Copolymerization synergistic flame-retardant polyamide 66 fiber and preparation method thereof

Abstract

The preparation method specifically comprises the following steps: adding pyridine heterocyclic ring-containing amide salt, aromatic structure amide salt, a cool compound additive, nylon 66 salt and deionized water into a polymerization reaction kettle to serve as a reaction system; regulating and controlling the temperature and the pressure of a reaction system in an inert gas atmosphere, and carrying out a staged reaction to obtain the copolymerized synergistic flame-retardant polyamide 66. The flame-retardant polyamide 66 fiber is obtained by carrying out melt spinning on the copolymerized and synergistic flame-retardant polyamide 66, so that the fabric is endowed with excellent cool feeling performance, the fabric is ensured to have excellent flame-retardant performance, the inherent high strength and flexibility of the polyamide 66 fiber are kept, the balance of functionality and spinnability is realized, and the flame-retardant polyamide 66 fiber has excellent flame-retardant performance. The method can be applied to the fields of outdoor sportswear, automotive interiors, home textiles and the like.

Description

Technical Field

[0001] This invention relates to the field of polyamide 66 fiber, and particularly to a copolymerized synergistic flame-retardant polyamide 66 fiber and its preparation method. Background Technology

[0002] Polyamide 66 fiber was the first synthetic fiber to be industrialized. Compared with other fibers, polyamide 66 fiber has advantages such as higher strength, fatigue resistance, and abrasion resistance. It is widely used in clothing, home textiles, and military industries, and is currently the most widely used polyamide material.

[0003] In recent years, with the continuous improvement of people's living standards, consumers' clothing concepts have begun to shift from basic needs to diversified functional requirements. Functional clothing has gradually gained attention, and cooling functional fabrics with cool and comfortable properties are more favored by consumers in hot and humid climates. To impart cooling properties to fabrics, the industry currently focuses on two main technical approaches: One approach involves designing the fiber cross-section into various shapes, such as cross-shaped or hollow tetrapods. These irregularly shaped cross-sections create numerous grooves on the fiber surface, enhancing capillary action and promoting moisture conduction. Furthermore, the irregular cross-section increases the fiber's specific surface area, allowing surface moisture to evaporate quickly, resulting in a cooling effect. Polyamide 66 possesses excellent water absorption, which is a significant advantage for developing cooling fibers. However, while fabrics made from irregularly shaped cooling fibers can produce an instant cooling sensation upon skin contact, this cooling effect is difficult to sustain over time, thus impacting long-term comfort.

[0004] Another method involves introducing highly thermally conductive inorganic powders into the fiber. The principle is to increase the fiber's thermal conductivity, thereby accelerating the rate at which heat is dissipated from the skin surface and achieving a cooling effect. Currently, common cooling fibers on the market typically achieve their cooling properties by adding mica powder, aluminum nitride, etc. However, to obtain excellent cooling performance, this requires increasing the amount of inorganic powder added, which not only affects the fiber's spinnability but also severely impacts its mechanical properties.

[0005] Furthermore, the inherent flammability of polyamide 66 (limiting oxygen index of only 22%-24%) greatly limits its application in fields with stringent safety requirements, such as outdoor sports, special protective equipment, and high-end home furnishings. Traditional flame retardant modification methods have significant shortcomings: halogenated flame retardants release toxic gases during combustion; phosphorus-based flame retardants may deteriorate the mechanical properties of materials or pose environmental and health risks; while inorganic or nitrogen-based flame retardants generally suffer from problems such as large addition amounts, low flame retardant efficiency, and poor compatibility with the matrix, leading to a significant decline in the mechanical properties of materials. Summary of the Invention

[0006] The purpose of this invention is to provide a copolymer synergistic flame-retardant polyamide 66 fiber and its preparation method. By introducing two cooling additives with different particle sizes to synergistically improve the cooling properties of polyamide 66 fiber, and introducing a pyridine heterocyclic structure to improve the flame-retardant properties of polyamide 66 fiber, the invention imparts excellent cooling properties to the fabric while ensuring excellent flame-retardant properties and maintaining the inherent high strength of polyamide 66 fiber. This achieves a balance between functionality and spinnability, and can be applied to outdoor sportswear, automotive interiors, and home textiles.

