Halogen-free flame-retardant polyester fiber and preparation method thereof

Abstract

The invention relates to the technical field of synthetic fibers, and particularly discloses a halogen-free flame-retardant polyester fiber and a preparation method thereof.The preparation method comprises the steps that firstly, boric acid modified polydimethylsiloxane is added into a polymer chain segment in a copolymerization mode, a borosilicate component with large steric hindrance is introduced into the polymer chain segment, and the viscosity and flame retardance of a polymer melt are enhanced; the preparation method comprises the following steps: firstly, carrying out melt spinning, then introducing a phosphorus-nitrogen-sulfur type DOPO-based flame retardant during melt spinning to further improve the flame retardance of the fiber, and finally, impregnating with an antibacterial flame-retardant finishing liquid containing a copper pyrophosphate-organic complex and an antistatic finishing liquid containing quaternized polyester, so that the fiber is endowed with antibacterial and antistatic capabilities while the flame retardance of the fiber is improved, and the functions of the fiber are enriched.

Description

Technical Field

[0001] The present invention relates to the technical field of synthetic fibers, in particular to a halogen-free flame-retardant polyester fiber and a preparation method thereof. Background Art

[0002] Polyester fiber is a thermoplastic synthetic fiber containing polyester segments in its molecular chain structure. It has the advantages of high strength and stable chemical properties. The fabric processed into it has good wear resistance, good wrinkle resistance, easy washing and quick drying. It is widely used in the textile, automotive, medical and other industries and is an important synthetic fiber. However, because it is derived from petroleum-based polymers and is limited by raw materials, polyester fiber is flammable. Moreover, when it reaches the melting point or comes into contact with a fire source, polyester fiber is prone to produce molten droplets that fall off from the original position. The detached molten droplets ignite the remaining polyester fibers or other flammable materials during movement, causing secondary fires. Therefore, people usually add flame retardants during the production process or post-processing of polyester fibers to improve the flame retardancy of polyester fibers, thereby improving the safety performance of polyester fibers.

[0003] Halogen flame retardants, such as decabromodiphenyl ether, tetrabromobisphenol A, and chlorinated paraffin, are commonly used in polyester fiber production. When burned, they release hydrogen halide gas, replenishing the free radicals produced during combustion and thus interrupting the combustion chain reaction. Halogen flame retardants are highly compatible with polymers and are suitable for a variety of polymer materials. They offer excellent flame retardant effects, typically requiring only 5%-10% to achieve a good flame retardant effect. However, these flame retardants release toxic and hazardous substances such as dioxins during combustion, making them unsuitable for environmental protection and are being phased out. Therefore, the development of a new halogen-free flame retardant for polyester fiber plays a significant role in the development of the polyester industry. Summary of the Invention

[0004] The purpose of the present invention is to provide a halogen-free flame-retardant polyester fiber and a preparation method thereof, and to develop a new type of halogen-free flame retardant polyester fiber to solve the problem that the use of halogen flame retardants to flame-retard polyester will produce toxic and harmful substances such as dioxins.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: A method for preparing halogen-free flame-retardant polyester fiber, specifically comprising: Step 1: Using terephthalic acid and ethylene glycol as raw materials, polymerizing under the action of tetrabutyl titanate catalyst, and adding boric acid-modified polydimethylsiloxane to prepare borosilicate-modified polyethylene terephthalate; Step 2: mixing the borosilicate modified polyethylene terephthalate with the dried phosphorus-nitrogen-sulfur type DOPO-based flame retardant, melt-extruding and granulating at 260-280° C. to obtain a flame retardant masterbatch, mixing the flame retardant masterbatch with the borosilicate modified polyethylene terephthalate, and melt-extruding and spinning to obtain a flame retardant polyester fiber; Step 3: After the flame retardant polyester fiber is impregnated with a 3-7 mmol / L dopamine hydrochloride solution, it is impregnated with an antibacterial flame retardant finishing liquid to obtain an antibacterial flame retardant polyester fiber; Step 4: The antibacterial flame retardant polyester fiber is impregnated with an antistatic finishing liquid to obtain a halogen-free flame retardant polyester fiber.

[0006] As a limitation of the present invention, the step 1 is specifically as follows: Mix hydroxyl-terminated polydimethylsiloxane, boric acid, and ethanol, stir evenly at room temperature, then heat to 70-80°C and react at 70-80°C, 300-500 rpm for 4-6 hours. After the reaction is complete, filter under reduced pressure to obtain boric acid-modified polydimethylsiloxane; Mix terephthalic acid, ethylene glycol and tetrabutyl titanate, heat to 240-250°C under 0.2-0.25 MPa nitrogen protection, and react for 1.5-2 hours. After 1.5-2 hours, add silane coupling agent KH-550 and boric acid-modified polydimethylsiloxane, and continue to react for 2-3 hours. After the reaction is completed, heat to 270-280°C, slowly evacuate to reduce the pressure to 80-100 Pa, and polycondense for 3-5 hours to obtain borosilicate-modified polyethylene terephthalate.

[0007] As a limitation of the present invention, the mass ratio of hydroxyl-terminated polydimethylsiloxane, boric acid and ethanol is (4-6):(0.8-1.2):(0.5-1.0); the mass ratio of terephthalic acid, ethylene glycol and boric acid-modified polydimethylsiloxane is (80-120):(40-60):(15-20).

[0008] As a limitation of the present invention, in step 2, the preparation method of the phosphorus-nitrogen-sulfur type DOPO-based flame retardant is: The mixture of terephthalaldehyde, p-aminobenzenesulfonamide and anhydrous ethanol was stirred evenly, and then the temperature was raised to 80-85°C and the mixture was reacted for 7-8 hours. After the reaction was completed, the mixture was cooled, filtered, washed with ethanol, and dried at 60-70°C to obtain a flame retardant intermediate. The flame retardant intermediate, DOPO and tetrahydrofuran are mixed and refluxed at 70-80° C. for 20-24 hours. After the reaction is completed, the mixture is cooled, filtered, washed with ethanol, and dried at 60-70° C. to obtain a phosphorus-nitrogen-sulfur DOPO-based flame retardant.

