Antimony-free flame-retardant polyester and preparation method thereof

Abstract

The invention belongs to the technical field of flame-retardant polyester, and discloses antimony-free flame-retardant polyester and a preparation method thereof.The antimony-free flame-retardant polyester is prepared from terephthalic acid, ethylene glycol, a titanium catalyst, a reactive phosphorus-based flame retardant and a modifier, the modifier contains zinc, and the mass ratio of the zinc in the modifier to the phosphorus in the phosphorus-based flame retardant is 0.1-0.5: 1; according to the polyester, by adding the titanium catalyst and the zinc-containing modifier, the side reaction of the titanium catalyst is reduced, the antimony-free flame-retardant polyester with good hue, flame retardance and spinnability is prepared, heavy metal pollution is avoided, and the polyester is safe and environmentally friendly.

Description

Technical Field

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

[0002] Polyethylene terephthalate (PET) has become the fiber material with the largest output and the widest application due to its good mechanical properties, thermal setting properties, heat resistance and acid and alkali resistance, accounting for more than 80% of chemical fibers. However, PET is very flammable, with a limiting oxygen index of only 21-22%. The combustion process is accompanied by severe melting droplets and releases a large amount of heat and smoke. According to incomplete statistics, among all types of fires, more than 50% of the fires are related to the ignition or combustion of textile materials, which greatly threatens people's lives and property safety. Therefore, the flame retardant property of PET has gradually become one of its necessary properties.

[0003] At present, the flame retardant modification of PET is mainly divided into two methods: blending and copolymerization. For example, Publication No. CN118516780A discloses a method for preparing a flame retardant polyester fiber, by preparing a flame retardant masterbatch in advance, and then melt-blending and spinning the flame retardant polyester masterbatch with polyester chips to obtain a flame retardant polyester fiber; another example is Publication No. CN105463610A discloses a flame retardant polyester fiber and a method for preparing the same, by introducing the flame retardant 2-carboxyethylphenylphosphinate into the polyester system by copolymerization, and using antimony and magnesium compounds to blend the catalyst to prepare the flame retardant polyester; the above two PET polyesters contain antimony catalysts, and the use of antimony compounds has the problems of heavy metal pollution and the difficulty of resource protection and development, which is not conducive to the concept of green and healthy development of the industry. Therefore, those skilled in the art are committed to developing non-antimony metal catalysts.

[0004] Currently, titanium-based catalysts have the highest chain growth reaction rate constant among all non-antimony metal catalysts. They are also affordable, green and environmentally friendly, making them one of the most studied polyester catalysts. However, their thermal degradation reaction rate is also very high, and a large number of side reactions occur during the polymerization process, which have an adverse effect on the performance and color value of PET products. In particular, the use of titanium-based catalysts to prepare flame-retardant polyesters will produce more side reactions due to the presence of phosphorus-based flame retardants, resulting in further deterioration in quality and even unusability, which poses many difficulties. Summary of the invention

[0005] The present invention aims to solve the problem in the prior art that titanium-based catalysts have high pyrolysis efficiency but are prone to produce side reactions with phosphorus-based flame retardants during polymerization, resulting in low PET performance and low color value; an antimony-free flame-retardant polyester fiber and a preparation method thereof are provided. By adding a titanium-based catalyst and a zinc-containing modifier, the side reactions of the titanium-based catalyst are reduced, and antimony-free flame-retardant polyester with good hue, flame retardant performance and spinnability is prepared, without heavy metal pollution, and is safe and environmentally friendly.

[0006] The specific technical scheme of the present invention is: Compared with the prior art, this application has the following technical effects: An antimony-free flame-retardant polyester is characterized in that the raw materials include terephthalic acid, ethylene glycol, a titanium catalyst, a reactive phosphorus flame retardant and a modifier, the modifier contains zinc element, and the mass ratio of the zinc element in the modifier to the phosphorus element in the phosphorus flame retardant is 0.1-0.5:1.

