Method for slicing anionic polymerization fiber-grade nylon 6

Abstract

The invention provides a method for slicing anionic polymerization fiber-grade nylon 6, and belongs to the technical field of chemical preparation. The method comprises the following steps: respectively pouring materials into corresponding reactors, heating, carrying out vacuum dehydration, feeding into a mixing reactor, heating, melting, stirring and devolatilizing after the reaction is completed, and drafting the melt to prepare slices. The technological process is simple, the product quality is stable, the relative viscosity of the obtained nylon 6 slices is 2.8-3.1, the molecular weight distribution is 1.8-2.0, the conversion rate is 98%, and the nylon 6 slices can be directly used for melt spinning without aftertreatment, so that the anionic polymerization nylon 6 breaks through the traditional casting molding field and can be applied to various melt processing environments.

Description

Technical Field

[0001] This invention relates to the field of chemical preparation technology, and in particular to a method for anionic polymerized fiber-grade nylon 6 chips. Background Technology

[0002] Nylon 6, as an important engineering plastic, is widely used in machinery, automobiles, and electronics due to its excellent mechanical strength, wear resistance, chemical corrosion resistance, and self-lubricating properties. Large-scale industrial production of nylon 6 mainly employs the hydrolytic polymerization process of caprolactam. This process requires high temperatures (typically above 260°C) and long durations (10-24 hours) to complete the polymerization reaction and extract low-molecular-weight compounds. This results in high energy consumption, low efficiency, and the product contains approximately 8-10% residual monomers and oligomers, making it unsuitable for direct use in spinning.

[0003] Anionic polymerization of nylon 6 uses caprolactam as a monomer and achieves rapid polymerization via anionic ring-opening polymerization in the presence of an alkaline catalyst and a co-catalyst (activator). Compared with traditional hydrolytic polymerization, anionic polymerization has significant advantages such as fast polymerization rate, relatively low polymerization temperature, and the ability to achieve in-situ casting. Since no water is involved in the reaction process, theoretically, a high monomer conversion rate can be achieved, and nylon 6 of any molecular weight can be rapidly synthesized.

[0004] A key technical challenge in the application of anionic polymerized nylon 6 is that the polymerization reaction of anionic polymerized nylon 6 needs to be carried out below the melting point of nylon 6. However, this reaction condition makes it impossible to directly stretch, cool and granulate the melt generated by the polymerization reaction, which seriously limits its industrial production efficiency and application promotion.

[0005] To address the aforementioned granulation challenges, existing technologies have proposed anionic polymerization of nylon 6 above its melting point. However, this approach has significant drawbacks: firstly, excessively high polymerization temperatures lead to a substantial decrease in the conversion rate of the polymer product; laboratory experiments have verified that the conversion rate using this method is only around 85%. Secondly, this high-temperature polymerization system imposes strict limitations on initiators, only allowing for the use of monofunctional initiators, which severely restricts the flexibility of the polymerization process and the potential for optimizing the polymer product's performance.

[0006] To address the shortcomings of the existing technologies, a method for direct anionic polymerization of fiber-grade nylon 6 chips is proposed, which is a technical problem that needs to be solved. Summary of the Invention

[0007] The purpose of this invention is to provide a method for anionic polymerizing fiber-grade nylon 6 chips to solve the above-mentioned technical problems.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for anionic polymerizing fiber-grade nylon 6 chips, comprising the following steps: 1) The caprolactam monomer was added to the catalyst reactor and the initiator reactor at a molar ratio of 1:1, and the caprolactam monomer in the two reactors was heated and melted respectively. 2) Simultaneously heat the catalyst reactor and the initiator reactor while maintaining a vacuum of ≥0.996 bar inside the reactor, and dehydrate for ≥30 min to obtain the active material components respectively; 3) Add the above active material components to a mixing reactor for mixing and reaction. After the reaction is completed, allow it to stand to obtain solid nylon 6; 4) Solid nylon 6 is heated and melted under vacuum conditions, and then the molten nylon 6 is stretched by a water bath at the bottom of the kettle and cut into shape by a pelletizer to obtain fiber-grade nylon 6 chips.

