A nylon 66 production device and production method

Abstract

The application discloses a nylon 66 production device and production method, prepares and distributes nylon 66 melt, and comprises a salt system, a salt liquid preparation system, a salt liquid reaction system, a composite reactor, a prepolymerization reaction system, a reduced pressure flash evaporation system, a front polycondensation reaction system, a rear polycondensation reaction system, a melt distribution unit and a rotary scraping structure; the application adds carbon fibers to fill the holes and defects of nylon 66 salt crystals, improves uniformity, increases the toughness of nylon 66 polymers, improves the quality of nylon 66 downstream products, sets reliable and stable reaction time and pressure control, prevents the thermal oxidation of yellowing and black particles of nylon 66 salt and salt crystals, sets the rotary scraping structure to scrape in time, prevents the blockage and accumulation of the reaction kettle, prevents the influence of shutdown on the process, and effectively improves the preparation quality of nylon 66 polymers.

Description

Technical Field

[0001] This invention relates to a nylon 66 production apparatus, and more particularly to a nylon 66 production apparatus and production method. Background Technology

[0002] As a very important member of modern synthetic fibers, the production and preparation of nylon 66 has had a wide-ranging impact on the world. Nylon 66 is produced by polycondensation (also known as polymerization) of the resulting nylon 66 salt under high temperature and high pressure using hexamethylenediamine (HMD) and adipic acid (ADA) as raw materials.

[0003] During the polycondensation (also known as polymerization) reaction of nylon 66 salt, the conversion rate is slow, so the nylon 66 salt crystals are prone to defects, namely vacancies and uneven crystallization. As a result, the physical properties of the nylon 66 melt formed by polycondensation (also known as polymerization) have the natural defect of being brittle, which affects the quality of subsequent nylon 66 chips and nylon 66 filaments.

[0004] Polycondensation (also known as polymerization) processes mainly include batch polycondensation and continuous polycondensation. Due to differences in production capacity, continuous polycondensation is used for large-scale industrial production. In continuous polycondensation, the temperature, pressure, and material and flow ratios vary in each reaction system. Nylon 66 has inherent defects such as easy thermal degradation and three-dimensional structure formation. Thermal degradation makes it highly susceptible to thermal oxidation, which manifests as yellowing and blackening of the product. Three-dimensional structure formation causes the melt viscosity to increase, resulting in a gel-like state that adheres to the inside of the reactor. Over time, this leads to reactor blockage and impurity accumulation, which can affect the quality of the nylon 66 melt or even cause a complete shutdown of production. Summary of the Invention

[0005] To address the shortcomings of the aforementioned technologies, this invention provides a nylon 66 production apparatus and production method.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: preparing and dispensing nylon 66 melt, which includes:

[0007] A salt-forming system is used to prepare an aqueous solution of hexamethylenediamine to form nylon 66 salt, and adipic acid is added to the aqueous solution of hexamethylenediamine to stir and react the two.

[0008] The brine preparation system is used to configure the flow rate of the nylon 66 brine solution obtained from the initial reaction in the salt formation system in order to achieve material balance.

[0009] The brine reaction system is used to perform two-stage vacuum crystallization, centrifugal separation, and airflow drying on a nylon 66 salt solution with a concentration of not less than 60% filtered during the transportation process to obtain nylon 66 salt crystals.

[0010] A composite reactor is used to heat nylon 66 salt crystals into a saturated aqueous solution and thoroughly impregnate and mix them with carbon fibers placed in the composite reactor.

[0011] A prepolymerization reaction system for heating nylon 66 salt-carbon fiber composite at 200°C for 2 hours;

[0012] The reduced pressure flash evaporation system is used to gradually depressurize and discharge water vapor from the prepolymerization reaction system after the evaporation operation, and then evacuate to 0.1 MPa and maintain it for 45 minutes;

[0013] A pre-condensation reaction system for condensation reaction of nylon 66 salt-carbon fiber composite with an initial reaction temperature of at least 214°C;

[0014] A post-condensation reaction system for post-condensation reaction of nylon 66 salt-carbon fiber composite;

[0015] The melt distribution unit is used to distribute the Nylon 66 salt-carbon fiber composite melt.