[0007] The invention provides an antimony-free flame-retardant polyester. The raw materials of the polyester include terephthalic acid, ethylene glycol, a titanium catalyst, a reactive phosphorus flame retardant and a modifier. The modifier contains a zinc element. The invention finds that the zinc-containing modifier can inhibit the reaction between the titanium catalyst and the reactive phosphorus flame retardant during the polymerization of PET polyester. The zinc element can participate in the coordination reaction of titanium and phosphorus during the polymerization process, reduce the coordination ratio of titanium and phosphorus, reduce the occurrence of side reactions, and reduce the inhibitory effect on the reaction activity of titanium. In addition, the zinc element also has a catalytic effect on the polyester body, and can play an auxiliary catalytic role in the synthesis process to ensure the synthesis efficiency and the color of the polyester.

[0008] Preferably, the modifier includes one or more of zinc oxide, zinc hydroxide, zinc acetate, zinc carbonate and zinc borate.

[0009] Preferably, the reactive phosphorus-based flame retardant includes one of 2-carboxyethylphenylphosphite (CEPPA) and [(6-oxo-6H-dibenzo[C,E][1,2]oxaphosphorin-6-yl)methyl]succinic acid (DDP).

[0010] Preferably, the titanium-based catalyst includes one or more of potassium fluorotitanate, potassium titanium oxalate, tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate, tetrabutyl titanate and tetraisooctyl titanate.

[0011] A method for preparing the above antimony-free flame-retardant polyester comprises the following steps: Step 1: pre-esterify the reactive phosphorus-containing flame retardant with ethylene glycol to prepare a flame retardant esterification liquid; Step 2: Mix terephthalic acid, ethylene glycol, flame retardant esterification liquid and modifier, stir and beat to carry out esterification reaction; Step 3: After the esterification reaction is completed, add titanium catalyst to carry out polycondensation reaction to prepare antimony-free flame retardant polyester.

[0012] 6. The preparation method according to claim 5, characterized in that the reaction temperature of the pre-esterification in step 1 is 150-200°C.

[0013] Preferably, in step 1, the molar ratio of the phosphorus-based flame retardant to ethylene glycol is 1:1-8.

[0014] Preferably, the pressure of the esterification reaction in step 2 is 0-0.3 MPa, and the temperature of the esterification reaction is 200-260°C.

[0015] Preferably, the molar ratio of terephthalic acid to ethylene glycol in step 2 is 1:1.05-1.5.

[0016] Preferably, the polycondensation reaction in step three includes a pre-polycondensation and a final polycondensation; the pre-polycondensation temperature is 250-280°C and the pressure is 50-3000Pa; the final polycondensation temperature is 260-290°C and the pressure is 20-200Pa.

[0017] The present invention also provides a method for preparing the above-mentioned antimony-free flame-retardant polyester, which optimizes the preparation process. In this method, the phosphorus-based flame retardant is prepared into a flame retardant esterification liquid by pre-esterification, thereby reducing the steric hindrance of the flame retardant during the polymerization reaction, increasing the flame retardant grafting rate, and improving the material utilization rate; in this method, the titanium-based catalyst is added after esterification and before polycondensation. The titanium-based catalyst is easily hydrolyzed. Adding it after esterification can reduce its contact with water, reduce hydrolysis, and increase the efficiency of catalyst use; zinc compounds and PTA are added in the pulping stage, which can better promote their dispersion, and at the same time contact and coordinate with the flame retardant in advance, reducing the coordination ratio after the titanium-based catalyst is added; the metal ions in the zinc compound have a certain catalytic effect, which can reduce the polymerization time and increase the polymerization efficiency, and the catalytic effect also has a certain carbon-promoting function during the combustion process, and has a synergistic flame retardant effect.

[0018] Compared with the prior art, this application has the following technical effects: (1) The zinc-containing modifier can reduce the side reaction between the titanium catalyst and the reactive phosphorus flame retardant, and reduce the inhibitory effect on the titanium reaction activity. In addition, the zinc element also has a catalytic effect on the polyester body, and can play an auxiliary catalytic role in the synthesis process, thereby ensuring the synthesis efficiency and the color of the polyester; (2) This method prepares the phosphorus-based flame retardant into a flame retardant esterification liquid by pre-esterification, thereby reducing the steric hindrance of the flame retardant during the polymerization reaction, increasing the flame retardant grafting rate, and improving the material utilization rate; (3) The titanium catalyst is added after esterification and before polycondensation. Titanium catalysts are easily hydrolyzed. Adding them after esterification can reduce their contact with water, reduce hydrolysis, and increase the efficiency of catalyst use. (4) The addition of zinc compounds and PTA during the pulping stage can better promote their dispersion, and at the same time, contact and coordinate with the flame retardant in advance, thereby reducing the coordination ratio after the addition of the titanium catalyst; the metal ions in the zinc compound have a certain catalytic effect, which can reduce the polymerization time and increase the polymerization efficiency. In addition, the catalytic effect also has a certain carbon-promoting function during the combustion process, which has a synergistic flame retardant effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of antimony-free flame-retardant polyester prepared in Example 1, Comparative Example 2 and Comparative Example 5. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with the embodiments.

