Preparation method of p / s / si flame-retardant system composite powder

Abstract

The application relates to a preparation method of a P / S / Si flame-retardant system composite powder, wherein nano-SiO2 is modified by phosphoric acid and 2-hydroxyethanesulfonic acid to obtain modified SiO2, and then the modified SiO2, PA6, an acidic solvent and sodium gluconate are mixed to prepare the P / S / Si flame-retardant system composite powder by a dissolution precipitation method; wherein the content of the sodium gluconate in the mixture of the modified SiO2, the PA6, the acidic solvent and the sodium gluconate is 4-5 wt%. The application can prepare regular flame-retardant composite powder by the dissolution precipitation method, the prepared composite powder can improve the size stability of pure PA6 powder, can further form a P / S / Si flame-retardant system to endow the powder with flame-retardant performance, and is beneficial to environmental protection and resource utilization.

Description

Technical Field

[0001] This invention belongs to the field of thermoplastic powders and relates to a method for preparing a P / S / Si flame-retardant composite powder system. Background Technology

[0002] PA6 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. However, ordinary PA6 powder retains the flammable properties of nylon-like materials, easily burning in the environment to form molten droplets and release harmful fumes. Furthermore, PA6 is a polymer formed by repeating amide groups, making it prone to forming hydrogen bonds with water molecules, resulting in high water absorption. When used in the laser sintering process of 3D printing, it also faces the problem of poor dimensional stability. Therefore, there is a need to develop a PA6 powder with excellent flame retardant properties and dimensional stability.

[0003] Reference 1, "A nanosilica / nylon-12 composite powder for selective lasersintering[J]. Journal of Reinforced Plastics and Composites, 2009, 28(23): 2889-2902," describes the use of a silane coupling agent to modify SiO2. Using the modified SiO2 as the core and a mixed solvent of ethanol / butanone / water as the mixed solvent, after completely dissolving PA12, the PA12 is precipitated on the SiO2 surface by cooling. The SiO2 modified with the silane coupling agent contains amino groups, which can undergo amidation reaction with the carboxyl groups of the PA12 macromolecular chain during the precipitation process, promoting the precipitation of PA12 on SiO2 and enhancing the interaction between the PA12 macromolecular chain and SiO2.

[0004] Nano-SiO2, as an inorganic particle, has good dimensional stability. If nano-SiO2 is introduced into PA6 powder using the method in Reference 1, it is expected to improve the dimensional stability of PA6 powder. However, the flame retardant properties of PA6 powder prepared by this method are still not ideal.

[0005] Reference 2, "Structures of H3PO4 / SiO2 catalysts and catalytic performance in the hydration of ethene[J]. Applied Catalysis A:General, 1998, 170(2):269-275," discloses a method for modifying SiO2 with phosphoric acid.

[0006] Theoretically, if Reference 2 and Reference 1 can be combined, and the phosphoric acid-modified SiO2 in Reference 2 can be used to replace the silane coupling agent modified SiO2 in Reference 1, and then PA6 powder can be prepared by dissolution and precipitation method, it is expected that PA6 powder with excellent flame retardant properties and dimensional stability can be obtained.

[0007] However, in the actual preparation process, it was found that the precipitation rate of PA6 on phosphoric acid modified SiO2 was very slow. This is because phosphoric acid modified SiO2 does not have amino groups and cannot undergo the amidation reaction in reference 1 with the carboxyl groups of the PA6 macromolecular chain. Summary of the Invention

[0008] The purpose of this invention is to solve the problems existing in the prior art and provide a method for preparing P / S / Si flame retardant composite powder.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing a P / S / Si flame-retardant composite powder involves first modifying nano-SiO2 with phosphoric acid and 2-hydroxyethanesulfonic acid to obtain modified SiO2. Then, phosphoric acid is used to link the nano-SiO2 with 2-hydroxyethanesulfonic acid. Next, the modified SiO2, PA6, an acidic solvent, and sodium gluconate are mixed, and the P / S / Si flame-retardant composite powder is prepared by a dissolution-precipitation method. The sodium gluconate content in the mixture of modified SiO2, PA6, acidic solvent, and sodium gluconate is 4–5 wt%.

