Phosphorus-nitrogen-silicon flame retardant for viscose fibers and use thereof

Abstract

The application belongs to the field of textile fibers, and particularly relates to a phosphorus-nitrogen-silicon flame retardant for viscose fibers and application thereof. The preparation raw materials comprise a phosphorus-nitrogen-silicon flame retardant, a surfactant A, a surfactant B and water, the phosphorus-nitrogen-silicon flame retardant is obtained by modifying a double-end amino siloxane p-dithio pyrophosphate flame retardant, and the concentration is 20-50 wt%; the surfactant A is polyacrylamide, and the concentration is 0.1-1 wt%; the surfactant B is one or a combination of two or more of fatty alcohol polyoxyethylene ether, phenyl phenol polyoxyethylene ether, castor oil polyoxyethylene ether and fatty amine polyoxyethylene ether, and the concentration is 1-8 wt%. The three-element synergistic flame retardant reduces the addition amount in the viscose fibers, effectively improves the spinneret blockage, and reduces the influence on the mechanical properties of the fibers. In the flame-retardant dispersion liquid, the polyacrylamide macromolecular dispersant is selected, the crosslinked network structure can effectively prevent the loss of the flame retardant in the spinning process, and the washing resistance of the flame-retardant fiber is improved.

Description

Technical Field

[0001] This invention belongs to the field of textile fibers, specifically relating to a phosphorus-nitrogen-silicon flame retardant for viscose fibers and its application. Background Technology

[0002] Viscose fiber is one of the most commonly used textile fibers. However, it is extremely flammable when exposed to fire, with a limiting oxygen index of only about 18%, which limits its use in daily life and industry. Flame-retardant modification of viscose fiber to obtain flame-retardant viscose fiber with good flame-retardant properties has always been a key research topic in fiber modification. Commonly used flame retardants for viscose fiber include silicon-based, phosphorus-based, and phosphorus-nitrogen-based retardants. However, directly purchased flame retardants have problems such as large particle size, wide particle size distribution, strong odor, poor compatibility with viscose dope solution, and poor stability of the flame retardant dispersion. During spinning, problems such as fiber breakage and spinneret blockage are very likely to occur, resulting in poor spinnability. Furthermore, existing flame retardants are mostly single-element or two-element compound flame retardants, requiring large amounts, which affects the tensile strength, elongation at break, and other mechanical properties of viscose fiber, and makes the fiber feel rough, affecting wearing comfort.

[0003] Phosphorus-based flame retardants are the main types of flame-retardant viscose fibers. They are additive flame retardants. When this type of flame retardant burns, it can generate metaphosphoric acid, which is then converted into polymetaphosphoric acid, a more stable and strong dehydrating agent. This causes the polymer material to dehydrate and carbonize, forming a carbon film that covers the material surface, isolating the material from oxygen and achieving the flame-retardant effect.

[0004] Nitrogen-based flame retardants readily release non-flammable gases such as N2, NH3, NO2, CO2, and H2O when heated. These gases can dilute the concentration of oxygen in the air and the concentration of flammable gases generated during polymer combustion. At the same time, the heat convection generated during the formation of these non-flammable gases can carry away some of the surrounding heat. Furthermore, N2 can capture free radicals and interrupt the chain reaction of polymers, thereby achieving the effect of flame retardancy.

[0005] Silicon-based flame retardants are currently a key focus in the development of low-smoke, low-toxicity flame-retardant materials. Flame-retardant viscose fibers are often used in blends with nylon and other synthetic fibers. Silicon promotes char formation during combustion, creating a dense silicon-carbon layer that prevents secondary combustion caused by molten dripping from the polymer material. Modified phosphorus-nitrogen-silicon flame retardants integrate acid, char, and gas sources into their molecular structure, embedding silicon flame-retardant elements to achieve ideal char formation while providing flame retardancy. Summary of the Invention

[0006] The primary technical objective of this invention is to provide a phosphorus, nitrogen, and silicon synergistic flame retardant for viscose fibers. This flame retardant, used for viscose dope coloring, features small particle size, good storage stability and spinnability, low addition amount, and good flame retardancy, effectively improving spinneret clogging and reducing the impact on fiber mechanical properties.

