A high oxygen index blended flame-retardant polyester masterbatch, its preparation method and application

Abstract

This invention provides a high oxygen index blended flame-retardant polyester masterbatch, its preparation method, and its application, belonging to the field of material blending and processing. The high oxygen index blended flame-retardant polyester masterbatch of this invention comprises the following components: PET, an intumescent flame retardant, a phosphorus-based flame retardant, a heat stabilizer, and a dispersant, in a mass ratio of (60-70):(15-25):(5-15):1:2. By precisely proportioning and shearing the high-efficiency flame retardant and the polyester carrier in a twin-screw extruder, a specialized masterbatch with highly dispersed flame-retardant components is obtained. During the process, vacuum temperature control, immediate sealing, and discarding of granulation head and tail materials further improve the compositional consistency and performance reliability of the final masterbatch product.

Description

Technical Field

[0001] This invention belongs to the field of material blending and processing, specifically relating to a high oxygen index blended flame-retardant polyester masterbatch, its preparation method, and its application. Background Technology

[0002] Polyethylene terephthalate (PET) is the world's largest-capacity and most widely used thermoplastic polyester material, possessing excellent mechanical, thermal, and heat-setting properties. It has become the most widely used and consumed fiber material in China. However, PET is highly flammable, with a limiting oxygen index of only 21%-22%. During combustion, it releases a large amount of heat and smoke, producing severe dripping. Statistics show that most fires are related to the combustion-supporting properties of textile materials, posing a significant threat to people's property and lives. Therefore, flame-retardant and anti-dripping modification of PET is of great significance.

[0003] Currently, flame retardant modification of PET is mainly divided into two methods: blending and copolymerization. However, when using copolymerization for flame retardant modification, the modifying unit may decompose under the high-temperature conditions of polymer synthesis, or be accompanied by side reactions, and may also have a certain adverse effect on the performance of the fiber. Patent CN120738787A discloses a flame retardant polyester fiber and its preparation method, which is prepared by using polyester chips, antioxidants and montmorillonite-based flame retardant polyester masterbatch. Although the flame retardant effect is good, the flame retardant synthesis process is complex and costly. Its preparation requires four steps: acidification, silanization, organic small molecule synthesis and grafting, involving multiple reactions, washing, centrifugation and drying. The cumbersome process leads to a significant increase in energy consumption, time and labor costs. The raw materials used, such as aminosilane coupling agents and 3-aminophenylboronic acid, are also much more expensive than ordinary flame retardants. Patent CN118516780A discloses a method for preparing flame-retardant polyester fiber. The method first reacts ammonium polyphosphate, hydroxybenzaldehyde, aniline and dicyandiamide, and obtains a surface-modified ammonium polyphosphate flame retardant through vacuum distillation and drying. Then, it is melt-blended and granulated with polyester powder to form a masterbatch. Finally, it is spun with polyester chips to obtain fiber. Although the product can achieve V0 flame retardancy and no dripping, its optimal limiting oxygen index (LOI) is 32.5%, which is only slightly higher than the threshold of high flame retardancy level (LOI>30%). The advantage is not significant. Considering that its preparation process involves multiple chemical reactions and fine post-processing, the process is complex and costly, and it is difficult to scale up industrially. Therefore, its limited performance improvement may lack sufficient competitiveness in terms of technology and economy. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a high oxygen index blended flame-retardant polyester masterbatch, its preparation method, and its applications. The objective of this invention is to solve the problems of delaying ignition time, suppressing heat release rate, and maintaining char layer structural integrity under extreme fire conditions by constructing a synergistic flame-retardant system with a condensed phase-gas phase dual flame-retardant effect through the compounding of intumescent flame retardants and phosphorus-based flame retardants. Another objective of this invention is to provide reliable moisture protection for subsequent processes through continuous operation with vacuum temperature control and immediate sealing, and by discarding granulation head and tail materials, thereby precisely improving the compositional consistency and performance reliability of the final masterbatch product.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: On one hand, the present invention provides a high oxygen index blended flame retardant polyester masterbatch, comprising the following components: PET, intumescent flame retardant, phosphorus-based flame retardant, heat stabilizer, and dispersant, in a mass ratio of (60-70): (15-25): (5-15): 1: 2.