[0021] Embodiment 1: A method for preparing antimony-free flame-retardant polyester comprises the following steps: Step 1: pre-esterify CEPPA and ethylene glycol in a mass ratio of 3:7 to prepare CEPPA esterification liquid, and the pre-esterification reaction temperature is 150°C; Step 2: 830g of terephthalic acid, 288g of ethylene glycol, 164.5g of CEPPA esterification liquid and a modifier (zinc oxide, the mass ratio of zinc to phosphorus is 0.1:1) are added to a 2.5L polymerization kettle for slurrying for 10 minutes, and nitrogen replacement is performed after slurrying, the air in the system is discharged, and the pressure is increased to 0.2MPa. The temperature of the esterification tower is controlled at 230°C for esterification reaction. When the water output reaches 95% of the theoretical water output, the esterification reaction is terminated; Step 3: After the esterification is completed, tetrabutyl titanate (titanium element 7ppm) is added to the polymerization kettle, and after stirring for 10 minutes, vacuum is evacuated, and the pressure is controlled to be less than 0.1kPa. The reaction temperature is controlled at 275°C. The polycondensation reaction is completed after 120 minutes, and the material is discharged and pelletized after standing to make antimony-free flame-retardant polyester chips; Step 4: Place the flame-retardant polyester chips in a vacuum drum dryer and dry them at 120°C for 12 hours. Use a small injection molding machine to prepare test strips after drying. The injection molding temperature is 260°C to obtain test strips. Use a small spinning machine to spin the dried chips. The spinning temperature is 278°C and the spinning specification is 83dtex / 48f to obtain flame-retardant polyester fibers.

[0022] Embodiment 2: A method for preparing antimony-free flame-retardant polyester comprises the following steps: Step 1: pre-esterify CEPPA and ethylene glycol in a mass ratio of 3:7 to prepare CEPPA esterification liquid, and the pre-esterification reaction temperature is 170°C; Step 2: 830g of terephthalic acid, 288g of ethylene glycol, 164.5g of CEPPA esterification liquid and a modifier (zinc oxide, the mass ratio of zinc to phosphorus is 0.3:1) are added to a 2.5L polymerization kettle for slurrying for 10 minutes, and nitrogen replacement is performed after slurrying, the air in the system is discharged, and the pressure is increased to 0.2MPa. The temperature of the esterification tower is controlled at 235°C for esterification reaction. When the water output reaches 95% of the theoretical water output, the esterification reaction is terminated; Step 3: After the esterification is completed, tetrabutyl titanate (titanium element 7ppm) is added to the polymerization kettle, and after stirring for 10 minutes, vacuum is evacuated, and the pressure is controlled to be less than 0.1kPa. The reaction temperature is controlled at 275°C. The polycondensation reaction is completed after 120 minutes, and the material is discharged and pelletized after standing to make antimony-free flame-retardant polyester chips; Step 4: Place the flame-retardant polyester chips in a vacuum drum dryer and dry them at 120°C for 12 hours. Use a small injection molding machine to prepare test strips after drying. The injection molding temperature is 260°C to obtain test strips. Use a small spinning machine to spin the dried chips. The spinning temperature is 278°C and the spinning specification is 83dtex / 48f to obtain flame-retardant polyester fibers.