[0007] To achieve the above objectives, this technical solution provides a method for preparing copolymerized synergistic flame-retardant polyamide 66 fibers, comprising the following steps: A reaction system consisting of pyridine heterocyclic amide salt, aromatic structural amide salt, cooling compound additive, nylon 66 salt, and deionized water was added to a polymerization reactor. The temperature and pressure of the reaction system were controlled under an inert gas atmosphere to carry out a staged reaction to obtain copolymerized synergistic flame retardant polyamide 66. Flame-retardant polyamide 66 fibers were obtained by melt spinning of the copolymerized synergistic flame-retardant polyamide 66.

[0008] This method introduces a cooling compound additive composed of two cooling aids with different particle sizes into nylon 66 salt through in-situ polymerization. The thermally conductive network structure formed by the two cooling aids achieves the effect of ensuring good and continuous cooling performance of polyamide 66 fiber while adding a low amount of cooling compound additive.

[0009] Specifically, the larger-particle-size cooling additives in this solution can generate a cooling sensation the moment the fabric comes into contact with the skin. They can also work with the smaller-particle-size cooling additives with high thermal conductivity to quickly and continuously transfer heat generated by the skin into the atmosphere. Furthermore, the two cooling additives with different particle sizes can form a dense thermally conductive network structure within the polyamide 66 matrix. The larger-particle-size cooling additives construct the main thermally conductive network structure, while the smaller-particle-size cooling additives fill the gaps between the larger-particle-size cooling additives. This dense packing method reduces the agglomeration of the cooling additives and increases the effective contact between them, enabling rapid heat transfer. In other words, the copolymerized synergistic flame-retardant polyamide 66 fiber prepared by this invention utilizes the size complementarity effect between cooling additives of different particle sizes to construct a highly efficient thermally conductive network within the fiber, thereby achieving good and continuous cooling performance while using a low amount of cooling additives. Lower amounts of cooling compound additives not only help ensure the spinnability of fibers, but also help achieve a high degree of orientation distribution of cooling compound additives in fibers, thereby minimizing the adverse effects on fiber mechanical properties.

[0010] Furthermore, the polyamide 66 fiber molecular backbone prepared by this invention incorporates pyridine heterocyclic and aromatic structures. At high temperatures, the pyridine heterocyclic structure releases nitrogen-containing free radicals to capture hydrogen and hydroxyl radicals during combustion, thereby rapidly interrupting the free radical chain reaction in the gas phase and preventing combustion. Moreover, the rigid structure of the pyridine heterocyclic and aromatic structures can be used to exert a plasticizing effect, reducing the melt viscosity of polyamide 66 and promoting melt flowability. This can improve the powder dispersibility of cooling compound additives and also allow the material to form droplets in time when heated to carry away heat, thereby blocking combustion in the condensed phase.

[0011] Specifically, in some embodiments, the cooling compound additive includes a first cooling aid and a second cooling aid with different particle sizes, wherein the particle size of the first cooling aid is 300-600 nm, and the particle size of the second cooling aid is 30-90 nm. As mentioned above, the first cooling aid acts as a skeleton to construct the main thermally conductive network framework inside the fiber, while the second cooling aid fills the skeleton formed by the first cooling aid to form a dense packing, avoiding the problem of low thermal conductivity caused by loose packing of cooling aids with a single particle size.

[0012] In some embodiments, the mass ratio of the first cooling agent to the second cooling agent is 1:(0.5~1.5).

[0013] In some embodiments, the first cooling agent is selected from one or a combination of mica or jade powder.

[0014] In some embodiments, the second cooling agent is selected from one or a combination of boron nitride and aluminum nitride.

[0015] In some embodiments, the air in the polymerization reactor is replaced with nitrogen 3-5 times and the reactor is then sealed to create an inert gas atmosphere. This method uses nitrogen to replace the air to prevent the oxidation reaction of pyridine-containing heterocyclic amide salts and aromatic amide salts with oxygen at high temperatures, thus avoiding side reactions and safety risks.

