CN111424328A - Nylon melt direct spinning method comprising vapor extraction and liquid phase extraction - Google Patents
Nylon melt direct spinning method comprising vapor extraction and liquid phase extraction Download PDFInfo
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- CN111424328A CN111424328A CN202010171444.7A CN202010171444A CN111424328A CN 111424328 A CN111424328 A CN 111424328A CN 202010171444 A CN202010171444 A CN 202010171444A CN 111424328 A CN111424328 A CN 111424328A
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
- D01F6/60—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyamides
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
- C08G69/02—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids
- C08G69/08—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from amino-carboxylic acids
- C08G69/14—Lactams
- C08G69/16—Preparatory processes
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
- C08G69/46—Post-polymerisation treatment
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D1/00—Treatment of filament-forming or like material
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D13/00—Complete machines for producing artificial threads
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Abstract
The invention relates to the field of nylon materials, and discloses a nylon melt direct spinning method comprising vapor extraction and liquid phase extraction, which comprises the following steps: 1) preparing materials: heating and mixing caprolactam, a blocking agent, water and a catalyst to obtain a mixture; 2) opening the ring: heating the mixture to carry out a ring opening reaction; 3) pre-polycondensation: heating the product obtained by ring opening, and carrying out pre-polycondensation reaction and devolatilization; 4) final polycondensation: heating the product obtained by pre-polycondensation, and carrying out final polycondensation reaction and devolatilization; 5) devolatilization before spinning: performing pre-spinning devolatilization on the product obtained by final polycondensation through a film evaporator; 6) spinning: directly conveying the devolatilized product to a spinning line for spinning before spinning to obtain the nylon 6 fiber. The method can realize direct spinning after polymerization of the nylon melt, and can effectively control the content of hot water extractables and cyclic dimer in the nylon melt.
Description
Technical Field
The invention relates to the field of nylon materials, in particular to a nylon melt direct spinning method comprising vapor extraction and liquid phase extraction.
Background
Since nylon fibers (PA fibers and chinlon) have excellent physical and mechanical properties and textile processing properties, the yield of the nylon fibers is the first of a synthetic fiber family for a long time since the introduction, but the nylon fibers are the second most-produced synthetic fibers due to the limitation of price and production cost and the rapid development of polyester fibers, and the yield of the chinlon in China exceeds 330 ten thousand tons in 2018. The nylon 6 fiber has excellent physical properties which cannot be compared with polyester fiber, such as higher breaking strength of the nylon 6 fiber, wear resistance of the nylon 6 fiber in the crown of general textile fiber, good moisture absorption, excellent elastic recovery rate and fatigue resistance, and good dyeability. The nylon 6 fiber has wide application in other industries besides the garment industry and the decoration industry, for example, new products are developed on tire cord fabric, textile for automobiles, filter materials and BCF carpet bulked yarns. Although the PA6 fiber is rapidly developed in recent years, the PA6 production device, process, product and application homogenization are serious, and the like, so that the PA6 polymerization, spinning and functional product high-efficiency preparation technology is urgently needed to be developed.
Currently, in the production process of PA6 fiber, the tension of the fiber is large, and the existence of bubbles or impurities can cause the breakage of filaments, so that the requirement of PA6 spinning on melt is high, and the content of hot water extractables in the melt is required to be less than 2 wt%. The conversion rate of caprolactam hydrolytic polymerization is generally about 90%, which means that about 10% of caprolactam monomer and oligomer (also called hot water extractables, wherein the monomer accounts for about 75% and the oligomer accounts for about 25%) remain in the polymer, and impurities in the melt have great influence on spinning, so that the chips need to be subjected to extraction treatment before PA6 spinning, and the hot water extractables content of the PA6 chips is less than 0.5wt% (superior products) according to FZ/T51004 and 2011. At present, the hot water continuous extraction process is widely adopted in industry to extract monomers and oligomers in PA6 chips, so that the content of extractables in the chips is lower than 0.5wt%, and the requirement of high-speed spinning is met. However, a large amount of water and energy are consumed in the extraction, drying and remelting processes, and according to statistics, in the production process of PA6 slices, the energy consumption in the extraction and drying processes accounts for 15-20% of that in the production process of PA6 slices, so that the production cost of PA6 fibers is greatly increased. In order to avoid the defects, the PA6 spinning technology is pushed to the direction of direct spinning in the future, and compared with the spinning by a slicing method, the melt direct spinning technology can greatly simplify the production flow, has low capital investment per unit yield and is beneficial to further reducing the production cost of fibers. Therefore, the content of oligomer generated in the hydrolysis polymerization process of caprolactam is reduced by developing a new polymerization process, and the trend of directly spinning nylon 6 melt into industrial development is realized.
The main method for reducing the oligomer content in the hydrolysis polymerization process of caprolactam is to control the polymerization temperature, because the caprolactam polymerization is a balance relation which changes along with the temperature change, and the caprolactam polymerization is more beneficial to the generation of oligomers, especially cyclic oligomers, along with the increase of the temperature, so the oligomer content can be effectively controlled by controlling the polymerization temperature, namely low-temperature polymerization. In order to ensure that the polymerization process is carried out in a liquid state, the polymerization temperature is required to be at least 10 ℃ below the melting point of nylon 6, the polymerization temperature can not control the oligomer in a range of direct spinning by a fusible body, and the low-temperature polymerization has another defect that the reaction speed is slow, and the obtained polymer has a low number average molecular weight; the process of polymerization at lower temperature is actually divided into two parts, one part is melt polymerization process and the other part is solid phase polymerization process, the solid phase polymerization process is to obtain polymer with enough number average molecular weight for product development, but no effective method for changing the solid polymer formed at low temperature into polymer suitable for spinning is found at present, if fiber is spun by the low temperature polymer, the polymer must be melted firstly, however, because of chemical reaction equilibrium, low molecular compound is formed, thus, compared with normal polymerization method, no advantage is provided.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a nylon melt direct spinning method comprising vapor extraction and liquid phase extraction based on a caprolactam thermodynamic principle and a kinetic strengthening process. The method can realize direct spinning after polymerization of the nylon melt, does not need to be made into slices, and can effectively control the content of hot water extractables and cyclic dimer in the nylon melt. In the present invention, the vapor extraction and the liquid extraction are those in which the oligomer in the nylon 6 is removed from the system in a gaseous state, that is, vapor extraction, and at this time, the nylon 6 is in a molten state, that is, liquid extraction.
The specific technical scheme of the invention is as follows: a nylon melt direct spinning method comprising vapor phase extraction and liquid phase extraction comprises the following steps:
1) preparing materials: the caprolactam, the blocking agent, the water and the catalyst are heated and mixed to obtain a mixture.
2) Opening the ring: heating the mixture to carry out a ring-opening reaction.
3) Pre-polycondensation: heating the product obtained by ring opening, and carrying out pre-polycondensation reaction and devolatilization.
4) Final polycondensation: heating the product obtained by pre-polycondensation, carrying out final polycondensation reaction and devolatilization.
5) Devolatilization before spinning: and (3) performing pre-spinning devolatilization on the product obtained by final polycondensation through a thin film evaporator.
