Smokeless flame-retardant polyester fiber and preparation method thereof

Abstract

The invention relates to the technical field of polyester fibers, in particular to a smokeless flame-retardant polyester fiber and a preparation method thereof.The smokeless flame-retardant polyester fiber is prepared from, by weight, 70-99 parts of polyester and 1-30 parts of composite flame retardant; the composite flame retardant comprises 21-30 parts by weight of modified aluminum hypophosphite, 1-2 parts by weight of nano aluminum hydroxide and / or 2-8 parts by weight of carbon nanotube modified aluminum hydroxide. The flame retardant property of the material is effectively improved, the molten drop phenomenon is prevented, the mechanical property, the thermal stability and the durability are effectively improved, and the release of smoke and toxic gas can be reduced; meanwhile, the addition amount of the flame retardant can be reduced to a certain extent, so that the influence on the mechanical property and the processability of the fiber is reduced. The prepared flame-retardant fiber has a wide application prospect in the fields of protective clothing, home textiles and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of polyester fibers, and particularly to a smokeless flame-retardant polyester fiber and a preparation method thereof. Background Art

[0002] Smokeless flame-retardant polyester fiber is a polyester fiber treated specially, which has flame-retardant performance and produces less smoke during combustion. This kind of fiber is widely used in fields that require high fire protection standards, such as fire-fighting suits, protective clothing, home textiles, and decorative materials for public places, etc.

[0003] Common smokeless flame retardants include phosphorus-based flame retardants, nitrogen-based flame retardants, inorganic flame retardants, halogen-based flame retardants, etc. Halogen-based flame retardants inhibit combustion by releasing hydrogen halide gas, but they will produce a large amount of smoke and toxic gases, causing great environmental pollution. Therefore, halogen-based flame retardants are being phased out due to environmental problems. While the halogen-free flame retardants mainly composed of phosphorus-based compounds and metal hydroxides have overcome the problems of traditional flame retardants such as being not environmentally friendly and producing highly toxic smoke after combustion, there are still problems of poor compatibility with polyester fibers in practical applications, being prone to migration and loss, and gradually losing the flame-retardant effect. Moreover, the halogen-free polyester flame retardants on the market only play a flame-retardant role and cannot play an anti-melting and dripping role. At the same time, the problem of poor compatibility may also lead to uneven dispersion of the flame retardant, a decrease in the mechanical properties of the material, and difficult processing, etc. Therefore, it is very necessary to avoid poor compatibility of the flame retardant during the fiber preparation process, and at the same time, improve the flame-retardant performance and anti-melting and dripping performance of polyester fibers. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a smokeless flame-retardant polyester fiber and a preparation method thereof to solve the problems of low flame-retardant performance, poor compatibility, and low anti-melting performance.

[0005] Based on the above purpose, the present invention provides a smokeless flame-retardant polyester fiber, comprising the following raw materials in parts by weight:

[0006] 70 - 99 parts of polyester and 1 - 30 parts of a composite flame retardant; the composite flame retardant comprises 21 - 30 parts by weight of modified aluminum hypophosphite, 1 - 2 parts by weight of nano aluminum hydroxide, and / or 2 - 8 parts by weight of carbon nanotube-modified aluminum hydroxide.

[0007] Preferably, the modified aluminum hypophosphite is obtained by surface treating aluminum hypophosphite with a titanate coupling agent. The surface treatment method is to pre-treat the aluminum hypophosphite powder to remove the adsorbed moisture on the surface, and then add the pre-treated aluminum hypophosphite powder into the titanate coupling agent solution. After heating and stirring at 60 - 80 °C for 1 - 2 hours, it is filtered and dried to obtain the modified aluminum hypophosphite. The titanate coupling agent forms an organic molecular layer on the surface of aluminum hypophosphite through chemical bonding and physical adsorption, thereby improving its dispersibility and compatibility with the polyester matrix, improving the interfacial bonding force, and enhancing the mechanical properties of the composite material; because the surface-modified aluminum hypophosphite is more uniformly dispersed in the polymer matrix, the flame retardant effect is more significant. At the same time, due to the improvement of dispersibility and compatibility, the addition amount of aluminum hypophosphite required to achieve the same flame retardant effect is reduced.

[0008] Preferably, the aluminum hypophosphite powder is dried at 80 - 120 °C to remove the adsorbed moisture on the surface.

