Flame-retardant heat-insulating polypropylene fiber and preparation method thereof

Abstract

The present invention relates to the field of synthetic fiber technology, and more specifically, to a flame-retardant and heat-insulating polypropylene fiber and a preparation method thereof. In the present invention, by preparing nano-cerium oxide-loaded catkin fibers and modifying them, the thermal stability, flame retardant properties, and compatibility of the catkin fibers with polypropylene resin are effectively improved. The modified nano-cerium oxide-loaded catkin fibers obtained can assist in improving the flame retardant and heat-insulating properties of the polypropylene fibers while ensuring that the mechanical properties of the polypropylene fibers are not affected. Halloysite nanotubes are modified using magnesium hydroxide to obtain modified halloysite nanotubes with good mechanical and flame-retardant properties. The modified halloysite nanotubes are then added to polypropylene fibers, which can improve the flame retardant properties of the polypropylene fibers and strengthen the mechanical properties of the polypropylene fibers, thereby obtaining flame-retardant and heat-insulating polypropylene fibers.

Description

Technical Field

[0001] The present invention relates to the technical field of synthetic fibers, and more particularly to a flame-retardant and heat-insulating polypropylene fiber and a preparation method thereof. Background Art

[0002] Polypropylene fiber, commonly known as polypropylene, is one of the four major synthetic fibers. It has advantages such as light weight, high strength, and chemical resistance, and is therefore widely used in textiles, construction, and other fields. However, polypropylene fiber has a low limiting oxygen index and is flammable. When burned, it produces molten droplets, which can easily cause fires. These characteristics limit its application in some fields with strict requirements for flame retardancy. To improve the flame retardancy of polypropylene fiber, a common method is to mix flame retardants (such as brominated flame retardants, phosphorus flame retardants, nitrogen flame retardants, etc.) with polypropylene resin and then prepare flame-retardant polypropylene fiber through a melt spinning process. However, this method has a significant problem: the amount of flame retardant added is usually large, which will lead to poor spinnability and reduced mechanical strength of the flame-retardant fiber produced by the blending method; if the amount of flame retardant added is small, the polypropylene fiber often cannot meet the required flame retardant performance standards and cannot effectively exert its flame retardant effect.

[0003] Catkin fiber is a natural fiber extracted from willow seeds. It has a soft structure, high hollowness and light weight. These characteristics make catkin fiber have good thermal insulation properties and softness and comfort, making catkin fiber regarded as an environmentally friendly thermal insulation material. In my country, willow trees are widely planted as greening tree species, which makes catkin fiber as a natural fiber resource have unique resource advantages. If it can be rationally developed and utilized, it will not only protect the environment, but also generate certain economic benefits, enrich the application range of natural fibers, provide new raw materials for the textile industry, save costs and reduce resource waste. However, catkin fiber also has some limitations, such as short fibers, low mechanical strength, and poor thermal stability. These characteristics limit the application of catkin fiber in textile fibers and make it impossible to use it alone to manufacture high-strength fiber fabrics. Even if attempts are made to co-melt-spin catkin fiber with a polymer matrix, the overall mechanical properties of the fiber after co-melt spinning will be affected due to problems such as poor dispersion of catkin fiber in the polymer matrix and insufficient thermal stability of the fiber itself.

[0004] Therefore, it is of great practical significance to develop a polypropylene fiber that can fully utilize catkin fibers and has good flame retardant and thermal insulation properties. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention provides a flame retardant and heat-insulating polypropylene fiber and a preparation method thereof.

[0006] A method for preparing flame-retardant and heat-insulating polypropylene fiber comprises the following steps:

[0007] S1: Preparation of nano-cerium oxide-loaded willow catkin fibers, comprising immersing the washed, alkalized, and combed willow catkin fibers in a cerium salt aqueous solution, stirring and ultrasonically dispersing the fibers, adding potassium chlorate and N,N-dimethylformamide, and then centrifuging, collecting, washing, and drying the precipitate to obtain nano-cerium oxide-loaded willow catkin fibers;

[0008] S2: Modification of the nano-cerium oxide loaded catkin fibers, wherein the nano-cerium oxide loaded catkin fibers are coupled and modified using a modifying agent, and then the coupled and modified nano-cerium oxide loaded catkin fibers are modified using glycidyl methacrylate to obtain modified nano-cerium oxide loaded catkin fibers;

[0009] S3: Preparation of modified halloysite nanotubes: adding halloysite nanotubes and 3-chloropropyltrimethoxysilane to toluene to pretreat the halloysite nanotubes; adding the pretreated halloysite nanotubes to a magnesium chloride solution; adding a sodium hydroxide solution dropwise while stirring; reacting with stirring, filtering, washing, and drying to obtain modified halloysite nanotubes;

[0010] S4: Preparation of flame-retardant and heat-insulating polypropylene fiber: polypropylene resin, polyethylene resin, modified halloysite nanotubes, modified nano-cerium oxide-loaded catkin fibers, antioxidants, and lubricants are mixed, and the mixture is granulated, melt-spinned, drawn, heat-set, and wound to obtain flame-retardant and heat-insulating polypropylene fiber.

