Flame-retardant super-hydrophobic polyamide fiber and preparation method thereof

Abstract

The invention relates to a flame-retardant super-hydrophobic polyamide fiber and a preparation method thereof. The method comprises the following steps: carrying out mixed polycondensation on a polycondensation unit of hexa (2-allylphenoxy)-cyclotriphosphazene and a polycondensation unit of nylon-66 to obtain a polymer containing an N-P flame-retardant block, then carrying out mixed spinning on the polymer, hexaphenoxy cyclotriphosphazene and octaphenoxy cyclotetraphosphazene according to a ratio, and finally, carrying out coating with siloxane, nano-silica and epoxy resin to complete the preparation. The polyamide fiber prepared by the technical scheme of the invention has excellent flame retardance, has a super-hydrophobic surface, can keep a substrate clean and dry, and provides a new method for solving the problem of low water resistance of a flame retardant; meanwhile, the fiber provided by the invention has a super-hydrophobic function, so that the subsequent process procedure of secondary processing by using a waterproof finishing agent can be omitted.

Description

Technical Field

[0001] The present application belongs to the field of polyamide fibers, and specifically relates to a flame retardant super-hydrophobic polyamide fiber and a preparation method thereof. Background Art

[0002] Polyamide fiber has been widely used in clothing, decoration, packaging, etc. due to its wear resistance, comfort, flexibility and other characteristics. However, the flammability of polyamide fiber often brings fire hazards, posing a serious threat to human life and property safety. Therefore, it is urgent to find a way to improve the flame retardancy of polyamide fiber to prevent the spread of fire, thereby reducing or eliminating the fire risk of cotton fabrics.

[0003] The search formula is ((polyamide OR nylon-66) AND (TA:("flame retardant" OR "fireproof" OR "fire-resistant"))) AND (IPC:(C08L77 / 00)) and combined with the analysis of the prior art published in papers, it can be found that in the prior art, flame retardants are generally added to polyamide fibers, among which halogen-containing compounds are the most effective and economical flame retardants. However, they are gradually being eliminated because they produce toxic and corrosive gases when burned, causing secondary pollution to the environment. As an alternative, halogen-free flame retardants have attracted widespread attention due to their low toxicity. However, this type of flame retardant is more susceptible to moisture, resulting in a decrease in material performance and a weakened flame retardant effect.

[0004] Therefore, how to develop a polyamide fiber with flame retardant and hydrophobic effects is crucial. Summary of the invention

[0005] In order to reconcile the flame retardant effect and hydrophobic effect of polyamide fiber, the present application provides a flame retardant super hydrophobic polyamide fiber and a preparation method thereof, wherein the polycondensation units of hexa(2-allylphenoxy)-cyclotriphosphazene and nylon-66 are mixed, and the three are polycondensed together to obtain a PA66 polymer containing an NP flame retardant block, and then the modified PA66 polymer is mixed with hexaphenoxy cyclotriphosphazene and octaphenoxy cyclotetraphosphazene in a specific proportion for spinning, and assisted by coating with siloxane, nano-silica and epoxy resin, to obtain a polyamide fiber, which has self-extinguishing properties during vertical combustion and significant hydrophobicity.

[0006] In a first aspect, the present application provides a method for preparing a flame retardant super-hydrophobic polyamide fiber, using the following technical solution: A method for preparing a flame-retardant super-hydrophobic polyamide fiber comprises the following steps: mixing and polycondensing hexa(2-allylphenoxy)-cyclotriphosphazene and polycondensation units of nylon-66 to obtain a polymer containing an NP flame-retardant block; then mixing the polymer with hexaphenoxy cyclotriphosphazene and octaphenoxy cyclotetraphosphazene in proportion and spinning the mixture; and finally coating the mixture with siloxane, nano-silica and epoxy resin to complete the preparation.