[0011] The formation process of the P / S / Si flame retardant composite powder in this invention is as follows: After mixing modified SiO2, PA6, acidic solvent, and sodium gluconate, as the temperature increases, PA6 gradually dissolves in the acidic solvent. Modified SiO2 can cause PA6 macromolecular chains to aggregate on the surface in a heterogeneous nucleation manner. As the temperature decreases, the PA6 macromolecular chains aggregated on the surface of modified SiO2 gradually become entangled and aggregate, precipitating out to form a P / S / Si flame retardant composite powder with a core-shell structure.

[0012] The P / S / Si flame retardant composite powder of the present invention has excellent flame retardant properties and dimensional stability because it contains nano-SiO2, phosphoric acid and 2-hydroxyethanesulfonic acid. Nano-SiO2, as an inorganic particle, has good dimensional stability. The three elements of nano-SiO2, phosphoric acid and 2-hydroxyethanesulfonic acid form the P / S / Si flame retardant system. The combination of multiple elements can achieve better flame retardant effect.

[0013] This invention ensures a rapid precipitation rate of PA6 on modified SiO2 because the modified SiO2 surface contains sulfonic acid groups, and the solvent is acidic. In the acidic solvent, the sulfonic acid groups on the modified SiO2 surface release negatively charged hydrogen ions, while the amino groups of the PA6 macromolecular chain combine with the positively charged hydrogen ions. The negatively charged sulfonic acid groups on the modified SiO2 surface can bind to the positively charged amino groups of the PA6 macromolecular chain via ionic bonds and hydrogen bonds, respectively. These two effects work together to promote the aggregation of PA6 macromolecular chains on the modified SiO2 surface.

[0014] The present invention adds sodium gluconate to the system, the function of which is as follows:

[0015] ①Sodium gluconate is a strong base weak acid salt. It can ionize in water to generate gluconate ions. After hydrolysis, gluconate ions form hydroxide ions, which can react with hydrogen ions released from the sulfonic acid groups on the surface of modified SiO2, thus preventing hydrogen ions from causing degradation of the macromolecular chain of PA6.

[0016] ② Sodium gluconate is a strong base weak acid salt. It can ionize in water to generate gluconate ions. The gluconate ions can combine with the positively charged amino groups of the PA6 macromolecular chain by ionic bonds. At the same time, the hydroxyl groups can combine with the PA6 macromolecular chain by hydrogen bonds. The two effects work together to prevent the PA6 macromolecular chains from violently entangled and contacting each other, thus avoiding irregular and rapid precipitation.

[0017] ③ Sodium gluconate has a high viscosity, which can stabilize the PA6 macromolecular chain, preventing it from being in a relatively free state, and enabling it to uniformly cover the surface of each modified SiO2 to form a regular shape.

[0018] In this invention, the content of sodium gluconate in the mixture of modified SiO2, PA6, acidic solvent, and sodium gluconate is controlled to be 4-5 wt%. If the content of sodium gluconate is too low, the effect will be insignificant; conversely, if the content is too high, it will affect the aggregation of PA6 macromolecular chains to SiO2.

[0019] As a preferred technical solution:

[0020] The preparation method of the P / S / Si flame retardant composite powder described above, which modifies nano-SiO2 with phosphoric acid and 2-hydroxyethanesulfonic 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 2-hydroxyethanesulfonic acid solution and reacted to obtain modified SiO2.

[0021] The method for preparing a P / S / Si flame-retardant composite powder as described above involves a phosphoric acid solution to nano-SiO2 mass ratio of 10–15:1; a phosphoric acid solution concentration of 13–18 wt%; and impregnation of nano-SiO2 in the phosphoric acid solution at a temperature of 120–130 °C for 24–36 h.

[0022] The preparation method of the P / S / Si flame retardant composite powder described above involves drying at a temperature of 60–70°C for 20–24 hours.

[0023] The method for preparing a P / S / Si flame-retardant composite powder as described above involves a mass ratio of nano-SiO2 adsorbing phosphoric acid to 2-hydroxyethanesulfonic acid of 1:1 to 2; the solvent in the 2-hydroxyethanesulfonic acid solution is formamide, and the mass ratio of 2-hydroxyethanesulfonic acid to formamide is 1:12 to 15; the reaction temperature is 130 to 150°C, and the reaction time is 3 to 5 hours.

[0024] The method for preparing a P / S / Si flame-retardant composite powder as described above, wherein PA6 is PA6 waste filament, PA6 plastic, PA6 fabric or PA6 powder.