[0006] This invention introduces a combination of phosphorus- and sulfur-containing polymeric intumescent flame retardants with phosphorus-based flame retardants to construct a highly efficient synergistic system for dual flame retardancy in the condensed phase and gas phase. Utilizing the synergistic effect of phosphorus and sulfur in the intumescent flame retardant, a dense and stable intumescent char layer is promoted in the condensed phase. The phosphorus-based flame retardant undergoes early thermal decomposition at a lower temperature during the initial stage of combustion, and its acidic decomposition products provide an initial acidic environment for the reaction between the acid source and carbon source in the intumescent flame retardant, significantly reducing the char formation activation energy and promoting earlier and faster cross-linking and char formation reactions of the polymer matrix, thereby constructing a more stable and dense early protective layer. Simultaneously, the phosphorus-based flame retardant releases phosphorus-containing free radicals during decomposition, exerting a gas-phase flame retardant effect and efficiently quenching key active free radicals in the flame. This invention precisely enhances the reaction kinetics of intumescent flame retardants in the initial stage and their gas-phase intervention capability throughout the entire combustion cycle by utilizing the pre-reaction effect and gas-phase extinguishing effect of phosphorus-based flame retardants. This significantly enhances the strength and density of the char layer, substantially improves flame retardant efficiency through gas-solid two-phase synergy, more effectively delays ignition time, suppresses heat release rate, and ensures the integrity of the char layer structure under extreme fire conditions. Because the high oxygen index blended flame-retardant polyester masterbatch of this invention possesses a highly efficient synergistic system of condensed phase-gas phase dual flame retardancy, it can achieve a high limiting oxygen index and UL-94 V-0 flame retardancy rating with a relatively low total addition amount, while effectively suppressing dripping and maintaining good mechanical properties and processing stability of the matrix.

[0007] Preferably, the intumescent flame retardant is one or more of PSPPP (polyphenylphosphonic diphenyl sulfone ester), PPS (polyphenyl sulfide), and RDP (resorcinol tetraphenyl diphosphate); the mass of the intumescent flame retardant is 10-30% of the total mass of the polyester. This invention introduces phosphorus- and sulfur-containing polymeric intumescent flame retardants to exert a highly efficient flame-retardant effect in the condensed phase. The acidic components catalyze dehydration and cross-linking reactions in the polymer matrix during the initial stage of combustion, promoting graphitization and converting combustible pyrolysis products into a solid char layer, thereby improving the material's char-forming ability and thermal stability. When heated, it forms a dense, porous foam char layer on the material surface, effectively isolating heat and oxygen and inhibiting the escape of combustible gases, thus achieving excellent flame retardancy and smoke suppression. This char layer also possesses good strength, significantly improving the material's anti-dripping performance and preventing secondary disasters caused by burning drips.

[0008] Preferably, the phosphorus-based flame retardant is one or more of diethylaluminum hypophosphite, alkylaluminum hypophosphite, aluminum polyphosphate, and aluminum methylphosphate; the mass of the phosphorus-based flame retardant is 5-20% of the total mass of the polyester. This invention utilizes the thermal stability of the phosphorus-based flame retardant to ensure that it does not decompose prematurely during high-temperature processing, thus maintaining long-lasting flame retardant performance. When the phosphorus-based flame retardant decomposes, the generated water vapor and other non-flammable gases can dilute the concentration of flammable gases and carry away some heat; simultaneously, the char layer structure it promotes can effectively prevent dripping and avoid secondary fire spread.

[0009] Preferably, the heat stabilizer is a hindered phenolic antioxidant and triphenyl phosphite; the mass ratio of the hindered phenolic antioxidant to triphenyl phosphite is 1:2; and the mass of the heat stabilizer is 1% of the total mass of the polyester.

[0010] Preferably, the dispersant is one or more of fatty acid dispersants, waxes, and phosphonates; the mass of the dispersant is 2% of the total mass of the polyester.

[0011] Preferably, the dispersant is oxidized polyethylene wax.

[0012] On the other hand, the present invention provides a method for preparing a high oxygen index blended flame-retardant polyester masterbatch, comprising the following steps: S1: After vacuum drying and pressure cooling of PET, intumescent flame retardant and phosphorus flame retardant for 4 hours, they are mixed with heat stabilizer and dispersant and sealed in a nitrogen-filled sealed space. S2: The mixture is fed into the screw hopper for granulation. The temperature is controlled in eight zones of the screw to obtain high oxygen index blended flame retardant polyester masterbatch.

[0013] This invention successfully prepared a special masterbatch with highly dispersed flame retardant components by precisely proportioning and shearing the high-efficiency flame retardant with a polyester carrier in a twin-screw extruder.

[0014] Preferably, in step S1, PET is dried in a vacuum oven for ≥12 hours at a temperature of 120°C and a vacuum degree of -0.08 to -0.1 MPa; the intumescent flame retardant is dried in a vacuum oven for ≥8-12 hours at a temperature of 60-80°C and a vacuum degree of -0.08 to -0.1 MPa; and the phosphorus-based flame retardant is dried in a vacuum oven for ≥12 hours at a temperature of 100±10°C and a vacuum degree of -0.08 to -0.1 MPa. This invention creates a dry processing environment through vacuum temperature control, immediate sealing, and nitrogen protection, ensuring the dryness of the materials and providing reliable moisture protection for subsequent processes.