[0016] In some embodiments, the reaction system is slowly heated to 215~235℃, and the pressure in the polymerization reactor is controlled at 1.8~2.0MPa for condensation for 2~3 hours; the temperature is further increased to 245~255℃, and after 0.5~1 hours, the pressure in the polymerization reactor is reduced to atmospheric pressure (0MPa); finally, the temperature is further increased to 270~280℃, and the pressure in the polymerization reactor is evacuated to -0.01~-0.10MPa, and the temperature and pressure are maintained for 1~3 hours to obtain copolymerized synergistic flame-retardant polyamide 66.

[0017] In some embodiments, 3-9 parts of a pyridine heterocyclic amide salt, 3-9 parts of an aromatic structural amide salt, 0.5-1.5 parts of a cooling compound additive, 100 parts of nylon 66 salt, and 60-80 parts of deionized water are added to a polymerization reactor as a reaction system.

[0018] Regarding the preparation of pyridine heterocyclic amide salts: A pyridine-containing dicarboxylic acid and an aliphatic diamine are added to water or ethanol and stirred at 60-90°C for 1-12 hours to carry out a salt formation reaction, yielding a pyridine-containing heterocyclic amide salt.

[0019] In some embodiments, the molar ratio of pyridine dicarboxylic acid to aliphatic diamine is 1:(1.02~1.05).

[0020] In some embodiments, the pyridine-containing dicarboxylic acid includes one or a combination of 2,6-pyridinedicarboxylic acid, 2,5-pyridinedicarboxylic acid, 2,4-pyridinedicarboxylic acid, 2,3-pyridinedicarboxylic acid, 3,5-pyridinedicarboxylic acid, and 3,4-pyridinedicarboxylic acid.

[0021] In some embodiments, the aliphatic diamine is a straight-chain aliphatic diamine with 4 to 10 carbon atoms.

[0022] Preparation of aromatic amide salts: Aromatic dicarboxylic acids and aliphatic diamines are added to water or ethanol and stirred at 60-90°C for 1-12 hours to carry out a salt formation reaction, yielding amide salts containing aromatic structures.

[0023] In some embodiments, the molar ratio of aromatic dicarboxylic acid to aliphatic diamine is 1:(1.02~1.05).

[0024] In some embodiments, the aromatic dicarboxylic acid includes one or a combination of 1,3-phthalic acid, 1,4-phthalic acid, 2,3-naphthalic acid, 1,3-naphthalic acid, 1,4-naphthalic acid, 2,6-naphthalic acid, and 2,7-naphthalic acid.

[0025] In some embodiments, the aliphatic diamine is a straight-chain aliphatic diamine with 4 to 10 carbon atoms.

[0026] In some embodiments, after drying at 95~105°C for 12~36h, the copolymerized flame-retardant polyamide 66 is added to a melt spinning machine for melt spinning to obtain flame-retardant polyamide 66 fiber.

[0027] Furthermore, the melt spinning temperature is 280~295℃, and the winding speed is 3000~4500m / min.

[0028] In some embodiments, the copolymerized flame-retardant polyamide 66 fiber obtained by this method has a breaking strength of 3.8~8.2 cN / dtex and a breaking elongation of 26.3~38.2%. The fabric prepared using the copolymerized flame-retardant polyamide 66 fiber of this invention has a contact cooling coefficient Q. max The concentration is 0.21~0.28 J / (cm). 2 The limiting oxygen index of the fabric is 29.0~37.0%.

[0029] Compared with existing technologies, this technical solution has the following characteristics and beneficial effects: 1. The cooling compound additive used in the copolymer synergistic flame-retardant polyamide 66 fiber prepared by this invention transfers heat very quickly. The thermally conductive network formed by cooling auxiliaries of different particle sizes in the cooling compound additive can further accelerate heat transfer, giving the fiber excellent cooling properties. Furthermore, the copolymer synergistic flame-retardant polyamide 66 fiber prepared by this invention does not have a significant impact on the fiber spinnability due to the cooling compound additive. Because of the size complementarity effect between powders, a good cooling effect can be achieved even with a low content of cooling additive, avoiding serious impacts on the fiber's spinnability and mechanical properties without affecting the cooling performance.

