CN109972228B

CN109972228B - Preparation method of polyamide and nylon fiber prepared by preparation method

Info

Publication number: CN109972228B
Application number: CN201910353480.2A
Authority: CN
Inventors: 刘驰; 秦兵兵; 郑毅; 刘修才
Original assignee: Cathay R&D Center Co Ltd; CIBT America Inc
Current assignee: Kasai Shanghai Biotechnology Co ltd; Cathay R&D Center Co Ltd; CIBT America Inc
Priority date: 2013-10-28
Filing date: 2013-10-28
Publication date: 2021-11-16
Anticipated expiration: 2033-10-28
Also published as: CN110117834B; CN110117831A; CN109972228A; CN104562271B; CN110117833A; CN110117832B; CN104562271A; CN110117833B; CN106884217B; CN110117835A; CN110117831B; CN110117835B; CN110117832A; CN106884217A; CN110117834A

Abstract

The invention provides a preparation method of polyamide, which comprises the steps of carrying out prepolycondensation on a nylon salt aqueous solution to obtain a prepolymer, and then further carrying out dehydration condensation on the prepolymer to obtain a nylon 56 melt. The nylon 56 melt can be used to prepare nylon fibers by direct spinning. The high-performance nylon fiber prepared by the invention can be further used for preparing textile materials such as yarns, woven fabrics, knitted fabrics or non-woven fabrics, can be applied to the fields of clothing, industry, decorative carpets and the like, and has wide industrial application prospect.

Description

Preparation method of polyamide and nylon fiber prepared by preparation method

Technical Field

The invention relates to a preparation method of polyamide and nylon fiber, in particular to a preparation method of nylon 56 and the fiber thereof.

Background

Nylon fiber is one of the synthetic fibers which are put into industrial production at the earliest time in the world, and the yield is the second place in the synthetic fibers. The nylon low-denier yarn (200-700 dtex) has the characteristics of high breaking strength, wear resistance, fatigue resistance, impact resistance, good dimensional stability and the like, and is widely applied to the fields of military products, rubber framework materials, airbag yarns, ropes, nets, cables, tarpaulins, industrial filter cloth and the like; meanwhile, the fabric has good market prospect in the fields of high-grade sewing thread silk, T-shirt silk, umbrella fabric, sports textiles and the like due to good serviceability such as soft hand feeling, light texture, good drapability, air permeability, moisture absorption, good elasticity, easy processing and the like.

Among them, nylon 6(PA6) and nylon 66 fibers account for 90% or more of the market share of nylon fibers. However, both have their own disadvantages in the polymerization and spinning processes, resulting in a decrease in economic efficiency. For PA6, because more unreacted monomers exist in the melt after polymerization, direct spinning by melting after polymerization cannot be realized, the melt after polymerization must be cooled, granulated, washed by water to remove the unreacted monomers, dried and melted to carry out spinning, and thus, a great deal of energy waste and environmental pollution are caused. For PA66, the crystallization speed is too fast, which results in poor spinnability, especially when spinning fine denier yarn, the dyeing uniformity is not easy to control, and the high melting point and structure of PA66 result in cross-linking phenomenon during spinning, so that the spinning cost of PA66 is ten thousand yuan/ton higher than that of PA 6.

In addition, the current nylon is basically prepared by using petroleum derivatives as raw materials, such as nylon 6 and nylon 66 with the largest market occupation amount, caprolactam and adipic acid which are used as raw materials are prepared by a series of reactions such as hydrogenation and reoxidation of benzene homologues, and hexamethylene diamine is prepared by firstly synthesizing adiponitrile from butadiene or acrylonitrile and then performing a catalytic hydrogenation method, so that the whole synthesis process is complex and has certain pollution.

For a long time, it has been expected that a renewable plant resource grown by absorbing carbon dioxide from the air is used as a starting material to produce a green nylon having performance equivalent to that of the existing nylon variety, thereby solving the dependence on non-renewable energy and building a recycling society. Under such circumstances, nylon produced from 1, 5-pentanediamine obtained by decarboxylation of lysine as a raw material, particularly nylon 56 (polyamide 56, PA56), is highly expected as a plant-derived polymer.

At present, the main continuous polymerization process in the world is researched for the polymerization of polyamide 66, and specifically, the main links of the process flow are as follows: concentration → high pressure precondensation → flash distillation → atmospheric or vacuum polycondensation.

The DuPont company, a world-wide and well-known polyamide producer, has improved the continuous polymerization process of polyamide 66, and its unique continuous polymerization process mainly includes the following steps: high pressure concentration precondensation → flash distillation → atmospheric polycondensation. However, in any of the polycondensation methods, there are the following problems: 1) the pre-polycondensation effect is not good, only prepolymer with lower molecular weight can be obtained, and the time and energy consumption of subsequent polymerization are increased. 2) The whole polymerization process system has more water, the existence of more water can increase the tendency of reverse reaction, which is unfavorable for the polymerization of polyamide, and the water removal process is difficult and complicated. For example: if water is removed by evaporation, the latent heat of water evaporation leads to foaming, solidification of the polyamide and changes in the liquid level during the reaction lead to degradation of the polyamide remaining on the reactor wall.

The above problems still remain with the simplified process for the polymerization of polyamides mentioned in prior art patent CN 102585216B. Non-patent document 1(j.polym.sci.2,306,1947) describes nylon 56 produced by a thermal polycondensation method. However, it has a low melting point and deteriorated heat resistance as compared with nylon 56 obtained by an interfacial polycondensation method in non-patent document 2(j. polym. sci.2,306,1947) and non-patent document 3(CN 200980118941.2). However, the interfacial polycondensation method is very complicated in process and is difficult to apply industrially.

Disclosure of Invention

Aiming at the defects of the prior polyamide, nylon fiber and preparation technology, the invention aims to provide a preparation method of polyamide, a method for preparing nylon 56 fiber by directly spinning polymerized nylon melt, and nylon 56 fiber prepared by the method and suitable for different application fields with different performance requirements.

The invention provides a preparation method of polyamide, which comprises the steps of carrying out pre-polycondensation on 70-95% by mass of nylon salt aqueous solution to obtain a prepolymer, and then further carrying out dehydration condensation on the prepolymer to obtain a nylon 56 melt.

According to another embodiment of the invention, the nylon salt aqueous solution with the mass fraction of 70% -95% is obtained by preparing 1, 5-pentanediamine and adipic acid into a nylon salt aqueous solution and concentrating the nylon salt aqueous solution; preferably, the concentration pressure is 0.01-0.5 MPa, and the concentration temperature is 80-150 ℃, more preferably 90-140 ℃.

According to another embodiment of the present invention, the pressure of the pre-polycondensation is 0.5 to 2.2MPa, and more preferably 0.8 to 1.7 MPa.

According to another embodiment of the present invention, the outlet temperature of the reactor for the pre-polycondensation is 220 to 260 ℃, more preferably 230 to 250 ℃.

According to another embodiment of the invention, the dehydration polymerization comprises a flash evaporation, the temperature of the flash evaporation being between 260 ℃ and 320 ℃, more preferably between 270 ℃ and 310 ℃.

According to another embodiment of the invention, the dehydration polymerization comprises a polycondensation, the temperature of which is between 250 ℃ and 290 ℃, more preferably between 260 ℃ and 280 ℃.

According to one embodiment of the present invention, when 1, 5-pentanediamine and adipic acid are prepared into a nylon salt aqueous solution, the molar ratio of 1, 5-pentanediamine to adipic acid is 0.95 to 1.05.

According to another embodiment of the present invention, when 1, 5-pentanediamine and adipic acid are prepared into a nylon salt aqueous solution, the pH value of the nylon salt aqueous solution is 7 to 9, more preferably 7.2 to 8.2 when the nylon salt aqueous solution is diluted to 10%.