[0011] Furthermore, step S1: preparation of nano-cerium oxide loaded catkin fibers, specifically comprising the following steps:

[0012] S1.1: Washing the catkins with water to remove dust and impurities, immersing the washed catkins in a 15% by mass sodium hydroxide solution, and alkalizing them at 50-70°C for 40-60 minutes. Filtering the alkalized catkins, washing them to neutrality, and air-drying them to obtain alkalized catkins.

[0013] S1.2: The alkalized willow catkins are combed by a carding machine to obtain pretreated willow catkin fibers for later use;

[0014] S1.3: Place the pretreated catkin fibers into a 30 g / L cerium salt aqueous solution in a mass ratio of (1-3) to (200-500) and stir evenly. After soaking at room temperature for 2-4 hours, ultrasonically disperse the mixture for 5-15 minutes to obtain a cerium salt aqueous solution dispersed in the catkin fibers.

[0015] S1.4: Add potassium chlorate to the aqueous solution of cerium salt dispersed in catkin fibers, the amount of potassium chlorate added is 0.3-0.6% of the mass of the aqueous solution of cerium salt dispersed in catkin fibers, after the potassium chlorate is stirred and dissolved, add N,N-dimethylformamide, wherein the amount of N,N-dimethylformamide added is 2-5% of the volume of the aqueous solution of cerium salt dispersed in catkin fibers, stir and mix for 20-30 minutes, seal and place in an oven at 150-180°C to react for 3-5 hours, then, after centrifugal separation, precipitate collection, precipitate washing and drying, nano-cerium oxide loaded catkin fibers are obtained.

[0016] Furthermore, the cerium salt in the cerium salt aqueous solution is at least one of cerium nitrate, cerium chloride, cerium sulfate or cerium acetate.

[0017] Furthermore, step S2: modification treatment of nano-cerium oxide loaded catkin fibers specifically includes the following steps:

[0018] S2.1: Adding nano-cerium oxide-loaded catkin fibers to a 50% by mass ethanol aqueous solution to prepare a nano-cerium oxide-loaded catkin fiber dispersion solution having a concentration of 2 g / L;

[0019] S2.2: Adding a modifying agent to the nano-cerium oxide-loaded catkin fiber dispersion solution in an amount of 1 to 3% by weight of the nano-cerium oxide-loaded catkin fiber dispersion solution, stirring and reacting at 50 to 70° C. for 1 to 2 hours. After the reaction is complete, vacuum filtration and drying are performed to obtain coupled modified nano-cerium oxide-loaded catkin fibers;

[0020] S2.3: Add the coupled modified nano-cerium oxide loaded willow catkin fibers and glycidyl methacrylate to a methanol solution with a volume fraction of 75%, wherein the mixing mass ratio of the coupled modified nano-cerium oxide loaded willow catkin fibers, glycidyl methacrylate and methanol solution is (1-5): (10-50): (100-200), and stir the reaction at 50-75°C for 2-5 hours. Subsequently, the modified nano-cerium oxide loaded willow catkin fibers are obtained by filtering, washing and drying.

[0021] Furthermore, the modifying agent is at least one of silane coupling agent KH-550 and silane coupling agent KH-570.

[0022] Furthermore, step S3: preparing modified halloysite nanotubes specifically comprises the following steps:

[0023] S3.1: Add 5 to 10 parts by weight of halloysite nanotubes and 4 to 8 parts by weight of 3-chloropropyltrimethoxysilane to 80 to 150 parts by weight of toluene, stir and react at 110 to 120° C. for 2 to 5 hours, collect the reacted halloysite nanotubes by filtration, wash, and dry to obtain pretreated halloysite nanotubes;

[0024] S3.2: Add the pretreated halloysite nanotubes to a 30% magnesium chloride solution by mass, wherein the mass ratio of the halloysite nanotubes to the 30% magnesium chloride solution by mass is (1-5):(30-90), and ultrasonically disperse for 30-50 minutes to obtain a halloysite nanotube dispersion. Add sodium hydroxide solution dropwise to the halloysite nanotube dispersion while stirring until the pH of the halloysite nanotube dispersion reaches 9.8-10.7, stop the dropwise addition, continue stirring for 20-40 minutes, and then filter, wash and dry to obtain modified halloysite nanotubes.

[0025] Furthermore, step S4: preparing flame retardant and heat-insulating polypropylene fibers, specifically comprises the following steps:

[0026] S4.1: 56-70 parts by weight of polypropylene resin, 24-30 parts by weight of polyethylene resin, 6-20 parts by weight of modified halloysite nanotubes, 1-8 parts by weight of modified nanocerium oxide-loaded catkin fibers, 0.5-1 part by weight of an antioxidant, and 0.5-1 part by weight of a lubricant are mixed uniformly in a high-speed mixer, and then melted and extruded into pellets through a twin-screw extruder at 200-220°C to obtain a flame-retardant polypropylene masterbatch;

[0027] S4.2: The flame retardant polypropylene masterbatch is melt-spun at 220-240°C, drawn at 80-120°C, heat-set and wound at 110-140°C to obtain flame retardant and heat-insulating polypropylene fiber.