[0015] Preferably, in step S2, the temperature control in the eight zones from the screw inlet to the extruder die is as follows: Zone 1: 220-235℃; Zone 2: 225-240℃; Zone 3: 225-240℃; Zone 4: 235-250℃; Zone 5: 245-255℃; Zone 6: 235-245℃; Zone 7: 240-255℃; and Die head temperature: 240-255℃. During granulation, the produced masterbatch is air-cooled. The first 500g of masterbatch at the start of granulation and the last 500g of masterbatch at the end of granulation are not included in the final masterbatch production. This invention, by discarding the head and tail materials of granulation, eliminates unstable components caused by equipment residue and production transition stages, further precisely improving the compositional consistency and performance reliability of the final masterbatch product.

[0016] On the other hand, the present invention provides an application of the high oxygen index blended flame retardant polyester masterbatch or the high oxygen index blended flame retardant polyester masterbatch obtained by the above preparation method in polyester fiber fabrics.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention provides an initial acidic environment for the reaction between the acid source and carbon source in intumescent flame retardants through the acidic decomposition products of phosphorus-based flame retardants. This reduces the char activation energy, initiates a pre-crosslinking reaction, and promotes the formation of a stable and dense early protective layer. This results in a char layer with good strength and improved anti-dripping properties. The invention utilizes the phosphorus-containing free radicals released during the decomposition of phosphorus-based flame retardants to exert a gas-phase flame-retardant effect. This quenches key active free radicals in the flame, dilutes the concentration of combustible gases, reduces the generated heat, and further enhances the gas-phase intervention capability of intumescent flame retardants throughout the entire combustion cycle. Furthermore, this invention can significantly improve the limiting oxygen index of the base polyester material and achieve a UL-94 V-0 flame-retardant rating by adding only a small amount of the highly dispersed flame-retardant component in a dedicated masterbatch during subsequent spinning or molding processes. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0019] General Implementation Examples A high oxygen index blended flame-retardant polyester masterbatch comprises the following components: PET, intumescent flame retardant, phosphorus-based flame retardant, heat stabilizer, and dispersant, in a mass ratio of (60-70): (15-25): (5-15): 1: 2.

[0020] In some embodiments of the present invention, the intumescent flame retardant is one or more of PSPPP, PPS, and RDP; the mass of the intumescent flame retardant is 10-30% of the total mass of the polyester.

[0021] In some preferred embodiments of the present invention, the intumescent flame retardant is PSPPP.

[0022] In some embodiments of the present invention, the phosphorus-based flame retardant is one or more of diethyl aluminum hypophosphite, alkyl aluminum hypophosphite, aluminum polyphosphate, and aluminum methyl phosphate; the mass of the phosphorus-based flame retardant is 5-20% of the total mass of the polyester.

[0023] In some embodiments of the present invention, the heat stabilizer is a hindered phenolic antioxidant and triphenyl phosphite; the mass ratio of the hindered phenolic antioxidant to triphenyl phosphite is 1:2; and the mass of the heat stabilizer is 1% of the total mass of the polyester.

[0024] In some embodiments of the present invention, the dispersant is one or more of fatty acid dispersants, waxes, and phosphonates; the mass of the dispersant is 2% of the total mass of the polyester.

[0025] In some preferred embodiments of the present invention, the dispersant is oxidized polyethylene wax.

[0026] A method for preparing a high oxygen index blended flame-retardant polyester masterbatch includes the following steps: S1: After vacuum drying and pressure cooling of PET, intumescent flame retardant and phosphorus flame retardant for 4 hours, they are mixed with heat stabilizer and dispersant and sealed in a nitrogen-filled sealed space. S2: The mixture is fed into the screw hopper for granulation. The temperature is controlled in eight zones of the screw to obtain high oxygen index blended flame retardant polyester masterbatch.

[0027] In some embodiments of the present invention, in step S1, PET is dried in a vacuum oven for ≥12 hours at a drying temperature of 120°C and a vacuum degree of -0.08 to -0.1 MPa; the intumescent flame retardant is dried in a vacuum oven for ≥8-12 hours at a drying temperature of 60-80°C and a vacuum degree of -0.08 to -0.1 MPa; and the phosphorus-based flame retardant is dried in a vacuum oven for ≥12 hours at a drying temperature of 100±10°C and a vacuum degree of -0.08 to -0.1 MPa.

[0028] In some embodiments of the present invention, in step S2, the masterbatch produced is subjected to air cooling during the granulation process, and the first 500g of masterbatch at the start of granulation and the last 500g of masterbatch at the end of granulation are not included in the total masterbatch produced.

[0029] In some embodiments of the present invention, in S2, the temperature control of the eight zones from the screw inlet to the extruder die is as follows: Zone 1 temperature 220-235℃, Zone 2 temperature 225-240℃, Zone 3 temperature 225-240℃, Zone 4 temperature 235-250℃, Zone 5 temperature 245-255℃, Zone 6 temperature 235-245℃, Zone 7 temperature 240-255℃, and Die head temperature 240-255℃.

[0030] The high oxygen index blended flame-retardant polyester masterbatch obtained by this invention was subjected to spinning or molding tests. The test results showed that it can significantly improve the limiting oxygen index, reaching 40% or more, and the vertical burning droplet number is less than 10.

