Flame-retardant anti-fouling copolymer nylon 6 as well as preparation method and application thereof

Abstract

The invention discloses flame-retardant anti-fouling copolymer nylon 6 and a preparation method and application thereof, and the preparation method comprises the following steps: adding a phosphorus-containing flame-retardant monomer, a silicon-containing reaction monomer, lactam, an initiator and a catalyst into a polymerization reaction kettle, and introducing nitrogen to replace air in the kettle; under the protection of nitrogen, firstly raising the temperature to 180-220 DEG C to carry out prepolymerization reaction, and then raising the temperature to 240-260 DEG C to carry out polymerization reaction; and after the polymerization reaction, removing water vapor in the system to react in a normal pressure state, then vacuumizing to react, filling nitrogen to recover to normal pressure after the reaction is finished, and discharging and cooling to obtain the flame-retardant and anti-fouling copolymer nylon 6. The phosphorus-containing comonomer and the silicon-containing comonomer are introduced into the copolymerized nylon, the intrinsic flame-retardant nylon material with high flame-retardant efficiency and permanent flame retardance is prepared through melt copolymerization at a relatively low introduction amount, and the intrinsic flame-retardant nylon material has certain hydrophobic and anti-fouling properties and also retains good mechanical properties and spinnability of the nylon material.

Description

Technical Field

[0001] The present invention relates to the field of polymer material synthesis, and in particular to a flame-retardant and anti-fouling copolymer nylon 6, a preparation method thereof, and an application thereof. Background Art

[0002] Polyamide (nylon), a thermoplastic polymer with repeating amide groups, is both an important engineering plastic and the second most popular synthetic fiber after polyester. It boasts excellent mechanical properties, thermal stability, oil resistance, wear resistance, and ease of processing and molding, making it widely used in various civil and industrial fields. Nylon 6 (PA6) is the most widely used nylon material, accounting for over 80% of total nylon consumption. However, its linear aliphatic structure makes it highly flammable, with an oxygen index of only 24%. The combustion process also releases large amounts of heat, accompanied by severe molten droplets that cause secondary damage. This significantly limits the application of nylon materials in a wide range of applications requiring fire protection. Therefore, flame-retardant modification of nylon materials is of great significance.

[0003] Currently, flame-retardant nylon 6 is primarily produced by physically adding flame retardants and blending them with a nylon base material. This often results in problems such as large amounts of flame retardant added, poor compatibility with the base material, and easy migration and precipitation. This leads to a decrease in the nylon's mechanical properties and a lack of sustained flame retardancy. For nylon 6 fiber, the large size and amount of flame retardants added also severely affect its spinnability. Only a small number of flame retardants are suitable for producing flame-retardant nylon 6 fiber on the market. Flame-retardant modification of nylon 6 can also be achieved by altering its molecular structure. This involves chemically modifying the material by copolymerizing reactive flame-retardant monomers with nylon monomers, covalently embedding the flame retardant molecules into the nylon molecular chain. The resulting flame-retardant nylon 6 not only has higher flame retardant efficiency, but also has the advantage of permanent flame retardancy without the flame retardant migrating or precipitating out, while also having minimal impact on the overall performance of the material itself. However, existing flame-retardant copolymerization technologies for nylon have issues with low thermal stability and significant steric hindrance. This significant steric hindrance, coupled with decomposition at high temperatures, leads to an imbalance in the acid-amine ratio of the copolymerized nylon, resulting in slow polymerization and low viscosity. Furthermore, the introduction of flame-retardant comonomers can negatively impact the crystallization properties of nylon, increasing its water absorption and making it susceptible to contamination. However, research in this area is relatively limited.

[0004] Patent CN112920410A discloses a phosphorus-silicon synergistic flame-retardant, anti-drip nylon 6 resin and its preparation method. This invention first caps a nylon 6 prepolymer with a phosphorus-based flame-retardant end-capping agent, then undergoes esterification and transesterification with a diol and a silicon-based flame retardant, respectively. The diol acts as a link to the silicon-based flame retardant, resolving the conflict between flame retardancy and anti-drip properties in flame-retardant nylon 6. This results in a flame-retardant nylon 6 with both excellent flame retardancy and anti-drip properties. However, the nylon 6 resin produced using this method suffers from low viscosity and poor spinnability, making it unsuitable for spinning applications.