6) Spinning: directly conveying the devolatilized product to a spinning line for spinning before spinning to obtain the nylon 6 fiber.
The method comprises the following specific steps: preparing raw materials through a material preparation kettle, conveying the prepared raw materials to a ring opening kettle, carrying out ring opening reaction to obtain a nylon 6 prepolymer, conveying the obtained prepolymer to a pre-polycondensation kettle, further increasing the number average molecular weight of the nylon 6 prepolymer, conveying the obtained melt to a final polycondensation kettle for further carrying out polycondensation reaction, wherein the polymer is in a liquid state in the pre-polycondensation and final polycondensation processes, and removing a low polymer (hot water extractables) from the melt in a gas phase (namely devolatilization), so that the liquid phase extraction of the nylon 6 is realized, the content of the hot water extractables of the obtained nylon 6 melt is less than or equal to 1.5wt%, and the content of cyclic dimer is less than or equal to 0.3 wt%; the melt obtained is then conveyed to a spinning assembly, before which it is passed through a thin-film evaporator to further reduce the hot water extractables content of the melt (this devolatilization is mainly aimed at the hot water extractables newly formed during the conveyance); the nylon 6 melt finally passes through a spinning assembly and is directly subjected to melt spinning and forming. The invention has simple process, improves the utilization rate of caprolactam, reduces energy consumption, can directly melt and spin the obtained melt, can also be directly prepared into plastic products, is easy to realize large-capacity large-scale production, and can be applied to the fields of clothing fibers, industrial yarns, automobiles and the like.
The invention has the advantages that: the polymerization process is decomposed into multiple steps, the process regulation flexibility is extremely high, and the polymerization process can be regulated according to the reaction principle and characteristics of each step. For example, the reaction temperature can be reduced in the ring opening stage, and the content of cyclic dimer can be regulated in advance; most of volatiles are removed in advance by adopting a method of reducing the vacuum degree and slowing down the devolatilization speed in the pre-polycondensation process, meanwhile, a longer reaction time is given to ensure that the molecular chains fully carry out chain exchange, and the devolatilization effect is further enhanced through high vacuum final polycondensation, so that the problems of wall adhesion phenomenon and wide distribution of number average molecular weight caused by a large amount of melt bubbles generated in the process of removing a large amount of volatiles can be avoided. Through the targeted adjustment of the process, the quality of the melt is ensured while the content of hot water extractables of the melt is reduced.
In addition, the invention combines the characteristics of heat release and number average molecular weight increase of caprolactam polycondensation reaction, and partial polycondensation reaction is carried out in a final polycondensation kettle, namely the final polycondensation kettle plays a role not only in liquid phase extraction, but also can further improve the number average molecular weight of nylon 6, so that the design has the advantages that when the number average molecular weight is lower, the melt viscosity is lower, and the mass transfer process is more facilitated; in the liquid phase devolatilization process, the number average molecular weight is inevitably increased, and the processing difficulty caused by the overlarge number average molecular weight of nylon 6 can be avoided by putting part of polycondensation reaction in final polycondensation; on the other hand, the polycondensation reaction is an exothermic reaction, the design of the invention can utilize the heat of the polycondensation reaction, avoid the problem that the melt problem is obviously reduced because a large amount of heat is taken away by the formation of gas phase in the gas phase extraction process, reduce the difference between the temperature of the heat medium and the temperature of the melt, and improve the quality of the melt.
Preferably, in step 1): relative to caprolactam, the addition amount of water is 1-5wt%, the addition amount of the blocking agent is 0.1-0.5wt%, and the addition amount of the catalyst is 0.01-1 wt%.
Preferably, in step 1): the end capping agent is HOOC (CH)2)nOne or more of COOH, terephthalic acid and phthalic acid; wherein n is 2 to 10.
Preferably, in step 1): the catalyst is nylon 66 salt and NH2(CH2)XOne or more of COOH; wherein X is 4-10.
Preferably, in step 1): the mixing temperature is 80-140 deg.C, stirring for 10-60min while mixing, and the rotation speed is 60-240 r/min.
Preferably, in the step 2), the ring opening temperature is 210-260 ℃, and the reaction pressure is controlled to be 0.1-2 MPa; the reaction was terminated when the following conditions were satisfied: the number average molecular weight of the obtained prepolymer is 3000-10000, the content of hot water extractables is less than or equal to 12wt%, and the content of cyclic dimer is less than or equal to 0.6 wt%.
Preferably, in the step 3), the pre-polycondensation reaction pressure is-0.1-0.02 MPa, and the reaction temperature is 230-260 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product has a number average molecular weight of 7000-16000 and a hot water extractables content of 12wt% or less, wherein the cyclic dimer content of 0.6wt% or less.
Preferably, in the step 4), the absolute pressure of the final polycondensation reaction is 100-2000Pa, and the reaction temperature is 240-270 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product has a number average molecular weight of 16000-26000 and a hot water extractables content of less than or equal to 1.5wt%, wherein the cyclic dimer content is less than or equal to 0.3 wt%.
The basis for respectively controlling the number average molecular weights of the products obtained in the steps 2-4 in the ranges is that the volatile proportion is reduced while the good fluidity of the melt is ensured, because the number average molecular weight is too low, the content of oligomers in the melt is higher, a large amount of volatiles are removed in the pre-polycondensation and final polycondensation processes, the production efficiency is reduced, and the pressure for recycling the volatiles is increased; when the number average molecular weight is higher, melt viscosity is great, be unfavorable for realizing the work of a large amount of oligomer desorption, and simultaneously, devolatilization process can take a large amount of heats, in order to guarantee the heat supply, need improve the heat medium temperature, when the heat medium temperature is too high, can cause the fuse-element temperature difference to appear, influence the fuse-element quality, and carry out the polycondensation reaction with number average molecular weight control in certain extent, can utilize the heat that the polycondensation process released, compensate the calorific loss of volatile desorption, thereby the melt temperature is even everywhere has been guaranteed.
Preferably, in the step 5), the devolatilization temperature before spinning is kept at 250-270 ℃, and the devolatilization lasts for 5-15 s; the process pressure is below 100 pa.
Preferably, the method is realized by a nylon melt direct spinning device which comprises a batching kettle, a melt filter, a first preheater, an open-loop kettle, a pre-polycondensation kettle, a final polycondensation kettle, a second preheater, a film evaporator and a spinning assembly which are sequentially connected in series.
The pre-polycondensation kettle is a conventional pre-polycondensation kettle or a devolatilization reaction kettle with a devolatilization function, and the final polycondensation kettle is a devolatilization reaction kettle with a devolatilization function; the devolatilization reaction kettle comprises a shell, a hollow rotating shaft, a motor and at least one devolatilization disc; the bottom of the shell is provided with a melt inlet and a melt outlet, the middle part of the side surface of the shell is provided with a gas inlet, and the top of the shell is provided with a gas outlet; the hollow rotating shaft is horizontally arranged in the shell, one end of the hollow rotating shaft is communicated with the gas inlet, and the motor is used for driving the hollow rotating shaft to rotate; the devolatilization discs are fixed on the hollow rotating shaft through hollow branch pipes communicated with the hollow rotating shaft, and when the number of the devolatilization discs is multiple, the multiple devolatilization discs are sequentially arranged on the hollow rotating shaft in parallel; the devolatilization disc is distributed with air holes; the gas outlet of the devolatilization reaction kettle is connected with a vacuum condensing system. Wherein, the gas inlet of the devolatilization reaction kettle of the pre-polycondensation kettle is filled with water-containing nitrogen. While the gas inlet of the devolatilization reaction kettle as the final polycondensation kettle is not ventilated.