[0009] First, terephthalaldehyde and p-aminobenzenesulfonic acid undergo Schiff base condensation. The aldehyde group of terephthalaldehyde OHC-C6H4-CHO condenses with the amino group of p-aminobenzenesulfonic acid (H2N-)2C6H4-SO3H, and dehydrates to form a Schiff base C6H4(-CH=N-C6H4-SO3H)2 containing an imine bond. Then, the Schiff base further undergoes an addition reaction with DOPO. The phosphorus-hydrogen bond pH of DOPO undergoes nucleophilic addition to the imine bond C=N of the Schiff base, generating an α-aminophosphonate derivative containing phosphorus, nitrogen, and sulfonic acid groups.

[0010] As a limitation of the present invention, the mass ratio of terephthalaldehyde to p-aminobenzenesulfonamide is (5-10):(18-22); the mass ratio of the flame retardant intermediate to DOPO is (1-3):(2-3).

[0011] As a limitation of the present invention, in step 2, the mass ratio of borosilicate modified polyethylene terephthalate to the phosphorus, nitrogen and sulfur type DOPO-based flame retardant is (6-7): (3-4); the mass ratio of the flame retardant masterbatch to the borosilicate modified polyethylene terephthalate is 1: (2-3); during the melt extrusion spinning process, the melt temperature is 260-280°C, the screw temperature is 270-290°C, the head temperature is 250-260°C, and the spinning rate is 50-70m / min.

[0012] As a limitation of the present invention, in step 3, the preparation method of the antibacterial flame retardant finishing liquid is: Add pyromellitic acid and copper pyrophosphate to deionized water, stir evenly, heat to 60-70°C and adjust the pH to 5-6, react at 60-70°C for 3-5 hours, filter after the reaction is completed, wash with deionized water, and dry at 50-60°C to obtain copper pyrophosphate-organic ligand, add the copper pyrophosphate-organic ligand to deionized water, and ultrasonically disperse to obtain an antibacterial flame retardant finishing liquid.

[0013] As a limitation of the present invention, the mass ratio of pyromellitic acid to copper pyrophosphate is (1.5-3.5):(2-4); and the concentration of the copper pyrophosphate-organic ligand in the antibacterial flame retardant finishing liquid is 40-60 g / L.

[0014] As a limitation of the present invention, in step 4, the preparation method of the antistatic finishing liquid is: Mix triethanolamine and adipic acid, heat to 100-110°C to completely dissolve them, then add p-toluenesulfonic acid and continue to heat to 130-140°C, stir and react at 130-140°C for 2-3 hours, add sodium hydroxyacetate, react at 80-90°C for 6-8 hours, heat to 160-170°C after the reaction is completed, and evaporate the solvent to obtain quaternized triethanolamine adipate. Mix quaternized triethanolamine adipate, poly(hexamethylene adipate) and tetrabutyl titanate, heat to 160-170°C and stir and react for 2-4 hours, cool after the reaction is completed to obtain a quaternized polyester antistatic agent, and dissolve the quaternized polyester antistatic agent in 30% by mass ethanol aqueous solution to obtain an antistatic finishing liquid.

[0015] Triethanolamine and adipic acid undergo esterification reaction under the catalysis of p-toluenesulfonic acid to produce triethanolamine adipate. The sodium carboxylate in the structure of sodium glycolate CH2OH-COONa and the tertiary amine nitrogen in the structure of triethanolamine adipate (R-COO-C2H4-)3N further undergo nucleophilic attack reaction under heating conditions to produce quaternary ammonium polyester (R-COO-C2H4-)3N + (CH2COO - )-CH2OH.

[0016] As a limitation of the present invention, the mass ratio of triethanolamine, adipic acid, p-toluenesulfonic acid, and sodium glycolate is (10-15):(8-12):(0.1-0.3):(20-25); and the concentration of the quaternary ammonium polyester antistatic agent in the antistatic finishing liquid is 20-40 g / L.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention first reacts hydroxyl-terminated polydimethylsiloxane with boric acid to obtain boric acid-modified polydimethylsiloxane, and then copolymerizes the obtained polydimethylsiloxane into polymethyl methacrylate chain segments. In this way, not only are boron and silicon elements introduced into the polymethyl methacrylate chain segments, facilitating the formation of a dense, highly heat-insulating carbon layer during combustion, but the steric hindrance can also hinder the movement and rotation of the chain segments, thereby increasing the viscosity of the polymer melt and reducing the generation of molten droplets.

[0018] During the melt spinning process, the present invention adds a phosphorus-nitrogen-sulfur type DOPO-based flame retardant obtained by reacting p-aminobenzenesulfonamide with DOPO. The DOPO-based flame retardant is a phosphaphenanthrene derivative and contains a DOPO structure on the side chain. In the early stage of combustion, the oxygen-phosphorus-carbon bond and the sulfur-oxygen bond in the structure are not as stable as the carbon-carbon bond, and decompose first to generate nitrogen- and sulfur-containing inert gas and phosphide. The inert gas dilutes oxygen and inhibits free radical reactions, reducing the concentration of combustible gases. The phosphide captures highly active free radicals during combustion, interrupting the combustion chain reaction while promoting the formation of a dense carbon layer. In addition, the sulfur component reacts with the nitrogen component to generate a thermally stable sulfur-nitrogen compound, which promotes the expansion of the carbon layer and enhances the barrier effect.

[0019] After melt-spinning, the fibers are first impregnated with a dopamine hydrochloride solution to form a polydopamine coating with an adhesive effect on the fiber surface, which is beneficial for further processing of the polyester fiber. Subsequently, the fibers are impregnated with an antibacterial flame-retardant finishing solution containing a copper pyrophosphate-organic complex. Pyromellitic acid is an organic carboxylic acid ligand with high symmetry, which is beneficial for forming a complex with a regular structure. When the complex decomposes under heat, a decarboxylation reaction occurs to produce some non-flammable gas, thereby achieving the purpose of flame retardancy. The copper pyrophosphate slowly releases copper ions on the fiber surface to kill bacteria, thereby imparting antibacterial properties to the fibers. During combustion, the copper pyrophosphate can decompose and release phosphorus-containing free radicals to block the combustion chain reaction. Furthermore, the phosphorus component promotes dehydration and carbonization of the polymer, and the copper ions accelerate the cross-linking of the carbon layer, helping to form a dense carbon layer that isolates heat and the diffusion of combustible gases.

