PBT fiber and preparation method thereof

Abstract

The invention discloses a PBT fiber and a preparation method thereof, and belongs to the technical field of polyester fibers. The PBT fiber is obtained by mixing modified PBT, an antioxidant mixture and a catalyst and then carrying out melt spinning and winding, wherein the modified PBT is obtained by carrying out copolymerization on terephthalic acid, isophthalic acid, 1, 4-butanediol and azido methyl oxetane; the antioxidant mixture is prepared from butyl hydroxy anisd, 2, 6-di-tert-butyl-4-methylphenol, L-sodium ascorbate and 2-acetylene phenol; the catalyst adopts copper sulfate pentahydrate; the PBT fiber prepared in the invention has the advantages of low melting point, easy spinning, good oxidation resistance and good antibacterial property.

Description

Technical Field

[0001] The invention relates to a PBT fiber and a preparation method thereof. Background Art

[0002] Polybutylene terephthalate (PBT) is a crystalline thermoplastic polyester known for its fast crystallization rate, high mechanical strength, dimensional stability and good electrical insulation properties. In addition, PBT also has excellent heat resistance, acid resistance, oil resistance and chemical corrosion resistance. These characteristics make PBT widely used in many industrial fields, especially PBT non-woven fabric fibers made by meltblowing. Due to its fineness and softness, as well as excellent oil resistance and heat resistance, it shows great potential in the filtration system and oil-water separation applications of diesel locomotives.

[0003] However, traditional PBT materials have some defects that limit their wider application. Specifically, PBT has high melt viscosity, high melting point, high melt index, low melt fluidity, slow spinning speed, and is not easy to spin, especially in the field of filter materials. In addition, PBT has poor antioxidant properties, which means that when used for a long time or exposed to an oxidizing environment, PBT materials may age, such as mechanical property degradation, color change, etc., which not only affects the service life of the material, but also limits its applicability in application scenarios that require long-term stable performance.

[0004] Therefore, the present invention modifies PBT and spins it, which is suitable for high-speed spinning. Summary of the invention

[0005] The purpose of the present invention is to provide a PBT fiber and a preparation method thereof to solve the technical problems mentioned in the above background technology.

[0006] The technical solution to achieve the purpose of the present invention is: a PBT fiber, wherein the PBT fiber is obtained by mixing modified PBT, an antioxidant mixture, and a catalyst and then performing melt spinning and winding.

[0007] Furthermore, the modified PBT is obtained by copolymerization of terephthalic acid, isophthalic acid, 1,4-butanediol and azidomethyloxetane.

[0008] Furthermore, the antioxidant mixture includes butylated hydroxyanisole, 2,6-di-tert-butyl-4-methylphenol, sodium L-ascorbate, and 2-ethynylphenol.

[0009] Furthermore, the catalyst is copper sulfate pentahydrate.

[0010] Furthermore, a method for preparing PBT fiber comprises the following preparation steps: The modified PBT, the antioxidant mixture and the catalyst are stirred and mixed together in a high-speed stirrer, then put into a screw extruder for melting and extruded and wound through a spinneret die to obtain PBT fibers with a diameter of 4 to 8 μm.

[0011] Furthermore, the preparation method of the modified PBT is as follows: terephthalic acid, 1,4-butanediol, isophthalic acid, azidomethyloxetane, catalyst tetrabutyl titanate, and stabilizer trimethyl phosphate are added to a stirred reactor for direct esterification and melt polycondensation reaction; the esterification reaction temperature is controlled at 220~240°C, the reaction pressure is 0.2MPa, the water output reaches 90% of the theoretical water output, and the reaction time is 2~3h; the melt polycondensation reaction temperature is controlled at 240°C~250°C, the pressure is 0.02~0.06MPa, and the reaction time is about 40~100min.