[0016] The rotary scraper structure is configured within the cavity of the post-condensation reaction system and moves to scrape away waste from the inner wall of the post-condensation reaction system.

[0017] Furthermore, the salt formation system has a circulating production line for hexamethylenediamine aqueous solution.

[0018] Furthermore, the two-stage vacuum crystallization of nylon 66 salt solution was treated with 85% ethanol, and the resulting nylon 66 salt crystals had a melting point of 195°C.

[0019] Furthermore, the carbon fiber in the composite reactor is high-modulus graphite fiber M40.

[0020] Furthermore, the dehydration reaction of the nylon 66 salt-carbon fiber composite in the prepolymerization reaction system is shown below: .

[0021] Furthermore, the evaporation operation pressure of the reduced pressure flash evaporation system is 1.72 MPa, and the residence time is 3 hours.

[0022] Furthermore, the swivel structure includes a rotating disk and an inner displacement steering disk spaced apart from and rotating relative to it on its inner circumference, the rotating disk being driven by a power shaft to rotate relative to the inner displacement steering disk;

[0023] The rotating disk includes multiple rotary scraper blades, each configured on the outer periphery of the rotating disk via a self-rotating extended connecting rod;

[0024] An avoidance notch is provided on the side wall of the inner steering wheel. The avoidance notch and the steering guide armature arranged at intervals at its lower end together form a steering channel between the two. The steering channel is arranged in an inverted V shape.

[0025] Furthermore, the end of the extension connecting rod extending inside the turntable is connected to a guide plate located between the turntable and the inner steering wheel. The guide plate is an arc-shaped plate that matches the circumference of the inner steering wheel, and a rotating guide wheel is connected inside the arc of the guide plate. The guide wheel movably abuts against the lower edge of the side wall of the inner steering wheel.

[0026] A method for producing nylon 66 using a nylon 66 production apparatus, the method comprising:

[0027] First, a hexamethylenediamine aqueous solution is prepared through a circulating production line of a salt-forming system. Then, adipic acid is added to the hexamethylenediamine aqueous solution in an equimolar ratio. The two are stirred at a temperature of not less than 60°C, and the nylon 66 salt aqueous solution with a concentration of not less than 60% is subjected to two-stage vacuum crystallization, centrifugation, and airflow drying to obtain nylon 66 salt crystals.

[0028] Secondly, after heating the nylon 66 salt crystals into a saturated aqueous solution, the high-modulus graphite fiber M40 in the composite reactor was impregnated and the two were thoroughly mixed.

[0029] Next, the nylon 66 salt-carbon fiber composite delivered to the vacuum flash evaporation system was heated to 230°C, then evaporated at 1.72 MPa and held for 3 hours. After that, the pressure was gradually released and the water vapor was discharged. Then, the vacuum was drawn to 0.1 MPa and held for 45 minutes.

[0030] Finally, the nylon 66 salt-carbon fiber composite was subjected to pre-condensation and post-condensation reactions, with the initial temperature of the pre-condensation reaction being at least 214°C.

[0031] During the post-polymerization reaction, the rotary scraping structure continuously operates to scrape away the gel on the inner wall of the post-polymerization reaction system.

[0032] This invention discloses a nylon 66 production apparatus and method. By adding carbon fibers to fill the voids and defects in nylon 66 salt crystals, the uniformity is improved, the toughness of the nylon 66 polymer is increased, and the quality of the downstream nylon 66 product is improved. Reliable and stable residence time and pressure control are set to prevent nylon 66 salt and its salt crystals from yellowing and blackening due to thermal oxidation. To address the problem of thermal degradation of nylon 66 polymer during repeated polycondensation operations, which may cause it to adhere to the reactor, a rotary scraper structure is set up to scrape it off in time, preventing reactor blockage and accumulation, preventing downtime from affecting the process, and effectively improving the preparation quality of nylon 66 polymer. Attached Figure Description

[0033] Figure 1 This is a process structure diagram of the reaction apparatus of the present invention.