[0020] Finally, the present invention adopts triethanolamine, adipic acid, sodium glycolate and other raw materials to synthesize quaternary ammonium polyester through esterification and quaternization. The quaternary ammonium cation contained in the quaternary ammonium polyester forms a conductive layer on the fiber surface, thereby enhancing the antistatic property of the fiber. In addition, the branched structure can form a mesh film on the fiber surface, thereby increasing the contact area with the fiber and binding the copper pyrophosphate-organic complex to prevent it from falling off. The ester group in the branched chain has good compatibility with the fiber, thereby enhancing the water resistance and washing resistance of the fiber. DETAILED DESCRIPTION

[0021] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0022] Hydroxyl-terminated polydimethylsiloxane (Mw=4200), DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, purity: >99.5%, OPP content: <1000ppm), poly(hexanediol adipate) (Mn=1000, hydroxyl value: 106-118mgKOH / g).

[0023] Example 1: A method for preparing halogen-free flame-retardant polyester fiber, specifically comprising: Step 1: 5 g of hydroxyl-terminated polydimethylsiloxane, 1 g of boric acid, and 1 mL of ethanol were mixed and stirred at room temperature. The mixture was then heated to 70°C and reacted at 70°C and 500 rpm for 6 h. After the reaction was completed, the mixture was filtered under reduced pressure to obtain boric acid-modified polydimethylsiloxane. Step 2: 100g of terephthalic acid, 50g of ethylene glycol and 1g of tetrabutyl titanate were mixed, heated to 240°C under 0.25MPa nitrogen protection, and reacted for 2h. After 2h, 1.5g of silane coupling agent KH-550 and 18g of boric acid-modified polydimethylsiloxane were added, and the reaction was continued for 2h. After the reaction was completed, the temperature was raised to 270°C, and the pressure was slowly reduced to 100Pa. Polycondensation was carried out for 4h to obtain borosilicate-modified polyethylene terephthalate; Step 3: 8 g of terephthalaldehyde, 20.6 g of p-aminobenzenesulfonamide and 150 mL of anhydrous ethanol were mixed, stirred evenly, heated to 85° C. and reacted for 8 h. After the reaction was completed, cooled, filtered, washed with ethanol, and dried at 60° C. to obtain a flame retardant intermediate; Step 4: 20.8 g of the flame retardant intermediate, 26.5 g of DOPO and 150 mL of tetrahydrofuran were mixed and refluxed at 80° C. for 24 h. After the reaction was completed, the mixture was cooled, filtered, washed with ethanol, and dried at 60° C. to obtain a phosphorus-nitrogen-sulfur DOPO-based flame retardant; Step 5: The phosphorus, nitrogen, and sulfur type DOPO-based flame retardant was dried at 70°C for 2 hours before use, and the borosilicate modified polyethylene terephthalate and the dried phosphorus, nitrogen, and sulfur type DOPO-based flame retardant were mixed in a mass ratio of 7:3, added to a twin-screw extruder, and melt-extruded and granulated at 270°C to obtain a flame-retardant masterbatch. The flame-retardant masterbatch was mixed with the borosilicate modified polyethylene terephthalate in a mass ratio of 1:3, added to a twin-screw extruder, and the melt temperature, screw temperature, and die head temperature were set to 270°C, 280°C, and 255°C, respectively. The spinning rate was 60m / min, and melt extrusion spinning was performed to obtain a flame-retardant polyester fiber; Step 6: Add 24 g of pyromellitic acid and 30 g of copper pyrophosphate to 500 mL of deionized water, stir evenly, heat to 70° C. and adjust the pH to 5, react at 70° C. for 4 h, filter after the reaction is completed, wash with deionized water, and dry at 50-60° C. to obtain a copper pyrophosphate-organic ligand. Add 48 g of the copper pyrophosphate-organic ligand to 1 L of deionized water and ultrasonically disperse for 20 min to obtain an antibacterial flame retardant finishing liquid; Step 7: dopamine hydrochloride is added to Tris buffer and stirred to obtain a 5 mmol / L dopamine hydrochloride solution, and the flame-retardant polyester fiber is immersed in the dopamine hydrochloride solution. After shaking in a water bath at 30°C for 24 hours, the fiber is taken out and dried at 60°C for 4 hours. Subsequently, the fiber is immersed in a 48 g / L antibacterial flame retardant finishing solution, after shaking in a water bath at 30°C for 24 hours, the fiber is taken out and dried at 60°C for 4 hours to obtain the antibacterial flame retardant polyester fiber; Step 8: 24g of triethanolamine and 20g of adipic acid were mixed, heated to 100°C to completely dissolve them, and then 0.4g of p-toluenesulfonic acid was added and the temperature was continued to be raised to 130°C. After stirring and reacting at 130°C for 2.5h, 46g of sodium hydroxyacetate was added and reacted at 80°C for 7h. After the reaction was completed, the temperature was raised to 160°C to evaporate the solvent to obtain quaternized triethanolamine adipate. 32g of quaternized triethanolamine adipate, 64g of poly(hexamethylene adipate) and 0.3g of tetrabutyl titanate were mixed, heated to 160°C and stirred for reaction for 3h. After the reaction was completed, the mixture was cooled to obtain a quaternized polyester antistatic agent. The quaternized polyester antistatic agent was dissolved in an ethanol aqueous solution having a mass fraction of 30% to obtain a 30g / L antistatic finishing liquid. Step 9: Immerse the antibacterial flame-retardant polyester fiber in the antistatic finishing solution, shake it in a 30°C water bath for 24 hours, take out the fiber, dry it at 100°C for 30 minutes, and then heat it to 160°C for curing for 2 minutes to obtain a halogen-free flame-retardant polyester fiber.

