Flame-retardant thermal-insulation polypropylene fiber and preparation method thereof

Abstract

The invention relates to the technical field of synthetic fibers, in particular to a flame-retardant thermal-insulation polypropylene fiber and a preparation method thereof. According to the invention, by preparing the nano cerium oxide loaded catkin fiber and modifying the nano cerium oxide loaded catkin fiber, the thermal stability and flame retardant property of the catkin fiber and the compatibility of the catkin fiber with polypropylene resin are effectively improved, and the obtained modified nano cerium oxide loaded catkin fiber can assist in improving the flame retardant property and thermal insulation property of the polypropylene fiber; meanwhile, the mechanical property of the polypropylene fiber is not influenced; according to the invention, magnesium hydroxide is utilized to modify halloysite nanotubes to obtain modified halloysite nanotubes with good mechanical properties and flame retardant properties, and then the modified halloysite nanotubes are added into polypropylene fibers, so that the flame retardant properties of the polypropylene fibers can be improved, and the mechanical properties of the polypropylene fibers can be enhanced; thus, the flame-retardant heat-insulating polypropylene fiber is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of synthetic fibers, and more particularly to a flame retardant 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 the advantages of light weight, high strength, and chemical corrosion resistance, so it has been widely used in textiles, construction and other fields. However, the limiting oxygen index of polypropylene fiber is low, it is flammable, and it will produce molten droplets when burning, which is easy to cause fire. These characteristics limit its application in some fields with strict requirements on flame retardant properties. In order to improve the flame retardant properties of polypropylene fiber, a common method is to mix flame retardants (such as bromine 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, there is a significant problem with this method: the amount of flame retardant added usually needs to be large, which will cause the flame retardant fiber obtained by the blending method to have poor spinnability and reduced mechanical strength; if the amount of flame retardant added is small, it is often impossible for the polypropylene fiber to meet the required flame retardant performance standards and cannot effectively play a flame retardant role.

[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 performance and softness and comfort, making catkin fiber regarded as an environmentally friendly thermal insulation material. In my country, willows are widely planted as greening tree species, which makes catkin fiber as a natural fiber resource have unique resource advantages. If it can be reasonably developed and utilized, it can not only protect the environment, but also produce certain economic benefits, enrich the application scope 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 you try 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 dispersibility of catkin fiber in the polymer matrix and insufficient thermal stability.

[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 deficiencies in 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 heat-insulating polypropylene fiber comprises the following steps:

[0007] 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, adding potassium chlorate and N,N-dimethylformamide, and then centrifugally separating, collecting, washing and drying the precipitate to obtain nano-cerium oxide loaded willow catkin fibers;

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

[0009] S3: Preparation of modified halloysite nanotubes, adding halloysite nanotubes and 3-chloropropyltrimethoxysilane into toluene, pre-treating the halloysite nanotubes, adding the pre-treated halloysite nanotubes into a magnesium chloride solution, adding a sodium hydroxide solution dropwise while stirring, reacting by 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 fiber, antioxidant, and lubricant are mixed, and flame retardant and heat-insulating polypropylene fiber is obtained through granulation, melt spinning, drawing, heat setting, and winding.

[0011] Further, 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, alkalizing at 50-70° C. for 40-60 min, filtering out the alkalized catkins, washing them to neutrality, and drying them with air blast to obtain alkalized catkins;

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

[0014] S1.3: placing the pretreated catkin fibers into a cerium salt aqueous solution with a concentration of 30 g / L, wherein the mass ratio of the pretreated catkin fibers to the cerium salt aqueous solution is (1-3): (200-500), stirring evenly, soaking at room temperature for 2-4 hours, and ultrasonically dispersing for 5-15 minutes to obtain a catkin fiber dispersed cerium salt aqueous solution;

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

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

[0019] S2.2: adding a modifying agent to the nano-cerium oxide loaded catkin fiber dispersion solution, the amount of the modifying agent added is 1-3% of the mass of the nano-cerium oxide loaded catkin fiber dispersion solution, stirring and reacting at 50-70° C. for 1-2 hours, and after the reaction is completed, vacuum filtering 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 into a 75% volume fraction methanol solution, 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), stir the reaction at 50-75°C for 2-5h, and then filter, wash and dry to obtain the modified nano cerium oxide loaded willow catkin fibers.

