Preparation method of halogen-free flame-retardant PET polyester chip

Abstract

The invention discloses a preparation method of halogen-free flame-retardant PET polyester chips, and belongs to the technical field of polyester materials. The preparation method of the PET polyester chip comprises the following steps: adding terephthalic acid, ethylene glycol, tetrabutyl titanate and 50% of a coagulation blocking auxiliary agent into a reaction kettle, heating, and carrying out stirring reaction at normal pressure to obtain an esterification system; vacuumizing and heating the esterification system, and carrying out condensation polymerization; at the initial stage of polycondensation, adding the rest 50% of the condensation blocking auxiliary agent; and in the middle stage of polycondensation, adding a modified organic flame retardant, phenyl polysiloxane microspheres, an antioxidant and a stabilizer, continuously reacting until the intrinsic viscosity is 0.7-0.8 dL / g, discharging, casting a strip and slicing to prepare the halogen-free flame-retardant PET polyester chip. The PET polyester chip prepared by the invention has high flame retardant property and does not contain halogen elements.

Description

Technical Field

[0001] The invention belongs to the technical field of polyester materials, and particularly relates to a method for preparing halogen-free flame-retardant PET polyester chips. Background Art

[0002] In the field of materials technology, polyethylene terephthalate (PET) polyester chips are widely used in industries such as packaging, textiles, and electronics due to their excellent mechanical properties, chemical stability, and processing capabilities. However, PET is a flammable material with a limiting oxygen index (LOI) of only around 21%. This makes it prone to flame spread in high-temperature and open-flame environments, significantly limiting its application in areas requiring high flame retardancy, such as electronic and electrical housings, automotive interiors, and architectural decorative materials.

[0003] The traditional method of improving the flame retardant properties of PET is to add halogen flame retardants. Although this can effectively impart flame retardancy to PET, halogen flame retardants release large amounts of toxic hydrogen halide gas and smoke during combustion, which not only harms human health but also causes secondary pollution. At the same time, halogen flame retardants have poor compatibility with the PET matrix and are prone to migration and precipitation, affecting the long-term performance and appearance of the material.

[0004] Therefore, the present invention provides a method for preparing halogen-free flame-retardant PET polyester chips, which is used to solve the contradiction between the high addition amount and performance degradation of traditional halogen-free flame retardants during use in the prior art, the failure to reasonably compound flame retardant components and other additives to simultaneously improve the glossiness and flame retardant properties of PET polyester chips, and the failure to reasonably compound flame retardant components through multiple flame retardant principles, which limits the technical problem of their application in the field of high-end PET materials. Summary of the Invention

[0005] The present invention aims to provide a method for preparing halogen-free flame-retardant PET polyester chips, which is used to solve the technical problem that traditional halogen-free flame retardants in the prior art have a contradiction between high addition amount and performance degradation during use, and that the glossiness and flame retardancy of PET polyester chips cannot be simultaneously improved by rationally compounding flame retardant ingredients and other additives, and that the flame retardant ingredients are not rationally compounded according to multiple flame retardant principles, which limits their application in the field of high-end PET materials.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The method for preparing halogen-free flame-retardant PET polyester chips comprises the following steps: (1) Add terephthalic acid, ethylene glycol, tetrabutyl titanate and 50% coagulant barrier additive into a reactor, heat, and react with stirring at normal pressure to obtain an esterification system; (2) The esterification system is evacuated and heated to carry out polycondensation reaction; in the early stage of polycondensation, the remaining 50% of the coagulant barrier additive is added; in the middle stage of polycondensation, a modified organic flame retardant, phenyl polysiloxane microspheres, an antioxidant and a stabilizer are added, and the reaction is continued until the characteristic viscosity reaches 0.7-0.8 dL / g, and the material is discharged, cast into strips and sliced ​​to obtain halogen-free flame-retardant PET polyester chips.

[0007] In the above process, the synthetic reaction formula of PET polyester is as follows:

[0008] Furthermore, in step (1), the acid value of the esterification system is less than or equal to 10 mg KOH / g, the stirring speed is 100-200 r / min, the mass ratio of terephthalic acid, ethylene glycol, tetrabutyl titanate and 50% coagulant barrier additive is (70-75): (30-32): (0.05-0.1): (3-4); the heating temperature is 240-250° C., the stirring reaction time is 2.5-3 h, and the stirring reaction speed is 150-200 r / min.

[0009] Among them, the purity of terephthalic acid is ≥99.5%, and the moisture content is ≤0.2%; the purity of ethylene glycol is ≥99.8%, and the moisture content is ≤0.1%.