According to one embodiment of the present invention, the method for preparing a polyamide comprises polymerizing a starting material comprising 1, 5-pentanediamine and adipic acid, the polymerization comprising the steps of:

1) preparing 1, 5-pentanediamine and adipic acid into a nylon salt aqueous solution, wherein the mass fraction of nylon salt in the nylon salt aqueous solution is 55-80%, and more preferably 60-80%;

2) concentrating the nylon salt aqueous solution, wherein the mass fraction of nylon salt in the concentrated nylon salt aqueous solution is 70-95%, and more preferably 80-90%;

3) pre-polycondensing the concentrated nylon salt aqueous solution to obtain a prepolymer, wherein the pressure of the pre-polycondensing is 0.5-2.2 MPa, and the outlet temperature of a pre-polycondensing reactor is 220-260 ℃;

4) and further dehydrating and polymerizing the prepolymer to obtain a nylon 56 melt.

According to one embodiment of the invention, the preparation method of the polyamide comprises the steps of carrying out pre-polycondensation on 80-90% by mass of a nylon salt aqueous solution to obtain a prepolymer, and then carrying out flash evaporation and polycondensation on the prepolymer to obtain a nylon 56 melt.

According to another embodiment of the present invention, the method further comprises the step of adding other comonomer and/or additive selected from one or more of antioxidant, heat-resistant stabilizer, weather-resistant agent, pigment, gloss enhancer, dye, crystal nucleating agent, delustering agent, plasticizer, antistatic agent, flame retardant, metal and metal salt.

According to another embodiment of the invention, said other comonomer is selected from the group consisting of amino acids, lactams, aromatic, aliphatic, cycloaliphatic dicarboxylic acids, aromatic, aliphatic, cycloaliphatic diols, aromatic, aliphatic, cycloaliphatic diamines, aromatic, aliphatic, cycloaliphatic hydroxycarboxylic acids, and one or several of the above-mentioned monomer derivatives.

The invention also provides a preparation method of the nylon fiber, which is characterized in that the nylon 56 melt prepared by any one method is directly spun to prepare the nylon fiber.

According to another embodiment of the invention, the pentanediamide building blocks comprise at least 50% of the repeating units of the nylon fiber.

According to another embodiment of the present invention, the nylon fiber comprises a copolymer formed by copolymerizing 1, 5-pentanediamine, adipic acid, and other monomers selected from the group consisting of amino acids, lactams, aromatic, aliphatic, and cycloaliphatic dicarboxylic acids, aromatic, aliphatic, and cycloaliphatic diols, aromatic, aliphatic, and cycloaliphatic diamines, aromatic, aliphatic, and cycloaliphatic hydroxycarboxylic acids, and one or more of the above-mentioned monomer derivatives.

The invention further provides a nylon fiber product, which comprises the nylon fiber.

The invention also provides a nylon 56 fiber preparation device, which comprises a reaction unit for polymerization reaction generation and a spinning unit communicated with the reaction unit, wherein the reaction unit comprises a salt forming kettle, an intermediate tank, a first preheater, a concentration tank, a second preheater, a reactor, a flash evaporator, a front polymerizer and a rear polymerizer which are sequentially communicated, the spinning unit comprises a spinning box body, a side blowing device, a spinning channel, an oiling device, a first godet, a second godet and a winding drum, and the reaction unit can further comprise an additive tank.

The invention adopts the mode of combining nylon polymerization and melt direct spinning to prepare the nylon 56 yarn, uses the nylon salt solution with high concentration and low pH value, and adopts the process conditions of low temperature and low pressure, thereby reducing the production cost, and reducing the emission of waste gas and the pollution to the environment.

The melt direct spinning after polymerization omits the processes of cooling, granulating, drying, melting and the like, greatly reduces the cost, and simultaneously overcomes the problems of broadening of molecular weight distribution caused by repeated cooling, heating and melting and overlong retention time at high temperature of nylon 56 and fuzz and broken filaments caused by difficult uniform orientation of molecular chains in the spinning and stretching processes.

The invention also prepares the nylon 56 melt with high molecular weight and narrow molecular weight distribution which can be obtained only by polymerization matched with solid phase polymerization in the past through process adjustment, controls the stability of the spinning melt, improves the spinnability of the melt, and lays a foundation for obtaining the nylon 56 fiber with excellent performance.

The method can adjust the fineness and the strength of the nylon 56 fiber by changing the process parameters according to different application fields and performance requirements, and has simple and convenient operation process. The nylon 56 fiber obtained by the method has a limit oxygen index (29-35%) higher than that of the traditional nylon, and can be used as a flame retardant material.

The nylon 56 fiber prepared by the method has faster water absorption and drainage rate than the traditional nylon, the water absorption can be adjusted by adjusting the crystallinity and the orientation degree through a spinning process, and the maximum moisture absorption rate can reach 12-14 percent (the maximum moisture absorption rate of the traditional nylon fiber is 8-10 percent), so that the nylon 56 fiber is popular chemical fiber which is closest to natural fiber. The performance of the fabric makes the fabric have wide development prospect in the field of clothes.

The nylon 56 fiber manufactured by the method of the invention has excellent tensile strength (3-12 cN/dtex), so the fiber can be further used for manufacturing yarns, woven fabrics, knitted fabrics, non-woven fabrics, carpets and the like for civil fiber fields, and can also be applied to industrial fiber fields with high strength requirements, such as tire cords, conveyor belts and the like. The nylon 56 yarn of the invention belongs to an environment-friendly material, the raw material of the nylon 56 yarn is from renewable plants, the dependence on non-renewable energy sources is solved, and the construction of a circulating society is facilitated.

Drawings

FIG. 1 is a schematic process flow diagram of the preparation method of nylon fiber of the present invention.

Wherein the reference numerals are as follows:

1. salt forming kettle 2, intermediate tank 3 and first preheater

4. A concentration tank 5, a second preheater 6 and a reactor;

7. additive tank 8, flash evaporator 9, pre-polymerizer

10. Post-polymerizer 11, spinning beam 12, and side blowing device

13. Spinning channel 14, oiling device 15, first godet roller

16. A second godet roller 17, a winding drum.

Detailed Description

The melt direct spinning after polymerization has the advantages of low energy consumption, low cost, less pollution, stable fiber quality and the like, but some polymer characteristics or technical problems cause that part of macromolecules can not be directly spun into fibers by melting after polymerization, and the process of the invention belongs to the first example for nylon 56.

The inventor carries out deep research on nylon 56 continuous polymerization and spinning processes, and prepares the green nylon 56 fiber with the molecular weight distribution of 1.2-3, the fineness of 0.1-10 dtex and the strength of 3-12 cN/dtex by controlling the concentration and pH value of a nylon salt aqueous solution, the polymerization temperature, the polymerization pressure, the polymerization vacuum degree, the spinning assembly pressure, the spinning box temperature, the speed and the stability of cross air blowing, and an oiling device.

The polymerization and spinning processes effectively inhibit the occurrence of crosslinking through pH value and polymerization temperature adjustment. The continuous and smooth polymerization process ensures narrow molecular weight distribution of the nylon 56 melt. The heating energy consumption is effectively reduced by improving the concentration of the nylon salt, reducing the polymerization temperature and the polymerization pressure. The steam emission of the 1, 5-pentanediamine is reduced and the pollution is reduced by adjusting the pH value and the polymerization pressure of the nylon salt. The molecular weight of the nylon 56 is adjusted by the catalyst, the pH value of the salt solution and the polymerization and spinning processes, and the strength of the nylon 56 yarn is indirectly controlled.

The nylon 56 fine denier yarn with excellent dyeing uniformity is obtained through the cross air blowing speed and stability, the spinning box temperature, the assembly pressure and the oiling agent. The method provided by the application overcomes the problem that the traditional commercial nylon 6 monomer residue cannot realize direct spinning after polymerization, overcomes the problems of poor spinnability, easy crosslinking and uneven dyeing of fine denier yarn of nylon 66, and is a major breakthrough in the field of nylon fiber, and the nylon 56 fiber prepared by the method provided by the invention has the limit oxygen index and the saturated moisture absorption rate higher than those of the traditional nylon fiber.

The preparation method of the nylon fiber comprises the steps of directly spinning after polymerizing raw materials containing 1, 5-pentanediamine and adipic acid.

The nylon polymerization process has two main methods, one is a continuous polymerization process, the other is a batch polymerization process, the two processes have the same principle, and the difference mainly lies in the process flow and the product application range. In the present invention, the polymerization reaction of 1, 5-pentanediamine and adipic acid is not limited, and may be carried out by any of the above-mentioned two processes.

