregated PA6 macromolecular chains in the modified SiO2 to become entangled, resulting in larger particle sizes. Furthermore, some of these chains may self-polymerize in the solvent, causing changes in particle size. Both of these factors contribute to an increase in PDI. When the amount of diethylamine is too high, it can lead to the formation of hydrogen bonds between diethylamine and the S=O bonds on the surface of the modified SiO2, affecting the PA6... The aggregation of macromolecular chains on modified SiO2 prevents PA6 macromolecular chains from aggregating on the modified SiO2. It also hinders the function of diethylamine, which forms hydrogen bonds with PA6 macromolecular chains, making it impossible for PA6 macromolecules to form a stable state. This results in irregular aggregation, causing the outermost layers of adjacent aggregated PA6 macromolecular chains on the modified SiO2 to become entangled, forming more irregular shapes. This leads to larger particle size, increased PDI, decreased particle size uniformity, non-uniform shape, difficulty in particle sliding, increased interparticle friction, and a decreased flowability index.

[0067] Example 2

[0068] A method for preparing flame-retardant PA6@SiO2 composite powder, comprising the following steps:

[0069] (1) Preparation of raw materials;

[0070] PA6: PA6 fabric, manufactured by Wujiang Fuhua Textile Co., Ltd. of Suzhou City, Jiangsu Province, with a molecular weight of 18000 g / mol;

[0071] Nano SiO2;

[0072] Phosphoric acid solution: 10 wt% concentration, water as solvent;

[0073] N,N-Di(2-hydroxyethyl)-2-aminoethanesulfonic acid solution: a mixture of N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid and formamide in a mass ratio of 1:13;

[0074] Neutral solvent: a mixture of methanol and ethanol in a volume ratio of 3:1;

[0075] Diethylamine;

[0076] Liquid soap: Composed of water and soap flakes;

[0077] (2) At 35°C, PA6 was immersed in a soaping solution with a concentration of 2 g / L and washed for 1 h, and then dried at 35°C for 12 h; wherein the bath ratio of PA6 to soaping solution was 1:30.

[0078] (3) After impregnating nano-SiO2 in phosphoric acid solution at 120℃ for 24h, and then drying at 70℃ for 20h, nano-SiO2 adsorbed with phosphoric acid is obtained. Finally, the nano-SiO2 adsorbed with phosphoric acid is mixed with N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid solution and reacted at 130℃ for 3h to obtain modified SiO2. The mass ratio of phosphoric acid solution to nano-SiO2 is 10:1, and the mass ratio of nano-SiO2 adsorbed with phosphoric acid to N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid is 1:1.

[0079] (4) After mixing modified SiO2, PA6, neutral solvent and diethylamine, the mixture is heated to 170℃ and held for 1 hour, then cooled to 30℃ at a cooling rate of 0.2℃ / min, and then dried in a vacuum at 60℃ for 24 hours to obtain flame-retardant PA6@SiO2 composite powder; wherein, the mass ratio of neutral solvent to PA6 is 7:1, the mass ratio of PA6 to modified SiO2 is 10:1, and the content of diethylamine in the mixture of modified SiO2, PA6, neutral solvent and diethylamine is 7wt%.

[0080] The final flame-retardant PA6@SiO2 composite powder had an average particle size of 20 μm, a yield of 70%, a PDI of 0.12, a limiting oxygen index of 29.9%, and a flowability index of 64°.

[0081] Example 3

[0082] A method for preparing flame-retardant PA6@SiO2 composite powder, comprising the following steps:

[0083] (1) Preparation of raw materials;

[0084] PA6: PA6 waste yarn, manufactured by Jiangsu Haiyang Chemical Fiber Co., Ltd., with a molecular weight of 18000 g / mol;

[0085] Nano SiO2;

[0086] Phosphoric acid solution: concentration 12.5 wt%, solvent is water;

[0087] N,N-Di(2-hydroxyethyl)-2-aminoethanesulfonic acid solution: a mixture of N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid and formamide in a mass ratio of 1:13.5;

[0088] Neutral solvent: a mixture of methanol and ethanol in a volume ratio of 3:1;

[0089] Diethylamine;

[0090] Liquid soap: Composed of water and soap flakes;

[0091] (2) At 30°C, PA6 was immersed in a soaping solution with a concentration of 2 g / L and washed for 1 h, and then dried at 30°C for 20 h; wherein the bath ratio of PA6 to soaping solution was 1:40.