[0010] Furthermore, in step (2), the esterification system is evacuated to 10-50 Pa, the heating temperature is 275-280°C, the viscosity is 0.3 dL / g in the initial stage of polycondensation, and the viscosity is 0.5 dL / g in the middle stage of polycondensation. The mass ratio of the remaining 50% coagulation barrier additive, modified organic flame retardant, phenyl polysiloxane microspheres, antioxidant and stabilizer is (3-4): (4-6): (1-2): (0.05-0.2): (0.03-0.1); the slices are vacuum dried at 120-140°C for 24-48 hours to reduce the moisture content of the slices to below 0.02%.

[0011] The preparation method of the coagulation barrier auxiliary agent comprises the following steps: Q1. Ultrasonic dispersion of red phosphorus in the hydrolyzate, addition of CuCO3 powder, ultrasonication, addition of KH560, stirring for reaction, centrifugation for washing, and drying to obtain a coupling complex; Q2, dispersing the coupling complex in ethanol, adding polyvinyl pyrrolidone, ultrasonicating, dropping the sol, stirring to react, gradient standing and aging, centrifuging and washing, drying, repeating the coating 2-3 times to obtain a whitening flame retardant; Q3. The whitening flame retardant and maleic anhydride are refluxed in toluene at a mass ratio of 1:0.15, centrifuged, washed, and dried to obtain a coagulation barrier additive.

[0012] Preferably, the amount ratio of red phosphorus, hydrolyzate, CuCO3 and KH560 in Q1 is 10g:200mL:2.5g:(1.8-2)g; the hydrolyzate is prepared by adding 1 part of deionized water and 0.1 part of glacial acetic acid to 100 parts of ethanol and stirring uniformly, the pH of the hydrolyzate is controlled at 4-4.5, and the pH of the hydrolyzate is adjusted using 0.1wt% dilute ammonia water or 0.1mol / L NaOH ethanol solution; the frequency of ultrasound is 40kHz, the power of ultrasound is 200W, and the ultrasonic time is 30min; the stirring reaction temperature is 60-65°C, and the stirring reaction time is 2-3h; the centrifugal speed is 6000-8000rpm, the centrifugal time is 10min, and the product is washed with ethanol three times; and the drying temperature is 75-80°C.

[0013] Preferably, the amount ratio of the coupling complex, ethanol, polyvinyl pyrrolidone and sol in Q2 is 10g:180mL:0.6g:(30-35)mL; the sol is prepared by mixing tetrabutyl titanate and ethanol in a volume ratio of 1:10, adding ammonia water to adjust the pH to 9-10, and stirring; the ultrasonic power is 150W, and the ultrasonic time is 20min; the stirring reaction speed is 600rpm, the stirring reaction time is 3h, and the stirring reaction temperature is 60°C; the gradient static aging is first standing at 70°C for 1h, and then standing at 50°C for 1h, so that the sol is condensed into a dense coating layer, and the thickness of the TiO2 layer of the whitening flame retardant is 30-50nm.

[0014] Preferably, the reflux reaction temperature in Q3 is 110-115° C., and the reflux reaction time is 4-5 h.

[0015] The preparation method of the modified organic flame retardant comprises the following steps: S1. Dissolve melamine, biphenylphosphinoyl dichloride, and boric acid in dimethyl sulfoxide, add p-toluenesulfonic acid, heat under nitrogen protection for reaction, centrifuge and wash, and dry to obtain an organic flame retardant; S2. Mixing CuCO3 powder and NH4H2PO4, ball milling, and drying to obtain pretreated CuCO3 powder; adding ethanol to the pretreated CuCO3 powder and the organic flame retardant, ultrasonicating, stirring, reacting, centrifuging, washing, and vacuum drying to obtain an organic composite; S3. Disperse the organic complex in ethanol, add polyvinyl pyrrolidone, sonicate, add the sol dropwise, stir to react, gradient static aging, centrifugal washing, dry, repeat coating 2-3 times to obtain a coated flame retardant; sonicate the coated flame retardant and KH560 in a hydrolyzate, centrifuge and dry to obtain a modified organic flame retardant.

[0016] Preferably, the usage ratio of melamine, biphenylphosphoryl dichloride, boric acid, dimethyl sulfoxide and p-toluenesulfonic acid in S1 is 1 mol: (1.1-1.2) mol: 0.8 mol: 20 mL: 0.05 g; the heating temperature is 110°C, the reaction time is 24-28 h, the product is washed with acetone three times, and the product is dried in vacuum at 80°C.

[0017] Preferably, the ball milling in S2 is carried out under vacuum conditions, the ball-to-material ratio is 5:1, the ball diameter is 3-5 mm, the ball milling speed is 300 rpm, the ball milling time is 2 h, and the amount ratio of the pretreated CuCO3 powder, organic flame retardant and ethanol is 1 g:4 g:20 mL; the ultrasonic frequency is 40 kHz, the ultrasonic power is 300 W, the ultrasonic time is 1 h, the stirring reaction time is 4 h, the stirring reaction temperature is 60 ° C, the stirring reaction speed is 500 rpm, the centrifugal speed is 8000 rpm, the centrifugal time is 10 min, and the product is washed with ethanol 3 times. The product is dried under vacuum conditions at a drying temperature of 80 ° C.