[0030] 2. This invention adds pyridine heterocyclic amide salts and aromatic structural amide salts as flame retardant materials. While improving the flame retardant performance, it is completely free of halogens (chlorine, bromine) and heavy metals. The amount of smoke produced during combustion is low and the toxicity is low. It does not produce corrosive hydrogen halide gas or carcinogenic substances such as polybrominated diphenyl ethers. It fully complies with the requirements of environmental regulations such as EU RoHS and REACH and has broad market application prospects. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0032] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the indicated orientation or positional relationship. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0033] Example 1 A method for preparing copolymerized synergistic flame-retardant polyamide 66 fibers, the specific steps of which are as follows: (1) By mass, 2,6-pyridinedicarboxylic acid and 1,6-hexanediamine were added to water in a molar ratio of 1:1.02 and stirred at 60°C for 2 h to carry out a salt formation reaction to obtain amide salt A containing pyridine structure; 1,3-phthalic acid and 1,6-hexanediamine were added to water in a molar ratio of 1:1.02 and stirred at 60°C for 2 h to carry out a salt formation reaction to obtain amide salt B containing aromatic structure; (2) Add 3 parts of amide salt A, 3 parts of amide salt B, 0.5 parts of cooling additive compound powder (mass ratio 1:0.5, mica, particle size 300~400nm; boron nitride, particle size 30~50nm), 100 parts of nylon 66 salt, and 60 parts of deionized water to the polymerization reactor. Replace the air in the reactor with nitrogen three times. Start heating and slowly raise the temperature to 215℃, control the pressure in the reactor to maintain 1.8MPa, and polycondense for 2h. Then continue to raise the temperature to 245℃, and after 0.5h, reduce the pressure in the reactor to atmospheric pressure 0MPa. Finally, continue to raise the temperature to 270℃, evacuate the pressure in the reactor to -0.01MPa, and keep it at the temperature and pressure for 1h to obtain copolymerized synergistic flame retardant polyamide 66. (3) The copolymerized flame-retardant polyamide 66 was dried at 95°C for 12 hours and then melt-spun in a melt spinning machine. The melt spinning temperature was 285°C and the winding speed was 4500 m / min to obtain copolymerized flame-retardant polyamide 66 fiber.

[0034] Example 2 A method for preparing copolymerized synergistic flame-retardant polyamide 66 fibers, the specific steps of which are as follows: (1) By mass, 2,5-pyridinedicarboxylic acid and 1,10-decanediamine were added to water in a molar ratio of 1:1.05 and stirred at 60°C for 3 h to carry out a salt formation reaction to obtain amide salt A containing a pyridine structure; 1,4-phthalic acid and 1,10-decanediamine were added to water in a molar ratio of 1:1.05 and stirred at 60°C for 3 h to carry out a salt formation reaction to obtain amide salt B containing an aromatic structure; (2) Add 6 parts of amide salt A, 6 parts of amide salt B, 1 part of cooling additive compound powder (mass ratio 1:1, mica, particle size 400~500nm; aluminum nitride, particle size 50~70nm), 100 parts of nylon 66 salt, and 70 parts of deionized water to the polymerization reactor. Replace the air in the reactor with nitrogen three times. Start heating and slowly raise the temperature to 225℃, control the pressure in the reactor to 1.9MPa, and polycondense for 3h. Then continue to raise the temperature to 250℃, and after 0.6h, reduce the pressure in the reactor to atmospheric pressure 0MPa. Finally, continue to raise the temperature to 275℃, evacuate the pressure in the reactor to -0.05MPa, and keep it at the same temperature and pressure for 2h to obtain copolymerized synergistic flame retardant polyamide 66. (3) The copolymerized flame-retardant polyamide 66 was dried at 105°C for 24 hours and then melt-spun in a melt spinning machine. The melt spinning temperature was 290°C and the winding speed was 3800 m / min to obtain copolymerized flame-retardant polyamide 66 fiber.

