Flame-retardant polyethylene terephthalate obtained using Co-MOF and preparation method thereof

Abstract

The present invention provides a flame-retardant polyethylene terephthalate (PET) obtained using Co-MOF, which is prepared by polycondensation of terephthalic acid and ethylene glycol in the presence of a cobalt metal organic framework (Co-MOF). The PET obtained using Co-MOF has good flame retardancy and spinnability, and its mechanical properties are effectively improved. The preparation process is simple, and no flame retardant or mechanical reinforcement is required, achieving green synthesis and having good prospects for promotion and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of flame-retardant polyesters, and particularly relates to flame-retardant polyethylene terephthalate obtained by using Co-MOF and a method for synthesizing flame-retardant polyethylene terephthalate by using Co-MOF. Background Art

[0002] Polyethylene terephthalate (PET) is an industrially produced linear thermoplastic polymer. It exhibits excellent mechanical properties, electrical insulation, chemical resistance, creep resistance, and fatigue resistance, and is widely used in various fields, primarily in the production of sheets, fibers, and beverage bottles.

[0003] With increasing demand for flame-retardant materials and the active research on polyester flame-retardancy, various flame-retardant polyester sheets and fibers are being developed. Currently, flame-retardant modification of polyester is primarily achieved through blending and copolymerization. The synthesis of flame-retardant PET through copolymerization offers more stable and long-lasting flame retardancy, making it an important method for flame-retardant modification of PET and other polyesters. However, in practical applications, it is necessary to improve both flame retardancy and spinnability to ensure its applicability as a fiber material in real-world production.

[0004] Currently, PET is primarily synthesized through the esterification or transesterification of terephthalic acid (TPA) or dimethyl terephthalate (DMT) with ethylene glycol (EG). Germanium, titanium, or antimony compounds are commonly used in the industrial production of PET during its synthesis. Germanium-based catalysts are expensive and have high synthesis costs, while PET synthesized with titanium-based catalysts exhibits a yellowish color and turbidity. Antimony-based catalysts, which are more commonly used and more active, are prone to producing gray antimony during the synthesis process, making the PET material somewhat toxic and limiting its application.

[0005] In addition, polyester materials such as PET generally use phosphorus-containing flame retardants, which leads to problems such as poor thermal and mechanical properties of polyester materials and poor spinning crystallinity. Therefore, further research and development of high-performance flame-retardant PET is needed to meet people's usage needs. Summary of the Invention

[0006] To address the above technical issues, the present invention provides a flame-retardant polyethylene terephthalate (PET) obtained using Co-MOF. The material is prepolymerized and polycondensed in the presence of Co-MOF (a cobalt-based metal organic framework), using terephthalic acid (TPA) and ethylene glycol (EG) as raw materials. Without the addition of other flame retardants, the resulting PET is obtained using Co-MOF. Its thermal stability, flame retardancy, and mechanical properties are significantly improved, expanding the application of PET. This is the basis for the present invention.

[0007] The object of the present invention is to provide a flame-retardant polyethylene terephthalate obtained by using Co-MOF, which is obtained by polycondensing terephthalic acid and ethylene glycol prepolymer in the presence of a cobalt organic metal framework material (Co-MOF).

[0008] The Co-MOF is prepared by a solvothermal reaction of a cobalt salt and an organic ligand under heating and pressure in a solvent environment.

[0009] The cobalt salt is preferably selected from one or more of cobalt nitrate, cobalt acetate, cobalt chloride, cobalt bromide and cobalt sulfate, preferably one or more of cobalt nitrate, cobalt acetate and cobalt chloride.

[0010] The organic ligand is selected from dicarboxylic acids, preferably diaromatic carboxylic acids, more preferably one or two of phthalic acid and phenylenedicarboxylic acid, such as terephthalic acid.

[0011] The present invention also aims to provide a method for preparing the flame-retardant polyethylene terephthalate obtained using Co-MOF. The method specifically comprises the following steps:

[0012] Step 1: Pretreatment of Co-MOF;

[0013] Step 2: mixing terephthalic acid, ethylene glycol and Co-MOF, heating and prepolymerizing to obtain reaction solution I;

[0014] Step 3: Add ethylene glycol, an antioxidant, and an anti-hydrolysis agent to the reaction solution I, first carry out the reaction at normal pressure, and then increase the temperature under vacuum conditions to carry out polycondensation to obtain flame-retardant polyethylene terephthalate obtained using Co-MOF.

[0015] Another object of the present invention is to provide flame-retardant polyethylene terephthalate fibers obtained using Co-MOF.

[0016] Another object of the present invention is to provide a method for preparing flame-retardant polyethylene terephthalate fiber using Co-MOF.

[0017] The flame-retardant polyethylene terephthalate obtained by using Co-MOF provided by the present invention has the following beneficial effects:

[0018] (1) In the present invention, the flame-retardant polyethylene terephthalate obtained by using Co-MOF is prepared in the presence of Co-MOF, which can not only catalyze the esterification and polycondensation reaction process, but also effectively improve the flame retardancy, spinnability and mechanical properties of the flame-retardant polyethylene terephthalate obtained by using Co-MOF.

[0019] (2) The flame-retardant polyethylene terephthalate obtained by using Co-MOF provided by the present invention has an increased coke residue at 700°C, and the maximum weight loss rate (R max ) is greatly reduced, so it has better thermal stability.

[0020] (3) The flame-retardant polyethylene terephthalate obtained using Co-MOF provided by the present invention has an LOI value of up to 28% and a UL-94 grade of V-2, indicating that it has good flame retardant properties.

[0021] (4) In the cone calorimetry test, the pHRR, av-EHC, THR, and TSP of the flame-retardant polyethylene terephthalate obtained using Co-MOF in the present invention were reduced to varying degrees. In addition, its ignition time was increased, the CO release amount was reduced, and the CO2 release amount was increased, indicating that its volatile combustible gas content was reduced. The flame-retardant polyethylene terephthalate obtained using Co-MOF in the present invention has good comprehensive thermal stability and flame retardancy.

[0022] (5) The flame-retardant polyethylene terephthalate obtained by using Co-MOF in the present invention can form a dense carbon layer after combustion, which can suppress smoke and reduce heat release, further improving its own flame retardant properties.