[0024] Example 2: A method for preparing halogen-free flame-retardant polyester fiber, specifically comprising: Step 1: 5 g of hydroxyl-terminated polydimethylsiloxane, 1 g of boric acid, and 1 mL of ethanol were mixed and stirred at room temperature. The mixture was then heated to 70°C and reacted at 70°C and 500 rpm for 6 h. After the reaction was completed, the mixture was filtered under reduced pressure to obtain boric acid-modified polydimethylsiloxane. Step 2: 100g of terephthalic acid, 50g of ethylene glycol and 1g of tetrabutyl titanate were mixed, heated to 240°C under 0.25MPa nitrogen protection, and reacted for 2h. After 2h, 1.5g of silane coupling agent KH-550 and 18g of boric acid-modified polydimethylsiloxane were added, and the reaction was continued for 2h. After the reaction was completed, the temperature was raised to 270°C, and the pressure was slowly reduced to 100Pa. Polycondensation was carried out for 4h to obtain borosilicate-modified polyethylene terephthalate; Step 3: 8 g of terephthalaldehyde, 20.6 g of p-aminobenzenesulfonamide and 150 mL of anhydrous ethanol were mixed, stirred evenly, heated to 85° C. and reacted for 8 h. After the reaction was completed, cooled, filtered, washed with ethanol, and dried at 60° C. to obtain a flame retardant intermediate; Step 4: 20.8 g of the flame retardant intermediate, 26.5 g of DOPO and 150 mL of tetrahydrofuran were mixed and refluxed at 80° C. for 24 h. After the reaction was completed, the mixture was cooled, filtered, washed with ethanol, and dried at 60° C. to obtain a phosphorus-nitrogen-sulfur DOPO-based flame retardant; Step 5: The phosphorus, nitrogen, and sulfur type DOPO-based flame retardant was dried at 70°C for 2 hours before use, and the borosilicate modified polyethylene terephthalate and the dried phosphorus, nitrogen, and sulfur type DOPO-based flame retardant were mixed in a mass ratio of 7:3, added to a twin-screw extruder, and melt-extruded and granulated at 270°C to obtain a flame-retardant masterbatch. The flame-retardant masterbatch was mixed with borosilicate modified polyethylene terephthalate in a mass ratio of 1:2.5, added to a twin-screw extruder, and the melt temperature, screw temperature, and die head temperature were set to 270°C, 280°C, 255°C, and 60m / min, and melt-extruded and spun to obtain a flame-retardant polyester fiber. Step 6: Add 24 g of pyromellitic acid and 30 g of copper pyrophosphate to 500 mL of deionized water, stir evenly, heat to 70° C. and adjust the pH to 5, react at 70° C. for 4 h, filter after the reaction is complete, wash with deionized water, and dry at 50-60° C. to obtain a copper pyrophosphate-organic ligand. Add 54 g of the copper pyrophosphate-organic ligand to 1 L of deionized water and ultrasonically disperse for 20 min to obtain an antibacterial flame retardant finishing liquid; Step 7: dopamine hydrochloride was added to the Tris buffer solution and stirred to obtain a 5 mmol / L dopamine hydrochloride solution. The flame-retardant polyester fiber was immersed in the dopamine hydrochloride solution. After shaking in a water bath at 30°C for 24 hours, the fiber was taken out and dried at 60°C for 4 hours. The fiber was then immersed in a 54 g / L antibacterial flame-retardant finishing solution. After shaking in a water bath at 30°C for 24 hours, the fiber was taken out and dried at 60°C for 4 hours to obtain the antibacterial flame-retardant polyester fiber. Step 8: 24g of triethanolamine and 20g of adipic acid were mixed, heated to 100°C to completely dissolve them, and then 0.4g of p-toluenesulfonic acid was added and the temperature was continued to be raised to 130°C. After stirring and reacting at 130°C for 2.5h, 46g of sodium hydroxyacetate was added and reacted at 80°C for 7h. After the reaction was completed, the temperature was raised to 160°C to evaporate the solvent to obtain quaternized triethanolamine adipate. 32g of quaternized triethanolamine adipate, 64g of polyhexamethylene adipate, and 0.3g of tetrabutyl titanate were mixed, heated to 160°C and stirred for reaction for 3h. After the reaction was completed, the mixture was cooled to obtain a quaternized polyester antistatic agent. The quaternized polyester antistatic agent was dissolved in an ethanol aqueous solution having a mass fraction of 30% to obtain a 40g / L antistatic finishing liquid; Step 9: Immerse the antibacterial flame-retardant polyester fiber in the antistatic finishing solution, shake it in a 30°C water bath for 24 hours, take out the fiber, dry it at 100°C for 30 minutes, and then heat it to 160°C for curing for 2 minutes to obtain a halogen-free flame-retardant polyester fiber.