[0035] Example 3 A method for preparing copolymerized synergistic flame-retardant polyamide 66 fibers, the specific steps of which are as follows: (1) By mass, 2,6-pyridinedicarboxylic acid and 1,8-octanediamine were added to water in a molar ratio of 1:1.05 and stirred at 80°C for 12 h to carry out a salt formation reaction to obtain amide salt A containing a pyridine structure; 2,6-naphthalenedicarboxylic acid and 1,8-octanediamine were added to water in a molar ratio of 1:1.05 and stirred at 80°C for 12 h to carry out a salt formation reaction to obtain amide salt B containing an aromatic structure; (2) Add 9 parts of amide salt A, 9 parts of amide salt B, 1.5 parts of cooling additive compound powder (mass ratio 1:1.5, jade powder, particle size 500~600nm; boron nitride, particle size 70~90nm), 100 parts of nylon 66 salt, and 80 parts of deionized water to the polymerization reactor. Replace the air in the reactor with nitrogen three times. Start heating and slowly raise the temperature to 235℃, control the pressure in the reactor to maintain 2.0MPa, and polycondense for 2.5h. Then continue to raise the temperature to 255℃, and after 0.8h, reduce the pressure in the reactor to atmospheric pressure 0MPa. Finally, continue to raise the temperature to 278℃, evacuate the pressure in the reactor to -0.08MPa, and keep it at the same temperature and pressure for 2h to obtain copolymerized synergistic flame retardant polyamide 66. (3) The copolymerized flame-retardant polyamide 66 was dried at 105°C for 24 hours and then melt-spun in a melt spinning machine. The melt spinning temperature was 295°C and the winding speed was 3500 m / min to obtain copolymerized flame-retardant polyamide 66 fiber.

[0036] Example 4 A method for preparing copolymerized synergistic flame-retardant polyamide 66 fibers, the specific steps of which are as follows: (1) By mass, 2,5-pyridinedicarboxylic acid and 1,8-octanediamine were added to ethanol in a molar ratio of 1:1.02 and stirred at 70°C for 12 h to carry out a salt formation reaction to obtain amide salt A containing a pyridine structure; 2,6-naphthalenedicarboxylic acid and 1,8-octanediamine were added to ethanol in a molar ratio of 1:1.02 and stirred at 70°C for 12 h to carry out a salt formation reaction to obtain amide salt B containing an aromatic structure; (2) Add 3 parts of amide salt A, 3 parts of amide salt B, 0.5 parts of cooling additive compound powder (mass ratio 1:0.5, jade powder, particle size 400~500nm; aluminum nitride, particle size 70~90nm), 100 parts of nylon 66 salt, and 70 parts of deionized water to the polymerization reactor. Replace the air in the reactor with nitrogen three times. Start heating and slowly raise the temperature to 225℃, control the pressure in the reactor to 1.9MPa, and polycondense for 3h. Then continue to raise the temperature to 250℃, and after 1h, reduce the pressure in the reactor to atmospheric pressure 0MPa. Finally, continue to raise the temperature to 280℃, evacuate the pressure in the reactor to -0.10MPa, and keep it at the temperature and pressure for 1h to obtain copolymerized synergistic flame retardant polyamide 66. (3) The copolymerized flame-retardant polyamide 66 was dried at 105°C for 36 hours and then melt-spun in a melt spinning machine. The melt spinning temperature was 280°C and the winding speed was 3000 m / min to obtain copolymerized flame-retardant polyamide 66 fiber.