[0005] Patent CN107501546A discloses a method for producing high-viscosity flame-retardant polyamide 6 by first performing a prepolymerization reaction and then adding the flame-retardant prepolymer in the middle or late stages of the polymerization process. This method overcomes the problems of low thermal stability of the flame retardant and low viscosity of the corresponding polymer. However, the method provided in this patent is complex and requires a high level of in-line piping and addition system, which is not conducive to the dispersion of the flame-retardant prepolymer. Summary of the Invention

[0006] The present invention aims to overcome the above-mentioned problems existing in the copolymerized flame-retardant nylon in the prior art and provides a flame-retardant and anti-fouling copolymerized nylon 6 and its preparation method and application. A phosphorus-containing comonomer and a silicon-containing comonomer are introduced into the copolymerized nylon. At a relatively low introduction amount, a high flame-retardant efficiency, permanent flame-retardant intrinsic flame-retardant nylon material is prepared by melt copolymerization. The material also has certain hydrophobic and anti-fouling properties while retaining the good mechanical properties and spinnability of the nylon material itself.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a method for preparing a flame retardant and anti-fouling copolymer nylon 6, comprising the following steps: A) adding a phosphorus-containing flame retardant monomer, a silicon-containing reactive monomer, a lactam, an initiator, and a catalyst into a polymerization reaction kettle, and introducing nitrogen to replace the air in the kettle; B) heating the mixture to 180-220° C. under nitrogen protection for prepolymerization, and then heating the mixture to 240-260° C. for polymerization; C) after the polymerization reaction, the water vapor in the system is removed to react to normal pressure, and then vacuum reaction is carried out. After the reaction is completed, nitrogen is filled to return to normal pressure, and the discharged material is cooled to obtain flame retardant and anti-fouling copolymer nylon 6; The structural formula of the phosphorus-containing flame retardant monomer is one or more of the following: The structural formula of the silicon-containing reactive monomer is:

[0008] The present invention introduces a phosphorus-containing flame-retardant monomer and a silicon-containing reactive monomer into nylon 6. The phosphorus-containing flame-retardant monomer and the silicon-containing reactive monomer are, respectively, a dicarboxyl phosphorus-containing reactive monomer and a diamino-terminated organosiloxane. The phosphorus-containing component plays the primary flame-retardant role, while the silicon-containing component plays an important auxiliary role as a flame-retardant synergist. Furthermore, the hydrophobicity of the silicon-containing component prevents the increased water absorption of flame-retardant nylon due to the destruction of its crystallinity, imparting a certain hydrophobicity to the material, significantly reducing its ability to bind stains, thereby imparting certain anti-fouling and self-cleaning properties. Furthermore, the material's easy cleanability is not limited by the number of washes. Compared to conventional single-component flame-retardant nylon copolymers, the phosphorus-silicon two-component flame-retardant nylon copolymers described in this invention offer higher flame retardancy: The phosphorus-containing component releases phosphorus-containing free radicals during combustion, exerting a gas-phase flame retardant effect while also generating phosphoric acid to promote carbonization. Furthermore, the silicon-containing component accumulates on the substrate surface during combustion, forming a dense and stable silicon-containing (primarily SiO2) carbon layer, which acts as a barrier and imparts smoke suppression properties to the flame-retardant material. Therefore, the phosphorus-silicon synergistic flame retardant approach reduces the overall amount of flame retardant components added, better preserving the material's original properties.

[0009] Furthermore, the present invention introduces a modified flame-retardant monomer by copolymerization, which can effectively avoid the precipitation and loss of flame retardants during later use. It has the advantages of being environmentally friendly and permanently flame-retardant, and avoids the disadvantages of poor mechanical properties and spinnability caused by poor compatibility of additive flame retardants. At the same time, the present invention adds a low-temperature prepolymerization process to avoid the decomposition of flame retardant monomers in a high-temperature polymerization environment, thereby overcoming the problems of slow polymerization and low viscosity of flame-retardant PA6 caused by the introduction of flame retardants. The relative viscosity of the copolymerized nylon can reach up to 2.6. Furthermore, when the present invention performs in-situ copolymerization of flame-retardant nylon, there is no need to prepare a flame-retardant prepolymer, and it can be added together with caprolactam. There is no need to modify the traditional nylon 6 production equipment, and the polymerization process is stable and controllable.

[0010] Preferably, in step A), the mass ratio of the phosphorus-containing flame retardant monomer, the silicon-containing reactive monomer, the lactam, the initiator and the catalyst is 0.01-0.99:0.01-0.99:1:0.02-0.1:0.002-0.01.

[0011] Preferably, the initiator in step A) is water or 6-aminocaproic acid; and the catalyst is selected from one or more of calcium phosphite, potassium phosphite, sodium phosphite, boric acid, and phosphoric acid.

[0012] Preferably, the prepolymerization reaction time in step B) is 0.5 to 2 hours; the polymerization reaction time is 1 to 2 hours, and the reaction pressure is 1.0 to 2.0 MPa.

[0013] Preferably, in step C), the reaction is carried out at normal pressure for 0.5 to 1 hour, and the reaction is carried out in vacuum for 0.5 to 3 hours.

[0014] In a second aspect, the present invention provides a flame retardant and anti-fouling copolymer nylon 6 prepared using the above-mentioned preparation method.