[0025] Example 3: A method for preparing halogen-free flame-retardant polyester fiber, specifically comprising: Step 1: 5 g of hydroxyl-terminated polydimethylsiloxane, 1 g of boric acid, and 1 mL of ethanol were mixed and stirred at room temperature. The mixture was then heated to 70°C and reacted at 70°C and 500 rpm for 6 h. After the reaction was completed, the mixture was filtered under reduced pressure to obtain boric acid-modified polydimethylsiloxane. Step 2: 100g of terephthalic acid, 50g of ethylene glycol and 1g of tetrabutyl titanate were mixed, heated to 240°C under 0.25MPa nitrogen protection, and reacted for 2h. After 2h, 1.5g of silane coupling agent KH-550 and 18g of boric acid-modified polydimethylsiloxane were added, and the reaction was continued for 2h. After the reaction was completed, the temperature was raised to 270°C, and the pressure was slowly reduced to 100Pa. Polycondensation was carried out for 4h to obtain borosilicate-modified polyethylene terephthalate; Step 3: 8 g of terephthalaldehyde, 20.6 g of p-aminobenzenesulfonamide and 150 mL of anhydrous ethanol were mixed, stirred evenly, heated to 85° C. and reacted for 8 h. After the reaction was completed, cooled, filtered, washed with ethanol, and dried at 60° C. to obtain a flame retardant intermediate; Step 4: 20.8 g of the flame retardant intermediate, 26.5 g of DOPO and 150 mL of tetrahydrofuran were mixed and refluxed at 80° C. for 24 h. After the reaction was completed, the mixture was cooled, filtered, washed with ethanol, and dried at 60° C. to obtain a phosphorus-nitrogen-sulfur DOPO-based flame retardant; Step 5: The phosphorus, nitrogen, and sulfur type DOPO-based flame retardant is dried at 70°C for 2 hours before use, and the borosilicate borosilicate modified polyethylene terephthalate and the dried phosphorus, nitrogen, and sulfur type DOPO-based flame retardant are mixed in a mass ratio of 7:3, added to a twin-screw extruder, and melt-extruded and granulated at 270°C to obtain a flame-retardant masterbatch. The flame-retardant masterbatch and borosilicate modified polyethylene terephthalate are mixed in a mass ratio of 1:2, added to a twin-screw extruder, and the melt temperature, screw temperature, and die head temperature are set to 270°C, 280°C, 255°C, and 60m / min, and melt-extruded and spun to obtain a flame-retardant polyester fiber; Step 6: Add 24 g of pyromellitic acid and 30 g of copper pyrophosphate to 500 mL of deionized water, stir evenly, heat to 70° C. and adjust the pH to 5, react at 70° C. for 4 h, filter after the reaction is completed, wash with deionized water, and dry at 50-60° C. to obtain a copper pyrophosphate-organic ligand. Add 60 g of the copper pyrophosphate-organic ligand to 1 L of deionized water and ultrasonically disperse for 20 min to obtain an antibacterial flame retardant finishing liquid; Step 7: dopamine hydrochloride was added to the Tris buffer solution and stirred to obtain a 5 mmol / L dopamine hydrochloride solution. The flame-retardant polyester fiber was immersed in the dopamine hydrochloride solution, and after shaking in a 30°C water bath for 24 hours, the fiber was taken out and dried at 60°C for 4 hours. The fiber was then immersed in a 60 g / L antibacterial flame retardant finishing solution, and after shaking in a 30°C water bath for 24 hours, the fiber was taken out and dried at 60°C for 4 hours to obtain the antibacterial flame retardant polyester fiber. Step 8: 24g of triethanolamine and 20g of adipic acid were mixed, heated to 100°C to completely dissolve them, and then 0.4g of p-toluenesulfonic acid was added and the temperature was continued to be raised to 130°C. After stirring and reacting at 130°C for 2.5h, 46g of sodium hydroxyacetate was added and reacted at 80°C for 7h. After the reaction was completed, the temperature was raised to 160°C to evaporate the solvent to obtain quaternized triethanolamine adipate, 32g of quaternized triethanolamine adipate, 64g of poly(hexamethylene adipate) and 0.3g of tetrabutyl titanate were mixed, heated to 160°C and stirred for reaction for 3h. After the reaction was completed, the mixture was cooled to obtain a quaternized polyester antistatic agent, and the quaternized polyester antistatic agent was dissolved in an ethanol aqueous solution having a mass fraction of 30% to obtain a 50g / L antistatic finishing liquid; Step 9: Immerse the antibacterial flame-retardant polyester fiber in the antistatic finishing solution, shake it in a 30°C water bath for 24 hours, take out the fiber, dry it at 100°C for 30 minutes, and then heat it to 160°C for curing for 2 minutes to obtain a halogen-free flame-retardant polyester fiber.

[0026] Based on Example 1, control experiments were conducted, specifically Comparative Example 1, Comparative Example 2, and Comparative Example 3, as described below: Comparative Example 1: This comparative example relates to a method for preparing a halogen-free flame-retardant polyester fiber. The difference from Example 1 is that the fiber is not impregnated with an antibacterial flame-retardant finishing liquid. Specifically, Step 1: 5 g of hydroxyl-terminated polydimethylsiloxane, 1 g of boric acid, and 1 mL of ethanol were mixed and stirred at room temperature. The mixture was then heated to 70°C and reacted at 70°C and 500 rpm for 6 h. After the reaction was completed, the mixture was filtered under reduced pressure to obtain boric acid-modified polydimethylsiloxane. Step 2: 100g of terephthalic acid, 50g of ethylene glycol and 1g of tetrabutyl titanate were mixed, heated to 240°C under 0.25MPa nitrogen protection, and reacted for 2h. After 2h, 1.5g of silane coupling agent KH-550 and 18g of boric acid-modified polydimethylsiloxane were added, and the reaction was continued for 2h. After the reaction was completed, the temperature was raised to 270°C, and the pressure was slowly reduced to 100Pa. Polycondensation was carried out for 4h to obtain borosilicate-modified polyethylene terephthalate; Step 3: 8 g of terephthalaldehyde, 20.6 g of p-aminobenzenesulfonamide and 150 mL of anhydrous ethanol were mixed, stirred evenly, heated to 85° C. and reacted for 8 h. After the reaction was completed, cooled, filtered, washed with ethanol, and dried at 60° C. to obtain a flame retardant intermediate; Step 4: 20.8 g of the flame retardant intermediate, 26.5 g of DOPO and 150 mL of tetrahydrofuran were mixed and refluxed at 80° C. for 24 h. After the reaction was completed, the mixture was cooled, filtered, washed with ethanol, and dried at 60° C. to obtain a phosphorus-nitrogen-sulfur DOPO-based flame retardant; Step 5: The phosphorus, nitrogen, and sulfur type DOPO-based flame retardant was dried at 70°C for 2 hours before use, and the borosilicate modified polyethylene terephthalate and the dried phosphorus, nitrogen, and sulfur type DOPO-based flame retardant were mixed in a mass ratio of 7:3, added to a twin-screw extruder, and melt-extruded and granulated at 270°C to obtain a flame-retardant masterbatch. The flame-retardant masterbatch was mixed with the borosilicate modified polyethylene terephthalate in a mass ratio of 1:3, added to a twin-screw extruder, and the melt temperature, screw temperature, and die head temperature were set to 270°C, 280°C, and 255°C, respectively. The spinning rate was 60m / min, and melt extrusion spinning was performed to obtain a flame-retardant polyester fiber; Step 6: 24g of triethanolamine and 20g of adipic acid were mixed, heated to 100°C to completely dissolve them, and then 0.4g of p-toluenesulfonic acid was added and the temperature was continued to be raised to 130°C. After stirring and reacting at 130°C for 2.5h, 46g of sodium hydroxyacetate was added and reacted at 80°C for 7h. After the reaction was completed, the temperature was raised to 160°C to evaporate the solvent to obtain quaternized triethanolamine adipate, 32g of quaternized triethanolamine adipate, 64g of poly(hexamethylene adipate) and 0.3g of tetrabutyl titanate were mixed, heated to 160°C and stirred for reaction for 3h. After the reaction was completed, the mixture was cooled to obtain a quaternized polyester antistatic agent, and the quaternized polyester antistatic agent was dissolved in an ethanol aqueous solution having a mass fraction of 30% to obtain a 30g / L antistatic finishing liquid; Step 7: Add dopamine hydrochloride to Tris buffer and stir evenly to obtain a 5 mmol / L dopamine hydrochloride solution. Immerse the flame-retardant polyester fiber in the dopamine hydrochloride solution, shake it in a 30°C water bath for 24 hours, take out the fiber, dry it at 60°C for 4 hours, and then immerse it in an antistatic finishing solution. Shake it in a 30°C water bath for 24 hours, take out the fiber, dry it at 100°C for 30 minutes, and then heat it to 160°C for curing for 2 minutes to obtain a halogen-free flame-retardant polyester fiber.