[0007] The second technical objective of this invention is to provide the application of the above-mentioned phosphorus, nitrogen and silicon synergistic flame retardant for viscose fibers.

[0008] The first technical objective of this invention is achieved through the following technical solution:

[0009] A phosphorus-nitrogen-silicon synergistic flame retardant for viscose fibers, the raw materials for which are prepared include: phosphorus-nitrogen-silicon flame retardant, surfactant A, surfactant B and water, wherein the phosphorus-nitrogen-silicon flame retardant is prepared by modifying dithiophosphate flame retardant with diaminosiloxane at a concentration of 20-50 wt%.

[0010] The surfactant A is polyacrylamide with a concentration of 0.1-1 wt%.

[0011] The surfactant B is one or a combination of two or more of fatty alcohol polyoxyethylene ether, phenylphenol polyoxyethylene ether, castor oil polyoxyethylene ether, and fatty amine polyoxyethylene ether, with a concentration of 1-8 wt%.

[0012] This invention modifies a dithiophosphate pyrophosphate flame retardant with dual-terminated aminosiloxanes to obtain a phosphorus-nitrogen-silicon tri-element flame retardant, which is then dispersed with polyacrylamide, polyoxyethylene ether, and deionized water to obtain a phosphorus-nitrogen-silicon flame retardant dispersion. The modified phosphorus-nitrogen-silicon flame retardant integrates an acid source, a char source, and a gas source in its molecular structure, and incorporates silicon flame retardant elements, achieving ideal char formation while providing flame retardancy. The synergistic flame retardancy of the three elements effectively reduces spinneret clogging and minimizes the impact on fiber mechanical properties by reducing the amount added to viscose fibers. In the flame retardant dispersion of this invention, polyacrylamide is selected as a high-molecular-weight dispersant; its cross-linked network structure effectively prevents the loss of flame retardant during spinning and improves the wash resistance of the flame-retardant fiber.

[0013] Preferably, the diaminosiloxane is one of: diaminopropyl polydimethylsiloxane (structural formula 1) or 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (structural formula 2).

[0014] Structural Formula 1

[0015]

[0016] Structural formula 2.

[0017] Preferably, the thiophosphate flame retardant (DDPS) is 2,2'-dioxo(5,5-dimethyl-1,3,2-dioxophosphorus heterocyclic) 2,2'-disulfide (structure 3):

[0018]

[0019] Structural formula 3.

[0020] Preferably, the preparation method of the phosphorus-nitrogen-silicon flame retardant includes the following steps:

[0021] Dithiophosphate ester was dissolved in xylene, heated to 80-100℃, and then diaminosiloxane was slowly added dropwise under nitrogen protection. The reaction was carried out for 5-10 hours. After filtration, washing, and drying, phosphorus-nitrogen-silicon flame retardants (structural formula 4, structural formula 5) were obtained.

[0022] The phosphorus-nitrogen-silicon flame retardant, surfactant A, surfactant B, and deionized water were mixed evenly and then ground in a grinder to obtain a phosphorus-nitrogen-silicon flame retardant dispersion.

[0023] Structural Formula 4

[0024]

[0025] Structural Formula 5

[0026]

[0027] Preferably, the preparation of the phosphorus-nitrogen-silicon flame retardant adopts a stirring reaction device with a reflux condensation structure and a water separator, including a four-necked flask body, and the outer end of the four-necked flask body is composed of an installation mechanism, a control mechanism, a clamping mechanism and a height adjustment mechanism.

[0028] The clamping mechanism also includes a mounting plate, two sets of fixed plates, two sets of clamping frames, and two sets of electric telescopic rods. The top and middle of the mounting plate are provided with pickup through holes. The tops of the two sets of fixed plates are respectively connected to the left and right ends of the bottom of the mounting plate. The fixed ends of the two sets of electric telescopic rods are respectively connected to the middle area of ​​the inner end of the two sets of fixed plates. The output ends of the two sets of electric telescopic rods are respectively connected to the middle area of ​​the outer end of the two sets of clamping frames. The two sets of electric telescopic rods are electrically connected to the control mechanism. The left and right ends of the mounting plate are provided with height adjustment mechanisms.