[0023] Embodiment 3: Step 1: pre-esterify CEPPA and ethylene glycol in a mass ratio of 3:7 to prepare CEPPA esterification liquid, the pre-esterification reaction temperature is 200°C; Step 2: 830g of terephthalic acid, 288g of ethylene glycol, 164.5g of CEPPA esterification liquid and a modifier (zinc oxide, the mass ratio of zinc to phosphorus is 0.5:1) are added to a 2.5L polymerization kettle for slurrying for 10 minutes, and nitrogen replacement is performed after slurrying, the air in the system is discharged, and the pressure is increased to 0.2MPa. The temperature of the esterification tower is controlled at 240°C for esterification reaction. When the water output reaches 95% of the theoretical water output, the esterification reaction is terminated; Step 3: After the esterification is completed, tetrabutyl titanate (titanium element 7ppm) is added to the polymerization kettle, and after stirring for 10 minutes, vacuum is evacuated, and the pressure is controlled to be less than 0.1kPa. The reaction temperature is controlled at 275°C. The polycondensation reaction is completed after 120 minutes, and the material is discharged and pelletized after standing to make antimony-free flame-retardant polyester chips; Step 4: Place the flame-retardant polyester chips in a vacuum drum dryer and dry them at 120°C for 12 hours. Use a small injection molding machine to prepare test strips after drying. The injection molding temperature is 260°C to obtain test strips. Use a small spinning machine to spin the dried chips. The spinning temperature is 278°C and the spinning specification is 83dtex / 48f to obtain flame-retardant polyester fibers.

[0024] Embodiment 4: Step 1: pre-esterify CEPPA and ethylene glycol in a mass ratio of 3:7 to prepare CEPPA esterification liquid, and the pre-esterification reaction temperature is 150°C; Step 2: 830g of terephthalic acid, 288g of ethylene glycol, 164.5g of CEPPA esterification liquid and a modifier (zinc hydroxide, the mass ratio of zinc to phosphorus is 0.1:1) are added to a 2.5L polymerization kettle for slurrying for 10 minutes, and nitrogen replacement is performed after slurrying, the air in the system is discharged, and the pressure is increased to 0.2MPa. The temperature of the esterification tower is controlled at 230°C for esterification reaction. When the water output reaches 95% of the theoretical water output, the esterification reaction is terminated; Step 3: After the esterification is completed, tetrabutyl titanate (titanium element 7ppm) is added to the polymerization kettle, and after stirring for 10 minutes, vacuum is evacuated, and the pressure is controlled to be less than 0.1kPa. The reaction temperature is controlled at 275°C. The polycondensation reaction is completed after 120 minutes, and the material is discharged and pelletized after standing to make antimony-free flame-retardant polyester chips; Step 4: Place the flame-retardant polyester chips in a vacuum drum dryer and dry them at 120°C for 12 hours. Use a small injection molding machine to prepare test strips after drying. The injection molding temperature is 260°C to obtain test strips. Use a small spinning machine to spin the dried chips. The spinning temperature is 278°C and the spinning specification is 83dtex / 48f to obtain flame-retardant polyester fibers.

[0025] Embodiment 5: Step 1: pre-esterify CEPPA and ethylene glycol in a mass ratio of 3:7 to prepare CEPPA esterification liquid, and the pre-esterification reaction temperature is 150°C; Step 2: 830g of terephthalic acid, 288g of ethylene glycol, 164.5g of CEPPA esterification liquid and a modifier (zinc carbonate, the mass ratio of zinc to phosphorus is 0.1:1) are added to a 2.5L polymerization kettle for slurrying for 10 minutes, and nitrogen replacement is performed after slurrying, the air in the system is discharged, and the pressure is increased to 0.2MPa. The temperature of the esterification tower is controlled at 230°C for esterification reaction. When the water output reaches 95% of the theoretical water output, the esterification reaction is terminated; Step 3: After the esterification is completed, tetrabutyl titanate (titanium element 7ppm) is added to the polymerization kettle, and after stirring for 10 minutes, vacuum is evacuated, and the pressure is controlled to be less than 0.1kPa. The reaction temperature is controlled at 275°C. The polycondensation reaction is completed after 120 minutes, and the material is discharged and pelletized after standing to make antimony-free flame-retardant polyester chips; Step 4: Place the flame-retardant polyester chips in a vacuum drum dryer and dry them at 120°C for 12 hours. Use a small injection molding machine to prepare test strips after drying. The injection molding temperature is 260°C to obtain test strips. Use a small spinning machine to spin the dried chips. The spinning temperature is 278°C and the spinning specification is 83dtex / 48f to obtain flame-retardant polyester fibers.