[0018] Preferably, the amount ratio of the organic complex, ethanol, polyvinyl pyrrolidone and sol in S3 is 10g:180mL:0.6g:(30-35)mL; the ultrasonic power is 200W, and the ultrasonic time is 20min; the stirring reaction speed is 600rpm, the stirring reaction time is 3h, and the stirring reaction temperature is 60°C; the gradient static aging is first standing at 70°C for 1h, and then standing at 50°C for 1h, so that the sol is condensed into a dense coating layer; the thickness of the TiO2 layer coated with the flame retardant is 30-50nm; the amount ratio of the coated flame retardant, KH560 and hydrolyzate is 10g:0.5g:100mL, the ultrasonic temperature is 60-65°C, and the ultrasonic time is 50-60min.

[0019] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. The present invention adds 50% of agglomeration barrier additives in the esterification stage and utilizes the good dispersibility of the terephthalic acid and ethylene glycol system to avoid agglomeration of the flame retardant during the polycondensation process; adds modified organic flame retardants and silicone microspheres in the middle stage of the polycondensation, so that the surface hydroxyl groups form hydrogen bonds with the PET ester groups to enhance interfacial bonding; and achieves high whiteness, high reactivity and halogen-free flame retardant properties of the flame retardant through a step-by-step modification and loading process. Specifically, during sol coating, the titanium dioxide layer generated by the hydrolysis of tetrabutyl titanate is coupled with copper carbonate on the surface of red phosphorus to form a complementary color. The dark red color of the red phosphorus is offset by light scattering, so that the prepared PET polyester chips have high whiteness and are suitable for high-end PET materials, such as polyester chips for optical films and environmentally friendly titanium-based bottle-grade polyester chips. The subsequent processing into flame-retardant polyester films has good appearance whiteness and gloss.

[0020] 2. The present invention prepares a coagulation barrier additive by subjecting red phosphorus to interfacial coupling, sol coating, and surface grafting modification. Red phosphorus itself is a highly effective flame retardant. During combustion, it generates polymetaphosphoric acid, a strong dehydrating agent that promotes the formation of a carbonized layer on the polymer surface. This carbonized layer blocks the transfer of oxygen and heat, thereby achieving flame retardancy. CuCO3 powder catalyzes carbonization. Combustion of CuCO3 powder generates CuO and CO2. CuO, acting as a Lewis acid catalyst, promotes the dehydration and crosslinking of PET molecular chains, forming a dense and continuous graphitized carbon layer that inhibits heat and oxygen transfer. CO2 releases combustible gases in the gas phase, reducing combustion intensity. This results in a synergistic gas-phase-coagulation flame retardancy, thereby enhancing the flame retardancy of PET resin. The TiO2 coating layer isolates oxygen and moisture, inhibiting red phosphorus oxidation and PH3 release. At temperatures above 500°C, the TiO2 transforms into a stable ceramic phase, enhancing the coagulation barrier effect and improving flame retardancy.

[0021] 3. The present invention forms a phosphorus-nitrogen cross-linked network by condensing melamine and biphenylphosphinoyl dichloride, and forms a BO-Si high-temperature resistant skeleton through hydroxyl cross-linking of boric acid to form an intumescent flame retardant system. At high temperatures, inert gas is released to dilute oxygen, and a BP-Si-O glassy carbon layer is simultaneously generated to isolate heat and oxygen. TiO2 sol coating isolates heat, and the KH560 silane coupling agent is bonded to the PET matrix through Si-O-Ti bonds to enhance dispersibility. Therefore, the modified organic flame retardant in PET improves the flame retardancy of PET polyester chips through a gas phase-condensed phase synergistic flame retardancy and carbonization enhancement mechanism, thereby effectively preventing the spread of flames. DETAILED DESCRIPTION

[0022] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention. Example 1:

[0023] This embodiment discloses a method for preparing a coagulation barrier additive, comprising the following steps: Q1. Ultrasonic dispersion of 10 g of red phosphorus in 200 mL of hydrolyzate. The hydrolyzate was prepared by adding 1 part of deionized water and 0.1 part of glacial acetic acid to 100 parts of ethanol and stirring. The pH of the hydrolyzate was 4. 2.5 g of CuCO3 powder was added and ultrasonicated at a frequency of 40 kHz, a power of 200 W, and a time of 30 min. 1.8 g of KH560 was added and stirred at 60 ° C for 2 h. The mixture was centrifuged at a speed of 6000 rpm for 10 min and washed with ethanol three times. The mixture was dried at 75 ° C to obtain a coupling complex. Q2, 10g of the coupling complex was dispersed in 180mL of ethanol, 0.6g of polyvinyl pyrrolidone was added, and ultrasonication was performed at a power of 150W for 20min; 30mL of sol was added dropwise, the sol was mixed by tetrabutyl titanate and ethanol in a volume ratio of 1:10, ammonia was added to adjust the pH to 9, and the mixture was stirred; the reaction was stirred at 60°C for 3h, the stirring reaction speed was 600rpm, the reaction was allowed to stand at 70°C for 1h, and then at 50°C for 1h for gradient standing aging, centrifugal washing, drying, and repeated coating twice to obtain a whitening flame retardant with a TiO2 layer thickness of 30nm; Q3. The whitening flame retardant and maleic anhydride were reacted in toluene at a mass ratio of 1:0.15 at 110°C for 4 hours, centrifuged, washed, and dried to obtain a coagulation barrier additive.