[0023] (6) The tensile strength, elastic modulus and elongation of the flame-retardant polyethylene terephthalate obtained using Co-MOF in the present invention are significantly improved. While the flame retardant performance is effectively improved, the mechanical properties are greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The infrared spectrum of Co-MOF prepared in Example 1 of the present invention is shown;

[0025] Figure 2 The XRD pattern of Co-MOF prepared in Example 1 of the present invention is shown;

[0026] Figure 3 The SEM and EDS images of the Co-MOF prepared in Example 1 of the present invention are shown, wherein: Figure 3 a, 3b and 3c are their SEM images, Figure 3 d is Figure 3 C distribution diagram of the sample position in c, Figure 3 e is the O distribution diagram, Figure 3 f is the Co distribution map;

[0027] Figure 4 TG and DTG test graphs of Co-MOF prepared in Example 1 of the present invention are shown;

[0028] Figure 5TG curves of the PET in Comparative Example 1 of the present invention and the PET-0.2Co-MOF, PET-0.3Co-MOF, PET-0.4Co-MOF, and PET-0.5Co-MOF prepared in Examples 2-5 are shown;

[0029] Figure 6 The DTG curves of the PET in Comparative Example 1 of the present invention and the PET-0.2Co-MOF, PET-0.3Co-MOF, PET-0.4Co-MOF, and PET-0.5Co-MOF prepared in Examples 2-5 are shown;

[0030] Figure 7 HRR curves of PET in Comparative Example 1 of the present invention and PET-0.2Co-MOF, PET-0.3Co-MOF, PET-0.4Co-MOF, and PET-0.5Co-MOF prepared in Examples 2-5 are shown;

[0031] Figure 8 The THR curves of the PET in Comparative Example 1 of the present invention and the PET-0.2Co-MOF, PET-0.3Co-MOF, PET-0.4Co-MOF, and PET-0.5Co-MOF prepared in Examples 2-5 are shown;

[0032] Figure 9 The SRR curves of the PET in Comparative Example 1 of the present invention and the PET-0.2Co-MOF, PET-0.3Co-MOF, PET-0.4Co-MOF, and PET-0.5Co-MOF prepared in Examples 2-5 are shown;

[0033] Figure 10 The TSP curves of the PET in Comparative Example 1 of the present invention and the PET-0.2Co-MOF, PET-0.3Co-MOF, PET-0.4Co-MOF, and PET-0.5Co-MOF prepared in Examples 2-5 are shown;

[0034] Figure 11 The carbon monoxide CO release rate (COP) of the PET in Comparative Example 1 of the present invention and the PET-0.2Co-MOF, PET-0.3Co-MOF, PET-0.4Co-MOF and PET-0.5Co-MOF prepared in Examples 2-5 are shown as a inverse time.

[0035] Figure 12 A comparison chart showing the flame growth rate index (FIGRA) and fire spread index (FPI) of the PET in Comparative Example 1 of the present invention and the PET-0.2Co-MOF, PET-0.3Co-MOF, PET-0.4Co-MOF, and PET-0.5Co-MOF prepared in Examples 2-5 is shown;

[0036] Figure 13 Showing the appearance of the samples of PET in Comparative Example 1 of the present invention and PET-0.4Co-MOF prepared in Example 4 after cone heat testing;

[0037] Figure 14 SEM images of the PET in Comparative Example 1 of the present invention and the PET-0.4Co-MOF prepared in Example 4 after cone thermal testing are shown;

[0038] Figure 15 The EDS graphs of the PET in Comparative Example 1 of the present invention and the PET-0.4Co-MOF prepared in Example 4 after cone thermal testing are shown;

[0039] Figure 16 The infrared spectra of the PET in Comparative Example 1 of the present invention and the PET-0.2Co-MOF, PET-0.3Co-MOF, PET-0.4Co-MOF and PET-0.5Co-MOF prepared in Examples 2-5 after cone calorimetry are shown;

[0040] Figure 17 The XPS full spectra of the PET in Comparative Example 1 of the present invention and the PET-0.4Co-MOF prepared in Example 4 after combustion by cone calorimetry are shown;

[0041] Figure 18 The XPS spectra of the C=C peak, CO peak and C=O peak in C1s of the PET in Comparative Example 1 and the PET-0.4Co-MOF prepared in Example 4 after combustion by cone calorimetry test are shown ( Figure 18 (a) and Figure 18 (b)) and CO peak and C=O peak analysis spectrum in O1s ( Figure 18 (c) and Figure 18 (d));

[0042] Figure 19 The Raman spectra of the residual samples after combustion of the PET in Comparative Example 1 and the PET-0.4Co-MOF prepared in Example 4 of the present invention are shown;

[0043] Figure 20 FTIR spectra of the cracking gas products of PET in Comparative Example 1 and PET-0.4Co-MOF prepared in Example 4 of the present invention are shown;

[0044] Figure 21 A gas chromatogram of the PET cracking gas product in Comparative Example 1 of the present invention is shown;

[0045] Figure 22The gas chromatogram of the cracking gas products of PET-0.4Co-MOF prepared in Example 4 of the present invention is shown. DETAILED DESCRIPTION

[0046] The present invention will be described in detail below through specific embodiments, and the features and advantages of the present invention will become clearer and more distinct with these descriptions.

[0047] The present invention provides a flame-retardant polyethylene terephthalate obtained using Co-MOF. In the presence of Co-MOF, terephthalic acid (TPA) and ethylene glycol (EG) are prepolymerized and polycondensed. Without adding other flame retardants, the flame-retardant polyethylene terephthalate obtained using Co-MOF is obtained, and its thermal stability, flame retardancy and mechanical properties are effectively improved.

[0048] The present invention provides a flame-retardant polyethylene terephthalate obtained by using Co-MOF, which is prepared by polycondensing terephthalic acid and ethylene glycol in the presence of a cobalt organic metal framework material (Co-MOF).

[0049] The Co-MOF is prepared by a solvothermal reaction of a cobalt salt and an organic ligand under heating and pressure in a solvent environment.

[0050] The cobalt salt is preferably selected from one or more of cobalt nitrate, cobalt acetate, cobalt chloride, cobalt bromide, and cobalt sulfate, and more preferably one or more of cobalt nitrate, cobalt acetate, and cobalt chloride. The organic ligand is selected from dicarboxylic acids, preferably diaromatic carboxylic acids, and more preferably one or two of phthalic acid and phenylenedicarboxylic acid, such as terephthalic acid.