[0031] Example 1 A method for preparing a high oxygen index blended flame-retardant polyester masterbatch includes the following steps: S1: Conventional PET is dried in a vacuum oven for 12 hours at a temperature of 120℃ and a vacuum degree of -0.08 to -0.1 MPa; intumescent flame retardant PSPPP is dried in a vacuum oven for 12 hours at a temperature of 60-80℃ and a vacuum degree of -0.08 to -0.1 MPa; phosphorus-based flame retardant diethyl aluminum hypophosphite is dried in a vacuum oven for 12 hours at a temperature of 100±10℃ and a vacuum degree of -0.08 to -0.1 MPa. S2: PET, PSPPP, and aluminum diethylphosphite are vacuum dried and then kept under pressure and cooled for 4 hours. They are then mixed with hindered phenolic antioxidants, triphenyl phosphite, and oxidized polyethylene wax and sealed in a nitrogen-filled sealed space to obtain a mixture. The mass ratio of PET, PSPPP, aluminum diethylphosphite, heat stabilizer, and dispersant is 67:20:10:1:2. The stabilizer is hindered phenolic antioxidant and triphenyl phosphite, with a mass ratio of 1:2. The dispersant is oxidized polyethylene wax. S3: The temperature control of the eight zones from the screw inlet to the extruder die is as follows: Zone 1: 225℃, Zone 2: 230℃, Zone 3: 230℃, Zone 4: 232℃, Zone 5: 238℃, Zone 6: 240℃, Zone 7: 235℃, and Die head: 235℃. The mixed material is fed into the screw hopper in equal amounts multiple times from a closed space for granulation. The screw speed is 150 rpm for the main machine and 20 Hz for the main feed, resulting in high oxygen index blended flame-retardant polyester masterbatch. During the granulation process, the masterbatch is air-cooled. The first 500g of masterbatch at the beginning of granulation and the last 500g of masterbatch at the end of granulation are not counted in the total masterbatch produced.

[0032] Example 2 A method for preparing a high oxygen index blended flame-retardant polyester masterbatch includes the following steps: S1: Conventional PET is dried in a vacuum oven for 12 hours at a temperature of 120℃ and a vacuum degree of -0.08 to -0.1 MPa; intumescent flame retardant PSPPP is dried in a vacuum oven for 12 hours at a temperature of 60-80℃ and a vacuum degree of -0.08 to -0.1 MPa; phosphorus-based flame retardant diethyl aluminum hypophosphite is dried in a vacuum oven for 12 hours at a temperature of 100±10℃ and a vacuum degree of -0.08 to -0.1 MPa. S2: PET, PSPPP, and aluminum diethylphosphite are vacuum dried and then kept under pressure and cooled for 4 hours. They are then mixed with hindered phenolic antioxidants, triphenyl phosphite, and oxidized polyethylene wax and sealed in a nitrogen-filled sealed space to obtain a mixture. The mass ratio of PET, PSPPP, aluminum diethylphosphite, heat stabilizer, and dispersant is 67:25:5:1:2. The stabilizer is hindered phenolic antioxidant and triphenyl phosphite, with a mass ratio of 1:2. The dispersant is oxidized polyethylene wax. S3: The temperature control of the eight zones from the screw inlet to the extruder die is as follows: Zone 1: 225℃, Zone 2: 230℃, Zone 3: 230℃, Zone 4: 232℃, Zone 5: 238℃, Zone 6: 240℃, Zone 7: 235℃, and Die head: 235℃. The mixed material is fed into the screw hopper in equal amounts multiple times from a closed space for granulation. The screw speed is 150 rpm for the main machine and 20 Hz for the main feed, resulting in high oxygen index blended flame-retardant polyester masterbatch. During the granulation process, the masterbatch is air-cooled. The first 500g of masterbatch at the beginning of granulation and the last 500g of masterbatch at the end of granulation are not counted in the total masterbatch produced.

