Nano film-coated flame-retardant nylon filament and preparation method thereof

Abstract

The invention provides a nano film-coated flame-retardant nylon filament and a preparation method thereof, and relates to the technical field of novel flame-retardant materials. Comprising a component A and a component B. The component A comprises the following raw materials in percentage by mass: 50-85% of polyamide slices; 10 to 40 percent of a melamine compound; 1 to 10% of diethyl phosphinate; 1-10% of a nanometer inorganic substance; 0.5 to 3 percent of antioxidant; and the component B is a polyamide slice. According to the invention, by compounding the melamine compound and the diethyl hypophosphite and combining with the assistance of the nano inorganic matter, the dispersity and the bonding strength of the flame retardant in polyamide are optimized; meanwhile, the nano inorganic matter can construct a compact physical barrier layer, so that the flame-retardant efficiency is improved; and the nano inorganic matter can also improve the thermal stability of the flame retardant, and finally industrial preparation of the nano film-coated flame-retardant nylon filament which has the characteristics of high flame-retardant efficiency and low molten drop and can be produced on a large scale is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of novel flame-retardant materials, and particularly relates to a nano-coated flame-retardant nylon filament and a preparation method thereof. Background Art

[0002] As one of the key polymer materials, polyamide is widely used in multiple economic fields due to its excellent tensile strength, stiffness, toughness, and outstanding wear and impact resistance characteristics. This material is not only commonly used in the manufacture of plastic products but also widely used in the textile industry due to its good spinnability. However, the flammability of nylon materials significantly restricts their application expansion. Its limiting oxygen index is close to the oxygen concentration in the air, and there is a severe molten dripping phenomenon during combustion at high temperatures. This characteristic severely limits its application in fields with strict fire safety requirements such as technical textiles, transportation, construction engineering, and electrical engineering.

[0003] Developing sustainable flame-retardant nylon fibers faces significant technical challenges. Among them, the preparation method of flame-retardant nylon filaments based on melt compounding masterbatches has attracted much attention due to its advantages of simple process, high production efficiency, and controllable cost. However, this process has two core bottlenecks: on the one hand, it is difficult to optimize the dispersion uniformity and compatibility between the flame retardant and the polymer matrix; on the other hand, the high-temperature environment during the melt spinning process of nylon fibers is likely to cause insufficient thermal stability of the flame retardant, resulting in a decrease in the tensile strength of nylon fibers and difficulty in continuous spinning. These technical barriers have limited the melt blending method mainly to laboratory-scale small-scale and pilot-scale tests so far and have not yet achieved large-scale production applications.

[0004] The invention publication number CN118978692A discloses a preparation method of a halogen-free flame-retardant nylon composite material, which modifies 2-carboxyethylphenylphosphinic acid with decanediamine and then extrudes and granulates through a twin-screw extruder to obtain the flame-retardant nylon composite material. The invention publication number CN112064138B discloses a preparation method of halogen-free flame-retardant nylon filaments, which uniformly mixes polyamide chips, graphite-like phase carbon nitride, a compound mixture composed of melamine polyphosphate and diethylphosphite encapsulated by silicon microcapsules, a compatibilizer, and an antioxidant in a mass ratio of 1:3:2, then extrudes and granulates through a twin-screw extruder to obtain a flame-retardant masterbatch, and then melts and spins the masterbatch and polyamide chips to obtain the flame-retardant nylon filaments. Although these existing technologies all provide preparation methods for halogen-free flame-retardant nylon materials, they have not solved the problems of poor dispersion of the flame retardant and the polymer, insufficient compatibility, and low high-temperature processing stability. Summary of the Invention