[0009] Furthermore, in step 2), the heating temperature is 90~110℃.

[0010] Furthermore, in step 3), the temperature of the mixing reaction is 155~175℃, and the standing time is 20~30min.

[0011] Furthermore, in step 1), the molar amount of catalyst in the catalyst reactor is 0.7~0.8 mol of caprolactam monomer.

[0012] Furthermore, in step 1), the molar amount of the carbonyl functional group of the initiator in the initiator reactor is 0.7~0.8 mol of the molar amount of caprolactam monomer.

[0013] Furthermore, in step 1), the molar amount of the added catalyst is equal to the molar amount of the carbonyl functional group in the initiator.

[0014] Furthermore, in step 4), the temperature for heating and melting / devouring is ≥240℃, the pressure is ≤0.002MPa, and the time is ≥30min.

[0015] Furthermore, the catalyst is an alkali metal, alkaline earth metal, or organoalkali metal compound.

[0016] Furthermore, the initiator is N-acetylcaprolactam or an isocyanate compound.

[0017] The beneficial effects of this invention are: 1. The synthesis method of the present invention achieves ultra-high conversion rate and product purity through precise selection and ratio of catalyst and initiator: The core advantage of the present invention lies in the precise selection of catalyst precursor and initiator, and the strict control of the molar fraction of the two added to the optimal ratio, thereby controlling the synthesis conversion rate to above 97%.

[0018] 2. The synthesis method of this invention produces nylon 6 products with high conversion rate and narrow molecular weight distribution. It eliminates the need for cumbersome and energy-intensive post-processing steps (such as extraction) required by traditional hydrolysis polymerization processes, allowing for direct use in spinning. This significantly shortens the production cycle, reduces equipment investment and energy consumption, and avoids wastewater discharge during post-processing, thereby significantly reducing production and environmental remediation costs.

[0019] 3. The synthesis method of the present invention has high catalyst activation efficiency. In steps 2) and 3), under specific pressure and temperature, the efficient generation and activation of sodium caprolactam catalyst are ensured by introducing inert gas (argon) for protection and by a step vacuum method. At the same time, impurities such as moisture and oxygen that inhibit anionic polymerization are eliminated to the greatest extent, laying a solid foundation for subsequent high-speed and high-conversion polymerization reactions.

[0020] 4. The synthesis method of the present invention combines vacuum melt devolatilization with anionic polymerized nylon 6, which not only solves the problem that anionic polymerized nylon 6 is not easy to form chips, but also removes its residual monomers and oligomers so that the extractable content is less than 2 wt%, thus enabling the continuous production of anionic polymerized nylon 6. Attached Figure Description

[0021] Figure 1 This is a flowchart of the method of the present invention; Figure 2 The figure shows the tensile properties test results of nylon 6 prepared in Example 1 of this invention. Detailed Implementation

[0022] This invention provides a method for anionic polymerizing fiber-grade nylon 6 chips, comprising the following steps: 1) The caprolactam monomer was added to the catalyst reactor and the initiator reactor at a molar ratio of 1:1, and the caprolactam monomer in the two reactors was heated and melted respectively. 2) Simultaneously heat the catalyst reactor and the initiator reactor while maintaining a vacuum of ≥0.996 bar inside the reactor, and dehydrate for ≥30 min to obtain the active material components respectively; 3) Add the above active material components to a mixing reactor for mixing and reaction. After the reaction is completed, allow it to stand to obtain solid nylon 6; 4) Solid nylon 6 is heated and melted under vacuum conditions, and then the molten nylon 6 is stretched by a water bath at the bottom of the kettle and cut into shape by a pelletizer to obtain fiber-grade nylon 6 chips.