The invention takes the self-designed devolatilization reaction kettle as a polycondensation reaction kettle, and when the self-designed devolatilization reaction kettle is taken as a pre-polycondensation reaction kettle, hot nitrogen containing moisture is blown out of the devolatilization disk through the air holes, so that nylon 6 melt attached to the devolatilization disk is bubbled to form a thinner melt film, the devolatilization area can be further increased, and the devolatilization efficiency is improved. When the melt bubbles grow to a certain extent they break and the gas is carried away from the system under vacuum. In addition, as the cyclic dimer and other nonvolatile components have better solubility in hot water, the moisture in the hot nitrogen gas flow can interact with the cyclic dimer and other nonvolatile components, the cyclic dimer and other nonvolatile components can be driven to volatilize, the content of the nonvolatile components in the melt is reduced, the content of oligomers in the melt is further reduced, and the quality of the melt is improved. Finally, the gas containing the devolatilized component is discharged from the gas outlet, and the devolatilized nylon 6 melt flows out from the melt outlet. When the reactor is used as a final polycondensation reactor, the gas inlet is not ventilated.
To the best of the applicant's knowledge, the prior art is directed to the hot water extraction and devolatilization of nylon 6 melt, and the devolatilization is performed after polymerization, and there is no nylon 6 devolatilization method similar to the above working principle of the present invention. In the conventional devolatilization process, a device is required to have a high devolatilization area and a high vacuum degree, and under the high-efficiency devolatilization effect, the number average molecular weight of nylon 6 can be rapidly increased, and the melt viscosity is greatly increased, so that the forming is difficult. The invention not only realizes devolatilization in the polycondensation process, but also has the advantages that: because the system contains a certain amount of water, the polycondensation reaction of the nylon 6 is inhibited, the phenomenon that the number average molecular weight of the nylon 6 swells under the vacuum condition to influence the spinning forming process is avoided, time is provided for nylon 6 amide exchange, the number average molecular weight distribution is narrowed, and the melt quality is improved. In addition, as the cyclic dimer and other nonvolatile components have better solubility in hot water, the moisture in the hot nitrogen gas flow can interact with the cyclic dimer and other nonvolatile components, the cyclic dimer and other nonvolatile components can be driven to volatilize, the content of the nonvolatile components in the melt is reduced, the content of oligomers in the melt is further reduced, and the quality of the melt is improved.
Preferably, the water content of the aqueous nitrogen is 0.1 to 10 wt%.
The water content is controlled depending on the number average molecular weight and devolatilization amount of the polymerization target, and too low a water content may not inhibit the polymerization reaction, and too high a water content may not inhibit the polymerization reaction and may cause the devolatilization effect to be lowered.
Preferably, the diameter of the air hole of the devolatilization reaction kettle is 0.1-10 mm.
The diameter of the air hole is limited within the range of 0.1-10mm, the air hole can be adjusted according to the viscosity of the melt in actual production, attention needs to be paid to avoid the melt from flowing into the air hole when the diameter is designed, and meanwhile, the resistance of the melt flowing on the devolatilization disc is reduced.
Preferably, the vacuum condensation system comprises a condenser, a vacuum buffer tank and a vacuum device which are connected in sequence; and a receiving tank is arranged at the bottom of the condenser.
Preferably, the vacuum device comprises one or a combination of multiple stages of a rotary vane vacuum pump, a molecular vacuum pump, a jet vacuum pump, a diffusion pump and a diffusion jet pump.
Preferably, the condenser adopts a multi-stage condensation mode, the bottom is condensed by hot water at the temperature of 70-90 ℃, the top is condensed by cold water at the temperature of 1-20 ℃, and 2-5 temperature gradients are arranged in the middle.
Preferably, a reflux mechanism is arranged on the ring opening kettle, a product with the reaction time of 0.5-1.5h is conveyed to the top of the kettle to be refluxed and mixed with fresh caprolactam, and the reflux amount is 0.1-2 wt% of the flow of the caprolactam; and a stirring mechanism is arranged at the top of the open-loop kettle.
The invention improves the ring opening kettle according to the physical property and the process characteristics of a caprolactam ring opening product, namely a reflux mechanism is arranged to reflux a caprolactam prepolymer to the top of the kettle to be mixed with fresh caprolactam, and because the caprolactam prepolymer contains a large amount of linear oligomers, the linear oligomers can greatly improve the ring opening speed of the caprolactam, the ring opening speed of the caprolactam at a lower temperature is accelerated, and the production cost is reduced. Specifically, the caprolactam ring-opening reaction is an endothermic reaction, which is slow in reaction without the action of a catalyst and needs a long time to reach a balance, and the catalyst for promoting the caprolactam reaction is most commonly aminocaproic acid (high industrial price and high direct addition cost), and linear caprolactam prepolymer also has a good catalytic effect.
Compared with the prior art, the invention has the beneficial effects that:
1. compared with the prior art, the invention provides a caprolactam polymerization and spinning method comprising gas phase extraction and liquid phase extraction, and the polymerization and spinning process is simple, and can be carried out by modifying the traditional caprolactam polymerization equipment, thereby improving the utilization rate of caprolactam, reducing energy consumption and being easy for large-scale production.
2. The invention decomposes the polymerization process into a plurality of steps, has extremely high process regulation flexibility, can regulate the polymerization process according to the reaction principle and the characteristics of each step, and can reduce the reaction temperature and regulate the content of the cyclic dimer in advance if the ring opening stage is adopted; most of volatiles are removed in advance by adopting a method of reducing the vacuum degree and slowing down the devolatilization speed in the pre-polycondensation process, meanwhile, a longer reaction time is given to ensure that the molecular chains fully carry out chain exchange, and the devolatilization effect is further enhanced through high vacuum final polycondensation, so that the problems of wall adhesion phenomenon and wide distribution of number average molecular weight caused by a large amount of melt bubbles generated in the process of removing a large amount of volatiles can be avoided. Through the targeted adjustment of the process, the quality of the melt is ensured while the content of hot water extractables of the melt is reduced.