[0005] Aiming at the problems of poor dispersibility of flame retardants, insufficient compatibility, and low high-temperature processing stability in the preparation of existing halogen-free flame-retardant nylon filaments, the present invention provides a nano-coated flame-retardant nylon filament and a preparation method thereof. Through the compounding of melamine compounds and diethyl hypophosphite, combined with the assistance of nano-inorganic substances, the present invention optimizes the dispersion uniformity and interfacial bonding strength of flame retardants in polyamides; at the same time, by utilizing the lamellar stacking effect of nano-inorganic substances and the synergistic carbonization ability of flame retardant decomposition products, a dense physical barrier layer is constructed to improve the flame retardancy efficiency; moreover, nano-inorganic substances can improve the thermal stability of flame retardants and enhance the tensile strength of nylon fibers, ultimately realizing the industrial preparation of nano-coated flame-retardant nylon filaments with high flame retardancy efficiency, low melting droplet characteristics, and scalable production.

[0006] The technical solutions adopted by the present invention to achieve the above objectives are as follows:

[0007] The present invention provides a nano-coated flame-retardant nylon filament, which includes component A and component B, and each component is composed of the following raw materials by mass fraction:

[0008] Component A includes: 50-85% of polyamide chips; 10-40% of melamine compounds; 1-10% of diethyl hypophosphite; 1-10% of nano-inorganic substances; 0.5-3% of antioxidant;

[0009] Component B is polyamide chips.

[0010] Preferably, the mass ratio of component A to component B is: (1-3):(7-9).

[0011] Preferably, the viscosity of the polyamide chips is 2.8-3.4 dl / g.

[0012] Preferably, the melamine compound is one or more of melamine, melamine cyanurate, melamine polyphosphate, or melamine hydrobromide.

[0013] More preferably, the particle size of the melamine compound is 0.1-5 mm.

[0014] Preferably, the nano-inorganic substance is one or more of calcium carbonate, barium sulfate, wollastonite, talc powder, mica, montmorillonite, aluminum hydroxide, magnesium hydroxide, or silicon dioxide.

[0015] More preferably, the particle size of the nano-inorganic substance is 10 nm-100 nm.

[0016] Preferably, the antioxidant is one or more of antioxidant 1010, antioxidant 1330, or antioxidant 1216.

[0017] The present invention also provides a method for preparing a nano-coated flame-retardant nylon filament, comprising the following steps:

[0018] (1) Weigh the raw materials of component A according to the proportion, mix them evenly, add them to a twin-screw extruder for extrusion granulation to obtain a nano-coated flame-retardant nylon masterbatch;

[0019] (2) Mix the nano-coated flame-retardant nylon masterbatch obtained in step (1) with component B according to the proportion, and use the melt spinning method for spinning to obtain a nano-coated flame-retardant nylon filament.

[0020] Preferably, in step (2), the temperature range of the melt spinning in the melt spinning method is 230-290 °C for zones 1-10, the melting temperature is 230-290 °C, the draw ratio is 3.0-5.0, and the spinning speed is 500-2000 m / min.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) Through the synergistic compounding of melamine compounds and diethyl hypophosphite, a gas-phase - condensed-phase synergistic flame-retardant mechanism is formed; (2) By adding nano-inorganic substances, the distribution uniformity and compatibility of the flame retardant in the polyamide matrix are optimized; and the nano-inorganic substances and the flame retardant cooperate with each other to form a physical barrier layer, which can effectively block the heat transfer and oxygen supply, improving the flame retardant performance; at the same time, the nano-inorganic substances and the flame retardant are combined to enhance the thermal stability of the flame retardant, effectively inhibiting the high-temperature thermal degradation of the flame retardant, and breaking through the problems of the spinning process stability and fiber strength retention in the continuous production of flame-retardant nylon filaments. Specific Embodiments

[0022] The present invention will be further described below in conjunction with embodiments:

[0023] Example 1

[0024] This example provides a nano-coated flame-retardant nylon filament, comprising component A and component B. The specific components are composed of the following raw materials by mass fraction: Component A includes: 70% polyamide chips; 20% melamine compounds; 5% diethyl phosphite; 4% nano-inorganic substances; 1% antioxidant;