[0027] Comparative Example 2: This comparative example relates to a method for preparing a halogen-free flame-retardant polyester fiber. The difference from Example 1 is that no boric acid-modified polydimethylsiloxane is added. Specifically: Step 1: 100g of terephthalic acid, 50g of ethylene glycol and 1g of tetrabutyl titanate were mixed, heated to 240°C under 0.25MPa nitrogen protection, and reacted for 4h. After the reaction was completed, the temperature was raised to 270°C, and the pressure was slowly reduced to 100Pa by vacuum, and polycondensed for 4h to obtain polyethylene terephthalate; Step 2: 8 g of terephthalaldehyde, 20.6 g of p-aminobenzenesulfonamide and 150 mL of anhydrous ethanol were mixed, stirred evenly, heated to 85° C. and reacted for 8 h. After the reaction was completed, cooled, filtered, washed with ethanol, and dried at 60° C. to obtain a flame retardant intermediate; Step 3: 20.8 g of the flame retardant intermediate, 26.5 g of DOPO and 150 mL of tetrahydrofuran were mixed and refluxed at 80° C. for 24 h. After the reaction was completed, the mixture was cooled, filtered, washed with ethanol, and dried at 60° C. to obtain a phosphorus-nitrogen-sulfur DOPO-based flame retardant; Step 4: The phosphorus, nitrogen, and sulfur type DOPO-based flame retardant was dried at 70°C for 2 hours before use, and polyethylene terephthalate and the dried phosphorus, nitrogen, and sulfur type DOPO-based flame retardant were mixed in a mass ratio of 7:3, added to a twin-screw extruder, and melt-extruded and granulated at 270°C to obtain a flame-retardant masterbatch. The flame-retardant masterbatch was mixed with polyethylene terephthalate in a mass ratio of 1:3, added to a twin-screw extruder, and the melt temperature, screw temperature, and die head temperature were set to 270°C, 280°C, and 255°C, respectively. The spinning rate was 60m / min, and melt extrusion spinning was performed to obtain a flame-retardant polyester fiber; Step 5: Add 24 g of pyromellitic acid and 30 g of copper pyrophosphate to 500 mL of deionized water, stir evenly, heat to 70° C. and adjust the pH to 5, react at 70° C. for 4 h, filter after the reaction is completed, wash with deionized water, and dry at 50-60° C. to obtain a copper pyrophosphate-organic ligand. Add 48 g of the copper pyrophosphate-organic ligand to 1 L of deionized water, and ultrasonically disperse for 20 min to obtain an antibacterial flame retardant finishing liquid; Step 6: dopamine hydrochloride is added to Tris buffer and stirred to obtain a 5 mmol / L dopamine hydrochloride solution, and the flame-retardant polyester fiber is immersed in the dopamine hydrochloride solution. After shaking in a water bath at 30°C for 24 hours, the fiber is taken out and dried at 60°C for 4 hours. Subsequently, the fiber is immersed in a 48 g / L antibacterial flame retardant finishing solution, after shaking in a water bath at 30°C for 24 hours, the fiber is taken out and dried at 60°C for 4 hours to obtain the antibacterial flame retardant polyester fiber; Step 7: 24g of triethanolamine and 20g of adipic acid were mixed, heated to 100°C to completely dissolve them, and then 0.4g of p-toluenesulfonic acid was added and the temperature was continued to be raised to 130°C. After stirring and reacting at 130°C for 2.5h, 46g of sodium hydroxyacetate was added and reacted at 80°C for 7h. After the reaction was completed, the temperature was raised to 160°C and the solvent was evaporated to obtain quaternized triethanolamine adipate. 32g of quaternized triethanolamine adipate, 64g of polyhexamethylene adipate, and 0.3g of tetrabutyl titanate were mixed, heated to 160°C and stirred for reaction for 3h. After the reaction was completed, the mixture was cooled to obtain a quaternized polyester antistatic agent. The quaternized polyester antistatic agent was dissolved in an ethanol aqueous solution having a mass fraction of 30% to obtain a 30g / L antistatic finishing liquid; Step 8: Immerse the antibacterial flame-retardant polyester fiber in the antistatic finishing solution, shake it in a 30°C water bath for 24 hours, take out the fiber, dry it at 100°C for 30 minutes, and then heat it to 160°C for curing for 2 minutes to obtain a halogen-free flame-retardant polyester fiber.