[0034] Figure 2 This is a schematic diagram of the rotary scraping structure of the present invention.

[0035] Figure 3 This is a schematic diagram of the rotary scraper and its connection structure according to the present invention.

[0036] Figure 4 This is a schematic diagram of the internal connection structure of the rotary scraping structure of the present invention.

[0037] In the diagram: 1. Salt formation system; 2. Salt solution preparation system; 3. Salt solution reaction system; 4. Composite reactor; 5. Prepolymerization reaction system; 6. Vacuum flash evaporation system; 7. Pre-condensation reaction system; 8. Post-condensation reaction system; 9. Melt distribution unit; 10. Scraper structure; 11. Rotary disk; 12. Scraper hand plate; 13. Power shaft; 14. Internal reversing disc; 15. Fixed sleeve; 16. Reversing channel; 17. Reversing guide armature; 18. Extension connecting rod; 19. Guide guard plate; 20. Guide wheel. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0039] This invention relates to a nylon 66 production apparatus and a production method thereof, the embodiments of which include a nylon 66 production apparatus and a production method thereof for preparing and dispensing nylon 66 melt.

[0040] The Nylon 66 production facility includes:

[0041] Salt-forming system 1 is used to prepare an aqueous solution of hexamethylenediamine to form nylon 66 salt, and adipic acid is added to the hexamethylenediamine aqueous solution to stir and react the two. Salt solution preparation system 2 is used to configure the flow rate of the nylon 66 salt aqueous solution obtained from the initial reaction in salt-forming system 1 to achieve material balance. Salt solution reaction system 3 is used to perform two-stage vacuum crystallization, centrifugal separation, and airflow drying on the nylon 66 salt aqueous solution with a concentration of not less than 60% filtered during the transportation process to obtain nylon 66 salt crystals. Composite reactor 4 is used to heat the nylon 66 salt crystals into a saturated aqueous solution and fully impregnate and mix it with carbon fibers placed in composite reactor 4. Prepolymerization reaction system 5 is used to heat the nylon 66 salt-carbon fiber composite at 200°C for 2 hours. Vacuum flash evaporation system 6 is used to prepolymerize the nylon 66 salt after the evaporation operation. The reaction system 5 is gradually depressurized and water vapor is discharged, then a vacuum is drawn to 0.1 MPa and maintained for 45 min; the pre-condensation reaction system 7 is used to carry out the condensation reaction of nylon 66 salt-carbon fiber composite and the initial reaction temperature is at least 214°C; the post-condensation reaction system 8 is used to carry out the post-condensation reaction of nylon 66 salt-carbon fiber composite; the melt distribution unit 9 is used to distribute the nylon 66 salt-carbon fiber composite melt; the swirl scraper structure 10 is configured in the inner cavity of the post-condensation reaction system 8 and moves to scrape off the waste on the inner wall of the post-condensation reaction system 8. This waste is an infusible and insoluble substance formed by the thermal decomposition of the molten polymer at high temperature, the cracking of the main chain causing molecular weight linkage, the decrease in melt viscosity, and the final three-dimensional structuring causing the melt viscosity to increase. This infusible and insoluble substance is in a gel state.

[0042] Salt formation system 1 has a circulating production line for hexamethylenediamine aqueous solution, which means that salt formation system 1 can prepare hexamethylenediamine aqueous solution to ensure the quality of downstream nylon 66 finished product, which is the prior art in this field.

[0043] In this embodiment, the two-stage vacuum crystallization of nylon 66 salt solution is treated with 85% ethanol to increase its reactivity in bonding with carbon fibers. The melting point of the nylon 66 salt crystals obtained after the treatment is 195°C.