[0012] Furthermore, the preparation method of the azidomethyloxetane is as follows: under an inert gas protection environment, 50 parts by mass of 3-(chloromethyl)-oxetane, 47 to 49 parts by mass of sodium azide, 106 to 108 parts by mass of water, and 7 parts by mass of methyltrioctylammonium chloride are heated at 95 to 100° C. for 3.8 to 4.2 hours, the organic phase is separated and diluted with 100 parts by mass of dichloromethane, and then washed 2 to 4 times with an isopropanol solution with a water content of 50%, then washed 2 to 4 times with deionized water, and dried with anhydrous sodium sulfate to obtain azidomethyloxetane.

[0013] Furthermore, the mass ratio of terephthalic acid, 1,4-butanediol, isophthalic acid, azidomethyloxetane, catalyst tetrabutyl titanate, and stabilizer trimethyl phosphate is: 1300~1400: 140~160: 1106~1108: 270~280: 3.5~4.5: 0.1~0.14.

[0014] Furthermore, the mass ratio of the modified PBT, the antioxidant mixture and the catalyst is 1000:80~90:4~6; the mass ratio of butylated hydroxyanisole, 2,6-di-tert-butyl-4-methylphenol, sodium L-ascorbate and 2-ethynylphenol in the antioxidant mixture is: 1:2~4:1~3:3~5.

[0015] Furthermore, the spinning speed of the screw extruder is 800 m / min, and the temperatures of the zones of the screw extruder are: 185-195° C. in zone one, 195-205° C. in zone two, 200-210° C. in zone three, 200-210° C. in zone four, and 200-210° C. in zone five.

[0016] By adopting the above technical solution, the present invention has the following beneficial effects: The PBT fiber of the present invention is obtained by mixing modified PBT, an antioxidant mixture and a catalyst and then performing melt spinning and winding; wherein the modified PBT is obtained by copolymerizing terephthalic acid, isophthalic acid, 1,4-butanediol and azidomethyloxetane; the antioxidant mixture includes butylated hydroxyanisole, 2,6-di-tert-butyl-4-methylphenol, L-sodium ascorbate and 2-ethynylphenol; and the catalyst is copper sulfate pentahydrate.

[0017] The present invention firstly adopts terephthalic acid, isophthalic acid, 1,4-butanediol and azidomethyloxetane to copolymerize to obtain modified PBT, and introduces isophthalic acid and azidomethyloxetane into PBT to destroy the regular structure of ordinary PBT molecular chain, hinder the movement of molecular chain, weaken the crystallization ability of modified PBT, require longer time to enter the crystal lattice, reduce the crystallization peak temperature, broaden the crystallization temperature curve, reduce the crystallization speed, and further reduce the melting point of modified PBT.

[0018] The present invention imparts good antioxidant properties to the PBT fiber by adding an antioxidant mixture into the PBT fiber. At the same time, under the action of a catalyst, the azide group on the modified PBT undergoes a click reaction with the alkyne in the antioxidant mixture to form a triazole derivative, thereby enabling the PBT fiber to have excellent antibacterial properties. DETAILED DESCRIPTION

[0019] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with specific implementation methods.

[0020] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0021] The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and are not intended to limit the protection scope of the present invention.

[0022] The catalysts used in the examples and comparative examples are all copper sulfate pentahydrate.

[0023] (Example 1) A method for preparing PBT fiber, comprising the following preparation steps: The modified PBT, antioxidant mixture and catalyst were stirred and mixed together in a high-speed stirrer at a mass ratio of 1000:80:4 at a speed of 2000 rpm, then put into a screw extruder for melting and extruded and wound through a spinneret die to obtain PBT fibers with a diameter of 4 μm; wherein, the spinning speed of the screw extruder was 800 m / min, and the temperatures of each zone of the screw extruder were: 185°C in zone one, 195°C in zone two, 200°C in zone three, 200°C in zone four, and 200°C in zone five.