[0028] Furthermore, the antioxidant is at least one of antioxidant 1010 and antioxidant 168 .

[0029] Furthermore, the lubricant is at least one of stearic acid, calcium stearate or zinc stearate.

[0030] A flame-retardant and heat-insulating polypropylene fiber is prepared by the above-mentioned method for preparing the flame-retardant and heat-insulating polypropylene fiber.

[0031] The present invention has the following advantages:

[0032] 1. In the present invention, nano-cerium oxide-loaded catkin fibers are prepared so that nano-cerium oxide particles are evenly and densely loaded on the surface of the catkin fibers. Nano-cerium oxide has thermal stability and flame retardancy, can stabilize the fiber structure of the catkin fibers at high temperatures, reduce the mass loss and performance degradation of the catkin fibers due to thermal decomposition, thereby reducing the burning rate of the catkin fibers, and effectively improving the thermal stability and flame retardancy of the catkin fibers, so that the nano-cerium oxide-loaded catkin fibers have thermal stability and flame retardancy.

[0033] 2. In the present invention, the surface of the nano-cerium oxide loaded catkins fiber is first modified by a silane coupling agent to form an organic layer on the surface of the nano-cerium oxide loaded catkins fiber, and then the silane-modified nano-cerium oxide loaded catkins fiber is modified by glycidyl methacrylate, so that the amino group on the organic layer on the surface of the silane-modified nano-cerium oxide loaded catkins fiber and the hydroxyl group on the surface of the nano-cerium oxide can react with the epoxy group on the glycidyl methacrylate, and the glycidyl methacrylate is fixed on the surface of the nano-cerium oxide loaded catkins fiber, and then the interfacial bonding force between the nano-cerium oxide loaded catkins fiber and the polypropylene resin is increased with the help of glycidyl methacrylate, which is beneficial to improve the compatibility of the modified nano-cerium oxide loaded catkins fiber and the polypropylene resin, so that the modified nano-cerium oxide loaded catkins fiber can be uniformly dispersed in the polypropylene fiber, and then the modified nano-cerium oxide loaded catkins fiber is used to assist in improving the flame retardant and thermal insulation properties of the polypropylene fiber, while ensuring that the mechanical properties of the polypropylene fiber are not affected.

[0034] 3. In the present invention, the halloysite nanotubes are modified by magnesium hydroxide to promote the deposition of magnesium hydroxide on the inner and outer surfaces of the halloysite nanotubes, which is conducive to obtaining modified halloysite nanotubes with good mechanical properties and flame retardant properties. The modified halloysite nanotubes are then added to polypropylene fibers, which can effectively improve the flame retardant properties of the polypropylene fibers and enhance the mechanical properties of the polypropylene fibers. DETAILED DESCRIPTION

[0035] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0036] Example 1

[0037] A method for preparing flame-retardant and heat-insulating polypropylene fiber comprises the following steps:

[0038] S1: Preparation of nano-cerium oxide loaded catkin fibers,

[0039] S1.1: Wash the catkins with water to remove dust and impurities, immerse the washed catkins in a 15% by mass sodium hydroxide solution, and alkalize them at 60°C for 60 minutes. Then, filter out the alkalized catkins, wash them until neutral, and air-dry them to obtain alkalized catkins.

[0040] S1.2: The alkalized willow catkins are combed by a carding machine to obtain pretreated willow catkin fibers for later use;

[0041] S1.3: Place the pretreated catkin fibers into a 30 g / L cerium chloride aqueous solution at a mass ratio of 3:500, stir evenly, soak at room temperature for 4 hours, and ultrasonically disperse for 15 minutes to obtain a cerium salt aqueous solution dispersed in the catkin fibers;

[0042] S1.4: Potassium chlorate is added to the aqueous solution of cerium salt dispersed in catkin fibers, the amount of potassium chlorate added being 0.6% by mass of the aqueous solution of cerium salt dispersed in catkin fibers. After the potassium chlorate is stirred and dissolved, N,N-dimethylformamide is added, wherein the amount of N,N-dimethylformamide added is 5% by volume of the aqueous solution of cerium salt dispersed in catkin fibers. The mixture is stirred for 30 minutes, sealed and placed in an oven at 160°C for reaction for 5 hours. Subsequently, the mixture is centrifuged, the precipitate is collected, washed, and dried to obtain nano-cerium oxide-loaded catkin fibers.