[0029] More preferably, the stirring reaction device with a reflux condensation structure and a water distributor, the installation mechanism further includes a support platform and two sets of stabilizing plates, the bottom of the support platform is placed on the table, and the bottom of the two sets of stabilizing plates are respectively connected to the left and right sides of the top of the support platform.

[0030] More preferably, the height adjustment mechanism of the stirring reaction device with reflux condensation structure and water distributor further includes two sets of cylinders and two sets of connecting plates. The two sets of stabilizing plates are provided with sliding grooves. The two sets of connecting plates are slidably engaged with the sliding grooves provided with the two sets of stabilizing plates. The bottom ends of the two sets of cylinders are respectively connected to the left and right ends of the top of the support platform. The output ends of the two sets of cylinders are respectively connected to the left and right ends of the bottom of the two sets of connecting plates. The inner ends of the two sets of connecting plates are respectively connected to the left and right ends of the mounting plate. Both sets of cylinders are electrically connected to the control mechanism.

[0031] More preferably, the stirring reaction device with a reflux condensation structure and a water distributor further includes a controller in the control mechanism. The controller is electrically connected to two sets of cylinders and two sets of electric telescopic rods.

[0032] More preferably, in the stirring reaction device with a reflux condensation structure and a water distributor, the two sets of clamping frames are arranged in an arc shape.

[0033] In summary, the present invention has the following beneficial effects:

[0034] 1. This invention modifies a dithiophosphate pyrophosphate flame retardant with a dual-terminated aminosiloxane to obtain a phosphorus-nitrogen-silicon tri-element flame retardant. This is then dispersed with polyacrylamide, polyoxyethylene ether, and deionized water through grinding to obtain a phosphorus-nitrogen-silicon flame retardant dispersion. The modified phosphorus-nitrogen-silicon flame retardant integrates an acid source, a char source, and a gas source in its molecular structure, and incorporates silicon flame retardant elements, achieving ideal charring effects while providing flame retardancy. The synergistic flame retardancy of the three elements effectively reduces spinneret clogging and minimizes the impact on fiber mechanical properties by reducing the amount added to viscose fibers. In the flame retardant dispersion of this invention, polyacrylamide is selected as a high-molecular-weight dispersant. Its cross-linked network structure effectively prevents the loss of flame retardant during spinning and improves the wash resistance of the flame-retardant fiber.

[0035] 2. In the preparation of the phosphorus-nitrogen-silicon flame retardant of the present invention, the four-necked flask body, mounting plate, two sets of fixing plates, two sets of clamping frames, two sets of electric telescopic rods, pickup through hole, support platform, two sets of stabilizing plates, two sets of cylinders, two sets of connecting plates and controller are used. When it is necessary to fix the four-necked flask, the controller starts the two sets of electric telescopic rods, which drive the two sets of clamping frames to clamp the four-necked flask. Then, the height adjustment mechanism is used to adjust the four-necked flask to a suitable heating height, and then the phosphorus-nitrogen-silicon flame retardant can be prepared. Through a mechanism that facilitates stable installation of the four-necked flask and easy height adjustment, the device is made more stable, thus enhancing the efficiency and effect of the reaction device.

[0036] 3. This flame retardant is used for viscose dope coloring. It features small particle size, good storage stability and spinnability, low addition amount and good flame retardancy, effectively improving spinneret clogging and reducing the impact on fiber mechanical properties. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the stirring reaction device with a reflux condensation structure and a water separator used in the preparation of the phosphorus-nitrogen-silicon flame retardant of the present invention.

[0038] Figure 2 This is a schematic diagram of the connection structure of the two sets of cylinders and the two sets of connecting plates of the present invention.