[0026] Embodiment 6: Step 1: pre-esterify CEPPA and ethylene glycol in a mass ratio of 3:7 to prepare CEPPA esterification liquid, and the pre-esterification reaction temperature is 150°C; Step 2: 830g of terephthalic acid, 288g of ethylene glycol, 164.5g of CEPPA esterification liquid and a modifier (zinc acetate, the mass ratio of zinc to phosphorus is 0.1:1) are added to a 2.5L polymerization kettle for slurrying for 10 minutes, and nitrogen replacement is performed after slurrying, the air in the system is discharged, and the pressure is increased to 0.2MPa. The temperature of the esterification tower is controlled at 230°C for esterification reaction. When the water output reaches 95% of the theoretical water output, the esterification reaction is terminated; Step 3: After the esterification is completed, tetrabutyl titanate (titanium element 7ppm) is added to the polymerization kettle, and after stirring for 10 minutes, vacuum is evacuated, and the pressure is controlled to be less than 0.1kPa. The reaction temperature is controlled at 275°C. The polycondensation reaction is completed after 120 minutes, and the material is discharged and pelletized after standing to make antimony-free flame-retardant polyester chips; Step 4: Place the flame-retardant polyester chips in a vacuum drum dryer and dry them at 120°C for 12 hours. Use a small injection molding machine to prepare test strips after drying. The injection molding temperature is 260°C to obtain test strips. Use a small spinning machine to spin the dried chips. The spinning temperature is 278°C and the spinning specification is 83dtex / 48f to obtain flame-retardant polyester fibers.

[0027] Embodiment 7: Step 1: pre-esterify CEPPA and ethylene glycol in a mass ratio of 3:7 to prepare CEPPA esterification liquid, and the pre-esterification reaction temperature is 150°C; Step 2: 830g of terephthalic acid, 288g of ethylene glycol, 164.5g of CEPPA esterification liquid and a modifier (zinc borate, the mass ratio of zinc to phosphorus is 0.1:1) are added to a 2.5L polymerization kettle for slurrying for 10 minutes, and nitrogen replacement is performed after slurrying, the air in the system is discharged, and the pressure is increased to 0.2MPa. The temperature of the esterification tower is controlled at 230°C for esterification reaction. When the water output reaches 95% of the theoretical water output, the esterification reaction is terminated; Step three: after the esterification is completed, tetrabutyl titanate (titanium element 7ppm) is added to the polymerization kettle, and after stirring for 10 minutes, vacuum is evacuated, and the pressure is controlled to be less than 0.1kPa. The reaction temperature is controlled at 275°C. After 120 minutes, the polycondensation reaction is completed, and after standing, the material is discharged and pelletized to produce antimony-free flame-retardant polyester chips; Step 4: Place the flame-retardant polyester chips in a vacuum drum dryer and dry them at 120°C for 12 hours. Use a small injection molding machine to prepare test strips after drying. The injection molding temperature is 260°C to obtain test strips. Use a small spinning machine to spin the dried chips. The spinning temperature is 278°C and the spinning specification is 83dtex / 48f to obtain flame-retardant polyester fibers.

[0028] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the titanium catalyst is added at the pulping stage; the following steps are included: Step 1: pre-esterify CEPPA and ethylene glycol in a mass ratio of 3:7 to prepare CEPPA esterification liquid, and the pre-esterification reaction temperature is 150°C; Step 2: 830g of terephthalic acid, 288g of ethylene glycol, 164.5g of CEPPA esterification liquid, tetrabutyl titanate (titanium element 7ppm) and a modifier (zinc oxide, the mass ratio of zinc to phosphorus is 0.1:1) are added to a 2.5L polymerization kettle for slurrying for 10min, and nitrogen replacement is performed after slurrying, the air in the system is discharged, and the pressure is increased to 0.2MPa. The temperature of the esterification tower is controlled at 230°C for esterification reaction. When the water output reaches 95% of the theoretical water output, the esterification reaction is terminated; Step 3: Control the pressure to be less than 0.1 kPa, control the reaction temperature to be 275° C., end the polycondensation reaction after 120 min, discharge the material after standing, and cut into pellets to produce antimony-free flame-retardant polyester chips; Step 4: Place the flame-retardant polyester chips in a vacuum drum dryer and dry them at 120°C for 12 hours. Use a small injection molding machine to prepare test strips after drying. The injection molding temperature is 260°C to obtain test strips. Use a small spinning machine to spin the dried chips. The spinning temperature is 278°C and the spinning specification is 83dtex / 48f to obtain flame-retardant polyester fibers.