[0051] In the present invention, under a protective atmosphere (such as N2 atmosphere), at a heating rate of 10°C / min, the flame retardant polyethylene terephthalate obtained by using Co-MOF has a coke residue greater than 10wt%, preferably greater than 12wt%, and more preferably greater than 13.5wt%; the maximum weight loss rate of the flame retardant polyethylene terephthalate obtained by using Co-MOF is less than 22%·℃ -1 .

[0052] The LOI value of the flame-retardant polyethylene terephthalate obtained by using Co-MOF is greater than or equal to 23%, preferably greater than 25%, and more preferably greater than 28%.

[0053] The flame-retardant polyethylene terephthalate obtained using Co-MOF has a tensile strength greater than 45 MPa, preferably greater than 50 MPa; an elastic modulus greater than 1250 MPa, preferably greater than 1300 MPa, more preferably greater than 1340 MPa; and an elongation of 330% to 400%, preferably 330% to 370%.

[0054] The present invention also provides a method for preparing the flame-retardant polyethylene terephthalate obtained by using Co-MOF, which specifically comprises the following steps:

[0055] Step 1: Pretreatment of Co-MOF.

[0056] The Co-MOF was dried at 110-130°C for 10-14 hours.

[0057] The Co-MOF is commercially available or self-made. In one embodiment of the present invention, the Co-MOF is obtained by heating and maintaining pressure in a solvent environment to perform a solvothermal reaction of a cobalt salt and an organic ligand, followed by filtering, washing, and drying.

[0058] The cobalt salt is preferably selected from one or more of cobalt nitrate, cobalt acetate, cobalt chloride, cobalt bromide and cobalt sulfate, preferably one or more of cobalt nitrate, cobalt acetate and cobalt chloride.

[0059] The organic ligand is selected from dicarboxylic acids, preferably diaromatic carboxylic acids, more preferably one or more of phthalic acid and phenylenedicarboxylic acid, such as terephthalic acid.

[0060] The molar ratio of the cobalt salt to the organic ligand is 3:(0.4-1.5), preferably 3:(0.5-1.2), and more preferably 3:(0.6-0.9).

[0061] In the present invention, the cobalt salt and the organic ligand are dissolved in a solvent selected from one or more of an amide solvent, a sulfone solvent, and an aromatic hydrocarbon solvent, preferably one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, toluene, and xylene, more preferably N,N-dimethylformamide (DMF). The molar volume ratio of the cobalt salt to the solvent is 3 mmol:(15-45) mL, preferably 3 mmol:(20-40) mL, and more preferably 3 mmol:(25-35) mL.

[0062] In the present invention, the solvent thermal reaction is carried out in a closed reaction vessel, and the volume ratio of the solvent to the reaction vessel is (2-4.5):5, preferably (3-3.5):5.

[0063] The solvent thermal reaction temperature is 90-150° C., preferably 110-130° C., and the reaction time is 10-18 h, preferably 12-16 h.

[0064] Step 2: mixing terephthalic acid, ethylene glycol and Co-MOF, heating and prepolymerizing to obtain reaction solution I.

[0065] The molar ratio of terephthalic acid to ethylene glycol is (2.0-6.5):5, preferably (3.0-5.5):5, and more preferably (4.0-4.5):5.

[0066] The mass ratio of Co-MOF to terephthalic acid is (0.1-2.5):100, preferably (0.15-1.5):100, and more preferably (0.2-0.5):100. In the present invention, the addition of Co-MOF during the prepolymerization and polycondensation of terephthalic acid and ethylene glycol can catalyze the prepolymerization and polycondensation reactions, shortening the reaction time. More importantly, the Co-MOF interacts with PET during the polymerization stage, thereby improving the spinnability, flame retardancy, and mechanical properties of PET.

[0067] The prepolymerization reaction is carried out under a protective atmosphere, such as nitrogen, argon, etc., at 200-260° C. for 1-4 hours, preferably at 220-240° C. for 2-3 hours.

[0068] Step 3: Add ethylene glycol, an antioxidant, and an anti-hydrolysis agent to the reaction solution I, first carry out the reaction at normal pressure, and then increase the temperature under vacuum conditions to carry out polycondensation to obtain flame-retardant polyethylene terephthalate obtained using Co-MOF.

[0069] The antioxidant is selected from one or more phosphite antioxidants, preferably triphenyl phosphite (TPI). The mass ratio of the antioxidant to the terephthalic acid in step 1 is (0.05-0.4):100, preferably (0.08-0.3):100, and more preferably (0.1-0.2):100.

[0070] The anti-hydrolysis agent is one or more of Stabilizer 7000 (N,N'-bis(2,6-diisopropylphenyl)carbodiimide), a biscarbodiimide anti-hydrolysis agent, and HyMax 1010, preferably HyMax 1010. The mass ratio of the anti-hydrolysis agent to the terephthalic acid in step 1 is (0.05-0.4):100, preferably (0.08-0.3):100, and more preferably (0.1-0.2):100.

[0071] In step 3, the molar ratio of the ethylene glycol to the terephthalic acid in step 1 is (0.06-0.24):5, preferably (0.10-0.20):4, and more preferably (0.14-0.16):4.

[0072] The reaction temperature at normal pressure is 200-260° C., preferably 210-250° C., more preferably 220-240° C.; the reaction time is 20-70 min, preferably 30-60 min, more preferably 40-50 min.

[0073] The vacuum condition is -0.05 to -0.1 MPa, preferably -0.08 to -0.1 MPa, and more preferably -0.1 MPa.

[0074] The polycondensation reaction temperature is 255-305°C, preferably 265-295°C, more preferably 275-285°C; the reaction time is 0.5-3h, preferably 1-2.5h, more preferably 1.5-2h.

[0075] In the present invention, the preparation process of flame-retardant polyethylene terephthalate obtained by using Co-MOF first performs the pre-polyesterification reaction in step 2 under normal pressure conditions to allow the esterification reaction to proceed fully, and then performs the polycondensation reaction in step 3 under vacuum conditions to accelerate the reaction rate.

[0076] Another object of the present invention is to provide flame-retardant polyethylene terephthalate fibers obtained using Co-MOF.

[0077] The flame-retardant polyethylene terephthalate fiber obtained by using Co-MOF is prepared by fiber stretching the flame-retardant polyethylene terephthalate obtained by using Co-MOF.