[0025] Component B is polyamide chips;

[0026] The mass ratio of the said component A and the said component B is: 2:8. Its technical effect lies in: precisely controlling the total concentration of the flame retardant through the gradient addition strategy, while maintaining the flame retardancy efficiency, avoiding excessive interference of the excessive flame retardant on the polyamide molecular chain, and maintaining the tensile strength and toughness of the fiber; component B serves as the main matrix to provide a continuous phase structure, endowing the melt with good fluidity and spinnability, while component A is introduced in the form of a masterbatch, and its pre-dispersion characteristic is utilized to ensure the uniform distribution of nano-talc powder and the flame retardant in the spinning melt. Combining the twin-screw extrusion and melt spinning processes, the tight interfacial bonding between the flame retardant nano-coating and the matrix is realized, and finally, the flame retardant durability, fiber mechanical properties and process stability of large-scale production are synergistically optimized.

[0027] The said melamine compound is melamine cyanurate, and 90% of the particle size of melamine cyanurate is less than 5 microns. Its technical effect lies in: in this embodiment, melamine cyanurate is used as the key flame retardant component, and by limiting its particle size distribution, the comprehensive performance of the material is significantly improved. The fine particle size control of melamine cyanurate ensures its uniform dispersion in the polyamide matrix, reducing the risk of agglomeration, thereby avoiding spinning defects caused by excessive local flame retardant concentration during the processing. At high temperatures, melamine cyanurate decomposes to release inert gases such as nitrogen and ammonia, diluting the combustible gas and absorbing heat to lower the temperature; in addition, the good interfacial bonding between the micron-sized MCA particles and the matrix effectively alleviates the negative impact of high addition amounts on the mechanical properties. Combining with the optimization of the spinning process, the nylon fiber simultaneously has excellent spinnability and strength stability.

[0028] The said diethyl phosphite is magnesium diethyl phosphite. Its technical effect lies in: in this embodiment, magnesium diethyl phosphite is selected as the phosphorus-based flame retardant. The magnesium phosphate generated by its high-temperature decomposition can catalyze the dehydration of polyamide to form a dense carbon layer, effectively isolating the diffusion of heat and oxygen and inhibiting the continuous combustion of the material; at the same time, it plays a phosphorus-nitrogen synergistic effect with melamine cyanurate. The nitrogen-containing gas released by melamine cyanurate dilutes the combustible, while magnesium diethyl phosphite strengthens the stability of the carbon layer in the condensed phase. The two synergistically significantly improve the flame retardancy efficiency. In addition, the decomposition temperature of this flame retardant is higher than the processing temperature, maintaining chemical inertness during the melt spinning process and avoiding flame retardant failure caused by premature decomposition; combined with its low addition amount characteristic, it reduces the damage to the polyamide molecular chain.

[0029] The nano-inorganic substance is talcum powder with a particle size of 10 nm. Its technical effects are as follows: The 10-nm talcum powder used in this example forms a uniform nano-coating structure through its nano-scale size, constructing a dense barrier on the fiber surface to delay heat transfer and the release of combustible gases; also, due to the high surface activity of talcum powder, it acts as a compatibilizer, which can effectively improve the dispersion of flame retardants such as melamine cyanurate and magnesium diethylphosphinate in the polyamide matrix, reduce particle agglomeration, and further enhance the flame retardancy efficiency of the flame retardant system; at the same time, the combination of the nano-inorganic substance and the flame retardant enhances the thermal stability of the flame retardant, effectively inhibiting the high-temperature thermal degradation of the flame retardant and ensuring the continuity of the spinning process.

[0030] The antioxidant is antioxidant 1010.

