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

Abstract

This invention discloses a method for preparing halogen-free flame-retardant PET polyester chips, belonging to the field of polyester material technology. The method for preparing the PET polyester chips includes the following steps: adding terephthalic acid, ethylene glycol, tetrabutyl titanate, and 50% coagulation barrier agent to a reaction vessel and heating, stirring under normal pressure to obtain an esterification system; evacuating the esterification system, heating, and carrying out a polycondensation reaction; adding the remaining 50% coagulation barrier agent in the initial stage of polycondensation; adding a modified organic flame retardant, phenyl polysiloxane microspheres, antioxidant, and stabilizer in the middle stage of polycondensation, and continuing the reaction until the intrinsic viscosity reaches 0.7-0.8 dL / g; discharging, casting into strips, and cutting to obtain halogen-free flame-retardant PET polyester chips. The PET polyester chips prepared by this invention have high flame-retardant properties and are free of halogen elements.

Description

Technical Field

[0001] This invention belongs to the field of polyester material technology, specifically relating to a method for preparing halogen-free flame-retardant PET polyester chips. Background Technology

[0002] In the field of materials technology, polyethylene terephthalate (PET) polyester chips are widely used in packaging, textiles, electronics, and other industries due to their excellent mechanical properties, chemical stability, and processing performance. However, PET is a flammable material with a limiting oxygen index (LOI) of only about 21%. It is prone to combustion and spread under high temperature and open flame conditions, which greatly limits its application in fields with high flame retardant requirements, such as electronic appliance housings, automotive interiors, and building decoration materials.

[0003] Traditional methods for improving the flame retardancy of PET often involve adding halogenated flame retardants. While these methods can effectively impart flame retardancy to PET, halogenated flame retardants release large amounts of toxic hydrogen halide gas and fumes during combustion, which not only harms human health but also causes secondary pollution. Furthermore, halogenated 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, this invention provides a method for preparing halogen-free flame-retardant PET polyester chips, which solves the technical problem that traditional halogen-free flame retardants have the contradiction of high addition amount and performance degradation during use. They do not improve the gloss and flame retardant performance of PET polyester chips at the same time through reasonable compounding of flame retardant components and other additives. Furthermore, the flame retardant components are not reasonably compounded through multiple flame retardant principles, which limits their application in the field of high-end PET materials. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing halogen-free flame-retardant PET polyester chips, which solves the technical problems in the prior art where traditional halogen-free flame retardants have the contradiction of high addition amount and performance degradation during use, and the lack of reasonable compounding of flame retardant components and other additives to simultaneously improve the gloss and flame retardant performance of PET polyester chips, and the lack of reasonable compounding of flame retardant components through multiple flame retardant principles, which limits their application in the field of high-end PET materials.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing halogen-free flame-retardant PET polyester chips includes the following steps:

[0008] (1) Add terephthalic acid, ethylene glycol, tetrabutyl titanate and 50% coagulation barrier agent to the reactor and heat, stir under normal pressure to obtain esterification system;

[0009] (2) Vacuum the esterification system, heat it, and carry out polycondensation reaction; in the early stage of polycondensation, add the remaining 50% of coagulation barrier agent; in the middle stage of polycondensation, add modified organic flame retardant, phenyl polysiloxane microspheres, antioxidant and stabilizer, and continue the reaction until the intrinsic viscosity is 0.7-0.8dL / g, discharge, cast strip and slice to obtain halogen-free flame retardant PET polyester chips.

[0010] The synthesis reaction formula for PET polyester in the above process is as follows:

[0011]

[0012] Further, 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, and the mass ratio of terephthalic acid, ethylene glycol, tetrabutyl titanate and 50% coagulation barrier agent is (70-75):(30-32):(0.05-0.1):(3-4); the heating temperature is 240-250℃, the stirring reaction time is 2.5-3 h, and the stirring reaction speed is 150-200 r / min.

[0013] 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%.

[0014] Further, in step (2), the esterification system is evacuated to 10-50 Pa and heated to 275-280 °C. The viscosity is 0.3 dL / g in the initial stage of polycondensation and 0.5 dL / g in the middle stage of polycondensation. The mass ratio of the remaining 50% coagulation barrier agent, 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%.

