Preparation method of modified regenerated polyester fiber

Abstract

The invention relates to a preparation method of modified regenerated polyester fibers, and belongs to the technical field of textile materials. The modified regenerated polyester fiber is prepared by taking waste polyester fiber, ethylene glycol, a catalyst, a flame-retardant bacteriostatic agent, a polycondensation catalyst antimony trioxide, a heat stabilizer trimethyl phosphate and a delustering agent titanium dioxide as raw materials. The preparation method comprises the following steps: firstly, decomposing the waste polyester fiber into small molecules by using ethylene glycol to obtain an alcoholysis product; according to the preparation method, waste polyester fibers are selected as raw materials, so that the preparation method is green and environment-friendly, a flame-retardant bacteriostatic agent and ethylene glycol are polymerized, an alcoholysis product, antimony trioxide, trimethyl phosphate and titanium dioxide are added into a polymerization product, modified PET is obtained through a condensation polymerization reaction, and finally, the modified PET is subjected to melt extrusion and spinning to obtain the modified regenerated polyester fibers. The prepared modified regenerated polyester fiber has good flame retardance and antibacterial activity, and can be widely applied to the field of clothing and home textiles.

Description

Technical Field

[0001] The invention belongs to the technical field of textile materials, and specifically relates to a method for preparing modified regenerated polyester fiber. Background Art

[0002] Polyethylene terephthalate (PET) fiber has good chemical stability and high strength, and is widely used in clothing, home textiles, automotive interiors and other fields. However, the natural degradation rate of polyester fiber is extremely slow, usually more than 60 years, so with the increase in the production of polyester textiles and the continuous expansion of application fields.

[0003] In the prior art, there are mainly physical and chemical methods for recycling waste polyester textiles. The physical method is simple to operate and low in cost. However, due to the complex composition of waste polyester, it is difficult to effectively separate impurities using only physical means, and the polyester fiber itself has poor flame retardant properties and lacks antibacterial properties. Based on this, the present invention provides a method for preparing modified regenerated polyester fiber, which uses a chemical method to recycle waste polyester fibers to prepare a regenerated polyester fiber with good flame retardant and antibacterial properties. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing modified regenerated polyester fiber, so as to solve the problems mentioned in the above background technology.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing modified regenerated polyester fiber comprises the following steps:

[0007] The first step is to mix p-formylbenzoic acid, 6-acetylpicolinic acid, sodium hydroxide solution and ethanol in a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at a temperature of 40-60° C. for 8 hours. After the reaction is completed, 20% hydrochloric acid by mass is added to the three-necked flask to adjust the pH of the system to 5, and then dichloromethane is added to the three-necked flask for extraction, and the organic layer is separated by a separatory funnel, the organic layer is rotary evaporated to remove the solvent, and the remaining solid is washed with deionized water and dried to obtain intermediate 1;

[0008] Step 2: Mix the intermediate 1, dimethyl phosphite, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene and ethanol in a three-necked flask, install a condenser and a thermometer, start magnetic stirring, and react at a temperature of 50-60°C for 4 hours. After the reaction is completed, remove the solvent by rotary evaporation, wash the remaining solid with deionized water and dry to obtain the intermediate 2;

[0009] Step 3: Mix the intermediate 2, lauryl bromide and acetonitrile in a three-necked flask, install a condenser and a thermometer, start magnetic stirring, and react at 80°C for 24 hours. After the reaction is completed, spin dry the reaction solution to obtain a flame retardant and antibacterial agent;

[0010] Step 4: Put waste polyester fiber, ethylene glycol and catalyst into a reactor, and introduce nitrogen into the reactor to exhaust the air in the reactor, then react at a temperature of 190-220°C for 8-10 hours. After the reaction, reduce the temperature of the reaction system to 150°C, filter while hot and remove the solid, add deionized water to the filtrate and cool to room temperature, then vacuum filter and wash the filter cake with deionized water and dry to obtain an alcoholysis product;

[0011] Step 5: Add the flame retardant and antibacterial agent and ethylene glycol into the reactor, react at a temperature of 80-90°C for 2h, then add the alcoholysis product, antimony trioxide, trimethyl phosphate, and titanium dioxide into the reactor, and evacuate the reactor to vacuum, and then react at a temperature of 260-280°C for 3-4h, during which the pressure in the reactor is controlled to be less than 0.1Kpa. After the reaction is completed, the product is cooled, pelletized, and dried to obtain the modified PET;

[0012] Step 6: Add the modified PET into a twin-screw extruder for melt extrusion and spinning to obtain a modified recycled polyester fiber.