[0043] S2: Modification of nano-cerium oxide loaded catkin fibers,

[0044] S2.1: Adding nano-cerium oxide-loaded catkin fibers to a 50% by mass ethanol aqueous solution to prepare a nano-cerium oxide-loaded catkin fiber dispersion solution having a concentration of 2 g / L;

[0045] S2.2: Adding a silane coupling agent KH-550 to the nano-cerium oxide-loaded catkin fiber dispersion solution in an amount of 3% by weight of the nano-cerium oxide-loaded catkin fiber dispersion solution, stirring and reacting at 70°C for 2 h. After the reaction is complete, vacuum filtration and drying are performed to obtain coupled modified nano-cerium oxide-loaded catkin fibers;

[0046] S2.3: Adding the coupled modified nano-cerium oxide-loaded catkin fibers and glycidyl methacrylate to a 75% by volume methanol solution, wherein the mixing mass ratio of the coupled modified nano-cerium oxide-loaded catkin fibers, glycidyl methacrylate, and methanol solution is 1:30:150, stirring and reacting at 60°C for 3 hours, and then filtering, washing, and drying to obtain the modified nano-cerium oxide-loaded catkin fibers;

[0047] S3: Preparation of modified halloysite nanotubes,

[0048] S3.1: 8 parts by weight of halloysite nanotubes and 8 parts by weight of 3-chloropropyltrimethoxysilane were added to 150 parts by weight of toluene and stirred at 120°C for 3 hours. The reacted halloysite nanotubes were collected by filtration, and the excess 3-chloropropyltrimethoxysilane was washed with toluene and then washed twice with ethanol. The washed halloysite nanotubes were dried in an oven at 60°C for 8 hours to obtain pretreated halloysite nanotubes.

[0049] S3.2: adding the pretreated halloysite nanotubes to a 30% by mass magnesium chloride solution at a mass ratio of 1:30, and ultrasonically dispersing the solution for 50 minutes to obtain a halloysite nanotube dispersion. Adding sodium hydroxide solution dropwise to the halloysite nanotube dispersion while stirring until the pH of the halloysite nanotube dispersion reaches 10.2, stopping the addition, and continuing stirring for 40 minutes. Subsequently, filtering, washing, and drying the solution to obtain modified halloysite nanotubes.

[0050] S4: Preparation of flame retardant and heat-insulating polypropylene fibers,

[0051] S4.1: 70 parts by weight of polypropylene resin, 30 parts by weight of polyethylene resin, 20 parts by weight of modified halloysite nanotubes, 7 parts by weight of modified nanocerium oxide-loaded catkin fibers, 1 part by weight of antioxidant 1010, and 1 part by weight of calcium stearate were mixed uniformly in a high-speed mixer. The mixture was then melted and extruded into pellets at 220°C through a twin-screw extruder to obtain a flame-retardant polypropylene masterbatch.

[0052] S4.2: The flame retardant polypropylene masterbatch is sequentially subjected to melt spinning at a spinning temperature of 240°C and a spinning speed of 1000 m / min, drawing at a drawing temperature of 100°C and a drawing ratio of 3.0, heat setting at a temperature of 120°C, and winding to obtain flame retardant and heat-insulating polypropylene fiber.

[0053] Example 2

[0054] A method for preparing flame-retardant and heat-insulating polypropylene fiber comprises the following steps:

[0055] S1: Preparation of nano-cerium oxide loaded catkin fibers,

[0056] S1.1: Wash the catkins with water to remove dust and impurities, immerse the washed catkins in a 15% by mass sodium hydroxide solution, and alkalize them at 70°C for 60 minutes. Then, filter out the alkalized catkins, wash them until neutral, and air-dry them to obtain alkalized catkins.

[0057] S1.2: The alkalized willow catkins are combed by a carding machine to obtain pretreated willow catkin fibers for later use;

[0058] S1.3: Place the pretreated catkin fibers into a 30 g / L cerium chloride aqueous solution at a mass ratio of 3:500. Stir evenly, soak at room temperature for 2 h, and ultrasonically disperse for 5 min to obtain a cerium salt aqueous solution dispersed in the catkin fibers.

[0059] S1.4: Potassium chlorate is added to the cerium salt aqueous solution dispersed in catkin fibers, the amount of potassium chlorate added being 0.6% by mass of the cerium salt aqueous solution dispersed in catkin fibers. After the potassium chlorate is stirred and dissolved, N,N-dimethylformamide is added, wherein the amount of N,N-dimethylformamide added is 5% by volume of the cerium salt aqueous solution dispersed in catkin fibers. The mixture is stirred for 20 minutes, sealed and placed in an oven at 180°C for reaction for 3 hours. Subsequently, the mixture is centrifuged, the precipitate is collected, washed, and dried to obtain nano-cerium oxide-loaded catkin fibers.