[0007] In a specific implementation scheme, the method comprises the following specific steps: Polymerization: adding hexa(2-allylphenoxy)-cyclotriphosphazene, hexamethylenediamine and adipic acid into a reactor at a weight ratio of (0.12-0.28):1:1, and performing polymerization reaction to obtain a PA66 polymer containing a NP flame retardant block; Mixing: adding hexaphenoxy cyclotriphosphazene and octaphenoxy cyclotetraphosphazene into a reaction kettle; controlling the temperature to be 245-270 degrees Celsius, and extruding and mixing to obtain a mixture; Spinning: After mixing, the mixture is spun to obtain a crude polyamide fiber with intrinsic flame retardancy; Infiltration coating: Nano-silica was dispersed in organic alcohol as solvent to prepare a 5% concentration solution for standby use, which was recorded as solution 1; PDMS was dissolved in xylene at room temperature and was set aside for standby use, which was recorded as solution 2; water-based epoxy resin solution, 20% to 55% solid content, was recorded as solution 3; Soak the crude polyamide fiber in solutions 1, 2, and 3, add 5% water-based epoxy curing agent, stir, and then take out and let stand; The coating is completed by drying at 80 degrees Celsius for 60 minutes on the surface of the polyamide fiber crude product, thereby obtaining the flame retardant super hydrophobic polyamide fiber.

[0008] In a specific embodiment, the polymerization step specifically includes the following: Prepolymerization: Mix hexa(2-allylphenoxy)-cyclotriphosphazene, adipic acid and hexamethylenediamine in a weight ratio of (0.12-0.28):1:1 and put them into a reactor; heat the reactor to 270-290 degrees Celsius; Evaporation: The prepolymerized material is passed into the evaporator to increase the mass fraction of the target product in the material from 50% to more than 70%; Further reaction; the material is sequentially passed into a flash evaporator and a post-polymerizer for dehydration to complete the polycondensation reaction, thereby obtaining a PA66 polymer containing a NP flame retardant block.

[0009] In a specific embodiment, in the mixing step, hexaphenoxy cyclotriphosphazene and octaphenoxy cyclotetraphosphazene are added in a weight ratio of PA66 polymer containing NP flame retardant block: hexaphenoxy cyclotriphosphazene: octaphenoxy cyclotetraphosphazene = 1: (0.02-0.08): (0.01:0.05).

[0010] In a specific embodiment, in the impregnation coating, the impregnation sequence is that the crude polyamide fiber is first impregnated in solution 1, then in solution 2, and finally in solution 3.

[0011] In a specific implementation scheme, the infiltration and coating step specifically includes: the crude polyamide fiber is first immersed in solution 1 for 1 to 3 minutes, and then allowed to stand at room temperature for 30 minutes; then immersed in solution 2 for 2 to 8 minutes, and cured at 60 to 80 degrees Celsius for 15 to 25 minutes; finally immersed in solution 3 for 2 to 4 minutes, and 5% water-based epoxy curing agent HTW-208 is added at the same time, stirred, and then taken out and allowed to stand for 15 minutes.

[0012] In a second aspect, the present application provides a flame retardant super hydrophobic polyamide fiber, which is prepared by the above preparation method.

[0013] Beneficial technical effects of the present application: The polyamide fiber prepared by the technical solution of the present application has excellent flame retardancy and a super-hydrophobic surface, which can keep the substrate clean and dry, and provides a new method for solving the problem of low water resistance of flame retardants; at the same time, the fiber of the present application has its own super-hydrophobic function, which can save the subsequent process of using a waterproof finishing agent for secondary processing. DETAILED DESCRIPTION

[0014] The present application is described in further detail below.