[0013] Furthermore, the sodium hydroxide solution used in the first step is a sodium hydroxide aqueous solution with a mass fraction of 30%.

[0014] Furthermore, the dosage ratio of p-formylbenzoic acid, 6-acetylpicolinic acid, sodium hydroxide solution and ethanol used in the first step is 0.1 mol: 0.1 mol: 40-50 mL: 60-80 mL.

[0015] Furthermore, the dosage ratio of the intermediate 1, dimethyl phosphite, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, and ethanol used in the second step is 0.07 mol: 0.07-0.08 mol: 0.016-0.024 mol: 40-60 mL.

[0016] Furthermore, the usage ratio of the intermediate 2, lauryl bromide and acetonitrile used in the third step is 0.06 mol: 0.06-0.08 mol: 40-60 mL.

[0017] Furthermore, the catalyst used in the fourth step is one of zinc acetate and manganese acetate.

[0018] Furthermore, in terms of mass fractions, the mass fraction ratio of the waste polyester fiber, ethylene glycol, and catalyst used in the fourth step is 100 parts: 60-70 parts: 1.2-2 parts.

[0019] Furthermore, in terms of mass proportions, the flame retardant and antibacterial agent, ethylene glycol, alcoholysis product, antimony trioxide, trimethyl phosphate, and titanium dioxide used in the fifth step are 5-6 parts: 10-18 parts: 100 parts: 2-2.8 parts: 0.01 parts: 1.4-1.8 parts.

[0020] Furthermore, in the sixth step, the temperature of the twin-screw extruder was set to 275°C in zone 1, 280°C in zone 2, 285°C in zone 3, 290°C in zone 4, 285°C in zone 5, and 280°C in zone 6.

[0021] Furthermore, in the sixth step, the spinning speed is 1000-1200 m / min, and the drafting multiple is 3-4 times.

[0022] Beneficial effects of the present invention:

[0023] 1) The present invention uses p-formylbenzoic acid and 6-acetylpicolinic acid as raw materials, and utilizes the formyl group of p-formylbenzoic acid and the α-hydrogen atom of 6-acetylpicolinic acid to undergo Claisen-Schmidt condensation in an alkaline environment to obtain intermediate 1, and then uses intermediate 1 and dimethyl phosphite as raw materials, and utilizes the double bond of intermediate 1 and dimethyl phosphite to undergo Michael addition reaction under the catalytic action of MTBD to obtain intermediate 2, and finally uses intermediate 2 and lauryl bromide as raw materials, and utilizes the pyridine nitrogen atom of intermediate 2 and the bromine of lauryl bromide to react with each other to obtain intermediate 2. The atoms react with quaternary ammonium salts to obtain a flame retardant and antibacterial agent; the flame retardant and antibacterial agent of the present invention has a phosphate structure, can be decomposed at high temperature to form a protective carbon layer to isolate the flame, prevent the polyester fiber from further burning, and can give the polyester fiber good flame retardancy. In addition, the flame retardant and antibacterial agent of the present invention also has a pyridyl quaternary ammonium salt structure, can adsorb bacteria and pierce bacterial cell membranes, and has good antibacterial properties. Moreover, the flame retardant and antibacterial agent of the present invention has two carboxyl groups, which can be combined in the polyester fiber in a polymerized manner to be effective for a long time.