[0009] Preferably, the concentration of the titanate coupling agent solution is 1 - 3%. Preferably, the titanate coupling agent is dissolved in an appropriate amount of organic solvent (ethanol or acetone) to prepare a 1 - 3% solution.

[0010] Optionally, the titanate coupling agent includes titanate TMC - 201 and TMC - 105.

[0011] Preferably, the preparation method of the carbon nanotube - modified aluminum hydroxide includes the following steps:

[0012] S1. Acidify the carbon nanotubes;

[0013] S2. Treat aluminum hydroxide and the acidified carbon nanotubes with a silane coupling agent respectively;

[0014] S3. Mix the coupling - treated carbon nanotubes and aluminum hydroxide according to a mass ratio of 2 - 5:1 - 3, then add them into ethanol and ultrasonically disperse for 10 - 15 min, and then stir and react at 60 - 80 °C for 1 - 2 h;

[0015] S4. After the reaction is completed, it is successively washed with ethanol, filtered and dried to obtain the carbon nanotube - modified aluminum hydroxide. By modifying aluminum hydroxide with carbon nanotubes (CNTs), its flame retardant performance and functionality can be significantly improved, and at the same time, the mechanical properties of the material can be improved. At the same time, the carbon nanotubes and aluminum hydroxide act synergistically to improve the flame retardant efficiency and reduce the release of smoke and toxic gases.

[0016] Preferably, the acidification treatment of the carbon nanotubes is to first acidify the carbon nanotubes in a mixed solution of concentrated nitric acid and sulfuric acid with a volume ratio of 3:1, reflux at 80 °C for 2 - 4 hours, then wash until neutral, and then filter and dry.

[0017] Optionally, the silane coupling agent includes KH-550 and KH-560.

[0018] The present invention also provides a method for preparing the smokeless flame-retardant polyester fiber, comprising the following steps:

[0019] Step 1: Uniformly mix the composite flame retardant with polyester chips through a twin-screw extruder, and then extrude and pelletize to obtain a smokeless flame-retardant polyester masterbatch;

[0020] Step 2: Blend the smokeless flame-retardant polyester masterbatch with polyester chips, and prepare the smokeless flame-retardant polyester fiber through a melt spinning machine.

[0021] Preferably, in Step 2, the blending temperature is 200 - 240 °C, the spinning temperature is 220 - 260 °C, the spinning rate is 1000 - 2500 m / min, and the drawing ratio is 1 - 5.

[0022] Preferably, the dosage ratio of polyester chips in Step 1 and Step 2 is 1:1.

[0023] Advantages of the present invention: By surface-treating aluminum hypophosphite with a titanate coupling agent, the dispersibility and compatibility with the polyester matrix can be significantly improved, thereby enhancing the flame retardancy and mechanical properties of the material. By treating carbon nanotubes and aluminum hydroxide with a silane coupling agent, their dispersibility and compatibility with the polyester matrix can be significantly improved. Meanwhile, by adding the composite flame retardant of the present invention, a three-dimensional network structure is formed inside the material, improving the thermal stability of the material, effectively enhancing the flame retardancy of the material and preventing the melt dripping phenomenon. Combining aluminum hydroxide modified by carbon nanotubes and modified aluminum hypophosphite to prepare a flame-retardant fiber can produce a significant synergistic effect. The carbon nanotubes form a network structure during combustion, promoting the formation of a carbon layer, enhancing the stability and compactness of the carbon layer. The high thermal conductivity of the carbon nanotubes helps to evenly disperse heat and delay the thermal degradation of the material; aluminum hypophosphite decomposes to generate aluminum phosphate, promoting carbonization and releasing phosphorus free radicals in the gas phase to capture active free radicals in the combustion chain reaction; the combined action of carbon nanotubes, aluminum hydroxide and aluminum hypophosphite forms a multi-level flame retardancy mechanism (gas-phase and condensed-phase flame retardancy), significantly improving the flame retardancy efficiency; the carbon nanotubes enhance the stability of the carbon layer, and aluminum hydroxide and aluminum hypophosphite synergistically promote carbonization, reducing the release of smoke and toxic gases and improving the safety of the fiber. While enhancing the flame retardancy, the mechanical properties of the fiber are maintained or enhanced. The synergistic effect of the three significantly improves the thermal stability of the fiber, delaying the thermal degradation and combustion process. At the same time, the addition amount of the flame retardant is reduced, thereby reducing the impact on the mechanical properties and processing properties of the fiber. The flame-retardant fiber prepared by the present invention has broad application prospects in the fields of protective clothing, home textiles, etc. Specific embodiments

[0024] To make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with specific embodiments.