[0024] The preparation method of the modified PBT is as follows: terephthalic acid, 1,4-butanediol, isophthalic acid, azidomethyloxetane, catalyst tetrabutyl titanate, and stabilizer trimethyl phosphate are added into a stirred reactor in a mass ratio of 1300:140:1106:270:3.5:0.1 for direct esterification and melt polycondensation reaction; the esterification reaction temperature is controlled at 220°C, the reaction pressure is 0.2MPa, the water output reaches 90% of the theoretical water output, and the reaction time is 2h; the melt polycondensation reaction temperature is controlled at 240°C, the pressure is 0.02MPa, the reaction time is about 40min, and then adjusted to 255°C, the vacuum degree is 70Pa and the holding time is 2.5h, and the viscosity average relative molecular mass of the modified PBT is 32036g / mol.

[0025] The preparation method of the azidomethyloxetane is as follows: under an inert gas protection environment, 50 parts by mass of 3-(chloromethyl)-oxetane, 47 parts by mass of sodium azide, 106 parts by mass of water, and 7 parts by mass of methyltrioctylammonium chloride are heated at 95° C. for 3.8 hours, the organic phase is separated and diluted with 100 parts by mass of dichloromethane, and then washed twice with an isopropanol solution with a water content of 50%, then washed twice with deionized water, and dried with anhydrous sodium sulfate to obtain azidomethyloxetane.

[0026] The mass ratio of butylated hydroxyanisole, 2,6-di-tert-butyl-4-methylphenol, sodium L-ascorbate and 2-ethynylphenol in the antioxidant mixture is 1:2:1:3.

[0027] (Example 2) A method for preparing PBT fiber, comprising the following preparation steps: The modified PBT, antioxidant mixture and catalyst were stirred and mixed together in a high-speed stirrer at a mass ratio of 1000:85:5 at a speed of 2000 rpm, then put into a screw extruder for melting and extruded and wound through a spinneret die to obtain PBT fibers with a diameter of 7 μm; wherein, the spinning speed of the screw extruder is 800 m / min, and the temperatures of each zone of the screw extruder are: 190°C in zone one, 200°C in zone two, 205°C in zone three, 205°C in zone four, and 205°C in zone five.

[0028] The preparation method of the modified PBT is as follows: terephthalic acid, 1,4-butanediol, isophthalic acid, azidomethyloxetane, catalyst tetrabutyl titanate, and stabilizer trimethyl phosphate are added into a stirred reactor in a mass ratio of 1350:150:1107:275:4:0.12 for direct esterification and melt polycondensation reaction; the esterification reaction temperature is controlled at 230°C, the reaction pressure is 0.2MPa, the water output reaches 90% of the theoretical water output, and the reaction time is 2.5h; the melt polycondensation reaction temperature is controlled at 245°C, the pressure is 0.04MPa, the reaction time is about 70min, and then adjusted to 260°C, the vacuum degree is 80Pa and the holding time is 3h, and the viscosity average relative molecular mass of the modified PBT is 29935g / mol.

[0029] The preparation method of the azidomethyloxetane is as follows: under an inert gas protection environment, 50 parts by mass of 3-(chloromethyl)-oxetane, 48 parts by mass of sodium azide, 107 parts by mass of water, and 7 parts by mass of methyltrioctylammonium chloride are heated at 98° C. for 4 hours, the organic phase is separated and diluted with 100 parts by mass of dichloromethane, and then washed three times with an isopropanol solution with a water content of 50%, then washed three times with deionized water, and dried with anhydrous sodium sulfate to obtain azidomethyloxetane.

[0030] The mass ratio of butylated hydroxyanisole, 2,6-di-tert-butyl-4-methylphenol, sodium L-ascorbate and 2-ethynylphenol in the antioxidant mixture is 1:3:2:4.

[0031] (Example 3) A method for preparing PBT fiber, comprising the following preparation steps: The modified PBT, antioxidant mixture and catalyst were stirred and mixed together in a high-speed stirrer at a mass ratio of 1000:90:6 at a speed of 2000 rpm, then put into a screw extruder for melting and extruded and wound through a spinneret die to obtain PBT fibers with a diameter of 8 μm; wherein, the spinning speed of the screw extruder was 800 m / min, and the temperatures of each zone of the screw extruder were: 195° C. for zone one, 205° C. for zone two, 210° C. for zone three, 210° C. for zone four, and 210° C. for zone five.