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

[0022] Further, step S3: preparation of modified halloysite nanotubes specifically comprises the following steps:

[0023] S3.1: adding 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, stirring and reacting at 110 to 120° C. for 2 to 5 hours, collecting the halloysite nanotubes after the reaction by filtration, washing and drying, and obtaining pretreated halloysite nanotubes;

[0024] S3.2: Add the pretreated halloysite nanotubes to a 30% magnesium chloride solution, the mass ratio of the halloysite nanotubes to the 30% magnesium chloride solution being (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 is 9.8-10.7, stop the dropping operation, continue stirring for 20-40 minutes, and then, filter, wash and dry to obtain modified halloysite nanotubes.

[0025] Further, step S4: preparing flame retardant 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 nano-cerium oxide loaded catkin fibers, 0.5-1 parts by weight of antioxidant, and 0.5-1 parts by weight of lubricant are uniformly mixed in a high-speed mixer, and then melted at 200-220° C. through a twin-screw extruder, extruded and granulated to obtain a flame-retardant polypropylene masterbatch;

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

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

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

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

[0031] The present invention has the following advantages:

[0032] 1. In the present invention, nano-cerium oxide loaded willow fiber is prepared so that nano-cerium oxide particles are uniformly and densely loaded on the surface of the willow fiber. Nano-cerium oxide has thermal stability and flame retardancy, can stabilize the fiber structure of the willow fiber at high temperature, reduce the mass loss and performance degradation of the willow fiber due to thermal decomposition, thereby reducing the burning rate of the willow fiber, effectively improving the thermal stability and flame retardancy of the willow fiber, so that the nano-cerium oxide loaded willow fiber has 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 groups on the organic layer on the surface of the silane-modified nano-cerium oxide loaded catkins fiber and the hydroxyl groups on the surface of the nano-cerium oxide can react with the epoxy groups on the glycidyl methacrylate, and the glycidyl methacrylate is fixed on the surface of the nano-cerium oxide loaded catkins fiber, and then the interface 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 evenly 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 beneficial to obtain modified halloysite nanotubes with good mechanical properties and flame retardant properties. Then, the modified halloysite nanotubes are added to the polypropylene fiber, which can effectively improve the flame retardant properties of the polypropylene fiber and enhance the mechanical properties of the polypropylene fiber. 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 described embodiments 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 creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] A method for preparing flame-retardant 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 and wash them to neutrality, and dry them with air to obtain alkalized catkins;

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

[0041] S1.3: placing the pretreated catkin fibers into a 30 g / L cerium chloride aqueous solution, the mass ratio of the pretreated catkin fibers to the cerium chloride aqueous solution being 3:500, stirring evenly, soaking at room temperature for 4 h, and ultrasonically dispersing for 15 min to obtain a catkin fiber dispersed cerium salt aqueous solution;

[0042] S1.4: adding potassium chlorate to the cerium salt aqueous solution dispersed in catkins fiber, the amount of potassium chlorate added is 0.6% of the mass of the cerium salt aqueous solution dispersed in catkins fiber, after the potassium chlorate is stirred and dissolved, adding N, N-dimethylformamide, wherein the amount of N, N-dimethylformamide added is 5% of the volume of the cerium salt aqueous solution dispersed in catkins fiber, stirring and mixing for 30 minutes, sealing and placing in an oven at 160°C for reaction for 5 hours, and then, through centrifugal separation, precipitate collection, precipitate washing and drying, nano-cerium oxide loaded catkins fiber is obtained;

[0043] S2: Modification of willow catkin fibers loaded with nano-cerium oxide.

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

[0045] S2.2: adding silane coupling agent KH-550 to the nano-cerium oxide loaded catkin fiber dispersion solution, the amount of silane coupling agent KH-550 added is 3% of the mass of the nano-cerium oxide loaded catkin fiber dispersion solution, stirring and reacting at 70°C for 2h, after the reaction is completed, vacuum filtration and drying are performed to obtain coupled modified nano-cerium oxide loaded catkin fiber;

[0046] S2.3: adding the coupled modified nano cerium oxide loaded catkins fiber 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 catkins fiber, glycidyl methacrylate and the methanol solution is 1:30:150, stirring and reacting at 60°C for 3h, and then filtering, washing and drying to obtain the modified nano cerium oxide loaded catkins fiber;