[0015] Preferably, the flame retardant and anti-fouling copolymer nylon 6 molecular structure includes the following structural units: (1) Wherein, R1 represents a C5 straight chain alkylene group; (2) Among them, the structure of R2 is (3) The structure of R3 is

[0016] Preferably, the molar ratio of the structural unit (2) to the structural unit (3) is 0.5-1.5:0.5-1.5; and the amount of the structural unit (2) is 1-99% of the amount of the structural unit (1).

[0017] Preferably, the relative viscosity of the flame-retardant and anti-fouling copolymer nylon 6 is 2.3 to 2.6, the vertical combustion grade is V-2 to V-0, and the limiting oxygen index is 24 to 34%.

[0018] In a third aspect, the present invention provides an application of the flame retardant and anti-fouling copolymer nylon 6, which is used to produce flame retardant and anti-fouling plastics or flame retardant and anti-fouling fibers, or as a flame retardant and anti-fouling masterbatch blended with other polyamide materials to produce flame retardant and anti-fouling nylon materials.

[0019] Therefore, the present invention has the following beneficial effects: (1) The present invention incorporates phosphorus-containing flame-retardant monomers and silicon-containing reactive monomers into the molecular chain of nylon by chemical copolymerization, effectively solving the problems of low flame retardant efficiency, easy precipitation of flame retardants, and deterioration of mechanical properties of blended flame-retardant nylon. The invention also achieves high-efficiency flame retardancy of PA6 at low flame retardant content through the synergistic effect of phosphorus and silicon. (2) The flame retardant and anti-fouling copolymer nylon 6 preparation method provided by the present invention adds a low-temperature prepolymerization process, thereby avoiding the decomposition of the flame retardant monomer in a high-temperature polymerization environment, thereby overcoming the problems of slow polymerization and low viscosity of flame retardant PA6 caused by the introduction of flame retardants. The relative viscosity of the copolymer nylon can reach up to 2.6; (3) The flame-retardant and anti-fouling copolymer nylon 6 provided by the present invention has a high flame retardant efficiency due to the synergistic effect of phosphorus and silicon in the phosphorus-containing and silicon-containing comonomers: that is, without the need to compound with other flame retardants or additives, the corresponding copolymer nylon can have an oxygen index greater than 28% at a relatively low addition amount (3-5wt%), becoming a flame-retardant material and passing the vertical combustion V-0 test; (4) The silicon-containing reactive monomer used in the present invention has a certain hydrophobic function, which can avoid the problem of increased water absorption of flame-retardant nylon due to the destruction of crystallinity, and can give flame-retardant nylon a certain degree of hydrophobicity, so that the binding ability of the material with stains is significantly reduced, thereby giving it a certain anti-fouling self-cleaning property, and the easy decontamination of the material is not limited by the number of washing times; (5) The phosphorus-containing and silicon-containing monomers used in the present invention are commercially available products and are easy to produce on a large scale, which is conducive to the scale-up production of the flame-retardant nylon. The preparation method is basically the same as the conventional method for synthesizing nylon, and there is no need to prepare a flame-retardant prepolymer. It can also be added together with caprolactam, avoiding the technical transformation and consumption of traditional nylon 6 production equipment. The operation is simple, the process is more mature, and it is suitable for industrial application. (6) No additional blended flame retardant synergist is added to the copolymer nylon prepared by the present invention, so no agglomerated particles are generated in the melt, and thus the copolymer nylon has good spinning processing performance. DETAILED DESCRIPTION

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

[0021] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0022] Overall embodiment: A method for preparing flame-retardant and anti-fouling copolymer nylon 6 comprises the following steps: A) adding a phosphorus-containing flame retardant monomer, a silicon-containing reactive monomer, a lactam, an initiator, and a catalyst into a polymerization reaction kettle, and introducing nitrogen to replace the air in the kettle; B) heating the mixture to 180-220° C. under nitrogen protection for prepolymerization, and then heating the mixture to 240-260° C. for polymerization; C) after the polymerization reaction, the water vapor in the system is removed to react to normal pressure, and then vacuum reaction is carried out. After the reaction is completed, nitrogen is filled to return to normal pressure, and the discharged material is cooled to obtain flame retardant and anti-fouling copolymer nylon 6; The structural formula of the phosphorus-containing flame retardant monomer is one or more of the following: The structural formula of the silicon-containing reactive monomer is:

[0023] As a specific embodiment, in step A), the mass ratio of the phosphorus-containing flame retardant monomer, the silicon-containing reactive monomer, the lactam, the initiator and the catalyst is 0.01-0.99:0.01-0.99:1:0.02-0.1:0.002-0.01.

[0024] As a specific embodiment, the initiator in step A) is water or 6-aminocaproic acid; the catalyst is selected from one or more of calcium phosphite, potassium phosphite, sodium phosphite, boric acid, and phosphoric acid.

[0025] As a specific implementation manner, the prepolymerization reaction time in step B) is 0.5 to 2 hours; the polymerization reaction time is 1 to 2 hours, and the reaction pressure is 1.0 to 2.0 MPa.