[0078] When the bundle fineness is 110-120 dtex, the flame-retardant polyethylene terephthalate fiber obtained using Co-MOF has a breaking strength greater than 3.45 cN / dtex, preferably greater than 3.50 cN / dtex; the breaking elongation is greater than 22%, preferably greater than 25%, and more preferably greater than 29%.

[0079] Another object of the present invention is to provide a method for preparing flame-retardant polyethylene terephthalate fiber obtained using Co-MOF, which uses the flame-retardant polyethylene terephthalate obtained using Co-MOF as a raw material, stretches the fiber 2-4 times, and then heat-sets it to obtain the fiber, for example, stretches it 3.5 times.

[0080] Preferably, the flame-retardant polyethylene terephthalate obtained using Co-MOF is pre-vacuum dried at a temperature of 115-145° C., preferably 125-135° C., and for a drying time of 8-16 hours, preferably 10-14 hours.

[0081] The flame-retardant polyethylene terephthalate obtained using Co-MOF provided by the present invention has good thermal stability, effectively improved flame retardancy, and good spinnability and mechanical properties. No additional flame retardants or other additives for enhancing mechanical properties are required. The preparation method is simple, reduces the use of harmful additives, achieves green flame retardancy, and makes the flame-retardant polyethylene terephthalate obtained using Co-MOF more applicable.

[0082] Example

[0083] Example 1

[0084] 0.75 mmol TPA and 3 mmol Co(NO₃)₂·6H₂O were dissolved in 30 mL of DMF. The resulting dispersion was sealed in a 50 mL polytetrafluoroethylene-lined hydrothermal reactor and maintained at 120°C in a forced-air drying oven for 14 hours. After the reaction, the product was collected by filtration using a cylindrical filter (0.22 μm pore size), washed several times with ethanol, and then dried in a vacuum oven at 150°C for 12 hours. The resulting Co-MOF was then placed in a desiccator for later use.

[0085]

[0086] Example 2

[0087] TPA (700 g, about 4.2 mol), EG (314 g, about 5.0 mol) and Co-MOF prepared in Example 1 (1.40 g, about 0.2 wt% of the mass of TPA) were added to a polymerization autoclave and mixed. Under a nitrogen atmosphere, the mixture was heated to 230°C to 240°C for esterification reaction. The reaction was completed after 235 minutes from the start of the addition of the materials, and the theoretical water production was 150 mL.

[0088] Then, under a nitrogen atmosphere, 10g EG, 0.7g TPI (triphenyl phosphite) and 0.7g HyMax 1010 (purchased from Shanghai Langyi Functional Materials Co., Ltd., China, industrial grade) were added to a polymerization autoclave and reacted at 230°C to 240°C at normal pressure for 40 minutes. Then, the temperature was raised to 280°C and the reaction was carried out under a high vacuum of -101 kPa. The reaction time was started from the addition of TPI, the stirring power reached the discharge power, and the polycondensation reaction was completed to prepare flame-retardant polyethylene terephthalate PET-0.2Co-MOF obtained using Co-MOF.

[0089] Example 3

[0090] Flame-retardant polyethylene terephthalate PET-0.3Co-MOF was prepared using Co-MOF according to the method in Example 2. The only difference was that the amount of Co-MOF added was 2.1 g (approximately 0.3 wt% of the mass of TPA).

[0091] Example 4

[0092] Flame-retardant polyethylene terephthalate PET-0.4Co-MOF was prepared using Co-MOF according to the method in Example 2. The only difference was that the amount of Co-MOF added was 2.8 g (approximately 0.4 wt % of the mass of TPA).

[0093] Example 5

[0094] Flame-retardant polyethylene terephthalate PET-0.5Co-MOF was prepared using Co-MOF according to the method in Example 2. The only difference was that the amount of Co-MOF added was 3.5 g (approximately 0.5 wt % of the mass of TPA).

[0095] Comparative Example

[0096] Comparative Example 1

[0097] PET was prepared according to the method of Example 2, except that 0.28 g of antimony trioxide (about 0.04 wt% of the mass of TPA) was added to the polymerization autoclave instead of 1.40 g of Co-MOF.

[0098] The esterification was completed in 280 min, and the polycondensation was completed in 178 min.

[0099] It can be seen from Example 2 and Comparative Example 1 that after the addition of Co-MOF, the reaction time and polycondensation time of the pre-polyesterification stage are significantly reduced, indicating that the reaction process is accelerated under the presence of Co-MOF.

[0100] Experimental example

[0101] Experimental Example 1

[0102] The Co-MOF prepared in Example 1 was subjected to infrared analysis (Fourier transform infrared spectrometer Nicolet Nexus 670, Thermo Fisher Scientific), and the infrared spectrum is shown in FIG. Figure 1 shown.

[0103] from Figure 1 It can be seen that TPA is at 1680cm -1 、931cm -1 and 720cm -1 The characteristic peaks at 1570 cm-1 correspond to the stretching vibrations of C=O, -OH of -COOH, and aromatic CH. -1 The characteristic peak at 931 cm corresponds to the vibrational stretching of C=O, which means that the carbonyl group moves to the lower wave number direction due to the coordination effect of metal Co. -1 The weakening or disappearance of the -OH peak at the position also confirms the successful preparation of Co-MOF.

[0104] Experimental Example 2

[0105] The Co-MOF prepared in Example 1 was subjected to X-ray diffraction (XRD, Bruke D 8) testing, and the test was carried out in the 2θ range of 1° to 20° at a scanning rate of 0.1s / time. The XRD pattern is as follows: Figure 2 shown.

[0106] from Figure 2 It can be seen that the diffraction peaks at 2θ = 8.35°, 10.28°, 16.81° and 23.28° correspond to the special crystal planes (022), (110), (310), (004) and (530) of Co-MOF, respectively, indicating that Co-MOF was successfully synthesized.

[0107] Experimental Example 3

[0108] The Co-MOF prepared in Example 1 was analyzed by scanning electron microscopy (SEM) and X-ray energy spectrum (EDS) (JEOL JSM-7500). The test results are as follows: Figure 3 shown.

[0109] from Figure 3 The SEM images in a, 3b and 3c show that the prepared Co-MOF has a lamellar structure. Figure 3 The sample position in c is scanned by EDS. Figure 3 d is the distribution of C, Figure 3 The distribution of O in e, Figure 3 f shows the distribution of Co. It can be seen that Co-MOF contains C, O and Co elements, and they are evenly distributed.