[0033] Example 3 A method for preparing a high oxygen index blended flame-retardant polyester masterbatch includes the following steps: S1: Conventional PET is dried in a vacuum oven for 12 hours at a temperature of 120℃ and a vacuum degree of -0.08 to -0.1 MPa; intumescent flame retardant PSPPP is dried in a vacuum oven for 12 hours at a temperature of 60-80℃ and a vacuum degree of -0.08 to -0.1 MPa; phosphorus-based flame retardant diethyl aluminum hypophosphite is dried in a vacuum oven for 12 hours at a temperature of 100±10℃ and a vacuum degree of -0.08 to -0.1 MPa. S2: PET, PSPPP, and aluminum diethylphosphite are vacuum dried and then kept under pressure and cooled for 4 hours. They are then mixed with hindered phenolic antioxidants, triphenyl phosphite, and oxidized polyethylene wax and sealed in a nitrogen-filled sealed space to obtain a mixture. The mass ratio of PET, PSPPP, aluminum diethylphosphite, heat stabilizer, and dispersant is 67:15:15:1:2. The stabilizer is hindered phenolic antioxidant and triphenyl phosphite, with a mass ratio of 1:2. The dispersant is oxidized polyethylene wax. S3: The temperature control of the eight zones from the screw inlet to the extruder die is as follows: Zone 1: 225℃, Zone 2: 230℃, Zone 3: 230℃, Zone 4: 232℃, Zone 5: 238℃, Zone 6: 240℃, Zone 7: 235℃, and Die head: 235℃. The mixed material is fed into the screw hopper in equal amounts multiple times from a closed space for granulation. The screw speed is 150 rpm for the main machine and 20 Hz for the main feed, resulting in high oxygen index blended flame-retardant polyester masterbatch. During the granulation process, the masterbatch is air-cooled. The first 500g of masterbatch at the beginning of granulation and the last 500g of masterbatch at the end of granulation are not counted in the total masterbatch produced.

[0034] Example 4 A method for preparing a high oxygen index blended flame-retardant polyester masterbatch includes the following steps: S1: Conventional PET is dried in a vacuum oven for 12 hours at a temperature of 120℃ and a vacuum degree of -0.08 to -0.1 MPa; intumescent flame retardant PPS is dried in a vacuum oven for 12 hours at a temperature of 60-80℃ and a vacuum degree of -0.08 to -0.1 MPa; phosphorus-based flame retardant diethyl aluminum hypophosphite is dried in a vacuum oven for 12 hours at a temperature of 100±10℃ and a vacuum degree of -0.08 to -0.1 MPa. S2: PET, PPS, and aluminum diethylphosphite were vacuum dried and then kept under pressure and cooled for 4 hours. They were then mixed with hindered phenolic antioxidants, triphenyl phosphite, and oxidized polyethylene wax and sealed in a nitrogen-filled sealed space to obtain a mixture. The mass ratio of PET, PPS, aluminum diethylphosphite, heat stabilizer, and dispersant was 67:20:10:1:2. The stabilizer consisted of hindered phenolic antioxidants and triphenyl phosphite in a mass ratio of 1:2. The dispersant was oxidized polyethylene wax. S3: The temperature control of the eight zones from the screw inlet to the extruder die is as follows: Zone 1: 225℃, Zone 2: 230℃, Zone 3: 230℃, Zone 4: 232℃, Zone 5: 238℃, Zone 6: 240℃, Zone 7: 235℃, and Die head: 235℃. The mixed material is fed into the screw hopper in equal amounts multiple times from a closed space for granulation. The screw speed is 150 rpm for the main machine and 20 Hz for the main feed, resulting in high oxygen index blended flame-retardant polyester masterbatch. During the granulation process, the masterbatch is air-cooled. The first 500g of masterbatch at the beginning of granulation and the last 500g of masterbatch at the end of granulation are not counted in the total masterbatch produced.

[0035] Example 5 A method for preparing a high oxygen index blended flame-retardant polyester masterbatch includes the following steps: S1: Conventional PET is dried in a vacuum oven for 12 hours at a temperature of 120℃ and a vacuum degree of -0.08 to -0.1 MPa; intumescent flame retardant RDP is dried in a vacuum oven for 12 hours at a temperature of 60-80℃ and a vacuum degree of -0.08 to -0.1 MPa; phosphorus-based flame retardant diethyl aluminum hypophosphite is dried in a vacuum oven for 12 hours at a temperature of 100±10℃ and a vacuum degree of -0.08 to -0.1 MPa. S2: PET, RDP, and aluminum diethylphosphite are vacuum dried and then kept under pressure and cooled for 4 hours. They are then mixed with hindered phenolic antioxidants, triphenyl phosphite, and oxidized polyethylene wax and sealed in a nitrogen-filled sealed space to obtain a mixture. The mass ratio of PET, RDP, aluminum diethylphosphite, heat stabilizer, and dispersant is 67:20:10:1:2. The stabilizer is hindered phenolic antioxidant and triphenyl phosphite, with a mass ratio of 1:2. The dispersant is oxidized polyethylene wax. S3: The temperature control of the eight zones from the screw inlet to the extruder die is as follows: Zone 1: 225℃, Zone 2: 230℃, Zone 3: 230℃, Zone 4: 232℃, Zone 5: 238℃, Zone 6: 240℃, Zone 7: 235℃, and Die head: 235℃. The mixed material is fed into the screw hopper in equal amounts multiple times from a closed space for granulation. The screw speed is 150 rpm for the main machine and 20 Hz for the main feed, resulting in high oxygen index blended flame-retardant polyester masterbatch. During the granulation process, the masterbatch is air-cooled. The first 500g of masterbatch at the beginning of granulation and the last 500g of masterbatch at the end of granulation are not counted in the total masterbatch produced.