In the preparation method of the nylon fiber of the present invention, the polymerization reaction further comprises the steps of: 1) preparing 1, 5-pentanediamine and adipic acid into a nylon salt aqueous solution; 2) concentrating the aqueous nylon salt solution; 3) pre-polycondensing the concentrated nylon salt aqueous solution to obtain a prepolymer; 4) and further dehydrating and polymerizing the prepolymer to obtain a nylon 56 melt.

In the preparation method of the nylon fiber of the present invention, the spinning step further comprises: a) ejecting the melt after the polymerization reaction through a spinneret plate to form melt trickle; b) the melt trickle is blown and solidified into strand silk; c) bundling and oiling the strand silk; d) and (3) drawing and post-processing the strand silk to obtain the nylon fiber.

The device for preparing the nylon fiber comprises a reaction unit for generating a polymerization reaction and a spinning unit communicated with the reaction unit, wherein the reaction unit comprises a salt forming kettle, a middle tank, a first preheater, a concentration tank, a second preheater, a reactor, a flash evaporator, a front polymerizer and a rear polymerizer which are sequentially communicated, and the spinning unit comprises a spinning box body (a built-in melt distribution pipe, a metering pump and a spinning assembly), a side blowing device, a spinning channel, an oiling device, a first godet roller, a second godet roller and a winding drum. Wherein, the reaction unit can also further comprise an additive tank.

The device for preparing nylon fiber of the invention, further, the reaction unit can also comprise an additive tank which is communicated with the reactor and the flash evaporator.

The device for preparing nylon fiber of the invention further comprises a third godet roller and a fourth godet roller according to actual needs.

The preparation method of the nylon fiber comprises the following specific processes: preparing a nylon salt aqueous solution from 1, 5-pentanediamine and adipic acid in a salt forming kettle, transferring the nylon salt aqueous solution to an intermediate tank, preheating the nylon salt aqueous solution by a first preheater at a certain flow rate, then feeding the nylon salt aqueous solution into a concentration tank, preheating the salt aqueous solution to a specified concentration by a second preheater, then feeding the nylon salt aqueous solution into a reactor, pre-polymerizing the nylon salt aqueous solution in the reactor at a high temperature and a high pressure, injecting a required additive through an additive tank, feeding the solution into flash steam to remove most of residual water, finally sequentially passing through a front polymerizer and a rear polymerizer to obtain a nylon 56 melt, driving the melt into a spinning box by a gear pump, spraying the melt from a spinneret plate, cooling in a spinning channel by an air blowing cooling device, bundling, oiling, drafting by guide rollers, shaping, relaxing and winding into fibers.

The source of the 1, 5-pentanediamine of the present invention is not limited, and the 1, 5-pentanediamine may be chemically or biologically produced. As is known to those skilled in the art, the removal of the carboxyl groups at both ends of lysine (salt) by lysine decarboxylase (EC 4.1.1.18) produces pentamethylene diamine. For example, L-lysine decarboxylase property and application research (Jiangli, Nanjing university, Master thesis) discloses a specific biological method for preparing pentanediamine. As another example, "research on converting L-lysine into cadaverine by microorganisms" (ZhuJing, Tianjin science and technology university, Master thesis, 2009.3) discloses a specific biological method for preparing pentanediamine.

In the preparation method of the nylon fiber, the concentration of the nylon salt aqueous solution in the step 1) is preferably 55-80% by mass, and the mass fraction refers to the ratio of the mass of the nylon salt to the mass of the nylon salt aqueous solution. The high hydrophilicity of the 1, 5-pentanediamine can cause the 1, 5-pentanediamine to evaporate and gasify along with water, and before the polymerization reaction occurs, a high-concentration nylon salt solution is ensured as much as possible to inhibit the proportion unbalance of acid and amine caused by the volatilization of the 1, 5-pentanediamine, and simultaneously, the pollution and the energy consumption can be reduced by reducing the volatilization of the 1, 5-pentanediamine.

The solubility of the salt of 1, 6-hexamethylenediamine and adipic acid, which is a raw material of ordinary nylon 66, in water does not increase significantly with an increase in temperature, and if the salt concentration is too high, there is a problem that crystallization occurs as a precipitate, whereby the salt concentration in the aqueous solution must be adjusted to about 50% by weight, but if the temperature of the aqueous solution is low, recrystallization occurs even if the concentration is 50% by weight or less. Therefore, it has been considered technically difficult to increase the salt concentration of the aqueous solution in the raw material preparation step. In contrast, we have found that the solubility of salts of 1, 5-pentanediamine and adipic acid as starting materials for nylon 56 in water is high and can continue to increase with further increases in temperature. However, the concentration of the aqueous solution of nylon salt is more preferably 60% to 80% because the nylon salt is easily oxidized or decomposed by an excessively high temperature.

In the preparation method of the nylon fiber, the ratio of the pentanediamine to the adipic acid in the nylon salt aqueous solution in the step 1) is preferably 0.95-1.05 (molar ratio), the pH value of the nylon salt aqueous solution is preferably 7-9, and since the nylon polymerization reaction is a process of dehydrating carboxyl and amino to form amide, theoretically, if the molar ratio of the dibasic acid to the diamine is equal, all monomers can form a molecular chain of the ultrahigh molecular weight polymer after reaction. On one hand, the molecular weight of a nylon product needs to be controlled, and if the molecular weight is too high, the nylon product is difficult to process, and on the other hand, the proportion of the 1, 5-pentanediamine and adipic acid is unbalanced due to the volatility of the 1, 5-pentanediamine in the polymerization process, so that the molecular weight of the generated polymer is reduced, and the pH value is a parameter reflecting the proportion of the dibasic acid and the diamine. Therefore, the pH value of the nylon salt aqueous solution is more preferably 7.2-8.2.

For comparison with the sample parameters, the pH values of the nylon salt aqueous solution of the present invention were all values measured when the nylon salt aqueous solution was diluted to 10% with water.

In the preparation method of the nylon fiber, the antioxidant with respect to the weight of the nylon salt can be added into the nylon salt aqueous solution in the step 1) according to the requirement, wherein the antioxidant is less than 1000 ppm. The antioxidant may be hindered phenol compounds, hydroquinone compounds, phosphite compounds or their substitutes, copper salts, iodides, etc. Part of the antioxidant contributes to the promotion of the polymerization reaction and the inhibition of the vaporization of 1, 5-pentanediamine.

In the method for preparing nylon fibers of the present invention, the ambient temperature for concentrating the aqueous solution of nylon salt, i.e., the temperature of the concentration tank, is preferably 80 to 150 ℃. Because the nylon salt is polymerized at a temperature of about 190-200 ℃, the nylon salt in the concentration tank does not undergo polymerization obviously at a temperature of 80-150 ℃, and we find that when the temperature exceeds 150 ℃, the volatilization speed of the 1, 5-pentanediamine along with water is very high, so that the temperature of the concentration tank needs to be controlled not to exceed 150 ℃ to achieve the dual purposes of concentration and inhibition of the volatilization of the 1, 5-pentanediamine. Among them, the temperature of the concentration tank is more preferably 90 to 140 ℃.

Further, for the same reason, the ambient pressure for concentrating the nylon salt aqueous solution, that is, the pressure of the concentration tank is preferably maintained in the range of 0.01 to 0.5MPa (gauge pressure), and more preferably 0.03 to 0.3 MPa. The concentration of the nylon salt at the outlet of the concentration tank is preferably 70% to 95%, and on the one hand, the concentration of the aqueous solution of the nylon salt is preferably 70% by weight or more, because this concentration can maintain a small amount of gasification of 1, 5-pentanediamine in the subsequent reactor. On the other hand, the concentration of the aqueous solution of nylon salt is preferably 95% by weight or less, so that a prepolymer can be produced in the pressure control step. Therefore, the concentration of the aqueous solution of nylon salt at the end of the concentration step is more preferably 80% to 90%.