[0039] Figure 3 This is a top view of the stirring reaction apparatus of the present invention.

[0040] The attached diagram is labeled as follows: 1. Four-necked flask body; 2. Mounting plate; 3. Two sets of fixing plates; 4. Two sets of clamping frames; 5. Two sets of electric telescopic rods; 6. Pick-up through hole; 7. Support platform; 8. Two sets of stabilizing plates; 9. Two sets of cylinders; 10. Two sets of connecting plates; 11. Controller; 12. Protective pad; 13. Anti-slip pad. Detailed Implementation

[0041] Example 1

[0042] 0.05 mol (17.31 g) of dithiophosphate was added to a 250 mL four-necked flask equipped with a mechanical stirrer, thermometer, reflux condenser, and water separator. The solution was dissolved in 100 mL of xylene. The mixture was heated to 100 °C, and under N2 protection, 0.06 mol (14.9 g) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane was slowly added dropwise. The mixture was then refluxed at 120 °C for 8 h, during which time the water generated in the water separator was promptly removed. After the reaction was stopped, the reaction solution was cooled to room temperature, filtered, and the filter cake was washed with xylene and water, respectively. The cake was then dried under vacuum at 60 °C for 10 h to obtain a phosphorus-nitrogen-silicon flame retardant (structural formula 4).

[0043] 0.5g of polyacrylamide and 6g of phenylphenol polyoxyethylene ether were added to 63.5g of deionized water and mixed evenly at 500rpm. Then, 30g of the above phosphorus-nitrogen-silicon flame retardant was added and stirred at 1000rpm for 1h. The mixture was then ground in a grinder for 2h. The particle size D95 was measured to be <0.5μm using a laser particle size analyzer, thus obtaining the phosphorus-nitrogen-silicon flame retardant dispersion.

[0044] The above phosphorus-nitrogen-silicon dispersion and viscose dispersion were mixed evenly at a ratio of 5:100. The mixed spinning solution was then spun through a 30-hole, 0.08 mm spinneret at a spinning speed of 15 m / min to obtain phosphorus-nitrogen-silicon ternary synergistic flame-retardant viscose fiber. No clogging of the spinneret was observed after 2 hours of continuous spinning. The limiting oxygen index (LOI) of the fiber was 29% according to FZ / T50016-2011 "Test Method for Flame Retardant Properties of Viscose Staple Fibers - Oxygen Index Method". The dry breaking strength of the fiber was 2.3 CN / dtex and the wet breaking strength was 1.2 CN / dtex according to GB / T 14337-2008 "Test Method for Tensile Properties of Chemical Fibers - Staple Fibers".

[0045] Example 2

[0046] 0.05 mol of 17.31 g of dithiophosphate was added to a 250 mL four-necked flask equipped with a mechanical stirrer, thermometer, reflux condenser, and water separator. The solution was dissolved in 100 mL of xylene. The mixture was heated to 100 °C, and 0.06 mol of 19.35 g of diaminopropyl polydimethylsiloxane was slowly added dropwise under N2 protection. The mixture was then refluxed at 130 °C for 10 h, during which time the water generated in the water separator was promptly removed. After the reaction was stopped, the reaction solution was cooled to room temperature, filtered, and the filter cake was washed with xylene and water, respectively. The cake was then dried under vacuum at 60 °C for 10 h to obtain a phosphorus-nitrogen-silicon flame retardant (structural formula 5).

[0047] like Figures 1 to 3 As shown, the preparation of phosphorus-nitrogen-silicon flame retardant in this embodiment adopts a stirring reaction device with a reflux condensation structure and a water separator, including a four-necked flask body 1. The outer end of the four-necked flask body 1 is composed of an installation mechanism, a control mechanism, a clamping mechanism and a height adjustment mechanism.