[0025] In the preparation method of the P / S / Si flame retardant composite powder as described above, the acidic solvent is a mixture of diethylene glycol, water, and hydrochloric acid in a volume ratio of 2:1:0.1 to 0.15.

[0026] The preparation method of the P / S / Si flame retardant composite powder described above involves a mixture of modified SiO2, PA6, acidic solvent, and sodium gluconate. The mass ratio of the acidic solvent to PA6 is 7-8:1. Under this ratio, the macromolecular chains of PA6 dissolved in the acidic solvent are more freely distributed, resulting in more uniform precipitation. The mass ratio of PA6 to modified SiO2 is 14-15:1. Under this ratio, modified SiO2 can be used as a core, thereby controlling the average particle size of the composite powder to achieve a suitable size.

[0027] The preparation method of P / S / Si flame retardant composite powder as described above, specifically the process of preparing P / S / Si flame retardant composite powder by dissolution precipitation method, is as follows: a mixture of modified SiO2, PA6, acidic solvent, and sodium gluconate is heated to 160-175℃ and held for 3-4 hours, then cooled to below 40℃ at a cooling rate of 0.2-1℃ / min to obtain precipitated particles, and then the particles are washed (using water) and dried (60℃, 24 hours) to obtain P / S / Si flame retardant composite powder.

[0028] In the process of preparing P / S / Si flame-retardant composite powder by dissolution and precipitation, the high temperature of 160-175℃ is set to achieve the dissolution of PA6 and sodium gluconate, and to promote the combination of PA6 with modified SiO2 and gluconate. The specific principle is that under superheated conditions, the ion product constant of water will increase, and the concentration of hydrogen ions and hydroxide ions in superheated water will increase. After sodium gluconate is dissolved, sodium ions can combine with hydroxide ions, thereby increasing the hydrogen ion content of the solvent, which in turn promotes the combination of PA6 with modified SiO2 and gluconate.

[0029] In the process of preparing P / S / Si flame-retardant composite powder by dissolution and precipitation, the present invention sets the temperature to be maintained for 3-4 hours after heating. This is to ensure that PA6 and sodium gluconate are completely dissolved, and to allow sodium gluconate to mix better with the PA6 macromolecular chain, so that gluconate ions can better enter the PA6 macromolecular chain during precipitation.

[0030] The preparation method of the P / S / Si flame retardant composite powder 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. The solution 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.

[0031] The method for preparing P / S / Si flame-retardant composite powder as described above has the following characteristics: the yield of P / S / Si flame-retardant composite powder is 70-80%, and the yield is calculated as: (mass of dried P / S / Si flame-retardant composite powder / (mass amount of PA6 added + mass amount of modified SiO2 added)) × 100%. The average particle size of the P / S / Si flame-retardant composite powder is 40-60 μm, the PDI is 0.1-0.2, the limiting oxygen index is 28.3-28.8%, and the elongation at break of the device printed from the P / S / Si flame-retardant composite powder is 14-15%.

[0032] The P / S / Si flame retardant composite powder obtained by this invention has a larger average particle size because the mass ratio of PA6 to modified SiO2 is relatively large. Sodium gluconate can prevent the PA6 macromolecular chains from violently entangled and contacting each other, avoid irregular and rapid precipitation, and ensure that more PA6 macromolecular chains are uniformly covered on the surface of each modified SiO2, thereby resulting in a larger average particle size of the composite powder formed after precipitation.

[0033] The P / S / Si flame-retardant 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). The multiple flame-retardant elements work synergistically to achieve higher flame-retardant efficiency.

[0034] The P / S / Si flame-retardant composite powder obtained in this invention, when printed into devices, exhibits excellent mechanical properties. This is because during the preparation of the P / S / Si flame-retardant composite powder, PA6 precipitates rapidly on modified SiO2, while sodium gluconate can control the uniform precipitation of PA6 macromolecular chains on modified SiO2 in a short time. Due to the strong hydrogen bonding between sodium gluconate and PA6 macromolecular chains, coupled with the rapid surrounding effect of PA6 macromolecular chains, sodium gluconate is difficult to remove, thus affecting the orderly arrangement of PA6 macromolecular chains. This results in a decrease in the crystallinity of PA6, an increase in the proportion of amorphous regions, and an improvement in mechanical properties.