[0060] S2: Modification of nano-cerium oxide loaded catkin fibers,

[0061] S2.1: Adding nano-cerium oxide-loaded catkin fibers to a 50% by mass ethanol aqueous solution to prepare a nano-cerium oxide-loaded catkin fiber dispersion solution having a concentration of 2 g / L;

[0062] S2.2: Adding silane coupling agent KH-550 to the nano-cerium oxide-loaded catkin fiber dispersion solution in an amount of 3% by weight of the nano-cerium oxide-loaded catkin fiber dispersion solution, stirring and reacting at 50°C for 1 hour. After the reaction is complete, vacuum filtration and drying are performed to obtain coupled modified nano-cerium oxide-loaded catkin fibers;

[0063] S2.3: Adding the coupled modified nano-cerium oxide-loaded catkin fibers and glycidyl methacrylate to a 75% by volume methanol solution, wherein the mixing mass ratio of the coupled modified nano-cerium oxide-loaded catkin fibers, glycidyl methacrylate, and methanol solution is 1:30:150, stirring and reacting at 50°C for 2 hours, and then filtering, washing, and drying to obtain the modified nano-cerium oxide-loaded catkin fibers;

[0064] S3: Preparation of modified halloysite nanotubes,

[0065] S3.1: 8 parts by weight of halloysite nanotubes and 8 parts by weight of 3-chloropropyltrimethoxysilane were added to 150 parts by weight of toluene and stirred at 110°C for 5 hours. The reacted halloysite nanotubes were collected by filtration, and the excess 3-chloropropyltrimethoxysilane was washed with toluene and then washed twice with ethanol. The washed halloysite nanotubes were dried in an oven at 70°C for 5 hours to obtain pretreated halloysite nanotubes.

[0066] S3.2: adding the pretreated halloysite nanotubes to a 30% by mass magnesium chloride solution at a mass ratio of 1:30, and ultrasonically dispersing the solution for 30 minutes to obtain a halloysite nanotube dispersion. Adding sodium hydroxide solution dropwise to the halloysite nanotube dispersion while stirring until the pH of the halloysite nanotube dispersion reaches 10.2, stopping the addition, and continuing stirring for 20 minutes. Subsequently, filtering, washing, and drying the solution to obtain modified halloysite nanotubes.

[0067] S4: Preparation of flame retardant and heat-insulating polypropylene fibers,

[0068] S4.1: 70 parts by weight of polypropylene resin, 30 parts by weight of polyethylene resin, 20 parts by weight of modified halloysite nanotubes, 7 parts by weight of modified nanocerium oxide-loaded catkin fibers, 1 part by weight of antioxidant 1010, and 1 part by weight of calcium stearate were mixed uniformly in a high-speed mixer. The mixture was then melted and extruded into pellets at 220°C through a twin-screw extruder to obtain a flame-retardant polypropylene masterbatch.

[0069] S4.2: The flame retardant polypropylene masterbatch is sequentially subjected to melt spinning at a spinning temperature of 240°C and a spinning speed of 1000 m / min, drawing at a drawing temperature of 100°C and a drawing ratio of 3.0, heat setting at a temperature of 120°C, and winding to obtain flame retardant and heat-insulating polypropylene fiber.

[0070] Example 3

[0071] A method for preparing flame-retardant and heat-insulating polypropylene fiber comprises the following steps:

[0072] S1: Preparation of nano-cerium oxide loaded catkin fibers,

[0073] S1.1: Wash the catkins with water to remove dust and impurities, immerse the washed catkins in a 15% by mass sodium hydroxide solution, and alkalize them at 60°C for 60 minutes. Then, filter out the alkalized catkins, wash them until neutral, and air-dry them to obtain alkalized catkins.

[0074] S1.2: The alkalized willow catkins are combed by a carding machine to obtain pretreated willow catkin fibers for later use;

[0075] S1.3: Place the pretreated catkin fibers into a 30 g / L cerium chloride aqueous solution at a mass ratio of 1:200. Stir evenly, soak at room temperature for 4 hours, and ultrasonically disperse for 15 minutes to obtain a cerium salt aqueous solution dispersed in the catkin fibers.

[0076] S1.4: Potassium chlorate is added to the aqueous solution of cerium salt dispersed in catkin fibers, the amount of potassium chlorate added being 0.3% by mass of the aqueous solution of cerium salt dispersed in catkin fibers. After the potassium chlorate is stirred and dissolved, N,N-dimethylformamide is added, wherein the amount of N,N-dimethylformamide added is 3% by volume of the aqueous solution of cerium salt dispersed in catkin fibers. The mixture is stirred for 30 minutes, sealed and placed in an oven at 160°C for reaction for 5 hours. Subsequently, the mixture is centrifuged, the precipitate is collected, washed, and dried to obtain nano-cerium oxide-loaded catkin fibers.