[0110] Experimental Example 4

[0111] The Co-MOF prepared in Example 1 was subjected to thermogravimetric analysis (TG 209, Netzsch) testing. Under nitrogen conditions, the sample was heated from ambient temperature to 700°C at a rate of 10°C / min for thermogravimetric testing. The TG and DTG test graphs are shown in FIG. Figure 4 shown.

[0112] from Figure 4 It can be seen that the highest thermogravimetric temperatures of Co-MOF are 289 and 401 °C, respectively, which shows good thermal stability and meets the processing temperature requirements of PET.

[0113] Experimental Example 5

[0114] Thermogravimetric analysis was performed on the PET in Comparative Example 1 and the flame-retardant polyethylene terephthalate obtained by using Co-MOF obtained in Examples 2-5. 5-8 mg of the sample was heated from 20-25°C to 700°C at a heating rate of 10°C / min under N2 conditions. The TG curve and DTG curve were obtained, as shown in the figure. Figure 5 and Figure 6 According to the TG curve and DTG curve of each material sample, the mass loss 5% temperature (T 5％ ), maximum mass loss temperature (T max ), maximum weight loss rate (R max ) and the coke residue at 700℃ (C w ) data, as shown in Table 1.

[0115] Table 1

[0116]

[0117] Compared with the PET in comparative example 1, the flame-retardant polyethylene terephthalate obtained by using Co-MOF in examples 2-5 of the present invention begins to decompose at a slightly lower temperature (391.48-397.63°C). 5％ A slight decrease.

[0118] Except for the maximum mass loss temperature (T max ) decreased slightly, the T values ​​of other flame-retardant polyethylene terephthalate obtained using Co-MOF were max It is closer to the PET in Comparative Example 1.

[0119] The PET prepared in Comparative Document 1 has a coke residue of only 8.2 wt% at 700°C. The flame-retardant polyethylene terephthalate obtained using Co-MOF in Examples 2-5 has an improved coke residue at 700°C. The coke residue of PET-0.4Co-MOF at 700°C increases to 14.8 wt%, an increase of 44.6% compared with the PET in Comparative Example 1.

[0120] In addition, the maximum weight loss rate (R max ) 22.28%·℃ of PET was obtained from Comparative Example 1 -1 The lowest dropped to 19.12%·℃ -1 , it can be seen that the addition of Co-MOF is beneficial to reducing R max The increase in the amount of residual char helps protect the internal matrix of PET from further combustion and improves the flame retardant effect of PET.

[0121] Experimental Example 6

[0122] The PET in Comparative Example 1 and the flame-retardant polyethylene terephthalate obtained using Co-MOF obtained in Examples 2-5 were tested for LOI value and UL-94 test. The test results are shown in Table 2.

[0123] Table 2

[0124]

[0125]

[0126] The LOI value of PET in Comparative Example 1 is about 22%, and the vertical combustion grade is NR. The LOI value of PET-0.4Co-MOF in Example 4 is the largest, increasing to 28%. This is mainly due to the metal Co 2+ Catalytic carbonization promotes the formation of a char layer, which isolates oxygen and prevents heat exchange, thereby increasing the limiting oxygen. The LOI value of Example 5 PET-0.5Co-MOF is slightly lower than that of PET-0.4Co-MOF. This may be because the increased amount of Co-MOF added increases gas release, easily destroying the char layer during combustion and reducing the flame retardant effect.

[0127] In the UL-94 test results, the flame burning time t1 of the PET in comparative example 1 was 32.4s, and that of the PET-0.3Co-MOF in example 3 was the lowest, reduced to 9.7s. The burning time was significantly shortened, but the flame dripping from the absorbent cotton quilt ignited it, and the UL-94 test reached the V-2 level.

[0128] Experimental Example 7

[0129] Cone calorimetry tests were performed on the PET in Comparative Example 1 and the flame-retardant polyethylene terephthalate obtained using Co-MOF obtained in Examples 2-5. The test results are shown in Table 3. The combustion behavior experiments were conducted using the ISO 5660 standard using a cone calorimeter (CCT, Stanton Redcroft, UK). The sample size was 100 mm × 100 mm × 3 mm and the pressure was 50 kW·m -2 The test results include time to ignition (TTI), peak heat release rate (pHRR), total heat release (THR), average effective heat of combustion (av-EHC), total smoke output (TSP), carbon monoxide release rate (COP) / peak carbon monoxide release rate (PCOP), and peak carbon dioxide release rate (PCO2P). The specific results are shown in Table 3.

[0130] Table 3

[0131]

[0132] (1) The PET in Comparative Example 1 exhibited early combustion with a TTI of 55 seconds. After the addition of Co-MOF, the TTI of PET-0.4Co-MOF and PET-0.5Co-MOF was delayed to 64 seconds, indicating that the addition of Co-MOF can prolong the ignition time of PET and improve its thermal stability.

[0133] The pHRR value of PET in Comparative Example 1 is 1085.62 kW·m -2 , which is significantly higher than the flame-retardant PET in Examples 2-5, among which the pHRR value of PET-0.2Co-MOF in Example 2 is the smallest, which is 642.60kW·m -2 , which is 40.81% lower than that of PET in Comparative Example 1. The minimum THR value of PET-0.4Co-MOF is 69.87MJ·m -2 , which is 12.48% lower than that of the PET in Comparative Example 1. The HRR curves of the PET in Comparative Example 1 and the flame retardant PET prepared in Examples 2-5 are as follows: Figure 7 As shown, the THR curve is as follows Figure 8 shown.

[0134] (2) The smoke release rate (SPR) curve and total smoke output (TSP) curve of the PET in Comparative Example 1 and the flame retardant PET prepared in Examples 2-5 are shown as follows: Figure 9 and Figure 10 As shown. Figure 9 and Figure 10 As can be seen, the maximum smoke release rate and TSP of the flame-retardant PET prepared in Examples 2-5 are significantly lower than those of the PET in Comparative Example 1. The maximum TSP of PET-0.4Co-MOF decreases by approximately 21% compared to Comparative Example 1. This indicates that the flame-retardant PET prepared in Examples 2-5 has excellent smoke suppression effects.