[0015] At present, polyamide fibers based on nylon-66 have the technical problem of being flammable, and adding flame retardants to them has requirements for their hydrophobicity. Therefore, on the basis of the flame retardancy of polyamide fibers, it is a crucial issue to develop a flame retardant polyamide fiber with hydrophobicity. After a large number of modification experiments on nylon-66, the inventor obtained the following technical scheme: the polycondensation units of hexa(2-allylphenoxy)-cyclotriphosphazene and nylon-66 are mixed, and the three are polycondensed together to obtain a PA66 polymer containing an NP flame retardant block, and then the modified PA66 polymer is mixed with hexaphenoxy cyclotriphosphazene and octaphenoxy cyclotetraphosphazene in a specific proportion for spinning, and assisted by the coating of siloxane, nano-silica and epoxy resin, a polyamide fiber can be obtained. The polyamide fiber has self-extinguishing properties during vertical combustion and has significant hydrophobicity. The specific preparation method is: Step 1: Aggregation: First, hexa(2-allylphenoxy)-cyclotriphosphazene, hexamethylenediamine, and adipic acid are added to the reactor in a weight ratio (0.12-0.28): 1:1 to carry out polymerization reaction; the polymerization reaction can be divided into three steps according to its reaction process: the first step is prepolymerization; the raw materials hexa(2-allylphenoxy)-cyclotriphosphazene, adipic acid, and hexamethylenediamine are mixed together and put into the reactor. The reactor is heated to a specific temperature (usually around 270-290 degrees Celsius). During the heating process, the agitator continues to stir to fully mix the three raw materials and ensure that the materials are in a good flow state; the mixture undergoes a polycondensation reaction to form an aqueous solution of the prepolymer. The reaction time is about 3 hours. During this period, the reaction conditions are monitored in real time by the temperature and pressure monitoring device on the reactor to ensure that the reaction proceeds stably. The second step is evaporation; the material is passed from the reactor through a pipeline into the evaporator, and the evaporator is heated by steam to evaporate the water and concentrate the salt solution, thereby increasing the mass fraction of the target product in the material from 50% to more than 70%. The evaporator uses two shell-and-tube heat exchangers to preheat the aqueous solution of the prepolymer from 150°C to the initial reaction temperature of 210°C, and the reaction time is 2 hours. The third step is further reaction; first, the material is passed into the flash evaporator; there is a snake in the flash evaporator that suddenly changes from thin to thick, the inlet pressure is 2 MPa, and the outlet pressure is normal pressure; after the material passes through the flash evaporator, the pressure drops rapidly to normal pressure, and the water with a temperature of up to 280°C is quickly vaporized. At the same time, the pressure energy is converted into kinetic energy, so that the mixture of material and water enters the cyclone separator at a high speed, the material is separated from the water, and the material enters the post-polymerizer. There is a screw propeller in the post-polymerizer, and the material forms a thin film only a few millimeters thick on the blades of the screw propeller, which is convenient for quickly removing water molecules, so that the relative molecular mass of the polymer meets the process requirements and completes the polycondensation reaction. The reaction time is 3.5 hours. After these three steps of reaction, a PA66 polymer containing NP flame retardant blocks is obtained, which is recorded as polymer A.

[0016] It should be noted that the reactor of the present application is made of industrial-grade stainless steel, and the heating method can be steam heating or electric heating. The built-in stirring system of the reactor can be an anchor propeller or a paddle stirrer; its capacity is 500L, and it is equipped with a safety valve and a bursting disc.

[0017] Step 2: Mixing: According to the ratio of polymer A obtained in step 1: hexaphenoxy cyclotriphosphazene: octaphenoxy cyclotetraphosphazene = 1: (0.02-0.08): (0.01:0.05) (weight ratio), hexaphenoxy cyclotriphosphazene and octaphenoxy cyclotetraphosphazene are added to the reactor; the addition method is to add by a precision weight loss scale, the PA66 polymer with NP flame retardant block is added as the main feed, and hexaphenoxy cyclotriphosphazene and octaphenoxy cyclotetraphosphazene are added as the two side feeds respectively, the temperature is controlled at 245-270 degrees Celsius, and the rotation speed of a co-rotating twin-screw extruder is controlled at 450rpm for mixing to obtain a mixture 1.

[0018] Step 3, Spinning: After mixing, the mixture 1 is spun to obtain a crude polyamide fiber having intrinsic flame retardancy and having more polar groups on its surface.