[0077] S2: Modification of nano-cerium oxide loaded catkin fibers,

[0078] S2.1: Adding nano-cerium oxide-loaded catkin fibers to a 50% by mass ethanol aqueous solution to prepare a nano-cerium oxide-loaded catkin fiber dispersion solution having a concentration of 2 g / L;

[0079] S2.2: Adding a silane coupling agent KH-550 to the nano-cerium oxide-loaded catkin fiber dispersion solution in an amount of 1% by weight of the nano-cerium oxide-loaded catkin fiber dispersion solution, stirring and reacting at 70°C for 2 h. After the reaction is complete, vacuum filtration and drying are performed to obtain coupled modified nano-cerium oxide-loaded catkin fibers;

[0080] S2.3: Adding the coupled modified nano-cerium oxide-loaded catkin fibers and glycidyl methacrylate to a 75% by volume methanol solution, wherein the mixing mass ratio of the coupled modified nano-cerium oxide-loaded catkin fibers, glycidyl methacrylate, and methanol solution is 1:50:200, stirring and reacting at 60°C for 3 hours, and then filtering, washing, and drying to obtain the modified nano-cerium oxide-loaded catkin fibers;

[0081] S3: Preparation of modified halloysite nanotubes,

[0082] S3.1: 5 parts by weight of halloysite nanotubes and 8 parts by weight of 3-chloropropyltrimethoxysilane were added to 100 parts by weight of toluene and stirred at 120°C for 3 hours. The reacted halloysite nanotubes were collected by filtration, and the excess 3-chloropropyltrimethoxysilane was washed with toluene and then washed twice with ethanol. The washed halloysite nanotubes were dried in an oven at 60°C for 8 hours to obtain pretreated halloysite nanotubes.

[0083] S3.2: adding the pretreated halloysite nanotubes to a 30% by mass magnesium chloride solution in a mass ratio of 1:90, and ultrasonically dispersing the solution for 50 minutes to obtain a halloysite nanotube dispersion. Adding sodium hydroxide solution dropwise to the halloysite nanotube dispersion while stirring until the pH of the halloysite nanotube dispersion reaches 10.7, stopping the addition, and continuing stirring for 40 minutes. Subsequently, filtering, washing, and drying the solution to obtain modified halloysite nanotubes.

[0084] S4: Preparation of flame retardant and heat-insulating polypropylene fibers,

[0085] S4.1: 70 parts by weight of polypropylene resin, 30 parts by weight of polyethylene resin, 20 parts by weight of modified halloysite nanotubes, 7 parts by weight of modified nanocerium oxide-loaded catkin fibers, 1 part by weight of antioxidant 1010, and 1 part by weight of calcium stearate were mixed uniformly in a high-speed mixer. The mixture was then melted and extruded into pellets at 220°C through a twin-screw extruder to obtain a flame-retardant polypropylene masterbatch.

[0086] S4.2: The flame retardant polypropylene masterbatch is sequentially subjected to melt spinning at a spinning temperature of 240°C and a spinning speed of 1000 m / min, drawing at a drawing temperature of 100°C and a drawing ratio of 3.0, heat setting at a temperature of 120°C, and winding to obtain flame retardant and heat-insulating polypropylene fiber.

[0087] Comparative Example 1

[0088] Compared with Example 1, the difference of Comparative Example 1 is that steps S1.3-S1.4 are removed, the nano-cerium oxide-loaded catkin fiber in step S2 is replaced by the pretreated catkin fiber obtained in step S1.2, a pretreated catkin fiber dispersion solution with a pretreated catkin fiber concentration of 2 g / L is prepared, and the nano-cerium oxide-loaded catkin fiber dispersion solution in step S2.2 is replaced by the pretreated catkin fiber dispersion solution. The other steps remain unchanged to prepare flame-retardant and thermal insulating polypropylene fiber, which is recorded as Comparative Example 1.

[0089] Comparative Example 2

[0090] Compared with Example 1, the difference of Comparative Example 2 is that step S2 is removed, and the modified nano-cerium oxide-loaded catkin fiber in step S4.1 is replaced by an equal weight portion of the nano-cerium oxide-loaded catkin fiber obtained in step S1.4. The other steps remain unchanged to prepare flame-retardant and thermal insulating polypropylene fiber, which is recorded as Comparative Example 2.

[0091] Comparative Example 3

[0092] Compared with Example 1, the difference of Comparative Example 2 is that the modified halloysite nanotubes in step S4.1 are replaced with halloysite nanotubes of equal weight, and the other steps remain unchanged to prepare flame retardant and heat-insulating polypropylene fibers, which is recorded as Comparative Example 3.

[0093] Performance Testing

[0094] Mechanical properties test: According to GB / T14344-2008, the flame retardant and thermal insulating polypropylene fibers prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to mechanical properties tests. The breaking strength and initial modulus of each flame retardant and thermal insulating polypropylene fiber were tested at 25°C. The test results are shown in Table 1.