[0028] Comparative Example 3: This comparative example relates to a method for preparing a halogen-free flame-retardant polyester fiber. The difference from Example 1 is that no phosphorus-nitrogen-sulfur DOPO-based flame retardant is added. Specifically, Step 1: 5 g of hydroxyl-terminated polydimethylsiloxane, 1 g of boric acid, and 1 mL of ethanol were mixed and stirred at room temperature. The mixture was then heated to 70°C and reacted at 70°C and 500 rpm for 6 h. After the reaction was completed, the mixture was filtered under reduced pressure to obtain boric acid-modified polydimethylsiloxane. Step 2: 100g of terephthalic acid, 50g of ethylene glycol and 1g of tetrabutyl titanate were mixed, heated to 240°C under 0.25MPa nitrogen protection, and reacted for 2h. After 2h, 1.5g of silane coupling agent KH-550 and 18g of boric acid-modified polydimethylsiloxane were added, and the reaction was continued for 2h. After the reaction was completed, the temperature was raised to 270°C, and the pressure was slowly reduced to 100Pa. Polycondensation was carried out for 4h to obtain borosilicate-modified polyethylene terephthalate; Step 3: Add borosilicate modified polyethylene terephthalate into a twin-screw extruder, set the melt temperature to 270°C, the screw temperature to 280°C, the die temperature to 255°C, and the spinning rate to 60m / min, and melt-extrude and spin to obtain flame-retardant polyester fiber; Step 4: Add 24 g of pyromellitic acid and 30 g of copper pyrophosphate to 500 mL of deionized water, stir evenly, heat to 70° C. and adjust the pH to 5, react at 70° C. for 4 h, filter after the reaction is completed, wash with deionized water, and dry at 50-60° C. to obtain a copper pyrophosphate-organic ligand. Add 48 g of the copper pyrophosphate-organic ligand to 1 L of deionized water, and ultrasonically disperse for 20 min to obtain an antibacterial flame retardant finishing liquid; Step 5: dopamine hydrochloride is added to Tris buffer and stirred to obtain a 5 mmol / L dopamine hydrochloride solution, and the flame-retardant polyester fiber is immersed in the dopamine hydrochloride solution. After shaking in a water bath at 30°C for 24 hours, the fiber is taken out and dried at 60°C for 4 hours. Subsequently, the fiber is immersed in a 48 g / L antibacterial flame retardant finishing solution, after shaking in a water bath at 30°C for 24 hours, the fiber is taken out and dried at 60°C for 4 hours to obtain the antibacterial flame retardant polyester fiber; Step 6: 24g of triethanolamine and 20g of adipic acid were mixed, heated to 100°C to completely dissolve them, and then 0.4g of p-toluenesulfonic acid was added and the temperature was continued to be raised to 130°C. After stirring and reacting at 130°C for 2.5h, 46g of sodium hydroxyacetate was added and reacted at 80°C for 7h. After the reaction was completed, the temperature was raised to 160°C to evaporate the solvent to obtain quaternized triethanolamine adipate, 32g of quaternized triethanolamine adipate, 64g of poly(hexamethylene adipate) and 0.3g of tetrabutyl titanate were mixed, heated to 160°C and stirred for reaction for 3h. After the reaction was completed, the mixture was cooled to obtain a quaternized polyester antistatic agent, and the quaternized polyester antistatic agent was dissolved in an ethanol aqueous solution having a mass fraction of 30% to obtain a 30g / L antistatic finishing liquid; Step 7: Immerse the antibacterial flame-retardant polyester fiber in the antistatic finishing solution, shake it in a 30°C water bath for 24 hours, take out the fiber, dry it at 100°C for 30 minutes, and then heat it to 160°C for curing for 2 minutes to obtain a halogen-free flame-retardant polyester fiber.

[0029] Detection experiment: Halogen-free flame-retardant polyester fiber samples were prepared according to the preparation methods in each embodiment and comparative example, and the halogen-free flame-retardant polyester fiber samples were further processed into halogen-free flame-retardant polyester fabric samples (warp yarn density of 30 tex, weft yarn density of 20 tex, warp density of 120 strands / inch, weft density of 100 strands / inch) through opening, carding, drafting, drawing, spinning, weaving and other processes for testing.

[0030] Fiber mechanical properties test: Halogen-free flame-retardant polyester fiber samples were selected for the test. The test was based on the "Test Method for Tensile Properties of Chemical Fiber Filaments" (GB / T 14344-2008). The test was carried out using a YG061 electronic fiber strength tester. The sample was fixed on a fixture with a fixture spacing of 250 mm and a tensile speed of 200 mm / min. A tensile force was applied to break the fiber, and the breaking strength and elongation of the fiber were measured.

[0031] Limiting Oxygen Index Test: Halogen-free flame-retardant polyester fabric samples measuring 158mm x 50mm were used for the test. The test was conducted in accordance with the "Textile Combustion Behavior Test - Oxygen Index Method" (GB / T 5454-1997). The test instrument was a TTech-GBT2406-1 Intelligent Critical Oxygen Index Analyzer (Testech). The fabric sample was fixed vertically on the specimen holder, ensuring that it was centered without tilt. The oxygen-nitrogen mixture ratio was adjusted to an initial oxygen concentration of 25%. The top of the fabric sample was then ignited with an igniter to observe whether the sample burned (burning length ≥ 50mm or lasted 120s) or did not burn (burning length < 50mm and self-extinguishing). The mixture ratio was adjusted accordingly to lower or increase the oxygen concentration to determine the limiting oxygen index of the fabric sample.

[0032] Vertical combustion test: Halogen-free flame-retardant polyester fabric samples measuring 300mm x 89mm were used. The test was conducted in accordance with the "Fire Performance of Textiles - Determination of Vertical Damage Length, Smoldering and Afterflaming Time" (GB / T 5455-2014). The test instrument was the TTech-GBT2408-UL94 Horizontal Vertical Flame Tester (Testech). Before the test, the flame height was adjusted to 20mm. The flame was then extinguished. The fabric sample was fixed vertically to the fixture. The fixture height was adjusted so that the lower end of the sample was 10mm from the burner. The burner was positioned so that the flame was aligned with the center of the lower end of the sample. A 10mm thick piece of absorbent cotton was placed 300mm below the sample. A timer was started and the flame was removed from the sample after 12 seconds of contact. The afterflame time (the time the sample continued to burn after the flame was removed) and the smoldering time (the time the sample burned flamelessly (glowing red) after the flame was extinguished) were recorded.

[0033]

[0034] Conclusion: It can be seen from the test data that the breaking strength and elongation at break of the halogen-free flame retardant polyester fibers prepared in each embodiment are better than those in Comparative Example 1, Comparative Example 2 and Comparative Example 3, and the halogen-free flame retardant fibers have good mechanical properties, which are beneficial to the processing of textiles. After the halogen-free flame retardant polyester fibers are processed into fabrics, the flame retardancy of the fabrics is tested. It is found that during the test, the limiting oxygen index and the damage length of the fabrics obtained by processing the fibers of each embodiment are better than those of the fabrics obtained by processing the comparative examples. Moreover, no molten droplets are generated in the vertical burning test of the fabrics processed from the fibers of the embodiments or the comparative examples, and the samples do not continue to burn after the flame is removed. The halogen-free flame retardant polyester fibers provided by the present invention have good mechanical properties and flame retardant properties.