[0031] This example also provides a method for preparing nano-coated flame-retardant nylon filaments, which specifically includes the following steps:

[0032] (1) Preparation of nano-coated flame-retardant masterbatch: Mix the above-mentioned component A, add it to a co-rotating twin-screw extruder for extrusion granulation, use strand water cooling and then traction cutting. The temperature of each zone of the twin-screw extruder is set at 200℃ - 220℃ - 220℃ - 230℃ - 230℃ - 230℃ - 240℃ - 230℃ respectively, and the cooling water temperature is controlled at 70℃. After melting extrusion granulation and cooling, a nano-coated flame-retardant masterbatch is obtained;

[0033] (2) Preparation of nano-coated flame-retardant nylon filaments: Add the nano-coated flame-retardant masterbatch and component B to the melt spinning machine in the above ratio by means of a loss-in-weight scale. The temperature for melt spinning is 230 - 240℃ in zone 1, 240 - 245℃ in zone 2, 240 - 245℃ in zone 3, 245℃ in zone 4, the spinning speed is 1000 m / min, the draw ratio is 3 times, and the draw speed is 500 m / min; the specifications of the obtained nano-coated flame-retardant nylon filaments are 83 dtex / 48 f, and the limiting oxygen index LOI is 30.6%.

[0034] Example 2

[0035] This example provides a nano-coated flame-retardant nylon filament, which includes component A and component B. The specific components are composed of the following raw materials by mass fraction: Component A includes: 70% polyamide chips; 17% melamine compound; 8% diethyl phosphite; 4% nano-inorganic substance; 1% antioxidant;

[0036] Component B is polyamide chips;

[0037] The mass ratio of the said component A to the said component B is: 2:8.

[0038] The melamine compound is melamine cyanurate, and 90% of the melamine cyanurate has a particle size of less than 5 microns.

[0039] The diethyl phosphite is magnesium diethyl phosphite.

[0040] The nano-inorganic substance is talcum powder with a particle size of 10 nm.

[0041] The antioxidant is antioxidant 1010.

[0042] This example also provides a method for preparing nano-coated flame-retardant nylon filaments, which specifically includes the following steps:

[0043] (1) Preparation of nano-coated flame-retardant masterbatch: Mix the above component A, add it to a co-rotating twin-screw extruder for extrusion granulation, cool it with a water-cooled draw bar and then cut it into pellets. The temperature of each zone of the twin-screw extruder is set at 200 °C - 220 °C - 220 °C - 230 °C - 230 °C - 230 °C - 240 °C - 230 °C, and the cooling water temperature is controlled at 70 °C. After melting extrusion granulation and cooling, a nano-coated flame-retardant masterbatch is obtained;

[0044] (2) Preparation of nano-coated flame-retardant nylon filaments: Add the nano-coated flame-retardant masterbatch and component B in the above ratio to a melt spinning machine by means of a loss-in-weight scale. The temperature of the melt spinning is 230 - 240 °C in zone 1, 240 - 245 °C in zone 2, 240 - 245 °C in zone 3, and 245 °C in zone 4. The spinning speed is 1000 m / min, the draw ratio is 3 times, and the draw speed is 500 m / min; The specifications of the spun nano-coated flame-retardant nylon filaments are 83 dtex / 48f, and the limiting oxygen index LOI is 31%.

[0045] Example 3

[0046] This example provides a nano-coated flame-retardant nylon filament, which includes component A and component B. The specific components are composed of the following raw materials by mass fraction: Component A includes: 66% polyamide chips; 17% melamine compound; 8% diethyl phosphite; 8% nano-inorganic substance; 1% antioxidant;

[0047] Component B is polyamide chips;

[0048] The mass ratio of component A to component B is: 2:8.

[0049] The melamine compound is melamine cyanurate, and 90% of the melamine cyanurate has a particle size of less than 5 microns.

[0050] The diethyl phosphite is magnesium diethyl phosphite.

[0051] The nano-inorganic substance is talcum powder with a particle size of 10 nm.

[0052] The antioxidant is antioxidant 1010.