[0029] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that no modifier is added, and the following steps are included: Step 1: pre-esterify CEPPA and ethylene glycol in a mass ratio of 3:7 to prepare CEPPA esterification liquid, and the pre-esterification reaction temperature is 150°C; Step 2: Add 830g of terephthalic acid, 288g of ethylene glycol and 164.5g of CEPPA esterification liquid into a 2.5L polymerization kettle and beat for 10min. After beating, nitrogen replacement is performed to exhaust the air in the system, and the pressure is increased to 0.2MPa. The temperature of the esterification tower is controlled at 230°C for esterification reaction. When the water output reaches 95% of the theoretical water output, the esterification reaction is terminated; Step three: after the esterification is completed, tetrabutyl titanate (titanium element 7ppm) is added to the polymerization kettle, and after stirring for 10 minutes, vacuum is evacuated, and the pressure is controlled to be less than 0.1kPa. The reaction temperature is controlled at 275°C. After 120 minutes, the polycondensation reaction is completed, and after standing, the material is discharged and pelletized to produce antimony-free flame-retardant polyester chips; Step 4: Place the flame-retardant polyester chips in a vacuum drum dryer and dry them at 120°C for 12 hours. Use a small injection molding machine to prepare test strips after drying. The injection molding temperature is 260°C to obtain test strips. Use a small spinning machine to spin the dried chips. The spinning temperature is 278°C and the spinning specification is 83dtex / 48f to obtain flame-retardant polyester fibers.

[0030] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that the adding position of the modifier is after esterification and before polycondensation, and the following steps are included: Step 1: pre-esterify CEPPA and ethylene glycol in a mass ratio of 3:7 to prepare CEPPA esterification liquid, and the pre-esterification reaction temperature is 150°C; Step 2: Add 830g of terephthalic acid, 288g of ethylene glycol and 164.5g of CEPPA esterification liquid into a 2.5L polymerization kettle and beat for 10min. After beating, nitrogen replacement is performed to exhaust the air in the system, and the pressure is increased to 0.2MPa. The temperature of the esterification tower is controlled at 230°C for esterification reaction. When the water output reaches 95% of the theoretical water output, the esterification reaction is terminated; Step three: after the esterification is completed, tetrabutyl titanate (titanium element 7ppm) and modifier (zinc oxide, the mass ratio of zinc to phosphorus is 0.1:1) are added to the polymerization kettle, and the mixture is stirred for 10 minutes and then vacuumed. The pressure is controlled to be less than 0.1kPa, and the reaction temperature is controlled at 275°C. After 120 minutes, the polycondensation reaction is terminated, and the mixture is discharged and pelletized after standing to form antimony-free flame-retardant polyester chips; Step four: the flame-retardant polyester chips are placed in a vacuum drum dryer for drying at 120°C for 12 hours, and the dried chips are prepared by a small injection molding machine for sample preparation at an injection molding temperature of 260°C to obtain test samples, and the dried chips are spun by a small spinning machine at a spinning temperature of 278°C and a spinning specification of 83dtex / 48f to obtain flame-retardant polyester fibers.

[0031] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that the amount of the modifier is too large, and the method comprises the following steps: Step 1: pre-esterify CEPPA and ethylene glycol in a mass ratio of 3:7 to prepare CEPPA esterification liquid, and the pre-esterification reaction temperature is 150°C; Step 2: 830g of terephthalic acid, 288g of ethylene glycol, 164.5g of CEPPA esterification liquid and a modifier (zinc oxide, the mass ratio of zinc to phosphorus is 0.7:1) are added to a 2.5L polymerization kettle for slurrying for 10 minutes, and nitrogen replacement is performed after slurrying, the air in the system is discharged, and the pressure is increased to 0.2MPa. The temperature of the esterification tower is controlled at 230°C for esterification reaction. When the water output reaches 95% of the theoretical water output, the esterification reaction is terminated; Step 3: After the esterification is completed, tetrabutyl titanate (titanium element 7ppm) is added to the polymerization kettle, and after stirring for 10 minutes, vacuum is evacuated, and the pressure is controlled to be less than 0.1kPa. The reaction temperature is controlled at 275°C. The polycondensation reaction is completed after 120 minutes, and the material is discharged and pelletized after standing to make antimony-free flame-retardant polyester chips; Step 4: Place the flame-retardant polyester chips in a vacuum drum dryer and dry them at 120°C for 12 hours. Use a small injection molding machine to prepare test strips after drying. The injection molding temperature is 260°C to obtain test strips. Use a small spinning machine to spin the dried chips. The spinning temperature is 278°C and the spinning specification is 83dtex / 48f to obtain flame-retardant polyester fibers.