[0025] It should be noted that unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meanings understood by those with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. The terms such as "comprising" or "including" mean that the elements or objects appearing before this term cover the elements or objects listed after this term and their equivalents, without excluding other elements or objects.

[0026] The modified aluminum hypophosphite used in the embodiments of the present invention is prepared by the following method:

[0027] Pretreatment of aluminum hypophosphite: The aluminum hypophosphite powder is dried at 80 - 120 °C to remove the moisture adsorbed on the surface.

[0028] Preparation of titanate coupling agent solution: Dissolve the titanate coupling agent (such as titanate TMC - 201, TMC - 105) in an appropriate amount of organic solvent (such as ethanol, acetone) to prepare a 1 - 3% solution.

[0029] Surface treatment: First, add the dried aluminum hypophosphite powder to the titanate coupling agent solution and stir evenly; then heat and stir at 60 - 80 °C for 1 - 2 hours to make the titanate coupling agent fully react with the surface of the aluminum hypophosphite.

[0030] Filtration and drying: First, filter the treated aluminum hypophosphite to remove the excess solvent; then dry it at 80 - 100 °C to obtain the surface - modified aluminum hypophosphite.

[0031] The nano - aluminum hydroxide used in the embodiments of the present invention is obtained by purchasing from the market.

[0032] The aluminum hydroxide modified by carbon nanotubes used in the embodiments of the present invention is prepared by the following method:

[0033] Pretreatment of carbon nanotubes: First, acidify the carbon nanotubes in a mixed solution of concentrated nitric acid and sulfuric acid (volume ratio 3:1), and reflux at 80 °C for 2 - 4 hours. Then wash with deionized water until neutral, filter and dry at 80 °C.

[0034] Preparation of silane coupling agent solution: Dissolve the silane coupling agent (such as KH - 550, KH - 560) in a mixed solvent of ethanol and water (ethanol:water = 9:1) to prepare a 1 - 3% solution. Adjust the pH to 4 - 5 with acetic acid to promote the hydrolysis of the silane coupling agent.

[0035] Surface treatment of carbon nanotubes with silane coupling agent: First, add the acid-treated carbon nanotubes into the silane coupling agent solution and ultrasonically disperse for 30 minutes. Then, stir and react at 60 - 80 °C for 2 - 4 hours to allow the silane coupling agent to fully react with the surface of the carbon nanotubes. After the reaction is completed, wash with ethanol to remove the unreacted silane coupling agent, filter, and dry at 80 °C.

[0036] Surface treatment of aluminum hydroxide with silane coupling agent: First, add the dry aluminum hydroxide powder into the silane coupling agent solution and stir evenly. Stir and react at 60 - 80 °C for 1 - 2 hours to allow the silane coupling agent to fully react with the surface of the aluminum hydroxide. After the reaction is completed, wash with ethanol to remove the unreacted silane coupling agent, filter, and dry at 80 °C.

[0037] Mix the coupled carbon nanotubes and aluminum hydroxide at a mass ratio of 2 - 5:1 - 3, then add them into ethanol and ultrasonically disperse for 10 - 15 min, and then stir and react at 60 - 80 °C for 1 - 2 h. After the reaction is completed, wash with ethanol to remove the unreacted silane coupling agent, filter, and dry at 80 °C to obtain aluminum hydroxide modified by carbon nanotubes.

[0038] Example 1

[0039] The titanate coupling agent solution used in this example:

[0040] Dissolve titanate TMC - 201 in ethanol to prepare a 1% solution.

[0041] Surface treatment and modification of aluminum hypophosphite: First, add the dry aluminum hypophosphite powder into the 1% titanate TMC - 201 solution and stir evenly. Then, heat and stir at 70 °C for 1.5 hours to allow the titanate coupling agent to fully react with the surface of the aluminum hypophosphite. Then filter the treated aluminum hypophosphite to remove the excess solvent. Finally, dry at 80 °C to obtain surface - modified aluminum hypophosphite.

[0042] Preparation of silane coupling agent solution: Dissolve silane coupling agent KH - 550 in a mixed solvent of ethanol and water (ethanol:water = 9:1) to prepare a 1% solution. Adjust the pH to 4.5 with acetic acid to promote the hydrolysis of the silane coupling agent.