[0053] This embodiment also provides a method for preparing nano-coated flame-retardant nylon filaments, which specifically includes the following steps:

[0054] (1) Preparation of nano-coated flame-retardant masterbatch: Mix the above-mentioned component A, add it to a co-rotating twin-screw extruder for extrusion granulation, use strand water cooling and then traction granulation. The temperature settings of each zone of the twin-screw extruder are 200°C - 220°C - 220°C - 230°C - 230°C - 230°C - 240°C - 230°C respectively, and the cooling water temperature is controlled at 70°C. After melting extrusion granulation and cooling, nano-coated flame-retardant masterbatch is obtained;

[0055] (2) Preparation of nano-coated flame-retardant nylon filaments: Add the nano-coated flame-retardant masterbatch and component B in the above proportion by means of a loss-in-weight scale to a melt spinning machine. The temperature of melt spinning is 230 - 240°C in zone 1, 240 - 245°C in zone 2, 240 - 245°C in zone 3, and 245°C in zone 4. The spinning speed is 1000 m / min, the draw ratio is 3 times, and the draw speed is 500 m / min; The specifications of the spun nano-coated flame-retardant nylon filaments are 83 dtex / 48f, and the limiting oxygen index LOI is 32.4%.

[0056] Example 4

[0057] This embodiment provides a nano-coated flame-retardant nylon filament, which includes component A and component B. The specific components are composed of the following raw materials in mass fractions: Component A includes: 66% polyamide chips; 17% melamine compound; 8% diethyl phosphite; 8% nano-inorganic substance; 1% antioxidant;

[0058] Component B is polyamide chips;

[0059] The mass ratio of component A to component B is: 4:6.

[0060] The melamine compound is melamine cyanurate, and 90% of the melamine cyanurate has a particle size less than 5 microns.

[0061] The diethyl phosphite is magnesium diethyl phosphite.

[0062] The nano-inorganic substance is talcum powder with a particle size of 10 nm.

[0063] The antioxidant is antioxidant 1010.

[0064] This embodiment also provides a method for preparing nano-coated flame-retardant nylon filaments, which specifically includes the following steps:

[0065] (1) Preparation of nano-coated flame retardant masterbatch: Mix the above component A, add it to a co-rotating twin-screw extruder for extrusion granulation, use strand water cooling and then traction granulation. The temperature of each zone of the twin-screw extruder is set at 200°C - 220°C - 220°C - 230°C - 230°C - 230°C - 240°C - 230°C respectively, and the cooling water temperature is controlled at 70°C. After melting extrusion granulation and cooling, the nano-coated flame retardant masterbatch is obtained;

[0066] (2) Preparation of nano-coated flame retardant nylon filaments: Add the nano-coated flame retardant masterbatch and component B according to the above ratio by means of a loss-in-weight scale to a melt spinning machine. The melt spinning temperature is 230 - 240°C in zone 1, 240 - 245°C in zone 2, 240 - 245°C in zone 3, 245°C in zone 4, the spinning speed is 1000 m / min, the draw ratio is 3 times, and the draw speed is 500 m / min; The obtained nano-coated flame retardant nylon filaments have a specification of 83 dtex / 48f and a limiting oxygen index LOI of 34.2%.

[0067] Comparative Example 1

[0068] The difference from Example 1 is that talcum powder is equivalently replaced with a styrene-maleic anhydride compatibilizer.

[0069] This comparative example provides a flame retardant nylon filament, including component A and component B. The specific components are composed of the following raw materials by mass fraction:

[0070] Component A includes: 70% polyamide chips; 20% melamine-based compounds; 5% diethyl phosphinate; 4% styrene-maleic anhydride compatibilizer; 1% antioxidant;

[0071] Component B is polyamide chips;

[0072] The mass ratio of the said component A to the said component B is: 2:8.

[0073] The melamine-based compound is melamine cyanurate, and 90% of the melamine cyanurate has a particle size less than 5 microns.

[0074] The diethyl phosphinate is magnesium diethyl phosphinate.

[0075] The antioxidant is antioxidant 1010.