3. The invention combines the characteristics of heat release and number average molecular weight increase of caprolactam polycondensation reaction, and partial polycondensation reaction is carried out in a final polycondensation kettle, namely the final polycondensation kettle plays a role not only in liquid phase extraction, but also can further improve the number average molecular weight of nylon 6, so that the design has the advantages that when the number average molecular weight is lower, the melt viscosity is lower, and the mass transfer process is more facilitated; in the liquid phase devolatilization process, the number average molecular weight is inevitably increased, and the processing difficulty caused by the overlarge number average molecular weight of nylon 6 can be avoided by putting part of polycondensation reaction in final polycondensation; in addition, the polycondensation reaction is an exothermic reaction, the design of the invention can utilize the heat of the polycondensation reaction, avoid the problem that the melt problem is obviously reduced because a large amount of heat is taken away by the formation of gas phase in the gas phase extraction process, reduce the difference between the temperature of the heat medium and the temperature of the melt, and improve the quality of the melt.
4. According to the invention, the film evaporator with the efficient devolatilization effect is added in front of the spinning assembly, so that the content of hot water extractables in the melt is further reduced, the spinnability of the melt is improved, the content of oligomers is less than or equal to 1.5wt%, the content of cyclic dimers is less than or equal to 0.3wt%, the relative viscosity of the product is 2.4-3.3, and the product can be directly conveyed to a spinning box to be spun into nylon 6 fibers.
5. The invention improves the ring opening kettle according to the physical property and the process characteristics of a caprolactam ring opening product, namely a reflux mechanism is arranged to reflux a caprolactam prepolymer to the top of the tower to be mixed with fresh caprolactam, and because the caprolactam prepolymer contains a large amount of linear oligomers, the linear oligomers can greatly improve the ring opening speed of the caprolactam, the ring opening speed of the caprolactam at a lower temperature is accelerated, and the production cost is reduced at the same time. The top of the tower is provided with a stirring device to ensure the even mixing of materials at the top of the tower.
6. The invention takes the devolatilization reaction kettle designed by the invention as the polycondensation reaction kettle according to the characteristics of mass transfer and heat transfer of the melt in the polycondensation process, namely the characteristic that a large amount of volatile matters need to be removed in the process. The devolatilization can be carried out simultaneously with the polycondensation. Effectively reduces the content of hot water extractables in the melt and realizes direct spinning of the melt.
Drawings
FIG. 1 is a schematic view of a nylon melt direct spinning apparatus according to examples 1-6 of the present invention;
FIG. 2 is a schematic view of the structure of a devolatilization disk in a devolatilization reactor of examples 1-6 of the present invention;
FIG. 3 is a schematic view of a nylon melt direct spinning apparatus according to example 7 of the present invention.
The reference signs are: the system comprises a batching kettle 1, a melt filter 2, a first preheater 3, a ring opening kettle 4, a pre-polycondensation kettle 5, a final polycondensation kettle 6, a second preheater 7, a thin film evaporator 8, a spinning assembly 9, a shell 101, a hollow rotating shaft 102, a motor 103, a devolatilization disc 104, a melt inlet 105, a melt outlet 106, a gas inlet 107, a gas outlet 108, a hollow branch pipe 109, an air hole 110, a condenser 11, a vacuum buffer tank 12, a vacuum device 13, a receiving tank 14, a reflux mechanism 15 and a stirring mechanism 16.
Detailed Description
The present invention will be further described with reference to the following examples.
General examples
A nylon melt direct spinning method comprising vapor phase extraction and liquid phase extraction comprises the following steps:
1) preparing materials: the caprolactam, the blocking agent, the water and the catalyst are heated and mixed to obtain a mixture.
2) Opening the ring: heating the mixture to carry out a ring-opening reaction.
3) Pre-polycondensation: heating the product obtained by ring opening, and carrying out pre-polycondensation reaction and devolatilization.
4) Final polycondensation: heating the product obtained by pre-polycondensation, carrying out final polycondensation reaction and devolatilization.
5) Devolatilization before spinning: and (3) performing pre-spinning devolatilization on the product obtained by final polycondensation through a thin film evaporator.
6) Spinning: directly conveying the devolatilized product to a spinning line for spinning before spinning to obtain the nylon 6 fiber.
Preferably, in step 1): relative to caprolactam, the addition amount of water is 1-5wt%, the addition amount of the blocking agent is 0.1-0.5wt%, and the addition amount of the catalyst is 0.01-1 wt%. The end capping agent is HOOC (CH)2)nOne or more of COOH, terephthalic acid and phthalic acid; wherein n is 2 to 10. The catalyst is nylon 66 salt and NH2(CH2)XOne or more of COOH; wherein X is 4-10. The mixing temperature is 80-140 deg.C, stirring for 10-60min while mixing, and the rotation speed is 60-240 r/min.
Preferably, in the step 2), the ring opening temperature is 210-260 ℃, and the reaction pressure is controlled to be 0.1-2 MPa; the reaction was terminated when the following conditions were satisfied: the number average molecular weight of the obtained prepolymer is 3000-10000, the content of hot water extractables is less than or equal to 12wt%, and the content of cyclic dimer is less than or equal to 0.6 wt%.
Preferably, in the step 3), the pre-polycondensation reaction pressure is-0.1-0.02 MPa, and the reaction temperature is 230-260 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product has a number average molecular weight of 7000-16000 and a hot water extractables content of 12wt% or less, wherein the cyclic dimer content of 0.6wt% or less.
Preferably, in the step 4), the absolute pressure of the final polycondensation reaction is 100-2000Pa, and the reaction temperature is 240-270 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product has a number average molecular weight of 16000-26000 and a hot water extractables content of less than or equal to 1.5wt%, wherein the cyclic dimer content is less than or equal to 0.3 wt%.
Preferably, in the step 5), the devolatilization temperature before spinning is kept at 250-270 ℃, and the devolatilization lasts for 5-15 s; the process pressure is below 100 pa.
The method is realized by a nylon melt direct spinning device which comprises a batching kettle 1, a melt filter 2, a first preheater 3, an open-loop kettle 4, a pre-polycondensation kettle 5, a final polycondensation kettle 6, a second preheater 7, a film evaporator 8 and a spinning assembly 9 which are sequentially connected in series.
The pre-polycondensation kettle is a conventional pre-polycondensation kettle or a devolatilization reaction kettle with a devolatilization function, and the final polycondensation kettle is a devolatilization reaction kettle 10 with a devolatilization function; the devolatilization reaction kettle comprises a shell 101, a hollow rotating shaft 102, a motor 103 and at least one devolatilization disk 104; the bottom of the shell is provided with a melt inlet 105 and a melt outlet 106, the middle of the side surface of the shell is provided with a gas inlet 107, and the top of the shell is provided with a gas outlet 108; the hollow rotating shaft is horizontally arranged in the shell, one end of the hollow rotating shaft is communicated with the gas inlet, and the motor is used for driving the hollow rotating shaft to rotate; the devolatilization discs are fixed on the hollow rotating shaft through hollow branch pipes 109 communicated with the hollow rotating shaft, and when the number of the devolatilization discs is multiple, a plurality of the devolatilization discs are sequentially arranged in parallel on the hollow rotating shaft; the devolatilization disc is distributed with air holes 110 (the diameter is 0.1-10 mm); the gas outlet of the devolatilization reaction kettle is connected with a vacuum condensing system. Wherein, the gas inlet of the devolatilization reaction kettle which is taken as the pre-polycondensation kettle is filled with water-containing nitrogen, and the water content is 0.1 to 10 weight percent.