[0015] The preparation method of the coagulation barrier agent includes the following steps:

[0016] Q1. Disperse red phosphorus in hydrolysate with ultrasound, add CuCO3 powder, sonicate, add KH560, stir to react, centrifuge and wash, dry to obtain the coupling complex.

[0017] Q2. Disperse the coupling complex in ethanol, add polyvinylpyrrolidone, sonicate, add sol dropwise, stir to react, allow to stand in a gradient for aging, centrifuge and wash, dry, repeat coating 2-3 times to obtain whitening flame retardant.

[0018] 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 agent.

[0019] As a preferred embodiment, the ratio of red phosphorus, hydrolysate, CuCO3, and KH560 in Q1 is 10g:200mL:2.5g:(1.8-2)g; the hydrolysate is obtained by adding 1 part deionized water and 0.1 part glacial acetic acid to 100 parts ethanol and stirring until homogeneous, and the pH of the hydrolysate is controlled at 4-4.5. The pH of the hydrolysate is adjusted using 0.1wt% dilute ammonia or 0.1mol / L NaOH ethanol solution; the ultrasonic frequency is 40kHz, the ultrasonic power is 200W, and the ultrasonic time is 30min; the stirring reaction temperature is 60-65℃, and the stirring reaction time is 2-3h; the centrifugation speed is 6000-8000rpm, the centrifugation time is 10min, and the sample is washed 3 times with ethanol; the drying temperature is 75-80℃.

[0020] As a preferred embodiment, the ratio of coupling complex, ethanol, polyvinylpyrrolidone and sol in Q2 is 10g:180mL:0.6g:(30-35)mL; the sol is obtained by mixing tetrabutyl titanate and ethanol at a volume ratio of 1:10, adding ammonia to adjust the pH to 9-10, and stirring; the ultrasonic power is 150W, the ultrasonic time is 20min; the stirring speed is 600rpm, the stirring time is 3h, and the stirring temperature is 60℃; the gradient static aging is first settling at 70℃ for 1h, and then settling at 50℃ for 1h, so that the sol condenses into a dense coating layer, and the thickness of the TiO2 layer of the whitening flame retardant is 30-50nm.

[0021] Preferably, the reflux reaction temperature in Q3 is 110-115℃, and the reflux reaction time is 4-5h.

[0022] A method for preparing modified organic flame retardants includes the following steps:

[0023] S1. Melamine, biphenylphosphoryl dichloride, and boric acid are dissolved in dimethyl sulfoxide, p-toluenesulfonic acid is added, the mixture is heated under nitrogen protection, centrifuged, washed, and dried to obtain an organic flame retardant.

[0024] S2. After mixing CuCO3 powder with NH4H2PO4, the mixture is ball-milled and dried to obtain pretreated CuCO3 powder. The pretreated CuCO3 powder and organic flame retardant are added to ethanol, sonicated, stirred and reacted, centrifuged and washed, and vacuum dried to obtain an organic complex.

[0025] S3. Disperse the organic complex in ethanol, add polyvinylpyrrolidone, sonicate, add sol dropwise, stir to react, allow to stand in a gradient for aging, centrifuge and wash, dry, repeat coating 2-3 times to obtain the coated flame retardant; sonicate the coated flame retardant and KH560 in hydrolysate, centrifuge and dry to obtain the modified organic flame retardant.

[0026] As a preferred embodiment, the ratio of melamine, biphenylphosphine 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 mixture is washed three times with acetone, and the drying is carried out under vacuum at 80 °C.

[0027] As a preferred embodiment, in S2, ball milling is performed under vacuum conditions, with a ball-to-material ratio of 5:1, a ball diameter of 3-5 mm, a ball milling speed of 300 rpm, and a ball milling time of 2 h. The ratio of 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 centrifugation speed is 8000 rpm, the centrifugation time is 10 min, the product is washed three times with ethanol, and the drying is performed under vacuum conditions at a temperature of 80 °C.