[0048] The clamping mechanism also includes a mounting plate 2, two sets of fixing plates 3, two sets of clamping frames 4, and two sets of electric telescopic rods 5. The mounting plate 2 has pickup through holes 6 at its top and middle. The tops of the two sets of fixing plates 3 are connected to the left and right ends of the bottom of the mounting plate 2, respectively. The fixed ends of the two sets of electric telescopic rods 5 are connected to the middle areas of the inner ends of the two sets of fixing plates 3, respectively. The output ends of the two sets of electric telescopic rods 5 are connected to the middle areas of the outer ends of the two sets of clamping frames 4, respectively. The two sets of electric telescopic rods 5 are electrically connected to the control mechanism. Height adjustment mechanisms are provided at both ends of the mounting plate 2. The mechanism utilizes the four-necked flask body, mounting plate, two sets of fixing plates, and two sets of clamping frames 4. The device comprises a frame, two sets of electric telescopic rods, a pickup through-hole, a support platform, two sets of stabilizing plates, two sets of cylinders, two sets of connecting plates, and a controller. When it is necessary to fix the four-necked flask, the controller activates the two sets of electric telescopic rods, which drive the two sets of clamping frames to clamp the four-necked flask. Then, the height adjustment mechanism adjusts the four-necked flask to a suitable heating height, and then the phosphorus-nitrogen-silicon flame retardant can be prepared. Through a mechanism that facilitates stable installation of the four-necked flask and easy height adjustment, the device is made more stable, thus enhancing the efficiency and effectiveness of the reaction apparatus.

[0049] The installation mechanism of this stirring reaction device also includes a support platform 7 and two sets of stabilizing plates 8. The bottom of the support platform 7 is placed on the table, and the bottom of the two sets of stabilizing plates 8 are respectively connected to the left and right sides of the top of the support platform 7. The use of the installation mechanism makes the device more stable, thereby enhancing its practicality.

[0050] This stirring reaction apparatus includes a height adjustment mechanism comprising two sets of cylinders 9 and two sets of connecting plates 10. The two sets of stabilizing plates 8 are provided with sliding grooves, and the two sets of connecting plates 10 are slidably engaged with these grooves. The bottom ends of the two sets of cylinders 9 are connected to the left and right ends of the top of the support platform 7, respectively. The output ends of the two sets of cylinders 9 are connected to the left and right ends of the bottom of the two sets of connecting plates 10, respectively. The inner ends of the two sets of connecting plates 10 are connected to the left and right ends of the mounting plate 2, respectively. Both sets of cylinders 9 are electrically connected to a control mechanism. The controller drives the two sets of cylinders, which in turn drive the two sets of connecting plates to adjust the height. The height adjustment mechanism then adjusts the four-necked flask to a suitable heating height, allowing for the preparation of the phosphorus-nitrogen-silicon flame retardant. This design, which facilitates stable installation of the four-necked flask and easy height adjustment, makes the apparatus more stable, thus enhancing the efficiency and effectiveness of the reaction apparatus and improving its practicality.

[0051] The control mechanism of this stirring reaction device also includes a controller 11, which is electrically connected to two sets of cylinders 9 and two sets of electric telescopic rods 5. The controller facilitates the adjustment of the device, thereby enhancing its practicality.

[0052] This invention provides a stirred reaction apparatus with a reflux condenser structure and a water separator, further comprising a protective pad 12 and an anti-slip pad 13. The protective pad 12 is installed inside both sets of clamping frames 4; the use of the protective pad prevents damage to the four-necked flask by the two sets of clamping frames. The bottom of the support platform 7 is provided with an anti-slip pad 13; the use of the anti-slip pad makes the support platform more stable, thereby enhancing practicality. The two sets of clamping frames 4 are arc-shaped; the use of the two sets of clamping frames makes the four-necked flask more securely fixed, preventing it from shaking, thereby enhancing practicality.

[0053] This invention discloses a stirring reaction device with a reflux condensation structure and a water separator. Before performing the aforementioned actions, the device is first moved to the desired location. Using the four-necked flask body, mounting plate, two sets of fixing plates, two sets of clamping frames, two sets of electric telescopic rods, a pickup through-hole, a support platform, two sets of stabilizing plates, two sets of cylinders, two sets of connecting plates, and a controller, when the four-necked flask needs to be fixed, the controller activates the two sets of electric telescopic rods. These rods drive the two sets of clamping frames to clamp the flask. Then, a height adjustment mechanism adjusts the flask to a suitable heating height, allowing for the preparation of the phosphorus-nitrogen-silicon flame retardant.