[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 are added to 150 parts by weight of toluene, and the mixture is stirred at 120° C. for 3 h, and the halloysite nanotubes after the reaction are collected by filtration, and the excess 3-chloropropyltrimethoxysilane is washed with toluene, and then washed twice with ethanol, and the washed halloysite nanotubes are placed in an oven at 60° C. and dried for 8 h to obtain pretreated halloysite nanotubes;

[0049] S3.2: adding the pretreated halloysite nanotubes to a 30% magnesium chloride solution, the mass ratio of the halloysite nanotubes to the 30% magnesium chloride solution being 1:30, and ultrasonically dispersing for 50 minutes to obtain a halloysite nanotube dispersion, and dripping a sodium hydroxide solution to the halloysite nanotube dispersion while stirring until the pH of the halloysite nanotube dispersion reaches 10.2, stopping the dripping operation, and continuing stirring for 40 minutes, and then filtering, washing and drying 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 nano-cerium oxide loaded catkin fibers, 1 part by weight of antioxidant 1010, and 1 part by weight of calcium stearate are uniformly mixed in a high-speed mixer, and then melted at 220° C. through a twin-screw extruder, extruded and granulated to obtain a flame-retardant polypropylene masterbatch;

[0052] S4.2: The flame retardant polypropylene masterbatch is successively 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 multiple of 3.0, heat setting at a temperature of 120°C and winding to obtain a flame retardant and heat-insulating polypropylene fiber.

[0053] Example 2

[0054] A method for preparing flame-retardant 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 and wash them to neutrality, and dry them with air to obtain alkalized catkins;

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

[0058] S1.3: placing the pretreated catkin fibers into a 30 g / L cerium chloride aqueous solution, the mass ratio of the pretreated catkin fibers to the cerium chloride aqueous solution being 3:500, stirring evenly, soaking at room temperature for 2 h, and ultrasonically dispersing for 5 min to obtain a catkin fiber dispersed cerium salt aqueous solution;

[0059] S1.4: adding potassium chlorate to the cerium salt aqueous solution dispersed in catkins fiber, the amount of potassium chlorate added is 0.6% of the mass of the cerium salt aqueous solution dispersed in catkins fiber, and after the potassium chlorate is stirred and dissolved, adding N, N-dimethylformamide, wherein the amount of N, N-dimethylformamide added is 5% of the volume of the cerium salt aqueous solution dispersed in catkins fiber, stirring and mixing for 20 minutes, sealing and placing in an oven at 180°C for reaction for 3 hours, and then, through centrifugal separation, precipitate collection, precipitate washing and drying, nano-cerium oxide loaded catkins fiber is obtained;

[0060] S2: Modification of willow catkin fibers loaded with nano-cerium oxide.

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

[0062] S2.2: adding silane coupling agent KH-550 to the nano-cerium oxide loaded catkin fiber dispersion solution, the amount of silane coupling agent KH-550 added is 3% of the mass of the nano-cerium oxide loaded catkin fiber dispersion solution, stirring and reacting at 50°C for 1 hour, after the reaction is completed, vacuum filtration and drying are performed to obtain coupled modified nano-cerium oxide loaded catkin fiber;

[0063] S2.3: adding the coupled modified nano cerium oxide loaded catkins fiber 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 catkins fiber, glycidyl methacrylate and the methanol solution is 1:30:150, stirring and reacting at 50°C for 2h, and then filtering, washing and drying to obtain the modified nano cerium oxide loaded catkins fiber;

[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 are added to 150 parts by weight of toluene, and the mixture is stirred at 110° C. for 5 hours. The halloysite nanotubes after the reaction are collected by filtration, and the excess 3-chloropropyltrimethoxysilane is washed with toluene, and then washed twice with ethanol. The washed halloysite nanotubes are placed in an oven at 70° C. and dried for 5 hours to obtain pretreated halloysite nanotubes;

[0066] S3.2: adding the pretreated halloysite nanotubes to a 30% magnesium chloride solution, the mass ratio of the halloysite nanotubes to the 30% magnesium chloride solution being 1:30, and ultrasonically dispersing for 30 minutes to obtain a halloysite nanotube dispersion, and dripping a sodium hydroxide solution to the halloysite nanotube dispersion while stirring until the pH of the halloysite nanotube dispersion reaches 10.2, stopping the dripping operation, and continuing stirring for 20 minutes, and then filtering, washing and drying 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 nano-cerium oxide loaded catkin fibers, 1 part by weight of antioxidant 1010, and 1 part by weight of calcium stearate are uniformly mixed in a high-speed mixer, and then melted at 220° C. through a twin-screw extruder, extruded and granulated to obtain a flame-retardant polypropylene masterbatch;

[0069] S4.2: The flame retardant polypropylene masterbatch is successively 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 multiple of 3.0, heat setting at a temperature of 120°C and winding to obtain a flame retardant and heat-insulating polypropylene fiber.