[0035] Beneficial effects:

[0036] (1) The method for preparing a P / S / Si flame retardant composite powder of the present invention can prepare a flame retardant composite powder with a combination of multiple flame retardant elements (P / S / Si) by dissolution precipitation method, which has high flame retardant efficiency.

[0037] (2) The P / S / Si flame retardant composite powder obtained by this invention is printed into a device with excellent mechanical properties.

[0038] (3) The method for preparing P / S / Si flame retardant composite powder of the present invention can prepare P / S / Si flame retardant composite powder using PA6 waste yarn as raw material, which effectively solves the problem of solid waste accumulation and pollution caused by PA6 waste fabric, and is conducive to environmental protection and resource utilization. Attached Figure Description

[0039] Figure 1 This is a schematic diagram comparing the TG values ​​of the P / S / Si flame retardant composite powder and PA6 after soaping in Example 1 of the present invention.

[0040] Figure 2 This is a schematic diagram comparing the DTG of the P / S / Si flame retardant composite powder and PA6 after soaping in Example 1 of the present invention.

[0041] Figure 3 This is a distribution diagram of Si element in the P / S / Si flame retardant composite powder of Example 1 of the present invention;

[0042] Figure 4 This is a distribution diagram of the S element in the P / S / Si flame-retardant composite powder of Example 1 of the present invention;

[0043] Figure 5 This is a distribution diagram of the P element in the P / S / Si flame-retardant composite powder of Example 1 of the present invention;

[0044] Figure 6 This is a morphology diagram of the P / S / Si flame-retardant composite powder prepared in Example 1 of the present invention. Detailed Implementation

[0045] 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.

[0046] In the following embodiments and comparative examples, the fabrication process of the devices printed from P / S / Si flame-retardant composite powder is as follows: using a German EOS P396 molding machine, the working chamber size is 340×340×600mm, the printed device size is 30×30×30mm, the layer thickness is 0.12mm, the preheating temperature is 170℃, the laser power is 39W, and the scanning speed is 3600mm / s.

[0047] The test methods for the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0048] 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.

[0049] PDI: Accurately weigh 0.1g of the P / S / Si flame retardant 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.

[0050] 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.

[0051] Elongation at break: The printed devices were tested on an electronic universal testing machine (manufacturer: Instron Corporation, USA, brand name: Instron 5967). The test standard was the national standard "GB / T 1040.1-2018 Determination of tensile properties of plastics - Part 1: General Rules". The tensile speed was 20 mm / min, the test environment was 23±2℃, and the relative humidity was 50±10%. Each group of samples was tested 5 times.

[0052] 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℃.

[0053] Example 1

[0054] A method for preparing a P / S / Si flame-retardant composite powder, comprising the following steps:

[0055] (1) Preparation of raw materials;

[0056] PA6: PA6 fabric, manufactured by Wujiang Fuhua Textile Co., Ltd. of Suzhou City, Jiangsu Province, with a molecular weight of 18000 g / mol;

[0057] Liquid soap: Composed of water and soap flakes;

[0058] Nano SiO2;

[0059] Phosphoric acid solution: solvent is water;

[0060] 2-Hydroxyethanesulfonic acid solution: a mixture of 2-hydroxyethanesulfonic acid and formamide in a mass ratio of 1:15;

[0061] Acidic solvent: a mixture of diethylene glycol, water, and hydrochloric acid in a volume ratio of 2:1:0.13;

[0062] Sodium gluconate;

[0063] (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 25°C for 24 h; wherein the bath ratio of PA6 to soaping solution was 1:50.

[0064] (3) Nano SiO2 was immersed in a 18wt% phosphoric acid solution at 120°C for 36h and dried at 60°C for 24h to obtain nano SiO2 adsorbed with phosphoric acid. Then, the nano SiO2 adsorbed with phosphoric acid at a mass ratio of 1:2 was mixed with a 2-hydroxyethanesulfonic acid solution and reacted at 130°C for 5h to obtain modified SiO2. The mass ratio of phosphoric acid solution to nano SiO2 was 10:1.

[0065] (4) After mixing modified SiO2, PA6, acidic solvent and sodium gluconate, the mixture is heated to 170℃ and held for 3h, then cooled to 35℃ at a cooling rate of 1℃ / min, and then vacuum dried at 60℃ for 24h to obtain P / S / Si flame retardant composite powder; wherein, the mass ratio of acidic solvent to PA6 is 8:1, the mass ratio of PA6 to modified SiO2 is 14:1, and the content of sodium gluconate in the mixture of modified SiO2, PA6, acidic solvent and sodium gluconate is 4.5wt%.