[0044] The carbon fiber in the composite reactor 4 is high-modulus graphite fiber M40. Before being put into operation, the high-modulus graphite fiber M40 is washed with acetone to remove the adhesive material for subsequent bonding reactions. After removing the adhesive material, it is repeatedly washed with distilled water. The washed high-modulus graphite fiber M40 is then put into the composite reactor 4 to react.

[0045] Nylon 66 salt crystals are heated to a saturated aqueous solution, which is then thoroughly impregnated and mixed with high-modulus graphite fibers M40. The saturated aqueous solution of nylon 66 salt fully encapsulates the high-modulus graphite fibers M40, accelerating the mixing conversion rate. In the prepolymerization reaction system 5, the nylon 66 salt-carbon fiber composite undergoes solid-state polycondensation. During this process, the high-modulus graphite fibers M40 are located in the cavities of the nylon 66 salt crystals, reducing structural defects and accelerating the nucleation rate. Subsequently, the dehydration reaction of the nylon 66 salt-carbon fiber composite is shown below: .

[0046] The evaporation pressure of the reduced pressure flash evaporation system 6 is 1.72 MPa, and the residence time is 3 hours. This ensures that the reaction proceeds smoothly, prevents the volatilization of ethylenediamine, and is beneficial for increasing the relative molecular weight during polymerization.

[0047] The rotary scraping structure 10 includes a rotary disk 11 and an inner reversing disk 14 that is spaced apart from and rotates relative to it on its inner circumference. The rotary disk 11 is driven by a power shaft 13 to rotate relative to the inner reversing disk 14. The rotary disk 11 includes a plurality of rotary scraping handles 12 that are respectively arranged on the outer circumference of the rotary disk 11 via rotatable extension connecting rods 18. An avoidance notch is provided on the side wall of the inner reversing disk 14. The avoidance notch and the reversing guide armature 17 arranged at their lower ends together form a reversing channel 16 located between them. The reversing channel 16 is arranged in an inverted V shape. It should be noted that the upper end of the power shaft 13 passes through the disk surface of the inner reversing disk 14 and is connected to the lower surface of the rotary disk 11. That is to say, the power shaft 13 drives the rotary disk 11 to rotate under power drive. In addition, the power shaft 13 is fitted with a fixed sleeve 15 whose upper end is connected to the lower surface of the inner reversing disk 14.

[0048] Preferably, the end of the extension connecting rod 18 extending inside the rotating disk 11 is connected to a guide plate 19 located between the rotating disk 11 and the inner steering wheel 14. The guide plate 19 is an arc-shaped plate that matches the circumference of the inner steering wheel 14, and a rotating guide wheel 20 is connected inside the arc of the guide plate 19. The guide wheel 20 movably abuts against the lower edge of the side wall of the inner steering wheel 14. It should be noted that there are two guide wheels 20, and the two guide wheels 20 are rotatably connected to the two ends of the guide plate 19 respectively.

[0049] Based on the above structure, the working principle of the rotary scraping structure 10 is as follows:

[0050] Driven by an external output device, such as an electric motor or cylinder, the power shaft 13 drives the rotating disk 11 to rotate, and the rotary scraper 12 on the rotating disk 11 rotates accordingly. During this process, the rotary scraper 12 rotates circumferentially to scrape away the gel-like substance on the inner wall of the polycondensation reaction system 8.