[0036] Comparative Example 1 A method for preparing polyester masterbatch includes the following steps: S1: Dry conventional PET in a vacuum oven for 12 hours at a temperature of 120°C and a vacuum degree of -0.08 to -0.1 MPa; dry phosphorus-based flame retardant diethyl aluminum hypophosphite in a vacuum oven for 12 hours at a temperature of 100 ± 10°C and a vacuum degree of -0.08 to -0.1 MPa. S2: PET and aluminum diethyl phosphite are vacuum dried and then kept under pressure and cooled for 4 hours. They are then mixed with hindered phenolic antioxidants, triphenyl phosphite, and oxidized polyethylene wax and sealed in a nitrogen-filled sealed space to obtain a mixture. The mass ratio of PET, PSPPP, aluminum diethyl phosphite, heat stabilizer, and dispersant is 67:10:1:2. The stabilizer is hindered phenolic antioxidant and triphenyl phosphite, with a mass ratio of 1:2. The dispersant is oxidized polyethylene wax. S3: The temperature control of the eight zones from the screw inlet to the extruder die is as follows: Zone 1: 225℃, Zone 2: 230℃, Zone 3: 230℃, Zone 4: 232℃, Zone 5: 238℃, Zone 6: 240℃, Zone 7: 235℃, and Die head: 235℃. The mixed material is fed into the screw hopper in equal amounts multiple times from a closed space for granulation. The screw speed is 150 rpm for the main machine and 20 Hz for the main feed, to obtain polyester masterbatch. During the granulation process, the masterbatch is air-cooled. The first 500g of masterbatch at the beginning of granulation and the last 500g of masterbatch at the end of granulation are not counted in the total masterbatch produced.

[0037] Comparative Example 2 A method for preparing polyester masterbatch includes the following steps: S1: Conventional PET is dried in a vacuum oven for 12 hours at a temperature of 120℃ and a vacuum degree of -0.08 to -0.1 MPa; intumescent flame retardant PSPPP is dried in a vacuum oven for 12 hours at a temperature of 60-80℃ and a vacuum degree of -0.08 to -0.1 MPa; phosphorus-based flame retardant diethyl aluminum hypophosphite is dried in a vacuum oven for 12 hours at a temperature of 100±10℃ and a vacuum degree of -0.08 to -0.1 MPa. S2: PET, PSPPP, and aluminum diethylphosphite are vacuum dried and then kept under pressure and cooled for 4 hours. They are then mixed with hindered phenolic antioxidants, triphenyl phosphite, and oxidized polyethylene wax and sealed in a nitrogen-filled sealed space to obtain a mixture. The mass ratio of PET, PSPPP, aluminum diethylphosphite, heat stabilizer, and dispersant is 67:5:25:1:2. The stabilizer is hindered phenolic antioxidant and triphenyl phosphite, with a mass ratio of 1:2. The dispersant is oxidized polyethylene wax. S3: The temperature control of the eight zones from the screw inlet to the extruder die is as follows: Zone 1: 225℃, Zone 2: 230℃, Zone 3: 230℃, Zone 4: 232℃, Zone 5: 238℃, Zone 6: 240℃, Zone 7: 235℃, and Die head: 235℃. The mixed material is fed into the screw hopper in equal amounts multiple times from a closed space for granulation. The screw speed is 150 rpm for the main machine and 20 Hz for the main feed, to obtain polyester masterbatch. During the granulation process, the masterbatch is air-cooled. The first 500g of masterbatch at the beginning of granulation and the last 500g of masterbatch at the end of granulation are not counted in the total masterbatch produced.

[0038] Comparative Example 3 A method for preparing polyester masterbatch includes the following steps: S1: Conventional PET is dried in a vacuum oven for 12 hours at a temperature of 120℃ and a vacuum degree of -0.08 to -0.1 MPa; intumescent flame retardant PSPPP is dried in a vacuum oven for 12 hours at a temperature of 60-80℃ and a vacuum degree of -0.08 to -0.1 MPa; phosphorus-based flame retardant diethyl aluminum hypophosphite is dried in a vacuum oven for 12 hours at a temperature of 100±10℃ and a vacuum degree of -0.08 to -0.1 MPa. S2: PET, PSPPP, and aluminum diethylphosphite are vacuum dried and then kept under pressure and cooled for 4 hours. They are then mixed with hindered phenolic antioxidants, triphenyl phosphite, and oxidized polyethylene wax and sealed in a nitrogen-filled sealed space to obtain a mixture. The mass ratio of PET, PSPPP, aluminum diethylphosphite, heat stabilizer, and dispersant is 67:10:20:1:2. The stabilizer is hindered phenolic antioxidant and triphenyl phosphite, with a mass ratio of 1:2. The dispersant is oxidized polyethylene wax. S3: The temperature control of the eight zones from the screw inlet to the extruder die is as follows: Zone 1: 225℃, Zone 2: 230℃, Zone 3: 230℃, Zone 4: 232℃, Zone 5: 238℃, Zone 6: 240℃, Zone 7: 235℃, and Die head: 235℃. The mixed material is fed into the screw hopper in equal amounts multiple times from a closed space for granulation. The screw speed is 150 rpm for the main machine and 20 Hz for the main feed, to obtain polyester masterbatch. During the granulation process, the masterbatch is air-cooled. The first 500g of masterbatch at the beginning of granulation and the last 500g of masterbatch at the end of granulation are not counted in the total masterbatch produced.