In the preparation method of the nylon fiber, the pressure of a reactor for high-pressure pre-polycondensation is preferably 0.5-2.2 MPa (gauge pressure), and if not specifically stated, the pressure is gauge pressure. Maintaining a certain pressure in the reactor is advantageous in order to suppress the vaporization of 1, 5-pentanediamine and to allow easy prepolymer formation while ensuring the melt temperature, while a low pressure is advantageous in order to allow rapid discharge of water vapor. Therefore, the reactor pressure is more preferably 0.8 to 1.7MPa (gauge pressure). The temperature of the outlet of the reactor is preferably 220-260 ℃, the melt is solidified and the reaction is terminated due to too low temperature, and the volatilization of the 1, 5-pentanediamine and the side reaction are easily caused due to too high temperature. Therefore, the outlet temperature of the reactor is more preferably 230 to 250 ℃.

The preparation method of the nylon fiber further comprises the step of adding additives into the prepolymer after the step 3) and before the step 4), wherein the additives can be various delustering agents which are not easy to dissolve in water, dyes, antistatic agents, flame retardants, metals, metal salts and the like with the concentration of less than 10000ppm and are used for improving and changing the performance of the nylon 56 fiber.

In the preparation method of the nylon fiber, the flash evaporator for the flash evaporation of the prepolymer preferably takes the o-phenylene ether as a heating medium, and the temperature is controlled to be 260-320 ℃. The ortho-phenylene ether vapor provides a large amount of latent heat by condensation to meet the requirements of the flash evaporator, and the vapor temperature is controlled by the vapor pressure so as not to cause side reactions due to overhigh temperature. The temperature for the flash evaporation of the prepolymer is further preferably from 270 ℃ to 310 ℃.

In the preparation method of the nylon fiber, the temperature ranges of the front polymerizer and the rear polymerizer used for normal-pressure polycondensation and vacuum polycondensation of the prepolymer are preferably 250-290 ℃, the temperature needs to be kept above the melting point of the polymer, the high temperature is beneficial to the reaction, the polymerization degree can be improved, but the side reaction is excessive, and the molecular weight distribution is widened. Therefore, the temperature is more preferably 260 to 280 ℃.

The vacuum degree of the postpolymerizer of the present invention is preferably from 0 to-0.09 MPa (gauge pressure). The vacuum pumping is beneficial to removing moisture, is beneficial to maintaining the uniformity of the reaction, and can improve the melt viscosity and the molecular weight of the polymer under the condition of not increasing the reaction temperature. The degree of vacuum is adjusted according to the requirements of the properties of the nylon 56 fiber, and the degree of vacuum is more preferably 0 to-0.07 MPa (gauge pressure).

In the present invention, the temperature of the spinning beam used for spinning is preferably controlled to 260 to 300 ℃, more preferably 270 to 290 ℃. The shape of the holes of the spinneret can be selected according to the cross-sectional shape of the filaments constituting the filament to be produced. However, if the polymer is to be uniformly discharged in the form of a single fiber having a circular sectional shape in the preferred mode of the present invention, a pore diameter of 0.1 to 0.5 mm and a pore length of 0.1 to 5mm are preferred.

Further, the spun fiber is cooled by a solidification method using cold water or a solidification method using cooling air in general, but in order to suppress moisture absorption, solidification using cooling air is preferable. As the cooling air, it is more preferable to perform cooling at a speed of 0.3 to 1 m/sec using air having a temperature of 15 to 25 ℃ and a relative humidity of 20 to 90%. Similar to the room temperature and humidity environment in which melt spinning and drawing are carried out, a temperature of 20 to 30 ℃ and a relative humidity as low as possible in the range of 20 to 70% are preferable. Further, in this case, it is preferable to control the temperature within ± 3 ℃ and the humidity within ± 5%. The means for generating cooling air may be of the uniflow type or of the loop type, but the loop type is preferred in view of uniform cooling between the single fibers.

The first godet take-up speed of the present invention is preferably 300 to 5000 m/min. The take-up speed is preferably 300 m/min or more because the spinning tension can be sufficiently increased to reduce the swing of the spun fiber. On the other hand, the take-up speed is preferably kept within a suitable range because high-ratio drawing can be performed to provide a high-strength filament. Meanwhile, the first roller is high in coiling speed, so that the production cost can be reduced, but the requirement on the melt is high. A more preferred take-up speed range is 500 to 4500 m/min depending on the strength requirements and the type of filament. The winding speed is preferably 2000-6000 m/min.

The draft ratio of the present invention is preferably 1 to 7 times. Draft ratio is winding speed/first roll winding speed. A plurality of godet rollers can be added between the winding roller and the first godet roller to realize step-by-step drafting. The multiple stage drawing can uniformly orient the molecular chains to form an oriented dense crystalline phase.

The first godet temperature in the present invention is preferably from room temperature to 50 deg.c, and the maximum temperature of the following godets is preferably from 100 deg.c to 180 deg.c.

The nylon 56 fiber prepared by the method has narrow molecular weight distribution of 1.2-3, has no phenomena of filament breakage and filament breakage after continuous operation for 10 days, has a yarn evenness irregularity as low as 1-2%, has a very high limit oxygen index of 29-35%, and has a limit oxygen index of only 26-28% of the traditional nylon.

The nylon 56 fiber prepared by the method has faster water absorption and drainage rate than the traditional nylon, and the saturated water absorption can be adjusted by adjusting the crystallinity and the orientation degree through a spinning process, and can reach 12-15% at most.

The nylon fiber prepared by the invention can be filament or staple fiber.

The invention also provides a nylon fiber product containing the nylon fiber, wherein the nylon fiber product can be yarns, woven fabrics, knitted fabrics, non-woven fabrics and the like.

The nylon 56 fiber of the present invention is preferably such that the pentamethyleneadipamide structural units account for 50 mol% or more of the repeating units of the nylon 56 fiber. The nylon 56 fiber may contain less than 50 mol% of comonomer component on the basis of not impairing the effects of the present invention, but preferably contains more units of pentamethyleneadipamide, because the regularity of the molecular chain can be improved so that orientation and crystallization more easily occur during film formation to provide a fiber excellent in mechanical properties and heat resistance. Therefore, the units of pentamethylene adipamide are more preferably 70 mol% or more, most preferably 90 mol% or more.

The nylon 56 fiber has a viscosity number of 120-280 mL/g in 96% sulfuric acid. The viscosity number is an indicator of the molecular weight, and a higher viscosity number indicates a higher molecular weight of the polymer, and a higher molecular weight allows the nylon fiber to have higher strength. This is because if the molecular weight is higher, the smaller the amount of molecular chain terminals present per unit, the fewer defects that may be fibers. Meanwhile, because the molecular chains are longer, each molecular chain interacts with more molecular chains (physical entanglement, hydrogen bonds, van der waals forces, etc.) so as to uniformly transfer spinning stress and tensile stress, the molecular chains are uniformly oriented in the process of manufacturing fibers. On the other hand, the viscosity number in sulfuric acid is preferably kept in an appropriate range because melt spinning at an appropriate spinning temperature may inhibit thermal decomposition of the polymer in a spinning machine to ensure excellent yarn formability and inhibit fiber coloration. The viscosity number kept in an appropriate range is also preferable because the low molecular weight distribution (Mw/Mn) can be maintained due to the thermal decomposition inhibition. The viscosity is more preferably 140mL/g to 260mL/g, and the most preferable range is 150mL/g to 240 mL/g.

The method of the present invention can produce nylon fibers having a narrow molecular weight distribution, and the molecular weight distribution must be 1.2 to 3 as an index (Mw/Mn), where Mw represents a weight average molecular weight and Mn represents a number average molecular weight. A smaller ratio of the weight average molecular weight to the number average molecular weight means a narrower molecular weight distribution. The above-mentioned nylon 56 fiber having a high viscosity number in sulfuric acid and a narrow molecular weight distribution with Mw/Mn of 3 or less is preferable because a fiber having high strength, no broken ends and good spinnability can be obtained. The reason is that if Mw/Mn is small, the interaction forces (physical entanglement force, hydrogen bonding force, van der waals force, etc.) of the interacting molecular chains and each molecular chain become approximately equal, so that spinning stress and tensile stress are uniformly applied to each molecular chain during film formation, and therefore, the molecular chains of the amorphous phase are uniformly oriented to form many highly dense oriented crystalline phases.