[0051] Next, the rotating disk 11 and the rotary scraper 12 continue to rotate. When the guide wheel 20 moves along the lower edge of the inner reversing disc 14 side wall to the reversing channel 16, one of the two guide wheels 20 moves along the reversing channel 16. The guide guard plate 19 tilts and flips, and drives the rotary scraper 12 to flip together through the extension connecting rod 18. At this time, the other guide wheel 20 moves along the lower edge of the reversing guide armature 17. When the guide wheel 20 in the reversing channel 16 travels to the latter half, because the stroke of the reversing channel 16 is greater than that of the reversing disc 14, the guide wheel 20 moves along the lower edge of the reversing guide armature 17. The travel distance to the lower edge of the guide armature 17 is longer, so the guide wheel 20 moving at the lower edge of the reversing guide armature 17 is switched to the front side, and the guide wheel in the reversing channel 16 is switched to the rear side position. In this way, a whole reversing operation is completed, and a whole circumferential rotation of the rotary scraper 12 is also completed. Through the circumferential rotation of the rotary scraper 12, the gel-like material on the inner wall of the polycondensation reaction system 8 is rotated and scraped off, improving the scraping efficiency, ensuring the completion quality of the polycondensation reaction, and improving the melt quality of the nylon 66-carbon fiber composite.

[0052] A method for producing nylon 66 using a nylon 66 production apparatus, the method comprising:

[0053] First, a hexamethylenediamine aqueous solution is prepared through the circulating production line of salt formation system 1. Then, adipic acid is added to the hexamethylenediamine aqueous solution in an equimolar ratio. The two are stirred at a temperature of not less than 60°C, and the nylon 66 salt aqueous solution with a concentration of not less than 60% is subjected to two-stage vacuum crystallization, centrifugation, and airflow drying to obtain nylon 66 salt crystals.

[0054] Secondly, after heating the nylon 66 salt crystals into a saturated aqueous solution, the high-modulus graphite fiber M40 in the composite reactor 4 was impregnated and the two were thoroughly mixed.

[0055] Next, the nylon 66 salt-carbon fiber composite delivered to the vacuum flash evaporation system 6 is heated to 230°C, then evaporated at 1.72 MPa and held for 3 hours. After that, the pressure is gradually released and the water vapor is discharged, and then the vacuum is drawn to 0.1 MPa and held for 45 minutes.

[0056] Finally, the nylon 66 salt-carbon fiber composite was subjected to pre-condensation and post-condensation reactions, with the initial temperature of the pre-condensation reaction being at least 214°C.

[0057] During the post-condensation reaction, the rotary scraping structure 10 continuously operates to scrape the gel on the inner wall of the post-condensation reaction system 8.

[0058] The nylon 66 production apparatus and method disclosed in this invention improve uniformity and increase the toughness of the nylon 66 polymer by adding carbon fibers to fill the voids and defects in the nylon 66 salt crystals, thereby improving the quality of the downstream nylon 66 products. Reliable and stable residence time and pressure control are implemented to prevent the nylon 66 salt and its crystals from yellowing and undergoing thermal oxidation. Addressing the issue of thermal degradation and adhesion to the reactor that may occur during repeated polycondensation of the nylon 66 polymer, a rotary scraper structure 10 is incorporated to promptly remove the degradation, preventing reactor blockage and accumulation, avoiding downtime that could affect the process, and effectively improving the quality of the nylon 66 polymer preparation.

[0059] The above embodiments are not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the technical solutions of the present invention are also within the protection scope of the present invention.