[0092] (3) Nano-SiO2 was immersed in phosphoric acid solution at 125℃ for 28h and then dried at 65℃ for 22h to obtain nano-SiO2 adsorbed with phosphoric acid. Finally, the nano-SiO2 adsorbed with phosphoric acid was mixed with N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid solution and reacted at 140℃ for 4h to obtain modified SiO2. The mass ratio of phosphoric acid solution to nano-SiO2 was 12.5:1, and the mass ratio of nano-SiO2 adsorbed with phosphoric acid to N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid was 1:1.5.

[0093] (4) After mixing modified SiO2, PA6, neutral solvent and diethylamine, the mixture is heated to 155℃ and held for 1.5h, then cooled to 30℃ at a cooling rate of 0.5℃ / min, and then dried in vacuum at 60℃ for 24h to obtain flame-retardant PA6@SiO2 composite powder; wherein, the mass ratio of neutral solvent to PA6 is 7.5:1, the mass ratio of PA6 to modified SiO2 is 11:1, and the content of diethylamine in the mixture of modified SiO2, PA6, neutral solvent and diethylamine is 8wt%.

[0094] The final flame-retardant PA6@SiO2 composite powder had an average particle size of 25 μm, a yield of 75%, a PDI of 0.1, a limiting oxygen index of 30.2%, and a flowability index of 65°.

[0095] Example 4

[0096] A method for preparing flame-retardant PA6@SiO2 composite powder, comprising the following steps:

[0097] (1) Preparation of raw materials;

[0098] PA6: PA6 plastic, manufactured by Dongguan Xianglian Plastic Raw Materials Co., Ltd., with a molecular weight of 28000 g / mol;

[0099] Nano SiO2;

[0100] Phosphoric acid solution: concentration 15 wt%, solvent is water;

[0101] N,N-Di(2-hydroxyethyl)-2-aminoethanesulfonic acid solution: a mixture of N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid and formamide in a mass ratio of 1:15;

[0102] Neutral solvent: a mixture of methanol and ethanol in a volume ratio of 3:1;

[0103] Diethylamine;

[0104] Liquid soap: Composed of water and soap flakes;

[0105] (2) At 25°C, PA6 was immersed in a soaping solution with a concentration of 2 g / L and washed for 1 h, and then dried at 25°C for 24 h; wherein the bath ratio of PA6 to soaping solution was 1:50.

[0106] (3) Nano SiO2 was immersed in phosphoric acid solution at 130°C for 36 h and then dried at 60°C for 24 h to obtain nano SiO2 adsorbed with phosphoric acid. Finally, the nano SiO2 adsorbed with phosphoric acid was mixed with N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid solution and reacted at 150°C for 5 h to obtain modified SiO2. The mass ratio of phosphoric acid solution to nano SiO2 was 15:1, and the mass ratio of nano SiO2 adsorbed with phosphoric acid to N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid was 1:2.

[0107] (4) After mixing modified SiO2, PA6, neutral solvent and diethylamine, the mixture is heated to 145℃ and held for 2 hours. Then, it is cooled to 35℃ at a cooling rate of 0.2℃ / min and dried in a vacuum at 60℃ for 24 hours to obtain flame-retardant PA6@SiO2 composite powder. The mass ratio of neutral solvent to PA6 is 7:1, the mass ratio of PA6 to modified SiO2 is 10:1, and the content of diethylamine in the mixture of modified SiO2, PA6, neutral solvent and diethylamine is 7wt%.

[0108] The final flame-retardant PA6@SiO2 composite powder had an average particle size of 29 μm, a yield of 80%, a PDI of 0.11, a limiting oxygen index of 30.5%, and a flowability index of 66°.