[0066] The final P / S / Si flame-retardant composite powder (such as...) Figure 6 The yield of the P / S / Si flame-retardant composite powder was 76%, the average particle size was 50 μm, the PDI was 0.2, the limiting oxygen index was 28.8%, and the elongation at break of the device printed from the P / S / Si flame-retardant composite powder was 14.5%. The distribution of Si in the P / S / Si flame-retardant composite powder is shown in the figure. Figure 3 As shown, the distribution of sulfur (S) in the P / S / Si flame-retardant composite powder is as follows: Figure 4 As shown, the distribution of P element in the P / S / Si flame-retardant composite powder is as follows: Figure 5 As shown;

[0067] The prepared P / S / Si flame-retardant composite powder and PA6 after soaping in step (2) were compared by TG and DTG. The results showed that... 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%. 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.

[0068] Comparative Example 1

[0069] A method for preparing a P / S / Si flame retardant composite powder is basically the same as in Example 1, except that the content of sodium gluconate in step (4) is 3wt%.

[0070] The final P / S / Si flame retardant composite powder had a yield of 76%, an average particle size of 50 μm, a PDI of 0.4, a limiting oxygen index of 28.8%, and a break elongation of 7% for devices printed from the P / S / Si flame retardant composite powder.

[0071] Comparative Example 2

[0072] A method for preparing a P / S / Si flame retardant composite powder is basically the same as in Example 1, except that the content of sodium gluconate in step (4) is 6 wt%.

[0073] The final P / S / Si flame retardant composite powder had a yield of 76%, an average particle size of 80 μm, a PDI of 0.38, a limiting oxygen index of 28.8%, and a break elongation of 16% for devices printed from the P / S / Si flame retardant composite powder.

[0074] Comparing Comparative Example 1, Comparative Example 2, and Example 1, it can be seen that excessive variation in sodium gluconate content leads to changes in the average particle size of the composite powder, PDI, and the elongation at break of the device printed from the P / S / Si flame-retardant composite powder. This is because when the amount of sodium gluconate used is too low, the binding ability of the PA6 macromolecular chains aggregated in the modified SiO2 is limited, causing some PA6 macromolecular chains to move and self-aggregate in the solvent, eventually forming particles, resulting in an increased particle size distribution index, i.e., an increased PDI. When the amount of sodium gluconate used is too high, although it can improve the elongation at break of the device printed from the P / S / Si flame-retardant composite powder, the binding ability of sodium gluconate on the PA6 macromolecular chains is too strong. Due to this strong binding effect, the outermost PA6 macromolecular chains of the modified SiO2 aggregated on adjacent surfaces become entangled, leading to the aggregation of modified SiO2, resulting in an increased particle size and an increased PDI.

[0075] Comparative Example 3

[0076] A method for preparing a P / S / Si flame retardant composite powder is basically the same as in Example 1, except that sodium gluconate in step (1) is replaced with sodium acetate, and sodium gluconate in step (4) is an equal mass of sodium acetate.

[0077] The final P / S / Si flame retardant composite powder had a yield of 76%, an average particle size of 48 μm, a PDI of 0.5, a limiting oxygen index of 28.8%, and a break elongation of 7.5% for devices printed from the P / S / Si flame retardant composite powder.

[0078] Comparing Comparative Example 3 and Example 1, it can be seen that the use of sodium acetate instead of sodium gluconate in Comparative Example 3 leads to an increase in the PDI of the P / S / Si flame-retardant composite powder and a decrease in the elongation at break of the device printed from the P / S / Si flame-retardant composite powder. This is because although sodium gluconate and sodium acetate are both strong base-weak acid salts, after sodium acetate ionizes, although sodium ions can combine with a certain amount of hydroxide ions to slightly increase the hydrogen ion content and promote the positive charge of the amino group of PA6, under high temperature and high pressure, acetate ions need to combine with the positively charged PA6. However, acetic acid is a weak acid, resulting in a limited number of positively charged amino groups of PA6. Its pH value is high, making it difficult to reach the isoelectric point and to become charged. Furthermore, after electrostatic binding, acetate ions cannot stabilize the PA6 macromolecular chain, causing the PA6 macromolecular chain to move and self-aggregate to form particles of different sizes.