[0024] 2) The present invention uses waste polyester fiber, ethylene glycol, a catalyst, a flame retardant and antibacterial agent, a condensation catalyst antimony trioxide, a heat stabilizer trimethyl phosphate, and a matting agent titanium dioxide as raw materials to prepare a modified regenerated polyester fiber. The present invention first decomposes the waste polyester fiber into small molecules with ethylene glycol to obtain an alcoholysis product, then polymerizes the flame retardant and antibacterial agent with ethylene glycol, and then adds the alcoholysis product and antimony trioxide, trimethyl phosphate, and titanium dioxide to the polymerization product to obtain a modified PET through a condensation reaction. Finally, the modified PET is melt-extruded and spun to obtain a modified regenerated polyester fiber. The preparation method of the present invention uses waste polyester fiber as raw material, is green and environmentally friendly, and conforms to the concept of sustainable development. The prepared modified regenerated polyester fiber has good flame retardancy and antibacterial properties and can be widely used in the field of clothing and home textiles. DETAILED DESCRIPTION

[0025] 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.

[0026] Example 1

[0027] A method for preparing modified regenerated polyester fiber comprises the following steps:

[0028] The first step is to mix 0.1 mol p-formylbenzoic acid, 0.1 mol 6-acetylpicolinic acid, 40 mL of 30% sodium hydroxide aqueous solution, and 60 mL of ethanol in a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at a temperature of 40° C. for 8 hours. After the reaction is completed, 20% hydrochloric acid is added to the three-necked flask to adjust the pH of the system to 5, and then dichloromethane is added to the three-necked flask for extraction, and the organic layer is separated by a separatory funnel. The organic layer is rotary evaporated to remove the solvent, and the remaining solid is washed with deionized water and dried to obtain intermediate 1;

[0029] Step 2: 0.07 mol intermediate 1, 0.07 mol dimethyl phosphite, 0.016 mol 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene and 40 mL ethanol were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the reaction was carried out at a temperature of 50°C for 4 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the remaining solid was washed with deionized water and dried to obtain intermediate 2;

[0030] Step 3: Mix 0.06 mol intermediate 2, 0.06 mol lauryl bromide and 40 mL acetonitrile in a three-necked flask, install a condenser and a thermometer, start magnetic stirring, and react at 80°C for 24 hours. After the reaction is completed, spin dry the reaction solution to obtain a flame retardant and antibacterial agent;

[0031] Step 4: 100 parts of waste polyester fiber, 60 parts of ethylene glycol and 1.2 parts of zinc acetate were put into a reactor by weight, and nitrogen was introduced into the reactor to exhaust the air in the reactor. The reaction was then carried out at a temperature of 190° C. for 8 hours. After the reaction was completed, the temperature of the reaction system was lowered to 150° C., and the solid was filtered while hot and removed. Deionized water was added to the filtrate and cooled to room temperature. The filter cake was then vacuum filtered and washed with deionized water and dried to obtain an alcoholysis product.

[0032] Step 5: Add 5 parts of flame retardant and antibacterial agent and 10 parts of ethylene glycol into the reactor by weight, react at 80°C for 2h, then add 100 parts of alcoholysis product, 2 parts of antimony trioxide, 0.01 parts of trimethyl phosphate, 1.4 parts of titanium dioxide into the reactor, evacuate the reactor, and then react at 260°C for 3h, during which the pressure in the reactor is controlled to be less than 0.1Kpa. After the reaction is completed, the product is cooled, pelletized, and dried to obtain modified PET;

[0033] Step 6. Add the modified PET into a twin-screw extruder for melt extrusion and then spin to obtain a modified recycled polyester fiber, wherein the temperature of the twin-screw extruder is set to 275°C in zone 1, 280°C in zone 2, 285°C in zone 3, 290°C in zone 4, 285°C in zone 5, and 280°C in zone 6, the spinning speed is 1000m / min, and the drafting multiple is 3 times.

[0034] Example 2

[0035] A method for preparing modified regenerated polyester fiber comprises the following steps:

[0036] The first step is to mix 0.1 mol p-formylbenzoic acid, 0.1 mol 6-acetylpicolinic acid, 45 mL of 30% sodium hydroxide aqueous solution, and 70 mL of ethanol in a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at a temperature of 50° C. for 8 hours. After the reaction is completed, 20% hydrochloric acid is added to the three-necked flask to adjust the pH of the system to 5, and then dichloromethane is added to the three-necked flask for extraction, and the organic layer is separated by a separatory funnel. The organic layer is rotary evaporated to remove the solvent, and the remaining solid is washed with deionized water and dried to obtain intermediate 1;