[0019] Step 4: Coating of silica nanoparticles and polydimethylsiloxane (PDMS) / epoxy resin (EP): ① Use organic alcohol as solvent (ethanol, isopropanol and mixture) to disperse nano-silica and prepare a 5% concentration solution for standby use, which is recorded as solution 1; PDMS is dissolved in xylene at room temperature (3% concentration) and is set aside for standby use, which is recorded as solution 2; water-based epoxy resin solution, 20% to 55% solid content, is recorded as solution 3; ② The crude polyamide fiber is first soaked in solution 1 for 1-3 minutes, and then allowed to stand at room temperature for 30 minutes; then soaked in solution 2 for 2-8 minutes, and cured at 60-80 degrees Celsius for 15-25 minutes; finally soaked in solution 3 for 2-4 minutes, and 5% water-based epoxy curing agent HTW-208 (60% solid content) is added at the same time, stirred, and then taken out and allowed to stand for 15 minutes; ③ Dry at 80 degrees Celsius for 60 minutes to complete the coating on the surface of the polyamide fiber crude product, thereby obtaining a flame retardant super hydrophobic polyamide fiber.

[0020] The polyamide fiber obtained by the above scheme not only has excellent flame retardancy (LOI oxygen index is above 32%, and WCA can still be maintained at > 150° after 250 linear frictions) The above scheme is further demonstrated and explained below in combination with specific embodiments and experimental data.

[0021] Example 1 This embodiment provides a flame retardant super hydrophobic polyamide fiber, and the preparation method thereof comprises the following steps: Step 1: Aggregation: The raw materials hexa(2-allylphenoxy)-cyclotriphosphazene, adipic acid, and hexamethylenediamine were mixed together in a weight ratio of 0.12:1:1 and put into a reactor; the reactor was heated to 270 degrees Celsius, the reaction time was 3 hours, and the mixture underwent a polycondensation reaction to form an aqueous solution of a prepolymer; the material was passed into an evaporator to evaporate the water and concentrate the salt solution, thereby increasing the mass fraction of the target product in the material to more than 70%; the material was then passed into a flash evaporator and a post-polymerizer in sequence to complete the polycondensation reaction and obtain a PA66 polymer containing an NP flame retardant block, which was recorded as polymer A.

[0022] Step 2: Mixing: According to the ratio of polymer A obtained in step 1: hexaphenoxy cyclotriphosphazene: octaphenoxy cyclotetraphosphazene = 1:0.02:0.01 (weight ratio), hexaphenoxy cyclotriphosphazene and octaphenoxy cyclotetraphosphazene are added to the reactor; the temperature is controlled at 245 degrees Celsius, and the rotation speed is controlled at 450 rpm by a co-rotating twin-screw extruder to obtain a mixture 1.

[0023] Step 3, Spinning: The mixture 1 is spun to obtain a crude polyamide fiber having intrinsic flame retardancy.

[0024] Step 4: Coating of silica nanoparticles and polydimethylsiloxane (PDMS) / epoxy resin (EP): ① Use ethanol to disperse nano-silica and prepare a 5% concentration solution for standby use, which is recorded as solution 1; PDMS is dissolved in xylene at room temperature (3% concentration) and is set aside for standby use, which is recorded as solution 2; water-based epoxy resin solution, 20% solid content, is recorded as solution 3; ② The crude polyamide fiber was first soaked in solution 1 for 1 minute, and then allowed to stand at room temperature for 30 minutes; then soaked in solution 2 for 2 minutes, and cured at 60 degrees Celsius for 25 minutes; finally soaked in solution 3 for 2 minutes, and 5% water-based epoxy curing agent HTW-208 (60% solid content) was added at the same time, stirred, and then taken out and allowed to stand for 15 minutes; ③ Dry at 80 degrees Celsius for 60 minutes to complete the coating on the surface of the polyamide fiber crude product, thereby obtaining a flame retardant super hydrophobic polyamide fiber.