[0043] Treat aluminum hydroxide and acid - treated carbon nanotubes with the silane coupling agent solution prepared in this example respectively to obtain the coupled carbon nanotubes and aluminum hydroxide.

[0044] Mix the coupled carbon nanotubes and aluminum hydroxide at a mass ratio of 2:1, then add them into ethanol and ultrasonically disperse for 10 min, and then stir and react at 70 °C for 1 h. After the reaction is completed, wash with ethanol to remove the unreacted silane coupling agent, filter, and dry at 80 °C to obtain aluminum hydroxide modified by carbon nanotubes.

[0045] Mix 25 parts by weight of modified aluminum hypophosphite and 2 parts by weight of aluminum hydroxide modified by carbon nanotubes to form a composite smokeless flame retardant.

[0046] The method for preparing smokeless flame-retardant polyester fiber in this example includes the following steps:

[0047] Step 1: Uniformly mix 2 parts by weight of the composite flame retardant with 49 parts by weight of polyester chips through a twin-screw extruder, and then extrude and pelletize to obtain a smokeless flame-retardant polyester masterbatch;

[0048] Step 2: Blend the obtained smokeless flame-retardant polyester masterbatch with another 49 parts by weight of polyester chips, and prepare smokeless flame-retardant polyester fiber through a melt spinning machine; among them, the blending temperature is 200 °C, the spinning temperature is 220 °C, the spinning speed is 1000 m / min, and the draw ratio is 2.

[0049] Example 2

[0050] The titanate coupling agent solution used in this example:

[0051] Dissolve titanate TMC-201 in ethanol to prepare a 2% solution.

[0052] Surface treatment of modified aluminum hypophosphite: First, add dry aluminum hypophosphite powder to a 2% solution of titanate TMC-201, and stir evenly; then heat and stir at 70 °C for 1.5 hours to make the titanate coupling agent fully react with the surface of aluminum hypophosphite. Then filter the treated aluminum hypophosphite to remove the excess solvent; finally, dry at 80 °C to obtain surface-modified aluminum hypophosphite.

[0053] Preparation of silane coupling agent solution: Dissolve silane coupling agent KH-550 in a mixed solvent of ethanol and water (ethanol:water = 9:1) to prepare a 2% solution. Adjust the pH to 4.5 with acetic acid to promote the hydrolysis of the silane coupling agent.

[0054] Treat aluminum hydroxide and acid-treated carbon nanotubes with the silane coupling agent solution prepared in this example respectively to obtain coupled carbon nanotubes and aluminum hydroxide.

[0055] Mix the coupled carbon nanotubes and aluminum hydroxide according to a mass ratio of 5:3, then add them to ethanol and ultrasonically disperse for 10 min, and then stir and react at 80 °C for 1.5 h; after the reaction is completed, wash with ethanol to remove the unreacted silane coupling agent, filter and dry at 80 °C to obtain aluminum hydroxide modified by carbon nanotubes.

[0056] Mix 30 parts by weight of modified aluminum hypophosphite and 8 parts by weight of aluminum hydroxide modified by carbon nanotubes to form a composite smokeless flame retardant.

[0057] The method for preparing the smokeless flame-retardant polyester fiber in this embodiment includes the following steps:

[0058] Step 1: Uniformly mix 8 parts by weight of the composite flame retardant with 46 parts by weight of polyester chips through a twin-screw extruder, and then extrude and pelletize to obtain a smokeless flame-retardant polyester masterbatch;

[0059] Step 2: Blend the obtained smokeless flame-retardant polyester masterbatch with another 46 parts by weight of polyester chips, and prepare the smokeless flame-retardant polyester fiber through a melt spinning machine; wherein the blending temperature is 210 °C, the spinning temperature is 230 °C, the spinning speed is 1500 m / min, and the drawing ratio is 3.

[0060] Example 3

[0061] The titanate coupling agent solution used in this embodiment:

[0062] Dissolve titanate TMC-105 in ethanol to prepare a 3% solution.

[0063] Surface treatment and modification of aluminum hypophosphite: First, add dry aluminum hypophosphite powder to a 3% titanate TMC-105 solution, and stir evenly; then heat and stir at 80 °C for 1.5 hours to make the titanate coupling agent fully react with the surface of aluminum hypophosphite. Then filter the treated aluminum hypophosphite to remove the excess solvent; finally, dry at 80 °C to obtain surface-modified aluminum hypophosphite.