[0028] As a preferred embodiment, the ratio of organic complex, ethanol, polyvinylpyrrolidone, 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 speed is 600rpm, the stirring time is 3h, and the stirring temperature is 60℃; the gradient static aging is first settling at 70℃ for 1h, and then settling at 50℃ for 1h, so that the sol condenses into a dense coating layer; the thickness of the TiO2 layer coating the flame retardant is 30-50nm; the ratio of flame retardant, KH560, and hydrolysate is 10g:0.5g:100mL, the ultrasonic temperature is 60-65℃, and the ultrasonic time is 50-60min.

[0029] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0030] 1. This invention avoids flame retardant agglomeration during polycondensation by adding 50% coagulation barrier agent during the esterification stage, utilizing the good dispersibility of the terephthalic acid and ethylene glycol system; in the middle stage of polycondensation, modified organic flame retardant and siloxane microspheres are added, and the surface hydroxyl groups form hydrogen bonds with PET ester groups, enhancing interfacial bonding; furthermore, through stepwise modification and loading processes, high whiteness, high reactivity, and halogen-free flame retardant properties of the flame retardant are achieved. In particular, during sol-gel coating, the titanium dioxide layer generated after the hydrolysis of tetrabutyl titanate and the copper carbonate coupled on the surface of red phosphorus can form a complementary color, which cancels the dark red color of red phosphorus through light scattering, resulting in high whiteness of the prepared PET polyester chips, suitable for high-end PET materials, such as polyester chips for optical films and environmentally friendly titanium-based bottle-grade polyester chips. Subsequent processing into flame-retardant polyester films results in good whiteness and gloss.

[0031] 2. This invention prepares a coagulation barrier agent by interfacial coupling, sol coating, and surface grafting modification of red phosphorus. Red phosphorus itself is a highly efficient flame retardant. During combustion, it generates poly(methoxyphosphoric acid), a strong dehydrating agent that promotes the formation of a carbonized layer on the polymer surface. This carbonized layer can block the transfer of oxygen and heat, thereby achieving flame retardancy. CuCO3 powder has a catalytic char-forming effect. When CuCO3 powder burns, it generates CuO and CO2. CuO, as a Lewis acid catalyst, promotes the dehydration and cross-linking of PET molecular chains, forming a graphitized carbon layer. The dense and continuous carbon layer structure can inhibit the transfer of heat and oxygen. The release of CO2 dilutes the combustible gas in the gas phase, reducing the combustion intensity. The gas-phase and condensed-phase synergistic flame retardancy improves the flame retardant performance of PET resin. The TiO2 coating layer can isolate oxygen and moisture, inhibit red phosphorus oxidation and PH3 release. At temperatures above 500℃, TiO2 transforms into a stable ceramic phase, enhancing the condensed-phase barrier effect and thus improving the flame retardant efficiency.

[0032] 3. This invention generates a phosphorus-nitrogen crosslinking network by condensing melamine and biphenyl phosphoric acid dichloride, and forms a BO-Si high-temperature resistant skeleton through hydroxyl crosslinking of boric acid, thus forming an intumescent flame retardant system. At high temperatures, it releases inert gas to dilute oxygen, while simultaneously generating a BP-Si-O glassy char layer to insulate against heat and oxygen. TiO2 sol coating insulates against heat, and KH560 silane coupling agent bonds to the PET matrix through Si-O-Ti bonds to enhance dispersibility. Therefore, the modified organic flame retardant in PET improves the flame retardant performance of PET polyester chips through a gas-phase-condensed phase synergistic flame retardant and char-forming enhancement mechanism, thereby effectively preventing the spread of flames. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1:

[0034] This embodiment discloses a method for preparing a coagulation barrier agent, including the following steps:

[0035] Q1. 10g of red phosphorus was ultrasonically dispersed in 200mL of hydrolysate, which was obtained by adding 1 part deionized water and 0.1 part glacial acetic acid to 100 parts ethanol and stirring until homogeneous. The pH of the hydrolysate was 4. 2.5g of CuCO3 powder was added, and the mixture was ultrasonicated at a frequency of 40kHz, a power of 200W, and a time of 30min. 1.8g of KH560 was added, and the mixture was stirred at 60℃ for 2h. The mixture was then centrifuged at 6000rpm for 10min and washed three times with ethanol. The mixture was dried at 75℃ to obtain the coupling complex.