Further, due to the action of the uniformly oriented molecular chains, many amorphous chains (interconnected molecules) for mutually linking the crystalline phases exist in the amorphous phase, and the molecular chain lengths of the interconnected molecules are equal. Therefore, many of them are assumed to exist in a state of tension (motion is limited by crystalline phases). That is, because they contain many highly dense oriented crystalline phases and are linked by many tensioned interconnecting molecules, they act in concert to provide nylon 56 fibers with high strength and low defects.

The Mw/Mn is preferably 2.6 or less, particularly preferably 2.4 or less. A ratio of 1.2 or higher is a level required to achieve production. The present inventors have made intensive studies and, as a result, have found that pentamethylenediamine, which is a raw material of nylon 56, is volatile during polymerization, has a lower crystallinity than that of conventional nylon 66, and more importantly, has not so high melt storage stability, and the molecular weight may be broadened by repeated cooling and heating, so that it is difficult to uniformly orient molecular chains and induce fuzz and filament breakage during spinning and drawing. The invention shortens the residence time of the melt at high temperature by process control and direct melt direct spinning after polymerization, thereby successfully solving the problem.

The nylon fiber of the present invention preferably has a single fiber fineness of 0.1 to 10 dtex. The single filament fineness can be adjusted by the device and the process according to different application fields. Due to the fact that the filament number is too low, abnormal phenomena such as end breakage and the like easily occur, and meanwhile, due to the fact that the filament number is too high, bending strength of the fabric is too high, and hand feeling is hard. Therefore, the single fiber fineness of the nylon fiber of the present invention is more preferably in the range of 1 to 8dtex, and most preferably in the range of 1.5 to 7 dtex. Meanwhile, if the monofilament fineness is kept within the range required by the invention, the appropriate number of filaments can be selected according to the application to meet the application requirement.

The strength of the nylon 56 fiber of the present invention is preferably 3 to 12 cN/dtex. The strength is too low, fluff is easy to appear in the weaving process, a finished product is easy to damage, the strength is too high, the spinnability is poor in spinning, the yarn breakage phenomenon is easy to occur, and the PA56 yarn is preferably adjusted by a polymerization and spinning process according to different application fields, wherein the strength range is 4-10 cN/dtex.

As the filament of the present invention, the cross-sectional shape of the monofilament may be various forms such as a circle, a Y-shape, a multilobal shape, a polygon, a flat form, a hollow form and a square cross form, but the circle or the flat form is preferable since a woven fabric having higher strength and lower air permeability can be stably obtained. Circular is most preferred. The cross-sectional form of the individual fibers may be identical to one another or different, but is preferably identical.

As each fiber of the present invention, a composite fiber (single core, multiple cores, or partially exposed core) or a bimetal composite fiber may be used, or an alloy fiber alloyed with another polymer may also be used, to the extent that the intended effect of the present invention is not impaired. With respect to filaments having higher strength, fibers containing only the nylon 56 component are preferred. For example, there may be mentioned polyesters (polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactic acid and the like), polyamides (polyamide m such as polyamide 6, the number of carbon atoms m in each repeating unit being 4 to 12, polyamide mn such as polyamide 66, the number of carbon atoms m in each repeating unit being 4 to 12, the number of carbon atoms n being 4 to 12, and the like), polycarbonates, polystyrenes, polypropylenes, polyethylenes, polyoxymethylenes, polymethyl methacrylates, polyethylene glycols and the like. Homopolymers, copolymers (the above-mentioned polymers containing the components listed below as comonomers) and the like can be appropriately selected.

Furthermore, the filaments of the present invention may also be mixed, spun or twisted with other fibers. Examples of the other fibers include natural fibers such as cotton, hemp, wool and silk, regenerated fibers such as rayon and cuprammonium rayon, semisynthetic fibers such as acetate, and synthetic fibers containing polyamides in the form of homopolymers and copolymers (the above-mentioned polymers containing the components listed below as comonomers) (polyamide m such as polyamide 6, the number of carbon atoms m in each repeating unit being 4 to 12, polyamide mn such as polyamide 66, the number of carbon atoms m in each repeating unit being 4 to 12, the number of carbon atoms n being 4 to 12, and the like), polyesters (polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polylactic acid, and the like), polyacrylonitrile, polypropylene, polyvinyl chloride, and the like.

The nylon 56 filaments of the present invention may also contain less than 10% by weight of the following components. For example, antioxidants, heat-resistant stabilizers (hindered phenol-based compounds, hydroquinone-based compounds, thiazole-based compounds, phosphorus-based compounds such as phenylphosphonic acid, imidazole-based compounds such as 2-mercaptobenzimidazole, substitution products thereof, copper halides, iodine compounds, etc.), weather-resistant agents (resorcinol-based, salicylate-based, benzotriazole-based, benzophenone-based, hindered amine-based, etc.), pigments (cadmium sulfide, phthalocyanine, carbon black, etc.), gloss enhancers (titanium oxide, calcium carbonate, etc.), dyes (nigrosine, etc.), crystal nucleating agents (talc, silica, kaolin, clay, etc.), plasticizers (octyl paraben, N-butylbenzenesulfonamide, etc.), antistatic agents (alkylsulfate-type anionic antioxidants, quaternary ammonium-type cationic antistatic agents, nonionic antistatic agents, such as polyoxyethylene sorbitan monostearate, betaine-based amphoteric antistatic agents, and the like), flame retardants (melamine cyanurate, hydroxides, such as magnesium or aluminum hydroxide, ammonium polyphosphate, brominated polystyrene, brominated polyphenylene oxide, brominated polycarbonate, brominated epoxy resins, combinations of any of these bromine-based flame retardants and antimony trioxide, and the like).

Further, the nylon 56 of the present invention may also be copolymerized with other compounds than 1, 5-pentanediamine and adipic acid to the extent that the object of the present invention is not impaired, and may contain, for example, a structural unit derived from:

aliphatic carboxylic acids (oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, octadecanedioic acid, etc.), alicyclic dicarboxylic acids (cyclohexanedicarboxylic acid, etc.) and aromatic dicarboxylic acids (terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, anthracenedicarboxylic acid, phenanthrenedicarboxylic acid, diphenyletherdicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylethanedicarboxylic acid, 1, 4-cyclohexanedicarboxylic acid, 5-sodiosulfoisophthalic acid, 5-tetrabutylphosphonium isophthalic acid, etc.).

Furthermore, the nylon 56 of the present invention may contain a nylon derivative derived from an aliphatic diamine such as ethylenediamine, 1, 3-diaminopropane, 1, 4-diaminobutane, 1, 6-diaminohexane, 1, 7-diaminoheptane, 1, 8-diaminooctane, 1, 9-diaminononane, 1, 10-diaminodecane, 1, 11-diaminoundecane, 1, 12-diaminododecane, 1, 13-diaminotridecane, 1, 14-diaminotetradecane, 1, 15-diaminopentadecane, 1, 16-diaminohexadecane, 1, 17-diaminoheptadecane, 1, 18-diaminooctadecane, 1, 19-diaminononadecane, 1, 20-diaminoeicosane or 2-methyl-1, 5-pentanediamine, alicyclic diamines, such as cyclohexanediamine or bis- (4-aminohexyl) methane, or aromatic diamines, such as xylylenediamine.

The nylon 56 of the present invention may contain structural units derived from aromatic, aliphatic or alicyclic diol compounds such as ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, 1, 4-cyclohexanedimethanol, neopentyl glycol, hydroquinone, resorcinol, dihydroxybiphenyl, naphthalene diol, anthracene diol, phenanthrene diol, 2-bis (4-hydroxyphenyl) propane, 4' -dihydroxydiphenyl ether or bisphenol S.

The nylon 56 of the present invention may contain a structural unit derived from an aromatic, aliphatic or alicyclic hydroxycarboxylic acid each having a hydroxyl group and a carboxylic acid, such as lactic acid, 3-hydroxypropionate, 3-hydroxybutyrate-valerate, hydroxybenzoic acid, hydroxynaphthalene carboxylic acid, hydroxyanthracene carboxylic acid, hydroxyphenanthrene carboxylic acid, or (hydroxyphenyl) vinyl carboxylic acid.

The polyamides 56 of the present invention may further contain structural units derived from amino acids, such as 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid or p-aminomethylbenzoic acid, or lactams, such as epsilon-caprolactam or epsilon-laurolactam.