[0135] (3) Compared with the PET in Comparative Example 1, the av-EHC values ​​of the flame-retardant PET in Examples 2-5 are significantly reduced, among which the av-EHC value of PET-0.4Co-MOF is the smallest, which is 14.06 MJ·kg -1 , a decrease of 30.77%. This shows that the combustion degree of volatile gases in the gas phase is significantly reduced.

[0136] As can be seen from Table 4, compared with the PET in Comparative Example 1, the peak CO2 release rate (PCO2P) of the flame-retardant PET in Examples 2-5 is improved.

[0137] The carbon monoxide release rate (COP) of the PET in Comparative Example 1 and the flame retardant PET in Examples 2-5 changes with the burning time as shown in the figure Figure 11 As shown, from Figure 11It can be seen that both the peak carbon monoxide release rate (PCOP) and the total carbon monoxide release amount of the flame retardant PET in Examples 2-5 are greatly reduced.

[0138] It is speculated that during the combustion process, CO is converted into CO2, and the increase in the production of CO2 also dilutes the concentration of oxygen and delays combustion in the gas phase.

[0139] (4) The flame growth rate index (FIGRA, defined as the maximum ratio of the heat release rate value of the sample combustion to its corresponding time pHRR / t-pHRR) and the fire spread index (FPI, defined as TTI / pHRR) of the PET in comparative example 1 and the flame retardant PET in examples 2-5 were tested and obtained. Specifically, Figure 12 As shown. Figure 12 It can be seen that compared with the PET in comparative example 1, the FIGRA of the flame-retardant PET in Examples 2-5 has decreased, and slightly increased with the increase in the amount of Co-MOF. The FPI has increased and increased with the increase in the amount of Co-MOF, indicating that the flame retardancy of the flame-retardant PET in Examples 2-5 has been improved.

[0140] Experimental Example 8

[0141] The appearance of the residual samples of PET in Comparative Example 1 and PET-0.4Co-MOF prepared in Example 4 after combustion in the cone calorimetry test of Experimental Example 7 was photographed, and SEM and EDS analysis were performed. The digital photos of the residual samples of PET in Comparative Example 1 and PET-0.4Co-MOF prepared in Example 4 after combustion are shown in FIG. Figure 13 As shown, SEM Figure 14 As shown, EDS Figure 15 shown.

[0142] from Figure 13 As can be seen in the image, the PET in Comparative Example 1 burned thoroughly, with the aluminum foil at the bottom of the PET completely burned through. The residual carbon content was significantly reduced compared to the PET-0.4Co-MOF (Example 4). The carbon layer of the PET-0.4Co-MOF expanded after combustion, and the residual carbon content increased significantly visually. The surface was covered with a layer of blue flocculent matter, which may be related to the structure of the metal oxide particles.

[0143] Figure 14From the low-magnification SEM image (scale of 100 μm), it can be seen that the PET of comparative example 1 has obvious holes, the residual carbon is loose and porous, and can hardly play a protective role. However, the residual carbon of PET-0.4Co-MOF is very dense, with a rough surface and no holes, forming a dense carbon layer. From the high-magnification SEM (scale of 1 μm), the holes of PET are enlarged, and PET-0.4Co-MOF presents a special tubular structure. The dense special tubular structure not only makes the carbon layer complete, but also increases the escape path of flammable small molecules, which plays a vital role in suppressing smoke and reducing heat release. The barrier effect of the carbon layer can prevent the spread of fire during combustion.

[0144] The elemental analysis of carbon residues from cone calorimetry was studied using EDS. Figure 15 It can be seen that the carbon element in PET-0.4Co-MOF is evenly distributed, with a small amount of Co. The carbon content in PET-0.4Co-MOF is significantly higher than that in PET, while the oxygen content is significantly lower. This also proves that Co-MOF promotes the carbonization of PET-0.4Co-MOF, and the high carbon residue mainly contributes to the improved flame retardancy of PET.

[0145] Experimental Example 9

[0146] FTIR, XPS and Raman spectroscopy tests were performed on the residual samples of the PET in Comparative Example 1 and the flame-retardant polyethylene terephthalate PET-0.4Co-MOF obtained by using Co-MOF prepared in Example 4 after combustion in Experimental Example 7.

[0147] Figure 16 FTIR spectra of the residual samples of PET and PET-0.2Co-MOF, PET-0.3Co-MOF, PET-0.4Co-MOF, and PET-0.5Co-MOF of Comparative Example 1 after combustion in Experimental Example 7. 1720 cm -1 The peak at 1080 cm corresponds to the stretching vibration peak of C=O. -1 The peak at 748 cm corresponds to the stretching vibration peak of CO, while the peak at 748 cm -1 The peak at 1080cm is due to the stretching vibration peak of the benzene ring. -1 The CO peak at π becomes a broad peak, and the C=O peak weakens.

[0148] XPS test results are as follows Figure 17 As shown in the figure, the XPS spectrum shows that C and O are the main elements of the carbon residue. Figure 18 From (a) and (b), we can see that the three typical characteristic peaks of carbon are located at 284.8eV, 286.2eV and 288.6eV, respectively, which belong to C=C in aromatic structure, CO in ether bond and C=O in carbonyl group. Figure 18In the O1s spectra in (c) and (d), the peaks at 531.62 eV and 533.22 eV correspond to C=O and CO, respectively. PET and PET-0.4-Co-MOF only change in peak intensity.

[0149] Table 5 shows the C1s area ratios of the residual samples of PET and PET-0.4Co-MOF after combustion in Experiment 7. It is obvious that the C=C bond area ratio of PET is 72.71%, while that of PET-0.4Co-MOF is 79.03%, which indicates an increase in the area ratio. In addition, the C=O area ratio decreases and the CO area ratio increases compared with PET, which is consistent with the Figure 16 The FTIR spectrum test results are consistent with those in Table 5. x / Ca represents the ratio of oxidized oxygen-containing carbon to unoxidized oxygen-free carbon, which indicates the thermal oxidation resistance of the material. The lower the ratio, the higher the thermal oxidation resistance. x The / Ca value is 26.53%, which is lower than 37.53% of PET. These all indicate that PET-0.4Co-MOF has better thermal oxidation resistance and flame retardant properties.