[0037] Example 5 A method for preparing copolymerized synergistic flame-retardant polyamide 66 fibers, the specific steps of which are as follows: (1) By mass, 2,6-pyridinedicarboxylic acid and 1,7-heptanediamine were added to ethanol in a molar ratio of 1:1.02 and stirred at 60°C for 2 h to carry out a salt formation reaction to obtain amide salt A containing a pyridine structure; 1,4-phthalic acid and 1,7-heptanediamine were added to ethanol in a molar ratio of 1:1.02 and stirred at 80°C for 2 h to carry out a salt formation reaction to obtain amide salt B containing an aromatic structure; (2) Add 6 parts of amide salt A, 6 parts of amide salt B, 1 part of cooling additive compound powder (mass ratio 1:1, jade powder, particle size 500~600nm; boron nitride, particle size 30~50nm), 100 parts of nylon 66 salt, and 80 parts of deionized water to the polymerization reactor. Replace the air in the reactor with nitrogen three times. Start heating and slowly raise the temperature to 235℃, control the pressure in the reactor to 2.0MPa, and polycondense for 2.5h. Then continue to raise the temperature to 250℃, and after 0.5h, reduce the pressure in the reactor to atmospheric pressure 0MPa. Finally, continue to raise the temperature to 275℃, evacuate the pressure in the reactor to -0.10MPa, and keep it at the same temperature and pressure for 2h to obtain copolymerized synergistic flame retardant polyamide 66. (3) The copolymerized flame-retardant polyamide 66 was dried at 95°C for 36 hours and then melt-spun in a melt spinning machine. The melt spinning temperature was 288°C and the winding speed was 4500 m / min to obtain copolymerized flame-retardant polyamide 66 fiber.

[0038] Example 6 A method for preparing copolymerized synergistic flame-retardant polyamide 66 fibers, the specific steps of which are as follows: (1) By mass, 2,5-pyridinedicarboxylic acid and 1,8-octanediamine were added to ethanol in a molar ratio of 1:1.02 and stirred at 60°C for 2 h to carry out a salt formation reaction to obtain amide salt A containing a pyridine structure; 1,4-phthalic acid and 1,8-octanediamine were added to ethanol in a molar ratio of 1:1.02 and stirred at 80°C for 2 h to carry out a salt formation reaction to obtain amide salt B containing an aromatic structure; (2) Add 9 parts of amide salt A, 9 parts of amide salt B, 1.5 parts of cooling additive compound powder (mass ratio 1:1.5, mica with a particle size of 300~400nm; aluminum nitride with a particle size of 50~70nm), 100 parts of nylon 66 salt, and 70 parts of deionized water to the polymerization reactor. Replace the air in the reactor with nitrogen three times. Start heating and slowly raise the temperature to 230℃, control the pressure in the reactor to maintain at 1.8MPa, and polycondense for 3h. Then continue to raise the temperature to 255℃, and after 1h, reduce the pressure in the reactor to atmospheric pressure of 0MPa. Finally, continue to raise the temperature to 273℃, evacuate the pressure in the reactor to -0.10MPa, and keep it at the temperature and pressure for 3h to obtain copolymerized synergistic flame retardant polyamide 66. (3) The copolymerized flame-retardant polyamide 66 was dried at 95°C for 12 hours and then melt-spun in a melt spinning machine. The melt spinning temperature was 282°C and the winding speed was 4000 m / min to obtain copolymerized flame-retardant polyamide 66 fiber.

[0039] Comparative Example A method for preparing polyamide 66 fiber is basically the same as that in Example 2, except that: in step (2), amide salt A containing pyridine structure, amide salt B containing aromatic structure, and cool-feeling compound additives are not added; the specific formula is: 100 parts of nylon 66 salt and 70 parts of deionized water are directly added to the polymerization reactor as the reaction system. The remaining polymerization process parameters and melt spinning process parameters are consistent with those in Example 2.

[0040] Table 1 Performance Test Tables for Various Embodiments and Comparative Examples

[0041] Those skilled in the art should understand that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0042] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A process for the preparation of a copolymerized synergistic flame retardant polyamide 66 fiber characterized in that, The method comprises the following steps: The pyridine heterocyclic amide salt, aromatic structure amide salt, cool complex additive, nylon 66 salt and deionized water are added into a polymerization reactor as a reaction system, and the temperature and pressure of the reaction system are controlled under inert gas atmosphere to perform staged reaction to obtain the copolymerized synergistic flame-retardant polyamide 66; The copolymerized synergistic flame-retardant polyamide 66 is melt spun to obtain the flame-retardant polyamide 66 fiber.