[0079] Comparative Example 4

[0080] A method for preparing a P / S / Si flame-retardant composite powder is basically the same as in Example 1, except that the hydrochloric acid in the acidic solvent is replaced with an equal mass of water.

[0081] The final P / S / Si flame retardant composite powder had a yield of 78%, an average particle size of 42 μm, a PDI of 0.39, a limiting oxygen index of 28.7%, and a break elongation of 14.5% for devices printed from the P / S / Si flame retardant composite powder.

[0082] Comparing Example 1 with Comparative Example 4, it can be seen that the PDI of the P / S / Si flame retardant composite powder finally prepared in Comparative Example 4 is significantly increased. This is because when the hydrochloric acid used is replaced with water, PA6 cannot be charged, so the aggregation of PA6 macromolecular chains on the modified silica surface is affected. The PA6 macromolecular chains will self-aggregate, resulting in a change in average particle size and an increase in PDI.

[0083] Example 2

[0084] A method for preparing a P / S / Si flame-retardant composite powder, comprising the following steps:

[0085] (1) Preparation of raw materials;

[0086] PA6: PA6 fabric, manufactured by Wujiang Fuhua Textile Co., Ltd. of Suzhou City, Jiangsu Province, with a molecular weight of 18000 g / mol;

[0087] Liquid soap: Composed of water and soap flakes;

[0088] Nano SiO2;

[0089] Phosphoric acid solution: solvent is water;

[0090] 2-Hydroxyethanesulfonic acid solution: a mixture of 2-hydroxyethanesulfonic acid and formamide in a mass ratio of 1:15;

[0091] Acidic solvent: a mixture of diethylene glycol, water, and hydrochloric acid in a volume ratio of 2:1:0.1;

[0092] Sodium gluconate;

[0093] (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 30°C for 18 h; wherein the bath ratio of PA6 to soaping solution was 1:30.

[0094] (3) Nano SiO2 was immersed in a 13wt% phosphoric acid solution at 125°C for 30h and dried at 70°C for 20h to obtain nano SiO2 adsorbed with phosphoric acid. Then, the nano SiO2 adsorbed with phosphoric acid at a mass ratio of 1:1 was mixed with a 2-hydroxyethanesulfonic acid solution and reacted at 150°C for 5h to obtain modified SiO2. The mass ratio of phosphoric acid solution to nano SiO2 was 15:1.

[0095] (4) After mixing modified SiO2, PA6, acidic solvent and sodium gluconate, the mixture is heated to 175℃ and held for 4 hours. Then, it is cooled to 30℃ at a cooling rate of 0.5℃ / min and then vacuum dried at 60℃ for 24 hours to obtain P / S / Si flame retardant composite powder. The mass ratio of acidic solvent to PA6 is 7:1, the mass ratio of PA6 to modified SiO2 is 15:1, and the content of sodium gluconate in the mixture of modified SiO2, PA6, acidic solvent and sodium gluconate is 5wt%.

[0096] The final P / S / Si flame retardant composite powder had a yield of 70%, an average particle size of 40 μm, a PDI of 0.1, a limiting oxygen index of 28.3%, and a break elongation of 15% for devices printed from the P / S / Si flame retardant composite powder.

[0097] Example 3

[0098] A method for preparing a P / S / Si flame-retardant composite powder, comprising the following steps:

[0099] (1) Preparation of raw materials;

[0100] PA6: PA6 fabric, manufactured by Wujiang Fuhua Textile Co., Ltd. of Suzhou City, Jiangsu Province, with a molecular weight of 18000 g / mol;

[0101] Liquid soap: Composed of water and soap flakes;

[0102] Nano SiO2;

[0103] Phosphoric acid solution: solvent is water;

[0104] 2-Hydroxyethanesulfonic acid solution: a mixture of 2-hydroxyethanesulfonic acid and formamide in a mass ratio of 1:12;

[0105] Acidic solvent: a mixture of diethylene glycol, water, and hydrochloric acid in a volume ratio of 2:1:0.15;

[0106] Sodium gluconate;

[0107] (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 1:50.

[0108] (3) Nano SiO2 was immersed in a 16wt% phosphoric acid solution at 130°C for 36h and dried at 65°C for 22h to obtain phosphoric acid-adsorbed nano SiO2. Then, the phosphoric acid-adsorbed nano SiO2 with a mass ratio of 1:1.5 was mixed with a 2-hydroxyethanesulfonic acid solution and reacted at 140°C for 3h to obtain modified SiO2. The mass ratio of phosphoric acid solution to nano SiO2 was 12:1.