[0023] In this invention, in step 2), the heating temperature is 90~110℃, preferably 95~105℃, and more preferably 100℃.

[0024] In this invention, in step 3), the temperature of the mixing reaction is 155~175℃, preferably 160~170℃, and more preferably 165℃; the standing time is 20~30min, preferably 25min.

[0025] In this invention, in step 3), the stirring speed during the mixing reaction is ≥60 r / min, and the stirring time is 1~3 min.

[0026] In this invention, in step 1), the molar amount of catalyst in the catalyst reactor is 0.7~0.8 mol% of the molar amount of caprolactam monomer, preferably 0.75 mol%.

[0027] In this invention, in step 1), the molar amount of carbonyl functional group of the initiator in the initiator reactor is 0.7~0.8 mol% of the molar amount of caprolactam monomer, preferably 0.75 mol%.

[0028] In this invention, in step 1), the molar amount of the catalyst added is equal to the molar amount of the carbonyl functional group in the initiator.

[0029] In this invention, in step 4), the temperature for heating and melting / devouring is ≥240℃, preferably 240~260℃, more preferably 245~250℃; the pressure is ≤0.002MPa; and the time is ≥30min, preferably 30~60min. During the heating and melting / devouring process, the stirring paddle speed is not less than 500rpm.

[0030] In this invention, the catalyst is an alkali metal, alkaline earth metal, or organoalkali metal compound, preferably sodium hydroxide.

[0031] In this invention, the initiator is N-acetylcaprolactam or an isocyanate compound, preferably N-acetylcaprolactam.

[0032] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0033] Example 1

[0034] Raw material preparation: Caprolactam, sodium hydroxide, and N-acetylcaprolactam were all purchased commercially. The first two were solid powders, and the latter was a liquid. Raw material ratio: Based on the total molar amount of caprolactam monomer, the amount of sodium hydroxide is 0.7 mol%, and the amount of N-acetylcaprolactam is 0.7 mol%; wherein, the molar ratio of caprolactam in the catalyst reactor to that in the initiator reactor is 1:1.

[0035] Catalyst reactor: 20L volume, stainless steel, equipped with a mechanical stirrer (paddle type, speed adjustable from 0-100r / min), electric heating jacket, vacuum interface, nitrogen inlet and bottom discharge valve, the ultimate vacuum degree of the vacuum system is ≤-0.098MPa; The initiator reactor has the same specifications as the catalyst reactor to ensure consistency in the pretreatment conditions of the two systems.

[0036] Mixing reactor: 3L volume, stainless steel (316L), electric heating jacket, equipped with variable frequency mechanical stirrer (power 0-5kW, real-time power monitoring accuracy ±0.01kW), vacuum system, argon gas inlet, temperature sensor and bottom discharge device, the reactor body is sealed with fluororubber sealing ring; Auxiliary equipment: vacuum pump, water-cooled cooling tank, pelletizer.

[0037] Method for slicing anionic polymerized fiber-grade nylon 6: 1) Add 10 mol (approximately 1131.4 g) of caprolactam monomer to the catalyst reactor, close the reactor top cover, and check the sealing performance of the reactor body to ensure there is no leakage; start the electric heating jacket and raise the temperature inside the reactor to 100℃, controlling the heating rate at 5℃ / min to avoid local overheating that could lead to caprolactam oxidation; turn on the vacuum unit, slowly open the vacuum valve, and gradually increase the vacuum level inside the reactor to -0.095 MPa, maintaining this condition for vacuum dehydration for 35 min, observing the bubble escape status of the system every 10 min until no obvious bubbles are generated (at this point, the water content of the system is ≤0.05 wt%); close the vacuum valve and vacuum unit, and slowly introduce nitrogen gas into the reactor, controlling the flow rate. Nitrogen gas was produced at a flow rate of 1.5 L / min until the pressure inside the reactor returned to atmospheric pressure (0.1 MPa), and the vacuum was broken. Under nitrogen protection, the reactor feed port was quickly opened, and metered sodium hydroxide (0.07 mol, about 2.8 g) was added. The feed port was immediately closed to ensure that the system was isolated from air. The vacuum unit was turned on again to maintain the vacuum degree inside the reactor at -0.095 MPa. The reaction was carried out at 100°C and a stirring speed of 30 r / min for 25 min, during which the system status was observed in real time until no more bubbles were generated. The heating jacket and vacuum unit were turned off, and the nitrogen protective atmosphere inside the reactor was maintained. The catalyst-monomer premixed system was temporarily stored at 100°C for later use.