2. The process for the preparation of copolymerized synergistic flame retardant polyamide 66 fibers according to claim 1, characterized in that, The cool complex additive comprises a first cool auxiliary agent and a second cool auxiliary agent with different particle sizes, wherein the particle size of the first cool auxiliary agent is 300-600 nm, and the particle size of the second cool auxiliary agent is 30-90 nm.

3. The process for the preparation of copolymerized synergistic flame retardant polyamide 66 fibers according to claim 1, characterized in that, The mass ratio of the first cool auxiliary agent to the second cool auxiliary agent is 1:(0.5-1.5).

4. The process for the preparation of copolymerized synergistic flame retardant polyamide 66 fibers according to claim 1, characterized in that, The first cool auxiliary agent is selected from one or a combination of mica or jade powder; and the second cool auxiliary agent is selected from one or a combination of boron nitride and aluminum nitride.

5. The process for the preparation of copolymerized synergistic flame retardant polyamide 66 fibers according to claim 1, characterized in that, The reaction system is slowly heated to 215-235 DEG C, the pressure of the polymerization reactor is controlled to be 1.8-2.0 MPa, and the polycondensation is performed for 2-3 h; then the temperature is continuously increased to 245-255 DEG C, the pressure in the polymerization reactor is reduced to normal pressure 0 MPa after 0.5-1 h; finally, the temperature is continuously increased to 270-280 DEG C, the pressure in the polymerization reactor is vacuumed to-0.01--0.10 MPa, and the temperature and pressure are kept for 1-3 h to obtain the copolymerized synergistic flame-retardant polyamide 66.

6. The process for the preparation of copolymerized synergistic flame retardant polyamide 66 fibers according to claim 1, characterized in that, 3-9 parts of the pyridine heterocyclic amide salt, 3-9 parts of the aromatic structure amide salt, 0.5-1.5 parts of the cool complex additive, 100 parts of the nylon 66 salt and 60-80 parts of deionized water are added into the polymerization reactor as a reaction system.

7. The process for the preparation of copolymerized synergistic flame retardant polyamide 66 fibers according to claim 1, characterized in that, The pyridine structure binary acid and the aliphatic binary amine are added into water or ethanol, and the salt formation reaction is performed under stirring at 60-90 DEG C for 1-12 h to obtain the pyridine heterocyclic amide salt; the aromatic binary acid and the aliphatic binary amine are added into water or ethanol, and the salt formation reaction is performed under stirring at 60-90 DEG C for 1-12 h to obtain the amide salt with aromatic structure.

8. The process for the preparation of copolymerized synergistic flame retardant polyamide 66 fibers according to claim 7, characterized in that, The pyridine structure binary acid comprises one or a combination of 2,6-pyridine dicarboxylic acid, 2,5-pyridine dicarboxylic acid, 2,4-pyridine dicarboxylic acid, 2,3-pyridine dicarboxylic acid, 3,5-pyridine dicarboxylic acid and 3,4-pyridine dicarboxylic acid; the aromatic binary acid is one or a combination of 1,3-benzenedicarboxylic acid, 1,4-benzenedicarboxylic acid, 2,3-naphthalene dicarboxylic acid, 1,3-naphthalene dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid and 2,7-naphthalene dicarboxylic acid; and the aliphatic binary amine is a straight-chain aliphatic binary amine with a carbon atom number of 4-10.

9. The process for the preparation of copolymerized synergistic flame retardant polyamide 66 fibers according to claim 1, characterized in that, After drying at 95-105 DEG C for 12-36 h, the copolymerized synergistic flame-retardant polyamide 66 is added into a melt spinning machine to perform melt spinning to obtain the flame-retardant polyamide 66 fiber.

10. The process for the preparation of copolymerized synergistic flame retardant polyamide 66 fibers according to claim 9, characterized in that, The temperature of the melt spinning is 280-295 DEG C, and the winding speed is 3000-4500 m / min.

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