[0024] This embodiment discloses a method for preparing a modified organic flame retardant, comprising the following steps: S1. Dissolve 1 mol of melamine, 1.1 mol of biphenylphosphoryl dichloride, and 0.8 mol of boric acid in 20 mL of dimethyl sulfoxide, add 0.05 g of p-toluenesulfonic acid, heat to 110°C under nitrogen protection, react for 24 hours, centrifuge, wash with acetone three times, and dry in vacuo at 80°C to obtain an organic flame retardant; S2. Mix CuCO3 powder and NH4H2PO4 and then ball mill them under vacuum conditions with a ball-to-material ratio of 5:1, a ball diameter of 3 mm, a ball milling speed of 300 rpm, a ball milling time of 2 h, and dry them to obtain pretreated CuCO3 powder; add 10 g of pretreated CuCO3 powder and 40 g of organic flame retardant into 200 mL of ethanol, ultrasonicate at a frequency of 40 kHz, a power of 300 W, and a ultrasonication time of 1 h, stir and react at 60°C for 1 h, stir and react at a speed of 500 rpm, centrifuge at 8000 rpm for 10 min, wash with ethanol 3 times, and vacuum dry at 80°C to obtain an organic composite; S3. Disperse 10g of the organic complex in 180mL of ethanol, add 0.6g of polyvinyl pyrrolidone, and ultrasonicate at a power of 200W for 20min. Add 30mL of sol dropwise, stir and react at 60℃ for 3h at a stirring reaction speed of 600rpm. First, let it stand at 70℃ for 1h, then let it stand at 50℃ for 1h for gradient standing aging. Centrifugal washing, drying, and repeat coating twice to obtain a coated flame retardant with a TiO2 layer thickness of 30nm. Ultrasonicate 10g of the coated flame retardant and 0.5g of KH560 in 100mL of hydrolyzate at 60℃ for 50min, centrifuge and dry to obtain a modified organic flame retardant.

[0025] This embodiment discloses a method for preparing a halogen-free flame-retardant PET polyester chip, comprising the following steps: (1) 700 g of terephthalic acid, 300 g of ethylene glycol, 0.5 g of tetrabutyl titanate and 30 g of 50% coagulant barrier additive were added to a reactor and heated to 240°C. The mixture was stirred at normal pressure for 2.5 h at a stirring speed of 150 r / min to obtain an esterification system. (2) The esterification system was evacuated to 10 Pa and heated to 275 ° C for polycondensation reaction; in the early stage of polycondensation, the remaining 30 g of 50% coagulant barrier additive was added; in the middle stage of polycondensation, 40 g of modified organic flame retardant, 10 g of phenyl polysiloxane microspheres, 0.5 g of Irganox 1010 and 0.3 g of pentaerythritol ester were added, and the reaction was continued until the intrinsic viscosity reached 0.7 dL / g. The material was discharged, cast into strips and sliced. The slices were vacuum dried at 120 ° C for 24 hours to reduce the moisture content of the slices to below 0.02%, thereby obtaining halogen-free flame retardant PET polyester chips. Example 2:

[0026] This embodiment discloses a method for preparing a coagulation barrier additive, comprising the following steps: Q1. Ultrasonic dispersion of 10 g of red phosphorus in 200 mL of pH hydrolyzate with a pH of 4.3 was performed. 2.5 g of CuCO3 powder was added and ultrasonicated at a frequency of 40 kHz, a power of 200 W, and a duration of 30 min. 1.9 g of KH560 was added and stirred at 63 ° C for 2.5 h. The mixture was centrifuged at a speed of 7000 rpm for 10 min and washed three times with ethanol. The mixture was dried at 78 ° C to obtain a coupling complex. Q2, 10g of the coupling complex was dispersed in 180mL of ethanol, 0.6g of polyvinyl pyrrolidone was added, and ultrasonication was performed at a power of 150W for 20min; 33mL of sol was added dropwise, the sol was mixed by tetrabutyl titanate and ethanol in a volume ratio of 1:10, ammonia was added to adjust the pH to 8.5, and the mixture was stirred; the reaction was stirred at 60°C for 3h, the stirring reaction speed was 600rpm, the reaction was allowed to stand at 70°C for 1h, and then at 50°C for 1h for gradient standing aging, centrifugal washing, drying, and repeated coating 3 times to obtain a whitening flame retardant with a TiO2 layer thickness of 40nm; Q3. The whitening flame retardant and maleic anhydride were reacted in toluene at a mass ratio of 1:0.15 at 113°C for 4.5 hours, centrifuged, washed, and dried to obtain a coagulation barrier additive.