[0054] 0.3g of polyacrylamide and 8g of fatty alcohol polyoxyethylene ether were added to 61.7g of deionized water and mixed evenly at 500rpm. Then, 30g of the above phosphorus-nitrogen-silicon flame retardant was added and stirred at 1000rpm for 1h. The mixture was then ground in a grinder for 2 hours. The particle size D95 was measured to be <0.5μm using a laser particle size analyzer to obtain the phosphorus-nitrogen-silicon flame retardant dispersion.

[0055] The above phosphorus-nitrogen-silicon dispersion and viscose dispersion were mixed evenly at a ratio of 5:100. The mixed spinning solution was then spun through a 30-hole, 0.08 mm spinneret at a spinning speed of 15 m / min to obtain phosphorus-nitrogen-silicon ternary synergistic flame-retardant viscose fiber. No clogging of the spinneret was observed after 2 hours of continuous spinning. The limiting oxygen index (LOI) of the fiber was 29.5% according to FZ / T50016-2011 "Test Method for Flame Retardant Properties of Viscose Staple Fibers - Oxygen Index Method". The dry breaking strength of the fiber was 2.4 CN / dtex and the wet breaking strength was 1.2 CN / dtex according to GB / T 14337-2008 "Test Method for Tensile Properties of Chemical Fibers - Staple Fibers".

[0056] Comparative Example 1

[0057] Similar to Example 1, except that surfactant A is not present; only surfactant B is used at a concentration of 10 wt%. The obtained phosphorus-nitrogen-silica dispersion and viscose dispersion are mixed evenly at a ratio of 5:100. The evenly mixed spinning solution is spun through a 30-hole, 0.08 mm spinneret at a spinning speed of 15 m / min to obtain phosphorus-nitrogen-silica ternary synergistic flame-retardant viscose fiber. The limiting oxygen index (LOI) of the fiber is 26% according to FZ / T 50016-2011 "Test Method for Flame Retardant Properties of Viscose Staple Fibers - Oxygen Index Method". The dry breaking strength of the fiber is 1.9 CN / dtex and the wet breaking strength is 0.9 CN / dtex according to GB / T 14337-2008 "Test Method for Tensile Properties of Chemical Fibers - Staple Fibers".

[0058] Comparative Example 2

[0059] Similar to Example 2, but without surfactant B, only surfactant A was used at a concentration of 0.08 wt%. The obtained phosphorus-nitrogen-silicon dispersion and viscose dispersion were mixed evenly at a ratio of 5:100. The mixed spinning solution was then spun through a 30-hole, 0.08 mm spinneret at a spinning speed of 15 m / min to obtain phosphorus-nitrogen-silicon ternary synergistic flame-retardant viscose fiber. After 1 hour of spinning, the spinneret became clogged.