[0025] Example 2 This embodiment provides a flame retardant super hydrophobic polyamide fiber, and the preparation method thereof comprises the following steps: Step 1: Aggregation: The raw materials hexa(2-allylphenoxy)-cyclotriphosphazene, adipic acid, and hexamethylenediamine were mixed together in a weight ratio of 0.18:1:1 and put into a reactor; the reactor was heated to 280 degrees Celsius, the reaction time was 3 hours, and the mixture underwent a polycondensation reaction to form an aqueous solution of a prepolymer; the material was passed into an evaporator to evaporate the water and concentrate the salt solution, thereby increasing the mass fraction of the target product in the material to more than 70%; the material was then passed into a flash evaporator and a post-polymerizer in sequence to complete the polycondensation reaction and obtain a PA66 polymer containing an NP flame retardant block, which was recorded as polymer A.

[0026] Step 2: Mixing: According to the ratio of polymer A obtained in step 1: hexaphenoxy cyclotriphosphazene: octaphenoxy cyclotetraphosphazene = 1:0.05:0.03 (weight ratio), hexaphenoxy cyclotriphosphazene and octaphenoxy cyclotetraphosphazene were added to the reactor; the temperature was controlled at 260 degrees Celsius, and the rotation speed was controlled at 450 rpm by a co-rotating twin-screw extruder to obtain a mixture 1.

[0027] Step 3, Spinning: The mixture 1 is spun to obtain a crude polyamide fiber having intrinsic flame retardancy.

[0028] Step 4: Coating of silica nanoparticles and polydimethylsiloxane (PDMS) / epoxy resin (EP): ① Disperse nano-silica in a mixed solvent of ethanol and isopropanol in a volume ratio of 1:2, and prepare a 5% concentration solution for standby use, which is recorded as solution 1; PDMS is dissolved in xylene at room temperature (3% concentration) and is set aside for standby use, which is recorded as solution 2; water-based epoxy resin solution, 36% solid content, is recorded as solution 3; ② The crude polyamide fiber was first soaked in solution 1 for 2 minutes, and then allowed to stand at room temperature for 30 minutes; then soaked in solution 2 for 5 minutes, and cured at 70 degrees Celsius for 20 minutes; finally soaked in solution 3 for 5 minutes, and 5% water-based epoxy curing agent HTW-208 (60% solid content) was added at the same time, stirred, and then taken out and allowed to stand for 15 minutes; ③ Dry at 80 degrees Celsius for 60 minutes to complete the coating on the surface of the polyamide fiber crude product, thereby obtaining a flame retardant super hydrophobic polyamide fiber.

[0029] Example 3 This embodiment provides a flame retardant super hydrophobic polyamide fiber, and the preparation method thereof comprises the following steps: Step 1: Aggregation: The raw materials hexa(2-allylphenoxy)-cyclotriphosphazene, adipic acid, and hexamethylenediamine were mixed together in a weight ratio of 0.28:1:1 and put into a reactor; the reactor was heated to 290 degrees Celsius, the reaction time was 3 hours, and the mixture underwent a polycondensation reaction to form an aqueous solution of a prepolymer; the material was passed into an evaporator to evaporate the water and concentrate the salt solution, thereby increasing the mass fraction of the target product in the material to more than 70%; the material was then passed into a flash evaporator and a post-polymerizer in sequence to complete the polycondensation reaction and obtain a PA66 polymer containing an NP flame retardant block, which was recorded as polymer A.

[0030] Step 2: Mixing: According to the ratio of polymer A obtained in step 1: hexaphenoxy cyclotriphosphazene: octaphenoxy cyclotetraphosphazene = 1:0.08:0.05 (weight ratio), hexaphenoxy cyclotriphosphazene and octaphenoxy cyclotetraphosphazene were added to the reactor; the temperature was controlled at 270 degrees Celsius, and the rotation speed was controlled at 450 rpm by a co-rotating twin-screw extruder to obtain a mixture 1.

[0031] Step 3, Spinning: The mixture 1 is spun to obtain a crude polyamide fiber having intrinsic flame retardancy.