[0027] This embodiment discloses a method for preparing a modified organic flame retardant, comprising the following steps: S1. Dissolve 1 mol of melamine, 1.2 mol of biphenylphosphoryl dichloride, and 0.8 mol of boric acid in 20 mL of dimethyl sulfoxide, add 0.05 g of p-toluenesulfonic acid, heat to 110°C under nitrogen protection, react for 26 hours, centrifuge, wash with acetone three times, and dry in vacuo at 80°C to obtain an organic flame retardant; S2. Mix CuCO3 powder and NH4H2PO4 and then ball mill them under vacuum conditions with a ball-to-material ratio of 5:1, a ball diameter of 4 mm, a ball milling speed of 300 rpm, a ball milling time of 2 h, and dry them to obtain pretreated CuCO3 powder; add 10 g of pretreated CuCO3 powder and 40 g of organic flame retardant into 200 mL of ethanol, ultrasonicate them at a frequency of 40 kHz, a power of 300 W, and a ultrasonicate time of 1 h, stir and react at 60°C for 1 h, stir and react at a speed of 500 rpm, centrifuge at 8000 rpm for 10 min, wash with ethanol 3 times, and vacuum dry at 80°C to obtain an organic composite; S3. Disperse 10g of the organic complex in 180mL of ethanol, add 0.6g of polyvinyl pyrrolidone, and ultrasonicate at a power of 200W for 20min. Add 33mL of sol dropwise, stir and react at 60℃ for 3h at a stirring reaction speed of 600rpm. First, let it stand at 70℃ for 1h, then let it stand at 50℃ for 1h for gradient standing aging. Centrifugal washing, drying, and repeat coating 3 times to obtain a coated flame retardant with a TiO2 layer thickness of 40nm. Ultrasonicate 10g of the coated flame retardant and 0.5g of KH560 in 100mL of hydrolyzate at 63℃ for 55min, centrifuge and dry to obtain a modified organic flame retardant.

[0028] This embodiment discloses a method for preparing a halogen-free flame-retardant PET polyester chip, comprising the following steps: (1) 730 g of terephthalic acid, 310 g of ethylene glycol, 0.7 g of tetrabutyl titanate and 35 g of 50% coagulant barrier additive were added to a reactor and heated to 245 °C. The mixture was stirred at normal pressure for 3 h at a stirring speed of 180 r / min to obtain an esterification system. (2) The esterification system was evacuated to 30 Pa and heated to 278 ° C for polycondensation reaction; in the early stage of polycondensation, the remaining 30-40 g of 50% coagulant barrier additive was added; in the middle stage of polycondensation, 50 g of modified organic flame retardant, 15 g of phenyl polysiloxane microspheres, 1 g of Irganox 1010 and 0.7 g of pentaerythritol ester were added, and the reaction was continued until the intrinsic viscosity reached 0.8 dL / g. The material was discharged, cast into strips and sliced. The slices were vacuum dried at 130 ° C for 26 hours to reduce the moisture content of the slices to below 0.02%, thereby obtaining halogen-free flame retardant PET polyester chips. Example 3:

[0029] This embodiment discloses a method for preparing a coagulation barrier additive, comprising the following steps: Q1. Ultrasonic dispersion of 10 g of red phosphorus in 200 mL of pH hydrolyzate with a pH of 4.5 was performed. 2.5 g of CuCO3 powder was added and ultrasonicated at a frequency of 40 kHz, a power of 200 W, and a duration of 30 min. 2 g of KH560 was added and stirred at 65 ° C for 3 h. The mixture was centrifuged at a speed of 8000 rpm for 10 min and washed three times with ethanol. The mixture was dried at 80 ° C to obtain a coupling complex. Q2, 10g of the coupling complex was dispersed in 180mL of ethanol, 0.6g of polyvinyl pyrrolidone was added, and ultrasonication was performed at a power of 150W for 20min; 35mL of sol was added dropwise, the sol was mixed by tetrabutyl titanate and ethanol in a volume ratio of 1:10, ammonia was added to adjust the pH to 10, and the mixture was stirred; the reaction was stirred at 60°C for 3h, the stirring reaction speed was 600rpm, the reaction was allowed to stand at 70°C for 1h, and then at 50°C for 1h for gradient standing aging, centrifugal washing, drying, and repeated coating 3 times to obtain a whitening flame retardant with a TiO2 layer thickness of 50nm; Q3. The whitening flame retardant and maleic anhydride were reacted in toluene at a mass ratio of 1:0.15 at 115°C for 5 hours, centrifuged, washed, and dried to obtain a coagulation barrier additive.