[0060] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A phosphorus-nitrogen-silicon three-element synergistic flame retardant for viscose fibers, characterized by The raw materials for preparation include: phosphorus-nitrogen-silicon flame retardant, surfactant A, surfactant B, and water. The phosphorus-nitrogen-silicon flame retardant is prepared by modifying dithiophosphate flame retardant with diaminosiloxanes, and the concentration is 20-50 wt%. The surfactant A is polyacrylamide, with a concentration of 0.1-1 wt%. The surfactant B is one or a combination of two or more of fatty alcohol polyoxyethylene ether, phenylphenol polyoxyethylene ether, castor oil polyoxyethylene ether, and fatty amine polyoxyethylene ether, with a concentration of 1-8 wt%. The dual-terminated aminosiloxane is one of: diaminopropyl polydimethylsiloxane (structural formula 1) or 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (structural formula 2). ； Structural Formula 1; ； Structural Formula 2; The dithiophosphate flame retardant (DDPS) is 2,2'-dioxo(5,5-dimethyl-1,3,2-dioxophosphorus heterocyclic)2,2'-disulfide (structural formula 3): ； Structure 3; The preparation method of the phosphorus-nitrogen-silicon flame retardant includes the following steps: Dithiophosphate esters were dissolved in xylene, and the mixture was heated to 80-100℃. Under nitrogen protection, diaminosiloxanes were slowly added dropwise. The reaction was allowed to proceed for 5-10 hours. After filtration, washing, and drying, a phosphorus-nitrogen-silicon flame retardant was obtained, with structural formula 4 or 5. The phosphorus-nitrogen-silicon flame retardant, surfactant A, surfactant B, and deionized water were mixed evenly and then ground to obtain a phosphorus-nitrogen-silicon flame retardant dispersion. Structural Formula 4; ； Structural formula 5; ； The preparation method of the phosphorus-nitrogen-silicon flame retardant includes dissolving dithiophosphate in xylene, heating to 80-100℃, slowly adding diaminosiloxane dropwise under nitrogen protection, refluxing at 110-140℃ for 5-10 hours, and separating the water generated in the water separator during the process; after stopping the reaction, cooling the reaction solution to room temperature, filtering, washing the filter cake with xylene and water respectively, and vacuum drying at 50-70℃ for 8-12 hours to obtain the phosphorus-nitrogen-silicon flame retardant; The preparation of the phosphorus-nitrogen-silicon flame retardant adopts a stirring reaction device with a reflux condensation structure and a water separator, including a four-necked flask body (1), and the outer end of the four-necked flask body (1) is composed of an installation mechanism, a control mechanism, a clamping mechanism and a height adjustment mechanism. The clamping mechanism also includes a mounting plate (2), two sets of fixed plates (3), two sets of clamping frames (4) and two sets of electric telescopic rods (5). The top and middle of the mounting plate (2) are provided with pickup through holes (6). The tops of the two sets of fixed plates (3) are respectively connected to the left and right ends of the bottom of the mounting plate (2). The fixed ends of the two sets of electric telescopic rods (5) are respectively connected to the middle area of ​​the inner end of the two sets of fixed plates (3). The output ends of the two sets of electric telescopic rods (5) are respectively connected to the middle area of ​​the outer end of the two sets of clamping frames (4). The two sets of electric telescopic rods (5) are respectively electrically connected to the control mechanism. The left and right ends of the mounting plate (2) are provided with height adjustment mechanisms. The installation mechanism also includes a support platform (7) and two sets of stabilizing plates (8). The bottom of the support platform (7) is placed on the table, and the bottom of the two sets of stabilizing plates (8) are respectively connected to the left and right sides of the top of the support platform (7). The height adjustment mechanism also includes two sets of cylinders (9) and two sets of connecting plates (10). The two sets of stabilizing plates (8) are provided with sliding grooves. The two sets of connecting plates (10) are slidably engaged with the sliding grooves provided by the two sets of stabilizing plates (8). The bottom ends of the two sets of cylinders (9) are connected to the left and right ends of the top of the support platform (7). The output ends of the two sets of cylinders (9) are connected to the left and right ends of the bottom of the two sets of connecting plates (10). The inner ends of the two sets of connecting plates (10) are connected to the left and right ends of the mounting plate (2). Both sets of cylinders (9) are electrically connected to the control mechanism. The control mechanism also includes a controller (11), which is electrically connected to two sets of cylinders (9) and two sets of electric telescopic rods (5); the two sets of clamping frames (4) are set in an arc shape.

2. The use of the phosphorus-nitrogen-silicon three-element synergistic flame retardant for viscose fibers according to claim 1, characterized by the fact that it is used in an amount of 0.5 to 2% by weight of the total weight of the viscose fibers. It is used to mix evenly with viscose dispersion, and the evenly mixed spinning solution is spun to obtain phosphorus, nitrogen and silicon ternary synergistic flame retardant viscose fiber.

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