[0032] The preparation method of the modified PBT is as follows: terephthalic acid, 1,4-butanediol, isophthalic acid, azidomethyloxetane, catalyst tetrabutyl titanate, and stabilizer trimethyl phosphate are added into a stirred reactor in a mass ratio of 1400:160:1108:280:4.5:0.14 for direct esterification and melt polycondensation reaction; the esterification reaction temperature is controlled at 240°C, the reaction pressure is 0.2MPa, the water output reaches 90% of the theoretical water output, and the reaction time is 3h; the melt polycondensation reaction temperature is controlled at 250°C, the pressure is 0.06MPa, the reaction time is about 100min, and then adjusted to 265°C, the vacuum degree is 90Pa and the holding time is 4h, and the viscosity-average relative molecular mass of the modified PBT is 30926g / mol.

[0033] The preparation method of the azidomethyloxetane is as follows: under an inert gas protection environment, 50 parts by mass of 3-(chloromethyl)-oxetane, 49 parts by mass of sodium azide, 108 parts by mass of water, and 7 parts by mass of methyltrioctylammonium chloride are heated at 100° C. for 4.2 hours, the organic phase is separated and diluted with 100 parts by mass of dichloromethane, and then washed 4 times with an isopropanol solution with a water content of 50%, then washed 4 times with deionized water, and dried with anhydrous sodium sulfate to obtain azidomethyloxetane.

[0034] The mass ratio of butylated hydroxyanisole, 2,6-di-tert-butyl-4-methylphenol, sodium L-ascorbate and 2-ethynylphenol in the antioxidant mixture is 1:4:3:5.

[0035] (Comparative Example 1) A method for preparing PBT fiber, comprising the following preparation steps: The modified PBT, antioxidant mixture and catalyst were stirred and mixed together in a high-speed stirrer at a mass ratio of 1000:85:5 at a speed of 2000 rpm, then put into a screw extruder for melting and extruded and wound through a spinneret die to obtain PBT fibers with a diameter of 7 μm; wherein, the spinning speed of the screw extruder is 800 m / min, and the temperatures of each zone of the screw extruder are: 190°C in zone one, 200°C in zone two, 205°C in zone three, 205°C in zone four, and 205°C in zone five.

[0036] The preparation method of the modified PBT is as follows: terephthalic acid, 1,4-butanediol, isophthalic acid, catalyst tetrabutyl titanate, and stabilizer trimethyl phosphate are added into a stirred reactor in a mass ratio of 1350:150:1107:275:4:0.12 for direct esterification and melt polycondensation reaction; the esterification reaction temperature is controlled at 230°C, the reaction pressure is 0.2MPa, the water output reaches 90% of the theoretical water output, and the reaction time is 2.5h; the melt polycondensation reaction temperature is controlled at 245°C, the pressure is 0.04MPa, the reaction time is about 70min, and then adjusted to 260°C, the vacuum degree is 80Pa and the holding time is 3h, and the viscosity average relative molecular mass of the modified PBT is 29809g / mol.

[0037] The mass ratio of butylated hydroxyanisole, 2,6-di-tert-butyl-4-methylphenol, sodium L-ascorbate and 2-ethynylphenol in the antioxidant mixture is 1:3:2:4.

[0038] (Comparative Example 2) A method for preparing PBT fiber, comprising the following preparation steps: The modified PBT, antioxidant mixture and catalyst were stirred and mixed together in a high-speed stirrer at a mass ratio of 1000:85:5 at a speed of 2000 rpm, then put into a screw extruder for melting and extruded and wound through a spinneret die to obtain PBT fibers with a diameter of 7 μm; wherein, the spinning speed of the screw extruder is 800 m / min, and the temperatures of each zone of the screw extruder are: 190°C in zone one, 200°C in zone two, 205°C in zone three, 205°C in zone four, and 205°C in zone five.