[0039] Comparative Example 4 A method for preparing polyester masterbatch includes the following steps: S1: Dry conventional PET in a vacuum oven for 12 hours at a temperature of 120°C and a vacuum degree of -0.08 to -0.1 MPa; dry intumescent flame retardant PSPPP in a vacuum oven for 12 hours at a temperature of 60-80°C and a vacuum degree of -0.08 to -0.1 MPa. S2: After vacuum drying and pressure-cooling for 4 hours, PET and PSPPP are mixed with hindered phenolic antioxidants, triphenyl phosphite, and oxidized polyethylene wax and sealed in a nitrogen-filled sealed space to obtain a mixture. The mass ratio of PET, PSPPP, heat stabilizer, and dispersant is 67:5:1:2. The stabilizer is hindered phenolic antioxidant and triphenyl phosphite in a mass ratio of 1:2. The dispersant is oxidized polyethylene wax. S3: The temperature control of the eight zones from the screw inlet to the extruder die is as follows: Zone 1: 225℃, Zone 2: 230℃, Zone 3: 230℃, Zone 4: 232℃, Zone 5: 238℃, Zone 6: 240℃, Zone 7: 235℃, and Die head: 235℃. The mixed material is fed into the screw hopper in equal amounts multiple times from a closed space for granulation. The screw speed is 150 rpm for the main machine and 20 Hz for the main feed, to obtain polyester masterbatch. During the granulation process, the masterbatch is air-cooled. The first 500g of masterbatch at the beginning of granulation and the last 500g of masterbatch at the end of granulation are not counted in the total masterbatch produced.

[0040] Test case The masterbatches obtained in Examples 1-5 and Comparative Examples 1-4 were respectively subjected to injection molding and spinning, including the following steps: (1) The obtained polyester masterbatch was dried in a vacuum oven for 12 hours at a drying temperature of 120°C; conventional PET was dried in a vacuum drum for 12 hours at a drying temperature of 120°C. (2) The dried masterbatch was mixed evenly with conventional PET and the sample was prepared by a small injection molding machine at an injection temperature of 245℃ to obtain the test sample; the amount of dried masterbatch added was 6% by mass percentage. (3) The dried masterbatch was mixed evenly with conventional PET and spun through a small spinning machine. The injection molding temperature was 283℃ and the spinning specification was 135dtex / 48f to obtain high oxygen index flame retardant polyester fiber. The amount of dried masterbatch added was 6% by mass percentage. The following testing methods are included: (1) The vertical burning of the specimens was performed according to GB / T 2408-2021 "Determination of the Burning Performance of Plastics - Horizontal and Vertical Methods"; (2) The limiting oxygen index of the fiber was tested according to FZ / T 50017-2011 "Test Method for Flame Retardant Properties of Polyester Fiber - Oxygen Index Method"; The test results are shown in Table 1.

[0041] Table 1 As can be seen from the test results in Table 1, the present invention can significantly improve the limiting oxygen index by adding only a small amount of the prepared highly dispersed flame retardant polyester masterbatch during the subsequent spinning or molding process, so that the limiting oxygen index can reach 34-42%, the vertical burning droplet number is 2-10, and the UL-94 V-0 flame retardant effect can be achieved.

[0042] According to the test results, Comparative Example 1, without the addition of an intumescent flame retardant, showed a significant decrease in the limiting oxygen index and a significant increase in the number of vertically burning droplets. This is because the intumescent flame retardant lacks the highly efficient flame-retardant effect that the intumescent flame retardant can exert in the condensed phase. When heated, the intumescent flame retardant can form a dense, porous foam char layer on the material surface to isolate heat and oxygen, preventing the escape of combustible gases and thus improving flame-retardant performance. Furthermore, phosphorus-based flame retardants can form a dual flame-retardant system of condensed phase and gas phase, capturing and quenching key active free radicals in the flame, promoting the cross-linking and charring reaction of the polymer matrix, and effectively preventing the generation of droplets.

[0043] In Comparative Examples 2 and 3, the use of excessively low amounts of intumescent flame retardant and excessive amounts of phosphorus-based flame retardant resulted in a significant decrease in the limiting oxygen index and a significant increase in the number of melt droplets. Therefore, this invention, by controlling the component ratio in the high oxygen index blended flame-retardant polyester masterbatch, ensures that the content of phosphorus-based flame retardant is not higher than that of intumescent flame retardant. This effectively promotes the synergistic effect between flame-retardant components, guarantees the stability of the char layer, utilizes the non-combustible gases generated during decomposition to dilute the concentration of combustible gases, reduces heat, effectively delays ignition time, reduces the heat release rate, increases the limiting oxygen index, and reduces the number of melt droplets.