Therefore, the method of the present invention may further comprise copolymerizing 1, 5-pentanediamine and adipic acid with other comonomers selected from one or more of amino acids, lactams, aromatic, aliphatic, alicyclic dicarboxylic acids, aromatic, aliphatic, alicyclic diols, aromatic, aliphatic, alicyclic diamines, aromatic, aliphatic, alicyclic hydroxycarboxylic acids, and derivatives of the above monomers, wherein the derivatives of the above monomers include reaction products of the above two monomers, for example, a product obtained by reacting one amino group of one molecule of certain diamine with one carboxyl group of one molecule of certain dicarboxylic acid to form a salt.

The nylon 56 fiber of the present invention has excellent mechanical properties, heat resistance, abrasion resistance and durability, can be used as various fiber structures such as fabrics (woven fabrics, knitted fabrics, nonwoven fabrics, napped fabrics and the like), ropes (dip cords, ropes, belts, fishing nets, woven belts and the like), and is widely applicable to industrial uses and clothing uses. For example, they are suitable for use as fibrous structures for constructing indoor and outdoor materials and safety parts of vehicles (e.g., automobiles and airplanes), including airbags, rubber-reinforced fibers, seat belts, sheets, mats, and the like.

Further, they are suitable for industrial use such as fishing nets, ropes, safety belts, slings, tarpaulins, tents, bag fabrics, braids, fenders, canvases, sewing threads and the like, grass protection cloths for agriculture, waterproof cloths for building materials and the like.

In addition, they may be suitable for apparel applications requiring strength and abrasion resistance, such as outdoor clothing and athletic clothing. In the field of carpets, can be used for producing bulked filaments for producing polyamide tufted carpets. The fiber structure may contain fibers other than nylon 56 fibers, but in order to utilize the excellent properties of the nylon 56 fibers of the present invention, the content of the nylon 56 fibers of the present invention is preferably 50% by weight or more. More preferably 70% by weight or more, still more preferably 90% by weight or more.

The nylon fiber and the method for producing the same of the present invention will be further described with reference to the following examples. It should be understood that the following examples are illustrative only and are not intended to limit the scope of the present invention.

The following examples, among others, characterize the properties of the inventive nylon 56 fiber as follows:

1. viscosity number

Concentrated sulfuric acid method with Ubbelohde viscometer: the dried nylon 66 sample was accurately weighed to 0.25. + -. 0.0002g, dissolved by adding 50mL of concentrated sulfuric acid (96%), and the concentrated sulfuric acid flow time t0 and the nylon 66 solution flow time t were measured and recorded in a thermostatic water bath at 25 ℃.

Viscosity number calculation formula: viscosity number VN ═ t/t 0-1/C;

t-solution flow time;

t 0-time of solvent flow;

c-concentration of polymer (g/mL).

2. Molecular weight distribution

The fiber sample was washed with hot water at 90 ℃ for 30 minutes and dried at 90 ℃ in vacuum to achieve a water content of 1000 ppm. The sample was dissolved in hexafluoroisopropanol to obtain a test solution. It was measured by Gel Permeation Chromatography (GPC) to obtain a weight average molecular weight in terms of pmma (Mw) and a number average molecular weight (Mn), and finally Mw/Mn. The measurement conditions were as follows:

GPC apparatus: waters 510;

column: two Shodex GPC HFIP-806M columns were connected;

solvent: hexafluoroisopropanol;

temperature: 30 ℃;

flow rate: 0.5 ml/min;

sample concentration: 2 mg/4 ml;

and (3) filtering: 0.45 μm-DISMIC 13HP (Toyo roshi);

injection amount: 100 mul;

a detector: differential refractometer RI (Waters 410);

standard sample preparation: PMMA (concentration: sample 0.25 mg/solvent 1 ml);

measuring time: for 62 minutes.

3. Fineness of fiber

Measured according to GB/T14343-2003.

4. High strength

Measured according to the method of GB/T14344-2008.

5. Elongation percentage

Measured according to the method of GB/T14344-2008.

6. Number of yarn breaks

The number of yarn breaks occurring when 100 kg of filaments were formed by spinning and drawing was counted. Less yarn breakage is considered to mean better spinnability.

7. Limiting oxygen index

Measured according to ISO 4589-2.

8. Saturated water absorption

Drying a fiber sample for 12 hours at 120 ℃ by using an electric vacuum oven, naturally cooling the fiber sample in a dryer for 2 hours, weighing about 10g of the fiber sample, putting the sample in a 98.5 ℃ water bath kettle, preserving the heat for 2 hours, soaking the sample in cold pure water for 15 minutes, taking out the water-containing fiber, filtering the water-containing fiber by using filter cloth, wiping the surface water by using cotton cloth, wiping the surface water by using filter paper, and weighing the water-containing fiber by wiping the surface water by using filter paper.

Saturated water absorption ═ fiber wet weight-fiber dry weight/fiber dry weight × 100%.

9. Unevenness of evenness

Measured according to the method of GB/T14346-93.

Examples

Example 1

1, 5-pentanediamine and adipic acid are prepared into 5 tons of 60% aqueous solution in a salification kettle 1, the pH value is adjusted to 7.6 (the salt solution is diluted to 10% of detection result), the temperature is controlled to be 50 ℃, the aqueous solution is transferred to an intermediate tank 2 through a filter, the aqueous solution is heated to 90 ℃ through a first preheater 3 and then enters a concentration tank 4 for further concentration to 80% of concentration, the outlet temperature of the concentration tank 4 is 120 ℃, the aqueous solution is further heated to 213 ℃ through a second preheater 5 and then enters a reactor 6, the pressure of the reactor 6 is 1.73MPa, the outlet temperature is controlled to be 240 ℃, steam is recycled through a cooling tower, the reaction solution then enters a flash evaporator 8 for removing most of water, and the pressure is reduced to normal pressure. And finally, completing polymerization reaction by a front polymerizer 9 and a rear polymerizer 10 to obtain a nylon 56 melt, wherein the temperature of heat conducting oil of jackets of the front polymerizer and the rear polymerizer is 280 ℃, the front polymerizer 9 is under normal pressure, and the vacuum degree of the rear polymerizer 10 is-0.02 MPa (gauge pressure). The nitrogen protection is maintained during the whole polymerization process.

The nylon 56 melt obtained by continuous polymerization is accurately metered by a spinning metering pump and evenly distributed into a spinning assembly, and the temperature of a spinning manifold 11 is 280 ℃. The melt is sprayed out through a spinneret plate to form melt fine flow, the diameter of the spinneret plate is 0.35mm, the length of the spinneret plate is 0.7mm, and the number of holes is 72. Cooling and forming by a side blowing device 12, wherein the air temperature of the side blowing device 12 is 21 ℃, the air humidity is 65 percent, and the air speed is 0.3 m/s. After passing through a spinning shaft 13, the cooled and formed filament bundle is bundled and oiled by an oiling device 14, drawn to a first godet roller 15, and the filament bundle falls down from a spinneret plate at a certain speed to obtain undrawn filament (UDY) or pre-oriented filament (POY), wherein the pre-oriented filament bundle is drawn to a second godet roller 16 after coming out from the first godet roller 15, and then enters a winding drum 17, and the finished filament is wound on the winding drum 17 and wound into a spinning cake on a winding machine to prepare nylon 56 undrawn filament. The winding speed was 1000 m/min. The results of the performance tests are shown in Table 1.

Example 2

1, 5-pentanediamine and adipic acid are prepared into a 60% aqueous solution 5 tons in a salification kettle 1, the pH value is adjusted to 7.6 (the salt solution is diluted to 10% of detection result), 5% nylon 66 salt with the weight of 56 nylon salt is added, the temperature is controlled to be 50 ℃, the aqueous solution is transferred to an intermediate tank 2 through a filter, the heating temperature is increased to 90 ℃ through a first preheater 3, the aqueous solution enters a concentration tank 4 for further concentration to 80% of concentration, the outlet temperature of the concentration tank 4 is 120 ℃, the aqueous solution is further heated to 213 ℃ through a second preheater 5 and then enters a reactor 6, the pressure of the reactor 6 is 1.73MPa, the outlet temperature is controlled to be 240 ℃, steam is recycled and reused through a cooling tower, the reaction solution enters a flash evaporator 8 for removing most of water, and the pressure is reduced to normal pressure. And finally, completing polymerization reaction by a front polymerizer and a rear polymerizer to obtain a nylon 56 melt, wherein the temperature of heat conducting oil of jacket of the front polymerizer and the rear polymerizer is 275 ℃, the front polymerizer 9 is at normal pressure, and the vacuum degree of the rear polymerizer 10 is-0.04 MPa (gauge pressure). The nitrogen protection is maintained during the whole polymerization process.