[0109] (4) After mixing modified SiO2, PA6, acidic solvent and sodium gluconate, the mixture is heated to 160℃ and held for 4 hours. Then, it is cooled to 30℃ at a cooling rate of 0.2℃ / min and then vacuum dried at 60℃ for 24 hours to obtain P / S / Si flame retardant composite powder. The mass ratio of acidic solvent to PA6 is 7.5:1, the mass ratio of PA6 to modified SiO2 is 14.5:1, and the content of sodium gluconate in the mixture of modified SiO2, PA6, acidic solvent and sodium gluconate is 4wt%.

[0110] The final P / S / Si flame retardant composite powder had a yield of 80%, an average particle size of 60 μm, a PDI of 0.12, a limiting oxygen index of 28.5%, and a break elongation of 14% for devices printed from the P / S / Si flame retardant composite powder.

[0111] Example 4

[0112] A method for preparing a P / S / Si flame-retardant composite powder, comprising the following steps:

[0113] (1) Preparation of raw materials;

[0114] PA6: PA6 plastic, Dongguan Xianglian Plastic Raw Materials Co., Ltd., with a molecular weight of 28000 g / mol;

[0115] Liquid soap: Composed of water and soap flakes;

[0116] Nano SiO2;

[0117] Phosphoric acid solution: solvent is water;

[0118] 2-Hydroxyethanesulfonic acid solution: a mixture of 2-hydroxyethanesulfonic acid and formamide in a mass ratio of 1:12.5;

[0119] Acidic solvent: a mixture of diethylene glycol, water, and hydrochloric acid in a volume ratio of 2:1:0.13;

[0120] Sodium gluconate;

[0121] (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.

[0122] (3) Nano SiO2 was immersed in a 18wt% phosphoric acid solution at 120°C for 24h and dried at 60°C for 24h to obtain nano SiO2 adsorbed with phosphoric acid. Then, the nano SiO2 adsorbed with phosphoric acid at a mass ratio of 1:2 was mixed with a 2-hydroxyethanesulfonic acid solution and reacted at 130°C for 4h to obtain modified SiO2. The mass ratio of phosphoric acid solution to nano SiO2 was 10:1.

[0123] (4) After mixing modified SiO2, PA6, acidic solvent and sodium gluconate, the mixture is heated to 170℃ and held for 3.5h, then cooled to 35℃ at a cooling rate of 1℃ / min, and then vacuum dried at 60℃ for 24h to obtain P / S / Si flame retardant composite powder; wherein, the mass ratio of acidic solvent to PA6 is 8:1, the mass ratio of PA6 to modified SiO2 is 14:1, and the content of sodium gluconate in the mixture of modified SiO2, PA6, acidic solvent and sodium gluconate is 4.5wt%.

[0124] The final P / S / Si flame retardant composite powder had a yield of 76%, an average particle size of 50 μm, a PDI of 0.2, a limiting oxygen index of 28.8%, and a break elongation of 14.5% for devices printed from the P / S / Si flame retardant composite powder.

[0125] Example 5

[0126] A method for preparing a P / S / Si flame-retardant composite powder, comprising the following steps:

[0127] (1) Preparation of raw materials;

[0128] PA6: PA6 powder, Shanghai Maclean Biochemical Technology Co., Ltd., CAS No. 25038-54-4;

[0129] Liquid soap: Composed of water and soap flakes;

[0130] Nano SiO2;

[0131] Phosphoric acid solution: solvent is water;

[0132] 2-Hydroxyethanesulfonic acid solution: a mixture of 2-hydroxyethanesulfonic acid and formamide in a mass ratio of 1:15;

[0133] Acidic solvent: a mixture of diethylene glycol, water, and hydrochloric acid in a volume ratio of 2:1:0.13;

[0134] Sodium gluconate;

[0135] (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 1:40.

[0136] (3) Nano SiO2 was immersed in a 18wt% phosphoric acid solution at 120°C for 36h and dried at 60°C for 24h to obtain nano SiO2 adsorbed with phosphoric acid. Then, the nano SiO2 adsorbed with phosphoric acid at a mass ratio of 1:2 was mixed with a 2-hydroxyethanesulfonic acid solution and reacted at 130°C for 5h to obtain modified SiO2. The mass ratio of phosphoric acid solution to nano SiO2 was 10:1.