[0032] Comparative Example 5: The difference between Comparative Example 5 and Example 1 is that the titanium catalyst is replaced by an antimony catalyst and no modifier is added, and the following steps are included: Step 1: pre-esterify CEPPA and ethylene glycol in a mass ratio of 3:7 to prepare CEPPA esterification liquid, and the pre-esterification reaction temperature is 150°C; Step 2: 830g of terephthalic acid, 288g of ethylene glycol, 164.5g of CEPPA esterification liquid, a modifier (zinc oxide, the mass ratio of zinc to phosphorus is 0.1:1) and ethylene glycol antimony (antimony content 200ppm) are added to a 2.5L polymerization kettle for slurrying for 10min, and nitrogen replacement is performed after slurrying, the air in the system is discharged, and the pressure is increased to 0.2MPa. The temperature of the esterification tower is controlled at 230°C for esterification reaction. When the water output reaches 95% of the theoretical water output, the esterification reaction is terminated; Step three: control the pressure to be less than 0.1 kPa, control the reaction temperature to be 275° C., end the polycondensation reaction after 120 min, discharge the material after standing, and cut into pellets to produce antimony-free flame-retardant polyester chips; Step 4: Place the flame-retardant polyester chips in a vacuum drum dryer and dry them at 120°C for 12 hours. Use a small injection molding machine to prepare test strips after drying. The injection molding temperature is 260°C to obtain test strips. Use a small spinning machine to spin the dried chips. The spinning temperature is 278°C and the spinning specification is 83dtex / 48f to obtain flame-retardant polyester fibers.

[0033] Test example: The properties of the antimony-free flame-retardant polyester chips and flame-retardant polyester fibers prepared in Examples 1 to 7 and Comparative Examples 1 to 5 were tested; the test method for the intrinsic viscosity of the chips was carried out in accordance with "GB / T 14190-2017 Test method for fiber-grade polyester (PET) chips"; the test method for the vertical burning of the specimens was carried out in accordance with "GB / T 2408-2021 Horizontal and vertical methods for determination of combustion properties of plastics"; The fiber limiting oxygen index test method is carried out in accordance with "FZ / T 50017-2011 Test method for flame retardancy of polyester fiber - oxygen index method"; The hue was tested using a colorimeter; The test results of low melting point antistatic nylon slices are shown in Table 1.

[0034] Table 1 Low melting point antistatic nylon chips Intrinsic viscosity (dL / g) L / b Number of vertical burning droplets Limiting oxygen index (%) Example 1 0.674 84.5 / 9.3 12 30.1 Example 2 0.692 81.1 / 8.9 9 31.2 Example 3 0.703 80.2 / 8.3 6 31.7 Example 4 0.668 83.5 / 9.4 12 30.8 Example 5 0.675 85.4 / 9.1 11 30.5 Example 6 0.665 82.7 / 9.8 13 30.1 Example 7 0.673 84.2 / 9.4 12 30.7 Comparative Example 1 0.539 82.5 / 11.3 15 28.6 Comparative Example 2 0.661 84.3 / 18.4 16 29.5 Comparative Example 3 0.671 83.9 / 11.8 12 29.9 Comparative Example 4 0.705 76.9 / 8.1 4 32.0 Comparative Example 5 0.685 83.5 / 9.0 18 29.7 As shown in Table 1, compared with Comparative Example 1, when the titanium-based catalyst is added before esterification, under the same polymerization conditions and time, the final slice viscosity is lower in Example 1, indicating that the activity of the titanium-based catalyst added before esterification is reduced. The reason is that a large amount of water is generated during the esterification process, which causes the titanium-based catalyst to hydrolyze and reduces the catalytic efficiency.