[0070] Example 3

[0071] A method for preparing flame-retardant 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 and wash them to neutrality, and dry them with air to obtain alkalized catkins;

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

[0075] S1.3: placing the pretreated catkin fibers into a 30 g / L cerium chloride aqueous solution, the mass ratio of the pretreated catkin fibers to the cerium chloride aqueous solution being 1:200, stirring evenly, soaking at room temperature for 4 h, and ultrasonically dispersing for 15 min to obtain a catkin fiber dispersed cerium salt aqueous solution;

[0076] S1.4: adding potassium chlorate to the cerium salt aqueous solution dispersed in catkins fiber, the amount of potassium chlorate added is 0.3% of the mass of the cerium salt aqueous solution dispersed in catkins fiber, after the potassium chlorate is stirred and dissolved, adding N, N-dimethylformamide, wherein the amount of N, N-dimethylformamide added is 3% of the volume of the cerium salt aqueous solution dispersed in catkins fiber, stirring and mixing for 30 minutes, sealing and placing in an oven at 160°C for reaction for 5 hours, and then, through centrifugal separation, precipitate collection, precipitate washing and drying, nano-cerium oxide loaded catkins fiber is obtained;

[0077] S2: Modification of willow catkin fibers loaded with nano-cerium oxide.

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

[0079] S2.2: adding silane coupling agent KH-550 to the nano-cerium oxide loaded catkin fiber dispersion solution, the amount of silane coupling agent KH-550 added is 1% of the mass of the nano-cerium oxide loaded catkin fiber dispersion solution, stirring and reacting at 70°C for 2h, after the reaction is completed, vacuum filtration and drying are performed to obtain coupled modified nano-cerium oxide loaded catkin fiber;

[0080] S2.3: adding the coupled modified nano cerium oxide loaded catkin fiber 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 catkin fiber, glycidyl methacrylate and the methanol solution is 1:50:200, stirring and reacting at 60°C for 3h, and then filtering, washing and drying to obtain the modified nano cerium oxide loaded catkin fiber;

[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 are added to 100 parts by weight of toluene, and the mixture is stirred at 120° C. for 3 h. The halloysite nanotubes after the reaction are collected by filtration, and the excess 3-chloropropyltrimethoxysilane is washed with toluene, and then washed twice with ethanol. The washed halloysite nanotubes are placed in an oven at 60° C. and dried for 8 h to obtain pretreated halloysite nanotubes;

[0083] S3.2: adding the pretreated halloysite nanotubes to a 30% magnesium chloride solution, the mass ratio of the halloysite nanotubes to the 30% magnesium chloride solution being 1:90, and ultrasonically dispersing for 50 minutes to obtain a halloysite nanotube dispersion, and dripping a sodium hydroxide solution to the halloysite nanotube dispersion while stirring until the pH of the halloysite nanotube dispersion reaches 10.7, stopping the dripping operation, and continuing stirring for 40 minutes, and then filtering, washing and drying 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 nano-cerium oxide loaded catkin fibers, 1 part by weight of antioxidant 1010, and 1 part by weight of calcium stearate are uniformly mixed in a high-speed mixer, and then melted at 220° C. through a twin-screw extruder, extruded and granulated to obtain a flame-retardant polypropylene masterbatch;

[0086] S4.2: The flame retardant polypropylene masterbatch is successively 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 multiple of 3.0, heat setting at a temperature of 120°C and winding to obtain a 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 fibers in step S2 are replaced by the pretreated catkin fibers obtained in step S1.2, a pretreated catkin fiber dispersion solution with a pretreated catkin fiber concentration of 2 g / L is prepared, the nano-cerium oxide-loaded catkin fiber dispersion solution in step S2.2 is replaced by the pretreated catkin fiber dispersion solution, and 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 fibers in step S4.1 are replaced by an equal weight portion of the nano-cerium oxide-loaded catkin fibers obtained in step S1.4, and the other steps remain unchanged to prepare flame-retardant and thermal insulating polypropylene fibers, which are 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 thermal insulating polypropylene fibers, which is recorded as Comparative Example 3.