[0137] (4) After mixing modified SiO2, PA6, acidic solvent and sodium gluconate, the mixture is heated to 170℃ and held for 3h, then cooled to 35℃ at a cooling rate of 0.2℃ / min, and then vacuum dried at 60℃ for 24h to obtain P / S / Si flame retardant composite powder; wherein, the mass ratio of acidic solvent to PA6 is 8:1, the mass ratio of PA6 to modified SiO2 is 14:1, and the content of sodium gluconate in the mixture of modified SiO2, PA6, acidic solvent and sodium gluconate is 4.5wt%.

[0138] The final P / S / Si flame retardant composite powder had a yield of 76%, an average particle size of 55 μm, a PDI of 0.2, a limiting oxygen index of 28.8%, and a break elongation of 14.5% for devices printed from the P / S / Si flame retardant composite powder.

Claims

1. A method for preparing a P / S / Si flame-retardant composite powder, characterized in that, First, nano-SiO2 is modified with phosphoric acid and 2-hydroxyethanesulfonic acid to obtain modified SiO2. Then, modified SiO2, PA6, acidic solvent, and sodium gluconate are mixed, and P / S / Si flame-retardant composite powder is prepared by dissolution-precipitation method. The content of sodium gluconate in the mixture of modified SiO2, PA6, acidic solvent, and sodium gluconate is 4-5 wt%. The specific process for modifying nano-SiO2 with phosphoric acid and 2-hydroxyethanesulfonic acid to obtain modified SiO2 is as follows: First, nano-SiO2 is impregnated in a phosphoric acid solution and dried to obtain phosphoric acid-adsorbed nano-SiO2. Then, the phosphoric acid-adsorbed nano-SiO2 is mixed with a 2-hydroxyethanesulfonic acid solution and reacted to obtain modified SiO2. The mass ratio of phosphoric acid solution to nano-SiO2 is 10~15:1; the concentration of phosphoric acid solution is 13~18 wt%. The acidic solvent is a mixture of diethylene glycol, water, and hydrochloric acid in a volume ratio of 2:1:0.1~0.

15.

2. The method for preparing a P / S / Si flame-retardant composite powder according to claim 1, characterized in that, The nano-SiO2 was impregnated in phosphoric acid solution at a temperature of 120~130℃ for 24~36h.

3. The method for preparing a P / S / Si flame-retardant 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 a P / S / Si flame-retardant composite powder according to claim 1, characterized in that, The mass ratio of nano-SiO2 adsorbing phosphoric acid to 2-hydroxyethanesulfonic acid is 1:1~2; the solvent in the 2-hydroxyethanesulfonic acid solution is formamide, and the mass ratio of 2-hydroxyethanesulfonic acid to formamide is 1:12~15; the reaction temperature is 130~150℃, and the time is 3~5h.

5. The method for preparing a P / S / Si flame-retardant 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 a P / S / Si flame-retardant composite powder according to claim 1, characterized in that, In the mixture of modified SiO2, PA6, acidic solvent, and sodium gluconate, the mass ratio of acidic solvent to PA6 is 7~8:1, and the mass ratio of PA6 to modified SiO2 is 14~15:

1.

7. The method for preparing a P / S / Si flame-retardant composite powder according to claim 6, characterized in that, The specific process for preparing P / S / Si flame-retardant composite powder by the dissolution-precipitation method is as follows: a mixture of modified SiO2, PA6, acidic solvent, and sodium gluconate is heated to 160~175℃ and held for 3~4h, and then cooled to below 40℃ at a cooling rate of 0.2~1℃ / min to obtain P / S / Si flame-retardant composite powder.

8. The method for preparing a P / S / Si flame-retardant composite powder according to claim 1, characterized in that, The yield of the P / S / Si flame retardant composite powder is 70-80%. The yield is calculated as: (mass of dried P / S / Si flame retardant composite powder / (mass of PA6 added + mass of modified SiO2 added)) × 100%. The average particle size of the P / S / Si flame retardant composite powder is 40-60 μm, the PDI is 0.1-0.2, the limiting oxygen index is 28.3-28.8%, and the elongation at break of devices printed from the P / S / Si flame retardant composite powder is 14-15%.

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