[0035] Compared with Comparative Example 2, under the same polymerization conditions, only the titanium catalyst was added, and the hue of the final product was poor, and the b value was as high as 18.4, indicating that the addition of zinc compounds can greatly improve the hue of the slices. Zinc can replace titanium and complex with phosphorus, reduce the occurrence of side reactions, and slightly reduce the number of vertical burning droplets. The limiting oxygen index is increased, and the flame retardant properties are improved. Figure 1 As shown, the hue of the polyester without adding a modifier is significantly lower than that of Example 1.

[0036] Compared with Comparative Example 3, in Example 1, the zinc compound is added after esterification and before polycondensation, and the degree of improvement in hue is reduced. This is because the zinc compound is added in the pulping stage before esterification, and can be complexed with phosphorus in advance, further reducing the effect of phosphorus on titanium, thereby ensuring the color quality of the slices.

[0037] Compared with Comparative Example 4, under the same polymerization conditions and time, the amount of zinc compound added in Examples 1 to 3 increases, and the intrinsic viscosity of the flame retardant slices also increases accordingly, indicating that the addition of the zinc compound has a synergistic catalytic effect. At the same time, as the amount of zinc compound added increases, the number of droplets of the slices decreases significantly, and the limiting oxygen index increases slightly, indicating that it has a significant effect on improving the flame retardant properties, but the L value of the slices will decrease accordingly, so the addition amount should not be too high.

[0038] Compared with Comparative Example 5, there is no obvious difference in color value and flame retardancy between the slices prepared by combining the titanium-based catalyst with the zinc compound and the slices obtained by the traditional antimony-based catalyst in Example 1, indicating that they have the potential for replacement use.

[0039] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. An antimony-free flame-retardant polyester, characterized in that: The raw materials include terephthalic acid, ethylene glycol, a titanium catalyst, a reactive phosphorus flame retardant and a modifier, wherein the modifier contains zinc element, and the mass ratio of the zinc element in the modifier to the phosphorus element in the phosphorus flame retardant is 0.1-0.5:

1.

2. The antimony-free flame-retardant polyester according to claim 1, characterized in that: The modifier includes one or more of zinc oxide, zinc hydroxide, zinc acetate, zinc carbonate and zinc borate.

3. The antimony-free flame-retardant polyester according to claim 1, characterized in that: The reactive phosphorus-based flame retardant includes one of 2-carboxyethylphenyl hypophosphorous acid and [(6-oxo-6H-dibenzo[C,E][1,2]oxaphosphorin-6-yl)methyl]succinic acid.

4. The antimony-free flame-retardant polyester according to claim 1, characterized in that: The titanium-based catalyst includes one or more of potassium fluorotitanate, potassium titanium oxalate, tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate, tetrabutyl titanate and tetraisooctyl titanate.

5. A method for preparing the antimony-free flame-retardant polyester according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: pre-esterify the reactive phosphorus-containing flame retardant with ethylene glycol to prepare a flame retardant esterification liquid; Step 2: Mix terephthalic acid, ethylene glycol, flame retardant esterification liquid and modifier, stir and beat to carry out esterification reaction; Step 3: After the esterification reaction is completed, add titanium catalyst to carry out polycondensation reaction to prepare antimony-free flame retardant polyester.

6. The preparation method according to claim 5, characterized in that: The reaction temperature of the pre-esterification in the step 1 is 150-200°C.

7. The preparation method according to claim 5 or 6, characterized in that: In the step 1, the molar ratio of the phosphorus flame retardant to ethylene glycol is 1:1-8.

8. The preparation method according to claim 5, characterized in that: The pressure of the esterification reaction in step 2 is 0-0.3 MPa, and the temperature of the esterification reaction is 200-260°C.

9. The preparation method according to claim 5 or 8, characterized in that: The molar ratio of terephthalic acid to ethylene glycol in step 2 is 1:1.05-1.

5.

10. The preparation method according to claim 5, characterized in that: The polycondensation reaction in step three includes pre-polycondensation and final polycondensation; the temperature of the pre-polycondensation is 250-280°C and the pressure is 50-3000 Pa; the temperature of the final polycondensation is 260-290°C and the pressure is 20-200 Pa.

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