[0038] 2) Add 10 mol (approximately 1131.4 g) of caprolactam monomer and a measured amount of N-acetylcaprolactam (0.07 mol, approximately 11.7 g) to the initiator reactor. Close the reactor top cover and check the sealing performance. Start the electric heating jacket and raise the temperature inside the reactor to 100°C at a heating rate of 5°C / min. Turn on the vacuum unit and slowly open the vacuum valve to raise the vacuum level inside the reactor to -0.095 MPa. Maintain this condition for vacuum mixing for 30 min, during which the stirring speed is controlled at 40 r / min to ensure that the activator is uniformly dispersed in the monomer and remove moisture and trace amounts of air from the system until no bubbles escape from the system. Close the vacuum valve and vacuum unit to maintain the vacuum seal inside the reactor for later use.

[0039] 3) Start the electric heating jacket of the mixing reactor to preheat the temperature inside the reactor to 165℃ at a heating rate of 8℃ / min. At the same time, turn on the vacuum unit to evacuate the vacuum inside the reactor to -0.095MPa. Maintain this temperature and vacuum for 20 minutes to remove the moisture and air adsorbed on the inner wall of the reactor. Simultaneously open the bottom discharge valves of the catalyst reactor and the initiator reactor, and feed the two premixed systems into the mixing reactor through a sealed stainless steel pipe (with an electric heating device installed over the pipe to maintain the temperature at 100°C to prevent material cooling and crystallization). Control the feed rate to 0.6 L / min to ensure that both systems are fed simultaneously (feed time difference ≤ 5 min). Maintain a vacuum seal throughout the process to prevent air and moisture from entering. After feeding is complete, start the agitator of the mixing reactor and set the speed to 50 r / min, monitoring the agitation power in real time. When the agitation power rises sharply from the initial value (approximately 0.3 kW) to above 1.5 kW, stop agitation immediately.

[0040] Maintain a vacuum of 165℃ and -0.095MPa inside the mixing reactor and allow the reaction to stand for 30 minutes to allow the molecular chains to grow fully and form a polymer. After the reaction is complete, raise the temperature inside the mixing reactor to 240℃ using an electric heating jacket at a rate of 5℃ / min and maintain the vacuum for 30 minutes to allow the polymer to melt fully. After melting, start the stirrer and set the speed to 30r / min, and continue stirring for 30 minutes to remove oligomers and residual monomers from the system.

[0041] 4) Close the vacuum unit and vacuum valve, slowly introduce argon gas into the mixing reactor, control the argon gas flow rate to 1.0 L / min, until the pressure inside the reactor rises to atmospheric pressure; open the drawing die at the bottom of the mixing reactor, and extrude the molten nylon 6 polymer through the die, controlling the extrusion rate to 1.0 m / min; the extruded polymer filaments enter the water-cooled cooling tank (water temperature controlled at 15℃), and after cooling to room temperature, send them to the pelletizer to be cut into granular products.

[0042] The granulated nylon 6 particles are fed into a hot air dryer at 100℃ and a hot air flow rate of 2m³ / h. 3 Drying at a rate of 1000 m / min for 4 h removed the adsorbed moisture from the particle surface, yielding anionic polymerized nylon 6. The obtained nylon 6 was tested and found to have a relative viscosity of 2.9, an extractable content of 1.05 wt%, and a molecular weight distribution of 1.98. Figure 2 The figure shows the tensile properties test results of the nylon 6 prepared in this embodiment. It can be seen from the figure that its tensile strength is 59~65MPa.