[0036] Q2. Disperse 10g of the coupling complex in 180mL of ethanol, add 0.6g of polyvinylpyrrolidone, and sonicate at 150W for 20min. Add 30mL of sol dropwise. The sol is made by mixing tetrabutyl titanate and ethanol at a volume ratio of 1:10, adjusting the pH to 9 with ammonia, and stirring. Stir at 60℃ for 3h at a stirring speed of 600rpm. Allow to stand at 70℃ for 1h, then at 50℃ for 1h for gradient aging. Centrifuge, wash, dry, and repeat the coating process twice to obtain a whitening flame retardant with a TiO2 layer thickness of 30nm.

[0037] Q3. The whitening flame retardant and maleic anhydride were refluxed in toluene at 110°C for 4 hours at a mass ratio of 1:0.15. After centrifugation, washing and drying, a coagulation barrier agent was obtained.

[0038] This embodiment discloses a method for preparing a modified organic flame retardant, comprising the following steps:

[0039] S1. Dissolve 1 mol melamine, 1.1 mol biphenylphosphine dichloride, and 0.8 mol boric acid in 20 mL dimethyl sulfoxide, add 0.05 g p-toluenesulfonic acid, heat to 110 °C for 24 h under nitrogen protection, centrifuge, wash 3 times with acetone, and dry under vacuum at 80 °C to obtain an organic flame retardant.

[0040] S2. CuCO3 powder was mixed with NH4H2PO4 and then ball-milled under vacuum conditions. The ball-to-powder ratio was 5:1, the ball diameter was 3 mm, the ball milling speed was 300 rpm, and the ball milling time was 2 h. After drying, pretreated CuCO3 powder was obtained. 10 g of pretreated CuCO3 powder and 40 g of organic flame retardant were added to 200 mL of ethanol and sonicated at a frequency of 40 kHz, a power of 300 W, and a time of 1 h. The mixture was stirred at 60 °C for 1 h at a stirring speed of 500 rpm. After centrifugation at 8000 rpm for 10 min, the mixture was washed three times with ethanol and dried under vacuum at 80 °C to obtain the organic complex.

[0041] S3. Disperse 10g of the organic complex in 180mL of ethanol, add 0.6g of polyvinylpyrrolidone, sonicate at 200W for 20min, add 30mL of sol, stir at 60℃ for 3h at 600rpm, let stand at 70℃ for 1h, then let stand at 50℃ for 1h for gradient aging, centrifuge, wash, dry, repeat coating twice to obtain the coated flame retardant with a TiO2 layer thickness of 30nm; sonicate 10g of the coated flame retardant and 0.5g of KH560 in 100mL of hydrolysate at 60℃ for 50min, centrifuge and dry to obtain the modified organic flame retardant.

[0042] This embodiment discloses a method for preparing halogen-free flame-retardant PET polyester chips, including the following steps:

[0043] (1) 700g terephthalic acid, 300g ethylene glycol, 0.5g tetrabutyl titanate and 30g 50% coagulation barrier agent were added to the reactor and heated to 240℃. The mixture was stirred at normal pressure for 2.5h and the stirring speed was 150r / min to obtain the esterification system.

[0044] (2) The esterification system was evacuated to 10 Pa and heated to 275 °C to carry out polycondensation reaction. In the early stage of polycondensation, the remaining 30 g of 50% coagulation barrier agent 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 continued until the intrinsic viscosity was 0.7 dL / g. The material was discharged, cast into strips and chips. The chips were vacuum dried at 120 °C for 24 hours to reduce the moisture content of the chips to below 0.02% to obtain halogen-free flame-retardant PET polyester chips. Example 2:

[0045] This embodiment discloses a method for preparing a coagulation barrier agent, including the following steps:

[0046] Q1. Disperse 10g of red phosphorus ultrasonically in 200mL of pH hydrolysate (pH 4.3), add 2.5g of CuCO3 powder, and sonicate at 40kHz, 200W, for 30min. Add 1.9g of KH560, stir at 63℃ for 2.5h, centrifuge at 7000rpm for 10min, wash three times with ethanol, and dry at 78℃ to obtain the coupling complex.