[0039] The preparation method of the modified PBT is as follows: terephthalic acid, 1,4-butanediol, isophthalic acid, azidomethyloxetane, catalyst tetrabutyl titanate, and stabilizer trimethyl phosphate are added into a stirred reactor in a mass ratio of 1350:150:1107:275:4:0.12 for direct esterification and melt polycondensation reaction; the esterification reaction temperature is controlled at 230°C, the reaction pressure is 0.2MPa, the water output reaches 90% of the theoretical water output, and the reaction time is 2.5h; the melt polycondensation reaction temperature is controlled at 245°C, the pressure is 0.04MPa, the reaction time is about 70min, and then adjusted to 260°C, the vacuum degree is 80Pa and the holding time is 3h, and the viscosity average relative molecular mass of the modified PBT is 29068g / mol.

[0040] The preparation method of the azidomethyloxetane is as follows: under an inert gas protection environment, 50 parts by mass of 3-(chloromethyl)-oxetane, 48 parts by mass of sodium azide, 107 parts by mass of water, and 7 parts by mass of methyltrioctylammonium chloride are heated at 98° C. for 4 hours, the organic phase is separated and diluted with 100 parts by mass of dichloromethane, and then washed three times with an isopropanol solution with a water content of 50%, then washed three times with deionized water, and dried with anhydrous sodium sulfate to obtain azidomethyloxetane.

[0041] The mass ratio of butylated hydroxyanisole, 2,6-di-tert-butyl-4-methylphenol and sodium L-ascorbate in the antioxidant mixture is 1:3:2.

[0042] (Comparative Example 3) A method for preparing PBT fiber, comprising the following preparation steps: The modified PBT and antioxidant mixture were stirred and mixed together in a high-speed stirrer at a mass ratio of 1000:85 at a speed of 2000 rpm, then put into a screw extruder for melting and extruded and wound through a spinneret die to obtain PBT fibers with a diameter of 7 μm; wherein, the spinning speed of the screw extruder was 800 m / min, and the temperatures of each zone of the screw extruder were: 190°C in zone one, 200°C in zone two, 205°C in zone three, 205°C in zone four, and 205°C in zone five.

[0043] The preparation method of the modified PBT is as follows: terephthalic acid, 1,4-butanediol, isophthalic acid, azidomethyloxetane, catalyst tetrabutyl titanate, and stabilizer trimethyl phosphate are added into a stirred reactor in a mass ratio of 1350:150:1107:275:4:0.12 for direct esterification and melt polycondensation reaction; the esterification reaction temperature is controlled at 230°C, the reaction pressure is 0.2MPa, the water output reaches 90% of the theoretical water output, and the reaction time is 2.5h; the melt polycondensation reaction temperature is first controlled at 245°C, the pressure is 0.04MPa, the reaction time is about 70min, and then adjusted to 260°C, the vacuum degree is 80Pa and the holding time is 3h.

[0044] The preparation method of the azidomethyloxetane is as follows: under an inert gas protection environment, 50 parts by mass of 3-(chloromethyl)-oxetane, 48 parts by mass of sodium azide, 107 parts by mass of water, and 7 parts by mass of methyltrioctylammonium chloride are heated at 98° C. for 4 hours, the organic phase is separated and diluted with 100 parts by mass of dichloromethane, and then washed three times with an isopropanol solution with a water content of 50%, then washed three times with deionized water, and dried with anhydrous sodium sulfate to obtain azidomethyloxetane.

[0045] The mass ratio of butylated hydroxyanisole, 2,6-di-tert-butyl-4-methylphenol, sodium L-ascorbate and 2-ethynylphenol in the antioxidant mixture is 1:3:2:4.