The vacuum condensation system comprises a condenser 11, a vacuum buffer tank 12 and a vacuum device 13 which are connected in sequence; the bottom of the condenser is provided with a receiving tank 14. The vacuum device comprises one or a combination formed by connecting multiple stages of a rotary vane vacuum pump, a molecular vacuum pump, an injection vacuum pump, a diffusion pump and a diffusion injection pump in series.
The condenser adopts a multi-stage condensation mode, the bottom adopts hot water condensation, the temperature is 70-90 ℃, the top adopts cold water condensation, the temperature is 1-20 ℃, and 2-5 temperature gradients are arranged in the middle.
The ring opening kettle is provided with a reflux mechanism 15, a product with the reaction time of 0.5-1.5h is conveyed to the top of the kettle to be refluxed and mixed with fresh caprolactam, and the reflux amount is 0.1-2 wt% of the flow of the caprolactam; and a stirring mechanism 16 is arranged at the top of the ring-opening kettle.
Example 1
The first step is as follows: under the condition of 80 deg.C making Caprolactam and HOOC (CH)2)2Mixing COOH, deionized water and nylon 66 salt in proportion, and stirring for 60min under the condition of mechanical stirring (60 r/min); wherein deionized water is used relative to caprolactamThe addition amount is 1wt%, HOOC (CH)2)2The addition amount of COOH is 0.5wt%, and the addition amount of nylon 66 salt is 1 wt%;
the second step is that: heating the mixture obtained in the first step by a melt pump and a preheater, and conveying the mixture to a ring opening kettle for ring opening reaction, wherein the polymerization temperature is controlled at 210 ℃, and the polymerization pressure is controlled at 2 MPa; the prepolymer having a reaction time of 0.5h was conveyed via a melt pump to the top of the column and mixed with fresh caprolactam at a reflux amount of 2% by weight of the caprolactam flow. The reaction was terminated when the following conditions were satisfied: the number average molecular weight of the obtained prepolymer is 3880, the content of extractables is less than or equal to 12wt%, and the content of cyclic dimer is less than or equal to 0.25 wt%;
the third step: conveying a product obtained by ring opening to a pre-polycondensation kettle for pre-polycondensation reaction, wherein the pressure of the pre-polycondensation reaction is-0.05 MPa, and the reaction temperature is 260 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product has a number average molecular weight of 7850 and an extractables content of less than or equal to 3.9wt%, wherein the cyclic dimer content is less than or equal to 0.20 wt%;
the fourth step: a final polycondensation reaction, wherein the material obtained by the pre-polycondensation reaction is conveyed to a final polycondensation kettle for further reaction, the absolute pressure of the reaction is 100Pa, and the reaction temperature is 270 ℃; the reaction was terminated when the following conditions were satisfied: the product obtained had a number average molecular weight of 15840 and an extractables content of 1.1% by weight, with a cyclic dimer content of 0.19% by weight;
the fifth step: conveying the final polycondensation reaction product to a spinning line, and further devolatilizing by adopting a thin film evaporator in front of a spinning box body; the devolatilization temperature was maintained at 250 ℃; the devolatilization lasts for 15 s; the process pressure is below 100 pa;
the condenser adopted in the third step to the fifth step adopts a multi-stage condensation mode, namely the bottom adopts hot water condensation, the temperature is 70 ℃, the top is condensed by cold water, the temperature is 20 ℃, and 5 temperature gradients (respectively 68, 62, 55, 41 and 28 ℃) are arranged in the middle; the adopted vacuum system adopts a jet vacuum pump and three stages are connected in series for use.
And a sixth step: and directly carrying out melt spinning on the product obtained in the previous step to obtain the nylon 6 fiber.
Example 2
The first step is as follows: under the condition of 140 ℃, caprolactam, terephthalic acid, deionized water and NH2(CH2)4Mixing COOH in proportion, and stirring for 10min under the condition of mechanical stirring (240 r/min); wherein the addition amount of deionized water is 5wt%, the addition amount of terephthalic acid is 0.1wt%, and NH relative to caprolactam2(CH2)4The addition amount of COOH was 0.01 wt%;
the second step is that: heating the mixture obtained in the first step by a melt pump and a preheater, and conveying the mixture to a ring opening kettle for ring opening reaction, wherein the polymerization temperature is controlled at 260 ℃, and the polymerization pressure is controlled at 0.1 MPa; the prepolymer having a reaction time of 1.5h was conveyed via a melt pump to the top of the column and mixed with fresh caprolactam at a reflux quantity of 0.1% by weight based on the caprolactam flow. The reaction was terminated when the following conditions were satisfied: the number average molecular weight of the obtained prepolymer is 9830, the content of extractables is less than or equal to 8wt%, and the content of cyclic dimer is less than or equal to 0.6 wt%;
the third step: conveying a product obtained by ring opening to a pre-polycondensation kettle for pre-polycondensation reaction, wherein the pressure of the pre-polycondensation reaction is 0MPa, and the reaction temperature is 230 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product has a number average molecular weight of 15720 and an extractables content of less than or equal to 5.4wt%, wherein the cyclic dimer content is less than or equal to 0.33 wt%;
the fourth step: a final polycondensation reaction, wherein the material obtained by the pre-polycondensation reaction is conveyed to a final polycondensation kettle for further reaction, the absolute pressure of the reaction is 2000Pa, and the reaction temperature is 240 ℃; the reaction was terminated when the following conditions were satisfied: the product obtained had a number average molecular weight of 25830 and an extractables content of 0.98% by weight, with a cyclic dimer content of 0.19% by weight;
the fifth step: conveying the final polycondensation reaction product to a spinning line, and further devolatilizing by adopting a thin film evaporator in front of a spinning box body; the devolatilization temperature was maintained at 250 ℃; the devolatilization lasts for 5 s; the process pressure is below 100 pa;
the condenser adopted in the third step to the fifth step adopts a multi-stage condensation mode, namely the bottom adopts hot water condensation, the temperature is 90 ℃, the top is condensed by cold water, the temperature is 1 ℃, and 2 temperature gradients (70 ℃ and 30 ℃ respectively) are arranged in the middle; the adopted vacuum system adopts a diffusion jet pump and two stages are connected in series for use.
And a sixth step: and directly carrying out melt spinning on the product obtained in the previous step to obtain the nylon 6 fiber.