[0043] Example 2

[0044] Raw material preparation: caprolactam (solid powder), potassium hydroxide (solid powder), and isocyanate compounds (liquid, toluene diisocyanate is selected), all of which are commercially available industrial-grade raw materials with a purity ≥99.5%.

[0045] Raw material ratio: Based on the total molar amount of caprolactam monomer, the amount of potassium hydroxide is 0.75 mol, and the molar amount of carbonyl functional group in toluene diisocyanate is 0.75 mol; the molar ratio of caprolactam in the catalyst reactor to that in the initiator reactor is 1:1.

[0046] Equipment specifications: Catalyst reactor: 20L volume, stainless steel, equipped with mechanical stirrer (paddle type, speed adjustable from 0-100r / min), electric heating jacket, vacuum interface, argon inlet and bottom discharge valve, vacuum system ultimate vacuum degree ≤-0.098MPa.

[0047] Initiator reactor: The specifications are completely consistent with those of the catalyst reactor to ensure uniformity of pretreatment conditions.

[0048] Mixing reactor: 3L volume, made of 316L stainless steel, with electric heating jacket, equipped with variable frequency mechanical stirrer (power 0-5kW, monitoring accuracy ±0.01kW), vacuum system, argon gas inlet, high-precision temperature sensor and bottom discharge device, and the reactor body is sealed with fluororubber sealing ring.

[0049] Auxiliary equipment: vacuum pump, water-cooled cooling tank, pelletizer, hot air dryer.

[0050] Preparation steps: Catalyst system pretreatment: Add 12 mol (approximately 1357.7 g) of caprolactam monomer to the catalyst reactor, close the top cover and check the seal. Start the electric heating jacket and raise the temperature to 105°C at a rate of 6°C / min. Turn on the vacuum unit and slowly increase the vacuum to -0.096 MPa. Maintain this condition for vacuum dehydration for 40 min until no obvious bubbles escape (moisture content ≤0.05 wt%). Close the vacuum valve and introduce argon gas at a flow rate of 2.0 L / min to atmospheric pressure. Under argon protection, quickly add potassium hydroxide (0.09 mol, approximately 5.04 g) and immediately close the feed port. Turn the vacuum unit back on and maintain a vacuum of -0.096 MPa. React at 105°C and a stirring speed of 35 r / min for 30 min until no bubbles are generated in the system. Then, keep the system at 105°C under argon protection for later use.

[0051] Initiator system pretreatment: Add 12 mol (approximately 1357.7 g) of caprolactam monomer and toluene diisocyanate (containing 0.09 mol of carbonyl functional group, approximately 15.2 g) to the initiator reactor, close the top cover and check the seal. Start the electric heating jacket and raise the temperature to 105°C at a rate of 6°C / min. Turn on the vacuum unit and raise the vacuum level to -0.096 MPa. Mix under vacuum for 35 min at a stirring speed of 45 r / min to remove moisture and trace amounts of air. Then maintain the vacuum seal for later use.

[0052] Mixed polymerization reaction: The electric heating jacket of the mixing reactor was started, and preheated to 170°C at a heating rate of 9°C / min. Simultaneously, the vacuum unit was activated to evacuate to -0.096 MPa, maintaining this preheating state for 25 min. The catalyst premix system and initiator premix system were simultaneously fed into the mixing reactor through a sealed stainless steel pipeline with heating tracing (105°C), controlling the feed rate at 0.8 L / min and ensuring a feed time difference ≤ 5 min. After feeding, the stirrer was started and set to 55 r / min. Stirring was stopped immediately when the stirring power increased from the initial 0.35 kW to above 1.6 kW. The reaction was allowed to stand at 170°C and -0.096 MPa vacuum for 28 min. Then, the temperature was increased to 245°C at a heating rate of 5°C / min, maintaining the vacuum state for 35 min to melt the polymer. The stirrer was then started again at 35 r / min for 35 min to remove oligomers and residual monomers.