[0030] This embodiment discloses a method for preparing a modified organic flame retardant, comprising the following steps: S1. Dissolve 1 mol of melamine, 1.2 mol of biphenylphosphoryl dichloride, and 0.8 mol of boric acid in 20 mL of dimethyl sulfoxide, add 0.05 g of p-toluenesulfonic acid, heat to 110°C under nitrogen protection, react for 28 hours, centrifuge, wash with acetone three times, and dry in vacuo at 80°C to obtain an organic flame retardant; S2. Mix CuCO3 powder and NH4H2PO4 and then ball mill them under vacuum conditions with a ball-to-material ratio of 5:1, a ball diameter of 5 mm, a ball milling speed of 300 rpm, a ball milling time of 2 h, and dry them to obtain pretreated CuCO3 powder; add 10 g of pretreated CuCO3 powder and 40 g of organic flame retardant into 200 mL of ethanol, ultrasonicate them at a frequency of 40 kHz, a power of 300 W, and a ultrasonicate time of 1 h, stir and react at 60°C for 1 h, stir and react at a speed of 500 rpm, centrifuge at 8000 rpm for 10 min, wash with ethanol 3 times, and vacuum dry at 80°C to obtain an organic composite; S3. Disperse 10g of the organic complex in 180mL of ethanol, add 0.6g of polyvinyl pyrrolidone, and ultrasonicate at a power of 200W for 20min. Add 35mL of sol dropwise, stir and react at 60℃ for 3h at a stirring reaction speed of 600rpm. First, let it stand at 70℃ for 1h, then let it stand at 50℃ for 1h for gradient standing aging. Centrifugal washing, drying, and repeat coating 3 times to obtain a coated flame retardant with a TiO2 layer thickness of 50nm. Ultrasonicate 10g of the coated flame retardant and 0.5g of KH560 in 100mL of hydrolyzate at 65℃ for 60min, centrifuge and dry to obtain a modified organic flame retardant.

[0031] This embodiment discloses a method for preparing a halogen-free flame-retardant PET polyester chip, comprising the following steps: (1) Add 750g of terephthalic acid, 320g of ethylene glycol, 1g of tetrabutyl titanate and 40g of 50% coagulant barrier additive into a reactor and heat to 250°C. Stir and react for 3h at normal pressure at a speed of 200r / min to obtain an esterification system. (2) The esterification system was evacuated to 50 Pa and heated to 280 ° C for polycondensation reaction; in the early stage of polycondensation, the remaining 40 g of 50% coagulant barrier agent was added; in the middle stage of polycondensation, 60 g of modified organic flame retardant, 20 g of phenyl polysiloxane microspheres, 2 g of Irganox 1010 and 1 g of pentaerythritol ester were added, and the reaction was continued until the intrinsic viscosity reached 0.8 dL / g. The material was discharged, cast into strips and sliced. The slices were vacuum dried at 140 ° C for 48 hours to reduce the moisture content of the slices to below 0.02%, thereby obtaining halogen-free flame retardant PET polyester chips.

[0032] Comparative Example 1: This embodiment discloses a method for preparing a halogen-free flame-retardant PET polyester chip, comprising the following steps: (1) Add 750g of terephthalic acid, 320g of ethylene glycol, 1g of tetrabutyl titanate and 7g of 50% red phosphorus flame retardant into a reactor and heat to 250°C. Stir and react for 3h at normal pressure at a speed of 150-200r / min to obtain an esterification system; (2) The esterification system was evacuated to 50 Pa and heated to 280 ° C for polycondensation reaction; in the early stage of polycondensation, the remaining 7g of 50% red phosphorus flame retardant was added; in the middle stage of polycondensation, 15g of modified organic flame retardant, 20g of phenyl polysiloxane microspheres, 2g of Irganox 1010 and 1g of pentaerythritol ester were added, and the reaction was continued until the intrinsic viscosity reached 0.7-0.8dL / g. The material was discharged, cast into strips and sliced. The slices were vacuum dried at 140 ° C for 48 hours to reduce the moisture content of the slices to below 0.02%, thereby obtaining halogen-free flame-retardant PET polyester chips.

[0033] Comparative Example 1 Compared with Example 3, in the preparation process of the halogen-free flame-retardant PET polyester chips in Comparative Example 1, the contents of the coagulant barrier additive and the modified organic flame retardant are reduced, while other conditions remain unchanged.