Claims

1. A nylon 66 production apparatus for preparing and dispensing nylon 66 melt, characterized in that, It includes: Salt-forming system (1) is used to prepare an aqueous solution of hexamethylenediamine to form nylon 66 salt, and adipic acid is added to the aqueous solution of hexamethylenediamine to stir and react the two. The brine preparation system (2) is used to configure the flow rate of the nylon 66 brine solution obtained from the initial reaction in the salt formation system (1) to achieve material balance. The salt solution reaction system (3) is used to perform two-stage vacuum crystallization, centrifugal separation, and airflow drying on the nylon 66 salt solution with a concentration of not less than 60% filtered during the transportation process to obtain nylon 66 salt crystals. A composite reactor (4) is used to heat nylon 66 salt crystals into a saturated aqueous solution and fully impregnate and mix them with carbon fibers contained in the composite reactor (4); A prepolymerization reaction system (5) is used to heat the nylon 66 salt-carbon fiber composite at 200°C for 2 hours; The reduced pressure flash evaporation system (6) is used to gradually depressurize the prepolymerization reaction system (5) after the evaporation operation and discharge water vapor, and then evacuate to 0.1 MPa and maintain it for 45 min; A pre-condensation reaction system (7) is used for condensation reaction of nylon 66 salt-carbon fiber composite and the initial reaction temperature is at least 214°C; Post-condensation reaction system (8) is used to perform post-condensation reaction on nylon 66 salt-carbon fiber composite; Melt distribution unit (9) is used to distribute nylon 66 salt-carbon fiber composite melt; A rotary scraping structure (10) is configured in the inner cavity of the post-condensation reaction system (8) to scrape off the gel on the inner wall of the post-condensation reaction system (8); the rotary scraping structure (10) includes a rotating disk (11) and an inner directional disk (14) spaced apart and rotating relative to it on its inner circumference. The rotating disk (11) is driven by a power shaft (13) to rotate relative to the inner directional disk (14); the rotating disk (11) includes a plurality of rotary scraping hand plates (12) respectively configured on the outer circumference of the rotating disk (11) via rotatable extension connecting rods (18); the inner directional disk (14) has a clearance notch on its side wall, and the clearance notch and the reversing guide armature (17) spaced apart at its lower end together form a reversing channel (16) between them, and the reversing channel (16) is arranged in an inverted V shape; The end of the extension connecting rod (18) extending inside the turntable (11) is connected to a guide plate (19) located between the turntable (11) and the inner displacement steering wheel (14). The guide plate (19) is an arc-shaped plate that matches the circumference of the inner displacement steering wheel (14), and two spaced guide wheels (20) are connected inside the arc of the guide plate (19). The guide wheels (20) movably abut against the lower edge of the side wall of the inner displacement steering wheel (14).

2. The nylon 66 production apparatus according to claim 1, characterized in that: The salt formation system (1) has a circulating flow line for hexamethylenediamine aqueous solution.

3. The nylon 66 production apparatus according to claim 1, characterized in that: The two-stage vacuum crystallization of the nylon 66 salt aqueous solution was treated with 85% ethanol, and the resulting nylon 66 salt crystals had a melting point of 195°C.

4. The nylon 66 production apparatus according to claim 1, characterized in that, The carbon fiber in the composite reactor (4) is high-modulus graphite fiber M40.

5. The nylon 66 production apparatus according to claim 1, characterized in that: The evaporation operation pressure of the reduced pressure flash evaporation system (6) is 1.72 MPa, and the residence time is 3 hours.

6. A method for producing nylon 66 using the nylon 66 production apparatus as described in any one of claims 1-5, characterized in that, The method includes: First, a hexamethylenediamine aqueous solution is prepared by circulating the salt formation system (1). Then, adipic acid is added to the hexamethylenediamine aqueous solution in an equal molar ratio. The two are stirred at a temperature of not less than 60°C, so that the nylon 66 salt aqueous solution with a concentration of not less than 60% undergoes two-stage vacuum crystallization, centrifugal separation, and airflow drying to obtain nylon 66 salt crystals. Secondly, after heating the nylon 66 salt crystals into a saturated aqueous solution, the high-modulus graphite fiber M40 in the composite reactor (4) was impregnated and the two were thoroughly mixed. Next, the nylon 66 salt-carbon fiber composite delivered to the vacuum flash evaporation system (6) is heated to 230°C, then evaporated at 1.72 MPa and held for 3 hours. After that, the pressure is gradually released and the water vapor is discharged. Then, the vacuum is drawn to 0.1 MPa and held for 45 minutes. Finally, the nylon 66 salt-carbon fiber composite was subjected to pre-condensation and post-condensation reactions, with the initial temperature of the pre-condensation reaction being at least 214°C. During the post-condensation reaction, the swirl scraper (10) continuously operates to scrape the gel on the inner wall of the post-condensation reaction system (8).

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