[0047] Q2. Disperse 10g of the coupling complex in 180mL of ethanol, add 0.6g of polyvinylpyrrolidone, and sonicate at 150W for 20min. Add 33mL of sol dropwise. The sol is made by mixing tetrabutyl titanate and ethanol at a volume ratio of 1:10, adjusting the pH to 8.5 with ammonia, and stirring. Stir at 60℃ for 3h at a stirring speed of 600rpm. Allow to stand at 70℃ for 1h, then at 50℃ for 1h for gradient aging. Centrifuge, wash, and dry. Repeat the coating process 3 times to obtain a whitening flame retardant with a TiO2 layer thickness of 40nm.

[0048] Q3. The whitening flame retardant and maleic anhydride were refluxed in toluene at 113°C for 4.5 h at a mass ratio of 1:0.15. After centrifugation, washing and drying, a coagulation barrier agent was obtained.

[0049] This embodiment discloses a method for preparing a modified organic flame retardant, comprising the following steps:

[0050] S1. Dissolve 1 mol melamine, 1.2 mol biphenylphosphine dichloride, and 0.8 mol boric acid in 20 mL dimethyl sulfoxide, add 0.05 g p-toluenesulfonic acid, heat to 110 °C for 26 h under nitrogen protection, centrifuge, wash 3 times with acetone, and dry under vacuum at 80 °C to obtain an organic flame retardant.

[0051] S2. CuCO3 powder was mixed with NH4H2PO4 and then ball-milled under vacuum conditions. The ball-to-powder ratio was 5:1, the ball diameter was 4 mm, the ball milling speed was 300 rpm, and the ball milling time was 2 h. After drying, pretreated CuCO3 powder was obtained. 10 g of pretreated CuCO3 powder and 40 g of organic flame retardant were added to 200 mL of ethanol and sonicated at a frequency of 40 kHz, a power of 300 W, and a time of 1 h. The mixture was stirred at 60 °C for 1 h at a stirring speed of 500 rpm. After centrifugation at 8000 rpm for 10 min, the mixture was washed three times with ethanol and dried under vacuum at 80 °C to obtain the organic complex.

[0052] S3. Disperse 10g of the organic complex in 180mL of ethanol, add 0.6g of polyvinylpyrrolidone, sonicate at 200W for 20min, add 33mL of sol, stir at 60℃ for 3h at 600rpm, allow to stand at 70℃ for 1h, then at 50℃ for 1h for gradient aging, centrifuge, wash, dry, repeat coating 3 times to obtain the coated flame retardant with a TiO2 layer thickness of 40nm; sonicate 10g of the coated flame retardant and 0.5g of KH560 in 100mL of hydrolysate at 63℃ for 55min, centrifuge and dry to obtain the modified organic flame retardant.

[0053] This embodiment discloses a method for preparing halogen-free flame-retardant PET polyester chips, including the following steps:

[0054] (1) 730g terephthalic acid, 310g ethylene glycol, 0.7g tetrabutyl titanate and 35g 50% coagulation barrier agent were added to the reactor and heated to 245℃. The mixture was stirred at normal pressure for 3h and the stirring speed was 180r / min to obtain the esterification system.

[0055] (2) The esterification system was evacuated to 30 Pa and heated to 278 °C to carry out polycondensation reaction. In the early stage of polycondensation, the remaining 30-40 g of 50% coagulation barrier agent 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 continued until the intrinsic viscosity was 0.8 dL / g. The material was discharged, cast into strips and chips. The chips were vacuum dried at 130 °C for 26 hours to reduce the moisture content of the chips to below 0.02% to obtain halogen-free flame-retardant PET polyester chips. Example 3:

[0056] This embodiment discloses a method for preparing a coagulation barrier agent, including the following steps:

[0057] Q1. Disperse 10g of red phosphorus ultrasonically in 200mL of pH hydrolysate (pH 4.5), add 2.5g of CuCO3 powder, and sonicate at 40kHz, 200W, for 30min. Add 2g of KH560, stir at 65℃ for 3h, centrifuge at 8000rpm for 10min, wash three times with ethanol, and dry at 80℃ to obtain the coupling complex.