[0046] Comparative Example 4 A method for preparing PBT fiber, comprising the following preparation steps: PBT, an antioxidant mixture and a catalyst are stirred and mixed together in a high-speed stirrer at a mass ratio of 1000:85:5 at a speed of 2000 rpm, then put into a screw extruder for melting and extruded and wound through a spinneret die to obtain PBT fibers with a diameter of 7 μm; wherein, the spinning speed of the screw extruder is 800 m / min, and the temperatures of the various zones of the screw extruder are: 190° C. in zone 1, 200° C. in zone 2, 205° C. in zone 3, 205° C. in zone 4, and 205° C. in zone 5; during the spinning process, the melt is difficult to extrude and is not easy to spin into fibers; this is because: the traditional PBT melt has a large viscosity, a high melting point, low fluidity, is difficult to extrude the melt, and is not easy to spin.

[0047] The preparation method of PBT is as follows: terephthalic acid, 1,4-butanediol, catalyst tetrabutyl titanate, and stabilizer trimethyl phosphate are added into a stirred reactor in a mass ratio of 1350:150:1107:275:4:0.12 for direct esterification and melt polycondensation reaction; the esterification reaction temperature is controlled at 230°C, the reaction pressure is 0.2MPa, the water output reaches 90% of the theoretical water output, and the reaction time is 2.5h; the melt polycondensation reaction temperature is controlled at 245°C, the pressure is 0.04MPa, the reaction time is about 70min, and then adjusted to 260°C, the vacuum degree is 80Pa and the holding time is 3h, and the viscosity average relative molecular mass of PBT is 26500g / mol.

[0048] The mass ratio of butylated hydroxyanisole, 2,6-di-tert-butyl-4-methylphenol, sodium L-ascorbate and 2-ethynylphenol in the antioxidant mixture is 1:3:2:4.

[0049] Effect example Average molecular weight of viscosity: The modified PBT and PBT prepared in the embodiment and the comparative example were placed in a vacuum drying oven at 120°C for drying, and a phenol tetrachloroethane solution with a mass ratio of 1:1 was prepared as a solvent for testing viscosity. 20 ml of the prepared solvent was accurately weighed and added to the rotor, and 0.10 g of PBT was accurately weighed in a reaction bottle. After standing at room temperature for 4 hours, it was placed in an oil bath at 80°C for dissolution, thereby obtaining 0.5 g·dL -1 The polyester solution is tested and the viscosity average molecular weight is calculated using the viscosity method using an Ubbelohde viscometer in a constant temperature water bath at 25°C.

[0050] Melting point: Weigh 6-9 mg of the modified PBT and PBT prepared in the examples and comparative examples on a precision electronic balance, and under the protection of a nitrogen flow, uniformly heat the temperature from 25°C to 250°C at a rate of 10°C / min; keep it for 5 min to eliminate the thermal history, and then cool it to 25°C at cooling rates of 5, 10, 15, and 20°C / min, respectively, and record its melting point Tm.

[0051] Antibacterial property: The PBT fibers prepared in the examples and comparative examples were tested for the antibacterial rate of Escherichia coli according to GBT20944.2.

[0052] Antioxidation property: The PBT fibers prepared in the examples and comparative examples were incubated with 500 μM hydrogen peroxide solution in a dark environment for 4 h, and the ability of the membranes to remove hydrogen peroxide was detected by the xylenol orange method.

[0053] Table 1 below shows the performance results of the PBT fibers obtained in the examples and comparative examples: Table 1

[0054] As shown in Table 1 above, compared with the comparative example, the PBT fiber prepared in the embodiment has a lower melting point and is easier to spin, and has better antibacterial and antioxidant properties.

[0055] Comparison of Comparative Example 1 with Example 2 shows that the modified PBT in Comparative Example 1 does not use azidomethyloxetane, and the PBT fiber prepared in Example 2 has a lower melting point and is easier to spin, and has better antibacterial and antioxidant properties.

[0056] Comparative Example 2 is compared with Example 2. The antioxidant mixture of Comparative Example 2 does not use 2-acetylene phenol. The PBT fiber prepared in Example 2 has a lower melting point and is easier to spin, and has better antibacterial and antioxidant properties.