[0064] Preparation of the silane coupling agent solution: Dissolve the silane coupling agent KH-550 in a mixed solvent of ethanol and water (ethanol:water = 9:1) to prepare a 2% solution. Adjust the pH to 4.5 with acetic acid to promote the hydrolysis of the silane coupling agent.

[0065] Treat aluminum hydroxide and acid-treated carbon nanotubes with the silane coupling agent solution prepared in this embodiment respectively to obtain the coupled carbon nanotubes and aluminum hydroxide.

[0066] Mix the coupled carbon nanotubes and aluminum hydroxide in a mass ratio of 5:3, then add them to ethanol and ultrasonically disperse for 10 min, and then stir and react at 80 °C for 1.5 h; after the reaction is completed, wash with ethanol to remove the unreacted silane coupling agent, filter and dry at 80 °C to obtain carbon nanotube-modified aluminum hydroxide.

[0067] Mix 25 parts by weight of the modified aluminum hypophosphite and 5 parts by weight of the carbon nanotube-modified aluminum hydroxide to form a composite smokeless flame retardant.

[0068] The method for preparing the smokeless flame-retardant polyester fiber in this embodiment includes the following steps:

[0069] Step 1: Uniformly mix 20 parts by weight of the composite flame retardant with 40 parts by weight of polyester chips through a twin-screw extruder, and then extrude and pelletize to obtain a smokeless flame-retardant polyester masterbatch;

[0070] Step 2: Blend the obtained smokeless flame-retardant polyester masterbatch with another 40 parts by weight of polyester chips, and prepare smokeless flame-retardant polyester fibers through a melt spinning machine; among them, the blending temperature is 220 °C, the spinning temperature is 220 °C, the spinning speed is 2200 m / min, and the drawing ratio is 4.

[0071] Example 4

[0072] The difference between this example and Example 2 is that 30 parts by weight of modified aluminum hypophosphite and 2 parts by weight of nano-aluminum hydroxide are mixed to form a composite smokeless flame retardant. The method for preparing smokeless flame-retardant polyester fibers is the same as that in Example 2.

[0073] Example 5

[0074] The difference between this example and Example 2 is that 30 parts by weight of modified aluminum hypophosphite, 1 part by weight of nano-aluminum hydroxide, and 7 parts by weight of carbon nanotube-modified aluminum hydroxide are mixed to form a composite smokeless flame retardant.

[0075] Comparative Example 1

[0076] Use 30 parts by weight of aluminum hypophosphite and 2 parts by weight of aluminum hydroxide as the smokeless flame retardant.

[0077] The method for preparing smokeless flame-retardant polyester fibers includes the following steps:

[0078] Step 1: Uniformly mix 8 parts by weight of the smokeless flame retardant with 46 parts by weight of polyester chips through a twin-screw extruder, and then extrude and pelletize to obtain a smokeless flame-retardant polyester masterbatch;

[0079] Step 2: Blend the obtained smokeless flame-retardant polyester masterbatch with another 46 parts by weight of polyester chips, and prepare smokeless flame-retardant polyester fibers through a melt spinning machine; among them, the blending temperature is 210 °C, the spinning temperature is 230 °C, the spinning speed is 1500 m / min, and the drawing ratio is 3.

[0080] Refer to the method of GB / T 14463-2008 to detect the physical indexes of the smokeless flame-retardant polyester fibers prepared in Examples 1-5 and the polyester fibers prepared in Comparative Example 1. The flame retardancy is measured by the limiting oxygen index, and the LOI is measured on an oxygen index measuring instrument according to GB / T5454-1997 "Textiles - Burning performance - Determination of oxygen index method", and finally the calculated LOI value is used as the final result. The combustion test is carried out with reference to GB / T5455-2014 "Textiles - Burning performance - Determination of the length of damage in the vertical direction, smoldering and afterflame time", and the ticking number refers to the number of times of molten ticking during the combustion process.

[0081] The comparative results of the physical indexes and flame retardant properties of the flame retardant polyester fibers prepared in Examples 1-5 and Comparative Example 1 are shown in Table 1 below.