The nylon 56 melt obtained by continuous polymerization is accurately metered by a spinning metering pump and evenly distributed into a spinning assembly, and the temperature of a spinning box is 278 ℃. The melt is sprayed out through a spinneret plate to form melt fine flow, the diameter of the spinneret plate is 0.35mm, the length of the spinneret plate is 0.7mm, and the number of holes is 72. Cooling and forming by a side blowing device 12, wherein the air temperature of the side blowing device 12 is 21 ℃, the air humidity is 65 percent, and the air speed is 0.3 m/s. After the cooled and formed filament bundle passes through a spinning channel 13, the filament bundle is bunched and oiled by an oiling device 14, and is wound into a spinning cake on a winding machine to be made into nylon 56 undrawn yarn. The winding speed was 1000 m/min. The results of the performance tests are shown in Table 1.

Example 3

1, 5-pentanediamine and adipic acid are prepared into 65% aqueous solution 5 tons in a salification kettle 1, the pH value is adjusted to 8.0 (the salt solution is diluted to 10% detection result), the temperature is controlled to be 50 ℃,10 ppm (relative to the weight of nylon salt) of Bluegman antioxidant is added into the solution, the solution is transferred to an intermediate tank 2 through a filter, the solution is heated to 90 ℃ through a first preheater 3 and then enters a concentration tank 4 for further concentration to 80% concentration, the outlet temperature of the concentration tank 4 is 120 ℃, the solution is further heated to 213 ℃ through a second preheater 5 and then enters a reactor 6, the pressure of the reactor 6 is 1.3MPa, the outlet temperature is controlled to be 242 ℃, steam is recycled through a cooling tower, the reaction solution then enters a flash evaporator 8 for removing most of water, and the pressure is reduced to normal pressure. And finally, the nylon 56 melt is obtained by the polymerization reaction of the front polymerizer and the rear polymerizer, the temperature of the heat conducting oil of the jacket of the front polymerizer and the jacket of the rear polymerizer are both 278 ℃, wherein the front polymerizer 9 is under normal pressure, and the vacuum degree of the rear polymerizer 10 is-0.06 MPa (gauge pressure). The nitrogen protection is maintained during the whole polymerization process.

The nylon 56 melt obtained by continuous polymerization is accurately metered by a spinning metering pump and evenly distributed into a spinning assembly, and the temperature of a spinning box is 280 ℃. The melt is sprayed out through a spinneret plate to form melt fine flow, the diameter of the spinneret plate is 0.25mm, the length of the spinneret plate is 0.6mm, and the number of holes is 72. Cooling and forming by a side blowing device 12, wherein the air temperature of the side blowing device 12 is 21 ℃, the air humidity is 75 percent, and the air speed is 0.38 m/s. After the cooled and formed tows pass through a spinning channel 13, bundling and oiling are carried out by an oiling device 14, the adopted spinning speed is 3200m/min, and the pre-drawn yarns are obtained. The results of the performance tests are shown in Table 1.

Example 4

1, 5-pentanediamine and adipic acid are prepared into 5 tons of 70% aqueous solution in a salification kettle 1, the pH value is adjusted to 8.2 (the salt solution is diluted to 10% detection result), the temperature is controlled to be 50 ℃, 50ppm (relative to the weight of nylon salt) of Bluegman antioxidant is added into the solution, the solution is transferred to an intermediate tank 2 through a filter, the solution is heated to 90 ℃ through a first preheater 3 and then enters a concentration tank 4 for further concentration to 80% concentration, the outlet temperature of the concentration tank 4 is 120 ℃, the solution is further heated to 213 ℃ through a second preheater 5 and then enters a reactor 6, the pressure of the reactor 6 is 1.0MPa, the outlet temperature is controlled to be 241 ℃, steam is recycled and reused through a cooling tower, the reaction solution then enters a flash evaporator 8 for removing most of water, and the pressure is reduced to normal pressure. And finally, the nylon 56 melt is obtained by the polymerization reaction of the front polymerizer and the rear polymerizer, the temperature of the heat conducting oil of the jacket of the front polymerizer and the jacket of the rear polymerizer are both 278 ℃, wherein the front polymerizer 9 is under normal pressure, and the vacuum degree of the rear polymerizer 10 is-0.06 MPa (gauge pressure). The nitrogen protection is maintained during the whole polymerization process.

The nylon 56 melt obtained by continuous polymerization is accurately metered by a spinning metering pump and evenly distributed into a spinning assembly, and the temperature of a spinning box is 280 ℃. The melt is sprayed out through a spinneret plate to form melt fine flow, the diameter of the spinneret plate is 0.25mm, the length of the spinneret plate is 0.6mm, and the number of holes is 72. Cooling and forming by a side blowing device 12, wherein the air temperature of the side blowing device 12 is 21 ℃, the wind speed is 83 percent, and the wind speed is 0.35 m/s. After the cooled and formed filament bundle passes through a spinning channel, the filament bundle is subjected to bundling and oiling by an oiling device 14, the temperature of a first godet roller 15 is 40 ℃, the coiling speed is 2700m/min, after the filament bundle is stretched by the multiplying power of 1.5, the highest temperature of a subsequent godet roller is set to be 140 ℃, and the filament bundle is coiled into a spinning cake on a coiling machine to prepare the nylon 56 fully drawn yarn. The winding speed used was 4000 m/min. The results of the performance tests are shown in Table 1.

Example 5

1, 5-pentanediamine and adipic acid are prepared into 5 tons of 75% aqueous solution in a salification kettle 1, the pH value is adjusted to 7.6 (the salt solution is diluted to 10% of detection result), the temperature is controlled at 80 ℃, the aqueous solution is transferred to an intermediate tank 2 through a filter, the aqueous solution is heated by a first preheater 3 to 90 ℃ and then enters a concentration tank 4 for further concentration to 80%, the outlet temperature of the concentration tank 4 is 120 ℃, the aqueous solution is further heated by a second preheater 5 to 213 ℃ and then enters a reactor 6, the pressure of the reactor 6 is 0.5MPa, the outlet temperature is controlled at 240 ℃, steam is recycled through a cooling tower, the reaction solution then enters a flash evaporator 8 for removing most of water, and the pressure is reduced to normal pressure. And finally, completing polymerization reaction by a front polymerizer and a rear polymerizer to obtain a nylon 56 melt, wherein the temperature of heat conducting oil of jacket of the front polymerizer and the rear polymerizer is 282 ℃, the front polymerizer 9 is under normal pressure, and the vacuum degree of the rear polymerizer 10 is-0.06 MPa (gauge pressure). The nitrogen protection is maintained during the whole polymerization process.

The nylon 56 melt obtained by continuous polymerization is accurately metered by a spinning metering pump and evenly distributed into a spinning assembly, and the temperature of a spinning box is 285 ℃. The melt is sprayed out through a spinneret plate to form melt fine flow, the diameter of the spinneret plate is 0.4mm, the length of the spinneret plate is 0.8mm, and the number of holes is 500. Cooling and forming by a side blowing device 12, wherein the air temperature of the side blowing device 12 is 21 ℃, the wind speed is 83 percent, and the wind speed is 0.32 m/s. The cooled and formed filament bundle passes through a spinning channel, is bunched and oiled by an oiling device 14, is wound into a spinning cake on a winding machine, and is then bunched, stretched, curled, heat-set and cut into nylon 56 short fibers. The winding speed was 800 m/min. The results of the performance tests are shown in Table 1.