[0076] This comparative example also provides a preparation method of a flame retardant nylon filament, which specifically includes the following steps:

[0077] (1) Preparation of flame retardant masterbatch: Mix the above-mentioned component A, add it to a co-rotating twin-screw extruder for extrusion granulation, and use a drawbar water cooling method followed by traction cutting. The temperature settings of each zone of the twin-screw extruder are 200°C - 220°C - 220°C - 230°C - 230°C - 230°C - 240°C - 230°C respectively, and the cooling water temperature is controlled at 70°C. After melting extrusion granulation and cooling, the flame retardant masterbatch is obtained;

[0078] (2) Preparation of flame retardant nylon filaments: Add the flame retardant masterbatch and component B according to the above ratio by means of a loss-in-weight scale to a melt spinning machine. The temperature for melt spinning is 230 - 240°C in zone 1, 240 - 245°C in zone 2, 240 - 245°C in zone 3, and 245°C in zone 4. The spinning speed is 1000 m / min, the draw ratio is 3 times, and the draw speed is 500 m / min; The specifications of the spun flame retardant nylon filaments are 83 dtex / 48 f, and the limiting oxygen index LOI is 30%.

[0079] Comparative Example 2

[0080] The difference from Example 1 is that: The flame retardants used are all melamine urate.

[0081] This comparative example provides a nano-coated flame retardant nylon filament, which includes component A and component B. The specific components are composed of the following raw materials by mass fraction: Component A includes: 70% polyamide chips; 25% melamine compounds; 4% nano-inorganic substances; 1% antioxidant;

[0082] Component B is polyamide chips;

[0083] The mass ratio of the said component A to the said component B is: 2:8.

[0084] The said melamine compound is melamine cyanurate, and 90% of the melamine cyanurate has a particle size less than 5 microns.

[0085] The said nano-inorganic substance is talcum powder, and its particle size is 10 nm.

[0086] The said antioxidant is antioxidant 1010.

[0087] This comparative example also provides a preparation method of a nano-coated flame retardant nylon filament, which specifically includes the following steps:

[0088] (1) Preparation of nano-coated flame retardant masterbatch: Mix the above-mentioned component A, add it to a co-rotating twin-screw extruder for extrusion granulation, and use a drawbar water cooling method followed by traction cutting. The temperature settings of each zone of the twin-screw extruder are 200°C - 220°C - 220°C - 230°C - 230°C - 230°C - 240°C - 230°C respectively, and the cooling water temperature is controlled at 70°C. After melting extrusion granulation and cooling, the nano-coated flame retardant masterbatch is obtained;

[0089] (2) Preparation of nano-coated flame-retardant nylon filaments: Add the nano-coated flame-retardant masterbatch and Component B into the melt spinning machine in the above proportion by means of a loss-in-weight scale. The temperature for melt spinning is 230 - 240 °C in Zone 1, 240 - 245 °C in Zone 2, 240 - 245 °C in Zone 3, and 245 °C in Zone 4. The spinning speed is 1000 m / min, the draw ratio is 3 times, and the draw speed is 500 m / min. The obtained nano-coated flame-retardant nylon filaments have a specification of 83 dtex / 48f and a limiting oxygen index (LOI) of 27%.

[0090] Comparative Example 3

[0091] The difference from Example 2 and Example 3 is that no talcum powder or compatibilizer is added.

[0092] This comparative example provides a flame-retardant nylon filament, including Component A and Component B. The specific components are composed of the following raw materials in mass fractions:

[0093] Component A includes: 74% polyamide chips; 17% melamine compounds; 8% diethyl phosphite; 1% antioxidant;

[0094] Component B is polyamide chips;

[0095] The mass ratio of the said Component A to the said Component B is: 2:8.

[0096] The melamine compound is melamine cyanurate, and 90% of the melamine cyanurate has a particle size less than 5 microns.

[0097] The diethyl phosphite is magnesium diethyl phosphite.