[0044] The test results of Comparative Example 4 show that, compared with Example 1 without the addition of phosphorus-based flame retardants, the limiting oxygen index is significantly reduced and the number of melt droplets increases. In high oxygen index blended flame-retardant polyester masterbatch, phosphorus-based flame retardants not only provide an acidic environment for the reaction between the acid source and carbon source in the intumescent flame retardant, reducing the char activation energy and initiating an earlier and faster pre-crosslinking reaction, thus promoting the formation of a more stable and denser early protective layer, but also act as a free radical scavenger released in the gas phase, inhibiting the occurrence of oxidation chain reactions. At the same time, by decomposing non-combustible gases, they reduce heat release and the concentration of combustible gases, maintaining a long-lasting flame-retardant effect.

[0045] According to the test results of Examples 1, 4 and 5, under the preferred flame retardant ratio, the use of PSPPP as a phosphorus-sulfur polymer intumescent flame retardant can further improve the limiting oxygen index and reduce the number of melt droplets in the ethical flame-retardant polyester.

Claims

1. A high oxygen index blended flame-retardant polyester masterbatch, characterized in that, It includes the following components: PET, intumescent flame retardant, phosphorus-based flame retardant, heat stabilizer, and dispersant, in a mass ratio of (60-70): (15-25): (5-15): 1:

2.

2. The high oxygen index blended flame-retardant polyester masterbatch according to claim 1, characterized in that, The intumescent flame retardant is one or more of PSPPP, PPS, and RDP; The intumescent flame retardant accounts for 10-30% of the total mass of the polyester.

3. A high oxygen index blended flame-retardant polyester masterbatch according to claim 1 or 2, characterized in that, The phosphorus-based flame retardant is one or more of diethyl aluminum hypophosphite, alkyl aluminum hypophosphite, aluminum polyphosphate, and aluminum methyl phosphate. The mass of the phosphorus-based flame retardant is 5-20% of the total mass of the polyester.

4. A high oxygen index blended flame-retardant polyester masterbatch according to claim 1 or 2, characterized in that, The heat stabilizer is a hindered phenolic antioxidant and triphenyl phosphite; The mass ratio of the hindered phenolic antioxidant to triphenyl phosphite is 1:2; The heat stabilizer is 1% of the total mass of the polyester.

5. The high oxygen index blended flame-retardant polyester masterbatch according to claim 1, characterized in that, The dispersant is one or more of fatty acid dispersants, waxes, and phosphonates; The mass of the dispersant is 2% of the total mass of the polyester.

6. A high oxygen index blended flame-retardant polyester masterbatch according to claim 1 or 5, characterized in that, The dispersant is oxidized polyethylene wax.

7. A method for preparing a high oxygen index blended flame-retardant polyester masterbatch, characterized in that, Includes the following steps: S1: After vacuum drying and pressure cooling of PET, intumescent flame retardant and phosphorus flame retardant for 4 hours, they are mixed with heat stabilizer and dispersant and sealed in a nitrogen-filled sealed space. S2: The mixture is fed into the screw hopper for granulation. The temperature is controlled in eight zones of the screw to obtain high oxygen index blended flame retardant polyester masterbatch.

8. The method for preparing a high oxygen index blended flame-retardant polyester masterbatch according to claim 7, characterized in that, In step S1, the PET is dried in a vacuum oven for ≥12 hours at a temperature of 120°C and a vacuum degree of -0.08 to -0.1 MPa. The intumescent flame retardant was dried in a vacuum oven for ≥8-12 hours at a temperature of 60-80℃ and a vacuum degree of -0.08~-0.1MPa. The phosphorus-based flame retardant was dried in a vacuum oven for ≥12 hours at a temperature of 100±10℃ and a vacuum degree of -0.08~-0.1MPa.

9. A method for preparing a high oxygen index blended flame-retardant polyester masterbatch according to claim 7 or 8, characterized in that, In S2, the temperature control of the eight zones from the screw inlet to the extruder die is as follows: Zone 1: 220-235℃; Zone 2: 225-240℃; Zone 3: 225-240℃; Zone 4: 235-250℃; Zone 5: 245-255℃; Zone 6: 235-245℃; Zone 7: 240-255℃; and Die head temperature: 240-255℃. During the granulation process, the masterbatch is subjected to air cooling. The first 500g of masterbatch at the start of granulation and the last 500g of masterbatch at the end of granulation are not included in the total masterbatch produced.

10. The application of a high oxygen index blended flame-retardant polyester masterbatch according to any one of claims 1-6 or a high oxygen index blended flame-retardant polyester masterbatch obtained by the preparation method according to any one of claims 7-9 in polyester fiber fabrics.

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