[0037] Step 2: 0.07 mol intermediate 1, 0.075 mol dimethyl phosphite, 0.02 mol 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene and 40 mL ethanol were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the reaction was carried out at a temperature of 55°C for 4 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the remaining solid was washed with deionized water and dried to obtain intermediate 2;

[0038] Step 3: Mix 0.06 mol intermediate 2, 0.07 mol lauryl bromide and 50 mL acetonitrile in a three-necked flask, install a condenser and a thermometer, start magnetic stirring, and react at 80°C for 24 hours. After the reaction is completed, spin dry the reaction solution to obtain a flame retardant and antibacterial agent;

[0039] Step 4: 100 parts of waste polyester fiber, 65 parts of ethylene glycol and 1.6 parts of zinc acetate were put into a reactor by weight, and nitrogen was introduced into the reactor to exhaust the air in the reactor. The reaction was then carried out at a temperature of 205°C for 9 hours. After the reaction, the temperature of the reaction system was lowered to 150°C, and the solid was filtered while hot and removed. Deionized water was then added to the filtrate to cool it to room temperature. The filter cake was then vacuum filtered and washed with deionized water and dried to obtain an alcoholysis product.

[0040] Step 5: Add 5.5 parts of flame retardant and antibacterial agent and 14 parts of ethylene glycol into the reactor by weight, react at 85°C for 2h, then add 100 parts of alcoholysis product, 2.4 parts of antimony trioxide, 0.01 parts of trimethyl phosphate, and 1.6 parts of titanium dioxide into the reactor, and evacuate the reactor to vacuum, and then react at 270°C for 3.5h, during which the pressure in the reactor is controlled to be less than 0.1Kpa. After the reaction is completed, the product is cooled, pelletized, and dried to obtain modified PET;

[0041] Step 6. Add the modified PET into a twin-screw extruder for melt extrusion and then spin to obtain a modified recycled polyester fiber, wherein the temperature of the twin-screw extruder is set to 275°C in zone 1, 280°C in zone 2, 285°C in zone 3, 290°C in zone 4, 285°C in zone 5, and 280°C in zone 6, the spinning speed is 1100 m / min, and the drafting multiple is 3.5 times.

[0042] Example 3

[0043] A method for preparing modified regenerated polyester fiber comprises the following steps:

[0044] The first step is to mix 0.1 mol p-formylbenzoic acid, 0.1 mol 6-acetylpicolinic acid, 50 mL of 30% sodium hydroxide aqueous solution, and 80 mL of ethanol in a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at a temperature of 60° C. for 8 hours. After the reaction is completed, 20% hydrochloric acid is added to the three-necked flask to adjust the pH of the system to 5, and then dichloromethane is added to the three-necked flask for extraction, and the organic layer is separated by a separatory funnel. The organic layer is rotary evaporated to remove the solvent, and the remaining solid is washed with deionized water and dried to obtain intermediate 1;

[0045] Step 2: 0.07 mol intermediate 1, 0.08 mol dimethyl phosphite, 0.024 mol 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene and 60 mL ethanol were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the reaction was carried out at a temperature of 60°C for 4 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the remaining solid was washed with deionized water and dried to obtain intermediate 2;

[0046] Step 3: Mix 0.06 mol intermediate 2, 0.08 mol lauryl bromide and 60 mL acetonitrile in a three-necked flask, install a condenser and a thermometer, start magnetic stirring, and react at 80°C for 24 hours. After the reaction is completed, spin dry the reaction solution to obtain a flame retardant and antibacterial agent;

[0047] Step 4: 100 parts of waste polyester fiber, 70 parts of ethylene glycol and 2 parts of manganese acetate were put into a reactor by weight, and nitrogen was introduced into the reactor to exhaust the air in the reactor. The reaction was then carried out at a temperature of 220° C. for 10 hours. After the reaction was completed, the temperature of the reaction system was lowered to 150° C., and the solid was filtered while hot and removed. Deionized water was then added to the filtrate to cool it to room temperature. The filter cake was then vacuum filtered and washed with deionized water and dried to obtain an alcoholysis product.