[0109] Example 5

[0110] A method for preparing flame-retardant PA6@SiO2 composite powder, comprising the following steps:

[0111] (1) Preparation of raw materials;

[0112] PA6: PA6 waste yarn, manufactured by Jiangsu Haiyang Chemical Fiber Co., Ltd., with a molecular weight of 18000 g / mol;

[0113] Nano SiO2;

[0114] Phosphoric acid solution: concentration 15 wt%, solvent is water;

[0115] N,N-Di(2-hydroxyethyl)-2-aminoethanesulfonic acid solution: a mixture of N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid and formamide in a mass ratio of 1:15;

[0116] Neutral solvent: a mixture of methanol and ethanol in a volume ratio of 3:1;

[0117] Diethylamine;

[0118] Liquid soap: Composed of water and soap flakes;

[0119] (2) At 25°C, PA6 was immersed in a soaping solution with a concentration of 2 g / L and washed for 1 h, and then dried at 25°C for 24 h; wherein the bath ratio of PA6 to soaping solution was 1:50.

[0120] (3) Nano SiO2 was immersed in phosphoric acid solution at 130°C for 36 h and then dried at 60°C for 24 h to obtain nano SiO2 adsorbed with phosphoric acid. Finally, the nano SiO2 adsorbed with phosphoric acid was mixed with N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid solution and reacted at 150°C for 5 h to obtain modified SiO2. The mass ratio of phosphoric acid solution to nano SiO2 was 15:1, and the mass ratio of nano SiO2 adsorbed with phosphoric acid to N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid was 1:2.

[0121] (4) After mixing modified SiO2, PA6, neutral solvent and diethylamine, the mixture is heated to 170℃ and held for 2 hours. Then, it is cooled to 40℃ at a cooling rate of 1℃ / min. After drying in a vacuum at 60℃ for 24 hours, flame-retardant PA6@SiO2 composite powder is obtained. The mass ratio of neutral solvent to PA6 is 8:1, the mass ratio of PA6 to modified SiO2 is 12:1, and the content of diethylamine in the mixture of modified SiO2, PA6, neutral solvent and diethylamine is 9wt%.

[0122] The final flame-retardant PA6@SiO2 composite powder had an average particle size of 23 μm, a yield of 70%, a PDI of 0.09, a limiting oxygen index of 30.5%, and a flowability index of 64.3°.

[0123] Example 6

[0124] A method for preparing flame-retardant PA6@SiO2 composite powder, comprising the following steps:

[0125] (1) Preparation of raw materials;

[0126] PA6: PA6 powder, manufactured by Shanghai McLean Biochemical Technology Co., Ltd., CAS No. 25038-54-4;

[0127] Nano SiO2;

[0128] Phosphoric acid solution: concentration 15 wt%, solvent is water;

[0129] N,N-Di(2-hydroxyethyl)-2-aminoethanesulfonic acid solution: a mixture of N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid and formamide in a mass ratio of 1:13;

[0130] Neutral solvent: a mixture of methanol and ethanol in a volume ratio of 3:1;

[0131] Diethylamine;

[0132] Liquid soap: Composed of water and soap flakes;

[0133] (2) At 25°C, PA6 was immersed in a soaping solution with a concentration of 2 g / L and washed for 1 h, and then dried at 25°C for 24 h; wherein the bath ratio of PA6 to soaping solution was 1:50.

[0134] (3) Nano-SiO2 was immersed in phosphoric acid solution at 130℃ for 36h and then dried at 60℃ for 24h to obtain nano-SiO2 adsorbed with phosphoric acid. Finally, the nano-SiO2 adsorbed with phosphoric acid was mixed with N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid solution and reacted at 150℃ for 5h to obtain modified SiO2. The mass ratio of phosphoric acid solution to nano-SiO2 was 10:1, and the mass ratio of nano-SiO2 adsorbed with phosphoric acid to N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid was 1:1.2.