[0026] As a specific embodiment, in step C), the reaction is carried out at normal pressure for 0.5 to 1 hour, and the reaction is carried out in vacuum for 0.5 to 3 hours.

[0027] A flame-retardant and anti-fouling copolymer nylon 6 prepared using the above-mentioned preparation method, whose molecular structure includes the following structural units: (1) Wherein, R1 represents a C5 straight chain alkylene group; (2) Among them, the structure of R2 is (3) The structure of R3 is

[0028] As a specific embodiment, the molar ratio of structural unit (2) to structural unit (3) is 0.5-1.5:0.5-1.5; the number of structural unit (2) is 1-99% of the number of structural unit (1); preferably, the number of structural unit (2) is 1-20% of the number of structural unit (1); more preferably, the number of structural unit (2) is 1-10% of the number of structural unit (1); further preferably, the number of structural unit (2) is 3-5% of the number of structural unit (1).

[0029] As a specific implementation manner, the relative viscosity of the flame retardant and anti-fouling copolymer nylon 6 is 2.3 to 2.6, the vertical combustion grade is V-2 to V-0, and the limiting oxygen index is 24 to 34%.

[0030] As a specific embodiment, the FDY fiber made from the flame retardant and anti-fouling copolymer nylon 6 has a tensile strength of 4.0 to 4.8 cN / dtex and an elongation at break of 35% to 45%.

[0031] Example 1: A method for preparing flame-retardant and anti-fouling copolymer nylon 6, comprising the following steps: 1000g of caprolactam, 40g of deionized water, 30g of DDP, 21.53g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and 2g of sodium phosphite were weighed and added to a polymerization reactor. The air in the reactor was replaced with nitrogen. The reactor was stirred at 180°C for 1 hour, then heated to 240°C for 2 hours to carry out ring-opening polymerization. The pressure was then slowly released to ambient pressure, and the temperature was simultaneously raised to 260°C for 1 hour. The reaction was then slowly evacuated for 2 hours. After the reaction, nitrogen was added to return the pressure to ambient pressure. The product was then cooled and pelletized. The pellets were extracted with boiling water for 8 hours, with the water changed every hour. The product was dried in a vacuum oven at 90°C for 12 hours to obtain flame-retardant and anti-fouling copolymerized nylon 6 pellets, which were melt-spun into 70D / 24f flame-retardant nylon FDY fibers.

[0032] Example 2: A method for preparing flame-retardant and anti-fouling copolymer nylon 6, comprising the following steps: 1000g of caprolactam, 40g of deionized water, 30g of DPO, 22.43g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and 2g of sodium phosphite were weighed and added to a polymerization reactor. The air in the reactor was replaced with nitrogen. The reactor was stirred at 190°C for 1 hour, then heated to 240°C for 2 hours to carry out ring-opening polymerization. The pressure was then slowly released to ambient pressure, and the temperature was simultaneously raised to 250°C for 1 hour. The reaction was then slowly evacuated for 1 hour. After the reaction, nitrogen was added to return the pressure to ambient pressure. The product was then cooled and pelletized. The pellets were extracted with boiling water for 8 hours, with the water changed every hour. The product was dried in a vacuum oven at 90°C for 12 hours to obtain flame-retardant and anti-fouling copolymerized nylon 6 pellets, which were melt-spun into 70D / 24f flame-retardant nylon FDY fibers.

[0033] Example 3: A method for preparing flame-retardant and anti-fouling copolymer nylon 6, comprising the following steps: 1000g of caprolactam, 40g of deionized water, 25g of CEPPA, 29.01g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and 2g of sodium phosphite were weighed and added to a polymerization reactor. The air in the reactor was replaced with nitrogen. The reactor was stirred at 200°C for 1 hour, then heated to 240°C for 2 hours to carry out ring-opening polymerization. The pressure was then slowly released to ambient pressure, and the temperature was simultaneously raised to 260°C for 1 hour. The reaction was then slowly evacuated for 2 hours. After the reaction, nitrogen was added to return the pressure to ambient pressure. The product was then cooled and pelletized. The pellets were extracted with boiling water for 8 hours, with the water changed every hour. The product was dried in a vacuum oven at 90°C for 12 hours to obtain flame-retardant and anti-fouling copolymerized nylon 6 pellets, which were melt-spun into 70D / 24f flame-retardant nylon FDY fibers.