Example 3
The first step is as follows: under the condition of 100 deg.C making Caprolactam and HOOC (CH)2)10COOH, deionized water and NH2(CH2)10Mixing COOH in proportion, and stirring for 40min under the condition of mechanical stirring (100 r/min); wherein the amount of deionized water added is 2wt% relative to caprolactam, HOOC (CH)2)10The amount of COOH added was 0.4wt%, NH2(CH2)10The addition amount of COOH was 0.5 wt%;
the second step is that: heating the mixture obtained in the first step by a melt pump and a preheater, and conveying the mixture to a ring opening kettle for ring opening reaction, wherein the polymerization temperature is controlled at 230 ℃, and the polymerization pressure is controlled at 1 MPa; the prepolymer having a reaction time of 1h was conveyed to the top of the column by means of a melt pump and mixed with fresh caprolactam at a reflux quantity of 1% by weight of the caprolactam flow. The reaction was terminated when the following conditions were satisfied: the number average molecular weight of the obtained prepolymer is 5470, the content of extractables is less than or equal to 12wt%, and the content of cyclic dimer is less than or equal to 0.46 wt%;
the third step: conveying a product obtained by ring opening to a pre-polycondensation kettle for pre-polycondensation reaction, wherein the pressure of the pre-polycondensation reaction is-0.05 MPa, and the reaction temperature is 250 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product has a number average molecular weight of 7520 and an extractables content of 3.5 wt.% or less, wherein the cyclic dimer content is 0.18 wt.% or less;
the fourth step: a final polycondensation reaction, wherein the material obtained by the pre-polycondensation reaction is conveyed to a final polycondensation kettle for further reaction, the absolute pressure of the reaction is 200Pa, and the reaction temperature is 260 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product had a number average molecular weight of 21490 and an extractables content of 0.76 wt.%, wherein the cyclic dimer content was 0.15 wt.%;
the fifth step: conveying the final polycondensation reaction product to a spinning line, and further devolatilizing by adopting a thin film evaporator in front of a spinning box body; the devolatilization temperature was maintained at 260 ℃; the devolatilization lasts for 10 s; the process pressure is below 100 pa;
the condenser adopted in the third step to the fifth step adopts a multi-stage condensation mode, namely the bottom adopts hot water condensation, the temperature is 80 ℃, the top is condensed by cold water, the temperature is 10 ℃, and 3 temperature gradients (respectively 70, 55 and 30 ℃) are arranged in the middle; the adopted vacuum system adopts a jet vacuum pump and is used independently.
And a sixth step: and directly carrying out melt spinning on the product obtained in the previous step to obtain the nylon 6 fiber.
Example 4
The first step is as follows: under the condition of 80 deg.C making Caprolactam and HOOC (CH)2)4COOH, deionized water and NH2(CH2)6Mixing COOH in proportion, and stirring for 20min under the condition of mechanical stirring (200 r/min); wherein the amount of deionized water added is 1.5wt% relative to caprolactam, HOOC (CH)2)4The amount of COOH added was 0.3wt%, NH2(CH2)6The addition amount of COOH was 0.8 wt%;
the second step is that: heating the mixture obtained in the first step by a melt pump and a preheater, and conveying the mixture to a ring opening kettle for ring opening reaction, wherein the polymerization temperature is controlled at 215 ℃, and the polymerization pressure is controlled at 0.5 MPa; the prepolymer having a reaction time of 1.2h was conveyed via a melt pump to the top of the column and mixed with fresh caprolactam at a reflux quantity of 1.5% by weight based on the caprolactam flow. The reaction was terminated when the following conditions were satisfied: the number average molecular weight of the obtained prepolymer is 7000, the content of extractables is less than or equal to 11.5wt%, and the content of cyclic dimer is less than or equal to 0.2 wt%;
the third step: conveying a product obtained by ring opening to a pre-polycondensation kettle for pre-polycondensation reaction, wherein the pressure of the pre-polycondensation reaction is-0.07 MPa, and the reaction temperature is 255 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product has a number average molecular weight of 8120, an extractables content of less than or equal to 2.8wt%, wherein the cyclic dimer content is less than or equal to 0.15 wt%;
the fourth step: a final polycondensation reaction, wherein the material obtained by the pre-polycondensation reaction is conveyed to a final polycondensation kettle for further reaction, the absolute pressure of the reaction is 1000Pa, and the reaction temperature is 262 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product had a number average molecular weight of 18730 and an extractables content of 1.1% by weight, with a cyclic dimer content of 0.14% by weight;
the fifth step: conveying the final polycondensation reaction product to a spinning line, and further devolatilizing by adopting a thin film evaporator in front of a spinning box body; the devolatilization temperature was maintained at 253 ℃; the devolatilization lasts for 11 s; the process pressure is below 100 pa;
the condenser adopted in the third step to the fifth step adopts a multi-stage condensation mode, namely the bottom adopts hot water condensation, the temperature is 75 ℃, the top is condensed by cold water, the temperature is 12 ℃, and 4 temperature gradients (respectively 70, 65, 60 and 30 ℃) are arranged in the middle; the adopted vacuum system adopts an injection vacuum pump and two stages are connected in series for use.
And a sixth step: and directly carrying out melt spinning on the product obtained in the previous step to obtain the nylon 6 fiber.
Example 5
The first step is as follows: under the condition of 90 ℃, caprolactam, phthalic acid, deionized water and NH2(CH2)8Mixing COOH in proportion, and stirring for 35min under the condition of mechanical stirring (180 r/min); wherein the addition amount of deionized water is 2.2wt%, the addition amount of phthalic acid is 0.15wt%, and NH relative to caprolactam2(CH2)8The addition amount of COOH is 1 wt%;
the second step is that: heating the mixture obtained in the first step by a melt pump and a preheater, and conveying the mixture to a ring opening kettle for ring opening reaction, wherein the polymerization temperature is controlled at 240 ℃, and the polymerization pressure is controlled at 0.8 MPa; the prepolymer having a reaction time of 1.3h was conveyed via a melt pump to the top of the column and mixed with fresh caprolactam at a reflux quantity of 1.9% by weight based on the caprolactam flow. The reaction was terminated when the following conditions were satisfied: the obtained prepolymer has a number average molecular weight of 7470, and an extractable content of less than or equal to 10.1wt%, wherein the content of cyclic dimer is less than or equal to 0.48 wt%;
the third step: conveying a product obtained by ring opening to a pre-polycondensation kettle for pre-polycondensation reaction, wherein the pressure of the pre-polycondensation reaction is-0.09 MPa, and the reaction temperature is 245 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product has a number average molecular weight of 9000 and an extractables content of not more than 2.5wt%, wherein the cyclic dimer content of not more than 0.14 wt%;
the fourth step: a final polycondensation reaction, wherein the material obtained by the pre-polycondensation reaction is conveyed to a final polycondensation kettle for further reaction, the absolute pressure of the reaction is 500Pa, and the reaction temperature is 265 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product had a number average molecular weight of 19210 and an extractables content of 0.95wt%, with a cyclic dimer content of 0.11 wt%;
the fifth step: conveying the final polycondensation reaction product to a spinning line, and further devolatilizing by adopting a thin film evaporator in front of a spinning box body; the devolatilization temperature is maintained at 255 ℃; the devolatilization lasts for 8 s; the process pressure is below 100 pa;
the condenser adopted in the third step to the fifth step adopts a multi-stage condensation mode, namely the bottom adopts hot water condensation, the temperature is 71 ℃, the top is condensed by cold water, the temperature is 18 ℃, and 5 temperature gradients (respectively 69, 65, 61, 50 and 30 ℃) are arranged in the middle; the adopted vacuum system adopts a rotary vane vacuum pump and three stages are connected in series for use.
And a sixth step: and directly carrying out melt spinning on the product obtained in the previous step to obtain the nylon 6 fiber.