[0095] The flame-retardant and heat-insulating polypropylene fibers obtained in Examples 1-3 and Comparative Examples 1-3 were respectively made into 200 mm*50 mm fabrics, and the following properties of the fabrics obtained in Examples 1-3 and Comparative Examples 1-3 were tested:

[0096] Flame retardant properties: According to GB / T5454-1997, the flame retardant properties of the above fabrics were tested. The test results are shown in Table 1 below;

[0097] Thermal insulation performance: According to GB / T11048-2018, the thermal insulation performance of the above fabrics was tested. The test results are shown in Table 1 below;

[0098] Table 1:

[0099] Group Breaking strength (cN / dtex) Initial modulus (cN / dtex) Limiting oxygen index (%) Thermal conductivity (W / m·K) Example 1 10.26 96.84 31.5 <![CDATA[3.65×10 -2 ]]> Example 2 9.78 97.51 30.7 <![CDATA[4.07×10 -2 ]]> Example 3 9.53 96.36 31.1 <![CDATA[3.88×10 -2 ]]> Comparative Example 1 6.47 75.22 25.6 <![CDATA[4.03×10 -2 ]]> Comparative Example 2 8.95 90.04 28.3 <![CDATA[5.74×10 -2 ]]> Comparative Example 3 7.28 85.13 22.8 <![CDATA[4.39×10 -2 ]]>

[0100] As can be seen from Table 1, the flame retardant and thermal insulation polypropylene fibers obtained in Examples 1-3 have better mechanical properties, flame retardant properties and thermal insulation properties than comparative examples 1-3. Compared with comparative example 1, it can be seen that the breaking strength, dehumidification modulus value and limiting oxygen index results of Examples 1-3 are significantly better than those of comparative example 1, indicating that the loading of nano-cerium oxide can effectively improve the mechanical properties and flame retardant properties of catkin fibers, thereby ensuring that the flame retardant and thermal insulation polypropylene fibers have good flame retardant properties and certain tear resistance and rigidity. Compared with comparative example 2, it can be seen that the modified nano-cerium oxide-loaded catkin fibers after modification of the nano-cerium oxide-loaded catkin fibers can further optimize the flame retardant properties, thermal insulation properties and mechanical properties of the flame retardant and thermal insulation polypropylene fibers. Compared with comparative example 3, it can be seen that the addition of modified halloysite nanotubes can significantly improve the flame retardant properties of the flame retardant and thermal insulation polypropylene fibers, and further enhance the mechanical properties of the flame retardant and thermal insulation polypropylene fibers.

[0101] It should be understood that those skilled in the art may make improvements or modifications based on the above description, and all such improvements and modifications shall fall within the scope of protection of the appended claims. Any portion of this specification not described in detail is prior art known to those skilled in the art.

Claims

1. A method for preparing flame-retardant and heat-insulating polypropylene fiber, characterized in that: The following steps are involved: S1: Preparation of nano-cerium oxide-loaded willow catkin fibers: immersing the washed, alkalized, and combed willow catkin fibers in a cerium salt aqueous solution, stirring and ultrasonically dispersing them, adding potassium chlorate and N,N-dimethylformamide, and then centrifuging, collecting, washing, and drying the precipitate to obtain nano-cerium oxide-loaded willow catkin fibers; S2: Modification of the nano-cerium oxide loaded catkin fibers, wherein the nano-cerium oxide loaded catkin fibers are coupled and modified using a modifying agent, and then the coupled and modified nano-cerium oxide loaded catkin fibers are modified using glycidyl methacrylate to obtain modified nano-cerium oxide loaded catkin fibers; S3: Preparation of modified halloysite nanotubes: adding halloysite nanotubes and 3-chloropropyltrimethoxysilane to toluene to pretreat the halloysite nanotubes; adding the pretreated halloysite nanotubes to a magnesium chloride solution; adding a sodium hydroxide solution dropwise while stirring; reacting with stirring, filtering, washing, and drying to obtain modified halloysite nanotubes; S4: Preparation of flame-retardant and heat-insulating polypropylene fiber: polypropylene resin, polyethylene resin, modified halloysite nanotubes, modified nano-cerium oxide-loaded catkin fibers, antioxidants, and lubricants are mixed, and the mixture is granulated, melt-spinned, drawn, heat-set, and wound to obtain flame-retardant and heat-insulating polypropylene fiber.

2. The method for preparing a flame-retardant and heat-insulating polypropylene fiber according to claim 1, characterized in that: Step S1: Preparation of nano-cerium oxide loaded catkin fibers, specifically comprising the following steps: S1.1: Washing the catkins with water to remove dust and impurities, immersing the washed catkins in a 15% by mass sodium hydroxide solution, and alkalizing them at 50-70°C for 40-60 minutes. Filtering the alkalized catkins, washing them to neutrality, and air-drying them to obtain alkalized catkins. S1.2: The alkalized willow catkins are combed by a carding machine to obtain pretreated willow catkin fibers for later use; S1.3: Place the pretreated catkin fibers into a 30 g / L cerium salt aqueous solution in a mass ratio of (1-3) to (200-500) and stir evenly. After soaking at room temperature for 2-4 hours, ultrasonically disperse the mixture for 5-15 minutes to obtain a cerium salt aqueous solution dispersed in the catkin fibers. S1.4: Add potassium chlorate to the aqueous solution of cerium salt dispersed in catkin fibers, the amount of potassium chlorate added is 0.3-0.6% of the mass of the aqueous solution of cerium salt dispersed in catkin fibers; after the potassium chlorate is stirred and dissolved, add N,N-dimethylformamide, wherein the amount of N,N-dimethylformamide added is 2-5% of the volume of the aqueous solution of cerium salt dispersed in catkin fibers; stir and mix for 20-30 minutes, seal and place in an oven at 150-180°C to react for 3-5 hours; then, centrifuge, collect the precipitate, wash the precipitate and dry it to obtain nano-cerium oxide loaded catkin fibers.