[0058] Q2. Disperse 10g of the coupling complex in 180mL of ethanol, add 0.6g of polyvinylpyrrolidone, and sonicate at 150W for 20min. Add 35mL of sol, which is a mixture of tetrabutyl titanate and ethanol at a volume ratio of 1:10, with ammonia added to adjust the pH to 10, and stir. Stir at 60℃ for 3h at a stirring speed of 600rpm. Allow to stand at 70℃ for 1h, then at 50℃ for 1h for gradient aging. Centrifuge, wash, dry, and repeat the coating process 3 times to obtain a whitening flame retardant with a TiO2 layer thickness of 50nm.

[0059] Q3. The whitening flame retardant and maleic anhydride were refluxed in toluene at 115°C for 5 hours at a mass ratio of 1:0.15. After centrifugation, washing, and drying, a coagulation barrier agent was obtained.

[0060] This embodiment discloses a method for preparing a modified organic flame retardant, comprising the following steps:

[0061] S1. Dissolve 1 mol melamine, 1.2 mol biphenylphosphine dichloride and 0.8 mol boric acid in 20 mL dimethyl sulfoxide, add 0.05 g p-toluenesulfonic acid, heat to 110 °C for 28 h under nitrogen protection, centrifuge, wash 3 times with acetone, and dry under vacuum at 80 °C to obtain organic flame retardant.

[0062] S2. CuCO3 powder was mixed with NH4H2PO4 and then ball-milled under vacuum conditions. The ball-to-powder ratio was 5:1, the ball diameter was 5 mm, the ball milling speed was 300 rpm, and the ball milling time was 2 h. After drying, pretreated CuCO3 powder was obtained. 10 g of pretreated CuCO3 powder and 40 g of organic flame retardant were added to 200 mL of ethanol and sonicated at a frequency of 40 kHz, a power of 300 W, and a time of 1 h. The mixture was stirred at 60 °C for 1 h at a stirring speed of 500 rpm. After centrifugation at 8000 rpm for 10 min, the mixture was washed three times with ethanol and dried under vacuum at 80 °C to obtain the organic complex.

[0063] S3. Disperse 10g of the organic complex in 180mL of ethanol, add 0.6g of polyvinylpyrrolidone, sonicate at 200W for 20min, add 35mL of sol, stir at 60℃ for 3h at 600rpm, allow to stand at 70℃ for 1h, then at 50℃ for 1h for gradient aging, centrifuge, wash, dry, repeat coating 3 times to obtain the coated flame retardant with a TiO2 layer thickness of 50nm; sonicate 10g of the coated flame retardant and 0.5g of KH560 in 100mL of hydrolysate at 65℃ for 60min, centrifuge and dry to obtain the modified organic flame retardant.

[0064] This embodiment discloses a method for preparing halogen-free flame-retardant PET polyester chips, including the following steps:

[0065] (1) 750g terephthalic acid, 320g ethylene glycol, 1g tetrabutyl titanate and 40g 50% coagulation barrier agent were added to the reactor and heated to 250℃. The mixture was stirred at normal pressure for 3h and the stirring speed was 200r / min to obtain the esterification system.

[0066] (2) The esterification system was evacuated to 50 Pa and heated to 280 °C to carry out polycondensation reaction. In the early stage of polycondensation, the remaining 40 g of 50% coagulation 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 continued until the intrinsic viscosity was 0.8 dL / g. The material was discharged, cast into strips and chips. The chips were vacuum dried at 140 °C for 48 hours to reduce the moisture content of the chips to below 0.02% and obtain halogen-free flame-retardant PET polyester chips.

[0067] Comparative Example 1:

[0068] This embodiment discloses a method for preparing halogen-free flame-retardant PET polyester chips, including the following steps:

[0069] (1) Add 750g terephthalic acid, 320g ethylene glycol, 1g tetrabutyl titanate and 7g 50% red phosphorus flame retardant to the reaction vessel and heat to 250℃. Stir the reaction under normal pressure for 3h. The stirring speed is 150-200r / min to obtain the esterification system.