[0032] Step 4: Coating of silica nanoparticles and polydimethylsiloxane (PDMS) / epoxy resin (EP): ① Use isopropanol as solvent to disperse nano-silica and prepare a 5% concentration solution for standby use, which is recorded as solution 1; PDMS is dissolved in xylene at room temperature (3% concentration) and is set aside for standby use, which is recorded as solution 2; water-based epoxy resin solution, 55% solid content, is recorded as solution 3; ② The crude polyamide fiber was first soaked in solution 1 for 3 minutes, and then allowed to stand at room temperature for 30 minutes; then soaked in solution 2 for 8 minutes, and cured at 80 degrees Celsius for 15 minutes; finally soaked in solution 3 for 4 minutes, and 5% water-based epoxy curing agent HTW-208 (60% solid content) was added at the same time, stirred, and then taken out and allowed to stand for 15 minutes; ③ Dry at 80 degrees Celsius for 60 minutes to complete the coating on the surface of the polyamide fiber crude product, thereby obtaining a flame retardant super hydrophobic polyamide fiber.

[0033] Comparative Example 1 This comparative example provides a flame-retardant super-hydrophobic polyamide fiber, and its preparation method is different from that of Example 1 only in that: in step 1, hexa(2-allylphenoxy)-cyclotriphosphazene, adipic acid, and hexamethylenediamine are mixed together in a weight ratio of 0.1:1:1 and put into a reactor.

[0034] Comparative Example 2 This comparative example provides a flame retardant super-hydrophobic polyamide fiber, and the preparation method thereof is different from that of Example 1 only in that: in step 2, all of the hexaphenoxy cyclotriphosphazene added in the reaction kettle is replaced with octaphenoxy cyclotetraphosphazene.

[0035] Comparative Example 3 This comparative example provides a flame-retardant super-hydrophobic polyamide fiber, and the preparation method thereof is different from that of Example 1 only in that in step 2, the octaphenoxy cyclotetraphosphazene added in the reaction kettle is completely replaced by hexaphenoxy cyclotriphosphazene.

[0036] Comparative Example 4 This comparative example provides a flame retardant super hydrophobic polyamide fiber, and the preparation method thereof is different from that of Example 1 only in that: in step 4, the crude polyamide fiber is first immersed in solution 2 for 2 minutes, and then allowed to stand at room temperature for 30 minutes; then immersed in solution 1 for 1 minute, and cured at 60 degrees Celsius for 25 minutes; finally immersed in solution 3 for 2 minutes, and 5% water-based epoxy curing agent HTW-208 (60% solid content) is added at the same time, stirred, and then taken out and allowed to stand for 15 minutes.

[0037] Verification experiment and result analysis: Self-extinguishing property: LOI oxygen index is obtained according to the national standard oxygen index test method; Hydrophobicity: The fiber was rubbed back and forth 250 times under a load of 500 g, and its contact angle WCA was measured using a contact angle tester.

[0038] From the above experimental results, we can know that: The LOI oxygen index of Examples 1-3 is all above 32%, showing excellent flame retardancy; at the same time, the WCA contact angles of Examples 1-3 are all above 150°, showing excellent hydrophobicity. Mechanism analysis: Phosphazene compounds are a unique class of inorganic and organic composite materials, whose main chain structure consists of alternating double bonds of P and N, and exist in cyclic or linear form. The introduction of phenoxy groups on phosphorus atoms gives phosphazene compounds unique properties, making them environmentally friendly halogen-free flame retardants, which are in line with the concept of green development.