3. The method for preparing a flame retardant and heat-insulating polypropylene fiber according to claim 2, characterized in that: The cerium salt in the cerium salt aqueous solution is at least one of cerium nitrate, cerium chloride, cerium sulfate or cerium acetate.

4. The method for preparing a flame-retardant and heat-insulating polypropylene fiber according to claim 3, characterized in that: Step S2: modification of nano-cerium oxide loaded catkin fibers, specifically comprising the following steps: S2.1: Adding nano-cerium oxide-loaded catkin fibers to a 50% by mass ethanol aqueous solution to prepare a nano-cerium oxide-loaded catkin fiber dispersion solution having a concentration of 2 g / L; S2.2: Adding a modifying agent to the nano-cerium oxide-loaded catkin fiber dispersion solution in an amount of 1 to 3% by weight of the nano-cerium oxide-loaded catkin fiber dispersion solution, stirring and reacting at 50 to 70° C. for 1 to 2 hours. After the reaction is complete, vacuum filtration and drying are performed to obtain coupled modified nano-cerium oxide-loaded catkin fibers; S2.3: Add the coupled modified nano-cerium oxide loaded willow catkin fibers and glycidyl methacrylate to a methanol solution with a volume fraction of 75%, wherein the mixing mass ratio of the coupled modified nano-cerium oxide loaded willow catkin fibers, glycidyl methacrylate and methanol solution is (1-5): (10-50): (100-200), and stir the reaction at 50-75°C for 2-5 hours. Subsequently, the modified nano-cerium oxide loaded willow catkin fibers are obtained by filtering, washing and drying.

5. The method for preparing a flame-retardant and heat-insulating polypropylene fiber according to claim 4, characterized in that: The modifying agent is at least one of silane coupling agent KH-550 and silane coupling agent KH-570.

6. The method for preparing a flame-retardant and heat-insulating polypropylene fiber according to claim 5, characterized in that: Step S3: Preparation of modified halloysite nanotubes, specifically comprising the following steps: S3.1: Add 5 to 10 parts by weight of halloysite nanotubes and 4 to 8 parts by weight of 3-chloropropyltrimethoxysilane to 80 to 150 parts by weight of toluene, stir and react at 110 to 120° C. for 2 to 5 hours, collect the reacted halloysite nanotubes by filtration, wash, and dry to obtain pretreated halloysite nanotubes; S3.2: Add the pretreated halloysite nanotubes to a 30% magnesium chloride solution by mass, wherein the mass ratio of the halloysite nanotubes to the 30% magnesium chloride solution by mass is (1-5):(30-90), and ultrasonically disperse for 30-50 minutes to obtain a halloysite nanotube dispersion. Add sodium hydroxide solution dropwise to the halloysite nanotube dispersion while stirring until the pH of the halloysite nanotube dispersion reaches 9.8-10.7, stop the dropwise addition, continue stirring for 20-40 minutes, and then filter, wash and dry to obtain modified halloysite nanotubes.

7. The method for preparing a flame-retardant and heat-insulating polypropylene fiber according to claim 6, characterized in that: Step S4: preparing flame-retardant heat-insulating polypropylene fibers, specifically comprising the following steps: S4.1: 56-70 parts by weight of polypropylene resin, 24-30 parts by weight of polyethylene resin, 6-20 parts by weight of modified halloysite nanotubes, 1-8 parts by weight of modified nano-cerium oxide loaded catkin fibers, 0.5-1 parts by weight of antioxidant, 0.5 to 1 parts by weight of lubricant are mixed uniformly in a high-speed mixer, then melted at 200 to 220° C. through a twin-screw extruder, extruded and granulated to obtain flame-retardant polypropylene masterbatch; S4.2: The flame retardant polypropylene masterbatch is melt-spun at 220-240℃, drawn at 80-120℃, and then The flame retardant and heat-insulating polypropylene fibers were obtained by heat setting and winding at 140°C.

8. The method for preparing a flame-retardant and heat-insulating polypropylene fiber according to claim 7, characterized in that: The antioxidant is at least one of the antioxidant 1010 and the antioxidant 168 .

9. The method for preparing a flame-retardant and heat-insulating polypropylene fiber according to claim 8, characterized in that: The lubricant is at least one of stearic acid, calcium stearate or zinc stearate.

10. A flame retardant and heat-insulating polypropylene fiber, characterized in that: The flame retardant and heat-insulating polypropylene fiber is prepared by the method for preparing the flame retardant and heat-insulating polypropylene fiber according to any one of claims 1 to 9.