[0070] (2) The esterification system was evacuated to 50 Pa and heated to 280 °C to carry out polycondensation reaction. In the early stage of polycondensation, the remaining 7 g of 50% red phosphorus flame retardant was added. In the middle stage of polycondensation, 15 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 continued until the intrinsic viscosity was 0.7-0.8 dL / g. The material was discharged, cast into strips and chips. The chips were vacuum dried at 140 °C for 48 hours to reduce the moisture content of the chips to below 0.02% and obtain halogen-free flame-retardant PET polyester chips.

[0071] Compared with Example 3, Comparative Example 1 reduced the content of coagulation barrier agent and modified organic flame retardant in the preparation process of halogen-free flame retardant PET polyester chips, while other conditions remained unchanged.

[0072] Comparative Example 2:

[0073] This embodiment discloses a method for preparing halogen-free flame-retardant PET polyester chips, including the following steps:

[0074] (1) Add 750g terephthalic acid, 320g ethylene glycol, 1g tetrabutyl titanate and 5g 50% coagulation barrier agent to the reactor and heat to 250℃. Stir the reaction under normal pressure for 3h. The stirring speed is 150-200r / min to obtain the esterification system.

[0075] (2) The esterification system was evacuated to 50 Pa and heated to 280 °C to carry out polycondensation reaction. In the early stage of polycondensation, the remaining 5g of 50% coagulation 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 continued until the intrinsic viscosity was 0.7-0.8dL / g. The material was discharged, cast into strips and chips. The chips were vacuum dried at 140 °C for 48 hours to reduce the moisture content of the chips to below 0.02% and obtain halogen-free flame-retardant PET polyester chips.

[0076] Compared with Example 3, Comparative Example 2 had a lower content of coagulation barrier agent and modified organic flame retardant in the preparation process of halogen-free flame retardant PET polyester chips, while other conditions remained unchanged.

[0077] Comparative Example 3:

[0078] Compared with Example 3, in the preparation process of halogen-free flame-retardant PET polyester chips, the coagulation barrier agent in Comparative Example 3 was replaced with an unmodified red phosphorus flame retardant, while other conditions remained unchanged.

[0079] Comparative Example 4:

[0080] Compared with Example 3, in the preparation of halogen-free flame-retardant PET polyester chips, the modified organic flame retardant in Comparative Example 4 was replaced with melamine polyphosphate flame retardant, while other conditions remained unchanged.

[0081] Experimental example:

[0082] The performance of the PET polyester chips prepared in Examples 1-3 and Comparative Examples 1-4 was tested, as follows:

[0083] I. Flame retardant performance test

[0084] According to GB / T 2406-2008 "Determination of Combustion Behavior by Oxygen Index Method for Plastics", 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 vertically fixed and ignited twice (10 seconds each time), and the combustion time and whether the dripping material ignited the cotton were recorded. According to GB / T8323-2008, a 25mm×25mm×3mm sample was burned in a sealed smoke chamber, and the maximum smoke density (Ds,max) was determined. The results are shown in Table 1.

[0085] Table 1 Flame retardant performance test

[0086] Group Minimum oxygen concentration (%) Vertical flammability rating 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 (Severe dripping) 300 Comparative Example 4 26 V-2 (dripping ignition) 230

[0087] According to the flame retardant performance test results in Table 1, it can be seen that the minimum oxygen concentration, verticality, and smoke density of Examples 1-3 are significantly higher than those of Comparative Examples 1-4. A comparison of the preparation processes of Examples 1-3 and Comparative Examples 1-4 shows that the addition of coagulation barrier agent and modified organic flame retardant can help improve the flame retardant performance of PET polyester chips.

[0088] II. Mechanical Property Testing

[0089] According to GB / T 1040-2006 "Determination of Tensile Properties of Plastics", the tensile strength and elongation at break of the injection-molded dumbbell-shaped specimens were tested. The test results are shown in Table 2.

[0090] Table 2 Mechanical property tests

[0091] 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

[0092] 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 coagulation barrier agent and modified organic flame retardant can help improve the mechanical properties of PET polyester chips. This may be because the flame retardant in Examples 1-3 is coupled with the PET matrix through KH560, resulting in uniform dispersion and reduced stress concentration, thus improving the mechanical properties.