[0098] The antioxidant is antioxidant 1010.

[0099] This comparative example also provides a preparation method of the flame-retardant nylon filament, which specifically includes the following steps:

[0100] (1) Preparation of the flame-retardant masterbatch: Mix the above Component A, add it to a co-rotating twin-screw extruder for extrusion granulation, and use strand water cooling and then traction cutting. The temperature of each zone of the co-rotating twin-screw extruder is set at 200 °C - 220 °C - 220 °C - 230 °C - 230 °C - 230 °C - 240 °C - 230 °C, and the cooling water temperature is controlled at 70 °C. The flame-retardant masterbatch is obtained through melt extrusion granulation and cooling.

[0101] (2) Preparation of flame-retardant nylon filaments: The flame-retardant masterbatch and component B were added to the melt spinning machine in the above proportions by means of a loss-in-weight scale. The melt spinning temperature was 230 - 240 °C in zone 1, 240 - 245 °C in zone 2, 240 - 245 °C in zone 3, and 245 °C in zone 4. The spinning speed was 1000 m / min, the drawing ratio was 3 times, and the drawing speed was 500 m / min. The specifications of the obtained flame-retardant nylon filaments were 83 dtex / 48f, and the limiting oxygen index LOI was 30.9%.

[0102] The differences in the formulations of each example and comparative example are shown in Table 1.

[0103] Table 1

[0104] Test example

[0105] The flame-retardant nylon filaments prepared using the formulations and preparation methods of Examples 1 - 4 and Comparative Examples 1 - 3 were tested for intrinsic viscosity of the chips, flame-retardant properties, and limiting oxygen index. The test methods are as follows:

[0106] The intrinsic viscosity of the chips was determined according to GB / T 38138 - 2019 "Test Methods for Fiber-grade Polycaprolactam (PA6) Chips";

[0107] The flame-retardant properties were determined according to GB / T 2408 - 2021 "Determination of Flammability of Plastics Horizontal and Vertical Methods";

[0108] The limiting oxygen index was determined according to GBT 5454 - 1997 "Textiles - Determination of Burning Behavior - Oxygen Index Method".

[0109] The relevant test results are shown in Table 2.

[0110] Table 2 Group Relative viscosity (dL / g) Number of molten drops in vertical burning Limiting oxygen index (%) Example 1 2.55 8 30.6 Example 2 2.53 7 31.2 Example 3 2.48 4 32.4 Example 4 2.35 3 33.6 Comparative example 1 2.69 8 30.1 Comparative example 2 2.60 16 27.6 Comparative example 3 2.58 12 30.9

[0111] As can be seen from Table 2, the nano-coated flame-retardant nylon filaments prepared by the technical solution of the present invention have significantly better flame-retardant properties than the comparative examples, and their relative viscosity is lower, which enhances the continuous spinning ability of the flame-retardant nylon filaments.

[0112] The comparison between Examples 1 - 2 and Comparative Example 2 shows that increasing the content of diethyl phosphite helps to improve the limiting oxygen index and anti-dripping performance, indicating that the present invention uses a compound of a melamine compound and diethyl phosphite as a flame retardant to form a gas-phase - condensed-phase synergistic flame-retardant mechanism; and this compound can significantly improve the dispersion of the flame retardant in the polyamide matrix, thereby improving the flame-retardant ability.

[0113] Compared with Comparative Example 1, Example 2 shows that talc can reduce the interaction force between polymer molecular chains and improve the compatibility of flame retardants in polymers. At the same time, talc has a synergistic effect with melamine compounds and diethyl hypophosphite, the number of vertical burning droplets is reduced, the limiting oxygen index is increased, and the flame retardant properties are improved.