[0034] Example 4: A method for preparing flame-retardant and anti-fouling copolymer nylon 6, comprising the following steps: 1000g of caprolactam, 40g of deionized water, 30g of DOPO-MA, 22.43g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and 2g of sodium phosphite were weighed and added to a polymerization reactor. The air in the reactor was replaced with nitrogen. The reactor was stirred at 180°C for 1 hour, then heated to 240°C for 2 hours to carry out ring-opening polymerization. The pressure was then slowly released to ambient pressure, and the temperature was simultaneously raised to 260°C for 1 hour. The reactor was then slowly evacuated for 1 hour. After the reaction, nitrogen was added to return the pressure to ambient pressure. The product was then cooled and pelletized. The pellets were extracted with boiling water for 8 hours, with the water changed every hour. The product was dried in a vacuum oven at 90°C for 12 hours to obtain flame-retardant and anti-fouling copolymerized nylon 6 pellets, which were melt-spun into 70D / 24f flame-retardant nylon FDY fibers.

[0035] Example 5: A method for preparing flame-retardant and anti-fouling copolymer nylon 6, comprising the following steps: 1000g of caprolactam, 40g of deionized water, 30g of DDP, 86.63g of bisaminopropyl polydimethylsiloxane (molecular weight 1000), and 2g of sodium phosphite were weighed and added to a polymerization reactor. The air in the reactor was replaced with nitrogen. The reactor was stirred at 180°C for 1 hour, then heated to 240°C for 2 hours to carry out ring-opening polymerization. The pressure was then slowly released to atmospheric pressure, and the temperature was simultaneously raised to 260°C for 1 hour. The reaction was then slowly evacuated for 3 hours. After the reaction, nitrogen was added to return the pressure to atmospheric pressure, and the product was cooled and pelletized. The pellets were extracted with boiling water for 8 hours, with the water changed every hour. The product was dried in a vacuum oven at 90°C for 12 hours to obtain flame-retardant and anti-fouling copolymerized nylon 6 pellets, which were melt-spun to produce 70D / 24f flame-retardant nylon FDY fibers.

[0036] Example 6: A method for preparing flame-retardant and anti-fouling copolymer nylon 6, comprising the following steps: 1000g of caprolactam, 30g of deionized water, 30g of DPO, 92.28g of bisaminopropyl polydimethylsiloxane (molecular weight 1000), and 2g of sodium phosphite were weighed and added to a polymerization reactor. The air in the reactor was replaced with nitrogen. The reactor was stirred at 190°C for 1 hour, then heated to 240°C for 2 hours to carry out ring-opening polymerization. The pressure was then slowly released to atmospheric pressure, and the temperature was simultaneously raised to 250°C for 1 hour. The reaction was then slowly evacuated for 2 hours. After the reaction, nitrogen was added to return the pressure to atmospheric pressure, and the product was cooled and pelletized. The pellets were extracted with boiling water for 8 hours, with the water changed every hour. The product was dried in a vacuum oven at 90°C for 12 hours to obtain flame-retardant and anti-fouling copolymerized nylon 6 pellets, which were melt-spun to produce 70D / 24f flame-retardant nylon FDY fibers.

[0037] Example 7: A method for preparing flame-retardant and anti-fouling copolymer nylon 6, comprising the following steps: 1000g of caprolactam, 40g of deionized water, 25g of CEPPA, 116.74g of bisaminopropyl polydimethylsiloxane (molecular weight 1000), and 2g of sodium phosphite were weighed and added to a polymerization reactor. The air in the reactor was replaced with nitrogen. The reactor was stirred at 200°C for 1 hour, then heated to 240°C for 2 hours to carry out ring-opening polymerization. The pressure was then slowly released to ambient pressure, and the temperature was simultaneously raised to 260°C for 1 hour. The reaction was then slowly evacuated for 2.5 hours. After the reaction, nitrogen was added to return the pressure to ambient pressure, and the product was cooled and pelletized. The pellets were extracted with boiling water for 8 hours, with the water changed every hour. The product was dried in a vacuum oven at 90°C for 12 hours to obtain flame-retardant and anti-fouling copolymerized nylon 6 pellets, which were melt-spun to produce 70D / 24f flame-retardant nylon FDY fibers.

[0038] Example 8: A method for preparing flame-retardant and anti-fouling copolymer nylon 6, comprising the following steps: 1000g of caprolactam, 40g of deionized water, 30g of DOPO-MA, 92.28g of bisaminopropyl polydimethylsiloxane (molecular weight 1000), and 2g of sodium phosphite were weighed and added to a polymerization reactor. The air in the reactor was replaced with nitrogen. The reactor was stirred at 180°C for 1 hour, then heated to 240°C for 2 hours to carry out ring-opening polymerization. The pressure was then slowly released to ambient pressure, and the temperature was simultaneously raised to 260°C for 1 hour. The reaction was then slowly evacuated for 2 hours. After the reaction, nitrogen was added to return the pressure to ambient pressure, and the pellets were cooled and pelletized. The pellets were extracted with boiling water for 8 hours, with the water changed every hour. The product was dried in a vacuum oven at 90°C for 12 hours to obtain flame-retardant and anti-fouling copolymerized nylon 6 pellets, which were melt-spun into 70D / 24f flame-retardant nylon FDY fibers.