[0150] Table 5

[0151]

[0152]

[0153] The residual carbon was tested using a laser Raman spectrometer (Renishaw inVia, UK) at room temperature with an excitation wavelength of 532 nm. The Raman spectra obtained are as follows: Figure 19 As shown. In the Raman spectrum of the residual sample after combustion, the D band is located at 1360 cm -1 Nearby, belongs to disordered carbon, and 1590cm -1 The G band is the stretching vibration peak of ordered carbon. The area integrated intensity ratio (the ratio of D peak to G peak I D / I G ) can be used to evaluate the degree of graphitization of residual carbon. The lower the ratio, the higher the degree of graphitization and the more regular the carbon layer. Using Gaussian model fitting, Figure 19 It can be seen that PET's I D / I G The value is 2.18, while the I D / I G The value dropped to 1.88, indicating that the carbonization degree of PET-0.4Co-MOF was high, which means that the addition of Co-MOF was beneficial to the generation of residual carbon and the inhibition of flame spread.

[0154] Experimental Example 10

[0155] The tensile strength, elastic modulus, and elongation of the PET in Comparative Example 1 and the flame-retardant polyethylene terephthalate obtained using Co-MOF and prepared in Examples 2-5 were tested. The test results are shown in Table 4.

[0156] Table 4

[0157]

[0158] Compared to the PET in Comparative Example 1, the flame-retardant polyethylene terephthalate obtained using Co-MOF in Examples 2-5 showed increased tensile strength, elastic modulus, and elongation. Clearly, the addition of Co-MOF improved the mechanical properties of the flame-retardant polyethylene terephthalate obtained using Co-MOF.

[0159] Experimental Example 11

[0160] The cracking gas products generated during the combustion of the PET in Comparative Example 1 and the PET-0.4Co-MOF prepared in Example 4 were analyzed.

[0161] The analysis was performed using a thermogravimetric analyzer (TGA METTLER TOLEDO) combined with an FTIR spectrophotometer (NicoletIs50) under a nitrogen atmosphere, with the temperature rising from 30°C to 800°C at a heating rate of 15°C min -1 .

[0162] The pyrolysis gas products were analyzed using pyrolysis-gas chromatography-mass spectrometry (py-GC-MS) and a pyrolysis instrument (EGA / PY-3030, Thermo Fisher, Waltham, MA, US) equipped with a GCMS-QP2010 Ultra system and operated in a helium atmosphere.

[0163] The FTIR spectra of the cracking gas products of PET in Comparative Example 1 and PET-0.4Co-MOF prepared in Example 4 are as follows: Figure 20 As shown, the gas chromatogram of the PET cracking gas product in Comparative Example 1 is as shown in FIG. Figure 21 As shown, the gas chromatogram of the cracking gas products of PET-0.4Co-MOF is as follows Figure 22 The chromatographic peak position analysis is shown in Table 6.

[0164] Table 6:

[0165]

[0166]

[0167] Gas chromatography of the pyrolysis gas products reveals that the pyrolysis products of PET-0.4Co-MOF are similar to those of PET, with benzoic acid and 4-carboxybenzaldehyde as the primary decomposition products. Compared to PET, PET-0.4Co-MOF exhibits a distinct CO₂ peak at 1.7 min, consistent with the TG-IR results. This indicates that the decomposition produces a greater amount of CO₂, diluting the combustible gas and achieving gas-phase flame retardancy.

[0168] PET-0.4Co-MOF shows a new peak in No. 10, attributed to 4-(methoxycarbonyl)benzoic acid. It is well known that PET combustion produces many active free radicals, including H· and ·OH, which further promote the decomposition of PET and accelerate its combustion. It is speculated that the addition of Co-MOF promotes the decomposition of PET-0.4Co-MOF to produce small molecular free radicals, which can capture H· and ·OH during the PET decomposition process, terminating the chain reaction while also producing a stable and dense gas barrier layer, promoting gas-phase flame retardancy.

[0169] Experimental Example 12

[0170] The slices of PET prepared in Comparative Example 1 and PET-0.4Co-MOF prepared in Example 4 were dried in a vacuum drying oven at 130°C for 12 hours. The dried slices were then made into nascent fibers on an SJ-120 single-screw spinning machine, and the fibers were stretched 3.5 times and heat-set to obtain PET and PET-0.4Co-MOF fibers. Table 7 shows the specific spinning process parameters, and the mechanical properties are shown in Table 8. Generally, the flame retardant modification of PET is often accompanied by a decrease in processing performance, especially the molding processing of the fiber. The breaking strength of the PET prepared in Comparative Example 1 is 3.44 cN / dtex, and the elongation at break is 21.45%, while the breaking strength and elongation at break of PET-0.4Co-MOF are both improved, and it has excellent spinnability and excellent mechanical properties.

[0171] Table 7

[0172]

[0173]

[0174] Table 8

[0175]

[0176] The present invention has been described in detail above with reference to specific embodiments and / or exemplary examples and the accompanying drawings. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

Claims

1. Flame-retardant polyethylene terephthalate obtained by using Co-MOF, which is obtained by polycondensing terephthalic acid and ethylene glycol prepolymer in the presence of cobalt organic metal framework material Co-MOF, The Co-MOF is prepared by a solvothermal reaction of a cobalt salt and an organic ligand under heating and pressure in a solvent environment; The organic ligand is a dibasic aromatic carboxylic acid.

2. The flame-retardant polyethylene terephthalate obtained using Co-MOF according to claim 1, characterized in that The cobalt salt is selected from one or more of cobalt nitrate, cobalt acetate, cobalt chloride, cobalt bromide and cobalt sulfate.

3. The flame-retardant polyethylene terephthalate obtained using Co-MOF according to claim 2, characterized in that: The cobalt salt is one or more of cobalt nitrate, cobalt acetate and cobalt chloride; The organic ligand is one or more of phthalic acid and phenylenedicarboxylic acid.

4. The flame-retardant polyethylene terephthalate obtained using Co-MOF according to claim 3, characterized in that The organic ligand is terephthalic acid.

5. The flame-retardant polyethylene terephthalate obtained using Co-MOF according to claim 1, characterized in that Under a protective atmosphere, the temperature is increased from 20°C to 700°C at a heating rate of 10°C / min, and the coke residue of the flame-retardant polyethylene terephthalate obtained by using Co-MOF is greater than 10wt%; The maximum weight loss rate of the flame-retardant polyethylene terephthalate obtained by using Co-MOF is less than 22%·℃ -1 ; The LOI value of the flame-retardant polyethylene terephthalate obtained by using Co-MOF is greater than or equal to 23%.