[0053] Drawing, pelletizing, and drying: The vacuum unit was shut off, and argon gas was introduced at a flow rate of 1.2 L / min to atmospheric pressure. The bottom drawing die was opened, and the extrusion rate was controlled at 1.2 m / min to extrude the molten nylon 6 into an 18°C ​​water-cooled cooling bath. The cooled filaments were fed into a pelletizer to be cut into pellets, and then sent to a hot air dryer at 105°C and a hot air flow rate of 2.5 m³ / min. 3 Drying at a rate of / min for 5 hours yielded the anionic polymerized nylon 6 product.

[0054] Product Performance

[0055] The obtained nylon 6 chips had a relative viscosity of 3.0, an extractable content of 0.92 wt%, a molecular weight distribution of 1.95, and a conversion rate of 98.5%, meeting the requirements for fiber-grade spinning.

[0056] Example 3

[0057] Raw material preparation: caprolactam (solid powder), organic alkali metal compound (sodium phenyl, solid), and N-acetylcaprolactam (liquid) are all commercially available industrial-grade raw materials with a purity of ≥99.5%.

[0058] Raw material ratio: Based on the total molar amount of caprolactam monomer, the amount of sodium phenyl is 0.8 mol%, and the molar amount of carbonyl functional group in N-acetylcaprolactam is 0.8 mol%; the molar ratio of caprolactam in the catalyst reactor and the initiator reactor is 1:1.

[0059] Equipment specifications: Same as in Example 1.

[0060] Preparation steps: Catalyst system pretreatment: Add 8 mol (approximately 905.1 g) of caprolactam monomer to the catalyst reactor, close the top cover and check for airtightness. Start the electric heating jacket to heat to 95°C at 4°C / min, turn on the vacuum unit to evacuate to -0.094 MPa, maintain this condition for vacuum dehydration for 32 min (moisture content ≤0.05 wt%). Close the vacuum valve, introduce argon gas at a flow rate of 1.3 L / min to atmospheric pressure, add sodium phenyl (0.064 mol, approximately 5.8 g) under argon protection, close the feed port, and evacuate again to -0.094 MPa. React at 95°C and stirring speed of 28 r / min for 22 min, then keep at 95°C under argon protection for later use.

[0061] Initiator system pretreatment: Add 8 mol (approximately 905.1 g) of caprolactam monomer and N-acetylcaprolactam (containing 0.064 mol of carbonyl functional group, approximately 10.8 g) to the initiator reactor, close the top cover and check for airtightness. Start the electric heating jacket to heat to 95°C at 4°C / min, turn on the vacuum unit to evacuate to -0.094 MPa, and mix under vacuum for 28 min at a stirring speed of 38 r / min to remove moisture and trace amounts of air, maintaining a vacuum-sealed state for later use.

[0062] Mixed polymerization reaction: The electric heating jacket of the mixing reactor was started, and the temperature was preheated to 160°C at a rate of 7°C / min, while the vacuum was evacuated to -0.094MPa. This preheating state was maintained for 18 min. Two premixed systems were simultaneously fed into the mixing reactor through a sealed stainless steel pipeline with heating (95°C), controlling the feed rate at 0.5 L / min and ensuring a feed time difference ≤ 5 min. After feeding, the stirrer was started and set to 48 r / min. Stirring was stopped when the stirring power increased from the initial 0.28 kW to above 1.4 kW. The reaction was allowed to stand at 160°C and -0.094MPa vacuum for 25 min, then the temperature was increased to 250°C at a rate of 5°C / min, and the vacuum was maintained for 40 min to melt the polymer. The mixture was then stirred at 40 r / min for 40 min to remove oligomers and residual monomers.