[0035] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A method for preparing a halogen-free flame-retardant polyester fiber, characterized in that: Specifically: Step 1: Using terephthalic acid and ethylene glycol as raw materials, polymerizing under the action of tetrabutyl titanate catalyst, and adding boric acid-modified polydimethylsiloxane to prepare borosilicate-modified polyethylene terephthalate; Step 2: mixing the borosilicate modified polyethylene terephthalate with the dried phosphorus-nitrogen-sulfur type DOPO-based flame retardant, melt-extruding and granulating at 260-280° C. to obtain a flame retardant masterbatch, mixing the flame retardant masterbatch with the borosilicate modified polyethylene terephthalate, and melt-extruding and spinning to obtain a flame retardant polyester fiber; Step 3: After the flame retardant polyester fiber is impregnated with a 3-7 mmol / L dopamine hydrochloride solution, it is impregnated with an antibacterial flame retardant finishing liquid to obtain an antibacterial flame retardant polyester fiber; Step 4: The antibacterial flame retardant polyester fiber is impregnated with an antistatic finishing liquid to obtain a halogen-free flame retardant polyester fiber.

2. The method for preparing a halogen-free flame-retardant polyester fiber according to claim 1, characterized in that: Step 1 is as follows: Mix hydroxyl-terminated polydimethylsiloxane, boric acid, and ethanol, stir evenly at room temperature, then heat to 70-80°C and react at 70-80°C, 300-500 rpm for 4-6 hours. After the reaction is complete, filter under reduced pressure to obtain boric acid-modified polydimethylsiloxane; Mix terephthalic acid, ethylene glycol and tetrabutyl titanate, heat to 240-250°C under 0.2-0.25 MPa nitrogen protection, and react for 1.5-2 hours. After 1.5-2 hours, add silane coupling agent KH-550 and boric acid-modified polydimethylsiloxane, and continue to react for 2-3 hours. After the reaction is completed, heat to 270-280°C, slowly evacuate to reduce the pressure to 80-100 Pa, and polycondense for 3-5 hours to obtain borosilicate-modified polyethylene terephthalate.

3. The method for preparing a halogen-free flame-retardant polyester fiber according to claim 2, characterized in that: The mass ratio of hydroxyl-terminated polydimethylsiloxane, boric acid and ethanol is (4-6):(0.8-1.2):(0.5-1.0); the mass ratio of terephthalic acid, ethylene glycol and boric acid-modified polydimethylsiloxane is (80-120):(40-60):(15-20).

4. The method for preparing a halogen-free flame-retardant polyester fiber according to claim 1, wherein: In step 2, the preparation method of the phosphorus-nitrogen-sulfur type DOPO-based flame retardant is: The mixture of terephthalaldehyde, p-aminobenzenesulfonamide and anhydrous ethanol was stirred evenly, and then the temperature was raised to 80-85°C and the mixture was reacted for 7-8 hours. After the reaction was completed, the mixture was cooled, filtered, washed with ethanol, and dried at 60-70°C to obtain a flame retardant intermediate. The flame retardant intermediate, DOPO and tetrahydrofuran are mixed and refluxed at 70-80° C. for 20-24 hours. After the reaction is completed, the mixture is cooled, filtered, washed with ethanol, and dried at 60-70° C. to obtain a phosphorus-nitrogen-sulfur DOPO-based flame retardant.

5. The method for preparing a halogen-free flame-retardant polyester fiber according to claim 4, characterized in that: The mass ratio of terephthalaldehyde and p-aminobenzenesulfonamide is (5-10):(18-22); the mass ratio of the flame retardant intermediate and DOPO is (1-3):(2-3).

6. The method for preparing a halogen-free flame-retardant polyester fiber according to claim 1, characterized in that: In step 2, the mass ratio of borosilicate modified polyethylene terephthalate to the phosphorus, nitrogen and sulfur type DOPO-based flame retardant is (6-7): (3-4); the mass ratio of the flame retardant masterbatch to the borosilicate modified polyethylene terephthalate is 1: (2-3); during the melt extrusion spinning process, the melt temperature is 260-280°C, the screw temperature is 270-290°C, the head temperature is 250-260°C, and the spinning rate is 50-70m / min.

7. The method for preparing a halogen-free flame-retardant polyester fiber according to claim 1, characterized in that: In step 3, the preparation method of the antibacterial flame retardant finishing liquid is: Add pyromellitic acid and copper pyrophosphate to deionized water, stir evenly, heat to 60-70°C and adjust the pH to 5-6, react at 60-70°C for 3-5 hours, filter after the reaction is completed, wash with deionized water, and dry at 50-60°C to obtain copper pyrophosphate-organic ligand, add the copper pyrophosphate-organic ligand to deionized water, and ultrasonically disperse to obtain an antibacterial flame retardant finishing liquid.

8. The method for preparing a halogen-free flame-retardant polyester fiber according to claim 7, characterized in that: The mass ratio of pyromellitic acid and copper pyrophosphate is (1.5-3.5):(2-4); and the concentration of copper pyrophosphate-organic ligand in the antibacterial flame retardant finishing liquid is 40-60 g / L.

9. The method for preparing a halogen-free flame-retardant polyester fiber according to claim 1, characterized in that: In step 4, the preparation method of the antistatic finishing liquid is: Mix triethanolamine and adipic acid, heat to 100-110°C to completely dissolve them, then add p-toluenesulfonic acid and continue to heat to 130-140°C, stir and react at 130-140°C for 2-3 hours, add sodium hydroxyacetate, react at 80-90°C for 6-8 hours, heat to 160-170°C after the reaction is completed, and evaporate the solvent to obtain quaternized triethanolamine adipate. Mix quaternized triethanolamine adipate, poly(hexamethylene adipate) and tetrabutyl titanate, heat to 160-170°C and stir and react for 2-4 hours, cool after the reaction is completed to obtain a quaternized polyester antistatic agent, and dissolve the quaternized polyester antistatic agent in an ethanol aqueous solution to obtain an antistatic finishing liquid.

10. The method for preparing a halogen-free flame-retardant polyester fiber according to claim 9, characterized in that: The mass ratio of triethanolamine, adipic acid, p-toluenesulfonic acid and sodium glycolate is (10-15):(8-12):(0.1-0.3):(20-25); and the concentration of the quaternary ammonium polyester antistatic agent in the antistatic finishing liquid is 20-40 g / L.

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