[0057] Comparative Example 3 is compared with Example 2. The PBT fiber in Comparative Example 3 does not use a catalyst, and the PBT fiber prepared in Example 2 has better antibacterial and antioxidant properties.

[0058] Compared with Example 2, the PBT in Comparative Example 4 is not modified, while the PBT fiber prepared in Example 2 has a lower melting point and is easier to spin, and has better antibacterial and antioxidant properties. This is because the unmodified PBT has a higher melting point and is more difficult to mix evenly with the antioxidant mixture, making the overall antioxidant property of the prepared PBT fiber uneven and the overall antioxidant property is poor.

[0059] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A PBT fiber, characterized in that: The PBT fiber is obtained by mixing modified PBT, an antioxidant mixture and a catalyst and then performing melt spinning and winding.

2. The PBT fiber according to claim 1, characterized in that The modified PBT is obtained by copolymerizing terephthalic acid, isophthalic acid, 1,4-butanediol and azidomethyloxetane.

3. The PBT fiber according to claim 1, characterized in that The antioxidant mixture comprises butylated hydroxyanisole, 2,6-di-tert-butyl-4-methylphenol, sodium L-ascorbate and 2-ethynylphenol.

4. The PBT fiber according to claim 1, characterized in that The catalyst is copper sulfate pentahydrate.

5. A method for preparing PBT fiber, characterized in that: The method comprises the following preparation steps: The modified PBT, the antioxidant mixture and the catalyst are stirred and mixed together in a high-speed stirrer, then put into a screw extruder for melting and extruded and wound through a spinneret die to obtain PBT fibers with a diameter of 4 to 8 μm.

6. The method for preparing PBT fiber according to claim 5, characterized in that: The preparation method of the modified PBT is as follows: terephthalic acid, 1,4-butanediol, isophthalic acid, azidomethyloxetane, catalyst tetrabutyl titanate, and stabilizer trimethyl phosphate are added to a stirred reactor for direct esterification and melt polycondensation reaction; the esterification reaction temperature is controlled at 220-240° C., the reaction pressure is 0.2 MPa, the water output reaches 90% of the theoretical water output, and the reaction time is 2-3 hours; the melt polycondensation reaction temperature is controlled at 240-250° C., the pressure is 0.02-0.06 MPa, and the reaction time is about 40-100 minutes.

7. The method for preparing PBT fiber according to claim 6, characterized in that: The preparation method of the azidomethyloxetane is as follows: under an inert gas protection environment, 50 parts by mass of 3-(chloromethyl)-oxetane, 47-49 parts by mass of sodium azide, 106-108 parts by mass of water, and 7 parts by mass of methyltrioctylammonium chloride are heated at 95-100° C. for 3.8-4.2 hours, the organic phase is separated and diluted with 100 parts by mass of dichloromethane, and then washed with an isopropanol solution with a water content of 50% for 2-4 times, then washed with deionized water for 2-4 times, and dried with anhydrous sodium sulfate to obtain azidomethyloxetane.

8. The method for preparing PBT fiber according to claim 6, characterized in that: The mass ratio of terephthalic acid, 1,4-butanediol, isophthalic acid, azidomethyloxetane, catalyst tetrabutyl titanate, and stabilizer trimethyl phosphate is: 1300-1400: 140-160: 1106-1108: 270-280: 3.5-4.5: 0.1-0.

14.

9. The method for preparing PBT fiber according to claim 5, characterized in that: The mass ratio of the modified PBT, the antioxidant mixture and the catalyst is 1000:80-90:4-6; the mass ratio of butylated hydroxyanisole, 2,6-di-tert-butyl-4-methylphenol, sodium L-ascorbate and 2-ethynylphenol in the antioxidant mixture is 1:2-4:1-3:3-5.

10. The method for preparing PBT fiber according to claim 5, characterized in that: The spinning speed of the screw extruder is 800 m / min, and the temperatures of the zones of the screw extruder are: 185-195° C. in zone one, 195-205° C. in zone two, 200-210° C. in zone three, 200-210° C. in zone four, and 200-210° C. in zone five.

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