[0039] Comparative Example 1: A method for preparing silicon-containing copolymerized nylon 6, comprising the following steps: 1000g of caprolactam, 40g of deionized water, 15g of adipic acid, 25.51g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and 2g of sodium phosphite were weighed and added to a polymerization reactor. The air in the reactor was replaced with nitrogen. The reactor was stirred at 200°C for 1 hour, then heated to 240°C for 2 hours to carry out ring-opening polymerization. The pressure was then slowly released to ambient pressure, and the temperature was simultaneously raised to 260°C for 1 hour. The reaction was then slowly evacuated for 0.5 hours. After the reaction, nitrogen was added to return the pressure to ambient pressure, and the product was cooled and pelletized. The pellets were extracted with boiling water for 8 hours, with the water changed every hour. The product was dried in a vacuum oven at 90°C for 24 hours to obtain silicon-containing copolymerized nylon 6 chips, which were melt-spun to produce 70D / 24f silicon-containing copolymerized nylon FDY fibers.

[0040] Comparative Example 2: A method for preparing silicon-containing copolymerized nylon 6, comprising the following steps: 1000g of caprolactam, 40g of deionized water, 15g of adipic acid, 102.64g of bisaminopropyl polydimethylsiloxane (molecular weight 1000), and 2g of sodium phosphite were weighed and added to a polymerization reactor. The air in the reactor was replaced with nitrogen. The reactor was stirred at 200°C for 1 hour, heated to 240°C for 2 hours to carry out ring-opening polymerization, and then the pressure was slowly released to normal pressure. The temperature was simultaneously raised to 260°C for 1 hour, and the reaction was slowly evacuated for 0.5 hours. After the reaction was completed, nitrogen was added to restore the pressure to normal pressure, and the material was cooled and pelletized. The slices were extracted with boiling water for 8 hours, with the water changed every hour. The product was dried in a vacuum oven at 90°C for 24 hours to obtain silicon-containing copolymerized nylon 6 slices, which were melt-spun to obtain 70D / 24f silicon-containing copolymerized nylon FDY fibers.

[0041] Comparative Example 3: A method for preparing phosphorus-containing copolymer nylon 6, comprising the following steps: 1000g of caprolactam, 40g of deionized water, 30g of DDP, 12.66g of hexamethylenediamine, and 2g of sodium phosphite were weighed and added to a polymerization reactor. The air in the reactor was replaced with nitrogen. The reactor was stirred at 180°C for 1 hour, then heated to 240°C for 2 hours to carry out ring-opening polymerization. The pressure was then slowly released to ambient pressure, and the temperature was simultaneously raised to 260°C for 1 hour. The reaction was then slowly evacuated for 2 hours. After the reaction, nitrogen was added to return the pressure to ambient pressure, and the product was cooled and pelletized. The pellets were extracted with boiling water for 8 hours, with the water changed every hour. The product was dried in a vacuum oven at 90°C for 12 hours to obtain phosphorus-containing copolymerized nylon 6 chips, which were melt-spun to produce 70D / 24f phosphorus-containing copolymerized nylon FDY fibers.

[0042] Comparative Example 4: A method for preparing phosphorus-containing copolymer nylon 6, comprising the following steps: 1000g of caprolactam, 40g of deionized water, 30g of DPO, 13.19g of hexamethylenediamine, and 2g of sodium phosphite were weighed and added to a polymerization reactor. The air in the reactor was replaced with nitrogen. The reactor was stirred at 190°C for 1 hour, then heated to 240°C for 2 hours to carry out ring-opening polymerization. The pressure was then slowly released to ambient pressure, and the temperature was simultaneously raised to 250°C for 1 hour. The reaction was then slowly evacuated for 1 hour. After the reaction, nitrogen was added to return the pressure to ambient pressure. The product was then cooled and pelletized. The pellets were extracted with boiling water for 8 hours, with the water changed every hour. The product was dried in a vacuum oven at 90°C for 12 hours to obtain phosphorus-containing copolymerized nylon 6 chips, which were melt-spun to produce 70D / 24f phosphorus-containing copolymerized nylon FDY fibers.

[0043] Comparative Example 5: A method for preparing phosphorus-containing copolymer nylon 6, comprising the following steps: 1000g of caprolactam, 40g of deionized water, 25g of CEPPA, 17.06g of hexamethylenediamine, and 2g of sodium phosphite were weighed and added to a polymerization reactor. The air in the reactor was replaced with nitrogen. The reactor was stirred at 200°C for 1 hour, then heated to 240°C for 2 hours to carry out ring-opening polymerization. The pressure was then slowly released to ambient pressure, and the temperature was simultaneously raised to 260°C for 1 hour. The reaction was then slowly evacuated for 2 hours. After the reaction, nitrogen was added to return the pressure to ambient pressure, and the product was cooled and pelletized. The pellets were extracted with boiling water for 8 hours, with the water changed every hour. The product was dried in a vacuum oven at 90°C for 12 hours to obtain phosphorus-containing copolymerized nylon 6 chips, which were melt-spun to produce 70D / 24f phosphorus-containing copolymerized nylon FDY fibers.