[0048] Step 5: Add 6 parts of flame retardant and antibacterial agent and 18 parts of ethylene glycol into the reactor by weight, react at 90°C for 2h, then add 100 parts of alcoholysis product, 2.8 parts of antimony trioxide, 0.01 parts of trimethyl phosphate, and 1.8 parts of titanium dioxide into the reactor, and evacuate the reactor to vacuum, and then react at 280°C for 4h, during which the pressure in the reactor is controlled to be less than 0.1Kpa. After the reaction is completed, the product is cooled, pelletized, and dried to obtain modified PET;

[0049] Step 6. Add the modified PET into a twin-screw extruder for melt extrusion and then spin to obtain a modified recycled polyester fiber, wherein the temperature of the twin-screw extruder is set to 275°C in zone 1, 280°C in zone 2, 285°C in zone 3, 290°C in zone 4, 285°C in zone 5, and 280°C in zone 6, the spinning speed is 1200m / min, and the drafting multiple is 4 times.

[0050] Comparative Example 1

[0051] The regenerated polyester fiber is prepared directly from waste polyester fiber without preparing a flame retardant and antibacterial agent. The preparation steps are as follows:

[0052] The first step is to put 100 parts of waste polyester fiber, 70 parts of ethylene glycol and 2 parts of manganese acetate into a reactor by weight, and introduce nitrogen into the reactor to exhaust the air in the reactor, and then react at a temperature of 220° C. for 10 hours. After the reaction, the temperature of the reaction system is lowered to 150° C., and the solid is removed by hot filtration. Deionized water is then added to the filtrate to cool it to room temperature, and then vacuum filtration is performed, and the filter cake is washed with deionized water and dried to obtain an alcoholysis product;

[0053] Step 2: 100 parts of alcoholysis product, 2.8 parts of antimony trioxide, 0.01 parts of trimethyl phosphate and 1.8 parts of titanium dioxide were added to the reactor by weight, and the reactor was evacuated to vacuum. The reaction was then carried out at a temperature of 280°C for 4 hours, during which the pressure in the reactor was controlled to be less than 0.1 KPa. After the reaction was completed, the product was cooled, pelletized and dried to obtain modified PET.

[0054] The third step is to add the modified PET into a twin-screw extruder for melt extrusion and then spin to obtain a modified regenerated polyester fiber, wherein the temperature of the twin-screw extruder is set to 275°C in zone 1, 280°C in zone 2, 285°C in zone 3, 290°C in zone 4, 285°C in zone 5, and 280°C in zone 6, the spinning speed is 1200m / min, and the drafting multiple is 4 times.

[0055] Comparative Example 2

[0056] This comparative example is a commercially available flame-retardant and antibacterial fiber.

[0057] The modified regenerated polyester fiber obtained in Examples 1-3 and Comparative Example 1 and the commercially available flame retardant and antibacterial fiber were tested for performance respectively. The limited oxygen index was tested with reference to FZ / T 50017-2011, and the flame retardant performance was evaluated by the limited oxygen index. The modified regenerated polyester fiber obtained in Comparative Example 1 was used as a blank control, and the antibacterial rate against Escherichia coli and Staphylococcus aureus was tested with reference to GB / T 20944.3-2008. After washing 50 times, the antibacterial rate was repeatedly tested. The test results are shown in Table 1:

[0058] Table 1

[0059]

[0060]

[0061] It can be seen from Table 1 that the limited oxygen index and the antibacterial rate against Escherichia coli and Staphylococcus aureus of the modified regenerated polyester fiber of the present invention in Examples 1-3 are better than those of the commercially available antibacterial regenerated polyester fiber, and the antibacterial effect hardly decreases after washing 50 times, indicating that the modified regenerated polyester fiber of the present invention has good flame retardancy and antibacterial effect, and can be widely used in the field of clothing and home textiles.