[0063] Drawing, pelletizing, and drying: The vacuum unit was shut off, and argon gas was introduced at a flow rate of 0.9 L / min to atmospheric pressure. The drawing die was opened, and the extrusion rate was controlled at 0.9 m / min to extrude the molten nylon 6 into a 12℃ water-cooled cooling bath. The cooled filaments were pelletized by a pelletizer and then sent to a hot air dryer at 98℃ with a hot air flow rate of 1.8 m³ / min. 3 Drying at a rate of / min for 4.5h yielded the anionic polymerized nylon 6 product.

[0064] Product Performance

[0065] The obtained nylon 6 chips had a relative viscosity of 2.85, an extractable content of 1.1 wt%, a molecular weight distribution of 1.92, and a conversion rate of 98.2%, which meets the standards for fiber-grade spinning applications.

[0066] As can be seen from the above embodiments, the present invention provides a method for anionic polymerization of fiber-grade nylon 6 chips. This method adopts a low-temperature reaction mode, and improves the monomer conversion rate from the source of synthesis by precisely controlling the addition ratio of initiator and catalyst and precisely regulating the reaction temperature. At the same time, in the subsequent process, residual monomers and oligomers in the system are effectively removed by heating and melting and vacuum stirring. This achieves the integrated integration of high monomer conversion rate and melt stretching and granulation, successfully breaking through the technical dilemma that traditional anionic polymerized nylon 6 can only be used in the field of casting molding.

[0067] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for anionic polymerizing fiber-grade nylon 6 chips, characterized in that, Includes the following steps: 1) The caprolactam monomer was added to the catalyst reactor and the initiator reactor at a molar ratio of 1:1, and the caprolactam monomer in the two reactors was heated and melted respectively. 2) Simultaneously heat the catalyst reactor and the initiator reactor while maintaining a vacuum of ≥0.996 bar inside the reactor, and dehydrate for ≥30 min to obtain the active material components respectively; 3) Add the above active material components to a mixing reactor for mixing and reaction. After the reaction is completed, allow it to stand to obtain solid nylon 6; 4) Solid nylon 6 is heated and melted under vacuum conditions, and then the molten nylon 6 is stretched by a water bath at the bottom of the kettle and cut into shape by a pelletizer to obtain fiber-grade nylon 6 chips.

2. The method for anionic polymerization of fiber-grade nylon 6 chips according to claim 1, characterized in that, In step 2), the temperature for heating is 90~110℃.

3. The method for anionic polymerizing fiber-grade nylon 6 chips according to claim 1 or 2, characterized in that, In step 3), the temperature of the mixing reaction is 155~175℃, and the standing time is 20~30min.

4. The method for anionic polymerization of fiber-grade nylon 6 chips according to claim 3, characterized in that, In step 1), the molar amount of catalyst in the catalyst reactor is 0.7~0.8 mol of caprolactam monomer.

5. The method for anionic polymerizing fiber-grade nylon 6 chips according to claim 1 or 4, characterized in that, In step 1), the molar amount of the carbonyl functional group of the initiator in the initiator reactor is 0.7~0.8 mol of the molar amount of caprolactam monomer.

6. The method for anionic polymerization of fiber-grade nylon 6 chips according to claim 5, characterized in that, In step 1), the molar amount of the added catalyst is equal to the molar amount of the carbonyl functional group in the initiator.

7. The method for anionic polymerizing fiber-grade nylon 6 chips according to claim 1 or 6, characterized in that, In step 4), the temperature for heating and melting / devouring is ≥240℃, the pressure is ≤0.002MPa, and the time is ≥30min.

8. The method for anionic polymerization of fiber-grade nylon 6 chips according to claim 7, characterized in that, The catalyst is an alkali metal, alkaline earth metal, or organoalkali metal compound.

9. The method for anionic polymerization of fiber-grade nylon 6 chips according to claim 8, characterized in that, The initiator is N-acetylcaprolactam or an isocyanate compound.

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