[0093] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0094] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing halogen-free flame-retardant PET polyester chips, characterized in that, Includes the following steps: (1) Add terephthalic acid, ethylene glycol, tetrabutyl titanate and some coagulation barrier agent to the reactor and heat, and stir at normal pressure to obtain esterification system; (2) Vacuum the esterification system, heat it, and carry out polycondensation reaction; in the early stage of polycondensation, add the remaining coagulation barrier agent; in the middle stage of polycondensation, add modified organic flame retardant, phenyl polysiloxane microspheres, antioxidant and stabilizer, react until the viscosity is 0.7-0.8dL / g, discharge, cast strip and slice to obtain halogen-free flame retardant PET polyester chips; In step (1), the mass ratio of terephthalic acid, ethylene glycol, tetrabutyl titanate, and part of the coagulation barrier agent is (70-75):(30-32):(0.05-0.1):(3-4). The preparation method of the coagulation barrier agent includes the following steps: Q1. Disperse red phosphorus in hydrolysate using ultrasound, add CuCO3 powder, sonicate, add silane coupling agent KH560, stir to react, centrifuge and wash, dry to obtain coupling complex. Q2. Disperse the coupling complex in ethanol, add polyvinylpyrrolidone, sonicate, add sol dropwise, stir to react, allow to stand in a gradient for aging, centrifuge and wash, dry, and repeat 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 agent. A method for preparing modified organic flame retardants includes the following steps: S1. Melamine, biphenylphosphoryl dichloride, and boric acid are dissolved in dimethyl sulfoxide, p-toluenesulfonic acid is added, the mixture is heated under nitrogen protection, centrifuged, washed, and dried to obtain an organic flame retardant. S2. After mixing CuCO3 powder with NH4H2PO4, the mixture is ball-milled and dried to obtain pretreated CuCO3 powder. The pretreated CuCO3 powder and organic flame retardant are added to ethanol, sonicated, stirred and reacted, centrifuged and washed, and vacuum dried to obtain an organic complex. S3. Disperse the organic complex in ethanol, add polyvinylpyrrolidone, sonicate, add sol dropwise, stir to react, allow to stand in a gradient for aging, centrifuge and wash, dry, repeat coating 2-3 times to obtain the coated flame retardant; sonicate the coated flame retardant and KH560 in hydrolysate, centrifuge and dry to obtain the modified organic flame retardant. The sols in Q2 and S3 were prepared by mixing tetrabutyl titanate and ethanol at a volume ratio of 1:10, adding ammonia to adjust the pH to 9-10, and stirring.

2. The method for preparing halogen-free flame-retardant PET polyester chips according to claim 1, characterized in that, In step (2), the viscosity is 0.3 dL / g at the initial stage of polycondensation and 0.5 dL / g at the middle stage of polycondensation. The mass ratio of the remaining coagulation barrier agent, 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 halogen-free flame-retardant PET polyester chips according to claim 1, characterized in that, The ratio of red phosphorus, hydrolysate, CuCO3 and KH560 in Q1 is 10g:200mL:2.5g:(1.8-2)g.

4. The method for preparing halogen-free flame-retardant PET polyester chips according to claim 1, characterized in that, The ratio of coupling complex, ethanol, polyvinylpyrrolidone and sol in Q2 is 10g:180mL:0.6g:(30-35)mL; the thickness of the TiO2 layer of the whitening flame retardant is 30-50nm.

5. The method for preparing halogen-free flame-retardant PET polyester chips according to claim 1, characterized in that, The reflux reaction temperature in Q3 is 110-115℃, and the reflux reaction time is 4-5h.

6. The method for preparing halogen-free flame-retardant PET polyester chips according to claim 1, characterized in that, The ratio of melamine, biphenylphosphine 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.

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

8. The method for preparing halogen-free flame-retardant PET polyester chips according to claim 1, characterized in that, The ratio of organic compound, ethanol, polyvinylpyrrolidone and sol in S3 is 10g:180mL:0.6g:(30-35)mL; the ratio of coating flame retardant, KH560 and hydrolysate is 10g:0.5g:100mL.

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