[0034] Comparative Example 2: This embodiment discloses a method for preparing a halogen-free flame-retardant PET polyester chip, comprising the following steps: (1) Add 750g of terephthalic acid, 320g of ethylene glycol, 1g of tetrabutyl titanate and 5g of 50% coagulant barrier additive into a reactor and heat to 250°C. Stir and react for 3h at normal pressure at a speed of 150-200r / min to obtain an esterification system. (2) The esterification system was evacuated to 50 Pa and heated to 280 ° C for polycondensation reaction; in the early stage of polycondensation, the remaining 5g of 50% coagulant barrier agent was added; in the middle stage of polycondensation, 10g of melamine polyphosphate flame retardant, 20g of phenyl polysiloxane microspheres, 2g of Irganox 1010 and 1g of pentaerythritol ester were added, and the reaction was continued until the intrinsic viscosity reached 0.7-0.8dL / g, and the material was discharged, cast into strips and sliced. The slices were vacuum dried at 140 ° C for 48 hours to reduce the moisture content of the slices to below 0.02%, thereby obtaining halogen-free flame-retardant PET polyester chips.

[0035] Comparative Example 2 Compared with Example 3, in the preparation process of the halogen-free flame-retardant PET polyester chips in Comparative Example 2, the contents of the coagulant barrier additive and the modified organic flame retardant are reduced, while other conditions remain unchanged.

[0036] Comparative Example 3: Comparative Example 3 Compared with Example 3, in the preparation process of the halogen-free flame-retardant PET polyester chips in Comparative Example 3, the coagulant barrier agent is replaced with an unmodified red phosphorus flame retardant, and other conditions remain unchanged.

[0037] Comparative Example 4: Comparative Example 4 Compared with Example 3, in the preparation process of the halogen-free flame-retardant PET polyester chips in Comparative Example 4, the modified organic flame retardant was replaced with a melamine polyphosphate flame retardant, and other conditions remained unchanged.

[0038] Experimental example: The performance tests of the PET polyester chips prepared in Examples 1-3 and Comparative Examples 1-4 were conducted as follows: 1. Flame retardant performance test According to GB / T 2406-2008 "Determination of Combustion Behavior of Plastics by Oxygen Index Method," a 100mm×10mm×3mm sample was placed in an oxygen index meter to determine the minimum oxygen concentration required to sustain combustion. According to GB / T 2408-2021, a 125mm×13mm×3mm sample was fixed vertically and ignited twice (10 seconds), and the burning time and whether the dripping material ignited the absorbent cotton were recorded. According to GB / T8323-2008, a 25mm×25mm×3mm sample was burned in a closed smoke box to determine the maximum smoke density (Ds,max). The results are shown in Table 1.

[0039] Table 1 Flame retardant performance test Group Minimum oxygen concentration (%) Vertical combustion level Maximum smoke density Example 1 32 V-0 170 Example 2 34 V-0 160 Example 3 35 V-0 150 Comparative Example 1 28 V-2 (Dripping Ignition) 260 Comparative Example 2 26 V-2 (Dripping Ignition) 270 Comparative Example 3 24 V-2 (heavy dripping) 300 Comparative Example 4 26 V-2 (Dripping Ignition) 230 According to the flame retardant test results in Table 1, it can be seen that the minimum oxygen concentration, vertical and smoke density of Examples 1-3 are significantly higher than those of Comparative Examples 1-4. By comparing the preparation processes of Examples 1-3 and Comparative Examples 1-4, it can be seen that the addition of agglomerate barrier additives and modified organic flame retardants can help improve the flame retardant properties of PET polyester chips.

[0040] 2. Mechanical properties test According to GB / T 1040-2006 "Determination of tensile properties of plastics", injection-molded dumbbell-shaped specimens were tested for tensile strength and elongation at break. The test results are shown in Table 2: Table 2 Mechanical properties test Group Tensile strength (MPa) Elongation at break (%) Example 1 56 115 Example 2 57 118 Example 3 59 120 Comparative Example 1 53 95 Comparative Example 2 49 86 Comparative Example 3 42 65 Comparative Example 4 52 100 According to the mechanical property test results in Table 2, it can be seen that the tensile strength and elongation at break of Examples 1-3 are higher than those of Comparative Examples 1-4. By comparing the preparation processes of Examples 1-3 and Comparative Examples 1-4, it can be seen that the addition of the coagulation barrier additive and the modified organic flame retardant can help improve the mechanical properties of the PET polyester chips. This may be because the flame retardant in Examples 1-3 is bonded to the PET matrix through KH560 coupling, resulting in uniform dispersion and reduced stress concentration, leading to improved mechanical properties.