[0044] Comparative Example 6: A method for preparing phosphorus-containing copolymer nylon 6, comprising the following steps: 1000g of caprolactam, 40g of deionized water, 30g of DOPO-MA, 13.19g of hexamethylenediamine, and 2g of sodium phosphite were weighed and added to a polymerization reactor. The air in the reactor was replaced with nitrogen. The reactor was stirred at 180°C for 1 hour, then heated to 240°C for 2 hours to carry out ring-opening polymerization. The pressure was then slowly released to ambient pressure, and the temperature was simultaneously raised to 260°C for 1 hour. The reaction was then slowly evacuated for 1 hour. After the reaction, nitrogen was added to return the pressure to ambient pressure. The product was then cooled and pelletized. The pellets were extracted with boiling water for 8 hours, with the water changed every hour. The product was dried in a vacuum oven at 90°C for 12 hours to obtain phosphorus-containing copolymerized nylon 6 chips, which were melt-spun to produce 70D / 24f phosphorus-containing copolymerized nylon FDY fibers.

[0045] Comparative Example 7 (without low-temperature prepolymerization): A method for preparing flame-retardant and anti-fouling copolymer nylon 6, comprising the following steps: 1000g of caprolactam, 40g of deionized water, 30g of DDP, 21.53g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and 2g of sodium phosphite were weighed and added to a polymerization reactor. The air in the reactor was replaced with nitrogen, and the temperature was raised to 240°C for 3 hours to carry out ring-opening polymerization. The pressure was then slowly released to ambient pressure, and the temperature was simultaneously raised to 260°C for 1 hour. The reaction was then slowly evacuated for 2 hours. After the reaction, nitrogen was added to return the pressure to ambient pressure, and the product was cooled and pelletized. The pellets were extracted with boiling water for 8 hours, with the water changed every hour. The product was dried in a vacuum oven at 90°C for 12 hours to obtain flame-retardant and anti-fouling copolymerized nylon 6 pellets, which were melt-spun into 70D / 24f flame-retardant nylon FDY fibers.

[0046] Comparative Example 8: Phosphorus-silicon synergistic flame retardant and anti-drip nylon 6 resin chips were prepared by the method in Example 1 of patent CN112920410A, and 70D / 24f flame retardant nylon FDY fibers were obtained by melt spinning.

[0047] The properties of the nylon chips prepared in the above examples and comparative examples were tested, and the results are shown in Table 1.

[0048] Table 1: Nylon slice performance test results.

[0049] As can be seen from Table 1, the nylon chips produced using the method of the present invention in Examples 1-8 exhibit excellent flame retardancy. Increasing the silicon-containing component content significantly reduces the number of droplets produced during vertical combustion, with Examples 5-8 producing significantly fewer droplets. However, in Comparative Examples 1-2, where no phosphorus-containing monomers were added for copolymerization, and in Comparative Examples 3-6, where no silicon-containing monomers were added for copolymerization, the flame retardancy of the nylon chips was significantly reduced compared to the examples. In Comparative Example 7, where no low-temperature prepolymerization was performed, the partial decomposition of the flame retardant at high temperatures resulted in an imbalance in the acid-amine ratio of the raw materials, hindering viscosity increase. The final relative viscosity was only 2.2, resulting in reduced mechanical and flame retardancy. Although Comparative Example 8 also incorporated both phosphorus-containing and silicon-containing monomers into the nylon, the method was complex, requiring intermediate additions and step-by-step synthesis, making it difficult to scale up. Furthermore, it introduced easily hydrolyzed ester bonds and a titanium-based catalyst, which is toxic to humans and the environment. Furthermore, the nylon produced by this method exhibited low viscosity and poor spinnability.

[0050] The mechanical properties of the nylon FDY fibers prepared in the above examples and comparative examples were tested, and the results are shown in Table 2.

[0051] Table 2: Mechanical properties test results of nylon FDY fiber.

[0052] As can be seen in Table 2, the nylon FDY fibers produced using the methods of the present invention in Examples 1-8 exhibit excellent mechanical properties. Comparative Examples 3-6, in which no silicon-containing monomer is added, exhibit lower elongation at break than the fibers in the Examples due to the inclusion of bisaminopropyl polydimethylsiloxane, which acts as a soft segment for energy dissipation and further reduces the crystallinity of the substrate, thus enhancing toughness. However, in Comparative Examples 7 and 8, due to the relatively low viscosity of the fibers, molecular chains are more susceptible to slippage, resulting in poorer mechanical properties.

[0053] The fibers obtained in the above examples and comparative examples were woven into garters and subjected to stain resistance testing. The results are shown in Table 3. Testing Method: The washing method described in "FZ T 01118-2012 - Anti-staining Properties of Textiles" was used for testing, with carbon black oily liquid being selected as the stain for stain removal testing.