Example 6
The first step is as follows: under the condition of 90 deg.C making Caprolactam and HOOC (CH)2)3COOH, deionized water and NH2(CH2)5Mixing COOH in proportion, and stirring for 60min under the condition of mechanical stirring (60 r/min); wherein the amount of deionized water added is 1wt% relative to caprolactam, HOOC (CH)2)3The amount of COOH added was 0.3wt%, NH2(CH2)5The addition amount of COOH is 1 wt%;
the second step is that: heating the mixture obtained in the first step by a melt pump and a preheater, and conveying the mixture to a ring opening kettle for ring opening reaction, wherein the polymerization temperature is controlled at 245 ℃, and the polymerization pressure is controlled at 1.3 MPa; the prepolymer having a reaction time of 0.8h was conveyed via a melt pump to the top of the column and mixed with fresh caprolactam at a reflux quantity of 0.8% by weight based on the caprolactam flow. The reaction was terminated when the following conditions were satisfied: the obtained prepolymer has the number average molecular weight of 5970, the content of extractables is less than or equal to 10.8wt%, and the content of cyclic dimer is less than or equal to 0.51 wt%;
the third step: conveying a product obtained by ring opening to a pre-polycondensation kettle for pre-polycondensation reaction, wherein the pressure of the pre-polycondensation reaction is-0.04 MPa, and the reaction temperature is 265 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product has a number average molecular weight of 7830 and an extractables content of less than or equal to 5.1wt%, wherein the cyclic dimer content is less than or equal to 0.31 wt%;
the fourth step: a final polycondensation reaction, wherein the material obtained by the pre-polycondensation reaction is conveyed to a final polycondensation kettle for further reaction, the absolute pressure of the reaction is 800Pa, and the reaction temperature is 265 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product had a number average molecular weight of 21470 and an extractables content of 1.2 wt.%, wherein the cyclic dimer content was 0.24 wt.%;
the fifth step: conveying the final polycondensation reaction product to a spinning line, and further devolatilizing by adopting a thin film evaporator in front of a spinning box body; the devolatilization temperature is maintained at 258 ℃; the devolatilization lasts for 6 s; the process pressure is below 100 pa;
the condenser adopted in the third step to the fifth step adopts a multi-stage condensation mode, namely the bottom adopts hot water for condensation, the temperature is 79 ℃, the top is condensed by cold water, the temperature is 12 ℃, and 4 temperature gradients (respectively 75, 64, 45 and 32 ℃) are arranged in the middle; the adopted vacuum system adopts a molecular vacuum pump and three stages are connected in series for use.
And a sixth step: and directly carrying out melt spinning on the product obtained in the previous step to obtain the nylon 6 fiber.
As shown in fig. 1, examples 1 to 6 were realized by a nylon melt direct spinning apparatus comprising a compounding tank 1, a melt filter 2, a first preheater 3, an open-loop tank 4, a pre-polycondensation tank 5, a final polycondensation tank 6, a second preheater 7, a thin film evaporator 8 and a spinning pack 9, which were connected in series in this order.
The pre-polycondensation kettle and the final polycondensation kettle are devolatilization reaction kettles 10 with devolatilization functions; as shown in fig. 1, the devolatilization reactor comprises a shell 101, a hollow rotating shaft 102, a motor 103 and at least one devolatilization disk 104; the bottom of the shell is provided with a melt inlet 105 and a melt outlet 106, the middle of the side surface of the shell is provided with a gas inlet 107, and the top of the shell is provided with a gas outlet 108; the hollow rotating shaft is horizontally arranged in the shell, one end of the hollow rotating shaft is communicated with the gas inlet, and the motor is used for driving the hollow rotating shaft to rotate; the devolatilization plates are fixed on the hollow rotating shaft through hollow branch pipes 109 communicated with the hollow rotating shaft, and 12 devolatilization plates are sequentially arranged on the hollow rotating shaft in parallel; as shown in fig. 2, the devolatilization plate is distributed with air holes 110 (diameter is 2 mm); the gas outlet of the devolatilization reaction kettle is connected with a vacuum condensing system. Wherein, the gas inlet of the devolatilization reaction kettle which is taken as the pre-polycondensation kettle is filled with water-containing nitrogen, and the water content is 5 wt%.
The vacuum condensation system comprises a condenser 11, a vacuum buffer tank 12 and a vacuum device 13 which are connected in sequence; the bottom of the condenser is provided with a receiving tank 14. Be equipped with return mechanism 15 on the ring opening cauldron, the ring opening cauldron top is equipped with rabbling mechanism 16.
Example 7
The first step is as follows: under the condition of 80 deg.C making Caprolactam and HOOC (CH)2)2Mixing COOH, deionized water and nylon 66 salt in proportion, and stirring for 60min under the condition of mechanical stirring (60 r/min); wherein the amount of deionized water added is 1wt% relative to caprolactam, HOOC (CH)2)2The addition amount of COOH is 0.5wt%, and the addition amount of nylon 66 salt is 1 wt%;
the second step is that: heating the mixture obtained in the first step by a melt pump and a preheater, and conveying the mixture to a ring opening kettle for ring opening reaction, wherein the polymerization temperature is controlled at 210 ℃, and the polymerization pressure is controlled at 2 MPa; the prepolymer having a reaction time of 0.5h was conveyed via a melt pump to the top of the column and mixed with fresh caprolactam at a reflux amount of 2% by weight of the caprolactam flow. The reaction was terminated when the following conditions were satisfied: the number average molecular weight of the obtained prepolymer is 3880, the content of extractables is less than or equal to 12wt%, and the content of cyclic dimer is less than or equal to 0.25 wt%;
the third step: conveying a product obtained by ring opening to a pre-polycondensation kettle for pre-polycondensation reaction, wherein the pressure of the pre-polycondensation reaction is 0.01MPa, and the reaction temperature is 260 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product has a number average molecular weight of 7850 and an extractables content of 10.7 wt.% or less, wherein the cyclic dimer content is 0.46 wt.% or less;
the fourth step: a final polycondensation reaction, wherein the material obtained by the pre-polycondensation reaction is conveyed to a final polycondensation kettle for further reaction, the absolute pressure of the reaction is 100Pa, and the reaction temperature is 270 ℃; the reaction was terminated when the following conditions were satisfied: the product obtained had a number average molecular weight of 18950 and an extractables content of 1.48% by weight, with a cyclic dimer content of 0.28% by weight;
the fifth step: conveying the final polycondensation reaction product to a spinning line, and further devolatilizing by adopting a thin film evaporator in front of a spinning box body; the devolatilization temperature was maintained at 250 ℃; the devolatilization lasts for 15 s; the process pressure is below 100 pa;
the condenser adopted in the third step to the fifth step adopts a multi-stage condensation mode, namely the bottom adopts hot water condensation, the temperature is 70 ℃, the top is condensed by cold water, the temperature is 20 ℃, and 5 temperature gradients (respectively 68, 62, 55, 41 and 28 ℃) are arranged in the middle; the adopted vacuum system adopts a jet vacuum pump and three stages are connected in series for use.