[0041] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

[0042] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a halogen-free flame-retardant PET polyester chip, characterized in that: The following steps are involved: (1) Add terephthalic acid, ethylene glycol, tetrabutyl titanate and part of the coagulation barrier additive into a reactor, heat, and react with stirring at normal pressure to obtain an esterification system; (2) The esterification system is vacuumed and heated to carry out polycondensation reaction; in the early stage of polycondensation, the remaining coagulation barrier additive is added; in the middle stage of polycondensation, a modified organic flame retardant, phenyl polysiloxane microspheres, an antioxidant and a stabilizer are added, and the reaction is carried out until the viscosity reaches 0.7-0.8 dL / g, and the material is discharged, cast into strips and sliced ​​to obtain halogen-free flame-retardant PET polyester chips; The mass ratio of terephthalic acid, ethylene glycol, tetrabutyl titanate and part of the coagulation barrier additive in step (1) is (70-75): (30-32): (0.05-0.1): (3-4).

2. The method for preparing a halogen-free flame-retardant PET polyester chip according to claim 1, wherein In step (2), the viscosity at the initial stage of polycondensation is 0.3 dL / g, and the viscosity at the middle stage of polycondensation is 0.5 dL / g. The mass ratio of the remaining coagulation barrier additive, modified organic flame retardant, phenyl polysiloxane microspheres, antioxidant and stabilizer is (3-4): (4-6): (1-2): (0.05-0.2): (0.03-0.1).

3. The method for preparing a halogen-free flame-retardant PET polyester chip according to claim 1, wherein: The preparation method of the coagulation barrier auxiliary agent comprises the following steps: Q1. Ultrasonic dispersion of red phosphorus in the hydrolyzate, addition of CuCO3 powder, ultrasonication, addition of silane coupling agent KH560, stirring for reaction, centrifugal washing, and drying to obtain a coupling complex; Q2, dispersing the coupling complex in ethanol, adding polyvinyl pyrrolidone, ultrasonicating, dropping the sol, stirring to react, gradient standing and aging, centrifuging and washing, drying, and repeating the coating to obtain a whitening flame retardant; Q3. The whitening flame retardant and maleic anhydride are refluxed in toluene at a mass ratio of 1:0.15, centrifuged, washed, and dried to obtain a coagulation barrier additive.

4. The method for preparing the halogen-free flame-retardant PET polyester chips according to claim 3, wherein: The dosage ratio of red phosphorus, hydrolyzate, CuCO3 and KH560 in Q1 is 10g:200mL:2.5g:(1.8-2)g.

5. The method for preparing the halogen-free flame-retardant PET polyester chips according to claim 3, wherein: The dosage ratio of the coupling complex, ethanol, polyvinyl pyrrolidone and sol in Q2 is 10 g:180 mL:0.6 g:(30-35) mL; the sol is prepared by mixing tetrabutyl titanate and ethanol in a volume ratio of 1:10, adding ammonia water to adjust the pH to 9-10, and stirring; the thickness of the TiO2 layer of the whitening flame retardant is 30-50 nm.

6. The method for preparing the halogen-free flame-retardant PET polyester chips according to claim 3, wherein: The reflux reaction temperature in Q3 is 110-115° C., and the reflux reaction time is 4-5 h.

7. The method for preparing halogen-free flame-retardant PET polyester chips according to claim 1, wherein: The preparation method of the modified organic flame retardant comprises the following steps: S1. Dissolve melamine, biphenylphosphinoyl dichloride, and boric acid in dimethyl sulfoxide, add p-toluenesulfonic acid, heat under nitrogen protection for reaction, centrifuge and wash, and dry to obtain an organic flame retardant; S2. Mixing CuCO3 powder and NH4H2PO4, ball milling, and drying to obtain pretreated CuCO3 powder; adding ethanol to the pretreated CuCO3 powder and the organic flame retardant, ultrasonicating, stirring, reacting, centrifuging, washing, and vacuum drying to obtain an organic composite; S3. Disperse the organic complex in ethanol, add polyvinyl pyrrolidone, sonicate, add the sol dropwise, stir to react, gradient static aging, centrifugal washing, dry, repeat coating 2-3 times to obtain a coated flame retardant; sonicate the coated flame retardant and KH560 in a hydrolyzate, centrifuge and dry to obtain a modified organic flame retardant.

8. The method for preparing halogen-free flame-retardant PET polyester chips according to claim 1, wherein: The usage ratio of melamine, diphenylphosphoryl dichloride, boric acid, dimethyl sulfoxide and p-toluenesulfonic acid in S1 is 1 mol: (1.1-1.2) mol: 0.8 mol: 20 mL: 0.05 g.

9. The method for preparing halogen-free flame-retardant PET polyester chips according to claim 1, wherein: The dosage ratio of pretreated CuCO3 powder, organic flame retardant and ethanol in S2 is 1g:4g:20mL.

10. The method for preparing halogen-free flame-retardant PET polyester chips according to claim 1, wherein: The dosage ratio of the organic complex, ethanol, polyvinyl pyrrolidone and sol in S3 is 10g:180mL:0.6g:(30-35)mL; the dosage ratio of the coated flame retardant, KH560 and hydrolyzate is 10g:0.5g:100mL.

Images