6. The flame-retardant polyethylene terephthalate obtained using Co-MOF according to claim 5, characterized in that The flame-retardant polyethylene terephthalate obtained by using Co-MOF has a coke residue content greater than 12 wt %; The LOI value of the flame-retardant polyethylene terephthalate obtained by using Co-MOF is greater than 25%.

7. The flame-retardant polyethylene terephthalate obtained using Co-MOF according to claim 6, characterized in that: The flame-retardant polyethylene terephthalate obtained by using Co-MOF has a coke residue content greater than 13.5 wt %; The LOI value of the flame-retardant polyethylene terephthalate obtained by using Co-MOF is greater than 28%.

8. The flame-retardant polyethylene terephthalate obtained using Co-MOF according to claim 1, characterized in that The flame-retardant polyethylene terephthalate obtained by using Co-MOF has a tensile strength greater than 45 MPa; The elastic modulus of the flame-retardant polyethylene terephthalate obtained by using Co-MOF is greater than 1250 MPa; The flame-retardant polyethylene terephthalate obtained by using Co-MOF has an elongation of 330% to 400%.

9. The flame-retardant polyethylene terephthalate obtained using Co-MOF according to claim 8, characterized in that The flame-retardant polyethylene terephthalate obtained by using Co-MOF has a tensile strength greater than 50 MPa; The elastic modulus of the flame-retardant polyethylene terephthalate obtained by using Co-MOF is greater than 1300 MPa; The flame-retardant polyethylene terephthalate obtained by using Co-MOF has an elongation of 330% to 370%.

10. The flame-retardant polyethylene terephthalate obtained using Co-MOF according to claim 9, characterized in that: The elastic modulus of the flame-retardant polyethylene terephthalate obtained by using Co-MOF is greater than 1340 MPa.

11. The method for preparing flame-retardant polyethylene terephthalate using Co-MOF according to any one of claims 1 to 10, characterized in that: The method specifically comprises the following steps: Step 1, pretreatment of Co-MOF; Step 2: mixing terephthalic acid, ethylene glycol, and Co-MOF, heating and prepolymerizing to obtain reaction solution I, wherein the molar ratio of terephthalic acid to ethylene glycol is (2.0-6.5):5, and the mass ratio of Co-MOF to terephthalic acid is (0.1-2.5):

100. The prepolymerization reaction is carried out under a protective atmosphere at 200-260° C. for 1-4 hours; Step 3: Add ethylene glycol, an antioxidant, and an anti-hydrolysis agent to the reaction solution I, first carry out the reaction at normal pressure, and then increase the temperature under vacuum conditions to carry out polycondensation to obtain flame-retardant polyethylene terephthalate obtained using Co-MOF.

12. The method according to claim 11, characterized in that In step 2, the molar ratio of terephthalic acid to ethylene glycol is (3.0-5.5):

5.

13. The method according to claim 12, characterized in that In step 2, the molar ratio of terephthalic acid to ethylene glycol is (4.0-4.5):

5.

14. The method according to claim 11, characterized in that In step 2, the mass ratio of the Co-MOF to terephthalic acid is (0.15-1.5):100; The prepolymerization reaction is carried out under nitrogen or argon protective atmosphere at 220-240° C. for 2-3 hours.

15. The method according to claim 14, characterized in that In step 2, the mass ratio of the Co-MOF to terephthalic acid is (0.2-0.5):

100.

16. The method according to claim 11, characterized in that In step 3, The antioxidant is selected from one or more phosphite antioxidants, and the mass ratio of the antioxidant to the terephthalic acid in step 1 is (0.05-0.4):100; The anti-hydrolysis agent is one or more of N,N'-bis(2,6-diisopropylphenyl)carbodiimide, biscarbodiimide anti-hydrolysis agents, and HyMax 1010; the mass ratio of the anti-hydrolysis agent to the terephthalic acid in step 1 is (0.05-0.4):100; The normal pressure reaction temperature is 200-260°C; The vacuum condition is -0.05~-0.1Mpa; The polycondensation reaction temperature is 255-305°C.

17. The method according to claim 16, characterized in that In step 3, The antioxidant is triphenyl phosphite (TPI), and the mass ratio of the antioxidant to the terephthalic acid in step 1 is (0.08-0.3):100; The anti-hydrolysis agent is HyMax 1010; the mass ratio of the anti-hydrolysis agent to the terephthalic acid in step 1 is (0.08-0.3):100; The normal pressure reaction temperature is 210-250°C; The vacuum condition is -0.08~-0.1Mpa; The polycondensation reaction temperature is 265-295°C.

18. The method according to claim 17, characterized in that In step 3, The mass ratio of the antioxidant to the terephthalic acid in step 1 is (0.1-0.2):100; The mass ratio of the anti-hydrolysis agent to the terephthalic acid in step 1 is (0.1-0.2):100; The normal pressure reaction temperature is 220-240°C; The vacuum condition is -0.1Mpa; The polycondensation reaction temperature is 275-285°C.

19. A flame-retardant polyethylene terephthalate fiber obtained by using Co-MOF, characterized in that: The flame-retardant polyethylene terephthalate fiber obtained using Co-MOF is prepared by fiber stretching the flame-retardant polyethylene terephthalate obtained using Co-MOF according to any one of claims 1 to 10. When the bundle fineness is 110~120 dtex, the flame-retardant polyethylene terephthalate fiber obtained using Co-MOF has a breaking strength greater than 3.45 cN / dtex; and an elongation at break greater than 22%.

20. The flame-retardant polyethylene terephthalate fiber obtained by using Co-MOF according to claim 19, characterized in that: When the bundle fineness is 110-120 dtex, the flame-retardant polyethylene terephthalate fiber obtained by using Co-MOF has a breaking strength greater than 3.50 cN / dtex and an elongation at break greater than 25%.

21. The flame-retardant polyethylene terephthalate fiber obtained by using Co-MOF according to claim 20, characterized in that: When the bundle fineness is 110-120 dtex, the elongation at break of the flame-retardant polyethylene terephthalate fiber obtained by using Co-MOF is greater than 29%.

22. A method for preparing flame-retardant polyethylene terephthalate fiber using Co-MOF according to any one of claims 19 to 21, characterized in that: The method uses the flame-retardant polyethylene terephthalate obtained by using Co-MOF according to any one of claims 1 to 10 as a raw material, and is prepared by stretching the fiber 2-4 times and then heat-setting.

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