Example 6

Preparing 65% aqueous solution 5 tons of 1, 5-pentanediamine and adipic acid in a salification kettle 1, adjusting the pH value to 7.8 (the salt solution is diluted to 10% of detection result), controlling the temperature to 60 ℃, transferring to an intermediate tank 2 through a filter, heating to 90 ℃ through a first preheater 3, then feeding into a concentration tank 4 for further concentration to 90% concentration, further heating the solution to 215 ℃ through a second preheater 5, then feeding into a reactor 6, controlling the pressure of the reactor 6 to be 1.2MPa, feeding 11% titanium dioxide aqueous solution into a melt through an additive tank 7 at the outlet of the reactor 6, wherein the titanium dioxide is 2500ppm of the weight of nylon salt, controlling the outlet temperature to be 242 ℃, recovering and recycling steam through a cooling tower, feeding the reaction solution into a flash evaporator 8 for removing most of water, and reducing the pressure to normal pressure. And finally, the nylon 56 melt is obtained by the polymerization reaction of the front polymerizer and the rear polymerizer, the temperature of the heat conducting oil of the jacket of the front polymerizer and the jacket of the rear polymerizer are both 278 ℃, wherein the front polymerizer 9 is under normal pressure, and the vacuum degree of the rear polymerizer 10 is-0.06 MPa (gauge pressure). The nitrogen protection is maintained during the whole polymerization process.

The nylon 56 melt obtained by continuous polymerization is accurately metered by a spinning metering pump and evenly distributed into a spinning assembly, and the temperature of a spinning box is 280 ℃. The melt is sprayed out through a spinneret plate to form melt fine flow, the diameter of the spinneret plate is 0.25mm, the length of the spinneret plate is 0.6mm, and the number of holes is 72. Cooling and forming by a side blowing device 12, wherein the air temperature of the side blowing device 12 is 21 ℃, the air humidity is 75 percent, and the air speed is 0.38 m/s. After the cooled and formed filament bundle passes through a spinning channel 13, bundling and oiling are carried out by an oiling device 14, the adopted spinning speed is 3000m/min, and the pre-drawn filament is obtained. The results of the performance tests are shown in Table 1.

Comparative example 1

50kg of nylon 66 chips purchased from Hippocampus project plastics Limited company are dried and continuously fed into a single-screw extruder, and are heated, extruded and melted into PA66 melt, the single-screw extruder is controlled in a partition mode along the axial direction, wherein the first-zone heating temperature is 255 ℃, the second-zone heating temperature is 280 ℃, the third-zone heating temperature is 285 ℃, the fourth-zone heating temperature is 295 ℃, the fifth-zone heating temperature is 308 ℃, the sixth-zone heating temperature is 294 ℃, and the spinning box temperature is 290 ℃. And then the melt is accurately metered by a spinning metering pump in a spinning manifold through a melt distribution pipe, the melt of the nylon 66 melt is uniformly distributed into a spinning assembly through an equal-length pipe, the supply amount of the metering pump is 60g/min, and the revolution number is 25 r/min. The outer diameter of the circular spinneret plate is 70mm, the number of spinneret holes is 48, and the diameter of the spinneret hole is 0.3 mm. The mixed melt in the spinning assembly is sprayed out from a spinneret plate, the mixed melt is sprayed out from the spinneret plate at the bottom of the spinning assembly at high pressure to form fiber yarns, the fiber yarns are cooled and formed under the condition of constant-temperature and constant-humidity side blowing, the air temperature of the side blowing is 20 ℃, the wind speed is 75%, and the wind speed is 0.38 m/s. After the cooled and formed filament bundle passes through a spinning channel, the filament bundle is subjected to cluster oiling by an oiling device, and then the filament bundle is stretched with the multiplying power of 1.5 and wound into a spinning cake on a winding machine to prepare the nylon 66 fully-drawn yarn. The spinning speed used was 4000 m/min. The results of the performance tests are shown in Table 1.

Comparative example 2

50kg of nylon 6 chips purchased from Xinhui Meida are dried, continuously fed into a single-screw extruder, and subjected to heating, extrusion and melting to obtain a PA6 melt, and the single-screw extruder is controlled in a partition mode along the axial direction, wherein the first-zone heating temperature is 240 ℃, the second-zone heating temperature is 275 ℃, the third-zone heating temperature is 285 ℃, the fourth-zone heating temperature is 290 ℃, the fifth-zone heating temperature is 295 ℃, the sixth-zone heating temperature is 288 ℃, and the spinning box temperature is 286 ℃. And then the melt is accurately metered by a spinning metering pump in a spinning manifold through a melt distribution pipe, the melt of the nylon 56 melt is uniformly distributed into a spinning assembly through an equal-length pipe, the supply amount of the metering pump is 60g/min, and the revolution number is 25 r/min. The outer diameter of the circular spinneret plate is 70mm, the number of spinneret holes is 48, and the diameter of the spinneret hole is 0.3 mm. The mixed melt in the spinning assembly is sprayed out from a spinneret plate, the mixed melt is sprayed out from the spinneret plate at the bottom of the spinning assembly at high pressure to form fiber yarns, the fiber yarns are cooled and formed under the condition of constant-temperature and constant-humidity side blowing, the air temperature of the side blowing is 20 ℃, the wind speed is 75%, and the wind speed is 0.38 m/s. After the cooled and formed filament bundle passes through a spinning channel, the filament bundle is subjected to cluster oiling by an oiling device, and then the filament bundle is stretched with the multiplying power of 1.5 and wound into a spinning cake on a winding machine to prepare the nylon 6 fully-drawn yarn. The spinning speed used was 4000 m/min. The results of the performance tests are shown in Table 1.

TABLE 1 Performance test

The above embodiments are merely illustrative of the technical solutions and do not limit the technical solutions in this aspect. According to the knowledge of the existing nylon preparation method, the preparation of nylon with different viscosity numbers can be realized by adjusting the raw material proportion in the preparation process and the temperature and pressure in the preparation process.

Although a few aspects of the present invention have been shown and discussed, it would be appreciated by those skilled in the art that changes may be made in this aspect without departing from the principles and spirit of the invention, the scope of which is therefore defined in the claims and their equivalents.

Claims

1. A preparation method of polyamide comprises the following steps:

1) preparing 1, 5-pentanediamine and adipic acid into a nylon salt aqueous solution, wherein the mass fraction of nylon salt in the nylon salt aqueous solution is 55-80%; when 1, 5-pentanediamine and adipic acid are prepared into a nylon salt aqueous solution, the pH value of the nylon salt aqueous solution is 7-9 when the nylon salt aqueous solution is diluted to 10%;

2) concentrating the nylon salt aqueous solution, wherein the mass fraction of nylon salt in the concentrated nylon salt aqueous solution is 70-95%;

4) and further dehydrating and polymerizing the prepolymer to obtain a nylon 56 melt, wherein the dehydrating and polymerizing comprise polycondensation, and the temperature of the polycondensation is 250-290 ℃.

2. The method according to claim 1, wherein the pressure of the concentration is 0.01 to 0.5MPa, and the temperature of the concentration is 80 to 150 ℃.

3. The process according to claim 2, wherein the concentration is carried out at a temperature of 90 ℃ to 140 ℃.

4. The process according to claim 1, wherein the pressure of the prepolycondensation is from 0.8 to 1.7 MPa; the outlet temperature of the pre-polycondensation reactor is 230-250 ℃.

5. The process according to claim 1, characterized in that said dehydration polymerization comprises a flash evaporation, the temperature of said flash evaporation being comprised between 260 ℃ and 320 ℃.

6. The process according to claim 5, characterized in that the temperature of the flash is 270 ℃ to 310 ℃.

7. The process according to claim 1, characterized in that said dehydration polymerization comprises a polycondensation, the temperature of said polycondensation being comprised between 260 ℃ and 280 ℃.

8. The process according to claim 7, characterized in that the postpolymerizer pressure of the polycondensation is from 0 to-0.09 MPa.

9. The process according to claim 8, characterized in that the postpolymerizer pressure of the polycondensation is from 0 to-0.07 MPa.

10. The method according to claim 1, wherein the mass fraction of the nylon salt in the aqueous solution of nylon salt is 60% to 80%.

11. The method of claim 1, wherein the mass fraction of the nylon salt in the concentrated aqueous solution of nylon salt is 80% to 90%.

12. A method for preparing nylon fiber, characterized in that nylon 56 melt prepared by the method according to any one of claims 1 to 11 is directly spun to prepare nylon fiber.