And a sixth step: and directly carrying out melt spinning on the product obtained in the previous step to obtain the nylon 6 fiber.
Example 7 differs from example 1 only in that, as shown in FIG. 3, a conventional prepolycondensation vessel is used for the prepolycondensation. Since the preliminary devolatilization in the preliminary polycondensation process is reduced, the extractable content and cyclic dimer content of the product of the preliminary polycondensation are higher than those in example 1, resulting in a larger devolatilization amount in the final polycondensation, a longer reaction time is required, and a larger number average molecular weight is obtained to achieve the desired extractable content and cyclic dimer content.
The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the protection scope of the technical solution of the present invention.
Claims (14)
1. A nylon melt direct spinning method comprising vapor extraction and liquid phase extraction is characterized by comprising the following steps:
1) preparing materials: heating and mixing caprolactam, a blocking agent, water and a catalyst to obtain a mixture;
2) opening the ring: heating the mixture to carry out a ring opening reaction;
3) pre-polycondensation: heating the product obtained by ring opening, and carrying out pre-polycondensation reaction and devolatilization;
4) final polycondensation: heating the product obtained by pre-polycondensation, and carrying out final polycondensation reaction and devolatilization;
5) devolatilization before spinning: performing pre-spinning devolatilization on the product obtained by final polycondensation through a film evaporator;
6) spinning: directly conveying the devolatilized product to a spinning line for spinning before spinning to obtain the nylon 6 fiber.
2. The method of claim 1, wherein in step 5), the pre-spinning devolatilization temperature is maintained at 250 to 270 ℃ for 5 to 15 seconds; the process pressure is below 100 pa.
3. The method of claim 1, wherein in step 1):
relative to caprolactam, the addition amount of water is 1-5wt%, the addition amount of a blocking agent is 0.1-0.5wt%, and the addition amount of a catalyst is 0.01-1 wt%; and/or
The end capping agent is HOOC (CH)2)nOne or more of COOH, terephthalic acid and phthalic acid; wherein n is 2 to 10; and/or
The catalyst is nylon 66 salt and NH2(CH2)XOne or more of COOH; wherein X is 4-10; and/or
The mixing temperature is 80-140 deg.C, stirring for 10-60min while mixing, and the rotation speed is 60-240 r/min.
4. The method as claimed in claim 1 or 3, wherein, in the step 2), the ring-opening temperature is 210 ℃ and 260 ℃, and the reaction pressure is controlled to be 0.1-2 MPa; the reaction was terminated when the following conditions were satisfied: the number average molecular weight of the obtained prepolymer is 3000-10000, the content of hot water extractables is less than or equal to 12wt%, and the content of cyclic dimer is less than or equal to 0.6 wt%.
5. The method of claim 4, wherein in step 3), the pre-polycondensation reaction pressure is-0.1 to 0.02MPa, and the reaction temperature is 230 to 260 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product has a number average molecular weight of 7000-16000 and a hot water extractables content of 12wt% or less, wherein the cyclic dimer content of 0.6wt% or less.
6. The method as claimed in claim 5, wherein in step 4), the absolute pressure of the final polycondensation reaction is 100-2000Pa, and the reaction temperature is 240-270 ℃; the reaction was terminated when the following conditions were satisfied: the obtained product has a number average molecular weight of 16000-26000 and a hot water extractables content of less than or equal to 1.5wt%, wherein the cyclic dimer content is less than or equal to 0.3 wt%.
7. The method of claim 1, wherein the method is realized by a nylon melt direct spinning device which comprises a batching kettle, a melt filter, a first preheater, an open-loop kettle, a pre-polycondensation kettle, a final polycondensation kettle, a second preheater, a film evaporator and a spinning assembly which are connected in series in sequence;
the pre-polycondensation kettle is a conventional pre-polycondensation kettle or a devolatilization reaction kettle with a devolatilization function, and the final polycondensation kettle is a devolatilization reaction kettle with a devolatilization function; the devolatilization reaction kettle comprises a shell, a hollow rotating shaft, a motor and at least one devolatilization disc; the bottom of the shell is provided with a melt inlet and a melt outlet, the middle part of the side surface of the shell is provided with a gas inlet, and the top of the shell is provided with a gas outlet; the hollow rotating shaft is horizontally arranged in the shell, one end of the hollow rotating shaft is communicated with the gas inlet, and the motor is used for driving the hollow rotating shaft to rotate; the devolatilization discs are fixed on the hollow rotating shaft through hollow branch pipes communicated with the hollow rotating shaft, and when the number of the devolatilization discs is multiple, the multiple devolatilization discs are sequentially arranged on the hollow rotating shaft in parallel; the devolatilization disc is distributed with air holes; the gas outlet of the devolatilization reaction kettle is connected with a vacuum condensing system.
8. The method of claim 7, wherein the vacuum condensing system comprises a condenser, a vacuum buffer tank and a vacuum device connected in series; and a receiving tank is arranged at the bottom of the condenser.
9. The method of claim 7 wherein said devolatilization reactor has a pore diameter of from 0.1 mm to 10 mm.
10. The method of claim 8, wherein the vacuum device comprises one or more of a rotary vane vacuum pump, a molecular vacuum pump, a jet vacuum pump, a diffusion pump, and a diffusion jet pump in series.
11. The method as claimed in claim 8, wherein the condenser is multi-stage condensing, the bottom is hot water condensing at 70-90 deg.C, the top is cold water condensing at 1-20 deg.C, and there are 2-5 temperature gradients in the middle.
12. The method as claimed in claim 7, characterized in that the ring opening kettle is provided with a reflux mechanism, the product with the reaction time of 0.5-1.5h is conveyed to the top of the kettle to be refluxed and mixed with fresh caprolactam, and the reflux amount is 0.1-2 wt% of the caprolactam flow; and a stirring mechanism is arranged at the top of the open-loop kettle.
13. The method of claim 7, wherein aqueous nitrogen is introduced as a gas inlet of said devolatilization reactor of the prepolycondensation reactor.
14. The method of claim 13, wherein the aqueous nitrogen has a water content of 0.1 to 10 wt.%.
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| CN112030250A (en) * | 2020-07-24 | 2020-12-04 | 苏州大学 | Multifunctional nylon 6 fiber with functions of heat preservation and moisture conduction and preparation method thereof |
| CN112064137A (en) * | 2020-08-05 | 2020-12-11 | 常州恒利宝纳米新材料科技有限公司 | Preparation method of polyamide 6 and melt direct-spun fiber of polyamide 6 graphene modified substance |
| CN113463214A (en) * | 2021-06-29 | 2021-10-01 | 浙江恒澜科技有限公司 | Direct spinning method and device for nylon 6 melt |
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| CN115317936A (en) * | 2022-06-30 | 2022-11-11 | 武汉纺织大学 | Thin film evaporator and method for removing monomers and oligomers in PA6 polymer melt |
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| CN115317936A (en) * | 2022-06-30 | 2022-11-11 | 武汉纺织大学 | Thin film evaporator and method for removing monomers and oligomers in PA6 polymer melt |
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