[0093] Performance Testing

[0094] Mechanical property test: According to GB / T14344-2008, the flame retardant thermal insulation polypropylene fibers prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to mechanical property tests. The breaking strength and initial modulus of each flame retardant thermal insulation 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 fabrics of 200 mm*50 mm, 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, and 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 the modification treatment 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 can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention. Parts not described in detail in this specification belong to the 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, adding potassium chlorate and N,N-dimethylformamide, and then centrifugally separating, collecting, washing and drying the precipitate to obtain nano-cerium oxide loaded willow catkin fibers; S2: modification of nano-cerium oxide loaded willow catkin fibers, wherein the nano-cerium oxide loaded willow catkin fibers are coupled and modified by a modification agent, and then the coupled and modified nano-cerium oxide loaded willow catkin fibers are modified by glycidyl methacrylate to obtain modified nano-cerium oxide loaded willow catkin fibers; S3: Preparation of modified halloysite nanotubes, adding halloysite nanotubes and 3-chloropropyltrimethoxysilane into toluene, pre-treating the halloysite nanotubes, adding the pre-treated halloysite nanotubes into a magnesium chloride solution, adding a sodium hydroxide solution dropwise while stirring, reacting by 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 fiber, antioxidant, and lubricant are mixed, and flame retardant and heat-insulating polypropylene fiber is obtained through granulation, melt spinning, drawing, heat setting, and winding.

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, alkalizing at 50-70° C. for 40-60 min, filtering out the alkalized catkins, washing them to neutrality, and drying them with air blast to obtain alkalized catkins; S1.2: The alkalized catkins are combed by a carding machine to obtain pre-treated catkin fibers for later use; S1.3: placing the pretreated catkin fibers into a cerium salt aqueous solution with a concentration of 30 g / L, wherein the mass ratio of the pretreated catkin fibers to the cerium salt aqueous solution is (1-3): (200-500), stirring evenly, soaking at room temperature for 2-4 hours, and ultrasonically dispersing for 5-15 minutes to obtain a catkin fiber dispersed cerium salt aqueous solution; 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.

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 willow catkin fibers to a 50% by mass ethanol aqueous solution to prepare a nano-cerium oxide loaded willow catkin fiber dispersion solution having a nano-cerium oxide loaded willow catkin fiber concentration of 2 g / L; S2.2: adding a modifying agent to the nano-cerium oxide loaded catkin fiber dispersion solution, the amount of the modifying agent added is 1-3% of the mass of the nano-cerium oxide loaded catkin fiber dispersion solution, stirring and reacting at 50-70° C. for 1-2 hours, and after the reaction is completed, vacuum filtering 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 into a 75% volume fraction methanol solution, 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), stir the reaction at 50-75°C for 2-5h, and then filter, wash and dry to obtain the modified nano cerium oxide loaded willow catkin fibers.

5. The method for preparing a flame retardant and heat-insulating polypropylene fiber according to claim 4, characterized in that: The modification 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: adding 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, stirring and reacting at 110 to 120° C. for 2 to 5 hours, collecting the halloysite nanotubes after the reaction by filtration, washing and drying, and obtaining pretreated halloysite nanotubes; S3.2: Add the pretreated halloysite nanotubes to a 30% magnesium chloride solution, the mass ratio of the halloysite nanotubes to the 30% magnesium chloride solution being (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 is 9.8-10.7, stop the dropping operation, 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: Preparation of flame retardant heat-insulating polypropylene fiber, 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, and then melted at 200 to 220° C. by a twin-screw extruder, extruded and granulated to obtain a flame-retardant polypropylene masterbatch; S4.2: The flame retardant polypropylene masterbatch is melt-spun at 220-240℃, drawn at 80-120℃, and heated at 110- 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 heat-insulating polypropylene fiber, characterized in that: The flame retardant heat-insulating polypropylene fiber is prepared by the method for preparing the flame retardant heat-insulating polypropylene fiber according to any one of claims 1 to 9.