[0082]

[0083]

[0084] It can be seen from the experimental results in Table 1 above that by combining modified aluminum hypophosphite with nano aluminum hydroxide, or modified aluminum hypophosphite with aluminum hydroxide modified by carbon nanotubes, the flame retardant properties and mechanical properties of the material can be effectively improved, while the thermal stability of the material is improved, the flame retardant properties of the material are effectively improved and the melt dripping phenomenon is prevented. The combined use of modified aluminum hypophosphite, nano aluminum hydroxide and aluminum hydroxide modified by carbon nanotubes can achieve better performance. Combining aluminum hydroxide modified by carbon nanotubes with modified aluminum hypophosphite to prepare flame retardant fibers can produce a significant synergistic effect. The carbon nanotubes form a network structure during combustion, promoting the formation of a carbon layer, enhancing the stability and compactness of the carbon layer. The high thermal conductivity of the carbon nanotubes helps to evenly disperse heat and delay the thermal degradation of the material; aluminum hypophosphite decomposes to generate aluminum phosphate, promoting carbon formation and releasing phosphorus free radicals in the gas phase to capture the active free radicals in the combustion chain reaction; the combined action of carbon nanotubes, aluminum hydroxide and aluminum hypophosphite forms a multi-level flame retardant mechanism (gas-phase and condensed-phase flame retardance), significantly improving the flame retardant efficiency; the carbon nanotubes enhance the stability of the carbon layer, and aluminum hydroxide and aluminum hypophosphite synergistically promote carbon formation, reducing the release of smoke and toxic gases and improving the safety of the fibers.

[0085] Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity. Any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A smokeless flame-retardant polyester fiber, characterized in that: The invention comprises the following raw materials in parts by weight: 70-99 parts of polyester and 1-30 parts of composite flame retardant; the composite flame retardant comprises 21-30 parts by weight of modified aluminum hypophosphite, 1-2 parts by weight of nano aluminum hydroxide and / or 2-8 parts by weight of aluminum hydroxide modified by carbon nanotubes.

2. The smokeless flame-retardant polyester fiber according to claim 1, characterized in that: The modified aluminum hypophosphite is obtained by treating the surface of aluminum hypophosphite with a titanate coupling agent. The surface treatment method is to pretreat the aluminum hypophosphite powder to remove the moisture adsorbed on the surface, then add the pretreated aluminum hypophosphite powder into a titanate coupling agent solution, heat and stir at 60-80° C. for 1-2 hours, filter and dry to obtain the modified aluminum hypophosphite.

3. The smokeless flame-retardant polyester fiber according to claim 2, characterized in that: The concentration of the titanate coupling agent solution is 1-3%.

4. The smokeless flame-retardant polyester fiber according to claim 2, characterized in that: The titanate coupling agent includes titanate TMC-201 and TMC-105.

5. The smokeless flame-retardant polyester fiber according to claim 1, characterized in that: The preparation method of the carbon nanotube-modified aluminum hydroxide comprises the following steps: S1, acid treatment of carbon nanotubes; S2, treating aluminum hydroxide and the acid-treated carbon nanotubes with a silane coupling agent respectively; S3, mixing the carbon nanotubes after coupling treatment and aluminum hydroxide in a mass ratio of 2-5:1-3, adding them into ethanol for ultrasonic dispersion for 10-15 minutes, and then stirring and reacting at 60-80° C. for 1-2 hours; S4. After the reaction is completed, the aluminum hydroxide modified with carbon nanotubes is obtained by washing with ethanol, filtering and drying.

6. The smokeless flame-retardant polyester fiber according to claim 5, characterized in that: The acid treatment of the carbon nanotubes is to firstly acidify the carbon nanotubes in a mixed solution of concentrated nitric acid and sulfuric acid in a volume ratio of 3:1, reflux at 80° C. for 2-4 hours, then wash to neutrality, and then filter and dry.

7. The smokeless flame-retardant polyester fiber according to claim 5, characterized in that: The silane coupling agent includes KH-550 and KH-560.

8. The method for preparing the smokeless flame-retardant polyester fiber according to any one of claims 1 to 7, characterized in that: The steps include: Step 1: uniformly mixing the composite flame retardant with the polyester chips through a twin-screw extruder, and then extruding and granulating to obtain a smokeless flame retardant polyester masterbatch; Step 2: blending the smokeless flame-retardant polyester masterbatch with polyester chips to prepare the smokeless flame-retardant polyester fiber through a melt spinning machine.

9. The method for preparing the smokeless flame-retardant polyester fiber according to claim 8, characterized in that: The blending temperature in step 2 is 200-240° C., the spinning temperature is 220-260° C., the spinning rate is 1000-2500 m / min, and the drafting multiple is 1-5.

10. The method for preparing the smokeless flame-retardant polyester fiber according to claim 8, characterized in that: The usage ratio of the polyester chips in step 1 and step 2 is 1:1.

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