[0054] Table 3: Antifouling performance test results.

[0055] As can be seen in Table 3, the anti-fouling properties of the fibers in Examples 1-4 are inferior to those in Examples 5-8, primarily due to the lower molecular weight and effective content of the silicon-containing monomers. Furthermore, higher molecular weight silicon-containing monomers have a greater impact on the fiber's surface properties and better anti-fouling properties. Although Comparative Example 8 also incorporates a silicon-containing monomer, its molecular structure is distinct from that used in the present invention. Furthermore, the silicon-containing monomer has only 2-4 repeating units, resulting in a shorter molecular chain and a lower effective content, resulting in no anti-fouling properties.

[0056] In summary, it can be seen that the present invention obtains flame-retardant fibers with mechanical properties equivalent to those of pure nylon fibers by spinning phosphorus-silicon-containing flame-retardant and anti-fouling copolymer nylon chips, which greatly improves the fire safety of nylon fiber fabrics; at the same time, it has a certain degree of easy decontamination and the easy decontamination of the material is not limited by the number of washing times.

[0057] The above embodiments are merely preferred examples of the present invention. For those skilled in the art, any obvious changes and improvements made without departing from the spirit of the present invention should be regarded as part of the present invention.

Claims

1. A method for preparing flame-retardant and anti-fouling copolymer nylon 6, characterized in that: The steps include: A) adding a phosphorus-containing flame retardant monomer, a silicon-containing reactive monomer, a lactam, an initiator, and a catalyst into a polymerization reaction kettle, and introducing nitrogen to replace the air in the kettle; B) heating the mixture to 180-220° C. under nitrogen protection for prepolymerization, and then heating the mixture to 240-260° C. for polymerization; C) after the polymerization reaction, the water vapor in the system is removed to react to normal pressure, and then vacuum reaction is carried out. After the reaction is completed, nitrogen is filled to return to normal pressure, and the discharged material is cooled to obtain flame retardant and anti-fouling copolymer nylon 6; The structural formula of the phosphorus-containing flame retardant monomer is one or more of the following: The structural formula of the silicon-containing reactive monomer is: n＝0～200。 2. The method for preparing the flame retardant and anti-fouling copolymer nylon 6 according to claim 1, characterized in that: In step A), the mass ratio of the phosphorus-containing flame retardant monomer, the silicon-containing reactive monomer, the lactam, the initiator and the catalyst is 0.01-0.99:0.01-0.99:1:0.02-0.1:0.002-0.

01.

3. The method for preparing the flame retardant and anti-fouling copolymer nylon 6 according to claim 1 or 2, characterized in that: The initiator in step A) is water or 6-aminocaproic acid; the catalyst is selected from one or more of calcium phosphite, potassium phosphite, sodium phosphite, boric acid, and phosphoric acid.

4. The method for preparing the flame retardant and anti-fouling copolymer nylon 6 according to claim 1, characterized in that: The prepolymerization reaction time in step B) is 0.5 to 2 hours; the polymerization reaction time is 1 to 2 hours, and the reaction pressure is 1.0 to 2.0 MPa.

5. The method for preparing the flame retardant and anti-fouling copolymer nylon 6 according to claim 1, characterized in that: In step C), the reaction is carried out at normal pressure for 0.5 to 1 hour, and in vacuum for 0.5 to 3 hours.

6. A flame retardant and anti-fouling copolymer nylon 6, characterized in that: It is prepared using the preparation method according to any one of claims 1 to 5.

7. The flame retardant and anti-fouling copolymer nylon 6 according to claim 6, characterized in that: The flame retardant and anti-fouling copolymer nylon 6 molecular structure includes the following structural units: (1) Wherein, R1 represents a C5 straight chain alkylene group; (2) Among them, the structure of R2 is n = 0 or 1; (3) The structure of R3 is n=0~200.

8. The flame retardant and anti-fouling copolymer nylon 6 according to claim 7, characterized in that: The structure The molar ratio of the unit (2) to the structural unit (3) is 0.5-1.5:0.5-1.5; the amount of the structural unit (2) is 1-99% of the amount of the structural unit (1).

9. The flame retardant and anti-fouling copolymer nylon 6 according to claim 6 or 7, characterized in that: The relative viscosity of the flame-retardant and anti-fouling copolymer nylon 6 is 2.3-2.6, the vertical combustion grade is V-2-V-0, and the limiting oxygen index is 24-34%.

10. An application of the flame retardant and anti-fouling copolymer nylon 6 according to any one of claims 6 to 9, characterized in that: It can be used to produce flame-retardant and anti-fouling plastics or flame-retardant and anti-fouling fibers, or as flame-retardant and anti-fouling masterbatch to be blended with other polyamide materials to produce flame-retardant and anti-fouling nylon materials.

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