[0062] The above is a detailed introduction to the preparation method of a modified regenerated polyester fiber provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enables any technician in the field to practice the present invention, including the manufacture and use of any device or system, and the implementation of any combination method. It should be pointed out that for ordinary technicians in this technical field, the present invention can also be improved and modified without departing from the principle of the present invention. In particular, as long as there is no structural conflict, the various features in the embodiments disclosed in the present invention can be combined with each other in any way. The reason why these combinations are not exhaustively described in this specification is only for the consideration of omitting space and saving resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for preparing modified regenerated polyester fiber, characterized in that: The following steps are involved: The first step is to mix p-formylbenzoic acid, 6-acetylpyridine carboxylic acid, sodium hydroxide solution and ethanol in a container, stir evenly, and react at a temperature of 40-60° C. for 8 hours. After the reaction is completed, add 20% by mass hydrochloric acid to the container to adjust the pH of the system to 5 to obtain intermediate 1; Step 2: Mix the intermediate 1, dimethyl phosphite, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene and ethanol in a container, stir evenly, and react at 50-60° C. for 4 hours to obtain the intermediate 2; Step 3: Mix the intermediate 2, lauryl bromide and acetonitrile in a container, stir, and react at 80°C for 24 hours to obtain a flame retardant and antibacterial agent; Step 4: Put waste polyester fiber, ethylene glycol and catalyst into a container, and introduce nitrogen into the container to exhaust the air in the container, then react at a temperature of 190-220°C for 8-10 hours. After the reaction, reduce the temperature of the reaction system to 150°C, filter while hot and remove the solid, then add deionized water to the filtrate and cool it to room temperature, then vacuum filter and wash the filter cake with deionized water and dry it to obtain an alcoholysis product; Step 5: Add the flame retardant and antibacterial agent and ethylene glycol into a container, react at a temperature of 80-90°C for 2h, then add the alcoholysis product, antimony trioxide, trimethyl phosphate, and titanium dioxide into the container, and evacuate the container to vacuum, and then react at a temperature of 260-280°C for 3-4h, during which the pressure in the container is controlled to be less than 0.1Kpa. After the reaction is completed, the product is cooled, pelletized, and dried to obtain modified PET; Step 6: Add the modified PET into a twin-screw extruder for melt extrusion and spinning to obtain a modified recycled polyester fiber.

2. The method for preparing a modified regenerated polyester fiber according to claim 1, characterized in that: The sodium hydroxide solution used in the first step is a sodium hydroxide aqueous solution with a mass fraction of 30%.

3. The method for preparing a modified regenerated polyester fiber according to claim 1, characterized in that: The amount ratio of p-formylbenzoic acid, 6-acetylpicolinic acid, sodium hydroxide solution and ethanol used in the first step is 0.1 mol: 0.1 mol: 40-50 mL: 60-80 mL.

4. The method for preparing a modified regenerated polyester fiber according to claim 1, characterized in that: The amount ratio of intermediate 1, dimethyl phosphite, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene and ethanol used in the second step is 0.07 mol: 0.07-0.08 mol: 0.016-0.024 mol: 40-60 mL.

5. The method for preparing a modified regenerated polyester fiber according to claim 1, characterized in that: The amount ratio of intermediate 2, lauryl bromide and acetonitrile used in the third step is 0.06 mol: 0.06-0.08 mol: 40-60 mL.

6. The method for preparing a modified regenerated polyester fiber according to claim 5, characterized in that: The catalyst used in the fourth step is one of zinc acetate and manganese acetate.

7. The method for preparing a modified regenerated polyester fiber according to claim 1, characterized in that: Calculated by mass, the mass ratio of the waste polyester fiber, ethylene glycol and catalyst used in the fourth step is 100 parts: 60-70 parts: 1.2-2 parts.

8. The method for preparing a modified regenerated polyester fiber according to claim 1, characterized in that: Calculated by mass, the mass ratio of the flame retardant and antibacterial agent, ethylene glycol, alcoholysis product, antimony trioxide, trimethyl phosphate, and titanium dioxide used in the fifth step is 5-6 parts: 10-18 parts: 100 parts: 2-2.8 parts: 0.01 parts: 1.4-1.8 parts.

9. The method for preparing a modified regenerated polyester fiber according to claim 1, characterized in that: In the sixth step, the temperature of the twin-screw extruder was set to 275°C in zone 1, 280°C in zone 2, 285°C in zone 3, 290°C in zone 4, 285°C in zone 5, and 280°C in zone 6.

10. The method for preparing a modified regenerated polyester fiber according to claim 1, characterized in that: In the sixth step, the spinning speed is 1000-1200 m / min and the drafting multiple is 3-4 times.

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