[0135] (4) After mixing modified SiO2, PA6, neutral solvent and diethylamine, the mixture is heated to 145℃ and held for 2 hours. Then it is cooled to 35℃ at a cooling rate of 1℃ / min. After drying in a vacuum at 60℃ for 24 hours, flame-retardant PA6@SiO2 composite powder is obtained. The mass ratio of neutral solvent to PA6 is 8:1, the mass ratio of PA6 to modified SiO2 is 12:1, and the content of diethylamine in the mixture of modified SiO2, PA6, neutral solvent and diethylamine is 9wt%.

[0136] The final flame-retardant PA6@SiO2 composite powder had an average particle size of 30 μm, a yield of 80%, a PDI of 0.08, a limiting oxygen index of 30.1%, and a flowability index of 66°.

Claims

1. A method for preparing flame-retardant PA6@SiO2 composite powder, characterized in that, First, nano-SiO2 is modified with phosphoric acid and N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid to obtain modified SiO2. Then, the modified SiO2, PA6, neutral solvent, and diethylamine are mixed and flame-retardant PA6@SiO2 composite powder is prepared by dissolution and precipitation method. In the mixture of modified SiO2, PA6, neutral solvent, and diethylamine, the content of diethylamine is 7~9wt%, the mass ratio of neutral solvent to PA6 is 7~8:1, and the mass ratio of PA6 to modified SiO2 is 10~12:

1. The specific process of modifying nano-SiO2 with phosphoric acid and N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid to obtain modified SiO2 is as follows: nano-SiO2 is first impregnated in phosphoric acid solution and dried to obtain nano-SiO2 adsorbed with phosphoric acid. Then, the nano-SiO2 adsorbed with phosphoric acid is mixed with N,N-di(2-hydroxyethyl)-2-aminoethanesulfonic acid solution and reacted to obtain modified SiO2.

2. The method for preparing flame-retardant PA6@SiO2 composite powder according to claim 1, characterized in that, The mass ratio of phosphoric acid solution to nano-SiO2 is 10~15:1; the concentration of phosphoric acid solution is 10~15wt%; the temperature for impregnating nano-SiO2 in phosphoric acid solution is 120~130℃, and the time is 24~36h.

3. The method for preparing flame-retardant PA6@SiO2 composite powder according to claim 1, characterized in that, The drying temperature is 60~70℃, and the time is 20~24h.

4. The method for preparing flame-retardant PA6@SiO2 composite powder according to claim 1, characterized in that, The mass ratio of nano-SiO2 adsorbing phosphoric acid to N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid is 1:1~2; the solvent in the N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid solution is formamide, and the mass ratio of N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid to formamide is 1:13~15; the reaction temperature is 130~150℃, and the time is 3~5h.

5. The method for preparing flame-retardant PA6@SiO2 composite powder according to claim 1, characterized in that, PA6 can be PA6 waste filaments, PA6 plastic, PA6 fabric, or PA6 powder.

6. The method for preparing flame-retardant PA6@SiO2 composite powder according to claim 1, characterized in that, The neutral solvent is a mixture of methanol and ethanol in a volume ratio of 3:

1.

7. The method for preparing flame-retardant PA6@SiO2 composite powder according to claim 1, characterized in that, The specific process for preparing flame-retardant PA6@SiO2 composite powder by the dissolution-precipitation method is as follows: a mixture of modified SiO2, PA6, neutral solvent, and diethylamine is heated to 145~170℃ and held for 1~2h, and then cooled to below 40℃ at a cooling rate of 0.2~1℃ / min to obtain flame-retardant PA6@SiO2 composite powder.

8. The method for preparing flame-retardant PA6@SiO2 composite powder according to claim 1, characterized in that, The yield of flame-retardant PA6@SiO2 composite powder is 70-80%. The yield is calculated as: mass of dried flame-retardant PA6@SiO2 composite powder / (mass of PA6 added + mass of modified SiO2 added) × 100%. The average particle size of the flame-retardant PA6@SiO2 composite powder is 20-30 μm, the PDI is 0.08-0.12, the limiting oxygen index is 29.9-30.5%, and the flowability index is 64-66°.

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