[0039] The advantage of phosphazene flame retardant lies in the synergistic effect between phosphorus and nitrogen. It has a high thermal decomposition temperature and excellent flame retardant properties. During the combustion process, it produces less smoke and relatively less toxic gases, which meets the environmental protection requirements of the EU RollS Directive and the WEEE Directive and is an environmentally friendly flame retardant material. Its flame retardant mechanism involves four key pathways: first, phosphazene absorbs heat when heated, which helps to cool and prevent the temperature from being too high; second, the phosphoric acid, metaphosphoric acid and polyphosphoric acid produced by decomposition form a protective film, which isolates the oxygen supply and prevents combustion; third, the released non-combustible gases such as carbon dioxide, ammonia and nitrogen dilute the combustion environment; finally, the PO· group combines with the active group during the combustion process to inhibit the spread of flames, interrupt the chain reaction, and enhance the flame retardant effect.

[0040] The addition amount of hexa(2-allylphenoxy)-cyclotriphosphazene in Comparative Example 1 is small, which will lead to a decrease in the hydrophobicity and self-extinguishing property of the polyamide fiber. This may be because the introduction of hexa(2-allylphenoxy)-cyclotriphosphazene can change the molecular chain structure of the polyamide fiber, increase the rigidity of its molecular chain, make the fiber surface smoother, and be conducive to the improvement of hydrophobicity. When the addition amount of hexa(2-allylphenoxy)-cyclotriphosphazene is reduced, the change of the molecular chain structure is weakened, the fiber surface may become rougher, and the contact area between water molecules and the fiber surface is increased, thereby reducing the hydrophobicity. At the same time, if the addition amount of hexa(2-allylphenoxy)-cyclotriphosphazene is insufficient, it may affect the bonding force between the coating layer and the fiber substrate or the uniformity of the coating layer, thereby reducing the hydrophobicity. During the combustion process, hexa(2-allylphenoxy)-cyclotriphosphazene can absorb heat and release flame-retardant gases such as water vapor, thereby reducing the combustion rate and increasing self-extinguishing properties. Reducing the amount of hexa(2-allylphenoxy)-cyclotriphosphazene added will weaken the thermal effect, making the fiber easier to burn and difficult to self-extinguish. On the contrary, if the amount of hexa(2-allylphenoxy)-cyclotriphosphazene added is increased, the melt viscosity may increase, the spinning rate may be reduced, and the mechanical properties of the fiber may also be affected. Therefore, the hexa(2-allylphenoxy)-cyclotriphosphazene addition range of Examples 1-3 is a better choice.

[0041] The polyamide fiber of Comparative Example 3 lacks hexaphenoxycyclotriphosphazene, and the polyamide fiber of Comparative Example 4 lacks octaphenoxycyclotetraphosphazene, both of which lead to reduced hydrophobicity and self-extinguishing properties of the polyamide fiber.

[0042] The wetting order of the crude polyamide fiber in Comparative Example 5 is different from that in Example 1, which significantly leads to a decrease in its hydrophobicity. This may be because: when the fiber is first soaked in the PDMS solution, the PDMS may partially penetrate into the surface and pores of the fiber, but at this time, a stable hydrophobic layer has not yet formed on the fiber surface; further, if the fiber is soaked in the nano-silica solution after being soaked in PDMS, the presence of PDMS may interfere with the binding of the nano-silica particles to the fiber surface, resulting in uneven particle distribution or weakened binding force. It can be seen that the wetting order not only affects the distribution and binding of each coating material on the fiber surface, but also may affect the interaction between the coatings and the overall structure. Reversing the wetting order may lead to unclear interfaces between the coatings, or even stratification or peeling, which seriously affects the hydrophobicity and durability of the polyamide fiber.

[0043] In summary, the polyamide fiber prepared by the technical solution of the present application has excellent flame retardancy and a super hydrophobic surface, which can keep the substrate clean and dry, providing a new method for solving the problem of low water resistance of flame retardants; at the same time, the fiber of the present application has its own super hydrophobic function, which can save the subsequent process of using a waterproof finishing agent for secondary processing.

[0044] The above description is only a preferred specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can make equivalent substitutions or changes within the technical scope disclosed in the present application according to the technical solution and improved ideas of the present application, which should be covered by the protection scope of the present application.