[0114] Comparison of Example 2 with Examples 3-4 and Comparative Example 3 shows that increasing the concentration of talc under the same process conditions can significantly reduce the viscosity of the system, which is due to the filling and lubrication effect of the talc nanosheet layer and its regulatory effect on the movement of the polymer chain. The flaky talc is stacked directionally on the surface of the material, and cooperates with the pyrolysis products of the flame retardant to construct a continuous and dense composite barrier layer, which reduces the number of vertical combustion droplets and improves the limiting oxygen index by blocking the thermal oxygen diffusion path. Furthermore, nano-scale talc, with its high surface activity and nano-size effect, not only improves the dispersion uniformity of melamine cyanurate / diethyl magnesium hypophosphite flame retardant, reduces interface defects, but also combines with the flame retardant component to inhibit high-temperature thermal degradation, ultimately achieving the simultaneous optimization of flame retardant efficiency and spinning process stability.

[0115] In summary, the present invention optimizes the dispersion uniformity and interface bonding strength of the flame retardant in polyamide by compounding melamine compounds and diethyl hypophosphite with the assistance of nano-inorganic substances; at the same time, the sheet stacking effect of nano-inorganic substances and the synergistic carbonization ability of the decomposition products of the flame retardant are utilized to construct a dense physical barrier layer to improve the flame retardant efficiency; and the nano-inorganic substances can improve the thermal stability of the flame retardant and the tensile strength of the nylon fiber, and finally realize the industrial preparation of nano-coated flame-retardant nylon filaments with high flame retardant efficiency, low droplet characteristics and large-scale production.

[0116] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A nano-coated flame-retardant nylon filament, characterized in that, It includes component A and component B, and each component is composed of raw materials with the following mass fractions: Component A includes: 50 - 85% of polyamide chips; 10 - 40% of melamine compounds; 1 - 10% of diethyl phosphite; 1 - 10% of nano-inorganic substances; 0.5 - 3% of antioxidant; Component B is polyamide chips.

2. The nano-coated flame-retardant nylon filament according to claim 1, wherein The mass ratio of the said component A to the said component B is: (1 - 3) : (7 - 9).

3. A nano-coated flame-retardant nylon filament according to claim 1, characterized in that, The viscosity of the said polyamide chips is 2.8 - 3.4 dl / g.

4. A nano-coated flame-retardant nylon filament according to claim 1, characterized in that, The said melamine compounds are one or more of melamine, melamine cyanurate, melamine polyphosphate or melamine hydrobromide.

5. A nano-coated flame-retardant nylon filament according to claim 1 or 4, characterized in that, The particle size of the said melamine compounds is 0.1 - 5 mm.

6. The nano-coated flame-retardant nylon filament according to claim 1, characterized in that, The said nano-inorganic substances are one or more of calcium carbonate, barium sulfate, wollastonite, talc powder, mica, montmorillonite, aluminum hydroxide, magnesium hydroxide or silicon dioxide.

7. A nano-coated flame-retardant nylon filament according to claim 1 or 6, characterized in that, The particle size of the said nano-inorganic substances is 10 nm - 100 nm.

8. The nano-coated flame-retardant nylon filament according to claim 1, wherein, The said antioxidant is one or more of antioxidant 1010, antioxidant 1330 or antioxidant 1216.

9. A method for preparing a nano-coated flame-retardant nylon filament according to any one of claims 1-8, characterized in that, It includes the following steps: (1) Weigh each raw material of component A in proportion, mix them evenly, add them to a twin-screw extruder for extrusion granulation to obtain a nano-coated flame-retardant nylon masterbatch; (2) Mix the nano-coated flame-retardant nylon masterbatch obtained in step (1) with component B in proportion, and spin using the melt spinning method to obtain nano-coated flame-retardant nylon filaments.

10. A method for preparing a nano-coated flame-retardant nylon filament according to claim 9, characterized in that, In step (2), the temperature range of the melt spinning in the melt spinning method is 230 - 290 °C for zones 1 - 10, the melting temperature range is 230 - 290 °C, the draw ratio is 3.0 - 5.0, and the spinning speed is 500 - 2000 m / min.

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