Claims

1. A method for preparing a flame retardant super-hydrophobic polyamide fiber, characterized in that: The method comprises the following steps: mixing and polycondensing the polycondensation units of hexa(2-allylphenoxy)-cyclotriphosphazene and nylon-66 to obtain a polymer containing an NP flame retardant block; then the polymer is mixed with hexaphenoxy cyclotriphosphazene and octaphenoxy cyclotetraphosphazene in a certain proportion and spun; and finally, the preparation is completed by coating with siloxane, nano-silica and epoxy resin.

2. The method for preparing a flame retardant super hydrophobic polyamide fiber according to claim 1, characterized in that: The specific steps include: Polymerization: adding hexa(2-allylphenoxy)-cyclotriphosphazene, hexamethylenediamine and adipic acid into a reactor at a weight ratio of (0.12-0.28):1:1, and performing polymerization reaction to obtain a PA66 polymer containing a NP flame retardant block; Mixing: adding hexaphenoxy cyclotriphosphazene and octaphenoxy cyclotetraphosphazene into a reaction kettle; controlling the temperature to be 245 to 270 degrees Celsius, and extruding and mixing to obtain a mixture; Spinning: After mixing, the mixture is spun to obtain a crude polyamide fiber with intrinsic flame retardancy; Infiltration coating: Nano-silica was dispersed in organic alcohol as solvent to prepare a 5% concentration solution for standby use, which was recorded as solution 1; PDMS was dissolved in xylene at room temperature and was set aside for standby use, which was recorded as solution 2; water-based epoxy resin solution, 20% to 55% solid content, was recorded as solution 3; Soak the crude polyamide fiber in solutions 1, 2, and 3, add 5% water-based epoxy curing agent, stir, and then take out and let stand; The coating is completed by drying at 80 degrees Celsius for 60 minutes on the surface of the polyamide fiber crude product, thereby obtaining a flame retardant super hydrophobic polyamide fiber.

3. The method for preparing a flame retardant super hydrophobic polyamide fiber according to claim 1, characterized in that: The polymerization step specifically includes the following: Prepolymerization: Mix hexa(2-allylphenoxy)-cyclotriphosphazene, adipic acid, and hexamethylenediamine in a weight ratio of (0.12-0.28): 1:1 and put them into a reactor; heat the reactor to 270-290 degrees Celsius; Evaporation: The prepolymerized material is passed into the evaporator to increase the mass fraction of the target product in the material from 50% to more than 70%; Further reaction; the material is sequentially passed into a flash evaporator and a post-polymerizer for dehydration to complete the polycondensation reaction, thereby obtaining a PA66 polymer containing a NP flame retardant block.

4. The method for preparing a flame retardant super hydrophobic polyamide fiber according to claim 1, characterized in that: In the mixing step, hexaphenoxy cyclotriphosphazene and octaphenoxy cyclotetraphosphazene are added in a weight ratio of PA66 polymer containing NP flame retardant block: hexaphenoxy cyclotriphosphazene: octaphenoxy cyclotetraphosphazene = 1: (0.02-0.08): (0.01:0.05).

5. The method for preparing a flame retardant super-hydrophobic polyamide fiber according to claim 1, characterized in that: In the impregnation coating, the impregnation sequence is that the crude polyamide fiber is firstly impregnated in solution 1, then in solution 2, and finally in solution 3.

6. The method for preparing a flame retardant super-hydrophobic polyamide fiber according to claim 5, characterized in that: The infiltration and coating steps specifically include: the crude polyamide fiber is first immersed in solution 1 for 1 to 3 minutes, and then allowed to stand at room temperature for 30 minutes; then immersed in solution 2 for 2 to 8 minutes, and cured at 60 to 80 degrees Celsius for 15 to 25 minutes; finally immersed in solution 3 for 2 to 4 minutes, and 5% water-based epoxy curing agent HTW-208 is added at the same time, stirred, and then taken out and allowed to stand for 15 minutes.

7. A flame retardant super hydrophobic polyamide fiber, prepared by the method for preparing a flame retardant super hydrophobic polyamide fiber according to any one of claims 1 to 6.

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